Claims:We Claim:

1. A CLC based steam generation scheme for carbonaceous solid fuel to produce steam, power and syngas, said scheme comprising of:
(a) a solid fuel reactor (1) for carrying out solid fuel (7) and a metal oxide (18) reaction;
(b) a syngas reactor (3) to carryout syngas (25) reaction with metal oxide (43);
(c) a metal oxide regeneration reactor (2), for carrying out the reaction of oxygen depleted metal oxide (19) with air (35);
(d) cyclone separators (11), (14), (27), (39) & (45) to separate solid and gaseous phases;
(e) a heat supply system to SFR (1) and GR (3) from MRR (2) using a dedicated compressible inert fluid (53) & (99) respectively;
(f) a heat recovery system in SFR (1) and GR (3) using steam (72) & (75) respectively;
(g) a flue gas recycle system for loop seals (30), (41), (47) & (54) and SFR (1);
(h) a syngas heating system (24) and air heating system (34) before sending to GR (3) and MRR (2) respectively;
(i) a carbonaceous solid fuel pulverizer (6) and pulverized fuel transportation system to SFR (1)
(j) a turbine-generator system for power production; and
(h) Gas cleaning system FGD (94) and cooling system (97) for CO2 capture.
2. The solid fuel based CLC scheme for steam generation as claimed in claim 1, wherine syngas (23) and fresh air (34) is heated with flue gas (65) and oxygen depleted air (50) respectively before admitting into GR (3) and MRR (2).
3. The solid fuel based CLC scheme for steam generation as claimed in claim 1, wherein the metallic oxygen carriers used for solid fuel (7) and syngas (25) reaction can be Ni, Fe, Co, Cu, Ca, Mn based metal oxides or natural ores or combination of these metals with support materials such as Al2O3, MgO, MgAl2O4, NiAl2O4, ZrO2, CeO2, Yettira Stabilized Zirconia (YSZ).
4. The solid fuel based CLC scheme for steam generation as claimed in claim 1, wherein the operating temperature range for MRR (2) is 750 0C to 1100 0C. Whereas the operating temperature range for SFR (1) and GR (3) is 700 0C to 1050 0C.
5. The solid fuel based CLC scheme for steam generation as claimed in claim 1, wherein the operating pressure of SFR (1), MRR (2) and GR (3) can be from 1 to 30 bar.
6. The solid fuel based CLC scheme for steam generation as claimed in claim 1, wherein the energy required for endothermic reaction between solid fuel and metal oxides in SFR (1) and syngas and metal oxides in GR (3) are supplied using a dedicated compressible inert fluid (53) and (99) from MRR (2) respectively.
7. The solid fuel based CLC scheme for steam generation as claimed in claim 1, wherein in the case of exothermic nature of fuel reaction in GR (3) and SFR (1), superheated steam (75) and (72) respectively are used to recover energy.
8. The solid fuel based CLC scheme for steam generation as claimed in claim 1, if SFR (1) is exothermic and GR (3) is endothermic or vice-versa, steam (72) and inert compressible fluid (99) are used recovery and supply energy or vice-versa respectively.
9. The solid fuel based CLC scheme for steam generation as claimed in claim 1, to regenerate metal oxides (31) and (90), a single MRR (2) is used for reaction between air (35) and oxygen depleted metal oxides (19).
10. The solid fuel based CLC scheme for steam generation as claimed in claim 1, part of the syngas (21b) generated from SFR (1), can be utilized for liquid fuel manufacturing.
11. The solid fuel based CLC scheme for steam generation as claimed in claim 1, wherein the flue gas (7) is used for loop seals (30, 41, 47 & 54), carbon stripper (49) and to fluidize the pulverized solid fuel (8) & metal oxides (18) in GR (3).
12. The solid fuel based CLC scheme for steam generation as claimed in claim 1, wherein the superheated steam (9) is used in SFR (1) to enhance the carbon conversion.
13. The solid fuel based CLC scheme for steam generation as claimed in claim 1, CO2 – rich flue gas (98) can also be used for fluidization of solid fuel in SFR (1).
14. The solid fuel based CLC scheme for steam generation as claimed in claim 1, wherein the cooled CO2-rich flue gas (98) can be send to CO2 capture or utilization.
15. The solid fuel based CLC scheme for steam generation as claimed in claim 1, the scheme can be used from wide thermal output ranges from 1 MWe to 500 MWe.
16. A CLC based steam generation scheme for gaseous fuels to produce steam, and/or power, comprising of:
(a) a gaseous fuel reactor (101) for carried out gaseous fuel (133) and metal oxide (143);
(b) a metal oxide regeneration reactor (102), for carrying out the reaction of oxygen depleted metal oxide (126) with air (144);
(c) cyclone separators (104), (107) & (134) to separate solid and gaseous phases;
(e) a heat supply system from MRR (102) to GR (101) using a dedicated compressible inert fluid (109);
(f) a heat recovery system in GR (101) using steam (147);
(g) a flue gas recycle system for loop seals (117), (118) and GR (101);
(h) a gaseous fuel heating system (130) and air heating system (125) before sending to GR (101) and MRR (102) respectively;
(i) a turbine-generator system for power production; and
(j) a CO2 capture system;
17. The gaseous fuel based CLC scheme for steam generation as claimed in claim 16, wherein the gaseous fuel (129) and fresh air (124) are heated with oxygen depleted air (108) before admitting into GR (101) and MRR (102) respectively.
18. The gaseous fuel based CLC scheme for steam generation as claimed in claim 16, wherein the metallic oxygen carriers used for gaseous fuel (133) reaction can be Ni, Fe, Co, Cu, Ca, Mn based metal oxides or natural ores or combination of these metals with support materials such as Al2O3, MgO, MgAl2O4, NiAl2O4, ZrO2, CeO2, Yettira Stabilized Zirconia (YSZ).
19. The gaseous fuel based CLC scheme for steam generation as claimed in claim 16, wherein the operating temperature range for MRR (102) is 750 0C to 1100 0C, whereas the operating temperature range for GR (101) is 700 0C to 1050 0C.
20. The gaseous fuel based CLC scheme for steam generation as claimed in claim 16, wherein the operating pressure of GR (101) and MRR (102) and can be from 1 to 30 bar.
21. The gaseous fuel based CLC scheme for steam generation as claimed in claim 16, wherein the energy required for endothermic reaction between gaseous fuel and metal oxides in GR (101) is supplied using inert compressible fluid (109) from MRR (102).
22. The gaseous fuel based CLC scheme for steam generation as claimed in claim 16, wherein in the case of exothermic in nature of fuel reaction in GR (101), superheated steam (147) is used to recover energy.
23. The gaseous fuel based CLC scheme for steam generation as claimed in claim 16, wherein the flue gas (162) is used in loop seals (115, 120), carbon stripper (113) and in GR (101).
24. The gaseous fuel based CLC scheme for steam generation as claimed in claim 16, CO2-rich flue gas (141) can also be used in GR (101).
25. The gaseous fuel based CLC scheme for steam generation as claimed in claim 16, wherein superheated steam (159) admitted into the GR (101) to increase fuel conversion.
26. The gaseous fuel based CLC scheme for steam generation as claimed in claim 16, wherein the cooled CO2-rich flue gas (141) can be send to CO2 capture or utilization.
27. The gaseous fuel based CLC scheme for steam generation as claimed in claim 16, wherein the scheme can be used from wide thermal output ranges from 1 MWe to 800 MWe.
, Description:FIELD OF THE INVENTION

[001] The present invention relates to fossil fuel-based steam generation using a solid metal oxide based combustion process. More particularly, the invention related to a chemical looping combustion and gasification for steam or power production applications.

Abbreviations Used
ASU: Air Separation Unit
CLC: Chemical Looping Combustion (technology)
CLOU: Chemical Looping Oxygen Uncoupling
CBFC: Circulating Fluidized Bed Combustion
ESP: Electrostatic Precipitator
FGD: Flue Gas Desulphurization
FD: Forced Draft (Fan)
GR: Gas Reactor
IGCC: Integrated Gasification Combined Cycle
MRR: Metal oxide Regeneration Reactor
SFR: Solid Fuel Reactor
SYNGAS: Synthetic Gas
YSZ: Yettira Stabilized Zirconia

BACKGROUND AND PRIOR ARTS OF THE INVENTION

[002] According to the United Nations’ Intergovernmental Panel on Climate Change (IPCC, 2007), 11 of the past 12 years are among the dozen warmest since 1850. The rise in earth temperature is directly correlated to the amount of greenhouse gases such as methane, CO2, nitrous oxide, and ozone, etc. present in the atmosphere. Among the greenhouse gases, CO2 contributes about 82% of the total “global warming”. This is largely produced by man-made emissions by burning fossil fuels such as coal, natural gas, oils, etc. In a sub-critical power plant with a typical Indian coal, for every MWh (megawatt-hour) of electric power generation, around 1 tons of CO2 is released into the atmosphere. According to International Energy Agency's 2017 statistics, thermal power plants consume a large portion of these fossil fuels; in the year 2015, 66.3% of the world electricity was produced by burning fossil fuels. Coal combustion alone contributed around 41% of the world total CO2 emissions. Since thermal power plants are large and stationary and can introduce additional equipment to cut down CO2 emissions from fossil fuel-fired power generation plants

[003] In order to meet these twin challenges of reduction of CO2 emissions and increasing the efficiency of the energy utilization, many technological advances have been introduced in the combustion process as well as the post-combustion process in the past few decades. Notable examples of these technological developments include excess air supply for complete combustion of fuel, staged combustion to reduce NOx formation, tangential firing for proper mixing and stable flame, atomization of liquid fuels for complete combustion, introducing swirl velocity for enhanced mixing, supercritical power plants & advanced ultra-supercritical power plants for improving the efficiency, Circulating Fluidized Bed Combustion (CFBC) for handling high sulphur, high ash coals, Integrated Gasification Combined Cycle (IGCC) for clean combustion and higher energy efficiency. In order to reduce hazardous pollutant emissions further, post-combustion treatment methods such as Flue Gas Desulphurization (FGD) for SO2 removal, selective catalytic or non-catalytic reduction methods for NOx removal, Electrostatic Precipitator (ESP) for fly ash particle removal are employed.

[004] While these technological advances have led to improved thermal efficiency and reduced pollutant emissions, none of these directly address the question of reducing CO2 emissions from concentrated sources such as power plants, cement industries, metallurgical industries, etc. Reduction in CO2 emissions is possible through improved thermal efficiency; however, this gain is insufficient in the context of the continued growth of demand for power from countries such as India and China. In this regard, oxy-fuel combustion technology and Chemical Looping Combustion (CLC) technology have been developed in the last couple of decades to capture CO2 from fossil fuel fired stations. In oxy-fuel combustion, combustion takes place with pure oxygen instead of air. Hence, the exhaust flue gas consists of only CO2 and water vapour, the later can be removed by directly cooling which results in highly concentrated CO2 which can be sent for compression and storage/usage. However, oxygen separation from air is highly energy intensive process which greatly increases the energy penalty in oxy-fuel combustion process. During CLC, the oxidant is in the form of a metal oxides and therefore presence of nitrogen during fuel reaction avoided. This results in CO2-rich flue gas that can be sent directly to capture after removing the water vapor. The oxygen depleted metal oxygen carriers reacts with air in a separate reactor to gain its oxygen. The advantage of CLC process is that the elimination of energy-intensive Air Separation Unit (ASU) to generate oxygen from air, which results in higher energy efficiency than with oxy-fuel combustion during CO2 capture and sequestration. The generalized reactions for fuel reaction with metal oxides is given as
CnH2m+ (2n+m) MexOy ? nCO2 + mH2O + (2n+m) MexOy-1
Similarly, air reaction with oxygen depleted metal oxides is given as
O2 + 3.77 N2 + (2n+m) MexOy-1 ? (2n+m) MexOy+ 3.77 N2
[005] Recently many inventions are proposed for CLC based systems. Recent US Patent No. US 2017/0321888 A1 describes the chemical looping oxidation-reduction combustion for hydrocarbon feed, where heat exchange has been proposed with active mass of particle when circulating between oxidation and reduction reactors. They proposed serval configurations for heat exchanging from active mass of particles. This invention does not discusses about the heat integration between fuel and air reactor using oxygen depleted air.

[006] US Patent No. US 2017/0321886 A1 describes the chemical looping oxidation-reduction combustion for hydrocarbon feed, where catalytic pre-reforming of the feed is performed in a pre-reforming zone. The oxidation zone and reduction zone are separated by pre-reforming zone but it allows heat transfer between the reduction and oxidation zone with pre-reforming zone. This invention discusses about heat integration with oxidation and reduction reactors but not discusses holistic heat integration in CLC process with different fuels.

[007] US Patent No. US 9810146 ?2 describes a calcium-based chemical looping combustion process especially for a gaseous fuel consisting of sour gas (H2S) where the CaO (metal oxide) reacts with H2S and produces CaS. The CaS reacts with air and produces CaSO4 which in turn reacts with CH4 in the sour gas. This invention discusses only H2S removal with calcium metal oxides but not on heat integration about the CLC process.

[008] US Patent No. US 9566546 ?2 describes a CLC process to produce in-site oxygen and in-situ removal SO2 from product gases using calcium-based sorbent. The release of oxygen from oxygen carriers is utilized to burn the sour gas and Ca-based metal oxides are used to remove the SO2 from product gases, thereby avoiding the contact between the sour gas and oxygen carriers. This invention significantly deviates from the present invention of heat integration of the CLC process.

[009] US Patent No. US 9557053 ?1 describes metal ferrite oxygen carrier (MFexOy) for the CLC of solid carbonaceous fuels, such as coal, coke, coal and biomass char. The MFexOy is a chemical composition and ? is one of Mg, Ca, Sr, Ba, Co, ??, and combinations of these metals. The metal ferrite oxygen carrier can be supported with inert supports. The proportion of inert support varies from 5% to 60% by weight of metal ferrite and the MFexOy comprises at least 30% of the metal ferrite oxygen carrier. This invention discusses metal oxide combination but deviates from the present invention of heat integration of the CLC process.

[0010] Indian Patent No. 201747035541 A describes a system and method for reducing emissions in a chemical looping combustion system in which Chemical Looping Oxygen Uncoupling (CLOU) materials are used for post-combustion gases (partially oxidized gases usually consists of C, CO, CH4, or H2S). The CLOU material is manganese, cobalt, copper. This invention deviates significantly from the present invention.

[0011] Patent No. WO 2017013038 A1 describes a CLC process with the main focus of producing high purity dinitrogen. In this process, the depleted air stream reacts with reduced active mass in multiple reactors to produce high purity stream of dinitrogen. This invention deviates significantly from the present invention.

[0012] US Patent No. US 2017/0259240 A1 describes a process for producing the black powder oxygen carrier for chemical looping combustion from gas pipelines. They have proposed a methodology to increase the reactivity of black powder to use in CLC. This invention discusses metal oxides usage, deviates significantly from the present invention.

[0013] The present invention focuses on heat integration between fuel and air reactors of the CLC system and whole scheme of CLC application with detailed arrangements for steam or syngas generation and therefore not relevant to the above-cited patented in this area.

OBJECTS OF THE INVENTION

[0014] It is, therefore, an object of the present invention to propose a carbonaceous fuel based steam generation cycle using the CLC process.

[0015] Another object of the present invention is to propose a flexible steam generation cycle consisting of solid fuel gasification reactor, synthesis gas (referred as syngas) combustion reactor and a common air reactor for regeneration of solid metal oxides used in solid fuel gasification and syngas combustion.

[0016] It is another object of the present invention to develop a steam cycle for combustion of gaseous fuels

[0017] It is another object of the present invention is to use a dedicated compressed inert fluid such as nitrogen or CO2, etc for providing the heat to the endothermic reaction between a fuel and metal-based oxygen carriers.

[0018] It is another object of the present invention is to recover exothermic energy in fuel or air reactor using steam.

[0019] It is another object of the invention is to provide steam-based power with CO2 capture

[0020] A further object of the present invention is to use steam generation cycle for gasification of solid fuel only.

SUMMARY OF INVENTION

[0021] The object of the invention provides a detailed scheme for implementing the CLC process for steam generation with easier CO2 separation from flue gases using carbonaceous fuels such as solid and gaseous fuels.

[0022] According to an embodiment of the invention, for solid fuels, two-stage conversion of fuel to heat is proposed such as solid carbonaceous fuel to syngas and from syngas to stable end products such as carbon dioxide (CO2) and H2O. The solid fuel after pulverizing to the desired size is admitted into Solid Fuel Reactor (SFR) where solid fuel undergoes partial conversion with available oxygen in solid metal oxides. These intermediate products are called syngas which includes carbon monoxide (CO), hydrogen (H2), methane (CH4), CO2, water vapor and minimal quantities of nitrogen oxides (NOx), sulfur dioxide (SO2), etc. The syngas after exiting from the SFR is passed through multiple cyclone separators to segregate from oxygen-depleted solid metal oxides and ash. The resulting syngas is then sent for Gas Reactor (GR) for complete combustion with metal oxides. The depleted metal oxide from SFR and GR are sent to Metal oxide Regeneration Reactor (MRR) to regain its lost oxygen by reacting with fresh air. The fresh air after preheating with exhaust oxygen-depleted air is sent to MRR from the bottom of the reactor for reaction with oxygen-depleted metal oxides. The regenerated metal oxides are separated from oxygen-depleted air and send to GR and SFR. The proportion of regenerated metal oxides to SFR and GR can be admitted as per the solid fuel and syngas composition respectively. The heat available in the flue gases from GR and SFR is utilized for heating the water to sub-critical or supercritical steam as per requirement. The flue gases after heat recovery send to ESP for ash removal. A portion of the flue gases after heat recovery is used for loop seal of SFR, GR and MRR and carbon stripper. The remaining flue gas is admitted to multiple heat exchangers to cool the flue gases close to ambient temperature to remove water vapor. The cooled fuel gases, rich in CO2 are sent for compression or further usage or both.

[0023] The present invention thus discloses and claims a CLC based steam generation scheme for carbonaceous solid fuel to produce steam, power and syngas, said scheme comprising of a solid fuel reactor (1) for carrying out solid fuel (7) and a metal oxide (18) reaction; a syngas reactor (3) to carryout syngas (25) reaction with metal oxide (43); a metal oxide regeneration reactor (2), for carrying out the reaction of oxygen depleted metal oxide (19) with air (35); cyclone separators (11), (14), (27), (39) & (45) to separate solid and gaseous phases; a heat supply system to SFR (1) and GR (3) from MRR (2) using a dedicated compressible inert fluid (53) & (99) respectively; a heat recovery system in SFR (1) and GR (3) using steam (72) & (75) respectively; a flue gas recycle system for loop seals (30), (41), (47) & (54) and SFR (1); a syngas heating system (24) and air heating system (34) before sending to GR (3) and MRR (2) respectively; a carbonaceous solid fuel pulverizer (6) and pulverized fuel transportation system to SFR (1); a turbine-generator system for power production; and a Gas cleaning system FGD (94) and cooling system (97) for CO2 capture.

[0024] The syngas (23) and fresh air (34) is heated with flue gas (65) and oxygen depleted air (50) respectively before admitting into GR (3) and MRR (2). The metallic oxygen carriers used for solid fuel (7) and syngas (25) reaction can be Ni, Fe, Co, Cu, Ca, Mn based metal oxides or natural ores or combination of these metals with support materials such as Al2O3, MgO, MgAl2O4, NiAl2O4, ZrO2, CeO2, Yettira Stabilized Zirconia (YSZ). The operating temperature range for MRR (2) is 750 0C to 1100 0C. Whereas the operating temperature range for SFR (1) and GR (3) is 700 0C to 1050 0C. The operating pressure of SFR (1), MRR (2) and GR (3) can be from 1 to 30 bar. The energy required for endothermic reaction between solid fuel and metal oxides in SFR (1) and syngas and metal oxides in GR (3) are supplied using a dedicated compressible inert fluid (53) and (99) from MRR (2) respectively. The case of exothermic nature of fuel reaction in GR (3) and SFR (1), superheated steam (75) and (72) respectively are used to recover energy. SFR (1) is exothermic and GR (3) is endothermic or vice-versa, steam (72) and inert compressible fluid (99) are used recovery and supply energy or vice-versa respectively. A single MRR (2) is used for reaction between air (35) and oxygen depleted metal oxides (19). It may be noted that a part of the syngas (21b) generated from SFR (1), can be utilized for liquid fuel manufacturing. The flue gas (7) is used for loop seals (30, 41, 47 & 54), carbon stripper (49) and to fluidize the pulverized solid fuel (8) & metal oxides (18) in GR (3). The superheated steam (9) is used in SFR (1) to enhance the carbon conversion. CO2 – rich flue gas (98) can also be used for fluidization of solid fuel in SFR (1). The cooled CO2-rich flue gas (98) can be send to CO2 capture or utilization. The scheme can be used from wide thermal output ranges from 1 MWe to 500 MWe.
Further the present invention claims CLC based steam generation scheme for gaseous fuels to produce steam, and/or power, comprising of a gaseous fuel reactor (101) for carried out gaseous fuel (133) and metal oxide (143); a metal oxide regeneration reactor (102), for carrying out the reaction of oxygen depleted metal oxide (126) with air (144); cyclone separators (104), (107) & (134) to separate solid and gaseous phases; a heat supply system from MRR (102) to GR (101) using a dedicated compressible inert fluid (109); a heat recovery system in GR (101) using steam (147); a flue gas recycle system for loop seals (117), (118) and GR (101); a gaseous fuel heating system (130) and air heating system (125) before sending to GR (101) and MRR (102) respectively; a turbine-generator system for power production; and a CO2 capture system;
[0025] The gaseous fuel (129) and fresh air (124) are heated with oxygen depleted air (108) before admitting into GR (101) and MRR (102) respectively. The metallic oxygen carriers used for gaseous fuel (133) reaction can be Ni, Fe, Co, Cu, Ca, Mn based metal oxides or natural ores or combination of these metals with support materials such as Al2O3, MgO, MgAl2O4, NiAl2O4, ZrO2, CeO2, Yettira Stabilized Zirconia (YSZ). The operating temperature range for MRR (102) is 750 0C to 1100 0C, whereas the operating temperature range for GR (101) is 700 0C to 1050 0C. The operating pressure of GR (101) and MRR (102) and can be from 1 to 30 bar. The energy required for endothermic reaction between gaseous fuel and metal oxides in GR (101) is supplied using inert compressible fluid (109) from MRR (102). The case of exothermic in nature of fuel reaction in GR (101), superheated steam (147) is used to recover energy. The flue gas (162) is used in loop seals (115, 120), carbon stripper (113) and in GR (101), and the CO2-rich flue gas (141) can also be used in GR (101). The superheated steam (159) admitted into the GR (101) to increase fuel conversion. The cooled CO2-rich flue gas (141) can be send to CO2 capture or utilization. Thus the scheme can be used from wide thermal output ranges from 1 MWe to 800 MWe.

[0026] According to another aspect of the invention, the metal oxides are nickel, manganese, copper, cobalt, ferrous, calcium, perovskites and natural ores such as ilmenite, iron ore, manganese ore or combination of these metal oxides. These metal oxides are provided with a suitable inert support material such as Al2O3, MgO, NiAl2O4, ZrO2, etc

[0027] According to another aspect of the invention, the operating temperature range for MRR is 750 0C to 1100 0C, whereas the operating temperature range for SFR and GR is 700 0C to 1050 0C.

[0028] According to one aspect of the invention, the GR is either endothermic or exothermic based on the type of metallic oxygen carriers used for converting the syngas fuel. If the reaction is endothermic then the heat is supplied using a dedicated inert compressible fluid such as CO2 or N2, etc from MRR to SFR and GR. Since the total amount of energy released per kilogram of fuel is the same, the heat integration makes CLC process more viable and efficient. In case of the exothermic nature of SFR and GR, the heat is recovered using steam from SFR, GR, and MRR. If SFR is endothermic and GR is exothermic or vice versa, energy is supplied using dedicated compressed inert fluid from MRR to SFR and super-heated steam is used to recover heat from GR or vice versa.

[0029] According to one aspect of the invention, steam is injected into SFR for fluidizing and as well as to enhance carbon conversion. It will also favour the hydrogen formation by reacting with carbon monoxide and carbon. The amount of steam injection varies from 10 to 80% of the solid fuel injection, which depends upon the type of solid fuel injected and application.

[0030] According to one aspect of the invention, a portion of the syngas after generation from SFR may be sent to chemical manufacturing application and rest will be sent to GR for complete combustion. The syngas sparing for chemical manufacturing should not exceed 25% of the total gas.

[0031] According to one aspect of the invention, carbon stripper is used to remove unburnt carbon deposited on the metal oxide surface after cyclone separator. Cooled flue gas is used in the carbon stripper to carry the carbon deposit to SFR.

[0032] According to one aspect of the invention, for gaseous fuels combustion using solid looping combustion involves only two reactors such as GR and MRR and hence SFR is not required. During gaseous fuel (natural gas, propane, butane, etc.) combustion, fuel reaction with metal oxides is mostly endothermic therefore high-temperature energy must be supplemented. In this methodology, it has been achieved using dedicated compressed fluid supplying heat from MRR, in order maintain a constant GR temperature, repeated heat pick-up, and discharge cycles are to be carried out between MRR and GR using the indirect heating technique.

[0033] According to one aspect of the invention, it explains a novel methodology of integrating the heat removal and heat supply between an air reactor and fuel reactor. The heat is utilized for steam generation and also heating of fresh fuel and fresh air.

[0034] According to one aspect of the invention, the steam generation process can be sub-critical or supercritical or advanced ultra-supercritical methodology as per application.

[0035] According to another aspect of the invention, after recovering heat from flue gases which is unsegregated at the end of dust cleaning system is send to Flue Gas Desulphurization (FGD) to remove sulfur dioxide before sent for cooling and CO2 compression or further usage or both.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0036] Figure 1 illustrates a schematic drawing of the chemical looping combustion process for solid fuels for generation of steam based power when SFR and GR are endothermic in nature.

[0037] Figure 2 illustrates another variant of schematic drawing in Figure 1, where SFR and GR are exothermic in nature for solid fuels.

[0038] Figure 3 illustrates a schematic drawing of the chemical looping combustion process for gaseous fuels for the generation of steam based power when GR is endothermic in nature.

[0039] Figure 4 illustrates another variant of schematic diagram in Figure 3 where GR is exothermic in nature for gaseous fuels.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION

[0040] The present invention provides a schematic drawing for solid looping combustion for carbonaceous fuels for generating steam-based power.

[0041] Figures 1 to 4 shows the detailed arrangement of the CLC process, wherein Figure 1 illustrates the application of CLC to solid fuel based power generation. The crushed raw solid carbonaceous fuel (4) is transported using a conveyer belt (5) to a pulverizer (6), where grinding the solid fuel takes place. The flue gas (7) is continuously injected into pulverizer (6) for transporting the pulverized solid fuel to SFR (1). The flue gas and finer solid fuel mixture (8) is admitted into SFR (1), where the SFR (1) is already loaded with selected solid oxides (18). Apart from that superheated steam (9) also admitted into SFR (1) for reaction with solid fuel. The endothermic reaction between solid oxides (18) and pulverized solid fuel (4) takes places in SFR (1). After this reaction, the metal oxides and ash-laden syngas gas (10) is passed through a cyclone separator (11) where heavy solid oxide particles (13) exit through the bottom and lighter particles and syngas (12) exit through the top of cyclone separator (11). The stream (12) passes again through another cyclone separator (14) where the heavy metal oxide particles (86) separate at the bottom and lighter particles and gases (15) exit through the top of cyclone separator (14). These metal oxides (86) are mixed with (13) and then send for carbon stripper (49). In the carbon stripper (49), flue gases (48) are used to remove the unburnt carbon deposited on the heavier metal oxide particles. The flue gas along with unburnt carbon (52) is sent to the SFR (1). The carbon stripped metal oxides (89) are send to loop seal (54), in which the flue gas (74) helps in sending the metal oxides (90) to MRR (2). The ash-laden syngas passes through heat exchanger (16) to supply heat to water/steam (85). The cooled ash-laden syngas (17) admitted ESP (20), where fine ash particles are removed at the bottom of ESP (20) and clean gases (21) are split into two parts. A major portion of syngas (21a) is sent to gas recirculation fan (22). The other portion of syngas (21b) is sent for liquid production. The ash (87) collected from ESP (20) are sent to disposal. The syngas (23) from gas recirculation fan (22) is heated with combustion flue gases (65) in a heat exchanger (24). The heated syngas (25) is admitted into GR (3). Where the reaction between syngas (25) and metal oxides (43) takes place, for endothermic reactions the additional heat required is being supplied using compressed inert fluid (99a) to GR (3). After exchanging heat, the compressed inert fluid (99) is send to MRR (2) for further heat recovery and this cycle continues unit it meets the energy demand by GR (3). The stream (61) is sent to a heat exchanger (59) to supply heat to steam (58). The hot flue gas (26) along with part of solid metal oxides from GR (3) is sent to cyclone separator (27), where heavier metal oxide particles (29) escapes through the bottom and flue gases (28) escapes through the top of cyclone separator (27). The metal oxide particles (29) are sent to loop seal (30) with help of flue gas stream (73), the metal oxides (31) admitted into MRR (2). The flue gas (28) exchanges heat with steam (60) in a heat exchanger (63).

[0042] The oxygen-depleted metal oxides (90) and (31) are reacting with air (35) in the MRR (2). The fresh air (32) from the atmosphere is supplied using a Forced Draft (FD) fan (33) to heating. The air stream (34) is sent through a heat exchanger (51) to gain energy and this high-temperature air (35) enters MRR (2). After reaction with air (35), the regenerated metal oxides along with oxygen-depleted air (36) are taken out and split into two streams. The stream (38) is controlled using a valve (37) as per requirement and then send to a cyclone separator (39). The heavier metal oxides (40) are escaped through the bottom and lighter oxygen depleted air (61) escapes through the top. These metal oxides (40) are sent to a loop seal (41) and with help of flue gas stream (72), the regenerated metal oxides (42) are injected to GR (3). The other stream of oxygen-depleted air along with regenerated metal oxides (44) are send to a cyclone separator (45), where the separated metal oxides (46) are sent to a loop seal (47), with help of flue gas stream (75) the regenerated metal oxides (48) are sent to SFR (1) and the oxygen-depleted air stream (50) exits at the top of the cyclone separator (45). The energy required for endothermic reaction between metal oxides (18) and solid fuel (4) in SFR (1) is supplied using a dedicated inert compressed fluid (53a), After exchanging heat to SFR (1), the compressed inert fluid stream (53) is sent to MRR (2) for further heat recovery. The stream (50) provides heat to incoming fresh air (34) in a heat exchanger (51) and then stream (55) pass through a heat exchanger (71) to provide heat to flue gas (70). The cooled oxygen depleted air (56) is sent to the atmosphere. The flue gas (66) was cooled in heat exchanger (67) and the cooled flue gas (68) is send through gas recirculation fan (69), the pressurized flue gas (70) is sent to a heat exchanger (71) to heat with oxygen-depleted air (55). The heated flue gas is sent to loop seal purpose and to solid fuel conveying purpose.

[0043] The steam (58) recovers heat from the hot oxygen-depleted air (61) in a heat exchanger (59) and then the steam (60) recovers heat from hot flue gas (28) in a heat exchanger (63). After heat recovery, the steam (64) is sent to MRR (2) for further heat recovery. The superheated steam (57) is then sent to the high-pressure turbine (77) the output steam (88) is sent again to MRR (2) where further heat recovery happens. The reheated steam (91) is sent to the intermediate turbine (77a). The discharged steam (92) is sent to the low-pressure turbine (78) for the generation of electricity. The low-pressure steam (79) and (79a) send to the condenser (80) for condensation and phase transfer. The water (81) is sent to deaerator (82) for removal of dissolved air. The water (83) is sent to a pump (84) for pressuring and then sent to heat recovery.

[0044] The remaining flue gases (93) after segregating for coal conveying and loop seal, are sent to flue gas desulphurization unit (94), where SO2 content in the flue gas is removed at the bottom (96). The sulfur-free flue gases (95) are sent to a cooler (97) for cooling and water vapor removal. The moisture free and sulfur free flue gas (98) is sent for CO2 storage or utilization.

[0045] Figure 2 illustrates the schematic drawing of Figure 1, but here the reaction of metal oxides with solid fuel and syngas in SFR (1) and GR (3) are exothermic in nature. The heat recovery from SFR (1) and GR (3) are carried out using steam. The steam (57) after recovering heat from MRR (2), send to SFR (1) for further heat recovery. After recovering heat, the superheated steam (57a) is sent to high-pressure turbine (77). Similarly, the heat generated due to the exothermic reaction in GR (3) is recovered using steam (91). After recovery, the steam (91a) is sent to the intermediate turbine (77a) for power generation.

[0046] Figure 3 illustrates the schematic drawing of the CLC of gaseous fuel based power generation where the gaseous fuel from the storage tank (162) is pumped using an FD fan (128). The gaseous fuel (129) is preheated in a heat exchanger (130) using oxygen depleted air (131) and the heated gaseous fuel (133) is sent to GR (101), where the reaction between a gaseous fuel (133) and metal oxides (143) is taking place. For endothermic nature of gaseous fuel (133) and metal oxides (143), the heat is being supplied using a dedicated compressed inert fluid stream (110). The stream (109) from GR (101) enters MRR (102) again to gain energy and supply to GR (102), this process continues until it meets energy requirement by endothermic reaction in GR (101). In order to maintain the fluidizing condition of metal oxides (143), cooled flue gas (158) is also admitted into the reactor. Superheated steam (159) is also injected into the reactor (101) to enhance gaseous fuel (133) reaction with metal oxides (143). The flue gas along with oxygen-depleted metal oxides (103) sends to cyclone separator (104), where the heavy metal oxide particles (111) get separated at the bottom and flue gas (105) exist at the top. The flue gas (105) is sent to another cyclone separator (134) to recover further fine metal oxides (145) and these are mixed with metal oxides (111) to send to carbon stripper (113). With help of flue gas (119), the carbon is removed from metal oxides and sent to GR (101) along with flue gas (164). The metal oxide particle (114) then sent to a loop seal (115), where the metal oxide particles (116) admitted into MRR (102) with help of flue gas (117). The flue gas (135) at the top of the cyclone separator (134) sends to a heat exchanger (136) to provide heat to water (156). The cooled flue gas (137) split into two streams, one flue gas stream (138) is sent for recycling and other flue gas stream (139) send to cooling in a heat exchanger (140). Where water (142) is removed and CO2 rich flue gas (141) is sent for storage or utilization. The flue gas stream (138) send to gas recirculation fan (160) for further pressurizing, the pressurized flue gas (161) send to loop seal purpose and to GR (101).

[0047] Using FD fan (123), fresh air (124) is sent for heating in a heat exchanger (125) with oxygen-depleted air (108). The heated air (126) is admitted into MRR (102) to react with oxygen-depleted metal oxides (116), during the reaction heat is liberated due to exothermic in nature. The oxygen-depleted air along with metal oxides (106) exist the MRR (102) then enters a cyclone separator (107) where heavier metal oxides (112) separates at the bottom and oxygen-depleted air (108) at the top. This oxygen depleted air (108) supplies heat to fresh air stream (124) and gaseous fuel stream (129) before leaving to the atmosphere.

[0048] The steam (157) after obtaining heat from flue gas (135) is sent to MRR (102) for further heat recovery. After heat recovery, the superheated steam (145) is sent to high-pressure turbine (122) for power generation. The steam (146) exits from the turbine (122) and recover heat from MRR (102). The reheated steam (147) is sent to the intermediate turbine (122a) for power generation. The steam (148) further admitted to low-pressure turbine (127) for further heat recovery. The low pressure steam (149) and (150) existed from LP turbine (127) and enters a condenser (151) for transformation into liquid water (152), which after preliminary heating is sent to deaerator (153), then the water (154) to a pump (155) for pressurizing to desired values. This cycle is continued for continuous power generation.

[0049] Figure 4 illustrates another variant of the schematic drawing described in Figure 3 where GR (101) is exothermic in nature. The heat recovery from GR (101) is carried out using steam. The superheated steam (147) after recovering heat from MRR (102), send to GR (101) for further heat recovery. After recovering the exothermic heat in GR (101), the superheated steam (147a) is admitted to intermediate pressure turbine (122a). The oxygen-depleted air is (108) directly send to heat the fresh air (124).

[0050] The following is the illustrative example of the working of the CLC process. It should be understood that the following examples are illustrative only and not limited the invention.

Example 1:
Details of the Experimentation

[0051] An experimental study of CLC process with Ni and Fe based metal oxides with alumina support in a lab scale 1 kW CLC facility indicated that fuel conversion 99.9% is possible and 100% regeneration of oxygen carriers is achieved. The heat release during the air reaction with metal oxide was approximately 1.25 kW and similarly, heat supply during fuel reaction with metal oxides was approximately 0.25 kW.

[0052] Based on the experimental results, a theoretical study for CLC based 662 MWth Natural Gas (NG) fired thermal power plant has been conducted with NiO:Al2O3 as an oxygen carrier. The NG (100% methane was assumed) and metal oxide quantity required is 47.7 t/h and 1065.4 t/h respectively and the NiO:Al2O3 ratio maintained was 60:40. In GR, the reaction between methane and metal oxides is endothermic; therefore the amount of energy to be supplied for methane and NiO/Al2O3 was 129 MWth, with the supply of preheated fuel (800 0C) and metal oxides, the net energy supplied to GR was approximately 63 MWth. The energy is supplied using dedicated compressed fluid, circulating between MRR and GR. In the MRR, the reaction between metal oxides and the air is exothermic; therefore approximately 791 MWth energy would be released. The remaining energy available at MRR is recovered using steam. The energy from flue gas after GR and oxygen-depleted air after MRR was utilized to heat the water/ steam, fresh fuel, and air respectively. The flue gas is cooled and sent for CO2 capture. The oxygen-depleted air after energy recovery left to the atmosphere.