Research On The Mechanism Of Back-pressure Filling Device For Powders And Granules

With the rapid development of modern industry, powder and granular materials packaging gradually emerge in industrial production and become increasingly mature.However, the traditional powders and granules packaging industry has many shortages, such as dust pollution, poor operating environment, low production efficiency. In today’s international situation of environment protection, industrial automation and intelligent,traditional packaging of powders and granules can’t meet the demand of new packaging industry. With the extensive range of applications for powders and granules, the development of new feeding device has become urgent. In recent years, a new type of packaging system named Back-pressure Filling Device, appears on the international packaging field. And,Back-pressure Filling Device has become the preferred method in powders and granules packaging industry. The filling mechanism of back-pressure filling device involves multidisciplinary theory. Based on the analysis of granular powders flow-ability tests and back-pressure limit values, the working mechanism of back-pressure filling device was studied using FLUENT numerical simulation methods.According to Jenike flow function methods, the particle size in three levels(0.25, 0.5,1)of sand, cement powder and dry-mixed mortar with nine groups mix ratios were researched to measurement the flow ability of typical granular powder. The results showed that flow ability of sand granules could be improved obviously by increasing particle size. Along with the mixture ratio from 1:9 to 9:1, the flow function curves slope of nine groups dry-mixed mortars increased gradually, and flow ability declined accordingly. The curve between dry-mixed mortars FF(Flow Function) values and radios indicated that FF values decreased with an increase in cement content levels. Wall friction test of M5, M10 industrial mortar provided material parameters for the structure optimization of back-pressure device and calculating back-pressure limit values.On the basis of Janssen theory and Rankine stress state, the dynamic stress distribution of steady flow was analysed to discuss back-pressure limit values. The analysis of effect of material properties on back-pressure limit values showed that back-pressure limit values increased with an increase in angle of internal friction. For M5 industrial mortar material, the paper obtained that back-pressure limit values of top back-pressure chamber range 1.703 k Pa from 10.530 k Pa, and bottom back-pressure chamber range 0.462 k Pa from 14.401 k Pa.Taking M5 industrial mortar, for example, the mechanism of back-pressure filling device with different back-pressure limit values and material levels were emulated by using Eulerian multiphase model of FLUENT simulation. As back-pressure values range 7k Pa from 12 k Pa,simulation result indicated that the average velocity of outlet raised observably with the increase of back-pressure limit values. And, this suggested that back-pressure filling device preformed the best filling capacity as back-pressure values was 12 k Pa. The numerical simulation analysis of different material levels displayed that material levels 0.80 m was appropriate, the production capacity of back-pressure filling device was 98.8 t/h.Based on Jenike theories of hopper design, the influence factors of back-pressure fillingmechanism were optimized, including half apex angle of hopper, back-pressure areas.FLUENT simulation results showed that, as half apex angle was 15° and back-pressure areas were 0.08m2, filling ability and production capacity of the device increased significantly compared to the previous one. As back-pressure values was 12 k Pa, the production capacity of back-pressure filling device was 106.668 t/h, increasing 8.25% than before.The innovation of this research is: According to Jenike flow function methods, the flow ability of typical powders and granules were characterized, which laid the test foundation of this research. The dynamic stress distribution of steady flow was analysed to discuss back-pressure limit values, which improved the calculation accuracy and more suitable for practical application.