Synthesis and optimization of Kraft process evaporator plants

Abstract

In this dissertation, a novel methodology based on process superstructures for the synthesis and optimization of multiple-effect evaporation systems is described. The methodology allows for the structure and heat transfer areas of multiple-effect evaporation systems to be simultaneously considered in optimization without having to resort to any previously selected arrangements. The methodology is applied to industrial evaporator case studies where it is necessary to simultaneously size and determine the best way to arrange additional evaporator bodies in an existing system to increase maximum load. An equation-oriented simulator for chemical pulp mill evaporator plants was developed and used in conjunction with differential evolution. A sequential-modular simulator was also developed for comparison. Multiple-effect evaporator plants were used as case studies to highlight the workings of the new method and to assess its viability in realistic systems. Through this methodology, it was possible to determine the optimal arrangement and heat transfer areas for the studied systems.