Cake washing, filtration process equipment

Lime-Sulfuric. Recovery of citric acid by calcium salt precipitation is shown in Figure 3. Although the chemistry is straightforward, the engineering principles, separation techniques, and unit operations employed result in a complex commercial process. The fermentation broth, which has been separated from the insoluble biomass, is treated with a calcium hydroxide (lime) slurry to precipitate calcium citrate. After sufficient reaction time, the calcium citrate slurry is filtered and the filter cake washed free of soluble impurities. The clean calcium citrate cake is reslurried and acidified with sulfuric acid, converting the calcium citrate to soluble citric acid and insoluble calcium sulfate. Both the calcium citrate and calcium sulfate reactions are generally performed in agitated reaction vessels made of 316 stainless steel and filtered on commercially available filtration equipment. 

It is evident that attention paid in the laboratory to the factors affecting particle size distribution will save on capital investments made for separation equipment and downstream process equipment. Specific cake resistance (a) can be determined in the laboratory over the life of a batch, to evaluate if time in the vessel and surrounding piping system is degrading the product s particle size to the point it impedes filtration, washing and subsequent drying. 

In this chapter practical methods of obtaining information for filtration, consolidation, cake washing, gas defiquoring and sedimentation are described. The aim is to illustrate how important data for equipment selection (see Chapter 5), scale-up and process simulafion (see Ch ters 6 and 7) can be measured in the laboratory using either weU established, manually operated apparatus or state-of-the-art, automated apparatus. In some cases details of step-by-step experimental procedures are presented to illustrate best practice. Methods of data analysis are also presented and their use is illustrated through worked examples. 

Staff profile page - the Engineering Faculty at Loughborough. .. Broad Interests and Expertise. Compressible cake filtration Selection, scale-up and process simulation of solid/liquid separation equipment Washing and. .. http //WWW. Iboro. ac. uk/departments/eng/research/staff/html/tarleton. html [More Results From www.lboro.ac.uk]... 

Horizontal Belt Vacuum Filter The final piece of equipment is the horizontal belt filter, in which the nnderflow from the hydroseparator (basically gypsum diluted with process liquor) will be filtered to produce marketable gypsum of -12% moisture. The filter cake will be washed to reduce the amount of dissolved solids and will be conveyed to a prodnct gypsnm storage area. Filtrate from this filter will be disposed of as an aqneons pnrge stream. 

The recovery of whole cells is best explained by the manufacturing procedure for baker s yeast. This process is almost identical to the early stage of protein recovery, except that the final product is the cell instead of the filtrate. After fermentation, the cells are spun out with a centrifuge, washed with water, and recentrifuged to yield a yeast cream with a solids concentration of approximately 18 percent. Cream yeast can be loaded directly into tanker trucks and delivered to customers equipped with an appropriate cream yeast handling system. Alternatively, the yeast cream can be pumped to a plate and frame filter press or an RDVF and dewatered to a cakelike consistency with 30-32 percent yeast solids content. The press cake yeast is crumbled into pieces and packed or spray-dried for dry products. After packaging, the yeast is ready for shipping to retail. 

At the end of the filtration cycle, the dewatered filter cake must be removed from the fabric in preparation for the next cycle. It is important that the cake is effectively discharged at this point since any delays will lead to extended filtration cycle times and therefore reduced process efficiency. This is particularly apt in filter press operations, where manual intervention may be necessary to remove sticky cakes. As a consequence, in addition to longer cycle times, the cost of the operator must also be considered. To some extent this topic may be linked to the cake moisture content because, broadly speaking, wetter cakes will adhere more tenaciously to the cloth. This problem has been partly addressed by the equipment manufacturers with the incorporation of high pressure wash jets and brush cleaning devices, and the filter media producers also continue to pursue the development of fabrics that will facilitate the ultimate goal of perfect, unassisted cake release and hence the achievement of a fully automated operation. 

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