FR2725643A1 - INSTALLATION FOR THE TREATMENT OF WASTE HAVING AN ORGANIC FRACTION - Google Patents

Abstract

Installation for the treatment of organic waste, which includes:. means (10) for conveying waste; . means (20, 21) for placing under reduced pressure; . a high temperature reduced pressure thermal dissociation reactor (30); . means for recovering solid residues; . means (34, 35, 63) for recovering and condensing the vapors formed during thermal dissociation; . a boiler (80) for treating the residual vapors, characterized in that: - the reduced pressure means consist of two parallel chambers (20, 21), each connected to the supply means (10) and to the reactor, each chamber (20, 21) comprising at least two valves (22, 23, 25, 26) arranged at the inlet and at the outlet of the chamber (20, 21); - it comprises means (50) for actuating said valves (22, 23, 25, 26) to allow loading at atmospheric pressure of one of the two chambers (20), while the other chamber (21) discharges at reduced pressure in the reactor (30).

Description

INSTALLATION FOR THE TREATMENT OF CONTAINING WASTE

AN ORGANIC FRACTION.

  Technical Field The invention relates to a new type of installation for the treatment of waste containing an organic fraction by dissociation

thermal under reduced pressure.

  The invention relates more particularly to an installation of the type in question for the treatment of petroleum sludge, hospital waste, petroleum products, sludge treatment plant, or

  soils contaminated with toxic products.

  PRIOR ART The thermal dissociation under reduced pressure at high temperature of materials containing an organic fraction is well known (see in particular US-A-4,077,868, 4,839,021 and Canadian CA-A-1,163,595).

  It is therefore not necessary to describe it here in detail.

  Essentially (see Figure 1), a reduced pressure thermal dissociation plant, waste containing an organic fraction, essentially comprises: - a loading unit (1) and supply of materials to be treated; - Means for placing under reduced pressure (2) of these materials; a reactor (3) for thermal dissociation under reduced pressure at high temperature, for example at a temperature of between 400 and 1000 ° C., in particular around 500 ° C., under a pressure of between 0.1 and one atmosphere; in a practical embodiment, the chamber (2) and the reactor (3) can be grouped into a single unit; means (4) for recovering the solid residues formed during the thermal dissociation; means for recovering the vapors (5) emitted during this thermal dissociation and means for condensing (6) these vapors, for recovering in (7) the liquids formed, and means (8) for recovering the residual vapors and combustion (9) of these vapors

  by a boiler, then released into the atmosphere.

  The thermal decomposition at reduced pressure of the materials containing an organic fraction was used in particular for the treatment of used tires and household waste. However, this technique has the disadvantage of operating discontinuously, which requires excessive handling and entails a significant labor cost. In addition, in this batch process, vapors loaded with various products are discharged into the atmosphere, which is not in accordance with the regulations in force. Moreover, the liquids recovered in (7) being rich in organic products are eliminated by

  combustion, especially in the boiler (9).

  The invention overcomes these disadvantages. It is aimed at an installation of the type in question which makes it possible to operate in a continuous manner, thus automatable and at a lower operating cost, and which allows treatment of solid residues as well as vapors conforming to

  current and future regulations, notably Community regulations.

Brief description of the invention

  The plant according to the invention for the treatment of materials containing an organic fraction by thermal dissociation at reduced pressure, which comprises: means for supplying the waste to be treated; means for placing these waste materials under reduced pressure; a high temperature reduced pressure thermal dissociation reactor; means for recovering solid residues formed; Means for recovering and condensing vapors formed during thermal dissociation; a boiler for treating the residual vapors, is characterized in that: the means for placing under reduced pressure consist of two chambers placed in parallel, each connected to the supply means and to the reactor, each chamber comprising at least two valves, respectively a valve disposed at the inlet to the supply means and a valve disposed at the outlet of the chamber to the reactor; and in that it comprises means for actuating said valves to allow loading at atmospheric pressure of one of the two chambers, while the other chamber is unloaded under pressure

reduced in the reactor.

  Thus, one of the atmospheric pressure chambers can be charged by conventional mechanical means, while the other chamber which has been previously charged and put under reduced pressure, sees its contents transferred to the reactor to be thermally dissociated therefrom. In this way, one operates continuously, at least without interruption of the

process of treatment.

  Advantageously, in practice - the reduced pressurizing chambers are heated by any appropriate means, such as in particular by the boiler so as to facilitate the evaporation of the liquids contained in the waste to be treated and thus dry before thermally dissociating them; the vapors thus formed are then discharged to the boiler; advantageously, the top of each chamber comprises a third valve disposed on the evacuation circuit to the boiler, this valve being also controlled by the actuating means of the two previous valves; - The reactor consists of a chamber in which the loading is from the top, while the evacuation of solid residues is from the bottom; in an advantageous embodiment variant, the evacuation of the vapors formed in the reactor during the thermal dissociation takes place coaxially with the supply of the waste; the heating of the reactor chamber is carried out by any known means, in particular with electricity, and during thermal dissociation, the treated waste is also stirred by any known means; as already said, in practice, the chamber is heated to a temperature between 400 and 1000 C, especially around 500 C; the pressure in the thermal dissociation chamber is maintained between 0.1 and an atmosphere, especially in the vicinity of 0.5 atmosphere; this reduced pressure is obtained by any known means of current use; the solids formed during the thermal dissociation are evacuated towards an assembly formed of two hoppers placed in parallel, also under reduced pressure, like the pressurizing chambers, so as to be able to work alternately with one another; to recover the residues while the other is unloaded to the storage area; the unloading of the solid residues from the hoppers towards the storage zone is done after delivery to atmospheric pressure by injecting into the hoppers a neutral gas, in particular nitrogen, together with the humidification of these solid residues; which makes it possible to avoid any risk of self-combustion in contact with the oxygen contained in the ambient air; the vapors formed in the reactor during the thermal dissociation are first discharged to a condenser, so as on the one hand to lower the temperature of these vapors in order to condense them and, on the other hand, to recover a liquid condensate that it is stored in a tank for later sending it to the boiler, and more precisely in the combustion chamber thereof; in addition, the residual vapors are then sucked and sent into the combustion chamber of the boiler; the boiler comprises means for combating vapors and condensed liquids and vapors formed during drying in the reduced-pressure chambers, so that this boiler essentially operates independently, except for the initial supply of fuel to bring the boiler to the operating temperature, for example at 850 C. In this way, we do not reject any

liquid waste.

Brief description of the Figures

  The manner in which the invention can be realized and the advantages that result therefrom will emerge more clearly from the embodiment which follows

the support of the annexed figures.

  Figure 1 is a schematic representation of an installation

  in accordance with the current state of the art.

  FIG. 2 is a schematic representation of

  the installation according to the invention.

  Figure 3 is a general view from above of the installation according to

to the invention.

  FIGS. 4 and 5 respectively show top views and side views, the pressurized and drying chambers,

features of the invention.

  Figures 6 and 7 are respectively seen from above and seen from

  side, the thermal dissociation reactor.

  Figures 8 and 9 are also respectively seen from

  top and side, the solid waste recovery circuit.

  FIG. 10 is a side view of the circuit of

  recovery of vapors formed during thermal dissociation.

  Finally, FIG. 11 is a schematic representation seen from above of the circuit for treating the vapors by the recycled boiler on the

  reduced pressurizing chambers.

  In the manner of carrying out the invention With reference to FIG. 2, the installation according to the invention essentially comprises, in the order of travel of the waste, a loading unit (10) similar to (1), intended to bring about waste at the treatment facility; in one embodiment, the loading unit (10) is formed of a hopper and a conveyor, for example with a helical screw, bringing the waste into a mill to bring it to the desired particle size, then there by a new conveyor (11) at the head of the characteristic chambers (20,21). The milled material then arrives at (see FIGS. 4 and 5), two cylindrical reduced-pressure chambers (20, 21) of stainless steel shape, each comprising on the top respectively a valve (22) and (23) connected to the tubing (24) connected to the feed (11) each containing feed means, for example helical screw, so as alternately fill a chamber (20) and the parallel chamber (21). Each chamber (20,21) has at its base a valve (25,26) connected by tubings similar to

  (24) to a pipe (27) for supplying the reactor (30).

  The references (28,29) each designate a valve for the evacuation of the vapors formed during the drying of the material in the chambers (20,21). These chambers (20,21) are heated by any appropriate means, in particular by recovering the energy of the boiler

(80).

  The dried material fed by the tubing (27) (see FIGS. 6 and 7) into the reactor (30) is introduced after being decompacted in the top of the reactor (30). This reactor (30) of known form is heated by any suitable thermal dissociation means, especially electricity. The reactor (30) comprises means for mixing the waste during thermal dissociation. The pressure inside the chamber (30) is set between 0.1 and an atmosphere, preferably around 0.5 atmosphere, depending on the nature of the waste to be treated. The duration of the thermal dissociation treatment also varies according to the operating conditions of pressure, temperature and

nature of the materials to be treated.

  The solid residues formed (see Figures 8 and 9) are discharged from the bottom of the chamber (30) by means of a conveying pipe (32) allowing, by indirect contact with water, to ensure a certain cooling of solid residues. In one embodiment, a second coaxial tubing can be made around the tubing (32) in which countercurrent water circulates. The solid residues are then taken up by another conveying pipe (33) which brings these residues into two hoppers (34,35) fed by two screws (36,37) similar to (24), thus making it possible to load at reduced pressure a first hopper (35) while discharging the other hopper (34) at atmospheric pressure to remove solids at room temperature by means of a conveyor (38) to the storage area (39). The solid materials thus formed and recovered during the thermal dissociation are stored in (39), then are regularly removed in a known manner,

especially to a landfill.

  In an advantageous variant (see FIG. 9), each hopper (34, 35) comprises in its upper part a valve (40, 41) similar to (22, 23), and a valve (42, 43) placed in bottom of each hopper. In a practical variant, the solid residues formed are moistened by a conventional means not shown just, before being stored in (39) and this

to avoid auto-ignition.

  As before, the solids are conveyed by all known systems, in particular helical screws actuated by

hydraulically controlled engines.

  Similarly, the actuation of all valves (22,23,25, 26,28,29,40,41,42,43) is provided by hydraulic cylinders

  unrepresented classics driven by an electronic controller (50).

  The vapors formed during thermal dissociation are discharged to the top of the reactor (30) by a pipe (60) coaxial with the feed (31) of the waste to be treated. These vapors are taken up by a pipe (61), to be brought to a condenser (62), for example a condenser type spray, also called "shower condenser", common in the industry. In this condenser (62), the vapors are entrained and condensed partially by droplets formed by a nozzle injecting a liquid formed by the condensate itself. The excess condensate formed is stored in a tank (63), connected by means of a pump (64) and brought into the combustion chamber (81)

of the boiler (80).

  The residual vapors are then sent through the tubing (65) to a suction means (66) to be discharged through the tubing (67) into the combustion chamber (81). In the tubing (65), the vapors are at a reduced pressure close to the pressure prevailing in the reactor (30), whereas after passing through the vacuum cleaner (66), these vapors are at atmospheric pressure in the tubing (67). ). The circuit for treating the vapors formed during thermal dissociation also comprises a second suction means (70) which sucks through the tubing (71, 73) the vapors formed in the pressurized chambers (20, 21). when drying, to collect them with the vapors recovered in the

  thermal dissociation at (67) in the combustion chamber (81).

  The burner (82) of the boiler (80) operates in a conventional manner.

  For its start-up, we use all kinds of known fuels, including gas. During the operation of the installation, the combustion chamber (81) is self-powered, at least partly essential. The operating conditions in the combustion chamber (81) and in the boiler (80) are such that the discharges comply with the regulatory requirements. For example, currently, the vapors released are subjected for at least two seconds, at a temperature of

minus 850 C.

  In an alternative embodiment, a portion of the energy produced by the boiler (80) is used to heat the characteristic chambers (20,21). In an industrial variant, the excess energy of the boiler (80) can be used to create electrical energy, which itself can be used for heating the reactor (30), so as to provide

  better energy independence of the installation.

  The installation according to the invention has many advantages over the thermal dissociation installations at reduced pressure known to date. There may be mentioned: the possibility of ensuring a continuous operation, thus automatable thanks to the two parallel chambers (20, 21) and the two hoppers (34, 35), both alternately at reduced pressure and / or at atmospheric pressure, which authorizes continuous and automatable loading and unloading operations; - discharges compliant with regulatory standards; - energy recovery by recovering and using all or part of the energy generated during the elimination of vapors and condensates;

- the absence of liquid discharges.

  In this way, this installation can be used successfully for the treatment of waste containing an organic fraction, such as for example petroleum waste, hospital waste, urban waste, sewage sludge, paper waste,

  used tires, contaminated soil or plastic waste.

Claims (8)

  1 / installation for the treatment of waste containing an organic fraction by thermal dissociation at reduced pressure, which comprises: means (10) for supplying the waste to be treated; means (20, 21) for reducing this waste to reduced pressure; a reactor (30) for thermal dissociation at reduced pressure at high temperature; means for recovering solid residues formed; means (34,35,63) for recovering and condensing the vapors formed during thermal dissociation; a boiler (80) for treating residual vapors, characterized in that: the reduced-pressure means consist of two chambers (20, 21) placed in parallel, each connected to the supply means (10) and reactor, each chamber (20,21) having at least two valves (22,23,25,26), respectively a valve (22,23) disposed at the inlet to the supply means (10) and a valve ( 25,26) disposed at the outlet of the chamber (20,21) to the reactor (30); - and in that it comprises means (50) for actuating said valves (22,23,25,26) to allow loading at atmospheric pressure of one of the two chambers (20), while the other   chamber (21) is discharged under reduced pressure into the reactor (30).   2 / Apparatus according to claim 1, characterized in that the chambers (20,21) for placing under reduced pressure are heated by any appropriate means, such as in particular by the boiler (80) so as to facilitate the evaporation of the liquids contained in the waste to be treated and thus dry them before thermally dissociating them, the vapors thus   formed then being evacuated to the boiler (80).   3 / Apparatus according to one of claims 1 and 2, characterized in   the top of each chamber (20,21) comprises a third valve (28,29) disposed on the evacuation circuit to the boiler (80), this valve (28,29) being also controlled by the means (50). ) actuating the two valves (22,23,25,26) above.   4 / Apparatus according to one of claims 1 to 3, characterized in that   that the reactor (30) consists of a chamber in which the loading is carried out from the top, while the evacuation of residues solids is from the bottom.   / Installation according to one of claims 1 to 4, characterized in that   that the evacuation of the vapors formed in the reactor (30) during the   Thermal dissociation takes place coaxially with the supply of waste.   6 / Apparatus according to one of claims 1 to 5, characterized in that   that the solids formed in the reactor (30) during the thermal dissociation are discharged to an assembly formed of two hoppers (34,35) placed in parallel, also under reduced pressure, like the chambers (20,21) reduced pressure, so as to be able to work alternatively with one (34) to recover the   residues while the other (35) is discharged to the storage area.   7 / Apparatus according to one of claims 1 to 6, characterized in that   that the unloading of the solid residues from the hoppers (34,35) to the storage zone (39) is done after resetting to atmospheric pressure by injecting into the hoppers (34,35) a neutral gas, in particular nitrogen,   together with the humidification of these solid residues.   8 / Apparatus according to one of claims 1 to 7, characterized in that   that the vapors formed in the reactor (30) during thermal dissociation are first discharged to a condenser (62), so as firstly to lower the temperature of these vapors to condense them and secondly, recovering a liquid condensate that is stored in a tank (63) for subsequent sending to the boiler (80), and more precisely in the combustion chamber (81) of the boiler (80), the residual vapors being then sucked up and   sent to the combustion chamber (81) of the boiler (80).   9 / Apparatus according to one of claims 1 to 8, characterized in that   the boiler (80) comprises means (82) for combating vapors and condensed liquids and means for recovering the vapors formed during drying in the chambers (20, 21) for reduced pressure.   / Installation according to one of claims 1 to 9, characterized in   that the chamber is heated to a temperature between 400 and 1000 C, in particular around 500 C and in that the pressure in the thermal dissociation chamber is maintained between 0.1 and   atmosphere, especially in the vicinity of 0.5 atmosphere.