System and process for preparing methanol from biomass

Abstract

The invention discloses a system and a process for preparing methanol from biomass, and relates to the technical field of biomass energy. The system comprises a raw material gasification unit used for heating raw materials at a high temperature to prepare crude synthesis gas; the dust removal unit is butted with the raw material gasification unit and is used for removing dust from the crude synthesis gas; the pure oxygen conversion unit is in butt joint with the dust removal unit and is used for performing high-temperature non-catalytic partial oxidation treatment on the crude synthesis gas; the impurity removal unit is in butt joint with the pure oxygen conversion unit and is used for performing dechlorination, desulfurization and decarbonization treatment on the converted crude synthesis gas; the methanol synthesis unit is in butt joint with the impurity removal unit and is used for synthesizing methanol from the synthesis gas subjected to dechlorination, desulfurization and decarbonization treatment; the steam utilization unit is connected with the dust removal unit and used for producing steam, and the output end is connected with the methanol synthesis unit and the impurity removal unit. The problems that an existing methanol preparation system is large in power consumption, high in operation cost and large in energy consumption are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of biomass energy, and in particular to a system and process for preparing methanol from biomass. Background Art

[0002] Biomass is a variety of organisms produced by photosynthesis using the atmosphere, water, and land, usually including wood and forest industry waste, agricultural waste, aquatic plants, oil plants, urban domestic waste, industrial waste, and excrement, etc. It is a renewable energy source. Biomass resources are widely distributed, have large reserves, and are renewable. Compared with fossil fuels, they have high volatile matter, low ash content, and low sulfur and nitrogen content. They are known as "green coal". Using biomass as raw material to produce hydrogen has the advantages of being clean, energy-saving, and not consuming mineral resources. During the reaction process, the total amount of CO2 generated is balanced with the CO2 absorbed during the growth of biomass, which will not cause a greenhouse effect and can achieve zero emissions in the true sense.

[0003] However, biomass has many defects, such as high water and oxygen content, low calorific value and energy density, poor crushing and hydrophilicity, easy to rot, and not suitable for long-distance transportation and long-term storage, which brings great challenges to the direct large-scale conversion and utilization of biomass. Most of the existing biomass pretreatment methods use the method of drying and extrusion molding to prepare biomass particles to solve the above problems, but the processing process, especially the extrusion molding, consumes a lot of electricity and is costly.

[0004] Traditional methanol production mainly uses natural gas, oil, coal and coke oven gas as raw materials. Through conversion or gasification, fuel gas containing hydrogen, carbon monoxide, carbon dioxide and other components is first prepared, and then qualified methanol is produced through purification, conversion, methanol synthesis, methanol distillation and other processes. This type of methanol is defined as gray methanol. Methanol can also be produced from biomass, mostly using a gasifier to convert biomass into gas, and then producing methanol through crushing, purification, reforming, compression, methanol synthesis, methanol distillation and other processes. This method has the problems of high power consumption, high operating costs, high energy consumption, high tar content and low carbon conversion rate. Summary of the invention

[0005] The technical problem to be solved by the present invention is that the existing biomass methanol preparation system has high power consumption, high operating cost, high energy consumption, high tar content and low carbon conversion rate.

[0006] The purpose is to provide a system for preparing methanol from biomass, which solves the problems of high power consumption, high operating cost and high energy consumption of the existing system for preparing methanol.

[0007] The second purpose is to provide a process for preparing methanol from biomass, and to prepare methanol in conjunction with a system, wherein the prepared green methanol has low tar content and high carbon conversion rate.

[0008] The present invention is achieved through the following technical solutions:

[0009] A system for preparing methanol from biomass, comprising:

[0010] A raw material gasification unit is used to heat the raw material at high temperature to make the raw material react at high temperature to produce a crude synthesis gas;

[0011] The dust removal unit is connected to the raw material gasification unit and is used to remove dust from the raw synthesis gas;

[0012] The pure oxygen conversion unit is connected to the dust removal unit and is used to perform high-temperature non-catalytic oxidation treatment on the raw synthesis gas and recover the heat;

[0013] The impurity removal unit is connected to the pure oxygen conversion unit to perform dechlorination, desulfurization and decarbonization on the raw synthesis gas after oxidation treatment;

[0014] The methanol synthesis unit is connected to the impurity removal unit to synthesize methanol from the synthesis gas treated with dechlorination, desulfurization and decarbonization;

[0015] The steam utilization unit has an input end connected to the dust removal unit and the methanol synthesis unit for producing steam, and an output end connected to the methanol synthesis unit and the impurity removal unit.

[0016] As a possible design, the raw material gasification unit includes a fluidized bed gasifier, which is used to make the raw materials react at high temperature to produce a raw synthesis gas.

[0017] As a possible design, the dust removal unit includes a coarse separator, a fine ash separator and a high-temperature dust collector;

[0018] The rough separator is connected to the gas outlet of the raw material gasification unit and is used to perform preliminary separation of the rough synthesis gas;

[0019] The air inlet end of the fine ash separator is connected to the air outlet end of the rough separator, and is used to separate the fly ash from the initially separated rough synthesis gas;

[0020] The air inlet of the high-temperature dust collector is connected to the air outlet of the fine ash separator for further dust removal of the crude synthesis gas. The air outlet of the high-temperature dust collector is connected to the pure oxygen conversion unit.

[0021] As a possible design, the pure oxygen conversion unit comprises a pure oxygen conversion furnace, which is used for carrying out a high-temperature non-catalytic oxidation reaction of methane and tar in the raw synthesis gas with oxygen.

[0022] As a possible design, the impurity removal unit includes a water scrubber, a first compressor, a shift desulfurization device and a low-temperature methanol scrubber;

[0023] The water washing tower is connected to the output end of the pure oxygen conversion unit and is used for water washing to remove chlorine and dust from the crude synthesis gas;

[0024] The first compressor is connected to the gas outlet of the water scrubber and is used to pressurize the crude synthesis gas;

[0025] The shift desulfurization device is connected to the gas outlet of the first compressor and is used for desulfurizing the raw synthesis gas and for converting CO and water into H2 and CO2;

[0026] The low-temperature methanol washing tower is connected to the gas outlet end of the conversion desulfurization device and is used for removing impurities from the crude synthesis gas. The gas outlet end of the low-temperature methanol washing tower is connected to the methanol synthesis unit.

[0027] As a possible design, the above-mentioned methanol synthesis unit includes a second compressor, a methanol synthesis tower and a three-tower distillation tower group;

[0028] The second compressor is connected to the impurity removal unit and the steam utilization unit, and is used to receive and compress the synthesis gas output by the impurity removal unit, and is used to work with the steam input by the steam utilization unit;

[0029] The methanol synthesis tower is connected to the second compressor and is used to synthesize methanol;

[0030] The input of the three-tower distillation tower group is connected to the output end of the methanol synthesis tower for distilling and purifying methanol.

[0031] As a possible design, the steam utilization unit includes a steam boiler;

[0032] The input end of the steam boiler is connected to the dust removal unit and the methanol synthesis unit, and is used to receive the crude synthesis gas output by the dust removal unit, the desorption gas and flash gas output by the methanol synthesis unit and produce steam. The output end of the steam boiler is connected to both the impurity removal unit and the methanol synthesis unit, and is used to provide the steam required to drive the impurity removal unit and the methanol synthesis unit.

[0033] A process for preparing methanol from biomass comprises the following steps:

[0034] reacting biomass raw materials with water vapor and oxygen to produce a crude synthesis gas;

[0035] After the raw synthesis gas is dusted, it is converted into pure oxygen to obtain high-temperature gas;

[0036] After removing impurities from the high temperature gas, reacting it, a mixed gas is obtained;

[0037] The mixed gas is reacted to obtain methanol, which is then distilled to obtain the finished product.

[0038] As a possible design, the particle size of the biomass raw material is ≤100 mm, the water content of the biomass raw material is ≤30%; the hourly addition ratio of the biomass raw material, water vapor and oxygen is (3.5-4)t:(600-1000)Nm 3:(600~1000)Kg.

[0039] As a possible design, the synthesis temperature of the above-mentioned crude synthesis gas is 600-900°C; the pure oxygen conversion treatment temperature is 1000-1500°C; after the high-temperature gas is decontaminated, it reacts at 200-300°C under the action of a Co-Mo catalyst to obtain a mixed gas with a hydrogen-to-carbon ratio of 2-2.2; the reaction conditions of the mixed gas are 200-300°C and 5-8MPaG.

[0040] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0041] The system provided by the present invention uses low-value resources and renewable biomass as raw materials to replace traditional fossil energy and achieve zero carbon emissions. At the same time, during the production process, a portion of the crude synthesis gas after gasification of the biomass raw materials is used as energy to produce steam, and the steam is used to drive the compressors and other equipment of the methanol synthesis unit and the impurity removal unit, thereby reducing electricity consumption and saving energy by more than 15%.

[0042] The present invention heats the raw materials at high temperature, uses oxygen and water vapor as gasifying agents to gasify the raw materials to obtain a crude synthesis gas, and then subjects the crude synthesis gas to a three-stage dust removal treatment to remove impurities such as fly ash, and then a pure oxygen conversion treatment to fully crack methane and tar in the crude synthesis gas, and to enhance the gasification of fly ash to produce a tar-free, low-methane high-temperature gas. The high-temperature gas is subjected to an impurity removal treatment to achieve dechlorination, desulfurization and decarbonization. The carbon monoxide conversion process can increase the hydrogen output, and a small portion of CO therein is converted into CO2. The gas is then washed with low-temperature methanol to ensure that the hydrogen-carbon ratio in the gas is at an optimal ratio for synthesizing methanol. The mixed gas is then reacted and distilled at a specific temperature and pressure to remove impurities, and good-quality green methanol can be obtained. The prepared green methanol has a low tar content and a high carbon conversion rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0044] Figure 1 A connection structure diagram of a system for preparing methanol from biomass according to the present invention;

[0045] Figure 2 The present invention is a process flow chart for preparing methanol from biomass.

[0046] Marks and corresponding parts names in the attached drawings:

[0047] 1- fluidized bed gasifier; 2- coarse separator; 3- fine ash separator; 4- high temperature dust collector; 5- pure oxygen converter; 6- water scrubber; 7- shift desulfurization device; 8- low temperature methanol scrubber; 9- methanol synthesis tower; 10- three-tower distillation tower group; 11- first compressor; 12- second compressor; 13- steam boiler; 14- sand bin; 15- ash bin; 16- waste heat recovery device; 17- heat exchanger; 18- silo; 19- methanol water cooler; 20- methanol separator; 21- flash steam; 22- pressure swing adsorption tower. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with examples and drawings. The illustrative embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention. If specific conditions are not specified in the examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0049] A system for preparing methanol from biomass, referring to Figure 1 , including raw material gasification unit, dust removal unit, pure oxygen conversion unit, impurity removal unit, methanol synthesis unit and steam utilization unit.

[0050] The raw material gasification unit uses air as the combustion-supporting air during the start-up phase. First, the raw material gasification unit is heated to above 600°C through the ignition burner, and then the furnace is fed through the silo 18. The temperature of the gasification device is increased by biomass combustion, and the load of the ignition burner is gradually reduced accordingly, and finally the operating conditions for the raw material gasification unit to enter the gasification condition are met. Under the gasification condition, the biomass raw material enters the furnace, is fully mixed with the circulating material in the furnace and heated, and is gasified with the gasification agent composed of water vapor and oxygen introduced into the bottom of the furnace. The crude synthesis gas produced by the gasification reaction carries the unreacted solid material upward and enters the dust removal unit from the top of the furnace.

[0051] The dust removal unit is connected to the raw material gasification unit. Through three-stage dust removal, the separated fly ash is sent back to the raw material gasification unit to continue to participate in the gasification reaction. After the crude synthesis product is dust removed, part of the crude synthesis gas is transported to the pure oxygen conversion unit for pure oxygen conversion; the other part of the crude synthesis gas is sent to the steam utilization unit to produce steam through combustion.

[0052] The pure oxygen conversion unit is connected to the dust removal unit. The methane and tar in the raw synthesis gas undergo a high-temperature non-catalytic partial oxidation reaction with oxygen to fully crack the methane and tar in the raw gas and enhance the gasification of fly ash to produce high-temperature gas with no tar and low methane content.

[0053] The impurity removal unit is connected to the pure oxygen conversion unit to dechlorinate, desulfurize and decarbonize the raw synthesis gas after oxidation treatment. Since the high-temperature gas still contains a small amount of fly ash, chlorine, organic sulfur, etc., and the carbon-hydrogen ratio in the high-temperature gas is not the optimal carbon-hydrogen ratio for synthesizing methanol, the impurity removal unit is first used for water washing to remove the fly ash and residual chlorine in the gas, so that the dust content is reduced to ≤2mg / Nm 3 , meeting the dust and chlorine requirements of methanol synthesis; then through transformation desulfurization, the oxygen and high hydrocarbons contained in the synthesis gas are removed, and part of the CO reacts with water to generate CO2 and H2, increasing the amount of hydrogen, which is beneficial to the subsequent increase in methanol production, and at the same time converting organic sulfur into hydrogen sulfide; then through low-temperature methanol decarbonization, part of the carbon dioxide, all sulfides, water and other impurities in the gas are removed, so that the carbon-hydrogen ratio in the gas is in the optimal ratio for synthesizing methanol, which is convenient for subsequent methanol synthesis.

[0054] The methanol synthesis unit is connected to the impurity removal unit to synthesize methanol from the dechlorinated, desulfurized and decarbonized synthesis gas. The outlet gas of the methanol synthesis unit is separated and purified after heat exchange, and most of the unreacted gas is recovered and recycled for reaction. A small part of the unreacted gas is concentrated into methane through pressure swing adsorption. The separated desorbed gas and flash steam are then returned to the steam utilization unit for recovery and used to generate steam as a power source to drive the compressor, reducing power consumption.

[0055] The steam utilization unit is connected to the dust removal unit and is used to produce steam. The output end is connected to the methanol synthesis unit and the impurity removal unit. Part of the crude synthesis gas enters the steam utilization unit and produces steam through combustion. The steam is used as a power source to drive the compressor, replacing electric energy, and is transported to the methanol synthesis unit and the impurity removal unit to drive the compressors therein to work, thereby saving electric energy.

[0056] In some embodiments of the present invention, the raw material gasification unit includes a fluidized bed gasifier 1, which is used to process the raw material at high temperature to obtain a crude synthesis gas. The lower end of the fluidized bed gasifier 1 is connected to a silo 18 through a conveyor belt, and the lower end is also connected to an oxygen and water vapor inlet to facilitate the gasification reaction of the raw material, oxygen, and water vapor.

[0057] Preferably, the side of the fluidized bed gasifier 1 is also connected to a sand bin 14, and the fluidized bed gasifier 1 can improve the combustion efficiency by adding sand through the sand bin 14. Due to the circulation of materials in the bed, the biomass is mixed with oxygen and water vapor more evenly, and the combustion is more complete, which further improves the combustion efficiency, improves the heat transfer, and reduces pollutant emissions.

[0058] In some embodiments of the present invention, the dust removal unit includes a coarse separator 2 , a fine ash separator 3 and a high-temperature dust collector 4 . The rough separator 2 is connected to the gas outlet of the raw material gasification unit, and is used for preliminary separation of the rough synthesis gas. The bottom of the rough separator 2 is connected to the bottom of the fluidized bed gasifier 1, and the collected fly ash can be transported back to the fluidized bed gasifier 1 to continue to participate in the gasification reaction. In addition, since the gas discharged from the fluidized bed gasifier 1 also contains some unreacted large particles, they are separated by the rough separator 2 and then recycled into the fluidized bed gasifier 1 for reuse; the air inlet end of the fine ash separator 3 is connected to the gas outlet end of the rough separator 2, and is used to re-separate the fly ash in the rough synthesis gas that has been preliminarily separated, and most of the small particle fly ash can be removed. Preferably, the rough separator 2 and the fine ash separator 3 can be cyclone dust collectors; the air inlet end of the high-temperature dust collector 4 is connected to the gas outlet end of the fine ash separator 3, and is used to dedust the rough synthesis gas again, remove the entrained fine fly ash, and further reduce the dust in the gas. Preferably, the high-temperature dust collector 4 performs high-temperature dust removal on the rough synthesis gas, and the gas outlet end of the high-temperature dust collector 4 is connected to the pure oxygen conversion unit.

[0059] Preferably, the bottom of the fine ash separator 3 and the high-temperature dust collector 4 are both connected to an ash bin 15, and the ash bin 15 is used to collect fly ash.

[0060] In some embodiments of the present invention, the above-mentioned pure oxygen conversion unit includes a pure oxygen conversion furnace 5, which is used to carry out a high-temperature non-catalytic partial oxidation reaction of methane and tar in the raw synthesis gas with oxygen. In the pure oxygen conversion furnace 5, by heating and introducing oxygen, the impurities methane, tar, etc. in the raw synthesis gas are fully cracked, and the gasification of fly ash can be enhanced, so that a high-temperature gas with no tar and low methane content can be produced.

[0061] In some embodiments of the present invention, the impurity removal unit includes a water scrubber 6, a first compressor 11, a shift desulfurization device 7 and a low-temperature methanol scrubber 8. The water scrubber 6 is connected to the output end of the pure oxygen conversion unit and is used to remove chlorine from the crude synthesis gas by water scrubbing. After the gas is processed by pure oxygen conversion, there is still less fly ash and chlorine in the gas. By spraying water scrubbing, the dust content can be reduced to ≤2mg / Nm 3, and at the same time, the chlorine in the crude synthesis gas is removed to meet the requirements of methanol synthesis on the dust and chlorine content of the synthesis gas; the first compressor 11 is connected to the gas outlet of the water washing tower 6 to pressurize the crude synthesis gas. The gas after water washing will also undergo a shift desulfurization treatment, but this treatment has certain requirements on the gas pressure. The gas is pressurized to 2-2.5MPaG by the first compressor 11; the shift desulfurization device 7 is connected to the gas outlet of the first compressor 11, which includes a detoxification tank and a shift reactor. In the detoxification tank, oxygen and high hydrocarbons contained in the synthesis gas are firstly removed, and the temperature is raised to 25 The gas is heated to 0~260℃, sprayed with water to cool down to 220~240℃, and then enters the conversion reactor. The isothermal conversion process is adopted to convert carbon monoxide and water into hydrogen and carbon dioxide, and 90% of the organic sulfur in the crude synthesis gas is converted into hydrogen sulfide. The conversion gas leaving the conversion reactor is then washed by a low-temperature methanol washing tower 8; the low-temperature methanol washing tower 8 is connected to the gas outlet end of the conversion desulfurization device 7, and uses low-temperature methanol for washing to remove carbon dioxide, all sulfides, water and other impurities therein. The gas outlet end of the low-temperature methanol washing tower 8 is connected to the methanol synthesis unit.

[0062] Preferably, a heat exchanger 17 is also connected between the low-temperature methanol washing tower 8 and the conversion desulfurization device 7. The temperature of the conversion gas in the conversion reactor is relatively high, and the heat is absorbed by the heat exchanger 17 to cool the gas to 35-45°C, so that the heat can be fully utilized.

[0063] In some embodiments of the present invention, the methanol synthesis unit includes a second compressor 12, a methanol synthesis tower 9 and a three-tower distillation tower group 10. The second compressor 12 is connected to the impurity removal unit, specifically to the low-temperature methanol washing tower 8, for receiving and compressing the synthesis gas, so that the synthesis gas reacts at 200-300°C and 5-8MPaG; the methanol synthesis tower 9 is connected to the second compressor 12 for synthesizing methanol, and the compressed gas is first heat-exchanged with the outlet gas of the synthesis tower before entering the synthesis tower to increase the gas temperature and facilitate the reaction; the inlet end of the three-tower distillation tower group 10 is connected to the outlet end of the methanol synthesis tower 9, and according to the difference in boiling points of each material, a three-tower distillation process is adopted to finally obtain a qualified methanol product and send it to the tank area for storage.

[0064] Preferably, the methanol synthesis unit further comprises a methanol water cooler 19, a methanol separator 20, a flash evaporator 21 and a pressure swing adsorption tower 22. The methanol water cooler 19 is connected to the methanol synthesis tower to cool the synthesis gas, and the cooled synthesis gas is input to the methanol separator 20 for treatment; the input end of the methanol separator 20 is connected to the methanol water cooling tower 19, and the synthesis gas is separated into liquid crude methanol and unreacted gas in the methanol separator 20, and an output end of the methanol separator 20 is connected to the input end of the second compressor 12 to return most of the unreacted gas for re-reaction, and the output end is also connected to the pressure swing adsorption tower 22, and a small amount of unreacted gas is transported to the pressure swing adsorption tower 22 for purification by pressure swing adsorption; the pressure swing adsorption tower 22 is filled with adsorption particles, the input end is connected to the methanol separator 20, and the output end is respectively connected to the second compressor 12 and the steam utilization unit. The steam boiler 13 is connected to enrich the methane in the unreacted gas. The methane content in the methanogenic gas is about 59.8 vol%. This part of the methane-rich gas is intended to be sent to the steam boiler for utilization. The desorbed gas and hydrogen are separated at the rear end. The hydrogen is transported to the second compressor 12, and the desorbed gas is transported to the steam boiler 13 of the steam utilization unit for reuse. The other output end of the methanol separator 20 is connected to the flash evaporator 21 for outputting liquid crude methanol; the flash evaporator 21 removes the dissolved gas in the liquid crude methanol, and then transports the methanol to the three-tower distillation tower group 10, and its output end is also connected to the steam boiler 13 of the steam utilization unit, and the flash gas separated by the flash evaporator 21 is transported to the steam boiler 13 of the steam utilization unit for reuse.

[0065] In some embodiments of the present invention, the steam utilization unit includes a steam boiler 13, which is connected to the dust removal unit (high-temperature dust collector 4) and the methanol synthesis unit (methanol separator 20 and flash evaporator 21), and is used to receive part of the crude synthesis gas, desorption gas and flash gas and produce steam. The output end of the steam boiler 13 is connected to both the impurity removal unit and the methanol synthesis unit, specifically, it is connected to the second compressor 12 and the first compressor 11, and is used to provide the steam required for driving the second compressor 12 and the first compressor 11.

[0066] Preferably, the steam boiler 13 adopts low nitrogen oxide combustion technology, and the combustion conditions can be controlled to reduce the NOx concentration in the combustion exhaust gas.

[0067] Preferably, the steam utilization unit also includes a waste heat recovery device 16, which is connected between the pure oxygen converter 5 and the impurity removal unit. Since the temperature of the gas treated by the pure oxygen converter 5 is above 1000°C, the temperature is very high. The heat can be recovered and utilized through the waste heat recovery device 16 to produce steam. The produced steam is used to be transported to the compressor as a driving power source, saving electric energy.

[0068] A process for preparing methanol from biomass comprises the following steps:

[0069] S1. Reacting biomass raw materials, water vapor and oxygen to produce crude synthesis gas.

[0070] In some embodiments of the present invention, the hourly addition ratio of the biomass raw material, water vapor and oxygen is (3.5-4)t: (600-1000)Nm 3 :(600~1000)Kg.

[0071] In some embodiments of the present invention, the above-mentioned crude synthesis gas synthesis temperature is 600-900°C, and can be 700°C, 750°C, 800°C, 850°C, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0072] When the temperature is 600-900°C, the reaction conversion efficiency is high and the methanol synthesis effect is good.

[0073] In some embodiments of the present invention, the particle size of the biomass raw material is ≤100 mm, and the water content of the biomass raw material is ≤30%.

[0074] After research, the inventors found that when the particle size of the biomass raw material is within 100 mm, there will be a lower pressure drop and a higher gas-solid reaction rate, and problems such as blockage can be avoided.

[0075] In the prior art, conventional methods require that the moisture content of biomass raw materials be less than 10%. This is because low moisture content leads to high calorific value of gas after gasification, which facilitates subsequent reactions. Otherwise, additional heating is required, which increases investment and operating costs. However, the process combined with the above-mentioned system can reduce the requirements for the moisture content of biomass raw materials and increase the moisture content to less than or equal to 30%, which can also meet the processing requirements and reduce the processing costs.

[0076] S2. After the raw synthesis gas is dusted, it is converted into pure oxygen to obtain high-temperature gas.

[0077] In some embodiments of the present invention, the pure oxygen conversion treatment temperature is 1000-1500°C, including but not limited to 1100°C, 1200°C, 1300°C, 1400°C, etc.

[0078] The pure oxygen conversion at this temperature can fully crack the impurities such as methane and tar in the raw synthesis gas, and can enhance the gasification of fly ash to produce high-temperature gas without tar and with low methane content.

[0079] Preferably, the dedusting of the crude synthesis gas is specifically performed by passing the gas through three stages of dedusting (coarse separator 2, fine ash separator 3 and high-temperature dust collector 4). The first stage separates the unreacted large particles in the crude synthesis gas and returns them to the gasifier for reuse. The second stage removes a large amount of small fly ash particles in the crude synthesis gas. The third stage removes a small amount of small fly ash particles in the crude synthesis gas. Gradient dedusting is performed to ensure the cleanliness of the gas and facilitate the subsequent pure oxygen conversion.

[0080] Preferably, the pure oxygen conversion treatment temperature is 1200° C. At this temperature, the methane and tar contents are lower, the gas quality is better, and there are fewer impurities.

[0081] S3, removing impurities from the high temperature gas, reacting it, and obtaining a mixed gas.

[0082] Preferably, the impurity removal is to sequentially subject the high temperature gas to water washing, conversion desulfurization and decarbonization treatment, and in the water washing step, the gas is further subjected to dust removal and dechlorination by spray water washing to reduce the dust content to ≤2mg / Nm 3 , and remove chlorine from the crude synthesis gas at the same time; in the shift desulfurization step, the gas is first heated to 240-260°C, including but not limited to 245°C, 250°C, and 250°C. At this temperature, the gas components react with oxygen, and the elemental oxygen is converted into compounds. Long-chain hydrocarbons can be reformed and converted into short-chain hydrocarbons, or directly oxidized and burned, thereby removing oxygen and high hydrocarbons contained in the synthesis gas, and then reacting at 200-300°C under the action of a Co-Mo catalyst, including but not limited to 255°C, 260°C, and 270°C. 270℃, using isothermal conversion process (heat exchange tubes are set in the reactor to remove the heat generated by the reaction in time to maintain a stable bed temperature), carbon monoxide and water are converted into hydrogen and carbon dioxide, and organic sulfur is converted into hydrogen sulfide; in the decarbonization step, the gas is first cooled to 30-40℃, and then washed with low-temperature methanol at -35℃ to -60℃ to remove part of the carbon dioxide, all the sulfides, water and other impurities such as CO2, H2S and COS in the gas, and a mixed gas with a hydrogen-carbon ratio of 2 to 2.2 is obtained.

[0083] Since the solubility of H2S in methanol is 6.1 times that of CO2 at -30°C, H2S can be selectively removed. Low-temperature methanol washing causes almost no loss of carbon monoxide (yield ≥ 99.5%) and hydrogen (yield ≥ 99.9%) in the synthesis gas, and at the same time, the requirement for the carbon dioxide content in the synthesis gas is not high.

[0084] S4, reacting the mixed gas to obtain methanol, and then distilling it to obtain the finished product.

[0085] Preferably, the reaction conditions of the mixed gas are 200-300° C. and 5-8 MPaG.

[0086] Example 1

[0087] A process for preparing methanol from biomass, referring to Figures 1-2 , combined with a biomass-to-methanol system, the preparation includes the following steps:

[0088] A biomass raw material (particle size ≤ 100 mm, water content ≤ 30%), water vapor and oxygen are introduced into a fluidized bed gasifier 1, and reacted at 700° C. to produce a crude synthesis gas;

[0089] The crude synthesis gas is sequentially sent to the crude separator 2, the fine ash separator 3 and the high-temperature dust collector 4 for dust removal, and then sent to the pure oxygen conversion furnace 5 for pure oxygen conversion treatment at 1000°C to obtain high-temperature gas;

[0090] The high-temperature gas first passes through a water scrubber 6, and then is heated to 230°C in a shift desulfurization device 7 to remove oxygen and high hydrocarbons contained in the synthesis gas, and then reacts under the action of a Co-Mo catalyst at 200°C in the shift desulfurization device 7, and then the gas is cooled to 30°C in a low-temperature methanol scrubber 8, and washed with low-temperature methanol at -35°C to obtain a mixed gas with a hydrogen-to-carbon ratio of 2;

[0091] The mixed gas is input into the methanol synthesis tower 9, reacted at 220°C and 5MPaG to obtain methanol, and then distilled by the three-tower distillation tower group 10 to obtain the finished product.

[0092] Example 2

[0093] A process for preparing methanol from biomass, referring to Figures 1-2 , combined with a biomass-to-methanol system, the preparation includes the following steps:

[0094] A biomass raw material (particle size ≤ 100 mm, the water content of the biomass raw material ≤ 30%), water vapor and oxygen are introduced into a fluidized bed gasifier 1, and reacted at 680° C. to produce a crude synthesis gas;

[0095] The crude synthesis gas is sequentially sent to the crude separator 2, the fine ash separator 3 and the high-temperature dust collector 4 for dust removal, and then sent to the pure oxygen conversion furnace 5 for pure oxygen conversion treatment at 1200°C to obtain high-temperature gas;

[0096] The high-temperature gas first passes through a water scrubber 6, and then is heated to 250°C in a shift desulfurization device 7 to remove oxygen and high hydrocarbons contained in the synthesis gas, and then reacts under the action of a Co-Mo catalyst at 240°C in the shift desulfurization device 7, and then the gas is cooled to 33°C in a low-temperature methanol scrubber 8, and washed with low-temperature methanol at -45°C to obtain a mixed gas with a hydrogen-to-carbon ratio of 2.1;

[0097] The mixed gas is input into the methanol synthesis tower 9, reacted at 240°C and 6MPaG to obtain methanol, and then distilled by the three-tower distillation tower group 10 to obtain the finished product.

[0098] Example 3

[0099] A process for preparing methanol from biomass, referring to Figures 1-2 , combined with a biomass-to-methanol system, the preparation includes the following steps:

[0100] A biomass raw material (particle size ≤ 100 mm, water content ≤ 30%), water vapor and oxygen are introduced into a fluidized bed gasifier 1, and reacted at 900° C. to produce a crude synthesis gas;

[0101] The crude synthesis gas is sequentially sent to the crude separator 2, the fine ash separator 3 and the high-temperature dust collector 4 for dust removal, and then sent to the pure oxygen conversion furnace 5 for pure oxygen conversion treatment at 1400°C to obtain high-temperature gas;

[0102] The high-temperature gas first passes through a water scrubber 6, and then is heated to 260°C in a shift desulfurization device 7 to remove oxygen and high hydrocarbons contained in the synthesis gas, and then reacts under the action of a Co-Mo catalyst at 250°C in the shift desulfurization device 7, and then the gas is cooled to 40°C in a low-temperature methanol scrubber 8, and washed with low-temperature methanol at -35°C to obtain a mixed gas with a hydrogen-to-carbon ratio of 2.2;

[0103] The mixed gas is input into the methanol synthesis tower 9, reacted at 260°C and 7MPaG to obtain methanol, and then distilled by the three-tower distillation tower group 10 to obtain the finished product.

[0104] Comparative Example 1

[0105] This comparative example is a conventional methanol preparation process, comprising the following steps:

[0106] Take coal as raw material to produce methanol as an example:

[0107] 1. In a fixed bed or fluidized bed gasifier, coal reacts with a gasifying agent (air + steam) to produce crude synthesis gas;

[0108] 2. After the crude synthesis gas is converted, transformed, purified (dust removal, desulfurization, decarbonization) and other processes, it is pressurized and heated to meet the process conditions required for methanol synthesis and then sent to the methanol synthesis tower;

[0109] 3. In the methanol synthesis tower, carbon monoxide, carbon dioxide and hydrogen react under the action of catalyst to produce crude methanol;

[0110] 4. After the crude methanol is purified by distillation, the product methanol is obtained.

[0111] Comparative Example 2

[0112] This comparative example is substantially the same as Example 2, except that the hydrogen-to-carbon ratio is 2.5.

[0113] Experimental Example 1

[0114] The finished methanol of Examples 1 to 3 and Comparative Examples 1 to 2 was tested with reference to the IMPCA Methanol Reference Standard, and the results are shown in Table 1.

[0115] Table 1

[0116]

[0117] From observing Table 1, it can be seen that the methanol tar content obtained by the process of the present invention is low and the carbon conversion rate is high.

[0118] Experimental Example 2

[0119] When the biomass-to-methanol system is producing methanol, it is tested and various values ​​are obtained as shown in Table 2. The following parameters are calculated based on a single ton of green methanol.

[0120] Table 2

[0121]

[0122] Referring to Table 2, it can be seen that the system of the embodiment of the present invention not only has high carbon conversion rate, high heat load, good temperature control, but also has excellent ability to process biomass of different properties, low tar content in the synthesis gas, and is suitable for large-scale methanol production projects.

[0123] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A system for preparing methanol from biomass, It is characterized in that include A raw material gasification unit is used to heat the raw material at high temperature to make the raw material react at high temperature to produce a crude synthesis gas; A dust removal unit, connected to the raw material gasification unit, for removing dust from the raw synthesis gas; A pure oxygen conversion unit, connected to the dust removal unit, is used to perform high-temperature non-catalytic oxidation treatment on the raw synthesis gas and recover and utilize the heat; An impurity removal unit, connected to the pure oxygen conversion unit, is used to perform dechlorination, desulfurization and decarbonization on the raw synthesis gas after oxidation treatment; A methanol synthesis unit is connected to the impurity removal unit to synthesize methanol from the synthesis gas treated with dechlorination, desulfurization and decarbonization; The steam utilization unit has an input end connected to the dust removal unit and the methanol synthesis unit for producing steam, and an output end connected to the methanol synthesis unit and the impurity removal unit.

2. A system for preparing methanol from biomass according to claim 1, It is characterized in that The raw material gasification unit includes a fluidized bed gasifier, and the fluidized bed gasifier is used to make raw materials react at high temperature to produce raw synthesis gas.

3. A system for preparing methanol from biomass according to claim 1, It is characterized in that The dust removal unit includes a coarse separator, a fine ash separator and a high-temperature dust collector. The rough separator is connected to the gas outlet of the raw material gasification unit and is used to perform preliminary separation of the rough synthesis gas; The air inlet end of the fine ash separator is connected to the air outlet end of the rough separator, and is used to separate the fly ash from the initially separated rough synthesis gas; The air inlet end of the high-temperature dust collector is connected to the air outlet end of the fine ash separator for further dust removal of the raw synthesis gas. The air outlet end of the high-temperature dust collector is connected to the pure oxygen conversion unit.

4. A system for preparing methanol from biomass according to claim 1, It is characterized in that The pure oxygen conversion unit comprises a pure oxygen conversion furnace, which is used for carrying out a high-temperature non-catalytic partial oxidation reaction of methane and tar in the raw synthesis gas with oxygen.

5. The system for preparing methanol from biomass according to claim 1, It is characterized in that The impurity removal unit includes a water scrubber, a first compressor, a shift desulfurization device and a low-temperature methanol scrubber. The water washing tower is connected to the output end of the pure oxygen conversion unit and is used for water washing to remove chlorine and dust from the crude synthesis gas; The first compressor is connected to the gas outlet of the water scrubber and is used to pressurize the crude synthesis gas; The shift desulfurization device is connected to the outlet of the first compressor and is used to desulfurize the raw synthesis gas and convert CO and water into H 2 and CO 2 ; The low-temperature methanol washing tower is connected to the gas outlet end of the conversion desulfurization device and is used to remove impurities from the crude synthesis gas. The gas outlet end of the low-temperature methanol washing tower is connected to the methanol synthesis unit.

6. A system for preparing methanol from biomass according to claim 1, It is characterized in that The methanol synthesis unit comprises a second compressor, a methanol synthesis tower and a three-tower distillation tower group; The second compressor is connected to the impurity removal unit and the steam utilization unit, and is used to receive and compress the synthesis gas output by the impurity removal unit, and is used to work with the steam input by the steam utilization unit; The methanol synthesis tower is connected to the second compressor and is used to synthesize methanol; The input of the three-tower distillation tower group is connected to the output end of the methanol synthesis tower for distilling and purifying methanol.

7. The system for preparing methanol from biomass according to claim 1, It is characterized in that The steam utilization unit includes a steam boiler, The input end of the steam boiler is connected to the dust removal unit and the methanol synthesis unit, and is used to receive the crude synthesis gas output by the dust removal unit, the desorbed gas and flash gas output by the methanol synthesis unit and produce steam. The output end of the steam boiler is connected to both the impurity removal unit and the methanol synthesis unit, and is used to provide the steam required for driving the impurity removal unit and the methanol synthesis unit.

8. A process for preparing methanol from biomass, It is characterized in that The steps include: reacting biomass raw materials with water vapor and oxygen to produce a crude synthesis gas; After the raw synthesis gas is dusted, it is converted into pure oxygen to obtain high-temperature gas; After removing impurities from the high temperature gas, reacting it, a mixed gas is obtained; The mixed gas is reacted to obtain methanol, which is then distilled to obtain the finished product.

9. A process for preparing methanol from biomass according to claim 8, It is characterized in that The particle size of the biomass raw material is ≤100mm, and the water content of the biomass raw material is ≤30%; the hourly addition ratio of the biomass raw material, water vapor and oxygen is (3.5-4)t:(600-1000)Nm 3 :(600~1000)Kg.

10. The process for preparing methanol from biomass according to claim 8, It is characterized in that The synthesis temperature of the crude synthesis gas is 600-900°C; the pure oxygen conversion treatment temperature is 1000-1500°C; after the high-temperature gas is decontaminated, it reacts at 200-300°C under the action of a Co-Mo catalyst to obtain a mixed gas with a hydrogen-to-carbon ratio of 2-2.2; the reaction conditions of the mixed gas are 200-300°C and 5-8MPaG.

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