基于离散元的膏体搅拌影响因素分析

Analysis of the Influence Factors of Paste Stirring Based on Discrete Element Method

膏体在泵送或自流输送至井下前,必须经过充分搅拌,以使其保持均质状态,增强可泵性能并确保充填强度。为研究搅拌工艺参数对膏体均质性的影响,首先探究膏体流变特性,开展坍落度试验测量膏体的流变参数;再以膏体流变性质为基础,将全尾砂膏体视为具有强黏性的湿颗粒群,采用Hertz-Mindlin with JKR接触方法建立膏体离散元模型,模拟坍落度试验,并将试验结果与模拟结果对比,校核模型参数。依据膏体离散元模型,构建了双轴螺旋输送机数值模型探究不同工艺参数对膏体混合程度的影响。研究表明:充盈率影响搅拌效果,充盈率为0.6时混合效果较好,充盈率最佳取值范围为0.5~0.7;搅拌转速能够促进颗粒间发生剧烈运动,但转速过大也会导致物料混合程度降低,影响膏体均质性,搅拌转速为10 rpm与30 rpm模型中料浆混合程度较好,考虑到出料效率,30 rpm为输送机最佳搅拌转速。

Before the paste is pumped or self-flowed to the well,it must be fully stirred to keep it homogeneous,enhance pumpability and ensure filling strength.In order to study the effect of mixing process parameters on paste homogeneity,the rheological characteristics of the paste were explored firstly,and the slump experiments were carried out to measure the rheological parameters of the paste.Based on the rheological properties of the paste,the full tailing paste was regard as a wet particle group with strong viscosity,a paste discrete element model was established by using Hertz-Mindlin with JKR contact method to simulate the slump experiment.The experiment and simulation results were compared to check the model parameters.Based on the paste discrete element model,a two-axis screw conveyor numerical model was constructed to investigate the effect of different process parameters on the degree of paste mixing.The research shows that the filling rate affects the stirring effect,and the mixing effect is better when the filling rate is 0.6,and the optimal filling rate should be in the range of 0.5~0.7;the stirring speed can promote vigorous movement between particles,but the rotation speed too large will also reduce the mixing degree of the material and affect the homogeneity of the paste.When the mixing speed is 10 rpm and 30 rpm,the mixing degree of the slurry is better.Considering the discharge efficiency,30 rpm is the optimal stirring speed of the conveyor.