Effect of Oxygen Enrichment in air on Acid Gas Combustion under Claus Conditions

摘要

The effect of oxygen enrichment (using a mixture of oxygen and nitrogen) in the oxidant on the combustion of acid gas (H_2S and CO_2) in hydrogen fuelled flames is examined under Claus condition (at equivalence ratio of Φ=3). The acid gas composition examined was 50% H_2S/50% CO_2 at different percentages of oxygen enrichment (0%, 19.5% and 69.3%) in the oxygenitrogen mixtures. Combustion of acid gas formed SO_2 with increase in O_2 mole fraction. The results showed that an increase in oxygen enrichment to combustion air results in reduced formation of elemental sulfur while simultaneously increasing the amounts of SO_2 that is less favorable. This is attributed to the release of oxygen from CO_2 at high temperatures into the reaction pool. Moreover, the mole fraction of carbon monoxide increased at increased oxygen enrichment which is an indicator of increased release of oxygen into the reaction pool. Other sulfurous-carbonaceous compounds formed (primarily COS and CS_2) are due to the presence of carbon monoxide. The results showed mitigation of CS_2 formation with oxygen enrichment in the combustion process and increased rate of COS formation from the increased availability of CO due to the dissociation CO_2 at higher temperatures. The reduction in CS_2 formation helps to improve efficiency of sulfur capture in Claus thermal reactor.