Chemical Forums

Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: hardy10 on October 09, 2014, 02:24:58 AM

Title: natural gas combustion , Heat
Post by: hardy10 on October 09, 2014, 02:24:58 AM

Hello,

I have a natural gas combustion in pure oxygen related query,

CH4 + 2 O2 = CO2 + 2 H2O + heat

The Heat of combustion is for CH4 is ΔHc = 802.3 KJ/mol, for complete combustion of methane.

Now, the natural gas is coming at a certain mass flow rate (Kg/hr), which I can convert to mol/hr by dividing the flow rate with Molar mass of methane (g/mol). The number of moles per hour (mol/hr) can be multiplied to determine the Heat generated (KJ/hr) or released upon the reacting with pure Oxygen.

The question is, Am i doing it right ? Also, How does flow rate (quantity) of oxygen supplied for combustion influence the heat released. In other words how do I account for Oxygen as it does not have a calorific value (not a fuel) ?

Will appreciate your response,

Thank You :)

Title: Re: natural gas combustion , Heat
Post by: Borek on October 09, 2014, 02:47:45 AM

You are given oxygen mass flow? Check stoichiometry.

Title: Re: natural gas combustion , Heat
Post by: hardy10 on October 09, 2014, 05:54:23 PM

Yes, I do have the mass flow rate for oxygen. Do you mean to say I should find Heat of reaction ?

thanks,

Title: Re: natural gas combustion , Heat
Post by: Borek on October 09, 2014, 05:57:58 PM

Check if there is enough oxygen for the complete combustion.

Title: Re: natural gas combustion , Heat
Post by: hardy10 on October 09, 2014, 06:33:26 PM

Yes, the oxygen is in abundance (pure O2) and process is known to causes high temperatures up till 3000 C.

Title: Re: natural gas combustion , Heat
Post by: Borek on October 10, 2014, 03:14:00 AM

If the combustion is complete, amount of heat produced per hour is - as you suggested in your first post - number of moles of methane times molar heat of methane combustion.

I have a gut feeling you are not asking the right question, as if you were solving different problem than you told us. But I can be wrong.

Title: Re: natural gas combustion , Heat
Post by: hardy10 on October 10, 2014, 03:48:52 AM

Thanks for your reply,

The question is right, might have worded it wrong (apologies).

Can the amount (no. of moles) of Oxygen (not a fuel) be applied towards heat of combustion adding to the ΔHc for amount of methane combusted?

Title: Re: natural gas combustion , Heat
Post by: Borek on October 10, 2014, 05:08:45 AM

Can't add anything that wasn't already said.

Oxygen is not a fuel, so it doesn't increase maximum heat output. But if there is not enough oxygen, you'll never reach the upper limit.