JPH0671531B2 - Liquid-liquid separator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial field of application" The present invention relates to an azeotropic mixture in industries such as food, fishery processing, pharmaceuticals, petrochemicals, general chemistry, etc., as well as industries using other various solvents. Related to a separation device used for concentrating or separating a mixed solvent, a mixed solvent, etc., more specifically, a liquid liquid mainly composed of water-hydrophilic organic solvent such as water-ethyl alcohol by a pervaporation method using a pervaporation membrane. The present invention relates to a separation device.

"Prior art" Membrane separation is an energy-saving technology because it separates the components according to the difference in the permeation rate in the membrane without changing the phase. Widely used for component concentration.

By the way, a liquid-liquid mixture such as water and alcohol, benzene and cyclohexane whose molecular sizes are not so different,
Since it is difficult to apply ordinary membrane separation technology to the separation and purification of an azeotropic mixture that cannot be separated by ordinary distillation, and further a liquid-liquid mixture with a small boiling point difference such as water and acetic acid that is difficult to separate, it is difficult in recent years to Attempts have been made to adopt a pervaporation method (pervaporation method) performed using a pervaporation membrane (hereinafter abbreviated as PV membrane).

Known PV films include a composite film of polyvinyl alcohol crosslinked with maleic acid, a film of a mixture of carboxymethyl cellulose and polyacrylate, and a film of chitosan treated with CoSO ₄ . Further, the pervaporation method performed using the PV membrane is as shown in FIG. 2, in which the raw material liquid 32 composed of a liquid-liquid mixture is supplied to the one-character side of the PV membrane 31 with a space between them.
This is a membrane separation method in which the secondary side is decompressed to preferentially take out components having an affinity for the membrane in the liquid mixture by vapor.

In order to industrially utilize and practically use such a pervaporation method, for example, when the raw material liquid consisting of water and ethanol contains an inorganic salt such as sodium chloride, it is necessary to selectively remove water by membrane separation. Along with this, the inorganic salt is partially supersaturated and deposited on the membrane, which blocks the intramolecular pores (usually 10 Å or less) of the PV membrane and impairs the original separation function. In addition, PV membranes generally correspond to non-porous membranes (even if they have a pore size of 10 Å or less), so-called back pressure cleaning is impossible by applying pressure from the permeate side and flowing the fluid to the retentate side. Once fouling is performed, cleaning is difficult, so it is necessary to pretreat the raw material liquid to remove the inorganic salt in advance. As a device for performing such pretreatment, it is possible to adopt a treatment device using various membranes, such as microfiltration membrane (MF), ultrafiltration membrane (UF) and loose RO.
Etc., the removal rate of fine particles is low, and in particular, the effect of removing water-soluble inorganic salts can hardly be expected. Even with a reverse osmosis membrane (RO), which is the only one that has the effect of removing water-soluble inorganic salts, it is 20wt due to osmotic pressure restrictions
It can only be applied to low-concentration aqueous solutions below 10%. Moreover, these membrane methods have an essential weakness that the recovery rate of the processing liquid to the raw material liquid is low because it is necessary to suppress fouling on the film surface, and it is difficult to put them into practical use. The evaporator that evaporates the liquid once to separate and remove the inorganic salts is the most effective PV membrane because of the high recovery rate of the processing liquid to the raw material liquid and the high removal rate of solids containing inorganic salts. It can be said to be a pretreatment method for the device.

[Problems to be Solved by the Invention] However, in order to perform the pervaporation method using the above-mentioned pretreatment device by the evaporator method, a large amount of energy is consumed to evaporate the raw material liquid as the pretreatment, so that the separation is performed. There is a problem that the operating cost of the entire device becomes high and it becomes uneconomical.

The present invention has been made in view of the above circumstances, and an object of the invention is to perform a pervaporation method using a PV membrane so that the operating cost can be kept low and the product cost can be reduced. To provide.

"Means for Solving the Problem" In the liquid-liquid separation device of the present invention, in a separation device for performing liquid-liquid separation by a pervaporation method using a PV membrane, a separation unit including the PV film and a raw material liquid The pretreatment unit has a pretreatment unit that processes and supplies the treated liquid to the separation unit, the pretreatment unit evaporates a raw material liquid, a compressor that pressurizes vapor derived from the evaporation can, and a compressor Equipped with a reboiler that uses the condensation heat of the derived steam as a heat source, the bottom liquid from the evaporator was introduced into the reboiler, and heat exchange was performed to recover the heat necessary for evaporating most of the raw material liquid. The means for solving the above-mentioned problems is to provide a circulation cycle for circulating the heat to the post-evaporator or to provide a reboiler for recovering the heat of condensation of the steam discharged from the compressor in the evaporator.

[Operation] According to the liquid-liquid separation device of the present invention, the treatment liquid can be obtained with a considerable recovery rate by temporarily evaporating most of the raw material in the pretreatment section, and further, the inorganic salt in the raw material liquid can be removed. It is possible to satisfactorily remove the solid content including the vapor, and after pressurizing the vapor from the evaporator, the condensed liquid is consumed by the heat of vaporization of the vapor of the above-mentioned raw material to be consumed in the pretreatment section. Energy is significantly reduced.

[Examples] Hereinafter, the present invention will be described in detail with reference to the drawings. First
The figure shows a schematic flow of one embodiment of the liquid-liquid separation device of the present invention. In the figure, reference numeral 1 is a pretreatment section, and 2 is a separation section.

In the pretreatment unit 1, a heat exchanger 4, an evaporator 5, a compressor 6, and a reboiler 7 are sequentially arranged in the raw material supply source 3 via respective pipes. The heat exchanger 4 uses the distillate from the evaporator 5 as a heat source, and preheats the raw material liquid introduced from the raw material supply source 3. The evaporator 5 heats the introduced raw material liquid to an appropriate temperature and evaporates it.
The vapor that is the distillate is discharged from the top portion 5a and the bottom liquid is discharged from the bottom portion 5b. In this case, the vapor that becomes the distillate is one in which impurities such as inorganic salts have been substantially removed, while the bottoms liquid is contained in a state where the impurities contained in the raw material liquid are concentrated. Will be things. As the compressor 6, a direct suction type compressor is used, and as the model, a screw compressor, a turbo compressor, a roots compressor or the like is appropriately selected according to the respective specifications. The compressor 6 pressurizes the steam discharged from the evaporator 5, and the condensation heat of the pressurized steam 34 is used for the heat source of the reboiler 7 described later. Here, the gas discharged from the evaporator 5 is approximately 5 to 5
The vapor 34 is pressurized by the compressor 6 so as to condense at a temperature higher by 20 ° C. The reboiler 7 heats almost all of the bottom liquid from the evaporator 5 using the heat of condensation of the pressurized distillate vapor 34 as a heat source, and introduces it into the evaporator 5 again. Here, the evaporation can 5, the extraction pipe 8 for extracting the extraction liquid from the evaporation can 5, the branch from the middle part of the extraction pipe 8 are connected and communicated with the reboiler 7, and the evaporation can 5 A recirculation pipe 9 connected to and communicates with the recirculation pipe 9, a pump 10 disposed between the recirculation pipe 7 and the recirculation pipe 7 and the reboiler 7 heats almost all of the recirculation liquid from the recirculation pipe 7. A circulation cycle 11 is then formed for returning to the evaporator 5. Further, the post-condensate introduced into the reboiler 7 as the heat source of the reboiler 7 is further guided to the heat exchanger 4 through the connecting pipe 12 and used as a heat source for preheating the raw material liquid. And in the heat exchanger 4,
A transfer pipe 13 is provided for transferring the condensate used as a heat source to the separation unit 2.

The separation unit 2 is for heating a heat exchanger 4 arranged in the middle of the transfer pipe 13 and a condensate (hereinafter, abbreviated as a distillate) which is a distillate from the evaporator 5. Heater 15 and multi-stage PV membrane module 16 connected to the heater 15 via respective pipes
And a separated liquid recovery pipe connected to the multi-stage PV membrane module 16
17 and a separated vapor recovery pipe 18. Heat exchanger
14 is for heating the distillate in which heat has been consumed by preheating the raw material liquid in the heat exchanger 4, and uses the liquid recovered from the multi-stage PV membrane module 16 described later as the heat source. is there. The heater 15 uses steam or electric power supplied from the outside as a heat source, and heats the distillate from the heat exchanger 4 to a temperature suitable for separating by a pervaporation method using a PV membrane. Is. In the multi-stage PV membrane module 16, a plurality of PV membrane modules 19 ... Are continuously arranged via connection pipes 20. The separated vapor recovery pipes 18 ... Are connected to each of the PV membrane modules 19 ... It was done. Here, each PV membrane module 19 is usually a plurality of PV membranes.
21 is placed in a container and integrated, and the primary side of the PV membrane 21 is used as a distillate flow path, and the separated vapor recovery pipe 18 is connected to the secondary side. In addition, connection pipe 20 ...
The two PV membrane modules 19, the PV membranes in the PV membranes 21 and 21 are to connect the respective primary sides of the PV membranes to form a distillate flow path, and the intermediate portion thereof is located in the heater 15.
As a result, the distillate derived from one PV membrane module 19 is reheated. Also, multi-stage PV membrane module
The PV membrane module 16a located on the most downstream side of 16 has the P
A separated liquid recovery pipe 17 is connected to the primary side of the V membrane 21. The separated liquid recovery pipe 17 is provided with the heat exchanger 14 in the middle thereof, and guides the separated liquid after the liquid-liquid separation process, which is derived from the PV module 16a, to the heat exchanger 14 as a heat source, and further The separated liquid after heat exchange is guided to a recovery tank (not shown). The separated vapor recovery pipe 18 has a multi-stage PV membrane module 16
A cooling unit 22 is provided for cooling and condensing the separated vapor derived from the. This cooling unit 22
Is composed of a cooling unit 23 and a heat exchange unit 24 for introducing and circulating the refrigerant cooled in the cooling unit 23 to condense the separated vapor discharged from the multi-stage PV membrane module 16. The heat exchange section 24 is provided with a condensate recovery pipe 25 and a non-condensable gas recovery pipe 26, and a vacuum pump 27 is provided in the non-condensable gas recovery pipe 26. A recovery tank (not shown) is connected to the condensate recovery pipe 25 so that the condensate of the separated vapor is recovered.

In order to separate and recover ethanol from a mixed liquid of water and ethanol (ethanol concentration: 68 wt%) at room temperature using the liquid-liquid separator having such a configuration, first, the mixed liquid is used as a raw material liquid in the heat exchanger 4. Supply. Next, the mixed liquid preheated to about 80 to 85 ° C. by the heat exchanger 4 is introduced into the evaporator 5,
93 ℃ under the pressure of 0.4kg / cm ² G using reboiler 7 as a heating source
When heated to a certain degree, the portion corresponding to the weight of about 12/3 of the raw material liquid becomes vapor (ethanol concentration 71 wt%) and distills from the evaporator, and then is introduced into the compressor 6 where the discharge pressure is 1.4. Pressurized to kg / cm ² G. In this case, the distillate obtained by evaporation has substantially removed solid components such as inorganic salts which were present as impurities in the mixed liquid. The distillate pressurized here is totally condensed at about 103 ° C. in the reboiler described later. In addition, the balance of the mixed liquid supplied to the evaporator 5 is concentrated to about 13 times as much as inorganic salts as impurities and becomes a bottom liquid, which is led to the bottom pipe 8. Also,
Almost all of the bottom liquid discharged to the bottom pipe 8 is sucked by the pump 10 provided in the circulation pipe 9 and guided into the circulation pipe 9, further passes through the reboiler 7, and is added as described above. After being heated by obtaining latent heat of condensation of the compressed distillate, the evaporator 5
Will be returned to. The condensed distillate 34 is introduced into the heat exchanger 4 as described above to preheat the supplied raw material mixture.

In addition, the bottom liquid obtained by concentrating the inorganic salts as impurities is equivalent to the difference in the amount of the raw material and the vapor distilled from the evaporator (in this case, 1/3 of the raw material), and the pump 10 It is discharged from the discharge side to the outside of the system to keep the impurity concentration in the evaporator within a certain range.

In this way, the large amount of evaporation energy required for the evaporator is the power of the compressor (1/10 of the evaporation energy concerned).
(About 1/15) will be able to cover substantially enough.

Next, the distillate (condensate) discharged from the heat exchanger 4 is introduced into the heat exchanger 14 to be heated, and further introduced into the heater 15 to be heated to about 80 to 90 ° C.

Then, the heated distillate is introduced into the multi-stage PV membrane module 16, and the PV membrane module 19 separates it by the pervaporation method to separate the water in the distillate as steam. And
The distillate from which some of the water has been separated and removed is led to the connecting pipe 20, and the next
Water is removed in the same manner by introducing it to the PV membrane module 19, and this is repeated in sequence to perform membrane separation in multiple stages to recover the ethanol of the desired concentration by removing water from the mixed liquid as the raw material liquid. The product is led to a pipe 17 and collected to obtain a product. Further, the water vapor led out from each PV membrane module 19 contains ethanol vapor as a trace depending on the membrane performance, but is condensed in the cooling unit 22 and collected as a waste liquid.

In the above example, a plurality of PV membrane modules 19 are arranged to form the series multi-stage PV module 16, but a single-stage PV membrane module may be used when the amount of dehydration from the raw material liquid is small. Good.

"Effects of the Invention" As described above, the liquid-liquid separation device of the present invention includes an evaporator that allows the pretreatment section to evaporate the raw material liquid, a compressor that pressurizes the vapor drawn from the evaporator, and the compressor. It is equipped with a reboiler that uses the condensation heat of the pressurized steam derived from
Introducing the bottom liquid from the evaporator to the reboiler, and since it is equipped with a circulation cycle in which heat is exchanged and then circulated to the evaporator, inorganic salts and the like in the raw material liquid to a degree suitable for the PV film in the subsequent stage. It can be removed satisfactorily, and a high-yield treatment liquid can be obtained, and it is consumed in the pretreatment part by using it as the heat source of the condensation heat reboiler of the pressurized steam from the evaporator. Energy can be significantly reduced, and thus the operating cost of the entire apparatus can be reduced, and the product cost can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a flow chart showing a schematic configuration of the liquid-liquid separation device described in claim 1 of the present invention, FIG. 2 is a principle diagram for explaining the pervaporation method, and FIG. 3 is claim 2 of the present invention. It is a flow diagram showing a schematic structure of a pretreatment unit in the liquid-liquid separation device described in. 1 ... Pretreatment section, 2 ... Separation section, 5 ... Evaporator, 6 ...
Compressor, 7 ... Reboiler, 8 ... Outlet pipe, 9 ... Circulation pipe, 10 ... Pump, 11 ... Circulation cycle, 16 ... Multi-stage PV membrane module 19 ... PV membrane module, 21 ... PV film.

Claims (2)

[Claims] 1. A separation device comprising a pervaporation membrane and performing liquid-liquid separation by this pervaporation membrane by a pervaporation method, comprising: a separation section having the pervaporation film; The pretreatment unit has a pretreatment unit for processing and supplying it to the separation unit, and the pretreatment unit includes an evaporator for evaporating the raw material liquid, a compressor for pressurizing the vapor derived from the evaporator, and a compressor for compressing the vapor. Equipped with a reboiler that uses the heat of condensation of the derived steam as a heat source, the liquid discharged from the evaporator is introduced into the reboiler, and heat is exchanged to recover the heat that evaporates most of the raw material liquid. A liquid-liquid separation device comprising a circulation cycle for circulating the liquid. 2. A separation device comprising a pervaporation membrane and performing liquid-liquid separation by this pervaporation membrane by a pervaporation method, comprising: a separation part having the pervaporation film; The pretreatment unit has a pretreatment unit for processing and supplying it to the separation unit, and the pretreatment unit includes an evaporation can for evaporating the raw material liquid and a compressor for pressurizing the vapor derived from the evaporation can. A liquid-liquid separation device, characterized in that a reboiler for recovering heat of condensation heat of vapor derived from a compressor is provided in the can.