CO2-rich synthesis gas methanol synthesis system

Abstract

The utility model discloses a CO2-rich synthesis gas methanol synthesis system which comprises a hydrogen storage unit, a synthesis gas decarbonization unit, a synthesis gas compression unit, a synthesis unit, a gas / gas heat exchanger, a cooler, a high-pressure flash evaporator, a hydrogen recovery unit, a low-pressure flash evaporator and a low-pressure flash vapor compression unit, the hydrogen storage unit can receive volatilly supplied hydrogen and recycled recovered hydrogen, and the hydrogen and the CO2-rich synthesis gas are jointly used as raw material gas for methanol synthesis after being cached by the hydrogen storage unit; the CO2-rich synthesis gas is formed by mixing synthesis gas generated by the synthesis gas decarbonization unit and low-pressure flash steam of the low-pressure flash steam compression unit. According to the system, the CO2 removal rate of the synthesis gas decarbonization unit is adjusted according to the supply quantity of hydrogen, and H2 and CO2 in methanol synthesis tail gas are recycled, so that hydrogen production by renewable energy fluctuation and methanol flexible synthesis by biomass synthesis gas are realized, the utilization rate of renewable carbon is high, and the methanol preparation cost is low.

Description

TECHNICAL FIELD

[0001] The utility model relates to a kind of rich CO2 synthesis gas methanol synthesis system, belong to green methanol preparation technical field. BACKGROUND

[0002] Methanol has the characteristics of efficient combustion, clean emission and renewable, and is known as a new clean energy source. In the application of ships, only a small amount of modification is needed for the existing ships, and methanol can be used as fuel, which can effectively save investment costs. Compared with liquefied natural gas, which needs to be liquefied at low temperature, methanol is in liquid state at room temperature, which is more convenient for storage and use. In the future, methanol will replace traditional high-carbon marine fuel and be widely used. Under the background of global carbon emission reduction and carbon neutralization, shipping giants have developed a plan to replace fuel oil with green methanol as ship fuel to achieve carbon emission reduction. The demand for green methanol in the shipping industry will grow rapidly in the future, and the clean and renewable energy industry for producing green methanol will also enter a fast lane.

[0003] Biomass gasification coupled with green hydrogen to produce chemical products such as methanol and green aviation kerosene is an important way for the development of clean chemical fuels. Biomass, as a renewable resource, has the characteristics of abundant resource output, wide geographical distribution and stable energy reserves. The synthesis gas produced by biomass gasification can be used as raw material gas for methanol synthesis after adjusting the hydrogen-carbon ratio through shift conversion, but the shift conversion system requires additional steam consumption and the discharge of part of CO2, resulting in a decrease in the utilization rate of renewable carbon sources. With the increase in installed capacity of renewable energy power generation in China, due to the instability of renewable energy output, there has been a serious problem of "abandoned wind and light". The problem of abandoned new energy power generation is gradually becoming prominent, hindering the development and utilization of new energy. Using renewable energy power generation (such as wind power and photovoltaic power) to produce hydrogen through water electrolysis is one of the effective ways to solve the problem of abandoned new energy power generation, and also can improve the utilization rate of CO2 in biomass synthesis gas and reduce the production cost of methanol.

[0004] In summary, there is an urgent need for a rich CO2 synthesis gas methanol synthesis system to solve the problem of low utilization rate of renewable carbon (CO2) in biomass gasification for green methanol production and the adaptability of biomass gasification coupled with fluctuating green hydrogen synthesis of green methanol. SUMMARY

[0005] Currently, the hydrogen produced by electrolysis of water is mostly produced by new energy (wind power, photovoltaic) power generation. Due to the strong volatility and randomness of new energy power generation, the hydrogen provided by the electrolysis of water also has strong volatility. When the hydrogen with strong volatility is used as a green methanol synthesis raw material, higher adaptability is required for the methanol synthesis system. On the other hand, green methanol requires that the source of carbon be renewable carbon, such as carbon in biomass. The utilization efficiency of carbon in the traditional methanol synthesis technology is low, and renewable carbon is a valuable resource that needs to be used as efficiently as possible.

[0006] The technical problem to be solved by the utility model is that the utilization rate of renewable carbon (CO2) in the green methanol produced by biomass gasification is low, and the adaptability of the system for synthesizing green methanol by coupling biomass gasification and volatile green hydrogen is difficult.

[0007] In order to solve the above technical problem, the technical scheme of the utility model is to provide a CO2-rich synthesis gas methanol synthesis system, and the technical scheme is as follows:

[0008] The system comprises a hydrogen storage unit, a synthesis gas decarburization unit, a synthesis gas compression unit, a synthesis unit, a gas / gas heat exchanger, a cooler, a high-pressure flash evaporator, a hydrogen recovery unit, a low-pressure flash evaporator, and a low-pressure flash gas compression unit.

[0009] The hydrogen storage unit can receive volatile hydrogen and recovered hydrogen from the hydrogen recovery unit, and after being buffered by the hydrogen storage unit, relatively stable hydrogen and CO2-rich synthesis gas are formed together as raw gas for methanol synthesis. The CO2-rich synthesis gas is formed by mixing synthesis gas produced by the synthesis gas decarburization unit and first low-pressure flash gas obtained by the low-pressure flash evaporator after being pressurized by the low-pressure flash gas compression unit. After the stable hydrogen and the CO2-rich synthesis gas are mixed, they enter the methanol synthesis loop, the hydrogen in the purge gas returns to the hydrogen storage unit for continuous use, and the flash gas of the low-pressure flash evaporator also returns to the methanol synthesis loop for continuous use.

[0010] Preferably, the hydrogen storage unit is a gaseous hydrogen storage unit, and the hydrogen storage pressure is 1.0 MPa to 8.0 MPa.

[0011] Preferably, the hydrogen storage pressure is 1.5 MPa to 3 MPa.

[0012] Preferably, the synthesis gas decarburization unit can achieve different CO2 removal rates according to requirements, so that the synthesis gas (202) has a wide range of CO2 concentrations, and the CO2 concentration is 1 mol% to 50 mol%.

[0013] Preferably, the CO2 concentration is 2 mol% to 30 mol%.

[0014] Preferably, the flash pressure of the low-pressure flash evaporator is 0.1-1.0 MPa; the first low-pressure flash gas is pressurized by a low-pressure flash gas compression unit and then returned to the methanol synthesis system for continuing methanol synthesis.

[0015] Preferably, the flash pressure of the low-pressure flash evaporator (900) is 0.3-0.5 MPa.

[0016] Preferably, the operation pressure of the hydrogen recovery unit is 0.3 MPa higher than the storage unit pressure, and the recovered hydrogen is sent to the storage unit.

[0017] Preferably, the methanol synthesis loop is composed of a synthesis gas compression unit, a synthesis unit, a gas / gas heat exchanger, a cooler (600) and a high-pressure flash evaporator, and the operation pressure of the synthesis loop is 5-10 MPa.

[0018] Preferably, the operation pressure of the synthesis loop is 5-10 MPa.

[0019] The CO2 content in the raw gas is adjusted to adapt to the volatility of green hydrogen. When the supply of green hydrogen is at a peak, the CO2 removal rate of the synthesis gas decarburization unit is reduced to increase the CO2 content in the synthesis gas entering the methanol synthesis loop, and the excess hydrogen reacts with CO and a large amount of CO2 in the synthesis gas to produce green methanol. When the supply of green hydrogen is at a trough, the CO2 removal rate of the synthesis gas decarburization unit is increased to reduce the CO2 content in the synthesis gas entering the methanol synthesis loop, and the appropriate hydrogen reacts with CO and a small amount of CO2 in the synthesis gas to produce green methanol.

[0020] The CO2-rich synthesis gas methanol synthesis system provided by the utility model realizes the preparation of green methanol from high-concentration CO2 synthesis gas coupled with volatile green hydrogen. The system is stable and reliable in operation, has high renewable carbon (CO2) utilization rate, and can adapt to hydrogen supplied in a volatile manner. Compared with the prior art, the utility model has the following beneficial effects:

[0021] (1) The utility model adjusts the hydrogen-carbon ratio in the methanol synthesis raw gas by using volatile green hydrogen, and the instability of volatile green hydrogen is eliminated by setting a hydrogen storage unit, so that the methanol synthesis is stably operated.

[0022] (2) Compared with conventional methanol synthesis systems, the utility model can convert a large amount of CO2 into methanol, thereby improving the renewable carbon (CO2) utilization rate. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 A CO2-rich synthesis gas methanol synthesis system provided by the utility model is shown in the figure.

[0024] 101 - fluctuating supply of hydrogen; 100 - hydrogen storage unit; 102 - stabilized hydrogen; 200 - syngas decarbonization unit; 201 - biomass syngas; 202 / 203 - CO2-rich syngas; 204 - CO2gas; 300 - syngas compression unit; 301 / 501 - methanol synthesis feed gas; 400 - methanol synthesis unit; 401 / 502 - methanol synthesis effluent gas; 500 - gas / gas heat exchanger; 600 - methanol cooler; 601 - methanol mixed gas; 700 - high pressure flasher; 701 - high pressure flash gas; 702 - recycle gas; 703 - hydrogen recovery feed gas; 800 - hydrogen recovery unit; 801 - recovered hydrogen; 802 - purge gas; 704 / 901 - crude methanol; 900 - low pressure flasher; 902 - first low pressure flash gas; 1002 - second low pressure flash gas; 1000 - low pressure flash gas compression unit. DETAILED DESCRIPTION

[0025] The utility model is further described below in combination with specific embodiments.

[0026] Embodiment: The purpose of the utility model is to make the most of renewable carbon in biomass, and at the same time solve the adaptability problem of a system for synthesizing green methanol by coupling biomass gasification with fluctuating green hydrogen. In order to achieve the above-mentioned goal, the utility model provides a CO2-rich syngas methanol synthesis system. In order to further illustrate the utility model, a specific embodiment with green methanol production capacity of 100,000 tons / year is described. As shown in Figure 1 The CO2-rich syngas methanol synthesis system mainly includes a hydrogen storage unit, a syngas decarbonization unit, a syngas compression unit, a synthesis unit, a gas / gas heat exchanger, a cooler, a high pressure flasher, a hydrogen recovery unit, a low pressure flasher, and a low pressure flash gas compression unit.

[0027] The methanol production is about 13t / h according to the annual operation of 8000 hours. The supply pressure of hydrogen (102) is 1.5MPa, the normal flow is 8000Nm3 / h, and the flow variation range is 1000Nm3 / h-17600Nm3 / h. The hydrogen storage pressure of the hydrogen storage unit (100) is 1.4MPa, and the hydrogen storage capacity is 200,000Nm3. The pressure of the biomass synthesis gas (201) is 0.3MPa, the normal component of the synthesis gas is CO 25mol%, CO2 30mol%, H2 35mol%, and other 10mol%, the normal flow is 34000Nm3 / h, and the flow variation range is 13600Nm3 / h-34000Nm3 / h; the CO2 content of the synthesis gas after the decarburization unit (200) is 2.6mol%-30mol%. From the parameters of the above raw gas, it can be seen that the hydrogen variation range is 12.5%-220% of the normal flow, and the flow variation range of the synthesis gas is 40%-100% of the normal flow. In order to adapt to the above fluctuation range, the utility model discloses a special methanol synthesis catalyst, which is filled in the methanol synthesis unit (400). At the same time, in order to adapt to the change of the load, the utility model also includes a special methanol synthesis reactor, which can adapt to the operation pressure range of 5MPa-10MPa.

[0028] The utility model needs to switch operation under different operation conditions, and the operation conditions are shown in table 1, and the operation condition is as follows.

[0029] Operating condition number Hydrogen flow (101) Hydrogen load ratio Hydrogen flow (102) Synthesis gas flow (201) Synthesis gas load ratio Synthesis gas flow (202) CO2 removal rate CO content (202) H2 content (202) CO2 content (202) Other component content (202) Methanol production, after water and impurities (901) Nm3 / h % Nm3 / h Nm3 / h % Nm3 / h mol% mol% mol% mol% mol% kg / h 1 17600 220.00% 26600 34000 100.00% 34000 0.00% 25.00% 35.00% 30.00% 10.00% 21735.71 2 17600 220.00% 22000 27200 80.00% 27200 0.00% 25.00% 35.00% 30.00% 10.00% 17388.57 3 17600 220.00% 17600 22100 65.00% 22100 0.00% 25.00% 35.00% 30.00% 10.00% 14128.21 4 17600 220.00% 10600 13600 40.00% 13600 0.00% 25.00% 35.00% 30.00% 10.00% 8694.29 5 8000 100.00% 11000 13600 40.00% 13600 0.00% 25.00% 35.00% 30.00% 10.00% 8694.29 6 8000 100.00% 9000 22100 65.00% 18070 60.78% 30.58% 42.81% 14.39% 12.23% 10098.21 7 8000 100.00% 8000 27200 80.00% 20840 77.94% 32.63% 45.68% 8.64% 13.05% 11028.57 8 8000 100.00% 8000 34000 100.00% 25300 85.29% 33.60% 47.04% 5.93% 13.44% 13035.71 9 4000 50.00% 4000 13600 40.00% 10520 75.49% 32.32% 45.25% 9.51% 12.93% 5614.29 10 1000 12.50% 2000 13600 40.00% 7816 95.10% 34.80% 48.72% 2.56% 13.92% 3891.43

[0030] Table 1 is the operation condition parameter table

[0031] When the supply flow of hydrogen is 17600Nm 3 / h, if the hydrogen storage unit is in full capacity state, 26600Nm3 / h of hydrogen directly enters the methanol synthesis loop until the inventory of the hydrogen storage tank reduces to the minimum value, and the whole process can be maintained for about 18 hours; the process does not need to remove CO2 in the biomass synthesis gas, the methanol synthesis loop is in the upper limit of the operating pressure, and the carbon source (CO / CO2) can be efficiently utilized;

[0032] When the supply flow of hydrogen is 17600Nm3 / h, if the hydrogen storage unit is in full capacity state, but it is predicted that the supply of hydrogen may be reduced, then 10600Nm3 / h-22000Nm3 / h of hydrogen directly enters the methanol synthesis loop until the inventory of the hydrogen storage tank reduces to the minimum value; the process needs to reduce the synthesis gas supply load to save the consumption of raw materials, the methanol synthesis loop is in the upper limit of the operating pressure, and the carbon source (CO / CO2) can still be efficiently utilized without removing CO2 in the biomass synthesis gas;

[0033] Case 5: When the supply flow of hydrogen is 8000 Nm3 / h, if the hydrogen storage unit is in full capacity, 11000 Nm3 / h of hydrogen directly enters the methanol synthesis loop until the inventory of the hydrogen storage tank is reduced to the minimum value, the whole process can be maintained for about 80 hours; this process needs to reduce the synthesis gas supply to the minimum load, the methanol synthesis loop is at the intermediate value of the operating pressure, and there is no need to remove CO2 in the biomass synthesis gas, and the carbon source (CO / CO2) can be efficiently utilized;

[0034] Case 6~Case 8: When the supply flow of hydrogen is 8000 Nm3 / h, whether the synthesis gas supply load needs to be increased is determined according to the annual methanol production demand, if so, the synthesis gas supply load is gradually increased to increase the methanol production, the methanol synthesis loop is at the intermediate value of the operating pressure, and part of the CO2 in the synthesis gas needs to be removed, and the utilization rate of the carbon source (CO2) is reduced;

[0035] Case 9~Case 10: When the supply flow of hydrogen is less than 4000 Nm3 / h, the synthesis gas supply load needs to be reduced to 40%, and most of the CO2 in the synthesis gas needs to be removed, the methanol synthesis loop is at the lower limit of the operating pressure, and the utilization rate of the source (CO2) is further reduced.

[0036] The above cases are only limited examples for understanding the present application. According to the hydrogen storage capacity of the hydrogen storage unit and the predicted hydrogen supply change, different combinations can be made in the hydrogen flow from the hydrogen storage tank, the synthesis gas supply load, the CO2 removal rate, the methanol synthesis loop operating pressure and other key indicators to achieve the annual production target.

[0037] As can be seen from the above examples, the present application realizes the relative stable operation of the biomass synthesis gas and green hydrogen coupling green methanol through the innovative system design and reasonable process parameter setting, the adjustment of the hydrogen-carbon ratio in the methanol synthesis raw gas by using new energy power generation to produce hydrogen, the provision of relatively stable green hydrogen to the synthesis unit by setting a hydrogen storage unit, the realization of the relative stable operation of the biomass synthesis gas and green hydrogen coupling green methanol by setting a synthesis gas purification unit with adjustable CO2 removal rate, the efficient utilization of renewable carbon source and hydrogen source by using a special methanol synthesis catalyst and reactor, and the reduction of the green methanol preparation cost.

[0038] The above examples 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 those skilled in the art without creative labor belong to the scope of protection of the present application.

Claims

1. A CO2-rich syngas methanol synthesis system, characterized in that, It comprises: a hydrogen storage unit (100), a syngas decarburization unit (200), a syngas compression unit (300), a synthesis unit (400), a gas / gas heat exchanger (500), a cooler (600), a high-pressure flash evaporator (700), a hydrogen recovery unit (800), a low-pressure flash evaporator (900), and a low-pressure flash gas compression unit (1000); The hydrogen storage unit (100) can receive fluctuating hydrogen (101) and recovered hydrogen (801) from the hydrogen recovery unit (800), and after being buffered by the hydrogen storage unit (100), relatively stable hydrogen (102) and CO2-rich syngas (203) are formed together as raw gas for methanol synthesis. The CO2-rich syngas (203) is formed by mixing syngas (202) produced by the syngas decarburization unit (200) and the second low-pressure flash gas (1002) obtained by the low-pressure flash gas compression unit (1000) after the first low-pressure flash gas (902) obtained by the low-pressure flash evaporator (900) is pressurized. After the stable hydrogen (102) and the CO2-rich syngas (203) are mixed, they enter the methanol synthesis loop.

2. The CO2-rich syngas methanol synthesis system according to claim 1, characterized in that: The hydrogen storage unit (100) is a gaseous hydrogen storage, and the hydrogen storage pressure is 1.0 MPa to 8.0 MPa.

3. The CO2-rich syngas methanol synthesis system according to claim 2, characterized in that: The hydrogen storage pressure is 1.5 MPa to 3 MPa.

4. The CO2-rich syngas methanol synthesis system according to claim 1, characterized in that: The syngas decarburization unit (200) can achieve different CO2 removal rates according to demand, so that the syngas (202) has a wide range of CO2 concentrations, and the CO2 concentration is 1 mol% to 50 mol%.

5. The CO2-rich syngas methanol synthesis system according to claim 4, characterized in that: The CO2 concentration is 2 mol% to 30 mol%.

6. The CO2-rich syngas methanol synthesis system according to claim 1, characterized in that: The flash evaporation pressure of the low-pressure flash evaporator (900) is 0.1 MPa to 1.0 MPa; and the first low-pressure flash gas (902) is pressurized by the low-pressure flash gas compression unit (1000) and returned to the methanol synthesis system to continue to synthesize methanol.

7. The CO2-rich syngas methanol synthesis system according to claim 6, characterized in that: The flash evaporation pressure of the low-pressure flash evaporator (900) is 0.3 MPa to 0.5 MPa.

8. The CO2-rich syngas methanol synthesis system according to claim 1, characterized in that: The operating pressure of the hydrogen recovery unit (800) is 0.3 MPa higher than the pressure of the hydrogen storage unit (100), and the recovered hydrogen (801) is sent to the hydrogen storage unit (100).

9. The CO2-rich syngas methanol synthesis system according to claim 1, characterized in that: The methanol synthesis loop is composed of a synthesis gas compression unit (300), a synthesis unit (400), a gas / gas heat exchanger (500), and a cooler (600), a high-pressure flash evaporator (700), and the operating pressure of the synthesis loop is 4-12 MPa.

10. The CO2-rich syngas methanol synthesis system of claim 1, wherein: The operating pressure of the synthesis loop is 5-10 MPa.

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