CN111533635A - Low-energy-consumption separation system and separation process for methanol-to-olefin reaction gas - Google Patents
Low-energy-consumption separation system and separation process for methanol-to-olefin reaction gas Download PDFInfo
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- 238000000926 separation method Methods 0.000 title claims abstract description 139
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- 238000011069 regeneration method Methods 0.000 claims abstract description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 11
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 claims description 83
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 0.000 claims description 83
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 73
- 238000001035 drying Methods 0.000 claims description 49
- 239000007788 liquid Substances 0.000 claims description 47
- 150000001336 alkenes Chemical class 0.000 claims description 45
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 claims description 44
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims description 41
- 239000005977 Ethylene Substances 0.000 claims description 41
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 claims description 36
- 239000007789 gas Substances 0.000 claims description 36
- 239000000047 product Substances 0.000 claims description 36
- -1 polyethylene Polymers 0.000 claims description 20
- 238000005516 engineering process Methods 0.000 claims description 19
- 239000012295 chemical reaction liquid Substances 0.000 claims description 18
- 239000001294 propane Substances 0.000 claims description 18
- 238000001816 cooling Methods 0.000 claims description 16
- 238000010992 reflux Methods 0.000 claims description 16
- 238000007599 discharging Methods 0.000 claims description 13
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- 239000006227 byproduct Substances 0.000 claims description 10
- 150000001875 compounds Chemical class 0.000 claims description 10
- 239000001301 oxygen Substances 0.000 claims description 10
- 229910052760 oxygen Inorganic materials 0.000 claims description 10
- 239000012071 phase Substances 0.000 claims description 10
- 229920000573 polyethylene Polymers 0.000 claims description 10
- 229920001155 polypropylene Polymers 0.000 claims description 10
- 239000002994 raw material Substances 0.000 claims description 10
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 claims description 9
- 239000002253 acid Substances 0.000 claims description 8
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- 238000006297 dehydration reaction Methods 0.000 claims description 4
- 239000001257 hydrogen Substances 0.000 claims description 4
- 229910052739 hydrogen Inorganic materials 0.000 claims description 4
- 238000006116 polymerization reaction Methods 0.000 claims description 4
- 239000002699 waste material Substances 0.000 claims description 4
- 239000002351 wastewater Substances 0.000 claims description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 abstract description 20
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- 229910052757 nitrogen Inorganic materials 0.000 abstract description 10
- 239000000126 substance Substances 0.000 abstract description 3
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- 239000000463 material Substances 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 239000011345 viscous material Substances 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
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- 238000002309 gasification Methods 0.000 description 1
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- 238000004519 manufacturing process Methods 0.000 description 1
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- 238000005120 petroleum cracking Methods 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/11—Purification; Separation; Use of additives by absorption, i.e. purification or separation of gaseous hydrocarbons with the aid of liquids
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/04—Purification; Separation; Use of additives by distillation
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P30/00—Technologies relating to oil refining and petrochemical industry
- Y02P30/40—Ethylene production
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- Oil, Petroleum & Natural Gas (AREA)
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- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention relates to the field of coal-based methanol-to-olefin in the novel coal chemical industry, and discloses a low-energy-consumption separation system for methanol-to-olefin reaction gas, wherein all devices are connected through a pipeline, and one section, two sections and three sections of a reaction gas compressor are connected through pipelines; the outlet of the second section of the reaction gas compressor is connected with a water washing tower, and the oil separation side at the side part of the water washing tower is connected with a condensate pre-separation tower; its separation process is also disclosed. According to the invention, heavy components are discharged from the tower kettle, are dehydrated and separated and are directly sent to the carbon four device for treatment, so that the invalid circulation of the heavy components in the system is avoided, and the process load of the separation system is reduced under the same treatment capacity of the methanol-to-olefin reaction gas, so that the process energy consumption and the main equipment size are reduced, and the nitrogen consumption in the regeneration process of the dryer is reduced; according to the invention, a cooler and a group of oil-water separators are additionally arranged on the heavy component line of the tower kettle of the condensate pre-separation tower, so that oil-water separation is more thorough, and the process energy consumption is lower.
Description
Technical Field
The invention relates to the field of coal-based methanol-to-olefin in the novel coal chemical industry, in particular to a low-energy-consumption separation system and a low-energy-consumption separation process for methanol-to-olefin reaction gas, which can separate polymerization-grade propylene and ethylene products from the methanol-to-olefin reaction gas by various low-energy-consumption means and separate byproducts such as propane and the like.
Background
Olefin products play an extremely important role in the economy of China, and are basic chemical raw materials of high polymer materials such as synthetic fibers, synthetic rubber, synthetic plastics and the like. The 'rich coal, lean oil and little gas' is the current energy situation of China, the traditional olefin product preparation technology is very dependent on petroleum product cracking, if olefin is prepared only by depending on petroleum, the method obviously does not accord with the energy innate endowments of China, and another olefin preparation technology is urgently needed. In recent years, with the development and application of the technology for preparing olefin from coal-based methanol in China, particularly the large-scale industrial popularization in northwest regions, the method not only fills the blank in the technical field of preparing olefin from coal-based in China, but also enables China to get rid of the limitation that the preparation of olefin depends on petroleum cracking for a long time. However, most coal-based methanol to olefin projects put into production in China still utilize foreign technologies, and currently, the development and research of coal-based methanol to olefin technologies with independent intellectual property rights in China becomes urgent.
Coal-based methanol to olefin technology usually uses coal as raw material, and finally produces polypropylene and polyethylene products through the processes of coal gasification, methanol synthesis, methanol to olefin, olefin separation, olefin polymerization and the like. The olefin separation is an important process in the field of coal-based methanol-to-olefin, and the process is used for separating reaction gas generated in an upstream coal-to-methanol reactor, separating polymerization-grade propylene and ethylene products for producing products such as polypropylene and polyethylene in a downstream olefin polymerization process, and simultaneously producing byproducts such as propane and ethane.
At present, the olefin separation technology mainly comprises a LUMMUS process, a KBR process and a benevolent process. Wherein, a water washing tower and an alkali washing tower are arranged behind the second stage of the LUMMUS olefin separation feed gas compressor, and a high pressure tower and a low pressure tower are arranged behind the third stage of the feed gas compressor for preventing scaling; the method is characterized in that a propane removal process of a KBR olefin separation process is performed in front of a propane removal process and after a hydrogenation process, a plurality of propane washes are arranged, a water washing tower, an alkaline washing tower and a depropanizer are arranged behind a feed gas compressor in three sections, and only one depropanizer is arranged because the polymerization reaction is not easy to occur due to low operation temperature; the separation process of the olefins from the propane is started before the hydrogenation process, and pre-cutting and oil absorption processes are provided.
The three olefin separation processes have respective advantages, but have some disadvantages in terms of energy conservation and enterprise cost reduction, for example, coal-made olefin reaction gas contains various components such as C1-C7, heavy components are easy to form process condensate after the reaction gas compressor two-stage in the compression separation process, especially process condensate in a washing tower, if the process condensate is discharged and treated in time, the energy consumption is increased and the equipment load in the system is increased due to the internal circulation of the system, and the part of the process condensate can react to generate viscous substances such as butter, red oil and the like under complex process conditions, so that process pipelines, valves and the like in the system are easy to block, and unnecessary loss is caused. For another example, a free water drying unit is an indispensable unit in an olefin separation process, but basically, two dryers are adopted in the unit at present, one dryer operates, and the other dryer regenerates, and the nitrogen consumption per unit time in the regeneration process is large, which inevitably causes higher operation cost. For another example, some rectifying tower reboilers still adopt steam as a heating source, so that the steam consumption is high, and the operation cost of enterprises is increased invisibly.
Disclosure of Invention
The invention aims to provide a low-energy-consumption separation system and a separation process for preparing olefin reaction gas from methanol, which solve the problems of large equipment selection, more process energy consumption, more side reactions and the like caused by the accumulative circulation of process condensate condensed from a reaction gas compressor in the second stage in the conventional olefin separation technology, large consumption of nitrogen in a drying unit per unit time, incomplete separation of process condensate from water, large steam consumption of a reboiler of a rectifying tower and the like, reduce the equipment investment of the olefin separation technology, reduce the consumption of low-pressure nitrogen and low-pressure steam, reduce the energy consumption, and effectively ensure the separation effect of the process condensate from water so as to solve the problems in the background technology.
In order to achieve the purpose, the invention provides the following technical scheme:
a low energy consumption methanol-to-olefin reaction gas separation system, all equipment are connected through the pipeline, the first section, the second section and the third section of the reaction gas compressor are connected through the pipeline; the outlet of the second section of the reaction gas compressor is connected with a water washing tower, and the oil separation side at the side part of the water washing tower is connected with a condensate pre-separation tower; the top of the condensate pre-separation tower is connected with a condenser, a reflux tank and a reflux pump, the reflux pump is connected with the condensate pre-separation tower, the reflux tank is connected with a two-section inlet pipeline of a reaction gas compressor, the bottom of the condensate pre-separation tower is connected with a cooler and an oil-water separator through a kettle liquid pump, and the condensate pre-separation tower is provided with two reboilers; the top of the water washing tower is connected with an alkaline washing tower, and the top of the alkaline washing tower is connected with a three-section inlet pipeline of a reaction gas compressor; a three-section outlet of the reaction gas compressor is connected with a gas-liquid separation tank, the top of the gas-liquid separation tank is connected with a process gas drying system, the side part of the gas-liquid separation tank is connected with an inclined tank, and the side part of the inclined tank is connected with a process liquid drying system; the process gas drying system and the process liquid drying system are connected with the high-pressure tower from different heights; the top of the high-pressure tower is connected with the four sections of the reaction gas compressor, the bottom of the high-pressure tower is connected with the low-pressure tower, and the top of the low-pressure tower is connected with the deethanizer; the outlet of the four sections of the reaction gas compressor is connected with a demethanizer, the top of the demethanizer is connected with a heat energy-saving exchanger, and the bottom of the demethanizer is connected with a deethanizer; the top of the deethanizer is sequentially connected with a C2 dryer and an ethylene tower, and the bottom of the deethanizer is connected with a propylene tower I; the top of the propylene tower I is connected with the bottom of the propylene tower II, and the top of the propylene tower II is connected with a propylene protector.
As a further scheme of the invention: the process gas drying system comprises six reaction gas dryers.
As a further scheme of the invention: the process liquid drying system comprises five reaction liquid dryers.
As a further scheme of the invention: the condensate pre-separation tower is arranged between the second section of the reactor compressor and the third section of the reactor compressor.
A separation process for separating low-energy-consumption methanol-to-olefin reaction gas comprises the following steps:
1) the reaction gas from the methanol-to-olefin process enters the olefin separation process and is sequentially compressed by a reaction gas compressor at a first section and a second section;
2) the reaction gas compressed by the first section and the second section of the reaction gas compressor enters a water washing tower to remove oxygen-containing compounds and a small amount of acid gas contained in the reaction gas, and a large amount of process condensate is clear in an oil separation cavity of the tower;
3) discharging a large amount of process condensate obtained in the step 2) into a condensate pre-separation tower through liquid level regulation to separate light components of C3 and below from heavy components of C4 and above;
4) discharging the heavy components C4 and above separated by the condensate pre-separation tower in the step 3) from the tower kettle, cooling by a cooler, and then sending into an oil-water separator for oil-water separation;
5) separating oil from water in the step 4), sending heavy components of C4 and above into a carbon four device for processing treatment, and discharging the wastewater into a methanol-to-olefin process for steam stripping treatment;
6) returning the C3 and the following light components separated from the top of the condensate pre-separation tower in the step 3) to a second-stage inlet of a reaction gas compressor;
7) the reaction gas after water washing in the step 2) enters an alkaline washing tower to remove acid gas contained in the reaction gas, waste alkali liquor is discharged from a tower kettle and then sent to a battery compartment for treatment, and the washed reaction gas enters a reaction gas compressor three sections for compression;
8) cooling the reaction gas compressed in the three sections, then feeding the cooled reaction gas into a gas-liquid separation tank for gas-liquid separation, feeding the gas phase at the top of the tank into a reaction gas drying system for removing moisture in the reaction gas, feeding the liquid phase at the bottom of the tank into a tilting tank for primary dehydration, and then feeding the liquid phase into a reaction liquid drying system for completely removing moisture in the reaction liquid;
9) respectively feeding the reaction gas and the reaction liquid dried in the step 8) into a high-pressure tower from different heights, feeding the light components of C3 and below preliminarily separated from the top of the tower into a reaction gas compressor for compression, feeding the heavy components of C4 and above and a small amount of C3 components in a tower kettle into a low-pressure tower, and further removing the C3 component;
10) c4 and above heavy components and a small amount of C3 components entering the low-pressure tower through the step 9) are further separated in the tower, C3 and below light components are discharged from the top of the tower and enter a deethanizer, and C4 and above heavy components and the step 5) are sent to a carbon four device together for processing;
11) compressing the light components of C3 and the following components separated in the step 9) by a reaction gas compressor in four sections, cooling, sending the light components into a demethanizer for separating the components of C1 from the components of C2-C3, sending the light components of C1 and a small amount of hydrogen at the tower top into a fuel gas pipe network of the whole plant after heat exchange by a heat energy-saving exchanger, and sending the components of C2-C3 at the tower bottom and the light components of C3 and the following components discharged at the tower top of the low-pressure tower in the step 10) into a deethanizer;
12) C2-C3 components enter a deethanizer to separate C2 and C3 components, C2 components discharged from the tower top enter a C2 drier to remove trace moisture contained in the C2 components and then enter an ethylene tower, C3 components discharged from the tower bottom are divided into two parts, one part is cooled and then is sent into the demethanizer as an absorbent of the demethanizer to reduce the loss of propylene and ethylene products at the tower top of the demethanizer, and the other part enters a propylene tower I;
13) the C2 component entering the ethylene tower in the step 12) is separated into ethylene and ethane in the tower, the polymerization-grade ethylene product obtained at the tower top is sent to a tank area for storage and is used as a raw material of a downstream polyethylene and polypropylene device, the ethane component at the tower bottom is divided into two strands, one strand is used as a byproduct and is merged into a fuel gas pipe network after heat exchange by a heat energy-saving exchanger, and the other strand is used as an absorbent of a demethanizer after being cooled and is sent to the demethanizer, so that the loss of propylene and ethylene products at the tower top of the demethanizer is reduced;
14) because the tower body of the propylene rectifying tower is too high, the on-site construction is inconvenient, the propylene tower is divided into two sections, namely a propylene tower I and a propylene tower II, the C3 component entering the propylene tower I through the step 12) is separated into propylene and propane in the propylene tower I and the propylene tower II, the propane component discharged from the tower bottom of the propylene tower I is divided into two sections, one section is cooled and then is sent into the demethanizer as an absorbent of the demethanizer, the loss of propylene and ethylene products at the tower top of the demethanizer is reduced, and the other section is sent to a tank area for storage as a propane byproduct;
15) and cooling a polymer grade propylene product discharged from the top of the propylene tower II, sending the cooled product into a propylene protector to remove trace water and oxygen-containing compounds contained in the product, and sending the product to a tank area for storage to serve as a raw material of a downstream polyethylene and polypropylene device.
Furthermore, the steps have the following characteristics:
1) the reaction gas from the methanol-to-olefin process enters the olefin separation process and is sequentially compressed by a reaction gas compressor at a first stage and a second stage. Wherein the reaction gas from the methanol to olefin process mainly comprises C1-C7 and has a pressure of 0.08-0.15 MPaG; the outlet pressure of one section of the reaction gas compressor is 0.2-0.35 MPaG; the pressure of the second section outlet of the reaction gas compressor is 0.6-0.8 MPaG.
2) The reaction gas compressed by the first and second stages of the reaction gas compressor enters a water washing tower to remove oxygen-containing compounds and a small amount of acid gas contained in the reaction gas, and a large amount of process condensate is clear in an oil separation cavity of the tower. Wherein the working pressure range of the water washing tower is 0.6-0.65 MPaG, and the working temperature range is 37-43 ℃; the washing water used by the washing tower is turbine condensate of the unit, so that the washing effect is ensured, and meanwhile, the process energy consumption is saved; the washing tower is a packed tower, the lower part of the washing tower is provided with an oil separating groove, and process condensate enters the oil separating groove and is discharged from the side part.
3) Discharging a large amount of process condensate obtained in the step 2) into a condensate pre-separation tower through liquid level regulation to separate light components of C3 and below from heavy components of C4 and above. Wherein the process condensate is discharged into a condensate pre-separation tower from the oil separation side of the water washing tower through self-pressure; the working pressure range of the condensate pre-separation tower is 0.3-0.4 MPaG, and the working temperature range is 20-80 ℃; two reboilers are arranged at the tower kettle of the condensate pre-separation tower.
4) Discharging the heavy components C4 and above separated by the condensate pre-separation tower in the step 3) from the tower kettle, cooling by a cooler, and then sending into an oil-water separator for oil-water separation. Wherein, the heavy components of C4 and above are pressurized and sent into a cooler through a condensate pre-separation tower kettle liquid pump and then cooled; in order to ensure the continuous and stable operation of the oil-water separator, the oil-water separator is opened, standby, normal operation and standby, 1 filter is arranged in front of each oil-water separator, so that impurities are prevented from entering the oil-water separator and affecting the oil-water separation effect; in order to ensure the separation effect of the oil-water separator, the temperature of the heavy components C4 and above is controlled to be 10-14 ℃.
5) Separating oil from water in the step 4), sending heavy components of C4 and above into a carbon four device for processing treatment, and discharging the wastewater into a methanol-to-olefin process for steam stripping treatment. Wherein the water content of the C4 and above heavy components can be controlled within 100-300 ppm by the oil-water separation.
6) C3 separated from the top of the condensate pre-separation tower in the step 3) and light components below the C3 are returned to the second-stage inlet of the reaction gas compressor. Wherein, the gas phase material at the top of the condensate preseparator tower is condensed and then flows back to the tower in a liquid phase, and the gas phase is discharged into the second-section inlet of the reaction gas compressor from the top of the reflux tank of the condensate preseparator tower.
7) And 2) the reaction gas after water washing in the step 2) enters an alkaline washing tower to remove acid gas contained in the reaction gas, waste alkali liquor is discharged from the tower kettle and then sent to a battery compartment for treatment, and the washed reaction gas enters a reaction gas compressor three section for compression. Wherein, the alkali liquor used by the alkaline tower is prepared by turbine condensate, and the washing water also uses the turbine condensate.
8) And cooling the reaction gas compressed in the three sections, then feeding the cooled reaction gas into a gas-liquid separation tank for gas-liquid separation, feeding the gas phase at the top of the tank into a reaction gas drying system for removing the moisture in the reaction gas, and feeding the liquid phase at the bottom of the tank into a tilting tank for primary dehydration, and then feeding the liquid phase into a reaction liquid drying system for completely removing the moisture in the reaction liquid. Wherein the pressure of the reaction gas compressed by the three stages is 1.3-1.5 MPaG.
9) The reaction gas and the reaction liquid dried in the step 8) respectively enter the high-pressure tower from different heights, the light components of C3 and below primarily separated from the top of the tower enter a reaction gas compressor for compression in four sections, and the heavy components of C4 and above and a small amount of C3 components in the tower kettle enter a low-pressure tower to further remove the C3 component. Wherein the dew point of the dried reaction gas is-70 to-80 ℃, and the water content of the dried process liquid is 0.1 to 1 ppm; the working pressure range of the high-pressure tower is 1.3-1.4 MPaG, and the working temperature range is-14-78 ℃.
10) And 9) further separating the heavy components of C4 and above and a small amount of C3 components entering the low-pressure tower in the tower, discharging light components of C3 and below from the top of the tower, and entering a deethanizer, wherein the heavy components of C4 and above and the heavy components in the step 5) are sent to a carbon four device for processing. Wherein the working pressure range of the low-pressure tower is 0.5-0.6 MPaG, and the working temperature range is 0-70 ℃; the above C3 and less light components are condensed into liquid by a condenser attached to the top of the low-pressure column and sent to the deethanizer.
11) Compressing the light components of C3 and below separated in the step 9) by a reaction gas compressor, cooling, sending into a demethanizer for separating the component C1 from the component C2-C3, exchanging heat of the light components of C1 and a small amount of hydrogen at the tower top by a heat energy-saving exchanger, sending into a fuel gas pipe network of the whole plant, and sending the components of C2-C3 at the tower bottom and the light components of C3 and below discharged from the tower top of the low-pressure tower in the step 10) into a deethanizer. Wherein, the pressure of the C3 and the following light components after four-stage compression by a reaction gas compressor is 2.9-3.1 MPaG; the working pressure range of the demethanizer is 2.5-2.8 MPaG, and the working temperature range is-52-21 ℃.
12) C2-C3 components enter a deethanizer to separate C2 and C3 components, C2 components discharged from the tower top enter a C2 drier to remove trace moisture contained in the components and then enter an ethylene tower, C3 components discharged from the tower bottom are divided into two parts, one part is cooled and then is used as an absorbent of the demethanizer to be sent into the demethanizer, the loss of propylene and ethylene products at the tower top of the demethanizer is reduced, and the other part enters a propylene tower I. Wherein the working pressure range of the deethanizer is 1.85-2.05 MPaG, and the working temperature range is-29-53 ℃.
13) The C2 component entering the ethylene tower through the step 12) is separated from ethylene and ethane in the tower, the polymerization-grade ethylene product obtained at the tower top is sent to a tank area for storage and is used as a raw material of a downstream polyethylene and polypropylene device, the ethane component at the tower bottom is divided into two strands, one strand is used as a byproduct and is merged into a fuel gas pipe network after heat exchange by a heat energy-saving exchanger, and the other strand is used as an absorbent of a demethanizer after being cooled and is sent to the demethanizer, so that the loss of propylene and ethylene products at the tower top of the demethanizer is reduced. Wherein the working pressure range of the ethylene tower is 1.89-2.05 MPaG, and the working temperature range is-30 to-5 ℃.
14) The propylene rectifying tower is divided into two sections, namely a propylene tower I and a propylene tower II, the C3 component entering the propylene tower I through the step 12) is separated into propylene and propane in the propylene tower I and the propylene tower II, the propane component discharged from the tower bottom of the propylene tower I is divided into two sections, one section is cooled and then is sent into a demethanizer as an absorbent of the demethanizer, the loss of propylene and ethylene products at the top of the demethanizer is reduced, and the other section is sent to a tank area for storage as a propane byproduct. Wherein the working pressure range of the propylene tower I is 1.8-1.9 MPaG, and the working temperature range is 45-50 ℃; the working pressure range of the propylene tower II is 1.9-2.0 MPaG, and the working temperature range is 50-60 ℃.
15) And cooling a polymer grade propylene product discharged from the top of the propylene tower II, sending the cooled product into a propylene protector to remove trace water and oxygen-containing compounds contained in the product, and sending the product to a tank area for storage to serve as a raw material of a downstream polyethylene and polypropylene device. Wherein, the cooler is attached to the top of the propylene tower II and adopts circulating water to cool so as to control the temperature at the top of the tower.
Further, the condensate pre-separation tower is arranged between the two sections and the three sections of the reactor compressor, and mainly has the functions of separating the process condensate condensed in the washing tower, so that light components C3 and below in the process condensate are separated from heavy components C4 and above, the gas phase of the light components C3 and below is returned to the inlet of the two sections of the reactor compressor, and the heavy components C4 and above are fully dehydrated in the oil-water separator after being cooled to 10-14 ℃ by the cooler, and are sent to the C4 device for treatment after being dehydrated. The condenser of the condensate preseparator adopts circulating water as a cold source, and the reboiler adopts steam as a heat source.
Further, the reaction gas drying system adopts a six-device alternate drying technology. Only two dryers are in the adsorption stage and the other four dryers are in the regeneration different stages respectively in the same time period through sequential control, so that the hourly consumption of regenerated nitrogen is reduced.
Furthermore, the reaction liquid drying system adopts a five-container alternate drying technology. Only one drier is in the adsorption stage and the other four driers are in the regeneration different stages respectively in the same time period through sequential control, so that the hourly consumption of regenerated nitrogen is reduced.
Furthermore, in the process of cooling the reaction gas after being compressed in the four stages and sending the reaction gas to the demethanizer, the third cooler utilizes a reboiler of the ethylene column for cooling, so as to realize thermal coupling.
Compared with the prior art, the invention has the beneficial effects that:
1) the separation process for preparing olefin reaction gas from methanol with low energy consumption, provided by the invention, is provided with the condensate pre-separation tower, the process condensate condensed in the oil separating tank at the side part of the tower kettle of the water washing tower can be discharged into the condensate pre-separation tower through self-pressure, the light components C3 and below are fully separated from the heavy components C4 and above in the separation tower, the light components C3 and below are returned to the inlet of the two sections of the reaction gas compressor, and the heavy components C4 and above are not required to be circulated in the three sections of the reaction gas compressor, but are directly discharged into the four-carbon device for treatment after oil-water separation, the sizes of the reaction gas compressor and other auxiliary equipment, a conveying pipeline and a control valve are correspondingly reduced, the investment cost of fixed assets of the device is obviously reduced, meanwhile, the consumption of steam and other public works of the corresponding operation equipment is reduced along with the reduction of the operation cost is also obviously reduced;
2) according to the low-energy-consumption separation process for preparing the olefin reaction gas from the methanol, the heavy components at the bottom C4 of the condensate pre-separation tower and above are cooled to 10-14 ℃ by a special cooler and then are sent to the oil-water separator for separation, the separation effect of the oil-water separator is better at the temperature, and the water content of the heavy components at C4 and above which are sent to a carbon four device is ensured to reach the standard;
3) the low-energy-consumption separation process for the reaction gas from the methanol to the olefin, provided by the invention, is provided with two oil-water separators, one oil-water separator is normally operated, and the other oil-water separator is standby, so that the other oil-water separator can be put into use at any time after the fault of the oil-water separator, the safety and stability of the system are ensured, the long-period operation is ensured, meanwhile, a filter is arranged in front of each oil-water separator, various impurities are prevented from entering the oil-water separator, and the oil-water separation effect of the oil-water separator is ensured;
4) according to the low-energy-consumption separation process for preparing the olefin reaction gas from the methanol, the process gas drying system adopts a six-device alternate drying technology, only two dryers are in an adsorption stage in the same time period through sequential control, and other four dryers are respectively in different regeneration stages, so that the hourly consumption of regenerated nitrogen is reduced, and the consumption of public works is reduced;
5) according to the low-energy-consumption separation process for preparing the olefin reaction gas from the methanol, the process liquid drying system adopts a five-device alternate drying technology, only one dryer is in an adsorption stage and the other four dryers are respectively in different regeneration stages in the same time period through sequential control, so that the hourly consumption of regenerated nitrogen is reduced, and the consumption of public works is reduced;
6) according to the low-energy-consumption separation process for preparing the olefin reaction gas from the methanol, the heavy components of C4 and above in the process condensate condensed in the washing tower are separated in the condensate pre-separation tower, and are dehydrated by the oil-water separator and then directly sent to the carbon four device for treatment, and do not enter the process liquid drying system for drying, so that the sizes of five dryers of the process liquid drying system and auxiliary pipelines thereof are correspondingly reduced, meanwhile, the consumption of the drying agent in each dryer is greatly reduced, and the investment cost and the operation cost are reduced;
7) according to the separation process for preparing the olefin reaction gas from the methanol with low energy consumption, the washing water of the washing tower adopts the turbine condensate generated by the reaction gas compressor and the turbine of the refrigerating unit as the washing water, so that the washing effect of the washing tower on oxygen-containing compounds in the process gas is ensured, the generation and aggregation of viscous substances such as butter and the like in a subsequent alkaline washing tower are reduced, and the turbine condensate is fully recycled;
8) according to the low-energy-consumption separation process for preparing the olefin reaction gas from the methanol, the alkali solution of the alkaline washing tower, the alkali-prepared water and the washing water are all used as the washing water by adopting the turbine condensate generated by the reaction gas compressor and the turbine of the refrigerating unit, so that the possibility of introducing oxygen-containing compounds into the alkaline washing tower is reduced, the alkaline washing effect is improved, and the turbine condensate is fully recycled;
9) according to the low-energy-consumption separation process for preparing the olefin reaction gas from the methanol, provided by the invention, the reaction gas at the four-section outlet of the reaction gas compressor is used as a heating heat source in one reboiler of the ethylene tower, and the heat coupling reduces one cooler, saves the cold source consumption of the cooler and the heat source consumption of the ethylene tower, and reduces the energy consumption of the process.
Drawings
FIG. 1 is a schematic flow diagram of a low energy consumption methanol-to-olefin reaction gas separation system.
FIG. 2 is a schematic flow diagram of a process condensate pre-separation technology system of a water scrubber in a separation system for methanol-to-olefin reaction gas with low energy consumption.
FIG. 3 is a schematic diagram of the connection of a multi-reactor alternate drying technique for reaction gas in a separation system for methanol-to-olefin reaction gas with low energy consumption.
FIG. 4 is a schematic diagram of a system connection of a multi-device alternate drying technique for reaction liquid in a separation system for methanol-to-olefin reaction gas with low energy consumption.
In the figure, 101-reaction gas compressor section; 102-a second reaction gas compressor section; 103-reaction gas compressor three-section; 104-reaction gas compressor four section; 201-gas-liquid separation tank; 202-a process gas drying system; 202A/B/C/D/E/F-reaction gas dryer; 203-reaction liquid drying system; 203A/B/C/D/E-process liquid dryer; 204-carbon two dryer; 205A/B-oil-water separator; 206-reflux tank of condensate pre-separation tower; 207-propylene protector; 208-a decant tank; 301-water washing tower; 302-caustic wash tower; 303-condensate pre-separation tower; 304-a high pressure column; 305-a low pressure column; 306-a demethanizer; 307-deethanizer; 308-an ethylene column; 309-propene column I; 310-propene column II; 401A/B-reboiler; 402-a condenser; 403-a cooler; 404-heat energy-saving exchanger; 501A/B-filter; 601-reflux pump; 602-kettle liquid pump.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1 to 4, in the embodiment of the present invention, a low energy consumption separation system for methanol to olefin reaction gas includes a first reaction gas compressor section 101, a second reaction gas compressor section 102, and a third reaction gas compressor section 103, which are connected to each other through pipes; the outlet of the second section 102 of the reaction gas compressor is connected with a water scrubber 301, and the side oil separation side of the water scrubber 301 is connected with a condensate pre-separation tower 303; the top of the condensate pre-separation tower 303 is connected with a condenser 402, a reflux tank 206 and a reflux pump 601, the reflux pump 601 is connected with the condensate pre-separation tower 303, the top of the reflux tank 206 is connected with a two-section inlet pipeline of a reaction gas compressor, the bottom of the condensate pre-separation tower 303 is connected with a cooler 403 and an oil-water separator 205A/B through a kettle liquid pump 602, and the condensate pre-separation tower 303 is provided with two reboilers 401A/B; the top of the water scrubber 301 is connected with an alkaline scrubber 302, and the top of the alkaline scrubber 302 is connected with a three-section inlet pipeline of a reaction gas compressor; the outlet of the three section 103 of the reaction gas compressor is connected with a gas-liquid separation tank 201, the top of the gas-liquid separation tank 201 is connected with a process gas drying system 202, the side part of the gas-liquid separation tank 201 is connected with an inclined tank 208, and the side part of the inclined tank 208 is connected with a process liquid drying system 203; the process gas drying system 202 and the process liquid drying system 203 are connected with the high-pressure tower 304 from different heights; the top of the high pressure tower 304 is connected with the four sections 104 of the reaction gas compressor, the bottom of the high pressure tower 304 is connected with the low pressure tower 305, and the top of the low pressure tower 305 is connected with the deethanizer 307; the outlet of the four section 104 of the reaction gas compressor is connected with a demethanizer 306, the top of the demethanizer 306 is connected with a heat energy-saving exchanger 404, and the bottom of the demethanizer 306 is connected with a deethanizer 307; the top of the deethanizer 307 is sequentially connected with a C2 dryer 204 and an ethylene tower 308, and the bottom of the deethanizer 307 is connected with a propylene tower I309; the top of the propylene column I309 is connected with the bottom of the propylene column II 310, and the top of the propylene column II 310 is connected with a propylene protector 207.
A low-energy-consumption separation process for preparing olefin reaction gas from methanol sequentially comprises the following process flows and steps:
1) the reaction gas from the methanol-to-olefin process enters the olefin separation process, mainly comprises C1-C7 and has the pressure of 0.08-0.15 MPaG, and is sequentially compressed by a first reaction gas compressor section 101 and a second reaction gas compressor section 102. Wherein, the outlet pressure of the first section 101 of the reaction gas compressor is 0.2-0.35 MPaG, and the outlet pressure of the second section 102 of the reaction gas compressor is 0.6-0.8 MPaG.
2) The reaction gas compressed by the first section 101 of the reaction gas compressor and the second section 102 of the reaction gas compressor enters a water washing tower 301 to remove oxygen-containing compounds (aldehyde, ketone and alcohol) and a small amount of acid gas (carbon dioxide) contained in the reaction gas, and meanwhile, a large amount of process condensate (mainly comprising C3-C7) is clearly obtained in an oil separation cavity of the tower. Wherein the working pressure range of the water washing tower 301 is 0.6-0.65 MPaG, and the working temperature range is 37-43 ℃; washing water used by the water washing tower 301 is turbine condensate of the unit; the washing tower 301 is a packed tower, the lower part of which is provided with an oil separating groove, and process condensate enters the oil separating groove and is discharged from the side part.
3) Discharging a large amount of process condensate which is obtained through the step 2) into a condensate pre-separation tower 303 through liquid level regulation to separate light components of C3 and below from heavy components of C4 and above. Wherein the process condensate is discharged from the oil separation side of the water washing tower 301 into a condensate pre-separation tower through self-pressure; the working pressure range of the condensate pre-separation tower 303 is 0.3-0.4 MPaG, and the working temperature range is 20-80 ℃; two reboilers 401A/B are arranged at the tower bottom of the condensate pre-separation tower 303.
4) The heavy components of C4 and above separated by the condensate pre-separation column 303 in step 3) are discharged from the column bottom by the tank liquid pump 602, cooled by the cooler 403, and sent to the oil- water separator 205A or 205B for oil-water separation. Wherein, the heavy components C4 and above are pressurized and sent into a cooler 403 through a column kettle liquid pump 602 of the condensate pre-separating column 303 and then cooled; in order to ensure the continuous and stable operation of the oil-water separators 205A/B, the oil-water separators 205A/B are opened one by one, operated normally and reserved the other by one, and 1 filter 501A/B is arranged in front of each oil-water separator 205A/B to prevent impurities from entering the oil-water separators 205A/B and influencing the oil-water separation effect; in order to ensure the separation effect of the oil-water separator 205A/B, the temperature of the heavy components C4 and above is controlled to be 10-14 ℃.
5) Separating oil from water in the step 4), sending heavy components of C4 and above into a carbon four device for processing treatment, and discharging the wastewater into a methanol-to-olefin process for steam stripping treatment. Wherein the water content of the C4 and above heavy components can be controlled within 100-300 ppm by the oil-water separation.
6) C3 separated from the top of the condensate pre-separating tower 303 in the step 3) and the following light components are returned to the inlet of the second section 102 of the reaction gas compressor. Wherein, the gas phase material at the top of the condensate preseparator 303 is condensed and then flows back to the tower, and the gas phase is discharged into the inlet of the second section 102 of the reaction gas compressor from the top of the reflux tank 206 of the condensate preseparator.
7) The reaction gas after water washing in the step 2) enters an alkaline washing tower 302 to remove acid gas (carbon dioxide) contained in the reaction gas, waste alkali liquor is discharged from the tower kettle and then sent to a battery compartment for treatment, and the washed reaction gas enters a reaction gas compressor three-section 103 for compression. Wherein, the alkali liquor used by the alkaline tower 302 is prepared by turbine condensate, and the washing water also uses the turbine condensate.
8) The reaction gas compressed by the three sections is cooled and then enters a gas-liquid separation tank 201 for gas-liquid separation, the gas phase at the top of the tank enters a reaction gas drying system 202 for removing the moisture in the reaction gas, the dew point of the reaction gas is controlled to be-70 to-80 ℃, the liquid phase at the bottom of the tank enters a tilting tank 208 for preliminary dehydration and then enters a reaction liquid drying system 203 for completely removing the moisture in the reaction liquid, and the moisture content in the reaction liquid is controlled to be 0.1 to 1 ppm. Wherein the pressure of the reaction gas compressed by the three stages is 1.3-1.5 MPaG.
9) The reaction gas and the reaction liquid dried in the step 8) respectively enter the high pressure tower 304 from different heights, C3 and the light components below the C3 primarily separated from the top of the tower enter the reaction gas compressor four section 104 for compression, and the C4 and the heavy components above and a small amount of C3 components in the tower bottom enter the low pressure tower 305 for further removing the C3 components. Wherein the working pressure range of the high-pressure tower 304 is 1.3-1.4 MPaG, and the working temperature range is-14-78 ℃.
10) The heavy components of C4 and above and a small amount of C3 entering the low-pressure tower 305 through the step 9) are further separated in the tower, the light components of C3 and below are discharged from the top of the tower and enter the deethanizer 307, and the heavy components of C4 and above and the step 5) are sent to a carbon four device for processing. Wherein the working pressure range of the low pressure tower 305 is 0.5-0.6 MPaG, and the working temperature range is 0-70 ℃; the above-mentioned C3 and less light components are condensed into a liquid by a condenser attached to the top of the low-pressure column 305, and sent to the deethanizer 307.
11) Compressing the light components of C3 and the following separated from the step 9) by a four-section 104 of a reaction gas compressor, cooling, sending the light components into a demethanizer 306 for separating the components of C1 from the components of C2-C3, sending the light components of C1 at the tower top and a small amount of hydrogen into a fuel gas pipe network of a whole plant after heat exchange by a heat energy-saving exchanger 404, and sending the components of C2-C3 at the tower bottom and the light components of C3 and the following discharged at the tower top of the low-pressure tower 305 in the step 10) into a deethanizer 307. Wherein, the pressure of the C3 and the following light components is 2.9-3.1 MPaG after being compressed by the four sections 104 of the reaction gas compressor; the working pressure range of the demethanizer 306 is 2.5-2.8 MPaG, and the working temperature range is-52-21 ℃.
12) C2-C3 components enter a deethanizer 307, and then C2 and C3 components are separated, C2 components discharged from the tower top enter a C2 drier 204 to remove trace moisture contained in the components and then enter an ethylene tower 308, C3 components discharged from the tower bottom are divided into two parts, one part is cooled and then is sent into a demethanizer 306 as an absorbent of the demethanizer 306, so that the loss of propylene and ethylene products at the tower top of the demethanizer 306 is reduced, and the other part enters a propylene tower I309. Wherein the working pressure range of the deethanizer 307 is 1.85-2.05 MPaG, and the working temperature range is-29-53 ℃.
13) The C2 component entering the ethylene tower 308 after the step 12) is separated into ethylene and ethane in the tower, the polymerization-grade ethylene product obtained at the tower top is sent to a tank area for storage and is used as a raw material of a downstream polyethylene and polypropylene device, the ethane component at the tower bottom is divided into two parts, one part is used as a byproduct and is merged into a fuel gas pipe network after heat exchange by the heat energy-saving exchanger 404, and the other part is used as an absorbent of the demethanizer 306 after being cooled and is sent to the demethanizer 306, so that the loss of propylene and ethylene products at the tower top of the demethanizer 306 is reduced. Wherein the working pressure range of the ethylene tower 308 is 1.89-2.05 MPaG, and the working temperature range is-30 to-5 ℃.
14) Because the tower body of the propylene rectifying tower is too high, the on-site construction is not convenient, the propylene tower is divided into two sections, namely the propylene tower I309 and the propylene tower II 310, the C3 component entering the propylene tower I309 through the step 12) is separated into propylene and propane in the propylene tower I309 and the propylene tower II 310, the propane component discharged from the tower bottom of the propylene tower I309 is divided into two sections, one section is cooled and then sent into the demethanizer 306 as an absorbent of the demethanizer 306, the loss of propylene and ethylene products at the tower top of the demethanizer 306 is reduced, and the other section is sent into a tank area for storage as a propane byproduct. Wherein the working pressure range of the propylene tower I309 is 1.8-1.9 MPaG, and the working temperature range is 45-50 ℃; the working pressure range of the propylene tower II 310 is 1.9-2.0 MPaG, and the working temperature range is 50-60 ℃.
15) And a polymer grade propylene product discharged from the top of the propylene tower II 310 is cooled and then sent to a propylene protector 207 to remove trace water and oxygen-containing compounds contained in the propylene product, and then sent to a tank area for storage to serve as raw materials of a downstream polyethylene and polypropylene device. Wherein, the top of the propylene tower II 310 is additionally provided with a cooler which adopts circulating water for cooling to control the temperature at the top of the tower.
Further, the condensate pre-separation tower 303 is arranged between the second section 102 of the reactor compressor and the third section 103 of the reactor compressor, and mainly functions to separate the process condensate (mainly comprising C2-C7) condensed in the washing tower 301, so that light components C3 and below in the process condensate are separated from heavy components C4 and above, the gas phase of the light components C3 and below is returned to the inlet of the second section 102 of the reactor compressor, and the heavy components C4 and above are fully dehydrated in the oil-water separator 205A/B after being cooled to 10-14 ℃ by the cooler 403, and are sent to a C4 device for treatment after being dehydrated. The condenser 402 of the condensate preseparator adopts circulating water as a cold source, and the reboiler 401A/B adopts steam as a heat source.
Further, the reaction gas drying system 202 adopts a six-device (202A/B/C/D/E/F) alternating drying technology. Only two dryers are in the adsorption stage and the other four dryers are in different regeneration stages (the regeneration stage comprises reverse discharging, heating flushing, cold blowing and boosting) respectively in the same time period through sequential control, and the hourly consumption of regenerated nitrogen is reduced.
Furthermore, the reaction solution drying system 203 adopts a five-device (203A/B/C/D/E) alternate drying technology. Only one drier is in the adsorption stage and the other four driers are in different regeneration stages (the regeneration stage comprises reverse discharge, heating flushing, cold blowing and pressure boosting) respectively in the same time period through sequential control, and the hourly consumption of regenerated nitrogen is reduced.
Further, the fourth stage of the compressed reactant gas is cooled and sent to the demethanizer 306, and the third cooler is cooled by a reboiler of the ethylene column 308 to achieve thermal coupling.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
Claims (8)
1. A low-energy-consumption separation system for methanol-to-olefin reaction gas comprises a reaction gas compressor section (101), a reaction gas compressor section (102) and a reaction gas compressor section (103) which are connected through pipelines, and is characterized in that an outlet of the reaction gas compressor section (102) is connected with a water washing tower (301), and an oil separation side at the side of the water washing tower (301) is connected with a condensate pre-separation tower (303);
the top of the condensate pre-separation tower (303) is connected with a condenser (402), a reflux tank (206) and a reflux pump (601), the reflux pump (601) is connected with the condensate pre-separation tower (303), the top of the reflux tank (206) is connected with an inlet pipeline of a reaction gas compressor second section (102), the bottom of the condensate pre-separation tower (303) is connected with a cooler (403) and oil-water separators (205A, 205B) through a kettle liquid pump (602), and the condensate pre-separation tower (303) is provided with two reboilers (401A, 401B);
the top of the water scrubber (301) is connected with an alkaline scrubber (302), and the top of the alkaline scrubber (302) is connected with a three-section (103) inlet pipeline of a reaction gas compressor;
the outlet of the three sections (103) of the reaction gas compressor is connected with a gas-liquid separation tank (201), the top of the gas-liquid separation tank (201) is connected with a process gas drying system (202), the side part of the gas-liquid separation tank (201) is connected with an inclined tank (208), and the side part of the inclined tank (208) is connected with a process liquid drying system (203);
the process gas drying system (202) and the process liquid drying system (203) are connected with the high-pressure tower (304) from different heights;
the top of the high-pressure tower (304) is connected with the four sections (104) of the reaction gas compressor, the bottom of the high-pressure tower (304) is connected with the low-pressure tower (305), and the top of the low-pressure tower (305) is connected with the deethanizer (307);
the outlet of the four sections (104) of the reaction gas compressor is connected with a demethanizer (306), the top of the demethanizer (306) is connected with a heat energy-saving exchanger (404), and the bottom of the demethanizer (306) is connected with a deethanizer (307);
the top of the deethanizer (307) is sequentially connected with a C2 dryer (204) and an ethylene tower (308), and the bottom of the deethanizer (307) is connected with a propylene tower I (309);
the top of the propylene tower I (309) is connected with the bottom of the propylene tower II (310), and the top of the propylene tower II (310) is connected with a propylene protector (207).
2. The separation system of a methanol-to-olefin reaction gas with low energy consumption according to claim 1, wherein the process gas drying system (202) comprises six reaction gas dryers (202A, 202B, 202C, 202D, 202E, 202F).
3. The separation system of the reaction gas for preparing the olefin from the methanol according to the claim 1, characterized in that the process liquid drying system (203) comprises five reaction liquid dryers (203A, 203B, 203C, 203D, 203E).
4. The separation system of the low-energy-consumption methanol-to-olefin reaction gas as claimed in claim 1, wherein the condensate pre-separation tower (303) is arranged between the two sections (102) and the three sections (103) of the reactor compressor.
5. A low-energy-consumption separation process for preparing olefin reaction gas from methanol is characterized by comprising the following steps:
1) the reaction gas sequentially enters a first section (101) of a reaction gas compressor and a second section (102) of the reaction gas compressor to be compressed;
2) the reaction gas compressed by the first section (101) of the reaction gas compressor and the second section (102) of the reaction gas compressor enters a water scrubber (301) to remove oxygen-containing compounds and a small amount of acid gas contained in the reaction gas, and a large amount of process condensate is clear;
3) discharging a large amount of process condensate obtained in the step 2) into a condensate pre-separation tower (303) through liquid level regulation to separate light components of C3 and below from heavy components of C4 and above;
4) discharging the heavy components C4 and above separated by the condensate pre-separating tower (303) in the step 3) from the tower kettle through a kettle liquid pump (602), cooling the heavy components by a cooler (403), and then sending the heavy components into oil-water separators (205A, 205B) for oil-water separation;
5) separating oil from water in the step 4), sending heavy components of C4 and above into a carbon four device for processing treatment, and discharging the wastewater into a methanol-to-olefin process for steam stripping treatment;
6) c3 separated from the top of the condensate pre-separating tower (303) in the step 3) and the following light components are returned to the inlet of the second section (102) of the reaction gas compressor;
7) the reaction gas after water washing in the step 2) enters an alkaline washing tower (302) to remove acid gas contained in the reaction gas, waste alkali liquor is discharged from a tower kettle and then sent to a battery compartment for treatment, and the washed reaction gas enters a reaction gas compressor three section (103) for compression;
8) cooling the three-section compressed reaction gas, then, introducing the cooled reaction gas into a gas-liquid separation tank (201) for gas-liquid separation, introducing a gas phase at the top of the tank into a process gas drying system (202) for removing moisture in the reaction gas, controlling the dew point of the reaction gas to be-70 to-80 ℃, introducing a liquid phase at the bottom of the tank into a tilting tank (208) for preliminary dehydration, and then, introducing the liquid phase into a process liquid drying system (203) for thoroughly removing moisture in the reaction liquid, so that the moisture content in the reaction liquid is controlled to be 0.1 to 1 ppm;
9) the reaction gas and the reaction liquid dried in the step 8) respectively enter a high-pressure tower (304) from different heights, C3 and the following light components which are primarily separated from the top of the tower enter a reaction gas compressor four section (104) for compression, and C4 and the above heavy components and a small amount of C3 components in the tower kettle enter a low-pressure tower (305) for further removing the C3 components;
10) c4 and above heavy components and a small amount of C3 components entering the low-pressure tower (305) through the step 9) are further separated in the tower, C3 and below light components are discharged from the top of the tower and enter a deethanizer (307), and C4 and above heavy components and the step 5) are sent to a carbon four device together for processing;
11) compressing the light components of C3 and the following separated in the step 9) by a four-section (104) of a reaction gas compressor, cooling, sending the light components into a demethanizer (306) for separating the components of C1 from the components of C2-C3, sending the light components of C1 and a small amount of hydrogen at the tower top into a fuel gas pipe network of the whole plant after heat exchange by a heat energy-saving exchanger (404), sending the components of C2-C3 at the tower bottom and the light components of C3 and the following discharged at the tower top of the low-pressure tower (305) in the step 10) into a deethanizer (307);
12) C2-C3 components enter a deethanizer (307), then C2 and C3 components are separated, the C2 component discharged from the tower top firstly enters a C2 drier (204) to remove trace moisture contained in the C2 component and then enters an ethylene tower (308), the C3 component discharged from the tower bottom is divided into two parts, one part is cooled and then is sent into a demethanizer (306) as an absorbent of the demethanizer (306), the loss of propylene and ethylene products at the tower top of the demethanizer (306) is reduced, and the other part enters a propylene tower I (309);
13) the C2 component entering the ethylene tower (308) through the step 12) is separated into ethylene and ethane in the tower, the polymerization-grade ethylene product obtained at the tower top is sent to a tank area for storage and is used as a raw material of a downstream polyethylene and polypropylene device, the ethane component at the tower bottom is divided into two streams, one stream is used as a byproduct and is merged into a fuel gas pipe network after heat exchange by a heat energy-saving exchanger (404), and the other stream is used as an absorbent of a demethanizer (306) after being cooled and is sent into the demethanizer (306), so that the loss of propylene and ethylene products at the tower top of the demethanizer (306) is reduced;
14) separating propylene and propane from the C3 component entering the propylene tower I (309) in the propylene tower I (309) and the propylene tower II (310) through the step 12), wherein the propane component discharged from the tower bottom of the propylene tower I (309) is divided into two parts, one part is cooled and then is sent into the demethanizer (306) as an absorbent of the demethanizer (306), so that the loss of propylene and ethylene products at the top of the demethanizer (306) is reduced, and the other part is sent to a tank area for storage as a propane byproduct;
15) and (3) cooling a polymerization grade propylene product discharged from the top of the propylene tower II (310), sending the cooled product into a propylene protector (207), removing trace water and oxygen-containing compounds contained in the product, and sending the product to a tank area for storage to serve as a raw material of a downstream polyethylene and polypropylene device.
6. The separation process of the reaction gas for preparing olefin from methanol according to the claim 5, characterized in that the process gas drying system (202) adopts six-device alternate drying technology: only two dryers are in the adsorption stage and the other four dryers are in different regeneration stages respectively in the same time period through sequential control.
7. The separation process of the reaction gas for preparing olefin from methanol according to the claim 5, wherein the process liquid drying system (203) adopts a five-container alternate drying technology: only one drier is in the adsorption stage and the other four driers are in different regeneration stages respectively in the same time period through sequential control.
8. The separation process of the reaction gas for preparing olefin from methanol according to the claim 5, characterized in that the reaction gas after the four-stage compression is cooled and sent to the demethanizer (306), and the third cooler is cooled by a reboiler of the ethylene column (308) to realize thermal coupling.
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