SIMULATION OF MULTIPLE EFFECT EVAPORATOR OF SUGAR INDUSTRY

Abstract

The present investigation pertains to a theoretical study of simulation of multiple effect evaporator of sugar industry. Basically, it deals with the development of mathematical model of .a triple effect sugar evaportor coupled with mechanical vapour recompression and flashing under forward feed arrangement. It also includes the comparison of steam economy of a triple effect sugar evaporator coupled with mechanical vapour recompression and flashing with the quadruple effect sugar evaportor. Finally it describes the parametric effect of operating variables on the steam economy and end product concentration. Using the basic equations of material balance, energy balance, phase equilibrium and the heat transfer rate, pertinent model of 12 nonlinear simultaneous algebraic equations has been developed for triple effect sugar evaporator coupled with mechanical vapour recompression and flashing under forward feed arrangement. Vapour recycle ratio, 0 is used as a parameter for solving this model. The equations have been linearized by Newton-Raphson method and then solved by L-U decomposition method to determine the values of unknown variables and thereby steam economy and the end product concentration. The model has predicted pertinent quantities of steam consumption, saturation temperature in each effect, concentration, flow rate, and temperature of sugar solution in each effect, for the known values of operating variables viz, feed temperature, feed concentration, feed rate, saturation temperature of steam and the saturation temperature of last effect. The validity of the model for its applicability to industrial situations has been ccmpared by comparing the steam economy of triple effect evaporator coupled with mechanical vapour recompression and flashing with the steam economy of quadruple effect sugar evaporator data, obtained from the thesis . of Agarwal 12J. It has been found that steam economy of triple. effect evaporator coupled. with. mechanical vapour recompression • and flashing, is more when vapour .recycle ratio d is greater than 0.475. Parametric effect . of operating variables on the steam economy has been investigated. Steam economy of a triple effect evaporator coupled with mechanical vapour recompression and flashing has been found to , increase with the increase of feed temperature, feed concentration, feed rate and to decrease with the, increase in saturation temperature of steam and saturation temperature of last effect. As a result of it the range of operating variables for the highest steam economy of the evaporator has been found for various values of vapour recycle ratio, 0. Present analysis has also been extended to investigate the. parametric effect of operating variables on the end product concentration. As a result of it end product concentration has been found to vary directly with feed temperature, saturated temperature of steam, and to vary inversely with feed concentration, feed rate and saturation temperature of last effect. Further, the effect of vapour recycle ratio on end product concentration is insignificant.