EP0837920B1 - Method and device for thermally processing hospital waste and the like - Google Patents

Description

The present invention relates to a method and a device for heat treatment, in an ecological manner, hospital waste and other waste containing combustible.

Waste disposal must ensure total incineration of fuel at high temperature, non-combustible residues and fumes to be free from germs, hazardous compounds and odors. Currently, most of the waste hospital is cremated with household waste in incineration plants. This process has the disadvantage of presenting a great risk of contamination during waste transportation contaminated dangerous, or to incur costs high disinfection before transport.

The incineration of such waste directly on the place of collection (in clinics, hospitals etc.) could significantly reduce the cost and risk of contamination linked to transport. However small devices (ovens) for incinerating waste is usually perfectible and does not do not meet the cleanliness requirements of smoke, reliability, and convenience of use. They pollute the environment, especially during on and off, as well as when refill of waste in the oven, due to the significant gas formation caused by inflammation waste and combustion. The functioning of such incinerators can be interrupted by variations in the composition and properties of waste (humidity, ash content, etc.), which leads to an increase in harmful releases.

FR-A-2 649 782 describes a method for incinerating solid hospital, household and which is intended to exclude pollution from the environment, and in which stages of ignition, pyrolysis, combustion and cooling are ensured in sequence under continuous piloting. Overload driven by the introduction of a new batch of waste in the oven is prevented by piloting air supply and burner operation depending on the pressure in the oven and the temperatures in the oven and in a post-combustion chamber. The main drawbacks of this process to consume a lot of energy, to require a complex installation, as well as a fuel additional (combustible gas) to maintain the pyrolysis and combustion.

EP-A-0 251 269 describes a process and a reactor to gasify solid fuels followed by the combustion of gaseous products, putting uses a gas generator for the gasification of solid fuels such as wood, coal, fuel in briquettes, household waste, etc ..., followed by a burner for the combustion of gaseous products directly after gasification in the oven. To improve the thermal efficiency of the combustion of the above-mentioned fuels, primary air injected into the gasification zone and the air secondary supplied to the burner are heated by the heat released by gasification. The heating of air is supplied by passing primary air and secondary air through passages in a multiple wall of the gasification chamber.

This principle excludes overloads when uses fuels such as coal or briquettes because new amounts of fuel are supplied to the gasification area so continues as the previous quantities are consumed. However, when the material to be treated consists of waste, it does not feed gasification area regularly because, due to their low density, the waste loaded in the gasification can adhere to the walls of the chamber. Another possible cause of burner overload is tar. emerging from the gasification zone may condense on the cooler waste going down to it and thus agglomerate the waste. The condensation of tar also has the effect of degrading friability waste and their gas permeability.

The process according to EP-A-0 251 269 has furthermore disadvantage of transferring heat from the gasification zone because it can result in a extinguishing the combustion of a low fuel calorific value, for example wet. This results in constraints regarding the composition of the combustible.

EP-A-0 188 073 describes an incinerator for solid fuels in which a gasifying agent is introduced as two streams split in half different points in the combustion zone.

The purpose of the present invention is to provide a ecological heat treatment, more particularly gasification for incineration, waste hospital and other solid waste containing combustibles, ensuring reliable operation regardless of staff experience and for a wide range of compositions, calorific values, and hygrometry of waste, this process having more particularly avoid to a large extent the agglomeration of waste in the gasification upstream of the gasification zone.

• on charge les déchets dans une chambre de gazéification ;
• on établit une zone de gazéification dans la chambre de gazéification en introduisant un agent de gazéification contenant de l'oxygène dans la zone de gazéification de sorte que les déchets se déplacent dans la chambre de gazéification en succession vers la zone de gazéification pour y être successivement gazéifiés,
• on retire des produits gazeux de gazéification de la zone de gazéification,

The invention relates, in accordance with EP-A-0 188 073, to a process for hot treatment of solid waste containing fuels, such as hospital waste, comprising the steps according to which:

• the waste is loaded into a gasification chamber;
• a gasification zone is established in the gasification chamber by introducing a gasification agent containing oxygen into the gasification zone so that the waste moves in the gasification chamber in succession to the gasification zone to be successively there carbonated,
• gaseous gasification products are removed from the gasification zone,

the gasifying agent being introduced into the gasification chamber in a distributed manner, by dividing into at least a first and a second part.

According to the invention, the method is characterized in that that we introduce the first part of the agent of gasification in a drying chamber chamber gasification so that this first part crosses waste moving to the gasification area together with the displacement of waste in the room the second part of the gasification agent being sent through the gasification zone only.

According to a second aspect of the invention, the device to implement the method, comprising a chamber gasification suitable for receiving solid waste containing fuel such as hospital waste, admission means to introduce a screening officer gasification in the gasification chamber and outlet means for withdrawing gaseous products from gasification of the gasification chamber, the means of admission into the gasification chamber being arranged, with respect to the outlet means for gaseous products, so that a flow of said gasifying agent is divided into at least a first and a second part entering the gasification chamber at points distant from each other in the direction of travel waste to the gasification zone, is characterized in that the entry for the first part of the agent gasification is positioned to pass the first part of the gasifier through the waste passing through a drying zone before reaching the zone gasification in the gasification chamber, and in this that the second part of the gasifying agent goes to through the gasification zone only.

Thanks to the invention, the gasification chamber is subdivided into a drying zone and a drying zone gasification. A gasifying agent, such as air is introduced into the gasification chamber in a distributed way, so that a first part enters the gasification chamber clearly in upstream of the gasification zone, and establishes a drying area. The first part of the agent gasification flows successively through the drying and gasification zones together with moving waste along the chamber. A second part of the gasifier crosses only the gasification zone, in which the non-combustible solid products such as ash, dross etc ... settle. Waste crosses the chamber and feed the gasification zone at as they are consumed by the process. The gaseous products are preferably sent to a post-combustion chamber through orifices in a wall separating the gasification and post-combustion. In the post-combustion chamber, they are completely oxidized in the presence of an excess secondary air. The fumes are evacuated from the post-combustion chamber. Agent flow gasification through the drying zone in concordance with the movement of waste through the room promotes said movement, leads to the gasification zone aqueous vapors and others volatile components released in the area of drying, and prevents tar produced by the gasification to push back to the drying zone and condense there. Such condensation could lead to the agglomeration of waste being treated, and adversely affect their porosity and friability. This could compromise the transportation of waste, and even gasification agent, in the area of gasification.

The process can use air as a gasification. However, when dealing with high calorific dry waste, you can also inject steam into the gasification so as to reduce the temperature in the gasification zone.

The process according to the invention is particularly efficient to be used in incinerators small in size and highly reliable for processing thermally waste directly at the place of their production, for example in a hospital.

To reduce the risk of contamination by germs or dangerous chemicals present in the waste, we can load the waste directly in disposable containers (provided that these are flammable, for example bags polyethylene), these containers also being incinerated at the same time as the waste.

The movement of waste to the area of gasification can be promoted by a design and a corresponding size of the gasification chamber, for example by making it flared down. We can also activate the movement by some sort of agitator.

The volume of the post-combustion chamber is chosen so that when operating at capacity nominal incinerator, smoke retention in the room exceeds the standard duration required, and under temperature and oxygen concentration exceeding the prescribed standard values. These duration and standard values are those determined as ensuring the elimination of organic pollutants.

The process can be initiated by an impulse thermal applied to waste in the area of gasification and / or in the agent flow gasification by means of a heat source additional, for example an electric heater of which the operation is interrupted when the process of gasification has established itself stably. We pilot gasification and combustion by regulating the consumption of gasifier and air secondary and redistributing the gasification agent and secondary air between the intake ports corresponding, depending on the temperatures in the gasification zone and in the post-combustion chamber. We keep the temperatures within the range whose lower limit is defined by necessity to prevent the release of organic compounds, by particular of dioxynes, in dangerous concentration. The upper temperature limit can be set by the thermal resistance of the constituent materials the incinerator. When the temperature in the area of gasification tends to exceed the upper limit prescribed, the feed rate of the agent is reduced gasification. If the temperature in the post-combustion exceeds the upper limit, we increases the secondary air supply rate. If the waste has a low calorific value, can maintain the additional heat source in operation by regulating its power, even after initiation of the gasification process, so as to keep the temperature above the limit lower.

The controls described above can be insured automatically. To this end, the incinerator can be fitted with a control device comprising probes for temperature measurements in gasification and post-combustion chambers, and means for controlling feed rates agents and the distribution of the agent gasification and secondary air on the different means of admission to the incinerator's chambers function of these temperatures. However, for particular waste which is known to remain in certain limits of composition and properties, a such control can result from a factory setting, by simple fitting of corresponding gas pipes, having correlated cross sections.

To extend the possibility of applying the process to various waste, we can preheat the air secondary supplying the post-combustion chamber to using the heat recovered from the fumes generated in the post-combustion chamber. The recovery of heat can be achieved by means of a heat exchanger heat mounted either directly in the post-combustion chamber or downstream of it in the path smoke flow. Such preheating of air secondary to incinerate waste which gives off gases with low calorific value during gasification.

Treatment of waste containing additives dangerous, e.g. chlorine or sulfur, can be further followed by a purification step post-combustion chamber fumes and / or gases of pyrolysis withdrawn from the gasification chamber, to extract harmful gases from it using techniques known, for example by passing the products gaseous through one or more layers of limestone or other materials absorbing and neutralizing these pollutants. If the purification stage concerns gas from pyrolysis, for example, these are passed through a conduit containing said materials and connecting the gasification chamber to the post-combustion chamber.

To reduce the risk of air pollution by particles, maybe the afterburner subdivided into separate volumes linked in series so let the smoke pass through them successively. Mon of these volumes is preferably arranged in a cyclone, the conduit leading to this volume being arranged to ensure there a circular gas flow. Such a cyclone clears gases of dust particles.

Before switching off the incinerator, when his room of gasification is substantially empty of waste to except the part of this room where is located the gasification zone, a supply of gasification is distributed so that the surfaces gasification chamber interns are processed thermally for disinfection purposes. For it, the gasification chamber is provided with an inlet for hot gasifier. Heating a such gasification agent can be insured in the same heat exchanger as the one preheating the air secondary.

To ensure a regular draw, the incinerator can be fitted, in addition to a chimney for smoke emerging from the combustion chamber, from a draw assist device, for example a extractor fan or ejector. We maintain thus a slight negative pressure in the rooms of gasification and post-combustion, which will avoid gas leaks from them.

Other features and advantages of the invention will emerge further from the description below, relating to nonlimiting examples.

• la figure 1 est un schéma en élévation d'un incinérateur selon l'invention ; et
• la figure 2 est un schéma analogue à la figure 1, mais à échelle légèrement réduite et relatif à une variante, avec un détail II vu de dessus.

In the accompanying drawings:

• Figure 1 is an elevational diagram of an incinerator according to the invention; and
• Figure 2 is a diagram similar to Figure 1, but on a slightly reduced scale and relating to a variant, with a detail II seen from above.

The incinerator in Figure 1 includes a chamber gasification 1 vertically elongated having a upper opening which is normally closed by a cover 21. When the cover is open, you can introduce into the gasification chamber 1 of the waste 22, such as hospital waste in disposable plastic containers.

The bottom of the gasification chamber is defined by a grid 8 through which the gasification 1 is in fluid communication with a post-combustion chamber 7, which is in turn in fluid communication with the outside through a chimney 23 for the fumes.

The gasification chamber has two intake ports 4, 5 for a gasification, namely air in the example. A first port 4 is relatively far from the grid 8, while a second orifice 5 is closer to the grid 8. The flow of gasification agent in the gasification chamber is thus divided into a first part 24, going from the admission orifice 4 to grid 8, and a second part 25 going from the second inlet 5 to the grille 8.

An electric heater 11 is mounted in the post-combustion chamber 7 just below the grid 8.

We will now explain the process of gasification. The waste 22 being loaded into the gasification chamber 1, we operate the heating 11 to start heating the part waste 22, and introducing the gasification through the intake ports 4 and 5. This initiates the gasification of the lower part waste, as a result of which the heater 11 can be shut down. As the parties successively lower waste is gasified, the other parts move successively by gravity towards the grid 8. A zone is thus established gasification 3 substantially stable in the chamber gasification against grid 8, and the second inlet 5 for the gasifying agent is well positioned as the second part 25 of the agent gasification only flows through the area of gasification 3. On the contrary, entry 4 is positioned so that the first part 24 of the gasifying agent enters the gasification well above the area of gasification 3, which establishes a drying zone 2 in which the volatile components including the water, released from the waste, is captured by the first stream of gasification agent and driven with him in the gasification zone 3.

The gasified gasification products 6 emerging from the gasification zone 3 flow through the grate 8 in the post-combustion chamber 7. A inlet 9 is provided in the chamber post-combustion 7 in the vicinity of the grate 8 for inject a gas into the post-combustion chamber 7 secondary oxidant, such as air, so that burn the gasification gas products in the post-combustion chamber. When a session incineration begins, heating 11 is not used only to initiate gasification but also to initiate the combustion of gaseous products from gasification 6. Secondary air is introduced in more than stoichiometric so that the smoke 10 in the post-combustion chamber 7 contain excess oxygen in proportion corresponding to the standards for the decontamination of gas. For better incineration of products gasification gasification, secondary air, before being introduced into the post-combustion chamber 7 to through the inlet 9, is heated through a heat exchanger 15 mounted in the post-combustion 7 in the vicinity of its outlet. In exchanger 15, secondary air recovers heat smoke from the post-combustion chamber 7.

The gasification chamber 1 is further provided an additional intake port 16 for introduce hot gasifier 17 in one point distant from the grid 8, in the vicinity of the cover 21.

Port 16 is supplied with gasification agent in the form of hot air available at the outlet of the heat exchanger 15, like secondary air supplying the inlet 9.

All gas inlet ports 4, 5, 9, 16 are equipped with flow adjustment means 14 connected to an automatic pilot device 12 which controls also the operation of the heater 11, and which is connected to temperature sensors 13, one in the gasification chamber 1 and the other in the chamber afterburner 7.

The flow control means 14 of the orifice additional intake 16 is ordered to provide hot gasifier through the orifice 16 when the gasification chamber is almost empty because a batch of waste has been almost completely carbonated so as to heat disinfect the internal surfaces of the gasification chamber. But as the gasification chamber is not yet completely empty, gaseous products continue to form clear the gasification area and be burned in the post-combustion chamber, so that the heat exchanger 15 remains capable of producing hot gasifier for port 16.

A draw assist device 18, under the form of an ejector, is mounted at the outlet of the post-combustion chamber 7 to produce so certain a depression in all of the incinerator, which avoids the risk of leakage harmful gas from the incinerator.

A filter 37, consisting for example of one or several layers of limestone particles is also mounted in the outlet of the post-combustion chamber 7.

In the example of Figure 2, which will only be described that for its differences with that of figure 1, the post-combustion chamber 7 is subdivided into two volumes 41, 42, which the fumes 10 pass through successively before leaving room 7. The volume downstream 42 is arranged in a cyclone with a vertical axis so as to dust off the fumes. The gas pipe 43 by which the upstream volume 41 adjacent to the grid 8 communicates with the downstream volume 42 at an opening of output directed in the circumferential direction of the volume 42 to generate the cyclone effect. The conduit 43 opens at the top of volume 42. An outlet duct 44 allowing the fumes to exit from the volume 42 has a opening close to the base of volume 42 'and extends axially upwards through volume 42. Thus, the outer surface of the conduit 44 serves as a guide rotation for fumes 10 in volume 42 around the duct 44. The heat exchanger 15 is placed downstream of volume 42, between it and ejector 18. A filter such as 37 (Figure 1) has not been shown in Figure 2 but could also be expected.

• textile 24% en poids
• papier 28%
• carton 12%
• polyéthylène 9%
• caoutchouc 2%
• feuilles d'aluminium 2%
• verre 7%, et
• eau 16%

   a été chargé dans la chambre de gazéification d'un incinérateur de laboratoire réalisé sous la forme d'un cylindre vertical subdivisé par une grille métallique en une chambre de gazéification supérieure et une chambre de post-combustion inférieure. L'échangeur de chaleur pour l'air secondaire a été placé dans la partie inférieure de la chambre de post-combustion. Un chauffage électrique a été placé dans la partie supérieure de la chambre de post-combustion, sous la grille, pour amorcer le processus de gazéification dans la chambre de gazéification et enflammer les produits gazeux qui s'en dégageaient. Il y avait également un orifice d'admission pour introduire de l'air secondaire.A sample of waste, imitating the composition of hospital waste (from the waste analysis of CHERNOGOLOVKA hospital, in the Moscow region, Russia) consisting of:

• textile 24% by weight
• paper 28%
• cardboard 12%
• polyethylene 9%
• rubber 2%
• aluminum sheets 2%
• glass 7%, and
• water 16%

was loaded into the gasification chamber of a laboratory incinerator produced in the form of a vertical cylinder subdivided by a metal grid into an upper gasification chamber and a lower post-combustion chamber. The heat exchanger for the secondary air was placed in the lower part of the post-combustion chamber. An electric heater was placed in the upper part of the post-combustion chamber, under the grate, to initiate the gasification process in the gasification chamber and ignite the gaseous products which were released. There was also an intake port for introducing secondary air.

In the lower part of the gasification there was above the grid a intake port to introduce a gasification (primary air) in the area of gasification, and there was in the top from the same room a second intake port for introduce primary air into the gasification for the forced drying of waste.

The mass and density of the charged mixture were 1.65 kg and 190 kg / m ³ , respectively. After applying the thermal pulse by means of the heating for ignition, the primary air was sent to the gasification chamber and the secondary air to the post-combustion chamber. With flow rates of 1.5 1 / second for the supply of primary air and 0.75 1 / second for the supply of secondary air, the treatment time was 30 min. The temperatures in the gasification zone and in the post-combustion chamber were approximately 700 to 800 ° C and respectively 900 to 1000 ° C; the temperature of the fumes leaving the post-combustion chamber (behind the heat exchanger) was below 170 ° C. The post-combustion chamber discharges contained no visible dust and had no odor. The weight of the non-combustible residues consisting of molten glass, aluminum foil and ash was 0.21 kg.

The average ratio of air consumption across the two primary air intake ports in the gasification chamber was 2: 1, the strongest consumption of corresponding gasification agent during most of the consumer process through the intake port in the area of gasification. But at the final stage of the process, this report has been reversed to ensure disinfection of bedroom. So in this incinerator of laboratory, the inlet ports 4 and 16 of the figure I were in fact a single orifice.

Claims (22)

1. A method of heat-treating fuel-containing solid wastes such as hospital wastes, comprising the steps of :

   charging the wastes (22) into a gasification chamber (1),

   establishing a gasification zone (3) in the gasification chamber by feeding an oxygen-containing gasifying agent into said gasification zone (3), whereby the wastes move in the gasification chamber successively towards the gasification zone to be successively gasified therein,

   withdrawing gaseous products of gasification (6) from the gasification zone (3),

      wherein said gasifying agent is introduced into the gasification chamber in a distributed mode, divided into at least a first and a second part ; characterized in that said first part of the gasifying agent (24) is injected into a drying zone (2) of the gasification chamber (1) to cause said first part to flow through the waste traveling towards the gasification zone (3) concurrently with the waste displacement in the chamber (1), and said second part (25) of said gasifying agent being directed through the gasification zone (3) only.
2. A method according to claim 1, characterized in that steam is introduced into said gasifying agent fed to the gasification zone (3).
3. A method according to claim 1 or 2, characterized by a step of cleaning gaseous products of the gasification.
4. A method according to claim 1, 2 or 3, characterized in that the wastes (22) are charged into said gasification chamber (1) directly in disposable containers.
5. A method according to anyone of claims 1-4 characterized in that prior to finishing a gasification operation, when said gasification chamber is substantially free of waste, with the exception of the part of said chamber where the gasification zone (3) is located, a hot gasifying agent (17) is injected into the gasification chamber in a manner that internal surfaces of the gasification chamber are heat-treated for desinfection thereof.
6. A method according to claim 5, characterized in that prior to injection, said hot gasifying agent is heated by heat produced by combustion of the gaseous products of gasification.
7. A method according to anyone of claims 1-6, characterized in that the gaseous products of gasification (6) withdrawn from the gasification zone are directed into a post-combustion chamber (7) in which secondary oxidant gas is injected.
8. A method according to claim 7, characterized in that the secondary oxidant gas is injected in superstoichiometric amounts.
9. A method to claim 7 or 8, characterized in that said secondary oxidant gas (9) is preheated by heat recovered from flue gaseous products (10) formed in said post-combustion chamber (7).
10. A method according to anyone of claims 7-9, characterized in that said flue gaseous products are cleaned of noxious gases.
11. A method according to claim 3 or 10, characterized in that said step of cleaning comprises passing said gaseous products through at least one layer of material absorbing or neutralizing the noxious gases.
12. A method according to anyone of claims 7-11, characterized by controlling the temperature in the post-combustion chamber (7) by increasing the flow rate of the secondary oxidant gas when said temperature tends to become too high.
13. A method according to anyone of claims 1-12, characterized by controlling the temperature in the gasification zone by reducing the flow rate of gasifying agent when said temperature tends to become too high.
14. A device for performing a method according to anyone of claims 1-13, comprising a gasification chamber (1) adapted to receive fuel-containing solid wastes (22) such as hospital wastes, inlet means (4, 5) for introducing a gasifying agent into said gasification chamber, and outlet means (8) for withdrawing gaseous products of gasification (6) from said gasification chamber, wherein the inlet means (4, 5) to the gasification chamber being arranged with respect to the outlet means (8) for the gaseous products so that a flow of said gasifying agent is divided into at least a first and a second part entering the gasification chamber at locations which are spaced apart from each other along the direction of travel of the wastes towards the gasification zone, characterized in that the inlet of the first part of the gasifying agent is positioned for causing the first part of the gasifying agent to pass through the waste passing through a drying zone (2) before reaching the gasification zone in the gasification chamber, and in that the second part of the gasifying agent passes through the gasification zone (3) only.
15. A device according to claim 14, characterized in that the outlet means (8) of the gasification chamber (1) provide a fluid communication between the gasification chamber (1) and a post-combustion chamber (7) provided with an inlet port (9) for a secondary oxidant gas and with an outlet for the gaseous products (10) of combustion of the gaseous products of gasification.
16. A device according to claim 15, characterized by heat-exchange means (15) mounted for heat exchange between the flue gaseous products of combustion and the secondary oxidant gas flowing to the inlet port (9) for secondary oxidant gas.
17. A device according to claim 15 or 16, characterized by the post-combustion chamber (7) being so arranged as to be subdivided in at least two volumes (41, 42), the gas flow (10) passing those volumes consecutively.
18. A device according to claim 17, characterized by at least one (42) of said volumes being arranged in the form of a cyclone wherein the gas flow (10) is cleansed of dust particles.
19. A device according to anyone of claims 14-18, characterized by comprising control means (12) connected to probes (13) for temperature measurements in the device and to flow control means (14) to control feed rates through the inlet ports (4, 5, 9) according to temperatures detected by the probes (13).
20. A device according to anyone of claims 14-19, characterized by its gasification chamber (1) being provided with at least one supplemental inlet port (16) for a heated gasifying agent (17), adapted to perform disinfection of internal surfaces of said gasification chamber (1).
21. A device according to claim 20, characterized in that said at least one supplemental inlet port (16) is located at a substantially maximum distance from said outlet means (8) for the gaseous products of gasification.
22. A device according to anyone of claims 14-21, characterized by being provided with a draught-promoting device (18), e.g., an exhaust fan or ejector.

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