温度对粉状活性焦的孔隙结构及SO2吸附性能的影响

为研究低成本、高性能脱硫用粉状活性焦的制备技术，采用褐煤为原料，在沉降炉试验台上进行粉状活性焦的制备，通过灰平衡方法分析了粉状活性焦的产率及挥发分含量，通过氮气吸附方法表征褐煤及粉状活性焦的孔容、比表面积及孔径分布，探索了不同温度条件下烟气活化对粉焦快速制备过程中孔隙结构的演变的影响机制，采用分形Frenkel-Halsey-Hill法分析了粉焦孔隙结构的分型特征，采用SO2性能测试装置分析了粉状活性焦的2 h吸附容量并探究粉焦的孔隙结构与SO2吸附性能的关系。结果表明，所获得活性焦的低吸附等温线的类型具备Ⅰ型和Ⅳ型等温线的特征，孔隙结构呈微孔-中孔-大孔的梯级孔结构特征，且以微孔结构为主。随着活化温度的增加，粉焦的产率呈线性下降的趋势，粉焦的比表面积及孔容值先增大后减小。温度为950 ℃时，比表面积最大，最大值为437.74 m2/g;温度为1 050 ℃时，总孔容最大，最大值为0.258 cm3/g;温度为1 200 ℃时，灰熔融造成孔隙堵塞大大降低了粉焦的孔隙结构。分形维数D2与活性焦比表面积变化趋势一致，可以较好的反应粉焦的微孔变化趋势。褐煤基粉焦的SO2吸附穿透曲线分为完全吸附阶段及穿透阶段，两个阶段的吸附由不同的孔隙结构主导，完全吸附阶段为微孔吸附，吸附速率快，吸附量大小取决于微孔，而穿透阶段的吸附量主要取决于中孔。

Effect of temperature on pore structure evolution during powder-activated coke preparation by flue gas activation at a high heating rate

In order to develop a low-cost and high-efficiency powder-activated coke for desulfuration,lignite coal powder was used to prepare powder-activated coke in a drop-tube reactor.The yield and volatile content were calculated by ash balance method.The specific surface area,pore volume and pore width distribution of the coal samples were characterized by nitrogen adsorption.The effect of temperature on the pore structure characteristics during powder-activated cokes preparation was investigated.The fractal dimension based on gas adsorption iso-therms was obtained using fractal Frenkel-Halsey-Hill method.The relationship between the pore structure and SO2 adsorption capacity of activated cokes was investigated using a self-designed adsorption device.The experi-mental results show that the absorption isotherms of activated cokes are of type I and IV adsorption isotherms.The pore structure showed a hierarchical micro-,meso-,and macroporous structure and the major pore type was micropore.With the increase of preparation temperature,the specific surface area of the activated coke first increased and then decreased and the changes of pore volume displayed a similar trend.The special surface area reached a maximum value 437.74 m2/g at 950 ℃ and the pore volume reached a maximum value 0.258 cm3/g at 1 050 ℃.The pore structure parameters decreased significantly caused by ash fusion and pore blocking at 1 020 ℃.The fractal dimensions D2 which showed a similar trend with the specific surface area as the temperature increased could indicate the evolution of the micropore structure.The breakthrough curves of SO2 adsorption showed two different stages (completely adsorption and breakthrough) because SO2 adsorption was influenced by different pore types.The SO2 adsorption capacity was closely related to micropore structure and the rate of adsorption was faster in the completely adsorption stage.The SO2 adsorption capacity of activated coke was determined by the mesopore in the breakthrough stage.