Development of Prognostic Tool for High-temperature Corrosion Risk Assessment in Pulverised Coal Boilers Based on the Waterwalls Boundary Layer Monitoring System and CFD Simulations

Abstract

The implementation of the low-emission combustion techniques for NOx emission reduction often results in the intensification of high-temperature corrosion of the boiler heating surfaces. The corrosion of boiler tubes increases the operational costs and have strong negative effect on the reliability and availability of the whole power unit. Low-emission combustion (for example the use of low-NOx burners and air staging) contributes to formation of a reducing atmosphere in the furnace chamber, that is accompanied by oxygen depletion and excess of CO in the vicinity (boundary layer) of waterwalls. A research has been conducted on the implementation of a monitoring system in the boundary layer of the combustion chamber walls. This system is based on the on-line measurement of the oxygen concentration in the boundary layer of the boiler chamber walls and allows to identify reduction zones and may be useful for preventing intensified corrosion. To improve the functionality of the monitoring system Computational Fluid Dynamics may appear helpful. A validated CFD model capable of properly predicting the CO and O2 concentration in the vicinity of the combustion chamber walls may help to adjust the monitoring system during variable boiler operating conditions or different fuel properties without the necessity to repeat the measurements for new conditions.