Mineral scale management. Part II, Fundamental chemistry

Abstract

The mineral scale that deposits in digesters and bleach plants is formed by a chemical precipitation process.As such, it is accurately modeled using the solubility product equilibrium constant. Although solubility product identifies the primary conditions that must be met for a scale problem to exist, the acid-base equilibria of the scaling anions often control where in the process scale will occur. These equilibria are the primary control method to minimize or prevent scale in a bleach plant. Both the acid-base equilibria and solubility product equilibria are influenced by temperature and ionic strength. This paper reviews the chemistry of precipitation and acid-base equilibria. The Gibbs free energy expression is presented as a method to estimate equilibrium constants at temperatures in the bleach plant.The effect of ionic strength on ion activity and its influence on these processes are also discussed.

Citation

Rudie, Alan W.; Hart, Peter W. 2006. Mineral scale management. Part II, Fundamental chemistry. Tappi journal. Vol. 5, no. 7 (2006) pages 17-23.