Effect of temperature on pore structure evolution during powder-activated coke preparation by flue gas activation

In order to develop a low-cost and high-efficiency powder-activated coke for desulfuration,lignite coal pow- der 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 char- acterized 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 iso-therms 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 tempera- ture,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 vol- ume 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 adsorp- tion 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.