Method of extracting organic compounds from water.

The invention relates to a method for separating organic compounds, especially halogenated hydrocarbons, from water by extraction, as it is indicated in the preamble of claim 1.

A method of this kind is described in DE-OS 29 o1 261st This solid and liquid lipophilic substances for the removal of organic compounds by means of extraction, adsorption and absorption suggested, but it no further details about the lipophilic substances are to be traversed by the water as in the practice of the method. As examples only laboratory tests are given, in which in a sample vessel, the lipophilic phase is formed by a filling of paraffin chips or by partially filling the vessel with liquid paraffin.

The EP-PS o o13 659 and AT-AS-A 2169/82 describe the separation of halogenated hydrocarbons from water by liquid extraction, the extraction agent is not present as a fixed bed, but the added water to be purified in liquid form or with is mixed to him in a counterflow mixer.

These known processes have considerable disadvantages. The paraffin described in solid form is very temperature sensitive. When hot waste water to be treated Shelf, may occur for melting and further flooding, which is open, as the continued geschwemmte extractant then separated who the soll.Bei liquid extraction agent is also not specified how the separation of the exhausted extraction agent is to take place from the purified water. Finally, the distribution coefficient is unfavorable for some organic compounds, that extremely long contact times and unacceptably large amounts of the extractant is required with the proposed elimination method. Does not get one these amounts and the treatment times, then there is unsatisfactory extraction degrees.

The invention has for its object a process of the type described above such that with a simple method implementing a particularly effective interaction of the water to be purified is achieved with the extraction medium and thus a particularly high efficiency of the extraction.

Two solutions provided by the invention are set forth in the claims. 1 and 2 They are based on the same solution principle, namely forcing the water through a support structure with a large internal surface a split into many fine flow channels flow path and to bring it in these flow channels in intimate contact with the extraction agent, which is either attached to the surface of the support structure and / or the pores or interstices of the support structure as a continuous liquid layer completely fills. The support structure has a triple task here. They dispersed first, the effluent to be purified to a high degree, so that the desired long contact times come about and the unfavorable distribution coefficient is eliminated. It provides secondly the extraction agent in the desired large contact area available. And the front in the flow direction of part of the support structure acts on the thirdly mitgeschwemmten droplets of the extraction agent as a adsorption and / or coalescence filter, so that the removed purified water is substantially free of extractant residues.

Further advantageous embodiments of the method are indicated in the dependent claims. In particular, a combination of the above two solutions can be applied in such a manner in an advantageous manner that both a support structure with unattached thereto extracting agent and a part of the support structure flooding contiguous extraction agent layer is applied.

A specific method must be employed if the organic compounds present in the gaseous state, for example, of devices for the chemical cleaning. These detergents gases and vapors are usually subjected to a gas scrubbing; but it creates significant difficulties to eliminate these most halogenated organic compounds from waste water. It is therefore usually worked in a closed circuit. A solution of the problem is given by the present extraction process by the gaseous compounds are dissolved in water by stripping and the water extraction is subjected in the supporting structure. It is also conceivable to carry out the stripping process simultaneously with the extraction, that is to enter the water at the same time with the gas in the supporting structure. A besönders advantageous process management, however, is given by the fact that passing the gases directly through the flooded only with extracting agent support structure and thereby eliminated.

The inventive method is explained in the following with reference to some embodiments thereof with reference to the drawings. It shows:<ul><li>Figure 1 is a schematic representation of a plant for implementing the method according to the invention.</li><li>Fig. 2- 9 schematic vertical sections through a portion of the extraction tank of Fig. 1 at different process variants.</li></ul>

In Fig. 1, 1 designates a tank or vessel which carries on a perforated support base 3 a filling 5 of a material forming a porous or grid-shaped support structure having numerous gaps and flow channels. To this end, candidate materials are further explained in detail below. The support structure may be covered at the top by a further perforated bottom 7, in particular if it consists of a loose packing porous granules or the like.. The water to be purified is supplied through the pipe 9 and passes through a riser 11 to the top of the support structure 5 and flows through it from top to bottom. The purified water is drawn off from the space 13 below the bottom 3 through a riser 15 and an overflow edge 17th The height of the overflow edge 17 and the flow resistance of the support structure 5 determine the amount of which is established in the basin 1 liquid level 19th

The support structure 5 may be coated on various types explained in more with the extractant or loaded. In the flow of the water to be purified through the numerous fine flow channels of the support structure 5 reach the separated organic compounds, especially halogenated hydrocarbons, in intimate contact with the extraction medium and be separated from the water. If exhausted after some time, the extraction means, that is substantially saturated with the separated organic compounds, and thus has become ineffective, the extractant may be separated by a backwashing of the support structure 5 and withdrawn via line 21 with shut-off 22nd The separation of organic compounds can be carried out in manner known per se by means of steam distillation. The regenerated extractant may by a pump to the extraction tank 1 again be supplied to deposit again to the support structure. For the backwash rinsing fluid and / or purge air, or the extraction agent itself through one or more conduits 31 and a manifold system 32 can be fed below the support structure. 5

As the material for the support structure 5 is either a bed of a granular or particulate material such as Raschig barren like. Of glass or plastic, particles of expanded perlite or expanded clay and the like., Or a single- or multi-part filling a space latticed material, in particular a reticulated foamed plastics such as polyurethane, in question. Also a filling of mineral fibers in the form of a random fiber fleece is conceivable.

It is particularly advantageous if the material forming the support structure material is made of a material or is coated with such a which has a coalescing and / or adsorbing action for the extractant used. The unused or flooded part of the support structure has then for the extractant used the characteristic of a filter, which can hold back the water to be purified as entrained particles or droplets of the extraction agent. If the material forming the support structure material does not have the desired surface property itself, it can with an appropriate material, in particular a suitable synthetic resin, as well as with activated carbon, metal or the like., Be coated be. As coating methods are vapor deposition, electrolysis, sinter bonding or the like. In question.

The extractant used for the extraction is not constant part of the support structure 5, but is contacted with this compound in temporarily. The extractant itself is generally a lipophilic liquid phase, in particular for waste water treatment, only those extracting agents there that can be deposited by gravity separation with at least one degree of separation from the water, which satisfies the provisions on direct and indirect discharge of waste water. An aromatic-free liquid paraffin fraction, as known from the prior art, is preferably also suitable in the inventive process as the extractant. It also discusses other extractants such as oils and waxes, for example, where even certain oils may be used in a particularly cost-effective manner as the extraction agent.

In a first embodiment of the inventive method the entire inner surface of the support structure 5 is provided with an adhesive covering by adhesion of the liquid extractant. This is done in such a way that when deflated extraction vessel 1, the liquid extractant is so long pass through the vessel and the support structure 5, until a sufficient amount of the extraction agent has attached to the support structure. 5 The excess liquid extractant is withdrawn, and then, the supply of the water to be purified through the line 9 and the extraction operation start. In this mode, the method according to the invention, the vertical section shown schematically in FIG. 2 provides an in vessel 1, wherein above and below the area occupied by the support structure 5 layer S + E is extraction-free water layers W are. Falls are entrained by the water flow extractant particles or droplets from the filling down, they can in the water-filled, flow-balanced chamber separated below the support structure 5 from the water and ascend back up to where they attach themselves again to the support structure. 5

Another embodiment of the inventive method is illustrated by FIG. 3. Here, above the support structure 5 constantly a floating extractant layer E present and the water is supplied by means of the riser 11 in Fig. 1 so that it) must flow above or within the extraction agent layer E *. There is thus already in the extracting agent layer E intimate contact with the extracting agent and extraction of the separated organic compounds instead. From the extraction agent layer E, the water then flows past an an intermediate layer W in the support structure 5, which can be loaded either at the beginning of extraction-free or, as in the embodiment of Fig. 2, on their inner surfaces with extractant. There is here a further extraction of organic compounds still present instead, and further, any extraction agent droplets, which are entrained from the layer E, retained in the support structure. 5 The purified water is drawn off below the support structure. 5 When the extraction agent in the support structure 5 accumulates into larger droplets and peel off, then swim these droplets on upwards and unite with the floating extraction agent layer E.

A particularly preferred embodiment is illustrated by FIG. 4. Here constantly located above the support structure 5 a floating extraction agent layer E of such thickness that it protrudes from the top of the support structure 5, so that the upper portion of the support structure 5 is constantly flooded with the liquid extractant E. The introduced from above into the extraction agent layer E water is forced a split in many finely distributed flow channels flow as it flows into the support structure 5, each of the flow channels is filled in the upper portion of the extraction agent E. It has been found that in this way a particularly effective and intensive interaction of the water is obtained with the extraction agent. The located below the extraction agent layer E remaining part of the support structure 5 may be either provided on its surface with an extraction agent layer, as in the example of Fig. 2, so that the water below the layer E finds a further extraction section, or the support structure 5 can be below the extraction agent layer e be free of extraction agent, so that it only as a filter for capturing and retaining extractant droplets entrained from the layer e, acts. *) Opens and thus the extraction agent layer E

With reference to FIG. 1-4 embodiments explained, the support structure is advantageously flows from top to bottom. However, it is also the reverse arrangement with water flow from bottom to top possible. Fig. 5 illustrates schematically the analogous to FIG. 2 arrangement, wherein the extraction agent contaminated with or loaded support structure 5 is flowed through from bottom to top, so that the purified water can be taken off above the support structure 5. This in the arrangement shown in Fig. 1 a corresponding permutation of the inlet and outlet, which in a simple manner is possible due to the skilled artisan. When about entrained extractant drops are to be retained, the trigger must be the scum-retaining baffle behind a deeper.

In the embodiment of FIG. 6, the water to be purified by also flows from bottom to top, first a loaded support structure 5 and then finds beyond the overflow edge 2 in front of a floating compact extractant layer E, which has to flow through it from top to bottom, before it behind the baffle 6 can be deducted.

The illustrated in Fig. 7 embodiment operates with a compact floating extractant layer E, whose thickness is greater than the height of the support structure 5 so that it projects upwardly and downwardly beyond the support structure 5 and and the inflowing water from above, first in the extraction agent layer E then flows into this from the flooded by support structure. 5

Although usually a liquid extraction agent is used, which is lighter than water and floats on water. However, it may in certain cases also be advantageous to use an extraction agent which is heavier than water. A corresponding embodiment is illustrated in Fig. 8. Here is located on the bottom of the vessel, an extraction agent layer E of such a height that it partially protrudes from the bottom of the support structure 5 and flooded the lower region thereof. Above the support structure 5 is water. The bottom fed, water to be purified flows first through the extraction agent layer E, and then the support structure 5. The embodiment of FIG. 8 thus provides the inverse of the embodiment of FIG. 4. Of course, when using a heavy extractant with inversions of the embodiments of Fig. 3 to be worked, 6 or 7.

The embodiment of FIG. 9 operates with a constantly newly occupied support structure 5. The tapered at 9 waste water is admixed 5 extractant E below the support structure. The mixture rises from the bottom of the support structure 5 and confirms this with extractant. Abgeschältes and possibly exhausted extraction agent drives to and accumulates in the floating layer E, while the purified water is discharged laterally under the floating layer. From the floating layer E can extractant continuously taken to regenerate R and returned to the circuit.

It is also possible to operate the inventive method so as to alternate between two different states described operation. For example, you can, starting from the embodiment of FIG. 3, the extractant layer embarrassed by temporarily lowering the water level E in the upper portion of the fixed bed F in, and thereby restore the operating state of FIG. 4 to eg a periodic refresh of the availability of the upper portion 5 of the support structure to effect with the extracting agent.

Finally, the case is conceivable, that the density of the extractant is only slightly below one and the density of compounds to be extracted is substantially higher than the first Then the density of the loaded extractant can rise to more than 1, so that a pre-existing floating layer sinks to the bottom and the Durchströmfolge then reverses. In terms of apparatus this change is taken into account by the liquid guide and posture shown in Fig. 6 and 7.

To the compact liquid extractant layer E to regenerate, in the embodiments according to Fig. 3, 4, 6, 7 and 8, this only needs to be drawn off and treated in an extraction vessel in a suitable manner. In contrast, the accreted on the inner surface of the support structure 5 extractant must be removed by a backwashing process, which is done by supplying a Rückspülmediums such as water and / or air through the line 31 and the manifold 32 of FIG. 1,. Preferably hot water is used, the additional washing-active substances or organic solvents can be added. Also supplying hot steam is possible. Together with the backwashing air can also equal regenerated extracting agent are supplied, so that the support structure is once again occupied.

One other method for the renewal of the extraction agent provides, in addition to be bubbled from the bottom air abandon water from above and below simultaneously pull a water supply amount exceeding water. Characterized the supporting structure is backwashed in layers from top to bottom. The consisting of depleted extractant and water Rückspülschlamm is subjected to a separation process in a separate container and passed the decanted water again through the extraction stage.

In special cases, several steps can be connected in series, are flowed through in succession. The pore size of the support structures may decrease in the flow. It can be carried out in stages with different extraction means in order to adapt the extraction of the compounds to be removed can. The regeneration of the support structures is advantageously carried out at different times.

If it is in the halogen organs readily volatile compounds, then the entire system must be sealed gas-tight. The gases or vapors are collected and subjected to stripping, as described earlier.