Research On Multi-stage Crystallization Coupling Technology And System Of Rebaudioside A Purification

With the development of the Cyber Physical System (CPS) and Internet of Things technology, the German first proposed the word "Industry 4.0", aiming to use Internet technology to promote the development of the fourth industrial revolution. Thus, faced with the energy and environmental issues, chemical industry should not only pursue production, but pay more attention to the comprehensive evaluation index such as energy consumption, output, emission. In actual production, if there is an effective solution to the problem of decentralization, discontinuity and low degree of automation in separation and purification process, it may become possible to produce high-quality products with energy conservation, and to achieve green production.In order to solve this problem, combined with the expertise and "Made in China 2025" major strategic objective, this paper proposed "Multi-stage Crystallization Coupling Technology and Control Methods," and successfully applied to the crystal preparation of Rebaudioside A (RA). According to the crystallization process, this paper design a multi-stage crystallization coupling system to integrate all devices effectively, coupling controlled by mechatronics technology, realizing the continuous operation of the system. This paper’s main contents are as follows:(1) According to the proposed multi-stage crystallization coupling technology, design a universal multi-stage coupling crystallization system and build a control system. Also, the corresponding control methods will be put forward to realize the coupling control at all levels of crystallization system.(2) Based on the existing crystallization method, the solubility curves in different solvent of RA will be measured. According to the solubility characteristics of RA, the appropriate RA crystallization program will be determined. By studying on extraction agent, solid-liquid ratio, water bath temperature, crystallization time and other factors that affects the primary and secondly crystallization, the process to produce stevia with RA purity greater than 97%will be determined.(3) Using orthogonal experiment method, response surface methodology, Markowitz Portfolios theory to optimize the above RA refining process. Comparing to the effect of each factor on crystallization, the best RA refining process control parameters will be obtained.(4) Based on the best crystallization process of RA, the multi-stage crystallization coupling system will be designed and the corresponding control systems will be built. In order to solve problems like system complexity and large area occupation, the crystallization tank design will be optimized. Besides, to solve the unstable product quality problem in RA refining process, an online detection system will be added to the crystallization tank.In this paper, the preliminary experiments and systems design are presented for the new technologies above. It is expected to provide a further guidance or reference for the future continuous crystallization system design.