Understanding flares: Safety devices used in refineries and chemical plants

Frequently Asked Questions

What is a flare?
A flare is a safety device that burns excess hydrocarbon gases which cannot be processed. Excess hydrocarbon gases are flared as an alternative to releasing the vapours directly into the atmosphere.

If left unburnt, these excess gases could accumulate and form a concentrated flammable vapour cloud.

What happens when excess gases are sent to the flare system?
Under normal situations, the gases are combined with steam and burnt off in the flare system to produce water vapour and carbon dioxide.

The process of burning these excess gases is similar to the burning of liquefied petroleum gases (LPG) which some of us use as fuel for home cooking.

When does flaring occur?
Flaring can occur in the following situations:
a) During unplanned operational interruptions or emergencies when the gases must be immediately depressurised from the process to avoid overpressure and damage to equipment which could cause the release of hydrocarbon gases into the atmosphere.
b) For safe start up and shutdown of refineries and chemical plants when gases generated during these processes cannot be safely channelled back into the refineries' and chemical plants' processes or storage tanks.

Why do we sometimes see black smoke from the flare?
The black smoke, which is mainly made up of carbon particles, occurs as a result of incomplete combustion when there is insufficient amount of air to support the burning of gases sent to the flare system.

This may happen when there is a sudden release of excess gases to the system with a delay in response before sufficient steam can be supplied to the burning process.

Steam is usually added to the gases to increase turbulence in the gas flow. This increases air intake which is necessary for complete combustion to take place and to achieve a smokeless flaring.

Why do we sometimes see a huge white cloud from the flare?
The white cloud which you observe is steam that is injected into the flare system to support clean combustion. This helps to reduce smoke which results from insufficient steam in the burning process.

Why do I sometimes hear a rumbling noise during flaring?
The noise is a result of the turbulent mixing of vapours, air and steam during the flaring process.

This is similar to the sound that you hear when you fan a campfire with oxygen mixed with the flame.

What are the steps which ExxonMobil takes when flaring occurs?
ExxonMobil strives to minimise flaring at all but to achieve smokeless flaring when flaring is required.

In unplanned flaring situations, it may not always be possible to keep the flare smokeless.

If this is the case, the National Environment Agency and other government agencies are notified.

Are there any health concerns when flaring occurs?
Flaring takes place at an elevated height to allow for the safe disposition and dispersion of flare emissions. As such, it does not pose a health hazard.

Remember ... when you see the flares burning, be assured that their role is to keep the refineries and chemical plants running safely.