Despite global oil production increasing by a half per cent, recent data from the World Bank revealed global gas flaring is in decline. Operators are becoming more conscious of the gas they are flaring and are willing to better utilise excess natural gas.
While flaring is decreasing, the data does not indicate whether the flaring that does still occur is efficient. This refers to the effective mixing of fuel and air, as well as appropriate ignition.
The common flare
Flaring involves the open-air burning of natural gas or the disposal of other waste gases produced in refinery processes. It is an important safety measure that helps dispose of excess gas during equipment failures, power outages and other operations emergencies.
Flaring is achieved when a metal pipe – known as the flare stack – ignites natural gas with a pilot light or electronic igniter. The fuel burns when reacting with oxygen in the air, producing water and Carbon Dioxide (CO2). An efficient flare does not produce visible smoke – as this indicates incomplete combustion. Complete combustion is the goal of flaring operations.
However, a common image in the flaring industry is one of plumes of black smoke.
What is a smoky flare?
Black smoke is a sign of incomplete combustion, which can be caused by wind, impurities in the fuel, or poor mixing with the air.
Incomplete combustion instead produces potentially harmful compounds such as: carbon monoxide, unburned hydrocarbons, Volatile Organic Compounds (VOC’s) and sulphur compounds. These products can have effects on public health – carbon monoxide affects people with heart disease and can harm the central nervous system.
EPA rules require that visible emissions are present for less than five minutes in any two-hour period
How do operators prevent incomplete combustion?
Key to preventing incomplete combustion is the correct mixing of air and fuel, and the continual presence of a source of ignition. Flare supplemental gas, steam and air can all be added to the flame to ensure ideal combustion conditions are produced. To ensure that gas is always burnt, flares should be operated with a pilot flame present. This needs to be monitored, although many facilities now use remote controlled or automatic electric igniters instead of pilot lights so there is no gas flared or flame visible except when the flare is burning. Maximum flare velocities are also set – at too high an exit velocity, the flame can lift off the tip and extinguish.
Most flare systems also use a liquids separator, known as a knockout drum. This removes water and petroleum liquids from the gas stream before it reaches the flare stack – allowing the flare to burn more efficiently.
To help ensure complete combustion at flaring sites, oil and gas companies will need to rely on accurate monitoring and measurement of natural gas.
One of the most accurate ways to measure flare gas is with ultrasonic technology. Fluenta’s FGM 160 Flare Gas Meter uses ultrasonic technology to effectively provide measurement data, allowing oil and gas companies to ensure flaring is performed efficiently.
For more information on Fluenta’s FGM 160 Flare Gas Meter, click here.