Effect of pore structure on mechanical strength of coal-based activated coke for desulfurization and denitration

The developed pore structure is an important reason for reducing the mechanical strength of coal-based activated coke for desulfurization and denitrification, which seriously shortens its service life. The eight fresh activated cokes (Fresh-AC), three activated cokes recycled by fixed bed different times (Fixed-AC), and one activated coke recycled by fluidized bed purifi-cation system (Fluidized-AC) were investigated. The mechanical strength index, stomatal charac-teristic index of activated coke samples were measured, and the correlations between compressive strength, abrasion resistance and pore opening-closing state, pore size distribution were analyzed. Then, the variation law of pore structure and mechanical strength of activated coke during recycling and the influence of pore structure on mechanical strength were clarified. The results show that the activated coke open pores in all pore size are further developed with the increase of the cycles number because of the activation effect from sulfuric acid decomposition on activated coke during thermal regeneration, and then the compressive strength and abrasion resistance continue to decrease accordingly. Compared with Fresh-AC, the 0-2 nm, 2-500 nm, and larger than 500 nm pore volume of Fluidized-AC increase by 45.3%, 50.5%, 5.5%, respectively, the strength is only about 70% of Fresh-AC, and the abrasion resistance is 1.7% higher than Fresh-AC. The open pore is the main pore type that reduces activated coke compressive strength. The 2-500 nm open pore has the greatest damage to compressive strength. For each increase of 2-500 nm pore volume of 0.01 cm3/g, the compressive strength decreases by 38.704 N. The compressive strength of Fresh-AC, Fixed-AC, Fluidized-AC all abide by this linear variation law with the change of 2-500 nm pore volume. There is no significant difference in the damage degree of the abrasion resistance between the open pore and the closed pore. The 0-2 nm pore has the most significant damage to abrasion resistance. For each increase of 0-2 nm pore volume of 0.01 cm3/g, the abrasion strength decreases by 1.769 9%. The abrasion resistance of Fresh-AC and Fixed-AC obey by this linear variation law with the change of 0-2 nm pore volume, yet the abrasion resistance of Fluidized-AC is significantly higher than this linear variation law because of its smoother particle surface. © 2019, Editorial Office of Journal of China Coal Society. All right reserved.