• What happens if during the catalyst sulfidation, Hydrogen flow is much higher than the target value?



  • Randy Alexander, Reactor Resources, ralexander@reactor-resources.com

    As Steve and Jake pointed out, you should normally recycle hydrogen during sulfiding since after break-through it will contain H2S that is needed to carry out the sulfiding reaction. Fresh "make-up" hydrogen should only be added to the recycle stream as needed to keep the hydrogen partial pressure above 70%. Our clients typically utilize one of our online hydrogen analyzers to constantly monitor the hydrogen purity during sulfiding. With the data streamed from the analyzer, the optimum amount of hydrogen can be added to the recycle gas stream.

    High hydrogen flow shouldn't cause any issues, but may be the result of excess venting of sour hydrogen downstream from the reactor. In this case, hydrogen is being wasted and sulfur emission issues may arise.




  • Steve Mayo, Eurecat US Inc, smayo@eurecat.com

    Excess hydrogen flow during catalyst sulfiding is generally not problematic, especially if the gas is recycled (with amine scrubber bypassed) so that unreacted H2S is recirculated. In the case of once through gas flow, additional DMDS injection may be necessary to compensate for lower H2S content in the gas, in particular if feedstock sulfur content is low.



  • Jake Gotham, InSite Technical Services, jake.gotham@insitetechnical.com

    Assuming the unit has a recycle compressor to recover hydrogen from the high pressure separator and return it to the reactor, high recycle hydrogen flow rate is unlikely to be a problem.

    A small number of hydrotreaters operate with once-through hydrogen (i.e. the gas from the high pressure separator is vented into a hydrogen header or to another hydrotreater).  In this case, during high temperature sulphiding, H2S is lost from the hydrotreater into the downstream system.  The higher the flow-rate, the more H2S will be lost and an increased amount of DMDS will be required in order to complete the sulphiding.