6 replies to this topic

[rgneengr]

Hello! I'm an engineering student and on my terminal semester currently taking Plant Design course. I'd like to ask something regarding the desulfurization process and its material balance. I have already sought literatures proving high H2S removal efficiency of approximately 100%, however, I wasn't able to continue my material balance again because I just saw from the literatures that there would be hydrocarbons losses or 95% above recovery of the hydrocarbons which implies losses (correct me if I'm wrong). What would be my basis in computing the losses of hydrocarbons during the desulfurization? Also, does the loss occur due to reaction or due to the catalyst bed? I hope someone would notice this, badly needed. Thank you in advance!

[breizh]

http://utpedia.utp.e...phurization.pdf

 

Hi,

Consider the link above , you may find pointers or hints

Good luck

Breizh 

[ShaikhaMS]

Hello, breizh,

 

how were you able to obtain the value of the effective diffusivity? 

[Art Montemayor]

Argene:

 

I was involved in designing and specifying process design for the removal of H₂S from natural gas streams fed into steam reformers for the production of pure Hydrogen.  That was 45 years ago.  We removed the H₂S, using zinc oxide, down to less than 0.1 part per million by volume.  That was more than sufficient to protect the catalyst in the steam reformer.  We never had any problems and I have not heard of any process improvements on that performance – especially from adsorption systems.  Therefore, I’m a bit confused because you fail to explain what process you intend to employ and you state you fear arriving at “hydrocarbon losses or 95% above recovery of the hydrocarbons”.  I don’t understand what you are proposing and what your difficulties are.  Allow me to explain basic process knowledge regarding the removal of H₂S from a gaseous hydrocarbon stream:

 

The H₂S is removed in the hot gaseous state by its chemical reaction with zinc oxide:

 

ZnO + H₂S = ZnS + H₂O

 

This simple, chemical reaction goes essentially to completion.  Normally, two reaction beds – each in separate reaction vessels filled with the ZnO reagent – are employed.  These vessels are piped such that they can be operated in series or as a single vessel.  When the ZnO in one vessel is exhausted, it is isolated and replenished with fresh ZnO while the alternate vessel is on stream.  There are essentially negligible losses of hydrocarbon gas in the process.  I don’t understand your concern for hydrocarbon losses in this process.  Please explain your process description in detail.  How does diffusivity play a role in your proposed process?

[johneyissac98]

Hello! I'm an engineering student and on my terminal semester currently taking Plant Design course. I'd like to ask something regarding the desulfurization process and its material balance. I have already sought literatures proving high H2S removal efficiency of approximately 100%, however, I wasn't able to continue my material balance again because I just saw from the literatures that there would be hydrocarbons losses or 95% above recovery of the hydrocarbons which implies losses (correct me if I'm wrong). What would be my basis in computing the losses of hydrocarbons during the desulfurization? Also, does the loss occur due to reaction or due to the catalyst bed? I hope someone would notice this, badly needed. Thank you in advance!

[johneyissac98]

In Catalytic desulfurization the removal of sulfur takes place at hight temperatures due to that high temperature cracking takes place therefore there would be some losses.

[Pilesar]

Hot zinc oxide is used where there is not much sulfur in the feed and the composition is light. I am familiar with it being used in a syngas process. The lighter components like methane pass through without much loss and it is very efficient at removing H2S. Heavy components tend to degenerate at high temperatures leaving carbon behind and fouling the zinc oxide bed. I cannot quantify the losses for you, but they should be negligible in your material balance if zinc oxide is suitable for your process. If the hydrocarbon losses were high, zinc oxide would not be used in the first place.

(I did not realize i was responding to an old post. Oh well.)

Edited by Pilesar, 19 January 2023 - 08:52 PM.