CN117945851A - Method and system for synthesizing methanol from carbon dioxide and hydrogen - Google Patents
Method and system for synthesizing methanol from carbon dioxide and hydrogen Download PDFInfo
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Abstract
The invention relates to a method for synthesizing methanol by carbon dioxide and hydrogen, which comprises the following steps: mixing carbon dioxide and hydrogen as reaction feed, performing a first reaction step, separating a first reaction discharge obtained after the reaction to obtain a first methanol product and a first gas phase material, performing a second reaction step on the first gas phase material, and separating a second reaction discharge obtained after the reaction to obtain a second methanol product and a second gas phase material; the first reaction discharging material exchanges heat with the reaction feeding materials of the first reaction step and the second reaction step before separation; or the second reaction discharging material is subjected to heat exchange with the reaction feeding materials of the first reaction step and the second reaction step before separation. The invention also relates to a system for synthesizing methanol from carbon dioxide and hydrogen.
Description
Technical Field
The invention belongs to the technical field of methanol synthesis, and particularly relates to a method and a system for synthesizing methanol from carbon dioxide and hydrogen.
Background
With the continuous development of society, greenhouse gases emitted by human beings are continuously increased, and the caused greenhouse effect is continuously increased; the increase in the content of carbon dioxide, which is a major greenhouse gas, in the atmosphere is one of the main causes of global warming. Carbon dioxide emission reduction is one of the major problems that are urgently needed to be faced and solved in countries around the world at present.
The carbon emission in China has huge scale and rapid growth speed, and the annual growth rate of the carbon emission in 2020 is 3.4 percent, which is higher than the average level of 2.4 percent of average growth in the past 10 years and the level of 0.5 percent of contemporaneous carbon emission growth. In the face of severe situations, china is greatly pushing the development of green low carbon, pushing the economic transformation of green low carbon and further shaping the future of low carbon. In 2020, china proposes a "two-carbon" target, namely carbon dioxide emission strives to reach a peak before 2030, and strives to achieve carbon neutralization before 2060. The carbon peak and the carbon neutralization become one of important strategies for the development of China.
With the development of the 'dual carbon' target, chemical utilization of carbon dioxide is attracting attention in the industry, and many chemical enterprises are accelerating to develop new technologies and promote recycling of carbon dioxide. For example, the carbon dioxide is used as raw material to produce high molecular materials such as urea, salicylic acid, methanol, polycarbonate and the like, clean fuel and the like. Among them, the hydroconversion of carbon dioxide is generally regarded as the most important carbon dioxide emission reduction method, which is beneficial to sustainable development of energy and environment. The carbon dioxide hydro-conversion not only can reduce the content of carbon dioxide in the atmosphere, but also can obtain fuel and valuable chemical products. Carbon dioxide is an inexpensive, safe, renewable carbon source, a basic feedstock for carbon-chemical industry, and can be used to produce organic compounds, materials, and carbohydrates. However, carbon dioxide has not been widely used in industry, and is limited mainly by the thermodynamic stability of carbon dioxide. The Nobel chemical prize, the well-known organic chemist, george, OLas proposed that the use of carbon dioxide and "renewable" hydrogen to produce methanol could be one solution to the energy shortage problem. The Nobel physics prize card Luolu is disclosed and suggested for many times more than ya to replace the existing carbon capture and sealing of the wind by adopting a mode of preparing methanol by carbon dioxide, so that the emission reduction is realized and the raw material is provided for industry.
Two routes, namely a direct method and an indirect method, exist mainly for preparing methanol by hydrogenation of carbon dioxide. The direct method is to directly hydrogenate carbon dioxide to prepare methanol, and the method is limited by thermodynamic equilibrium, the equilibrium conversion rate of the carbon dioxide is 20% -30%, and the equilibrium yield of the methanol is less than or equal to 20%, so that the method has the advantages of simple process flow and mild reaction conditions; the indirect method is that carbon dioxide is firstly converted into carbon monoxide through reverse water gas, and then the carbon monoxide, the carbon dioxide and hydrogen are synthesized into methanol, the route can break balance limit, the carbon dioxide balance conversion rate is more than or equal to 45%, and the methanol balance yield is more than or equal to 40%.
CN101386564B describes a process for synthesizing methanol from hydrogen and carbon dioxide, in which two identical reactors are connected in series, hydrogen and carbon dioxide are directly synthesized into methanol by copper-based catalyst, in the first reactor, hydrogen and carbon dioxide react under the action of copper-based catalyst to obtain products such as methanol, water and carbon monoxide, the first reaction product is condensed, gas-liquid separated, liquid phase stream containing methanol and water is separated as product, gas phase stream containing carbon monoxide, hydrogen and carbon dioxide is fed into the second reactor, continuous reaction is carried out under the action of copper-based catalyst to obtain products such as methanol and water, the second reaction product is condensed, gas-liquid separated, liquid phase stream containing methanol and water is separated as product, gas phase stream containing carbon monoxide, hydrogen and carbon dioxide is returned to the first reactor, and two sets of reaction systems are identical. Document "Carbon Dioxide Hydrogenation To Form Methanol via a Reverse-Water-Gas-Shift Reaction"(Ind.Eng.Chem.Res.1999,38,1808-1802) describes a method for preparing methanol by hydrogenation of carbon dioxide, which adopts an indirect method to produce methanol and mainly comprises two isothermal reactors, wherein in a first isothermal reactor, carbon dioxide is subjected to reverse water gas shift reaction to generate carbon monoxide, a part of reaction products are recycled to the first reactor after being dehydrated by a separator, and the other part of reaction products are removed from a second isothermal reactor to synthesize methanol; after the second reaction product is subjected to gas-liquid separation, the liquid-phase crude methanol product is further refined in a subsequent rectifying tower, and unreacted gas is returned to the second reactor for recycling. CN113045383a describes a device and process for preparing methanol by hydrogenation of carbon dioxide, the method includes at least three stages of methanol preparation units connected in series, each stage of methanol preparation unit includes a preheater, a methanol synthesis tower, a methanol water cooler and a methanol separator, the raw material mixture gas enters the methanol synthesis tower to react after preheating, the reaction product enters the methanol separator after heat exchange and cooling, the methanol water cooler is cooled, the gas phase discharge of the methanol separator enters the preheater of the next stage of methanol preparation unit, and the preparation process of the second stage and the third stage is continuously completed by the same process flow of the first stage of methanol preparation unit, so as to obtain the methanol aquatic product. In the prior art, the direct methanol synthesis reaction by carbon dioxide hydrogenation has the problems of large gas circulation amount and insufficient heat utilization.
Disclosure of Invention
The invention provides a method and a system for synthesizing methanol from carbon dioxide and hydrogen. The new method for synthesizing the methanol has the characteristics of small circulation quantity of the reaction gas and good heat utilization effect.
To this end, a first aspect of the present invention provides a process for the synthesis of methanol from carbon dioxide and hydrogen comprising: mixing carbon dioxide and hydrogen as reaction feed, performing a first reaction step, separating a first reaction discharge obtained after the reaction to obtain a first methanol product and a first gas phase material, performing a second reaction step on the first gas phase material, and separating a second reaction discharge obtained after the reaction to obtain a second methanol product and a second gas phase material; the first reaction discharging material is subjected to heat exchange with the reaction feeding materials of the first reaction step and the second reaction step before separation.
In some embodiments of the invention, the second reaction output is heat exchanged with the reaction feeds of the first and second reaction steps, respectively, prior to separation.
In some embodiments of the invention, the first and second reaction steps are adiabatic or isothermal reactions.
In some embodiments of the invention, the first reaction step and the second reaction step are different reactions.
In some embodiments of the invention, the first reaction step is an adiabatic reaction and the second reaction step is an isothermal reaction.
In some embodiments of the invention, the reaction pressure of the first reaction step is from 5.0 to 9.0MPaG.
In some embodiments of the invention, the second vapor phase material is returned to the first reaction step as recycle gas.
In some embodiments of the invention, a portion of the second vapor phase material is returned to the first reaction step as recycle gas.
In some embodiments of the invention, the second gas phase material comprises 96% or more by volume of the recycle gas.
In some embodiments of the invention, the mass ratio of the second gaseous material to the carbon dioxide feed as recycle gas is from 1.5 to 3, preferably from 1.8 to 2.7.
In some embodiments of the invention, another portion of the second vapor phase material is discharged as purge gas.
In some embodiments of the invention, the first reaction vent is split into two first reaction vents prior to separation; the first strand of the first reaction discharging material exchanges heat with the first reaction feeding material of the first reaction step, and the second strand of the first reaction discharging material exchanges heat with the second reaction feeding material of the second reaction step.
In some embodiments of the invention, the ratio of the mass flow rate of the first stream of said first reaction output to the total mass flow rate of the first reaction output is from 0.25 to 0.75, preferably from 0.3 to 0.7.
In some embodiments of the invention, the second reaction vent is split into two second reaction vents prior to separation; the first strand of the second reaction discharging material exchanges heat with the second reaction feeding material of the second reaction step, and the second strand of the second reaction discharging material exchanges heat with the first reaction feeding material of the first reaction step.
In some embodiments of the invention, the ratio of the mass flow rate of the first stream of said second reaction output to the total mass flow rate of the second reaction output is from 0.25 to 0.75, preferably from 0.3 to 0.7.
In some embodiments of the invention, the molar ratio of hydrogen to carbon dioxide in the reaction feed is 3 to 3.5, for example 3.
In some embodiments of the invention, the method comprises the specific steps of:
S1: mixing carbon dioxide and hydrogen as reaction feed, and dividing the reaction feed into two parts by an adiabatic reaction step; the first strand of adiabatic reaction discharging material exchanges heat with the adiabatic reaction feeding material in the adiabatic reaction step, and the second strand of adiabatic reaction discharging material exchanges heat with the isothermal reaction feeding material in the isothermal reaction step;
S2: the first strand of adiabatic reaction discharge material and the second strand of adiabatic reaction discharge material are mixed after heat exchange, and then cooled and separated to obtain an adiabatic methanol product and an adiabatic gas phase material, wherein the adiabatic gas phase material is used as a reaction feed of an isothermal reaction step and subjected to the isothermal reaction step;
S3: and cooling and separating the isothermal reaction discharge to obtain isothermal methanol products and isothermal gas-phase materials, and returning the isothermal gas-phase materials as circulating gas to the adiabatic reaction step.
In some embodiments of the invention, the method comprises the specific steps of:
S1: mixing carbon dioxide and hydrogen as reaction feed, performing isothermal reaction, cooling and separating isothermal reaction discharge obtained after the reaction to obtain isothermal methanol product and isothermal gas phase material;
S2: the isothermal gas phase material is used as a reaction feed of the adiabatic reaction step, and the adiabatic reaction discharge obtained after the reaction is divided into two parts; the first strand of adiabatic reaction discharging material exchanges heat with the adiabatic reaction feeding material in the adiabatic reaction step, and the second strand of adiabatic reaction discharging material exchanges heat with the isothermal reaction feeding material in the isothermal reaction step;
s3: and the first strand of adiabatic reaction discharge and the second strand of adiabatic reaction discharge are mixed after heat exchange, and then cooled and separated to obtain an adiabatic methanol product and an adiabatic gas phase material, and the adiabatic gas phase material is used as recycle gas to return to the isothermal reaction step.
In some embodiments of the invention, the adiabatic reaction step has a feed temperature of 220 to 260 ℃.
In some embodiments of the invention, the feed temperature of the isothermal reaction step is 220-290 ℃.
In some embodiments of the invention, the catalysts employed in the adiabatic reaction step and isothermal reaction step include methanol synthesis catalysts that use hydrogen and carbon dioxide as reaction raw materials.
In some embodiments of the present invention, copper-based catalysts are used in the adiabatic reaction step and isothermal reaction step, but are not limited thereto.
In some embodiments of the present invention, copper-based catalysts containing copper zinc aluminum are used in the adiabatic reaction step and isothermal reaction step, but are not limited thereto.
In a second aspect, the invention provides a system for synthesizing methanol from carbon dioxide and hydrogen, comprising: the device comprises an adiabatic reactor and an isothermal reactor which are connected in a communicated manner, wherein the adiabatic reactor is connected with a first discharging pipeline and a second discharging pipeline in a communicated manner, and one ends of the first discharging pipeline and the second discharging pipeline, which are far away from the adiabatic reactor, are respectively connected with an adiabatic reaction discharging mixed pipeline in a communicated manner; an adiabatic reaction second heat exchanger is arranged between the first discharging pipeline and the feeding pipeline of the adiabatic reactor.
In some embodiments of the invention, an isothermal reaction second heat exchanger is provided between the second discharge line and the feed line to the isothermal reactor.
In some embodiments of the invention, the adiabatic reactor is connected in communication with the isothermal reactor through a feed line to the isothermal reactor.
In some embodiments of the invention, the isothermal reactor is in communication with the adiabatic reactor via a feed line to the adiabatic reactor
In some embodiments of the invention, the system further comprises; the adiabatic reactor is connected with the adiabatic reaction gas-liquid separation tank through an adiabatic reaction discharging mixed pipeline.
In some embodiments of the invention, the isothermal reactor is connected in communication with an isothermal reaction gas-liquid separation tank via an isothermal reaction take off line.
In some embodiments of the invention, the adiabatic reaction gas-liquid separation tank is connected in communication with the isothermal reactor through a feed line of the isothermal reactor, and the isothermal reaction gas-liquid separation tank is connected in communication with a feed line of the adiabatic reactor through a recycle gas line.
In some embodiments of the invention, the isothermal reaction gas-liquid separation tank is in communication with the adiabatic reactor via a feed line of the adiabatic reactor, and the adiabatic reaction gas-liquid separation tank is in communication with the feed line of the isothermal reactor via a recycle gas line.
In some embodiments of the invention, the adiabatic reaction discharge mixing line is provided with an adiabatic reaction cooler.
In some embodiments of the invention, an adiabatic reaction first heat exchanger is disposed between the adiabatic reaction output mixing line and the feed line to the adiabatic reactor.
In some embodiments of the invention, an isothermal reaction cooler is disposed on the isothermal reaction discharge line.
In some embodiments of the invention, an isothermal reaction first heat exchanger is disposed between the isothermal reaction discharge line and the feed line to the isothermal reactor.
In some embodiments of the invention, a recycle compressor is provided on the recycle gas line.
In some embodiments of the invention, the adiabatic reactor is an axial or radial adiabatic fixed bed reactor.
In some embodiments of the invention, the isothermal reactor is an isothermal shell-and-tube fixed bed reactor.
The technical effects are as follows:
(1) According to the invention, the carbon dioxide and the hydrogen are directly reacted to generate the methanol by adopting a combined reaction mode of adiabatic reaction and isothermal reaction, and the reaction is carried out by adopting the adiabatic reactor and the isothermal reactor, so that the gas circulation amount of a reaction system is greatly reduced.
(2) According to the invention, by adopting an adiabatic reaction scheme, heat generated by an adiabatic reaction is respectively used for heating the temperature of the material at the inlet of the adiabatic reactor and the isothermal reactor to a specified temperature, so that the defect that external heating equipment and energy are usually required to be introduced for heating the material at the inlet of the reactor to the specified temperature is avoided, the investment of a device is reduced, the comprehensive heat utilization effect and the environmental protection level of a system are improved, and a better technical effect is obtained.
Drawings
FIG. 1 is a schematic diagram of the process flow of the method for synthesizing methanol from carbon dioxide and hydrogen according to the invention;
FIG. 2 is a schematic process flow diagram of the method for synthesizing methanol from carbon dioxide and hydrogen according to the invention, which differs from FIG. 1 in the reaction sequence of the adiabatic reactor and the isothermal reactor.
Icon: 1-carbon dioxide raw material, 2-hydrogen raw material, 3-adiabatic reaction feeding, 4-first adiabatic reaction discharging, 5-second adiabatic reaction discharging, 6-adiabatic methanol raw material, 7-adiabatic gas phase raw material, 8-isothermal reaction feeding, 9-isothermal reaction discharging, 10-isothermal methanol raw material, 11-isothermal gas phase raw material, 12-recycle gas, 13-purge gas, R1-adiabatic reactor, R2-isothermal reactor, E1-adiabatic reaction first heat exchanger, E2-adiabatic reaction second heat exchanger, E3-adiabatic reaction cooler, E4-isothermal reaction first heat exchanger, E5-isothermal reaction second heat exchanger, E6-isothermal reaction cooler, V1-adiabatic reaction gas-liquid separation tank, V2-isothermal reaction gas-liquid separation tank and K1-recycle compressor.
Detailed Description
In order that the invention may be more readily understood, the invention will be further described in detail with reference to the following examples, which are given by way of illustration only and are not limiting in scope of application. The starting materials or components used in the present invention may be prepared by commercial or conventional methods unless specifically indicated.
The carbon dioxide used in the invention is commercial steel cylinder gas or high-purity carbon dioxide gas from a factory, and the hydrogen is commercial steel cylinder gas or high-purity hydrogen from the factory.
The flow descriptions and examples are described with reference to the process flow shown in fig. 1:
According to the flow shown in FIG. 1, a carbon dioxide raw material 1 and a hydrogen raw material 2 are mixed and then sequentially enter an adiabatic reaction first heat exchanger E1 and an adiabatic reaction second heat exchanger E2, an adiabatic reaction feeding material 3 subjected to heat exchange and temperature rise enters an adiabatic reactor R1, and methanol is generated under the action of a catalyst; the adiabatic reaction discharge is divided into two parts, wherein a first part of adiabatic reaction discharge 4 enters an adiabatic reaction second heat exchanger E2 to heat the adiabatic reaction feed 3 to a specified temperature, and a second part of adiabatic reaction discharge 5 enters an isothermal reaction second heat exchanger E5 to heat the isothermal reaction feed 8 to the specified temperature; the first strand of adiabatic reaction discharging material 4 after heat exchange and cooling is mixed with the second strand of adiabatic reaction discharging material 5, and enters an adiabatic reaction gas-liquid separation tank V1 for gas-liquid separation after being subjected to heat exchange and cooling by an adiabatic reaction first heat exchanger E1 and an adiabatic reaction cooler E3 in sequence; the method comprises the steps that an adiabatic methanol material 6 is obtained at the bottom of an adiabatic reaction gas-liquid separation tank V1, an adiabatic gas-phase material 7 is obtained at the top of the tank, and sequentially enters an isothermal reaction first heat exchanger E4 and an isothermal reaction second heat exchanger E5, isothermal reaction feeding 8 subjected to heat exchange and temperature rise enters an isothermal reactor R2, and methanol is generated under the action of a catalyst; the isothermal reaction discharging material 9 is subjected to heat exchange and temperature reduction through an isothermal reaction first heat exchanger E4, cooled by an isothermal reaction cooler E6 and then enters an isothermal reaction gas-liquid separation tank V2 for gas-liquid separation; isothermal methanol material 10 is obtained at the bottom of isothermal reaction gas-liquid separation tank V2, isothermal gas phase material 11 is obtained at the top of the tank, most of isothermal gas phase material 11 is taken as circulating gas 12, pressurized by circulating compressor K1 and returned to adiabatic reactor R1, and the other part is taken as purge gas 13 to be discharged.
Example 1
As shown in FIG. 1, the carbon dioxide feed rate was 500mol/h, the hydrogen feed rate was 1500mol/h, the feed temperature in the adiabatic reaction step was 220℃and the reaction pressure was 5.0MPaG, the feed temperature in the isothermal reaction step was 220℃and both the adiabatic reactor and the isothermal reactor were charged with copper-based catalyst (specific composition copper content 50%, zinc content 40% and aluminum content 10%). The ratio of the mass flow of the first adiabatic reaction discharge to the total mass flow of the adiabatic reaction discharge is 0.75, 97% of isothermal gas phase materials obtained by heat exchange, cooling and separation of isothermal reaction discharge are returned to the adiabatic reactor as circulating gas, the circulating ratio is 2.2 (the ratio of the mass flow of the circulating gas to the mass flow of carbon dioxide as a raw material is the same below), the methanol yield is 90.6% (relative to the carbon dioxide as a raw material, the same below), and the heat exchange amount of each kilogram of raw material carbon dioxide is 3393kJ (the sum of the heat exchange amounts of the heat exchangers E1, E2, E4 and E5 is the same below).
Example 2
As shown in FIG. 1, the carbon dioxide feed rate was 500mol/h, the hydrogen feed rate was 1500mol/h, the feed temperature in the adiabatic reaction step was 240℃and the reaction pressure was 7.0MPaG, the feed temperature in the isothermal reaction step was 250℃and both the adiabatic reactor and the isothermal reactor were charged with copper-based catalyst (specific composition copper content 60%, zinc content 20% and aluminum content 20%). The ratio of the mass flow of the first adiabatic reaction discharge to the total mass flow of the adiabatic reaction discharge is 0.6, 97% of the gas phase materials obtained after heat exchange, cooling and separation of the isothermal reaction discharge are returned to the adiabatic reactor as circulating gas, the circulating ratio is 1.8, the methanol yield is 92.2%, and the heat exchange amount of the treated carbon dioxide per kilogram of raw material is 3258kJ.
Example 3
As shown in FIG. 1, the carbon dioxide feed rate was 500mol/h, the hydrogen feed rate was 1500mol/h, the feed temperature in the adiabatic reaction step was 260℃and the reaction pressure was 6.0MPaG, the feed temperature in the isothermal reaction step was 290℃and both the adiabatic reactor and the isothermal reactor were charged with copper-based catalyst (specific composition copper content 70%, zinc content 10% and aluminum content 20%). The ratio of the mass flow of the first adiabatic reaction discharge to the total mass flow of the adiabatic reaction discharge is 0.25, 98% of the gas phase material obtained by heat exchange, cooling and separation of the isothermal reaction discharge is returned to the adiabatic reactor as circulating gas, the circulating ratio is 2.1, the methanol yield is 93.9%, and the heat exchange amount of the treated carbon dioxide per kilogram of raw material is 4125kJ.
Example 4
As shown in FIG. 1, the carbon dioxide feed rate was 500mol/h, the hydrogen feed rate was 1500mol/h, the feed temperature in the adiabatic reaction step was 230℃and the reaction pressure was 9.0MPaG, the feed temperature in the isothermal reaction step was 270℃and both the adiabatic reactor and the isothermal reactor were charged with copper-based catalyst (specific composition copper content: 30%, zinc content: 50% and aluminum content: 20%). The ratio of the mass flow of the first adiabatic reaction discharge to the total mass flow of the adiabatic reaction discharge is 0.4, and 98.5% of the gas phase material obtained by heat exchange, cooling and separation of the isothermal reaction discharge is returned to the adiabatic reactor as circulating gas. The recycle ratio was 2.2, the methanol yield was 95.1% and the heat exchange capacity per kg of carbon dioxide of the feed was 3734kJ.
Example 5
As shown in FIG. 1, the carbon dioxide feed rate was 500mol/h, the hydrogen feed rate was 1500mol/h, the feed temperature in the adiabatic reaction step was 250℃and the reaction pressure was 8.0MPaG, the feed temperature in the isothermal reaction step was 260℃and the isothermal reactor and the isothermal reactor were filled with copper-based catalyst (specific composition copper content 40%, zinc content 30% and aluminum content 30%). The ratio of the mass flow of the first adiabatic reaction discharge to the total mass flow of the adiabatic reaction discharge is 0.5, 99% of the gas phase materials obtained after heat exchange, cooling and separation of the isothermal reaction discharge are returned to the adiabatic reactor as circulating gas, the circulating ratio is 2.7, the methanol yield is 96.0%, and the heat exchange amount of each kilogram of raw material carbon dioxide is 4442kJ.
Comparative example 1
This comparative example is identical to the method and system employed in example 1, with the only difference that: the adiabatic reactor is replaced by an isothermal reactor, the heat exchange amount of the carbon dioxide per kilogram of raw material is 3002kJ (the sum of the heat exchange amounts of the heat exchangers E1 and E4), the heat exchange amount 391kJ of the reaction feed is required to be provided externally (the heat exchange amount of the heat exchangers E2 and E5 is compensated), and the external heat supply accounts for 11.5% of the total heat of the heat exchangers E1, E2, E4 and E5.
Comparative example 2
This comparative example is identical to the method and system employed in example 1, with the only difference that: with only a single isothermal reactor, and with the same methanol yield as in example 1 maintained, the recycle ratio was 5.0, the heat exchange capacity for treating carbon dioxide per kg of feedstock was 3051kJ (heat exchange capacity for heat exchanger E4), 390kJ of reactor feed heat was provided externally (heat exchange capacity for offset heat exchanger E5), and the external heat supply was 11.3% of the total heat of heat exchangers E4, E5.
It should be noted that the above-described embodiments are only for explaining the present invention and do not constitute any limitation of the present invention. The invention has been described with reference to exemplary embodiments, but it is understood that the words which have been used are words of description and illustration, rather than words of limitation. Modifications may be made to the invention as defined in the appended claims, and the invention may be modified without departing from the scope and spirit of the invention. Although the invention is described herein with reference to particular means, materials and embodiments, the invention is not intended to be limited to the particulars disclosed herein, as the invention extends to all other means and applications which perform the same function.
Claims (10)
1. A process for synthesizing methanol from carbon dioxide and hydrogen comprising: mixing carbon dioxide and hydrogen as reaction feed, performing a first reaction step, separating a first reaction discharge obtained after the reaction to obtain a first methanol product and a first gas phase material, performing a second reaction step on the first gas phase material, and separating a second reaction discharge obtained after the reaction to obtain a second methanol product and a second gas phase material; the first reaction discharging material exchanges heat with the reaction feeding materials of the first reaction step and the second reaction step before separation;
Or the second reaction discharging material is subjected to heat exchange with the reaction feeding materials of the first reaction step and the second reaction step before separation.
2. The method according to claim 1, wherein the first reaction step and the second reaction step are adiabatic or isothermal reactions, preferably the first reaction step and the second reaction step are different reactions;
Preferably, the first reaction step is an adiabatic reaction, and the second reaction step is an isothermal reaction;
preferably, the reaction pressure of the first reaction step is 5.0-9.0MPaG.
3. The process according to claim 1 or 2, characterized in that the second gas phase material is returned as recycle gas to the first reaction step;
Preferably, a portion of the second gaseous material is returned to the first reaction step as recycle gas, preferably more than 96% by volume of the second gaseous material is used as recycle gas.
4. A process according to any one of claims 1 to 3, wherein the first reaction effluent is split into two first reaction effluents prior to separation; a first strand of the first reaction discharging material exchanges heat with a first reaction feeding material of a first reaction step, and a second strand of the first reaction discharging material exchanges heat with a second reaction feeding material of a second reaction step; preferably, the ratio of the mass flow rate of the first reaction output to the total mass flow rate of the first reaction output is from 0.25 to 0.75, preferably from 0.3 to 0.7;
Or, the second reaction output is split into two second reaction outputs prior to separation; the first strand of the second reaction discharging material exchanges heat with the second reaction feeding material of the second reaction step, and the second strand of the second reaction discharging material exchanges heat with the first reaction feeding material of the first reaction step; preferably, the ratio of the mass flow rate of the first stream of said second reaction output to the total mass flow rate of the second reaction output is from 0.25 to 0.75, preferably from 0.3 to 0.7.
5. The process of any one of claims 1 to 4 wherein the molar ratio of hydrogen to carbon dioxide in the reaction feed is from 3 to 3.5.
6. The method according to any one of claims 1-5, characterized by the specific steps of:
S1: mixing carbon dioxide and hydrogen as reaction feed, and dividing the reaction feed into two parts by an adiabatic reaction step; the first strand of adiabatic reaction discharging material exchanges heat with the adiabatic reaction feeding material in the adiabatic reaction step, and the second strand of adiabatic reaction discharging material exchanges heat with the isothermal reaction feeding material in the isothermal reaction step;
S2: the first strand of adiabatic reaction discharge material and the second strand of adiabatic reaction discharge material are mixed after heat exchange, and then cooled and separated to obtain an adiabatic methanol product and an adiabatic gas phase material, wherein the adiabatic gas phase material is used as a reaction feed of an isothermal reaction step and subjected to the isothermal reaction step;
S3: the isothermal reaction discharge is cooled and separated to obtain isothermal methanol products and isothermal gas phase materials, and the isothermal gas phase materials are returned to the adiabatic reaction step as circulating gas;
or, S1: mixing carbon dioxide and hydrogen as reaction feed, performing isothermal reaction, cooling and separating isothermal reaction discharge obtained after the reaction to obtain isothermal methanol product and isothermal gas phase material;
S2: the isothermal gas phase material is used as a reaction feed of the adiabatic reaction step, and the adiabatic reaction discharge obtained after the reaction is divided into two parts; the first strand of adiabatic reaction discharging material exchanges heat with the adiabatic reaction feeding material in the adiabatic reaction step, and the second strand of adiabatic reaction discharging material exchanges heat with the isothermal reaction feeding material in the isothermal reaction step;
s3: and the first strand of adiabatic reaction discharge and the second strand of adiabatic reaction discharge are mixed after heat exchange, and then cooled and separated to obtain an adiabatic methanol product and an adiabatic gas phase material, and the adiabatic gas phase material is used as recycle gas to return to the isothermal reaction step.
7. The process according to any one of claims 1 to 5, wherein the adiabatic reaction step has a feed temperature of 220 to 260 ℃; and/or, the feeding temperature of the isothermal reaction step is 220-290 ℃;
Preferably, copper-based catalysts are used in the adiabatic reaction step and the isothermal reaction step.
8. A system for synthesizing methanol from carbon dioxide and hydrogen, comprising: the device comprises an adiabatic reactor and an isothermal reactor which are connected in a communicated manner, wherein the adiabatic reactor is connected with a first discharging pipeline and a second discharging pipeline in a communicated manner, and one ends of the first discharging pipeline and the second discharging pipeline, which are far away from the adiabatic reactor, are respectively connected with an adiabatic reaction discharging mixed pipeline in a communicated manner; an adiabatic reaction second heat exchanger is arranged between the first discharging pipeline and the feeding pipeline of the adiabatic reactor; and/or an isothermal reaction second heat exchanger is arranged between the second discharging pipeline and the feeding pipeline of the isothermal reactor;
Preferably, the adiabatic reactor is connected in communication with the isothermal reactor through a feed line of the isothermal reactor; or the isothermal reactor is communicated with the adiabatic reactor through a feeding pipeline of the adiabatic reactor.
9. The system of claim 8, wherein the system further comprises; the adiabatic reactor is connected with the adiabatic reaction gas-liquid separation tank through an adiabatic reaction discharging mixed pipeline; and/or the isothermal reactor is connected with the isothermal reaction gas-liquid separation tank through an isothermal reaction discharge pipeline;
Preferably, the adiabatic reaction gas-liquid separation tank is connected with the isothermal reactor through a feed pipeline of the isothermal reactor, and the isothermal reaction gas-liquid separation tank is connected with a feed pipeline of the adiabatic reactor through a circulating gas pipeline; or the isothermal reaction gas-liquid separation tank is communicated and connected with the adiabatic reactor through a feed pipeline of the adiabatic reactor, and the adiabatic reaction gas-liquid separation tank is communicated and connected with the feed pipeline of the isothermal reactor through a circulating gas pipeline;
preferably, an adiabatic reaction cooler is arranged on the adiabatic reaction discharge mixing pipeline, and/or an adiabatic reaction first heat exchanger is arranged between the adiabatic reaction discharge mixing pipeline and the feeding pipeline of the adiabatic reactor; and/or an isothermal reaction cooler is arranged on the isothermal reaction discharging pipeline, and/or an isothermal reaction first heat exchanger is arranged between the isothermal reaction discharging pipeline and a feeding pipeline of the isothermal reactor;
Preferably, a recycle compressor is provided on the recycle gas line.
10. The system of claim 8 or 9, wherein the adiabatic reactor is an axial or radial adiabatic fixed bed reactor; and/or the isothermal reactor is an isothermal shell-and-tube fixed bed reactor.
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