Investigation of the use of horizontal baffles in a gas-liquid agitated tank

Abstract

The objective of this investigation was to study horizontal baffle parameters and determine their effect on the mixing performance of a gas-sparged agitated contactor and compare to contactors of standard design. Unlike standard baffle design, horizontal baffles are located at the dispersion surface. The following horizontal baffle parameters were investigated; the number of horizontal baffles and the inclination of each baffle. The performance criterion to be examined was the mass transfer coefficient for a given power input.

The experiments were conducted on a 7.5-gallon lab-scale agitated tank. The sodium sulfite method was used to determine the mass transfer coefficient. The primary independent variables were the impeller speed and the air injection rate. The impeller speed and air injection rate were varied from 500 to 1500 RPM and 160 to 1280 cm3/s, respectively.

The number of horizontal baffles and their inclination had little effect on mixing performance. For a gas injection rate of 160 cm^/s, contactors equipped with horizontal baffles showed only a 25% improvement in the mass transfer coefficient compared to a contactor of standard design. At larger gas injection rates there is little or no difference in mixing performance for contactors of different baffle design. Results of this investigation were compared to previous research and it was found that the design of the tank (specifically, the horizontal baffles) is a crucial factor for improving the performance of a contactor equipped with horizontal baffles.