Categories => Just Asking => Topic started by: Greg Chamberlain on September 27, 2007, 12:18:54 PM

Title: Methane Hydrates
Post by: Greg Chamberlain on September 27, 2007, 12:18:54 PM
While searching for the density of frozen methane (which I didn't find in the first 6 pages of Google results), I came across a description of methane hydrate.  It was interesting enough that I thought I'd share the details here, and some of my speculations.

The average composition of methane clathrate is 5.75 molecules of water to 1 molecule of methane, or 1 molecule methane per approximately 119.5 AMU.  The heat of combustion of methane is
23875 BTU/lbm, or about 212 kcal/mol if I've done my numbers right.

Here's where I get speculative.  I've read that methane hydrates form easily in water which is sufficiently pressurized (deep) and cold.  If the formation created a lot of heat, you'd expect
that the process would be rate-limited by the ability to conduct heat away (else the temperature would rise too high to keep forming more hydrate).  I've read nothing to indicate that this
happens.  So I'll assume for the sake of speculation that the heat of formation of methane hydrate is -10 cal/gram, or about 1/8 the heat of formation of water-ice.

A quantity of methane hydrate containing a mole of methane masses 119.5 grams.  My speculative number indicates that this hydrate would require at most 1195 calories of heat to dissociate it into
free methane and liquid water.

This is less than 1% of the heat of combustion of the methane.

The lesson seems obvious:  methane hydrate deposits on the ocean floor can potentially be liberated by warming them gently using the combustion of a small fraction of the methane, and the rest harvested for whatever use is contemplated.  Who needs foreign oil?

(And if anyone can tell me the density of frozen methane, and the volume fraction of crystals in liquid you can get before the "slush" stops flowing, please tell me.  I'm intensely curious about the possibilities for rocketry.)
Title: Re: Methane Hydrates
Post by: utility slug on September 27, 2007, 12:22:14 PM
Give a minute, Greg...
Title: Re: Methane Hydrates
Post by: BigRedDog on September 27, 2007, 12:24:44 PM
I used to run around with that information right on the tip of my tongue...   seems to have slipped my mind right now though....    memory is 2nd function to go you know ;D
Title: Re: Methane Hydrates
Post by: cc on September 27, 2007, 12:27:08 PM
I'm working on it.....I have my big white board and dry erase markers out now....

actually I think I may have missed that day in math class, or science class, or biology, or chemistry, or shoot in reading class as some of that went right over, around and under me and knocked me right on my.......

Title: Re: Methane Hydrates
Post by: Dime Store Cowboy on September 27, 2007, 02:31:02 PM
I believe after what he just wrote .  He has just burned up a months frozen supply!
Depending on what sea level & baro was at when he wrote.,..
I know there sure was a lot of hot air on the forum!!!
Title: Re: Methane Hydrates
Post by: Dadof7 on September 27, 2007, 04:16:24 PM
I just figured this stuff out last night for my daughters 7th grade science fair project... but dammit, she took the notes with her...

Title: Re: Methane Hydrates
Post by: schrodingers_cat on September 28, 2007, 08:33:01 AM
Well, this is my first post.  Yea  :)

Anywho, I am not sure why you're looking for the denisty of solid methane, as it freezes around -182 degrees Celsius (around -297 deg F).  But I did find in one paper that solid methane's density is that of 0.45g/mL.

As for your proposal related to methyl/methane hydrates, I don't know about that.  I am not sure that there's all that much methane hanging out in the deep ocean floors.  I could be wrong though, my specialty is not in the area of hydrates.

I figured that I would try to answer your original query.
Title: Re: Methane Hydrates
Post by: Greg Chamberlain on October 02, 2007, 09:07:40 AM
It looks like there were some studies in the late 80s/early 90s on the amount of methane hydrate hanging out in the deep ocean floors.

The oceanic reservoir has been estimated to be about 10,000 to 11,000 GtC (e.g., MacDonald, 1990; Kvenvolden, 1998).

10,000 GtC represents like 600 million quad. (quad = 1 quadrillion BTU)
The United States uses like 100 quad per year.
600 million divided by 100 is 6 million years.

I think this should be studied as an alternative fuel source, although it isn't exactly carbon neutral (or is it?)
Title: Re: Methane Hydrates
Post by: Chips on October 04, 2007, 08:46:38 PM
  The density of solid methane is classified.
   If I told you I would have to kill you.
Title: Re: Methane Hydrates
Post by: Greg Chamberlain on May 19, 2017, 11:02:50 AM
So it would appear I was on to something... (
Title: Re: Methane Hydrates
Post by: old salt on May 19, 2017, 03:35:41 PM
Kudos Greg!  10 years ahead of everyone else.  I hope this catches on and becomes a viable source.

My only experience with methane is when I fart in my wallet to say I have gas money.