Sweetland pressure filter

Figure 14-7. Sweetland pressure filter. (Courtesy of GL V/Dorr-Oliver.)...

Equipment type (A) filter press (B> leaf pressure filters, such as Kelly, Sweetland, etc. (C) continuous vacuum filter (D) batch rotary filter (E) continuous rotary filter. 

Filtration is the most straightforward, probably the oldest form of sugar liquor clarification process. Filtration is effected with plate and frame pressure-filters or some type of leaf pressure-filter such as Sweetland filters with stationary suspended circular leaves covered on both sides with filter cloth. A filter aid of some sort (diatomaceous earth, paper pulp, or kieselghur) is essential to the operation. The precipitated calcium carbonate serves as a filter aid in the carbonation process. The liquor is mixed with the filter aid and forced under pump pressure through the fabric, which retains the cake and allows the clear liquor to flow through. The retained sugar in the cake can be washed out with hot water. Filtration is no longer used as the sole means of clarification. The process is used for further clarification of the liquor from a carbonation or phosphatation process. 

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