阅读说明：本技术 一种甲烷氧化偶联反应产品气的分离方法 (Separation method of product gas of oxidative coupling reaction of methane ) 是由 孙丽丽 刘罡 赵百仁 盛在行 王振维 聂毅强 李少鹏 丁利伟 于 2019-03-27 设计创作，主要内容包括：本发明属于石油化工领域,具体涉及一种甲烷氧化偶联反应产品气的分离方法。所述甲烷氧化偶联反应产品气含有氢气、甲烷、CO、CO<Sub>2</Sub>、乙烯、乙烷、碳三及以上烃类,以及任选的乙炔、硫氧化物、氮氧化物；所述分离方法包括将产品气依次进行急冷降温、一次升压、胺洗、碱洗、二次升压、二次降温、精馏脱除轻组分、膨胀机制冷并与产品气换热、变压吸附分离甲烷及CO、碳二与碳三及更重组分分离、碳二组分精制。与现有技术相比,本发明的工艺流程简单,特别是减少了冷箱的数量,避免了复杂的换热网络,降低了能耗和设备投资。(The invention belongs to the field of petrochemical industry, and particularly relates to a separation method of a product gas of a methane oxidative coupling reaction. The product gas of the oxidative coupling reaction of methane contains hydrogen, methane, CO and CO 2 Ethylene, ethane, hydrocarbons of three and above carbons, and optionally acetylene, sulfur oxides, nitrogen oxides; the separation method comprises the steps of quenching and cooling the product gas, boosting pressure for the first time, washing with amine, washing with alkali, boosting pressure for the second time, cooling for the second time, rectifying to remove light components, refrigerating by an expander, exchanging heat with the product gas, separating methane and CO by pressure swing adsorption, separating carbon dioxide from carbon III and heavier components, and refining the carbon dioxide component. Compared with the prior art, the process flow of the invention is simple, especially the number of cold boxes is reduced, a complex heat exchange network is avoided, and the energy consumption and the equipment investment are reduced.)

1. The method for separating the product gas of the oxidative coupling reaction of methane is characterized in that the product gas of the oxidative coupling reaction of methane contains hydrogen, methane, CO and CO₂Ethylene, ethane, hydrocarbons of three and above carbons, and optionally acetylene, sulfur oxides, nitrogen oxides;

the separation method comprises the steps of quenching and cooling the product gas, boosting pressure for the first time, washing with amine, washing with alkali, boosting pressure for the second time, cooling for the second time, rectifying to remove light components, refrigerating by an expander, exchanging heat with the product gas, separating methane and CO by pressure swing adsorption, separating carbon dioxide from carbon III and heavier components, and refining the carbon dioxide component.

2. The separation method of claim 1, wherein the light components comprise hydrogen, methane and CO.

3. The separation method according to claim 1, characterized in that it comprises the steps of:

(1) quenching and cooling the product gas through a quenching unit, wherein the product gas generates steam and is cooled to a gas phase at the temperature of 30-50 ℃;

(2) the gas phase from the quenching unit is subjected to primary pressure increase to 1.0-2.5 MPaG through a compressor;

(3) removing CO in the product gas from the gas phase after pressure boosting according to the sequence of amine washing and alkali washing₂And sulfur oxides to obtain CO₂A gas phase having a sulfur oxide concentration in the range of 1 to 20 ppm;

(4) performing secondary pressure boosting on the gas phase obtained in the step (3) to 3.0-4.5 MPaG through a compressor;

(5) the boosted gas phase enters a cold separation unit for secondary cooling, the separation of hydrogen, methane, CO and carbon dioxide and heavier components is realized in the cold separation unit, the operation in the cold separation unit comprises the steps of gradually reducing the temperature of the gas phase by using a cold box or/and a heat exchanger, the cooled material is refrigerated by using an expander after hydrogen, methane and CO are removed from the top of the tower in a demethanizer, and the obtained cold energy is used for exchanging heat with the product gas to reduce the temperature of the product gas; then the separation of methane, hydrogen and CO is realized through pressure swing adsorption operation;

(6) the carbon dioxide, the carbon III and heavier components obtained in the cold separation unit are separated from the carbon III and heavier components through a deethanizer, and the carbon dioxide component is subjected to selective hydrogenation to remove acetylene hydrocarbon and then subjected to rectification operation to obtain polymer-grade ethylene.

4. The separation method according to claim 3, wherein the quenching and cooling process utilizes the heat of the product gas to generate 0.2-5.0 MPaG steam, and the steam generator is one or more stages.

5. The separation method according to claim 3, wherein the methane obtained by pressure swing adsorption separation is recycled to the upstream oxidative coupling reaction system to participate in the reaction again.

6. The separation process of claim 3, wherein the demethanizer is operated at a pressure of 3.0 to 4.5MPaG and an overhead temperature of-70 ℃ to-102 ℃.

7. A separation process according to any one of claims 1 to 3, characterised in that a benzene removal step is provided during the primary and/or secondary pressure increase of the product gas to control the benzene content entering the downstream process.

8. A separation method according to any one of claims 1-3, wherein the expander is a gas expander.

9. The separation process of any one of claims 1 to 3, wherein the expander refrigeration outlet pressure is in the range of 0.05 to 1.0 MPaG.

10. The separation method according to any one of claims 1 to 3, wherein ethane obtained in the purification of the carbon dioxide component is fed back to the upstream oxidative coupling reaction system to participate in the reaction.

Technical Field

The invention belongs to the field of petrochemical industry, and particularly relates to a separation method of a product gas of a methane oxidative coupling reaction.

Background

Ethylene is one of the chemical products with the largest yield in the world, the ethylene industry is the core of the petrochemical industry, and the ethylene product accounts for more than 75 percent of petrochemical products and occupies an important position in national economy. Ethylene production has been used worldwide as one of the important indicators for the development of petrochemical in one country.

With the large fluctuation of the international crude oil price and the technical progress, in order to change the condition that the raw materials for producing ethylene depend on petroleum resources excessively, the raw materials for producing ethylene are changed, and the technology for producing ethylene by taking methanol as the raw material is developed and becomes a technology with wide industrial application in the novel coal chemical industry technology.

The technology for preparing ethylene by Oxidative Coupling of Methane (OCM) is an important technology for producing ethylene, takes natural gas as a raw material, can prepare ethylene by only one-step reaction process, and has high theoretical value and economic value. After more than 30 years of research, the research on ethylene preparation by a methane one-step method has made a breakthrough, and the industrial demonstration device for preparing ethylene by methane coupling is successfully put into production, which is moving towards the beginning of industrialization. The method has great significance for breaking the bottleneck of raw material sources in the ethylene industry, reducing the production cost and enhancing the competitiveness of the ethylene industry and downstream industries.

Research and development at home and abroad are most typical of Siluria technology company in the United states, and the Siluria develops an industrially feasible methane direct ethylene catalyst by precisely synthesizing a nanowire catalyst by using a biological template. The catalyst can efficiently catalyze the conversion of methane into ethylene under the condition of 200-300 ℃ lower than the operation temperature of the traditional steam cracking method and under the pressure of 5-10 atmospheric pressures. The technology prolongs the service life of the catalyst, greatly reduces the operation temperature, but has no substantial breakthrough on the conversion rate of methane and the yield of ethylene.

The separation method of the product gas of the methane oxidative coupling reaction is an important part in the OCM process, and the product gas is separated by adopting a multi-stage cold box in the prior art, so that the process method is complex and has high energy consumption. The industrialization of the OCM process is greatly limited by the economical efficiency of practical application, so that the development of a low-energy-consumption separation method for the product gas of the oxidative coupling reaction of methane is of great significance.

Disclosure of Invention

The invention aims to provide a method for separating a product gas of a methane oxidative coupling reaction. In particular to a technical scheme for separating components such as high value-added hydrocarbons, such as ethylene, and the like in methane coupling reaction product gas, which has the advantages of reliability, low energy consumption and simple process flow.

In order to achieve the above object, the present invention provides a method for separating a product gas of oxidative coupling of methane, which contains hydrogen, methane, CO, and CO₂Ethylene, ethane, hydrocarbons of three and above carbons, and optionally acetylene, sulfur oxides, nitrogen oxides;

the separation method comprises the steps of quenching and cooling the product gas, boosting pressure for the first time, washing with amine, washing with alkali, boosting pressure for the second time, cooling for the second time, rectifying to remove light components, refrigerating by an expander, exchanging heat with the product gas, separating methane and CO by pressure swing adsorption, separating carbon dioxide from carbon III and heavier components, and refining the carbon dioxide component.

According to the present invention, preferably, the light components include hydrogen, methane and CO.

According to a particular embodiment of the invention, the separation method comprises the following steps:

(1) quenching and cooling the product gas through a quenching unit, wherein the product gas generates steam and is cooled to a gas phase at the temperature of 30-50 ℃;

(2) the gas phase from the quenching unit is subjected to primary pressure increase to 1.0-2.5 MPaG through a compressor;

(3) removing CO in the product gas from the gas phase after pressure boosting according to the sequence of amine washing and alkali washing₂And sulfur oxides to obtain CO₂A gas phase having a sulfur oxide concentration in the range of 1 to 20 ppm;

(4) performing secondary pressure boosting on the gas phase obtained in the step (3) by a compressor to 3.0-4.5 MPaG;

(5) the boosted gas phase enters a cold separation unit for secondary cooling, the separation of hydrogen, methane, CO and carbon dioxide and heavier components is realized in the cold separation unit, the operation in the cold separation unit comprises the steps of gradually reducing the temperature of the gas phase by using a cold box or/and a heat exchanger, the cooled material is refrigerated by using an expander after hydrogen, methane and CO are removed from the top of the tower in a demethanizer, and the obtained cold energy is used for exchanging heat with the product gas to reduce the temperature of the product gas; then the separation of methane, hydrogen and CO is realized through pressure swing adsorption operation;

(6) the carbon dioxide, the carbon III and heavier components obtained in the cold separation unit are separated from the carbon III and heavier components through a deethanizer, and the carbon dioxide component is subjected to selective hydrogenation to remove acetylene hydrocarbon and then subjected to rectification operation to obtain polymer-grade ethylene.

According to the invention, preferably, the heat of the product gas is utilized to generate 0.2-5.0 MPaG steam in the quenching and cooling process, and the steam generator is one-stage or multi-stage.

According to the invention, preferably, the methane obtained by pressure swing adsorption separation is recycled to the upstream oxidative coupling reaction system to participate in the reaction again.

According to the invention, the operating pressure of the demethanizer is preferably 3.0-4.5 MPaG, and the tower top temperature is-70 ℃ to-102 ℃.

According to the present invention, preferably, a benzene removal step is provided in the primary pressure increasing and/or secondary pressure increasing process of the product gas to control the benzene content entering the downstream process.

According to the present invention, preferably, the expander is a gas expander.

According to the invention, the refrigerating outlet pressure of the expander is preferably 0.05-1.0 MPaG.

According to the present invention, it is preferable that ethane obtained during the refining of the carbon two component is sent back to the upstream oxidative coupling reaction system to participate in the reaction.

The invention has the beneficial effects that:

(1) the heat of the methane oxidative coupling product gas is fully utilized, and the utilization efficiency of the device on the heat is effectively improved.

(2) By adopting cryogenic separation and low-temperature expansion processes, the loss of ethylene is less, and the energy consumption is saved.

(3) The pressure swing adsorption is adopted to separate methane and CO, so that unreacted methane is fully recovered, the purity is high, and the material utilization efficiency is improved, which is difficult to realize through the separation of a multi-stage cold box in the prior art.

(4) The gas expander is adopted, so that a liquid-containing expander adopted in the prior art is avoided, the efficiency can be improved, and the cost is reduced.

(5) Compared with the prior art, the process flow of the invention is simple, especially the number of cold boxes is reduced, a complex heat exchange network is avoided, and the overall energy consumption and equipment investment are reduced.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent by describing in more detail exemplary embodiments thereof with reference to the attached drawings.

FIG. 1 shows a schematic flow diagram of a process for the separation of product gas from the oxidative coupling of methane reaction according to the present invention.

Detailed Description

Preferred embodiments of the present invention will be described in more detail below. While the following describes preferred embodiments of the present invention, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein.