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Solids separation
INVENTIONSINl?ILTRATIONANDSE
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Abstracts of British Patents Air filter
Filtration of liquids
In GB 2256602 Thomas Goodwin describes a radial flow hollow air filter. It comprises a band of filter material such as foam plastics wound spirally around a hollow perforated former. The band has axially abutting sections with different pore sizes, so that the pore size of the filter varies radially. The band is wound under tension, and the resulting compression of the material may be maintained by an encircling strap or an outer perforated casing. A further band filter material may be wound around the casing. Preferably sections of coarse, medium and fine filter properties are attached together, by adhesive. (4 &ures, 4500 words)
In GB 2257053 Schenk-Filterbau GmbH describes the filtration of liquids. Here chemical or pharmaceutical liquids (in particular h+ction solutions, blood plasma or photogelatines) are filtered using chemically inert filter media emitting virtually no metallic ions. The polymer may be a urea formaldehyde condensation. The media in question are incorporated in a paper-like material also comprising cellulose fibres, which is used as a filter sheet or is crushed and used as a filter aid. (no jzsures,3500 words)
Solids separation In GB 2256819 Multiserv International Ltd describes a method of separating solids. Slag containing a metal fraction is passed through a magnetic separator to provide fractions containing an enhanced metal content and a waste product with reduced metal content. The metal-containing fractions are then passed through a separator containing a trough with an endless path and containing dry sand. The path floor is air-permeable and includes a depthwise partition, the metal and non-metal components being separated according to their density. The material treated may be any slag containing a metal or alloy. Preferably the metal is a ferroalloy (e.g. ferrochrome or ferronickel) , or an aluminium alloy or similar. It is an advantageous feature of the invention that the material treated can be in lump form, e.g. from about 5 mm to above 75 mm in diameter. The lumps may be supplied to the magnetic separator at up to 20 tonne/hr/metre width of belt. (3fIguw?s, 3000 words)
Separator/filter unit In GB 2256820 Pall Corporation describes a separator/filter unit which can be used for separating water from an air/water mixture in an aircraft where the air is to be supplied to electronic equipment. It comprises a chamber containing a generally tangential inlet tube through which a mixture is supplied to a curved sidewall section of the chamber to separate water from the air by centrifugal action. The unit has a filter positioned away from the chamber centre, or spaced by a guide plate from the curved sidewall, on which the water coalesces. In this latter case, the filter unit can be offset from the chamber centre for greater efficiency. (3JIgu7?rs,3500 wonls) Flltratlon & Separation
September/October
Magnetic separation process In GB 2257060 Shell Intemationale Research Maatschappll BV describes a process for separating relatively magnetic mineral particles from relatively non-magnetic particles suspended in a liquid stream. The suspension passes through a container provided with an arrangement of magnetisable matrix elements, with the hydrodynamic conditions and magnetic field strength controlled in such a way that the relatively magnetic particles are deposited on the downstream side of the elements. The suspension may comprise a mixture of particles of many differing susceptibilities. The matrix elements may be steel wool, expanded metal, wires or a screen. The container may be periodically flushed for cleaning or may be one of a carousel. The process may be applied to the separation of wolframite, arsenophyrite, sphalerite, bornite, chalcopyrite, rutile, hematite, cassiterite and magnetite. (2J?gures, 3000 words)
Sludge solids content control In GB 2257640 Patrick Torpey describes a method for controlling the solids content of sludge produced from a continuous belt filter press. Sewage sludge is dewatered by gravity on an endless filter belt where it passes over a first filtrate tray. A variable fraction of the sludge is then removed by a first scraper and diverted to a hopper, while the rest of the sludge is carried by the belt around a pressing roller before being removed by a second scraper to the hopper. The scraper is adjustable, so that the overall solids content of the mixed sludges obtained from the hopper may be controlled. The viscosity of the mixture may be monitored, and the scraper automatically controlled. The scraper may comprise a single bowed and flexible blade, or a series of separate blades individually movable relative to the belt. Thus most 1993
of the sludge remaining on the belt is near its centre, to counteract the lateral squeezing where the belt goes around a roller (which may be grooved). Filtrate from a tray is used to backwash the belt downstream of the pressing stage, and the resulting mixture is separated by gravity. (5JIgures, 3500 words)
Separating production fluids In GB 2258167 British Petroleum Plc describes a method for separating a production fluid obtained from an oil well into separate components by means of at least one separator. Water is added to the production fluid before passage to the separator in an amount sufficient to raise the water content of the production fluid to a level where the tendency for the formation of a stable water-in-oil emulsion is reduced. Some of the water to be added is obtained from the first separator (a hydrocyclone) and some from a sepamte supply, and may be added to the fluid from a welI up- or downstream of a pressure control valve. Gas is discharged from a second hydrocyclone. Relatively pure oil is fed to a secondstage electrostatic separator; a demulsifier may also be added. In an example, increasing the initial water content from 10% to 60% causes a reduction in the final water content of the oil from 8.4% to 1.0%. (1 &w-e, 1000 words)
Improved separation apparatus In GB 2258172 Christopher Morris describes an improved separating apparatus. The separation chamber has an upper and lower outlet. The lower part of the chamber has a pair of plates which are downward inclined towards the lower outlet, and which have apertures arranged in zones. The apertures in adjacent zones are angled in opposite directions, with one set inclined to the surface of the plate in a direction away from the lower outlet. The apertures in adjacent sets are inclined in the opposite direction. The lower outlet has a sidewall with a number of apertures inclined upwards at an angle of 70” to the axis of the outlet. Air is fed through these apertures from plenum chambers to create a venturi effect negative pressure below the lower outlet, resulting in a zero pressure area in the outlet. This enables the heavier material to fall from the chamber under gravity. The apparatus can be used to separate tobacco leaf and stem, tea, cereals etc. (2_lIgures, 2000 words)
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537
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Abstracts of British Patents Air filter
Filtration of liquids
In GB 2256602 Thomas Goodwin describes a radial flow hollow air filter. It comprises a band of filter material such as foam plastics wound spirally around a hollow perforated former. The band has axially abutting sections with different pore sizes, so that the pore size of the filter varies radially. The band is wound under tension, and the resulting compression of the material may be maintained by an encircling strap or an outer perforated casing. A further band filter material may be wound around the casing. Preferably sections of coarse, medium and fine filter properties are attached together, by adhesive. (4 &ures, 4500 words)
In GB 2257053 Schenk-Filterbau GmbH describes the filtration of liquids. Here chemical or pharmaceutical liquids (in particular h+ction solutions, blood plasma or photogelatines) are filtered using chemically inert filter media emitting virtually no metallic ions. The polymer may be a urea formaldehyde condensation. The media in question are incorporated in a paper-like material also comprising cellulose fibres, which is used as a filter sheet or is crushed and used as a filter aid. (no jzsures,3500 words)
Solids separation In GB 2256819 Multiserv International Ltd describes a method of separating solids. Slag containing a metal fraction is passed through a magnetic separator to provide fractions containing an enhanced metal content and a waste product with reduced metal content. The metal-containing fractions are then passed through a separator containing a trough with an endless path and containing dry sand. The path floor is air-permeable and includes a depthwise partition, the metal and non-metal components being separated according to their density. The material treated may be any slag containing a metal or alloy. Preferably the metal is a ferroalloy (e.g. ferrochrome or ferronickel) , or an aluminium alloy or similar. It is an advantageous feature of the invention that the material treated can be in lump form, e.g. from about 5 mm to above 75 mm in diameter. The lumps may be supplied to the magnetic separator at up to 20 tonne/hr/metre width of belt. (3fIguw?s, 3000 words)
Separator/filter unit In GB 2256820 Pall Corporation describes a separator/filter unit which can be used for separating water from an air/water mixture in an aircraft where the air is to be supplied to electronic equipment. It comprises a chamber containing a generally tangential inlet tube through which a mixture is supplied to a curved sidewall section of the chamber to separate water from the air by centrifugal action. The unit has a filter positioned away from the chamber centre, or spaced by a guide plate from the curved sidewall, on which the water coalesces. In this latter case, the filter unit can be offset from the chamber centre for greater efficiency. (3JIgu7?rs,3500 wonls) Flltratlon & Separation
September/October
Magnetic separation process In GB 2257060 Shell Intemationale Research Maatschappll BV describes a process for separating relatively magnetic mineral particles from relatively non-magnetic particles suspended in a liquid stream. The suspension passes through a container provided with an arrangement of magnetisable matrix elements, with the hydrodynamic conditions and magnetic field strength controlled in such a way that the relatively magnetic particles are deposited on the downstream side of the elements. The suspension may comprise a mixture of particles of many differing susceptibilities. The matrix elements may be steel wool, expanded metal, wires or a screen. The container may be periodically flushed for cleaning or may be one of a carousel. The process may be applied to the separation of wolframite, arsenophyrite, sphalerite, bornite, chalcopyrite, rutile, hematite, cassiterite and magnetite. (2J?gures, 3000 words)
Sludge solids content control In GB 2257640 Patrick Torpey describes a method for controlling the solids content of sludge produced from a continuous belt filter press. Sewage sludge is dewatered by gravity on an endless filter belt where it passes over a first filtrate tray. A variable fraction of the sludge is then removed by a first scraper and diverted to a hopper, while the rest of the sludge is carried by the belt around a pressing roller before being removed by a second scraper to the hopper. The scraper is adjustable, so that the overall solids content of the mixed sludges obtained from the hopper may be controlled. The viscosity of the mixture may be monitored, and the scraper automatically controlled. The scraper may comprise a single bowed and flexible blade, or a series of separate blades individually movable relative to the belt. Thus most 1993
of the sludge remaining on the belt is near its centre, to counteract the lateral squeezing where the belt goes around a roller (which may be grooved). Filtrate from a tray is used to backwash the belt downstream of the pressing stage, and the resulting mixture is separated by gravity. (5JIgures, 3500 words)
Separating production fluids In GB 2258167 British Petroleum Plc describes a method for separating a production fluid obtained from an oil well into separate components by means of at least one separator. Water is added to the production fluid before passage to the separator in an amount sufficient to raise the water content of the production fluid to a level where the tendency for the formation of a stable water-in-oil emulsion is reduced. Some of the water to be added is obtained from the first separator (a hydrocyclone) and some from a sepamte supply, and may be added to the fluid from a welI up- or downstream of a pressure control valve. Gas is discharged from a second hydrocyclone. Relatively pure oil is fed to a secondstage electrostatic separator; a demulsifier may also be added. In an example, increasing the initial water content from 10% to 60% causes a reduction in the final water content of the oil from 8.4% to 1.0%. (1 &w-e, 1000 words)
Improved separation apparatus In GB 2258172 Christopher Morris describes an improved separating apparatus. The separation chamber has an upper and lower outlet. The lower part of the chamber has a pair of plates which are downward inclined towards the lower outlet, and which have apertures arranged in zones. The apertures in adjacent zones are angled in opposite directions, with one set inclined to the surface of the plate in a direction away from the lower outlet. The apertures in adjacent sets are inclined in the opposite direction. The lower outlet has a sidewall with a number of apertures inclined upwards at an angle of 70” to the axis of the outlet. Air is fed through these apertures from plenum chambers to create a venturi effect negative pressure below the lower outlet, resulting in a zero pressure area in the outlet. This enables the heavier material to fall from the chamber under gravity. The apparatus can be used to separate tobacco leaf and stem, tea, cereals etc. (2_lIgures, 2000 words)
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537