Automatic control of continuous chemical processes - esp. phosphate rock decomposition with acid, by measuring amt. of titrant required to neutralise reaction mixt. sample

摘要

Automatic control of a continuous chemical process in which pH measurements are not significant, involves addition of a reactant and continuous removal of a sample stream. The rate of addition of titrant (I) needed to change the sample pH to a particular endpoint is measured; a small change in the amt. of (I) will cause an appreciable change in pH. The flow rate of the (I) stream is interpreted by an electronic analogue comparison device so that the intensity of the current passing to an electrolysis cell in which (I) is produced, is controlled. The rate of (I) is then converted by an analogue calculator-comparison device to adjust the reactant addition rate. Specifically used for (a) wet-process H3PO4 prodn.; (b) decompsn. of phosphate rock with HCl to produce either H3PO4 by solvent extraction or a diCa phosphate. The rates of addition of phosphate rock and H2SO4 or HCl are controlled.