Prediction of metals distribution in mill processes, Part 2: Fiber line metals profiles

In a mill system, metals content in process streams depends on metals intake, process configuration, and equipment operating conditions. While fiber flows in all processes are straightforward, filtrate configuration is becoming increasingly complicated because of mill closure. Determining the impact of alternative process and filtrate configurations on mill metals profiles is a challenge because there are many combinations and permutations. Estimating the effects of new technologies on full mill metals management before mill implementation is another important challenge. This paper-part 2 of 3-addresses these challenges by showing that the metals profile in any mill system can be predicted by process simulation, coupled with the multiphase, multi-component metals equilibrium calculations described in Part 1 of this series of papers. A general free-energy minimization engine has been integrated into a commercial process simulator, WinGEMS.The result is a WinGEMS block, named MetEQs, that is able to allocate metals among pulp binding sites, precipitates, and solutes in any stream according to specified equilibrium models. By inserting MetEQs into any existing WinGEMS simulation, we can predict metals profiles in mill processes. In this paper, we have validated simulation results in three mills: a totally chlorine free (TCF) fiber line, an elemental chlorine free (ECF) fiber line and a thermomechanical pulp (TMP) plant.