Patent GB-673075-A (GB)
Title: Improvements in and relating to apparatus for the digestion or alkaline fermentation of organic material
Inventor: BOTTOMLEY CHARLES DENIS
IPC: C12M1/107
Filed: 1949-04-12
Abstract: 673,075. Treating sewage. DORR CO. Feb. 2, 1950 [April 12, 1949], No. 9911/49. Class 111 [Also in Group XIII] Apparatus for the digestion of .alkaline fermentation of organic material such as sewage sludge of the kind comprising a closed tank from which evolved gas can be collected is provided with a chamber supported by the tank and including compartments for a pump and a removable heat exchange element through which the sludge is circulated; the heat exchange element can be cleaned during its operation without removal from its compartment. A chamber 2 with removable covers, Figs. 1 and 2, is formed integrally with the upper part of the wall 1 of a circular sewage digestion tank and houses a pump 10a in a compartment 5 and a heat exchange unit 21, 23 in a compartment 6. Sludge is withdrawn from the tank 1 by the pump 10a through a port 15 and delivered to a subcompartment 12 whence it flows by gravity through a port 17 into the upper part of compartment 6 and then over a closely-coiled heating spiral 21 accommodated between a hollow metal core member 23 and the walls 1, 3, 4, 7 and 9. Hot water is circulated through the coil from an inlet pipe 25 and leaves by a pipe 27, Fig. 3. The coil 21 is supported and may be lifted by three angle-section straps 22, which also space it from the surrounding wall. The core 23 is in turn spaced from the coil 21 by members 29, which also serve as guides when it is being raised or lowered by a cable -24. The coil may alternatively be constructed from a pair of concentric cylinders separated by a thin membrane formed into a spiral guide. The heated sludge passes back into the tank the coil 21 to the port 18a and guide 19 guide 19, 20, which induces a spiral motion of the tank contents. An auxiliary compartment 34, Fig. 5, may be attached to the compartment 6 for introduction of fresh sludge into the tank 1, from pipe 33. The fresh sludge may pass from compartment 34 through a port 38 and flow down over through a port 18a and in inclined guide 20, or it may be introduced directly from the compartment 34 to - the port 18a through pipe 36. To effect the dispersal by heating of scrum or supernatant liquor a siphon member 42, Fig. 9, may be provided, which conducts the scum to a port 40, Fig. 7, arranged behind a weir 39 in an extension of the compartment 5. The scum is drawn up by the pump 10a along with the.sludge and returned past the heater to the tank. The weir 39 ensures a liquid seal at the inner end of the siphon 42, which prevents excape of gas into the pump compartment 5 if the tank lever falls below the top of the funnel 42. The siphon pipe may be extended and the siphon member 42 supported on a pier 45 within the tank instead of on a wall-bracket 43. The surfaces of the heater unit may be cleaned by inserting a brush or the like without interrupting the operation of the plant, and material removed by cleaning is carried by the sludge back into the tank. Also the heater unit, core and pump may be withdrawn for servicing without interrupting the process. The heater or core, or both, may be supported from below by brackets, columns, or the like. Also, the heater may be suspended in a separate framework. The cleaning of the heater unit may be effected by scraper elements attached to the heater core member, the latter being mounted for rotation about its longitudinal axis. The chamber may be separate from but closely associated with the digestion tank.