To allow the combustion and destruction efficiencies of a flare system to be estimated, the molecular weight of the flare gas can be helpful. This is normally derived from the composition of the flare gas.
If taking a sample for laboratory analysis or on-line compositional analysis is not possible, then, if a gas ultrasonic meter is installed on the flare system and the speed of sound is available as an output, then the molecular weight of the gas can be derived as a direct relationship to the SoS.
How it Works
To derive MW from the SoS, we need to understand the relationship of SoS in an ideal gas, this is as follows:
This calculation can then be entered into either the flare meter controller/ flow computer or within the DCS / ICSS and the corresponding MW can be utilised to enable the calculation of the combustion and destruction efficiency.
Utilisation of the inference of MW from SoS is not a common application but can be used when no sampling or analysis facilities are available on the flare systems.
No Equipment costs
Minimal Maintenance costs
On-line continuous calculation
An assumption on the adiabatic constant must be made, based on the likely composition of the flare gas
No case study available at this time.
On-line analytical methods involve extracting a sample from a flare system via an automatic sampling system and analysing it continuously with a field installed analyser system.