DE3316062A1 - Process for eliminating solvents from waste waters - Google Patents

Abstract

In a process for the recovery of solvents from air, the solvent is adsorbed on activated charcoal and desorbed again by means of steam, after which the steam/solvent mixture is condensed and is separated into a solvent phase and an aqueous phase. The essence of the invention comprises first freeing the aqueous phase from residual solvent by stripping in a column using the steam which is intended for the desorption of the solvent from the activated charcoal filter. All parts of the apparatus at risk of corrosion are composed of borosilicate glass.

Description

Description:

The present invention relates to a method for removing Solvent residues from wastewater produced during the adsorptive recovery of solvent vapors arise from air.

It is known that in workshops where solvents, in particular chlorine-containing, such as z.fl. Trichlorethylene is worked, the solvent-based Air must be extracted. Before it is released into the environment, this air must cleaned of the solvent vapors. This is done in an advantageous manner by means of activated carbon filters. The activated carbon adsorbs the solvent vapors; the Air freed from them flows out into the environment.

Such a method is for example in DE-OS 29 09 030 described.

When the capacity of the activated carbon is exhausted, the air flow stops directed to the activated charcoal filter connected in parallel and the loaded filter switched off.

With saturated or superheated steam the solvent becomes desorbed from the activated carbon; a mixture of water vapor and solvent vapor is created, which is condensed in a cooler. The condensate is in a separator in which, thanks to the different densities, two phases diverge from each other separate.

One phase is the solvent, in which a small proportion is dissolved in water. It will be put back into use.

The other phase is water, in which small amounts of solvent and its decomposition products are. This sewage is chemically aggressive and must not enter the sewer for reasons of environmental protection be directed. Therefore one strives to make it the adsorption system in the circuit to feed again. However, this has the disadvantage that the evaporator due to corrosion is at great risk and the solvents still contained in the water as a result of longer dwell time at high temperature decompose more strongly.

The aim of the present invention is to overcome these drawbacks.

This aim is achieved with a method according to the claims.

With the method according to the invention it is achieved that the in the Separation vessel resulting aqueous phase of solvent and decomposition products is largely exempted.

According to one embodiment of the invention, the purified in this way Water as feed water for the steam generator of the recovery system with clearly reused with less risk of corrosion.

Lin an essential feature of the invention is that all parts at risk of corrosion that have been exposed to solvents or solvent / water mixtures come into contact, made of the corrosion-resistant material BorosiliCatglas.

The invention is described below and with reference to the drawing explained in more detail.

Figure 1 shows a working according to DE-OS 29 09 030 device, in The solvent-containing exhaust air is cleaned by adding the solvent to activated carbon adsorbed and then desorbed by means of steam. The water-solvent vapor mixture is condensed. The water phase separated from the condensate contains residues Solvent and decomposition products and is returned to the evaporator.

Figure 2 shows the method according to the invention, in which the for the desorption of the solvent from the activated carbon initially required water vapor in whole or in part for stripping the solvent from the separated water is used and the purified water flows back to the steam generator.

The solvent-containing air (A) extracted from the workshop is Passed through a filter 18 into the container 21, flows through the activated carbon filter 22 and, freed from the solvent, cleaned (B) from the chimney 23 into the environment the end. If the activated charcoal is so heavily loaded with solvent that there is no more Can adsorb more solvent, the valves 24 and 25 are closed and the valve 26 is opened. The energy then supplied to the evaporator 27 is generated Water vapor that flows through the activated carbon filter and desorbs the solvent and records. The vapor mixture is condensed in the cooler 28. The condensate runs into the separation vessel 1, in which there are two liquid phases with different Separate density from each other. The heavy phase (C) consists of solvent with a small proportion of dissolved water, it runs in a collecting container 29. The light phase (D) is water with a share of dissolved in it Solvent; it runs into the container 2 and is according to the previous method (FIG. 1) conveyed into the evaporator 27 by the pump 3.

According to the invention (Figure 2) is now coming from the container 2, applied solvent-containing water by the pump 3 to the stripper column 30, which is arranged between the steam generator 27 and the adsorber 22.

The water freed from the solvent flows into the steam generator 27 again as feed water. The amount of steam used for stripping can be adjusted using of the valve 32, which is built into the pipe 31, which the steam generator 27 connects directly to the adsorber 22, can be set so that either the all or only a portion of the steam generated in the steam generator by the Stripper column is passed.

All in contact with solvents or solvent / water mixtures Coming, corrosion-prone parts of the device described exist according to a special feature of the invention made of borosilicate glass.

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Claims (5)

Process for removing solvents from wastewater Patent claims: 1. Process for removing solvents from wastewater during recovery of solvent vapors from air, whereby the solvent-containing air freed from the adsorbed solvent on activated carbon adsorption filters Solvent desorbed by water vapor generated in a steam generator, the resulting vapor / solvent mixture condenses and the two-phase condensate in a solvent phase. a phase which has a residual solvent content separated is characterized in that at least a portion of the steam, which is intended for the desorption of the solvent upstream of the activated carbon filter the aqueous phase by stripping in a column of residual content of the solvent is released. 2. The method according to claim 1, characterized in that in the steam generator generated steam is completely passed through this stripping column. 3. The method according to claim 1, characterized in that in the steam generator generated steam is only partially passed through this stripping column. 4. The method according to any one of claims 1 to 3, characterized in that that the draining from the stripping column, purified water to the steam generator is fed back as feed water. 5. The method according to any one of claims 1 to 4, characterized in that that for all components that are exposed to the aggressive decomposition products of the solvent come into contact, the corrosion-resistant material borosilicate glass is used will.