CN108358739B - Oil-water-gas separation system and method for methanol-to-propylene process - Google Patents
Oil-water-gas separation system and method for methanol-to-propylene process Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 330
- 230000008569 process Effects 0.000 title claims abstract description 307
- 238000000926 separation method Methods 0.000 title claims abstract description 275
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims abstract description 480
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 476
- 229930195733 hydrocarbon Natural products 0.000 claims abstract description 286
- 150000002430 hydrocarbons Chemical class 0.000 claims abstract description 286
- 239000004215 Carbon black (E152) Substances 0.000 claims abstract description 271
- 238000011084 recovery Methods 0.000 claims abstract description 107
- 239000007795 chemical reaction product Substances 0.000 claims abstract description 44
- 238000010790 dilution Methods 0.000 claims abstract description 34
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- 238000003809 water extraction Methods 0.000 claims description 71
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- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 claims description 12
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 0.000 claims description 12
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- 239000007789 gas Substances 0.000 abstract description 114
- LCGLNKUTAGEVQW-UHFFFAOYSA-N Dimethyl ether Chemical compound COC LCGLNKUTAGEVQW-UHFFFAOYSA-N 0.000 description 80
- HEMHJVSKTPXQMS-UHFFFAOYSA-M sodium hydroxide Inorganic materials [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 56
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- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 2
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- 230000006978 adaptation Effects 0.000 description 2
- 229910052783 alkali metal Inorganic materials 0.000 description 2
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Classifications
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C1/00—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon
- C07C1/20—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon starting from organic compounds containing only oxygen atoms as heteroatoms
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/005—Processes comprising at least two steps in series
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/10—Purification; Separation; Use of additives by extraction, i.e. purification or separation of liquid hydrocarbons with the aid of liquids
Abstract
The invention provides an oil-water-gas separation system and a method for a methanol-to-propylene process, wherein the oil-water-gas separation system comprises a hydrocarbon-water separation unit, an oil-gas separation unit, a process steam production unit and a methanol recovery unit; a hydrocarbon-water separation unit for separating a stream containing MTP reaction products and dilution steam; the oil-gas separation unit is used for separating the gaseous hydrocarbon separated by the hydrocarbon-water separation unit and the water entrained in the heavy hydrocarbon component; the process steam production unit is used for extracting condensed water at least partially separated from the heavy hydrocarbon components and also used for treating the water extracted with the hydrocarbon components to obtain process steam; the methanol recovery unit is configured to treat condensed water at least partially separated from the heavy hydrocarbon components to separate methanol, DME and light component noncondensable gases contained therein. The separation system can more completely separate MTP reaction products from reaction water and process steam, and ensures long-period stable operation of the device.
Description
Technical Field
The invention relates to an oil-water-gas separation technology of a product obtained in a process of preparing propylene from methanol, in particular to an oil-water-gas separation system and method for the process of preparing propylene from methanol.
Background
Propylene is the most important basic organic feedstock next to ethylene. With the years of expansion of the application fields of the derivatives, the demand is increasing. However, as petroleum resources are increasingly depleted, development of a process for producing propylene other than petroleum is highly desired. At present, the preparation of methanol by using coal/natural gas as raw materials enters large-scale production, and the preparation of low-carbon olefin (MTO/MTP) by using methanol has the advantages of wide raw material sources, low cost and the like, and is suitable for the national conditions of rich coal and lean oil in China.
The process for preparing propylene (MTP) from methanol is to chemically react the mixture of dimethyl ether and methanol under the action of catalyst to obtain the mixed product containing unconverted methanol and hydrocarbon. The product cooling and separating process is to return unreacted methanol to the reactor to connect propylene and ethylene rectifying process, i.e. the product produced from the MTP reactor is cooled down during the product cooling and separating process to separate gas, oil and water fully. Cooling and separation of the MTP reaction product is necessary and therefore separation efficiency is of paramount importance. Reasonable separation systems can improve the efficiency of MTP process design, and thus how to design separation systems is an important part of MTP technology.
10 months 2010, shenhuaining Xia Meiye group was put into industrial production from the 50 ten thousand tons/year coal-based methanol-to-propylene (MTP) project introduced by Lurgi, germany. Up to now, the device has been operated for more than 5 years. As with most of the first commercial commodity chemical production technologies, the Lurgi MTP process has many points to be improved while producing propylene with high selectivity. In the operation process of the MTP device, the problem of oil-water separation is always a bottleneck which puzzles the stable operation of the device. The oil-water separation mainly relates to a quenching tower and a pre-quenching tower, an oxide extraction tower and an extraction tower, wherein the oil-water separation problem of the quenching tower and the pre-quenching tower is most remarkable. Poor oil-water separation effect can cause the oil-carrying cavitation at the inlet of the chilled water pump to jump, thereby causing accidents such as high temperature at the inlet of the hydrocarbon compressor and jump. However, the current chilling system process flow design is not enough to consider the actual production requirement, and has poor gas, oil and water separation effect on the product separation system. How to completely and efficiently separate the gas, oil and water in the MTP production process is one of the technical difficulties that the skilled person is urgent to break through.
Disclosure of Invention
In view of this, the present invention provides an oil-water-gas separation system for a methanol-to-propylene process, and also provides an oil-water-gas separation method for a product obtained in the methanol-to-propylene process based on the separation system. The separation system can be used for more completely separating MTP reaction products from reaction water and process steam, ensures long-period stable operation of the coal-based methanol-to-propylene device, and is beneficial to operation of a subsequent gas compression system and drying of hydrocarbon products.
In order to achieve the purpose, the invention adopts the following technical scheme:
the first aspect of the invention provides an oil-water-gas separation system for a methanol-to-propylene process, which comprises a hydrocarbon-water separation unit, an oil-gas separation unit, a process steam production unit and a methanol recovery unit;
the hydrocarbon-water separation unit is used for separating a stream containing MTP reaction products and dilution steam so as to obtain gaseous hydrocarbon, heavy hydrocarbon components and condensed water from which the heavy hydrocarbon components are separated;
the oil-gas separation unit is used for separating the gaseous hydrocarbon separated by the hydrocarbon-water separation unit from water entrained in the heavy hydrocarbon component to obtain a gas phase component, hydrocarbon condensate and residual water;
the process steam production unit is used for extracting at least part of condensed water separated by the hydrocarbon-water separation unit and separated heavy hydrocarbon components to extract hydrocarbon components from the condensed water and obtain water extracted with the hydrocarbon components, and is also used for treating the water extracted with the hydrocarbon components to obtain process steam separated from salt-containing liquid drops;
The methanol recovery unit is used for treating at least part of condensed water separated by the heavy hydrocarbon component and obtained by the separation of the hydrocarbon-water separation unit so as to separate methanol, DME and light component noncondensable gas contained in the condensed water.
In some preferred embodiments of the present invention, the hydrocarbon-water separation unit comprises a pre-quench tower, a quench tower, and a quench water separation tank;
wherein the pre-quench tower is provided with a first inlet for inputting quench water and lye and a second inlet for inputting a stream containing MTP reaction products and dilution steam, the first inlet is positioned above the second inlet, and the pre-quench tower is used for contacting the stream containing MTP reaction products and dilution steam with the quench water and lye so as to cool and wash the stream containing MTP reaction products and dilution steam to obtain a gaseous stream, heavy hydrocarbon components and condensed water;
the quenching tower is provided with a third inlet for inputting quench water and lye, and is also provided with a fourth inlet for inputting a gaseous stream from the pre-quenching tower, the third inlet is positioned above the fourth inlet, and the quenching tower is used for contacting the gaseous stream from the pre-quenching tower with the quench water and the lye so as to cool and wash the gaseous stream to obtain gaseous hydrocarbon, heavy hydrocarbon components and condensed water;
The quenching water separation tank is respectively communicated with the pre-quenching tower and the quenching tower through condensed water conveying pipelines, and is used for receiving condensed water conveyed by the condensed water conveying pipelines and separating residual heavy hydrocarbon components in the condensed water so as to obtain heavy hydrocarbon components and condensed water from which the heavy hydrocarbon components are separated;
in some preferred embodiments of the present invention, the quench water separation tank is respectively communicated with the first inlet of the pre-quench tower and the third inlet of the quench tower through a quench water circulation pipeline, and is used for respectively circulating at least part of condensed water obtained by the quench water separation tank and separated from heavy hydrocarbon components to the pre-quench tower and the quench tower as quench water.
In some preferred embodiments of the present invention, the oil-gas separation unit comprises a compressor surge tank, a compressor, and an oil-gas separation tank;
the compressor buffer tank is communicated with the quenching tower through a gaseous hydrocarbon conveying pipeline, and is used for separating water entrained in the gaseous hydrocarbon from the quenching tower so as to obtain liquid materials and the gaseous hydrocarbon from which the entrained water is separated; preferably, a liquid material conveying pipeline is further connected between the compressor buffer tank and the quenching tower so as to recycle the liquid material separated by the compressor buffer tank to the quenching tower;
The compressor is communicated with the compressor buffer tank, and is used for receiving the gaseous hydrocarbon separated from the entrained water and obtained by separation of the compressor buffer tank, and compressing and cooling the gaseous hydrocarbon to obtain an oil-gas mixture;
the oil-gas separation tank is communicated with the compressor through an oil-gas mixture conveying pipeline, the oil-gas separation tank is communicated with the pre-quenching tower, the quenching tower and the quenching water separation tank through heavy hydrocarbon component conveying pipelines respectively, and the oil-gas separation tank is used for separating the oil-gas mixture from the compressor and water entrained in the heavy hydrocarbon components from the pre-quenching tower, the quenching tower and the quenching water separation tank so as to obtain gas phase components, hydrocarbon condensate and residual water; preferably, the oil-gas separation tank is communicated with the compressor buffer tank through a residual water conveying pipeline, and is used for conveying the residual water to the compressor buffer tank.
In some preferred embodiments of the present invention, the process steam production unit comprises a process water extraction column, a process steam generator, and a process steam separation tank;
the process water extraction tower is communicated with the quenching water separation tank through a first quenching water conveying pipeline, and the first quenching water conveying pipeline is used for inputting at least part of condensed water, obtained from the quenching water separation tank, from which heavy hydrocarbon components are separated, into the process water extraction tower; the process water extraction tower is provided with a process steam input port for inputting process steam, and is used for contacting the condensed water which is input by the first quenching water conveying pipeline and is separated from the heavy hydrocarbon component with the process steam to extract residual hydrocarbon component and obtain water from which the hydrocarbon component is extracted; preferably, the process water extraction tower is communicated with the pre-quenching tower through a hydrocarbon component conveying pipeline, and is used for recycling hydrocarbon components extracted by the process water extraction tower to the pre-quenching tower;
The process steam generator is communicated with the process water extraction tower through a conveying pipeline for conveying the water extracted with the hydrocarbon components, and is used for converting the water extracted with the hydrocarbon components into steam;
the process steam separation tank is communicated with the process steam generator through a steam conveying pipeline and is used for separating salt-containing liquid drops carried in the steam input by the steam conveying pipeline so as to obtain process steam; preferably, a demister is arranged in the process steam separation tank;
the process steam separating tank is communicated with a process steam input port of the process water extraction tower through a process steam conveying pipeline so as to convey at least part of the process steam obtained from the process steam separating tank to the process water extraction tower.
In some preferred embodiments of the present invention, the methanol recovery unit comprises a methanol recovery column and a methanol recovery column reflux drum;
the methanol recovery tower is communicated with the quenching water separation tank through a second quenching water conveying pipeline, the second quenching water conveying pipeline is used for inputting at least part of condensed water obtained from the quenching water separation tank and separated from heavy hydrocarbon components into the methanol recovery tower, and the methanol recovery tower is used for rectifying the condensed water input into the methanol recovery tower and separated from the heavy hydrocarbon components so as to obtain process water and liquid phase components containing methanol and DME; preferably, the methanol recovery tower is communicated with the process steam generator through a sewage conveying pipeline, the sewage conveying pipeline is used for conveying sewage discharged by the process steam generator, and the methanol recovery tower is also used for receiving the sewage conveyed by the sewage conveying pipeline and rectifying the sewage to obtain process water and a liquid phase component containing methanol and DME (dimethyl ether);
The methanol recovery tower reflux tank is communicated with the methanol recovery tower through a liquid phase component conveying pipeline and is used for separating liquid phase components input into the methanol recovery tower reflux tank so as to obtain methanol, DME and light component noncondensable gas;
preferably, a reflux pipeline is connected between the methanol recovery tower reflux tank and the methanol recovery tower, and the reflux pipeline is used for refluxing at least part of methanol and DME obtained by separation of the methanol recovery tower reflux tank to the methanol recovery tower.
In a second aspect the present invention provides a process for the separation of oil-water-gas from a product of a methanol to propylene process using a separation system as described above, the process comprising:
separating the MTP reaction product and dilution steam containing stream with the hydrocarbon-water separation unit to obtain gaseous hydrocarbons, heavy hydrocarbon components, and condensed water from which the heavy hydrocarbon components are separated;
separating the water entrained in the gaseous hydrocarbons and heavy hydrocarbon components separated by the hydrocarbon-water separation unit by the oil-gas separation unit to obtain a gas phase component, a hydrocarbon condensate and residual water;
extracting at least a portion of the condensed water separated by the heavy hydrocarbon component separation by the hydrocarbon-water separation unit with the process steam production unit to separate out the remaining hydrocarbon component therein; the water from which the hydrocarbon components are extracted is treated, and salt-containing liquid drops carried in the water are separated to obtain process steam;
And (3) treating at least part of condensed water separated from heavy hydrocarbon components and obtained by separating the hydrocarbon-water separation unit by utilizing the methanol recovery unit, and separating to obtain methanol, DME and light component noncondensable gas.
In the present invention, the separation of MTP reaction product from reaction water and process water is achieved in a hydrocarbon-water separation unit.
In some preferred embodiments of the present invention, the hydrocarbon-water separation unit comprises a pre-quench tower, a quench tower, and a quench water separation tank; the pre-quench tower is provided with a first inlet and a second inlet, and the first inlet is positioned above the second inlet; the quench tower is provided with a third inlet and a fourth inlet, the third inlet being located above the fourth inlet, the method comprising:
feeding a material flow containing MTP reaction products and dilution steam into a pre-quenching tower from the second inlet, feeding quench water and alkali liquor into the pre-quenching tower from the first inlet, and cooling and washing the material flow containing MTP reaction products and dilution steam by contacting with the quench water and the alkali liquor from bottom to top after the material flow containing MTP reaction products and dilution steam enters the pre-quenching tower to obtain a gaseous material flow, heavy hydrocarbon components and condensed water; the alkali liquor can be a NaOH solution and the like, and the concentration of the alkali liquor is preferably 15-60wt%.
Feeding the gaseous stream obtained from the pre-quenching tower into a quenching tower through the fourth inlet, feeding the quenching water and the lye into the quenching tower through the third inlet, and cooling and washing the gaseous stream by fully contacting the quenching water and the lye from bottom to top after entering the quenching tower, wherein the temperature is preferably reduced to 35-70 ℃, more preferably 40-55 ℃, so as to obtain gaseous hydrocarbon, heavy hydrocarbon components and condensed water;
the condensate water obtained by the pre-quenching tower and the quenching tower is sent to a quenching water separation tank, residual heavy hydrocarbon components in the condensate water are separated, and condensate water from which the heavy hydrocarbon components are separated is obtained;
in some preferred embodiments of the present invention, at least a portion of the condensed water obtained from the quench water separation tank from which heavy hydrocarbon components are separated is recycled to the pre-quench tower and quench tower as quench water. In a preferred embodiment, 90 to 96 mass% of the condensed water from the quench water separation tank, from which heavy hydrocarbon components are separated, is recycled as quench water to the pre-quench tower and quench tower.
Preferably, the MTP reaction product and dilution steam containing stream is heat recovered and temperature controlled from 170 ℃ to 210 ℃ prior to being fed to the pre-quench tower;
Preferably, the temperature of the quench water and the lye used in the pre-quench tower is 48-52 ℃; the gaseous stream from the pre-quench tower fed to the quench tower has a temperature of 50-60 ℃; the temperature of the quench water and the alkali liquor used in the quenching tower is 38-42 ℃.
In the invention, the separation of the oil and the gas generated by the MTP reaction is achieved in the oil-gas separation unit, and the residual water is further removed.
In some preferred embodiments of the present invention, the oil-gas separation unit comprises a compressor surge tank, a compressor, and an oil-gas separation tank; the method comprises the following steps:
sending the gaseous hydrocarbon separated by the quenching tower into a compressor buffer tank, and separating out water entrained in the gaseous hydrocarbon to obtain liquid materials and the gaseous hydrocarbon from which the entrained water is separated; preferably, the liquid material is fed into a quench tower;
and sending the gaseous hydrocarbon separated with the entrained water obtained by the compressor buffer tank to a compressor, and obtaining an oil-gas mixture after the gaseous hydrocarbon is compressed and cooled by the compressor. Preferably the compressor outlet pressure is controlled to be 2.0-2.5MPa, preferably the temperature reduction is to reduce the temperature to 35-50 ℃.
The oil-gas mixture obtained by the compressor and the heavy hydrocarbon components obtained by separation of the pre-quenching tower, the quenching tower and the quenching water separation tank are sent to the oil-gas separation tank, and water entrained in the heavy hydrocarbon components is separated out to obtain gas phase components, hydrocarbon condensate and residual water;
Preferably, the residual water is fed to a compressor surge tank. Preferably, the hydrocarbon condensate is passed to the next separation unit to separate the C4, C5-6 components therein, and the vapor phase component is passed to the next stage of compression unit.
In the present invention, process steam is produced in a process steam production unit, and the remaining hydrocarbon components are further removed and possibly entrained salt-containing droplets (e.g., sodium salt-containing droplets) are separated. The process steam produced may be returned to the MTP reactor.
In some preferred embodiments of the present invention, the process steam production unit comprises a process water extraction column, a process steam generator, and a process steam separation tank; the method comprises the following steps:
feeding at least part of the condensed water separated with the heavy hydrocarbon components obtained from the quenching water separation tank into the process water extraction tower, inputting process steam into the process water extraction tower, and extracting the condensed water separated with the heavy hydrocarbon components in the process water extraction tower by utilizing the process steam so as to separate residual hydrocarbon components and obtain hydrocarbon components and water extracted with the hydrocarbon components; preferably, the hydrocarbon component separated by the process water extraction tower is recycled to the pre-quenching tower; preferably, at least a portion of the condensed water obtained from the quench water separation tank, from which heavy hydrocarbon components are separated, is pressurized (preferably to 0.4 to 1.2 MPa) with a quench water pump and filtered to separate particulates therein prior to entering the process water extraction column. In some preferred embodiments, 4 to 10 mass% of the condensed water from the quench water separation tank, from which heavy hydrocarbon components are separated, is fed to the process water extraction column.
Feeding the water extracted with the hydrocarbon components obtained from the process water extraction tower into a process steam generator to obtain steam; preferably, the water from which the hydrocarbon components are extracted is pressurized and preheated, preferably to 180-250 ℃, before being fed to the process steam generator; the pressurization can be specifically performed by a water pump (for example, a process water pump), and is preferably performed to 1.0-2.6 MPa.
The steam generated by the process steam generator is sent to a process steam separation tank, and salt-containing liquid drops (such as sodium salt-containing liquid drops) carried in the steam are separated out to obtain process steam; in a specific embodiment, a demister can be arranged in the process steam generator to effectively remove salt-containing liquid drops possibly entrained in the steam.
At least part of the process steam obtained by the process steam generator is input into a process water extraction tower. In particular, the process steam enters the process water extraction tower through a process steam inlet of the process water extraction tower, and no additional process steam is required to be supplied. In a preferred embodiment, a portion of the process steam is also fed to the MTP reactor as dilution steam after being heated to 430℃in combination with recycle hydrocarbon and DME. In the invention, unreacted methanol in the process water is recovered in a methanol recovery unit, and light component noncondensable gas is separated.
In some preferred embodiments of the present invention, the methanol recovery unit comprises a methanol recovery column and a methanol recovery column reflux drum; the method comprises the following steps:
feeding at least part of condensed water obtained from the quenching water separation tank and separated from heavy hydrocarbon components into a methanol recovery tower, and rectifying and separating to obtain process water and liquid phase components containing methanol and DME; preferably, the sewage discharged from the process steam generator (the process steam generator discharges part of sewage while generating steam) is also sent to the methanol recovery tower for rectification so as to obtain process water and a liquid phase containing methanol and DME; in a preferred embodiment, the effluent from the process steam generator is mixed with the condensed water from the quench water separator tank after heat exchange with the heavy hydrocarbon components separated therefrom and fed to the methanol recovery column; in a preferred embodiment, the process water obtained by rectification and separation in the methanol recovery tower is cooled and sent to an oxide extraction unit for use.
Sending the liquid phase component obtained by the methanol recovery tower to a reflux tank of the methanol recovery tower, and separating to obtain methanol, DME and light component noncondensable gas; refluxing at least a portion of the separated methanol and DME to the methanol recovery column. In a preferred embodiment, a portion of the separated methanol and DME are also returned to the DME reactor and the separated light component noncondensable gas is recycled to the MTP reactor.
In some preferred embodiments, both the pre-quench column and quench column structures used in the separation system of the present invention may employ the column structures disclosed in patent CN 202860169U; the process steam separator tank used in the separation system of the present invention may employ the steam tower structure disclosed in patent CN204328982U or CN 202191808U.
The technical scheme provided by the invention has the following beneficial effects:
the separation system solves the problem of poor gas, oil and water separation effect in the prior art by skillful combination of the multi-stage separation units of the hydrocarbon-water separation unit, the oil-gas separation unit, the process steam production unit and the methanol recovery unit. The separation system can effectively and completely separate the methanol-to-propylene reaction product (MTP reaction product) from the reaction water and the process water, separate the outlet logistics of the MTP reactor into oil, water and gas, and achieve the purpose of more thorough separation of oil, water and gas, thereby ensuring the operation of a subsequent gas compression system, avoiding the greater difficulty in the drying of subsequent hydrocarbon products, ensuring the long-period stable operation of the MTP production device, and avoiding the occurrence of vehicle jump accidents.
In the preferred scheme of the invention, the process steam production unit adopts a mode of combining the process steam generator and the process steam separation tank to further remove the small fog drops in the steam, thereby ensuring that the salt liquid drops, especially sodium ions, contained in the steam are effectively removed.
The separation method has the advantages of simple and reliable process, good stability and the like.
Drawings
FIG. 1 is a schematic diagram of an oil-water-gas separation system for a methanol-to-propylene process of the present invention in one embodiment.
Detailed Description
For a better understanding of the technical solution of the present invention, the following examples are further described below, but the present invention is not limited to the following examples.
As shown in fig. 1, an oil-water-gas separation system for a process of preparing propylene from methanol includes a hydrocarbon-water separation unit 100, an oil-gas separation unit 200, a process steam production unit 300, and a methanol recovery unit 400.
Wherein the hydrocarbon-water separation unit 100 is used for separating a stream containing MTP reaction products and dilution steam, which is input through a material conveying pipeline 1, and gaseous hydrocarbon, heavy hydrocarbon components and condensed water from which the heavy hydrocarbon components are separated are obtained through the hydrocarbon-water separation unit 100.
In some preferred embodiments, the hydrocarbon-water separation unit 100 consists essentially of a pre-quench tower 101, a quench tower 102, and a quench water separation tank 103.
Wherein, the pre-quenching tower 101 is provided with a first inlet for inputting quench water and alkali liquor, the first inlet of the pre-quenching tower 101 is communicated with the alkali liquor conveying pipeline 11, which can be directly communicated or indirectly communicated, and the alkali liquor is input into the pre-quenching tower through the alkali liquor conveying pipeline 11; the first inlet of the pre-quench tower 101 is also in communication with a quench water transfer conduit 2 into which quench water is fed via the quench water transfer conduit 2. In one embodiment, the lye delivery pipe 11 is in communication with the quench water delivery pipe 2, and the lye and quench water are introduced into the same pipe and then enter the pre-quench tower 101 through the first inlet. The pre-quench tower 101 is also provided with a second inlet for inputting a stream comprising MTP reaction products and dilution steam, which second inlet is in communication with the feed transfer line 1, the first inlet of the pre-quench tower 101 being located above the second inlet. The "first inlet" and "second inlet" are described herein for convenience only to distinguish and depict the feed ports of different materials in the pre-quench tower 101, and are not intended to be limiting as to the number of inlets. The pre-quench tower 101 is configured to substantially contact the MTP reaction product and dilution steam containing stream fed from the second inlet with the quench water and lye fed from the first inlet to cool and scrub the MTP reaction product and dilution steam containing stream to obtain a gaseous stream, heavy hydrocarbon components, and condensate. Wherein the alkali liquor used can be NaOH solution with the concentration of 15-60 wt%. The gaseous stream obtained consists mainly of C1-C5 mixed hydrocarbons, also containing small amounts of CO, c5+ hydrocarbons, etc. Since the first inlet is located above the second inlet, stream 1 containing MTP reaction product and dilution steam fed from the second inlet is fully contacted with quench water and lye fed from the first inlet from bottom to top after entering pre-quench tower 101.
Quench tower 102 is provided with a third inlet for feeding quench water and lye and a fourth inlet for feeding a gaseous stream from pre-quench tower 101, the third inlet being located above the fourth inlet. The "third inlet" and "fourth inlet" are described herein for convenience only to distinguish and depict the feed ports of different materials in quench tower 102, and are not intended to be limiting as to the number of inlets or sequencing of inlets. In a specific embodiment, the third inlet of the quenching tower 102 is in communication with the lye delivery conduit 12, which may be direct or indirect, into which lye is fed via the lye delivery conduit 12; the third inlet of quench tower 102 is also in communication with quench water transfer line 4, into which quench water is fed via quench water transfer line 4. In one embodiment, the lye delivery line 12 is in communication with the quench water delivery line 4, and the lye and quench water are introduced into the same line and then enter the quench tower 102 via a third inlet. The fourth inlet of the quenching tower 102 is communicated with the gaseous stream outlet of the pre-quenching tower 101 through a gaseous stream conveying pipeline 3, and the quenching tower 102 is used for contacting the gaseous stream from the pre-quenching tower 101 with quench water and lye entering the quenching tower 102 from the third inlet so as to cool and wash the gaseous stream to obtain gaseous hydrocarbon, heavy hydrocarbon components and condensed water. Since the third inlet is located above the fourth inlet, the gaseous stream fed in from the fourth inlet is after entering the quench tower 102 in sufficient contact with the quench water 4 and the lye 12 fed in from the third inlet from bottom to top.
Quench water separation tank 103 is in communication with pre-quench tower 101 and quench tower 102 via condensate water transfer lines 6 and 7, respectively, for receiving condensate water from pre-quench tower 101 and quench tower 102 and separating the remaining heavy hydrocarbon components from the condensate water to obtain heavy hydrocarbon components and condensate water separated from the heavy hydrocarbon components, which condensate water separated from the heavy hydrocarbon components may be used as quench water, and thus the condensate water may also be referred to as quench water.
In some preferred embodiments, the quench water separation tank 103 is in communication with the first inlet of the pre-quench tower 101 and the third inlet of the quench tower 102, respectively, via a quench water circulation line 10. In one embodiment, the quench water circulation line 10 is in communication with quench water transfer lines 2, 4, respectively, whereby at least a portion of the separated condensate water from the separation of the heavy hydrocarbon components in the quench water separation tank 103 is recycled as quench water to the pre-quench tower 101 and quench tower 102, respectively. In some embodiments, a majority (e.g., 90-96%) of the condensed water separated from the heavy hydrocarbon components in quench water separation tank 103 is recycled as quench water to pre-quench tower 101 and quench tower 102.
The MTP reaction product is separated from the reaction water and process water by a hydrocarbon-water separation unit 100.
The oil-gas separation unit 200 in the separation system is used to separate the water entrained in the gaseous hydrocarbons and heavy hydrocarbon components separated by the hydrocarbon-water separation unit 100 to obtain a gas phase component, a hydrocarbon condensate, and residual water. Wherein the gaseous hydrocarbon is mainly composed of C1-C5 mixed hydrocarbon. The heavy hydrocarbon component consists essentially of C5-C11 mixed hydrocarbons. The gas phase component consists essentially of C1-C4 mixed hydrocarbons.
In some preferred embodiments, the oil-gas separation unit 200 consists essentially of a compressor surge tank 201, a compressor 203, and an oil-gas separation tank 202. Wherein the compressor surge tank 201 is used to separate water entrained in the gaseous hydrocarbons from the quench tower 102 to obtain a liquid material and the gaseous hydrocarbons from which the entrained water is separated. As a preferred embodiment, the compressor buffer tank 201 and the quenching tower 102 are communicated with each other through a gaseous hydrocarbon transfer pipe 5, and the gaseous hydrocarbon obtained in the quenching tower 102 is fed to the compressor buffer tank 201 through the gaseous hydrocarbon transfer pipe 5. In one embodiment, a liquid material transfer line 9 is also connected between the compressor buffer tank 201 and the quench tower 102, so that the liquid material separated by the compressor buffer tank 201 is recycled to the quench tower 102 for further separation.
The compressor 203 is used for compressing and cooling the gaseous hydrocarbon separated from the entrained water, separated by the compressor buffer tank 201, specifically, cooling to 35-60 ℃ to obtain the oil-gas mixture 33. In a specific embodiment, the compressor 203 and the compressor surge tank 201 are in communication via a conduit 31 to feed the gaseous hydrocarbon separated from entrained water separated by the compressor surge tank 201 to the compressor 203.
The oil-gas separation tank 202 and the compressor 203 are communicated through an oil-gas mixture conveying pipeline 33. The oil and gas separation tank 202 is also in communication with the pre-quench tower 101, quench tower 102, and quench water separation tank 103 via heavy hydrocarbon component transfer lines 17, 16, 8, respectively. In one embodiment, the heavy hydrocarbon component transfer lines 17, 16, 8 may merge into the same line and the heavy hydrocarbon components from the three may be fed into the hydrocarbon separation tank. The oil-gas separation tank 202 is used to separate the oil-gas mixture from the compressor 203 and possibly entrained trace amounts of water in the heavy hydrocarbon components from the pre-quench tower 101, quench tower 102 and quench water separation tank 103, respectively, and to obtain a gas phase component, a hydrocarbon condensate and residual water.
In one embodiment, a residual water transfer line 28 is connected between the oil and gas separation tank 202 and the compressor surge tank 201, for transferring residual water separated in the oil and gas separation tank 202 to the compressor surge tank 201 for further separation. And may further comprise a next oxide extraction unit (not shown in the figure), to which the hydrocarbon condensate separated by the oil-gas separation tank 202 is fed through a hydrocarbon condensate conveying pipe 29, for extraction separation of C4, C5-6 oxygen-containing organic components contained in the hydrocarbon condensate. The oxide extraction unit can adopt the existing extraction separation unit in the field to separate C4, C5-6 methanol/dimethyl ether components from hydrocarbon condensate, and the details are not repeated. And may further comprise a next-stage separation unit (not shown in the figure), wherein the oil-gas separation tank 202 is communicated with the next-stage separation unit through a gas-phase component conveying pipeline 30; the next stage separation unit is configured to receive the gas phase component separated by the oil-gas separation tank 202, and further separate the gas phase component to obtain C2 and C3 components.
The oil-gas separation unit 200 mainly separates oil and gas generated by MTP reaction, and further removes residual water, thereby facilitating subsequent procedures such as drying and compression of hydrocarbon components.
The process steam production unit 300 is used for extracting hydrocarbon components remaining in condensed water from which at least a part of the heavy hydrocarbon components are separated by the hydrocarbon-water separation unit 100, thereby obtaining hydrocarbon components and water from which the hydrocarbon components are extracted; and is also used for treating the water from which the hydrocarbon component is extracted to separate out salt-containing droplets entrained therein, thereby obtaining process steam from which the salt-containing droplets are separated.
In one embodiment, the process steam production unit 300 consists essentially of a process water extraction column 301, a process steam generator 302, and a process steam separator tank 303.
Wherein, the process water extraction tower 301 is communicated with the quenching water separation tank 103 through a first quenching water conveying pipeline 14, and condensed water which is obtained by the quenching water separation tank 103 and is at least partially separated from heavy hydrocarbon components is input into the process water extraction tower 301 through the first quenching water conveying pipeline 14. The process water extraction tower 301 is also provided with a process steam input port for inputting process steam into the process water extraction tower 301. The process water extraction column 301 is used to contact the condensed water separated from the quench water separation tank 103 at least partially from the heavy hydrocarbon components with process steam to extract the hydrocarbon components remaining therein, thereby obtaining water from which the hydrocarbon components are extracted and hydrocarbon components. In a preferred embodiment, a hydrocarbon component transfer line 15 is connected between the process water extraction column 301 and the pre-quench column 101 for recycling the separated hydrocarbon component to the pre-quench column 101 for further separation. In one embodiment, a quench water pump and filtration device (not shown) are also provided between the quench water separation tank 103 and the process water extraction column 301 for pressurizing and filtering, respectively, the condensed water from which heavy hydrocarbon components are separated, which is to be fed to the process water extraction column 301, to separate particulates therein.
The process steam generator 302 is used to treat the water from the process water extraction column 301 from which the hydrocarbon components are extracted, thereby generating steam. Specifically, the process steam generator 302 and the process water extraction tower 301 are connected via a transfer pipe 27, and water from which hydrocarbon components are extracted is sent to the process steam generator 302 via the transfer pipe 27. Part of the sewage is generated during the steam generation of the process steam generator 302. The sewage is discharged through the sewage delivery pipe 19 and is sent to the subsequent methanol recovery unit 400 for further treatment. In a preferred embodiment, a water pump (such as a process water pump in particular) and a preheating device (not shown in the figure) are also provided between the process steam generator and the process water extraction column for pressurizing and preheating, respectively, the water from which the hydrocarbon components are extracted, to be fed to the process steam generator 302, for example to 170-250 ℃.
The process steam separator tank 303 is used to treat the steam from the process steam generator 302 and separate therefrom droplets containing salts (e.g., sodium salt droplets) that may be entrained therein, thereby obtaining process steam. Specifically, the process steam separation tank 303 and the process steam generator 302 are communicated with each other through the steam delivery pipe 18, and the steam is sent to the process steam separation tank 303 through the steam delivery pipe 18. In a preferred embodiment, a demister is installed in the process steam separation tank 303 to effectively separate salt-containing droplets, and any device in the art having a function of separating salt-containing droplets may be used as the demister.
In a specific embodiment, a process steam delivery pipe 20 is provided between the process steam separation tank 303 and the process water extraction column 301 for delivering at least part of the process steam obtained from the process steam separation tank to the process water extraction column 301, the part of the process steam 20 specifically entering from the process steam inlet of the process water extraction column 301, so that no additional supply of process steam into the process water extraction column 301 is required. In a preferred embodiment, a further portion of the process steam is output via process steam transfer line 21 and recycled to the MTP reactor, specifically such as by heating the portion of the process steam in combination with recycled hydrocarbon and DME to 430 c before being fed to the MTP reactor.
The process steam obtained via process steam production unit 300 can be supplied to a process water extraction column 301 and an MTP reactor where it is further stripped of residual hydrocarbon components and possibly entrained salt-containing droplets (e.g., sodium-containing droplets).
The methanol recovery unit 400 is configured to treat condensed water from the separation of the hydrocarbon-water separation unit 100, at least partially separated heavy hydrocarbon components, to separate methanol, DME and light component noncondensable gases contained therein.
In some embodiments, the methanol recovery unit 400 consists essentially of a methanol recovery column 401 and a methanol recovery column reflux drum 402.
Wherein the methanol recovery tower 401 is communicated with the quenching water separation tank 103 through a second quenching water conveying pipeline 13, so that condensed water which is obtained by separating the quenching water separation tank 103 and at least partially separates heavy hydrocarbon components is input into the methanol recovery tower 401, and is rectified in the methanol recovery tower 401 to obtain liquid phase components (or simply referred to as a liquid phase) containing methanol and DME and process water. In a preferred embodiment, the methanol recovery column 401 is also in communication with the process steam generator, either directly or indirectly, via a wastewater transfer line 19, for receiving wastewater from the process steam generator 302, rectifying it, separating out liquid phase components comprising methanol and DME, and obtaining process water. In a preferred embodiment, the effluent transfer line 19 is in communication with the second quench water transfer line 13, and effluent from the process steam generator 302 is combined with condensed water from the quench water separator tank 103, separated from heavy hydrocarbon components, into the same transfer line, where they exchange heat with each other and are mixed into the methanol recovery column 401. The process water obtained by rectification and separation in the methanol recovery tower 401 can be sent to a subsequent oxide extraction unit for use after being cooled.
The methanol recovery tower reflux tank 402 is communicated with the methanol recovery tower 401 through a liquid-phase component conveying pipeline 22 and is used for receiving the liquid-phase component obtained by the methanol recovery tower 401 and separating the liquid-phase component, and separating methanol and DME and light component noncondensable gas in the liquid-phase component. In a preferred embodiment, a reflux line 25 is further connected between the methanol recovery column reflux drum 402 and the methanol recovery column 401, and in a specific embodiment, the reflux line is connected to a reflux pump (not shown) to reflux at least part of the methanol and DME separated in the methanol recovery column reflux drum 402 to the methanol recovery column 401 through the reflux line 25. In a preferred embodiment, a portion of the separated methanol and DME may be returned to the DME reactor (not shown) as feed via transfer line 26, and the separated light component non-condensable gases may be output via light component non-condensable gas transfer line 23 and recycled to the MTP reactor (not shown).
The unreacted methanol in the process water is separated and recovered through the methanol recovery unit 400, and the light component noncondensable gas is also obtained through separation.
In the separation system provided by the invention, specific equipment or elements used in each separation unit can specifically adopt corresponding equipment or elements existing in the field, and the details are not described in detail. While in some preferred embodiments, both the pre-quench tower 101 and quench tower 102 configurations used in the separation system may employ the tower configurations disclosed in patent CN 202860169U; the process steam knockout drum 303 used may employ the steam tower structure disclosed in patent CN204328982U or CN 202191808U.
The invention also provides a method for separating oil-water-gas in a product obtained in the process of preparing propylene from methanol by using the separation system. The method comprises the following steps:
separating the MTP reaction product and dilution steam containing stream using a hydrocarbon-water separation unit 100 to obtain gaseous hydrocarbons, heavy hydrocarbon components, and condensed water from which the heavy hydrocarbon components have been separated;
separating the water entrained in the resulting gaseous hydrocarbons and heavy hydrocarbon components by the hydrocarbon-water separation unit 100 using the oil-gas separation unit 200 to obtain a gas phase component, a hydrocarbon condensate and residual water;
extracting at least part of condensed water separated by the heavy hydrocarbon component by the hydrocarbon-water separation unit 100 by using the process steam production unit 300, and separating residual hydrocarbon components by extraction; and the water from which the hydrocarbon components are extracted is treated, and salt-containing liquid drops possibly entrained in the water are separated, and process steam is obtained;
at least part of the condensed water from which heavy hydrocarbon components have been separated, which has been obtained before and separated by the hydrocarbon-water separation unit 100, is treated by the methanol recovery unit 400, thereby separating methanol and DME contained therein, and light component noncondensable gas, and obtaining process water.
In some preferred embodiments, the hydrocarbon-water separation unit 100 primarily includes a pre-quench tower 101, a quench tower 102, and a quench water separation tank 103.
Wherein the pre-quench tower 101 is provided with a first inlet and a second inlet, the first inlet being located above the second inlet; the quench tower 102 is provided with a third inlet and a fourth inlet, the third inlet being located above the fourth inlet.
In the separation process of the present invention, in the hydrocarbon-water separation unit 100, a stream containing the MTP reaction product and dilution steam is fed into it from the feed transfer line 1 via the second inlet of the pre-quench tower 101, and quench water and lye are fed into it from the first inlet of the pre-quench tower 101; the stream containing MTP reaction products and dilution steam is contacted with quench water and lye from bottom to top after entering pre-quench tower 101, thereby being cooled and scrubbed to obtain a gaseous stream, heavy hydrocarbon components and condensed water. In some preferred embodiments, the MTP reaction product is specifically derived from an MTP reactor, and the MTP reaction product and dilution steam containing stream is subjected to heat recovery prior to being fed to pre-quench tower 101, and is controlled to a temperature of about 170 to 210 ℃, before being fed to pre-quench tower 101. Preferably, the quench water and lye used in pre-quench tower 101 is at a temperature of 48-52 ℃.
Feeding the gaseous stream obtained in the pre-quenching tower 101 through a gaseous stream feeding pipeline 3 from the fourth inlet of the quenching tower 102, and feeding the quenching water and the lye into the quenching tower 102 from the third inlet thereof; the gaseous stream enters quench tower 102 and contacts quench water and lye from bottom to top, thereby being further cooled and scrubbed to obtain gaseous hydrocarbons, heavy hydrocarbon components, and condensed water. Preferably, the gaseous stream from the pre-quench tower fed to quench tower 102 has a temperature of 50-60 ℃; the quench water and lye used in quench tower 102 is at a temperature of 38-42 ℃.
The condensed water obtained in the pre-quench tower 101 and the quench tower 102 is sent to a quench water separation tank 103 through condensed water conveying pipelines 6 and 7, respectively, and the heavy hydrocarbon components remained in the condensed water are separated, and the condensed water from which the heavy hydrocarbon components are separated is obtained. Condensate water obtained from the quench water separation tank 103, at least partially separated from heavy hydrocarbon components, is circulated as quench water to the pre-quench tower 101 and the quench tower 102 through the quench water circulation pipeline 10, specifically, is output from the quench water circulation pipeline 10 and then enters the quench water conveying pipelines 2 and 4 to be sent to the pre-quench tower and the quench tower respectively. In preferred embodiments, at least a portion of the condensed water separated from heavy hydrocarbon components obtained in quench water separation tank 103 is split into three streams, one of which is recycled as quench water to pre-quench tower 101 and quench tower 102, one of which is fed to a subsequent process water production unit 300 and the other of which is fed to a subsequent methanol recovery unit 400. In a preferred embodiment, 90-96% of the condensed water obtained from quench water separation tank 103, from which heavy hydrocarbon components are separated, is recycled as quench water to the pre-quench tower 101 and quench tower 102.
In some preferred embodiments, the oil-gas separation unit 200 mainly includes a compressor surge tank 201, a compressor 203, and an oil-gas separation tank 202; the separation method of the invention comprises the following steps:
The gaseous hydrocarbon separated by the quenching tower 102 is sent to the compressor buffer tank 201 through the gaseous hydrocarbon conveying pipeline 5, and water entrained in the gaseous hydrocarbon is separated, so as to obtain liquid material and the gaseous hydrocarbon from which the entrained water is separated. In a preferred embodiment, the liquid material is recycled via liquid material transfer line 9 to quench tower 102 for further separation.
The gaseous hydrocarbon separated from the entrained water obtained in the compressor buffer tank 201 is sent to the compressor 203 through the conveying pipeline 31, compressed and cooled by the compressor 203, specifically cooled to 35-60 ℃ for example, and then an oil-gas mixture is obtained.
The oil-gas mixture obtained by the compressor 203 is sent to the oil-gas separation tank 202 through the oil-gas mixture conveying pipeline 33, and the heavy hydrocarbon components separated by the pre-quenching tower 101, the quenching tower 102 and the quenching water separating tank 103 are respectively output through the heavy hydrocarbon component conveying pipelines 17, 16 and 8 and sent to the oil-gas separation tank 202, so that water possibly entrained in the heavy hydrocarbon components is separated, and a gas phase component, hydrocarbon condensate and residual water are obtained. In preferred embodiments, the residual water is further fed to the compressor surge tank 201 via residual water feed line 28 for separation. In preferred embodiments, the hydrocarbon condensate may be further fed to a next separation unit (not shown) to separate the C4, C5-6 components thereof; the gas phase component 30 may also be sent to a next stage separation unit (not shown) for further separation to obtain C2 and C3 components.
In some preferred embodiments, the process water production unit 300 mainly comprises a process water extraction tower 301, a process steam generator 302, and a process steam separator tank 303. The separation method of the invention comprises the following steps:
at least part of condensed water obtained from the quench water separation tank 103 and separated from heavy hydrocarbon components is fed into the process water extraction column 301 through the first quench water feed line 14, fed into the process water extraction column 301 through the quench water inlet of the process water extraction column 301, and process steam is fed into the process water extraction column 301 through the process steam inlet of the process water extraction column. In a preferred embodiment, 28 to 42wt% of the condensed water obtained from the quench water separator tank 103, from which heavy hydrocarbon components are separated, is fed to the process water extraction column 301 via the first quench water transfer line 14. The condensed water from which the heavy hydrocarbon components are separated is extracted by the process steam in the process water extraction column 301, thereby separating the hydrocarbon components remaining therein to obtain the hydrocarbon components and water from which the hydrocarbon components are extracted. In some preferred embodiments, the hydrocarbon component separated in process water extraction column 301 is recycled to pre-quench column 101 for further separation via hydrocarbon component transfer line 15. In some preferred embodiments, at least a portion of the condensed water obtained from the quench water separation tank 103 that is separated from the heavy hydrocarbon components is pre-pressurized with a quench water pump and filtered to separate particulates that may be contained therein prior to entering the process water extraction column 301.
The water from the process water extraction column 301 from which hydrocarbon components are extracted is sent to a process steam generator 302 via a transfer line 27, and steam is obtained in the process steam generator 302. In a preferred embodiment, the water from which the hydrocarbon component is extracted is pressurized and preheated, preferably to 140-150 ℃, using a water pump (e.g., process water pump) prior to being fed to the process steam generator 302.
The steam generated by the process steam generator 302 is sent to a process steam separation tank 303 through a steam conveying pipeline 18, and salt-containing liquid drops (for example, sodium salt-containing liquid drops) possibly entrained in the steam are separated to obtain the process steam.
At least part of the process steam obtained in the process steam separation tank 303 is fed into the process water extraction column 301 through the process steam feed line 20, in particular through the process steam inlet of the process water extraction column 301, without additional supply of process steam into the process water extraction column 301. In a preferred embodiment, a further portion of the process steam is fed to the MTP reactor for use after being heated to 430℃as dilution steam in combination with recycle hydrocarbon and DME via process steam feed line 21.
In some preferred embodiments, the methanol recovery unit 400 mainly includes a methanol recovery column 401 and a methanol recovery column reflux drum 402. The separation method of the invention comprises the following steps:
At least part of condensed water obtained from the quench water separation tank 103 and separated from heavy hydrocarbon components is sent to the methanol recovery column 401 through the second quench water transfer line 13, and is subjected to rectification separation in the methanol recovery column 401 to separate liquid phase components containing methanol and DME, and process water is obtained. In a preferred embodiment, the effluent from the process steam generator 302 is also fed via effluent transfer line 19 to a methanol recovery column 401 for rectification to separate the liquid phase components comprising methanol and DME and to obtain process water. In a preferred embodiment, the effluent from process steam generator 302 is mixed with condensed water from quench water separator tank 103, separated from heavy hydrocarbon components, after heat exchange with each other, into methanol recovery column 401. In a preferred embodiment, the process water obtained by rectification and separation in the methanol recovery tower 401 is cooled and then sent to a subsequent oxide extraction unit through a process water delivery pipeline 24 for use.
The liquid phase component containing methanol and DME obtained in the methanol recovery column 401 is sent to a methanol recovery column reflux drum 402 through a liquid phase component delivery line 22, and methanol and DME and light component noncondensable gas are separated therefrom. At least part of the separated methanol and DME are refluxed to the methanol recovery column via reflux line 25. In a preferred embodiment, a portion of the separated methanol and DME are also returned to the DME reactor via transfer line 26 for use as a reaction feed, and the separated light component noncondensable gas can be recycled to the MTP reactor via light component noncondensable gas transfer line 23.
The process of separating oil-water-gas from the reaction product of the methanol-to-propylene process using the separation system of the present invention will be described in detail with reference to fig. 1:
after heat is recovered from the flow of reaction products and dilution steam from the upstream MTP reactor through a heat recovery system, the temperature is reduced to about 190 ℃, the reaction products and the flow of dilution steam enter a pre-quenching tower 101 through a material conveying pipeline 1, and the reaction products and the flow of dilution steam are fully contacted, cooled and washed with quench water and alkali liquor at 48-52 ℃ in the pre-quenching tower 101 to obtain gaseous flow and condensed water cooled to 50-60 ℃; the gaseous matter flows through the gaseous matter flow conveying pipeline 3 to enter the quenching tower 102, and is further fully contacted with quenching water and alkali liquor at 38-42 ℃, cooled and washed. Most of the heavy hydrocarbon components are condensed in the pre-quench tower 101 and the quench tower 102 to obtain heavy hydrocarbon components, respectively, which are output from the heavy hydrocarbon component delivery lines 17, 16, respectively.
Gaseous hydrocarbons exiting the top of quench tower 102 enter compressor surge tank 201 via gaseous hydrocarbon feed line 5, further removing liquid droplets (water) that may be entrained therein.
The condensed water from the bottom of the pre-quench tower 101 and the condensed water from the bottom of the quench tower 102 are respectively output by the condensed water conveying pipelines 6 and 7 and all enter the quench water separation tank 103 to separate oil (hydrocarbon) by gravity. Separating the remaining heavy hydrocarbon components therefrom and obtaining condensed water separated heavy hydrocarbon components, the condensed water being in three streams, a majority of which is recycled in the system as quench water to the pre-quench tower and the quench tower; specifically, the part of quenching water for circulation is cooled to 50 ℃ after heat recovery and air cooling, is output through a quenching water circulation pipeline 10 and is divided into two parts continuously, wherein most part of the quenching water is taken as quenching water to enter a quenching water conveying pipeline 2 to be input into a pre-quenching tower 101, and the other part of the quenching water is further cooled to 38 ℃ and enters a quenching tower 102 through a quenching water conveying pipeline 4 to further cool MTP reaction products, so that the water content in gaseous hydrocarbon leaving the top of the quenching tower 102 is minimized.
After being pressurized and filtered by a quench water pump, a small part of condensed water separated from the quench water separation tank 103 and separated from heavy hydrocarbon components is taken as quench water, particulate matters accumulated in the quench water are removed, the condensate water is conveyed to the process water extraction tower 301 through a first quench water conveying pipeline 14, and the rest of condensed water separated from the heavy hydrocarbon components from the quench water separation tank 103 is conveyed to the methanol recovery tower 401 through a second quench water conveying pipeline 13.
The liquid stream separated from the bottom of the compressor surge tank 201 is returned to the quench tower 102 via liquid stream transfer line 9. The gaseous hydrocarbon separated from the entrained water from the top of the compressor surge tank 201 is compressed by the delivery pipe 31 into the compressor 203 and cooled to 50 c to obtain an oil-gas mixture, and the oil-gas mixture is delivered to the oil-gas separation tank 202 through the oil-gas mixture delivery pipe 33.
The heavy hydrocarbon components separated by the pre-quenching tower 101, the heavy hydrocarbon components condensed and separated by the quenching tower 102 and the heavy hydrocarbon components separated by the quenching water separation tank 103 are respectively output through heavy hydrocarbon component conveying pipelines 17, 16 and 8 and are sent to the oil-gas separation tank 202, so that water possibly entrained is further separated.
The hydrocarbon condensate and residual water are separated from the gas phase components in the oil and gas separator tank 202. The gas phase component is output through a gas phase component conveying pipeline 30 and can be continuously sent to a next-stage separation unit (not shown in the figure); the hydrocarbon condensate is output through a hydrocarbon condensate conveying pipeline 29 and can be sent to a next separation unit (such as an oxide extraction unit) to separate C4, C5-6 oxygen-containing organic components (not shown in the figure), and part or all of the components are returned to the MTP reactor; the residual water is fed into the compressor buffer tank 201 via the residual water feed line 28.
In the process water extraction column 301, condensed water (also referred to as "quench water") from which heavy hydrocarbon components are separated is extracted with process steam from a process steam knock-out drum 303. The extracted hydrocarbon component is returned to the pre-quench tower 101 via the hydrocarbon component transfer line 15. The quenched water after extraction (i.e. the water from which the hydrocarbon components are extracted) is preheated to 140-150 ℃ after being pressurized by a process water pump, and is sent into a process steam generator 302 through a conveying pipeline 27 to generate steam, and the generated steam enters a process steam separation tank 303 through a steam conveying pipeline 18. In the process steam separator tank 303, where a demister is added, droplets of salt that may be entrained in the steam are separated.
The sewage discharged from the process steam generator 302 is mixed into the methanol recovery column 401 after exchanging heat with condensed water from the rest of the quench water separation tank 103, from which heavy hydrocarbon components are separated, through the sewage delivery pipe 19, and is rectified therein. A part of the process steam flowing out from the top of the process steam separation tank 303 is sent to the process water extraction tower 301 through the process steam conveying pipeline 20, and the other part of the process steam is mixed with recycle hydrocarbon and DME as dilution steam through the process steam conveying pipeline 21 and is sent to the MTP reactor after being added to 430 ℃.
Part of the condensed water from the quench water separation tank 103 from which heavy hydrocarbon components are separated is fed through a second quench water transfer line 13 to a methanol recovery column 401, and methanol and DME contained therein are separated by rectification in the methanol recovery column 401, and condensed at the top of the column to obtain a liquid phase component 22 containing methanol and DME. The overhead condensed liquid phase component enters the methanol recovery column reflux drum 402 via liquid phase component transfer line 22. Methanol and DME separated from the methanol recovery column reflux drum 402 are fed by a reflux pump (not shown) through reflux line 25, with a portion of the methanol and DME fed to the methanol recovery column 401 for reflux and another portion returned to the DME reactor through feed line 26. The light component noncondensable gas obtained from the reflux drum 402 of the methanol recovery tower is recycled to the MTP reactor through the light component noncondensable gas conveying pipeline 23. The process water separated by the methanol recovery column 401 is sent to a subsequent oxide extraction unit (not shown in the figure) through a process water delivery pipe 24.
The separation system and the method of the invention are adopted in production practice, and the separation system formed by combining the multi-stage separation units of the hydrocarbon-water separation unit 100, the oil-gas separation unit 200, the process water production unit 300 and the methanol recovery unit 400 can effectively completely separate the methanol-to-propylene reaction product (MTP reaction product) from the reaction water and the process water, so that the outlet material flow of the MTP reactor is more thoroughly separated into oil, water and gas, the smooth and stable operation of a subsequent gas compression system is ensured, the great difficulty in drying subsequent hydrocarbon products is avoided, the long-period stable operation of the MTP production device is also ensured, and the vehicle jump accident is avoided. The separation method has the characteristics of simple and reliable process, good stability and the like.
The separation system of the present invention is an improvement over the separation systems previously developed by the applicant (e.g. as in CN102363084 a). The separation system of the invention further separates the gaseous hydrocarbon obtained in the separation process of the MTP reaction product, and further separates hydrocarbon components and unreacted methanol and dimethyl ether from the quenching water obtained by the separation of the quenching system for recycling; the separated water is further converted into process steam without entrainment of salt-containing droplets by the process steam generator 302 and the process steam separation tank 303, effectively avoiding rapid deactivation of the catalyst by feeding the alkali metal belt into the MTP reactor. Compared with the prior separation system, the separation system provided by the invention has the advantages that the moisture content of the oil gas obtained by separation is lower, and the moisture content is reduced from more than 500ppm to less than 100ppm, so that the switching frequency of an oil gas drying device is reduced, and the replacement frequency of a drying agent is prolonged. In addition, the long-period stable operation of the production device is ensured by reducing the water entrainment quantity in the oil gas and producing the process steam without alkali metal entrainment. The technology of the invention is used for improving the existing industrial device, the effect is good after the device is put into use, the device can run for a long period, and the device is not stopped because of high water content of oil gas or excessive alkali metal ions carried by process steam.
Those skilled in the art will appreciate that certain modifications and adaptations of the invention are possible and can be made under the teaching of the present specification. Such modifications and adaptations are intended to be within the scope of the present invention as defined in the appended claims.
Claims (16)
1. An oil-water-gas separation system for a process of preparing propylene from methanol is characterized by comprising a hydrocarbon-water separation unit, an oil-gas separation unit, a process steam production unit and a methanol recovery unit;
the hydrocarbon-water separation unit is used for separating a stream containing MTP reaction products and dilution steam so as to obtain gaseous hydrocarbon, heavy hydrocarbon components and condensed water from which the heavy hydrocarbon components are separated;
the oil-gas separation unit is used for separating the gaseous hydrocarbon separated by the hydrocarbon-water separation unit from water entrained in the heavy hydrocarbon component to obtain a gas phase component, hydrocarbon condensate and residual water;
the process steam production unit is used for extracting at least part of condensed water separated by the hydrocarbon-water separation unit and separated heavy hydrocarbon components to extract hydrocarbon components from the condensed water and obtain water extracted with the hydrocarbon components, and is also used for treating the water extracted with the hydrocarbon components to obtain process steam separated from salt-containing liquid drops;
The methanol recovery unit is used for treating at least part of condensed water separated by the heavy hydrocarbon component and obtained by the separation of the hydrocarbon-water separation unit so as to separate methanol, DME and light component noncondensable gas contained in the condensed water;
the hydrocarbon-water separation unit comprises a pre-quench tower, a quench tower and a quench water separation tank;
wherein the pre-quench tower is provided with a first inlet for inputting quench water and lye and a second inlet for inputting a stream containing MTP reaction products and dilution steam, the first inlet is positioned above the second inlet, and the pre-quench tower is used for contacting the stream containing MTP reaction products and dilution steam with the quench water and lye so as to cool and wash the stream containing MTP reaction products and dilution steam to obtain a gaseous stream, heavy hydrocarbon components and condensed water;
the quenching tower is provided with a third inlet for inputting quench water and lye, and is also provided with a fourth inlet for inputting a gaseous stream from the pre-quenching tower, the third inlet is positioned above the fourth inlet, and the quenching tower is used for contacting the gaseous stream from the pre-quenching tower with the quench water and the lye so as to cool and wash the gaseous stream to obtain gaseous hydrocarbon, heavy hydrocarbon components and condensed water;
The quenching water separation tank is respectively communicated with the pre-quenching tower and the quenching tower through condensed water conveying pipelines, and is used for receiving condensed water from the pre-quenching tower and the quenching tower and separating residual heavy hydrocarbon components in the condensed water so as to obtain heavy hydrocarbon components and condensed water from which the heavy hydrocarbon components are separated;
the quenching water separation tank is communicated with the first inlet of the pre-quenching tower and the third inlet of the quenching tower through quenching water circulation pipelines respectively and is used for respectively circulating at least part of condensed water obtained by the quenching water separation tank and separated from heavy hydrocarbon components to the pre-quenching tower and the quenching tower as quenching water;
the process steam production unit comprises a process water extraction tower, a process steam generator and a process steam separation tank;
the process water extraction tower is communicated with the quenching water separation tank through a first quenching water conveying pipeline, and the first quenching water conveying pipeline is used for inputting at least part of condensed water, obtained from the quenching water separation tank, from which heavy hydrocarbon components are separated, into the process water extraction tower; the process water extraction tower is provided with a process steam input port for inputting process steam, and is used for contacting the condensed water which is input by the first quenching water conveying pipeline and is separated from the heavy hydrocarbon component with the process steam to extract residual hydrocarbon component and obtain water from which the hydrocarbon component is extracted; the process water extraction tower is communicated with the pre-quenching tower through a hydrocarbon component conveying pipeline and is used for recycling hydrocarbon components extracted by the process water extraction tower to the pre-quenching tower;
The process steam generator is communicated with the process water extraction tower through a conveying pipeline for conveying the water extracted with the hydrocarbon components, and is used for converting the water extracted with the hydrocarbon components into steam;
the process steam separation tank is communicated with the process steam generator through a steam conveying pipeline and is used for separating salt-containing liquid drops carried in the steam input by the steam conveying pipeline so as to obtain process steam;
the process steam separating tank is communicated with a process steam input port of the process water extraction tower through a process steam conveying pipeline so as to convey at least part of process steam obtained from the process steam separating tank to the process water extraction tower;
the oil-gas separation unit comprises a compressor buffer tank, a compressor and an oil-gas separation tank;
the compressor buffer tank is communicated with the quenching tower through a gaseous hydrocarbon conveying pipeline, and is used for separating water entrained in the gaseous hydrocarbon from the quenching tower so as to obtain liquid materials and the gaseous hydrocarbon from which the entrained water is separated;
the compressor is communicated with the compressor buffer tank, and is used for receiving the gaseous hydrocarbon separated from the entrained water and obtained by separation of the compressor buffer tank, and compressing and cooling the gaseous hydrocarbon to obtain an oil-gas mixture;
The oil-gas separation tank is communicated with the compressor through an oil-gas mixture conveying pipeline, the oil-gas separation tank is communicated with the pre-quenching tower, the quenching tower and the quenching water separation tank through heavy hydrocarbon component conveying pipelines respectively, and the oil-gas separation tank is used for separating the oil-gas mixture from the compressor and water entrained in heavy hydrocarbon components from the pre-quenching tower, the quenching tower and the quenching water separation tank so as to obtain gas phase components, hydrocarbon condensate and residual water.
2. The oil-water-gas separation system for a methanol-to-propylene process according to claim 1, wherein a liquid material transfer pipe is further connected between the compressor buffer tank and the quenching tower to circulate the liquid material separated by the compressor buffer tank to the quenching tower.
3. An oil-water-gas separation system for a methanol-to-propylene process as claimed in claim 1, wherein,
the oil-gas separation tank is communicated with the compressor buffer tank through a residual water conveying pipeline and is used for conveying the residual water to the compressor buffer tank.
4. An oil-water-gas separation system for a process for the production of propylene from methanol according to any one of claims 1 to 3, characterized in that a demister is provided in the process steam separation tank.
5. An oil-water-gas separation system for a methanol-to-propylene process according to any one of claims 1 to 3, wherein the methanol recovery unit comprises a methanol recovery column and a methanol recovery column reflux drum;
the methanol recovery tower is communicated with the quenching water separation tank through a second quenching water conveying pipeline, the second quenching water conveying pipeline is used for inputting at least part of condensed water obtained from the quenching water separation tank and separated from heavy hydrocarbon components into the methanol recovery tower, and the methanol recovery tower is used for rectifying the condensed water input into the methanol recovery tower and separated from the heavy hydrocarbon components so as to obtain process water and liquid phase components containing methanol and DME;
the methanol recovery tower reflux tank is communicated with the methanol recovery tower through a liquid phase component conveying pipeline, and the methanol recovery tower reflux tank is used for separating liquid phase components input into the methanol recovery tower reflux tank so as to obtain methanol, DME and light component noncondensable gas.
6. An oil-water-gas separation system for a methanol-to-propylene process as set forth in claim 5 wherein said methanol recovery column and said process steam generator are in communication via a wastewater transfer line for transferring wastewater discharged from the process steam generator, said methanol recovery column being further configured to receive said wastewater transferred by said wastewater transfer line and rectify it to obtain process water and a liquid phase component containing methanol and DME.
7. The oil-water-gas separation system for a methanol-to-propylene process as set forth in claim 5, wherein a reflux pipe for refluxing at least part of methanol and DME separated in the reflux tank of the methanol recovery tower to the methanol recovery tower is connected between the reflux tank of the methanol recovery tower and the methanol recovery tower.
8. A method of separating oil-water-gas from a product of a methanol-to-propylene process using the separation system of any one of claims 1-7, the method comprising:
separating the MTP reaction product and dilution steam containing stream with the hydrocarbon-water separation unit to obtain gaseous hydrocarbons, heavy hydrocarbon components, and condensed water from which the heavy hydrocarbon components are separated;
separating the water entrained in the gaseous hydrocarbons and heavy hydrocarbon components separated by the hydrocarbon-water separation unit by the oil-gas separation unit to obtain a gas phase component, a hydrocarbon condensate and residual water;
extracting at least a portion of the condensed water separated by the heavy hydrocarbon component separation by the hydrocarbon-water separation unit with the process steam production unit to separate out the remaining hydrocarbon component therein; the water from which the hydrocarbon components are extracted is treated, and salt-containing liquid drops carried in the water are separated to obtain process steam;
Treating at least part of condensed water separated by heavy hydrocarbon components and obtained by separating the hydrocarbon-water separation unit by utilizing the methanol recovery unit, and separating to obtain methanol, DME and light component noncondensable gas;
the hydrocarbon-water separation unit comprises a pre-quench tower, a quench tower and a quench water separation tank; the pre-quench tower is provided with a first inlet and a second inlet, and the first inlet is positioned above the second inlet; the quench tower is provided with a third inlet and a fourth inlet, the third inlet being located above the fourth inlet, the method comprising:
feeding a material flow containing MTP reaction products and dilution steam into a pre-quenching tower from the second inlet, feeding quench water and alkali liquor into the pre-quenching tower from the first inlet, and cooling and washing the material flow containing MTP reaction products and dilution steam by contacting with the quench water and the alkali liquor from bottom to top after the material flow containing MTP reaction products and dilution steam enters the pre-quenching tower to obtain a gaseous material flow, heavy hydrocarbon components and condensed water;
feeding a gaseous stream obtained from the pre-quenching tower into the quenching tower through the fourth inlet, feeding the quenching water and the alkali liquor into the quenching tower through the third inlet, and cooling and washing the gaseous stream which is contacted with the quenching water and the alkali liquor from bottom to top after entering the quenching tower to obtain gaseous hydrocarbon, heavy hydrocarbon components and condensed water;
The condensate water obtained by the pre-quenching tower and the quenching tower is sent to a quenching water separation tank, residual heavy hydrocarbon components in the condensate water are separated, and condensate water from which the heavy hydrocarbon components are separated is obtained;
recycling at least a portion of said condensed water separated from heavy hydrocarbon components obtained from said quench water separation tank as quench water to said pre-quench tower and quench tower;
the process steam production unit comprises a process water extraction tower, a process steam generator and a process steam separation tank; the method comprises the following steps:
feeding at least part of the condensed water separated with the heavy hydrocarbon components obtained from the quenching water separation tank into the process water extraction tower, inputting process steam into the process water extraction tower, and extracting the condensed water separated with the heavy hydrocarbon components in the process water extraction tower by utilizing the process steam so as to separate residual hydrocarbon components and obtain hydrocarbon components and water extracted with the hydrocarbon components; recycling the hydrocarbon component separated by the process water extraction tower to a pre-quenching tower;
feeding the water extracted with the hydrocarbon components obtained from the process water extraction tower into a process steam generator to obtain steam;
the steam generated by the process steam generator is sent to a process steam separation tank, salt-containing liquid drops entrained in the steam are separated, and process steam is obtained;
At least part of the process steam obtained by the process steam generator is input into a process water extraction tower.
9. The process of claim 8 wherein the MTP reaction product and dilution steam containing stream is heat recovered and temperature controlled from 170 ℃ to 210 ℃ prior to being fed to the pre-quench tower.
10. The process according to claim 8, wherein the quench water and lye used in the pre-quench tower has a temperature of 48-52 ℃; the gaseous stream from the pre-quench tower fed to the quench tower has a temperature of 50-60 ℃; the temperature of the quench water and the alkali liquor used in the quenching tower is 38-42 ℃.
11. The method of claim 8, wherein the oil-gas separation unit comprises a compressor surge tank, a compressor, and an oil-gas separation tank; the method comprises the following steps:
sending the gaseous hydrocarbon separated by the quenching tower into a compressor buffer tank, and separating out water entrained in the gaseous hydrocarbon to obtain liquid materials and the gaseous hydrocarbon from which the entrained water is separated;
the gaseous hydrocarbon separated with the entrained water and obtained by the compressor buffer tank is sent to a compressor, and after being compressed and cooled by the compressor, an oil-gas mixture is obtained;
And sending the oil-gas mixture obtained by the compressor and the heavy hydrocarbon components obtained by separation of the pre-quenching tower, the quenching tower and the quenching water separation tank to the oil-gas separation tank, and separating out water entrained in the heavy hydrocarbon components to obtain gas phase components, hydrocarbon condensate and residual water.
12. The method of claim 11, wherein the liquid material is fed into a quench tower;
the residual water is sent to a compressor surge tank.
13. The process of any one of claims 8 to 12 wherein at least a portion of said condensed water separated from heavy hydrocarbon components obtained from said quench water separation tank is pressurized with a quench water pump and filtered to separate particulates therefrom prior to entering said process water extraction column;
the water from which the hydrocarbon components are extracted is pressurized and preheated prior to being fed to the process steam generator.
14. The method of claim 13, wherein the preheating is to 140-150 ℃.
15. The method of claim 13, wherein the methanol recovery unit comprises a methanol recovery column and a methanol recovery column reflux drum; the method comprises the following steps:
feeding at least part of condensed water obtained from the quenching water separation tank and separated from heavy hydrocarbon components into a methanol recovery tower, and rectifying and separating to obtain process water and liquid phase components containing methanol and DME;
Sending the liquid phase component obtained by the methanol recovery tower to a reflux tank of the methanol recovery tower, and separating to obtain methanol, DME and light component noncondensable gas; refluxing at least a portion of the separated methanol and DME to the methanol recovery column.
16. The method of claim 15, wherein the step of determining the position of the probe is performed,
and sending the sewage discharged from the process steam generator into the methanol recovery tower for rectification to obtain process water and a liquid phase containing methanol and DME.
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| CN102304009A (en) * | 2011-05-30 | 2012-01-04 | 中国石油天然气集团公司 | Method and system for separating MTP (Methanol to Propylene) reaction mixed gas |
| CN104784953A (en) * | 2015-03-26 | 2015-07-22 | 浙江大学 | Reaction product separation system for preparing propylene with methanol and quenching system of reaction product separation system |
| CN105503492A (en) * | 2015-12-30 | 2016-04-20 | 中国寰球工程公司 | MTP (methanol to propylene) device and novel separation process thereof |
| CN208346066U (en) * | 2018-04-16 | 2019-01-08 | 国家能源投资集团有限责任公司 | A kind of oil-water-gas separating system for process for preparing propylene from methanol |
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| US7161051B2 (en) * | 2002-12-30 | 2007-01-09 | Exxonmobil Chemical Patents Inc. | Integration of a methanol synthesis system with a methanol to olefin reaction system |
| US20050038304A1 (en) * | 2003-08-15 | 2005-02-17 | Van Egmond Cor F. | Integrating a methanol to olefin reaction system with a steam cracking system |
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| CN102304009A (en) * | 2011-05-30 | 2012-01-04 | 中国石油天然气集团公司 | Method and system for separating MTP (Methanol to Propylene) reaction mixed gas |
| CN104784953A (en) * | 2015-03-26 | 2015-07-22 | 浙江大学 | Reaction product separation system for preparing propylene with methanol and quenching system of reaction product separation system |
| CN105503492A (en) * | 2015-12-30 | 2016-04-20 | 中国寰球工程公司 | MTP (methanol to propylene) device and novel separation process thereof |
| CN208346066U (en) * | 2018-04-16 | 2019-01-08 | 国家能源投资集团有限责任公司 | A kind of oil-water-gas separating system for process for preparing propylene from methanol |
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