低品位铁矿石内配煤球团的回转窑脱水工艺研究

内配煤球团在进入回转窑还原前通常需要在圆筒中进行干燥,以增强入窑球团的强度。为了获得较高性能的干燥球团,对影响干燥球团性能的主要因素进行了研究。结果表明:(1)湖南某低品位铁矿石(-0.074 mm占95.66%)与某神木煤粉(-0.074 mm占83.47%)在碳铁质量比为0.3,膨润土添加量为1%(占铁矿粉+内配煤+膨润土的质量分数),钠盐添加量为3%(与铁矿粉+内配煤的质量比)的情况下制得粒径为5~8 mm、含水量为11.8%的内配煤球团,在内径(装料部分)为150 mm(转速为2.3 r/min)的回转管中进行脱水,适宜的回转管填充率为30%,升温速率为45℃/min,干燥球团的残余水分为7.8%,对应的干燥球团抗压强度为21.76 N/个、落下强度为5.5次/0.5 m,干燥粉化率为1.52%,群落粉化率为1.57%。(2)以实验室试验结果为依据的干燥球团在煤基回转窑中进行直接还原(温度为960℃、有效还原时间为24 min)工业试验,获得了性能指标更优(落下强度为15.70次/0.5 m,抗压强度为23.37 N/个,烘干粉化率为0.82%)的干燥球团,焙烧球团铁的金属化率达83.10%。(3)焙烧球团在磨矿细度为-0.045 mm占96.15%情况下进行1次湿式弱磁选(磁场强度为180 k A/m),可获得铁品位达80.33%、铁回收率为78.20%的精矿。

Rotary Kiln Dehydration Process of Carbon Pellets of Low Grade Iron Ore

Pellets with coal are usually dried in the cylinder kiln to enhance the strength of the pellets before entering in-to the rotary kiln. In order to obtain high performance dry pellets,the main factors affecting the performance of dry pellets were studied. The result shows:① With the quality ratio of carbon and iron 0. 3,bentonite content of 1% (mass fraction of iron ore powder +inner coal+bentonite);sodium salt content was 3% ( quality ratio of sodium salt and iron ore+coal blending) ,and sodium salt content of 3% ( quality ratio of sodium salt and iron ore+coal blending) ,a low-grade iron ore in Hunan (-0. 074 mm accounted for 95. 66%) and a Shenmu coal powder (-0. 074 mm accounted for 83. 47%) were mixed to prepare pellets with particle size of 5~8 mm,and moisture content of 11. 8%. The pellets were dried in a rotary tube with inner diameter of 150 mm(the speed at 2. 3 r/min). Under the optimum conditions of filling rate of the rotary tube 30%,the heating rate 45℃/min,the residual moisture of dry pellets 7. 8%,the corresponding compressive strength of the dry pellet was 21. 76 N/,the drop strength was 5. 5 times /0. 5 m, powdering rate after drying was 1. 52% and powdering rate after falling together was 1. 57%.②Based on the laboratory test results,industrial tests on the dried pellet are directly reduced at coal-based rotary kiln ( temperature at 960 ℃,and effective reduction time for 24 min) ,obtained better performance index ( drop strength was 15. 70 times/0. 5 m,the compressive strength was 23. 37 N/,the powder rate after drying was 0. 82%) of drying pellet,and metallic rate of roasting pellet iron reached 83. 10%.③The concentrate with 80. 33% iron grade and 78. 20% iron recovery was ob-tained under the condition of 1-stage wet low intensity magnetic separation with magnetic field strength of 180 kA/m,when the grinding fineness of roasting pellet was -0. 045 mm accounted for 96. 15%.