煤与糠醛渣混燃的热重分析及基于分布活化能模型的动力学研究

通过热重技术研究煤与糠醛渣混燃的燃烧动力学,采用分布活化能模型(DAEM)进行了动力学分析,比较纯煤、纯糠醛渣及两者在3种不同掺混比例、不同升温速率下燃烧反应的差异。结果表明:糠醛渣能够促进煤的燃烧,随着糠醛渣加入量增大,试样着火温度下降,燃烧性能改善;糠醛渣掺混比例增大,燃烧反应的活化能呈下降趋势。     

淮北矿区煤矸石与煤混合燃烧特性的研究

本文利用STA-409PC热重分析仪,研究了淮北矿区不同质量比的煤矸石与煤混配样品的燃烧性能与动力学特性。结果表明：随着混配样品中的煤比例的增加,其着火温度和燃尽温度都有所降低,综合燃烧特性指数都有所增大,着火和燃烧特性都得到改善。本文还利用Coats--Redfern积分法对上述样品燃烧过程进行了动力学分析,得出淮北矿区煤矸石与煤混煤的燃烧反应历程服从1．5级的化学反应,对优化超临界流化床（简称CFB）锅炉混配燃料的运行具有重要意义。     

O2/CO2气氛下污泥与烟煤混合燃烧特性

在热重分析仪上开展不同参数条件下污泥和烟煤混合燃烧实验,分析污泥掺混比、升温速率和O2/CO2体积比对燃烧特性的影响,进行燃烧动力学分析.结果表明:O2/CO2气氛下,烟煤掺烧污泥的混合燃烧特性表现为污泥与烟煤燃烧叠加的结果;随着升温速率由10℃/min增加至25℃/min,着火和燃尽温度均升高,着火时间延迟和燃尽时间延长,表观活化能升高;随着O2/CO2体积比的增大,着火温度和燃尽温度均降低,着火时间提前且燃尽时间缩短,表观活化能降低,当O2体积分数超过30%时,燃烧性能改善的幅度越来越小.     

焦粉粒径对烧结床中燃烧带分布的影响

在烧结杯台架上采用石英砂和焦粉混合模拟铁矿石烧结过程,研究焦粉粒径对烧结燃烧过程的影响.随着焦粉粒径的增加,烧结生料床的透气性改善,燃烧过程中的火焰前锋速度增加.焦粉粒径对燃烧带宽度有重要影响,保持总的焦粉质量分数不变,在1.0~1.4mm焦粉基础上,增加0.71~1.0mm焦粉质量分数,燃烧带宽度先增加,当增加至30%时,床层温度分布出现双峰现象,燃烧带宽度减少.提高焦粉质量分数,有利于提高燃烧带温度和增加燃烧带持续时间,减缓甚至消除燃烧带温度分布出现双峰现象.燃烧带中的温度分布出现双峰主要是由于焦粉粒径分布不均或是燃烧带中由于氧量较低造成了焦粉在主燃区内未能燃尽,随着燃烧带的下移,氧气体积分数增加,未燃尽焦粉燃烧加速,燃烧热释放速率增加,床层温度上升.     

高炉渣气雾粒化性能试验研究

针对高炉熔渣的粒化环节,在气淬的基础上加入喷雾射流,通过实验研究了不同气压、水流量和出渣温度对熔渣粒化性能的影响,包括熔渣颗粒的飞行轨迹、粒径分布、成珠率等。结果表明：气量和水量的增大有助于提供给渣流更多的动量,使渣粒的飞行时间越长,渣粒落地粘壁的比例越小;喷雾射流的加入在水流量小于1.5 L/min时,在一定程度上可以强化熔渣的破碎过程,使渣粒平均粒径减小,随着喷雾量的持续增加,熔渣的粒径分布整体呈先减小后增大的趋势,熔渣成珠率先增大后减小;随着气流速度的增大,渣粒的平均粒径先逐渐减小,后趋于稳定,渣粒的成珠率随着气体流速逐渐增大后逐渐趋于稳定值,最大约83%;渣流温度的不同导致其具有不同的黏度,渣流温度越大,黏度越低,成珠率越好,粒径越小,熔渣的粒化性能越好。     

煤粉粒度对元宝山褐煤燃烧特性的影响

为了给实际工程应用中煤粉粒度的确定提供参考,采用热重分析的方法,研究煤粉粒度对元宝山褐煤燃烧特性的影响.对燃烧热重曲线特征参数分析表明,粒度减小,煤粉着火提前、燃尽时间缩短;粒度减小,可燃指数C和综合燃烧指数S增加,表明煤粉燃烧性能得到改善;用Coats-Redfern方法求解燃烧反应的动力学参数,燃烧反应动力学分析表明,元宝山褐煤的热天平燃烧反应为一级反应;在最大燃烧速度对应温度前后燃烧过程分成两个阶段;粒度减小,各段燃烧反应的表观活化能和质量平均表观活化能均降低.减小煤粉粒度对改善煤粉燃烧性能是有利的.     

熔盐法从提钒尾渣中制取白炭黑的研究

以提钒尾渣为原料,NaOH为熔盐,NaF为氧化剂,研究熔盐法提取硅的实验过程。以浸取硅酸钠溶液作为硅源,利用化学沉淀法制备无定型白炭黑。结果表明:硅浸出率随着碱渣比、煅烧温度及煅烧时间的增大而先增大后减小;通过正交试验对实验数据进行分析,对硅浸出率的影响由大到小为:碱渣比煅烧温度煅烧时间;最佳试验条件为碱渣比3∶1、反应温度550℃、反应时间3h,此条件下硅浸出率可达到96%以上。对制备白炭黑样品进行XRD、红外光谱、SEM表征和粒度分析,结果表明:白炭黑为无定形结构,粒子呈球形,粒径大小均一,平均粒径为200nm。.     

木材热解与着火特性试验研究

在自行研制的火灾固体可燃物热解与着火早期特性试验台上,对建筑装潢常用的几种木材以及森林常见的木材进行了热解和着火特性试验研究.试验木材尺寸为100 mm×100 mm×15 mm,试验选择辐射热流强度范围为20～60 kW/m2.分别就不同含水率、不同氧气体积分数、木材的纹理方向、不同的材料、不同厚度以及外加辐射热流强度等6个方面,对木材热解和着火特性的影响进行了研究.结果表明,随着辐射热流的增加,着火时间缩短、着火温度下降;随着木材含水率的增加,着火时间延长;不同环境氧气体积分数对木材热解和着火特性影响很大.预测了木材着火时间,通过试验值和理论计算值比较,两者吻合较好.     

生物质与不同变质程度煤混合燃烧特性的研究

采用TG／DTG／DTA技术研究了不同变质程度煤(褐煤、烟煤和无烟煤)、生物质(小麦秸秆和玉米芯)以及煤和不同比例生物质的混合燃料的燃烧特性，升温速率为15c／min，温度范围为25～900℃，分析了燃烧特征参数如着火温度、燃烧速率最大时的温度、燃尽温度和最大燃烧速率以及燃烧特性指数．采用Freeman-carroll(FC)法计算了燃烧动力学参数．结果表明，生物质和煤相比具有较低的燃烧特征温度和较快的燃烧速率；在褐煤和烟煤中加入生物质后，燃烧特征温度降低，燃烧速率增大；无烟煤中加入生物质后，对其着火温度影响较小，燃尽温度降低；此外，加入生物质后煤的燃烧表观活化能降低，表观活化能E与指前因子A存在动力学补偿效应。     

流化床燃烧中煤含灰量对灰渣形成特性的影响

为了研究煤颗粒灰质量分数对煤在流化床燃烧过程中灰渣形成特性的影响,在一台小型流化床反应炉上进行煤的灰质量分数对灰渣形成特性的实验.按煤颗粒的灰质量分数,把义马烟煤分为6个颗粒组,并选用各颗粒组的3个粒径范围的煤颗粒进行燃烧实验,研究煤颗粒的灰质量分数对底渣质量分数、底渣与飞灰中的碳量质量分数和粒径分布的影响.结果表明,随着煤颗粒灰质量分数的增加,燃烧形成的底渣质量分数增加,而煤颗粒的燃尽率和飞灰中的碳质量分数都降低.在粒径和燃烧时间相同的条件下,随着颗粒灰质量分数的增加,底渣中留在本粒径档的颗粒质量分数明显增加,而细颗粒的质量分数明显减少.而颗粒灰质量分数对飞灰的粒径分布没有明显的影响.     

煤/生物质恒温混燃的协同特性

为探讨煤/生物质恒温混燃的协同特性,利用自制实验系统对煤/生物质恒温混燃进行实验,探讨了掺混比、温度及煤种等对煤/生物质恒温混燃协同特性的影响规律。研究表明:在煤/生物质恒温混燃初期,煤粉燃烧受到一定的抑制作用,生物质掺混比加大或温度升高均能缩短抑制作用时间。此外,挥发分含量高的煤种受到的抑制作用较大;在混燃后期,掺混生物质对煤粉的燃烧与燃尽存在促进作用,生物质掺混比增大,促进作用加强,燃尽时刻提前程度增大。温度升高,促进作用减弱,燃尽时刻提前程度减小。此外,难燃的煤种受掺混生物质的促进燃烧和燃尽作用较明显。     

Combustion characteristics of semicokes derived from pyrolysis of low rank bituminous coal

Various semicokes were obtained from medium-low temperature pyrolysis of Dongrong long flame coal. The proximate analysis, calorific value and Hardgrove grindability index (HGI) of semicokes were determined, and the ignition temperature, burnout temperature, ignition index, burnout index, burnout ratio, combustion characteristic index of semicokes were measured and analyzed using thermogravimetry analysis (TGA). The effects of pyrolysis temperature, heating rate, and pyrolysis time on yield, composition and calorific value of long flame coal derived semicokes were investigated, especially the influence of pyrolysis temperature on combustion characteristics and grindability of the semicokes was studied combined with X-ray diffraction (XRD) analysis of semicokes. The results show that the volatile content, ash content and calorific value of semicokes pyrolyzed at all process parameters studied meet the technical specifications of the pulverized coal-fired furnaces (PCFF) referring to China Standards GB/T 7562-1998. The pyrolysis temperature is the most influential factor among pyrolysis process parameters. As pyrolysis temperature increases, the yield, ignition index, combustion reactivity and burnout index of semicokes show a decreasing tend, but the ash content increases. In the range of 400 and 450 °C, the grindability of semicokes is rational, especially the grindability of semicokes pyrolyzed at 450 °C is suitable. Except for the decrease of volatile content and increase of ash content, the decrease of combustion performance of semicokes pyrolyzed at higher temperature should be attributed to the improvement of the degree of structural ordering and the increase of aromaticity and average crystallite size of char. It is concluded that the semicokes pyrolyzed at the temperature of 450 °C is the proper fuel for PCFF.     

纳米TiO2对两种煤燃烧脱硫的对比分析

对纳米TiO2催化CaO燃烧脱硫进行了实验研究.探讨了纳米TiO2添加量、Ca/S摩尔比及燃烧温度对CaO脱硫的影响,还比较了纳米TiO2对不同煤种的脱硫效果.并对反应产物进行了X射线衍射、红外光谱和扫描电镜分析,讨论了纳米TiO2催化脱硫和催化燃烧机理.结果表明,纳米TiO2最佳的添加量为8％;在Ca/S摩尔比为2、...     

Pyrolysis and co-pyrolysis of lignite and plastic

The study firstly discusses the pyrolysis characteristics and kinetics by thermogravimetric analysis (TGA), and then investigates the pyrolysis of lignite and co-pyrolysis with plastic (polyethylene or polypropylene) in tube furnace. Meanwhile, the research focuses on the co-pyrolysis products under different mixing ratios as well as pyrolysis products at different testing temperatures and heating rates. The results show that higher final testing temperature and lower heating rate contribute to bond fission in lignite pyrolysis, resulting in less char product. In co-pyrolysis, lignite acts as hydrogen donor, and the yields of char and water rise with increasing amount of plastic in the mixture, while the yields of gas and tar decrease; and a little admixture of plastic will promote the production of gas and tar. Kinetic studies indicate that in temperature range of 530–600 °C, activation energies of lignite are higher than those of lignite/plastic blends, and as plastic mass ratio increases from 0% to 10%, samples need less energy to be decomposed during co-pyrolysis.     

褐煤与稻草混合半焦燃烧特性及动力学研究

用热重法研究了褐煤与稻草混合半焦的燃烧特性,考察了稻草比例和半焦制备温度对混合半焦燃烧特性的影响,并对其燃烧动力学参数进行了计算．结果表明：半焦制备温度为350℃和550℃时,稻草比例对混合半焦的燃烧几乎没有影响;在750℃时,稻草比例为20％的混合半焦其TG和DTG曲线明显向高温区偏移．随着制备温度的提高,混合半焦着火温度提高,失重率减少．半焦燃烧为一级反应（n=1）,活化能在49．78～83．04kJ／mol范围内,制备温度越高,混合半焦的活化能也越高．随着稻草比例的变化,活化能没有表现出明显的规律性．     

Effect of NaOH treatment on combustion performance of Xilinhaote lignite

The combustion characteristics of NaOH treated and untreated Xilihaote lignite was investigated by thermogravimetric analysis. The relationship between physico-chemical properties, including the ash content, oxygen-containing functional groups, mean pore diameter and specific surface area and combustion performance, was also studied in this paper. Combustion kinetic parameters were calculated through Coasts Redfern Method. The results show that ignition of treated samples takes place at higher temperature compared to raw lignite, and peak temperature also occurs at higher temperature. The maximum combustion rate of the sample, which was treated by 0.01 mol/L NaOH lignite, was the biggest. Reaction orders of 0.6, 2.0, and 0.8 were found to be effective mechanism for definite three temperature regions. Average activation energies of these three temperature regions of XLHTR, XLHT0.01, XLHT0.50 and XLTH1.00 are 19.17, 23.87, 10.77, and 10.93 kJ/mol, respectively. Treatment of lignite with NaOH can reduce the reactivity of lignite at proper concentration.