Research on N2O reduction technologies from sewage sludge incinerator

Greenhouse gas from N2O, which is generated during the combustion process in sewage sludge incinerators, accounts for 20% of the greenhouse gas emitted from wastewater facilities. Since N2O has a high global warming potential of 310, it has a great impact even if the concentration level is low. In this report, we summarized the N2O reduction technologies by types, and investigated the benefits of implementation.N2O is reduced by a two-step combustion process in bubbling fluidized bed incinerator (bubbling FBI) and circulating fluidized bed incinerator (circulating FBI). The two-step combustion process is a technology that promotes high-temperature pyrolysis of N2O by promoting pyrolysis with primary air and forming high temperature area with secondary air. Step grate stoker incinerator promotes high-temperature pyrolysis of N2O by drying dewatered sludge to raise the combustion temperature. This technology recovers heat from combustion effluent and uses it as heat source for drying.Regarding the benefits of implementation, we studied N2O emission intensity, greenhouse gas emissions, and energy saving effect using data from actual facilities. From this study, it was confirmed that there is a high correlation between the maximum temperature inside the incinerator and the N2O emission intensity, regardless of the types or scales. It was also confirmed that the target N2O reduction technologies regulate the supplemental fuel usage.