Effect of orange waste pretreatment on the fluid dynamics of spouted beds with mechanical agitation.

The spouted bed has a vigorous cyclic movement of the solids and high rates of heat and mass transfer, allowing for effective contact between the different phases. However, the spouted bed may exhibit instabilities for inherently cohesive solids due to unwanted agglomeration, preferential channels, particle segregation and high energy consumption. In this context, the present work analyzed the effect of a preliminary treatment of the orange waste, through the addition of lime and mechanical pressing, on the fluid dynamics in two spouted bed configurations of same dimensions, one conventional (CSB) and the other one modified with mechanical agitation (modified mechanically spouted bed, MMSB). The preliminary treatment of the biomass allowed reducing the moisture content by 31.7%, thereby improving the movement of solids in the CSB as when the in natura (raw) biomass was loaded, as the latter underwent agglomeration until it no longer circulated. Persistent instability issues in the CBS were overcome through mechanical stirrers, which made the bed uniform by improving the movement of solids in the annular region. Furthermore, mechanical agitation allowed increasing the maximum static bed height from 21.1 to 27.0 cm, as well decreasing the air flow by up to 91.74%, since the air stream is only that required for bed expansion. [Display omitted] • The complete pretreatment reduced the moisture content of the biomass by 31.7%. • The pretreatment was mandatory to the motion of particles in both configurations. • Mechanical stirring prevented the agglomeration of solids close the inner walls. • Movement of the biomass was made primarily by the rotation of the stirrer. • Stirring reduced minimum spout velocity by 91.74% and pressure drop by 18.1%. [ABSTRACT FROM AUTHOR]