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Benefit Of Ng Preheating For Reformer Fuel


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#1 Hiren Parmar

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Posted 04 May 2018 - 10:28 PM

We have a haldor topsoe reformer where Fuel NG appx. 2800 nm3/hr is preheated from ambient 25-30 deg C to 60 deg C by using 33barg saturated steam (not in fluegas heat recovery path). Combustion air is preheated in flue gas recovery path to 270 deg C. Flue gas final temp. is 115-120 deg C. If we heat fuel NG  to furthur high temperatures, will it be beneficial? How? Thank you



#2 PingPong

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Posted 05 May 2018 - 03:07 AM

2800 Nm3/h NG gives a fired duty of about 28000 kW (based on LHV). On top of that comes the fired duty of the PSA tail gas.

 

Preheating 2800 Nm3/h NG from 25 to 60 oC adds a duty of only 45 kW.

 

As you can see, preheating fuel gas has a negligeble effect on furnace performance, which is why normally nobody does it (except sometimes in gasturbines). Combustion air quantity is many times bigger and therefor more suitable for preheating.

 

In your case it is moreover questionable whether the small effect is worth the value of the HP steam.

 

Sometimes the NG is supplied at high pressure, and is therefor preheated upstream the control valve so as to avoid too low temperature downstream the control valve (due to Joule-Thomson cooling) and risk of hydrate formation. That could be the reason why in your unit the NG is preheated a little.



#3 Hiren Parmar

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Posted 22 May 2018 - 05:04 AM

Pingpong,

You are correct about preheating NG from ambient to 60deg C i.e to avoid low temperature and potential hydrate formation. I was unsure about the benefits of fuel heating and if any, how to calculate the benefit. Thanks for the explanation.



#4 FIRAOL MITIKU

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Posted 26 May 2021 - 02:36 AM

what shall I do to improve my boiler combustion efficiency in order to reduce the smoke at the exit chimney. Does it has a benefit to preheat the combustion air to have good (approximately full) combustion?



#5 Pilesar

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Posted 26 May 2021 - 05:55 AM

I suggest you begin a new thread with your question (instead of posting your question in an old thread.) That will help avoid confusion for everyone. Explain the problem you have and include enough details to perhaps get a useful answer. For your question, details might mean equipment size, type, configuration, fuel, history of performance, recent changes, solutions already tried, your role in finding a solution, etc. 






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