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US 4,050,390 AGranted
Method of treating sewage sludge
AssigneeNGK Insulators, Ltd.
InventorsShinichi Hara, Taro Kato
Life of this patent
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Abstract
A method of treating sewage sludge is disclosed. The method makes use of an unitary multi-hearth furnace and the sewage sludge is dried in an upper part of the furnace and subjected to pyrolyzation in a lower part thereof to cause the sewage sludge to be reduced to ashes whereby a relatively small amount of exhaust gas is produced. The exhaust gas is also utilized as a heat supply source.
Claims2
A method of treating sewage sludge comprising
- drying sewage sludge in an upper part of a multi-hearth furnace,
- subjecting the sewage sludge to pyrolyzation in a lower part thereof to cause it to reduce to ashes,
- extracting from the multi-hearth furnace both exhaust gas produced during the drying of the sewage sludge and the exhaust gas produced during the pyrolyzing independent of each other,
- dehumidifying the exhaust gas produced during the drying of the sewage sludge,
- mixing the exhaust gas thus dehumidified with the exhaust gas produced during the pyrolyzing of the sewage sludge,
- adding preheated gas to the mixed exhaust gas and burning the preheated mixed gas in an after-burner and
- discharging the combustion gas into atmospheric air, heat generated in the after-burner being used again to preheat gas to be fed into the after-burner and to an air-heating furnace and preheat the exhaust gas to be fed into the after-burner and a part of the exhaust gas burned in the after-burner together with the preheated air being heated in the air-heating furnace and then fed into the multi-hearth furnace.
4 more elements
Dependencies are inferred from the claim text.