System for preparing green methanol by means of biomass gasification coupled with green hydrogen

Abstract

Disclosed in the present invention is a system for preparing green methanol by means of biomass gasification coupled with green hydrogen. The system comprises: a gasification unit (A), a purification unit (B), a hydrogen and oxygen unit (C) and a synthesis unit (D), wherein synthesis gas (104) produced by the gasification unit (A) passes through the purification unit (B) and serves as a raw material gas (107) of the synthesis unit; oxygen (109) produced by the hydrogen and oxygen unit (C) serves as oxygen of the gasification unit, and hydrogen (113) produced by the hydrogen and oxygen unit (C) serves as a hydrogen source for adjusting the hydrogen-carbon ratio of the raw material gas of the synthesis unit (D); and part of a purge gas (121) of the synthesis unit (D) is returned to the gasification unit for recycling. The system of the present invention operates stably and reliably, and has a high utilization rate of renewable carbon sources, and a low methanol preparation cost.

Description

A system for producing green methanol by biomass gasification coupled with green hydrogen TECHNICAL FIELD

[0001] The present application relates to a system for producing green methanol by biomass gasification coupled with green hydrogen, belonging to the technical field of green methanol preparation. BACKGROUND

[0002] Shipping giants have formulated a plan to replace fuel oil with green methanol as a ship fuel to achieve carbon emission reduction. The demand for green methanol in the shipping industry will grow rapidly in the future, and the industry of producing green methanol from clean and renewable energy will also enter a fast lane.

[0003] Biomass gasification coupled with green hydrogen to produce chemical products such as methanol and green aviation kerosene is an important way for the development of clean chemical fuels. Biomass, as a renewable resource, has the characteristics of abundant resource yield, wide geographical distribution, and stable energy reserves. The synthesis gas produced by biomass gasification can be used as raw material gas for methanol synthesis after adjusting the hydrogen-carbon ratio through a shift conversion system. However, the shift conversion system requires additional steam consumption and the discharge of part of CO2, resulting in a decrease in the utilization rate of renewable carbon sources. With the increase in installed capacity of renewable energy power generation in China, due to the instability of renewable energy output, there is a serious problem of "abandoned wind and light". The problem of abandoned new energy power generation is gradually becoming prominent, hindering the development and utilization of new energy. One of the effective ways to solve the problem of abandoned new energy power generation is to use renewable energy (such as wind power and photovoltaic power) to produce hydrogen through water electrolysis, and to synthesize methanol from CO2 captured by CO2 capture technology. However, this technical route has high cost and poor technical economy.

[0004] In summary, there is an urgent need for a system for producing green methanol by biomass gasification coupled with green hydrogen to solve the problems of low renewable carbon source utilization rate in biomass gasification for methanol production and high cost of CO2 and electrolytic hydrogen synthesis for methanol. SUMMARY

[0005] The technical problem to be solved by the present application is the low renewable carbon source utilization rate in biomass gasification for methanol production and the high cost of CO2 and electrolytic hydrogen synthesis for methanol.

[0006] To solve the above technical problems, the technical solution of the present application provides a system for producing green methanol by biomass gasification coupled with green hydrogen, and the technical solution is as follows:

[0007] The system comprises a gasification unit, a purification unit, a hydrogen-oxygen unit, and a synthesis unit. The synthesis gas produced by the gasification unit is used as the raw material gas of the synthesis unit after being purified by the purification unit. The oxygen produced by the hydrogen-oxygen unit is used as the oxygen of the gasification unit, and the hydrogen produced by the hydrogen-oxygen unit is used as the hydrogen source for adjusting the hydrogen-carbon ratio of the raw material gas of the synthesis unit. Part of the purge gas of the synthesis unit is returned to the gasification unit for recycling.

[0008] Preferably, the gasification unit mainly comprises a gasifier, a reformer, and a waste heat boiler; the gasifier operates at a pressure of 50 kPa(g) to 2 MPa(g) and a temperature of 700 DEG C to 900 DEG C; the reformer operates at a temperature of 900 DEG C to 1200 DEG C; and the waste heat boiler operates at a temperature of 120 DEG C to 1200 DEG C.

[0009] Preferably, the purification unit mainly comprises a compressor, an oil removal tower, and a desulfurization and decarburization tower; the compressor has an outlet pressure of 0.5 MPa(g) to 4.0 MPa(g); the oil removal tower is a spray absorption tower, which operates at a pressure of 0.5 MPa(g) to 4.0 MPa(g) and a temperature of -40 DEG C to 40 DEG C; the desulfurization and decarburization tower is a multilayer spray absorption tower, which operates at a pressure of 0.5 MPa(g) to 4.0 MPa(g) and a temperature of -60 DEG C to -10 DEG C; and the desulfurization and decarburization tower has a function of adjustable CO2 removal rate.

[0010] Preferably, the hydrogen-oxygen unit mainly comprises an electrolytic cell, a hydrogen storage tank, and an oxygen storage tank; the electrolytic cell is an alkaline electrolytic cell or a PEM electrolytic cell or a combination of the two, and operates at a pressure of 50 kPa(g) to 4 MPa(g); the hydrogen storage tank and the oxygen storage tank are one of a spherical tank, a vertical storage tank, and a horizontal storage tank; the hydrogen storage tank operates at a pressure of 0.5 MPa(g) to 4 MPa(g); and the oxygen storage tank operates at a pressure of 0.3 MPa(g) to 2.5 MPa(g).

[0011] Preferably, the synthesis unit mainly comprises a compressor, a methanol synthesis tower, a heat exchanger, a gas-liquid separator, and a hydrogen recovery device; the compressor has an outlet pressure of 5.0 MPa(g) to 10 MPa(g); the methanol synthesis tower operates at a pressure of 5.0 MPa(g) to 10 MPa(g);

[0012] The purge gas generated by the hydrogen recovery device is divided into two routes, one of which returns to the reformer of the biomass gasification unit, and the other of which is discharged out of the system.

[0013] Preferably, the gasifier is a fluidized bed, a circulating fluidized bed, a fixed bed gasifier, or a circulating fluidized bed gasifier; and the oxygen required by the gasifier and the reformer is obtained from the oxygen generated by the water electrolysis unit or the oxygen obtained from an air separation facility.

[0014] Preferably, the fuel used by the reformer is synthetic purge gas, waste gas containing heat value, methane, or diesel fuel.

[0015] Preferably, the gasifier operates at a pressure of 150 kPa(g) to 1.2 MPa(g) and a temperature of 750 DEG C to 850 DEG C; the reformer operates at a temperature of 950 DEG C to 1100 DEG C; and the waste heat boiler operates at a temperature of 140 DEG C to 1100 DEG C.

[0016] Preferably, the compressor outlet pressure is 0.8-3.3 MPa(g); the deoiling tower operating pressure is 0.8-3.3 MPa(g), and the operating temperature is-20℃-35℃; the desulfurization and decarburization tower operating pressure is 0.8-3.3 MPa(g), and the operating temperature is-50℃--20℃.

[0017] Preferably, the electrolytic cell is an alkaline electrolytic cell or a PEM electrolytic cell or a combination of the two, and the operating pressure is 0.8-3.3 MPa(g); the hydrogen storage tank and the oxygen storage tank are spherical tanks; the hydrogen storage tank operating pressure is 0.8-3.3 MPa(g);

[0018] The oxygen storage tank operating pressure is 0.3-1.8 MPa(g).

[0019] Preferably, the compressor outlet pressure is 6.0-8 MPa(g); the methanol synthesis tower operating pressure is 6.0-8 MPa(g).

[0020] The system provided by the present application realizes the preparation of green methanol from biomass gasification coupled with green hydrogen. The system is stable and reliable in operation, has high utilization rate of renewable carbon sources, and low methanol preparation cost. Compared with the prior art, the present application has the following beneficial effects:

[0021] (1) The present application adjusts the hydrogen-carbon ratio in the methanol synthesis raw material gas by using new energy power generation to produce hydrogen, and eliminates the instability of hydrogen production for energy generation by setting hydrogen storage tanks and oxygen storage tanks, thereby realizing the stable operation of biomass gasification and methanol synthesis;

[0022] (2) The present application uses a reformer in the biomass gasification unit to further heat the synthesis gas generated by the gasifier to improve the quality of the synthesis gas. The required energy comes from the purge gas of the methanol synthesis unit, without additional energy. Combined with the CO2-rich synthesis gas methanol synthesis unit, the renewable carbon source and hydrogen source are efficiently utilized, and the methanol preparation cost is low. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a schematic diagram of a system for preparing green methanol from biomass gasification coupled with green hydrogen provided by the present application;

[0024] Figure 2 is another embodiment of a system for preparing green methanol from biomass gasification coupled with green hydrogen provided by the present application.

[0025] Legend: A-gasification unit, B-purification unit, C-hydrogen-oxygen unit, D-synthesis unit; 1-biomass gasifier; 2-reforming furnace; 3-waste heat boiler; 4-compressor; 5-oil removal tower; 6-desulfurization and decarburization tower; 7-electrolytic cell; 8-oxygen storage tank; 9-hydrogen storage tank; 10-compressor; 11-methanol synthesis tower; 12-heat exchanger; 13-gas-liquid separator; 14-hydrogen recovery device; 100-biomass raw material; 101 / 109 / 110 / 111-oxygen; 102 / 103 / 104 / 105 / 106-syngas; 107 / 114 / 115-methanol synthesis raw gas; 108-water; 112 / 113-hydrogen; 116 / 117-methanol, recycle gas; 118-raw methanol; 119-recycle gas; 120-recycle gas; 121-circulating purge gas; 122-external exhaust purge gas. DETAILED DESCRIPTION

[0026] The application will be further described below in combination with specific examples.

[0027] Example 1: Figure 1 is a schematic diagram of a system for producing green methanol by coupling biomass gasification with green hydrogen provided by the application. As shown in Figure 1, the system for producing green methanol by coupling biomass gasification with green hydrogen mainly includes a biomass gasification unit for producing syngas, a syngas purification unit, a water electrolysis unit for producing hydrogen and storing hydrogen and oxygen, and a CO2-rich syngas methanol synthesis unit.

[0028] The biomass gasification unit for producing syngas, referred to as the gasification unit, mainly includes a gasifier 1, a reforming furnace 2, and a waste heat boiler 3.

[0029] The syngas purification unit, referred to as the purification unit, mainly includes a compressor 4, an oil removal tower 5, and a desulfurization and decarburization tower 6.

[0030] The water electrolysis unit for producing hydrogen and storing hydrogen and oxygen, referred to as the hydrogen-oxygen unit, mainly includes an electrolytic cell 7, a hydrogen storage tank 9, and an oxygen storage tank 8.

[0031] The CO2-rich syngas methanol synthesis unit, referred to as the synthesis unit, mainly includes a compressor 10, a methanol synthesis tower 11, a heat exchanger 12, a gas-liquid separator 13, and a hydrogen recovery device 14.

[0032] The syngas 104 produced by the gasification unit is used as the raw gas 107 of the synthesis unit after being purified by the purification unit; the oxygen 109 of the hydrogen-oxygen unit is used as the oxygen of the gasification unit, and the hydrogen 113 is used as the hydrogen source for adjusting the hydrogen-carbon ratio of the raw gas of the synthesis unit; part of the purge gas 121 of the synthesis unit is returned to the gasification unit for recycling.

[0033] The desulfurization and decarburization tower 6 has the function of adjustable CO2 removal rate.

[0034] The hydrogen recovery device 14 produces two streams of purge gas, one of which is returned to the reformer 2 of the gasification unit, and the other of which is discharged outside the system.

[0035] The gasifier 1 can be a fluidized bed, a circulating fluidized bed, or a fixed bed gasifier. The oxygen required by the gasifier 1 and the reformer 2 is obtained from the oxygen 109 produced by the water electrolysis unit or the oxygen 101 obtained from the air separation facility.

[0036] The fuel used in the reformer 2 is synthetic purge gas 121, waste gas containing heat value, methane, diesel, and the like.

[0037] The biomass raw material 100 enters the biomass gasifier 1 to produce synthesis gas. The gasifier 1 mainly includes a fluidized bed gasifier body, a cyclone separator, a slag discharge pipe, a gasification agent preheater, and the like. The gasification agent is usually a mixture of pure oxygen / steam, and CO2 gas can also be added. After preheating, the gasification agent enters the gasifier, and the optimal gasification temperature of the gasifier is 750-850°C. The synthesis gas 102 produced by the gasifier after dust removal by the cyclone separator is sent to the reformer 2. The particles captured by the cyclone separator are returned to the gasifier for reaction.

[0038] After the synthesis gas produced by the gasifier enters the reformer 2, the temperature is raised to 1000-1100°C, and the tar and methane in the synthesis gas are sent to the reformer at high temperature, and their content is greatly reduced. The fuel for raising the temperature of the reformer 2 is obtained from the recycle purge gas 121 of the methanol synthesis unit. The purge gas of a conventional methanol synthesis device is usually vented or used as fuel gas, and the purge gas contains a large amount of renewable carbon source (CO / CO2 / CH4) and renewable H2. In the present application, the methanol purge gas is used as the fuel of the reformer, which improves the utilization efficiency of renewable hydrogen and renewable carbon of the system.

[0039] The high-temperature synthesis gas 103 from the reformer 2 has a high temperature and enters the waste heat recovery boiler 3. The waste heat boiler usually includes a synthesis gas dust remover, a steam generator, an economizer, a synthesis gas cooler, and the like. After dust removal and temperature reduction, the synthesis gas has a dust content of less than 1 mg / Nm3 and a temperature of 40°C, and is sent to the inlet of the compressor 4 of the synthesis gas purification unit. The steam produced by the waste heat boiler is partially used as the gasification agent of the gasifier and partially supplied externally.

[0040] The synthesis gas purification unit is an improved low-temperature methanol washing process, mainly including a deoiling tower, a desulfurization and decarburization tower, a desorption tower, a methanol recovery tower, a refrigeration system and the like. The low-temperature methanol washing process is to remove the acid gas and light oil in the raw material gas by using the excellent characteristics of methanol, i.e., the solubility of methanol is extremely large under low temperature and high pressure. The process has high gas purification degree and good selectivity, and the deoiling, desulfurization and decarburization of the gas can be selectively carried out in the same process. The total sulfur content of the synthesis gas after the purification unit is less than 0.1 ppm, and the CO2 content is adjustable in the range of 5-35%, which can be used as the raw material gas of the CO2-rich synthesis unit. The hydrogen-carbon ratio of the methanol synthesis raw material gas after the purification unit cannot meet the requirement of the methanol synthesis on the hydrogen-carbon ratio, and hydrogen needs to be supplemented.

[0041] The electrolytic water hydrogen production unit is arranged to produce hydrogen for adjusting the hydrogen-carbon ratio of the methanol synthesis raw material gas. The electrolytic water hydrogen production unit mainly includes an electrolytic tank, a purification system and a pure water preparation system. The electrolytic tank is an alkaline electrolytic tank. In view of the instability of the renewable energy, a hydrogen storage tank and an oxygen storage tank are arranged to stably supply hydrogen and oxygen. The hydrogen storage tank 9 is a gaseous spherical tank, and the oxygen storage tank is a gaseous spherical tank. The storage capacity of the spherical tank is selected according to the characteristics of the new energy power generation, and the storage capacity usually needs to meet the gas consumption for 24-72 hours.

[0042] In order to utilize the renewable carbon in the biomass as much as possible, the methanol synthesis unit of the present application is a CO2-rich synthesis unit, and the methanol reactor and the catalyst can adapt to the CO2 content of 5-35% in the raw material gas. When the CO2 content in the raw material gas is high, the required amount of hydrogen increases. Therefore, when the new energy power generation (wind power, photovoltaic) is fully generated, the high-load operation of the electrolytic water hydrogen production provides a large amount of hydrogen for the methanol synthesis unit, and the methanol synthesis unit can accept the raw material gas with high CO2 concentration, thereby efficiently utilizing the renewable carbon source.

[0043] Embodiment two: Fig. 2 is another embodiment of a system for producing green methanol by coupling biomass gasification with green hydrogen provided by the present application. The difference between embodiment two and embodiment one is whether the synthesis gas at the outlet of the reformer 2 is subjected to waste heat recovery. Embodiment one recovers the heat of the synthesis gas by using a waste heat boiler. Embodiment two does not recover the heat of the synthesis gas, but uses chilled water to chill the synthesis gas. The temperature of the chilled synthesis gas is about 70-150℃. This embodiment is beneficial for reducing the investment cost, but the overall energy consumption is higher than that of embodiment one.

[0044] It can be seen from the above examples that, by virtue of the innovative system design and reasonable process parameter setting, the present application uses new energy power generation to produce hydrogen to adjust the hydrogen-carbon ratio in the raw gas for methanol synthesis, sets a hydrogen storage tank and an oxygen storage tank to eliminate the instability of the hydrogen production from the new energy power generation, and realizes the stable operation of the biomass gasification and methanol synthesis; the biomass gasification unit uses a reformer to further heat the synthesis gas generated by the gasifier to improve the quality of the synthesis gas, and the required energy is from the purge gas of the methanol synthesis unit, without additional energy, combined with the methanol synthesis unit of the CO2-rich synthesis gas, the renewable carbon source and hydrogen source are efficiently utilized, and the cost of methanol preparation is low.

[0045] The above examples are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the protection scope of the present application.

Claims

1. A system for biomass gasification coupled with green hydrogen to produce green methanol, characterized in that, Comprise: Gasification unit (A), purification unit (B), hydrogen oxygen unit (C), synthesis unit (D); The synthesis gas (104) produced by the gasification unit (A) is used as the raw material gas (107) of the synthesis unit after being purified by the purification unit (B); The oxygen (109) produced by the hydrogen oxygen unit (C) is used as the oxygen of the gasification unit, and the hydrogen (113) produced by the hydrogen oxygen unit (C) is used as the hydrogen source for adjusting the hydrogen-carbon ratio of the raw material gas of the synthesis unit (D); Part of the purge gas (121) of the synthesis unit (D) is returned to the gasification unit for recycling.

2. The system for preparing green methanol by biomass gasification coupled with green hydrogen according to claim 1, characterized in that: The gasification unit (A) mainly comprises a gasification furnace (1), a conversion furnace (2) and a waste heat boiler (3); The operating pressure of the gasification furnace (1) is 50kPa(g)-2MPa(g), and the gasification temperature is 700-900℃; The operating temperature of the conversion furnace (2) is 900-1200℃, and the operating temperature of the waste heat boiler (3) is 120-1200℃.

3. The system for preparing green methanol by biomass gasification coupled with green hydrogen according to claim 1, characterized in that: The purification unit (B) mainly comprises a compressor (4), a deoiling tower (5) and a desulfurization and decarburization tower (6); The outlet pressure of the compressor (4) is 0.5-4.0MPa(g); The deoiling tower (5) is a spray absorption tower, and the operating pressure is 0.5-4.0MPa(g), and the operating temperature is -40-40℃; The desulfurization and decarburization tower (6) is a multi-layer spray absorption tower, and the operating pressure is 0.5-4.0MPa(g), and the operating temperature is -60--10℃; The desulfurization and decarburization tower (6) has the function of adjustable CO2 removal rate.

4. The system for preparing green methanol by biomass gasification coupled with green hydrogen according to claim 1, characterized in that: The hydrogen oxygen unit (C) mainly comprises an electrolytic cell (7), a hydrogen storage tank (9) and an oxygen storage tank (8); The electrolytic cell (7) is an alkaline electrolytic cell or a PEM electrolytic cell or a combination of the former two, and the operating pressure is 50kPa(g)-4MPa(g); The hydrogen storage tank (9) and the oxygen storage tank (8) are one of spherical tanks, vertical storage tanks and horizontal storage tanks; the operating pressure of the hydrogen storage tank (9) is 0.5-4MPa(g); The operating pressure of the oxygen storage tank (8) is 0.3-2.5MPa(g).

5. The system for preparing green methanol by biomass gasification coupled with green hydrogen according to claim 1, characterized in that: The synthesis unit (D) mainly comprises a compressor (10), a methanol synthesis tower (11), a heat exchanger (12), a gas-liquid separator (13) and a hydrogen recovery device (14); The outlet pressure of the compressor (10) is 5.0-10MPa(g); The operating pressure of the methanol synthesis tower (11) is 5.0-10MPa(g); The purge gas produced by the hydrogen recovery device (14) is divided into two paths, one of which is returned to the conversion furnace (2) of the biomass gasification unit, and the other of which is discharged out of the system.

6. The system for producing green methanol by biomass gasification coupled with green hydrogen according to claim 2, characterized in that: The gasifier (1) is a fluidized bed, a circulating fluidized bed, a fixed bed gasifier, or a circulating fluidized bed gasifier; the oxygen required by the gasifier (1) and the reformer (2) is obtained from the oxygen (109) of the water electrolysis unit or the oxygen (101) of the air separation facility.

7. The system for biomass gasification coupled with green hydrogen to produce green methanol according to claim 2, characterized in that: The fuel used by the reformer (2) is synthetic purge gas (121), or waste gas containing heat value, or methane, or diesel fuel.

8. The system for producing green methanol by biomass gasification coupled with green hydrogen according to claim 2, wherein: The operating pressure of the gasifier (1) is 150 kPa(g) to 1.2 MPa(g); the gasification temperature is 750°C to 850°C; the operating temperature of the reformer (2) is 950°C to 1100°C; The operating temperature of the waste heat boiler (3) is 140°C to 1100°C.

9. The system for producing green methanol by biomass gasification coupled with green hydrogen according to claim 3, wherein: The outlet pressure of the compressor (4) is 0.8 MPa(g) to 3.3 MPa(g); The operating pressure of the deoiling tower (5) is 0.8 MPa(g) to 3.3 MPa(g), and the operating temperature is -20°C to 35°C; The operating pressure of the desulfurization and decarburization tower (6) is 0.8 MPa(g) to 3.3 MPa(g), and the operating temperature is -50°C to -20°C.

10. The system for producing green methanol by biomass gasification coupled with green hydrogen according to claim 4, wherein: The electrolytic cell (7) is an alkaline electrolytic cell or a PEM electrolytic cell or a combination of the two, and the operating pressure is 0.8 MPa(g) to 3.3 MPa(g); The hydrogen storage tank (9) and the oxygen storage tank (8) are spherical tanks; the operating pressure of the hydrogen storage tank (9) is 0.8 MPa(g) to 3.3 MPa(g); The operating pressure of the oxygen storage tank (8) is 0.3 MPa(g) to 1.8 MPa(g).

11. The system for producing green methanol by biomass gasification coupled with green hydrogen according to claim 5, wherein: The outlet pressure of the compressor (10) is 6.0 MPa(g) to 8 MPa(g); The operating pressure of the methanol synthesis tower (11) is 6.0 MPa(g) to 8 MPa(g).

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