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微波加热干燥单宁锗酸的工艺研究
【作者】 苏斌；
【导师】 彭金辉；
【作者基本信息】 昆明理工大学 ， 有色金属冶金， 2009， 硕士
【摘要】 本文介绍了锗的性质与用途。对比了红外加热干燥、燃料加热干燥以及微波加热干燥的特点,体现了微波加热干燥的优越性。论述了微波加热在国内外冶金领域的应用。通过常规电加热干燥、微波加热干燥、微波加热-自然蒸发干燥三种方法对粘结性物料单宁沉锗的脱水过程进行了研究。得到如下结论：(1)在常规电加热干燥中,单宁沉锗的相对脱水率随着干燥温度的增加而增大；随着保温时间的延长而增大；随着物料质量的增加而减少,但是减少的趋势越来越缓慢。得出最佳工艺参数为：干燥温度120℃,保温时间170min,物料重量10g,单宁沉锗的相对脱水率为98.69%。(2)在微波加热干燥中,单宁沉锗的相对脱水率随着干燥温度的增加而增大；随着保温时间的延长而增大；随着物料质量的增加而减少,且这种下降趋势越来越小。条件实验下的最佳工艺参数为：干燥温度为90℃,保温时间为8min,物料重量10g,单宁沉锗的相对脱水率为97.33%。(3)采用微波加热-自然蒸发干燥单宁沉锗这种方法,相对脱水率先随温度的增加而增大,继续升温相对脱水率基本没有变化；在一定时间范围内,相对脱水率随着保温时间的延长而增大；相对脱水率随着物料重量的增加而降低,且降低的趋势趋于平缓。条件实验下的最佳工艺参数为：干燥温度为80℃,保温时间为6min时,物料重量10g,单宁沉锗的相对脱水率为98.73%。(4)对于粘结性物料,微波加热干燥的优势在于：降低了干燥温度,缩短了保温时间。微波加热-自然蒸发干燥的优势表现为：缩短了微波作用在物料上的时间,提高了相对脱水率,节约了能耗。(5)对常规电加热、微波加热-自然蒸发干燥单宁沉锗的实验过程进行了分析,得出不同干燥方式下的动力学指数模型MR=exp(-ktn),为进一步研究单宁沉锗的干燥机理奠定了理论基础。(6)通过采用Design-Expert7软件优化了微波加热干燥、微波加热-自然蒸发干燥的实验结果,得出了两种方法的干燥模型,预测了实验的最佳工艺条件。(7)由常规电加热干燥和微波加热干燥后SEM微观结构图,物料的形态变化可知：微波加热干燥后物料结构的孔隙较多、较大,更疏松,且硬度较低,有利于充分煅烧,可能会提高锗的回收率。由此可见,微波加热-自然蒸发干燥单宁沉锗不仅可以发挥微波加热干燥选择性加热、迅速升温、节约能源的优势,而且能够利用微波加热停止后的余热,使水分进一步的排除。因此,微波加热-自然蒸发干燥单宁沉锗是一种高效、节能、经济可行的的干燥新工艺。
【Abstract】 The properties and the application of germanium is introduced, a comparison of characteristics of infrared dehydration, fuel heating dehydration and microwave heating dehydration is made, the advantage of the microwave heating dehydration is proposed and the application in national and international metallurgy field is discussed. Three methods including conventional electric heating dehydration, microwave heating dehydration and microwave heating-natural evaporation dehydration, are taken to study the relative dehydrationrate of cohesive material-tannins germanium acid。(1)When dehydrated by conventional electric heating, the relative dehydrationrate of tannins germanium acid increases along with the increase of the dehydrated temperature. The relative dehydrationrate increases along with the increase of the holding time. The relative dehydrationrate decreases along with the increases of material weight, but tends to flat. The recommended technological parameters are as follows:the dehydrated temperature is 120℃, the holding time is 170min, the material weight is lOg and the relative dehydrationrate of tannins germanium acid is 98.69%.(2)In microwave heating, the relative dehydrationrate of tannins germanium acid increases along with the increase of the dehydrated temperature. The relative dehydrationrate increases along with the increase of the holding time. The relative dehydrationrate decreases along with the increases of material weight, but tends to mininum. The recommended technological parameters are as follows:the dehydrated temperature is 90℃, the holding time is 8min, the material weight is 10g and the relative dehydrationrate of tannins germanium acid is 97.33%.(3)By microwave heating-natural evaporation, the relative dehydrate-onrate of tannins germanium acid increases along with the increase of the dehydrated temperature. When the temperature reaches a given value, the temperature’s increasing has no obvious effect on relative dehydrationrate. In a given period, the relative dehydrationrate increases with the increase of treating time. The relative dehydrationrate decreases along with the increases of material weight, but tends to flat. The recommended technological parameters are as follows:the dehydrated temperature is 80℃, the holding time is 6min, the material weight is lOg and the relative dehydrationrate of tannins germanium acid is 98.73%.(4) For cohesive material, microwave heating dehydration reduces the temperature for a large scale and shortens the reaction period comparing with the conventional electric heating dehydration. Microwave heating-natural evaporation dehydration shortens the time that microwave takes effect on the material, which saves energy.(5)A kinetic exponential model MR=exp(-ktn)in different dehydrate-ions is developed by analyzing the experimentations tannins germanium acid heated by conventional electricity and microwave heating-natural evaporation dehydration.(6) The experiment results of microwave heating dehydration and microwave heating-natural evaporation dehydration are optimized by adopting the Design-Expert7 software and the development of dehydration models of these two methods.(7) It can be seen from the SEM analysis by comparing conventional electric heating dehydration with microwave heating dehydration and the change of configuration materials that the material processed with the latter method gets much more and much larger structural pores, more loosen and less hardness which makes it easy to calcine and raises the recovery of germanium.It can be concluded that microwave heating-natural evaporation dehyd-ration not only shows its advantages on selectively heating, temperature rising rapidly and energy saving but also utilize the excess heat to eliminate moisture further. Therefore, microwave heating-natural evaporation dehydrating tannins germanium acid is an efficient, energy-saving and economically feasible new dehydration technics.