The refinery I work in has a 40 year old hydrotreating reactor with a very high design minimum pressurization temperature (MPT) of 120degC. it always takes ages to clear the MPT before we can proceed to the next step in the unit startup. We run our 2x recycle gas compressors which are fixed volume reciprocating compressors, loaded to 200%. The question I would like to ask is: is it better to have higher purity H2 for heating up? Higher H2 purity would mean less mass flow at constant volume. However, H2 thermal conductivity is way higher than other gases such as N2 or CH4, C2H6. The other school of thought is to bring in less pure H2 source to boost the mass circulation.
This is probably a heat transfer question also. Would like to hear if anyone has done any research on this.