Experimental research of mitigation strategy for high-temperature corrosion of waterwall fireside in a 630 MWe tangentially fired utility boiler based on combustion adjustments

Abstract

With the extensive use of the staged combustion systems to meet the stricter standard for NOx emission, the high-temperature corrosion caused by reducing atmosphere has become much serious. In this study, seven groups of industrial-scale experiments of combustion adjustments were conducted in a 630 MW tangentially fired utility boiler to study the effects of different operating conditions on the high-temperature sulfur corrosion, NOx emission and boiler efficiency. The experimental results showed that the reducing atmosphere in the vicinity of the waterwall was mainly controlled by distributions of O2 concentration and combustion temperature. For alleviating the reductive gases, the increase of the O2 concentration near the waterwall was much effective but more vigorous combustion with the higher temperature was negative (except increasing the CFS air). The overall excess air factor, the distribution of DFS air, the flow rates of CFS air, CCOFA and SOFA had great effects on the reducing atmosphere near the waterwall while the impacts of the flow rate of primary air and coal fineness were unobvious. Through the comprehensive assessment, the optimal operation parameters which reached the balance among the low high-temperature sulfur corrosion, low NOx emission and high boiler efficiency can be obtained.