A biomass-to-methanol process based on adsorption-enhanced gasification coupled with carbon utilization

Abstract

The present invention discloses a biomass-to-methanol process based on adsorption-enhanced gasification coupled with carbon utilization, comprising: a gasification unit, an adsorption-enhanced water-gas change unit, a calcination unit, an H2 purification unit / CO purification unit, a gas-steam combined power generation unit, a solid oxide electrolyzer unit, and a methanol synthesis unit; the present invention realizes biomass gasification, CO2 capture, CO2 reuse, on-site consumption of gasified carbon, and efficient synthesis of methanol in an integrated process, and compared with the existing biomass gasification-to-methanol technology, the carbon conversion rate, synthesis gas yield, and H2 / CO dispatchability are all greatly improved.

Description

Technical Field

[0001] The invention relates to the field of biomass gasification to methanol, and in particular to a biomass methanol production method based on adsorption enhanced gasification coupled carbon utilization. Background Art

[0002] As a global challenge in the 21st century, global warming has attracted widespread attention from the international community for its extensive and far-reaching impact. With the continuous increase in greenhouse gas emissions, the global average temperature continues to rise, leading to frequent extreme climate events, damage to ecosystems, rising sea levels and other serious consequences. In this context, reducing dependence on fossil fuels, reducing carbon emissions and developing clean energy have become important strategies for global energy transformation and addressing climate change. As a renewable carbon-neutral resource, biomass has gradually increased its share in the energy structure. As an emerging biomass energy utilization technology, biomass gasification to produce methanol has attracted much attention due to its low carbon emission characteristics. Methanol, as a multifunctional chemical raw material, is widely used in plastics, solvents, fuels and other fields, and plays an important role in energy transformation. Biomass gasification to produce methanol technology, by converting biomass into synthesis gas under high temperature conditions and then synthesizing methanol, can not only reduce dependence on fossil fuels, but also effectively reduce carbon emissions.

[0003] As one of the biomass gasification technologies, adsorption-enhanced gasification technology increases the CO2 capture rate by adding adsorbents during the gasification process to achieve CO2 conversion and utilization. This technology is considered to be the most promising biomass gasification technology because it can simultaneously achieve CO2 capture and conversion and efficient methanol synthesis in an integrated process. However, adsorption-enhanced gasification technology also faces some challenges in practical applications.

[0004] First, the reaction temperature in the adsorption-enhanced gasification process is generally between 600 and 700 °C. Compared with higher gasification temperatures (>800 °C), this temperature range will lead to a decrease in the total yield and carbon conversion rate of syngas. This means that in the adsorption-enhanced gasification process, more biomass feedstock is required to obtain the same amount of methanol, which undoubtedly increases the production cost. Secondly, carbon-rich solid products will remain after the adsorption-enhanced gasification process. The treatment and utilization of these solid products is an urgent problem to be solved. If not handled properly, these solid products may cause secondary pollution to the environment. In addition, it is also a challenge to obtain the correct H2 / CO ratio in the biomass to methanol process. The H2 / CO ratio is a key factor affecting the efficiency of methanol synthesis. If the H2 / CO ratio is too high or too low, it will affect the synthesis efficiency and selectivity of methanol. Therefore, how to accurately control the H2 / CO ratio in the biomass gasification process is the key to improving the efficiency of methanol synthesis. Despite these challenges, adsorption-enhanced gasification technology still has great potential in the production of methanol from biomass gasification. Through continuous technological innovation and optimization, these challenges can be overcome and biomass gasification can be used to produce methanol efficiently, at low cost and in an environmentally friendly manner. For example, the gasification efficiency can be improved by improving the design of the gasification reactor, the CO2 capture rate can be increased by developing new adsorbents, and the methanol synthesis efficiency can be improved by optimizing the synthesis gas purification and methanol synthesis processes.

[0005] In summary, biomass gasification technology for producing methanol has important application prospects in reducing dependence on fossil fuels and reducing carbon emissions. As an efficient biomass gasification technology, adsorption-enhanced gasification technology faces some challenges, but through technological innovation and process optimization, it is expected to achieve large-scale application in biomass gasification for producing methanol. This study aims to explore and optimize the application of adsorption-enhanced gasification technology in the process of biomass gasification for producing methanol, in order to provide new solutions for global energy transformation and addressing climate change. Summary of the invention

[0006] In order to solve the problems of low carbon conversion rate and obtaining a correct H2 / CO ratio in the biomass to methanol process based on adsorption enhanced gasification, the present invention provides a biomass to methanol process based on adsorption enhanced gasification coupled with carbon utilization, aiming to improve the carbon conversion rate in the biomass adsorption enhanced gasification process and obtain a suitable H2 / CO ratio.

[0007] In order to achieve the above object, the present invention provides a biomass to methanol process based on adsorption enhanced gasification coupled carbon utilization, comprising the following steps:

[0008] (1) After the biomass is formed and processed, it is gasified in a gasifier to obtain three-phase products of gas, liquid and solid;

[0009] (2) subjecting the gas-liquid mixture to an adsorption-enhanced water-gas shift reaction to generate synthesis gas, wherein the synthesis gas passes through a limestone layer, and CaO adsorbs CO2 in the synthesis gas to obtain H2-rich gas and CaCO3 generated by a carbonation reaction of CaO;

[0010] (3) calcining the CaCO3 generated by the carbonation reaction in a calcining furnace, with N2 acting as a protective gas, to obtain regenerated CaO and CO2-rich gas;

[0011] (4) collecting the gasified carbon and placing it in a calcining furnace to react with CO2-rich gas in a reverse Boudouard reaction to obtain CO2-rich gas;

[0012] (5) Cooling the H2-rich gas and the CO-rich gas respectively and separating them into high-purity H2 and high-purity CO by pressure swing adsorption (PSA), and passing the separated excess gas into a combustion chamber for combustion to generate high-temperature flue gas; (6) Exchanging heat between the high-temperature flue gas and a small amount of water to obtain water vapor and flue gas after heat exchange;

[0013] (7) passing the high temperature steam into a solid oxide electrolytic cell (SOEC) to electrolyze water to produce H2 and O2;

[0014] (8) The mixed gas of H2 and CO is introduced into a methanol synthesis reactor to undergo a methanol synthesis reaction, and the synthesized crude methanol is distilled into a distillation tower to obtain high-purity methanol.

[0015] (9) Exhaust heat from the biomass-to-methanol process based on adsorption-enhanced gasification coupled carbon utilization is exchanged with water to generate steam, which is then introduced into a steam turbine to generate electricity.

[0016] (10) The electric energy generated by the gas turbine and the steam turbine is used for water electrolysis, and the insufficient part is supplemented by wind / photovoltaic energy.

[0017] Preferably, in the biomass-to-methanol process based on adsorption-enhanced gasification coupled carbon utilization, the reaction temperature in step (1) and step (2) is 600-700°C, which is conducive to the occurrence of CaO carbonation reaction and can obtain about 10-25wt.% C-rich gasified carbon; further preferably, the implementation of the present invention is not limited by the type of adsorption-enhanced water-gas shift catalyst.

[0018] Preferably, in the biomass-to-methanol process based on adsorption-enhanced gasification coupled carbon utilization, the CaCO3 calcination temperature in step (3) and step (4) is 800-1000°C; further preferably, the CO2 gas stream generated by the calcination passes through the gasified carbon and reacts at the calcination temperature; further preferably, an external C source can be added to completely react with CO2 to obtain CO-rich gas; further preferably, the external C source includes activated carbon, wood charcoal, etc.

[0019] Preferably, in this biomass-to-methanol process based on adsorption-enhanced gasification coupled with carbon utilization, the H2-rich gas and CO-rich gas in step (5) come from a gasifier and a calciner, respectively; further preferably, the H2-rich gas and the CO-rich gas are respectively introduced into PSA for separation to obtain high-purity H2 and high-purity CO; further preferably, the excess gas after separation mainly contains a small amount of H2, CO, CH4, CO2 and C2-C3.

[0020] Preferably, in the biomass-to-methanol process based on adsorption-enhanced gasification coupled carbon utilization, the temperature of the SOEC electrolyzer described in step (6) is 600-1000°C; further preferably, the small amount of water vapor is obtained by calculating the molar ratio of high-purity H2 and high-purity CO described in step (5).

[0021] Preferably, in the biomass-to-methanol process based on adsorption-enhanced gasification coupled with carbon utilization, the temperature of the high-temperature steam in step (7) is 600-1000°C.

[0022] Preferably, in the biomass-to-methanol process based on adsorption-enhanced gasification coupled with carbon utilization, the H2 in step (8) is derived from high-purity H2 obtained by PSA of H2-rich gas produced in a gasifier and H2 produced by electrolysis of water, and the CO is derived from high-purity CO obtained by PSA of CO-rich gas produced in a calciner; further preferably, the molar ratio of H2 to CO in the mixed gas is approximately equal to 2; and further preferably, methanol synthesis is carried out at a pressure of 10-100 bar and a temperature of 200-300°C, and the catalyst is copper / zinc oxide / aluminum oxide (Cu / ZnO / Al2O3).

[0023] Preferably, in the biomass-to-methanol process based on adsorption-enhanced gasification coupled with carbon utilization, part of the electricity generated by the gas turbine and the steam turbine in steps (9) and (10) is used for water electrolysis, and the remaining electricity is used for internal use in the factory.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0025] 1. The biomass-to-methanol process based on adsorption-enhanced gasification coupled with carbon utilization of the present invention realizes biomass gasification, CO2 capture, CO2 reuse, on-site consumption of gasified carbon and efficient synthesis of methanol in an integrated process. Compared with the existing adsorption-enhanced gasification technology, the carbon conversion rate, synthesis gas yield and H2 / CO dispatchability are greatly improved.

[0026] 2. The biomass-to-methanol process based on adsorption-enhanced gasification coupled carbon utilization of the present invention realizes the regeneration of CaO and the generation of CO-rich gas in a calciner simultaneously by combining gasified carbon with CaCO3 produced after carbonation. Compared with the existing CaO calcination and regeneration technology, it reduces the purification, compression and transportation of CO2.

[0027] 3. The biomass-to-methanol process based on adsorption-enhanced gasification coupled with carbon utilization of the present invention obtains H2-rich gas and CO-rich gas respectively in a two-stage manner, thereby reducing the difficulty of gas separation. At the same time, the electricity generated by the gas turbine and the steam turbine meets the electricity required for the SOEC to electrolyze water to supplement part of the H2. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The invention discloses a biomass-to-methanol process based on adsorption-enhanced gasification coupled with carbon utilization. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0030] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, an indirect connection through an intermediate medium, or the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] Unless otherwise specified, the raw materials, reagents or devices used in the examples can be obtained from conventional commercial sources or can be obtained by prior art methods. Unless otherwise specified, the experiments or test methods are conventional methods in the art.

[0032] Example 1

[0033] like Figure 1 As shown, a biomass-to-methanol process based on adsorption-enhanced gasification coupled with carbon utilization includes a connected gasification unit, an adsorption-enhanced water-gas change reaction unit, a calcination unit, an H2 purification unit / CO purification unit, a gas-steam combined power generation unit, a solid oxide electrolyzer unit, and a methanol synthesis unit in sequence;

[0034] The gasification unit is connected to the adsorption enhanced water-gas change unit and the calcination unit respectively, and the adsorption enhanced water-gas change unit is connected to the H2 purification unit, the calcination unit and the gas-steam combined power generation unit respectively; the calcination unit is connected to the gas-steam combined power generation unit and the CO purification unit respectively; the H2 purification unit and the CO purification unit are both connected to the gas-steam combined power generation unit; the gas-steam combined power generation unit is connected to the solid oxide electrolyzer unit and the methanol synthesis unit in sequence, and the methanol synthesis unit is also connected to the gas-steam combined power generation unit; the H2 purification unit and the CO purification unit are both connected to the methanol synthesis unit.

[0035] Example 2

[0036] This embodiment adopts the connection unit described in Embodiment 1.

[0037] The biomass molded fuel produced by the biomass molding plant is transported to the biomass methanol synthesis plant, and the biomass molded fuel is sent to the gasification unit and undergoes a gasification reaction in a gasifier at a temperature of 650°C. The generated pyrolysis gas and pyrolysis liquid enter the adsorption enhanced water-gas change reaction unit to undergo an adsorption enhanced water-gas change reaction. The CO2 in the synthesis gas is absorbed by CaO to generate CaCO3, producing H2-rich gas.

[0038] The H2-rich gas enters the H2 purification unit, the obtained high-purity H2 is passed into the methanol synthesis unit, and the other gases are passed into the combustion chamber of the gas-steam combined power generation unit to burn and generate electricity.

[0039] The gasified carbon produced by the gasification unit and the CaCO3 produced by the adsorption enhanced water gas change reaction unit are sent to the calcination unit together. CaCO3 is calcined at a calcination temperature of 900°C to produce CaO and CO2. CO2 undergoes a reverse Boudouard reaction with the gasified carbon and the supplemented activated carbon to produce CO-rich gas and a small amount of ash.

[0040] The CO-rich gas enters the CO purification unit, the high-purity CO obtained is passed into the methanol synthesis unit, and the other gases are passed into the combustion chamber of the gas-steam combined power generation unit to burn and generate electricity.

[0041] The high-temperature flue gas generated in the combustion chamber of the gas-steam combined power generation unit heats a small amount of water into high-temperature steam at 800°C. The high-temperature steam is introduced into the solid oxide electrolyzer unit to electrolyze water and generate high-purity H2 and high-purity O2.

[0042] The high-purity H2 produced by the electrolysis of water in the solid oxide electrolyzer unit is introduced into the methanol synthesis unit, and the H2 / CO in the mixed gas at the inlet of the methanol synthesis unit is adjusted to 2. The methanol synthesis reaction is carried out under the conditions of pressure of 7.8 MPa, temperature of 250°C and catalyst of Cu / ZnO / Al. The crude methanol produced by the reaction is purified by a distillation tower to obtain high-purity methanol. The gas produced in the distillation process is introduced into the combustion chamber of the gas-steam combined power generation unit for combustion and power generation.

[0043] The waste heat generated by the entire process is exchanged with water to produce steam, which is then fed into a steam turbine to generate electricity. Part of the electricity generated by the steam turbine and gas turbine is used in the solid oxide electrolyzer unit, and the remaining electricity is used within the biomass methanol synthesis plant.

[0044] Example 3

[0045] The straw pellet fuel produced by the biomass pelletizing plant is transported to the biomass methanol synthesis plant. The straw pellet fuel is fed into the gasification unit through a feeder at a rate of 1 kg / s. The temperature in the gasifier is 650°C and the pressure is normal pressure. Water vapor is pumped into the gasifier at a rate of 0.25 kg / s to enhance the water-gas reaction.

[0046] The generated pyrolysis gas and pyrolysis liquid enter the adsorption enhanced water-gas change reaction unit at a temperature of 650°C, normal pressure, and a water vapor rate of 0.25 kg / s. Initially, CaO enters the adsorption enhanced water-gas change reaction unit at a rate of 1.1 kg / s, and as CaO deactivates, fresh CaO is added at a rate of 0.11 kg / s. The CO2 in the synthesis gas is absorbed by CaO to generate CaCO3. The water-gas change catalyst is Co-Mo, and H2-rich gas is generated through adsorption enhanced water-gas change reaction.

[0047] The H2-rich gas enters the H2 purification unit, and the H2 separation efficiency of PSA is ~90%. H2 with a purity of 99.99% is separated, and the temperature is reduced to 40°C through the heat exchanger and passed into the methanol synthesis unit. Other gases (H2, CO, CH4, etc.) separated by PSA are passed into the combustion chamber of the gas-steam combined power generation unit for combustion and power generation. The water vapor generated by heat exchange is passed into the gas-steam combined power generation unit to drive the steam turbine to generate electricity.

[0048] The gasified carbon produced by the gasification unit and the CaCO3 produced by the adsorption enhanced water-gas change reaction unit are sent to the calcination unit together. CaCO3 is calcined to produce CaO and CO2 under the conditions of calcination temperature of 900°C, normal pressure and N2 gas as carrier gas. CO2 undergoes reverse Boudouard reaction with the gasified carbon and the supplemented activated carbon to produce CO-rich gas and a small amount of ash.

[0049] The CO-rich gas enters the CO purification unit, and the CO separation efficiency of PSA is ~90%. CO with a purity of 99.99% is separated and passed into the methanol synthesis unit. After heat exchange in the heat exchanger to a temperature of 40°C, other gases (CO, H2, CH4, etc.) separated by PSA are passed into the combustion chamber of the gas-steam combined power generation unit for combustion and power generation. The water vapor generated by heat exchange is passed into the gas-steam combined power generation unit to drive the steam turbine to generate electricity.

[0050] The high-temperature flue gas generated in the combustion chamber of the gas-steam combined power generation unit heats a small amount of water into high-temperature steam at 800°C. The high-temperature steam is introduced into the solid oxide electrolyzer unit, where it undergoes a water electrolysis reaction under normal pressure to generate high-purity H2 and high-purity O2.

[0051] The high-purity H2 produced by the electrolysis of water in the solid oxide electrolyzer unit is introduced into the methanol synthesis unit, and the H2 / CO in the mixed gas at the inlet of the methanol synthesis unit is adjusted to 2. The methanol synthesis reaction is carried out under the conditions of pressure of 7.8 MPa, temperature of 250°C and catalyst of Cu / ZnO / Al. The crude methanol produced by the reaction is purified by a distillation tower to obtain methanol with a purity of 99.99%. The gas (mainly H2 and CO) produced during the distillation process is introduced into the combustion chamber of the gas-steam combined power generation unit for combustion and power generation.

[0052] The electricity generated by the entire process gas-steam combined power generation unit is partly used in the solid oxide electrolyzer unit, and the remaining electricity is used internally in the biomass methanol synthesis plant.

[0053] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A biomass-to-methanol process based on adsorption-enhanced gasification coupled carbon utilization, characterized in that: The steps include: (1) After being formed and processed, the biomass is gasified in a gasifier to obtain three-phase products of gas, liquid and solid; (2) subjecting the gas-liquid mixture to an adsorption-enhanced water-gas shift reaction to generate synthesis gas, wherein the synthesis gas passes through a limestone layer, and CaO adsorbs CO2 in the synthesis gas to obtain H2-rich gas and CaCO3 generated by a carbonation reaction of CaO; (3) calcining the CaCO3 generated by the carbonation reaction in a calcining furnace, with N2 acting as a protective gas, to obtain regenerated CaO and CO2-rich gas, and regularly adding fresh limestone to replenish the CaO lost during the circulation process; (4) collecting the solid product in step (1) and placing it in a calcining furnace to react with CO2-rich gas in a reverse Boudouard reaction to obtain CO2-rich gas; (5) Cooling the H2-rich gas and the CO-rich gas respectively, separating the high-purity H2 and high-purity CO through pressure swing adsorption (PSA), and introducing the excess gas after separation into the combustion chamber of the gas turbine for combustion to generate high-temperature flue gas; (6) exchanging heat between the high-temperature flue gas and a small amount of water to obtain high-temperature water vapor and high-temperature flue gas after heat exchange; (7) passing the high temperature steam into a solid oxide electrolysis cell SOEC to electrolyze water to produce H2 and O2; (8) Passing the H2 and CO mixed gas into a methanol synthesis reactor to undergo a methanol synthesis reaction, and obtaining high-purity methanol from the synthesized crude methanol through a distillation tower; (9) Exchanging waste heat from the biomass-to-methanol process based on adsorption-enhanced gasification coupled carbon utilization with water to generate steam, passing steam from the calcination unit, the adsorption-enhanced water-gas change unit, and the methanol synthesis unit into a steam turbine for power generation, and passing part of the unreacted raw gas from the methanol synthesis unit into a combustion chamber of a gas-steam combined power generation unit for combustion; (10) The electric energy generated by the gas-steam combined power generation unit is used for water electrolysis, and the insufficient part is supplemented by wind / photovoltaic.

2. The biomass-to-methanol process based on adsorption-enhanced gasification coupled carbon utilization according to claim 1 is characterized in that: The process includes, in sequence, a gasification unit, an adsorption enhanced water-gas change unit, a calcination unit, an H2 purification unit, a CO purification unit, a gas-steam combined power generation unit, a solid oxide electrolyzer unit and a methanol synthesis unit; The gasification unit is connected to the adsorption enhanced water-gas change unit and the calcination unit respectively, and the adsorption enhanced water-gas change unit is connected to the H2 purification unit, the calcination unit and the gas-steam combined power generation unit respectively; the calcination unit is connected to the gas-steam combined power generation unit and the CO purification unit respectively; the H2 purification unit and the CO purification unit are both connected to the gas-steam combined power generation unit; the gas-steam combined power generation unit is connected to the solid oxide electrolyzer unit and the methanol synthesis unit in sequence, and the methanol synthesis unit is also connected to the gas-steam combined power generation unit; the H2 purification unit and the CO purification unit are both connected to the methanol synthesis unit.

3. The biomass-to-methanol process based on adsorption-enhanced gasification coupled carbon utilization according to claim 1, characterized in that: In step (1), the gasification temperature is 600-700 °C.

4. The biomass-to-methanol process based on adsorption-enhanced gasification coupled carbon utilization according to claim 1, characterized in that: In step (2), the calcination temperature of CaCO3 is 800-1000°C; in step (4), the solid product and CaCO3 undergo a reverse Boudouard reaction in the same calcination furnace to generate CO-rich gas.

5. The biomass-to-methanol process based on adsorption-enhanced gasification coupled carbon utilization according to claim 1 is characterized in that: In step (5), the H2-rich gas and the CO-rich gas come from the gasifier and the calciner, respectively, and are purified by two PSAs to obtain high-purity H2 and high-purity CO, respectively.

6. The biomass-to-methanol process based on adsorption-enhanced gasification coupled carbon utilization according to claim 1 is characterized in that: In step (8), H2 at the inlet of the methanol synthesis reactor comes from the H2 purification unit and the solid oxide electrolyzer unit, and CO comes from the CO purification unit.

7. The biomass-to-methanol process based on adsorption-enhanced gasification coupled carbon utilization according to claim 1 is characterized in that: In steps (9) and (10), the high-temperature flue gas generated in the combustion chamber of the gas-steam combined power generation unit needs to be heated to steam using a small amount of water.

8. The biomass-to-methanol process based on adsorption-enhanced gasification coupled carbon utilization according to claim 3 is characterized in that: The solid product undergoes a reverse Boudouard reaction with CaCO3 in the same calciner to generate CO-rich gas, which supplements the external carbon source and fully reacts with CO2 to generate CO-rich gas. The CO yield is adjusted by controlling the amount of gasified carbon added, thereby controlling the H2 / CO ratio.

9. The biomass-to-methanol process based on adsorption-enhanced gasification coupled carbon utilization according to claim 4, characterized in that: The adsorption enhanced water-gas shift reaction occurs in the adsorption enhanced water-gas shift unit and the reverse Boudouard reaction occurs in the calciner to obtain high concentrations of H2 and CO, thereby reducing the difficulty of gas separation in the H2 purification unit / CO purification unit.

10. The biomass-to-methanol process based on adsorption-enhanced gasification coupled carbon utilization according to claim 7, characterized in that: The amount of water vapor is calculated by the molar ratio of high-purity H2 produced by the H2 purification unit to high-purity CO produced by the CO purification unit.

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