Abstract Method for treating municipal waste comprised of solid heatdecomposable materials wherein the waste material is heated directly by convection in a rotary kiln and preferably also by radiation from an open flame to effect pyrolysis. A portion of the gaseous pyrolytic decomposition gases produced are burned in situ within the kiln, through the addition of controlled amounts of oxygen, while concurrently substantially maintaining the pyrolyzing waste in a substantially non-oxidizing atmosphere. The waste material is charged at the raised end of the inclined rotary kiln and the open flame projected by a burner at the other end of the kiln is spatially disposed such that the flame is in an unrestricted, spaced relationship with the waste material. The gases move counter-current to the bed of waste material and are withdrawn from the kiln proximate the waste material feed end. Agitation of the bed of pyrolyzing waste material is effected, without significant amounts of the waste material becoming entrained in the moving gases, by a rotary tumbling action coupled with the hot knife and separating action of heatconductive members which protrude from the shell of the kiln. In specific embodiments the withdrawn gases may be totally combusted in a separate combustion chamber and then may be scrubbed to remove particulates prior to being discharged to the atmosphere. The hot solid residue may be quenched and subjected to resource recovery separations. In a further embodiment, an aqueous scrubber for the gases and an aqueous quench bath for the hot solid residue may be operated in conjunction with each other to avoid any discharge of water to a sewer.
A method according to claim 1 wherein said resulting gaseous mixture is continuously charged into a combustion chamber together with further oxygen in an amount such as to provide at least the theoretical quantity of oxygen necessary for complete oxidation of the remaining uncombusted gaseous pyrolytic decomposition products in said gaseous mixture.
Claim 2
Dependent Claim
24 words
A method according to claim 2 wherein the total gaseous mixture within said combustion chamber is at a temperature above the auto-ignition temperature thereof.
Claim 3
Dependent Claim
36 words
A method according to claim 2 wherein the total gaseous mixture within said combustion chamber is ignited with a burner in the event the temperature of said total gaseous mixture falls below the auto-ignition temperature thereof.
Claim 4
Independent Claim
447 words
A method for treating shredded solid municipal waste comprised of solid heat decomposable material and which tends to form an entangled mass upon rotary tumbling, within an inclined rotary tubular chamber by the pyrolytic decomposition thereof to form a solid residue and environmentally acceptable off-gases, which method comprises: a. feeding said material into said rotary tubular chamber proximate a first end thereof, said first end being elevatEd with respect to the opposite end thereof; b. heating the resulting bed of said material within said rotary tubular chamber to a temperature sufficient to result in at least partial pyrolytic decomposition of said material into gaseous pyrolytic decomposition products and a hot solid residue, the bed of said material being maintained in a substantially non-oxidizing atmosphere as said material is being pyrolyzed; said heating of said material resulting in part from an open flame from a burner located proximate said opposite end of said rotary tubular chamber such that said open flame is disposed within said rotary tubular chamber in an unrestricted, spaced relationship with said material so that said material is heated by direct radiation from said open flame, and the remainder of said heating of said material resulting from the oxidation of said gaseous pyrolytic decomposition products in step (c); c. concurrently admitting oxygen into said rotary tubular chamber proximate said opposite end thereof in an amount sufficient to result in the oxidation of at least part but not more than 60 percent of said gaseous pyrolytic decomposition products, said oxygen mixing with said gaseous pyrolytic decomposition products and resulting in at least partial combustion thereof, based upon the oxygen present, within said rotary tubular chamber, said substantially non-oxidizing atmosphere referred to in step (b) being substantially maintained between said bed of material and said combusting gaseous pyrolytic decomposition products; d. concurrently agitating said bed of material within said rotary tubular chamber by the rotary motion thereof coupled with a mechanical hot knifing and separating action applied to said bed of material in a manner which minimizes entrainment of said material in the moving stream of gases; e. continuously withdrawing the resulting gaseous mixture of said gaseous pyrolytic decomposition products and the partial combustion products thereof from said rotary tubular chamber proximate said first end thereof; f. discharging said hot solid residue from said rotary tubular chamber proximate said opposite end thereof; g. continuously charging said resulting gaseous mixture withdrawn from step (e) into a combustion chamber together with further oxygen and oxidizing the remaining uncombusted gaseous pyrolytic decomposition products contained in said resulting gaseous mixture, and h. subjecting the gases leaving said combustion chamber to an aqueous scrubbing prior to discharging said gases to the atmosphere.
Claim 5
Dependent Claim
31 words
A method according to claim 5 wherein liquid from said aqueous scrubbing is at least partially separated from entrained solid particulate matter, and said liquid is recycled to said aqueous scrubbing.
Claim 6
Dependent Claim
17 words
A method as in claim 5 wherein said hot solid residue is quenched in an aqueous bath.
Claim 7
Dependent Claim
71 words
A method as in claim 6 wherein (a) said hot solid residue is quenched in an aqueous bath (b) the aqueous phase from said aqueous scrubbing is at least partially separated from solid particulate matter contained therein in a clarifier, (c) the relatively particulate-free liquid from said clarifier is recycled to said aqueous scrubber, and (d) the particulate containing aqueous slurry from said clarifier is recycled to said aqueous quench bath.