高铝粉煤灰水热法提铝浸出液制备铝酸钠研究

Preparation of sodium aluminate from the leaching solution of high alumina fly ash by hydrothermal method

以母液苛性比和结晶率为考察指标,对高铝粉煤灰水热法浸出液结晶铝酸钠的行为进行了研究。主要考察了Na_(2)O浓度、结晶时间、结晶温度和晶种添加量对铝酸钠结晶的影响。结果表明,铝酸钠溶液中氧化钠浓度的升高和结晶时间的延长,有利于提高铝酸钠结晶率。但升高温度,会导致铝酸钠结晶率小幅下降。其次,研究还发现添加晶种能显著提高铝酸钠的结晶率,但晶种添加量对铝酸钠结晶影响不大。水合铝酸钠结晶工序优化的操作条件为:Na_(2)O浓度600 g/L、结晶温度60℃、晶种添加量20 g/L、结晶时间16 h。在此条件下,铝酸钠结晶率达到66.67%,结晶母液苛性比超过了25,能够满足循环溶出的要求。结晶获得的固相主要是水合铝酸钠,分子式为4NaAlO_(2)·5H_(2)O。

Taking caustic ratio of mother liquor and crystallization rate as indicators,the behavior of crystallization sodium aluminate from the leaching solution of high alumina fly ash was studied.The effects of Na_(2)O concentration,crystallization time,crystallization temperature and seed crystal addition on the crystallization of sodium aluminate were investigated.The results show that increases of sodium oxide concentration and crystallization time are beneficial to the increase of the crystallization rate of sodium aluminate.The sodium aluminate crystallization rate decreases slightly with the increase of temperature.The addition of seed crystals added can significantly improve the sodium aluminate crystallization rate,but the amount of seed has little effect on the crystallization rate.The optimized operating conditions of the hydrated sodium aluminate crystallization process are:Na_(2)O concentration 600g/L,crystallization temperature 60℃,seed addition of 20g/L,crystallization time of 16h.Under the process conditions,the crystallization rate of sodium aluminate reaches 66.67%,and the causticity ratio of the crystallization mother liquor can be increased to more than 25,which can meet the requirements of cyclic dissolution.The solid phase obtained by crystallization is mainly sodium aluminate hydrate,and the molecular formula is 4NaAlO_(2)·5H_(2)O.