System and method for producing methanol from biomass gasification

Abstract

The present application provides a system and method for preparing methanol by gasification of biomass, based on the different energy grades of high-pressure flash gas, dissolved gas, non-condensable gas generated by methanol synthesis and rectification process, and part of synthesis gas from the gasification unit, using high-pressure flash gas to generate electricity by gas turbine power generation device, and using dissolved gas, non-condensable gas and part of synthesis gas from the gasification unit to generate electricity by steam turbine power generation device; medium-pressure steam by-produced from the gasification unit and the methanol synthesis unit is reduced in temperature and pressure to become low-pressure steam, and the insufficient part is generated into low-pressure steam by the high-temperature tail gas waste heat of the gas turbine to supply low-pressure steam required for steam as gasification agent, decarburization and methanol rectification. The present application can realize self-balance of electricity and steam of the production system, effectively improve energy efficiency, and meet the limit value requirement of carbon emission of green methanol product.

Description

Technical Field

[0001] This invention belongs to the field of green methanol preparation technology, and relates to a system and method for preparing methanol by biomass gasification. Background Technology

[0002] With the decarbonization of the shipping industry, research and industrialization of green fuels, represented by green methanol, are continuously advancing. Methanol synthesis involves two types of catalytic technologies: carbon monoxide hydrogenation to methanol and carbon dioxide hydrogenation to methanol. Based on this, current industrial-scale related technological routes include: biomass gasification followed by carbon monoxide hydrogenation to methanol; biomass gasification coupled with wind, solar, and water electrolysis to produce hydrogen followed by carbon monoxide hydrogenation to methanol; and biomass combustion to produce carbon dioxide integrated with wind, solar, and water electrolysis to produce hydrogen followed by carbon dioxide hydrogenation to methanol, etc.

[0003] CN 118165766 B discloses an off-grid system and method for producing green methanol from biomass by coupling gasification and direct combustion. The syngas produced from the combustion of biomass feedstock enters a steam turbine power generation system (generating electricity through a gas turbine or internal combustion engine, or a combined cycle of a gas turbine and a steam turbine), a syngas treatment system, and a direct-fired boiler (syngas that does not meet calorific value requirements is burned together with the biomass feedstock in the direct-fired boiler, and oxygen from electrolysis for hydrogen production is introduced into the direct-fired boiler). The gasification and direct combustion processes are coupled, and approximately 10% carbon monoxide is added to the carbon dioxide hydrogenation process to improve reaction performance. CN 118165767 B discloses an off-grid system and method for producing green methanol from biomass based on a gasifier. A portion of the syngas enters a steam turbine power generation system (including a combined cycle of a gas turbine and a steam turbine) to generate electricity for plant use, and oxygen from the electrolyzer is used to supply oxygen to the gasifier and high-temperature reforming chamber. CN 116496141 A discloses a green methanol production process and system, providing a combination of new energy power generation and biomass fuel power generation (biomass is burned to generate flue gas and electricity under the action of a combustion aid), overcoming the power generation stability problem of using only new energy power generation to produce green hydrogen. CN 120381682 A discloses a green methanol production system and method coupled with hydrogen, in which purge gas in the methanol synthesis unit is recycled to hydrogen and returned to the methanol synthesis unit through a hydrogen recovery unit, and methane-rich non-permeable gas is sent as purge gas to the direct-fired boiler in the power island unit for power generation. CN 119500003 A discloses a biomass coupled with green hydrogen to produce green methanol system and method, integrating biomass gasification, direct combustion and water electrolysis hydrogen production devices, and using the biomass direct combustion device to generate electricity to achieve off-grid green power supply. CN 120574613 A discloses a method and apparatus for preparing green methanol from biomass, in which purge gas is burned in a cogeneration module, and electricity is generated through an internal combustion engine to achieve energy self-sufficiency. CN119736107 A discloses a biomass-based green methanol production system, which uses the purge gas from the synthesis unit to superheat the saturated steam produced by the gasifier and then generates electricity via a steam turbine to power the system. If the power is insufficient, the purge gas can be supplemented by superheated steam produced by the gas boiler.

[0004] The aforementioned publicly disclosed green methanol production system design integrates wind, solar, and water electrolysis for hydrogen production and biomass energy (gasification or combustion, etc.). It employs either carbon monoxide hydrogenation or carbon dioxide hydrogenation to produce methanol and includes both electricity and steam production systems. The process scheme mainly includes: new energy coupled with biomass power generation, direct biomass combustion, biomass gasification syngas via a combined cycle of gas turbine and steam turbine, and methanol synthesis off-gas via steam turbine power generation. However, in actual operation, the design of green methanol plants is affected by many factors: the reliable supply of wind and solar power is uncertain, the cost of water electrolysis for hydrogen production is still high, the biomass resource utilization system is continuously being established and improved, and the carbon emission limits for green methanol products are in place. These factors pose new requirements for production route design that meets product carbon emission limits while considering resource endowment, supply conditions, and economic viability.

[0005] Therefore, developing a biomass gasification system for producing green methanol that meets the carbon emission limits for green methanol products, ensures a stable power supply, and is low in cost has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a system and method for preparing methanol by biomass gasification, which solves the problems of high methanol preparation cost, insufficient carbon emissions, and unstable power supply in the prior art.

[0007] To achieve the above and other related objectives, the present invention provides a system for producing methanol from biomass gasification, the system comprising:

[0008] A gasification unit that converts raw materials into crude synthesis gas for methanol synthesis includes a feed inlet, a crude synthesis gas outlet, a first medium-pressure steam outlet, and a first low-pressure steam inlet.

[0009] The syngas regulating unit that converts the crude syngas into purified syngas includes a crude syngas inlet, a first medium-pressure steam inlet, a purified syngas outlet, a second low-pressure steam inlet, and a first low-pressure steam outlet, wherein the crude syngas inlet and the crude syngas outlet are connected.

[0010] The methanol production unit includes a purified syngas inlet, a second medium-pressure steam outlet, a third low-pressure steam inlet, a high-pressure purge gas outlet, a dissolved gas outlet, a non-condensable gas outlet, and a methanol product outlet. The purified syngas inlet is connected to the crude syngas outlet.

[0011] The utility unit includes a gas turbine power generation unit, a steam turbine power generation unit, and a steam conversion unit. The gas inlet of the gas turbine power generation unit is connected to the high-pressure venting gas outlet. The gas inlet of the steam turbine power generation unit is connected to the crude syngas outlet, the dissolved gas outlet, and the non-condensable gas outlet, respectively. The steam inlet of the steam conversion unit is connected to the first medium-pressure steam outlet and the second medium-pressure steam outlet, respectively. The steam conversion unit converts the introduced medium-pressure steam into low-pressure steam, and simultaneously produces the low-pressure steam based on the exhaust gas generated by the gas turbine power generation unit, and delivers the low-pressure steam to the gasification unit, the syngas regulating unit, and the methanol production unit.

[0012] Optionally, the gasification unit includes an air separation unit and a biomass gasification unit. The feed inlet of the gasification unit includes an air inlet of the air separation unit, a biomass inlet of the biomass gasification unit, and an oxygen inlet of the biomass gasification unit. The oxygen inlet is connected to the oxygen outlet of the air separation unit. The air separation unit is used to separate air to obtain oxygen and transport the oxygen to the oxygen inlet through the oxygen outlet. The biomass gasification unit is used to gasify biomass to obtain crude syngas and simultaneously produce medium-pressure steam as a byproduct. The first low-pressure steam inlet is connected to the low-pressure steam outlet of the steam conversion unit.

[0013] Optionally, the syngas regulating unit includes a pretreatment device, a shift device, and a decarbonization device; the pretreatment device is used to cool, wash, compress, and purify the crude syngas to obtain pretreated syngas; the shift device is used to perform water-gas shift on the pretreated syngas to adjust the hydrogen-to-carbon ratio to obtain water-gas shifted syngas, and the shift device includes a first medium-pressure steam inlet and a first low-pressure steam outlet; the decarbonization device is used to remove carbon dioxide from the water-gas shifted syngas to obtain purified syngas, and the decarbonization device includes a second low-pressure steam inlet.

[0014] Optionally, the methanol production unit includes a methanol synthesizer and a methanol separator. The purified synthesis gas inlet of the methanol synthesizer serves as the purified synthesis gas inlet of the methanol production unit and is connected to the purified synthesis gas outlet of the synthesis gas regulating unit. The methanol synthesizer converts the purified synthesis gas into methanol. The methanol separator is used to separate the reaction product from the methanol synthesizer to obtain crude methanol, high-pressure purge gas, and recycle gas. The reaction product inlet of the methanol separator is connected to the reaction product outlet. The methanol separator includes a crude methanol outlet for discharging the crude methanol, a high-pressure purge gas outlet for discharging the high-pressure purge gas, and a recycle gas outlet for discharging the recycle gas.

[0015] Optionally, the methanol production unit further includes a methanol flash tank and a methanol distillation unit; the methanol inlet of the methanol flash tank is connected to the crude methanol outlet, and the methanol flash tank generates the dissolved gas during the flash evaporation of the methanol to be flashed; the methanol inlet of the methanol distillation unit is connected to the methanol outlet after flash evaporation of the methanol flash tank, and the distillation reboiler steam inlet of the methanol distillation unit serves as the third low-pressure steam inlet and is connected to the low-pressure steam outlet of the steam conversion unit, and the methanol distillation unit generates the non-condensable gas during the distillation of the flash evaporated methanol.

[0016] Optionally, the gas turbine power generation device includes a first combustion chamber, a gas turbine, and a first generator. The gas inlet of the first combustion chamber serves as the gas inlet of the gas turbine power generation device. The first combustion chamber is used to burn the high-pressure purge gas to generate first high-temperature flue gas. The flue gas inlet of the gas turbine is connected to the flue gas outlet of the first combustion chamber. The gas turbine uses the expansion of the first high-temperature flue gas to drive the first generator to generate electricity. The steam turbine power generation device includes a second combustion chamber, a waste heat recovery steam generator, a steam turbine, and a second generator. The gas inlet of the second combustion chamber serves as the gas inlet of the steam turbine power generation device. The second combustion chamber is used to burn the dissolved gas, the non-condensable gas, and part of the crude syngas to generate second high-temperature flue gas. The flue gas inlet of the waste heat recovery steam generator is connected to the flue gas outlet of the second combustion chamber. The waste heat recovery steam generator uses the second high-temperature flue gas to generate steam. The steam outlet of the waste heat recovery steam generator is connected to the steam inlet of the steam turbine. The steam turbine uses the expansion of the steam to drive the second generator to generate electricity.

[0017] Optionally, the steam conversion device includes a desuperheating and pressure reducing device and a waste heat boiler. The first medium-pressure steam outlet and the second medium-pressure steam outlet are respectively connected to the medium-pressure steam inlet of the desuperheating and pressure reducing device. The low-pressure steam outlet of the desuperheating and pressure reducing device is connected to the low-pressure steam pipeline network. The exhaust gas outlet of the gas turbine power generation device is connected to the flue gas inlet of the waste heat boiler, and the low-pressure steam outlet of the waste heat boiler is connected to the low-pressure steam pipeline network.

[0018] The present invention also provides a method for preparing methanol by biomass gasification, the method comprising:

[0019] The raw material enters the gasification unit through the feed inlet. The gasification unit converts the raw material into crude syngas and produces medium-pressure steam as a byproduct. Part of the crude syngas is sent from the crude syngas outlet of the gasification unit to the crude syngas inlet of the syngas regulating unit. The remaining crude syngas is sent from the crude syngas outlet to the gas inlet of the steam turbine power generation unit of the utility unit. The medium-pressure steam generated during the conversion of the crude syngas is sent from the first medium-pressure steam outlet of the gasification unit to the steam inlet of the steam conversion unit of the utility unit.

[0020] The syngas regulating unit converts the crude syngas into purified syngas that meets the requirements for methanol synthesis and then delivers the purified syngas from the purified syngas outlet of the syngas regulating unit to the purified syngas inlet of the methanol production unit.

[0021] The methanol production unit converts the purified synthesis gas into methanol product and discharges the methanol product through the methanol product outlet of the methanol production unit. The dissolved gas generated during the methanol production process is transported through the dissolved gas outlet of the methanol production unit to the gas inlet of the steam turbine power generation unit. The non-condensable gas generated during the methanol production process is transported through the non-condensable gas outlet of the methanol production unit to the gas inlet of the steam turbine power generation unit. The high-pressure purge gas generated during the methanol production process is transported through the high-pressure purge gas outlet of the methanol production unit to the gas inlet of the gas turbine power generation unit of the utility unit. The medium-pressure steam generated during the methanol production process is transported to the steam inlet of the steam conversion unit.

[0022] The utility unit supplies the crude syngas and dissolved gas and non-condensable gas generated during the methanol production process to a steam turbine power generation unit for power generation. The high-pressure purge gas generated during the methanol production process is supplied to a gas turbine power generation unit for power generation. The medium-pressure steam generated from the gasification unit and the methanol production unit is de-cooled and depressurized to convert it into low-pressure steam. The low-pressure steam is also produced using the tail gas generated during the power generation process of the gas turbine power generation unit and supplied to the gasification unit, the syngas regulating unit and the methanol production unit.

[0023] Optionally, the steam conversion device includes a desuperheating and pressure reducing device and a waste heat boiler, and the method includes:

[0024] The medium-pressure steam from the gasification unit and the methanol production unit byproducts is depressurized and reduced to low-pressure steam using the depressurization and pressure reduction device; the waste heat boiler is used to recover waste heat from the exhaust gas from the gas turbine power generation unit to generate the low-pressure steam.

[0025] Optionally, the medium-pressure steam has a pressure range of 1.6-4.0 MPa and a temperature range of 200-250 ℃; the low-pressure steam has a pressure range of 0.3-1.6 MPa and a temperature range of 130-200 ℃; the high-pressure vent gas has a pressure of 5.0-10.0 MPa(G); the exhaust gas temperature of the gas turbine power generation unit has a range of 500-600 ℃, and the exhaust gas temperature of the gas turbine power generation unit after waste heat recovery by the waste heat boiler has a range of 120-150 ℃.

[0026] As described above, the present invention provides a system and method for producing methanol from biomass gasification. In this system, the steam turbine power generation unit of the utility unit generates electricity using crude syngas and dissolved and non-condensable gases produced during methanol production. The gas turbine power generation unit generates electricity using high-pressure purge gas produced during methanol production. The steam conversion unit de-cools and depressurizes the medium-pressure steam from the gasification unit and methanol production unit, converting it into low-pressure steam. Simultaneously, it utilizes the waste heat from the exhaust gas generated during the gas turbine power generation process to produce low-pressure steam, which is then transported to the gasification unit, syngas regulation unit, and methanol production unit to supply the steam required for gasification, decarbonization, and methanol distillation. This achieves a self-balancing of power and steam in the production system, ensuring a stable power supply without external supply, meeting the carbon emission limits for green methanol products, and reducing costs. From the perspective of power source, it effectively avoids the uncertainty of reliable wind and solar power supply and avoids the problem of insufficient carbon emissions for green methanol products due to purchasing grid power. From the perspective of system energy efficiency, compared with current biomass gasification systems for methanol production, this application can effectively improve energy efficiency, reduce the consumption of biomass straw as raw material, and ultimately reduce operating costs and improve economic benefits, with a 5-10% reduction in cost per ton of methanol. From the perspective of carbon emissions from green methanol products, it can meet, for example, the EU's carbon emission limits for green methanol products, further enhancing the product's green premium. From a regional perspective, this technology is more suitable for regions with relatively abundant straw resources but insufficient renewable energy power development, and for the early stages of green methanol industrialization. Attached Figure Description

[0027] Figure 1 The diagram shown is a schematic diagram of a biomass gasification system for producing methanol according to the present invention. Detailed Implementation

[0028] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0029] Please see Figure 1 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0030] Currently, for byproduct fuel gases such as methanol synthesis off-gas, dissolved gas, and non-condensable gas, the common practice is to collect them uniformly and then generate electricity using steam turbines or internal combustion engines. This fails to utilize the different energy grades of these gases in a tiered manner, resulting in insufficient energy efficiency optimization. Furthermore, existing systems often rely on purchased electricity or steam, which not only increases operating costs but may also lead to excessive carbon emissions due to the higher carbon emission factors of purchased grid electricity. This invention aims to address the following technical problems in the existing technology: Existing green methanol production systems fail to utilize byproduct fuel gases in a tiered manner based on their energy grades, resulting in low overall system energy efficiency and high biomass feedstock consumption; existing systems rely on purchased electricity or steam, making them susceptible to fluctuations in external energy supply, and the purchased grid electricity may lead to high carbon emissions, making it difficult to meet the carbon emission limits for green methanol products; in regions with insufficient wind and solar renewable energy supply or high costs for hydrogen production via water electrolysis, there is a lack of a technological route that can achieve complete energy self-sufficiency and excellent economic efficiency. To solve these technical problems, this invention provides a biomass gasification system for producing green methanol that achieves energy self-sufficiency, as well as a process method based on this system. This invention utilizes and optimizes the energy grade differences of high-pressure purge gas, dissolved gas, non-condensable gas, and a portion of the synthesis gas from the gasification unit generated during methanol synthesis and distillation. Simultaneously, it coordinates the demand for medium-pressure and low-pressure steam produced as byproducts throughout the plant, and achieves steam self-balancing through desuperheating, pressure reduction, and waste heat recovery from gas turbine exhaust gas, thereby achieving complete self-sufficiency in electricity and steam for the entire plant.

[0031] Example 1

[0032] This invention provides a system for producing methanol from biomass gasification, such as... Figure 1 As shown, Figure 1This is a schematic diagram of a biomass gasification system for methanol production. The system includes a gasification unit, a syngas regulation unit, a methanol production unit, and a utility unit. The gasification unit converts the feedstock into crude syngas for methanol synthesis. The gasification unit includes a feed inlet, a crude syngas outlet, a first medium-pressure steam outlet, and a first low-pressure steam inlet. The syngas regulation unit converts the crude syngas into purified syngas. The syngas regulation unit includes a crude syngas inlet, a first medium-pressure steam inlet, a purified syngas outlet, a first low-pressure steam inlet, a second low-pressure steam inlet, and a first low-pressure steam outlet. The crude syngas inlet and outlet are connected. The methanol production unit includes a purified syngas inlet, a second medium-pressure steam outlet, a third low-pressure steam inlet, and a high-pressure purge gas outlet. The system includes a dissolved gas outlet, a non-condensable gas outlet, and a methanol product outlet. The purified syngas inlet is connected to the crude syngas outlet. The utility units include a gas turbine power generation unit, a steam turbine power generation unit, and a steam converter. The gas turbine power generation unit's gas inlet is connected to the high-pressure purge gas outlet. The steam turbine power generation unit's gas inlet is connected to the crude syngas outlet, dissolved gas outlet, and non-condensable gas outlet, respectively. The steam converter's steam inlet is connected to the gas turbine power generation unit's tail gas outlet, the first medium-pressure steam outlet, and the second medium-pressure steam outlet, respectively. The steam converter converts the incoming medium-pressure steam into low-pressure steam and simultaneously produces low-pressure steam based on the tail gas generated by the gas turbine power generation unit, which is then transported to the gasification unit, the syngas conditioning unit, and the methanol production unit. It should be noted that... Figure 1 The power and steam systems in the system include gas turbine power generation units, steam turbine power generation units, and steam conversion units.

[0033] Specifically, the raw materials include biomass and a gasifying agent, which includes oxygen and low-pressure steam. The type and amount of biomass can be selected according to actual needs. The crude syngas must include at least the purified syngas required for methanol synthesis or a precursor of the purified syngas required for methanol synthesis. The specific structure, size, and production specifications of the gasification unit can be selected according to actual needs, provided that the biomass is converted into crude syngas. The size, shape, and quantity of each inlet / outlet in this application (crude syngas outlet, first medium-pressure steam outlet, first low-pressure steam inlet, crude syngas inlet, purified syngas outlet, first medium-pressure steam inlet, second low-pressure steam inlet, first low-pressure steam outlet, purified syngas inlet, high-pressure purge gas outlet, dissolved gas outlet, non-condensable gas outlet, third low-pressure steam inlet, second medium-pressure steam outlet, gas inlet of the gas turbine power generation unit, gas inlet of the steam turbine power generation unit, steam inlet of the steam converter, tail gas outlet, and low-pressure steam outlet of the steam converter) can be selected according to actual needs.

[0034] Specifically, low-pressure steam is output from the low-pressure steam outlet of the steam conversion unit and then enters the gasification unit, syngas conditioning unit, and methanol production unit. The crude syngas contains at least the gases required for methanol synthesis; the feed inlet is used to input raw materials, the crude syngas outlet is used to discharge crude syngas, and the first medium-pressure steam outlet is used to discharge the medium-pressure steam generated during the conversion of raw materials into crude syngas. The raw materials include biomass and a gasifying agent, which includes oxygen and low-pressure steam. The low-pressure steam in the gasifying agent enters the gasification unit through the first low-pressure steam inlet.

[0035] In one exemplary embodiment, the gasification unit includes an air separation unit and a biomass gasification unit. The feed inlet of the gasification unit includes an air inlet of the air separation unit, a biomass inlet of the biomass gasification unit, and an oxygen inlet of the biomass gasification unit. The oxygen inlet is connected to the oxygen outlet of the air separation unit. The air separation unit is used to separate air to obtain oxygen and transport the oxygen through the oxygen outlet to the oxygen inlet of the gasification unit. The biomass gasification unit is used to gasify biomass to obtain crude syngas and simultaneously produce medium-pressure steam as a byproduct. The first low-pressure steam inlet is connected to the low-pressure steam outlet of the steam conversion unit.

[0036] Specifically, the medium-pressure steam generated by the biomass gasification unit is discharged through the first medium-pressure steam outlet and transported to the steam inlet of the steam converter, where it is used for power generation. The crude syngas is discharged through the crude syngas outlet of the gasification unit and then enters the syngas regulating unit through the crude syngas inlet. The biomass gasification unit also includes a first low-pressure steam inlet.

[0037] Specifically, provided that the purity of the prepared oxygen is 99.5%, the specific structure, model, and size of the air separation unit can be selected according to actual needs. The specific structure, model, and size of the biomass gasification unit can also be selected according to actual needs; for example, a circulating fluidized bed gasifier can be used as the biomass gasification unit. Oxygen is one of the gasifying agents used in the biomass gasification. Simultaneously, the low-pressure steam produced by the utility unit is mixed with the oxygen prepared by the air separation unit and used together as a gasifying agent in the circulating fluidized bed gasifier. For example, a low-temperature air separation unit can be used to separate air to obtain oxygen, which is then used as a gasifying agent component for biomass gasification, reducing the inert gas content in the syngas.

[0038] For example, the gasification unit also includes a feeder, a cyclone separator, a return feeder, a dust collector, a storage silo, a waste heat boiler, and a dust collector. Biomass is fed into the circulating fluidized bed gasifier through the feeder. The gasifying agent (low-pressure steam and oxygen) is fed into the circulating fluidized bed gasifier from the bottom inlet. A gasification reaction occurs in the circulating fluidized bed gasifier at a reaction temperature of 700-900℃ (the gasification temperature can be adjusted according to the characteristics of the biomass). The crude syngas produced by the reaction carries semi-coke particles and is discharged from the top of the circulating fluidized bed gasifier. After separation in the cyclone separator, the semi-coke particles are returned to the circulating fluidized bed gasifier through the return feeder. The slag produced by gasification is discharged through the slag discharge system at the bottom of the circulating fluidized bed gasifier. The fly ash produced by gasification is fed into the storage silo through the dust collector and then through the pneumatic input system. The syngas after the reaction is successively fed into the waste heat boiler for waste heat recovery and dust collector for dust removal before being transported to the syngas regulating unit. The waste heat boiler recovers the waste heat of the syngas to generate medium-pressure steam. The steam outlet of the waste heat boiler (as the first medium-pressure steam outlet) is connected to the steam inlet of the steam conversion device. The steam conversion device uses the medium-pressure steam discharged from the steam outlet of the waste heat boiler to reduce the temperature and pressure to generate low-pressure steam.

[0039] In one exemplary embodiment, the syngas conditioning unit includes a pretreatment device, a shift device, and a decarbonization device; the pretreatment device is used to cool, wash, compress, and purify the crude syngas to obtain pretreated syngas; the shift device is used to perform water-gas shift on the pretreated syngas to adjust the hydrogen-to-carbon ratio to obtain water-gas shifted syngas, and the shift device includes a first medium-pressure steam inlet and a first low-pressure steam outlet; the decarbonization device is used to remove carbon dioxide from the water-gas shifted syngas to obtain purified syngas, and the decarbonization device includes a second low-pressure steam inlet.

[0040] Specifically, the medium-pressure steam required for the syngas regulating unit conversion enters the conversion device through the first medium-pressure steam inlet, and the low-pressure steam generated by the syngas regulating unit conversion exits the conversion device through the first low-pressure steam outlet; the low-pressure steam required for the syngas regulating unit decarbonization enters the decarbonization device through the second low-pressure steam inlet.

[0041] Specifically, the purified syngas meets the hydrogen-to-carbon ratio and purity requirements for methanol synthesis. Provided that the crude syngas can be converted into purified syngas, the specific structure of the syngas regulating unit can be selected according to actual needs. For example, the syngas regulating unit can perform processes such as syngas pretreatment, water-gas conversion, and acid gas removal.

[0042] Specifically, considering that the crude syngas contains impurities such as ammonia and sulfur in addition to carbon monoxide, carbon dioxide, and hydrogen, as well as the impact of the hydrogen-to-carbon ratio on subsequent processes, the syngas conditioning unit needs to treat the crude syngas. The syngas conditioning unit includes at least a pretreatment device, a shift converter, and a decarbonization device. The pretreatment device is used to cool, wash, and compress the crude syngas. The shift converter is used to perform a water-gas shift reaction on the pretreated syngas with the participation of shift steam to adjust the hydrogen-to-carbon ratio. The decarbonization device is used to remove carbon dioxide under the heating of decarbonization reboiling steam to obtain purified syngas. For example, the syngas conditioning unit includes a water washing tower, a compressor, a shift converter, an acid gas removal device, and a gas qualitative and quantitative analysis device to meet the following steps: After the crude syngas is cooled and washed by the water washing tower, it is pressurized by the compressor and subjected to ammonia washing. The purified crude gas is then pressurized by the compressor and enters the shift converter for water-gas shift. The shifted gas then enters the acid gas removal process to remove acid gases through desulfurization and other steps. It then continues with the MDEA (N-Methyldiethanolamine) decarbonization process to remove carbon dioxide from the shifted gas, meeting the requirements for methanol synthesis feedstock gas indicators. In addition, it includes a sulfur-containing component removal step. For example, the shift converter is at least used for water-gas shift of the crude syngas, and the low-pressure steam inlet of the acid gas removal device is connected as a second low-pressure steam inlet to the low-pressure steam outlet of the steam conversion device.

[0043] Specifically, the syngas conditioning unit is used to adjust the crude syngas from the gasification unit into purified syngas that meets the hydrogen-to-carbon ratio and purity requirements for methanol synthesis through pretreatment, water-gas conversion, and decarbonization processes.

[0044] Specifically, the purified syngas obtained from the syngas conditioning unit is discharged through the purified syngas outlet and transported to the purified syngas inlet to enter the methanol production unit. The methanol production unit is used to produce methanol by hydrogenation of carbon monoxide, and includes at least a methanol synthesis unit and a methanol distillation unit. The second medium-pressure steam outlet is used to discharge the medium-pressure steam generated during the methanol production process using the purified syngas; the third low-pressure steam inlet is used to input the low-pressure steam required for the methanol production process; and the by-product fuel gas outlet is used to discharge the by-product fuel gas generated during the methanol production process.

[0045] In one exemplary embodiment, the methanol production unit includes a methanol synthesizer and a methanol separator. The purified synthesis gas inlet of the methanol synthesizer serves as the purified synthesis gas inlet of the methanol production unit and is connected to the purified synthesis gas outlet of the synthesis gas regulating unit. The methanol synthesizer converts the purified synthesis gas into methanol. The methanol separator is used to separate the reaction material from the methanol synthesizer to obtain crude methanol, high-pressure purge gas, and recycle gas. The reaction material inlet of the methanol separator is connected to the reaction material outlet. The methanol separator includes a crude methanol outlet for discharging crude methanol, a high-pressure purge gas outlet for discharging high-pressure purge gas, and a recycle gas outlet for discharging recycle gas.

[0046] Specifically, the methanol synthesizer is used to perform a carbon monoxide hydrogenation reaction on the purified synthesis gas to produce the reacted materials. The steam outlet of the methanol synthesizer (exemplarily, a methanol synthesis tower) serves as a second medium-pressure steam outlet to discharge the medium-pressure steam generated during the methanol synthesis process. During the methanol synthesis process, the medium-pressure steam generated by the exothermic reaction in the methanol synthesizer is discharged through the steam outlet of the methanol synthesizer and conveyed to the steam inlet of the steam converter, where it is depressurized and converted into low-pressure steam.

[0047] In one exemplary embodiment, the methanol production unit further includes a methanol flash tank and a methanol distillation unit; the methanol flash tank has an inlet for methanol to be flashed connected to a crude methanol outlet, and the methanol flash tank generates dissolved gas during the flashing process of the methanol to be flashed; the methanol distillation unit has an inlet for methanol to be distilled connected to a flash-exit methanol outlet from the methanol flash tank, and the distillation reboiler steam inlet of the methanol distillation unit is connected as a third low-pressure steam inlet to a low-pressure steam outlet from a steam conversion unit, and the methanol distillation unit generates non-condensable gas during the distillation process of the flash-exit methanol.

[0048] Specifically, the dissolved gas outlet of the methanol flash evaporator serves as the dissolved gas outlet of the methanol production unit, used to discharge the dissolved gas generated during the flash evaporation of the methanol to be flashed. Similarly, the non-condensable gas outlet of the methanol distillation unit serves as the non-condensable gas outlet of the methanol production unit, used to discharge the non-condensable gas generated during the methanol distillation process after flash evaporation.

[0049] Specifically, the methanol production unit includes a methanol synthesis unit (including a gas compression unit, a methanol synthesizer, a methanol separator, and a methanol flash tank) and a methanol distillation unit. The methanol synthesis unit is used to compress and preheat the purified synthesis gas and then perform a carbon monoxide hydrogenation reaction to produce crude methanol, and separates high-pressure purge gas and dissolved gas, while producing medium-pressure steam as a byproduct (the second medium-pressure steam outlet of the methanol synthesis unit). The methanol distillation unit is used to distill the crude methanol to obtain refined methanol product and separate non-condensable gas.

[0050] In one exemplary embodiment, the circulating gas outlet of the methanol separator is connected to the pre-compression gas inlet of the gas compression device, and the post-compression gas outlet of the gas compression device is connected to the purified syngas inlet.

[0051] Specifically, the gas compression device compresses the gas. The specific structure and materials of the gas compression device can be selected according to actual needs.

[0052] Specifically, the gas compression unit compresses the recycle gas from the methanol separator and inputs the compressed recycle gas into the methanol synthesizer. It should be noted that the function of the gas compression unit is not limited to compressing the recycle gas from the methanol separator and inputting the compressed recycle gas into the methanol synthesizer; it is also used to compress recycle gas discharged from other devices in the system or other gases that require compression, and input the compressed recycle gas into devices that require such compressed recycle gas, or input other gases that require compression into devices that require such compressed gas. For example, the purified syngas from the syngas conditioning unit is mixed with the circulating gas after passing through a gas compression device. The gas is further pressurized to the reaction pressure in the gas compression device. After being preheated by the outlet gas, it enters the shell-and-tube isothermal methanol synthesis tower. After heat exchange between the outlet gas and the inlet gas in the shell-and-tube isothermal methanol synthesis tower, the inlet gas is heated to above the active temperature. The outlet gas (the material after the reaction) is cooled to 40°C by a water cooler and enters the methanol separator for gas-liquid separation. Part of the gas exiting the methanol separator is discharged as purge gas to maintain the balance of inert gas in the circulation loop. The vast majority of the remaining gas is sent as circulating gas to the compression process and then enters the methanol synthesizer. The crude methanol separated by the methanol separator is then sent to the methanol flash tank under reduced pressure. Most of the dissolved gas is flashed out in the methanol flash tank. The crude methanol obtained after flashing is sent to the methanol distillation unit.

[0053] Specifically, in the methanol distillation unit, the reboiler steam inlet, which requires low-pressure steam input, is connected as the third low-pressure steam inlet to the low-pressure steam outlet of the steam converter. For example, the methanol distillation employs a three-tower process, with the methanol distillation unit including a pre-distillation tower, a pressurized tower, and an atmospheric tower. The methanol vapor stream from the top of the pressurized tower serves as the heat source for the reboiler in the atmospheric tower; that is, the high-temperature methanol vapor emerging from the top of the pressurized tower heats the liquid at the bottom of the atmospheric tower.

[0054] Specifically, the methanol distillation unit generates non-condensable vapors during the methanol distillation process. The non-condensable vapor outlet of the methanol distillation unit serves as the non-condensable vapor outlet for the methanol production unit and is connected to the gas inlet of the steam turbine power generation unit. The steam turbine power generation unit recovers these non-condensable vapors for power generation. The high-pressure purge gas is then used as fuel gas in the gas turbine power generation unit for combustion and power generation.

[0055] Specifically, after the crude syngas produced by the gasification unit meets the requirements of the syngas regulating unit, the remaining crude syngas is fed into the utility unit. At least one crude syngas outlet of the circulating fluidized bed gasifier is connected to the gas inlet of the steam turbine power generation unit via a pipeline. The remaining crude syngas from the gasification unit, after meeting the requirements of the syngas regulating unit, is transported through the crude syngas outlet to the gas inlet of the steam turbine power generation unit and enters the unit, where it is burned and used for steam power generation.

[0056] Specifically, the methanol production unit is used to produce methanol via carbon monoxide hydrogenation. For example, the methanol production unit includes a methanol synthesis unit and a methanol distillation unit. The methanol synthesis unit compresses and preheats the purified synthesis gas before subjecting it to a carbon monoxide hydrogenation reaction to produce crude methanol, separating high-pressure purge gas and dissolved gas, while simultaneously producing medium-pressure steam as a byproduct. The copper catalyst used in methanol synthesis can generally operate at 210-290 °C and 5.0-10.0 MPa(G). The purified gas from the synthesis gas conditioning unit is compressed and mixed with the recycle gas, further pressurized to the reaction pressure in the compressor recycle section, and then preheated before entering a shell-and-tube isothermal methanol synthesis tower. After heat exchange between the tower outlet gas and the tower inlet gas, the inlet gas is heated above its active temperature, then cooled by a water cooler before entering a methanol separator for gas-liquid separation. A portion of the gas exiting the methanol separator is discharged as high-pressure purge gas to maintain the balance of inert gases in the recycle loop; the majority of the remaining gas is sent as recycle gas to the compression process and then enters the methanol synthesis reactor. The separated crude methanol is fed into a methanol flash tank under reduced pressure, where most of the dissolved gases are flashed out. The pressure of the high-pressure purge gas is 5.0-10.0 MPa(G).

[0057] The methanol distillation unit is used to distill crude methanol to obtain refined methanol product and separate non-condensable gases. The methanol distillation employs a three-tower process, including a pre-distillation tower, a pressurized tower, and an atmospheric tower. The methanol vapor stream from the top of the pressurized tower serves as the heat source for the reboiler in the atmospheric tower. The non-condensable gases separated from the tops of the pre-distillation tower and the atmospheric tower are collected.

[0058] Specifically, the utility unit provides the entire system with electricity, steam, circulating water, boiler feedwater, etc. The utility unit also includes a cooling tower and a water treatment module. The water treatment module is used to provide the water source required by the system and to recycle and treat the wastewater generated by the system. The cooling tower is used in the processes in the system that require cooling treatment.

[0059] In one exemplary embodiment, the gas turbine power generation device includes a first combustion chamber, a gas turbine, and a first generator. The gas inlet of the first combustion chamber serves as the gas inlet of the gas turbine power generation device. The first combustion chamber is used to burn high-pressure purge gas to generate first high-temperature flue gas. The flue gas inlet of the gas turbine is connected to the flue gas outlet of the first combustion chamber. The gas turbine uses the expansion of the first high-temperature flue gas to drive the first generator to generate electricity. The steam turbine power generation device includes a second combustion chamber, a waste heat recovery steam generator, a steam turbine, and a second generator. The gas inlet of the second combustion chamber serves as the gas inlet of the steam turbine power generation device. The second combustion chamber is used to burn dissolved gas, non-condensable gas, and part of crude syngas to generate second high-temperature flue gas. The flue gas inlet of the waste heat recovery steam generator is connected to the flue gas outlet of the second combustion chamber. The waste heat recovery steam generator uses the second high-temperature flue gas to generate steam. The steam outlet of the waste heat recovery steam generator is connected to the steam inlet of the steam turbine. The steam turbine uses the expansion of the steam to drive the second generator to generate electricity.

[0060] Specifically, high-pressure purge gas mixes and burns with compressed air in the combustion chamber to produce high-temperature flue gas. The high-temperature flue gas enters the gas turbine, expands, does work, and drives the generator to generate electricity. Dissolved gas, non-condensable gas, and part of the crude syngas burn in the combustion chamber to produce high-temperature flue gas. The high-temperature flue gas enters the waste heat recovery steam generator to produce steam. The steam enters the steam turbine, expands, does work, and drives the generator to generate electricity.

[0061] In one exemplary embodiment, the steam conversion device includes a desuperheating and pressure reducing device and a waste heat boiler. A first medium-pressure steam outlet and a second medium-pressure steam outlet are respectively connected to the medium-pressure steam inlet of the desuperheating and pressure reducing device. The low-pressure steam outlet of the desuperheating and pressure reducing device is connected to a low-pressure steam pipeline network. The exhaust gas outlet of the gas turbine power generation device is connected to the flue gas inlet of the waste heat boiler, and the low-pressure steam outlet of the waste heat boiler is connected to a low-pressure steam pipeline network.

[0062] Specifically, provided that the low-pressure steam network can supply low-pressure steam to the gasification unit, syngas regulating unit, and methanol production unit, the specific structure, material, and size of the low-pressure steam network can be selected according to actual needs. The low-pressure steam network is connected to the first, second, and third low-pressure steam inlets.

[0063] In one exemplary embodiment, the utility unit further includes a medium-pressure steam supply device connected to a first medium-pressure steam inlet, which supplies medium-pressure steam to the syngas regulating unit.

[0064] For example, the utility unit, used to provide electricity and steam to the production system and achieve a balance between electricity and steam supply, includes a gas turbine power generation unit, a steam turbine power generation unit, a desuperheating and pressure reducing device, and a waste heat boiler. Depending on the energy grade, the high-pressure purge gas outlet of the methanol production unit is connected to the first fuel gas inlet of the gas turbine power generation unit. The high-pressure purge gas has a high pressure energy range of 5.0~10.0 MPa(G). The high-pressure purge gas is directly transported to the gas turbine power generation unit, where it mixes and burns with compressed air in the combustion chamber to produce high-temperature flue gas. The high-temperature flue gas enters the gas turbine, expands, and performs work, driving the generator to generate electricity, thus achieving efficient utilization of high-grade energy. For example, the gas inlet of the steam turbine power generation unit includes a first gas inlet, a second gas inlet, and a third gas inlet. The dissolved gas outlet of the methanol production unit is connected to the first gas inlet of the steam turbine power generation unit; the non-condensable gas outlet of the methanol production unit is connected to the second gas inlet of the steam turbine power generation unit; and the crude syngas outlet of the gasification unit is connected to the third gas inlet of the steam turbine power generation unit. Dissolved gas, non-condensable gas, and some crude syngas are fuel gases with relatively low energy grades. After being collected, they are transported to a steam turbine power generation unit, where they are burned in the combustion chamber to produce high-temperature flue gas. The high-temperature flue gas enters the waste heat recovery steam generator to produce steam, which then enters the steam turbine to expand and do work, driving the generator to generate electricity.

[0065] Specifically, the by-product medium-pressure steam (typically 1.6-4.0 MPa, 200-250 °C) from the gasification unit, shift unit, and methanol synthesis unit enters the desuperheating and pressure reducing device, where it is desuperheated and reduced to low-pressure steam (typically 0.3-1.6 MPa, 130-200 °C). The low-pressure steam outlet of the desuperheating and pressure reducing device is connected to the first low-pressure steam inlet of the gasification unit, the second low-pressure steam inlet (decarbonization reboiling steam inlet) of the syngas regulating unit, and the third low-pressure steam inlet (rectification reboiling steam inlet) of the methanol production unit.

[0066] Specifically, the exhaust gas outlet of the gas turbine power generation unit is connected to the flue gas inlet of the waste heat boiler. The high-temperature exhaust gas (approximately 500-600 ℃) discharged from the gas turbine enters the waste heat boiler, where it recovers waste heat to generate low-pressure steam (typically 0.3-1.6 MPa, 130-200 ℃) to supplement the insufficient low-pressure steam after desuperheating and depressurization. The low-pressure steam outlet of the waste heat boiler is connected to the low-pressure steam pipeline network.

[0067] Preferably, the gasifying agent steam inlet of the gasification unit, the decarbonization reboiling steam inlet of the syngas regulating unit, and the distillation reboiling steam inlet of the methanol production unit are all connected to the same low-pressure steam network; the low-pressure steam outlet of the desuperheating and pressure reducing device and the low-pressure steam outlet of the waste heat boiler are all connected to the low-pressure steam network to form a unified low-pressure steam supply system.

[0068] Example 2

[0069] The present invention also provides a method for preparing methanol by biomass gasification, the method comprising:

[0070] The raw material enters the gasification unit through the feed inlet. The gasification unit converts the raw material into crude syngas and produces medium-pressure steam as a byproduct. Part of the crude syngas is sent from the crude syngas outlet of the gasification unit to the crude syngas inlet of the syngas regulating unit. The remaining crude syngas is sent from the crude syngas outlet to the gas inlet of the steam turbine power generation unit of the utility unit. The medium-pressure steam generated during the conversion of crude syngas is sent from the first medium-pressure steam outlet of the gasification unit to the steam inlet of the steam conversion unit of the utility unit.

[0071] The syngas regulating unit converts crude syngas into purified syngas required for methanol synthesis and then delivers the purified syngas from the purified syngas outlet of the syngas regulating unit to the purified syngas inlet of the methanol production unit.

[0072] The methanol production unit converts the purified syngas into methanol and discharges the methanol product through the methanol product outlet of the methanol production unit. The dissolved gas generated during the methanol production process is transported to the gas inlet of the steam turbine power generation unit through the dissolved gas outlet of the methanol production unit. The non-condensable gas generated during the methanol production process is transported to the gas inlet of the steam turbine power generation unit through the non-condensable gas outlet of the methanol production unit. The high-pressure purge gas generated during the methanol production process is transported to the gas inlet of the gas turbine power generation unit of the utility unit through the high-pressure purge gas outlet of the methanol production unit. The medium-pressure steam generated during the methanol production process is transported to the steam inlet of the steam conversion unit through the second medium-pressure steam outlet of the methanol production unit.

[0073] In the utilities unit, dissolved gas and non-condensable gas generated during the production of crude syngas and methanol are transported to a steam turbine power generation unit for power generation. High-pressure purge gas generated during methanol production is transported to a gas turbine power generation unit for power generation. Medium-pressure steam generated from the gasification unit and methanol production unit is de-cooled and depressurized to convert it into low-pressure steam. Waste heat from the exhaust gas generated during the power generation process of the gas turbine power generation unit is used to produce low-pressure steam, which is then transported to the gasification unit, syngas regulation unit, and methanol production unit.

[0074] In one exemplary embodiment, the steam conversion device includes a desuperheating and pressure reducing device and a waste heat boiler, and the method includes:

[0075] The medium-pressure steam from the gasification unit and methanol production unit by-products is de-cooled and de-pressurized into low-pressure steam using a de-cooling and de-pressurization device; the waste heat boiler is used to recover waste heat from the exhaust gas from the gas turbine power generation unit to generate low-pressure steam.

[0076] In one exemplary embodiment, the pressure range of the medium-pressure steam is 1.6-4.0 MPa, and the temperature range of the medium-pressure steam is 200-250 °C; the pressure range of the low-pressure steam is 0.3-1.6 MPa, and the temperature range of the low-pressure steam is 130-200 °C; the pressure of the high-pressure vent gas is 5.0-10.0 MPa(G); the exhaust gas temperature range of the gas turbine power generation unit is 500-600 °C, and the exhaust gas temperature range of the gas turbine power generation unit after waste heat recovery by the waste heat boiler is 120-150 °C.

[0077] Specifically, exhaust gas temperature refers to the temperature of the exhaust gas from the gas turbine power generation unit after waste heat recovery by the waste heat boiler. The pressure of medium-pressure steam can be any value within the range of 1.6-4.0 MPa; the temperature of medium-pressure steam can be any value within the range of 200-250 ℃; the pressure of low-pressure steam can be any value within the range of 0.3-1.6 MPa; and the temperature of low-pressure steam can be any value within the range of 130-200 ℃.

[0078] Specifically, the gasification process includes: producing oxygen through an air separation unit; feeding biomass feedstock and gasifying agent into a biomass gasification unit for gasification reaction to generate crude syngas and produce medium-pressure steam as a byproduct. Specifically, the biomass feedstock is fed into a circulating fluidized bed gasifier via a feeder, while oxygen and steam are introduced from the bottom of the gasifier as gasifying agents, undergoing a gasification reaction at 700-900 °C. The crude syngas produced, carrying semi-coke particles, is discharged from the top of the gasifier and enters a cyclone separator for gas-solid separation. The separated semi-coke particles are returned to the gasifier via a return feeder. The separated syngas is then fed through a waste heat boiler to recover waste heat and produce medium-pressure steam as a byproduct, and after dust removal by a dust collector, it is sent to the syngas conditioning unit. The slag produced during gasification is discharged through a slag discharge system, and the fly ash is pneumatically conveyed to a storage silo. Simultaneously, a portion of the crude syngas is extracted from the gasification unit as supplementary syngas and sent to a steam turbine power generation unit as supplementary fuel gas.

[0079] Specifically, the syngas conditioning step involves purifying, pretreating, shifting, and decarbonizing the crude syngas to obtain purified syngas that meets the hydrogen-to-carbon ratio and purity requirements for methanol synthesis. Specifically, the crude syngas is cooled and washed in a water scrubbing tower, then pressurized by a compressor for ammonia removal via water washing. The purified crude syngas is then pressurized again and enters a sulfur-resistant shift converter, where a water-gas shift reaction is performed with the participation of shift steam to adjust the hydrogen-to-carbon ratio to meet the requirements for methanol synthesis. After desulfurization, the shift gas enters a decarbonization unit, where carbon dioxide is removed via the MDEA method under decarbonization reboiling steam heating, yielding purified syngas that meets the feedstock gas requirements for methanol synthesis.

[0080] Specifically, the methanol synthesis steps are as follows: The purified synthesis gas undergoes a carbon monoxide hydrogenation reaction to produce crude methanol, separating high-pressure purge gas and dissolved gas, while also producing medium-pressure steam as a byproduct. Specifically, the purified synthesis gas is compressed and mixed with recycle gas, further pressurized to the reaction pressure, and then preheated before entering a shell-and-tube isothermal methanol synthesis tower. The carbon monoxide hydrogenation reaction is carried out at 210-290 °C and 5.0-10.0 MPa(G) under the action of a copper-based catalyst. The heat of reaction is removed using the medium-pressure steam produced as a byproduct in the shell side. After the reaction, the gas is cooled and separated. A portion of the gas is discharged as high-pressure purge gas to maintain the balance of inert gases in the recycle loop; the pressure of the high-pressure purge gas is 5.0-10.0 MPa(G). The majority of the remaining gas is returned to the methanol synthesis reactor as recycle gas. The separated crude methanol is sent to a methanol flash evaporator under reduced pressure to flash off the dissolved gas before being sent to the methanol distillation step.

[0081] Specifically, the methanol distillation process involves: distilling crude methanol to obtain refined methanol product and separating non-condensable gases. Specifically, the crude methanol after flash distillation undergoes a three-tower distillation process, including a pre-distillation tower, a pressurized tower, and an atmospheric distillation tower. Light components are removed in the pre-distillation tower, and non-condensable gases are separated at the top. The pre-distilled methanol enters the pressurized tower, where methanol vapor from the top serves as a heat source for the reboiler in the atmospheric distillation tower. The methanol from the bottom of the pressurized tower enters the atmospheric distillation tower for further distillation, yielding refined methanol product at the top and wastewater at the bottom. The non-condensable gases separated at the top of the atmospheric distillation tower are collected.

[0082] Specifically, the plant utilizes utilities units to achieve energy recovery and self-balancing. Based on different energy grades, various byproduct fuel gases and steam generated during production are utilized and optimized in a tiered manner to achieve complete self-sufficiency in electricity and steam for the entire plant. High-pressure purge gas is fed into a gas turbine power generation unit for combustion and power generation. Because high-pressure purge gas has high pressure energy, direct feeding into the gas turbine avoids throttling and pressure reduction losses, achieving high-efficiency power generation with high-grade energy. Non-condensable gases, dissolved gases, and a portion of the syngas from the gasification unit are fed into a steam turbine power generation unit for combustion and power generation. These fuel gases, with relatively low energy grades, are collected and used as fuel for the steam turbine, generating steam to drive the steam turbine for power generation.

[0083] Specifically, the by-product medium-pressure steam (pressure 1.6-4.0 MPa, temperature 200-250 ℃) from the gasification unit and methanol production unit is depressurized and reduced to low-pressure steam (pressure 0.3-1.6 MPa, temperature 130-200 ℃) using a desuperheating and depressurization device. The exhaust gas (temperature 500-600 ℃) from the gas turbine power generation unit is fed into a waste heat boiler to recover waste heat and generate low-pressure steam to supplement the insufficient low-pressure steam after desuperheating and depressurization, reducing the flue gas temperature to 120-150 ℃. This low-pressure steam is then supplied to the gasification step as gasification agent steam, to the syngas conditioning unit as decarbonization reboiling steam, and to the methanol distillation unit as distillation reboiling steam.

[0084] Through the above steps, the entire plant achieves complete self-sufficiency in electricity and steam, eliminating the need for external purchases of electricity or steam. This invention utilizes the energy grade differences of the high-pressure purge gas, dissolved gas, non-condensable gas, and a portion of the syngas from the gasification unit generated during methanol synthesis and distillation in a tiered manner: the high-pressure purge gas is used to generate electricity via a gas turbine, while the dissolved gas, non-condensable gas, and a portion of the syngas are used to generate electricity via a steam turbine. Simultaneously, the demand for by-product medium-pressure steam and low-pressure steam is coordinated, with low-pressure steam supplemented through desuperheating, pressure reduction, and waste heat recovery from gas turbine exhaust, achieving complete self-sufficiency in electricity and steam for the entire plant, eliminating the need for external purchases of electricity or steam.

[0085] Specifically, the crude syngas produced by the gasification unit, the dissolved gas and non-condensable gas produced by the methanol production unit enter the steam turbine power generation unit through the gas inlet of the steam turbine power generation unit and are recycled for power generation; the high-pressure purge gas produced by the methanol production unit enters the gas turbine power generation unit through the gas inlet of the gas turbine power generation unit and is recycled for power generation; the medium-pressure steam produced by the gasification unit and the methanol production unit is discharged through the medium-pressure steam outlet of each unit and enters the steam conversion unit through the steam inlet of the steam conversion unit, where it is de-heated and depressurized to become low-pressure steam. This low-pressure steam is discharged through the low-pressure steam outlet of the steam conversion unit and is transported to the feed inlet, the first low-pressure steam inlet, the second low-pressure steam inlet and the third low-pressure steam inlet to supply the gasification unit, the syngas regulating unit and the methanol production unit. For the insufficient low-pressure steam, the steam conversion unit generates low-pressure steam based on the waste heat of the exhaust gas from the gas turbine power generation unit to supply the gasification unit, the syngas regulating unit and the methanol production unit.

[0086] Specifically, this system includes a gasification unit, a syngas regulation unit, a methanol production unit, and a utilities unit. These units are connected through specific material and energy flows, forming an integrated whole.

[0087] The gasification unit produces oxygen using a standard low-temperature air separator for biomass gasification to obtain crude syngas. To reduce the inert components in the crude syngas, the oxygen purity should be maintained above 99.5% (vol%). Biomass feedstock is fed into a circulating fluidized bed gasifier via a feeder. The gasifying agents (low-pressure steam and oxygen) are introduced from the bottom of the gasifier, where a gasification reaction occurs at a temperature of 700-900℃ (adjustable depending on the feedstock characteristics). The crude syngas, carrying semi-coke particles, is discharged from the top of the gasifier and separated in a cyclone separator. The semi-coke particles are then returned to the gasifier via a return feeder. Slag produced during gasification is discharged through a slag removal system at the bottom of the circulating fluidized bed. Fly ash is collected by a dust collector and then transported to a storage silo via a pneumatic conveying system. The crude syngas after reaction undergoes waste heat recovery and dust removal via a waste heat boiler and dust collector before being fed into the syngas conditioning unit.

[0088] Considering the impurities such as ammonia and sulfur in the crude syngas and the impact of the hydrogen-to-carbon ratio on subsequent processes, the crude syngas needs to be purified by a syngas regulating unit. The raw materials for methanol synthesis are typically carbon monoxide, carbon dioxide, and hydrogen. For example, this invention uses carbon monoxide and hydrogen as the syngas for methanol synthesis, since the crude syngas includes carbon monoxide, carbon dioxide, hydrogen, and other gases. After being cooled and washed in a water scrubbing tower, the crude syngas is pressurized by a compressor and subjected to ammonia washing. The purified crude syngas is then pressurized again and enters a sulfur-resistant shift converter. When the molar ratio of hydrogen to carbon monoxide in the crude syngas does not meet the hydrogen-to-carbon ratio requirements for methanol synthesis, the syngas regulating unit adjusts the amount of carbon monoxide (for example, converting some carbon monoxide to carbon dioxide). The carbon dioxide is then removed from the shift gas through a decarbonization process, resulting in purified syngas that meets the raw material requirements for methanol synthesis. The syngas regulating unit then delivers the purified syngas to the methanol production unit.

[0089] In the methanol production unit, a methanol synthesis tower is used as the methanol synthesizer. The copper catalyst used in methanol synthesis can generally operate at 210-290 ℃ and 5.0-10.0 MPa(G), depending on the type of catalyst and reactor type. In the methanol synthesis tower, the copper catalyst catalyzes the synthesis of methanol from carbon monoxide and hydrogen in the purified synthesis gas. Since methanol synthesis is a strongly exothermic reaction, the heat of reaction is removed using medium-pressure steam produced as a byproduct in the shell side. The purified synthesis gas from the synthesis gas conditioning unit is compressed and mixed with the recycle gas. It is further pressurized to the reaction pressure in the compressor circulation section. After being preheated by the outlet gas, it enters the shell-and-tube isothermal methanol synthesis tower. After heat exchange between the gas exiting and entering the synthesis tower, the gas entering the tower is heated above the active temperature, then cooled to 40°C by a water cooler before entering the methanol separator for gas-liquid separation. A portion of the gas exiting the methanol separator is discharged as purge gas to maintain the balance of inert gases in the circulation loop; the majority of the remaining gas is sent as recirculated gas to the compression process and then to the methanol synthesis reactor. The separated crude methanol is sent to a methanol flash tank under reduced pressure, where most of the dissolved gases are flashed out. The flashed crude methanol is then sent to the methanol distillation unit. The methanol distillation uses a three-tower process, including a pre-distillation tower, a pressurized tower, and an atmospheric tower. The methanol vapor stream at the top of the pressurized tower serves as the heat source for the reboiler of the atmospheric tower.

[0090] The utilities unit provides electricity, steam, circulating water, and boiler feedwater to the various units within the aforementioned production system. Depending on the energy grade, the utilities unit generates electricity using high-pressure purge gas from the methanol synthesis process via a gas turbine; it also generates electricity using dissolved gas, non-condensable gas, and a portion of the synthesis gas from the methanol synthesis and distillation processes via a steam turbine; and it depressurizes and cools medium-pressure steam from the gasification and methanol synthesis units to produce low-pressure steam. Any shortfall is supplemented by generating low-pressure steam from the waste heat of the high-temperature exhaust gas from the gas turbine, which is then used to supply the steam required for gasification, decarbonization, and methanol distillation. This achieves a self-balancing system for electricity and steam, eliminating the need for external supply.

[0091] The utility unit also includes a cooling tower and a water treatment unit. The cooling tower is used to provide the circulating water required for the operation of each unit, and the water treatment unit is used to treat the wastewater generated by the operation of each unit.

[0092] For ease of understanding, the following describes a system and method for producing methanol from biomass gasification, provided by this invention. The system includes a gasification unit, a syngas regulation unit, a methanol production unit, and a utility unit. These units are connected through specific material and energy flows, forming an integrated whole. High-pressure purge gas, a byproduct, is used to generate electricity via a gas turbine. A steam turbine utilizes byproduct gas (e.g., dissolved gas and non-condensable gas) and a portion of the crude syngas to generate electricity, achieving a balance between power and steam.

[0093] The gasification unit comprises an air separation unit and a biomass gasification unit. The air separation unit employs a standard low-temperature air separation process, producing oxygen with a purity of 99.6 vol%, sufficient to meet the gasifier's requirements. The oxygen output of the air separation unit is connected to the oxygen inlet of the biomass gasification unit. The biomass gasification unit uses a circulating fluidized bed gasifier, receiving crushed and dried biomass straw pellets at its feedstock inlet, with a processing capacity of 416,069 tons / year. The first low-pressure steam inlet is connected to a low-pressure steam network, receiving 0.9 MPa low-pressure saturated steam as the gasifying agent. Inside the circulating fluidized bed gasifier, the biomass feedstock and gasifying agent undergo a gasification reaction at approximately 800 °C, generating crude syngas. The crude syngas, carrying semi-coke particles, is discharged from the top of the gasifier and enters a cyclone separator for gas-solid separation. The separated semi-coke particles are returned to the gasifier via a return feeder. The separated syngas is sequentially fed through a waste heat boiler to recover waste heat and produce medium-pressure saturated steam (3.1 MPa) as a byproduct. After dust removal by a dust collector, it is sent to the syngas regulating unit through the crude syngas outlet. The slag produced by gasification is discharged through the slag discharge system, and the fly ash is pneumatically conveyed to the storage silo. In addition, the gasification unit also extracts a portion of the crude syngas (approximately 8960 Nm³ / h) and connects it to the third gas inlet of the steam turbine power generation unit through the crude syngas outlet to supplement the fuel for power generation in the steam turbine power generation unit.

[0094] The syngas conditioning unit includes a pretreatment unit, a shift converter, and a decarbonization unit. The pretreatment unit comprises a water scrubbing tower and a compressor. The crude syngas (approximately 350 °C) is cooled and scrubbed in the water scrubbing tower to approximately 40 °C, removing most of the tar and dust. It is then pressurized by the compressor to approximately 2.5 MPa for water scrubbing and ammonia removal, reducing the ammonia content to <10 ppm. The purified crude syngas is then pressurized again by the compressor and enters the shift converter. The shift converter is a sulfur-resistant unit, with the first medium-pressure steam inlet receiving 3.1 MPa medium-pressure saturated steam as the shift steam inlet. Under the action of the sulfur-resistant shift catalyst, CO reacts with water vapor to produce H2 and CO2, adjusting the hydrogen-to-carbon ratio (H2-CO2 / CO+CO2) to approximately 2.05~2.15, meeting the requirements for methanol synthesis. The shift gas then enters the desulfurization unit, where the total sulfur content is reduced to <0.1 ppm under the action of a desulfurizing agent. The desulfurized shift gas then enters the decarbonization unit. The decarbonization unit uses the MDEA method to remove CO2. The decarbonization reboiler steam inlet of the decarbonization unit is connected to the low-pressure steam network, receiving 0.9 MPa low-pressure saturated steam to heat the reboiler. The purified syngas after decarbonization is connected to the purified syngas inlet of the methanol production unit through the purified syngas outlet.

[0095] The methanol production unit comprises a methanol synthesis unit and a methanol distillation unit. The methanol synthesis unit includes a synthesis gas compressor, an outlet gas preheater, a methanol synthesis tower, a water cooler, a methanol separator, and a methanol flash evaporation unit. Purified gas from the synthesis gas regulating unit is compressed to approximately 5.0 MPa by the synthesis gas compressor and then mixed with recycle gas from the methanol separator. In the recycle section, the mixture is further compressed to a reaction pressure of approximately 5.1 MPa. After preheating by the outlet gas preheater, the gas enters a shell-and-tube isothermal methanol synthesis tower. Under the action of a copper-based catalyst, carbon monoxide hydrogenation occurs at 250 °C and 5.0 MPa(G) to produce methanol. The reaction is strongly exothermic, and medium-pressure saturated steam (3.1 MPa) is produced as a byproduct of the shell-side boiler water. The outlet gas is cooled by heat exchange with the inlet gas in the outlet gas preheater and then further cooled to 40 °C by the water cooler before entering the methanol separator for gas-liquid separation. The separated crude methanol is then depressurized and sent to the methanol flash evaporation unit to flash off dissolved gases. A portion of the gas exiting the methanol separator is discharged as high-pressure purge gas, which is sent to the gas turbine power generation unit through the high-pressure purge gas outlet; the remainder is returned to the syngas compressor as recycle gas. The methanol distillation unit adopts a three-tower process, including a pre-distillation tower, a pressurized tower, and an atmospheric tower. The crude methanol after flash distillation enters the pre-distillation tower, where non-condensable gas is separated at the top and sent to the steam turbine power generation unit, while the methanol at the bottom enters the pressurized tower. The methanol vapor at the top of the pressurized tower serves as the heat source for the reboiler in the atmospheric tower. The top of the atmospheric tower yields methanol product that meets industrial methanol standards, with a production capacity of 100,000 tons / year. Wastewater containing trace amounts of methanol is discharged from the bottom of the tower and sent to the wastewater treatment system. The reboiler steam inlet of the distillation tower is connected to the low-pressure steam network to receive supplemental heat from low-pressure steam during start-up or when the pressurized tower lacks sufficient steam.

[0096] The utility unit, specifically the gas turbine power generation unit, includes a first combustion chamber, a gas turbine, and a first generator. The gas inlet of the first combustion chamber is connected to the high-pressure purge gas outlet of the methanol production unit. The high-pressure purge gas is directly fed into the first combustion chamber, mixed with compressed air, and combusted to produce high-temperature flue gas. This high-temperature flue gas enters the gas turbine, expands, and performs work, driving the first generator to produce electricity. The gas turbine's exhaust outlet is connected to the flue gas inlet of the waste heat boiler. The exhaust gas temperature from the gas turbine is approximately 550°C; it enters the waste heat boiler to recover waste heat, and after waste heat recovery, the exhaust gas temperature is approximately 130°C. The steam turbine power generation unit includes a second combustion chamber, a waste heat recovery steam generator, a steam turbine, and a second generator. The second combustion chamber receives gas (approximately 8960 Nm³ / h) from the non-condensable gas inlet, the dissolved gas inlet, and the crude syngas outlet. These relatively low-energy-grade fuel gases are combusted in the second combustion chamber to produce high-temperature flue gas. High-temperature flue gas enters the waste heat recovery steam generator, which generates medium-pressure steam that enters the steam turbine to expand and do work, driving the second generator to generate electricity.

[0097] The utilities unit serves as the steam balance system. Its desuperheating and pressure-reducing device receives medium-pressure steam from the gasification unit and the methanol synthesis tower byproducts, desuperheats and reduces its pressure to 0.9 MPa low-pressure saturated steam before feeding it into the low-pressure steam network. The waste heat boiler receives exhaust gas (approximately 550 °C) from the gas turbine, generating 0.9 MPa low-pressure saturated steam, which is also fed into the low-pressure steam network to supplement the low-pressure steam demand. The low-pressure steam network uniformly supplies low-pressure steam to the first low-pressure steam inlet of the gasification unit, the second low-pressure steam inlet of the syngas regulating unit, and the rectification and reboiling steam inlet of the methanol production unit, achieving steam self-balance for the entire plant.

[0098] The following comparative and implementation cases illustrate this point:

[0099] This implementation case describes a process for producing green methanol from biomass gasification using the system described in Example 1, which is an energy-self-sufficient method.

[0100] Gasification Steps: Oxygen with a purity of 99.6 vol% is prepared by an air separation unit. Biomass straw raw material (416,069 tons / year) is fed into a circulating fluidized bed gasifier via a feeder. Oxygen and 0.9 MPa low-pressure steam are introduced as gasifying agents from the bottom of the gasifier, and a gasification reaction occurs at 800 °C under slightly positive pressure. The crude syngas produced by the reaction, carrying semi-coke particles, is discharged from the top of the gasifier and enters a cyclone separator for gas-solid separation. The separated semi-coke particles are returned to the gasifier via a return feeder. The separated syngas is then fed through a waste heat boiler to recover waste heat and produce medium-pressure saturated steam (3.1 MPa), and after dust removal by a dust collector, it is sent to the syngas conditioning unit. The slag produced by gasification is discharged through a slag discharge system, and the fly ash is pneumatically conveyed to a storage silo. Simultaneously, approximately 8960 Nm³ is extracted from the gasification unit. 3 A portion of the syngas produced per hour is sent to a steam turbine power generation unit as fuel gas for backup.

[0101] Syngas conditioning steps: The crude syngas is fed into a water scrubbing tower, where it is cooled and scrubbed with cooling water to approximately 40 °C to remove tar and dust. The scrubbed syngas is then pressurized to 2.5 MPa by a compressor and subjected to water scrubbing to remove ammonia, reducing the ammonia content to <10 ppm. The purified crude syngas is then pressurized again by a compressor and enters a sulfur-resistant shift converter. Medium-pressure steam is introduced into the sulfur-resistant shift converter, and a water-gas shift reaction is carried out under the action of a sulfur-resistant catalyst to adjust the hydrogen-to-carbon ratio to meet the requirements for methanol synthesis. The shifted gas is then desulfurized (total sulfur <0.1 ppm) by a desulfurization unit and enters a decarbonization unit. Low-pressure steam at 0.9 MPa is introduced into the reboiler of the decarbonization unit, and CO2 is removed by the MDEA method to obtain purified syngas that meets the requirements for methanol synthesis.

[0102] Methanol synthesis and distillation steps: Purified synthesis gas is compressed to 5.0 MPa by a synthesis gas compressor, mixed with recycle gas, and further compressed to 5.1 MPa in the recycle section. After being preheated to 220 °C by the outlet gas preheater, it enters a shell-and-tube isothermal methanol synthesis tower. Under the action of a copper-based catalyst, carbon monoxide hydrogenation occurs at 250 °C and 5.0 MPa(G) to produce methanol. The heat of reaction is passed through the shell-side boiler water to produce medium-pressure saturated steam (3.1 MPa). The outlet gas is cooled by exchanging heat with the inlet gas in the outlet gas preheater, and then cooled to 40 °C by a water cooler before entering a methanol separator for gas-liquid separation. The separated crude methanol is depressurized and sent to a methanol flash evaporator to flash off dissolved gas. Part of the gas exiting the methanol separator is discharged as high-pressure purge gas to the gas turbine power generation unit, and the remainder is returned to the synthesis gas compressor as recycle gas. The flash-evaporated crude methanol is sent to the methanol distillation unit, using a three-tower distillation process. The methanol first enters the pre-distillation column, where non-condensable gas is separated at the top and sent to a steam turbine power generation unit. Methanol from the bottom of the column enters the pressurization column. The methanol vapor at the top of the pressurization column serves as the heat source for the reboiler in the atmospheric distillation column. The atmospheric distillation column yields methanol product meeting industrial standards, with a production capacity of 100,000 tons per year. Wastewater from the bottom of the column is sent to a wastewater treatment system.

[0103] Energy recovery and self-balancing steps: High-pressure purge gas from the methanol synthesis unit is directly fed into the gas turbine power generation unit, where it mixes and combusts with compressed air in the first combustion chamber. The high-temperature flue gas drives the gas turbine to power the first generator. The non-condensable gas from the methanol distillation unit, the dissolved gas from the methanol flash evaporation unit, and a portion of the synthesis gas (approximately 8960 Nm³) from the gasification unit are also processed. 3 The high-temperature flue gas from combustion is fed into the steam turbine power generation unit. The high-temperature flue gas is then converted into medium-pressure steam by the waste heat recovery steam generator, which drives the steam turbine to power the second generator. The medium-pressure steam produced as a byproduct of the gasification unit's waste heat boiler and the medium-pressure steam produced as a byproduct of the methanol synthesis tower shell side of the methanol production unit are fed into a desuperheating and depressurization unit to reduce the pressure to 0.9 MPa low-pressure saturated steam. The exhaust gas from the gas turbine (approximately 550 °C) is fed into the waste heat boiler to recover waste heat and generate 0.9 MPa low-pressure saturated steam to supplement the low-pressure steam after desuperheating and depressurization. This low-pressure steam is then fed into the low-pressure steam network and supplied to: the gasification unit as steam for gasification, the decarbonization reboiling steam for the syngas regulating unit, and the methanol distillation unit as supplementary reboiling steam.

[0104] Through the above steps, the entire plant achieves complete self-balancing of electricity and steam, eliminating the need for external purchases. Calculations show that in this embodiment, the biomass straw consumption is 416,069 tons / year, and the product carbon emission value (excluding planting and harvesting) is 23.98 gCO2eq / MJ, meeting the EU's green methanol carbon emission limits.

[0105] Comparative Case: Utilizing byproduct fuel gases (purge gas, dissolved gas, and non-condensable gas) and a portion of crude syngas for steam turbine power generation to achieve power and steam balance. The main difference between the comparative case and the implementation case lies in the energy recovery method of the utility unit. In the comparative case, the system does not include a gas turbine power generation unit or a waste heat boiler. The high-pressure purge gas, dissolved gas, non-condensable gas produced by the methanol production unit, as well as a portion of the syngas from the gasification unit, are all collected and sent to the steam turbine power generation unit for combustion and power generation. That is, the high-pressure purge gas is not utilized in a cascade manner but is fed into the steam turbine system along with the dissolved gas, non-condensable gas, and a portion of the syngas as ordinary fuel gas. Simultaneously, the medium-pressure steam produced by the gasification unit, the syngas regulating unit, and the methanol production unit is all sent to the steam turbine power generation unit to generate electricity or produce steam. The low-pressure steam required by the system is provided by steam turbine extraction or exhaust steam, with any shortfall supplemented by steam generated from additional fuel gas combustion.

[0106] Based on a methanol production scale of 100,000 tons / year, for the example, the biomass straw consumption is 416,069 tons / year, and in addition to the by-product fuel gas, 8,960 Nm³ of biomass straw is also required. 3 The biomass gasification process generates syngas per hour to achieve power self-balancing; in the comparative case, the biomass straw consumption is 465,171 tons / year, and in addition to the by-product fuel gas, it also requires 19,040 Nm³ of syngas. 3 The system achieves power self-balancing through the production of crude syngas from biomass gasification per hour. In terms of biomass straw raw material consumption, the example reduces consumption by 10.56%, resulting in lower operating costs and improved economic benefits. Based on a biomass straw raw material price of 500 yuan / ton, the cost per ton of methanol will be reduced by 245 yuan. Regarding carbon emissions (excluding crop planting and harvesting), the carbon emissions of the example and the comparative case are 23.98 and 26.81 g CO2eq / MJ, respectively, meeting EU methanol carbon emission intensity requirements. The example shows an 11% reduction in carbon emissions compared to the comparative case, leading to a higher green premium. The technology adopted in the implementation case effectively avoids the uncontrollable impact of external renewable energy power, exhibits strong adaptability, and possesses competitive carbon emission and economic indicators, making it suitable for the early stages of industrialization and regions with insufficient renewable energy power development.

[0107] Table 1. Data Comparison Table between Implementation Cases and Comparative Cases

[0108]

[0109] As can be seen from the comparison in Table 1, the embodiments of the present invention optimize the configuration of the steam system for by-product fuel gas according to the energy grade difference, thereby significantly reducing the consumption of biomass raw materials and the carbon emission value of products while maintaining complete energy self-sufficiency, and improving economic benefits and green premium of products.

[0110] Specifically, this invention discloses a biomass gasification methanol production system. The utility unit utilizes the different energy grades of the high-pressure purge gas, dissolved gas, non-condensable gas, and a portion of the synthesis gas from the gasification unit during methanol synthesis and distillation processes. It generates electricity using a gas turbine powered by the high-pressure purge gas from methanol synthesis, and uses a steam turbine powered by the dissolved gas, non-condensable gas, and a portion of the synthesis gas from the gasification unit. Combined with the system's byproduct of medium-pressure steam and its demand for low-pressure steam, the system achieves self-balancing power and steam supply, eliminating the need for external power sources. From a power source perspective, it effectively avoids the uncertainty of reliable wind and solar power supply, and avoids the problem of insufficient carbon emissions from green methanol products due to purchasing grid power. In terms of system energy efficiency, compared to current biomass gasification methanol production systems, this application effectively improves energy efficiency, reduces the consumption of biomass straw as a raw material, ultimately reducing operating costs and improving economic benefits, with a 5-10% reduction in cost per ton of methanol. From a green methanol product carbon emission perspective, it meets, for example, the EU's carbon emission limits for green methanol products, further enhancing the product's green premium. From the perspective of regional conditions, this technical route is more suitable for regions with relatively abundant straw resources, insufficient renewable energy power development, and the initial stage of green methanol industrialization.

[0111] In summary, the present invention provides a system and method for producing methanol from biomass gasification. In this system, the utility unit utilizes crude syngas and dissolved and non-condensable gases generated during methanol production to generate electricity via a steam turbine generator. High-pressure purge gas generated during methanol production is used to generate electricity via a gas turbine generator. A steam conversion device de-heats and depressurizes the medium-pressure steam from the gasification unit and methanol production unit, converting it into low-pressure steam. When the low-pressure steam supply is insufficient, the waste heat from the exhaust gas generated during the gas turbine generator process is used to generate low-pressure steam, which is then transported to the gasification unit, syngas regulating unit, and methanol production unit to supply the steam required for gasification, decarbonization, and methanol distillation. This achieves a self-balancing power and steam supply for the production system, ensuring a stable power supply without external supply, meeting the carbon emission limits for green methanol products, and reducing costs.

[0112] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A system for producing methanol from biomass gasification, characterized in that, The system includes: A gasification unit that converts raw materials into crude synthesis gas for methanol synthesis includes a feed inlet, a crude synthesis gas outlet, a first medium-pressure steam outlet, and a first low-pressure steam inlet. The syngas regulating unit that converts the crude syngas into purified syngas includes a crude syngas inlet, a first medium-pressure steam inlet, a purified syngas outlet, a second low-pressure steam inlet, and a first low-pressure steam outlet, wherein the crude syngas inlet and the crude syngas outlet are connected. The methanol production unit includes a purified syngas inlet, a second medium-pressure steam outlet, a third low-pressure steam inlet, a high-pressure purge gas outlet, a dissolved gas outlet, a non-condensable gas outlet, and a methanol product outlet. The purified syngas inlet is connected to the crude syngas outlet. The utility unit includes a gas turbine power generation unit, a steam turbine power generation unit, and a steam conversion unit. The gas inlet of the gas turbine power generation unit is connected to the high-pressure venting gas outlet. The gas inlet of the steam turbine power generation unit is connected to the crude syngas outlet, the dissolved gas outlet, and the non-condensable gas outlet, respectively. The steam inlet of the steam conversion unit is connected to the first medium-pressure steam outlet and the second medium-pressure steam outlet, respectively. The steam conversion unit converts the introduced medium-pressure steam into low-pressure steam, and simultaneously produces the low-pressure steam based on the exhaust gas generated by the gas turbine power generation unit, and delivers the low-pressure steam to the gasification unit, the syngas regulating unit, and the methanol production unit.

2. The system for preparing methanol from biomass gasification according to claim 1, characterized in that: The gasification unit includes an air separation unit and a biomass gasification unit. The feed inlet of the gasification unit includes an air inlet of the air separation unit, a biomass inlet of the biomass gasification unit, and an oxygen inlet of the biomass gasification unit. The oxygen inlet is connected to the oxygen outlet of the air separation unit. The air separation unit is used to separate air to obtain oxygen and transport the oxygen to the oxygen inlet through the oxygen outlet. The biomass gasification unit is used to gasify biomass to obtain crude syngas and simultaneously produce medium-pressure steam as a byproduct. The first low-pressure steam inlet is connected to the low-pressure steam outlet of the steam conversion unit.

3. The system for preparing methanol from biomass gasification according to claim 1, characterized in that: The syngas conditioning unit includes a pretreatment device, a conversion device, and a decarbonization device; the pretreatment device is used to cool, wash, compress, and purify the crude syngas to obtain pretreated syngas. The conversion device is used to perform water-gas conversion on the pretreated syngas to adjust the hydrogen-carbon ratio and obtain water-gas-converted syngas. The conversion device includes a first medium-pressure steam inlet and a first low-pressure steam outlet. The decarbonization device is used to remove carbon dioxide from the water-gas-converted syngas to obtain the purified syngas. The decarbonization device includes a second low-pressure steam inlet.

4. The system for preparing methanol from biomass gasification according to claim 1, characterized in that: The methanol production unit includes a methanol synthesizer and a methanol separator. The purified synthesis gas inlet of the methanol synthesizer serves as the purified synthesis gas inlet of the methanol production unit and is connected to the purified synthesis gas outlet of the synthesis gas regulating unit. The methanol synthesizer converts the purified synthesis gas into methanol. The methanol separator separates the reaction product from the methanol synthesizer to obtain crude methanol, high-pressure purge gas, and recycle gas. The reaction product inlet of the methanol separator is connected to the reaction product outlet. The methanol separator includes a crude methanol outlet for discharging the crude methanol, a high-pressure purge gas outlet for discharging the high-pressure purge gas, and a recycle gas outlet for discharging the recycle gas.

5. The system for preparing methanol from biomass gasification according to claim 4, characterized in that: The methanol production unit further includes a methanol flash tank and a methanol distillation unit; the methanol flash tank has an inlet for methanol to be flashed connected to the crude methanol outlet, and the methanol flash tank generates the dissolved gas during the flash evaporation of the methanol to be flashed; the methanol distillation unit has an inlet for methanol to be distilled connected to the methanol outlet after flash evaporation of the methanol flash tank, and the distillation reboiler steam inlet of the methanol distillation unit serves as the third low-pressure steam inlet and is connected to the low-pressure steam outlet of the steam conversion unit, and the methanol distillation unit generates the non-condensable gas during the distillation of the methanol after flash evaporation.

6. The system for preparing methanol from biomass gasification according to claim 1, characterized in that: The gas turbine power generation device includes a first combustion chamber, a gas turbine, and a first generator. The gas inlet of the first combustion chamber serves as the gas inlet of the gas turbine power generation device. The first combustion chamber is used to burn the high-pressure purge gas to generate first high-temperature flue gas. The flue gas inlet of the gas turbine is connected to the flue gas outlet of the first combustion chamber. The gas turbine uses the expansion of the first high-temperature flue gas to drive the first generator to generate electricity. The steam turbine power generation device includes a second combustion chamber, a waste heat recovery steam generator, a steam turbine, and a second generator. The gas inlet of the second combustion chamber serves as the gas inlet of the steam turbine power generation device. The second combustion chamber is used to burn the dissolved gas, the non-condensable gas, and a portion of the crude syngas to generate second high-temperature flue gas. The flue gas inlet of the waste heat recovery steam generator is connected to the flue gas outlet of the second combustion chamber. The waste heat recovery steam generator uses the second high-temperature flue gas to generate steam. The steam outlet of the waste heat recovery steam generator is connected to the steam inlet of the steam turbine. The steam turbine uses the expansion of the steam to drive the second generator to generate electricity.

7. The system for preparing methanol from biomass gasification according to claim 1, characterized in that: The steam conversion device includes a desuperheating and pressure reducing device and a waste heat boiler. The first medium-pressure steam outlet and the second medium-pressure steam outlet are respectively connected to the medium-pressure steam inlet of the desuperheating and pressure reducing device. The low-pressure steam outlet of the desuperheating and pressure reducing device is connected to the low-pressure steam pipeline network. The exhaust gas outlet of the gas turbine power generation device is connected to the flue gas inlet of the waste heat boiler, and the low-pressure steam outlet of the waste heat boiler is connected to the low-pressure steam pipeline network.

8. A method for preparing methanol by biomass gasification, characterized in that, The method includes: The raw material enters the gasification unit through the feed inlet. The gasification unit converts the raw material into crude syngas and produces medium-pressure steam as a byproduct. Part of the crude syngas is sent from the crude syngas outlet of the gasification unit to the crude syngas inlet of the syngas regulating unit. The remaining crude syngas is sent from the crude syngas outlet to the gas inlet of the steam turbine power generation unit of the utility unit. The medium-pressure steam generated during the conversion of the crude syngas is sent from the first medium-pressure steam outlet of the gasification unit to the steam inlet of the steam conversion unit of the utility unit. The syngas regulating unit converts the crude syngas into purified syngas that meets the requirements for methanol synthesis and then delivers the purified syngas from the purified syngas outlet of the syngas regulating unit to the purified syngas inlet of the methanol production unit. The methanol production unit converts the purified synthesis gas into methanol product and discharges the methanol product through the methanol product outlet of the methanol production unit. The dissolved gas generated during the methanol production process is transported through the dissolved gas outlet of the methanol production unit to the gas inlet of the steam turbine power generation unit. The non-condensable gas generated during the methanol production process is transported through the non-condensable gas outlet of the methanol production unit to the gas inlet of the steam turbine power generation unit. The high-pressure purge gas generated during the methanol production process is transported through the high-pressure purge gas outlet of the methanol production unit to the gas inlet of the gas turbine power generation unit of the utility unit. The medium-pressure steam generated during the methanol production process is transported to the steam inlet of the steam conversion unit. The utility unit supplies the crude syngas and dissolved gas and non-condensable gas generated during the methanol production process to a steam turbine power generation unit for power generation. The high-pressure purge gas generated during the methanol production process is supplied to a gas turbine power generation unit for power generation. The medium-pressure steam generated from the gasification unit and the methanol production unit is de-cooled and depressurized to convert it into low-pressure steam. The low-pressure steam is also produced using the tail gas generated during the power generation process of the gas turbine power generation unit and supplied to the gasification unit, the syngas regulating unit and the methanol production unit.

9. The method for preparing methanol by biomass gasification according to claim 8, characterized in that: The steam conversion device includes a desuperheating and pressure reducing device and a waste heat boiler, and the method includes: The medium-pressure steam from the gasification unit and the methanol production unit byproducts is depressurized and reduced to low-pressure steam using the depressurization and pressure reduction device; the waste heat boiler is used to recover waste heat from the exhaust gas from the gas turbine power generation unit to generate the low-pressure steam.

10. The method for preparing methanol by biomass gasification according to claim 9, characterized in that: The medium-pressure steam has a pressure range of 1.6-4.0 MPa and a temperature range of 200-250 ℃; the low-pressure steam has a pressure range of 0.3-1.6 MPa and a temperature range of 130-200 ℃; the high-pressure vent gas has a pressure of 5.0-10.0 MPa(G); the exhaust gas temperature of the gas turbine power generation unit has a range of 500-600 ℃, and the exhaust gas temperature of the gas turbine power generation unit after waste heat recovery by the waste heat boiler has a range of 120-150 ℃.

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