The Study On Combined Spin-Flow Pressure Spray Drying Technology

The dried powder product was formed in the spray dryer by pressure nozzle which atomized liquid into small droplets and heat and mass transferring was performed between droplets and hot medium in the drying chamber. This type of dryer was fitful for liquid drying in concurrent, counter-current or mixed air-flow. The dryer can produce powders, granules, hollow spherical particles and agglomerates products. The spraying capacity and particle size were changed by altering the parts assembled in the nozzle. Pressure spray dryers have been widely used in foodstuff, chemicals, medicaments, building materials, environmental protection, etc. As one of the most energy consumption, it is quite valuable to study how to make the spray dryer save energy consumption, enhance volumetric evaporation intensity, decrease its environmental pollution and running cost, improve its productivity through automatic controlling system and cut down the investment on equipment. In this dissertation, the author summed up the muti-technique in fluid dynamics, heat and mass transferring, mechanical designing and computational technique and studied the conventional pressure spray dryers with different air disperse structure and outlet equipment, at last put forward the theme i.e. the study on combined spin-flow pressure spray drying technology, the main contents were as follows:(1) The combined spin-flow pressure nozzle was designed whose novel structure has no report at present, and the structural designing parameters were obtained through analyzing the physical characteristic of materials and distribution of particles.(2) Base on the analysis of the atomizing principles of spray nozzle, mathematical model of combined spin-flow pressure spray drying was set up and the essential parameters such as spraying pressure, liquid quantity, temperature, spraying angle, inject distance, particle diameter and distribution, hollow diameter for several materials in normal conditions by experiment and LDV. The key items influent on the characteristics of spraying have been also studied in the dissertation, we can get a good spraying result by adjusting the related parameters efficiently.(3) The theoretical model of the dynamical parameters such as temperature, moisture, pressure and contour for hot medium and particle inside the drying chamber were obtained by model, utilized the Computational Fluid Dynamics technique to solve the problem between spraying droplets medium by arranging the double grid dispersing structure and rotary outlet structure and the developed structure improved the drying efficiency and product quality.(4) The droplets diameter of the combined spin-flow pressure spray drying are between 30um and 150um and the ranges of the droplets are narrow. The average diameter of the droplets is between 50 um and 100 um and the spraying angle can be adjusted from 30 to 180 . The dehydration time is square of the droplets diameter so the small diameters of the droplets can cut down the drying time then reduce the height of the drying chamber. To the combined spin-flow pressure spray drying, the diameters of droplets are small and the dehydration rate is higher so keeping the qualities of the dried products we can increase the speed of the inlet wind and reduce the temperature of the outlet wind thus can improve the evaporation intensity of the drying chamber and the average energy utilization of the drying equipment.A novel type double grid dispersing structure is designed and set on the top of the drying chamberwhich increase the mingling degree of the liquid with the gas and reducing the invalid area of the drying chamber. The combined spin-flow pressure spray drying equipment has more superiority to the thermal sensitive material.The preliminary results obtained from the industrial production showed that the volumetric evaporation intensity and energy consumption efficiency would be up to 12kgH2O/m3.h and 60% respectively to use the combined spin-flow pressure spray dryer. Moreover, the combined spin-flow...