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为了解生物质热解过程中固体焦孔隙结构的演变行为,采用氮气等温吸附法研究了热解过程中棉杆颗粒孔隙结构的变化规律,并引入分形维数对其进行定量的描述。结果表明,热解过程中棉杆焦孔隙结构微孔与中孔先增多后减少,而大孔比例变化不大。棉杆热解焦的BET比表面积(SBET)随着热解温度的升高,经历了一个先增大后减小的过程,从450℃开始,SBET迅速增大,在650℃时达到最大值,而后逐渐减小。随着热解温度的升高,棉杆焦表面分形维数先增大后减小,表明棉杆焦在热解过程中孔隙表面经历了复杂的结构变化。分形维数与BET比表面积存在一定的关联性,且分形维数能更好地表征热解焦表面孔隙结构特征。
In order to understand the evolution behavior of solid coke pore structure during biomass pyrolysis, the change rule of pore structure of cotton stalk particles during pyrolysis was studied by isothermal adsorption of nitrogen, and the fractal dimension was introduced to quantitatively describe it. The results show that micropore and mesopore increase first and then decrease, while the proportion of macropores does not change much. The BET specific surface area (SBET) of cotton pyrolysis pyrolyzed coke increased with the increase of pyrolysis temperature, and then increased from below 450 ℃. SBET rapidly increased and reached the maximum at 650 ℃ , Then gradually reduced. With the pyrolysis temperature increasing, the fractal dimension of the surface of cotton stalk first increased and then decreased, indicating that the pore surface of cotton stalk underwent complicated structural changes during the pyrolysis process. Fractal dimension and BET specific surface area have certain relevance, and the fractal dimension can better characterize pyrolysis coke surface pore structure.