Patent GB-928066-A (GB)
Title: Sludge thickener
IPC: C02F11/126
Filed: 1961-08-18
Abstract: 928,066. Rotary filters. EQUIPMENT DEVELOPMENT CO. Aug. 18, 1961 [Aug. 23, 1960], No. 29956/61. Class 46. At least one outwardflow filter drum is fed with sludge from a constantlevel feed trough disposed within the drum, through a pipe extending through the trough, and the residue is discharged piecemeal over an annular flange at at least one end of the drum. First embodiment (Figs. 3, 4). Coaxial drums 1, 2, Fig. 4, are mounted on rollers 6, 7, Fig. 3, parallel to coaxial drums 3, 4 (3 not shown). All the rollers 7 are driven by a single motor to rotate drums 1, 2 counterclockwise and drums 3, 4, clockwise. Sludge is supplied by a pipe 57, Fig. 4, to the base of two feed troughs 55, the level in each being maintained by a weir 58, Fig. 4, at the far end, discharging to a common drain pipe 60, Figs. 3 and 4. From the troughs the sludge is supplied to the drums by eccentrically-mounted buckets 63 rotated by shafts 61 and discharging through funnels 70 and pipes 71 on to spreader plates 72. In each drum the residue forms a plug 42 which is repeatedly tumbled by the motion of the drum, and portions of the plug discharge over the narrower (43) of the two end flanges of the drum into the region between adjacent ends of coaxial drums, where a hopper 48, Fig. 3, is provided. Each hopper extends through the filtrate drain pan 36 of its coaxial pair and the hoppers discharge to a common zone. Likewise, the filtrate drain pipes 40 are joined, Fig. 3. The inner surfaces of the screens 13 are washed by sprays 81, Fig. 3. Preferably the screens are of nylon previously boiled and then steamed and dried whilst in a stretched condition. When thus treated and then applied under tension, subsequent sag is reduced. Agglomeration of the plug may be expedited by addition of a pulp. Second embodiment (Fig. 11). Each pair of coaxial drums is linked by tie rods covered, in the region between the drums, by shields (see 88a, Fig. 18), which scrape clean part of the respective hopper; air or water jets impinge on the outside of the screens to clean them, Figs. 7 to 9 and 13 (not shown), the screen material may be adjustably tensioned axially, Fig. 10 (not shown). The feed trough 55a, Fig. 11, has an inlet chamber 97a fed by a pipe 57, the chamber communicating at 97b with the region between a longitudinal wall 99 and one of the walls of the trough. Sludge reaches the main portion 100 of the trough by flowing under the wall 99; the level is regulated by an adjustable weir 58a discharging to an outlet chamber 98a. Each feed bucket 63a consists of a cylinder symmetrically divided by three radial partitions 103, each compartment being filled through an opening 104 and being discharged through a central sleeve 69a into a funnel 70. A fixed curved deflecting plate (not shown), in close proximity to each screen, engages the leading edge of each residue plug to assist in formation and turning. Third embodiment (Figs.. 18, 19). One of the two drums of each coaxial pair is formed as a double cylinder 2a, Fig. 18, and residue is discharged from both ends of each drum. The feed trough 55b is similar to 55a in Fig. 11 but is fed by a pump 122 and a pipe 123 which communicates with an end wall 112. Discharge from the trough is by open-ended pipes 124 which are wiped by twin-bladed paddles 127 serving also as agitators. The liquid level in the feed trough 55b may be maintained constant by appropriate control of the pump driving- motor by a float-operated switch 133, Fig. 19, associated with a float-chamber 130 connected to the trough. U.S.A. Specification 2,798,609 is referred to.