不同裂解温度对梨树枝条生物炭理化性质的影响

Influence of different pyrolysis temperatures on physical and chemical properties of biochar derived from pear branches

[目的]本文旨在研究梨树枝条在不同温度下裂解所得生物炭的理化性质差异,确定适宜的制备生物炭温度范围,为梨树修剪枝条资源化利用提供新的途径。[方法]以粉碎梨树枝条为原料,在惰性气体包围下,在不同裂解温度(300~900℃)下制备生物炭,研究不同裂解温度对生物炭理化性质的影响。[结果]裂解温度由300℃上升到900℃,生物炭产率由61%显著降低到24%(P<0.05),pH值由7.3显著上升到11.7(P<0.05),生物炭中碳含量增加而氮含量显著降低,钾、钙、镁、硼、铁、铜等元素含量均先升高后保持稳定;阳离子交换量随温度的升高先显著下降后保持稳定。红外光谱分析表明随着裂解温度的升高,枝条内O—H和C—H键断裂,形成难降解的芳香烃类物质;扫描电镜分析表明生物炭孔隙度随着裂解温度升高而增加,温度越高,孔数量越多,比表面积越大,700℃下制备的生物炭比表面积相比300℃增加了50%;同时,比表面积及孔体积也随温度的升高而增加,吸附性增强。[结论]制备枝条生物炭时,将裂解温度设置为500~700℃时,元素含量相差不大,微孔和大孔数量基本达到最高水平,吸附性能达到最佳。

[Objectives] We investigated the differences in physical and chemical properties of biochar derived from pear branches at different pyrolysis temperature,aiming to determine the suitable temperature for the preparation of biochar which provides a new way for the utilization of pear branches.[Methods] Biochar was prepared by crushed pear branches under anaerobic conditions with a series of temperatures(300-900 ℃)to sudy the effect of different pyrolysis temperatures on physical and chemical properties of biochar.[ Results ] The yield of biochar derived from pear branches was about 61% at 300 ℃ and significantly decreased to 24% at 900 ℃( P <0.05 ).The pH of biochar increased from 7.3 to 11.7 from 300 ℃ to 900 ℃( P <0.05).The carbon content in biochar increased with the pyrolysis temperature,while the nitrogen content decreased significantly.The content of K,Ca,Mg,B,Fe,Cu increased firstly and then remained unchanged.The cation exchange capacity of pear-branches-biochar decreased firstly and then remained unchanged with the increase of pyrolysis temperature.The fourier transform infrared spectroscopy showed that the O-H and C-H in the branches broke and degraded to refractory aromatic hydrocarbons as the pyrolysis temperature increased;scanning electron microscope showed that the porosity of biochar derived from pear branches increased with the pyrolysis temperature and the greater number of pores and specific surface area were detected at higher pyrolysis temperatures.The specific surface area of the biochar pyrolysis at 700 ℃ was 50% larger than that at 300 ℃,the specific surface area and pore volume also increased with the pyrolysis temperature,and the adsorption was enhanced as well.[Conclusions] When the pyrolysis temperature ranged from 500℃ to 700℃,the element content of the pear-branches-biochar did not differ significantly,while the number of micropores and macropores remained at high level and the adsorption performed best.