Filtration System Characterisation

Further a hydrodynamic analysis of the shear forces in the cell is carried out to understand the impact of shear on agglomerates in the cells. 

In essence, the results show that agglomerates larger than 9 fim are prone to break-up. This may explain the presence of smaller aggregates as shown in Chapter 4. 

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In some cases the interaction between the particles and the surrounding fluid is of little significance, although at other times this can have a dominating effect on the behaviour of the system. Thus, in filtration or the flow of fluids through beds of granular particles, the characterisation of the porous mass as a whole is the principal feature, and the resistance to flow is dominated by the size and shape of the free space between the particles. In such situations, the particles are in physical contact with adjoining particles and there is... 

Alkylation of 1. To a mixture of the ester 1 (5 g, 25 mmol) and 6% of Aliquat 336 (715 mg, 1.5 mmol) was added t-BuOK (3.3 g, 25 mmol, 1 equiv.) under magnetic stilling over 15 min alkyl bromide (25 mmol, 1 equiv.) was then added slowly. The flask was left under the experimental conditions indicated in Table 1. Finally, the mixture was diluted with ethyl acetate (50 ml) and filtered on Florisil (10 g). The crude products were analysed by GC and characterised by MS and HNMR. 2-Alkylcyclohexanones. A mixture of lithium bromide (1.73 g, 20 mmol), tetrabutylammonium bromide (323 mg, 1 mmol), water (360 mm, 0.36 mL, 20 mmol) and ethyl l-alkyl-2-oxocyclohexanecarboxylate 2 (10 mmol) was placed in a Pyrex tube. The tube was then introduced into a Maxidigest MX 350 Prolabo microwave reactor fitted with a rotational system. Microwave irradiation was carried out for a suitable power and time (Table 2). An approximate final temperature was measured by introducing a digital thermometer at the end of irradiation. The mixture was cooled to ambient temperature. After elution with ethyl acetate (50 mL) and subsequent filtration on Florisil, organic products were analyzed by GC and finally purified by chromatography on silica gel (pentane-ethyl acetate, 95 5). 

A freshly calcined zeolite catalyst was added to a mixture of 2,3-dimethyl-2-butene (1), acetic anhydride, and chlorobenzene (internal standard). The suspension was stirred at room temperature or heated for a few hours (see Tables for details). The solid was filtered off with suction and rinsed with acetone. The filtrate was analysed by GC on a Pye Unicam Series 104 chromatographic system using a glass coliunn packed with SE-30 stationary phase. A sample of pure 3,3,4-trimethyl-4-penten-2-one (2) was prepared and characterised according to literature indications [ 13] and used for calibration. Yields were determined using the internal standard method. 

In summary, although the MF of coUoids is generally well understood, the literature is somewhat limited in the areas of filtration of colloids much smaller than the membrane pore size, and in systems where aggregation occurs. Systems are, in this regard, often poorly characterised, especially in the presence of humic substances. As shown in Chapter 2 organics stabilise inorganic colloids at sizes much smaller than pores, and their behaviour in MF or surface waters is largely unknown. 

The results confirm the presence of an organic cake, observed in the filtration of surface water. Flux decline is very high considering the small amount of organics deposited, as it would take a considerable amount of time to fill the membrane pores with the small organics. In a surface water system, particles are also important contributors to membrane fouling (as was shown in Figure 5.1). The colloidal systems of interest were described and characterised in Chapter 4. 

Various types of filter are available which are designed for cake formation and sqne ing. The broadest classification is between the batch and continuous units. Batch variable-dtamber filters are all characterised by having a diaphragm fitted intide the filter firame at a predetermined point in the separation, the feed to the system is interrupted and the diaphragm is inflated. A typical filtrate volume-time curve is depicted in Figure 11.34. Typical examples of this type of unit are ... 

One of the expert systems/computational tools for sizing worthwhile highlighting is the filter sizing software - called FILOS - which has been on the market for some years now. It is regularly optimised and it combines the available theoretical basics with a manageable amount of laboratory tests for determination of the key parameters which characterise the filtration process. This system is a very useful additional tool to the conventional lab-scale tests for filter sizing [7]. 

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