Total Gravimetric Efficiency

The total, or overall efficiency E, can also be calculated from gravimetric analyses of particle size distributions of the solids in all the streams, because the mass balance may also be referred to any given fraction of particles of the 

Diagram of mass balance in a separator M mass flow rate of solids in the feed, M mass flow rate of separated solids, M, mass flow rate of nonseparated solids, F(x) cumulative percentage oversize of feed solids, F (x) cumulative percentage oversize of separated solids, F,(a ) cumulative percentage oversize of nonseparated solids, Q. volumetric flow rate of feed suspension, U volumetric flow rate of underflow suspension, O volumetric flow rate of overflow suspension. 

A disadvantage of this way of expressing efficiency is due to the fact that errors in measuring particle size distributions are usually greater than those involved in measuring mass flow rates. 

Rietema, 1961) but, possibly, the most widely employed is that known as the reduced efficiency (Kelsall, 1966) defined by 

Equation 10.17 satisfies the basic requirements for a definition of efficiency as it takes the extreme values of zero for null separation and unity for complete separation. It is important to note that the reduced efficiency is equivalent to the clarification number sometimes employed in liquid filtration (Purchas, 1971). 

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The three efficiency definitions quoted in this section suffer from the same disadvantage as for the total gravimetric efficiency in section 3.2.1 because their values for any specific equipment depend on the size distribution of the feed solids and they are therefore unsuitable as a general criterion of efficiency. This is, of course, unless they could be used in a differential form defined in the same way but for different particle sizes in turn only Newton efficiency can be rearranged for that purpose. ... 

Gravimetric efficiency The efficiency of a dust collector to remove a given weight of particulate matter related to the total weight present in the air stream. 

The total lipid content of a sample can be assessed gravimetrically if the lipid is first extracted and then completely dried until a constant weight is recorded. For accurate results, the whole procedure must be designed to minimize the loss of lipids at every stage. This includes using highly efficient extraction and purification techniques under appropriate analytical conditions. 

The extracts of biological samples usually contain high concentration of lipids which must be removed before the analysis. Particularly if GC is used in the analysis, efficient removal of lipids is crucial. As the concentrations of many liphophilic FRs are related to the amount of lipids, the lipid content is often measured gravimetrically prior to the cleanup, or determined separately by a total lipid determination. Lipids can be removed by destructive or nondestructive methods. For serum or plasma samples, the lipid determination can be conveniently done on separate aliquots by enzymatic tests. 

Determine gravimetrically the total efficiency of the separation process. 

The experimental grade efficiency given in Figure 7.3 was evaluated from size distributions of the feed and the overflow suspensions (measured by the Ladal X-ray Centrifugal Sedimentometer ), and from the total efficiency obtained by simple gravimetric concentration measmements (see chapter 3, Efficiency of Separation for the method). Figure 7.3 also gives the predicted curve from equation 7.9 (K = 1.2 x 10 m s , X2 = 30.87 s) which in this case becomes... 

The electrical charge of emulsion droplets was determined via zeta-potential measurement by electrophoretic light scattering. The oil droplet size of the emulsions was analysed by static light scattering after dilution of the emulsion to the required optical density or, in the case of spray-dried particles, after dissolution of an aliquot of the microcapsules. Microencapsulation efficiency was calculated from total oil content in the formulation and the gravimetric determination of the oil extracted from the microcapsules with petrol ether [62]. 

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