Gas Measurement in Oil & Gas Processing

Most petroleum processing facilities use generated heat to run boilers for site power requirements, which involves measuring combustion air  flow and fuel  flow to boilers, and measuring stack exhaust gas. Many applications in the petroleum industry involve waste gas handling, emission monitoring, waste burning, vapor recovery, and odor control. Read article for full list of flow meter applications in the Oil and Gas industry.

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Petroleum Processing Plant Gas Metering Applications

Flare Gas
Excess gas which still contains hydrocarbons is sent to the stack to be burned. Waste gas is minimized because fuel is a valuable commodity and because expelled CO2 waste is measured as a pollutant.

Gas Characteristics:
Varying Composition, Errosive, Corrosive, Particulates
Primary Air
Oxygen is pumped into the furnace and burned with fuel to heat and liquify the crude oil. Careful measurement is crucial to ensure a proper fuel/air ratio for a clean and efficient burn.

Gas Characteristics:
High Volume, High Flow Rate
Secondary Air
Oxygen is pumped into the furnace above the fire ball to help completely burn noxious gases.

Gas Characteristics:
High Volume, High Flow Rate
Tertiary Air
Oxygen is pumped into the furnace above the fire ball to help completely burn noxious gases.

Gas Characteristics:
High Volume, High Flow Rate
Stack Gas
Hot gas is exhausted from the combustion chamber and recirculated back to the bottom of the furnace to be more completely burned, diverted to cogeneration stations or to heat exchangers. Once it has cycled through enough to remove maximum impurities it is filtered and sent to the stack to be released. Exhausting harmful gas is prohibited by environmental regulations so continous monitoring and measuring is required.

Gas Characteristics:
Hot, Particulates, Condensing, High Volume, High Flow Rate

Petroleum Processing Plant Gas Metering Instruments

Primary Air

Primary air is piped separately into the power plant combustion chamber, steam plant boiler and cracking plant distillation furnace. Each combustion location requires precise airflow measurement and air/fuel ratio control. In the distillation furnace oxygen is pumped into the chamber and burned with fuel to heat and liquefy the crude oil. Oxygen is also pumped into the combustion chamber above the fireball to ensure a more complete burn of fuel.

Combustion Gas

Excess hot gas is expelled from the furnace and recirculated to many applications in the plant. It may be piped back to the base of the furnace to be re-burned, used to preheat the incoming air or fuel, power recovery boilers and cogeneration systems. All these systems require combustion gas measurement and control. Air exiting the furnace is very hot and full of particles, corrosive and erosive compounds and moisture. This gas must be cooled and filtered before it is sent to the stack for release. With this dangerous mix of chemicals the stack must be constantly monitored for emissions.

Stack Gas

The act of burning hydrocarbons with oxygen creates water as carbon releases its hydrogen molecules which combine with oxygen to form H2O. Over decades the efficiency of combustion processes has lowered the average temperature of flue gas so condensation occurs lower down in the stack and less water vapor is emitted from the top of the stack. This condensate forms droplets of varying size that rain down in the stack. Ash particles, unburned fuel and carbon dioxide are present in the flue gas. Water and other gases in both vapor and condensed form are also present. The biphasic nature of condensate in the stack presents a gas flow that contains vapor, droplets and particles, all at high heat and traveling at a high rate and volume, flowing up with stack draft and falling down as rain.

Flare Gas

The petroleum distillation process produces many valuable materials at different temperatures. While most of these are collected and stored there is sometimes excess waste gases which must be flared off. A petroleum refinery may be processing many different distilled compounds in different storage locations. Emergencies may require rapid elimination of multiple process gases. For these reasons flare gas varies widely in composition and flow rate. Flare gas measuring instruments must be able to handle extreme variance in flow rate and widely differing gas compositions. Rapid, accurate reporting is required for safe and clean flaring operations.