Basic Elevated Flare Design Considerations
Per 40 CFR 60 AP 42 TCEQ
Over 100 years experience designing flares!
Flares must always have a minimum heat content in btu/scf:
- Steam-assisted - 300 btu/scf
- Air-assisted - 300 btu/scf
- Non-assisted - 200 btu/scf
- Tip exit velocity is limited based on BTU content in the flare stream.
- Tip exit velocity is the velocity of the gas stream at the point where it exits the flare tip, not in the flare header itself.
Steam-assisted and non-assisted flares:
- 300 Btu/scf = 60 fps maximum
- Greater than 1,000 btu/scf = 400 fps maximum
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Steam-assisted and non-assisted flares:
- Log10(Vmax)=(HT+28.8)/31.7
- Vmax=maximum velocity (m/sec)
- (note: never exceed 400 fps)
- HT=net heating value (MJ/scm)
Air-assisted flares:
- Vmax=8.706 +0.7084(HT)
- Vmax=maximum velocity (m/sec)
- HT=net heating value MJ/scm
Types of flare pilot monitors include
(all flares must have a continuous pilot when in operation):
- Thermocouple
- IR scanner
- Video camera
Open elevated flare system testing:
- Sample at inlet to flare stack
- Measure flow rate to the flare
- Sample and determine Btu content
- 98% Destruction efficient by definition
Low BTU Gas - enrich before sampling point and prove enrichment by:
- Fixed ratio injection assuming 0 BTU content
- On line monitoring and gas control
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