流化床粉煤气体热载体快速热解反应器的计算

在冷态模拟实验和煤热解动力学计算的基础上,对粉煤气体热载体快速热解提升管反应器的高度进行了计算。利用高速摄像粒子测速法结合互相关算法研究了不同气体流量和不同颗粒粒径时固体颗粒在热解提升管中的运动速度,通过求解神府煤热解动力学方程,得到了不同粒径神府煤颗粒热解挥发分析出的时间,从而确定了快速热解提升管反应器的高度。研究结果表明:当气体流量在850 m3/h,粉煤的粒径主要集中在0.7—3.0 mm时,提升管的高度应选择在10.0 m。     

Cross‐Scale Modeling and Simulation of Coal Pyrolysis to Acetylene in Hydrogen Plasma Reactors

Coal pyrolysis to acetylene in hydrogen plasma is carried out under ultrahigh temperature and milliseconds residence time. To better understand the complex gas‐particle reaction behavior, a comprehensive computational fluid dynamics with discrete phase model has been established, with special consideration of the particle‐scale physics such as the heat conduction inside particle. The improved chemical percolation devolatilization model that incorporates the tar cracking reactions is adopted. The model predictions are in good agreement with the performances of two pilot‐plant reactors. The simulations reveal the detailed unmeasurable information of gas phase and particle‐scale behaviors, then point out the facts that coal devolatilization almost finishes in the first 100 mm of the reaction chamber and the optimal particle diameter is suggested to be 20–50 μm. The different reactor performances during the scale‐up from 2‐ to 5‐MW unit are analyzed based on the detailed simulation results in combination with the operational experience. © 2012 American Institute of Chemical Engineers AIChE J, 59: 2119–2133, 2013     

煤等离子热解制乙炔反应器可用能利用研究

介绍了煤等离子热解制乙炔的工艺过程及煤等离子热解制乙炔反应器装置的结构形式。通过对煤等离子热解反应器系统的热力学分析,得出了该反应器系统的分析模型,分析了（yong）损失产生的原因,提出降低损失的措施。改进后的反应器系统采用淬冷器、换热器的多级热传递及原料的预热等热量利用方式。实验结果表明,改进后的反应器系统的（yong）损失由改进前的591．4kJ／kg—coal下降为448．0kJ／kg—coal,减少了24．2％。     

Release of volatiles from large coal particles in a hot fluidized bed

Coal particles with diameters of 3–11 mm were injected into a small, hot bed of sand fluidized by nitrogen. Volatiles evolution was followed by sampling the exit gas stream and subsequent analysis by gas chromatography. Three Australian coals covering a range of volatile matter were studied and the effects of coal particle size and bed temperature were determined. The yields of gaseous components, char and tar are explained by consideration of the competitive reactions for coal hydrogen and oxygen and secondary reactions of the volatile species within the coal particle. The pore structure developed during devolatilization has a significant effect on the extent of these secondary reactions. It is concluded that heat transfer is the main process controlling the volatilization time in fluidized bed combustors. The time required for heat transfer into the coal particle, determined by calculation and experiment, agrees with the measured volatilization time. Significant factors are external heat transfer to the surface of the particle, internal conduction through the coal substance and radiation through the pores, and the counterflow of volatiles out of the coal particle. For different coals, variations in the volatilization time appear to be caused by the development of different pore structures, which affect radiant heat transfer through the pores.     

Particle‐scale modeling of coal devolatilization behaviors for coal pyrolysis in thermal plasma reactors

A generalized heat transfer and devolatilization model coupled with the thermal balance between the heating gas and particles was established to predict the complex coal pyrolysis behaviors in the practical plasma reactors. It was proved that this model could well describe the coal devolatilization behaviors in both the pilot‐scale and lab‐scale plasma reactors as the mechanisms of coal chemistry and particle‐scale physics were incorporated. The achieved understanding on the reactor energy balance demonstrated that the heat recovery of the quenching process was crucial to the thermal efficiency and economic benefit of the overall project. The in‐depth discussion of the influences of coal feed rate and particle size on the reactor performance revealed the dominant roles and presented the optimal values of these two factors. In particular, the simulation results of several coals could help to provide a simple, quick method of coal type selection for industrial plasma processes. © 2014 American Institute of Chemical Engineers AIChE J, 61: 913–921, 2015     

热分析在煤燃烧和热解及气化动力学研究中的应用

论述了煤的燃烧、热解、气化反应动力学的常用的单一升温速率法、多重扫描速率法、动力学补偿效应以及分布活化能动力学模型等热分析研究方法，分析了现用热分析动力学方法的局限性；并对反应控制热分析、微热分析技术、微波热分析以及热分析技术与其他分析技术的联用，热分析技术间的联用等热分析新技术在煤的燃烧、热解、气化反应动力学研究上的应用进行了展望．     

下行床煤拔头工艺的产品产率分布和液体组成

基于循环流化床锅炉燃烧技术和下行床技术相结合,在处理能力为8 kg/h的煤拔头工艺热态实验装置上,以内蒙古霍林河褐煤为原料,普通河砂为固体热载体,考察了反应温度和煤粉粒径对气液固产品产率分布和液体组成的影响规律. 结果表明,在实验温度范围内,随着温度的升高,气体和液体产品的产率增加;液体产率随粒径的增大而降低. 当反应温度为660℃、煤粉粒径小于0.28 mm、加料率为4.7 kg/h时,轻质焦油(焦油中的正己烷可溶物)的产率可达7.5%(干煤基,w),其中酚类占57.1%,粗汽油(脂肪烃类)占12.9%,芳香烃占21.4%,极性组分和其他组分占8.6%. 实验表明,下行床由于气固沿重力场并流向下流动的特点,是适合煤拔头工艺的比较理想的反应器.     

直立内热干馏炉所产不同粒度半焦的组成与结构特征

针对现有直立内热式干馏炉不同粒级半焦产物进行深入分析有助于认识原煤在炉内的热解反应行为和物料在炉内的运动与破碎等物理变化规律,采用国标方法研究了5座相同工业规模的直立内热干馏炉所产半焦的粒度分布、工业分析与发热量、有害元素与无机矿物组成情况,分别采用N₂吸附法和Raman光谱法测定了不同粒度半焦的孔隙分布与碳化学结构特征,并结合生产工艺分析了不同粒级半焦性质差异产生的可能原因。结果表明:13mm~25mm和6mm~13mm粒级在干馏炉所产半焦中占比最高,原煤的热稳定性是影响干馏炉内粒度降解的最重要因素;随着半焦粒度降低,受热解程度和矿物质作用共同影响,挥发分和灰分先降低后增高;小粒度半焦灰分中较高的碳酸盐降低了其发热量;小粒度半焦中全硫含量最高,各种形态硫随粒级变化规律不同;N、P和Cl元素在不同粒级半焦中无明显分布规律;随着粒度降低,CaO含量先降低后提高,而SiO₂含量先增高后降低;半焦中料和小料的孔隙结构最发达,碳结构有序化程度最高。     

固定床中热气体非稳态渗流传热与煤热解过程

针对煤燃烧前热解脱硫工艺 ,研究固定床中气体渗流传热传质与煤热解反应综合过程 ,建立多孔介质非稳态渗流传热传质与煤热反应相互作用的物理数学模型 ,研究不同情况下床内气固温度和煤热解挥发分析出浓度瞬态分布规律 .计算结果表明 ,固定床中煤料的热解反应主要发生在床层下部的热渗透作用区域 ,随着运行时间的延长 ,煤热解区段不断向床高方向推移 .提高热气入口温度 ,热渗透作用区域内的物料温度水平提高 ,煤粒热解反应期缩短 .在热作用区域 ,煤热解反应与渗流传热传质过程密切相关 .模型计算结果与文献中的实验数据进行了比较 ,两者符合较好 .研究结果对于煤燃烧前热解脱硫装置的设计与运行具有一定的参考作用     

以颗粒煤为助滤剂对城市污泥进行二段过滤脱水的研究

以颗粒煤为助滤剂,采用二段过滤方式来强化城市污泥的脱水,并对滤饼进行热值分析,探讨城市污泥资源化利用前景.在研究中,具体分析探讨了煤的类型、煤的添加比、煤的粒径、搅拌强度、过滤压力以及煤的添加方式对过滤过程中相关参数的影响.得到以下结论:在污泥和煤的添加比为1:2,颗粒煤粒度为0.15～0.18 mm,低强度搅拌,常温...     

低阶煤热解増油技术的研究现状与趋势

煤热解及热解产物深加工是实现煤的清洁高效利用的有效途径,具有重要的理论和战略意义。结合煤热解最新研究动态,从煤热解机理出发,论述了提高煤焦油产量的5种因素,提出今后应加强煤热解增油技术开发及煤热解产品深加工,提高煤分质分级利用的附加值。     

FD模型应用于煤热解过程的数值模拟

为将煤热解FD模型引入对煤热解实际过程的数值计算与分析,提出了适用于煤热解实际过程的数值计算方法。分别对3种不同的煤在热管反应器中的热解过程进行了数值计算,并与实验结果以及已有的FG-DVC模型、CPD模型的数值计算结果进行了对比分析。并分析了热解温度、颗粒粒径对煤热解产物的影响。结果表明,与FG-DVC模型、CPD模型相比,FD模型的计算精度更高,能更好地用于数值计算煤热解的实际过程;随着热解温度的升高,气体产量先快速增大,当热解温度高于1373 K时,气体产量的变化很小;而随着热解温度的升高,焦油产量一直逐渐减小,且达到焦油产量最大值所需的时间也缩短;随着颗粒粒径的增大,气体与焦油的产量都逐渐减小,而达到焦油产量最大值所需的时间却延长。     

煤等离子热解制乙炔热流场模拟的对比研究

简要介绍了煤热解制乙炔反应器的流程以及该工艺存在的结焦严重,热能损失较大,连续稳定运行时间短,整体反应器效率低,负荷小等缺陷,为了减少或抑制煤这种不足,利用GAMB IT前处理和FLUENT数值模拟软件针对工艺在不同保护气速度下进行了热流场的优化模拟及对比研究(默认等离子的温度5 000 K),并最终得出了保护气速度为70 m/s,煤热解的反应空间是最大的,有利于反应的充分进行,热量的利用率较高,此时出口截面的温度约为3 700 K,出口截面的速度约为18 m/s,防止结焦的效果最好。     

回转窑内利用液化残渣共热褐煤以抑制其粉化的影响因素分析

在公斤级回转窑中研究了共热解过程不同液化残渣与褐煤质量配比及粒度配比因素对抑制褐煤粉化效果的影响。结果表明：550℃共热解条件下,随液化残渣的添加比例由10%升至40%,共热解半焦的粉化率β由7.55%降至1.98%,造粒率λ由2.73%升至4.90%,液化残渣添加量的提升有效促进了对粉化的抑制及混合造粒;3～1 mm液化残渣与3～1 mm褐煤的共热解半焦β为2.82%,较与6～3/13～6/25～13 mm褐煤颗粒热解后的产物粉化率均低,而λ则达到24.99%,远高于其他粒度配比下的产物造粒率。灰色关联分析显示,粒度配比因素对β和λ的影响权重均大于质量配比因素。结合分析上述配比因素影响粉化抑制作用的内在诱因（强化粘连捕集颗粒行为,促进孔隙充填补强作用,颗粒穿层行为影响）,形成了回转窑热解过程配比因素对抑制褐煤粉化的影响过程模型。     

Influence of transport effects on pyrolysis reaction of coal at high heating rates

The kinetics of coal pyrolysis may be influenced either by chemical reaction or by transport processes, the latter becoming rate-determining at increasing heating rate, particle size and pressure. Quantitative data are reported for those parameters which cause pyrolysis to become transport-controlled. The experiments have been performed with three different coals in H₂ and N₂, at heating rates ranging from 10³ to 10⁴ K s^?1, pressure from 0.1 to 150 bar and particle size from 0.063 to 0.8 mm.     

固体热载体法褐煤热解过程中的传质传热特性

为揭示在固定床反应器中固体热载体法快速热解褐煤工艺过程中的热、质传递机理,建立了固体热载体法褐煤热解过程中的传质传热模型。模型包括球型颗粒的一维非稳态导热方程和基于分布活化能模型的动力学模块,分别采用有限容积法与Matlab软件中遗传算法工具箱对二者进行数值计算。通过呼伦贝尔褐煤热重实验数据与温度测定实验数据分别验证了预测的动力学参数及颗粒传热模型结果。研究发现,热、质变化在固体热载体法褐煤热解工艺中呈现复杂的耦合特性。此外,考察了在不同初始温度、热载体进料比与煤颗粒半径条件下,褐煤在热解过程中颗粒内部温度场在径向上随时间的变化规律,并分析了产物释放速率与温度场的关联性,结果表明热历程改变是工艺条件对热解产物分布造成影响的根本原因。     

Experimental study on mass transfer from pyrolysing coal particles

The molecular weight distributions of coal tars and coal char extracts were examined in an effort to learn more about the process of mass transfer during coal pyrolysis. Evidence was obtained which suggests that the majority of the tar evolved during rapid pyrolysis of pulverized coal escapes by a process limited by gas film diffusion. However, there is also some evidence that the tar includes a small amount of heavy material which could have been ejected from the particle in a condensed phase. Data were also obtained which suggest that the tar precursors (within the parent coal) are formed over a wide range of temperature and do not seem to be present as such in the raw coal. The rather large effect of pressure on yields of tar from bituminous coal pyrolysis has previously been attributed to the effect of pressure on evaporation rates of tar precursors from the particle surface. This study shows that the molecular weight distributions of both the tar and extractable tar precursors within the particle are consistent with such a mechanism.     

煤裂解制取化学品的研究进展

煤裂解制取高附加值化学品是煤炭利用的一个新课题。围绕着如何提高总挥发性馏分和某些特定组分产率的核心,从煤的裂解技术、预处理煤的裂解、煤与其它物质的共裂解以及裂解反应器等方面综述了煤裂解技术的研究新进展,讨论了存在的问题和今后的研究方向。     

煤气热电三联供系统能量利用系数的分析

引言 煤气、热、电三联产对于联合循环发电或同时需要煤气和热量的工厂是较为经济的[1],不仅简化了气化炉的结构,降低了投资,而且可以提高碳的利用率,减少环境污染[2].     

Model for devolatilization of coal particles in fluidized beds

A model for the devolatilization of coal in a non-combusting fluidized bed is proposed. Previous studies have either considered devolatilization as a non-rate process or assumed the devolatilization coal particle as isothermal. The assumption of an isothermal particle requires the heat transfer Biot number ?0.02. In view of the larger Biot numbers predicted using existing fluidized bed gas-solid heat exchange correlations and reported values for thermophysical properties, the present model considers the devolatilizing particle to be, in general, non-isothermal. The temperature profiles are computed from the analytical solution of the one-dimensional spherical coordinate unsteady heat transport equation with a convective boundary condition. The temperatures are then used in the non-isothermal coal decomposition kinetic expression proposed by Anthony et al., integrated over the particle to obtain the fractional volume average devolatilization at any given time. Parametric studies show a chemical kinetics controlled regime for small particles, a heat transfer controlled regime for larger particles and a mixed regime for intermediate particle sizes. The extent of the mixed regime depends on the type of coal as well as the operating conditions. The model results are also compared with the fluidized CH₄ and CO evolution data reported in the literature for various particle sizes and different temperatures.