Fixed filter area

Cake thickness per chamber (mm) Total filtration area (m ) Total cycle time (h)+ Nominal solids production rate (te h )  

The complexity of interacting variables is fiirther emphasised by the summary data in Table 6.17. While both the mass of solids processed per batch and the cycle time increase sequentially with formed cake thickness, for the chosen simulation conditions the nominal solids production rate, which is the ratio of these two parameters, passes through a minimum for a filter cycle with cakes initially formed at 30 mm thickness. For cakes formed at the maximum 40 mm thickness the durations of the filtration, compression and gas deliquoring phases are longer, however, these adverse effects are positively counteracted by the greater amount of solids processed per batch which results in the observed improvement in solids production rate. However, higher production rates are obtained when thinner cakes are processed which reinforces the findings presented in Section 6.5.1. 

By repeated use of simulations for a given cycle configuration it is possible to identify the optimum cake thickness to be formed during the overall filtration process. The optimum is application specific and a compromise between the efficiency of cycle operations and the overall economics and time scale of the filter cycle operation. It is clear that the effects of other process parameters on filter performance can also be readily assessed using simulations. 

The methods described in this chapter show how calculations can be performed for batch filters in a way that takes some account of physical properties and operating conditions. The models employed are based on fundamental theories and practical results of varying complexity, all of which are sufficiently well developed to facilitate filter design and optimisation. The simulations, which make use of the Filter Design Software described in Chapter 5, show how detailed calculation procedures can be implemented to investigate what if questions as well as the general influence of process variables on filter cycle performance. 

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Table 6.17 Effects of formed cake thickness on filter size and productivity for a fixed filter area.

E20 0.009 E8 AflHtraiy multiplyer of filter area used to fix time increment during solution... 

Plugging value n. In the manufacture of acetate fibers, a measure of filterability. It is the weight of solids in an acetate dope that can be passed through a fixed area of filter before the filter becomes plugged. It is expressed as weight of solids per square unit of filter area, e.g., g/crn. 

Biofilters—Processes in which contaminants are biodegraded in a fixed-film bioreactor, typically consisting of a bed of high surface area filter media, such as GAC, that acts as a support matrix for a thin film consisting of microbes that are acclimated to the biodegradation of MTBE or other contaminants. 

Table 15.5 shows the factors that influence the prioritization of hits by medicinal chemists. Three factors (molecular weight, CLOGP, and selectivity) appear on both sides of the table, as both more important and less important factors in the prioritization. At first, this appears contradictory but in fact it reflects the different schools of thought mentioned above, where some chemists use these factors to filter the hits, while others view problems in these areas as something that can be fixed at a later time. In our experience, most chemists do filter out compounds with extreme values of molecular weight and hydrophobicity. 

All types of catalytic reactors with the catalyst in a fixed bed have some common drawbacks, which are characteristic of stationary beds (Mukhlyonov et al., 1979). First, only comparatively large-grain catalysts, not less that 4 mm in diameter, can be used in a filtering bed, since smaller particles cause increased pressure drop. Second, the area of the inner surface of large particles is utilized poorly and this results in a decrease in the utilization (capacity) of the catalyst. Moreover, the particles of a stationary bed tend to sinter and cake, which results in an increased pressure drop, uneven distribution of the gas, and lower catalyst activity. Finally, porous catalyst pellets exhibit low heat conductivity and as a result the rate of heat transfer from the bed to the heat exchanger surface is very low. Intensive heat removal and a uniform temperature distribution over the cross-section of a stationary bed cannot, therefore, be achieved. The poor conditions of heat transfer within... 

The conditions (6.3.5a,b) merely state that at the outer edges of the filter the electrolyte concentrations are assumed fixed equal to the bulk concentrations in the vessels I and II. Conditions (6.3.5c,d) fix the electric potential and the pressure at the left I edge of the filter at zero reference level. Condition (6.3.5e) is just a combination of (6.1.1), (6.1.2) of 6.1, N is the average number of pores per unit cross-sectional area of the filter. 

Albino rats of the CF strain were kept on a diet containing 4% salt (sodium chloride) for 7 days. They were anaesthetized and fixed on a stereotaxic table. A glass coated silver microelectrode (tip 3.5 pm in diam, resistance 1.5 - 2.5 MG) was inserted into the lateral hypothalamic area and connected through a head-stage, a pre-amplifier and a filter to an oscilloscope. After recording the neuronal activity by a two-channel recorder for 5 min, Natrum mur 30 (Natrum muriaticum 30) and Natrum... 

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