Process for the combined utilization of waste products and clarification of water and multi-stage filtration device therefor

The invention relates to a process for the combined treatment and disposal of solid waste and sewage comprising the steps of: providing at least one upper reactor, at least one lower * reactor which is proximate but spaced from the upper reactor, and a housing enclosing the reactors;

providing a multi-stage filter system consisting of a coarse filter or prefilter and one or several fine filters, whereby the coarse filter or the prefilter is stocked with loose fillings of non-activated filter coal, and the fine filter (s) is stocked with loose fillings of activated filter coal;

flowing the sewage initially through the coarse filter or the prefilter to remove therefrom particulate matter entrained in the sewage, whereby the particulate matter adheres to the non-activated filter coal and eventually substantially saturates the coal with particulate matter;

flowing the effluent from the coarse filter or the prefilter through the fine filter (s) to remove any remaining particulate matter and dissolved pollutants through adsorption by the activated filter coal of the fine filter(s), whereby the filter coal eventually is saturated with particulate matter; discharging usable water from the fine filter(s);

placing solid waste into the lower reactor, and at least initially heating the lower reactor to a temperature capable of maintaining the incineration of solid waste therein; flowing into the lower reactor a limited amount of oxygen in order to sustain the incineration process, liberate heat energy and generate a first combustible gas while heat liberated in the lower reactor causes a corresponding heating of gas in the housing and thereby heats the upper reactor; periodically removing from the coarse.fliter or prefilter, or the fine filter(s) filter coal saturated with particulate matter;

placing saturated filter coal into the upper reactor and maintaining the interior of the upper reactor substantially oxygen-free, whereby heat energy from the lower reactor heats the saturated filter coal in the upper reactor and causes degassing and a resulting carbonization of organic matter adhering to the filter coal to thereby regenerate the filter coal and generate additional filter coal and a second combustible gas;

removing from the lower reactor ash formed therein and discarding the same, and removing from the upper container regenerated and additional filter coal;

treating at least part of the regenerated filter coal to improve its adsorption and adhesion capacity;

placing regenerated and at least partially treated filter coal in the coarse filter or prefilter or in the fine filter (s) to replenish saturated filter coal removed therefrom;

and utilizing energy contained in the heat-treated gases before their final disposal.

The invention concerns additionally multi-stage filtration devices for carrying out the process.

From DE-OS 25 58 703 of the applicant, a process of the first-named type is known. In this process a simple and at the same time economic method shows how:

1) the used water is employed as transport means for the waste as well as to separate it into substantially inorganic and organic components;

2) the contaminated waste-laden water is clarified by filtration using normal and active coal;

5) a part of i^he waste or of the active coal carrying sludge is incinerated giving off a combustible gas, which delivers energy for thermolysis; and also

4) the majority of the filter coal laden with sludge is thermally decomposed in a thermolysis reactor, whereby the filter coal is regenerated and a carbonization gas rich in hydrocarbons is produced.

Even though by this process many advantages are obtained, and especially an optimal use of the energy content of the waste as well as its utilization additionally for the treatment of waste water is made possible, in the practical implementation of the process, some difficulties have appeared.

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These appear especially if waste of a constantly changing initial composition is fed into the system, and there is simultaneously a variation in the composition of the waste water being supplied. Hereby, due to particularly obstinate and unpleasant pollutants there may be difficulties particularly for the vital separation and filtration processes. The continuous processing of waste and used water may be impeded by the clogging or stopping-up of the coal filter, by changes of flow and by excessive abrasion of the filter coal. Thereby there may also be some passage of impurities, especially of polar substances, through the fine filter which is charged with active coal.

The invention therefore is based on the objective of improving the filtration processes and separation methods in the process mentioned initially in simple and continuously-operating ways. Thus in particular, by varying the filter conditions or by establishing a new type of filtration device and operating them, an improvement of the adhesion process of the pollutants at the filter media is attained, without the passage of the used water which is to be clarified being impeded. By chosen variations of the filter media and use of the waste assembling, lastly a further improvement of the attainable filter effect with additional collection of the strongly polar substances should be achieved.

This objective is thereby attained in that the used water carrying waste is led through a moving multi-stage system of filters, in which the roughing filtration is at least partly effected by loose fillings of coal, which are produced from ־9the organic components of the waste and are optionally pretreated to increase the adsorption and adhesion, and the filling laden with organic contaminants is led back into the multireactor pile for the carbonization of the sludge.

The invention is substantially built upon the recognition that by using a multi-stage filter system, in which the filtration processes take place at least' partly through loose fillings which contain coal, the avoidance of the formerly observed dis advantages is made possible. By dividing the filtration processes into several stages, and especially by the previous use of the roughing filters which contain loose fillings of filtration materials, a mechanical and partly also adsorptive separation of the sludge from the used water is possible, without stoppages or the clogging of the perforated walls, screens and similar filtration devices. The blockage or clogging of the perforated walls and screening units is avoided by the fact that the sludge adheres to the particles of the filtration fillings, and the removal by a simple tipping or tilting process of the filtration material which is laden with sludge together with the freeing of the unclogged perforated screen surfaces is possible. Thus the continuous refilling of the emptied filter system with fresh filtration material and thereby an undisturbed cycle of the filtration process becomes possible. The fillings laden with sludge which are extracted are then led back for the subsequent carbonization of the contaminants into a reactor of the multi-stage reactor pile, producing new filtration coal.

It is advisable to carry out the filtration by loose fillings in suitable devices as roughing filtration, before later a a further filtration and clarification of the used water which is passed through non-activated and activated coal contained in further filter units takes place. Even though it is possible to switch in a mechanical raking unit before the prefilter which has a loose filling of filtration material containing coal, the unit can be completely replaced by the prefilter itself, since the blockage of the operational parts of the filtration devices is largely excluded by the filtration by means of the fillings.

The prefilters which serve as the first roughing filter are in general operated in counter current to the passing polluted used water, whereby a filtration takes place on the basis of the gravity effects. But the roughing filters can also be rotated in standing water or can be moved by used water flowing away.

The fillings of filtration material contain mainly coal.

In the roughing filters which are first passed through, the coal is in general in non-activated lumps and thus serves as a mechanical filter. The coals are produced from the organic components of the waste without activation. Depending on the type of composition of the waste water to be treated or of its contaminants, a certain proportion of activated coal can be added to the roughing filter, and this too is produced from the organic components of the waste.

’ According to a preferred embodiment of the invention, the fillings contain coal in a pelletized state, to keep the abrasion into coal dust as low as possible. This pelletization of the coal fillings is preferably performed both for the roughing filtration and for the fine filtration, in the case of the latter with activated coal.

Proceeding from the coal produced by carbonization in the reactor from waste, this is finely crushed after cooling, mixed with an organic binding means such as tar, briquette pitch, etc and then compacted at high temperature and pressure, e.g. 80° C with a pressure of 1200 kp/cm .This compacted coal can then be again reduced to the desired core size by crushing. It is then non-activated filter coal which is suitable for roughing filtration. Should the.us.e of the coal for fine filters be planned, the splint granubte obtained is activated in the per׳־ se known manner, which for example can be achieved by heat treatment for several hours in the gas-tight sealed reactor of the multireactor pile, by introducing steam and/or zinc chloride. The active coal which is pelletized and thus obtained from the organic components.״ of the waste has a good abrasive quality with a simultaneously high surface development.

The quality of the pelletized coal can be additionally increased by spraying the waste before it is fed into the first thermal stage or in the first thermal stage with liquid combustible organic waste products, such as used oil, for example.

By this kind of pelletizing, the abrasion effects on the coal and the stoppages caused by it can be largely avoided.

Specially favorable filtration effects are achieved by loose coal filtration material which contains a proportion of polar substances. This share of polar substances can be achieved by mixing with the waste and/or used water such waste products as appear during the heat treatment in filtration-productive and actively adsorptive form.

-ItThis can be achieved for example by adding to the household and industrial waste to be treated, which is conveyed on the used water, usually communal effluent, a certain proportion of used water from paper manufacture or porcelain processing. Waste or used water from industry usually contain polar substances, e.g. fillings such as alumina,silicon oxide, titanium oxide, etc which are obtained during conversion of the organic components present in coal at coking temperatures of from 300 to maximally 800° C. in activated form. Other polar metal oxides which come into question , which frequently have a small positive charge, are e.g. iron oxide and magnesium oxide, as they are found in the ceramic and aluminum producing industries as waste sludge. By the planned admixture of waste sludge which yield during the coking process activated polar oxides, it is possible to attain at the mechanical coal filters not only additional filtration effects due to polar electrostatic effects, but there is also a favorable effect on the clarification and sedimentation behavior of the used water. Therefore this step of the composition of the loose fillings from both coal and also polar waste products, apart from the pelletization of the fillings, is preferred in the embodiment of the ' process according to the invention especially. This is particularly true of the fine filtration.

According to a further embodiment of the process according to the invention, at least the fine filters are backwashed with usable water before the charged filling is emptied out, and this water is preferably taken from already clarified used water in a branch current.

The filtration processes using loose fillings, preferably in pelletized form, can thereby be partly further improved by ־13achieving the constant motion of the fillings. In the motion of the fillings, e.g. by the motion of the container holding them, care must be taken that this does hot attain a fluidized bed state, since that reduces the mechanical filter effect.

The process according to the invention is prefrably carried out so that the filtration system is constantly filled with fillings, then traversed by the used water laden with waste, optionally freed of polluted fillings after previous backwashing, and after refilling with fillings is again used for filtration. These various measures undertaken continuously can for example be achieved at spatially separated stations of a single filtration device. Such multi-stage filtration devices are later described for the performance of the invention’s process as preferred embodiments in Fig 1 to Ja. Even though these fugures show specially suitable embodiments of the filtration devices proposed, the execution of the process according to the invention is not exclusively limited to such devices, since it is easy for the man skilled in the art to note that by certain modifications similar effects can be attained within the framework of the invention's process.

Fig. la, lb describe the principal stages of a multi-stage filtration process according to the invention;

Fig. Ic shows a circulating bucket filter, which can be used both as roughing filter and as fine filter;

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Fig.2 shows a belt filter, and

Fig.5a,pb represent a continuously operating filtration belt.

Fig. la shows the main‘filtration cycle of the process according to the invention, whereby the necessary reactors required for the system to regenerate and optionally to combust the filtration coal which is polluted in the multireactor pile, in which the' organic component⁵ of the waste are converted into coal, partly in activated and partly in non-activated form, as well as the waste combustion can take place, are not shown. Re these additional devices, the first-named DE.OS 25 58 705 of the applicant, as well as the parallel patent application to the present application which was simultaneously filed ״Process for combined waste utilization and clarification of waste water” File No ?A'״(, are expressly mentioned. As multireactor pile, the process according to the invention uses an arrangement which consists of at least two, preferably 5 or more, essentially cylindrical, horizontally mounted and parallel drums which can each be rotated about their axis. In a preferred reactor arrangement, they are mounted in a triangle above one another, so that one may speak of a pair of reactors below and an upper reactor above them mounted between them.

In the following the filtration process according to the invention is explained separately on the basis of following the path of the used water and the solid waste:

Th® used water, both urban used water and industrial effluent, is led through an effluent intake channel 108 via a nozzle system 170, in which by gas injection, e.g. air, a mixing and fine distribution of the incoming pollutants takes place, to a settling basin 110, a screen 112 and then to a multi-stage filter device 106.In front of the multi-stage coal filter 106, a prefilter 142 is provided. which can be inserted in the used water as a roughing filter. This prefilter serves according to the invention to catch very heavy or stubborn impurities, 9 and can if desired fully replace the mechanical rake or the screen 112. This prefilter 142 rotates in counter current to the arriving used water. In a preferred form of the Invention, as shown in Fig. lb, the prefilter consists of individual filter elements 144, which contain a coal filling, whereby the filter elements are mounted on a slowly or intermittently moving chain belt 146 or the like, which transports the filter element in the direction of the arrow in Fig.2 into the used water conduit in the outflow end of the prefilter 148 and then in the counter flow direction upstream to the upstream point 150, at which the now polluted single filter elements are withdrawn from the flow in the upstream direction. An advantage of this design of the rotating prefilter is that the duration of the insertion of the filter elements in the used water can easily be made dependent on the observed degree of impurities by increasing or reducing the speed of the conveyor chain 146. Naturally this type or a similar design can also be used for the subsequent roughing filter 114 and fine filter 116.

The filter elements 144 of the prefilter comprise in general a suitable frame, which contains a loose filling at least of a proportion of coal particles, preferably in pelletized form. This frame is perforated in the area laden with fillings, to allow the passage of liquids.

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After removal of the filter elements of the coarse filter or prefilter or the fine filter (s) ' from the used water flow, the polluted coal fillings are led by a chain conveyor to a reactor of the multireactor pile (not shown in the figure) in which the regeneration of the coal takes place. In Fig. 1b this is shown for a prefilter (142), a coarse filter (114) and a fine filter (116) via chain conveyors (146, 120, 126). The most heavily loaded filter elements (150, 124 and 130)are removed from the series of filter elements and transported to the multireactor pile in which the heavily loaded filter material can either be

a) thermolyzed in a thermolysis reactor to yield reusable filter coal, or

b) pyrolyzed in order to provide heat energy.

Thermolysis under a) is carried out in an atmosphere free of oxygen; the sludge which adheres to the filter coal is thermally decomposed yielding a carbonization gas and regenerated filter . coal. In this step the impurities are transformed directly into usable filter coal.

Pyrolysis of step b) takes place in the pyrolysis reactor in an atmosphere of sub-stoichiometrical supply of oxygen at a temperature not above 800°C, providing a combustible gas rich in hydrocarbons and heat.

When removing filter elements via a chain conveyor it is advantageous tjQ^grovide a dripping mechanism for the filter elements, through the liquid assembled on the polluted filter coal can be best removed before the coal is regenerated or incinerated.

This drip device can contain e.g. a shaker mechanism (not shown) to improve the removal of water.

The now empty filter elements, whose perforated screen surfaces are maintained in a non-blocked and non-clogged form by the β

filling can now be charged with fresh, regenerated coal from a reactor of the multireactor pile (not shonw in the figure, but also marked as furance). In this way the regenerated filter coal is recycled into the filter elements, using advantageously loose fillings of non-activated filter coal for the coarse filter or the prefilter and loose fillings of activated filter coal for the fine filter(s).

It may also be advisable to provide interim washing processes in the event of stoppages, but this it not shown in the figure. The filter elements are then led back with fresh coal fillings, e.g. to the prefilter (1 42), the coarse filter (11 4) or the fine filter (116). Between the coal outlet of the (not shown) reactor and the filter(s) a heat collector device (156) for cooling the hot regenerated coal via suitable heat exchangers (not separately shown) by heat transporting media, e.g. water, can be provided.

By the rotating prefilter (142), to which optionally a mechanical rake can be connected before or after it, a large part of the suspended or floating organic components in the water, which have been brought into the used water by the waste, can be relatively simply removed. Further it can be seen from the figure that the floating or suspended, primarily organic impurties, which are caught by the screen or rake (112) can be led through by means of an upwards moving conveyor belt (132) from the used water and fed into the combustion or coking process. Here the conveyor (132) is so designed or arranged that relatively unimpeded passage of water is possible through the collection and removal of the floating und suspended particles.

The prepurified used water cleaned by the prefilter (142) and obtionally by screen (112) now enters a system of roughing filters (114) and fine filters (116), before it leaves as usable water via outlet conduit (118). The roughing or coarse filter (114) consists of a multitude of coarse filter elements (120) which leave the coarse filter by raising and lowering it for regeneration or can be. led back into it. The filter elements (120) are usually filled with normal filter coal of suitable particle size, preferably in pelletized form. The filter elements are moved during operations in

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counter-current from the end of filter (122) to the start of filter (124).

As soon as filter element (124) is too heavily loaded with waste it leaves the series of filter elements and is led to the reactor for regeneration. When the filter coal of filter element (124) is regenerated in the thermolysis reactor it is filled into container J-120) and led back to the coarse filter into position (122).

The fine filter (116) consists also of a number of filter elements (126), which are also moved in counter-current to the used water from the lower end (128) to the upper end (130) by stages. The fine flter can be cleaned by backwashing, optionally in a backwashing unit (134) which is provided for the purpose.

Preferably the backwash water is taken direct from the usable water conduit (118) and can if desired be stored in the reservoir (136) which has a heater coil (138). The water contaminated by the backwashing flows through a return conduit back to the used water inlet (108).

After the end of the backwashing, the filter element (126) can again be led back into the fine filter (116) to be used again. The backwash is, however, only an optional measure, since the usual regeneration of the individual filter elements which arg polluted and used up is carried out in a reactor of the (not shown) multireactor pile, where itis regenerated and at least partly treated to improve the capacity

ר of the filter coals' adsorption and adhesion and then returned to the series of filter elements in the end-position (128). Optionally in the multireactor pile a complete ashing and removal of the ash can take place in case there is no more filter coal needed or the filter coal is too heavily contaminated and not worth regenerating it. For recycling the fine filter elements (126) the latter are filled with fresh active coal from the regeneration reactor of the multireactor pile. The heat content of the filter coal is still usable within the heat collector (156) before inserting the filter coal in the used water.

If we now follow the path of the mainly solid waste to be processed, which inter alia may comprise foodstuffs wastes, paper, synthetic materials, oil and tar residues, old tyres, wood, glass, ashes, etc., this is subjected to a first treatment or separation from a bin (160) via a magnetic belt (162) , a conveyor belt '166) , and the shredding rollers (164). In the settling basin (110) the substances of a density of 71־ are left, and removed by means of a conveyor, e.g. the bucket conveyor (168). Via a series of jet nozzles (170) a basic mixing of used water and waste takes place to improve the desired separation into organic and inorganic components. Via a conveyor ΐ(ί -u132 the swimming organic components of the waste are removed from the screen 112 and are transferred to a reactor for coking. In the multireactor pile takes place in the individual reactors which are directly adjacent to each other(not shown in the figure) a thermolysis and pyrolysis both of the mechanically removed impurities and of the polluted filling coal and other caol filters, whereby to the desired degree a partly direct introduction of waste into the reactors can be provided.

In Fig. Ic another preferred embodiment of a prefilter 188, which also can be used as a fine filter, is shown. This consists of mainly a track 180 mounted sytem of tipping, upwards opened single buckets 182, whose floors 184 are perforated and contain loose filter material 186, whereby the track 180 makes possible the unloading of the polluted filter material and the reloading with fBesh filter material by e.g. a tipping, tilting or weight-induced guide motion etc. As can be seen from Fig. Ic, the single containers 182, here shown as buckets, move to meet the used water, which unloads its sludge onto the fillings and then penetrates the perforated floors. Here the filtration can easily be adjusted to the requirements depending on speed, charge of used water with contaminants etc, so that a selected number of containers 182 are led toward the used water.Thus a used water flow through one or more containers can be achieved as desired, as the single bins can be taken sideways out of the used water stream 194 round the track 180 and can be inserted in it. The emptying provoked e.g. by the tipping of the polluted filtration material leads the polluted filtration material to a belt which leads to the furnace 190.

The refilling of the container 182 with filtration material then takes place with a conveyor device, e.g. 192. coming from the furnace.

This device has proved itself for the constantly changing conditions of the waste water/waste utilization operation to be excellent, since both a stoppage of the filter media is avoided by a 'simple feeding and removal of filtration material, and also by the easy switching in of containers 182, whose speed can be regulated against that of the used water,a very flexible system is attained.

In Fig. 2 an equally suitable filtration system is shown, which has an endless bucket filter 330 on a belt, which can be placed in the used water flow at a suitable point. The bucket filter comprises in general a pair of laterally mounted conveyor belts 332 which are driven by rollers 33¼ that an upper part of the belt 336 is moved upwards to the left, as shown in Fig.2,on the belt a number of buckets are mounted, of which the solid floor surfaces 340 may be square, rectangular or the like, and are closed off by a pair of e.g. triangular side walls. The single buckets are connected with each other by perforated walls 344, which allow the flow of the used water to be clarified and the deposit of the suspended contaminants from the filtration materials.Via correspondingly topped up fillings, the protection of the screen walls is attained and thereby a continuous operation of the process is possible.As can well be seen from Fig 2, a loading of fresh filtration materials or the emptying of polluted filtration materials can easily be acrried out at the ends of the arrangement.

It

-ϊίIt is preferable that the floor surface of the buckets 358 is structured, i.e. knubbed, to prevent as far as possible strong movements of the filter materials. For this, optionally further subdivisions of the surface of the containers can be provided, which is preferably done in the longitudinal direction.

In Fig 3a and 3b there is finally a device 400 usable as prefilter and/or as fine filter shown in cross-section and in longitudinal section, which essentially consists of a circulating endless belt 402 which is perforated and is loaded with filtration materials at spatially separated stations 420, 430 440, passed through by polluted used water and freed of contaminated fillings. As shown in Fig 3b, in the loading area 440 via a conveyor coming from the furnace 428, fresh filtration materials are carried, while the fillings which are polluted in the throughput area 420 are then tipped in a suitable manner in the unloading area 430 onto a belt 426 leading' to the furnace. Here the belt can be driven by suitable drive elememnts 422, which preferably are located outside the throughput area.

According to a preferred embodiment of the process according to the invention, the circulating belt is V-shaped in the throughput area 420, in the loading area 440 it is V-shaped or flat and in the unloading area 430 it is led flat on the drive elements’ 422 in the tipping or tilted position. In Fig. 3a, there is a V-shaped guide track of the belt 402 visible in the throughput area.Here the belt 402 is led on the drive rollers 404 whereby the filtration materials 406 are located on the surface structure of the belt 412. By these or similar means, the strong displacement of the filtration materials can be prevented. In

Fig j5a the unloading of sludge particles is shown as 410, while the water 408 exits via the porous belt downwards at 424.

It should be noted that the belt can be continuously driven at varying speeds or intermittently.Here too the continuous supply aid removal of the filtration fillings permits a surface protection of the otherwise easily blocked perforated filter elements.

It is easily recognised that by the use of filter elements which provide; a continuous protection for the perforated screen surfaces of the system by means of filtration materials and which can conveniently be continuously supplied or removed, a flexible and trouble-free operation of the whole system is achieved. This is especially favored by the pelletization of coal materials, which are used in the prefilters, roughing filters and fine filters, as well as by the planned presence of proportions of polar materials, which are also producible from waste and/or used water, particularly calcinated metal oxides, such as ferrous oxide, alumina, silica etc, as they emerge from the multireactor pile.