System and method for preparing methanol from biomass

Abstract

The invention relates to a system and a method for preparing methanol from biomass. The system for preparing methanol from biomass comprises at least one pyrolysis carbonization unit and a gasification synthesis unit; the pyrolysis carbonization unit comprises a pyrolysis reactor; the gasification synthesis unit comprises a second gasification reactor, a reforming reactor and a synthesis reactor; the preparation method of methanol comprises the following steps: S1, carrying out pyrolysis carbonization on primarily crushed biomass in a pyrolysis reactor to obtain biochar and pyrolysis gas; s2, the charcoal, oxygen and steam are subjected to a pressurized gasification reaction in the second gasification reactor, and second gasified gas is obtained; s3, the second gasified gas is subjected to a reforming reaction in the reforming reactor, and synthesis gas is obtained; and S4, carrying out a synthesis reaction on the synthesis gas in the synthesis reactor. The methanol production process can be amplified on a large scale, and the production cost is reduced.

Description

Technical Field

[0001] The invention relates to a biomass-to-methanol system and method. Background Art

[0002] Carbon emissions from international shipping account for about 2.4% of the world's total anthropogenic carbon emissions, making it one of the key areas of global emission reduction. The accelerated decarbonization process in the shipping industry has sent a strong signal of demand for green alternative marine fuels. Green methanol is liquid at room temperature and does not require the installation of large gas tanks. The cost of ship construction is controllable. At the same time, the technology of methanol fuel power equipment is mature, making it a new favorite alternative fuel in the shipping industry. However, the current global production of green methanol is very limited. According to data from the Global Methanol Industry Association, the current global production capacity of green methanol is only more than 800,000 tons, which cannot meet the growing demand for alternative shipping fuels.

[0003] The current mainstream route is to use biomass as raw material to produce green methanol through gasification synthesis process. However, the bulk density of biomass is low, and the bulk density after baling is only 130 kg / m 3 , resulting in high raw material storage and transportation costs; limited by the storage and transportation radius of biomass raw materials, the scale of biomass gasification synthesis to produce methanol is much smaller than that of coal gasification. Generally speaking, the economically reasonable biomass collection radius is 50 km, and the corresponding biomass mass is 300,000 tons / year. Therefore, biomass gasification synthesis to produce methanol cannot reduce costs through scale, and the unit investment and operating costs are relatively high; in addition, large-scale biomass gasification technology is not yet mature, and the conventional biomass fluidized bed gasification technology produces a high tar content in the synthesis gas (tens of grams / Nm 3 ), complex gasification gas purification process is required to meet the subsequent synthesis process (1 ppm), and the gasification gas purification cost is high. These factors ultimately lead to a high cost for green methanol production.

[0004] CN102557869A discloses a method for preparing methanol fuel from biochar, which uses biochar as a carbon source and water vapor as an activator, prepares synthesis gas (H2 / CO) through the decomposition reaction of biochar water vapor; adjusts the ratio of hydrogen and carbon in the synthesis gas through a water gas shift reaction and a calcium hydroxide suspension absorption method; and uses a copper-zinc-aluminum oxide ternary catalyst to catalytically convert the synthesis gas into methanol fuel. The problem with this solution is that it uses water vapor as a gasification agent alone, and requires the outside world to provide the heat required for the gasification reaction; the reaction temperature is only 600-800°C, the biochar conversion rate is low, and the tar content in the generated gas is high, which ultimately leads to a low methanol yield and high subsequent purification costs.

[0005] CN115125036A discloses a method and system for preparing methanol from biomass, the method comprising: (1) hydrothermally treating biomass raw materials to obtain hydrothermal biomass slurry; (2) subjecting hydrothermal biomass to biomass gasification reaction to generate biomass gasification reaction mixed gas containing CO and H2; (3) using CO and H2 as raw materials to carry out methanol synthesis reaction to prepare methanol; wherein the treatment atmosphere during the hydrothermal treatment process includes CO2, and the gasifying agent in the biomass gasification reaction includes CO2 and water vapor. The problem with this scheme is that CO2 and water vapor are used as gasifying agents, and external biomass combustion flue gas is required to provide heat required for gasification, and finally impurities such as N2 are additionally introduced into the gasified gas, resulting in high subsequent purification costs; hydrothermal biochar obtained by hydrothermal process cannot be produced continuously, and it is difficult to scale up, and the operating cost is high; the gasification temperature is low (900°C), the tar content is high, and the purification cost is high; and the hydrothermal-gasification process is carried out in the same site, and the storage and transportation cost of biomass raw materials required for scale up is high.

[0006] CN116814300A provides a high-efficiency biomass gasification system for producing green methanol, which includes: a solar and wind power generation electrolysis water subsystem, a biomass gasification subsystem, a synthesis gas conversion subsystem, and a methanol synthesis subsystem. The oxygen produced by the solar and wind power generation electrolysis water subsystem is used as a gasification medium of the biomass gasification subsystem to synthesize a biomass synthesis gas with a higher calorific value, and the biomass synthesis gas is sent to the methanol synthesis subsystem to synthesize methanol after passing through the synthesis gas conversion subsystem. The problem with this scheme is that it uses biomass as raw material, and the required biological mass after large-scale amplification is large, and the raw material storage and transportation cost is high; the gasification reaction temperature is low (850°C), the gasification gas tar content is high, and the purification cost is high; in addition, in order to meet the demand for green methanol, the production process needs to use green electricity, and the green electricity has large volatility, while the gasification synthesis process requires a stable power supply, the two do not match, and electrochemical energy storage is required, and the operating cost is high. Summary of the invention

[0007] The present invention provides a biomass-to-methanol system and method to solve the problems of low gasification temperature, high tar content in gasified gas, high production cost and unsuitability for large-scale production when preparing methanol from biomass in the prior art. The system can scale up the methanol production process and reduce production costs.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a biomass-to-methanol system, which includes at least one pyrolysis carbonization unit and a gasification synthesis unit;

[0010] The pyrolysis carbonization unit comprises a pyrolysis reactor; the pyrolysis reactor is provided with a second biomass feed port, a first biochar discharge port and a first pyrolysis gas discharge port;

[0011] The gasification synthesis unit includes a second gasification reactor, a reforming reactor and a synthesis reactor;

[0012] The second gasification reactor is provided with a biochar feed port, an oxygen feed port, a first steam feed port, a second gasification gas discharge port and a slag discharge port;

[0013] The reforming reactor is provided with a second gasification gas feed port, a second steam feed port and a first synthesis gas discharge port; the synthesis reactor is provided with a first synthesis gas feed port and a methanol discharge port;

[0014] The second gasification gas outlet is connected to the second gasification gas feed inlet, and the first synthesis gas outlet is connected to the first synthesis gas feed inlet.

[0015] In the present invention, the first biochar discharge port can be connected to the biochar feed port. The above-mentioned "connection" can be directly connected through components, or can be formed as a "soft connection" by means of logistics transportation.

[0016] In the present invention, the pyrolysis carbonization unit may further include a dryer, which is provided with a first biomass feed port, a biomass discharge port, a first flue gas feed port and a first flue gas discharge port; the first biomass discharge port is connected to the second biomass feed port, and the first pyrolysis gas discharge port is connected to the first flue gas feed port.

[0017] Wherein, a jacket may be further provided outside the pyrolysis reactor, and the jacket is provided with a first pyrolysis gas inlet and a first flue gas outlet; the first flue gas outlet is connected to the first flue gas feed inlet, and the first pyrolysis gas outlet is connected to the first pyrolysis gas inlet.

[0018] In the present invention, the pyrolysis carbonization unit may further include a cyclone dust collector, the cyclone dust collector is provided with a first pyrolysis gas feed port, a second biochar discharge port and a second pyrolysis gas discharge port; the first pyrolysis gas discharge port is connected to the first pyrolysis gas feed port, and the second biochar discharge port is connected to the biochar feed port. Preferably, the second pyrolysis gas discharge port is connected to the first pyrolysis gas inlet.

[0019] In the present invention, the pyrolysis carbonization unit may also include a first gasification reactor and a first internal combustion engine, the first gasification reactor is provided with a second pyrolysis gas feed port, an air feed port and a first gasification gas outlet port; the first internal combustion engine is provided with a first gasification gas feed port and a first flue gas outlet port; the second pyrolysis gas feed port is connected to the first pyrolysis gas outlet port, and the first gasification gas outlet port is connected to the first gasification gas feed port. Preferably, the second pyrolysis gas feed port is connected to the second pyrolysis gas outlet port. Preferably, the dryer also includes a second flue gas feed port, and the first flue gas outlet port is connected to the second flue gas feed port.

[0020] Wherein, a tar removal device may be further provided between the first gasification gas outlet and the first gasification gas feed port. The tar removal device may include a heat exchanger and an electrostatic precipitator connected in sequence, the feed port of the heat exchanger is connected to the first gasification gas outlet, and the discharge port of the electrostatic precipitator is connected to the first gasification gas feed port.

[0021] In the present invention, the gasification synthesis unit may further include a ball mill, the feed port of the ball mill is connected to the first biochar discharge port, and the discharge port of the ball mill is connected to the biochar feed port. Preferably, the feed port of the ball mill is connected to the second biochar discharge port.

[0022] In the present invention, the gasification synthesis unit may also include a second waste heat boiler and a second internal combustion engine, the second waste heat boiler is provided with a second boiler jacket outside; the second waste heat boiler is provided with a water injection port and a second steam outlet; the second boiler jacket is provided with a second flue gas inlet and a second flue gas outlet; the second internal combustion engine is provided with a second flue gas outlet and a second synthesis gas feed port; the second steam outlet is connected to the first steam feed port and the second steam feed port, the second flue gas outlet is connected to the second flue gas inlet, and the second synthesis gas feed port is connected to the first synthesis gas outlet.

[0023] Wherein, the gasification synthesis unit may also include a first waste heat boiler, a first boiler jacket is provided outside the first waste heat boiler, the first waste heat boiler is provided with a first steam outlet and a second steam feed port, the first boiler jacket is provided with a second gasification gas inlet and a second gasification gas outlet; the first steam outlet is connected to the first steam feed port and the second steam feed port, the second gasification gas inlet is connected to the second gasification gas outlet, and the second gasification gas outlet is connected to the second gasification gas feed port.

[0024] In the present invention, the gasification synthesis unit may further include a synthesis gas purifier, and the synthesis gas purifier is provided with a third synthesis gas feed port, a third synthesis gas discharge port and a residual gas discharge port; the third synthesis gas feed port is connected to the first synthesis gas discharge port, and the third synthesis gas discharge port is connected to the first synthesis gas feed port. Preferably, the third synthesis gas discharge port is connected to the second synthesis gas feed port. Preferably, the residual gas discharge port is connected to a carbon dioxide purification reactor. Preferably, the residual gas discharge port is connected to a connecting port, and the connecting port is provided on a connecting pipe between the discharge port of the ball mill and the biochar feed port. The structure of the synthesis gas purifier is conventionally selected in the art, and a filter device and / or a gas washing absorption liquid may be provided inside. The filter device may be a ceramic filter dust removal device. The gas washing absorption liquid may be methanol or N-methyldiethanolamine (MDEA).

[0025] In the present invention, the gasification synthesis unit may further include a distillation tower, and a feed inlet of the distillation tower is connected to the methanol discharge outlet.

[0026] In the present invention, the oxygen feed port can be connected to an oxygen generator.

[0027] In a second aspect, the present invention provides a method for preparing methanol, which uses the biomass-to-methanol system as described above, and comprises the following steps:

[0028] S1, pyrolyzing and carbonizing the initially crushed biomass in the pyrolysis reactor to obtain biochar and pyrolysis gas;

[0029] S2, subjecting the biochar to a pressurized gasification reaction with oxygen and steam in the second gasification reactor to obtain a second gasification gas;

[0030] S3, subjecting the second gasified gas to a reforming reaction in the reforming reactor to obtain synthesis gas;

[0031] S4, subjecting the synthesis gas to a synthesis reaction in the synthesis reactor.

[0032] In the present invention, the biomass to methanol system may include the dryer. In step S1, the biomass is dried in the dryer and then subjected to low-temperature pyrolysis and carbonization in the pyrolysis reactor.

[0033] The drying temperature may be 200-400° C. That is, the temperature of the drying medium used during drying is 200-400° C.

[0034] In the present invention, in step S1, the processing amount of the biomass in the pyrolysis reactor may be ≤300,000 tons / year, for example, 300,000 tons / year.

[0035] In the present invention, in step S1, the temperature of the pyrolysis carbonization may be 275-350°C, for example, 300°C.

[0036] In the present invention, in step S1, the residence time of the pyrolysis carbonization may be 0.5-1.5 h.

[0037] In a specific embodiment of the present invention, in step S1, after the pyrolysis gas passes through the cyclone dust collector, the carried biochar falls off and then partially enters the jacket outside the pyrolysis reactor to form flue gas.

[0038] In the present invention, the biomass to methanol system may include the first gasification reactor and the first internal combustion engine. In step S1, part of the pyrolysis gas and air undergo a gasification reaction in the first gasification reactor, and the generated first gasification gas is burned in the first internal combustion engine to produce flue gas.

[0039] The temperature of the gasification reaction may be 700-900°C, for example 850°C.

[0040] The pressure of the gasification reaction may be -2000~2000 Pa, for example -200 Pa.

[0041] The residence time of the gasification reaction may be 1-40 s, for example 2 s.

[0042] The air equivalence ratio of the gasification reaction may be (0.25-0.4): 1. The air equivalence ratio means the ratio of the amount of air actually provided to the amount of air required for complete combustion.

[0043] The pyrolysis gas entering the first gasification reactor for gasification reaction accounts for 50%-80%, for example, 70%, of all the generated pyrolysis gas.

[0044] In the present invention, in step S2, the temperature of the pressurized gasification reaction may be 1200-1600°C, for example, 1300°C.

[0045] In the present invention, in step S2, the pressure of the pressurized gasification reaction may be 2-8 MPa, for example, 5 MPa.

[0046] In the present invention, in step S2, the residence time of the pressurized gasification reaction may be 1-30 s, for example, 2 s.

[0047] In the present invention, in step S2, in the pressurized gasification reaction, the mass ratio of biochar, oxygen and steam can be 1: (0.7-1.4): (0.02-0.25).

[0048] In the present invention, in step S2, the second gasification reactor can adopt a liquid slagging form, and the generated second gasification gas has a low tar content and does not need to be detarred.

[0049] In the present invention, in step S3, conventionally, the reforming reactor is loaded with a catalyst for reforming reaction, such as an iron catalyst.

[0050] In the present invention, in step S3, the temperature of the reforming reaction may be 200-250°C, for example 210°C.

[0051] In the present invention, in step S3, the pressure of the reforming reaction may be 2-8 MPa, for example, 5 MPa.

[0052] In the present invention, in step S3, the residence time of the reforming reaction may be 0.5-30 s, for example 3 s.

[0053] In the present invention, in step S3, in the reforming reaction, the volume ratio of the second gasification gas to steam may be 1:(0.02-0.25), for example, 1:0.08.

[0054] In the present invention, the biomass-to-methanol system may include the second waste heat boiler and the second internal combustion engine. In step S3, part of the synthesis gas is burned in the second internal combustion engine to produce flue gas for heating the second waste heat boiler.

[0055] The gasification gas entering the second internal combustion engine accounts for 5%-25%, for example, 10%, of all the gasification gas produced.

[0056] In a specific embodiment of the present invention, in step S3, the syngas passes through the syngas purifier to remove impurities such as CO2, H2S and dust, and 10% of the purified syngas enters the second internal combustion engine for combustion and work, forming flue gas for heating the second waste heat boiler. The syngas purifier may include dust removal and deacidification and gas washing parts. The dust removal may be wet dust removal or ceramic filtration dust removal. The deacidification and gas washing may be washed with low-temperature methanol or N-methyldiethanolamine (MDEA).

[0057] In the present invention, in step S4, conventionally, the synthesis reactor is filled with a catalyst for performing a synthesis reaction, such as a copper-based catalyst Cu / ZnO / Al2O3.

[0058] In the present invention, in step S4, the temperature of the synthesis reaction may be 200-300°C, for example 250°C.

[0059] In the present invention, in step S4, the pressure of the synthesis reaction may be 2-8 MPa, for example, 5 MPa.

[0060] In the present invention, in step S4, the residence time of the synthesis reaction may be 0.5-20 s, for example 2 s.

[0061] In the present invention, the biomass-to-methanol system may include the distillation tower, and in step S4, crude methanol produced by the reaction in the synthesis reactor is distilled by the distillation tower to obtain methanol. The distillation is performed according to conventional process conditions in the art.

[0062] In a specific embodiment of the present invention, the pressure of the pressurized gasification reaction, the pressure of the reforming reaction and the pressure of the synthesis reaction are equal, preferably all 5 MPa.

[0063] Without violating the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0064] The reagents and raw materials used in the present invention are commercially available.

[0065] The positive and progressive effects of the present invention are:

[0066] (1) The biomass-to-methanol system of the present invention is divided into a distributed pyrolysis carbonization unit and a centralized gasification synthesis unit. With biomass as raw material, biochar is first obtained through distributed carbonization, which can greatly reduce the storage and transportation costs of renewable carbon. With biochar as the raw material for gasification synthesis, the generated gasification gas is tar-free and the subsequent purification cost is low.

[0067] (2) The biomass-to-methanol system of the present invention can couple biomass gasification power generation, pyrolysis carbonization and gasification synthesis to provide a stable power supply for the biomass-to-green methanol process, overcoming the contradiction between the large volatility of wind power and photovoltaic power generation and the need for a stable power supply for the chemical system;

[0068] (3) The biomass-to-methanol method of the present invention uses biochar as the gasification synthesis raw material. Since the physical and chemical properties of biochar are similar to those of coal and the grindability index is high, a high-temperature, pressurized, liquid slag removal gasification process can be used. The generated gasification gas is tar-free and the subsequent purification cost is low.

[0069] (4) The biomass-to-methanol method of the present invention adopts pressurized gasification, and the pressure is the same as the subsequent reforming and synthesis reaction pressure, which can omit the compression process; at the same time, the process is easy to scale up to achieve large-scale preparation of green methanol, and can also produce high-value CO2 products, further reducing the production cost of green methanol. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 This is a schematic diagram of the pyrolysis carbonization unit in Example 1;

[0071] Figure 2 This is a schematic diagram of the gasification synthesis unit in Example 1;

[0072] As shown in the figure, the symbols are: dryer 1, pyrolysis reactor 2, cyclone dust collector 3, first gasification reactor 4, heat exchanger 5, electrostatic precipitator 6, first internal combustion engine 7, ball mill 8, second gasification reactor 9, first waste heat boiler 10, reforming reactor 11, synthesis gas purifier 12, synthesis reactor 13, distillation tower 14, second internal combustion engine 15, second waste heat boiler 16, carbon dioxide purification reactor 17, oxygen generator 18. DETAILED DESCRIPTION

[0073] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0074] Example 1

[0075] A biomass to methanol system, such as Figure 1-2 , which includes 9 distributed pyrolysis carbonization units and 1 centralized gasification synthesis unit; the pyrolysis carbonization unit includes a dryer 1, a pyrolysis reactor 2, a cyclone dust collector 3, a first gasification reactor 4, a heat exchanger 5, an electrostatic precipitator 6 and a first internal combustion engine 7; the gasification synthesis unit includes a ball mill 8, a second gasification reactor 9, a first waste heat boiler 10, a reforming reactor 11, a synthesis gas purifier 12, a synthesis reactor 13, a distillation tower 14, a second internal combustion engine 15, a second waste heat boiler 16 and a carbon dioxide purification reactor 17.

[0076] In this embodiment, the dryer 1 is provided with a first biomass feed inlet, a biomass discharge port, a first flue gas feed inlet, a first flue gas discharge port and a second flue gas feed inlet; the pyrolysis reactor 2 is provided with a second biomass feed inlet, a first biochar discharge port and a first pyrolysis gas discharge port, and the pyrolysis reactor 2 is also provided with a jacket, and the jacket is provided with a first pyrolysis gas inlet and a first flue gas outlet; the cyclone dust collector 3 is provided with a first pyrolysis gas feed inlet, a second biochar discharge port and a second pyrolysis gas discharge port; the first gasification reactor 4 is provided with a second pyrolysis gas feed inlet, an air feed inlet and a first gasification gas discharge port; the first internal combustion engine 7 is provided with a first gasification gas feed inlet and a first flue gas discharge port.

[0077] In this embodiment, the first biomass outlet is connected to the second biomass feed port, the first flue gas outlet is connected to the first flue gas feed port, the second pyrolysis gas outlet is connected to the first pyrolysis gas inlet, the first pyrolysis gas outlet is connected to the first pyrolysis gas feed port, and the second pyrolysis gas feed port is connected to the second pyrolysis gas outlet. The feed port of the heat exchanger 5 is connected to the first gasification gas outlet, the outlet of the electrostatic precipitator 6 is connected to the first gasification gas feed port, and the first flue gas outlet is connected to the second flue gas feed port. The first biochar outlet and the second biochar outlet are connected to the feed port of the ball mill 8 through a logistics conveying method to form a soft connection.

[0078] In this embodiment, the second gasification reactor 9 is provided with a biochar feed port, an oxygen feed port, a first steam feed port, a second gasification gas outlet port and a slag outlet port; a connection port is provided on the connecting pipe between the outlet port of the ball mill 8 and the biochar feed port. The first waste heat boiler 10 is provided with a first boiler jacket, the first waste heat boiler 10 is provided with a first steam outlet port and a second steam feed port, and the first boiler jacket is provided with a second gasification gas inlet port and a second gasification gas outlet port; the reforming reactor 11 is provided with a second gasification gas feed port, a second steam feed port and a first synthesis gas outlet port; the synthesis gas purifier 12 is provided with a third synthesis gas feed port, a third synthesis gas outlet port and a residual gas outlet port; the synthesis reactor 13 is provided with a first synthesis gas feed port and a methanol outlet port; the second internal combustion engine 15 is provided with a second flue gas outlet port and a second synthesis gas feed port; the second waste heat boiler 16 is provided with a second boiler jacket; the second waste heat boiler 16 is provided with a water injection port and a second steam outlet port.

[0079] In this embodiment, the discharge port of the ball mill 8 is connected to the biochar feed port. The first steam discharge port is connected to the first steam feed port and the second steam feed port, the second gasification gas inlet is connected to the second gasification gas discharge port, the second gasification gas outlet is connected to the second gasification gas feed port, and the oxygen feed port is connected to the oxygen generator 18. The second steam discharge port is connected to the second steam feed port, and the second flue gas discharge port is connected to the second flue gas inlet. The third synthesis gas feed port is connected to the first synthesis gas discharge port, the third synthesis gas discharge port is connected to the first synthesis gas feed port, and the third synthesis gas discharge port is connected to the second synthesis gas feed port. The residual gas discharge port is connected to the carbon dioxide purification reactor 17, and the residual gas discharge port is connected to the connecting port. The feed port of the distillation tower 14 is connected to the methanol discharge port.

[0080] In this embodiment, in the distributed pyrolysis carbonization unit, the biomass raw material is initially crushed and then sent to the drum dryer 1 for drying using the waste heat of the flue gas. After drying, the biomass raw material is sent to the pyrolysis reactor 2 for low-temperature pyrolysis carbonization. After the pyrolysis gas is removed from the carried biochar by the cyclone dust collector 3, it is divided into two paths. One path is sent to the jacket of the pyrolysis reactor 2 to provide the required heat for low-temperature pyrolysis carbonization; the other path is sent to the first gasification reactor 4 to react with the gasification medium air to generate the first gasification gas. After the first gasification gas is removed from the tar, dust and other impurities by the shell and tube heat exchanger 5 and the electrostatic precipitator 6, it enters the first internal combustion engine 7 to generate electricity. The generated electricity is used for the system itself to maintain the power demand of the system. The flue gas generated by the first internal combustion engine 7 and the flue gas generated by the jacket of the pyrolysis reactor 2 are sent to the drum dryer 1 for biomass drying.

[0081] The biochar produced by the 9 distributed pyrolysis carbonization units is transported and aggregated to the centralized gasification synthesis unit for gasification synthesis. After the biochar is ball-milled by the ball mill 8, it is pneumatically transported by CO2 to the second gasification reactor 9, where it undergoes a gasification reaction with oxygen and water vapor. The generated second gasification gas is recovered by the first waste heat boiler 10, enters the reforming reactor 11 for syngas reforming, and then enters the syngas purifier 12. The syngas purifier 12 contains methanol, which is used to remove impurities such as CO2, H2S and dust. The CO2 gas containing a small amount of H2S impurities produced by the syngas purifier 12 is partially used for pneumatic transportation of biochar, and the rest is purified in the carbon dioxide purification reactor 17 to obtain a pure CO2 product. The syngas purified by the syngas purifier 12 is divided into two paths, one of which enters the methanol synthesis reactor 13 to produce crude methanol, and the crude methanol is refined by the methanol distillation tower 14 to produce green methanol; the other path is sent to the second internal combustion engine 15 to generate electricity, and the generated electricity is used for the system itself. The flue gas generated by the second internal combustion engine 15 enters the second waste heat boiler 16 to recover waste heat, and the generated steam enters the first waste heat boiler 10 to be further heated and then used as a gasification medium.

[0082] Example 2: Annual production of 500,000 tons of methanol

[0083] A method for producing methanol from biomass, using the biomass-to-methanol system in Example 1, the system consists of a centralized biochar gasification synthesis unit that processes 1.05 million tons of biochar annually and 9 distributed pyrolysis carbonization units that process 300,000 tons of biomass annually, and includes the following steps:

[0084] S1. The initially crushed biomass, straw, is dried in a dryer 1 with high-temperature flue gas at 300°C, and then pyrolyzed and carbonized in a pyrolysis reactor 2 to obtain biochar and pyrolysis gas; the temperature of each pyrolysis and carbonization is 300°C, and the residence time is 0.5 h. After the pyrolysis gas passes through the cyclone dust collector 3, the carried biochar is shed, and 30% of the pyrolysis gas enters the jacket outside the pyrolysis reactor 2 to form flue gas, which flows back to the dryer 1. The remaining part of the pyrolysis gas and air undergo gasification reaction in the first gasification reactor 4. The first gasification gas produced is burned in the first internal combustion engine 7 to produce flue gas, which flows back to the dryer 1. The temperature of the gasification reaction is 850°C, the pressure is -200 Pa, the residence time is 2 s, and the air equivalent ratio is 0.3: 1. 1 ton of biochar is produced for every 2.6 tons of biomass. The produced biochar can be concentrated to the biochar centralized gasification synthesis unit by transportation such as road and rail. The bulk density of biochar is about 500 kg / m 3 Based on a 50 km transportation radius, the transportation price of biochar is 84 yuan / ton, while the volume energy density of biomass is only 1 / 10 of that of biochar. Calculated at the same calorific value, the transportation cost of biomass with a 50 km transportation radius is as high as 840 yuan / ton.

[0085] S2. After the biochar is ball-milled in a ball mill 8, it is subjected to a pressurized gasification reaction with oxygen and steam in a second gasification reactor 9 to obtain a second gasification gas; the temperature of the pressurized gasification reaction is 1300°C, the pressure is 5 MPa, the residence time is 2 s, the mass ratio of biochar, oxygen and steam is 1: 0.8: 0.10, and the produced second gasification gas has a low tar content and does not require detarring.

[0086] S3. After heating the first waste heat boiler 10 with the second gasification gas, a reforming reaction is carried out in the reforming reactor 11. The catalyst is an iron catalyst to obtain synthesis gas. The temperature of the reforming reaction is 210°C, the pressure is 5 MPa, the residence time is 3 s, and the volume ratio of the second gasification gas to steam is 1: 0.08. The synthesis gas passes through the synthesis gas purifier 12, and after wet dust removal and low-temperature methanol washing coupled purification process, impurities such as CO2, H2S and dust are removed. 10% of the purified synthesis gas enters the second internal combustion engine 15 for combustion and work, forming flue gas for heating the second waste heat boiler 16 and providing steam to the first waste heat boiler 10. 3% of the CO2 gas containing a small amount of H2S impurities produced by the synthesis gas purifier 12 is used for pneumatic transportation of biochar, and the rest is purified in the carbon dioxide purification reactor 17. The purification reactor 17 can remove H2S by physical absorption through solid adsorbents such as activated carbon, zeolite or molecular sieve to obtain pure CO2 products.

[0087] S4. The other part of the purified synthesis gas is subjected to synthesis reaction in the synthesis reactor 13. The catalyst is a copper-based catalyst Cu / ZnO / Al2O3. The crude methanol produced is distilled by the distillation tower 14 to obtain green methanol. The temperature of the synthesis reaction is 250°C, the pressure is 5 MPa, and the residence time is 2 s. In the centralized gasification synthesis process of biochar, 1 ton of green methanol is produced for every 2.1 tons of biochar, that is, 1 ton of green methanol is produced for 5.4 tons of biomass.

[0088] In this embodiment, through scale-based cost reduction, the cost of preparing green methanol is approximately RMB 3,000 per ton.

[0089] Comparative Example 1: Annual production of 100,000 tons of methanol

[0090] A method for producing methanol from biomass. The biomass-to-methanol system is provided with a biomass gasification synthesis station capable of processing 400,000 tons of biomass annually.

[0091] After being crushed, dried and granulated, the biomass is sent to a circulating fluidized bed for gasification reaction. The gasification temperature is 850°C and the tar content produced is 10-20 g / Nm 3 .

[0092] After the waste heat of the gasification gas is recovered, it passes through the purification system and undergoes the processes of water washing for dust removal - organic solvent washing for decoking - wet H2S removal - carbon capture for CO2 removal to remove tar, H2S, CO2, dust and other impurities. After being compressed and freed from waste heat, it is sent to the reforming reactor. The pressure and temperature of the reforming reactor is 210°C and the pressure is 5 MPa.

[0093] The reformed synthesis gas is fed into the synthesis reactor at a temperature of 250°C and a pressure of 5 MPa.

[0094] In this comparative example, 1 ton of green methanol can be produced from every 4 tons of biomass. Due to the small scale and high cost of gasification gas detarring, the cost of green methanol production is about 4,500 yuan / ton.

[0095] In summary, the present invention proposes a new process for producing methanol by coupling distributed pyrolysis carbonization with centralized biochar gasification. The process converts biomass such as straw into biochar through a distributed pyrolysis carbonization station, and then transports it. A centralized gasification process is used to gasify the biochar to produce synthesis gas, and then the synthesis gas is catalytically synthesized to prepare green methanol. The present invention converts biomass into biochar through a distributed pyrolysis carbonization process, which can greatly increase the volume energy density of renewable carbon carriers and greatly reduce the storage and transportation costs of raw materials; the process is suitable for large-scale expansion and reduces costs through scale; at the same time, through the supporting gasification power generation system, it can meet the green electricity required for continuous and stable operation of the system, providing a mature, reliable and economically feasible new solution for the preparation of green methanol.

Claims

1. A biomass to methanol system, characterized in that: It includes at least one pyrolysis carbonization unit and a gasification synthesis unit; The pyrolysis carbonization unit comprises a pyrolysis reactor (2); the pyrolysis reactor (2) is provided with a second biomass feed port, a first biochar discharge port and a first pyrolysis gas discharge port; The gasification synthesis unit comprises a second gasification reactor (9), a reforming reactor (11) and a synthesis reactor (13); The second gasification reactor (9) is provided with a biochar feed inlet, an oxygen feed inlet, a first steam feed inlet, a second gasification gas discharge port and a slag discharge port; The reforming reactor (11) is provided with a second gasification gas feed port, a second steam feed port and a first synthesis gas discharge port; the synthesis reactor (13) is provided with a first synthesis gas feed port and a methanol discharge port; The second gasification gas outlet is connected to the second gasification gas feed inlet, and the first synthesis gas outlet is connected to the first synthesis gas feed inlet.

2. The biomass to methanol system according to claim 1, characterized in that: The pyrolysis carbonization unit further comprises a dryer (1), wherein the dryer (1) is provided with a first biomass feed port, a biomass discharge port, a first flue gas feed port and a first flue gas discharge port; the first biomass discharge port is connected to the second biomass feed port, and the first pyrolysis gas discharge port is connected to the first flue gas feed port; preferably, the pyrolysis reactor (2) is further provided with a jacket, wherein the jacket is provided with a first pyrolysis gas inlet and a first flue gas outlet; the first flue gas outlet is connected to the first flue gas feed port, and the first pyrolysis gas discharge port is connected to the first pyrolysis gas inlet; And / or, the pyrolysis carbonization unit further comprises a cyclone dust collector (3), the cyclone dust collector (3) being provided with a first pyrolysis gas feed port, a second biochar discharge port and a second pyrolysis gas discharge port; the first pyrolysis gas discharge port is connected to the first pyrolysis gas feed port, and the second biochar discharge port is connected to the biochar feed port; preferably, the second pyrolysis gas discharge port is connected to the first pyrolysis gas inlet port.

3. The biomass-to-methanol system according to claim 2, characterized in that: The pyrolysis carbonization unit may further include a first gasification reactor (4) and a first internal combustion engine (7), wherein the first gasification reactor (4) is provided with a second pyrolysis gas feed port, an air feed port and a first gasification gas outlet port; the first internal combustion engine (7) is provided with a first gasification gas feed port and a first flue gas outlet port; the second pyrolysis gas feed port is connected to the first pyrolysis gas outlet port, and the first gasification gas outlet port is connected to the first gasification gas feed port; preferably, the second pyrolysis gas feed port is connected to the second pyrolysis gas outlet port; preferably, the dryer (1) further includes a second flue gas feed port, and the first flue gas outlet port is connected to the second flue gas feed port; Preferably, a tar removal device is further provided between the first gasification gas outlet and the first gasification gas feed port; the tar removal device preferably comprises a heat exchanger (5) and an electrostatic precipitator (6) connected in sequence, the feed port of the heat exchanger (5) being connected to the first gasification gas outlet, and the discharge port of the electrostatic precipitator (6) being connected to the first gasification gas feed port.

4. The biomass to methanol system according to claim 1, characterized in that: The gasification synthesis unit further comprises a second waste heat boiler (16) and a second internal combustion engine (15); the second waste heat boiler (16) is provided with a second boiler jacket; the second waste heat boiler (16) is provided with a water injection port and a second steam discharge port; the second boiler jacket is provided with a second flue gas inlet and a second flue gas outlet; the second internal combustion engine (15) is provided with a second flue gas outlet and a second synthesis gas feed port; the second steam outlet is connected to the first steam feed port and the second steam feed port, the second flue gas outlet is connected to the second flue gas inlet, and the second synthesis gas feed port is connected to the first synthesis gas outlet; Preferably, the gasification synthesis unit may further comprise a first waste heat boiler (10), the first waste heat boiler (10) being provided with a first boiler jacket, the first waste heat boiler (10) being provided with a first steam discharge port and a second steam feed port, the first boiler jacket being provided with a second gasification gas inlet and a second gasification gas outlet; the first steam discharge port being connected to the first steam feed port and the second steam feed port, the second gasification gas inlet being connected to the second gasification gas discharge port, and the second gasification gas outlet being connected to the second gasification gas feed port; The gasification synthesis unit further comprises a ball mill (8), the feed port of the ball mill (8) being connected to the first biochar discharge port, and the discharge port of the ball mill (8) being connected to the biochar feed port; preferably, the feed port of the ball mill (8) is connected to the second biochar discharge port.

5. The biomass-to-methanol system according to claim 4, characterized in that: The gasification synthesis unit further comprises a synthesis gas purifier (12), wherein the synthesis gas purifier (12) is provided with a third synthesis gas feed port, a third synthesis gas discharge port and a residual gas discharge port; the third synthesis gas feed port is connected to the first synthesis gas discharge port, and the third synthesis gas discharge port is connected to the first synthesis gas feed port; preferably, the third synthesis gas discharge port is connected to the second synthesis gas feed port; preferably, the residual gas discharge port is connected to a carbon dioxide purification reactor (17); preferably, the residual gas discharge port is connected to a connecting port, and the connecting port is provided on a connecting pipe between the discharge port of the ball mill (8) and the biochar feed port; the interior of the synthesis gas purifier (12) is preferably provided with a filter device and / or a gas washing absorption liquid; And / or, the gasification synthesis unit further comprises a distillation tower (14), and a feed inlet of the distillation tower (14) is connected to the methanol discharge outlet; And / or, the oxygen feed port is connected to an oxygen generator (18).

6. A method for preparing methanol, characterized in that: The biomass-to-methanol system according to any one of claims 1 to 5 comprises the following steps: S1, pyrolyzing and carbonizing the initially crushed biomass in the pyrolysis reactor (2) to obtain biochar and pyrolysis gas; S2, subjecting the biochar to a pressurized gasification reaction with oxygen and steam in the second gasification reactor (9) to obtain a second gasification gas; S3, subjecting the second gasified gas to a reforming reaction in the reforming reactor (11) to obtain synthesis gas; S4, subjecting the synthesis gas to a synthesis reaction in the synthesis reactor (13).

7. The method for preparing methanol according to claim 6, characterized in that: The biomass-to-methanol system further comprises a dryer (1). In step S1, the biomass is dried in the dryer (1) and then subjected to low-temperature pyrolysis and carbonization in the pyrolysis reactor (2); the drying temperature is preferably 200-400° C.; And / or, in step S1, the processing amount of the biomass in the pyrolysis reactor (2) is ≤ 300,000 tons / year, for example 300,000 tons / year; And / or, in step S1, the temperature of the pyrolysis carbonization is 275-350°C, for example, 300°C; And / or, in step S1, the residence time of the pyrolysis carbonization is 0.5-1.5 h; Preferably, in step S1, the pyrolysis carbonization unit further comprises a cyclone dust collector (3), and after the pyrolysis gas passes through the cyclone dust collector (3), the carried biochar falls off and then partially enters the jacket outside the pyrolysis reactor (2) to form flue gas; And / or, the biomass to methanol system comprises a first gasification reactor (4) and a first internal combustion engine (7), in step S1, part of the pyrolysis gas and air undergo a gasification reaction in the first gasification reactor (4), and the generated first gasification gas is burned in the first internal combustion engine (7) to produce flue gas; the temperature of the gasification reaction is preferably 700-900°C, for example 850°C; the pressure of the gasification reaction is preferably -2000~2000 Pa, for example -200 Pa; the residence time of the gasification reaction is preferably 1-40 s, for example 2 s; the air equivalent ratio of the gasification reaction is preferably (0.25-0.4): 1; the pyrolysis gas entering the first gasification reactor (4) for the gasification reaction preferably accounts for 50%-80%, for example 70%, of all the pyrolysis gas generated.

8. The method for preparing methanol according to claim 6, characterized in that: In step S2, the temperature of the pressurized gasification reaction is 1200-1600°C, for example, 1300°C; and / or, in step S2, the pressure of the pressurized gasification reaction is 2-8 MPa, for example, 5 MPa; And / or, in step S2, the residence time of the pressurized gasification reaction is 1-30 s, for example 2 s; And / or, in step S2, in the pressurized gasification reaction, the mass ratio of biochar, oxygen and steam is 1: (0.7-1.4): (0.02-0.25); And / or, in step S2, the second gasification reactor (9) adopts a liquid slagging form.

9. The method for preparing methanol according to claim 6, characterized in that: In step S3, the reforming reactor (11) is filled with an iron catalyst; and / or, in step S3, the temperature of the reforming reaction is 200-250° C., for example, 210° C.; and / or, in step S3, the pressure of the reforming reaction is 2-8 MPa, for example, 5 MPa; And / or, in step S3, the residence time of the reforming reaction is 0.5-30 s, for example 3 s; And / or, in step S3, in the reforming reaction, the volume ratio of the second gasification gas to steam is 1: (0.02-0.25), for example, 1: 0.08; And / or, the biomass-to-methanol system comprises a second waste heat boiler (16) and a second internal combustion engine (15), and in step S3, part of the synthesis gas is burned in the second internal combustion engine (15) to produce flue gas for heating the second waste heat boiler (16); the gasification gas entering the second internal combustion engine (15) preferably accounts for 5%-25%, for example 10%, of all the generated gasification gas; Preferably, in step S3, after the synthesis gas passes through the synthesis gas purifier (12), 10% of the purified synthesis gas enters the second internal combustion engine (15) to burn and perform work, thereby forming flue gas for heating the second waste heat boiler (16).

10. The method for preparing methanol according to claim 6, characterized in that: In step S4, the synthesis reactor (13) is filled with a copper-based catalyst Cu / ZnO / Al2O3; and / or, in step S4, the temperature of the synthesis reaction is 200-300° C., for example, 250° C.; and / or, in step S4, the pressure of the synthesis reaction is 2-8 MPa, for example 5 MPa; And / or, in step S4, the residence time of the synthesis reaction is 0.5-20 s, for example 2 s; And / or, the biomass-to-methanol system comprises a distillation tower (14), and in step S4, crude methanol produced by the reaction in the synthesis reactor (13) is distilled in the distillation tower (14) to obtain methanol; Preferably, the pressure of the pressurized gasification reaction, the pressure of the reforming reaction and the pressure of the synthesis reaction are equal, preferably all 5 MPa.

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