Furnaces – Refuse incinerator – Rotary drum
Patent
1988-05-20
1990-01-02
Favors, Edward G.
Furnaces
Refuse incinerator
Rotary drum
110226, 110238, 110346, 432106, 432111, A47D 3600, A47D 3624
Patent
active
048905631
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention relates to a method of, and apparatus for, the treatment of waste. In particular, the apparatus preferably includes a rotary kiln.
(2) Prior Art
The disposal of urban solid waste and/or liquid wastes is a major problem facing modern man. Waste materials generally have a negative economic value and many toxic wastes are extremely difficult to neutralize or destroy.
Examples of waste treatment methods are disclosed in U.S. Pat. Nos. 1,859,159 (Greenwalt); 3,249,551 (Bixley); 3,383,228 (Rekate et al); 3,957,528 (Ott et al) and 4,112,033 (Linge).
SUMMARY OF THE PRESENT INVENTION
It is an object of the present invention to provide a method for the treatment of waste materials.
It is a preferred object to provide a method where the end product can be used as an aggregate, where the aggregate has a positive economic value e.g. for concrete production, road making or as porous fill.
It is a further preferred object to provide a rotary kiln suitable for the method.
Other preferred objects will become apparent from the following description.
In one aspect the present invention resides in a method for the treatment of waste materials including the steps of: off at least portion of the volatile gases in the waste; the excess oxygen causes the remaining volatile gases and at least a portion of the fixed carbon in the waste to be oxidized; and vitrify the silicates present in the pellets to form a solid aggregate.
The binding material will be selected on the basis that, when fired, it will form a hard inert ceramic material and may include clay, shale or similar material with suitable ceramic properties.
Preferably the pellets are passed through a dryer before they are fed to the furnace or kiln, the pellets preferably being dried by a counter-current flow of hot gas from at least one of the zones of the furnace or kiln.
Preferably the aggregate is cooled in a cooler by a flow of air, the air heated in the cooler preferably being fed to the dryer to dry the pellets.
The exhaust gas from the dryer is preferably split into two streams, one being fed to an afterburner and gas cleaning system, the second to the oxidation and/or vitrification zones of the furnace or kiln.
Preferably the pellets are heated to approximately 650.degree. C. in the pyrolysis zone by the controlled burning of some of the volatiles driven off from the waste and by hot gases transferred from the oxidation zone, the resulting volatile-rich gas stream being used to fuel gas in the oxidation and/or vitrification zones. Some of the fuel gas may be supplied to the afterburner.
Preferably the oxidation of the pellets, to burn off the remaining volatiles and the fixed carbon solids, occurs in the oxidation zone at or below 1000.degree. C., the oxidation and the combustion of some of the fuel gas from the pyrolysis zone providing the heat in the oxidation zone. A portion of the fixed carbon may be left in the pellets to promote bloating, which reduces the specific gravity (S.G.) of the final aggregate.
A portion of the exhaust air from the dryer may be fed to the oxidation zone by a pipe passing through the vitrification zone to supply oxygen to the oxidation zone.
Preferably the vitrification of the silicates occurs at 1200.degree. C..+-.200.degree. C. in the vitrification zone, the heat in the zone being generated by the the burning of fuel gas from the pyrolysis zone and by air from the dryer.
While it is preferred that the solids and gases in the kiln flow in counter-current direction, the gas flow in the oxidation and vitrification zones may be concurrent with the solids flow, where the exhaust gas from the dryer is fed to the oxidation zone. The hot gas is then fed to the vitrification zone and burn with some of the fuel gas from the pyrolysis zone to vitrify the solids. The gas from the vitrification zone is separated into two streams, one being directed to the pyrolysis zone to provide heat and oxygen for combustion in that zone, the other stream being directed to the gas clea
REFERENCES:
patent: 1895159 (1933-01-01), Greenawalt
patent: 3249551 (1966-05-01), Bixby et al.
patent: 3383228 (1968-05-01), Rekate et al.
patent: 3954069 (1976-05-01), Loken
patent: 3957528 (1976-05-01), Ott et al.
patent: 4112033 (1978-09-01), Lingl
patent: 4232614 (1980-11-01), Fitch et al.
patent: 4670054 (1987-06-01), Hohman et al.
Hazardous Waste Management Techniques, pp. 100-105.
White Kenneth L.
Wight Harold B.
Favors Edward G.
Neutralysis Industries Pty. Ltd.
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