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The Upper Chamber is the Glove Box. The top of the chamber incorporates a Viewing Window of clear laminated glass. This allows the Operator to see into the Upper Chamber to control the feed and filtration process, and to manipulate the filter cake using the fitted Glove . The Product Chute is positioned to enable the Operator to scoop up the cake and deliver it to a receiving vessel. The side wall of the Upper Chamber incorporates an insulated Jacket . Heating/cooling during filtration and subsequent drying may be aided by circulating a heat transfer fluid through this jacket. Opening or closing the filter requires two Operators – or small lifting tackle – to lift the Upper Chamber. Otherwise, the filter requires only one Operator. Preparation for Filtration The most commonly used media is a relatively lightweight (polyester) top cloth combined with a heavier (cotton) backing cloth. With the Upper Chamber removed, the position of the two O-ring Body Seals can first be checked. The outer ring provides the liquid and vacuum tight seal between the two chambers. The inner ring prevents escape of the solids. The filter media is installed over the Filter Plate, which has 10mm perforations and lies flush with the flange of this Lower Chamber. A Teflon packaging – Filter Cloth Retainer – may be fitted in the groove between the O-rings to hold the cloths in position – there are no screws for fixing bolts within the filter. A long sleeved Dry Box Glove is fitted to the Glove Port and secured using a clamp ring. A scoop of appropriate material for the substances being processed and the filter finish may be placed inside the filter. The Upper Chamber is lifted back into position and the filter secured closed using the four Swing Bolts. A Sanitary Fitting Cap may be used to close off the Product Chute and the inertisation media - typically nitrogen – is admitted to the filter by Nozzle ‘D’ for a period prior to commencing filtrations. The assembled filter, mounted on Casters can easily be moved into position for filtration. A receiving container is attached to the Product Chute. For example a flexible plastic sack, supported in a shipping drum, may be taped to seal off the chute. The Filtration Process There are four flanged process connections in the top of the filter and three flanged process connections to the Lower Chamber. (Nozzles that are not in use must be closed off with valves or blank caps for flanges.) Nozzle ‘A’ is used to exhaust the filter to the facility’s vent system. The Operator should observe the pressure in the Glove to guide in maintaining a small positive pressure of nitrogen in the filter throughout the process. Slurry is admitted via Nozzle ‘B’ to about ¾” below Product Chute. Filtrate is extracted from the base of the Lower Chamber via Nozzle ‘G’. (To avoid any electrical requirement in the area, a pneumatically operated variable speed diaphragm pump is typically employed.) Periodically the Operator should admit more slurry to the filter. During this phase of operation, the filtrate extraction will maintain vacuum conditions in the Lower Chamber. If the filtration requires other than ambient temperature, an appropriate heat transfer fluid is supplied to the jacket via nozzles ‘J’ and ‘K’. If the process scheme requires the filter cake to be washed, solvent may be admitted through the Wash Inlet Nozzle ‘C’. The Operator may manipulate the cake using the Glove and Scoop to assist in reslurrying the solids or to manipulate the cake to ensure effective drainage. As the end of the filtration cycle is reached, vacuum may be applied via Nozzle ‘E’, just below the Filter Plate, to suck the maximum amount of liquid out of the cake. As necessary, the nitrogen flow via Nozzle ‘D’ must be increased to maintain the small positive pressure in the Upper Chamber. Drying If the positive flow of nitrogen, or other blanket media, is now applied through Nozzle ‘F’, just below the Filter Plate, drying of the cake can be accomplished in the filter. Connections to the Upper Chamber, other than the Vent Nozzle ‘A’, should now be closed. The Jacket temperature should be increased to the maximum – within the filter’s range – which can be tolerated by the product. Periodically the Operator may manipulate the cake to ensure exposure of all moist cake to the drying gas. Discharge of Filter Cake The Operator uses the Glove and Scoop to discharge the filter cake down the Product Chute into the receiving container. When completed, with the flow of nitrogen still maintaining a positive pressure, the container may be sealed off and disconnected from the filter. Cleaning After use, appropriate solvents may be admitted through the Wash Inlet Nozzle ‘C’ to wash out the filter. (A frequently selected option is a C.I.P. Spray Ball Assembly.) The Upper Chamber is now lifted off to allow cleaning, inspection and cloth replacement. The Glove and Scoop should remain installed as part of the filter for cleaning prior to the next operation |
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