As the EPA works towards additional methane regulations, the emphasis on compressor emissions will increase. Methane is a greenhouse gas with over 20x the global warming potential as carbon dioxide. Technologies must progress to ensure oil & gas companies meet the growing requirements of regulatory committees and monitor their methane emissions accurately.
Gas Flow Measurement Challenges
A leading oil & gas company required a gas flow measurement technology that could accurately measure natural gas flow rates at their compressor stations. One of the applications of interest was measuring vent gas emissions from the packing systems of compressors. This application not only required flow measurement at very low flows and low pressures, but the capability of achieving high turndown as well. Emissions can tend to increase over time as components wear, thus increasing the potential flow rates. Any instrument measuring these flow rates would need to be able to track any potential increases.
Flow Meter Solutions for Monitoring Methane Emissions
Magnetrol® produces a thermal mass flow meter, the Thermatel® Model TA2, that is based on thermal dispersion technology. The TA2 measures air and gas flow directly and has excellent low flow sensitivity, as well as high turndown ratios. Turndown is the range that the flow meter is accurate within. Most thermal mass flow meters offer 100:1 turndown, which is a drastic improvement over most technologies such as differential pressure, but certain applications demand greater. This presented an improvement opportunity for the TA2.
Since the TA2 is capable of holding multiple calibration curves, users requested added functionality of these features. To meet this need, MAGNETROL developed auto switching to fully utilize two distinct calibration curves. Auto switching will automatically alternate between a low flow curve and a high flow curve to maximize data in the customer flow range and extend the turndown. This ensures optimal performance at both low flows and the abrupt high flow (upset) condition or an increase in flow over time due to degradation of components. Plants can trust that the methane emissions levels they report are accurate because the TA2 is able to measure low and high flow rates with precision.