赤泥的脱碱及钠硅肥化研究

Study on Application Process of Dealkalization of Red Mud

为解决拜耳法赤泥附碱带来的碱污染环境问题,从两种赤泥脱碱工艺:加入脱碱剂(CaO)的常压石灰脱碱法和加入草酸的酸浸脱碱法,以及赤泥附碱钠硅肥化应用路线进行研究,充分利用赤泥附碱加入气相法白炭黑进行快速反应形成钠硅肥,并以赤泥为载体得到具有土壤改良和增效的硅肥产品。得到的最佳实验条件分别为:在常压石灰脱碱法中,液固比(L/S)为4、反应温度85℃、反应时间3.5 h、CaO/Na_(2)O摩尔比为4时,Na_(2)O可由原赤泥中的6.29%降到4.31%;在酸浸脱碱法中,液固比(L/S)为4、反应温度80℃、反应时间40 min、H_(2)C_(2) O_(4)/Na_(2)O摩尔比为2的条件下,Na_(2)O可由原赤泥中的6.29%降到2.53%;赤泥钠硅肥化研究中,与游离氧化钠等量的气相法白炭黑用量是最佳的用量,使之快速反应形成硅酸钠,以赤泥为载体的硅酸钠是良好的钠硅肥。通过对比发现,对拜耳法赤泥脱碱来讲,加入草酸的酸浸脱碱法效果更好;赤泥钠硅肥化研究中,与游离氧化钠等量的气相法白炭黑用量是最佳的用量,可更好地应用于土壤化。

In order to solve the problem of alkali pollution caused by alkali in red mud of Bayer process.In this paper,two kinds of red mud dealkalization processes were studied:atmospheric pressure lime dealkalization with CaO,acid leaching dealkalization with oxalic acid,and application route of red mud with sodium silicon fertilizer.Red mud with sodium silicon fertilizer was formed by rapid reaction of red mud with alkali and fumed silica,and red mud was used as carrier to obtain silicon fertilizer products with soil improvement and efficiency.The optimum experimental conditions are as follows:in the atmospheric lime dealkalization process,when the liquid-solid ratio(L/s)is 4,the reaction temperature is 85℃,the reaction time is 3.5 h,and the CaO/Na_(2)O molar ratio is 4,Na_(2)O can be reduced from 6.29%in the original red mud to 4.31%;in the acid leaching dealkalization process,the liquid-solid ratio(L/s)is 4,the reaction temperature is 80℃,the reaction time is 40 min,When the mole ratio of H_(2)C_(2) O_(4)/Na_(2)O is 2,Na_(2)O can be reduced from 6.29%in the original red mud to 2.53%.In the study of sodium silicon fertilizer of red mud,the amount of fumed silica with the same amount as free sodium oxide is the best amount to make it react quickly to form sodium silicate.Sodium silicate with red mud as carrier is a good sodium silicon fertilizer.Through comparison,it is found that the acid leaching method with oxalic acid is better for Bayer red mud dealkalization;in the study of red mud sodium silicon fertilizer,the amount of fumed silica with the same amount as free sodium oxide is the best amount,which can be better applied to soil treatment.