Replenishing acid in cleaning bath during cleaning polycrystalline silicon fragments comprises measuring concentrations of acid and determining average acid consumption

摘要

Replenishing an acid in a cleaning bath during cleaning polycrystalline silicon fragments comprises (a) measuring the concentrations of the acid in the cleaning bath using an analysis device, in a discontinuous manner, and (b) determining the average acid consumption as a slope of a straight line determined by extrapolating over at least two of the measured values, and an automatic control system, where the slope of the extrapolated straight line serves as a control variable.