Investigation of the layering mechanism of agglomerate growth during drum pelletization

Conventional drum pelletization circuits exhibit undesirable surging behavior that is known to result from uncontrolled occurrence of the mechanisms of nucleation, coalescence and layering. This study was undertaken to investigate the mechanism of pellet growth by layering. Several laboratory experiments were carried out to delineate the effect of feed moisture content and feed quantity. This paper presents an analysis of the experimental results and a simple model to describe the layering process.     

Effect of the preparation of cellulose pellets on the dispersion of cellulose fibers into polypropylene matrix during extrusion

Cellulose fibers are rarely used for the extrusion of composites because of the problems in feeding them into the extruder and in dispersing them properly. Pelletization made it possible to feed cellulose fibers into extruder, but it reduced dramatically the fiber length. The goal of this study was to optimize the pelletization process for extrusion applications. Bleached sulfite cellulose fibers were pelletized at different moisture contents and with the optional addition of carboxymethyl cellulose (CMC). The pellets were subsequently extruded with polypropylene matrix without compatibilizer. Fiber dispersion and fiber breakage during extrusion were investigated. Pre‐blending of polymer and fiber pellets and introduction of the fibers through a side extruder were compared. CMC acted as a processing aid during pelletization, resulting in lower fiber breakage but in compact and stiff pellets. Lower moisture content also increased the compactness of the pellets. The dispersability of the fibers during extrusion decreased with increased pellets' compactness. CMC created inter‐fiber bonds, decreasing further the fibers' dispersability. The fiber length in the composites was the same regardless of the pelletization parameters. Early introduction of the fibers improved fiber dispersion. Feeding through side extruder was more stable and more reliable than pre‐blending. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Al-Si复合Al_2O_3-β-SiAlON-C材料加热过程中性能、相组成和显微结构的变化

以电熔白刚玉(≤0.5、≤0.088和≤0.045 mm)、熔融石英(≤0.5 mm)、鳞片石墨(≤0.15 mm)、矾土基β-SiAlON(≤0.088 mm)、Al粉(≤0.074 mm)和Si粉(≤0.074 mm)为主要原料,以热固性酚醛树脂为结合剂,制成25 mm×25 mm×125 mm的Al-Si复合Al2O3-β-SiAlON-C试样,经200℃固化24 h后,分别在800、1 000、1 200、1 400和1 600℃下埋炭(石墨)保温3 h,冷却后测定其体积密度、显气孔率、常温耐压强度、常温抗折强度、高温抗折强度和抗热震性,并进行XRD和SEM分析.结果表明:1)随着热处理温度的升高,Al-Si复合Al2O3-β-siAlON-C试样的显气孔率均下降,体积密度、常温耐压强度、常温抗折强度、高温抗折强度、热震后残余抗折强度均逐渐提高,但其抗折强度保持率在经1 000℃热处理后最高,随后逐渐降低;2)在高温还原气氛的热处理过程中,试样中的Al、Si与C(CO)或N2反应,原位生成了AlN、β-SiC、Al4C3和β-SiAlON等非氧化物,对试样具有填充气孔及增强增韧的作用.     

Ability for Self-Pelletization of Iron Ores and Magnetite Concentrates

 A procedure for evaluating the susceptibility of raw materials for the process of sintering of iron ore mixes is presented. The procedure relies on the evaluation of the amount and quality of the finest grain fraction. The method is based on determination of particular grain fractions. For the grain less than 015 mm, the determination of the amount is performed using an IPS (Infrared Particles Sizer) grain size analyzer and for the grain larger than 015 mm, the fraction is determined using the (wet and dry) screening methods. This allows for quantity assessment of the quality of material in terms of its susceptibility to self pelletizing by calculating Total Ability for Self Pelletizing (TASP) index fT. The presented method, in combination with the grain size and chemical analyses, can serve for evaluation of suitability of raw material and mixes for the sintering process. Furthermore, the TASP index for 10 types of iron ores and concentrates was determined. The usability of the TASP index was verified by determination of its impact on yield of sintering process both in laboratory and in industry scale.     

球团配加新矿种的应用研究

为了开发新的铁矿资源,对球团配加俄罗斯和伊朗铁精粉进行研究。分析了不同铁精粉的化学成分、粒度组成和矿石颗粒形状,对比了不同原料配比下的造球实验结果和球团质量,藉此选取合适的矿种和配比来替代巴西加斯铁精粉,并进行了工业试验。结果表明,俄罗斯铁精粉造球效果较好,可以替代国内和巴西加斯铁精粉。     

36m小断面高温隧道窑

介绍了３６ｍ小面高温隧道窑的设计技术数据、燃料的燃烧计算、结构特点、风机的选择及使用效果．运行实践表明：该赛温度调整灵活，烧成温度可达到１７３０℃，标准燃料消耗量１８７ｋｇ／ｔ砖，每年可生产铝炭砖６００ｔ，合格率９０％以上。     

Influences of ZrO_2-SiC Composite Powder and Commercial SiC on Properties of Al_2O_3-C Refractories

In order to improve oxidation resistance and thermal shock resistance of Al2O3-C refractories, two groups of specimens were prepared with phenolic resin as binder, adding 0, 2 wt%, 4 wt% and 6 wt% commercial SiC or ZrO2-SiC composite powder synthesized from zircon respectively to Al2O3-C refractories, pressing at 200 MPa, drying fully at 250 ℃, and then carbon embedded firing at 1 400 ℃ for 2 h. Oxidation resistance and thermal shock resistance were researched, phase composition was analyzed by XRD. The res...     

改性天然磷灰石废水处理剂的造粒研究

探讨了改性天然磷灰石废水处理剂的造粒方法及其影响因素。试验表明 :在烧结温度一定时 ,造粒颗粒的强度随粘结剂 (粘土 )加入比例的增加而增加 ;当加入粘结剂粘土比例一定时 ,造粒颗粒强度随烧结温度的升高而增加 ,而造粒颗粒的比表面积却随烧结温度的升高 ,先缓慢升高 (低于 70 0℃ )再缓慢下降 (70 0～ 80 0℃ ) ,烧结温度高于 80 0℃时烧结颗粒的比表面积下降较快 ,烧结温度达 12 5 0℃时 ,造粒颗粒的比表面积几乎为零。造粒颗粒的吸附试验表明 :改性天然磷灰石废水处理剂造粒后对废水中Pb2 +仍然具有良好的吸附性能     

Effect of ZrO_2-nitrides Composite Powder Addition on Oxidation Resistance of Al_2O_3-C Refractories

Oxidation of carbon is the main problem of Al2O3-C refractories.ZrO2-nitrides composite powder was synthesized through carbothermal reduction and nitridation (CRN) of zircon.The effect of ZrO2-nitrides composite powder addition on oxidation resistance of the Al2O3-C refractories was investigated by measuring the thickness of oxidation layer.Phase compositions of the Al2O3-C refractories before and after oxidation were investigated by X-ray diffraction (XRD).Results show that the oxidation resistance of the ...     

Aqueous Ions in Process Water and Cake Moisture During Iron Ore Filtration

In mineral beneficiation plants, aqueous ions from the process water concentrate within the filter cake moisture. These high concentrations of ions can lead to operational issues during downstream processes. This paper examines the ionic content of iron ore slurry before it was filtered at an operating hematite beneficiation plant and compared it with the ionic content of the moisture in the resultant filter cake. Water analyses were conducted to determine the sodium, potassium, calcium, magnesium, fluoride, chloride, nitrate, nitrite, carbonate, sulfate, and phosphate concentrations in both filter feed slurry and filter cake moisture. Results have shown that all tested ions within the process are more concentrated within the filter cake moisture than in the filter feed slurry. This has been attributed to the physical and chemical interactions of these ions with the iron ore particle surfaces. Of these ions, phosphorus concentrates most with the filter cake moisture content having a phosphorus content that is 24.67 times that of the filter feed slurry.