焦粉粒度对烧结混合料制粒的影响

摘要：研究了焦粉粒度对烧结混合料制粒的影响,包括焦粉在制粒小球中的分布规律与混合料制粒效果。结果表明：粒度小于0.5mm焦粉主要起黏附粉作用,较为均匀地黏附到各粒级制粒小球中;粒度在0.5~1mm的焦粉作为核颗粒,分布在0.5~1mm、1~3mm制粒小球中的占比总和为81.3%,部分以共核形式存在于3~5mm及以上粒级的制粒小球中;粒度在1~3mm及以上粒级焦粉作为核颗粒分布于相同粒级与大一粒级的制粒小球中;粒度在1~3mm及以上粒级焦粉对烧结混合料制粒无明显影响,粒度小于1mm的焦粉会提高制粒后混合料中小粒径制粒小球的含量,不利于混合料制粒,应尽可能减少焦粉中粒度在05~1mm的含量,将焦粉中粒度小于0.5mm的质量分数控制在20%~30%。     

Optimising method for improving granulation effectiveness of iron ore sintering mixture

Abstract

The structure of granules has been investigated and a model of granulation determined. The results show that a granule consists of an adhesive layer and a nucleus. Particles with diameter under 0.5 mm act as adhesive fines, while the remainders act as nuclei. By studying the influencing factors of granulation, two significant particle characteristics assessing granulation performance were determined. One is the relative proportion of adhesive fines and nucleus particles, and the other is the specific surface area of adhesive fines. The method of optimising granulation of sinter mixtures is proposed as follows: the proportion of adhesive fines should be 40–50% and the specific surface area should exceed 1000 cm² g^?1, which contributes to achieving a better bed permeability, a faster sintering speed and higher productivity.     

铁矿粉颗粒特性对其烧结制粒性的影响

 掌握铁矿粉的烧结制粒性是进行制粒工艺参数优化以保证混匀矿优良制粒效果的基础,确定铁矿粉颗粒特性对其制粒性的影响,是值得深入研究的工艺理论问题。通过微型圆筒制粒法研究铁矿粉的圆形度[（Ψw）]、气孔率[（P）]、润湿性[(cosθ)]以及粒度分布对其制粒性的影响,在此基础上,采用回归方法预测混匀矿的制粒性。结果表明,铁矿粉的圆形度和气孔率对其制粒性有负面影响,而提高润湿性则有利于铁矿粉制粒;铁矿粉粗颗粒群的制粒性与其等效表面积呈反比,细颗粒群的制粒性与其黏附粉与中间粒级的比值[(R<0.25 mm/0.25～1.00 mm)]呈正比;混匀矿的制粒性可以根据各组元的配比和颗粒特性进行有效预测。     

烧结混合料适宜制粒水分的预测

水分是影响铁矿混合料制粒、烧结的重要因素.研究结果表明,随着制粒水分增加,制粒后混合料中细粒级颗粒含量减少,平均粒径增大,透气性迅速提高但随后增幅放缓或有所下降.透气性增幅达到缓和的水分点可作为适宜制粒水分的判据,且烧结速度在适宜制粒水分时达到最大值.通过筛分分级的方法将混合料分成-0.5 mm的黏附粉和+0.5 mm的核颗粒,并检测核颗粒的比例X_+0.5,通过饱和吸水法检测黏附粉的最大毛细水量W_p,通过离心法检测核颗粒的持水量W_c,另外根据数学模型W=X_+0.5·W_c+0.72(1-X_+0.5)·Wp预测适宜的制粒水分.适宜制粒水分绝对误差为±0.3%的情况下预测准确率可达93.3%,能满足混合料适宜制粒水分预测对精度的要求.      

熔剂颗粒在烧结过程中的特征演变及影响

 对烧结现场生产进行全流程取样,分析熔剂颗粒在烧结过程中的演变规律,及其对烧结过程的影响。结果表明,在烧结混合料制粒过程中,小于0.5 mm熔剂颗粒较铁矿粉颗粒更容易黏附至核颗粒表面形成新的颗粒,从而相对均匀地分布至混合料各粒级中。大于0.5 mm粒级熔剂颗粒作为核黏附一定厚度的黏附层形成新的颗粒,黏附层厚度均小于1 mm,因此,新颗粒直径仅在原始颗粒粒径基础上增大不超过2 mm。同时由于熔剂原始颗粒粒级较细,导致制粒后大于5 mm粒级混合料中熔剂含量较少。而在烧结台车布料过程中粒级存在偏析,大颗粒向下分布,最底层大于5 mm粒级颗粒分布最多,从而导致熔剂的偏析,混合料中大于5 mm粒级颗粒增多加大了熔剂的偏析,混合料中3~5 mm粒级颗粒增多减弱了熔剂的偏析。料层粒级偏析使烧结料层,最底层混合料中熔剂总量变少,大颗粒熔剂增多,熔剂颗粒数量减少,导致熔剂分布点变少,熔剂分布不均匀程度增加,局部高碱度环境变少,液相产生的难度增加。同时,由于颗粒的偏析,最底层混合料中大颗粒铁矿粉增加,出现更多的未熔原矿,最终导致烧结料层最底层烧结矿质量变差。     

制粒准颗粒堆积行为的数值模拟

制粒准颗粒的粒度组成是影响烧结生料层透气性的主要因素之一。通过配料操作、制粒工艺优化等措施能够在一定程度上调节制粒后准颗粒的粒度分布。为探讨准颗粒级配模式对烧结生料层床层结构的影响规律,对制粒准颗粒在烧结杯内的堆积行为进行了数值仿真。首先,在实验室条件下对1种烧结混合料进行了变含水量的常规制粒实验,实验结果表明:调节制粒含水量可以显著地改变准颗粒群的粒度组成,生料层透气性也随之得到调整。随后,基于刚性球体颗粒模型,运用离散单元法对准颗粒群的堆积行为进行了数值仿真。研究发现:准颗粒的级配模式对烧结杯堆积床层的模拟空隙率有显著的影响,在颗粒不发生显著塑性变形时,仿真所得的稳态空隙率与实验所得的生料层透气性指数有很好的线性正相关关系。     

焦粉粒度对烧结烟气中CO排放的影响

摘要：针对钢铁企业大气污染物排放问题,生态环境部提出了NOx、SO2、烟气颗粒物等超低排放的要求,京津冀地区在此基础上对烧结工序的CO排放浓度也做了相应要求。为探究不同粒度焦粉对烧结烟气中CO排放的影响,进行烧结杯实验,使用紫外差分烟气分析仪实时测定烧结烟气中CO浓度,并测定烧结矿的性能指标。结果表明：焦粉粒径小于1mm时,生料层透气性差,焦粉燃烧不完全,CO排放量大,随着焦粉粒径增大,制粒得到强化,生料层透气性、氧化性气氛得到改善,在焦粉粒径达到3～4mm时达到最佳,较小于1mm降低约41%;随着粒径增大,烧结矿强度、成品率均有所增加,冶金性能得到改善,在焦粉粒径达到2～3mm时,综合性能达到最优。     

强力混合对高比例精矿烧结的影响及机制

通过混合试验、制粒试验以及烧结杯试验研究了强力混合技术对高比例精矿烧结的影响,包括混合效果、制粒效果以及烧结指标,阐明了强力混合影响高比例精矿烧结的作用机制.结果表明,与圆筒混合机相比,采用强力混合机时混合料中水分、生石灰和核颗粒分布更为均匀;制粒效果得到改善,制粒小球中粒度大于3 mm含量提高了8.25％(质量分数)...     

HfC含量对钼钛锆合金显微组织和力学性能的影响

在钼钛锆(titanium zirconium molybdenum alloy,TZM)合金粉末中分别添加质量分数为0、0.25％、0.50％、1.00％的HfC粉末颗粒,利用粉末冶金结合轧制变形的方法制备多元复合强化钼合金.通过金相组织观察、扫描电子显微镜形貌表征、能谱分析以及力学性能测试等手段,研究了HfC颗粒对...     

New method to determine optimum water content for iron ore granulation

Abstract

Granulation is necessary before iron ore sintering. The optimum granulation moisture added to the mixture of iron ores, fuel and coke for obtaining suitable size distribution of the granules after tumbled in a drum is of vital importance for the sintering. In order to investigate the optimum moisture content, the moisture capacity of the iron ore, which means the maximum water content held in iron ores of unit mass, is defined and measured in a self-designed apparatus. The relationship between the moisture capacity and some other characteristics of iron ores, which include mineral and chemical composition, size distribution and mineralogy, is discussed. It was found that the mineral composition and the size distribution of the iron ore particles greatly influence the moisture capacity of the iron ores. The moisture capacity of the iron ore was also applied to optimise the granulation by finding the relationship between the moisture capacity of the mixture and the optimum water content. The moisture capacity has positive correlation with the optimum water content. The iron ore, which has high moisture capacity, needs more water added in the granulation process in order to get high permeability. The correlation was given to predict the optimum water content in the granulation based on the moisture capacity measurement.     

硅铁合金离心粒化工艺

提出采用多孔转杯作为粒化器的硅铁合金离心粒化工艺。为了研究该工艺的可行性,采用不同转杯开孔孔径和转速对硅铁合金进行粒化试验并对试验后所形成的颗粒进行分析。结果表明,通过该工艺可得到球形度好、粒度均匀可控的合金产品,同时避免小于1 mm的细小颗粒产生;在本试验条件下采用开孔孔径为12 mm的转杯,转速为100～200 r/min得到颗粒平均粒径在10 mm左右,结果最佳;粒化后硅铁合金颗粒粒径为10～13 mm的硅铁合金吸氧率和氧化率分别为0.5%、0.14%,满足目前工业要求。     

镜铁矿粉在铁矿烧结混合料中的制粒行为

 对镜铁矿粉在铁矿烧结混合料中的制粒行为进行了研究,结果表明：水分对制粒效果有显著的影响,随着镜铁矿粉配比增加,适宜制粒水分逐渐降低。不同配比镜铁矿粉的制粒动力学研究表明：制粒时间小于3 min时,镜铁矿黏附率快速增长;制粒时间大于3 min时,镜铁矿黏附率趋于稳定。随着镜铁矿粉配比增加,达到黏附平衡所需时间延长。因此,延长制粒时间是改善高配比镜铁矿粉制粒效果的有效措施之一。准颗粒黏附层微观结构研究表明：镜铁矿颗粒呈散点状分布于黏附层中,微细粒级褐铁矿粉颗粒作为黏结剂使黏附层具有一定的强度,促进镜铁矿粉的黏附。镜铁矿粉与制粒性能优良的褐铁矿粉合理搭配使用,有利于改善制粒效果,提高镜铁矿粉配比。     

高炉渣干式离心粒化实验研究

针对水冷高炉渣耗水量大、能量未回收、污染重等问题,进行了高炉渣干式离心粒化实验研究。结果表明:(1)高炉渣的玻璃体含量均在95%以上,可以作为水泥原料使用;(2)渣温度高、流量小、粒化盘直径大,粒化后渣粒越小,粒化理想时,88%渣粒径<4.75mm;(3)粒化盘的表面特性影响其粒化效果。其表面光洁度越高,渣粒的粒径越小且均匀,粒化后的渣粒越接近于球形;粗糙的粒化盘易拉出玻璃丝。     

Granule Size Distribution and Porosity of Granule Packing

The granule size distribution and the porosity of the granule packing process were researched. For realizing the optimizing control of the whole sintering production process, researchers must know the factors influencing the granule size distribution and the porosity. Therefore, tests were carried out in the laboratory with regard to the influences of the size and size distribution of raw materials and the total moisture content on the size and size distribution of granule. Moreover, tests for finding out the influences of the moisture content and the granule volume fraction on the porosity were also carried out. The results show that （1） the raw material has little influence on granulation when its size is in the range of 0. 51 mm to 1.0 mm; （2） the influence of the material size on granule size plays a dominant role, and in contrast, the moisture content creates a minor effect on granule size; （3） in binary packing system, with the increase in the constituent volume fraction, the porosity initially increases and then decreases, and there is a minimum value on the porosity curve of the binary mixture system; （4） the minimum value of the porosity in binary packing system occurs at different locations for different moisture contents, and this value shifts from right to left on the porosity curve with increasing the moisture content; （5） the addition of small granules to the same size component cannot create a significant influence on the porosity, whereas the addition of large granules to the same system can greatly change the porosity.     

Some characteristics of hydroxylapatite powder particles after plasma spraying

We have studied the particles of hydroxylapatite (HA) powder, the particles after plasma spraying, their distribution on substrate surface and their condition after transfer through the plasma torch. Mean particle size of HA powders was as follows: HA-A: 3.8 microm, HA-B 88.2 microm. The area of HA coating after plasma spraying, when the torch had a constant position against the substrate surface, shows two characteristic zones: the central part of coating formed mainly from deformed particles and the marginal part of coating with small non-deformed particles. These small non-deformed particles can be found in all zones of the coating and together with greater non-deformed particles and partially deformed particles will unfavourably affect the adhesive and cohesive strength of the coating and its porosity. The maximum diameter of the molten (spherical) particles in the conditions of Ar + H2 plasma, output P = 24 kW was: DA = 25 microm (HA-A) and DB = 65 microm (HA-B). The intervals of dimensions in which most of molten particles occurred were HA-A: 0-15 microm (98%), HA-B: 5-35 microm (84%). From comparison of HA-A and HA-B powders it can be concluded that the transport of HA-A powder was not continuous, the amount of molten HA-A particles was considerably greater (90%) than that of HA-B powder (63%). Phase decomposition and also solubility of HA-A powder (at in vitro tests) was greater. If we consider transport of particles, their melting, splitting and spraying efficiency, the suitable size of HA powder particles for the given spraying conditions is somewhere between the size of HA-A and HA-B particles--let us say--in the interval from 20 to 60 microm.     

强化制粒对含铬型钒钛混合料烧结的影响

 含铬型钒钛混合料制粒效率低,料层透气性差,严重影响了其发展低温高料层烧结。在基准方案基础上,通过烧结杯试验研究了生石灰配比、混合料水分、润湿时间和制粒时间对含铬型钒钛混合料烧结的影响,并对强化制粒效果进行了观察。试验结果表明：在碱度为2.15、配碳量为3.2%(质量分数)、混合料配加生石灰为5%、水分为7.5%、消化时间为10 min,制粒时间为8 min时,平均粒径[d]、拟似粒化指数[GI0]、制粒效率[E]、抗粉化指数[B]分别由2.26 mm、66.30%、54.11%、48.15%提高到2.58 mm、80.43%、90.82%、73.53%,烧结速度、成品率、利用系数、转鼓强度分别由16.54 mm/min、70.39%、1.22 t/(m2·h)、55.36%提高到19.70 mm/min、77.94%、1.64 t/(m2·h)、59.36%。含铬型钒钛混合料对水分敏感度高,应严格控制水分波动。采用强化制粒措施,提高料层透气性,增加氧势,可提高烧结矿中铁酸钙质量分数改善其矿物组成与结构,提高产质量。     

Effect of the method of introduction of Y2O3 into NiAl-based powder alloys on their structure: II. Mechanical activation

Effect of mechanical activation of NiAl powders produced by calcium hydride reduction in an attritor and a ball mill on the specific surface, the oxygen concentration, the strain hardening, and the coherent domain size (CDS) of the powders is studied. It is found that the powder specific surface milled in the attritor for 10–15 h is larger by a factor of 1.7–1.8 and the oxygen concentration in a powder is lower by a factor of 1.35 as compared to the its milling in the ball mill for 150 h. The powders milled in the attritor for 15 h have the level of microstresses higher by a factor of ～2.4 and the CDS smaller by a factor of 2 as compared to the powder treated in the ball mill for 150 h. When milling a powder in the attritor, the milling time decreases by a factor of 10 and the degree of powder refinement increases, which improves the technological characteristics of the powders. As a result of the combination (in one operation) of mechanical activation of an NiAl intermetallic matrix powder in the attritor and the introduction of dispersed particles of a refractory oxide Y₂O₃ powder, the produced composite alloy has a density close to the theoretical one and has no aggregates of dispersed oxide particles at grain boundary junctions. Submicro- and nanosized oxide particles are homogenously distributed in the intermetallic matrix volume, which is characterized by a homogeneous distribution of nickel and aluminum.     

离子型稀土矿土壤粒度分布特征研究——以赣县姜窝子稀土矿山为例

颗粒粒度分布对土壤水分运动和溶质迁移,以及水土流失有重要影响. 利用水洗分筛和激光粒度分析技术研究了江西赣县姜窝子稀土矿土壤颗粒粒度并探讨了土壤颗粒粒度在垂直方向的分布规律. 研究表明,姜窝子稀土矿山土壤颗粒粒度分布受风化程度、颗粒垂向迁移因素的影响,呈如下分布:①离子型稀土矿土壤颗粒按直径分为粗、细、粉、黏粒结构,且土壤粗颗粒以石英为主,稀土矿土壤颗粒粒度呈驼峰式分布,即粒径在粗颗粒（ > 2 mm） 和黏粒（ < 0.075 mm）含量较高,粒径在细、粉粒（0.075~2 mm）含量相对较低;②受风化程度和颗粒垂向迁移的影响,稀土矿土壤细、黏粒组分的含量随深度增大呈先升后降的曲线形态;③黏粒（ < 0.075 mm）激光粒度分析表明,颗粒分布随粒径的大小变化与粒径大于0.075 mm的颗粒在深度上的分布相似.      

AlN在Hi-B钢铁素体相中析出的形核机制

通过理论计算的方法,系统分析了AlN在Hi-B钢铁素体中的析出形核机制。结果表明,第二相AlN粒子不同析出形核机制下的临界形核尺寸随着温度的降低而降低,形核机制不同,临界形核尺寸不相同,但均匀形核和晶界形核的临界形核尺寸较为接近,同一温度条件下,位错形核的临界形核尺寸最小。第二相AlN粒子以位错形核、均匀形核、晶界形核3种形核机制形核的最快析出温度分别为1 273、1 193、1 293K。同时,温度在1 293K以下时,取向硅钢中AlN在铁素体中以位错形核为主,温度高于1 293K后,AlN的形核机制以晶界形核为主。     

A diffusional creep law for powder compacts

The creep of powder due to diffusional mass transport on the interparticle contacts is modelled. It is assumed that diffusion is very rapid on the free surface of the powder particles so that the critical phenomenon is mass transport on the interparticle boundary. An interparticle shear viscosity is allowed for also. To characterize the creep law, the macroscopic strain rate in the powder aggregate is specified and the energy dissipated in mass transport and interparticle shear is computed. This work rate is used in a potential to determine the macroscopic creep parameters. The effective macroscopic shear and bulk viscosities resulting from this model depend on the relative density of the powder and disappear at random close packed density. The viscosities depend also on parameters controlling mass transport, the size of the powder particles and, in the case of shear viscosity, on the interparticle shear drag. A term driving sintering arises naturally in the model.