Flare stacks are used in many industries to burn
off unwanted waste gas byproducts, or flammable gasses released by
pressure relief valves during unplanned over-pressuring of plant
Applications include oil and gas well drilling
operations, oil refineries, chemical process plants, gas distribution
infrastructure, and landfills. In many cases, regulations require the
monitoring of a stack’s flame, or the pilot flame that ignites the
gasses, to avoid having unburned hydrocarbons enter the atmosphere.
|Thermal imaging cameras are an ideal monitoring
tool, since they allow automated remote monitoring on a 24/7 basis in
virtually any weather. In addition, thermal imaging cameras avoid many
of the technical and cost-related problems associated with other
technologies such as ultraviolet (UV) flame detectors, flame ionization
spectrometers, thermocouples, and pyrometers.
FLIR thermal imaging cameras
- Verify combustion, minimize unburned pollutant
- Instantly report loss of combustion with visual and audible alarms
- Provide remote visual monitoring with a TV or PC display
- Provide a quantitative temperature readout
- Can notify plant management via email and intranet connections
- Can be connected to a central control room via Ethernet
- Work day and night, seven days a week and in any weather
Flaring is a complex process
Flare systems are often a last line of defense
that prevents dangerous hydrocarbon pollutants from entering the
atmosphere. One example is methane, which is not only combustible, but
is also 23 times more potent than CO2 as a greenhouse gas.
A plant manager needs to know immediately if
flare stack combustion is lost, and get the flame reignited quickly to
prevent a plant shutdown.
Various technologies have been tried for
monitoring the pilot flame that ignites gas flow and detects the stack
flame, with varying degrees of success. Many of these technologies are
useless or poor at minimizing smoke from stake combustion, an important
indicator of burn efficiency.
One of the problems is that flare gas flows can
range from low volumes during fuel gas purges in normal operations, to
very large flows during emergency relief valve dumps or during total
plant blowdowns. The size and brightness of the resulting stack flame,
and the amount of smoke generated, depends on how much flammable
material is released. Assist gases such as air or steam may be injected
into the gas flow to improve combustion and help minimize smoke.
Although invisible to the naked eye a thermal imaging camera can monitor whether a flare is burning or not. If the flare is not burning, harmfull gasses can enter the atmosphere, an alarm can go off and immediate action can be taken.
FLIR thermal imaging cameras offer a solution
FLIR thermal imaging cameras recognize the
difference in the heat signature of a flare stack flame and the
surrounding background (usually, the sky or clouds). In addition to
detecting stack flame, these cameras can be positioned to monitor the
igniter flame. Typically, cameras are mounted on a pedestal or other
rigid structure in moisture resistant housings to protect them from
harsh weather conditions.
Schematical overview of a flare detection installation
The camera’s spectral response and calibration
allows it to see through moisture in the air to obtain a good image and
relative temperature reading of the flare stack or pilot flame. The
images obtained with FLIR thermal imaging cameras even allow an observer
to detect stack flame that might not be visible to the naked eye
because of its composition or low gas flow volume.
This overcomes problems associated with UV
flame detectors, which can be blinded by smoke. Thermal and visual
images can be transmitted in real time to a central control room as
either analog or digitized data.
In addition to visual monitoring of stack flame
and smoke, automatic control of the assist gas to waste gas ratio is
possible. When this ratio is properly adjusted, it improves combustion
and minimizes smoke. Upset conditions require immediate adjustment of
the air or steam volume to maintain proper combustion. As a bonus,
automated assist gas injection control can help avoid excessive steam
consumption, and provide significant cost savings.
|The FLIR A310 cameras provide several features
that facilitate automatic control. As a starting point, the camera
senses flame temperature and size, key elements in a control scheme.
This calibrated data can be communicated through the A310 Ethernet port
to a PLC or PC running the assist gas control program, using either a
wireless access point, fiberoptic cable, or CAT-6 Ethernet cable.
If data falls outside the user’s preset limits,
the camera can send alarm signals to the control room via the data I/O
port. In addition, A310 cameras can also be configured to automatically
send numerical data and images via Ethernet to a PC via e-mail (SMTP) or
FTP protocol whenever a data setpoint is reached, thereby creating a
record for subsequent review.
Flares invisible to the naked eye can be clearly seen on a thermal image.