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Linden based Hydrogen unit, NG is using as feed for hydrogen generation. There is a hydrogenation reactor with COMOX catalyst where hydrogenation reaction takes place after that desulfurization reaction in next reactor with ZNO catalyst. NG feed having no sulfur and we operate the hydrogenation reactor in line for many hours. Since there is no S in NG feed no H2S formation will occur in that reactor. Catalytic reaction will not occur. As per requirement, we take sometime RFG (refinery fuel gas) , which having sulfur content for Hydrogenation reaction in COMox based reactor. My question is this type of feed variation, deactivated catalyst may work after taking RFG feed or how we can make activate COMoX catalyst when NG feed in line alone.
21/02/2019 A: Peter Marsh, XBP Refining Consultants Ltd, peter.marsh@xbprefining.co.uk
It is important to maintain the hydrotreating reactor CoMo catalyst in the sulphided state to prevent reduction to elemental metals as this would enable hydrocracking of any heavy ends in the NG stream at reactor inlet temperatures as low as 350 Deg C. Hydrocracking reactions will cause a temperature excursion with potential to escalate to an extremely hazardous temperature runaway. The tendency for reduction to free metals increases with temperature, duration and hydrogen partial pressure.
The hydrotreating reactor may have been designed to be bypassed when there is no sulphur in the feed but please be beware that the CoMo catalyst could be inadvertently reduced to elemental metal if the hydrotreating reactor isolation valves are passing or if the hydrotreating reactor is heated up with treat gas only.