Butadiene extraction device

Abstract

The utility model discloses a butadiene extraction device which comprises a first extractive distillation tower and a second extractive distillation tower, a second extractive distillation tower; a material inlet of the stripping tower is communicated with the tower kettle of the first extractive distillation tower in series, the tower top of the stripping tower is communicated with the tower kettle of the second extractive distillation tower in series, and a lean solvent outlet of the tower kettle of the stripping tower is communicated with the first extractive distillation tower; and the side line extraction port of the stripping tower is communicated and connected with the upper part of the evaporation tower, and the desorbed lean solvent outlet of the tower kettle of the evaporation tower is communicated and connected with the second extractive distillation tower. And when any stream of lean solvent is not completely resolved, the other stream of solvent is not influenced. Two sets of heating and heat exchange systems are arranged, and different grades of lean solvents extracted from a stripping tower kettle and an evaporation tower kettle are respectively heated and subjected to heat exchange, so that waste heat can be fully utilized; and meanwhile, process gas is used for replacing nitrogen to supplement pressure to the extraction solvent tank, so that the nitrogen is saved, and the C4 loss caused by nitrogen emission of the system is further reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of chemical processes, and particularly relates to a butadiene extraction device. Background Art

[0002] The existing butadiene extraction device mainly adopts a set of solvent systems. After the solvent extracts C4, the organic matter is resolved in the stripping column, then taken out from the bottom of the stripping column, and finally recycled back to the first extraction and rectification column and the second extraction and rectification column. When the solvent is not completely resolved, both extraction and rectification columns will be affected, the concentration of the solvent decreases, and the extraction effect deteriorates. In addition, all solvents are resolved through the stripping column, resulting in high steam consumption. The solvent is taken out from the bottom of the stripping column, and after multi-stage heat exchange, it is recycled, without any available low-grade heat sources, and the waste heat utilization is insufficient. In addition, during the process of solvent recycling in the existing butadiene extraction device, the solvent tank of a set of solvent systems uses nitrogen for pressure compensation. A small amount of nitrogen will enter the top of the extraction and rectification column along with the solvent, and nitrogen needs to be discharged in the reflux tank of the extraction and rectification column. The discharged nitrogen will entrain C4, resulting in the loss of C4. Content of the Utility Model

[0003] Aiming at the technical problem that when the existing butadiene extraction technology has incomplete solvent resolution during the extraction process, using the lean solvent after stripping and resolution as the extraction solvent in the first extraction and rectification column and the second extraction and rectification column will lead to poor extraction effect, the utility model aims to provide a butadiene extraction device.

[0004] The butadiene extraction device of the utility model includes:

[0005] The first extraction and rectification column;

[0006] The second extraction and rectification column;

[0007] A stripping column, the feed inlet of the stripping column is connected in series with the bottom of the first extraction and rectification column, the top of the stripping column is connected in series with the bottom of the second extraction and rectification column, and the outlet of the lean solvent after stripping at the bottom of the stripping column is connected to the first extraction and rectification column;

[0008] A stripping column, the side draw outlet of the stripping column is connected to the upper part of the stripping column, and the outlet of the lean solvent after resolution at the bottom of the stripping column is connected to the second extraction and rectification column.

[0009] Preferably,

[0010] Another solvent supplement bypass is provided at the outlet of the lean solvent after stripping and is connected to the stripping column. Preferably, the stripping column is an alkyne stripping column.

[0011] Preferably,

[0012] The butadiene extraction unit includes:

[0013] A first extraction solvent tank, the lean solvent after stripping at the bottom of the stripping column is connected to the inlet of the first extraction solvent tank, and the bottom outlet of the first extraction solvent tank is connected to the first extraction rectification column;

[0014] A second extraction solvent tank, the outlet of the lean solvent after analysis at the bottom of the stripping column is connected to the inlet of the second extraction solvent tank, and the bottom outlet of the second extraction solvent tank is connected to the second extraction rectification column.

[0015] Preferably,

[0016] The butadiene extraction unit further includes:

[0017] A first reflux tank, the overhead product of the first extraction rectification column is connected to the first reflux tank, and there is a first pressure compensation gas path between the top of the first reflux tank and the first extraction solvent tank;

[0018] A second reflux tank, the overhead product of the second extraction rectification column is connected to the second reflux tank, and there is a second pressure compensation gas path between the top of the second reflux tank and the second extraction solvent tank;

[0019] A stripping column reflux tank, the overhead product of the stripping column is connected to the stripping column reflux tank.

[0020] Preferably,

[0021] The bottom of the first reflux tank has a first reflux passage and a first product outlet communicating with the upper part of the first extraction rectification column;

[0022] The bottom of the second reflux tank has a second reflux passage and a second product outlet communicating with the upper part of the second extraction rectification column;

[0023] The bottom of the stripping column reflux tank has a third reflux passage and a third product outlet at the bottom communicating with the upper part of the stripping column.

[0024] Preferably,

[0025] The first product outlet has a product extraction branch, and the product extraction branch is connected to the stripping column.

[0026] Preferably,

[0027] The first extraction rectification column includes:

[0028] An upper tower, the bottom outlet of the first extraction solvent tank is connected to the upper tower of the first extraction rectification column;

[0029] The lower column, the bottom of the upper column is connected and communicated with the top of the lower column, and the feed inlet of the stripping column is connected in series and communicated with the bottom of the lower column of the first extractive distillation column.

[0030] Preferably,

[0031] The top draw of the upper column is connected with a first reflux drum.

[0032] The lower column also has a feed inlet.

[0033] Preferably,

[0034] The butadiene extraction unit further includes:

[0035] A first condenser, the top draw of the upper column of the first extractive distillation column is condensed via the first condenser and then connected to the first reflux drum;

[0036] A lower column reboiler, which is arranged at the bottom of the lower column;

[0037] A stripping column reboiler, which is arranged at the bottom of the stripping column;

[0038] A second condenser, the top draw of the second extractive distillation column is condensed via the second condenser and then connected to the second reflux drum;

[0039] A distillation column condenser, the top draw of the distillation column is condensed via the distillation column condenser and then connected to the distillation column reflux drum;

[0040] A distillation column reboiler, which is arranged at the bottom of the distillation column.

[0041] Preferably,

[0042] The butadiene extraction unit further includes:

[0043] A first multi-stage heat exchange system, the stripped lean solvent outlet at the bottom of the stripping column is connected and communicated with the inlet of the first extraction solvent tank via the first multi-stage heat exchange system;

[0044] A second multi-stage heat exchange system, the desorbed lean solvent outlet at the bottom of the distillation column is connected and communicated with the inlet of the second extraction solvent tank via the second multi-stage heat exchange system.

[0045] The butadiene extraction unit of the present utility model adopts a butadiene extraction method, which includes the following steps:

[0046] S1, the mixed C4 raw material enters the first extractive distillation column and contacts countercurrently with the extraction solvent, and the heavy components including butadiene and alkynes dissolve in the extraction solvent to form a rich solvent, which is drawn from the bottom of the first extractive distillation column and enters the stripping column;

[0047] S2. The rich solvent is stripped and resolved in the stripping column to form the lean solvent after stripping. The lean solvent after stripping is withdrawn from the bottom of the stripping column and recycled into the first extractive distillation column as the extraction solvent.

[0048] S3. The side stream of the stripping column is fed into the stripping tower. After resolution, the lean solvent after resolution is withdrawn from the bottom of the stripping tower.

[0049] S4. The lean solvent after resolution enters the second extractive distillation column as the extraction solvent and contacts countercurrently with the gas phase containing butadiene and a small amount of alkynes after stripping and resolution in the stripping column. The crude butadiene is withdrawn from the top of the second extractive distillation column. The heavy components including alkynes are dissolved in the extraction solvent to form the rich solvent, which is withdrawn from the bottom of the second extractive distillation column and fed into the stripping column.

[0050] Preferably,

[0051] In step S2, the lean solvent after stripping is withdrawn from the bottom of the stripping column. A small stream of the lean solvent is separated and fed into the stripping tower as a supplement to the solvent for the side stream of the stripping column described in step S3. The large stream of the lean solvent continues to be recycled into the first extractive distillation column as the extraction solvent.

[0052] Preferably,

[0053] The step that the large stream of the lean solvent is recycled into the first extractive distillation column as the extraction solvent in step S2 specifically includes: the large stream of the lean solvent is first withdrawn to the first extraction solvent tank and then enters the first extractive distillation column as the extraction solvent.

[0054] The step that the lean solvent after resolution enters the second extractive distillation column as the extraction solvent in step S4 specifically includes: the lean solvent after resolution is first withdrawn to the second extraction solvent tank and then enters the second extractive distillation column as the extraction solvent.

[0055] Preferably,

[0056] Step S1 further includes: the raffinate C4 is withdrawn from the top of the first extractive distillation column to the first reflux drum.

[0057] Step S4 further includes: the crude butadiene is withdrawn from the top of the second extractive distillation column to the second reflux drum.

[0058] Step S3 further includes: the alkynes and C4 are withdrawn from the top of the stripping tower to the stripping tower reflux drum.

[0059] Preferably,

[0060] Step S1 further includes: the gas phase of the first reflux drum pressurizes the first extraction solvent tank.

[0061] Step S4 further includes: the gas phase of the second reflux drum pressurizes the second extraction solvent tank.

[0062] Preferably,

[0063] Step S1 further includes: the first part of raffinate C4 from the first reflux drum is refluxed to the upper part of the first extractive distillation column, and the second part of raffinate C4 is withdrawn through the first extraction outlet;

[0064] Step S4 further includes: the first part of crude butadiene from the second reflux drum is refluxed to the upper part of the second extractive distillation column, and the second part of crude butadiene is withdrawn through the second extraction outlet;

[0065] Step S3 further includes: the first part of alkynes and C4 from the stripping column reflux drum is refluxed to the upper part of the stripping column, and the second part of alkynes and C4 is withdrawn through the third extraction outlet at the bottom of the drum.

[0066] Preferably,

[0067] Step S3 further includes: a part of the second part of raffinate C4 is separated and supplemented into the stripping column through the extraction branch on the first extraction outlet.

[0068] Preferably, the first extractive distillation column includes an upper column and a lower column;

[0069] Step S2 specifically includes: the extraction solvent in the first extraction solvent tank comes out from the bottom of the first extraction solvent tank and enters the upper column of the first extractive distillation column;

[0070] Step S1 specifically includes: the solvent in the upper column contacts the mixed C4 countercurrently, dissolves the heavy components including butadiene and alkynes and enters the top of the lower column from the bottom of the upper column as a liquid phase; the gaseous mixed C4 and the gaseous solvent enter the bottom of the upper column from the top of the lower column; the rich solvent withdrawn from the bottom of the lower column enters the stripping column from the feed port of the stripping column;

[0071] Preferably, step S1 specifically includes:

[0072] Raffinate C4 is withdrawn from the top of the upper column of the first extractive distillation column to the first reflux drum;

[0073] The mixed C4 raw material enters the lower column of the first extractive distillation column from the feed port of the lower column of the first extractive distillation column.

[0074] Preferably,

[0075] Step S1 further includes: raffinate C4 is withdrawn from the top of the upper column of the first extractive distillation column, condensed by the first condenser and then sent to the first reflux drum;

[0076] Step S4 further includes: crude butadiene is withdrawn from the top of the second extractive distillation column, condensed by the second condenser and then sent to the second reflux drum;

[0077] Step S3 further includes: the alkyne and C4 are taken out from the top of the stripping column, condensed by the stripping column condenser, and then sent to the stripping column reflux drum;

[0078] Preferably, the lower column of the first extractive distillation column is heated by a lower column reboiler, the bottom of the stripping column is heated by a stripping column reboiler, and the bottom of the alkyne stripping column is heated by a stripping column reboiler.

[0079] More preferably,

[0080] The step that the lean solvent after stripping is recycled into the first extractive distillation column as an extraction solvent in step S2 specifically includes: the lean solvent after stripping is first taken out, heat-exchanged through the first multi-stage heat exchange system, then sent to the first extraction solvent tank, and finally enters the first extractive distillation column as an extraction solvent;

[0081] The step that the lean solvent after desorption enters the second extractive distillation column as an extraction solvent in step S4 specifically includes: the lean solvent after desorption is first taken out, heat-exchanged through the second multi-stage heat exchange system, then sent to the second extraction solvent tank, and finally enters the second extractive distillation column as an extraction solvent.

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

[0083] 1) The present utility model adopts two sets of solvent systems. The extraction solvent of the first extractive distillation column comes from the lean solvent after stripping and desorption in the stripping column, and the extraction solvent of the second extractive distillation column comes from the lean solvent after desorption in the alkyne stripping column. When any one of the lean solvents is not completely desorbed, it will not affect the other solvent, and the operation is simpler.

[0084] 2) The lean solvents of the two sets of solvent systems are respectively taken out from the bottoms of the stripping column and the alkyne stripping column, and the bottom temperatures are inconsistent. Therefore, there are a stripping column reboiler and a first multi-stage heat exchange system, as well as a stripping column reboiler and a second multi-stage heat exchange system, which are respectively connected to the bottoms of the stripping column and the alkyne stripping column. In this way, the high-grade lean solvent taken out from the bottom of the stripping column and the low-grade lean solvent taken out from the bottom of the alkyne stripping column can be heated and heat-exchanged respectively, the amount of steam required at the bottom of the column is reduced, and the waste heat utilization is more sufficient.

[0085] 3) Both sets of solvent systems use process gas to pressurize the solvent tank. The process gas generated in the first reflux drum is extracted to conduct gas-phase pressurization on the first extraction solvent tank, and the process gas generated in the second reflux drum is extracted to pressurize the second extraction solvent tank, saving nitrogen, and further reducing the loss of C4 caused by the system discharging nitrogen. Description of the Drawings

[0086] Figure 1 It is a schematic diagram of the overall connection of the butadiene extraction device of the present utility model;

[0087] Figure 2Schematic diagram of the acetonitrile extraction device for a set of solvent systems in Comparative Example 1 of the present utility model.

[0088] In the figure, T1 is the lower tower; T2 is the upper tower; T3 is the stripping tower; T4 is the distillation tower; T5 is the second extractive distillation tower; E1 is the first condenser; E2 is the second condenser; E3 is the distillation tower condenser; E4 is the distillation tower reboiler; E5 is the lower tower reboiler; E6 is the stripping tower reboiler; V1 is the first reflux drum; V2 is the first extraction solvent tank; V3 is the second reflux drum; V4 is the second extraction solvent tank; V5 is the distillation tower reflux drum. Detailed implementation manners

[0089] The following uses specific specific examples to illustrate the implementation manners of the present utility model. Those skilled in the art can easily understand 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 implementation manners, 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.

[0090] As Figure 1 Shown is the butadiene extraction device of the present utility model, specifically including a first extractive distillation tower, a second extractive distillation tower T5, a stripping tower T3 and a distillation tower T4, as well as a first condenser E1, a second condenser E2, a distillation tower condenser E3, a distillation tower reboiler E4, a lower tower reboiler E5, a stripping tower reboiler E6, a first reflux drum V1, a first extraction solvent tank V2, a second reflux drum V3, a second extraction solvent tank V4 and a distillation tower reflux drum V5. The first extractive distillation tower further includes a lower tower T1 and an upper tower T2, and the distillation tower T4 is an alkyne distillation tower T4.

[0091] Continue as Figure 1As shown, in the first extractive distillation column, there is a feed inlet on the lower column T1. The top of the lower column T1 is connected to the bottom of the upper column T2. The mixed C4 raw material enters from the feed inlet of the lower column T1, and the liquid extraction solvent enters from the upper part of the upper column T2. The mixed C4 raw material and the extraction solvent contact countercurrently in the first extractive distillation column. The heavy components including butadiene and alkynes dissolve in the extraction solvent to form a rich solvent, which is the bottom liquid 7 of the bottom of the lower column T1. At the same time, as shown continuously, the top of the upper column T2 is also connected to one end of the first condenser E1, and the other end of the first condenser E1 is connected to the first reflux drum V1. Therefore, the overhead gas 2 formed at the top of the upper column T2, that is, the raffinate C4, is withdrawn. After being condensed by the first condenser E1, it enters the first reflux drum V1. A first reflux passage is provided between the bottom of the first reflux drum V1 and the upper part of the upper column T2 of the first extractive distillation column. The first reflux drum V1 is also provided with a first extraction port communicating with a downstream device (not shown in the figure) and an extraction branch provided on the first extraction port, and this extraction branch is connected to the alkyne stripping tower T4 to dilute the alkyne concentration in the stripping tower T4. As shown continuously, the bottom of the lower column T1 is connected to the feed inlet of the upper part of the stripping tower T3. Therefore, the rich solvent bottom liquid 7 formed at the bottom of the lower column T1 enters the stripping tower T3 from the lower column T1, and a reboiler E5 of the lower column is provided at the bottom of the lower column T1. The top of the stripping tower T3 is connected in series with the bottom of the second extractive distillation column T5. The stripped lean solvent outlet at the bottom of the stripping tower T3 is connected to the first multi-stage heat exchange system and is connected to the top of the first extraction solvent tank V2 through this first multi-stage heat exchange device, and the bottom of the first extraction solvent tank V2 is also connected to the upper part of the upper column T2; another solvent supplement bypass road is provided at the stripped lean solvent outlet at the bottom of the stripping tower T3 and is connected to the alkyne stripping tower T4. Therefore, the C4 in the rich solvent in the stripping tower T3 is stripped and resolved to form a stripped lean solvent at the bottom of the tower. A reboiler of the stripping tower is also connected at the bottom of the stripping tower T3 to supply the heat energy required for stripping and resolution. The large amount of lean solvent withdrawn from the stripped lean solvent outlet at the bottom of the stripping tower T3 enters the first extraction solvent tank V2 after heat exchange through the first multi-stage heat exchange system, and finally enters the upper column T2 from the bottom of the first extraction solvent tank V2 as an extraction solvent for recycling. At the same time, there is a pressure supplement gas path between one end of the top of the first reflux drum V1 and the top of the first extraction solvent tank V2. The process gas generated in the first reflux drum V1 is supplemented into the first extraction solvent tank V2 to supplement the pressure of the first extraction solvent tank V2. Ensure that the pressure of the first extraction solvent tank V2 is maintained at a positive pressure to avoid a negative pressure situation.

[0092] Continuing as shown in the figure, the side draw outlet in the middle and lower part of the stripping column T3 is connected to the alkyne stripping column T4. That is, a small part of the extraction solvent in the middle and lower part of the stripping column T3 enters the alkyne stripping column T4 through the side draw outlet. When the solvent drawn from the side is insufficient, a small stream of lean solvent drawn from the bottom of the stripping column T3 will be separated and enter the alkyne stripping column T4 through the solvent supplement bypass described above. At this time, the alkyne concentration in the alkyne stripping column T4 is relatively high. For explosion prevention, part of the raffinate C4 is introduced into the alkyne stripping column T4 through the extraction branch of the first draw outlet at the bottom of the first reflux drum V1, and this raffinate C4 is used to dilute the alkynes in the column. The alkynes and C4 in the alkyne stripping column T4 are desorbed and drawn from the top of the column, condensed by the distillation column condenser E3 and then enter the distillation column reflux drum V5, and finally are drawn from the third draw outlet at the bottom of the distillation column reflux drum V5, and the first part of the alkynes and C4 is refluxed into the alkyne stripping column T4. The lean solvent after desorption accumulates in the bottom of the alkyne stripping column T4. Continuing as shown in Figure 1, a distillation column reboiler E4 is provided at the bottom of the alkyne stripping column T4, and part of the solvent enters the alkyne stripping column T4 for desorption. The temperature required for the alkyne stripping column T4 is relatively lower than that of the stripping column T3, so the required heat energy consumption is small. Continuing as Figure 1As shown in the figure, the bottom of the acetylene stripping column T4 at a relatively lower temperature than the stripping column T3 forms a low-grade solvent for continued utilization. For example, it is connected to the second multi-stage heat exchange system for utilization and is connected to the top of the second extraction solvent tank V4 through this second multi-stage heat exchange system. The bottom of the second extraction solvent tank V4 is connected to the upper part of the second extractive distillation column T5. Furthermore, the lean solvent after desorption accumulated at the bottom of the acetylene stripping column T4 is withdrawn from the bottom of the column, enters the second extraction solvent tank V4 after heat exchange through the second multi-stage heat exchange system, and finally enters the second extractive distillation column T5 as an extraction solvent for recycling. Since the bottom of the second extractive distillation column T5 is connected to the top of the stripping column T3. Therefore, the gas phase containing butadiene and acetylene flowing to the top of the stripping column T3 enters the bottom of the second extractive distillation column T5 from the top of the column and contacts countercurrently with the lean solvent after desorption as an extraction solvent in the column. The heavy components including acetylene dissolve in the extraction solvent to form a rich solvent in the second extractive distillation column T5 and enter the stripping column T3 from the bottom of the second extractive distillation column T5. The crude butadiene in the gas phase formed after extractive distillation in the second extractive distillation column T5 is withdrawn from the top of the second extractive distillation column T5. At this time, the top of the second extractive distillation column T5 is connected to the second condenser E2; the second condenser E2 is connected to one end of the top of the second reflux tank V3; there is a second reflux passage between the bottom of the second reflux tank V3 and the second extractive distillation column T5. Thus, the crude butadiene withdrawn from the top of the second extractive distillation column T5 enters the second reflux tank V3 after being condensed by the second condenser E2, and because there is also a second extraction port at the bottom of the second reflux tank V3, a part of the crude butadiene is refluxed into the second extractive distillation column T5 through the second reflux passage at the bottom of the second reflux tank V3. Another part of the crude butadiene is directly withdrawn from the second extraction port. In addition, similarly, there is a pressure-compensating gas passage between the other end of the top of the first reflux tank V1 and the second reflux tank V3 and the top of the second extraction solvent tank V4. The process gas generated in the second reflux tank V3 is supplemented into the second extraction solvent tank V4 to pressurize the second extraction solvent tank V4. Ensure that the pressure of the second extraction solvent tank V4 remains positive pressure to avoid the situation of negative pressure.

[0093] Example 1

[0094] As shown in the figure, the mixed C4 raw material 1 with a temperature of 40 °C, a pressure of 0.7 MPaG, and a flow rate of 16480 kg / hr enters the upper part of the lower tower T1 of the first extractive distillation column from the feed port, and countercurrently contacts with the overhead circulating solvent 8 of the upper tower T2 of the first extractive distillation column with a flow rate of 113535 kg / hr and a temperature of 53 °C in the column. Butadiene, alkynes, etc. dissolve in the extractive solvent to form a rich solvent 7 and enter the stripping column T3 from the bottom of the lower tower T1. The gas-phase raffinate C4 2 at the top of the upper tower T2 passes through the first condenser E1 and is condensed and then enters the first reflux drum V1. Among them, the first part of the raffinate C4 in the first reflux drum V1 refluxes into the upper tower T2, and the second part of the raffinate C4 is divided into two parts 5 and 6. The raffinate C4 5 enters the downstream device, and the raffinate C4 6 enters the alkyne stripping column T4 to dilute the alkynes. The gas 4 drawn from the first reflux drum V1 is sent to the first extractive solvent tank V2. The rich solvent 7 enters the stripping column T3, and the C4 in the rich solvent is resolved. After the resolution, the stripped lean solvent 10 at 138.8 °C is drawn from the bottom of the column, and is divided into a large stream of lean solvent 11 and a small stream of lean solvent 12. The large stream of stripped lean solvent 11 with a flow rate of 112889.7 kg / hr passes through the first multi-stage heat exchange system for heat exchange, and then enters the first extractive solvent tank V2 at a temperature of 53 °C. The lean solvent 8 is drawn from the bottom of the tank as an extractive solvent and enters the upper tower T2 for recycling. Since the solvent tank V2 is under negative pressure without pressure supplementation, 0.6 kmol / hr of process gas 4 is drawn from the first reflux drum V1 to supplement the pressure of the solvent tank V2, and the pressure after pressure supplementation is 0.03 MPaG. The small stream of lean solvent 12 enters the upper part of the alkyne stripping column T4, the raffinate C4 6 enters the top of the alkyne stripping column T4, and the side stream 9 is drawn into the upper part of the alkyne stripping column T4. In the alkyne stripping column T4, alkynes and C4 are resolved from the solvent. The flow rate of the stripped lean solvent 15 at the bottom of the column is 24589.0 kg / hr and the temperature is 124.5 °C. After passing through the second multi-stage heat exchange system for heat exchange, the resolved lean solvent 16 at a temperature of 42 °C enters the second extractive solvent tank V4. The resolved lean solvent 20 at the bottom of the tank is used as an extractive solvent and enters the second extractive distillation column T5 for recycling. Since the solvent tank V4 is under negative pressure without pressure supplementation, 0.3 kmol / hr of process gas 19 is drawn from the second reflux drum V3 to supplement the pressure of the solvent tank V4, and the pressure after pressure supplementation is 0.03 MPaG. The gas-phase crude butadiene 17 at the top of the second extractive distillation column T5 passes through the second condenser E2 and the condensate 18 enters the second reflux drum V3. The gas 19 at the top of the drum goes to the second extractive solvent tank for pressure supplementation, and the crude butadiene product 21 is at the bottom of the tank.

[0095] Comparative Example 1

[0096] This comparative example is a butadiene extraction device with a set of solvent systems, as Figure 2As shown, different from this embodiment, the solvent withdrawn from the bottom of the alkyne distillation column T4 returns to the stripping column T3. The temperature of the solvent withdrawn from the bottom of the stripping column T3 is 138.8 °C, the pressure is 0.482 MPaG, and the flow rate of the solvent is 137478.7 kg / hr. After multi-stage heat exchange, the temperature reaches 42 °C. After passing through the solvent tank, part of the solvent returns to the upper tower T2 of the first extraction column, and part of it returns to the second extractive distillation column T5 for recycling. And there is no reboiler for the alkyne distillation column T4 at the bottom of the column.

[0097] The nitrogen supplementation amount, C4 loss amount, and unit product energy consumption of Example 1 and Comparative Example 1 were compared, and the results are shown in Table 1:

[0098] Table 1 Comparison of nitrogen supplementation amount, C4 loss amount, and unit product energy consumption

[0099]

[0100] According to Table 1, it can be seen that Example 1 with two solvent systems does not require nitrogen supplementation, there is no loss of C4, and the unit product energy consumption can be reduced by about 10%.

[0101] The present utility model designs two solvent systems. The two solvent systems respectively introduce the lean solvents withdrawn from the stripping column T3 and the alkyne distillation column T4, and are independently analyzed and recycled in their respective extractive distillation columns without affecting each other. And there are respectively provided a stripping column reboiler, a first multi-stage heat exchange system, a distillation column reboiler, and a second multi-stage heat exchange system, which can heat and exchange heat for the two grades of solvents respectively, making full use of waste heat. At the same time, the present utility model also uses the process gas in the first reflux tank V1 and the second reflux tank V3 to replace nitrogen to pressurize the first extraction solvent tank V2 and the second extraction solvent tank V4 respectively, saving nitrogen, and thus also reducing the loss of C4 caused by the system discharging nitrogen.

[0102] The above has described the present utility model in detail with reference to the embodiments accompanied by drawings. Those of ordinary skill in the art can make various variations to the present utility model according to the above description. Therefore, some details in the embodiments should not constitute a limitation to the present utility model, and the present utility model will take the scope defined by the appended claims as the protection scope.

Claims

1. A butadiene extraction device, characterized in that The butadiene extraction device comprises: a first extractive distillation tower; a second extractive distillation tower; A stripping tower, wherein the feed inlet of the stripping tower is connected in series with the kettle of the first extractive distillation tower, the top of the stripping tower is connected in series with the kettle of the second extractive distillation tower, and the stripped lean solvent outlet of the kettle of the stripping tower is connected in series with the first extractive distillation tower; A distillation tower, wherein the side line outlet of the stripping tower is connected to the upper part of the distillation tower, and the outlet of the decomposed lean solvent in the bottom of the distillation tower is connected to the second extractive distillation tower.

2. The butadiene extraction device according to claim 1, characterized in that A solvent replenishment auxiliary path connected to the distillation tower is also provided at the outlet of the stripping lean solvent.

3. The butadiene extraction device according to claim 2, characterized in that The distillation tower is an alkyne distillation tower.

4. The butadiene extraction device according to claim 1 or 2, characterized in that The butadiene extraction device comprises: A first extraction solvent tank, wherein the stripped lean solvent in the stripping tower kettle is connected to the inlet of the first extraction solvent tank, and the tank bottom outlet of the first extraction solvent tank is connected to the first extraction distillation tower; The second extraction solvent tank, the outlet of the decomposed lean solvent of the bottom of the distillation tower is connected to the inlet of the second extraction solvent tank, and the tank bottom outlet of the second extraction solvent tank is connected to the second extraction distillation tower.

5. The butadiene extraction device according to claim 4, characterized in that The butadiene extraction device also includes: A first reflux tank, the top of the first extractive distillation tower is connected to the first reflux tank, and a first pressure-compensating gas path is provided between the top of the first reflux tank and the first extraction solvent tank; A second reflux tank, the top of the second extraction and distillation tower is connected to the second reflux tank, and a second pressure-compensating gas path is provided between the tank top of the second reflux tank and the second extraction solvent tank; A reflux tank of a distillation tower, wherein the top of the distillation tower is connected to the reflux tank of the distillation tower.

6. The butadiene extraction device according to claim 5, characterized in that The bottom of the first reflux tank has a first reflux passage and a first production port connected to the upper part of the first extraction distillation tower; The bottom of the second reflux tank has a second reflux passage and a second production port communicating with the upper part of the second extraction distillation tower; The tank bottom of the reflux tank of the distillation tower is provided with a third reflux passage connected with the upper part of the distillation tower and a third production outlet at the tank bottom.

7. The butadiene extraction device according to claim 6, characterized in that The first production outlet has a production branch, and the production branch is connected to the distillation tower.

8. The butadiene extraction device according to claim 4, characterized in that The first extractive distillation tower comprises: An upper tower, wherein the bottom outlet of the first extraction solvent tank is connected to the upper tower of the first extraction distillation tower; The lower tower, the kettle of the upper tower is connected to the top of the lower tower, and the feed inlet of the stripping tower is connected in series with the kettle of the lower tower of the first extractive distillation tower.

9. The butadiene extraction device according to claim 8, characterized in that The top of the upper tower is connected to a first reflux tank. The lower tower also has a feed inlet.

10. The butadiene extraction device according to claim 5, characterized in that The butadiene extraction device also includes: A first condenser, wherein the top of the first extractive distillation tower is condensed by the first condenser and then connected to the first reflux tank; A lower tower reboiler, provided in the kettle of the lower tower of the first extractive distillation tower; A stripping tower reboiler, arranged in the bottom of the stripping tower; A second condenser, wherein the second extractive distillation tower overhead is condensed by the second condenser and then connected to the second reflux tank; A distillation tower condenser, wherein the distillation tower top is condensed by the distillation tower condenser and then connected to the distillation tower reflux tank; The reboiler of the distillation tower is arranged in the kettle of the distillation tower.

11. The butadiene extraction device according to claim 4, characterized in that The butadiene extraction device also includes: A first multi-stage heat exchange system, wherein the stripping lean solvent outlet of the stripping tower kettle is connected to the inlet of the first extraction solvent tank via the first multi-stage heat exchange system; The second multi-stage heat exchange system, the outlet of the decomposed lean solvent of the tower kettle of the distillation tower is connected to the inlet of the second extraction solvent tank through the second multi-stage heat exchange system.

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