FR2715087A1 - Heat treatment plant for hazardous waste - Google Patents

Abstract

The plant, e.g. for treating contaminated medical waste including sharps, consists of a treatment and decontamination chamber (2) with a grinder (22) for the waste material, and a chamber (23) with vanes axial rotor (24, 25) in which the waste is heated and decontaminated, a heat generator (1) to provide steam, incinerate waste and crack gases, and a series of filters (14, 15, 16) to clean combustion gases before they are released into the atmos..

Description

 The present invention relates to an installation for the treatment and elimination of hazardous waste, for example medical waste, including that which is said to be contaminated or assimilated, including sharp-edged objects ", coming from health centers, hospitals or all health professionals.

 This invention also relates to industrial waste, or not, which cannot be treated, neutralized or eliminated except by incineration or by suitable thermal means.

 The elimination of hazardous waste poses serious pollution problems, especially medical waste, given the galloping increase in the risks of contamination that they run (severity of newly discovered communicable diseases, ever increasing use of products for use unique etc ...).

 Proposals for treatment are currently being made to safely resolve the problem of disposing of this contaminated waste.

 While many medical wastes are not yet subject to any legislation, some hospital wastes are processed directly on site by incineration. However, although some of these hospitals are disposing of them correctly, very many establishments have unsatisfactory practices due to obsolete equipment.

 The authorities are currently aware of the problem of disposal of hazardous waste and intend to remedy it. Two possible master plans are currently proposed: group incineration and decontamination at the place of production.

 The first scheme implies the construction of large capacity incineration plants capable of treating contaminated waste at the same time as household waste. The installation and operation of such power plants pose serious problems because they are very expensive, which requires involvement at the departmental and even regional levels. In addition, the many nuisances caused by these "cathedrals" make it difficult to choose their location.

This method, which requires the collection and transportation of contaminated products from their places of production to the place of treatment does not allow for any unforeseen events such as social conflicts, transport strikes, breakdowns, etc. on pain of conflict with the legislation and safety standards it wants to impose
- storage period of 48 hours maximum (which can be increased to 8 days, under certain conditions),
- quota for the elimination of this waste at the plant, limited to 10% of the volume of incinerated household waste,
- drastic safety rules regarding the handling of the waste itself, of the equipment and materials handled during the collection or sorting of this waste in the production center, loading, removal, transfer and handling of containers, maintenance and maintenance of materials or equipment.

 This method also has the disadvantage of leading to a transfer of responsibility for waste between the departments or different companies which provide part of their treatment one after the other.

 Furthermore, this process does not satisfactorily resolve the problem of disposing of contaminated waste from small producing centers.

 Another disadvantage of these power stations is that since the introduction of recycling centers, household waste is sorted and large incinerators no longer find in household waste enough fuel to self-dispose of it (absence of paper, rags, plastics , etc ...) and must use additional energies, such as gas or fuel, sources of pollution and additional costs.

 The decontamination of waste carried out on site, for example in the hospital, is obtained in most cases by heating at high temperature after grinding, under certain conditions of pressure and humidity, for a time long enough to ensure the destruction of any microorganism.

 After this treatment, the so-called unmarked waste is mixed with the household waste of the establishment and then transported to the incineration plants where it is destroyed. Such treatment presents the risk that in the event of insufficient decontamination of the waste, all of the garbage is contaminated.

Four methods of decontamination after grinding are currently known
- the STHEMOS process consists of wetting the waste with steam and heating the mixture by means of microwaves. In order not to risk damaging the microwave transmitter, the process requires careful sorting of the waste, which makes it difficult to use,
- the GABLER GDA 130S process wets the waste with water vapor and heats the mixture by means of a heat-transfer oil itself heated by resistors. This process does not guarantee the treatment at the heart of the material, hence the need, in some cases, to add a disinfectant,
- the same goes for the ZDMA M3 process, which wets the waste and heats it with electrical resistances.

 - the VIRHOLAN process is the only one not to treat waste by heating. It consists of grinding them very finely, then immersing them in a bactericidal, fungicidal and virocidal bath before wringing them out and compacting them for their evacuation.

 The first three processes provide more or less satisfactory decontamination but at very high costs and are large consumers of electricity.

 The fourth process requires the handling of chemical materials and produces a residual bath which is contaminated and therefore becomes a new hazardous waste which must be eliminated.

 A fifth process, the CULTIMAT process, is based on ozone decontamination. This process attempts to meet the needs of liberal producers.

 The problems which continue to arise in the treatment of contaminated materials are due to the fact that only certain processes treat metallic objects and that, after decontamination, it is necessary to transport the unmarked waste to the centers of incineration of household waste so that they are permanently eliminated.

 The invention proposes an installation for treating hazardous waste and more particularly medical or hospital waste which, by meeting current legislation and anticipating future standards, makes it possible to decontaminate and then eliminate waste on site. The treatment installation according to the invention also ensures decontamination of the waste containers before they are put back into circulation.

 The installation is still such that it is self-decontaminated without external intervention.

 The facility meets the needs of both large and small producers of waste because it is self-sufficient from an energy standpoint and can therefore be fixed or mobile.

 Finally, it is also suitable for many industrial wastes, risky or not, requiring to be neutralized a thermal process, such as varnish residues, bottoms of pots before recycling, paints, chemical and pharmaceutical products that can be incinerated or neutralized by steam or heat. .

The invention provides an installation for treating hazardous waste, for example contaminated waste, by heat, characterized in that it comprises
a treatment and decontamination enclosure comprising a waste shredder, a waste mixing and decontamination chamber comprising an axial rotor carrying blades, a waste discharge conveyor from the kneading and decontamination chamber,
- a heat generator allowing the supply of steam, the incineration of waste and the cracking of gases,
- a set of filters for purifying the burnt gases with a view to their release into the atmosphere.

The installation according to the invention is also remarkable in that
- the heat generator is solid fuel and ember bed,
- the mixing and decontamination chamber is in a double-walled enclosure inside which the burnt gases of the generator circulate,
- the waste is supplied to the decontamination enclosure from a loading airlock on which the container is positioned and by which the waste is poured to be subjected to the action of the crusher, said container and said enclosure forming a sealed assembly,
- said sealed assembly with its empty container is automatically decontaminated during the waste decontamination cycle,
said sealed assembly with its empty container is automatically cleaned, during the cycle, by spraying of steam and runoff on the walls,
- during the decontamination of the waste, the blades prevent the progression of this waste towards the exit of the mixing and decontamination chamber,
- the waste is incinerated in the heat generator while the gases released during the treatment of said waste are destroyed by cracking at high temperature,
- all of the filters include a water filter, a dechlorination unit and an active carbon filter,
- it uses densified wood.

The invention will be better understood from the description which follows, given by way of nonlimiting example with reference to the appended drawings in which
FIG. 1 schematically represents the installation for processing hazardous waste according to the invention,
FIG. 2 is a diagrammatic representation of the steam and energy supply circuit of the installation according to the invention,
- Figure 3 shows an embodiment of the heat generator used in the installation according to the invention.

 In order to ensure the treatment of waste by the action of heat, the installation according to the invention firstly comprises a heat generator 1 supplied with fuel of 50 and comprising a water tank 10 allowing the supply of dry steam.

 Heat generators of the solid fuel type and ember bed allowing the pyrolysis of waste and the cracking of gas thanks to the high temperatures reached in the heart of the hearth, are particularly suitable for use in the installation according to the invention.

 Among these solid fuel heat generators, those using densified wood make it possible to treat a waste by recovering another waste and to reduce operating costs by using an inexpensive fuel since it is obtained from waste and widely available wood by-products.

 The heat generator may be a single hearth but will preferably be a multiple-hearth, concomitant, multi-function, solid fuel generator. At least one of said fireplaces has a very high temperature (1400 / 1600iC) ember bed, and allows the pyrolysis of waste and the cracking of gas.

 The generator also includes a regulated assembly for injecting fresh air and extracting smoke intended to control the vacuum levels in each of the homes.

 The dry steam supplied by the generator is sent in two networks, a dry steam network and a decompression network.

 In the dry steam network 11, said steam is transformed into mechanical and / or electrical energy by the mechanical and electrical energy generator 54.

The installation is thus able to meet its own non-calorific energy needs.

 In the decompression network 12, said vapor is transformed into saturated vapor at the temperature required by the type of waste to be treated. In known manner, this temperature is between 90 ° C and 140-C.

 A saturated vapor reservoir, not shown, is provided in a known manner in these networks.

 The installation is supplied with waste through the loading airlock 20 against which the container 4 is presented. This container, hermetically closed, is brought in front of the enclosure or it is taken up by automatic means which position it at the - above the hatch. The container 4 and the loading hatch 21 open simultaneously, so that the content pours into the upper part of the crusher 22 without the possibility of contact with the external environment.

 The container thus forms with the treatment and decontamination enclosure 2 a sealed assembly.

 The waste is then subjected to the action of the crusher 22 in order to obtain a particle size allowing mechanical stirring and to break any bottle, reservoir, aerosol, etc., to allow any contents to escape.

 As they are crushed, the waste falls into the treatment and decontamination chamber 23 in the form of an inclined cylinder.

 During the entire grinding phase, the entire installation is put under vacuum by the circuit 27 in order to absorb the gases which may be contained in the waste, for example aerosols, and thus avoid any risk of explosion. .

 The ground waste present in the decontamination chamber 23 is then subjected to stirring by the rotation of the rotor 24 while saturated steam from the decompression unit 12 is injected into the chamber 23 under the temperature and pressure conditions. required for decontamination.

 The rotor 24 carries blades 25 forming an angle with the axis of said rotor. The rotor is rotated during stirring so that the orientation of said blades 25 allow them to raise the waste that gravity drives down the decontamination chamber 23. When the decontamination of the waste is complete, the direction of rotation of the rotor is reversed in order to allow the evacuation of the waste by the evacuation door 26 situated at the bottom of the chamber 23, the blades 25 then help the progression of the waste towards said evacuation door 26.

 The injection of saturated vapor, during this stirring phase, is preferably carried out through the blades 25 of the rotor 24. This thus ensures penetration of this vapor into the heart of the waste to be treated.

 This ensures decontamination in good conditions of this waste by the action of heat while working under maximum safety conditions since, from that moment, the complete enclosure is decontaminated at the same time as the waste. This eliminates any risk for the rest of the process.

 Provision can be made to automatically clean the empty container, which is still integral with the enclosure in a leaktight manner by spraying steam and trickling onto the walls during the decontamination cycle.

 In order to obtain the required temperature, pressure and humidity conditions ensuring decontamination of the waste, the injection of saturated steam inside the enclosure is controlled by internal pressure sensors. The treatment and decontamination enclosure 2 is surrounded by a double wall through which hot gases pass in order to guarantee that the interior temperature of the enclosure is maintained at the required level.

 The hot gases circulating in this double wall are the burnt gases coming from the heat generator 1 and conveyed by the pipe 19.

 Inside the enclosure, pressure and temperature sensors make it possible to regulate, in a known manner, the injection of saturated vapor into the decontamination chamber 23 and the flow of hot gases in the double wall.

 The decontamination chamber being sealed, it obeys the law of equilibrium between pressure and temperature. It is therefore possible to control the state of internal saturated vapor sought by the regulation of one or the other parameter.

 The waste to be treated is of all kinds, paper, broken glass, plastic materials, etc. In order to avoid the melting of certain materials, a percentage is determined based on their percentage of the mass of waste to be treated. temperature not to be exceeded, for example 950C (or 100, 110 * c, etc.), so as not to disturb the stirring by amalgamating the shredded waste. This temperature value is between 90iC and 120in.

 From the time / wet sterilization temperature charts and the mass of waste contained in the decontamination chamber 23, the duration of the treatment is determined. These parameters determine the programming until the waste is removed from the decontamination chamber.

 When the treatment time has elapsed, the assembly comprising the decontamination chamber 23 and an evacuation conveyor 31 is put under vacuum by the circuit 17 which allows the waste to be dried.

 At the same time, the evacuation door 26 is gradually opened and the progressive feeding, by the evacuation conveyor 31, of the treated waste begins.

 The conveyor can be of any known type, for example with an Archimedes screw or carpet.

 The conveyor 31, located in the enclosure 2, is also surrounded by the double wall in which hot gases circulate, which ensures that the decontaminated waste continues to dry. It is also possible to provide additional means making it possible to further improve the drying of the waste during its disposal.

 According to the invention, the decontaminated waste is incinerated in the heat generator. To this end, said waste is poured from the airlock 32 into the hearth 41, above the bed of embers at high temperature (1400 μl at approximately 1600 ° C.).

 When all of the waste is extracted from chamber 23, the complete enclosure is subjected to a new saturated vapor cycle with condensation on the walls in order to be definitively cleaned and washed.

 The decontamination cycle is then complete and can start again with the waste from a new container.

 In the foregoing, we have only talked about the disposal and destruction by pyrolysis of solid waste, we will now describe how to remove liquids and gases that may be present in the treated waste.

 During the treatment of the waste in the decontamination chamber 23, the liquids which they contain flow along the interior walls of said decontamination chamber 23 in the form of sludge entraining fine particles. This sludge flows, by gravity, down the decontamination chamber. The mixing of the waste picks them up and reintroduces them into the mass where they are mixed, treated and dried.

 The gases sucked in by the vacuum circuit 27 are injected into the heart of the first focus of the generator / incinerator where they are burned.

 The gases from this precombustion, to which are added those from the precombustion of waste as well as the unburnt particles entrained by these gases, are mixed with the combustion air of the second hearth where they are cracked and completely burnt as they pass through the high temperature ember bed (1400 to 1600in).

 The combustion gases leaving the generator are decontaminated gases but can contain toxic waste; they must therefore be treated before being released into the atmosphere.

 We take advantage of the need to channel these gases to treatment means to recover a large part, or even all, of their heat energy.

 The combustion gases leaving the generator / incinerator 1 at a temperature of around 1100 c are sent to a cyclone / exchanger 13 inside which they are dusted off and, simultaneously, used to obtain water vapor, at around 200in, required for installation. The vapors from the return circuit 17 via the bypass 33 are also supplied to said cyclone / exchanger.

 It is around this cyclone / exchanger that we can predict the vapor reserve. This designation is used to simplify although it is not strictly speaking a tank but rather a volume in which the vapor enters at low pressure and leaves, due to the heat exchange, at high pressure and temperature (15 to 18 bars, around 2000C).

 In fact, in a steam circuit, there is a constant circulation back to the tank, tank 10, and regulation must be carried out in all sensitive points so as to locally maintain the necessary values of temperature and pressure.

 They are then channeled through circuit 19 to the double wall of the decontamination enclosure 2 surrounding the decontamination chamber 23, the waste supply airlock 20 and the decontaminated waste conveyor 31. This forced passage allows heat exchange which, as previously described, maintains the enclosure 2 at the temperature required for decontamination and drying of the waste.

 These gases, after having freed most of their calories, leave the double wall of the enclosure via the pipe 29.

They then pass through a filtration unit comprising
- a smoke extractor of known type,
- a water filter 14, ensuring gas washing and sanitation (particles, gases and harmful elements, odors) at more than 95%,
- a dechlorinator 15,
- an active carbon filter 16 in which the gases lose all odor and residual particles by releasing the last calories.

 These gases can then be safely discharged into the atmosphere below 30 C.

 The water in the filter 14 is then treated in a filter 51 which retains any suspended particle before being evaporated in the evaporator 52. The vapor obtained is injected into the return circuit of the active vapors 17.

 The filtration and evaporation residues are recovered and destroyed, during the system maintenance phase, in the generator / incinerator.

 During this same maintenance phase of the system, the residual ash is reduced by compaction and sent to appropriate centers.

 A set of condensation 18 and return to the reservoir 10 equipped, in a known manner, with a pump and return circuits 17 ensures the recycling of the low pressure vapors after their use. The pump allows the decontamination chamber and the conveyor to be placed under vacuum during the drying phase. The vapors extracted during this phase are filtered in unit 53 before being injected into the condenser.

 The installation for treating hazardous waste according to the invention makes it possible to treat all the waste at high temperature, without requiring prior sorting of this waste, even with regard to metals and glass.

 An installation according to the invention is capable of treating 1000 kg of waste per hour, at the rate of three 20-minute treatment cycles.

 Therefore, it is not necessary that the treatment enclosure 2 is large.

The complete decontamination installation is then of reasonable dimensions.

 As will have been understood, the decontamination installation makes it possible to ensure complete treatment of the contaminated waste in a manner that is fairly simple to implement and at low cost, both for installation and for operation.

 Such an installation can then be provided, in a fixed manner, in centers generating large quantities of contaminated waste. It can also be designed to be mobile, by being placed in a truck or on a trailer. Thus, the same installation can process the waste of several producers by passing from one to the other.

 A decontamination installation according to the invention provides a very significant advantage, by the fact that it can operate at the very place where the waste is generated, which eliminates the transport of contaminated waste from one place to another and therefore many risks of accidents.

 There is shown in more detail in Figure 3 an embodiment of the heat generator used in the installation according to the invention.

 In the variant shown, said generator has two communicating homes 41, 42.

 The hearth 41 is intended for the incineration of the waste brought to the airlock 32 at the end of the treatment.

 The hearth 42 is intended for the combustion of the solid fuel chosen, brought to a grid 45, from a storage 50, through the airlock 47.

 The hearth 41 comprises a grid 44 on which the waste is brought, and a secondary hearth 41a disposed under this grid 44, and resting on a grid 46.

 The hearth 42 also has a bottom grid 45.

 Said grids 45 and 46 are inclined to allow the embers to flow from the hearth 42 to the hearth 41a.

 Said hearths 41 and 42 are separated by a vertical partition 43 with a blade of water carrying at its base a door 48 allowing communication between hearth 42 and secondary hearth 41a.

 Nozzles 7, 8 and 81 ensure the arrival of combustion air.

 During the combustion of solid fuel on the grate 45 of the hearth 42, the embers flow by gravity towards the hearth 41a where they are admitted in a regulated manner. These embers are then of small particle size.

They thus form the bed of incandescent embers on which one ensures the pyrolysis of the waste particles and the ashes which pass through the grate 44. This bed of embers, by its ascending combustion flow, ensures the ignition of the waste in from the airlock 32.

 The opening of the door 48 can be controlled by embers detection probes in the hearth 41a.

 The combustion air, forced into the generator enclosure by the turbine 7, passes through the ember bed of the hearth 41a, then the waste to be incinerated from bottom to top.

 The combustion gases thus generated, circulate above the partition 43 and pass into the mixing chamber of the hearth 42 where they are supplied with combustion air supplied by the nozzle 8, before passing through the solid fuel of the hearth 42. The gases from the decontamination enclosure, during the depressurization and degassing, during the introduction of the contaminated waste and their grinding, are injected during this phase of mixing in primary air of the hearth 42.

 The hearth 42 is thus reverse combustion.

 The gas mixture is cracked when passing through the grid 45. Its combustion then ends at the same time as that of the gases of the solid fuel in the combustion chamber 49 supplied with oxidizing gas by the nozzles 81.

 The grates are, in a manner known per se, oscillating grids in order to allow the ashes completely burned to fall into ashtrays 60.

Claims (10)

 1 - Installation for treating hazardous waste, for example waste contaminated by heat treatment, characterized in that it comprises  - a treatment and decontamination enclosure (2) comprising a waste shredder (22), a waste mixing and decontamination chamber (23) comprising an axial rotor (24) carrying blades (25), a conveyor evacuation (31) of waste from the mixing and decontamination chamber,  - a heat generator (1) allowing the supply of steam, the incineration of waste and the cracking of gases,  - a set of filters (14, 15,, 16) for purifying the burnt gases with a view to their rejection into the atmosphere.  2 - Installation according to claim 1, characterized in that the heat generator is solid fuel and ember bed.  3 - Installation according to claim 1 or claim 2, characterized in that the mixing and decontamination chamber (23) is in a double wall enclosure inside which circulate the burnt gases of the generator.  4 - Installation according to any one of the preceding claims, characterized in that the supply of waste to the treatment and decontamination enclosure is done from a loading airlock on which the container is positioned and by which the waste is poured to be subjected to the action of the crusher (22), said container and said enclosure forming a sealed assembly.  5 - Installation according to claim 4 characterized in that said sealed assembly with its empty container is automatically decontaminated during the decontamination cycle of waste.  6 - Installation according to claim 4 or claim 5, characterized in that said sealed assembly with its empty container is automatically cleaned, during the cycle, by spraying steam at high temperature and runoff on the walls.  7 - Installation according to any one of the preceding claims, characterized in that, during the decontamination of the waste, the blades (25) prevent the progression of this waste towards the exit of the mixing and decontamination chamber (23).  8 - Installation according to any one of the preceding claims, characterized in that the waste is incinerated in the heat generator while the gases released during the treatment of said waste are destroyed by cracking at high temperature.  9 - Installation according to any one of the preceding claims, characterized in that the set of filters comprises a water filter (14), a dechlorination unit (15) and an active carbon filter (16).  10 - Installation according to any one of the preceding claims, characterized in that it uses densified wood.