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Hydrogen Production


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#1 CEEXPD

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Posted 04 October 2018 - 09:58 AM

Dear All,

 

We have been tasked with designing a facility to produce hydrogen from natural gas. I have attached a project brief for your perusal. 

 

We are a week away from starting the project, so are looking to simply get an idea of the potential mature technologies that could be used for the facility with respect to the project brief.

 

Initial searches have provided the following, with their respective advantages and disadvantages:

 

Three primary techniques are used to produce hydrogen from a hydrocarbon source, such as methane. The techniques are: steam reforming, autothermal reforming, and partial oxidation. Each of these techniques has advantages and disadvantages which must be considered in choosing a final design.

Steam reforming

Advantages: industrially mature, no oxygen needed, lowest process operation temperature

Disadvantage: large volume of air emissions

Autothermal reforming

Advantage: low methane slip

Disadvantages: requires air/oxygen, little commercial experience

Partial oxidation

Advantages: no catalyst needed, needs less desulfurization, low methane slip

Disadvantages: high process temperatures, process has high a degree of complexity, poor hydrogen to carbon monoxide ratio

 

We need to produce three concept designs for the facility. Then we will analyse and evaluate them via a safety analysis, environmental assessment and economics analysis to determine the one taken forward to the detailed design stage.

 

Are these most likely to be the three concepts? Or are there others that may work? Perhaps some reasons the above wouldn't be even considered in your view?

 

It is also my understanding that different methods of steam reforming are counted as different concepts, so if that was an option I would value your view on what options would be available. 

 

Regards,

 

CEEXPD

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#2 Nikolai T

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Posted 04 October 2018 - 08:51 PM

Hello,

 

Have you sent a technical proposal request to Licensors of the processes yet?

 

Regards


Edited by Nikolai T, 04 October 2018 - 08:51 PM.


#3 gegio1960

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Posted 05 October 2018 - 04:33 AM

an interesting project...

as a professional of the refinery sector, I'd say that h2 from ng is produced by steam reforming.

the project outline seems to suggest the identification of the 3 alternatives thru the energy / water / co2 savings.

in this case, as nikolay highlights above, the study can only be performed with the help of licensors avilable to provide quite detailed data.

(i suspect it is not very simple to find 3 licensors that are happy to follow a "theoretical" project...)

anyway, once assumed those obstacles as removed, you should have 3 different proposals that will be mainly different in:

- inestment cost

- catalysts

- process scheme (reactors / heaters)

- yields

- utility consumptions

- h2 purification method (a PSA unit...but the pressure ratio ng/h2 could make interesting the evaluation of membranes)

- effluents, mainly co2 but also nox.

moreover, the huge quantities of co2 produced by the steam reforming processes would require additional facilities to reduce co2 emissions to the environment (ie sequestration or, maybe, purification and sale)

...

good luck!



#4 PingPong

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Posted 05 October 2018 - 05:24 AM

Licensors will not provide detailed, and essentially confidential, information to students.

 

Which of the three options is best depends mainly on the intended use of the produced syngas.

For example:

- pure hydrogen only, for use in a hydrocracker,

- pure hydrogen only, for ammonia production,

- syngas for methanol production,

- syngas for producing hydrocarbon using Fischer-Tropsch process,

- ....................



#5 gegio1960

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Posted 05 October 2018 - 05:57 AM

the scope of work speaks about 23-28 knm3/h of h2 at 97.2%v purity to be provided at 18 barg to the hds units of the refinery (stanlow has an fcc-based processing scheme, no hck).

the new unit would replace the existing ones, to be dismissed.

so, steam reforming plus psa (or membranes?) is the choice.

i agree that licensors won't provide data, unless the university has built-up some ways of cooperation.

anyway, good universities have good libraries... with publications like PERP or similar.

ps: the indicated area is very wide (about 330 m x190 m, according to google earth)...it could host at least 3 of those plants  :)



#6 PingPong

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Posted 05 October 2018 - 12:44 PM

I previously had not noticed the attachment in message #1.

 


Excess hydrogen produced by the new facility can be utilised in the on-site steam generation unit.

Producing excess hydrogen and then burn it to generate steam is crazy, Producing excess hydrogen should be avoided by a proper control system.

#7 gegio1960

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Posted 05 October 2018 - 01:19 PM

i agree. it shall be a misprint...maybe "hydrogen" could be read as "steam".

also excess steam is not good and shall be minimized by the design...but it will appear when the operating conditions wiill change


Edited by gegio1960, 05 October 2018 - 01:24 PM.


#8 Bobby Strain

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Posted 05 October 2018 - 03:49 PM

You can usually find licensor's public information in published literature. I don't know what details you are required to include in your study. The devil is in the details. You are unlikely to generate accurate capital cost for the facility, so you need to carefully choose how you will derive the cost. When you finalize all the information, you should find that conventional steam/methane reforming is the most cost effective. Also, your results should confirm that PSA is the choice for hydrogen purification. And you will get 99+% purity.

 

Happy hunting!

 

Bobby



#9 Nikolai T

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Posted 07 October 2018 - 08:15 PM

Hello,

 

I think these books can help: Petroleum Refining Technology and Economics James H. Gary, Glenn E. Handwerk;

Handbook of Petoleum Refining Processes Robert A. Meyers.

 

My early suggestion won't interest Licensors obviously, because it’s only for study purpose.

 

Regards



#10 CEEXPD

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Posted 13 October 2018 - 03:28 PM

Dear All,

 

I appreciate the replies so far.

 

The following is regarding SMR:

 

For the WGS section, is it preferable to have both the HTS and LTS, or simply a single HTS?

 

I understand that the HTS favours the kinetics of the WGSR, and that the LTS favours the thermodynamics. Some information is suggesting that HTS alone is a more modern approach, and that LTS is mostly used to increase throughput. I have no idea whether 50-60 tonnes of finished product requires an LTS, but only that the amount is tiny in comparison to what was being produced in the report case.

 

Hydrogen will be required for the HDS, and I am unsure as to whether recycling some of the product from the facility is the way to approach this. Although we are not meant to ask academics at the University, someone else did mention that one of them said to “Buy it in.”. I have no idea whether this is or isn’t a better option, so I am left wondering whether it is safer to do that than recycle it? Or perhaps whether it is to do with the pressure requirements?

 

Condensate will be produced after the WGS and prior to purification. At the amount we’re likely to produce, would It be more sensible to send it off-site for water treatment? Or would treating it on-site and using it for steam be the better choice?

 

Regards,

 

CEEXPD

 



#11 PingPong

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Posted 14 October 2018 - 08:49 AM

For the WGS section, is it preferable to have both the HTS and LTS, or simply a single HTS?
You can chose to have a single HTS, or an HTS plus an LTS, or a single MTS, but not a single LTS.
 
Some information is suggesting that HTS alone is a more modern approach, and that LTS is mostly used to increase throughput.

I would say: an MTS is the more modern approach.

 


Hydrogen will be required for the HDS, and I am unsure as to whether recycling some of the product from the facility is the way to approach this. Although we are not meant to ask academics at the University, someone else did mention that one of them said to “Buy it in.”. I have no idea whether this is or isn’t a better option, so I am left wondering whether it is safer to do that than recycle it? Or perhaps whether it is to do with the pressure requirements?

I have no idea what you are talking about here.

 

Condensate will be produced after the WGS and prior to purification. At the amount we’re likely to produce, would It be more sensible to send it off-site for water treatment? Or would treating it on-site and using it for steam be the better choice?
Normally an SMR includes a stripper for its own condensate which is then reused as BFW in its steam drum. Whether that makes sense in your case (small SMR) is normally discussed with the client as it depends on the specific design and spare capacity of its offsite utility systems.
For your student project it is easiest to assume that it can simply be sent to off-site, and import all BFW for the steam drum from off-site. 


#12 gegio1960

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Posted 15 October 2018 - 03:02 AM

from wikipedia....

The water-gas shift reaction (WGSR) describes the reaction of carbon monoxide and water vapor to form carbon dioxide and hydrogen (the mixture of carbon monoxide and hydrogen (not water) is known as water gas):

CO + H2O ⇌ CO2 + H2

#13 breizh

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Posted 15 October 2018 - 05:24 AM

Hi,

You may find some pointers reading the document attached .

hope this is helping you.

Breizh

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Edited by breizh, 15 October 2018 - 05:33 AM.


#14 CEEXPD

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Posted 15 October 2018 - 12:48 PM

I agree that MTS is the most modern approach, but it says to use proven technology. Apparently the catalyst option isn't as tried and tested as for HTS and LTS reactors. So I think for now it is going to be a single HTS reactor. 

 

I was referring to recycling hydrogen, such as from the product line downstream of the PSA unit. Sorry if it wasn't clear.

 

I understand the reactions taking place, hence asking about the impurities in the condensate. If it was to be removed, is this via a deaerator?

 

 

 

 

 

 

 



#15 PingPong

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Posted 15 October 2018 - 02:17 PM

1) I am sure that Haldor Topsoe uses MTS.

 

2) Unless the feed already contains sufficient hydrogen, every steam reformer has a small hydrogen recycle compressor to add 3 - 5 % H2 to the feed to facilitate the HDS reactor, as is also shown in the article posted by Breizh:

New+Picture+(22).png

 

Recycling additional hydrogen to suppress hydrogen production capacity is not a good idea as it wastes energy.

 

 

3) Normally a steam reformer has a stripper column to remove volatile impurities (H2 , CO , CO2 , methanol, ....) from the condensate. If the deaerator in the off-sites has enough trays or packing height it might also do the trick. Question is whether client wants to risk that.






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