EP0206803A2

EP0206803A2 - Installation for the treatment of solid residues

Info

Publication number: EP0206803A2
Application number: EP86304828A
Authority: EP
Inventors: José Manuel Lago Lucio; Quintiliano Moreno Llorente
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-06-21
Filing date: 1986-06-23
Publication date: 1986-12-30
Also published as: ES544453A0; ES8609667A1; EP0206803A3

Abstract

Solid residues received in a bunker (1) are driven to a hopper (2) with a bag tearing device and are deposited on a conveyor (3) with a device for controlling the maximum height of the residues. Glass is removed on the belt (3) and the remaining residues pass to a hammer mill (4) from which the ground elements are collected by a conveyor (5) passing a suction device (6) removing light materials. The remaining materials continue past an elctromagnet (9) which separates ferromagnetic material. The remaining material mostly organic matter, is introduced into a hopper (10) which feeds pyrolysis reactors by means of a conveyor (11) with a device for adjusting the maximum height of the residues. The reactors are connected to a suction line including a gas heater, a tar condensor, a water condensor, a chemical gas washing system, and a light solvent separating system. Non-condensable gas is recycled as a combustible gas in the installation.

Description

The present invention refers to an installation for the treatment of solid residues.
The volume of urban solid residues increases with the standard of living of the society. Due to the rapid evolution thereof, in our times, various communities are faced with serious problems at present. A rapid analysis of this situation brings to light that the majority of City Councils have difficulty in finding suitable spaces for dumping the residues, and they must frequently meet heavy charges in their budgets to combat the elimination or treatment thereof.
Thus, the conventional procedure of eliminating the residues, dumping, is being replaced by other elimination or treatment procedures. Apart from the controlled dumping, which does not solve the problem of space, the remaining methods normally employed are characterised in that they operate in a relatively small space, but all of them have a common factor, that is the high operating costs, wherefore the problem of dealing with the residues faced by City Councils still continues.
It must also be taken into account that the majority of the methods employed do not act on a fraction of the tailings, such as plastic, rubber, glass and metal, wherefore, once dumped, this fraction remains for a long time causing serious difficulties.
Three different alternatives have been developed in an attempt to solve these problems:

- Elimination of the residues
- Treatment of the residues to recover raw materials
- Treatment of the residues to obtain practical power-producing products.

The first alternative referring to the elimination of the residues, includes the methods of controlled dumping and incineration without energetic recovery.
Controlled dumping, a solution which is habitually resorted to, requires large available spaces with well-defined geological characteristics; it does not reduce the costs substantially, and the problems of the non-degradative matter which is always present in the dumping ground and its surroundings still persist, with the consequent deterioration of the environment and the contamination. The advantages of this method are its ability to avoid to a large extent the propagation of odours and rodents since the residues are covered daily.
The advantages of incineration without energetic recovery, are that a small space is required and environmental distrubances motivated by the presence of garbage are avoided. Its main disadvantages are the high operating cost and high contamination produced in the atmosphere by the combustion smoke. This is avoided by sophisticated purification systems which further increase the high operating costs.
This philosophy is becoming somewhat out of step, mainly due to the fact that none of the materials are recovered with a possiblity of being recycled. It has a poorly brilliant future since, because of the constant rise in the cost of raw materials and energy,
there is a constant need to reutilise the materials and to use alternative energies.
The utilisation of the residues is included in the two alternatives to be indicated.
The first refers to the recycling of raw materials which is beginning to have a wider applicability in Europe.
The separation of the recyclable materials, such as plastic, metal, paper and glass, is achieved by mechanical means, an organic matter remaining which is generally treated for manufacturing compost.
This method presents the advantage that it operates on a small piece of ground, preventing environmental impact, since the residues are treated in a closed block; it does not produce contamination and its investments are moderate.
The disadvantages presented thereby are fundamentally those derived from the fact that since compost is a fertilizer which has limited powers and is faced with serious difficulties at the time of its sale (due to transportation, competition with chemical fertilizers, wherefore it can only be sold at specific periods of times and in specific areas, etc.), its price must be low, wherefore the entire method of treament is not profitable and it does not generally solve the problem faced by City Councils.
The recovery of the materials without posterior treatment of the organic matter also does not solve the problem since, apart from not being economically practical, it also requires a large dumping space and it does not prevent the problems of the dumping grounds.
The second alternative of utilising the residues, in which there is an energetic recovery thereof, is the current practice predominating in the handling of solid residues. It is fundamentally based on utilising the energetic power thereof and reaching a practical manner to utilise it in the industry.
Three different processes have fundamentally been followed in an attempt to accomplish this:

- Incineration with energetic recovery: This is accomplished with the energy development by means of combustion and the heat development for producing steam or electric energy.

It presents all the advantages of the incineration without energetic recovery and its operating costs are lower, but it also presents the disadvantages of the said method and it further restricts its possibility of operating to areas in which the calorific power of the residues is elevated and to those in which energy and steam consumers can exist relatively nearby. Despite this, its operating cost is high.
- Pelletization: This is accomplished with the formation of combustible pellets for use in industries. The advantages consist of its relatively moderate cost, operation in a closed site and it does not present excessive contamination problems. Its main disadvantages include the difficulty of selling the combustible material, since it has a low calorific power and a high ash content. For this reason the plant is unprofitable and it frequently has high operating costs, due to the low price of the combustible in the market.
- Pyrolysis: This method operates with organic matter, subjecting it to coking to obtain a solid combustible (residual coke) having good thermal results and a low ash content which is readily accepted by the industry as a fuel for injection into suitable burners. A pyrolysis gas is also produced which is reutilised for producing the energy required by the process. As a sub-product there is a low temperature tar, rich in aromatic solvents and capable of being used in the coating industry and in the recovery of solvents.
As a result of the good selling possibilities of the products obtained and of a positive energetic balance, this process has low operating costs. It must also be emphasised that it is active with all materials and that the remaining inert residues are contamination free. It does not emit harmful smoke to the atmosphere, since the combustible employed is a previously washed and treated gas.
Further, it must also be taken into account that since the residues are treated in a closed site and there are no problems as to emissions of smoke, these plants can be installed close to towns, wherefore transportation costs are reduced. The installation costs are moderate.
The present invention provides a n installation as defined in claim 1.
Preferably, the rpsidues are received in a bunker which drives them to a hopper provided at its bottom with a bag tearing device comprised of two rotary rollers with chains, to be deposited on a conveyor belt provided with a device for controlling the maximum height of the residues and on which belt glass elements are removed, whereas the remaining residues pass to a feed hopper of a hammer mill from which the ground elements are collected by a second conveyor belt which passes through a vacuum chamber in which the light materials are absorbed, the remaining materials continuing on an electromagnetic belt which separates the ferromagnetic material, the remaining material, 95% of which is composed of organic matter, being introduced into a hopper which feeds a plurality of reactors by means of a third conveyor belt provided with a device for adjusting the maximum height of the residues, these organic matter residues being driven to a plurality of pyrolysis reactors which, after loading and closing their doors pneumatically, are gradually heated and are connected to a vacuum line including a gas heater, a tar condensor, a water condensor, a chemical gas washing system, and a light solvent separating system; steam is pro- diced basically which is condensed in a heat exchanger and other vapours are also condensed as the temperature increases and these condensable products are collected by the condensors with which the vacuum line is provided, only the fraction of non-condensable gas passes through the liquid washing and separating bowls to the vacuum pumps which drive it to the feed tank of the compressors, recycling it for its consumption as a combustible of the installation; a pyrolysis process takes place in these latter reactors in which the volume of organic matter is reduced for its carbonisation, to a coking tailing and inert materials; the separated glass fraction is stored in a corresponding recycling plant and the light fraction is driven to a cyclone so that, due to the loss in speed of the hauling air, it drops into an inclined separating trommel having deflecting wings which cause movement to its lower part; the said trommel is provided with a basic water pulverization device which wets the materials, paper and the like, which are torn in its turbulent path, and are collected by a lower hopper upon passing through a padded zone of the trommel and are stored for drying and subsequent introduction into the furnace, whereas the plastic materials are discharged through the lower opening to a hopper which feeds a packaging device; the ferromagnetic fraction is discharged onto a belt which transports it to a feed pipe of a scrap trommel in which it is cleaned by rubbing together during turning, and to the outlet of which is disposed the feed hopper of a scrap press for packaging; these packets pass into detinning reactors in which they are subjected to a detinning process by means of chlorine, to obtain various tin compounds, the remaining material being stored; the tar is collected at the outlet of the pyrolysis reactors, in condensors provided with a dual tank system, one of which acts as a vacuum tank,.passing through a pump to the distillation columns to extract the benzole and toluol fractions; the aqueous fraction of the condensors is pumped to a pool in which it successively passes through filtering columns, some with caking carbon produced in the reactors and others with active carbon, and is collected by a recycling tank after a solid decanting process; the carbonated fraction is collected, after the pyrolysis process, upon opening the closure door of the reactors, by a conveyor belt common to all of them and which feeds a container which is discharged onto the feed hopper of a vibrating screen provided with electromagnets, in which the carbonated fraction is separated from the metal scraps and the inert materials, the carbonated fraction passes through an attrition mill which reduces it to dust to be stored as a combustible material, whereas a small amount of the inert fraction is separated in the vibrating screen and is.ready for transportation and compactation.
.Referring to the functioning and characteristics of the preferred installation for the treatment of solid
residues, the following must be pointed out:

Reception

The residues are received in a bunker located at the upper part of the plant at which the garbage trucks unload directly.
This bunker is provided with a metal door which, once the residue receiving process has terminated, is closed, therefore isolating it from the outside.

Selection Line

The residues are reloaded from the bunker by means of a hooking device located on a travelling crane, to a hopper provided at its lower part with a bag tearing device. The product is collected by a conveyor belt including a device for controlling the maximum height of the residues, which must not be greater than a determined height.
The only contact which an operator makes with the residues takes place on this conveyor belt, since the glass is removed here manually. This operation has an overall duration of two hours daily to totally select the residues.
Then the residues are introduced in a feed hopper provided with a hammer mill in which they are ground to diameter thicknesses of less than 15 cm.
This mill feeds a belt which passes through a suction chamber in which the light materials (plastic, paper) are absorbed by means of the pneumatic pick up, the remaining material continuing on the belt to pass to an electromagnetic belt from which the fraction of ferromagnetic materials is picked up.
The excess residues, 95% of which consists of organic matter, are introduced in the hopper for loading the reactors,through the lower part of which there passes a conveyor belt provided with a maximum height adjusting device and having a residue transference capacity of 85 tons/hour and a reactor loading time of 5.2 minutes.

Pyrolysis process

The organic matter is introduced into four reactors and once loading has taken place, the loading door is closed pneumatically and a gradual heating takes place whilst the reactor is connected to the vacuum line. Steam is basically produced in a first phase, which is condensed in the heat exchanger provided for such purpose. As the temperature increases, other condensable gases are obtained. The condensable,products are cooled and condensed in the two condensers with which the vacuum line is provided, only the fraction of non-condensable gas passing through the liquid separating and washing bowls, to the vacuum pumps which drive it to the feed tank of the compressors. This fraction is a combustible gas which, by means of the compression line, is recycled to be consumed by the plant itself.
During the pyrolysis process the volume of the organic matter is reduced and this is in turn car- bonised, wherefore in the end there is a tailing of coked organic matter and inert materials not separated in the prior selection phase.

Treatment of the products obtained

The glass fraction, once separated and selected, is then stored to be transported to the glass recycling plant.
The light fraction, after the pneumatic pick up, reaches a cyclone to be dropped, due to the loss in speed of the hauling air, into a separating trommel. This trommel nas an inclination of 15⁰ and is internally provided with deflecting wings located in such a manner that upon turning they cause the residues to move towards the lower part thereof. It is in turn provided with a water spraying system for wetting the materials contained therein, wherefore the paper loses consistency and is torn during the turns in the interior, dropping through the screen of the trommel to a hopper located at the lower part. This wet paper is stored for drying and is then introduced into the furnace to be subjected to the pyrolysis process.
The plastic materials are discharged through the lower opening of the trommel to be collected by a hopper which feeds a packaging device which leaves them ready for storage.
The ferromagnetic fraction is discharged through an electromagnetic belt onto a belt which transports the material to the feed pipe of the scrap trommel. This trommel has an inclination of 5° and the scrap is cleaned therein by rubbing together during turning of the trommel.
The outlet of the trommel is disposed on the feed hopper of the scrap press which presses it into packets which pass to the detinning process in which they are introduced into two reactors and are subjected to the reaction, obtaining from,95 to 96% of the tin contained therein which is melted and stored in ingots. The detin- ned scrap is stored ready for sale.
The non-magnetic scrap is not taken into account since its volume is not sufficiently high for its recovery to be useful.
The tar fraction is collected by condensing its steam at the outlet of the reactors in the condensors installed for such purpose. These condensors are provided with a dual system of condensor outlet tanks to enable the interior to be isolated when transferring the tar to the vacuum tank. This is moved by a suitable pump ,and is stored outside, from where it passes to the distillating columns for extracting the methol and toluol fractions. The remainder is ready for sale as a charge for industrial waterproof coatings.
The aqueous fraction is collected fundamentally in the condensate pools similar to the tar tanks. It is also pumped to the pool in which it passes successively through two filtering columns: one with coking carbon produced in the reactor and the other with active carbon. At the outlet of the columns, it passes to the recycling tank, after a solid decanting process, before being ready for reutilisation.
The deposit from the cooling system is directly poured into the decanting zone without passing through the filtering process.
The carbonated fraction is obtained, upon termination of the pyrolysis process, by opening the lower door, so that it drops directly onto a conveyor belt which moves along the reactors and which feeds a container. This container is discharged onto the feed hopper of the vibrating screen provided with electromagnets and in which the carbonated fraction is separated from the metal tailings and inert materials. This carbonated fraction passes through an attrition mill and is converted into dust, ready for storage as injectable combustible material.
The inert fraction entails a small amount; it is separated on the vibrating belt and is deposited in a bunker which transports it to the outside to be compacted at a suitable site.
The type of chemical process to which the residues are subjected is mainly a dry distillation at a low temperature (450-550 C) and under vacuum conditions. During this treatment two different effects can clearly be distinguished inside the reactor:

A - Elimination of surface water:
At the steam pressure equivalent to the operating conditions of the system, the water has a boiling point of from 42 to 52°C.

Due to these characteristics and since the walls of the reactor are above this temperature when the residues are introduced, the boiling point of water is rapidly reached and steam is liberated to the heat exchange system.
Due to this effect and by means of the steam which ascends along the inside of the mass, all the residues in the reactor are more rapidly and more homogenously heated, thereby favouring the normal elimination of the surface water contained in the solid residues.
During this phase, a rapid drying of the entire reaction mass and a pre-heating of the initial conditions of the pyrolysis reaction suffered by the molecules during the thermal treatment to which they are subjected, are produced.

B - Pyrolysis reactions

Due to the increase in the temperature, there is gradually produced at the hotest points of the reaction mass, pyrolytic breaking of the molecules of the organic matter in the reactor. Low molecular weight car- boxy lie acids are produced i.n this reaction which, in turn, accelerate the degradation process of the molecules, in this phase by means of an acid hydrolysis.
Other more complex molecule reorganisation and formation of new molecular structure reactions are also produced in the reaction mass.
As the reaction progresses, the molecules are degraded into other smaller molecules reaching, in the final cases, molecules having a more simple structure, obtaining a fraction of compounds having an aromatic nature, the majority of which are present in the condensed tar and besides, a series of totally carbonated molecular skeletons forming fundamentally the resultant solid part of the process.
The studies concerning the amount of the products obtained are based on condiserations as to the quality and quantity of the residues taken in a national measure and throughout the year.
The approximate composition of the garbages on a wet basis has been found to be of about:
The overall moisture of the residues is also considered to range from 40-50% and the density from 0.2 to 0.3 tons per m .
On the basis of these values, the following comments can be made:

Glass

From 20 to 50 kg. per ton of treated residues are obtained.
This fraction is selected on the basis of colouring, due to its difference in price.

Plastic

From 22 to 28 kg of dry material/ton of treated residues are obtained.
The percentage found among the plastic materials can be divided into:
And as to formulation or composition thereof, it can be separated into:
They are fundamentally characterised by their low density which ranges from 25 to 50 kg per m³ as a whole, on which their system of selection is based.
These materials are perfectly recoverable due to their thermoplastic nature, polymers having an acceptable quality being obtained in the majority of the cases.

Metal

From 25 to 50 kg per ton of treated residues are obtained.
Two groups can be made in this fraction:

- Ferromagnetic materials
- Non-ferromagnetic materials

The majority of the ferromagnetic materials are separated in the magnetic pick up of the selection process. This is about 95% of the total of the metal fraction which is recycled. This fraction has an average of about 3% by weight of tin both in coatings as well as in alloys.
D_Jring the detinning process 95-96% of the total tin is recovered, the residual iron having tin percentages ranging from 0.10 to 0.13%, wherefore its quality is increased.
From 0.75 to 1.25 kg of tin per ton of treated residues are obtained in this process, which is practically pure.

Tar

About 35-45 kg per ton of treated residues are produced in this process.
The characteristics of this tar are the following:

Carbon

From 100-140 kg per ton of treated residues are obtained.
This product is defined by the following characteristics:

- Lower calorific power: 6,100-6,500 kcal/kg.
- The chemical analysis gave the following results in the fundamental elements:

Combustible gas

About 143-175 m³ per ton of treated residues are obtained.
The characteristics defining this gas are the following:

The percentage denominated "others", includes a complex mixture of molecules having 4-7 carbon atoms, with different branches and unsaturations.

Inert Materials

Entail from 35-80 kg per ton of treated residues.
They do not present decayable organic matter tailings and they are also odourless.

Aqueous fraction

From 360-450 kg per ton of treated residues are obtained.
It is characterised by a slightly basic pH 8.5-9.5 and by including, in solution, some organic salts and rests of organic solvents, such as traces of silene, toluene and benzene.
For a better understanding of the foregoing comments, a set of drawings is accompanied to this specification forming an integral part thereof, in which, illustratively and not limiting, the following is represented:

Figure 1 is a schematic elevational view of the installation for the treatment of solid residues of the invention.
Figure 2 is a general scheme of the treatment of the solid residues by pyrolysis.
Figure 3 is a section along a diametral plane of the pyrolysis reactor of the invention.
Figure 4 is a plan view of figure 3.
Figure 5 is a section on line A-B of figure 3.
Figure 6 is a schematic view of the water treating system of the invention.
Figure 7 is an elevational view of the installation corresponding to the vacuum line.
Figure 8 is a plan view of figure 7.
Figure 9 is a view similar to that of figure 3, illustrating a vertical section of the pyrolysis furnace of products having an easy heat transmission.
Figure 10 is a section on line C-D of figure 9.
Figure 11 is a plan view of figure 9, illustrating partially with dotted lines an adjacent furnace.
Figure 12 is a schematic plan view of the installation corresponding to the treatment of tin.
Figure 13 is an elevational view of figure 12.
Figure 14 is a horizontal, enlarged section of a detail of figure 12.
Figure 15 is a section on line E-F of figure 14.

Referring to the drawings and especially to figure l, it can be seen that the solid residues are received in the bunker 1 and sent to the hopper 2 provided at its bottom with a bag tearing device. This bag tearing device consists basically and preferably of two rollers with chains which turn in converging directions, causing the garbage bags to pass between them to be torn.
Tne tearing hopper 2 has a capacity of 20 tons/hour and proportions a constant flow of residues which is collected by a conveyor belt 3 moving preferably at a speed of 0.5 m per second. This belt 3 includes a device for controlling the maximum height of the residues which must not be greater than 10 cm , obtaining as a final result a transference capacity of 17.2 tons/hour.
From the said conveyor belt 3 the residues pass to the feed hopper of a hammer mill 4 which, in the case of the preferred embodiment, has a capacity of 17 tons/hour and in which they are ground into fragments having diameters of less than 15 cm.
The mill 4 feeds a belt 5 which moves at 0.5 m per second and which passes through the vacuum chamber 6 to separate the light materials, the remaining materials continuing on the belt 7 to pass to the conveyor belt 8 of magnetic products separated by the electromagnet 9.
The excess residues, 95% of which is composed of organic matter, are introduced in the hopper 10 to be driven by the conveyor belt 11 including a device for adjusting the maximum height at 20 cm , to the reactors in which a pyrolysis process takes place.
With further reference to this figure 1, the light fraction picked up by the pneumatic hood 6 reaches a cyclone 12 to drop into the 15° inclined trommel 12. The trommel 12 includes the water spraying device to wet the materials contained therein which drop through the screen of the trommel into the hopper 13, being stored in the tank 14.
The plastic materials which do not pass through the screen are collected by a hopper 15 which feeds the packaging device 16.
As it can be seen in the lower diagram of figure 1, the electromagnetic belt 8 discharges the magnetised fraction onto another belt 17 which drives it to the scrap trommel 18, preferably having an inclination of 5°, From the trommel 18 the scrap is sent to the hopper 19 for feeding the scrap press 20.
Figure 2 which schematically shows the pyrolysis process of the solid residues, illustrates that the organic matter driven by the conveyor belt 11 (see figure 1) is driven to the reactors 21, preferably four reactors, each having a capacity of 23 m3. The steam produced in a first phase is condensed in the heat exchanger 22 and since the temperature increases, other condensable gases are obtained. The condensable products are cooled and condensed in the condensors 23 in which tar is deposited, the fraction of non-condensable gas passing through the liquid washing 24 and separating 25 bowls to the vacuum pumps 26, having previously been filtered in the corresponding filters 27. The vacuum pumps 26 do not drive the tank 28 for feeding the compressors 29. As it can be seen in this figure 2, the combustible gases are stored in the gas tanks 30, recycling them for their consumption in the plant, to feed the gas burners of the reactor 21 through the duct 31.
Figures 3 to 5 show the arrangement of the reactor 21 which includes the coupling 32 of the burner, the duct 33 for the outlet of the pyrolysis gases, the duct 34 for the combustion gases and the cooling pipes 35.
Figure 6 shows the installation for cooling the aqueous fraction. At the outlet of the condensation water tank 36 there is a pump 37 which sends it along the filtering columns 38 and 39. The column 38 includes coking carbon produced in the reactors 21, whilst column 39 includes active carbon. The water, once filtered, is decantered in the recycling tank 40 which includes different successive passage compartments, the excess water being driven by the water overflow pipe to the collection box 41.
According to figures 7 and 8, the vacuum line included in the four pyrolysis reactors 21, has filling inlets 42 and corresponding pipes 43 for the outlet of combustion smoke.
The tar condensors 23 are common to two reactors 21. Figures 7 and 8 also show the water condensor 22 and the gas washing tanks 24, as well as the liquid separating tank 25.
Figure 9, corresponding to the elevational section of a furnace or pyrolysis reactor, similar to that of figure 3 but more simplified,shows the pyrolysis reactions to which the products having an easy heat transmission are subjected, not requiring therefore the inner radiating pipes referenced 35 in figure 3.
This figure 9 shows the heat inlet 44 for the gas combustion chamber 45; this type of simplified reactor is generically referenced by 21'.
Apart from the pyrolysis reactions taking place in the reactors of figures 3 to 5, or in the particular case of utilising the reactors 21' of figures 9 to 11, in cases of high production and for products having a very low heat transmission, a horizontal rotary pyrolysis reactor will preferably be employed, comprised of a rotary cylindrical casing and an inner axial spiral secured to its periphery, which embodiment has not been represented in the drawings.
Figures 12 and 13 show the installation corresponding to the treatment of tin, which comprises the drying chamber 46 and the reactors 47 and 48 connected to the electrolytic bath 49; the zinc chloride deposit 50 is shown in figure 12 and is more broadly indicated in figures 14 and 15, the tin treating reactors 47 and 48 include gratings 51 with cooling pipes which are adjacent to the cooling chambers 52.,
The detinning process which takes place in the reactors 47 and 48 is carried out with chlorine accumulated in bottles 53, obtaining various tin compounds.

Claims

1. An installation for the treatment of solid residues, characterised in that a hopper (2) for receiving the residues is provided at its bottom with a bag tearing device and deposits the residues on a conveyor (3), preferably with means for controlling the maximum height of the residues, on which belt glass elements are removed, the remaining residues passing to a mill (4) from which the ground residues are collected by a second conveyor (5) which passes suction means (6) for removing light materials, the remaining materials continuing past magnetic means (9) for separating ferromagnetic material, the remaining material being to one or more pyrolysis reactors (21) by means of a third conveyor (11), preferably with means for adjusting the maximum height of the residues, means being provided for separating non-condensable gas from the pyrolysis products and recycling the said gas to the reactor(s) (21) as a combustible gas.

2. An installation as claimed in claim 1, in which the reactor(s) (21) is or are connected to an extraction line including a gas heater, a tar condensor, a water condensor, a chemical gas washing system, and a light solvent separating system.

3. An installation as claimed in claim 1 or 2, including a cyclone (12) in which the light materials removed by the suction means (6) are separated from the entraining air and drop into an inclined separating trommel (12') having a perforated zone, means being provided for wetting the contents of the trommel (12').

4. An installation as claimed in any of claims 1 to 3, in which the magnetic means (9) discharges the ferromagnetic material onto a conveyor (8) which transports it to a scrap trommel (18) in which it is cleaned by rubbing together during turning, the outlet of the scrap trommel (18) communicating with a scrap press (20).

5. An installation as claimed in claim 4, in which the scrap press (20) produces packets which pass into a detinning reactor (47,48) in which they are subjected to a detinning process by means of chlorine.

6. An installation as claimed in any of claims 1 to 5, in which a conveyor is arranged to convey the carbonized product of the pyrolysis reactor(s) (21) to a container supplying the feed hopper of a vibrating screen provided with magnets, on which the carbonized fraction is separated from metal scraps and inert materials, the carbonated fraction passing to a mill which reduces it to dust to be stored as a combustible material.