Study On Screen-penerating Performance Of Grains With Different Material And Shape

As the most effective methold to grade materials by grain size, technology of screen separation has been widely used in mining, metallurgy, chemical industry, medication,construction material,food processing and environment industry etc. In the process of screening,it is deeply complicated for the movement law of material grain. At present,in the comparatively mature theory of single grain screen-penetrating probability,most kinds of grain were taken as spherical ones,and by making this premise,the probability model of spherical grain penetrating the square hole was funded as well as the calculating equation. However, it can't describe the penetrating condition of materials with other shapes accurately because of the big difference among them. In addition, few studys on screening efficiency of different gains penetrating the different sieve deck are in process and there're many vacacies that need to be filled.In this paper,on the basis of theory of single grain screen-penetrating probability,the probability model and equation of square grain penetrating the square hole as well as spherical grain and square grain penetrating the rectangle hole and circular hole were founded by extending the the probability model and equation of F.Mogensen's theory. Then,experiment method and procedures will be fixed and used to check the probability model and equation. And in this experiment,the sieve decks and the screening specifications suit to different ideal grains will be established and summarized by conducting comparison and ananlysis. Still, the conclusion will be tested by screening kinds of industrial material. Aiming to analyzing the blocking problem,the concept and calculating method of block rate will be presented.The experiment results showed that the probability model and equation of square grain penetrating the square hole, spherical grain and square grain penetrating the rectangle hole and circular hole were available. And the concept and calculating equation of block rate presented in this paper were efficient for quantitative analysis of block problem. Other conclusions were summarized as follow.When being screened on plane sieve deck, small obliquity of sieve deck is recommended to choose and amplitude of vibration will be choosed according to its density; And on scalariform sieve deck, big obliquity of sieve deck is recommended to choose and amplitude of vibration will be choosed according to its density,still; High screening efficiency can be achieved by taking sieve deck with sticks and polyurethane sieve deck.Spherical grain is easy to penetrate and barely blocks sieve hole;Square grain is comparatively easy to penetrate; Grain of triangular prism is comparatively easy to penetrate except on comb tooth sieve deck;Grains with block shape is hard to penetrate on sieve deck with circular hole or square hole while easy to penetrate on stick sieve deck or polyurethane sieve deck,on which particles out of regulated size also penetrate, grain with Triangle shape is easy to penetrate. Comparing to rectangular particle, triangle particle is easier to penetrate. In order to get comparatively high screening efficiency and grade the grains,sieve deck with comb tooth will be recommended to choose ;Blended grains that consist of square grain and grain with triangular prism is easy to penetrate. It is similar with the square grains since the square grains take up more amount in it.The conclusions are dependable on ground that they match the result of screening of practical material, so they can be refered in industrial screening.