炭化程度对核桃壳焦孔隙结构和燃烧特性的影响

利用傅里叶变换红外光谱仪(FT-IR)、扫描电子显微镜(SEM)和X射线衍射仪(XRD)研究了炭化程度对核桃壳焦孔隙及微晶结构的影响,并使用热重-差示扫描量热仪(TG-DSC)对核桃壳焦及其原料的燃烧特性进行了分析。结果表明,合适的炭化程度(焦炭挥发分含量为6%-15%)使焦炭内乱层石墨变得无序,碳质微晶结构中缺陷增多,导致焦炭内孔隙结构相对发达;热解温度为500℃时,核桃壳焦的比表面积最大,为374.60 m~2/g;热解温度为600℃时,核桃壳焦的燃烧特性最优,其燃烧特性指数为7.16×10~6;合适的炭化程度可使焦炭内的挥发分含量减少,从而使得核桃壳焦的高位热值升高,且由于相对发达的孔隙使焦炭在燃烧时与空气的接触面积增大,导致焦炭的燃烧速率加快。

Influence of carbonization degree of walnut shell char on pore structure and combustion characteristics

The effect of carbonization degree on pore structure and microstructure of walnut shell chars was studied by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The combustion characteristics of raw material and walnut shell chars were analyzed using a thermogravimetry coupled with differential scanning calorimeter (TG-DSC). The results show that the appropriate degree of carbonization (volatile content is 6%-15%) leads to the disorderly crystallization of turbostratic and the increase of defects in the carbonaceous microcrystalline structure, which causes a relatively flourishing pore structure and an increase of specific surface. Pyrolysis char at temperature of 500℃ has the maximum specific surface area of 374.60 m²/g, while walnut shell char prepared at 600℃ has the optimal combustion characteristics with the combustion characteristics index of 7.16×10⁶, which indicate that the appropriate carbonization degree of char could reduce the volatile content and increase the higher calorific value of char during combustion process. Moreover, the developed pore structure can increase the contact area between char and air, leading to the accelerated combustion rate of char.