Method and device for removing volatile contaminants from soil or the same.

The invention relates to a method for removing volatile pollutants from soils and similar materials according to the preamble of claim 1 and means for performing this process.

Such a method is known as so-called Bodenluftabsaugungsverfahren per se. Here, the contaminated soil in situ is provided with Bodenluftabsaugbrunnen, by the Resistant air is sucked, in which there are to be removed volatiles. Such soil vapor extraction extends with respect to a satisfactory cleaning result over months or even years and can hardly be used in cohesive soils. The extracted air is at high pollutant concentrations prior to entry into the atmosphere purified by already proven active carbon filter.

Here are usually used either disposable activated carbon filter or self-regenerable activated carbon systems.

The disadvantages of this working in situ methods are thus seen in the sometimes extremely long treatment times and the Anwendungseinschschränkung in cohesive soils.

Here to provide a more effective and economically usable method with appropriate means is the object of the present invention.

The fundamental solution of this task is inventively in a method according to the characterizing portion of claim 1.

Thereafter, the contaminated soil and similar materials are not treated in situ, but excavated for processing. Thus, a mechanical pulping in terms of an effective surface enlargement is possible, which is especially for clay / bonded materials is of great importance. The loaded material is quasi with inert gases, such as air in particular, flows through, wherein the volatile pollutant components desorbed from the surfaces of the material particles and are stripped from moist fabric portions. In this way, the treatment times can be significantly reduced and that in beonders favorable cases, for example, up to two weeks. Even at very unfavorable conditions, such as very high pollutant availability in strong clay minerals materials can be expected as a rule with a treatment time barely over 3 months.

The inventive treatment of the material, it is possible to distribute ventilation lines through the entire interior of aufzübereitenden material. The treatment in an enclosed space to the atmosphere also offers other advantages. One of them is that the treatment gas in the circulation can be performed by switching of a cleaning process, whereby emissions are avoided altogether in the atmosphere. By circulating the gas, it can also be heated at a reasonable economic cost, which the outgoing gas from the Strip effect can be considerably increased within the soil material. The activated carbon plant for gas purification may be as a double-filtration system designed so that an automatic desorption of pollutants occupied activated carbon is possible. In a regenerable gas purification plant only the separated from the gas pollutants must be disposed of.

A generally usable for implementing the method according to the invention device is subject of the claim. 3

Especially effective and economically viable is the embodiment of the closed space as a transportable container or container combination of claim 4.

Also, a former, of abandoned railway tunnel, unless it is gas-tight, take over the function of the closed space.

Further ultimately refer back respectively to claim 3 claims 5 to 13 include substantially to the container construction especially tailored configurations of the contaminated materials receiving for ventilation single container with respect to the gas connections and their storage within the container with the related loading and emptying possibilities. Full details will be explained in connection with the description of embodiments in more detail.

The rear-related only to the method claims in claim 14 describes a first alternative embodiment of the closed space required. Thereafter, the excavated material is aerated in a kind of screw conveyor with the cleaning gas introduced into the interior of the screw and the surface in contact with the material through aufzübereitenden flowing into the worked up material. The advantage of this embodiment is the excellent due to the continuous mixing of the soil material aeration, which allows particularly short treatment times. While the treatment of dormant in containers in a closed space floor materials in batches must be in weekly to monthly periods, the treatment with this auger-solution can take place continuously. This may, however, be necessary to connect a plurality of screw conveyors parallel or in series. By heating or heating the cleaning gas, the desorption rate can be increased considerably. In addition, the passage of the heated gas leads to a gradual drying of moist materials. Under such conditions the trokkenen Desorptionsneigungen be again increased significantly.

In a second continuously operable device according to claims 15 and 16, the contaminated material is loaded on a befindliches in a closed container endless filter belt which is porous. To complete the container to the atmosphere, carried inlet and outlet of the material via a rotary. On the filter belt the material to be treated is transported through the apparatus and cleaned at the same time by the air drawn through the material Bahandlungsgas of the volatile contaminants. The required treatment inert gas is again passed over a adsorption / desorption system in a circle and brought it to a higher temperature expediently before the passing of the material and thereafter, so as not to reduce the working capacity of the activated carbon, cooled below the dew point of the entrained water , The water is collected and disposed of separately. To clean the filter band this can be against flushed with the inert gas or water.

Other options for removing volatile contaminants from soils or comparable materials in conjunction with a charcoal-gas purification plant are apparatuses in the type of ovens or dryers plate.

In systems continuously operated, a power supply by irradiation with infrared or other radio-frequency radiation in the wavelength range of 1 mm - 1 m done.

In all treatment facilities, it is in the case where it is carried out with heated cleaning gas, for energy saving low to isolate the related with the atmosphere device parts against heat loss.

Ausfühungsbeispiele are shown in the drawing.

Show it:<ul><li>1 is a schematic representation of an aeration floor cleaning device with a closed treatment space, </li><li>2 is a plan view of a ventilation device with a transportable container as a closed space,</li><li>3 shows a section through the container along line III-III,</li><li>4 shows a section through the container along line IV-IV,</li><li>5 is a schematic illustration of a treatment device with screw conveyors as a closed space,</li><li>Fig.5.1 shows an enlarged detailed view of a section V.1 of the screw of a screw conveyor insurer,</li><li>6 is a schematic illustration of a treatment device comprising a closed band filter</li></ul>

In the schematic representation of the method according to FIG. 1, the closed space of a on a base plate 1 tightly attached bell 2 is formed. The bottom plate and the bell can be made of any, but gas-tight material. In this respect it is even possible to use corresponding tent material for the bell. The excavated of volatile pollutants to be cleaned soil is piled up within the bell 2 as pile 3 on the base plate first Within the pile material 3 perforated aeration tubes 4 are mounted with spacing from one another at a small distance from the bottom plate. Through these tubes 4 is blown as a quasi inert gas through a conduit 5 air. The pass has flowed through the bed, pollutant-laden air is sucked out of the bell 2 through line 6 and fed to an activated charcoal-gas cleaning system. 7 The activated carbon purifying device 7 is comprised of two filled with activated carbon containers which are switched so that during the adsorption of the noxious gases to the active carbon in the one container the other container is desorbed with superheated steam. The cooled liquid mixture of water and pollutants is separated according to density and the aqueous phase removed by striping of dissolved pollutants. The gas phase is fed back into the cycle and the cycle extracted freed of contaminants water supplied to a receiving stream. The withdrawn from the gas discharge line 6 gas, which is loaded with contaminants, advantageously passes through a compressor 8 (side channel compressor) and a cooler 25 before it enters the gas cleaning system. 7 Due to high temperatures the adsorption of activated carbon is adversely affected. After passing through the gas purification unit 7, the clean gas is again compressed in a compressor 8 and optionally fed back via a heat exchanger 24 to the contaminated soil via line 5th

Besides the described gas cleaning plant 7 with two parallel-connected selbstdesorbierenden carbon canisters a plant with an activated charcoal filter as a disposable system is possible. In the case of poorly adsorbing substances such. As vinyl chloride must, possibly two systems are connected in series to prevent competing adsorption.

A practical implementation of a purification plant show the Fig.2-4. Here, the closed space is transported tabler box-shaped steel container 9. Such a container, for example, the standard dimensions have 12.2 mx 2.4 mx 2.6 m. To open this container on one of its narrow end faces via a gas-tight closable doors 10. As porous container for receiving the material to be cleaned serve commercial grid boxes 11, which may have 1 mx 1 mx 1.2 m in the present specific example, the size. This grid boxes 11 can in pairs one above the other in stacked on the container 9 laid side by side two pairs of rails 12 are inserted into the container. Each of the 11 grid boxes is crisscrossed with installed at a distance from the closed bottom of the box perforated ventilation pipes. 13 The perforation may be unevenly distributed over the circumference of each tube 13, with the largest by perforations generally geodetically upward. The container 9 is provided with air intake and discharge lines 14 and 15 respectively. The containing via line 15 extracted pollutants air is purified in an activated carbon purification device not further shown here, and the container 9 resupplied circulated via the line 14th The activated carbon-cleaning device can in particular be such as it is described in the first exemplary embodiment in detail.

The feed of the grid boxes 11 with contaminated material that pressurisation of the mesh boxes and their introduction into the container 9 is as follows.

The individual already filled with material or before the container opening to be filled mesh boxes 11 will temporarily before the containers opening laid rails gesetzt.Die from the grid boxes 11 outstanding free open ends of the ventilation pipes 13 on quick closures 16 with the aid of individual Rohrpaßstücken 17 with each other connected. The insertion of the mesh boxes 11 into the container 9 can be done in pairs at each of stacked boxes or it is also all the boxes outside the container are joined together and then inserted together into the container. 9 The connections of the tubing fittings on the air feed and discharge lines 14 and 15 can be made from the outside. The container of the above described size takes on forty-four of dimensionally above also specified grid boxes 11 in the specified assembly. The treatment of the material in the container 9 istorical usually for periods between days and several weeks. Apart from the type of the respectively present contamination, the duration of treatment also depends largely on the through sent by the container mass flow of air and its temperature. In the present example of a filling volume of the grid boxes 11 of 1.2 cubic meters and a filling by a recycled at a specific gravity of 1.3 t / cubic meters of material the amount of air flow is set so that 1 cubic meter of material per hour of about 20 cubic meters of air flows becomes. The temperature of the air is adjusted on entry into the container 9 with about 50 degrees Celsius or more, also temperatures above 100 degrees Celcius may be possible and advantageous. To avoid derived from the material particle sweeps in the activated carbon filter, it is recommended that the grid boxes 11 to be covered by fleece-like filter materials.

A particular advantage of the design of the required enclosed space as steel containers is that such a container readily transported to the respective place of an impurity, and there tion to imple the cleaning may be employed. It can of course also buy several containers simultaneously used at a treatment site. To this end, all plant components including the gas cleaning device are designed in a modular manner networked. Compared to the in situ cleaning of the floor can be largely optimize for different materials each with different and often also still unknown in detail constraints by, for example, loosening and warming the material in the ventilation in the inventive process.

A further means for carrying out the method according to the invention are the in Fig.5 and 5.1 shown screw conveyor 18. The treatment gas is again guided by these in the circuit, with a countercurrent or cocurrent to the feed direction of the aufzübereitenden material is possible. The special feature of this embodiment is that the screws 26 are hollow and have a layer adjacent to the porous material aufzübereitende connected to the cavity surface. The porosity can be generated by a plurality of individual openings 27th Of the screw conveyors 18 are expediently several cascaded to possible to obtain in this way a purification process with continuously durchzusetzendem material and be able to make do with very short treatment times. The material is a hopper 19 inputted into the first screw conveyor 18 and removed via a rotary valve 20 from the third and so in the example shown last screw conveyor. The short treatment times are achieved here by the excellent mixing of directly emerging from the worm 26 treatment gas with the actions supported by the screw flights material. This process engineering and apparatus-budget approach is combined with a special heating of the desorption at about 40 to 220 degrees Celsius. Using an appropriate drying process the polluted material a very effective and fast working thermal desorption is introduced which ensures a particularly effective cleaning in strongly cohesive soils. The hot pollutant-laden air must be cooled in this purification variant via a separator to about 30 degrees Celsius to ensure adequate absorption of the remaining gaseous pollutants in the downstream activated carbon plant. This process variant may be operated continuously.

Another continuously operable device shows Fig.6. There, the material to be treated is fed onto a befindliches in a closed container 21 endless filter belt 22nd The filter belt 22 is porous. On the filter belt 22, the material to be treated is transported through the vessel 21 and drawn off from the container decontaminated. The required treatment inert gas is again circulated, wherein the regeneration of the gas in the already described above cleaning system 7 takes place. On the way from the object to the filter belt 22 which aufzübereitende material through the porous formed filter band traversed by the recirculated inert gas for receiving the contaminants through. In order to achieve this targeted flow in the area of ​​the filter band 22, passes through the filter belt, together with the aufzübereitenden material a closed acted on by the inert gas exhaustion device 23. Prior to entering into the suction device 23, the inert gas is heated in a heater 24, while it from admission is cooled in the activated carbon purification system 7 in a heat exchanger 25 to a beneficial for the activated carbon filter system temperature. With such a belt filter system, the inventive method can be performed continuously in turn. The filter belt 22 can be adjusted with respect to its rotational speed to the type and degree of contamination of each aufzübereitenden material. To 22 continuously to maintain the porosity of the filter belt upright, the tape can outside the suction device 23 through a purification system in which it is washed, for example with water or by blowing with compressed air.

Substances that can be used with the process and proposed for its execution facilities invention eliminates, for example, be: aliphatic and aromatic hydrocarbons, halogenated hydrocarbons, especially chlorinated hydrocarbons, chlorofluorocarbon and low-boiling solvent such as tetrahydrofuran, Cyclohexanan etc. and chlorobenzenes, alcohols, phenols and chlorophenols, etc. Overall, however, all low-boiling and / or steam-volatile compounds as removable in question.

The inventive method is essentially based on the principle to desorb the removable volatiles through specific fumigation one hand, and suction on the other hand in a closed room or thermally desorbing and thereafter adsorb the desorbed substances to an adsorber such as activated carbon and the gas thereby to avoid pollution of the atmosphere as resistant as possible to lead the district.