|
Posted by Zephyr on February 16, 2007, 9:23 am
> YouDontNeedToKnow@Somewhere.edu writes:
>>Would someone please fill me in on why we use propane and not natural
>>gas? I read the Wikipedia article at
>>
>>http://en.wikipedia.org/wiki/Propane
>>
>>and I still don't understand the difference. I do know that propane
>>appliances such as ranges require adjustment to or different burners
>>for each. Why not eliminate this problem and just use LNG only? In
>>terms of household heating the only difference then would be that in
>>one case you have a pipe coming in from the utility and in the other
>>you have a big tank in the back/front yard and a tanker comes and
>>fills you up from time to time. Or for your barbeque you go to the
>>home center and instead of propane you get a tank or a refill of LNG.
>
> Natural gas is mostly methane. It's attractive as a fuel because it's
> plentiful, but it's also very difficult to turn into a liquid. Any fuel
> that you transport in tanks wants to be a liquid because you can store
> many times as much fuel in a given volume tank as a liquid than as a
> compressed gas.
>
> Let's back up a bit:
> Butane is easy to handle because the amount of pressure needed to keep
> it liquid at room temperature can be provided by a plastic container
> (e.g. cheap butane lighter) or a very thin aluminum can. Thus, you
> can carry a lot of fuel in a small, light tank. But it's relatively
> expensive.
>
> Propane requires considerably higher pressure to be liquid at room
> temperature, so it has to be stored in heavier steel tanks that can
> withstand the pressure. But it *is* liquid in there, so again you can
> have quite a bit of fuel inside one small tank.
>
> Methane cannot be practically compressed into a liquid at room
> temperature. You can make it liquid by making it very cold; that's how
> LNG (liquid natural gas) is produced. But it's got to stay cold to stay
> liquid, just like liquid oxygen or nitrogen. It's practical to ship
> very large volumes of it in specially-insulated tanks in ships, but it's
> not practical to keep that cold in a tank on your car or barbecue.
>
> So when you see a car or bus powered by compressed natural gas (CNG), it
> tends to have very large tanks to hold a relatively small amount of gas,
> since there is no liquid in the tanks. Propane will power a car for
> much longer with a smaller tank. So CNG isn't very popular as a vehicle
> fuel.
>
> It isn't practical for house heating or stove or barbecue either. If a
> trunk brought you liquid natural gas, you'd need cryogenic storage
> (which is expensive) and you would continually lose some fuel to boil
> off. If a truck brought you compressed natural gas, you'd need large
> tanks, and you'd have to wait for a compressor to re-pressurize them
> during fillup.
>
> Natural gas *is* practical if it can be brought to you in gas form at
> normal temperature by pipeline. It's just not practical to store or
> distribute in a tank except on an enormous scale.
>
> Dave
Dave,
Great Post.
Dave
| 
Yahoo! 
Google 
Windows Live 
del.icio.us 
digg 
Netscape 
XML Sitemap