The filtration of tallow for use as a constituent in bio-fuel or as a base ingredient for other products can be successfully achieved using a precoat filter. Filtration Services Ltd has many installations in operation, producing tallow of better than 0.15% solids. The contaminants within tallow are, by their very nature, difficult to remove and are prone to blinding any conventional filter medium. In addition, the densities of some of the particles are close to the density of tallow thereby making centrifugation inefficient.
The solution to the problem is to use a sacrificial filter medium – a precoat. This is where a precoat filter (rotary drum filter) excels. Typically, precoat filters achieve residual insoluble solids of between 0.03% and 0.07% which is less than half the permissible solids in filtered tallow.
The precoat filter is coated with a thick layer of highly permeable precoat material, such as wood flour, to form the 75 to 100mm (3 to 4”) deep sacrificial filter medium. Raw tallow is then filtered through the precoat layer and the bulk of the insoluble solids, which are retained on the outer surface of the precoat layer, start to blind off the filter medium. In order to maintain the flow of tallow through the filter it is necessary to ‘peel’ the contaminants from the surface of the precoat in a steady and controlled manner using a sharp discharge blade. In fact, the use of precoat filters to produce clean, filtered liquids is not new; the food, beverage and pharmaceutical industries have been using these systems for decades.
All of the precoat filters supplied by Filtration Services are fitted with the unique automatic knife advance system (AKAS) which provides an extremely high degree of controllability on the knife advance rate. The AKAS is fully synchronous to the drum rotation and can be set to cut in increments of as little as 5 microns (0.0002”) per drum revolution. By fine tuning the operation of the filter, the amount of precoat used per tonne of filtered tallow can be optimised. The AKAS can also be retrofitted onto other manufacturer’s RDVFs. Click here to see our AKAS in action. Filtration through a precoat bed produces high quality, high value tallow. Precoat filters are easy to operate, require minimal supervision, simple to maintain and extremely reliable.
We are pleased to work with the members of the United Kingdom Renderers’ Association to continue developing and improving our specialist filtration.