Some Remarks on Large-Scale Biomass Co-Combustion

Abstract. The investigations were conducted at the CFB boiler and focused on the assessment of the effect of agrobiomass co-combustion on the quantity and nature of deposits formed on heat exchanger tube surfaces and the determination of the corrosion kinetics. Industrial trials included a reference test, burning coal only, and two co-combustion tests (short- and long-term). The analysis revealed that the co-combustion of agrobiomass resulted in increased deposit formation, and the majority of the solids accumulated at the tube surfaces were directly exposed to the hot flue gases. These deposits revealed dense and hard structures, and their removal was difficult. On the contrary, the deposits formed at the aerodynamic shadow zone exhibited a loose consistency and could be removed relatively easily. The results also indicated that the rate of corrosion of the steel samples was quite similar regardless of the fuel type but was significantly higher for shorter exposure times. Despite that, the results indicated that co-combustion of up to 15 wt% of agrobiomass with coal did not pose a serious threat to the boiler heat transfer surfaces due to the protective effect of the deposits that limited the diffusion of corrosive agents from the flue gas to the steel tube surface.