| Nowadays, bag filters which were an effective method in controlling emissions of fine dust were widely used. The movement of smoke in the bag filter was a complicate 3-dimensional flow with two phase of gas-solid. The test of the internal flow field in bag filter was quite difficult. In order to study the characteristics of internal flow field in bag filter, computer simulation analysis of air distribution in bag filter was concerned.A filter unit model of bag filter with 240 bags (Ф130×6000mm) and filter area of 590m2 was built. Numerical simulation of the bag filter was divided into two parts; two-phase flow field in the bag filter was numerically simulated and each bag of the flow distribution, particle trajectory and internal flow field characteristics was given respectively. Another part, filtration velocity distribution was analyzed based on the simulation results of flow field.Flow field simulation results show that as follow:Flow flied distribution in the bag was apparent from top to bottom, spatial flow field above the bottom was very uniform, spatial flow field below the bottom was relatively disordered and there was a clear vortex formatted between the ash bucket and the bottom of the bag. When ascending velocity between air bags was almost 1m/s, it was benefit to the settlement of dust, especially the particle size greater than 100 microns could be fully settlement. The distribution of static pressure inside and outside bag had a significant pressure jumping on the border. The pressure in bag below 1~2m department and the dust hopper were very high. Filtration velocity increases with height along a single bag filter. Filtration velocity in the vicinity of the filter outside has reached 6m/min, almost 6 times of the design filtration velocity. By analogy with uniformity determination formula of air distribution of electrostatic precipitators, the non-uniform coefficient achieved a good request when filtration velocity is 0.8m/min, 1.0m/min, 1.2m/min. It is suggested that the internal air distribution was uniform in the air bag filter. |
