Can Modified Starch be Used As A Binder For Iron Ore Pellets?

Organic binders are often desired when making low-silica iron ore pellets. Corn and wheat are grown in large quantities near certain iron ore pelletizing facilities and their starches are easily modified to form cold-water-soluble powders that can be used as binders. We investigated how starch cold-water solubility, starch dose, starch hydration time, green ball moisture content, and firing temperature affected pellet quality. With a fluxed, hematite concentrate, the high-soluble starch led to good wet and dry balls, but weak and friable indurated pellets compared to the standard binder, bentonite clay. As expected, the low-soluble starch did not make as good green balls as the high-soluble starch. Thermogravimetric analyses of unfired pellets and their abrasion products showed that modified starch was inhomogeneously distributed in pellets, with a high concentration near the ball surfaces. The surface concentration increased, and the core concentration decreased, as pellets grew during the pelletizing process. This suggests that starch enrichment near surfaces is a consequence of the agglomeration–compaction process, and may occur with other pelletizing binders. Abrasion mass losses were 81% greater with modified starch than with bentonite at 1100°C, and 31% greater at 1250°C. However, starch contents near the surfaces did not qualitatively correlate to roughness, as the highest starch dose tested gave the smoothest and least dusty pellets.     

原位生成O'-SiAlON晶须增强铝碳耐火材料

以板状刚玉、石墨为主要原料,基质部分分别添加3%、5%和7%的O’-SiAlON前驱体混合粉(即β-Si3N4微粉、SiO2微粉和α-Al2O3微粉的混合球磨粉),以酚醛树脂为结合剂制成试样,于200℃烘烤后,在空气中埋(SiO2 C)混合粉,分别于1000℃、1300℃、1500℃保温3h原位合成了含O’-SiAlON晶须的铝碳耐火材料。对烧后试样的物理性能、物相及显微结构进行了分析,并对烧结有重要影响的反应进行了热力学分析。结果表明:埋(SiO2 C)混合粉能有效抑制反应体系中SiO2在高温烧结过程中的分解,从而促进O’-SiAlON晶须的原位生成。1500℃时,含有O’-SiAlON前驱体混合粉的试样原位生成了针状和絮状的O’-SiAlON晶须,这些晶须交织于试样的骨料与基质之间,能显著增强试样的强度;且随着O’-SiAlON前驱体含量的增加,试样的强度逐渐增加。     

浅谈酒钢竖炉球团生产实践与探索

本文简单介绍了酒钢竖炉球团生产的一些经验及探索,并对完善竖炉焙烧设备与工艺提出了一些设想。     

喷雾造粒对固相烧结SiC陶瓷的影响

采用离心式喷雾造粒技术对SiC浆料进行造粒,研究了喷雾造粒对SiC粉体的流动特性、成型行为、烧结性能、力学性能及显微结构的影响机制。研究结果表明:喷雾造粒后,碳化硅粉体流动性得到较大改善,素坯密度增加,微观结构致密;固相烧结后,碳化硅陶瓷的烧结性能提高,陶瓷显微结构得到改善。     

热处理温度对有机硅树脂结合不烧铝碳滑板性能的影响

以板状刚玉、石墨、Al粉、Si粉和B4C为主要原料,有机硅树脂作结合剂制备了不烧铝碳滑板试样。研究了在空气中先经240℃24h预处理,然后分别于400℃、600℃、800℃、1000℃、1350℃和1450℃保温3h处理后试样的烧结性能、物相组成和显微结构等变化规律。结果表明:热处理温度对有机硅树脂结合不烧铝碳滑板的性能、物相变化和显微结构影响显著。热处理温度为240~600℃时,有机硅树脂裂解产生质量损失,使试样内部结构松散,显气孔率显著增大,常温耐压强度较低;800~1000℃时,试样边缘部分B4C、Al、Si优先氧化,生成须状Al2O3和针状硼酸铝,有利于边缘骨料与基质结构紧密结合,同时,试样内部局部有柱状氮化物生成,相应的体积密度明显增加,显气孔率急剧下降,常温耐压强度达到最高值;温度>1000℃,试样中石墨大量氧化而留下很多气孔,同时Al、Si等氧化反应加剧,试样质量增加和体积膨胀明显,体积密度下降,显气孔率上升,常温耐压强度有下降趋势。     

Pilot scale test of producing nickel concentrate from low-grade saprolitic laterite by direct reduction-magnetic separation

The enrichment of Ni from a low-grade saprolitic laterite ore,which has been pre-treated by high pressure grinding roller（HPGR） to be 74% passing 0.074 mm and contains 0.92% Ni,18.47% Fe,10.61% MgO and 42.27% SiO2,was conducted by using pelletizing,rotary kiln reduction and magnetic separation process on a semi industrial scale,and the effects of reduction duration,mass ratio of coal to pellets（C/P）,the types of magnetic separator,the sections of grinding-separation and the grinding fineness on the recovery of Ni and Fe were examined.It is shown that nickel concentrate containing 3.13 % Ni and 59.20 % Fe was achieved at recoveries of 84.36 % and 71.51% for Ni and Fe,respectively under the following conditions：reducing at （1120±40） ℃ for 120 min,C/P being 1.0,wet grinding of reduced pellets up to 70%-87% passing 0.074 mm and a magnetic field intensity of 238.8 kA/m during the first section of grinding-magnetic separation,and a grinding fineness of 84%-91% passing 0.045 mm and a magnetic intensity of 39.8 kA/m during the second section of grinding-magnetic separation.The enriched Ni containing concentrate has a low content of S and P,and can be used for further processing to produce high-grade ferronickel alloy.     

Development of rapidly dissolving pellets within the Quality by Design approach

Abstract

The purpose of this study was the development of novel, fast disintegrating, effervescent pellets by employing the direct pelletization technique as a single step process. In line with the Quality by Design (QbD) regulatory framework, statistical experimental design was extensively applied to correlate significant formulation and process variables with the critical quality attributes of the product. Pellets were studied with regards to sphericity, size and size distribution. In contrast to the existing multiparticulate platforms, this development integrated only water-soluble excipients to facilitate the multifunctional use of the final dosage form. The application of a screening fractional factorial design augmented to a full factorial design set the roadmap for the rational selection of the composition and process parameters, revealing in parallel the positive contribution of the powder feeder on the CQAs, when the critical process and formulation factors were properly adjusted. The response surface methodology was exploited for the final process optimization phase, which allowed the construction of appropriate mathematical models connecting the input variables and the CQAs under study. The implementation of the desirability function, lead to the optimum formulation and process settings for the production of pellets with narrow size distribution and geometric mean diameter of approximately 800?μm. In conclusion, using a lean approach supported by design of experiments (DoE) techniques within the QbD framework, a novel multifunctional formulation platform has been developed.     

改进圆筒制粒造球效果的生产实践

通过对炉料在圆筒内制粒造球效果的影响因素进行细致的分析和探讨,找出主要原因是炉料的粒级组成;水分大小及加入方式;炉料在混合制粒圆筒内的运行状态、制粒时间和圆筒内部结构等因素决定其制粒成球效果。并主要针对圆筒内衬材质、扬料器规格及间距、炉料混合强度变化等采取了相应措施,以提高圆筒制粒造球效果,改善炉料透气性及操控条件,增加精矿处理量。     

程潮铁矿球团配加黏结剂试验研究

对程潮铁矿高压辊磨前后的铁精矿分别添加膨润土、有机黏结剂、复合黏结剂进行造球试验。结果表明,单独添加少量的膨润土或有机黏结剂,其生球爆裂温度指标合格,生球强度指标不合格;采用膨润土质量分数为2.0%、有机黏结剂质量分数为0.05%的复合黏结剂,其生球抗压强度为14.5N/个、生球落下强度为（0.5m）12.1次/个、生球爆裂温度为630℃、成品球抗压强度为3 024N/个,球团质量有较大的提高。     

Cold Bonding of Iron Ore Concentrate Pellets

Iron ore concentrate pellets are traditionally hardened at high temperatures in horizontal grates and grate-kiln furnaces. However, heat induration requires tremendous quantities of energy to produce high-quality pellets, and is consequently expensive. Cold bonding is a low-temperature alternative to heat induration. Pellets can be cold bonded using lime, cement, sponge iron powder, and organic materials such as starch and flour. Cold bonding consumes less energy than heat induration, and has found favor for bonding self-reducing pellets and for refractory ores that are difficult to heat-treat. Herein, we review the principal cold bonding methods and their fundamentals.