HiOXY Measurement of Methane Gas
Goal:
To measure oxygen for the purpose of detecting methane gas.
Hardware Used:
• Phase Fluorometer Electronics (MFPF)
• Bifurcated Fiber Optic Cable
• HiOXY-R Sensor.
Abstract:
This application note explains how partial pressure of oxygen is measured even in the presence of gases like Methane.
Background:
Methane is a chemical compound with the chemical formula CH4. It is the simplest alkane, and the principal component of natural gas. Burning methane in the presence of oxygen produces carbon dioxide and water. The relative abundance of methane makes it an attractive fuel. Several oil companies have approached Ocean Optics to provide a solution of measuring oxygen in the presence of Methane.
The HiOXY oxygen sensor design by Ocean Optics was tested for this application.
Feasibility Test Procedure:
The MFPF electronics is an instrument platform for measurement of fluorescence lifetime and phase. This frequency domain electronics uses a blue LED excitation and a photodiode for detection. A fluorescence method is used to measure the partial pressure of dissolved or gaseous oxygen. A bifurcated optical fiber carries excitation light produced by the blue LED to the thin-film coating of the Hioxy-R sensor. Fluorescence generated at the tip of the probe is collected by the probe and carried by the optical fiber to the detector of the MFPF. The phase shift between the blue LED excitation and emission signal of fluorescence is used to calculate the lifetime. The Lifetime is an essential parameter for the calculation of oxygen.
A short term feasibility test has been performed using HiOXY sensor in Methane gas.
The chart below first shows the response of the HiOXY sensor in Nitrgoen and Air first. The sensor is again exposed to nitrogen and a small flow of methane is introduced. There is no observed change in the lifetime due to the introduction of methane in the nitrogen flow.
The sensor is now exposed back to air to see if there are any effects or changes caused in the lifetime due exposing the sensor to Methane gas. It is observed that there is no change in the lifetime in Air. A small flow of Methane is introduced in the air stream and a slight increase in the lifetime caused from the methane.
When only methane is exposed to the sensor, it behaves in the same way as nitrogen as the sensor does not see any oxygen.
In conclusion, the HiOXY sensor can be used to measure oxygen in the presence of Methane gas without affect the intensity or the lifetime of the sensor.
