4 replies to this topic

[abbaschemical]

Dear all,
I find in the Material Specification sheet of Cold box unit of the PGHRU(Purge Gas Hydrogen Recovery Unit) that "Copper, Brass and its alloy are strictly prohibited". I found from property of copper that it is has a high degree of ductility. So contractory to its property why the statement would have arised? Is there anything to deal with Thermal Conductivity?

[Bobby Strain]

I'm not sure that the references will provide your answer. Copper and its allows are usually prohibited where olefins, dienes, acetylenes and other compounds are present in the gas stream. They will react under certain conditions with copper, and when warmed become explosive. But low level copper allows are not necessarily a problem. And I believe that copper is used in manufacturing the brazed aluminum heat exchangers that are used in the hydrogen recovery process. You can ask your equipment provider.

Bobby

[Technical Bard]

Is it possible you have sulfur species in the gas? If so, that would explain it.

[abbaschemical]

there is no sulphur in the feed gas......

[Pilesar]

There are no bolted flanges inside a cold box because it is intended to never need internal inspection or maintenance. All piping inside the box is welded. Welded dissimilar metals are prone to corrosion due to electrical activity. Sometimes all piping and equipment are made out of aluminum, but then this leaves aluminum flanges outside the fire-safe region of the cold box. So for fire protection reasons, the aluminum to steel transition is usually made inside the box. Everywhere stainless and aluminum connect inside the cold box, special bimetallic transition joints are used at the welds. These transition joints are explosion bonded to virtually eliminate additional electrical resistance.