Effect of storage time on the flowability of biomass-coal granular system

• The exponential relationship between discharge rate and storage time is revealed.
• The effect of the relaxation on the discharge rate has been studied in detail.
• The model results including the type of approach has been proved to be validity.

The influence of storage time on the flowability of biomass-coal blends is experimental and theoretical investigated. The results show that there exists exponential relationship between discharge rate and storage time in an appropriate rice straw mass fraction range (less than 10%). In addition, the mechanism of gravity discharge rate variation for biomass-coal blends is theoretically investigated by analyzing the porosity variation of particle bed. The mechanism of porosity variation in the binary granular system is theoretically analyzed on the basis of emergent gas, mutual compression and particle rearrangement, and a mathematical model has been developed which agrees well with the experimental results. Furthermore, relaxation effect is proposed, which is mainly induced by elasticity of rice straw particle and cohesion of blends. Relaxation time is the most important parameters determining this effect. The latter decreases with increasing of coal particle size and biomass mass fraction.