铬铁精矿球团烧结工艺与机理

来源期刊:中南大学学报(自然科学版)2010年第5期

论文作者:朱德庆 熊守安 仉宏亮 潘建

文章页码:1658 - 1667

关键词:铬铁精矿;球团烧结;球磨预处理;固相固结;液相黏结

Key words:chromite concentrate; pellet sintering process; wet ball milling; solid diffusion consolidation; liquid phase bonding

摘    要:对铬铁精矿球团烧结新工艺以及球团烧结矿冶金性能和固结机理进行研究。研究结果表明:铬铁精矿粒度粗,成球差,必须经过球磨机细磨,使其比表面积达到1 700 cm2/g,才具有良好的成球性;在膨润土配比为1.5%(质量分数)、造球水分为9.0%(质量分数)、造球时间为12 min的条件下,生球落下强度5次/(0.5 m),抗压强度11 N/个,爆裂温度480 ℃。优化的球团烧结工艺参数为:焦粉用量7%(质量分数)(内配比例30%),烧结混合料水分为9.5%,料层高度为650 mm,干燥温度为300~350 ℃,干燥负压为4 kPa,干燥时间为3 min,点火温度为1 100 ℃,点火负压为5 kPa,点火时间为1.5 min,烧结负压为8 kPa,取得了良好的指标:烧结矿产量为3.01 t/(m2·h),转鼓强度为89.33%,固体燃耗为79.19 kg/t。铬铁精矿球团烧结矿在900 ℃时很难还原,但还原膨胀率只有5%~6%,还原粉化率RDI+3.15大于94%,还原过程将具有较好的强度;在烧结料层的中上部,烧结矿的宏观结构以单个散状球团为主;在烧结料层下部以葡萄状烧结矿为主。铬铁精矿球团烧结矿矿物组成以铁铬尖晶石和硅酸盐矿物为主,单颗粒的球状烧结矿以固相固结为主,葡萄状烧结矿中液相量占30%左右,由固相固结和液相黏结共同维持烧结矿强度。

Abstract: Pellets sintering of finely ground chromite concentrates was conducted, metallurgical performance and consolidation mechanism of sinter were examined. The results show that the tested chromite concentrate possesses poor pelletability due to coarser size and lower specific surface areas, which can be significantly improved by finely grinding the chromite concentrate up to 1 700 cm2/g through wet ball milling. Good green pellets are manufactured from the finely ground chromite concentrate under the following conditions: 1.5% bentonite (mass fraction), 9.0% moisture (mass fraction) of pellet feed and balling for 12 min, and drop number of 5 times from 0.5 m height, compressive strength of 11 N per pellet and cracking temperature of 480 ℃ are achieved. The operation parameters of pellets sintering process are optimized as follows: 7% coke breeze (mass fraction) (30% of it added into pellet feed before balling), 9.5% moisture, 650 mm bed height, drying at 300-350 ℃ and 4 kPa suction for 3 min, ignition at 1 100 ℃ and 5 kPa suction for 1.5 min, and sintering at 8 kPa, and the excellent sintering indexes are attained as follows: unit productivity of3.01 t/(m2·h), tumble index of 89.33%, and solid fuel consumption of 79.19 kg/t. Chromite sinter is difficult to reduce at 900 ℃ due to chromium spinel occurring, and has high strength during reduction because of reduction swelling of 5%-6% and reduction degradation index RDI+3.15 over 94%. The consolidation mechanism of pellet sintering of chromite is demonstrated that macrostructure of sinter is classified into two groups, the first is individual fired pellets in the middle and top layers of sinter bed, and the second is racemose sinter in the bottom of sinter bed. The main minerals of chromite sinter comprise chromohercynite and silicate. The individual fired pellets are hardened by solid phase diffusion and the racemose sinter are consolidated by both solid phase diffusion and liquid phase bonding, the latter is 30% in sinter.

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