AC Flare Systems
Simple elevated flares with visible flames and minimal control over the combustion process
- open flame, elevated flare
- pre-aerated flame
- manual flame temperature control
- low luminosity
- operator control of flame height
- Flow rate in this standard range : 250 to 10,000 Nm3/h
- Pressure rise across gas booster : 150 mbarg (approx)
- Flame temperature : 800 to 1000oC
- Retention time : Not specified
- Minimum methane concentration for combustion to be sustained : 20%
The AC range of flare stacks is designed to offer a degree of control over the combustion process in an elevated flame burner. The burner tip design is based upon the principle of pre-aerated combustion giving the option of a short sharp, non-luminous flame, as opposed to the yellow-tipped long lazy flame typical of diffusion burners.
Flame temperatures are controlled in the range of 800 to 1000oC, depending upon the methane concentration, flow rate and prevailing wind conditions.
Ignition is automatic upon start up and re-ignition upon flame failure will be automatic for an operator adjustable period.
The unit may be run as a dispersal and vent station, should gas levels be such that combustion cannot be maintained.
The operator has the further option of running the unit in the "run on" mode. Upon flame failure the unit will attempt re-ignition for an operator set period and then continue running as a vent, should re-ignition not be successful.
This latter feature is particularly useful when methane levels are dropping and it is important to keep migration control active regardless of whether combustion is occurring or not.
Whilst this unit is designed to provide greater control over the combustion process it is not able to provide the flame temperature control that is required by certain emission standards now coming into force.
With an elevated flare there is essentially no control possible over secondary combustion air, that air which mixes with the combustion gases after the burner port, and the dilution factor will vary with, for example, wind conditions.
In certain ambient conditions a flame temperature of 1,000oC can be held with reasonable stability but, if methane percentage is low and wind speed is high, it will be very difficult to approach this figure.
It is certainly not possible to obtain extended residence times at elevated temperatures with an elevated flare.
This is a factor governing all types of elevated flare system.
For flares which meet combustion conditions required by current standards it is necessary to move up to the SC Range, the MC Range and the RB Range of flare units.