GB2251294A

GB2251294A - Incinerating refuse.

Info

Publication number: GB2251294A
Application number: GB9122604A
Authority: GB
Inventors: Gunter H Kiss
Original assignee: Thermoselect AG
Current assignee: Thermoselect AG
Priority date: 1990-12-17
Filing date: 1991-10-24
Publication date: 1992-07-01
Anticipated expiration: 2011-10-24
Also published as: DK174091D0; SE503709C2; DK174091A; CH682079A5; BE1004228A3; SE9103577D0; NL9101786A; FR2670501B1; DE4040377C1; GB2251294B; ES2059225A1; SE9103577L; AT402552B; ITMI913364A1; ES2059225B1; ITMI913364A0; ATA206991A; GB9122604D0; IT1252528B; FR2670501A1

Description

2 2 531 2J4 1 1 Process for roTisionally storing, transporting and/or

energeticaliv as well as material1v utilisin2 m-aterial Ofall kind that is to be disposed of The hitherto ij,--,ctised or tested -it,ic.ds of garDagC ZI-fC a-.,n-d little -zonrincinz vith regara C.:,.1. -1 1 - 1 to the resulting environmental -or,:YbLems. This holds true. for L-otb the provisional storage and the transport fro-,,.-.t-cl to the plants effecting disposal and, in particular, fo-!he preparation of the material to be disposed of, be it ordinarv domestic or industrial aarbaae, extra aarbaTe or 11 C1 I" cl even material to be disposed of that is already stored.

-n 2C Even nowadays, the classic way of getting rid of domestic and industrial waste of all kind still resides in gettingr rid of same by pouring said waste into and towards largecapacity plants effecting disposal, very long transport paths, in part, being involved. Environmental problems associated therewith are known in practice; until now, they could not be overcome.

so 1 A known alternative solution to disDosal bv pouring makes use of aarbaae incineratina plants. The burning of waste, 0 -1 however, entails many other drawbacks. Burning, namely, has hitherto been carried out with very poor efficiency, resulting in a high yield of pollutants. The relevant C> incinerating plants necessitate high investment and operating cost. Moreover, garbage incinerating plants have proven to make at least adequate economic sense for conurbations only.

With the equally known degasification of organic waste, 1 0 z> the hope was nourished to be provided With a possibility to avoid garbage incineration at least for Dart of the material to be disposed of which is being obtained and to be able to oDerate economically approp-ciate small plants.

Irrespective of these facts, various processes for pyrolysin- had been developed and tested which. above all, differ Lroi-., one iinother with respect to the degasifying metLods- Preceding or subsequent acrcrreaats, such as 1 1 C sorting and pulverising plants, post-combustion chambers, w dust filtering and exhaust gas cleansing, with pyrnli-ysis o'..garbage, can, for the most Dart, be compared to one another.

The known processes for pyrolysing use three types of furnaces., and that:

so shaft furnaces into which the material to be pyrolysed is introduced from above, said material passing through the furnace shaft in vertical direction, 2.

rotary furnaces in which, by rotation of the tubular shaft, the pourable material to be pyrolysed is thoroughly mixed and repeatedly brought into contact with I the heated tube walls, and 3 3. fluid-bed furnaces in which a sand bed, being in constantly turbulent motion, pTovides for a heat transmission with the material to be pyrolysed.

Degasifying reactors, such as have become known e. g. from Austrian Patent Specifications 115,725 and 363,577, give rise to a plurality of not yet satisfactorily solved problems. For instance, the waste to be pyrolysed must be prepulverised there for enhancing heat transmission, causing high cost. Furthermore, it is necessary that, with the organic substances, atmospheric air in high cl cl throughput quantities, possibly with oxygen, be introduced for pyrolysing. Thus, the pyrolysing reactor operates but w--;-".h low eflEiciency. Heating up of the waste is relatively slow and entails considerable heat losses. The known pyrolysing furnaces, for economic reasons, must have a relativelv large volume and, with prevailing temperatures of ovei. 1SO'C, are at the limit of mechanical stress so that Ific.,- are suited for o- Deration at aDpro-Iii,,iate"Lv ati-,.cispheric pressure only. Finally, absolute gastightness has to be demanded of the degasifying reactors in order to prevent pollutants from issueing, necessitating costly - cemperature-loaded sluice structures and seals.

Due to the problems mentioned above and hitherto not solved the known processes and their appertaining plants have not succeeded in practice. About 80 per cent of the plants hitherto operated have been shut down in the meantime.

Hitherto, further processing of the pyrolysed coke which is being obtained substantially in the form of dust has also been an especially delicate matter since gassing of which, because of its flow-through characteristics being absent, is not possible or only after process- complex briquetting of the coal dust.

4 1 2 0 so Storage and transport of matter to be disposed of and of the kind of interest here are effected with relatively low bulk density, the physical and chemical instability of same and, in case of biologically decomposable garbage, Z' 1 0 the release of smell and gas having a special adverse effect. Worse still, a lot of matter to be disposed of contain liquids which, in their turn, contain pollutants, said matter losing said liquids, at least partially, during transport or storage. In case of inexpert storage, washouts due to rainfall can hardly be avoided. The low bulk density of the material to be disposed of leads to large storage and transport volumes. When a provisional storage of the material to be disposed of is intended e. because the nate,ial to be disposed of is to be prepared for recycling and/or thermal utilisation - I I bunkers resistant to washouts and of considerable conFtructional volume or specially equipped subterra-ieari storage sites are prescribed by public decrees witn the resultant high additional investment cost. Moreover,, the rransport uf such matter to be disposed of, last but not least because of the low bulk density of same, causes considerable cost.

In case of chemically instable material to be disposed of, formation of gas or the like may occur apart from consi- 0 - derable formation of smell so that, in particular to storage bunkers without additional gas disposal, there is 0 an explosion hazard. Permanent venting, repeated change of 1 C> air per hour as well as additional filtering and safety plants are factors of cost also with the provisional storage of the material to be disposed of.

1 As to the transport of some matter to be disposed of, it has been known to transport e. g. domestic garbage with presses integrated into the vehicle in slightly pre- 1 compressed manner. Subsequent thermal utilisation of the material to be disposed of is technically made more difficult by its low bulk density and the resultant large volumes.

When a tubular pyrolysing chamber according to the invention is used, into which the material to be disposed of, while maintaining a compressed state, is introduced, a very good heat conductivity for and into the compacted material to be disposed of results because of the given air void-free pressure contact with the wall of said chamber. The use of tubular chambers. the length of which to the diameter cl exceeds 10: 1, was found to be advantageous with regard to the length- diameter ratio. Such a geometry of said pyro- C1 0 lysing chamber, however, constitutes a restriction with respect to the capacity of plants of this kind. If, e. g., c> di-ameters are applied for high throughput -volumes, said diameters beinc remarkably larger than 400 millimetres 11 1 ? p'..iits of Lip-re..il:oj-iabl Y great constructional height will ly uncomplicated esuit therefron; diameters for technical' constructional heights, in their turn, restrict the passagre capacity of the material to be disposed of and pyrolysed. Besides, considerably increased push-through forces will result when relatively long pyrolysing tubes are applied. Due to the resulting mechanical loads, the practicable pyrolysing temperature confines itself to values which should not exceed SOCC so that deformations of the pyrolysing tube are avoided.

1 It is the object of the present invention to not only provide improved conditions of provisional storage and transport for industrial and domestic garbage as well as 1 1 all kinds of material to be disposed of, but, in particular, to also reconceive its energetic and material utilisation with enhanced efficiency.

6 1 1,:

.) C)

Claims

According to the invention, this obiect is solved by the features stated

in the characterising part of Claim, 1. Advantageous developments and refinements of the solution to said object can be taken from the subclaims.

By precompacting the material to be disposed of, while, at first, maintaining its mixing and composite structures, i. e. without applying expensive SOrting methods and plants, to packages of approximately the same geometry, said material to be disposed of, without any difficulties, may be compressed into a container, which, advantageously, is of approximately tubular shape, by means of a stuffing device, which can be effected in uncomplicated manner and in a manner unsusceptible to trouble. Precompacting into I geometric form which, e. g., is adapted to a tubular container prevents, during subsequent post-compressing wit filling -of the container, bulky components of the material to be disposed of from impeding the post- compressing oDeration. The material tc be disDosed of, in compressed state, bai-ly has about 1/35 to about 1 /20 of its original volume, resulting in a correspondingly reduced storage and transport volume, irrespective of a subsequent thermal degasification resp. pyrolysis of said material to be disposed of.

It is true that, properly speaking, the first step of compressing the material to be disposed of may be carried out by means of an open packing, such as a net wrapping or a strap packing; however, introduction of same into a container, open only at its end faces, results in the advantage that, in this case, it, in addition to that, is tightly incased so that formation of smell is reduced to a minimum and washouts, e. g. due 1 to rainfall, need not be feared. For this purpose, also the end faces of the containers mav be closed tem-norarilv 1 I.

1 so without remarkable cost. A whole series of advantages result in connection with the thermal and material utilisation of the material to be disposed of thus com-oressed and sealed, said utilisation being possibly subsequent to transport and/or provisional storage. For instance, tubular, crammed containers may readily be subiected to degasification in a chamber or continuous furnace. According to criteria of process economy, the residence time in such pyrolysing chambers can be optimised. With tubular containers, there are no restricting length-diameter conditions; said containers, in their turn, pass through the degasifying furnace. Since also containers of larger diameter may be employed, also larger and bulky spoilage of industrial goods cain equally be disposed of in this manner.

Advantageous conditions of thermally utilising the mate- C, rials to be disposed of are due to the fact that all de(,a:;ification products,i.,,,iv, directly and without intermediate cool.iTi,t:T, be subiect.ed to a high-teniperatule treat- C> ment. The resulting compressed coke, the remaining resi- cl 0 dual carbon, can easily. be discharged from such containers and admitted to said high-temperature treatment in 1.1 order to become at least partially gassed. In the course 1 thereof, cracked gas (CO, H22) is produced by cracking a 1 portion of the entrained water vapour. The products formed by degasification are cracked into low-dimensional 1 C> components. Reaction temperature is maintained by exothermic reaction of the formed close-grained coke with oxygen. The carbon dioxide thus released reacts, with carbon, to carbon monoxide according to the producer-gas 0 cl equilibrium. In a high-temperature reactor, optimal reaction and utilisation of all products are ensured.

8 1 so The high temDeratures associated with crassino, of carbon -1 I Inand formation of cracked gas give rise to a directlv usable high-enercry process gas, without any condensable, organic constituents with a greatly reduced fraction of water being obtained. Due to the close-grained coke formed during pressure pyrolysis and the low flow velocities conditioned by the process, fractions of dust being obtained are reduced to a minimum in the process gas.

I The smeltable metallic and mineral components of the reaction products, with hightemperature treatment, form C> a metal resp. slag smelt in a smelting gasifier with, in part, quite different densities so that material components may simply be separated from one another and subjected to efficient utilisation.

Gasification of carbon and formation of cracRed gas, 1 coupled 1vith smelting of utilisable riatter of value, can also be carried out in a shaft furnace or- a type of construction known per se in advantageous manner, oxygen beina fed to the shaft, containing the close- grained > 0 process coke, in 1known manner. In this case, temperatures exceeding 1, 5OCC can readily be generated in the solid cl 1 C1 pyrolysed residua, at which temperatures both steels and other metals as well as glasses will smelt. Discharging C> of said matter of value may be effected by way of a fractionated tapping or an overflow. Applying oxygen instead of z> C:1 1 1 air is of considerable advantage to ensuring high tempera- -1 1 Z:1 tures, low gas velocities and volumes as well as to avoid- 0 ing formation of nitrogen-oxygen combinations.

1 1 1 Escape of the volatile combinations, formed by thermal cracking, in the crammed containers is made more easv when open-ended and perforated metal tubes or the like are used.

1 1 j; 9 When they are appropriately dimensioned, ODtimal conditions will result with regard to gas exit, production cost and the applicable degasification temperatures.

For transport and provisional storage, the material to be disposed of may also be introduced into thermally utilisable containers, made of chemically solid material, in prepacked manner and, later on, into the thermally stable degasifying tubes which are subjected to pyrolysis.

1 C, - When applying the process according to the invention, it is of advantage to compress the ungraded material to be disposed of into containers preheated to more than 1000C in order to ensure a shortening of the subsequent degasi-arial to be fication time and, by preheating of said mat disposed of, to vapourise as much moiszure as possible.

According to the invention, a plurality Df containers, with advantage, tubular cirtou(hes with additional radial rings enlarging th,i-, outer surface, are circulated in zA continuous furnace. Thus, tne capacity of a plant can be maximised. When the containers are left in tile furnace for filling in compressed manner prior to the heat treatment and for dischargina after said heat treatment, the heat losses thereof, additionally, reduce themselves and that of the overall system is minimised.

Compression of domestic garbage or the like may be decisively enhanced when, during precompacting, the material to be disposed of is charged with a sterilising hot gas, preferably superheated steam. Hereby, the possibility of its plastification is increased as well as the chemical stability of the material to be disposed of and the storage stability without any nasal nuisance and formation of gas.

1 2 cl so Because of the desired high heat conductivity towards and within the material to be disposed of in the container but also on the grounds of the storage, transport and optimal disposal volumes for degasification, it is convenient to fill the containers in such a way that the filling iieicrht in case of domestic aarbage amounts to approximately 1 kilogram per cubic decimetre. As stuffina device for the filliner of the tubular containers in compressed manner, a periodically operating hammer may be used which is driven mechanically, hydraulically or pneumatically.

When the tubes filled in compressed manner are provisionally stored for quite a long time before they are admitted to a thermal utilisation, it is of advantage when the end faces of the tubular container filled with Dost-compressed material to he disposed of are cover-ed t,!-+lh thermally decom-posable foils or coatinas. Thus, direct release of pollutants into the e,-i-,,rironmeili, on zhe one hand. is excluded; on the oiher hand, also nasal nuisance is avoided. Then, the thermally decomposable cover may be thermally used directly during py-rolvs-is.,kpart from foils of plastics material, e. cr g. bituminous coatings are suited for this purpose, which can be applied in inexpensive and simple manner. Otherwise, the tubes, when the - pyrolysinc, -Process accordina to the invention is applied, behave practically selfcleansing. Using same not only optimises the conditions of the Pyrolysis as such but also reduces the transport volume by about 80 -Der cent when they are employed as transport containers. The compressed pyrolysed coke being obtained within the tubular containers as a result of the pyrolysis possesses excellent flow-through characteristics so that it is espeC4ally Z:1 -L suited for subsequent coal gasification.

1 1 11 1 2 C.

With the process described above, at least part of the natural moisture of the garbage is transformed into com- 1 - bustible gas by the described coal-water-gas reaction for the first time.

1 Patent Claims 1.

no Process for provisionally storing, transporting and/or energetically as well as materially utilising industrial, extra and domestic waste as well as spoilage of industrial goods of different composition and the like material of all kind that is to be disposed of, c h a r a c t e r i s e d i n that the material to be diSDOsed of, while maintaining its mixing and composite structures, is compressed to a multiple of its original bulk density and, in compressed form, subjected to a pyrolysis; that the total of the pyrolysates, which are under elevated pressure, are directly, without intermediate cooling, subjected to a hizh-tem-Derature charge, in the course of which th-e compressed fractions of carbur. ot" said T)yrolysate-b, W, He at least par-I -r the ent-ained. water va-oour 's o. being crocked, are Eassed and the iTaseous co-nstituent_z from sa--d total of the pyrolysates are crac---d into low-molecular components and equally gassed and that, finally, the metallic and mineral constituents from the remaining tctal arc smelted and separated.

Process according to Claim 1, characterised in that said high-temperature charge, while oxygen is being added, is effected such that the carbon dioxide from the exothermic reaction of the carbon with oxygen. in accordance with the air-carbon reaction, is transformed into carbon monoxide and that therewith. temperatures exceeding 1.500'C act on the total of the reaction products.

3. Process according to Claim 1 and Claim 2, characterised in that the material to be disposed of is first compacted to packages geometrically adapted to the shape 13 1 2C of a container and of approximately the same geometry; that the material to be disposed of, thus compacted, is compressed into such containers with the help of a stuffing device and that said material to be disposed of is then subjected to the pyrolysis, while remaining in said container in this compressed state.

4. Process according to Claim 1, characterised in that open-ended metal tubes are used as containers.

Process according to Claim 1, characterised in that 0 the material to be disposed of is compressed into tubular containers at a temperature exceeding 1nooC, J Lhe vapour resulting from the moisture of the material to be disposed of being exhausted through gas exit ducts of said container.

Process according to Claims 1 tn 5, ch--ract--rised in that heat reatment of said,ia--erial. to be disposed of, remaining in said curitainer in compressed state, is effected in a contirlious furriace n which a plurality of said containers are circulated.

7. Process according to at least one of the -precedino 1 Claims, characterised in that said material to be disposed of, at least during compacting, is passed through by a sterilising hot gas.

ZI I:> 8. Process according to at least one of the Dreceding 1 - - Claims, characterised in that the end faces of said tubular containers filled with compressed material to be dis-Dosed of are sealed with thermally. decomposable foils or coatings.