Method and device for preparing methanol through carbon dioxide hydrogenation

Abstract

The invention provides a method and a device for preparing methanol through carbon dioxide hydrogenation. The method comprises the following steps: enabling synthesis gas to enter from a first shell pass of a first shell-and-tube reactor, carrying out deoxidation treatment on the synthesis gas through a catalyst bed layer arranged in the first shell pass to obtain deoxidized synthesis gas, and enabling the heated deoxidized synthesis gas to enter from a first tube pass of the first shell-and-tube reactor, reacting under the catalytic action of a first catalyst arranged in the first tube pass to obtain a reaction system; and cooling and separating the reaction system to obtain methanol. The synthesis gas enters from the first shell pass, heat in the first tube pass can be taken away, the synthesis gas is preheated, the synthesis gas reaches the temperature of the deoxidation reaction, the efficiency of the deoxidation reaction is improved, and the deoxidized synthesis gas obtained through the deoxidation reaction can continue to remove heat released by the reaction of the first tube pass; the efficiency of preparing methanol through carbon dioxide hydrogenation is improved, and the equipment investment and energy consumption are reduced.

Description

Technical Field

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

[0002] In the process of hydrogenating carbon dioxide to methanol, the raw material hydrogen generally comes from electrolytic water for hydrogen production, and a small amount of oxygen is contained in the hydrogen. The presence of oxygen will cause the deactivation of the carbon dioxide hydrogenation catalyst.

[0003] In the traditional process of preparing methanol by hydrogenating carbon dioxide, a deoxidation reactor is usually set before the methanol synthesis reaction to remove the oxygen in the raw material gas. Since the deoxidation catalyst has a certain activation temperature, a heater is also required to preheat the raw material gas before the deoxidation reactor, which not only increases the equipment investment but also causes excessive energy consumption. Summary of the Invention

[0004] The present application provides a method and device for preparing methanol by hydrogenating carbon dioxide to solve the problems in the prior art that not only increases the equipment investment but also generates excessive energy consumption.

[0005] In a first aspect, the present application provides a method for preparing methanol by hydrogenating carbon dioxide, comprising the following steps:

[0006] Let the syngas enter from the first shell side of the first shell-and-tube reactor, and after being deoxidized by the catalyst bed layer arranged in the first shell side, the deoxidized syngas is obtained. The syngas includes carbon dioxide, hydrogen and oxygen;

[0007] Let the heated deoxidized syngas enter from the first tube side of the first shell-and-tube reactor, and react under the catalytic action of the first catalyst arranged in the first tube side to obtain a reaction system;

[0008] Perform temperature reduction and separation treatment on the reaction system to obtain methanol.

[0009] In the present application, letting the heated deoxidized syngas enter from the first tube side of the first shell-and-tube reactor and react under the catalytic action of the first catalyst arranged in the first tube side to obtain a reaction system includes:

[0010] Heat the deoxidized syngas to obtain the first-stage inlet gas to the tower;

[0011] Let the first-stage inlet gas to the tower enter from the second tube side of the second shell-and-tube reactor, and react under the catalytic action of the second catalyst arranged in the second tube side to obtain the first-stage reaction gas;

[0012] Cool the first-stage reaction gas to obtain the second-stage inlet gas to the tower;

[0013] Let the secondary gas entering the tower enter from the first tube pass and react with the first catalyst provided in the first tube pass to obtain a reaction system.

[0014] In this application, the pressure of the synthesis gas is 4.0 MPaG - 10.0 MPaG.

[0015] In this application, after the synthesis gas is preheated to 130°C - 170°C at the lower part of the first shell pass, it enters the catalyst bed at the upper part of the first shell pass.

[0016] In this application, the temperature of the deoxygenated synthesis gas is 150°C - 200°C.

[0017] In this application, the temperature of the primary gas entering the tower is 220°C - 240°C; and / or,

[0018] The temperature of the primary reaction gas is 240°C - 280°C; and / or,

[0019] The temperature of the secondary gas entering the tower is 210°C - 230°C; and / or,

[0020] The temperature of the reaction system is 220°C - 240°C.

[0021] In a second aspect, this application provides a device for preparing methanol by hydrogenating carbon dioxide, which is used to implement the preparation method of the first aspect. The device includes a first shell-and-tube reactor and a cooling and separation system;

[0022] The first shell-and-tube reactor includes a first shell pass and a first tube pass. The inlet of the first shell pass is used to input synthesis gas into the first shell pass. A catalyst bed is provided between the inlet and the outlet in the first shell pass. The outlet of the first shell pass is communicated with the inlet of the first tube pass, and the outlet of the first tube pass is communicated with the inlet of the cooling and separation system.

[0023] In this application, the device further includes a second shell-and-tube reactor;

[0024] The second shell-and-tube reactor includes a second tube pass and a second shell pass. The inlet of the second tube pass is communicated with the outlet of the first shell pass through a first gas pipeline entering the tower. The outlet of the second tube pass is communicated with the inlet of the first tube pass through a second gas pipeline entering the tower. The inlet of the second shell pass is used to input saturated boiler water, and the outlet of the second shell pass is used to output saturated steam.

[0025] In this application, the device further includes a heat exchanger;

[0026] The cold end of the heat exchanger is connected in series on the first gas pipeline entering the tower, and the hot end of the heat exchanger is connected in series on the second gas pipeline entering the tower.

[0027] In this application, the cooling and separation system includes an air cooler, a water cooler, and a methanol separator;

[0028] The inlet of the air cooler is connected to the outlet of the first tube pass, the outlet of the air cooler is connected to the inlet of the water cooler, the outlet of the water cooler is connected to the inlet of the methanol separator, the gas-phase outlet of the methanol separator is connected to the inlet of the first shell pass, and the liquid-phase outlet of the methanol separator is used to output methanol.

[0029] The method and device for preparing methanol by hydrogenating carbon dioxide provided by this application enable syngas to enter from the first shell pass of the first shell-and-tube reactor. After being deoxidized by the catalyst bed arranged in the first shell pass, deoxidized syngas is obtained. The syngas includes carbon dioxide, hydrogen, and oxygen. The deoxidized syngas enters from the first tube pass of the first shell-and-tube reactor and reacts under the catalytic action of the first catalyst arranged in the first tube pass to obtain a reaction system. The reaction system is subjected to temperature reduction and separation treatment to obtain methanol. By enabling the syngas to enter from the first shell pass, on the one hand, the heat in the first tube pass can be taken away, which is beneficial to the catalytic reaction in the first tube pass and improves the methanol preparation efficiency; on the other hand, the syngas can be preheated to make the syngas reach the temperature for the deoxidation reaction and improve the deoxidation reaction efficiency; on the third hand, the deoxidized syngas obtained from the deoxidation reaction can continue to remove the heat released by the reaction in the first tube pass. It improves the methanol preparation efficiency and reduces equipment investment and energy consumption. Brief Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention or related technologies. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0031] Figure 1 It is a schematic diagram of the methanol preparation device in the embodiment of the present invention.

[0032] Explanation of the Reference Numerals in the Drawings:

[0033] 101 - Feed gas

[0034] 102 - Compressed feed gas

[0035] 103 - Compressed recycle gas

[0036] 104 - Syngas

[0037] 105 - Deoxidized syngas

[0038] 106 - Primary inlet gas to the tower

[0039] 107 - Primary reaction gas

[0040] 108 - Secondary inlet gas to the tower

[0041] 109 - Secondary reaction gas;

[0042] 110 - Gas-liquid two-phase flow;

[0043] 111 - Purge gas;

[0044] 112 - Recycle gas;

[0045] 113 - Crude methanol;

[0046] 114 - Saturated boiler water;

[0047] 115 - Saturated steam;

[0048] 201 - Feed gas compressor;

[0049] 202 - Recycle gas compressor;

[0050] 203 - First shell-and-tube reactor;

[0051] 204 - Heat exchanger;

[0052] 205 - Second shell-and-tube reactor;

[0053] 206 - Air cooler;

[0054] 207 - Water cooler;

[0055] 208 - Methanol separator. Detailed implementation mode

[0056] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0057] In the first aspect of the present invention, a method for preparing methanol by hydrogenating carbon dioxide is provided, including the following steps:

[0058] Let the syngas enter from the first shell side of the first shell-and-tube reactor, and after being deoxidized by the catalyst bed arranged in the first shell side, the deoxidized syngas is obtained. The syngas includes carbon dioxide, hydrogen and oxygen;

[0059] Let the heated deoxidized syngas enter from the first tube side of the first shell-and-tube reactor, and react under the catalytic action of the first catalyst arranged in the first tube side to obtain a reaction system;

[0060] Perform temperature reduction and separation treatment on the reaction system to obtain methanol.

[0061] In the present invention, the syngas may include the raw material gas that has been compressed. The composition of the raw material gas can be flexibly adjusted to meet different process requirements. Usually, the raw material gas may include carbon dioxide and hydrogen mixed in a certain proportion.

[0062] By adjusting the ratio of carbon dioxide to hydrogen, the properties of the syngas can be optimized to meet the requirements of specific chemical reactions or industrial applications.

[0063] In addition, the pressure range of the syngas can be adjusted between 4.0 MPaG and 10.0 MPaG. The selection of this pressure range can ensure that the syngas has sufficient driving force during subsequent chemical reaction processes. At the same time, the reaction rate and selectivity can also be affected by pressure control, thereby improving the overall process efficiency and the quality of the product. Through the method of the present invention, the efficient preparation of syngas can be achieved, and high-quality raw gas can be provided for downstream chemical production.

[0064] In the process of preparing methanol by hydrogenation of carbon dioxide, the composition of the syngas not only includes the initial compressed raw material gas, but may further include compressed recycle gas. The recycle gas refers to the gas recovered after temperature reduction and separation treatment in the reaction system. This gas usually contains unreacted raw material gas and by-product gas generated during the reaction process. By reintroducing the recycle gas into the reaction system, the utilization rate of resources can be effectively improved, the consumption of raw materials can be reduced, and the production cost can be lowered.

[0065] The reuse of the recycle gas can also help maintain the stability and efficiency of the reaction system. By appropriately treating the recycle gas, such as removing unnecessary by-products or adjusting its composition ratio, the reaction conditions can be optimized, and the methanol yield can be further increased. In addition, the compression treatment of the recycle gas can ensure that it has appropriate pressure and flow rate when re-entering the reaction system, so as to be fully mixed with the fresh raw material gas and promote the reaction.

[0066] This strategy of recycling not only helps to improve the economy and sustainability of the production process, but also can reduce the impact on the environment, meeting the requirements of modern industry for green production. Through reasonable recycle gas management, the present invention provides a more efficient and environmentally friendly method for methanol production.

[0067] The first shell-and-tube reactor may refer to a device specifically used for gas-cooled reactions, and its design and structure make it suitable for handling chemical reactions that require effective heat management. The basic structure of the shell-and-tube reactor includes a bundle of tubes, called the tube side, and an outer shell surrounding it, called the shell side.

[0068] This design allows the reactants to flow through the tube side while the cooling medium flows through the shell side, thus achieving efficient heat exchange. During the gas-cooled reaction process, the reactants usually release a large amount of heat, so an effective cooling mechanism is required to maintain the stability and safety of the reaction.

[0069] Through its unique structure, the shell-and-tube reactor can carry out reactions inside the tube side while quickly removing the heat generated by the reaction through the cooling medium in the shell side. This heat management not only helps control the reaction temperature and prevent overheating, but also improves the reaction selectivity and product recovery rate.

[0070] In addition, the modular design of the shell-and-tube reactor makes it easy to maintain and expand, and it can be adjusted according to different process requirements. For example, the processing capacity of the reactor can be adjusted by changing the number or diameter of the tubes, or the heat exchange efficiency can be optimized by selecting different cooling media. This flexibility makes the shell-and-tube reactor widely used in chemical production, especially in high-temperature or exothermic reactions that require precise temperature control.

[0071] By adopting the first shell-and-tube reactor, the present invention can achieve an efficient gas-cooled reaction process, ensure the safety and stability of the reaction, and at the same time improve production efficiency and product quality.

[0072] The catalyst bed layer can refer to a fixed area or layer composed of deoxygenation catalyst particles or other forms of deoxygenation catalyst materials for removing oxygen in the syngas.

[0073] The first catalyst can refer to a gas-cooled synthesis catalyst used for methanol synthesis reaction with the heated deoxygenated syngas, such as a low-temperature synthesis catalyst.

[0074] In the design of the first shell-and-tube reactor, the first catalyst is configured in the first tube side to promote the methanol synthesis reaction. When the heated deoxygenated syngas contacts the first catalyst, the methanol synthesis reaction occurs and releases a large amount of heat. This heat is not only a by-product of the reaction process, but also cleverly used to improve the energy efficiency of the whole system. When the new syngas enters the first shell side, it will be preheated by the heat released from the first tube side. In this way, the syngas reaches the appropriate temperature before entering the reaction stage, thus improving the reaction efficiency and rate.

[0075] The preheated synthesis gas is deoxidized under the action of a deoxygenation catalyst to remove oxygen therein and form deoxygenated synthesis gas. This step is crucial to improving the selectivity and product purity of the methanol synthesis reaction, because the presence of oxygen may lead to side reactions. The deoxygenated synthesis gas can be called deoxygenated synthesis gas. In order to meet the reaction temperature requirements of the first catalyst, the deoxygenated synthesis gas needs to be heated, and then the heated deoxygenated synthesis gas is introduced into the first tube pass, and is contacted with the first catalyst again to perform a methanol synthesis reaction to form a reaction system. At this time, the chemical reaction in the reaction system continues to further generate methanol.

[0076] After the reaction is completed, the reaction system needs to be cooled and separated to extract the methanol product. The cooling process can be achieved by a heat exchanger or other cooling equipment to ensure that the reaction products are separated at a suitable temperature, thereby improving the recovery rate and purity of methanol. Through the above process, the present invention not only achieves efficient synthesis of methanol, but also makes full use of the heat generated during the reaction, optimizes energy use, and reduces production costs.

[0077] In some embodiments, the synthesis gas can be preheated to 130°C-170°C in the lower part of the first shell side before entering the catalyst bed in the upper part of the first shell side. The temperature of the deoxygenated synthesis gas obtained after the deoxygenation reaction can be 150°C-200°C.

[0078] According to the technical solution provided by the present invention, the above-mentioned method for preparing methanol by hydrogenating carbon dioxide is adopted, and the synthesis gas enters from the first shell side. On the one hand, the heat in the first tube side can be taken away, which is beneficial to the catalytic reaction in the first tube side and improves the preparation efficiency of methanol; on the other hand, the synthesis gas can be preheated to make the synthesis gas reach the temperature of the deoxygenation reaction and improve the efficiency of the deoxygenation reaction; on the third hand, the deoxygenated synthesis gas obtained by the deoxygenation reaction can continue to remove the heat released by the reaction in the first tube side. The efficiency of preparing methanol by hydrogenating carbon dioxide is improved, and equipment investment and energy consumption are reduced.

[0079] In some embodiments, the deoxygenated synthesis gas is introduced into the first tube side of the first shell-and-tube reactor, and reacted under the catalytic action of the first catalyst disposed in the first tube side to obtain the reaction system, which may include:

[0080] The deoxygenated synthesis gas is heated to obtain a first-stage tower inlet gas;

[0081] The first-stage inlet gas enters the second tube side of the second shell-and-tube reactor and reacts under the catalytic action of the second catalyst disposed in the second tube side to obtain the first-stage reaction gas;

[0082] The first-stage reaction gas is cooled to obtain the second-stage tower inlet gas;

[0083] Let the secondary incoming tower gas enter from the first tube pass and react under the catalysis of the first catalyst provided in the first tube pass to obtain a reaction system.

[0084] In the present invention, in order to further improve the efficiency of methanol production by hydrogenation of carbon dioxide and make the reaction of deoxygenated syngas more complete, a second shell-and-tube reactor can be added to carry out the first methanol synthesis reaction on the deoxygenated syngas, and then the secondary methanol synthesis reaction is carried out through the first tube pass.

[0085] The second shell-and-tube reactor can refer to a shell-and-tube reactor used for water-cooled reaction, and a second catalyst is provided in the second tube pass of the second shell-and-tube reactor.

[0086] The second catalyst can refer to a water-cooled synthesis catalyst used for methanol synthesis reaction with deoxygenated syngas, such as a high-temperature synthesis catalyst.

[0087] Specifically, since the reaction temperature required by the second catalyst is higher, in order to make the deoxygenated syngas reach the catalytic reaction temperature, the deoxygenated syngas is first heated to obtain the primary incoming tower gas, and then the primary incoming tower gas enters from the second tube pass of the second shell-and-tube reactor and reacts with the second catalyst to obtain the primary reaction gas. Since more heat is released in the water-cooled synthesis reaction, the primary reaction gas needs to be cooled to obtain the secondary incoming tower gas, and then the secondary incoming tower gas enters from the first tube pass and reacts with the first catalyst in an air-cooled synthesis reaction to obtain a reaction system.

[0088] Under the action of the water-cooled synthesis catalyst, carbon dioxide and hydrogen react to form by-products such as methanol and dimethyl ether. The first catalyst can also include a by-product conversion catalyst for reacting with the by-products in the primary reaction gas to further convert the by-products into methanol.

[0089] In the above process, under the action of the water-cooled synthesis catalyst in the second shell-and-tube reactor, carbon dioxide and hydrogen react to form by-products such as methanol and dimethyl ether. Under the action of the air-cooled synthesis catalyst in the first shell-and-tube reactor, carbon dioxide and hydrogen continue to react to form methanol. At the same time, by-products such as dimethyl ether are further converted into methanol, improving the conversion rate of syngas and the selectivity of methanol.

[0090] In some embodiments, in order to reduce energy consumption, heat exchange treatment can also be carried out on the deoxygenated syngas and the primary reaction gas, for example, a heat exchanger is incorporated into the pipelines of the deoxygenated syngas and the primary reaction gas to achieve heat transfer.

[0091] In some embodiments, in order to improve the reaction efficiency of the second shell-and-tube reactor, the temperature of the primary inlet gas to the tower can be 220°C - 240°C, and the temperature of the primary reaction gas output can be 240°C - 280°C. If the temperature of the primary inlet gas to the tower is lower than 220°C, the reaction rate is slower, reducing the production efficiency; if the temperature of the primary inlet gas to the tower is higher than 240°C, the lifespan of the second catalyst will be reduced, and more by-products, such as methane, will be produced.

[0092] In some embodiments, in order to improve the reaction efficiency of the first shell-and-tube reactor, the temperature of the secondary inlet gas to the tower can be 210°C - 230°C, and the reaction system temperature can be 220°C - 240°C.

[0093] In a second aspect of the present invention, there is provided a device for hydrogenating carbon dioxide to produce methanol for implementing the method of the first aspect. The device includes a first shell-and-tube reactor and a cooling and separation system;

[0094] The first shell-and-tube reactor includes a first shell side and a first tube side. The inlet of the first shell side is used to input synthesis gas into the first shell side. A catalyst bed is provided between the inlet and the outlet in the first shell side. The outlet of the first shell side is communicated with the inlet of the first tube side, and the outlet of the first tube side is communicated with the inlet of the cooling and separation system.

[0095] Among them, the inlet of the first shell side can be located at the lower end of the first shell side for inputting synthesis gas into the first shell side. The catalyst bed can be located on the upper side of the first shell side, and the outlet of the first shell side can be located at the upper end of the catalyst bed, enabling the synthesis gas to react with the deoxidation catalyst after being fully preheated at the lower end of the first shell side and then output from the outlet of the first shell side.

[0096] The inlet of the first tube side can be located at the upper end of the first tube side, and the outlet of the second tube side can be located at the lower end of the second tube side.

[0097] In some embodiments, a heating device is provided in the pipeline between the outlet of the first shell side and the inlet of the first tube side for heating the gas in the pipeline. The heating device can be the heating part of a heat exchanger.

[0098] In some embodiments, the device can further include a second shell-and-tube reactor; the second shell-and-tube reactor includes a second tube side and a second shell side. The inlet of the second tube side is communicated with the outlet of the first shell side through a first inlet gas pipeline to the tower, the outlet of the second tube side is communicated with the inlet of the first tube side through a second inlet gas pipeline to the tower, the inlet of the second shell side is used to input saturated boiler water, and the outlet of the second shell side is used to output saturated steam.

[0099] Among them, the inlet of the second tube pass can be located at the upper end of the second tube pass, and the outlet of the second tube pass can be located at the lower end of the second tube pass. The inlet of the second shell pass can be located at the lower end of the second shell pass, and the outlet of the second shell pass can be located at the upper end of the second shell pass. The saturated boiler water is input from the inlet of the second shell pass, and the saturated steam is output from the outlet of the second shell pass, which is convenient for better cooling the second tube pass.

[0100] The pressure of the saturated boiler water and the saturated steam can be 2 MPaG - 3.5 MPaG.

[0101] In some embodiments, the device may further include a heat exchanger; the cold end of the heat exchanger is connected in series on the first inlet gas pipeline, and the hot end of the heat exchanger is connected in series on the second inlet gas pipeline.

[0102] A heat exchanger may refer to a device used to transfer heat between two or more fluids without the need for these fluids to come into direct contact. A heat exchanger may include:

[0103] A shell-and-tube heat exchanger: It consists of a group of tubes encapsulated in a shell. One fluid flows inside the tubes, and the other fluid flows inside the shell.

[0104] A plate heat exchanger: It consists of a series of metal plates with flow channels formed between the plates, and the fluids flow in these flow channels.

[0105] A finned-tube heat exchanger: Fins are added outside the tubes to increase the surface area and improve the heat transfer efficiency.

[0106] A plate-fin heat exchanger: It consists of alternately arranged flat plates and fins, and has high heat transfer capacity.

[0107] In some embodiments, the cooling and separation system may include an air cooler, a water cooler, and a methanol separator; the inlet of the air cooler is connected to the outlet of the first tube pass, the outlet of the air cooler is connected to the inlet of the water cooler, the outlet of the water cooler is connected to the inlet of the methanol separator, the gas-phase outlet of the methanol separator is connected to the inlet of the first shell pass, and the liquid-phase outlet of the methanol separator is used to output methanol.

[0108] Specifically, an air cooler may refer to an air-cooling device that uses air as the cooling medium and cools the process fluid by forcing air to flow. It usually consists of a group of finned tubes, and air flows through the finned tubes by a fan or natural convection to take away heat.

[0109] A water cooler may refer to a device that takes away the heat in the process fluid through the flow of water. It is usually a shell-and-tube heat exchanger, and water flows inside the tubes or inside the shell to exchange heat with another fluid.

[0110] A methanol separator may refer to a device used to separate methanol from a mixture, such as a distillation column, a rectification column, or other separation devices.

[0111] The temperature of the gas-liquid two-phase flow obtained after cooling by the air cooler and the water cooler can be 35 - 45 °C.

[0112] The operating pressure of the methanol separator can be 4.0 MPaG - 10.0 MPaG.

[0113] In some embodiments, the above device may further include a recycle gas compressor and a feed gas compressor. The gas phase outlet of the methanol separator can be connected to the air to output purge gas, and can also be connected to the inlet of the recycle gas compressor to output recycle gas. The recycle gas is compressed by the recycle gas compressor and then mixed with the compressed feed gas to obtain synthesis gas. The feed gas compressor is used to compress the feed gas into compressed feed gas.

[0114] The process flow of hydrogenating carbon dioxide to produce methanol will be further described below in conjunction with the above device.

[0115] Figure 1 This is the process flow diagram of hydrogenating carbon dioxide to produce methanol in the embodiment of the present invention. As Figure 1 shown, the process flow is as follows:

[0116] The feed gas 101 obtained by mixing carbon dioxide and hydrogen in a certain proportion is pressurized by the feed gas compressor 201 to obtain compressed feed gas 102. The compressed feed gas 102 is mixed with the compressed recycle gas 103 pressurized by the recycle gas compressor 202 to obtain synthesis gas 104.

[0117] The synthesis gas 104 enters the first shell side of the first shell-and-tube reactor 203. After being preheated by the first tube side at the lower part of the first shell side, it passes through the catalyst bed, and oxygen is removed under the action of the deoxidation catalyst to obtain deoxidized synthesis gas 105.

[0118] The deoxidized synthesis gas 105 enters the heat exchanger 204 for further preheating to obtain the first-stage inlet gas 106.

[0119] The first-stage inlet gas 106 enters the second tube side of the second shell-and-tube reactor 205. Under the action of the water-cooled synthesis catalyst, carbon dioxide and hydrogen react to generate methanol and by-products such as dimethyl ether and release heat, and the first-stage reaction gas 107 is output from the outlet of the second tube side. At the same time, saturated boiler water 114 enters from the inlet of the second shell side, cools the second tube side, and the generated saturated steam 115 is output from the outlet of the second shell side.

[0120] The first-stage reaction gas 107 is cooled by the heat exchanger 204 to obtain the second-stage inlet gas 108.

[0121] The secondary inlet gas 108 enters the first tube pass of the first shell-and-tube reactor 203. Under the action of the gas-cooled synthesis catalyst, carbon dioxide and hydrogen continue to react to produce methanol. At the same time, by-products such as dimethyl ether are further converted into methanol, and the secondary reaction gas 109 is output from the outlet of the first tube pass.

[0122] The secondary reaction gas 109 is cooled by an air cooler 206 and a water cooler 207 in sequence to obtain a gas-liquid two-phase flow 110.

[0123] The gas-liquid two-phase flow 110 enters a methanol separator 208 for gas-liquid separation. A part of the separated gas phase is purged as the purge gas 111, and the other part is used as the recycle gas 112.

[0124] The recycle gas 112 enters a recycle gas compressor 202 to obtain compressed recycle gas. The compressed recycle gas is mixed with the compressed feed gas 102 to obtain synthesis gas 104. The separated liquid-phase crude methanol 113 is sent to downstream processes for treatment.

Claims

1. A method for preparing methanol by hydrogenating carbon dioxide, characterized in that: The following steps are involved: The synthesis gas is introduced into the first shell side of the first shell-and-tube reactor, and is subjected to deoxygenation treatment in the catalyst bed disposed in the first shell side to obtain deoxygenated synthesis gas, wherein the synthesis gas includes carbon dioxide, hydrogen and oxygen; The heated deoxygenated synthesis gas enters the first tube side of the first shell-and-tube reactor and reacts under the catalytic action of the first catalyst disposed in the first tube side to obtain a reaction system; The reaction system is subjected to a cooling and separation treatment to obtain methanol.

2. The method according to claim 1, characterized in that The heated deoxygenated synthesis gas is allowed to enter the first tube side of the first shell-and-tube reactor and react under the catalytic action of the first catalyst disposed in the first tube side to obtain a reaction system, comprising: Heating the deoxygenated synthesis gas to obtain a first-stage tower inlet gas; The first-stage inlet gas enters the second tube side of the second shell-and-tube reactor and reacts with the second catalyst disposed in the second tube side to obtain the first-stage reaction gas; Cooling the primary reaction gas to obtain secondary tower inlet gas; The secondary inlet gas is allowed to enter from the first tube pass and react with the first catalyst disposed in the first tube pass to obtain a reaction system.

3. The method according to any one of claims 1-2, characterized in that: The pressure of the synthesis gas is 4.0 MPaG-10.0 MPaG.

4. The method according to any one of claims 1-2, characterized in that: The synthesis gas is preheated to 130° C.-170° C. in the lower part of the first shell side and then enters the catalyst bed in the upper part of the first shell side.

5. The method according to any one of claims 1-2, characterized in that: The temperature of the deoxygenated synthesis gas is 150°C-200°C.

6. The method according to claim 2, characterized in that The temperature of the first-stage inlet gas is 220°C-240°C; and / or, The primary reaction gas temperature is 240°C-280°C; and / or, The secondary inlet gas temperature is 210°C-230°C; and / or, The temperature of the reaction system is 220°C-240°C.

7. A device for preparing methanol by hydrogenating carbon dioxide, characterized in that: Used to implement the preparation method according to any one of claims 1 to 6, the device comprises a first shell and tube reactor and a cooling separation system; The first shell and tube reactor includes a first shell side and a first tube side, the inlet of the first shell side is used to input synthesis gas into the first shell side, a catalyst bed is provided between the inlet and the outlet in the first shell side, the outlet of the first shell side is connected to the inlet of the first tube side, and the outlet of the first tube side is connected to the inlet of the cooling separation system.

8. The device according to claim 7, characterized in that The apparatus also includes a second shell and tube reactor; The second shell and tube reactor includes a second tube side and a second shell side, the inlet of the second tube side is connected with the outlet of the first shell side through a first tower gas inlet pipeline, the outlet of the second tube side is connected with the inlet of the first tube side through a second tower gas inlet pipeline, the inlet of the second shell side is used to input saturated boiler water, and the outlet of the second shell side is used to output saturated steam.

9. The device according to claim 8, characterized in that The device also includes a heat exchanger; The cold end of the heat exchanger is connected in series to the first tower inlet gas pipeline, and the hot end of the heat exchanger is connected in series to the second tower inlet gas pipeline.

10. The device according to any one of claims 7 to 9, characterized in that: The cooling and separation system includes an air cooler, a water cooler and a methanol separator; The inlet of the air cooler is connected to the outlet of the first tube side, the outlet of the air cooler is connected to the inlet of the water cooler, the outlet of the water cooler is connected to the inlet of the methanol separator, the gas phase outlet of the methanol separator is connected to the inlet of the first shell side, and the liquid phase outlet of the methanol separator is used to output methanol.

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