Abstract:

Municipal sewage sludge was pyrolyzed, under various pyrolysis temperatures and holding times, to investigate the pore structure characteristics of the sludge-based biochars obtained. The pore structure of the obtained sludge biochars was measured by the N₂ adsorption/desorption at 77 K. The concept of fractal dimension was introduced to determine the pore surface roughness. Experimental results showed that the BET surface area of the sludge biochars increased with pyrolysis temperature increasing, achieving the maximum (i.e. 92.3 m²/g) at 600ºC; the further increase of pyrolysis temperature decreased it. When pyrolysis temperature was less than 500ºC, mesopores were dominant on the obtained biochars and micropores were not observed; over 500ºC, the main pore species were micropores and mesopores. The shape of pores on the sludge biochars differed as pyrolysis temperature increased, varying from silt-shaped pattern to thorough and plate-like patterns. The increase of holding time little altered the pores’ shape but did the pore volume. The pore surface fractal dimensions of the obtained biochars intended to increase with pyrolysis temperature, whereas the prolonging of holding time decreased it at 600-700ºC and augmented it over 700ºC.

Key words: municipal sewage sludge, pyrolysis, temperature, holding time, biochar, pore structure

摘要：

通过低温(77 K)氮气吸附/脱附等温实验, 结合分形维数的概念, 分析生活污水污泥在不同热解终温和保留时间下经热解获得的生物质炭孔隙结构变化特征。实验结果表明, 随着热解终温的提高, 污泥生物质炭BET 的比表面积呈先升高后降低的趋势, 在 600ºC 时达到最大, 为 92.3 m²/g。在低温(不超过 500ºC)下, 污泥生物质炭中的孔以介孔为主, 无微孔出现; 在高温(超过 500ºC)下, 则以微孔和介孔为主。随热解终温的升高, 孔的形状由狭缝型向开放性和平行板式转变, 保留时间的延长不改变孔的形状, 但改变孔的容积。污泥生物质炭表面分形维数随热解终温升高呈增大趋势; 而保留时间的延长, 在中高温(600~700ºC)下使污泥生物质炭表面分形维数降低, 高温(超过700ºC)下又使其提高。

关键词: 生活污水污泥, 热解, 温度, 保留时间, 生物质炭, 孔隙结构