JPS60174736A - Method for concentrating alcohol - Google Patents

Abstract

PURPOSE:To separate and concentrate effectively an alcohol from an aqueous solution of the alcohol to the permeated water side at a relatively low energy cost, by feeding the aqueous solution of the alcohol containing a soluble organic substance other than the alcohol to a reverse osmosis membrane of relatively low desalination ratio under pressure. CONSTITUTION:An alcohol is separated and concentrated from an aqueous solution thereof 2. In the process, a soluble organic substance 3, e.g. raffinose or lactose, other than the alcohol is present in the above-mentioned aqueous solution 2, which is fed to a reverse osmosis membrane 5 of <=90%, preferably 10- 80% desalination ratio under preferably <=20kg/cm<2> pressure to separate and concentrate the alcohol 6 on the permeated water side. The alcohol can be concentrated under a lower pressure by this method than by the well-known method, and this method is advantageous to energy cost. The unpermeated water side 7 is circulated, and a concentrated solution of the alcohol 6 is obtained on the permeated water side. Thus, the recovery ratio of the alcohol is high, and an aqueous solution of a lower alcohol in a low concentration at which the distillation method cannot be applied can be concentrated to a concentration at which the distillation method is applicable at a low cost.

Description

Detailed Description of the Invention The present invention relates to a method for concentrating alcohol, and in particular to a method for concentrating alcohol from a relatively low concentration aqueous solution of a lower alcohol such as methanol or ethanol. The aim is to effectively concentrate alcohol with relatively low energy using a osmotic membrane. Distillation has traditionally been used to recover alcohol from an aqueous alcohol solution. The distillation method utilizes the difference in boiling point between alcohol and water to recover alcohol, and is an effective method for recovering alcohol from a relatively high concentration aqueous alcohol solution. However, in the case of an alcohol aqueous solution with a relatively low concentration, such as an alcohol concentration of 5% or less, a large amount of thermal energy is required, which has the disadvantage that it is not industrially profitable. Therefore, in recent years, attempts have been made to use reverse osmosis membranes to recover alcohol from relatively low concentration alcohol aqueous solutions.

In other words, for example, an alcohol aqueous solution is supplied under pressure to a reverse osmosis membrane device, the alcohol aqueous solution is circulated to the non-permeated water side, the passage of alcohol is blocked by the reverse osmosis membrane, water is removed on the permeated water side, and the non-permeated water is removed. The purpose is to obtain a concentrated alcohol solution on the permeate side.

However, this method also has various drawbacks as described below.

In other words, the types of reverse osmosis membranes that can be applied to this method are limited (for example, PE0-1000 manufactured by Toshi ■), and the operating pressure of the membrane is relatively high at 5 ok/cr6 or higher, so although it is not advantageous in terms of energy costs, it is do not have.

Furthermore, since the alcohol aqueous solution is circulated to the non-permeated water side and the alcohol concentration of the circulating liquid is gradually increased, there is also a drawback that concentration takes time.

Furthermore, the behavior of lower alcohols, such as methanol and ethanol, and water in a membrane is generally similar.Therefore, even if a membrane is used that can concentrate alcohol on the non-permeated water side, there will still be a relatively large amount of alcohol on the permeated water side. It has the disadvantage that the recovery rate of alcohol is low because it permeates through the water.

In view of this, the present inventors have investigated various methods of concentrating alcohol at low cost using reverse osmosis membranes. - Allowing soluble organic substances other than alcohol to coexist in the alcohol aqueous solution. When supplied to the permeable membrane under pressure,
It has been found that alcohol can pass through the reverse osmosis membrane more easily and therefore alcohol can be concentrated on the permeate side, and that the alcohol concentration on the permeate side becomes higher when the operating pressure during the permeation treatment is lower.

The present invention is based on the above-mentioned findings.In separating and concentrating alcohol from an aqueous alcohol solution, the aqueous solution is coexisted with soluble organic substances other than alcohol, resulting in a desalination rate of 90%.
The present invention relates to a method for concentrating alcohol, which is characterized in that alcohol is separated and concentrated on the permeated water side by supplying the following to a reverse osmosis membrane under pressure.

The present invention will be explained in detail below.

Concentration of alcohol using conventional reverse osmosis membranes concentrates alcohol on the non-permeated water side, but in the present invention, soluble organic substances other than alcohol coexist in an alcohol aqueous solution and are supplied to the reverse osmosis membrane under pressure.・Alcohol passes through the reverse osmosis membrane! Alcohol is concentrated on the permeated water side; this point is different from conventional methods.

When a soluble organic substance other than alcohol coexists in an alcohol aqueous solution, the reason why alcohol passes through the reverse osmosis membrane more easily is probably because the water molecules in the aqueous solution have a strong affinity for the coexisting organic substances. It is presumed that this is because it accompanies organic matter. In other words, when a soluble organic substance coexists in an alcohol aqueous solution, there are alcohol molecules, dissolved organic substance molecules, and water molecules in the aqueous solution, but when the aqueous solution is supplied to a reverse osmosis membrane under pressure, the organic molecules are absorbed by reverse osmosis. The water does not pass through the membrane and remains on the non-permeate side. On the other hand, alcohol molecules and water molecules originally have the property of easily passing through a reverse osmosis membrane, but as mentioned above, water molecules have a strong affinity for organic matter molecules, so water molecules accompany organic matter, and the permeation of water molecules becomes difficult. This is thought to be the reason why it is relatively easier for alcohol molecules to pass through the reverse osmosis membrane.

Although the above effects are just speculations, when an aqueous solution of a lower alcohol such as methanol or ethanol is permeated through a reverse osmosis membrane, when soluble organic matter is not allowed to coexist, the alcohol tends to be concentrated in the non-permeated water side. However, it is true that alcohols and alcohols can be reliably concentrated on the permeate side if soluble organic substances are present.

The soluble organic substance used in the present invention can be anything other than alcohol, as long as it is a relatively high molecular weight substance that is difficult to pass through a reverse osmosis membrane, and has a high solubility in water.For example, rough nose p
Lactose, glucose, fructose, sucrose = each 8 amino acids, sodium diethylenediaminetetraacetate (HD
TA-4Na) etc. can be used. In general, the larger the amount of the soluble organic substance dissolved, the greater the alcohol permeability.9 Usually, the soluble organic substance is dissolved in the alcohol aqueous solution to a concentration of 5% (wt%) or more.

In addition, if the alcohol aqueous solution to be treated originally coexists with the above-mentioned soluble organic substances, if the amount present is sufficient, then this is the case! If the amount of soluble organic matter present is insufficient, the insufficient amount of soluble organic matter may be additionally dissolved and the permeation treatment may be performed.

In short, in the present invention, the object of the present invention can be achieved if a predetermined soluble organic substance coexists in the alcohol aqueous solution.

In the present invention, the above-mentioned soluble organic substances are allowed to coexist in an alcohol aqueous solution for permeation treatment, but inorganic salts such as IJium and sodium sulfate are coexisting at least 3% (by weight). It is possible to concentrate alcohol on the permeated water side even if

However, inorganic salts permeate through reverse osmosis membranes more easily than organic substances, so in order to obtain an alcohol concentrate with low impurity content, it is necessary to use a reverse osmosis membrane with a high desalting rate. Furthermore, when inorganic salts are dissolved, the osmotic pressure of the liquid becomes too high, and therefore the operating pressure for permeation treatment must be made high, and the permeation flow rate also decreases considerably. Therefore, the objective of the present invention, which is to effectively concentrate alcohol at low energy cost, cannot be achieved.

On the other hand, when using soluble organic substances, the organic substances themselves do not pass through the reverse osmosis membrane, and the osmotic pressure does not become so large.・A reverse osmosis membrane with a low salt removal rate can be used.・Even if the operating pressure is relatively low. The permeation flow rate can be increased and the processing time can be shortened.

Next, the reverse osmosis membrane used in the present invention will be explained below.

The reverse osmosis membrane used in the present invention has a desalination rate (1000 to 5000)
A sodium chloride solution with a sodium chloride removal rate ts) of 90eI6 or less is used.

That is, if a reverse osmosis membrane with a salt removal rate of 90% or more is used, the operating pressure for permeation treatment must be increased, which increases energy costs, which is undesirable, and as shown in the examples, the alcohol concentration ratio is also undesirable.

Note that the operating pressure can be lowered by using a reverse osmosis membrane with a lower salt removal rate; however, if the salt removal rate is less than 10%, coexisting organic matter will permeate to the permeate side, and the present invention Preferably, the desalination rate is 1 because it will not be possible to achieve the purpose.
It is preferable to use a 0 to 80 inch reverse osmosis membrane.

Examples of reverse osmosis membranes used in the present invention described above include G-51G-10 and G-20 (both trade names) manufactured by Desalination Co., Ltd., and NTIL-7250+ manufactured by Nitto Denko ■.
N'll'R1550+ (all product names) Sollox 5C-5000+ 8O-eooo manufactured by Sumitomo Chemical ■
(all are product names).

Next, to explain the operating pressure for permeation treatment in the present invention, in the present invention, performing permeation treatment at too high a pressure is not preferable as it will only unnecessarily increase energy costs! The permeation treatment is usually carried out at a pressure of 40 kg/crll or less, but as shown in the examples, the lower the operating pressure, the higher the concentration ratio of alcohol, so it is preferable to perform the permeation treatment at an operating pressure of 20 kg/ai or less.

Embodiments of the present invention will be described below with reference to the drawings.

The drawing is an explanatory diagram showing the flow of the present invention. ・Receive alcohol aqueous solution 2 in stock solution tank 1 ・Dissolve soluble organic matter 3 other than alcohol in the container ・The solution is transferred to reverse osmosis membrane device 5 under pressure by pump 4 supply By such an operation, the alcohol in the solution passes through the reverse osmosis membrane, and an alcoholic liquid 6 with a higher alcohol concentration is obtained on the permeated water side. On the other hand, the non-permeated water contains the added soluble organic matter and residual alcohol, and by circulating this to the raw water tank 1 and continuing this circulation permeation, a concentrated alcohol solution is collected from the permeated water side. do.

Since the soluble organic matter 3 added to the stock solution tank 1 remains in the stock solution tank 1 as a concentrated solution in the latter half of the permeation treatment, the soluble organic matter can be recovered and used by, for example, adding the alcohol aqueous solution 2 again. It is also possible to dissolve the soluble organic matter again in the alcohol solution 6 obtained from the permeated water side and perform the permeation treatment once again. In this way, if you re-concentrate the alcoholic liquid once concentrated, you can obtain an alcoholic liquid with a higher concentration.

- If the membrane treatment is not satisfactory, the above-mentioned multi-stage treatment may be performed at any time.

As explained above, the present invention can concentrate alcohol at a lower pressure than the conventional reverse osmosis membrane device, is advantageous in terms of energy cost, and circulates through the non-permeated water side. Since the alcohol concentrate is obtained on the water side, it has the advantage of a high recovery rate of alcohol.

Therefore, it is possible to concentrate low-concentration aqueous solutions of lower alcohols such as methanol and ethanol, to which distillation methods cannot be applied conventionally, at low cost to a concentration where distillation methods can be applied. By using it for pre-treatment, it is possible to effectively recover low-concentration alcohol aqueous solutions, which until now had to be discarded by going through extra operations such as biological treatment.The present invention brings great benefits to industry.

Examples will be described below to make the effects of the present invention more clear.

Note that the present invention is not limited to the following examples.

Example-1 A low salt removal rate reverse osmosis membrane G-5 made by Desalination Co., Ltd. with a diameter of 5 G'llQ and a salt removal rate of 60 to 70 inches and a high salt removal rate reverse osmosis membrane made by UOP Co., Ltd. with a salt removal rate of 99 inches or more. Insert the membrane PA-300 into a flat membrane tester, use a 10% ethanol aqueous solution as the liquid to be treated, and add 10% each of raffinose and lactose (wt%).
) and apply the solution at a pressure of 15 kg/d.
・It was supplied to the flat membrane tester under pressure at a temperature of 25° C., and while the non-permeated water was circulated, ・the alcohol solution was recovered from the permeated water side.

On the other hand, for comparison, the same alcohol aqueous solution that does not dissolve any soluble organic substances such as raffinose and lactose was also permeabilized under the same conditions. Table 1 shows the alcohol concentration of each permeate water. In the table, 0 indicates the concentration ratio of the alcohol concentration on the permeated water side to the alcohol concentration on the non-permeated water side.

Table 1) Example-2 A flat membrane tester was used for an ethanol 2-containing aqueous solution for reverse osmosis membrane G-5 made by Desalination Co., Ltd. and PA-300 made by UOP Co., Ltd., which had the same diameter of 5 ann as used in Example-1. The permeation treatment was carried out in the same manner as in Example-1. The operation was carried out at four different operating pressures: 10, 20+so, and 4okg/c111. ED'I'A-4N a was used as the soluble organic substance to be added. This was added to each ethanol aqueous solution at a concentration of 20 dino (wt%). It was dissolved as follows.

These results are shown in Table 2. In addition, in the table, 0 indicates the concentration ratio of the alcohol concentration of permeated daffodil to the alcohol concentration of non-permeated daffodil.

Table 2 Operating temperature 25℃

[Brief explanation of the drawing]

The drawing is an explanatory diagram of a flow showing an example of an embodiment of the present invention.L is a stock solution tank, 2 is an alcohol aqueous solution, 3 is a soluble organic substance, 4 is a pump, 5 is a reverse osmosis membrane device, 6 is an alcohol solution, and 7 indicates non-permeable water.

Claims (1)

[Claims] (11) In separating and concentrating alcohol from an alcohol aqueous solution - Allowing the aqueous solution to coexist with soluble organic substances other than alcohol - Supplying under pressure to a reverse osmosis membrane with a low salt removal rate of 90% or less A method for concentrating alcohol characterized by separating and concentrating the alcohol on the permeate side. (2) Supplying the alcohol to the reverse osmosis membrane at a pressure of 20 kg/aM or less according to claim 1. Concentration method.