Continuous tetrahydrofuran recovery system for PBAT production device

Abstract

The utility model discloses a tetrahydrofuran continuous recovery system for a PBAT (poly (butylene adipate-co-terephthalate)) production device, which is characterized in that an outlet of a crude product tank is connected with a middle inlet of a first rectifying tower through a first pump and a tube pass of a first heat exchanger, and the side wall of the lower part of the first rectifying tower is provided with a side extraction opening and is connected with a THF (tetrahydrofuran) low-position tank; an outlet of the THF low-position tank is connected with a natural gas heat-conducting oil furnace through a No.7 pump; a bottom outlet of the first rectifying tower is connected with a wastewater receiving tank; an outlet of the wastewater receiving tank is connected with a wastewater treatment device through a second pump; a top exhaust port of the first rectifying tower is connected with an inlet of a first air cooler, a bottom outlet of the first air cooler is connected with a first receiving tank, and a bottom outlet of the first receiving tank is connected with a top backflow port of the first rectifying tower and a shell pass inlet of a second heat exchanger through a third pump. A shell pass outlet of the second heat exchanger is connected with an upper side wall inlet of the second rectifying tower. The system can prevent tetrahydrofuran from accumulating in the tower kettle and reduce COD (Chemical Oxygen Demand) and hazardous waste amount of the tower kettle.

Description

Technical Field

[0001] The utility model relates to a PBAT production device, in particular to a continuous tetrahydrofuran recovery system for a PBAT production device, belonging to the technical field of biodegradable material production devices. Background Art

[0002] Poly(butylene adipate terephthalate) (PBAT), as a biodegradable material, its product waste can be quickly degraded in soil or water, and the degradation products are non-toxic. It has a wide range of applications and can be made into disposable shopping bags, agricultural films, biomedical polymer materials, packaging bottles, etc. It can effectively solve white pollution and is used more and more widely.

[0003] 1,4-Butanediol (BDO) is a raw material for producing PBAT. It participates in the reaction in the esterification stage to generate an esterified product and water. At high temperature, side reactions generate tetrahydrofuran and water. The by-product of tetrahydrofuran per ton of PBAT is 0.1 - 0.12 tons. Comprehensive utilization of the by-product tetrahydrofuran can not only solve the problem of esterification wastewater, but also reduce costs and increase efficiency, and improve product benefits.

[0004] The Chinese utility model patent with the publication number of CN 209828309U discloses a tetrahydrofuran low-emission recovery system. The bottom outlet of the crude product tank is connected to the tube side inlet of the first heat exchanger through the first pump. The tube side outlet of the first heat exchanger is connected to the middle inlet of the first distillation column. The top outlet of the first distillation column is successively connected to the third pump through the first air cooler and the first collection tank. The outlet of the third pump is connected to the shell side inlet of the second heat exchanger. The shell side outlet of the second heat exchanger is connected to the inlet of the second distillation column. The bottom of the first distillation column is connected to the tube side inlet of the third heat exchanger through the waste water receiving tank and the second pump. The tube side outlet of the third heat exchanger is connected to the upper inlet of the stripping column. The lower heat medium inlet of the stripping column is connected to the steam pipe. The bottom outlet of the stripping column is connected to the waste water treatment device through the shell side of the third heat exchanger; the top outlet of the stripping column is connected to the reflux port of the crude product tank through the third air cooler. This device can reduce equipment investment, lower the sewage COD, save operation costs and increase product revenue, but there are still the following problems:

[0005] 1. In order to solve the problem of high COD of the waste water at the bottom of the first tower, a stripping column system is set up, increasing equipment investment;

[0006] 2. In order to ensure product purity, the second tower and the third tower systems are provided with side draws of light components and heavy components, which enter the waste liquid tank and then are filled, increasing the investment in filling machines;

[0007] 3. The waste liquid belongs to hazardous waste and needs to be entrusted to a qualified unit for treatment, increasing operation costs. Content of the Utility Model

[0008] The purpose of the present utility model is to overcome the problems existing in the prior art and provide a continuous tetrahydrofuran recovery system for a PBAT production device, which can prevent tetrahydrofuran from accumulating in the bottom of the tower, reduce the COD of the bottom of the tower, reduce the amount of hazardous waste, and even not generate hazardous waste externally.

[0009] To solve the above technical problems, a continuous tetrahydrofuran recovery system for a PBAT production device of the present utility model includes a crude product tank. The outlet of the crude product tank is connected to the tube side inlet of a first heat exchanger through a first pump. The tube side outlet of the first heat exchanger is connected to the middle inlet of a first distillation column. A first reboiler is provided at the lower part of the first distillation column. A side draw port is arranged on the lower side wall of the first distillation column and is connected to a THF low-level tank. The outlet of the THF low-level tank is connected to a natural gas heat-conducting oil furnace through a seventh pump.

[0010] The bottom outlet of the first distillation column is connected to the inlet of a waste water receiving tank. The outlet of the waste water receiving tank is connected to a waste water treatment device through a second pump.

[0011] The top exhaust port of the first distillation column is connected to the inlet of a first air cooler. The bottom outlet of the first air cooler is connected to a first receiving tank. The bottom outlet of the first receiving tank is connected to the inlet of a third pump. The outlet of the third pump is connected to the top reflux port of the first distillation column and the shell side inlet of a second heat exchanger. The shell side outlet of the second heat exchanger is connected to the upper side wall inlet of a second distillation column.

[0012] Further, the heat medium inlet of the first reboiler is connected to a first steam pipe with a pressure of 0.3 MPa.

[0013] Further, a second reboiler is provided at the lower part of the second distillation column. The heat medium inlet of the second reboiler is connected to a second steam pipe with a pressure of 0.1 MPa.

[0014] Further, the bottom outlet of the second distillation column is connected to the tube side inlet of the second heat exchanger. The tube side outlet of the second heat exchanger is connected to the middle inlet of a third distillation column. A third reboiler is provided at the lower part of the third distillation column. The top gas phase outlet of the second distillation column is connected to the heat medium inlet of the third reboiler. The heat medium outlet of the third reboiler is connected to the inlet of a second receiving tank. The bottom outlet of the second receiving tank is connected to the inlet of a fourth pump. The outlet of the fourth pump is connected to the shell side inlet of the first heat exchanger. The shell side outlet of the first heat exchanger is connected to the upper inlet of the first distillation column.

[0015] Further, the top gas phase outlet of the second distillation column is also connected to a tail gas incineration pipe.

[0016] Further, the top gas outlet of the third rectification column is connected to the upper inlet of the third air cooler, the bottom outlet of the third air cooler is connected to the upper inlet of the third receiving tank, and the bottom outlet of the third receiving tank is connected to the top reflux port of the third rectification column and the finished product filling pipeline through the sixth pump.

[0017] Further, the bottom outlet of the first rectification column and the outlet of the third pump are respectively connected to the THF low-level tank.

[0018] Further, the tube-side outlet of the second heat exchanger and the outlet of the fourth pump are respectively connected to the THF low-level tank.

[0019] Further, the bottom outlet of the third rectification column is connected to the THF low-level tank through the fifth pump.

[0020] Compared with the prior art, the present utility model has achieved the following beneficial effects: 1. When the tetrahydrofuran in the bottom of the tower is high, the bottom temperature of the tower will decrease. According to the calculation, a side draw port is set between the 1st layer and the 2nd layer of packing in the first tower, which is cascade controlled with the bottom temperature of the tower to timely draw out the tetrahydrofuran at the lower part of the tower, prevent the accumulation of tetrahydrofuran in the bottom of the tower, and reduce the COD of the bottom of the tower;

[0021] 2. The waste liquid tank is cancelled, and the drained liquid from the second rectification column and the third rectification column is sent to the THF low-level tank; the waste liquid filling machine is cancelled, reducing the one-time investment and daily operation cost;

[0022] 3. The exhaust gas of the second rectification column is used as the heat source of the third rectification column, reducing energy consumption;

[0023] 4. The tetrahydrofuran content in the THF low-level tank is high and the calorific value is high. It is sent to the natural gas heat-conducting oil furnace as fuel, reducing the consumption of natural gas, saving energy and reducing consumption, and at the same time saving costs;

[0024] 5. The side-drawn liquid is used as fuel without going out, without hazardous waste, saving the cost of hazardous waste treatment and supervision;

[0025] 6. The device has a low one-time investment, a low operation cost, good energy-saving and consumption-reducing effects, the COD is as low as below 6000 mg / m³, is safe and environmentally friendly, and has good product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The following further describes the present utility model in detail with reference to the drawings and specific embodiments. The drawings are only for reference and illustration, and are not intended to limit the present utility model.

[0027] Figure 1 It is a flowchart of the continuous recovery system for tetrahydrofuran used in the PBAT production device of the present utility model;

[0028] In the figure: L1. The first rectification column; L2. The second rectification column; L3. The third rectification column; L1a. The first reboiler; L2a. The second reboiler; L3a. The third reboiler;

[0029] E1. The first air cooler; E2. The third air cooler;

[0030] T1. The first receiving tank; T2. The second receiving tank; T3. The third receiving tank;

[0031] H1. The first heat exchanger; H2. The second heat exchanger; H3. The third heat exchanger;

[0032] V1. The crude product tank; V2. The waste water receiving tank; V3. The low-level THF tank;

[0033] P1. The first pump; P2. The second pump; P3. The third pump; P4. The fourth pump; P5. The fifth pump; P6. The sixth pump; P7. The seventh pump;

[0034] G1. The first steam pipe; G2. The first condensate pipe; G3. The second steam pipe; G4. The second condensate pipe; G5. The nitrogen pipe; G6. The tail gas incineration pipe; G7. The finished product filling pipeline. Detailed implementation manners

[0035] In the following description of the present utility model, the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present utility model and simplifying the description, rather than indicating that the device must have a specific orientation.

[0036] In order to make the technical means, creative features, achieved purposes and effects realized by the present utility model easy to understand, the present utility model will be further described below with reference to specific drawings.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present utility model belongs. The terms used in the description of the present utility model herein are only for the purpose of describing specific embodiments, and are not intended to limit the present utility model.

[0038] Such as Figure 1As shown in the figure, the continuous recovery system for tetrahydrofuran in the PBAT production device of the present utility model includes a crude product tank V1, a wastewater receiving tank V2, a THF low-level tank V3, a first distillation column L1, a second distillation column L2, and a third distillation column L3. The outlet of the crude product tank V1 is connected to the inlet of the first pump P1. The outlet of the first pump P1 is connected to the inlet of the tube side of the first heat exchanger H1. The outlet of the tube side of the first heat exchanger H1 is connected to the middle inlet of the first distillation column L1. A first reboiler L1a is provided at the lower part of the first distillation column L1. The heat medium inlet of the first reboiler L1a is connected to the first steam pipe G1, and the steam pressure of the first steam pipe G1 is 0.3 MPa; the heat medium outlet of the first reboiler L1a is connected to the first condensate pipe G2.

[0039] A side draw port is provided on the side wall between the first layer of packing and the second layer of packing of the first distillation column L1. This side draw port is connected to the THF low-level tank V3 through a side draw pipeline. The outlet of the THF low-level tank V3 is supplied to the natural gas heat-conducting oil furnace for incineration through the seventh pump P7.

[0040] The bottom outlet of the first distillation column L1 is connected to the inlet of the wastewater receiving tank V2. The outlet of the wastewater receiving tank V2 is connected to the wastewater treatment device through the second pump P2. In addition, the bottom outlet of the first distillation column L1 is also connected to the THF low-level tank V3.

[0041] The top exhaust port of the first distillation column L1 is connected to the upper inlet of the first air cooler E1. The bottom outlet of the first air cooler E1 is connected to the first receiving tank T1. The bottom outlet of the first receiving tank T1 is connected to the inlet of the third pump P3. One of the outlets of the third pump P3 is connected to the top reflux port of the first distillation column L1. The second outlet of the third pump P3 is connected to the shell side inlet of the second heat exchanger H2. The shell side outlet of the second heat exchanger H2 is connected to the upper side wall inlet of the second distillation column L2; the third outlet of the third pump P3 is connected to the THF low-level tank V3.

[0042] A second reboiler L2a is provided at the lower part of the second distillation column L2. The heat medium inlet of the second reboiler L2a is connected to the second steam pipe G3, and the steam pressure of the second steam pipe G3 is 0.1 MPa; the heat medium outlet of the second reboiler L2a is connected to the second condensate pipe G4.

[0043] The bottom outlet of the second distillation column L2 is connected to the tube side inlet of the second heat exchanger H2. The tube side outlet of the second heat exchanger H2 is connected to the middle inlet of the third distillation column L3. A third reboiler L3a is provided at the lower part of the third distillation column L3; the tube side outlet of the second heat exchanger H2 is also connected to the THF low-level tank V3.

[0044] The top gas-phase outlet of the second rectification column L2 is connected to the heat medium inlet of the third reboiler L3a. The heat medium outlet of the third reboiler L3a is connected to the inlet of the second receiving tank T2. The bottom outlet of the second receiving tank T2 is connected to the inlet of the fourth pump P4. The outlet of the fourth pump P4 is connected to the shell-side inlet of the first heat exchanger H1. The shell-side outlet of the first heat exchanger H1 is connected to the upper inlet of the first rectification column L1. The outlet of the fourth pump P4 is also connected to the THF low-level tank V3.

[0045] The top gas-phase outlet of the second rectification column L2 is also connected to the nitrogen pipe G5 and the tail gas incineration pipe G6.

[0046] The bottom outlet of the third rectification column L3 is connected to the THF low-level tank V3 through the fifth pump P5.

[0047] The top gas-phase outlet of the third rectification column L3 is connected to the upper inlet of the third air cooler E2. The bottom outlet of the third air cooler E2 is connected to the upper inlet of the third receiving tank T3. The bottom outlet of the third receiving tank T3 is connected to the inlet of the sixth pump P6. The outlet of the sixth pump P6 is connected to the top reflux port of the third rectification column L3 and the finished product filling pipeline G7.

[0048] The esterification wastewater generated in the esterification process contains 20 - 30% THF, a small amount of BDO, and impurities. It is stored in the crude product tank V1, then sent out by the first pump P1, enters the cold side of the first heat exchanger H1, exchanges heat with the discharge of the fourth pump P4 in the recovery system, and is fed into the middle part of the first rectification column L1. The first reboiler L1a of the first rectification column L1 is heated by 0.3 MPa steam. The bottom discharge of the first rectification column L1 is wastewater containing trace amounts of THF, with a COD concentration of 4000 - 6000 mg / L. The bottom liquid enters the wastewater receiving tank V2 for temporary storage, and then is sent to the wastewater treatment device for treatment by the second pump P2.

[0049] The top discharge of the first rectification column L1 is THF steam with a concentration of about 93%. After being condensed by the first air cooler E1, the condensate enters the first receiving tank T1. Part of it is used as the top reflux of the first rectification column L1, and the other part is pressurized by the third pump P3 and sent to the middle part of the second rectification column L2 as the feed of the second rectification column L2. To reduce the COD of the bottom liquid in the first rectification column L1 and reduce the enrichment of THF, a side draw port is set between the first layer of packing and the second layer of packing, and the temperature is cascade-controlled for side draw to the THF low-level tank V3.

[0050] 93% crude THF from pump P3 enters the shell side of heat exchanger H2 and exchanges heat with the bottom discharge of distillation column L2, then enters distillation column L2 from the top of the fourth section of packing in distillation column L2. The reboiler L2a of distillation column L2 is heated by 1.0 MPa steam. The THF purity of the bottom discharge of distillation column L2 is 99.5%, and after heat exchange, it serves as the feed for distillation column L3.

[0051] The steam at the top of distillation column L2 is used as the heat source for distillation column L3. After heat exchange and condensation in reboiler L3a, the condensate enters receiving tank T2. Part of it serves as the reflux for distillation column L2, part is pressurized by pump P4 and sent to the upper part of distillation column L1, and part is sent to the THF low-level tank V3 after light component removal.

[0052] The bottom liquid from distillation column L2 enters above the second section of packing in distillation column L3. The reboiler L3a of distillation column L3 is heated by the top steam of distillation column L2. The bottom discharge of distillation column L3 is high-boiling impurities, which are regularly pumped to the THF low-level tank V3 by pump P5. The product THF with a purity of 99.99% is distilled from the top of distillation column L3. After condensation in air cooler E2, the condensate enters receiving tank T3. Part of it serves as the reflux for distillation column L3, and part is pressurized by pump P6 and sent to the product filling pipeline G7.

[0053] The top tail gas of distillation column L2 can also be sent to the natural gas heat-conducting oil furnace for fuel combustion.

[0054] The low discharge of the system, the side draw liquid of distillation column L1, the light components of distillation column L2, and the bottom heavy components of distillation column L3 all enter the THF low-level tank V3, and then are pumped to the natural gas heat-conducting oil furnace by pump P7 for fuel combustion.

[0055] The above is only the preferred and feasible embodiment of the present utility model, which shows and describes the basic principles, main features and advantages of the present utility model. It does not limit the patent protection scope of the present utility model. Those skilled in the art should understand that the present utility model is not limited by the above embodiments. Except for the above embodiments, without departing from the spirit and scope of the present utility model, the present utility model can have other implementation manners. The present utility model will also have various changes and improvements. All technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope required by the present utility model. The protection scope required by the present utility model is defined by the appended claims and their equivalents. The technical features not described in the present utility model can be achieved by or adopt the existing technology, and will not be elaborated here.

Claims

1. A continuous tetrahydrofuran recovery system for a PBAT production device, including a crude product tank, characterized in that, The outlet of the crude product tank is connected to the inlet of the tube side of the first heat exchanger through the first pump. The outlet of the tube side of the first heat exchanger is connected to the middle inlet of the first distillation column. The lower part of the first distillation column is equipped with a first reboiler. A side draw port is arranged on the lower side wall of the first distillation column and is connected to the THF low-level tank. The outlet of the THF low-level tank is connected to the natural gas heat transfer oil furnace through the seventh pump; The bottom outlet of the first distillation column is connected to the inlet of the wastewater receiving tank. The outlet of the wastewater receiving tank is connected to the wastewater treatment device through the second pump; The top exhaust port of the first distillation column is connected to the inlet of the first air cooler. The bottom outlet of the first air cooler is connected to the first receiving tank. The bottom outlet of the first receiving tank is connected to the inlet of the third pump. The outlet of the third pump is connected to the top reflux port of the first distillation column and the inlet of the shell side of the second heat exchanger. The outlet of the shell side of the second heat exchanger is connected to the inlet of the upper side wall of the second distillation column.

2. The continuous tetrahydrofuran recovery system for the PBAT production device according to claim 1, characterized in that, The heat medium inlet of the first reboiler is connected to the first steam pipe with a pressure of 0.3 MPa.

3. The continuous tetrahydrofuran recovery system for a PBAT production device according to claim 1, wherein, The lower part of the second distillation column is equipped with a second reboiler. The heat medium inlet of the second reboiler is connected to the second steam pipe with a pressure of 0.1 MPa.

4. The continuous tetrahydrofuran recovery system for the PBAT production device according to claim 1, wherein The bottom outlet of the second distillation column is connected to the inlet of the tube side of the second heat exchanger. The outlet of the tube side of the second heat exchanger is connected to the middle inlet of the third distillation column. The lower part of the third distillation column is equipped with a third reboiler; The top gas phase outlet of the second distillation column is connected to the heat medium inlet of the third reboiler. The heat medium outlet of the third reboiler is connected to the inlet of the second receiving tank. The bottom outlet of the second receiving tank is connected to the inlet of the fourth pump. The outlet of the fourth pump is connected to the inlet of the shell side of the first heat exchanger. The outlet of the shell side of the first heat exchanger is connected to the upper inlet of the first distillation column.

5. The continuous tetrahydrofuran recovery system for the PBAT production device according to claim 4, wherein, The top gas phase outlet of the second distillation column is also connected to the tail gas incineration pipe.

6. The continuous tetrahydrofuran recovery system for the PBAT production device according to claim 4, characterized in that, The top gas phase outlet of the third distillation column is connected to the upper inlet of the third air cooler. The bottom outlet of the third air cooler is connected to the upper inlet of the third receiving tank. The bottom outlet of the third receiving tank is connected to the top reflux port of the third distillation column and the finished product filling pipeline through the sixth pump.

7. The continuous tetrahydrofuran recovery system for the PBAT production device according to claim 1, wherein, The bottom outlet of the first distillation column and the outlet of the third pump are respectively connected to the THF low-level tank.

8. The continuous tetrahydrofuran recovery system for the PBAT production device according to claim 4, characterized in that, The outlet of the tube side of the second heat exchanger and the outlet of the fourth pump are respectively connected to the THF low-level tank.

9. The continuous tetrahydrofuran recovery system for a PBAT production device according to claim 6, characterized in that, The bottom outlet of the third distillation column is connected to the THF low-level tank through the fifth pump.

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