Simulation of thermal desalination processes

Different flow sheets for thermal desalination processes were simulated using the computer program Evapolund. This general software is modular in structure and includes a number of modules describing different components in an evaporation process such as evaporators, different types of heat exchangers, condensers, flash drums, compressors, steam jet ejectors, etc. The program includes a comprehensive database for the physical properties of seawater as well as other liquors, and a library containing correlations for the heat transfer coefficient of different heat transfer surfaces and flow regimes. Designed to be very flexible, the program can be used as an excellent tool for the design and evaluation of all types of thermal desalination processes. Account is made to different thermodynamic losses in the process such as boiling point elevation, non-equilibrium allowance inside the evaporators and flashing drums, temperature drops due to pressure drops in demisters, transmission lines, and condensers. The user can easily construct the flow sheet of the process and provide a minimum of input data, depending on the calculation case at hand. Simulation results can be displayed either graphically, or converted as text file, or in any other form chosen by the user and can be studied either for the whole plant such as temperature, pressure and concentration profiles, or for a particular piece of equipment in the plant. The paper gives simulation results of four thermal desalination processes to demonstrate the capabilities of the program.