On-line estimation of the dissolved zinc concentration during ZnS precipitation in a CSTR

Abstract In this paper a method is presented to estimate the reaction term of zinc sulphide precipitation and the zinc concentration in a CSTR, using the read-out signal of a sulphide selective electrode. The reaction between zinc and sulphide is described by a non-linear model and therefore classical observer theory cannot be applied directly, as this theory was initially developed for linear systems. However, by linear reparametrization of this nonlinear system, the linear observer theory can be applied in an effective way. This is illustrated by a zinc sulphide example using real data.