Pressure fluctuations in a three phase bubble column reactor operating at relatively low pressure (92 KPa) have been analyzed by adopting the spectral and fractal analyses to get the engineering informations for the on-line control and fault diagnosis of the reactors. The mean value, standard deviation, skewness and kurtosis of the pressure fluctuations have been obtained. The local fractal dimension has been determined from the Pox diagram obtained by means of the rescaled range analysis of the pressure fluctuations based on the fractional Brownian motion. The local fractal dimension of pressure fluctuations has increased and thus the pressure fluctuation signals have become less persistent and irregular, with increases in the gas flow rate reaction temperature, particle size and solid content in the slurry phase. The local fractal dimension has been well correlated in terms of the operating variables.

Fractal analysis of pressure fluctuations in a three phase bubble column reactor operating at low pressure

Comminution characteristics of diatomaceous earth have been investigated in a vertical type jet mill of pilot plant scale; the diameter of the chamber of mill is 26.3 cm. Fluidization of the particles in the chamber has been proposed to enhance the comminution efficiency of the jet mill by promoting the effective contacting of powders with compressed air as well as the chamber wall. Effects of the pressures or densities of pulverizing-air and fluidizing-air and comminution time on the mean size of the particles and the rate of comminution have been examined. The statistical analysis of pressure fluctuations in the chamber of the mill has been utilized to predict the characteristics of the vertical-type jet mill taking advantage of the fluidization technique. The particle size and comminution rate have been correlated with the operating variables, respectively.

Seung Ho Cho

Papers

Effective comminution of diatomaceous earth in a vertical type jet mill