污泥热解过程中焦的表面孔隙结构分形生长

Fractal growth of char surface pore structure during sewage sluge pyrolysis

主要对污水污泥在高温热解和低温热解条件下热解焦炭的表面孔隙结构特性进行了研究。结果表明,污泥热解过程中随着挥发分的析出,污泥热解焦炭的孔隙结构逐渐发达。低温和高温热解过程中挥发分的析出,使得孔径为3.75 nm的孔得到了极大的发展。通过对污泥热解焦炭的N2吸附过程进行的分形分析发现,不同停留时间低温和高温热解焦炭的表面分形维数可以分为FD-1和FD-2。其中,FD-1主要表征了较大孔(>0.86 nm)的表面分形维数,FD-2则主要表征了超微孔(<0.86 nm)的表面分形维数。随着热解停留时间的延长,FD-1和FD-2逐渐增大并趋于稳定。与高温热解焦炭的超微孔表面分形维数相比低温热解焦炭出现了较大的增加,而较大孔的表面分形维数则相对低温热解焦炭未见有较大的改变。

The present work focused on the evolution of char surface structure during pyrolysis of sewage sludge.It shows that the char pore structure is developed greatly as the release of volatile.Both high temperature and low temperature pyrolysis increase the pore with a diameter of 3.75 nm.The fractal analysis of char surface with N2 adsorption shows that there are two fractal dimensions： FD-1 and FD-2,which are mainly account for the larger pore（0.86 nm） and ultra-micropore（0.86 nm） fractal characteristics,respectively.The increase in pyrolysis residence time increases the FD-1 and FD-2 firstly,and then tends to be stable.The FD-2 increases greatly at high temperature pyrolysis compared with that at low temperature,which shows a great development in ultra-micropore,while FD-1 is not the case.