High-temperature conversion of SO2 to SO3: homogeneous experiments and catalytic effect of fly ash from air and oxy-fuel firing

Belo, Lawrence P.; Elliott, Liza K.; Stanger, Rohan J.; Spörl, Reinhold; Shah, Kalpit V.; Maier, Jörg; Wall, Terry F.

Title: High-temperature conversion of SO2 to SO3: homogeneous experiments and catalytic effect of fly ash from air and oxy-fuel firing
Creator: Belo, Lawrence P.; Elliott, Liza K.; Stanger, Rohan J.; Spörl, Reinhold; Shah, Kalpit V.; Maier, Jörg; Wall, Terry F.
Relation: Energy and Fuels Vol. 28, Issue 11, p. 7243-7251
Publisher Link: http://dx.doi.org/10.1021/ef5020346
Publisher: American Chemical Society (ACS)
Resource Type: journal article
Date: 2014
Description: The reaction of SO2 with fly ash in the presence of O2 and H2O involves a series of reactions that lead to the formation of SO3 and eventually H2SO4. Homogeneous experiments were conducted to evaluate the effects of the procedural variables, i.e., temperature, gas concentrations, and residence time, on the post-combustion conversion of SO2 to SO3. The results were compared to existing global kinetics and found to be dependent upon SO2, O2, residence time, and temperature and independent of H2O content. For a residence time of 1 s, temperatures of about 900 °C are needed to have an observable conversion of SO2 to SO3. Literature suggested that the conversion of SO2 to SO3 is dependent upon the iron oxide content of the fly ash. Experiments using three different fly ash samples from Australian sub-bituminous coals were used to investigate the catalytic effects of fly ash on SO2 conversion to SO3 at a temperature range of 400–1000 °C. It was observed that fly ash acts as a catalyst in the formation of SO3, with the largest conversion occurring at 700 °C. A homogeneous reaction at 700 °C, without fly ash present, converted 0.10% of the available SO2 to SO3. When fly ash was present, the conversion increased to 1.78%. The catalytic effect accounts for roughly 95% of the total conversion. Average SO3/SO2 conversion values between fly ash derived from air and oxy-fuel firing and under different flue gas environments were found to be similar.
Subject: sulfur-trioxide formation; coal combustion; emissions; sulphur dioxide
Identifier: http://hdl.handle.net/1959.13/1297921
Identifier: uon:19538
Identifier: ISSN:0887-0624
Language: eng
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