Flow field simulation and structure optimization on desulfurization-dust removal-denitrification system of sintering flue gas

Sintering flue gas is the main pollutant emission source in the steel industry and its effective treatment is the key to achieving ultra-low emission. In order to improve the flow field distribution of the sintering flue gas desulfuriza- tion-dust removal-denitrification system in a steel factory and the operating efficiency of the system,a numerical simu- lation of flow field of the system was carried out by means of computational fluid dynamics software,ANSYS-Fluent. The feasibility and cost of integrated simulation were analyzed. Flow field uniformity was evaluated qualitatively and quantitatively by the velocity, concentration, temperature distribution and their deviation coefficient. A four-factor three-level multi-index orthogonal test was designed to analyze the effects of the gradual expansion tube of desulfurization tower,the inlet section of dust removal,deflector and static mixer with different structural parameters on the flow field uniformity of the system. The results show that the integrated simulation is closer to the actual situation of the pro- ject than the single simulation and it can accurately analyze the flow field of the dust removal section and the denitrifi- cation section. The number of integrated simulation grids is about 16 million,the parallel computing time is about 60 h and the calculation cost is within the acceptable range. The improvement plan is to reduce the gradually expanding tube angle of the desulfurization tower,change the inlet straight tube of the dust removal section to a gradually expan- ding tube,add a deflector with an arc of 75° and a static mixer with a grid spacing of 400 mm. Flow field uniformity is significantly improved. The area of the dimensionless flow rate with 0. 5 -1. 5 is significantly increased at 1 / 2 of the main bed height in desulfurization section. The deviation coefficient of velocity in the center plane of the dust removal section is reduced by 7. 6% and 9. 6% . The deviation coefficient of concentration and temperature distribution at 1 000 mm above the first layer of catalyst is decreased to less than 10% in denitrification section.