Propylene production system for increasing propylene yield

Abstract

The propylene production system for improving propylene yield provided by the present invention belongs to the field of propane dehydrogenation to propylene systems, and includes a reaction unit and a separation unit. The reaction unit includes a reflux flow controllable module and a reactor. The reflux flow controllable module includes an oil removal tower body and an external reflux part. The separation unit includes a dryer, a C3 separation module, and a propylene separation module. The C3 separation module includes a cold box, a deethanizer, and a C3 recovery component. The propylene separation module includes a product separation tower body, a liquid leakage amount controllable component, and a propylene storage tank. The external reflux part makes the reflux flow of the oil removal tower body controllable, so that the C4 components in the raw material are separated from the C3 components. The C3 recovery component recovers the C3 components separated with the C2 gas phase in the deethanizer. The liquid leakage amount controllable component enables the liquid leakage amount of the product separation tower body to be controlled during the separation process to improve the separation efficiency. The combined action of the external reflux part, the C3 recovery component, and the liquid leakage amount controllable component improves the yield of propylene.

Description

Technical Field

[0001] The present invention relates to the technical field of propane dehydrogenation to propylene systems, and particularly to a propylene production system for improving the propylene yield. Background Art

[0002] Currently, the patented technologies for propane dehydrogenation to propylene in the world include: the Oleflex process of UOP, the Catofin process of LUMMUS, the Star process of Uhde, the FBD-4 process of Snamprogetti / Yarsintz, and the PDH process of Linde / BASF. These processes generally adopt cryogenic processes to separate the reaction products of propane dehydrogenation to propylene. The cryogenic separation process is the main method for separating the products of naphtha steam cracking. It has mature technology and wide application. Since the refrigerant temperature is low, almost all of the C3 in the reaction products condenses, so the propylene yield is high. However, it has high requirements for the equipment material and high energy consumption. The present invention provides a new propylene production system to improve the propylene yield. Summary of the Invention

[0003] In view of this, the present invention provides a propylene production system for improving the propylene yield.

[0004] The technical solution adopted by the present invention to solve its technical problems is:

[0005] An acrylonitrile production system for improving acrylonitrile yield, comprising a reaction unit and a separation unit. The reaction unit includes a reflux flow rate controllable module and a reactor. The reflux flow rate controllable module includes an oil removal tower body and an external reflux part. The separation unit includes a dryer, a C3 separation module, and an acrylonitrile separation module. The C3 separation module includes a cold box, a deethanizer, and a C3 recovery assembly. The acrylonitrile separation module includes a product separation tower body, a weeping rate controllable assembly, and an acrylonitrile storage tank. The external reflux part is connected to the oil removal tower body. The oil removal tower body is connected to the inlet of the reactor. The outlet of the reactor is connected to the inlet of the dryer. The outlet of the dryer is connected to the inlet of the cold box. The outlet of the cold box is connected to the inlet of the deethanizer. The top outlet of the deethanizer is connected to the inlet of the C3 recovery assembly. The outlet of the C3 recovery assembly is connected to the recycle inlet of the deethanizer. The bottom outlet of the deethanizer is connected to the inlet of the product separation tower body. The weeping rate controllable assembly is arranged inside the product separation tower body. The weeping rate controllable assembly is located inside the product separation tower body and is connected to the product separation tower body. The bottom outlet of the product separation tower body is connected to the inlet of the oil removal tower body. The top outlet of the product separation tower body is connected to the acrylonitrile storage tank. The external reflux part makes the reflux flow rate of the oil removal tower body controllable, separating the C4 components from the C3 components in the raw material, so that the removed C4 components do not contain the required C3 components. The C3 recovery assembly recovers the C3 components separated out with the C2 gas phase in the deethanizer. The weeping rate controllable assembly makes the weeping rate of the product separation tower body controllable during the separation process to improve the separation efficiency. The combined action of the external reflux part, the C3 recovery assembly, and the weeping rate controllable assembly improves the acrylonitrile yield.

[0006] Preferably, the external reflux part includes a plugging member, a reflux pipe, and a first valve. The oil removal tower body includes an upper tower and a lower tower. The upper tower is provided with a first downcomer, and the first downcomer is provided with a first overflow hole. The plugging member plugs the first overflow hole. One end of the reflux pipe is connected to the lower part of the upper tower, and the other end of the reflux pipe is connected to the upper part of the lower tower. The first valve is arranged on the reflux pipe.

[0007] Preferably, the C3 recovery assembly includes a condenser, a reflux drum, and a batch distillation column. The batch distillation column is provided with a gas phase circulation pipeline. The top of the deethanizer is connected to the inlet of the condenser. The outlet of the condenser is connected to the inlet of the reflux drum. The liquid phase outlet of the reflux drum is connected to the inlet of the deethanizer. The gas phase outlet of the reflux drum is connected to the bottom of the batch distillation column. One end of the gas phase circulation pipeline is connected to the lower end of the batch distillation column, and the other end of the gas phase circulation pipeline is connected to the top of the batch distillation column.

[0008] Preferably, the bubble-cap rectification column is provided with a second downcomer, a second downcomer pipe, and a second liquid receiving tray. The second downcomer pipe includes a vertical pipe fitting and a horizontal pipe fitting. A plurality of second overflow holes are provided on the bottom wall of the horizontal pipe fitting. One end of the vertical pipe fitting is connected to the second downcomer, and the other end of the vertical pipe fitting is connected to the horizontal pipe fitting. The horizontal pipe fitting is located above the second liquid receiving tray.

[0009] Preferably, the diameter of the second downcomer pipe is 85 mm - 95 mm, and the diameter of the second overflow hole is 12 mm - 16 mm.

[0010] Preferably, the bubble-cap rectification column is provided with an auxiliary cooling pipeline. The bubble-cap rectification column is provided with a liquid phase outlet. The liquid phase outlet of the bubble-cap rectification column and the second downcomer are on the same horizontal line. The other end of the auxiliary cooling pipeline is connected to the inlet of the cold box.

[0011] Preferably, the liquid leakage amount controllable assembly includes a tray, a plurality of fixed valves, and a plurality of adjustable blocking members. A plurality of sieve holes are provided on the tray. The number of the adjustable blocking members is equal to or less than the number of the sieve holes. The plurality of fixed valves and sieve holes are arranged at intervals on the tray, and the fixed valves and sieve holes are evenly distributed on the tray. The adjustable blocking member covers the sieve hole.

[0012] Preferably, the adjustable blocking member includes a screw rod and a nut. A nut is provided at the top of the screw rod. The nut covers the sieve hole. The screw rod passes through the sieve hole and is connected to the nut.

[0013] Preferably, the bottom outlet of the product separation tower body is also connected to the inlet of the dryer.

[0014] Preferably, a second valve is provided on the pipeline connecting the bottom outlet of the product separation tower body to the inlet of the oil removal tower, and a third valve is provided on the pipeline connecting the bottom outlet of the product separation tower body to the inlet of the dryer.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] In a propylene production system for improving propylene yield, after the propane raw material enters the main body of the oil removal tower, the external reflux section enables the reflux amount of the main body of the oil removal tower to be controllable, so that the C4 components in the raw material are separated from the C3 components, ensuring that the removed C4 components do not contain the required C3 components. Then, the separated C3 components are transported into the reactor for the reaction of propane dehydrogenation to synthesize propylene. The generated product gas is transported to the dryer, where the dryer dries the moisture in the product gas. The dried product gas first enters the cold box, and the cold box condenses the product gas, producing a hydrogen-rich tail gas and C3 condensate. The C3 condensate enters the deethanizer, and the deethanizer separates the C2 components in the C3 condensate. The C2 components are separated from the top of the deethanizer to the C3 recovery assembly. The C3 recovery assembly recovers the C3 components separated with the C2 gas phase in the deethanizer and re-enters them into the deethanizer. The C3 components come out from the bottom of the deethanizer and enter the main body of the product separation tower. The main body of the product separation tower separates propylene and propane. The liquid leakage amount controllable assembly enables the liquid leakage amount to be controlled during the separation process of the main body of the product separation tower. The separated propylene comes out from the top of the main body of the product separation tower and is stored in the propylene storage tank. By the external reflux section and the C3 recovery assembly, the loss of C3 components is reduced. Furthermore, during the final product separation process, the prepared propylene is completely separated through the liquid leakage amount controllable assembly, improving the propylene yield. Description of the Drawings

[0017] Figure 1 Flow chart of a propylene production system for improving propylene yield.

[0018] Figure 2 Schematic diagram of the reflux amount controllable module.

[0019] Figure 3 Schematic diagram of the plugging member.

[0020] Figure 4 Schematic diagram of the structure of the bubble-cap distillation column.

[0021] Figure 5 Schematic diagram of the propylene separation module.

[0022] Figure 6 Schematic diagram of the liquid leakage amount controllable assembly.

[0023] Figure 7 Schematic diagram of the adjustable blocking member.

[0024] In the figure: Propylene production system 10 for increasing propylene yield, reaction unit 100, reflux flow rate controllable module 110, oil removal tower body 111, upper tower 1111, first downcomer 11111, first overflow hole 11112, lower tower 1112, external reflux section 112, plugging member 1121, reflux pipe 1122, first valve 1123, second valve 1124, reactor 120, separation unit 200, dryer 210, third valve 211, C3 separation module 220, cold box 221, deethanizer 222, C3 recovery assembly 223, condenser 2231, reflux drum 2232, bubble-cap distillation column 2233, gas phase circulation pipeline 22331, second downcomer 22332, second downcomer 22333, vertical pipe member 223331, horizontal pipe member 223332, second overflow hole 223333, second liquid receiving tray 22334, auxiliary cooling pipeline 22335, propylene separation module 230, product separation tower body 231, liquid leakage amount controllable assembly 232, tray 2321, sieve hole 23211, fixed valve 2322, adjustable blocking member 2323, screw 23231, nut 23232, cap nut 23233, propylene storage tank 233. Detailed implementation manners

[0025] The following further elaborates in detail on the technical solutions and technical effects of the embodiments of the present invention in conjunction with the drawings of the present invention.

[0026] Please refer to Figures 1 to 7, A propylene production system 10 for improving propylene yield, comprising a reaction unit 100 and a separation unit 200. The reaction unit 100 includes a reflux flow rate controllable module 110 and a reactor 120. The reflux flow rate controllable module 110 includes an oil removal tower body 111 and an external reflux part 112. The separation unit 200 includes a dryer 210, a C3 separation module 220, and a propylene separation module 230. The C3 separation module 220 includes a cold box 221, a deethanizer 222, and a C3 recovery assembly 223. The propylene separation module 230 includes a product separation tower body 231, a weeping rate controllable assembly 232, and a propylene storage tank 233. The external reflux part 112 is connected to the oil removal tower body 111. The oil removal tower body 111 is connected to the inlet of the reactor 120. The outlet of the reactor 120 is connected to the inlet of the dryer 210. The outlet of the dryer 210 is connected to the inlet of the cold box 221. The outlet of the cold box 221 is connected to the inlet of the deethanizer 222. The top outlet of the deethanizer 222 is connected to the inlet of the C3 recovery assembly 223. The outlet of the C3 recovery assembly 223 is connected to the recycle inlet of the deethanizer 222. The bottom outlet of the deethanizer 222 is connected to the inlet of the product separation tower body 231. The weeping rate controllable assembly 232 is arranged inside the product separation tower body 231. The weeping rate controllable assembly 232 is located inside the product separation tower body 231 and is connected to the product separation tower body 231. The bottom outlet of the product separation tower body 231 is connected to the inlet of the oil removal tower body 111. The top outlet of the product separation tower body 231 is connected to the propylene storage tank 233. The external reflux part 112 makes the reflux flow rate of the oil removal tower body 111 controllable, separating the C4 components from the C3 components in the raw material, so that the removed C4 components do not contain the required C3 components. The C3 recovery assembly 223 recovers the C3 components separated out with the C2 gas phase in the deethanizer 222. The weeping rate controllable assembly 232 makes the weeping rate of the product separation tower body 231 controllable during the separation process to improve the separation efficiency. The combined action of the external reflux part 112, the C3 recovery assembly 223, and the weeping rate controllable assembly 232 improves the yield of propylene.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] In a propylene production system 10 for improving propylene yield provided by the present invention, after propane raw materials enter the deoiling tower body 111, the external reflux part 112 enables the reflux amount of the deoiling tower body 111 to be controllable, so that C4 components in the raw materials are separated from C3 components, and the removed C4 components do not contain the required C3 components. Then, the separated C3 components are transported into the reactor 120 for the reaction of propane dehydrogenation to synthesize propylene. The generated product gas is transported into the dryer 210. The dryer 210 dries the moisture in the product gas. The dried product gas first enters the cold box 221. The cold box 221 condenses the product gas. After condensation, rich hydrogen tail gas and C3 condensate are generated. The C3 condensate enters the deethanizer 222. The deethanizer 222 separates C2 components from the C3 condensate. The C2 components are separated from the top of the deethanizer 222 to the C3 recovery component 223. The C3 recovery component 223 recovers the C3 components separated out with the C2 gas phase in the deethanizer 222 and re-enters the deethanizer 222. The C3 components come out from the bottom of the deethanizer 222 and enter the product separation tower body 231. The product separation tower body 231 separates propylene and propane. The liquid leakage amount controllable component 232 enables the liquid leakage amount in the product separation tower body 231 to be controlled during the separation process. The separated propylene comes out from the top of the product separation tower body 231 and is stored in the propylene storage tank 233. By the external reflux part 112 and the C3 recovery component 223, the loss of C3 components is reduced. Furthermore, during the final product separation process, the prepared propylene is completely separated by the liquid leakage amount controllable component 232, so that the yield of propylene is improved.

[0029] Further, the external reflux part 112 includes a plugging member 1121, a reflux pipe 1122, and a first valve 1123. The deoiling tower body 111 includes an upper tower 1111 and a lower tower 1112. The upper tower 1111 is provided with a first downcomer 11111. The first downcomer 11111 is provided with a first overflow hole 11112. The plugging member 1121 plugs the first overflow hole 11112. One end of the reflux pipe 1122 is connected to the lower part of the last tray of the upper tower 1111, and the other end of the reflux pipe 1122 is connected to the upper part of the first tray of the lower tower 1112. The first valve 1123 is arranged on the reflux pipe 1122.

[0030] Specifically, the plugging member 1121 is a plate body, the plate body has the same shape as the first overflow hole 11112, the plate body covers the first overflow hole 11112, the plate body is welded to the side wall of the first downcomer 11111, the first overflow hole 11112 is plugged through the plate body, the liquid return flow rate of the upper tower 1111 is controlled through the return pipe 1122, and because the internal space of the tower itself is narrow and it is not convenient to transform inside the upper tower 1111, the first overflow hole 11112 is directly partially plugged, so that the liquid no longer enters the lower tower 1112 through the first downcomer 11111, and the first downcomer 11111 is used as a gas passage, enabling gas to enter the upper tower 1111, and then an external circulation between the upper tower 1111 and the lower tower 1112 is established through the return pipe 1122 outside the deoiling tower body 111. A first valve 1123 is arranged on the return pipe 1122, and the return flow rate between the upper tower 1111 and the lower tower 1112 is controlled by the opening degree of the first valve 1123, ensuring that the upper tower 1111 can maintain a normal liquid level, so that the C3 component contained when the C4 component is removed is less, reducing waste.

[0031] Further, the diameter of the return pipe 1122 is 40 mm - 60 mm.

[0032] Further, the C3 recovery assembly 223 includes a condenser 2231, a reflux drum 2232, and a Barth rectification column 2233. The Barth rectification column 2233 is provided with a gas-phase circulation pipeline 22331. The top of the deethanizer 222 is connected to the inlet of the condenser 2231, the outlet of the condenser 2231 is connected to the inlet of the reflux drum 2232, the liquid-phase outlet of the reflux drum 2232 is connected to the inlet of the deethanizer 222, the gas-phase outlet of the reflux drum 2232 is connected to the bottom of the Barth rectification column 2233, one end of the gas-phase circulation pipeline 22331 is connected to the lower end of the Barth rectification column 2233, and the other end of the gas-phase circulation pipeline 22331 is connected to the top of the Barth rectification column 2233. The C3 condensate after condensation in the cold box 221 enters the deethanizer 222. The deethanizer 222 separates the C2 component in the C3 condensate, and the C2 component is transported from the top of the deethanizer 222 to the condenser 2231 for condensation. The condenser 2231 condenses the C2 component gas and returns it to the reflux drum 2232. The liquefied gas returns from the reflux drum 2232 to the deethanizer 222 for further separation. The unliquefied gas is refluxed from the reflux drum 2232 into the Barth rectification column 2233. The Barth rectification column 2233 circulates and rectifies the gas phase through the gas-phase circulation pipeline 22331, so that the C3 component doped in the gas phase is condensed and enters the reflux drum 2232, and then enters the deethanizer 222 again for separation, reducing the waste of the C3 component.

[0033] Furthermore, the bubble-cap distillation column 2233 is provided with a second downcomer 22332, a second downcomer pipe 22333, and a second liquid receiving tray 22334. The second downcomer pipe 22333 includes a vertical pipe fitting 223331 and a horizontal pipe fitting 223332. A plurality of second overflow holes 223333 are provided on the bottom wall of the horizontal pipe fitting 223332. One end of the vertical pipe fitting 223331 is connected to the second downcomer 22332, and the other end of the vertical pipe fitting 223331 is connected to the horizontal pipe fitting 223332. The horizontal pipe fitting 223332 is located above the second liquid receiving tray 22334, and the length of the horizontal pipe fitting 223332 is less than or equal to the length of the second liquid receiving tray 22334.

[0034] Furthermore, the diameter of the second downcomer pipe 22333 is 85 mm - 95 mm, and the diameter of the second overflow holes 223333 is 12 mm - 16 mm.

[0035] Specifically, a plurality of the second overflow holes 223333 are uniformly arranged axially on the horizontal pipe fitting 223332. By uniformly arranging the second overflow holes 223333 on the horizontal pipe fitting 223332 of the downcomer pipe, the liquid is evenly distributed on the liquid receiving tray, and the gas phase entering the bubble-cap distillation column 2233 is liquid-sealed so that the gas phase directly undergoes gas-liquid exchange after entering the bubble-cap distillation column 2233, causing most of the C3 components in the gas phase to liquefy into liquid, enter the reflux drum 2232, and then enter the deethanizer 222 to improve the recovery rate of C3 components.

[0036] Furthermore, the bubble-cap distillation column 2233 is provided with an auxiliary cooling pipeline 22335. The bubble-cap distillation column 2233 is provided with a liquid phase outlet. The liquid phase outlet of the bubble-cap distillation column 2233 is on the same horizontal line as the second downcomer 22332. The other end of the auxiliary cooling pipeline 22335 is connected to the inlet of the cold box 221. Most of the ethane liquid will be condensed in the second downcomer 22332 at the liquid phase outlet of the bubble-cap distillation column 2233, and the ethane liquid is pumped out and transported to the cold box 221 to provide refrigerant for the cold box 221 for auxiliary refrigeration.

[0037] Furthermore, the liquid leakage amount controllable component 232 includes a tray 2321, a plurality of fixed valves 2232, and a plurality of adjustable blocking members 2323. A plurality of sieve holes 23211 are provided on the tray 2321. The number of the adjustable blocking members 2323 is equal to or less than the number of the sieve holes 23211. The plurality of fixed valves 2232 and sieve holes 23211 are arranged at intervals on the tray 2321, and the fixed valves 2232 and sieve holes 23211 are evenly distributed on the tray 2321. The adjustable blocking members 2323 cover the sieve holes 23211.

[0038] Specifically, the fixed valve 2322 is formed by punching the tray 2321.

[0039] Furthermore, the adjustable blocking member 2323 includes a screw 23231 and a nut 23232. A nut 23233 is provided at the top of the screw 23231. The nut 23233 covers the sieve hole 23211. The screw 23231 passes through the sieve hole 23211 and is connected to the nut 23232. When the liquid leakage amount on the tray 2321 is too large and the separation effect cannot be satisfied, the screw 23231 and the nut 23232 are covered on the sieve hole 23211, so that the sieve hole 23211 is blocked to prevent the liquid from overflowing downward, further reducing the liquid leakage amount, making the separation of propylene and propane more thorough, and improving the yield and purity of propylene.

[0040] Furthermore, the bottom outlet of the product separation tower body 231 is also connected to the inlet of the dryer 210. The propane separated from the product separation tower body 231 is used as the regeneration gas of the dryer 210 to regenerate the 3A molecular sieve in the dryer 210.

[0041] Furthermore, a second valve 1124 is provided on the pipeline connecting the bottom outlet of the product separation tower body 231 to the inlet of the oil removal tower body 111, and a third valve 211 is provided on the pipeline connecting the bottom outlet of the product separation tower body 231 to the inlet of the dryer 210.

[0042] The solution of the present invention is further introduced through the following examples and comparative examples. Example 1

[0043] After the propane raw material enters the main body 111 of the oil removal tower, there are 26 trays arranged in the oil removal tower. There are 8 trays in the upper tower 1111, and the trays in the upper tower 1111 are arranged with double overflow. The lower tower 1112 has 18 trays, and the trays in the lower tower 1112 are arranged with single overflow. The blocking member 1121 is a plate body, and the shape of the plate body is the same as that of the first overflow hole 11112. There are 4 first overflow holes 11112, and the diameter of the first overflow hole 11112 is 29.3 mm. The plate body covers the first overflow hole 11112, and the plate body is welded to the side wall of the first downcomer 11111 to block all the first overflow holes 11112 through the plate body. Then, an external circulation between the upper tower 1111 and the lower tower 1112 is established through the reflux pipe 1122 outside the degreasing tower body 111. The diameter of the reflux pipe 1122 is: 50 mm. A first valve 1123 is provided on the reflux pipe 1122 to control the reflux amount between the upper tower 1111 and the lower tower 1112 by adjusting the opening of the first valve 1123. Gas enters the upper tower 1111 from the lower tower 1112 through the first downcomer 11111, so that the C4 components removed from the degreasing tower body 111 do not contain the required C3 components. Then, the separated C3 components are transported into the reactor 120 for the reaction of propane dehydrogenation to synthesize propylene, and the generated product gas is transported into the dryer 210. The dryer 210 dries the moisture in the product gas. The dried product gas first enters the cold box 221, and the cold box 221 condenses the product gas. The condensed C3 condensate enters the deethanizer 222. The deethanizer 222 separates the C2 components from the C3 condensate. The C2 components are transported from the top of the deethanizer 222 to the condenser 2231 for condensation. The condenser 2231 condenses the C2 component gas and then refluxes it into the reflux drum 2232. The liquefied gas returns from the reflux drum 2232 to the deethanizer 222 for further separation. The unliquefied gas refluxes from the reflux drum 2232 into the batch rectification column 2233. The batch rectification column 2233 circulates and rectifies the gas phase through the gas phase circulation pipeline 22331, and the length of the horizontal pipe fitting 223332 is equal to the length of the second liquid receiving tray 22334. The diameter of the second downcomer 22333 is 88 mm. There are 4 second overflow holes 223333, and the diameter of the second overflow holes 223333 is 14 mm. The liquid on the batch rectification column 2233 flows out from the second overflow holes 223333 through the channel formed by the vertical pipe fitting 223331 and the horizontal pipe fitting 223332 and is evenly distributed on the liquid receiving tray, providing a liquid seal for the gas phase entering the batch rectification column 2233 so that the gas phase directly undergoes gas-liquid exchange after entering the batch rectification column 2233, causing most of the C3 components in the gas phase to liquefy into liquid, enter the reflux drum 2232, and then enter the deethanizer 222. The C3 components come out from the bottom of the deethanizer 222 and enter the product separation tower body 231. The product separation tower body 231 separates propylene and propane. In the product separation tower, the ratio of the lifting hole area of the sieve holes 23211 and the fixed valves 2322 to the total cross-sectional area of the tower is 17.03%, fix all the sieve holes 23211 through the screw 23231 and nut 23232, and only perform gas-liquid exchange through the fixed valve 2322, so that propylene and propane are separated more thoroughly. The separated propylene enters the propylene storage tank. The yield of propylene is: 86% - 88%, and the purity of propylene is: 99.5%.

[0044] Comparative Example 1:

[0045] When the propane raw material enters the deoiling tower body 111, 26 trays are arranged in the deoiling tower. There are 8 trays in the upper tower 1111, and the trays in the upper tower 1111 are arranged in a double overflow layout. The lower tower 1112 has 18 trays, and the trays in the lower tower 1112 are arranged in a single overflow layout. The shape of the plate body is the same as that of the first overflow hole 11112. There are 4 first overflow holes 11112, and the diameter of the first overflow hole 11112 is 29.3 mm. Liquid reflux is carried out through the downcomer to separate the C3 component, and then the separated C3 component is transported into the reactor 120 for the reaction of propane dehydrogenation to synthesize propylene. The generated product gas is transported into the dryer 210. The dryer 210 dries the moisture in the product gas. The dried product gas first enters the cold box 221. The cold box 221 condenses the product gas. The condensed C3 condensate enters the deethanizer 222. The deethanizer 222 separates the C2 component in the C3 condensate. The C2 component is transported from the top of the deethanizer 222 to the condenser 2231 for condensation. The condenser 2231 condenses the C2 component gas and refluxes it into the reflux drum 2232. The liquefied gas returns from the reflux drum 2232 to the deethanizer 222 for further separation. The unliquefied gas is refluxed into the Barth rectification tower 2233 through the reflux drum 2232. The Barth rectification tower 2233 circulates and rectifies the gas phase through the gas phase circulation pipeline 22331, liquefies part of the C3 component into a liquid, enters the reflux drum 2232, and then enters the deethanizer 222. The C3 component comes out from the bottom of the deethanizer 222 and enters the product separation tower body 231. The product separation tower body 231 separates propylene and propane, and performs gas-liquid exchange through the fixed valve 2322 and sieve holes 23211. The ratio of the ascending hole area of the sieve holes 23211 and the fixed valve 2322 to the total cross-sectional area of the tower is 17.03%. This makes the separation of propylene and propane more thorough. The separated propylene enters the propylene storage tank. The yield of propylene is: 75% - 78%, and the purity of propylene is: 99.2%.

[0046] Other conditions not mentioned in the above Example 1 and Comparative Example 1 are the same.

[0047] By comparing Example 1 with Comparative Example 1, it is found that by reforming the tower in the propane production system process of the present invention, the tray efficiency of each tower is maximized, and then the separation amount of the required components is optimal, and thus the yield of propylene is increased.

[0048] The above-disclosed are only the preferred embodiments of the present invention. Of course, the scope of the rights of the present invention cannot be limited thereby. Those of ordinary skill in the art can understand all or part of the processes of implementing the above embodiments, and the equivalent changes made according to the claims of the present invention still fall within the scope covered by the invention.

Claims

1. An acrylonitrile production system for improving acrylonitrile yield, characterized in that, It includes a reaction unit and a separation unit. The reaction unit includes a reflux flow rate controllable module and a reactor. The reflux flow rate controllable module includes an oil removal tower body and an external reflux part. The separation unit includes a dryer, a C3 separation module, and a propylene separation module. The C3 separation module includes a cold box, a deethanizer, and a C3 recovery component. The propylene separation module includes a product separation tower body, a weeping rate controllable component, and a propylene storage tank. The external reflux part is connected to the oil removal tower body. The oil removal tower body is connected to the inlet of the reactor. The outlet of the reactor is connected to the inlet of the dryer. The outlet of the dryer is connected to the inlet of the cold box. The outlet of the cold box is connected to the inlet of the deethanizer. The top outlet of the deethanizer is connected to the inlet of the C3 recovery component. The outlet of the C3 recovery component is connected to the recycle inlet of the deethanizer. The bottom outlet of the deethanizer is connected to the inlet of the product separation tower body. The weeping rate controllable component is arranged inside the product separation tower body. The weeping rate controllable component is located inside the product separation tower body and is connected to the product separation tower body. The bottom outlet of the product separation tower body is connected to the inlet of the oil removal tower body. The top outlet of the product separation tower body is connected to the propylene storage tank. The external reflux part makes the reflux flow rate of the oil removal tower body controllable so as to separate the C4 component and the C3 component in the raw material, such that the removed C4 component does not contain the required C3 component. The C3 recovery component recovers the C3 component separated out with the C2 gas phase in the deethanizer. The weeping rate controllable component makes the weeping rate of the product separation tower body controllable during the separation process to improve the separation efficiency. The combined action of the external reflux part, the C3 recovery component, and the weeping rate controllable component increases the yield of propylene. The external reflux part includes a plugging member, a reflux pipe, and a first valve. The oil removal tower body includes an upper tower and a lower tower. The upper tower is provided with a first downcomer, and the first downcomer is provided with a first overflow hole. The plugging member plugs the first overflow hole. One end of the reflux pipe is connected to the lower part of the upper tower, and the other end of the reflux pipe is connected to the upper part of the lower tower. The first valve is arranged on the reflux pipe. The C3 recovery component includes a condenser, a reflux drum, and a barometric rectifying column. The barometric rectifying column is provided with a gas phase circulation pipeline. The top of the deethanizer is connected to the inlet of the condenser. The outlet of the condenser is connected to the inlet of the reflux drum. The liquid phase outlet of the reflux drum is connected to the inlet of the deethanizer. The gas phase outlet of the reflux drum is connected to the bottom of the barometric rectifying column. One end of the gas phase circulation pipeline is connected to the lower end of the barometric rectifying column, and the other end of the gas phase circulation pipeline is connected to the top of the barometric rectifying column.The said Bartsch rectifying column is provided with a second downcomer trough, a second downcomer pipe, and a second liquid receiving tray. The second downcomer pipe includes a vertical pipe fitting and a horizontal pipe fitting. A plurality of second overflow holes are provided on the bottom wall of the horizontal pipe fitting. One end of the vertical pipe fitting is connected to the second downcomer trough, and the other end of the vertical pipe fitting is connected to the horizontal pipe fitting. The horizontal pipe fitting is located above the second liquid receiving tray, and the length of the horizontal pipe fitting is less than or equal to the length of the second liquid receiving tray. The liquid leakage amount controllable component includes a tray, a plurality of fixed valves, and a plurality of adjustable blocking members. A plurality of sieve holes are provided on the tray. The number of the adjustable blocking members is equal to or less than the number of the sieve holes. The plurality of fixed valves and sieve holes are arranged at intervals on the tray, and the fixed valves and sieve holes are evenly distributed on the tray. The adjustable blocking member covers the sieve holes.

2. The acrylonitrile production system for improving acrylonitrile yield according to claim 1, characterized in that, the diameter of the second downcomer is 85 mm - 95 mm, and the diameter of the second overflow hole is 12 mm - 16 mm.

3. The acrylonitrile production system for improving acrylonitrile yield according to claim 1, characterized in that, an auxiliary cooling pipeline is provided for the Barth rectification column, a liquid phase outlet is provided for the Barth rectification column, the liquid phase outlet of the Barth rectification column is on the same horizontal line as the second downcomer tank, and the other end of the auxiliary cooling pipeline is connected to the inlet of the cold box.

4. The acrylonitrile production system for improving acrylonitrile yield according to claim 1, characterized in that, the adjustable blocking member includes a screw rod and a nut, a cap nut is provided at the top of the screw rod, the cap nut covers the sieve hole, and the screw rod passes through the sieve hole and is connected to the nut.

5. The acrylonitrile production system for improving acrylonitrile yield according to claim 1, characterized in that, the bottom outlet of the product separation tower body is also connected to the inlet of the dryer.

6. The acrylonitrile production system for improving acrylonitrile yield according to claim 5, characterized in that, a second valve is provided on the pipeline connecting the bottom outlet of the product separation tower body to the inlet of the degreasing tower body, and a third valve is provided on the pipeline connecting the bottom outlet of the product separation tower body to the inlet of the dryer.

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