Patent ID: 7919067
Filing Date: 2011-04-05
Classification: D21C,G05B,Y02P

Abstract:
1. A method for controlling a causticizing process for producing white liquor from green liquor by feeding green liquor (H 2 O, Na 2 CO 3 , and Na 2 S) and lime (CaO) into a slaker to produce hydrated lime (Ca(OH) 2 ) according to the equation caustizing the green liquor by reacting the hydrated lime and sodium carbonate (Na separating the calcium carbonate from the sodium hydroxide, the method comprising controlling the causticizing process by: measuring the density of the green liquor being fed to the slaker; controlling the density of the green liquor being fed to the slaker towards a set value with a density controller wherein green liquor density is controlled on the basis of a total titratable alkali by applying the following equation: D=(TTA+os)/kk, where D is the green liquor density; TTA is the total titratable alkali of the green liquor; os is an offset; and kk is a coefficient, wherein the coefficient is a constant angular coefficient having a value selected from between 0.9 and 1.4 when the unit used for expressing the TTA and the density is the same, the offset being determined on the basis of the model; and, specifying the set value by: updating the model by using the measurement result of the density and the measurement result of the total titratable alkali.