Burning of low cal waste gas

[Thomasmac]

Hey there,

I have an interesting question that I think the experts may be able to point me in the right direction on.

The CO2 waste stream from a process I am involved in has a tiny amount of entrained methane which needs to be combusted before release to atmosphere, It varys from around 1-3% in a flow of around 50Nm3/hr so obviously it will not combust without some assistance.

I know very little if anything about combustion but if anyone here knows of a cost effective yet energy efficient method for eliminating this entrained methane Id be very interested!.

Thanks in advance

Ryan

 

[dcasto]

On a small stream, a catalytic element would lower the amount of added fuel required to burn the methane.

Why waste the energy? Can the process be modified.

 

[Thomasmac]

Thanks dcasto

Where could I find some more information on Catalytic elements?, ie how they work and what they do.

Regards

R

 

[dcasto]

I believe most flare makers have the info, NAO, John Zink, Calus(spelling?).

 

[crysta1c1ear]

I may be completely wrong but I'm thinking that methane must be a lighter [strictly speaking, less dense] gas than carbon dioxide as CH4 weighs 12+4=16 and CO2 weighs 12+2*16=44 by my calculations, in atomic mass units. (For liquids it would depend on how the moluecules are packed, but gases are molecules flying round with empty space between them and so packing isn't an issue.)

So can the waste gas be channelled into the middle of a big container and the methane just be tapped off the top and the carbon dioxide be thrown away from the bottom?

=

I wonder why it needs to be combusted before it is released to the atmosphere and not by the atmosphere. Surely that amounts to the same thing. Cows belch methane. If it accumulated in the atmosphere, then one day, lightning may strike somewhere and set the whole sky on fire! I think it is lighter than air molecules and rises to the sort of height where we have monatomic oxygen (also weighing 16) and particle collissions just cause one to react with the other - if it hasn't been consumed before that.

Are we pretending that the methane accumlates (careful the sky might catch fire!), somehow lets heat from the sun in, but doesn't let it back out, etc, lol.

 

[dcasto]

Methane is a greenhouse gas, it is 21 times CO2 in its ability to reflect heat back to the earth. Molecular seperation by bouyency would take weeks to concentrate the gas enough to allow the methane to burn.


You could "speed up" molecular seperation with a activated carbon or molecular gate from englehard.

 

[Oxidation]

Flare companies are Zeeco, John Zink, Callidus
Membrane systems: Borsig or UOP
You will find it difficult to separate the methane out cheaply. The bet solution is possibly a membrane system plus a compression unit. The membrane would get rid of the CO2 (or most of it) & give you an amount of concentrated methane. This is expensive & will use large amounts of energy to recover the methane.
Flaring it will also be expensive, you will need a "support" gas (combustible gas)to ensure you burn off the methane....producing even more CO2, plus you'll have a large capital expense to plan it, license it with the local authority, build it, maintain it.