拜耳法溶出过程降低赤泥碱耗

拜耳法生产氧化铝的过程中,碱耗的主要原因是因为有钠硅渣的生成,碱耗可以用赤泥钠硅比(N/S)表征。通过对钠硅渣和水化石榴石反应行为的热力学分析,发现高饱和系数(x>1)的水化石榴石不易被苛性碱分解,低饱和系数的水化石榴石易被分解而转化为钠硅渣,且钠硅渣也可以转化为水化石榴石,而在Na2CO3溶液中,任何形式的水化石榴石均能被分解生成钠硅渣。实验研究结果表明,不同矿区的铝土矿对赤泥N/S影响不明显,母液中Na2CO3浓度升高、石灰加入量降低、母液中碱浓度降低均会导致赤泥N/S升高,引起碱耗增大。因此,降低母液中Na2CO3浓度、提高石灰添加量将明显有利于赤泥N/S的降低。

Reducing loss of soda in red mud in process of Bayer digestion

In the process of alumina production by Bayer process,the loss of soda is mainly caused by the formation of sodium hydrate alumino-silicate.Based on the thermodynamic analysis of the reaction law between sodium hydrate alumino-silicate and hydrogarnet,it is found that hydrogarnet with more amount of SiO_2(x>1) can not be decomposed by caustic solution easily,while hydrogarnet with x<0.5 can be decomposed into sodium hydrate alumino-silicate,and sodium hydrate alumino-silicate can also be transformed into hydrogarnet with the addition of CaO.But in sodium carbonate solution,any form of hydrogarnet can be decomposed into sodium hydrate alumino-silicate.Experimental results show that bauxite in different areas has little influence on the loss of soda,while more concentration of Na_2CO_3 or lower concentration of Na_2O in spent solution,or worse quality of limes will enhance N/S in red mud,and cause more loss of soda.Therefore,decreasing the concentration of Na_2CO_3 or obtaining better quality of limes will reduce N/S.