A simple and robust approach for early detection of defluidization

•A simple approach is presented for the early detection of defluidization in a bubbling gas-solid fluidized bed.•The new approach relies on the simultaneous monitoring of temperature and pressure signals.•It effectively predicted the onset of agglomeration minutes to hours before complete defluidization.•It was robust with respect to the changes in gas velocity, operating temperature, and bed inventory.

This study presents a simple approach for the early detection of agglomeration in a bubbling gas-solid fluidized bed. This monitoring approach is based on the simultaneous measurements of local temperatures and the in-bed differential pressure drop from the well-stabilized section of the bed. Defluidization experiments (800-1000 °C) showed that when a bubbling gas-solid fluidized bed approaches complete defluidization the average in-bed differential pressure drop progressively decreases from a reference value obtained under normal conditions while the temperature difference along the axis, particularly between a temperature reading right above the distributor plate and others at higher levels within the dense bed, simultaneously increases. This novel approach was thus proposed for the concurrent occurrence of these drifts to provide an opportune recognition of the onset of agglomeration in a bubbling gas-solid fluidized bed. The results demonstrated that it could effectively detect the defluidization condition minutes to hours before the complete defluidization state depending on the growth rate of agglomeration within the bed. Two pairs of detection thresholds for the timely recognition of agglomeration in bubbling fluidized beds of coarse silica sand particles were introduced according to the observations made in this study. The approach exhibited minimal sensitivity to variations in the superficial gas velocity (±10%), operating temperature (±100 °C), and bed inventory (±20%) while both legs of the in-bed differential pressure transducer were well below the splash zone and above the jetting zone formed in the vicinity of the distributor plate.