【作者】 刘佳；

【导师】 汪一； 江龙；

【作者基本信息】 华中科技大学 ， 动力工程及工程热物理， 2023， 硕士

【摘要】 生物油是唯一含碳的液体可再生能源。目前,生物油旨在通过热化学转化的方式利用,但其因组分复杂且活性组分含量高,加热便极易结焦,焦炭会积累并导致诸多运行问题,阻碍生物油的规模化应用。此外,目前仅能通过如调节温度等方法延缓生物油结焦速率,而难以避免其生成。受碳氢化合物热解制备碳材料的启发,本文旨在利用生物油的结焦特性,定向调控热解结焦过程以制备高附加值的纳米碳球。首先,考察了温度对生物油热解生成纳米碳球的影响。结果表明,生物油在800～1100℃下热解会产生纳米碳球和薄片状碳两种焦炭。生物油在800℃下热解不生成纳米碳球,薄片状碳产率为20.12 wt.%。随着热解温度从800℃升至1100℃,碳球的产率、石墨化程度和热稳定性均提高,平均粒径减小。碳球的主要前驱体为气相小分子,碳球与薄片状碳生成存在竞争,温度的升高促使碳球在竞争中占据优势。其次,研究了生物油中单一特征组分甲醇、乙酸、丙酮、糠醛、愈创木酚及原始生物油重质组分单独热解过程中纳米碳球生成机制。结果表明,芳香环是纳米碳球形成的关键因素。实验选取的特征组分中,纳米碳球产率高低顺序为愈创木酚>糠醛>重质组分>乙酸=丙酮=甲醇=0 wt.%,其中愈创木酚在1100℃热解生成碳球产率可达38.24 wt.%。特征组分化学成分差异及重质组分交互作用也会导致纳米碳球品质差异。进而,通过制备五种调制生物油探究了单一特征组分与生物油特征组分交互作用对生物油热解制备纳米碳球的影响。结果表明,单一特征组分含量的提高会强化其与生物油特征组分的交互作用,且添加各单一特征组分对焦炭产率有不同影响。添加愈创木酚后,900℃下碳球产率就可达12.70 wt.%。此外,碳球的平均粒径、热稳定性和石墨化程度也因单一特征组分与生物油特征组分交互作用强弱程度而显著不同。最后,基于生物油中特征组分单独作用及其交互作用的解析,提出了生物油热解制备纳米碳球反应机理。利用灰色关联分析法建立了纳米碳球综合品质的评价方法,为生物油热解制备纳米碳球工艺的发展提供有效指导。更多还原

【Abstract】 Bio-oil is the only liquid renewable energy source that contains carbon.Currently,biooil is intended to be utilised through thermochemical conversion,but due to its complex composition and high active component content,it is highly susceptible to coking when heated,which can accumulate and lead to numerous operational problems and hinder the application of bio-oil on a large scale.In addition,the rate of bio-oil coking can only be slowed down by,for example,adjusting the temperature,but it is difficult to avoid its formation.Inspired by hydrocarbon pyrolysis for the production of carbon materials,this paper aims to exploit the coking characteristics of bio-oil to target and control the pyrolytic coking process to produce high value-added carbon nanospheres.Firstly,the influence of temperature on the generation of carbon nanospheres from biooil pyrolysis was examined.The results showed that bio-oil pyrolysis at 800～1100 ℃produced two types of cokes,carbon nanospheres and flake carbon.Bio-oil pyrolysis at 800 ℃did not produce carbon nanospheres,the yield of flake carbon is 20.12 wt.%.As the pyrolysis temperature increased from 800 ℃ to 1100 ℃,the yield,graphitization degree,and thermal stability of carbon spheres increased,and the average particle size decreased.The main precursor of carbon spheres is small molecules in the gas phase,and there is competition between carbon spheres and flake carbon formation.The temperature increase promotes the advantages of carbon spheres in the competition.Secondly,the mechanism of carbon nanospheres generation during the pyrolysis of single characteristic components of bio-oil,including methanol,acetic acid,acetone,furfural,guaiacol,and heavy components of raw bio-oil,was studied.The results showed that the aromatic structure is the key factor in the formation of carbon nanospheres.The order of carbon nanospheres yield among the selected characteristic components was guaiacol >furfural > heavy components > acetic acid = acetone = methanol = 0 wt.%,the yield of carbon spheres generated by the pyrolysis of guaiacol at 1100 ℃ can reach 38.24 wt.%.The chemical composition differences of characteristic components and the interaction of heavy components can also lead to differences in the quality of carbon nanospheres.Furthermore,by preparing five modified bio-oils,the influence of the interaction between single characteristic components and bio-oil characteristic components on the preparation of carbon nanospheres by pyrolysis of bio-oil was explored.The results showed that increasing the content of single characteristic components strengthens their interaction with bio-oil characteristic components,and the addition of each single characteristic component has different effects on coke yield.By adding guaiacol,the carbon spheres yield can reach 12.70 wt.% at 900 ℃.In addition,the average particle size,thermal stability,and graphitization degree of carbon nanospheres also vary significantly depending on the strength of the interaction between single characteristic components and bio-oil characteristic components.Finally,based on the analysis of the effects of single characteristic components and their interactions in bio-oil,the reaction mechanism for preparing carbon nanospheres by pyrolyzing bio-oil was proposed.The grey correlation analysis method was used to establish an evaluation method for the comprehensive quality of carbon nanospheres,providing effective guidance for the development of the process for preparing carbon nanospheres by pyrolyzing bio-oil.更多还原