Study on the volatilization kinetics of lead in carbon- containing pellets made of Zn- Pb- bearing dusts

This study investigated the volatilization kinetics of lead in pellets made of Zn-Pb-bearing dusts mixed with coal powder,in a nitrogen atmosphere and in the temperature range between 1 100 ℃ - 1 300℃ ,and showed that the reduction temperature has a significant effect on the volatilization rate of lead and that neither the particle size of the coal powder nor the extra carbon content has any effect on the volatilization rate. The obtained activation energy for the volatilization of lead is 88.74 kJ/mol. The volatilization rate of lead is controlled by both the lead evaporation reaction and the diffusion of gaseous lead through the gas boundary layer covering the surface of the reduced liquid lead.

Kinetics of Evaporation of Zn and Pb from Carbon-bearing Pellets Made of Dust Containing Zn-Pb-Fe Oxides

The influence of reduction temperature, size of coal powder and the carbon content on the evaporation rates of Zn and Pb in pellets made of ZnO-PbO-FeO bearing dust has been investigated between 1100-1300℃. The evaporation rate of Zn and Pb obtained from the experiments has been analyzed with kinetic models. The results show that the control step for evaporation of Zn is reduction reaction of ZnO by CO at the interface，and that the evaporation rate of Pb is controlled by the volatilization of reduction products, i.e. liquid lead. The overall apparent activation energies of Zn and Pb evaporation from the pellet are 79.42kJ/mol and 88.74kJ/mol respectively.

Study on the volatilization kinetics of zinc in carbon-containing pellets made of Zn-bearing dusts

A study was carried out on the volatilization kinetics of Zn in the pellets made of Zn-bearing dusts mixed with coal powder in a nitrogen atmosphere and within the temperature range between 1 100℃and 1 300℃. The study shows that the reduction temperature has a significant effect on the volatilization rate of zinc and that either the coal particle size or the excess carbon content has no effect on the volatilization rate. The obtained activation energy for the volatilization of zinc is 79.42 kJ/mol. The volatilization rate of zinc is controlled by the reaction between the zinc oxides and CO.

REDUCTION BEHAVIOR OF IRON ORE PELLETS CONTAININGCARBON UNDER NON-ISOTHERMAL CONDITION

The reduction behavior of iron ore pellets containing carbon under non-isothermal condition in the temperature range from 573 to 1373 K was investigated in a laboratory scale setup. The test results show that carbon content has no obvious effect on reduction degree of composite pellets (C/O mole ratio=1.0) by CO in the temperature range from 573 to 1373 K under linear temperature-rising program; reduction degree of iron ore pellets containing carbon is large in 90%CO-10%CO2 mixture than that of in 100%CO atmosphere or in 80%CO-20%CO2 mixture; the s type temperature-rising program has a better effect than that of linear one in increasing the reduction degree; and reduction degree of slower linear temperature-rising program is greater than that of faster one, but the final reduction degrees, i.e., those at the highest temperature are about the same for various CO partial pressures or temperature-rising programs. The kinetic analysis also shows that the reduction of iron ore-carbon composite pellets by CO or CO-CO2 mixture under non-isothermal condition should be controlled by surface reaction, and the apparent reduction activation energy changes with the reduction progress under various test conditions.

Effect of CaO and CaCO3 on Reduction Rate of Iron Ore Pellets Containing Carbon

The effect of metallurgical fluxes CaO and CaCO3 on the reduction rate of iron ore pellets containing carbon in nitrogen atmosphere has been studied by a weight-loss thermal balance. The experimental results showed that adding CaO or CaCO3 can promote reduction reaction as the added CaO or CaCO3 probably decrease the apparent activation energy of iron ore concentrate-carbon-CaO or CaCO3 reaction, and the reduction rate constant changes with mass percent of CaO and CaCO3. The kinetic analysis also showed that the rate-controlling step of the reaction is inner gas diffusion.

Kinetics Analyzing of Direction Reduction on Manganese Ore Pellets Containing Carbon

Using high temperature carbon tube furnace, reduction of manganese ore pellets containing carbon was investigated. The reaction was divided into two stages at five minutes after reaction, and the kinetics model of reduction process was established. The experimental results showed that, the reaction rate in the earlier stage was controlled by the chemical reactions between FeO, MnO and carbon reductant, and the activation energy was 28.85 KJ/mol. In the later stage, as the carbon reductant replaced by CO, the reaction rate was controlled by CO-diffusing in solid products, and the cor- responding activation energy was 86.56 KJ/mol. Reaction rate of the later stage was less than the earlier one.

Influence of furnace temperature and non-uniform heat flux density on direct reduction process of newly designed carbon containing pellet

In this study,innovative ellipsoid pellet with craters on its surface was designed,and the direct reduction process was compared with ellipsoid(without craters)and sphere pellets.In addition,furnace temperature and uneven heat flux density effects on the pellet direct reduction process were also studied.The results show that ellipsoid pellet is better than that of spherical pellet on metallization ratio.However,under the condition of non-uniform heat flow,the ellipsoid pellet final metallization rate and zinc removal rate were lower.Although the heat transfer effect of ellipsoid pellet with craters was not improved significantly,the metallization rate and zinc removal rate were found improved,which will have a cumulative effect on the pellets direct reduction process in rotary hearth furnace.Under varying furnace temperature conditions,the pellet temperature was higher than that of the constant furnace temperature.After 1200 s,pellet Fe concentration increased to 123.6%,metallization rate and zinc removal rate increased to 113.7%and 102.2%,respectively.These results can provide references for the carbon-containing pellet design used in rotary hearth furnace.

Effect of Pelletized Graphite Addition on Properties of Al_2O_3-SiC-C Castables

Al2O3 - SiC - C castables with pelletized graphite addition of 0. 2%, 4% or 6% （by mass, the same hereinafter ） were prepared using brown fused corundum （8 - 5, 5 - 3 and 3 - 1 mm ） , dense fused corundum （ ≤1 and 0. 045 mm） and SiC （ ≤1 and ≤0. 064 mm） its main starting materials with mass ratio of aggregate： matrix = 71： 29, 2% silicon powder and 0. 4% B4C as antioxidants, and pelletized graphite as carbon source, Effect of pelletized graphite addition on physical properties, oxidation resistance, slag resistance arid thermal shock resistance of Al2O3 -SiC- C eastables was researched. The results show that： with the in.crease of pelletized graphite addition, the required water amount of castables increases, the bulk density and strength reduce; with 4% pelletized graphite, the eastable performs the best oxidation resistance; the increase of graphite is beneficial to the improvement of slag penetration resistance and corrosion resistance; with 6% pelletized graphite, the thermal shock resistance is the best.

含铁含碳冶金固体废物转底炉热还原协同处置

针对转底炉处置冶金固体废物过程中金属化率低、脱锌率低、粉化率高等问题,本文通过优化原料结构配比,改善球团的成球特性及高温还原性能,采用固体废物粉尘物理性能分析试验和圆盘造球机成球试验,研究含铁含碳冶金固体废物球团的成球性能变化,并在高温还原炉中进行热还原试验,考察球团的金属化率、脱锌率及粉化率。结果表明,原料结构配比优化显著改善了球团的成球特性和高温还原性能。当黏结剂添加量为6%,水添加量为13%时,生球性能最佳,其抗压强度、落下强度以及爆裂温度分别4.6 N/P、3次/(0.5 m)和442℃。在温度为1100~1150℃,高温还原时间为45~60 min时,球团金属化率可达88%,最佳脱锌率可达96%,粉化率为3%~5%。通过优化原料结构配比,可显著改善冶金固体废物球团的成球特性和高温还原性能,从而解决转底炉处置冶金固体废物的技术难题,为提高固体废物资源化利用提供技术支持。

低品位铁矿球团微波加热煤基直接还原-磁选试验研究

针对某铁品位48.92%的赤褐铁矿采用内配煤粉的方式造球,再进行微波加热直接还原-磁选分离。研究结果表明,微波对整个内配碳球团同时加热,且优先加热其中的煤颗粒和铁矿物,有助于赤褐铁矿快速分解和还原成金属铁,此时脉石矿物温度较低,不仅抑制了铁橄榄石等化合物的生成,而且在热应力的作用下有利于金属化球团的磨选分离。在物料量270 g,微波输出功率1.4 k W,内配碳球团经62 min焙烧后温度可达1 200℃,此时球团金属化率高达96.23%;当磨矿时间20 min,磁场强度120 k A/m时,可获得铁品位75.83%、铁回收率91.45%的铁精矿。

废旧塑料在冶金领域资源化利用的方法

废旧塑料含有较高的热能与化学能,将其直接丢弃到环境中会给生态环境带来严重污染,焚烧、填埋、再生处理等传统手段虽具备一定应用优势,但造成了较为严重的资源浪费现象和较高的实施难度。深入分析废旧塑料在当前冶金领域高炉炼铁、含碳球团制备、焦炉和转炉炼钢中的具体应用方法,不仅可以充分利用废旧塑料的热值资源,实现废旧塑料的资源化利用,而且能为冶金行业提供充足的能量来源,使塑料行业与冶金领域共同实现节能减排的发展目标,对于废旧塑料资源化利用和冶金产业节能发展具有重要意义。

铌精矿配碳球团熔分过程与元素迁移试验研究

以白云鄂博铌精矿及半焦粉为原料,使用高温热台原位观察碱度对配碳球团还原产物熔分过程的影响。在不同熔分条件下对最佳碱度的样品进行淬火并制样,采用SEM-EDS分析熔分过程中元素迁移规律,采用XRD、同步热分析仪以及ICP相结合定量分析了熔分过程中Nb、Si元素反应率。结果表明:二元碱度为1.0时能够有效抑制熔分过程中渣液喷溅现象并提高熔分效果。在碱度1.0条件下,1 350℃时渣中SiO_(2)在渣金界面发生还原反应并进入铁相,1 400℃保温2 min后在渣金界面上铁液中C优先与渣中铌氧化物发生还原反应生成NbC。少量NbC溶入铁相,其余大部分NbC将粒铁包裹形成滞留带,阻碍渣金界面传质,降低还原反应速率。1 400℃保温10 min后,Nb、Si元素的反应率分别为36%和1.7%。Ti、RE元素在熔分过程中全程不参与反应。

烧结烟气脱硫石膏含碳球团还原脱硫实验研究

基于含碳球团减重还原实验,研究了还原剂摩尔比、反应温度、气氛、添加剂对脱硫石膏还原脱硫的影响。还原实验结果表明,脱硫石膏含碳球团还原脱硫最适宜的工艺参数是n(C)/n(CaSO_(4))为0.5~0.6,反应温度1 150℃,H_(2)气氛,添加剂的作用不明显。综合实验结果表明,扩大实验量级不会降低含碳球团脱硫石膏的脱硫效果,由此可指导扩大试验。

黏结剂对含碳球团强度影响的试验研究及机理分析

含碳球团的强度是制约含碳球团在低碳炼铁领域应用的主要原因之一。文章针对含碳球团强度难以满足装备要求的问题,研究了膨润土、硅酸钠、HPMC等3种黏结剂对冷压含碳球团落下强度和抗压强度的影响,并对黏结剂成球机理及生球微观结构进行分析。研究结果表明:球团强度随着铁矿颗粒粒径降低而降低,随着煤粉颗粒粒径降低而升高;随着膨润土、硅酸钠、HPMC用量的增加,含碳球团的抗压强度及落下强度均表现为升高趋势。对球团的微观结构形貌用SEM分析发现,膨润土在铁矿颗粒表面附着并呈聚集状,而HPMC可浸入铁矿周围或内部,可显著提高含碳球团的落下强度与抗压强度。

气固基作用下含碳球团还原试验研究

为探究含碳球团在不同条件下的还原特点,进一步揭示其还原反应机理,本文通过热重还原试验研究温度为800~1100℃范围内含碳球团还原过程的特点,并分析不同条件下反应速率、金属化率及抗压强度等指标对球团还原过程及还原产物的影响。结果表明,在还原气氛下发生反应时,各因素对含碳球团还原过程影响的主次顺序:还原温度、碳氧比、还原气氛;在试验过程中,含碳球团的反应速率先上升后下降;适当升高温度、调节碳氧比及还原气氛组成均可促进含碳球团的还原;升高温度,金属化率也随之上升,当金属化率达到一定程度时,温度对其作用效果减弱。当还原温度为800~1000℃时,含碳球团的抗压强度随温度的升高无明显变化,当还原温度高于1000℃时,含碳球团的抗压强度得到明显提高。

焙烧温度与碳结构对钙碳球团抗压强度的影响

电弧法生产电石的过程中,原料应具备一定的强度,保证产物一氧化碳顺利通过。为了提升两步法中钙碳球团的抗压强度,以混合均匀的氧化钙和贫瘦煤为原料,通过嵌样机在压力为8MPa、时长为1min条件下压制直径为15mm、质量为2.5g的钙碳球团,在温度为350-750℃时进行了焙烧,研究了在不同焙烧温度下碳结构对钙碳球团抗压强度的影响。结果表明:当温度为350-<550℃时,煤发生分解和解聚反应,半焦缺陷碳结构相对数量增加,抗压强度随着温度的升高而减小;温度为550-<650℃时,煤固化收缩成半焦,导致抗压强度升高,达到最大值为59.9kPa;温度为650-750℃时,半焦发生缩聚反应,缺陷结构向有序性发展,发生石墨化,导致抗压强度降低。

冷压铁矿球团用于高炉低碳炼铁的研究进展

当前,高炉炼铁所用含铁原料多为高碱度烧结矿、氧化球团矿和天然块矿。然而,随着全球铁矿石资源的日渐消耗和炼铁低碳技术的发展以及高炉炼铁资源高效利用等问题,高炉炉料的配比模式也逐步迈向多元化发展。冷压铁矿球团工艺与常规烧结和球团工艺相比,对原料的适应性强、工艺灵活简单,且可以降低制备过程的能源消耗,不失为高炉含铁炉料的一种补充。文章着重简述了冷压铁矿球团的冶金性能,分析了应用冷压铁矿球团对高炉冶炼的影响以及其节能减排效果。结果表明,冷压铁矿球团的冶金性能可基本满足高炉冶炼的需求,使用此球团生产1 t生铁理论上可减少的CO_(2)排放量约为522 kg。

含碳球团生产工艺参数优化及固结机理研究

实验研究了含碳球团高温自还原特性,考察了焙烧温度、C/O、焙烧时间等工艺参数对含碳球团还原后金属化率和强度指标的影响,利用XRD和SEM显微分析研究了球团还原过程和固结机理.正交实验结果表明,焙烧温度是影响两项指标的最重要因素,C/O次之,焙烧时间的影响不显著.在焙烧温度1350℃、C/O比1.15、焙烧时间25min的最佳工艺条件下,金属化率最高为85.33%,球团的抗压强度达到2248N.

CO/CO_2气氛下含碳球团还原动力学模型及其应用

分析了 CO/CO2 气氛下含碳球团的还原步骤 ,以此为基础建立了含碳球团还原动力学的微分方程组 ,并编制了相应的计算机程序 ,在验证了该数学模型准确性的基础上 ,对 CO/CO2 气氛中含碳球团的还原行为进行了计算机模拟。该模型全面考虑了 FASTMET工艺条件下还原过程中的各种影响因素 ,模拟计算结果与文献 [1]的实测结果相符合 ,证明用此模型可以优化含碳球团的直接还原工艺条件。

提高尘泥含碳球团烘干后强度的实验研究

针对尘泥含碳球团烘干后强度降低进行实验研究,通过改变原料配比、粘结剂种类、球团烘干制度和造球方法提高含碳球团烘干后强度。结果表明:使用钙基含碳球团粘结剂配合复式法造球,钙基含碳球团粘结剂加入量为原料总质量的1.8%,造球时间30 min,球团烘干风温180℃,风速1.0 m/s。该实验条件下烘干后球团平均抗压强度为152.1 N,落下强度为4.5次/0.5 m。