Simulation of stability and dynamics of multistage flash desalination

gPROMS software was used to study the dynamics of a multistage flash desalination brine circulation system (MSF-BR) as a function of major operating parameters. Most of the previous studies focused on MSF-BR dynamic model development however; it gave very little information on dynamic response of the system to the most significant process independent parameters. The present model was first validated against available industrial data of different plants. System dynamics were obtained upon increasing/decreasing several of the operating parameters over a range of +/- 15%. Results show that increase/decrease of the cooling seawater flow rate have limited effect on the system dynamics. Increasing/decreasing the brine recycle flow had more sizeable effects on the system performance. Therefore, it was not possible to operate the system below 7% decrease of the design value. The most sensitive system response was obtained as function of the heating steam temperature. As a result, increase/decrease of this parameter was limited to 2% and 3%, respectively. The system seizes to operate because of the following: increase in the brine level above the design limits (approximately 0.5 m below the demister), decrease in brine level below gate height (blow through phenomena), decrease in the production capacity below the minimum design value. (C) 2011 Elsevier B.V. All rights reserved.