Texaco Inc.

Kenneth W McKenzie

Matthew A McMahon

Motasimur R Khan

Ronald J McKeon

Robert F Heyl

Michael C Martin

Enrique F dePaz

A process for disposing of sewage sludge by heating and shearing an aqueous mixture of sewage sludge in a tubular-shaped processing means containing a plurality of rotating agitators to produce a pumpable aqueous slurry of sewage sludge. The aqueous slurry of sewage sludge is mixed with solid carbonaceous fuel or an aqueous slurry of solid carbonaceous fuel to produce a pumpable aqueous slurry of sewage sludge and solid carbonaceous fuel. The aqueous slurry of sewage sludge and solid carbonaceous fuel is heated in a first steam jacketed rotary disc mixing-heating means. Alternately, first and second hoppers are filled with said heated aqueous slurry of sewage sludge and solid carbonaceous fuel and cycled between a second steam jacketed rotary disc mixing-heating means; wherein while one hopper is being filled the contents in the other hopper are being dewatered. The thickened pumpable slurry is burned in a partial oxidation gasifier, furnace, boiler, or incinerator to produce a hot effluent gas steam. By this process, noxious sewage sludge may be disposed of without contaminating the environment. By-product synthesis gas, reducing gas, or fuel gas may be produced.

Process for disposing of sewage sludge

A process for disposing of sewage sludge comprising the steps of, (1) dewatering the sewage sludge to produce an aqueous slurry of sewage sludge having a solids content of about 10 to 30 wt. %; (2) simultaneously heating and shearing said dewatered sewage sludge at about 150.degree. F. to 210.degree. F. in the absence of air for 0.5 seconds to 60 minutes while being continuously passed through a tubular-shaped processing means containing a plurality of rotating agitators, thereby producing a pumpable slurry having a viscosity of less than about 2000 centipoise; (3) dewatering the sewage sludge if necessary; (4) mixing at a temperature in the range of about ambient to 180.degree. F. in a ribbon or in-line static mixer the slurry of sewage sludge from (2) and/or (3) with a supplemental solid carbonaceous fuel e.g. coal and/or petroleum-coke to produce a pumpable aqueous slurry of sewage sludge and supplemental fuel having a solids content in the range of about 50 to 60 wt. %; (5) mixing the slurry of sewage sludge and supplemental fuel from (4) in a steam jacketed continuous rotary disc mixer at about 180.degree. F. to 250.degree. F. while removing steam to produce a pumpable slurry of dewatered sewage sludge and solid fuel having a solids content of 50 to 65 wt. % and a HHV of 6,000 to 18,000 BTU/LB; and (6) burning said pumpable slurry from (5) in a partial oxidation gasifier, furnace, boiler, or incinerator to produce an effluent gas stream. In a preferred embodiment, the effluent gas stream is cleaned and purified and non-contaminating ash and slag are separated. By this process, noxious sewage sludge may be disposed of without contaminating the environment. By-product synthesis gas, reducing gas, or fuel gas may be produced.

An improved process for the low-cost disposal of noxious municipal sewage sludge in a safe way without polluting the environment. In the process, a portion of a stream of dewatered sewage sludge having a solids content in the range of about 17 to 40 wt.% is dried to produce dried sewage sludge having a solids content in the range of about 75 to 99 wt.%. The dried sewage sludge is ground to a small particle size. A pumpable aqueous feed slurry having a solids content in the range of about 45 to 70 wt.% is produced comprising (a) solid carbonaceous fuel, (b) ground dried sewage sludge, and (c) sheared and/or unsheared dewatered sewage sludge. The parts by weight of (a):(b):(c) are respectively in the range of about 3 to 8:0.5 to 2:0.5 to 2, and preferably 6:1:1. The aqueous feed slurry is gasified in a free-flow partial oxidation gas generator. Synthesis gas, reducing gas or fuel gas is produced, Ash and slag are separated from the gas stream and safely disposed. Waste heat produced in the process may be used to dry the sewage sludge.

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Apple Valley, CA, United States of America

Kenneth W McKenzie