Multi-phase thermodynamics in process simulation

The feasibility of using multi-phase chemistry as part of the large-scale process simulation was evaluated. Three methods for calculating thermodynamic equilibrium were studied: equilibrium constants, Gibbs' energy minimization and neural networks. These methods were tested in three different process models: pulp suspension in the short circulation of paper machine, boiler water of power plants and pulp suspension in the pulp bleaching line. The Gibbs'ian method appears as the best option for the calculation of equilibrium in multi-phase systems. However, the computational speed required for dynamic problems is yet not sufficient. Additional studies should be made to optimize the present calculation routines and to exploit possibilities of parallel computing in order to fully utilize the multi-phase chemistry approach in process simulation