Methanol synthesis system and methanol synthesis method

Abstract

The invention provides a methanol synthesis system which comprises a preheater, a synthesizer, a heater and a pump, the preheater is provided with a first heat conduction oil cavity, the synthesizer is provided with a second heat conduction oil cavity, the preheater is further provided with a preheating flow path, the synthesizer is further provided with a synthesis cavity, and the preheating flow path is communicated with the synthesis cavity; the methanol synthesis system further comprises a synthesis gas input branch and a reacted gas output branch, the synthesis gas input branch is connected with an inlet of the preheating flow path, and the reacted gas output branch is connected with an outlet of the synthesis cavity; the methanol synthesis system further comprises a heat conduction oil condenser which is connected with the preheater. The invention also provides a methanol synthesis method. The conduction oil condenser and the preheater are connected to form the conduction oil cooling loop, and high-temperature conduction oil gas flows into the conduction oil condenser for cooling through the circulation effect of the conduction oil circulation loop, so that the temperature of the conduction oil is kept in a constant-temperature state, and the thermal stability of the conduction oil in the running process of the methanol synthesis system is improved.

Description

Technical Field

[0001] The present application belongs to the field of new energy, and specifically, relates to a methanol synthesis system and a methanol synthesis method. Background Art

[0002] After oil and gas, methanol is known as the "most ideal" renewable clean fuel. In addition, methanol is also a carrier of hydrogen energy, which can realize the conversion of hydrogen-methanol-hydrogen, and also provides a new solution to the storage and transportation problems that have been plaguing the hydrogen energy industry.

[0003] Biomass methanol production is one of the ways to produce green methanol. In the process of biomass methanol synthesis, the gas after pyrolysis needs to be cracked and reformed at high temperature to obtain synthesis gas rich in hydrogen (H2) and carbon monoxide (CO), and then the synthesis gas is processed for methanol synthesis. For the methanol synthesis reaction, appropriately increasing the temperature can accelerate the reaction rate, so that the reaction can reach equilibrium in a shorter time, so that the reaction rate and yield can reach a better level, and at the same time, the activity, life and stability of the catalyst can be improved. Therefore, heat transfer oil plays a vital role in the process of methanol synthesis. However, the methanol synthesis reaction is an exothermic reaction, which will cause the temperature of the heat transfer oil to rise. If the temperature of the heat transfer oil is not controlled, the heat transfer oil will overheat and may cause safety accidents such as fire and explosion. Therefore, the stability of the heat transfer oil temperature directly affects the operating efficiency and overall efficiency of the production equipment. Summary of the invention

[0004] This application aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the main technical solutions adopted in this application include:

[0005] In a first aspect, the present application provides a methanol synthesis system, comprising a preheater, a synthesizer, a heater and a pump, wherein the preheater has a first heat transfer oil chamber, the synthesizer has a second heat transfer oil chamber, the first heat transfer oil chamber, the second heat transfer oil chamber, the heating chamber in the heater and the flow chamber of the pump are connected to form a heat transfer oil circulation loop; the preheater also has a preheating flow path, the synthesizer also has a synthesis chamber, the preheating flow path is connected to the synthesis chamber, the methanol synthesis system also includes a synthesis gas input branch and a post-reaction gas output branch, the synthesis gas input branch is connected to the inlet of the preheating flow path, and the post-reaction gas output branch is connected to the outlet of the synthesis chamber;

[0006] The methanol synthesis system further comprises a heat transfer oil condenser, and the heat transfer oil condenser is connected to the preheater.

[0007] The methanol synthesis system provided by the present application forms a heat transfer oil circulation loop by connecting the first heat transfer oil chamber, the second heat transfer oil chamber, the heating chamber in the heater and the flow chamber of the pump. The heat transfer oil condenser is connected to the preheater to form a heat transfer oil cooling loop. Through the circulation effect of the heat transfer oil circulation loop, the high-temperature heat transfer oil gas flows into the heat transfer oil condenser for cooling, so that the temperature of the heat transfer oil in the heat transfer oil circulation loop is maintained at a constant temperature, thereby improving the thermal stability of the heat transfer oil during the operation of the methanol synthesis system.

[0008] In a second aspect, the present application provides a method for synthesizing methanol, comprising:

[0009] The heat transfer oil in the heat transfer oil circulation loop is heated to a set temperature by a heater;

[0010] The synthesis gas enters the preheater through the synthesis gas input branch for preheating, and at the same time, the heating of the heater is stopped, and the first cooling flow path connected to the heat transfer oil condenser is started;

[0011] The synthesis gas is preheated in the preheater and then enters the synthesizer for synthesis reaction. The mixed gas containing methanol and synthesis gas is then output through the post-reaction gas output branch.

[0012] In the methanol synthesis method provided by the present application, the heater stops heating while the synthesis gas is input, and the first cooling flow path is started. The heat released by the reaction of the synthesis gas in the synthesizer can be exchanged with the heat exchange medium of the first cooling flow path in the heat transfer oil condenser to cool the heat transfer oil, so that the temperature of the heat transfer oil is maintained at a constant temperature, thereby improving the thermal stability of the heat transfer oil during the operation of the methanol synthesis system. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0014] Figure 1 A schematic diagram of a methanol synthesis system provided in an embodiment of the present application;

[0015] Figure 2 This is a structural diagram of the Venturi tube provided in an embodiment of the present application. DETAILED DESCRIPTION

[0016] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0017] It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0018] After oil and gas, methanol is hailed as the "most ideal" renewable clean fuel. Methanol has gradually been regarded as liquid "hydrogen" and mobile "electricity" in the industry. Green methanol belongs to green hydrogen-based energy, an important part of the new energy system, and has huge market potential. Hydrogen is a major raw material for the preparation of methanol. Accordingly, the production of green methanol requires a large amount of green hydrogen. Green alcohol provides a huge new scenario and way out for hydrogen energy consumption, which can drive the demand for the entire green hydrogen industry. In addition, methanol is also a carrier of hydrogen energy, which can realize the conversion of hydrogen-methanol-hydrogen, which also provides a new solution to the storage and transportation problems that have been plaguing the hydrogen energy industry.

[0019] Green methanol is chemically identical to methanol produced from fossil fuels and has similar uses. However, unlike "black methanol" or "grey methanol" made from coal, green methanol not only reduces carbon emissions from the coal-to-methanol process, but also improves the local consumption capacity of renewable energy and has great application prospects. The EU's standards are relatively strict: Different from traditional coal-to-methanol and natural gas-to-methanol, methanol produced from the following two types of raw materials is identified as "green methanol": biomass-to-methanol, green hydrogen and renewable carbon dioxide-to-electricity-to-methanol.

[0020] Biomass methanol synthesis first requires the conversion of biomass into raw gas rich in hydrogen (H2) and carbon monoxide (CO). The raw gas contains inert gases, tar, solid particles and hydrocarbons, so it cannot be directly converted into methanol. It needs to go through intermediate links to form a biomass gasification methanol synthesis system, which mainly includes biomass pretreatment, pyrolysis gasification, gas reforming, methanol synthesis, etc. Methanol synthesis is an important link in biomass methanol synthesis. For the methanol synthesis reaction, appropriately increasing the temperature can accelerate the reaction rate, so that the reaction can reach equilibrium in a shorter time, so that the reaction rate and yield can reach a better level. At the same time, it can improve the activity, life and stability of the catalyst. Therefore, in the process of methanol synthesis, heat transfer oil plays a vital role. Heat transfer oil, also known as heat carrier oil or heat conduction medium, is a special oil used for indirect heat transfer. It is an indispensable and important heat transfer medium in the methanol synthesis process. In the methanol synthesis process, the control of reaction temperature is crucial. Heat transfer oil can achieve precise control of reaction temperature through its stable heat transfer performance. By adjusting the temperature of the heat transfer oil, the reaction rate of methanol synthesis can be adjusted, thereby optimizing the reaction conditions and improving the purity and yield of the product. In addition, the main reactions of methanol synthesis include CO+2H2→CH3OH, CO2+3H2→CH3OH+H2O, etc., which are all exothermic reactions. During the reaction, the chemical bond breaking of the reactants requires energy absorption, while the chemical bond formation of the products releases energy. Since the energy released by the chemical bonds of the products is greater than the energy absorbed by the chemical bond breaking of the reactants, the entire reaction process will release heat, which will cause the temperature of the heat transfer oil to rise. If the temperature of the heat transfer oil is not controlled, the heat transfer oil will overheat and may cause safety accidents such as fire and explosion. Therefore, the stability of the heat transfer oil temperature directly affects the operating efficiency and overall efficiency of the production equipment. By accurately controlling the temperature of the heat transfer oil, it can ensure that the production equipment operates in the best state, thereby improving production efficiency, while ensuring product quality and ensuring the safe operation of the equipment.

[0021] To do this, see Figure 1The present embodiment provides a methanol synthesis system with a heat transfer oil constant temperature function. Specifically, the methanol synthesis system includes a methanol synthesis section 3, which includes a preheater 31, a synthesizer 32, a heater 33 and a pump 34. The preheater 31 has a first heat transfer oil chamber 31a, and the synthesizer 32 has a second heat transfer oil chamber 32a. The first heat transfer oil chamber 31a, the second heat transfer oil chamber 32a, the heating chamber in the heater 33 and the flow chamber of the pump 34 are connected to form a heat transfer oil circulation loop 30; the preheater 31 also has a preheating flow path 31b, and the synthesizer 32 has a second heat transfer oil chamber 32a. The synthesizer 32 also has a synthesis chamber 32b, and the preheating flow path 31b is connected to the synthesis chamber 32b. The methanol synthesis system also includes a synthesis gas input branch 100 and a post-reaction gas output branch 200. The synthesis gas input branch 100 is connected to the inlet of the preheating flow path 31b, and the post-reaction gas output branch 200 is connected to the outlet of the synthesis chamber 32b; the methanol synthesis system also includes a heat transfer oil condenser 35, and the heat transfer oil condenser 35 is connected to the preheater 31.

[0022] In this embodiment, a heat transfer oil circulation loop 30 is formed by connecting the first heat transfer oil chamber 31a, the second heat transfer oil chamber 32a, the heating chamber in the heater 33 and the flow chamber of the pump 34. In addition, the heat transfer oil condenser 35 has a first heat exchange passage 35a, and the first heat exchange passage 35a is connected to the first heat transfer oil chamber 31a to form a heat transfer oil cooling circuit. During the operation of the methanol synthesis system, the heat transfer oil with a certain temperature in the second heat transfer oil chamber 32a promotes the synthesis gas to undergo an exothermic reaction in the synthesizer 32, and the heat released by the reaction is transferred to the heat transfer oil in the second heat transfer oil chamber 32a. Under the circulation flow of the heat transfer oil circulation loop 30, the heat transfer oil flows to the first heat transfer oil chamber 31a. When the heat transfer oil is over-temperature, the heat transfer oil boils to produce gas. The high-temperature heat transfer oil gas flows to the heat transfer oil condenser 35 for cooling and re-condensation into liquid, and then flows back to the first heat transfer oil chamber 31a and enters the heat transfer oil circulation loop 30 for circulation, thereby achieving the effect of constant temperature of the heat transfer oil and precise control of the temperature of the heat transfer oil, thereby improving production efficiency and ensuring safe operation of the system.

[0023] In this embodiment, the heat transfer oil condenser 35 also has a second heat exchange passage 35b, and the methanol synthesis system also has a first cooling flow path 300, and the first cooling flow path 300 is connected to the second heat exchange passage 35b. During the operation of the methanol synthesis system, a heat exchange medium flows in the first cooling flow path 300, and the heat exchange medium exchanges heat with the heat transfer oil in the first heat exchange passage 35a in the second heat exchange passage 35b, cools the heat transfer oil, and keeps the heat transfer oil at a constant temperature. In this embodiment, the first cooling flow path 300 includes a first pump 301 and a first storage tank 302, and the flow cavity in the first pump 301, the inner cavity of the first storage tank 302 and the second heat exchange passage 35b are connected to form a loop, and the heat exchange medium in the first cooling flow path 300 can be water. In this embodiment, the first storage tank 302 can also be a water system, or the first storage tank 302 is provided with a cooler to cool the heat transfer medium. Since there are many possible implementation methods, they are not listed here one by one.

[0024] In this embodiment, in order to allow the heat transfer oil gas generated by overheating in the preheater 31 to smoothly enter the first heat exchange passage 35a of the heat transfer oil condenser 35 for heat exchange and cooling, the heat transfer oil condenser 35 is further away from the ground plane than the preheater 31. In other words, the heat transfer oil condenser 35 is set at a higher height than the preheater 31. This setting does not require additional conveying equipment, reduces system equipment costs, and is more economical.

[0025] Furthermore, the preheater 31 and the synthesizer 32 are connected as an integrated device, and the connection interface between the preheater 31 and the heat transfer oil condenser 35 is located at the top of the preheater 31. It is convenient for the heat transfer oil gas to gather upward and flow to the heat transfer oil condenser 35 from the top.

[0026] Please refer again Figure 1In this embodiment, the methanol synthesis system further includes an oil storage device 36, a first cut-off valve 37, a second cut-off valve 38 and a third cut-off valve 39, wherein the first cut-off valve 37 connects the outlet of the oil storage device 36 and the thermal oil circulation loop 30; the second cut-off valve 38 is arranged in the thermal oil circulation loop 30; and the third cut-off valve 39 connects the thermal oil circulation loop 30 and the inlet of the oil storage device 36. In addition, the methanol synthesis system further includes a controller 7, and the first cut-off valve 37, the second cut-off valve 38 and the third cut-off valve 39 are all electrically connected to the controller 7. When the methanol synthesis system is initially operated, the thermal oil in the oil storage device 36 enters the thermal oil circulation loop 30 by opening the oil storage device 36 and the first cut-off valve 37. When the methanol synthesis system is in normal operation, the first cut-off valve 37 and the third cut-off valve 39 are closed, the second cut-off valve 38 is opened, and the thermal oil circulates in the thermal oil circulation loop 30. When the methanol synthesis system fails or needs to be cleaned, the first shutoff valve 37 and the second shutoff valve 38 are closed, and the third shutoff valve 39 is opened to recover the heat transfer oil into the oil storage device 36 for easy maintenance and cleaning. In this embodiment, the first shutoff valve 37, the second shutoff valve 38 and the third shutoff valve 39 are all electric shutoff valves.

[0027] Among them, the synthesis gas input branch 100 includes a synthesis gas input pipeline 1, and the synthesis gas input pipeline 1 includes a compressor 11, and the compressor 11 is connected between the outlet of the synthesis gas source A and the inlet of the preheating flow path 31b. In this embodiment, the synthesis gas source A can be the previous section before the current section in the biomass to methanol process, such as a gas reforming section, or a gas storage tank containing hydrogen (H2) and carbon monoxide (CO). Specifically, the synthesis gas input pipeline 1 includes a compressor 11, and the input end of the compressor 11 is connected to the synthesis gas source A. Since methanol synthesis is a process of converting carbon monoxide and hydrogen into methanol, this process needs to be carried out under specific pressure conditions. Increasing the pressure can increase the collision frequency between the reactant molecules, thereby promoting the reaction to improve the conversion rate and production efficiency of the reaction. In addition, the methanol synthesis reaction is a reaction in which the number of molecules decreases, so increasing the pressure is conducive to the chemical equilibrium moving in the direction of generating methanol, and at the same time, the activity of the catalyst can be fully exerted to improve the yield and selectivity of methanol. Therefore, in this embodiment, a compressor 11 is provided in the synthesis gas input pipeline 1, and the synthesis gas is pressurized by the compressor 11 to ensure the stability of production efficiency and quality of synthetic products.

[0028] In the present embodiment, the synthesis gas input pipeline 1 also includes a high-pressure gas storage device 12, and the high-pressure gas storage device 12 connects the outlet of the compressor 11 and the inlet of the preheating flow path 31b. In other words, the high-pressure gas storage device 12 is arranged downstream of the compressor 11 and upstream of the preheating flow path 31b. The high-pressure gas storage device 12 is provided to store high-pressure synthesis gas so as to provide a stable supply of synthesis gas when needed, and a certain reaction pressure can be maintained to ensure the smooth progress of the reaction. In addition, in the methanol synthesis process, the high-pressure gas storage device 12 can also be used as an energy storage device. When the reaction system needs additional energy, the required energy can be provided by releasing high-pressure gas. At the same time, the excess energy generated during the reaction process can also be stored in the high-pressure gas storage tank in the form of compressed gas for later use.

[0029] In this embodiment, the synthesis gas input pipeline 1 further includes a low-pressure gas storage device 13, which connects the outlet of the synthesis gas source A and the inlet of the compressor 11. In other words, the low-pressure gas storage device 13 is arranged downstream of the synthesis gas source A and upstream of the compressor 11. The low-pressure gas storage device 13 is used to store the low-pressure synthesis gas input from the synthesis gas source A, and provide a stable supply of synthesis gas for subsequent methanol synthesis, so as to ensure production efficiency and improve the stability of product quality.

[0030] Please refer again Figure 1 In this embodiment, the post-reaction gas output branch 200 includes a methanol gas-liquid separation device 4 and a methanol storage tank 8, and the inlet 41 of the methanol gas-liquid separation device 4 is connected to the outlet of the synthesis chamber 32b. The liquid outlet 43 of the methanol gas-liquid separation device 4 is connected to the methanol storage tank 8. The methanol synthesized during the operation of the methanol synthesis system flows to the methanol storage tank 8 for storage.

[0031] In the methanol synthesis process, due to the influence of factors such as catalyst, reaction temperature and reaction pressure, the one-way conversion rate of methanol is usually between 50% and 85%. In order to improve the total conversion rate of methanol, in the related art, the unreacted synthesis gas is re-pressurized by a compressor and mixed with the newly pressurized synthesis gas to enter the synthesis stage to synthesize methanol. Accordingly, it will cause problems such as increased system equipment costs, more complicated system pipeline connections, and more leaks.

[0032] To do this, please refer again to Figure 1 , and combined with Figure 2In this embodiment, the synthesis gas input branch 100 further includes a venturi tube 2, and the post-reaction gas output branch 200 includes a recovery pipeline 5, the venturi tube 2 has an inlet 2a, an outlet 2b and a recovery pipeline interface 2c, the synthesis gas input pipeline 1 is connected to the inlet 2a of the venturi tube 2, the outlet 2b of the venturi tube 2 is connected to the input end of the methanol synthesis section 3, the output end of the methanol synthesis section 3 is connected to the inlet 41 of the methanol gas-liquid separation device 4, one end of the recovery pipeline 5 is connected to the gas outlet 42 of the methanol gas-liquid separation device 4, and the other end is connected to the synthesis gas input branch 100. Specifically, the other end of the recovery pipeline 5 is connected to the recovery pipeline interface 2c of the venturi tube 2. In this embodiment, the inlet of the preheating flow path 31b is the input end of the methanol synthesis section 3, and the outlet of the synthesis chamber 32b is the output end of the methanol synthesis section 3.

[0033] In this embodiment, a venturi tube 2 is provided, and the recovery pipeline interface 2c of the venturi tube 2 is connected to the recovery pipeline 5. The unreacted synthesis gas is recovered and mixed with the new synthesis gas through the venturi tube 2, and the gas is output after pressurization. The connection of the recovery pipeline 5, the synthesis gas input pipeline 1 and the methanol synthesis section 3 is realized through the venturi tube 2, and the recovery and mixing of the unreacted synthesis gas and the function of controlling the gas pressure are realized at the same time. There is no need to set a compressor in the recovery pipeline 5, so that the system can become simpler and more economical. Compared with the pressurization method of setting a compressor in the recovery pipeline 5, the venturi tube 2 has a lower operating cost, a small size, a simple structure, easy installation and disassembly, and is convenient for daily inspection and maintenance. At the same time, the overall pipeline connection of the system is also simpler and more convenient.

[0034] See also Figure 2 The venturi tube 2 includes a main pipe, which includes an inlet section 21, a contraction section 22, a throat section 23, a diffusion section 24 and an outlet section 25. The inlet section 21, the contraction section 22, the throat section 23, the diffusion section 24 and the outlet section 25 are connected in sequence and the internal pipelines are connected. The venturi tube 2 also includes a recovery pipe section 26, which is connected and communicated with the side of the throat section 23. The inlet 2a is located at the inlet section 21 and connected to the synthesis gas input pipeline 1. The outlet 2b is located at the diffusion section 24 and connected to the input end of the methanol synthesis section 3. The recovery pipeline interface 2c is located at the recovery pipe section 26 and connected to the recovery pipeline 5.

[0035] In this embodiment, the cross-sectional area of ​​the contraction section 22 decreases from the inlet section 21 toward the throat section 23; the cross-sectional area of ​​the diffusion section 24 increases from the throat section 23 toward the outlet section 25. In other words, the main pipe of the venturi tube 2 is a pipe that contracts first and then gradually expands. The inlet section 21 serves as the inlet of the synthesis gas, and the contraction section 22 is in the shape of a conical pipe, which is used to gradually reduce the diameter of the synthesis gas from the inlet section 21 to the diameter of the throat section 23. As the cross-sectional area of ​​the pipe gradually decreases, the flow rate increases accordingly. According to the continuity equation, the flow rate is inversely proportional to the cross-sectional area. Therefore, the pressure gradually decreases while the flow rate increases in the contraction section 22. The synthesis gas enters the throat section 23 through the contraction section 22. The throat section 23 is the area with the smallest cross-sectional area of ​​the main pipe. Here, the flow rate reaches the maximum value, and the pressure drops to the lowest point. According to Bernoulli's principle, p+1 / 2ρv2+ρgh=constant, where p represents the static pressure of the fluid, ρ represents the density of the fluid, v represents the flow rate of the fluid, g represents the acceleration of gravity, and h represents the height (or potential) of the fluid. The faster the flow rate, the lower the pressure, so an obvious low-pressure area is formed in the throat section 23. After passing through the throat section 23, the synthesis gas enters the diffusion section 24. The cross-sectional area of ​​the pipe gradually increases, and the flow rate begins to decrease. As the flow rate decreases, the pressure gradually recovers. In the diffusion section 24, the kinetic energy of the synthesis gas is partially converted into pressure energy, causing the pressure to gradually increase until it approaches or recovers to the pressure level of the inlet section 21.

[0036] When the unreacted synthesis gas flowing out of the gas outlet 42 of the methanol gas-liquid separation device 4 needs to be recovered and synthesized again, the unreacted synthesis gas is guided to flow into the recovery pipeline 5, and then enters the throat section 23 after passing through the recovery pipeline interface 2c and the recovery pipe section 26 to mix with the synthesis gas flowing in through the synthesis gas input pipeline 1. The pressure of the mixed synthesis gas gradually increases when passing through the diffusion section 24 until it approaches or returns to the pressure level of the inlet section 21.

[0037] In this embodiment, the synthesis gas input pipeline 1 is used to connect the inlet 2a of the venturi tube 2 and the synthesis gas source A, and the output end of the compressor 11 is connected to the inlet 2a of the venturi tube 2. More specifically, the high-pressure gas storage device 12 connects the output end of the compressor 11 and the inlet 2a of the venturi tube 2. In other words, the high-pressure gas storage device 12 is arranged downstream of the compressor 11 and upstream of the inlet 2a of the venturi tube 2.

[0038] Please refer again Figure 1, the recovery pipeline 5 has a recovery pipeline cut-off valve 51, and the recovery pipeline cut-off valve 51 is used to open and close the recovery pipeline 5. In addition, the methanol synthesis system also includes a purge gas pipeline 6, the purge gas pipeline 6 is connected to the gas outlet 42 of the methanol gas-liquid separation device 4, and the purge gas pipeline 6 has a purge gas pipeline cut-off valve 61, and the purge gas pipeline cut-off valve 61 is used to open and close the purge gas pipeline 6. During the operation of the methanol synthesis system, one of the recovery pipeline cut-off valve 51 and the purge gas pipeline cut-off valve 61 is in an open state, and the other is in a closed state. The recovery or release of unreacted synthesis gas is achieved by switching the recovery pipeline cut-off valve 51 and the purge gas pipeline cut-off valve 61. Further, the methanol synthesis system also includes a controller 7, and the recovery pipeline cut-off valve 51 and the purge gas pipeline cut-off valve 61 are both electrically connected to the controller 7. The controller 7 is used to control the switching operation of the recovery pipeline shut-off valve 51 and the purge gas pipeline shut-off valve 61. When the unreacted synthesis gas needs to be recovered and resynthesized, the recovery pipeline shut-off valve 51 is opened for recovery and recirculation, and the purge gas pipeline shut-off valve 61 is closed; when the unreacted synthesis gas needs to be purged, the purge gas pipeline shut-off valve 61 is opened for purge, and the recovery pipeline shut-off valve 51 is closed. In this embodiment, the recovery pipeline shut-off valve 51 and the purge gas pipeline shut-off valve 61 are both electric shut-off valves.

[0039] Please refer again Figure 1, the post-reaction gas output branch 200 also includes a methanol condenser 9, the methanol condenser 9 has a heat exchange pipeline for methanol heat exchange, that is, the methanol condenser 9 has a first circulation passage 91, the first circulation passage 91 connects the outlet of the synthesis chamber 32b and the inlet 41 of the methanol gas-liquid separation device 4, and is used to circulate the product after the synthesis reaction. More specifically, the first circulation passage 91 has a first port 91a and a second port 91b, the first port 91a is connected to the output end of the methanol synthesis section 3, and the second port 91b is connected to the inlet 41 of the methanol gas-liquid separation device 4. The methanol condenser 9 also has a second circulation passage 92 for circulating a cooling medium, and the methanol synthesis system also has a second cooling flow passage 400, and the second cooling flow passage 400 is connected to the second circulation passage 92. During the operation of the methanol synthesis system, a heat exchange medium flows in the second cooling flow passage 400, and the heat exchange medium exchanges heat with the gas in the first circulation passage 91 during the process of flowing through the second circulation passage 92, and the methanol gas in the gas is condensed into liquid methanol. The methanol condenser plays a vital role in the production and processing of methanol. Its main function is to convert methanol vapor into liquid methanol. At the same time, the unreacted synthesis gas in the mixed gas is still in gaseous state. Through the condensation process, a relatively pure methanol product can be obtained. In addition, it is convenient for the methanol gas-liquid separation device 4 to perform gas-liquid separation, so that the unreacted synthesis gas can be recycled for synthesis, thereby improving the overall conversion rate and increasing the output of methanol.

[0040] In this embodiment, the connection point between the branch where the first shutoff valve 37 is located and the thermal oil circulation loop 30 is located downstream of the second shutoff valve 38, and the connection point between the branch where the third shutoff valve 39 is located and the thermal oil circulation loop 30 is located upstream of the second shutoff valve 38. When the methanol synthesis system is in normal operation, the first shutoff valve 37 and the third shutoff valve 39 are closed, and the second shutoff valve 38 is opened. When the thermal oil is injected in the initial stage, the second shutoff valve 38 and the third shutoff valve 39 are closed, and the first shutoff valve 37 is opened; when the thermal oil injection is completed, the first shutoff valve 37 is closed, and the second shutoff valve 38 is opened. When the methanol synthesis system fails or needs to be cleaned, the first shutoff valve 37 and the second shutoff valve 38 are closed, and the third shutoff valve 39 is opened.

[0041] This embodiment also provides a methanol synthesis process, that is, a methanol synthesis method, comprising the following steps:

[0042] Thermal oil filling and heating stage: open the first shutoff valve 37, the oil storage device 36 releases the thermal oil, and the pump 34 pumps the thermal oil into the heater 33 and the synthesizer 32. After the thermal oil is released, close the first shutoff valve 37, open the second shutoff valve 38, and the thermal oil circulates in the thermal oil circulation loop 30 through the pump 34. The thermal oil in the thermal oil circulation loop 30 is heated to a set temperature through the heater 33. The set temperature is 240°C to 280°C, and the thermal oil is in a gaseous state when it exceeds the set temperature.

[0043] Intake air pressurization stage: the synthesis gas enters the preheater 31 through the synthesis gas input branch 100 for preheating, and the heater 33 is stopped for heating at the same time, and the first cooling flow path 300 is started. Specifically, the synthesis gas flowing out of the synthesis gas source A first enters the low-pressure gas storage device 13, and the synthesis gas flowing out of the low-pressure gas storage device 13 is pressurized to a set pressure by the compressor 11 and then enters the high-pressure gas storage device 12. The high-pressure synthesis gas flowing out of the high-pressure gas storage device 12 enters the venturi tube 2 through the inlet 2a of the venturi tube 2, and is depressurized through the contraction section 22, for example, the pressure drops to 2Mpa to 2.4Mpa, and then enters the throat section 23, and then is pressurized through the diffusion section 24 to a pressure level close to the pressure level when entering the inlet 2a of the venturi tube 2, and then flows out from the outlet 2b of the venturi tube 2, and then enters the preheating flow path 31b of the preheater 31. During the process of the synthesis gas flowing through the preheating flow path 31b, it exchanges heat with the heat transfer oil in the first heat transfer oil chamber 31a, and the synthesis gas is preheated. The set pressure is 5Mpa to 10Mpa, for example, it can be set to 6Mpa, 7Mpa, 8Mpa, etc.

[0044] Gas preheating and synthesis stage: After being preheated by the preheater 31, the synthesis gas enters the synthesizer 32 for synthesis reaction, and then the mixed gas containing methanol and synthesis gas is output through the post-reaction gas output branch 200. Specifically, the preheated synthesis gas enters the synthesis chamber 32b of the synthesizer 32. Under the action of the catalyst in the synthesis chamber 32b, at least part of the synthesis gas undergoes an exothermic reaction to generate methanol. The released heat is exchanged with the heat-conducting oil in the second heat-conducting oil chamber 32a of the synthesizer 32. The heat-conducting oil flows to the preheater 31 under the action of the pump 34. The gaseous heat-conducting oil flows out from the top of the preheater 31 and enters the heat-conducting oil condenser 35 for cooling. Then it becomes liquid and returns to the second heat-conducting oil chamber 32a to enter the heat-conducting oil circulation loop 30 for circulation. The heat-conducting oil condenser 35 is used to maintain the heat-conducting oil at a set temperature. More specifically, the gaseous heat transfer oil exchanges heat with the heat transfer medium in the second heat transfer passage 35b connected to the first cooling flow path 300 in the first heat transfer passage 35a of the heat transfer oil condenser 35 to dissipate heat and condense into liquid.

[0045] Gas condensation and gas-liquid separation stage: After the mixed gas containing methanol and unreacted synthesis gas flows out from the synthesizer 32, it first passes through the methanol condenser 9 to condense the methanol in the mixed gas into a liquid state, and then enters the methanol gas-liquid separation device 4 through the inlet 41 of the methanol gas-liquid separation device 4 for gas-liquid separation. The liquid methanol separated from the methanol gas-liquid separation device 4 flows into the methanol storage tank 8 through the liquid outlet 43 for storage. The methanol condenser 9 is used to cool the methanol gas in the mixed gas to a liquid state, and the unreacted synthesis gas remains in a gaseous state. In some embodiments, the methanol condenser 9 cools the mixed gas to 50°C to 65°C, for example, 60°C.

[0046] Gas recovery stage: When the separated unreacted synthesis gas needs to be recovered and resynthesized, the recovery pipeline shut-off valve 51 is opened, the purge gas pipeline shut-off valve 61 is closed, and the separated gas enters the recovery pipeline 5 and is mixed with the synthesis gas input from the synthesis gas input branch 100 and then resynthesized. Specifically, the unreacted synthesis gas flowing out of the gas outlet 42 of the methanol gas-liquid separator 4 enters the venturi tube 2 through the recovery pipeline interface 2c of the venturi tube 2 through the recovery pipeline 5, is mixed with the synthesis gas input from the synthesis gas input pipeline 1 in the throat section 23, and re-enters the methanol synthesis section 3 to synthesize methanol after being pressurized by the venturi tube 2. During the methanol synthesis process, the pressure of the unreacted synthesis gas flowing out from the gas outlet 42 of the methanol gas-liquid separation device 4 is lower than the pressure of the synthesis gas input into the venturi tube 2 through the synthesis gas input pipeline 1. Similarly, the pressure of the unreacted synthesis gas flowing out from the gas outlet 42 of the methanol gas-liquid separation device 4 is lower than the pressure of the synthesis gas flowing out of the venturi tube 2, but slightly higher than the gas pressure in the throat section 23. Therefore, the unreacted synthesis gas in the recovery pipeline 5 is guided to be sucked into the throat section 23, mixed with the new synthesis gas, and then re-pressurized through the diffusion section 24 and then flows out into the methanol synthesis section.

[0047] Gas release stage: After several recycling cycles, the impurity content in the unreacted synthesis gas becomes higher and higher. If it is recycled again, the system yield will be reduced. For this reason, the unreacted synthesis gas needs to be released regularly. Specifically, when the separated unreacted synthesis gas needs to be released, the release gas pipeline shut-off valve 61 is opened, the recovery pipeline shut-off valve 51 is closed, and the unreacted synthesis gas is released through the release gas pipeline 6. The released unreacted synthesis gas can be discharged to the combustion chamber of the biomass pyrolysis section in the biomass to methanol processing system for combustion to improve the utilization rate of the synthesis gas.

[0048] The methanol synthesis system and methanol synthesis process in this embodiment recover and resynthesize the unreacted synthesis gas by setting up a venturi tube 2, and there is no need to add an additional compressor. The recovered unreacted synthesis gas and the new synthesis gas can be mixed and pressurized to restore the pressure level of the inlet section 21 for output through the venturi tube 2, and the system is simpler and more economical. In addition, the heat transfer oil is kept in a constant temperature range through the constant temperature circulation of the heat transfer oil, so that the methanol synthesis system is kept running in the best state, thereby improving production efficiency, ensuring product quality, and ensuring the safe operation of the equipment.

[0049] Some technical implementations in the above embodiments may be combined or replaced.

[0050] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0051] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0052] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0053] The technical principles of the present application are described above in combination with specific implementations, but it should be noted that the above descriptions are only for explaining the principles of the present application and cannot be interpreted in any way as a specific limitation on the protection scope of the present application. Based on the explanation here, technicians in this field can think of other specific implementations or equivalent replacements of the present application without creative work, and they will all fall within the protection scope of the present application.

Claims

1. A methanol synthesis system, characterized in that: The invention comprises a preheater, a synthesizer, a heater and a pump, wherein the preheater has a first heat transfer oil chamber, the synthesizer has a second heat transfer oil chamber, the first heat transfer oil chamber, the second heat transfer oil chamber, the heating chamber in the heater and the flow chamber of the pump are connected to form a heat transfer oil circulation loop; the preheater also has a preheating flow path, the synthesizer also has a synthesis chamber, the preheating flow path is connected to the synthesis chamber, the methanol synthesis system also comprises a synthesis gas input branch and a post-reaction gas output branch, the synthesis gas input branch is connected to the inlet of the preheating flow path, and the post-reaction gas output branch is connected to the outlet of the synthesis chamber; The methanol synthesis system further comprises a heat transfer oil condenser, and the heat transfer oil condenser is connected to the preheater.

2. The methanol synthesis system according to claim 1, characterized in that: The heat transfer oil condenser has a first heat exchange passage, and the first heat exchange passage is connected with the first heat transfer oil chamber to form a heat transfer oil cooling circuit; The thermal oil condenser further comprises a second heat exchange passage, and the methanol synthesis system further comprises a first cooling flow passage, wherein the first cooling flow passage is connected to the second heat exchange passage.

3. The methanol synthesis system according to claim 2, characterized in that: Compared with the preheater, the thermal oil condenser is further away from the ground plane.

4. The methanol synthesis system according to claim 1, characterized in that: The methanol synthesis system further comprises an oil storage device and a first cut-off valve, wherein the first cut-off valve connects the outlet of the oil storage device and a heat transfer oil circulation loop; The methanol synthesis system further comprises a second shut-off valve and a third shut-off valve, wherein the second shut-off valve is arranged in the thermal oil circulation loop, and the third shut-off valve is connected to the thermal oil circulation loop and the inlet of the oil storage device.

5. The methanol synthesis system according to claim 3, characterized in that: The methanol synthesis system further includes a controller, and the first shut-off valve, the second shut-off valve and the third shut-off valve are all electrically connected to the controller.

6. The methanol synthesis system according to claim 2, characterized in that: The preheater and the synthesizer are connected as an integrated device, and the connection interface between the preheater and the heat-conducting oil condenser is located on the top of the preheater.

7. The methanol synthesis system according to any one of claims 1 to 6, characterized in that: The synthesis gas input branch includes a compressor, which is connected between the outlet of the synthesis gas source and the inlet of the preheating flow path. The synthesis gas input branch also includes a high-pressure gas storage device and a low-pressure gas storage device. The high-pressure gas storage device is connected to the outlet of the compressor and the inlet of the preheating flow path, and the low-pressure gas storage device is connected to the outlet of the synthesis gas source and the inlet of the compressor; The post-reaction gas output branch includes a methanol condenser, a methanol gas-liquid separation device and a methanol storage tank. The methanol condenser has a first flow passage and a second flow passage. The first flow passage connects the outlet of the synthesis chamber and the inlet of the methanol gas-liquid separation device. The liquid outlet of the methanol gas-liquid separation device is connected to the methanol storage tank.

8. The methanol synthesis system according to claim 7, characterized in that: The methanol synthesis system also includes a recovery pipeline and a purge gas pipeline, both of which are connected to the gas outlet of the methanol gas-liquid separation device, and the other end of the recovery pipeline is connected to the synthesis gas input branch.

9. A method for synthesizing methanol, characterized in that: include The heat transfer oil in the heat transfer oil circulation loop is heated to a set temperature by a heater; The synthesis gas enters the preheater through the synthesis gas input branch for preheating, and at the same time, the heating of the heater is stopped, and the first cooling flow path connected to the heat transfer oil condenser is started; The synthesis gas is preheated in the preheater and then enters the synthesizer for synthesis reaction. The mixed gas containing methanol and synthesis gas is then output through the post-reaction gas output branch.

10. The method for synthesizing methanol according to claim 9, characterized in that: Before the heat transfer oil in the heat transfer oil circulation loop is heated to a set temperature by the heater, the method further includes: opening a first cut-off valve, releasing the heat transfer oil from the oil storage device, pumping the heat transfer oil into the heater, the synthesizer and the preheater by a pump, closing the first cut-off valve after the heat transfer oil is released, opening a second cut-off valve, and circulating the heat transfer oil in the heat transfer oil circulation loop by the pump; The set temperature is 240°C to 280°C, and the heat transfer oil is in a gaseous state when it exceeds the set temperature; The step of preheating the synthesis gas by entering the preheater through the synthesis gas input branch includes: the synthesis gas flowing out of the synthesis gas source is pressurized to a set pressure by a compressor, enters the high-pressure gas storage device, and then enters the preheater, and the synthesis gas exchanges heat with the heat transfer oil in the first heat transfer oil chamber during the synthesis gas flows through the preheating flow path, and the synthesis gas is preheated; wherein the set pressure is 6Mpa; The step of preheating the synthesis gas in the preheater and then entering the synthesizer for synthesis treatment comprises: the preheated synthesis gas enters the synthesis chamber, under the action of the catalyst in the synthesis chamber, at least part of the synthesis gas undergoes an exothermic reaction to generate methanol, the released heat is exchanged with the heat transfer oil in the second heat transfer oil chamber, the heat transfer oil flows to the preheater under the action of a pump, the gaseous heat transfer oil enters the heat transfer oil condenser for heat exchange and cooling, and then becomes liquid and returns to the second heat transfer oil chamber to enter the heat transfer oil circulation loop for circulation, and the heat transfer oil condenser is used to maintain the heat transfer oil at a set temperature; The step of outputting the mixed gas containing methanol and synthesis gas through the gas output branch after the reaction includes: after the mixed gas containing methanol and synthesis gas flows out from the synthesizer, it first passes through a methanol condenser to condense the methanol in the mixed gas into liquid, and then enters the methanol gas-liquid separation device through the inlet of the methanol gas-liquid separation device for gas-liquid separation, and the separated liquid methanol flows into a methanol storage tank for storage; wherein, The separated gas enters the recovery pipeline and is mixed with the synthesis gas input from the synthesis gas input branch for re-synthesis treatment, or the separated gas enters the purge gas pipeline for purge.

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