Multi-stage CO2 hydrogenation methanol preparation system

Abstract

The utility model provides a multi-stage CO2 hydrogenation methanol preparation system which comprises a first-stage methanol synthesis reactor, a steam superheater, a water cooler I, a gas-liquid separation tank I, a second-stage preheater, a second-stage methanol synthesis reactor, a water cooler II, a gas-liquid separation tank II and a crude methanol flash tank, the first-stage methanol synthesis reactor is a double-channel isothermal coupling adiabatic reactor; the method comprises the following steps: preheating raw material gas by using reaction heat, raising the temperature to a catalyst activation temperature, then carrying out first-stage methanol synthesis reaction, carrying out first-stage gas-liquid separation on the obtained first-stage methanol synthesis gas after heat exchange, preheating the obtained first-stage gas phase to the catalyst activation temperature, and then carrying out second-stage methanol synthesis reaction; second-stage methanol synthesis gas produced by the second-stage methanol synthesis reaction is subjected to heat exchange and then is subjected to second-stage gas-liquid separation, and an obtained second-stage liquid phase is subjected to crude methanol flash evaporation. The gas circulation ratio can be effectively reduced, and the energy consumption of the device is reduced; meanwhile, system heat can be fully utilized, the saturated steam yield is high, and economic benefits are improved.

Description

Technical Field

[0001] The utility model relates to the technical field of methanol preparation, in particular to a multi-stage CO2 hydrogenation system for preparing methanol. Background Art

[0002] In response to carbon neutrality, the resource utilization of carbon dioxide has become a hot topic of research. Methanol is a basic organic chemical raw material with a simple structure and a wide range of applications. Producing methanol by hydrogenating carbon dioxide is relatively easy to achieve based on the reaction principle.

[0003] At present, the CO2 hydrogenation process for methanol production is usually a single-stage reaction. The synthesis loop pressure drop of the single-stage reactor methanol synthesis technology is low and the device investment is small. However, the synthesis conversion rate is not high and the energy utilization efficiency is low, resulting in increased production costs. In addition, there are two problems that need to be improved in this process: (1) The boiler water heat exchange produces saturated steam, which is prone to condensation when the temperature drops, and cannot be transported through the steam network, resulting in poor availability. (2) During the start-up, the initial and final stages of the reaction, and when the device load changes, once the reactor temperature collapses or overheats, the temperature cannot be adjusted quickly.

[0004] Currently, mainstream methanol synthesis reactors are broadly categorized as axial and radial. Axial reactors are simple in structure, easy to operate, and utilize reaction heat to meet reaction temperature requirements. They also produce higher steam pressure and smaller temperature differences across the catalyst bed. However, axial reactors, in which the catalyst is loaded into the tubes, are not only inconvenient to maintain but also have a low volumetric efficiency. This results in larger equipment for the same production capacity and higher manufacturing costs. While radial reactors offer larger catalyst loadings and lower radial flow resistance, they suffer from large temperature differences across the catalyst bed, leading to uneven gas distribution across the catalyst bed and reduced catalyst contact efficiency.

[0005] To address these issues, CN111362777A provides a methanol synthesis system and method. This utilizes a multi-stage methanol synthesis unit, with each stage performing a single-pass conversion, thus reducing reaction heat generation. This system eliminates the need for large amounts of gas circulation, reducing power consumption compared to prior art methods that utilize superchargers. However, this technology fails to improve steam quality, hinders subsequent utilization, and presents a complex process.

[0006] CN105664804A provides an axial-radial isothermal reactor. By installing a cooling unit within the reaction zone, the reaction heat is promptly removed, effectively controlling the reaction zone temperature. Axial-radial feeding avoids pressure drop, and the suspended reaction zone solves the problem of thermal expansion during the reaction. However, this isothermal reactor consumes a lot of energy, lacks flexibility in operating conditions such as start-up and shutdown, and load fluctuations, and cannot solve the problem of saturated steam byproducts. Utility Model Content

[0007] Methanol synthesis is carried out under high temperature and high pressure conditions. The single-pass conversion rate of this reaction is low. After the gas after the reaction is cooled and the liquid is separated, most of the unreacted gas is used as circulating gas, which is pressurized to the system pressure by a compressor and sent to the inlet of the methanol synthesis system to mix with the raw gas before entering the reactor to continue synthesizing methanol.

[0008] The use of a multi-stage methanol synthesis unit can reduce the gas circulation ratio, minimize compressor energy consumption, and increase the single-pass carbon dioxide conversion rate. The methanol synthesis gas adopts a staged reaction, and by promptly removing the reaction products, the single-pass conversion rate can be increased, thereby reducing the catalyst loading requirement and reactor size. Furthermore, traditional methanol synthesis processes often use a shell-and-tube water-cooled isothermal reactor. The catalyst is loaded in a shell-and-tube fixed bed. Boiler water in the shell side removes the reaction heat and produces high-pressure saturated steam. The reaction temperature is controlled by the pressure of the boiling water in the shell side. The saturated steam produced by this type of reactor is prone to condensation due to temperature drop during transportation through the pipeline network. Moreover, temperature control using boiling water pressure has a lag problem.

[0009] The technical problem to be solved by the present invention is to provide a multi-stage CO2 hydrogenation to methanol system and process based on the current status of the existing technology, which can flexibly respond to working conditions such as start-up and load changes, can produce high-quality high-pressure steam as a by-product, and is easy to operate and has low investment cost.

[0010] According to one aspect of the present invention, a multi-stage CO2 hydrogenation system for producing methanol is provided, comprising a primary methanol synthesis reactor, a steam superheater, a water cooler I, a gas-liquid separation tank I, a secondary preheater, a secondary methanol synthesis reactor, a water cooler II, a gas-liquid separation tank II and a crude methanol flash tank;

[0011] The first-stage methanol synthesis reactor is a dual-channel isothermal coupled adiabatic reactor;

[0012] The dual-channel isothermal coupled adiabatic reactor comprises a cylinder, the top of which is provided with a syngas main inlet, a syngas preheating outlet, and a high-pressure saturated steam outlet, and the bottom of which is provided with a methanol syngas outlet; the cylinder is divided into an isothermal section and an adiabatic section from top to bottom; a syngas side inlet is provided between the isothermal section and the adiabatic section; a high-pressure boiler water inlet and a syngas preheating inlet are provided on the cylinder of the isothermal section near the syngas side inlet; the high-pressure boiler water inlet is connected to the high-pressure saturated steam outlet after passing through the isothermal section; and the syngas preheating inlet is connected to the syngas preheating outlet after passing through the isothermal section;

[0013] The primary methanol synthesis gas outlet at the bottom of the primary methanol synthesis reactor passes through the steam superheater and the water cooler I, and is connected to the side inlet of the gas-liquid separation tank I;

[0014] The bottom outlet of the gas-liquid separation tank I is connected to the side inlet of the crude methanol flash tank, and the top outlet is connected to the top inlet of the secondary methanol synthesis reactor after passing through the secondary preheater;

[0015] The secondary methanol synthesis gas outlet at the bottom of the secondary methanol synthesis reactor passes through the secondary preheater and the water cooler II and then communicates with the side inlet of the gas-liquid separation tank II;

[0016] The bottom outlet of the gas-liquid separation tank II is communicated with the side inlet of the crude methanol flash tank.

[0017] 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, wherein the gap I forms a gas channel I connected to the main inlet of the synthesis gas; a plurality of external air inlet annular gaps I are provided on the side wall of the catalyst cylinder I;

[0018] The catalyst cylinder I is sheathed with a central tube I, the upper end of the central tube I is closed, and the lower end is connected to the thermal insulation section; a plurality of inner air intake annular gaps I are provided on the side wall of the central tube I;

[0019] The reaction zone I is located between the catalyst cylinder I and the central tube I.

[0020] Optionally, the synthesis gas preheating outlet is communicated with the gap I, that is, the synthesis gas preheating outlet is located inside the reactor, and the preheated synthesis gas does not discharge out of the reactor through the synthesis gas preheating outlet, but directly enters the gap I.

[0021] 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, wherein the gap II forms a gas channel II communicating with the adiabatic section; a plurality of inner air intake annular gaps II are provided on the side wall of the catalyst cylinder II;

[0022] The catalyst cylinder II is provided with a central tube II, the upper end of the central tube II is connected to the main inlet of the synthesis gas, and the lower end is closed; a plurality of external air inlet annular gaps II are provided on the side wall of the central tube II;

[0023] The reaction zone II is located between the catalyst cylinder II and the central tube II.

[0024] Optionally, multiple plate heat exchange modules are independently provided in the reaction zone I and the reaction zone II, and the plate heat exchange modules are radially arranged with the central tube I or the 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.

[0025] Optionally, a plurality of spoiler structures are provided on the side of the plate heat exchange module.

[0026] Optionally, the plate heat exchange module includes a high-pressure boiler water channel and a synthesis gas preheating channel; the refrigerant input pipeline includes a high-pressure boiler water riser and a synthesis gas riser; the refrigerant output pipeline includes a high-pressure saturated steam riser and a preheated synthesis gas riser;

[0027] The high-pressure boiler water riser is connected to the high-pressure saturated steam riser through the high-pressure boiler water channel, and the high-pressure saturated steam riser is connected to the high-pressure saturated steam outlet; the synthesis gas riser is connected to the preheated synthesis gas riser through the synthesis gas preheating channel, and the preheated synthesis gas riser is connected to the synthesis gas preheating outlet.

[0028] Optionally, the inlet of the high-pressure boiler water channel is connected to multiple high-pressure boiler water riser pipes, the multiple high-pressure boiler water riser pipes are gathered and connected to a high-pressure boiler water collecting ball, and the high-pressure boiler water collecting ball 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 riser pipes, the multiple high-pressure saturated steam riser pipes are gathered in a high-pressure saturated steam collecting ring, and the high-pressure saturated steam collecting ring is connected to the high-pressure saturated steam outlet.

[0029] Optionally, the inlet of the synthesis gas preheating channel is connected to multiple synthesis gas risers, and the multiple synthesis gas risers are converged and connected to the synthesis gas collecting annulus, and the synthesis gas collecting annulus is connected to the synthesis gas preheating inlet; the outlet of the synthesis gas preheating channel is connected to multiple preheating synthesis gas risers, and the multiple preheating synthesis gas risers are converged to the preheating synthesis gas collecting ring, and the preheating synthesis gas collecting ring is connected to the synthesis gas preheating outlet.

[0030] Optionally, the system further includes a steam drum for separating water vapor from the high-pressure saturated steam generated by the primary methanol synthesis reactor; the high-pressure saturated steam outlet is connected to the high-pressure boiler water inlet through the steam drum, and the saturated steam outlet of the steam drum is connected to the steam superheater.

[0031] Optionally, the saturated steam outlet of the secondary methanol synthesis reactor is connected to the steam superheater.

[0032] Optionally, the synthesis gas side inlet is connected to a gas distributor inside the cylinder.

[0033] Optionally, a gas guide plate is provided inside the cylinder of the insulation section close to the synthesis gas inlet.

[0034] Optionally, the insulation section is provided with an axial reaction catalyst bed.

[0035] Optionally, 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 with a high-temperature resistant catalyst, and the reaction gas passes through the upper end plate, the cavity and the lower end plate in sequence to produce an adiabatic reaction.

[0036] Optionally, the insulation section is provided with a radial reaction catalyst bed.

[0037] Optionally, the radial reaction catalyst bed is fixed to the cylinder through a bottom plate, and 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 cavity through the left and right side plates to produce an adiabatic reaction.

[0038] 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 vents are provided on the side wall of the central tube III; the upper port of the central tube III is closed, and the lower port is connected to the methanol synthesis gas outlet.

[0039] According to another aspect of the present invention, a multi-stage CO2 hydrogenation process for producing methanol using the above system is provided, comprising compressing the feed gas to the system pressure and then preheating it, raising the temperature to the catalyst activation temperature using the reaction heat, and then performing a first-stage methanol synthesis reaction;

[0040] The obtained primary methanol synthesis gas is subjected to primary gas-liquid separation after heat exchange, the obtained primary gas phase is preheated to the catalyst activation temperature and then subjected to secondary methanol synthesis reaction, and the obtained primary liquid phase is subjected to crude methanol flash evaporation to obtain product methanol; the secondary methanol synthesis gas produced by the secondary methanol synthesis reaction is subjected to secondary gas-liquid separation after heat exchange, the obtained secondary gas phase is compressed to the system pressure and then recycled, and the obtained secondary liquid phase is subjected to crude methanol flash evaporation to obtain product methanol.

[0041] Optionally, the high-pressure saturated steam produced by the primary methanol synthesis reaction undergoes water vapor separation in a steam drum, and the resulting liquid re-enters the primary methanol synthesis reactor for use as a heat exchange medium, while the generated saturated steam is superheated together with the saturated steam produced by the secondary methanol synthesis reaction to generate superheated steam.

[0042] Optionally, the saturated steam produced by the primary methanol synthesis reaction and the secondary methanol synthesis reaction are superheated together to generate superheated steam.

[0043] Optionally, the superheat degree of the superheated steam is 1 to 100°C, preferably 50 to 80°C.

[0044] Optionally, the pressure of the saturated steam is 0.5-5.0 MPaG, preferably 2-4 MPaG.

[0045] Optionally, the CO2 molar content in the feed gas is greater than 50%, preferably greater than 90%.

[0046] Optionally, the temperature of the preheated raw gas is 150-400°C, preferably 180-350°C; the temperature of the primary methanol synthesis gas is 200-500°C, preferably 250-400°C.

[0047] Optionally, the temperature of the primary gas phase after preheating is 150-400°C, preferably 180-350°C; the temperature of the secondary methanol synthesis gas is 200-500°C, preferably 250-400°C.

[0048] Optionally, the gas temperature for the primary gas-liquid separation is 30-200°C, preferably 50-100°C.

[0049] The utility model adopts a new type of adiabatic isothermal coupling reactor in the first-stage methanol synthesis module, which fully utilizes the waste heat of the process gas, simplifies the process, and saves energy and reduces consumption. The new reactor removes the reaction heat through radially arranged heat exchange modules and loads catalysts between adjacent modules to ensure the heat transfer rate while improving the volume ratio; through the coupling adiabatic section, high-temperature resistant catalysts are loaded and the reaction exotherm is used to ensure that the outlet temperature is above 250°C (can be heated to above 400°C), which is used to superheat saturated steam and preheat synthesis gas, solving the problem of difficult pipeline transportation; by setting a synthesis gas bypass inlet between the isothermal section and the adiabatic section, the reactor temperature control can be achieved more easily, ensuring the smooth operation of the process flow. After the bypass synthesis gas is mixed with the reaction gas from the isothermal section, it is heated to the activation temperature of the catalyst in the adiabatic section and enters the high-temperature resistant catalyst bed through the gas distributor and guide plate to carry out the synthesis reaction. Adjusting the bypass flow can flexibly control the outlet temperature of the reaction gas.

[0050] In the present invention, the catalysts in the isothermal section and the adiabatic section have different temperature tolerances. The isothermal section can use a conventional catalyst, and the adiabatic section can use a high-temperature resistant catalyst with a maximum temperature tolerance of 500°C.

[0051] Compared with the prior art, the utility model has the following advantages:

[0052] (1) No additional heat source is required to heat the synthesis gas. The reaction heat is used to preheat the synthesis gas to the catalyst activation temperature in the isothermal section. The first-stage methanol synthesis reactor uses the reaction gas produced in the isothermal section to heat the bypass synthesis gas, so that the temperature of the mixed synthesis gas reaches the catalyst activation temperature in the adiabatic section. This fully utilizes the waste heat of the process gas, improves system integration, and reduces equipment investment.

[0053] (2) The first-stage methanol synthesis module utilizes a novel adiabatic isothermal coupled reactor. The isothermal section transfers heat between boiler water and feed gas, simplifying the process flow, reducing equipment investment, and improving the economic efficiency of the unit. Furthermore, the coupling of the first-stage methanol synthesis reactor with an adiabatic section effectively increases the reactor outlet temperature. Combined with the adjustment of the bypass inlet flow rate, the reaction gas outlet temperature can be flexibly controlled to above 250°C.

[0054] (3) A steam superheater is installed in the first-stage methanol synthesis module to superheat the high-pressure saturated steam produced by the entire methanol synthesis system, thereby improving the stability and quality of steam utilization and facilitating pipeline transportation and subsequent use.

[0055] (4) The first-stage methanol synthesis reactor uses the synthesis gas bypass inlet to adjust the ratio of the main and bypass flow rates of the synthesis gas and control the reaction heat release. It can flexibly respond to temperature fluctuations caused by changes in operating conditions and ensure stable operation of the process flow.

[0056] (5) The first-stage methanol synthesis reactor is equipped with a high-pressure boiler water collection ball and a synthesis gas collection annulus, which divides the heat exchange module into a water-cooling channel and an air-cooling channel within a limited space. This can effectively remove and utilize the reaction heat to preheat the synthesis gas and produce high-pressure saturated steam.

[0057] (6) Multi-stage reaction can improve the methanol conversion rate per pass, reduce the reaction cycle ratio, reduce the diameter of the circulating gas pipeline, reduce the energy consumption of the device, and reduce the operating cost of the device.

[0058] (7) The use of heat exchange modules increases the contact area and improves the heat exchange efficiency compared to the traditional shell-and-tube structure. It also greatly increases the catalyst loading capacity and reduces the equipment size.

[0059] (8) The multi-stage reactor process can make the total steam production basically unchanged at the beginning and end of the catalyst by adjusting the load of each stage of the reactor, and the comprehensive energy consumption is significantly lower than that of the single-stage reactor process. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 This is a flow chart of a multi-stage CO2 hydrogenation process for producing methanol as described in Example 1 of the present utility model;

[0061] Figure 2 This is a schematic diagram of the external cylinder structure of the first-stage methanol synthesis reactor of the utility model;

[0062] Figure 3 This is a schematic diagram of the internal structure of a first-stage methanol synthesis reactor of the utility model;

[0063] Figure 4 This is another schematic diagram of the internal structure of the first-stage methanol synthesis reactor of the present utility model;

[0064] Figure 5This is a schematic diagram of a plate heat exchange module (collecting ring) including dual-channel heat exchange in the present invention;

[0065] Figure 6 This is a schematic diagram of a plate heat exchange module (collecting ball) including dual-channel heat exchange in the present invention;

[0066] Among them, a-synthesis gas compressor, b-primary methanol synthesis reactor, c-steam drum; d-steam superheater; e-water cooler I; f-gas-liquid separation tank I; g-secondary preheater; h-secondary methanol synthesis reactor; i-water cooler II; j-gas-liquid separation tank II; k-crude methanol flash tank; l-circulating gas compressor;

[0067] 1-Cylinder; 2-High-pressure boiler water inlet; 3-High-pressure saturated steam outlet; 4-Synthesis gas preheating outlet; 5-Synthesis gas main inlet; 6-Synthesis gas preheating inlet; 7-Main inspection port; 8-Catalyst upper discharge port; 9-Synthesis gas side inlet; 10-Catalyst lower discharge port; 11-Reaction gas outlet; 12-High-pressure saturated steam collection ring; 13-Preheated synthesis gas collection ring; 14-Preheated synthesis gas riser; 15-Heat exchange module; 16-Center pipe I / II; 17-High-pressure boiler water riser; 18-High-pressure boiler Water collecting ball; 19-synthesis gas riser; 20-synthesis gas collecting annulus; 21-isothermal section inspection port; 22-gas guide plate; 23-high-temperature resistant catalyst; 24-insulation section inspection port; 25-collecting ball inspection port; 26-gas distributor; 27-pressure grid; 28-high-pressure saturated steam riser; 29-catalyst tube; 30-ceramic ball; 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-center pipe III. DETAILED DESCRIPTION

[0068] The present invention will be further described below with reference to specific embodiments, but this does not constitute any limitation to the present invention.

[0069] The two-stage methanol synthesis reactor of the present invention can be any conventional and widely used methanol synthesis reactor on the market, such as a shell-and-tube isothermal methanol synthesis reactor.

[0070] Example 1

[0071] like Figure 1As shown, the raw gases, carbon dioxide and hydrogen, are compressed to system pressure by syngas compressor a before entering the primary methanol synthesis module. The process flow is as follows: First, they enter the air cooling channel (syngas preheating channel) of the primary methanol synthesis reactor b, where they are heated to the catalyst activation temperature using the heat of reaction. They then re-enter the primary methanol synthesis reactor b for reaction. The primary methanol synthesis reaction gas exiting the primary methanol synthesis reactor b is superheated to saturated steam in steam superheater d, then cooled by water cooler II e before entering a gas-liquid separator If. Gas from the overhead of separator If enters the secondary methanol synthesis module. The process flow is as follows: Gas from the primary module first enters secondary preheater g to be heated to the catalyst activation temperature, then enters the secondary methanol synthesis reactor h for reaction. The saturated steam produced from the overhead of the secondary methanol synthesis reactor is sent to steam superheater d in the primary module to generate superheated steam. The secondary methanol synthesis reaction gas exiting the secondary methanol synthesis reactor passes through secondary preheater g and water cooler II i before entering a gas-liquid separator II j. At the top of separator tank II j, most of the gas is compressed to system pressure by recycle gas compressor l and then sent to the primary module for recycling, while some purge gas is discharged. The liquid at the bottom of separator tanks 1 f and II j is sent to crude methanol flash tank k, which is then sent to the methanol distillation unit to produce 99.5% refined methanol.

[0072] In this embodiment, the raw gas carbon dioxide and hydrogen are compressed to a system pressure of 8MPa by the synthesis gas compressor and then go to the first-level methanol synthesis module. The process is as follows: first, they enter the air-cooling channel (synthesis gas preheating channel) of the first-level methanol synthesis reactor and use the reaction heat to heat up to the catalyst activation temperature of 210-220°C. Then they enter the first-level methanol synthesis reactor again for reaction. The first-level methanol synthesis reactor is divided into an upper isothermal section and a lower adiabatic section. The water vapor mixture formed by heat exchange with boiler water in the upper isothermal section produces high-pressure saturated steam in the steam drum, and the lower adiabatic section ensures that the reactor outlet temperature is above 250°C. The outlet reaction gas of the first-level methanol synthesis reactor is superheated by the steam superheater and then cooled to 100°C by the water cooler I and enters the gas-liquid separation tank I. The gas from the top of Separator Tank I is fed to the secondary methanol synthesis module. The process is as follows: Gas from the primary module first enters the secondary preheater to be heated to 210-220°C before entering the secondary methanol synthesis reactor for reaction. The saturated steam produced from the reactor top is fed to the steam superheater in the primary module to generate superheated steam. The reaction gas from the secondary methanol synthesis reactor passes through the secondary preheater and then through water cooler II before entering Separator Tank II. Most of the gas from the top of Separator Tank II is compressed to a system pressure of 5-8 MPa by a recycle gas compressor before being recycled to the primary module. A portion of the purge gas is then sent to the outside as fuel gas. The liquid from the bottom of both Separator Tanks I and II is fed to the crude methanol flash tank. The gas from the flash tank top is also discharged to the outside as fuel gas, while the liquid from the bottom is fed to the methanol distillation unit to produce refined methanol with a yield exceeding 99.85%.

[0073] like Figure 2 、 Figure 3 As shown, the primary methanol synthesis reactor used in this embodiment has a vertical cylindrical shape, divided into two sections. In the upper section, the catalyst cartridge is sleeved within the cartridge, forming a gap between the cartridge and the cartridge. This gap connects to the main synthesis gas inlet, forming a synthesis gas inlet channel. A central tube I is positioned at the center of the catalyst cartridge. The upper end of the central tube I is sealed, and the lower end connects to the insulation section. An inner and outer annular gaps are defined between the central tube I and the sidewalls of the catalyst cartridge, respectively. The area between the catalyst cartridge and central tube I is called the reaction zone. This zone is filled with partitioned catalyst, which can be discharged through the catalyst upper discharge port at the lower end of the reaction zone.

[0074] In order to keep the upper reaction zone in an isothermal state and preheat the synthesis gas to the catalyst activation temperature and the by-product high-pressure saturated steam, a zoned heat exchange is set up in the upper reaction zone of the reactor. Multiple plate heat exchange modules are provided in the two zones. The plate heat exchange modules are arranged in the reaction zone in a central radial manner with the central tube I as the axis. The synthesis gas is preheated in the secondary catalyst zone, and the high-pressure saturated steam is generated in the primary catalyst zone.

[0075] The plate heat exchanger in the secondary partition of the catalyst is provided with a synthesis gas preheating channel, and the plate heat exchanger in the primary partition of the catalyst is provided 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 synthesis gas riser is connected to the preheated synthesis gas riser via the synthesis gas preheating channel, and the preheated synthesis gas riser is connected to the synthesis gas preheating outlet.

[0076] like Figure 3 As shown, the syngas preheating outlet is located outside the reactor. After passing through the plate heat exchange module, the preheated syngas is discharged from the reactor through the syngas preheating outlet on the top of the reactor and then enters the syngas preheating inlet. This air intake method can adjust the amount of syngas and preheated syngas, and the adjustment is flexible. The preheated syngas can also be discharged from the reactor without passing through the syngas preheating outlet (the syngas preheating outlet is located inside the reactor and is directly connected to the gap. Figure 3 Not shown), but directly enters the gap through the synthesis gas preheating outlet. This air intake method does not require the preheated synthesis gas to bypass the reactor, but the gas volume regulation performance is poor.

[0077] like Figure 5 As shown, the upper end of the high-pressure boiler water riser is connected to the high-pressure boiler water channel, and the lower end is collected in the high-pressure boiler water collection ring; the upper end of the synthesis gas riser is connected to the synthesis gas preheating channel, and the lower end is collected in the synthesis gas collection ring. In addition, the collection ring involved in the present invention can also be replaced by a collection ball, such as Figure 6 shown.

[0078] A synthesis gas side 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 tube, and passes through the gas distributor and the gas guide plate in sequence to enter the lower adiabatic reaction section, and enters the high-temperature resistant catalyst layer from the axial direction to carry out the methanol synthesis reaction. After the reaction is completed, the primary methanol synthesis gas is discharged from the bottom outlet.

[0079] like Figure 3 As shown, the adiabatic reaction section is provided with an axial reaction catalyst bed, and 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 turn to produce an adiabatic reaction.

[0080] The isothermal section of the first-stage methanol synthesis reactor is filled with a low-temperature, high-conversion catalyst, and the adiabatic section is filled with a high-temperature resistant catalyst.

[0081] During startup, the reactor outlet temperature may be insufficient to preheat the syngas to the catalyst activation temperature. Therefore, for the first-stage methanol synthesis reactor, the syngas bypass flow can be adjusted to increase its bypass flow rate to stabilize the reactor outlet temperature above 250°C and control the hotspot temperature inside the reactor.

[0082] In the early stages of the reaction, when catalyst activity is high and the methanol synthesis reaction is effective, the reactor may experience a temperature spike. In this case, the first-stage methanol synthesis reactor can be cooled to normal temperatures by adjusting the syngas bypass flow rate, reducing the bypass flow rate, and controlling the exothermic reaction in the adiabatic section. In the late stages of the reaction, when catalyst deactivation leads to insufficient reactor outlet temperature, the syngas bypass flow rate can be increased to raise the reactor gas outlet temperature to above 250°C.

[0083] When the load of the device changes, the reactor temperature and its outlet temperature fluctuate, far exceeding or failing to meet the system requirements. For the first-stage methanol synthesis reactor, the temperature can be controlled by reducing or increasing the synthesis gas bypass flow.

[0084] Example 2

[0085] Different from Example 1, Figure 4 As shown, the primary methanol synthesis reactor used in this embodiment has a vertical cylindrical shape, divided into two sections, upper and lower. In the upper section, the catalyst cartridge is sleeved within the cartridge, forming a gap between the cartridge and the cartridge. This gap serves as the syngas outlet channel, which is connected to the insulation section. A central tube II is provided within the catalyst cartridge. The top of central tube II is connected to the main syngas inlet, extending from the main syngas inlet to the bottom of the cartridge. The bottom of central tube II is sealed. External and internal air inlet annuli are provided on the sidewalls of central tube II and the catalyst cartridge, respectively. The region between the catalyst cartridge and central tube II is referred to as the reaction zone, where the zoned catalyst is loaded.

[0086] The gas flowing out through the synthesis gas external outlet channel is mixed with the synthesis gas entering through the synthesis gas side inlet, passes through the gas distributor and the gas guide plate in sequence, and enters the lower adiabatic reaction zone in a uniform distribution manner, and then passes through the catalyst bed in a radial manner from both sides to react. The generated primary methanol synthesis gas enters the central tube III of the lower section of the reactor through the vent holes on the central tube III and is collected, and then discharged through the bottom outlet.

[0087] like Figure 4As shown, the adiabatic section is provided with a radial reaction catalyst bed, which is fixed to the cylinder through a bottom plate. The bottom plate is connected to the top plate and the left and right side plates to form a cavity. A central tube III is provided in the cavity, and the remaining part of the cavity is used to fill a high-temperature resistant catalyst; the reaction gas enters the central tube III through the left and right side plates and is collected, during which an adiabatic reaction occurs.

[0088] Any numerical value mentioned in this utility model includes all values that increase by one unit each time from the lowest value to the highest value if there is only an interval of two units between any minimum value and any maximum value. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, time, etc. is stated to be 50-90, it means in this specification that 51-89, 52-88... and 69-71 and 70-71 are specifically listed. For non-integer values, 0.1, 0.01, 0.001 or 0.0001 can be appropriately considered as one unit. These are just some special examples. In this application, in a similar manner, all possible combinations of numerical values between the listed lowest value and the listed highest value are considered to have been disclosed.

[0089] It should be noted that the embodiments described above are only used to explain 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 words, rather than restrictive words. The present invention may be modified as provided within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A multi-stage CO2 hydrogenation system for producing methanol, characterized in that: The system comprises a primary methanol synthesis reactor, a steam superheater, a water cooler I, a gas-liquid separation tank I, a secondary preheater, a secondary methanol synthesis reactor, a water cooler II, a gas-liquid separation tank II and a crude methanol flash tank; The first-stage methanol synthesis reactor is a dual-channel isothermal coupled adiabatic reactor; The dual-channel isothermal coupled adiabatic reactor comprises a cylinder, the top of which is provided with a syngas main inlet, a syngas preheating outlet, and a high-pressure saturated steam outlet, and the bottom of which is provided with a methanol syngas outlet; the cylinder is divided into an isothermal section and an adiabatic section from top to bottom; a syngas side inlet is provided between the isothermal section and the adiabatic section; a high-pressure boiler water inlet and a syngas preheating inlet are provided on the cylinder of the isothermal section near the syngas side inlet; the high-pressure boiler water inlet is connected to the high-pressure saturated steam outlet after passing through the isothermal section; and the syngas preheating inlet is connected to the syngas preheating outlet after passing through the isothermal section; The primary methanol synthesis gas outlet at the bottom of the primary methanol synthesis reactor passes through the steam superheater and the water cooler I, and is connected to the side inlet of the gas-liquid separation tank I; The bottom outlet of the gas-liquid separation tank I is connected to the side inlet of the crude methanol flash tank, and the top outlet is connected to the top inlet of the secondary methanol synthesis reactor after passing through the secondary preheater; The secondary methanol synthesis gas outlet at the bottom of the secondary methanol synthesis reactor passes through the secondary preheater and the water cooler II and then communicates with the side inlet of the gas-liquid separation tank II; The bottom outlet of the gas-liquid separation tank II is communicated with the side inlet of the crude methanol flash tank.

2. The system according to claim 1, wherein: 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, wherein the gap I forms a gas channel I connected to the main inlet of the synthesis gas; a plurality of external air inlet annular gaps I are provided on the side wall of the catalyst cylinder I; The catalyst cylinder I is sheathed with a central tube I, the upper end of the central tube I is closed, and the lower end is connected to the thermal insulation section; a plurality of inner air intake 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, wherein: 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 communicating with the adiabatic section. A plurality of inner air intake annular gaps II are provided on the side wall of the catalyst cylinder II. The catalyst cylinder II is provided with a central tube II, the upper end of the central tube II is connected to the main inlet of the synthesis gas, and the lower end is closed; a plurality of 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, wherein: A plurality of plate heat exchange modules are provided in the reaction zone I, and the plate heat exchange modules are radially arranged with the central tube I as the center; the inlet of the plate heat exchange module is connected to the refrigerant input pipeline, and the outlet of the plate heat exchange module is connected to the refrigerant output pipeline.

5. The system according to claim 3, wherein: A plurality of plate heat exchange modules are provided in the reaction zone II, and the plate heat exchange modules are radially arranged with the central tube II as the center; the inlet of the plate heat exchange module is connected to the refrigerant input pipeline, and the outlet of the plate heat exchange module is connected to the refrigerant output pipeline.

6. The system according to claim 4 or 5, characterized in that The plate heat exchange module includes a high-pressure boiler water channel and a synthesis gas preheating channel; the refrigerant input pipeline includes a high-pressure boiler water riser and a synthesis gas riser; the refrigerant output pipeline includes a high-pressure saturated steam riser and a preheated synthesis gas riser; 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 synthesis gas riser is connected to the preheated synthesis gas riser via the synthesis gas preheating channel, and the preheated synthesis gas riser is connected to the synthesis gas preheating outlet; And / or, a plurality of spoiler structures are provided on the side of the plate heat exchange module.

7. The system according to claim 6, characterized in that The inlet of the high-pressure boiler water channel is connected to a plurality of high-pressure boiler water rising pipes, which are converged and connected 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 a plurality of high-pressure saturated steam rising pipes, which are converged to a high-pressure saturated steam collecting ring, which is connected to the high-pressure saturated steam outlet; And / or, the inlet of the synthesis gas preheating channel is connected to multiple synthesis gas risers, the multiple synthesis gas risers are gathered and connected to the synthesis gas collecting annulus, and the synthesis gas collecting annulus is connected to the synthesis gas preheating inlet; the outlet of the synthesis gas preheating channel is connected to multiple preheating synthesis gas risers, the multiple preheating synthesis gas risers are gathered in the preheating synthesis gas collecting ring, and the preheating synthesis gas collecting ring is connected to the synthesis gas preheating outlet.

8. The system according to claim 1, wherein: The synthesis gas side inlet is connected to a gas distributor inside the cylinder; And / or, a gas guide plate is provided inside the cylinder of the insulation section close to the synthesis gas inlet.

9. The system according to claim 1, wherein: 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 with high-temperature resistant catalyst. The reaction gas passes through the upper end plate, the cavity and the lower end plate in sequence to produce an adiabatic reaction.

10. The system according to claim 2, wherein: The insulation section is provided with a radial reaction catalyst bed; the radial reaction catalyst bed is fixed to the cylinder through a bottom plate, and the bottom plate is connected to the top plate and the left and right side plates to form a cavity, and the cavity is used to fill the high-temperature resistant catalyst. The reaction gas enters the cavity through the left and right side plates to produce an adiabatic reaction.

11. The system according to claim 3, wherein: The insulation section is provided with a radial reaction catalyst bed; the radial reaction catalyst bed is fixed to the cylinder through a bottom plate, and the bottom plate is connected to the top plate and the left and right side plates to form a cavity, and the cavity is used to fill the high-temperature resistant catalyst. The reaction gas enters the cavity through the left and right side plates to produce an adiabatic reaction.

12. The system according to claim 10, wherein: The radial reaction catalyst bed is provided with a central tube III, which is coaxially arranged with the central tube I; a plurality of vents 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.

13. The system according to claim 11, wherein: The radial reaction catalyst bed is provided with a central tube III, which is coaxially arranged with the central tube II; a plurality of vents 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.

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