Mixed C4 acetonitrile extraction device with low 1, 3-butadiene content

Abstract

The utility model relates to the technical field of mixed C4 extraction, in particular to a mixed C4 acetonitrile extraction device with low 1, 3-butadiene content. The mixed C4 acetonitrile extraction device with low 1, 3-butadiene content comprises a deacetylation tower, an extractive distillation tower, a stripping tower, a butadiene water washing tower and a refining tower which are connected in sequence, as well as a raffinate C4 water washing tower connected with the extractive distillation tower and a dimer water washing tower connected with the butadiene water washing tower. Aiming at mixed C4 with low 1, 3-butadiene content, an acetonitrile extraction process is adopted, the comprehensive energy consumption is low, the use amount of an acetonitrile solvent is reduced, the loss of the acetonitrile solvent is reduced, and the yield of 1, 3-butadiene is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of mixed C4 extraction, in particular to a mixed C4 acetonitrile extraction device with low 1,3-butadiene content. Background Art

[0002] The C4 fraction produced by thermal cracking of petroleum hydrocarbons contains 40-60wt.% butadiene, which is usually purified by an extraction process mainly based on extraction and rectification. Due to the different types of solvents used in the extraction and rectification process, there are many extraction processes. The three most commonly used butadiene extraction processes in industry are the acetonitrile (ACN) method, the dimethylformamide (DMF) method, and the N-methylpyrrolidone (NMP) method.

[0003] At present, the most common extraction process for butadiene production in my country is the acetonitrile (ACN) method. The lightening of cracking raw materials, the growth of light intermediate products under the premise of the growth of light crude oil supply, and the growth of light hydrocarbons, light naphtha and other light oil products are overall and long-term trends, which has led to a general trend of lightening of cracking raw materials. Under such a general trend, the feed structure of the cracking unit has undergone a huge change in the past few years. With the increasing proportion of light hydrocarbons in the raw materials of the upstream ethylene cracking unit, especially the presence of butane in the ethylene cracking raw materials, the concentration of 1,3-butadiene in the mixed carbon four fractions of the by-product is getting lower and lower, and some are close to 20%. In the acetonitrile extraction unit, the reduction of butadiene concentration will increase the energy consumption of butadiene production, and the temperature of the bottom of the extraction tower will increase, which will accelerate the polymerization of butadiene and affect the production operation cycle. For this reason, it is required to improve the acetonitrile butadiene extraction unit so that the unit can meet the production requirements and improve the economic benefits of the unit. Utility Model Content

[0004] In view of the shortcomings of the prior art mixed C4 acetonitrile method butadiene extraction device, the purpose of the utility model is to provide a mixed C4 acetonitrile method extraction device with low 1,3-butadiene content, which has low comprehensive energy consumption, reduces the amount of acetonitrile solvent used, reduces the loss of acetonitrile solvent, and improves the yield of 1,3-butadiene.

[0005] The utility model discloses a mixed C4 acetonitrile extraction device with low 1,3-butadiene content, comprising a deacetylening tower, an extracting distillation tower, a stripping tower, a butadiene water washing tower and a refining tower connected in sequence, a C4 raffinate water washing tower connected to the extracting distillation tower, and a dimer water washing tower connected to the butadiene water washing tower;

[0006] The deacetylene tower feed port is connected to a mixed C4 pipeline, a 1# steam reboiler and a 1# heat exchange reboiler are arranged at the bottom, a top discharge port is connected to a heat medium inlet of the 1# heat exchange reboiler after passing through a 1# condenser, a 1# reflux tank, and a compressor in sequence, and a heat medium outlet of the 1# heat exchange reboiler is divided into two routes, one route is returned to the 1# reflux tank after passing through a 1# cooler and a throttle valve, and then refluxes to the top of the deacetylene tower after passing through a 1# reflux pump, and the other route is connected to a lower feed port of an extractive distillation tower after passing through an evaporator, and a heater is arranged at the bottom of the evaporator;

[0007] The bottom of the extractive distillation tower is provided with a 2# intermediate solvent heat exchange reboiler, a 2# bottom solvent heat exchange reboiler, a 2# steam reboiler and a 2# heat exchange reboiler. The top discharge port is divided into two paths after passing through a 2# condenser, a 2# reflux tank and a 2# reflux pump in sequence. One path refluxes to the top of the extractive distillation tower, and the other path is connected to the lower feed port of the residual carbon four water washing tower. The bottom discharge port is connected to the middle feed port of the stripping tower after passing through a 2# bottom pump and a 2# heat exchange reboiler.

[0008] A 3# steam reboiler is provided at the bottom of the stripping tower, and the top discharge port is divided into two paths after passing through a 3# condenser, a 3# reflux tank, and a 3# reflux pump in sequence, one path refluxes to the top of the stripping tower, and the other path is connected to the lower feed port of the butadiene water washing tower;

[0009] The upper feed port of the butadiene water washing tower is connected to the 2# water inlet pipeline, the bottom discharge port is respectively connected to the 2# acetonitrile-containing water recovery pipeline and the middle feed port of the dimer water washing tower, and the top discharge port is connected to the middle feed port of the refining tower;

[0010] The bottom of the refining tower is provided with a 4# heat exchange reboiler, the top discharge port is sequentially refluxed to the top of the refining tower after passing through a 4# condenser, a 4# reflux tank, and a 4# reflux pump, the bottom discharge port is connected to the heavy component pipeline, and the middle discharge port is connected to the 1,3-butadiene pipeline after passing through a product cooler;

[0011] The bottom discharge port of the stripping tower is connected to the upper feed port of the extraction distillation tower after passing through the 3# bottom pump, the 2# bottom solvent heat exchange reboiler, the 2# intermediate solvent heat exchange reboiler, the heater, the 4# heat exchange reboiler, and the 2# cooler.

[0012] Preferably, the upper feed port of the C4 extraction water washing tower is connected to 1# upper water inlet pipeline, the middle feed port is connected to 1# middle water inlet pipeline, the lower feed port is connected to the top discharge of the extractive distillation tower, the top discharge port is connected to the C4 extraction pipeline, and the bottom discharge port is connected to 1# acetonitrile-containing water recovery pipeline.

[0013] Preferably, the upper feed port of the dimer water washing tower is connected to the 3# water inlet pipeline, the lower feed port is connected to the circulating acetonitrile solvent pipeline and the bottom discharge pipeline of the deacetylenic tower, the top discharge port is connected to the alkyne-containing heavy component pipeline after passing through a buffer tank and a recovery pump, and the bottom discharge port is connected to the 3# acetonitrile-containing water recovery pipeline; wherein, a 3# cooler is provided on the circulating acetonitrile solvent pipeline, and a 1# bottom pump and a 4# cooler are provided on the bottom discharge pipeline of the deacetylenic tower.

[0014] Preferably, the top of the 4# reflux tank at the top of the refining tower is connected to a non-condensable gas pipeline, and the bottom is connected to a water phase pipeline.

[0015] Preferably, a 4# bottom pump is provided on the bottom heavy component pipeline of the refining tower.

[0016] Preferably, the C4 extraction water washing tower, butadiene water washing tower and dimer water washing tower are all turbo extraction towers.

[0017] Compared with the prior art, the utility model has the following beneficial effects:

[0018] (1) The utility model changes the existing mixed C4 separation process, first uses heat pump distillation to remove heavy components such as alkynes, reduces the concentration of alkynes, reduces the residence time of alkynes in the device, and does not produce gas-phase alkynes, thereby increasing the safety of the device and reducing the consumption of high-quality refrigerants. At the same time, it reduces the amount of solvent required for extractive distillation, and eliminates the second extraction tower and the deacetylation system;

[0019] (2) The utility model combines the light-removal tower and the heavy-removal tower of the 1,3-butadiene refining unit into one refining tower. Due to the pretreatment of the utility model, the content of heavy components entering the refining tower is very small, and the 1,3-butadiene product can meet the purity and recovery requirements by side-line extraction, and the process is simpler and easier to operate;

[0020] (3) The exhaust carbon four water washing tower, butadiene water washing tower, and dimer water washing tower of the utility model all adopt a turbine extraction tower, replacing the traditional sieve plate tower, which greatly improves the extraction efficiency of the tower, reduces the amount of water used and the amount of wastewater generated, and optimizes and reduces the load of the acetonitrile recovery tower;

[0021] (4) The mixed C4 acetonitrile extraction process of the utility model has low comprehensive energy consumption, reduces the amount of acetonitrile solvent used, reduces the loss of acetonitrile solvent, and improves the yield of 1,3-butadiene. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the structure of a mixed C4 acetonitrile extraction device with low 1,3-butadiene content according to the utility model;

[0023] In the figure: 1, mixed C4 pipeline; 2, deacetylene tower; 3, compressor; 4, 1# cooler; 5, throttle valve; 6, 1# condenser; 7, 1# reflux tank; 8, 1# reflux pump; 9, 2# cooler; 10, 1# steam reboiler; 11, 1# tower bottom pump; 12, 1# heat exchange reboiler; 13, evaporation tank; 14, heater; 15, 2# intermediate solvent heat exchange reboiler; 16, 2# bottom solvent 1. Refrigerant heat exchange reboiler; 17. 2# tower bottom pump; 18. Extraction distillation tower; 19. 2# condenser; 20. 2# reflux drum; 21. 2# reflux pump; 22. 2# steam reboiler; 23. 2# heat exchange reboiler; 24. C4 extraction pipeline; 25. 1# upper water inlet pipeline; 26. 1# middle water inlet pipeline; 27. C4 extraction water washing tower; 28. 1# acetonitrile water recovery pipeline; 29. ​​3# Condenser; 30, 3# reflux tank; 31, stripping tower; 32, 3# reflux pump; 33, 3# steam reboiler; 34, 3# bottom pump; 35, butadiene water washing tower; 36, 2# water inlet pipeline; 37, 4# condenser; 38, non-condensable gas pipeline; 39, 4# reflux tank; 40, water phase pipeline; 41, 4# reflux pump; 42, refining tower; 43, product cooler; 44, 1,3-butanediol olefin pipeline; 45, 2# acetonitrile water recovery pipeline; 46, 4# heat exchange reboiler; 47, 4# tower bottom pump; 48, heavy component pipeline; 49, buffer tank; 50, recovery pump; 51, heavy component pipeline containing alkyne; 52, 3# water inlet pipeline; 53, dimer water washing tower; 54, 3# acetonitrile water recovery pipeline; 55, circulating acetonitrile solvent pipeline; 56, 3# cooler; 57, 4# cooler. DETAILED DESCRIPTION

[0024] The specific implementation methods of the present invention will be described in detail below. In order to avoid too many unnecessary details, the well-known structures or functions will not be described in detail in the following embodiments. Unless otherwise defined, the technical and scientific terms used in the following embodiments have the same meanings as those generally understood by those skilled in the art to which the present invention belongs.

[0025] Example 1

[0026] like Figure 1 As shown, the mixed C4 acetonitrile extraction device with low 1,3-butadiene content described in the utility model comprises a deacetylene tower 2, an extractive distillation tower 18, a stripping tower 31, a butadiene water washing tower 35 and a refining tower 42 connected in sequence, and a residual C4 water washing tower 27 connected to the extractive distillation tower 18, and a dimer water washing tower 53 connected to the butadiene water washing tower 35;

[0027] The feed inlet of the deacetylene tower 2 is connected to the mixed carbon four pipeline 1, and a 1# steam reboiler 10 and a 1# heat exchange reboiler 12 are arranged at the bottom. The top discharge port is connected to the heat medium inlet of the 1# heat exchange reboiler 12 after passing through the 1# condenser 6, the 1# reflux tank 7, and the compressor 3 in sequence. The heat medium outlet of the 1# heat exchange reboiler 12 is divided into two paths, one of which returns to the 1# reflux tank 7 after passing through the 1# cooler 4 and the throttle valve 5, and then refluxes to the top of the deacetylene tower 2 after passing through the 1# reflux pump 8, and the other is connected to the lower feed inlet of the extractive distillation tower 18 after passing through the evaporator 13, and a heater 14 is arranged at the bottom of the evaporator 13;

[0028] The bottom of the extractive distillation tower 18 is provided with a 2# intermediate solvent heat exchange reboiler 15, a 2# bottom solvent heat exchange reboiler 16, a 2# steam reboiler 22 and a 2# heat exchange reboiler 23. The top discharge port is divided into two paths after passing through a 2# condenser 19, a 2# reflux tank 20 and a 2# reflux pump 21 in sequence. One path refluxes to the top of the extractive distillation tower 18, and the other path is connected to the lower feed port of the residual carbon four water washing tower 27. The bottom discharge port is connected to the middle feed port of the stripping tower 31 after passing through a 2# bottom pump 17 and a 2# heat exchange reboiler 23.

[0029] The bottom of the stripping tower 31 is provided with a 3# steam reboiler 33, and the top discharge port is divided into two paths after passing through the 3# condenser 29, the 3# reflux tank 30, and the 3# reflux pump 32 in sequence, one path refluxes to the top of the stripping tower 31, and the other path is connected to the lower feed port of the butadiene washing tower 35;

[0030] The upper feed port of the butadiene water washing tower 35 is connected to the 2# water inlet pipeline 36, the bottom discharge port is respectively connected to the 2# acetonitrile water recovery pipeline 45 and the middle feed port of the dimer water washing tower 53, and the top discharge port is connected to the middle feed port of the refining tower 42;

[0031] A 4# heat exchange reboiler 46 is disposed at the bottom of the refining tower 42, and the top discharge port is refluxed to the top of the refining tower 42 after passing through a 4# condenser 37, a 4# reflux tank 39, and a 4# reflux pump 41 in sequence, the bottom discharge port is connected to a heavy component pipeline 48, and the middle discharge port is connected to a 1,3-butadiene pipeline 44 after passing through a product cooler 43.

[0032] The bottom discharge port of the stripping tower 31 is connected to the upper feed port of the extraction distillation tower 18 after passing through the 3# bottom pump 34, the 2# bottom solvent heat exchange reboiler 16, the 2# intermediate solvent heat exchange reboiler 15, the heater 14, the 4# heat exchange reboiler 46, and the 2# cooler 9.

[0033] The upper feed port of the residual carbon four water washing tower 27 is connected to the 1# upper water inlet pipeline 25, the middle feed port is connected to the 1# middle water inlet pipeline 26, the lower feed port is connected to the top discharge of the extraction distillation tower 18, the top discharge port is connected to the residual carbon four pipeline 24, and the bottom discharge port is connected to the 1# acetonitrile water recovery pipeline 28.

[0034] The upper feed port of the dimer water washing tower 53 is connected to the 3# water inlet pipeline 52, the lower feed port is connected to the circulating acetonitrile solvent pipeline 55 and the bottom discharge pipeline of the deacetylene tower 2, the top discharge port is connected to the alkyne-containing heavy component pipeline 51 after passing through the buffer tank 49 and the recovery pump 50, and the bottom discharge port is connected to the 3# acetonitrile-containing water recovery pipeline 54; wherein, the circulating acetonitrile solvent pipeline 55 is provided with a 3# cooler 56, and the bottom discharge pipeline of the deacetylene tower 2 is provided with a 1# bottom pump 11 and a 4# cooler 57.

[0035] The top of the 4# reflux tank 39 at the top of the refining tower 42 is connected to the non-condensable gas pipeline 38, and the bottom is connected to the water phase pipeline 40.

[0036] A 4# bottom pump 47 is provided on the bottom heavy component pipeline 48 of the refining tower 42 .

[0037] The C4 extraction water washing tower 27, butadiene water washing tower 35 and dimer water washing tower 53 are all turbo extraction towers.

[0038] The working process of the mixed C4 acetonitrile extraction device with low 1,3-butadiene content is as follows:

[0039] 1) After ethylene cracking, the mixed C4 enters the deacetylene tower 2. The tower top steam recompression type heat pump technology is adopted. When the deacetylene tower 2 is started, the 1# steam reboiler 10 at the bottom of the tower is started to heat with steam, and the 1# condenser 6 at the top of the tower is started to cool with circulating water. After the circulation is established, it is switched to the heat pump distillation system. A light component A containing 1,3-butadiene, butene-1, isobutylene, part of normal butane and carbon three is evaporated from the top of the deacetylene tower 2, and is compressed by the first reflux tank 7 and the compressor 3 in turn, and then enters the first heat exchange reboiler 12 of the deacetylene tower 2 as a heating medium. After condensation, a part of the light component A is extracted into the evaporation tank 13, and a part of it is cooled by the first cooler 4 and reduced in pressure by the throttle valve 5, and then enters the first reflux tank 7, where part of the flashed gas enters the compressor 3 together with the gas from the top of the tower, and most of the condensate enters the bottom of the first reflux tank 7, is pressurized by the first reflux pump 8 and enters the top of the deacetylene tower 2 as reflux; a heavy component A containing vinyl acetylene, butyne, 1,2-butadiene, carbon five, most of butene-2 ​​and normal butane is extracted from the bottom of the deacetylene tower 2, is pressurized by the first bottom pump 11, cooled by the fourth cooler 57, and enters the dimer washing tower 53 for washing or is directly discharged from the device.

[0040] 2) The light component A enters the evaporation tank 13, is heated and evaporated by the heater 14, and enters the lower part of the extractive distillation tower 18, and contacts with the acetonitrile solvent from the top of the tower in countercurrent. The heat required for heating the extractive distillation tower 18 is provided by the 2# intermediate solvent heat exchange reboiler 15, the 2# bottom solvent heat exchange reboiler 16, the 2# steam reboiler 22 and the 2# heat exchange reboiler 23. Compared with butadiene, part of the light components B such as C3, butane, butene, butene-2, etc. with a relative volatility higher than 1.0 are distilled from the top of the tower. After condensation by the 2# condenser 19, the light components B are returned to the extractive distillation tower 18 as reflux through the 2# reflux pump 21, and the other part enters the residual C4 water washing tower 27; the acetonitrile solution containing 1,3-butadiene, propyne and a small amount of butene is discharged from the bottom of the tower as the heavy component B, and provides heat energy for the 2# heat exchange reboiler 23 of the extractive distillation tower 18, and enters the stripping tower 31 after heat exchange cooling.

[0041] Among them, the C4 water washing tower 27 is a mechanically stirred liquid-liquid extraction equipment. The light component B enters from the bottom of the tower, and fresh water and regenerated water from the acetonitrile recovery tower enter from the 1# upper water inlet pipeline and 1# middle water inlet pipeline of the tower respectively. They are in countercurrent contact in the tower. Under the stirring of the fixed turbine, the dispersed phase forms small droplets, and the static ring baffle condenses the dispersed phase and prevents back mixing. After the extraction process is completed, the C4 light phase and the water heavy phase flow out from the outlets at the top and bottom of the tower respectively. The C4 with the solvent removed is sent to the downstream MTBD device, and the water containing acetonitrile enters the acetonitrile recovery tower.

[0042] 3) The 3# steam reboiler 33 of the stripping tower 31 is heated by steam, and the heavy component B enters the stripping tower 31, in which the hydrocarbon components are stripped from the acetonitrile solvent, and the acetonitrile solvent is discharged from the bottom of the tower as a circulating solvent, and is sequentially provided with heat energy by the 2# bottom solvent heat exchange reboiler 16, the 2# intermediate solvent heat exchange reboiler 15, the heater 14 of the evaporator 13, and the 4# heat exchange reboiler 46 of the refining tower 42, and then cooled to about 50° C. by the 2# cooler 9, and enters the extractive distillation tower 18 as the acetonitrile solvent; 1,3-butadiene and propyne with a relative volatility close to that of the light component C are evaporated from the top of the tower, condensed by the 3# condenser 29, and pressurized by the 3# reflux pump 30, a part of which returns to the stripping tower as reflux, and the other part is sent to the butadiene washing tower 35.

[0043] 4) Butadiene water washing tower 35 is a mechanically stirred liquid-liquid extraction device, in which the acetonitrile solvent is removed, the light component C enters from the bottom of the tower, and fresh water enters from the top of the tower, and they are in countercurrent contact in the tower. Under the stirring of the fixed turbine, the dispersed phase forms small droplets, and the static ring baffle condenses the dispersed phase and prevents back mixing. After the extraction process is completed, the oil phase containing 1,3-butadiene and propyne is discharged from the top of the tower and enters the refining tower; the water containing acetonitrile is used as a washing liquid and discharged from the bottom of the tower, a part of which enters the acetonitrile recovery tower, and the other part is sent to the dimer water washing tower 53 through the pressure difference.

[0044] Among them, the circulating solvent may contain impurities such as dimers. In order to remove dimers, a stream (i.e., the regenerated solvent) is extracted from the circulating solvent. Based on the principle that liquefied hydrocarbons and dimers are similarly miscible, the heavy component A (containing alkynes) of a part of the dehydrogenation tower is introduced and sent to the bottom of the dimer water washing tower. The tower is a mechanically stirred liquid-liquid extraction equipment. The washing liquid (water containing acetonitrile) and the regenerated water from the bottom of the butadiene water washing tower enter the dimer water washing tower from the middle and upper parts of the tower respectively, and are in countercurrent contact in the tower. Under the stirring of the fixed turbine, the dispersed phase forms small droplets, and the static ring baffle condenses the dispersed phase and prevents back mixing. After the extraction process is completed, impurities such as dimers are dissolved in the light phase of the alkyne heavy component, and enter the buffer tank from the top of the tower. After being pressurized by the recovery pump, they are sent out of the device together with another part of the heavy component A of the dehydrogenation tower 2. The acetonitrile solvent and the washing water enter the tower kettle together, and then are sent to the acetonitrile recovery tower for solvent recovery.

[0045] 5) The oil phase enters the refining tower 42. The 4# heat exchange reboiler 46 of the refining tower 42 is heated by the circulating solvent discharged from the bottom of the stripping tower 31. The light component D containing propyne, water, and 1,3-butadiene is evaporated from the top of the tower, condensed by the 4# condenser 37, and enters the 4# reflux tank 39. The non-condensable gas is sent out of the device from the top of the 4# reflux tank 39. The water phase stratified in the tank is extracted from the liquid separator, and the remaining liquid is then pumped out by the 4# reflux pump 41 and returned to the top of the tower as reflux. The 1,3-butadiene product with a purity higher than 99.6% is extracted from the side line of the middle and lower part of the refining tower 42, cooled to about 20°C by the product cooler, and sent out of the device; the heavy component D containing dimer and butene is pumped out by the 4# bottom pump and sent out of the device.

Claims

1. A mixed C4 acetonitrile extraction device with low 1,3-butadiene content, characterized in that: The invention comprises a deacetylening tower (2), an extracting distillation tower (18), a stripping tower (31), a butadiene water washing tower (35) and a refining tower (42) which are connected in sequence, a C4 extraction water washing tower (27) connected to the extracting distillation tower (18), and a dimer water washing tower (53) connected to the butadiene water washing tower (35); The deacetylation tower (2) is connected to the mixed C4 pipeline (1) with a 1# steam reboiler (10) and a 1# heat exchange reboiler (12) arranged at the bottom, and the top discharge port is connected to the heat medium inlet of the 1# heat exchange reboiler (12) after passing through the 1# condenser (6), the 1# reflux tank (7) and the compressor (3) in sequence, and the heat medium outlet of the 1# heat exchange reboiler (12) is divided into two paths, one path passes through the 1# cooler (4) and the throttle valve (5) and returns to the 1# reflux tank (7), and then refluxes to the top of the deacetylation tower (2) after passing through the 1# reflux pump (8), and the other path passes through the evaporation tank (13) and is connected to the lower feed port of the extractive distillation tower (18), and a heater (14) is arranged at the bottom of the evaporation tank (13); The bottom of the extractive distillation tower (18) is provided with a 2# intermediate solvent heat exchange reboiler (15), a 2# bottom solvent heat exchange reboiler (16), a 2# steam reboiler (22) and a 2# heat exchange reboiler (23); the top discharge port is sequentially connected to a 2# condenser (19), a 2# reflux tank (20) and a 2# reflux pump (21) and then divided into two paths, one path refluxes to the top of the extractive distillation tower (18), and the other path is connected to the lower feed port of the residual carbon four water washing tower (27); the bottom discharge port is connected to the middle feed port of the stripping tower (31) after passing through a 2# bottom pump (17) and a 2# heat exchange reboiler (23); A 3# steam reboiler (33) is provided at the bottom of the stripping tower (31), and the top discharge port is divided into two paths after passing through a 3# condenser (29), a 3# reflux tank (30), and a 3# reflux pump (32) in sequence, one path refluxes to the top of the stripping tower (31), and the other path is connected to the lower feed port of the butadiene washing tower (35); The upper feed port of the butadiene water washing tower (35) is connected to the 2# water inlet pipeline (36), the bottom discharge port is respectively connected to the 2# acetonitrile water recovery pipeline (45) and the middle feed port of the dimer water washing tower (53), and the top discharge port is connected to the middle feed port of the refining tower (42); The bottom of the refining tower (42) is provided with a 4# heat exchange reboiler (46); the top discharge port is sequentially passed through a 4# condenser (37), a 4# reflux tank (39), and a 4# reflux pump (41) and then refluxed to the top of the refining tower (42); the bottom discharge port is connected to a heavy component pipeline (48); and the middle discharge port is connected to a 1,3-butadiene pipeline (44) after passing through a product cooler (43); The bottom discharge port of the stripping tower (31) is connected to the upper feed port of the extractive distillation tower (18) after passing through the 3# bottom pump (34), the 2# bottom solvent heat exchange reboiler (16), the 2# intermediate solvent heat exchange reboiler (15), the heater (14), the 4# heat exchange reboiler (46), and the 2# cooler (9).

2. The mixed C4 acetonitrile extraction device with low 1,3-butadiene content according to claim 1, characterized in that: The upper feed port of the C4 extraction water washing tower (27) is connected to the 1# upper water inlet pipeline (25), the middle feed port is connected to the 1# middle water inlet pipeline (26), the lower feed port is connected to the top discharge of the extraction distillation tower (18), the top discharge port is connected to the C4 extraction pipeline (24), and the bottom discharge port is connected to the 1# acetonitrile water recovery pipeline (28).

3. The mixed C4 acetonitrile extraction device with low 1,3-butadiene content according to claim 1, characterized in that: The upper feed port of the dimer water washing tower (53) is connected to the 3# water inlet pipeline (52), the lower feed port is connected to the circulating acetonitrile solvent pipeline (55) and the bottom discharge pipeline of the deacetylene tower (2), the top discharge port is connected to the alkyne-containing recombinant pipeline (51) after passing through a buffer tank (49) and a recovery pump (50), and the bottom discharge port is connected to the 3# acetonitrile-containing water recovery pipeline (54).

4. The mixed C4 acetonitrile extraction device with low 1,3-butadiene content according to claim 3, characterized in that: A 3# cooler (56) is provided on the circulating acetonitrile solvent pipeline (55), and a 1# tower bottom pump (11) and a 4# cooler (57) are provided on the bottom discharge pipeline of the deacetylene tower (2).

5. The mixed C4 acetonitrile extraction device with low 1,3-butadiene content according to claim 1, characterized in that: The top of the 4# reflux tank (39) at the top of the refining tower (42) is connected to the non-condensable gas pipeline (38), and the bottom is connected to the water phase pipeline (40).

6. The mixed C4 acetonitrile extraction device with low 1,3-butadiene content according to claim 1, characterized in that: A 4# bottom pump (47) is provided on the heavy component pipeline (48) at the bottom of the refining tower (42).

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