Gas holdups and bubble characteristics in a bubble column operated at high temperature

The local gas-phase characteristics in a bubble column were investigated using refractive spherical bulb optical sensors. The local gas holdup, bubble rise velocity, bubble chord length, and bubble chord length distribution were measured at several radial and axial locations in a 0.2-m-diameter bubble column in the presence of a paraffinic oil and nitrogen. The gas superficial velocity was varied between 2.2 and 14.7 cm/s, while two operating temperatures were studied: T = 100 C and T = 175 C. The radial gas holdup profile was found to be a function of the axial position (prior to stabilization), the operating temperature, and the gas superficial velocity. The bubble rise velocity and the bubble chord length were found to increase with both an increase in the gas superficial velocity and a decrease in the operating temperature, the effect of the gas superficial velocity being maximum in the central region of the column. The bubble chord length distribution was found to be well represented by the inverse Gaussian probability distribution function, and the standard deviation of the bubble chord length distribution was found to be a function of the radial position, the gas superficial velocity, the axial position, and the operation temperature.