煤的微波热解研究进展

煤炭是我国的主要能源,煤的清洁高效利用是我国能源安全和生态环境建设的重要保障。热解是在温和条件下将煤转化为洁净的气体、液体和固体燃料,是改善煤炭利用、加工转化成清洁高效的二次能源的重要手段之一。微波作为一种新的加热方式在煤的热解方面的应用的优势越来越明显。本文概述了微波热解的机理与优点、微波吸收剂的应用以及国内外微波热解研究进展,得出了低阶煤介电常数较小,需要添加一定量的微波吸收剂才能达到热解温度;和常规热解相比,微波热解改变了物质的加热方式,改善了热解产物的品质,热解气中CO、H₂含量增加,焦油品质较好,提高了煤的热解效率。作为一种新型加热方式,微波技术为煤热解效率的提高提供了新的解决方案和思路。     

煤炭的微波干馏技术研究进展

将煤炭加工转化成洁净、高效的二次能源以替代石化产品,对于缓解石油供需矛盾、实现煤炭清洁利用、保障国家能源安全具有重要的战略意义。本文概述了微波加热的机理、特点与优势以及国内外微波加热煤干馏技术的研究进展,提出了煤分级加工及清洁化利用技术研发思路,指出与常规的煤干馏技术相比,微波干馏煤焦油的性质更好,更适合于加工生产化工产品和汽油、柴油产品。所产煤气纯度高,富含甲烷、氢等高价值组分,利于综合利用。该技术易与现有电厂、钢厂等用煤大户企业结合,形成煤分级加工及清洁利用组合体,有利于资源的高效利用。与现有石油加工企业组合,更能优化产品的加工利用方案。     

微波热裂解木屑的基础研究

利用微波热裂解的方法将木屑转化为生物能源,是一种非常有前景的处理和利用废弃生物质转化为能源的工艺,考察了多模谐振腔和单模谐振腔对热裂解的影响,并研究了含水率和加热速率在微波加热下对木屑热裂解的影响,讨论了微波加热与传统加热下生物质热解机理。研究发现单模谐振腔比多模谐振腔更有助于生物质的快速热解。孔隙中的水分是微波热解生物质的主要因素,可以提高加热速率。生物质热解在微波加热与传统加热下的最大差别在于前者是由里及外的加热,可以减少二次反应的发生,提高生物油的收率和质量,固体产物炭的性质也得到了改善。热解油主要是由脂肪族含氧化合物和芳香烃类物质的复杂混合物,热解气体产物主要为CO、CO₂、甲烷和乙烷。     

升温速率及热解温度对煤热解过程的影响

为了研究煤热解过程中升温速率及热解温度对热解产物分布及热解过程吸热量的影响,采用热重和热红联用技术对煤热解过程进行了分析.研究了不同升温速率和热解温度对煤热解过程的气态产物分布的影响,并对所产生的焦炭性质进行了分析.结果表明:煤的整个热解过程的吸热量随升温速率的增加而减小;煤热解产生的焦油组分含量包括芳香族、脂环族和脂肪族含量达到最大值所对应的热解温度随升温速率的增加产生滞后现象,但是煤热解产生的煤气成分随着升温速率增加而急剧释放;随着热解温度的升高,焦炭结构逐渐致密,裂纹及裂缝产生,芳香晶核增大,同时焦炭中的氧和氮含量由于含氮和含氧化合物的继续分解而降低.     

煤炭低温干馏微波加热技术的研究进展

随着石油能源储量的日趋减少,清洁煤转化技术得到越来越多的重视。如何将现有的低阶煤炭资源进行高效转化及利用,对缓解我国能源危机和带动当地经济迅速发展具有重要作用。论述了国内外传统煤加热技术现状及微波热解煤的技术进展,微波热解的工艺特点和反应机理,最后对微波热解应用于煤炭低温干馏的前景进行了展望,为煤热解技术日后的研究提供有效的参考。     

燃料电池发动机电堆散热的控制

在对质子交换膜燃料电池(PEMFC)进行热分析的基础上,搭建起36kW的燃料电池发动机散热系统的测试平台。借助测试平台,对燃料电池散热系统作了极端工况测试分析。分析表明,该散热系统能满足系统的散热要求。此外通过对不同组合散热风扇的散热能力进行了测试,积累了大量的基础数据和控制经验。最后以电堆出水温度误差、温度误差变化量和燃料电池功率为输入量,散热风扇的运行组数为输出量,制定出一套三维模糊控制规则。结果表明,该模糊控制规则能够保证燃料电池工作在最佳温度区间,温控误差符合设计要求。     

微波吸收剂辅助吸波快速热解稻壳的气化特性

以稻壳为研究对象,采用碳化硅、残炭为微波吸收剂,运用新型微波辅助催化气化技术以及微波吸附剂辅助加热技术,研究微波吸收剂辅助吸波快速热解稻壳气化特性,通过气相色谱等手段对裂解气体进行分析。结果表明,微波吸收剂辅助吸波快速热解稻壳产物以气体为主,最高达53%,热解气体产物主要成分为H₂、CO₂、CO、CH₄,占到纯热解气总量的97%以上,氢气体积分数最高,均高于38%。稻壳与残炭添加量质量比为1:1时,氢气体积分数可达48.12%,合成气(H₂+CO)含量大于60%。研究结果证明了微波吸收剂辅助吸波快速热解稻壳气化制备富氢燃气的可行性。     

温度梯度与产物流动对先锋褐煤热解产物分布的影响

通过两段固定床反应器分离了煤热解和二次反应过程,模拟了传统外热式固定床反应器和外热式内构件固定床反应器内挥发性热解产物流动与固相反应颗粒间的相互作用,研究了不同温度的半焦对先锋褐煤热解产物分布和品质的影响。结果表明：当半焦的温度在500～900℃时,焦油发生剧烈的二次反应,热解气收率增加,焦油收率大幅下降,H/C同时大量降低且均低于空白样,油品质下降;在100～400℃半焦作用下,焦油发生轻微的二次反应,热解气收率略微增加,焦油收率缓慢下降,但H/C均高于空白样,油品质提升。该结果验证内构件外热式固定床反应器热解产生的焦油具有更高的收率及品质。     

Understanding the influence of microwave on the relative volatility used in the pyrolysis of Indonesia oil sands

In this paper, pyrolysis of Indonesian oil sands(IOS) was investigated by two different heating methods to develop a better understanding of the microwave-assisted pyrolysis. Thermogravimetric analysis was conducted to study the thermal decomposition behaviors of IOS, showing that 550 °C might be the pyrolysis final temperature. A explanation of the heat–mass transfer process was presented to demonstrate the influence of microwave-assisted pyrolysis on the liquid product distribution. The heat–mass transfer model was also useful to explain the increase of liquid product yield and heavy component content at the same heating rate by two different heating methods. Experiments were carried out using a fixed bed reactor with and without the microwave irradiation. The results showed that liquid product yield was increased during microwave induced pyrolysis,while the formation of gas and solid residue was reduced in comparison with the conventional pyrolysis. Moreover, the liquid product characterization by elemental analysis and GC–MS indicated the significant effect on the liquid chemical composition by microwave irradiation. High polarity substances(ε N 10 at 25 °C), such as oxyorganics were increased, while relatively low polarity substances(ε b 2 at 25 °C), such as aliphatic hydrocarbons were decreased, suggesting that microwave enhanced the relative volatility of high polarity substances. The yield improvement and compositional variations in the liquid product promoted by the microwave-assisted pyrolysis deserve the further exploitation in the future.     

非等温热重分析长焰煤热解过程与动力学特征

为提高煤热解过程中焦油的产率,用非等温热重分析方法研究了不同粒径、热解终温和升温速率条件下长焰煤的热解过程和机理,分析了20和100℃/min升温速率下长焰煤热解过程特征,并求解了热解动力学参数。结果表明,煤颗粒在2.8mm以下时,粒径对热解过程影响较小;热解终温越高,热解最终固体产物中挥发分产率越低;升温速率越快,挥发分的析出速率越快。在同一升温速率下,不同热解温度段得到的活化能呈现两头大中间小的特征,且指前因子随活化能的增大而增大。     

低变质粉煤热解过程研究

在管式电炉上研究了碱房沟、王家沟、孙家岔煤热解过程中温度变化对其热解产物收率和性能的影响。研究结果表明,管式炉电加热25 min温度达到500℃左右,热解气体大量析出,且随温度的升高,煤样失重率、煤气收率呈递增趋势,焦油收率基本不变;加热终温为800℃时,除CO外三种煤热解气体成分变化趋势基本一致,这和煤样的组织结构有关。     

An update of german non-isothermal coal pyrolysis work

Pyrolysis is an essential and inseparable process in all aspects of coal conversion and utilization, the most common product of coal pyrolysis being coke. It is part of combustion and plays an important role in coal gasification and liquefaction. Over the last fifteen years Bergbau-Forschung GmbH has sponsored research in the basic processes and fundamentals of pyrolysis to optimize the properties and/or yield of the coke, gas and liquids produced. The work is summarized and the theoretical framework used for the analysis is described. Results with heating rates from degrees per day to degrees per micro second in inert and reactive gases are presented. Emphasis is placed on the kinetics of gas formation. Further work in the area of pressurized pyrolysis is planned.     

内构件固定床反应器中不同水分煤的热解特性

通过在有无内构件(传热板和中心集气管)固定床反应器中研究不同水分含量煤的热解特性,考察了两反应器中煤料的升温特性、热解产物分布、焦油品质以及气体产物组成和半焦热值。结果表明,内构件可以强化传热和调节热解产物在反应器内的流动,相对无内构件反应器,有内构件反应器的反应时间缩短近一半。在有内构件反应器中,当煤水分增加,导致煤热解反应要求的时间延长,焦油中轻质组分(沸点低于360℃)含量明显升高,焦油收率先增加后降低,热解水和热解气产率升高,而无内构件反应器的热解产物无明显差异。当加热温度900℃时,煤水分从0.41%(本文中无特殊说明的均为质量分数) 增加至11.68%,焦油产率从9.21%增长到10.74%;当煤水分增加到15.93%,焦油产量下降到10.26%。两反应器气体平均组成随水分增加的变化趋势相似,气体热值均随水分增加呈下降趋势。     

微波热解煤的实验研究

采用微波加热的方式对褐煤进行了热解实验研究,研究结果表明,用微波进行煤的热解,温度可以达到800℃,是一种热解煤的有效方法,其热解速度快,微波热解产生的炉气,其有效成分浓度高,热解后的最终固体产物与兰炭的成分相近。     

Inlet effect on the coal pyrolysis to acetylene in a hydrogen plasma downer reactor

Coal pyrolysis to acetylene in hydrogen plasma is a clean process for the coal utilization. A gas–solid downer reactor was employed to facilitate the high temperature reactions of coal pyrolysis in milliseconds. The effect of the inlet design on the coal injection was studied using CFD simulations, which were qualitatively compared with the cold model experiments in the prototype of a 2 MW hydrogen plasma reactor. The results revealed that the distribution of the coal particles near the inlet nozzles was significantly influenced by the layout of the flat‐shaped nozzles and the operating conditions. Accordingly the heating efficiency of the particles by the hot gas showed strong dependence on the inlet design. The hot model tests demonstrated that the reactor performance characterized by the concentration of acetylene in the product gas increased from ～7.6 to 9.6% by optimizing the nozzle design, which indicated the critical role of the nozzle design in the coal pyrolysis process.     

基于正交实验的低阶粉煤与玉米芯微波共热解研究

生物质协助低阶粉煤微波热解可改善热解产物的分布和特性,尤其是油气收率和品质。采用四因素四水平正交实验法研究了微波功率(420 W,280 W,700 W,560 W)、热解时间(30min,20min,10min,40min)、玉米芯粒径(0.250mm~0.420mm,0.177mm~0.250mm,0.841mm~1.680mm,0.420mm~0.841mm)和玉米芯添加量(10%,40%,30%,20%,质量分数)对低阶粉煤与玉米芯微波共热解中焦油收率的影响,对比分析了低阶粉煤、玉米芯单独微波热解和微波共热解的升温特性和产物特性。结果表明:影响焦油收率由主到次的因素分别为玉米芯添加量、微波功率、玉米芯粒径、热解时间。在本实验参数范围内,正交实验得到的最佳工艺条件为:微波功率700W、热解时间40min、玉米芯粒径0.841mm~1.68mm、玉米芯添加量40%,此时的半焦和气体产物收率分别为51.22%和32.17%,焦油收率达到最大,为8.85%。与低阶粉煤单独微波热解相比,微波共热解生成的焦油中轻油含量提高了11.89%,而杂原子化合物含量降低了7.09%,实现了热解焦油的轻质化和高品质化。     

低温煤热解焦油产率和品质影响因素研究

煤焦油是低温煤热解技术的主要产物,是重要的化工原料,其产率和品质是评价煤热解工艺的重要指标。从原煤性质(煤种和煤粒径)、热解反应器结构形式及热解工艺条件(原煤预处理、热解温度、压力、升温速率、停留时间、热解气氛及催化剂)等方面综合分析了煤热解焦油产率和品质的影响因素,认为通过优选煤种和热解反应器,对煤样进行适当预处理,选择合适的工艺操作条件和引入加氢催化热解等有助于提高焦油产率和品质。     

Dielectric loss microwave degradation of polymers: Cellulose

The pyrolysis of organic waste polymers to produce fuels and chemicals is of interest to augment petroleum-based processes. The wide variety of pyrolysis products of low yield and the uncertain role that heat transfer rate plays in determining these have been deterrents to utilization in the past. A possible approach to increased selectivity for products is to heat them rapidly and homogeneously with the aim of narrowing the product distribution. A very rapid means of homogeneous heat transfer throughout the substrate is microwave heating. A laboratory study has been done to determine what effect high-intensity microwave energy has on the thermal degradative pathways of cellulose. The product distribution found when cellulose is pyrolyzed in the absence of a microwave discharge is similar to that found in conventional furnace pyrolysis. The major products are levoglucosan (27%), carbon dioxide (2–5%), water, and charred residue. However, the total heat-up and reaction times for even large pellets are reduced to less than 2–3 min when high-intensity microwave irradiation is employed. Effects of pressure and microwave power are reported. Low external gas temperature also prevents secondary reactions.     

Experimental studies on pyrolysis of Datong coal with solid heat carrier in a fixed bed

An experimental apparatus was set up for batch simulation of coal pyrolysis with solid heat carrier in a fixed bed. Quartz sand as heat carrier preheated to about 700–800°C was mixed with Datong bituminous coal by an agitator. The thermal history of the coal particle has been followed by a K-type thermocouple. The effects of particle size, pyrolysis time and temperature on the gas yield during pyrolysis of coal with solid heat carrier were examined for different conditions. The experimental results showed that a dominant percentage of the gas product is produced during the first 1–3 min, although gas evolution would last for as long as 10 min. The total gas yield, insensitive to particle size of the heat carrier, depends on carrier temperature and coal particle size under tested conditions. The contact heat transfer of cold and hot particles was analyzed.     

油页岩微波热解气态产物析出特性

利用微波化学试验装置研究了油页岩微波热解过程中挥发分析出特性, 考察了微波功率、热解温度、不同热解温度阶段和催化剂对气体组成的影响。结果表明:微波加热能够提高油页岩热解气中H₂、CO和C₂H₄的析出, 降低CO₂的析出;50%(1600W)微波功率时烃类的析出量最大;在150~350℃的低温阶段热解气的析出量大, 主要由吸附气体的释放, 不稳定支链和基团的分解产生;温度升高, 气态产物的析出主要由脱氢、芳构化、缩聚和自由基反应产生。催化剂促进了气体的析出, 但不同类型催化剂对油页岩热解气组成的影响不同, 分子筛的吸附作用促进二次分解和缩聚反应;黏土类催化剂在质子酸作用下促进有机质催化裂解加氢反应, 加快断链和基团的稳定;金属类催化剂是强吸波性介质, 能够提高升温速率, 促进热解反应, 其次促进氢自由基的产生和转移。