 Flares are used at oil and gas facilities to safely dispose of excess gases through combustion. However, flaring wastes valuable energy resources and contributes to air pollution and greenhouse gas emissions. Flare gas recovery systems aim to reduce flaring by capturing and processing these gases.
What are flare gases?
During oil and gas production, transportation and processing, some amount of associated gas is produced along with liquids. This associated gas contains light hydrocarbons like methane which cannot be separated and recycled back into the production system due to limitations in gas handling capacities of facilities or during plant upsets. This surplus gas is burned through flares to dispose it safely. Flare gases are a mixture of hydrocarbon gases like methane, ethane, propane etc and some amount of nitrogen, carbon dioxide and hydrogen sulfide.
How do flare gas recovery systems work?
A Flare Gas Recovery System consists of a header system to collect the flare gas from multiple sources, a compressor to boost the pressure, removal of impurities like sulfur and moisture, gas cooling and liquid separation systems. The treated sales gas is then compressed and fed into the gas transmission pipelines for sales. Some systems also have the provision to recover valuable condensate liquids from the flare gas stream. Advanced digital control systems aid in efficient operation of the recovery units.
Benefits of flare gas recovery
Recovering flare gases helps facilities optimize gas utilization. It leads to reduced operational costs by monetizing an previously wasted resource. Significant greenhouse gas emissions reductions can be achieved by minimizing flaring. Captured gases can be used as a low-cost fuel within the facility or sold for revenue. Local communities also benefit from reduced air and noise pollution levels. Regulatory compliance is ensured by minimizing flaring. Overall, recovery systems improve profitability, sustainability and environmental performance of oil and gas operations.
Key components of a flare gas recovery system
Header and Gathering System: A network of pipes collects low pressure flare gases from multiple sources into a centralized header.
Compressor: Reciprocating, centrifugal or screw type compressors are used to boost the pressure of raw flare gases to pipeline conditions.
Dehydration: Glycol dehydration removes bulk of water vapor to avoid hydrate formation downstream.
Amine treating: Amines like MDEA selectively remove acid gases like H2S to low ppm levels for corrosion control and pipeline regulations.
Refrigeration: Joule-Thomson valves or chillers cool and condense heavy hydrocarbon liquids and water.
Storage: RecoveredCondensate is stored in tanks prior to trucking away. Sales gas is treated as per downstream pipelinespecifications.
Controls: PLC/DCS automates operations, monitors quality and optimizesperformance of recovery units for maximizedthroughput.
Instrumentation: Analyzers, flow meters and safety instruments precisely measure andcontrol allcriticalprocessparameters.
Power Generation: Recovered gases can fuel engine-generators to meet facility power needs.
The need for effective flare gas recovery has never been more important from economic and environmental viewpoints. Technologies now exist to prevent waste and liability by monetizing what was once considered useless emissions from oil and gas operations.
