菱铁矿直接还原-低阶煤提质一体化扩大试验

菱铁矿作为中国重要的铁矿资源,因具有"贫、细、杂"的特点,常规选矿工艺无法对其进行有效分选;此外,中国低阶煤通常被用作低级燃料直接燃烧使用,导致大气污染严重。因此,开发复杂难选铁矿石及低阶煤资源高效清洁利用新技术,将具有重要现实意义。以难选的低品位菱铁矿和难利用低阶煤为对象,开展菱铁矿直接还原与低阶煤提质一体化扩大试验研究。以神府烟煤为还原剂,在直接还原温度为1 050℃,时间为120 min,C/Fe质量比为2.50,脱硫剂配比为6%,干式磁选磁场强度为0.15 T,一段磨矿细度小于0.074 mm占50%左右,湿式磁选磁场强度为0.08 T,二段磨矿细度小于0.074 mm占90%左右,磁选磁场强度为0.043 T的条件下,可获得直接还原铁(DRI)粉铁品位91.03%、铁总回收率81.33%的良好指标;同时每吨DRI固定碳质量分数为76.11%的半焦产品产出率为1 340 kg,其质量达到工业及民用燃料兰炭Ⅰ级品标准。在煤基直接还原工艺中一步成功实现低阶煤半焦化提质和铁矿直接还原,不仅可制备电炉炼钢原料,还可以生产新型的清洁燃料半焦。

Pilot-scale research on integrated process of direct reduction of siderite and synchronous coal upgrading

Siderite resource is abundant in China but characterized by low iron grade,multiple metals co-existence and fine dissemination;thus,siderite is refractory to beneficiate and difficult to upgrade by traditional beneficiation processes.On the other hand,the low-rank coal in China is generally used for direct combustion which leads to serious air pollution.Therefore,it is of considerable realistic significance to utilize the domestic refractory iron ores and low-rank coal effectively and cleanly.The typical low-grade siderite and refractory low-rank coal are used as raw materials to develop the pilot-scale research on integrated process of coal-based direct reduction of siderite and synchronously coal upgrading.With Shenfu bituminous coal as reducing agent,the final DRI powder assaying 91.04%Fe was obtained at a total iron recovery of 81.33%,under conditions of reduction at 1 050℃for 120 min,mass ratio of C/Fe of 2.50,6%desulfurizer,and dry magnetic field intensity of 0.15 T,following the procedure of the first-stage wet grinding of reduced siderite sample up to 50%passing 0.074 mm,separating at magnetic field intensity of 0.08 T,the second-stage wet grinding up to 90%passing 0.074 mm,and then separating at 0.043 T.At the same time,the yield of semi-coke with fixed carbon content of 76.11%was 1 340 kg per ton DRI and the quality of this semi-coke reached the Grade I of industrial and civil fuel standard.The integrated process simultaneously achieves semi-coking upgrading of low-rank coal and direct reduction of iron ore,which can produce not only raw material for steelmaking in electric furnace but also new clean fuel.