Powder activated coke prepared from coal fast pyrolysis: fractal characteristics and SO₂ adsorption

The rapid and low-cost preparation of powder activated coke (PAC) is very important for the promotion of fluidized dry desulfurization technology of activated coke. In order to explore the effect of rapid pyrolysis process on SO₂ adsorption capacity of PAC, the fractal analysis of PAC prepared under different atmospheres was carried out. The Frenkel-Halsey-Hill (FHH) method was used to determine two fractal dimensions D₁ and D₂, under relative pressures of 0-0.5 and 0.5-1, respectively. The results indicate that the fractal dimensions were influenced by the concentrations of activation agents with D₁ ranging from 2.1838 to 2.8643 and D₂ ranging from 2.7485 to 2.9257. The effect of steam on the fractal dimension of PAC sample is small, but oxygen has a great promotion effect on the fractal dimension. An n-shaped curve-based relationship between fractal dimensions and coke yields is observed with a peak values of fractal dimensions appearing around 64% yield. The SO₂ adsorption capacity shows a consecutively positive linear correlation with D₂, while it illustrates distinctly different linear rates with D₁ in intervals of 2-2.6 and 2.6-3, respectively. Taking advantage of fractal analysis as research method, this paper clarified the influence of activation atmosphere and ablative degree on the SO₂ adsorption capacity of PAC, and the research conclusion provided a basis for the PAC preparation with high SO₂ capacity.