Indirect Detection of Nitrogen Oxide Emission on Actual PFBC (Pressurized Fluidized Bed Combustion)

Abstract

A potential method for evaluating the concentration of gaseous nitrogen oxides in the exhaust gas from the pressurized fluidized bed combustion (PFBC) system was developed, and then its effectiveness was certified in a 71MWe PFBC demonstration plant at Wakamatsu Work, Electric Power Development Co. The total amount of nitrogen oxides (NO, NO₂ and N₂O) in the exhaust gas was closely related with the N content in the coal used as a fuel and contained no thermal-and prompt-NO_x (NO and NO₂) originating from N₂ in air, due to a low combustion temperature of around 1, 130K in the PFBC system. The concentration of NO_x and N₂O was estimabed as a function of the temperature and oxygen partial Pressue in the exhaust gas, if burning coal was specified. By pseudo thermodynamic equilibrium over the fluidized bed under the successive supply of the slurry fuel and pressurized air, conversions of N in the fuel coal into NO_x and N₂O could be expressed by ASH^TR-NO_x and -N₂O equations, respectively, based on the temperature measured by thermocouple and the oxygen partial pressure by a YSZ oxygen sensor. The calculated NO_x and N₂O concentrations by the equations were well agreed with the measured values by commercially available instruments, demonstrating the potential use of this method for rapid and indirect monitoring of gaseous nitrogen oxides in the exhaust gas from the PFBC system.