GB1365864A - Treatment of sludge - Google Patents

Abstract

1365864 Treating sludge HYDRO CHEMICAL & MINERAL CORP 4 Oct 1971 [12 Oct 1970] 28788/73 Divided out of 1363449 Heading C1C [Also in Division C5] In a method of treating sludge, e.g. municipal sewage wastes and paper processing wastes, utilizing direct contact liquid-liquid heat exchange, sludge under pressure entering through a conduit 242 is heated as it passes downwardly through a first heat exchanger 200 by direct contact with a countercurrent flow of oil. The heated sludge is passed into a holding vessel 249 and then downwardly through a second heat exchanger 201 to be cooled by direct contact with upwardly flowing oil, the cooled sludge thereafter being separated, e.g. by settling, centrifuging or vacuum filtering into its solid and liquid components in a separator 250. The oil is continuously recycled between the first and second heat exchangers 200 and 201, the oil giving up heat to the sludge in the first exchanger and recovering heat from the sludge in the second. Fats or fatty materials, such as lipids, which become dissolved in the oil are separated therefrom by directing part of the oil through a two stage oil flash evaporation column 202 and an oil condensing device 203, fat-free oil being returned for reuse via conduits 240 and 264 and a pump 266. The twostage evaporation column 202 comprises an upper first stage flash chamber 204 and a lower second stage flash chamber 206 from which a plurality of tubular passages 214 extend downwardly to a fat residue settling chamber 216. The residue exits via a valve 224 into a collection chamber 226. An oil vapour conduit 218 connects the upper region of the first stage chamber 204 to a condensing chamber 220 surrounding the passages 214, the condensed vapours in chamber 220together with oil vapours produced in the second stage flash chamber 206 being transferred via lines 238 and 236 to the upper region of the oil condenser 203. In a modification (see Fig. 2, not shown), sludge after having been heated in the first heat exchanger is sprayed into a pair of series arranged flash evaporation chambers (270, 274) to remove the water content therefrom prior to being cooled in the second heat exchanger, the vapours produced in the flash evaporation chambers 270 and 274 being transferred to the two successive condensing stages (278 and 280) of a condenser column (283). In a further embodiment (see Fig. 3, not shown) heated sludge from a first heat exchanger (302) is mixed with heated oil, the resulting oilsludge mixture being passed into multistage flash evaporation and condensation apparatus (304 and 306) to remove water from the sludge; the mixture is then passed through filtration apparatus (316) to separate the oil from the sludge solids.