Biofuel-firing is an emerging technology in power production. Predominantly, biofuels are well suitable for utility and power boilers. The high concentrations of potassium and chlorine in some of the biofuels make their use rather devastating. Fouling is typically related to
biofuel-firing, and all biofuels can be regarded as more or less corrosive. Chlorine-induced corrosion in biofuel-firing was studied both in laboratory and with field tests. Field tests revealed that sulfation of alkali chlorides in the deposits are involved in the corrosion process. In laboratory tests, a phenomenon named the memory effect was observed. In the memory effect, HCl induced rapid oxidation continued also after the HCI flow was turned off. This confirms the existence of the so-called chlorine circulation theory. According to the field experiments, the best way to prevent corrosion in biofuel-firing is to keep the S/Cl-ratio in the fuel higher than 2.0, preferably over 4.0. Keywords: biofuels, corrosion, superheaters, chlorine, potassium, boiler