Methanol Reformer furnace Tube Skin Temperature

[MIANCH]

Hi All,
Problem: Methanol Plant Steam reformer Tube rupture.
Our operation department requested that, provide furnace trip logic on high tube skin temperature, I have not seen justification for furnace tripping on high skin temperatures.
Can anyone here, advice how to deal with such demand of operation guys.
Regards

 

[Dhurjati Sen]

This is a common practice for hydrogen reformer furnaces. I guess the tube material is a high nickel cobalt casting, same as that of above.

DHURJATI SEN
Kolkata, India

 

[georgeverghese]

This is a primary operating concern for steam reformers. High tubeskin temp at hot spots reduces tube life, and is caused by flow maldistribution inside the tube or poisoning of the nickel catalyst at that location. This is due to the fact that the reforming reaction is highly endothermic( ie the process absorbs heat). Localised flow maldistribution can also be due to local disintegration of the catalyst pellets which in turn results in lower flow ( less heat absorbed) at that location. You should do everything you can to prevent hot spots on these expensive Hastelloy reformer tubes. Beware of temp measurement errors when using IR pyrometers (IR "guns").

 

[MIANCH]

Hi
What is the reasons of mal-distribution and how it can be avoided. furnace tripping on high skin temperature will damage more tubes in reformer because of expansion and contraction of catalyst.
Regards

 

[georgeverghese]

Local flow maldistribution is due to attrition of the catalyst pellets - can be due to poor loading procedures during commissioning, poor startup practices,. Talk to your catalyst supplier for other reasons also. Agreed, nickel catalyst is expensive but can be replaced at short notice, but reformer tubes are even more expensive and almost impossible to replace.