Energy Utilization Analysis And Research Of Energy Saving For Alumina Evaporation Progress

Energy is the blood of modern society, and metallic material is the skeleton of modern society. Owing to their plenty of excellent performances, aluminum and its alloys have become the widely-used metallic material in modern society. The intensively demand of aluminum has stimulated the rapid development of alumina production industry. Alumina production industry is an important part of the metallurgical industry, and also is an important foundation of the national economy. The evaporation process is one of the key processes of alumina production, whose energy consumption directly restricts the development of the alumina production industry. Therefore, it is important and significant to carry through the energy utilization analysis and research of energy saving for alumina production evaporation.Based on the thermal balance test, the material balance calculation and analysis for evaporation process were carried out in this paper. Two problems of evaporation process were found out, firstly the vaporize ability was not enough relatively and secondly steam consumption per tons of water was high. To this end, this paper selected an economic, practical and strong pertinent route of energy saving from the whole to the local:Firstly, a systematic energy analysis for whole evaporation process was carried out, and the results showed that:the thermodynamic sophistication of the whole evaporation process was about 0.4682, the thermal efficiency was about 30.67%, and the exergy efficiency was about 15.09%, which indicated that energy losses were serious, the energy utilization was very low, and the energy saving potential was great. The key areas of high energy consuming identified by thermal analysis were the condensed water and the 4th effect evaporator. The key areas of energy consumption identified by exergy analysis were not only the condensed water and the 4th effect evaporator, but also the four evaporators, which were indistinct areas of high energy consumption could not be identified by thermal analysis. This clearly reflects that exergy analysis is the supplement and evolution of thermal analysis. Exergy analysis can be more richly in identifying the key areas of energy consuming and the potential of energy saving and more accurate in pointing out the direction of energy saving.Secondly, an energy analysis for condensate water evaporator and an energy analysis for evaporators were carried out respectively. The results of energy analysis for condensate water evaporator showed that:the thermal efficiency and exergy efficiency of four condensed water evaporators were very low, thus energy losses were serious and the level of energy utilization was very low. Energy losses were due to the waste of waste heat by condensed water discharged. The model was established and calculated in this paper as follows:properly increasing the liquid temperature into the 4th effect evaporator can effectively reduce the steam consumption. Therefore, the method of using the recover waste heat to preheat the liquor was proposed. The results of energy analysis for evaporators showed that:the thermal efficiencies of evaporators were high but the exergy efficiencies were low relatively, thus energy losses were low seemingly while the level of energy utilization was very illogical. Energy losses were the exergy losses due to heat transfer and the exergy losses due to flow in the evaporators. After research and analysis, a method of obtaining the optimal temperature difference of heat transferring by establishing inevitable optimization model of the exergy losses due to heat transfer for evaporators was proposed. Also, by cleaning up or cleaning away the scales in time can effectively reduce the exergy losses due to heat transfer and exergy losses due to flow.