NO782737L - PROCEDURE FOR COMBINED UTILIZATION OF WASTE AND PURIFICATION OF WATER AND APPARATUS FOR CARRYING OUT THE PROCEDURE - Google Patents

Description

Procedure for combined utilization of sewage and purification of waste water and apparatus for carrying out the procedure

The invention relates to a method for the combined utilization of waste and purification of waste water, where the waste water is mixed with at least part of the ground waste and a separation into organic and inorganic components is carried out, the waste water flow with those dissolved in this resp. suspended components of garbage are passed through a two-stage filter of unactivated and activated carbon, the main part of the filter carbon which is saturated with the dirt is thermally treated for regeneration in a first reactor of a multi-reactor mile, whereby the dirt which has been deposited on the carbon filter is thermally decomposed under extraction of coal and fuel gas, solid waste or part of the dirt-saturated filter coal is incinerated or is partially combusted in at least one other reactor during extraction of heat and fuel gas,

and the regenerated filter carbon from the first reactor is returned to the filtration zone for the wastewater.

The invention also relates to multi-stage filtering devices for carrying out the method.

A method of the above-mentioned type is known from German patent application No. 2585703. With this method, it is simple and, moreover, economical

CL) the dewatered water used as a means of transport for the rubbish and also for separating the rubbish into essentially inorganic and organic components,

(2) the waste water contaminated by the rubbish is cleaned by filtration using normal carbon and activated carbon, (3) part of the rubbish or the dirt-laden activated carbon is combusted to release a fuel gas that supplies energy for the thermolysis, and (4) the bulk of the dirt-laden filter carbon is thermally decomposed in a thermolysis reactor, whereby the filter carbon is regenerated and a hydrocarbon-rich coking gas is recovered.

Although this method offers several advantages and in particular an optimal utilization of the energy content of the garbage and also makes it possible to use the garbage for the treatment of waste water, certain difficulties have still appeared in the practical execution of the method. These appear especially when garbage with constantly changing output composition is supplied to the system and at the same time a variation can be observed in the composition of the similarly supplied wastewater.Thereby, but also

due to particularly stubborn, unpleasant dirt materials,

difficulties may arise in particular during the separation and filtration processes which are of decisive importance for the system. The continuous processing of rubbish and waste water can be particularly hindered by a blockage or sticking together of the carbon filters, flow changes and too strong rubbing of the filter carbon. Thereby, it may also happen that pollutants, especially polar materials, can pass through the fine filters which are filled with activated carbon.

The invention therefore aims to improve the filtration processes and separation processes in a simple and continuously implementable manner by a method of the above-mentioned type. Thereby, in particular, an improvement of the adhesion processes for the dirt materials to the filter media is to be achieved by a variation in the filtration conditions or by providing new filtration devices and handling them, without thereby obstructing the flow of the wastewater to be cleaned. In the case of a purposeful variation of the filter media, an improvement in the achievable filtering effect with additional capture of strongly polar materials must also be achieved during the utilization of the waste in question.

According to the invention, this task is solved by the special features that the waste water containing rubbish is passed through a multi-stage filter system which is kept in motion and in which a coarse filtration is carried out at least in part by using loose coatings of coal, the organic components in the rubbish being extracted and optionally pretreated to increase adsorption and adhesion, and the fill loaded with fouling materials is returned to the multi-reactor mile:.to coke the fouling materials.

The invention is based on the realization that by using a multi-stage filtration system in which the filtration at least partially takes place in loose fillings containing coal, it is possible to avoid the hitherto observed disadvantages. Due to the division of the filtration into several stages and especially due to the pre-connection of coarse filters that contain loose fillings of filter material, it is possible to carry out a mechanical and partly also adsorptive separation of the dirt in the wastewater without this leading to a clogging or bonding of the perforated walls, sieves and similar devices in the filtering devices. The to-stop resp. the sticking together of the perforated walls and screening units is avoided by the fact that the dirt adheres to the particles of the filtering material and by the fact that the filtering material loaded with dirt can be removed while exposing the non-glued, perforated screening surfaces by using simple tipping steps or deflection step. The fill material which is removed and which is loaded with dirt, is then returned to a reactor in the multi-reactor mill for subsequent coking of the dirt materials and obtaining new filter coal.

It is advantageous to carry out the filtration as a coarse filtration through loose fillings in suitable devices before a more extensive filtration and clarification of the passed waste water is then carried out in further filtration units containing unactivated and activated carbon. Although it is possible before the pre-filter, which contains a loose filling of filter material containing coal, to switch on a mechanical raking system, this can also be completely replaced by the pre-filter as such, as clogging of the device parts in the filtering devices is largely excluded due to the filtration by means of bulk goods.

The pre-filter, which serves as the first coarse filter, is generally led in counter-current to the flowing-through waste water which is contaminated, whereby a filtration is obtained due to gravity effects. However, the coarse filters can also be introduced rotating into stagnant waste water or moved through flowing waste water.

The fillings of filter material contain a significant amount of coal. In the coarse filters which are to be passed through first, the charcoal is usually present as pieces of unactivated charcoal and therefore acts as a mechanical filter. The charcoal is extracted from the organic components in the rubbish without activation. Depending on the type of composition - for the waste water to be treated or of the waste water's dirt content, a certain proportion of activated carbon can also be added to the coarse filter, which is likewise extracted from the organic components in the rubbish.

According to a preferred embodiment of the invention, the fillings contain coal in a pelletized state in order to keep the rubbing off of coal dust as low as possible. This pelletisation of the coal filling material is preferably carried out both for the coarse filtration and for the fine filtration, and in the latter case with activated charcoal. If it is started with coal that has been extracted from the waste in the reactor during coking, this is finely ground after cooling, mixed with an organic binder, such as e.g. tar or briquette pitch, and pressed at elevated temperature and pressure, e.g. at 80°C at a pressure of 1200 kp/cm. This pressed coal can then be ground again to the desired average grain size. The charcoal then constitutes a non-activated filter charcoal which is suitable for coarse filtration. If the coal is to be used for the fine filters, the obtained split granules are activated in a manner known per se, and this can e.g. is carried out by heat treatment for several hours in the gas-tight closed reactor in the multi-reactor mile by introducing water vapor and/or zinc chloride. The pelletized activated carbon that has thereby been obtained from the organic components in the rubbish has a good abrasion resistance at the same time as a high surface development.

The quality of the pelletized coal can be further increased by spraying the rubbish with liquid, combustible, organic waste products, such as e.g. used oil, before it is used in the first thermal stage or in the first thermal stages.

With such pelletisation, rubbing effects on the coal and thus related disturbances can largely be avoided.

Particularly favorable filtering effects are obtained with a loose charcoal filter material which also contains a proportion of polar materials. This proportion of polar materials can be provided by mixing with the rubbish and/or waste water such waste substances which, during the heat treatment, are present in a filtration-promoting form which also partly takes an active part in the adsorption. This can be achieved e.g.

in that a certain proportion of waste water from paper manufacturing or also from por-

selenium production• Rubbish or waste water from this area of industry usually contains polar materials, e.g. fillers such as aluminum oxides, silicon oxides or titanium oxides etc., which are obtained in an activated state by the conversion of the organic components present into coal at the charring temperatures in the range from approx. 300 to a maximum of 800°C. Other polar metal oxides which come into question and which often have a low positive charge, are e.g. iron oxides and magnesium oxides that are formed as waste sludge in the ceramic industry and in aluminum production. With this purposeful addition of waste sludge, which produces activated, polar oxides during the carbonization, not only can additional filtering effects be achieved for the mechanical carbon filters due to polar, electrostatic effects, but a beneficial effect is also obtained for the clarification and sedimentation process for the waste water. For this reason, this precaution regarding the composition of the loose filling material of both coal and polar waste substances, in addition to the pelletisation of the filling material, is particularly preferred when carrying out the present method. This applies in particular with regard to the fine filtration.

According to a further embodiment of the present method, at least the fine filters are washed with service water before the emptying of the dirt-laden filler material, whereby the service water is preferably diverted as a partial flow of already purified waste water.

The filtration process when loose filler is used, preferably in a pelletized state, can thereby be partially further favored, by a constant movement of the filler being achieved. When the filler is moved, e.g. by moving the container which contains this, however, care must be taken that the filling material is not transferred to a swirling layer state, as the mechanical filtering effect is thereby cancelled.

The present method is preferably carried out in that the filtration system is filled with filling material during continuous operation, then dirty waste water flows through it, is freed from dirt-laden filling material, possibly after washing it in advance, and is again used for filtration after a renewed filling with filling material. These various precautions which are taken during continuous operation can be carried out e.g. on spaced apart stations for a single filtering device. Such multi-stage filtration devices for execution

of the present method is described in more detail below in the form of preferred embodiments and with reference to

Fig. 1 - Fig. 3a. Although particularly suitable embodiments of the filtering device according to the invention are shown in the drawings,

the present method is not exclusively bound to

had to be carried out using such devices, as a person skilled in the art will easily understand that with certain changes, similar effects can be achieved within the framework of the present method.

From the drawings show

Fig. 1a and Fig. 1b the principle steps for a multi-stage filtering process according to the invention, Fig. 1c a circulating paddle filter that can be used both

as a coarse and fine filter,

Fig. 2 a band filter and

Fig. 3 and Fig. 3b a continuously working filtering

band.

In Fig. 1a, the main filtration process in the execution of the present method is shown, where, however, the reactors of the multi-reactor mile which are necessary for the system'

for the regeneration and possibly incineration of the dirt-containing filter coal and in which also the organic components in the rubbish

is transferred to coal, partly to activated coal and partly to non-activated coal, and in which a incineration of the rubbish can take place,

is not shown. With regard to these additional devices, reference can be made to the above-mentioned German patent application no. 2558703 and also to the parallel patent application submitted at the same time as the present patent application, which is based on German patent application no. 782736. As a multi-reactor mile, a device is used for the present method which consists of at least two, preferably three or more, essentially cylindrical, horizontally arranged and parallel drums which can rotate about their axes. For a preferred reactor arrangement, these are arranged in the form of a triangle above each other, so that these can also be described as a pair of. lower reactors and an upper reactor which is arranged between the lower reactors.

The filtering device according to the invention is explained in more detail below using the treatment sequence which dewatered or the solid waste passes through.

The waste water, which can include both municipal waste water and industrial waste water, is led through a waste water inlet channel 108 via a nozzle system 170 in which thorough mixing and fine division of the applied dirt materials takes place by blowing in gas", e.g. air, and from there to a settling basin 110, a sieve 112 and to a multi-stage charcoal filter device 106. Before the multi-stage charcoal filter 106

a pre-filter 142 is arranged which can be lowered into the waste water and which constitutes a coarse filter. According to the invention, this pre-filter serves to capture very heavy or stubborn contaminants and can, if desired, even completely replace the mechanical raking or sieve 112. This pre-filter 142 rotates countercurrently in relation to the flow direction of the waste water that flows through it. According to a preferred embodiment of the invention, as shown in Fig. 1g, the pre-filter consists of individual filter elements 144 which contain a carbon filling, whereby the filter elements are arranged on a transport chain 14 6 or a similar device which moves slowly or periodically and which transports the filter element in the same direction as the arrows shown in Fig. 2 into the waste water flow at the pre-filter's outflow end 140 and then in a counter-current direction upwards to the upper flow point 150 where the individual filter elements which now contain dirt are removed upwards from the water flow. It is an advantage of this design of the rotating pre-filter that the residence time of the filter elements in the waste water can be easily regulated depending on the observed degree of contamination by a corresponding increase or decrease of the speed of the transport chain 146. Of course, such or a similar construction can also be used for the subsequent coarse filters 114 and fine filters 116.

■ The filter elements 144 of the pre-filter usually comprise a suitable frame which contains a loose filling of at least a proportion of coal particles, preferably in a pelletised state. This frame is perforated within the area of the applied filling to allow the passage of liquid. After the filter elements are. having been removed from the waste water stream, the dirty coal fillings are transferred by means of the transport chain 146 to a reactor of the multi-reactor mill (not shown), in which the coal is regenerated and at the same time

the adhering, organic contaminants are pyrolysed.- Thereby over-

the contaminants are fed directly onto new, usable filter carbon. It is then advantageous to use a draining device for the filter elements by means of which liquid adhering to the dirty filter carbon can be removed in the best possible way before the filter carbon is regenerated and/or incinerated. This draining device can e.g. contain a shaking mechanism (not shown) to improve the removal of water.

The filter elements which are now empty and which have perforated viewing surfaces which, due to the filling, are in a non-glued or unclogged condition, can now be filled with fresh, regenerated coal from a reactor of the multi-reactor mill (not shown, but also often referred to as a "furnace"). It may then be beneficial, even if this is not shown in the drawing, to possibly use intermediate washings should disturbances occur. The empty filter elements are then returned with fresh coal filling again to the pre-filter 14 2. Between the reactor's (not shown) coal outlet and the pre-filter, a heat collection device 156 can be arranged to cool the hot, calcined coal and to transfer the heat from the coal to heat-transporting means, f .ex;, water, via suitable heat exchanger devices (not shown).

With the help of the rotating pre-filter 142, which can possibly follow and/or be followed by a mechanical raking device, a large part of the organic components that are suspended or float up in the water and that were brought into the wastewater together with the rubbish is removed in a relatively simple way. It also appears from the drawing that the floated or suspended primary organic pollutants that have been captured by the sieve or the raking device 112, can be removed from the waste water by means of an upwardly directed conveyor belt 132 and supplied for combustion or the coking. The conveyor belt 132 is then designed respectively arranged so that a relatively unimpeded passage of water is possible during the capture and removal of the floating and suspended particles.

The waste water that has been cleaned in advance in the pre-filter 142, optionally with the support of the sieve 112, now passes through a system of coarse filters 114 and fine filters 116 before it is removed as service water via the outlet channel 113.

The coarse filter 114 consists of a number of coarse filter elements 120 which, by raising and lowering the coarse filter, can be removed from it to be calculated respectively. again can be traced back to this. The filter elements 120 are usually filled with normal filter carbon of a suitable particle size, preferably in a pelletized state.

During operation, the filter elements are moved countercurrently from the end of the filter 122 to the beginning of the filter 124.

The fine filter .116 likewise consists of a number of filter elements 126 which are optionally moved step by step in countercurrent to the waste water from the lower end 128 to the upper end 130. The fine filter can be cleaned by backwashing, possibly in the backwashing devices 134 which are intended for this purpose . The backwash^ water is preferably taken directly from the service water channel and can, if desired, be stored in the reservoir 136 which is provided with heating coils 138. The water that has been contaminated by the backwash flows through a return line back to the waste water inlet 108.

After the backwash is finished, the filter element can

126 is again returned to the fine filter 116 to be used again. However, the backwash is only an eventual feature as it usually

equal calculation of the dirt-laden and used single-fin filter elements is carried out in one reactor of the multi-reactor mile

(not shown), in which also a complete ashing and the removal of the ash from the reactor can possibly be carried out. In the latter case, the collection spaces in the fine filter elements 126 are filled with activated carbon from another reactor of multiple reactors

the mile, as the heat content of the activated carbon can still be utilized in the heat collection device 156 before it is brought into the waste water.

If the treatment route as the predominantly solid waste

which must be processed, followed, and where the solid waste includes e.g. food waste, paper, plaster, oil and tar residues, used car tyres, wood, glass or ash etc., the rubbish which is transferred from a silo 160 via a magnetic belt 162 and a conveyor belt 166 to the crushing rollers 164, is subjected to a first treatment or separation. In the deposition basin 110, the materials with a density of 1 or more may be deposited and removed by means of a transport device, e.g. a beaker 168. Due to the series of air nozzles 170, a thorough mixing of waste water and garbage is facilitated in order to improve the desired separation into organic and inorganic components. Via the transport device 132 is removed

the floating organic components of the rubbish from the raking plant 112 and are transferred to the reactor to be coked. In multireactor- . the mile thereby takes place a thermolysis and pyrolysis of both the mechanically removed pollutants, the dirty fill coal and other coal filters in the individual reactors which are arranged close to each other (not shown), whereby it can be facilitated for an intentionally partially direct introduction of the waste in the reactors.

Another particularly preferred embodiment of a pre-filter 188 is shown on Fig. Ic, which, incidentally, can also be used as a fine filter. This essentially consists of a system of tiltable, top-opening individual containers 182 with a perforated bottom wall 184 and which contain the loose filter material 186 running on a guide 180, whereby the guide 180 makes it possible to empty the dirty filter material and again fill the containers with fresh filter material by e.g. a tipping movement, bending movement or forced guidance influenced by gravity. It appears from Fig. 1c that the individual containers 182, which are shown here as buckets, move in the direction of the waste water, which releases its contents of dirt onto the filling material and then flows out through the perforated bottom wall. Depending on the speed or the content of dirty materials in the waste water, etc., the filtration can be easily adapted to the needs by moving a correspondingly selected number of containers 182 towards the waste water. Thereby, it can be achieved, as desired, that the waste water flows through only one or more of the containers, as the individual containers can also intentionally be removed laterally from the waste water inflow 194 around the guide 180 or moved into the waste water inflow 194. The emptying of the dirty filter material by e.g. . a yaw bending movement means that the filtering material is discharged onto a conveyor belt 190 which transports the dirty filtering materials to the furnace. The renewed filling of filtering materials into the containers 182 is then carried out by means of a transport device that comes from the furnace, e.g. a conveyor belt 192.

This device has proven to be excellently suited to the changing needs of the continuous utilization of waste water as it prevents clogging of the filter media due to a simple supply and discharge of filter material, and also due to the simple connection of the containers 132, which has a speed that is also adjustable in relation to the speed of the water, also represents a very flexible system. In Fig. 2, a suitable filtering device is also shown with an endless bucket filter 330 on a belt which can be fed into the waste water stream at a suitable place. The bucket filter includes regular

show a pair of laterally arranged conveyor belts 332 or a similar transport device". which is driven via rollers 334 so that the upper part of the belt 336 moves upwards to the left, as shown in Fig.2.

A series of upwardly open buckets are arranged on the belt with square, square or similar fixed bottom surfaces 340 and which are closed by means of a pair, e.g. triangular side walls 342. The individual buckets are connected to each other via upright, perforated walls 344 through which the wastewater to be cleaned can flow so that the suspended dirt materials remain on the filter filling. With the help of a correspondingly filled infill material, a protection is again obtained for the perforated screening walls, and there-

by it is possible to carry out the method continuously. As clearly shown in Fig. 2, fresh filter material can easily be filled in or the dirt-containing filter material is easily removed on the relevant end sides of the device.

It is preferred that the buckets 3 38 have a bottom surface with structure, e.g. pinched, thereby preventing as much as possible strong displacements of the filter filling material. For this purpose, the surface of the individual containers may also be further divided, preferably in the longitudinal directions.

Finally, in Fig. 3 and Fig. 3b is a device 400 which can be used as a pre-filter and/or as a fine filter, shown in cross- and longitudinal sections and which essentially comprises a circumferential, through-holed, endless band 402 which is at a distance from each other arranged stations 420, 430, 440 are filled with filtration filler material, dirty waste water flows through and freed from the dirty filler material. As shown in Fig. 3b, fresh filter material is applied in the filling area 440 from a transport device 428 that comes from the furnace, while in the flow-through area 420 the dirt-containing filling material is then tipped in a suitable manner into the discharge area 430

on a belt 4 26 leading to the furnace. The belt can then be driven by means of suitable drive elements 4 22 which are preferably located outside the flow-through area.

According to a preferred embodiment of the present method, the revolving belt is guided V-shaped within its flow-through area 420, V-shaped or flat within its filling area 440 and at an angle. respectively tipping position within its discharge area 430 flat on the drive elements 422. From Fig. 3a, such a V-shaped guidance of the band 402 within the flow-through area can be seen. Here, the belt 402 is guided on drive rollers 404, while the filter material

406 is located on the belt's surface structure 412. Because of this or a similar surface structure, displacement of the filter material can again be prevented. In Fig. 3a, the deposit of dirt particles is denoted by 410, while the water 408 flows out downwards at 4 24 through the porous band.

It should be noted that the belt can be operated continuously at different speeds or intermittently. Even then, the continuous supply and discharge of filtration filler enables a surface protection of the perforated filter elements which would otherwise be easily clogged.

It is clear that by using filter elements such as

of filtering material gets a continuous protection of the system's perforated viewing surface, since the filtering material can also be supplied in a simple way and removed continuously, it is possible to achieve a flexible and undisturbed operation of the overall system. This is further favored particularly due to the pelletisation of the carbon materials used in the pre-filters, coarse filters and fine filters and also due to the deliberately maintained presence of proportions of polar materials which can also be recovered from rubbish or waste water, especially calcined metal oxides, such as iron oxide, aluminum oxide or silicon dioxide, etc., in the state in which they come from the multi-reactor mill.

Claims (20)

1. Procedure for combined utilization of waste/cleaning of waste water, where the waste water is mixed with at least a part of crushed waste and a separation into organic and inorganic components is carried out, the waste water stream with those dissolved in it or suspended components of the garbage are passed through a two-stage filter of unactivated and activated carbon, the main part of the filter carbon saturated with dirt is thermally treated in a first reactor of the multi-reactor mile to be regenerated, whereby the dirt stored on the carbon filter is thermally decomposed during the extraction of coal and fuel gas, solid waste or..part of the filter coal which is saturated with dirt, is incinerated or is partially incinerated in at least one other reactor during extraction of heat and fuel gas, and the regenerated filter coal from the first reactor is again returned to the filtration zone for waste water, characterized in that the waste water containing garbage is passed through a multi-stage filtration system that is kept in motion and in which the coarse filtration in the is at least partially carried out by using loose fillings of coal which are extracted from the organic components in the rubbish and which are possibly pre-treated to increase adsorption and adhesion, and that the filling containing organic dirt materials is returned to the multi-reactor mill to coke the dirt materials. 2. Method according to claim 1, characterized in that the fillings for the coarse filters to be passed through first contain unactivated charcoal. 3.. Method according to claim 2, characterized in that the fillings for the filters that follow the coarse filter, at least partially contains activated carbon. 4. Method according to claims 1-3, characterized in that the fillings contain coal in a pelletized state. 5. Method according to claims 1-4, characterized in that the fillings also contain a proportion of polar materials. • . 6. Method according to claim 5, characterized in that the polar materials consist of aluminum oxide and/or silicon oxide. 7. Method according to claim 6, characterized in that the proportion of aluminum oxide and/or silicon oxide is obtained by mixing rubbish or waste water from paper manufacturing to the output systern, and that the coal is extracted from this admixture. 8. Method according to claims 1-7, characterized in that the filter is fed in countercurrent to the untreated waste water. 9. Method according to claims 1-8, characterized in that at least the fine filters are washed with service water before the dirty filling is emptied. 10. Method according to claims 1-9, characterized in that the filtration system is continuously filled with filler material and is then flowed through with waste water, optionally after a previous washing it is freed from dirty filler material and after renewed filling with filler material is again used for filtration. 11. Method according to claims 1-11, characterized in that the filters are moved in such a way to improve the filtering effect that a constant movement of the filling material is effected. 12. Multi-stage filtration device for carrying out the method according to claims 1-11, characterized in that it comprises a coarse filter (114) of at least partially sieve-shaped containers (120) containing unactivated, coarse coal, and a rotating pre-filter arranged in front of these ( 142) which can be swung into the waste water system and whose individual filter elements (144) which contain the charcoal filling can possibly be separated. 13. Multi-stage filtration device according to claim 12, characterized in that the rotating pre-filter (142) consists of a transport chain device which is provided with a draining mechanism. 14. Multi-stage filtration device for carrying out the method according to claims 1-11, characterized in that it as a pre-filter or as a downstream filter contains a bucket filter (330) which has buckets (338) which are open upwards and which are placed on a conveyor belt and which in the flow direction has a perforated wall (344), and-wherein the buckets contain filtering material. 15. Multi-stage filtration device according to claim 14, characterized in that the bottom surface of the buckets (338) is notched and optionally divided (350) in the longitudinal direction. 16 . Multi-stage filtration device according to claim 12-J5, characterized in that as a pre-filter and/or fine filter (400) it contains a revolving, through-holed, endless belt (402) which is filled with filtration filler at spaced stations (420, 430, 440) , is flowed through by contaminated waste water and freed from the dirty filling material. 17. Multi-stage filtration device according to claim 16, characterized in that the revolving band within its flow-through area (420) is guided V-shaped, within its filling area (440) V-shaped or flat and within its emptying area (430) in an inclined or tilt position flat on the drive elements (422). 18. Multi-stage filtration device according to claim 16 or 17, characterized in that the belt has a surface structure (412) which prevents a strong movement of the coal filling within the flow area (420). 19. Multi-stage filtering device according to claims 16-18, characterized in that the endless band is designed as a system of at least three single bands (428,426, 402) which are guided at an angle in relation to each other and which mutually serve each other and of which one belt (428) takes up fresh filtering material and delivers this to the following filtering belt (402) which transports the dirty filtering material onto the last belt (426 .) for transporting the filter material into the multi-reactor mile. 20. Multi-stage filtration device according to claim 12 or 13, characterized in that the pre-filter and/or fine filter (188) consists of a revolving system of tiltable, top-open single buckets (182) on a guide (180) which have a perforated bottom wall (184) and which contains the loose filter material (186), whereby the guide (180) enables emptying of the uncleaned filter material and renewed filling of fresh filter material by means of a tipping or deflection movement.