A refinery at full capacity produces far more gas than it needs. It is not economical to capture it, clean it, compress it, store it, and finally transport it, so it’s flared off. Stringent federal, state, and local laws govern the flaring process. As time has gone on, the laws have become stricter with heavier fines for non-compliant companies.
A Challenging Application
The new EPA 40 CFR Part 63 rule, effective February 4, 2020, now requires oil engineers to provide flow measurement data on 20% of reading at velocities from 0.1 to 1 ft/s and 5% of reading greater than 1 ft/s. For Plant Engineers in the field, this is a very challenging application due to several factors:
- Very high turndown from 0.1 fps to 1000 fps during an emergency shutdown
- Constantly changing flare gas compositions
- Very low pressure drop (5 psig)
- Asymmetric flow profile, stratification, turbulence, pulsating flow (60” pipe header)
Multipath Ultrasonic flow meters for flare gas have been the traditional instrument used to report flow data to the EPA for compliance. However, there are issues with ultrasonic meters for flare gas that make it an unreliable choice to meet the new EPA 40 CFR Part 63 rule:
- Most of the installed base of ultrasonic meters have been calibrated to 1 fps prior to the new rule.
- Additionally, very low velocity is difficult for transit time due to small Delta T.
- CO2, H2 attenuate the signal, so ultrasonic meters cannot read to low flows in these gases
- Stratification causes reflection/refraction at the layer
- Turbulence reduces signal strength so the reading is not reliable.
EPA 40 CFR Part 63 requires flow measurement at much lower rates (0.1 sfps) and individual limits on gas constituents have been imposed. These changes require a gas analyzer and a flow measurement device that can handle low flow rates and changing gas compositions. What oil & gas engineers need to comply with the EPA rule is a mass flow meter with a very large turndown, low-pressure drop, ability to measure down to 0.1 fps and the ability to maintain accuracy even with changing gas composition. Easy integration into the current infrastructure improves speed to compliance and saves on costs.
Meeting EPA Regulations Head on with NEW qMix RealTime FMS System
With Sierra’s new QuadraTherm® qMix RealTime Flare Measurement System (FMS), for the first time a system based on thermal mass flow meters can adjust flow readings when flare gas composition changes within seconds to match real-time readings from a gas chromatograph-retaining accuracy without factory recalibration.
Now Plant Engineers have the perfect solution to comply with EPA Refinery Sector Rule 40 CFR 63 rule which requires refineries to measure and report flare gas measurement at flow rates as low as 0.1 sfps (0.03 smps) where traditional multi-path ultrasonic flow meters can’t operate.
The qMix RealTime FMS harnesses the accuracy and computational power of QuadraTherm thermal mass flow meters and proprietary qMix RealTime software.
Easy Integration to Your Current Process
The system integrates with current flow meters, infrastructure, and gas analyzer to give accurate flows over a wide 1000:1 turndown to meet the low end of EPA regulations at a fraction of the cost.
qMix RealTime FMS is made of three major components:
- QuadraTherm 640i/780i Thermal Mass Flow Meter
- qMix RealTime Software Application
- Window-based laptop computer (included)
When the gas composition changes, the qMix RealTime App, loaded onto the supplied laptop, reads the outputs from your gas analyzer for updated flare gas composition, then creates a new gas composition that is automatically uploaded to the 640i/780i.
With qMixRealTime FMS, users can connect, read, and update new flare gas composition from a gas analyzer-real time with no recalibration need. Engineers will also be able to set update frequency by time or by the percentage change in the gas composition.