I recently came across an article with the title of combustible ice, also called “fire ice.” I realize that anything can be made to combust. I never thought of ice doing that. My next thought was that ice might mean something else than frozen water. Diamonds are referred to as ice because of their ability to transfer heat. The United States Immigration and Customs Enforcement (ICE) can be a hot topic in some quarters. Snow Crash has linked frozen water with the mes collected by Enlil. As you can see I was very curious about the article.
It turns out the ice referenced in this particular article is hydrocarbons frozen in ice crystals. It is natural gas (mostly methane) that has been trapped in the crystalline structure of water as it froze. We can easily imagine the liquid methane atmosphere of Neptune or methane sheets and snow on Makemake (a newly discovered plutoid in the Kuiper Belt) and Eris, but it is not something we think about on earth.
Methane needs to be below -297 degrees Fahrenheit for it to become solid, but because it is inside the ice, the “fire ice” can remain stable at much higher temperatures (around 29 degrees Fahrenheit). Methane is in the atmosphere of all the gas giants in our solar system and might be found in ice form on the dwarf planets like Pluto (we’ll have to wait for the New Horizon’s fly by in 2015. None of the extrasolar planets seem to have methane in their atmosphere (although HD 209458 b might have water vapor in its atmosphere).
The “fire ice” on Earth usually forms deep under the surface of the oceans – down hundreds of meters into the dark depth. That’s not the only place on the Earth where it is. China has reported that it has found this “fire ice” in Qinghai Province.
Methane hydrates have been known since the 1960’s, but they have not been in the news much. You might ask why. The early known methane hydrates despots were deep on the ocean floor and mining for them was too expensive for what they could sell the methane for. With the current rise in the cost of fuel, the “fire ice” is looking more attractive. Japan plans to have a full scale mining operation up and running by 2016 and China is putting aside nearly a billion dollars on research of mining and using “fire ice”.
So how does “fire ice” differ from the run of the mill natural gas? Well, they don’t. Hydrates are routinely formed during the refining process. The hydrates can cause damage to the pipelines by blocking the flow. Ethylene glycol (antifreeze) can be used to stop the hydrates from forming.
Since methane hydrates are a form of natural gas, why are methane hydrates important? One reason is that it is natural gas. Natural gas is used primary in electrical generation in the US. Natural gas burns cleaner then coal or petroleum. Another reason the “fire ice” can be important is in transportation. To ship natural gas around the world, it is common to change it from a gaseous form to a liquid. This, very logically, is called liquefied natural gas. It takes a lot of energy to cool the gas down to – 256 degrees Fahrenheit. The “fire ice” remains stable at much higher temperatures, -4 degrees Fahrenheit.
“Fire ice” might be cheaper to transport, but it will not be a “silver bullet” that solves all our energy needs. For that there is no single, easy answer.