Our customer experienced severe dust lumping issues in the plant's basic oxygen furnace and enlisted our CFD expertise to reduce maintenance downtime and optimize the overall process.
In the steelmaking process, a basic oxygen furnace (BOF) refines molten pig iron and scrap into steel. This process typically involves multiple stages, but starts with scrap and molten pig iron entering a blast furnace. During this process significant ash, soot and other pollutants are generated and enter, through a duct, the BOF's evaporative cooling tower. Here, the gas enters the tower's apex where it is quickly and powerfully cooled by a spray via nozzle lances. The polluted dust then falls to the tower's base where it's incinerated. If the nozzle lance layout is not optimal, as was the case with our customer, severe dust lumping occurs, where spray that does not evaporate sticks to the wall and collects dust. Our task was to design an optimal nozzle layout to match the gas flow field, while minimizing wall wetting in short time and space domains.
Conventional nozzle layouts place six injectors at evenly spaced increments along the circular cooling tower wall just as the gas enters the tower. Rather than follow conventional rules, as this was clearly causing our customer severe problems, we sought to answer questions such as: How should we layout the nozzles? At what depth should they be inserted for this particular tower? Is there an optimal injection and spray angle? We then meshed the entire tower, the inlet and exit ducts, and the nozzle lances. This allowed our CFD software to perform advanced flow mechanics calculations at small, finite points throughout the entire application. We could then assess both what was happening during the current process, as well as, the nozzle layout design that would optimize the evaporative cooling application.
When we visualized the spray plume colored by temperature gradients, we found that six nozzle lances situated at close intervals directly opposite the gas inlet effectively avoided wall wetting caused by entrained gas. Furthermore, this nozzle layout greatly reduced the particle mass wall impingement, as shown by the low predicted particle concentration throughout the evaporation tower in this image.
Using our modeling services, this company benefited from an analysis of the current situation, revealing why dust lumping was such a significant issue, as well as a much improved solution. Moreover, the project benefited from the measured data collected in our labs, which validated the overall nozzle layout solution. In environments like this, where physical testing is impossible, our CFD services offer a solution unmatched by other modeling software.