Steady State Design of Triple-effect Evaporator
Evaporation is the removal of a volatile solvent as vapor from a solution.
It is commonly used to concentrate solutions. This process is achieved by a single or, as widely used, multiple-effect evaporators in series. Operation of evaporators involves simultaneous heat and mass transfer. Modeling these systems, therefore, results in a set of nonlinear algebraic equations. This paper presents a case study which is applied to a triple-effect evaporator system used to produce 40,000 tons/year of 80% by weight sodium chloride solution from a 40% by weight fresh feed sodium chloride solution. The product is further dried and packed as table salt. Feed forward operation with equal heat transfer areas of the effects is employed. A computer program using FORTRAN language is employed to solve the set of non-linear algebraic equations which involves a trial and error procedure. The convergence of the steady state solution is speeded up by a proper pre-calculation of the initial data required to run the program. The results show that the heat transfer area of each effect, the fresh steam consumption rate, and the steam economy are 24.0 m2, 1762.4 kg/hr, and 2.87, respectively.