5 replies to this topic

[Bee5]

I am working on an assignment in air dispersion modelling. Please not - I am not using software but rather calculations in order to gain understanding of the theory.I am struggling to model the area source. We have been given a 100m x 100m area source where spontaneous combustion of 3% Sulphur coal takes place, which is located approximately 400m from a village. We have to model the worst case concentrations. My questions are:

• Do area sources have a plume rise?
• Do the coal and the sulphur in the coal start combustion at the same temperature? i.e. If combustion of coal begins above 230 degrees celsius, will the sulphur ignite with it, or would it have ignited already at a lower temperature? i.e. at which temperature will SO2 formation begin?

Thank you
Bjanka

[Steve Hall]

I think I can answer your first question: No. As you must know, the dispersion models use plume rise along with the atmospheric conditions to place the source into a category (A through F) and then estimate ground concentrations at specific distances and direction from the source. The plume rise is determined primarily from the velocity through -- it is assumed -- a stack. Since your area source is at ground level, its only vertical velocity is imparted by the atmospheric conditions. For example, in windless conditions and no cloud cover you would expect the smoke to rise straight up, but with wind and heavy cloud cover you would expect it to travel horizontally near to the ground. Imagine images of small forest fires.

[breizh]

You might consider this document to support what Steve explained :
http://chemengineeri...ersion modeling


Breizh

[Bee5]

Thank you very much. I read the document.

Do you have any advice on at which temperature SO2 formation will begin? This is more for interest since temperature is not a necessary parameter unless you have plume rise.

[breizh]

Bjanka ,
Consider this resource about the hazard of SO2 :

http://www.georgiagu...r.com/fires.htm

Breizh

[Bee5]

Thank you!