3 replies to this topic

[CEEXPD]

Hello,

 

For a PSA that is producing almost pure hydrogen as the final product in a steam methane reforming process, what adsorbents would be used?

 

I believe that activated carbon is used in the first packed bed to remove H2O and CO2, and that zeolites are used in the second bed to mop up what breaks through. 

 

What zeolites would normally be used for this purpose?

 

I am performing a HAZID on the process and as a part of it I am required to get material safety data sheets for materials used, but I don't even know what it is other than being a zeolite. 

 

Regards,

 

C

Edited by CEEXPD, 09 November 2018 - 08:48 PM.

[Art Montemayor]

Why are you selecting a PSA adsorption process to purify a hydrogen stream?  Are you planning on purging all the regeneration gas?   Or are you going to recover the regen gas as useful fuel?  Are you aware of the trade-offs in extra equipment and lower efficiencies?  Even impure hydrogen is an expensive fuel to burn.

 

Why do you "believe" that activated carbon is used to adsorb water and CO2?  What is your source of this information?  I've done a lot of adsorbing in my career and this is the first time of I've heard of this.  I've  used Mol Sieves for that and used carbon only for adsorbing heavy hydrocarbons.  Are you familiar with the adsorption process and particularly the abilities and uses for Mol Sieves and other adsorbents?

 

If you are going to do a HazOp, have you generated a detailed sketch of the adsorption unit showing all the equipment and its piping and step-wise operation?   You should furnish that information.

[CEEXPD]

I posted in another thread regarding hydrogen purification within the SMR process, and it was suggested that PSA would be the most economical choice to produce high-purity hydrogen at the desired quantities. It seems to be the standard approach in modern SMR plants with a similar process scheme from what I have found through searches.

 

Tailgas from the PSA is going to be used as fuel for the reformer. 

 

With regards to the PSA, then I know only the most basic aspects. I am currently at the conceptual design stage and didn't need to know anything else until it came to the HAZID - I am only performing a HAZOP in the detailed design stage of the task - where I found I needed material safety data sheets for whatever adsorbents are used.

 

https://www.hindawi....rn/2012/982934/

 

"One frequent case is to have a multicomponent mixture of gases and that the number of compounds to be separated cannot be removed by a single adsorbent. The solution to this problem was found for the case of H2purification from methane steam reforming. In this application, H2 is mixed with H2O, CO2, CO, unconverted CH4, and possibly other gases like N2. Activated carbon can be used to remove H2O and CO2 quite selectively but the loading for CO is rather limited for small partial pressures."

 

I may have misunderstood the above, but that is where I took it from.

 

What kind of molecular sieves or adsorbents would you suggest for purifying hydrogen from the other components?

 

Flow rate will be fairly small in industrial terms, as the process is meant to produce 50-60 tonnes per day of hydrogen. 

 

 

[breizh]

Hi ,

you may take a look at the specification sheet .

good luck.

Breizh