均匀磁场中磁种聚并脱除燃煤PM_(10)实验研究

Experimental Study on Aggregation of PM_(10) From Coal Combustion by Magnetic Seeding in Uniform Magnetic Field

在均匀磁场中,通过添加Fe3O4磁种对东胜烟煤燃烧产生的0.023-9.314μm粒径范围内飞灰粒子进行了聚并实验,研究了磁种对飞灰粒子聚并的形态以及粒径、磁感应强度、质量浓度、停留时间和磁种添加比例对聚并的影响。实验结果表明:磁种与多个飞灰粒子聚并,将飞灰粒子连接在一起;添加磁种可提高所有粒径飞灰粒子的聚并脱除效率,其中对小粒子更为明显;磁种对飞灰粒子的聚并可通过增大磁感应强度、粒子质量浓度、粒子在磁场中停留时间以及磁种的添加质量比来加强,从而提高粒子的聚并总脱除效率;在粒子达到饱和磁化时,磁感应强度的增大对聚并无作用;在磁种添加比例不变时,粒子数目中位直径随总聚并脱除效率的提高而降低;在其它条件不变而增大磁种添加质量比时,粒子数目中位直径增大。数值模拟结果表明,当飞灰粒子质量浓度为40g.m-3时,聚并总脱除效率可达80%,数目中位直径从初始的0.151μm减小到0.098μm。

Aggregation experiments on fly ash particles in the size range of 0.023-9.314gm from Dongsheng bituminous coal combustion were conducted by magnetic seeding in a uniform magnetic field. The modalities of the aggregates between magnetic seeds and fly ash particles, and the influence of particle size, magnetic flux density, particle residence time and mass concentration on aggregation were examined. Experimental results showed that the fly ash particles are connected by magnetic seeds. Removal efficiencies of all sized particles can be increased by magnetic seeding, which is more obvious for the smaller particles. The aggregation by magnetic seeding can be enhanced by increasing the magnetic flux density, the particle mass concentration, the particle residence time in magnetic field and the mass ratio of magnetic seeds to fly ash, so that total particle removal efficiency is raised. When particles are saturatedly magnetized, the increase in magnetic flux density has no effect on particle aggregation. Keeping the mass ratio of magnetic seeds to fly ash, the particle number median diameter decreases with increase in the total particle removal efficiency, and keeping other conditions constant, the rising of the mass ratio causes an increase in particle number median diameter. Numerical simulation results indicated that the total particle removal efficiency attains 80% and particle number median diameter decrease from 0.151μm to 0.098 when particle mass concentration is 40g·m^-3.