铁矿石烧结中混合料特性对火焰烽面与烧结性能的影响机理研究

通过中试规模烧结杯试验和综合烧结模型,将返矿平衡和非平衡条件相结合,研究了混合料特性(烧结碱度、焦炭和水分添加量)对火焰烽面特性和烧结性能的影响机理。模拟研究涉及多种烧结条件下的125个烧结杯工况。为揭示火焰烽面区域中熔体生成与凝固行为,使用FactSage软件进行化学热力学模拟并建立了更完善的熔化和凝固子模型。模拟与试验研究表明,随着碱度和焦炭添加量的变化,火焰烽面速度、成品率、焦比和利用系数会出现局部最大或最小值。在本文烧结条件下,最大利用系数工况为碱度2.0、水分7.7%、焦炭6.4%。最小焦比工况为碱度2.0、水分6.5%、焦炭6.4%。最小焦比和最大利用系数的条件并不相同,而最终烧结操作取决于每个烧结厂的控制目标。     

混合料特性对烧结火焰烽面传播特性影响的数值模拟研究

铁矿石烧结过程涉及传热、传质、流动、燃烧、相变等物理化学过程,且各过程之间相互耦合,实验研究难度较大。本文通过建模和数值计算研究混合料特性对火焰烽面传播过程的影响。研究结果表明,随着烧结负压的提高,进口空气流量增大。当床层初始堆积密度增大时,火焰烽面速度几乎线性下降。实际烧结生产中,最佳火焰烽面速度床应由烧结矿产量和质量共同决定。     

碱度对含铬型钒钛磁铁矿烧结性能的影响

以承德建龙特殊钢有限公司现场条件为依据,通过烧结杯实验模拟碱度(R)对含铬型钒钛磁铁矿烧结性能的影响,分析了其显微结构.结果表明,随碱度提高,烧结速度先增大后减小,R=2.5时最大,为19.70 mm/min,烧损增大;R=2.7时转鼓强度最高,为63.53%;碱度提高改善含铬型钒钛烧结矿的低温还原粉化指数(RDI),R=2.7时大于3.15mm的颗粒的RDI最高,为75.09%;碱度增大生产率先增大后减小,R=2.5时最高,为1.35 t/(m2·h).R=2.1~2.5时燃耗比上升,R=2.1时最低,为43.21 kg/t.碱度提高有利于提高软化开始和软化终了温度,改善含铬型钒钛烧结矿的软化性能、矿物组成及结构,是其性能改善的内因.该矿适宜的生产碱度为2.5.     

料层减荷烧结支撑板支撑结构优化

通过在料层内安装支撑板,减轻下部料层荷重,改善料层尤其是燃烧带的透气性,达到提高生产率的目的.以利用系数、转鼓强度为考察对象,通过正交实验,研究了烧结混合料水分、支撑板高度、支撑面积对利用系数、烧结矿转鼓强度的影响,应用综合分析法确定了最佳支撑结构,即支撑板高度约为料层高度的1/2,支撑面积为所支撑烧结饼面积的1.0%～1.2%.最优方案与基准实验的对比表明,应用料层减荷烧结,烧结生产率最大提高28.05%,转鼓强度下降3.75%,料层收缩减小28 mm,还原性提高0.46%.     

烧结烟气中成分对焦炭还原NO影响的实验研究

利用烧结烟气循环流化床燃烧的深度净化技术,可低成本、高效地实现烧结烟气中污染物的超低排放。为了探究该技术中循环流化床密相区内焦炭还原NO的机理,以焦作无烟煤所制焦炭为实验对象,利用高温立式管式炉实验台模拟循环流化床密相区,在750℃～950℃温度下,研究烧结烟气中分别加入组分CO,CO₂,O₂时,焦炭还原NO的转化率随时间变化规律。结果表明：在无O₂通入的反应条件下,随着反应温度的提高,焦炭对NO的还原率逐渐增加;CO的加入提升了焦炭对NO的还原率,在反应温度为900℃时,加入体积分数为0.4%的CO可最大提升17%的NO还原率;CO₂的加入则抑制了焦炭对NO的还原率,在反应温度为950℃时,加入体积分数为10%的CO₂使得NO还原率最大降低了21%;O₂的加入明显抑制了焦炭对NO的还原效果,在反应温度为950℃,通入气体中体积分数为13%的O₂时,NO的还原率下降至31%,且明显缩短了焦炭的还原时间。研究结果可为烧结烟气循环流化床燃...     

烧结助剂对堇青石-莫来石复相陶瓷的致密化和烧结特性的影响（英文）

以高岭土、滑石、工业氧化铝为原料,加入不同含量的B_2O_3、Nd_2O_3、Y_2O_3烧结助剂,通过原位反应烧结法合成了堇青石-莫来石复相陶瓷,研究了烧结助剂对其致密度和烧结特性的影响。采用X射线衍射(XRD)、扫描电子显微镜(SEM)和能谱仪(EDS)表征试样的晶相组成和微观结构。利用FactSage 6.0软件对系统的相组成和液含率进行了模拟对比分析。结果表明:B_2O_3具有最好的助烧结性。添加2.0%B_2O_3的复相陶瓷样品的烧结温度降低,致密度和机械强度提高,其经1 420℃烧成后吸水率和抗折强度分别为0.03%和116.70 MPa。经XRD分析和FactSage模拟证实,由于B_2O_3的液相烧结作用,物质间的固相扩散转变为液相扩散,促进了样品中四方堇青石的生成(未添加B_2O_3样品相组成为六方堇青石)。SEM和EDS结果表明,2.0%B_2O_3促进了晶体的生长与发育,四方柱状或块状堇青石与针棒状莫来石相互交织穿插排列,赋予样品较高的致密度和强度。     

铁矿烧结过程SO2的排放特性及过程脱硫的可行性研究

通过烧结杯实验,探究铁矿烧结过程中SO2的生成及排放特性,并基于SO2排放特性提出了在过湿层内添加尿素颗粒与烧结过程同步脱硫的新方法. 结果表明,铁矿烧结过程前期生成的SO2被料层内水分吸收并积聚在过湿层内,烟气中的SO2浓度稳定在较低水平;当过湿层被高温烟气干燥完成并开始消失时,被水分吸收的SO2会大量、迅速地释放,与尿素脱硫剂快速反应生成硫酸铵超细颗粒,并通过除尘捕获,既不进入烧结矿,也不随烟气排向大气. 工业试验表明,该方法可将SO2排放浓度从基准期时694.2 mg/m3降低至108.0 mg/m3,脱硫率为84.4%. 另外,该工艺与现有脱硫工艺相比,具有投资成本低、脱硫过程简单等优点.     

双层配碳烧结过程的传热传质分析

为了研究双层配碳下的铁矿石烧结过程及其节能效益,建立了铁矿石烧结过程的二维非稳态数学模型。模型基于多孔介质理论,考虑了烧结过程中的主要物理变化和化学反应,以烧结杯为求解对象,利用FLUENT软件及C语言自定义编程对烧结过程进行了数值模拟,并利用烧结杯实验数据对模型进行了验证。通过对常规均匀配碳和双层非均匀配碳烧结的传热传质过程进行仿真计算,分析了两种烧结方式下床层温度和物料熔化分数分布,并通过熔化分数对烧结矿成品率进行判定。研究结果表明：在不改变整个床层配碳量的条件下,相对于单层均匀配碳,双层配碳条件下热效率更高,床层温度和物料熔化分数沿料层高度分布更加均匀;上下层物料配碳分别为5%和3.4%且料层厚度相同时,烧结成品率提高10%;降低上层高配碳区料层厚度,即当上下层厚度比为5：9,配碳为5%和3.756%时,成品率能够进一步提高。     

双层配碳烧结过程的传热传质分析

为了研究双层配碳下的铁矿石烧结过程及其节能效益,建立了铁矿石烧结过程的二维非稳态数学模型。模型基于多孔介质理论,考虑了烧结过程中的主要物理变化和化学反应,以烧结杯为求解对象,利用FLUENT软件及C语言自定义编程对烧结过程进行了数值模拟,并利用烧结杯实验数据对模型进行了验证。通过对常规均匀配碳和双层非均匀配碳烧结的传热传质过程进行仿真计算,分析了两种烧结方式下床层温度和物料熔化分数分布,并通过熔化分数对烧结矿成品率进行判定。研究结果表明:在不改变整个床层配碳量的条件下,相对于单层均匀配碳,双层配碳条件下热效率更高,床层温度和物料熔化分数沿料层高度分布更加均匀;上下层物料配碳分别为5%和3.4%且料层厚度相同时,烧结成品率提高10%;降低上层高配碳区料层厚度,即当上下层厚度比为5:9,配碳为5%和3.756%时,成品率能够进一步提高。     

稀薄燃气多孔介质燃烧二维火焰数值模拟

对稀薄低热值气体在多孔介质燃烧中的二维火焰温度分布进行了数值模拟。在一定工况参数下,考察了多孔介质二维火焰峰面和温度分布特性,以及火焰峰面传播过程。详细分析了当量比、燃气流速、及壁面热损失等工况参数对燃烧火焰和高温峰值的影响。结果表明,在火焰传播过程中,火焰峰面形状逐渐变化,导致高温区域分布逐渐改变;随着当量比增加,近壁面处的火焰峰面倾斜程度逐渐减少,火焰峰面逐渐向上游传播,火焰峰面形状由梯形分布逐渐转变成两侧向下倾斜的直线分布;燃气流速对火焰峰面形状和位置的影响与当量比相反;壁面热损失引起火焰峰面倾斜,对火焰位置影响较小。     

Influence of coke rate on thermal treatment of waste selective catalytic reduction (SCR) catalyst during iron ore sintering

Waste selective catalytic reduction (SCR) catalyst as a hazardous waste has a significant impact on the environment and human health. In present study, a novel technology for thermal treatment of waste SCR catalyst was proposed by adding it to sinter mix for iron ore sintering. The influences of coke rate on the flame front propagation, sinter microstructure, and sinter quality during sintering co-processing the waste SCR catalyst process were studied. In situ tests results indicated the maximum sintering bed temperature increased at higher coke rate, indicating more liquid phase generated and higher airflow resistance. The sintering time was longer and the calculated flame front speed dropped at higher coke rate. Sinter microstructure results found the coalescence and reshaping of bubbles were more fully with increasing coke rate. The porosity dropped from 35.28% to 25.66%, the pore average diameter of large pores decreased from 383.76 μm to 311.43 μm. With increasing coke rate, the sinter indexes of tumbler index, productivity, and yield, increased from 33.2%, 9.2 t·m^-2·d^-1, 28.9% to 58.0%, 36.0 t·m^-2·d^-1, 68.9%, respectively. Finally, a comprehensive index was introduced to systematically assess the influence of coke rate on sinter quality, which rose from 100 to 200 when coke rate was increased from 3.5% (mass) to 5.5% (mass).     

Thermogravimetric Analysis of Moisture Desorption from Coal

In coke production, the moisture content of the initial coal is an important parameter. The moisture present in the pores of coal changes the properties of the coking batch. Note also that, together with methane and/or carbon dioxide, water may form gaseous hydrates in the coal bed. In the present work, to study the state of the moisture in coal, attention focuses on eight samples of natural gas saturated to constant moisture content in an atmosphere where the relative partial pressure of water vapor is 91%. The moisture sorbed from the atmosphere has a U-shaped dependence on the metamorphic stage of the coal, with a minimum at coking coal (K coal). In similar conditions, the more mature T and A coal contains twice as much moisture as K coal, while the younger D and G coal contains about four times as much moisture. Thermogravimetric analysis of coal samples saturated to constant moisture content permits calculation of the rate of mass loss and activation energy for the evaporation of moisture in the heating of the given samples. For each coal sample, the temperature range where the evaporation of moisture may be described by a first-order Arrhenius equation is determined. The upper limit of this range is compared with the temperature corresponding to maximum rate of mass loss and also with the temperature corresponding to the maximum thermal effect.     

入炉煤水分对炼焦过程及焦炭质量的影响

通过测定入炉煤水分分别为1%、6%和12%时煤料堆密度、升温速度及坩埚焦性质,得出入炉煤水分对其性质的影响。降低入炉煤水分虽然对煤料本身性质影响不大,但是其在炭化室内结焦过程的动态发生了显著变化,可显著提高焦炉生产能力及改善焦炭质量。入炉煤水分为1%时,煤料堆密度、升温速度及坩埚焦的性质都大大好于入炉煤水分为6%和12%这两种情况。     

Numerical modeling of straw combustion in a fixed bed

Straw is being used as main renewable energy source in grate boilers in Denmark. For optimizing operating conditions and design parameters, a one-dimensional unsteady heterogeneous mathematical model has been developed and experiments have been carried out for straw combustion in a fixed bed. The straw combustion processes include moisture evaporation, straw pyrolysis, gas combustion, and char combustion. The model provides detailed information of the structure of the ignition flame front. Simulated gas species concentrations at the bed surface, ignition flame front rate, and bed temperature are in good agreement with measurements at different operating conditions such as primary air-flow rate, pre-heating of the primary air, oxygen concentration, moisture content in straw, and bulk density of the straw in the fixed bed. A parametric study indicates that the effective heat conductivity, straw packing condition, and heat capacity of the straw have considerable effects on the model predictions of straw combustion in the fixed bed.     

Coal blend moisture—a boon or bane in cokemaking?

A by-product coke making plant is required to supply sufficient coke of good quality and adequate gas of high calorific value for the integrated steel plant to be a going concern. The one element that influences the handling of coal and impacts the operation and efficiency of the plant is moisture. Compared to other important properties of the coal blend, moisture can be easily manipulated. The coal moisture can be increased simply by adding water through hose pipes. Also, it can be reduced to 5–6 mass percent using Coal Moisture Control (CMC) and 2–4 mass percent using Dry-cleaned & Agglomerated Pre-compaction System (DAPS). Moisture content is one among the many variables affecting the bulk density of coal blend and those controlling the coke qualities and yield. Increase in moisture reduces coal grindability, coking pressure and internal gas pressure; helps in dust suppression during charging and hence reduces jamming of ascension pipes and hydraulic main. Batteries charging coals with high moisture content are not troubled with roof carbon deposits. It was observed that when moisture content in coal blend of SAIL-Bokaro Steel Plant increased to more than 8.50%, the calorific value of coke oven gas improved. In the working moisture range of 9–11%, the increase of the yield of coke oven gas per 1% of working moisture is 5.2 m³. Studies have shown, however, that the increase in moisture content of coal beyond 8% hampers strong coke formation. Pre-carbonization preheating process generally showed an increase in the proportion of 40–80 mm coke, compared with wet charges. For SAILBokaro coke ovens, driving out 1% moisture from coal blend requires 125 Mega-calories of heat/oven. With lesser moisture, the emission of NO _x in atmosphere will also be low. On using dry to low moisture coal blend, the swelling of coke mass increases leading to difficulty in oven pushings. Hence, an optimum level of moisture content of charge coal needs to be maintained for improving coke oven productivity, coke quality and operational smoothness. The coke oven managers all around the globe maintain this optimum level according to their requirement, the operating conditions, the quality of product and by products, the oven health & age and the ease of handling.     

Sintering properties of composites consisting of carbon filler and binder

The sintering properties of composites consisting of coke and coal pitch are considered. The coke yield from pitch cannot be used to assess the sintering properties. The increase in coke yield from the pitch in the presence of filler is found to be correlated with increase in sintering properties and strength of the composite.     

Potential utilization of oil sludge incineration bottom ash for glass-ceramics: Crystallization kinetics,properties and toxicological evaluation

The bottom ash (OIBA) generated from the incineration of hazardous oil sludge is classified as a hazardous waste. In this work, the OIBA was applied as raw material to prepare SiO₂-Al₂O₃-CaO system glass-ceramics by melt-sintering with the addition of waste glass wool (GW). The effects of basicity (CaO/SiO₂ ratio, 0.52-1.05) and sintering temperature (900–1050 °C) on the crystallization kinetics, properties, microstructure, leaching concentrations of heavy metals and potential toxicity of glass-ceramics were investigated. The results showed that the crystallization pattern was two-dimensional crystallization, and with the decrease of basicity, the main crystalline phase evolved from gehlenite to diopside. And the glass-ceramics with basicity of 0.88 and sintering temperature of 950 °C exhibited the best comprehensive properties, including density (2.72 g/cm³), water absorption (0.06%), compressive strength (452.45 MPa) and chemical corrosion resistance. In addition, the reduction of heavy metal leaching concentration indicates that produced glass-ceramics showed excellent solidification effect on heavy metals, the low toxicity of glass-ceramics leaching solution to the wheat seeds and Artemia suggests the environmental protection characteristics of OIBA-based glass-ceramics. These findings proved that the glass-ceramics produced by OIBA and GW could be a promising method to dispose hazardous waste with preparing high value-added construction materials.     

焦炭颗粒增强铜-石墨复合材料的制备与性能研究

以改性酚醛树脂为粘结剂,以焦炭粉为颗粒增强相,采用传统模压成型工艺制备了一系列铜-石墨复合材料,并研究了焦炭粉的添加对复合材料的力学性能、导电性能及磨损性能的影响.结果表明:当焦炭粉质量分数为35%时,复合材料具有较好的综合性能.随着焦炭粉的加入,复合材料的弯曲强度有了显著提高,在焦炭粉质量分数为35%时弯曲强度达到最大值68.8MPa,比未添加焦炭粉时提高了近36%;同时,当焦炭粉质量分数为35%时,复合材料的电阻率已经达到了现用浸金属滑板的导电水平;焦炭粉质量分数35%的复合材料具有最低的磨损率,且在磨损过程中能在磨损表面形成较为完整的自润滑膜.     

Comparison of flame propagation properties of petroleum coke and coals of different rank

Ignition and flame propagation characteristics of 18 kinds of coal and a petroleum coke were investigated through a laser ignition experiment. Flame stability was strongly influenced by amount of volatile matter and pyrolysis rate. Lean limit of flame propagation was strongly influenced by amount of volatile matter. Flame propagation was observed when pyrolized volatile matter was mixed with surrounding air or oxygen, until the concentration of pyrolized volatile matter reached a constant value. Flame propagation velocity was strongly influenced by pyrolysis rate. As the pyrolysis rate increased, the flame propagation velocity increased. The flame propagation velocity of petroleum coke was higher than that of coal with the same volatile content. The flame propagation of petroleum coke was superior to what was expected based on the volatile content, primarily because the high pyrolysis rate caused a shorter ignition delay than what would be expected given the volatile content. A database for the lean limit of flame propagation was used to develop a flame stability model to estimate lean flammability of a large-scale burner. The model could predict the effect of the coal rank, the particle diameter distribution for lean flammability limit. The estimated lean flammability limit of petroleum coke (volatile content 11.5%) was equal to that of lv bituminous coal with volatile content of about 15%.