重介质悬浮液具有非均相性,在离心浓缩作用下极易降低悬浮液的稳定性,继而直接影响重介质旋流器的分选精度。为削弱重悬浮液浓缩的影响并提高其稳定性,根据重介质磁铁矿粉具有顺磁性的特点,引入径向向内的磁场力以调节重介质颗粒在旋流器中的分布状态。采用理论计算、单因素试验以及三因素三水平的Box-Behnken正交试验方法,解释了磁力复合场中颗粒的运动规律;分析了入料压力、电流强度和线圈匝数对重介质分配以及悬浮液稳定性的影响规律;探究了各因素对重悬浮液浓缩效率Eth的影响规律,给出了各因素与响应值Eth的数学模型及其极小值。结果表明:在离心力场中引入径向向内的磁场力使重介质颗粒拥有更低的离心沉降末速vmro,改变了重介质分配规律,使溢流悬浮液密度升高,底流密度降低;随入料压力增大,重悬浮液浓缩度C1、澄清度C2、分层度C3以及浓缩效率Eth均呈相似增加的趋势;随电流强度和线圈匝数增加,均呈相似降低的趋势;在正交区间内,浓缩效率Eth与入料压力正线性相关,与电流强度和线圈匝数负线性相关,影响程度按大小排序:入料压力>线圈匝数>电流强度;最终得到Eth的线性模型和极小值,即当入料压力为0.03MPa,电流强度为3A,线圈匝数为1000时,Eth=0.067,相较于无磁场状态下的浓缩效率0.37,重悬浮液稳定性提高了81.89%。

The dense-medium suspension has heterogeneity, which can easily reduce the stability of the suspension under the centrifugal concentration, thereby directly affecting the sorting accuracy of the dense-medium cyclone. In order to reduce the concentration of thesuspension and improve its stability, and according to the paramagnetism characteristic of the dense medium magnetite powder, the radialinward magnetic field force was introduced to adjust the distribution state of the dense medium particles in the cyclone. Herein, the motionlaws of particles in magnetic composite fields were explained using the theoretical calculations, single factor experiment and Box-Behnkenorthogonal experiment design with three factors and three levels. The influence of the feed pressure, the intensity of the excitation currentand the number of coil turns on the distribution of the dense medium and the stability of the suspension was analyzed. The influence of various factors on the concentration efficiency Eth of the suspension was explored; the mathematical model and and its minimum values of response value Eth were provided. The results show that the introduction of radially inward magnetic field force into the centrifugalfield makes the dense medium particles have a lower centrifugal sedimentation velocity and changes the distribution of the dense medium,which increases the density of the overflow and decreases the density of the underflow. With the increase of feed pressure, the concentration C1, clarity C2, stratification C3 and concentration efficiency Eth of the suspension show a similar increasing trend, and a similar decreasing trend with the increase of the excitation current intensity and the number of turns of the coil. In the orthogonal interval, the concentration efficiency Eth is positively linearly correlated with the feed pressure, and negatively linearly correlated with the current intensityand the number of coil turns. The degree of influence is sorted in order of magnitude: feed pressure> coil turns> current intensity. Finally,the linear mathematical model minimum value of Eth is given. When the feed pressure is 0.03 MPa, the current intensity is 3 A, and thenumber of coil turns is 1 000 turns, the concentration efficiency Eth is 0.067. Compared with the concentration efficiency of 0.37 in the absence of a magnetic field, the stability of the suspension is increased by 81.89%.

0 引言

1 理论基础

   1.1 重介质颗粒在离心场中的沉降末速

   1.2 重介质颗粒在磁力复合场中的沉降末速

2 试验

   2.1 重介质性能检测

   2.2 试验平台

   2.3 试验内容与评价标准

3 单因素试验

   3.1 重介质分配试验

   3.2 各因素对悬浮液稳定性的影响规律

4 正交试验

   4.1 Box-Behnken正交试验

   4.2 各因素对浓缩效率的数学模型

   4.3 响应面优化与验证

5 结论