Development Of Equipment For The Preperation Of Solid Citric Acid Bran Koji

Citric acid is a very important organic acid, it is been widely used in food industry, pharmacy, spinning, daily chemical, construction and other industrial department. The traditional process of citric acid bran koji preparation by solid-state fermentation has some disadvantages:large labor intensity, high possible to infected bacteria. To solve these problems, it’s very important to develop a large-scale system for the preparation of citric acid bran koji, and it’s also very significant for the standardization of the production of Aspergillus niger and the normalization of the preparation of bran koji. The system for bran koji contain lots of sub-system, such as steam sterilizing system, aerated system, the tank, the mixer, temperature control system, humility control system and so on. Since these sub-system made it more complex, to investigate each sub-system is very meaningful. The following works have be done:The materials and bacteria for the preparation of citric acid bran koji were identified. Two methods, inoculated by liquid strain or solid strain, of preparing citric acid bran koji had been compared through experiments. Further experiments had also been done to assess the quality of these bran koji productions. According to these experiments, the process of preparing bran koji from raw materials was identified.A fermenter with double helical ribbon screw mixer was designed. A pilot-scale mixer model has been set up to investigate it’s function for particle mixing. The component concentration, mixedness, mixing velocity, Ashton mixing index at different simulation time had been studied to invistigate the function of mixing. According to the simulation results, some modified on the width of double helical ribbon had been done to study how to improve the mixed efficiency.The thermostatic water jacket had been chose to ensure an appropriate temperature condition in the process of fermentation. The structure and passageway of jacket were designed and optimized by a self-compiled program base on MATLAB software. A math model of temperature control system of fermenter was built according to the mechanism of heat flow. The simulation for the temperature control system of fermenter which choose PID controller as the control strategy was succeeded finishing by Simulink module in MATLAB. According to the results we get the suitable parameter of PID controller (Kp, Ti, Td). These provided technical basis for the temperature control of real fermenter.