Destroying hazardous wastes

Patent Board

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The Netherlands @ ATerzagegging ïr 8501034 @ NL θ Process for the disposal of hazardous waste.

g) lnt.CI⁴F23G 7/04.

@ Applicant: SKF Steel Engineering Aktiebolag in Hofors, Sweden.

(74) Av .: Ir. LW Kooy et al

Vriesendorp &amp; Gaade patent office

Dr. Kuyperstraat 6

2514 BB The Hague.

@ Application Nr. 8501034.

@ Submitted April 9, 1985.

@ Priority from September 21, 1984, December 3, 1984.

@ Country of priority: Sweden (SE).

(g) Numbers of the priority applications: 8404764,8406090.

- @ Laid for inspection April 16, 1986.

The documents attached to this sheet are a print of the originally submitted description with claim (s) and any drawing (s).

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The invention relates to a method for destroying solid and / or liquid hazardous waste materials, such as materials comprising chlorinated hydrocarbons and similar toxic compounds that are not degraded in nature.

The accumulation of hazardous waste is a growing problem in all industrialized countries of the world. Until now, there is no efficient method for destroying these materials and attempts are being made to dispose of them by dumping them somewhere or by burning them in all types of furnaces.

Examples of non-degradable compounds that pose a serious threat to the environment are PCBs, i.e. polychlorinated biphenyls. This type of substance is often used as a dielectric fluid in capacitors and transformers and is also present in waste oil and in insecticides and herbicides, etc.

If these materials are deposited somewhere, they are a danger to the environment, because they cannot be rendered harmless by natural decomposition. Incineration by normal methods is incomplete and at low temperatures new toxic substances are mentioned, which are sometimes even more toxic than the original waste material.

The object of the present invention is to provide a method for destroying solid and / or liquid hazardous waste materials containing substances which are not degraded in nature and which method guarantees the formation of stable, non-hazardous end products.

This is achieved with the method according to the invention in which the waste material, which is primarily available in liquid form, is subjected to a

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bottom-stoichiometric combustion at a temperature of at least 1200 ° C whereby the ratio between injected waste material and oxidizing agent is controlled such that a quotient CO 2 / CO + CO 2 is reached of less than 0.1. The combustion process is preferably carried out at a temperature above approximately 1400 ° C. The advantage of destroying or breaking down the substance at high temperature, i.e. preferably above 1400 ° C, in an atmosphere with an under-oxidizing agent is that the high temperature in the process leads to a rapid and complete disintegration of the substance. waste material into substances such as CO, CO ^, H ^, H ^ O, HCl and C ^ ·

Reforming toxic substances that are dangerous to the environment that occurs in conventional processes is counteracted by the high temperature, the prevailing oxygen deficiency and the short residence time.

The residence time is of the order of approximately 0.5 to 1 second.

According to a preferred embodiment of the invention, the heat energy required for the process is supplied by a gas which is heated in a plasma generator to the ionization temperature. This guarantees (the achievement of) the required high temperatures in the process under operating conditions. In the piasma generator, electrical energy in a suitable gas is converted into heat energy and. . . dip with an electric arc discharge ', is generated in the piasma generator. The gas may, for example, at least partially consist of the oxidizing agent that is supplied to the reaction chamber. Furthermore, ultraviolet radiation emitted by the gas at the ionization temperature effectively causes cracking of any toxic chlorine compounds remaining in the gas.

The oxidizing agent may, for example, consist of a gas containing air, oxygen (O ^), carbon dioxide (CO ^) and / or water vapor (H ^ O) and which may be supplied to the process wholly or partly via the plasma generator.

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-3 The reaction chamber consists of a closed, heat-insulated container equipped with a refractory lining, which is provided with connections for one or more piasma generators, injection lances for waste material and oxidizing agent, and with an outlet for the evolved gas.

According to a suitable embodiment according to the invention, after the combustion step in which external energy is supplied by means of a plasma generator, the gases can still be subjected to a carbonization step in which ζθ are forced to flow through a reactor filled with a solid carbon carrier such as coke possibly an additive for increasing the reactivity, for example an alkal metal compound, has been added. The physical heat of the gas is thus used to heat the coke to the temperature of the gas at which the carbon and the coke are forced to react with oxygen, carbon dioxide and water vapor in the gas to form carbon monoxide and hydrogen gas, thereby reducing the calorific coefficient of the gas is increased.

The gas can be freed from its chlorine compound content in a conventional manner by passing it into a washer in which the gas is cooled and the chlorine-containing compounds are removed. The chlorine-free gas can then be led to a final combustion chamber or used directly in an industrial process.

According to an embodiment of the invention, in order to reduce the amount of re-toxic compounds and / or new toxic chlorine compounds being formed, an additional treatment step can be carried out, wherein after heat exchange (temperature reduction) to a temperature of 350 - 700 ° C, the gases are fed into a reactor filled with a suitable chlorine acceptor to remove chlorine and / or hydrogen chloride and to condense any remaining metal vapors. Hydrated lime or

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- Burned lime and / or dolomite are used as a chlorine acceptor.

The invention will now be described in more detail with reference to the drawing, in which Fig. 1 shows a simplified diagram of a device for carrying out the method according to the invention and Fig. 2 shows an embodiment of a reaction chamber in combination with a carbon shaft.

The installation shown in Fig. 1 comprises a reaction chamber 1 which is covered with a refractory material. The waste material to be treated is introduced via at least one lance 2. According to the preferred embodiment of the invention, the required energy is supplied by means of a gas that is heated in at least one plasma generator 3. The gas to be heated is supplied through a line 4. That gas may suitably consist of at least a portion of the oxidizing agent used in the process. Additional oxidizing agent and / or other reagents is (are) supplied by lances 5.

The volume of the reaction chamber is adapted to other process parameters such as the gas velocity, the energy density in the plasma gas, the amount of waste material supplied per unit of time, etc., in order to achieve the necessary residence time for effecting the reactions, i.e. a residence time of the order from 0.5-1 sec. The gas is discharged from the reaction chamber through a line 6 to a washer 7 where the gas is cooled and all chlorine-containing compounds are removed.

The washed gas is then passed through a conduit 8 to a final combustion chamber 9 in which it is burned with air supplied through a lance 10.

The gas can of course also immediately after leaving

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-5 the washer can be used if it has a composition and an energy content suitable for some industrial process or the like.

FIG. 2 shows a reaction chamber 11 which is connected to a carbonization shaft 12. The reaction chamber is provided with an inlet 13 for the material to be destroyed. A gas is supplied to a plasma generator 14 and heated there to ionization temperature. The gas is supplied to the reaction chamber temperature, releasing heat to the material and simultaneously exposing it to ultraviolet radiation. The physical heat content of the gas generated here is used in the subsequent carbonization shaft 12. It comprises a coke supply means 15 at the top end and an outlet 16 at the top

J5 bottom end for non-combustible material. The gas developed is introduced at the bottom of the reactor and discharged through a gas outlet at the top 17.

The filling of coke in the reactor is heated by the physical heat of the gas to the temperature of the gas, and oxygen, carbon dioxide and water vapor are reacted with the carbon of the coke to form carbon monoxide and hydrocarbon gas. If necessary, sulfur can then be removed from the gas in a conventional manner.

After a possible cleaning of sulfur, the gas is cooled or brought into heat exchange so that it reaches a temperature of approximately 350 - 700 ° C and is passed out of the gas through a suitable acceptor for chlorine and hydrogen chloride. A suitable chlorine acceptor consists of slaked or unsleached (burned) lime and / or dolomite.

For this purpose a vertical reactor is preferably used which is filled with the acceptor, for which purpose a reactor of the type as used for the carbon shaft can be suitably used.

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