GB407001A - Improvements in or relating to apparatus for separating solids, semisolids and the like from liquids - Google Patents

Abstract

407,001. Gravity-separation apparatus. PARTRIDGE, H. E., 79, Craigloekart, Edinburgh. Aug. 26, 1932, No. 23872. [Class 111.] Apparatus for separating suspended matter in the form of froth or foam from liquids, e.g. sewage or waste liquids from paper, dye or chemical works, comprises a main vessel within which is arranged a primary vessel in which the liquid is directed, or moves, upwardly and one or more further vessels arranged concentrically around the primary vessel, the liquid flow being reversed on passage from one vessel to the succeeding vessel. The primary vessel has an open port or mouth through or to which the liquid moves to a boundary with the atmosphere, the foam passing through the boundary as the liquid holding it moves up to or along the boundary and means being provided for removing the foam from above the boundary. The construction shown in Fig. 1 comprises a main vessel 14, an upwardly directed inlet pipe 11 for the liquid to be treated, a primary vessel 10 and a secondary vessel 13 both open at each end, and a discharge weir 16 for the clarified liquid. An inner sleeve 18 is mounted in the primary vessel 10 immediately above the mouth of the inlet pipe. The liquid passes through the apparatus along the path indicated by the arrows ; compressed air introduced through a perforated pipe 19 serves to reverse the flow of liquid in the vessel 10, and also to facilitate the complete clarification of the liquid by removing very minute particles of impurities in the form of foam. The major portion of the foam separates at the liquid boundary at the mouth of the sleeve 18 and the remainder at the liquid boundary at the mouth of the vessel 13. The main chamber is extended above the level of the weir 16 to form a retention vessel for the separated foam and a rotatable helical scraper 25 mounted on bridge pieces 27 directs the froth to a discharge chute 26. Heavier solid particles fall to the cone shaped base of the main chamber and may be removed by discharge pipes 23, 24. In order to reduce the flow velocity of the liquid to facilitate the separation of the heavier particles under gravity, apertures 44 may be formed around the mouth of the primary vessel 10. The modified construction shown in Fig. 3 is particularly intended for the simultaneous treatment of several forms of trade waste, which forms may react to bring down suspended matter in a flocked condition, e.g. paper mill wastes such as bleach waste, lime waste, caustic waste and chlorine waste may be delivered together to the apparatus. In this construction the primary vessel 28 is disposed within a reaction tank 29 surrounded by a further vessel 33. The liquid to be treated enters the apparatus by the inlet pipe 11 and passes along the path indicated by the arrows to a discharge weir 34. The major portion of the suspended matter flocked by the reaction of different wastes falls to the conical base of the vessel 29 and may be removed through a valve 39 or discharge pipe 40. Suspended matter carried by the liquid out of the tank 29 falls to the conical base of the main vessel 32 and may be removed through a valve 37 or discharge pipe 38. The major portion of the foam separates at the liquid boundary at the top of the vessel 28 and is collected in a retention vessel 41 but in order to trap small particles of foam passing into the main vessel the retention vessel 41 is formed with a truncated conical apron 42 ; the foam is discharged through an opening 43 by a helical' scraper. In both constructions, in order to facilitate movement of the foam to the discharge part, the upper edge of the vessels at which foam separation boundaries are formed may be disposed at slightly reduced heights from the inflow to the discharge part of the apparatus. The retention vessel may be provided with an annular flange disposed substantially in the plane of the final separation surface for the foam so that foam moving under the slight head between the different levels passes to the annular flange. In addition to injecting air to reverse the direction of flow of liquid, compressed air may be injected into the liquid in the inflow pipe through a porous membrane or partition to increase the formation of foam. Moreover instead of using compressed air to reverse the direction of flow of liquid steam may be passed through an annular unperforated pipe to cause reversal of direction by convection. The surface of the liquid in the main vessel may be raised, e.g. to flush the foam discharge apparatus, by means of an adjustable weir or discharge valve. The apparatus may be combined with suction or drying devices for extracting moisture from the removed foam. According to the Provisional Specification the apparatus may be used for the separation of cream from milk or for grading solid materials suspended in a suitable carrier such as water.