Apparatus and method for simultaneous co2 enrichment and gasification by a two-step chemical looping

Abstract

The application provides a device and method for two-step chemical looping gasification and CO2 enrichment. The method comprises two oxygen carrier circulation, the first circulation adopts weak oxidizing oxygen carrier, lattice oxygen of which is used as medium to partially oxidize volatile matter, and then the reduced oxygen carrier and steam are used for deoxidation gasification of semi-coke to realize two-step chemical looping gasification; the second circulation adopts strong oxidizing oxygen carrier, and CO2 enrichment is realized by complete oxidation of part of gas produced by the strong oxidizing oxygen carrier, and then the strong oxidizing oxygen carrier is oxidized by air to produce heat, thereby realizing energy supply of the system. The application can realize step-by-step conversion of solid fuel, strengthen effective conversion of volatile matter in raw material, and avoid influence of tar on gas production. Meanwhile, decoupling of chemical looping gasification can be realized, CO-rich gas and H2-rich gas with different H2 / CO are obtained. CO2 generated in the conversion process can be reduced, and the generated CO2 can be enriched and recovered, thereby effectively reducing carbon emission. The raw material has good adaptability, the product has high quality, and the application is friendly to environment.

Description

Technical Field

[0001] This invention belongs to the field of syngas production technology and relates to an apparatus and method for simultaneous CO2 enrichment through two-step chemical looping gasification. It is an apparatus and method that utilizes metal oxides or composite metal oxides as oxygen carriers, catalysts and heating media to simultaneously enrich CO2 through two-step chemical looping gasification of solid carbon-containing fuels. Background Technology

[0002] Gasification is an important way to efficiently utilize solid carbon fuels. Its purpose is to produce syngas, mainly composed of CO, H2, and CH4, for use in heat and electricity generation or further processing to produce fuels and chemical products. Developing new gasification technologies to produce clean syngas while capturing CO2 during the process is of great significance for implementing the "dual-carbon" strategy, alleviating current energy and environmental problems, and safeguarding national energy security. Traditional gasification processes occur simultaneously in time and space, involving a series of reactions such as feedstock pyrolysis, volatile matter reforming, semi-coke gasification, and combustion. Due to reaction coupling, there are mutual influences between the reactions. For example, volatiles produced by pyrolysis can inhibit the semi-coke gasification process and result in high tar content in the produced gas. When air is used as the gasification medium, the syngas is also easily diluted by nitrogen and CO2, leading to a decline in syngas quality.

[0003] Chemical looping gasification is a novel decoupled gasification technology. A chemical looping gasification system typically consists of two reactors: a fuel reactor and an air reactor, with a high-temperature solid bed circulating between them. The high-temperature solid bed acts as a heat carrier, providing energy for the gasification process, and simultaneously as an oxygen carrier, providing the gasification medium in the form of lattice oxygen. Compared to traditional technologies, this technology has the following advantages: (1) lattice oxygen serves as the gasification medium, eliminating the need for an air separation system and preventing nitrogen dilution of the produced gas; (2) the oxygen carrier has a catalytic effect, improving the gasification reaction efficiency; and (3) the tar content in the syngas is relatively low. Therefore, chemical looping gasification of solid carbon fuels has extremely high research and application value.

[0004] In current solid carbon fuel chemical looping gasification processes, the highly oxidizing oxygen carrier consumes H2 and CO in the products, resulting in syngas characterized by high CO2 and low effective syngas. This often necessitates specific CO2 separation units to improve syngas quality and enrich CO2. The fundamental reason is that lattice oxygen in the oxygen carrier is transferred to the syngas, ultimately existing as CO2 and H2O. Patent CN 113072981 A discloses a functional composite oxygen carrier chemical looping deoxygenation gasification synergistic CO2 conversion method. This method involves gasifying biomass and deoxygenated calcium ferrite in a CO2 atmosphere, followed by catalytic cracking and reforming of tar and hydrocarbons to produce biochar, light tar, and high-quality syngas. Subsequently, the biochar is gasified at high temperature, reducing calcium ferrite to deoxygenated calcium ferrite for reuse in a new cycle. This method achieves the gasification of deoxygenated calcium ferrite and biomass, reducing the impact of lattice oxygen in the oxygen carrier on gas production. However, this method has the following drawbacks: It is carried out under a CO2 atmosphere, resulting in a still high CO2 concentration in the produced gas, requiring further separation to reduce the CO2 concentration. Furthermore, the method lacks an H2 / CO control mechanism, leading to a CO concentration in the syngas that is much higher than the H2 concentration, thus the syngas quality still needs improvement. Finally, the method uses biochar as the oxygen carrier, and this solid-solid reaction may result in a slow reaction rate in actual reaction systems due to low heat and mass transfer efficiency. Summary of the Invention

[0005] This invention addresses the problems of high CO2 concentration and low effective syngas in existing solid carbon fuel chemical looping gasification processes, as well as the need for specific CO2 separation units to achieve syngas upgrading and CO2 enrichment. It proposes a two-step chemical looping gasification apparatus and method for simultaneous CO2 enrichment.

[0006] The technical solution of the present invention is as follows:

[0007] A two-step chemical looping gasification and CO2 enrichment device mainly consists of a reduction reactor, a gasification reactor, a lifting and heating reactor, a particle classifier, and a CO2 enrichment reactor, forming two circulation paths.

[0008] The first cycle includes a reduction reactor, a gasification reactor, a lifting and heating reactor, and a particle classifier; the solid discharge port of the reduction reactor is connected to the feed port of the gasification reactor, the solid discharge port of the gasification reactor is connected to the lower part of the lifting and heating reactor, and the upper part of the lifting and heating reactor is connected to the feed port of the reduction reactor via the particle classifier;

[0009] The second circulation path includes a CO2 enrichment reactor, a lifting and heating reactor, and a particle classifier; the solid discharge port of the CO2 enrichment reactor is connected to the lower part of the lifting and heating reactor, and the upper part of the lifting and heating reactor is connected to the solid feed port of the CO2 enrichment reactor via the particle classifier.

[0010] The reduction reactor reacts the high-temperature, high-valence oxygen carrier 1 fed from the particle classifier with the solid carbon fuel fed from the feed inlet to undergo a devolatileization and chemical looping gasification reaction, generating syngas 1, semi-coke, and oxygen-deprived oxygen carrier 1. Part of the syngas 1 is extracted, and the other part is fed into the gas inlet of the CO2 enrichment reactor. The portion of syngas 1 diverted from the reduction reactor and the high-temperature, high-valence oxygen carrier 2 fed from the particle classifier undergo a redox reaction in the CO2 enrichment reactor to generate a mixture of CO2 and H2O, as well as low-temperature oxygen-deprived oxygen carrier 2. The mixture is condensed with H2O to obtain high-concentration CO2.

[0011] The gasification reactor gasifies the semi-coke and deoxygenated oxygen carrier 1 fed from the solid discharge port of the reduction reactor to generate syngas 2, ash and low-temperature high-valence oxygen carrier 1. Syngas 2 is extracted, and ash and low-temperature high-valence oxygen carrier 1 are fed into the lifting and heating reactor.

[0012] The heating reactor mixes low-temperature, high-valence oxygen carrier 1 and low-temperature, oxygen-depleted oxygen carrier 2 and raises the temperature to obtain high-temperature, high-valence oxygen carrier 1 and high-temperature, high-valence oxygen carrier 2. These are then sent to a particle classifier for separation, and the high-temperature, high-valence oxygen carrier 1 and high-temperature, high-valence oxygen carrier 2 are respectively sent to a reduction reactor and a CO2 enrichment reactor.

[0013] A two-step chemical looping gasification method for simultaneous CO2 enrichment, the method comprising two cycles of oxygen carriers with different oxidizing properties.

[0014] In the reduction reactor, dried solid carbon fuel and high-temperature, high-valence oxygen carrier 1 undergo rapid heat exchange and volatile matter removal and chemical looping gasification reactions to generate syngas 1, semi-coke, and deoxygenated oxygen carrier 1. Syngas 1 is then split, with a portion extracted as product gas and the remainder introduced into a CO2 enrichment reactor. The portion introduced into the CO2 enrichment reactor accounts for 0.3–0.8% of the mass of syngas 1.

[0015] In the gasification reactor, the oxygen carrier 1 and semi-coke deoxygenated from the reduction reactor are vaporized with steam to generate syngas 2, ash and oxygen carrier 1; syngas 2 is extracted as produced gas.

[0016] In the CO2 enrichment reactor, the diverted syngas 1 and the high-temperature, high-valence oxygen carrier 2 undergo a redox reaction to generate CO2, H2O, and a low-temperature deoxygenated oxygen carrier 2; the generated water is condensed and separated to obtain a high concentration of CO2.

[0017] The low-temperature oxygen carrier 2 formed in the CO2 enrichment reactor enters the bottom of the lifting and heating reactor. The low-temperature oxygen carrier 2 is oxidized by the hot air that is introduced into a high-valence oxygen carrier 2. The heat released is used to heat the high-valence oxygen carrier 2 to raise its temperature, thereby obtaining a high-temperature high-valence oxygen carrier 2.

[0018] High-temperature, high-valence oxygen carrier 2 is mixed with ash from the gasification reactor and low-temperature, high-valence oxygen carrier 1, causing the temperature of low-temperature, high-valence oxygen carrier 1 to rise and become high-temperature, high-valence oxygen carrier 1. Then, the ash, high-temperature, high-valence oxygen carrier 1, and high-temperature, high-valence oxygen carrier 2 are lifted by hot air to the particle classifier. The dust-laden exhaust gas, high-temperature, high-valence oxygen carrier 1, and high-temperature, high-valence oxygen carrier 2 are separated in the particle classifier. The dust-laden exhaust gas is discharged after dust removal and heat recovery, while the high-temperature, high-valence oxygen carrier 1 is returned to the reduction reactor, forming the first cycle. The high-temperature, high-valence oxygen carrier 2 is returned to the CO2 enrichment reactor, forming the second cycle.

[0019] The molar ratio of H2 to CO in syngas 1 is less than 1.5; the molar ratio of H2 to CO in syngas 2 is greater than 1.5.

[0020] The oxygen carrier 1 includes, but is not limited to, single-metal oxides (FeO, CeO2, Cr2O3) or bimetallic oxides (LaFeO2, CaFe2O4, Ca2Fe2O5, Ba2Fe2O5), etc. Preferably, the oxygen carrier 1 is a bimetallic oxide; preferably, the particle size of the oxygen carrier 1 is 0.2-0.4 mm.

[0021] The oxygen carrier 2 includes, but is not limited to, single-metal oxides (Fe2O3, Fe3O4, and oxides of Mn, Ni, Co, Cu, etc., such as MnO, Mn3O4, NiO, CoO, Co3O4, CuO), bimetallic oxides (Cu2Fe2O5, FeTi2O3, etc.), salts (such as CaSO4), or modified natural ores (iron-loaded / nickel-loaded olivine, nickel-loaded spinel, etc.). Preferably, the oxygen carrier 2 is Fe2O3 or Fe3O4; preferably, the particle size of the oxygen carrier 2 is 0.4-0.8 mm.

[0022] The temperature gradient between the reduction reactor and the gasification reactor is achieved by controlling the temperature of the oxygen carrier 1 entering the reduction reactor and its mass ratio to the solid carbon fuel, thereby controlling the reaction at each stage.

[0023] Preferably, the temperature of the oxygen carrier 1 entering the reduction reactor is 900-950℃;

[0024] Preferably, the mass ratio of oxygen carrier 1 to solid carbon fuel entering the reduction reactor is 2:1 to 50:1.

[0025] The temperature of the CO2 enrichment reactor is controlled by controlling the temperature of the oxygen carrier 2 entering the CO2 enrichment reactor and its mass ratio to that of the solid carbon-containing fuel entering the reduction reactor.

[0026] Preferably, the temperature of the oxygen carrier 2 entering the CO2 enrichment reactor is 900-950℃;

[0027] Preferably, the mass ratio of the oxygen carrier 2 entering the CO2 enrichment reactor to the solid carbon fuel entering the reduction reactor is 2:1 to 40:1.

[0028] In the first cycle, the reduction reaction temperature is not lower than 800℃, preferably 800-850℃. High temperature is beneficial for the reduction of volatiles from the oxygen carrier, and simultaneously maintains a high temperature for the solid at the reducer outlet, providing suitable conditions for the subsequent gasification reaction. The gasification reaction temperature is not lower than 750℃, preferably 750-820℃. Maintaining a higher temperature can suppress the methanation reaction and the water-gas shift reaction. The heating temperature is increased to not lower than 850℃, preferably 850-950℃, to avoid excessively high temperatures leading to ash melting. In the second cycle, the CO2 enrichment temperature is not lower than 750℃, preferably 750-950℃.

[0029] The mass ratio of the gasifying agent water vapor added to the gasification reactor to the solid carbon-containing fuel added to the reduction reactor is 0.1:1 to 1.2:1.

[0030] The solid carbon-containing fuel includes, but is not limited to, one or a mixture of two or more of low-rank coal, biomass, petroleum coke, coke, charcoal, plastics, rubber, and asphalt. Preferably, the particle size of the solid carbon-containing fuel is 0.2-20 mm.

[0031] The solid carbon fuel needs to be dried. Water in the carbon fuel will react with the reduced oxygen carrier. Therefore, the moisture content needs to be controlled between 2-10% to ensure the normal progress of the reduction reaction, preferably 2-5%.

[0032] The basic principle of this invention is as follows:

[0033] In the reduction reactor, the primary characteristic of the circulating oxygen carrier 1 in the first cycle is its weak oxidizing capacity; it can only partially oxidize the carbon-containing fuel into CO and H2, but cannot further oxidize it into CO2 and H2O. Furthermore, the reduced oxygen carrier 1 can decompose CO2 and H2O to generate CO and H2. First, the dried solid carbon-containing fuel and the high-temperature, high-valence oxygen carrier 1 undergo rapid heat exchange and a volatile matter removal reaction. During this process, the high-valence oxygen carrier 1 comes into full contact with the volatiles, partially oxidizing them into a CO-rich gas, primarily composed of CO and H2 but with a low H2 / CO ratio. Second, the deoxygenated oxygen carrier 1 and the semi-coke after the reaction enter the gasification reactor for steam gasification, generating a tar-free, high-H2 / CO-rich syngas and the high-valence oxygen carrier 1. Finally, after heat exchange in the lifting and heating reactor, lifting, and particle classification in the particle classifier, the high-valence oxygen carrier 1 mixes with the newly added solid carbon-containing fuel to begin a new cycle.

[0034] The second cycle utilizes a circulating oxygen carrier 2 characterized by its strong oxidizing capacity, capable of completely oxidizing carbon-containing fuels into CO2 and H2O. Furthermore, the reduced oxygen carrier 2 can be re-oxidized by air to a higher oxidation state, releasing heat. First, the CO-rich gas generated in the reduction reactor of the first cycle is split; part is extracted as product gas, and the other part contacts and reacts with the high-oxidation-state oxygen carrier 2. During this process, the high-oxidation-state oxygen carrier completely oxidizes the CO-rich gas into CO2 and H2O, while itself being reduced to a lower oxidation state. Second, the deoxygenated oxygen carrier 2 is contacted with air, oxidizing it to a higher oxidation state and raising its temperature. Third, the second-cycle oxygen carrier 2 is mixed with the first-cycle oxygen carrier 1 in a lifting and heating reactor for heat exchange, increasing the temperature of the first-cycle oxygen carrier 1. Finally, the oxygen carrier 2 undergoes lifting in the lifting and heating reactor and particle classification in a particle classifier, and is then re-contacted with the CO-rich gas to begin a new cycle.

[0035] When starting the equipment from a cold state, first ignite the oil gun at the bottom of the lifting and heating reactor to heat it to the predetermined temperature. Then, add oxygen carrier 1 and oxygen carrier 2, raising their temperature and allowing them to pass through the particle classifier to the reduction reactor and CO2 enrichment reactor, respectively. The high-temperature oxygen carriers 1 and 2 carry heat from the lifting and heating reactor to the two circulation paths, bringing each reactor to the preset temperature. Afterward, stop the oil gun and begin feeding solid carbon fuel.

[0036] Specifically, the first cycle includes a reduction reactor, a gasification reactor, a booster reactor, and a particle classifier. In the reduction reactor, the fuel rapidly exchanges heat with the high-temperature oxygen carrier 1 and undergoes a volatile matter removal reaction to generate volatiles and semi-coke. The volatiles are in full contact with the oxygen carrier 1, and the tar vapors and hydrocarbon gases therein exhibit strong reducing properties, being preferentially consumed by the oxygen carrier, thus avoiding blockage problems caused by tar condensation in the produced gas during subsequent processes. Because the lattice oxygen in the oxygen carrier 1 is transferred out and exists in the produced gas in the form of CO, the produced gas exhibits high CO characteristics and is called CO-rich gas. During this process, the oxygen carrier 1 itself is reduced to a low valence state and enters the gasification reactor together with the semi-coke. At the same time, the oxygen carrier 1 acts as a heat carrier to provide heat for the reaction, and its own temperature decreases. In the gasification reactor, the semi-coke is gasified under the action of water vapor, generating H2, CO, and CO2. Unused H2O and CO2 produced during gasification are cracked by low-valence oxygen carrier 1 to generate H2 and CO, increasing the H2 / CO ratio and decreasing the CO2 content in the gas produced at this stage. Since the tar has already been consumed in the reduction reactor and does not participate in the gasification process, the gas produced by the gasification reactor is tar-free, high-H2 / CO, H2-rich gas. The semi-coke gasification process is a strongly endothermic reaction; high temperature and a suitable supply of steam favor the reaction towards H2 and CO production. However, excessive steam will cause a sudden drop in temperature, inhibiting the semi-coke gasification reaction and promoting the water-gas shift reaction towards CO2 production. By controlling the mass ratio of steam to solid carbon fuel, complete semi-coke gasification is ensured without producing large amounts of CO2. To avoid localized excessive steam, one or more steam inlets can be designed, with steam input divided into one or more zones. Priority is given to ensuring complete semi-coke conversion, followed by ensuring the complete conversion of low-valence oxygen carrier 1 to high-valence oxygen carrier 1. During this process, oxygen carrier 1 also acts as a heat transfer medium to provide heat for the reaction, further reducing its own temperature. The low-temperature oxygen carrier 1 and ash are fed into the booster heater reactor, where they are mixed and reheated to a high temperature by heat exchange with the second oxygen carrier 1. Subsequently, they enter the particle classifier, where, under the action of the classifying gas, the oxygen carrier and ash are separated based on differences in physical properties such as density and particle size. The separated first high-temperature oxygen carrier 1 returns to the reduction reactor to begin a new cycle.

[0037] Specifically, the second cycle includes a CO2 enrichment reactor, a booster heater, and a particle classifier. In the CO2 enrichment reactor, a portion of the CO-rich gas from the first cycle is separated and undergoes a redox reaction with the second oxygen carrier 2. During this process, the CO-rich gas is completely oxidized to CO2 and H2O, and CO2 enrichment can be achieved by condensing the water. Oxygen carrier 2 is reduced to a lower valence state and sent to the booster heater, where it is thoroughly mixed with the first oxygen carrier 1 under the fluidization of air. In this process, the lower valence state of oxygen carrier 2 is oxidized by air, releasing heat and raising the temperature of both oxygen carriers. Subsequently, it enters the particle classifier under the booster of air to achieve separation of the oxygen carriers. The separated second oxygen carrier 2 is recycled back to the CO2 enrichment reactor. This process utilizes the second oxygen carrier 2 to first oxidize the CO-rich gas and then be oxidized by air to obtain heat for heating the system. Since the CO-rich gas is oxidized using oxygen lattice in the oxygen carrier instead of air, the generated CO2 is not diluted by other gases, thus eliminating the need for an additional CO2 separation system.

[0038] The beneficial effects of this invention are:

[0039] (1) Two-way circulation is set up using oxygen carriers with different oxidation capacities to realize the gasification of solid carbon fuels and the chemical looping combustion of some of the produced gas; thereby realizing the stepwise conversion of solid carbon fuels and the self-sufficiency of system heat. It realizes the efficient utilization of volatiles, reduces the production of tar, and obtains high-quality clean syngas; it also realizes the enrichment of CO2 and reduces carbon emissions during the process.

[0040] (2) By utilizing the decoupling of reduction and oxidation of the first oxygen carrier, volatiles reduce the oxygen carrier, while H2O and CO2 oxidize the oxygen carrier; this effectively enhances the conversion of volatiles and avoids the influence of tar on gas production; it also effectively suppresses the generation of CO2 during the gasification process. Compared with traditional chemical looping gasification, this method achieves the segmentation of syngas, obtaining two gases with different H2 / CO ratios.

[0041] (3) By utilizing the decoupling of reduction and oxidation of the second oxygen carrier, the oxygen carrier is reduced by CO-rich gas and oxidized by air; thereby achieving the purpose of consuming part of the CO-rich gas to heat the system, and realizing the energy balance of the reaction system without the need for external heat supply; compared with the combustion of semi-coke for heat supply in traditional chemical loop gasification, the CO2 generated by the system is separated from the flue gas, realizing the enrichment and recovery of CO2, and effectively reducing carbon emissions.

[0042] (4) The method has good raw material adaptability and can process highly volatile solid carbon fuels. It has a high raw material conversion rate, high product quality, and is environmentally friendly. Attached Figure Description

[0043] Figure 1 This is a schematic diagram illustrating the operating principle of a two-step chemical looping gasification method for simultaneous CO2 enrichment according to the present invention.

[0044] Figure 2 This is a schematic diagram of the process flow of a two-step chemical looping gasification method for simultaneous CO2 enrichment according to the present invention. Detailed Implementation

[0045] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0046] The process flow of this invention is as follows: Figure 2 As shown, its principle is as follows Figure 1 As shown, the first cycle includes a reduction reactor, a gasification reactor, a lift-heating reactor, and a particle classifier; the second cycle includes a CO2 enrichment reactor, a lift-heating reactor, and a particle classifier; the two cycles share the lift-heating reactor and the particle classifier.

[0047] Example 1

[0048] Pine sawdust was used as raw material, and its industrial and elemental analyses are shown in Table 1. Calcium ferrite (mainly Ca2Fe2O5) and iron ore (mainly Fe2O3) were used as oxygen carrier 1 and oxygen carrier 2, respectively. Pine sawdust was fed into the reduction reactor, where it contacted and exchanged heat with calcium ferrite from the particle classifier. The mass ratio of pine sawdust to calcium ferrite was 1:40, and the temperature of the calcium ferrite was 950℃. The pine sawdust underwent rapid pyrolysis to generate volatiles and semi-coke. Subsequently, the volatiles reacted with calcium ferrite in a redox reaction. Oxygen from the calcium ferrite was transferred to the tar and small-molecule hydrocarbons in the volatiles, converting them into CO-rich gas with a low H2 / CO ratio. Part of this gas was collected as product gas (its composition analysis is shown in Table 2), and the rest was fed into a CO2 enrichment unit. The calcium ferrite itself was reduced to deoxygenated calcium ferrite and its temperature was lowered to 850℃, then fed into the gasification reactor along with the unreacted semi-coke.

[0049] In the gasification reactor, semi-coke is gasified under the action of water vapor, producing H2, CO, and CO2. The mass ratio of input water vapor to pine sawdust is 0.8:1. The unreacted H2O and CO2 produced during gasification are decomposed by calcium ferrite, producing H2 and CO, as shown below. Figure 1 As shown, the H2 / CO ratio of the produced gas in this stage was increased and the CO2 content in the produced gas was reduced. The produced gas was a tar-free H2 / CO high H2-rich gas, and its component analysis is shown in Table 2. At the same time, the deoxygenated calcium ferrite itself was re-oxidized to calcium ferrite, the temperature was reduced to 817℃, and it was sent to the booster heater.

[0050] The CO-rich gas from the reduction reactor enters the CO2 enrichment unit to reduce the iron ore. The temperature of the iron ore entering the CO2 enrichment unit is 950℃, and the mass ratio of pine sawdust to it is 1:29. The CO-rich gas itself is oxidized to CO2 and H2O, and water is separated by condensation (circulating water cooling) to obtain a high concentration of CO2, thereby achieving CO2 enrichment; the iron ore is reduced to deoxygenated iron ore and sent to the booster heater (3).

[0051] Calcium ferrite from the gasification reactor and deoxidized iron ore from the CO2 enrichment unit are fed into the lifting and heating reactor, where they are rapidly mixed and fluidized under the action of hot air. Simultaneously, in the presence of oxygen in the air, the deoxidized iron ore is completely oxidized to a higher valence state, releasing a large amount of heat and causing its temperature to rise. Meanwhile, the calcium ferrite is heated under thorough mixing and contact. The calcium ferrite and iron ore are separated in a particle classifier and returned to the reduction reactor and CO2 enrichment reactor, respectively, to begin a new cycle; ash is also separated and discharged from the system.

[0052] Example 2

[0053] use Figure 2 The process flow diagram shows that bituminous coal was used as the solid carbonaceous fuel, and its industrial and elemental analysis results are shown in Table 1. LaFeO2 and Cu2Fe2O5 were used as oxygen carrier 1 and oxygen carrier 2, respectively. The mass ratio of bituminous coal to LaFeO2 was 1:32. The mass ratio of steam to bituminous coal was 1:1. Other conditions were the same as in Example 1. The component analysis of CO-rich and H2-rich gases is shown in Table 2.

[0054] Example 3

[0055] use Figure 2 The process flow diagram shows that a mixture of plastic and pine wood chips in a 1:1 mass ratio was used as solid carbon fuel. The industrial and elemental analyses of the plastic are shown in Table 1. Ba₂Fe₂O₅ and FeTi₂O₃ were used as oxygen carrier 1 and oxygen carrier 2, respectively. The mass ratio of the mixture to Ba₂Fe₂O₅ was 1:26, and the mass ratio of water vapor to the plastic and pine wood chip mixture was 1.2:1. Other conditions were the same as in Example 1. The component analyses of CO-rich and H₂-rich gases are shown in Table 2.

[0056] Comparative Example

[0057] A conventional chemical looping gasification system was used as a comparative example. The system consisted of two reactors: a fuel reactor and an air reactor. High-temperature hematite was used as the oxygen carrier, circulating between the two reactors. Pine sawdust was fed into the fuel reactor at a mass ratio of 1:35 to hematite, at an input temperature of 850℃. Steam was used as the gasification agent at a mass ratio of 0.8:1 to the pine sawdust. In the fuel reactor, the pine sawdust was gasified by the action of hematite and steam, producing syngas and semi-coke. The hematite itself was reduced to deoxidized hematite. The semi-coke and deoxidized hematite were fed into the air reactor. In an air atmosphere, the semi-coke was completely burned, and the deoxidized hematite was completely oxidized, producing CO2-rich flue gas. The flue gas was vented, and the high-temperature hematite was returned to the fuel reactor to begin a new cycle. Syngas analysis is shown in Table 2.

[0058] Table 1 Industrial and Elemental Analysis of Raw Materials

[0059]

[0060] Table 2 Product distribution under different conditions

[0061]

[0062] All the above embodiments were carried out under normal pressure. Compared with conventional chemical looping gasification, the two-step chemical looping gasification can reduce the generation of CO2 in the produced gas and increase the proportion of effective syngas; at the same time, the two-step gasification can achieve the separation of the produced gas components, obtaining CO-rich gas and H2-rich gas with different H2 / CO ratios respectively; by using a two-way oxygen carrier circulation method, zero carbon emissions of the system can be achieved; no tar was detected during the embodiments.

Claims

1. A device for two-step chemical looping gasification and simultaneous CO2 enrichment, characterized in that, The device mainly consists of a reduction reactor, a gasification reactor, a lifting and heating reactor, a particle classifier, and a CO2 enrichment reactor, forming a two-way circulation. The first cycle includes a reduction reactor, a gasification reactor, a lifting and heating reactor, and a particle classifier; the solid discharge port of the reduction reactor is connected to the feed port of the gasification reactor, the solid discharge port of the gasification reactor is connected to the lower part of the lifting and heating reactor, and the upper part of the lifting and heating reactor is connected to the feed port of the reduction reactor via the particle classifier; The second circulation path includes a CO2 enrichment reactor, a lifting and heating reactor, and a particle classifier; the solid discharge port of the CO2 enrichment reactor is connected to the lower part of the lifting and heating reactor, and the upper part of the lifting and heating reactor is connected to the solid feed port of the CO2 enrichment reactor via the particle classifier. The reduction reactor reacts the high-temperature, high-valence oxygen carrier 1 fed from the particle classifier with the solid carbon fuel fed from the feed inlet to undergo a devolatileization and chemical looping gasification reaction, generating syngas 1, semi-coke, and oxygen-deprived oxygen carrier 1. Part of the syngas 1 is extracted, and the other part is fed into the gas inlet of the CO2 enrichment reactor. The portion of syngas 1 diverted from the reduction reactor and the high-temperature, high-valence oxygen carrier 2 fed from the particle classifier undergo a redox reaction in the CO2 enrichment reactor to generate a mixture of CO2 and H2O, as well as low-temperature oxygen-deprived oxygen carrier 2. The mixture is condensed with H2O to obtain high-concentration CO2. The gasification reactor gasifies the semi-coke and deoxygenated oxygen carrier 1 fed from the solid discharge port of the reduction reactor to generate syngas 2, ash and low-temperature high-valence oxygen carrier 1. Syngas 2 is extracted, and ash and low-temperature high-valence oxygen carrier 1 are fed into the lifting and heating reactor. The heating reactor mixes low-temperature, high-valence oxygen carrier 1 and low-temperature, oxygen-depleted oxygen carrier 2 and raises the temperature to obtain high-temperature, high-valence oxygen carrier 1 and high-temperature, high-valence oxygen carrier 2. These are then sent to a particle classifier for separation, and the high-temperature, high-valence oxygen carrier 1 and high-temperature, high-valence oxygen carrier 2 are respectively sent to a reduction reactor and a CO2 enrichment reactor.

2. A two-step chemical looping gasification method for simultaneous CO2 enrichment, characterized in that, The method includes the circulation of two oxygen carriers with different oxidizing properties; In the reduction reactor, the dried solid carbon fuel and the high-temperature, high-valence oxygen carrier 1 undergo rapid heat exchange and volatile matter removal and chemical looping gasification reactions to generate syngas 1, semi-coke, and oxygen-depleted oxygen carrier 1. The syngas 1 is split, with one part being extracted as product gas and the other part being introduced into the CO2 enrichment reactor. In the gasification reactor, the deoxygenated oxygen carrier 1 and semi-coke from the reduction reactor are vaporized with steam to generate syngas 2, ash and oxygen carrier 1; syngas 2 is extracted as the produced gas. In the CO2 enrichment reactor, the diverted syngas 1 and the high-temperature, high-valence oxygen carrier 2 undergo a redox reaction to generate CO2, H2O, and the low-temperature deoxygenated oxygen carrier 2; the generated water is condensed and separated to obtain a high concentration of CO2. The low-temperature oxygen carrier 2 formed in the CO2 enrichment reactor enters the bottom of the lifting and heating reactor. The low-temperature oxygen carrier 2 is oxidized by the hot air that is introduced into a high-valence oxygen carrier 2. The heat released is used to heat the high-valence oxygen carrier 2 to raise its temperature, thereby obtaining a high-temperature high-valence oxygen carrier 2. High-temperature, high-valence oxygen carrier 2 is mixed with ash from the gasification reactor and low-temperature, high-valence oxygen carrier 1, causing the temperature of low-temperature, high-valence oxygen carrier 1 to rise and become high-temperature, high-valence oxygen carrier 1. Then, the ash, high-temperature, high-valence oxygen carrier 1, and high-temperature, high-valence oxygen carrier 2 are lifted by hot air to the particle classifier. The dust-laden exhaust gas, high-temperature, high-valence oxygen carrier 1, and high-temperature, high-valence oxygen carrier 2 are separated in the particle classifier. The dust-laden exhaust gas is discharged after dust removal and heat recovery, while the high-temperature, high-valence oxygen carrier 1 is returned to the reduction reactor, forming the first cycle. The high-temperature, high-valence oxygen carrier 2 is returned to the CO2 enrichment reactor, forming the second cycle.

3. The method for simultaneous CO2 enrichment through two-step chemical looping gasification according to claim 2, characterized in that, The oxygen carrier 1 is one or more of a single metal oxide or a mixture of two or more bimetallic oxides; the oxygen carrier 2 is one or more of a single metal oxide, a bimetallic oxide, a salt substance, or a modified natural ore.

4. The method for simultaneous CO2 enrichment through two-step chemical looping gasification according to claim 3, characterized in that, The oxygen carrier 1 is one or a mixture of two or more of FeO, CeO2, Cr2O3, LaFeO2, CaFe2O4, Ca2Fe2O5, and Ba2Fe2O5, with a particle size of 0.2-0.4 mm; the oxygen carrier 2 is one or a mixture of two or more of Fe2O3, Fe3O4, MnO, Mn3O4, Mn2O3, NiO, CoO, Co3O4, CuO, Cu2Fe2O5, FeTi2O3, CaSO4, nickel-loaded olivine, iron-loaded olivine, and nickel-loaded spinel, with a particle size of 0.4-0.8 mm.

5. A two-step chemical looping gasification method for simultaneous CO2 enrichment according to claim 2, 3, or 4, characterized in that, The temperature gradient between the reduction reactor and the gasification reactor is achieved by controlling the temperature of the oxygen carrier 1 entering the reduction reactor and its mass ratio to the solid carbon fuel, thereby controlling the reaction at each stage. The temperature of the oxygen carrier 1 entering the reduction reactor is 900-950℃; the mass ratio of the oxygen carrier 1 entering the reduction reactor to the solid carbon fuel is 2:1 to 50:

1. The temperature of the CO2 enrichment reactor is controlled by controlling the temperature of the oxygen carrier 2 entering the CO2 enrichment reactor and its mass ratio to that of the solid carbon-containing fuel entering the reduction reactor; wherein, the temperature of the oxygen carrier 2 entering the CO2 enrichment reactor is 900-950℃; and the mass ratio of the oxygen carrier 2 entering the CO2 enrichment reactor to the solid carbon-containing fuel entering the reduction reactor is 2:1 to 40:

1.

6. A two-step chemical looping gasification method for simultaneous CO2 enrichment according to claim 2, 3, or 4, characterized in that, The portion introduced into the CO2 enrichment reactor accounts for 0.3 to 0.8% of the mass of syngas 1; the mass ratio of the gasifying agent water vapor added to the gasification reactor to the solid carbon-containing fuel added to the reduction reactor is 0.1:1 to 1.2:1; the molar ratio of H2 to CO in syngas 1 is less than 1.5; the molar ratio of H2 to CO in syngas 2 is greater than 1.

5.

7. A two-step chemical looping gasification method for simultaneous CO2 enrichment according to claim 2, 3, or 4, characterized in that, In the first cycle, the reduction reaction temperature is not lower than 800℃, the gasification reaction temperature is not lower than 750℃, and the heating temperature is not lower than 850℃; in the second cycle, the CO2 enrichment temperature is not lower than 750℃.

8. The method for simultaneous CO2 enrichment through two-step chemical looping gasification according to claim 7, characterized in that, In the first cycle, the reduction reaction temperature is 800-850℃, the gasification reaction temperature is 750-820℃, and the boosting heating temperature is 850-950℃; in the second cycle, the CO2 enrichment temperature is 750-950℃.

9. A two-step chemical looping gasification method for simultaneous CO2 enrichment according to claim 2, 3, 4, or 8, characterized in that, The solid carbon-containing fuel is one or more of the following: low-rank coal, biomass, petroleum coke, coke, charcoal, plastics, rubber, and asphalt, with a particle size of 0.2-20 mm.

10. A two-step chemical looping gasification method for simultaneous CO2 enrichment according to claim 2, 3, 4, or 8, characterized in that, The solid carbon-containing fuel needs to be dried, and after drying, the moisture content of the carbon-containing fuel is 2-10% by mass.

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