CN115253941A - Device and method for improving conversion rate of methanol prepared from carbon dioxide - Google Patents

Device and method for improving conversion rate of methanol prepared from carbon dioxide Download PDF

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Publication number
CN115253941A
CN115253941A CN202210286503.4A CN202210286503A CN115253941A CN 115253941 A CN115253941 A CN 115253941A CN 202210286503 A CN202210286503 A CN 202210286503A CN 115253941 A CN115253941 A CN 115253941A
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reactor
gas
methanol
carbon dioxide
outlet
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顾英
陈金锋
耿淑远
刘泽远
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Sinopec Engineering Group Co Ltd
Sinopec Ningbo Engineering Co Ltd
Sinopec Ningbo Technology Research Institute
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Sinopec Engineering Group Co Ltd
Sinopec Ningbo Engineering Co Ltd
Sinopec Ningbo Technology Research Institute
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Priority to CN202210286503.4A priority Critical patent/CN115253941A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/0006—Controlling or regulating processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J4/00—Feed or outlet devices; Feed or outlet control devices
    • B01J4/001—Feed or outlet devices as such, e.g. feeding tubes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J4/00—Feed or outlet devices; Feed or outlet control devices
    • B01J4/008—Feed or outlet control devices
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
    • C07C29/15—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively
    • C07C29/151—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases
    • C07C29/152—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases characterised by the reactor used
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2204/00—Aspects relating to feed or outlet devices; Regulating devices for feed or outlet devices
    • B01J2204/005—Aspects relating to feed or outlet devices; Regulating devices for feed or outlet devices the outlet side being of particular interest
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2204/00—Aspects relating to feed or outlet devices; Regulating devices for feed or outlet devices
    • B01J2204/007—Aspects relating to the heat-exchange of the feed or outlet devices
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00002—Chemical plants
    • B01J2219/00004—Scale aspects
    • B01J2219/00006—Large-scale industrial plants

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  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

The invention relates to a device and a method for improving conversion rate of methanol prepared from carbon dioxide. The invention adopts a two-stage reactor series flow to produce steam with different specifications, a cooling and liquid separating device is added at the outlet of the first reactor to reduce the alcohol partial pressure and the water partial pressure at the inlet of the second reactor, which is beneficial to improving the methanol conversion rate of the second reactor, carbon dioxide and hydrogen are added into the interstage liquid separating device in a step reaction, which is beneficial to improving the conversion rate of the whole device to the maximum, unreacted gas in the reactor is separated and enters the synthesis reactor for recycling, which is beneficial to improving the total carbon conversion rate of carbon dioxide, fresh synthesis gas is introduced into the second reactor through a bypass, and when the catalyst activity of the first reactor is reduced in the later stage of the reaction, the reacted gas is transferred to the second reactor, thereby ensuring the conversion rate and the yield of the whole device.

Description

Device and method for improving conversion rate of methanol prepared from carbon dioxide
Technical Field
The invention relates to the technical field of chemical production, in particular to a device and a method for improving conversion rate of methanol prepared from carbon dioxide.
Background
Carbon dioxide is a common greenhouse gas, and in the industrial field of China, particularly industries depending on coal resources, a large amount of CO is generated every year2And (4) generating.
The concept of 'methanol economy' is proposed in 2005 by george, andrew and Euler of Nobel prize-winning chemists, and the methanol economy can be used as a solution for solving the problem of later energy in the oil and gas era. It is considered that hydrogen is produced from renewable energy sources, and carbon dioxide is recycled to synthesize methanol, which can be directly used as fuel, or synthesized into fuel or chemicals through processes of methanol-to-gasoline (MTG), methanol-to-aromatics (MTA), methanol-to-olefin (MTO), and methanol-to-propylene (MTP), and is a promising technology.
At present, a plurality of scientific research institutions and colleges in China collate CO2Catalyst for preparing methanol and CO2The research and development of the methanol preparation technology tend to be mature, and the technology plays a positive promoting role in national carbon peak reaching and carbon neutralization targets. Compared with the preparation of methanol from carbon monoxide, the preparation of methanol from carbon dioxide mainly depends on the use of a catalyst and the control of reaction temperature.
The prior catalyst preparation technology can realize the oxidation of dioxideThe industrial demand of carbon to methanol. For example, patent application publication No. CN110975938A discloses a catalyst for preparing methanol by carbon dioxide hydrogenation and a preparation method thereof, wherein a metal organic framework material MIL-101 (Cr) -NH with modified framework is adopted2As a carrier, the shape selection selectivity of the pore channel structure of MIL-101 (Cr) is utilized to improve the selectivity of methanol; meanwhile, the MIL-101 (Cr) has high specific surface area to CO2Has high adsorption capacity and effectively improves CO2Catalytic selectivity of (2). The Chinese patent with the publication number of CN110833843B discloses a catalyst for synthesizing methanol by carbon dioxide hydrogenation, which takes molybdenum disulfide as a main component of the catalyst for synthesizing methanol by carbon dioxide hydrogenation, and the catalyst for preparing methanol by carbon dioxide hydrogenation has the characteristics of low price, simple and convenient operation, high carbon dioxide conversion rate, high methanol selectivity in products, good stability and the like.
The patent application with publication number CN105622344A discloses a process for preparing methanol from carbon dioxide, which adopts a single-stage reactor and has a hydrogen-to-carbon ratio (H)2/CO2) In the range of 2.0 to 3.0, adopting CO2Reverse steam shift, methanol synthesis reaction and gas recycling process. Application publication No. CN113045383A, using a single stage reactor, hydrogen to carbon ratio (H)2+CO)/(CO+CO2) Is 3.05 to 3.1, and the process introduces CO, thus approaching the conventional methanol manufacturing process. The existing process for preparing methanol from carbon dioxide mostly adopts a first-stage reactor and a cooling separation process, so that the total carbon conversion rate is low, the energy consumption of a device is high, the content of methanol in a product is low, the load of subsequent rectification is large, and the comprehensive energy consumption is high.
Disclosure of Invention
The first technical problem to be solved by the invention is to provide a device for improving the conversion rate of methanol prepared from carbon dioxide, which has high total carbon conversion rate and low total energy consumption of the device, aiming at the current situation of the prior art.
The second technical problem to be solved by the invention is to provide a method for improving the conversion rate of carbon dioxide to methanol, which has high total carbon conversion rate and low total energy consumption of the device, aiming at the current situation of the prior art.
The technical scheme adopted by the invention for solving at least one technical problem is as follows:
an apparatus for increasing conversion of carbon dioxide to methanol, comprising:
the first reactor is used for preparing methanol from carbon dioxide for reaction; the top of the first reactor is provided with an inlet for inputting raw material gas, and the bottom of the first reactor is provided with an outlet for outputting a first reaction product;
the second reactor is used for further reaction of methanol prepared from carbon dioxide; the top of the second reactor is provided with an inlet for inputting reaction raw materials, and the bottom of the second reactor is provided with an outlet for outputting a second reaction product;
the first gas-gas heat exchanger is connected to the outlet of the first reactor;
the first cooler is connected with the first outlet of the first gas-gas heat exchanger;
the first separator is connected with the downstream of the first cooler and is used for carrying out gas-liquid separation on the first reaction product output by the first reactor; the top outlet of the first separator is connected with the inlet of a first gas-gas heat exchanger, and the second outlet of the first gas-gas heat exchanger is connected with the inlet of a second reactor;
the second gas-gas heat exchanger is connected to the outlet of the second reactor;
the second cooler is connected with a third outlet of the second gas-gas heat exchanger; and
the second separator is connected with the downstream of the second cooler and is used for carrying out gas-liquid separation on a second reaction product output by the second reactor; and the top outlet of the second separator is connected with the inlet of a second gas-gas heat exchanger, and the fourth outlet of the second gas-gas heat exchanger is connected with the inlet of the first reactor.
Preferably, a feeding pipeline is connected to the inlet of the second gas-gas heat exchanger, the gas phase produced at the top of the second separator is input into the feeding pipeline as circulating gas through the first joint, and the fresh synthesis gas is input into the feeding pipeline through the second joint.
Preferably, a return line is connected between the second outlet of the first gas-gas heat exchanger and the inlet of the second reactor, a bypass line is connected between the feed line and the return line, and a valve for controlling the opening of the bypass line according to the temperature is arranged on the bypass line.
As can be seen from the following reaction scheme: the preparation of methanol from carbon dioxide is an exothermic reaction, the preparation of methanol from carbon dioxide consumes more hydrogen and generates more water than the traditional preparation of methanol from carbon monoxide, and one water is generated simultaneously when one part of methanol is generated.
CO2+3H2≒CH3OH+H2O
CO+2H2≒CH3OH
In the invention, part of fresh gas is directly introduced into the inlet of the second reactor, the inlet temperature of the second reactor is reduced, the partial pressure of carbon dioxide and hydrogen is improved, and the driving force of the inlet of the second reactor is favorably improved, thereby further improving the conversion rate of methanol in the second reactor.
Preferably, the connection of the bypass line to the feed line is between the first junction and the second junction.
Preferably, the input of the fresh synthesis gas is provided with a first compressor, and the input of the recycle gas is provided with a second compressor.
Preferably, the top of the first reactor is connected with a # 1 steam drum, the bottom of the second reactor is connected with a # 2 steam drum, and the # 1 steam drum and the # 2 steam drum are communicated with each other and provided with a pipeline for inputting boiler water.
A method for improving conversion rate of methanol prepared from carbon dioxide comprises the following steps:
reacting fresh synthesis gas at the high temperature of a first reactor in the presence of a catalyst to generate a first reaction product containing methanol, wherein the first reaction product contains a large amount of unreacted gas carbon dioxide and hydrogen;
cooling the first reaction product, performing first separation, and separating the first reaction product into a gas phase and a liquid phase in a first separator, wherein the liquid phase is methanol and water and enters a downstream rectification system, and the gas phase mainly comprises unreacted carbon dioxide and hydrogen and enters a second reactor for continuous reaction to obtain a second reaction product; the methanol concentration of the second reactant is greater than that of the first reaction product;
and (2) cooling the first reaction product, then carrying out first separation, forming a gas phase and a liquid phase in a first separator, wherein the content of methanol in the process gas is reduced from 2 to 6% (moL) to 1 to 2.5% (moL), the content of water is reduced from 2 to 6% (moL) to 0.5 to 2% (moL), the partial pressure of alcohol in the process gas at the inlet of a second reactor is reduced from 2 to 6% (moL) to 1 to 2.5% (moL), the partial pressure of water is reduced from 2 to 6% (moL) to 0.5 to 2% (moL), the reaction driving force in the second reactor is increased, unreacted carbon dioxide and hydrogen continue to react to generate a second reaction product containing methanol, and the carbon dioxide conversion rate and the methanol yield of the whole methanol synthesis system are increased.
The invention adopts two-stage methanol to synthesize CO of the methanol synthesis system2The conversion per pass is increased from 10 to 20 percent of the traditional conversion per pass to 15 to 35 percent, and the CO is pressurized and circulated by adopting unreacted process gas2The total conversion rate is increased from 10 to 20 percent of conversion per pass to 80 to 95 percent.
Preferably, the inlet temperature of the first reactor is 230-280 ℃ for generating high-grade steam; the outlet temperature of the first reactor is 250-300 ℃ and is used for preheating the inlet temperature of the second reactor.
Preferably, the reaction liquid at the outlet of the first reactor is cooled to 90-150 ℃ by the first gas heat exchanger and the first cooler, the liquid fraction is 5-15% by weight.
Preferably, the gas phase at the outlet of the first separator is preheated by a first gas-gas heat exchanger, and enters a second reactor after being preheated to 220-250 ℃. The outlet temperature of the second reactor is 230-280 ℃ and is used for preheating the inlet temperature of the first reactor.
Preferably, the gas phase at the outlet of the second separator is used as circulating gas after being subjected to pressure compensation by a second compressor, and enters the reaction system for continuous reaction, wherein the circulation ratio is 5-8.
Preferably, a return line is connected between the second outlet of the first gas-gas heat exchanger and the inlet of the second reactor, a bypass line is connected between the feed line and the return line, a valve for controlling the opening of the bypass line according to the temperature is arranged on the bypass line, and the opening of the valve is 0% -30% of the total amount of the fresh synthesis gas.
Preferably, the content of the alcohol at the inlet of the first reactor is 0.2 to 1% (moL); the alcohol content at the inlet of the second reactor is 1 to 2.5 percent (moL).
Preferably, the alcohol content at the outlet of the first reactor is 2 to 6% (moL); the alcohol content at the outlet of the second reactor is 3 to 7% (moL).
In the invention, the gas-gas heat exchanger is arranged between the first reactor and the second reactor, the high-temperature gas at the outlet of the first reactor is used for preheating the gas at the inlet of the second reactor, the high-temperature gas at the outlet of the second reactor is used for preheating the gas at the inlet of the first reactor, and the reaction heat is reasonably utilized.
Compared with the prior art, the invention has the advantages that: the invention adopts a two-stage reactor series flow, and simultaneously produces steam with different specifications, a cooling and liquid separating device is added at the outlet of a first reactor, so that the alcohol partial pressure and the water partial pressure at the inlet of a second reactor are reduced, and the improvement of the methanol conversion rate of the second reactor is facilitated.
Drawings
FIG. 1 is a process flow diagram of an embodiment of the present invention.
Detailed Description
The invention is described in further detail below with reference to the following examples of the drawings.
As shown in fig. 1, the apparatus for increasing the conversion rate of methanol from carbon dioxide in the present embodiment includes:
a first reactor 1 for preparing methanol from carbon dioxide; the top of the first reactor 1 is provided with an inlet for inputting raw material gas, and the bottom is provided with an outlet for outputting a first reaction product;
the second reactor 2 is used for preparing methanol from carbon dioxide for reaction; the top of the second reactor 2 is provided with an inlet for inputting reaction raw materials, and the bottom is provided with an outlet for outputting second reaction products;
a first gas-gas heat exchanger 10 connected to the outlet of the first reactor 1;
a first cooler 100 connected to a first outlet of the first gas-gas heat exchanger 10;
a first separator 01 connected to a downstream of the first cooler 100 for gas-liquid separation of the first reaction product output from the first reactor 1; the top outlet of the first separator 01 is connected with the inlet of the first gas-gas heat exchanger 10, and the second outlet of the first gas-gas heat exchanger 10 is connected with the inlet of the second reactor 2;
a second gas-gas heat exchanger 20 connected to the outlet of the second reactor 2;
the second cooler 200 is connected with a third outlet of the second gas-gas heat exchanger 20; and
a second separator 02 connected to a downstream of the second cooler 200 for gas-liquid separation of the second reaction product output from the second reactor 2; the top outlet of the second separator 02 is connected to the inlet of the second gas-gas heat exchanger 20, and the fourth outlet of the second gas-gas heat exchanger 20 is connected to the inlet of the first reactor 1.
In the above scheme, the inlet of the second gas-gas heat exchanger 20 is connected with a feeding line 201, the gas phase produced at the top of the second separator 02 is input into the feeding line 201 as the circulating gas through a first junction, and the fresh synthesis gas is input into the feeding line 201 through a second junction.
A return pipeline 101 is connected between the second outlet of the first gas-gas heat exchanger 10 and the inlet of the second reactor 2, a bypass line 003 is connected between the feeding pipeline 201 and the return pipeline 101, and a valve 031 for controlling the opening degree according to the temperature is arranged on the bypass line 003. The junction of bypass line 003 and feed line 201 is between the first junction and the second junction. The input of the fresh synthesis gas is provided with a first compressor 04 and the input of the recycle gas is provided with a second compressor 05.
This can be seen from the following equation: the method has the advantages that the heat release reaction is carried out in the process of preparing the methanol by the carbon dioxide, hydrogen consumption and water generation are more in the process of preparing the methanol by the carbon dioxide than those in the conventional method for preparing the methanol by the carbon monoxide, and one water is generated simultaneously when one water is generated.
CO2+3H2≒CH3OH+H2O
CO+2H2≒CH3OH
In this embodiment, a part of the fresh gas is directly introduced into the inlet of the second reactor 2, so as to reduce the inlet temperature of the second reactor 2, increase the partial pressure of carbon dioxide and hydrogen, and facilitate the improvement of the driving force of the inlet of the second reactor 2, thereby further improving the conversion rate of methanol in the second reactor 2.
In the embodiment, the top of the first reactor 1 is connected with a # 1 steam drum, the bottom of the second reactor 2 is connected with a # 2 steam drum, and the # 1 steam drum and the # 2 steam drum are communicated with each other and are provided with pipelines for inputting boiler water.
Taking a 20-million-ton scale process technology for preparing methanol from carbon dioxide as an example, the method for improving the conversion rate of preparing methanol from carbon dioxide in the embodiment includes the following steps:
CO2and hydrogen gas in a ratio of 33Pressurized to 8MpaG, and pressurized methanol plant recycle gas 444600Nm3After mixing, preheating to 240 ℃ through second gas heat exchange, entering a primary reactor, reacting in the presence of a catalyst, generating a methanol synthesis reaction and releasing heat:
CO2+3H2≒CH3OH+H2O
first order inversionReactor outlet temperature 280 ℃ and CH in the first reaction product3OH content 2.6% (moL) and water content 2.3% (moL). Cooling the first reaction product to 90 deg.C with a liquid fraction of 7% by weight in a first gas-gas heat exchanger, separating in a first separator into a gas phase and a liquid phase, the liquid phase comprising 35% (moL) methanol and 63% (moL) water, the gas phase comprising mainly unreacted 11% (moL) carbon dioxide and 86% (moL) hydrogen, and separating CH in the gas phase3The OH content is 1.8 percent (moL), the water content is 0.8 percent (moL), the gas phase at the outlet of the first separator is preheated by a first gas-gas heat exchanger, preheated to 220 ℃, enters a second reactor to continue to react, and a second reaction product is obtained; the outlet temperature of the second reactor is 250 ℃, and CH in the second reactant3OH content 3.2% (moL), water content 2.1% (moL), methanol concentration greater than the first reaction product;
the temperature of a reaction product at the outlet of the second reactor is 250 ℃, the reaction product enters a second gas-gas heat exchanger and a downstream cooler, a second reactant is cooled to 40 ℃ after the cooler, the reaction product enters a second separator, and the separated liquid phase contains 58 percent (moL) of methanol and 41 percent (moL) of water;
liquid phase products of the first-stage separator and the second-stage separator are mixed and then enter a downstream rectification system, the methanol content is 49% (moL), the per pass conversion rate of carbon dioxide of the whole methanol synthesis system is 25%, and the total conversion rate of carbon dioxide is 90%;
in this example, after the second reactant was cooled and separated, the unreacted process gas was circulated into the synthesis system at a circulation ratio of 6, the methanol content in the recycle gas was 0.38% (moL), and a small amount of inert gas was discharged as purge gas.
In this example, the fresh synthesis gas is provided with a bypass line directly entering the inlet of the second reactor, the bypass line is provided with a valve for controlling the opening of the second reactor according to the inlet temperature of the second reactor, when the inlet temperature of the second reactor is 220 ℃, the valve is in a closed state, and in order to ensure that the inlet temperature of the second reactor is stabilized at 220 ℃, the valve flux is about 10 percent of the total amount of the fresh synthesis gas when the inlet temperature of the second reactor is increased by 5 ℃ in operation.
In this embodiment, set up gas heat exchanger in the middle of first reactor and the second reactor, utilize to export high temperature gas to the first reactor and preheat second reactor entry gas, utilize second reactor export high temperature gas to preheat first reactor entry gas, first gas heat exchanger heat load ~38MW, second gas heat exchanger heat load ~22MW, the reaction heat has obtained rational utilization.

Claims (10)

1. The utility model provides an improve device of carbon dioxide system methyl alcohol conversion, its characterized in that includes:
the first reactor is used for preparing methanol from carbon dioxide for reaction; the top of the first reactor is provided with an inlet for inputting raw material gas, and the bottom of the first reactor is provided with an outlet for outputting a first reaction product;
the second reactor is used for preparing methanol from carbon dioxide for reaction; the top of the second reactor is provided with an inlet for inputting reaction raw materials, and the bottom of the second reactor is provided with an outlet for outputting a second reaction product;
the first gas-gas heat exchanger is connected to the outlet of the first reactor;
the first cooler is connected with the first outlet of the first gas-gas heat exchanger;
the first separator is connected with the downstream of the first cooler and is used for carrying out gas-liquid separation on the reaction liquid output by the first reactor; the top outlet of the first separator is connected with the inlet of a first gas-gas heat exchanger, and the second outlet of the first gas-gas heat exchanger is connected with the inlet of a second reactor;
the second gas-gas heat exchanger is connected to the outlet of the second reactor;
the second cooler is connected with a third outlet of the second gas-gas heat exchanger; and
the second separator is connected with the downstream of the second cooler and is used for carrying out gas-liquid separation on the reaction liquid output by the second reactor; and the top outlet of the second separator is connected with the inlet of a second gas-gas heat exchanger, and the fourth outlet of the second gas-gas heat exchanger is connected with the inlet of the first reactor.
2. The apparatus for increasing conversion rate of methanol from carbon dioxide according to claim 1, wherein: and a feeding pipeline is connected to an inlet of the second gas-gas heat exchanger, a gas phase produced at the top of the second separator is input into the feeding pipeline through a first joint as a circulating gas, and a fresh synthesis gas is input into the feeding pipeline through a second joint.
3. The apparatus for increasing conversion rate of methanol from carbon dioxide according to claim 2, wherein: a return pipeline is connected between the second outlet of the first gas-gas heat exchanger and the inlet of the second reactor, a bypass is connected between the feeding pipeline and the return pipeline, and a valve for controlling the opening of the bypass according to the temperature is arranged on the bypass.
4. The apparatus for increasing conversion rate of methanol from carbon dioxide according to claim 3, wherein: the junction of the bypass line and the feed line is between the first junction and the second junction.
5. The apparatus for increasing conversion rate of methanol from carbon dioxide according to claim 2, wherein: and a first compressor is arranged at the input part of the fresh synthesis gas, and a second compressor is arranged at the input part of the circulating gas.
6. The apparatus for increasing conversion rate of methanol from carbon dioxide according to any one of claims 1 to 4, wherein: the top of the first reactor is connected with a 1# steam drum, the bottom of the second reactor is connected with a 2# steam drum, and the 1# steam drum and the 2# steam drum are communicated with each other and are provided with pipelines for inputting boiler water.
7. A method for improving conversion rate of methanol prepared from carbon dioxide is characterized by comprising the following steps:
reacting fresh synthesis gas at the high temperature of a first reactor in the presence of a catalyst to generate a first reaction product containing methanol, wherein the first reaction product contains a large amount of unreacted gases of carbon dioxide and hydrogen;
cooling the first reaction product, performing first separation, and separating the first reaction product into a gas phase and a liquid phase in a first separator, wherein the liquid phase is methanol and water and enters a downstream rectification system, and the gas phase mainly comprises unreacted carbon dioxide and hydrogen and enters a second reactor to continuously react to obtain a second reaction product; the methanol concentration of the second reactant is greater than that of the first reaction product;
cooling the first reaction product, performing first separation, dividing the first reaction product into a gas phase and a liquid phase in a first separator, reducing the methanol content in the process gas from 2 to 6 mol to 1 to 2.5 mol, reducing the water content from 2 to 6 mol to 0.5 to 2 mol, reducing the alcohol partial pressure in the process gas at the inlet of a second reactor from 2 to 6 mol to 1 to 2.5 mol, reducing the water partial pressure from 2 to 6 mol to 0.5 to 2 mol, increasing the reaction driving force in the second reactor, and continuously reacting unreacted carbon dioxide and hydrogen to generate a second reaction product containing methanol, thereby improving the carbon dioxide conversion rate and the methanol yield of the whole methanol synthesis system.
8. The method for increasing the conversion rate of carbon dioxide to methanol according to claim 7, wherein: the reaction temperature in the first reactor is 230-280 ℃, and the first reactor is used for generating high-grade steam; the outlet temperature of the first reactor is 250-300 ℃ and is used for preheating the inlet temperature of the second reactor.
9. The method for increasing the conversion rate of carbon dioxide to methanol according to claim 7, wherein: cooling the reaction liquid at the outlet of the first reactor to 90-150 ℃ by the first gas-gas heat exchanger and the first cooler, wherein the liquid fraction is 5-15% by weight.
10. The method for increasing the conversion rate of carbon dioxide to methanol according to claim 7, wherein: and preheating the gas phase at the outlet of the first separator to 220-250 ℃ through a first gas-gas heat exchanger, and allowing the gas phase to enter a second reactor, wherein the outlet temperature of the second reactor is 230-280 ℃.
CN202210286503.4A 2022-03-23 2022-03-23 Device and method for improving conversion rate of methanol prepared from carbon dioxide Pending CN115253941A (en)

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Application Number Priority Date Filing Date Title
CN202210286503.4A CN115253941A (en) 2022-03-23 2022-03-23 Device and method for improving conversion rate of methanol prepared from carbon dioxide

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