【作者】 唐利刚；

【导师】 赵跃民；

【作者基本信息】 中国矿业大学 ， 矿物加工工程， 2010， 博士

【摘要】 气固流化床干法分选技术为世界干旱地区煤炭提供了一种高效分选方法。在工业性分选试验过程中,该技术所用的加重质(磁铁矿粉)粒级较窄,存在制备困难,成本较高的问题。此外,鉴于传统选煤厂建筑方式基建投资较大,中国矿业大学与唐山神州机械有限公司合作建立了40~60t/h的KZX40型模块式气固流化床干法选煤系统。因此,有必要拓展加重质适用粒级,增强该技术的适用性。本文应用实验与数值计算相结合的方法,研究了不同粒级加重质流化床的动力学特征。在此基础上,考察了宽粒级颗粒流化床的分选性能,优化了加重质设计,拓展了加重质的适用粒级。进而基于宽粒级复合加重质,研究了工业性流化床的流化特性及分选性能。同时,就工业分选试验过程中出现的相关问题进行了研究,为该技术的工业推广提供了基础。研究了Geldart B类粗磁铁矿粉的流化特性。结果表明:适宜采用Syamlal-O’Brien模型作为曳力方程,归还系数为0.9。此外,当静床高Hs≤300mm时,静床高对床层的流化特性影响较小。对于床层的流体动力学特征,数值计算结果与实验结果有较好的一致性。该Geldart B类粗颗粒流化床的表观气速不宜超过2.0Umf。基于来自南非的煤样,应用该粗磁铁矿粉与<1mm煤粉组成复合加重质,研究了气固流化床中试分选系统的分选特性。随入选煤粒度减小,流化床分选质量下降。应用颗粒动力学及数值模拟方法分析了分选差异产生的原因。该流化床对50~6mm煤炭分选性能很高,但床层活性相对较差,加重质制备困难,随后开展了降低磁铁矿粉适用粒度下限的研究。研究了颗粒的在流化床中的混合机理。实验及数值计算结果表明,增大细颗粒含量,可提高床层流化特性,同时,0.3~0.06mm颗粒总体上分布较为均匀,并没有产生分层分级现象。因此,以0.3~0.06mm为主导粒级(≥80%)的磁铁矿粉可用于煤炭分选。为了维持该宽粒级磁铁矿粉床层的稳定,气速的适宜操作范围为1.5Umf~1.8Umf。提出了宽粒级加重质流化床的高度及平均密度预测模型,为流化床自动化测控系统开发提供了基础。研究了宽粒级复合加重质分选特性以及煤粉在流化床中的分布行为。详细考察了流化数、布风板与床层压降比ΔPd/ΔPb、1.5~0.5mm煤粉含量对流化床的影响,得到了密度分布标准差、E值、各粒级煤粉分布标准差与三个因素间的函数关系。实验结果表明,ΔPd/ΔPb≥1时,压降比并不是影响床层流化质量和分选性能的显著因素。1.5~0.9mm煤粉不适合与该磁铁矿粉混合而作为加重质,应控制其在加重质中的含量不超过3.09%。0.9~0.5mm煤粉与该磁铁矿粉的混合物可作为加重质。此外,基于以0.3~0.06mm为主导粒级的磁铁矿粉,通过改变<1mm煤粉来调控床层密度的方法是合理的。在工业性分选试验过程中,采用了较大筛孔尺寸(3mm)的脱介筛。<1mm煤炭对流化床的影响已有报道。本文研究了3~1mm煤粉对气固流化床性能的影响。为了维持床层良好的流化及分选性能,在干法选煤过程中应控制加重质中的3~1mm煤粉含量小于4.5%。考察了0.3~0.06mm为主导粒级的磁铁矿粉和<1mm煤粉组成的复合加重质对模块式分选系统的适应性。工业性试验结果表明,床层流化质量优越。在低密度或高密度条件下,系统对50~6mm煤炭分选效果良好,E值为0.05~0.07g/cm~3。更多还原

【Abstract】 Gas-solid fluidized bed separation expands the choices of highly-efficient beneficiation methods for world coals located in areas deficient in water resources. However, the following problem occurred with the medium solids (i.e. magnetite powder) during industrial scale separation experiments: it is difficult and costly to prepare a great deal of medium solids of narrow size range. To decrease the construction cost a modularized 40-60 ton per hour KZX40 dry coal beneficiation system was constructed by the workers of China University of Mining and Technology (CUMT) and Tangshan Shenzhou Manufacturing, Co. Ltd (TSM). Therefore, it is necessary to expand the suitable size range of medium solids for an increase in applicability of the system. The hydrodynamics of medium solids of various size ranges were studied using a combination of experimental and numerical methods. Furthermore, the separation performance of wide-size-range medium-solids fluidized bed was investigated. The design of medium solids was optimized thus expanding the applicable size range of medium solids. The characteristics of fluidization and beneficiation of the industrial-scale bed were studied. Moreover, some problems were detected and studied during industrial-scale experiment. This is beneficial to commercialization of the technique.The fluidization characteristics of large Geldart B magnetite powder were studied. The results show that Syamlal-O’Brien drag model is suitable for simulating the bed at a particle restitution-coefficient of 0.9. Moreover, for the static bed height Hs≤300mm there is little effect of the static bed height on the fluidization characteristics. The simulated hydrodynamic results are consistent with the experimental data. The superficial gas velocity should be adjusted to no more than 2.0Umf.Based on coal from South Africa, the separating performance of a pilot gas-solid fluidized bed beneficiation system using a compounded medium solids of mixed the large Gelart B particles and <1mm fine coal was investigated . The separating quality of the fluidized bed drops gradually as the feed-coal particle size decreases. The cause of the differences in separating characteristics was analyzed by particle dynamics and numerical modeling. Although the Geldart B bed has excellent separation performance for 50~6mm coal the bed activity is relatively low and it is difficult and costly to prepare a great deal of the large Geldart B magnetite powder for an industrial scale separation experiment. Then the study on decrease of the lower size limit of the magnetite powder was performed.The mixing mechanism of particles in bed was studied. The experimental and simulated results show that when the content of fine Geldart B particles increases the fluidization performance is improved. Furthermore, 0.3-0.06mm particles distributes uniformly overall with no strasfication. The magnetite powder having a major component, 0.3-0.06 mm particles (≥80% by wt.), can be, hence, used as medium solids for coal separation. The gas velocity should be adjusted in a range of 1.5Umf-1.8Umf to maintain the stability of the bed. Moreover, the models for prediction of the height and average-density of bed were proposed. This laid a foundation for the development of automatic control system of bed.The separation characteristics of the compounded medium solids having a wide size range and distribution of fine coal were studied. The effect of fluidization number, distributor-to-bed pressure drop ratioΔPd/ΔPb and 1.5-0.5mm fine coal content of medium solids on the bed was investigated. The experimental results show that, atΔPd/ΔPb≥1, the ratio is not a significant factor influencing the bed fluidization and separation performance. A mixture of 1.5-0.9mm coal and the magnetite powder is not suitably used as medium solids. The 1.5-0.9mm coal content in the medium solids should be controlled to no more than 3.09%. A mixture of 0.9-0.5mm coal and the magnetite powder is suitable for coal separation. Moreover, based on the magnetite powder having a major component, 0.3-0.06 mm particles, a method to adjust the bed density is reasonable by changing <1mm fine coal content in medium solids. During industrial-scale experiments screens of a large aperture diameter (3mm) were used to separate the medium solids from the products. The effect of the < 1mm fine coal on the performance of the fluidized beds has been reported. This paper emphasizes the effect of 3-1mm fine coal on the bed performance. To maintain good fluidization performance and separation quality the value of 3-1mm coal content in medium solids should be controlled to less than 4.5% during dry beneficiation processing of coal.The suitability of the medium solids, consisting of the magnetite powder having a major component (0.3-0.06 mm particles) and <1mm fine coal, for the modularized system was investigated. The industrial experimental results show that the fluidization quality of bed was good. The separation performance of the system was excellent at a low or high separating density. Effective separation of 50-6mm coal can be implemented by the system at a high or low separating density, with an E value in the range of 0.05-0.07g/cm3.更多还原