Estimation of the Gibbs Free Energy for Calcium Aluminate Sulphate Hydrates Using Iterative Least Squares Regression Method

The iterative least squares method was used for the estimation of the Gibbs free energy △G of calcium aluminate sulphate hydrates the lime desulfurization product in alumina production. By means of the tree diagram theory, the optimal selection of exponential power Xi in the regression equation is realized. The recursive least square method was used to solve the regression equation, and a regression method for estimating the Gibbs free energy of calcium aluminate sulphate hydrates was obtained. The Gibbs free energies of two kinds of calcium aluminate sulphate hydrates at 343K were estimated by this method. The experimental results were consistent with the estimated Gibbs free energies. It shows that the estimated method is correct and the result is reliable. The Gibbs free energy of calcium aluminate sulphate hydrates at any temperature can be estimated by this means. The study will provide theoretical and experimental basis for the lime desulfurization and synthesis of calcium aluminate sulphate hydrates by process of alumina production. (paper)