Deposition and high temperature corrosion in a 10 MW straw fired boiler

High Temperature Corrosion under Laboratory Conditions Simulating Biomass-Firing: A Comprehensive Characterization of Corrosion Products

“…However, both KCl and K2SO4 exhibit melting temperatures above 560 o C. A potential explanation for such melts at 560 o C could be the formation of a eutectic, since neither pure KCl, nor K2SO4 can melt in the temperature range considered in the present experiments. The ability of KCl to form low-melting eutectics with transition metal chlorides in the temperature range (200 -500 o C) has been reported previously [17,39]. With the depletion of Cr in the oxide and subsurface regions, due to reaction with K, according to equation (1), Fe-chloride formation from the chlorination reaction in equation (4), becomes thermodynamically favourable, and thus the formation of a eutectic melt with KCl below 560 o C is possible.…”

“…The catastrophic corrosion observed is frequently explained by the active oxidation mechanism catalyzed by Cl [2,17,18,38]. Initiation and sustaining mechanisms for the corrosion process are still being discussed in literature [22,27,30,38,39].…”

“…Generally, the high corrosion rate observed during straw-firing is attributed to the following active oxidation mechanism caused by Cl [17][18][19]. Sulphation of the condensed KCl close to the superheater tubes generates Cl.…”

Release of K, Cl, and S during Pyrolysis and Combustion of High-Chlorine Biomass

“…The release of Cl-associated species during combustion is the main cause of the induced active corrosion in the grate combustion of biomass. 2,5,13 In addition, Cl is known to facilitate the release of K, causing fouling problems upon condensation. 31 Figure 2 summarizes pathways for Cl release during biomass combustion.…”

“…30 In addition, data from equilibrium studies and controlled release experiments have contributed to an increased understanding of the stability and behavior of released species. 5,21 Chlorine Release Path. The release of Cl-associated species during combustion is the main cause of the induced active corrosion in the grate combustion of biomass.…”