Precoat filtration with filter aids

Among the commonly used filter aids, diatomaceous earth is especially versatile and efficient. These fossilized skeletons of diatoms (single-celled algae) also known as kieselguhr offer benefits such as chemical inertness, a large surface area of up to 20 m² per gram and highest possible purity.

The most important manufacturer of diatomaceous earth filter aids with the largest and purest deposits of diatomaceous earth in the world is the Celite Corp. in Lompoc, California. Other Celite deposits are located in the US state of Washington as well as in France, Spain, Mexico, Chile and China. Celite diatomaceous earth filter aids are prepared from especially high-grade diatomaceous earth deposits. 

The selection of a suitable Celite filter aid depends on which liquid is to be filtered and what requirements are placed on the result of the filtration process. Diatomaceous earth filter aids permit optimum clarification even for slimy colloidal turbidities smaller than 0.1 µ. In these applications they achieve highest possible throughputs while ensuring maximum purity and chemical inertness. The product to be filtered does not undergo any deterioration in terms of taste, odour or chemical composition, which, especially in the case of beer or fruit juice, is a crucial factor. The constant quality of the Celite filter aids ensures this.

Celite Cynergy^® is a beer-stabilising diatomaceous earth which, in addition to the usual filtration properties of a medium-fine diatomaceous earth, has additional protein stabilising properties due to targeted surface modification. Like a silica gel, Celite Cynergy^® acts adsorptively to remove selective proteins and thus improves the colloidal stability of the beer. In terms of quantity, Celite Cynergy^® replaces the usual amount of silica gel as well as proportionally the normal diatomaceous earth dosage. Celite Cynergy^® is added to the beer immediately before the filter via the diatomaceous earth dosage vessel or a separate dosage unit for stabilising agents. A contact time is not required.

Higher permeability

Very fine diatomaceous gel particles block parts of the diatomaceous earth pores during filtration. The blocked diatomaceous earth pores no longer actively participate in the filtration and have a negative effect on the pressure curve. When using Celite Cynergy^®, the negative effect of partially blocked diatomaceous earth pores is eliminated.

In contrast to Celite diatomaceous earth filter aids, which consist of almost pure silicic acid, Harborlite perlite filter aids are produced from volcanic obsidian rock by thermal expansion. Chemically, this is aluminium silicate which is almost as inert as silicic acid. 

In terms of their structure, Harborlite perlite filter aids correspond to irregular fragments of spheres which do not have the same porosity as the intricate skeletons of the diatoms. Consequently, Harborlite perlite filter aids cannot be expected to produce the same degree of clarification with the same throughput as Celite diatomaceous filter aids. The benefits lie quite clearly in their cost-effectiveness: for instance, Harborlite perlite filter aids are more economical in the clarification of apple juice concentrate and are also free of cristobalite.

In three European plants, Celite Corp produces high-quality perlite grades using state-of-the-art processing methods that usefully supplement the diatomaceous earth range of filter aids.