Dynamic modelling and simulation of a cogeneration system integrated with a salt recrystallization process

The aim of this study is to optimise a Portuguese industrial three integrated process system, by studying the effect of some operational and atmospheric conditions on the system. For this main goal it was built a dynamic model, which includes the cogeneration system, the plate heat exchangers and the salt production unit. The cogeneration system was modelled and analysed in GateCycle 5.34.0.r. and the interface variables were used as input of the dynamic model of the remaining integrated process. This model was developed and exploited through gPROMS 2.3. Some particular issues (start-up, scheduling and atmospheric conditions) were investigated to forecast the performance of the integrated system. The best start-up conditions were established. Several atmospheric conditions were studied and the minimum number of ponds required for each situation was calculated. The scheduling of the evaporation ponds in operation was also investigated to enhance the salt production and to optimise the salt harvesting. The process simulation indicated that it is better to work with the corresponding minimum number of ponds, having a "turbo" pond that receives a larger quantity of heated brine. The efficiency of the cogeneration system (thermal plus electric power divided by natural gas consumption) was approximately 92%. However, the global process efficiency (accounting for energy losses in the evaporation step of the salt production process) was in the range of 70-80%, depending on the atmospheric and operational conditions considered. (c) 2005 Elsevier Ltd. All rights reserved.