CN112028734A - Recovery device and recovery process for reaction product of propane dehydrogenation propylene preparation - Google Patents
Recovery device and recovery process for reaction product of propane dehydrogenation propylene preparation Download PDFInfo
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- CN112028734A CN112028734A CN201910477400.4A CN201910477400A CN112028734A CN 112028734 A CN112028734 A CN 112028734A CN 201910477400 A CN201910477400 A CN 201910477400A CN 112028734 A CN112028734 A CN 112028734A
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Abstract
The invention belongs to the field of chemical industry, and particularly discloses a device and a process for recovering reaction products of propylene preparation through propane dehydrogenation, wherein the process for recovering the reaction products of propylene preparation through propane dehydrogenation comprises the following steps: the invention selects a cold box and a propylene refrigerating system to provide the cold box for recovering a reaction product of propylene prepared by propane dehydrogenation, wherein the propylene refrigerating system provides the cold box with the temperature of minus 40 ℃ to 13 ℃, the low temperature below minus 40 ℃ is provided by outlet material flows of the first section of the expansion machine and the second section of the expansion machine, and circulating propane subjected to cryogenic cooling by the cold box, a tail gas passing cooling tower and a carbon three washing tower can provide the cold box with the cold energy of minus 120 ℃ to minus 40 ℃ after being mixed with hydrogen-rich gas at the outlet of the second section of the expansion machine. Meanwhile, the carbon three washing tower is introduced, so that the number of equipment is reduced, the energy is saved by at least 10% compared with the traditional process, and the energy-saving effect is obvious.
Description
Technical Field
The invention belongs to the field of chemical industry, and particularly relates to a recovery device and a recovery process for a reaction product of propylene preparation through propane dehydrogenation.
Background
Propylene is an important basic organic chemical raw material in the chemical industry, and statistically, the global propylene demand is increased by more than 15% in the Chinese market, and the consumption is increased at a rate of about 5% -6% per year, and the gap between the supply and demand of propylene is increasing in recent years. For a long time, the source of propylene at home and abroad mainly depends on naphtha cracking co-production and FCC by-production, the price is continuously increased with the shortage of petroleum resources, the price of natural gas is low relative to the price of crude oil, C3 and C4 alkanes derived from the petroleum resources are more and more concerned, and the propane catalytic dehydrogenation technology (PDH) is undoubtedly the most concerned focus in the C3 utilization field.
In the future domestic market, with the continuous operation of Methanol To Olefin (MTO) devices, the impact on the traditional FCC and ethylene cracking olefin production line is bound to be generated. The production of propylene and isobutylene as by-products of FCC and ethylene cracking will be less and less. Therefore, the technology for preparing propylene by propane dehydrogenation faces a very good development opportunity and has huge market potential.
At present, the patent technologies for preparing propylene by propane dehydrogenation in the world are as follows: the Oleflex process from UOP, the Catofin process from LUMMUS, the Star process from Uhde, the FBD-4 process from Snamprogetti/Yarsintz, and the PDH process from Linde/Pasteur. These processes generally employ cryogenic processes to separate the reaction product of propane dehydrogenation to propylene. The cryogenic separation process is a main method for separating naphtha steam cracking products, has mature technology and wide application, and almost all three carbon in reaction products are condensed due to low temperature of refrigerant, so that the yield of propylene is high, but the requirement on equipment materials is high, and the energy consumption is high.
CN102795956B discloses a recovery method of a reaction product of propane dehydrogenation to propylene, which adopts a mode of combining membrane separation and cryogenic separation to separate the reaction product of propane dehydrogenation to propylene. However, the recovery rate of the hydrogen-rich gas in the membrane separation is low, and if the hydrogen-rich gas is required to be sent out as a product and needs to be compressed separately, the total energy consumption is not reduced.
Pasteur corporation discloses a series of patents CN100567230C, CN101087740B, CN101137605A, CN101415661A, which include the entire process from the dehydrogenation of propane to the separation of products containing H2O、CO2、CO、N2CN100567230C discloses the use of washing processes to remove part of the impurities, and CN101087740B, CN101137605A disclose the use of inert absorbents to separate the part of the impurities. CN101415661A discloses a method for separating propylene products by pressure swing adsorption, but the hydrogen-rich gas obtained by the methods has low hydrogen content and high hydrocarbon content and can only be used as fuel gas for burning.
CN102040445 discloses a process flow for preparing propylene by dehydrogenation of a low-carbon hydrocarbon rich in propane, which adopts gasoline as an absorbent to separate light components and carbon three in a propane dehydrogenation product, but the content of hydrogen in the propane dehydrogenation product is high, the circulation volume of the required absorbent is very large, and the energy consumption is high.
Disclosure of Invention
The invention aims to provide a recovery device and a recovery process for a reaction product of propylene preparation by propane dehydrogenation, which can reduce the comprehensive energy consumption of the recovery process for the reaction product of propylene preparation by propane dehydrogenation, and compared with the traditional separation process, the recovery process not only reduces the number of equipment, but also can save energy by at least 10% under the same working condition and separation task.
In order to achieve the above object, one aspect of the present invention provides a process for recovering reaction products of propane dehydrogenation to propylene, the process comprising:
1) pretreatment: purifying, compressing and cooling a reaction product for preparing propylene by propane dehydrogenation, and then sending the reaction product to a cold box;
2) deep cooling: the pretreated propane dehydrogenation propylene product gas sequentially passes through a cooling box and a tail gas supercooling tower for deep cooling and then is sent to a carbon-three washing tower, and part of condensate in the cooling box is sent to a deethanizer;
3) c, washing with carbon III: feeding the material flow from the tail gas supercooling tower into a carbon triple washing tower, feeding the bottom material flow of the carbon triple washing tower into a deethanizer, and feeding the gas phase at the top of the tower into a first section of an expander;
4) deethanizing: feeding material flows from a carbon-III washing tower and a cold box into a deethanizer, feeding a bottom material flow of the deethanizer into a propylene rectifying tower, condensing a gas phase at the top of the tower through a condenser and then feeding the gas phase at the top of a reflux tank into a reflux tank, feeding the gas phase at the top of the reflux tank into a tail gas supercooling tower, feeding a liquid phase at the bottom of the tank back to the deethanizer, feeding the gas phase at the top of the tail gas supercooling tower into a fuel gas system through the cold box, and feeding the liquid phase at the bottom of;
5) and (3) propylene rectification: feeding the material flow from the bottom of the deethanizer into a propylene rectifying tower, extracting the gas phase at the top of the propylene rectifying tower as a polymer-grade propylene product, and optionally mixing the material flow at the bottom of the propylene rectifying tower with raw material propane and then feeding the mixture to a depropanizer;
6) depropanizing: optionally mixing material flow from a propylene rectifying tower with raw material propane, then feeding the mixture into a depropanizing tower, sending the bottom material flow of the depropanizing tower to the outside, sending the gas phase at the top of the depropanizing tower to a propylene preparation reactor by propane dehydrogenation or mixing the gas phase at the top of a secondary gas-liquid separation tank after cryogenic cooling by a cooling box, a tail gas supercooling tower and a carbon three washing tower;
7) expansion for one section: the gas phase from the top of the carbon three washing tower enters an expansion machine for first section throttling and then enters a first-stage gas-liquid separation tank for gas-liquid separation, the liquid phase at the bottom of the first-stage gas-liquid separation tank is sent to a deethanizer, one part of the gas phase at the top of the tank is sent to the second section of the expansion machine, and the other part of the gas phase is sent to a PSA system after being reheated by the carbon three washing tower, a tail gas supercooling tower and a cooling box;
8) and (2) an expansion second stage: and (2) feeding the gas phase from the top of the first-stage gas-liquid separation tank into a second-stage expander, feeding the material flow from the outlet of the second-stage expander into a second-stage gas-liquid separation tank for gas-liquid separation, feeding the liquid phase at the bottom of the second-stage gas-liquid separation tank into a deethanizer, reheating the gas phase at the top of the second-stage gas-liquid separation tank through a third carbon washing tower, a tail gas supercooling tower and a cooling box, and feeding the gas phase at the top of the second-stage expander into a PSA system, or mixing the gas phase at the top of the second-stage expander with the gas phase at the top of a depropanizer which is deep-cooled through the cooling box.
According to the present invention, preferably, the pretreatment of step (1) comprises: drying, impurity removal and purification treatment are carried out on a reaction product obtained in the process of preparing propylene by propane dehydrogenation, the reaction product is compressed to 1.0-2.6 MPaG, and then the reaction product is cooled to-25 ℃.
According to the present invention, preferably, the reaction product of propane dehydrogenation to propylene pretreated in step (2) is cooled to-95 ℃ to-60 ℃ in a cold box.
According to the invention, preferably, the operation pressure of the carbon triple washing tower in the step (3) is 1.0-2.6 MPaG, and the operation temperature is-125 ℃ to-72 ℃.
According to the invention, preferably, in the step (4), the operation pressure at the top of the deethanizer is 1.0-2.6 MPaG, the operation temperature is 7-22 ℃, and the operation temperature at the bottom of the deethanizer is 25-50 ℃; condensing the gas phase at the top of the deethanizer to-23 ℃ to-18 ℃ through a cold box, and then feeding the gas phase into a reflux tank, wherein the operation temperature of the reflux tank is-23 ℃ to-20 ℃; the operation pressure of the top of the tail gas supercooling tower is 1.0-2.6 MPaG, the operation temperature is-65 ℃ to-35 ℃, and the tail gas supercooling tower provides cold energy at-65 ℃ to-35 ℃ from material flows at the tops of the primary gas-liquid separation tank and the secondary gas-liquid separation tank.
In the invention, the propylene rectifying tower in the step (5) can select a heat pump flow or a conventional flow according to specific situations, and the depropanizing tower can also adopt the conventional flow.
In the invention, the depropanizer in the step (6) is mainly set up to refine the raw material propane before the propane enters a reactor for preparing propylene by propane dehydrogenation so as to remove heavy components of carbon four and more than carbon four. In the invention, the depropanization tower is arranged conventionally, the feeding materials in the tower mainly comprise a propane raw material from a tank area and a bottom material flow of the propylene rectifying tower, and a mixed carbon four product at the bottom of the tower is discharged from a boundary area.
In the invention, the gas phase at the top of the carbon three washing tower is expanded and throttled by the first section of the expander and then subjected to gas-liquid separation, the separated liquid phase returns to the deethanizer in a reflux mode, one part of the separated gas phase is reheated by a condenser at the top of the carbon three washing tower, a tail gas supercooling tower and a cooling box and then enters a PSA system, and the rest gas phase enters the second section of the expander.
And (3) allowing the material flow at the second-stage outlet of the expansion machine to enter a second-stage gas-liquid separation tank for gas-liquid separation, conveying the separated liquid phase to a deethanizer, and allowing the separated gas phase to be a hydrogen-rich gas which is respectively conveyed to a PSA system or a propane dehydrogenation propylene preparation reactor according to whether the propane dehydrogenation propylene preparation reaction needs hydrogen supplement or not. When the reaction of preparing propylene by propane dehydrogenation needs to supplement hydrogen, the hydrogen-rich gas is mixed with the gas phase at the top of the depropanizing tower which is cryogenically cooled by the cold box, the tail gas supercooling tower and the carbon triple washing tower, and then is reheated by the carbon triple washing tower, the tail gas supercooling tower and the cold box and then is sent to the reactor for preparing propylene by propane dehydrogenation, wherein the mixed material flow can provide cold energy of-120 ℃ to-40 ℃ for the cold box; when the reaction for preparing propylene by propane dehydrogenation does not need to supplement hydrogen, the hydrogen-rich gas is reheated to 35-40 ℃ by a carbon three washing tower, a tail gas supercooling tower and a cooling box and then sent to a PSA system.
According to the invention, preferably, in the step (7), a part of gas phase at the top of the primary gas-liquid separation tank is reheated to 35-40 ℃ by a carbon-three washing tower, a tail gas supercooling tower and a cooling box and then sent to a PSA system.
According to the invention, preferably, in the step (8), the gas phase at the top of the secondary gas-liquid separation tank is reheated to 35-40 ℃ by the carbon three washing tower, the tail gas supercooling tower and the cooling box and then sent to the PSA system, or the gas phase at the top of the secondary gas-liquid separation tank is mixed with the gas phase at the top of the depropanizer which is cryogenically cooled by the cooling box, the tail gas supercooling tower and the carbon three washing tower, and then sent to the propylene reactor for propane dehydrogenation after being reheated to 35-40 ℃ by the carbon three washing tower, the tail gas supercooling tower and the cooling box, and the gas phase at the top of the secondary gas-liquid separation tank is at a temperature of-120 ℃ to-40.
Another aspect of the present invention provides a recovery apparatus for reaction products of propane dehydrogenation to produce propylene, the recovery apparatus comprising: the system comprises a compressor, a cooler, a cold box, a carbon-three washing tower, a deethanizer, a propylene rectifying tower and a depropanizer which are sequentially connected in series; the first stage of the expansion machine, the first stage gas-liquid separation tank, the second stage of the expansion machine and the second stage gas-liquid separation tank;
wherein the bottom of the cold box is connected with the deethanizer;
a condenser, a reflux tank and a tail gas supercooling tower are arranged at the top of the deethanizer, the top of the deethanizer is sequentially connected with the cooling box and a fuel gas system, and the bottom of the deethanizer is connected with the propylene rectifying tower;
the bottom of the carbon three washing tower is connected with the deethanizer, the top of the tower is sequentially connected with the first-stage expansion machine and the first-stage gas-liquid separation tank, the bottom of the first-stage gas-liquid separation tank is connected with the deethanizer, the top of the first-stage gas-liquid separation tank is respectively connected with the second-stage expansion machine, and the carbon three washing tower, the tail gas supercooling tower, the cooling box and the PSA system are connected in series;
the second section of the expansion machine is connected with the second-stage gas-liquid separation tank, the bottom of the second-stage gas-liquid separation tank is connected with the deethanizer, and the top of the second-stage gas-liquid separation tank is connected with the carbon three washing tower, the tail gas supercooling tower and the cooling box in sequence and then respectively connected with the PSA system and the propane dehydrogenation propylene preparation reactor;
a polymer-grade propylene product extraction line is arranged at the top of the propylene rectifying tower, and the bottom of the propylene rectifying tower is connected with the depropanizing tower;
the depropanization tower is connected with a propane feeding pipeline, the tower bottom is connected with the outside, the tower top is respectively connected with the propane dehydrogenation propylene preparation reactor, and the cooling box, the tail gas supercooling tower, the carbon-gas three-washing tower and the tank top of the secondary gas-liquid separation tank are connected.
In the invention, no special requirement is made on the selection of the carbon three washing tower and the tail gas supercooling tower, the carbon three washing tower and the tail gas supercooling tower can be a traditional rectifying tower, a condenser at the top of the rectifying tower is a high-efficiency heat exchanger, and more particularly, a common plate-fin heat exchanger can be adopted; the carbon three washing tower and the tail gas supercooling tower can also be a fractional Condensation Fractionating Tower (CFT), the upper part of the carbon three washing tower and the tail gas supercooling tower is a plate-fin fractional condensation fractionator filled with rectification packing, the lower part of the carbon three washing tower and the tail gas supercooling tower is a plate tower or a packed tower, and preferably, the theoretical plate number of the carbon three washing tower is 5-15.
In the invention, because the whole product gas separation process only needs the propylene refrigerant to provide cold energy, preferably, the recovery device for the reaction product of preparing propylene by propane dehydrogenation further comprises a propylene refrigeration system, and the propylene refrigeration system is connected with the cold box.
The invention selects a cold box, a tail gas supercooling tower, a carbon three washing tower, a secondary expansion throttling system and a propylene refrigerating system to provide the cold box for recovering a reaction product for preparing propylene by propane dehydrogenation, wherein the propylene refrigerating system provides cold energy at-40 ℃ to 13 ℃ for the cold box, low temperature below-40 ℃ is provided by outlet material flows of a first section of an expansion machine and a second section of the expansion machine, and circulating propane subjected to deep cooling of the cold box is mixed with hydrogen-rich gas at an outlet of the second section of the expansion machine to provide cold energy at-120 ℃ to-40 ℃ for the cold box. Meanwhile, the carbon three washing tower is introduced, so that the number of equipment is reduced, the energy is saved by at least 10% compared with the traditional process, and the energy-saving effect is obvious.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent by describing in more detail exemplary embodiments thereof with reference to the attached drawings, in which like reference numerals generally represent like parts throughout.
FIG. 1 shows a schematic diagram of the recovery process of the reaction product of propane dehydrogenation to propylene in example 1 of the present invention.
FIG. 2 shows a schematic diagram of the recovery process of the reaction product of propane dehydrogenation to propylene in example 2 of the present invention.
Description of reference numerals:
1. a compressor REC; 2. a cooler; 3. a cold box; 4. a carbon three washing tower; 5. a first section of an expander; 6. a second section of the expander; 7. a propylene refrigeration compressor PRC; 8. a deethanizer; 9. a propylene rectification column; 10. a depropanizer; 11. tail gas supercooling tower; 12. a first-stage gas-liquid separation tank; 13. a secondary gas-liquid separation tank;
100. dehydrogenating propane to prepare propylene reaction product; 200. raw material propane; 300. a PSA system feed; 400. a hydrogen-rich gas; 500. deethanizer tail gas; 600. a polymer grade propylene product; 700. recycling the propane; 800. mixing carbon four; 900. the reactor is fed.
Detailed Description
Preferred embodiments of the present invention will be described in more detail below. While the following describes preferred embodiments of the present invention, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein.
Example 1
The recovery device for the reaction product of propane dehydrogenation to propylene comprises: a compressor REC1, a cooler 2, a cold box 3, a carbon three-washing tower 4, a deethanizer 8, a propylene rectifying tower 9 and a depropanizer 10 which are sequentially connected in series; the first section of the expansion machine 5, the first-stage gas-liquid separation tank 12, the second section of the expansion machine 6 and the second-stage gas-liquid separation tank 13;
wherein, the bottom of the cold box 3 is connected with a deethanizer 8;
a condenser, a reflux tank and a tail gas supercooling tower 11 are arranged at the top of the deethanizer 8, the top of the deethanizer 8 is sequentially connected with the cold box 3 and a fuel gas system, and the bottom of the deethanizer is connected with the propylene rectifying tower 9;
the number of theoretical plates of a carbon three washing tower 4 is 5, the tower bottom of the carbon three washing tower is connected with a deethanizer 8, the tower top is sequentially connected with a first section 5 of an expander and a first-stage gas-liquid separation tank 12, the tank bottom of the first-stage gas-liquid separation tank 12 is connected with the deethanizer 8, the tank top is respectively connected with a second section 6 of the expander, and the carbon three washing tower 4, a tail gas supercooling tower 11, a cooling box 3 and a PSA system are connected in series;
the second section 6 of the expansion machine is connected with a second-stage gas-liquid separation tank 13, the bottom of the second-stage gas-liquid separation tank 13 is connected with a deethanizer 8, and the top of the tank is sequentially connected with a carbon-three washing tower 4, a tail gas supercooling tower 11, a cold box 3 and a PSA system;
a polymer-grade propylene product extraction line is arranged at the top of the propylene rectifying tower 9, and the bottom of the tower is connected with a depropanizing tower 10;
the depropanizer 10 is connected with a propane feed line, the bottom of the depropanizer is connected with the outside, and the top of the depropanizer is connected with a reactor for preparing propylene by propane dehydrogenation.
The device for recovering the reaction product of propylene preparation by propane dehydrogenation further comprises a propylene refrigeration system, wherein the propylene refrigeration system is a propylene refrigeration compressor PRC7 and is connected with the cold box 3.
The recovery process of the reaction product of the propylene preparation by the propane dehydrogenation (as shown in figure 1) is carried out in the device, and comprises the following steps:
1) pretreatment: drying, impurity removal and purification treatment are carried out on a reaction product 100 for preparing propylene by propane dehydrogenation, the reaction product is compressed to 1.0-2.6 MPaG by a compressor REC1, and then the reaction product is cooled to the temperature of-25 ℃ to 25 ℃ by a cooler 2 and then sent to a cold box 3;
2) deep cooling: the pretreated reaction product of propylene preparation by propane dehydrogenation is cooled to-95 ℃ to-60 ℃ in a cooling box 3, then is sent to a tail gas cooling tower 11, then enters a carbon-three washing tower 4, and a part of condensate is extracted from the cooling box and sent to a deethanizer 8;
3) c, washing with carbon III: and feeding the material flow from the tail gas supercooling tower 11 into a carbon triple washing tower 4, feeding the bottom material flow of the carbon triple washing tower 4 into a deethanizer 8, and feeding the gas phase at the top of the tower into an expander section 5, wherein the operating pressure of the carbon triple washing tower 4 is 1.0-2.6 MPaG, and the operating temperature is-125 ℃ to-72 ℃.
4) Deethanizing: feeding material flows from a carbon three washing tower 4 and a cold box 3 into a deethanizer 8, feeding a bottom material flow of the deethanizer 8 into a propylene rectifying tower 9, condensing a gas phase at the top of the tower to-23 ℃ to-18 ℃ through a condenser, feeding the gas phase at the top of a reflux tank into a tail gas supercooling tower 11, feeding a liquid phase at the bottom of the tank back to the deethanizer 8, feeding the gas phase at the top of the tail gas supercooling tower 11 into a fuel gas system after passing through the cold box 3, and feeding a liquid phase at the bottom of the tower into the reflux tank;
wherein the operation pressure at the top of the deethanizer 8 is 1.0-2.6 MPaG, the operation temperature is 7-22 ℃, and the operation temperature at the bottom of the deethanizer 8 is 25-50 ℃; the operation temperature of the reflux tank is-23 ℃ to-18 ℃; the operation pressure at the top of the tail gas supercooling tower 11 is 1.0-2.6 MPaG, the operation temperature is-65 ℃ to-35 ℃, and the tail gas supercooling tower 11 provides cold energy at the temperature of-65 ℃ to-35 ℃ by material flows of a first section 5 of an expansion machine and a second section 6 of the expansion machine;
5) and (3) propylene rectification: feeding the material flow from the bottom of the deethanizer 8 into a propylene rectifying tower 9, taking the gas phase at the top of the propylene rectifying tower 9 as a polymer-grade propylene product 600, mixing the material flow at the bottom of the propylene rectifying tower with the raw material propane 200, and then feeding the mixture to a depropanizer 10;
6) depropanizing: the material flow from the propylene rectifying tower 9 is mixed with the raw material propane 200 and then enters a depropanizing tower 10, the mixed carbon four 800 at the bottom of the depropanizing tower 10 is sent out, and the circulating propane 700 at the top of the tower is sent to a reactor for preparing propylene by propane dehydrogenation;
7) expansion for one section: gas phase from the top of the carbon three washing tower 4 enters an expander section 5 for throttling and then enters a first-stage gas-liquid separation tank 12 for gas-liquid separation, liquid phase at the bottom of the first-stage gas-liquid separation tank 12 is sent to a deethanizer 8, one part of the gas phase at the top of the tank is sent to an expander section 6, and the other part of the gas phase is reheated to 35-40 ℃ by the carbon three washing tower 4, a tail gas cooling tower 11 and a cooling box 3 and then sent to a PSA system;
8) and (2) an expansion second stage: and the gas phase from the top of the first-stage gas-liquid separation tank 12 enters the second-stage expander 6, the product flow from the outlet of the second-stage expander 6 is sent to the second-stage gas-liquid separation tank 13 for gas-liquid separation, the liquid phase at the bottom of the second-stage gas-liquid separation tank 13 returns to the deethanizer 8 in a reflux mode, and the gas phase at the top of the tank from-120 ℃ to-40 ℃ is reheated to 35 ℃ to 40 ℃ through the carbon-three washing tower 4, the tail gas supercooling tower 11 and the cooling box 3 and then sent to the PSA system.
Example 2
The recovery device for the reaction product of propane dehydrogenation to propylene comprises: a compressor REC1, a cooler 2, a cold box 3, a carbon three-washing tower 4, a deethanizer 8, a propylene rectifying tower 9 and a depropanizer 10 which are sequentially connected in series; the first section of the expansion machine 5, the first-stage gas-liquid separation tank 12, the second section of the expansion machine 6 and the second-stage gas-liquid separation tank 13;
wherein, the bottom of the cold box 3 is connected with a deethanizer 8;
a condenser, a reflux tank and a tail gas supercooling tower 11 are arranged at the top of the deethanizer 8, the top of the deethanizer 8 is sequentially connected with the cold box 3 and a fuel gas system, and the bottom of the deethanizer is connected with the propylene rectifying tower 9;
the number of theoretical plates of a carbon three washing tower 4 is 15, the tower bottom of the carbon three washing tower is connected with a deethanizer 8, the tower top is sequentially connected with a first section 5 of an expander and a first-stage gas-liquid separation tank 12, the tank bottom of the first-stage gas-liquid separation tank 12 is connected with the deethanizer 8, the tank top is respectively connected with a second section 6 of the expander, and the carbon three washing tower 4, a tail gas supercooling tower 11, a cooling box 3 and a PSA system are connected in series;
the second section 6 of the expansion machine is connected with a second-stage gas-liquid separation tank 13, the bottom of the second-stage gas-liquid separation tank 13 is connected with a deethanizer 8, and the top of the second-stage gas-liquid separation tank is sequentially connected with a carbon-three washing tower 4, a tail gas supercooling tower 11, a cooling box 3 and a reactor for preparing propylene by propane dehydrogenation;
a polymer-grade propylene product extraction line is arranged at the top of the propylene rectifying tower 9, and the bottom of the tower is connected with a depropanizing tower 10;
the depropanization tower 10 is connected with a propane feeding pipeline, the tower bottom is connected with the outside, and the tower top is sequentially connected with the cooling box 3, the tail gas supercooling tower 11, the carbon-three washing tower 4 and the tank top of the secondary gas-liquid separation tank 13;
the device for recovering the reaction product of propylene preparation by propane dehydrogenation further comprises a propylene refrigeration system, wherein the propylene refrigeration system is a propylene refrigeration compressor PRC7 and is connected with the cold box 3.
The recovery process of the reaction product of the propylene preparation by the propane dehydrogenation (as shown in figure 2) is carried out in the device, and comprises the following steps:
1) pretreatment: drying, impurity removal and purification treatment are carried out on a reaction product 100 for preparing propylene by propane dehydrogenation, the reaction product is compressed to 1.0-2.6 MPaG by a compressor REC1, and the reaction product is cooled to the temperature of-25 ℃ to 25 ℃ by a cooler 2 and then sent to a cold box 3;
2) deep cooling: the pretreated reaction product of propylene preparation by propane dehydrogenation is cooled to-95 ℃ to-60 ℃ in a cooling box 3, then is sent to a tail gas cooling tower 11, then enters a carbon-three washing tower 4, and a part of condensate is extracted from the cooling box and sent to a deethanizer 8;
3) c, washing with carbon III: and feeding the material flow from the tail gas supercooling tower 11 into a carbon triple washing tower 4, feeding the bottom material flow of the carbon triple washing tower 4 into a deethanizer 8, and feeding the gas phase at the top of the tower into an expander section 5, wherein the operating pressure of the carbon triple washing tower 4 is 1.0-2.6 MPaG, and the operating temperature is-125 ℃ to-72 ℃.
4) Deethanizing: feeding material flows from a carbon three washing tower 4 and a cold box 3 into a deethanizer 8, feeding a bottom material flow of the deethanizer 8 into a propylene rectifying tower 9, condensing a gas phase at the top of the tower to-23 ℃ to-18 ℃ through a condenser, feeding the gas phase at the top of a reflux tank into a tail gas supercooling tower 11, feeding a liquid phase at the bottom of the tank back to the deethanizer 8, feeding the gas phase at the top of the tail gas supercooling tower 11 into a fuel gas system after passing through the cold box 3, and feeding a liquid phase at the bottom of the tower into the reflux tank;
wherein the operation pressure at the top of the deethanizer 8 is 1.0-2.6 MPaG, the operation temperature is 7-22 ℃, and the operation temperature at the bottom of the deethanizer 8 is 25-50 ℃; the operation temperature of the reflux tank is-23 ℃ to-18 ℃; the operation pressure at the top of the tail gas supercooling tower 11 is 1.0-2.6 MPaG, the operation temperature is-65 ℃ to-35 ℃, and the tail gas supercooling tower 11 provides cold energy at the temperature of-65 ℃ to-35 ℃ by material flows of a first section 5 of an expansion machine and a second section 6 of the expansion machine;
5) and (3) propylene rectification: feeding the material flow from the bottom of the deethanizer 8 into a propylene rectifying tower 9, taking the gas phase at the top of the propylene rectifying tower 9 as a polymer-grade propylene product 600, mixing the material flow at the bottom of the propylene rectifying tower with the raw material propane 200, and then feeding the mixture to a depropanizer 10;
6) depropanizing: the material flow from the propylene rectifying tower 9 is mixed with the raw material propane 200 and then enters a depropanizing tower 10, the mixed carbon four 800 at the bottom of the depropanizing tower 10 is sent out, and the circulating propane 700 at the top of the tower is mixed with the gas phase at the top of a secondary gas-liquid separation tank 13 after being subjected to deep cooling in sequence by a cooling box 3, a tail gas supercooling tower 11 and a carbon three washing tower 4;
7) expansion for one section: gas phase from the top of the carbon three washing tower 4 enters an expander section 5 for throttling and then enters a first-stage gas-liquid separation tank 12 for gas-liquid separation, liquid phase at the bottom of the first-stage gas-liquid separation tank 12 is sent to a deethanizer 8, one part of the gas phase at the top of the tank is sent to an expander section 6, and the other part of the gas phase is reheated to 35-40 ℃ by the carbon three washing tower 4, a tail gas cooling tower 11 and a cooling box 3 and then sent to a PSA system;
8) and (2) an expansion second stage: gas phase from the top of a first-stage gas-liquid separation tank 12 enters a second-stage expander 6, the outlet flow of the second-stage expander 6 is sent to a second-stage gas-liquid separation tank 13 for gas-liquid separation, liquid phase at the bottom of the second-stage gas-liquid separation tank 13 returns to a deethanizer 8 in a reflux mode, the gas phase at the top of the second-stage gas-liquid separation tank 13 is mixed with cryogenic overhead circulating propane 700 passing through a cooling box 3, a tail gas supercooling tower 11 and a carbon triple washing tower 4, and then the mixture is reheated to 35-40 ℃ by passing through the carbon triple washing tower 4, the tail gas supercooling tower 4 and the cooling box 3 in sequence and sent to a reactor for preparing propylene by propane dehydrogenation.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.
Claims (10)
1. A recovery process of a reaction product of propane dehydrogenation to propylene is characterized by comprising the following steps:
1) pretreatment: purifying, compressing and cooling a reaction product for preparing propylene by propane dehydrogenation, and then sending the reaction product to a cold box;
2) deep cooling: the pretreated propane dehydrogenation propylene product gas sequentially passes through a cooling box and a tail gas supercooling tower for deep cooling and then is sent to a carbon-three washing tower, and part of condensate in the cooling box is sent to a deethanizer;
3) c, washing with carbon III: feeding the material flow from the tail gas supercooling tower into a carbon triple washing tower, feeding the bottom material flow of the carbon triple washing tower into a deethanizer, and feeding the gas phase at the top of the tower into a first section of an expander;
4) deethanizing: feeding material flows from a carbon-III washing tower and a cold box into a deethanizer, feeding a bottom material flow of the deethanizer into a propylene rectifying tower, condensing a gas phase at the top of the tower through a condenser and then feeding the gas phase at the top of a reflux tank into a reflux tank, feeding the gas phase at the top of the reflux tank into a tail gas supercooling tower, feeding a liquid phase at the bottom of the tank back to the deethanizer, feeding the gas phase at the top of the tail gas supercooling tower into a fuel gas system through the cold box, and feeding the liquid phase at the bottom of;
5) and (3) propylene rectification: feeding the material flow from the bottom of the deethanizer into a propylene rectifying tower, extracting the gas phase at the top of the propylene rectifying tower as a polymer-grade propylene product, and optionally mixing the material flow at the bottom of the propylene rectifying tower with raw material propane and then feeding the mixture to a depropanizer;
6) depropanizing: optionally mixing material flow from a propylene rectifying tower with raw material propane, then feeding the mixture into a depropanizing tower, sending the bottom material flow of the depropanizing tower to the outside, sending the gas phase at the top of the depropanizing tower to a propylene preparation reactor by propane dehydrogenation or mixing the gas phase at the top of a secondary gas-liquid separation tank after cryogenic cooling by a cooling box, a tail gas supercooling tower and a carbon three washing tower;
7) expansion for one section: the gas phase from the top of the carbon three washing tower enters an expansion machine for first section throttling and then enters a first-stage gas-liquid separation tank for gas-liquid separation, the liquid phase at the bottom of the first-stage gas-liquid separation tank is sent to a deethanizer, one part of the gas phase at the top of the tank is sent to the second section of the expansion machine, and the other part of the gas phase is sent to a PSA system after being reheated by the carbon three washing tower, a tail gas supercooling tower and a cooling box;
8) and (2) an expansion second stage: and (2) feeding the gas phase from the top of the first-stage gas-liquid separation tank into a second-stage expander, feeding the material flow from the outlet of the second-stage expander into a second-stage gas-liquid separation tank for gas-liquid separation, feeding the liquid phase at the bottom of the second-stage gas-liquid separation tank into a deethanizer, reheating the gas phase at the top of the second-stage gas-liquid separation tank through a third carbon washing tower, a tail gas supercooling tower and a cooling box, and feeding the gas phase at the top of the second-stage expander into a PSA system, or mixing the gas phase at the top of the second-stage expander with the gas phase at the top of a depropanizer which is deep-cooled through the cooling box.
2. The process for recovering a reaction product for the dehydrogenation of propane to produce propylene according to claim 1, wherein the pretreatment of step (1) comprises: drying, impurity removal and purification treatment are carried out on a reaction product obtained in the process of preparing propylene by propane dehydrogenation, the reaction product is compressed to 1.0-2.6 MPaG, and then the reaction product is cooled to-25 ℃.
3. The process for recovering the reaction product of propane dehydrogenation to propylene according to claim 1, wherein the reaction product of propane dehydrogenation to propylene pretreated in step (2) is cooled to-95 ℃ to-60 ℃ in a cooling box.
4. The process for recovering the reaction product of propane dehydrogenation to propylene according to claim 1, wherein the operating pressure of the carbon triple scrubber in the step (3) is 1.0-2.6 MPaG, and the operating temperature is-125 ℃ to-72 ℃.
5. The process for recovering the reaction product of propane dehydrogenation to propylene according to claim 1, wherein in the step (4), the operation pressure at the top of the deethanizer is 1.0 to 2.6MPaG, the operation temperature is 7 to 22 ℃, and the operation temperature at the bottom of the deethanizer is 25 to 50 ℃;
condensing the gas phase at the top of the deethanizer to-23 ℃ to-18 ℃ through a cold box, and then feeding the gas phase into a reflux tank, wherein the operation temperature of the reflux tank is-23 ℃ to-20 ℃;
the operation pressure of the top of the tail gas supercooling tower is 1.0-2.6 MPaG, the operation temperature is-65 ℃ to-35 ℃, and the tail gas supercooling tower provides cold energy at-65 ℃ to-35 ℃ from material flows at the tops of the primary gas-liquid separation tank and the secondary gas-liquid separation tank.
6. The process for recovering the reaction product in the preparation of propylene by propane dehydrogenation according to claim 1, wherein in the step (7), a part of the gas phase at the top of the primary gas-liquid separation tank is reheated to 35-40 ℃ by a carbon-three washing tower, a tail gas supercooling tower and a cooling box, and then sent to a PSA system.
7. The process for recovering reaction products of propylene production through propane dehydrogenation according to claim 1, wherein in step (8), the gas phase at the top of the secondary gas-liquid separation tank is reheated to 35 to 40 ℃ through a carbon three washing tower, a tail gas supercooling tower and a cooling box and then sent to a PSA system, or the gas phase at the top of the secondary gas-liquid separation tank is mixed with the gas phase at the top of the depropanizer which is cryogenically cooled through the cooling box, the tail gas supercooling tower and the carbon three washing tower, then is reheated to 35 to 40 ℃ through the carbon three washing tower, the tail gas supercooling tower and the cooling box and then is sent to the propylene production reactor through propane dehydrogenation, and the temperature of the gas phase at the top of the secondary gas-liquid separation tank is-120 ℃ to-40 ℃.
8. The utility model provides a propane dehydrogenation system propylene reaction product recovery unit which characterized in that, this propane dehydrogenation system propylene reaction product recovery unit includes: the system comprises a compressor, a cooler, a cold box, a carbon-three washing tower, a deethanizer, a propylene rectifying tower and a depropanizer which are sequentially connected in series; the first stage of the expansion machine, the first stage gas-liquid separation tank, the second stage of the expansion machine and the second stage gas-liquid separation tank;
wherein the bottom of the cold box is connected with the deethanizer;
a condenser, a reflux tank and a tail gas supercooling tower are arranged at the top of the deethanizer, the top of the deethanizer is sequentially connected with the cooling box and a fuel gas system, and the bottom of the deethanizer is connected with the propylene rectifying tower;
the bottom of the carbon three washing tower is connected with the deethanizer, the top of the tower is sequentially connected with the first-stage expansion machine and the first-stage gas-liquid separation tank, the bottom of the first-stage gas-liquid separation tank is connected with the deethanizer, the top of the first-stage gas-liquid separation tank is respectively connected with the second-stage expansion machine, and the carbon three washing tower, the tail gas supercooling tower, the cooling box and the PSA system are connected in series;
the second section of the expansion machine is connected with the second-stage gas-liquid separation tank, the bottom of the second-stage gas-liquid separation tank is connected with the deethanizer, and the top of the second-stage gas-liquid separation tank is connected with the carbon three washing tower, the tail gas supercooling tower and the cooling box in sequence and then respectively connected with the PSA system and the propane dehydrogenation propylene preparation reactor;
a polymer-grade propylene product extraction line is arranged at the top of the propylene rectifying tower, and the bottom of the propylene rectifying tower is connected with the depropanizing tower;
the depropanization tower is connected with a propane feeding pipeline, the tower bottom is connected with the outside, the tower top is respectively connected with the propane dehydrogenation propylene preparation reactor, and the cooling box, the tail gas supercooling tower, the carbon-gas three-washing tower and the tank top of the secondary gas-liquid separation tank are connected.
9. The recovery device for the reaction product of propane dehydrogenation to propylene according to claim 8, wherein the number of theoretical plates of the carbon triple scrubber is 5-15, the tail gas supercooling tower and the carbon triple scrubber are dephlegmation fractionators, each dephlegmation fractionator comprises a dephlegmator, a tower section and a tower kettle, and the dephlegmator is a plate-fin heat exchanger.
10. The recovery device for the reaction product of propane dehydrogenation to propylene as claimed in claim 8, wherein the recovery device for the reaction product of propane dehydrogenation to propylene further comprises a propylene refrigeration system, and the propylene refrigeration system is connected with the cold box.
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