大孤山磁铁精粉微观结构与氧化焙烧性能

Microstructure and oxidation roasting properties of Dagushan magnetite flavor powder

为探究大孤山磁铁矿精粉微观结构对其氧化焙烧性能的影响,本文采用SEM-EDS分析大孤山球团厂两种高硅磁铁矿粉中SiO_(2)的赋存形式,利用TG/DTA分析高硅磁铁矿粉的氧化性能,并对高硅磁铁矿进行压块焙烧,分析高硅磁铁矿粉的连晶生长特征。XRD-Rietveld精修结果表明:1^(#)磁铁矿中主要物相为Fe_(3)O_(4),含有部分Fe_(2)O_(3)和SiO_(2);2^(#)磁铁矿主要物相为Fe_(3)O_(4)和SiO_(2)。SEM分析结果表明,两种高硅磁铁矿中SiO_(2)主要以石英形式与Fe_(3)O_(4)磁铁矿紧密结合。TG/DTA差热分析发现:1^(#)磁铁矿开始氧化温度为270℃,综合氧化性指数为2.4422,1^(#)磁铁矿中原生赤铁矿较多,原生赤铁矿氧化连晶所需温度更高,氧化性相对较差;2^(#)磁铁矿开始氧化温度为237℃,综合氧化性指数为9.0462,2^(#)磁铁矿氧化焙烧性能更好。通过调整1^(#)、2^(#)磁铁矿配比可知,随着1^(#)磁铁矿配比的增加,氧化开始温度增加,综合氧化性指数由5.1609降低到3.6719。单种磁铁矿压块氧化焙烧后抗压强度测试表明:2^(#)磁铁矿压块抗压强度为2300 N/P,1^(#)磁铁矿压块抗压强度为2100 N/P,2^(#)磁铁矿压块抗压强度优于1^(#)磁铁矿。SEM分析发现:1^(#)磁铁矿中新生的赤铁矿多呈点状连晶,微细孔较多,固结效果较差;2^(#)磁铁矿中新生赤铁矿多呈片状连晶,固结效果更好。因此,配加1^(#)高硅磁铁矿制备球团时,需适当提高预热焙烧温度,使磁铁矿充分氧化,并保证新生赤铁矿连晶生长充分。

In order to investigate the influence of microstructure of Dagushan magnetite flavor powder on its oxidation roasting properties,SEM-EDS is used to analyze the presence modes of SiO_(2) in two high-silica magnetite powders from Dagushan Pellet Plant,and TG/DTA is used to analyze the oxidation properties of high-silica magnetite powders,and briquetting and roasting of high-silica magnetite is used to analyze the continuous crystal growth characteristics of high-silica magnetite powders.The XRD-Rietveld refinement results show that the main phase of 1^(#)magnetite is Fe_(3)O_(4),which contains part of Fe_(2)O_(3) and SiO_(2);the main phase of 2^(#)magnetite is Fe_(3)O_(4) and SiO_(2).SEM analysis results show that SiO_(2) in both high-silica magnetites is mainly in the form of quartz tightly bound to Fe_(3)O_(4) magnetite.TG/DTA differential thermal analysis founds that:the initial oxidation temperature of 1^(#)magnetite is 270℃,and the comprehensive oxidation index is 2.4422.There are more primary hematite in 1^(#)magnetite,the temperature required for oxidation of primary hematite is higher and the oxidation is relatively poor;the initial oxidation temperature of 2^(#)magnetite is 237℃,and its comprehensive oxidation index is 9.0462.So the oxidation roasting property of 2^(#)magnetite is better.By adjusting the ratio of 1^(#)and 2^(#)magnetite,the initial oxidation temperature increases with the increase of 1^(#)magnetite ratio,and the comprehensive oxidizability index decreases from 5.1609 to 3.6719.The compressive strength test of single magnetite briquettes after oxidation and roasting shows that:the compressive strength of 2^(#)magnetite briquette is 2300 N/P,and the compressive strength of 1^(#)magnetite briquette is 2100 N/P.The compressive strength of 2^(#)magnetite briquette is better than the one of 1^(#)magnetite.SEM analysis founds that the newly-born hematite in 1^(#)magnetite is mostly dot-like contiguous crystals with many micropores,and the consolidation effect is poor.The newly-born hematite in 2^(#)magnetite mostly presents lamellar contiguous crystals,so its consolidation effect is better.Therefore,when preparing pellets by adding 1^(#)high-silica magnetite,the preheating roasting temperature should be increased appropriately to make the magnetite fully oxidized and ensure the growth of newborn hematite continuous crystals.