Evolution of the physicochemical properties and SO2 adsorption performance of powdered activated coke during adsorption–desorption cycle

The use of carbonaceous adsorbent to remove SO2 from flue gas is regarded as the most environmentally friendly flue gas desulfurization technology presently known because of the extensive pores and rich functional groups characterizing the adsorbents. The main purpose of this work is to clarify the effects of the thermal regeneration temperature and cycle times on SO2 adsorption performance by analyzing the physicochemical properties of carbon adsorbent and to reveal the synergistic relationship between adsorbent mass loss and gas release. Commercial powdered activated coke (PAC) prepared from coal was used. Experimental results show that the influence of the regeneration temperature on the physicochemical properties of the adsorbent leads to different variation trends in the circulating desulfurization performance. The regeneration rates of the regenerated PACs after 10 cycles at 250/450/650/850 °C were 37.71%, 72%, 118.66%, and 148.06%, respectively. Pore blockage and oxygen accumulation on the carbon surface are the reasons for the decline in the desulfurization performance of regenerated PAC at 250–450 °C. Pore development, primarily in the form of micropores, and the inhibition of surface oxidation cause the optimization of the desulfurization performance of regenerated PAC at 650–850 °C. The release of carbon atoms in CO2/CO gas during regeneration causes loss of PAC mass; meanwhile, oxygen atoms mainly originate from the adsorption process. This study systematically clarifies the relationship between the physicochemical properties of PAC and the evolution of SO2 cyclic adsorption properties, which provides guidance for the design of regeneration parameters for desulfurization systems.