Abstract:

The effect of fluidized bed first stage pyrolysis temperature (300—800℃) on the physicochemical structure and combustion properties of bamboo pyrolytic carbon (BPC) was investigated on a self-designed fluidized bed-rotary furnace two-stage pyrolysis system by using bamboo powder as raw material. Meanwhile, the pyrolysis gas release behavior of bamboo was also investigated by using the TG-FTIR instrument. The elemental analysis results showed that the influence of fluidized bed pyrolysis temperature on the composition of BPC was weakened due to the existence of secondary pyrolysis process in rotary furnace. And the carbon content of BPC produced under different pyrolysis temperatures varied between 71.19% to 78.41%. The proximate analysis showed that the volatile matter and fixed carbon of the raw bamboo were 78.88% and 18.64%, respectively. After the pyrolysis process, volatile matter of samples decreased to ＜18% while fixed carbon increased significantly. Moreover, with the increase of pyrolysis temperature, the volatile matter of BPC decreased gradually, the ash content showed an increasing trend, and the fixed carbon was relatively stable. Scanning electron microscopy (SEM) results showed that the BPC possessed relative regular pore structure and maintained the skeleton structure of raw bamboo under pyrolysis temperatures of 300—500℃. While as the pyrolysis temperature continues to rise, the skeleton structure of BPC was destroyed and resulted in fracture and collapse. The specific surface area and pore volume reached the maximum at pyrolysis temperature of 700℃, which were 2.53m²/g and 0.67cm³/g, respectively. Raman and X-ray photoelectron spectroscopy (XPS) were applied to analyze the surface chemical structure of BPC. The results showed that higher pyrolysis temperature was favored for dehydrogenation, decarboxylation and aromatization reactions, and thus promoted the polymerization and transition of small aromatic ring system into large aromatic ring structure in BPC. TG-FTIR analysis showed that the prominent volatile components produced during the bamboo pyrolysis process were CO₂, alkanes, phenols, aldehydes, ketones, organic acids and aromatic hydrocarbons, etc. The combustion process BPC samples basically only showed a fixed carbon combustion stage, indicating the bamboo was fully carbonized during two-stages pyrolysis process.

Key words: pyrolysis temperature, two-stage pyrolysis, bamboo carbon, physiochemical structure, combustion property

摘要：

利用自行设计搭建的流化床-回转炉两级连续式热解装置对竹粉进行热解炭化，考察流化床一级热解温度（300～800℃）对竹粉热解炭理化结构及燃烧性能的影响规律。结果表明，由于回转炉二次热解过程的存在，使得流化床热解温度对竹粉炭元素组成的影响减弱，碳元素质量分数介于71.19%～78.41%间，随热解温度增加，竹粉炭中挥发分含量降低，灰分呈现增加趋势，固定碳含量相对稳定；扫描电镜结果显示热解温度在300～500℃时，热解炭呈现规则的孔隙结构，同时可保持原料的骨架结构，随着热解温度继续升高，竹粉炭骨架结构被破坏，产生断裂坍塌的现象，比表面积和总孔孔容在700℃热解温度时达到最大，分别为2.53m²/g和0.012cm³/g。利用拉曼光谱和X射线光电子能谱法对热解炭表面化学结构分析，表明较高的热解温度促进了小芳环体系聚合转变为大的芳环结构，有利于脱氢脱羧及芳构化进程。热重-红外联用分析表明竹粉热解过程中气体释放相对含量较多的三类物质分别是CO₂，烷烃、酚类、醇类，以及醛、酮、酸类等有机成分。热解炭样品的燃烧基本仅呈现出固定碳燃烧阶段，热解温度为600℃左右时，所得竹炭综合燃烧特性较好。

关键词: 热解温度, 两级热解, 竹粉炭, 理化结构, 燃烧特性