新型复合粘结剂提高生球质量的作用机理及构效关系

Mechanism and structure-activity relationship of a new composite binder to improve the quality of green pellets

  • 摘要: 降低膨润土用量是提高球团品位、实现节能减排的有效途径之一。基于新型高效复合粘结剂,通过生球制备、线性拟合分析、生球力学特征分析等手段研究了复合粘结剂对生球质量的影响规律及与重要指标的构效关系,阐明了复合粘结剂提高生球质量的作用机理。结果表明:配比(质量分数)为1.2%膨润土+0.028%有机粘结剂的复合粘结剂球团,落下强度(0.5 m高度落下次数)达到6.2、平均抗压强度达到14.5 N、爆裂温度达到542 ℃,与2.0%膨润土球团相比,生球质量相近,但膨润土消耗减少40%;基于构效关系分析,有机粘结剂对生球落下强度、爆裂温度作用显著,膨润土对干球强度影响更大;有机粘结剂通过增强颗粒的亲水性、毛细力和黏性力强化了生球落下强度,干燥时在表层形成少量孔隙,有利于球团内水分的排出,提高了生球爆裂温度,干燥后以固态连接桥的形式强化干球强度,但是孔隙的位点和尺寸可能会降低干球强度,因此,对干球强度起决定性作用的是膨润土,有机粘结剂对干球强度的影响呈现多面性。

     

    Abstract: Reducing bentonite consumption is one of the effective ways to improve the grade of pellets and realize energy saving and emission reduction. Based on the new high-efficiency composite binder, the effect of the composite binder on the quality of green pellets and structure-activity relationship with important indexes were studied by means of green pellet preparation, linear fitting analysis, and green pellet mechanical characteristics analysis. Moreover, the mechanism of the composite binder to improve the quality of the green pellets was expounded. Results show that the composite binder pellet, with a ratio of 1.2% bentonite and 0.028% organic binder, has a drop number (dropped from 0.5 m height) of 6.2, a average crushing strength of 14.5 N, and a shock temperature of 542 ℃. Compared with the pellet with 2.0% bentonite, the mass of the green pellets is similar; however, the bentonite consumption is reduced by 40%. Based on the analysis of the structure-activity relationship, the organic binder has a considerable effect on the drop number and the shock temperature of the green pellets, and the bentonite has a greater effect on the dry-crushing strength. The organic binder strengthens the drop number of the pellets by enhancing the hydrophilicity, capillary force, and viscosity, and it forms small amounts of pores on the surface layer during drying, which is beneficial for discharging water in the pellets and improving the shock temperature of the pellets. After drying, the organic binder strengthens the pellets in the form of a solid connection bridge; however, the site and the size of the pores may reduce the dry-crushing strength. Therefore, bentonite plays a decisive role in the strength of the dry pellets, and the influence of the organic binder on the strength of the dry pellets is multifaceted.

     

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