磁铁矿粉对煤泥水沉降特性的影响机理

Effect of magnetite on the sedimentation characteristics of coal slurry

近年来随煤矿开采机械化程度的提高,选煤厂入料原煤中细泥含量越来越高。在处理微细粒煤泥时传统的煤泥水处理技术常出现沉降效果差、溢流浓度高等问题。磁种絮凝作为一种高效絮凝方法,在水处理领域已得到广泛应用,但对选煤厂产生的难沉降煤泥水的研究较少。以内蒙古某选煤厂煤泥水为研究对象,以磁铁矿粉为磁种,研究了磁铁矿粉单独作用以及与聚合氯化铝(PAC)和阳离子型聚丙烯酰胺(CPAM)共同作用对煤泥水沉降特性的影响,采用多重散射光稳定性分析仪研究磁铁矿粉用量对煤泥水体系稳定性的影响,采用Zeta电位分析仪研究磁铁矿粉用量对颗粒表面Zeta电位的影响。结果表明:磁铁矿粉单独作用时,随磁铁矿粉用量的增加,煤泥水上清液浊度逐渐降低后略有增加,沉降速度逐渐升高然后略有降低,当磁铁矿粉用量为每吨干煤泥48.00 kg时,煤泥水上清液浊度达到最低,为53.50 NTU,沉降速度达到最大,为3.89×10^(-3)mm/s;磁铁矿粉与PAC共同作用时,随磁铁矿粉用量的增加,煤泥水上清液浊度和沉降速度呈现出与磁铁矿粉单独使用时相同的趋势,稳定性指数(I_(TS))先升高后降低,表明随磁铁矿粉用量的增加,煤泥水沉降效果逐渐提高,但过量的磁铁矿粉会使煤泥水重新恢复稳态,不利于煤泥水沉降;磁铁矿粉、PAC与CPAM共同作用于煤泥水沉降时,在三者用量分别为每吨干煤泥10.00 kg、2.00 g和1.00 g时,煤泥水沉降效果明显提升,煤泥水上清液浊度为64.30 NTU,沉降速度为3.09 mm/s。Zeta电位分析表明磁铁矿粉的加入降低了煤泥水颗粒表面的Zeta电位绝对值,机理分析表明煤泥水中颗粒与磁铁矿粉之间通过静电吸附作用形成以磁铁矿粉为核心的絮团,提高了絮团的密度和沉降速度。

The content of fine mud in the raw coal of coal preparation plant is getting higher and higher with the increase in the mechanization of coal mining.Problems such as poor settlement effect and high overflow concentration often appear when the traditional slime water treatment technology is used to treat high ash and fine coal slurry.As an efficient flocculation method,magnetic flocculation has been widely used in water treatment,but there is less research on the difficult to settle coal slurry water produced by coal preparation plant.Fine coal slurry from a coal preparation plant in Inner Mongolia was used in this study.The effects of magnetite alone and together with polyaluminum chloride and cationic polyacrylamide on the sedimentation characteristics of coal slurry were studied.The stability of the coal slurry system with different magnetite dosages was studied by the Turbiscan analyzer,and the influence of the amount of magnetite powder on the zeta potential of particle surface was studied by Zeta potential analyzer.The results show that when the magnetite is used alone,the turbidity of the supernatant decreases with the increase in magnetite dosages,and then increases,while the sedimentation velocity increases with increasing magnetite dosages,and then decreases.When the magnetite dosage is 48.00 kg/t,the turbidity of the supernatant reaches the lowest value(53.50 NTU),while the sedimentation velocity reaches the maximum value(3.89×10-3 mm/s).When magnetite and PAC is used,the change of the turbidity of supernatant and the sedimentation velocity shows the same trend as the magnetite used alone with the increase of the amount of magnetite powder,and the stability index(ITS)value first increases and then decreases,indicating that with the increase of the amount of magnetite powder,the sedimentation effect of slime water gradually improves.The results of the Turbiscan analyzer shows the coal slurry became steady when excessive magnetite is used,which is not conducive to the settlement of coal slurry.When magnetite,PAC and CPAM are added into coal slurry with the dosages of 10.00 kg/t,2.00 g/t,and 1.00 g/t,respectively,the initial sedimentation velocity and the turbidity of the supernatant are reached 3.09 mm/s and 64.30 NTU,respectively.The sedimentation effect of the coal slurry improves significantly.The Zeta potential value reduces with the increase of magnetite.The flocs with magnetite as the core are formed by the electrostatic adsorption between the particles and the magnetite in the coal slurry.Moreover,magnetite increases the density and sedimentation velocity of the flocs.