## 4 Experimental Results and Discussion  
### Sensitivity Analysis for Different Distributor Plates  
In the first stage, three different distributor plate design configurations were tested experimentally for a fixed set of operational parameters to investigate their design sensitivity for fluidized bed overall hydrodynamics. Pressure drop across the bed, and minimum fluidization velocities for each distributor plate were measured, and the difference in pressure drop and minimum fluidization velocity was observed. Afterward, operational variables were also varied to comprehend each operational variable's effect on the fluidization hydrodynamics for every distributor plate. It is revealed from Figure 3 that for a fixed set of initial bed height and particle size, minimum fluidization velocity is found to be lowest for perforated plate distributor and highest for 45\({}^{\circ}\) slotted plate. Furthermore, pressure drop across the bed is highest for a 45\({}^{\circ}\) slotted plate, whereas it is lowest for a hybrid plate due to the highest open area ratio. For the geometric parameters, minimum fluidization velocity depends on the size and shape of the openings of the distributor plate, which, intern depends upon the bubble dynamics within the fluidized bed. These geometric parameters prescribed how the air bubbles travel up the column and ultimately rupture the bed surface after successive coalescence and collapse. Due to many smaller holes, numerous smaller size bubbles were instigated on the upper portion of the perforated distributor plate, causing a straight vertical motion of bubbles. The bubbles' front area raised the solid particles, and the bubbles' wake also sucked the lower portion of solid particles due to lower pressure region formation resulting in the entire upward motion of the emulsion phase. These bubbles coalesce and then collapse during their upward movement within the bed but with the axially dominant flow. It might be the main reason for early fluidization (lower U\({}_{\text{mf}}\)) in perforated distributor plate due to the straight upward movement of solids and bubbles with very little lateral dispersion. Figure 3: Experimental results of characteristic fluidization curves for different distributor plates (L/D = 0.833, particle size = 590 \(\upmu\)m). On the other hand, due to the larger angular openings of slots in the 45\({}^{\circ}\) slotted plate, relatively bigger bubbles arise initially with deflected path partially toward the gasifier periphery. Similar phenomena of uplift and suction of solid particles occurred for a 45\({}^{\circ}\) slotted plate but with compromised axial flow due to air entering at 45\({}^{\circ}\) through slots. Due to the angular entrance of airflow, a portion of velocity is diverted into the lateral component. Hence, an axial component is reduced compared to the case in the perforated plate where all the holes are 90\({}^{\circ}\) to the sand bed, causing air inflow to be almost 100% axial as it emerges through the holes. Therefore, in a 45\({}^{\circ}\) slotted plate, fluidization will be delayed due to a reduction in the axial component of flow, and hence minimum fluidization velocity will be higher. It can be observed from Figure 3 above that there is a significant difference in the slope of the pressure drop curve slope between the hybrid plate and the other two plates. This observation is due to the substantial difference in the open area ratio between the hybrid and the other two plates. The pressure drop is highest for the 45\({}^{\circ}\) slotted plate due to the smallest open area ratio. However, due to the largest open area ratio of the hybrid plate, a pressure drop is found to be lowest due to the reduction in the kinetic head compared to the perforated plate, where smaller holes increase the velocity of air inflow. Moreover, minimum fluidization velocity for a hybrid plate was found between perforated and 45\({}^{\circ}\) slotted plate scenarios. This effect is due to the blend of angular slots and small straight holes in the hybrid plate.