Optimization of Combustion and Prevention of Water Wall Corrosion at a Pulverised Coal fired Power Plant

摘要

To enhance the efficiency of a power plant by reducing stack loss, without running the risk of water wall corrosion, it is necessary to control the water wall atmosphere. Water wall corrosion is a well known problem in coal fired boilers. Combustion modifications to reduce stack loss increase the probability of water wall corrosion in coal-fired boilers. Minimizing the excess air often leads to reducing conditions at the water wall, what causes the typical chemical reactions, taking place during the corrosion process.rnInvestigations have been carried out at a 1225 MW_(th) pulverised coal fired boiler. For this purpose the investigated boiler was equipped with 110 measuring ports, for oxygen and carbon monoxide measurements, equally distributed at the boiler walls. The water wall atmosphere was measured at different combustion conditions.rnSupported by the results of the wall atmosphere measurements, the amount of excess air was set up to the lowest possible value without reducing the oxygen coverage of the waterwalls or decreasing the burnout.rnTo minimize the primary NO_x formation, new settings for the combustion air distribution at the burners have been developed, aided by computational simulations. As predicted by the computational simulations, the primary NO_x formation was reduced, by about 100 mg/Nm~3, additionally the oxygen coverage of the waterwalls was increased too.