DESIGNING A SEQUENTIAL-MODULAR STEADY-STATE SIMULATOR FOR KRAFT RECOVERY CYCLE EVAPORATIVE SYSTEMS.

A sequential-modular process simulator was developed for simulating Kraft recovery cycle evaporation plants under steadystate conditions. The simulation engine was written in C++ and has been made freely available to the scientific and technical communities. The engine included subroutines for ordering, partitioning, and tearing flowsheets, as well as for converging torn flowsheet streams. In this paper, these core subroutines are described. Evaporator calculations are based on steam table correlations and black liquor enthalpy correlations described in literature. The numerical method used for converging torn streams in this implementation was the well-known Wegstein Method. Five multiple-effect counter-current evaporator scenarios, ranging from 3 to 7 effects, were used to profile the simulator. The simulator was shown to be robust enough to be used for simulating evaporator arrangements that are typically found in the pulp and paper industry. The robustness of convergence found in the tested scenarios suggests that the simulator could be extended to accommodate more complex systems. The simulator converged quickly to all solutions, suggesting that it may be used for performing optimization of evaporative systems. [ABSTRACT FROM AUTHOR]