Enclosed Filters Offer New Promise for Chemically Produced Toner

Chemically produced toner is quickly becoming the technology of choice for the imaging field. The process, however, requires a solid-liquid separation step to recover the toner. The filter cake also needs to be washed very efficiently to a very low residual contaminant level. Early producers of CPT have primarily used horizontal filter presses, but Larox' range of vertical presses are changing the industry. The Larox DS Series filter is a totally enclosed design of vertical automatic pressure filter that utilizes a unique polypropylene plate design to enable filtration of difficult materials in a contained cleanable environment.

Each chamber has a filtrate collector plate on both the upper and lower side, each covered with a section of the endless filter cloth. This produces double sided (DS) filtration. The filter cake forms on both the upper and lower sides of the chamber as the slurry is fed into each filter chamber. After successful filtration, the cake washing and subsequent squeezing and blowing can be configured to provide the optimum product.

The filtration chamber design is suitable for slurries that filter slowly. The design causes the chamber to expand as the filter cake forms. By using both chamber sides to build up the cake, the Larox DS Series reduces the number of chambers required, since thinner cakes build on double the surface area. The horizontal configuration of the filter plates ensures an even cake build-up on both sides.

The Larox DS Series filter is an enclosed design that can be configured for hygienic processes and can also be made totally Gas Tight to operate under an inert nitrogen atmosphere for solvent wetted or flammable processes. For foodstuffs and pharmaceutical intermediates, a full CIP (clean-in-place) system ensures total cleaning of all parts of the filter, including both sides of the filter cloth and the filter plates.

Several different washing options are available with the Larox DS Series including slurry channel washing (via the slurry feed line), corner channel washing (from top of the cake down and across) and counter-flow washing (from the bottom of the cake up and across).

With filters ranging from 1.8 to 160 m2 filtration area in three filter plate sizes; 800 x 800, 1200 x 1200 and 1200 x 2400, there is a Larox DS filter to meet any application.

Separations technology
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