【作者】 李时民；

【导师】 彭小奇；

【作者基本信息】 中南大学 ， 热能工程， 2011， 硕士

【摘要】 能源是现代社会的血液,金属材料是现代社会的骨骼。由于铝及其合金具有许多优良性能而成为现代社会大量使用的金属材料,铝的强烈需求刺激了氧化铝生产工业的迅猛发展。氧化铝生产工业是冶金工业的重要组成部分,是国民经济的重要基础。其中,蒸发工序是氧化铝生产过程中的重要工序之一,其能耗的高低直接制约了氧化铝生产工业的发展。因此,对氧化铝生产蒸发工序进行用能分析及节能研究具有重要的意义。论文通过对蒸发工序进行热平衡测试,根据测试数据对该工序进行了物料平衡计算与分析,指出蒸发工序存在蒸水能力(139.304t’h-1)不足和吨水汽耗(0.426t-汽/t-H20)高两个问题。为此,论文选用从整体到局部的经济实用且具较强针对性的节能技术路线：首先,对蒸发工序进行系统热分析和系统(?)分析,结果表明：整个工序的热力学完善度仅为0.4682,热效率仅为30.67%,(?)效率仅为15.09%,能量损失严重,用能水平很低,节能潜力巨大。热分析确定出的高耗能环节为冷凝水自蒸发器和Ⅳ效蒸发器,(?)分析不仅确定出冷凝水自蒸发器和Ⅳ效蒸发器为高耗能环节,而且发现了热分析所没能发现的隐性高耗能环节—蒸发器,表明(?)分析是热分析的补充和发展,(?)分析能够比热分析更充分地确定出关键耗能环节和节能潜力,更准确地指出节能方向。其次,分别对冷凝水自蒸发器和蒸发器进行能量分析和(?)分析。冷凝水自蒸发器能量分析结果表明：四个冷凝水自蒸发器的热效率和(?)效率都很低,其能量利用程度低,能量损失较大,能量损失是因饱和冷凝水外排而引起余热资源浪费；利用本文所建立的能量分析模型计算发现：适当提高Ⅳ效蒸发器入口料液的温度,可以有效地降低新蒸汽的消耗和吨水汽耗,为此,本文提出应通过余热利用将冷凝水外排余热用于预热原液。蒸发器火(?)分析结果表明：四效蒸发器的热效率高但(?)效率相对较低,蒸发器表面看似能量损失较小,但其用能极不合理,(?)损失表现为传热过程(?)损失和流动过程(?)损失；利用本文所建立的不可避免传热过程(?)损失优化模型进行分析计算,可获得最优的有效传热温差,通过及时除垢或清除结疤等方法,可有效降低传热过程(?)损失和流动过程(?)损失。更多还原

【Abstract】 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.更多还原