Technical comparison and economic evaluations of moving grate and circulating fluidized bed combustion technologies

The following work is the result of an internship carried out at STC POWER Company, in the proposal office, with the aim to make a technical comparison of two combustion technologies, Moving Grate (MG) and Circulating Fluidized Bed (CFB), in order to find out which is the optimal solution for a specific biomass power plant. After a preliminary description of the fuel considered (biomass) and an overview of the operating principle of a combined heat and power (CHP) plant, the attention has been paid to the main differences of the two boilers, focusing on: fuel characteristics, pollutant emissions, corrosion and fouling problems, performances and auxiliaries. Then, the technical comparison has been applied to a biomass CHP plant that will be realized in France following a tendering process to which STC Power is participating. The overall power plant has been simulated with the software Thermoflex both with MG boiler and CFB boiler and, after several optimizations, the results in terms of performances and efficiencies have been compared. Particularly critical has been the corrosion problem, caused by the fuel composition, that has led to a limitation on the maximum temperature of the steam produced with MG boiler, thus limiting also the overall efficiency of the plant. After the technical analysis, also the economic aspects have been evaluated, with a comparison of the main costs (CAPEX and OPEX) of MG and CFB boilers. Finally, the reasons that have led to choose one specific boiler instead of the other have been explained.