循环流化床粉煤灰与煤粉炉粉煤灰磁选除铁差异性研究

粉煤灰中氧化铁是其高值化利用过程的主要杂质，高效去除铁杂质对于粉煤灰高值利用具有重要意义。采用湿法磁选方法对循环流化床粉煤灰（CFB灰）、碳热还原循环流化床粉煤灰（R-CFB灰）及煤粉炉粉煤灰（PC灰）进行除铁研究，并对不同类型粉煤灰中铁的存在形式进行对比，最后对粉煤灰中铁的去除和铝的回收进行了考察。结果表明:CFB灰直接磁选铁的去除率仅为17.6%，PC灰直接磁选铁的去除率可达到55.8%，这与CFB中的铁主要以赤铁矿形式存在，而PC灰中的铁主要以磁铁矿形式存在有关；经碳热还原后CFB灰中的铁由赤铁矿转变为磁铁矿，在磁场强度为400 mT，磁选3次，液固比为20:1的条件下，R-CFB灰的除铁率为64.7%，，铁含量从3.4%降低到1.2%，且铝的回收率为78.6%。与PC灰磁选法除铁效果对比，经碳热还原的CFB灰可达到较高的除铁率。

DIFFERENCE OF IRON REMOVAL EFFICIENCIES FROM CIRCULATING FLUIDIZED BED FLY ASH AND PULVERIZED COAL FLY ASH BY MAGNETIC SEPARATION

Iron oxide in fly ash is the main impurity for its high value utilization process. Efficient removal of iron impurities is of great significance for the high value utilization of fly ash. In this paper, the wet magnetic separation method was used to remove iron from circulating fluidized bed fly ash (CFB ash), carbonthermal reduction circulating fluidized bed fly ash (R-CFB ash) and pulverized coal furnace fly ash (PC ash). Research and comparison of the existence forms of iron in different types of fly ash were studied and compared, and finally the removal of iron and recovery of aluminum in fly ash were examined. The results showed that the iron removal efficiency of CFB ash using direct magnetic separation method was only 17.6%, and the iron removal efficiency of PC ash using direct magnetic separation method could reach 55.8%. The iron in CFB mainly existed in the form of hematite, while iron was mainly related to the existence of magnetite in PC ash. The hematite in CFB ash was converted to magnetite after carbonthermal reduction, and the iron removal of R-CFB ash was 64.7%, with a magnetic field strength of 400 mT, magnetic separation 3 times and liquid-solid ratio of 20:1. The iron content was reduced from 3.4% to 1.2%, and the recovery of aluminum was 78.6%. Compared with the iron removal of PC ash, the carbonthermal reduction CFB ash could achieve higher iron removal efficiency.