Cake washing batch filters

The two equipment simulation modules provide calculation sequences for more than 20 types of vacuum and pressure filters, potentially involving combinations of cake formation, compression, gas deliquoring and washing. Batch filters include single and multi-element leaf filters, filter presses and diaphragm and tube presses while continuous filters include the horizontal belt, drum, disc, table and tilting pan filters. The user is able to define filter... 

Optimization of Cycle Times. In batch filters, one of the important decisions is how much time is allocated to the different operations such as filtration, displacement dewatering, cake washing, and cake discharge, which may involve opening of the pressure vessel. Ah. of this has to happen within a cycle time /. which itself is not fixed, though some of the times involved may be defined, such as the cake discharge time. 

In general, pan filters are selected for freely filtering soHds and thick filter cakes. Cake washing can be introduced easily. Most appHcations are in the mining and metallurgical industries for small-scale batch filtration. 

The isolated wet cake after the first filtration was reslurried in a solvent system which dissolved completely the excess Iso and a small amount of Mono. The slurry was filtered and the wet cake washed. This isolated cake after the second filtration contained Mono and Bis, but not Iso. The mother liquors and washes of the second filtration contained all the unreacted Iso. The second filtration mother liquors and washes were concentrated and recycled to the next batch. 

Pilot Plant Extraction - ERRC An outline of the pilot plant extraction steps is shown in Figures 1 and 2. Batches of pollen (5 batches of 45.5 kg each, for a total of 227 kg pollen) were extracted first with deionized water in a 227 L kettle to remove simple sugars. The aqueous slurry was filtered via a Sparkler filter and the filter cake continuously washed with water until the filtrate was clear and colorless. The washed pollen (filter cake) was then freeze-dried, moved back to the extraction kettle and extracted with 114 L of 2-propanol. The slurry was pumped to a Sparkler filter, allowed to soak, and the 2-propanol drained off. The pollen cake was extracted in this manner 7 more times and then it was recycled to the extraction kettle where it was again extracted with 114 L of 2-propanol. After filtration, the pollen was washed twice with 2-propanol and then recycled to the extraction kettle for a final 2-propanol extraction (a total of eleven 2-propanol extractions). The 2-propanol was evaporated in a glass evaporator at <40°C to yield ca. 7.6 L of concentrate... 

Washing is also commonly done by collecting the solids on a filter and then washing the filter cake. This approach, which is often used for crystals and precipitates that may be too small to setde quickly and is often a batch operation, is discussed by Mullin (2001) and Harrison et al. (2QQ3). 

Depending on the type and mode of operation of a batch filter, a cycle may comprise up to two filtration phases followed by a number of compression, gas deliquoring and washing phases, essentially in any order, as well as a cake discharge operation (see also Tarleton and Hancock, 1997 , Tarleton and Wakeman, 1994c, 2005b Wakeman and Tarleton, 1994a,b, 1999). 

As described in Section 6.1, the cycle for a batch filter can comprise one or more cake formation phases followed by any sequential combination of consolidation, displacement washing and gas deliquoring phases. While a complex batch cycle may involve the list of operations shown in Table 6.2, a more typical cycle can be represented by... 

Many of the calculation procedures for cake washing on continuous filters are similar to those previously described for batch filters in Section 6.2.3. Several aspects are different, however, and to help avoid confusion the principal equations are reiterated here. The superficial velocity (u) and pore velocity (v) of wash liquor are related to the intrinsic properties of the cake by... 

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