Larox DS and PF Filters Meet all the Needs for Successfully Processing Chemically Produced Toner

With the move to Chemically Produced Toner (CPT) now taking firm hold in the imaging field, Larox has proven to have the winning equipment for the separation and washing step with their DS and C Series line of automatic filter presses.

Chemically produced toner is fast becoming the technology of choice in the imaging field as it produces a more controlled particle shape and size at lower cost by using less energy while producing less waste than conventional processing. The process does however require a solid-liquid separation step to recover the toner and at the same time the filter cake needs to be washed very efficiently to a very low residual contaminant level. Early producers of CPT have concentrated on using horizontal filter presses, but the latest installations are now using the Larox range of vertical presses for a number of reasons.

Both the Larox C Series and DS Series filters can be used for the CPT isolation process, but the Larox DS filter especially offers considerable advantage over all other filter types.

These advantages include:
• Totally enclosed operation – the filters can even be made gas-tight and operated under an inert atmosphere if needed.
• Multi-step washing – the DS offers up to 3 alternative wash paths guaranteeing the most effective cake washing.
• The filter cake is kept under pressure while washing occurs, eliminating the risk of cake cracking, which leads to poor washing.
• This results in highly efficient dynamic solids washing with wash ratios less than 30 m3/ton compared to filter presses using as much as 120 m3/ton or more.
• Conductivities in the filter cake down to ~ 6 µS can be achieved.
• Less waste water treatment is required as much less wash is used.
• 70% or better dry solids at the discharge form the filter.
• Very low solids losses of < 1000 ppm.
• Fully automatic clean-in-place (CIP) both internally inside the filter chamber and externally throughout the housing means one unit can easily handle 4 – 6 colours.
• 100% automatic operation including cake discharge and cloth cleaning during every discharge cycle.
• Filtrations areas available up to 160 m2

Magenta filter cake with slurry feed and combined mother liquor and wash filtrate

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 produces 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.

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.

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.

Larox is committed to helping its clients meet the following goals
– Reduced lifetime production costs – especially energy based costs
– Improved product quality, value and consistency
– Improved safety, health and environmental performance
– Improved yield and productivity

The Larox range of pressure filters is fully supported by the Larox Service group, the most comprehensive and experienced network in the industry, covering the world with operations in over 40 countries and providing reliable support throughout the entire lifecycle of the product – "Performance for Life".

For more information please contact:

Larox Corporation
P.O. Box 29
53101, Lappeenranta, Finland
Phone +358 207 687 425
Fax +358 207 687 277
E-mail [email protected]