-100degC to 100degC
Sounds like a stainless steel line, lots of straight run, correct?
What flow rate range or ranges? Flare applications often require extreme turndown to indicate the sweep and some normal venting - and to cover major blowdown releases. Turndown is a significant issue with selecting the type of flow meter or meters.
What pipe size?
How accurately?
What ambient?
I assume electronic.
I have seen multiple range thermal mass flow meters in flare applications except not that cold.
The head type flow meters have less turndown than some technologies. The annubar is an example of a head type flow element. We accept higher claims for turndown these days due to the high transmitter accuracy. In a warm climate the temperature is not a significant factor. Mount the transmitter two meters from the element and the transmitter is not exposed to the extreme cold. However, if this is Siberia then heat trace may be the solution.
There are many choices for other technologies. These include vortex shedders, ultrasonic transit time transmitters, etc.
Corriolis meters might be good for cold service but not big flow.