INVENTIONS IN FILTRATION AND SEPARATION

Abstracts of recent British Patents

Froth flotation device In GB 2281521 Supaflo Technologies Pty Ltd describes a froth flotation device. It includes a tank to contain a slurry incorporating minerals which are to be extracted. There is a zone of mineralised froth above the slurry, and a launder directing the mineralised froth away from the tank. It includes a porous diffusion surface in direct con- tact with the froth, to dispense wash water directly onto the froth zone. The porous diffusion surface comprises a flexible, perforated rubber membrane, with water being supplied from behind the membrane by a conduit with an inclined guide surface. (1 figure, 4250 words)

Particulate separation from an entraining gas

In GB 2283691 Hosokawa Micron Ltd describes an apparatus for separating particulate and/or powdery material from an entraining gas. It includes a means for in S&L washing, comprising a housing which defines a closed cham- ber with an inlet for powder and gas. There is an outlet in the lower section of the housing for the particulate and/ or powdery material, an outlet for filtered gas, and a filter fitted between the inlet and gas outlet. This filter is mounted so that the gas must pass through it to reach the gas outlet. A means for introducing washing liquid is provided in the chamber, and fitted to wash the interior of the housing filter. (1 figure, 4000 words)

Oil spill recovery centrifuge In GB 2282087 Exxon Production Research Company describes a centri fuge for the separation of a mixture of oil and water, such as for example for oil spill recovery. It has an outer stationary housing and an inner rotor, both of which have an open-ended design, to allow visual and physical access for separation monitoring and cleaning of debris from the centrifuge. A stationary feedpipe connected to the housing feeds the mixture into the rotor. Weirs connected to the rotor remove the separated components from the centrifuge. Debris removal ports on the housing, and wash nozzles on the feedpipe, aid cleaning and the removal of debris from the rotor.

Cyclone separator In GB 2282088 K.-E. Larsson describes a cyclone separator for separating substances from a Kbre/liquid suspen- sion, in particular a paper slip suspen- sion. The separator’s main feature is an Filtration & Separation October 1995

inner, conical chamber provided with an essentially tangentially directed in- let at the wider end of the chamber. The chamber tapers conically downwards, and the inner surface of the chamber has a screw-like configuration.

This configuration includes an upper and a lower surface or flank. The flank that faces towards the wider end of the chamber defines an angle with the chamber centre line, and the second flank (which faces towards the narrower end of the chamber) defines an angle with the first flank. The second flank and its extension, together with the first flank of the nearest underlying helix of the screw-like configuration, form a triangle which has a line that extends through the apex of the nearest underlying part of the helix or helical screw-thread, and which ex- tends parallel with the chamber centre line. (1 figure, 3000 words)

Filter adparatus In GB 2282977 D&C Ltd describes an assembly of parallel filter plates. It is enclosed by a rigid shell, while the liquid to be filtered is pumped through an inlet. Subsequently the shell is moved, to expose the plates and allow filter cake to be removed from between them. The rigid shell is lined by a tubular membrane (and possibly an end membrane), which is inflated with water during filtration, and subse- quently deflated to allow easy separa- tion of the shell from the plates. The end membrane may also squeeze the plates together at the end of the filtration step.

The plates are flat discs, covered with filter cloth or made of sintered steel, and are spaced apart by crescent- shaped elastomeric members. The plates and members are mounted on an end-plate by draw-rods extending through the assembly and tensioned by rams mounted on a plate. Filtrate drainage channels in the discs open into ducts through the assembly, to which suction may be applied to assist filtration. Before or after the rigid shell is withdrawn, the plate and disc assembly is rotated through 90”, to place the elastomeric members in a vertical position. When the tensioning rams are relaxed, the cake falls from the plates, possibly assisted by a rake moving in an arc. (14 figures, 3500 words)

High-temperature gas filter In GB 2282980 Babcock & Wilcox Espanola SA describes a filter for gases at high temperature and pressure. It comprises ceramic filter candles

whose open upper ends are sealed to horizontal ducts which collect the filtered gas. The closed lower ends are urged upwards by supports, which may comprise compression springs, or pneu- matic rams or ceramic bladders sup- plied with compressed air at variable pressure from outside the filter hous- ing. The housing encloses several banks of candles, each comprising three groups of parallel ducts, which open at one end into radial main ducts. The housing has an upper inlet and a lower dust outlet. The lower support incorpo- rates a screw connection for vertical adjustment when candles are installed. (5 figures, 8000 words)

Filter for molten metal In GB 2282764 Michael White de- scribes a filter for molten metal. It comprises a stack of ceramic gratings whose ‘slots are partly obstructed by ribs spaced from the upper and lower faces of the gratings, to define tortuous passages through the stack. Adjacent gratings may have their slots aligned, staggered or oriented at right angles, and may be welded together. The gratings may be flat or frusto-conical. (1 figure, 3000 words)

Dust separator In GB 2284165 Winton Eurotech Ltd describes a device for the separation of particles from a stream of air or other gas. The particles are separated from the gas stream in a cyclonic separator, whose lower end feeds into a cylindrical chamber enclosing a falling cylindrical film of liquid, into which the separated particles are fed, so as to be entrapped. The entrapped particles are then en- trained in the liquid for analysis.

A second device includes two cy- clones in tandem. The first acts as a prefilter to separate over-large parti- cles, prior to the airstream going to the second cyclone for entrainment of the remaining particles in the liquid. (2 jZgwres, 2 750 words)

Composite filter In GB 2284563 SEB SA describes a composite filter, which comprises a filter cloth adapted to retain particles contained in a liquid. There is also a second filter cloth, with the space between the first and second filter cloths adapted to contain substances for treatment of the liquid. This is claimed to eliminate unpleasant tastes in water. (3figures, 2750 words) q

In the UK Br&.sh Patmt spepecifications can be ordered from: The Patent Ofice {Sates Branch) Unit 6, Nins Mile Point Cwmf&&ach, Cross&ys NewpoT%, Gwmt NPl zfz, UK. Tel: 01495 201100

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