Temperature shift catalyst reduction

[rotw]

Hello
Methodology is described here

http://fr.slideshare.net/GerardBHawkins/low-temperature-shift-catalyst-reduction-procedure

My concern is as follows (see slide number 2 / procedure step 4):

During initial phase of reduction a known amount of inert gas flow (Nm3/h) is needed to ensure under normal conditions :

a/- high space velocity at the catalyst, thereby enablioing homogenous temperature control during reduction process as hot spot can be created in the bed
b/- continous heat removal of the highly exothermic reaction due to the reduction of the catalyst;

However, when approaching the final reduction phase of the catalyst, the inert gas contains now more than 2% of the reducing gas (in this case hydrogen), whereby the overall molecular weight of the gas has decreased.

To ensure mechanisms a/ and b/ above are working properly given a lower MW gas composition, how should I adjust the amount of floz (inert gas mixed with hydrogen) to the catalyst ? In other words, for a fixed set of pressure/temperature conditions at the inlet of the catalyst, should I keep the mass flow constant or should I keep the Nm3/h constant ?




"If you want to acquire a knowledge or skill, read a book and practice the skill".

 

[Mutt]

Considering that the vendor states a wide range space velocity of between 200 and 800/hr and you can use methane or nitrogen as the inert material and a temperature of 'between 330 and 350F' I don't think a less than 2% error in your flow mass rate will matter. I would suggest keeping the nm3/hr the key parameter for ease of control... Controlling the level of hydrogen precisely seems more of concern to prevent exotherms....my view anyway .