WO1996011742A1

WO1996011742A1 - Plant for the treatment of waste material containing an organic fraction

Info

Publication number: WO1996011742A1
Application number: PCT/FR1995/001360
Authority: WO
Inventors: Eric Chambe; Maurice Chambe; Pascal Haxaire; Gérard SEVENIER
Original assignee: Traidec S.A.
Priority date: 1994-10-17
Filing date: 1995-10-16
Publication date: 1996-04-25
Also published as: FR2725643B1; AU3749795A; FR2725643A1

Abstract

Plant for the heat treatment of waste material, comprising means (10) for supplying the waste material to be treated, two chambers (20, 21) arranged in parallel, a thermal dissociation reactor (30) for treating the waste material, means for collecting the solid residues formed in the reactor (30) and means (34, 35, 36) for collecting and condensing the formed residual vapors; the plant is characterized in that the chambers (20, 21) are provided with pressure reducing means (8), and in that the plant is also provided with a combustion chamber (81) supplied by the residual vapors formed in the reactor (30) and in the chambers (20, 21).

Description

PLANT FOR THE TREATMENT OF WASTE CONTAINING AN ORGANIC FRACTION.

Technical area

The invention relates to a new type of installation for the treatment of waste containing an organic fraction by thermal dissociation under reduced pressure.

The invention relates more particularly to an installation of the type in question for the treatment of hospital waste, petroleum products, sludge from sewage treatment plants, or soils contaminated with toxic products, or other industrial waste.

Previous techniques

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

There is therefore no need to describe it here in detail.

Essentially (see Figure 1), a thermal dissociation installation at reduced pressure, of waste containing an organic fraction, essentially comprises:

- a loading unit (1) and supply of the materials to be treated;

- means for placing under reduced pressure (2) these materials;

- A reactor (3) for thermal dissociation under reduced pressure at high temperature, for example at a temperature between 400 and 1000 ° C, especially around 500 ° C, under a pressure between 0.1 and one atmosphere; in a practical embodiment, the chamber (2) and the reactor (3) can be combined into a single assembly; - Means (4) for recovering the solid residues formed during thermal dissociation;

means for recovering the vapors (5) emitted during this thermal dissociation and means for condensing (6) these vapors, in order to recover in (7) the liquids formed,

- And means (8) for recovering residual vapors and for combustion (9) of these vapors by a boiler, then discharge into the atmosphere.

The thermal dissociation at reduced pressure of materials containing an organic fraction has been 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 results in a non-negligible labor cost. In addition, in this discontinuous process, vapors loaded with various products are discharged into the atmosphere, which does not comply with the regulations in force. Furthermore, the liquids recovered in (7) being rich in organic products are eliminated by combustion, in particular in the boiler (9).

Document WO-A-93/08936 describes a waste treatment installation which operates around a thermal reactor, optionally treatment under reduced pressure. The supply to this reactor is obtained by the alternating discharge of two loading chambers. Reduced pressure is obtained by the action of a vacuum pump which sucks and evacuates the vapors obtained during the heating of the waste inside the reactor. The entrainment of these vapors is facilitated by the circulation of a stream of nitrogen, through the waste to be treated. This vapor extraction method unfortunately facilitates the entrainment of dust. In addition, the treatment in the reactor takes place on raw waste which very often has a significant wet fraction, which then affects the yield of the treatment. Last but not least, the residual vapors are not treated, which necessarily results in a significant release of polluting products.

The invention overcomes these drawbacks. It targets an installation of the type in question which makes it possible to operate continuously, therefore that can be automated and at lower operating cost, and which authorizes treatment of residues as well solid as vapors in accordance with current and future regulations, in particular community regulations.

Description of the Invention

The invention relates to an installation for the thermal treatment of waste containing an organic fraction of the type which comprises:

. means for supplying the waste to be treated;

. two chambers placed in parallel, each connected to the supply means, each chamber comprising at least two valves, respectively a valve arranged at the inlet to the supply means, and a valve, arranged at the outlet towards a reactor;

. means for actuating said valves to allow loading of the two chambers;

. a thermal dissociation reactor for treating waste;

. means for recovering the solid residues formed in the reactor and means for recovering and condensing the vapors from the waste. -

This installation is characterized:

- in that the chambers connected to the supply means have means for putting under reduced pressure, so as to allow the loading at atmospheric pressure of one of the two chambers while the other discharges at reduced pressure into the reactor which thus finds at the same reduced pressure;

- And in that the installation also includes a combustion chamber supplied by the vapors from the waste, formed on the one hand in the reactor and on the other hand in the chambers when the pressure is reduced, so that all the vapors from the waste being treated are burned in the combustion chamber of the boiler.

Thus, on the one hand, one of the chambers can be charged at atmospheric pressure by traditional mechanical means, while the other chamber which has been previously charged is put under reduced pressure, then sees its content transferred to the reactor for be thermally dissociated there; in this way, it operates continuously, at least without interrupting the treatment process. On the other hand, all the vapors from the heating of the waste are brought into a combustion chamber in order to be completely burned there, which avoids the rejection of polluting materials. In this way, from the arrival of the waste in the installation, all the gases which have been in contact or from the waste undergo combustion, which avoids any discharge of polluting product.

To solve the problem of the efficiency of the thermal dissociation operation, the installation also includes a boiler intended to produce water vapor, and means for supplying this water vapor to the reduced pressure chambers. to heat them, these means being intended to facilitate the evaporation of the liquids contained in the waste to be treated and thus to dry them before treating them thermally in the reactor.

In a preferred embodiment, the means for supplying water vapor to the chambers comprise:

- a double envelope, surrounding each room, heated by steam from the boiler,

- And inside these chambers, a rotary hollow brewing drum, fed by said water vapor to stir and heat the waste to be treated to the core.

Advantageously, the thermal dissociation reactor comprises:

- a sealed cylindrical enclosure,

- a loading opening for dried waste, brought under reduced pressure, located on the upper face of the enclosure,

a plurality of semi-cylindrical buckets parallel to the longitudinal axis of the enclosure, and arranged one below the other to form paths parallel to said axis and in alternating directions,

a plurality of helical screws, each disposed in the buckets and having an axis of rotation parallel to the longitudinal axis of the enclosure,

- means for synchronized rotation of the helical screws,

- And an opening for evacuation of solid residues formed, located on the underside of the enclosure.

In practice, the first helical screw arranged upwards, and the last arranged downwards being constituted by two half-helices with inverted pitch. Two successive screws in the path have threads in opposite directions, so that the waste passes through the reactor, traversing the different buckets, being driven by the helical screws to arrive gradually by gravity, in the successive buckets, up to the discharge opening. In practice, the evacuation of the vapors formed in the reactor during the thermal dissociation is carried out as close as possible, for example coaxially to the supply of waste, and against the flow of waste, which makes it possible to reduce the areas where tightness must be maintained and above all to avoid entrainment of particles by vapors.

In a preferred form, intended for treating waste containing aggressive components such as halogens or sulfur, the installation comprises a means of adding to the dried waste, a chemical neutralizing agent of the aggressive components, disposed between the chambers reduced pressure and the reactor.

In an advantageous form for obtaining the energy autonomy of the installation, it also comprises a turbo-alternator driven by part of the water vapor produced by the boiler, said turbo-alternator in turn supplying electricity to the thermal dissociation reactor.

In one embodiment of the invention which makes it possible to solve the problem of eliminating all the waste, the vapors from waste, s formed in the reactor during thermal dissociation are first evacuated to a condenser, on the one hand to lower the temperature of these vapors to condense them, and on the other hand, to thereby recover a liquid condensate which is stored in a tank for later sending to the boiler, and more precisely in the combustion chamber of the boiler, the cooled vapors then being sucked up and sent into the combustion chamber of the boiler.

Typically, the reactor is heated to a temperature comprised between 400 and 1000 ° C, especially near 500 ° C, and the pressure is maintained between 0.1 and one atmosphere, especially in the vicinity of 0.5 atmosphere.

Brief description of the drawings

The manner in which the invention can be implemented and the advantages which result therefrom will emerge more clearly from the embodiment which follows, supported by the appended figures.

Figure 1 is a schematic representation of an installation according to the current state of the prior art.

Figure 2 is also a schematic representation of the installation according to the invention.

Figure 3 is a general top view of the installation according to the invention.

Figures 4 and 5 show respectively top views and side views, the reduced pressure and drying chambers, characteristics of the invention.

Figure 6 is a longitudinal sectional view of a reduced pressure chamber and its hollow mixing drum.

Figures 7 and 8 show respectively seen from above and seen from the side, the thermal dissociation reactor.

Figures 9 and 10 are views in respectively transverse and longitudinal section of the reactor, showing the waste transport buckets.

Figures 11 and 12 also show respectively seen from above and from the side, the solid residue recovery circuit.

Figure 13 is a side view representation of the vapor recovery circuit formed during thermal dissociation.

Figure 14 is a schematic representation seen from above of the vapor treatment circuit by the recycled boiler on the reduced pressure chambers. Way of carrying out the Invention

Referring to Figure 2, the installation according to the invention essentially comprises and in the order in which the waste travels, a loading unit (10) similar to (1), intended to bring the waste to the installation treatment. In one embodiment, the loading unit (10) is formed by a hopper and a sealed conveyor, for example with a helical screw, bringing the waste into a grinder to obtain the desired particle size, then from there by a new conveyor (11) at the head of the characteristic chambers (20,21).

In a variant, the crusher-hopper assembly is placed in slight depression by means of a suction hood connected to the boiler (80) to avoid any exchange with the air from the workshop, and in particular the the free air of bacteria, and the emanation of odors.

In addition, this recovered air loaded with volatile matter can be used as a complement to the combustion of the boiler.

The ground material then arrives at (see FIGS. 4 and 5), two reduced pressure chambers (20, 21) of cylindrical shape made of stainless steel, each comprising respectively on the top a valve (22) and (23) connected to the tube (24) connected to the supply (11) each containing supply means, for example with helical screw, so as to alternately fill a chamber (20), then the parallel chamber (21). Each chamber (20,21) has at its lower base a valve (25,26) connected by pipes similar to (24) to a pipe (27) 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 96/11742 PC-7FR95 / 01360

rooms (20,21). These rooms (20, 21) are heated by any appropriate means. In a preferred version, these chambers (20, 21) are heated by steam produced by recovering energy from the boiler (80).

In the preferred embodiment (see Figure 6), the chambers (20, 21) have a double jacket (91) in which the steam from the boiler (80) circulates. The chamber inside comprises a rotary hollow mixing drum (92) having hollow blades (93). The steam heats on the one hand the envelope (91) and therefore the peripheral material, and on the other hand, the drum and therefore the core of the material.

Depending on the direction in which the waste travels, the supply pipe (27) to the reactor (30) includes means (115) for adding an agent for neutralizing aggressive components such as halogens (chlorine, fluorine) and sulfur, which avoids the subsequent presence of harmful compounds (SO2, HC1, HF) in atmospheric emissions.

This means consists in incorporating into the lower part of the tubing (27), at the level of the drive screw, for example baking soda, whitewash or liquid soda, such that for example chlorine turns into sodium chloride.

The dried material brought through the tubing (27) (see FIGS. 6 and 7) into the reactor (30), is introduced after being unpacked into the top of the reactor (30). The vapors in the driers (20,21) are sucked through the tubing (71, 73) (see Figure 3) by a multi-stage vacuum cleaner or any other equivalent means. The reactor (30) of known form is heated by any suitable thermal dissociation means, in particular with electricity. It includes means for mixing waste during thermal dissociation. The pressure inside the reactor enclosure (30) is set between 0.1 and one atmosphere, preferably in the vicinity of 0.5 atmosphere, depending on the nature of the waste to be treated. The duration of the thermal dissociation treatment also varies depending on the operating conditions of pressure, temperature and the nature of the materials to be treated. The heavy metals (other than mercury) present in the waste thus remain in the solid state and are not oxidized during thermal dissociation.

The reactor (30) as shown in FIGS. 9 and 10 comprises several buckets (95-103) equidistant and arranged parallel to the axis of revolution of the reactor enclosure.

Each bucket (95-102) receives an Archimedes screw (105-112) allowing the advancement of the materials to be treated in the buckets. The first propeller at the top (105) and the last at the bottom (112), combine two half-propellers with reverse pitch. The pitches of the other screws (105-110) are alternated from one bucket to another.

Thus, when the materials to be treated arrive through the loading orifice (116), they fall into the upper bucket (95) and are driven half in one direction (SI) and half in the other (S2). At the ends of the first bucket (95), the waste falls into the lower buckets (96,97) and is driven in the opposite direction (S3) by the screws (106,107). The same change of direction takes place at the fall in the lower troughs (98.99), and so on, until arriving in the last trough of the bottom (102) in which the screw (112) collects the waste until '' at the bottom discharge opening (117).

All these screws (105-112) are driven by a set of sprockets (120) and chain (118) controlled by a single central shaft (119). 96/11742 -

1 1

The internal peripheral face of the reactor enclosure (30) comprises a plurality of electrical resistors (121) supplied either by the sector or advantageously by a turbo-alternator (123) driven by the steam from the boiler (80), which makes the installation autonomous.

In this way, the waste is disposed of in thin layers, and travels as long as possible, which allows a gradual decomposition. In addition, the circulation of materials takes place from the top to the bottom, while the vapors rise from the bottom to the top, which provides useful heating against the current and limits the entrainment of particles, because the most pulverulent is located towards the bottom of the reactor in an area where the flow of extracted vapors is low.

The solid residues formed (see FIGS. 11 and 12) are discharged from the bottom of the reactor (30) by means of a conveying tube (32) allowing, by indirect contact with water, to ensure a certain cooling. solid residues. In one embodiment, it is possible to produce around the tube (32) a second coaxial tube in which water flows against the current. The solid residues are then taken up by another conveying tube (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 the other hopper (34) is discharged at atmospheric pressure to ensure the elimination of solid materials at room temperature by means of a conveyor (38) to the storage area (39).

The solid materials thus formed and recovered during thermal dissociation are inert and are stored in (39), then are regularly eliminated in a known manner, in particular to a landfill. The energy content of these carbon-rich residues can be valued as fuel in cement works or the like.

In an advantageous variant (see FIG. 12), each hopper (34,35) has in its upper part, a valve (40,41) similar to (22,23), as well as a valve (42,43) placed in bottom of each hopper. In a practical variant, the solid residues formed are humidified by a conventional means not shown, just before being stored in (39) and this to avoid auto-ignition. To save money, steam produced in the boiler can be used for this purpose.

As before, the inert solid materials are conveyed by all known systems, in particular helical screws actuated by motors with hydraulic control.

Similarly, the actuation of all the valves (22,23,25,26,28,29,40,41,42,43) can be ensured in particular by conventional hydraulic or pneumatic cylinders not shown, or even by electrical systems. , controlled by an electronic automaton (50).

The vapors formed during the thermal dissociation are discharged towards the top of the reactor (30) by a pipe (60) coaxial with the supply (31) of the waste to be treated (see FIGS. 7 and 8). These vapors are taken up by a pipe (61), to be brought to a condenser (62), for example a condenser of the spray type, also called "shower condenser", in common use in the chemical industry. In this condenser (62), the vapors are entrained and partially condensed by droplets formed by a nozzle injecting a liquid formed by the condensate itself. The surplus 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) by the pipe (90). This embodiment is advantageous for the treatment of waste containing mercury because it makes it possible to recover it from the bottom of the tank (63). On the other hand, for waste containing no mercury, this condenser (62) can be replaced by an appropriate suction means.

The residual vapors are then sent through the pipe (65) to a suction means (66) to be discharged through the pipe (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 passage 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 includes a second suction means (70) which sucks the vapors formed in the reduced pressure chambers (20,21) through the pipe (71,73). during drying, to collect them with the vapors recovered in the thermal dissociation reactor at (67) in the combustion chamber (81).

In order not to reject pollutants, the pyrolysis chamber and the sectors comprising safety valves are connected to the pipe (73) supplying the combustion chamber (81).

The burner (82) of the boiler (80) operates in a conventional manner. For its start-up, use is made of all kinds of known fuels, in particular gas. During the operation of the installation, the combustion chamber (81) is self-supplied, at least in essential part, thanks to the calorific power of the vapors sucked by the pipes (71, 73) in the reduced pressure chambers, and vapors from the condenser (62) and the reactor. When the installation does not process the waste, the burner (82) can continue to be supplied with gas to allow the production of electricity thanks to the turbo-alternator. This electricity can be used elsewhere, which improves the profitability of the installation.

The operating conditions in the combustion chamber (81) and in the boiler (80) are such that the discharges comply with regulatory requirements. For example, currently, the released vapors are subjected for at least two seconds to a temperature of at least 850 ° C.

In an alternative embodiment, part of the energy produced by the boiler (80) is used to generate steam to heat the characteristic chambers (20,21). In an industrial variant, the surplus energy from the boiler (80) can be used to create electrical energy, which can itself be used for heating the reactor (30), so as to ensure almost total energy autonomy of the installation.

The installation according to the invention has many advantages compared to thermal dissociation installations at reduced pressure known to date. We can cite :

- the possibility of ensuring continuous operation, therefore 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 operations continuous and automated loading and unloading;

- discharges in accordance with regulatory standards, namely:

- no emission of acid gases (Sθ2, HCl, HF) thanks to the neutralization of chlorine, sulfur and fluorine upstream of the thermal dissociation phase,

- trapping of heavy metals in inert solid residues, - no emission of nitrogen oxides (NOx), thanks to combustion temperatures well below 1100 ° C,

- no possibility of dioxin or furan formation;

- 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;

- the absence of air exchange between the waste and the work building thanks to a suction system in the reception and grinding area;

- an optimal energy yield and a complete treatment of waste, thanks to the use of a grinder and dryers allowing the thermal dissociation of waste under a small, constant and regular particle size.

Industrial applications possibilities

In this way, this installation can be successfully used for the treatment of waste containing an organic fraction, such as for example petroleum waste, hospital and biomedical waste, urban waste, sludge from sewage treatment plants, paper waste , used tires, contaminated soil, plastic waste or industrial waste.

Claims

1 / Installation for the thermal treatment of waste containing an organic fraction which includes:

. means (10) for supplying the waste to be treated;

. two chambers (20,21) placed in parallel, each connected to the supply means, each chamber comprising at least two valves, respectively a valve (22, 23) disposed at the inlet to the supply means, and a valve (25, 26), arranged at the outlet to a reactor (30); . a thermal dissociation reactor (30) for treating the waste; . actuating means (50) of said valves (22, 23 - 25, 26) to allow the loading of the two chambers (20,21); . means for recovering the solid residues formed in the reactor (30) and means (34, 35, 36) for recovering and condensing the vapors from the waste; characterized:

- in that the chambers (20, 21) have means for putting under reduced pressure (8), thereby allowing the loading at atmospheric pressure of one of the two chambers (20) while the other (21) is discharging at reduced pressure in the reactor (30) which is thus at the same reduced pressure;

- And in that the installation also includes a combustion chamber (81) fed by the vapors from the waste formed on the one hand in the reactor (30) and on the other hand in the chambers (20, 21) during placing under reduced pressure, so that all the vapors from the waste being treated are burned in the combustion chamber (81). 2 / Installation according to claim 1, characterized in that it comprises a boiler (80) intended to produce steam, means for bringing said steam to the chambers (20, 21) for heating said chambers, said means being intended to facilitate the evaporation of the liquids contained in the waste to be treated and thus to dry them before treating them thermally in the reactor (30).

3 / Installation according to claim 2, characterized in that the means for supplying water vapor to the chambers (20, 21) comprise:

- a double envelope (91), surrounding each chamber, heated by the steam from the boiler (80),

- And inside these chambers (20,21), a rotary hollow stirring drum (92), fed by said steam to stir and heat the waste to be treated to the core.

4 / Installation according to one of claims 1 to 3, characterized in that the reactor (30) comprises:

- a sealed cylindrical enclosure (122),

- a loading opening (116) of the dried waste, situated on the upper face of the enclosure (122),

- a plurality of semi-cylindrical buckets (95-102) parallel to the longitudinal axis of the enclosure, and arranged one below the other to form paths parallel to said axis and in alternating directions,

- a plurality of helical screws (105-112), each arranged in the buckets (95-102),

- means (118) for synchronized rotation of the helical screws (105-112),

- And a discharge opening (117) for solid residues located on the underside of the enclosure (116) 5 / Installation according to claim 4, characterized

- in that the first helical screw (105) disposed upwards, and the last (112) disposed downwardly consist of two half-propellers with inverted pitch,

- And in that two successive screws (107, 109, 111; 106, 108, 110) of the path have threads in opposite directions, so that the waste passes through the reactor (30) by traversing the various buckets (95-102) in being driven by the helical screws (105-112) to pass by fall in the successive buckets (95-102), up to the discharge orifice (117).

6 / Installation according to one of claims 1 to 5, characterized in that the evacuation of the vapors formed in the reactor (30) during the thermal dissociation takes place near the supply of waste (116), and against the flow of waste.

7 / Installation according to one of claims 1 to 6, characterized in that it comprises a means of adding (115) to the dried waste, an agent for chemical neutralization of the aggressive components contained in this waste, between the chambers (20, 21) and the reactor (30).

8 / Installation according to one of claims 1 to 7, characterized in that it comprises a turbo-alternator (123) driven by part of the water vapor produced by the boiler, said turbo-alternator supplying in turn in electricity the thermal dissociation reactor (30). 9 / Installation according to one of claims 1 to 8, characterized in that the vapors formed in the reactor (30) during thermal dissociation are first discharged to a condenser (62), so on the one hand to lower the temperature of these vapors to condense them and on the other hand, to thereby recover a liquid condensate which is stored in a tank (63) to subsequently send it to the boiler (80), and more precisely in the combustion chamber (81) of the boiler (80), the cooled residual vapors then being sucked up and sent into the combustion chamber (81) of the boiler (80).

10 / Installation according to one of claims 1 to 9, characterized in that the reactor (30) is heated to a temperature between 400 and 1000 ° C, especially around 500 ° C and in that the pressure in the reactor is maintained between 0.1 and one atmosphere, in particular in the vicinity of 0.5 atmosphere.