Current status and challenges within fluidized bed combustion

Fluidized-bed technology is rapidly expanding. Today, more than 600 large (20+ MWth) FBC boilers with a total installed thermal capacity of more than 70,000 MWth have been built. Around 75% of this capacity is circulating fluidized beds (CFBC) technology, the rest mostly bubbling fluidized beds (BFBC). The size of the boilers has increased steeply; the largest CFBC units being constructed approach a thermal capacity of 1,000 MWth. At present a major expansion in the FBC capacity is happening in the Far-East, especially in China. Several hundred major boiler projects for coal are underway which may double the global FBC capacity within just 5 years. The boilers in Europe are more and more often designed to burn several fuels simultaneously. Besides coal, wood, biomasses and various waste derived fuels have become important fuels in various recent FBC projects. Creative analysis and laboratory-scale fuel characterization have become very important in the assessment of the feasibility of the various fuels for FBC. Firing of several solid fuels simultaneously has in principle been considered to be an advantage of the FBC technology. However, some fuel mixtures show surprising behaviors and there is a lot of interesting research to be done to more quantitatively establish the influence of the fuel mixture on the key operating parameters, such as boiler efficiency, flue gas emissions, ash behavior and corrosion.