Significance of temperature and pressure on minimum fluidization velocity in a fluidized bed reactor: An experimental analysis

This investigation addresses the minimum fluidization velocity (Umf) determination in a refractory insulated fluidized bed reactor (FBR) of 200 mm ID. Umf is determined with respect to different particle sizes and operating parameters like temperature and pressure up to 900 °C and 1 MPa respectively. This study has the main thrust into the establishment of Umf at elevated temperature and pressure during the thermochemical process, involving uniform mixing of gas-solid by fluidization phenomena at a pilot scale FBR. So, to understand the significance and impact of temperature along with pressure on Umf, a set of fluidization experiments have been demonstrated in FBR. Two waste materials are abundantly available, similar to Geldart’s group-B type bed materials, i.e. Calcined-clay and Coal-ash of an average size of 1.04 and 0.92 mm respectively, and apparent density of 883 and 850 kg/m3 respectively, have been selected as bed material. Experimental results revealed that Umf directly relates to particle size and inverse relationship with operating temperature and pressure. Results revealed that Umf decreases by 59.7% and 59.2% for both bed materials such as Calcined-clay and Coal-ash respectively as the temperature increases from 30 to 900°C at atmospheric pressure. Similarly, Umf also decreases by 63.3% and 66.0% for bed materials such as Calcined-clay and Coal-ash respectively as the pressure increases from atmospheric pressure to 1 MPa at room temperature. An empirical model has been developed for predicting Umf at elevated temperature and pressure during fluidization phenomena. The experimental Remf shows a good agreement with the predicted Remf by using the developed model proving its robustness.