Emissions of SO2 and NOx during Oxy-Fuel CFB Combustion Tests in a Mini-Circulating Fluidized Bed Combustion Reactor

Anthropogenic CO2 production is primarily driven by by fossil fuel combustion, and the current energy demand situation gives no indication that this will change in the near future. In consequence, it is increasingly necessary to find ways to reduce these emissions when fossil fuel is used. CO, capture and storage (CCS) appears to be among the most promising approaches. All of the CCS technologies involve producing it nearly pure stream of CO2, either by concentrating it in some manner from the flue gases or by using Pure oxygen as the combustion gas. The latter option, oxy-fuel combustion, has now been well Studied for pulverized coal combustion, but to date has received relatively little attention in the case of oxy-fuel circulating fluidized bed combustion (CFBC), Recently, oxy-fuel I-BC has been examined in a 100 kW pilot plant operating with flue gas recycle at CanmetEnergy. The results strongly support the view that this technology offers all of the advantages of air-fired FBC, with one possible exception. Emissions Such as CO or NOx are lower or comparable to those of air firing. It is possible to switch from air firing to oxy firing easily, with oxygen concentrations as high as 60-70%, and flue gas recycle levels of 50-60%. Only sulfation is poorer, which is not in good agreement with other studies, and the reasons for this discrepancy need further exploration. However, longer tests have confirmed these findings with two coals and a petroleum coke. It also appears that changing from direct to indirect sulfation with the petroleum coke improves the sulfation, although a similar effect could not be confirmed with coal from these results.