【作者】 杨秀伦；

【导师】 吴振卿；

【作者基本信息】 郑州大学 ， 材料加工工程， 2007， 硕士

【摘要】 筛分作业是目前应用最广泛和最有效的物料按粒度分类方法，在矿业、冶金、化工、医药、建材、粮食加工和环境等领域有着广泛的应用。筛分过程中，物料在筛面上的运动规律极为复杂。目前，已较为成熟的单颗粒透筛概率理论是将物料形状都看着是球形颗粒，研究了其在正方形筛孔的透筛概率，建立起了透筛模型和计算公式，但由于不同物料形状差异较大，都当作球形颗粒来处理，则难以准确反映各物料具体的透筛情况。此外，针对不同形状颗粒在不同筛面的实际筛分率情况的研究，也亟待开展。本文首先在单颗粒透筛概率理论的基础上，通过拓展F.Mogensen球形颗粒透筛概率理论与计算公式，分析、推导并建立正方体颗粒在正方形筛孔以及球形颗粒和正方体颗粒在长方形筛孔和圆形筛孔上的筛分概率模型以及概率计算公式。然后，制定了实验方案与操作步骤，进行筛分试验，验证建立的模型和计算公式；通过比较，总结出适合于各种理想物料颗粒筛分的筛板及其相应的筛分参数，并用实际物料进行试筛，检验结论的合理性。为便于分析，本文提出了堵塞率的概念以及计算方法，定量的分析物料堵塞问题。实验结果表明，本文所建立的球形颗粒在圆孔筛板、正方体颗粒在方孔筛板和圆孔筛板的透筛概率模型及概率计算公式是可行的；提出堵塞率的概念以及计算方法，对定量分析物料堵塞问题有积极作用。试验得到的主要结论有：各物料在平面筛板筛分时，宜采用较小倾角，激振力大小根据颗粒的比重确定。而在阶梯面筛板上筛分时，宜采用较大倾角，激振力大小根据颗粒的比重确定。除用板块状颗粒外，各物料在棒条筛和聚氨酯筛板筛分可得到较好筛分效果。球形颗粒容易透筛，在各种筛板都不易堵孔；方块颗粒，包括正方体状颗粒和长方体状颗粒都较易透筛，但后者堵塞情况略微重一点；三角柱状颗粒与方块相似，较易透筛，但在梳齿筛板上筛分时颗粒易卡在筛缝；板块状颗粒，其中的长方形板块状颗粒与三角形块板状颗粒情况基本相似，在方孔筛板和圆孔筛板上不易透筛，而在聚氨酯和棒条等条缝形筛板上容易透筛，但在分级筛分时，大于筛分粒级的颗粒也易透过。实际筛分时，三角块颗粒的透筛率，略高一点，但卡在在筛缝也容易一些。为能达到分级目的，又能保证一定的筛分率，用梳齿筛板筛分效果较好；混合的颗粒主要由正方体颗粒、长方体颗粒和三角柱状颗粒组成的，其中方块含量多，该颗粒较易透筛。结论经过检验，基本与实际情况相符，可靠性较高。对工业筛分有一定参考意义。更多还原

【Abstract】 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.更多还原