Effects of four methods on homogeneity of filter cake and operational variables during filtration of mash in beer production

Beer is a widely consumed alcoholic beverage which is mostly produced from barley. The first step of beer production is, turning barley into the malt. Malted grains are ground and they are added into the hot water and heated for mashing process. After mashing process, mash is transferred to the lauter tun for lautering. Lautering is a filtration process in which mash particles were separated from the wort. Mash particles settle and form a filter cake on top of the filter during filtration. At the end of the lautering, wort is transferred into kettle and boiled with hops. After removal of hops, wort is fermented and aged to obtain beer. Filter cake which is formed during lautering process has a heteregeneous structure and fine particles form coating on top of the filter cake. Formation of this layer can cause blocking of the filter and slow down or stops the lautering process. This problem can be solved by transferring the mash into another tank but this causes significant loss of time and extra cost. In this study, the effects of four different methods on the structure of filter cake and filtration variables during filtration of mash in production of beer were investigated. For this purpose, sedimentation at increased concentrations, creating cross flow by stirring of feed, cutting of the filter cake during filtration and addition of fillers were studied as methods. Mass of permeate was measured against time during filtration to determine flux and filtration time. Structure of filter cake obtained from different methods was analyzed by dividing the cake into three layers and determining particle size distribution by sieving method. Homogeneity values were calculated by using particle size data for three layers of filter cake. When filtration variables were compared in terms of flux, filtration time and amount of permeate, cutting and sedimentation methods showed better results compared with the other methods. But cutting method didn't improve the heterogeneous structure of filter cake and stirring method caused blocking of the filter, thus no further analysis of filter cake was performed for these two methods. The effects of usage of filler particles and sedimentation at increased concentration on the structure of filter cake were investigated. In sedimentation method, 32, 49 and 65% mash concentrations were studied. All three layers of filter cake obtained from each mash concentration were found to have similar particle size distribution. While top two layers of filter cake had similar particle size distribution at all concentrations, bottom layer contained more fine particles at 49 and 65% mash concentrations than 32% mash concentration and lesser coarse particles at 65% mash concentration than other concentrations. Calculated homogeneity values also supported these results. However, flow rate of mash was slow and filter cake was hardly obtained in filtration of 65% mash concentration, mash concentration of 49% was selected as the best concentration. Sedimentation method and usage of filler particles were further compared at 49% mash concentration. All three layers of filter cake obtained from the method of usage of filler particles were found to have similar particle size distribution as in sedimentation method. While particle size distributions of three layers of filter cake obtained from two methods were similar in terms of particles with a diameter smaller than 3.55 mm, coarse particles with a diameter greater than 3.55 mm were more in all three layers of filter cake obtained from sedimentation method. As a result, among all studied methods, sedimentation method at 49% mash concentration was found to yield a homogeneous filter cake with appropriate flux during filtration of mash in beer production