Stack sampling for different contaminants requires state-of-the-art technology. For such an endeavor, an even flow profile at all sampling points is necessary. This latter parameter allows for representative results, which is critical to conform to environmental regulation in effect.
Indeed, government authorities require the use of isokinetic stack sampling methods. To that effect, only an even flow will comply to this requirement. Such a flow profile will show parallel flow lines of equal speeds. The flow will only be recognized as such if actual of flow lines are within ± 20% of the average speed. Also, the ratio between maximum and minimum speeds cannot be greater than 3:1.
However, in some cases an isokinetic sample is not possible, such as when a non conventional stacks is at work. For example, this will occur when the stack height is not enough to create a turbulent flow. In this case study, the work was equiped with a short stack that had three independant inlets, which led to the formation of vortices instead of am isokinetic profile. Here, isokinetic sampling was not possible.
The goal in this project was to create an even flow profile in the stack to enable standard sampling. The challenge was thus to design mechanical attachments which, once installed in the stack, would render a uniform flow at the sampling point.
Stack flow modeling
Ore furnace off-gas processing