Development of Dry type Fluidized High Gradient Magnetic Separation Device for Coal Powder Beneficiation

为满足电厂煤粉分选的需要，研制了一种新型干式高梯度磁选装置。已经测试了三种类型的FHGMS。对由平行和直线型铁磁丝组成的基本A型进行了考察，考察了丝径、丝数、煤粉粒度范围、磁通密度、载气速度、给煤量等参数。研究发现，磁粉重量最大的载气速度与降灰比最大的载气速度不同。也就是说，良好分离过程的最佳气速略大于MAGS峰的气速，这表明流态化具有良好的特征分离性能。最佳导线尺寸没有准确定义，但通常情况下，较粗的导线(例如，直径0.8 mm)比较小的导线(直径0.1或0.3 mm)更好，这与理论估计相反，因为较小的导线具有与导线横截面归一化的相对较大的捕获截面。从技术原因来看，粗硬导线或其他机构是可取的。还测试了用开槽钢板(B型和C型)代替铁磁丝的FHGMS新器件。B型水平开槽钢板具有较大的降灰效果，但煤的损失系数也很大，是三种类型中分选效果最差的。C型竖缝钢板具有很高的降灰率，煤耗大多与A型一样小，还进行了更大规模的试验，如插入并移动可移动的长钢板，以检查半连续模式的运行。研究发现，要实现良好的分离效果，必须对内部的气体流动进行更多的检测。

A novel dry type high gradient magnetic separation (HGMS) device comprized with a fluidized-bed has been developed for the purpose of coal powder beneficiation for the electric power plant. Three types of FHGMS have been tested. The basic type A consisting of parallel and straight ferro-magnetic wires was examined with parameters of wire size, number of wires, coal particle size range, magnetic flux density, carrier gas velocity, amount of feed (processed coal) and so on. The carrier gas velocity where weight of mags (trapped part on wires) is maximum, and the gas velocity where the ash reduction ratio is maximum, are found to be different. That is, the optimum gas velocity for good separation process is slightly larger than that of mags peak indicating good and characteristic separation performance of fluidization. The optimum wire size was not defined exactly, but in general, a rather thick wire ( for example, 0.8 mm in diameter) is better than a small wire ( 0.1 or 0.3 mm in diamter ), contrary to the theoretical estimation where a small wire has relatively large capturing cross section normalized with the wire cross section. From the view point of technological reason, thick and hard wire or other mechanism is desirable. New devices of FHGMS with slotted steel plates (types B and C) in place of ferro-magnetic wires were also tested. Type B with horizontally slotted steel plates shows large ash reduction, however, the coal loss factor is also very large, resulting the worst separation performance among three types. Vertically slotted steel plates type C are very well with high ash reduction ratio where coal loss is as mostly small as type A. More large scale was also tested, for example, movable long steel plates were inserted and were moved to check the semi-continuous mode operation. It was found that the gas flow inside must be examined more to realize good separation performance.