Effect of vapor-bleeding and its configurations on multiple-effect sugarcane juice evaporator performance

Abstract

Improving process performance is always important in any processing industry with the aim of reducing operation costs and improving  the profit.Vapor bleeding may be used in processing industries using multiple-effect evaporatorsto reduces steam consumption and  increases steam economyThe effect of vapor bleeding on separation performance using multiple-effect sugarcane juice evaporator was  analyzed. The effect of increasing percent of vapor bled and determination of the most effective bleeding configuration in terms of  energy efficiency and operating costs. The performance factors assessed were: steam requirement, total heat transfer area (At), steam  economy, total utilized heat (Qt), mass flow rate of bottoms (Bi), percent solids in the bottoms (XBi), and mass flow rate of vapors. To  carry out this work, a five-effect evaporator, forward feed computer model was developed based on mass and energy balance equations,  calibrated by data from steam tables. Simulations incorporating different configurations of vapor bleeding were carried out. Bleeding  from each of the first four effects, E_i , and from a combination of effects (E₁&E₃, E₂&E₄) were carried out. The E₁&E₃ configuration  showed a highest decrease in steam consumption by 23.73% and improved steam economy by 31.28%. Also, vapor bleeding reduced At and X_Bi while increasingBi. This work suggests that to improve energy efficiency during separation of mixtures using evaporators, vapor bleeding should be practiced while maintaining a balance between vapors used to preheat the feed and that used for heating the  subsequent effects.