EP0354731A1 - Method and apparatus for plasma pyrolysis of liquid waste - Google Patents
Method and apparatus for plasma pyrolysis of liquid waste Download PDFInfo
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- EP0354731A1 EP0354731A1 EP89307930A EP89307930A EP0354731A1 EP 0354731 A1 EP0354731 A1 EP 0354731A1 EP 89307930 A EP89307930 A EP 89307930A EP 89307930 A EP89307930 A EP 89307930A EP 0354731 A1 EP0354731 A1 EP 0354731A1
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- Prior art keywords
- gases
- waste material
- water
- chamber
- scrubber
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
- C10B19/00—Heating of coke ovens by electrical means
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
- C10B53/00—Destructive distillation, specially adapted for particular solid raw materials or solid raw materials in special form
Definitions
- This invention relates to an apparatus and to a method for pyrolytically decomposing waste material, and in particular, it pertains to apparatus and method for disposing of toxic and hazardous materials by pyroplasmic decomposition.
- waste material is a growing problem due primarily to the fact that the volume of waste material is growing faster than existing disposal equipment and methods can handle it economically.
- Most attempts to dispose of waste materials by combustion have included furnaces or rotary kilns.
- apparatus and methods for waste destruction have included plasma pyrolysis, such as disclosed in the specification of U.S. Patent No. 4,644,877, by which waste materials are fed into a plasma arc burner where they are atomized, ionized, and subsequently discharged into a reaction chamber to be cooled and recombined into product gases and particulate matter.
- the method of this patent involves the use of a solvent that is miscible with the waste materials, such as methyl ethyl ketone with PCBS.
- a method for pyrolytically decomposing waste material includes the steps of producing a plasma by use of oxygen as the torch gas, atomizing waste material and a source of hydrogen and oxygen, then injecting the atomized waste material and source of hydrogen and water into the plasma, having a temperature in excess of 5000°C to form a mixture of produce gases and solid particulate, separating the gases and particulate mixture in a recombination chamber into separate phases of gases and solid particulate, transferring the solid particulate to separate compartment and subjecting the particulate to a partial vacuum to separate any carryover gases from the particulate which carryover gases are combined with the gases from the recombination chamber, transferring the gas from the recombination chamber to a scrubber and subjecting the gas to a water spray to eliminate any carryover solid particulate from the gases, and removing the scrubbed gases from the scrubber.
- the invention includes an apparatus for pyrolytically decomposing waste material
- a plasma torch productive of a plasma having an operating temperature of at least 5000°C to destroy a solution of a waste material to form a mixture of gases and solid particulate, said torch in co-operation with means for introducing the waste material in an atomized state, a recombination chamber adatped to receive and separate the mixture of gases and solid particulate, a separator to provide a partial vacuum to remove any carryover gases from the solid particulate, a transfer chamber to receive gases from the recombination chamber, a scrubber to clean the gases from the chamber by passing the gases through a water spray, and storage means for gases from the scrubber.
- the invention involves a method for the pyrolytic destruction of waste material including the steps of mixing the waste material, water, and/or methanol into a plasma arc having a temperature in excess of 5000°C to form a mixture of product gases and solid particulate, separating the gases and the particulate mixture in a recombination chamber into separate phases of gases and solid particulate; transferring the solid particulate to a separate compartment and subjecting the particulate to a partial vacuum to separate any carry-over gases from the particulate which carry-over gases are conbined with the gases from the recombination chamber; transferring the gas from the recombination chamber to a scrubber and subjecting the gas to a water spray to eliminate any carry-over solid particulate from the gases; and removing the scrubbed gases from the product gas stream.
- the apparatus for pyrolytically decomposing waste material comprises a plasma torch productive of an electric arc having an operating temperature of at least 5000°C for incinerating a solution of waste material to form a mixture of gases and solid particulate; a recombination chamber for receiving and separating the mixture of gases and solid particulate; a solid separator for providing a partial vacuum for removing any carry-over gases from the solid particulate; a transfer chamber for receiving gases from the recombination chamber; a scrubber for cleaning the gas from the transfer chamber by passing the gas through a water spray; and storage means for gases from the scrubber.
- the transfer chamber is a combustion chamber for the gases and the burned gases are directed to a draft means, such as a stack, for delivery of the burned gases into the atmosphere.
- An advantage of this method and apparatus is that there is at least a threefold increase in the feed throughput with a reduction of the flue gas volume compared with prior art procedures.
- This process removes the free carbon directly from the recombination chamber and flares the product gases in the combustion chamber.
- the high heating values of the product gases can bypass the combustion process for other use by closing the combustion air stream.
- a system for pyrolytically decomposing waste material of an existing, or prior art, method is shown diagrammatically in Figure 1. It comprises a plasma torch 5, a recombination chamber 7, a scrubber 9, a draft fan 11, an inertial trap 13, and a stack 15.
- the plasma torch by which the process of this invention is preferably performed includes a so-called arc heater which is similar in construction and operation to that disclosed in the specifications of U.S. Patent Nos. 3,765,870; 3,791,949; and 4,644,877 in which an electric arc extends between spaced electrodes with the generation of heat for the destruction of hazardous and toxic wastes.
- Waste material is fed into the torch 15 at inlet 17 together with a solvent at an inlet 19.
- a typical waste material is hazardous and toxic and contains a mixture of about 60% polychlorinated biphenyls (PCB) and of about 40% trichlorobenzene (TCB) which is derived from the operation of electric transformers and is commonly referred to as Askarel.
- Liquid waste material is introduced into the torch feed inlet 17 which together with a solvent comprising a mixture of methyl ethyl ketone (MEK) (50% by weight) and methanol (50%) is introduced (Fig. 1) to supply the hydrogen source to produce hydrogen chloride (HCl).
- MEK methyl ethyl ketone
- the mixture of the feed and solvent is processed at the high temperatures of operation of the plasma arc, typically ranging from 5000°C to 15,000°C, forming a mixture of product gases and solid particulate, which is directed into the recombination chamber 7, where in the presence of air introduced at inlet 21, produces a gaseous mixture consisting of H2O, H2, CO, CO2, N2, and HCl.
- the gaseous mixture is then directed into the scrubber 9 where a caustic solution of water (NaOH + H2O) sprays at 22 the gaseous mixture to eliminate solid particulates and to convert the HCl to NaCl mixed with water.
- the resulting blow-down water containing NaCl and carbon particulate is drained from the scrubber at outlet 23.
- the draft fan 11 transfers the gas from the scrubber 9 to the inertial trap 13 where it is subjected to additional water spray 25 to further eliminate carbon particulate. Blow-down water is drained at 26. From the inertial trap 13 the gas products are flared and vented into the atmosphere through the stack 27.
- the torch 15 (Fig. 2) provides a high temperature ionized, conductive gas that is created within the torch.
- the torch comprises a pair of cylindrical electrodes 28, 29 that are longitudinally spaced by a gap 31, into which a pressurized gas, such as air, is injected to blow an electric arc 33 into the interior of the torch.
- a pressurized gas such as air
- the upstream and downstream ends of the arc are located on the electrodes 28, 29.
- An annular nozzle 35 is located between the electrode 29 and a burner chamber 37 that is contained within a cylindrical insulation 39 through which the plasma plume 41 extends.
- the nozzle 35 includes a plurality of peripherally spaced, radially extending inlets 43.
- the prior art procedure involves the use of a mixture of a solvent of MEK and methanol with the waste material (Askarel) which mixture is introduced into the torch 15 through the inlets 43 of the nozzle 35.
- This prior art procedure processes about 0.1 gallons of PCB per minute. It is noted that the solvent mixture of MEK and methanol is miscible with the PCB and air is used as torch gas to create plasma.
- the solution is water, which is immiscible with non-polar type waste material, such as PCB and TCB.
- the water which is mixed with the waste material before introduction into the plasma torch. Pure oxygen (not air) is used as the torch gas. Water supplies hydrogen and oxygen that allows for an increased throughput of waste at a rate of up to twelve times that which is possible in the prior art system of Fig 1.
- the waste material or feed is the Askarel fluid.
- An alternate method to preliminarily mixing the feed and water is to inject the feed and water separately through an air atomizing nozzle into the torch.
- the amount of water mixed with waste is from about 30% to 200% by wt.
- the preferred amount of water is about 50% that of waste.
- the system for pyrolytically decomposing waste material of this invention preferably involves the use of the flow diagram of Figure 3.
- the apparatus includes a plasma torch 43, a recombination chamber 45, a combustion chamber 47, a scrubber 49, a draft fan 51, a stack 53, and a storage tank 55.
- the torch 43 ( Figure 4) provides a high temperature ionized, conductive gas which is created within the torch by the interaction of a gas with an electric or plasma arc 57 produced by the torch 43.
- the interaction within the torch 43 disassociates the gas into electrons and ions which cause the gas to become both thermally and electrically conductive.
- the conductive properties of the ionized gas in the arc region provides a means to transfer energy from the arc to the incoming process gas. This state is called a "plasma" and exists within the immediate confines of the arc in the torch and is superheated to an extremely high temperature having a typical range of from 5000°C to 15,000°C.
- the extremely high temperatures and the ultraviolet radiation associated with the ionized superheated gases provides sufficient bond breaking energy to destroy the hazardous and toxic wastes.
- This pyrolytic process is designed to destroy pumpable liquid/solid mixtures with the pyroplasma arc torch 43.
- the feed is injected through a plurality of air atomizing nozzles 59 (Fig. 4) into a manifold 61 where it is mixed with air before it encounters with the plasma plume 57 at temperatures in excess of 5000°C.
- the compounds in the feed are reformed into compounds which are more stable at reactor temperatures according to basic thermodynamic equilibrium principles.
- the water (without methanol) and feed are mixed homogeneously and introduced through a feed inlet 63 and air enters through an air inlet 65.
- the air atomizing nozzle 59 receives the waste feed that is mixed with water and/or methanol (up to 25%) and conducted through a static mixer 67, after which it is combined with compressed air at 69.
- the waste feed 63 is introduced into the manifold 61 which is secured to the recombination chamber 45 by a mounting flange 71.
- the manifold 61 is annular and is disposed between an outer housing 72 and a sleeve 73 which is comprised of refractory or silicon carbide coated graphite.
- the waste feed 63 is mixed with the air 65 and is emitted through outlets 75 to form a flame zone 77 with the plasma 79 which zone is the result of partial combustion of waste feed mixtures.
- the plasma 79 results from the combination of the electric arc 57 and torch gas 81 introduced through a gap 83 between cylindrical electrodes 85, 87 of the plasma torch 43. The resulting products are projected into the recombination chamber 45.
- the plasma system of this invention usually operates in a slightly reducing atmosphere and the resulting flue gases are mostly H2, CO, CO2, C, N2, H2O, and HCl. From a thermodynamic standpoint all of the chlorine forms HCl because of the high concentrations of H2 and low concentrations of 02. Therefore, there are no free or very low Cl2, O2, Cl, and OH radicals to form dioxins and furans.
- the product gases together with solid particulate, such as carbon enter the recombination chamber 45 which is an air filter such as a cyclone separator.
- the product gases and solid particulate entering the recombination chamber 45 have temperatures ranging from 1000° to 1500°C with a preferred temperature of 1200°C.
- the product gases exit through an outlet 89 and through a valve 91 to the combustion chamber 47.
- the dominant portion of the solid particulate 93 settles at the bottom of the chamber 45. There it accumulates until it is dumped.
- a high temperature dump valve 95 is provided in the bottom wall of the chamber 45 which valve comprises an elongated tube 97 in which a sliding stopper rod 99 is slidably mounted.
- a rod actuator 101 is provided for lowering the rod in order to open the tube 97 to enable the accumulated solid particulate 93 to drop through the tube and through a conduit 103 into a separator 105.
- the purpose of the separator is to remove any carry-over gases which are mixed with the particulate in the recombination chamber 45.
- the separator 105 is a cyclone separator into which the solid particulate enters from the conduit 103 with sufficient centrifugal force to throw the solid particulate out against the wall and drop into the lower portion of the separator tank.
- the separated gas exits from the separator 105 through a filter 107 and through a conduit 109 and a valve 111 from where it is conducted to the combustion chamber 47.
- a heat exchanger having a coolant inlet 113 and a coolant outlet 115 is provided to cool the accumulated gas-free solid particulate 93 .
- the solid particulate 93 is discharged from the separator 105 through a discharge valve.
- the purpose of the filter 107 is to filter out any remaining solid particulate that may be carried by the gas as it exits from the separator 105.
- the gases exit from the chamber through a filter 119 and into the outlet 89.
- the filter 119 like the filter 107 eliminates most of the particulate that may be carried by the gas into the outlet 89 and therefrom into the combustion chamber 47.
- the valve 91 is open and the valve 111 in the conduit 109 is closed. Inasmuch as the entire system is closed, the draft fan 51 sustains a partial vacuum through the several parts 45, 47, 49, and the interconnecting conduits therebetween. Accordingly, the gas moves from the recombination chamber 45 through the conduit 119 when valve 91 is opened.
- valve 91 is closed and valve 111 is opened, whereby the gas leaving the separator 105 is carried through the conduit 109 to the combustion chamber 47 in response to the partial vacuum created by the draft fan 51.
- the combustion chamber 47 has a primary function of burning the process gases (H2, CO, CO2, N2, H2O, HCl) which enter the chamber.
- process gases H2, CO, CO2, N2, H2O, HCl
- an air inlet 123 is provided to convert those gases to a gas mixture comprising CO2, H2O, N2, and HCl. Thereafter the gas mixture moves through the scrubber 49.
- a secondary function of the combustion chamber 47 is to act as a conduit for the product gases leaving the recombination chamber 45.
- the gas leaves the combustion chamber 47 through a conduit 125 into the scrubber where it is subjected to a water spray having an inlet 127 in order to eliminate any solid particulate which lingers in the gas.
- the resulting blow-down water 129 containing particulate accumulates in the lower portion of the scrubber 49 from where it is periodically drained through an outlet 131.
- a caustic solution is introduced into the water at 133 for the purpose of converting the HCl in the gas to a chloride compound.
- a preferred caustic solution is sodium hydroxide (NaOH) which reacts with the HCl in accordance with the following formula: NaOH + HCl NaCl + H2O.
- NaOH sodium hydroxide
- the resulting compound (NaCl) is drained from the scrubber with the blow-down water 129.
- the resulting gas mixture includes CO2, H2O, and N2 which move through a conduit 135 through the draft fan and through a conduit 137 to the stack 53 where it is dissipated into the atmosphere as a non-toxic gas and devoid of solid particulate.
- the combustion chamber 47 serves as a mere conduit for the product gases entering through the conduit 109, without being burned, the gases pass through the scrubber 49. Again the gases are subjected to the caustic solution to eliminate the HCl and exit from the scrubber via the conduit 135 as combustable fuel consisting of H2, CO, CO2, N2, and H2O. From the draft fan 51 the fuel is diverted by a valve 139 and through a conduit 141 to the storage tank 55 from which the fuel is withdrawn as required.
- the foregoing system includes a recycle means for reintroducing the water into the scrubber at 127.
- some of the blow-down water is eliminated at outlet 143 with the remaining blow-down water moving through a liquid solid separator 143 and a heat exchanger 145.
- the liquid solid separator 143 functions to eliminate any lingering solid particulate.
- the heat exchanger 145 functions to adjust the water to the desired temperature. Manifestly, any caustic solution remaining in the blow-down water in the scrubber tank is recirculated to the scrubber tank for the purpose intended.
- the system of this invention increases the feed throughput at least three gallons/minute and dramatically reduces the fuel gas volume over the system shown in Figure 1.
- the system of this invention also removes the free carbon directly from the recombination chamber and flares the product gas in the combustion chamber.
- the high heating values of the product gases can bypass the combustion process for other usage by closing the combustion air inlet 123.
- the principle of the solid removal system is initially based on high temperature dump valve 95 which is opened at designated intervals. When the dump valve is closed, valve 91 is opened while valve 111 is closed. Conversely, when the dump valve 95 is opened, valve 91 is closed and valve 111 is opened.
- the feed system of prior art injects the waste feed solution directly into the plasma arc to produce a lot of undesirable carbon especially when processing the chlorinated aromatic compounds.
- the feed system of the system of Fig. 4 alleviates the carbon formation by mixing air or oxygen before it contacts with the plasma plume.
- the recombination chamber 45 of this method removes most of the solid before entering the combustion chamber. Because the recombination chamber separates most of the particulate, a higher feed throughout the plasma torch is possible compared to the prior art. At the same time larger particles of particulate can be fed because it is readily eliminated through the solid separator.
- combustion chamber may be used as a conduit for the product gases from the recombustion chamber without burning the gases so that the gases may be used as a fuel instead of being flared and discarded through the stack.
- water consumption can be reduced by recycling the blowdown water from the scrubber.
Abstract
Description
- This invention relates to an apparatus and to a method for pyrolytically decomposing waste material, and in particular, it pertains to apparatus and method for disposing of toxic and hazardous materials by pyroplasmic decomposition.
- The disposal of waste material is a growing problem due primarily to the fact that the volume of waste material is growing faster than existing disposal equipment and methods can handle it economically. Most attempts to dispose of waste materials by combustion have included furnaces or rotary kilns. More recently, apparatus and methods for waste destruction have included plasma pyrolysis, such as disclosed in the specification of U.S. Patent No. 4,644,877, by which waste materials are fed into a plasma arc burner where they are atomized, ionized, and subsequently discharged into a reaction chamber to be cooled and recombined into product gases and particulate matter. The method of this patent involves the use of a solvent that is miscible with the waste materials, such as methyl ethyl ketone with PCBS.
- While the disposal of waste materials with systems of the type described have been satisfactory, it is an object to increase the feed throughput and reduce the formation of carbon particulate without the use of expensive solvents such as methyl ethyl ketone (MEK).
- According to the present invention, a method for pyrolytically decomposing waste material includes the steps of producing a plasma by use of oxygen as the torch gas, atomizing waste material and a source of hydrogen and oxygen, then injecting the atomized waste material and source of hydrogen and water into the plasma, having a temperature in excess of 5000°C to form a mixture of produce gases and solid particulate, separating the gases and particulate mixture in a recombination chamber into separate phases of gases and solid particulate, transferring the solid particulate to separate compartment and subjecting the particulate to a partial vacuum to separate any carryover gases from the particulate which carryover gases are combined with the gases from the recombination chamber, transferring the gas from the recombination chamber to a scrubber and subjecting the gas to a water spray to eliminate any carryover solid particulate from the gases, and removing the scrubbed gases from the scrubber.
- Furthermore, the invention includes an apparatus for pyrolytically decomposing waste material comprising a plasma torch productive of a plasma having an operating temperature of at least 5000°C to destroy a solution of a waste material to form a mixture of gases and solid particulate, said torch in co-operation with means for introducing the waste material in an atomized state, a recombination chamber adatped to receive and separate the mixture of gases and solid particulate, a separator to provide a partial vacuum to remove any carryover gases from the solid particulate, a transfer chamber to receive gases from the recombination chamber, a scrubber to clean the gases from the chamber by passing the gases through a water spray, and storage means for gases from the scrubber.
- Advantageously the invention involves a method for the pyrolytic destruction of waste material including the steps of mixing the waste material, water, and/or methanol into a plasma arc having a temperature in excess of 5000°C to form a mixture of product gases and solid particulate, separating the gases and the particulate mixture in a recombination chamber into separate phases of gases and solid particulate; transferring the solid particulate to a separate compartment and subjecting the particulate to a partial vacuum to separate any carry-over gases from the particulate which carry-over gases are conbined with the gases from the recombination chamber; transferring the gas from the recombination chamber to a scrubber and subjecting the gas to a water spray to eliminate any carry-over solid particulate from the gases; and removing the scrubbed gases from the product gas stream.
- Conveniently, the apparatus for pyrolytically decomposing waste material comprises a plasma torch productive of an electric arc having an operating temperature of at least 5000°C for incinerating a solution of waste material to form a mixture of gases and solid particulate; a recombination chamber for receiving and separating the mixture of gases and solid particulate; a solid separator for providing a partial vacuum for removing any carry-over gases from the solid particulate; a transfer chamber for receiving gases from the recombination chamber; a scrubber for cleaning the gas from the transfer chamber by passing the gas through a water spray; and storage means for gases from the scrubber. In the alternative the transfer chamber is a combustion chamber for the gases and the burned gases are directed to a draft means, such as a stack, for delivery of the burned gases into the atmosphere.
- An advantage of this method and apparatus is that there is at least a threefold increase in the feed throughput with a reduction of the flue gas volume compared with prior art procedures. This process removes the free carbon directly from the recombination chamber and flares the product gases in the combustion chamber. Alternatively, as in the first design the high heating values of the product gases can bypass the combustion process for other use by closing the combustion air stream.
- The invention will now be described, by way of example, with reference to the accompanying drawings in which:
- Figure 1 is a flow diagram of a pyroplasma unit of prior art structure.
- Figure 2 is a sectional view through a pyroplasma unit of prior art construction.
- Figure 3 is a flow diagram of the pyroplasma system of this invention.
- Figure 4 is a sectional view through a pyroplasma unit of this invention.
- A system for pyrolytically decomposing waste material of an existing, or prior art, method is shown diagrammatically in Figure 1. It comprises a
plasma torch 5, a recombination chamber 7, ascrubber 9, adraft fan 11, aninertial trap 13, and astack 15. - The application of plasma technology to high temperature processes in the organic and inorganic material areas is recognized. The plasma torch by which the process of this invention is preferably performed includes a so-called arc heater which is similar in construction and operation to that disclosed in the specifications of U.S. Patent Nos. 3,765,870; 3,791,949; and 4,644,877 in which an electric arc extends between spaced electrodes with the generation of heat for the destruction of hazardous and toxic wastes.
- Waste material is fed into the
torch 15 atinlet 17 together with a solvent at aninlet 19. A typical waste material is hazardous and toxic and contains a mixture of about 60% polychlorinated biphenyls (PCB) and of about 40% trichlorobenzene (TCB) which is derived from the operation of electric transformers and is commonly referred to as Askarel. Liquid waste material is introduced into thetorch feed inlet 17 which together with a solvent comprising a mixture of methyl ethyl ketone (MEK) (50% by weight) and methanol (50%) is introduced (Fig. 1) to supply the hydrogen source to produce hydrogen chloride (HCl). The solvent is miscible with Askarel. The mixture of the feed and solvent is processed at the high temperatures of operation of the plasma arc, typically ranging from 5000°C to 15,000°C, forming a mixture of product gases and solid particulate, which is directed into the recombination chamber 7, where in the presence of air introduced atinlet 21, produces a gaseous mixture consisting of H₂O, H₂, CO, CO₂, N₂, and HCl. The gaseous mixture is then directed into thescrubber 9 where a caustic solution of water (NaOH + H₂O) sprays at 22 the gaseous mixture to eliminate solid particulates and to convert the HCl to NaCl mixed with water. The resulting blow-down water containing NaCl and carbon particulate is drained from the scrubber atoutlet 23. - The
draft fan 11 transfers the gas from thescrubber 9 to theinertial trap 13 where it is subjected toadditional water spray 25 to further eliminate carbon particulate. Blow-down water is drained at 26. From theinertial trap 13 the gas products are flared and vented into the atmosphere through thestack 27. The foregoing comprises the prior art procedure as shown in the flow diagram of Figure 1. - The torch 15 (Fig. 2) provides a high temperature ionized, conductive gas that is created within the torch. As shown in the above mentioned patent specification regarding "arc heaters", the torch comprises a pair of
cylindrical electrodes gap 31, into which a pressurized gas, such as air, is injected to blow anelectric arc 33 into the interior of the torch. The upstream and downstream ends of the arc are located on theelectrodes annular nozzle 35 is located between theelectrode 29 and aburner chamber 37 that is contained within acylindrical insulation 39 through which theplasma plume 41 extends. Thenozzle 35 includes a plurality of peripherally spaced, radially extendinginlets 43. - Primarily, the prior art procedure involves the use of a mixture of a solvent of MEK and methanol with the waste material (Askarel) which mixture is introduced into the
torch 15 through theinlets 43 of thenozzle 35. This prior art procedure processes about 0.1 gallons of PCB per minute. It is noted that the solvent mixture of MEK and methanol is miscible with the PCB and air is used as torch gas to create plasma. - In accordance with this invention the solution is water, which is immiscible with non-polar type waste material, such as PCB and TCB. The water which is mixed with the waste material before introduction into the plasma torch. Pure oxygen (not air) is used as the torch gas. Water supplies hydrogen and oxygen that allows for an increased throughput of waste at a rate of up to twelve times that which is possible in the prior art system of Fig 1. The waste material or feed is the Askarel fluid. An alternate method to preliminarily mixing the feed and water is to inject the feed and water separately through an air atomizing nozzle into the torch.
- The use of the water instead of the MEK-methanol solvent is conducive to higher output of up to one gallon per minute when used in the
torch 15 of the prior art Fig. 2. - As was set forth above water provide satisfactory results for the success of this invention. The amount of water mixed with waste is from about 30% to 200% by wt. The preferred amount of water is about 50% that of waste.
- The system for pyrolytically decomposing waste material of this invention preferably involves the use of the flow diagram of Figure 3. The apparatus includes a
plasma torch 43, arecombination chamber 45, acombustion chamber 47, ascrubber 49, adraft fan 51, astack 53, and astorage tank 55. The torch 43 (Figure 4) provides a high temperature ionized, conductive gas which is created within the torch by the interaction of a gas with an electric orplasma arc 57 produced by thetorch 43. The interaction within thetorch 43 disassociates the gas into electrons and ions which cause the gas to become both thermally and electrically conductive. The conductive properties of the ionized gas in the arc region provides a means to transfer energy from the arc to the incoming process gas. This state is called a "plasma" and exists within the immediate confines of the arc in the torch and is superheated to an extremely high temperature having a typical range of from 5000°C to 15,000°C. - The extremely high temperatures and the ultraviolet radiation associated with the ionized superheated gases provides sufficient bond breaking energy to destroy the hazardous and toxic wastes. This pyrolytic process is designed to destroy pumpable liquid/solid mixtures with the
pyroplasma arc torch 43. - To expedite movement of the material through the system, the feed is injected through a plurality of air atomizing nozzles 59 (Fig. 4) into a
manifold 61 where it is mixed with air before it encounters with theplasma plume 57 at temperatures in excess of 5000°C. The compounds in the feed are reformed into compounds which are more stable at reactor temperatures according to basic thermodynamic equilibrium principles. According to the preferred embodiment of this invention the water (without methanol) and feed are mixed homogeneously and introduced through afeed inlet 63 and air enters through anair inlet 65. - Alternatively, the air atomizing nozzle 59 (Fig. 4) receives the waste feed that is mixed with water and/or methanol (up to 25%) and conducted through a
static mixer 67, after which it is combined with compressed air at 69. From thenozzle 59 thewaste feed 63 is introduced into themanifold 61 which is secured to therecombination chamber 45 by amounting flange 71. Themanifold 61 is annular and is disposed between anouter housing 72 and asleeve 73 which is comprised of refractory or silicon carbide coated graphite. Within the manifold 61 thewaste feed 63 is mixed with theair 65 and is emitted through outlets 75 to form aflame zone 77 with the plasma 79 which zone is the result of partial combustion of waste feed mixtures. As described in the above-mentioned U.S. patents the plasma 79 results from the combination of theelectric arc 57 andtorch gas 81 introduced through a gap 83 betweencylindrical electrodes 85, 87 of theplasma torch 43. The resulting products are projected into therecombination chamber 45. - These products can be controlled by choosing different torch gases, such as pure oxygen, by adding solvent to adjust the elements input to the system, or by choosing the reactor temperature to optimize, or minimize, the formation of certain compounds. In the combustion process, the chlorine will compete with oxygen to form HCL over H₂O. According to the thermo-equilibrium formula, some of the initial chlorine will become Cl₂, while the rest of the chlorine converts to HCl. With this relatively high concentration of chlorine and oxygen, coupled with the locally high carbon loading, the formations of chlorinated dioxins and furans are highly possible in a conventional incinerator. It is known that flyash and flue gases from municipal incinerators contain dioxins and furans.
- The plasma system of this invention usually operates in a slightly reducing atmosphere and the resulting flue gases are mostly H₂, CO, CO₂, C, N₂, H₂O, and HCl. From a thermodynamic standpoint all of the chlorine forms HCl because of the high concentrations of H₂ and low concentrations of 02. Therefore, there are no free or very low Cl₂, O₂, Cl, and OH radicals to form dioxins and furans.
- From the
torch 43 the product gases together with solid particulate, such as carbon, enter therecombination chamber 45 which is an air filter such as a cyclone separator. The product gases and solid particulate entering therecombination chamber 45 have temperatures ranging from 1000° to 1500°C with a preferred temperature of 1200°C. In thechamber 45 the product gases exit through anoutlet 89 and through avalve 91 to thecombustion chamber 47. The dominant portion of thesolid particulate 93 settles at the bottom of thechamber 45. There it accumulates until it is dumped. - For that purpose a high
temperature dump valve 95 is provided in the bottom wall of thechamber 45 which valve comprises anelongated tube 97 in which a slidingstopper rod 99 is slidably mounted. Arod actuator 101 is provided for lowering the rod in order to open thetube 97 to enable the accumulated solid particulate 93 to drop through the tube and through aconduit 103 into aseparator 105. The purpose of the separator is to remove any carry-over gases which are mixed with the particulate in therecombination chamber 45. For that purpose theseparator 105 is a cyclone separator into which the solid particulate enters from theconduit 103 with sufficient centrifugal force to throw the solid particulate out against the wall and drop into the lower portion of the separator tank. The separated gas exits from theseparator 105 through afilter 107 and through aconduit 109 and avalve 111 from where it is conducted to thecombustion chamber 47. To cool the accumulated gas-free solid particulate 93 a heat exchanger having acoolant inlet 113 and acoolant outlet 115 is provided. Ultimately, thesolid particulate 93 is discharged from theseparator 105 through a discharge valve. The purpose of thefilter 107 is to filter out any remaining solid particulate that may be carried by the gas as it exits from theseparator 105. - During normal operation of the system with product gases from the torch entering the
recombination chamber 45 under centrifugal force and with the particulate 93 accumulating in the lower portion of the chamber, the gases exit from the chamber through afilter 119 and into theoutlet 89. Manifestly, thefilter 119 like thefilter 107 eliminates most of the particulate that may be carried by the gas into theoutlet 89 and therefrom into thecombustion chamber 47. During that operation thevalve 91 is open and thevalve 111 in theconduit 109 is closed. Inasmuch as the entire system is closed, thedraft fan 51 sustains a partial vacuum through theseveral parts recombination chamber 45 through theconduit 119 whenvalve 91 is opened. - Conversely, when the
dump valve 95 is opened,valve 91 is closed andvalve 111 is opened, whereby the gas leaving theseparator 105 is carried through theconduit 109 to thecombustion chamber 47 in response to the partial vacuum created by thedraft fan 51. - The
combustion chamber 47 has a primary function of burning the process gases (H₂, CO, CO₂, N₂, H₂O, HCl) which enter the chamber. For that purpose anair inlet 123 is provided to convert those gases to a gas mixture comprising CO₂, H₂O, N₂, and HCl. Thereafter the gas mixture moves through thescrubber 49. - A secondary function of the
combustion chamber 47 is to act as a conduit for the product gases leaving therecombination chamber 45. The gas leaves thecombustion chamber 47 through aconduit 125 into the scrubber where it is subjected to a water spray having aninlet 127 in order to eliminate any solid particulate which lingers in the gas. The resulting blow-downwater 129 containing particulate accumulates in the lower portion of thescrubber 49 from where it is periodically drained through anoutlet 131. - In addition to the water entering through the
inlet 127, a caustic solution is introduced into the water at 133 for the purpose of converting the HCl in the gas to a chloride compound. A preferred caustic solution is sodium hydroxide (NaOH) which reacts with the HCl in accordance with the following formula:
NaOH + HCl NaCl + H₂O.
The resulting compound (NaCl) is drained from the scrubber with the blow-downwater 129. The resulting gas mixture includes CO₂, H₂O, and N₂ which move through aconduit 135 through the draft fan and through aconduit 137 to thestack 53 where it is dissipated into the atmosphere as a non-toxic gas and devoid of solid particulate. - In the alternative, where the
combustion chamber 47 serves as a mere conduit for the product gases entering through theconduit 109, without being burned, the gases pass through thescrubber 49. Again the gases are subjected to the caustic solution to eliminate the HCl and exit from the scrubber via theconduit 135 as combustable fuel consisting of H₂, CO, CO₂, N₂, and H₂O. From thedraft fan 51 the fuel is diverted by avalve 139 and through aconduit 141 to thestorage tank 55 from which the fuel is withdrawn as required. - In order to conserve water the foregoing system includes a recycle means for reintroducing the water into the scrubber at 127. For that purpose some of the blow-down water is eliminated at
outlet 143 with the remaining blow-down water moving through a liquidsolid separator 143 and aheat exchanger 145. The liquidsolid separator 143 functions to eliminate any lingering solid particulate. Theheat exchanger 145 functions to adjust the water to the desired temperature. Manifestly, any caustic solution remaining in the blow-down water in the scrubber tank is recirculated to the scrubber tank for the purpose intended. - The system of this invention, as shown in Figure 3 increases the feed throughput at least three gallons/minute and dramatically reduces the fuel gas volume over the system shown in Figure 1. The system of this invention also removes the free carbon directly from the recombination chamber and flares the product gas in the combustion chamber. The high heating values of the product gases can bypass the combustion process for other usage by closing the
combustion air inlet 123. The principle of the solid removal system is initially based on hightemperature dump valve 95 which is opened at designated intervals. When the dump valve is closed,valve 91 is opened whilevalve 111 is closed. Conversely, when thedump valve 95 is opened,valve 91 is closed andvalve 111 is opened. In this manner the free carbon (solid particulate) is sucked out of therecombination chamber 45 into thesolid separator 105. The quenched free carbons then are removed bylock valve 117. The scrubber effluent is recycled back without the carbon overloading the problem existent in the system of Figure 1. - The primary differences between the system of this invention (Figure 4) and that of the prior art (Figure 1) is that in accordance with this invention water or methanol is used to mix with the feed or waste material to supply hydrogen and oxygen couples with the modified new feed system as shown in Fig. 4 which enables the increase of the throughput of waste approximately 10 times faster than that of the prior art. Moreover, water and methanol is a cheaper solvent than the methyl ethyl ketone/methanol solvent used in the prior art system. Additionally, the method of this invention employs the use of an air atomization nozzle to spray the feed into the plasma stream which improves on the single feed ring of the prior art structure.
- The feed system of prior art (Fig. 1) injects the waste feed solution directly into the plasma arc to produce a lot of undesirable carbon especially when processing the chlorinated aromatic compounds. The feed system of the system of Fig. 4 alleviates the carbon formation by mixing air or oxygen before it contacts with the plasma plume.
- Further, the
recombination chamber 45 of this method removes most of the solid before entering the combustion chamber. Because the recombination chamber separates most of the particulate, a higher feed throughout the plasma torch is possible compared to the prior art. At the same time larger particles of particulate can be fed because it is readily eliminated through the solid separator. - Furthermore, the combustion chamber may be used as a conduit for the product gases from the recombustion chamber without burning the gases so that the gases may be used as a fuel instead of being flared and discarded through the stack.
- Additionally, water consumption can be reduced by recycling the blowdown water from the scrubber.
- Finally, alternate torch gases, such as oxygen, may be employed instead of air to increase the throughput and to reduce the formation of cyanide (HCN) which results from nitrogen in the air. Thus, the problem of the formation of cyanide in the prior art system is virtually eliminated.
Claims (18)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US22988488A | 1988-08-10 | 1988-08-10 | |
US229884 | 1988-08-10 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0354731A1 true EP0354731A1 (en) | 1990-02-14 |
EP0354731B1 EP0354731B1 (en) | 1992-05-20 |
Family
ID=22863053
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19890307930 Expired EP0354731B1 (en) | 1988-08-10 | 1989-08-03 | Method and apparatus for plasma pyrolysis of liquid waste |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0354731B1 (en) |
JP (1) | JP2756505B2 (en) |
CA (1) | CA1324823C (en) |
DE (1) | DE68901592D1 (en) |
Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1991013532A1 (en) * | 1990-02-26 | 1991-09-05 | Maschinen- Und Anlagenbau Grimma Gmbh | Plasmatron with steam as the plasma gas and process for stable operation of the plasmatron |
US5206879A (en) * | 1990-08-03 | 1993-04-27 | Tioxide Group Services Limited | Destruction process |
WO1993017759A1 (en) * | 1992-03-04 | 1993-09-16 | Commonwealth Scientific And Industrial Research Organisation | Material processing |
DE4231771A1 (en) * | 1992-09-23 | 1994-03-24 | Bayer Ag | Process for electricity generation from plastic waste |
AU669158B2 (en) * | 1992-03-04 | 1996-05-30 | Srl Plasma Pty Ltd | Material processing |
WO1996041505A1 (en) * | 1995-06-07 | 1996-12-19 | Physical Sciences, Inc. | Microwave-driven plasma spraying apparatus and method for spraying |
WO1997022556A1 (en) * | 1995-12-20 | 1997-06-26 | Alcan International Limited | Thermal plasma reactor and wastewater treatment method |
GB2490175A (en) * | 2011-04-21 | 2012-10-24 | Tetronics Ltd | Treatment of waste |
CN109737430A (en) * | 2019-01-03 | 2019-05-10 | 鲁西化工集团股份有限公司硅化工分公司 | A kind of hazardous waste processing system and method |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
NZ254978A (en) * | 1992-09-07 | 1997-02-24 | Friends Of Freesia Co Ltd | Nested frustoconical hopper liners |
FR2866414B1 (en) * | 2004-02-18 | 2006-03-17 | Commissariat Energie Atomique | DEVICE AND METHOD FOR DESTRUCTION OF LIQUID, PULVERULENT OR GASEOUS WASTE BY INDUCTIVE PLASMA |
JP4827520B2 (en) * | 2005-12-21 | 2011-11-30 | 出光興産株式会社 | Resin pellet storage device and cleaning method thereof |
JP2007296415A (en) * | 2006-03-14 | 2007-11-15 | Nippon Steel Corp | Treatment method of polybiphenyl chloride pollutant and treatment system therefor |
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US3828162A (en) * | 1964-10-01 | 1974-08-06 | Ppg Industries Inc | Method for heating corrosive gases with arc heater |
WO1982000509A1 (en) * | 1980-07-25 | 1982-02-18 | I Faeldt | A method and an apparatus for thermal decomposition of stable compounds |
GB2113815A (en) * | 1982-01-18 | 1983-08-10 | Skf Steel Eng Ab | Method and plant for conversion of waste material to stable final products |
US4644877A (en) * | 1984-01-23 | 1987-02-24 | Pyroplasma International N.V. | Plasma pyrolysis waste destruction |
-
1989
- 1989-08-01 CA CA 607224 patent/CA1324823C/en not_active Expired - Lifetime
- 1989-08-03 EP EP19890307930 patent/EP0354731B1/en not_active Expired
- 1989-08-03 DE DE8989307930T patent/DE68901592D1/en not_active Expired - Lifetime
- 1989-08-08 JP JP1206586A patent/JP2756505B2/en not_active Expired - Lifetime
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
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US3828162A (en) * | 1964-10-01 | 1974-08-06 | Ppg Industries Inc | Method for heating corrosive gases with arc heater |
WO1982000509A1 (en) * | 1980-07-25 | 1982-02-18 | I Faeldt | A method and an apparatus for thermal decomposition of stable compounds |
GB2113815A (en) * | 1982-01-18 | 1983-08-10 | Skf Steel Eng Ab | Method and plant for conversion of waste material to stable final products |
US4644877A (en) * | 1984-01-23 | 1987-02-24 | Pyroplasma International N.V. | Plasma pyrolysis waste destruction |
Cited By (14)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1991013532A1 (en) * | 1990-02-26 | 1991-09-05 | Maschinen- Und Anlagenbau Grimma Gmbh | Plasmatron with steam as the plasma gas and process for stable operation of the plasmatron |
US5498826A (en) * | 1990-02-26 | 1996-03-12 | Maschinen- Und Anlagenbau Grimma Gmbh (Mag) | Plasmatron with steam as the plasma gas and process for stable operation of the plasmatron |
US5206879A (en) * | 1990-08-03 | 1993-04-27 | Tioxide Group Services Limited | Destruction process |
WO1993017759A1 (en) * | 1992-03-04 | 1993-09-16 | Commonwealth Scientific And Industrial Research Organisation | Material processing |
AU669158B2 (en) * | 1992-03-04 | 1996-05-30 | Srl Plasma Pty Ltd | Material processing |
DE4231771A1 (en) * | 1992-09-23 | 1994-03-24 | Bayer Ag | Process for electricity generation from plastic waste |
WO1996041505A1 (en) * | 1995-06-07 | 1996-12-19 | Physical Sciences, Inc. | Microwave-driven plasma spraying apparatus and method for spraying |
US5793013A (en) * | 1995-06-07 | 1998-08-11 | Physical Sciences, Inc. | Microwave-driven plasma spraying apparatus and method for spraying |
US5973289A (en) * | 1995-06-07 | 1999-10-26 | Physical Sciences, Inc. | Microwave-driven plasma spraying apparatus and method for spraying |
WO1997022556A1 (en) * | 1995-12-20 | 1997-06-26 | Alcan International Limited | Thermal plasma reactor and wastewater treatment method |
US6187206B1 (en) | 1995-12-20 | 2001-02-13 | Alcan International | Thermal plasma reactor and wastewater treatment method |
GB2490175A (en) * | 2011-04-21 | 2012-10-24 | Tetronics Ltd | Treatment of waste |
US9744575B2 (en) | 2011-04-21 | 2017-08-29 | Tectronics (International) Limited | Treatment of waste |
CN109737430A (en) * | 2019-01-03 | 2019-05-10 | 鲁西化工集团股份有限公司硅化工分公司 | A kind of hazardous waste processing system and method |
Also Published As
Publication number | Publication date |
---|---|
EP0354731B1 (en) | 1992-05-20 |
JP2756505B2 (en) | 1998-05-25 |
CA1324823C (en) | 1993-11-30 |
JPH0283079A (en) | 1990-03-23 |
DE68901592D1 (en) | 1992-06-25 |
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