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US 4,245,396 AGranted
Process for drying and granulating sewage sludge
AssigneeUop LLC
InventorVere Maffet
Life of this patent
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Abstract
A process for drying and granulating sewage sludge. Wet sewage sludge is at least partially dried in a thermal drying zone, which preferably is a toroidal dryer. A plasticizer is added to the dried sludge and the resultant mixture is extruded to form fertilizer granules. An extrusion aid may also be admixed with the dried sludge.
Claims7
A process for drying sewage sludge which comprises the steps of:
- (a) passing a feed stream comprising sewage sludge into a drying zone operated at drying conditions and effecting the evaporation of water contained in the feed stream, and the production of a drying zone effluent stream comprising particles of sewage sludge derived from the feed stream and water vapor;
- (b) separating the drying zone effluent stream in a solids-vapor separating zone and producing a vapor stream comprising water vapor and a dry solids stream comprising dried sewage sludge and containing less than about 15 wt.% water;
- (c) admixing a plasticizer into at least a first portion of the dry solids stream, with the amount of plasticizer which is added being less than 5 wt.% of the first portion of the dry solids stream;
- and,
- (d) extruding the first portion of the dry solids stream in an extrusion zone under conditions sufficient to effect the formation of a product stream having a bulk density greater than about 30 lb/ft.sup.3.
2 more elements
Dependencies are inferred from the claim text.