Experiments On Sulfur Transformation And Desulfurization With Calcite In O₂/CO₂ Coal Combustion

O₂/CO₂ combustion is a new technology that can achieve carbon capture and storage and control pollutants such as SO₂,NOX and particulate matter cooperatively. Currently precursor sulfur emission and transformation mechanism during combustion and SO₂ control after combustion is not well understood. For a better understanding, the paper focuses on the above questions. Firstly, research the organic sulfur and inorganic sulfur transformation under CO₂ atmosphere is taken; Further, this paper focus on limestone calcinations and sintering characteristic under O₂/CO₂ atmosphere. Finally, Using a drop tube furnace to research injection limestone desulfurization efficiency as well as impact on the particulate matter control under O₂/CO₂ atmosphere.Firstly, Liuzhi high pyritic sulfur coal and Zunyi high organic sulfur coal were chosen to do systematic research about sulfur transformation under CO₂ atmosphere. Experimental results show that there are two ways of pyretic sulfur transform into organic sulfur during thermal chemical conversion process. One is the activity S2 which is decomposed from pyretic sulfur react with char to form organic sulfur. The other one is that FeSx (1≤x<2) decomposed from pyretic sulfur react with organic functional groups in char to form organic sulfur. H2S,SO₂ and CS2 are the main gaseous products that containing sulfur under CO₂ atmosphere.SO₂ is mainly produced by decomposition of sulfates. CS2 emission is likely relation to pyretic sulfur content. COS can be detected under CO₂ atmosphere while can not be detected under N2 atmosphere.Secondly, Using thermal gravity and drop tube furnace to research impact of temperature, CO₂ partial pressure and atmosphere on limestone calcinations and sintering characteristics of CaO. The results show that, compared with O₂/N₂ atmosphere, decomposition temperature is higher and decomposition rate is slower under O₂/CO₂ atmosphere. CO₂ partial pressure affect limestone decomposition temperature. During 900-1300℃, specific surface area and porosity increased first and then decrease under O₂/N₂ atmosphere while they increase during temperature rise under O₂/CO₂ atmosphere.Finally, Using drop tube furnace to research injection limestone desulfurization efficiency as well as impact on the particulate matter control under O₂/CO₂ atmosphere. The results show that SO₂ emission is lower under O₂/CO₂ atmosphere than O₂/N₂ atmosphere. The desulfurization mechanism is changed from indirect desulfurization mechanism under O₂/N₂ atmosphere to indirect desulfurization mechanism and direct desulfurization mechanism under O₂/CO₂ atmosphere. The best desulfurization temperature under O₂/CO₂ atmosphere is wider than O₂/N₂ atmosphere. What's more, inject limestone is not only achieve SO₂ control as well as PM10 especially PM1 control under O₂/CO₂ atmosphere coal combustion.