4. Destruction Processes
4.3 Novel Incinerators
- 4.3.1 Oxygen Incinerators
- 4.3.1.1 Pyro-Magnetics Mobile Hazardous Waste Processor (MWP-6000)
- 4.3.1.2 Chemical Plasma Process
- 4.3.2 Molten Salt Processes
- 4.3.2.1 Rockwell's Molten Salt Destruction Process
- 4.3.3 Fluid Bed Processes
- 4.3.3.1 Rockwell's Fluidized Bed Incinerator
- 4.3.3.2 Other Fluidized Bed Combustors
- 4.3.4 Diesel Processes
- 4.3.4.1 The D & D Group, Inc.
Novel incineration, a second category of destruction process by incineration, while still deriving its thermal energy from the oxidation of a fuel, has some special features that sets it apart from ordinary incinerators which burn fuel with air in a simple combustion zone. We have identified four types of novel incinerators:
oxygen incinerators; molten salt incinerators; fluid bed incinerators; and diesel processes.
Oxygen incinerators use pure oxygen or at least enriched air to oxidize the fuel. Higher temperatures are achieved and smaller volumes of products are produced for subsequent scrubbing. Molten beds achieve a similar effect and also provide a higher unit volume concentration of oxygen. Fluid beds make use of fluidized solids in the combustion zone to increase the heat transfer to the waste. Catalysts can also be supported on the fluidized solid. Finally the diesel process involves waste destruction during the combustion of fuel in a diesel engine.
4.3.1 Oxygen Incinerators
Incineration using oxygen instead of air as the fuel oxidizer has the advantages of
- higher temperatures than conventional incinerator; and
- reduced combustion product volume.
Burner design and materials of construction tend to create some problems which are being overcome. Pure oxygen requires special handling and the use of tempering air can lead to additional chemical consumption on scrubbing by virtue of nitrogen oxidation.
4.3.1.1 Pyro-Magnetics Mobile Hazardous Waste Processor (MWP-6000)
Head Office: Pyro-Magnetics Corporation
200 Essex Street
P.O. Box 288
Whitman, Massachusetts, 02382
Contact: D.M. Dyer
(617) 447-0448
The Pyro-Magnetics Mobile Hazardous Waste Process (MWP-6000) is an integrated waste processor which makes use of an oxygen incinerator as its central waste destruction unit. The oxygen incinerator accepts liquid wastes directly or processes off gases from a rotary kiln or a Special Melting Treatment (SMT) Unit. The SMT Unit appears to be the technology base for Pyro-Magnetics Corporation and they have used it to advantage in their integrated waste processor.
The MWP-6000 process configuration is shown in Figure 5. Solid wastes, depending on waste make-up are fed either to the rotary kiln unit or to the SMT Unit. Rotary kiln feed can be shredded and screw fed into the kiln or fed through a sludge injector. The kiln, when operated, burns fuel with air producing an operating temperature of 980°C. The combustion products are ducted to the Secondary/Liquid Combustor (Oxygen Incinerator). Ash is removed through as ash breach.
Solids fed to the SMT Unit are pyrolyzed and melted in an inductively heated molten iron bath operating at 1650°C. Siliceous materials are slagged off. The atmosphere in the SMT Unit is controlled to control the bath composition and the volume of product gases that are ducted to the Secondary/Liquid Combustor.
Liquids are injected directly into the Secondary/Liquid Combustor through two oxygen burners. Additional air is blown in to temper the combustor temperature to about 2200°C. If necessary, liquid wastes like PCBs can be blended with fuel oil to maintain heat content and operating temperature. The combustor is 0.8 m in diameter by 2.4 m long followed by a secondary chamber, 10.7 m, that gives a 2 second dwell time at 1260°C exit temperature.
The product gas scrubber is driven by an induced draft fan that keeps the whole system under a negative pressure. All breaches are interconnected so the processor runs at a negative pressure ensuring that no spurious gases are emitted. A caustic scrubber and quenching system is used to cleanse acids and trace organics from the flue gases.
The unit is designed to handle 2700 kg/h of solid waste. PCB liquids (50% in fuel oil) are designed to be fed up to 0.6 m3/h. Oxygen consumption of 3 kg/kg of PCB is only slightly in excess of stoichiometric requirements. Power requirements amount to 1000 kW when the SMT is utilized and only 100 kW for the liquid system.
In concept form the MWP 6000 can handle a variety of PCB waste types. The multiple feed systems for solids and liquids should provide enough flexibility to handle most PCB wastes. Destruction efficiencies of 99.999 943 were obtained during the March, 1982 test burn held in Tullahoma, Tenn. for the EPA. All the integrated units are mounted on 2.4 x 14 m mobile truck beds. In addition to the units described, a mobile lab and a chemical service trailer complete the MWP 6000 package.
As suggested above, it is believed Pyro-Magnetics main technological advantage is the SMT Unit and the oxygen incinerator, which are both unique. The wedding of this controlled atmosphere high temperature material processsor with a controlled atmosphere burner is a natural outgrowth. The rotary kiln unit is a useful adjunct to complete the waste handling package. The units are apparently being tested one by one. The Liquid Combustor was the subject of EPA approved tests at Arnolds Labs (University of Tennessee, Tullahoma, Tennessee) in March 1982. Test results were excellent.
The solid technology has not been totally tested on PCB wastes. The ability for such a system to successfully destroy solids in the form of shredded capacitors, etc. should be more closely examined as the original technology described here included a rotary kiln upstream of the SMT equipment whereas a more recent version of the system omits the rotary kiln. The system appears to have the capability of readily destroying liquid PCB wastes.
The cost per unit PCB destruction by this technology is estimated to be $5.00 US dollars per gallon of low grade waste $10.00 US dollars per gallon of medium grade waste and $15.00 US dollars per gallon of high grade waste. This cost includes the rental charged by contractor for equipment in addition to heavy fuel oil and electrical operating costs.
The technology also carries the stipulation that approximately 30 by 30 m of land be made available. Capital allowances were built in to compensate for additional effluent water treatment facilities such as a lagoon.
The equipment is readily available from the contractor on a cost per unit destroyed basis.
Public impacts would be minimal if the company plans are implemented. The MWP 6000 system is fundamentally a non-polluting process; effluents are inert solids and innocuous gases. The mobile aspects could satisfy public demands that wastes be destroyed where they are generated or exist. Worker impacts are those of a hazardous waste handling operation and are usually well controlled.
As indicated above, the MWP 6000 process has undergone testing according to US EPA rules. The procedure appears to be running smoothly, the oxygen combustor was tested in March 1982. High levels of destruction were achieved.
References: (M.M. Dillon Ltd.,1981, 1982, Pyro-Magnetics, 1981).
Figure 5 Mobile Hazardous Waste Processor (Pyro-Magnetics Corp.)
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