ARRANGEMENTS FOR CHEMICAL LOOPING COMBUSTION SYSTEMS

Abstract

The invention discloses partial conversion of a hydrocarbon fuel to CO and H.sub.2 within a heat exchanger reformer, prior to injection of the fuel into fuel reactor of a chemical looping combustion system, including reforming portion of the fuel used for the chemical looping combustion system in the heat exchange reformer through reaction with steam and/or other suitable gas, or reforming portion of the fuel used for the chemical looping combustion system in the heat exchange reformer through reaction with recycled flue gas. The invention further discloses the use of recycled flue gas, without the use of a heat exchange reformer prior to injection of the fuel into the fuel reactor of a chemical looping combustion system.

Claims

1. A process for a chemical looping combustion, comprising: compressing ambient air in an air compressor to produce a compressed air; feeding the compressed air into an air reactor; reacting the compressed air with a reduced metal oxide contained within the air reactor to produce an oxidized metal oxide; moving the oxidized metal oxide from the air reactor to a fuel reactor in communication with the air reactor; mixing a fuel gas with steam to produce a mixture of fuel gas and steam; feeding the mixture of fuel gas and steam to a heat exchanger reformer to produce a reformed gas; feeding the reformed gas to the fuel reactor to react with the oxidized metal oxide in the fuel reactor to produce a gaseous combustion product and the reduced metal oxide; and moving the reduced metal oxide from the fuel reactor to the air reactor.

2. The process as claimed in claim 1, wherein the gaseous combustion product exiting the fuel reactor is cooled in a first heat exchanger or in the heat exchanger reformer.

3. The process as claimed in claim 1 or 2, further comprising pre-heating the compressed air in a second heat exchanger and feeding the preheated compressed air into an air reactor connected to the second heat exchanger.

4. The process as claimed in any one of claims 1 to 3, further comprising preheating a fuel gas in a third heat exchanger to produce a preheated fuel gas.

5. The process as claimed in any one of claims 1 to 4, wherein the heat exchange reformer sources heat from: the fuel reactor, the gaseous combustion product from the fuel reactor, or the air reactor.

6. A process for a chemical looping combustion, comprising: compressing ambient air in an air compressor to produce a compressed air; feeding the compressed air into an air reactor; reacting the compressed air with a reduced metal oxide contained within the air reactor to produce an oxidized metal oxide; moving the oxidized metal oxide from the air reactor to a fuel reactor in communication with the air reactor; mixing a fuel gas with a recycled flue gas to produce a mixture of the fuel gas with the recycled flue gas; feeding the mixture of the fuel gas with the recycled flue gas to a heat exchanger reformer to produce a reformed gas; feeding the reformed gas to the fuel reactor to react with the oxidized metal oxide in the fuel reactor to produce a gaseous combustion product and the reduced metal oxide; moving the reduced metal oxide from the fuel reactor to the air reactor; feeding a portion of the gaseous combustion product to a recycle compressor to produce the recycled flue gas; and feeding a remaining portion of the gaseous combustion product to a condensing heat exchanger for water removal before scrubbing and cooling the remaining gas in a direct contact cooler.

7. The process as claimed in claim 6, wherein the gaseous combustion product exiting the fuel reactor is cooled in a first heat exchanger or in the heat exchanger reformer before being fed to a recycle compressor.

8. The process as claimed in claim 6 or 7, further comprising pre-heating the compressed air in a second heat exchanger and feeding the preheated compressed air into an air reactor connected to the second heat exchanger.

9. The process as claimed in any one of claims 6 to 8, further comprising preheating a fuel gas in a third heat exchanger to produce a preheated fuel gas.

10. The process as claimed in any one of claims 6 to 9, wherein the heat exchange reformer sources heat from: the fuel reactor, the gaseous combustion product from the fuel reactor, or the air reactor.

11. A process for a chemical looping combustion, comprising: compressing ambient air in an air compressor to produce a compressed air; feeding the compressed air into an air reactor; reacting the compressed air with a reduced metal oxide contained within the air reactor to produce an oxidized metal oxide; moving the oxidized metal oxide from the air reactor to a fuel reactor in communication with the air reactor; mixing a fuel gas with a recycled flue gas to produce a mixture of the fuel gas with the recycled flue gas; feeding the mixture of the fuel gas with the recycled flue gas to a heat exchanger reformer to produce a reformed gas; feeding the reformed gas to the fuel reactor to react with the oxidized metal oxide in the fuel reactor to produce a gaseous combustion product and the reduced metal oxide; moving the reduced metal oxide from the fuel reactor to the air reactor; feeding the gaseous combustion product to a condensing heat exchanger for water removal to produce a partially condensed gaseous combustion product; feeding a portion of the partially condensed gaseous combustion product to a recycle compressor to produce the recycled flue gas; and feeding a remaining portion of the partially condensed gaseous combustion product for scrubbing and cooling in a direct contact cooler.

12. The process as claimed in claim 11, wherein the gaseous combustion product exiting the fuel reactor is cooled in a first heat exchanger or in the heat exchanger reformer before being fed to the condensing heat exchanger.

13. The process as claimed in claim 11 or 12, further comprising pre-heating the compressed air in a second heat exchanger and feeding the preheated compressed air into an air reactor connected to the second heat exchanger.

14. The process as claimed in any one of claims 11 to 13, further comprising preheating a fuel gas in a third heat exchanger to produce a preheated fuel gas.

15. The process as claimed in any one of claims 11 to 14, wherein the heat exchange reformer sources heat from: the fuel reactor, the gaseous combustion product from the fuel reactor, or the air reactor.

16. A process for a chemical looping combustion, comprising: compressing ambient air in an air compressor to produce a compressed air; feeding the compressed air into an air reactor; reacting the compressed air with a reduced metal oxide contained within the air reactor to produce an oxidized metal oxide; moving the oxidized metal oxide from the air reactor to a fuel reactor in communication with the air reactor; mixing a fuel gas with a recycled flue gas to produce a mixture of the fuel gas with the recycled flue gas; feeding the mixture of the fuel gas with the recycled flue gas to a heat exchanger reformer to produce a reformed gas; feeding the reformed gas to the fuel reactor to react with the oxidized metal oxide in the fuel reactor to produce a gaseous combustion product and the reduced metal oxide; moving the reduced metal oxide from the fuel reactor to the air reactor; feeding the gaseous combustion product to a condensing heat exchanger for water removal to produce a partially condensed gaseous combustion product; feeding the partially condensed gaseous combustion product for scrubbing and cooling in a direct contact cooler to produce a purified CO.sub.2 product; and feeding a portion of the CO.sub.2 to the recycle compressor to produce the recycled flue gas.

17. The process as claimed in claim 11, wherein the gaseous combustion product exiting the fuel reactor is cooled in a first heat exchanger or in the heat exchanger reformer before being fed to the condensing heat exchanger.

18. The process as claimed in claim 11 or 12, further comprising pre-heating the compressed air in a second heat exchanger and feeding the preheated compressed air into an air reactor connected to the second heat exchanger.

19. The process as claimed in any one of claims 11 to 13, further comprising preheating a fuel gas in a third heat exchanger to produce a preheated fuel gas.

20. The process as claimed in any one of claims 15 to 19, wherein the heat exchange reformer sources heat from: the fuel reactor, the gaseous combustion product from the fuel reactor, or the air reactor.

21. The process as claimed in claim 1, combined or supplemented with the process as claimed in any one of claims 6, 10 and 16.

22. The process as claimed in any one of claims 1 to 21, wherein the heat exchanger reformer is in a separate process vessel from the fuel reactor.

23. The process as claimed in any one of claims 1 to 21, wherein the heat exchanger reformer comprises a plurality of vertically disposed catalyst tubes containing catalyst bed filling a portion of the catalyst tubes, the plurality of vertically disposed catalyst tubes of the heat exchange reformer are contained within freeboard of the fuel reactor but are maintained separate from a fluidized bed entrained with the oxidized metal oxide, said fluidized bed contained within the fuel reactor.

24. The process as claimed in any one of claims 1 to 21, wherein the heat exchanger reformer comprises a plurality of vertically disposed catalyst tubes containing catalyst bed filling a portion of the catalyst tubes, the plurality of vertically disposed catalyst tubes of the heat exchange reformer are contained within freeboard of the air reactor but are maintained separate from a fluidized bed entrained with the reduced metal oxide, said fluidized bed contained within the air reactor.

25. The process as claimed in any one of claims 1 to 21, wherein the heat exchanger reformer comprises a plurality of vertically disposed catalyst tubes containing catalyst bed filling a portion of the catalyst tubes, the plurality of vertically disposed catalyst tubes of the heat exchange reformer are in contact with both the gaseous combustion product exiting the fuel reactor in the freeboard and are also in contact with a fluidized bed entrained with the oxidized metal oxide, said fluidized bed contained within the fuel reactor.

26. The process as claimed in any one of claims 1 to 21, wherein the heat exchanger reformer comprises a plurality of vertically disposed catalyst tubes containing catalyst bed filling a portion of the catalyst tubes, the plurality of vertically disposed catalyst tubes of the heat exchange reformer are in contact with both gaseous combustion product exiting the air reactor in the freeboard and are also in contact with a fluidized bed entrained with the reduced metal oxide, said fluidized bed contained within the air reactor.

27. The process as claimed in any one of claims 1 to 21, wherein the heat exchanger reformer comprises a plurality of vertically disposed catalyst tubes containing catalyst bed filling a portion of the catalyst tubes, the plurality of vertically disposed catalyst tubes of the heat exchange reformer are contained within a fluidized bed entrained with the reduced metal oxide, said fluidized bed contained within the air reactor.

28. A process for a chemical looping combustion, comprising: compressing ambient air in an air compressor to produce a compressed air; feeding the compressed air into an air reactor; reacting the compressed air with a reduced metal oxide contained within the air reactor to produce an oxidized metal oxide; moving the oxidized metal oxide from the air reactor to a fuel reactor in communication with the air reactor; mixing a fuel gas with a recycled flue gas to produce a mixture of the fuel gas with the recycled flue gas; feeding the mixture of the fuel gas with the recycled flue gas to the fuel reactor to react with the oxidized metal oxide in the fuel reactor to produce a gaseous combustion product and the reduced metal oxide; moving the reduced metal oxide from the fuel reactor to the air reactor; feeding a portion of the gaseous combustion product to a recycle compressor to produce the recycled flue gas; and feeding a remaining portion of the gaseous combustion product to a condensing heat exchanger for water removal before scrubbing and cooling the remaining gas in a direct contact cooler.

29. A process for a chemical looping combustion, comprising: compressing ambient air in an air compressor to produce a compressed air; feeding the compressed air into an air reactor; reacting the compressed air with a reduced metal oxide contained within the air reactor to produce an oxidized metal oxide; moving the oxidized metal oxide from the air reactor to a fuel reactor in communication with the air reactor; mixing a fuel gas with a recycled flue gas to produce a mixture of the fuel gas with the recycled flue gas; feeding the mixture of the fuel gas with the recycled flue gas to the fuel reactor to react with the oxidized metal oxide in the fuel reactor to produce a gaseous combustion product and the reduced metal oxide; moving the reduced metal oxide from the fuel reactor to the air reactor; feeding the gaseous combustion product to a condensing heat exchanger for water removal to produce a partially condensed gaseous combustion product; feeding a portion of the partially condensed gaseous combustion product to a recycle compressor to produce the recycled flue gas; and feeding a remaining portion of the partially condensed gaseous combustion product for scrubbing and cooling in a direct contact cooler.

30. A process for a chemical looping combustion, comprising: compressing ambient air in an air compressor to produce a compressed air; feeding the compressed air into an air reactor; reacting the compressed air with a reduced metal oxide contained within the air reactor to produce an oxidized metal oxide; moving the oxidized metal oxide from the air reactor to a fuel reactor in communication with the air reactor; mixing a fuel gas with a recycled flue gas to produce a mixture of the fuel gas with the recycled flue gas; feeding the mixture of the fuel gas with the recycled flue gas to the fuel reactor to react with the oxidized metal oxide in the fuel reactor to produce a gaseous combustion product and the reduced metal oxide; moving the reduced metal oxide from the fuel reactor to the air reactor; feeding the gaseous combustion product to a condensing heat exchanger for water removal to produce a partially condensed gaseous combustion product; feeding the partially condensed gaseous combustion product for scrubbing and cooling in a direct contact cooler to produce a purified CO.sub.2 product; and feeding a portion of the CO.sub.2 to the recycle compressor to produce the recycled flue gas.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0134] By way of example only, embodiments of the present invention are described hereinafter with reference to the accompanying drawings, wherein:

[0135] FIG. 1 is a schematic representation of an embodiment of a configuration of a known chemical looping combustion system (prior art);

[0136] FIG. 2a is a schematic representation of an embodiment wherein gaseous fuel is mixed with steam and then sent to a heat exchanger reformer in a chemical looping combustion system according to the present invention;

[0137] FIG. 2b is a schematic representation of another embodiment wherein gaseous fuel is mixed with steam and then sent to a heat exchanger reformer in a chemical looping combustion system according to the present invention;

[0138] FIG. 2c is a schematic representation of a further embodiment wherein gaseous fuel is mixed with steam and then sent to a heat exchanger reformer in a chemical looping combustion system according to the present invention;

[0139] FIG. 3a is a schematic representation of an embodiment wherein gaseous fuel is mixed with recycled flue gas and then sent to a heat exchanger reformer in a chemical looping combustion system according to the present invention;

[0140] FIG. 3b is a schematic representation of another embodiment wherein gaseous fuel is mixed with recycled flue gas and then sent to a heat exchanger reformer in a chemical looping combustion system according to the present invention;

[0141] FIG. 3c is a schematic representation of a further embodiment wherein gaseous fuel is mixed with recycled flue gas and then sent to a heat exchanger reformer in a chemical looping combustion system according to the present invention;

[0142] FIG. 4a is a schematic representation of an embodiment wherein gaseous fuel is mixed with recycled flue gas which has been partially condensed in a scrubber or similar device, drawn before a direct contact cooler and then sent to a heat exchanger reformer in a chemical looping combustion system according to the present invention;

[0143] FIG. 4b is a schematic representation of another embodiment wherein gaseous fuel is mixed with recycled flue gas which has been partially condensed in a scrubber or similar device, drawn before a direct contact cooler and then sent to a heat exchanger reformer in a chemical looping combustion system according to the present invention;

[0144] FIG. 4c is a schematic representation of a further embodiment wherein gaseous fuel is mixed with recycled flue gas which has been partially condensed in a scrubber or similar device, drawn before a direct contact cooler and then sent to a heat exchanger reformer in a chemical looping combustion system according to the present invention;

[0145] FIG. 5a is a schematic representation of an embodiment wherein gaseous fuel is mixed with recycled flue gas which has been drawn after a direct contact cooler and then sent to a heat exchanger reformer in a chemical looping combustion system according to the present invention;

[0146] FIG. 5b is a schematic representation of another embodiment wherein gaseous fuel mixed with recycled flue gas which has been drawn after a direct contact cooler and then sent to a heat exchanger reformer in a chemical looping combustion system according to the present invention;

[0147] FIG. 5c is a schematic representation of a further embodiment wherein gaseous fuel mixed with recycled flue gas which has been drawn after a direct contact cooler and then sent to a heat exchanger reformer in a chemical looping combustion system according to the present invention;

[0148] FIG. 6 is a schematic representation of an embodiment of the physical configuration of a heat exchange reformer according to the present invention;

[0149] FIG. 7 is a schematic representation of another embodiment of the physical configuration of a heat exchange reformer according to the present invention;

[0150] FIG. 8 is a schematic representation of a further embodiment of the physical configuration of a heat exchange reformer according to the present invention;

[0151] FIG. 9 is a schematic representation of an additional embodiment of the physical configuration of a heat exchange reformer according to the present invention;

[0152] FIG. 10 is a schematic representation of an embodiment wherein gaseous fuel is mixed with recycled flue gas in a chemical looping combustion system according to the present invention;

[0153] FIG. 11 is a schematic representation of an embodiment wherein gaseous fuel is mixed with recycled flue gas which has been partially condensed in a scrubber or similar device, drawn before a direct contact cooler in a chemical looping combustion system according to the present invention; and

[0154] FIG. 12 is a schematic representation of an embodiment wherein gaseous fuel is mixed with recycled flue gas which has been drawn after a direct contact cooler in a chemical looping combustion system according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0155] It is to be understood that the disclosure is not limited in its application to the details of the embodiments as set forth in the following description. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. By way of example only, preferred embodiments of the present invention are described hereinafter with reference to the accompanying drawings.

[0156] Furthermore, it is to be understood that the terminology used herein is for the purpose of description and should not be regarded as limiting. Contrary to the use of the term consisting, the use of the terms including, containing, comprising, or having and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The use of the term a or an is meant to encompass one or more.

[0157] In this disclosure, the fuel is considered to be composed of alkanes, but a person skilled in the art would understand that the present invention is also applicable for any hydrocarbon fuel that can be injected into the chemical looping combustion system in a gas phase.

[0158] According to the present invention: [0159] (1) A heat exchange reformer is used to partially oxidize fuels in a chemical looping combustion system to increase the extent of fuel conversion or to reduce the relative increase or relative change in volumetric flow rate in fuel reactors in a chemical looping combustion system. [0160] (2) Recycling of the flue gas of a chemical looping combustion system is used to decrease the relative change in volumetric flow rate in the fuel reactor.

Reforming of Fuel for Chemical Looping Combustion System in a Heat Exchange Reformer to Address Low Reactivity and/or Gas Expansion

[0161] The process involves: [0162] 1. Reform at least a portion of the fuel used for a chemical looping combustion system in a heat exchange reformer through reaction with steam and/or other suitable gas containing components composed of oxides, [0163] or [0164] Reform at least a portion of the fuel used for a chemical looping combustion system in a heat exchange reformer through reaction with recycled flue gas. The recycled flue gas may be supplemented with steam and/or other suitable gas containing components composed of oxides. [0165] 2. Pass the reformed gas into the fuel reactor of a chemical looping combustion system in order to increase the extent of oxidation of the fuel/gas by reaction with an oxygen carrier. [0166] 3. Pass the oxygen carrier into an air reactor in which the oxygen carrier is oxidized by O.sub.2 thereby releasing heat. [0167] 4. Pass the oxidized oxygen carrier to the fuel reactor transferring both oxygen and heat to the fuel reactor thereby providing both the heat and the oxygen required for oxidation of the fuel to proceed. [0168] 5. Pass the hot flue gas from fuel reactor to the heat exchange reformer to provide the heat for the endothermic reforming reactions via indirect heat exchange for some embodiments, heat could also come from the air reactor for the heat exchange reformer.

[0169] According to a first embodiment of the invention shown in FIGS. 2a, 2b, and 2c, steam is used as a reforming gas.

[0170] In a preferred embodiment, the water to be vaporized is sourced from flue gas condensate and most preferably from high temperature condensate.

[0171] Referring to FIGS. 2a, 2b and 2c, ambient air is compressed, pre-heated in a heat exchanger HX1 and then sent to an air reactor 10. In the air reactor 10, oxygen in the air reacts with a reduced metal oxide, producing an oxidized metal oxide and a vitiated air stream, composed primarily of nitrogen. Heat is removed from the air reactor 10 via an in-bed heat exchanger HX2 and a convective heat exchanger HX3. The vitiated air stream is cooled in heat exchanger HX1 and filtered through a vitiated air filter 15 before being expanded in a vitiated air expander 20 to produce power to run an air compressor 30. The vitiated air is then vented to atmosphere.

[0172] In contrast to the process shown in FIG. 1 where gaseous fuel (fuel gas) is pre-heated in a heat exchanger HX5 and enters a fuel reactor 40, in FIGS. 2a, 2b and 2c, gaseous fuel (fuel gas) is pre-heated in a heat exchanger HX5, and mixed with steam and then sent to a heat exchanger reformer HX-R.

[0173] The heat exchange reformer HX-R can source heat from, for example, fuel reactor 40 (FIG. 2a), the exhaust gas from the fuel reactor 40 (FIG. 2b) or the air reactor 10 (FIG. 2c). The product is reformed gas (H.sub.2, CO, CO.sub.2, H.sub.2O), which is sent to the fuel reactor 40 which comprises a heat exchanger HX6 where it reacts with the oxidized metal oxide to produce gaseous combustion products (H.sub.2O, CO.sub.2) and reduced metal oxide.

[0174] The combustion products are subsequently cooled in a heat exchanger HX7 in FIGS. 2a and 2c or HX-R in FIG. 2b, heat exchangers HX5 and HX8. Water is then removed in a condensing heat exchanger HX9 before the gas is scrubbed and cooled further in a direct contact cooler 50 which comprises a heat exchanger HX10 to produce a purified CO.sub.2 product. The CO.sub.2 product is then further dried by a heat exchanger HX11 and compressed by a CO.sub.2 compressor 70.

[0175] The position of the heat exchange reformer HX-R in FIGS. 2a, 2b and 2c differs from each other. The selection of the reformer HX-R position is based on optimizing the heat exchange network for the overall process, which is significantly impacted by the metal oxide selected for use in the fuel reactor 40 and the air reactor 10. The options presented herewith are the locations with high temperature heat required for the reformer.

[0176] According to a second embodiment of the invention (see FIGS. 3a, 3b and 3c), recycled flue gas is used as a reforming gas; it is recycled from a location in the flue gas processing train above the dew point of water in the flue gas.

[0177] Instead of using steam as shown in FIGS. 2a, 2b and 2c, recycled flue gas is used as a reforming gas as shown in FIGS. 3a, 3b and 3c.

[0178] Referring to FIGS. 3a, 3b and 3c, ambient air is compressed, pre-heated in a heat exchanger HX1 and then sent to an air reactor 10. In the air reactor 10, oxygen in the air reacts with a reduced metal oxide, producing an oxidized metal oxide and a vitiated air stream, composed primarily of nitrogen. Heat is removed from the air reactor 10 via an in-bed heat exchanger HX2 and a convective heat exchanger HX3. The vitiated air stream is cooled in heat exchanger HX1 and filtered through a vitiated air filter 15 before being expanded in a vitiated air expander 20 to produce power to run an air compressor 30. The vitiated air is then vented to atmosphere.

[0179] In contrast to the process shown in FIGS. 2a, 2b and 2c, where gaseous fuel (fuel gas) is pre-heated in a heat exchanger HX5, and then mixed with steam and then sent to a heat exchanger reformer HX-R, in FIGS. 3a, 3b and 3c, gaseous fuel is mixed with recycled flue gas (H.sub.2O, CO.sub.2), pre-heated in a heat exchanger HX5, and then sent to a heat exchanger reformer HX-R. The heat exchange reformer HX-R can source heat from fuel reactor 40 (FIG. 3a), the exhaust gas from the fuel reactor 40 (FIG. 3b) or the air reactor 10 (FIG. 3c). The product is reformed gas (H.sub.2, CO, CO.sub.2, H.sub.2O), which is sent to the fuel reactor 40 which comprises a heat exchanger HX6 where it reacts with the oxidized metal oxide to produce gaseous combustion products (H.sub.2O, CO.sub.2) and reduced metal oxide. The combustion products are subsequently cooled in a heat exchanger HX7 in FIGS. 3a and 3c or HX-R in FIG. 3b, heat exchangers HX5 and HX8. A portion of the flue gas is then sent to a recycle compressor 60 to function as the reforming gas. The balance of the flue gas is sent to a condensing heat exchanger HX9 for bulk water removal before the gas is scrubbed and cooled further in a direct contact cooler 50 which comprises a heat exchanger HX10 to produce a purified CO.sub.2 product. The CO.sub.2 product is then further dried by a heat exchanger HX11 and compressed by a CO.sub.2 compressor 70.

[0180] Similar to FIGS. 2a, 2b and 2c, the position of the heat exchange reformer HX-R in FIGS. 3a, 3b and 3c differs from each other. The selection of the reformer HX-R position is based on optimizing the heat exchange network for the overall process, which is significantly impacted by the metal oxide selected for use in the fuel reactor 40 and the air reactor 10. The options presented herewith are the locations with high temperature heat required for the heat exchange reformer HX-R.

[0181] According to a third embodiment of the invention, the recycled flue gas is used as a reforming gas. In contrast to the second embodiment shown in FIGS. 3a, 3b and 3c, the recycled flue gas in the third embodiment is recycled from a location at which the flue gas has been partially condensed in a scrubber or similar device that removes particulate matter from the flue gas. Adjusting the temperature of the scrubber allows the hydrogen to carbon ratio of the recycled flue gas to be easily adjusted in order to achieve a desirable reformed gas composition. See FIGS. 4a, 4b, and 4c.

[0182] In a preferred embodiment, the heat transferred to the heat exchange reformer HX-R is sourced from HX6 or HX7 (FIGS. 4a and 4b, respectively).

[0183] Referring to FIGS. 4a, 4b and 4c, ambient air is compressed, pre-heated in a heat exchanger HX1 and then sent to an air reactor 10. In the air reactor 10, oxygen in the air reacts with a reduced metal oxide, producing an oxidized metal oxide and a vitiated air stream, composed primarily of nitrogen. Heat is removed from the air reactor 10 via an in-bed heat exchanger HX2 and a convective heat exchanger HX3. The vitiated air stream is cooled in heat exchanger HX1 and filtered through a vitiated air filter 15 before being expanded in a vitiated air expander 20 to produce power to run an air compressor 30. The vitiated air is then vented to atmosphere.

[0184] In contrast to the process shown in FIGS. 3a, 3b and 3c, the recycled flue gas is recycled from a location at which the flue gas has been partially condensed in a scrubber or similar device that removes particulate matter from the flue gas.

[0185] In FIGS. 4a, 4b and 4c, gaseous fuel is mixed with recycled flue gas (H.sub.2O, CO.sub.2), pre-heated in a heat exchanger HX5, and then sent to a heat exchanger reformer HX-R. The heat exchange reformer HX-R can source heat from fuel reactor 40 (FIG. 4a), the exhaust gas from the fuel reactor 40 (FIG. 4b) or the air reactor 10 (FIG. 4c). The product is reformed gas (H.sub.2, CO, CO.sub.2, H.sub.2O), which is sent to the fuel reactor 40 which comprises a heat exchanger HX6 where it reacts with the oxidized metal oxide to produce gaseous combustion products (H.sub.2O, CO.sub.2) and reduced metal oxide. The combustion products are subsequently cooled in a heat exchanger HX7 in FIGS. 4a and 4c or HX-R in FIG. 4b, heat exchangers HX5 and HX8. Water is then removed in a condensing heat exchanger HX9. A portion of the flue gas is sent to the recycle compressor 60 to function as the reforming gas. The balance of the flue gas is scrubbed and cooled further in a direct contact cooler 50 to produce a purified CO.sub.2 product. The CO.sub.2 product is then further dried by a heat exchanger HX11 and compressed by a CO.sub.2 compressor 70.

[0186] Similar to FIGS. 2a, 2b and 2c, the position of the heat exchange reformer HX-R in FIGS. 4a, 4b and 4c differs from each other. The selection of the reformer HX-R position is based on optimizing the heat exchange network for the overall process, which is significantly impacted by the metal oxide selected for use in the fuel reactor 40 and the air reactor 10. The options presented herewith are the locations with high temperature heat required for the heat exchange reformer HX-R.

[0187] According to a fourth embodiment of the invention, recycled flue gas is used as a reforming gas. In contrast to third embodiment shown in FIGS. 4a, 4b and 4c, in FIGS. 5a, 5b and 5c, the recycled flue gas is recycled from a location where the flue gas has been cooled and is composed primarily of unreacted fuel components and carbon dioxide.

[0188] Referring to FIGS. 5a, 5b and 5c, ambient air is compressed, pre-heated in a heat exchanger HX1 and then sent to an air reactor 10. In the air reactor 10, oxygen in the air reacts with a reduced metal oxide, producing an oxidized metal oxide and a vitiated air stream, composed primarily of nitrogen. Heat is removed from the air reactor 10 via an in-bed heat exchanger HX2 and a convective heat exchanger HX3. The vitiated air stream is cooled in heat exchanger HX1 and filtered through a vitiated air filter 15 before being expanded in a vitiated air expander 20 to produce power to run an air compressor 30. The vitiated air is then vented to atmosphere.

[0189] The difference between FIGS. 4a, 4b and 4c and FIGS. 5a, 5b and 5c is the location from which the recycled flue gas is taken. In FIGS. 4a, 4b and 4c, the recycled flue gas is drawn after HX9 and before the director contact cooler 50/HX10 whereas in FIGS. 5a, 5b and 5c, the recycle flue gas is drawn after the director contact cooler 50/HX10 but before the CO.sub.2 compressor 70.

[0190] In FIGS. 5a, 5b and 5c, gaseous fuel is mixed with recycled flue gas (H.sub.2O, CO.sub.2), pre-heated in a heat exchanger HX5, and then sent to a heat exchanger reformer HX-R. The heat exchange reformer HX-R can source heat from fuel reactor 40 (FIG. 5a), the exhaust gas from the fuel reactor 40 (FIG. 5b) or the air reactor 10 (FIG. 5c). The product is reformed gas (H.sub.2, CO, CO.sub.2, H.sub.2O), which is sent to the fuel reactor 40 which comprises a heat exchanger HX6 where it reacts with the oxidized metal oxide to produce gaseous combustion products (H.sub.2O, CO.sub.2) and reduced metal oxide. The combustion products are subsequently cooled in a heat exchanger HX7 in FIGS. 5a and 5c or HX-R in FIG. 5b, heat exchangers HX5 and HX8. Water is then removed in a condensing heat exchanger HX9 and is scrubbed and cooled further in a direct contact cooler 50 to produce a purified CO.sub.2 product. A portion of the CO.sub.2 is sent to the recycle compressor 60 to function as the reforming gas. The balance of the CO.sub.2 product is then further dried by a heat exchanger HX11 and compressed by a CO.sub.2 compressor 70.

[0191] Similar to FIGS. 2a, 2b and 2c, the position of the heat exchange reformer HX-R in FIGS. 4a, 4b and 4c differs from each other. The selection of the reformer HX-R position is based on optimizing the heat exchange network for the overall process, which is significantly impacted by the metal oxide selected for use in the fuel reactor 40 and the air reactor 10. The options presented herewith are the locations with high temperature heat required for the heat exchange reformer HX-R.

[0192] Regarding the second, third and fourth embodiments described above, the size of equipment, process efficiency and recycled flue gas condition (pressure, temperature, composition) are all impacted by where in the process the recycled flue gas is drawn from.

[0193] According to a fifth embodiment of the invention, any of the second, third and fourth embodiments described above where the recycled flue gas is used can be combined or supplemented with the first embodiment where steam and/or other suitable gases containing components composed of oxides.

[0194] Regarding the physical configurations of the heat exchange reformer HX-R as described above in the first, second, third, fourth and fifth embodiments, several different configurations can be applied.

[0195] According to the present invention, a first configuration of the heat exchange reformer HX-R is shown in FIG. 6.

[0196] Referring to FIG. 6, the fuel reactor 40 has a distributor 42 at the bottom of the fuel reactor 40. A fluidized bed 45 of entrained oxygen carrier bed material is configured within the fuel reactor 40. The heat exchange reformer HX-R is contained in a process vessel 80, said process vessel 80 is separated from the fuel reactor 40, as is currently practiced with heat exchange reformers associated with autothermal reforming and steam methane reforming. The heat exchange reformer HX-R comprises a plurality of vertically disposed catalyst tubes containing catalyst bed 90 which fill a portion of the catalyst tubes. The gas for heating the heat exchange reformer HX-R can come from the fuel reactor 40 or the air reactor 10 as described above (see for example FIGS. 2b, 3b and 4b for the configuration using gas from the fuel reactor).

[0197] According to the present invention, a second configuration of the heat exchange reformer HX-R is shown in FIG. 7.

[0198] Referring to FIG. 7, the plurality of vertically disposed catalyst tubes of the heat exchange reformer HX-R are contained within the freeboard of the fuel reactor 40 but are maintained separate from the fluidized bed 45. This configuration of the HX-R can be applied in the embodiments as shown in FIGS. 2a, 3a and 4a.

[0199] Similarly, in a third configuration of the heat exchange reformer HX-R, the plurality of vertically disposed catalyst tubes of the heat exchange reformer HX-R are located in the freeboard of the air reactor 10. This configuration of the HX-R can be applied in the embodiments shown in FIGS. 2c, 3c and 4c.

[0200] According to the present invention, a fourth configuration of the heat exchange reformer HX-R is shown in FIG. 8.

[0201] Referring to FIG. 8, the plurality of vertically disposed catalyst tubes of the heat exchange reformer HX-R are in contact with both the gases leaving the fuel reactor 40 in the freeboard and also with the oxygen carrier bed material entrained in the fluidized bed 45 in the fuel reactor 40. This configuration of the HX-R can be applied in the embodiments shown in FIGS. 2a, 3a and 4a.

[0202] Similarly, in a fifth configuration of the heat exchange reformer HX-R, the plurality of vertically disposed catalyst tubes of the heat exchange reformer HX-R are in contact with both the gases leaving the air reactor 10 in the freeboard and also with the oxygen carrier bed material entrained in the fluidized bed 105 in the fuel reactor 10. This configuration of the HX-R can be applied in the embodiments shown in FIGS. 2c, 3c and 4c.

[0203] According to the present invention, a sixth configuration of the heat exchange reformer HX-R is shown in FIG. 9.

[0204] Referring to FIG. 9, an air reactor 10 with a distributor 102 at the bottom of the air reactor 10 and a fluidized bed 105 entrained with oxygen carrier bed material configured within the air reactor 10 is shown. The plurality of vertically disposed catalyst tubes of the heat exchange reformer HX-R are located in fluidized bed 105 of the air reactor 10. This configuration of the HX-R can be applied in the embodiments shown in FIGS. 2c, 3c and 4c.

Recycle of Flue Gas

[0205] Instead of using a heat exchange reformer as described above to address the issue of low reactivity and/or gas expansion, the process involves: [0206] 1. Recycle a portion of the flue gas from the flue gas treatment system of a chemical looping combustion system back to the gas inlet of the fuel reactor with the fuel feed in order to achieve the desired volumetric gas expansion and to achieve a desired ratio of superficial velocity divided by minimum fluidization velocity. [0207] 2. Oxidize the fuel and recycled flue gas mixture through reaction with oxidized oxygen carrier thereby reducing the oxygen carrier. [0208] 3. Pass the reduced oxygen carrier into an air reactor in which the oxygen carrier is oxidized by O.sub.2 thereby releasing heat. [0209] 4. Pass the oxidized oxygen carrier to the fuel reactor transferring both oxygen and heat to the fuel reactor thereby providing the oxygen required for oxidation of the fuel to proceed.

[0210] The source of recycled flue gas contains unreacted fuel, carbon dioxide, and/or water.

[0211] In the first to fifth embodiments described above, a heat exchanger reformer HX-R is used. In the following embodiments (sixth to eighth), no heat exchanger reformer HX-R is used.

[0212] According to a sixth embodiment of the present invention, the recycled flue gas is recycled from a location in the flue gas processing train above the dew point of water in the flue gas.

[0213] Referring to FIG. 10, ambient air is compressed, pre-heated in a heat exchanger HX1 and then sent to an air reactor 10. In the air reactor 10, oxygen in the air reacts with a reduced metal oxide, producing an oxidized metal oxide and a vitiated air stream, composed primarily of nitrogen. Heat is removed from the air reactor 10 via an in-bed heat exchanger HX2 and a convective heat exchanger HX3. The vitiated air stream is cooled in heat exchanger HX1 and filtered through a vitiated air filter 15 before being expanded in a vitiated air expander 20 to produce power to run an air compressor 30. The vitiated air is then vented to atmosphere.

[0214] In contrast to the process shown in FIG. 3a, where gaseous fuel (fuel gas) is mixed with recycled flue gas (H.sub.2O, CO.sub.2), pre-heated in a heat exchanger HX5 and then sent to a heat exchanger reformer HX-R, in FIG. 10, no heat exchanger reformer is used. In FIG. 10, gaseous fuel is mixed with recycled flue gas (H.sub.2O, CO.sub.2), pre-heated in a heat exchanger HX5, and then sent to the fuel reactor 40 which comprises a heat exchanger HX6 where it reacts with the oxidized metal oxide to produce gaseous combustion products (H.sub.2O, CO.sub.2) and reduced the metal oxide. The combustion products are cooled in a heat exchanger HX7, heat exchangers HX5 and HX8. A portion of the flue gas is sent then to a recycle compressor 60. The balance of the flue gas is sent to a condensing heat exchanger HX9 for bulk water removal before the gas is scrubbed and cooled further in a direct contact cooler 50 to produce a purified CO.sub.2 product. The CO.sub.2 product is then further dried by a heat exchanger HX11 and compressed by a CO.sub.2 compressor 70.

[0215] According to a seventh embodiment of the invention, the recycled flue gas is recycled from a location at which the flue gas has been partially condensed in a scrubber or similar device that removes particulate matter from the flue gas. Adjusting the temperature of the scrubber allows the hydrogen to carbon ratio of the recycled flue gas to be easily adjusted in order to achieve a desirable mixed inlet fuel gas composition.

[0216] Referring to FIG. 11, ambient air is compressed, pre-heated in a heat exchanger HX1 and then sent to an air reactor 10. In the air reactor 10, oxygen in the air reacts with a reduced metal oxide, producing an oxidized metal oxide and a vitiated air stream, composed primarily of nitrogen. Heat is removed from the air reactor 10 via an in-bed heat exchanger HX2 and a convective heat exchanger HX3. The vitiated air stream is cooled in heat exchanger HX1 and filtered through a vitiated air filter 15 before being expanded in a vitiated air expander 20 to produce power to run an air compressor 30. The vitiated air is then vented to atmosphere.

[0217] In contrast to the process shown in FIG. 4a, where gaseous fuel is mixed with recycled flue gas (H.sub.2O, CO.sub.2), pre-heated in a heat exchanger HX5, and then sent to a heat exchanger reformer HX-R, in FIG. 11, no heat exchanger reformer is used. In FIG. 11, gaseous fuel is mixed with recycled flue gas (H.sub.2O, CO.sub.2), pre-heated in a heat exchanger HX5, and then sent to the fuel reactor 40 which comprises a heat exchanger HX6 where it reacts with the oxidized metal oxide to produce gaseous combustion products (H.sub.2O, CO.sub.2) and reduced the metal oxide. The combustion products are cooled in a heat exchanger HX7, heat exchangers HX5 and HX8. Water is then removed in a condensing heat exchanger HX9. A portion of the flue gas is sent to the recycle compressor 60. The balance of the flue gas is scrubbed and cooled further in a direct contact cooler 50 to produce a purified CO.sub.2 product. The CO.sub.2 product is then further dried by a heat exchanger HX11 and compressed by a CO.sub.2 compressor 70.

[0218] According to an eighth embodiment of the invention, the recycled flue gas is recycled from a location where the flue gas has been cooled and is composed primarily of unreacted fuel components and carbon dioxide.

[0219] Referring to FIG. 12, ambient air is compressed, pre-heated in a heat exchanger HX1 and then sent to an air reactor 10. In the air reactor 10, oxygen in the air reacts with a reduced metal oxide, producing an oxidized metal oxide and a vitiated air stream, composed primarily of nitrogen. Heat is removed from the air reactor 10 via an in-bed heat exchanger HX2 and a convective heat exchanger HX3. The vitiated air stream is cooled in heat exchanger HX1 and filtered through a vitiated air filter 15 before being expanded in a vitiated air expander 20 to produce power to run an air compressor 30. The vitiated air is then vented to atmosphere.

[0220] In contrast to the process as shown in FIG. 5a, where gaseous fuel is mixed with recycled flue gas (H.sub.2O, CO.sub.2), pre-heated in a heat exchanger HX5, and then sent to a heat exchanger reformer HX-R, in FIG. 12, no heat exchanger reformer is used. In FIG. 12, gaseous fuel is mixed with recycled flue gas (H.sub.2O, CO.sub.2), pre-heated in a heat exchanger HX5, and then sent to the fuel reactor 40 which comprises a heat exchanger HX6 where it reacts with the oxidized metal oxide to produce gaseous combustion products (H.sub.2O, CO.sub.2) and reduced the metal oxide. The combustion products are cooled in a heat exchanger HX7, heat exchangers HX5 and HX8. Water is then removed in a condensing heat exchanger HX9 and is scrubbed and cooled further in a direct contact cooler 50 to produce a purified CO.sub.2 product. A portion of the CO.sub.2 is sent to the recycle compressor 60. The balance of the CO.sub.2 product is then further dried by a heat exchanger HX11 and compressed by a CO.sub.2 compressor 70.

[0221] Although the present invention has been described in considerable detail with reference to certain preferred embodiments thereof, other embodiments and modifications are possible. Therefore, the scope of the appended claims should not be limited by the preferred embodiments set forth in the examples but should be given the broadest interpretation consistent with the description as a whole.