Short term online corrosion measurements in biomass fired boilers. Part 1: Application of a newly developed mass loss probe

摘要

Online corrosion probes enable the online determination of high-temperature corrosion rates in biomass combustion plants. These probes are exposed to the flue gas and require a layer of corrosion products and deposits on their surface to be able to perform the corrosion measurements. The formation of this layer takes time and depends on the build-up rate of the deposits as well as on the ability of the deposits to form a conductive layer. During this initial phase, which lasts about 300 h based on experiences with forest wood chip combustion, the measurements are inaccurate. This inaccuracy can be neglected during long-term measurements performed at real-scale plants which last more than several 1000 h. Since high-temperature corrosion in biomass combustion plants is known to generally follow a paralinear trend, high corrosion rates prevail in the beginning. Following, if short-term measurements shall reflect or come close to real-life conditions, this "start-up" effect cannot be neglected.