论文部分内容阅读
草酸钙的稳定性对于铝酸钠溶液中草酸钠的脱除至关重要。研究了草酸钙在含有碳酸钠的铝酸钠溶液中的反应行为。结果表明,在铝酸钠溶液和碳酸钠溶液中,草酸钙能够分别被转化为铝酸三钙(TCA)和碳酸钙。在铝酸钠溶液中,升高温度、延长反应时间以及增加苛性碱浓度会使得草酸钙的转化率增加,进而发生反苛化反应。此外,含钙化合物的稳定性在含有碳酸钠的铝酸钠溶液中与其在单一的铝酸钠或者碳酸钠溶液中不同。铝酸钠溶液中的碳酸钠会促进草酸钙的转化,因此4CaO·Al_2O_3·CO_2·11H_2O和TCA的形成会导致氧化铝的损失。在铝酸钠溶液中,温度升高会促进碳酸钙、4CaO·Al_2O_3·CO_2·11H_2O和草酸钙转化为TCA。在低温稀铝酸钠溶液中,短停留时间操作条件下,草酸钙可以保持相对稳定。研究的新型石灰苛化去除草酸钠工艺已经应用于国内某氧化铝厂。
The stability of calcium oxalate is crucial for the removal of sodium oxalate in sodium aluminate solution. The reaction behavior of calcium oxalate in sodium aluminate solution containing sodium carbonate was studied. The results show that calcium oxalate can be converted to tricalcium aluminate (TCA) and calcium carbonate respectively in sodium aluminate solution and sodium carbonate solution. In sodium aluminate solution, increasing the temperature, prolonging the reaction time and increasing the concentration of caustic increases the conversion of calcium oxalate and leads to a counter-caustic reaction. In addition, the stability of the calcium-containing compound differs from that in a single sodium aluminate or sodium carbonate solution in a sodium aluminate solution containing sodium carbonate. Sodium carbonate in sodium aluminate solution promotes the conversion of calcium oxalate, so the formation of 4CaO · Al 2 O 3 · CO 2 · 11H 2 O and TCA will lead to the loss of alumina. In sodium aluminate solution, elevated temperature will promote the conversion of calcium carbonate, 4CaO · Al 2 O 3 · CO 2 · 11H 2 O and calcium oxalate to TCA. In low temperature dilute sodium aluminate solution, the short residence time operating conditions, calcium oxalate can be kept relatively stable. Study of the new lime caustic removal of sodium oxalate process has been applied to a domestic alumina plant.