Centrate rate calculation

As an intermediate parameter in the calculations, it is necessary to calculate the centrate rate, Q, by conducting a total and a solids mass balance across the decanter. Total mass balance ... 

Each test run in any test programme requires a number of basic calculations depending upon the source of the data. The formulae required are given in Chapter 4. Which calculations are necessary depend upon what instrumentation is installed on the test facility. For instance, if centrate rate is measured then the feed rate needs to be calculated, and if the feed rate is measured then centrate rate has to be calculated. Both these rates are needed to calculate solids recovery, another of the calculations needed. 

When flocculants are used the polymer dosage level has to be calculated. On special applications unique calculations will need to be performed. In three-phase work the mass balance needed to work out centrate rates is more complex. Oil recoveries and losses will need to be assessed. With three mass balances, solids, oil and water, some imbalance is to be expected due to experimental error, and care is needed to ensure that these errors are not allowed to affect the reliability of the result. 

A detailed reaction scheme has been formulated to account for the laboratory data of Altshuller et al. (12). In Figure 3 the calculated con-centration-time behavior based on this scheme is compared with the experimental data for C3H6, NO, NO2, and O3. More than 150 elementary reactions were initially considered in constructing this model. About 50 of these were eliminated from the scheme because their rate constant and/or the relative concentrations of the reactants are too small to be competitive with other reactions. Another 20 reactions were discarded... 

Figure 6.15 gives the recovery for each feed rate, which is needed to calculate the centrate frequency curve, and thus the cake frequency curve. 

The centrate and cake discharge at approximately the same diameter and therefore it is not necessary to work out the components of power for these two streams separately. Were the discharge diameters to be markedly different, then the rate for each stream would need to be calculated, and equation (4.131) would then need to be used for each stream. 

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