A Rapid Screening Tool to Predict Optimal Feed Flow Sequence of A Multiple

Abstract

A simple mathematical model based on principles of Process Integration (PI) has been developed to screen the optimal feed flow sequence (OFFS) of a multiple effect evaporators (MEE) system which will offer best steam economy. The model assumes fresh feed to be composed of streams of product and different condensate streams. It also takes in to account temperature paths followed by each stream and internal heat exchange between hot and cold parts of a stream along with variable physical properties of steam/vapor and condensates. A septuple effect flat falling film evaporator (SEFFFE) system with steam splitting and feed, product and condensate flashing, used to concentrate weak black liquor, is considered for simulation. The set of linear algebraic equations of the model is solved simultaneously using Gaussian elimination method with partial pivoting. Backward feed flow sequence is found to be the optimum for the system. The results of the present model are also compared with other models and found to agree well as far as selection of OFFS is concerned. Key words: Multiple effect evaporator, Rapid screening tool, Optimal feed flow sequence, Linear model.