The filtration process of mint in water was done by using plate–frame filter that consist of 4 frames at0,4 bar and 0,9 bar pressure. Slurry entered at one end of the assembly of plates and frames. It passed through a channel running lengthwise through one corner of the assembly. Auxiliary channels carried slurry from the main inlet channel into each frame. Here the black pepper particles were deposited on the cloth covered faces of the plates. Liquor passed through the cloth, down grooves or corrugations in the plate faces, and out of the press. Filtration is a kind of separation method which is widely used in food industry. In fruit juice industry, to clarify fruit juice, filtration is applied. Moreover, filtration is applied for clarifying vinegar, beer, wine, brines and sugar syrups. And also refining of edible oils contains filtration process. For example, crude oils contain some impurities such as gums.
These impurities are removed by filtration. Shortly degumming, decolorization and winterization of oils are the applications of filtration in oil industry. In addition during the hydrogenation of oil, nickel is used to speed up the reaction, after reaction, nickel catalyst is removed by filtration There is not so many deviations in the experimental results when considering the normal plate-frame filtration procedures. Similar results were obtained from this experiment when the general constant filtration results are examined. The volume of filtrate was decreased and this caused a positive slope of PQ/V vs. V graph.
In filtration the liquid passes through two resistances in series; that of the cake and that of the filter medium. The filter-medium resistance, which is the only resistance in clarifying filters, is normally important only during the early stages of cake filtration. The cake resistance is zero at the start and increases with time as filtration proceeds (W. McCabe, J. Smith and P. Harriot, 1987, Unit Operation Of Chemical Engineering). In the experiment, the cake resistance of mint increased with time and it reduced the volume of filtrate.
The intercept points of the graphs confirmed the predicted values due to suitable initial flow rates. Since the viscosity of water is not high, the viscosity of fluid was not problem for filtration. After assembly of the press, slurry is admitted from a pump or blow case under a pressure of 3 to 10 atm (G. Brennan et al., 1976, Food Engineering Operations). The applied pressure was low to exercise the industrial filtration procedure when considering this statement. At higher constant pressure the time to remove more filtrate is smaller; this is another result that takes attention.