Centrate monitoring

Klamerus, K.J. Munger, M.A. Effect of clinical pharmacy services on appropriateness of serum digoxin con- 53. centration monitoring. Am. J. Hosp. Pharm. 1988, 45, 1887-1893. 

With main drive and back-drive systems under control, it remains to control centrate quality. For this, a good centrate monitor is required, capable of assessing the level of suspended solids in the centrate. This has been difficult but there are a few reliable devices now available on the market [20]. The monitor is then coupled via a PID controller to the polymer pump speed control. 

Batch reactors are used primarily to determine rate law parameters for homo, geneous reactions. This determination Ls usually achieved by measuring coa centration as a function of time and then using either the differential, integral, or least squares method of data analysis to determine the reaction order, a, and specific reaction rate, k. If some reaction parameter other than concentration i s monitored, such as pressure, the mole bMance must be rewritten in terms of the measured variable (e.g., pressure). 

Rewrite the design equation in temis of the measured variable. When there is a net increase or decrease in the total number of moles in a gas phase reaction, the reaction order may be determined from experiments performed with a constant-volume batch reactor by monitoring the total pressure as a function of time. The total pressure data should not be convertedto conversion and then analyzed as conversion-time data just because the design equations are written in terms of the variable conversions. Rather, transfoim the design equation to the measured variable, which in this case is pressure. Consequently, we need to express the con-centration in terms cf total pressure and then substitute for the concentration of A in Equation (E5-1.1). 

From measurements of some of the eight process parameters mentioned, it is required to assess the performance of the decanter. It is normal to monitor the feed rate, Qf. and the additive rate. Qp, with flow meters. Periodically, gravimetric analyses are conducted on samples of feed, cake, centrate and, if necessary, the additive. Performance is judged by how high is the solids recovery, R, and how low is the flocculant dose, Pd, when this is used. Recovery is the percentage of solids in the feed that reports to the cake discharge. Flocculant dose, sometime referred to as polymer dose, is the amount of dry polymer used per unit dry solids in the feed, usually expressed as kg/t db (kilograms per tonne dry basis). 

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