The Electromagnetic and Thermal Effects of Microwave on Reactive Precipitation Process

Abstract Microwave has triggered huge interests for its efficient control of precipitation process. However, quantitative study of the coupling effect of thermal radiation and electromagnetic radiation of microwave on precipitation is limited. In this paper, the effect of microwave energy input on precipitation is studied experimentally and numerically at different temperature firstly. Sauter mean diameter of crystal products ( d 32 ) is found to decrease with higher inflow concentration and increase with stronger microwave energy intensities ( E ) and higher temperature. In order to assess the influence of temperature and microwave energy input on nucleation, growth, aggregation, and crystal breakage, a population balance model coupled with empirical precipitation kinetics is performed. These kinetic parameters, including nucleation rate constant ( k n ) and exponent ( n ), growth rate constant ( k g ) and exponent ( g ), aggregation efficiency ( Ψ ag ), and breakage rate constant ( k br ) are fitted against experimental data. It is found that the electromagnetic effect of microwave can improve nucleation, crystal growth, and aggregation without breaking crystal product. Meanwhile, the thermal effect of microwave can enhance crystal growth, aggregation, and breakage while restrain nucleation. By choosing proper temperature, microwave provides a promising approach to produce larger crystals without additional risk of extra nucleation and crystal breakage.