GB1175888A - Apparatus and Process for Dehydrating Waste Solids Concentrates - Google Patents

Abstract

1,175,888. Drying sewage sludge. C. GREENFIELD. 31 May, 1967, No. 25104/67. Heading F4G. In apparatus for drying waste solids concentrates, e.g. sewage sludge, the concentrate is mixed with a relatively non-volatile oil in a tank 4 to obtain a pumpable fluid and then subjected to a plurality of sequential dehydration steps in evaporators 9, 21, 32 through which the mixture passes in co-current downward flow with steam originally from a furnace 11 to evaporate off a portion of the moisture, the vapours evolved being utilized in all but the last evaporator to supply a substantial portion of the heat requirements of next dehydration step but at successively lower temperatures and successively higher solids concentration. The resultant mixture of substantially anhydrous waste solid and oil slurry is withdrawn from the evaporator 32 for centrifuging in means 50. The oil constituent thereafter re-enters the centrifuge means 50 to fluidize the material or passes to the mixing tank 4 with a proportion passing to the furnace 11 if in sufficient quantity. The solid constituent passes to a press 59 and may be ground at 63 and bagged or pass to the furnace as a fuel source. A portion of the vapour evolved in the first evaporator is used for evaporation in the second evaporation but a portion of steam from the second evaporator is mixed with and compressed with a fresh steam supply in a Venturi-tube and supplied to the first evaporator.