Flare installed at our refinery is 200 ft tall.i have checked the design basis where following formula has been used (Designed in early 70's)
Cmax = W/(V*H2*M) (Reference : Lees' Loss Prevention in the Process Industries: Hazard Identification By Frank Lees)
Where,
Cmax = Max ground concentration (% Volume) (admissible limit is 3% by weight)
W = lb/hr
V = Miles per hour
H = Height
M = Molecular Weight.
On the basis of above formula the flare height calculated is 186 ft and our flare is 200 ft, it seems good.
However, when i have calculated flare height from API-521 formula by Hajek and Ludwig Equation by considering Heat radiation 6,31 (2 000) kW/m2 (Btu/h·ft2) the flare height value is >350 ft which seems very high.however i have checked flare height by different methods as well. In all methods the flare height is more than 300 ft.
At 200 ft flare height radiation level is very beyond the Permissible design level of thermal radiation.
My question is that how to encounter this problem ? Is criteria of Cmax is acceptable?
Thank you.
Edited by Arsal, 04 October 2016 - 02:54 AM.