煤与生物质共热解的基础研究

GIEC OpenIR > 中国科学院广州能源研究所

	煤与生物质共热解的基础研究
其他题名	The Experimental Study on Co-pyrolysis
	武宏香
导师	李海滨
	2005-05-31
学位授予单位	中国科学院广州能源研究所
学位授予地点	广州能源研究所
学位名称	硕士
关键词	煤生物质共热解协同效应
摘要	煤炭是我国主要的化石能源，在一次能源中占主导地位，但其利用过程中排放的污染物带来了较严重的环境问题。生物质是一种清洁能源，但受到季节与自身特征的限制，其转化利用规模较小、转化效率较低。煤和生物质的共利用可以实现资源互补，提高生物质利用的转化效率、减少污染气体的排放。因此研究生物质与煤的共利用过程对于研究洁净煤技术以及污染物控制有着重要的意义。本论文首先对煤与生物质直接混合后的共热解进行研究，在热天平反应装置和管式炉反应器中对反应特性进行分析，并对共热解过程中存在的协同效应的机理进行分析，探讨了碱/碱土元素在热解中所起的作用；最后采用一种新型共热解方式，在两段式热解炉中将生物质热解气通过灼热的煤焦层，煤焦催化裂解生物质焦油，并与气体发生气化反应转化为可燃气。经过试验，得到以下主要结论：（1）生物质与褐煤直接混合后共热解能促进固体焦产率的提高，热解过程中生物质挥发分析出温度段向高温段移动，煤析出向低温段移动。木屑与煤的共热解中起始温度tv比木屑单独热解高10℃以上，协同效应最明显，生物质与煤混合后最大挥发分析出温度tmax均比单独热解高3.0-11.8℃之间。说明生物质与煤共热解过程中存在协同作用。生物质中半纤维素、纤维素、木质素与褐煤共热解中热解产物分布基本与理论计算值相符，反应过程中协同效应不明显。（2）在生物质与煤直接混合的管式炉热解实验中，对热解产物分析得到如下结论：生物质和褐煤混合热解产物分布与计算值一致，但共热解气体中H2的含量低于理论计算值，CO和CO2的实际含量略高于计算值，在煤含量为50%时，与计算值相比较，木屑/煤的热解气中H2的含量低5.89%、CO高4.63%，生物质与褐煤在共热解过程中发生了协同作用。稻秆与煤共热解焦中C/H比明显大于理论计算值，而木屑/煤混合热解焦的C/H比基本低于理论计算值。生物质与褐煤的共热解焦油组成基本上与单独热解焦油成份类似，协同效应不明显。（3）添加到生物质中的四种金属元素对热解催化作用的顺序为：K> Na> Mg> Ca。碱金属能促进纤维素在较低温度下热解，能够降低纤维素的表观活化能，当纤维素中以KAc形式添加的K含量为3.57%时，可使纤维素的起始热解温度降低约115℃。碱金属添加量低时对纤维素热解几乎没有催化作用。碱金属存在形态对热解催化作用有影响，生物质中以有机结合态存在的碱金属对热解的催化能力大于以无机态存在的同种金属。KAc能够促进纤维素热解产物中小分子物质，尤其是羧酸类物质的生成。（4）在两段式热解中对生物质煤焦进行分段共热解，生物质热解气经过灼热的煤焦后，气体中所携带的焦油被裂解为可燃气体。增加稻秆热解气在煤焦中的停留时间及提高裂解温度，都有利于促进焦油裂解，高温也能促进煤焦的气化反应，使气体产率增加。裂解温度对出口端气体产率、组分影响更明显，在1000℃时H2和CO的含量可以达到94.51%。当稻秆热解气在煤焦中停留时间大于一定值后，气体中各组分和焦油裂解效率变化趋于平稳。不同热解条件所制煤焦对生物质热解气中所携带焦油裂解效果不同，降低制焦温度、缩热解时间都有利于增加煤焦的反应活性，促进焦油分解，使气体中H2和CO含量增加，CH4与CO2含量下降。减小煤焦颗粒直径可以增加焦油裂解率，但对气体组分影响不大。
其他摘要	Coal plays a dominating role in the primary energy in China which brings serious environmental problems during its utilization. Biomass is a renewable energy. But its utilization is easily limited by seasonal restriction and its own characteristics. The co-gasification of coal and biomass can improve the conversion efficiency of biomass and reduce the emissions of contaminants. Experimental studies on co-pyrolysis of biomass and coal were performed in the thermogravimetric analyzer and in the furnace reactor. The studies were focused on possible synergetic effects between biomass and coal. The synergetic effects were studied from the yield and component of the major prolysis products. The effects of alkali and alkaline earth metals on the biomass characteristics were also studied in the thermogravimetric analyzer. A new co-pyrolysis method was introduced to use coal and biomass. In a two-stage fixed bed, the cracking characteristics of tar derived from biomass pyrolysis in coal char were studied. The main conclusions are drawn as following: (1) The results in the thermogravimetric analyzer show that in co-pyrolysis progress, the biomass volatile releasing temperature increase with increasing amount of lignite in blends. Co-pyrolysis of coal and biomass produces more char than the summation of individual lignite and biomass pyrolysis. The synergistic effects in the co-pyrolysis of biomass and coal are suggested. The co-pyrolysis results of hemicellulose, cellulose and lignin mixed with lignite show synergetic effects litte. The diameter of sample particle has no influence on the synergetic effects between biomass and coal. (2) The co-pyrolysis results of biomass and lignite in furnace reactor show that the yield of gas, liquid and char is coincide with the calculated value. But the content of H2 in gas is lower and the content of CO and CO2 is higher both in blends of RS/lignite and wood/lignite. The H2 from wood/lignite blends was5.89% lower than the calculated value at lignite content 50% while CO was 4.63% higher . The C/H ratio of RS/lignite blends is much higher while that of wood/lignite blends is lower than expectation. Both the gas and char show synergetic effects obviously. The component of tar from blends of biomass and lignite is similar with the tar from biomass or lignite which showes additional effect only. (3) The pyrolysis results of microcrystalline cellulose (mcc) and biomass loaded K, Na, Mg, Ca investigated by thermogravimetric analysis with measurement of products by means of Fourier Transform Infrared Spectroscopy (TG–FTIR) show that the catalytic effect of the metals added on the cellulose is K>Na>Mg>Ca. Potassium catalysed pyrolysis increase the char yields markedly, shift the pyrolysis process to lower temperature, and increase the light organic fraction in volatile components. The alkali metals can lower the average apparent first-order activation energy for pyrolysis. The catalysis of KCl and NaCl is relatively weak compared to KAc and NaAc. KAc and NaAc can prompt the pyrolysis of cellulose into light fractions at lower temperature, especially acids. In biomass, the organically bound alkali metals may catalyse pyrolysis of biomass more than the inorganically alkalis. (4) In a two-stage fixed bed, the cracking results of tar derived from biomass pyrolysis in a high temperature coal char show that both long residence time in char and the higher cracking temperature can decrease the tar yield with the increase of gas yield and H2 percentage. The percentage of H2 and CO can reach 94.51% at the craking temperature 1000℃. The prepare condition of char has influence on the gas yield and composition. Low pyrolysis temperature and short residence time can increase reactivity of coal char and is favor to the higher H2 and CO percentage in gas.
页数	83
语种	中文
文献类型	学位论文
条目标识符	http://ir.giec.ac.cn/handle/344007/4035
专题	中国科学院广州能源研究所
推荐引用方式 GB/T 7714	武宏香. 煤与生物质共热解的基础研究[D]. 广州能源研究所. 中国科学院广州能源研究所,2005.

条目包含的文件		下载所有文件
文件名称/大小	文献类型	版本类型	开放类型	使用许可
200628014937029武宏香_p（40651KB）			开放获取	--	浏览下载