Heat value - help, please!

[Asha Bo]

Hi, everybody.
I've been following this forum for a while, but this is my first post. I need your help with calculation of the heat value of syngas. You can see the results of the measurement in the graph below. Also, could someone explain into detail what's going on in the graphs? I'm kind of new to this kind of things and am more or less still illiterate when it comes to reading this things :embarrassedt:
The data I have on this is:
-the gasificator is a FICFB type
-wood pellets are used as a fuel

I'd be more than happy if anyone could help. :)

Thank you.

[Dave Turpin]

Syngas is exremely dangerous stuff... What are you planning?

[Rob Beckers]

What's syngas? Is this what comes out of a wood gasifier?
This was used on a large scale in Europe to run cars during WWII; there was no gasoline for civilian use so inventive souls build wood gasifiers on small trailers towed behind the car.

Can't help you with the caloric value though.

-RoB-

[Dave Turpin]

Syngas is a mixture of carbon monoxide and flammable gasses. Used to be used in street lamps before electric street lamps became the norm.

If you breath it, you die.

[Joe Blake]

If you get a chance, take a look at this episode of National Geographic's series "Big, Bigger, Biggest".
http://natgeotv.com.au/tv/big-bigger-biggest/episode.aspx?id=2890

There's a reconstruction of the King's cross tube station fire, showing (a) the trench effect and (b) the flammability of gas from the heating of wood chips.

There are no figures or graphs, but it shows the stuff is pretty dangerous.


Joe

[Asha Bo]

Yes, I know it's very dangerous. And I'm not doing anything with it. So, no worries:noworry:
I just got this assigment at school and have no idea how to solve it. :weird:

Thanks for the documentary tip!

[Dave Turpin]

Okay, the graph isn't going to help much. Basically one is for a mixture of wood and water, and the other charcoal and water. The x-axis is temperature of the autoclave and the y-axis is the resulting gas concentrations. To find the heat value you first need to come up with the chemical reactions occurring, then do the usual steps of calculating energy needed to break bonds and energy gained by forming bonds. You need help with that?

[Asha Bo]

Excellent!! I'll try to do it myself first, but yes, please, I'll probably need some more help with it later on... huh:unsure: Thank you!:)

[Dave Turpin]

So firstly, depending on concentrations, there are a few reactions occurring. Assuming no added Oxygen, you get:

8CO + 4CH4 -> 3C4 + 8H2O (ash and water)
4CO + 4H2 -> C4 + 4H2O (more ash and water)

And, if you allow the burn in the presence of air, you also get:

2CO + O2 -> 2CO2
2H2 + O2 -> 2H2O
CH4 + 2O2 -> CO2 + 2H2O

Which is a more common non-ashy burn. What you actually get depends on your initial concentrations, corrected to Molarity.

At high temps, you might also get Nitrogen interaction, but just assume that doesn't happen or it gets really complex. Combustion can be a tough subject. :p

[Aawebdev Piter]

Thanks a lot for. This is just awesome.

[Marvin jordan]

So firstly, depending on concentrations, there are a few reactions occurring. Assuming no added Oxygen, you get:

8CO + 4CH4 -> 3C4 + 8H2O (ash and water)
4CO + 4H2 -> C4 + 4H2O (more ash and water)

And, if you allow the burn in the presence of air, you also get:

2CO + O2 -> 2CO2
2H2 + O2 -> 2H2O
CH4 + 2O2 -> CO2 + 2H2O

Which is a more common non-ashy burn. What you actually get depends on your initial concentrations, corrected to Molarity.

At high temps, you might also get Nitrogen interaction, but just assume that doesn't happen or it gets really complex. Combustion can be a tough subject. :p

woo that calculation looks dangerous...