神木煤-CH_4微波共热解产物生成规律研究

以半焦作为微波吸收剂和CH4裂解催化剂,在固定床反应器上考察了CH4气氛下神木煤微波热解特性,对CH4气氛下神木煤-半焦混合物在不同温度(450℃~700℃)下微波热解产物的生成规律进行了研究,并与相同条件的N2气氛下微波热解结果进行了比较.研究表明,CH4气氛下神木煤的微波热解半焦产率比N2气氛下的半焦产率低;而焦油产率和热解水产率高于相同条件N2气氛下的焦油和热解水产率.在CH4气氛下煤-半焦混合物微波热解,H2和CO产率高于N2气氛下的结果,而CO2产率低于N2气氛下微波热解的CO2产率.综合对比两种气氛下热解产物的生成规律可知,在半焦催化作用下,CH4在微波加热条件下可以实现对神木煤的直接加氢,提高煤的热解转化率.     

含油污泥混煤热解动力学及气体产物分析

采用热重分析法在不同掺混比例、不同升温速率和不同掺混煤种下对含油污泥混煤进行热解实验研究,并通过气相色谱仪分析热解产生的气体产物.结果表明,含油污泥混煤的热解失重过程可以分为水分及吸附气的挥发、轻烃的析出、重烃的裂解和煤小分子链脱除、重烃的二次裂解和煤大分子链脱除、半焦的缩聚反应以及无机矿物质的分解5个阶段.进行热解动力学分析,采用Coats-Redfern积分方法求解含油污泥混煤的热解动力学参数,并得到了掺混比例、升温速率、煤种对动力学参数的影响规律.利用气相色谱仪检测生成的气体产物有H2,N2,CO2,CO,CH4,C2H6,C2H4,C3H8和C3H6等,并分析了主要气体产物H2,N2,CO2和CH4的生成规律.     

煤热解过程中气态产物分布的研究

利用固定床热解装置对3种不同煤种进行了热解研究,考察了温度和煤的性质对热解气态产物以及硫元素逸出规律的影响,结果表明:除了煤的性质外,温度是影响热解产物分布的重要影响因素;同时CO和CO2的逸出量与煤中氧元素的含量有关,而生成CH4和气态烃的量与H/O原子比有很大关系;热解过程中含硫物质以H2S和少量COS的方式逸出到气相,而逸出的气态硫也与煤的含硫量有直接关系.     

核桃壳催化热解特性及动力学实验研究

利用TG-FTIR联用技术研究了升温速率和催化剂(γ-Al2O3,KCl和USY)对核桃壳热解失重特性和产物生成的影响,并对热解过程进行了动力学分析。结果表明,核桃壳热解主要失重发生在200~450℃,失重78%~82%;升温速率对热解特性的影响较大,随升温速率的增大,核桃壳热解转化率有所降低,热解起始温度及最大失重峰对应的温度向高温侧移动;核桃壳热解符合一级动力学模型,活化能为58~62 k J/mol。热解的气态产物主要有CO2、H2O、CO、CH4及酸、醛、酮等羰基化合物,催化剂不仅提高了核桃壳热解的转化率,而且改善热解产物的组成与分布。     

利用TG-FTIR研究三种典型烟煤的热解特性及生烃行为

文章借助热重联用红外技术(TG-FTIR)考察了三种典型烟煤的热解失重特性和轻烃生成行为。结果显示所选三种煤的热解反应活性顺序为济宁煤神木煤大同煤。热解气相产物中所鉴别出的轻烃包括CH4、C2+脂肪烃以及C2H4。大同煤的热解产物中CH4含量最高,C2+脂肪烃在济宁煤的热解产物中浓度最大,而神木煤热解产物中C2H4含量最高。此外,C2H4与C2+脂肪烃在煤热解过程中同时形成,其生成机制相同;而CH4虽也属轻烃,但不与C2H4和C2+脂肪烃同时产生,其形成机制与C2H4和C2+脂肪烃不同。     

煤与生物质共热解特性初步研究

初步研究了煤与生物质共热解时的协同作用,热解实验研究了大雁煤、木屑和两者混合物三个样品的热解特性,木屑与大雁煤热解特性相比,热解产物产率随温度变化特性形似,但热解的起始温度和热解温度区间有一定差别,两者混合物共热解时出现了协同作用,结果是半焦产率降低,焦油和气产率增加,热解气组成中H2和CH4 降低,CO和CO2增加.     

不同温度区间内污泥热解气固相产物特征

对城市污水污泥(简称污泥)进行工业分析和热重分析,考察污泥的基本组成和热重特性;采用气相色谱(GC)检测了不同热解温度区间内污泥热解生成的气体产物成分,并利用SEM和BET分别分析了不同热解终温下裂解炭的形貌特征和比表面积。结果表明:污泥热解可以分为水分析出阶段、挥发分析出阶段和焦炭化阶段;不同热解温度区间内污泥热解气体产物的组成有很大差别,热解温度350℃后H2在热解气中的含量快速增加,CH4含量在350~450℃时达到最大值,而CO主要在热解温度为350~750℃时生成,CO2含量随着热解温度的增加迅速下降;随着热解终温的不断升高,裂解炭结构变得越来越疏松,比表面积也随之增大,750℃达到最大值55 m2·g-1。     

褐煤热解及半焦成型特性研究

以褐煤为原料,通过原煤热解与半焦成型实验,研究了热解终温对产物分布的影响及半焦的成型特性与反应活性;利用气体在线分析仪、GC-MS对热解产物进行表征;研究结果表明,热解温度由450℃提高到750℃,热解气体产率持续增大,半焦收率则持续减少,焦油收率在550℃时最高;气相组分中H2含量持续增加,CO2和CH4含量减小,CO含量在650℃时最高;热解焦油主要由萘及其衍生物、高碳数直链烷烃、苯酚及其衍生物、蒽、菲及衍生物、稠环芳烃和中性含氧化合物(醛、酮、呋喃)组成,随热解温度升高,多侧链取代化合物含量减少,稠环化合物含量增加;热解改质后,半焦型煤强度提高了3 MPa,半焦型煤的CO2反应活性高于半焦。     

大同煤热解和加氢热解过程中产物生成规律的研究

在压力2MPa,温度350—650℃范围内,对比研究了大同煤分别在氮气和氢气气氛下热解过程中产物的分布和气体生成规律。研究表明,煤的热解和加氢热解转化率和水产率都随温度上升而增加;在热解条件下,焦油产率在500℃出现最大值。氢气对煤热解转化只有超过一定温度才具有促进作用,此时与热解相比具有较高的CO、CH4和C2^＋产率以及较低的CO2产率。     

催化剂对不同粒径褐煤热解特性及其煤焦微晶结构的影响

以内蒙褐煤为研究对象,在固定床反应器上考察了催化剂对不同粒径褐煤热解过程中的各气体组分含量以及产气率的影响,通过XRD研究了热解后煤焦的微晶结构特性。研究结果表明:无论是原煤还是负载催化剂的褐煤,随着粒径增大,其热解产气率下降;对于各气体组分,CO,H2,CH4含量均随原煤颗粒粒径增大而下降,CO_2却呈相反趋势。而在粒径相同的情况下,负载催化剂的试样热解产气率稍大于原煤试样,且随着催化剂含量的增大,产气率提高,试样热解产生的CO_2和CH4含量呈增加趋势,但H2,CO含量却有所下降。对于粒径较大的试样,由于挥发分脱除不够完全,生成的煤焦碳化程度较低,使得煤焦石墨化程度也较低。此外,当粒径相同的情况下,负载催化剂的煤焦碳微晶结构越无序,则随着催化剂负载量的增加,越阻碍试样石墨化的进程。     

煤岩显微组分分离富集物热化学反应特性

依据煤中不同类型有机质性质差异对其进行分离，进而分质利用是实现煤炭清洁高效利用的有效手段。论文利用重选法将一种低变质烟煤分质得到镜质组较原煤48.25%增加至76.02%的富镜样，惰质组较原煤43.96%增加至63.98%的富惰样，以及矿物质含量高于61.99%的富矿样。利用热重-质谱分析仪，考察了分离富集物的热解反应特性及气体逸出规律，及其燃烧和气化反应特性。结果表明，分离所得富镜样热解反应失重量及热解过程中逸出的小分子挥发分的量及组成与富惰样和富矿样均有明显差异，表明分质实现了煤中不同类型官能团的分离富集。而由分离所得富镜样、富惰样和原煤热解失重峰温基本一致则表明分质所得煤的主体官能团结构仍较为接近，但含量有明显差距。富镜、富惰与原煤的燃烧曲线整体趋势较为类似，燃烧活性差别不大。以气化反应峰值温度高低判断，富镜样气化反应活性最低，富惰样与原煤气化反应活性较为接近，富矿样气化反应活性最高。将原煤在对应热反应时的理论反应曲线与实验曲线进行对比，发现煤分质过程及煤中镜质组、惰质组和矿物质的分离与否对热解过程挥发分的逸出影响较小，但导致了其燃烧和气化反应活性有所降低。     

Chemical looping gasification of maceral from low-rank coal:Products distribution and kinetic analysis on vitrinite

The product distribution and kinetic analysis of low-rank coal vitrinite were investigated during the chemical looping gasification (CLG) process.The acid washing method was used to treat low-rank coal,and the density gradient centrifugation method was adopted to obtain the coal macerals.By combining thermogravimetric analysis and online mass spectrometry,the influence of the heating rate and oxygen carrier (Fe2O3) blending ratio on product distribution was discussed.The macroscopic kinetic parameters were solved by the Kissinger-Akahira-Sunose (KAS) method,and the main gaseous product formation kinetic parameters were solved by the iso-conversion method.The results of vitrinite during slow heating chemical looping gasification showed that the main weight loss interval was 400-600 ℃,and the solid yield of sample vitrinite-Fe-10 at different heating rates was 64.30％-69.67％.When β =20 ℃·min-1,the maximum decomposition rate of vitrinite-Fe-10 was-0.312％·min-1.The addition of Fe2O3 reduced the maximum decomposition rate,but by comparing the chemical looping conversion characteristic index,it could be inferred that the chemical looping gasification of vitrinite might produce volatile sub-stances higher than the pyrolysis process of vitrinite alone.The average activation energy of the reaction was significantly reduced during chemical looping gasification of vitrinite,which was lower than the average activation energy of 448.69 kJ·mol-1 during the pyrolysis process of vitrinite alone.The gaseous products were mainly CO and CO2.When the heating rate was 10 ℃·min-1,the highest activation energy for CH4 formation was 21.353 kJ·mol-1,and the lowest activation energy for CO formation was 9.7333 kJ·mol-1.This study provides basic data for exploring coal chemical looping gasification mecha-nism and reactor design by studying the chemical looping gasification process of coal macerals.     

神木煤热解的挥发分收率与岩相组成的关系

引　言从构成煤的微观层次的显微组分入手研究煤的组成、结构和性质已成为煤化学研究的一个重要方面 ,在这方面一些研究者已做过许多有意义的尝试 ,主要集中在有关配煤制优质焦炭等方面[1] ,对于煤的热解挥发分收率与岩相组成相关联的研究也有零星报道 .Ｄｕｘｂｕｒｙ[2 ] 对一系列煤及其显微组分的热解研究结果表明 :不同煤的镜质组和惰质组的热解挥发分产率相差不大 ,相同量的不同煤种挥发分量的不同是由壳质组引起的 .其他研究者因不能得到纯度较高的显微组分而仅对热解过程中镜质组和惰质组的相互影响做过推测 .对于煤的挥发分收率与岩…     

Formation of HCN and NH3 during coal macerals pyrolysis and gasification with CO2

Three coal macerals with high purities were separated from Pingshuo gas coal. The formation rules of HCN and NH₃ during macerals pyrolysis and gasification were investigated. Experiments were carried out in a tubular quartz reactor at atmospheric pressure. The reactor allowed coal particles to be heated up rapidly and held for a prespecified period of time at a peak temperature. The amount of HCN and NH₃ were quantified by ion chromatography. The influence of temperature and macerals type on the formation rules of HCN and NH₃ was discussed. Results showed that the formation of HCN was mainly due to the thermal cracking of volatile, and NH₃ formed both from the thermal cracking of volatile and the cracking of nascent char. The HCN yield increased with an increase in pyrolysis temperature. For three coal macerals (liptinite, vitrinite and inertinite), the yield of HCN depended not only on their volatile contents but also nitrogen-containing functional groups, in which more pyrrole-type nitrogens would form more amount of HCN at lower temperature. The yield of NH₃ depended on the ability of forming ‘H’ radical. Under the experiment condition in this study, inertinite could convert more nitrogen into NH₃ than vitrinite and liptinite. The yield of HCN during gasification was almost the same as that during pyrolysis, the yield of NH₃ during gasification was little higher than that during pyrolysis.     

低阶煤显微组分对混煤热解过程含氧官能团析出及转移规律的影响

采用化学滴定法,结合傅里叶红外分析,研究低阶煤显微组分对混煤含氧官能团析出及转移规律的影响,分析低阶煤镜质组分和惰质组分对混煤含氧官能团交互作用及析出转移规律的影响. 结果表明,混煤中酚、醇、醚、酯的C-O含氧官能团在热解温度达600℃时脱除达到基本稳定;400~600℃析氧率逐渐增加,之后稳定在30%左右,700℃后氧析出完全. 加入低阶煤使混煤热解过程中氢流失少于氧流失,有利于提高胶质体质量.     

基于显微组分化学键特征的宁夏庆华煤热解特性及动力学分析

通过X射线光电子能谱和傅里叶红外光谱表征宁夏宁东庆华煤不同显微组分的官能团种类、表面结构元素价态分布及化学键赋存特征。采用热重-质谱联用考察庆华煤镜质组和惰质组在不同热解温度下的失重行为和关键气体组分变化。进一步基于Coats-Redfern模型从化学键断裂特征和反应动力学角度探讨煤镜质组和惰质组的热解行为差异。结果表明,庆华煤显微组分的热解失重峰与相应化学键断裂信息能够很好地吻合。不同显微组分的热重曲线变化趋同,但相同热解温度下镜质组的失重率始终高于惰质组。快速热解阶段镜质组较惰质组表现出更大的失重率和最大失重速率。其主要原因在于镜质组的脂肪族官能团相对含量更高,快速热解阶段会发生更多的C_al—C_al断裂。不同热解温度下庆华煤显微组分三个主要热解阶段的活化能和频率因子大小次序为：快速热解阶段>快速缩合阶段>缓慢热解阶段。在快速热解阶段,镜质组和惰质组的平均活化能均约为75 kJ/mol,但镜质组的频率因子更高。     

Experimental and mechanistic study on chemical looping combustion of caking coal

Under high-temperature batch fluidized bed conditions and by employing Juye coal as the raw material,the present study determined the effects of the bed material,temperature,OC/C ratio,steam flow and oxygen carrier cycle on the chemical looping combustion of coal.In addition,the variations taking place in the surface functional groups of coal under different reaction times were investigated,and the varia-tions achieved by the gas released under the pyrolysis and combustion of Juye coal were analyzed.As revealed from the results,the carbon conversion ratio and rate were elevated significantly,and the vol-ume fraction of the outlet CO2 remained more than 92％ under the oxygen carriers.The optimized reac-tion conditions to achieve the chemical looping combustion of Juye coal consisted of a temperature of 900℃,an OC/C ratio of 2,as well as a steam flow rate of 0.5 g·min-1.When the coal was undergoing the chemical looping combustion,volatiles primarily originated from the pyrolysis of aliphatic-CH3 and-CH2,and CO and H2 were largely generated from the gasification of aromatic carbon.In the CLC process,H2O and CO2 began to separate out at 270 ℃,CH4 and tar began to precipitate at 370 ℃,and the amount of CO2 was continuously elevated with the rise of the temperature.     

胜利褐煤快速热解特性

为考察热解温度对热解产物品质及挥发分残留的影响,在10 kg/h自制褐煤快速热解提质试验设备上,以胜利褐煤为试验原料,考察了400~900℃热解提质温度对热解产物产率、气体产物组成、半焦微观结构以及残余挥发分的影响。结果表明,随着热解温度的升高,半焦产率逐渐降低,气体产率升高,焦油的产率先升高后降低,700℃时焦油产率最大;热解气体中的CO_2随着热解温度的升高逐渐降低,H_2和CO含量随着热解温度的升高而增加;随着热解温度的升高,挥发分不断释放导致半焦含氧官能团以及高活性的小的缩合芳环减少;热解温度≥700℃,半焦残留的挥发分较低,固定碳较多,基本满足电石用焦的要求。