Analysis of mechanical vapour compression desalination process

Abstract

Characteristics of the single-effect mechanical vapour-compression (MVC) are analysed as a function of the system design and operating parameters. The analysis focuses on prediction of the specific power consumption for the vapour compressor and the specific heat transfer areas for the evaporator/condenser unit and the plate-type feed preheaters. The mathematical model includes material and energy balance equations as well as a set of correlations for evaluation of the thermophysical properties and the heat transfer coefficients. The correlations are dependent on the transport properties of the flowing streams, i.e. temperature, concentration, and velocity. In addition, the model considers the effects of the boiling point elevation and the pressure losses in the demister. Results show decrease in the specific power consumption and the specific heat transfer area of the evaporator/condenser at higher top brine temperatures. On the other hand, the specific power consumption decreases at low-temperature differences between the boiling brine and steam condensate, while the specific heat transfer area increases. Model predictions are found consistent with the available industrial data. Finally, comparison of the performance of the MVC system and the single-effect thermal vapour compression (TVC) is made as a function of design and operating parameters. Although, the results show comparable performance, choice between the two systems should take into consideration other operational parameters. Copyright © 1999 John Wiley & Sons, Ltd.