Decarbonisation Technology - November 2023 Issue

Decarbonisation through innovation

Explore some of the latest available sustainable technologies

Flue gas analyser identifies leaking burner during normal operation

A number of years ago, a refiner in the US Gulf Coast had a vertical, cylindrical fired heater with a Thermox combustion gas analyser to measure excess oxygen and methane/hydrocarbons (using a catalytic detector). In one anomalous instance, the plant operators started seeing an alarmingly high methane/ hydrocarbon reading (of approximately 0.6- 0.7% by volume) in their firebox during normal operation, even though process was online and the heater was operating at high temperatures. A high reading of this type is unusual during the normal operation, which raised suspicion, leading the technicians to contact their local AMETEK representative for support. The representative visited the site and began diagnosing the analyser and performing multiple calibrations. They ran span gas to validate the measurement further, only to find that the readings were spot on – and all tests showed the measurement was solid. Something in the process was causing the high methane/hydrocarbon spike and affecting the reading. The refinery technicians investigated the

service, the high methane readings went away. Thankfully, the plant and the team were safe after this uncommon instance, although unwelcome methane emissions and process risk had occurred. Most operators do not expect unburnt fuel to be in the firebox because fired heaters typically operate at high temperatures – well above the auto-ignition temperature of methane. However, as this case study suggests, there are instances where pockets of unburnt fuel can exist, flow through the system, and become detected downstream by the flue gas analyser. Beyond a leaking burner, a high methane/ hydrocarbon reading can also occur from a loss of flame at the burner or a process tube leak during normal operation – in addition to an accumulation of fuel during start-up and light-off after insufficient purging between ignition cycles. In these instances, there may not be sufficient oxygen, turbulent mixing of the flue gases, or temperature to fully oxidise the pockets of methane and hydrocarbon within the firebox, prompting these high methane/ hydrocarbon readings and fuel-rich conditions. The use of a flue gas analyser to monitor for unburnt fuel, methane, hydrocarbons, and even hydrogen fuels in the firebox can ensure safe combustion control and reduced emissions even in the most unexpected of cases. Example of horizontal, natural gas-fired burners in operation

process further and did not find any visible issues that day. However, about a week later, the refinery was informed that plant operators had found a leaking burner on that heater, which was causing the very high methane readings. Once that burner was taken out of

The Thermox WDG-V combustion analyser


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