Batch 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. 

By operating cycle. Filtration may be intermittent (batch) or continuous. Batch filters may be operated with constant-pressure driving force, at constant rate, or in cycles that are variable with respect to both pressure and rate. Batch cycle can vary greatly, depending on filter area and sohds loading. 

Scaling Up Test Results The results of small-scale tests are determined as dry weight of sohds or volume of filtrate per unit of area per cycle. This quantity multiplied by the number of cycles per day permits the calculation of either the filter area reqiiired for a stipulated daily capacity or the daily capacity of a specified plant filter. The scaled-up filtration area should be increased by 25 percent as a factor of uncertainty. In the calculation of cycle length, proper account must be made of the downtime of a batch filter. 

Media made from woven or nonwoven fabrics coated with a polymeric film, such as Primapor, made by SCAPA Filtration, and Gore-Tex, made by W. L. Gore and Associates, combine the high retentivity charac teristics of a membrane with the strength and durability of a thick filter cloth. These media are used on both continuous and batch filters where excellent filtrate clarity is required. 

Nutsche Filters A nutsche is one of the simplest batch filters. It is a tank with a false bottom, perforated or porous, which may either support a filter medium or act as the filter medium. The shiny is fed into the filter vessel, and separation occurs by gravity flow, gas pressure, vacuum, or a combination of these forces. The term nutsche comes from the German term for sucking, and vacuum is the common operating mode. 

To apply these equations, let s consider the following example. Determine a constant rate of filtration and the time of operation corresponding to the maximum capacity of a batch filter having the following conditions maximum permissible pressure difference AP = 9x10 N/m sludge viscosity /r = 10 N-s/m filter plate resistance Rf = 56x 10 ° m specific cake resistance r = 3 X 10 m ° x = 0.333 auxiliary time = 600 s maximum permissible cake thickness h = 0.025 m. The solution is as follows ... 

This is the simplest type of batch filter. It consists of a tank with a perforated base, which supports the filter medium. 

The oldest and most commonly used batch filter. Versatile equipment, made in a variety of materials, and capable of handling viscous liquids and cakes with a high specific resistance. 

Batch esterification, 10 478—480 Batch experimental reactor, 21 352 Batch extraction, 10 756 Batch extractor, holdup in, 10 764 Batch fermentation, 10 267 Batch filter cycles, 11 344, 345-346 Batch furnaces, 12 288—289 Batch gasoline blending, 12 413 Batch hydrogenation, 10 811 Batching, ceramics processing, 5 648 Batch injection analysis (BLA) technique, 9 586-587... 

The disadvantages of cyclic operation, attributable to the need to remove the cake from batch filters, have been largely overcome by the development of a wide range of continuous vacuum filters as summarised in Table 7.2 which includes data on the selection for a given duty. This is further detailed in Table 7.3 and is based on the work of G. H. Duffield of Stockdale Engineering and E. Davies of ED ACS Ltd. 

Snated filter, e.g., a glass fiber mat impregnated with a mercurous salt ition and a humectant (29). Although detectabilities well below 100 pptv were obtainable, batch to batch filter performance showed marked variability and impregnated filters could not be stored over a month-long period without loss of performance. We therefore carried out the desired reaction using a diffusion scrubber air was sampled through a porous hydrophobic membrane tube while a dilute mercurous nitrate solution was circulated on the outside of the membrane tube. Mercury liberated by reaction at the gas-liquid interface in the pores is carried by the air stream to the detector. 

For q - 0 or Tb -> 0, Ucond - 0, and at q - <=° or xb -> <=°, Ucond -> u. That is, to increase the filter capacity, filtration time should be increased. However, such an increase is limited by the maximum allowable pressure drop which at constant operating conditions, establishes a maximum cake thickness. Let s consider the following example for the first case in this analysis. We wish to determine the capacity of a batch filter operating at a constant rate. The rate of filtration is q = 0. 1 X 10 3 m3/m2-s and the auxiliary time is 900 s. The solution to this problem is as follows. The filter capacity is characterized by the average conditional filtration rate, q. Values of ucord calculated are shown plotted in Figure 41. As shown, an increase in the amount of filtrate causes a sharp increase in filter capacity initially, with a limiting value of u attained eventually. 

Process data for the same polymer recipe were analyzed for 50 noncon-secutive, sequential batches. As before, the data were preprocessed to remove outliers and sorted to reflect normal operation. The data are sampled at 1-minute intervals during production of each batch. Filtering and normalization of the data is done prior to analysis. The final polymer quality... 

Equations (37) and (38) are directly applicable for use in the design of batch filters. The constants a , s, and VF must be evaluated experimentally, and the general equations can then be applied to conditions of varying A, AP, V, 6, w, and p. One point of caution is necessary, however. In the usual situations, the constants are evaluated experimentally in a laboratory or pilot-plant filter. These constants may be used to scale up to a similar filter with perhaps 100 times the area of the experimental unit. To reduce scale-up errors, the constants should be obtained experimentally with the same slurry mixture, same filter aid, and approximately the same pressure drop as are to be used in the final designed filter. Under these conditions, the values of a and s will apply adequately to the larger unit. Fortunately, VF is usually small enough for changes in its value due to scale-up to have little effect on the final results. 

All necessary storage tanks and receiving tanks The slurry tank complete with agitator Batch filter and meal desolventizer Decanter still Water still... 

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