CN105536476A - Heat recovery from a carbon dioxide capture and compression process for fuel treatment - Google Patents

Abstract

This application relates to heat recovery from carbon dioxide capture and compression processes for fuel processing. A system and process for capturing _CO2 is disclosed. The process involves reusing the heat from the _CO2 compression process by providing the heat to the fuel processing process. This heat can be used to dry fossil fuels to improve the efficiency of fossil fuel combustion.

Description

Recovery of heat from the carbon dioxide capture and compression process for fuel processing

This application is a PCT patent application submitted on May 7, 2010 that has entered the Chinese national phase (Chinese national application number is 201080020343.4, international application number is PCT/US2010/034016, the title of the invention is "Heat recovery from carbon dioxide capture and compression process for fuel treatment”).

technical field

This application relates generally to heat recovery. More specifically, the present application relates to systems and methods for recovering waste heat from carbon dioxide capture processes and using the waste heat to dry fossil fuels.

Background technique

Carbon dioxide (CO ₂ ) gas is released into the atmosphere from various industrial facilities such as fossil fuel power plants and waste incineration plants. While substantial reductions in _CO2 emissions are achievable through improved energy conversion and utilization efficiencies, such reductions may not be sufficient to achieve atmospheric _CO2 stabilization. Accordingly, efforts have been made to capture and sequester _CO2 emitted by fossil fuel power plants.

One type of fossil fuel power plant uses pulverized coal as a combustion source. The pulverized coal can have a moisture content that can vary from about 3% by weight to about 5% by weight. In some cases, it may be necessary to dry the pulverized coal before it can be efficiently burned to generate heat. In these cases, plant steam, furnace flue gas, or regenerative air heaters can be used to dry the pulverized coal. Typically, bituminous or sub-bituminous coal is dried by passing the same air that is used to combust pulverized coal in a pulverizer that reduces the particle size of the coal. For example, flue gas may flow through tubular or regenerative air heaters to heat the primary air. For lower rank, wetter coals, the furnace flue gas can also be mixed with ambient air and supplied to the coal drying unit. Where steam heat is used in a coal drying unit, the steam supplies heat to the fluidized bed and serves as a fluidizing medium and a drying medium. Another type of fossil fuel used in power plants is lignite, which has a high water content and usually needs to be dried before burning.

Various systems and methods have been developed to capture and reuse _CO2 gas. For example, ammonia-based processes have been developed to treat cooled flue gas with aqueous ammonia, which reacts with _CO2 in the flue gas to form ammonium carbonate or bicarbonate. The capture reaction can be reversed by increasing the temperature of the material that binds the captured _CO2 to release the _CO2 under pressure. In another example, various amine processes have been developed that treat flue gas with aqueous amine solutions in absorption/stripping type regeneration processes to absorb _CO2 for subsequent desorption and capture.

In these exemplary _CO2 capture methods, as well as in other similar methods, the captured _CO2 is compressed after regeneration for transport and storage. The regeneration and compression of _CO2 results in a large amount of waste heat.

What is needed is a system and method for recovering waste heat generated in a _CO2 capture process, and in particular, a method for improving a plant by recovering the waste heat for other plant or plant operations, such as coal drying Systems and methods for overall efficiency.

Intended advantages of the disclosed systems and methods satisfy one or more of these needs or provide other advantageous features. Other features and advantages will be apparent from the description. The disclosed teachings extend to those embodiments that fall within the scope of the claims, regardless of whether they satisfy one or more of the aforementioned requirements.

Contents of the invention

According to aspects presented herein, there is provided a method for recovering heat. The method includes: separating a substantial amount of _CO2 from a gas stream through a capture process; providing the separated _CO2 to a compression process; capturing heat released during the compression process; and providing the heat released during the compression process to the fuel process.

According to other aspects presented herein, there is provided a system for recovering heat comprising a capture system for separating _CO from a gas stream and a compression system for compressing the _CO separated from the gas stream, and fuel handling system. The compression system includes at least one stream of heated air heated by the compression system. A fuel processing system receives the at least one heated air stream.

According to other aspects presented herein, there is provided a _CO2 capture system comprising a combustion system for generating a flue gas stream comprising _CO2 , a capture system for separating a substantial amount of _CO2 from the flue gas stream, Compression systems for compressing _CO2 separated from flue gas streams, and fuel treatment systems. The compression system includes a stream of heated air heated by the compression system. A fuel processing system receives the stream of heated air.

The features described above, as well as other features, are exemplified by the following figures and detailed description.

Description of drawings

FIG. 1 is a schematic diagram of one embodiment of a process to recover waste heat from a CO ₂ capture process according to a first embodiment of the present invention.

Figure 2 is a schematic diagram of an exemplary _CO2 capture process.

Fig. 3 is a schematic diagram of an embodiment of a lignite drying process according to the present invention.

Fig. 4 is a schematic diagram of another embodiment of the lignite drying process according to the present invention.

detailed description

Figure 1 is a process flow diagram of one exemplary embodiment of a _CO2 capture process 100 (hereinafter "process 100") in accordance with the present invention. Referring to FIG. 1 , process 100 includes CO ₂ capture or removal process 110 , CO ₂ compression process 120 , and waste heat reuse process 130 . In this exemplary embodiment, CO ₂ removal process 110 is an amine-based process. In another embodiment, the CO ₂ removal process 110 may be an ammonia-based process or other process for removing acid gas pollutants from a gas stream. The gas stream may be a flue gas stream from a fossil fuel combustion process.

The CO ₂ removal process 110 includes a CO ₂ absorption unit 201 , hereinafter referred to as "absorption unit 201 ", configured to contact a gas stream to be purified with one or more scrubbing liquids. In one embodiment, the gas stream is a flue gas stream comprising _CO2 . In one embodiment, the wash may be a water/amine wash. In another embodiment, the wash solution may contain an amine compound. In one embodiment, the gas stream is a CO ₂ -containing flue gas stream and the wash is a water/amine wash. The flue gas stream from which CO ₂ is to be removed is supplied to the absorption unit 201 via a flue gas line 202 . The flue gas stream is cooled by heat exchanger 203 . Cooling fluid from a cooling fluid feed line 204 is provided to the heat exchanger 202 . The cooling fluid removes heat from the flue gas stream and exits the heat exchanger through cooling fluid discharge line 205 .

In the absorption unit 201 the flue gas is contacted with a scrubbing liquid. During this contact, _CO2 from the flue gas is absorbed into the scrubbing liquid. In one embodiment, the contacting of the flue gas with the wash solution is accomplished by bubbling the flue gas through the wash solution or by spraying the wash solution into the flue gas. The absorption unit 201 is supplied with wash liquid through a wash liquid feed line 220 . Absorption unit 201 may be supplied with additional make-up wash liquid via make-up line 222 . The flue gas depleted of CO ₂ leaves the absorption unit 201 through discharge line 207 . The flue gas may be further cooled by heat exchanger 208 and/or may be polished by direct contact with water in a water wash unit (not shown). Cooling fluid is provided to heat exchanger 208 through line 209 . The cooling fluid exits the heat exchanger through discharge line 210 .

The wash solution containing absorbed CO ₂ and pollutants leaves the absorption unit 201 through discharge line 211 . The wash solution is pumped by pump 212 through heat exchanger 213 to stripper 214 where _CO2 is separated from the wash water. Gaseous CO ₂ exits stripper 214 through line 215 . The regenerated wash liquid, stripped of absorbed _CO , exits stripper 214 through discharge line 216 and is sent through heat exchanger 213 where the regenerated wash liquid removes heat from the wash liquid containing absorbed _CO . The regenerated wash liquid is then cooled by heat exchanger 217. Cooling fluid is supplied to heat exchanger 217 from feed line 218 . The cooling fluid exits the heat exchanger through discharge line 219 . The cooled regenerated wash is then returned to absorber 201 through feed line 220 to complete the absorption cycle.

Gaseous CO ₂ exiting the CO ₂ removal process 110 via line 215 is provided to the CO ₂ compression process 120 . The CO ₂ is supplied to a first flash unit 310 where the CO ₂ is cooled. CO ₂ is provided to the first flash unit 310 in a temperature range of about 90°C to about 235°C. The first flash unit 310 may be or act as a heat exchanger. The first flash unit 310 is provided with a first flow of air through a first air line 309a. During the first flash process, _CO2 is cooled by transferring heat to the first air stream. In the first flash unit 310, moisture is removed from the _CO2 during the flash process. The moisture is returned to the stripper 214 through a first moisture discharge line 312 . In another embodiment, the moisture may be provided to other processes or systems having the _CO2 capture process 100, or to provide other plant operations. The term "moisture" is intended to include residual wash liquor, liquid water, water vapor, and combinations thereof, as well as any contaminants and impurities in the water. CO ₂ is withdrawn from the first flash unit 308 through a first CO ₂ withdraw line 313 and supplied to a second flash unit 314 . _CO2 is provided to the second flash unit 314 in a temperature range of about 90°C to about 235°C. The first stream of heated air exits the first flash unit 310 through a first heated air line 309 b and is provided to a mixer 330 . As discussed below, additional flash units may also be or act as heat exchangers.

In the second flash unit 314, additional moisture is removed from the _CO2 during the second flash process. The moisture removed from the CO ₂ is exhausted from the second flash unit 314 through a second moisture exhaust line 316 and provided to a second mixer 335 . The second air stream is provided to the second flash unit 314 through the second air line 315 . During the second flash process in the second flash unit 314, heat is transferred from the CO ₂ to the second air stream. The second heated air stream is exhausted from the second flash unit 314 and provided to the mixer 330 through the second heated air line 315b. CO ₂ is withdrawn from the second flash unit 314 through the second CO ₂ discharge line 317 and provided to the first compressor unit 318 .

The first compressor unit 318 compresses the CO ₂ to an increased pressure and the pressurized CO ₂ is discharged to the first heat exchanger 380 through the first compressor discharge line 319 . The first heat exchanger 380 is a first intercooler. A first intercooler air stream is provided to first intercooler 380 via first intercooler air line 380a. In the first intercooler 380 heat is transferred from the CO ₂ to the first intercooler air stream. The first heated intercooler air stream exits the first intercooler 380 through the first intercooler via heated air line 380b and is provided to the mixer 330 . The CO ₂ exhausted from the first intercooler 380 is provided to the third flash unit 320 through the first intercooler exhaust line 319a. _CO2 is provided to the third flash unit 320 in a temperature range of about 90°C to about 235°C.

In the third flash unit 320 additional moisture is removed from the CO ₂ and provided to the second mixer 335 through the third moisture discharge line 322 . The third air stream is provided to the third flash unit 320 through the third air line 321a. In the third flash unit 320, heat is transferred from the _CO2 to the third air stream during the third flash process. A third stream of heated air is discharged from the third flash unit 320 through a third heated gas line 321 b and provided to a mixer 330 . CO ₂ is withdrawn from the third flash unit 320 through a third CO ₂ discharge line 323 and provided to a second compressor unit 324 .

The second compressor unit 324 compresses the CO ₂ to an increased pressure. The pressurized CO ₂ is discharged to the second heat exchanger 382 through the second compressor discharge line 325 . The second heat exchanger 382 is a second intercooler. The second intercooler air stream is provided to the second intercooler 382 via the second intercooler air line 331a. In the second intercooler 382 heat is transferred from the CO ₂ to the second intercooler air stream. The second heated intercooler air stream exits the second intercooler 382 through the second intercooler via heated air line 331 b and is provided to the mixer 330 . The CO ₂ exhausted from the second intercooler 382 is provided to the fourth flash unit 326 through the second intercooler exhaust line 325b. _CO2 is provided to the fourth flash unit 316 in a temperature range of about 90°C to about 235°C.

In the fourth flash unit 326 additional moisture is removed from the CO ₂ and provided to the second mixer 335 through a fourth moisture discharge line 328 . The fourth air stream is provided to the fourth flash unit 326 via the fourth air line 327a. In the fourth flash unit 326, heat is transferred from the _CO2 to the fourth air stream during the fourth flash process. A fourth stream of heated air is exhausted from the fourth flash unit 326 through a fourth heated air line 327 b and provided to a mixer 330 . The CO ₂ is exhausted from the fourth flash unit 326 through a fourth CO ₂ exhaust line 329 and is available for further processing.

As discussed above, the heated air lines passing through the first heated air line 309b, the second heated air line 315b, the third heated air line 321b and the fourth heated air line 327b and the first intercooler respectively 315b and the second intercooler through the heated air line 331b, the heated air from the first flash unit 310, the second flash unit 314, the third flash unit 320 and the fourth flash unit 326 and the heated air from the first The heated air from the intercooler 380 and the second intercooler 382 is provided to the mixer 330 forming a reuse heated air line 330b.

In another embodiment, one or more flash units and one or more intercoolers may be used to provide heated air to mixer 330 . In another embodiment, heated air lines may be combined and/or excluded by one or more mixers and/or bypasses to form reuse heated air line 330b. In one embodiment, the first, second, third and fourth air streams and the first and second intercooler air streams are initially at ambient temperature to about 65°C. In one embodiment, the flash and intercooling process heats the air to a temperature between about 65°C and about 180°C.

In another embodiment, heated air from air lines 315 , 331 , and 337 may be exhausted from CO ₂ compression process 120 and/or provided to mixer 330 in any combination. In yet another embodiment, fewer or more flash units 310, 314, 320, 326 and compressor units 318, 325 may be used depending on the amount of compression achieved by each unit and the amount of pressurization desired.

As can be further seen in FIG. 1 , heated air from the CO ₂ compression process 120 is provided from the mixer 330 to the waste heat reuse process 130 through the reuse heated air line 330b. The waste heat reuse process 130 is a fuel treatment process. In this exemplary embodiment, the waste heat reuse process 130 is a coal pulverization process with a drying process. The heated air is provided to damper 410 , which may bypass some of the heated air before exhausting it through line 411 . This heated air is combined with additional heated air from additional heated air line 412 . Additional heated air may be provided by at least one regenerative air heater (not shown) or other source typically found in a power plant. At least some of the additional heated air may be bypassed by the second damper 413 .

The heated air and additional heated air are combined in primary air line 414 . The primary air line 414 is in fluid communication with an air flow device 415 that controls the volume and velocity of air in the primary air line 414 . In one embodiment, the air movement device 415 may be a primary air (PA) fan. The flow rate of heated air in primary air line 414 is measured by flow measurement device 416 . In one embodiment, the flow measurement device may be a pitot tube.

The heated air is provided to a pulverizer 420 where it contacts the fossil fuel provided to the pulverizer 420 through a feed line 421 . The fossil fuel may be coal fuel. In one embodiment, the coal fuel may be a high moisture coal such as, but not limited to, bituminous or sub-bituminous coal.

In the pulverizer, heated air removes moisture from the coal and/or preheats the coal. The pulverized coal and heated air exit the pulverizer through pulverized fuel feed line 422 . In this way, heated air from flash units 310, 314, 320, and 326 can be used to dry the coal. The pulverized coal and heated air are supplied to a boiler (not shown) for combustion. In one embodiment, coal and heated air are provided to the boiler at a temperature between about 50°C and about 80°C. In another embodiment, one or more pulverizers 420 may be used to process the coal.

In another embodiment of the invention, the CO ₂ removal process 110 ( FIG. 1 ) is the ammonia-based process 111 shown in FIG. 2 . Referring to Figure 2, the ammonia based process 111 comprises a _CO2 absorption unit 1101, hereinafter referred to as "absorption unit 1101", arranged to contact the gas stream to be purified and the scrubbing liquid stream. The gas flow may be a flue gas flow. The wash liquid stream includes ammonia. The scrubbing stream removes pollutants including _CO2 from the flue gas.

The flue gas from which CO ₂ is to be removed is supplied to the CO ₂ absorption unit 1101 through line 1102 . The flue gas may be cooled by a first heat exchanger 1121 before entering the absorption unit 1101 . In the _CO2 absorption unit 1101, the flue gas is contacted with a scrubbing liquid. The contacting of the flue gas with the wash solution can be effected by bubbling the flue gas through the wash solution or by spraying the wash solution into the flue gas. The wash solution is supplied to the _CO2 absorption unit through line 1103. In the absorption unit 1101 the _CO2 in the flue gas is absorbed in the scrubbing liquid by forming ammonium carbonate or ammonium bicarbonate either in dissolved or solid form. The used wash solution containing absorbed _CO2 leaves the absorption unit 1101 through line 1104 and is sent to a stripping unit 1111 where the _CO2 is separated from the wash solution. The separated CO ₂ exits the stripping unit through line 1112 and is provided to CO ₂ compression process 120 ( FIG. 1 ). The flue gas depleted of CO ₂ leaves the absorption unit 1101 through line 1105 .

The cooled ammonia process 111 further includes a water wash unit 1106 . The water wash unit 1106 is configured to contact the CO ₂ -depleted flue gas with a second wash water. The second washing water is supplied to the water washing unit 1106 through the line 1107 . In the water washing unit 1106, pollutants remaining in the depleted flue gas, such as ammonia, are absorbed in the washing water. Wash water containing absorbed contaminants exits the water wash unit through line 1108 . The depleted flue gas from which pollutants have been removed exits the water washing unit 1106 through line 1109 . The second washing water may be recovered through the regeneration unit 1110 in which pollutants are separated from the second washing water. In yet another embodiment, other CO ₂ capture processes may be used to provide CO ₂ to the CO ₂ compression process 120 .

In yet another embodiment of the invention, the waste heat reuse process 130 (FIG. 1) is a lignite drying process. One embodiment of a lignite drying process 500 is shown in FIG. 3 . Referring to FIG. 3 , heated air from the CO ₂ compression process 120 ( FIG. 1 ) is provided to the fluidized bed reactor 510 through a heated air supply line 511 . Heated air supply line 511 receives heated air line 331 of CO ₂ compression process 120 ( FIG. 1 ). Heated air removes moisture from lignite supplied to the fluidized bed via lignite feed line 512 . The lignite is coarsely ground by the lignite coarse grinder 513 before being supplied to the fluidized bed reactor 510 to reduce the particle size of the lignite. In another embodiment, one or more coarse grinders 513 may be used.

In the fluidized bed reactor 510, the lignite is contacted with heated air and moisture is removed from the lignite. Heated air from the _CO2 compression process may be combined with heated air from a regenerative air heater or other source before being introduced into the fluidized bed reactor 510. In one embodiment, heated air may be provided to the fluidized bed reactor at a temperature up to about 80°C. In another embodiment, heated air from separate sources may be provided to fluidized bed reactor 510 separately. Thus, the present invention utilizes waste heat to dry lignite or to perform supplementary drying of lignite, as opposed to conventional lignite drying operations that use steam to dry lignite. Thus, the present invention reduces the steam used in the operation of the plant.

The heated air containing moisture exits fluidized bed reactor 510 through discharge line 514 and is provided to separator 515 . Separator 515 may be an electrostatic precipitator. At separator 515, any solids, including any lignite, are separated from the heated air containing moisture. Solids exit the separator through discharge line 516 . The heated air containing moisture exits separator 515 through exhaust line 517 . The heated air containing the moisture can then either be returned to the fluidized bed reactor via line 518 and fan 519, released to the atmosphere via line 520, or provided to vapor condenser 521 to extract from the gas exiting via line 522 Moisture and/or vapor condensates are further separated off. Cooling fluid may be provided to vapor condenser 521 via feed line 523 and return line 524 . The cooling fluid removes heat from the heated air containing moisture to further condense the moisture.

At fluidized bed reactor 510 , the lignite from which moisture has been removed is discharged through discharge line 525 . The lignite is then cooled by cooler 526 and provided to mill 527 to further reduce the lignite particle size. The dried lignite is then combined with any lignite separated from the dust collector and discharged via line 530 to a boiler (not shown). In another embodiment, heated air from the CO ₂ compression process 120 ( FIG. 1 ) may be used to remove moisture from the lignite before the lignite is provided to the at least one lignite coarse grinder 513 . In this example, heated air may contact lignite in a second fluidized bed reactor (not shown).

Another embodiment of a lignite drying process 500 according to the present disclosure is shown in FIG. 4 . As can be seen in Figure 4, a dryer 510a is used in place of the fluidized bed reactor 510 of the embodiment depicted in Figure 3 . Referring to FIG. 4 , heated air from the CO ₂ compression process 120 ( FIG. 1 ) is provided to dryer 510 a through heated air supply line 511 . Heated air circulates through tube 545 in dryer 510a and does not contact the lignite. The heated air heats the lignite and causes moisture to be removed from the lignite. Moisture is removed from dryer 510a through discharge line 514 . The heated air that has lost heat to the lignite then exits dryer 510a through discharge line 531 . Other components in FIG. 4 are the same as those described in the embodiment shown in FIG. 3 .

While only certain features and embodiments of the present invention have been shown and described, many modifications and changes (for example, size, dimension, structure, shape and proportion of various elements, parameters such as but not limited to temperature, pressure), mounting arrangement, use of materials, pigments, orientation, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in the claims. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention. Furthermore, in an effort to provide a concise description of the exemplary embodiments, not all features of an actual implementation (i.e., those not related to the best mode presently contemplated of carrying out the invention, or to enabling the practice of the claimed invention) may not be described. those not connected). It should be appreciated that when developing any such actual implementation, as in any engineering or design project, many implementation-specific decisions may be made. Such a development effort could be complex and time-consuming, but nonetheless would be a routine undertaking of design, production, and fabrication for those of ordinary skill having the benefit of this disclosure without undue experimentation.

Claims (22)

CLAIMS 1. A method for heating fuel provided to a combustion system, the method comprising: separating a substantial amount of _CO2 from the first gas stream leaving the combustor to provide a _CO2 gas stream; compressing the _CO2 gas stream to provide a compressed _CO2 gas stream; cooling the compressed _CO2 gas stream with the first air stream to thereby provide a heated first air stream and a cooled _CO2 gas stream; and The fuel supplied to the combustion system is heated by the heated first air flow. 2. The method of claim 1, wherein cooling the compressed _CO2 gas stream comprises: providing said _CO2 gas stream and said first air stream to a flash unit; flashing the _CO gas stream in the flash unit; and Heat is exchanged between the flashed _CO2 gas stream and the first air stream to provide a heated first air stream and a cooled _CO2 gas stream. 3. The method of claim 1, wherein separating _CO2 from the first gas stream comprises: Absorbing _CO2 using a wash solution with an absorbent in an absorption unit to form a wash solution with absorbed _CO2 ; The _CO2 is stripped from the wash with absorbed _CO2 to provide a _CO2 gas stream. 4. The method of claim 3, wherein the absorbent comprises an ammonium compound. 5. The method of claim 3, wherein the absorbent comprises ammonia. 6. The method of claim 2, wherein the flash unit is a heat exchanger. 7. The method of claim 6, wherein the heat exchanger is an intercooler. 8. The method of claim 1, wherein the fuel is at least one of pulverized coal or pulverized lignite. 9. The method of claim 8, wherein the heated first air flow directly heats the fuel and fluidly provides the fuel to the combustion system. 10. The method of claim 6, further comprising: heating the second air stream with a second heat exchanger to provide a heated second air stream; combining the heated first air flow and the heated second air flow; and The fuel is heated with the combined heated first and second airflows. 11. The method of claim 2, wherein cooling the _CO2 gas stream comprises: providing a _CO2 gas stream and a second air stream to a second flash unit; flashing the _CO gas stream in the second flash unit; and exchanging heat between a second flashed _CO2 gas stream and said second air stream to provide a heated second air stream and a cooled _CO2 gas stream; and The heated first air flow and the heated second air flow are mixed to provide a combined heated gas flow for heating the fuel. 12. The method of claim 11, wherein the second flash unit is a heat exchanger. 13. A combustion system comprising: a _CO2 capture system having an absorption unit and a stripping unit to separate a substantial amount of _CO2 from the first gas stream leaving the combustor to provide a _CO2 gas stream; a compressor for compressing said _CO2 gas stream; a heat exchanger configured for exchanging heat between the _CO2 gas stream and the first air stream to thereby provide a cooled _CO2 gas stream and a heated first air stream; and A fuel processing system for preparing fuel for the combustion system, wherein the heated first airflow is used to heat the fuel provided to the combustion system. 14. The combustion system of claim 13, wherein the heat exchanger is configured as a flash unit, and wherein the _CO2 gas stream is flashed in the flash unit. 15. The combustion system of claim 13, further comprising: an absorption unit for contacting said first gas stream and a wash solution with an absorbent to absorb _CO to form a wash solution with absorbed _CO ; and A stripping unit that strips CO _{2 from the wash with absorbed CO 2 to} provide a CO ₂ gas stream. 16. The combustion system of claim 15, wherein the absorbent comprises an ammonium compound. 17. The combustion system of claim 15, wherein the absorbent comprises ammonia. 18. The combustion system of claim 13, wherein the heat exchanger is an intercooler. 19. The combustion system of claim 13, wherein the fuel is at least one of pulverized coal or pulverized lignite. 20. The combustion system of claim 19, wherein the heated first air flow directly heats the fuel and fluidly provides the fuel to the combustion system. 21. The combustion system of claim 14, further comprising: A second flash unit that receives the _CO gas stream and a second air stream to flash the _CO gas stream in the second flash unit and flash the _CO gas in the second flash unit flow and said second air flow, thereby providing a heated second air flow and a cooled _CO2 gas flow; and A mixer that combines the heated first air flow and the heated second air flow to provide a combined heated air flow for heating the fuel. 22. The combustion system of claim 13, further comprising: a second heat exchanger receiving the _CO2 gas stream and the second air stream to exchange heat between the compressed _CO2 gas stream and the second air stream to provide heated second air stream and cooling _CO2 gas flow; and A mixer that combines the heated first air flow and the heated second air flow to provide a combined heated air flow for heating the fuel.