AU638497B2

AU638497B2 - Waste disposal process

Info

Publication number: AU638497B2
Application number: AU65004/90A
Authority: AU
Inventors: Bernd Michael Wolf
Original assignee: PKA Pyrolyse Kraftanlagen GmbH
Current assignee: PKA Pyrolyse Kraftanlagen GmbH
Priority date: 1989-10-10
Filing date: 1990-10-06
Publication date: 1993-07-01
Anticipated expiration: 2010-10-06
Also published as: EP0495814A1; CA2067147A1; HUT62322A; CZ280918B6; CS490990A3; FI921469A0; AU6500490A; HU9201162D0; SK278524B6; BR9007730A; EP0495814B1; WO1991005834A1; HU209940B; FI921469A; NO921350D0; DE3933809A1; NO921350L; ES2055446T3; DE59005476D1; DK0495814T3

Abstract

In a process for the disposal of toxic and/or infectious waste, especially highly halogenated solids, plastic containers, hospital waste and the like, to recover useful substances and render inert non-recyclable and unoutgassable residues, outgassing by the pyrolytic process is used, with air excluded and a reduced oxygen content, followed by the direct incineration of the distillation gases obtained from pyrolysis or their cracking to form a pyrolysis separation gas. The waste to be disposed of is inserted in an autoclave (2), partially outgassed there for a period of 20 minutes to 6 hours at about 250 to 320 C in an initial outgassing stage, then cooled and made into a granulate or pellets measuring from 1 to 50 mm, which are subsequently treated by the pyrolysis outgassing method in a second outgassing stage at a temperature of 550 to 600 C. This generates distillation gas which is separated from the residues, like carbon, ash, heavy metal particles and other components. The liquid partial outgassing intermediate products, like oil and/or coal tars, produced in the autoclave (2) are taken to the second outgassing stage, while the distillation gas separated off in the first outgassing stage in the autoclave (2) is taken off and added to the stream of distillation gas from the second outgassing stage.

Description

1 1 2 The invention relates to a process for the disposal of 3 toxic and/or infectious waste especially highly 4 halogenated waste solids, plastic containers, hospital waste and the like, and for the recovery of useful 6 substances and for rendering inert non-recyclable and 7 non-degassable residue, by degassing by pyrolysis with 8 the exclusion of air and a reduced oxygen content, with 9 subsequent direct combustion of the carbonisation gases obtained by pyrolysis or cracking of the carbonisation 11 gas to form a pyrolysis cracked gas and with 12 mineralisation of the degassing residue. The invention 13 also relates to an installation for carrying out the 14 process.

e 15 Process for the disposal of household and/or industrial 16 waste by pyrolysis with a degassing drum are already 17 known, e.g. from DE-A 33 47 554, DE-A 35 29 445 and DE-A 18 37 27 004.

19 However, only waste containing only a small quantity of ecologically"harmful or noxiods matter can be disposed 21 of, further processed or treated for the recovery of 22 fuels by means of these processes.

23 This involves in particular highly halogenated solids and

*SSS

24 containers for hospital materials with toxic and/or S 25 infectious contents, and for various plastics, e.g. PVC

Q*

26 and plastics containing superchlorinated or 27 superbrominated additives, e.g. flameproofing agents 28 (decabromo biphenyl ether) and the like. If this waste 29 were to be treated by pyrolysis with the high temperatures prevailing in this process, the high 1 la- 2 chlorine content would cause problems in the resulting 3 carbonisation gas. In addition, e.g. highly toxic 4 dioxins and furans with more than three chlorine atom bonds would be contained in relatively large quantities 6 in the carbonisation gas, the complete destruction of 7 which in the subsequent treatment process would be 8 difficult. In addition, the risk of accidents would be 9 increased. In addition, poisonous gases, e.g.

fluorocarbons from styropor of refrigerators and the like 11 are already released when crushing and granulating waste 12 of this kind'. Similarly, infectious waste cannot be 13 simply crushed immediately for reasons of hygiene.

14 e .00 17 17 2 i24 19 21 8 22 S 23 S24 26 27 28 29

A

n 1 1 2 3 4 6 7 8 9 11 12 13 14 OS*0 16 17 18 .*0 o 19 is 021 22 23 24 S 25 26 27 28 29 2 Autoclaves for degassing products are already known (see, e.g. EP-B 0 007 620).

However, the autoclaving of waste has hitherto been regarded as uneconomical, particularly on account of the necessary batchwise operation of the autoclave and the associated intermittent and therefore irregular flow of waste gases.

A further disadvantage of the known process consists in that temperatures of approximately 4500 are provided for in the autoclave, the resulting gas being advanced to a subsequent burner of a heat generator. However, with high degassing temperatures of this kind, environmentally harmful and poisonous substances are formed and are released by the subsequent carbonisation gas combustion, so that, e.g. highly halogenated solids and other special waste cannot be treated by a process of this kind.

The object of this invention is to provide a process and an installation for the disposal of waste by means of which toxic and/or infectious waste can also be disposed of and possibly made recyclable without causing problems for the environment and/or the health of humans and animals.

According to one aspect of the present invention there is provided a process for the removal of toxic and/or infectious waste, especially highly halogenated waste solids, plastic containers, hospital waste and the like, and for the recovery of useful substances and for rendering inert non-recyclable and non-degassable residue, by degassing by pyrolysis with the exclusion of 1 -2a 2 air and a reduced oxygen content, with subsequent direct 3 combustion of the carbonisation gases obtained by 4 pyrolysis or cracking of the carbonisation gas to form a pyrolysis cracked gas and with mineralisation of the 6 degassing residue, characterised in that 7 the waste to be disposed of is fed to an autoclave 8 where partial degassing is carried out in a 9 first degassing stage for a dwell time of minutes to 6 hours at 250-320 0 C, then it is cooled 11 and worked up to granules or pellets of 1 to 50 )un 12 in size, which are then treated by the pyrolytic 13 degassing process in a second degassing stage at a 14 degassing temperature of 550-600 0 C, carbonisation 15 gas being produced and being separated from the 16 residue, such as carbon, ash, heavy metal fractions So. 17 and other constituents; S 18 liquid partial degassing intermediate products such S 19 as oil and/or coal tars produced in the autoclave are advanced to the second degassing stage, and 21 carbonisation gas separated off at the first oe* 22 degassing stage in the autoclave is withdrawn 23 and mixed with the carbonisation gas flow from the 24 second degassing stage.

25 Tests have in fact surprisingly shown that by coupling an C0 26 autoclave as a first degassing stage for carrying out 27 partial degassing with subsequent residue pyrolysis, the 28 problems mentioned at the outset can be solved in a 44e 29 hygienic, economical and ecological manner.

-3- In temperature-controlled autoclave partial degassing for the disinfection of the feed material, the halogens can split off from plastics simultaneously at a temperature of approximately 310 0 C, for which dwell times of approximately 20 minutes to 6 hours are required, according to the type.

The oil and coal tar-like intermediate product of autoclave partial degassing at below 320 0 C no longer contains any aromatics and therefore has no mutagenic or carcinogenic properties. It can therefore be further processed without difficulty, giving the particular advantage with respect to the subsequent treatment thereof that, if it is introduced into the autoclave in advance, the active carbon-like pyrolysis residue from the pyrolysis absorbs the fluid components and thus allows for the discharge of a solid from the autoclave.

Residual solid structures of the intermediate product can be granulated without any difficulty once they have been cooled and discharged from the autoclave, so that they can then be completely degassed in a second degassing stage in a degasser, e.g. a rotary drum degasser, at approximately 600 0 C, together with the pyrolysis residue enriched with oily and tarry matter.

It has been found to be advantageous in this connection to mix the feed material in the degassing drum with other waste material having such a high carbon content that the degassing product pyrolysis residue contains more than 30 by weight of carbon. In this case, it has been surprisingly shown that, if it is pressed through a water bath before contact with air, the hot pyrolysis residue forms an active carbon structure with such a great pore surface that its absorption and adsorption properties correspond to approximately 70 of those of active carbon produced normally. As a result of this property, this pyrolysis residue can then be used, inter alia, for filtering waste containing harmful substances, especially for absorbing the waste produced when washing the pyrolysis cracked gas (prior to oxidation), or when wet scrubbing carbonisation gas waste gases. Unless there is complete absorption of the waste as a medium of the water bath for the formation of the active carbon structure by evaporation, the excess water is almost of drinking water quality.

It is also advantageous that the prccess according to the invention is virtually free of waste, i.e. no waste is produced. The water required in the process can be recirculated.

The carbonisation gas produced intermittently in the autoclave can be mixed directly with the carbonisation gas from the continuously operating pyrolysis degasser for further processing thereof. The irtermittently produced carbonisation gas from the autoclave, which led to corresponding problems according to the prior art, especially with respect to economical treatment, can then be further treated without difficulty in that it is advanced to the second degassing stage. In this case, it is simply necessary for the continuously operating second degassing stage to have a maximum load such that it can handle the intermittent operation, i.e.

the batchwise delivery of the granulated waste.

If, in an advantageous development of the invention, several autoclaves are provided and these are operated staggered over time in a corresponding manner, load peaks are further established and, if desired, a subsequent second degassing stage can also be operated continuously by means of pyrolysis degassing via autoclaves. This means that in a case of this kind, normal household waste or industrial waste does not necessarily have to be mixed, but the special waste can also be disposed of separately in an economical manner.

It may be advantageous to free the carbonisation gas of hydrochloric acid before mixing with the carbonisation gas from the second degassing stage via a cooling path by condensation, in order to reduce the load of the subsequent washing stage.

In this case, the carbonisation gas is then heated again to over 300 0 C, preferably approximately 450 0 C, in order to prevent it cooling when it is mixed with the carbonisation gas of the second degassing stage and thus to prevent the condensation of tarry substances resulting in blocking in the pipeline network.

In order to improve the method of operation and the efficiency of the autoclave and to reduce the quantity of waste gas of the entire process, it has been found to be advantageous to use the hot waste gases from the carbonisation drum as a heating medium from their indirect heating by combustion of self-produced pyrolysis cracked gas or other fuels. Por rapid heating, part of the even hotter (approximately 920 0 C) cracked gas after the gas converter before the washer can be removed by means of a separate pipeline network and can then be returned to the washer after passage through the autoclave.

A cooling medium which must be oxygen-free is required for temperature control and for cooling the feed chamber in connection with the required batchwise feed of the autoclave.

To this end, it is advantageous to use cold pyrolysis cracked -6gas, which is removed at approximately 350C after the gas washer and can then be returned to the gas converter enriched with carbonisation gas for dispo-l and reuse or can be advanced to the combustion chamber of the carbonisation drum Tor direct combustion.

Once the feed chamber has been cooled to an internal temperature below the minimum spontaneous ignition temperature and the degassing termination temperature (approximately 45 0

C),

the feed chamber of the autoclave can then be flooded with cold air for the purposes of accessibility, said cold air being sucked out for its disposal as combustion air for the gas converter or other burners of the disposal system. It is therefore possible to achieve accessible temperatures without having to reduce the autoclave casing temperature of approximately 3100C if, as in one embodiment of the invention, a double-walled autoclave is used, a flow channel being provided between the wall of the feed chamber and the outer wall of the autoclave, through which the hot gases flow. In this manner, the feed interval and thus the flow rate and thus the efficiency of the autoclave can be considerably improved.

In order to further reduce the climate-re±ated trace gases, such as C02, CO, NO x produced upon the disposal and energy conversion processes and to increase the thermal value of the pyrolysis cracked gas by reducing the nitrogen content thereof, in so far as this originates as atmospheric nitrogen from the supply of combustion air to the gas converter for the temperature control thereof by substoichiometric carbonisation gas combustion, it has been found to be possible and advantageous to split oxygen with a purity of more than 80 from the atmospheric air by means of a pressure swing -7adsorption installation and then to mix the waste gas partial flows from the carbonisation drum in such a manner that the mixing product has an oxygen content of more than 25 by volume and to return this mixture in order to cover the oxygen requirement of the gas converter and the combustion chambers and the gas motors used to drive generators for generating current.

In the case of the gas converter feed, oxygen enrichment of up to 45 may be advantageous, as this considerably reduces the cracked gas mass and means that it is possible to increase the thermal value of the cracked gas by more than 10 In order to work the pyrolysis residue from the second degassing stage into a completely inert final product for disposal, which can then be sent to normal dumps or can be used as a building material aggregate, it has been found to be advantageous to mix a certain quantity of puzzolana, i.e.

silicate and aluminate materials, with the wet pyrolysis residue, together with calcium-containing compounds such as lime, lime hydrate or lime hydrate waste, wherein it must be ensured that the mole ratio of Sio 2 A1 2 0 3 CaO, ZnO, Fe203 and/or MgO, on the one hand, to the entire mole content of the metals lead, chromium, manganese, cadmium, beryllium, barium, selenium, arsenic, vanadium, antimony, bismuth, strontium and/or zircon is at least 6:1, and similarly that the mole ratio of calcium, magnesium and sodium, on the one hand, to the entire sulphur, chlorine and fluorine content is at least 2:1.

If this mixture is pressed into ovoid-shaped pellets at between 200 and 5.,0 kg/cm 2 and is hardened at normal temperatures for a period of at least 4 days, compounds such as calcium silicate -8hydrate, calcium aluminate hydrate and calcium ferrite hydrate are produced, these being slightly water-soluble and having hydraulic properties such that the structure is dimensionally stable and can be used without difficulty for ca2rying out an annealing process, e.g. in a direct-current shaft furnace, in order to be annealed therein at approximately 1200-1250 0 C using the carbon energy content. This means that the heavy metals are incorporated into the mineralogical structure of complex calcium pilicates, for which reason the waste gas flow is substantially free of heavy metals, and the sand-like solid residue corresponding to its ceramic structure is almost unleachable and thus can be used a building material.

If it is ensured that the carbon content in the pyrolysis residue is more than 30 by weight, its thermal value is sufficient to ensure temperatures of up to 1300 0 C in the direct-current shaft furnace, taking account of the required mixing described hereinbefore when supplying sufficient combustion air, in order to make the annealing residue relatively insoluble. In leaching tests, all of the completely buI'nt out briquette residue of the type described hereinbefore displayed cadmium values of less than 0.2 ppm, chromium values of less than 0.4 ppm and lead values of less than 0.3 ppm, even when the maximum metal content in the briquette was in excess of 8000 ppm in the case of cadmium and in excess of 6000 ppm in the case of lead. No measurable losses of lead or cadmium could be established in the waste gas flow, so that the hot waste gases can also be used without purification for heating the autoclave and carbonisation drum and for drying moist waste before it is introduced into the degassers.

By virtue of the invention, industrial residue, components or -9the like and waste displaying great inhomogeneity, possibly with interstitial, attached and structural water, etc., which are toxic or become toxic upon thermal conversion, can be subjected without difficulty to the desired pyrolytic treatment, thereby producing useful gases for an energy use without special waste and sewage being produced. Inorganic materials of composite materials can thus be recovered in some cases, so that real recycling of useful basic materials and the like is possible in that, after the pyrolytic coating removal, e.g. metal components are subjected to suitable coating once again and can be used as finished components.

Further advantages and developments according to the invention will be clear from further subclaims and an installation according to the invention for carrying out the process, which will now be described in diagrammatic form with reference to the accompanying drawings.

The material to be disposed of or recycled is advanced from an autoclave pre-chamber 1 to an autoclave 2, e.g. via an appropriate feeding apparatus in the form of a manually operable sliding platform having correspondingly track-bound special wagons. The conveying can take place, e.g. in mAal skeleton containers, below which a metal tank is fitltd, previously filled with active carbon-like pyrolysis residue from the second degassing stage, in order to absorb the heavier degassing products, oils and tars. The metal wagons loaded with pallets or baskets described hereinbefore are advanced from the pre-chamber 1 into the reaction chamber of the autoclave 2. A continuously adjustable temperature limit between 250 0 C and 320 0 C can be selected and provided. The charge times depend on the organic portions i, association with 1 0 the magnitude of the heat transfer. When loading per autoclave and per charge with pallets or wire baskets, there are different charge times according to the introduction of the organic substances. As mixed loading is possible, average charge times can be kept constant. The pre-chamber 1 can be supplied with air for purification and cooling via a pipe 4, removed via a discharge pipe 3A. A flow channel 6 of the autoclave 2 is supplied via a pipe 5 with hot waste gases from a carbonisation drum combustion chamber 16A for heating the casing thereof. in order to heat the walls thereof. After the addition of heat to the internal chamber of the autoclave, the substantially cooled waste gases are reused via a discharge pipe 3C for reheating in the carbonisation drum or, enriched with oxygen from a pressure swing absorber 7, are reused as combustion air for a gas converter 8 or the burner of a carbonisation drum 16.

Hotter cracked gas from the gas converter 3 can be added via a pipe 10 for rapid heating of the cracking chamber, said gas leaving the gas converter at approximately 920 0

C.

Once the autoclave 2 has been charged with the material to be degassed the degassing chamber is first flooded via a pipe 9 with inert gas (hot waste gas) and is withdrawn via a discharge pipe 3B in order to remove the oxyqen from the reaction chamber of the autoclave 2. Subsequently, e reaction chamber of the autoclave 2 is flooded with hot cracked gas via a pipe 10A in order to accelerate the commencement of the degassing of the feed material. The pipe 10A can be a branch of the pipe with the hot cracked gases of the gas converter 8. This hot cracked gas is discharged via the pipe 3B. Removal from the pipes 3A and 3B is effected via the pipes 3 and 33 by supplying -11the gas converter 8 or the burner of a carbonisation drum 16.

After the commencement of degassing, the discharge pipe 3B is closed. The carbonisation gas is advanced via a heat exchanger 11 to a carbonisation discharge pipe 17 after the carbonisation drum 16. Condensable contents such as aqueous hydrochloric acid from the carbonisation gas flow can be separated if necessary in the heat exchanger 11 and collected in a container 12. Subsequently, the carbonisation gas is heated again by means of a heat exchanger 13 to at least 450 0 C, in order then to be mixed via a pipe 17A with the pipe 17. The carbonisation gas is then advanced via the pipe 17 to the high-temperature gas converter 8. At the end of the degassing process below 320 0 C in the reaction chamber of the autoclave 2, in order to prevent the formation of aromatics, for discharge of the feed material, the autoclave 2 is flooded via a pipe 2B with cold cracked gas which is removed after a gas washer 21 and 24.

Discharge is again effected via the pipe 3E. Flooding is effected until the temperatures in the internal chamber fall to below 80 0 C, in spite of the autoclave casing being at a temperature of approximately 300 0 C. Subsequently, the autoclave 2 is flooded with fresh air before the autoclave doors are unlocked and the wagon with the degassed material is removed. New feeding can be effected simultaneously during this removal via the points.

The degassed solid material including the pyrolysis residue enriched with oils and tars in the discharged tank of the wagon is then advanced via a path 67 into a shredder or a granulating means 14 where it is mixed if necessary with other carboncontaining waste from the supply pipe 70. If necessary, metals coated in plastic or metal plastic composite materials already present can first be removed, in order to return them for -12recycling.

The only partially degassed but now disinfected and crushed material in the reaction chamber of the autoclave 2, mixed with other granulated waste from the supply pipe 70, can then be advanced via a rotary vane feeder or a similar feeding apparatus, such as a filling screw 15, to the carbonisation drum 16, in which carbonisation gas is produced in the known manner by pyrolysis at temperatures of 550 600 0 C, said carbonisation gas being fed via a discharge pipe 17B and a dust removing apparatus 18 into the pipe 17 leadini to the hightemperature gas converter 8. The carbonisation is treated or converted in the gas converter 8 over a coal or coke bed.

A gas converter of this type is described, e.g. in DE-A 33 17 977, for which reason it will not be described in more detail here. The design of the carbonisation drum 16, the gas converter 8 and the subsequent gas purification means is such that these can be operated continuously by the degassing of the waste flow fed via the supply pipe 70 and tng lntermittently produced carbonisation gas flow and the solid waste from the batchwise degassing by the autoclave 2 serve as a peak load, wherein it is also possible to use several autoclaves 2 out of phase in parallel operation in order to guarantee more uniform feeding of the installation module. After passage through a heat exchanger 20, the cracked gas from the gas converter 8 arrives at a gas washing installation consisting essentially of a water spray tower 21, a blower 22 and a purifying cyclone 23 and a drop separator 24. The purified gas is advanced via a gas pipe 25 to a gasometer 26 in which, if too much gas is supplied, excess gas can be advanced via a by-pass 27 to a flaring apparatus 28. The gas from the gasometer 26 is -13normally advanced to a gasometer 29 which is connected to a generator 30, the burnt waste gases being fed via a waste gas pipe 31 to a chimney 32. However, these waste gases or a partial waste gas flow 75 can also be advanced to a mixing chamber 76, which is mixed with air enriched with oxygen by the pressure swing absorber 7, which again can be returned as combustion air for the gasometer 29 and via the pipe 33 to the gas converter for maintaining its crack temperature by substoichiometric carbonisation gas combustion. The gas converter 8 receives coke via a coke inlet 34A and water via a pipe 34B. Ash and slag are withdrawn via an outlet pipe If desired, a coke return pipe 36 can also be provided for the coke freed of slag in order to save energy. The coke is returned to the carbonisation drum 1,6 together with the solid residue from the washing water settling tank of a gas purification means 41. A by-pass 37 branches off from the gas pipe 25 and leads to a gas burner 38 serving to supply heat to the carbonisation drum 16. During the start-up phase of the installation, an oil burner 39 or even a separate gas burner serves to heat the carbonisation drum 16. Subsequently, however, in the course of operation, the heat required for the carbonisation drum 16 can be supplied entirely by the burner 38.

The washing water resulting from the gas purification arrives at a washing water tank 40 and subsequently at a filtering apparatus 41, which is generally a settling tank. Solids separated in the filtering apparatus are introduced via a pipe 42 into an ash container 43. The residue from the ash container 43 is carried away via an outlet pipe 44 and is returned to the carbonisation drum 16 via a feeding apparatus, e.g. the filling screw -14- The purified washing water is led from the filtering apparatus 41 via a return pipe 45, after passage through a cooling tower 46, back into the spray tower 21 of the gas-washing installation. Part of the purified washing water is fed into a washing water neutralising plant 47/48. From the washing water neutralising plant 47/48, the washing water is advanced via a return pipe 53 for recycling treatment to the spray tower 21, while part of it is advanced via a removal pipe to the batch treatment plant of the water neutralising plant 47/48. Here, the washing water is chemically purified in the known manner by appropriate chemicals which are supplied via a chemical pipe 49, unless the chemical oxidation is effected by ozonisation means 54, as a result of which the quantity of residueincreasing additives added can be sharply reduced. The washing water is partly guided via a recycle pipe 50 through an air filter. 51 for the removal of foam, waste gases being blown off through a pipe 52 via the chimney 32, and is partly returned via a pipe 52B to the spray tower 21. The excess water from the gas purification collected in the container 48 is advanced via a pipe 55 to a water bath 57 for the discharge of the pyrolysis residue after the carbonisation drum 16. During the evaporation process taking place there, this excess quantity of washing water is absorbed by the pyrolysis residue as interstitial and attached water, the Larmful substances contained therein being adsorbed and absorbed by the active carbon. The washing water is disposed of in this manner.

If more excess water should be produced from the gas washing than is absorbed by the pyrolysis residue, it is discharged via a pipe 58. However, as a result of the filtering action of the active carbon-like pyrolysis residue, this excess water is almost of drinking water quality. However, as a rule, there is no excess water. The wet pyrolysis residue can be advanced via a pipe 56 to a mixing apparatus 60 in which silicate and aluminate materials are mixed, together with calcium-containing compounds. Subsequently, it is fed to a briquetting press 61, in which dimensionally stable ovoid-shaped pressed pieces are produced from the mixing product. These are then annealed in a direct-current shaft furnace 62 at approximately 1250 0

C.

The resulting hot waste gases at a temperature of more than 1000 0 C can then be advanced via the pipe 74 as a partial flow pipe for heating the carbonisation drum or as a partial flow pipe 71 for drying other waste to a drier 72. The partial flow not required to this end is advanced via the pipe 65 to the chimney 32. The fresh air required for the direct-current shaft furnace 22 is advanced via a heat exchanger 64 via the pipe 63.

The annealing residue from the shaft furnace 62 is rendered completely inert and can be advanced via a discharge means 66 for reuse as a building material.

As an alternative to the carbonisation gas cracking described hereinbefore via a gas converter 19 with subsequent cracked gas washing, in which case purification of the gas prior to oxidation is effected at approximately 40 0 C and thus only a very small volume of gas has to be purified, the carbonisation gas from the pipe 17 can also be advanced to a combustion chamber 77 directly via the connecting pipe 170 indicated only by a dotted line, followed by a boiler plant 78, a mixing chamber 79 which is supplied with lime via a nozzle means via an air pipe 85, and a filtering installation 81. The residue from the filtering apparatus can be removed via a line -16- 59A in the mixing chamber 60. The waste gas purified or filtered in the filtering installation 81 is returned via a waste gas pipe 82 to the chimney 32B or, optionally, after passage through a condensation installation 83, via a pipe 84 for heating or drying purposes into the installation, e.g. to the partial flow pipe 71.

An air pipe 86 leads in the conventional manner into the combustion chamber 86 and optionally also a secondary fuel line 87. A feed water pipe 88 leads to the boiler plant 78 and a steam pipe 89 leads therefrom. Coiipressed air is blown into the filtering installation 81 via a compressed air pipe 89 for purification.

Whereas the autoclave 2 and the carbonisation drum 16 must be operated together, the installation unit 60-62 can also be operated in another manner if an appropriate energy consumer is present.

Claims

1. A process for the removal of toxic and/or infectious waste, especially highly halogenated waste solids, plastic containers, hospital waste and the like, and for the recovery of useful substances and for rendering inert non-recyclable and non-degassable residue, by degassing by pyrolysis with the exclusion of air and a reduced oxygen content, with subsequent direct combustion of the carbonisation gases obtained by pyrolysis or cracking of the carbonisation gas to form a pyrolysis cracked gas and with mineralisation of the degassing residue, characterised in that the waste to be disposed of is fed to an autoclave where partial degassing is carried out in a first degassing stage for a dwell time of 20 minutes to 6 hours at 250-320°C, then it is cooled and worked up to granules or pellets of 1 to 50)um in size, which are then treated-by the pyrolytic S degassing process in a second degassing stage at a degassing temperature of 550-600 0 C, carbonisation gas being produced and being separated from the residue, such as carbon, ash, heavy metal fractions and other constituents; liquid partial degassing intermediate products such as oil and/or coal tars produced in the autoclave are advanced to the second degassing stage, and carbonisation gas separated off at the first degassing stage in the autoclave is withdrawn and mixed with the carbonisation gas flow from the 1 2 3 4 6 7 8 9 11 12 13 14 0 16 17 18 19 20 0* 21 22 23 24 26 27 28 29 BA 0 18 second degassing stage.

2. A process according to Claim 1, characterised in that granules or pellets of 1-50 im in size consisting of household and/or industrial waste are also introduced into the pyrolysis degassing as a second degassing stage.

3. A process according to Claim 1 or Claim 2, characterised in that carbonisation gas produced in the autoclave is cooled and freed of condensed hydrochloric acid, after which it is heated before being mixed with the carbonisation gas flow of the second degassing stage.

4. A process according to any one of Claims 1 3, characterised in that after each new feed the autoclave is heated with hot waste gases from heating means used for generating the temperature for the second degassing stage or by means of at least part of the hot cracked gases obtained from the gas cracking.

5. A process according to any one of Claims 1 4, characterised in that the cooling of the autoclave is effected by rinsing with the cracked gas obtained by the gas cracking and cooled after gas washing and that after cooling to temperatures of less than 80 0 C the subsequent rinsing and cooling is carried out with fresh air at less than 450C.

6. A process according to Claim 5, characterised in that, for disposal, the cooling gases from the autoclave are advanced as suction air for burner means for heating the second degassing stage by the pyrolytic degassing process or the burner of a gas converter for 1 19 2 the production of cracked gas or directly to the gas 3 converter. 4

7. A process according to any one of Claims 1-6, characterised in that the waste from the carbonisation 6 gas and/or pyrolysis cracked gas purification is advanced 7 to a water bath (57) for the pyrolysis residue from the 8 second degassing stage. 9

8. A process according to any one of Claims 1 7, characterised in that the pyrolysis residue from the 11 second degassing stage is mixed with calcium-containing 12 compounds such as lime, lime hydrate, and puzzolana, such 13 as silicate materials, and is then pressed into *me: 14 briquettes and is then annealed at 1200°C, the heavy o. 15 metals being incorporated into the mineralogical 16 structure of complex calcium silicates. o s 17

9. A process according to any one of Claims 1-8, 18 characterised in that in order to reduce the emission of 19 trace gases, the waste gases from the combustion chambers of the pyrolysis degassing and other means in the process 21 requiring combustion air are advanced to these means as 22 combustion air, these being mixed by means of a pressure 23 swing absorption installation with air obtained from the 24 atmosphere and enriched with oxygen in such a manner that 25 the return flow contains at least 25% by volume of 26 oxygen. 27

10. A process according to any one of Claims 1-9, 28 characterised in that at least part of the solid pyrolysis residue in the autoclave is advanced for 31 a,,,sorbing the liquid partial degassing intermediate 1 2 3 4 6 7 8 9 11 12 13 14 15 S S 16 o°° 17 18 19 20 21 22 23 S 24 SS** 25 26 27 28 29 20 products.

11. An installation for carrying out the process according to one of Claims 1-10, having a means (14) for crushing and granulating refuse, a means (16) for subsequently degassing by the crushed refuse pyrolysis and a gas converter following the degassing means for the recovery of cracked gas or a combustion chamber (78) following the degassing means for subsequent thermal combustion with subsequent gas purification, characterised in that an autoclave is arranged in front of the refuse grinding and granulating means (14).

12. An installation according to Claim 11, characterised in that several autoclaves are arranged in parallel.

13. An installation according to Claim 11 or Claim 12, characterised in that the waste from the gas purification is advanced via a pipe (55) to a water bath (57) for the pyrolysis residue, that the hot waste gases are advanced by means of a gas pipe to the autoclave for heating and rinsing the internal chamber and that the carbonisation gas flow jrom the autoclave is connected via a gas pipe (45) having a cooling means (46) for condensation of residual hydrochloric acid to the carbonisation gas pipe (53) after the second degassing stage (16).

14. An installation according to Claim 11, 12 or 13, characterised in that the autoclave is double-walled, a flow channel being formed for hot gases.

An installation according to Claim 14, characterised S 0 I. a I 1 2 3 4 6 7 8 9 11 12 13 14 15 ome 16 17 9 S I 18 i9 20 21 22 23 S 24 m* 25 26 27 28 29 21 in that after the condensation of aqueous hydrochloric acid, the gas pipe (45) is provided with a means (13) for heating to a temperature of more than 300°C, preferably 450 0 C.

16. An installation according to any one of Claims 11 15, characterised in that a pressure swing absorption installation is provided for oxygen enrichment of the air required for combustion means (16A).

17. An installation according to any one of Claims 11 16, characterised in that an annealing furnace (62), especially a direct-current shaft furnace, is provided for annealing the pyrolysis residue.

18. An installation according to Claim 17, characterised in that a waste gas pipe (31) of a shaft furnace (62) is connected via connecting pipes to the autoclave the means (16) for degassing by pyrolysis or a waste drying installation (72) for the heating thereof.

19. A process for the removal of toxic and/or infectious waste substantially as hereinbefore described with reference to the accompanying drawing.

20. An installation for carrying out the process according to Claim 1, substantially as hereinbefore described with reference to the accompanying drawing. DATED APRIL 6 1993 PKA PYROLYSE KRAFTANLAGEN GMBH By their Patent Attorneys SKELVIN LORD AND COMPANY \0 PERTH, WESTERN AUSTRALIA.