| What is a flare?
A flare is a tall stack equipped with a burner,
used to destroy any excess gases produced by refineries, sulfur recovery plants,
and hydrogen production plants. Flare systems are in operation all of the
time. Most of the time these systems are in standby mode, ready to
combust gases as soon as they enter the flare.
How do flares work?
Oil refining is a dynamic process. Temperatures, pressures and other
processing conditions are carefully controlled to maintain steady-state production
operations. When
operating conditions in a refinery, sulfur recovery plant, or hydrogen
production plant cause the pressure in the plant to rise, valves automatically
open to divert the gases to the flare. There, the burning of excess
hydrocarbons yields water and carbon dioxide.
What does flaring look like?
A pilot flame must be lit whenever a flare is in operation so that purge
gases (used to keep air out of the flare) and vent gases can be readily
combusted. The pilot flame is located at the tip of the flare. When vent gases are combusted in a flare, a
larger flame is
generally visible at the flare tip. Sometimes steam, which is used to
help burn the vent gases completely, is also seen at the flare tip.
However, during a flare event when steam cannot be added to the system
quickly enough, or if the smokeless capacity of the flare is exceeded, smoke may also be visible at the
edge of the flame.
What is the difference between smoke and steam?
Smoke is combustion-generated particulate matter which becomes entrained
in air; the smaller the particle, the longer it is likely to remain
suspended in air. Suspended particulates obscure visibility by refracting
(bending) and scattering light. Measuring the density of these
particles against a reference standard provides an indication of relative
opacity. Whenever smoke is generated during a flaring event, it appears
immediately downstream of the flame.
Steam is condensed water vapor that is added to the flare to increase
turbulence, thereby improving combustion of vent gases and reducing the
potential for smoking.
What kinds of emissions are vented from flares?
Flare emissions can include oxides of sulfur (SOx),
oxides of nitrogen (NOx),
particulate matter (PM10),
carbon monoxide (CO), and reactive organic gases (ROG) including Volatile
Organic Compounds (VOC).
Under what circumstances does flaring occur?
During an emergency caused by an equipment breakdown, power outage or
other upset beyond a refinery's control, flares are used to safely burn compressed gases
that could otherwise pose potential risks to workers, the community or the
environment.
Flares are also used to ensure safety during the startup and shutdown of
refinery equipment when gases generated by those processes cannot be safely
recycled into the refinery.
Flaring is allowed as necessary during emergencies, but flaring for any
other reasons is controlled by AQMD
Rule 1118 - Control of Emissions from
Refinery Flares (96.4 Kb pdf).
How many flares fall within AQMD's jurisdiction?
Every petroleum refinery operating within the AQMD's jurisdiction has one
or more flares to control emissions from process units, storage vessels,
loading operations (such as trucks) and some waste water processes. At
present, 29 such flares are in operation at the seven petroleum refining
facilities (at eight locations), two hydrogen plants and one sulfur
recovery plant located within
the South Bay region of Los Angeles County.
How can I find out about flare events when they occur?
Facilities with flares maintain 24-hour telephone
numbers available to the public to answer questions about flares and
flare events.
In addition, these facilities are also required to
notify AQMD of all
planned or unplanned flare events that
exceed or may exceed either 100 pounds of volatile organic compounds (VOC)
or 500 pounds of sulfur dioxide released, or which may exceed 500,000
standard cubic feet of vent gas.
How can I access technical data that show when and how much flaring
has occurred?
Rule 1118 requires operators of flares subject to its requirements to monitor
vent gas during flaring
events and submit the recorded information to AQMD on a
quarterly basis.
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