GB2154891A - Mixing and distributing solid materials - Google Patents

Abstract

The material is continuously introduced into a vessel (10) and a pressurized gas is introduced into the lower portion (14) of the vessel (10) at a velocity sufficient to pass upwardly through the material in the vessel (10) to promote mixing of the material. A plurality of outlets lo (18) are disposed in an angularly spaced relation along the vessel (10) for permitting the material to continuously discharge to a plurality of selected locations. The excess gas in the vessel (10) is removed, cleaned and introduced back thereinto. <IMAGE>

Description

SPECIFICATION Apparatus and method for mixing and distributing solid particulate material This invention relates to a mixing and distributing apparatus and method, and more particularly to such an apparatus and method in which one or more materials are mixed in a vessel and distributed from the vessel.

The use of fluidized beds has long been recognized as an attractive way of generating heat. In these type of arrangements, a particulate material, including a mixture of fuel material, such as coal, and an absorbent material for the sulfur released as a result of the combustion of the fuel material, are disposed on a grate or grate-like plate. Air is passed through the bed to fluidize the material so that the bed behaves as a boiling liquid which promotes the combustion of the fuel.

Additional fuel and absorbent material must be continuously supplied to the bed through a plurality of overbed or inbed feeders disposed at spaced locations along the walls of the vessel housing of the fluidized bed. Since in many arrangements a plurality of material inlets are provided through two or more walls of the vessel, it becomes difficult from a materials handling standpoint to receive the fuel materials and the absorbent materials from separate sources, mix them and uniformly distribute them to the selected locations along the walls of the vessel.

In order to promote the mixing and improve the handling capability of the material it has been suggested to pass a stream of air through the materials. However, since the air discharged with the mixed solids is only a relatively small percentage of the air flow required to insure proper mixing, a considerable amount of excess air is present in the system which must be removed to insure proper operation.

It is therefore an object of the present invention to provide an apparatus and method in which solid particulate material is received from separate sources, is mixed and is discharged in a precise and uniform manner.

It is a further object of the present invention to provide an apparatus and method of the above type in which a stream of air is passed through a bed of the materials to be mixed to insure a uniform mixture of the material before it is discharged.

It is a still further object of the present invention to provide an apparatus and method of the above type in which the excess air in the system is removed, cleaned, and injected back into the bed of material.

Toward the fulfillment of these and other objects, a vessel is provided for supporting a bed of particulate material and for receiving additional material. Pressurized air is introduced into the vessel at a velocity sufficient to pass through the material in the vessel and cause spouting to induce a flow of the material within the vessel to promote mixing. The excess air is removed from the vessel, cleaned and reinjected back into the bed.

The above brief description, as well as further objects, features and advantages of the present invention will be more fully appreciated by reference to the following detailed description of the presently preferred but nonetheless illustrative embodiment in accordance with the present invention when taken in conjunction with the accompanying drawings in which: Figure 1 is a schematic view of the system of the present invention; Figure 2 is a front elevational view, partially in section, of the mixing and distributing apparatus of the system of Fig. 1.

Figure 3 is a cross-sectional view taken along the line 3-3 of Fig. 2; Figure 4 is a vertical cross-sectional view taken along the line 4-4 of Fig. 3; Figure 5 is a view similar to Fig. 4 but depicting an alternate embodiment of the apparatus of the present invention; and Figure 6 is a horizontal cross-sectional view taken along the line 6-6 of Fig. 5.

Referring specifically to Figs. 1 and 2 of the drawings, the reference numeral 10 refers in general to an elongated cylindrical vessel having an upper inlet 1 2 which is adapted to receive particulate material from one or more sources (not shown). The particulate material can, for the purpose of example, be a source of crushed coal for a fluidized bed and a source of limestone for adsorbing the sulfur formed as a result of combustion of the coal.

The lower end portion of the vessel 10 is formed into a conically shaped hopper 1 4 which has an inlet 1 6 registering with its apex for receiving a pressurized gas, such as air, from an external source, which air passes upwardly through the vessel in a manner to be described in detail later.

Four equiangularly spaced outlet pipes 1 8 (two of which are shown in Fig. 1) extend at an acute angle with respect to a horizontal plane from a point within the vessel 1 0, through the vessel wall and to a point externally of the vessel.

The material from the source or sources mentioned above is introduced into the upper inlet 1 2 of the vessel 10 and flows downwardly through the vessel by gravity before accumulating in the vessel. Air is introduced into the inlet 1 6 and passes through the hopper 14, and upwardly through the material accumulating in the vessel 1 0. The velocity and flow of the air are regulated so that "spouting" occurs, i.e., a portion of the materials from the bed in the vessel will be discharged upwardly from the upper surface of the bed. As will be described later, this induces a circulation of materials in the bed and an improved mixing of same.

The considerable amount of excess air ris ing upwardly in the vessel 10 from the bed of particulate material exits through an opening formed in the upper portion of the vessel 10 and into an outlet line 20. A recirculating blower 22 is provided which operates to drain the air from the upper portion of the bed vessel through the line 20 and into a solid separating device 24 of any conventional design, such as a cyclone separator. The separating device 24 operates in a conventional manner to remove a great majority of the solid bed particles from the air, which solids are passed vertically downwardly through a line 26 containing a rotary valve 28 to a reinjection nozzle 30.The output of the blower 22 is connected, via a line 32, to the inlet wside of the reinjecting nozzle 30 which operates to entrain the solid particles passing from the valve 28 and introduce them, via a line 34, to the inlet 16 of the vessel 10. The rotary valve 28 functions as a seal to prevent back-flow of air from the high pressure side of the blower 22 to the low pressure zone in the separating device 24.

The air outlet of the separating device 24 is connected, via a line 36, to a second-stage separating device 38 which also can be in the form of a cyclone separator. Although not shown in the drawings, it is understood that the solids outlet from the separating device 38 can be discharged to another vessel or the like.

The air outlet from the separating device 38 is connected, via a line 40, back to the inlet side of the recirculation blower 22 for injection back into the system. Thus, the suction from the blower 22 draws the air from the vessel 10, through the separators 24 and 38 and to the blower 22. A heat exchanger 42 can be provided in the line 40 to cool the recycled air passing through the latter line, especially if the heat removed with the airsolids mixture from the vessel 10 is not sufficient to compensate for the heat added by the recirculation blower 22 without excessive temperature buildup in the bed in the vessel 10.

Figs. 2-4 depict the specifics of the vessel 10 in more detail. More particularly, it is noted that four outlet pipes 1 8 extend from the vessel and are covered by a refractory material 44. As better shown in Fig. 4, a filler plug 46 is provided in the vessel immediately above the hopper portion 14 and has a central bore 48 through which the air from the inlet 1 6 passes, which bore widens out into a substantially conical shaped opening 50 which receives the material flowing downwardly in the vessel. As a result of this flow of the air through the material, a central zone, shown in general by the reference numeral 60 is formed which is concentric with the axis of the vessel 10 and in which the concentration of the particles is low and the general movement of the particles is upward.An annular zone 62 is also formed which extends around the central zone 60 and in which the concentration of the particles is high and the general movement is downward. The central zone 60 is continually supplied with particles from the annular zone 62 in the vicinity of the opening 50 which particles are thus transported to the upper part of the bed by means of the pressurized air and then fall back down into the annular zone 62 and repeat the cycle. As a result, a thorough mixing of the particles within the bed is achieved.

During movement of the particles in the annular zone 62 downwardly, a portion will enter the upper end of the discharge pipe 1 8 and be transported, by gravity, through the entire length of the pipes to areas external of the vessel 10. In the present embodiment in which four such pipes 1 8 are provided, it can be appreciated that a precise distribution of the mixed particles into four separate locations is thus achieved. In the case of a fluidized bed discussed above, a ducting system, or the like, can be provided to connect the outlet ends of the pipes 1 8 to the feeders associated with the walls of the vessel housing the fluidized bed.

Of course, the supply of new particulate material to the inlet 1 2 of the vessel 10 is regulated according to the discharge from the pipes 1 8 so that a continuous replenishing of the particle material in the vessel 10 is achieved.

Of course, the excess air (usually in excess of 90% of the air discharged from the pipes 18) passes upwardly into the upper portion of the vessel and out through the line 20 for treatment and recirculation by the separating device 24, the blower 22, etc., as described above.

An alternative embodiment of the vessel 10 is depicted in Figs. 5 and 6 and includes identical components of the latter vessel which are given the same reference numerals, with the particulate material being omitted from the drawings in the interest of clarity. In this embodiment, the filler plug 46 of the previous embodiment is omitted and four equiangularly spaced inlet pipes 64 are provided which extend through the wall of the hopper portion 14 of the vessel and at an angle to the horizontal. The pipes 64 receive the particulate material from one or more sources as in the previous embodiment and feed the material into the lower portion of the hopper 1 4 immediately above the air inlet 1 6.

A central zone and an annular zone are thus formed and the flow pattern of the material in the vessel is the same as discussed in connection with the previous embodiment.

Four vertically extending, angularly spaced, discharge pipes 66 extend from a point inside th vessel 10, and through the inclined walls of the hopper 14 for discharging the particulate material to four separate external locations in a manner similar to that in connection with the embodiments of Figs. 2-4. Of course, the vessel of the embodiment of Figs.

5 and 6 can be used with the recirculating, separating and reinjection apparatus depicted in Fig. 1.

It is thus seen that, as a result of the foregoing, a precise mixing and distribution of the particulate material from one or more sources to a plurality of discharge points is achieved in a relatively simple and efficient manner while the excess air from the vessel is used in an efficient manner.

It is noted that several variations may be made in the foregoing. For example, if the vessel 10 is operated at, or near, atmospheric pressure, the recycled air line 40 (Fig. 1) and the heat exchanger 42 can be omitted, and the air leaving the second-stage separating device 38 can be discharged to atmosphere and the blower 22 can take suction from the atmosphere.

As will be apparent to those skilled in the art, various changes and modifications may be made to the apparatus of the present invention without departing from the spirit and scope of the present invention as recited in the appended claims and their legal equivalent.

Claims (31)

1. An apparatus for mixing and distributing solid particulate material, said apparatus comprising a vessel for supporting a bed of said material, inlet means associated with said vessel for receiving additional material for said bed, means for introducing a pressurized gas into said vessel at a velocity sufficient to pass through said bed of material and promote mixing of said material, outlet means for permitting said mixed material to discharge from said vessel, outlet means for permitting said gas to discharge from said vessel, means connected to said gas outlet means for separating from said gas the solid particles entrained in said gas and means for injecting said solid particles back into said bed.

2. The apparatus of claim 1 wherein said material outlet means comprises a plurality of outlets disposed in a spaced relation around said vessel for permitting said mixed material to discharge from a plurality of areas of said vessel.

3. The apparatus of claim 1 wherein said gas is introduced into the lower portion of said vessel and passes through said bed at a velocity sufficient to cause a spouting of said particles from the upper surface of said bed.

4. The apparatus of claim 3 wherein said gas passes through a central portion of said bed creating a central zone in which the concentration of particles in the gas is relatively low and said particles move upwardly with the gas, and an outer zone surrounding said central zone in which the concentration of said particles is relatively high and their general movement is downwardly.

5. The apparatus of claim 4 wherein said plurality of outlet means communicates with corresponding portions of said outer zone.

6. The apparatus of claim 5 wherein each of said outlet means is in the form of a pipe extending from said outer zone, through said vessel and to an area external of said vessel.

7. The apparatus of claim 6 wherein said vessel has a generally cylindrical shape and wherein said pipes extend through circumferentially spaced openings extending through said vessel.

8. The apparatus of claim 1 wherein said separating means comprises a cyclone separator.

9. The apparatus of claim 1 or 8 wherein said injecting means comprises an injecting nozzle, and a blower connected to the inlet of said injecting nozzle.

10. The apparatus of claim 9 further comprising a second-stage separating means connected between the gas outlet means of said separating means and said blower.

11. The apparatus of claim 9 further comprising means connecting said blower to the gas outlet of said separating means for injecting the clean gas from said separating means to said nozzle.

1 2. The apparatus of claim 10 further comprising means connecting said blower to the gas outlet of said second-stage separating means for injecting the clean gas from said second-stage separating means to said nozzle.

1 3. The apparatus of claim 11 or 1 2 further comprising a heat exchanger connected to said connecting means.

14. The apparatus of claim 6 wherein said pipes extend at an angle relative to the axis of said vessel.

1 5. The apparatus of claim 6 wherein said pipes extend parallel to the axis of said vessel.

16. The apparatus of claim 1 wherein said inlet means for said material is located in the upper portion of said vessel.

1 7. The apparatus of claim 1 wherein the inlet means for said material is located in the lower portion of said vessel.

1 8. The apparatus of claim 1 wherein the inlet means for said material is in the form of a plurality of spaced pipes extending through said vessel at an angle relative to the axis of said vessel and communicating with the lower portion of said vessel.

19. The apparatus of claim 1 further comprising means disposed in said vessel for defining a conical hopper portion in said vessel, said gas introducing means registering with the apex of said hopper portion.

20. A method for mixing and distributing solid particulate material, said method comprising the steps of introducing said particu late material to a vessel to form a bed of said material in said vessel, introducing a pressurized gas into said vessel at a velocity sufficient to pass through said bed of material and promote mixing of said material, discharging the mixed material from said vessel, discharging said gas from said vessel, separating from said gas the solid particles entrained in said gas, and injecting said solid particles back into said bed.

21. The method of claim 20 wherein said mixed material is discharged from a plurality of areas of said vessel.

22. The method of claim 20 wherein said gas is introduced into the lower portion of said vessel and passes through said bed at a velocity sufficient to cause a spouting of said particles from the upper surface of said bed.

23. The method of claim 20 or 21 wherein said gas passes through a central portion of said bed creating a central zone in which the concentration of particles in the gas is relatively low and said particles move upwardly with the gas, and an outer zone surrounding said central zone in which the concentration of said particles is relatively high and their general movement is downwardly.

24. The method of claim 23 wherein said mixed material is discharged from said outer zone.

25. The method of claim 20 wherein said step of injecting includes drawing the gas from said bed, through a separator and to the inlet of an injector nozzle.

26. The method of claim 25 further comprising the step of drawing the gas through a second-stage separator before passing it to said nozzle.

27. The method of claim 26 further comprising the step of cooling the gas before it is passed to said nozzle.

28. The method of claim 20 wherein said material is introduced to the upper portion of said vessel.

29. The method of claim 20 wherein said material is introduced to the lower portion of said vessel.

30. An apparatus for mixing and distributing solid particulate material substantially as described herein with reference to the accompanying drawings.

31. A method for mixing and distributing solid particulate material substantially as described herein with reference to the accompanying drawings.