Patent GB-904709-A (GB)
Title: Improvements in or relating to vacuum filters for liquids
IPC: B01D33/09
Filed: 1960-03-03
Abstract: 904,709. Rotary filters. GEWERKSCHAFT ERDOL-RAFFINERIE DEURAG-NERAG. March 3, 1960 [March 3, 1959], No. 7514/60. Class 46. A vacuum-operated rotary drum filter 4, Fig. 1, has a control head 8, Fig. 3, and a control cylinder arranged in front of the face of the control head 8, the two parts of which comprise a revolving valve seat 10 with outlet openings 30 from the filtrate pipes 6 of the individual compartments I to XII and a fixed valve chamber 9 having openings 15 to 22, Fig. 4, corresponding to those in the valve seat 10, the ground face of which is held pressed to that of the chamber 9 by springs 11. The openings 15 to 22 communicate by way of pipes 15<SP>1</SP> to 221 with the cylinder 23 which is provided with at least one piston 24, Fig. 2, which is displaceable from outside e.g. by a handle 25, and enables the continuous separations of the oil-rich from the oil-deficient wash filtrate to be effected in variable ratios, the former being drawn off through the flanged opening 13 and the latter through a similar opening 14, while the initial filtrate is drawn off through the central opening 12. As the filter drum 4 rotates in the tank 1, suctions actuated primary flow, of solvent and oil occurs through the cloth and screen grid covered compartments XI XII, I and II, paraffin cake 5 being deposited on the cloth. The primary flow, containing 18À7% by volume of de-paraffined oil, is drawn off from the compartments XI, XII, I and II and travels by way of the pipes 6 and openings 30 in the valve head 10 to the arcuate slot 29 in the valve chamber 9 and thence out through the opening 12. Paraffin cake 5 deposited on the cloth covering of the filter drum 4 with increasing thickness forms an impermeable layer by the time a particular compartment emerges from the solid-liquid mixture and evacuation of the oil-rich filtrate from compartments IV and V is obtained by venting them to the atmosphere, or the casing interior, by way of pipes 27, connected to all the compartments and to the openings 31 in the valve seat 10, the arcuate slot 28 in the valve chamber 9 controlling the number and angular position of the cells to be vented. Compartments IV to IX are sprayed with pure solvent, but wash filtrate may only be drawn off from compartments VI to IX, the zone corresponding to these compartments being divided into eight filtrate openings 15 to 22 which, as previously stated, communicate with the control cylinder 23. If more than one piston 24 is used in the cylinder 23, for example two, then an additional wash filtrate discharge opening will be required to remove the filtrate from the region between the two pistons. The solvent toluol methyl ethyl ketone used for washing the paraffin cake 5 is also used for a controlled two-stage dilution of the paraffin-bearing oil, the second stage of which is supplemented by the oil-rich and oil-deficient filtrates, the resulting mixture being cooled to -28C. before entering the tank 1. A conveyer worm 2 discharges the washed crude paraffin cake removed from the drum 4. The number of holes 15 to 22 and pipes 15<SP>1</SP> to 22<SP>1</SP> in and leading from respectively the valve chamber 9 can be made equal to or greater than the number of openings 30 in the valve seat 10, depending upon the size of the filter compartments around the periphery of the drum 4.