Carbon consumption and adsorption-regeneration of H2S on activated carbon for coke oven flue gas purification.

Carbon consumption of activated carbon varies with sulfur-containing products. In this work, differential thermogravimetric (DTG), electron paramagnetic resonance (ESR), X-ray photoelectron spectroscopy (XPS), and temperature programmed desorption (TPD) we re used to reveal the adsorption-regeneration process of H2S and the effect of adsorption products on carbon consumption. The results show that H2S reacts with the C=C bond to form the C-S bond as an intermediate state, followed by the formation of elemental sulfur. It directly sublimates at approximately 380 °C, about 30 °C higher than the decomposition temperature of H2SO4. In the thermal regeneration process, the elemental sulfur in the form of monoclinic sulfur (S8) first breaks into infinitely long chain molecules (S∞) and then into small molecules, finally into sulfur vapor. The desorption of elemental sulfur consumes less oxygen and carbon functional groups, reducing the chemical carbon consumption by 59.8% than H2SO4; moreover, the compressive strength reduces less due to its slight effect on the disordered graphitic structure. H2S also reacts with the C=O bond to form H2SO3 or H2SO4. The desorption of H2SO3 does not require carbon consumption. The decomposition of H2SO4 needs to react with the C=C bond to release SO2, CO2, and CO, and the compressive strength of activated carbon significantly decreases. The carbon consumption originates from two aspects; the one from the regeneration of sulfur-containing products is more than twice the other one from the decomposition of oxygen-containing functional groups.