CN219743939U - Energy-saving tetrahydrofuran aqueous solution rectifying system - Google Patents

Energy-saving tetrahydrofuran aqueous solution rectifying system Download PDF

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CN219743939U
CN219743939U CN202320955398.9U CN202320955398U CN219743939U CN 219743939 U CN219743939 U CN 219743939U CN 202320955398 U CN202320955398 U CN 202320955398U CN 219743939 U CN219743939 U CN 219743939U
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文婷
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Hefei Jiangxin Chemical Technology Co ltd
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Abstract

The utility model relates to an energy-saving tetrahydrofuran aqueous solution rectifying system, which comprises a low-pressure tower, a pressurizing tower and a zeolite membrane dehydration unit which are mutually coupled; the mutual coupling means that the top of the low-pressure tower is communicated with the feed inlet of the pressurizing tower, the top of the pressurizing tower is communicated with the feed inlet of the zeolite membrane dehydration unit, the permeate side outlet of the zeolite membrane dehydration unit is communicated with the feed inlet of the low-pressure tower, and the retentate side outlet is communicated with the top reflux port of the pressurizing tower; wherein, the raw material inlet of the rectification system is the feed inlet of the low-pressure tower; the zeolite membrane dehydration unit adopts gas phase feeding; the technical scheme of the utility model is suitable for being modified on the existing THF double-tower rectifying system, can greatly reduce the material circulation quantity between the double towers, and achieves the purposes of reducing cost and enhancing efficiency.

Description

Energy-saving tetrahydrofuran aqueous solution rectifying system
Technical Field
The utility model relates to an energy-saving tetrahydrofuran aqueous solution rectifying system, which can be used in the fields of Polytetrahydrofuran (PTMEG), polybutylene adipate/terephthalate (PBAT), polybutylene terephthalate (PBT) and the like, and is particularly suitable for the technical transformation of the existing tetrahydrofuran aqueous solution rectifying system.
Background
Tetrahydrofuran (THF, atmospheric boiling point 66 ℃) is a solvent with excellent performance, is a necessary raw material for synthesizing Polytetrahydrofuran (PTMEG), and has wide application in the paint and medicine industries.
Tetrahydrofuran and water form an azeotrope, so that conventional single-tower rectification cannot separate high-purity tetrahydrofuran, and a special rectification method is required to separate the tetrahydrofuran. At present, a low-pressure tower and a pressurizing tower double-tower rectification process is widely adopted to separate THF and water. At normal pressure, THF forms an azeotrope with water, the azeotrope composition being 95.1% by weight THF and 4.9% by weight water; the azeotrope composition was 88.9wt% THF and 11.1wt% water at 0.6 MPaG.
In the double-tower pressure swing rectification process, THF aqueous solution firstly enters a low-pressure tower, the THF aqueous solution with the water content of 5-6wt% after being concentrated at the top of the low-pressure tower is further dehydrated and light components are removed from a pressurizing tower, and the THF aqueous solution with the water content of 9-10wt% after being concentrated at the top of the pressurizing tower is recycled to an atmospheric tower for treatment. In the rectification process, a large amount of THF aqueous solution is continuously circulated among the top of the normal pressure tower, the feeding of the pressurizing tower, the top of the pressurizing tower and the feeding of the normal pressure tower, so that the treatment load of double towers is increased, a large amount of steam and circulating water are consumed, and the operation cost is increased.
In order to solve the problem of large-scale circulation of THF aqueous solution in a double tower, attempts to couple a membrane dehydration device with a double tower rectification system to reduce the circulation amount of THF aqueous solution exist in the prior art.
For example, chinese patent CN104027996a, in which a pervaporation membrane separator 5 is introduced into a double-column rectification system, a permeate outlet and a retentate outlet of the membrane separator are respectively connected to an atmospheric column 8 and a pressurization column 9, and then, overhead streams of the atmospheric column 8 and the pressurization column 9 are condensed and recycled back to the raw material tank 1, and are heated again by the preheater 3 and then enter the evaporator 4, and a gas phase generated by evaporation enters the membrane separator 5 again. The technical scheme can only be used for treating materials with low water content, if the water content of the materials is high, the membrane area required by membrane separation and dehydration is large, the investment is high, and the practical value is not realized.
For another example, chinese patent CN111909120a discloses an energy-saving separation process of an aqueous ternary azeotropic system for separating water, toluene and tetrahydrofuran, comprising the steps of: the raw materials enter a first separation tower after being preheated, and materials extracted from the bottom of the tower are conveyed to a second separation tower for further rectification; the steam extracted from the top of the second separation tower exchanges heat with the material at the bottom of the first separation tower to obtain tetrahydrofuran, and the toluene finished product extracted from the bottom of the second separation tower exchanges heat with the raw material to obtain toluene; and (3) refluxing a material extracted from the top of the first separation tower, conveying the material to a membrane separation assembly for dehydration, and extracting and collecting the dehydrated retentate (namely tetrahydrofuran finished product) as a heat exchange medium to obtain tetrahydrofuran as a product after heat exchange with the bottom material of the second separation tower. This patent is for treating toluene and tetrahydrofuran mixed solvents having relatively low water content with virtually no stream recycle between the double columns. The solution of this patent is not essentially a double column and membrane dehydration coupling system, where the second separation column 4 is used only for normal rectification separation, and the patent is likewise not used for treating mixed solvents with a higher water content.
Disclosure of Invention
The utility model aims to provide an energy-saving tetrahydrofuran aqueous solution rectifying system, which is a system for coupling zeolite membrane dehydration and double-tower rectifying process, so that a large amount of THF aqueous solution is prevented from circulating between double towers, and the separation energy consumption of the tetrahydrofuran aqueous solution is reduced.
The technical scheme adopted by the utility model is as follows:
an energy-saving tetrahydrofuran aqueous solution rectifying system comprises a low-pressure tower 1, a pressurizing tower 8 and a zeolite membrane dehydration unit 13 which are mutually coupled; the mutual coupling means that: the top of the low-pressure tower 1 is communicated with a feed inlet of the pressurizing tower 8, the top of the pressurizing tower 8 is communicated with a feed inlet of the zeolite membrane dehydration unit 13, a permeate side outlet of the zeolite membrane dehydration unit 13 is communicated with the feed inlet of the low-pressure tower 1, and a retentate side outlet is communicated with a top reflux port of the pressurizing tower; wherein, the raw material inlet of the rectification system is the feed inlet of the low-pressure tower 1.
Preferably, the zeolite membrane dehydration unit 13 is fed in a gas phase, i.e. the gas phase light components withdrawn from the top of the pressurizing tower 8 directly enter the zeolite membrane dehydration unit 13 without condensation. THF and a small amount of water vapor in the gas phase light component are intercepted by a membrane component of a zeolite membrane dehydration unit 13 to form a retentate, then the retentate is condensed by a pressurizing tower condenser 10 and stored in a pressurizing tower reflux tank 11, and the retentate is conveyed by a pressurizing tower reflux pump 12 and then partially refluxed to the top of the pressurizing tower 8, and the partially recovered light component is taken out. The vapor and a small amount of THF in the vapor phase light component permeate through the membrane component of the zeolite membrane dehydration unit 13 to form permeate vapor, and then the permeate vapor is condensed by the permeate vapor condenser 14 and then recycled to the feed inlet of the low-pressure tower 1.
Preferably, the low pressure column 1 comprises a feed pipe 18, a low pressure column reboiler 2, a low pressure column bottoms pump 3, a low pressure column condenser 4, a low pressure column reflux drum 5, and a low pressure column reflux pump 6. The feed solution and the recycled permeate may be pre-mixed in the feed tube 18 or communicated to the feed inlet of the low pressure column 1 via separate pipes; the low-pressure tower kettle pump 3 is communicated with the tower kettle of the low-pressure tower 1 and the waste water pipe 19 and is used for extracting system waste water from the tower kettle of the low-pressure tower 1 so as to separate water in the raw materials; the low-pressure tower condenser 4 is used for condensing light components at the top of the low-pressure tower 1, the outlet of the low-pressure tower condenser is communicated with the low-pressure tower reflux tank 5, the outlet of the low-pressure tower reflux tank 5 is communicated with the low-pressure tower reflux pump 6, the outlet of the low-pressure tower reflux pump 6 is divided into two paths, one path is communicated with the top of the low-pressure tower 1 to construct a reflux path, and the other path is communicated with the feeding pipe of the pressurizing tower.
Preferably, a pressurizing tower preheater 7 is arranged on the pressurizing tower feeding pipe, and a hot material inlet of the pressurizing tower preheater 7 is communicated with the tower kettle of the pressurizing tower 8 through a product pipe 20 so as to preheat the pressurizing tower feeding by utilizing the temperature of the high-purity THF product extracted from the tower kettle of the pressurizing tower 8.
Preferably, the pressurization tower 8 further comprises a pressurization tower reboiler 9.
Preferably, the outlet of the permeate condenser 14 is connected to the permeate water tank 15, and the bottom of the permeate water tank 15 is connected to the feed inlet of the low-pressure tower 1 via the permeate pump 17 and the permeate pipe 22.
Preferably, a vacuum pump 16 is connected to the top of the permeate water tank 15, and the vacuum pump 16 is used for constructing a negative pressure condition on the permeate side of the zeolite membrane dehydration unit 13, thereby improving the permeation efficiency of water vapor.
Preferably, the low pressure tower 1 is an atmospheric tower, the pressurizing tower adopts pressurizing operation, and the operation pressure is 0.2-0.8 MPaG.
Preferably, the zeolite membrane dehydration unit 13 comprises zeolite membrane modules connected in parallel or in series in multiple stages; the zeolite membrane module is an inorganic zeolite membrane, preferably a NaA membrane or a CHA membrane.
When in use, the energy-saving tetrahydrofuran water solution rectifying system provided by the utility model adopts the following flow:
(1) The tetrahydrofuran water solution raw material from outside the boundary is firstly fed into an atmospheric tower, and is rectified and separated by the atmospheric tower, the azeotrope of tetrahydrofuran/water is obtained at the tower top, and the wastewater is obtained at the tower bottom.
(2) After the tetrahydrofuran/water azeotrope from the top of the atmospheric tower exchanges heat with the tetrahydrofuran product at the bottom of the pressurizing tower, the water content at the top of the pressurizing tower is further concentrated as the feeding of the pressurizing tower, and the tower top gas is dehydrated by a zeolite membrane dehydration unit. The dehydrated gas enters a pressurizing tower condenser for condensation, then enters a pressurizing tower reflux tank for buffering, part of the gas is taken as reflux liquid after being pressurized by a pressurizing tower reflux pump, and the other part of the gas is taken as light components to remove the boundary, so that the tetrahydrofuran product is obtained at the bottom of the pressurizing tower.
(3) The aqueous tetrahydrofuran gas is dehydrated in a zeolite membrane dehydration unit to obtain a dehydrated tetrahydrofuran gas and a small amount of permeate water, which is returned to the atmospheric tower for further recovery of the low content tetrahydrofuran contained therein.
The beneficial effects of the utility model are as follows:
(1) The system of coupling zeolite membrane dehydration and double-tower rectification technology is adopted, tetrahydrofuran aqueous solution concentrated at the top of a pressurizing tower is not required to be recycled to an atmospheric tower for further separation, the zeolite membrane is directly adopted for dehydration concentration and then is used as reflux component for reflux or light component extraction, only water (the amount of water is small compared with the amount of THF) penetrating through a zeolite membrane component participates in circulation, the material circulation amount between double towers is greatly reduced, the separation energy consumption and the operation cost are reduced, and the purposes of reducing cost and enhancing efficiency are achieved;
(2) By adopting a system of coupling zeolite membrane dehydration and double-tower rectification technology, the double-tower operation load is reduced, the size of tower equipment is reduced, and the total equipment investment is reduced;
(3) The operation flexibility of the double towers is increased, the pressurizing towers can be used for reducing the pressure, and the operation difficulty is reduced;
(4) The method is suitable for technical transformation on the existing tetrahydrofuran aqueous solution double-tower rectifying system, needs less added equipment, and has low transformation cost, small transformation difficulty and high implementation speed.
Drawings
Fig. 1 is a schematic diagram of an energy-saving tetrahydrofuran aqueous solution rectification system.
In the figure: 1 is a low-pressure tower, 2 is a low-pressure tower reboiler, 3 is a low-pressure tower kettle pump, 4 is a low-pressure tower condenser, 5 is a low-pressure tower reflux tank, 6 is a low-pressure tower reflux pump, 7 is a pressurizing tower preheater, 8 is a pressurizing tower, 9 is a pressurizing tower reboiler, 10 is a pressurizing tower condenser, 11 is a pressurizing tower reflux tank, 12 is a pressurizing tower reflux pump, 13 is a zeolite membrane dehydration unit, 14 is a permeation steam condenser, 15 is a permeation water tank, 16 is a vacuum pump, 17 is a permeation water pump, 18 is a raw material pipe, 19 is a waste water pipe, 20 is a product pipe, 21 is a light component pipe, 22 is a permeation water pipe, CWS is circulating cooling water, and LS is low-pressure steam.
Detailed Description
In order to more clearly illustrate the present utility model, the present utility model will be further described with reference to examples. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and that this utility model is not limited to the details given herein.
FIG. 1 is a schematic diagram of an energy-efficient aqueous tetrahydrofuran solution rectification system, exemplified by the separation of aqueous tetrahydrofuran solution by-produced in a PBAT factory, having a flow rate of 2.3t/h, containing 60wt% water and 40wt% THF.
(1) The tetrahydrofuran water solution raw material from outside the boundary is firstly processed into a low-pressure tower 1, the low-pressure tower 1 is operated under normal pressure, and a rectification system of the low-pressure tower 1 is provided with a low-pressure tower reboiler 2, a low-pressure tower kettle pump 3, a low-pressure tower condenser 4, a low-pressure tower reflux tank 5 and a low-pressure tower reflux pump 6. The water content of tetrahydrofuran water solution with 5.3wt% is obtained at the top of the low-pressure tower, the flow is 0.98t/h, and the waste water is extracted from the bottom of the tower.
(2) The tetrahydrofuran aqueous solution obtained from the tower top of the low-pressure tower is preheated by a pressurizing tower preheater 7, the waste heat of tetrahydrofuran products obtained from the tower bottom of a pressurizing tower 8 is utilized in the preheating process, and the tetrahydrofuran aqueous solution enters the pressurizing tower 8 for refining after being preheated. The water content of the pressurized column overhead stream was 7.4wt% and the overhead gas was dehydrated by zeolite membrane dehydration unit 13. The dehydrated gas (the residual seepage side) enters a pressurizing tower condenser 10 for condensation, then enters a pressurizing tower reflux tank 11 for buffering, part of the gas is taken as reflux liquid after being pressurized by a pressurizing tower reflux pump 12, the other part of the gas is taken as light components for boundary removal, a pressurizing tower reboiler 9 is arranged at the tower bottom of the pressurizing tower, and the tetrahydrofuran product is obtained at the tower bottom.
(3) In the zeolite membrane dehydration unit 13, the aqueous tetrahydrofuran gas is dehydrated by using membrane modules connected in parallel or in series in multiple stages to obtain dehydrated tetrahydrofuran gas (water content 2-3 wt%) and a small amount of permeate water, and the permeate water is returned to the low-pressure column 1 to further recover the low-content tetrahydrofuran contained therein.
Operating conditions of the low pressure column 1: the pressure at the top of the tower is 0.02MPaG, the temperature at the top of the tower is 66 ℃, the temperature at the bottom of the tower is 105 ℃, and the reflux ratio at the top of the tower is 1.5;
operating conditions of the pressurization column 8: the pressure at the top of the tower is 0.56MPaG, the temperature at the top of the tower is 130 ℃, the temperature at the bottom of the tower is 140 ℃, and the reflux ratio at the top of the tower is 20;
the vacuum side pressure of the zeolite membrane dehydration system is 5-10 kPaA.
Compared with the traditional high-low pressure rectification, the utility model reduces the circulation quantity between the double towers, and greatly reduces the processing load of the dehydration tower (low-pressure tower) and the light component removal tower (pressurizing tower). The consumption of the circulating water is 136m 3 Reducing/h to 58m 3 /h, reduced by 78m 3 And/h. The total heat load of the reboiler is reduced from 2076kW to 699kW, 1377kW is reduced, and the energy-saving effect is achievedThe effect is obvious. The cost of the circulating water is 0.5 yuan/m 3 The heat unit price of the reboiler is calculated according to 0.37 yuan/kW, the annual operation time is calculated according to 8000h, and the operation cost can be saved by about 438.8 yuan/year.
It should be understood that the foregoing examples of the present utility model are provided merely for clearly illustrating the present utility model and are not intended to limit the embodiments of the present utility model, and that various other changes and modifications may be made therein by one skilled in the art without departing from the spirit and scope of the present utility model as defined by the appended claims.

Claims (8)

1. An energy-saving tetrahydrofuran aqueous solution rectifying system comprises a low-pressure tower (1), a pressurizing tower (8) and a zeolite membrane dehydration unit (13) which are mutually coupled; the method is characterized in that: the mutual coupling means that the top of the low-pressure tower (1) is communicated with the feed inlet of the pressurizing tower (8), the top of the pressurizing tower (8) is communicated with the feed inlet of the zeolite membrane dehydration unit (13), the permeation side outlet of the zeolite membrane dehydration unit (13) is communicated with the feed inlet of the low-pressure tower (1), and the permeation side outlet is communicated with the top reflux port of the pressurizing tower; wherein, the raw material inlet of the rectification system is the feed inlet of the low-pressure tower (1); the zeolite membrane dehydration unit (13) is fed in the gas phase.
2. The energy-efficient tetrahydrofuran aqueous solution rectifying system according to claim 1, wherein: the residual gas of the zeolite membrane dehydration unit (13) is stored in a pressurizing tower reflux tank (11) after being condensed by a pressurizing tower condenser (10), and is partially refluxed to the top of the pressurizing tower (8) after being pressurized by a pressurizing tower reflux pump (12), and is partially extracted as light components; the permeate gas is condensed by a permeate gas condenser (14) and then circulated back to the feed inlet of the low-pressure tower (1).
3. The energy-efficient tetrahydrofuran aqueous solution rectifying system according to claim 2, wherein: the low-pressure tower (1) comprises a raw material pipe (18), a low-pressure tower reboiler (2), a low-pressure tower kettle pump (3), a low-pressure tower condenser (4), a low-pressure tower reflux tank (5) and a low-pressure tower reflux pump (6); the low-pressure tower kettle pump (3) is communicated with the tower kettle of the low-pressure tower (1) and the waste water pipe (19); the outlet of the low-pressure tower condenser (4) is communicated with the low-pressure tower reflux tank (5), the outlet of the low-pressure tower reflux tank (5) is communicated with the low-pressure tower reflux pump (6), the outlet of the low-pressure tower reflux pump (6) is divided into two paths, one path is communicated with the top of the low-pressure tower (1), and the other path is communicated with the feeding pipe of the pressurizing tower.
4. The energy-efficient tetrahydrofuran aqueous solution rectifying system according to claim 3, wherein: a pressurizing tower preheater (7) is arranged on the pressurizing tower feeding pipe, and a hot material inlet of the pressurizing tower preheater (7) is communicated with a tower kettle of the pressurizing tower (8) through a product pipe (20) so as to preheat the pressurizing tower feeding by utilizing the waste heat of THF (tetrahydrofuran) products extracted from the tower kettle of the pressurizing tower (8); the pressure column (8) comprises a pressure column reboiler (9).
5. The energy-saving tetrahydrofuran water solution rectifying system according to claim 4, wherein: the outlet of the permeate steam condenser (14) is communicated with the permeate water tank (15), and the bottom of the permeate water tank (15) is communicated with the feed inlet of the low-pressure tower (1) through the permeate water pump (17) and the permeate water pipe (22).
6. The energy-saving tetrahydrofuran aqueous solution rectifying system according to claim 5, wherein: the top of the infiltration water tank (15) is connected with a vacuum pump (16).
7. The energy-saving tetrahydrofuran water solution rectifying system according to claim 6, wherein: the low-pressure tower (1) is an atmospheric tower.
8. The energy-efficient tetrahydrofuran aqueous solution rectifying system according to claim 7, wherein: the zeolite membrane dehydration unit (13) comprises zeolite membrane components connected in parallel or in multi-stage series; the zeolite membrane module is a NaA membrane or a CHA membrane.
CN202320955398.9U 2023-04-24 2023-04-24 Energy-saving tetrahydrofuran aqueous solution rectifying system Active CN219743939U (en)

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CN202320955398.9U CN219743939U (en) 2023-04-24 2023-04-24 Energy-saving tetrahydrofuran aqueous solution rectifying system

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CN202320955398.9U CN219743939U (en) 2023-04-24 2023-04-24 Energy-saving tetrahydrofuran aqueous solution rectifying system

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