Influence of acid leaching and calcination on iron removal of coal kaolin

Calcination and acid leaching of coal kaolin were studied to determine an effective and economical preparation method of calcined kaolin. Thermogravimetric-differential thermal analysis （TG-DTA） and X-ray diffraction （XRD） demonstrated that 900＆#176;C was the suitable temperature for the calcination. Leaching tests showed that hydrochloric acid was more effective for iron dissolution from raw coal kaolin （RCK）, whereas oxalic acid was more effective on iron dissolution from calcined coal kaolin （CCK）. The iron dissolution from CCK was 28.78wt%, which is far less effective than the 54.86wt% of RCK under their respective optimal conditions. Through analysis by using M？ssbauer spectroscopy, it is detected that nearly all of the structural ferrous ions in RCK were removed by hydrochloric acid. However, iron sites in CCK changed slightly by oxalic acid leaching because nearly all ferrous ions were transformed into ferric species after firing at 900＆#176;C. It can be concluded that it is difficult to remove the structural ferric ions and ferric oxides evolved from the structural ferrous ions. Thus, iron removal by acids should be conducted prior to calcination.

二次酸浸法提取煤灰中的氧化铝(英文)

目的:煤灰渣酸浸提铝通常效率不高,主要因为灰渣中存在含铝晶体矿物(如莫来石、尖晶石和长石等)。为解决含铝晶体不易与硫酸反应的问题,本文提出二次酸浸提铝法。创新点:基本实现铝硅分离,第一步酸浸实现非晶态铝的浸出,残渣经焙烧和水浸后,第二步酸浸实现剩余铝的浸出。方法:1.一次酸浸时,硫酸直接与煤灰渣反应浸出部分氧化铝,提铝残渣加碳酸钠焙烧后,含铝晶体遭到破坏;2.焙烧产物经水浸溶解出硅酸钠,水浸残渣做X射线衍射分析表明其主要为铝硅非晶体活性物质,此时可用硫酸在温和条件下浸出剩余的铝。结论:1.一次酸浸提铝在10 mol/L硫酸、120°C、2 h和1:2固液比的条件下,铝浸出率为81.72%;2.用5 mol/L硫酸二次酸浸时,20°C下铝浸出率已经达到87.31%,100°C下更是达到99.06%;3.综合两次酸浸结果,铝的浸出总效率在97%以上。