If you’ve ever driven past an oil refinery, you’ve probably noticed a tall stack with a bright flame burning at the top.
For many people, it raises the same questions:
- Is something on fire?
- Is the refinery wasting fuel?
- Is the plant having an emergency?
The truth is much less dramatic.
In most cases, the flame is completely normal—and it’s one of the most important safety systems in the entire refinery.
Without flare systems, modern refineries, gas plants, and petrochemical facilities couldn’t operate safely.
Let’s look at why these flames exist and what they’re actually doing.
What Is a Refinery Flare?
A refinery flare is a controlled combustion system designed to safely burn excess hydrocarbon gases.
Instead of releasing flammable gases directly into the atmosphere, operators send them through large pipes to a flare stack, where they’re burned in a controlled manner.
Think of it as the refinery’s pressure relief valve.
Just as the pressure relief valve on your home’s water heater protects it from excessive pressure, the flare system protects an entire industrial facility.
Why Can’t the Gas Be Released Directly?
Hydrocarbon gases are highly flammable.
If large amounts of methane, propane, hydrogen, or refinery gas were simply vented into the atmosphere, they could create an explosive cloud.
Burning the gas converts most hydrocarbons into carbon dioxide and water vapor, making it a much safer option than releasing raw fuel gas.
Flaring also reduces emissions of methane, which is a much more potent greenhouse gas than carbon dioxide over the short term. That’s why environmental regulations generally prefer combustion over routine venting where it can be done safely.
When Does a Refinery Use the Flare?
Contrary to popular belief, flares are not used only during emergencies.
There are several situations where operators send gas to the flare.
1. Plant Startups
When a refinery starts up after maintenance or a turnaround, process units are gradually brought online.
During this period, off-specification gases and excess hydrocarbons are often routed to the flare until normal operating conditions are reached.
2. Plant Shutdowns
During planned shutdowns, equipment must be depressurized before maintenance crews can safely begin work.
Rather than venting those gases directly into the atmosphere, they’re safely burned in the flare.
3. Equipment Upsets
Even well-operated plants occasionally experience process upsets.
Examples include:
- Compressor trips
- Pump failures
- Power outages
- Instrument failures
- Unexpected pressure increases
If pressure rises beyond safe limits, pressure relief valves automatically direct gas into the flare system.
This protects equipment from damage and helps prevent dangerous overpressure conditions.
4. Emergencies
During an emergency shutdown (ESD), large amounts of hydrocarbon gas may need to be removed from process equipment quickly.
The flare provides a safe location to dispose of that gas while protecting personnel and equipment.
Large flames during emergencies often look alarming, but they’re usually a sign that the refinery’s safety systems are working exactly as designed.
Why Is the Flame Always Burning?
Many people assume the flame stays lit because gas is constantly being burned.
That’s usually not the case.
Most flare stacks have a pilot flame that burns continuously.
The pilot works much like the pilot light found on older gas furnaces or water heaters.
Its job is simple:
If gas reaches the flare stack, it ignites immediately.
Without a pilot flame, unburned hydrocarbons could escape into the atmosphere before ignition occurred.
Modern facilities continuously monitor these pilots using flame detection systems to ensure they’re always operating correctly.
What Happens Inside a Flare System?
Although the visible flame gets most of the attention, the flare stack is only one part of a much larger system.
A typical refinery flare system includes:
- Pressure relief valves
- Flare headers
- Knockout drums
- Liquid seals
- Steam or air assist systems
- Pilot burners
- Ignition systems
- Flare stack
Each component plays a role in ensuring that gases reach the flare safely and burn efficiently.
One important piece is the knockout drum.
Before gases reach the flare, this vessel removes liquids that could damage equipment or create unstable combustion.
Why Are Some Flames Black?
Sometimes refinery flares produce thick black smoke.
This usually indicates incomplete combustion.
Black smoke forms when there isn’t enough oxygen to burn all of the hydrocarbons completely.
To reduce smoke, many modern flare systems inject steam or air into the flame.
This improves mixing with oxygen and helps produce cleaner combustion.
A well-adjusted flare often produces very little visible smoke.
Why Is the Flame Sometimes Huge?
One day the flare might barely be visible.
The next day it may look like a giant torch.
Several factors affect flame size:
- Plant startups
- Planned shutdowns
- Maintenance activities
- Process upsets
- Emergency depressurization
- Increased gas flow
A larger flame doesn’t automatically mean something has gone wrong.
In many cases, operators are carrying out planned work.
Are Refinery Flares Bad for the Environment?
No industrial combustion system has zero environmental impact.
However, flaring is generally considered much safer than releasing raw hydrocarbon gases into the atmosphere.
Modern refineries work to minimize routine flaring through:
- Improved process control
- Better equipment reliability
- Vapor recovery systems
- Leak detection programs
- Preventive maintenance
Many countries now require facilities to monitor and report flare emissions as part of their environmental compliance programs.
Why Don’t Refineries Capture All the Gas?
It’s a reasonable question.
If the gas has value, why burn it?
The answer is that safety always comes first.
During normal operation, refineries recover and use as much fuel gas as possible.
But during sudden pressure increases or emergency situations, operators don’t have time to compress, store, or process every cubic metre of gas.
The flare is designed for those situations where protecting people and equipment is more important than recovering every bit of fuel.
Common Myths About Refinery Flares
Myth: The refinery is wasting fuel.
Reality: Most flaring occurs for safety reasons or during temporary operating conditions.
Myth: A large flame means the refinery is on fire.
Reality: A large flare often means pressure is being safely relieved.
Myth: The flare burns continuously because the refinery can’t stop it.
Reality: The small pilot flame remains lit so the system is ready whenever it’s needed.
Myth: Refineries could simply turn the flare off.
Reality: Operating without a flare would remove one of the facility’s most important safety systems.
Interesting Facts
- Some refinery flare stacks exceed 150 metres (500 feet) in height.
- Steam-assisted flares can reduce visible smoke during high flow events.
- Offshore platforms also use flare systems to safely dispose of excess gas.
- The bright flame you see is only the visible end of an extensive pressure-relief network throughout the refinery.
Final Thoughts
To most people, a refinery flare looks like wasted energy.
To an operator, it’s something very different.
It’s the final layer of protection that safely handles excess hydrocarbons when process conditions change unexpectedly.
Whether the plant is starting up, shutting down, or responding to an upset, the flare allows operators to protect workers, equipment, and the surrounding community.
So the next time you see a flame rising above a refinery, remember: it’s usually not a sign that something has gone wrong.
More often than not, it’s a sign that one of the refinery’s most important safety systems is doing exactly what it was designed to do.
Frequently Asked Questions
Why are refinery flares so tall?
The height helps disperse heat and combustion products away from personnel, buildings, and equipment while improving safety.
Can refinery flares be turned off?
The pilot flame normally stays lit, but the main flare burns only when gas is routed to the system.
Why do refinery flares make noise?
High gas flow rates, steam injection, and combustion turbulence can create the roaring sound often heard near flare stacks.
Do all refineries have flare systems?
Nearly all modern refineries, gas processing plants, LNG facilities, and petrochemical plants have some type of flare system because it is a critical part of process safety.