JPH02184319A - Method for recovering gaseous organic solvent - Google Patents

Abstract

PURPOSE:To reduce the cost of maintenance and control required to treat raw gas by feeding carrier gas mixed with an aq. ammonia soln. into an adsorber in which an org. component has been adsorbed on activated carbon, desorbing the org. component and carrying out liquefaction and recovery. CONSTITUTION:At least the org. component of a gaseous org. solvent is adsorbed on activated carbon in an adsorber 13. Carrier gas 20 mixed with an aq. ammonia soln. or gaseous ammonia is fed into the adsorber 13 and the org. component adsorbed on the activated carbon is desorbed with the carrier gas 20. This carrier gas 20 contg. the desorbed org. component is discharged from the adsorber 13 and liquefied. An org. solvent phase 70 is then separated from an aq. phase 60 and recovered. The cost of maintenance and control required to treat raw gas can be reduced without requiring large-scale subsidiary treating facilities such as neutralizing and purifying apparatus and the production of secondary impurities by neutralization is prevented.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an organic solvent gas recovery method using an adsorption device equipped with activated carbon, and more specifically, it eliminates the need for neutralization and stabilization treatment of the recovered solvent. This paper relates to an organic solvent gas recovery method.

(Prior art) Conventionally, manufacturing processes for magnetic tapes, dry film forming, dry spinning, paints, etc. have generated organic solvent gases that are undesirable for the working environment, and organic solvent gases have been generated during dry cleaning, metal degreasing, etc. A solvent is used, and organic solvent gas is generated during the process, and for subsequent treatment, a recovery method called the activated carbon adsorption method, in which the organic solvent is adsorbed using activated carbon, is usually used.

In this activated carbon adsorption method, for example, as shown in FIG. activated carbon layer) 14a or 14b
One side of the two activated carbon storage chambers 13a and 13b having
In this case, it is transferred to step 13a) and adsorbed. The gas from which organic components have been removed is then released into the atmosphere. In this way, organic components are adsorbed, and the adsorption device 1
3 is for example 2 so that the adsorption process can be alternated continuously.
At least three activated carbon storage chambers 13a113b are provided. That is, during the adsorption process in the activated carbon storage chamber 13a, the organic component already adsorbed on one of the activated carbon layers 14b is desorbed (hereinafter also referred to as "desorption j"), but at this time, the activated carbon layer +3b At the same time, a carrier gas 20 such as steam, nitrogen gas, or air is introduced into the activated carbon storage chamber 13b, and the organic components attached to the activated carbon Fj 13b are desorbed by the carrier gas 20. At the same time, the carrier gas 20 taken out is taken out of the adsorption device 13.
The liquid is sent out through a pipe 30, cooled in a condensing cooler using cooling water 40, etc., and condensed and liquefied.
9 and is separated into an organic solvent phase and an aqueous phase, and is sent to waste liquid water 60 and recovered organic solvent 7 by a liquid sending pump 21 or 22.
Take out 0. Note that the two activated carbon storage chambers 13a and 13b of the adsorption device 13 are used properly by a plurality of valves 12a, 12b, 15a, l5b,
16 a, 16 b, l 7 a17b
This can be done by appropriate operations. Further, in the drawings, the open state of the valve is shown in white, and the closed state is shown in black.

During recovery as described above, the carrier gas 20 is usually
The condensate contains impurities such as organic acids, inorganic acids, and peroxides produced by the catalytic action of activated carbon and the unique properties of organic solvents, leading to deterioration in the quality of the recovered solvent.

Therefore, in the prior art, the condensed liquid of the carrier scum 20 is transferred to a tank 26 with an agitator through a pipe 51 (indicated by a solid line).
, the sodium hydroxide aqueous solution diluted in the alkaline water tank 24 is sent into the neutralization/purification device 23 which is composed of an alkaline water tank 24 and the like, and the p+-+ of the tank 26 is measured. The condensate was neutralized and stabilized by adding an appropriate amount and stirring as appropriate, and then sent to the liquid storage tank (decanter) 19.

Therefore, in order to successfully implement the conventional method, in addition to the N absorbing device 13 equipped with activated carbon, large-scale auxiliary treatment equipment such as the neutralization and purification device 23 is required, and its maintenance and management are necessary. , which cost a lot of money.

In addition, some organic solvents hydrolyze with strong bases such as sodium hydroxide, causing a so-called saponification reaction and producing secondary impurities, so equipment to further process secondary impurities was required. .

(Object of the Invention) The object of the present invention was made in view of the above circumstances, and it is possible to reduce the maintenance and management costs required for the raw gas processing without requiring large-scale auxiliary processing equipment such as the neutralization and purification equipment. It is an object of the present invention to provide an effective organic solvent gas recovery method that does not peel off and does not generate primary impurities due to neutralization treatment.

(Structure of the Invention) The above-mentioned object of the present invention is to provide an organic solvent gas recovery method in which at least an organic component of an organic solvent gas is adsorbed and recovered by an adsorption device equipped with activated carbon, in which the activated carbon has already adsorbed the organic component. A carrier gas to which ammonia water or ammonia gas has been added in advance is supplied to the activated carbon, the organic component adhering to the activated carbon is desorbed by the carrier gas, and the carrier gas containing the desorbed organic component is adsorbed. This is achieved by an organic solvent gas recovery method that is characterized by taking it out from the device, liquefying it, and separating and recovering it into an organic solvent phase and an aqueous phase.

(Embodiments) Hereinafter, embodiments of the present invention will be described based on the drawings. FIG. 1 is a schematic diagram of a raw gas processing facility for carrying out the method of the present invention.

In FIG. 1, raw waste 10 is transferred from an organic solvent gas generation source through a duct or the like, is blown with increased pressure by a raw gas blowing fan 11, and is sent to an activated carbon storage chamber +38 of an adsorption device 13 via a suction valve 12a. sent. In this adsorption step, most of the organic components in the raw gas 10 are adsorbed, and the treated residue free of organic components is discharged into the atmosphere via the exhaust valve 15a.

On the other hand, in the activated carbon storage chamber 13b of the other chamber of the adsorption device 13, the activated carbon layer 14b that has already adsorbed organic components is desorbed by the steam carrier gas 20 flowing in through the suction valve 16b, or The difference between the method according to the present invention and the conventional method described in FIG.
There are three steps in the process of removing organic components.

That is, ammonia (liquid) stored in an ammonia tank for 2 days is injected into the activated carbon storage chamber 13b having the activated carbon layer 14b on which organic components are adsorbed, and the ammonia liquid is vaporized by the temperature of the vapor gas. Organic components are desorbed by the carrier gas 20 which has become alkaline. Note that ammonia in the ammonia tank 28 is supplied by a liquid feed pump 31 via a regulating valve 29. The regulating valve 29 is controlled by a controller 33 based on a pt-+ meter 32 disposed inside the decanter 19 to control the valve opening degree.

Further, although not shown, an ammonia gas cylinder may be connected instead of the ammonia tank 28, and the ammonia sludge may be press-fitted into the adsorption device 13. In this case as well, the control valve 29, pH meter 32 and controller 33 are of course provided in the same manner.

Note that both activated carbon storage chambers +3a of the adsorption device 13,
In +3b, the adsorption and desorption steps are performed alternately, so that the raw waste processing equipment can be used efficiently.

The carrier gas 20, which has become a mixed gas containing organic components, is taken out from the adsorption device 13 via the exhaust valve 17b1 piping 30, as in the conventional case, and sent to the condensing cooler 18, whereupon the carrier gas 20 is condensed and cooled. It is cooled and liquefied by the cooling water 40 passing through the vessel 18. Thereafter, the mixed liquid containing organic components is supplied through a pipe 50 to a continuous decanter 19 having continuous tanks, where it is separated into an organic solvent phase and an aqueous phase due to the difference in specific gravity. The waste water 60 and recovered solvent 70 are taken out by pumps 21 and 22. The recovered solvent 70 obtained by the equipment using the present invention can be reused as is without any inconvenience. This means that
Conventionally, the catalytic action of activated carbon at high temperatures increases the acidity, making it impossible to reuse it as it is, so either neutralization or purification treatment was separately performed to improve quality. Equipment such as the sum/refining device 23 becomes unnecessary. Furthermore, since the mixed liquid containing an organic component as well as an ammonia component is not an acidified aqueous solution as in the conventional method, it can also have the effect of reducing the problem of corrosion of equipment such as piping.

The embodiment of the present invention is not limited to that shown in FIG. 1, and it goes without saying that the adsorption device 13, the condensing cooler 18, the decanter 19, etc. can be modified as appropriate. For example, the adsorption device 13 can be said to be a fixed bed activated carbon adsorption device, but the present invention is also applicable to a moving type moving bed activated carbon adsorption device and a fluidized bed activated carbon adsorption device.

Further, as the carrier gas, instead of steam gas as in the above embodiment, a non-condensable gas such as nitrogen gas or air, which is not very high temperature, may be used. In this case, ammonia water is added to the gas. It is desirable to vaporize the ammonia water by indirect heating and inject it into the carrier gas.

(Effects of the Invention) As described above, the method of the present invention involves supplying a carrier gas to which ammonia water or ammonia gas has been added in advance into an adsorption device that has already adsorbed activated carbon or organic components;
The organic component attached to the activated carbon is desorbed by the carrier gas, and the carrier gas containing the desorbed organic component is taken out from the adsorption device and liquefied, and is separated and recovered into an organic solvent phase and an aqueous phase. Therefore, there is no need for separate incidental equipment for neutralization and stabilization treatment as in the past. This eliminates equipment costs, operating costs, and maintenance costs, resulting in significant cost reductions. Further, according to the present invention, since an acidified aqueous solution is not poured as in the conventional method, oxidation corrosion of the equipment can be reduced, and equipment life and maintainability can be improved.

Furthermore, ammonia added to the carrier gas is a weak base, and therefore does not generate secondary impurities, and the pH value of the separated waste water can be set close to neutral, and can be discharged as is.

Further, a part of the ammonia added to the carrier gas remains adsorbed on the activated carbon. As a result, this ammonia acts as a stabilizer when adsorbing organic solvent gas and organic components in the adsorption process, and it also acts as a stabilizer when adsorbing organic solvent gas and organic components. It is also possible to suppress the amount of impurities produced.

(Example) Hereinafter, the effects of the present invention can be further clarified by examples.

(Example 1) Raw gas was processed using the equipment shown in FIG. 1 under the following conditions. The results and recovered solvent quality are shown in Table 1. In addition, this example No. and 3 in Table 1 are shown, respectively.

Table 1 Note that the acid value of the recovered solvent is based on the acid value measurement method in JIS K1511. In addition, in the comparative example shown as No. 2, by adding 1% NaOH, butyl alcohol 1
5 ppm was detected. This indicates that because a strong base was added to butyl acetate, a so-called saponification reaction occurred and impurities were produced. Therefore, by repeatedly reusing this recovered solvent, the impurities accumulate in the recovered solvent and become highly concentrated, so that it is necessary to separate and remove them by purification treatment (distillation separation).

As is clear from the above results, according to the method of the present invention shown in No. 3+ 4, the recovered solvent was different from the case where aqueous ammonia was injected in the acid value chart 1 to the case No. 4 of the present example.
Similarly, in FIG. 1, the results are shown when ammonia gas is injected under pressure.

(1) Raw gas and adsorption conditions-1 Raw gas N 100 Nm3/m1n
2) Organic solvent gas name Butyl acetate 3 Organic solvent gas concentration L350ppρm (vol) 4) Raw gas temperature 30°C5) Adsorption time
60 minutes (2) Desorption conditions 1) Desorption steam N 230 kg/Hr-
2) Desorption time: 60 minutes (Comparative example-1) Two examples of this comparative example were conducted under the same conditions as in the previous example except for the following. The results are shown in Table 1. In addition, Comparative Example No. 1 listed in Table 1 is a case where the neutralization/purification treatment shown in FIG. 2 is not performed, and Comparative Example No. 2 is a case where the neutralization/purification treatment shown in FIG. 2 is performed. Since it can be kept to a low level, it can be fully reused. Furthermore, since the pH value of the waste water can be made close to neutral, it can be discharged as waste water.

(Example-2) Using the equipment shown in FIG. 1, raw waste was treated under the following conditions. The results and recovered solvent quality are shown in Table 2. In addition, Example No. 3 in Table 2 shows the results when ammonia water was injected in Fig. 1, and Example No. 4 shows the results when ammonia gas was injected under pressure in Fig. 1. It shows.

(1) Raw gas and adsorption conditions-1) Raw residue amount 2) Organic solvent gas name 150 Nm3/m1n 1, I, I-1-lichloroethane 1, 200ρρm (vol) 30°C 60 minutes Organic solvent gas concentration Raw gas Temperature, adsorption time, desorption conditions, amount of desorbed vapor: 320 kg/Hr 2) Desorption time: 60 minutes (Comparative Example-2) Two comparative examples were conducted under the same conditions as in the previous example except as described below. The results are shown in Table 2. Note that No. 1 in Table 2 indicates the case where the neutralization/purification treatment shown in FIG. 2 was not performed, and No. 12 indicates the case where the neutralization/purification treatment shown in FIG. 2 was performed.

Table 2 The acid value of the recovered solvent is based on the acid value measurement method in JIS K1511. In addition, since the organic solvent used in this example has a specific gravity greater than 1, it is separated into an organic solvent phase and an aqueous phase in a decanter. , ・Ammonia tank, ・Adjusting valve, 50.51 ・Piping, ・pH meter, 33 ・Controller, ・Waste liquid water, 70 ・Recovered solvent.

In this example, the treatment by the gas recovery method of the present invention suppresses the oxidation value of the recovered solvent and lowers the oxidation value of the recovered solvent. It can be seen that the pH value of the waste water is also adjusted to the appropriate level.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of raw gas processing equipment for carrying out the method of the present invention. Codes in the figure: 10...12a. b11 3... 3a, a s 8... 9... 20... Figure 2 shows the conventional raw waste processing equipment...Blower fan, 15b, 16a+ 1...Valve, Raw gas, 11 +2b, 15a . 7a, 17b... Adsorption device, +3b... Activated carbon storage chamber, 14b... Activated carbon layer, - Condensing cooler, - Continuous tank bottom decanter - Carrier gas, 2133... Liquid sending pump,

Claims (1)

[Claims] In an organic solvent gas recovery method in which at least an organic component of an organic solvent gas is adsorbed and recovered by an adsorption device equipped with activated carbon, ammonia water or ammonia gas is added in advance into the adsorption device in which the activated carbon has already adsorbed the organic component. The organic component adhering to the activated carbon is desorbed by the carrier gas, and the carrier gas containing the desorbed organic component is taken out from the adsorption device and liquefied, and is combined with an organic solvent phase. An organic solvent gas recovery method characterized by separating and recovering the gas from an aqueous phase.