Process and device for the combined utilization of waste products and clarification of water

The invention relates to a process for the combined treatment and disposal of solid waste and of 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 first filter and stocking the first filter with non-activated filter coal;

providing a second filter and stocking the second filter with activated filter coal;

flowing the sewage initially through the first filter 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 first filter through the second filter to remove any remaining particulate matter and dissolved pollutants through adsorption by the activated filter coal of the second filter;

discharging usable water from the second filter; placing solid waste into the lower reactor, and at least initially heating the lower reactor to a temperature capable of maintaining the incineration of the solid waste therein; flowing into the lower reactor a sub-stoichiometrical amount of oxygen in order to sustain the incineration process, which is maintained at a temperature not essentially above 800°C, liberate heat energy and generate a fi^st 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 first filter, filter coal saturated with particulate matter;

placing saturated first 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 first filter coal in the upper reactor and causes degassing arid a resulting carbonization of organic matter adhering to ithe first filter coal to thereby regenerate the first filter coal and generate additional filter coal and second combustible gas;

removing from the lower reactor ash formed therein and removing from the upper reactor regenerated and additional filter coal, at least part of which is subjected to a pelletization process;

discarding the ash and placing such amount of filter coal in the first filter to replenish saturated filter coal removed therefrom;

collecting the first and second combustible gases and heating the gases under substantial exclusion of oxygen to a temperature sufficient, to split relatively long chain hydrocarbons into relatively short cheuin hydrocarbons; and utilizing the energy contained in the heat treated gases before their final disposal.

The invention also relates to a device for carrying out this process.

DE-CS 25 58 705 discloses a method of combined waste products utilization and clarification of waste water. This method functions in a comparatively simple way, in that

1. the waste water serves as a means of transport for the waste as well as to separate the latter into inorganic and organic components,

2. the waste water which is contaminated. with the waste is purified by mechanical and adsorptive filtration using normal and active coal;

5. a part of the waste or the active coal saturated with sludge is incinerated, and emits, apart from combustible gas, the heat necessary for thermolysis;

4. the main part of the filter coal saturated with sludge is thermally decomposed in a thermolysis reactor, whereby the filter coal is regenerated and new coal and carbonization gas are produced.

Even though the said process has a number of advantages, it is still desirable to improve it with a view to the optimal use of energy.Moreover, it is necessary to eliminate disadvantages and difficulties which occur during the performance of the process. Thus when using active coal or coal produced according to the above-named DE-OS, abrasion of the coal may occur, which leads to coal losses, stoppages or clogging in the filter towers,and to the pollution of the usable water so produced.

It is the objective of the invention to improve the energy balance of the process by the optimal use of all the energy sources and to ensure the trouble-free course of the process, which is particularly to be attained by the planned choice of the reaction conditions within the multireactor pile, and a corresponding treatment or processing of the products which emerge from the multireactor pile.

Ths objective of the present invention is solved by ensuring that the oxygen input in the first reactor of a multireactor pile takes place in a sub-stoichiometric ratio, so that the pyrolysis is maintained, the temperature does not rise substantially above 800° C ,whereby a combustible gas rich in hydrocarbons is produced and heat is released, which heats the second reactor(this process step will be henceforth described as pyrolysis);

the filter coal saturated with sludge is degassed in a second reactor in an oxygen- free atmosphere and the sludge which adheres to the filter coal is thermally decomposed, whereby a carbonization gas rich in hydrocarbons and more coal are produced (this process stage will henceforth be called thermolysis);

at least a part of the coal produced or regenerated in the second reactor is subjected to a pelletization process;

and optionally at least a part of the combustible or carbonization gas formed, which contains long-chain hydrocarbons, is split jn a thermal cracker unit into short-chain hydrocarbons, optionally using the thermal content of the gas by means of a heat exchanger.

The multireactor pile which is provided according to the invention may comprise several reactors of the first and second types, which preferably constitute continuously operating rotary drum furnaces. It is also preferable that the first reactor is located in the lower part of the multireactor pile, while the second reactor is preferably in the upper part of the pile above and immediately adjacent to the first reactor, so that it can be heated by the latter via convection heating.

In general, the first reactor serves for pyrolysis of the waste, while in the second reactor the coal saturated with sludge is thermolysed. Moreover at periodic intervals, the first reactor can be charged with saturated normal or active r

-μcoal, which is followed by incineration of the coal contaminated with heavy metals, and the heavy metals together with the ash are removed from the reactor. Moreover it is possible to charge the second reactor(thermolysis reactor) with solid, preferably organic waste or to mix waste into the furnace charge.

According to the invention, the process is marked by a particularly advantageous combination of different process steps, which permit a maximal utilization of energy from the processes taking place in the multireactor pile, whereby the heat generated during pyrolysis or combustion is controlled by measured inputs of oxygen, and the remaining energy is obtained in the form of a combustible gas which is relatively rich in hydrocarbons. By using the process according to the invention, it is possible, depending on the composition of the waste, to operate the combined installation for waste utilization and waste water clarification without the input of external energy, and moreover to produce additional energy as well.

On the basis of the selected, particularly favorable conditions within the multireactor pile, a filter coal with good adsorption properties as well as a carbonization gas which is particularly strongly enriched with hydrocarbons are obtained during the thermolyzatlcn stage. By the special processing of the combustible or carbonization gas emerging from the multireactor pile, storable energy is produced, whereby the thermal content of the gas is used by means of a heat exchanger in the installation to carry out the process according to the invention for predrying, heating the backwash water, or for the thermolyzation process. f4oreover by the planned treatment of the filter coal emerging from the multireactor pile, difficulties in the execution of the process are avoided. The invention provides that the

-XXregenerated filter coal used in the coarse filter is either pelletized.,i.e. pressed into a compact form of the desired particle size, whereby the abrasion effects on the coal and the resulting pollution of the water produced, as well as the stoppages caused by fine filter coal in the filter elements ־ are avoided , or a filter'material with a particularly large surface area,i.e. with a high adsorption capacity, is produced by pretreat'ing the coal to be activated which is’ subsequently used in the fine filter .These process steps will later be more precisely explained.

According to the invention pyrolysis takes place at a temperature which should not rise substantially above 800° C. A specially preferable temperature range lies between 500 and 800° C. Sometimes it is preferable to work at temperatures between 300 and 400° C , to avoid the vaporization of certain heavy metals.

The oxygen input for the first reactor takes place at a substoichiometric ratio. The oxygen is thereby adjusted in such a way that pyrolysis is maintained, yet the temperature is so controlled that it does not rise substantially above 800° C. The oxygen volume added amounts preferably to 30 to 90% of the stoichiometrlcally necessary oxygen volume, optimally 50 to 80%. The oxygen volume here is varied according to the composition of the furnace charge to be incinerated and its degree of humidity.

The combustible gas which is generated by pyrolysis in the first reactor, because of the controlled heat production, is relatively rich in hydrocarbons; the carbonization gas which appears in the second reactor during thermolysis of the contaminated filter coal or of the solid waste is particularly rich in hydrocarbons, especially long-chain hydrocarbons.

The combustible or carbonization gas so formed can be used as an additional energy source for the thermolysis process or as fuel for a separate boiler, gas combustion device, preferably a combustion engine, or the like.

Moreover it is possible to treat the combustible or carbonization gas in a cracker device, to split long-chain hydrocarbons into short-chain molecules, which can again be used directly in combustion engines, turbines and the like, or which after being liquified form an easily storable source of energy.

According to the invention it is advantageous to cool the gases emerging from the high temperature zone adequately to liquify them, whereby optionally a separation into liquid nitrogen and a liquid, combustible, nitrogen-free gas, e.g. a methane gas, takes place.

In one of the preferred designs of a cracker device according to the invention, which works with high efficiency, the splitting of the long-chain hydrocarbons into short-chain hydrocarbons takes place in an oxygen-deficient high temperature zone at a temperature of at least 1^00° C. The cracking of the long-chain hydrocarbons can also take place in said apparatus with oxygen excluded, so that no combustion or oxidation of the gas produced results.

The said high temperature zone is produced within the cracker ־. unit by filling an upright container with combustible materials such as wood or coal, for example with filter coal, the fuel is then incinerated at the lower end of the container by injecting a measured quantity of oxygen, and the combustible gas is led through the device in a downward direction, whereby the oxygen volume is so adjusted that a controlled incineration of the materials as well as the attainment of the desired temperature is ensured.

The combustible materials are fed into the device in adequate quantities in such a way that during operations a part of the materials shows a relatively low temperature, whereby when the said combustible or carbonization gas is led over or through the materials at a low temperature, the solid and liquid particles carried by the gases are caught, and the latter, as soon as the said materials arrive in the high temperature zone, are also burnt.

It is advantageous to lead the exhaust gases which occur through a heat exchanger, whereby the thermal energy of the exhaust gases is transferred to the heat exchanger medium. The heat produced by the exhaust gas can either be used for predrying the solid waste and/or the filter coal saturated with sludge, or it can be used to support the pyroly.tic or thermolytic steps which are taking place in the multireactor pile. Moreover, by using a second heat exchanger, the heat produced from the exhaust gas can be employed for heating the water used in the backwashing of the saturated active coal, to facilitate the desorption of the materials filtered out, which adhere to the active coal. Moreover, it is advantageous to lead the exhaust gas through a coal filter for the removal of particlelike impurities.

The invention provides that tie filter coal produced in the second reactor is specially treated, to avoid the difficulties which may arise during the process as a result of coal abrasion. For this, the regenerated coal, which is relatively soft and has a greatly varying particle size, is pelletized according to one of the conventional processes, optionally with the use of a binding material. Here it is necessary to separate off the fine coal particles and the coal dust, e.g by use of a sieve or screen, which are then fed intothe pelletizing device; subsequently the , pellets - can be mixed with the residue from the sieve,i.e. with the coarser coal particles. This mixture then serves as the filling for the coarse or roughing filter elements (1st filtration section).

For the production of active coal, regenerated coal is pretreated according to the invention, to give it an adequate hardness and to some extent a uniform particle size.

Therefore, the coal obtained in the second reactor is finely crushed and mixed with e.g. tar or pitch in the ratio 10:1 to 5: 1. This coal/tar or coal/pitch mixture is then compacted using high pressures, preferably at 1000 to 2000 kp/cm , and at temperatures which are just above the softening point of the tar or pitch concerned. Then the resulting coal/tar or coal/pitch mixture is ground down to the desired particle size. This can preferably be done with the aid of a roller frame, to keep the fine part as small as possible. But of course other crushing installations, e.'g. hammer mills, can be used.

The particle size, to which the filter coal is crushed, depends on the purpose foreseen: active coal which is to be used for purification of water , should preferably have a particle size between 0.5 and 1.5 mm. The cative coal used for gas cleansing has a preferred particle size of 2 to 3 ram.

To the extent that the coal which is later to be activated is to be used for gas cleansing, the following process is useful: the coal produced in the second reactor is finely crushed, /«?

-XX- .

mixed with tar or pitch in a ratio of 10: 1 to 5: 1, and then pressed direct into briquettes at high pressures, preferably

פ

1000 kp/cm , and at temperatures which are just above the softening point of the tar or pitch used, by means of extrusion presses.

The splint granualate or briquettes thus obtained can then be activated in an activating device according to the usual technical methods either with superheated steam or by chemicals. Thus an active coal with a specially high adsorption capacity is obtained. This activated coal is preferably pelletized in a pelletizing device.

The figures show advantageous embodiments according to the invention, which should not restrict the scope thereof, and they will be explained below:

Fig.l: Schematic flow diagram of the process according to the invention for combined waste utilization and clarification of waste water;

Fig.2a and 2b: Combined process for waste utilization and clarification of waste water according to the invention;

Fig.3: Schematic flow diagram for the manufacture, utilization and regeneration of normal and activated filter coal according, to the invention;

Fig.4: Frontal view₄in cross-section, of the multireactor pile according to the invention;

Fig.5: Sideview, in cross-section, of the multireactor pile shown in Fig.4 along the line 5-5;

Fig.6: Cracker device according to the invention.

Fig.l shows in a schematic flow diagram the material flow in treating solid and liquidwaste within the waste utilization and waste water clarification installation (102) ,according to the invention. The installation comprises a multireactor pile 104. The solid waste to be processed, which inter alia may be foodstuff residues, paper, synthetic materials, oil or tar residues, old tyres, wood, glass, ashes and the like, is so pretreated by magnetic belt selection, shredding ., and flotation in waste water that it consists substantially of organic componentfe;-for further treatment. In the multireactor pile 104, the solid waste is pyroly ,ed in a first reactor in an oxygen-deficient atmosphere, forming heat, combustible gas, and ashes.

The waste water can be either urban waste effluent or industrial waste water. A multistage coal filter 106 serves to clarify the waste water, so that the latter can at least be used for industrial purposes. The coal filter 106 is preferably a two-stage filter, which consists of a coarse and a fine filter. The filter coal of the coarse filter is periodically regenegarated in the pile 104 with the particles and sludge adhering to the coal, i.e it is subjected to heat treatment under , exclusion of oxygen. The coal losses are compensated for by the newly-produced and regenerated coal.

Fig. 2a and 2 b, supplemented by Fig.3. show a general view of the process method used in the waste utilization and waste water clarification installation 102. A waste waterinlet conduit 108 takes waste water via a settling basin 110 and a sieve 112 to the roughing filter 114. Then in the fine filter 116 the final clarification of the water takes place, and it is emitted from the installation via the outlet conduit 118.

The roughing filter 114 consists of a multitude of roughing filter elements 120, which can exit from the roughing filter 114 by raising and lowering them for regeneration or for leading them back into the roughing filter. '”

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H ־ // Each of the filter elements (120) is filled with normal filter coal of a suitable particle size, preferably with pelletized filter coal. These filter elements which represent a roughing filter are moved counter-currently to the waste water flow, i.e. they are moved from the end of the filter containers (122) towards the flow of the waste water to filter container (124). This counter-current movement of the filtercontainers provides the possibility that e.g. container (124), which is most heavily loaded with absorbed waste, may be removed from the series of filter containers for regeneration. In this way it is possible to regenerate the series of roughing filter elements continuously, having the most heavily loaded filter element on top of this series and freshly regenerated filter element at the end thereof.

Fine filter(116) consists equally of a series of fine filter elements (126), which are equally moved by stages in countercurrent to the waste water from the bottom end (128) to the top end (130). This counter-current movement allows - as desribed already for the roughing filter - to remove the most heavily loaded filter element to be regenerated and to provide a new filter element loaded with freshly regenerated carbon at the end of the series. The fine filter can be cleaned by backwashing, optionally in the backwashing device (134). Preferably the backwash water is taken direct from the outlet conduit (118) , and can for some time be stored in the Reservoir (136), which is equipped with a heater coil (138). The water cdhtaminated by the backwashing flows through the return conduit (140) back to the w’aste water inlet (108).

For processing the waste, the solid waste is unloaded into a bin (160), whereby means of a magnetic belt (162), the conveyor belt (166), and the shredding rollers (164), a first treatment of separation of the waste takes place. In the settling basin (110) the materials with a density of >1 are deposited and are removed with the aid of a bucket elevator (168). A series of air jets (170) provides for a thorough mixing of the waste water and waste, by which a turbulance is created to help scparating the solid waste into the lighter, floating organic !3

- /U substances and the more heavy inorganic substances, which sink to the bottom (110) . In this way the separation into organic and inorganic components is facilitated. By means of a conveyor (112) the floating organic substance can be transported to storage chambers (172) of the multireactor pile (104),where it is pre-dried and afterwards pyrolyzed or thermolyzed in the reactor pile (104). Such organic waste can be continuously ' moved to the storage chambers via the transport belts (174).

The multireactor pile (104), in which simultaneously both pyrolysis and thermolysis of the waste and/or sludge-charged filter coal takes place in different reactors, is shown in Fig. 4 and 5. The reactors (178) serve for the incineration of pyrolysis of the waste and/or filter coal charged with sludge. The thermolysis of saturated filter coal or waste takes place in reactor (186) .

-ζχCasing 222 surrounds ths interior of the pile 190. The shafts 224 are journaled on bearings 226, and are driven by the drive unit 228 with its motor 230. Via openings 2p2 for the filling and emptying, with a doer 234 and a door 236, with a further device for closing the doors, the furnace charge is filled or emptied into or out of the reactors. Doors 234 and 236 have hinges 262. Moreover the reactors 178 are equipped with an air intake 238, combustible gas outlet 240, and convex screens242. Reactor 178 is also connected to the gas line 184, which has a one-way check valve 246 as well as cracker unit 192, washer 196, the combustion engine 202, generator 204, and the branch line 248 with the valve 250.

The release receptacle 252 for waste has a closure plate 254, which shuts off the cavity 256. At the lower end of cavity 256 there is a hinged plate 258 and the thermal insulation 260.

The cavity 264 which opens downwards is limited by a hinged plate 266. After thermolysis or pyrolysis the solid substances from the reactors are deposited in the funnel-shaped hoppers 268, and 270. The latter are equipped with heat exchanger coils 272 and a damper 274. Under the containers 268,270 is the conveyor belt 276.

Moreover an air supply can take place in the pile chamber I90 via the air inlet lead 278 and the valve 280. Above the thermolysis reactor 186 is the gas conduit 282 with valve 284. in ‘ addition the thermolysis reactor 186 is equipped with a heat transfer conduit 288.

The coal formed in reactor 186 is then sorted by means of the /f -Μscreen 290(Fig.3). The bigger coal particles can be used directly in the roughing filter 114. The screened-out smaller coal particles and the coal dust are formed into pellets of the desired particle size in the pelletizer 292 (Fig.3). These pellets are alsoused for filling the roughing filter elements 120. To produce active coal, the filter coal emerging from reactor 186 is pretreated,i.e. it is finely crushed in a crusher unit, then is optionally pelletized and again crushed to the desired core size. The activation takes place in the activator 294, to which a further pelletizer 296 may be optionally connected. The active coal produced serves as filling for the fine filter 116 or it can be used for commercial purposes.

The statements above show clearly that the waste utilization /waste water clarification installation 102 can be used for the production and regeneration of the normal coal and active coal which are required for the clarification of waste water, to the fullest extent.

In Fig.6 a cracker unit I92 is shown in a preferred embodiment according to the invention. The cracker unit consists of an upright double-walled container 298, in which an inner container 300 is suspended from the upper end of an outer, supporting vessel 304. The inner container has an upper end 306, which is covered by an openable closure plate 308.The lower end of the inner container 300 has a reduced throat 310 and a screen 312. Under that is another screen J16.

A circular air supply line JIB surrounds the reduced diameter throat 3IO. This air line 31θ has a multitude of air nozzles 320, which serve to inject oxygen or combustion air into the interior of the inner vessel 300 directly over the screen 312. The line 184 leads the gas to be split into the upper part of inner container 300 and ends in a downwardly facing head 322.

The interior of the container 300 is filled with relatively large particles of a combustible material, preferably wood, and in such a way that the latter fills the larger part of the cavity between the screen 312 and the gas discharge head 322. The wood which is located directly above screen 312 is ignited, and oxygen is supplied via the air nozzles for combustion, so that a high temperature zone forms, ivhich nevertheless extends to a relatively small area above the screen, while the rest of the combustible material remains comparatively cool in the interior of container 300. After the high temperature zone has reached the desired temperature, combustible gas or carbonization gas is introduced into the cracker unit via gas line 184 and the head 322. Moreover the blower 324 is operated, whereupon a slight vacuum forms in the outer vessel 324, whereby the gas fed in via the head 322 is drawn past the cool zone of combustible material and through the high temperature zone into the annular shaped space 326 between the vessels via the suction line 328 and the blower 324,

The split gas obtained can either be used direct in a combustion engine 202 or it can be liquified in the liquid gas plant 206, and optionally it can be separated into a gas on preferably a methane base and liquid nitrogen.

At periodic intervals the cracker device is supplied with fresh combustible material via the closure plate 308. This supply can also take place continuously.