Filter plates in the food and beverage industries are subjected to a broad range of demands: high levels of TS content, optimal washing outcomes and even-level cake. Klinkau filter plates are being used successfully in many operations. They are often to be found in filtering processes for sugar, starch, beer, whiskey, wine yeast, baking yeast and edible oils. The filter elements are exposed to both high and sub-zero temperatures depending on the type of application. Low-temperature applications require the membrane material to be highly elastic.
Specific examples of applications in the food industry
The sugar industry requires a minimum TS content of 70% at a maximum 0.5% of residual sugar within the filter cake. Such high rates of extraction need to be achieved using wash-water volumes lower than cake volumes. Membranes are subjected to extreme stresses during 24-hour operational periods with 12- to 30-minute cycle times and temperatures of between 80°C and 85°C. Klinkau membrane filter plates in their welded and replaceable versions are being successfully used in the sugar industry.
Membrane filter plates are now also being used for filtering sugar substitutes such as aspartame. This is a specialized application performed at extremely low temperatures. The membrane filter also needs to be made from a highly chemically resistant material as the slurries to be filtered can contain very high levels of hydrochloric acid.
A careful filtration process is used to extract malt from grain residues at high levels of quality and yields. This requires membrane filter elements that deliver highly efficient washing as well as a special water circulation and feed eye configuration. The Klinkau membrane filter elements used here significantly reduce water consumption while also being capable of high-gravity brewing.
The membrane filter plates are subjected to constant temperatures of between 75°C and 80°C during filtration. Resistance to thermal aging is therefor a major factor in the choice of filter material.
The production of palm kernel oil involves a special type of fractionation. The intended product here, in contrast to normal palm oil fractionation, is stearine cake. To achieve the lowest possible iodine count in the stearine, as much oelic acid as possible needs to be squeezed out. Specially designed filter elements capable of squeeze pressures of up to 30 bar are therefore used at operational temperatures of below 10°C. The cake chamber needs to be restricted to 25mm, achieved using a combination of membrane and filter plates. Because the slurry is highly viscose, Klinkau use a specially designed dual feed.
Rice bran oil
Rice bran oil is subjected to a winterization process whereby wax is extracted by cooling to +4°C. The wax particles are then separated from the oil via a filtration process. Standard filtration techniques are based on filter additives as well as filter coating prior to filtration. Using plate and frame systems, oil yields are then low and filter-additive consumption high, thereby placing limits on the profitability of the process.
A specially designed filtering process now makes coating unnecessary. The cooled wax suspension undergoes direct pressurized filtration, and membrane squeezing extracts any oil residues in the pores of the wax cake. This process significantly increases its profitability.
Soy sauce production mainly involves the fermentation of finely crushed and mashed soya. Protein solids are then separated from the extract. Membrane filter plates are ideal here because of the filter cake’s compressibility. Squeeze pressures of more than 10 bar enable cake dewatering in excess of 50%.
To get the extract into a marketable state, polish filtration is then required to isolate very finely spread cloudy substances. Klinkau have developed special filter elements for this process which are set up in a filter tower formation.
Selected yeast strains are cultivated in sugar solutions with 4–5 pH values and at temperatures from +2°C to +5°C depending on the strain. The fast growing and multiplying yeast cells then cause the suspension to become increasingly viscose by up to a 20% TS content. The yeast is then filtered through a filter press with the yeast cake undergoing squeezing. The cake's solid content can then be increased from 30%–38% depending on subsequent processing requirements. TS content settings can be made from the squeeze pressures and times. The design of the membrane plate is crucial because high hygiene levels require the filter elements to undergo frequent cleaning. The plate should therefore have no inaccessible areas for CIP procedures. For this application, Klinkau use copolymere polypropylene which is highly resistant to flexing at low temperatures and provides long service lives for the membrane filter elements.