Two-channel isothermal coupling adiabatic CO2 hydrogenation methanol preparation system and process

Abstract

The invention provides a dual-channel isothermal coupling adiabatic CO2 hydrogenation methanol preparation system and process, and belongs to the technical field of methanol preparation. The system comprises a methanol synthesis reactor, a steam superheater, a water cooler and a gas-liquid separation tank, wherein the methanol synthesis reactor is a dual-channel isothermal coupling adiabatic reactor. The process comprises the following steps: preheating a raw material gas compressed to a system pressure, heating to a catalyst activation temperature by using reaction heat, then carrying out a methanol synthesis reaction, carrying out gas-liquid separation on the obtained methanol synthesis gas after heat exchange, and compressing the obtained gas phase to the system pressure for recycling, and performing methanol rectification on the obtained liquid phase to obtain the product methanol. The invention provides the system and the process for preparing methanol through CO2 hydrogenation, which can flexibly cope with the working conditions of driving, load change and the like, and are convenient to operate and low in investment cost.

Description

Technical Field

[0001] This invention relates to the field of methanol preparation technology, specifically to a dual-channel isothermal coupled adiabatic CO2 hydrogenation system and process for producing methanol. Background Technology

[0002] The resource utilization of carbon dioxide has become a research hotspot. Methanol is a basic organic chemical raw material with a simple structure and wide range of applications. The preparation of methanol using carbon dioxide hydrogenation is relatively easy to implement from a reaction principle perspective, and it is of great significance to green and sustainable development.

[0003] The main problems with the current CO2 hydrogenation to methanol process are as follows: (1) It involves a lot of equipment, long routes, and large investments. It requires a feed gas heater, and the heat exchanger tube sheet has a large temperature difference, which makes it prone to leakage. The methanol synthesis reactor outlet is equipped with multiple coolers, making the process complex. (2) It has high energy consumption and poor economic efficiency. The biggest factor restricting the application of the CO2 hydrogenation to methanol process is the economic efficiency of the equipment. In conventional processes, an additional heat source is required to heat the feed gas to the activation temperature, which increases the cost of equipment and pipelines, resulting in high energy consumption and poor economic efficiency. (3) The methanol synthesis unit can only produce saturated steam as a byproduct, which has low utilization value and cannot be transported over long distances.

[0004] Traditional mainstream methanol synthesis reactors are broadly classified into axial and radial reactors. Axial reactors have a simple structure, are easy to operate, can utilize the heat of reaction to meet the required reaction temperature, and produce high-pressure steam with a small temperature difference in the catalyst bed. However, the catalyst in an axial reactor is packed in the tube side, which not only makes maintenance inconvenient but also results in a low volumetric efficiency, leading to a larger equipment size and higher manufacturing cost for the same production capacity. While radial reactors have a large catalyst loading and low radial flow resistance, they suffer from a large temperature difference in the catalyst bed, resulting in uneven gas distribution as it flows through the catalyst bed and affecting catalyst contact efficiency.

[0005] CN115259997A discloses a self-heating carbon dioxide hydrogenation process for methanol synthesis. This process utilizes heat generated by the catalyst bed, allowing the mixed feed gas to enter the reactor only after preheating to 140–180°C in a preheater, eliminating the need for continuous preheating to the activation temperature of the methanol synthesis catalyst. Compared to traditional methanol synthesis processes, this significantly reduces the heat load on the preheater, requires a smaller heat exchange area, and results in lower equipment investment. The synthesis gas from the self-heating reactor first undergoes high-grade heat recovery via a waste heat boiler before entering the preheater to preheat the mixed feed gas, improving the heat recovery level and overall system efficiency. While this process is energy-efficient, it still requires a feed gas preheater, making the process complex and requiring significant equipment investment. Summary of the Invention

[0006] In the syngas-to-methanol process, the reactor outlet gas needs to be transported to the feed heater to preheat the inlet gas to the catalyst activation temperature. After passing through the feed heater, the calorific value of the reactor outlet gas decreases, making it unsuitable for effective recovery of by-product steam, resulting in low thermal efficiency. Furthermore, traditional methanol synthesis processes often employ tubular water-cooled isothermal reactors. The catalyst is packed in a tubular fixed bed, with the heat of reaction removed by boiler water in the shell side, producing high-pressure saturated steam. The reaction temperature is controlled by the pressure of the boiling water in the shell side. In this type of reactor, the temperature of different catalyst beds is essentially the same, and the produced saturated steam is prone to condensation due to temperature drop during pipeline transportation. Moreover, temperature control via boiling water pressure is indirect, resulting in control lag and easily leading to reactor temperature collapse and overheating.

[0007] The technical problem to be solved by the present invention is to provide a simplified CO2 hydrogenation methanol production system and process that can flexibly cope with operating conditions such as start-up and load changes, make full use of reaction waste heat, is easy to operate, and has low investment cost, in light of the current state of the prior art.

[0008] According to one aspect of the present invention, a dual-channel isothermal coupled adiabatic CO2 hydrogenation to methanol system is provided, comprising a methanol synthesis reactor, a steam superheater, a water cooler, and a gas-liquid separator.

[0009] The methanol synthesis reactor is a dual-channel isothermal coupled adiabatic reactor.

[0010] The dual-channel isothermal coupled adiabatic reactor includes a cylindrical body. The top of the cylindrical body has a main syngas inlet, a syngas preheating outlet, and a high-pressure saturated steam outlet, while the bottom has a methanol syngas outlet. The cylindrical body is divided into an isothermal section and an adiabatic section from top to bottom. A syngas-side inlet is located between the isothermal section and the adiabatic section. A high-pressure boiler water inlet and a syngas preheating inlet are located on the cylindrical body of the isothermal section near the syngas-side inlet. The high-pressure boiler water inlet connects to the high-pressure saturated steam outlet after passing through the isothermal section. The syngas preheating inlet connects to the syngas preheating outlet after passing through the isothermal section.

[0011] The methanol synthesis gas outlet at the bottom of the methanol synthesis reactor passes sequentially through the steam superheater and the water cooler, and then connects to the side inlet of the gas-liquid separator.

[0012] Optionally, the isothermal section is provided with a catalyst cylinder I, which is sleeved inside the cylinder and forms a gap I with the inner wall of the cylinder. The gap I forms a gas channel I that connects to the main inlet of the synthesis gas. Multiple external air inlet annular gaps I are provided on the side wall of the catalyst cylinder I.

[0013] The catalyst cylinder I is fitted with a central tube I, the upper end of the central tube I is closed, and the lower end is connected to the insulation section; multiple internal air inlet annular gaps I are provided on the side wall of the central tube I;

[0014] The reaction zone I is located between the catalyst cylinder I and the central tube I.

[0015] Optionally, the syngas preheating outlet is connected to the gap I, that is, the syngas preheating outlet is located inside the reactor, and the preheated syngas does not exit the reactor through the syngas preheating outlet, but directly enters the gap I.

[0016] Optionally, the isothermal section is provided with a catalyst cylinder II, which is sleeved inside the cylinder and forms a gap II with the inner wall of the cylinder. The gap II forms a gas channel II that connects to the adiabatic section. Multiple inner air inlet annular gaps II are provided on the side wall of the catalyst cylinder II.

[0017] The catalyst cylinder II is fitted with a central tube II, the upper end of which is connected to the main inlet of the synthesis gas, and the lower end is closed; multiple external air inlet annular gaps II are provided on the side wall of the central tube II;

[0018] The reaction zone II is located between the catalyst cylinder II and the central tube II.

[0019] Optionally, multiple plate heat exchange modules are independently provided in reaction zone I and reaction zone II, and the plate heat exchange modules are arranged radially with central tube I or central tube II as the center; the inlet of the plate heat exchange module is connected to a refrigerant input pipe, and the outlet of the plate heat exchange module is connected to a refrigerant output pipe.

[0020] Optionally, the plate heat exchange module has multiple protrusions on its side.

[0021] Optionally, the plate heat exchange module includes a high-pressure boiler water channel and a syngas preheating channel; the refrigerant input pipeline includes a high-pressure boiler water riser and a syngas riser; and the refrigerant output pipeline includes a high-pressure saturated steam riser and a preheated syngas riser.

[0022] The high-pressure boiler water riser pipe is connected to the high-pressure saturated steam riser pipe via the high-pressure boiler water channel, and the high-pressure saturated steam riser pipe is connected to the high-pressure saturated steam outlet; the syngas riser pipe is connected to the preheated syngas riser pipe via the syngas preheating channel, and the preheated syngas riser pipe is connected to the syngas preheating outlet.

[0023] Optionally, the inlet of the high-pressure boiler water channel is connected to multiple high-pressure boiler water risers, which converge and connect to a high-pressure boiler water collecting ball, which is connected to the high-pressure boiler water inlet; the outlet of the high-pressure boiler water channel is connected to multiple high-pressure saturated steam risers, which converge to a high-pressure saturated steam collecting ring, which is connected to the high-pressure saturated steam outlet.

[0024] Optionally, the inlet of the syngas preheating channel is connected to multiple syngas risers, which converge and connect to a syngas collection annulus, and the syngas collection annulus is connected to the syngas preheating inlet; the outlet of the syngas preheating channel is connected to multiple preheated syngas risers, which converge to a preheated syngas collection ring, and the preheated syngas collection ring is connected to the syngas preheating outlet.

[0025] Optionally, the system further includes a steam drum for separating the high-pressure saturated steam generated by the methanol synthesis reactor into water and steam; the high-pressure saturated steam outlet is connected to the water inlet of the high-pressure boiler via the steam drum, and the saturated steam outlet of the steam drum is connected to the steam superheater.

[0026] Optionally, the syngas-side inlet is connected to a gas distributor inside the cylinder.

[0027] Optionally, a gas guide plate is provided inside the cylinder of the insulation section near the syngas inlet.

[0028] Optionally, the adiabatic section is provided with an axial reaction catalyst bed.

[0029] Optionally, the adiabatic section is provided with a radial reaction catalyst bed.

[0030] Optionally, the radial reaction catalyst bed is provided with a central tube III, which is coaxially arranged with the central tube I or the central tube II; a plurality of vent holes are provided on the side wall of the central tube III; the upper end of the central tube III is closed, and the lower end is connected to the methanol synthesis gas outlet.

[0031] According to another aspect of the present invention, a dual-channel isothermal coupled adiabatic CO2 hydrogenation to methanol process employing the above-described system is provided, comprising preheating the feed gas compressed to the system pressure, using the heat of reaction to raise the temperature to the catalyst activation temperature, and then carrying out the methanol synthesis reaction.

[0032] The obtained methanol synthesis gas is subjected to gas-liquid separation after heat exchange. The obtained gas phase is compressed to the system pressure and then recycled. The obtained liquid phase is subjected to methanol distillation to obtain the product methanol.

[0033] Optionally, the saturated steam produced by the methanol synthesis reaction is superheated to generate superheated steam.

[0034] Optionally, the superheat of the superheated steam is 1 to 100°C, preferably 50 to 80°C.

[0035] Optionally, the pressure of the saturated steam is 0.5 to 5.0 MPaG, preferably 2 to 4 MPaG.

[0036] Optionally, the CO2 molar content in the feed gas is greater than 50%, preferably greater than 90%.

[0037] Optionally, the temperature of the preheated raw material gas is 150–400°C, preferably 180–350°C; the temperature of the methanol synthesis gas is 200–500°C, preferably 250–400°C.

[0038] Optionally, the gas temperature for gas-liquid separation is 30–200°C, preferably 50–100°C.

[0039] This invention provides a simplified CO2 hydrogenation to methanol process using a novel adiabatic isothermal coupled reactor. In this process, the reactor removes reaction heat through radially arranged plate heat exchange modules. Catalysts are packed between adjacent modules to ensure heat transfer rate while increasing volumetric efficiency. Heat is transferred via boiler water and feed gas in the isothermal section, simplifying the process flow, reducing equipment investment, and improving the plant's economics. A coupled adiabatic section, filled with a high-temperature resistant catalyst, utilizes the reaction exothermics to ensure an outlet temperature above 250°C for superheated saturated steam, solving the problem of difficult pipeline transportation. A syngas bypass inlet between the isothermal and adiabatic sections facilitates reactor temperature control. The bypass syngas mixes with the reaction gas from the isothermal section, is heated to the catalyst activation temperature in the adiabatic section, and then enters the high-temperature resistant catalyst bed for the synthesis reaction via a gas distributor and guide plates. Adjusting the bypass flow rate allows for flexible control of the reaction gas outlet temperature.

[0040] In this invention, the catalysts in the isothermal section and the adiabatic section have different temperature tolerances. The isothermal section can use conventional catalysts with a maximum temperature tolerance of 350°C, while the adiabatic section can use high-temperature resistant catalysts with a maximum temperature tolerance of 500°C.

[0041] Compared with the prior art, the advantages of the present invention are as follows:

[0042] (1) No feed heater is required. The syngas is preheated to the catalyst activation temperature in the isothermal zone directly using the heat of reaction in the reactor. The syngas produced in the isothermal zone is used to heat the bypass syngas, so that the temperature of the mixture reaches the catalyst activation temperature in the adiabatic zone. This makes full use of the waste heat of the process gas, improves the system integration, and reduces equipment investment.

[0043] (2) By setting a syngas bypass inlet, adjusting the syngas main and bypass flow ratio, controlling the amount of fresh gas participating in the reaction in the adiabatic section, thereby controlling the reaction heat release and the reaction gas outlet temperature, and flexibly responding to start-up, load changes and other situations.

[0044] (3) The lower part of the reactor is coupled with an insulation section, which can effectively increase the reactor outlet temperature to above 400°C. By setting a steam superheater at the reactor outlet, high-pressure saturated steam is produced by superheating, which improves the steam quality, facilitates pipeline transportation and subsequent use, and improves the stability of steam utilization.

[0045] (4) By setting up a high-pressure boiler water collection ball and a syngas collection ring gap, the plate heat exchange module is divided into a water-cooled channel and a gas-cooled channel in a limited space, which can effectively remove and utilize the reaction heat to preheat the syngas and produce high-pressure saturated steam.

[0046] (5) The plate heat exchange module is adopted, which increases the contact area and improves the heat exchange efficiency compared with the traditional tube heat exchange, and also greatly increases the catalyst loading.

[0047] (6) The dual-channel reactor uses different phase media (boiler water and synthesis gas) for heat extraction based on the different amounts of catalysts loaded in the outer and inner layers. The temperature gradient distribution is more reasonable, the equipment diameter is smaller than that of conventional tubular methanol synthesis reactors, and the energy utilization rate is higher. Attached Figure Description

[0048] Figure 1 This is a flow chart of a dual-channel isothermal coupled adiabatic CO2 hydrogenation to methanol process described in Embodiment 1 of the present invention.

[0049] Figure 2 This is a schematic diagram of the external cylindrical structure of the methanol synthesis reactor of the present invention;

[0050] Figure 3 This is a schematic diagram of the internal structure of the methanol synthesis reactor of the present invention;

[0051] Figure 4 This is another schematic diagram of the internal structure of the methanol synthesis reactor of the present invention.

[0052] Figure 5 This is a schematic diagram (collection ring) of a plate heat exchange module with dual-channel heat exchange according to the present invention;

[0053] Figure 6 This is a schematic diagram (collecting ball) of a plate heat exchange module including dual-channel heat exchange according to the present invention;

[0054] Wherein, a-syngas compressor, b-methanol synthesis reactor, c-steam drum; d-steam superheater; e-demineralized water heat exchanger, f-water cooler; g-gas-liquid separator; h-recirculating gas compressor;

[0055] 1-Shell body; 2-High-pressure boiler water inlet; 3-High-pressure saturated steam outlet; 4-Synthetic gas preheating outlet; 5-Synthetic gas main inlet; 6-Synthetic gas preheating inlet; 7-Main maintenance port; 8-Catalyst top discharge port; 9-Synthetic gas side inlet; 10-Catalyst bottom discharge port; 11-Reactant gas outlet; 12-High-pressure saturated steam collection ring; 13-Preheated synthetic gas collection ring; 14-Preheated synthetic gas riser pipe; 15-Heat transfer module; 16-Center pipe I / II; 17-High-pressure boiler water riser pipe; 18-High-pressure boiler 19-Water collecting ball; 20-Synthesis gas riser pipe; 21-Synthesis gas collecting annular gap; 22-Isothermal section inspection port; 23-Gas guide plate; 24-High temperature resistant catalyst; 25-Insulation section inspection port; 26-Collector ball inspection port; 27-Gas distributor; 28-Pressure grid; 29-High pressure saturated steam riser pipe; 30-Catalyst cylinder; 31-Expansion joint; 32-High pressure boiler water channel; 33-Synthesis gas preheating channel; 34-High pressure boiler water collecting ring; 35-Synthesis gas collecting ball; 36-Central tube III. Detailed Implementation

[0056] The present invention will be further described below with reference to specific embodiments, but this does not constitute any limitation on the present invention.

[0057] Example 1

[0058] like Figure 1 As shown, the raw materials carbon dioxide and hydrogen are compressed to the system pressure by the syngas compressor a, and then proceed to the gas cooling channel (syngas preheating channel) in the methanol synthesis reactor b. There, the heat of reaction is used to raise the temperature to the catalyst activation temperature, and the gas then re-enters the methanol synthesis reactor b for further reaction. The outlet reaction gas passes through the steam superheater d (superheated saturated steam), then through the demineralized water heat exchanger e for heat utilization, and finally through the water cooler f (cooled) before entering the gas-liquid separator g. The gas phase is compressed to the system pressure by the circulating gas compressor h from the top and then sent to the reactor inlet for recycling. The liquid phase proceeds from the bottom to the methanol distillation unit to produce methanol with a purity of over 99.89%.

[0059] In this embodiment, the raw materials carbon dioxide and hydrogen are compressed to a system pressure of 8 MPa by a syngas compressor and then preheated to the catalyst activation temperature of 210–220°C in the isothermal zone of the methanol synthesis reactor before re-entering for reaction. The reactor is divided into an upper isothermal zone and a lower adiabatic zone. The upper isothermal zone forms a water-steam mixture with boiler water in the steam drum, which travels to the top of the reactor to produce high-pressure saturated steam. The lower adiabatic zone ensures that the reactor outlet temperature is above 250°C. The reacted materials pass through a steam superheater and a demineralized water heat exchanger for heat utilization, then enter a water cooler to cool to 50°C, and subsequently enter a gas-liquid separator. Unreacted syngas flows from the top, is compressed to a system pressure of 8 MPa by a circulating gas compressor, and then recirculated to the reactor inlet. The crude methanol obtained from the reaction proceeds from the bottom of the gas-liquid separator to the methanol distillation system to obtain 99.89% purified methanol.

[0060] like Figure 2 , Figure 3 As shown, the methanol synthesis reactor used in this embodiment has a vertical cylindrical shape, divided into upper and lower sections. The catalyst cylinder is housed within the upper section, forming a gap between it and the cylinder. This gap connects to the main synthesis gas inlet, forming a synthesis gas inlet channel. A central tube I is located at the center of the catalyst cylinder. The upper end of the central tube I is closed, and the lower end connects to the insulation section. An inner and outer air inlet annular gap are respectively provided on the side wall of the central tube I and the catalyst cylinder. The area between the catalyst cylinder and the central tube I is called the reaction zone, which is filled with a partitioned catalyst. The catalyst can be discharged through the catalyst discharge port at the lower end of the reaction zone.

[0061] To ensure that the upper reaction zone is in an isothermal state and to preheat the syngas to the catalyst activation temperature and produce high-pressure saturated steam as a byproduct, a zoned heat exchange system is set up in the upper reaction zone of the reactor. Multiple plate heat exchange modules are installed in the two zones. These plate heat exchange modules are arranged radially around the central tube I in the reaction zone. The catalyst secondary zone is used for syngas preheating, and the catalyst primary zone is used for the generation of high-pressure saturated steam.

[0062] The plate heat exchanger in the secondary zone of the catalyst is equipped with a syngas preheating channel, and the plate heat exchanger in the primary zone of the catalyst is equipped with a high-pressure boiler water channel. The high-pressure boiler water riser is connected to the high-pressure saturated steam riser via the high-pressure boiler water channel, and the high-pressure saturated steam riser is connected to the high-pressure saturated steam outlet. The syngas riser is connected to the preheated syngas riser via the syngas preheating channel, and the preheated syngas riser is connected to the syngas preheating outlet.

[0063] like Figure 3As shown, the syngas preheating outlet is located outside the reactor. The preheated syngas passes through a plate heat exchange module and exits the reactor from the syngas preheating outlet at the top, then re-enters the syngas preheating inlet. This intake method allows for flexible adjustment of the syngas and preheated syngas flow rates. Alternatively, the preheated syngas can also exit the reactor without passing through the syngas preheating outlet (which is located inside the reactor and directly connected to the gap). Figure 3 (Not shown), instead, it enters the gap directly through the syngas preheating outlet. This gas intake method does not require the preheated syngas to be routed outside the reactor, but the gas volume regulation performance is poor.

[0064] like Figure 5 As shown, the upper end of the high-pressure boiler water riser pipe is connected to the high-pressure boiler water channel, and the lower end collects water in the high-pressure boiler water collection ring; the upper end of the syngas riser pipe is connected to the syngas preheating channel, and the lower end collects water in the syngas collection ring. Furthermore, the collection ring involved in this invention can also be replaced by a collection ball, such as... Figure 6 As shown.

[0065] A synthesis gas inlet is provided between the upper and lower sections of the cylinder. The synthesis gas from the bypass can be directly and fully mixed with the methanol synthesis gas flowing out of the upper central pipe I. It then passes through the gas distributor and the gas guide plate in sequence and enters the lower adiabatic reaction section. It enters the high-temperature resistant catalyst layer in an axial direction to carry out the methanol synthesis reaction. The generated gas after the reaction is completed is discharged from the bottom outlet.

[0066] like Figure 3 As shown, the adiabatic section is provided with an axial reaction catalyst bed. The upper and lower end plates of the axial reaction catalyst bed are connected to the cylinder to form a cavity, which is used to fill the high-temperature resistant catalyst. The reaction gas passes through the upper and lower end plates in sequence to undergo an adiabatic reaction.

[0067] The reactor body 1 is equipped with an upper catalyst discharge port 8 for loading and unloading the catalyst in the upper isothermal reaction zone; and a lower catalyst discharge port 10 for loading and unloading the catalyst in the lower adiabatic reaction zone. A main inspection port 7 allows maintenance personnel to enter the reactor interior. An isothermal section inspection port 21 and an adiabatic section inspection port 24 are used by maintenance personnel to perform maintenance on the upper and lower parts of the reactor, respectively. Ceramic balls 30 are also arranged inside the reactor body 1 to protect and support the high-temperature resistant catalyst 23 and the catalyst bed in the upper isothermal reaction zone. A pressure grid 27 is used to fix the high-temperature resistant catalyst 23 and the ceramic balls 30. Gas guide plates 22 and gas distributors 26 are used for the distribution and mixing of the reactant gas. Each high-pressure saturated steam riser pipe 28 and each preheated synthesis gas riser pipe 14 is equipped with an expansion joint 31 in the middle, effectively solving the problem of thermal expansion caused by temperature differences in the upper section of the reactor.

[0068] The isothermal section of the methanol synthesis reactor is filled with a low-temperature, high-conversion catalyst, while the adiabatic section is filled with a high-temperature resistant catalyst.

[0069] For start-up conditions, the bypass flow rate can be adjusted by regulating the syngas bypass to ensure that the reactor outlet temperature reaches above 300°C.

[0070] In the initial stage of the reaction, when the catalyst activity is high and the methanol synthesis reaction is efficient, reactor overheating may occur. In this case, the syngas bypass flow rate can be reduced to control the exothermic reaction in the adiabatic section, thereby lowering the temperature to normal. In the later stage of the reaction, when catalyst deactivation leads to insufficient reactor outlet temperature, the syngas bypass flow rate can be increased to raise the reactant outlet temperature to above 300°C.

[0071] When the unit load changes and the reactor temperature and its outlet temperature fluctuate, exceeding or failing to meet the system requirements, the temperature can be controlled by reducing or increasing the syngas bypass flow rate.

[0072] Example 2

[0073] Unlike Example 1, as Figure 4 As shown, the methanol synthesis reactor used in this embodiment has a vertical cylindrical shape, divided into upper and lower sections. In the upper section, a catalyst cylinder is fitted inside the cylinder, forming a gap between it and the cylinder body. This gap serves as the external outlet channel for the synthesis gas, which is connected to the insulation section. A central tube II is located within the catalyst cylinder. The top of the central tube II is connected to the main synthesis gas inlet, extending from the main inlet to the bottom of the catalyst cylinder. The bottom of the central tube II is sealed. An external inlet annular gap and an internal inlet annular gap are respectively provided on the side walls of the central tube II and the catalyst cylinder. The area between the catalyst cylinder and the central tube II is called the reaction zone, which is filled with a partitioned catalyst.

[0074] The gas flowing out through the external outlet channel of the syngas mixes with the syngas entering through the side inlet of the syngas, passes through the gas distributor and the gas guide plate in sequence, and enters the lower adiabatic reaction zone in a uniform distribution manner. Then, it passes through the catalyst bed in a radial manner from both sides to react. The generated methanol syngas enters the central tube III through the vent on the lower section of the reactor, collects in the central tube III, and then exits through the bottom outlet.

[0075] like Figure 4 As shown, the adiabatic section is provided with a radial reaction catalyst bed, which is fixed to the cylinder by a bottom plate. The bottom plate is connected to the top plate and the left and right side plates to form a cavity, which is used to fill the high-temperature resistant catalyst. The reaction gas enters the central tube III through the left and right side plates, during which an adiabatic reaction occurs.

[0076] Any numerical value mentioned in this invention, if there is only a two-unit interval between any minimum and any maximum value, includes all values ​​that increase by one unit each time from the minimum to the maximum value. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, or time, is stated as 50-90, in this specification it means specifically listing values ​​such as 51-89, 52-88… and 69-71 and 70-71, etc. For non-integer values, it may be appropriately considered that a unit is 0.1, 0.01, 0.001, or 0.0001. These are merely some specifically specified examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed minimum and maximum values ​​are considered to have been disclosed.

[0077] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A dual-channel isothermal coupled adiabatic CO2 hydrogenation to methanol system, characterized in that, The system includes a methanol synthesis reactor, a steam superheater, a water cooler, and a gas-liquid separator. The methanol synthesis reactor is a dual-channel isothermal coupled adiabatic reactor. The dual-channel isothermal coupled adiabatic reactor includes a cylindrical body. The top of the cylindrical body has a main syngas inlet, a syngas preheating outlet, and a high-pressure saturated steam outlet, while the bottom has a methanol syngas outlet. The cylindrical body is divided into an isothermal section and an adiabatic section from top to bottom. A syngas-side inlet is located between the isothermal section and the adiabatic section. A high-pressure boiler water inlet and a syngas preheating inlet are located on the cylindrical body of the isothermal section near the syngas-side inlet. The high-pressure boiler water inlet connects to the high-pressure saturated steam outlet after passing through the isothermal section. The syngas preheating inlet connects to the syngas preheating outlet after passing through the isothermal section. The methanol synthesis gas outlet at the bottom of the methanol synthesis reactor passes sequentially through the steam superheater and the water cooler, and then connects to the side inlet of the gas-liquid separator.

2. The system according to claim 1, characterized in that, The isothermal section is provided with a catalyst cylinder I, which is sleeved inside the cylinder and forms a gap I with the inner wall of the cylinder. The gap I forms a gas channel I that connects to the main inlet of the synthesis gas. Multiple external air inlet annular gaps I are provided on the side wall of the catalyst cylinder I. The catalyst cylinder I is fitted with a central tube I, the upper end of the central tube I is closed, and the lower end is connected to the insulation section; multiple internal air inlet annular gaps I are provided on the side wall of the central tube I; The reaction zone I is located between the catalyst cylinder I and the central tube I.

3. The system according to claim 1, characterized in that, The isothermal section is provided with a catalyst cylinder II, which is sleeved inside the cylinder and forms a gap II with the inner wall of the cylinder. The gap II forms a gas channel II that connects to the adiabatic section. Multiple inner air inlet annular gaps II are provided on the side wall of the catalyst cylinder II. The catalyst cylinder II is fitted with a central tube II, the upper end of which is connected to the main inlet of the synthesis gas, and the lower end is closed; multiple external air inlet annular gaps II are provided on the side wall of the central tube II; The reaction zone II is located between the catalyst cylinder II and the central tube II.

4. The system according to claim 2 or 3, characterized in that, Multiple plate heat exchange modules are independently provided in reaction zone I and reaction zone II. The plate heat exchange modules are arranged radially with central tube I or central tube II as the center. The inlet of the plate heat exchange module is connected to the refrigerant input pipe, and the outlet of the plate heat exchange module is connected to the refrigerant output pipe. Preferably, the plate heat exchange module has multiple protrusions on its side.

5. The system according to claim 4, characterized in that, The plate heat exchange module includes a high-pressure boiler water channel and a syngas preheating channel; the refrigerant input pipeline includes a high-pressure boiler water riser and a syngas riser; the refrigerant output pipeline includes a high-pressure saturated steam riser and a preheated syngas riser. The high-pressure boiler water riser pipe is connected to the high-pressure saturated steam riser pipe via the high-pressure boiler water channel, and the high-pressure saturated steam riser pipe is connected to the high-pressure saturated steam outlet; the syngas riser pipe is connected to the preheated syngas riser pipe via the syngas preheating channel, and the preheated syngas riser pipe is connected to the syngas preheating outlet.

6. The system according to claim 5, characterized in that, The inlet of the high-pressure boiler water channel is connected to multiple high-pressure boiler water risers, which converge and connect to a high-pressure boiler water collecting ball, which is connected to the high-pressure boiler water inlet. The outlet of the high-pressure boiler water channel is connected to multiple high-pressure saturated steam risers, which converge to a high-pressure saturated steam collecting ring, which is connected to the high-pressure saturated steam outlet. And / or, the inlet of the syngas preheating channel is connected to multiple syngas risers, which converge and connect to a syngas collection annulus, and the syngas collection annulus is connected to the syngas preheating inlet; the outlet of the syngas preheating channel is connected to multiple preheated syngas risers, which converge and connect to a preheated syngas collection ring, and the preheated syngas collection ring is connected to the syngas preheating outlet.

7. The system according to any one of claims 1-6, characterized in that, The synthesis gas side inlet is connected to a gas distributor inside the cylinder; And / or, the interior of the insulating section near the syngas inlet is provided with a gas guide plate; And / or, the adiabatic section is provided with an axial reaction catalyst bed; And / or, the adiabatic section is provided with a radial reaction catalyst bed; preferably, the radial reaction catalyst bed is provided with a central tube III, the central tube III being coaxially arranged with the central tube I or the central tube II; a plurality of vent holes are provided on the side wall of the central tube III; the upper end of the central tube III is closed, and the lower end is connected to the methanol synthesis gas outlet.

8. A dual-channel isothermal coupled adiabatic CO2 hydrogenation process for methanol production, characterized in that, The CO2 hydrogenation to methanol system using the dual-channel isothermal coupled adiabatic CO2 hydrogenation system according to any one of claims 1-7 includes preheating the feed gas compressed to the system pressure, raising the temperature to the catalyst activation temperature using the heat of reaction, and then carrying out the methanol synthesis reaction. The obtained methanol synthesis gas is subjected to gas-liquid separation after heat exchange. The obtained gas phase is compressed to the system pressure and then recycled. The obtained liquid phase is subjected to methanol distillation to obtain the product methanol.

9. The process according to claim 8, characterized in that, The saturated steam produced by the methanol synthesis reaction is superheated to generate superheated steam. Preferably, the superheat of the superheated steam is 1 to 100°C, and more preferably 50 to 80°C; Preferably, the pressure of the saturated steam is 0.5 to 5.0 MPaG, more preferably 2 to 4 MPaG.

10. The process according to claim 8 or 9, characterized in that, The CO2 molar content in the raw gas is greater than 50%, preferably greater than 90%; And / or, the temperature of the preheated feed gas is 150–400°C, preferably 180–350°C; the temperature of the methanol synthesis gas is 200–500°C, preferably 250–400°C; And / or, the gas temperature for gas-liquid separation is 30–200°C, preferably 50–100°C.

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