WO2004046001A2 - Pneumatic conveying system for particulate material - Google Patents

Abstract

Disclosed herein are high solids flow systems and methods for conveying particulates including a high solids flow outlet that induces high solids flow in a substantially vertical direction. Also disclosed are high solids flow outlets that can be employed to induce high solids flow in a vertical direction, devices for reducing saltation in a particulate conveyance system, a stream splitter, and a solids feed system.

Description

HIGH SOLIDS FLOW SYSTEMS, DEVICES AND METHODS

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 60/426,966, filed November 15, 2002, entitled "High Solids Flow Systems, Devices and Methods," which application is incorporated herein by this reference.

FIELD OF THE INVENTION

The invention generally relates to the conveying of particulates. More specifically, the invention relates to systems, devices and methods for pneumatically conveying particulate matter in a high solids flow mode.

BACKGROUND

Powders are processed in a wide variety of industries, including cement, chemicals, food, plastics and coal-fired power plants, to name a few. The facilities where the powders are processed or stored commonly require conveyors to transport them around the plant. The powders are usually conveyed pneumatically, which is preferred to the alternative, mechanical conveying, because of its versatility and cleanliness. There are two general types of pneumatic conveying systems, pressurized conveying systems and vacuum conveying systems. Pressure applications typically require more pressure than practicable with vacuum systems, and are limited to a single source of particulates to be conveyed. Vacuum systems are preferred in applications where there are multiple sources of material and/or where there isn't height available for an airlock at the conveying-line's inlet. Vacuum systems are inherently limited by the vacuum that can be economically generated - a maximum of about 10 psi. A pressurized system is shown in Figure 1; a vacuum system, in Figure 2.

As depicted in Figure 1, a pressurized pneumatic conveying system generally includes a conveying pipe 12 with a source 8 of compressed gas (e.g., air), introduced at its entrance, followed by an airlock 6 for injecting the powder into the pipe. The airlock enables the powder to enter the conveying pipe while minimizing the escape of compressed gas. Without the airlock, the compressed gas would escape at the solids- injection point 10 instead of conveying the solids down the pipe 12. At the outlet end of the conveying pipe, the powder falls into a receiving vessel 16 while the conveying fluid emerges from the receiver through a dust collector 14 before being exhausted through conduit 18 and induced-draft fan 20 to atmosphere.

In vacuum conveying, as illustrated in Figure 2, the inlet 10 to the conveying pipe 12 is at atmospheric pressure and a vacuum blower 20 at the conveying pipe's outlet creates the vacuum that causes the flow through the pipe. An airlock 6 is located at the dust collector outlet to permit the receiving vessel 16 to he at atmospheric pressure.

The alternative to pneumatic conveying is mechanical conveying with such devices as feedscrews, belt conveyors and bucket elevators. A key benefit of pneumatic conveying is that it seals the material from its environment, and vice versa, thereby eliminating contamination of each. Pneumatic conveyors are also more flexible with regard to changes in conveying direction, and generally have lower maintenance and capital costs. The main limitation of pneumatic conveyors is their relatively large power consumption, much of it for the conveying air. There are three conventional flow modes: dilute phase, dense phase, and two- phase.

Dilute phase flow provides for a uniform mixture of particles within the pipe that is homogeneous across the cross-section of the piping as well as along it. Conveying occurs by the entrainment of individual particles in the gas stream. Powders are conveyed because the conveying gas sweeps up the small particles.

In dilute phase flow, the friction with the piping is lower than with the other flow modes. The flow is free of any significant amount of pulsation, resistant to blockage even when there are geometrical restrictions in the piping such as sharp elbows or sudden contractions in the piping's cross-section. Unlike the other flow modes, the flow is insensitive to variations in particle size distribution and other powder properties such as surface roughness, though higher velocities are needed for denser or larger particles. When the flow of solids is discontinued during a shutdown, the pipe can be cleared of solids without special procedures. Dilute phase flow works with both aeratable powders and coarser, non-aerated materials. For dilute-phase flow to work, both the air velocity and the air-to-solids ratios must be kept high enough to prevent saltation (the settling of material in the bottom of horizontal sections of piping). Saltation leads to high pressure drops in the convey piping and may result in its plugging. The primary limitation of dilute phase has been the relatively low solids-to-air ratio that can be conveyed without saltation. To provide sufficient gas flow to accommodate a given solids flowrate, either the pipe size or the air velocity must be increased beyond optimal values. In dense phase flow, some sections along the conveying pipe are completely filled with solids. The slugs of solids are separated axially by air bubbles, and conveying occurs by pumping, or the transmission of pressure through the materials in the conveying pipe.

Even if the slugs of material are aerated, there are relatively high friction forces between the powder and the pipe walls. Accordingly, dense phase conveying requires the highest pressures of any conveying mode. When powders are conveyed in dense phase, the longer the slug, the higher the wall friction, and if the slug is long enough, the material in the pipe becomes jammed, whereby no amount of pressure will maintain flow. Much of the air to separate the slugs is introduced at the airlock, with additional air commonly added at injectors along the conveying pipe.

Dense-phase flow is subject to pressure fluctuations that can contribute to plugging. Other causes of high-pressure drop or plugging include changes in the material properties, such as particle size distribution, from that for which the system has been designed. With coarse materials, some of the particles settle in horizontal sections of piping at the end of a flow cycle, and may interfere with the resumption of flow in the next cycle.

Dense phase flow uses both lower air-to-solids ratios and lower velocities than do the other flow modes, which minimizes the demand for conveying airflow. The pipe sizing is also the smallest of the systems, which reduces capital costs. Dense-phase systems are used to convey materials too coarse to be aerated, such as sand and crushed coal, particularly if these are also abrasive.

The pressure tank is the preferred airlock with dense-phase systems because it has the highest-pressure capability of the airlocks. Pressure tanks for high tonnage applications need to be large enough to avoid too-frequent cycling. The height of such tanks can be a limitation to their use in low headroom applications.

Intermediate in performance between the other flow modes is two-phase flow (also called "extrusion flow"), typically used for conveying solids over long distances, and is limited to use with aerateable powders. With two-phase flow, much of the material injected into the conveying line settles to the bottom of the pipe at the injection point 10, while the conveying air and some entrained powder flow overhead. The settled solids are nearly stationary, having been dropped there from the airlock. A combination of compressor pressure and wind shear, or friction between the overhead airstream and the settled solids, gradually accelerates the bed. Clumps of material are periodically lifted into the airstream and moved some diameters down the piping before settling again. After a succession of such movements, the settled material picks up speed, until at some juncture (if the convey pipe is long enough), the solids reach the same speed as the conveying air. At this juncture, flow becomes dense phase, forming long slugs of material separated by similarly long air bubbles. Most of the power consumption for the conveying in two-phase is at the entrance regions of the pipe where acceleration occurs. Screw pumps can be used as airlocks for two-phase systems, as they are capable of higher pressures than, e.g., rotary valves, and can withstand more abrasive materials. The conveying-line pressures and pipe sizes are intermediate between dilute-phase and dense-phase systems. One limitation of two-phase systems is that the screwpump itself uses significant amounts of power, as it compresses the conveyed powder in order to form the sealing action of the airlock. The power for the airlock is typically a quarter, or more, of the total system power. In sum, while there are significant differences in the appearance and properties of the flow modes, the main properties affecting the economics of conveying: power and conveying line pipe size, are comparable for the three systems. While one system may be somewhat cheaper than another in a particular application, until now the overall costs of all of the systems have been of similar magnitude and economically significant.

SUMMARY OF THE INVENTION

A new high solids flow mode, or SUPERAERATED™ or SUPERA™ flow mode has been discovered. The high solids flow mode not only more efficiently conveys solids, but also prevents the accumulation of solids upon a change in the direction of flow. The systems, devices and methods of the instant invention leverage this discovery to significantly reduce the pressure, airflow, and thus compressor power required to pneumatically convey particulates. Significantly, the systems, devices and methods of the invention also reduce the explosion hazard of conveying combustible powders by reducing the air-fuel ratio below the combustible limit. The invention provides higher solids-to-air ratios than are currently possible. The improvement in solids-to-air ratio can be achieved by homogenizing and accelerating particulates in a vertical conduit prior to being conveyed horizontally.

Moreover, the low pressure-drop achieved by the systems, devices and methods of the invention increase the flexibility and potential applications of conventional systems such as vacuum systems. The invention also significantly reduces conveying costs, such as power consumption and equipment costs. Furthermore, existing systems can be retrofitted to take advantage of the discovery, and such retrofitted systems are provided by the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features, and advantages of the present invention, as well as the invention itself, will be more fully understood from the following description of preferred embodiments, when read together with the accompanying drawings, in which: Figure 1 is a schematic cross-sectional side view of an exemplary pressurized pneumatic conveying system.

Figure 2 is a schematic cross-sectional side view of an exemplary vacuum pneumatic conveying system.

Figure 3 is a table summarizing the differences between dense phase, two-phase, dilute phase, and high solids flow modes.

Figure 4 is a schematic cross-sectional side view of an exemplary airlock outlet used to inject particulates into conveying lines, shown as used in a pressurized- conveying system.

Figure 5 is a schematic cross-sectional side view of an exemplary airlock outlet of the invention, shown as used in a pressurized-conveying system.

Figure 6 is a bar graph comparing the performance of the high solids flow systems with dilute-phase flow systems, and demonstrating the benefits of the high solids-to-air ratio capability of the invention.

Figure 7 is a graph depicting and comparing the pipe friction factor of high solids flow and two-phase flow.

Figure 8 is a bar graph comparing the performance of the high solids flow systems of the invention with an exemplary two-phase flow system, and demonstrating the benefits of the present invention. Figure 9 A is a table comparing key performance parameters of the high solids flow systems and two-phase flow systems over a wide range of throughputs and conveying distances.

Figure 9B is a table comparing key performance parameters of the high solids flow systems and two-phase flow systems with the same conditions as Figure 9A, but with conveying velocities increased with conveying line diameter.

Figure 10 depicts views of an exemplary air injector for homogenizing an air- powder mixture as it enters the downcomer of a high solids flow outlet.

Figure 11 is a cross-sectional side view of an exemplary mechanical homogenizer used to disperse particulates in an air stream.

Figure 12 is a cross-sectional side view, of another exemplary mechanical homogenizer.

Figure i 3-4 is a cross-sectional side view of a riser assembly for conveying powder upwardly in a high solids flow system of the invention that includes a high solids flow outlet.

Figure 13B depicts a riser assembly for converting high solids flow into dense- phase flow.

Figure 14A is a cross-sectional side view of a high solids flow system including a hydrostatic airlock. Figure 14B is a cross-sectional side view of a high solids flow system including a hydrostatic airlock having a flow limiter.

Figure 15A and Figure 15B are a cross-sectional side views illustrating how an airlock can be incorporated into a system of the invention. In Figure 15 A the maximum feedrate of the airlock is controlled; In Figure 15B, the feedrate is not limited. , Figure 16 is a cross-sectional side view illustrating how a rotary valve can be incorporated into a system of the invention.

Figure 17 is a cross-sectional side view illustrating how a pressure tank system can be incorporated into a system of the invention.

Figure 18 is a side view in partial cross-section, illustrating how a screwpump can be incorporated into a system of the instant invention.

Figure 19 A is a cross-sectional side view of a system of the invention for conveying pulverized-fuel to combustors with a multiplicity of fuel lances. Figure i PR is a cross-sectional side view of the stream splitter depicted Figure 19A.

Figure 20 is a cross-sectional side view of a system of the invention for conveying a combustible powder to a single conveying line. Figure 21 is a side view of a system of the invention for unloading powder from vessels with live bottoms.

Figure 22 depicts the inlet to the riser depicted in Figure 21.

Figure 23 A and Figure 23B depict a system of the invention for removing powder from vessels without live bottoms; Figure 23B depicts the inlet to the riser depicted in Figure 23 A.

Figure 24 A and Figure 24B are cross-sectional side views of systems of the invention for unloading powder from railcars.

Figure 25 is a cross-sectional side view of a system for conveying powder from a multiplicity of hoppers. Figure 26 is a front view, side view, and a perspective view of a ribbon or coil device of the invention that can utilized with devices and systems of the invention to reduce saltation velocity.

DETAILED DESCRIPTION OF THE INVENTION

The systems, devices and methods of the present invention provide for the pneumatic conveyance of particulates at a significant increase in the solids-to-air ratio that could previously be achieved. This increase can be on the order of at least 20-fold as compared to dilute-phase flow. Moreover, the invention provides homogenous flow in both dimensions (along pipe cross-section and pipe length), low friction, minimal or no pressure fluctuations, minimal or no blockage even with severe geometry changes, insensitivity to material properties such as size distribution, wide turndown capability, and self-cleaning during system shut down.

In addition, the higher solids-to-air ratio provided by the invention reduces the conveying power required in the pneumatic conveying of powder by as much as 85% compared with two-phase flow. A summary of the differences between the invention and the conventional flow systems, including dilute-phase flow, is provided in Figure 3. Furthermore, the new system may be retrofitted to existing conveying systems with only a minimum of changes to the piping, and frequently also retains the use of the existing compressor, resulting in a low capital cost that contributes significantly to its value. The invention can be used to convey any particulate solid or semi-solid. One significant application of the invention is in the pneumatic conveying of aeratable powders (Geldart particulate classification "A"), including materials from about 20 to 100 microns in diameter which are expensive to convey. Powders for which the cost of conveying is significant include, for example, cement and flyash. The invention is also useful for improving the safety of conveying explosive powders, including pulverized coal, petroleum coke, flour, plastics and chemicals. The invention can also be used to convey coarser particulates (Geldart Class B particulates), which include, but are not limited to, granular materials such as sand, grain, plastic pellets, abrasives, and chemicals. In the systems, devices and methods of the invention the high solids-to-air ratio can be achieved by an improvement in the design of the outlet under the airlock. Referring to Figure 4, the outlet is the flow element 10 where the conveyed material is introduced into the conveying pipeline. In conventional systems, the outlet includes a tee 10 having a vertical leg connected to the outlet of the airlock 6. Conveying air supplied by blower 8 enters the tee through one of the horizontal legs, and the mixture of powder and conveying air leave through the other leg 12.

As is shown in Figure 4, the conveying air immediately entrains some of the particles, creating a cloud 26 of particles in the upper reaches of the convey pipe. At sufficiently low solids throughputs, all of the material becomes entrained before it reaches the bottom of the tee. However, at higher solids throughputs, because of the solids stream's high downward momentum and its relatively brief exposure to horizontal airflow, a mound 24 is formed at the bottom of the tee.

Considerable energy can be required to dissipate the mound, as its density is far higher than that of the conveying air. The mechanism by which the mound is dispersed, is the two-phase flow described above, with the attendant high pressure drop. To avoid the formation of a mound and the resulting high pressures, dilute phase flow should operate at solids throughputs below the conditions creating two-phase flow. In the present invention, the mound in the airlock outlet is eliminated, thereby allowing for an increase in the solids-to-air ratio that could be achieved with dilute- phase flow. The device that accomplishes this is the high solids flow outlet 28 depicted in Figure 5 that generally includes a homogenizer 30, and equalizer 32, and an elbow 34. The homogenizer disperses particles across the cross-section of the downcomer. The equalizer further accelerates the particles to a velocity approaching that of the conveying airstream. The elbow changes the direction of the solids-gas mixture.

The homogenizer avoids the mounding that occurs in conventional systems by homogenizing the gas and solids stream. Flow emerging from an airlock 6 generally is not uniform, but rather is concentrated in coherent streams whose appearance is not unlike that of water flowing from a faucet. Because there is little interaction between the particles in such streams and the surrounding air, the streams remain coherent for even extensive drop distances. When such streams reach an elbow, they decelerate and, unaffected by the surrounding air velocity, form a mound, as in a conventional outlet. The homogenizer serves to change the flow conditions in the downcomer such that individual particles are easily entrained by the surrounding air stream and quickly approach its velocity.

The equalizer further increases the unifoπnity of mixing by providing an additional opportunity for the particles to approach the airstream's velocity. It includes a length of vertical piping 31 below the homogenizer that provides sufficient time for clusters of particles, larger than individual particles, but still small enough to be accelerated in a short time, to approach the conveying air velocity before the mixture reaches the elbow.

The elbow turns the falling gas-solids mixture into a substantially horizontal direction, where it is connected to the conveying line 12. In one embodiment, the elbow's cross-section diminishes in the direction of flow, creating a pressure gradient along the elbow to avoid the separation of flow along the bottom of the elbow, with its attendant stagnation and the possible formation of a mound. Conveying line 12 transports the particulates toward their final destination. The conveying line may be any combination of piping, horizontal, vertical, and sloping, either upwards or downwards. The Homogenizer

In one embodiment, dispersion may be provided by air jets that use conveying air to stir the downward-flowing stream of particles as illustrated by the homogenizer depicted in Figure 10. In another embodiment, the homogenizer includes baffles located below the conveying air inlet to the downcomer as illustrated in Figures 11 and 12. The baffle homogenizer reduces the compressor power of the air injector but can be subject to clogging by tramp materials. In yet another embodiment, the homogenizer includes a vortex elbow at the top of a riser in which slug flow occurs (Figure 13).

Homogenizers Including Air Injectors Figure 10 depicts a homogenizer that includes air jets that mix the powder into the air stream. It includes an array of nozzles 38 that are used to inject the conveying air into top of the downcomer 36. The nozzles are distributed about the periphery of the downcomer 36, and preferably are aimed to contact as much of the cross-section of the downcomer as possible. The combined internal area of all the nozzles is sufficiently small such that the conveying air exit the nozzles at relatively high velocities, e.g., several hundred feet per second. The angle of the nozzles may vary, from horizontal, to being pointed downward, to further promote homogenization. Air is supplied to the nozzles by a manifold 40 that receives its conveying gas through conduit 42.

Homogenizers Including Baffles

An example of a homogenizer that uses one or more baffles instead of air jets to disperse the solids is shown in Figure 11. The conveying-gas is introduced into the downcomer 36 at inlets 44 above the baffles, creating a significant downward air velocity in the vicinity of the baffles 46. The baffles depicted in Figure 11 include several sections of chain 46 of various lengths that are positioned in various orientations by the supports 48 across the cross-section of the downcomer. When a stream of powder collides with a chain, it breaks up from the impact and creates a spray in the surrounding airstream. As many chains are used as desired to provide sufficient dispersion to avoid the formation of a mound in the elbow below. By using chains of different lengths, the amount of coverage that is provided may be increased to whatever level is desired, without significantly blocking the flow passage. Figure 12 depicts a homogenizer that includes static baffles 50, instead of the chains depicted in Figure 11, to break up the downward-flowing columns of solids, by deflecting them into the surrounding airstream with deflector bars 50. Riser assembly Flow through a segment of vertical piping that is the same diameter as the horizontal piping is much more restrictive than horizontal piping because its pressure drop is much greater. For example, the pressure drop can be 50 times greater in a vertical pipe as compared to a horizontal pipe of equal length. The increase in pressure drop is due in part to the recirculation of solids as they flow upwards. In vertical segments of piping, the particles are blown upwards near the middle of the riser but are slowed by friction at the walls to such an extent that the momentum of the surrounding air is no longer sufficient to keep the particles airborne, and they start to fall. The falling particles then entrain surrounding particles, forming falling cascades that gather both mass and velocity as they fall. Eventually, the cascades break up and the particles are redirected upwards, but the cycle repeats multitudinous time as the particles fight their way up the pipe.

The resulting pressure drop, as much as 30 psi for a 100-foot riser, is not desirable as it would eliminate the pressure drop improvements in the horizontal sections of the conveying lines of the present invention. This is particularly true when long vertical sections are employed, e.g., to fill silos. To eliminate the excessive pressure drop in such applications, the riser assembly and system depicted of Figure 13A can be employed. The riser assembly 51 includes a substantially vertical pipe 56 followed by a high solids flow outlet that reestablishes high solids flow in the horizontal segments of piping 74 following the riser assembly. The system further includes a reducer 54 that significantly increases the diameter of riser 56 relative to horizontal pipe 12. The reducer creates choked flow such that the flow in the riser includes a series of particulate slugs, separated by slugs or bubbles of air. Because the recirculation of solids is virtually eliminated by the reducer, and the transport velocity is low, the pipe friction in the riser is similarly low. Typically, less than 10% of the pressure drop in a riser is due to friction. The rest is the pressure required to overcome the hydrostatic forces. In the riser, pressure rise of the riser due to hydrostatic forces, 9P, can be calculated as follows: 3P = .007 x H x p x Qp / (Qa + Qp) Equation (1) where:

H = riser feet (ft) p = powder bulk density (lb/cu ft) Qp = volumetric flowrate of the powder (CFM)

Qm = volumetric flowrate of the mixture (ACFM)

The pressure drops of exemplary vertical segments of piping are illustrated in column 10 of Figures 9 A and 9B. The upward flow through a high solids conveying system of the present invention preferably is vertical, or substantially vertical, as upwardly-sloped piping suffers from the same problems as a vertical riser, and slug flow is difficult to maintain in a slanted riser. No such restrictions apply to downcomers, which may be vertical or slanted.

Homogenizer at the top of a riser

At the riser 56 outlet, a homogemzer 70 as illustrated in Figure 13A can be used to reestablish the high solids flow conditions. The homogenizer 70 includes a wye 60. Wye 60 is blanked at its top by cap 62. Slugs emerging from the top of the riser are arrested by the cap 62 and reverse their flow, before emerging at the side outlet of the wye. The resulting turbulence creates a cloud that enables the wye 60 and the cap 62 to serve as a homogenizer 70. The wye outlet is in fluid communication with an elbow 64, which is in fluid communication with the equalizer 68. At the bottom of the downcomer is another elbow 72 that restores the horizontal direction of flow. Reducers 58 and 66 return the piping diameter from that of the riser to that of high solids flow segment 74.

Comparison of high solids flow systems with dilute-phase flow systems Figure 6 illustrates that the solids-to-air ratio increase achieved by the invention substantially reduces the power consumption compared with dilute-phase flow. Figure 6 compares the performance of systems in which 100 tons/hr of cement is conveyed through a horizontal 1000-ft long 10" diameter pipe.

With high solids flow, the conveying-pipe airflow is determined by the mimmum pickup velocity (the air velocity at the airlock outlet) of about 30 ft/sec. Below that velocity, with high solids flow, cement can settle in the pipe. The solids-to-air ratio (by weight) that results in the illustrative system from this is 34 to 1, which is significantly higher than the ratio of 10 to 1 achieved by the dilute phase flow system (Figure 6). Systems of the present invention can further achieve even higher solids-to-air ratios, e.g., a ratio of 200 to 1 has been measured.

With dilute phase flow, the criterion for selecting the conveying-line airflow is the 10-to-l maximum solids-to-air ratio. To convey the 100 tons/hr, the dilute-phase system uses 10 tons/hr of airflow, 2.4 times that of the high solids flow. If both systems use the same pipe diameter, the higher airflow of dilute phase requires a correspondingly higher velocity, and with it, a higher pressure drop. These factors combine to give the dilute-phase system a 6-times higher power requirement for its compressor motor.

Comparison of high solids flow systems with two-phase flow systems A comparison of the high flow solids systems of the present invention with a typical two-phase system shows a similar improvement to that seen for dilute phase flow systems. The results of this comparison are illustrated in Figure 8. As can be seen in Figure 8, both systems are used to convey 100 tons/hr of cement through a horizontal 10" pipe that is 1000 ft long. To determine the pressure drop of each system, the pipe friction factor was determined, which is shown in Figure 7.

The total pressure drop, 3Ps, for high solids flow can be determined by: dPs = pipe friction + acceleration pressure drop Equation (2) and the pressure drop for two-phase flow, dP₂, can be determined by: dP₂ = pipe friction (only) = f₂ x L/D x q-mix where: pipe friction = f_s x L/D x q-mix Equation (3) f_s is the friction factor for high solids flow (Figure7)

L D is the pipe's effective length-to-diameter ratio Q-mix is the dynamic head of the mixture in the pipe: q-mix *= q-air x Mm / Ma Equation (5)

Mm = mixture flowrate, (lb/sec) = (Ma + Mp)

Ma = conveying-line air flowrate, (lb/sec)

Mp = powder flowrate, (lb/sec) acceleration pressure drop = Vm x Mp / g ÷ Ax Equation (4) Vm = mixture velocity at the pickup point, (ft/sec)

Mp ^•= powder flowrate, (lb/sec) g — acceleration of gravity, = 32.2 ft/sec ²

Ax = the cross-section of the conveying pipe, (sq. ft) p = density of the air at the pickup point, (lb/cu ft) Vm, the mixture velocity at the pickup point, typically in ft/sec, is determined by:

Vm = Va x (Qa + Qp) / Qa Equation (6)

Va = air velocity at the pickup point, (ft/sec) Qp = powder volumetric flowrate, (CFM)

The air volumetric flowrate at the pickup point, Qa, typically in ACFM, is determined by:

Qa = p x Va Equation (7)

The airflow, Qs, entering the conveying-line blower, in SCFM is determined by: Qs = Qa x γ Equation (8)

The specific gravity of the air at the pickup point, γ, is determined by: γ = ((3P + 14.7) / 14.7) / ((((((P + 14.7) / 14.7) ²⁸⁶) - 1) / η)+l) Equation (9) where η = blower efficiency The blower power requirement can be determined by: Equation (10) kW = 60 x Ma x ((((((P + 14.7) / 14.7) ^exp' °^'286) - 1) / η) x Ta x Cp) / 3413 where kW = the kilowatts needed to drive the blower

Ta = ambient temperature, (°R) c_p = specific heat of air, (BTU/lb -°F)

As illustrated in Figure 7, the friction factor for a two-phase flow system varies significantly with pipe length: high for short lengths of piping and diminishing with pipe length. The curve reflects the high pressure needed to accelerate the mounds of powder near the pipe entrance, and the progressively lower pressure requirements as the powder approaches the velocity of the conveying gas. The acceleration pressure drop has been included in the total pipe pressure drop because there isn't a practical way to separate the two effects.

With the high solids flow system, the friction factor is low from the outset and independent of the length of the pipe. For the conditions used in Figure 8, friction factors differ by a factor of five for the two systems (Figure 7).

When the acceleration pressure drop is added to provide the total pressure drop of high solids flow, the difference between the two systems becomes a factor of three.

This three-fold reduction of piping pressure drop has a double benefit: Not only does it directly reduce the compressor power, but it also reduces the airflow needed to provide sufficient pickup velocity. The combined effect is that the conveying line air compressor power requirements for the high solids flow systems of the invention are 15% of the requirement of the two-phase system of Figure 8. As illustrated by the bottom row of column 16 in Figure 9A, the conveying air compressor power of the high solids flow systems is 18% of the two-phase flow system. The data used to calculate this result is shown in columns 5 through 15 of Figure 9 A. The power savings of Figure 9 A are slightly lower than that of Figure 8 because the injector pressure drop has been included in the latter, but not the former. The low pressure drops of the invention shown in column 12 of Figure 9 A, also illustrates the feasibility of incorporating vacuum conveying, with its attendant benefits, into systems and methods of the present invention. Such systems could be utilized for many applications that until now had been unavailable and/or impractical for pneumatic conveying. Optimal pipe sizes

Where existing systems are incorporated, converted and/or retrofitted into systems of the present invention, the ability to use existing piping provides a great economic benefit. In new installations, the present invention makes it possible to use significantly smaller piping, reducing the capital costs of both the piping and the compressor. However, the optimal economics may nevertheless occur with piping sizes similar to those currently in use, as shown in columns 1 through 4 of Figure 9A.

Equations (1) through (10) may readily be used to trace through the effect of pipe size on pressure drop and power requirements. Generally, the power requirement is approximately inversely proportional to the square of the pipe diameter. Cutting the diameter in half, e.g., quadruples the power consumption. The effect can be decreased at lower pressures, and at a line pressures approaching zero, the power requirements are only doubled when the pipe diameter is halved.

Thus, although the invention enables the use of considerably smaller piping than is currently used with two-phase flow, the optimal economics are likely to occur with piping sizes similar to those now in use. The bottom row of column 17 of Figure 9 A shows that the solids-to-air ratio of high solids flow applications average 46 to 1, well above the maximum capability of the conventional systems. The high ratio is also particularly advantageous in explosion-proof applications, where high solids-to-air ratios are required to bring the solids-to-air ratio above the combustibility limits for the powder.

Scaleup Figure 9B shows the improvement that high solids flow would have over two- phase flow if the mixture velocity were to be increased with the square root of diameter. Such a rise would keep the Froude number constant over the range of pipe sizes.

In Figure 9A, the power used in a typical high solids flow installation is only 18% that of a two-phase system at 100 tons/hr conveyed 1000 ft, including 100 ft vertically, through a 10-inch pipe as shown, e.g., row 11 of Figure 9 A. Figure 9A uses a conveying gas velocity of 30 ft/sec for all pipe sizes. If the velocity through the piping is increased to keep the Froude number constant, as shown in Figure 9B, for the same operating conditions the mixture velocity is increased to 40 ft/sec, and the compressor power of high solids flow rises from 18% of the two-phase system to 26% as shown in row 11 of Figure 9B. The conveying gas velocity in Figure 9B is 20 ft/sec in a three- inch pipe and increased with the square-root of velocity. As can be seen from Figures 9A and 9B, even though the savings progressively decrease for the higher throughputs and larger diameter installations, the savings are nonetheless significant.

One method that can be used to reduce the saltation velocity is to energize the bottom of the piping, where saltation begins, by diverting high- velocity material to that region. An example of a baffle that may be used for this is shown in Figure 12. The blades of the deflector can be pointed downwards towards the bottom of the piping, before straightening out as they reach the bottom. In one embodiment, a succession of such deflectors can be combined into a continuous coil and inserted into a pipe with a minimum of modification.

High solids flow systems with dense phase flow

Another method of avoiding the need for high velocities in the piping is to begin with high solids flow and then convert it to dense-phase flow along the pipe, using the devices and system illustrated in Figure 13B. Saltation doesn't occur in dense-phase flow because pumping rather than entrainment conveys the particulates, and thus low conveying velocities can be utilized. By using high solids flow rather than windshear to accelerate the particulates, conveying in this manner can achieve the best of both systems: low acceleration pressure drop, and low friction in downstream sections. In Figure 13B, solids enter conduit 4 through airlock 6 and air is introduced to the solids from conveying air blower 8. The solids enter the conveying pipe 12 in high solids flow mode from high solids flow outlet 28. After the flow is then converted to slug flow in riser 78 through elbow 52 and reducer 76. From there, it enters elbow 80 that reverts the flow back into the horizontal direction in conveying pipe 82. Since there is no homogenizer at the top of the riser, the flow remains in dense phase. High solids flow outlet 28 includes a homogenizer, equalizer, and elbow as previously described.

Coil for reducing high velocities in piping

An alternative method of avoiding the high velocities in large piping is to insert a coil 288 into the conveying pipe 286, as illustrated in Figure 26. The upper sections of the coil are bent downward through angle 292. It has been observed that saltation begins at the low-velocity boundary layer at the bottom of the conveying pipe. Coil 288 reduces the stagnant boundary layer by diverting high-velocity mix from higher elevations of the piping. This is achieved by the twisting the upper portions of coil 288 downward through angle 292. The coil can be continued down the piping (not shown), as desired or until the higher velocities in the downstream sections of piping preclude the need for it.

High solids flow may be applied in a number of ways. Several exemplary applications of the invention in pressure and vacuum systems are described below. High solids flow system incorporating a hydrostatic airlock

In one embodiment, the present invention is a high solids flow system including a hydrostatic airlock. Hydrostatic airlocks can be used to seal the pressure in conveying lines in such applications as airlifts. A hydrostatic airlock typically includes a column of fluidized powder whose hydrostatic head exceeds the pressure drop of the conveying line. Its benefits are simplicity, reliability, and low capital and operating costs. Its limitation is its headroom requirement. The column height (minimum column height of powder needed to form a seal), H, for sealing line pressure (in feet) can be determined by:

H = 144 / p x P Equation (11) where p = powder bulk density (lb/cu ft), and

3P — the conveying air pressure to be sealed (psi). For cement with a bulk density of 60 lb/cu ft, the minimum column height for sealing is about 2.4 ft per psi. Using a high solids flow system has a line pressure of under 7 psi (see, e.g., column 12 minus column 8, Figure 9A), a column height of about 15 ft is sufficient, plus a few extra feet to accommodate the flow-controlling orifice at the bottom of the standpipe.

In one embodiment (Figure 14A), a hydrostatic airlock includes a single downcomer 86. When used with high solids flow, the outlet of the downcomer is connected to the inlet of the high solids flow outlet 28. The hydrostatic airlock of Figure 14A is utilized for installations in which the solids flowrate to the airlock is controlled by a metering device such as a feedscrew, and in which the surges of flowrate are sufficiently small such that the conveying system isn't choked.

Hydrostatic airlock 84 includes a downcomer 86 for receiving the incoming powder, a flow-restricting orifice 92 and shutoff valve 94 at the bottom of the downcomer 86. A fluidizing pad 88 at the inlet to the orifice keeps the material in the downcomer fluidized, thereby creating the hydrostatic pressure that seals the conveying air. The fluidizing pad is supplied by a source of compressed air such as a blower (not shown) which flows to the fluidizing pad 88 through inlet 90 and plenum 91.

Some of the hydrostatic pressure is used to overcome the pressure drop of the orifice. The orifice is used to limit flowrate of the solids transmitted to the conveying pipe. This limits the conveying line pressure drop and keeps it from exceeding the pressure-sealing capacity of the hydrostatic airlock. If the solids flowrate diminishes, the solids level in the downcomer drops, reducing the sealing capability of the airlock. While the reduced level also causes the flowrate to diminish, the possibility exists that the pressure drop of the conveying line exceeds the sealing capability of the hydrostatic airlock under these circumstances. Once the seal is broken, the blow-by of conveying air up the downcomer prevents the flow of solids, and conveying can be arrested. To avoid this, a level gage 96 can be installed in the downcomer that maintains the solids level in the downcomer at a desired setpoint regardless of the solids flowrate. This means that valve 94 is gradually closed as the incoming flowrate drops, and opened as it rises. High solids flow system incorporating a hydrostatic airlock with a flow limiter

In another embodiment, a system of the invention includes an airlock with a flow limitation device, as illustrated in Figure 14B. hi unmetered applications, or metered applications subject to flow surges, a hydrostatic airlock is used to limit the solids flowrate to the conveying system. Without it, the flowrate into the conveying system will seek to exceed the system capacity thereby choking it. The design depicted in Figure 14B is the subject of U.S. Patent Nos. 5,655,853 and 5,997,220, both entitled "Vertical Shaft Airlock," incorporated herein in their entirety by this reference. An example of an unmetered application includes applications that feed particulates directly to a silo. The invention can also be applied to systems and devices where flow surges occur with metered systems, particularly if there is a flow element with significant storage capacity between the feeder and the airlock in which solids can temporarily be accumulated and then released. The hydrostatic airlock of Figure 14B is similar to that of Figure 14A, however a

"dogleg" 98 is installed above hydrostatic airlock 84 in Figure 14B. A dogleg is an inlet conduit connected by an elbow to a second conduit that is sufficiently long and shallow to prevent the free-fall of solids, but sufficiently steep to permit the solids to flow freely, attached by a second elbow to third, substantially vertical outlet conduit. The dogleg 98 is used instead of a mechanical feeder such as a rotary valves or screw feeder. The dogleg includes a top downcomer 100, whose inlet is attached to the supply 2. Its outlet is attached to sloping pipe 106. The outlet of sloping pipe 106 is in communication with the inlet to hydrostatic airlock 84.

If dogleg 98 is installed at the bottom of a silo, an upper fluidizing pad 110 is located at the entrance of downcomer 100. The fluidizing pad is supplied with a source of compressed which enters through inlet 112 and plenum 114.

The purpose of dogleg 98 is to isolate the hydrostatic airlock's lower downcomer 84 from whatever material may be contained in the piping overhead. Without the dogleg, the hydrostatic pressure in the upper regions of piping, or in supply vessels such as silo 2, would be exerted on the orifice of airlock 84, causing an excess of flow through the hydrostatic airlock. With the dogleg, the material in the upper regions of piping has no effect on the pressure on the lower dogleg or its orifice because the material in the dogleg is not fluidized. The particulates in the upper leg of the dogleg are unfluidized as follows. The angle of the slanted pipe segment causes the fluidizing air from fluidizing pad 92 to rise to the top of the pipe, where it collects and forms a flow channel. When the stream of fluidizing air reaches the bottom of the upper downcomer, its concentration into a channel causes it to rat-tail through the upper downcomer, instead of fluidizing it. At the top of slanted pipe 106, is vent 104 that allows the fluidizing air to escape. This further reduces the effect of the material in the upper downcomer on the pressure in the lower downcomer.

The angle of slanted pipe 106 is sufficiently steep (e.g., about 45°) such that material flows freely into the lower downcomer, but not so steep that the fluidization of the lower downcomer is transmitted to the upper downcomer. The length of the slanted pipe should be sufficient to prevent line-of-site through it in the vertical direction.

High solids flow system incorporating an AUTOSEAL® airlock

Another application of the invention is a system that incorporates an airlock, such as an AUTOSEAL® airlock available from Wormser Systems, Inc. (Salem, MA). AUTOSEAL® airlocks are preferred because they accommodate low headroom, provide high particulate throughput, the ability to convey abrasive powders, and low power costs. This system is particularly advantageous if the headroom available is insufficient for a hydrostatic standpipe. Exemplary systems incorporating an airlock 134 axe depicted in Figures 15A and

15B. Figure 15A depicts a systems where flow to the airlock is controlled, and Figure 15B depicts a system where flow to the airlock is not controlled. Figures 15A and 15B are similar, however, a dogleg 98 has been added to the system of Figure 15B.

When used to convey powders, the AUTOSEAL® airlock includes an inlet 132 that contains a short hydrostatic airlock. Inlet 132 is described in U.S. Patent Nos. 5,655,853 and 5,997,220, both entitled "Vertical Shaft Airlock," incorporated by reference herein. The inlet is advantageous for the following reasons.

1. The pressure in airlock 132 exceeds the pressure of the AUTOSEAL® airlock vent. Without this arrangement, some vent air would go up the downcomer, reducing the throughput capacity.

2. The inlet supplies sufficient powder to match the relatively small inlet area of the airlock. 3. The inlet prevents splashing of powder if the downcomer is very tall; Such splashing would increase the dust loading in the vent and the resulting vent pressure.

4. The inlet decreases the flow to the airlock below the level that would choke it. 5. The inlet automatically accommodates variations in the powder flowrate without requiring active controls.

Inlet 132 is in communication with a powder supply conduit 4 that feeds material to the top of orifice 122. Fluidizing pad 116 keeps the material in downcomer 4 fluidized. The fluidizing air enters through inlet 120 and plenum 118. The orifice limits the flow of powder to the airlock and prevents choking of the conveying system. An inner downcomer 124 conveys the powder to the inlet of airlock 134. Air displaced by the entering powder is vented through annulus 128 that is formed between outer conduit 126 and inner conduit 124. The vented gas exits through outlet 130, and preferably is ducted to a dust collector. High solids flow system incorporating a rotary valve airlock

Another embodiment of the invention is a high solids flow system that incorporates a rotary valve airlock, a portion of such a system is depicted in Figure 16. The low line pressures of a high solids flow installation make it feasible to use in a conventional rotary valve as an airlock instead of (e.g-., an AUTOSEAL® airlock), at a savings in both first costs and operating costs. The system depicted in Figure 16 is useful, e.g., as a firelock in the pneumatic conveying of nonabrasive explosive powders. The system includes a rotary valve airlock 136 mounted over a high solids flow outlet 28. In one embodiment, an inlet such as that depicted in Figures 15A-B can be installed on top of the rotary valve to minimize the effects of blowby and increase throughput. High solids flow system incorporating a pressure tank

Another embodiment of the invention is a high solids flow system that incorporates a pressure tank. Figure 17 illustrates a portion of such a system incorporating a pressure tank. In pressure tank 138, particulates are blown into the pressure tank during the fill cycle through inlet 140. During the conveying part of the cycle, the valve under inlet 140 is closed. The tank is then pressurized by conveying air from conveying air blower 8 through conduit 150 and introduced directly into the tank, pushing the conveyed material out of the tank outlet into conduit 4. When the material being conveyed is a powder, its flow is enhanced by the use of a fluidizing assembly 142 whose air supply enters through inlet 144.

With the high solids flow system, the conveying air inlet is injected at the top of the outlet downcomer as depicted in greater detail in Figure 5. The conveying air can be inj ected through the nozzles of the inj ector homogenizer (e.g. , the homogenizer depicted in Figure 10), and/or a mechanical homogenizer (e.g., the homogenizers depicted in Figures 11 and 12).

When powder is conveyed, the outlet conduit 4 of pressure tank 138 serves as a flow-limiting orifice, and the flowrate through the opening depends on the pressure difference across it, some of which is hydrostatic pressure of the material in the pressure tank. As the tank empties, the pressure driving material through the orifice diminishes, reducing the throughput. To avoid this, supplemental air is added to the top of the tank through conduit 150 to maintain the pressure across the orifice. The pressure in conduit is controlled by the pressure in conduit 4 that acts on the bonnet of pressure regulator 148 and feeds high solids flow outlet 28.

The modification of the pressure tank of Figure 17 allows existing facilities to be retrofitted to achieve the economic benefits of the high solids flow of the invention with a minimum of capital expenditure.

High solids flow system incorporating a screwpump In yet another embodiment, the invention provides a high solids flow system that incorporates a screwpump. The screwpump be converted for use in systems and methods of the present invention by a modification such as the one illustrated in Figure 18. The outlet piping of the screwpump 152 is connected to elbow 154 which feeds high solids flow outlet 28, with includes a homogenizer 43 (e.g., a mechanical homogenizer as illustrated in greater detail in Figures 11 or 12). The conveying air is introduced into the screwpump to help break up the conglomerates emerging from the screwpump screw and also to transport the material out of the screwpump windbox. The material flowing out of the screwpump 152 is diverted downwards by elbow 154 before entering high solids outlet 28 and leaving through horizontal conduit 12. High solids flow system incorporating a pulverized solid fuel feed system with multiple lances

In yet another embodiment, high solids flow systems and devices of the present invention can be used to improve the feed of pulverized fuel, e.g., coal and petroleum coke, to multiple-nozzle combustors, such as those used in power plants and the blast furnaces in steel plants. The feed system pneumatically conveys the fuel from the mill to the multiplicity of fuel lines leading to the furnace.

The main requirements of these systems are:

1. Uniform, pulse-free feeding If there are pulses in the flowrate of the pulverized fuel to the combustor, the combustion efficiency suffers and the air pollution emissions are increased. If the pulses are very severe, the flame may be extinguished, and an explosion may occur. There are many sources of pulsation, e.g., feeders such as rotary valves and screwpumps are nonuniform in their feedrate. The conveying line can produce fluctuations unless the flow regime is dilute phase. Blockages in the conveying system due to condensate or tramp materials are another source of flow interruptions.

2. Equal distribution of fuel to each lance.

Providing the same fuel-to-air ratio to each lance of the combustor is desired to maximize combustion efficiency and minimize air pollution emissions. One method of dividing the single stream of fuel from the pulverizer into streams for each lance to the combustor, is a static stream splitter. Located in the pneumatic conveying system just upstream of the furnace, it includes a manifold in which the feed pipe from the mill divides into several smaller pipes, one to each fuel lance. Static stream splitters can suffer from a lack of precision, however, due to the unevenness of the pressure drop of the piping downstream of the splitter, whereby the longer, more restrictive pipes are fed less fuel. Powder conveyed in dilute-phase powder also can "rope" or form concentrated streams of powder that switch arbitrarily from one lance and then another. Having an independent pneumatic conveying system for each lance, including a hopper, feeder, airlock, etc. can restore flow division accuracy. A disadvantage is the cost and complexity of these systems . 3. Explosions and fires.

Most pulverized fuels are explosive as well as combustible. Explosions can occur in pulverizers when sparked by tramp metals in the feed. If the feed through a fuel lance is below the flame velocity, the flames can flashback from the furnace and ignite the fuel in the lance, causing an explosion. The greatest danger is of an explosion in the furnace, caused by a momentary interruption in the fuel supply. Fires also occur in dust collectors when the temperature of the fuel particles leaving the pulverizer exceeds the ignition temperature of the fuel, which can lead to explosion. Preferably, inert gases are included in the carrier gas to mitigate the potential of explosions and fires. Products of combustion from the furnace may be used, particularly as they may also be used to help dry the fuel in the pulverizer, although condensate may create plugging as the gases cool. Nitrogen is also used to convey the fuel through the pulverizer, at added cost.

Figure 19A illustrates a system and devices of the present invention designed to address the above problems. As shown in Figure 19 A, the pulverized fuel is conveyed to the novel feed system through inlet 158 at a first stage separator 156 such as a cyclone. Most of the fuel drops out of the bottom of the cyclone through outlet 168, while the conveying gas leaves overhead through conduit 160 and is cleaned into a high efficiency dust collector 162 such as a fabric filter, whose powder exits through conduit 166. While the mechanical dust collector 156 is not required, the use of a mechanical first-stage separator reduces the fire hazard in the second-stage dust collector by reducing the amount of combustible material there, and also reducing the fuel-too-air ratio of gases below the ignition level. Solids from the separators enter airlock 134 through inlet 132, which feeds the fuel into the stream splitter. In one embodiment, a flowmeter (not shown) can be included to control the flowrate to the pulverizer system may be located at the entrance of inlet 132.

Below the airlock is conduit 178 that feeds rotary stream splitter 167, depicted in greater detail in Figure 19B. Stream splitter 167 divides the fuel flow evenly into the lances going to the furnace. Stream splitter 167 includes an enclosed cylindrical vessel that includes a top cap 176, a casing 166, and a lower cap 180. Fuel enters the cylindrical vessel through inlet 178 and exits through holes 174 in the bottom cap.

Inside the cylindrical vessel are pie-shaped pockets on the top of bottom cap 180, which are formed by radial segments 182 and interior ring 184. The pockets are equally sized and there is one for each fuel lance. Also included in the cylindrical vessel is a rotating conduit 186 attached to shaft 188. Motor 194 is mounted underneath the housing and drives the shaft, which enters the cylindrical vessel through seal 190 and is mounted in bearings 192. In operation, fuel entering the stream splitter falls into, and then through, the rotating conduit 186. Because the outlet of the rotating conduit spends an equal amount of time over each pocket, the amount of fuel going to each lance is also the same.

The fuel leaves the stream splitter through holes 174, enters downcomers 178, and exits at orifices 198. This combination dampens out the fluctuations caused by the rotor speed that would otherwise occur. Underneath each standpipe is a high solids flow outlet 28. The conveying air for outlets 28 may be either gases emitted from conduit 164 and/or from a blower.

The system depicted in Figure 19A illustrates the following improvements of the invention over the art.

.1. Uniform, pulse-free feeding Pulses from the airlock are reduced to negligible levels by the use of the stream splitter and the accumulator formed by downcomers 178 and outlets 198, in which a short column of material collects. Operating the stream splitter rotor at relatively high speeds minimizes pulsing. The flowrate though orifices 198 depends on the height of the column of material in downcomers 178. Since this changes little over the course of one cycle of the stream splitter, the flow to lances 168, 170 is also very uniform. The accumulator thereby further attenuates any pulsing caused by the rotation of the stream splitter. Pulsing originating in the conveying pipe is all but eliminated by the pulse-free nature of the high solids flow induced by the homogenizer, equalizers, and elbows, collectively the high solids flow outlet 28, in communication with outlets 198. 2. Equal distribution of fuel to each lance

The outlet of the rotor of the stream splitter spends an equal amount of time over each pocket, so each fuel lance is provided with an equal amount of fuel. Tests have demonstrated that the fuel is distributed evenly by this technique, within about 3% of the average, even when the conveying pipes differ greatly in their length and pressure drop. 3. Explosion and fire hazards

Even in the absence of an inert conveying gas such as nitrogen, the use of the cyclone in the dust collection system of Figure 19A reduces the risk of fires in the bag house by minimizing the amount of fuel there. The danger of flashback in the lances is all but eliminated by operating the high solids flow at sufficiently high fuel-to-air ratios to exceed the combustibility limits for the fuel. A further firebreak is provided by the airlock, which itself prevents a flashback from being transmitted through it. High solids flow system incorporating a combustible powder system In yet another embodiment, the present invention includes a combustible powder system. Figure 20 A illustrates an exemplary system of the invention that includes a pulverized fuel supply system with a single lance. The system is the similar to that depicted in Figure 19A, except that the stream splitter has been removed. An accumulator pipe 28 with a fluidizing pad 206 in communication with inlet 208 having orifice 204 at its bottom, is used to even out the flow pulses in the conveying pipe due to fluctuations caused by the individual pockets of the airlock 134 being emptied. Conduit 210 prevents the top of the material in the accumulator pipe 28 from being pressurized; without it, the flow-evening function of the accumulator would be diminished. High solids flow system incorporating a ship unloading system In yet another embodiment, the present invention includes a ship unloading system. The following are some of the requirements for unloading cement and other granular materials from ships or barges.

1. Conveying-system capacity

The lower the capacity and the longer it takes to unload the vessel, the higher the costs, for demurrage as well as labor.

2. Conveying power

The power required to operate the conveying equipment is so great that in many cases, it limits the size of conveying equipment that can feasibly be installed. This is particularly true of self-unloading vessels, where the power supply is ship borne. The high power consumption also adds to operating costs.

3. Removal efficiency

Settled powder has the consistency of a solid. Its removal from the vessel includes drilling the bed of material multiple times. This is time-consuming, particularly for removing the remnants at the vessel's bottom as the removal process nears completion. 4. All-weather capability

Mechanical systems that require open holds to operate can't be used in inclement weather, as the moisture would set up the cement. This further delays the unloading, further adding to the cost. The optimal system can operate with the hold covers in place. 5. Reversible flow

Reversibility refers of a system's ability to both load and unload a vessel with the same equipment. Frequently, ship-unloading terminals also are used to load ships. Capital costs are reduced if most, if not all, of the same equipment can be used for both loading and unloading. A high solids flow system of the present invention that addresses the above problems is shown in Figure 21. The system includes a live bottom, in which the hull of the vessel 212 is provided with a fluidizing pad 216 that receives its air through plenum 214. The powder leaves the hold through the inlet of a permanently installed riser 222, whose opening is at the bottom of the hold and just far enough above it to allow the powder to enter through opening 218. Referring to Figure 22, which provides greater detail with respect to the bottom portion of the riser 222, conduit 232 introduces conveying air into an array of nozzles (not shown) at the bottom 220 of the riser. The bottom of the riser also contains control valve 230 used to control the powder flowrate. The riser is attached to an opening in the cover 224 of the hold. The diameter of riser 222 is sufficiently large enough to create slug flow.

A positive-displacement blower (not shown) is used to supply conveying air to inlet 220. A second blower (not shown) provides the fluidizing air to plenum 214. Attached to the top of the opening in the hold cover is an upper riser 225, which is supported at hoist 226 by a land-based crane. There, the riser homogenizer 51 connects the top of the upper riser to the horizontal high solids conveying pipe 12 through the remainder of a high solids flow outlet and flexible hose 228 and on to a silo (not shown). During operation, all three blowers are turned on. The fluidizing air de-solidifies the settled material and enables it to flow automatically to the riser's inlet. The positive displacement blower at the entrance of the conveying air conduit provides a controlled amount of conveying air and also prevents the clogging of the nozzles at the bottom of the riser. Complete emptying is provided by the fluidizing pad, which causes the material to flow along the sloping surfaces of the ship's bottom until it is completely empty, along with the use of the vacuum system, whose feed inlet can be located right at the ship's bottom.

Another embodiment of the invention includes a conveying system that uses high solids flow for removing powder from a vessel without a live bottom. An exemplary system is depicted in Figure 23 A. The system is similar to that of Figures 21 and 22, however, in Figure 23B the riser is boom-mounted which enables it to move both vertically and laterally.

Referring to Figure 23B that depicts the inlet assembly 234 of Figure 23 A in greater detail, the riser 236 is used to drill holes in the settled material (not shown). Particulates are conveyed through the riser 236, using the nozzle 242. Conduit 240 introduces conveying air to the nozzle 242 to create an air jet that loosens the settled material. The conduit 242 is surrounded by an annulus defined by the riser 236 and conduit 240 which vacuums the loosened material and conveys it up the riser. Use of the air jet or nozzle greatly speeds the removal of material, compared to the use of the vacuum alone.

High solids flow system incorporating a rail unloading system In yet another embodiment, the present invention includes a rail unloading system. Railcars are used to deliver cement and other powders to both terminals and to end-users. Railcars that are built as pressure tanks are preferred in some applications because they seal the powder from the environment, and vice versa, but are costly to build and take a relatively long time to unload, so they aren't commonly available and/or practical in some countries.

Covered hopper cars are used to deliver cement, but require high-capacity unloading systems to prevent bridging within the cars as they unload. Since the minimum critical flowrate from hopper cars exceeds the throughput capacity of conventional unloading conveying systems, terminals that handle hopper cars commonly have deep under-the-track pits into which the cement can fall unhindered. The cost of such systems exceeds their economic use by most end users, however, because annual tonnage doesn't justify the investment Two exemplary high solids flow systems for use in unloading rail hopper cars are depicted in Figures 24A and 24B. As with the ship unloading system, the pressure drop required is sufficiently low to enable the use of a vacuum system. This allows the equipment for conveying to be housed at the customer's silo, a more convenient and low-cost site than the remote rail siding. Use of a vacuum system also minimizes the under-the-track equipment required, and may be used to collect any dust emerging from the unloading site, including the hopper car roof vent.

When the train arrives at the site, it is spotted to locate a hopper 248 over the unloading tray 254, and boot 252 is raised into place. The conveying air vacuum blower is turned on, and the hopper door 250 is opened. The fluidizing-air pad 256 is provided to promote flow from the hopper to the top of the high solids flow outlet 28. Control valve 260 is used to keep the flowrate from exceeding the conveying system capacity. The cement is conveyed through the convey line 12 to the top of the silo and into the dust collector. The powder falls out of the dust collector hopper into the airlock and into the silo. Clean air leaving the dust collector is vented to atmosphere.

A modified version of the rail-unloading system may be used to speed the unloading of pressure-tank trucks and railcars to speed up their unloading. The fluidizing-pads inside the pressurized tanks allow the cement to free-fall through a boot and into a feed system similar to the one described for rail cars.

High solids flow system incorporating a dust collection system

In yet another embodiment, the present invention includes a dust collection system. The reliable collection of flyash at coal-fired power plants is difficult to achieve because of the many requirements that the equipment typically must meet. The same or similar technology can be used to collect fine powder from dust collectors in cement plants, steel mills, etc.

In dust collection systems, the powder is collected locally from a multitude of dust collector hoppers and combined into a single pipe for conveying to a disposal. The system must cope with a number of problems that include the following. 1. Flowrate fluctuations

The system must cope with significant variations in the flowrates from individual hoppers.

2. Han p

The material in a hopper may hang up and then at some later point, flood into the conveying system. This is particularly true for systems that are emptied intermittently. Bin vibrators are designed to avert this, but aren't always able to do this. 3. Condensation

Intermittently emptied systems are subject to condensation (from the products of combustion), which hopper heaters are designed to avert, and failure of which causes shutdowns. 4. Clogging

Vacuum systems are suited to collecting material from a multiplicity of feedpoints. In particular, they eliminate the need for an airlock (or mechanical conveyor) at each feedpoint, and the separate pneumatic conveying system at the multiple-pipe collection point. Until recently, they have been the preferred technology, particularly in the smaller systems. Vacuum systems for collecting from multiple feedpoints, however, are subject to clogging when one pipe feeds more solids than expected. This makes that pipe the path of greatest resistance, so the conveying air preferably goes through the other conveying pipes. To avoid this problem, vacuum systems empty the hoppers individually, one at a time. However, this means that the flow from the hoppers is intermittent, causing the hang-ups and flooding problems described above. Intermitted operation can also create plugging due to condensation in the conveying lines, due to the intermittent usage that allows the ash to cool below the dew point.

5. Erosion Pressure systems lend themselves to continuous emptying of the hoppers.

Depending on the layout, either mechanical conveyors (typically, screw conveyors) or dense-phase pneumatic conveyors are used to collect the dust from each hopper. Both are subject to damage from the hot, abrasive powder at e.g., the screw conveyors at the bearings and the pressure tank conveyors at the dome valve. Pressure systems also require two conveying systems, one to collect the material, and another to convey it. At the entrance of the second is a full-fledged conveying system: dust collector, airlock (commonly a screwpump), and compressor. The former is subject to wear from the highly abrasive flyash. Even the piping and pipe fittings, and auxiliary equipment such as lockhoppers used with vacuum systems are quickly worn out by erosion. The greater amount of equipment of the pressure systems has its cost, both in capital outlays and maintenance costs. Because of their greater reliability, the pressurized systems have become favored in recent years, despite their high capital cost. High solids flow systems of the present invention enable systems incorporating the simplicity of vacuum flow systems while further improving the reliability of the overall systems. An exemplary system is depicted in Figure 25. Material is continuously emptied from each hopper 272 through a rotary valve 136 (to prevent flooding) and into the local conveying pipe through high solids flow outlets 28. Even with abrasive materials, the rotary valve feeders aren't subjected to wear because there is no pressure drop across them. The outlets from the hoppers are fed into a single conveying line from the elbow of the initial high solids flow outlet 28, or through wyes 276 and 289. Pipes 274, 278, and 282 joining the outlets are progressively larger, to accommodate the increasing flows without increasing the velocities and pressure drops. Several exemplary embodiments of the present invention are described below. While illustrating potential means by which the present invention may be practiced, these embodiments are not intended to limit the scope of the pending application. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein.

In one embodiment of the present invention, a conveying system for providing a homogeneous flow of particulates in a stream of conveying gas is provided. This conveying system is capable of maintaining high concentrations of particulates in the conveying gas. These concentrations particulates in the conveying gas are substantially in excess of 10 to 1 by weight.

The particulates maybe powders, consisting of materials whose mean diameter is 100 microns or less. The minimum velocity of the conveying gas to prevent the settling of particulates in the horizontal segments of conveying piping may be on the order of 30 ft/sec. hi practicing this embodiment, a first conduit exists in which particulates are fed into the inlet of a high solids pneumatic flow outlet. This high solids pneumatic flow outlet includes a homogenizer, and equalizer, and direction changing elbow.

The homogenizer includes a substantially vertical conduit through which said particulates flow. Within the conduit are means for dispersing said particulates across the cross-section of said conduit. In accomplishing the dispersion of particulate across the cross-section of the conduit, a gas is ducted into an opening, or openings, located either above said homogenizer, at said homogenizer, or both. This gas is delivered at an elevated pressure, due to the use of a compression means such as a pressure blower. This gas is introduced in a sufficient quantity to prevent the settling of particulates in the horizontal segments of conveying piping. In one embodiment of the invention, the conveying gas may be air. h one embodiment, the homogenizer includes a gas injector, wherein means for injecting the conveying gas into the homogenizer are provided. These means may include or consist of an array of nozzles located around the perimeter of the essentially- vertical conduit. The inlets of the nozzles are connected to the outlet of a conduit whose inlet is connected to the compression means noted previously. The inside diameters of a first array of nozzles may be selected to disperse said solids by air jets emitted at the outlets the nozzles, wherein said jets are fast enough to disperse the particulate matter, but are not so high as to cause an uneconomically-high pressure drop. The location being of these nozzles is selected to maximally disperse said solids. Additionally, a second nozzle, or array of nozzles, whose flow may be controlled to limit the pressure drop through the first array of nozzles, may be provided.

An alternative homogenizer may be employed in a setting where the mixture is introduced into a substantially vertical conduit into which said conveying-gas is introduced at one or more opemngs. In this embodiment, the velocity of the conveying- gas is insufficient to satisfactorily disperse the partiulate material, therefore a mechanical baffle is located beneath the particulate inlet openings. This baffle causes steams of falling material to be dispersed by their collision with members of said baffle.

The outlet of the homogenizer is connected to an equalizer. The equalizer constitutes a substantially vertical conduit in which said particulates are accelerated until they approach the velocity of said conveying gas. Upon exiting the equalizer, the particulate matter is directed to an elbow which redirects the flow of said gas-solids mixture from the substantially vertical direction to the substantially horizontal direction, said elbow preferably having a diminishing diameter in the direction of flow.

A conveying line may be connected to the outlet of the elbow, wherein said line includes one or more segments of conduits and possibly other flow elements such as elbows and diverter valves, that are connected in a leakproof manner to one another, and whose direction is an arbitrary combination connected vertical, horizontal, or sloping conduits. During the conveyance of particulate matter in the upward direction for substantial distances (i.e., substantially vertical conduits, or risers) the diameters of said risers may be significantly enlarged when compared with the diameter of said horizontal i piping. Enlargement of the diameter such as this yields a slug flow within the conveyance line. The creating of a vertical slug flow such as this proves economical at substantial distances wherein absent a significant pressure drop utilizing enlarged piping, the economic advantages of slug flow particulate transmission would not be realized. Upon reaching the apex of vertical flow, an assembly for reestablishing homogeneous flow may be located at the top of the riser. This assembly includes a homogenizer that includes a reducing fitting attached to the bottom of a wye, a cap attached to the top of said wye, wherein the side outlet of said wye is directed downward, and the downstream end of the side outlet is attached to an elbow. This reducing fitting, wye, pipe cap and elbow serve as a homogenizer,

The outlet of the elbow may then be attached to a substantially vertical segment of pipe, which serves as an equalizer. The outlet of the vertical segment of pipe may be attached to a second reducing fitting, wherein the bottom of second reducing fitting is attached to a second elbow. This second elbow may then be connected to one or more additional piping segments, whose direction is an arbitrary combination of vertical, horizontal, or sloping conduits. These additional piping segment or segments may be extended to reach the destination where said particulates are intended to be conveyed. The conveying line then terminates at a final destination at which said particulates are intended to be conveyed. The velocity through this conveying line is such that the settling of solids in the horizontal sections of the conveying line is prevented. The outlet of the conveying line is connected to the inlet of a dust collection system, in which said solids are separated from the conveying gas, and dropped into a receiving vessel. Additionally, a conduit for conveying the cleaned conveying gas leaving the dust collector system into a second compression means, such as a blower is provided. Gas compressed by the secondary compression means may then be injected into the atmosphere or are returned to the inlet of said first compression means.

In another embodiment of the present invention, a pressurized conveying system includes a means for limiting the flowrate of particulates within the conveying system. Additionally, an airlock serves to convey the particulates into the conveying system, while minimizing the escape of the conveying gases. The outlet of the airlock is connected to the inlet of a conduit of which subsequently delivers the particulate matter to a final destination, wherein a dust collector for separating particulate matter from conveying gas is located. This conveying system may utilize a positive displacement blower whose flowrate controls the velocity within the conveying line. Additionally, a second compression means may be employed, wherein this second compression means takes the form of an induced-draft fan. This fan serves to place the dust collector in a vacuum, thereby preventing the emission of dust. The airlock of the present embodiment may take the form of, for example, an AUTOSEAL® airlock, rotary valve, or screwpump.

In another embodiment of the present invention, the conveying system may include a pressure tank. The inlet of this pressure tank is connected to the outlet of the first conduit through which the incoming particulates are fed. This pressure tank contains a dome valve which is open when particulates are being fed to said pressure tank, and closed when said pressure tank is used to convey particulates. Additionally, an outlet opening at the bottom of said pressure tank is provided, wherein said outlet opening is surrounded by a fluidizing pad. This fluidizing pad is supplied with a source of pressurized air whenever the conveying system is in operation. The pressurized tank outlet may contain a flow-restricting orifice that limits the maximum outflow of particulates to a rate within the conveying-system' s capacity, as well as a tank. Furthermore, a means for supplying compressed air at a controlled pressure to the opening is provided, wherein the pressure places a constant pressure drop across the flow-restricting orifice regardless of the amount of material in the pressurized tank. The outlet of this pressure tank assembly may then be connected to a homogenizer in accordance to the aforementioned embodiments of the present invention.

In a further embodiment of the present invention, a conveying system wherein there is a vacuum created in the conveying line when it is in operation is provided. This embodiment utilizes a second compression means which provides a vacuum that creates the required flow through the conveying line and dust collector. There additionally may exist a means for controlling the flowrate of the second compression means to cause the entrance of a homogenizer to be kept under at a low vacuum. This vacuum may be low enough to avoid the excessive entrainment of air with the incoming particulates. Furthermore, airlocks may be located at the outlets of the dust collector hopper, or hoppers, wherein the outlets of these hoppers are attached to openings in the storage vessel. Additionally, an airlock may be installed at the inlet of the homogenizer, wherein this airlock serves to additionally limit the entrainment or blowby of air to and from the homogenizer.

An additional embodiment of the present invention provides a vacuum conveying system wherein there are a multiplicity of sources of particulates, all of which sources are conveyed simultaneously. The outlet of each source may be connected to the inlet of a homogenizer. The outlet of the first homogemzer may be connected to the inlet of an elbow, and the outlets of the remaining homogenizers are connected to branches of wyes, wherein said elbow and wyes are connected by a series of conduits. The outlet from the last of these conduits is connected to a conveying system in accordance with the prior embodiments of the present invention. In this embodiment, the succession of conduits are progressive larger in the direction of flow to control the velocity within each conduit within desirable limits.

Another exemplary embodiment of the present invention includes a vacuum conveying system where there is a multiplicity of sources of particulates to said conveying system, in which said sources are conveyed one at a time. The outlet of each source is connected to the inlet of a homogenizer, whereby the outlet of the first of the homogenizers is connected to the inlet of an elbow, and the outlets of the remaining homoginizers are connected to branches of wyes. These elbow and wyes are connected by a series of conduits, wherein said conduits connecting said branches are of the same diameter. Additionally, the solids flow stream from each source of particulates other than the one in use is isolated by the use of a first set of valves. Furthermore, the airflow to each source of particulates, other than the one in use, is isolated by a second set of valves. The outlet from the last wye may be connected to a pneumatic conveying system. In yet another embodiment of the present invention, when utilizing an airlock to convey particulates into the conveying system, the airlock may be a hydrostatic airlock. The sealing of pressure in the conveying system is provided by a column of fluidized material in a downcomer. The said hydrostatic airlock may be applied to pneumatic conveying systems in which the flowrate of solids entering the airlock is limited by a flow metering device, and any flow surges are within the capacity of the conveying system. Additionally, the downcomer is a substantially vertical conduit whose top is connected to the source of conveyed material and the bottom of the downcomer is connected to the inlet of a homogenious conveying system. Additionally, an orifice at the bottom of the downcomer restricts the flow through the downcomer. The airlock may also incorporate a fluidizing pad at the inlet of the orifice that promotes the flow of material through the orifice, as well as a fluidizing the material in the downcomer above the orifice. The fluidizing pad may include or consist of a porous material that uniformly fluidizes the powder above it as well as a means for supplying compressed air to the fluidizing pad. Furthermore a flow control valve located at the bottom of the downcomer may be provided, as well as a level measuring device for measuring the depth of the material in the downcomer. Coupled with said devices may be a means for adjusting the control valve with the signal from the measuring device, so that the level of material in said downcomer remains at a setpoint.

In another embodiment of the invention, the system includes a hydrostatic airlock for use in applications where the flow rate of powder entering the airlock is not controlled, or if controlled, is subject to flow surges exceeding the capacity of said conveying system may be employed. This airlock includes an upper downcomer whose inlet is attached to the source of powder to be conveyed, wherein the upper downcomer is attached to a slanted conduit whose length and angle are chosen to prevent fluidizing air being transmitted through it, but steep enough to enable the powder to flow freely. The outlet of said sloping conduit is connected to the inlet of a hydrostatic airlock, h light of this, in the event that the airlock of the present embodiment is attached at its inlet to the bottom of a storage vessel, a fluidizing pad at the outlet of said vessel, said fluidizing pad being supplied by a source of compressed air whenever said airlock is in use, h another embodiment, the present invention provides a pneumatic conveyance system wherein the powder to be conveyed is in a hold of a vessel such as a ship or barge. In such an embodiment, the initial flow of material to the conveying system is upwards. In this embodiment, the bottom of the vessel is covered wholly or in part by a fluidizing pad. Additionally, a means for supplying compressed air to the fluidizing air is provided. This air is turned on whenever said conveying systems is in operation. The conveyance system is comprised of a first riser whose entrance is located at the lowest point in the hold, and whose exit is located at an opening in the hold cover of said vessel. Additionally, this riser has an opening at its bottom to allow the adequate flow of powder and is of sufficient diameter to provide for slug flow. This riser also has a control valve at its inlet, wherein said control valve is capable of being adjusted to maintain the flowrate within said convey line below a maximum setpoint. Furthermore, an upper segment of the riser may be supported by an overhead crane. This upper segment may be attached to the inlet of a vortex elbow. The powder may be conveyed for the remaining distance by a pneumatic conveyance system as know by one skilled in the art.

In another embodiment, the present invention provides a conveying system for removing powder from a vessel such as a ship or barge, in which the bottom of said vessel is devoid of means for fluidizing the bed of material in said vessel. This system includes a riser whose upper end is mounted on a crane, wherein said riser is tall enough to reach to the bottom of the vessel and the crane is capable of moving the bottom of said riser horizontally and vertically throughout the hold of said vessel. Additionally, a means for conducting conveying air to the inlet of said riser is provided, wherein means for compressing said conveying airflow with a positive-displacement blower is provided. This conveying air is conveyed to a conduit, or array of conduits, near the center of the bottom of said riser. The flow to which center conduit or conduits is controlled by a valve, and additionally said conveying air is also ducted to an array of nozzles for injecting conveying air near the bottom of the riser. The annulus formed by the center conduits and riser is the opening through which the conveyed powder enters the riser, wherein the riser has a control valve at its inlet. This control valve is capable of being adjusted to maintain the flowrate within the convey line below a maximum setpoint. The outlet of the riser may then be attached to the inlet of a vortex elbow of a conveyance system. Powder may then be conveyed for the remaining distance by a conveying system as know by one skilled in the art.

In another embodiment, the present invention provides a conveying system for the simultaneous unloading powder from all outlets of a hopper railcar. The car may have two or more hoppers at its bottom with doors for allowing the powder to fall out. Each door is capable of being opened after the hopper to be unloaded has been attached to the conveying system through a flexible boot, and the conveying system blowers have been turned on. The boots enclose the powder flowing from the railcar to the conveying system. Furthermore, the outlet from each boot is connected to a conical conduit. The bottoms of said conical conduits contain fluidizing pads that are supplied with a source of compressed air whenever said system is in operation. Furthermore, the conduits contain a control valve at the bottom of each conical conduit. In another embodiment, the present invention provides a conveying system for the unloading of powder from a hopper railcar, one hopper at a time. The car may have two or more hoppers at its bottom with doors for allowing said powder to fall out, wherein each door is capable of being opened after the hopper to be unloaded has been attached to the conveying system through a flexible boot and the conveying system blowers have been turned on. The boot encloses the powder flowing from the railcar to the inlet of a conical conduit. Additionally, the bottom of the conical conduit contains fluidizing pads that are supplied with a source of compressed air whenever the system is in operation. Furthermore, the conduit contains a control valve at the bottom of the comcal conduit.

In yet another embodiment, the present invention provides a conveying system for accelerating the unloading of powder from a pressurized- vessel in either a railcar or a truck, hi this embodiment, there are a multiplicity of outlets at the bottom of said vessel, whereby all of said outlets are used to empty said pressurized vessel simultaneously. Each outlet has a fluidizing pad at its entrance, wherein each pad is supplied by a source of compressed air when said conveying system is in operation. Additionally, a means for controlling the pressure in the pressurized vessel is provided to control the flowrate of powder from said outlets. The outlets of the vessel are connected to the to the inlets of flexible boots. The boots enclose the powder flowing from the pressurized vessel into comcal conduits into which the powder falls. Additionally, the bottom of each said comcal conduit contains a fluidizing pad that is supplied with a source of compressed air whenever said system is in operation

In another embodiment, the present invention provides a conveying system for accelerating the unloading of powder from a pressurized- vessel of either a railcar or a truck, wherein there is a multiplicity of outlets at the bottom of said vessel whereby the powder is emptied one outlet at a time. In this embodiment, each outlet has a fluidizing pad at its entrance, which is supplied by a source of compressed air when it is in use, as well as a stop valve at its exit, which is kept closed unless flow is required from said outlet. Additionally, a means for controlling the pressure in the pressurized vessel to control the flowrate of powder from said outlet is provided. The bottom of the outlet in use being connected to the inlet of a flexible boot, wherein said boot enclosed the powder flowing from said vessel. There is also a connection between the outlet of said boot and a conical collector into which powder falls. The bottom of the conical collector contains a fluidizing pad that is supplied with a source of compressed air whenever said outlet is in operation.

In another embodiment, the present invention provides a pneumatic conveying system for supplying equal quantities of pulverized fuel to a multiplicity of conveying conduits. The conveying system includes a source of fuel connected to a feeder for controlling the rate at which said fuel is fed to a pulverizer system. Additionally a source of conveying gas is provided as well as a means for compressing said conveying gas, and a means for transporting said conveying gas to said pulverizer system, wherein a mixture of said pulverized fuel and conveying gas are emitted from said pulverizer system through an exit conduit. The exit conduit conveying the mixture of said fuel and conveying gas to a dust collector is also provided, wherein the solids outlet is connected to the inlet of a stream splitter through an opening at its top. In addition, the gaseous outlet is connected to a second inlet in said stream splitter, located at its side. The stream splitter includes a cylindrical drum with top and bottom caps, said assembly of drum and caps being sealed, wherein there being at the center of the top of said drum an opening that is attached to the outlet of said airlock, into which said fuel enters said stream splitter, and an array of radial, equally-spaced partitions mounted on the top surface of said bottom cap, whose inside diameters are connected by a ring of equal height, and which ring is concentric with the axis of said drum. Furthermore, there exists a sealed opening through the center of said lower cap through which a shaft protrudes on either side of said opening, as well as a bearing mounted at the outside surface of said lower cap, which enables said shaft to rotate. Additionally, a means for rotating said shaft, such as a gear motor and drive chain, and which rotates said shaft whenever said stream splitter is in use is provided. A sloping conduit is attached to the top of said shaft, whose inlet is immediately below the opening in said top cap, and whose outlet is immediately above the top surfaces of said array of radial partitions. Said sloping conduit is caused to rotate by its attachment to said shaft. The stream splitter also contains openings in said bottom cap, one per pocket formed by each said pair of partitions, and a conduit attached to the bottom of each said opening in said bottom cap, which conveys an equal mixture of pulverized fuel and conveying gas to its destination. Additionally, a flowmeter may be inserted between the outlet of said dust collector and the entrance of said stream splitter, such that the signals from which are used to control the feed rate of said feeder. Furthermore, the present embodiment may permit the use of a non-pressurized pulverizer system, wherein the compression means are located downstream of said dust collector and the dust collector is sufficiently efficient to allow cleaned conveying gases to be compressed without damaging the compression means. Additionally, an airlock is inserted between the outlet of the dust collector and the inlet of the stream splitter.

In another embodiment, the present invention provides a conveying system for reliably removing the powder from the hoppers of dust collectors, wherein the outlet of each dust collector hopper is connected to the inlet of a rotary valve, and the outlet of each rotary valve is attached to the inlet of a vacuum conveying system. In an additional embodiment of the present invention, a conveying system for reliably removing the powder from the hoppers of a multiplicity of dust collector hoppers is included, wherein only one said source of particulates is conveyed at any time, and the outlet of each dust collector hopper is connected to the inlet of a rotary valve feeder such that the outlet of each rotary valve is attached to the inlet of a conveying system. Additionally, the rotary valves are used to stop the flow of powder, instead of separate valves, as required.

In yet another embodiment, the present invention provides a conveyance system wherein a conveying line is connected near the entrance to a riser assembly, and the riser assembly is sufficiently large to create slug flow. Additionally, an elbow at the top of said riser assembly converts the direction of flow into the horizontal direction, and a conveying pipe is connected to the outlet of said elbow. The diameter of this conveying pipe is sufficiently large to create dense phase flow in subsequent sections of said conveying line.

EQUIVALENTS/OTHER EMBODIMENTS The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting of the invention described herein. Scope of the invention is thus indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced herein.

Claims

What is claimed is:

1. A high solids flow outlet comprising: a homogemzer comprising a particulate dispersion device; an equalizer in fluid communication with the homogemzer; and

an elbow in fluid communication with the equalizer, wherein the homogenizer and the equalizer are in a vertical direction or a substantially vertical direction.

2. A high solids flow outlet comprising a means for inducing high solids flow in a vertical direction or a substantially vertical direction.

3. A high solids flow system for conveying particulates comprising a high solids flow outlet that induces high solids flow in a substantially vertical direction.

4. The system of claim 3, wherein the high solids flow outlet comprises: a homogenizer comprising a particulate dispersion device; an equalizer in fluid communication with the homogenizer; and

an elbow in fluid communication with the equalizer.

5. The system of claim 4 wherein the elbow cross section diminishes in the direction of flow to increase the velocity of flow in a substantially horizontal direction.

6. The system of claim 4 wherein the homogenizer comprises: a plurality of air jets disposed about the periphery of a downcomer; and a manifold in fluid communication with the air jets.

7. The system of claim 4 wherein the homogenizer comprises: one or more baffles disposed within a downcomer.

8. The system of claim 4 further comprising a riser assembly in fluid communication with the homogemzer, the riser assembly comprising: a substantially vertical pipe; and a reducer at a proximal end of the substantially vertical pipe that induces slug flow.

9. The system of claim 8 wherein the homogenizer comprises: a wye at a distal end of the substantially vertical pipe; and a cap at the distal end of the wye.

10. The system of claim 9, further comprising an elbow disposed between the homogemzer and the equalizer, wherein the elbow cross section diminishes in the direction of flow to increase the velocity of flow in a substantially vertical direction.

11. The system of claim 8 wherein the homogenizer precedes the riser assembly such that the riser assembly converts the high solids flow at its proximal end to dense phase flow at its distal end.

12. The system of claim 3 comprising an airlock in fluid communication with the homogenizer.

13. The system of claim 12 comprising a hydrostatic airlock in fluid communication with the homogenizer.

14. The system of claim 13 comprising: a downcomer disposed between the hydrostatic airlock and the homogenizer; a flow restricting orifice and a shutoff valve disposed between the downcomer and the homogenizer; and a fluidizing bed at an inlet of the flow restricting orifice.

15. The system of claim 13 comprising: a first inlet adjacent to the airlock; a second inlet coupled with and in fluid communication with the first inlet, the second inlet defining an orifice that limits particulate flow to the airlock; a fluidizing pad disposed about the orifice that fluidized particulates; a inner downcomer disposed between and in fluid communication with the first inlet and the second inlet; an outer downcomer coaxially disposed about the inner downcomer and defining an annulus between the inner downcomer and the outer downcomer; and a gas vent to the annulus disposed on the periphery of the outer downcomer.

16. The system of claim 12 comprising an airlock in fluid communication with the homogemzer, the airlock having a flow limiter.

17. The system of claim 16 comprising: a dogleg in fluid communication with the airlock and disposed above the airlock; a downcomer disposed between the hydrostatic airlock and the homogenizer; a flow restricting orifice and a shutoff valve disposed between the downcomer and the homogenizer; and a fluidizing bed at an inlet of the flow restricting orifice.

18. The system of claim 12 comprising a rotary valve airlock in fluid communication with the homogenizer.

19. The system of claim 3 comprising a pressure tank in fluid communication with the high solids flow outlet.

20. The system of claim 19, wherein the pressure tank further comprises a fluidizing assembly.

21. The system of claim 3 comprising a screwpump in fluid communication with the high solids flow outlet.

22. The system of claim 3 comprising a pulverized fuel furnace having a plurality of fuel lances in fluid communication with the high solids flow outlet.

23. The system of claim 22 comprising a feed system disposed between a fuel source and the high solids flow outlet, the feed system comprising: a separator in fluid communication with the fuel source that separates fuel from conveying gas; an airlock in fluid communication with the separator; and a stream splitter in fluid communication with the airlock that feeds a plurality of lances, and that is in fluid communication with a plurality of high solids flow outlets, the stream splitter comprising: an enclosed cylindrical housing having a cylindrical wall, a top cap and a bottom cap, a plurality of wedge-shaped pockets defined by radial segments and an interior ring disposed on the bottom cap, and a rotatable conduit attached to a shaft disposed within the enclosed cylindrical housing.

24. The system of claim 3 comprising a ship unloading system in fluid communication with the high solids flow outlet.

25. The system of claim 3 comprising a rail unloading system in fluid communication with the high solids flow outlet.

26. The system of claim 3 comprising a dust collection system in fluid communication with the high solids flow outlet.

27. The system of claim 3 comprising a plurality of deflectors in a substantially horizontal conduit in fluid communication with the high solids flow outlet for mediating saltation.

28. The system of claim 27 wherein the plurality of deflectors for a coil in a substantially horizontal conduit for mediating saltation.

29. The system of claim 3 wherein the system is a vacuum conveying system or a pressure conveying system.

30. A method of conveying particulates, the method comprising the steps of: providing a particulate stream; inducing high solids flow in the particulate stream in a high solids flow outlet; and conveying the particulates in high solids flow mode.

31. The method of claim 30 wherein the solids-to-conveying gas ratio is greater than 10 to 1 by weight.

32. The method of claim 30 wherein the step of inducing high solids flow comprises the steps of: homogenizing the particulate stream in a substantially vertical direction; equalizing the particulate stream in the substantially vertical direction; and turning the particulate stream from the substantially vertical direction to a substantially horizontal direction.

33. The method of claim 32, wherein following high solids flow, the flow direction is changed to a substantially vertical direction by inducing slug flow in a riser with a reducer, and then to a substantially horizontal direction by inducing dense phase flow in an elbow.

34. The method of claim 30 comprising providing a particulate stream in slug flow mode.

35. The method of claim 30 comprising the step of providing a particulate stream from an AUTOSEAL® airlock.

36. The method of claim 30 comprising the step of providing a particulate stream from a hydrostatic airlock.

37. The method of claim 30 comprising the step of providing a particulate stream from a rotary valve airlock.

38. The method of claim 30 comprising the step of providing a particulate sfream from a pressure tank.

39. The method of claim 30 comprising the step of providing a particulate stream from a screwpump.

40. The method of claim 30 comprising the step of providing a particulate sfream from a pulverized fuel feed system.

41. The method of claim 40, wherein the step of providing a particulate stream from a pulverized fuel feed system, comprises the steps of: providing a fuel sfream mixed with a conveying air; separating the fuel stream from the conveying air; feeding the fuel sfream through an airlock; splitting the fuel stream in a sfream splitter to form a plurality of feed sfreams; and feeding the split fuel streams into a plurality of a high solids flow outlets.

42. The method of claim 26 comprising the step of providing a particulate sfream from a ship unloading system.

43. The method of claim 42 wherein the step of providing a particulate sfream from a ship unloading system comprises: fluidizing particulates in a ship with a fluidizing pad; inducing particulate flow in a riser by injection of conveying air into a bottom portion of the riser; converting the particulate flow to high solids flow upon exit from the riser in a high solids flow outlet in fluid communication with a top portion of the riser.

44. The method of claim 26 comprising the step of providing a particulate sfream from a rail unloading system.

45. A device for reducing saltation in a particulate conveyance system comprising: a conduit; and a deflector blade disposed in the conduit, at least a portion of which is angled in a generally downward direction.

46. The device of claim 45 where the deflector blade is a coil disposed in the conduit.

47. A method of reducing saltation in a particulate conveyance system comprising the steps of: providing a particulate sfream in a conduit; diverting the particulates with a baffle disposed in the conduit.

48. A sfream splitter for splitting a sfream of particulate, the stream splitter comprising: an enclosed cylindrical housing having a cylindrical wall, a top cap and a bottom cap, a plurality of wedge-shaped pockets defined by radial segments and an interior ring disposed on the bottom cap, and a rotatable conduit attached to a shaft disposed within the enclosed cylindrical housing.

49. A solids feed system comprising: a separator in fluid communication with the fuel source that separates fuel from conveying gas; an airlock in fluid communication with the separator; and a stream splitter in fluid communication with the airlock that feeds one or more lances, and that is in fluid communication with the homogenizer, the stream splitter comprising: an enclosed cylindrical housing having a cylindrical wall, a top cap and a bottom cap, a plurality of wedge-shaped pockets defined by radial segments and an interior ring disposed on the bottom cap, and a rotatable conduit attached to a shaft disposed within the enclosed cylindrical housing.