High-temperature corrosion due to lead chloride mixtures simulating fireside deposits in boilers firing recycled wood

Abstract One of the biggest operational concerns in recycled wood combustion, is the risk for formation of low melting, corrosive deposits. The deposits present on low-temperature heat transfer surfaces (material temperature  K 2 SO 4 is commonly regarded as non-corrosive, but there have been indications that K 2 SO 4 may worsen the PbCl 2 induced corrosion. Consequently, a more detailed study with these compounds was of very high interest. This paper reports the results obtained from 24-hour isothermal laboratory corrosion tests with PbCl 2 mixed with either K 2 SO 4 or SiO 2 . The tests were carried out at 350 °C using low alloy steel (16Mo3). The interaction between PbCl 2 and K 2 SO 4 was investigated in a furnace with a temperature gradient. As a result, a mixture of PbCl 2 and K 2 SO 4 is more corrosive than PbCl 2 mixed with SiO 2 . Corrosion was noticed below the deposit's first melting temperature. However, for a mixture of FeCl 2 , KCl and PbCl 2 , the first melting temperature is below 350 °C which could explain the high oxidation rate observed below the first melting temperature of the deposit. A solid phase or a mixture of phases with the composition of K 3 Pb 2 (SO 4 ) 3 Cl was observed in the tests with SEM/EDX for the first time.