In this research, the combustion of iron dust cloud through a narrow channel is simulated. Particles are randomly distributed within a rectangular control volume. Both conductive heat transferred from ignited to unignited particles and radiative heat scattered from burning particles are considered in the simulation. Radiative heat loss to the ambient gas as well as conductive heat loss to the channel walls are also taken into account. Besides, in conjunction with uniform size dust clouds, conditions in which the dust cloud is composed of poly-sized iron particles are considered to calculate flame propagation speeds and quenching distances. The results are compared with the existing experimental data. The comparison shows that they are in good agreement with the experimental measurements. Generally, an increment in dust cloud concentration leads to flame front velocity enhancement. Furthermore, flame propagation through iron powders composed of smaller particles is faster, and the quenching distance is lower. In addition, the effects of both channel wall temperatures and channel width on combustion characteristics of iron particles are investigated. The results show that flame propagation velocity usually increases with increasing the channel width. Besides, when wall temperature increases, the flame front speed increases and the quenching distance decreases.