A parametric study pf powder holdups in a packed bed under decreasing gas velocity condition
The injection of pulverised coal along with the hot air blast in an iron-making blast furnace has contributed to lower the green house emissions and improve both the stability and productivity of the furnace. However, at high injection rates, some coal in the form of powder accumulates in the lower part of the furnace and obstructs the gas and liquid flows. Therefore, there is an urgent need to understand the physics and aerodynamics of gas-powder flow in such systems to improve the flow conditions. In this article, the flow of gas and fines in a packed bed is studied under decreasing gas velocity as it represents the blast furnace aerodynamics more accurately if it is not being considered as a moving bed reactor. A two-dimensional (2-D) model was developed for this purpose. More specifically, a parametric study is performed to determine the effects of the gas blast velocity, particle size adn powder loading on the powder holdups. Results are presented in terms of fines accumulation area. This work shows the dependency of the powder holdups on the packed bed flow parameters.
Keywords: Packed bed, turbulent flow, mathematical modelling, decreasing gas velocity, gas-fines flow, powder holdups.