Device and method for preparing methanol through hydrogenation of carbon dioxide

Abstract

The invention discloses a device and a method for preparing methanol through hydrogenation of carbon dioxide. The device for preparing methanol through hydrogenation of carbon dioxide comprises a circulating compressor, a feed gas preheater, a primary heat exchanger, a methanol reactor, a first cooling gas-liquid separator and a second cooling gas-liquid separator, the circulating compressor is used for compressing feed gas entering the circulating compressor to a preset pressure range to obtain compressed feed gas; the raw material gas preheater can be used for receiving the compressed raw material gas and preheating the compressed raw material gas to obtain preheated raw material gas; the primary heat exchanger can be used for receiving the preheated raw material gas and inputting the preheated raw material gas and a product mixture of the methanol reactor into the methanol reactor after heat exchange; the methanol reactor comprises a shell and a plurality of reaction sections arranged in the shell, wherein the plurality of reaction sections comprise a first-stage reaction section, a second-stage reaction section, a third-stage reaction section and the like. The total carbon conversion rate can be increased, and the energy consumption, the circulating gas amount and the equipment investment cost can be reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of methanol preparation, and in particular to a device and method for preparing methanol by hydrogenating carbon dioxide. Background Art

[0002] Methanol is the fourth largest basic chemical raw material after ethylene, propylene and benzene. It has a wide range of uses. It can not only be used to produce a variety of chemical products, but also used as fuel. With the development of methanol downstream industries and the promotion of methanol fuel, methanol demand and production capacity will continue to grow.

[0003] There are many ways to synthesize methanol. Currently, industrial methanol is mainly produced from coal and natural gas, and is produced through synthesis gas composed of carbon monoxide and hydrogen. The synthesis of methanol consumes fossil energy and is accompanied by carbon dioxide emissions, especially from coal-to-methanol. Taking the production of methanol from water-coal slurry gasification as an example, if the carbon dioxide emissions are not converted into public works consumption, about 2.2 tons of carbon dioxide are emitted for every ton of methanol produced. Therefore, methanol produced from fossil energy belongs to "grey methanol".

[0004] The production of green methanol using carbon dioxide and green hydrogen as raw materials not only does not produce carbon dioxide emissions, but also can absorb carbon dioxide, which is an important means of carbon emission reduction; at the same time, the reaction of carbon dioxide and green hydrogen to produce methanol is also an effective storage method for green hydrogen and renewable energy. Its essence is to use renewable energy to convert carbon dioxide and water into methanol, and to store unstable and intermittent solar energy in methanol that is easy to store and transport. Therefore, the research on the use of carbon dioxide hydrogenation to produce methanol has received widespread attention in recent years. However, the traditional process of producing methanol by hydrogenation of carbon dioxide still needs to be solved, such as large circulating gas volume, high equipment investment cost, high energy consumption, and heat waste.

[0005] Therefore, it is necessary to provide a device and method for producing methanol by hydrogenating carbon dioxide to solve at least one of the above problems. Summary of the invention

[0006] In view of the defects of the prior art, an apparatus and method for producing methanol by hydrogenating carbon dioxide are provided in an embodiment of the present invention. Through the design of process equipment and thermal coupling of the process flow, the total carbon conversion rate is improved, and the energy consumption, circulating gas volume and equipment investment cost are reduced.

[0007] The specific technical solution of the implementation mode of the present invention is:

[0008] A device for preparing methanol by hydrogenating carbon dioxide, the device comprising: a circulating compressor, a raw gas preheater, a primary heat exchanger, a methanol reactor, a first cooling gas-liquid separator and a second cooling gas-liquid separator; the circulating compressor is used to compress the raw gas entering the circulating compressor to a predetermined pressure range to obtain compressed raw gas; the raw gas preheater can be used to receive the compressed raw gas and preheat the compressed raw gas to obtain preheated raw gas; the primary heat exchanger can be used to receive the preheated raw gas and heat-exchange the preheated raw gas with the product mixture of the methanol reactor and then input it into the methanol reactor; the methanol reactor comprises a shell and a The multiple reaction sections in the shell include: a primary reaction section, a secondary reaction section and a tertiary reaction section; the product mixture produced by the primary reaction section is passed into the primary heat exchanger to exchange heat with the preheated raw gas entering the primary heat exchanger, and then passed into the secondary reaction section after heat exchange. The product mixture produced by the secondary reaction section passes through the first cooling gas-liquid separator to obtain a crude methanol product and a portion of unreacted raw gas. The obtained unreacted raw gas is passed into the tertiary reaction section of the methanol reactor for reaction. The obtained product mixture is passed into the raw gas preheater for heat exchange with the raw gas, and then separated by the second cooling gas-liquid separator.

[0009] In a preferred embodiment, the device for producing methanol by hydrogenating carbon dioxide also includes: a methanol water washing tower, in which the unreacted synthesis gas obtained after separation by the second cooling gas-liquid separator is passed into the methanol water washing tower for water washing treatment, so as to absorb residual methanol molecules in the unreacted synthesis gas and obtain unreacted gas after water washing treatment.

[0010] In a preferred embodiment, an annular gap is formed between the shell and the reaction section, and a temperature detector for detecting the temperature of the raw gas and a temperature increaser for increasing the temperature of the raw gas are arranged in the annular gap.

[0011] In a preferred embodiment, when the temperature of the raw gas is raised to between 220°C and 320°C by the temperature raiser, it is then fed into the corresponding reaction section.

[0012] In a preferred embodiment, the reaction section includes two primary reaction sections, two secondary reaction sections and one tertiary reaction section; the tertiary reaction section is located in the middle, the two secondary reaction sections are located on both sides of the tertiary reaction section, and the two primary reaction sections are respectively located on both sides of the two secondary reaction sections.

[0013] In a preferred embodiment, the predetermined pressure range is between 4 MPa and 5 MPa.

[0014] In a preferred embodiment, the device for producing methanol by hydrogenating carbon dioxide further includes: a hydrogen replenishment distributor, through which the unreacted gas after water washing treatment in the methanol water washing tower is passed through the hydrogen replenishment distributor to adjust the ratio of carbon dioxide and hydrogen to obtain hydrogen-treated gas, and the hydrogen-treated gas is mixed with the raw gas as circulating gas and introduced into the circulating compressor.

[0015] In a preferred embodiment, the molar ratio of carbon dioxide to hydrogen is 1:3.05 to 1:3.15.

[0016] A method for producing methanol by hydrogenating carbon dioxide in the above-mentioned device for producing methanol by hydrogenating carbon dioxide, the method for producing methanol by hydrogenating carbon dioxide comprising:

[0017] The purified mixed raw gas is introduced into the circulating compressor for compression, and then subjected to a heat exchange with a product mixture from the tertiary reaction section of the methanol reactor, and then split into two equal-flow streams for a secondary heat exchange with a product mixture from the two primary reaction sections of the methanol reactor, and then introduced into the two primary reaction sections of the methanol reactor for reaction;

[0018] The product mixtures produced by the two primary reaction sections of the methanol reactor are introduced into the adjacent secondary reaction sections for secondary reaction after preheating the feed gas entering the primary reaction section;

[0019] Passing the product mixture produced by the two secondary reaction stages of the methanol reactor into the cooling gas-liquid separator for cooling and depressurization to separate into crude methanol and unreacted raw gas;

[0020] The crude methanol produced by the cooling gas-liquid separator is sent to the subsequent distillation section, and the separated unreacted raw gas enters the annular gap of the methanol reactor for preheating and then enters the tertiary reaction section for tertiary reaction;

[0021] The product mixture produced by the tertiary reaction section of the methanol reactor is passed into the raw gas preheater for preliminary heat exchange with the raw gas, and then passed into the cooling gas-liquid separator for gas-liquid separation to obtain liquid phase crude methanol and gas phase unreacted gas.

[0022] In a preferred embodiment, the method for producing methanol by hydrogenating carbon dioxide further comprises: sending the liquid phase crude methanol separated by the cooling gas-liquid separator to a distillation section, and passing the separated gas phase unreacted gas into a methanol water washing tower to absorb residual methanol molecules in the gas.

[0023] In a preferred embodiment, the method for producing methanol by hydrogenating carbon dioxide further includes: adjusting the ratio of carbon dioxide to hydrogen to a predetermined range through a hydrogen replenishment distributor through which the unreacted gas after dealcoholization by the methanol water washing tower is supplied, and after hydrogen replenishment, the gas is mixed with the raw gas as a circulating gas to form a reaction cycle.

[0024] The technical solution of the present invention has the following significant beneficial effects:

[0025] The device for producing methanol by hydrogenation of carbon dioxide provided in the embodiment of the present application is provided with a methanol reactor which is a multi-stage reactor, and the material stream is diverted into the reactor multiple times, thereby improving the conversion rate of carbon dioxide to methanol. The product mixture output by the methanol reactor improves the heat utilization rate by optimizing the heat coupling method, thereby reducing the heat loss. The feed of the tertiary reaction stage of the methanol reactor is dehydrated unreacted gas, and the conversion rate of carbon dioxide throughout the process is further improved by adding the tertiary reaction stage. After the tertiary reaction stage is fully reacted, the residual carbon dioxide content is lower, thereby reducing the circulating gas volume, reducing the requirements for equipment and the compression power consumption.

[0026] With reference to the following description and drawings, specific embodiments of the present invention are disclosed in detail, indicating the manner in which the principles of the present invention can be adopted. It should be understood that the embodiments of the present invention are not limited in scope. Within the spirit and scope of the appended claims, the embodiments of the present invention include many changes, modifications and equivalents. Features described and / or shown for one embodiment can be used in one or more other embodiments in the same or similar manner, combined with features in other embodiments, or replace features in other embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings described herein are only for explanation purposes and are not intended to limit the scope of the present invention in any way. In addition, the shapes and proportional dimensions of the various components in the figures are only schematic, used to help understand the present invention, and are not specifically limited to the shapes and proportional dimensions of the various components of the present invention. Those skilled in the art can select various possible shapes and proportional dimensions to implement the present invention according to the teachings of the present invention.

[0028] Figure 1 This is a schematic structural diagram of a device for producing methanol by hydrogenating carbon dioxide provided in an embodiment of the present application;

[0029] Figure 2 A schematic flow chart of the steps of a method for producing methanol by hydrogenating carbon dioxide provided in an embodiment of the present application.

[0030] Reference numerals of the present application:

[0031] 1. Circulation compressor;

[0032] 2. Raw gas preheater;

[0033] 3. Primary heat exchanger;

[0034] 4. Methanol reactor;

[0035] 41. Primary reaction section;

[0036] 42. Secondary reaction section;

[0037] 43. Tertiary reaction section;

[0038] 51. The first cooling gas-liquid separator;

[0039] 52. Second cooling gas-liquid separator;

[0040] 6. Methanol water washing tower;

[0041] 7. Hydrogen replenishment distributor. DETAILED DESCRIPTION

[0042] The technical solution of the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0043] It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0045] One of the existing technologies:

[0046] Chinese patent CN216550214U discloses a system for producing methanol by multi-stage synthesis of carbon dioxide. The specific steps disclosed in the patent are:

[0047] S1: The hydrogen in the raw gas is compressed and mixed with part of the carbon dioxide that has been pressurized and vaporized and the circulating gas, and then enters the first to nth methanol synthesis and separation systems in sequence, where crude methanol is synthesized;

[0048] S2: A portion of the gas generated from the nth stage methanol synthesis and separation system is compressed as circulating gas and then returned to the first stage methanol synthesis and separation system;

[0049] S3: The remaining gas enters the n+1 stage methanol synthesis and separation system;

[0050] S4: The carbon dioxide supply system runs through each section of the methanol synthesis and separation system to adjust the carbon-hydrogen ratio of the reaction.

[0051] The equipment cost investment of the multi-stage reaction and separation system in the above process is huge, and the multi-stage heat exchange separation and compression process further increases the power consumption and heat waste of the entire process. In addition, since there is a large amount of by-product water separation problem in the production of methanol from carbon dioxide, the energy consumption load caused by the distillation process is too large.

[0052] Prior art 2:

[0053] Chinese patent CN116983945 discloses a method and system for producing methanol from carbon dioxide and hydrogen. The specific steps disclosed in the patent are:

[0054] S1: Carbon dioxide gas and hydrogen are compressed by a carbon dioxide turbine compressor and a hydrogen turbine compressor respectively, and then mixed and enter a preheater for preheating;

[0055] S2: The preheated carbon dioxide gas and hydrogen enter the methanol reactor for reaction, and the reaction products enter the preheater as a heating source to preheat the carbon dioxide gas and hydrogen;

[0056] S3: The reaction product after being cooled by the preheater enters the high-pressure distillation tower for distillation;

[0057] S4: The gas phase after rectification in the high-pressure distillation tower enters the pressure blower through the top of the tower and is pressurized, then returns to the preheater for preheating and re-enters the methanol reactor to participate in the reaction;

[0058] S5: The bottom liquid phase after distillation in the high-pressure distillation tower enters the methanol recovery tower for methanol distillation.

[0059] This patent fails to fully utilize heat coupling to reduce heat loss; in addition, since there is a problem of separating a large amount of by-product water in the production of methanol from carbon dioxide, the energy consumption load caused by the distillation section is too large.

[0060] The present invention provides a device and method for preparing methanol by hydrogenating carbon dioxide, which mainly aims at the problems of low carbon conversion rate, high energy consumption of the device, serious heat loss and excessive circulating gas volume in preparing methanol by hydrogenating carbon dioxide. Through the design of process equipment and heat coupling of the process flow, the total carbon conversion rate is improved, and the energy consumption, circulating gas volume and equipment investment cost are reduced.

[0061] See also Figure 1 In the embodiment of the present application specification, a device for producing methanol by hydrogenating carbon dioxide is provided, and the device for producing methanol by hydrogenating carbon dioxide may include: a circulating compressor 1, a raw gas preheater 2, a primary heat exchanger 3, a methanol reactor 4, a first cooling gas-liquid separator 51, and a second cooling gas-liquid separator 52; the circulating compressor 1 is used to compress the raw gas entering the interior thereof to a predetermined pressure range to obtain compressed raw gas; the raw gas preheater 2 can be used to receive the compressed raw gas and preheat the compressed raw gas to obtain preheated raw gas; the primary heat exchanger 3 can be used to receive the preheated raw gas and heat-exchange the preheated raw gas with the product mixture of the methanol reactor 4 and input it into the methanol reactor 4; the methanol reactor 4 includes a shell and Multiple reaction sections are arranged in the shell, and the multiple reaction sections include: a primary reaction section 41, a secondary reaction section 42 and a tertiary reaction section 43; the product mixture produced by the primary reaction section 41 is passed into the primary heat exchanger 3, and is used to exchange heat with the preheated raw gas entering the primary heat exchanger 3. After heat exchange, it is passed into the secondary reaction section 42. The product mixture produced by the secondary reaction section 42 passes through the first cooling gas-liquid separator 51 to obtain a crude methanol product and a part of the unreacted raw gas. The obtained unreacted raw gas is passed into the tertiary reaction section 43 of the methanol reactor 4 for reaction. The obtained product mixture is passed into the raw gas preheater 2 for heat exchange with the raw gas, and then separated by the second cooling gas-liquid separator 52.

[0062] In the embodiment of the present application, the device for producing methanol by hydrogenation of carbon dioxide mainly includes: a circulating compressor 1, a raw gas preheater 2, a primary heat exchanger 3, a methanol reactor 4, a first cooling gas-liquid separator 51, a second cooling gas-liquid separator 52, and necessary connecting pipelines, etc. In addition, the device for producing methanol by hydrogenation of carbon dioxide may also include: a methanol water scrubber 6, a hydrogen replenishment distributor 7, etc.

[0063] In this embodiment, the circulating compressor 1 is used to compress the purified mixed raw gas, so that the mixed raw gas is compressed to a predetermined pressure range after passing through the circulating compressor 1 to obtain compressed raw gas. In this embodiment, the mixed raw gas can specifically be a mixed gas of carbon dioxide and hydrogen.

[0064] Specifically, when in use, the mixed raw gas entering the circulating compressor 1 can reach a pressure of 4Mpa to 5Mpa after being compressed by the raw gas compressor.

[0065] The raw gas preheater 2 is used to perform heat exchange on the fluid flowing through it. In this embodiment, the raw gas preheater 2 can be used to receive the compressed raw gas and preheat the compressed raw gas to obtain the preheated raw gas. Specifically, the compressed raw gas can be preheated with the product mixture produced by the tertiary reaction section 43 of the methanol reactor 4, thereby improving the heat utilization rate and reducing the heat loss by optimizing the heat coupling.

[0066] The primary heat exchanger 3 can also be used to exchange heat for the fluid flowing through it. In this embodiment, the primary heat exchanger 3 can be used to receive the preheated raw gas, and after heat exchange, the preheated raw gas and the product mixture of the methanol reactor 4 are input into the methanol reactor 4, thereby improving the heat utilization rate and reducing the heat loss by optimizing the heat coupling.

[0067] In this embodiment, the methanol reactor 4 may include a shell and a plurality of reaction sections disposed in the shell, wherein the plurality of reaction sections include a primary reaction section 41, a secondary reaction section 42, and a tertiary reaction section 43. In this embodiment, the methanol reactor 4 is a multi-stage reactor, and the conversion rate of carbon dioxide to methanol is improved through multi-stage split flow reactions.

[0068] The product mixture produced by the primary reaction section 41 is passed into the primary heat exchanger 3 for heat exchange with the preheated raw gas entering the primary heat exchanger 3. After heat exchange, it is passed into the secondary reaction section 42. The product mixture produced by the secondary reaction section 42 passes through the first cooling gas-liquid separator 51 to obtain a crude methanol product and a portion of unreacted raw gas. The obtained unreacted raw gas is passed into the tertiary reaction section 43 of the methanol reactor 4 for reaction. The obtained product mixture is passed into the raw gas preheater 2 for heat exchange with the raw gas, and then separated by the second cooling gas-liquid separator 52.

[0069] The product mixture produced by the methanol reactor 4 improves heat utilization and reduces heat loss by optimizing heat coupling. The feed of the tertiary reaction section of the methanol reactor 4 is dehydrated unreacted gas, and the conversion rate of carbon dioxide in the whole process is further improved by adding the tertiary reaction section.

[0070] After the three reaction stages are fully reacted, the residual carbon dioxide content is lower, thereby reducing the amount of circulating gas, lowering the requirements for equipment and compression power consumption.

[0071] In one embodiment, the reaction section may include two primary reaction sections 41, two secondary reaction sections 42 and one tertiary reaction section 43. The tertiary reaction section 43 is located in the middle, the two secondary reaction sections 42 are located on both sides of the tertiary reaction section 43, and the two primary reaction sections 41 are respectively located on both sides of the two secondary reaction sections 42. The methanol reactor 4 adopts a structural design of a total of 5 reaction sections, which ensures that the reaction temperature can meet the requirements of efficient reaction.

[0072] Of course, in some other embodiments, the number and arrangement of the primary reaction section 41, the secondary reaction section 42 and the tertiary reaction section 43 in the reaction section can also be other arrangements and combinations, and are not limited to the above description. Technical personnel in the relevant field may make other changes inspired by the technical essence of this application, but as long as the functions and effects achieved are the same or similar to those of the present application, they should be covered within the scope of protection of this application.

[0073] For the above-mentioned embodiment with two primary reaction sections 41 and two secondary reaction sections 42, the number of the primary heat exchangers 3 can be divided into two. The fluid (the raw fluid after preheating and compression) flowing out of the raw gas preheater 2 can be divided into two branches through a three-way valve and connected to the two primary heat exchangers 3 respectively. Since the raw gas enters the primary heat exchanger 3 in the form of split streams, the requirements for the equipment size are reduced and the heat recovery rate is improved.

[0074] For each primary heat exchanger 3, it can have a gas input port for receiving the fluid flowing out of the above-mentioned raw gas preheater 2, two gas output ports, respectively connected to the primary reaction section 41 and the secondary reaction section 42, and a gas reflux port for receiving the fluid output from the reaction section.

[0075] The outlets of the two secondary reaction sections 42 can be converged through a three-way valve and then enter the first cooling gas-liquid separator 51 for gas-liquid separation to obtain liquid phase crude methanol and gas phase unreacted gas. Among them, cooling water flows through the first cooling gas-liquid separator 51 to cool the fluid entering the first cooling gas-liquid separator 51. After the cooling water absorbs the heat in the fluid, it can form medium-pressure steam, which can be used for other generation purposes. The unreacted gas enters the tertiary reaction section 43 for reaction.

[0076] In one embodiment, an annular gap is formed between the shell and the reaction section, and a temperature detector for detecting the temperature of the raw gas and a temperature increaser for increasing the temperature of the raw gas are arranged in the annular gap. When the temperature increaser increases the temperature of the raw gas to between 220°C and 320°C, the raw gas is then fed into the corresponding reaction section, thereby improving the reaction efficiency and conversion rate.

[0077] The gas reacted in the tertiary reaction section 43 can be detected by a temperature detector before the reaction. When the temperature does not reach the preset temperature (220°C to 320°C), it can be heated by a heater in the annular gap of the shell. After the temperature detector detects that the current reaction gas reaches the preset temperature, the gas is passed into the tertiary reaction section 43 for reaction. Among them, the product produced by the secondary reaction section 42 in the methanol reactor 4 is first separated by gas and liquid by the first cooling gas-liquid separator 51 before being passed into the tertiary reaction section 43 for reaction. After the water component is removed, the conversion rate of carbon dioxide to methanol is improved.

[0078] The product mixture after the reaction in the tertiary reaction section 43 can flow through the raw gas preheater 2 as a heat source for the raw gas preheater 2 to preheat the raw gas. By optimizing the heat coupling method, the heat utilization rate is improved and the heat loss is reduced.

[0079] The product mixture flowing through the raw gas preheater 2 enters the second cooling gas-liquid separator 52 for gas-liquid separation to obtain liquid phase crude methanol and gas phase unreacted gas. The obtained liquid phase crude methanol can be combined with the crude methanol generated in the secondary reaction section and separated by the first cooling gas-liquid separator 51 and then output to a designated location.

[0080] In one embodiment, the device for producing methanol by hydrogenating carbon dioxide may also include: a methanol water washing tower 6, in which the unreacted synthesis gas obtained after separation by the second cooling gas-liquid separator 52 is introduced into the methanol water washing tower 6 for water washing treatment, so as to absorb the residual methanol molecules in the unreacted synthesis gas and obtain the unreacted gas after the water washing treatment.

[0081] Furthermore, the device for producing methanol by hydrogenating carbon dioxide also includes: a hydrogen replenishment distributor 7, through which the unreacted gas after water washing treatment in the methanol water washing tower 6 is passed through the hydrogen replenishment distributor 7 to adjust the ratio of carbon dioxide and hydrogen to obtain hydrogen-treated gas, and the hydrogen-treated gas is mixed with the raw gas as circulating gas and introduced into the circulating compressor 1.

[0082] The ratio of carbon dioxide to hydrogen is within a predetermined ratio range, and the preferred molar ratio is 1:3.05 to 1:3.15, to ensure that carbon dioxide and hydrogen react effectively within a reasonable ratio range and prevent excess or insufficient amounts of a certain gas from affecting the reaction efficiency and conversion rate.

[0083] On the whole, before the raw gas first enters the reactor, the heat of the reactor product will be fully utilized through thermal coupling to increase its temperature, thereby reducing heat loss and energy consumption. Only the products produced after sufficient reaction in the three-stage reaction section of the methanol reactor 4 will be mixed with the raw gas to form a reaction cycle after gas-liquid separation, alcohol removal, and hydrogen supplementation. This arrangement reduces the circulating gas volume, equipment investment cost, and compressor power consumption.

[0084] See also Figure 2 Based on the device for producing methanol by hydrogenating carbon dioxide provided in the above embodiment, a method for producing methanol by hydrogenating carbon dioxide is also provided in the embodiment of the present application. The method for producing methanol by hydrogenating carbon dioxide may include the following steps:

[0085] S11: the purified mixed raw gas is introduced into the circulating compressor 1 for compression, and then subjected to a heat exchange with the product mixture from the tertiary reaction section 43 of the methanol reactor 4, and then split into two equal-flow streams for a secondary heat exchange with the product mixture from the two primary reaction sections 41 of the methanol reactor 4, and then introduced into the two primary reaction sections 41 of the methanol reactor 4 for reaction;

[0086] S12: the product mixtures produced by the two primary reaction sections 41 of the methanol reactor 4 are introduced into the adjacent secondary reaction sections 42 for secondary reaction after preheating the feed gas entering the primary reaction section 41;

[0087] S13: passing the product mixture produced by the two secondary reaction sections 42 of the methanol reactor 4 into the cooling gas-liquid separator for cooling and depressurization to separate into crude methanol and unreacted raw gas;

[0088] S14: the crude methanol produced by the cooling gas-liquid separator is sent to the subsequent distillation section, and the separated unreacted raw gas enters the annular gap of the methanol reactor 4 for preheating and then enters the tertiary reaction section 43 for tertiary reaction;

[0089] S15: The product mixture produced by the tertiary reaction section 43 of the methanol reactor 4 is introduced into the raw gas preheater 2 for preliminary heat exchange with the raw gas, and then introduced into the cooling gas-liquid separator for gas-liquid separation to obtain liquid phase crude methanol and gas phase unreacted gas.

[0090] In one embodiment, the method for producing methanol by hydrogenating carbon dioxide further comprises:

[0091] S16: The liquid phase crude methanol separated by the cooling gas-liquid separator is sent to the distillation section, and the separated gas phase unreacted gas is passed into the methanol water washing tower 6 to absorb the residual methanol molecules in the gas.

[0092] In one embodiment, the method for producing methanol by hydrogenating carbon dioxide further comprises:

[0093] S17: The unreacted gas after dealcoholization in the methanol water washing tower 6 is adjusted to a predetermined ratio range of carbon dioxide and hydrogen through a hydrogen replenishing distributor 7. After hydrogen replenishing, the gas is mixed with the raw gas as a circulating gas to form a reaction cycle.

[0094] The device for producing methanol by hydrogenating carbon dioxide provided in the above embodiment of the present application is used according to Figure 1 As shown, the purified mixed raw gas is compressed to 4Mpa to 5Mpa by the circulating compressor 1, and then heat exchanged with the product mixture from the tertiary reaction section 43 of the methanol reactor 4, and then divided into two equal-flow streams and heat exchanged with the product mixture produced by the two-stage primary reaction section 41 of the methanol reactor 4 for a second time, and then passed into the two-stage primary reaction section 41 of the methanol reactor 4 for reaction. A heating device and a temperature detector are arranged in the annular gaps between the primary reaction section 41, the secondary reaction section 42, the tertiary reaction section 43 of the methanol reactor 4 and the methanol reactor 4, and when the raw gas temperature reaches 220°C to 320°C, it is sent to the reaction section for reaction. The product mixture produced by the two-stage primary reaction section 41 of the methanol reactor 4 is preheated to the raw gas entering the primary reaction section 41 and then passed into the adjacent secondary reaction section 42 for secondary reaction. The product mixture produced by the two-stage secondary reaction section 42 of the methanol reactor 4 is passed into the first cooling gas-liquid separator 51 for cooling and pressure reduction to separate into crude methanol and unreacted raw gas, and a certain amount of medium-pressure steam produced as a by-product in this section is used for other purposes. The crude methanol produced by the first cooling gas-liquid separator 51 is sent to the subsequent distillation section, and the separated unreacted raw gas enters the annular gap of the methanol reactor 4 for preheating and then enters the tertiary reaction section 43 for tertiary reaction. The product mixture produced by the tertiary reaction section 43 of the methanol reactor 4 is passed into the raw gas preheater 2 for preliminary heat exchange with the raw gas, and then passed into the second cooling gas-liquid separator 52 for gas-liquid separation. This section produces a certain amount of medium-pressure steam as a by-product. The liquid phase crude methanol separated by the second cooling gas-liquid separator 52 is sent to the distillation section, and the separated gas phase unreacted gas is passed into the methanol water washing tower 6 to absorb the residual methanol molecules in the gas. The unreacted gas after dealcoholization in the methanol water washing tower 6 is adjusted to a ratio of carbon dioxide to hydrogen to 1:3.05 to 1:3.15 by the hydrogen replenishment distributor 7. After hydrogen replenishment, the gas is mixed with the raw gas as a circulating gas to form a reaction cycle, so that the raw gas in the entire device can be fully utilized, greatly improving the total carbon conversion rate.

[0095] The method for producing methanol by hydrogenation of carbon dioxide based on the above-mentioned device for producing methanol by hydrogenation of carbon dioxide provided in the embodiment of the present application has the following beneficial effects:

[0096] 1. The methanol reactor 4 is a multi-stage reactor, which improves the conversion rate of carbon dioxide to methanol through multi-stage split reactions.

[0097] 2. The product mixture produced by the methanol reactor 4 improves heat utilization and reduces heat loss by optimizing heat coupling.

[0098] 3. The feed of the tertiary reaction section of the methanol reactor 4 is dehydrated unreacted gas, and the conversion rate of carbon dioxide in the whole process is further improved by adding the tertiary reaction section.

[0099] 4. After the three reaction stages are fully reacted, the residual carbon dioxide content is lower, thereby reducing the circulating gas volume, reducing the requirements for equipment and compression power consumption.

[0100] It should be noted that, in the description of this application, the terms "first", "second", etc. are only used for descriptive purposes and to distinguish similar objects. There is no order of precedence between the two, and they cannot be understood as indicating or implying relative importance. In addition, in the description of this application, unless otherwise specified, the meaning of "plurality" is two or more.

[0101] The above-mentioned various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other. Each embodiment focuses on the differences from other embodiments.

[0102] The above are only a few embodiments of the present invention. Although the embodiments disclosed by the present invention are as above, the contents are only embodiments adopted for facilitating the understanding of the present invention and are not used to limit the present invention. Any technician in the technical field to which the present invention belongs can make any modification and change in the form and details of the embodiments without departing from the spirit and scope disclosed by the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined by the attached claims.

Claims

1. A device for producing methanol by hydrogenating carbon dioxide, characterized in that: The device for producing methanol by hydrogenating carbon dioxide comprises: a circulating compressor, a raw gas preheater, a primary heat exchanger, a methanol reactor, a first cooling gas-liquid separator and a second cooling gas-liquid separator; The circulating compressor is used to compress the raw gas entering the circulating compressor to a predetermined pressure range to obtain compressed raw gas; The raw gas preheater can be used to receive the compressed raw gas and preheat the compressed raw gas to obtain preheated raw gas; The primary heat exchanger can be used to receive the preheated raw gas, and after heat exchange between the preheated raw gas and the product mixture of the methanol reactor, input it into the methanol reactor; The methanol reactor comprises a shell and a plurality of reaction sections arranged in the shell, wherein the plurality of reaction sections comprise: a primary reaction section, a secondary reaction section and a tertiary reaction section; The product mixture produced in the primary reaction section is passed into the primary heat exchanger for heat exchange with the preheated raw gas entering the primary heat exchanger, and then passed into the secondary reaction section after heat exchange. The product mixture produced in the secondary reaction section passes through the first cooling gas-liquid separator to obtain a crude methanol product and a portion of unreacted raw gas. The obtained unreacted raw gas is passed into the tertiary reaction section of the methanol reactor for reaction. The obtained product mixture is passed into the raw gas preheater for heat exchange with the raw gas, and then separated by passing through the second cooling gas-liquid separator.

2. The device for preparing methanol by hydrogenating carbon dioxide according to claim 1, characterized in that: The device for producing methanol by hydrogenating carbon dioxide also includes: a methanol water washing tower, in which the unreacted synthesis gas obtained after separation by the second cooling gas-liquid separator is introduced into the methanol water washing tower for water washing treatment, so as to absorb residual methanol molecules in the unreacted synthesis gas and obtain unreacted gas after water washing treatment.

3. The device for preparing methanol by hydrogenating carbon dioxide according to claim 1, characterized in that: An annular gap is formed between the shell and the reaction section, and a temperature detector for detecting the temperature of the raw gas and a temperature increaser for increasing the temperature of the raw gas are arranged in the annular gap.

4. The device for producing methanol by hydrogenating carbon dioxide as claimed in claim 3, characterized in that: When the temperature of the raw gas is raised to between 220°C and 320°C by the temperature raiser, it is then sent to the corresponding reaction section.

5. The device for preparing methanol by hydrogenating carbon dioxide according to claim 1, characterized in that: The reaction section includes two primary reaction sections, two secondary reaction sections and one tertiary reaction section; The tertiary reaction section is located in the middle, the two secondary reaction sections are located on both sides of the tertiary reaction section, and the two primary reaction sections are located on both sides of the two secondary reaction sections respectively.

6. The device for preparing methanol by hydrogenating carbon dioxide according to claim 1, characterized in that: The predetermined pressure range is between 4 MPa and 5 MPa.

7. The device for producing methanol by hydrogenating carbon dioxide according to claim 2, characterized in that: The device for producing methanol by hydrogenating carbon dioxide also includes: a hydrogen replenishing distributor, The unreacted gas after water washing treatment in the methanol water washing tower is adjusted to a ratio of carbon dioxide and hydrogen through the hydrogen replenishment distributor to obtain hydrogen-replenished gas, which is mixed with the raw gas as circulating gas and introduced into the circulating compressor.

8. The device for producing methanol by hydrogenating carbon dioxide according to claim 7, characterized in that: The molar ratio of carbon dioxide to hydrogen is 1:3.05 to 1:3.

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9. A method for producing methanol by hydrogenating carbon dioxide based on the device for producing methanol by hydrogenating carbon dioxide according to any one of claims 1 to 8, characterized in that: The method for preparing methanol by hydrogenating carbon dioxide comprises: The purified mixed raw gas is passed through a circulation compressor for compression, and then subjected to a heat exchange with a product mixture from a tertiary reaction section of a methanol reactor, and then split into two equal-flow streams for a secondary heat exchange with a product mixture from two primary reaction sections of the methanol reactor, and then passed through the two primary reaction sections of the methanol reactor for reaction; The product mixtures produced by the two primary reaction sections of the methanol reactor are introduced into the adjacent secondary reaction sections for secondary reaction after preheating the feed gas entering the primary reaction section; Passing the product mixture produced by the two secondary reaction stages of the methanol reactor into a cooling gas-liquid separator for cooling and depressurization to separate into crude methanol and unreacted raw gas; The crude methanol produced by the cooling gas-liquid separator is sent to the subsequent distillation section, and the separated unreacted raw gas enters the annular gap of the methanol reactor for preheating and then enters the tertiary reaction section for tertiary reaction; The product mixture produced by the tertiary reaction section of the methanol reactor is passed into the raw gas preheater for preliminary heat exchange with the raw gas, and then passed into the cooling gas-liquid separator for gas-liquid separation to obtain liquid phase crude methanol and gas phase unreacted gas.

10. The method for preparing methanol by hydrogenating carbon dioxide according to claim 9, characterized in that: The method for producing methanol by hydrogenating carbon dioxide further includes: sending the liquid phase crude methanol separated by the cooling gas-liquid separator to a distillation section, and passing the separated gas phase unreacted gas into a methanol water washing tower to absorb residual methanol molecules in the gas.

11. The method for preparing methanol by hydrogenating carbon dioxide according to claim 9, characterized in that: The method for producing methanol by hydrogenating carbon dioxide also includes: adjusting the ratio of carbon dioxide to hydrogen to a predetermined range through a hydrogen replenishing distributor for the unreacted gas after dealcoholization in the methanol water washing tower, and mixing the gas with the raw gas as a circulating gas after hydrogen replenishment to form a reaction cycle.

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