Pressure Fluctuations in a Gas-Solid Fluidized Bed at Temperatures up to 1650°C

We, at the Shenyang University of Chemical Technology, have recently generated strong interest in transforming some ultra-high temperature solid-state reaction processes that have been taking place in traditional shaft/rotary kilns into fluidized bed operations, aiming to lower reaction temperatures and increase reaction rates, thereby cutting energy consumption and carbon emissions. For the successful development of energy-saving and environmental-friendly alternative technologies, it is significantly important to understand fluidization behavior at temperatures above 1000°C, but previous investigations at such high temperatures are scarce. In general, the operation of fluidized beds at such ultra-high temperatures is limited by defluidization caused by the agglomeration tendency of bed particles. For this reason, we conducted experiments in a laboratory fluidized bed of 30 mm diameter at temperatures from 800 to 1650℃ with corundum and magnesite oxide particles. The pressure fluctuation signals are recorded at different superficial gas velocities and bed temperatures. Statistical and spectral analyses are performed to characterize high-temperature fluidization behavior by the corresponding minimum fluidization velocity, standard deviation, mean pressure amplitude, power spectrum, and dominant frequency. Great efforts are made to determine conditions at which stable fluidization or defluidization can be attained. The results show that we can achieve and maintain stable fluidization at ultra-high temperatures with some technical and experimental measures. The experimental results demonstrate that fluidization behavior at high temperatures is unique and cannot be fully predicted by the experience and theory applicable to low-temperature fluidization.