高铝粉煤灰拜耳法溶出渣碱回收

Alkali Recovery from the Bayer Leaching Slag of High Alumina Fly Ash

针对高铝粉煤灰拜耳法溶出渣进行了脱碱工艺研究,考察了[n(C)/n(S)](Ca O与Si O2物质的量比)、反应温度、反应时间、液固比及体系碱浓度等对脱碱的影响,同时考察了脱碱过程对氧化铝溶出率的影响.结果表明:添加石灰的方式可以实现高铝粉煤灰拜耳法溶出渣中氧化钠的脱除,并回收部分氧化铝;反应温度对氧化钠和氧化铝回收率均造成显著影响,而[n(C)/n(S)]仅对氧化钠的溶出率影响较大;在温度260℃、氧化钠质量浓度小于80 g/L、液固比4、[n(C)/n(S)]为1. 8、反应时间2 h条件下,脱碱率为91. 2%,氧化铝回收率为28. 0%;拜耳渣脱碱过程物相由水合铝硅酸钠向水化石榴石及铁水化石榴石转变.

The dealkalization process of the Bayer leaching slag of high alumina fly ash was studied.The influences of[ n(C)/ n(S)](the molar ratio of CaO to SiO 2),reaction temperature,reaction time,liquid-solid ratio and alkaline concentration on dealkalization rate,and the effect of dealkalization process on the alumina leaching efficiency were investigated.The results indicated that the lime-adding method can realize the removal of sodium oxide from the Bayer leaching slag of high alumina fly ash and recover part of alumina.The recovery of sodium oxide and alumina is significantly affected by reaction temperature,but[ n(C)/ n(S)] only affects the dissolution of sodium oxide.The alkali removal ratio and alumina recovery ratio are 91.2 % and 28.0 % respectively under the conditions of 260 ℃,NaO concentration less than 80 g/L,liquid-solid ratio 4,[ n(C)/ n(S)] 1.8 and reaction time 2 h.The phase of Bayer leaching slag transforms from sodium aluminosilicate hydrate to hydrogarnet in the dealkalization process.