A study on carbothermal reduction of sulfur dioxide to elemental sulfur using oilsands fluid coke

Experiments and reaction equilibrium calculations were carried out for the SO2 gas and oilsands fluid coke system. The goal was to develop a coke-base d sulfur-producing flue gas desulfurization (SP-FGD) process that removes S O2 from flue gases and converts it into elemental sulfur. The conversion of SO2 to elemental sulfur proceeded efficiently at temperatures higher than 600 degreesC, and the sulfur yield reached a maximum (>95%) at about 700 de greesC. An increase of temperature beyond 700 degreesC enhanced the reducti on of product elemental sulfur, resulting in the formation of reduced sulfu r species (COS and CS2), which lowered the sulfur yield at 900 degreesC to 90%. Although equilibrium calculations suggest that a lower temperature fav ors the conversion of SO2 as well as the yield of elemental sulfur, experim ents showed no formation of elemental sulfur at 600 degreesC and below, lik ely due to hindered kinetics. Faster reduction of SO2 was observed at a hig her temperature in the range of 700-1000 degreesC. A complete conversion of SO2 was achieved in about 8 s at 700 degreesC. Prolonging the product gas- coke contact, the yield of elemental sulfur decreased due to the formation of COS and CS2 while the SO2 conversion remained complete. Equilibrium calc ulations suggest that the ultimate yield of elemental sulfur maximizes at t he C/SO2 ratio of 1, which represents the stoichiometry of SO2 + C --> CO2 + S. For the C/SO2 ratio < 1, equilibrium calculations predict elemental su lfur and CO2 being major products, suggesting that SO2 + C --> CO2 + S is t he predominant reaction if SO2 is in excess. Experiments revealed that elem ental sulfur and CO2 were only major products if the conversion of SO2 was incomplete, which is in agreement with the result of the equilibrium modeli ng.