高炉瓦斯灰含碳球团粘结剂研究

在掌握高炉瓦斯灰和粘结剂特性的基础上,通过测试生球、干球和焙烧后球团的抗压强度和落下强度,实验考察单一粘结剂和复合粘结剂对高炉瓦斯灰含碳球团强度的影响. 结果表明,加入淀粉类粘结剂能改善球团的低温强度,生球的抗压和落下强度分别达到72 N/个和5.9次/0.5 m;干球的抗压和落下强度分别达到58 N/个和4.3次/0.5 m;但焙烧后球团的抗压强度相对较低. 加入水玻璃含硅类粘结剂能改善其高温强度,焙烧后球团抗压强度最高达到1764 N/个,但生球和干球的强度较低,达不到生产要求. 加入玉米淀粉和水玻璃组成的复合粘结剂后球团强度的改善效果更明显,生球的抗压和落下强度最高达到60 N/个和5.5次/0.5 m;干球的抗压和落下强度达到55 N/个和3.4次/0.5 m;焙烧后球团的抗压强度最高达到1958 N/个.     

鞍钢大孤山球团厂内配碳工业实践研究

球团内配碳可以改善球团质量,降低燃料消耗,实现高炉增产节焦,节能减排。鞍钢大孤山球团厂通过实验室造球及焙烧实验确定适宜煤粉配比,将煤粉按比例混入膨润土后参与配料,进行工业实践研究。结果发现:当煤粉配比小于0.3%时,对生球指标未产生明显影响,而预热球抗压强度有明显提高,成品球抗压强度略有降低。在煤粉配比为0.2%时,各项指标满足了球团生产工艺要求,煤耗降低了1 kg·t~(-1)球团矿,NO_x排放量减少了25%。     

钢-聚丙烯混杂纤维增强超高性能混凝土强度试验研究

考虑钢纤维体积率、聚丙烯纤维体积率和长径比三种因素,设计并制作了171个超高性能混凝土试块,进行立方体抗压强度、轴心抗压强度和劈裂抗拉强度试验,分析纤维特征参数对超高性能混凝土强度的影响规律.结果表明,掺入钢-聚丙烯混杂纤维后,超高性能混凝土的立方体抗压强度可提高36.3％,轴心抗压强度可提高31.9％,劈裂抗拉强度可提高539％;混杂纤维最佳配比为,钢纤维体积率1.50％、聚丙烯纤维长径比167、体积率0.10％;基于试验结果建立了考虑纤维参数的超高性能混凝土立方体抗压强度预测模型,提出了超高性能混凝土轴心抗压强度、劈裂抗拉强度与立方体抗压强度的关系式.     

助磨剂在钢渣复合水泥中的应用

研究通过掺加助磨剂粉磨钢渣的方法,提高钢渣微粉的细度和活性,达到高效利用钢渣目的.结果表明,随着钢渣掺量的增加,钢渣复合水泥的抗折强度呈先上升后下降趋势,掺量为30％时抗折强度最高.钢渣复合水泥的28 d抗压强度直线下降,3 d抗压强度先增加后再下降,30％掺量时强度最高,达4.75 MPa.结合实际经济效益,最终确定钢渣复合水泥的配比为熟料-65％、钢渣-30％、石膏-5％,助磨剂A掺量为0.1％时效果最好,相比无助磨剂的钢渣复合水泥,细度降低了49.0％,且28 d抗压强度提高了6 MPa.     

鞍钢大孤山球团厂内配碳的试验研究

以铁精矿球团为研究对象,在实验室进行了内配碳的试验研究。结果表明:添加适量固体燃料可以提高球团矿强度,降低焙烧燃耗,同时能改善球团矿的冶金性能;在备选燃料中优选出0.2%的煤粉进行内配,生球的落下强度有所提高,但是抗压强度随着配煤量的增加略有降低,而爆裂温度则变化不明显。当配煤量为0.2%时,焙烧球的强度最高。配煤量对焙烧球强度的影响比较显著,过少或过多都对强度有不利影响。在预热温度为950℃,焙烧温度为1 250℃的条件下,随着焙烧温度和预热温度的逐渐提高,抗压强度也逐渐增强。     

掺橡胶颗粒轻集料混凝土力学性能的试验研究

为了研究橡胶颗粒等体积替换轻集料混凝土中河砂对轻集料混凝土力学性能的影响,对20组共60个试件在替换率为10％、20％和30％时的力学性能进行了试验,测得不同替代率的轻集料混凝土的表观密度、立方体抗压强度、劈裂抗拉强度、抗折强度、弹性模量、轴心抗压强度以及棱柱体单轴受压应力-应变曲线,并对试验结果进行了分析.试验结果表明:轻集料混凝土的表观密度、立方体抗压强度、劈裂抗拉强度、抗折强度、弹性模量和轴心抗压强度随着橡胶颗粒替代率的提高而降低,棱柱体单轴受压应力-应变全曲线的峰值应变随着橡胶颗粒替代率的提高不断增大,峰值应变后曲线随着替代率的提高越发趋于平缓,抗压破坏模式由脆性破坏转变成延性破坏.     

钢纤维改善混凝土力学性能和微观结构的研究

研究了水胶比为0.45,钢纤维掺量为0、0.5％、1.0％、1.5％和2.0％的五种混凝土的力学性能以及其水化28天后的微观形貌.结果表明:钢纤维对混凝土的抗压强度改善并不明显,当钢纤维掺量为1.5％时,混凝土的抗压强度仅比普通混凝土提高了7.4％;但钢纤维的掺入大大提高了混凝土的劈裂抗拉强度和抗折强度,当钢纤维掺量为1.5％时,混凝土劈裂抗拉强度提高了80％,当钢纤维掺量为2.0％时,混凝土抗拉强度提高了近一倍.混凝土的宏观力学性能特征与微观结构分析结果相吻合.     

基于混料试验设计的水泥-钢渣-矿渣三元胶凝体系的配比优化

针对钢铁渣粉用作水泥辅助性胶凝材料时胶凝体系的配比优化,采用混料设计方法并基于抗压强度测试建立了水泥-钢渣-矿渣三元胶凝体系的强度与各组分含量之间的数学拟合模型.模型可准确预测三组分任意配比时不同龄期的抗压强度;利用混料设计中的“响应优化器”工具可获得最大限度利用钢铁渣粉条件下不同目标强度等级水泥的最优配比.基于52.5强度等级水泥,在钢铁渣粉的取代量为50％时制备42.5和42.5R强度等级的复合水泥,水泥、钢渣和矿渣的最优配比分别为0.50∶0.33∶0.17和0.50∶0.15∶0.35.     

改性煤气化渣用于矿山充填的试验研究

针对煤气化渣应用于矿山充填中强度低的问题,研究激发剂对煤气化渣活性的影响,并将其部分替代粉煤灰用于矿山充填.初选三种激发剂,确定单掺激发剂时最优掺量;随后,采取正交试验对三组分激发剂进行优化设计,确定复合激发剂最优掺量.结果 表明,单掺激发剂时,最优激发剂及其掺量为:0.5％氢氧化钙、2.5％硫酸钙、2.0％聚合盐,对比未激发组其3d抗压强度比分别为116.9％、113.9％、117.0％.复掺激发剂时,最优激发剂掺量组合为:0.125％氢氧化钙、0.625％硫酸钙、1.000％聚合盐,对比未激发组其3d抗压强度比可达到127.4％.试验表明,改性后的煤气化渣充填体强度可以满足矿山充填强度要求.     

聚丙烯纤维对两种聚合物改性砂浆力学性能的影响

试验研究了不同掺量的聚丙烯纤维对两种聚合物改性砂浆的抗折强度、抗压强度、折压比、抗拉强度和粘结强度的影响,这两种聚合物分别为玻璃转换温度为2℃的乙烯/醋酸乙烯共聚物乳胶粉和固体含量为48％的苯丙乳液.结果表明:在这两种聚合物改性砂浆中掺入聚丙烯纤维,增加了改性砂浆的抗折强度、抗拉强度和粘结强度,尤其是抗拉强度的增幅更加明显,相较于未掺入纤维时的强度,其最高增幅分别达到了12.71％和8.96％;当纤维含量为0％ ～0.5％时,随着纤维含量的增加,EVA改性砂浆的抗压强度先增加后减小.     

钙基膨润土提纯制备球团黏结剂试验

以朝阳钙基膨润土为原料,采用擦洗-分散-分选的流程对其进行提纯,并对提纯膨润土进行挤压钠化改型试验.试验结果表明,当选用朝阳钠化提纯膨润土做球团黏结剂,粘结剂添加量为1.1％时,生球的落下强度为4.0次,爆裂温度为525℃,干球抗压强度为306 N/个,可以满足冶金球团性能需要.采用钠化提纯膨润土制备球团黏结剂可以有效降低球团中黏结剂的添加量.     

水热氧化预处理对棉秆成型颗粒理化性质的影响

以棉秆为研究对象,经180～280℃水热氧化预处理后热压制备成型颗粒。利用热重分析、X射线衍射(XRD)及傅里叶变换红外光谱(FTIR)等分析手段,考察了水热氧化预处理温度对棉秆成型颗粒理化性能及燃烧性能的影响。结果表明:随着水热氧化温度的升高,棉秆的固相产物产率降低,半纤维素于180℃之前完全分解,无定形纤维素于200℃完全分解,结晶纤维素于260℃完全分解,水热氧化固相产物的纤维素结晶度呈现逐渐减小的趋势,而木质素相对含量增加;棉秆成型颗粒的固定碳含量、热值和能量密度增加,但燃烧性能变差。水热氧化预处理后棉秆成型颗粒的表观密度保持在1300kg/m³左右,抗压强度则随着水热氧化温度的增加而下降,其中180℃水热氧化预处理后棉秆成型颗粒的抗压强度相比原料成型燃料增加了183.33%。本研究范围内,经180℃水热氧化预处理后获得的棉杆成型颗粒的燃烧性能和物理性能最佳,其热值为17.76MJ/kg,能量密度为23.44GJ/m³,抗压强度达11.90MPa,可作为优质生物质成型燃料使用。     

A study on plasticity and compression strength in wet iron ore green pellets related to real process variations in raw material fineness

The main binding force in wet iron ore green pellets has been found to be the cohesive force of the viscous binder. The wet compression strength (wet-CS) in green pellets is, however, also influenced by the green pellet plasticity. A certain degree of plasticity is needed to sustain the green pellet growth rate. Too much plasticity results in decreased bed permeability and production problems. As the plasticity increases, wet-CS decreases. The amount of moisture needed to create a given degree of plasticity depends on particle properties and on the particle size distribution. Therefore, it was of interest to study how wet-CS would be influenced by variations in raw material fineness, if the green pellet plasticity was kept constant, i.e. the green pellet properties would be compared under relevant industrial balling conditions. For this purpose, magnetite concentrates of different particle size distributions were balled in a laboratory drum and the moisture content for constant plasticity was determined for each of the materials.No difference in green pellet wet-CS as a function of the raw material fineness was found when the bentonite binder was used and the plasticity was adjusted to a constant level. Green pellets prepared of raw materials with narrow size distributions were just as strong as those with broader ones. This is because the main binding force is the cohesive force of the viscous binder. In green pellets balled without the bentonite binder, wet-CS increased with increasing specific surface area in the raw material, in a similar manner as has been shown in earlier agglomeration literature. In this case, the capillary forces prevail. Comparison of wet-CS at constant moisture, instead of constant plasticity, would lead to erroneous conclusions. Fineness, or rather the slope of the particle size distribution curve, had a major impact on the moisture content needed for constant plasticity. If the slope increases, more water is needed to keep the plasticity on a constant level. Implications of these results in control of industrial iron ore balling circuits are discussed.     

Pelletization kinetics of an earthy iron ore and the physical properties of the pellets produced

The iron ore sample used in this investigation was brought from the El-Gedida iron ore deposit, Baharia Oasis, Egypt. This ore is porous, earthy, hard, and has a relatively high specific surface area.The batch balling kinetics of this ore show that the ball growth rate increased by increasing the moisture content. The water content required for pelletizing this ore ranged between 16 and 19% of the dry weight of the charge. As expected, increase in bentonite content retarded the ball growth. Finer feed produced by more dry grinding increased the ball growth rate.The average drop number of pellets was improved by increasing the moisture content to a certain limit, after which the quality of the pellets decreased. The drop number also went up as the amount of bentonite was increased. Increasing the degree of fineness of ore improved the level of drop number.The crushing strength of dried pellets improved with increasing water content to a certain limit, then the trend reversed. Bentonite addition slightly improved the crushing strength of pellets. Increasing the degree of fineness of the ore decreased the crushing strength of dry pellets.The bulk density of pellets increased with higher moisture content to a certain limit and then the trend reversed. Small amounts of bentonite addition decreased the bulk density, but when bentonite exceeded 0.5% the bulk density slightly increased with increasing amount of bentonite. Denser pellets were produced when finer feed was used.     

Studies on the influence of a flotation collector reagent on iron ore green pellet properties

The properties of iron ore green pellets with varying additions of a surface-active flotation collector reagent (Atrac) were studied by small-scale balling. The compression strength and plasticity were measured with a semi-automatic measuring device and the pressure curves were saved and subjected to further mathematical treatment. The green pellet breakage was also filmed with a high-speed camera. Adding Atrac to the pellet feed seriously damaged the quality of green pellets, even in small dosages. This is because an increasing amount of air bubbles became so strongly attached on the particle surfaces that they could not be removed during compaction by balling. The adsorption of air in green pellets was seen as an increase in porosity and a decrease in the filling degree (proportion of pores filled with water). Both the wet and dry compression strength decreased. The air bubbles behaved in wet green pellets like large, plastic particles and the plasticity increased beyond an acceptable level. Breakage started inside the green pellets, along the air bubbles, and generated multi-breakage patterns in wet as well as dry green pellets. Green pellet breakage to crumbs instead of a few distinct segments, promotes the generation of dust and fines and leads to lower bed permeability in the pelletizing machine.The results show that the decrease in iron ore green pellet wet strength in the presence of surface-active agents is not fully described by the so called Rumpf equation, where surface tension and contact angle are used as variables to describe the capillary forces. The green pellet breakage in the presence of air bubbles took place by crack propagation along pore structures rather than through the loss of the capillary forces.     

Effects of raw material particle size distribution on the characteristics of Scots pine sawdust fuel pellets

In order to study the influence of raw material particle size distribution on the pelletizing process and the physical and thermomechanical characteristics of typical fuel pellets, saw dust of Scots pine was used as raw material for producing pellets in a semi industrial scaled mill (∼ 300 kg h^− 1). The raw materials were screened to a narrow particle size distribution and mixed into four different batches and then pelletized under controlled conditions. Physical pellet characteristics like compression strength, densities, moisture content, moisture absorption and abrasion resistance were determined. In addition, the thermochemical characteristics, i.e. drying and initial pyrolysis, flaming pyrolysis, char combustion and char yield were determined at different experimental conditions by using a laboratory-scaled furnace. The results indicate that the particle size distribution had some effect on current consumption and compression strength but no evident effect on single pellet and bulk density, moisture content, moisture absorption during storage and abrasion resistance. Differences in average total conversion time determined for pellet batches tested under the same combustion conditions was less than 5% and not significant.     

BaSO4对球团矿抗压强度的影响

以磁铁精矿粉和膨润土为原料、BaSO4为添加剂生产球团,基于直接配入法的组分调控方式,结合热重实验结果,研究了BaSO4对球团矿抗压强度的影响,并采用压汞仪、矿相显微镜和扫描电子显微镜?能谱仪等分析了球团矿焙烧过程中BaSO4对球团矿抗压强度的影响机理和钡的转变行为。结果表明,随BaSO4含量增加,预热球团抗压强度变化较小,焙烧球团抗压强度先升高后逐渐降低。BaSO4添加量小于1.5wt%时,有利于焙烧球团内部磁铁矿氧化和新生赤铁矿再结晶,孔隙率略有增加,内部氧分压提高,增强了晶粒间的固结程度,球团抗压强度提高。BaSO4含量进一步增加,球团矿内部孔隙尺寸增大,降低了内部基体的整体性,使晶粒间的连晶程度减弱,球团矿抗压强度降低。     

The role of normal and activated bentonite on the pelletization of barite iron ore concentrate and the quality of pellets

The essential parameters affecting the pelletization process of high barite iron ore concentrate were studied using the Egyptian normal and activated bentonite as binder materials. The metallurgical properties of green, dried and fired pellets were studied using chemical and X-ray analyses. The average strength of fired pellets 1.5% normal bentonite and fired 1300 °C for 25 min exceeded 200 kg/pellet. Using activated bentonite produced a lower kg/pellet value. Meanwhile, the productivity of green pellets decreased when the last binder was used.     

Binding mechanisms in wet iron ore green pellets with a bentonite binder

Fundamental research during the past decade has been focussed on understanding the role of viscous forces on agglomerate deformability and strength. Much of this work has been done on glass spheres using Newtonian liquids as a binder. In this work, we show the variations in plasticity and strength of magnetite iron ore green pellets with varying liquid saturations and binder dosages (viscosities). For this purpose, a new measuring instrument was built to analyze the green pellet wet compression strength, plastic deformation and breakage pattern.Industrial iron ore green pellets are over-saturated and a supporting “network” of viscous liquid is formed on the green pellet surface. At least half, probably more, of the total binding force appeared to be due to the cohesive force of the network. The other half (or less) of the total compression strength can be explained by the capillary force. Due to irregularities on green pellet surfaces, both fully developed concave pore openings and saturated areas are expected to be found at the same time.Wet green pellets started showing plastic behaviour as they became over-saturated. In over-saturated green pellets, an explosive increase in plasticity with increasing moisture content was seen, due to the contemporary increase in porosity. Plasticity is an important green pellet property in balling and should gain the status of a standard method in green pellet characterization. It is suggested that the control strategy for the balling circuits be based on plastic deformation and compression strength of green pellets instead of the rather inaccurate drop number. The results also point out the importance of knowing whether the balling process should be controlled by adjusting the moisture content (plasticity) or by adjusting the bentonite dosage (viscosity). These two operations are not interchangeable—even if they would compensate in growth rate, the green pellet properties would differ.A new green pellet growth mechanism is suggested, based on the measured over-saturation. Firstly, green pellet plasticity needs to exceed a minimum level to enable growth. This limiting plasticity defines the material-specific moisture content needed in balling. Secondly, it is suggested that the growth rate be controlled by the viscosity of the superficial water layer rather than by the mobility of the pore water.     

瓮福磷矿浮选精矿分级成型试验研究

瓮福磷矿浮选精矿经三段水力旋流器分级，可以获得＋２００含量大于９６％的粗粒精矿，沉砂中的磷精矿质量有明显提高。其溢流磷精矿也能满足一般磷肥生产需要。浮选精矿用磷酸作粘合剂在圆盘造粒机中造粒，用量为３．２１％时造粒的抗压强度为７７３ｇ／粒。细粒物料用磷酸１．６２％，抗压强度达２３９６ｇ／粒，造粒效果较好。建议该浮选精矿分级，粗粒外销，细粒造球以减少运输中的损失。