Exergy Analysis Of Three-effect Falling-film Evaporation System For Potassium Carbonate

Through the design for three-effect falling-film evaporation system of ordinal flow, the exergy analysis of the evaporation system was carried out. By the same time, the links which losing most exergy was found. The internal losing exergy mainly caused by the difference in temperature of heat conduction. The external losing exergy mainly concentrated in the discharged first-effect condensated water and the steam of the last-effect.On the basis of the exergy analysis, exergy optimization of the evaporation system was carried out. The steam of the last effect was used for preheating the material liquid. Taking the most prifit per year for the target function and using the optimize method of golden section, we can get the optimized area of preheater and output liquid temperature. Compared with the profit of the condensated water using to flash, using the water to preheat the material liquid can bring more profit. Through the optimization, the best area of the preheater and the output liquid temperature also acquired. Taking the lest total internal losing exergy for target function, the distribute of difference in temperature among the three-effect is also acquired.An experimental device for three-effect falling-film evaporation was designed and constructed. The experiments of potassium carbonate solution was finished under different temperature of vapor and different input material liquid volume. The distribution of losing exergy was acquired. The result is that the steam of the last effect and the emission of the first effect water is the main cause of losing exergy.