INVENTIONSINFILTRATIONANDSEPARATION

Abstracts of recent British Patents

Ceramic filter and membrane In GB 2277885 R J Wakeman, J L Henshall and S G Ng describe a filter element or membrane. It mainly comprises silicon nitride, but it also contains some other elements which affect its properties, such as Al, 0, Y, Ca, Mg, Li, Nd, La, Ce, Sm, Dy and Yb. The material may form a porous support for a finer membrane of the same material or a monolithic filter element, and it can be in the form of a flat section, a tube, a cylindrical block with parallel passages or in the form of a layer on a mesh support. Its porosity exceeds 25% and its pore size is between CO.005 and 1000 pm.

Filtration may be assisted by sonic or ultrasonic vibrations and/or a constant, varying or alternating electric field. Applica- tions include the separation of fluids from each other and from solids by filtration, dialysis, reverse osmosis etc. (1500 words, 4 Awes)

Leucocyte depleting filter In GB 2277886 Pall Corporation describes a filter comprising fibres which remove leuco- cytes from blood. There is also provision for degassing the blood, comprising a tangen- tial inlet, an upstream sponge-structure degassing filter element, and vent outlets bridged by a liquophobic ITFE membrane on the underside of the housing lid. The membrane and outlets bleed separated gas from upstream and downstream of another element. (13,000 words, 3 jigures)

Flow control in filters In GB 2278177 Process Developments Ltd describes a method of flow control for selectively limiting the flow through a conduit in a polymer filtering apparatus. It comprises a side passage communicating with a conduit, with the side passage adapted to contain a partially solidified sealing plug of the polymer being filtered. There is an actuator for urging the plug into the conduit, in order to limit fluid flow, and thermal control with the conduit is possible for selectively augmenting or reducing the degree of solidification of the sealing plug. (‘12,000 words, 14jZgures)

Detecting fluid filter clogging In GB 2278295 the Societe Nationale d’Etude et de Construction de Moteurs d’Aviation describes a method and appara- tus for detecting clogging of fluid filters. Clogging is detected by monitoring a pressure difference, which is corrected by a factor which depends on the flow through the filter, so that an alarm is activated when the flow is less than the maximum. The direct pressure drop across the filter can be measured, and then corrected electronically by changing the engine speed. Alternatively, the pressure monitor is subjected to pressure control, measured in a venturi upstream of the filter. The pressure moni- tor is subject to the pressure in a centrifugal

324

fuel pump, the speed of which depends on that of the engine. (4250 words, 4 &ures)

Exhaust gas scrubber/filter In GB 2279271 Wagner Mining & Constmc- tion Equipment Co describes an exhaust treatment system. It has a water scrubber, a centrifugal water trap for removing water droplets from the exhaust flow, and a filter for cleaning the exhaust gases. The compo- nents are housed contiguously, so that there is no need for exhaust piping between the components. The filter is annular in form. (4000 words, 6jigures)

Cyclone separators In GB 2279276 Serck Baker Ltd describes a cyclone separator for gas, liquid(s) and solids. It has a tangential inlet which may be closed or opened by moving the cyclone body, or a piston-like member inside the body, in the axial direction. The body is integral with a piston subjected to the fluid pressure between the inlet space and the underflow outlet space acting against a spring. The body moves to the left so that the inlet is closed by a lug. The overflow outlet is also closed. Alternatively, a piston moves inside the cylindrical part of the cyclone body to open or close the inlet. The piston is moved by the pressure of the fluid being separated, or by an external ram or screw, and in some cases against spring- loading. A number of cyclones arranged in a common housing enables more or fewer cyclones to come into use as the overall flow varies, with an optimum flow through each cyclone in use. Not all the cyclones need to be adjustable. The springs are of snap- action type, so that the inlet is either wide- open or closed. Different cyclones may come into use at different differential pressures. (6000 words, 6 jigures)

Pipeline filter In GB 2279268 Technical Fabricators Inc describes a pipeline filter designed to be fitted within a section of pipeline. It comprises a flexible filter bag secured by stitching to a ferrule on a flat annular flange, which is of resilient impervious material. There are bolt holes whereby it may be clamped between rigid flanges on adjacent pipeline sections, in order to form a seal between them, and to support bag inside one of them. The whole filter may be made of PI’FE, with the bag comprising three layers of different pore sizes. A rigid perforated tube mounted on a further flange may locate inside the bag to support the bag against the inward flow filtration pressure. (2250 words, I.fTgures)

Engine fuel supply separator In GB 2279269 M A Hobbs describes a separator in a fuel supply to an engine. It comprises a housing divided by an annular baftle from the top, and dividing into inner and outer chambers. These are fitted with a

fuel outlet and inlet. The inner chamber encloses a float of dumb-bell shape, which is lifted, by accumulating water to close the outlet and shut off the fuel. Water is drawn off by a manual valve. The float members may comprise plastic spheres filled with fuel or foamed plastic with impervious skins, and have a density intermediate between the fuel and water. (3000 words, 3jI9wres)

Fuel filter In GB 2279581 Kyosan Denki Co Ltd describes a fuel filter for fitting inside an automobile fuel tank It comprises a filter bag of welded construction. There is an internal support comprising a base and spaced uprights; the corners presented by the support are rounded, to prevent damage to the bag. The support also has a pipe fitting, designed to connect to the fuel pump. The fitting can be connected by a hinge to the support base, to allow relative movement. A downward-inclined baffle ensures that fuel is drawn from the lower part of the bag interior. The baffle carries rounded extensions to prevent damage to the bag fabric. [2750 words, 10 figures)

Moving band filter In GB 2280857 P A Miller describes an endless filter band. It extends between a lower filtrate-receiving shell and an upper shell, which is movable vertically to clamp a section of the band between the shells during the filtration operation. A periph- eral seal is maintained by feeding com- pressed gas into a space defined by a peripheral groove in the shell and a pair of sealing rings in the opposite face of a second shell, at a pressure exceeding that inside the shells. The shells, band and supporting rolls are enclosed by an outer housing, which is lined with plastics and external recesses which accommodate various me- chanisms, such as the rams which raise and lower the second shell via sliding seals.

Magnetic markers on the band edges enable sensors to adjust a supporting roll, in order to correct lateral deviations of the band during its moving periods between filtration. A scraper which removes cake for the band is automatically withdrawn as the markers or the join in the belt approaches, in order to avoid damage.

During filtration, liquid is fed into the second shell by gas pressure from a pre- filled chamber, and then more gas is fed to the second shell until a maximum pressure is reached. The gas flow is then monitored to detect when the gas breaks through the cake; when this occurs, the cake is washed in sir&, passing the same liquid repeatedly through the cake between a succession of reservoirs. The cake is finally dried by gas before raising the second shell and moving the band. (‘9500 words, 7fi9ures)

la

April 1995 Filtration %I Separation