Use of Excel Ion Exchange Equilibrium Solver with WinGEMS to Model and Predict NPE Distribution in the MeadWestvaco Evandale, TX Hardwood Bleach Plant, 2003 Fall Technical Conference

An Excel spreadsheet developed to solve the ion-exchange equilibrium in wood pulps has been linked by dynamic data exchange to WinGEMS and used to model the non-process elements in the hardwood bleach plant of the MeadWestvaco Evadale mill. Pulp and filtrate samples were collected from the diffusion washers and final wash press of the bleach plant. A WinGEMS model of the bleach plant was tuned to match the mill data using the sodium and chloride analysis. The spreadsheet was then activated to calculate the bound and free concentrations for H+, Na+, Mg2+, Ca2+, Mn2+, and Ba2+. It adjusted the WinGEMS mass balance by distributing the cations into dissolved solid and suspended solid stream components. Dynamic data exchange enables the Excel spreadsheet to update the nonprocess element (NPE) partition in the WinGEMS model on each iterative cycle. The accuracy in matching estimated NPE concentrations to actual NPE concentrations is used as the test of NPE modeling. The model was then used to predict changes to be expected in a bleach plant rebuild that included replacing the existing D0 and Eo+p stage diffusion washers with presses. This model accurately predicts changes in calcium concentrations throughout the bleach plant.