Study On Process Intensification Of Mass Transfer Under Ultrasound Effects

Sonochemistry is a new branch in chemistry and chemical engineering. The effects of ultrasound can be used to intensify the process of mass transfer, heat transfer and chemical reaction, and raising the rate of chemical process.The testing was made in the ultrasound chamber of 300mm X 150mm X 150mm with square shape sodium chloride-water system, the conductivity of different distance from salt block and the dissolving velocity of the salt block was measured under the effects of continuous ultrasound, intermittent ultrasound and no ultrasound. The film thickness, the coefficient of mass transfer and the diffusion coefficient in liquid was gained at different conditions. According to the characteristics of ultrasonic cavitation in solid-liquid system resulting surface, energy, turbulent and micro-disturbing effects, the mechanism of ultrasound to intensify mass transfer process was analyzed.The experiments show that the mass transfer rate evidently was accelerated under the ultrasonic irradiation, The coefficient of mass transfer under the ultrasound effects is 1.986X10"1 m/s while the coefficient is 9.456X10" m/s without ultrasound effects, the enhancing factor is 2.1; the film thickness of liquid clearly becomes thinner, the film thickness under the ultrasound effects is 1.53X10~3m while the value is 1.98X10~3m without ultrasound effects, the former value is 0.77 times as much as the later, decreasing by 23 percent ; the diffusion coefficient increases from 3. 04X10"7m2/s to 1.872X10 -7 m2/s under the ultrasound effects, the former value is 1.623 times as much as the later.Based on the former-mentioned study, the experiment on extracting gardenia yellow and geniposide from cape jasmine was made under the ultrasound effects. The influence of ultrasound on the extraction time and gainings of gardania yellow was investigated. 2-The experiment shows that the extracting rate of gardenia yellow and geniposide from cape jasmine quickens the gainings of gardenia yellow rises in some degree under the ultrasound effects, being 1.15 times as much as that without the ultrasound effects, meanwhile gainings of geniposide under the ultrasound effects is 1.25 times as much as that without the ultrasound effects.