燃煤PM_(10)在磁场中聚并脱除理论与实验研究

Theoretical and Experimental Study of Aggregation and Removal of Fuel Coal PM_(10) in Magnetic Fields

提出了燃煤可吸入颗粒物在均匀磁场中的二元碰撞聚并模型,模型通过直接跟踪在磁偶极子力、气体曳力、布朗力和重力作用下做相对运动的粒子,根据粒子的相对运动轨迹确定燃煤细微飞灰粒子间的聚并系数。在数值计算获得聚并系数的基础上,应用求解粒子聚并动力学方程的区域算法,计算了东胜烟煤燃烧产生的飞灰细微粒子在均匀磁场中的聚并脱除效率,并与实验进行了比较。结果表明,在0.098～9.314μm粒径范围内,0.576～3.758μm粒径的飞灰粒子聚并脱除效率最高;总脱除效率随外磁场强度、颗粒质量浓度以及粒子在磁场中停留时间的增加而增大,粒子饱和磁化时,总脱除效率达到最大值;实验结果与数值模拟结果相一致。模型预测结果表明,当颗粒质量浓度为40 g/m3时,燃煤飞灰细微粒子的总脱除效率可达52%。

A two-dimensional collision and aggregation model has been presented for fuelcoal inhalable particles in uniform magnetic fields.Through a direct tracking of particles in relative motion under the action of a magnetic dipole force,gas drag force,Brown force and gravity force,the model can determine the aggregation coefficient among fuel-coal-produced fine fly ash particles according to the relative motion trajectory of the particles.On the basis of the aggregation coefficient obtained from a numerical calculation,a regional algorithm was employed to seek solutions to the particle aggregation dynamic equation to calculate the aggregation and removal efficiency of fine fly ash particles produced in the combustion of Dongsheng-origin bituminous coal.A comparison has been made between the calculated efficiency and experimental one.The result shows that in the particle diameters ranging from 0.098 to 9.314μm,the fly ash particles with a diameter between 0.578 and 3.758μm have a maximal aggregation and removal efficiency.The total removal efficiency will increase with an increase in intensity of external magnetic fields,particle mass concentration and residence time of particles in the magnetic fields.When the particles are saturation magnetized,the total removal efficiency attains a maximum value.The test results are in good agreement with the numerical simulation ones.The forecast made by using the model under discussion indicates that when the particle mass concentration attains 40 g/m3,the total removal efficiency of fuel-coal-produced fly ash fine particles can reach 52%.