A method and system for direct hydrogenation of flue gas

Abstract

The present invention provides a method and system for direct hydrogenation of flue gas, the method comprising compressing and pressurizing the flue gas after desulfurization and refining, allowing the pressurized flue gas to enter a synthetic methanol reactor and react with green hydrogen produced by electrolysis of water to synthesize methanol, after the reaction is completed, the obtained mixed gas is cooled and separated to obtain liquid methanol and water, the remaining mixed gas is compressed and enters a synthetic ammonia reactor and reacts with green hydrogen produced by electrolysis of water to synthesize ammonia, after the reaction is completed, the obtained mixed gas is cooled and separated to obtain liquid ammonia and gas components; or allowing the pressurized flue gas to enter a synthetic ammonia reactor and react with green hydrogen produced by electrolysis of water to synthesize ammonia, after the reaction is completed, the obtained mixed gas is cooled and separated to obtain liquid ammonia, the remaining mixed gas is compressed and enters a synthetic methanol reactor and reacts with green hydrogen to synthesize methanol, after the reaction is completed, the obtained mixed gas is cooled and separated to obtain liquid methanol and water and gas components.

Description

Technical Field

[0001] The invention relates to a method and a system for direct hydrogenation of flue gas, belonging to the technical field of flue gas treatment. Background Art

[0002] The huge consumption of fossil energy by human activities has led to the greenhouse gas CO 2 Huge amounts of CO are emitted into the atmosphere. Currently, the world emits CO 2 As high as 40 billion tons, and continue to accumulate in the atmosphere, causing the greenhouse effect and causing the temperature to rise year by year. For this reason, the United Nations Climate Organization has set a limit for the temperature increase (relative to the pre-industrial climate temperature), that is, it is best not to exceed 1.5℃, and absolutely not to exceed 2℃. If effective measures are not taken immediately to mitigate CO 2 If the global average surface temperature rises by 3.7-4.8℃ and the sea level rises by 0.6-0.8m by 2100, the global ecological disaster will be irreversible. For example, if the temperature control target of 2℃ is to be achieved, the remaining carbon emission space is about 1 trillion tons of CO 2 , the world can only continue to emit carbon at the current level for more than 20 years. If the temperature control target of 1.5℃ is to be achieved, the remaining carbon emission space is about 4200~7700 trillion tons of CO 2 , which means that the world can only continue to emit CO for 10 to 20 years. 2 Rapid, far-reaching and unprecedented changes are therefore needed worldwide to reduce global net anthropogenic CO2 emissions by 45% by 2030 compared to 2010 levels, and to achieve net zero emissions by 2050.

[0003] For decades, academia and industry have been actively exploring ways to reduce CO 2 The measures and technical routes to reduce emissions can be summarized into two aspects: one is to reduce the consumption of fossil energy such as coal and oil. The main measure is to replace fossil energy with renewable energy such as solar energy, wind energy, hydropower, nuclear energy, hydrogen energy and bio-based fuels; the other is to firstly reduce the CO2 generated in the process of fossil energy consumption. 2 The CCUS technology route can avoid CO 2 emissions into the atmosphere, thus achieving the goal of zero emissions.

[0004] Solar energy and wind energy in renewable energy sources are greatly affected by geographical location and climatic conditions, making the electricity they generate unstable and difficult to store, which is the so-called abandoned electricity. In order to make full use of abandoned electricity, some energy storage technologies are constantly being developed, which are mainly divided into three categories, namely heat storage, cold storage and electricity storage. For example, green hydrogen is produced by electrolyzing water through solar or wind energy, and then the green hydrogen is stored in gaseous, liquid or solid form. Among them, liquid hydrogen storage is a good path for the production and utilization of green and zero-carbon energy.

[0005] Another ideal hydrogen storage route is to utilize the abundant N in the air. 2 Hydrogenation to synthesize ammonia. Ammonia is not only an important chemical raw material for the preparation of fertilizers and medicines, but also a zero-carbon fuel with a high energy density (4.32kWh / L) and a high hydrogen content (17.8w%). Ammonia is highly soluble in water and easy to liquefy, making the transportation cost of ammonia very low. 2 Hydrogenation to synthesize ammonia is a long-standing and relatively mature industrial technology, namely the Haber-Bosch process (HB process), which was proposed in 1918. 2 Derived from air separation process, H 2 It is produced from fossil energy such as coal or natural gas. However, the HB process of synthesizing ammonia not only emits a large amount of CO 2 In addition, the reaction conditions for synthesizing ammonia are harsh, with high temperature (about 500°C) and high pressure (about 20MPa). In order to overcome the shortcomings of traditional ammonia synthesis, technicians in this field have developed a novel ammonia synthesis system with CO 2 There has been a lot of research on electrocatalytic and photocatalytic ammonia synthesis with zero emissions and mild reaction conditions.

[0006] The flue gas generated by industrial equipment contains a large amount of N 2 In addition, another major component is the greenhouse gas CO 2 It is well known that excessive CO2 produced by human activities 2 It is the main greenhouse gas that causes global warming and must be captured to prevent it from being emitted into the atmosphere. 2 CCUS technology has been proposed as a way to prevent CO 2 The only technical route to prevent emissions into the atmosphere. In the CCUS route, the first step is CO 2 The capture technology of CO can be divided into absorption, adsorption and membrane separation. 2 The capture technology uses chemical absorption of amine solution, but its absorption cost is relatively high, about 400 yuan / ton CO 2 The second step is to collect the captured CO 2Processing and utilization can be summarized into two categories: one is the synthesis of bulk basic chemicals, such as methanol, synthesis gas, etc.; the other is the synthesis of fine chemicals, such as acids, esters, etc. Among them, methanol is an important basic chemical raw material, through which low-carbon olefins, gasoline, aromatics, dimethyl ether, etc. can be synthesized.

[0007] Although researchers or developers have made many efforts to reduce production costs and improve production efficiency in various aspects of CCUS, 2 The capture and utilization of CO2 are completed separately. In the field of synthetic ammonia hydrogen storage, the nitrogen source and the hydrogen source are also separated. In short, in the current flue gas treatment, CO2 in flue gas 2 Take measures to capture first and then process and utilize, and treat N in flue gas 2 Nor was it utilized.

[0008] Therefore, in order to reduce production costs and green process, it is urgent to develop a method for efficient utilization of flue gas and reduce CO 2 Method of emission. Summary of the invention

[0009] In order to solve the above-mentioned shortcomings and deficiencies, an object of the present invention is to provide a method for direct hydrogenation of flue gas.

[0010] Another object of the present invention is to provide a system for direct hydrogenation of flue gas.

[0011] In order to achieve the above objectives, on the one hand, the present invention provides a method for direct hydrogenation of flue gas, wherein the method for direct hydrogenation of flue gas comprises:

[0012] The flue gas after desulfurization and refining is compressed and pressurized, and the pressurized flue gas enters a synthetic methanol reactor and reacts with green hydrogen produced by electrolysis of water to synthesize methanol. After the reaction is completed, the obtained mixed gas is cooled and separated to obtain liquid methanol and water. The remaining mixed gas (i.e., decarbonized gas) is compressed and enters a synthetic ammonia reactor and reacts with green hydrogen produced by electrolysis of water to synthesize ammonia. After the reaction is completed, the obtained mixed gas is cooled and separated to obtain liquid ammonia and gas components.

[0013] Alternatively, the flue gas after desulfurization and purification is compressed and pressurized, and the pressurized flue gas enters a synthetic ammonia reactor and reacts with green hydrogen produced by electrolysis of water to synthesize ammonia. After the reaction, the obtained mixed gas is cooled and separated to obtain liquid ammonia. The remaining mixed gas is compressed and enters a synthetic methanol reactor and reacts with green hydrogen produced by electrolysis of water to synthesize methanol. After the reaction, the obtained mixed gas is cooled and separated to obtain liquid methanol and water and gas components.

[0014] As a specific embodiment of the method for direct hydrogenation of flue gas described above in the present invention, the method further comprises: mixing the gas component as circulating gas with the flue gas after desulfurization and purification, and then compressing and increasing the pressure.

[0015] As a specific embodiment of the method for direct hydrogenation of flue gas described above in the present invention, the method further comprises: utilizing waste heat of flue gas to heat the ammonia synthesis reaction and / or the methanol synthesis reaction respectively.

[0016] As a specific embodiment of the method for direct hydrogenation of flue gas described above in the present invention, the method further comprises: utilizing waste heat of flue gas to heat the ammonia synthesis reaction and the methanol synthesis reaction in sequence.

[0017] The flue gas used in the present invention can be directly taken from an industrial device. Since the temperature of the flue gas from the industrial device is very high, about 500-800°C, the waste heat of the flue gas can be used to heat the synthetic ammonia reaction and / or the synthetic methanol reaction. Among them, the best way to use the waste heat of the flue gas is: first, the heat of the high-temperature flue gas is used to heat the synthetic ammonia reactor, at which time the flue gas temperature is reduced, and then the waste heat of the flue gas is used to heat the synthetic methanol reactor to meet the reaction temperature requirements of the methanol hydrogenation synthesis reaction. Through these two steps, the heat in the flue gas can be fully utilized.

[0018] As a specific embodiment of the method for direct hydrogenation of flue gas described above, the desulfurization agent used in the desulfurization refining is a solid adsorbent, and the main component of the solid adsorbent is metal oxide and / or non-metal oxide.

[0019] As a specific embodiment of the method for direct hydrogenation of flue gas described above in the present invention, the solid adsorbent includes one or a combination of zinc oxide, aluminum oxide, and silicon dioxide.

[0020] As a specific embodiment of the method for direct hydrogenation of flue gas described above, the solid adsorbent is in the shape of a strip, and its diameter ranges from 2 to 4 mm.

[0021] As a specific embodiment of the method for direct hydrogenation of flue gas described above in the present invention, the sulfur content of the flue gas after desulfurization and purification is less than 0.1 ppm.

[0022] As a specific embodiment of the method for direct hydrogenation of flue gas described above, the compression and pressure raising is to raise the pressure of the flue gas after desulfurization and purification to 5-30 MPa.

[0023] As a specific embodiment of the flue gas direct hydrogenation method of the present invention, the temperature of the synthetic methanol reaction is 100-400°C, the pressure is 5-30 MPa, and the space velocity is 5000-20000 h -1 ;

[0024] Preferably, the temperature of the methanol synthesis reaction is 150-250° C. and the pressure is 10-20 MPa.

[0025] As a specific embodiment of the flue gas direct hydrogenation method described above, in the inlet mixed gas of the synthetic methanol reactor, H 2 With CO 2 The volume ratio is 3.0-3.3.

[0026] As a specific embodiment of the method for direct hydrogenation of flue gas described above in the present invention, the active component of the catalyst used in the synthetic methanol reaction is CuO, and the carrier is other metal oxides except CuO. Based on the total weight of the catalyst as 100%, the content of CuO is 20-90%, preferably 25-75%, and more preferably 25-50%.

[0027] As a specific embodiment of the flue gas direct hydrogenation method of the present invention, in the catalyst used in the methanol synthesis reaction, the carrier includes ZnO and / or Al 2 O 3 .

[0028] As a specific embodiment of the flue gas direct hydrogenation method of the present invention, the temperature of the synthetic ammonia reaction is 300-700°C, the pressure is 10-30 MPa, and the space velocity is 5000-20000 h -1 ;

[0029] Preferably, the temperature of the synthetic ammonia reaction is 400-500° C. and the pressure is 15-25 MPa.

[0030] As a specific embodiment of the flue gas direct hydrogenation method described above, in the inlet mixed gas of the synthetic ammonia reactor, H 2 With N 2 The volume ratio is 3.0-3.3.

[0031] As a specific embodiment of the flue gas direct hydrogenation method described above, the active components of the catalyst used in the ammonia synthesis reaction are FeO and / or Fe 2 O 3 Based on the total weight of the catalyst as 100%, the content of FeO is 30-40%, and the content of Fe 2 O 3The content of is 55-65%, and the sum of the contents of each component in the catalyst is 100%;

[0032] Alternatively, the catalyst used in the ammonia synthesis reaction is a Ba-Ru / BN catalyst, and based on the total weight of the Ba-Ru / BN catalyst being 100%, the contents of Ba and Ru are 0.5-3%wt respectively.

[0033] As a specific embodiment of the method for direct hydrogenation of flue gas described above, the methanol synthesis reaction and / or the ammonia synthesis reaction are performed to raise the system temperature to the target reaction temperature according to the following heating program:

[0034] The system temperature was raised to 80% of the target reaction temperature in 10 h, and then raised from 80% of the target reaction temperature to 90% of the target reaction temperature in 20 h, and then raised from 90% of the target reaction temperature to the target reaction temperature in 5 h.

[0035] As a specific embodiment of the method for direct hydrogenation of flue gas described above in the present invention, the cooling can be performed in a slow-first-fast-later-fast manner, or can be performed at a constant cooling rate to reduce the system temperature to below the boiling point of the target product;

[0036] Preferably, the cooling is performed at a constant cooling rate, wherein the cooling rate is 0.1-5°C / min, more preferably 0.5-2°C / min; or the cooling is firstly cooled to 80% of the reaction temperature at a cooling rate of 0.5-1°C / min, and then cooled to below the boiling point of the target product at a cooling rate of 1-5°C / min.

[0037] As a specific embodiment of the method for direct hydrogenation of flue gas described above in the present invention, the electricity used in the process of electrolyzing water to produce green hydrogen comes from green electricity provided by renewable energy.

[0038] On the other hand, the present invention also provides a system for direct hydrogenation of flue gas, wherein the system for direct hydrogenation of flue gas comprises: a refining desulfurizer, a compressor, a synthetic methanol reactor, a methanol separator, a synthetic ammonia reactor, an ammonia separator and a water electrolysis hydrogen production device;

[0039] Wherein, the gas outlet of the refining desulfurizer is connected to the raw gas inlet of the synthetic methanol reactor through a pipeline via a compressor, the outlet of the synthetic methanol reactor is connected to the raw gas inlet of the synthetic ammonia reactor through a pipeline via a methanol separator, the outlet of the synthetic ammonia reactor is connected to the inlet of the ammonia separator through a pipeline, and the hydrogen outlet of the water electrolysis hydrogen production device is connected to the raw gas inlets of the synthetic methanol reactor and the synthetic ammonia reactor respectively through pipelines;

[0040] Alternatively, the gas outlet of the refining desulfurizer is connected to the raw gas inlet of the synthetic ammonia reactor through a pipeline via a compressor, the outlet of the synthetic ammonia reactor is connected to the raw gas inlet of the synthetic methanol reactor through a pipeline via an ammonia separator, the outlet of the synthetic methanol reactor is connected to the inlet of the methanol separator through a pipeline, and the hydrogen outlet of the water electrolysis hydrogen production device is connected to the raw gas inlets of the synthetic ammonia reactor and the synthetic methanol reactor respectively through pipelines.

[0041] As a specific embodiment of the system for direct hydrogenation of flue gas described above in the present invention, the gas outlet of the ammonia separator is connected to the compressor through a pipeline, or the gas outlet of the methanol separator is connected to the compressor through a pipeline.

[0042] As a specific embodiment of the system for direct hydrogenation of flue gas described above in the present invention, the system further comprises a methanol storage tank and an ammonia storage tank, which are respectively connected to the liquid outlet of the methanol separator and the liquid outlet of the ammonia separator.

[0043] As a specific embodiment of the system for direct hydrogenation of flue gas described above in the present invention, the synthetic ammonia reactor and the synthetic methanol reactor may be respectively provided with only one raw gas inlet, or may be respectively provided with two raw gas inlets. However, even if only one raw gas inlet is respectively provided for both, two feed pipes are required to control the feed of two components (i.e., flue gas and green hydrogen after desulfurization and refining, decarbonized gas and green hydrogen, or the remaining mixed gas and green hydrogen separated after the synthetic ammonia reaction).

[0044] As a specific embodiment of the system for direct hydrogenation of flue gas described above in the present invention, the synthetic methanol reactor is a fixed bed reactor or a fluidized bed reactor.

[0045] As a specific embodiment of the system for direct hydrogenation of flue gas described above in the present invention, the synthetic ammonia reactor is a fixed bed reactor or a fluidized bed reactor.

[0046] In the present invention, the refining desulfurizer, compressor, synthetic methanol reactor, methanol separator, synthetic ammonia reactor, ammonia separator and water electrolysis hydrogen production device are all conventional equipment used in the art.

[0047] The method and system for direct hydrogenation of flue gas provided by the present invention utilizes renewable energy to prepare green hydrogen, and uses green hydrogen to reduce the main component CO in flue gas emitted by industrial devices. 2 and N 2 Direct hydrogenation of CO 2 Hydrogenation to methanol and N 2 Hydrogenation to produce ammonia, omitting CO 2Capture process and air separation to produce N 2 process, thus significantly reducing CO 2 The methanol and ammonia produced by the present invention have a wide range of industrial applications, especially they can replace fossil energy such as coal and oil, thereby further reducing CO 2 In summary, the method and system for direct hydrogenation of flue gas provided by the present invention have both environmental protection and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0049] Figure 1 This is a schematic diagram of the structure of the system for direct hydrogenation of flue gas provided in Example 1 of the present invention.

[0050] Figure 2 This is a schematic diagram of the structure of the system for direct hydrogenation of flue gas provided in Example 2 of the present invention.

[0051] Description of main figures:

[0052] 1. Refining desulfurization tank;

[0053] 2. Compressor;

[0054] 3. Synthetic methanol reactor;

[0055] 4. Methanol separator;

[0056] 5. Methanol storage tank;

[0057] 6. Ammonia synthesis reactor;

[0058] 7. Ammonia separator;

[0059] 8. Ammonia storage tank;

[0060] 9. Hydrogen production device by water electrolysis. DETAILED DESCRIPTION

[0061] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical scheme of the present invention is now described in detail in conjunction with the following specific embodiments, but it should not be understood as limiting the applicable scope of the present invention.

[0062] "Scope" disclosed by the present invention is given in the form of lower limit and upper limit. It can be one or more lower limits, and one or more upper limits respectively. A given scope is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the boundary of a particular scope. All scopes defined in this way are combinable, i.e. any lower limit can be combined with any upper limit to form a scope. For example, the scope of 60-120 and 80-110 is listed for a specific parameter, and it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value listed is 1 and 2, and the maximum range value listed is 3, 4 and 5, then the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.

[0063] In the present invention, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, where a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed in the present invention, and "0-5" is just an abbreviation of these numerical combinations.

[0064] In the present invention, unless otherwise specified, all embodiments and preferred embodiments mentioned in the present invention can be combined with each other to form a new technical solution.

[0065] In the present invention, unless otherwise specified, all technical features and preferred features mentioned in the present invention can be combined with each other to form a new technical solution.

[0066] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and Examples. The following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention. If the specific conditions are not specified in the embodiments, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0067] The present invention will be further described below in conjunction with specific examples:

[0068] Example 1

[0069] This embodiment provides a system for direct hydrogenation of flue gas, and its structural schematic diagram is as follows: Figure 1 As shown, from Figure 1It can be seen that the flue gas direct hydrogenation system includes: a refined desulfurization tank 1, a compressor 2, a synthetic methanol reactor 3, a methanol separator 4, a methanol storage tank 5, a synthetic ammonia reactor 6, an ammonia separator 7, an ammonia storage tank 8 and a water electrolysis hydrogen production device 9;

[0070] The gas outlet of the refining desulfurization tank 1 is connected to the first raw gas inlet of the synthetic methanol reactor 3 through a pipeline via the compressor 2, the outlet of the synthetic methanol reactor 3 is connected to the first raw gas inlet of the synthetic ammonia reactor 6 through a pipeline via the methanol separator 4, the outlet of the synthetic ammonia reactor 6 is connected to the inlet of the ammonia separator 7 through a pipeline, and the hydrogen outlet of the water electrolysis hydrogen production device 9 is connected to the second raw gas inlets of the synthetic methanol reactor 3 and the synthetic ammonia reactor 6 through pipelines respectively;

[0071] The methanol storage tank 5 and the ammonia storage tank 8 are respectively connected to the liquid outlet of the methanol separator 4 and the liquid outlet of the ammonia separator 7;

[0072] The gas outlet of the ammonia separator 7 is connected to the compressor 2 through a pipeline.

[0073] In this embodiment, the synthetic methanol reactor 3 and the synthetic ammonia reactor 6 are both fixed bed reactors.

[0074] Example 2

[0075] This embodiment provides a system for direct hydrogenation of flue gas, and its structural schematic diagram is as follows: Figure 2 As shown, from Figure 2 It can be seen that the flue gas direct hydrogenation system includes: a refined desulfurization tank 1, a compressor 2, a synthetic methanol reactor 3, a methanol separator 4, a methanol storage tank 5, a synthetic ammonia reactor 6, an ammonia separator 7, an ammonia storage tank 8 and a water electrolysis hydrogen production device 9;

[0076] The gas outlet of the refined desulfurization tank 1 is connected to the first raw gas inlet of the synthetic ammonia reactor 6 through a pipeline via the compressor 2, the outlet of the synthetic ammonia reactor 6 is connected to the first raw gas inlet of the synthetic methanol reactor 3 through a pipeline via the ammonia separator 7, the outlet of the synthetic methanol reactor 3 is connected to the inlet of the methanol separator 4 through a pipeline, and the hydrogen outlet of the water electrolysis hydrogen production device 9 is connected to the second raw gas inlets of the synthetic ammonia reactor 6 and the synthetic methanol reactor 3 through pipelines respectively;

[0077] The methanol storage tank 5 and the ammonia storage tank 8 are respectively connected to the liquid outlet of the methanol separator 4 and the liquid outlet of the ammonia separator 7;

[0078] The gas outlet of the methanol separator 4 is connected to the compressor 2 through a pipeline.

[0079] In this embodiment, the synthetic methanol reactor 3 and the synthetic ammonia reactor 6 are both fixed bed reactors.

[0080] Example 3

[0081] This embodiment provides a method for direct hydrogenation of flue gas, which is implemented by using the system for direct hydrogenation of flue gas provided in Example 1, wherein the method includes the following specific steps:

[0082] The fresh flue gas used in this embodiment is pure CO 2 Gas and pure N 2 The gas mixture is prepared, wherein the total volume of fresh flue gas is 100%, CO 2 Gas and pure N 2 The composition of the gas is 15v% and 85v% respectively;

[0083] The fresh flue gas is compressed and pressurized to a pressure of 5 to 30 MPa, and the pressurized flue gas enters a synthetic methanol reactor and reacts with green hydrogen produced by electrolysis of water to synthesize methanol. After the reaction, the obtained mixed gas is cooled and separated to obtain liquid methanol and water. The remaining mixed gas (i.e., decarbonized gas) is compressed and enters a synthetic ammonia reactor and reacts with green hydrogen produced by electrolysis of water to synthesize ammonia. After the reaction, the obtained mixed gas is cooled and separated to obtain liquid ammonia and gas components; the gas components are then mixed with the fresh flue gas as circulating gas and compressed and pressurized;

[0084] The reaction conditions of the synthetic methanol reactor are: H 2 / CO 2 is 3.0; the space velocity of the mixed gas is 15000h -1 ; The reaction temperature is 250°C; the reaction pressure is 5MPa;

[0085] The synthetic methanol reaction is carried out by raising the system temperature to the target reaction temperature according to the following heating program:

[0086] In 10 hours, the system temperature is raised to 80% of the target reaction temperature (i.e., 200°C), and in 20 hours, the system temperature is raised from 80% of the target reaction temperature (i.e., 200°C) to 90% of the target reaction temperature (i.e., 225°C), and in 5 hours, the system temperature is raised from 90% of the target reaction temperature (i.e., 225°C) to the target reaction temperature (i.e., 250°C);

[0087] Based on the total weight of the catalyst used in the methanol synthesis reaction as 100%, it contains 50% CuO, 40% ZnO and 10% Al 2 O 3; The catalyst is in strip shape, and its diameter ranges from 2 to 4 mm;

[0088] Reaction conditions of the synthetic ammonia reactor: H 2 / N 2 is 3.0; the space velocity of the mixed gas is 15000h -1 ; Reaction temperature is 400°C; Reaction pressure is 12MPa;

[0089] The ammonia synthesis reaction is carried out by raising the system temperature to the target reaction temperature according to the following heating program:

[0090] In 10 hours, the system temperature is raised to 80% of the target reaction temperature (i.e., 320°C), and in 20 hours, the system temperature is raised from 80% of the target reaction temperature (i.e., 320°C) to 90% of the target reaction temperature (i.e., 360°C), and in 5 hours, the system temperature is raised from 90% of the target reaction temperature (i.e., 360°C) to the target reaction temperature (i.e., 400°C);

[0091] Based on the total weight of the catalyst used in the ammonia synthesis reaction as 100%, it contains 35% FeO, 60% Fe 2 O 3 , 2.5% Al 2 O 3 , 0.5% K 2 O and 2.0% CaO.

[0092] In this embodiment, the electricity used in the process of electrolyzing water to produce green hydrogen comes from green electricity provided by renewable energy.

[0093] In this embodiment, the reaction product contents were measured from the outlets of the synthetic methanol reactor and the synthetic ammonia reactor, and the gas volume composition of the total reaction product was obtained after conversion, which was 16.7% H 2 , 1.8% CO, 0.6% CO 2 4.4% CH 3 OH, 6.2% H 2 O, 5.0% N 2 and 65.3% of NH 3 .

[0094] Example 4

[0095] This embodiment provides a method for direct hydrogenation of flue gas, which is implemented by using the system for direct hydrogenation of flue gas provided in Example 2, wherein the method comprises the following specific steps:

[0096] Taking the total volume of the fresh flue gas used in this example as 100%, it contains 15v% CO 2 Gas, 84v% N 2and 1% O 2 and CO;

[0097] The fresh flue gas is compressed and pressurized to a pressure of 5 to 30 MPa, and the pressurized flue gas enters a synthetic ammonia reactor and reacts with green hydrogen produced by electrolysis of water to synthesize ammonia. After the reaction is completed, the obtained mixed gas is cooled and separated to obtain liquid ammonia. The remaining mixed gas is compressed and enters a synthetic methanol reactor and reacts with green hydrogen produced by electrolysis of water to synthesize methanol. After the reaction is completed, the obtained mixed gas is cooled and separated to obtain liquid methanol and water and gas components; the gas components are then mixed with the fresh flue gas as circulating gas and compressed and pressurized;

[0098] The reaction conditions of the synthetic ammonia reactor are: H 2 / N 2 is 3.0; the space velocity of the mixed gas is 20000h -1 ; Reaction temperature is 400°C; Reaction pressure is 12MPa;

[0099] The ammonia synthesis reaction is carried out by raising the system temperature to the target reaction temperature according to the following heating program:

[0100] In 10 hours, the system temperature is raised to 80% of the target reaction temperature (i.e., 320°C), and in 20 hours, the system temperature is raised from 80% of the target reaction temperature (i.e., 320°C) to 90% of the target reaction temperature (i.e., 360°C), and in 5 hours, the system temperature is raised from 90% of the target reaction temperature (i.e., 360°C) to the target reaction temperature (i.e., 400°C);

[0101] Based on the total weight of the catalyst used in the ammonia synthesis reaction as 100%, it contains 35% FeO, 60% Fe 2 O 3 , 2.5% Al 2 O 3 , 0.5% K 2 O and 2.0% CaO;

[0102] Reaction conditions of the synthetic methanol reactor: H 2 / CO 2 is 3.0; the space velocity of the mixed gas is 20000h -1 ; The reaction temperature is 250°C; The reaction pressure is 10MPa;

[0103] The synthetic methanol reaction is carried out by raising the system temperature to the target reaction temperature according to the following heating program:

[0104] In 10 hours, the system temperature is raised to 80% of the target reaction temperature (i.e., 200°C), and in 20 hours, the system temperature is raised from 80% of the target reaction temperature (i.e., 200°C) to 90% of the target reaction temperature (i.e., 225°C), and in 5 hours, the system temperature is raised from 90% of the target reaction temperature (i.e., 225°C) to the target reaction temperature (i.e., 250°C);

[0105] Based on the total weight of the catalyst used in the methanol synthesis reaction as 100%, it contains 50% CuO, 40% ZnO and 10% Al 2 O 3 ; The catalyst is in strip shape with a diameter ranging from 2 to 4 mm.

[0106] In this embodiment, the electricity used in the process of electrolyzing water to produce green hydrogen comes from green electricity provided by renewable energy.

[0107] In this embodiment, the reaction product contents were measured from the outlets of the synthetic methanol reactor and the synthetic ammonia reactor, and the gas volume composition of the total reaction product was obtained after conversion, which was 7.9% H 2 , 0.8% CO, 0.4% CO 2 , 6.2% CH 3 OH, 6.9% H 2 O, 2.4% N 2 and 75.4% of NH 3 .

[0108] Example 5

[0109] This embodiment provides a method for direct hydrogenation of flue gas, which is implemented by using the system for direct hydrogenation of flue gas provided in Example 2, wherein the method comprises the following specific steps:

[0110] Taking the total volume of the fresh flue gas used in this example as 100%, it contains 14v% CO 2 Gas, 85v% N 2 and 1% O 2 and CO;

[0111] The fresh flue gas is compressed and pressurized to a pressure of 5 to 30 MPa, and the pressurized flue gas enters a synthetic ammonia reactor and reacts with green hydrogen produced by electrolysis of water to synthesize ammonia. After the reaction is completed, the obtained mixed gas is cooled and separated to obtain liquid ammonia. The remaining mixed gas is compressed and enters a synthetic methanol reactor and reacts with green hydrogen produced by electrolysis of water to synthesize methanol. After the reaction is completed, the obtained mixed gas is cooled and separated to obtain liquid methanol and water and gas components; the gas components are then mixed with the fresh flue gas as circulating gas and compressed and pressurized;

[0112] The reaction conditions of the synthetic ammonia reactor are: H 2 / N 2 is 3.0; the space velocity of the mixed gas is 20000h -1 ; Reaction temperature is 400°C; Reaction pressure is 12MPa;

[0113] The ammonia synthesis reaction is carried out by raising the system temperature to the target reaction temperature according to the following heating program:

[0114] In 10 hours, the system temperature is raised to 80% of the target reaction temperature (i.e., 320°C), and in 20 hours, the system temperature is raised from 80% of the target reaction temperature (i.e., 320°C) to 90% of the target reaction temperature (i.e., 360°C), and in 5 hours, the system temperature is raised from 90% of the target reaction temperature (i.e., 360°C) to the target reaction temperature (i.e., 400°C);

[0115] Based on the total weight of the catalyst used in the ammonia synthesis reaction as 100%, it contains 35% FeO, 60% Fe 2 O 3 , 2.5% Al 2 O 3 , 0.5% K 2 O and 2.0% CaO;

[0116] Reaction conditions of the synthetic methanol reactor: H 2 / CO 2 is 3.0; the space velocity of the mixed gas is 20000h -1 ; Reaction temperature is 200°C; reaction pressure is 5MPa;

[0117] The synthetic methanol reaction is carried out by raising the system temperature to the target reaction temperature according to the following heating program:

[0118] In 10 hours, the system temperature is raised to 80% of the target reaction temperature (i.e., 160°C), and in 20 hours, the system temperature is raised from 80% of the target reaction temperature (i.e., 160°C) to 90% of the target reaction temperature (i.e., 180°C), and in 5 hours, the system temperature is raised from 90% of the target reaction temperature (i.e., 180°C) to the target reaction temperature (i.e., 200°C);

[0119] Based on the total weight of the catalyst used in the methanol synthesis reaction as 100%, it contains 50% CuO, 40% ZnO and 10% Al 2 O 3 ; The catalyst is in strip shape with a diameter ranging from 2 to 4 mm.

[0120] In this embodiment, the electricity used in the process of electrolyzing water to produce green hydrogen comes from green electricity provided by renewable energy.

[0121] In this embodiment, the reaction product contents were measured from the outlets of the synthetic methanol reactor and the synthetic ammonia reactor, and the gas volume composition of the total reaction product was obtained after conversion, which was 7.1% H 2 , 0.5% CO, 0.4% CO 2 , 6.5% CH 3 OH, 6.8% H 2 O, 2.0% N 2 and 76.7% of NH 3 .

[0122] The raw material composition, reaction parameters of the methanol synthesis reaction and the ammonia synthesis reaction, and the obtained result data in Examples 3-5 of the present invention are shown in Table 1 below.

[0123] Table 1

[0124]

[0125]

[0126] As can be seen from Table 1 above, the flue gas direct hydrogenation method provided in Examples 3-5 of the present invention uses renewable energy to prepare green hydrogen, and the green hydrogen is used to convert the main component CO in fresh flue gas into 2 and N 2 Direct hydrogenation of CO 2 Hydrogenation to methanol and N 2 Hydrogenation to produce ammonia, omitting CO 2 Capture process and air separation to produce N 2 process, thus significantly reducing CO 2 The methanol and ammonia produced in Examples 3-5 of the present invention have a wide range of industrial applications, especially they can replace fossil energy such as coal and oil, thereby further reducing CO 2 In summary, the method and system for direct hydrogenation of flue gas provided by the embodiments of the present invention have both environmental protection and economic benefits.

[0127] The above is only a specific embodiment of the present invention, and cannot be used to limit the scope of the invention. Therefore, the replacement of equivalent components, or equivalent changes and modifications made according to the protection scope of the patent of the present invention, should still fall within the scope of this patent. In addition, the technical features of the present invention can be freely combined with each other, with each other and with each other, and with each other.

Claims

1. A method for direct hydrogenation of flue gas, characterized in that: The method for direct hydrogenation of flue gas comprises: The flue gas after desulfurization and refining is compressed and pressurized, and the pressurized flue gas enters the synthetic ammonia reactor and reacts with the green hydrogen produced by electrolysis of water to synthesize ammonia. After the reaction is completed, the obtained mixed gas is cooled and separated to obtain liquid ammonia. The remaining mixed gas is compressed and enters the synthetic methanol reactor and reacts with the green hydrogen produced by electrolysis of water to synthesize methanol. After the reaction is completed, the obtained mixed gas is cooled and separated to obtain liquid methanol and water and gas components. The sulfur content of the flue gas after desulfurization and purification is less than 0.1 ppm; the compression and pressure increase is to increase the pressure of the flue gas after desulfurization and purification to 5-30 MPa; The temperature of the methanol synthesis reaction is 100-400 o C, pressure 5~30MPa, air velocity 5000~20000 h -1 , the volume ratio of H2 to CO2 in the inlet mixed gas of the synthetic methanol reactor is 3.0-3.3; the active component of the catalyst used in the synthetic methanol reaction is CuO, and the carrier is other metal oxides except CuO, and the content of CuO is 20-90% based on the total weight of the catalyst as 100%; The temperature of the synthetic ammonia reaction is 400-500 o C, pressure is 15~25MPa, air velocity is 5000~20000 h -1 , the volume ratio of H2 to N2 in the inlet mixed gas of the synthetic ammonia reactor is 3.0-3.3, the active components of the catalyst used in the synthetic ammonia reaction are FeO and / or Fe2O3, and the content of FeO is 30-40% and the content of Fe2O3 is 55-65% based on the total weight of the catalyst as 100%; Alternatively, the catalyst used in the ammonia synthesis reaction is a Ba-Ru / BN catalyst, and the contents of Ba and Ru are 0.5-3%wt respectively, based on the total weight of the Ba-Ru / BN catalyst being 100%; The synthetic methanol reaction and / or the synthetic ammonia reaction are performed according to the following temperature increase program to raise the system temperature to the target reaction temperature: the system temperature is raised to 80% of the target reaction temperature in 10 hours, and then the system temperature is raised from 80% of the target reaction temperature to 90% of the target reaction temperature in 20 hours, and then the system temperature is raised from 90% of the target reaction temperature to the target reaction temperature in 5 hours; the cooling is performed at a constant cooling rate, wherein the cooling rate is 0.1-5 o C / min; or the cooling is first 0.5-1 o C / min to 80% of the reaction temperature, and then o The temperature was cooled to below the boiling point of the product at a cooling rate of 0.1 °C / min.

2. The method for direct hydrogenation of flue gas according to claim 1, characterized in that: The method further comprises: mixing the gas components as circulating gas with the flue gas after desulfurization and purification, and then compressing and increasing the pressure.

3. The method for direct hydrogenation of flue gas according to claim 1 or 2, characterized in that: The method further comprises: utilizing waste heat of flue gas to heat the ammonia synthesis reaction and / or the methanol synthesis reaction respectively.

4. The method for direct hydrogenation of flue gas according to claim 1 or 2, characterized in that: The desulfurizing agent used in the desulfurization refining is a solid adsorbent, and the main component of the solid adsorbent is metal oxide and / or non-metal oxide.

5. The method for direct hydrogenation of flue gas according to claim 4, characterized in that: The solid adsorbent includes one or a combination of zinc oxide, aluminum oxide, and silicon dioxide.

6. The method for direct hydrogenation of flue gas according to claim 4, characterized in that: The solid adsorbent is in strip shape, and its diameter ranges from 2 to 4 mm.

7. The method for direct hydrogenation of flue gas according to claim 1 or 2, characterized in that: The temperature of the methanol synthesis reaction is 150~250 o C, pressure is 10~20MPa.

8. The method for direct hydrogenation of flue gas according to claim 1 or 2, characterized in that: The CuO content is 25~75%.

9. The method for direct hydrogenation of flue gas according to claim 8, characterized in that: The CuO content is 25-50%.

10. The method for direct hydrogenation of flue gas according to claim 1 or 2, characterized in that: The support includes ZnO and / or Al2O3.

11. The method for direct hydrogenation of flue gas according to claim 1 or 2, characterized in that: The cooling rate is 0.5-2 o C / min.

12. A system for direct hydrogenation of flue gas for implementing the method for direct hydrogenation of flue gas according to any one of claims 1 to 11, characterized in that: The flue gas direct hydrogenation system comprises: a refining desulfurizer, a compressor, a synthetic methanol reactor, a methanol separator, a synthetic ammonia reactor, an ammonia separator and a water electrolysis hydrogen production device; Among them, the gas outlet of the refining desulfurizer is connected to the raw gas inlet of the synthetic ammonia reactor through a pipeline via a compressor, the outlet of the synthetic ammonia reactor is connected to the raw gas inlet of the synthetic methanol reactor through a pipeline via an ammonia separator, the outlet of the synthetic methanol reactor is connected to the inlet of the methanol separator through a pipeline, and the hydrogen outlet of the water electrolysis hydrogen production device is connected to the raw gas inlets of the synthetic ammonia reactor and the synthetic methanol reactor respectively through pipelines.

13. The system for direct hydrogenation of flue gas according to claim 12, characterized in that: The gas outlet of the methanol separator is connected to the compressor through a pipeline.

14. The system for direct hydrogenation of flue gas according to claim 12 or 13, characterized in that: The system further comprises a methanol storage tank and an ammonia storage tank, which are respectively connected to the liquid outlet of the methanol separator and the liquid outlet of the ammonia separator.

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