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MEI Online: Solid-Liquid Separation: Latest News: February 5th 2007


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:: Larox DS Series Automatic Pressure Filter Proves its Worth for Fine Particle Size Products where Cake Washing Combined with the Driest Possible Cake are Required

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. Several large orders over the last few months have proven the suitability of the Larox DS for fine particulate products where cake washing is critical and the filter cakes need to be as dry as possible when discharged.

Larox has booked orders in the last 12 months from 6 different clients for 8 Larox DS automatic pressure filters ranging from 7.2 up to 117 m2 filtration area. In each case the major reason for the selection of the equipment was successful filtration and washing of filter cakes averaging below 5 particle size. In one case the application is a bio-pharmaceutical process and the filter will be used on several steps in the process. In another application the product is in the liquid phase and the DS produces high clarity filtrate leading to improved downstream performance and higher yields.

The success of the filter is a result of the design of the filter chamber. 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 ensures double sided (DS) filtration as 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.

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). This ensures the best wash result with the least amount of wash liquid and can be optimized to each product. The most difficult washing requirements can therefore be carried out efficiently at low cost.

The high squeezing pressures used after washing lead to lower residual moistures compared to other filtration processes. When combined with high pressure blowing of air or nitrogen through the cake during the squeezing step, the residual moisture can be reduced even further.

The filtration chamber design is also perfectly suitable for slurries that filter slowly. The fail-safe design effectively causes the chamber to expand as the filter cake forms. By using both chamber sides to build up the cake it reduces the number of chambers required, as thinner cakes build on double the surface area. The horizontal configuration of the filter plates ensures an even cake build-up on both sides and, as a result of this even cake structure the optimum conditions are created for subsequent process steps.

The filter cakes all discharge to the same side of the filter. During discharge the integrated cloth-washing system cleans the filter cloth with high-pressure water preventing the cloth from blinding and ensuring consistent filtration conditions.

The Larox DS Series filter is an enclosed design that can also 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 is a standard feature and ensures total cleaning of all parts of the filter, including both sides of the filter cloth and the filter plates.

Applications to date include white minerals and zeolites, dyestuffs and pigments, intermediate pharmaceuticals, fermentation broths, enzymes, yeasts, foodstuffs and fine & specialty chemicals.

With filters ranging from 1.8 to 160m2 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.




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