JPS58128107A - Separating or concentrating method for liquid mixture - Google Patents

Abstract

PURPOSE:To separate or concentrate liquid mixtures by controlling the temp. of the liquid mixtures in sections which use polymer membranes in many stages and separate or concnetrate said mixtures by means of the respective polymer membranes in a prescribed temp. range. CONSTITUTION:For example, 10 pieces each of membrane separating units V1- Vn and heat exchangers H1-Hn are connected in series, and the pressures of primary sides of the units V1-Vn are maintained at 760Torr and the pressures of secondary sides at 150Torr with a vacuum pump 4. The heat exchangers H1-Hn are put in a thermostatic bath of about 70 deg.C to maintain the outlet temp. t1 thereof at about 65 deg.C. When 94wt% aq. ethanol soln. M is supplied from a tank 1 with a pump 2 to the units V1-Vn and the heat exchangers H1- Hn the aq. ethanol soln. concd. to about 95wt% is obtained in a tank 5a and 90.7wt% aq. ethanol soln. is obtained in a tank 5b.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating or concentrating a liquid mixture by pervaporation using a polymer membrane.

When a liquid mixture is supplied to the primary side (high pressure equipment) of a non-porous polymer membrane and permeated to the secondary side C (low pressure side), the concentration of substances that easily permeate through the membrane is made higher than that on the primary side. The method of separating or concentrating the components of is called the pervaporation (P@rvaporaHon) process and has been known for a long time.

The queen perturbation process is a conventional method for separating or concentrating liquid mixtures that cannot be separated by simple methods, such as azeotropic mixtures or mixtures with low specific volatility*0, and also separations that require a large amount of energy such as distillation. Also, its principle is attracting attention as an energy-saving type method separate from the concentration method.

Normally, non-porous polymers made from polyethylene, polypropylene, polystyrene, polytetrafluoroethylene, boria 2, Cel-A-N polymers, etc. or copolymers thereof are used for pervaporation. It's crowded. The next pressure is 0.01 to 100 #/l
sa ” abs, the secondary pressure is the primary pressure)
A pressure that is low and below the operating temperature K times the saturated vapor pressure of the liquid mixture to be treated is employed.

By the way, the method of separating or concentrating a liquid mixture by the pervaporation method has its industrial use (XFI
There is no I, and in order to use it industrially, the following technical issues must be determined.

The size of the membrane area required when separating or concentrating a liquid mixture by the pervaporation method is:
The permeation rate Q (P/sa”hr) is expressed by the separation coefficient αAB of the membrane and the amount of vapor that permeates the attitude lIw product per unit time.
K! Tute decision. (l, +ms number αAB is the weight ratio of the liquid mixture Om, B component to the membrane permeation.
If the weight percentage after permeation through the membrane is 2% B2, it is expressed as 9 mlBz α""t=Ir■".

The larger the above αAB and Q, the smaller the required membrane area. The above αAB and Q vary depending on the temperature 11 of the liquid mixture before membrane permeation, the downstream pressure P1, and the secondary side pressures P and K. Normally, α5B becomes larger as tl is lower, and Q becomes larger as tl is higher.

The smaller P2/Pt is, the larger Q becomes. However, as P and /P1 become smaller, the power required for steam suction increases, and as P2 becomes smaller, the condensation Il of the permeated vapor becomes lower, and a refrigerator may be required to recover it. Therefore, in order to carry out the pervaporation method most economically for industrial use, it is necessary to set an appropriate liquid mixture temperature f for the combination of the polymer membrane and the liquid mixture.
It is necessary to set t□ and select the primary pressure P and the secondary pressure P based on this.

In addition, the pervaporation method involves O
Then, the temperature of the liquid on the negative side decreases by an amount corresponding to the latent heat of vaporization of the vapor that passes through. As a result, the downstream liquid mixture is not maintained at the correct temperature. Therefore, by simply supplying the Kfi mixture on the primary side of the membrane and applying low pressure to the secondary side, it is not possible to economically separate or concentrate the liquid mixture for industrial use by the pervaporation method. This will cause unnecessary inconvenience.

Furthermore, the permeation rate fQ in polymer 1IIK is generally a maximum of 5.
In order to obtain an industrial-scale throughput with 00017m"br ill!, the possible film area of a single 〇enit polymer film has a limited optical range, and the separation coefficient αAn is at most 10, and a single 〇enit polymer membrane has a limited area. In some cases, it may be insufficient for separating or concentrating liquid mixtures.

In view of the above-mentioned circumstances, the present invention enables industrial use of the pervaporation method and provides a method for efficiently and economically separating or concentrating a liquid mixture under optimal operating conditions at all times. This method is characterized in that the temperature of the liquid mixture discharged into the dye separation or concentration section is adjusted to a predetermined temperature range using a polymer membrane used in multiple stages.

The present invention will be explained below with reference to the drawings.

FIG. 1 is a schematic diagram of an external heating type IT showing the basic flow of the apparatus used in the method for separating or concentrating a liquid mixture according to the present invention. 1uet"Do raw material liquid mixture M is pumped from tank 1 by pump 2. The pumped raw material liquid mixture M passes through line a0 to heat exchanger H.
After being heated to tl°C, the membrane is introduced into the primary side of the membrane separation unit v through the line mini. The pressure on the primary side of the separation 5-et VI is maintained by the pump 2, and the pressure on the secondary side is reduced by the vacuum pump 4 via the condenser 3.
It is held in M 2 W Hx*'bs. In this case, the liquid collected in the condenser 3 is stored in a tank 5bK. The vapor that has passed through the polymer membrane s1 and is enriched with easily permeable components is led out through line d. On the other hand, the membrane l111
The liquid mixture, which is enriched with components that are difficult to pass through, is discharged through line b0. The temperature of the liquid mixture discharged from line b1 is lowered to %t, 0 due to the heat of evaporation of the vapor that has passed through the membrane.
1 (D liquid mixing is done by heat exchange @H) 1 Membrane separation 3
- Knit VO liquid - heated with at1 t and introduced into the second membrane separation enit v2 from line a. In V and K sils, in the same way as vl, a mixed liquid rich in components that are difficult to pass through the membrane s3 is heated to a temperature t.
, and line b comes out. This is repeated one after another, and the components that are difficult to pass through the membranes are concentrated, and the product in the tank 5ail is taken out from the outlet line bn of the membrane separation unit Vn. 9, each membrane separation enit, v (v□, v
, -Vn) on the secondary side @ attack (Tsuru 1, wh, -m
611), the components that are easily permeable through the membrane are concentrated, and the vapor is collected by condenser II3 and sent to condensation tank 5b.
is stored in

Membrane separation) Vl, V, -・1- The superior temperature is V□
+Vz +-◆vnO Optimum temperature l at which the required expansion area is as small as possible! The key point of the present invention is to adjust to a range close to . This optimum temperature is the desired concentration or separation O@degrees, α,
Q1 equipment cost and running cost) It is selected based on the design based on the comparison, and is not unambiguous, but the point is that vl
, V, -Vn In order to take a large expedient KQ so that each am is not p larger than ζ01Lf,
A high usable temperature can be employed, such as the maximum working temperature of the membrane or a temperature as high as not to boil the liquid mixture.

Inlet temperature rI of Vl, V, ・V,
/lt1 and outlet temperature 1ft, is tl-t, xΔ
j, then t for the optimum temperature inside the membrane separator t op
-1+''t/, t-t-'!'t/, 1 0p
2 2 0p is set. In addition, each membrane separation device @V1, V, -V.

Let the membrane area of each membrane s, , s, --- be so large that the decrease in * of the liquid mixture due to evaporation there is Δt. Furthermore, the temperature of the liquid mixture at the inlet and outlet of the membrane separation units V1, V, -Vn is adjusted so that the temperature increase at each heat exchanger H1, H1, etc. becomes Δt. ~t2 is maintained at ±''t/2, therefore, the total membrane separation efficiency) Vl, V.

...V is operated around the optimum iit to, which enables the most economical separation or reduction in terms of energy and equipment.

If the above Δt is too large, αmB%Q will deviate greatly from the optimum value, and the required membrane area will increase to 1! If t% is too small, the total membrane area approaches the minimum value, and as a result, the number of stages n of membrane separation units v□, ■2-vn and heat exchangers H1, H, -H, . A large scale would actually be uneconomical. Usually Δt is 1 to 30°C, preferably 3 to 20°C
It is ℃.

- The pressure P1 on the downstream side is determined by the operability since it does not affect the membrane separation ability unless it is at a low pressure, and is usually 0 to 10kg7cm'' Gl!f.8E force P on the secondary side, In general, the smaller Q is, the larger Q becomes, and depending on the combination of membrane and liquid mixture, α also becomes larger, so it is preferable, but it is determined by taking into account the economical efficiency of condensing the permeated vapor tC1? and the decompression power cost. For example, permeated vapor of 10 parts water/90 parts ethanol is heated to 50 Torr at 20°C.
olK pressure is 150 Torr at 40℃, so if it is more economical to cool with industrial water, P
2 is 150 Torr V (it is a good idea to keep it at a maximum of 150 Torr V).

Examples of the membrane separator knit V used in the above-mentioned externally heated membrane separator include a spiral lug in which a non-porous polymer membrane is wrapped in a spiral, a plate frame filter in which a plate frame is formed by the membranes, and these are stacked one on top of the other. The most typical type is the hollow fiber type.

The hollow fiber type is 40, as shown in FIG. 2, in which a large number of hollow fibers 6 made of a non-porous polymer such as polyethylene are bundled together in a barrel 7, and i18 are provided on both sides to communicate the hollow fibers 6. Normally, the communication side is the primary side, and the raw material is press-fitted into the inlet pipe 9, and the outlet pipe 1
The vapor that passes through the membrane is extracted through the exhaust pipe 11.

Any type of heat exchanger can be used, but shells and chain tubes are usually convenient.

Furthermore, FIG. 3 is a schematic diagram showing an internal heating type membrane separation apparatus for carrying out the method of the present invention. The flow of the liquid mixture and vapor is essentially the same as in the external heat exchanger shown in Figure 1, and the same parts are given the same reference numerals. In this case, the heat exchanger H in Figure 1, H
, -, %, , h, -hn are - of the respective membrane separation units V1, V, , -V, -
Built in on the next side. The raw material liquid temperature room M from the raw material tank 10 is introduced into the downstream side of the membrane separation unit v0 via the line 11 by the pump 2. Steam rich in components that easily permeate through the membrane part □ is discharged from line d1,
The mixed liquid rich in components that are difficult to pass through w11 is supplied to the primary side of membrane separation unit v2 via line a. This is repeated in sequence, and a product with an acid concentration that is difficult to pass through the target membrane is taken out from the exit line 'n+''11. Since the primary side has a built-in heat exchanger h1% h, ・hn, the above Δt is small compared to the number of stages n, and is kept within a range close to the optimum operation ILllll!, so that external heat This enables more efficient separation compared to No. 11.

The membrane separation unit used in the above-mentioned internal heating type includes one in which a part of the hollow strip bundle is used as a heat exchanger, or one in which a plate frame is used.

A typical example is the plate frame I with a built-in heat exchange plate in lI4111! An O membrane separation unit is shown.

In the figure, 9 is an inlet pipe for the raw material mixture, 10 is an outlet pipe, and while the raw material liquid mixture passes through the negative side 91, components that are easily permeable pass through the polymer membrane and enter the secondary side 11m. Steam exhaust pipe 11XF) is led to the condenser 3. The heat medium is introduced through the heat medium introduction pipe 12, heats the mixed liquid on the primary side 91 via the heat exchange plate 14, maintains it at a predetermined temperature, and is led out through the discharge pipe 13.

Moreover, FIG. 5 is a diagram of an apparatus in which the membrane separation units v1 to vn shown in FIG. 1 or $1!3 are arranged in series, and a pigeon separator is further combined in parallel. In the above apparatus, the number of membrane separation units is nxm.

1'3 That is, V-V:V"~V 2.,,V-~v1 and n
With InIn, a membrane separation device having an arbitrary area and an arbitrary number of stages can be obtained.

Next, the present invention will be explained in more detail with reference to Examples.

Implementation Ga 1 As the membrane separator, an external heating type shown in FIG. 1 was used.

In addition, the membrane separation unit has a membrane thickness of 120μ and an inner diameter of III.
jIlψ, 50 Nafion membranes with an effective length of 405I are
It was configured and used as shown in Figure 12. Further, the heat exchanger was a stainless steel tube IS with four inner diameters wound in a spiral shape and immersed in a constant temperature bath.

The above separation units and 10 heat exchangers each are connected in series as shown in Figure 1, and the above membrane separation units) V□ to V□ are obtained. 76OTorrb secondary side to vacuum pump 4! p150TorrK was retained. In addition, heat exchanger H8~
■,. The samples were placed in a constant temperature bath at 0°C and the outlet temperature t1 of ~H1° to each heat exchanger was maintained at 65°C.

Using the above apparatus, 94wt1G of ethanol aqueous solution was put into tank 1 as raw material liquid mixture-M, and supplied to membrane separation apparatus V at a rate of 2.2 m/hour by raw material pump 2. The inlet temperature ft of each membrane separation unit V□~v1° was kept at 5°C by each heat exchange @It1~H1°, and the outlet temperature of each membrane separation unit V□~v8° was kept at 5°C. The temperature decreased by about 17 degrees Celsius and reached about 48 degrees Celsius.

In the tank Sm, an aqueous ethanol solution concentrated to 98vt is obtained at a rate of 1 #/hr, and in the condensate tank sb, 9G,'! -The condensed ethanol aqueous solution is 1-2#
It was collected at the /hrowari meeting.

Example 2 A plate frame membrane separation unit with a built-in heat exchange unit as shown in % $1411 was used as a membrane separation device. This membrane separation unit consisted of 33 Nafion membranes of 10 cm 2 and a thickness of 130 μm and 17 stainless steel heat exchanger plates of 10 clI and a thickness of 11131 μm. Also,
- Outlet pressure is 760 Torr % Outlet pressure is 50 Torr
Torr is maintained, and the vapor permeated through the exhaust membrane is transferred to the condenser 3 at a temperature of 10 Torr.
It was condensed and collected at ℃. The primary liquid temperature of the membrane separation unit is
70°C hot water was flowed through the stainless steel heat exchanger to maintain the temperature at 60°C.

When an isopropyl alcohol aqueous solution of 60 wt I6 was supplied to the membrane separator at a rate of 160 P/hr, an isopropyl alcohol aqueous solution concentrated to 82 wt% was obtained at a rate of 100 P/hr, and 23 wt% of condensed vapor was obtained. An aqueous isopropyl alcohol solution was obtained at a rate of 60 P/hr9.

Implementation fP43 The temperature of the liquid mixture on the primary side of each membrane separation unit was maintained at 40°C by flowing hot water at 50°C through the stainless steel heat exchanger plates. Nine units were operated under the same conditions as in Example 2. As a result, 76
vt Improvil alcohol aqueous solution is ll0
P/hr, and 20 vt* of isopropyl alcohol aqueous solution was condensed at a rate of Sot/hr.

Comparative Example 1 The operation was carried out in exactly the same manner as in Example 2, except that hot water was not flowed through the stainless steel heat exchanger plate, o*ii in the membrane separator was free, and the introduced Inglobil alcohol water**0 temperature was set at 60°C. Nine. As a result, from the outlet of the membrane separator, the temperature decreased to 5°C, and an aqueous solution of 965 wt % isopropyl alcohol was obtained at a ratio of 146 f/bro.
The isopropyl alcohol aqueous solution of tlG is 14 P/
Obtained in hr O proportion.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a schematic flow of an external heating lid membrane separation device, No. 21I is a diagram showing an example of a membrane separation unit used for external heating 11, and WXS is a schematic diagram of an internal heating type membrane separation device. A diagram showing the flow, Figure IIE4 is a diagram showing an example of a 7CR-type membrane separator with a plate frame, and Figure 115 is a schematic diagram when external heating or internal heating type equipment is used in parallel. - is a figure showing. 1... Raw material liquid mixture tank, 2-... Raw material pump, 3... Condenser, 4-... Vacuum pump, 51...-Tank, 5b... ...Condensate tank, 6...-Hollow fiber, 7-...Body, 8...
...Chamber with which hollow fibers communicate, 9...-Liquid mixture inlet pipe, 9a...-Next side, 10...-Liquid mixture outlet pipe, 11...-Vapor Exhaust/outlet pipe, l1m...
...Secondary side, 12...
・Heat medium inlet pipe, 13---Heat medium outlet tube%14---Heat exchange plate, A, B---Component, a, b
, d-"... line, H, h-... heat exchanger,
■・・・-The king of incorrect separation ennit,■・・・・-Membrane separation unit, T--1 Each membrane separation 2-nit polymer membrane, t-
---KL to. ...Optimum temperature, M...- Raw material liquid mixture. Applicant: Showa Denko K.K.

Claims (1)

[Claims] 19 A method for separating or concentrating a liquid mixture by a pervaporation process using a polymer membrane, in which the polymer membrane is used in multiple stages and each polymer membrane separates or concentrates the mixture. A method for separating or concentrating a liquid mixture, characterized in that the temperature of the liquid mixture oia* is adjusted to a predetermined temperature range. (2) A heat exchanger installed outside the separation device is used to adjust the temperature of the liquid mixture in the portion where the polymer membrane separates or concentrates the liquid mixture.
A method for separating or concentrating a liquid mixture according to item 1. (31 Heat exchanger 1 installed in the separation device to adjust the OAM of the liquid mixture in the part to be separated or concentrated by the polymer membrane.
Claim 1 characterized in that:
Method for separating or concentrating a liquid mixture as described in Section 1.