【作者】 李皓；

【导师】 黄力群；

【作者基本信息】 湘潭大学 ， 环境工程， 2012， 硕士

【摘要】 为解决钛白粉行业废水处理后的回用问题同时减少外排废水对环境造成的污染，本次研究以经中和除渣后的钛白粉废水为研究对象，提出了两种回用方案，其一是采用CO₂气体预脱钙—碱渣脱钙—CO₂气体反调pH值的新工艺对原废水进行脱钙处理后回用，其二是将原废水直接回用于钛白粉生产中的一洗工序和二洗工序前段，二洗后段工序采用生产中的砂滤水将残留的钙洗涤除去。研究结果表明：采用CO₂气体预脱钙—碱渣脱钙—CO₂气体反调pH值的新工艺对中和除渣后钛白粉废水的脱钙效果较好，其中CO₂气体可以采用废气，相对于纯碱脱钙—硫酸反调pH的传统方法极大地减少了废水处理的成本，且废水盐含量降低，水质有所改善。在添加晶种、伴以机械搅拌的条件下，通入CO₂气体反应25min，CO₂气体的预脱钙率达到35%以上，CO₂气体预脱钙需要满足两个条件：一是废水pH值在11.2以上，二是添加适量晶种。该过程可用拟二级动力学曲线进行拟合，相关系数R²＞0.99，预脱钙废水在机械搅拌条件下，投加碱渣反应5min，钙浓度降低至50mg/L以下。脱钙后的废水和原废水与生产中的二洗出水和砂滤水相比，洗铁速度更快，用水量更少，钛白粉产品产量有所提高，脱钙回用的最佳工艺条件为：一洗洗涤时间75min，水温45℃，二洗洗涤时间100min，水温45℃，洗后钛白粉铁含量低于30mg/Kg，各性能指标均满足要求。原废水一洗代替二洗出水洗铁，在二洗前期代替砂滤水将铁洗至30mg/Kg以下，原废水洗后钙在偏钛酸浆料中积累，二洗后期使用砂滤水洗钙，原废水回用的最佳工艺条件为：一洗洗涤时间75min，水温45℃，二洗废水洗涤时间45min，水温45℃，砂滤水洗涤时间45min，45℃，洗后钛白粉产品中钙含量低于50mg/Kg，产品各性能指标达到要求。砂滤水洗钙过程中钙的去除规律可用溶解—扩散模型进行拟合，相关系数R²＞0.92,具有一定的实用价值。更多还原

【Abstract】 To solve the problem of recycling wastewater after processing from titanium factory andreduce the environment pollution caused by the discharged sewage, this study was aimed tothreat the titanium wastewater after neutralization and deslagging, in order to explore a newmethod to remove the calcium in the sewage and improve the water quality. Based on thenew technology, the water treated and untreated were recycled in the washing process, andthen two different recycling schemes were raised. The routine analysis indicated that thewastewater contained high concentration of calcium, major was calcium sulfate, and theywere oversaturation. The content of heavy metal is less than the washing water in theproduction.The results indicated that the new technology of CO₂pretreatment—sludgedecalcification—CO₂regulate PH value done well in removing the calcium of wastewater.Especially, the CO₂was exhaust gas. Compare with the traditional method of sodiumcarbonate decalcification—sulfuric acid regulate PH value, the new technology tremendouslyreduced the cost of processing wastewater and the salinity, so the water quality was improved.On condition that adding seed crystal and stirring, the CO₂started to react with wastewaterfor25minutes. The percentage of taking off calcium by CO₂was above35%. Moreover, tomake use of CO₂for taking off calcium, there were two necessary conditions. The first, theseed crystal should be added. The second, the PH value was above11.2. The procedure oftaking off calcium by CO₂can be described through pseudo-second-order rate model and therelated coefficient was greater than0.99. On condition that stirring, the calcium concentrationof wastewater after processing by CO₂was below50mg/L when the sludge was added andthe response time was5minutes. Compare to the effect of washing iron, the wastewateruntreated and through decalcification were better. The speed was faster and the waterconsumption was still less, so the output of titanium was even more. The optimum processconditions of recycling water after decalcification were that the time of the first wash was75minutes, the temperature was45℃, the time of the second wash was100minutes and thetemperature was45℃. With these conditions, the iron content of titanium was below30mg/Kg. The wastewater untreated took place of water outflowing from the second wash inthe first wash and water through sand leach in the earlier stage of the second wash. Similarly,the content of iron was below30mg/Kg but calcium accumulated in the titanium.Consequently, the water through sand leach has to be used to wash calcium in the later periodof the second wash. The optimum process conditions of recycling water untreated were thatthe time of the first wash was75minutes, the temperature was45℃, the time of the earlier second wash was75minutes, the temperature was45℃, the time of the later second washwas45minutes and temperature was45℃. After that, the content of calcium was below50mg/Kg. The model of diffusing and dissolving imitated the process of washing calcium bywater through sand leach. The related coefficient was greater than0.92so it is of somepractical value.更多还原