【作者】 唐艳云；

【导师】 朱德庆；

【作者基本信息】 中南大学 ， 钢铁冶金， 2008， 硕士

【摘要】 近年来,我国钢铁工业快速发展,对进口铁矿的依赖度由1993年的6%上升到2006年的55%以上。尤其球团原料严重不足,进口数量不断提高。巴西镜铁矿虽然成球性和可烧性差,但其铁品位高,储量丰富,价格低廉,如能找到合适方法对其加以利用,对缓解我国钢铁原料缺乏具有十分重要的意义。本文采用高压辊磨技术预处理镜铁矿,对强化其球团工艺进行了研究。在优化辊磨参数下,设计了两种不同的高压辊磨闭路流程对铁精矿进行预处理,并就不同的循环负荷进行了实验。实验结果表明:最佳工艺条件为:辊速68r/min,辊压为1MPa,入磨混合料水分为8.0%左右,造球时间15 min,造球水分8.0%,71%产品循环高压辊磨闭路流程,经该条件处理后,配比PFC/磁铁矿M=40/60和PFC/磁铁矿M=70/30混合矿的成球性及其球团的预热焙烧性最好,前者在膨润土配比2.1%时,其球团的抗压强度、落下强度、爆裂温度分别为10.02N/个、5.9次/（0.5m）、463℃,可满足球团生产的要求;后者成球性虽较前者差,但其生球的抗压强度和落下强度度分别达到10.25 N/个、4.5次/（0.5m）,较其未处理混合矿生球的抗压强度4.7 N/个和落下强度2.0次/（0.5m）均有大幅度提高,爆裂温度455℃,也可满足球团生产的要求。小型试验中在预热温度1050℃,预热时间10min,焙烧温度1280℃,焙烧时间12min条件下,两种配比的抗压强度分别为3560.88 N/个和2690.88N/个,铁品位达65%左右,矿相及冶金性能研究表明,通过高压辊磨预处理后,两种配比的成品球团矿均能满足大型高炉冶炼的要求。实验中巴西PFC镜铁矿配比高达70%,解决了巴西镜铁矿制备球团的技术难题。铁精矿经高压辊磨预处理后,细粒级含量大幅度增加,粒度分布明显朝细粒级分布偏移。其比表面积、润湿热增大,且颗粒粉碎后,凹面、尖角、棱角处增多,表面活性增强,成球性指数提高,成球性能得到明显改善,生球指标大幅度提高。磁铁矿的加入改善了单一赤铁矿的预热焙烧性能。磁铁矿氧化生成Fe₂O₃晶粒并形成颗粒之间的粘结相,氧化生成的Fe₂O₃晶粒表面原子具有较高的迁移能力,可在较低温度下促进相邻颗粒之间形成晶键,使球团矿强度提高。同时高压辊磨处理后,矿物粒度变细,物料充分混合,有利于磁铁矿均匀分布到赤铁矿中,在预热焙烧过程中便于晶键的进一步联结,球团矿强度进一步提高。更多还原

【Abstract】 In recent years, the demand for imported iron ores has been greatly growing with the quick development of the Chinese steel industry, amounting to from 6 percent in 1993 to more than 55 percent in 2006 used as burden for blast furnace. Especially, the imported amount of pellet feed is growing gradually for serious shortage. Though Brazilian specularite is characterized by poor ballability and refractory roasting behaviours but high iron grade, abundant reserves, low price. Therefore, it will be of far-reaching significance to solve the tackle shortage by effective using PFC as pellet feed.In this paper, Brazilian specularite was pretreated by using high pressure roll grinding（HPRG） for improving the technology of pelletizing. Under the optimized parameters conditions of HPRG, two close circuits of HPRG to pretreat iron ore concentrates have been developed. The test results showed that the optimum conditions are as follows: the rotation rate 68 r/min, the roll pressure 1MPa, 8.0% moisture of mixed feed, balling for 15min, balling at 8.0% moisture, and at 71% product circulation load in closed circuit. After preheated by this condition, the two suitable pellet feeds （comprising 40% specularite and 60% magnetite, 70% specularite and 30% magnetite, respectively） achieve the best performance in ballibality, preheating and roasting. The former, under the conditions of bentonite 2.1%, the compressive strength, drop strength and thermal shock temperature is 10.02 Newton per one, 5.9 times from 0.5m and 463℃, respectively. Which is meets the demand of blast furnace. The latter is inferior to the former one, the compressive strength and drop number is 10.25 Newton per one and 4.5 times from 0.5m with bentonite 2.4%, respectively. All of which is much higher than that of the unpretreated pellet feed. The green balls are hardened by preheating at 1050℃for 10min and firing at 1280℃for 12min, fired pellets are manufactured with compressive strength of 3560.88N per pellet and 2690.88N per pellet, respectively, assaying 65% iron. The study of mineralogy and metallurgic performance results show that by pretreating PFC by HPRG, the two types of fired pellets can meet the product requirement of blast furnace, with a ration of PFC as high as 70%.The mechanism of HPRG has been revealed that, after PFC pretreated by HPRG , finer size fractions is increased greatly, higher specific surface areas are achieved and surface wetting heat is elevated, due to higher surface activity by forming unsmootheness face, sharp corner and crest edges, leading to better balling performance.In addition, adding magnetite improves the preheating and roasting behaviours of single hematite pellets, newly formed Fe₂O₃ crystal from oxidation reaction has higher ability in transference and can bond each other in lower temperature, then, the strength of pellet is improved. In the other side, after the HPRG pretreated, material mixed again, magnetite can adequate distribute to hematite profitable, the crystal bonding each other was better during the preheat and boast process, the pellet strength was enhance.更多还原