HK1193371B - Oxycombustion in transport oxy-combustor - Google Patents

Abstract

A pressurized transport oxy-combustor with different configurations is disclosed. Substantially pure oxygen is fed to the transport oxy-combustor under pressure to combust fossil fuels, generating steam for power generation. The end product is the flue gas containing substantially pure CO2 after moisture condensation. The low excess oxygen necessary to achieve complete combustion in the combustor is scavenged by adding another fuel so that substantially all oxygen fed to the combustor is completely consumed. The capability to operate the transport oxy-combustor as a circulating fluidized bed combustor at very high solids circulation rates makes it unnecessary to use recycled CO2 or flue gas as a means to moderate and control the combustion temperature. The temperature in the combustor is effectively controlled by relatively cooler circulating solids that enter the combustion zone (200). A small amount of CO2 is recycled for aeration and to convey solids fuel to the combustor.

Description

Oxy-combustion in transport oxy-burners

Statement regarding federally sponsored research or development

The invention was made with some government support under cooperative agreement No. DE-NT0000749, department of energy, usa. The government has certain rights in this invention.

Technical Field

The present invention relates generally to the design of coal-fired power plants, and more particularly to a transport oxy-combustor. Transport oxy-burners are used for the combustion of coal with oxygen as the oxidant to produce substantially pure CO2 after condensation of moisture from the flue gas stream.

Background

Oxy-combustion is part of the design of coal-fired power plants, which has the potential to significantly reduce CO2 emissions compared to conventional coal-fired power plant designs. In oxy-combustion, coal is combusted in an oxygen-rich environment using substantially pure oxygen or substantially pure oxygen diluted with recycled flue gas. From this process, the flue gas is composed primarily of CO2 and H2O, and therefore, a concentrated stream of CO2 can be produced by simply condensing the water in the exhaust stream. One point that oxy-combustion has an advantage over air combustion is that it offers a high potential for greatly reducing the cost of CO2 separation and capture, since almost all of the exhaust gas effluent can be captured and sequestered.

U.S. patent No. 6505567 to Anderson et al discloses operating a method of operating an atmospheric circulating fluidized bed by feeding substantially pure oxygen as the oxidant into a combustor to combust a fossil fuel within the combustor. A portion of the fine solids entrained in the flue gas are cooled in an external fluidized bed heat exchanger and recycled to the lower portion of the combustor. The cooling of the solids produces a small portion of the steam used to generate electricity. A small portion of the recycled entrained, cooled solids may help control the temperature of the combustor.

Anderson et al also disclose recycling a sufficient quantity of gaseous combustion products to the combustor to control the temperature of the combustor. The method of operation of such a circulating fluidized bed Combustor (CFB) is substantially the same as that of a conventional circulating fluidized bed combustor, except that oxygen is used as the oxidant instead of air. However, in order to control the temperature of the combustor, the flue gas needs to be recirculated back to the combustor at a rate that is nearly the same as the amount of nitrogen in the air fed combustion process.

While the Anderson et al process has significant advantages over drum air combustion when it is necessary to capture CO2 from the flue gas, the large amount of flue gas recirculation results in high energy consumption and reduces the reliability of the operation. Therefore, such conventional operation methods need improvement.

Furthermore, as with any air combustion process, excess oxygen is required to achieve complete combustion and, therefore, oxygen is present in the flue gas. However, the presence of oxygen in the flue gas of the CO2 stream is undesirable for CO2 sequestration or other applications. Also, the mixture of CO2 and oxygen is more corrosive, even if only a small amount of moisture is present. Furthermore, the production of oxygen involves a costly step in the combustion process, and it is therefore highly undesirable to discharge flue gases together with valuable oxygen.

The circulation loop arrangement shown in the Anderson et al patent is similar to a widely used commercial circulating fluidized bed. Aeration of the fluidized bed heat exchanger can adversely affect the cyclone performance and overall solids circulation rate.

Oxy-fuel combustion and air-fuel combustion processes in circulating fluidized beds have some common disadvantages. For example, it requires a large calcium to sulfur ratio to remove more than 90% of the sulfur compounds from the flue gas. Therefore, Flue Gas Desulfurization (FGD) equipment is necessary for strict sulfur removal or near zero emission of sulfur components from power plants. However, adding FGD in the process increases investment and operating costs.

High calcium is required for sulfur compound removal for at least two reasons. One is due to the atmospheric nature of the operation-the sulfur compounds in the coal will be converted primarily to SO2, which reacts relatively slowly with calcium compounds. The second reason is that the large size particles used in the circulating fluidized bed are all large and only the surface layer of limestone particles is used to fix the sulfur-while the core particles have less opportunity to contact the sulfur compounds in the flue gas.

For purposes of capturing CO2, substantially pure oxygen is used in place of air used in conventional Pulverized Coal (PC) boilers as disclosed in, for example, U.S. patent nos. 7282171 and 6918253, and 2009-. The methods described in these references also recycle large amounts of CO2 or flue gas to moderate and control the temperature of the boiler.

As mentioned above, for oxy-fired circulating fluidized bed processes, such control of the combustion temperature by large scale recirculation of CO2 or flue gas can result in a reduction in the efficiency of the power plant and reliability of operation. Furthermore, the flue gases from the oxygen fired PC boilers described in these references contain an excess of oxygen significantly in excess of the amount necessary for operation of the boiler. Therefore, an additional process step is required to reduce the oxygen concentration to a relatively low ppm level to produce a substantially pure CO2 gas stream.

Unlike circulating fluidized bed combustion, in situ sulfur removal is inconvenient for PC boilers. Furthermore, the grinding cost of the fuel burned by the PC boiler is significantly higher, since it requires a finer fuel to burn the supplied coal virtually completely.

What is needed is a better circulating fluidized bed loop arrangement and a better method of operation that can overcome the above-mentioned disadvantages. The present invention is primarily directed to such systems and methods. The present invention provides a new arrangement for a CFB cycle and a method of operating the cycle in a pressurized oxy-combustion environment.

Disclosure of Invention

Briefly described, in one preferred form, the present invention provides a transport oxy-combustor, particularly for the combustion of coal with oxygen as an oxidant to produce substantially pure CO2 upon condensation of moisture in the flue gas stream.

In the present transport oxy-combustor, the fuel is combusted in the riser with substantially pure oxygen (O2) and substantially completely oxidized, as a result of which the flue gas mainly comprises CO2 and water vaporThe CO2 can be easily separated from the H2O by a condensed steam cooling step. The net flue gas then contains about 80-98% CO2, depending on the particular fuel and oxy-fuel combustion process used. The flue gas stream may be compressed, dried and further purified to provide it to pipeline transport and storage conditions.

The transport oxy-combustor includes a riser, a first gas-solid separation device (preferably a first stage cyclone) and a solids cooler. All combustion reactions, gas-solid mixing, take place in the riser transporting the oxy-combustor. The riser comprises a primary oxygen feed and a solid fuel stream feed. In exemplary embodiments, the riser may further comprise a sorbent stream feed and/or a secondary oxygen feed.

The flow of solids from the cooler to the lower section of the riser is mixed with oxygen from the main oxygen feed to fully disperse the oxygen by circulating the solids across the cross section of the circulating riser. In an exemplary embodiment, the mass flow rate of solids in the circulating solids stream is about 150 to 400 times the feed rate of the solid fuel stream riser. Since combustion will be substantially complete in each element of the invention, the carbon content in the circulating solids is almost zero and there is a low temperature rise of the solids during mixing in the lower section of the riser. The substantially complete combustion and solid zero carbon recycled process is achieved by a combination of riser design and fuel grind size. The height of the riser is designed to have sufficient residence time so that the less reactive fuel can still be completely converted. Depending on the fuel properties, the grind size of the solid fuel stream may be set to a size small enough to achieve higher carbon conversion by providing a high surface area of solids.

The mixture of recycled solids, flue gas, and other combustion products (including optional reactive sorbent particulates) flows to the top of the riser and enters the first stage cyclone. The first stage cyclone provides a flow of solids to the solids cooler.

The transport oxy-combustor may further comprise a separation assembly between the riser and the primary cyclone to facilitate separation of the solids portion from the gas-solids mixture. Preferably, the separation assembly facilitates two streams that differ primarily in solids concentration, namely a high solids concentration stream and a low solids concentration stream. In a preferred embodiment, the separation module includes an inclined cross that uses the gravity and inertia of the solid particles to form the high and low solids concentration streams.

A solids cooler cools the solids stream from the first stage cyclone and the solids are returned to the lower section of the riser.

The flue gas stream exiting the present transport oxy-combustor may be cooled by a flue gas cooler and then may be passed through a filter or other device to remove remaining trace particles from the gas stream. The gas stream may be further treated to condense moisture, remove impurities, leaving a substantially pure CO2 stream for subsequent or other use.

The present transport oxy-combustor may also include a second gas-solid separation device (preferably a second stage cyclone) downstream of the first stage cyclone to collect additional fine solid particles entrained in the gas stream. The solids collected by the second stage cyclone are returned to the solids cooler. In this exemplary embodiment, the flue gas stream leaves the second stage cyclone with substantially less dust.

The present transport oxy-combustor is configured to process fuels having different characteristics. For large capacity and scale combustors, typically those used in power generation, exemplary embodiments of the present invention accommodate, including but not limited to, various arrangements of embedded solids coolers to generate steam. In a further exemplary embodiment of the present transport oxy-combustor, excess oxygen in the flue gas is removed by injecting a scavenging fuel. The exemplary embodiment of the transport oxy-combustor operates in a pressurized environment with sorbent injection and can remove substantially all of the contaminating sulfur components in the flue gas.

The transport oxy-combustor includes a pressurized circulating fluidized bed loop that facilitates the oxy-combustion of coal and overcomes the limitations of the prior circulating fluidized bed units and PC boilers noted above. New arrangement, here "transport oxy-combustor" (TROC)^TM) An embedded solids cooler is included and the solids are circulated at a higher mass flow rate per unit cross-sectional area of the riser.

According to one aspect of the invention, oxygen is distributed to the circulating fluidized bed without an internal distributor. The burner for the particle circulation arrangement in the bed provides the opportunity to distribute the oxygen in the circulation loop evenly so that the oxygen does not have hot spots during combustion in the reactor at high temperatures, which are known to generate coal slag in the burner.

Another aspect of the present transport oxy-combustor is its ability to operate at elevated pressures. Preferably, it operates at a pressure above about 150psia, thereby reducing the size of the equipment and reducing the size and number of downstream equipment in the recycle loop. Higher operating pressure, improved heat transfer, emission control, treatment efficiency, and reduced overall capital cost.

Since there is a large amount of solids circulating in the loop, one of the objects of the present invention is to circulate the solids directly to the solids cooler from the natural flow separation occurring in the separation module. According to one aspect of the invention, the separation assembly comprises an inclined intersection between the riser and the first stage cyclone. The solids are inclined downwardly from the top of the riser and between the outlet of the riser and the solids inlet of the solids cooler. The gas and residual solids stream then flows horizontally into the inlet of the first stage cyclone. Preferably, more than 50% of the solids are separated from the inclined cross-flow and enter the solids cooler.

It is another object of the present invention that a portion of the aeration gas introduced into the solids to assist in the flow of solids in the cooler while increasing the heat transfer rate of the cooler flows upward to the solids inlet of the cooler. The aeration gas flows further into the first stage cyclone downstream of the solids inlet to the cooler inlet along with the flue gas from the riser. The mixture of aeration and flue gas assists in maintaining the solids flowing into the first stage cyclone in a state of complete suspension in the gas stream. The increased solids flow rate and the even distribution of solids throughout the cross-section of the inlet to the first stage cyclone can improve the solids collection efficiency of the cyclone. The solids suspended solids collected by the first stage cyclone flow directly into the standpipe.

According to another aspect of the invention, the flow of solids to the cooler, and thus the steam generation rate of the solids cooler, is controlled by the amount of aeration in the cooler. Another means of controlling the solids flow rate of the solids cooler is to provide a narrow circular throat at the inlet. In addition, the upward flow of gas through the throat also slows the solids flow to the cooler.

Another aspect according to the present invention is to provide a unique solids cooler height and level of solids in the cooler. When low steam production rates are required, the solids level in the cooler will cover only a portion of the heat transfer area. The overall steam yield from the cooler solids will be reduced due to the lower heat transfer coefficient of the uncovered heat transfer surface area relative to the covered solids. Thus, the height of the solids in the cooler becomes a means of achieving the desired steam yield.

A second stage cyclone may be used to further collect the escaping solids from the collection process of the first stage cyclone. The solids collected by the second stage cyclone will be returned to the solids cooler via a downcomer and a seal leg or seal ring arrangement. The solid column in the seal leg prevents gas backflow which can disrupt the cyclone and reduce its collection efficiency. The type of solids collection system and whether a second stage cyclone is required depends largely on the characteristics of the solid fuel selected for combustion.

The present invention may further comprise adding gaseous fuel or non-volatile solids to the outlet of one or both of the first and second stage cyclones. The added fuel reflects the excess oxygen present in the flue gas, thereby scavenging oxygen from the flue gas. The cleaning reaction takes place in the crossover and in the cyclone. Preferably, the fuel injected into the crossover for oxygen scavenging is nearly essentially sulfur free. If the scavenging fuel contains sulfur compounds that form SO2 and SO3, sulfur sorbents are injected with the fuel to remove sulfur oxides from the flue gas.

The present invention may also include injecting high pressure CO2 atomized water into the crossover to reduce excessive temperatures that may result from the combustion of the oxygen scavenging fuel. The necessity of water injection depends on the level of residual oxygen in the combustor. Since the transport oxy-combustor is operated at elevated pressure, one advantage of water injection is the recycling of latent heat when cooling the flue gas to condense moisture, thereby producing a substantially pure stream of CO 2.

The solid fuel selected for combustion, the excess oxygen that may be necessary for complete combustion, and any oxygen scavenging solid fuel characteristics required to produce a flue gas stream that is substantially free of oxygen may necessitate a third gas-solid separation device (preferably a third stage cyclone) for reducing the concentration of fine solid particles to ensure safe operation of downstream equipment. The third stage cyclones also increase the gas residence time and reduce the carbon monoxide content of the flue gas. The temperature of the flue gas at the outlet of the burner and the tertiary cyclone depends on the melting temperature of the fly ash. Preferably, the flue gas temperature is about 50 ° F to 150 ° F below the ash melting temperature of the ash.

In another preferred embodiment of the invention, the transport oxy-combustor is operated at pressures in excess of 10 bar to effectively remove about 100% of sulfur oxides from flue gas with a sorbent injected into the combustor having a calcium-to-sulfur molar ratio of less than 1.3. Such low molar ratios are feasible due to the pressurized environment in the transport oxy-combustor and the high circulating solids mass flux. A low molar ratio may allow for reduced operating costs because less adsorbent is required and thus less waste is produced to be disposed of.

Improved process efficiency is also provided as the transport oxy-combustor is operated at elevated pressures. Steam is generated in the flue gas cooler by cooling the flue gas stream discharged from the combustor. Higher pressures can achieve higher heat transfer coefficients because it is nearly proportional to pressure. The flue gas stream is further cooled and the water vapour is condensed to produce a substantially pure CO2 stream at elevated pressure. Operating at elevated pressures can have a significant advantage. If the pure CO2 stream is compressed to a relatively high pressure for transportation, sequestration, or other end use, the marginal cost of compressing the pure CO2 stream from the transport oxy-combustor may be significantly reduced because of the relatively elevated operating pressure of the transport oxy-combustor. Useful thermal energy can be extracted by condensation of moisture at high pressure because the saturation temperature at elevated pressure is also higher.

According to a preferred embodiment of the present invention, the superficial velocity of the gas phase in the riser of the circulating fluidized bed is in the range of about 18 to 50 feet per second. Such high gas velocities increase the solids circulation rate because the combustor operates in a flow regime, known as the transport regime, in which the gas carrying capacity contributes to the circulating solids flow through the riser.

The high mass flux of solid particles through the riser has the following beneficial advantages over conventional systems: (i) which promotes the completion of the combustion reaction, (ii) which exponentially increases the ability to absorb a large amount of the released heat while maintaining the temperature of combustion without the need for any recycled CO2 or flue gas (as is required in the prior art), (iii) which enables substantially complete capture of the sulfur component and high sorbent utilization.

The mixing of the large amount of circulating cooler solid fuel and oxygen can maintain stable combustion conditions (temperature). As with refrigeration, the present invention rapidly absorbs heat from the combustion zone and releases it in a solids cooler, where the circulating solids are "refrigerant" in nature.

In another preferred embodiment according to the present invention, the ratio of solids circulation rate to mass of carbonaceous solid fuel is in the range of about 150 to 400 in order to limit, if not avoid, hot spots that may occur when combustion is carried out using substantially pure oxygen. The high solids throughput rate also makes it possible to use for high steam yield and high solid carbonaceous fuel throughput in the combustion chamber.

Such high solids circulation velocities enable unusually high energy throughput based on cross-sectional area of the riser in the range of about 20000 to 70000 or 7 million to 2.5 hundred million thermal units per square foot-hour. The solids circulation rate is primarily controlled by the solids level in the standpipe and solids cooler, and is fine tuned by the aeration rate to adjust and maintain the desired riser temperature.

These and other objects, features and advantages of the present invention will become more apparent upon reading the following specification in conjunction with the accompanying drawings.

Drawings

The various features and advantages of this invention may be more readily understood by referring to the following detailed description in conjunction with the accompanying drawings, in which like reference numerals designate like structural elements, and in which:

FIG. 1 is a schematic illustration of a circuit configuration of a transport oxy-fuel burner of the present invention having an upflow of gas in a riser, a downflow solids cooler, a two stage gas-solid separation device and a seal leg between the second stage cyclone and the solids cooler in accordance with an exemplary embodiment.

FIG. 2 is a schematic diagram of a transported oxy-fuel burner circuit configuration with more than one downflow solids cooler, according to an exemplary embodiment.

FIG. 3 is a schematic diagram of a circuit configuration for a transport oxy-fuel burner having more than one upflowing solids cooler and one standpipe, according to an exemplary embodiment of the present invention.

FIG. 4 is a schematic illustration of a transport oxy-fuel burner cycle configuration with both downward and upward flow solids coolers according to an exemplary embodiment of the invention.

FIG. 5 is a schematic view of a transport oxy-fuel burner circuit configuration with oxygen scavenger injection and tertiary swirler in accordance with an exemplary embodiment of the invention.

FIG. 6 is a schematic view of a circuit configuration for a transport oxy-fuel burner with seal legs between the dip tube and the standpipe of the first stage cyclone in accordance with an exemplary embodiment of the present invention.

Detailed description of the invention

To facilitate an understanding of the principles and features of various embodiments of the present invention, various illustrative embodiments are explained below. While exemplary embodiments of the invention have been explained in detail, it should be understood that other embodiments are also contemplated. Therefore, it is not intended that the invention be limited to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. Furthermore, in describing the exemplary embodiments, specific terminology will be resorted to for the sake of clarity.

It must also be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. For example, reference to a component is also intended to include a plurality of components of the composition. Reference to a composition containing "a" component is intended to include reference to components in addition to the recited components.

Also, in describing the exemplary embodiments, terminology will be resorted to for the sake of clarity. Each term is intended to cover a broad meaning thereof understood by those of skill in the art and includes all technical equivalents which operate in a similar manner to accomplish a similar purpose.

Ranges may be expressed herein as from "about" or "approximately" or "substantially" one particular value and/or to "about" or "approximately" or "substantially" another particular value. When such a range is expressed, other exemplary embodiments include from the one particular value and/or to the other particular value.

Similarly, as used herein, "substantially free of" something, or "substantially pure" and similar feature descriptions may include both "at least substantially free of" something, or "at least substantially pure," and "completely free of" something, or "completely pure.

"comprising" or "containing" or "including" means that at least the recited compound, element, particle, or method step is present in the composition or product or method, but does not exclude the presence of other compounds, materials, particles, method steps, even if other such compounds, materials, particles, method steps have the same function as recited.

It should also be understood that the mention of one or more method steps does not preclude the presence of additional method steps or intervening method steps between those steps expressly identified. Likewise, it will also be understood that reference to one or more components in a composition does not preclude the presence of other components than those explicitly identified.

The materials described as individual elements of the invention are intended to be illustrative and not limiting. Many suitable materials that will perform the same or similar function as the materials described herein are intended to be within the scope of the present invention. Such other materials not described herein can include, but are not limited to, for example, materials developed after the time of the development of the present invention.

The present invention is a transport oxy-combustor comprising: a riser comprising a primary oxygen feed and a solid fuel stream feed, a first gas-solid separation device, and a solids cooler having an outlet cooler solids stream, wherein the outlet cooler solids stream travels from the solids cooler to a lower section of the riser where the outlet cooler solids stream disperses oxygen from the primary oxygen feed, wherein combustion of the outlet cooler solid fuel stream with the dispersed oxygen in the presence of the outlet cooler solids stream moderates and controls combustion temperature in the riser, wherein a gas-solid mixture in the riser enters the first gas-solid separation device, wherein the first gas-solid separation device provides a solids stream to the solids cooler.

The riser may further comprise one or more sorbent stream feeds and a secondary oxygen feed. The mass flow rate of solids in the circulating solids stream may be in the range of about 150 to 400 times the feed rate of the solid fuel stream riser. The transport oxy-combustor may further include a separation assembly positioned between the riser and the first gas-solid separation device, the separation assembly facilitating separation of a portion of the solids from the gas-solid mixture. The transport oxy-combustor further comprises a second gas-solid separation device disposed downstream of the first gas-solid separation device to collect fine solid particles entrained in the gas stream and return them to the solids cooler.

The invention also relates to a transport oxy-combustor comprising: a riser tube comprising an outer shell and an insulating, corrosion-resistant, refractory lining, wherein a carbonaceous solid fuel is combusted in the riser tube in the presence of oxygen and circulating solids, the combustion forming a flue gas stream comprising a gas-solid mixture; a first stage cyclone having an inclined tangential inlet; an inclined first cross connecting the riser and the first stage cyclone; a second stage cyclone; a second crossover connecting the outlet of the first stage cyclone and the second stage cyclone; a third cyclone for removing excessive oxygen in the solid fuel consumption flue gas flow; a vertical tube; a seal leg disposed below at least one of the cyclones of the first and second stages for returning solids to the standpipe and in counter-flow with respect to the flue gas flow; and at least one solids cooler, wherein the riser provides communication between the cyclone and the at least one solids cooler, wherein the at least one cooler is configured to transfer heat of combustion from the circulating solids to one or more of water and steam to form steam and superheated steam.

The riser may further comprise: at least one fuel injection nozzle in the lower section of the riser feeding a carbonaceous solid fuel into the riser; at least two primary oxygen injection nozzles in the lower section of the riser feeding oxygen into the riser at different heights along the lower section of the riser; at least two secondary oxygen injection nozzles above the at least one fuel injection nozzle that feed oxygen into the riser at different heights; and at least two sets of aeration nozzles that feed aeration gas into the lower section and seal legs of the at least one solids cooler to facilitate solids flow and heat transfer. The riser may further comprise a sorbent feed that adds a sorbent to the riser to remove at least a portion of the undesired species from the flue gas, and the undesired species may be sulfur oxides, wherein the sorbent is one of limestone or dolomite, and wherein the molar ratio of calcium to sulfur is less than about 1.3.

The transport oxy-combustor may have an operating pressure in the range of about 30psia to 1000 psia. The transport oxy-combustor may have a ratio of solids circulation rate to mass of carbonaceous solid fuel in the range of about 150 to 400, wherein combustion of the solid fuel with oxygen in the riser in the presence of the circulating solids moderates and controls the combustion temperature in the riser. The transport oxy-combustor may have a ratio of solids circulation rate to carbonaceous solid fuel mass in the range of about 150 to 400, wherein at least one of the at least one solids cooler is an upflow solids cooler located below the riser.

The first stage cyclone may have an inclined inlet solids loading capacity in the range of about 10 pounds to 40 pounds of solids per pound of gas. The first stage cyclone may have an inlet velocity in the range of about 25 feet per second to 55 feet per second.

One of the at least one solids cooler of the transport gas combustor may be located at the bottom of the riser such that circulating solids flow down into the at least one solids cooler located at the bottom of the riser and flow up and merge into the riser of one of the at least one solids cooler located at the bottom of the riser.

A transport oxy-combustor having at least two solids coolers can include one solids cooler having downward flow of solids through the at least two solids coolers and one solids cooler having upward flow of solids through the at least two solids coolers. The upflow solids cooler may use oxygen as the aeration gas at the bottom of the solids cooler to reduce CO2 recycled to the transport oxy-combustor to a minimum of tilt.

Excess oxygen may be utilized by injecting a gas or solids scavenging fuel at the outlet of one of the first or second stage cyclones.

The present invention also includes a transport oxy-combustor comprising: a riser comprising a primary oxygen feed and a fossil fuel stream feed, a first gas-solids separation device, and a solids cooler having an outlet cooler solids stream, wherein the outlet cooler solids stream moves from the solids cooler to a lower section of the riser where the outlet cooler solids stream disperses pressurized oxygen from the primary oxygen feed, wherein combustion of the fossil fuel stream and oxygen in the riser forms a flue gas that exits the riser, wherein the flue gas in the riser enters the first gas-solids separation device, wherein the first gas-solids separation device provides a solids stream that enters the solids cooler, and wherein the flue gas contains substantially pure CO2 after moisture condensation.

The transport oxy-combustor can function as a circulating fluidized bed combustor at a solids circulation rate high enough so that there is no need to use recycled CO2 or flue gas as a means to moderate and control the combustion temperature in the riser.

The temperature in the riser can be effectively controlled by the relatively cooler circulating solids entering the lower section of the riser. An amount of CO2 may be recycled for limited aeration and transport of solid fuel to the riser. The excess oxygen required to achieve complete combustion in the riser can be purged by adding a purging fuel so that substantially all of the oxygen fed to the riser is completely consumed.

In fig. 1, the solids recycle loop of the transport oxy-combustor is represented by 100. The transport gas burner comprises a riser 200 having a high cylindrical outer shell 202 preferably lined with a refractory material (not shown). The refractory material comprises a double layer: an outer insulation layer maintaining the carbon steel case below about 300 ° F; an inner erosion resistant layer that protects the outer shell and the thermal insulation layer from erosion due to high solids circulation rates. Substantially all of the combustion reaction and gas-solid mixing occurs in the riser of the combustor.

The primary oxygen 150 is fed via individual nozzles along the riser height. About 20-80% of the primary oxygen is fed through nozzles in the lower section of the riser 204 to react with carbon remaining in the circulating solids. Depending on the desired solids circulation rate, the total gas superficial velocity after addition of oxygen stream 150 may range from about 8 feet per second to 35 feet per second. Preferably, the gas superficial velocity is in the range of about 10 feet per second to 25 feet per second.

The oxygen fed to section 204 is mixed with the solids stream 206 from the solids cooler to completely disperse the oxygen by circulating the solids through the cross section of the riser. The mass flow rate of solids in the circulating solids stream 206 is preferably about 150 to 400 times the carbon feed rate of the carbonaceous material into the combustor. Because the combustion after use of the various components of the present invention is substantially complete, the carbon content in the circulating solids 206 is substantially zero and the mixing process in the lower section of the riser has a low solids temperature rise.

The method of achieving substantially complete combustion and essentially zero carbon in the circulating solids is through a combination of riser design and fuel grind size. The height of riser 200 is designed with sufficient residence time such that fuel with a low reactivity of a few minutes is completely converted. Depending on the fuel characteristics, the grind size of the solid fuel stream 210 is set to be small enough to facilitate higher carbon conversion by providing a larger solid surface area. For example, on a mass average diameter basis, low reactivity fuels can be pulverized to an average particle size of about 100-250 microns, and high reactivity fuels can be pulverized to an average particle size of about 200-700 microns. The flexible average particle size is one of the operating modalities of the present invention that is different from conventional operating CFB units used for power generation.

The circulating solids entering the bottom section of riser 204 have a temperature in the range of about 700 ° F to 1200 ° F, depending on the feed fuel reactivity. According to one aspect of the invention, the pulverized carbonaceous feed stream 210 is added to the combustor via a nozzle located above the primary oxygen feed nozzle. The solid fuel, having been recycled with CO2 gas, is sent to the coal feeder after the combustion products have been purified.

The required mass flow rate of the conveying gas per unit mass of coal feed depends on the burner operating pressure and the type of conveying method (e.g., dilute phase or dense phase) selected to convey the coal. The amount of carbon in the feed stream entering the burner may be greater than the amount required to deplete substantially all of the primary feed oxygen entering the burner section below the feed nozzle. Thus, the combustion reaction in the lower section of the riser is sub-stoichiometric and the combustion products are substantially free of NOX compared to the flow from complete combustion. The combustion products and remaining unconverted carbon flow upward in the riser because the velocity of the gas in the riser is greater than the final velocity of the large grain of a turn of a clock.

Additional secondary oxygen streams 152 may be added via various nozzles from the middle to the upper portion of the riser to further combust the remaining combustibles. In a preferred embodiment, the number of secondary oxygen nozzles in stream 152 may be at up to five different levels along the riser height; at each level, two to six nozzles are designed to inject secondary oxygen into the riser. After the addition of secondary oxygen from 152, the percentage by volume of oxygen in the gas phase in the riser is about 2-5%. The temperature in the riser upper section 221 above the secondary oxygen stream 152 nozzle is in the range of about 1550 ° F to 2000 ° F, depending on the fuel reactivity and ash melting temperature.

According to an exemplary embodiment of the invention, the sorbent stream 220 is added to the riser section transporting the oxy-combustor. The sorbents locked into the riser can be, for example, limestone (mainly calcium carbonate CaCO3), dolomite (calcium carbonate and carbonic acid)

Mixtures of magnesium) or other adsorbents that remain in a solid phase over an operating temperature range of about 1550 ° F to 2000 ° F. The primary purpose of feeding the sorbent into the riser is to remove substantially all of the sulfur components from the flue gas. CaCO3 is known to react with both SO2 and SO3 generated by the combustion reaction, but does not react very efficiently with H2S. In a preferred embodiment, the lower feed position of sorbent stream 220 is at least above one level of secondary oxygen stream 152, since the sorbent should be fed into the oxidizing atmosphere in the riser. The average sorbent particle size should be in the range of about 30-300 microns in order to effectively remove sulfur oxides from the flue gas. The molar ratio of calcium in the sorbent to sulfur in the coal should be in the range of about 1.0 to 1.3 in order to remove substantially all of the sulfur components from the flue gas.

The mixture of circulating solids, flue gas and other combustion products and reacted sorbent particles flows to the top of the riser and enters the inclined crossover 250. For the configuration shown in fig. 1, the gas superficial velocity at the top of the riser is in the range of about 25 feet per second to 75 feet per second, and the preferred gas velocity is in the range of about 25 feet per second to 50 feet per second.

The function of the inclined intersection is not only to connect the riser 200 with the first stage cyclone 300, but also to promote separation of a portion of the solids from the gas-solid mixture by gravity. During the turn into the cross and flowing along the slanted length of the cross, the gas-solid mixture stream 260 will naturally split into two streams under the influence of both the gravity and inertia of the solid particles. The two streams are distinguished primarily by their solids concentration; a high solids concentration stream 262 and a low solids concentration stream 264.

The high solids concentration stream 262 flows along the bottom of the cross and the amount of solids salted out in this stream increases as the gas-solid mixture flows down the inclined cross, the more solids-loaded stream 264 flows along the top of the cross. In addition to the solids concentration, the particle size in the two streams is also different. The larger particles remain primarily in the high solids concentration stream 262 and the smaller particles are suspended in the low solids concentration stream 264.

When both streams 262 and 264 enter the first stage cyclone 300, the solids in the stream 262 fall into the cyclone cylinder as a stream that has not experienced any substantial swirling action. As the small particles spin along the cyclone wall, they acquire centrifugal force and are thereby separated from the gas stream. The lifetime of the cyclone is significantly increased since smaller particles cause much less severe erosion in the cyclone inner wall 320.

As disclosed in U.S. patent No. 7,771,585, which is hereby incorporated by reference in its entirety, the first stage cyclone is preferably a refractory-lined vessel that reliably facilitates high solids circulation rates and mass fluxes important for proper transport oxy-combustor operation.

The solids stream 320 collected by the first stage cyclone 300 flows into a solids cooler or heat exchanger 700. Inside the cooler 700 is a heat transfer surface, where solid particles exchange heat with a fluid inside the cooling surface. The cooling fluid inside the heat exchanger surfaces may be water or steam, for example.

In an exemplary embodiment of the invention, the solids in the solids cooler 700 are fluidized. The particles exchange heat with a heat transfer surface built into the solids cooler. When the coolant is in a fluidized state, the solids side is at substantially the same temperature and in the range of about 800"° F to 1400 ° F. Fluidization of particles in a fluidized bed depends primarily on the velocity difference between the solid and the gas. A small amount of aeration gas may be added via aeration vapors 730 and 735 to facilitate movement of solid particles in the cooler bottom outlet.

In the fluidized state, the solids downflow velocity is in the range of about 3 feet per second to 10 feet per second, with a preferred solids velocity in the range of about 4 feet per second to 6 feet per second. The velocity difference between the solid and the gas is between about 0.2 ft/sec and

in the range of 0.8 ft/sec. The solids velocity is primarily controlled by the solids level in the solids cooler and the aeration rate through 730 and 735, while the gas velocity in the riser has a minor effect. The circulating solid particles mainly comprise ash generated by burning carbonaceous fuel like coal and have a particle size in the range of about 60 to 200 microns.

In another exemplary embodiment of the present invention, the solids cooler may operate as a moving bed solids cooler. In this mode of operation, the solids circulation rate is relatively low and the solids downward velocity is in the range of about 0.5 feet/second to 1.5 feet/second. This mode of operation is achieved by larger particles in the circulation loop in the size range of about 150 to 400 microns. The aeration rate through 730 and 735 was reduced to a period of time of turndown using moving bed operation. For this mode of operation, the velocity difference between the gas and the solid is in the range of about 0.03 to 0.1 ft/sec. The moving bed mode is achieved primarily by reducing the solids level in the cooler.

While fluidization operation is a desirable mode of operation of the solids cooler of the embodiment shown in fig. 1, moving bed mode is advantageous when, for example, there are situations where short duration equipment that does not require power production or steam generation, etc. is substantially idle. In order to keep the burner warm and ready for production, it is advantageous to operate the cooler in moving bed mode in order to reduce the energy consumption during standby mode to a period of time of a shorter duration.

In either mode of operation, the outlet temperature of the solids cooler will be similar. The only difference between the two operating modes for a given design is the amount of steam generated by the chiller, which is due to the variation in the operating parameters as described above.

The cooled solids stream 740 exiting the solids cooler at a temperature in the range of about 900 ° F to 1400 ° F flows through the non-mechanical valve 800, the non-mechanical valve 800 having an angle in the range of about 0 degrees to 45 degrees upward relative to horizontal. Aeration gas 810 may be added to the non-mechanical valve to facilitate the flow of solids through the valve to the riser and to maintain the desired solids circulation rate around the burner loop.

In the configuration shown in fig. 1, another cyclone 400 is added downstream of the first stage cyclone to collect other fine solid particles entrained in the gas stream. This second stage cyclone is of conventional design due to the low solids loading in the gas stream at the inlet. Solids collected by the second stage cyclone are returned to the solids cooler through a downcomer 500 and a seal leg or ring seal arrangement 600. The solids column in the seal leg limits or prevents gas backflow, which can damage the cyclone and reduce its collection efficiency. Aeration streams 510 and 610 may be added to promote solids flow in the downcomer and seal legs.

The gas stream 900 leaving the second stage cyclone 400 is substantially free of dust and instead contains 2% to 5% oxygen. The gas stream may be cooled via a flue gas cooler (not shown in fig. l) and then passed through a filter vessel or other means to remove trace particles remaining in the gas stream. The gas stream may be further processed to condense moisture and remove impurities, and generate substantially pure CO2 for sequestration or other applications.

The pressure of the flue gas stream 900 exiting the cyclone 400 may be in the range of about 30psia to 1000psia, with preferred operating pressures being in the range of about 150psia to 700 psia. Oxy-burners operate under pressure to overcome the disadvantages of boilers and burners operating at atmospheric or slightly negative pressure, such as air leakage into the flue gas stream and high recycle CO2 rates. Operating at high operating pressures is advantageous because it promotes high solids circulation rates with gases having greater solids carrying capacity at high densities. Even a high mass ratio of recycled solids to carbon fed to the transport gas burner can be used to achieve a hot spot free heat distribution.

In one embodiment of the invention, the feed rate of the solid fuel into the riser is in the range of about 20000 to 70000 or 7 to 2.5 million thermal units per square foot-hour. Another advantage of operating at high pressure in transport oxy-combustors is the nearly complete removal of sulfur oxides from flue gas using adsorbents, eliminating the need for scrubbers.

The transport gas combustor 102 shown in fig. 2 has more than one solids cooler 702 and 704 to cool the circulating solids before returning them to the lower portion of the riser. As the combustor capacity increases, handling more fuel and releasing more heat, the heat transfer surface area in the solids cooler should also increase in order to transfer the released heat to the cooling (preferably water and steam) system. For large commercial plants, two solids coolers can accommodate the necessary heat transfer area.

Solids collected by the first stage cyclone 300 flow downwardly into a distributor and then into a solids cooler. The solids level in the cyclone diplegs 322 controls the flow of solids to the cooler. The solids level in the cyclone diplegs is preferably above the split point so that the solids cooler is full of solids. The flow of solids to each cooler may also be controlled by a non-mechanical valve. The connection between the first stage cyclone diplegs 322 and the solids coolers 702 and 704 may be a seal leg or an L-valve (not shown) to control solids flow via aeration. The flow rate of solids through the solids cooler can also be controlled by the flow rate of aeration streams 731 and 732. In a preferred embodiment, aerated streams 731 and 732 comprise oxygen to reduce the consumption of recycled aerated gas, and preferably mix solids with oxygen before the streams enter the lower portion of the riser. The use of oxygen for aeration of the cooler solids outlet has little adverse effect on the burner operation. By design, the carbon content in the circulating solids is essentially zero due to the rapid combustion reaction in the riser, which will deplete substantially all of the carbon in the fuel.

Both solids streams 705 and 706 from the solids cooler are fed to a single non-mechanical valve 802. The configuration of the non-mechanical valve may be, for example, one of: an L-valve (as shown in fig. 2), a J-valve, or a ring seal, each of which is well known to those skilled in the art. The aeration stream 812 may be fed to a plurality of nozzles in the L-valve to fluidize and assist the flow of solids. The aeration gas entering these nozzles may also contain oxygen.

The transport oxy-combustor configuration shown in fig. 3 also has two solids coolers with solids flowing through the coolers in an upward direction. The upflow cooler makes full use of the burner loop for highly reactive fuels because the gas residence time required in the riser to achieve substantially complete carbon conversion is in the range of about 0.5 seconds to 1.5 seconds. These relatively short residence times require smaller risers, and the solids cooler can be located below the risers. The combustor loop of fig. 3 includes a riser 201, primary cyclone 301, a standpipe 305, a non-mechanical valve 801 and upflowing solids coolers 701 and 703. The coarse solids stream 311 from the primary cyclone 301 is mixed with the fine solids stream 613 exiting the secondary cyclone 401 and its diplegs 501 and the mixture stream 741 moves down the standpipe under the influence of gravity and flows through the non-mechanical valve 801 to the solids cooler and riser, completing the recycle loop. This embodiment reduces the overall height of the combustor for highly reactive fuels.

Oxygen streams 151 and 153 may be added to the cone of the solids cooler to partially convey the solids upward and to fluidize the solids in the cooler. Since the solids returned from the standpipe are substantially free of combustible materials, the chance of temperature rise due to the combustion reaction is relatively low. Even if a small amount of carbon is present in the circulating solids streams 745 and 747, the temperature increase is suppressed by the cooling surfaces in the cooler.

In a preferred embodiment of the present invention, aeration stream 814 flowing into non-mechanical valve 801 comprises oxygen. The temperature of the gas-solid mixture exiting the solids cooler is in the range of about 800 ° F to 1400 ° F. The need to recycle CO2 was reduced to a brief moment since oxygen was used for aeration and fluidization in the non-mechanical valves and solids cooler.

The solids coolers 701 and 703 in fig. 3, and in other configurations, may be used to heat water, generate steam, or generate superheated steam. It is also possible to have one part of the solids cooler act as a heat exchanger surface for steam generation and another part as a steam superheater and a third part as an economiser.

Solids from the solids coolers 701 and 703 passing through the connecting pipe are merged into the riser flow 207. Although only two solids coolers are illustrated in the configurations shown in fig. 2 and 3, one of ordinary skill in the art will appreciate that the appropriate number of coolers depends on the characteristics of the feed fuel. The acceleration zone at the bottom of the riser is known to be a limiting factor in the solids transport or solids flux through the riser. In the case of multiple coolers at the bottom of the riser, the solids flux in the riser can be further improved. With multiple coolers below the riser, the mass ratio of circulating solids to carbon feed rate into the riser can be in the range of about 150 to 400. An increase in solids circulation rate also promotes favorable steam production rates.

A stream of carbonaceous solid fuel 211 is added to the bottom of the riser to react with the oxygen exiting the solids cooler. The temperature increase is in the range of about 50 ° F to 300 ° F after the fuel reacts with substantially all of the oxygen fed from below the fuel nozzle. Sorbent stream 221 and secondary oxygen stream 155 flow into the riser to effect in-bed desulfurization and completion of substantially all of the combustion reaction. In the configuration shown in fig. 3, the concept and function of both the gas-solid separation system and the riser portion of solids return from the standpipe to the combustor are similar to the configuration shown in fig. 1 and 2.

FIG. 4 illustrates another configuration of the transport oxy-combustor of the present invention having both a solids downflow cooler and an upflow cooler. The basic combustor circuit configuration 104 of fig. 4 is similar to the configuration 103 of fig. 3, except for the cooler configuration. Although fig. 4 shows one upflow cooler and one downflow cooler, a plurality of coolers can be installed for upflow as illustrated in fig. 3 and downflow as illustrated in fig. 2. In a preferred embodiment, a single unit of the transport oxy-combustor has sufficient steam generation capacity to generate power in the range of about 500 to 1000 MWe. These high capacity burners require a large heat transfer surface area to extract heat from the circulating solids. Even with multiple coolers in the configuration shown in fig. 2 or 3, the cooler height becomes too large to accommodate substantially all of the heat transfer area. Configuring the coolers in both the downflow and upflow configurations, as shown in fig. 4, allows for more coolers to be implemented, sharing heat transfer area between the downflow cooler and the upflow cooler. The total height of the mass transit oxy-combustor can be reduced. The steam generating and superheater heat transfer surface area is part of a downflow solids cooler with hot water or saturated steam entering through stream 715 and saturated water or superheated steam exiting through stream 717. In an upflow solids cooler, the driving force for heat transfer is small because the withered solids entering the cooler are at a lower temperature after transferring heat in the downflow cooler. The upflow cooler contains the larger heat transfer area required for the economizer, with the boiler feed water entering via stream 711 being heated to steam drum operating conditions and exiting the economizer via stream 713.

FIG. 5 illustrates another configuration (configuration 105) of a transport oxy-combustor of the present invention that generates a flue gas that is substantially free of oxygen. It is generally necessary to feed excess oxygen into the riser via a flow indicated at 155 in order to complete the conversion of carbon in the riser. However, excess oxygen in the flue gas stream must be separated during CO2 purification for all CO2 applications (including CO2 sequestration). In addition, the air separation process consumes energy, capital, and is costly to operate and maintain. Therefore, it is necessary to raise the process efficiency and the economical efficiency regarding oxygen consumption.

In the present invention, excess oxygen is substantially completely consumed by the addition of a scavenger, preferably another fuel stream, thereby generating energy and eliminating the need to separate oxygen from the flue gas to purify CO 2. The scavenging fuel may be in gaseous or solid form. The fuel for gas removal is typically methane, and the fuel for solids removal is typically a non-volatile solid, such as coke breeze.

In the preferred embodiment of the invention shown in fig. 5, purge fuel to consume excess oxygen is injected at the outlet of the second stage swirler 401. The additional residence time provided by the tangential inflow of the scavenging fuel into the flue gas stream may facilitate oxygen consumption. The exit concentration of oxygen in the flue gas is in the range of about 50ppm to 500 ppm. The scavenger fuel injected via stream 910 can be a gas or a solid fuel. At operating temperatures in excess of about 1550 ° F at the outlet of the second stage cyclone 401, substantially all of the injected fuel will react with the remaining oxygen to produce primarily CO2 and trace CO. The additional energy released by the scavenging reaction can be recycled with the flue gas cooler.

If gaseous fuel is used to purge oxygen, the purging fuel may be nearly stoichiometric to consume excess oxygen in the flue gas stream. There is trace or no scavenging fuel in the flue gas stream exiting the combustor, thereby eliminating any other steps that may be necessary to remove the scavenging fuel in the CO2 purification step. If solid fuel is used for purging, the purging fuel may be slightly excess or insufficient to consume excess oxygen. If the purge solid fuel is slightly in excess of the stoichiometric amount, the excess purge fuel in the flue gas stream is collected with some fine ash particles in the third stage cyclone and the collected particles flow to receiving vessel 951 via cyclone leg 921. The solids collected in the vessel 951 are cooled by the heat exchanger surfaces installed in the vessel. The cooling medium in the vessel may be, for example, water or steam that enters or exits the vessel via streams 955 and 957. The cooled solids are discharged via stream 953 into a fuel handling system for other applications.

Fig. 6 is another configuration of the present invention. Solids collected by the first stage cyclone flow through the seal leg into the standpipe and down-flow solids cooler. In this configuration 106, the finer particles collected by the second stage cyclone flow down the dipleg directly into the standpipe without passing through a seal leg or annulus.

Depending on the characteristics of the feed fuel, it may not be feasible to dispose of fines through the seal legs and ring seals. In such cases, the arrangement of fig. 6 substantially avoids the finer particles having to flow through the bends in the seal legs or ring seals and the operation becomes more reliable. Depending on the characteristics of the solid feed fuel and the characteristics of the desired excess oxygen and solid scavenging fuel, a scavenging fuel 910 may be injected at the outlet of the first stage cyclone. The third stage cyclones can be eliminated because the crossover and second stage cyclones provide a residence time sufficient to consume excess oxygen. Any excess purge fuel is collected by the second stage cyclone and flows with the circulating solids to the riser where it will be substantially completely combusted.

Many features and advantages are set forth in the above description, along with details of structure and function. While the invention has been disclosed in several forms, it will be apparent to those skilled in the art that: many modifications, additions, and deletions may be made therein, particularly in regard to the shape, size, and arrangement of parts, without departing from the spirit and scope of the invention and its equivalents as set forth in the following claims. Accordingly, other modifications or embodiments that may be devised by the teachings herein are particularly reserved as they fall within the breadth and scope of the claims appended hereto.

Claims (22)

1. A pressurized transport oxy-combustor comprising

A riser tube comprising an outer shell and a thermally insulating, corrosion resistant, refractory lining; wherein in the riser, a carbonaceous solid fuel is combusted under conditions of substantially pure oxygen and the presence of circulating solids, the combustion forming a flue gas stream comprising a gas-solid mixture;

a first stage cyclone having an inclined tangential inlet;

a first cross-over connecting the riser top to the first stage cyclone at an incline;

a second stage cyclone;

a second crossover connecting the outlet of the first stage cyclone to the second stage cyclone;

a third stage cyclone that consumes excess oxygen in the flue gas stream with a scavenging fuel;

a vertical tube;

a seal leg below one of the at least one first and second cyclones to feed solids back to the standpipe and provide a seal against reverse flow of the flue gas stream;

at least one solids cooler, wherein the standpipe provides communication between the cyclone and the at least one solids cooler;

wherein the at least one solids cooler is for transferring heat of combustion from the circulating solids to one or more of water and steam to form steam and superheated steam;

wherein the mass flow rate of the circulating solids stream is in the range of 150 to 400 times the feed rate of the carbonaceous solid fuel to the riser;

wherein the transport oxy-combustor operates at a pressure range of 30psia to 1000 psia.

2. The transport oxy-combustor of claim 1, the riser further comprising

At least one fuel injection nozzle in a lower section of the riser to feed carbonaceous solid fuel to the riser;

at least two primary oxygen injection nozzles in a lower section of the riser to inject substantially pure oxygen into the riser along different elevations of the lower section of the lift roll;

at least two secondary oxygen injection nozzles positioned above the at least one fuel injection nozzle to inject substantially pure oxygen into the riser at different heights; and

at least two sets of aeration nozzles to feed aeration gas into a lower section of the at least one solids cooler and the seal leg to facilitate solids flow and heat transfer.

3. The transport oxy-combustor of claim 1, wherein combustion of the solid fuel with substantially pure oxygen within the riser in the presence of circulating solids is moderated and controls the riser combustion temperature.

4. The transport oxy-combustor of claim 1, wherein at least one of the at least one cooler is an upflow solids cooler located below the riser.

5. The transport oxy-combustor of claim 1, the riser further comprising a sorbent feed that feeds sorbent into the riser to at least partially remove undesired species from the flue gas stream.

6. The transport oxy-combustor of claim 5, wherein the undesirable species is sulfur oxide, wherein the sorbent is limestone or dolomite, and wherein the molar ratio of calcium to sulfur is less than 1.3.

7. The transport oxy-combustor of claim 1, wherein the first stage cyclone has an inclined inlet solids loading capacity in a range of 10 pounds to 40 pounds of solids per pound of gas.

8. The transport oxy-combustor of claim 1, wherein the first stage cyclone has an inlet velocity in a range of 25 ft/sec to 55 ft/sec.

9. The transport oxy-combustor of claim 1, wherein one of the at least one solids coolers is positioned at the bottom of a riser such that circulating solids flow downward into the at least one solids cooler positioned at the bottom of the riser and upward and merge into the riser through one of the at least one solids coolers at the bottom of the riser.

10. The transport oxy-combustor of claim 9, wherein the solids cooler in which the solids stream flows upward uses oxygen as an aeration gas at the bottom of the solids cooler to cause CO recycled to the transport oxy-combustor₂To a minimum.

11. The transport oxy-combustor of claim 1, wherein excess oxygen is utilized by injecting a gas or solid phase scavenging fuel at the outlet of the first or second stage cyclones.

12. The pressurized transport oxy-combustor of claim 1, wherein high mass flux of circulating solids through the riser promotes completion of the combustion reaction, increases the ability to absorb a substantial amount of released heat while maintaining combustion temperatures without the need for recycled flue gas components, and enables capture of virtually any sulfur components with high sorbent utilization.

13. The pressurized transport oxy-combustor of claim 5, the rate of circulating solids enabling energy throughput based on a cross-sectional area of the riser in a range of 20,000 btus/sq ft-sec to 70,000 btus/sq ft-sec.

14. The pressurized transport oxy-combustor of claim 1, wherein at least one of the at least one solids cooler is an upflow solids cooler located in a lower portion of the riser, and

wherein a portion of the substantially pure oxygen feed is injected into the bottom of the upflowing solids cooler; and

wherein the upflow solids cooler operates in a transport mode in which: the transport capacity of the gas facilitates the flow of circulating solids through the riser.

15. The pressurized transport oxy-combustor of claim 1, wherein excess oxygen is utilized by injecting a gas or solids scavenging fuel at the outlet of one of the first or second stage cyclones and said mixture of injected fuel and flue gas enters the other cyclone to extend reaction time and reduce oxygen content in the flue gas to 50-500 ppm.

16. The pressurized transport oxy-combustor of claim 5, wherein the undesirable matter is sulfur oxides, wherein the sorbent is one of limestone or dolomite, and wherein a molar ratio of calcium to sulfur is less than 1.3 to remove all sulfur components from the flue gas stream.

17. A transport oxy-combustor for combustion of a fuel with substantially pure oxygen as an oxidant to produce a flue gas stream containing moisture, wherein CO is separated from the flue gas stream when at least a portion of the moisture is separated₂The rich-in-middle clean flue gas exits the transport oxy-combustor, which comprises:

a riser comprising a primary oxygen feed and a solid fuel stream feed;

a gas-solid separation device that receives a gas-solid mixture from the riser; and

a downflow solids cooler receiving a solids stream comprising solids from said gas-solids separation device and providing an outlet cooler solids stream;

an upflow solids cooler;

wherein the exit cooler solids stream travels from the downflow solids cooler through the upflow solids cooler to a lower section of the riser where the exit cooler solids stream disperses substantially pure oxygen from the primary oxygen feed;

wherein combustion of the solid fuel stream and the dispersed substantially pure oxygen within the riser in the presence of the outlet solid stream is moderated and combustion temperature within the riser is controlled;

wherein the riser operates at a pressure range from 30psia to 1000 psia; and is

Wherein the mass flow rate of the circulating solids stream through the riser is in the range of 150 to 400 times the feed rate of the solid fuel stream to the riser.

18. The transport oxy-combustor of claim 17, wherein high mass flux of circulating solids through the riser promotes completion of the combustion reaction, increasing the ability to absorb a substantial amount of released heat without the need for recycled CO while maintaining combustion temperature₂Or flue gas, and can accomplish virtually any sulfur component capture with high sorbent utilization.

19. The transport oxy-combustor of claim 18, wherein the transport oxy-combustor functions as a circulating fluidized bed combustor at a sufficiently high solids circulation rate such that there is no need to utilize recycled CO₂Or flue gas as a means of moderating and controlling the combustion temperature within the riser.

20. The transport oxy-combustor of claim 17, wherein the solid fuel stream comprises a carbon-containing solid fuel stream and is combusted with substantially pure oxygen in a substantially complete oxidation reaction with the result that a net flue gas comprises 80-98% CO₂。

21. The transport oxy-combustor of claim 17, wherein the transport oxy-combustor is operated as a circulating fluidized bed combustor at a sufficiently high solids circulation rate;

wherein the superficial velocity of the gas phase in the riser of the circulating fluidized bed is in the range of from 18 to 50 feet per second; and is

Wherein the burner is operated in a transport mode in which: the transport capacity of the gas facilitates the flow of circulating solids through the riser.

22. The transport oxy-combustor of claim 17, wherein the rate of circulating solids enables energy throughput based on a cross-sectional area of the riser in a range of 20,000 btus/sq ft-sec to 70,000 btus/sq ft-sec.