Analysis of concentration characteristics in ultrasonic atomization by droplet diameter distribution.

The droplet diameter distribution and concentration characteristics in ultrasonic atomization were experimentally studied. The samples were aqueous solutions of methanol, ethanol and 1-propanol. The diameter distribution of atomized droplets showed the normal distribution, and the median diameter and standard deviation were expressed by means of the ultrasonic condition and the liquid properties. The concentration characteristic in ultrasonic atomization was analyzed by using the model of shell and core to the atomized droplet, where the former and latter consist of solute and solution, respectively. The value, which was surface solute amount in droplet multiplied by the molecular volume, increased with increasing solute molar fraction in bulk liquid and was independent of alcohol kinds. The rate of accompanying liquid and the solute molar fraction in accompanied liquid were estimated from the diameter distribution and the surface solute amount in droplet.

Development of rectangular airlift bubble column installed with support material for enhancement of nitrogen removal.

To enhance nitrogen removal during wastewater treatment using activated sludge, a rectangular airlift bubble column installed with support material is proposed. The flow characteristics and nitrogen removal performance were examined and compared with those of a column without support material. In the two columns, the riser was aerobic and the lower part of downcomer was anaerobic. The effects of operational conditions on the liquid circulation flow rate and liquid-phase volumetric mass transfer coefficient were examined. Using these flow characteristics, the distribution of dissolved oxygen (DO) concentration in the column was calculated. From the DO distribution, the anaerobic volume fraction in the column was estimated. The optimal anaerobic volume fraction for nitrogen removal was found to be approximately 50%. The column installed with support material showed higher nitrogen removal than the column without it.