Investigations of operation problems at a 200 MWe PF boiler

Abstract

To minimize oxides of nitrogen (NOx) emission, maximize boiler combustion efficiency, achieve safe and reliable burner combustion, it is crucial to master global boiler and at-the-burner control of fuel and air flows. Non-uniform pulverized fuel (PF) and air flows to burners reduce flame stability and pose risk to boiler safety by risk of reverse flue gas and fuel flow into burners. This paper presents integrated techniques implemented at pilot ESKOM power plants for the determination of global boiler air/flue gas distribution, wind-box air distribution and measures for making uniform the flow being delivered to burners within a wind-box system. This is achieved by Process Flow Modelling, at-the-burner static pressure measurements and CFD characterization. Global boiler mass and energy balances combined with validated site measurements are used in an integrated approach to calculate the total (stoichiometric + excess) air mass flow rate required to burn the coal quality being fired, determine the actual quantity of air that flows through the burners and the furnace ingress air. CFD analysis and use of at-the-burner static, total pressure and temperature measurements are utilized in a 2-pronged approach to determine root-causes for burner fires and to evaluate secondary air distribution between burners.

Assessing the Importance of Pyrolysis Process Conditions and Feedstock Type on the Combustion Performance of Agricultural-Residue-Derived Chars

“… 11 Knowledge of the combustion performance and kinetics of biomass chars is of great importance to properly design industrial-scale combustors, where the residence time of fuel particles is very short. 12 …”

“…11 Knowledge of the combustion performance and kinetics of biomass chars is of great importance to properly design industrial-scale combustors, where the residence time of fuel particles is very short. 12 Previous research has compared the combustion (or cocombustion) performance of a number of biomass-derived chars produced from different feedstocks and under different operating conditions. 13−16 These preliminary studies pointed out that char reactivity is affected by pyrolysis operating conditions under which char is obtained.…”

“…From thermogravimetric analysis (TGA) data, it is possible to estimate both ignition and burnout temperatures and also calculate the so-called combustion performance index ( S ), as has recently been reported by Mundike et al and Wang et al This index is a measure of the burning ability of a fuel, and a higher value reflects a more satisfactory combustion performance . Knowledge of the combustion performance and kinetics of biomass chars is of great importance to properly design industrial-scale combustors, where the residence time of fuel particles is very short …”