Prediction of bed expansion of polydisperse quartz sand mixtures fluidized with water

• Minimum fluidization velocity and bed expansion of quartz filtration sand was investigated.
• New model for bed expansion of polydisperse quartz sand mixtures fluidized with water was proposed.
• The mean absolute deviation in predicting bed voidage was 2.66%.
• New model for minimum fluidization velocity prediction was proposed.

In this paper, the minimum fluidization velocity and bed expansion of polydisperse sand mixtures fluidized with water were investigated. The fluidization experiments were carried out using 19 different fractions of quartz filtration sand with sieve diameters in the interval dm = 0.359 to 2.596 mm. The intercept fluid velocity UE was determined from the plot of fluid superficial velocity vs. porosity. The results obtained indicated that UE was about 11% higher than particle terminal velocity Ut, for all of the sand fractions investigated.Based on the experimental data, the new model for bed expansion of quartz filtration sand was proposed. Using the proposed model, the mean absolute deviation in predicting the bed porosity ε, for a given superficial velocity U, was 2.66%, while the mean absolute deviation in predicting U at a given ε was 8.75%. For the prediction of the minimum fluidization velocity, Umf, several literature models were tested. The best results were obtained using the Ergun model, with mean absolute deviation in predicting Umf of 12.42%. A new simple correlation for the prediction of the minimum fluidization velocity Umf was proposed. The proposed correlation is the function only of the mean sieve diameter of the filtration sand fraction. The mean absolute deviation between the experimental and the predicted values of Umf was 7.65%.

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