In November 1996 the QAL refinery changed bauxite feed composition, which led to a rapid and significant decrease in causticity in the plant. The flow-on impacts on precipitation yield and product quality were higher than predicted from available literature.
This paper outlines the observed changes in the operation of the plant. The paper details laboratory data exploring the impact of liquor causticity. A significant direct impact of causticity on yield was observed. Additional secondary effects were also explored.
The combination of primary and secondary effects was sufficient to account for the observed yield loss in the operating plant. Simple process modifications have been developed to allow future processing of low silica bauxite without impacting plant productivity.