Experimental and numerical study of the impinging aerosols method for the micro-encapsulation of phosphate solubilising microorganisms (PSMs)

Abstract

This study demonstrates the application of the impinging aerosols method in encapsulating phosphate solubilising microorganisms (PSMs), replacing the microbial inoculant method. The method encapsulates PSMs in microbeads by impinging the bacteria-alginate droplets and CaCl2 sprays. Efficient coalescences between the bacteria-alginate and CaCl2 droplets warrant the birth of microbead-encapsulating microorganisms. The proposed method is modelled using a Eulerian–Lagrangian approach. The primary and secondary breakups and wall impingement are modelled using the Huh atomisation, Reitz–Diwakar models, and Bai–Gosman model, respectively. The resulting model is validated against the sizes and spray angles of experimental droplets with different flow rates. The simulation demonstrates that the flow rate, spray angle, droplet size, spray pattern, and alginate and CaCl2 concentrations must be considered to produce robust alginate microbeads and minimise the material loss caused by the formation of a fluid film on the wall. A lower alginate flow rate and concentration of CaCl2 should be used to promote the formation of the alginate microbeads.