JPS5820293B2 - Continuous recovery method for volatile organic substances - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering volatile organic substances present in a gas.

More specifically, the present invention efficiently removes water-insoluble volatile organic substances present in a gas by using (1) a 20-37v% aqueous solution A of diethylene glycol monobutyl ether and (2) liquid paraffin B that is immiscible therewith. Regarding the method of collection.

BACKGROUND ART In recent years, large amounts of volatile organic substances have been scattered into the atmosphere, and they have become a problem as a cause of pollution.

Sources of these volatile organic substances into the atmosphere include oil storage tanks, oil refineries, petrochemical complexes, gas stations, paint factories, painting plants, printing plants, chemical plants,
Rubber factories, etc., too numerous to list.

Among them, organic solvents are consumed in large quantities in the petrochemical industry, various organic chemical industries, and related fields such as inks, paints, coatings, and printing, and a huge amount of these transpire into the atmosphere.

A large amount of volatile organic substances exist in the atmosphere, and while these volatile organic substances are a source of various types of pollution including photochemical smog, it is difficult to use resources effectively. From this perspective, the presence of volatile substances in the atmosphere is a resource recovery issue that cannot be overlooked.

As a result of intensive research into a method for continuously recovering volatile organic substances existing in the atmosphere, the inventors of the present invention have succeeded in recovering volatile organic substances using an extremely efficient and simple system. , we have completed a method that can be recycled.

Accordingly, the present invention provides an efficient method for continuously recovering water-insoluble volatile organic substances present in a gas.

The rice invention will be explained in detail below.

Conventionally, methods for recovering volatile organic substances from gases include adsorption using an adsorbent and absorption into a solution, but in both of these methods, adsorption saturation and absorption equilibrium are affected. Because of the presence of adsorbents, good adsorption and absorption can only be maintained for a relatively short period of time; therefore, in order to maintain a certain high adsorption capacity and absorption capacity, the adsorbent and absorption liquid must be replaced frequently. There were drawbacks.

For example, in the case of volatile organic substances that evaporate when materials are taken in and out of oil storage tanks, the amount of volatile organic substances that transpire is enormous, so they must be treated using the adsorption method described above. If this is attempted, a state of adsorption saturation is quickly reached, and adsorption/desorption operations such as replacing the adsorbent must be performed frequently, making it difficult to put it into practical use.

There are also wet absorption methods that use absorption liquids, but in the case of volatile organic substances, they are generally neutral substances and cannot be absorbed into so-called acidic or alkaline liquids. Since many volatile organic substances are insoluble in water, water cannot be used as an absorbing liquid, so common oils such as kerosene, spindle oil, or similar oils are used as absorbing liquids. However, the problem of absorption saturation is unavoidable, and it is extremely difficult to carry out efficient absorption continuously.

The present invention overcomes the drawbacks of such conventional methods and provides a simple and efficient recovery method.

The present invention will be explained in detail below.

In the method of the present invention, the gas containing the volatile organic substance P to be recovered is first treated with a 20-37v% aqueous solution of diethylene glycol monobutyl ether (hereinafter referred to as BDG). This is one important feature of the method of the present invention.

This BDG aqueous solution A will be hereinafter referred to as liquid A.

By the above treatment, the volatile organic substance P is dissolved in the liquid A and captured.

Next, the liquid A in which the volatile organic substance P is dissolved is brought into contact with liquid paraffin which is immiscible therewith.

This liquid paraffin has the property of being immiscible with liquid A, and the distribution coefficient PB of the volatile organic substance P with respect to this liquid paraffin is larger than the partition coefficient PA with respect to liquid A.

This liquid paraffin is hereinafter referred to as B liquid.

The combined use of Parts A and B forms a second feature of the process of the invention.

When liquid A and liquid B are brought into contact as described above, the volatile organic substance P (hereinafter referred to as substance P) in liquid A is transferred to liquid B, and liquid A immediately loses its initial absorption capacity. take it back.

This A liquid is used for circulation in order to bring it into contact with new gas.

The present inventors have developed a 20-37v% aqueous solution of BDG (liquid A).
It has been found that the substance P can be efficiently absorbed by the substance P, and that when the liquid A and the liquid B in which the substance P is dissolved are brought into liquid-liquid contact, the substance P is efficiently transferred to the liquid B.

This transition depends on the liquid composition of liquid A and the type of liquid B, but in general, when the concentration of the substance used in liquid A is high and the ratio of the amount used of liquid B is small, substance P is transferred to liquid B. The extraction rate will be lower.

Therefore, in order to remove substance P from liquid A using liquid B, which has a small usage ratio, it is better that the concentration of BDG in liquid A is low.

This is of great significance as a finding of the present inventors in the present invention.

This will now be explained with reference to FIG.

In FIG. 1, the vertical axis represents the maximum solubility of substance P (1-luene) in a BDG aqueous solution, and the horizontal axis represents the aqueous concentration (%) of BDG.

As seen in FIG. 1, the 60% BDG aqueous solution can dissolve 20m of toluene in 80TLl at 25°C.

This amount is 20v as absorption of toluene at 25°C.
This shows that toluene can be absorbed from a gas containing toluene up to a gas concentration that reaches liquid equilibrium.

Similarly, a 40v% aqueous solution of BDG has the ability to dissolve 8ml of toluene for 92 genera.

Therefore, in this case, A
It can be seen that if used as a liquid, exhaust gas of any concentration can be treated.

Looking at this relationship alone, it seems preferable that the BDG concentration in liquid A be higher as it can absorb more substance P; however, on the other hand, regardless of the content (concentration) of BDG in liquid A in dogs, Although the amount of substance P dissolved increases as the concentration increases, in terms of the extraction rate due to changes in the liquid volume ratio of liquid A and liquid B, the lower the concentration of BDG in liquid A, the lower the concentration of BDG in liquid A and liquid B. It was found that the change in quantity ratio had little effect on the extraction rate.

This will be explained with reference to FIGS. 2-4.

Figure 2 (B DG/B DG+*: 3" section (A"') Toluene maximum 7.25 v Dissolved horizontal axis Toluene concentration vertical axis Toluene extraction rate Measured at 25℃ ○...Liquid A: Liquid B 10:10 (quantity ratio) x...Liquid A:Liquid B 10:5 (quantity ratio)・△...Liquid A:Liquid B
10: 3 (amount ratio) Note: Liquid paraffin is liquid paraffin in Figure 3 (BDG/BDG+7k: 29). Toluene maximum 4.28v% dissolved at 25℃. is the same as Figure 2.

Figure 4 BDG/BDG Jusui: 20v% (T...maximum 0.7% dissolved) Measured at 25°C Horizontal axis, vertical axis, ○, ×, △ are all the same as Figure 2 Figure 2 This is a graph in which toluene was absorbed using a 37 v% BDG aqueous solution, and the extraction rate of toluene was measured for a toluene-containing absorbed BDG aqueous solution in which toluene was dissolved up to a maximum of 7.25 v%.

The extraction rate of toluene is plotted on the vertical axis, and the toluene concentration in the 37v% BDG aqueous solution (a value calculated using the saturation concentration of toluene as a factor of 100) is plotted on the horizontal axis.

Figure 3.4 shows B,! ') The % of G/BDG+water and the maximum amount of toluene dissolved are shown in the same way as in FIG. 2, with the toluene extraction rate on the vertical axis and the toluene concentration in the BDG aqueous solution on the horizontal axis.

As can be seen from these figures, the higher the concentration of BDG, the more significant the decrease in the extraction rate when lowering the amount of liquid B relative to liquid A, and the lower the concentration of BDG, the lower the The drop in extraction rate when lowering the liquid volume is extremely small <20v%
When it gets close to this point, there is almost no change in the extraction rate due to a decrease in the amount of liquid B.

This means that in the method of the present invention, when the concentration of BDG in liquid A is reduced, even though the amount of substance P dissolved decreases, the extraction rate remains the same when the amount of liquid B is reduced. This means that the advantage of being able to efficiently recover the substance P can be obtained.

The method of the present invention will be explained in detail based on one embodiment using FIG. 5.

Air containing 140 ppm of toluene (substance P)10
0 m''/min (at room temperature) is guided into the absorption tower 1 from the bottom of the tower by a blower 2.

From the top of the absorption tower (-!-// rack ring packing), B
A 35v% aqueous solution of DG (liquid A) is supplied at a rate of In' per minute at a liquid temperature of 20° C. using the liquid circulation pump 3, and brought into gas-liquid contact.

The BDG aqueous solution (liquid A) dissolves and absorbs toluene from the gas, is discharged from the bottom of the tower, and is collected in a liquid reservoir 4.

Brine 5 is provided for cooling the A liquid.

Brine 5 is used when it is necessary to adjust the temperature of liquid A that has absorbed substance P.

The BDG aqueous solution (liquid A) in which toluene (substance P) is dissolved is led from the liquid reservoir 4 to the recovery tower 6 .

In this recovery tower 6, liquid B for extraction and recovery (liquid paraffin)
is brought into liquid-liquid contact with the above BDG aqueous solution (liquid A).

Through this recovery tower, toluene (substance P) is transferred into liquid paraffin (liquid B).

Liquid B is stored in a liquid reservoir 7 and sent to a recovery tower 6 by a pump 8.

The above-mentioned BDG solution (liquid A) has its absorption capacity regenerated by contact with this liquid B, and is returned to the absorption tower 1 from the liquid reservoir 10 by the pump 9.

The concentration of toluene in the bath log gas from absorption tower 1 was 7 ppm, indicating a removal rate of 95%.

Liquid A in the liquid reservoir 4 can be circulated and used in the absorption tower 1 by the pump 3 until its absorption capacity is reduced.

The method for recovering the substance P from the B liquid in the liquid reservoir 7 is carried out by a conventional method for separating a dissolved substance and a solution.

In this case as well, the liquid can be recycled in the liquid recovery tower 6 until the absorption capacity of liquid B decreases.

The above-mentioned absorption tower 1 may be any type of absorption tower normally used in gas-liquid contact, such as a packed tower, a spray tower, or a liquid film base.

The target removal rate is set in advance according to the purpose of removing volatile organic substances P in the gas to be treated that is sent to the absorption tower, and the amount of air flow, gas temperature, and liquid A are adjusted according to the concentration of the substance P in the gas. ,
The type of B liquid, gas to human liquid, volume ratio of A liquid to B liquid, etc. can be selected.
It is determined.

Furthermore, one feature of the method of the present invention will be explained with reference to FIG.

In FIG. 6, the vertical axis represents the concentration of BDG in the BDG aqueous solution (liquid A), and the horizontal axis represents the extraction rate of toluene (substance P).

Figure 6 shows the usage ratio of liquid A: liquid paraffin B (liquid paraffin). Ai B liquid X...10:10 0...10:5 △...10:3 It is shown by .

According to Figure 6, in an aqueous solution of BDG with a coefficient of 80, the extraction rate of toluene is about 30 to 60;
The zero coefficient aqueous solution shows a value of 90% or more, and the value shows that there is almost no difference depending on the usage ratio of liquid B to liquid A.

This means that it is possible to efficiently recover substance P using a small amount of liquid B, and B
This means that it can be recovered from the liquid.

Therefore, the energy required for its recovery is much saved, ranging from a few minutes to several tens of minutes compared to direct recovery.
Energy savings can be achieved in units of .

As explained in detail above, the method of the present invention includes the following steps: (1) A 20-37v% aqueous solution of BDG is used as the treatment liquid that comes into first contact with the gas containing the volatile organic substance P to be recovered. ■ For liquid A containing substance P,
Liquid paraffin (
This is characterized by the fact that substance P is transferred to liquid B by contacting liquid B), and as a result, 1) substance P can be transferred extremely efficiently using a relatively small amount of liquid B. It can be recovered.

2) Since liquid A is an aqueous solution, it is extremely difficult and complicated to process and operate. 3) Liquid A can be used in circulation, and liquid B can also be circulated, so continuous operation can be easily performed. 4) The whole system is extremely simple and efficient. 5) It can be used for the purpose of pollution prevention and resource saving.

It offers many advantages such as:

[Brief explanation of drawings]

Figures 1 to 6 are all diagrams for explaining the present invention. Figure 1 is a graph comparing the BDG concentration in a BDG aqueous solution and the concentration of toluene dissolved in it, and Figures 2 to 4 are graphs comparing toluene dissolved in it. For BDG aqueous solutions of various concentrations,
A graph showing the comparison between the extraction rate of toluene and the maximum concentration of toluene dissolved when it comes into contact with liquid paraffin. Figure 5 is a diagram of a flow sheet showing an embodiment of the present invention. Figure 6 is a graph showing the comparison between the extraction rate of toluene and the maximum concentration of toluene dissolved when it is brought into contact with liquid paraffin. It is a graph comparing the BDG concentration of the BDG aqueous solution and the toluene extraction rate with liquid paraffin.

Claims (1)

[Claims] 1 A method for recovering a water-insoluble volatile organic substance present in a gas, in which a gas containing the volatile organic substance P is first mixed with a 20 to 37 v% aqueous solution A of diethylene glycol monobutyl ether and a gas- The volatile organic substance P is dissolved and captured in the aqueous solution A by liquid contact, and then the aqueous solution A after the gas-liquid contact is brought into liquid-liquid contact with liquid paraffin B which is immiscible therewith. The volatile organic substance P is converted into this liquid paraffin B by
Then, the above aqueous solution A after this liquid-liquid contact is recycled to be brought into contact with a new gas containing the volatile organic substance P, and on the other hand, the above-mentioned liquid-liquid A continuous method for collecting volatile organic substances in gas, which consists of recovering volatile organic substances P from liquid paraffin B after contact.