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EnerFAQs 6: Flaring and Incineration
There are a number of methods for handling waste gases at upstream oil and gas facilities, the most common being combustion. Flaring and incineration are two methods of combustion considered acceptable by the Energy resources Conservation Board (ERCB). Historically, the most common type of combustion has been flaring. In recent years, incineration technology has emerged as another method of combusting waste gases. This EnerFAQs explains why flaring and incineration are sometimes necessary and how the ERCB ensures that flaring and incineration are carried out in a manner protective of public safety and the environment.
What are flaring and incineration?
Flaring and incineration are two technologies used to combust waste gases that are unable to be processed or sold.
-
Flaring
is the igniting of natural gas at the end of a flare stack—a long metal tube up which the gas is sent. This causes the characteristic flame associated with flaring.
-
Incineration
is the mixing and combusting of waste gas streams, air, and fuel in an enclosed chamber. Air and gas are mixed at a controlled rate and ignited. No flame is visible from an incinerator that is operating properly.
What emissions does the combustion of waste gases produce?
The emissions depend upon a number of factors. Ultimately, combustion efficiency determines the types of emissions. For example, high efficiency combustion ensures that nearly all methane is converted to carbon dioxide (CO
2
) and water vapour. If hydrogen sulphide (H
2
S) is included in the waste gas stream, nearly all of the hydrogen sulphide is converted to sulphur dioxide (SO
2
).
If the waste gas stream contains both methane and H
2
S, a lower combustion efficiency flare or incinerator may emit some H
2
S and methane as unburned products. Lower efficiency combustion can also result in other emissions, including black smoke and particulates. ERCB regulations of minimum combustion temperature and minimum heating value of the waste gas stream ensure that components in the waste gas, including but not limited to methane and H
2
S, are adequately combusted.
Does the use of incinerators result in less of an impact to the environment?
Flaring and incineration are two different technologies by which natural gas waste is combusted. Emissions depend on factors such as combustion efficiency and heating value of the gas being combusted. Generally, the higher the combustion efficiency and heating value, the lower the impact on the environment.
Many factors can affect combustion efficiency. For example, a flare stack exposed to windy conditions may perform at a lower efficiency than a stack that operates in calm conditions. However, due to their height, flare stacks often better disperse emissions into the atmosphere in hilly or mountainous terrain than do incinerators. Meanwhile, incinerators are not affected by wind conditions. A correctly operated incinerator can yield higher efficiencies through proper mixing, gas composition, retention time, and combustion temperature.
Properly designed incinerators can result in higher combustion efficiency than flares. However, incinerators can be affected by a narrow range of flow rates compared to flares and therefore have difficulty adequately dispersing emissions with higher H2S concentrations in the waste gas. It is important to select the combustion technology suitable for the particular application.
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What is combustion efficiency?
Combustion efficiency, generally expressed as a percentage, is essentially the amount of methane converted to CO
2
, or H
2
S converted to SO
2
. The more converted, the better the efficiency. Combustion efficiency can be affected by many factors, including meteorological conditions, operator competency, and waste gas composition.
For flares, the ERCB has requirements for the minimum energy content of the gas mixture (20 megajoules per cubic metre), which has been shown to result in higher combustion efficiencies. If a waste gas stream contains low amounts of hydrocarbons, fuel gas must be added to allow the mixture to combust efficiently.
To ensure combustion efficiency for incinerators, the ERCB requires that the stack top temperature is maintained at least 600 Celsius or higher and have a minimum residence time (the time the gas remains within the incinerator before being released to the atmosphere) of 0.5 seconds. Incinerators equipped with refractory lining—which help contain most of the combustion heat and control the combustion airflow into the incinerator—can increase combustion efficiency. Properly designed incinerators can achieve very high combustion efficiency.
The ERCB requires all waste gas combustion technologies, including those for SO
2
, to be designed to comply with the Alberta Ambient Air Quality Objectives.
What are the Alberta Ambient Air Quality Objectives?
The Government of Alberta has set out acceptable minimal levels of safety and environmental protection related to air quality. These are called the Alberta Ambient Air Quality Objectives and are among the most stringent in Canada.
What are the ERCB's regulations regarding flaring and incineration?
The ERCB regulates flaring and incineration through performance and reporting requirements, permits, and data collection, as detailed in
Directive 060: Upstream Petroleum Industry Flaring Guide
.
A permit is required for well test flaring or incineration when the waste gas contains more than 5 per cent H
2
S or the total well test volume exceeds 200, 400, or 600 thousand cubic metres, depending on the type of the well.
The ERCB requires companies to evaluate flaring and incineration at existing facilities and determine if the gas should be conserved. The operators are expected to consider the following:
- Are there residents in the area?
- Are there directly affected local residents with environmental or health concerns?
- Are there economic alternatives to burning the gas?
- Would clustering of flares be economically viable?
- Are the environmental impacts of eliminating or reducing flaring greater than the environmental benefits?
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Are companies required to notify the ERCB and residents prior to flaring or incinerating?
Prior to planned, as opposed to emergency, flaring or incineration, operators are required to provide 24-hour advance notice to the appropriate ERCB Field Centre, to all residents within a 3 kilometre (km) radius for sour gas well tests and to all residents within a 1.5 km radius for oil well tests (regardless of the H
2
S content) and sweet (containing no H
2
S) gas well tests.
Additional "good neighbour" notification, including notice for short-duration events, should be conducted if members of the public have identified themselves as being sensitive to emissions from the facility or if they are interested in receiving notice of planned flaring or incineration for other reasons.
The ERCB expects operators to provide an information package to the public prior to planned flaring or incineration. The information package must include
- company name and contact information,
- location of the test flaring or incineration,
- duration (start date and latest expected completion date),
- expected flaring or incineration volumes and rates,
- information on the type of well (oil or gas) and, if applicable, information on the H
2
S content of the gas to be burned, and
- telephone numbers of operator and ERCB Field Centre contacts.
How are flaring and incineration complaints handled?
The ERCB expects the operator to address any concerns raised by the public prior to flaring or incinerating. If, after reasonable attempts, outstanding concerns remain unresolved, the operator or the public may request the assistance of the appropriate ERCB Field Centre (see list on last page).
In situations
where a flaring or incineration permit is required
or where an application has been made for such a permit and your concerns have not been addressed by the operator, you may submit a written objection to the ERCB. The Board will consider the objection to the application.
In situations where a
flaring or incineration permit is not required
and your concerns have not been addressed by the operator, you may contact the appropriate ERCB Field Centre. ERCB staff will then respond to the inquiry according to established procedures. If the operator is in compliance with Directive 060 and has appropriately considered any unique circumstances related to the flaring or incineration and Field Centre staff have determined that all procedures for the planned event are acceptable, it will be allowed to proceed.
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