WO2008136011A1

WO2008136011A1 - Plasma pyrolysis system and process for the disposal of waste using graphite plasma torch

Info

Publication number: WO2008136011A1
Application number: PCT/IN2007/000181
Authority: WO
Inventors: Kudaligi Sethuramachar Ganesh Prasad; Sudhir Kumar Nema; Vishal Jain
Original assignee: Institute For Plasma Research
Priority date: 2007-05-08
Filing date: 2007-05-08
Publication date: 2008-11-13

Abstract

A plasma pyrolysis device is provided for dispensing-off a variety of waste materials. The device has two metallic chambers, a plasma torch, a number of electrodes, means to provide air and means for transfer of pyrolysed gases, a feeder, scrubber and control circuits. The process for carrying out pyrolysis, under oxygen starved environment, is also provided. The process is optimized to operate at extremely low power levels. The device is energy efficient, simple in construction and cost- effective.

Description

"PLASMA PYROLYSIS SYSTEM AND PROCESS FOR THE DISPOSAL OF WASTE USING GRAPHITE PLASMA TORCH"

FIELD OF INVENTION The present invention relates to a plasma pyrolysis device for disposing waste more particularly plastic, municipal waste and medical waste.

BACKGROUND OF THE INVENTION

Microwave disinfection is a non-incineration process that is used for sterilization (disinfection) of medical waste. Subsequently, the sterilized waste is either dumped along with the municipal waste or is treated by incinerators. The microwave process has potential for getting the workers expose to a contaminated shredder. In incineration, merely the burning of waste material takes place in the presence of oxygen. The major disadvantage with incinerator is, it has significant air emission control problem.

Thermal plasmas have been used for high temperature gas heating application for more than a century. Thermal plasma is used as an effective source for the efficient conversion of electrical energy into thermal energy. These high temperature plasmas are employed for a large number of applications, for example cupola for steel foundries, thermal decomposition of Zircon sand, spherodization, production of fine ceramic powders etc. Clean disposal of hazardous waste is one of the most important applications of thermal plasma.

At present, predominantly the plasma pyrolysis is done using air or nitrogen plasma torches. The electrodes are copper or thoriated tungsten and the life of the electrodes used to be 100-1000 hours. After the specified life one need to change the electrodes.

Introduction of N₂ through the electrodes requires uninterrupted nitrogen supply or nitrogen generator. It is constrained by logistics and cost factors. In the case of air as a plasmagen gas here is a possibility of incineration in small pyrolysis systems (waste disposal -30 - 100 kg/hr). The air can also result in the formation of dioxins and furans. The majority of plants utilizing the different plasma torches and plasma heating system have been use typically 24 hours a day year round at industrial capacity. For example, a plasma plant in Defiance, Ohio, employs six 2.5 megawatt torches simultaneously, handling over 40 tons per hour scrap metals. The existing plasma torches use nitrogen or air as a plasmagen gas. The electrodes need proper cooling thus appreciable part of energy is lost in electrode cooling.

US patent # 5,090,340 discloses apparatus and method for the disintegration of waste by subjecting the waste within a closed chamber to any array of plume of an electrically generated high temperature plasma.

US patent # 4,644,877 of Pyroplasma International disclosed a method and apparatus for the pyrolytic destruction of materials. The waste is fed into a plasma arc burner where it is atomized and ionized and then discharged into a reaction chamber. Plasma burner has a pair of co-linear hallow graphite electrodes connected through a 500 kW power supply.

The plasma arc is stabilized by annular electromagnetic field coils which spin the arc.

Vortex air is supplied to plasma burner at a flow rate of 20 cubic feet per minute.

Integrated environment technologies has developed plasma enhanced melter for the disposal of medical and hazardous waste and toxic ash. Waste is converted in an arc plasma-joule heated melter system utilizing one or more graphite electrodes to produce arc plasma and a plurality of joule heating electrodes. The arc plasma electrodes are powered by AC or DC source or for switching between AC or DC source or for switching between AC and DC power. The graphite electrodes are mounted vertically and the molten glass bed is used to transfer the energy. The joule heating is done simultaneously with the arcing without any detrimental interaction with the arcing electrodes. C. H. Titus et al. invented an arc furnace that utilizes a combined DC arc system and an AC joule heating system to melt and disposed the waste and keep the waste material in a molten condition.

Plascon is an in-flight plasma arc system developed by Australia's CSIRO. A liquid or gaseous waste steam mixed with argon is injected directly into a plasma flame, which provides temperatures in excess of 3000⁰C for pyrolysis. The residence time of the waste in the reaction chamber is of the order of 20-50 milliseconds, resulting in a small process inventory. The end products include gases consisting of argon, carbon dioxide and water vapor and an aqueous solution of inorganic sodium salts. Chlorinated organics yield very high destruction performance and release very low dioxins and furnace. The measured emission of dioxins and furans in the off gases has been found to be in the range of 0.005-0.009 ng/m³, which is well below the strictest proposed environmental standard in the word.

Parcon is the product of Plasma Environmental Technologies, Inc. developed and designed specifically for destruction of the environment's most problematic liquid chemical wastes, including pesticides, PCBs, chemical weapons, fungicides, and petroleum derivatives. Destruction and Removal Efficiency exceeds the EPA standard of 99.9999%, with documented DRE as high as > 99.999998%. For example, the PARCON emission of dioxin/ furan has been documented at 0.03 nanograms per cubic meter (ng/Nm³).. PARCON technology is available in transportable units ranging from 12.5 kilograms per hour to > 200 kg/hour feed capacity. The furnace uses a transferred arc plasma torch to heat the bath material.

The plasma Arc Centrifugal Treatment process is developed by Retech. The waste is fed continuously by a screw feeder into the centrifugal reactor. A copper throat, at the bottom of the primary chamber, is used to strike the arc of the plasma torch. Solid material is retained in the tub by centrifugal force. The heat of the plasma gas volatilizes organic components. The destruction and removal efficiency (DRE) of organic compounds is claimed to be greater than 99.99%. The system can operate under pyrolytic conditions and a reducing atmosphere avoiding dioxin formation in the primary chamber. Given the total air emission volumes are less than or conventional combustion processes, the potential impact of emissions is expected to be lower. Investment costs are located in the range 3.8-7.6 millions of ECU while the operating costs may be evaluated around 120- 1590 ECU/ton. The Startech Environmental Corporation developed the STARTECH Plasma-electric Waste Converted (PWC) in the US. The system was designed to treat both hazardous and non-hazardous wastes. The PWC is a plasma heated pyrolysis system, operating in a oxygen deficient of reducing atmosphere. Organic and inorganic wastes can be introduced into the plasma chamber as solids, liquids, gases, and sludges. Gas recovered from the top of the chamber is treated and can be reused as fuel gas or chemical feed stock to produce, for example, polymers.

Incidis is an Aerospatiale product, built to prove the efficiency of plasma treatment in disposing of solids holding high percentage of chlorinate compounds such as PCBs. The torch used has got a power of 800 kW and waste held in bins are reduced in a liquid mixture and pumped in contact with plasma flame which destroys harmful molecules and produces neutral slag. Trials carried out with pentaclorophenol showed a DRE>99.999% and a VOC (volatile organic compounds) <2.6 mg/Nm3. The total cost of disposal is fixed around 450 ECU ton.

In 1986 Westinghouse developed a trailer for a mobile unit plasma plant disposing of liquid organic material such as PCBs. The plasma plant was based on a IMW non- transferred plasma torch, a reaction chamber and an analysis, control laboratory on line and an end of pipe effluents treatment. This plant demonstrated good results for the disposal of methanol, ethanol, methyl ethylketone, and carbon tetrachloride. The most interesting results arise from PBCs incineration infact, with a torch power supply of 850 kW, a destruction efficiency (DRE) beyond 99.99999% had been reached with emissions of HCI, particulate and NOx which were below the accepted Canadian regulatory agency guidelines. Furthermore dioxins and furans emissions were usually undetectable.

EPA' s Hazardous Waste Engineering Research Laboratory and the New York State department of environmental conservation established in 1982 a co-operative agreement for the construction of a mobile pilot scale plasma system for the destruction of hazardous waste such as PCBs. The system is basically composed by a plasma torch able to reach the typical temperature of 10000⁰C, a reactor where the reaction takes place, a scrubber system and a gas effluent system; emissions had been measured by a monitoring system. In 1985 trials for PCB destruction have been carried out by highlighting DRE efficiency beyond 99.9999% and a HCl formation rate below 4 kg/hr. Li the scrubber effluents and in the exhausted gases as well, an appreciable concentration of dioxins or furans has not been noticed.

Plasmarc plant is closed reactor vessel equipped with a transferred plasma torch and an oxygen-fuel lance. The oxygen-fuel is added to heat up the system and to keep the reactor on required temperature during treatment of low caloric material. Within Plasma reactor the amount of dust in the off-gas is normally low.

Westinghouse Environmental Services USA demonstrated a prototype unit of dc arc incinerator in 1987. Barton et al. has devised an apparatus in 1987 for pyrolytic destruction of toxic and hazardous waste. Electrical Industry Research Institute at Hungary developed a plasma reactor pilot plant in 1988, for the destruction of halogenated chemical industry wastes. Retech Incorporation of California and U.S. Department of Energy initiated a collaborative program to destroy a variety of waste using plasma arc technologies in 1989 and later in 1994 developed a rotating plasma furnace. Plascon designed in-flight plasma arc system to treat chlorinated organic compound. Destruction efficiencies of better than 99.99% were achieved for organic contaminants. All these systems mentioned here work at very high power. Donald A. Burgess has developed an apparatus for plasma disintegration of waste in which he employed array of nozzles to generate plasma plumes. S. L. Camacho developed a plasma pyrolysis and vitrification system in 1996 for the disposal of municipal waste.

The prior art plasma pyrolysis processes are predominantly carried out using air or nitrogen plasma torches. The electrodes are copper or thoriated tungsten which need to be changed after specified life of 100-1000 hours. Introducing of N₂ through electrodes requires uninterrupted nitrogen supply or nitrogen generator. Using air as plasmagen gas results in formation of dioxins and furans. These drawbacks have been overcome in the present invention. OBJECTS OF THE INVENTION

The primary object of the present invention is to propose a plasma pyrolysis device which is energy efficient and meets the emission norms.

Another object of the present invention is to propose a plasma pyrolysis device which eliminates the use of nitrogen or plasmagen gas in the process of pyrolysis.

Yet another object of the present invention is to propose a plasma pyrolysis device which is simple in construction and cost effective.

Other objects and advantages of the present invention will be clear from the ensuring description, claims, examples and drawings.

DESCRIPTION OF ACCOMPANYING DRAWINGS Fig. 1 gives schematic diagram for the plasma pyrolysis device.

Fig. 2 shows the arrangement of graphite electrodes of the plasma torch.

Fig.3 shows the automation flow diagram for electrode movement.

Fig. 4 illustrates the automation flow diagram of waste feeding system

Fig. 5 depicts the block diagram of secondary chamber

STATEMENT OF INVENTION

According to the present invention there is provided a plasma pyrolysis device for disposing waste comprising:

a metallic primary chamber,

a plurality of plasma torch comprising a plurality of electrodes mounted inside the said primary chamber, means for coxial rotation, and linear motion of the electrodes,

a feeder to feed waste material into the primary chamber,

a means to purge inert gas or steam in the feeder and to send the pyrolysed gases to secondary chamber,

a secondary chamber connected to the primary chamber,

means to provide air in secondary chamber and to transfer pyrolysed gases from primary chamber into the secondary chamber,

means to ignite pyrolysed gases in the secondary chamber,

a scrubber to neutralize the acids present in the burnt pyrolysed gases,

control circuits for automation of motion of electrodes, opening of feeder doors and equilibrium of gases in the primary chamber and feeder,

a power source to supply dc power to the electrodes.

According to the present invention there is also provided a process for disposing waste using plasma pyrolysis device as claimed in claim 1 comprising:

a) feeding waste through a feeder into a primary chamber;

b) initiating and maintaining the plasma torch to increase the temperature within the primary chamber to about 800-1000°C causing pyrolysis of the constituents of the waste to produce pyrolysed gases comprising CO, H₂, hydrocarbons, transferring said pyrolysed gases to the secondary chamber, c) burning the pyrolysed gases in the secondary, chamber thereby producing combustion products at temperature of about 1000-1200°C,

d) neutralizing the combustion products with diluted sodium hydroxide to get neutralized combustion products,

e) quenching the neutralized combustion products to about 40-70⁰C,

f) discharging the gases to atmosphere thereby disposing the waste.

DETAILED DESCRIPTION OF INVENTION WITH REFERENCE TO ACCOMPANYING DRAWINGS

Plasma pyrolysis system of present state of the art shown in figure 1, consists of primary chamber (1), hydraulic system (2), Igniter (3) secondary chamber (4), scrubber (5), water tank (6), power supply (7), induced draft fan (8) plasma torch (9), feeder (10), PLC automation arrangement (11).

Schematic of plasma torch and arc stabilization is shown in Figure 2, consists of anode (12) and cathode (13).

Schematic of automation arrangement to move electrode is shown in Fig 3. 415/220 V Δ/Y n Transformer (14), 3 ph Bridge Rectifier (15), OCV Detector (16), Isolation & Calibration Ckt (17), Forward and reverse mechanism (18), Anode electrode motor supply (19), 12 V motor (20\

Flow diagram of automation arrangement in feeding system is shown in Fig 4. Primary Chamber (Temp. >550°C) (21), Door Opening T_0n =6 sec (22), Proximity Switch (23), Purging T_0n - 120 sec (24), Fish mouth opening T_0n delay = 90 sec (25), Proximity switch (26), Time delay = 3.5 Min (27). Block diagram of secondary chamber is given in Fig.5. Multiple pipes used for burning the combustible gas (28), 3 inch hole for Air admission (29), Flame Igniter (30), multiple small apertures for air introduction (31), Cera-wool to reduce heat losses (32), MS outer pipe (33), Multi-pipe arrangement to improve residence time (34)

• The first step of the process is pre-heating of the primary chamber with external resistive heater or by plasma torch.

• In the second step plasma torch is energized and then waste material is introduced in the primary chamber, where the material is subjected to intense heating by plasma torch. The organic material breaks up into small molecules due to intense heating in an oxygen starved environment. The plasma torch is placed at one end of the primary chamber as shown in figure 1.

• These fragmented molecules enter in the secondary chamber where they are combusted in the excess of air. The induced draft fan creates a negative pressure into the primary chamber, drives the pyrolysed gases into secondary chamber. The induced draft fan also sucks in the required air for complete combustion.

• The gases after the combustion are very hot (~900°C) as well as contain some hydrochloric acid. These gases are sent to scrubber to remove hydrochloric acid.

• The scrubbed gases pass through a filter to further reduce soot content in the exhaust Finally, the exhaust gases (mainly CO₂, O₂, N₂ and H₂O) are released in the atmosphere through small chimney.

Plasma pyrolysis technology is state of the art technology for safe disposal of medical waste. It is environment friendly technology, which converts organic waste into commercially useful byproducts. Plasma, the state of matter formed by removing the bound electrons from the atoms, is an electrically conducting fluid consisting of charged and neutral particles. These charged particles have high kinetic energies. When the ionized species in the plasma recombine with the stripped electrons, significant amount of energy in the form of ultraviolet radiation is released. The particle kinetic energy takes the form of heat and can be used for decomposing chemicals, hi addition, the presence of charged and excited species renders the plasma environment highly reactive which catalyses homogeneous and heterogeneous chemical reactions.

The important feature of the present work is pyrolysis carried out in oxygen starved environment using specific graphite plasma torch. The present torch benefited the plasma pyrolysis through elimination of nitrogen and the problems associated with nitrogen or air plasma torches. The problems include replacement of electrodes by handling the contaminated torch particularly in the case of hospital waste, hi order to enhance the life of electrodes, the cooling and arc rotation by producing magnetic field in the vicinity of anode was essential. The cooling of anode and cathode was carrying substantial amount of heat thus reducing the efficiency of torch. The plasmagen gas was also extracting substantial amount of heat energy, therefore, it was difficult to increase the temperature of reaction zone at low power (20-25kW). With the use of graphite plasma torch it has become possible to enhance the temperature of reaction zone. At higher temperature (>1000°C), super thermal pyrolysis takes place which provide high solid to gas conversion efficiency. The use of nitrogen generator or gas cylinders has been completely eliminated, hi the absence of plasmagen gas (N₂ or air), the pyrolysis gas composition has changed and large quantity of combustible gases produced in the primary chamber. Further the pyrolysis is endothermic process and needs external input energy. Present pyrolysis systems around the world are in few hundred kW range, hi this invention we have optimized the process to operate at power levels of few tens of kW. Performance of each of the sub-systems was optimized to meet the emission norms.

La plasma pyrolysis the most likely compounds that form from carbonaceous matter are methane, carbon monoxide, hydrogen, carbon dioxide and water molecules. The intense and versatile heat generation capabilities of plasma pyrolysis technology enable it to dispose of all type of waste including biomedical waste and hazardous waste in a safe and reliable manner. Medical waste is pyrolysed into CO, H₂, and hydrocarbons when it comes in contact with the plasma arc. These gases are burned and produce high temperature of 1000-1200⁰C (around 1200°C). In the plasma pyrolysis process the hot gases are quenched from 500°C to 40-70⁰C to avoid recombination reactions of gaseous molecules that inhibit the formation of dioxins and furans. The gas analysis results reveal that toxic gases found after the combustion are well within the limit of Central Pollution Control Board's emission standards. It is shown in Table 1. Dioxins and furans

5. analysis results are shown in Table 2. The analysis was done at RRL Trivandrum.

TABLE 1: EMISSIONS - A COMPARISON WITH CPCB STANDARDS

0

As shown in Figure 1, Primary chamber (1) is constructed out of mild steal of suitable dimension . The inner wall has ceramic wool lining to prevent the dissipation of heat. The chamber has an arrangement to mount three graphite electrodes. In this chamber the pyrolytic destruction of medical waste takes place. The dimensions of the . primary5 chamber vary with the increase in capacity.

Feeder (10) has double door arrangement. The top lid (first door) opens only when the second door is closed. The feeder has asbestos lining in all the inner surfaces which prevents the heat losses and material does not stick during the feed cycle. The0 dimensions of the feeder vary with the change in capacity.

Arrangement has been made to purge steam in the feeder. Steam is introduced continuously in the feeder to replace the pyrolysed gases. The pyrolysed gases fill in the feeder at the time of material feeding in the primary .chamber. Another connection is5 made from feeder to secondary chamber for replacing the pyrolysed gases. Steam feeding is essential to prevent explosive reactions during the transfer of waste from feeder to primary chamber.

.. I l Graphite plasma torch (9) used in the present set up comprises of: a tubular anode (12), two rod shaped cathode (13), means for holding the anode and cathode in position, arrangement to rotate cathodes, arrangement for linear motion. of anode and cathode, means for initiating the arc. The electrodes are mounted at angle of 90° as shown in Figure 2. The electrodes are powered by indigenously designed and fabricated 200A and 125 V power supply. The plasma arc is produced between the three electrodes by short- circuiting them.

The power supply (7) is capable of delivering electrical power up to 25 kW. It has interlocks and is used to energize the plasma torch. The power supply has following protections: secondary flame disappearance, induced draft fan failure, pressure limit in the secondary and primary chamber, scrubber water temperature, failure of water circulation motor for scrubber, etc. Arc is initiated by short-circuiting anode and cathode and auxiliary anode. The pilot arc then transferred to the main anode.

Secondary chamber (4) is made up of two co-axial cylindrical, mild steel chambers. The inner cylinder has multiple holes to suck in air for combustion. It is connected to scrubber and induced draft fan. The outer cylinder is open from the top and lined outside by compressed glass wool. This arrangement is made to reduce heat losses. Li his chamber pyrolysed gases gets combusted to form carbon dioxide and water. The necessary condition for the secondary chamber as per the environment regulation is that the residence time of the gas should be nearly 1 sec and the temperature should be maintained approximately 1050⁰C for complete destruction of aromatic hydrocarbons. The pyrolysed gas from the primary chamber and excess air from the holes of cylindrical chamber is sucked in by induced draft fan and burn into the secondary chamber. A sparker mounted in the secondary chamber ignites he flame. A self sustained flame exists as long as the pyrolysis is taking place at an adequate rate in the primary chamber. Reduction in flame temperature is used as an indication for less pyrolytic reaction or reduction of material in primary chamber. A dilute alkali solution, preferably sodium hydroxide solution is sprayed into the chamber of the scrubber (5) by a pump. The direction of the spray is opposite to the gas flow. The gases coming out of the secondary chamber contain Hydrochloric acid due to the PVC present in the primary chamber. The alkali solution react with hydrochloric acid forming chloride and water. Thus it is necessary to continuously monitor the pH of the scrubbing solution.

The induced draft fan (8) sucks the gases from the primary chamber and provides a negative pressure into the system. It is also used in the present setup to provide necessary air for combustion in the secondary chamber. The capacity depends on the disposal capacity of the system.

The cathode (13) and anode (12) are automatically moved in linear direction with the help of PLC automation circuit (11). The cathodes are also rotated along the axis for uniform erosion, using another PLC circuit (H)₅ the opening of feeder doors and bringing the equilibrium of gaseous environment in primary chamber and feeder has been automized.

EXAMPLE The primary chamber is preheated to 750°C in the beginning by the plasma torch (it takes typical 50-60 minutes). The Medical waste was placed in the feeder and the top lid was closed. It was purged with steam for sufficient time. The fish mouth door was opened for feeding. The pyrolysis begins within couple of minutes. The igniter in the secondary chamber was switched to initiate combustion of pyrolysed gasses emitted from the primary chamber. This helps in maintaining a sable flame in the secondary chamber and in getting suitable temperature (1000 ± 50° C). Material in the primary chamber is continuously stirred to complete pyrolysis.

The chemical reactions taking place during pyrolysis are given below: C₆H₁₀O₅ + Heat O CH₄ + 2CO + 3H₂O + 3C — (1)

Cellulose

[-CH₂-CH₂ -]n + H₂O + Heat => XCH₄ + yH₂ + zCO — (2)

Polyethylene Experiments were also carried, out with contaminated medical waste. The emission norms were met by adjusting the plasma power and temperature of the order of 1000 ± 5O⁰C. The emissions from the system are found well within the limit of Central Pollution Control Board's Standards. We have added additional electrical heaters in the primary chamber to increase overall temperature of the primary chamber above 400°C preferably between 800-1000⁰C, to reduce formation of toxic compounds such as dioxin and furans. Additional heaters surrounding the secondary chamber provide sufficient temperature to combust pyrolysed gasses completely during the startup of the process.

The present device can be scaled to increase the capacity by increase in number of plasma torches, increase in primary chamber volume and shape. This will also calls for scale up in secondary chamber volume, scrubber capacity and induced draft fan capacity.

Claims

1. . A plasma pyrolysis device for disposing waste comprising:

a metallic primary chamber,

a plurality of plasma torch comprising a plurality of electrodes mounted inside the said primary chamber,

means for coxial rotation, and

linear motion of the electrodes,

a feeder to feed waste material into the primary chamber,

a means to purge pyrolysed gases in the feeder and to send the gases to secondary chamber,

a secondary chamber connected to the primary chamber,

means to ignite pyrolysed gases in the secondary chamber,

a scrubber to neutralize the acids present in the burnt pyrolysed gases,

a power supply to supply dc power to the electrodes.

2. The device as claimed in claim 1, wherein the primary chamber made of mild steel, is provided with a ceramic wool lining and has provision for mounting the electrodes.

3. The device as claimed in claim 1, wherein the control circuit is a PLC.

4. The device as claimed in claim 1 wherein the secondary chamber is made of two mild steel co-axial cylindrical chambers, the outer chamber being open from top and lined at its outside surface with compressed glass wool, the inner chamber having a plurality of holes to suck in air for combustion.

5. The device as claimed in claim 1 wherein the feeder has two doors, the first door opens when the second door is closed.

6. The device as claimed in claim 4 wherein the means to purge pyrolyzed gas in the feeder is a steam generator supplying steam to the feeder.

7. The device as claimed in claim I₅ wherein the means to provide air in secondary chamber and to transfer pyrolysed gasses from primary chamber into the secondary chamber is induced draft fan.

8. The device as claimed in claim 6, wherein the means to ignite pyrolyzed gases in secondary chamber is a sparker mounted in the secondary chamber.

9. The device as claimed in claim 3, wherein the electrodes are made of graphite and comprise an anode and two cathodes.

10. The device as claimed in claim 8, wherein the anode and cathode are tubular hi shape.

11. The device as claimed in claim 9, wherein the two cathodes are mounted axially with their respective tips facing each other and the anode is mounted with its axis at an angle of 90°C to the axis of cathodes and tip of the anode is spatially located on the mid line between the tips of the cathodes.

12. The device as claimed in claim 1, wherein the scrubber comprises a pump to spray dilute sodium hydroxide solution into secondary chamber opposite to direction of flow of the gases.

13. A process for disposing waste using plasma pyrolysis device as claimed in claim 1 comprising:'

a) feeding waste through a feeder into a primary chamber;

b) initiating and maintaining the plasma torch to increase the temperature within the primary chamber to about 800-1000⁰C causing pyrolysis of the constituents of the waste to produce pyrolysed gases comprising CO, H₂, hydrocarbons, transferring said pyrolysed gases to the secondary chamber,

c) burning the pyrolysed gases in the secondary chamber thereby producing combustion products at temperature of about 1000- 1200⁰C, ^"

d) neutralizing the combustion products with diluted alkali to get neutralized combustion products,

e) cooling the neutralized combustion products by quenching to about 70⁰C₅

f) discharging the gases to atmosphere thereby disposing the waste.