Optimal design of hybrid MSF/RO desalination plant

This study is conducted & thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Chemical Engineering, College of Engineering, King Saud University, Riyadh, Kingdom of Saudi Arabia, December 2006GThis thesis addressed a very important subject in the desalination field. It is called “hybrid desalination”. Hybrid desalination systems combining both thermal and membrane desalination processes in the same site are currently considered a good economic alternative to either of these two processes when operated individually. The research work carried out to simulate hybrid desalination processes is limited. The main objective of the thesis is to carry out an in-depth and comprehensive simulation study to determine the optimum design configuration of hybrid desalination systems combining synergistically multi-stage flash (MSF) desalination with seawater reverse osmosis (SWRO) process. The impact of combining MSF and SWRO desalination processes in different hybrid configurations on water production cost was explored. Mathematical steady state models which incorporated mass and energy balances equations were combined with economic relationships to predict the unit water production cost as a targeted objective function. The simulation models developed in this work and the results obtained can be as an appropriate guide by designers and operators to optimize the design and operating conditions of hybrid desalination systems. A total of eleven desalination systems were simulated and analyzed. For comparison, the first three desalination arrangements include SWRO and MSF with and without brine recirculation. The fourth and fifth systems considered a simple hybrid configuration where The MSF and SWRO processes are operating in parallel forming simple hybrid arrangements. The remaining six systems include partially or totally integrated SWRO/MSF hybrid desalination systems. For each system mass, energy balance and heat capacity equations together with economic relationships were developed and solved by a using MATLAB computer programs to estimate the water production cost for a specific seawater feed. For each of the eleven examined desalination systems the init water production cost (objective function) was predicted as an output of the MATLAB simulation programs. The desalinated water production cost ranged between 0.6279 $/m3 and 1.025$/m3 .The standalone SWRO and MSF without recirculation represent the two boundaries of the water production cost spectrum. The cost comparison identified the hybrid configuration that results in relatively low water production cost. The study revealed hybridization of SWRO and MSF processes would result in better economic viability than those corresponding to the standalone MSF processes