Thermoeconomics of some options of large mechanical vapor-compression units

The performance and the cost of three vapor-compression (VC) seawater disti llation systems of unit capacities 2 to 10 mgd are analyzed within the curr ent distillation technology and its scale control. The results of the analy sis are summarized in a cost-efficiency diagram, increased unit size is ach ieved at the expense of a tolerable decrease in efficiency. The design feat ures of the desired compressors and the models used for cost-performance an alysis are described elsewhere. The trend of the results points to the impo rtance of developing a reliable chemical treatment that controls the scale for boiling seawater at atmospheric pressure. Excluding thr: cost contribut ion of the treatment to production cost of distillate, the development can reduce the current cost of seawater distillation by as much as 30% while in creasing efficiency by about 50%.