| A mathematic model for vacuum belt drying (VBD) process of Salvia miltiorrhiza Bge extract was constructed. According to the model, the operation parameters of VBD process were investigated, which contributed to the foundation of technical standards and application rules of VBD technique for Traditional Chinese Medicine (TCM). The research content is as follows:(1) The orthogonal test design and grading method for multi-index were used to identify key technical parameters of VBD and to identify the optimum conditions of the VBD for Salvia miltiorrhiza Bge extract. The key technical parameters impacting the water content of the dried product are listed as follows: the feeding speed, the belt speed, the initial water content of extract and heating system temperature. The critical technical parameter impacting the drying speed is the feeding speed. The optimum conditions of the VBD determined by orthogonal test method and the grading method are: water content of extract before drying is 30%, the temperature of feeding extract is 40 °C, the temperature of the first heating system is 95 °C, the second is 90 °C, the third is 80 °C, and the temperature of cooling water is the temperature of environmental water, the vacuum degree is close to -1330 Pa, the feeding speed is 6 kg.h-1, the belt speed is 6 m.h-1. The result is: the water content of the dried product is 2.97%, the drying speed is 2.04 kg.h-1.(2) The mathematic model of VBD process was constructed based on the Heat Conservation Law, and the measuring methods of model parameters were investigated. A set of dedicated simulation software was designed by using the graphical user interface (GUI) programming tool embedded in Matlab. Salvia miltiorrhiza Bge extract was selected as the research example, and excellent agreement was observed between model predictions and experiment results.(3) A drying optimization, which the water content of dried product below 5% was imposed, the drying speed was selected as the index mark, was studied to determine the optimum conditions for the Vacuum Belt Drying process of Salvia miltiorrhiza Bge extract.
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