Measurement of void fractions at high gas velocities: a summary of pilot plant experiments 85-cg-8 to 32

Abstract

A 52-day series of experiments to measure the mean void fractions and pitch conversions in the CANMET hydrocracking PP-1 reactor as a function of temperature and superficial gas velocity is described. Interprovincial pipeline vacuum bottoms (feedstock 31-IPPL-84 900 0F+) to be used for the demonstration plant startup were used. Results of observed mean void fractions, pitch conversions of each A run, concentrations of ash, PI, TI, asphaltene and TIOR and ratio of TIOR/ash as functions of operating time are also reported. The flow regimes as a function of superficial gas velocity and temperature above 400°C were identified using selected gamma-ray data and the drift-flux model of Zuber and Findlay. At a void fraction of <0.55, the flow was in the homogeneous fine bubbling flow regime. Above a void fraction of 0.55, the bubbly churn-turbulent regime was observed. The effect of wall friction on the distribution of void fraction was found to be small. Therefore the derived correlation of void fraction versus superficial gas velocity is reasonable for predicting void fractions for any large scale reactors above 400°C. A maximum void fraction of 0.76 at a relatively low superficial gas velocity (>8 cm/s) was observed. The pitch conversions at high gas rates were low, consistent with the high void fractions observed.