Insights into the effect of regeneration temperature on physicochemical properties and SO2 removal over powdered activated coke

Abstract

Porous carbon materials have emerged as a new technology with tremendous potential as energy-saving and environmentally friendly pathways for SO2 removal due to its advantages, which include recyclability and a high adsorption capacity. However, the degradation of the performance of adsorbents using thermal regeneration has become a key issue limiting the scaling-up of this new technology. The main purpose of this study is to clarify the effect of the regeneration temperature on the physicochemical properties of activated coke and secondary SO2 removal performance, as well as explore the mechanism by which the circulating adsorbent is deactivated. Using powdered activated coke (PAC) prepared from coal. Experimental results show that adsorbed SO2 desorbs at temperatures between 200 and 500 ℃, while both excess CO2 and CO are released over a wide temperature range owing to the regeneration reaction and decomposition of newly formed oxygen-containing functional groups. The physicochemical properties of PAC are significantly affected by the regeneration temperature. As this temperature rises, the adsorbed sulfuric acid in the pores evaporates and the functional groups decompose, producing several micropores and a large specific surface area. Moreover, the SO2 adsorption–desorption process increases the number of C–O groups such that the active adsorption sites are occupied and SO2 adsorption is prevented. The C-O groups decompose to produce CO2 when exposed to even higher temperatures. The secondary SO2 adsorption experiment demonstrated that the ability of the adsorbent to perform desulfurization could be recovered completely by controlling the regeneration temperature.