In-situ monitoring of transient gas phase K–Cl–S chemistry in a pilot-scale combustor

Abstract

Biomass and waste derived fuels contain large amounts of sodium, potassium, and chlorine that form NaCl and KCl, that is, compounds that cause operational problems, such as slagging, fouling, and high-temperature corrosion. Therefore, alkali chlorides are the main reasons that explain why steam parameters are less advanced and efficient in biomass and waste-based power generation when compared to coal. These problems can be mitigated by introducing sulphur into the system to form alkali sulphates that are not as problematic on steel surfaces as alkali chlorides. However, the alkali sulphation process in realistic combustion environments needs further exploration. Thus, new diagnostic methods for in-situ monitoring of alkali sulphation kinetics in combustion systems are required. In this work, the simultaneous monitoring of KCl and KOH concentrations in a pilot-scale combustor using Collinear Photofragmentation and Atomic Absorption Spectroscopy (CPFAAS) during stationary and transient operation of the combustor, is introduced. The CPFAAS information is complemented by monitoring SO2 and HCl concentrations using Fourier-transform infrared spectroscopy (FTIR). The temporal performance of the system is demonstrated by measuring the temporal combustor response curves for KCl sulphation for different Cl/K ratios during rapid changes in gaseous SO2 concentrations. The temporal concentration curves obtained imply that the Cl/K ratio has a significant impact on the temporal alkali sulphation behaviour. The measurement system described enables further exploration of K–Cl–S chemistry in realistic large-scale power plant environments.