【作者】 邹文杰；

【导师】 曹亦俊； 刘炯天；

【作者基本信息】 中国矿业大学 ， 矿物加工工程， 2014， 博士

【摘要】 炼焦煤是我国的稀缺煤种，近几年我国炼焦煤原煤年产量超过12亿吨，肥焦煤约3.8亿吨，其中超过1亿吨的肥焦煤中煤作为民用和电厂燃料使用，因而中煤的深度脱硫降灰对缓解稀缺煤资源短缺，提高资源利用率意义重大。但由于缺乏对炼焦中煤物料特性的认知，煤泥分选调控方法复杂且适应性差，迫切需要研究炼焦中煤的界面调控方法，通过选择性絮凝-浮选分离的强化实现浮选效率的提高。论文从浮选中煤的煤岩学特征入手，探索了颗粒的尺度效应，研究了中煤粒度变细后对浮选过程的影响，研究了通过分散、选择性絮凝提高微细颗粒的表观粒径并实现细粒浮选强化的界面调控方法；通过试验研究与理论计算相结合，探讨了煤泥浮选体系中絮凝剂PAM的选择性吸附行为及矿物颗粒间界面作用的影响，提出了选择性絮凝-浮选分离实现微细煤泥高效分选的方法。论文首先研究了浮选中煤的煤岩学特征、表面热力学特性及尺度效应。钱家营矿浮选中煤磨碎后（-45μm占65.80%），与矿物质共生的显微组分由51.99%降低至20.75%，得到了较好的解离。浮选中煤具有较低的表面自由能，而高岭石表面自由能的非极性成分和极性成分中基于氢键作用的碱性分量远大于浮选中煤，使其对极性和非极性液体的润湿速率均高于浮选中煤。中煤粒度变细后的尺度效应体现在颗粒的几何特征、界面化学性质及浮选行为三方面：随着粒度变细，其比表面积和总孔容呈数倍增大，Ⅱ类孔增多，平均孔径增加；基于毛细管作用的非选择性捕收剂吸附作用增强，对去离子水的润湿热值急剧降低；中等紊流强度的浮选环境中，疏水颗粒（θ≥80o）粒径在-200+45μm范围内上浮概率最大。因此，选择性的增大煤的表观粒径，并强化矿物质的分散，可以增加二者的可浮性差异。通过纯矿物和人工混合样品的浮选试验及分析，研究了浮选过程中微细粒矿物质的凝聚分散行为及对浮选的影响。高岭石和煤在酸性及Ca2+浓度大于0.1mM的溶液环境中均发生了异相凝聚，使煤的浮选回收率降低，精煤灰分提高，同时烃类油捕收剂加剧了高岭石的夹带；浮选时间随物料粒度变细而延长，水回收率随之增加，矿物质的夹带程度加剧；浮选中加入聚丙烯酰胺（PAM）显著提高了微细粒煤的回收率，同时增大了水回收率。研究了PAM在固液界面的吸附行为及对颗粒表面性质的影响。煤与高岭石吸附A401均以物理吸附为主，反应吸热并自发进行，PAM的碳链与煤表面以疏水键合作用为主，与高岭石以静电和氢键作用为主；煤吸附A401的驱动力大于高岭石，煤对分子量为300万的阴离子型聚丙烯酰胺（APAM A401）的吸附量是高岭石的2.15倍，选择性最好；煤吸附PAM A401后，亲水性官能团特征峰（酰胺基、游离的-NH2、仲酰胺N-H、C-N）增强，疏水性官能团甲基（-CH3）及亚甲基（-CH2-）减少，煤样的疏水性略有降低，极性成分增加，非极性成分降低，表面自由能由39.92mN·m1增大为40.43mN·m1；高岭石吸附PAM A401后疏水性略有增高，极性成分由58.27mN·m-2降低为55.05mN·m-2，表面自由能略有降低。研究了PAM、分散剂、搅拌强度、搅拌时间对煤和高岭石絮体表观粒径分布的影响。絮体的分形维数与粒径呈正相关性，而六偏磷酸钠可强烈抑制高岭石絮体的形成，提高了PAM吸附的选择性。PAM A401浓度为12mg/L时，煤絮体的d10、d50、d90分别是高岭石絮体的8.42、2.60和2.75倍，所形成絮体的分形维数为1.56，絮体体积较小但密实。量子化学模拟计算表明，PAM分子片段中与氮原子相连的氢原子和煤本体的芳香结构形成大π键作用，协同O—H…O作用极大的提高了PAM与煤的吸附能，使PAM与煤吸附结合的稳定性高于所构建的高岭石的硅氧层和铝氧层。对吸附PAM前后煤和高岭石颗粒间的界面作用进行了扩展的DLVO理论计算，研究表明：相互作用能量参数是影响微细煤泥浮选体系颗粒间相互作用势能的主要因素；煤颗粒之间的疏水吸引势能高于静电及范德华势能2个数量级，吸附A401后煤颗粒之间静电排斥力增强，疏水吸引势能大小及作用范围减小，导致其吸引势能的绝对值减小；吸附PAM的煤和高岭石颗粒之间静电排斥力增大，亲水排斥势能减小，颗粒间总势能仍为排斥势能。在以上研究的基础上进行了选择性絮凝-浮选分离试验，与常规浮选试验相比，精煤灰分相当时，选择性絮凝-浮选提高了精煤产率6.38个百分点，捕收剂用量降低了30%，实现了浮选中煤的高效回收。更多还原

【Abstract】 Re-separation of middlings can achieved deep desulfurization and ash reductionof coal. And it has important strategic significance to ensure sustainable supply ofscarce coal resources. Coal petrology characteristics and surface thermodynamiccharacterization of flotation middlings was researched firstly. Scale effect of particleswith its impact on flotation behavior and process characteristics of the fine coal wasstudied. Apparent size of fine particles was improved by dispersing and selectiveflocculation to enhance the fine coal flotation. In coal flotation system, selectiveadsorption behavior of flocculants PAM onto coal or kaolinite, surface modification ofparticles, the role of mineral particles surface-modified particles, action mechanismbetween PAM and particles and interfacial interaction between particles werediscussed by experimental study and theoretical calculations. Efficient separation offine coal by selective flocculation-flotation separation was achieved.Firstly, coal petrology characteristics, surface thermodynamic characterization offlotation middlings and scale effect of particles was studied. Particles will be fine ofthe re-separation which was determined by its petrology characteristics. After grindingof flotation middlings (-45μm about65.80%), macerals associated with mineralsdecreased from51.99%to20.75%. and it was well liberated. The flotation middlingswas strong hydrophobic with low surface free energy. The non-polar component andalkaline part based on hydrogen bonding of polar components of surface free energyof kaolinite is much larger than that of coal. Scale effect is reflected in geometriccharacteristics, interface chemistry and flotation behavior of particles. Therefore,when the surface hydrophobicity of coal was less affected, floatability difference canimprove by increase the apparent particle size of coal selectively, or mineral particleswere dispersed.Flotation behavior and process characteristics of fine coal was studied bymirco-flotation tests of pure mineral and artificial mixed samples, flocculation-flotation test, sedimentation test, zeta potential measurement and scanning electronmicroscopy test. It showed that heterogeneous agglomeration between coal andkaolinite was occurred in acidic environment or in Ca2+solution (>0.1mMconcentrations), which lead to reduce of coal recovery and increase of coal ashcontent. Collector aggravated the entrainment of kaolinite. Quartz particles weretransported into foam mainly by water entrainment. The finer the particle sizebecomes, the longer the flotation time. Thus, water recovery and entrainment degree increases. PAM can improve recovery of fine coal significantly, and water recoverywas increased together.It showed that selectivity of anionic polyacrylamide with molecular weight3×106(A401) is the best. The coal adsorbance of this polyacrylamide is2.15times largerthan that of kaolinite. Adsorption of A401onto coal or kaolinite was mainlyendothermic and spontaneous physical adsorption reaction. Hydrophobic bondingdominated the interaction between carbon chain of PAM and coal surface, whileelectrostatic and hydrogen bonding interactions was the main effect between PAM andkaolinite. When different polyacrylamide was absorbed onto different mineralsurfaces, the effect of compression or penetration with different intensity ofpolyacrylamide occurred.After adsorption of PAM A401, the hydrophobicity of coaldecreased. The hydrophobicity of Kaolinite increased slightly, and the polarcomponent was reduced from58.27mN m-2to55.05mN m-2.The laser particle size analyzer was used to measure the flocs size distribution ofcoal or kaolinite with different types of PAM, dispersing agent, stirring intensity andstirring time. Hexametaphosphate can inhibit the formation of flocs kaolinite strongly,which improved the adsorption selectivity of PAM. Quantum chemistry calculationproved that large π bonding effect was formatted between the hydrogen atom attachedto the nitrogen atom of PAM fragment and the phenyl ring of coal. The stability ofadsorption of PAM onto coal is higher than that of the constructed kaolinite siliconoxide layer and the aluminum oxide layer. Before and after PAM adsorption,interfacial interaction between particles of kaolinite was calculated by the extendedDLVO theory. Repulsion potential between coal particles after PAM adsorption and iskaolinite decreased, while the electrostatic repulsion increases, and the hydrophilicrepulsion potential reduced.Efficient separation of fine coal was achieved through the selectiveflocculation-flotation. Compared with the conventional flotation, collector dosage ofthe selective flocculation-flotation reduced, flotation rate of fine coal was improved.Clean coal recovery of selective flocculation-flotation was improved6.38percent,saving30%of collectors.更多还原