【作者】 杨素文；

【导师】 丘克强；

【作者基本信息】 中南大学 ， 应用化学， 2009， 博士

【摘要】 生物质能是可再生能源十分重要的组成部分,资源丰富,是取之不尽、用之不竭的可持续利用能源。生物质能源的开发利用是缓解我国能源和环境压力,建立可持续发展能源系统的有效措施。热化学技术是生物质高效利用的主要途径,是国内外专家学者密切关注的研究开发热点。其中,生物质热裂解技术由于可以将低品位的生物质能转化为高品质的液体燃料或高附加值产品而受到广泛关注。在生物质各种热化学转化过程中,热解过程的研究是最基本的内容,通过对生物质热解过程变化规律及其影响因素的研究,为实现高效热转化利用生物质能技术提供科学依据和帮助。本研究采用真空热重分析仪和自制的真空热解实验装置,对益阳地区7种农林废弃生物质进行了真空热重、真空热解液化和真空化学活化等实验研究,以探讨生物质真空热解特性行为和生物质真空化学活化法制备活性炭的规律等,主要内容包括以下几个方面:（1）对7种生物质进行了真空热重分析,考察了不同生物质原料、升温速率对生物质真空热解反应的影响。结果表明,7种生物质真空热解规律基本一致。热解过程主要分3个阶段:自由水解吸附及抽取物析出阶段、热裂解急剧失重阶段和残余物缓慢分解阶段。相同条件下7种生物质总失重率大小顺序为:杉木屑＞玉米秸秆＞松木屑＞刺桐木屑＞豆秆＞稻壳＞花生壳。其中林业生物质的最大峰值温度、热解速率、起始分解温度、热稳定性均大于农业生物质。热解温度为500℃时,7种生物质的真空热解反应基本完成。随着升温速率的增加,生物质的热重曲线右移,峰值温度向高温方向偏移,生物质真空热分解的主反应温度区间增宽。杉木屑真空热解反应近似为一级反应。（2）以杉木屑为原料,进行了真空热解液化实验研究,探讨了过程参数对热解产物的影响。结果表明,杉木屑真空热解液化较佳热解温度为500℃,较佳体系压力为20kPa,较佳保温时间为60min。与快速热解相比,杉木屑真空热解在较低的升温速率下也能得到较高的生物油产率。真空热解产物以生物油为主,在较佳工艺条件下杉木屑真空热解制备生物油的产率可达67%以上。不同热解条件下制得生物油样品的主要化学成分及其相对含量差别较大,通过选择合适的热解参数可获取附加值较高的生物油,以提高生物油的应用价值。杉木屑真空热解炭已经具有初步的孔隙结构,孔隙以微孔为主,具备进一步扩展的潜力,是优良的制备活性炭的原材料。（3）以7种生物质为原料,进行了真空热解液化制取生物油的实验研究,考察了生物质种类对真空热解产物产率、生物油理化性质的影响。7种生物质的真空热解产物均以生物油为主,生物油产率均在55%以上。其中林业生物质的生物油产率较农业生物质高,杉木屑的生物油产率最高,为67.25%,玉米秸秆的生物油产率最低,为55.46%。7种生物油的pH值为1.82～3.24,pH_{林业生物油}＜pH_{农业生物油},密度为1.0163～1.1670,ρ_{林业生物油}＞ρ_{农业生物油},粘度较小,为2.29～7.36mm²/s,η_{林业生物油}＞η_{农业生物油}。7种生物油所含化合物类型相似,但具体化学组分及其相对含量有一定的差别,如稻壳生物油中呋喃衍生物相对含量最高,为22.8%,杉木屑生物油中呋喃衍生物含量最少,仅为0.99%。杉木屑生物油中苯酚及其衍生物的相对含量最高达72.81%,豆秆生物油中这类化合物的相对含量最少,为23.97%。仅杉木屑生物油中检测出具有抗菌、健胃、麻醉、降血压等药理作用的丁香酚。（4）根据原料的化学组成、分子结构以及真空热解产物生物油组分的结构,对生物质真空热解制备生物油的机理进行了初步探讨,得出生物油主要组分的形成机理。（5）采用自制的真空热解装置,以氯化锌为活化剂,对7种生物质进行了真空化学活化法制备活性炭以及以杉木屑为原料常压化学活化法制备活性炭的实验研究。讨论了体系压力、活化条件等过程参数对活性炭性能的影响。结果表明,7种生物质的活性炭产率在40%左右。杉木屑是制备活性炭的最适宜原料。杉木屑真空化学活化制备活性炭的最佳反应体系压力为20.5kPa。在较佳工艺条件下通过真空化学活化,可以同时得到性能优良的活性炭和高附加值的生物油。活性炭以微孔结构为主,比表面积为1070.59m²/g,微孔体积为0.5581cm³/g,平均孔径为2.085nm,碘吸附值和亚甲基蓝吸附值分别为1142.92mg/g和131.24mg/g。杉木屑真空条件下制备的活性炭,其对氮气的吸附等温线均属于Ⅰ类型吸附等温线,可以使用Langmiur方程描述。随反应体系压力的下降,所得活性炭对氮气的吸附平衡常数增大。真空化学活化法制得活性炭的孔结构特性和吸附性能优于常压化学活化法制备的活性炭。更多还原

【Abstract】 Biomass energy is a very important part of the renewable energy. The biomass resources are very abundant,inexhaustible and sustainable in the world.The exploitation and utilization of the biomass energy is an effective method for relieving the pressure of the shortage of conventional energy resources and environment pollution in China. Thermochemical conversion is the major way for high efficient utilization of biomass and a hot point of research both in China and abroad.Biomass pyrolysis technology has been paid great attention through which low-quality biomass can be converted to higher quality liquid fuel or high add-value products.Pyrolysis process is the most essential content in a variety of thermochemical conversion processes of biomass.From the study of the changing rules and influence factors during the biomass pyrolysis process,it provides scientific basis and help to achieve efficient biomass thermal conversion technology.In this study,TGA and self-made vacuum pyrolysis apparatus were used to detect the characteristics of biomass pyrolysis liquation and the rules of preparation of activated carbon under vacuum.The seven kinds of common agricultural and forestry waste biomass were from Yiyang. The main contents studied are as follows:(1) TGA was used to detect the influence of biomass species and heating rate on the pyrolysis reaction.The results show that the vacuum pyrolysis laws of seven kinds of biomass are almost the same.There are three stages mainly:free hydrolysis adsorption and precipitation extraction stage,rapid weight loss stage of pyrolysis,and slow decomposition stage of residue.The order of total weight loss rate of biomass under the same condition is as follows:fir sawdust＞corn stalk＞pine sawdust＞erythrina sawdust＞bean stalk＞rice husk＞peanut shell.The maximum peak temperature,thermal decomposition rate,the initial decomposition temperature and thermal stability of forestry biomass are higher than that of agricultural biomass.Vacuum pyrolysis reaction almostly complete when the temperature is 500℃.As the heating rate increased,the TG curves shift to right,peak temperature shift to high temperature,the temperature range of main reaction widen. The pyrolysis of fir sawdust under vacuum keeps the first order reaction rules approximately.(2) Fir sawdust was taken as raw material to study the biomass vacuum pyrolysis liquation.The influence of process parameters on the pyrolysis products was researched.The results show that the optimum conditions of pyrolysis as follows:pyrolysis temperature is 500℃,the system pressure is 20kPa,and holding time is 60min.Compared with fast pyrolysis,vacuum pyrolysis of fir sawdust can also get a higher yield of bio-oil with a lower heating rate.The pyrolysis product is mainly bio-oil and the yield of bio-oil can reach to above 67%under better preparation condition.There are larger differences of the main chemical composition and its relative content when the pyrolysis parameters are different.We can get bio-oil with higher additional value by choosing appropriate pyrolysis parameters.The vacuum pyrolysis carbon already has an initial pore structure,and the pores are mainly micropores,which can be excellent raw materials for activated carbon preparation.(3) Seven kinds of biomass were taken as raw material to prepare bio-oils.The effects of biomass species on the yield of the pyrolysis product and the physical and chemical properties of bio-oil were studied. The main product of pyrolysis is bio-oil,and the yield of which is all above 55%.The bio-oil yields of forest biomass are higher than that of agriculture biomass,and for fir sawdust the highest yield is 67.25%and for corn straw the lowest yield is 55.46%.The pH value of bio-oil is 1.82～3.24,and the pH value of the forest bio-oils are less than that of agriculture bio-oil.The density is 1.0163～1.1670,and the density of the forest bio-oils are more than that of agriculture bio-oil.The viscosity is 2.29～7.36,which is small,and the viscosity of the forest bio-oils are more than that of agriculture bio-oil.The types of compounds contained in the bio-oil were similar,but there are some difference in the specific chemical composition and its relative content.For example,the furan derivatives content of the rice husk bio-oil is the highest(22.8%),and that of the fir sawdust is the lowest(0.99%).While relative content of phenol and its derivatives in fir sawdust bio-oil can up to 72.81%,but which in bean stalk bio-oil is only 23.97%.Only fir sawdust bio-oil has eugenol which has antibacterial,stomachic,anesthesia,lowing blood pressure and other pharmacological effects.(4) The vacuum pyrolysis mechanism of biomass was studied according to the chemical composition and molecular structure of raw material and the structure of bio-oil components.The formation mechanism of the main components of bio-oil was obtained.(5) Activated carbon was prepared from biomass under vacuum by zinc chloride activation.Activated carbons prepared by fir sawdust under atmosphere and vacuum were compared.Effects of system pressure,activation condition and other process parameters on the properties of activated carbon were studied.Results show that the yield of activated carbon is about 40%.Fir sawdust is the most appropriate precursor for activated carbon preparation.The best system pressure of preparing activated carbon from fir sawdust is 20.5kPa.We can get activated carbon with excellent properties and bio-oil with high additional value under better preparation conditions.The mainly structure of activated carbon is microspore.The surface area of prepared activated carbon is 1070.59m~2/g,microspore volume is 0.5581cm~3/g, average pore diameter is 2.085nm,iodine adsorption value and methylene blue adsorption values are 1142.92mg/g and 131.24mg/g respectively.The nitrogen adsorption isotherms of activated carbon prepared from fir sawdust under vacuum are all belong to typeⅠadsorption isotherm,they are can be described by the Langmiur equation。With the system pressure dropped,the nitrogen adsorption equilibrium constant of the activated carbon increased.The pore structure characteristic and adsorption performance of activated carbon prepared under vacuum are better than that of the one prepared under atmosphere.更多还原