单极与双极电袋复合除尘器增效作用对比试验

Comparative experiments for effect and efficiency enhancement of unipolar and bipolar charged particles in the bag-type vacuum cleaner

将尘粒双极荷电,使沉降在滤袋表面异极性带电粉尘产生静电中和,有利于消减带电粉尘与滤袋间的静电粘附力,改善电袋复合除尘器清灰效果。然而,将现有电袋复合除尘器的单极荷电改为双极荷电后,电袋复合除尘的静电增效作用尚不明晰。为此,采用一种单电源双极线管式预荷电器,在相同试验条件下进行单极与双极电袋复合除尘器增效作用对比试验研究。为明确双极预荷电器的荷电效果,先进行预荷电器的伏安特性对比试验。结果表明,在相同的电晕线根数、异极距和外加电压下,双极预荷电器的电晕电流高于单极预荷电器。而后,采用中位径1.74μm硅微粉进行单极与双极电袋复合除尘器除尘效率对比试验。在入口粉尘质量浓度2500mg/m3、过滤风速3m/min、预荷电器的平均场强在4.5~6.0kV/cm条件下,双极荷电布袋除尘器的排放浓度比单极荷电布袋除尘器的排放浓度降低25%以上。从单极荷电和双极荷电粉尘在滤料上沉积的扫描电镜观察发现,沉降到滤料表面双极荷电粉尘的聚团现象明显,表明沉降到滤料表面的双极荷电粉尘的静电凝并作用是双极布袋除尘器的除尘效果优于单极电袋复合除尘器的主要原因。

The given paper is aimed to present the results of its comparative experiments for the effect and efficiency enhancement of unipolar and bipolar charged particles in the bag-type vacuum cleaner.As is well known,the electrostatic neutralization of the charged particles tends to appear on the filter bag surface of the vocuum cleaner when the particles are bipolarly charged.In such a situation,the dust can be easily removed from the bag because it is easy for the electrostatic adhesion of the charged particles on the filter bag to be relieved.However,it would not be easy to remove the electrostatic enhancement effect on the bag filtration efficiency if the unipolar charged particles can be replaced by the bipolar charged ones.Therefore,a wire-tube bipolar precharger with the D-C voltage supply can be used to compare such a kind of enhancement in the bag-type vocuum cleaner under the same experimental conditions.In order to clarify the charge performance of the bipolar precharger,we have made efforts to conduct some comparative experiments to expound the voltage current characteristics of the unipolar and bipolar prechargers.The results of our experiments indicate that the corona current of the bipolar prechargers is higher than that of the unipolar one in case when the voltage is applied with a number of corona wires in the distance between the wire electrodes,with the tube electrodes being the same.And,then,the silicon powder with 1.74 μm medium diameter can be used for the collection efficiency measurement of the bag filter in the experimentally comparative investigation.Thus,the emission concentration of the bipolar charged particles has been found 25 per cent lower than that of the unipolar charged ones on the condition when the inlet silicon particle concentration is 2 500 mg/m3,the filtration velocity of the bag filter is 3 m/min,and the average electric field strength is within the range of 4.5-6.0 kV/cm.It has been observed and detected from the scanning electric microscopy(SEM) that the bipolar charged particles on the surface of the filter material are more likely agglomerated than that of the unipolar charged ones.Therefore,it can be concluded that the electrostatic agglomeration helps to enhance the collection efficiency and effect of the bipolar charged particles on the bag filter,which proves more advantageous than that of the unipolar charged ones.