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Method, system and process for recycling fuel gas by-produced in methanol to olefins plant

发布日期:2020-01-18 03:51 Document serial number: 19730128 Release date: 2020-01-18 03:51
Method, system and process for recycling fuel gas by-produced in methanol to olefins plant

The present invention relates generally to the technical field of comprehensive utilization of resources of chemical products, and more particularly, to a method and system for recovering and utilizing fuel gas by-produced from a methanol-to-olefins plant.



Background technique:

The methanol to olefin (mto) unit includes a methanol to olefin unit and an olefin separation unit. The main process is to heat and vaporize mto-level liquid methanol from the outside area of the unit into the reactor for reaction; the reaction product passes through a three-stage cyclone The separator recovers a small amount of entrained fines, removes the catalyst through the quench tower and water washing tower, and condenses most of the water to obtain the reaction gas, and sends it to the olefin separation unit for separation and purification; The stripping column recovers a small amount of organic matters such as methanol and dimethyl ether.

The olefin separation unit uses the olefin separation technology of de-ethanization and hydrogenation to separate the reaction gas to produce olefin products mainly composed of polymer-grade ethylene and polymer-grade propylene. At the same time, a fuel gas is produced as a by-product. The main components are methane, hydrogen, ethane, propane, nitrogen, carbon monoxide, and a small amount of ethylene and propylene. Generally, this fuel gas is directly discharged or re-emitted through torch combustion, which will cause waste of resources and air pollution. If this fuel gas can be used for combustion and heating, so that it can be effectively used, it will reduce the waste of resources and reduce air pollution while improving the economic benefits of enterprises.



Technical realization elements:

In view of the above problems, the purpose of the present invention is to provide a method and a system for recovering fuel gas by-produced from a methanol-to-olefins plant, in order to overcome the waste of resources caused by the emission of fuel gas by-produced from a methanol-to-olefins plant in the prior art, The problem of air pollution.

The present invention provides the following technical solutions:

According to a first aspect of the present invention, a method for recovering and utilizing fuel gas produced by a methanol-to-olefins plant is provided. In the network, it is merged with natural gas in the natural gas pipeline network and used as fuel for downstream devices in the natural gas pipeline network.

According to an embodiment of the first aspect of the present invention, the fuel gas is generated from an olefin separation unit of a methanol-to-olefins plant, and includes methane and hydrogen from a reflux tank at the top of an absorption tower, and from the bottom of an ethylene distillation tower Ethane and propane coming out of the bottom of the propylene distillation column.

According to an embodiment of the first aspect of the present invention, passing the fuel gas into a fuel gas main pipe connected to a natural gas pipeline network includes: methane and hydrogen coming out of a reflux tank at the top of the absorption tower; and The ethane coming out of the bottom of the ethylene rectification tower and propane coming out of the bottom of the propylene rectification tower are respectively subjected to cold recovery, and then passed into the fuel gas main pipe.

According to an embodiment of the first aspect of the present invention, the cold recovery of ethane coming out of the bottom of the ethylene rectification tower includes: passing ethane coming out of the bottom of the ethylene rectification tower into ethane After the carburetor is vaporized, the cold recovery is performed.

According to an embodiment of the first aspect of the present invention, the inputting the fuel gas into a natural gas pipeline network through a fuel gas main pipe includes: installing a pressure regulating valve on the fuel gas main pipe to adjust the pressure of the fuel gas, The pressure of the fuel gas is made higher than or equal to the pressure of the natural gas in the natural gas pipeline network, and then the fuel gas is input into the natural gas pipeline network through the fuel gas main pipe.

According to an embodiment of the first aspect of the present invention, adjusting the pressure of the fuel gas includes detecting a pressure of natural gas in a natural gas pipeline network, controlling an opening degree of the pressure regulating valve according to the pressure of the natural gas, and adjusting the fuel. Gas pressure.

According to an embodiment of the first aspect of the present invention, the downstream device includes one or more of a magnesium metal device, an ethylene pvc device, a methyl base device, and a catering center.

According to an embodiment of the first aspect of the present invention, the fuel gas main is connected to a flare line, so that the fuel gas is input into the flare line through the fuel gas main, and the fuel gas is burned in the flare.

According to an embodiment of the first aspect of the present invention, a control valve is installed on the flare line to control the input of the fuel gas into the flare.

According to a second aspect of the present invention, a fuel gas recovery and utilization system by-produced from a methanol-to-olefins plant is provided, including: a fuel gas main pipe and a natural gas pipe network, the fuel gas main pipe being connected to the natural gas pipe network so that the The fuel gas is fed into the natural gas pipeline network through the fuel gas main pipe, merged with the natural gas in the natural gas pipeline network, and used as fuel for downstream devices in the natural gas pipeline network.

According to an embodiment of the second aspect of the present invention, the fuel gas is generated from an olefin separation unit of a methanol-to-olefins plant, and includes methane and hydrogen from a reflux tank at the top of an absorption tower, and from the bottom of an ethylene rectification tower. Ethane and propane coming out of the bottom of the propylene distillation column.

According to an embodiment of the second aspect of the present invention, it further comprises a cold box, which is connected to the input end of the fuel gas main pipe, and is used for methane and hydrogen coming out of the reflux tank at the top of the absorption tower, The ethane from the bottom of the ethylene rectification tower and propane from the bottom of the propylene rectification tower are separately recovered for cold recovery and passed into the fuel gas main pipe.

According to an embodiment of the second aspect of the present invention, it further comprises an ethane vaporizer, which is used to vaporize the ethane coming out of the bottom of the ethylene rectification tower, so that the ethane comes from the ethylene rectification tower The ethane coming out of the bottom is vaporized and then recovered for cooling.

According to an embodiment of the second aspect of the present invention, it further includes a pressure regulating valve installed on the fuel gas main pipe for regulating the pressure of the fuel gas.

According to an embodiment of the second aspect of the present invention, it further comprises a pressure transmitter and a pressure controller, the pressure transmitter is installed on the natural gas pipeline network, and is used for detecting the pressure of natural gas in the natural gas pipeline network, and Transmitting the detected pressure signal to the pressure controller; the pressure controller is configured to control the opening degree of the pressure regulating valve according to the received pressure signal to adjust the pressure of the fuel gas.

According to an embodiment of the second aspect of the present invention, the downstream device includes one or more of a magnesium metal device, an ethylene pvc device, a methyl base device, and a catering center.

According to an embodiment of the second aspect of the present invention, it further comprises a flare line, a first end of the flare line is connected to the fuel gas main pipe, and a second end is connected to the torch, so that the fuel gas passes through the fuel gas The main pipe is input into the flare line, so that the fuel gas is burned in the flare.

According to an embodiment of the second aspect of the present invention, it further comprises a control valve installed on the flare line to control the input of the fuel gas into the flare.

Compared with the prior art, the present invention provides a method and system for recycling fuel gas by-produced from a methanol-to-olefins device, which has the following advantages: connecting a fuel gas main pipe to a natural gas pipeline network so that the fuel gas passes through the fuel gas main pipe Entered into the natural gas pipeline network, merged with the natural gas in the natural gas pipeline network, and used as fuel for the downstream devices in the natural gas pipeline network, so that the by-product fuel gas produced by the methanol-to-olefins plant can be effectively used, reducing resource waste and reducing atmospheric pollution While improving the economic efficiency of the enterprise.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic structural diagram of a fuel gas recovery and utilization system by-produced in a methanol-to-olefins device provided by the present invention.

FIG. 2 is a schematic structural diagram of a second embodiment.

FIG. 3 is a schematic structural diagram of a third embodiment.

detailed description

The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Reference numerals refer to components and technologies in the present invention, so that the advantages and features of the present invention can be more easily understood in a suitable environment. The following description is an embodiment of the claims of the present invention, and other specific implementations that are not explicitly related to the claims also belong to the scope of the claims.

FIG. 1 is a schematic structural diagram of a fuel gas recovery and utilization system by-produced in a methanol-to-olefins plant provided by the present invention.

As shown in FIG. 1, the recycling system provided by the present invention includes a fuel gas main pipe 1 and a natural gas pipe network 2, and the fuel gas main pipe 1 is connected to the natural gas pipe network 2 so that the fuel gas passes through the fuel gas main pipe 1. It is input into the natural gas pipeline network 2 and merged with the natural gas in the natural gas pipeline network 2 to be used as fuel for the downstream device 21 in the natural gas pipeline network 2.

The fuel gas described above is produced from the olefin separation unit of the methanol-to-olefins plant, including methane and hydrogen from the reflux tank at the top of the absorption tower, ethane from the bottom of the ethylene distillation tower, and from the bottom of the propylene distillation tower. Propane.

Specifically, the reaction gas generated by the methanol-to-olefins unit in the methanol-to-olefins unit is subjected to two stages of compression in the olefins separation unit to remove oxides containing water and alkali to elute and remove the pickling gas, and then compressed in the third stage to enter deacetylation. An alkane column separates components below c2 and components above c3. The c2 light component material at the top of the deethane tower is compressed in the fourth stage and sent to the demethanizer tower. The gas at the top of the demethanizer tower is passed through the absorption tower to recover the ethylene. By-products containing methane and hydrogen are produced in the reflux tank at the top of the absorption tower. Fuel gas. The material at the bottom of the demethanizer is hydrodesulfurized to remove acetylene and then enter the ethylene rectification column to separate ethylene and ethane. At the bottom of the ethylene rectification column, ethane-containing fuel gas is co-produced. The material at the bottom of the deethane tower is passed through the high and low pressure depropane tower, and the c3 component at the top of the depropane tower is sent to the propylene rectification tower to separate propylene and propane, and propane-containing fuel gas is co-produced at the bottom of the propylene rectification tower. The three fuel gas streams are combined into a single stream and then fed into the fuel gas main pipe 1 and then input into the natural gas pipeline network 2.

In this embodiment, the methanol-to-olefin unit technology in the methanol-to-olefins unit adopts a dmto patented process technology jointly developed by the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences, Xinxing Energy Technology Co., Ltd. and Luoyang Petrochemical Engineering Company of Sinopec Group. The olefin separation unit adopts the olefin separation technology of Sinopec Group Luoyang Petrochemical Engineering Company's pre-deethane and then hydrogenation to produce olefin products mainly composed of polymer grade ethylene and polymer grade propylene.

In this example, the components of the fuel gas produced by methanol-to-olefin plant are: methane 35.78%, hydrogen 28.73%, propane 16.78%, ethane 8.24%, nitrogen 4.79%, carbon monoxide 2.62%, ethylene 2.39%, propylene 0.66 %, Molecular weight is 19.23g / mol, flow rate is 3205kg / h, 3733m 3 n / h, calorific value is 9265kcal / nm 3 , the pressure of this fuel gas can be adjusted between 0.5-1.5mpa. The composition of natural gas is: methane 99.74%, ethane 0.07%, carbon dioxide 0.04%, nitrogen 0.13%, and low calorific value is 7990kcal / nm 3. Therefore, the composition of this fuel gas is similar to that of natural gas, and the flow rate and pressure are similar. The composition is relatively stable, without moisture, impurities and a slightly higher heating value than natural gas. This fuel gas is integrated into the natural gas pipeline network so that this fuel gas can be effectively used, which can reduce the waste of resources and reduce air pollution while improving the enterprise. Economic benefits and ease the economic pressure caused by the use of natural gas.

The recycling system provided by the present invention further includes a pressure regulating valve 3, which is installed on the fuel gas main pipe 1 and is used to regulate the pressure of the fuel gas so that the pressure of the fuel gas is higher than Or equal to the pressure of the natural gas in the natural gas pipeline network 2, so that the fuel gas is input into the natural gas pipeline network through the fuel gas main pipe 1. For example, the pressure of the natural gas pipeline network is 0.5mpa. Before this fuel gas is combined with the natural gas of the natural gas pipeline network, adjust the pressure regulating valve 3 so that the pressure of this fuel gas entering the natural gas pipeline network is higher than or equal to 0.5mpa, so that Ensure that this fuel gas is smoothly incorporated into the natural gas pipeline network 2. Among them, the pressure higher than the natural gas pipeline network means slightly higher than 0.5mpa, for example, it can be 0.6mpa or 0.7mpa. The purpose is to ensure the smooth incorporation of fuel gas, but the pressure should not be too high. In actual production, because the pressure of the natural gas pipeline network is controlled by the natural gas distribution center, which is generally about 0.5mpa, a pressure transmitter with a range of 0-1mpa can be selected to adjust the pressure of the fuel gas main pipe at 0.5mpa-0.7mpa between.

FIG. 2 shows a schematic structural diagram of a second embodiment.

As shown in FIG. 2, this embodiment is that in the above embodiment, a pressure transmitter 4 and a pressure controller 5 are added, and the pressure transmitter 4 is installed on the natural gas pipeline network 2 for detecting natural gas The pressure of the natural gas in the pipe network 2 and transmits the detected pressure signal to the pressure controller 5; the pressure controller 5 is configured to control the opening degree of the pressure regulating valve 3 according to the received pressure signal, and adjust the pressure Fuel gas pressure.

Since the pressure of the natural gas pipeline network fluctuates at any time with the amount of natural gas in actual production, in order to keep the pressure of the input fuel gas consistent with the pressure of the natural gas in the natural gas pipeline network at any time or maintain a pressure slightly higher than the pressure of natural gas, the pressure is installed The transmitter 4 and the pressure controller 5 enable the fuel gas pressure in the fuel gas main pipe 1 to be adjusted at any time in accordance with the pressure fluctuations in the natural gas pipeline network 2 to further ensure that the fuel gas is smoothly incorporated into the natural gas pipeline network 2.

The recycling system provided by the present invention, wherein the downstream device includes one or more of a magnesium metal device, an ethylene pvc device, a methyl-alkali device, and a catering center.

The magnesium metal device uses the combined gas for the dehydration section and the ingot section. The dehydration section is used to burn the air and hcl gas used for heating and drying, and the ingot section is used to burn and heat the mold to ensure that the mold is in the mold before injection. No residual moisture.

The ethylene process PVC unit uses this combined gas for a cracking and incineration unit.

The potassium-alkali plant uses an ion-membrane electrolytic potassium chloride process route, and the combined gas is used as a solid-alkali molten salt furnace fuel.

The catering center uses the combined gas for cooking food and reduces the amount of natural gas used.

In the present invention, it was decided in the early stage to send this fuel gas to the lime kiln of the calcium carbide plant instead of natural gas. However, considering the need for a new pipeline and the production rhythm of the methanol-to-olefins plant and the calcium carbide plant did not match, this plan was not implemented; After discussion and negotiation, this fuel gas was sent to the gas boiler of the power plant, but considering the need to retrofit the gas boiler, the cost was too high, and this plan was not implemented; eventually it was decided to merge this fuel gas into the methanol system through the fuel gas main. For the natural gas pipeline network outside the olefin plant boundary, simply adjust the pressure of this fuel gas to above the natural gas pipeline network pressure (0.5mpag), and then send it out for the downstream equipment of the natural gas pipeline network.

FIG. 3 is a schematic structural diagram of a third embodiment.

As shown in FIG. 3, this embodiment adds a cold box 6 and an ethane vaporizer 7 to the first embodiment or the second embodiment. The cold box 6 is connected to the input end of the fuel gas main pipe 1 for methane and hydrogen coming out of the reflux tank at the top of the absorption tower, ethane coming out of the bottom of the ethylene rectification tower, and from the bottom of the ethylene distillation tower. The propane coming out of the bottom of the propylene rectification tower is separately recovered for cooling and passed into the fuel gas main pipe 1.

The three fuel gases, methane and hydrogen coming out of the reflux tank at the top of the absorption tower, ethane coming out of the bottom of the ethylene distillation tower, and propane coming out of the bottom of the propylene distillation tower, have different temperatures due to production, Therefore, it is necessary to separately recover the cold capacity, and then combine the three fuel gases from the cold box 6 into one gas, and then pass it into the fuel gas main pipe 1. In this embodiment, a 6 ° C propylene refrigerant is selected for recovering the cooling capacity, and the 6 ° C propylene refrigerant is used in the cold box 6 and the methane and hydrogen from the reflux tank at the top of the absorption tower, and the ethylene The ethane coming out of the bottom of the rectifying tower and the propane coming out of the propylene rectifying tower undergo heat exchange, so as to achieve the effect of recovering the cold capacity.

The recycling system provided by the present invention further includes an ethane vaporizer 7 for vaporizing ethane coming out of the bottom of the ethylene rectification tower, so that the ethane comes out of the bottom of the ethylene rectification tower. The resulting ethane is vaporized and then recovered for cooling.

The recycling system provided by the present invention further includes a torch line 8, a first end of the torch line 8 is connected to the fuel gas main pipe 1, and a second end is connected to the torch, so that the fuel gas passes through the fuel gas The main pipe 1 is input into the flare line 8 so that the fuel gas is burned in the flare.

The recycling system provided by the present invention further includes a control valve 9 which is installed on the flare line 8 to control the input of the fuel gas into the flare.

When a methanol-to-olefin plant is started or in an accident state, the fuel gas component generated is unstable, and it needs to be input into the flare line 8 through the fuel gas main pipe 1 to burn the fuel gas in the flare. After the methanol-to-olefins plant runs normally, the control valve 9 is closed, and the pressure regulating valve 3 is opened, so that the fuel gas is input into the natural gas pipeline network 2 through the fuel gas main pipe 1 and supplied to the downstream device 21 for use.

The invention also provides a method for recovering and utilizing fuel gas produced by-product from a methanol-to-olefins plant, comprising: connecting a fuel gas main pipe to a natural gas pipeline network, so that the fuel gas is input into the natural gas pipe network through the fuel gas main pipeline and connected with natural gas The natural gas in the pipeline network is merged and used as fuel for downstream devices in the natural gas pipeline network.

The recycling method provided by the present invention, wherein the fuel gas is generated from an olefin separation unit of a methanol-to-olefins plant, and includes methane and hydrogen from a reflux tank at the top of an absorption tower, and ethane from a bottom of an ethylene rectification tower. And propane from the bottom of the propylene distillation column.

The recycling method provided by the present invention, wherein passing the fuel gas into a fuel gas main pipe connected to a natural gas pipeline network comprises: rectifying methane and hydrogen from a reflux tank at the top of the absorption tower, and ethylene distillation The ethane coming out of the bottom of the column and the propane coming out of the bottom of the propylene distillation column are separately recovered for cooling and passed into the fuel gas main pipe.

The recycling method provided by the present invention, wherein cold recovery of ethane from the bottom of the ethylene rectification tower comprises: passing ethane from the bottom of the ethylene rectification tower to an ethane vaporizer and vaporizing Cold recovery is performed.

The recycling method provided by the present invention, wherein the fuel gas is input into a natural gas pipeline network through a fuel gas main pipe, includes: installing a pressure regulating valve on the fuel gas main pipe to adjust the pressure of the fuel gas to make the fuel gas The pressure is higher than or equal to the pressure of the natural gas in the natural gas pipeline network, so that the fuel gas is input into the natural gas pipeline network through the fuel gas main pipe.

The recycling method provided by the present invention, wherein adjusting the pressure of the fuel gas includes detecting the pressure of natural gas in a natural gas pipeline network, controlling the opening degree of the pressure regulating valve according to the pressure of the natural gas, and adjusting the pressure of the fuel gas. .

The recycling method provided by the present invention, wherein the downstream device comprises one or more of a magnesium metal device, an ethylene PVC device, a methyl-alkali device, and a catering center.

The recycling method provided by the present invention, wherein the fuel gas main pipe is connected with a flare line, so that the fuel gas is input into the flare line through the fuel gas main line, and then the fuel gas is burned in the flare.

The recycling method provided by the present invention, wherein a control valve is installed on the flare line to control the input of the fuel gas into the flare.

The invention provides a method and a system for recovering fuel gas by-produced from a methanol-to-olefins device. The fuel gas is passed into a fuel gas main pipe connected to a natural gas pipeline network, so that the fuel gas is input into the natural gas pipe network through the fuel gas main pipeline. Combined with the natural gas in the natural gas pipeline network and used as fuel for the downstream devices in the natural gas pipeline network, so that the by-product fuel gas from the methanol-to-olefins plant can be effectively used, reducing the amount of natural gas and pollution to the atmospheric environment, and reducing enterprises Production costs, improve the economic benefits of the enterprise, and achieve economical, stable, and low-carbon operation of methanol-to-olefins plants.

The invention combines the advantages of the industrial chain of the metal-magnesium integration project, and considers from the aspects of energy conservation, consumption reduction, carbon emission reduction, relief of the increasingly high use of natural gas, and improvement of economic benefits. The by-product fuel gas is input through the fuel gas main pipe. In the natural gas pipeline network, the downstream equipment is used for safe and stable production, which not only solves the problem of the whereabouts of this fuel gas, but also improves the utilization rate of resources.

It should be noted that the above-mentioned embodiments illustrate the invention rather than limit the invention, and that those skilled in the art may design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

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