Study on decoupling of carbonization and activation processes in the preparation of powdered activated coke via one-step method under flue gas atmosphere

Abstract

This study built on the one-step method for preparing powdered activated coke (PAC), conducting pure carbonization, single-component activation, and flue gas activation experiments using SL-coal and JJ-coal. It examined how carbonization and activation affect PAC yield, burn-off, gas-phase product yield, physicochemical properties and SO₂ adsorption capacities of PACs, and their distinct contributions. Results show that the activation mechanisms of O₂, CO₂, and H₂O(g) varied with coal types. O₂ primarily consumes volatiles in SL-coal, converting them into CO₂/H₂O(g) to enhance active component diffusion, while in JJ-coal, it ablates liquid-phase products to expose pores; CO₂ mainly promotes micropore development; H₂O(g) expands and creates pores in SL-coal but is less effective in JJ-coal due to pore blockage. Flue gas components synergistically form hierarchical pores and enriched surface oxygen-containing functional groups. Besides, the carbonization process dominates the burn-off contribution, the contribution degrees of the carbonization and activation processes to burn-off are in a ratio of 4:1 for SL-PAC and 2.4:1 for JJ-PAC. For SL-PAC, the carbonization process primarily governs pore structure and SO₂ adsorption performance, the contribution degrees of the carbonization and activation processes to S_BET are in a ratio of 1.7:1, to V_Tot of 1.5:1, and to SO₂ adsorption capacity of 1.7:1. In contrast, the activation process dominates JJ-PAC’s S_BET and SO₂ adsorption, the contribution degrees of the carbonization and activation processes to S_BET are in a ratio of 0.18:1, and to SO₂ adsorption capacity of 0.8:1. This work provides theoretical insights for the tailored preparation of coal-based PAC.