Influence of the environment on the operational safety of a fluidized bed boiler

The use of fluidized bed boilers in modern power engineering is a promising solution for clean and economically acceptable combustion of various fuels, including coal, biomass and waste, for the generation of electricity. The fluidized bed boilers are nowadays technically advanced and complex combustion facilities where all individual boiler elements are subjected to withstand continuous structural and thermal loads during their operation. Intensive loading of boiler elements can be quite easily linked with boiler operational safety and is quite often one of the main reasons for emergency shutdowns followed by necessary replacements of the damaged items. In case of industrial large-scale circulating fluidized bed boilers the frequency of unplanned shutdowns is also quite often affected by the hydrodynamics of the fluidized bed and some other parameters, such as the intensity of solids circulation, temperature, solids concentration, flue gas composition and velocity, solids accumulation and deposition, as well as the corrosion or erosion of heat transfer surfaces. The present paper briefly reports the results of authors investigation focused on the morphology and structure of some chosen elements (steel anchors) sampled from one of Polish circulating fluidized bed boilers. The anchors were degraded during boiler operation and lost their mechanical durability. In order to determine the reasons of anchors’ degradation chemical composition of the elements was determined with the use of a spark spectrometer SPECTROLAB and sample morphology was investigated with JEOL JSM-6610LV scanning microscope equipped with LaB6 cathode.