SO 2 Emissions from Oil Shale Oxyfuel Combustion in a 60 kWth Circulating Fluidized Bed

Mais Baqain, Dmitri Neshumayev and Alar Konist ()
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Mais Baqain: Department of Energy Technology, Tallinn University of Technology, 19086 Tallinn, Estonia
Dmitri Neshumayev: Department of Energy Technology, Tallinn University of Technology, 19086 Tallinn, Estonia
Alar Konist: Department of Energy Technology, Tallinn University of Technology, 19086 Tallinn, Estonia

Energies, 2024, vol. 17, issue 18, 1-18

Abstract: Carbon capture, utilization, and storage (CCUS) have emerged as pivotal technologies for curtailing emissions while maintaining fossil fuel. Estonia faces a challenge due to its dependence on carbon-intensive oil shale, but the need for energy security, highlighted by the war in Ukraine, makes reducing CO 2 emissions a priority while maintaining energy independence. In this context, the presented study determines the environmental impact of combustion of the Estonian oil shale from the release of SO 2 emission and compares sulfur retention in the ash between different oxyfuel combustion campaigns in a 60 kWth CFB test facility. The pilot was operated under air, O 2 /CO 2 , and with recycled flue gas (RFG), and we tested the application of extremely high inlet O 2 up to 87% vol . The key objective of this study is to examine how different combustion atmospheres, operating temperatures, and excess oxygen ratios influence SO 2 formation. Additionally, the research focuses on analyzing anhydrite (CaSO 4 ), calcite (CaCO 3 ), and lime (CaO) in ash samples collected from the dense bed region (bottom ash) and the external heat exchanger (circulating ash). The results indicate that increased inlet O 2 % does not significantly affect SO 2 emissions. Compared to air-firing, SO 2 emissions were higher than 40 mg/MJ under a 21/79% vol O 2 /CO 2 environment but were significantly reduced, approaching zero, as the inlet O 2 % increased to 50%. Under O 2 /RFG conditions, higher SO 2 concentrations led to increased sulfur retention in both the bottom and circulating ash. The optimal temperature for sulfur retention in air and oxyfuel combustions is below 850 °C. This study for the first time provides a technical model and discusses the effects of operating parameters on sulfur emissions of the Estonian oil shale CFB oxyfuel combustion.

Keywords: SO 2 emissions; oil shale; Ca-rich fuel; circulating fluidized bed; oxyfuel; ash sulfur retention (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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