Mineral scale management Part III, Nonprocess elements in the paper industry

Abstract

Efforts to comply with effluent standards have led to a situation where mills have little leeway in managing trace metals without developing mineral scale deposits. In most cases, the trace metals can be managed with minor process changes and siitable levels of process control. The principal tools available to the mill are pH and good washing in the first chorine dioxide stage washer. In some cases, mills may need to change shower sources on washers or upgrade the Do washer. By determining the chmical equilibrium for critical points in the process and in some cases modeling the chemical eqilibrium-mass balance, it is possible to identify operating conditions that will eliminate mineral scale buildup in nearly all mill situtaitons. This paper provides information on hwo trace metals enter the mill and how pulp ion exchange influences where the metals go in the bleach plant. It also demonstrates how a fundamental chemical analysis of the effect of pH on anion speciation and solubility product on scale formation can be used to troubleshoot and prvent scale problems.

Citation

Rudie, Alan W.; Hart, Peter W. 2006. Mineral scale management Part III, Nonprocess elements in the paper industry. Tappi journal. Vol. 5, no. 8 (Aug. 2006): pages 3-9.