System for preparing green methanol by coupling photo-thermal fused salt energy storage

Abstract

The invention provides a photo-thermal fused salt energy storage coupled green methanol preparation system which comprises a reverse water-gas shift unit, a methanol synthesis unit, a photo-thermal energy storage unit, a power generation unit and an electrolytic hydrogen production unit, and the photo-thermal energy storage unit absorbs light energy and generates heat energy; a heat energy outlet of the photo-thermal energy storage unit is communicated with a heat energy inlet of the reverse water-gas conversion unit; a heat energy outlet of the reverse water-gas conversion unit is communicated with a heat energy inlet of the power generation unit; a heat energy outlet of the methanol synthesis unit is communicated with a heat energy inlet of the power generation unit; an electric energy outlet of the power generation unit is communicated with an electric energy inlet of the electrolytic hydrogen production unit, and the electrolytic hydrogen production unit generates hydrogen; the carbon dioxide and the hydrogen enter a reverse water gas shift unit to generate shift gas; and the shift gas and hydrogen enter a methanol synthesis unit to generate methanol. The system can supply power and heat to the outside, and therefore co-production of products such as hydrogen, oxygen, synthesis gas and methyl alcohol, electric power and thermal power is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of manufacturing methanol using hydrogen and carbon dioxide, and particularly to a molten salt energy storage coupled with solar thermal energy for producing green methanol system. Background Art

[0002] Green methanol is a type of methanol prepared using carbon dioxide and green hydrogen as raw materials. The raw materials for producing green methanol are hydrogen and carbon dioxide. Among them, hydrogen is "green hydrogen", that is, hydrogen obtained by electrolyzing water using renewable energy such as photovoltaic and wind power generation. Carbon dioxide mainly comes from processes such as biomass or carbon capture. Therefore, its preparation process has the characteristic of negative carbon emissions. After combustion, water and carbon dioxide are emitted, and the net emissions are zero. Methanol can also be used as a carrier for hydrogen. Methanol can be converted into hydrogen through reforming technology. This method can solve the problems of hydrogen storage and transportation. Therefore, green methanol is considered a carbon-neutral clean energy, and efficient green methanol preparation technology plays an important role in achieving carbon neutrality goals in the fields of energy, chemical industry, transportation, etc.

[0003] The overall reaction of producing methanol from carbon dioxide and hydrogen is as follows:

[0004] CO2 + 3H2 → CH3OH + H2O - 48.6 kJ / mol

[0005] Industrially, this process is also completed through a two-step method, namely reverse water gas shift and methanol synthesis:

[0006] CO2 + H2 → CO + H2O + 42.1 kJ / mol

[0007] CO + 2H2 → CH3OH - 90.7 kJ / mol

[0008] The advantage of the two-step method for producing methanol industrially is that by in-situ removing water, the chemical equilibrium shifts towards the methanol production direction, improving the methanol yield, and can alleviate problems such as catalyst deactivation exacerbated by the presence of water. This method is considered one of the effective ways to produce green methanol because it improves the CO2 conversion rate and methanol selectivity.

[0009] However, there are also certain disadvantages in using the two-step method to produce methanol. Mainly, since the overall reaction of producing methanol from carbon dioxide and hydrogen is an exothermic reaction, but the reverse water gas shift is an endothermic reaction, the reaction temperature of the water gas (450 - 600 °C) is much higher than the exothermic temperature of methanol synthesis (≤ 400 °C), making it difficult to achieve efficient energy utilization. Therefore, the energy consumption of this methanol preparation process is still relatively high. Summary of the Invention

[0010] In view of the above-mentioned disadvantages of the prior art, the object of the present invention is to provide a solar-thermal molten salt energy storage coupled green methanol production system, which is used to solve the problems of high energy consumption and energy loss in the process of preparing methanol from carbon dioxide and hydrogen in the prior art.

[0011] To achieve the above object and other related objects, the present invention provides a solar-thermal molten salt energy storage coupled green methanol production system, including a reverse water-gas shift unit, a methanol synthesis unit, a solar-thermal energy storage unit, a power generation unit, and an electrolytic hydrogen production unit. The solar-thermal energy storage unit absorbs light energy and generates heat energy. The heat energy outlet of the solar-thermal energy storage unit is communicated with the heat energy inlet of the reverse water-gas shift unit. The heat energy outlet of the reverse water-gas shift unit is communicated with the heat energy inlet of the power generation unit. The heat energy outlet of the methanol synthesis unit is communicated with the heat energy inlet of the power generation unit. The electric energy outlet of the power generation unit is communicated with the electric energy inlet of the electrolytic hydrogen production unit, and the electrolytic hydrogen production unit generates hydrogen. Carbon dioxide and hydrogen enter the reverse water-gas shift unit to generate syngas. The syngas and hydrogen enter the methanol synthesis unit to generate methanol.

[0012] Preferably, the reverse water-gas shift unit includes a raw material gas compression and mixing assembly, a raw material gas condenser, a raw material gas heat exchanger, a fixed-bed reactor, and a syngas gas-liquid separation assembly. Carbon dioxide and hydrogen are introduced into the inlet of the raw material gas compression and mixing assembly. The outlet of the raw material gas compression and mixing assembly is communicated with the inlet of the raw material gas condenser. The outlet of the raw material gas condenser is communicated with the inlet of the raw material gas heat exchanger. The outlet of the raw material gas heat exchanger is communicated with the inlet of the fixed-bed reactor. The outlet of the fixed-bed reactor passes through the raw material gas condenser and is communicated with the inlet of the syngas gas-liquid separation assembly. The outlet of the syngas gas-liquid separation assembly is communicated with the methanol synthesis unit. The heat energy inlet of the raw material gas heat exchanger is communicated with the heat energy outlet of the solar-thermal energy storage unit.

[0013] Preferably, the raw material gas compression and mixing assembly includes a carbon dioxide compressor, a raw material gas mixer, and a raw material gas compressor. Carbon dioxide is introduced into the inlet of the carbon dioxide compressor. The outlet of the carbon dioxide compressor is communicated with the inlet of the raw material gas mixer. Hydrogen is also introduced into the inlet of the raw material gas mixer. The outlet of the raw material gas mixer is communicated with the inlet of the raw material gas compressor. The outlet of the raw material gas compressor is communicated with the inlet of the raw material gas condenser.

[0014] Preferably, the methanol synthesis unit includes a shift gas mixer, a shift gas heat exchanger, a reaction assembly, and a syngas gas-liquid separation assembly; the inlet of the shift gas mixer is fed with shift gas and hydrogen, the outlet of the shift gas mixer is communicated with the inlet of the shift gas heat exchanger, the outlet of the shift gas heat exchanger is communicated with the inlet of the reaction assembly, and the outlet of the reaction assembly is communicated with the inlet of the syngas gas-liquid separation assembly; the outlet of the syngas gas-liquid separation assembly is further connected to a purge gas treatment assembly, and the liquid outlet of the syngas gas-liquid separation assembly is further connected to a methanol refining assembly.

[0015] Preferably, the reaction assembly includes a first isothermal reactor and a steam drum; the outlet of the shift gas heat exchanger is communicated with the inlet of the first isothermal reactor, and the outlet of the first isothermal reactor passes through the shift gas heat exchanger and is communicated with the inlet of the syngas gas-liquid separation assembly; a heat cycle is formed between the first isothermal reactor and the steam drum.

[0016] Preferably, the reaction assembly includes a first isothermal reactor and a second isothermal reactor; the outlet of the shift gas heat exchanger is respectively communicated with the inlet of the first isothermal reactor and the inlet of the second isothermal reactor; the outlet of the first isothermal reactor passes through the shift gas heat exchanger and is communicated with the inlet of the second isothermal reactor; the outlet of the second isothermal reactor is communicated with the inlet of the syngas gas-liquid separation assembly, and a syngas heat exchanger is further arranged between the outlet of the second isothermal reactor and the inlet of the syngas gas-liquid separation assembly.

[0017] Preferably, the syngas gas-liquid separation assembly includes a first syngas gas-liquid separator, a syngas condenser, and a second syngas gas-liquid separator; the inlet of the first syngas gas-liquid separator is communicated with the outlet of the reaction assembly, the inlet of the syngas condenser is communicated with the outlet of the first syngas gas-liquid separator, and the outlet of the syngas condenser is communicated with the inlet of the second syngas gas-liquid separator; the outlet of the second syngas gas-liquid separator is connected to the purge gas treatment assembly; the liquid outlets of the first syngas gas-liquid separator and the second syngas gas-liquid separator are both connected to the methanol refining assembly.

[0018] Preferably, the solar thermal energy storage unit includes a solar thermal component and an energy storage component; the solar thermal component includes a tower-type solar thermal collector; the energy storage component includes a high-temperature molten salt tank and a low-temperature molten salt tank; the heat energy inlet of the high-temperature molten salt tank is communicated with the tower-type solar thermal collector, the heat energy outlet of the high-temperature molten salt tank is communicated with the heat energy inlet of the reverse water-gas shift unit, the heat energy outlet of the reverse water-gas shift unit is communicated with the heat energy inlet of the low-temperature molten salt tank, and the heat energy outlet of the low-temperature molten salt tank is communicated with the tower-type solar thermal collector.

[0019] Preferably, the power generation unit includes a steam turbine, a generator, an AC / DC rectifier, a water recovery component, a water polishing component, and a steam heat exchanger. The rotating shaft of the steam turbine is drivingly connected to the generator, and the generator is electrically connected to the AC / DC rectifier. The steam heat exchanger is arranged between the heat energy outlet of the reverse water-gas shift unit and the heat energy inlet of the low-temperature molten salt tank, and the gas outlet of the steam heat exchanger is communicated with the gas inlet of the steam turbine. The gas outlet of the steam turbine is connected to the water recovery component, and the water recovery component is connected to the water polishing component. The water in the water polishing component circulates back to the steam turbine through the syngas condenser, the steam drum, and the steam heat exchanger; or the water in the water polishing component circulates back to the steam turbine through the syngas condenser, the syngas heat exchanger, and the steam heat exchanger.

[0020] Preferably, the electrolytic hydrogen production unit includes an electrolytic cell, a drying tower, and a hydrogen compressor. The electrolytic cell is electrically connected to the AC / DC rectifier. The hydrogen generated at the negative electrode of the electrolytic cell is communicated with the gas inlet of the drying tower through a pipeline, the gas outlet of the drying tower is communicated with the gas inlet of the hydrogen compressor, and the gas outlet of the hydrogen compressor is respectively communicated with the reverse water-gas shift unit and the methanol synthesis unit.

[0021] As described above, the solar-thermal molten salt energy storage coupled green methanol production system of the present invention has the following beneficial effects:

[0022] 1. The present invention combines tower-type solar-thermal technology, molten salt heat storage technology, and green methanol technology to form a process system for producing green methanol from carbon dioxide and water as raw materials. The energy storage system in this system uses the solar-thermal molten salt system to generate electricity and uses electrolyzed water to produce hydrogen, and at the same time provides energy for the reverse water-gas shift reaction to produce carbon monoxide, and then carbon monoxide and hydrogen react to generate methanol, and the heat generated in this process is collected for power generation. All the energy in the production of methanol comes from solar-thermal, and efficient green methanol production is achieved through a series of hierarchical energy utilization.

[0023] 2. In the process of producing green methanol, the present invention can extract syngas, hydrogen, oxygen, etc. from different process nodes to form by-products, and the system in this application can also supply power and heat externally, so as to realize the co-production of products such as hydrogen, oxygen, syngas, and methanol with electricity and heat.

[0024] 3. The present invention stores solar-thermal energy using molten salt heat storage and slowly releases the energy by the flow of molten salt. When there is no sunlight, it can also ensure the continuous and stable operation of the production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of energy flow in the isothermal conversion of the solar-thermal molten salt energy storage coupled green methanol production system of the present invention;

[0026] Figure 2 Schematic flow diagram of the first embodiment of the molten salt energy storage coupled with photo-thermal conversion for green methanol production system of the present invention;

[0027] Figure 3 Schematic flow diagram of the second embodiment of the molten salt energy storage coupled with photo-thermal conversion for green methanol production system of the present invention.

[0028] Description of reference numerals:

[0029] C101, carbon dioxide compressor; M101, raw gas mixer; C102, raw gas compressor; E101, raw gas condenser; E102, raw gas heat exchanger; R101, fixed bed reactor; T101, shift gas gas-liquid separation module; M201, shift gas mixer; E201, shift gas heat exchanger; R201, first isothermal reactor; R202, second isothermal reactor; E202, syngas heat exchanger; T201, steam drum; T202, first syngas gas-liquid separator; E203, syngas condenser; T203, second syngas gas-liquid separator; T301, high-temperature molten salt tank; E301, steam heat exchanger; T302, low-temperature molten salt tank; ER401, electrolyzer; T401, drying tower; C401, hydrogen compressor. Detailed implementation manners

[0030] The following specific embodiments illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0031] It should be noted that the structures, ratios, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those skilled in the art to understand and read, and are not used to limit the implementation conditions of the present invention. Therefore, they do not have technical essence. Any modification of the structure, change of the proportional relationship or adjustment of the size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope covered by the technical content disclosed in the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" cited in this specification are only for the convenience of clear description and are not used to limit the implementation scope of the present invention. The change or adjustment of their relative relationships, without substantial change in the technical content, should also be regarded as the scope within which the present invention can be implemented.

[0032] As Figures 1 - 3As shown in the figure, the present invention provides a solar-thermal molten salt energy storage coupled green methanol production system, which includes a reverse water-gas shift unit, a methanol synthesis unit, a solar-thermal energy storage unit, a power generation unit, and an electrolytic hydrogen production unit. The solar-thermal energy storage unit absorbs light energy and generates heat energy. The heat energy outlet of the solar-thermal energy storage unit is connected to the heat energy inlet of the reverse water-gas shift unit. The heat energy outlet of the reverse water-gas shift unit is connected to the heat energy inlet of the power generation unit. The heat energy outlet of the methanol synthesis unit is connected to the heat energy inlet of the power generation unit. The electric energy outlet of the power generation unit is connected to the electric energy inlet of the electrolytic hydrogen production unit, and the electrolytic hydrogen production unit generates hydrogen. Carbon dioxide and hydrogen enter the reverse water-gas shift unit to generate syngas. The syngas and hydrogen enter the methanol synthesis unit to generate methanol.

[0033] The solar-thermal molten salt energy storage coupled green methanol production system involved in the present invention uses carbon dioxide and water as raw materials to produce green methanol. The heat required by the reverse water-gas shift unit comes from the solar-thermal energy storage unit. At the same time, the unused heat in the reverse water-gas shift unit enters the power generation unit for power generation, and the electric energy generated by the power generation unit is used to generate hydrogen through the electrolytic hydrogen production unit. The heat released in the methanol synthesis unit also enters the power generation unit for power generation. That is, all the energy in the green methanol production system of this application comes from solar heat, and a series of energy gradients in the system are effectively utilized, with low energy consumption and good environmental protection effects.

[0034] To describe in detail the solar-thermal molten salt energy storage coupled green methanol production system involved in this application, two embodiments are now disclosed to specifically describe the process preparation flow of the system:

[0035] The first embodiment:

[0036] Preferably, as Figure 2 shown, the reverse water-gas shift unit includes a raw material gas compression and mixing assembly, a raw material gas condenser E101, a raw material gas heat exchanger E102, a fixed bed reactor R101, and a syngas gas-liquid separation assembly T101. Carbon dioxide and hydrogen are introduced into the intake port of the raw material gas compression and mixing assembly. The outlet of the raw material gas compression and mixing assembly is connected to the intake port of the raw material gas condenser E101. The outlet of the raw material gas condenser E101 is connected to the intake port of the raw material gas heat exchanger E102. The outlet of the raw material gas heat exchanger E102 is connected to the intake port of the fixed bed reactor R101. The outlet of the fixed bed reactor R101 passes through the raw material gas condenser E101 and is connected to the intake port of the syngas gas-liquid separation assembly T101. The outlet of the syngas gas-liquid separation assembly T101 is connected to the methanol synthesis unit. The heat energy inlet of the raw material gas heat exchanger E102 is connected to the heat energy outlet of the solar-thermal energy storage unit. The reaction temperature in the reverse water-gas shift unit is in the range of 450 - 600 °C.

[0037] Further, as Figure 2As shown, the raw material gas compression and mixing assembly includes a carbon dioxide compressor C101, a raw material gas mixer M101, and a raw material gas compressor C102. Carbon dioxide is introduced into the intake port of the carbon dioxide compressor C101. The outlet of the carbon dioxide compressor C101 is communicated with the intake port of the raw material gas mixer M101. Hydrogen is also introduced into the intake port of the raw material gas mixer M101. The outlet of the raw material gas mixer M101 is communicated with the intake port of the raw material gas compressor C102. The outlet of the raw material gas compressor C102 is communicated with the intake port of the raw material gas condenser E101.

[0038] In the reverse water gas shift unit, carbon dioxide is first boosted by the carbon dioxide compressor C101 and then enters the raw material gas mixer M101. At the same time, hydrogen generated in the electrolytic hydrogen production unit enters the raw material gas mixer M101 to form the raw material gas. The raw material gas is further boosted to about 4 MPa by the raw material gas compressor C102 and then enters the raw material gas condenser E101. The raw material gas is heated to above 350 °C by the shift gas from the outlet of the fixed bed reactor R101 in the raw material gas condenser E101, and then the raw material gas enters the raw material gas heat exchanger E102. In the raw material gas heat exchanger E102, the high-temperature molten salt in the high-temperature molten salt tank T301 heats the raw material gas to above 550 °C, and then the raw material gas enters the fixed bed reactor R101 for the reverse water gas shift reaction to generate shift gas, which contains carbon monoxide and water vapor. The shift gas flows through the raw material gas condenser E101 from the outlet of the fixed bed reactor R101, is cooled by releasing heat to below 240 °C in the raw material gas condenser E101, and then enters the shift gas gas-liquid separation assembly T101. The shift gas gas-liquid separation assembly T101 removes the water vapor in the shift gas. The carbon monoxide in the shift gas enters the methanol synthesis unit, and the water in the shift gas enters the water recovery system for recovery.

[0039] Further, in this embodiment, the carbon dioxide and hydrogen entering the raw material gas mixer M101 are properly proportioned to ensure that the components of the shift gas are carbon monoxide and water. Or slightly more hydrogen is used to ensure that the carbon dioxide reacts completely, so that the components of the shift gas are carbon monoxide, hydrogen, and water. Since hydrogen is still needed in the methanol synthesis unit, a small amount of hydrogen in the shift gas will not cause any impact.

[0040] Preferably, as Figure 2As shown in the figure, the methanol synthesis unit includes a shift gas mixer M201, a shift gas heat exchanger E201, a reaction assembly, and a syngas gas-liquid separation assembly; the inlet of the shift gas mixer M201 is fed with shift gas and hydrogen, the outlet of the shift gas mixer M201 is connected to the inlet of the shift gas heat exchanger E201, the outlet of the shift gas heat exchanger E201 is connected to the inlet of the reaction assembly, and the outlet of the reaction assembly is connected to the inlet of the syngas gas-liquid separation assembly; the outlet of the syngas gas-liquid separation assembly is also connected to a purge gas treatment assembly, and the liquid outlet of the syngas gas-liquid separation assembly is also connected to a methanol refining assembly. The process in the methanol synthesis unit is a heat release process, and high-temperature and high-pressure steam with a temperature of 240-280°C can be generated.

[0041] Preferably, as Figure 2 shown, the reaction assembly includes a first isothermal reactor R201 and a steam drum T201. The outlet of the shift gas heat exchanger E201 is connected to the inlet of the first isothermal reactor R201, and the outlet of the first isothermal reactor R201 is connected to the inlet of the syngas gas-liquid separation assembly through the shift gas heat exchanger E201; a heat cycle is formed between the first isothermal reactor R201 and the steam drum T201.

[0042] Furthermore, as Figure 2 shown, the syngas gas-liquid separation assembly includes a first syngas gas-liquid separator T202, a syngas condenser E203, and a second syngas gas-liquid separator T203. The inlet of the first syngas gas-liquid separator T202 is connected to the outlet of the first isothermal reactor R201, the inlet of the syngas condenser E203 is connected to the outlet of the first syngas gas-liquid separator T202, and the outlet of the syngas condenser E203 is connected to the inlet of the second syngas gas-liquid separator T203; the outlet of the second syngas gas-liquid separator T203 is connected to the purge gas treatment assembly; the liquid outlets of the first syngas gas-liquid separator T202 and the second syngas gas-liquid separator T203 are both connected to the methanol refining assembly.

[0043] In the methanol synthesis unit, the shifted gas and hydrogen enter the shifted gas heat exchanger E201 after a certain adjustment of the hydrogen-carbon ratio in the shifted gas mixer M201, and are heated to 220°C by the syngas from the outlet of the first isothermal reactor R201 and then enter the first isothermal reactor R201. The shifted gas and hydrogen carry out methanol synthesis in the first isothermal reactor R201 and release heat. The heat circulates in the first isothermal reactor R201 and the steam drum T201. Water required in the power generation unit flows through the steam drum T201, and the water absorbs heat in the steam drum T201 to generate high-temperature and high-pressure steam (≥250°C) at 3.4 MPa. The syngas in the first isothermal reactor R201 flows out from the outlet, is cooled and condensed in the shifted gas heat exchanger E201, and then enters the first syngas gas-liquid separator T202 to separate part of the methanol in the syngas. Part of the methanol enters the methanol refining component from the liquid outlet of the first syngas gas-liquid separator T202. The unliquefied syngas in the first syngas gas-liquid separator T202 is further cooled and condensed by the syngas condenser E203 and then enters the second syngas gas-liquid separator T203 to separate methanol and purge gas. Methanol enters the methanol refining component from the liquid outlet of the second syngas gas-liquid separator T203, and the purge gas enters the purge gas treatment component for recovery and is recycled as raw material gas after purification.

[0044] Furthermore, in this embodiment, the shifted gas and hydrogen entering the shifted gas mixer M201 are properly proportioned to ensure that the composition of the syngas is methanol. Or the amount of hydrogen is slightly more to ensure that the shifted gas completely reacts, and the composition of the syngas is methanol and hydrogen. When methanol is condensed and separated by the syngas gas-liquid separation component, that is, only hydrogen remains, and the hydrogen is the purge gas. After being recovered and purified by the purge gas treatment component, it can be recycled as raw material gas.

[0045] Preferably, as Figure 2 shown, the solar thermal energy storage unit includes a solar thermal component and an energy storage component. The solar thermal component includes a tower-type solar thermal collector; the energy storage component includes a high-temperature molten salt tank T301 and a low-temperature molten salt tank T302. The heat energy inlet of the high-temperature molten salt tank T301 is connected to the tower-type solar thermal collector, the heat energy outlet of the high-temperature molten salt tank T301 is connected to the heat energy inlet of the raw material gas heat exchanger E102, the heat energy outlet of the raw material gas heat exchanger E102 is connected to the heat energy inlet of the low-temperature molten salt tank T302, and the heat energy outlet of the low-temperature molten salt tank T302 is connected to the tower-type solar thermal collector. The heat storage temperature of the solar thermal energy storage unit can reach 570 - 600°C.

[0046] In this embodiment, the tower-type solar thermal collector includes a collector tower, a collector, and a mirror field. The collector is arranged on the collector tower, and the mirror field is arranged around the collector tower and focuses light on the collector. The heat energy inlet of the high-temperature molten salt tank T301 is communicated with the collector, and the heat energy outlet of the low-temperature molten salt tank T302 is communicated with the collector. The molten salt (290°C) in the low-temperature molten salt tank T302 is heated to 570°C by the collector and then stored in the high-temperature molten salt tank T301. The high-temperature molten salt in the high-temperature molten salt tank T301 heats the raw material gas in the raw material gas heat exchanger E102, and its own temperature drops to 520°C after heating. After the molten salt with the reduced temperature continues to release heat in the steam heat exchanger E301 of the power generation unit, its own temperature drops to 290°C, and finally it flows back to the low-temperature molten salt tank T302.

[0047] Preferably, as Figure 2 shown, the power generation unit includes a steam turbine, a generator, an AC / DC rectifier, a water recovery component, a water fine treatment component, and a steam heat exchanger E301. The rotating shaft of the steam turbine is in transmission connection with the generator, and the generator is electrically connected to the AC / DC rectifier; the steam heat exchanger E301 is arranged between the heat energy outlet of the raw material gas heat exchanger E102 and the heat energy inlet of the low-temperature molten salt tank T302, and the air outlet of the steam heat exchanger E301 is communicated with the air inlet of the steam turbine; the air outlet of the steam turbine is connected to the water recovery component, and the water recovery component is connected to the water fine treatment component; the water in the water fine treatment component circulates back to the steam turbine through the syngas condenser E203, the steam drum T201, and the steam heat exchanger E301.

[0048] The power generation unit starts from the water fine treatment component. The demineralized water is preliminarily heated to 150°C by the syngas condenser E203 to form low-temperature steam, and then the low-temperature steam enters the steam drum T201. The low-temperature steam absorbs the heat released in the first isothermal reactor R201 in the steam drum T201 and is converted into medium-temperature steam at 3.4 MPa (≥250°C). The medium-temperature steam enters the steam heat exchanger E301 to absorb the heat of the 520°C molten salt discharged from the heat energy outlet of the raw material gas heat exchanger E102, and the medium-temperature steam is heated to 500°C and converted into high-temperature steam. The high-temperature steam enters the steam turbine to drive the generator to work. A part of the alternating current generated by the generator is converted into direct current by the AC / DC rectifier to supply power for the electrolytic hydrogen production unit to carry out electrolytic water hydrogen production, and the other part of the alternating current is used as plant electricity for equipment operation or is output to the power grid as on-grid electricity.

[0049] Preferably, as Figure 2As shown in the figure, the electrolytic hydrogen production unit includes an electrolytic cell ER401, a drying tower T401, and a hydrogen compressor C401. The electrolytic cell ER401 is electrically connected to an AC / DC rectifier; the hydrogen generated at the negative electrode of the electrolytic cell ER401 is communicated with the air inlet of the drying tower T401 through a pipeline, the air outlet of the drying tower T401 is communicated with the air inlet of the hydrogen compressor C401, and the air outlet of the hydrogen compressor C401 is respectively communicated with the reverse water gas shift unit and the methanol synthesis unit.

[0050] In this embodiment, the electrolytic cell ER401 adopts an alkaline electrolytic cell or a PEM electrolytic cell. The raw water after purification treatment enters the electrolytic cell ER401. After electrolysis, hydrogen is generated at the negative electrode and the hydrogen is sent to the drying tower T401 for dehydration treatment. Then, after being pressurized by the hydrogen compressor C401, it is divided into two parts. One part enters the raw material gas mixer M101 to perform reverse water gas shift with carbon dioxide; the other part enters the shifted gas mixer M201 to perform methanol synthesis with carbon monoxide.

[0051] In addition, since both the reverse water gas shift and methanol synthesis reactions need to reach a specific temperature to proceed, it is necessary to heat the raw material gas and the shifted gas. In this application, the heating of the raw material gas and the shifted gas relies on the temperature carried by the gas at the air outlet of the reaction component. Therefore, at the beginning of the reaction, it is necessary to rely on a small-power external heat to heat the raw material gas in the raw material gas condenser E101 and the shifted gas in the shifted gas heat exchanger E201 to promote the normal progress of the reaction. When the reaction normally enters the steady state, the small-power external heat is removed, and it is only necessary to preheat the raw material gas and the shifted gas by relying on the temperature carried by the other gas at the air outlet of the reaction component.

[0052] In addition, the raw material gas is first preheated in the raw material gas condenser E101 and then heated by molten salt in the raw material gas heat exchanger E102 to avoid the temperature in the raw material gas heat exchanger E102 being too low, resulting in the precipitation of crystals after the molten salt releases heat and blocking the flow of the molten salt.

[0053] For a clearer description of the functions of each component in the first embodiment, see the following table:

[0054]

[0055]

[0056] Second Embodiment:

[0057] The difference between the second embodiment and the first embodiment lies only in the reaction component in the methanol synthesis unit.

[0058] Preferably, as Figure 3As shown in the figure, the reaction component includes a first isothermal reactor R201 and a second isothermal reactor R202. The outlet of the shift gas heat exchanger E201 is respectively connected to the inlet of the first isothermal reactor R201 and the inlet of the second isothermal reactor R202; the outlet of the first isothermal reactor R201 is connected to the inlet of the second isothermal reactor R202 through the shift gas heat exchanger E201; the outlet of the second isothermal reactor R202 is connected to the inlet of the syngas gas-liquid separation component, and a syngas heat exchanger E202 is also provided between the outlet of the second isothermal reactor R202 and the inlet of the syngas gas-liquid separation component.

[0059] In the methanol synthesis unit, the shift gas and hydrogen enter the shift gas heat exchanger E201 after a certain hydrogen-carbon ratio adjustment in the shift gas mixer M201, and are heated to 210°C by the syngas at the outlet of the first isothermal reactor R201 and then divided into two streams, which respectively enter the first isothermal reactor R201 and the second isothermal reactor R202. The shift gas and hydrogen entering the first isothermal reactor R201 synthesize methanol, flow through the shift gas heat exchanger E201 to cool down at the outlet of the first isothermal reactor R201, and then enter the second isothermal reactor R202, where they are mixed with the shift gas and hydrogen in the second isothermal reactor R202 and continue to react to synthesize methanol. The syngas generated in the second isothermal reactor R202 flows out from the outlet of the second isothermal reactor R202, cools down through the syngas heat exchanger E202 and condenses part of the methanol, and then enters the first syngas gas-liquid separator T202 to separate part of the methanol in the syngas. Part of the methanol enters the methanol refining component from the liquid outlet of the first syngas gas-liquid separator T202. The unliquefied syngas in the first syngas gas-liquid separator T202 enters the second syngas gas-liquid separator T203 after further cooling and condensation by the syngas condenser E203, and methanol and purge gas are separated. Methanol enters the methanol refining component from the liquid outlet of the second syngas gas-liquid separator T203, and the purge gas enters the purge gas treatment component for recovery and is recycled as raw material gas after purification.

[0060] The power generation unit in this embodiment is slightly different from that in the first embodiment. Specifically, the power generation unit in this embodiment starts with the water purification component. The desalted water is preliminarily heated to 150 °C by the syngas condenser E203 to form low-temperature steam, and then the low-temperature steam enters the syngas heat exchanger E202. The low-temperature steam absorbs the energy released by methanol synthesis in the syngas heat exchanger E202 and is converted into medium-temperature steam at 3.4 MPa (≥250 °C). The medium-temperature steam enters the steam heat exchanger E301 to absorb the heat of the 520 °C molten salt discharged from the heat energy outlet of the raw material gas heat exchanger E102. The medium-temperature steam is heated to 500 °C and converted into high-temperature steam. The high-temperature steam enters the steam turbine to drive the generator to work. A part of the alternating current generated by the generator is converted into direct current through the AC / DC rectifier to supply the electrolytic hydrogen production unit for electrolytic water hydrogen production, and the other part of the alternating current is used as plant electricity for equipment operation or output to the power grid as on-grid electricity.

[0061] For a clearer description of the functions of each component in the second embodiment, see the following table:

[0062]

[0063]

[0064] In summary, the reaction component in the first embodiment uses the first isothermal reactor R201 and the steam drum T201, which is an isothermal conversion; by using the heat cycle between the steam drum T201 and the first isothermal reactor R201, the heat released by methanol synthesis in the first isothermal reactor R201 is prevented from being too high, which may damage the first isothermal reactor R201. The reaction component in the second embodiment uses the first isothermal reactor R201 and the second isothermal reactor R202, which is an adiabatic conversion; by using the first isothermal reactor R201 and the second isothermal reactor R202 to separately synthesize methanol by splitting the conversion gas, the heat released during methanol synthesis is prevented from being too high, which may damage the first isothermal reactor R201 and the second isothermal reactor R202.

[0065] The integrated solar molten salt energy storage and green methanol production system involved in the present invention converts solar energy into the heat energy of molten salt for storage, ensuring the continuous and stable production process. It is equipped with a power generation unit and an electrolytic hydrogen production unit, which can utilize the heat in the methanol synthesis process in a gradient manner, improving the energy utilization rate, and can realize the co-production of products such as hydrogen, oxygen, syngas, and methanol with electricity and heat. In the present invention, the impurity content of the syngas, which is the raw material for synthesizing methanol, is low and the ratio is flexible, and it can be combined with different methanol synthesis processes such as the isothermal conversion process and the adiabatic conversion.

[0066] Therefore, the present invention effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0067] The above embodiments are only illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A molten salt energy storage coupled with solar thermal energy for green methanol production system, characterized in that: It includes a reverse water gas shift unit, a methanol synthesis unit, a solar thermal energy storage unit, a power generation unit, and an electrolytic hydrogen production unit. The solar thermal energy storage unit absorbs light energy and generates heat energy. The heat energy outlet of the solar thermal energy storage unit is communicated with the heat energy inlet of the reverse water gas shift unit. The heat energy outlet of the reverse water gas shift unit is communicated with the heat energy inlet of the power generation unit. The heat energy outlet of the methanol synthesis unit is communicated with the heat energy inlet of the power generation unit. The electric energy outlet of the power generation unit is communicated with the electric energy inlet of the electrolytic hydrogen production unit, and the electrolytic hydrogen production unit generates hydrogen. Carbon dioxide and hydrogen enter the reverse water gas shift unit to generate shift gas. The shift gas and hydrogen enter the methanol synthesis unit to generate methanol.

2. The molten salt energy storage coupled with solar heat for producing green methanol system according to claim 1, wherein: The reverse water gas shift unit includes a raw material gas compression and mixing assembly, a raw material gas condenser (E101), a raw material gas heat exchanger (E102), a fixed bed reactor (R101), and a shift gas gas-liquid separation assembly (T101). Carbon dioxide and hydrogen are introduced into the intake port of the raw material gas compression and mixing assembly. The outlet of the raw material gas compression and mixing assembly is communicated with the intake port of the raw material gas condenser (E101). The outlet of the raw material gas condenser (E101) is communicated with the intake port of the raw material gas heat exchanger (E102). The outlet of the raw material gas heat exchanger (E102) is communicated with the intake port of the fixed bed reactor (R101). The outlet of the fixed bed reactor (R101) passes through the raw material gas condenser (E101) and is communicated with the intake port of the shift gas gas-liquid separation assembly (T101). The outlet of the shift gas gas-liquid separation assembly (T101) is communicated with the methanol synthesis unit. The heat energy inlet of the raw material gas heat exchanger (E102) is communicated with the heat energy outlet of the solar thermal energy storage unit.

3. The molten salt energy storage coupled with solar heat to produce green methanol system according to claim 2, characterized in that: The raw material gas compression and mixing assembly includes a carbon dioxide compressor (C101), a raw material gas mixer (M101), and a raw material gas compressor (C102). Carbon dioxide is introduced into the intake port of the carbon dioxide compressor (C101). The outlet of the carbon dioxide compressor (C101) is communicated with the intake port of the raw material gas mixer (M101). Hydrogen is also introduced into the intake port of the raw material gas mixer (M101). The outlet of the raw material gas mixer (M101) is communicated with the intake port of the raw material gas compressor (C102). The outlet of the raw material gas compressor (C102) is communicated with the intake port of the raw material gas condenser (E101).

4. The molten salt energy storage coupled with solar thermal energy to produce green methanol system according to claim 1, wherein: The methanol synthesis unit includes a shift gas mixer (M201), a shift gas heat exchanger (E201), a reaction assembly, and a synthesis gas gas-liquid separation assembly. The shift gas and hydrogen are introduced into the intake port of the shift gas mixer (M201). The outlet of the shift gas mixer (M201) is communicated with the intake port of the shift gas heat exchanger (E201). The outlet of the shift gas heat exchanger (E201) is communicated with the intake port of the reaction assembly. The outlet of the reaction assembly is communicated with the intake port of the synthesis gas gas-liquid separation assembly. A purge gas treatment assembly is also connected to the outlet of the synthesis gas gas-liquid separation assembly, and a methanol refining assembly is also connected to the liquid outlet of the synthesis gas gas-liquid separation assembly.

5. The solar thermal molten salt energy storage coupled green methanol production system according to claim 4, wherein: The reaction assembly includes a first isothermal reactor (R201) and a steam drum (T201). The outlet of the shift gas heat exchanger (E201) is communicated with the inlet of the first isothermal reactor (R201). The outlet of the first isothermal reactor (R201) is communicated with the inlet of the syngas gas-liquid separation assembly through the shift gas heat exchanger (E201). A heat cycle is formed between the first isothermal reactor (R201) and the steam drum (T201).

6. The molten salt energy storage coupled with solar thermal power generation for green methanol production system according to claim 4, wherein: The reaction assembly includes a first isothermal reactor (R201) and a second isothermal reactor (R202). The outlet of the shift gas heat exchanger (E201) is respectively communicated with the inlets of the first isothermal reactor (R201) and the second isothermal reactor (R202). The outlet of the first isothermal reactor (R201) is communicated with the inlet of the second isothermal reactor (R202) through the shift gas heat exchanger (E201). The outlet of the second isothermal reactor (R202) is communicated with the inlet of the syngas gas-liquid separation assembly, and a syngas heat exchanger (E202) is further provided between the outlet of the second isothermal reactor (R202) and the inlet of the syngas gas-liquid separation assembly.

7. The molten salt energy storage coupled with solar thermal conversion for green methanol production system according to claim 5 or 6, characterized in that: The syngas gas-liquid separation assembly includes a first syngas gas-liquid separator (T202), a syngas condenser (E203), and a second syngas gas-liquid separator (T203). The inlet of the first syngas gas-liquid separator (T202) is communicated with the outlet of the reaction assembly. The inlet of the syngas condenser (E203) is communicated with the outlet of the first syngas gas-liquid separator (T202). The outlet of the syngas condenser (E203) is communicated with the inlet of the second syngas gas-liquid separator (T203). A purge gas treatment assembly is connected to the outlet of the second syngas gas-liquid separator (T203). A methanol refining assembly is connected to the liquid outlets of the first syngas gas-liquid separator (T202) and the second syngas gas-liquid separator (T203).

8. The molten salt energy storage coupled with solar thermal energy to produce green methanol system according to claim 7, characterized in that: The solar thermal energy storage unit includes a solar thermal component and an energy storage component. The solar thermal component includes a tower-type solar thermal collector. The energy storage component includes a high-temperature molten salt tank (T301) and a low-temperature molten salt tank (T302). The heat energy inlet of the high-temperature molten salt tank (T301) is communicated with the tower-type solar thermal collector. The heat energy outlet of the high-temperature molten salt tank (T301) is communicated with the heat energy inlet of the reverse water gas shift unit. The heat energy outlet of the reverse water gas shift unit is communicated with the heat energy inlet of the low-temperature molten salt tank (T302). The heat energy outlet of the low-temperature molten salt tank (T302) is communicated with the tower-type solar thermal collector.

9. The molten salt energy storage coupled with solar thermal conversion for green methanol production system according to claim 8, wherein: The power generation unit includes a steam turbine, a generator, an AC / DC rectifier, a water recovery assembly, a water fine treatment assembly, and a steam heat exchanger (E301). The rotating shaft of the steam turbine is in transmission connection with the generator. The generator is electrically connected to the AC / DC rectifier. The steam heat exchanger (E301) is arranged between the heat energy outlet of the reverse water-gas shift unit and the heat energy inlet of the low-temperature molten salt tank (T302), and the gas outlet of the steam heat exchanger (E301) is communicated with the gas inlet of the steam turbine; the gas outlet of the steam turbine is connected with the water recovery assembly, and the water recovery assembly is connected with the water fine treatment assembly; The water in the water fine treatment assembly circulates back to the steam turbine through the syngas condenser (E203), the steam drum (T201), and the steam heat exchanger (E301); or the water in the water fine treatment assembly circulates back to the steam turbine through the syngas condenser (E203), the syngas heat exchanger (E202), and the steam heat exchanger (E301).

10. The molten salt energy storage coupled with solar thermal energy to produce green methanol system according to claim 9, wherein: The electrolytic hydrogen production unit includes an electrolytic cell (ER401), a drying tower (T401), and a hydrogen compressor (C401), and the electrolytic cell (ER401) is electrically connected to an AC / DC rectifier; the hydrogen generated at the negative electrode of the electrolytic cell (ER401) is communicated with the gas inlet of the drying tower (T401) through a pipeline, the gas outlet of the drying tower (T401) is communicated with the gas inlet of the hydrogen compressor (C401), and the gas outlet of the hydrogen compressor (C401) is respectively communicated with the reverse water-gas shift unit and the methanol synthesis unit.

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