湿式氧化法去除铝酸钠溶液中有机物的研究

【作者】 张浩；

【导师】 陈文汨；

【作者基本信息】 中南大学 ， 冶金物理化学， 2011， 硕士

【摘要】 铝酸钠溶液中的有机物主要来源于铝土矿以及生产流程中添加的絮凝剂(包括淀粉)、结晶助剂、防泡剂等,这些有机杂质进入溶液并在流程中循环累积,给生产带来负面影响,主要表现为降低氧化铝产量和产品质量,导致设备结疤,而且废气排放,还对环境造成破坏。过去三十年间,人们一直在寻求如何高效经济地去除铝酸钠溶液中有机物,其中很有潜力的就是湿式氧化法,即给铝酸钠溶液通入氧气,有机物在高温高压条件下发生氧化分解,最终形成CO2和水。本文提出用红外碳硫分析仪定量分析铝酸钠溶液中的总有机碳,研究了湿式氧化法和催化湿式氧化法对去除铝酸钠溶液中有机物的影响,并且对有机碳氧化分解过程中具体走向作了初步的研究,考查了草酸钠和碳酸钠的浓度变化。结果将对氧化铝生产提供一定的技术支持和理论依据,主要内容摘要如下：1建立了用红外碳硫分析仪定量铝酸钠溶液中总有机碳的方法,首次提出先将样品用(1+1)的盐酸酸化,赶走无机碳,然后再烘干制得固体样的原则流程。该方法稳定性好,操作方便；2研究了湿式氧化法对去除中州循环母液中有机物的影响,发现湿式氧化法对铝酸钠溶液中有机物具有良好的去除效果,是种很有潜力的有机物去除方法。温度越高越有利于有机物分解,当溶出温度为260℃,氧气分压为1MPa,搅拌速度250r/min,反应60mmin后,有机物的转换率达到64.1%,180min后能够达到79%；3研究了CuO催化氧化法对去除中州循环母液中有机物的影响,发现CuO是良好的催化剂。有CuO存在时,有机物分解得更快且更加彻底,当温度为260℃,氧气分压为1MPa,反应60min后,有机物的转换率达到86.2%,180min后能够达到94.6%；4湿式氧化铝酸钠溶液过程中,有机物分解,部分生成了较难氧化分解的草酸钠,反应初期,草酸钠浓度会逐步升高。当溶出温度为260℃,氧气分压为1MPa,有催化剂CuO存在,反应180min后,草酸钠能够完全被分解,这为草酸钠的去除提供了一个可能的方案。更多还原

【Abstract】 Organic compounds enter the Bayer process liquor from a number of sources other than bauxite, including various chemical additives such as flocculants (including starch), crystal modifiers, and anti-foaming agents. However, the bauxite is the main source of organic compounds in terms of both quantity and complexity. The organic impurities recycled in the liquor has significant implications for all aspects of the Bayer process, including process yield, product quality,scale formation and environmental emission, all of which affect the overall viability of the process. Despite extensive research and development work over three decades, the quest continues for an effective low cost removal technology. One approach that has received considerable interest is wet oxidation. In this method, oxygen is introduced to the liquor under conditions of high temperature and pressure, resulting in the oxidative degradation of the organic compounds present.Organic compounds degrade via complete oxidation to carbon dioxide and water.Quanititation of total organic carbon concentrations in Bayer liquors was coducted by CS-140 High Frequency Infrared Carbon-Sulphur Analyzer for the first time. Wet oxidation/CuO-catalyzed wet oxidation of Zhongzhou spent liquor was investigated in this paper, also concerned the concentations of sodium oxalate, sodium carbonate. Those results may be a technical support and theoretical guidance for alumina production. Main conclusions are drawn as follows:1 Total organic carbon concentrations in Bayer liquors were abtained using CS-140 High Frequency Infrared Carbon-Sulphur Analyzer, which involves first exclude the inorganic carbon by acidification to a pH of 2 or less with 6 M HC1, followed by drying to solid phase. The precision results showed that this method has emerged as a potentially more rapid, cost-effecitive method;2 Wet oxidation of Zhongzhou spent liquor was studied in this paper. Wet oxidation is a promising organics removal process being applied in Bayer process.The higher temperature, the more organic compounds removed. The results suggested that in the reaction conditions of temperature at 260℃, oxygen partial pressure of 1MPa, stirring speed at 250r/min,64.1% removal after 60min and 79% removal after 180min;3 CuO-catalyzed wet oxidation of Zhongzhou spent liquor was studied in this paper. CuO was found to catalyze the wet oxidation of Zhongzhou spent liquor. With the 5g/L of CuO catalyst, using the same reaction temperature, oxygen partial pressure, and stirring speed as wet oxidation,94.6% organic compounds removed after 180 min; and4 Sodium oxalate and carbonate concentrations actually increased in the wet oxidation and CuO-catalyzed wet oxidation tests, but hard-to-oxidise sodium oxalate only can be oxidised when reaction conditions become more tough, such as higher temperature, CuO catalyst.CuO catalyst is also capable of co-oxidizing the hard-to-oxidize compound, sodium oxalate, in a highly alkaline solution. The results suggested that in the reaction conditions of temperature at 260℃, oxygen partial pressure of IMPa,5g/L of CuO, stirring speed at 250r/min, sodium oxlate was complete oxidised.This method privide a appliable way to remove sodium oxalate from Bayer liquor.更多还原