Energy-saving and consumption-reducing butadiene extraction device

Abstract

The utility model discloses an energy-saving and consumption-reducing butadiene extraction device which comprises a first extractive distillation tower, a second extractive distillation tower communicated with a side line extraction opening of the first extractive distillation tower and a desorption tower communicated with a tower kettle of the first extractive distillation tower, the tower kettle of the first extractive distillation tower is directly communicated with the upper part of the desorption tower in an isothermal manner; a tower kettle of the first extractive distillation tower is provided with a first extractive distillation tower first reboiler and a first extractive distillation tower second reboiler, and the tower top of the desorption tower is communicated with the tower kettle of the first extractive distillation tower through a circulating gas cooling tower. The first extractive distillation tower adopts two reboilers for heating, so that the extractive distillation temperature in the first extractive distillation tower is increased, and the content of butadiene in the liquid phase discharged material of the tower kettle of the lower tower is reduced; the circulating quantity of butadiene in the tower kettle of the lower tower of the first extractive distillation tower, the desorption tower, the circulating gas cooling tower, the compressor and the tower kettle of the lower tower of the first extractive distillation tower can be obviously reduced, and the energy consumption of the system is reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of chemical engineering processes, and particularly relates to a butadiene extraction device for energy conservation and consumption reduction. Background Technique

[0002] Butadiene is an important basic chemical raw material, which is used to produce styrene-butadiene rubber (SBR), polybutadiene rubber (PBR), styrene thermoplastic elastomer (SBS), acrylonitrile-butadiene-styrene copolymer (ABS), nitrile rubber, styrene-butadiene latex, etc. In addition, it can also be used to produce organic chemical products such as adiponitrile, hexamethylenediamine, nylon 66, and 1,4-butanediol. Butadiene can also be used to produce fine chemical products such as sulfolane, n-octanol, hexanediol, cyclooctadiene, 1,5,9-cyclododecatriene, etc.

[0003] There are two main sources of butadiene. One is the by-product butadiene from ethylene cracking, accounting for more than 90% of the butadiene production. The other source is the crude butadiene obtained by oxidative dehydrogenation of refinery C4, UPC mixed C4, MTO C4, or raffinate C4 after pretreatment. The butadiene content in the C4 components of these two butadiene sources is 10-85 wt%. In addition to butadiene, the C4 from these two butadiene sources also contains butene, butane, alkynes, and a small amount of C3 and C5. The boiling points of each component are extremely close, and some components also form azeotropes with butadiene. The relative volatility between the key components is close to 1 during ordinary distillation, and it is difficult to separate polymer-grade butadiene from them by ordinary distillation. Special methods need to be used for separation. In industry, the combination of extractive distillation tower and ordinary distillation is commonly used for separation. Currently, the commonly used solvents for extractive distillation process are acetonitrile (ACN), N-methylpyrrolidone (NMP), and dimethylformamide (DMF). Due to the toxicity and environmental protection problems of DMP, it has rarely been used in newly built plants in recent years. Compared with the extraction using CAN solvent, the NMP solvent extraction method has the advantages of low energy consumption, low material consumption, low toxicity, less sewage generation, less investment, and low operating cost.

[0004] Patent CN110198923 discloses a method for separating pure 1,3-butadiene from a crude C4 fraction by using selective solvent extraction distillation. The crude C4 fraction is introduced into a pre-distillation column, and a first low-boiling fraction containing C3 hydrocarbons is taken out as the top stream, a gaseous C4 fraction is taken out as the side stream, and a first high-boiling fraction is taken out as the bottom stream. The gaseous C4 fraction is brought into contact with a selective solvent in at least one extraction column to obtain a top fraction containing butanes and butenes and a bottom fraction containing 1,3-butadiene and the selective solvent. Crude 1,3-butadiene is stripped from the bottom fraction in at least one stripping column to obtain the stripped selective solvent, and the stripped selective solvent is recycled to the extraction column, and at least part of the crude 1,3-butadiene is supplied to a pure distillation column to separate a second high-boiling fraction. However, the pre-distillation function and structure of this method are relatively complex, the heat carried by the lean solvent is not fully utilized, and the temperature of the solvent entering the extraction column cannot be flexibly regulated, and there is still room for research in terms of energy conservation and consumption reduction and the stable long-term operation of the system. Utility Model Content

[0005] In view of the technical problem of high energy consumption of the existing butadiene extraction device, the purpose of the present utility model is to provide a butadiene extraction device with energy conservation and consumption reduction.

[0006] The butadiene extraction device with energy conservation and consumption reduction of the present utility model includes:

[0007] A first extractive distillation column, having a feed inlet;

[0008] A second extractive distillation column, the bottom of the second extractive distillation column is communicated with the side draw outlet of the first extractive distillation column, and a crude butadiene draw outlet is provided at the top of the second extractive distillation column;

[0009] A stripping column, the bottom of the first extractive distillation column is communicated with the upper part of the stripping column, and the top of the stripping column is communicated with the bottom of the first extractive distillation column through a recycle gas cooling tower;

[0010] Wherein, the bottom of the first extractive distillation column is directly isothermally communicated with the upper part of the stripping column, and the bottom of the first extractive distillation column has a first reboiler of the first extractive distillation column and a second reboiler of the first extractive distillation column.

[0011] Preferably,

[0012] The bottom of the stripping column is connected to the inlet end of a solvent circulation loop, wherein the first outlet end of the solvent circulation loop is communicated with the upper part of the first extractive distillation column after being temperature-adjusted by a first solvent cooler, and the second outlet end of the solvent circulation loop is communicated with the upper part of the second extractive distillation column after being temperature-adjusted by a second solvent cooler.

[0013] Preferably,

[0014] The gas phase at the top of the circulating gas cooling tower is pressurized by a compressor and then connected to the gas phase space at the bottom of the first extractive distillation column.

[0015] The liquid phase in the first branch of the bottom of the circulating gas cooling tower is heat-exchanged and cooled by the feed evaporation tower second reboiler and then refluxed to the upper part of the circulating gas cooling tower.

[0016] The second branch of the bottom of the circulating gas cooling tower is connected to the liquid phase space at the bottom of the first extractive distillation column through a pump.

[0017] Preferably,

[0018] The energy-saving and consumption-reducing butadiene extraction device further includes:

[0019] A butadiene light component removal tower, the crude butadiene extraction outlet at the top of the second extractive distillation column is connected to the feed inlet of the butadiene light component removal tower, and the butadiene light component removal tower has a light component extraction outlet at the top.

[0020] A butadiene heavy component removal tower, the bottom of the butadiene light component removal tower is connected to the feed inlet of the butadiene heavy component removal tower, the butadiene heavy component removal tower has a polymer-grade butadiene extraction outlet at the top, and the butadiene heavy component removal tower has a heavy component extraction outlet at the bottom.

[0021] Preferably,

[0022] The first extractive distillation column further has:

[0023] An upper tower, the feed inlet is at the bottom of the upper tower;

[0024] A lower tower, the bottom of the upper tower is connected to the top of the lower tower, and the side line extraction outlet is at the side of the lower tower.

[0025] Preferably,

[0026] The energy-saving and consumption-reducing butadiene extraction device further has:

[0027] A feed evaporation tower, which has a feed inlet at the upper part, and the top of the feed evaporation tower is connected to the feed inlet at the gas phase space at the bottom of the upper tower of the first extractive distillation column;

[0028] Preferably, the bottom of the feed evaporation tower has a feed evaporation tower first reboiler and a feed evaporation tower second reboiler.

[0029] Preferably,

[0030] The lower tower of the first extractive distillation column has a first extractive distillation column middle reboiler, a first extractive distillation column first reboiler and a first extractive distillation column second reboiler;

[0031] The first outlet end of the solvent circulation loop has a first downstream circulation branch, and the second outlet end of the solvent circulation loop has a second downstream circulation branch. The first downstream circulation branch is connected to the upper part of the upper tower of the first extractive distillation column, and the second downstream circulation branch is connected to the upper part of the second extractive distillation column;

[0032] The solvent circulation loop is sequentially heat-exchanged and connected with the second reboiler of the first extractive distillation column, the intermediate reboiler of the first extractive distillation column, the first reboiler of the de-heavy tower, and the first reboiler of the feed evaporation tower;

[0033] The first downstream circulation branch is connected to the upper part of the upper tower of the first extractive distillation column after being temperature-adjusted and heat-exchanged by the first solvent cooler;

[0034] The second downstream circulation branch is connected to the upper part of the second extractive distillation column after being temperature-adjusted and heat-exchanged by the second solvent cooler.

[0035] Preferably,

[0036] The liquid phase in the first branch of the bottom of the circulation gas cooling tower is heat-exchanged through the second reboiler of the feed evaporation tower and then cooled by the circulating wash water cooler and then refluxed to the upper part of the circulation gas cooling tower.

[0037] Preferably,

[0038] The bottom of the butadiene de-lighting tower is equipped with a de-lighting tower reboiler;

[0039] The bottom of the butadiene de-heavy tower is equipped with a first de-heavy tower reboiler and a second de-heavy tower reboiler;

[0040] The bottom of the stripping tower is equipped with a stripping tower reboiler.

[0041] Another object of the present utility model is to provide an energy-saving and consumption-reducing butadiene extraction method. The energy-saving and consumption-reducing butadiene extraction method includes the following steps:

[0042] Step S1, the mixed C4 raw material enters the first extractive distillation column and contacts countercurrently with the extraction solvent from the stripping tower. After extractive distillation, the gas phase containing crude butadiene is taken out from the side draw part of the first extractive distillation column;

[0043] Step S2, the taken-out gas phase enters the bottom of the second extractive distillation column and contacts countercurrently with the extraction solvent from the stripping tower in the second extractive distillation column. After extractive distillation, the gas-phase crude butadiene is taken out from the top of the second extractive distillation column, and the liquid phase at the bottom of the second extractive distillation column circulates into the first extractive distillation column from the side draw part of the first extractive distillation column;

[0044] Step S3: The liquid-phase rich solvent at the bottom of the first extractive distillation column enters the stripping column for stripping. The gas phase formed after stripping is taken out from the top of the stripping column, cooled by the recycle gas cooling tower, and then recycled into the first extractive distillation column. The lean solvent after stripping is taken out from the bottom of the stripping column as the extraction solvent and enters the first extractive distillation column and the second extractive distillation column respectively.

[0045] Among them,

[0046] In step S3, the bottom of the first extractive distillation column is heated by a total of two reboilers, namely the first reboiler of the first extractive distillation column and the second reboiler of the first extractive distillation column. Moreover, the liquid phase taken out from the bottom of the first extractive distillation column enters the stripping column for stripping without passing through heating.

[0047] Preferably,

[0048] The top temperature range in the first extractive distillation column is 44 - 50 °C, the bottom temperature range in the first extractive distillation column is 105 °C - 135 °C, and the extraction solvent feed temperature range in the first extractive distillation column is 35 °C - the temperature of the solvent feed plate.

[0049] The top temperature range in the second extractive distillation column is 40 - 45 °C, the bottom temperature range in the second extractive distillation column is 65 - 85 °C, and the extraction solvent feed temperature range in the second extractive distillation column is 35 °C - the temperature of the solvent feed plate. Among them, the extraction solvent feed temperature in the second extractive distillation column is 5 - 15 °C lower than the extraction solvent feed temperature in the first extractive distillation column.

[0050] Preferably,

[0051] The mass ratio of the extraction solvent feed in the first extractive distillation column to the feed of mixed C4 is 4 - 16;

[0052] The range of the amount of the extraction solvent entering the second extractive distillation column: The mass ratio of the extraction solvent feed in the second extractive distillation column to the bottom feed in the second extractive distillation column is 2 - 5.

[0053] Preferably,

[0054] In step S3, the lean solvent after stripping is taken out from the bottom of the stripping column as the extraction solvent and enters the first extractive distillation column and the second extractive distillation column respectively, which specifically includes the following sub-steps:

[0055] Sub-step T1: The lean solvent after stripping is taken out from the bottom of the stripping column as the extraction solvent, and first exchanges heat with the second reboiler of the first extractive distillation column, the middle reboiler of the first extractive distillation column, the first reboiler of the de-heavy tower, and the first reboiler of the feed evaporation tower in sequence through the solvent circulation loop.

[0056] In sub-step T2a, the first part of the solvent after heat exchange in sub-step T1 enters the first downstream circulation branch, is temperature-adjusted by the first solvent cooler, and then enters the first extractive distillation column as the extraction solvent.

[0057] In sub-step T2b, the second part of the solvent after heat exchange in sub-step T1 enters the second downstream circulation branch, is temperature-adjusted by the second solvent cooler, and then enters the second extractive distillation column as the extraction solvent.

[0058] Preferably,

[0059] In step S3, the gas phase formed after analysis is taken out from the top of the analysis column, cooled by the circulating gas cooling tower, and then recycled into the first extractive distillation column. Specifically, it includes the following sub-steps:

[0060] In sub-step E1, the overhead gas phase cooled by the circulating gas cooling tower is taken out from the top, pressurized by a compressor, and then enters the lower part of the first extractive distillation column.

[0061] In sub-step E2, the bottom liquid phase cooled by the circulating gas cooling tower is taken out from the bottom, divided into a first liquid phase and a second liquid phase. The first liquid phase exchanges heat with the second reboiler of the feed evaporation tower and is cooled, and then returns to the top of the circulating gas cooling tower to counter-currently contact and exchange heat with the gas phase formed after analysis. The second liquid phase is pumped into the lower part of the first extractive distillation column by a pump.

[0062] Preferably, the first liquid phase exchanges heat with the second reboiler of the feed evaporation tower, is cooled by the circulating wash water cooler, and then returns to the top of the circulating gas cooling tower to counter-currently contact and exchange heat with the gas phase formed after analysis.

[0063] Preferably,

[0064] The energy-saving and consumption-reducing butadiene extraction method further includes:

[0065] In step S4, the crude butadiene taken out from the top of the second extractive distillation column enters the butadiene light component removal tower to remove light components and the butadiene heavy component removal tower to remove heavy components in sequence, and finally the polymer-grade butadiene is taken out from the top of the butadiene heavy component removal tower.

[0066] Preferably,

[0067] The first extractive distillation column further has an upper tower and a lower tower. Step S1 specifically includes:

[0068] The mixed C4 raw material enters the upper tower and counter-currently contacts with the extraction solvent from the analysis column for extractive distillation. The gas phase is taken out from the top of the upper tower, and the liquid phase enters the lower tower.

[0069] Continue extractive distillation in the lower column. The gas phase including crude butadiene is withdrawn from the side draw position of the lower column and then enters the second extractive distillation column from the bottom of the second extractive distillation column for continued extractive distillation. The liquid phase at the bottom of the second extractive distillation column is recycled into the lower column from the side draw position. The gas phase at the top of the lower column enters the bottom of the upper column, and the liquid phase rich in solvent is formed at the bottom of the lower column.

[0070] Preferably,

[0071] The energy-saving and consumption-reducing butadiene extraction method further includes:

[0072] Step S0: The mixed C4 raw material first enters the feed evaporation column for vaporization to remove the heavy components in the raw material, and a gaseous mixed C4 raw material is formed at the top of the column. Then, the gaseous mixed C4 raw material enters the upper column of the first extractive distillation column.

[0073] Preferably,

[0074] The bottom of the feed evaporation column is heated by the first reboiler of the feed evaporation column and the second reboiler of the feed evaporation column respectively;

[0075] The lower column of the first extractive distillation column is further heated by the middle reboiler in the first extractive distillation column;

[0076] The bottom of the stripping column is heated by the stripping column reboiler;

[0077] The bottom of the butadiene de-lighting column is heated by the de-lighting column reboiler;

[0078] The bottom of the butadiene de-heavying column is heated by the first de-heavying column reboiler and the second de-heavying column reboiler.

[0079] Preferably,

[0080] The mixed C4 raw material is selected from one or more of the following raw materials: ethylene cracking C4, butene oxidative dehydrogenation C4, butane oxidative dehydrogenation C4, and crude oil direct olefin production C4; preferably, the content range of 1,3-butadiene in the mixed C4 raw material is 10-85 wt%;

[0081] The extraction solvent is selected from acetonitrile (ACN), N-methylpyrrolidone (NMP), and dimethylformamide (DMF), and preferably the extraction solvent is selected from N-methylpyrrolidone (NMP).

[0082] The positive and progressive effects of the present utility model are as follows:

[0083] 1) The energy-saving and consumption-reducing butadiene extraction device of the present utility model uses two reboilers, namely the first reboiler of the first extractive distillation column and the second reboiler of the first extractive distillation column, to heat the bottom of the lower column of the first extractive distillation column, which increases the temperature of extractive distillation in the first extractive distillation column, thereby reducing the content of butadiene in the liquid phase discharged from the bottom of the lower column. Further, the circulation amount of butadiene between the bottom of the lower column of the first extractive distillation column, the stripping column, the recycle gas cooling tower, the compressor, and then back to the bottom of the lower column of the first extractive distillation column can be significantly reduced, and the extraction rate of butadiene is improved. At the same time, the diameters of the stripping column and the recycle gas cooling tower are also reduced, and the system energy consumption is lowered.

[0084] 2) The present utility model also correspondingly sets a first solvent cooler and a second solvent cooler in front of the solvent inlets of the first extractive distillation column and the second extractive distillation column, which can specifically adjust the respective temperatures and dosage ratios of the extraction solvent entering the first extractive distillation column and the second extractive distillation column, so as to improve the quality of butadiene extracted by extractive distillation at a higher temperature.

[0085] 3) The lean solvent at the bottom of the stripping column of the present utility model further exchanges heat with the middle reboiler of the first extractive distillation column. Compared with the heat exchange process of the bottom reboiler, the heat exchange temperature difference is large, and the waste heat is utilized more fully, significantly reducing the steam consumption.

[0086] 4) The energy-saving and consumption-reducing butadiene extraction method and device of the present utility model can be applied to ethylene cracking C4, butene (butane) oxidative dehydrogenation C4, crude oil direct olefin production C4, etc., or mixtures of these several C4s, and has wide applicability.

[0087] 5) The present utility model introduces the second reboiler of the first extractive distillation column and the second reboiler of the butadiene deweighting column, which are heated by steam and condensate respectively, to solve the problems of excessive heat consumption in the feed evaporation tower and the lower column of the first extractive distillation column caused by the low content of butadiene in the feed, and the insufficient heat provided by the lean solvent after stripping at the bottom of the stripping column for the feed evaporation tower, the lower column of the first extractive distillation column, and the butadiene deweighting column, thereby improving the applicability and stability of the butadiene extraction device. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] Figure 1 is a schematic structural diagram of the energy-saving and consumption-reducing butadiene extraction device of the present utility model;

[0089] Figure 2 is a schematic structural diagram of a comparative butadiene extraction device. DETAILED DESCRIPTION OF THE INVENTION

[0090] The following describes the embodiments of the present utility model through specific examples. Those skilled in the art can easily understand the other advantages and effects of the present utility model from the content disclosed in this specification. The present utility model can also be implemented or applied through specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present utility model.

[0091] As Figure 1 shown in the structural schematic diagram of the energy-saving and consumption-reducing butadiene extraction device of the present utility model, which specifically includes a feed evaporation tower T1, a first extraction rectification tower, a second extraction rectification tower T4, an analytical tower T5, a circulating gas cooling tower T6, a butadiene deweighting tower T7, a butadiene de-lighting tower T8, a compressor K1, a first reboiler E1 of the feed evaporation tower, a second reboiler E2 of the feed evaporation tower, a first solvent cooler E3, a second solvent cooler E4, a middle reboiler E6 of the first extraction rectification tower, a first reboiler E7 of the first extraction rectification tower, a second reboiler E5 of the first extraction rectification tower, a circulating wash water cooler E8, a reboiler E9 of the analytical tower, a first reboiler E10 of the deweighting tower, a second reboiler E11 of the deweighting tower, and a reboiler E13 of the de-lighting tower. The first extraction rectification tower further includes an upper tower T2 and a lower tower T3.

[0092] Continuing as Figure 1 shown, the upper part of the feed evaporation tower T1 has a feed inlet, and the top of the tower is connected to the feed inlet at the gas phase space at the bottom of the upper tower T2 of the first extraction rectification tower. The bottom of the feed evaporation tower T1 is provided with a first reboiler E1 and a second reboiler E2 of the feed evaporation tower, which are used to heat the C4 raw materials in the feed evaporation tower T1 to remove some heavy components. The bottom of the upper tower T2 is connected to the top of the lower tower T3. The side of the lower tower T3 is provided with a side line extraction port, which is also the side extraction part, located at a higher butadiene concentration and is connected to the bottom of the second extraction rectification tower T4. The top of the second extraction rectification tower T4 is provided with a crude butadiene extraction port, and the second extraction rectification tower T4 is connected to the feed inlet at the upper part of the butadiene de-lighting tower T8 through this crude butadiene extraction port. The top of the butadiene de-lighting tower T8 is provided with a light component extraction port, and the bottom of the tower is provided with a reboiler E13 for heat supply, which is heated by steam condensate. At the same time, the bottom of the butadiene de-lighting tower T8 is also connected to the upper part of the butadiene deweighting tower T7. The top of the butadiene deweighting tower T7 has a polymer-grade butadiene extraction port, the bottom has a heavy component extraction port, and the bottom of the tower is also provided with a first reboiler E10 and a second reboiler E11 of the deweighting tower. Among them, the second reboiler E11 of the deweighting tower is heated by condensate steam. Continuing as Figure 1As shown in the figure, the lower column T3 is also provided with a middle reboiler E6 of the first extractive distillation column, a first reboiler E7 of the first extractive distillation column, and a second reboiler E5 of the first extractive distillation column. Among them, the first reboiler E7 and the second reboiler E5 of the first extractive distillation column, a total of two reboilers, are both arranged at the bottom of the lower column T3 to supply heat to the lower column T3, and the first reboiler E7 of the first extractive distillation column is heated by steam. The bottom of the lower column T3 can be directly isothermally connected to the upper part of the analytical column T5, that is, the bottom liquid of the bottom of the lower column T3 enters the analytical column T5 directly without heating after being taken out.

[0093] The top of the analytical column T5 is also connected to the bottom of the lower column T3 through the recycle gas cooling tower T6. Specifically, as Figure 1 shown, the top of the analytical column T5 is first connected to the lower part of the recycle gas cooling tower T6, and then the top of the recycle gas cooling tower T6 is connected to the gas phase space at the bottom of the lower column T3 through the compressor K1. The bottom of the recycle gas cooling tower T6 is provided with a first bottom branch and a second bottom branch. Among them, the first bottom branch is connected to the upper part of the recycle gas cooling tower T6 after heat exchange through the second reboiler E2 of the feed evaporation tower and the recycle wash water cooler E8 in sequence, and the second bottom branch is directly connected to the liquid phase space at the bottom of the lower column T3 through a pump. Continuing as shown in the figure, a solvent circulation loop is provided at the bottom of the analytical column T5, and the bottom of the analytical column T5 is connected to the inlet end of the solvent circulation loop, and the outlet end of the solvent circulation loop is divided into a first outlet end and a second outlet end. Among them, a first downstream circulation branch is provided at the first outlet end, and a second downstream circulation branch is provided at the second outlet end. The first downstream circulation branch is connected to the upper part of the upper column T2 of the first extractive distillation column after temperature adjustment and heat exchange through the first solvent cooler E3, and the second downstream circulation branch is connected to the upper part of the second extractive distillation column T4 after temperature adjustment and heat exchange through the second solvent cooler E4. That is, the bottom of the analytical column T5 is connected to the upper column T2 of the first extractive distillation column through the solvent circulation loop and the first outlet end and the first downstream circulation branch of the solvent circulation loop in sequence, and at the same time, the bottom of the analytical column T5 is also connected to the upper column T4 of the second extractive distillation column through the solvent circulation loop and the second outlet end and the second downstream circulation branch of the solvent circulation loop. In addition, the above-mentioned solvent circulation loop is connected to the second reboiler E5 of the first extractive distillation column, the middle reboiler E6 of the first extractive distillation column, the first reboiler E10 of the deweighting column, and the first reboiler E1 of the feed evaporation tower in sequence for heat exchange, so that the lean solvent extracted from the analytical column T5 can be heat-exchanged with the above-mentioned reboilers in sequence to further improve the thermal energy utilization rate. Of course, a reboiler E9 is also provided at the bottom of the analytical column T5 for analytical heating, and a side line discharge port and an aqueous solution replenishment port for the solvent are also provided on the side of the analytical column T5.

[0094] The energy-saving and consumption-reducing butadiene extraction method of the present invention adopts the above-mentioned energy-saving and consumption-reducing butadiene extraction device, and the specific steps are as follows:

[0095] In step S0, the mixed C4 raw material first enters the feed evaporation tower T1 from the feed inlet of the feed evaporation tower T1 for vaporization to remove some heavy components in the raw material, and a gaseous mixed C4 raw material is formed at the top of the tower. Then, the gaseous mixed C4 raw material enters the upper tower T2 of the first extractive distillation tower. The bottom of the feed evaporation tower T1 is heated by the first reboiler E1 and the second reboiler E2 of the feed evaporation tower. The mixed C4 raw material is selected from one or more of the following raw materials: ethylene cracking C4, butene oxidative dehydrogenation C4, butane oxidative dehydrogenation C4, and crude oil direct olefin production C4, and the content range of 1,3-butadiene in the mixed C4 raw material is 10-85 wt%.

[0096] In step S1, the gaseous mixed C4 raw material enters the upper tower T2 of the first extractive distillation tower and contacts countercurrently with the extraction solvent from the stripping tower T5. The extraction solvent is selected from acetonitrile, N-methylpyrrolidone, and dimethylformamide. Preferably, the extraction solvent is selected from N-methylpyrrolidone (NMP). After extractive distillation in the upper tower T2, the gaseous phase containing propylene, butane, and butene is taken out from the top of the upper tower T2, and the liquid phase containing butadiene, vinylacetylene, butyne, propyne, C5, and a small amount of 2-butene and the NMP solvent enters the lower tower T3 from the bottom of the tower and continues extractive distillation in the lower tower T3. The gaseous phase containing crude butadiene is taken out from the side draw position of the lower tower T3.

[0097] In step S2, the gaseous phase containing crude butadiene taken out enters the bottom of the second extractive distillation tower T4 and contacts countercurrently with the extraction solvent such as NMP from the stripping tower T5 in the second extractive distillation tower T4. After extractive distillation in the second extractive distillation tower T4, the gaseous crude butadiene is taken out from the top of the second extractive distillation tower T4, and the liquid phase containing vinylacetylene, butyne, and butadiene enters the lower tower T3 again from the side draw position of the bottom of the second extractive distillation tower T4 and circulates into the lower tower T3 along with the solvent.

[0098] Step S3: After extractive distillation in the lower column T3, the formed gas phase enters the bottom of the upper column T2 from the top of the lower column T3, and the formed liquid-phase rich solvent accumulates at the bottom of the lower column T3. The lower column T3 is heated by the intermediate reboiler E6 of the first extractive distillation column, the first reboiler E7 of the first extractive distillation column, and the second reboiler E5 of the first extractive distillation column. Among them, two reboilers, namely the first reboiler E7 of the first extractive distillation column and the second reboiler E5 of the first extractive distillation column, are used to heat the bottom of the lower column T3. Compared with the existing butadiene extraction unit, the extractive distillation temperature of the lower column T3 of the first extractive distillation column is increased, the content of butadiene in the liquid-phase discharge at the bottom of the column is reduced, and the liquid-phase rich solvent withdrawn from the bottom of the column can directly enter the stripping column T5 for stripping without reheating. Thus, the circulation amount of butadiene between the bottom of the lower column T3 of the first extractive distillation column, the stripping column T5, the recycle gas cooling tower T6, the compressor K1, and then back to the bottom of the lower column T3 of the first extractive distillation column can be significantly reduced, and the extraction rate of butadiene is increased. In addition, the diameters of the stripping column T5 and the recycle gas cooling tower T6 are reduced, and the extraction energy consumption of the system is lowered. Specifically, the bottom of the stripping column T5 is heated by the stripping column reboiler E9, and the gas phase containing butadiene formed after stripping in the stripping column T5 is also withdrawn from the top of the stripping column T5 and enters the recycle gas cooling tower T6 for cooling. The gas phase cooled by the recycle gas cooling tower T6 is withdrawn from the top of the tower, pressurized by the compressor K1, and then enters the lower part of the lower column T3. The cooled liquid phase is withdrawn from the bottom of the recycle gas cooling tower T6 and is divided into a first liquid phase and a second liquid phase. The first liquid phase exchanges heat with the second reboiler E2 of the feed evaporation tower and is cooled by the recycle wash water cooler E8, and then returns to the top of the recycle gas cooling tower T6 to countercurrently contact and exchange heat with the gas phase formed after stripping, making full use of the heat energy. The second liquid phase is pumped into the lower column T3 by a pump. In addition, in the stripping column T5, a part of the gas phase containing vinylacetylene is withdrawn from the side discharge port on the side of the tower. At the same time, in order to maintain the solvent balance in the tower, an aqueous solution containing solvent is supplemented from the solvent aqueous solution make-up port on the side of the tower. Further, the lean solvent formed after stripping into a liquid phase is withdrawn from the bottom of the stripping column T5. After being connected in heat exchange with the second reboiler E5 of the first extractive distillation column, the intermediate reboiler E6 of the first extractive distillation column, the first reboiler E10 of the deweighting column, and the first reboiler E1 of the feed evaporation tower through the solvent circulation loop, it is divided into a first part of the solvent and a second part of the solvent. The first part of the solvent enters the first downstream circulation branch and enters the upper column T2 of the first extractive distillation column as an extraction solvent after being temperature-adjusted by the first solvent cooler E3. At this time, the top temperature range of the upper column T2 of the first extractive distillation column is 44 - 50 °C, the bottom discharge temperature range of the lower column T3 of the first extractive distillation column is 105 °C - 135 °C, the extraction solvent feed temperature range of the upper column T2 is 35 °C - the temperature of the tray at the solvent feed port, and the mass ratio of the extraction solvent feed of the upper column T2 of the first extractive distillation column to the feed of the mixed C4 is 4 - 16.The second part of the solvent enters the second downstream circulation branch, is temperature-adjusted by the second solvent cooler E4, and then enters the second extractive distillation column T4 as the extractive solvent. At this time, the top temperature range of the second extractive distillation column T4 is 40 - 45 °C, the bottom temperature range is 65 - 85 °C, and the feed temperature range of the extractive solvent to the second extractive distillation column T4 is 35 °C to the temperature of the tray at the solvent feed port. The mass ratio of the extractive solvent feed to the bottom feed of the second extractive distillation column is 2 - 5.

[0099] Since the lower column T3 is heated by two reboilers and one intermediate reboiler, the temperature inside the entire first extractive distillation column is thus increased. With these two independent first solvent cooler E3 and second solvent cooler E4, the optimal feed temperature and mass ratio of the extractive solvent entering the first and second extractive distillations can be targeted and regulated respectively. Compared with using one solvent cooler, the consumption of circulating water and heating steam can be further reduced.

[0100] In step S4, the crude butadiene drawn from the top of the second extractive distillation column T4 enters the butadiene de-lighting column T8 and the butadiene de-heavying column T7 in sequence. Among them, the bottom of the butadiene de-lighting column T8 is heated by the de-lighting column reboiler E13, and light components such as propyne and water are removed in the butadiene de-lighting column T8. The bottom of the butadiene de-heavying column T7 is heated by the de-heavying column first reboiler E10 and the de-heavying column second reboiler E11, and heavy components such as cis-2-butene carried over are removed in the butadiene de-heavying column T7. Finally, polymer-grade butadiene is drawn from the top of the butadiene de-heavying column T7.

[0101] Example 1

[0102] According to Figure 1As shown in the figure, the mixed C4 raw material 1 with a butadiene content of 54.7 wt% and a flow rate of 40.6 t / h enters the top of the feed evaporation tower T1. After removing some heavy components in the feed evaporation tower T1, the vaporized product at the top of the tower enters the bottom of the upper tower T2 of the first extractive distillation tower, and countercurrently contacts with the extractive solvent feed 21 with a flow rate of 444 t / h and a temperature of 53 °C (N-methylpyrrolidone content 91.7 wt%) entering the upper tower T2 of the first extractive distillation tower in the tower for extractive distillation. The top temperature of the upper tower T2 is 45 °C, and butane and butene 5 are distilled out from the top of the upper tower T2 of the first extractive distillation tower. A gas-phase material 6 with a flow rate of 49.6 t / h is withdrawn from the side line of the lower tower T3 of the first extractive distillation tower and enters the bottom of the second extractive distillation tower T4, and countercurrently contacts with the extractive solvent feed 22 with a flow rate of 99.7 t / h and a temperature of 38 °C entering the second extractive distillation tower T4 in the tower. The top temperature of the second extractive distillation tower T4 is 43 °C, and the bottom temperature is 76 °C. Crude butadiene 8 is obtained at the top of the tower, and a mixed stream 7 is formed at the bottom of the tower and returned to the lower tower T3 of the first extractive distillation tower. A liquid-phase stream is withdrawn from the middle of the lower tower T3 of the first extractive distillation tower, heated by the lean solvent stream 17, and then returned to the tower. The second reboiler E5 of the first extractive distillation tower in the lower tower T3 of the first extractive distillation tower provides heat through the lean solvent 16 at the bottom of the stripping tower T5, and the second reboiler E7 of the first extractive distillation tower in the lower tower T3 of the first extractive distillation tower provides heat through steam. The bottom pressure of the lower tower T3 of the first extractive distillation tower is 0.41 MPag, and the temperature is 120 °C. The flow rate of the bottom liquid 9 of the lower tower T3 of the first extractive distillation tower is 522 t / h, and then it is depressurized and enters the top of the stripping tower T5. The pressure of the stripping tower T5 is 0.075 MPag, and the temperature of the vapor-phase product 10 at the top of the tower is 104 °C. It enters the bottom of the circulating cooling tower T6 and countercurrently contacts with the circulating coolant to be cooled to 43 °C, and then is sent to the compressor K1 to be pressurized to 0.45 MPag. The pressurized circulating crude butadiene 12 enters the bottom of the lower tower T3. Vinyl acetylene and other streams 23 are withdrawn from the side line of the stripping tower T5 and enter the subsequent water washing system, and the solvent-containing aqueous solution 24 after water washing is returned to the stripping tower T5. The reboiler E9 at the bottom of the stripping tower T5 uses steam to provide heat. The temperature of the lean solvent 16 after stripping at the bottom of the stripping tower T5 is 150 °C, and it recovers heat successively through the second reboiler E5 of the first extractive distillation tower, the middle reboiler E6 of the first extractive distillation tower, the first reboiler E10 of the butadiene deweighting tower, and the first reboiler E1 of the feed evaporation tower. It is further cooled to 53 °C and 38 °C by the first solvent cooler E3 and the second solvent cooler E4 respectively with circulating water and returned to the upper tower T2 of the first extractive distillation tower and the second extractive distillation tower T4 for recycling.

[0103] Example 2

[0104] According to Figure 1As shown in the figure, the mixed C4 raw material 1 with a butadiene content of 28.1 wt% and a flow rate of 49.9 t / h enters the top of the feed evaporation tower T1. After removing some heavy components in the feed evaporation tower T1, the gasified product at the top of the tower enters the bottom of the upper tower T2 of the first extractive distillation tower, and countercurrently contacts with the extractive solvent feed 21 with a flow rate of 296 t / h and a temperature of 53 °C (N-methylpyrrolidone content 91.7 wt%) entering the upper tower T2 of the first extractive distillation tower in the tower for extractive distillation. The top temperature of the upper tower T2 is 45 °C, and butane and butene 5 are distilled out from the top of the upper tower T2 of the first extractive distillation tower. A gas-phase material 6 with a flow rate of 32.7 t / h is extracted from the side line of the lower tower T3 of the first extractive distillation tower and enters the bottom of the second extractive distillation tower T4, and countercurrently contacts with the extractive solvent feed 22 with a flow rate of 66.1 t / h and a temperature of 38 °C entering the second extractive distillation tower T4 in the tower. The top temperature of the second extractive distillation tower T4 is 43 °C, and the bottom temperature is 76 °C. Crude butadiene 8 is obtained at the top of the tower, and the mixed stream 7 at the bottom of the tower returns to the lower tower T3 of the first extractive distillation tower. A liquid-phase stream is drawn from the middle of the lower tower T3 of the first extractive distillation tower, and after being heat-exchanged with the lean solvent stream 17, it returns to the tower. The second reboiler E5 of the first extractive distillation tower in the lower tower T3 of the first extractive distillation tower provides heat through the lean solvent 16 at the bottom of the stripping tower T5, and the first reboiler E7 of the first extractive distillation tower in the lower tower T3 of the first extractive distillation tower provides heat through steam. The bottom pressure of the lower tower T3 of the first extractive distillation tower is 0.41 MPag, and the temperature is 120 °C. The flow rate of the bottom liquid 9 of the lower tower T3 of the first extractive distillation tower is 397 t / h, and then it enters the top of the stripping tower T5 after being depressurized. The pressure of the stripping tower T5 is 0.075 MPag, and the temperature of the vapor-phase product 10 at the top of the tower is 104 °C. It enters the bottom of the circulating cooling tower T6 and countercurrently contacts with the circulating coolant to be cooled to 43 °C, and then is sent to the compressor K1 to be pressurized to 0.45 MPag. The pressurized circulating crude butadiene 12 enters the bottom of the lower tower T3. Vinyl acetylene and other streams 23 are extracted from the side line of the stripping tower T5 and enter the subsequent water washing system, and the solvent-containing aqueous solution 24 after water washing returns to the stripping tower T5. The reboiler E9 of the stripping tower at the bottom of the stripping tower T5 uses steam to provide heat. The temperature of the lean solvent 16 after stripping at the bottom of the stripping tower is 150 °C, and it recovers heat through the second reboiler E5 of the first extractive distillation tower, the middle reboiler E6 of the first extractive distillation tower, the first reboiler E10 of the butadiene deweighting tower, and the first reboiler E1 of the feed evaporation tower in sequence, and is further cooled to 53 °C and 38 °C by the first solvent cooler E3 and the second solvent cooler E4 respectively with circulating water and returns to the upper tower T2 of the first extractive distillation tower and the second extractive distillation tower T4 for recycling.

[0105] Comparative Example 1

[0106] The process corresponding to this Comparative Example 1 is as Figure 2As shown in the figure, the mixed C4 raw material 1 with a butadiene content of 54.7 wt% and a flow rate of 40.6 t / h enters the feed evaporation tower T1. The difference from Example 1 is that after the extraction solvent is only heated to 38°C through a common solvent cooler E14, the amount entering the upper tower T2 of the first extractive distillation tower is 487 t / h, and the amount entering the second extractive distillation tower T4 is 99.7 t / h. The top temperature of the upper tower T2 of the first extractive distillation tower is 43°C, the top temperature of the second extractive distillation tower T4 is 45°C, and the bottom temperature is 76°C. Except for the medium reboiler E6, the lower tower T3 of the first extractive distillation tower is only heated by a first extractive distillation tower bottom liquid heater E5A. The bottom pressure is 0.41 MPag, and the temperature is 103°C. A gas-phase material 6 with a flow rate of 49.6 t / h is withdrawn from the side line of the lower tower T3 of the first extractive distillation tower and enters the bottom of the second extractive distillation tower T4, where it contacts the 99.7 t / h of extraction solvent feed 22 entering the second extractive distillation tower T4 in countercurrent in the tower. The bottom liquid 9 of the lower tower T3 of the first extractive distillation tower is pressurized and enters the analytical tower feed heater E12 to be preheated to 120°C, and then enters the top of the analytical tower T5 after depressurization. The lean solvent 16 after analysis at the bottom of the analytical tower has a temperature of 150°C. Similar to Example 1, it also recovers heat successively through the first extractive distillation tower bottom liquid heater E5A, the butadiene stripping tower reboiler E10, and the feed evaporation tower first reboiler E1. However, the difference is that finally, the circulating water is further cooled to 38°C only through a common solvent cooler E14 and returned to the two extraction systems for recycling.

[0107] Comparative Example 2

[0108] The process corresponding to this Comparative Example 2 is as Figure 2As shown in the figure, the mixed C4 raw material 1 with a butadiene content of 28.1 wt% and a flow rate of 49.9 t / h enters the feed evaporation tower T1. The difference from Example 2 is that after the extraction solvent is only heat-exchanged to 38°C through a common solvent cooler E14, the amount entering the upper tower T2 of the first extractive distillation column is 324 t / h, and the amount entering the second extractive distillation column T4 is 66.1 t / h. The top temperature of the upper tower T2 of the first extractive distillation column is 43°C, the top temperature of the second extractive distillation column T4 is 45°C, and the bottom temperature is 76°C. The lower tower T3 of the first extractive distillation column is only heated by a first bottom liquid heater E5A of the lower tower of the first extractive distillation column in addition to the medium reboiler E6. The bottom pressure is 0.41 MPag, and the temperature is 103°C. A gas-phase material 6 with a flow rate of 32.7 t / h is withdrawn from the side line of the lower tower T3 of the first extractive distillation column and enters the bottom of the second extractive distillation column T4, where it contacts the 66.1 t / h of extraction solvent feed 22 entering the second extractive distillation column T4 in countercurrent in the tower. The bottom liquid 9 of the lower tower T3 of the first extractive distillation column is pressurized and preheated to 120°C in the analytical tower feed heater E12, and then depressurized and enters the top of the analytical tower T5. The lean solvent 16 after analysis at the bottom of the analytical tower has a temperature of 150°C. Similar to Example 1, it also recovers heat through the first bottom liquid heater E5A of the lower tower of the first extractive distillation column, the butadiene deweighting tower reboiler E10, and the first reboiler E1 of the feed evaporation tower in sequence. However, the difference is that finally, the circulating water is further cooled to 38°C only through a common solvent cooler E14 and then returned to the extraction system for recycling.

[0109] Table 1 Energy consumption data of Example 1 and Comparative Example 1 of the present utility model

[0110]

[0111]

[0112] As shown in Table 1, for the mixed C4 raw material with a butadiene content of 54.7 wt% in Example 1, the energy consumption is 181.23 kg of standard oil per ton of butadiene, and for the mixed C4 raw material with a butadiene content of 54.7 wt% in Comparative Example 1, the energy consumption is 195.86 kg of standard oil per ton of butadiene. The energy consumption per ton of butadiene product is reduced by 14.63 kg of standard oil. Among them, the consumption of steam, electric energy, and circulating water all decreases to varying degrees.

[0113] Table 2 Energy consumption data of Example 2 and Comparative Example 2 of the present utility model

[0114]

[0115]

[0116] As shown in Table 2, the energy consumption of the mixed C4 raw material with a butadiene content of 28.1 wt% in Example 2 is 261.63 kg of standard oil / t of butadiene, and the energy consumption of the mixed C4 raw material with a butadiene content of 28.1 wt% in Comparative Example 2 is 275.89 kg of standard oil / t of butadiene. The energy consumption per ton of butadiene product is reduced by 14.26 kg of standard oil. Among them, the consumption of steam, electric energy, and circulating water all decreases to varying degrees.

[0117] Table 3 Comparison of the compositions of Stream 5 and Stream 8 between Example 1 and Comparative Example 1 of the present utility model

[0118]

[0119] As can be seen from Table 3, the content of 1,3-butadiene in the raffinate C4 drawn from the top of the first extractive distillation column in Example 1 and Comparative Example 1 of the present utility model is 0.0000 wt%, showing no obvious change; the contents of 1,3-butadiene in the crude butadiene stream drawn from the top of the second extractive distillation column in Example 1 and Comparative Example 1 of the present utility model are 98.8683 wt% and 98.8702 wt% respectively, and there is no significant change in the product quality.

[0120] Table 4 Comparison of the compositions of Stream 5 and Stream 8 between Example 2 and Comparative Example 2 of the present utility model

[0121]

[0122] As can be seen from Table 4, the content of 1,3-butadiene in the raffinate C4 drawn from the top of the first extractive distillation column in Example 2 and Comparative Example 2 of the present utility model is 0.0000 wt%, showing no obvious change; the contents of 1,3-butadiene in the crude butadiene stream drawn from the top of the second extractive distillation column in Example 2 and Comparative Example 2 of the present utility model are 98.8523 wt% and 98.8546 wt% respectively, and there is no significant change in the product quality.

[0123] Table 5 Influence of different process flows on equipment size and butadiene loss

[0124]

[0125] As can be seen from Table 5, compared with Comparative Example 1, Example 1 reduces the butadiene loss by 51 kg / h, and the equipment size also decreases to a certain extent; compared with Comparative Example 2, Example 2 reduces the butadiene loss by 37 kg / h, and the equipment size also decreases to a certain extent.

[0126] The utility model uses two reboilers and one intermediate boiler in the lower column of the first extractive distillation column, and by coordinating and setting the optimal temperatures and solvent ratios for the solvent to enter the first extractive distillation column and the second extractive distillation column, it can reduce the consumption of steam, electric energy and circulating water, and can significantly reduce the circulation amount of the butadiene-rich material in turn in the bottom of the lower column of the first extractive distillation column, the stripping column, the circulating gas cooling tower, the compressor and the bottom of the lower column of the first extractive distillation column, and further reduce the energy consumption of the device and the size of the main equipment, and improve the device efficiency and the butadiene extraction rate.

[0127] The above has described the utility model in detail in combination with the embodiments with the attached drawings. Those of ordinary skill in the art can make various variations to the utility model according to the above description. Therefore, some details in the embodiments should not constitute a limitation to the utility model, and the scope defined by the appended claims will be taken as the protection scope of the utility model.

Claims

1. An energy-saving and consumption-reducing butadiene extraction device, characterized in that The butadiene extraction unit for energy conservation and consumption reduction includes: A first extractive distillation column with a feed inlet; A second extractive distillation column, the bottom of which is connected to the side draw outlet of the first extractive distillation column, and the top of which is provided with a crude butadiene draw outlet; A stripping column, the bottom of the first extractive distillation column is connected to the upper part of the stripping column, and the top of the stripping column is connected to the bottom of the first extractive distillation column through a recycle gas cooling tower; It is characterized in that the bottom of the first extractive distillation column is directly isothermally connected to the upper part of the stripping column, and the bottom of the first extractive distillation column is provided with a first reboiler and a second reboiler of the first extractive distillation column.

2. The butadiene extraction unit for energy conservation and consumption reduction according to claim 1, characterized in that The bottom of the stripping column is connected to the inlet end of the solvent circulation loop, wherein the first outlet end of the solvent circulation loop is connected to the upper part of the first extractive distillation column after being temperature-adjusted by a first solvent cooler, and the second outlet end of the solvent circulation loop is connected to the upper part of the second extractive distillation column after being temperature-adjusted by a second solvent cooler.

3. The butadiene extraction unit for energy conservation and consumption reduction according to claim 1, characterized in that The gas phase at the top of the recycle gas cooling tower is pressurized by a compressor and then connected to the gas phase space at the bottom of the first extractive distillation column; The liquid phase in the first branch of the bottom of the recycle gas cooling tower is heat-exchanged and cooled by a second reboiler of the feed evaporation tower and then refluxed to the upper part of the recycle gas cooling tower; The second branch of the bottom of the recycle gas cooling tower is connected to the liquid phase space at the bottom of the first extractive distillation column through a pump.

4. The butadiene extraction device for energy conservation and consumption reduction as described in claim 1, characterized in that The butadiene extraction unit for energy conservation and consumption reduction further includes: A butadiene de-lighting tower, the crude butadiene draw outlet at the top of the second extractive distillation column is connected to the feed inlet of the butadiene de-lighting tower, and the top of the butadiene de-lighting tower is provided with a light component draw outlet; A butadiene de-heavy tower, the bottom of the butadiene de-lighting tower is connected to the feed inlet of the butadiene de-heavy tower, the top of the butadiene de-heavy tower is provided with a polymer-grade butadiene draw outlet, and the bottom of the butadiene de-heavy tower is provided with a heavy component draw outlet.

5. The butadiene extraction device for energy conservation and consumption reduction according to claim 1, characterized in that The first extractive distillation column further has: An upper tower, the feed inlet is at the bottom of the upper tower; A lower tower, the bottom of the upper tower is connected to the top of the lower tower, and the side draw outlet is at the side of the lower tower.

6. The butadiene extraction device for energy conservation and consumption reduction according to claim 1, characterized in that The butadiene extraction unit for energy conservation and consumption reduction further has: A feed evaporation tower, the upper part of which has a feed inlet, and the top of the feed evaporation tower is connected to the feed inlet at the gas phase space at the bottom of the upper tower of the first extractive distillation column.

7. The butadiene extraction unit for energy conservation and consumption reduction according to claim 6, characterized in that The bottom of the feed evaporation tower is provided with a first reboiler and a second reboiler of the feed evaporation tower.

8. The butadiene extraction unit for energy conservation and consumption reduction according to claim 2, characterized in that The lower tower of the first extractive distillation column is provided with a middle boiler of the first extractive distillation column, the first reboiler of the first extractive distillation column and the second reboiler of the first extractive distillation column; The first outlet end of the solvent circulation loop has a first downstream circulation branch, and the second outlet end of the solvent circulation loop has a second downstream circulation branch. The first downstream circulation branch is connected to the upper part of the upper tower of the first extractive distillation column, and the second downstream circulation branch is connected to the upper part of the second extractive distillation column; The solvent circulation loop is successively connected in heat exchange with the second reboiler of the first extractive distillation column, the middle reboiler of the first extractive distillation column, the first reboiler of the de - heavy tower, and the first reboiler of the feed evaporation tower; The first downstream circulation branch is connected in communication with the upper part of the upper tower of the first extractive distillation column after being temperature - adjusted and heat - exchanged through the first solvent cooler; The second downstream circulation branch is connected in communication with the upper part of the second extractive distillation column after being temperature - adjusted and heat - exchanged through the second solvent cooler.

9. The energy-saving and consumption-reducing butadiene extraction device according to claim 3, characterized in that The liquid phase in the first branch of the bottom of the circulating gas cooling tower passes through the second reboiler of the feed evaporation tower for heat exchange and then passes through the circulating wash water cooler for cooling and then returns to the upper part of the circulating gas cooling tower.

10. The energy - saving and consumption - reducing butadiene extraction device according to claim 4, wherein The bottom of the butadiene de - light tower is provided with a de - light tower reboiler; The bottom of the butadiene de - heavy tower is provided with a first de - heavy tower reboiler and a second de - heavy tower reboiler; The bottom of the stripping tower is provided with a stripping tower reboiler.

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