Model on devolatilization of coal particle in fluidized bed under pressurized oxy⁃fuel combustion

Pressurized oxy⁃fuel combustion is considered as one in the most promising CO2 capture technologies， which has gradually attracted the attention of academia and industry in recent years. However，due to the difficulty in the pressurization experiment，the combustion process is like a “black box”，and the acquisition of combustion infor⁃ mation is not sufficient，the combustion mechanism of coal under pressurized oxy⁃fuel conditions is not well understood. In this work，the influence mechanism of O2 / CO2 and O2 / N2 atmospheres on a devolatilization process of a single coal particle was studied by establishing a devolatilization model. The model considered the heat transfer and the tempera⁃ ture gradient inside the coal particle. The model used the unsteady one⁃dimensional particle model to describe the dr⁃ ying and devolatilization processes of the single coal particle. The results show that the model has good applicability，and the error between the calculated and experimental results is less than 20%. The sensitivity analysis of the model shows that the specific heat capacity of bed material and fuel， fuel size， fuel density， fuel moisture content and total heat transfer coefficient between bed material and fuel have a great influence on the drying time. The specific heat capacity of bed material， transfer coefficient， fuel density and size greatly influence the devolatilization time. The specific heat capacity of bed material，heat transfer coefficient，fuel density and fuel size are the main factors affecting the peak value of temperature gradient inside and outside the particle. With the increase of pressure and bed temperature，the heat transfer between coal particle and bed material increases，which also results in lower drying time and devolatilization time and increases the peak temperature difference between inside and out⁃ side the particles. Compared with N2 atmosphere，the drying time and devolatilization time decreases slightly under CO2 atmosphere，and the temperature difference between inside and outside particles increases. With the increase in fluidization number (w)，the heat transfer between particles and bed is strengthened，and the drying and devolatiliza⁃ tion processes are shortened.