Liquid dispersion and gas absorption in a multi-stage high-speed disperser

Abstract

Liquid dispersion and gas absorption in a high-speed disperser with four rotors were studied by experiments and models. The liquid films on the rotors and the droplets in the cavity zones of an air-water system were captured by a high-speed camera. When liquid is dispersed on the rotors, its flow pattern transforms from initial droplet, liquid film, rivulet, and ligament into a large number of small droplets in the next cavity zone. Moreover, a modified inclined impact model was established to describe the impact and spread of the initial droplet. The effects of rotational speed and liquid flow rate on liquid film maximum spread length and mean droplet diameter were evaluated. A novel mass transfer area model based on the dispersion process was proposed to calculate the total mass transfer area. The total mass transfer area includes the area of the liquid films on the inner surface of the four rotors and the reactor wall, as well as the area of the droplets in the four cavity zones. The chemical absorption of CO2 into a NaOH solution was conducted, and a chemical method was adopted to verify the mass transfer area model. The total mass transfer area and absorption quality under different operating conditions such as rotational speed, gas flow rate, and liquid flow rate were measured. In addition, the increases of droplet area and liquid film area were compared, and it was found that the effect of rotational speed on the droplet area and the effect of liquid flow rate on the liquid film area were significant.