Formation of ammonia bisulfate in coal-fired power plant equipped with SCR reactors and the effect of reduced load operation

Abstract

Coal fired power plant are still responsible for vast amount of electricity and heat production in Poland in 2019. Increasing number of units is equipped with SCR reactors in order to mitigate NOx emission. Older units have been designed to work in a base load operation· however increasing number of intermittent energy sources on the market· forces power plant owners to operate such units in reduced load for significant number of hours in a year. Most of parameters in coal-fired boiler would change in reduced load operation· particularly flue gas parameters. That would affect the formation of ammonia bisulfate (NH4HSO4) as well as operation of SCR reactors in the boiler. The NH4HSO4 formation is highly undesired as it can plug the catalyst or heating surfaces in the boiler. To investigate this phenomenon· the NH4HSO4 formation was comprehensively studied. Moreover· reduced load operation of boiler in a medium size CHP plant was simulated· using computer modelling tools. Obtained parameters were used to analyse· how different flue gas parameters affect NH4HSO4 formation and what consequences does it have for boiler operation. In particular, effect related with operation of SCR reactors equipped with V2O5-WO3/TiO2 catalyst was deeply studied.

Study on the equilibrium constants and initial formation temperature of NH4HSO4 and (NH4)2SO4 in coal‐fired flue gas

“…The concentration of ammonia leakage in the flue gas should be below 3 ppm 22 . Regarding SO 3 in the flue gas, Maciej Ż 23 estimated its concentration to be roughly 9.1 ppm and 19.1 ppm in the flue gas. Cai M 24 observed that the SO 3 concentration of a particular 600 MW unit decreased from 18–95 ppm at the inlet to 6–27 ppm after passing through the SCR unit.…”