burner for hydrogen-rich fuel 1

[imans]

Dear Readers,

We would like to introduce our excess hydrogen-rich offgas to our fuel gas system. The major concern is the hydrogen content on the fuel gas would be between 50-60 %. What should we do to ensure that our burner is suitable for high-hydrogen service? What is the limitation of hydrogen in the fuel gas? Is the limit is the material or operational?

Thanks

 

[reena1957]

Dearimans,
the problem with hydrogen is its very low density. So inspite of its higher calorific value you have to burn a larger volume of gas to get the same heat release. The other two slightly minor points are
1. reduced flame emissivity compared to normal fuel gas which will reduce the radiation section heat absorption.
2. Requirement of more stochiometric air than normal fuel gas for a given heat release.
So expect problems in:
1. Fuel gas header pressure drop
2. Fuel gas control valve
3. Requirement of more burners than for Fuel gas
4. Furnace draft problems and positive pressurisation
5. Inability to consume the gas and resultant flaring

In short it is hydraulics of Fuel gas and Flue gas you have to work on. get the Volumetric flow of the new fuel gas for equivalent heat release and work the hydraulics based on it.
Best of luck

 

[Mutt]

You will also need to check the burner design itself - hydrogen has very high flame speed and if current gas velocity ex the burner is too low, could get flame back inside the burner. Check Wobbe number, flame speed and capacity of new fuel mix against exising hardware's design burner triangle.

Comment on above from Reena : My experience is that hydrogen has a lower calorofic value, as measured in MJ/nm3, than typical fuel gas mixes in refineries......

 

[reena1957]

Mutt, You are right. I meant CV on mass basis.

 

[liberoSimulation]

We have Tail gas rich in H2 reaching up to 50% and burners designed for that without major impact.
Application is Ethylene Crackers (Furnaces).

Cheers

 

[liberoSimulation]

Also, I have seen burners designed and running with hydogen up to 88 mol%.

Cheers

 

[oxilume]

Dear Imans,

A little about hydrogen; first look at the LEL and UEL; 4% to 92%. Now, compare that to the fuel you are using. You will find that the LEL and UEL window for hydrocarbons is very small compared to hydrogen.

I can ignite the H2 with any amount of hydrocarbons with limited air using my Plasma RamJet. Operating rich or lean is not a problem. The sole problem is simply a matter of electrical costs. If you can afford the costs, then the Plasma RamJet will ignite it. However I prefer to crack the hydrocarbons prior to mixing with hydrogen. Thus, the entire fuel stream consists of hydrogen and carbon or hydrogen and CO (syngas). It burns quite well in the Plasma Whirl Reactor. see

http://www.oxilume.com

Todd

Todd

http://www.oxilume.com

 

[dan21703]

You probably need replacement burners to avoid NOX emission problems and to result in a stable flame. A large change in chemistry can affect the flame release rates. If your application is a heater you will need to consider these effects on the design.

Like others above, I have seen projects with this much hydrogen done with refinery heaters and the result was successful.

Depending on the calorific value of the original system you may or may not require new burner trains. In one application in the past we only had to change the burner drawers, not the fuel gas trains. If you are thinking to switch between this fuel and the original fuel your problems may be more challenging.