Study On The Nucleation Of Solution Crystallization Enhanced By Coupled Double Ultrasonic Field

Solution crystallization technology is widely used in many fields and its crucial aspect is nucleation. Glucose is a kind of monosaccharide, which is the most widely distributed and most important in nature. It is an indispensable part of the life of animal and the main source of human energy. The glucose of crystallization of the industrial has three kinds which are hydrated α-glucose, anhydrous α-glucose and anhydrous β-glucose. Anhydrous glucose has better quality, higher purity, amplified energy and can also help bolster a person’s immune system relative to hydrated glucose. It has the important application value in the food industry, medicine and health, and so on. So the technology of enhance the nucleation of anhydrous glucose solution crystallization deserves research and exploitation. The major production process of anhydrous glucose in the industry is adding crystal seed and evaporating crystallization in vacuum. However, there are disadvantages to this approach, which requires a lot of moderate size and evenly crystal seeds. So it will increase production costs.In order to overcome the problem, ultrasound technology is introduced into nucleation of solution crystallization research. As it displays unique superiority in the nucleation of solution crystallization. And it has found widespread use. An overwhelming majority of the nucleation research are using single frequency ultrasonic irradiation. The uneven acoustic field is irradiated by single frequency ultrasonic, so it is usually associated with a standing wave. Double frequency ultrasonic could increase mass transfer interfacial area, significantly increase cavitation effect, reduce ―dead area‖ which caused by standing wave. In order to increase the nucleation rate and achieve good crystal nucleus, this article will introduce double ultrasonic irradiation technology into the nucleation of solution crystallization. The mechanism enhanced by double ultrasonic irradiation is studied.The effects of the concentration of the solution, the ultrasonic power and ultrasonic processing time on the nucleation rate are studied in the condition of single and double ultrasonic irradiation. The crystal size under the double ultrasonic irradiation is analyzed by comparison with the single ultrasonic irradiation. The results show that ultrasonic irradiation could enhance the nucleation of anhydrous glucose solution crystallization under certain conditions. The double ultrasound could, under the same condition, reduce the initial concentration of the nucleation of anhydrous glucose solution, increase the nucleation rate and achieve the crystal nucleus, which has regular morphology and uniform particle size distribution by comparison with single ultrasound. That is to say, a significant synergetic effect of double ultrasound exists. Consequently, nucleation under the double ultrasonic irradiation is a rapid, high-effective and energy-saving method.The cavitation bubble dynamic model of double ultrasound is established by modifying the Rayleigh-Plesset equation, and the numerical result is obtained by using the Runge-Kutta algorithm provided by MATLAB software. The effects of some sound field parameters, physical parameters of fluid and different coupling conditions like frequency, phase difference and ultrasonic intensity for double ultrasound cavitation dynamics are studied. The results show that the double ultrasound could, under the same condition, increase the ratio of the maximum radius to the initial radius of cavitation bubble by comparison with single ultrasound and the amplitude become the biggest when the phase difference is zero(that is, sin-sin wave combination). The ratio of the maximum radius to the initial radius of cavitation bubble decreases along with the increasing initial radius of bubble, and the cavitation intensity becomes weaken; meanwhile the cavitation intensity becomes stronger along with the increasing of ultrasonic intensity; and with the increasing of hydrostatic pressure or liquid viscous, the cavitation intensity becomes weaken. In achieving the same cavitation effect, the double ultrasound could decrease the ultrasonic intensity and occur transient cavitation to a bigger initial radius nucleus or relatively large hydrostatic pressure and liquid viscous. It can be known that the cavitation intensity becomes stronger by combining low and the same low frequency ultrasound in double ultrasound. Keeping same-phase, avoiding phase inversing and distributing the total ultrasonic intensity equally help to improve cavitation effect. When taking different frequency ultrasonic, the dual ultrasound should choose suitable coupling factors according to experimental conditions in order to get a significant synergetic effect. In the end, the iodine released from potassium iodide is determined to assess the cavitation yields of double and single ultrasound. The results of absorbency experiments indicate that the cavitation yields, i.e. the iodine content, of double ultrasound is more than the algebra sum of a single 25 kHz and 40 kHz ultrasound.Based on the lab-scale’s experiment, the pilot scale experiment was carried out. The results show that the nucleation rate and the evenness of crystal nucleus have fallen with the increase of solution volume. But there will have a synergetic effect of double ultrasound by adding agitator. Compared with lab-scale experiment, the effect of probe model ultrasound is not acceptably high in the pilot scale experiment. So we can consider selecting different frequency divergent ultrasound to enhance result.