Methanol production system

Abstract

The present application provides a methanol preparation system, which comprises a hydrogen production device, a synthesis gas treatment device, a carbon dioxide treatment device and a synthesis device. The synthesis gas treatment device comprises a gasification section for generating a crude synthesis gas for reaction; a first energy utilization section arranged downstream of the gasification section for recycling heat generated by the gasification section. The carbon dioxide treatment device comprises a carbon capture section arranged downstream of the first energy utilization section for receiving the crude synthesis gas and capturing carbon dioxide to obtain carbon dioxide and a second mixed gas respectively; a carbon storage section arranged downstream of the carbon capture section for receiving and storing the carbon dioxide of the carbon capture section; a carbon dioxide expansion energy utilization section arranged downstream of the carbon storage section for converting energy generated by expansion of the carbon dioxide into electric energy; and the synthesis device for synthesizing methanol is arranged downstream of the hydrogen production device, the gasification section, the carbon capture section and the carbon storage section for receiving the gas as reaction gas.

Description

Technical Field

[0001] This invention relates to the field of methanol preparation technology, and in particular to a methanol preparation system. Background Technology

[0002] Methanol, as a fuel, has the advantages of high combustion efficiency, clean emissions, and renewability. Furthermore, methanol is liquid at normal temperature and pressure, making its storage, transportation, and use safer and more convenient, thus becoming a recognized ideal new type of clean and renewable fuel in the industry.

[0003] Compared to traditional gasoline, methanol directly reduces carbon dioxide emissions and effectively lowers pollutants such as nitrogen oxides and particulate matter. Furthermore, methanol boasts advantages such as high octane rating, strong anti-knock properties, abundant resources, uniform hydrocarbon and oxygen distribution, smoother engine operation, and improved energy conversion efficiency, making it a significant asset in the automotive, marine, and aviation industries. Compared to hydrogen fuel, methanol offers advantages such as ease of storage, high cost-effectiveness, convenient storage and use, high safety, and immediate availability, facilitating large-scale adoption.

[0004] Currently, methanol is typically produced by reacting hydrogen generated from water electrolysis with syngas. However, this synthesis reaction involves significant energy waste, resulting in high energy consumption for the entire methanol production process. Summary of the Invention

[0005] The purpose of this invention is to provide a low-cost methanol preparation system to solve the problems in the prior art.

[0006] To address the aforementioned technical problems, this invention provides a methanol production system, comprising a hydrogen production device, a syngas treatment device, a carbon dioxide treatment device, and a synthesis device, wherein the hydrogen production device is used to produce hydrogen gas.

[0007] The syngas processing equipment includes: The gasification section is used to supply the crude syngas produced by the reaction, the crude syngas including carbon monoxide, carbon dioxide and hydrogen; The first energy utilization section is located downstream of the gasification section and is used to recover and utilize the heat generated by the gasification section. The carbon dioxide processing equipment includes: A carbon capture section, located downstream of the first energy utilization section, is used to receive the crude syngas and capture carbon dioxide to obtain carbon dioxide and a second mixed gas, respectively. A carbon storage section, located downstream of the carbon capture section, is used to receive and store carbon dioxide from the carbon capture section. A carbon dioxide expansion energy utilization section is located downstream of the carbon storage section to convert the energy generated during carbon dioxide expansion into electrical energy. The synthesis equipment is used to synthesize methanol and is simultaneously located downstream of the hydrogen production equipment, the gasification section, the carbon capture section, and the carbon storage section, for receiving gases as reactants.

[0008] In one embodiment, the first energy utilization section includes a waste heat recovery section located downstream of the gasification section. The waste heat recovery section is also located upstream of the carbon capture section and the synthesis equipment. The waste heat recovery section includes a first channel and a second channel that can exchange heat with each other. The gasification section is connected to the first channel, and the inlet of the second channel is used to connect an external heating medium to absorb the heat of the crude synthesis gas and convert it into steam.

[0009] In one embodiment, a steam energy utilization section is provided downstream of the waste heat recovery section. The steam energy utilization section is connected to the outlet of the second channel and is used to receive steam and convert it into electrical energy.

[0010] In one embodiment, the hydrogen production equipment includes: The hydrogen production section is used to produce hydrogen gas. A hydrogen storage section, located downstream of the hydrogen production section, is used to compress and store hydrogen. A hydrogen expansion energy utilization section is located downstream of the hydrogen storage section to convert the energy generated during hydrogen expansion into electrical energy.

[0011] In one embodiment, the carbon storage section includes a liquefier disposed downstream of the carbon capture section, a storage container disposed downstream of the liquefier, and a gasifier disposed downstream of the storage container. The liquefier is used to receive carbon dioxide from the carbon capture section and liquefy it to obtain liquid carbon dioxide. The storage container is used to store the liquid carbon dioxide. The gasifier is used to gasify the carbon dioxide to obtain carbon dioxide gas.

[0012] In one embodiment, a heat storage tank is provided downstream of the liquefier, and the outlet of the heat storage tank is connected to the vaporizer.

[0013] In one embodiment, a cold storage tank is provided downstream of the vaporizer, and the outlet of the cold storage tank is connected to the liquefier.

[0014] In one embodiment, a hydrogen recovery section is provided downstream of the synthesis equipment. The hydrogen recovery section is used to receive unreacted hydrogen in the synthesis equipment and transport the hydrogen to the upstream of the synthesis equipment.

[0015] In one embodiment, a methane enrichment section and a methane conversion and utilization section are sequentially provided downstream of the hydrogen recovery section. The hydrogen recovery section is used to provide the residual gas after dehydrogenation to the methane enrichment section, the methane enrichment section is used to increase the concentration of methane, and the methane conversion and utilization section is used to receive the enriched methane and convert and utilize it.

[0016] In one embodiment, the syngas equipment includes a hydrogen-to-carbon ratio adjustment section located downstream of the first energy utilization section to receive the crude syngas and perform a water-gas shift reaction to generate hydrogen, thereby obtaining a first mixed gas. The syngas equipment has a first synthesis mode, a second synthesis mode, and a third synthesis mode. In the first synthesis mode, the synthesis equipment receives hydrogen from the hydrogen production equipment and crude synthesis gas from the gasification section as reaction gases; In the second synthesis mode, the hydrogen-to-carbon ratio adjustment section and the carbon storage section are activated. The synthesis equipment receives hydrogen from the hydrogen production equipment, crude synthesis gas from the gasification section, and the first mixed gas from the hydrogen-to-carbon ratio adjustment section as reaction gases. At the same time, the carbon storage section receives carbon dioxide from the carbon capture section for storage. In the third synthesis mode, the hydrogen-to-carbon ratio adjustment section is shut down, and the synthesis equipment receives hydrogen from the hydrogen production equipment, crude synthesis gas from the gasification section, and carbon dioxide gasified in the carbon storage section as reaction gases.

[0017] As can be seen from the above technical solution, the advantages and positive effects of the present invention are as follows: The methanol preparation system of this invention, by adding a first energy utilization section during the preparation process, recovers and utilizes the heat generated in the gasification section, and converts the energy of carbon dioxide expansion into electrical energy through a carbon dioxide expansion energy utilization section, makes full use of the energy in the entire methanol synthesis process, saves energy, reduces costs, and is green and environmentally friendly. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the methanol preparation system in this invention.

[0019] Figure 2 This is a schematic diagram of the carbon dioxide treatment equipment in this invention.

[0020] The annotations in the attached figures are explained as follows: 111. Hydrogen production section; 112. Hydrogen purification section; 113. Hydrogen compression section; 114. Hydrogen storage tank; 115. Hydrogen expansion energy utilization section; 121. Renewable power generation equipment; 122. Power supply cables; 131. Gasification section; 132. Hydrogen-to-carbon ratio adjustment section; 133. Waste heat recovery section; 134. Steam energy utilization section; 135. Syngas purification section; 136. Syngas compression section; 141. Carbon capture section; 142. Liquefaction unit; 143. Storage container; 144. Gasifier; 145. Thermal storage tank; 146. Cold storage tank; 147. Carbon dioxide expansion energy utilization section; 148. Energy release tank; 151. Synthesis section; 152. Methanol distillation section; 153. Methanol storage tank; 161. Hydrogen recovery section; 171. Methane enrichment section; 172. Methane conversion and utilization section. Detailed Implementation

[0021] Although the invention can be readily embodied in various forms, only some specific embodiments are shown in the accompanying drawings and will be described in detail in this specification. It is understood that this specification should be regarded as an exemplary illustration of the principles of the invention and is not intended to limit the invention to what is described herein.

[0022] Therefore, a feature pointed out in this specification is used to illustrate one feature of one embodiment of the invention, and does not imply that every embodiment of the invention must have the described feature. Furthermore, it should be noted that this specification describes many features. While certain features may be combined to illustrate possible system designs, these features may also be used in other combinations not explicitly stated. Therefore, unless otherwise stated, the described combinations are not intended to be limiting.

[0023] In the embodiments shown in the accompanying drawings, the directional indications (such as up, down, left, right, front, and back) used to explain the structure and movement of the various elements of the invention are relative rather than absolute. These descriptions are appropriate when these elements are in the positions shown in the drawings. If the descriptions of the positions of these elements change, these directional indications also change accordingly.

[0024] This invention provides a methanol preparation system that makes full use of the various forms of energy generated during the synthesis process, saving energy, reducing costs, and being environmentally friendly.

[0025] Figure 1 A schematic diagram of the methanol preparation system is shown. (See attached diagram.) Figure 1 The methanol production system includes hydrogen production equipment, syngas treatment equipment, carbon dioxide treatment equipment, and synthesis equipment.

[0026] The target main reaction for preparing methanol is as follows: CO + 2H₂ → CH₃OH CO2 + 3H2 → CH3OH + H2O The main side effects include the following: CO + 3H₂ → CH₄ + H₂O CO2 + 4H2 → CH4 + 2H2O nCO + H2 → 2nCH2 + nH2O 2CO + 4H2 → CH3OCH3 + H2O To ensure the conversion rate, selectivity, and yield of methanol synthesis using feed gas primarily composed of CO, CO2, and H2, and to minimize side reactions, it is generally necessary to maintain a high hydrogen-to-carbon ratio (V0 / V2) in the feed gas used for methanol synthesis. H2 -V CO2 ): (V CO +V CO2 The hydrogen-to-carbon ratio is 2.0–3.0. When the hydrogen-to-carbon ratio is less than 2.0, hydrogen is deficient in the feed gas. When the hydrogen-to-carbon ratio is greater than 3.0, hydrogen is abundant in the feed gas.

[0027] The inventors of this application combined the above-mentioned main reaction and side reaction, and adjusted the hydrogen-carbon ratio in the gas used to synthesize methanol by increasing the hydrogen content and decreasing the carbon dioxide content, thereby achieving the full synthesis of methanol.

[0028] Therefore, the methanol production system of the present invention provides the power required by the hydrogen production equipment with the power supply equipment. When the power supply equipment output is insufficient, the hydrogen-to-carbon ratio in the crude synthesis gas is adjusted and the carbon dioxide is further separated and stored. When the power supply equipment output is sufficient and the hydrogen production is high, the stored carbon dioxide is replenished to increase the methanol production.

[0029] The methanol preparation system is described in detail below.

[0030] The hydrogen production equipment is used to produce hydrogen gas required for the reaction. Specifically, the hydrogen production equipment includes a hydrogen production section 111 and a hydrogen storage section located downstream of the hydrogen production section 111. The hydrogen production section 111 is used to produce hydrogen gas.

[0031] Hydrogen production section 111 can produce hydrogen through water electrolysis, hydrocarbon or alcohol reforming, or a combination of both. The specific method depends on actual needs.

[0032] The hydrogen storage section is located downstream of the hydrogen production section 111 and is used to compress and store hydrogen. The hydrogen storage section is connected to the synthesis equipment to supply hydrogen.

[0033] Specifically, the hydrogen storage section includes a hydrogen compression section 113 and a hydrogen storage tank 114. The hydrogen compression section 113 is used to compress purified hydrogen, and the hydrogen storage tank 114 is used to store the compressed hydrogen.

[0034] The hydrogen storage tank 114 can be a combination of one or more of the following: cryogenic liquefaction hydrogen storage devices, large-scale high-pressure gaseous hydrogen storage devices, solid material hydrogen storage devices, and organic liquid hydrogen storage devices. Further, the solid material hydrogen storage device includes one or more synergistic solid material hydrogen storage devices selected from physical adsorption material hydrogen storage devices, metal-based hydrogen storage alloys, and coordination hydride hydrogen storage devices.

[0035] The hydrogen expansion energy utilization section 115 is located downstream of the hydrogen storage section to convert the energy generated by hydrogen expansion into electrical energy. The hydrogen expansion energy utilization section 115 is connected to the power supply equipment.

[0036] A hydrogen purification section 112 is also provided between the hydrogen production section 111 and the hydrogen storage section. The hydrogen purification section 112 is used to purify the hydrogen produced by the hydrogen production section 111.

[0037] The methanol production system includes power supply equipment for providing electricity. For example, electricity is supplied to the hydrogen production section 111 to produce hydrogen, and to the carbon storage section to liquefy carbon dioxide. The power supply equipment includes a renewable power generation device 121, the output of which is connected to the hydrogen production equipment and the hydrogen storage section. The renewable power generation device 121 transmits electricity to the required structures via a power cable 122.

[0038] Among them, the renewable power generation equipment 121 includes at least one of hydropower generation equipment, biomass power generation equipment, wind power generation equipment, photovoltaic power generation equipment, geothermal power generation equipment, and waste pressure / waste heat recovery power generation equipment.

[0039] Hydropower generation equipment, biomass power generation equipment, wind power generation equipment, photovoltaic power generation equipment, geothermal power generation equipment, and waste pressure / waste heat recovery power generation equipment are installed individually or in parallel.

[0040] The power supply equipment can be solely hydropower, biomass power, wind power, solar power, geothermal power, or waste pressure / waste heat recovery power. Alternatively, it can be a combination of any two of the following: wind power and solar power; hydropower and wind power; hydropower and solar power; wind power and biomass power; solar power and geothermal power; or any three of the following: hydropower, wind power, and solar power; or all four. The specific choice depends on the actual needs.

[0041] Hydropower refers to generating electricity using water, that is, converting the potential energy of water into electrical energy.

[0042] Biomass power generation refers to thermal power generation technology that uses biomass and its processed solid, liquid, or gaseous forms as fuel.

[0043] Wind power refers to generating electricity using wind power, that is, converting the kinetic energy of wind into electrical energy.

[0044] Photovoltaic power generation refers to solar photovoltaic power generation or solar thermal power generation. Photovoltaic power generation uses the photoelectric effect to directly convert sunlight into electricity; solar thermal power generation refers to converting solar energy into heat energy and then converting heat energy into electricity.

[0045] Geothermal power generation refers to the conversion of low-temperature thermal energy into electrical energy.

[0046] Waste pressure / waste heat recovery power generation equipment refers to equipment that converts excess pressure energy / heat energy of fluids into electrical energy.

[0047] When the aforementioned power supply equipment is used in combination, multiple power generation devices are connected in parallel. Using renewable electricity makes hydrogen production more environmentally friendly, and consequently, the entire methanol production system is more environmentally friendly.

[0048] Generally speaking, renewable electricity has unstable characteristics such as intermittency and fluctuation. For example, hydropower has a wet season and a dry season, and the output of wind power and solar power not only varies every hour, but also varies greatly every month, showing seasonal changes. Changes in renewable electricity output will lead to changes in the amount of hydrogen produced by water electrolysis.

[0049] The power supply equipment may also include non-renewable power generation equipment 121.

[0050] Syngas processing equipment is used to process syngas. Specifically, the syngas processing equipment includes a gasification section 131 and a hydrogen-to-carbon ratio adjustment section 132.

[0051] The gasification section 131 is used to supply crude syngas for the reaction.

[0052] Specifically, crude syngas is obtained through biomass gasification. Biomass includes forestry and agricultural waste and byproducts, biogas, wastewater, municipal solid waste, and black liquor from the pulp and paper industry.

[0053] The crude syngas produced after biomass gasification, by volume percentage, includes 35%~39% CO, 10%~30% CO2, 39%~45% H2, 100~1000ppm H2S, 200~500ppm COS (carbonyl sulfide), and less than 1% CH4.

[0054] In other embodiments, crude syngas can also be produced by gasification of solid fuels such as coal or coke, or by light hydrocarbons such as natural gas and naphtha, or by partial oxidation of heavy oil.

[0055] Gasification section 131 is a co-current gasification structure consisting of two or more of the following: co-current or counter-current fixed bed, moving bed, gas flow bed, fluidized bed, circulating fluidized bed, and jet-driven bed.

[0056] For example, one or more components selected from pure oxygen, water vapor, and CO2 with a purity of 99-100% are preheated and mixed, and then used as a conversion agent and continuous phase dispersion medium. Through a combination of two or more phases in co-current or counter-current fixed beds, moving beds, air-flow beds, fluidized beds, circulating fluidized beds, or spouted beds, efficient thermal conversion of carbon-containing materials is achieved, transforming the materials into a composition primarily of CO, CO2, and H2, with small amounts of CH4 and C. n H m (n≤3) Low-carbon hydrocarbons, with the volume fraction of the effective component (CO+CO2+H2) between 70% and 99% vol%, C n H m (n≤10) The content of hydrocarbons is between 0 and 10 vol.

[0057] The hydrogen-carbon ratio adjustment section 132 is located downstream of the gasification section 131 to receive crude syngas and generate hydrogen through a water-gas shift reaction, thereby obtaining the first mixed gas.

[0058] The water-vapor shift reaction is: CO + H2O → CO2 + H2.

[0059] That is, by adjusting the hydrogen-carbon ratio in section 132, carbon monoxide reacts with water to generate hydrogen, thereby increasing the hydrogen content and adjusting the hydrogen-carbon ratio to meet the requirements for full methanol synthesis.

[0060] The main components of the first mixed gas and the crude syngas are carbon monoxide, carbon dioxide and hydrogen, the difference being the hydrogen-to-carbon ratio.

[0061] In this embodiment, the hydrogen-to-carbon ratio adjustment section 132 includes at least two of the following: a low water-to-carbon ratio conversion tower and a catalytic / non-catalytic oxidation tower, a thermal cracking furnace, a catalytic cracking furnace, a steam cracking furnace, a steam wet reforming furnace, a self-heating oxygen-steam reforming furnace, a CO2 dry reforming furnace, and a self-heating oxygen-steam-CO2 mixed reforming furnace. This allows for the simultaneous conversion of mixed hydrocarbons in crude syngas into effective syngas components and the regulation of the hydrogen-to-carbon ratio in the syngas.

[0062] The first energy utilization section is located downstream of the gasification section 131 and is used to recover and utilize the heat generated in the gasification section. Specifically, the first energy utilization section includes a waste heat recovery section 133 located downstream of the gasification section 131, and the waste heat recovery section 133 is also located upstream of the carbon capture section 141 and the synthesis equipment. Specifically, the waste heat recovery section 133 includes a first channel and a second channel capable of exchanging heat with each other. The gasification section 131 is connected to the first channel, and the inlet of the second channel is used to connect an external heating medium to absorb the heat of the crude synthesis gas and convert it into steam. The heating medium is used to absorb the heat of the crude synthesis gas and then provide heat; for example, boiler water.

[0063] Among them, the steam produced by the waste heat recovery section 133 is saturated steam or superheated steam with a pressure of 0-15 MPaG and a temperature of 100-500℃.

[0064] The waste heat recovery section 133 utilizes a radiant and convective heat recovery structure consisting of a two-stage superheater, evaporator, reheater, preheater, and heater connected in sequence to recover all the sensible heat in the 80–1500°C range of the high-temperature crude syngas output from the carbonaceous material gasification section 131. In this embodiment, the waste heat recovery section 133 includes at least two types of waste heat boilers: shell-and-tube, coaxial, serpentine, finned, flat, spiral, hot plate, fire-tube, water-tube, and fluidized bed types, to achieve full-process recovery of the sensible heat of the high-temperature crude syngas.

[0065] Downstream of the waste heat recovery section 133 is a steam energy utilization section 134. The steam energy utilization section 134 is connected to the outlet of the second channel to receive steam and convert it into electrical energy. The steam energy utilization section 134 is connected to power supply equipment. Specifically, the steam energy utilization section 134 is connected to a power supply cable 122, thereby providing the generated electrical energy to the sections that require electrical energy through the power supply cable 122.

[0066] The steam energy utilization section 134 makes full use of the superheated steam produced by the waste heat recovery section 133, and prioritizes its generation through a fully condensing, partially condensing, or partially extracting steam generator set. Preferably, the exhaust steam of different temperatures and pressure levels remaining in the generator set is then used as the reaction feedstock required for the hydrogen-to-carbon ratio adjustment section 132, the syngas purification section 135, and the methane enrichment and conversion utilization section 172.

[0067] The syngas treatment equipment also includes a syngas purification section 135 located downstream of the gasification section 131. The syngas purification section 135 is located upstream of the synthesis equipment and between the carbon capture section 141 and the carbon storage section. The syngas purification section 135 is used to remove hydrogen sulfide and carbonyl sulfide.

[0068] This means that the crude syngas undergoes desulfurization and decarbonization treatment before entering the synthesis equipment.

[0069] Syngas purification section 135 is used to purify syngas to reduce the impact on the catalyst during the methanol synthesis reaction and ensure the catalyst's activity.

[0070] In this embodiment, the syngas purification section 135 includes a dust removal device, a decarbonization purification device, a desulfurization purification device, and a denitrification purification device arranged sequentially. The decarbonization purification device is used to remove carbonyl sulfide. The desulfurization purification device is used to remove hydrogen sulfide. The denitrification purification device is used to remove HCN, HCNO, and NH3, etc.

[0071] The syngas treatment equipment includes a syngas compression section 136 located between the gasification section 131 and the synthesis equipment. Specifically, the syngas compression section 136 is located downstream of the syngas purification section 135, meaning the syngas treatment equipment includes the gasification section 131, the syngas purification section 135, and the syngas compression section 136 arranged sequentially. A waste heat recovery section 133 is located between the gasification section 131 and the syngas purification section 135.

[0072] The syngas compression section 136 is located downstream of the carbon storage section.

[0073] Carbon dioxide processing equipment is used to capture and process carbon dioxide from syngas. (See also...) Figure 2 The carbon dioxide treatment equipment includes a carbon capture section 141 and a carbon storage section.

[0074] The carbon capture section 141 is located downstream of both the gasification section 131 and the hydrogen-carbon ratio adjustment section 132. It receives crude syngas or the first mixed gas and captures carbon dioxide to obtain carbon dioxide and the second mixed gas, respectively. That is, desulfurization and decarbonization treatment is performed before carbon capture treatment of the crude syngas or the first mixed gas.

[0075] The carbon capture section 141 in this application is used to capture carbon dioxide.

[0076] In this embodiment, the carbon capture section 141 can employ at least one of the following: low-temperature methanol washing, amine solution absorption, pressure swing adsorption, or low-temperature distillation separation.

[0077] The carbon storage section is located downstream of the carbon capture section 141 and is used to receive and store the carbon dioxide from the carbon capture section 141.

[0078] Specifically, the carbon storage section includes a liquefier 142 located downstream of the carbon capture section 141, a storage container 143 located downstream of the liquefier 142, and a gasifier 144 located downstream of the storage container 143. The liquefier 142 is used to receive and liquefy carbon dioxide from the purifier, the storage container 143 is used to store the liquefied carbon dioxide, and the gasifier 144 is used to gasify the carbon dioxide to obtain carbon dioxide gas.

[0079] After liquefaction by liquefaction unit 142, a normal temperature high-pressure liquid or a low temperature low-pressure liquid is obtained, which is then stored in storage container 143.

[0080] In this embodiment, the liquefier 142 adopts a pressurized cooling distillation method, and its refrigerant is a single refrigerant or a mixture of refrigerants.

[0081] The storage temperature of liquid carbon dioxide is -18℃. Therefore, the storage container 143 can be made of ordinary carbon steel with ordinary thermal insulation measures, which is low cost.

[0082] That is, the carbon dioxide captured in the carbon capture section 141 is liquefied in the liquefaction unit 142 and then transported to the storage container 143 for storage. Since the storage container 143 has a lower cost, the overall cost of the methanol production system is also lower.

[0083] Preferably, a heat storage tank 145 is provided downstream of the liquefier 142, and the outlet of the heat storage tank 145 is connected to the vaporizer 144. Specifically, when gaseous carbon dioxide is liquefied, it releases heat and generates heat, which is recovered into the heat storage tank 145 and used by the vaporizer 144 to vaporize carbon dioxide, making full use of energy and saving energy.

[0084] A cold storage tank 146 is provided downstream of the vaporizer 144, and the outlet of the cold storage tank 146 is connected to the liquefier 142. Specifically, when liquid carbon dioxide is vaporized, it absorbs heat and generates cold energy, which is recovered into the cold storage tank 146 for use by the liquefier 142 when liquefying carbon dioxide, making full use of energy and saving energy.

[0085] A carbon dioxide expansion energy utilization section 147 is located downstream of the carbon storage section to convert the energy generated during carbon dioxide expansion into electrical energy. The carbon dioxide expansion energy utilization section 147 is connected to a power supply. Specifically, the carbon dioxide expansion energy utilization section 147 is located between the gasifier 144 and the syngas compression section 136.

[0086] Furthermore, an energy release storage tank 148 is also provided downstream of the carbon dioxide expansion energy utilization section 147.

[0087] The synthesis unit is used to produce methanol through a reaction. It is located downstream of the hydrogen production unit, gasification section 131, carbon capture section 141, and carbon storage section. The main reactions in the synthesis unit are hydrogen and carbon monoxide, followed by the reaction of hydrogen with carbon dioxide to produce methanol.

[0088] Specifically, the synthesis equipment includes a synthesis section 151, a methanol distillation section 152, and a methanol storage tank 153 arranged sequentially. The synthesis section 151 is used to synthesize crude methanol through reaction, the methanol distillation section 152 is used to receive crude methanol and perform distillation, and the methanol storage tank 153 is used to receive and store the distilled methanol.

[0089] Based on the power output capacity of the power supply equipment, the synthesis equipment has three synthesis modes: a first synthesis mode, a second synthesis mode, and a third synthesis mode. In the first synthesis mode, the synthesis equipment receives hydrogen from the hydrogen production unit and crude synthesis gas from the gasification section 131 as reactants. In the second synthesis mode, the hydrogen-to-carbon ratio adjustment section 132 and the carbon storage section are activated. The synthesis equipment receives hydrogen from the hydrogen production unit, crude synthesis gas from the gasification section 131, and the first mixed gas from the hydrogen-to-carbon ratio adjustment section 132 as reactants. Simultaneously, the carbon storage section receives carbon dioxide from the carbon capture section 141 for storage. In the third synthesis mode, the hydrogen-to-carbon ratio adjustment section 132 is deactivated. The synthesis equipment receives hydrogen from the hydrogen production unit, crude synthesis gas from the gasification section 131, and carbon dioxide gasified in the carbon storage section as reactants.

[0090] That is, the first synthesis mode refers to the direct synthesis of methanol, the second synthesis mode refers to the decarbonization synthesis of methanol, and the third synthesis mode refers to the carbon supplementation synthesis of methanol.

[0091] Specifically, when the output value of the power supply equipment falls within a preset range, the synthesis equipment reacts in the first synthesis mode. When the output value of the power supply equipment is less than the preset range, the synthesis equipment reacts in the second synthesis mode. When the output value of the power supply equipment is greater than the preset range, the synthesis equipment reacts in the third synthesis mode. The preset range refers to the range of output values ​​of the power supply equipment within a relatively stable period based on the local meteorological conditions of the methanol preparation system. This preset range is typically less than the maximum output value and greater than the minimum output value.

[0092] When the amount of hydrogen produced by the hydrogen production equipment is sufficient, the hydrogen from the hydrogen production equipment and the crude synthesis gas from the gasification section 131 are directly fed into the synthesis equipment, where the hydrogen and crude synthesis gas react to produce methanol. This is the direct synthesis of methanol, i.e., the first synthesis mode.

[0093] Furthermore, in the first synthesis mode, the hydrogen-to-carbon ratio adjustment section 132 can be activated to adjust the hydrogen-to-carbon ratio in the crude synthesis gas. The synthesis equipment receives the first mixed gas and hydrogen as reaction gases. That is, the crude synthesis gas output from the gasification section 131 is output as the first mixed gas after passing through the hydrogen-to-carbon ratio adjustment section 132. The first mixed gas directly enters the synthesis equipment to react with hydrogen in the methanol synthesis reaction.

[0094] By increasing the water-gas conversion reaction to adjust the hydrogen-carbon ratio, the hydrogen-carbon ratio of the gases used in the synthesis reaction can be ensured, thus making the methanol synthesis reaction more complete.

[0095] When the amount of hydrogen produced by the hydrogen production equipment is small, the hydrogen directly enters the synthesis equipment. The crude synthesis gas from the gasification section 131 first undergoes a water-gas conversion, and then passes through the carbon capture section 141 to capture at least part of the carbon dioxide before entering the synthesis equipment. The hydrogen and the mixed gas react in the synthesis equipment to produce methanol. This is the decarbonization synthesis of methanol, i.e., the second synthesis mode. At this time, the carbon dioxide obtained after decarbonization is liquefied and stored separately. The water-gas conversion further ensures the hydrogen-to-carbon ratio in the gases reacting in the synthesis equipment, further ensuring the completeness of the methanol synthesis reaction. At the same time, the water-gas conversion increases the proportion of hydrogen, thereby reducing the amount of hydrogen produced by the hydrogen production equipment, and thus reducing the output value requirements of the power supply equipment.

[0096] The captured and stored carbon dioxide can not only provide a source for subsequent carbon supplementation and methanol synthesis, but can also be used in other fields that require carbon dioxide, such as refrigerants, expanding agents, and welding shielding gases.

[0097] When the hydrogen production equipment has a surplus of hydrogen, both the hydrogen from the hydrogen production equipment and the crude synthesis gas from the gasification section 131 are directly fed into the synthesis equipment. At the same time, the carbon dioxide from the storage section is also gasified and fed into the synthesis equipment. The hydrogen, crude synthesis gas, and carbon dioxide react together in the synthesis equipment to produce methanol. This is the carbon supplementation synthesis of methanol, i.e., the third synthesis mode.

[0098] The hydrogen production capacity of the hydrogen production equipment 11 is determined by the output capacity of the power supply equipment, that is, the selection is to directly synthesize methanol, decarbonize methanol, or supplement methanol based on the output capacity of the power supply equipment.

[0099] Furthermore, when the output of the power supply equipment exceeds a preset range, the synthesis equipment also has a fourth synthesis mode. In this fourth synthesis mode, the synthesis equipment is connected to an external carbon dioxide gas supply source under controlled conditions. The external carbon dioxide can be purchased, self-produced, or produced by another non-methanol synthesis system.

[0100] Therefore, when synthesizing methanol by carbon supplementation, the source of carbon dioxide should be selected based on the specific circumstances.

[0101] Meanwhile, the carbon capture section 141 also selects the degree of carbon capture based on the output capacity of the power supply equipment, and the degree of carbon capture is negatively correlated with the output capacity of the power supply equipment. That is, the smaller the output capacity of the power supply equipment, the greater the degree of carbon capture.

[0102] The degree of carbon capture refers to the percentage of carbon dioxide captured by volume relative to the total crude syngas or the first mixture. Examples include 25% carbon capture, 50% carbon capture, and 75% carbon capture. After 25% carbon capture, the remaining carbon dioxide in the second mixture accounts for 75% of the total second mixture. The second mixture may contain some carbon dioxide or none at all, depending on the amount of hydrogen used to select the degree of carbon capture.

[0103] The amount of carbon dioxide that the storage device 17 supplements to the synthesis device 19, i.e., the degree of carbon replenishment, is selected based on the output capacity of the power supply equipment. The degree of carbon replenishment is positively correlated with the output capacity of the power supply equipment. That is, the greater the output capacity of the power supply equipment, the greater the degree of carbon replenishment.

[0104] When the power supply equipment has a good output capacity, the hydrogen production capacity of hydrogen production equipment 11 is good. When the power supply equipment has a poor output capacity, the hydrogen production capacity of hydrogen production equipment 11 is poor.

[0105] For example, when the power supply equipment uses only wind power, the output capacity of the power supply equipment is related to the wind force. When the wind force is sufficient, the output capacity is better, and when the wind force is poor, the output capacity is worse.

[0106] When the power supply equipment uses only photoelectric power, the output capacity of the power supply equipment is related to the amount of light. When the light is sufficient, the output capacity is better, and when the light is scarce, the output capacity is worse.

[0107] In other words, the methanol production system of this application, when the power supply capacity is low, resulting in low hydrogen production, adjusts the hydrogen-to-carbon ratio and performs carbon capture treatment on the crude synthesis gas to increase the hydrogen content. It also reduces or even completely removes carbon dioxide to ensure sufficient hydrogen for the reaction. The carbon dioxide obtained after decarbonization is stored separately for use when hydrogen production is sufficient, thereby increasing methanol production.

[0108] Furthermore, the power supply equipment can serve as the plant power supply for the methanol synthesis system, as the internal power supply for the hydrogen production section 111, and as the internal power supply for liquefied gas. When serving as the internal power supply for the hydrogen production section 111, the output value of the steam energy utilization section 134 accounts for 0 to 100% of the electricity required by the hydrogen production section 111.

[0109] To improve the overall energy efficiency of the methanol system and ensure the stable production capacity of the methanol synthesis equipment, the power supply equipment prioritizes providing power to the liquefier 142, and secondarily to the hydrogen production section 111.

[0110] The gasification section 131 is connected to the hydrogen production equipment to provide the equipment with the energy generated during gas expansion. Specifically, the energy generated when liquid carbon dioxide is vaporized and expands into a gaseous state is converted into electrical energy by a turbine, which then provides electrical energy to the hydrogen production equipment 11, thus utilizing energy efficiently and saving energy.

[0111] Downstream of the synthesis unit is a hydrogen recovery section 161, which receives unreacted hydrogen from the synthesis unit and transports it upstream. Specifically, the hydrogen recovery section 161 is located downstream of the synthesis section 151 and upstream of the synthesis gas compression section 136. The synthesis unit obtains hydrogen through methanol synthesis purge gas.

[0112] That is, after the methanol synthesis reaction occurs in the synthesis section 151, the methanol enters the methanol distillation section 152, and the unreacted hydrogen enters the hydrogen recovery section 161. The recovered hydrogen re-enters the synthesis gas compression section 136 to provide hydrogen for the synthesis reaction in the synthesis section 151.

[0113] Furthermore, downstream of the hydrogen recovery section 161 are sequentially a methane enrichment section 171 and a methane conversion and utilization section 172. The residual gas after dehydrogenation in the hydrogen recovery section 161 enters the methane enrichment section 171. Specifically, the gas in the hydrogen recovery section 161 is dehydrogenated and released to obtain methane, which then enters the methane enrichment section 171.

[0114] The methane enrichment section 171 is used to increase the concentration of methane. The methane conversion and utilization section 172 is used to receive the enriched methane and convert it for utilization.

[0115] The methane concentration section 171 can be carried out by two or more of the following: organic membrane separation device, pressure swing adsorption device, temperature swing adsorption device, and inorganic membrane separation device, in parallel or series connection.

[0116] The methane conversion and utilization section 172 can generate electricity using a gas-fired boiler-steam turbine, an internal combustion engine, or a gas-steam combined cycle generator set. Alternatively, it can use two or more of the following methods to convert the methane into syngas components, which can then be used as feedstock for the methanol synthesis section 151: catalytic / non-catalytic oxidation, steam cracking, wet steam reforming, self-heating oxygen-steam reforming, CO2 dry reforming, or self-heating oxygen-steam-CO2 mixed reforming.

[0117] The methanol preparation system of this invention includes a method for preparing methanol, comprising the following steps: S1. Provide a power supply device to electrolyze water to produce hydrogen.

[0118] Specifically, this means that the power supply equipment provides electricity, and the hydrogen production equipment electrolyzes water to produce hydrogen.

[0119] S2 provides crude syngas.

[0120] Specifically, the raw materials are fed into the gasification section 131, where they react to produce crude syngas. The raw materials can be biomass or other materials.

[0121] S3. Based on the output capacity of the power supply equipment, methanol is produced by reaction in one of the first synthesis mode, the second synthesis mode, and the third synthesis mode.

[0122] In the first synthesis mode, hydrogen and crude synthesis gas are used as reactant gases. At this time, the hydrogen produced by the hydrogen production unit 11 and the crude synthesis gas produced by the gasification section 131 enter the synthesis unit to undergo a methanol synthesis reaction.

[0123] Specifically, in this embodiment, the gasification section 131, syngas purification section 135, and carbon capture section 141 are started and operated, while the hydrogen-carbon ratio adjustment section 132 and the gasifier 144 of the carbon storage section are stopped. The carbon dioxide source for the synthesis equipment is only one. The operating load rate of the liquefier 142 in the carbon storage section is between 0% and 30%. The hydrogen output from the hydrogen production equipment and the crude syngas provided by the gasification section 131 are combined and pressurized to 4.0~10.0 MPaG by the syngas compression section 136, and then enter the synthesis section 151 for the synthesis reaction. In the second synthesis mode, the crude syngas is converted into a first mixed gas by water vapor, and then treated by carbon capture to obtain a second mixed gas and carbon dioxide respectively. The carbon dioxide is liquefied and stored, and hydrogen, crude syngas, and the first mixed gas are used as reaction gases.

[0124] Specifically, in this embodiment, the gasification section 131, syngas purification section 135, hydrogen-to-carbon ratio adjustment section 132, and carbon capture section 141 are started and operated. The liquefaction unit 142 of the carbon storage section is in operation, and the gasifier 144 of the carbon storage section is stopped. The carbon dioxide source for the synthesis equipment is two-way: the crude syngas provided by the gasification section 131 and the first mixed gas provided by the hydrogen-to-carbon ratio adjustment section 132. The hydrogen output from the hydrogen production equipment, the crude syngas provided by the gasification section 131, and the first mixed gas provided by the hydrogen-to-carbon ratio adjustment section 132 are combined, purified by the syngas purification section 135, and then enter the syngas compression section 136. After being pressurized to 4.0~10.0 MPaG by the syngas compression section 136, it enters the synthesis section 151 for the synthesis reaction.

[0125] Among them, the operating load rate of liquefier 142 in the carbon storage section is between 50% and 100%.

[0126] In the third synthesis mode, liquefied carbon dioxide is vaporized to obtain gaseous carbon dioxide, and hydrogen, crude synthesis gas, and gaseous carbon dioxide are used as reactants. Since hydrogen is abundant at this stage, carbon dioxide is added to synthesize methanol.

[0127] Specifically, in this embodiment, the gasification section 131, syngas purification section 135, and hydrogen-carbon ratio adjustment section 132 are started and operated. The carbon capture section 141 and the liquefaction unit 142 of the carbon storage section are stopped, while the gasifier 144 of the carbon storage section is operated. The carbon dioxide source for the synthesis equipment is twofold: the crude syngas provided by the gasification section 131 and the carbon dioxide provided by the gasifier 144. The hydrogen output from the hydrogen production equipment, the crude syngas provided by the gasification section 131, and the carbon dioxide provided by the gasifier 144 are combined and pressurized to 4.0~10.0 MPaG by the syngas compression section 136 before entering the synthesis section 151 for the synthesis reaction.

[0128] In this invention, liquid carbon dioxide in storage container 143 of the carbon storage section passes sequentially through vaporizer 144 and carbon dioxide expansion energy utilization section 147 before merging with crude syngas and hydrogen. Based on the main and side reactions in the methanol preparation reaction, the methanol preparation system of this invention creatively proposes a flexible carbon storage synthesis method. It adds a low-cost hydrogen-to-carbon ratio adjustment section 132, a carbon capture section 141, and a carbon storage section. First, the crude syngas undergoes water-to-vapor conversion to adjust the hydrogen-to-carbon ratio, followed by carbon capture and storage. The degree of carbon capture or supplementation is determined based on the power supply output to achieve peak shaving. When the power supply output is insufficient, resulting in low hydrogen production, the hydrogen-to-carbon ratio is adjusted, and carbon dioxide in the crude syngas is captured and stored as liquid carbon dioxide. At this time, the hydrogen-to-carbon ratio in the crude syngas is high, allowing the methanol synthesis reaction to proceed fully. Simultaneously, the reduction in carbon dioxide significantly reduces hydrogen consumption, offering a greater advantage than proportionally reducing the crude syngas load. When the power supply equipment has surplus output, that is, when there is an abundance of electricity, the hydrogen production is high. The stored carbon dioxide is then vaporized and added to the synthesis equipment, increasing methanol production to make up for the methanol production gap in months with insufficient output.

[0129] For example, when the power supply equipment uses only wind power, based on wind and meteorological data, the first, second, or third synthesis mode (i.e., decarbonization synthesis, carbon replenishment synthesis, or direct synthesis) is selected according to wind conditions. Carbon replenishment synthesis is selected in months with strong winds, direct synthesis is selected in months with moderate winds, and decarbonization synthesis is selected in months with weak winds. Specifically, a curve showing the change in wind power density with the month can be plotted based on local wind conditions. Then, combined with power generation forecasts based on medium- and long-term weather forecasts, monthly adjustments to output, decarbonization, and carbon replenishment are arranged. These adjustments include selecting the degree of decarbonization and carbon replenishment based on wind conditions.

[0130] The solution in this embodiment also has the following effects: (1) It realizes the coupling of biomass renewable carbon and hydrogen sources with renewable electricity and hydrogen, and maximizes the utilization efficiency of renewable carbon in the methanol synthesis process. Theoretically, all carbon elements in biomass can be converted into carbon in methanol, which greatly reduces the pressure on the raw material storage and supply side of conventional biomass methanol plants, and effectively resolves the natural contradiction of mismatch between biomass resources and wind and photovoltaic power resources.

[0131] (2) By flexibly adjusting the capture, liquefaction and storage of CO2 to replace electricity storage and hydrogen storage, the effect of "peak shaving and valley filling" of wind power and photovoltaic power generation equipment is well achieved. The impact of obvious day and night and seasonal differences in renewable electricity output on the operation of methanol synthesis unit is minimized. The methanol synthesis unit can be stably and continuously operated within the controllable adjustment range of 80 to 120% of normal operating load, which improves the operational safety and stability of conventional wind and solar coupled biomass to methanol projects.

[0132] (3) With minimal energy input and capital investment, it replaces the large-scale investment in energy storage and hydrogen storage devices and the extremely high energy input, thus effectively overcoming the huge disadvantage of the large fluctuation in the production capacity of methanol synthesis devices caused by the inherent peak-valley difference of wind power and photovoltaic power generation, making it difficult to achieve large-scale and economically competitive production.

[0133] (4) By coupling the internal power supply constructed from the steam energy utilization section, hydrogen expansion energy utilization section and carbon dioxide expansion energy utilization section in the biomass thermal conversion process with the external renewable power supply of wind power and photovoltaic power, the cascade utilization of biomass energy can be realized, the overall energy cycle efficiency of the system can be maximized, the energy efficiency level of the methanol production process can be significantly improved, and the greenhouse gas GHG emissions in the methanol production process can be fundamentally reduced.

[0134] (5) Based on the diurnal and seasonal fluctuations in the load of the water electrolysis hydrogen production unit caused by the diurnal and seasonal fluctuations of the exported renewable electricity, the production and operation modes of the syngas production, green hydrogen production, CO2 liquefaction and capture, and methanol synthesis units are divided into three modes. At the same time, the material balance and energy balance of the entire methanol plant are taken into account, which significantly reduces the methanol production cost and improves the economic competitiveness of the methanol plant.

[0135] Although the invention has been described with reference to several typical embodiments, it should be understood that the terminology used is descriptive and exemplary, and not restrictive. Since the invention can be embodied in many forms without departing from the spirit or essence of the invention, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims. Therefore, all variations and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. A methanol preparation system, characterized in that, It includes hydrogen production equipment, syngas processing equipment, carbon dioxide processing equipment, and synthesis equipment, wherein the hydrogen production equipment is used to produce hydrogen gas. The syngas processing equipment includes: The gasification section is used to supply the crude syngas produced by the reaction, the crude syngas including carbon monoxide, carbon dioxide and hydrogen; The first energy utilization section is located downstream of the gasification section and is used to recover and utilize the heat generated by the gasification section. The carbon dioxide processing equipment includes: A carbon capture section, located downstream of the first energy utilization section, is used to receive the crude syngas and capture carbon dioxide to obtain carbon dioxide and a second mixed gas, respectively. A carbon storage section, located downstream of the carbon capture section, is used to receive and store carbon dioxide from the carbon capture section. A carbon dioxide expansion energy utilization section is located downstream of the carbon storage section to convert the energy generated during carbon dioxide expansion into electrical energy. The synthesis equipment is used to synthesize methanol and is simultaneously located downstream of the hydrogen production equipment, the gasification section, the carbon capture section, and the carbon storage section, for receiving gases as reactants.

2. The methanol preparation system according to claim 1, characterized in that, The first energy utilization section includes a waste heat recovery section located downstream of the gasification section. The waste heat recovery section is also located upstream of the carbon capture section and the synthesis equipment. The waste heat recovery section includes a first channel and a second channel that can exchange heat with each other. The gasification section is connected to the first channel. The inlet of the second channel is used to connect an external heating medium to absorb the heat of the crude synthesis gas and convert it into steam.

3. The methanol preparation system according to claim 2, characterized in that, A steam energy utilization section is provided downstream of the waste heat recovery section. The steam energy utilization section is connected to the outlet of the second channel and is used to receive steam and convert it into electrical energy.

4. The methanol preparation system according to claim 1, characterized in that, The hydrogen production equipment includes: The hydrogen production section is used to produce hydrogen gas. A hydrogen storage section, located downstream of the hydrogen production section, is used to compress and store hydrogen. A hydrogen expansion energy utilization section is located downstream of the hydrogen storage section to convert the energy generated during hydrogen expansion into electrical energy.

5. The methanol preparation system according to claim 1, characterized in that, The carbon storage section includes a liquefier located downstream of the carbon capture section, a storage container located downstream of the liquefier, and a gasifier located downstream of the storage container. The liquefier is used to receive carbon dioxide from the carbon capture section and liquefy it to obtain liquid carbon dioxide. The storage container is used to store the liquid carbon dioxide. The gasifier is used to gasify the carbon dioxide to obtain carbon dioxide gas.

6. The methanol preparation system according to claim 5, characterized in that, A heat storage tank is provided downstream of the liquefier, and the outlet of the heat storage tank is connected to the vaporizer.

7. The methanol preparation system according to claim 5, characterized in that, A cold storage tank is provided downstream of the vaporizer, and the outlet of the cold storage tank is connected to the liquefier.

8. The methanol preparation system according to claim 1, characterized in that, Downstream of the synthesis equipment is a hydrogen recovery section, which is used to receive unreacted hydrogen in the synthesis equipment and transport the hydrogen to the upstream of the synthesis equipment.

9. The methanol preparation system according to claim 8, characterized in that, Downstream of the hydrogen recovery section are a methane enrichment section and a methane conversion and utilization section. The hydrogen recovery section is used to provide the residual gas after dehydrogenation to the methane enrichment section. The methane enrichment section is used to increase the concentration of methane. The methane conversion and utilization section is used to receive the enriched methane and convert and utilize it.

10. The methanol preparation system according to any one of claims 1 to 9, characterized in that, The syngas processing equipment includes a hydrogen-to-carbon ratio adjustment section located downstream of the first energy utilization section to receive the crude syngas and perform a water-gas shift reaction to generate hydrogen, thereby obtaining a first mixed gas. The syngas processing equipment has a first syngas mode, a second syngas mode, and a third syngas mode. In the first synthesis mode, the synthesis equipment receives hydrogen from the hydrogen production equipment and crude synthesis gas from the gasification section as reaction gases; In the second synthesis mode, the hydrogen-to-carbon ratio adjustment section and the carbon storage section are activated. The synthesis equipment receives hydrogen from the hydrogen production equipment, crude synthesis gas from the gasification section, and the first mixed gas from the hydrogen-to-carbon ratio adjustment section as reaction gases. At the same time, the carbon storage section receives carbon dioxide from the carbon capture section for storage. In the third synthesis mode, the hydrogen-to-carbon ratio adjustment section is shut down, and the synthesis equipment receives hydrogen from the hydrogen production equipment, crude synthesis gas from the gasification section, and carbon dioxide gasified in the carbon storage section as reaction gases.

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