What is Coal Liquefaction?

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ralphhugh's picture
ralphhugh
Status: Member (Offline)
Joined: Jan 19 2009
Posts: 3
What is Coal Liquefaction?

Coal liquefaction is the conversion of coal to produce synthetic fuels.
To convert coal to synthetic fuels, a process has been developed that
requires the coal to be in contact with a hydrogen environment at high
temperatures and pressures.

The major objective of coal liquefaction is to produce synthetic oil to
supplement the natural sources of petroleum. Liquid and solid products
from coal can be used for fueling transportation vehicles, providing fuels
for power generation, and yielding raw materials for chemicals.
Coal-liquefaction plants will be expensive, but their products
should be very competitive when world oil production declines.

bearing01's picture
bearing01
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Joined: Sep 8 2008
Posts: 153
Re: What is Coal Liquefaction?

 

This has been around since the first world war and was used by Nazi Germay in WWII to reduce their independence on foreign oil.  They use the  Fischer-Tropsch synthesis process to make gasoline (or Diesel fuel) from Coal.

 http://en.wikipedia.org/wiki/Fischer-Tropsch_process

 If you saw Chris's video on the Coal resources.  The USA is claimed to be the "Saudi Arabia of Coal" with 200 year supply.  However, if you look at it from an energy density standpoint (BTU / Lb) we don't really have all that many years of worthy coal afterall.

Also keep in mind that Coal is the highest carbon content fuel (it's all carbon) and gives off the most CO2  green house gas when burnt or converted to whatever.  Fortunately we're now in a global cooing phase rather than warming.  But this process makes the coal to liquid fuel procedure expensive and can't compete while oil is at $40 or so.  

There are other ideas as well.  I really liked the book "Then Methanol Economy" that describes turning smoke stack CO2 emissions into methane gas which you then can turn into Methanol liquid fuel to power the transportation fleet.  It sounds scientifically possible and the better option.  The technology still needs to be developed however.

 http://www.amazon.com/Beyond-Oil-Gas-Methanol-Economy/dp/3527312757/ref=pd_bbs_sr_1?ie=UTF8&s=books&qid=1232417780&sr=8-1

http://en.wikipedia.org/wiki/Methanol_economy 

DurangoKid's picture
DurangoKid
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Joined: Oct 25 2008
Posts: 174
Re: What is Coal Liquefaction?

      Coal to liquids has been an interesting experiment in small molecule chemistry at best and an act of depiration at worst.  The famous Third Reich dependence on Fischer-Tropsch was a failure.  Toward the end of the war, fuel was in extreme short supply.  Vehicles ground to a halt.  Aircraft were grounded, period.  The anticipated advance into the Soviet oil fields never materialized.  The stop in Stalingrad saw to that.  So, yes the Nazi's did get a lot of their fuel from coal, it just wasn't enough.  This tells us something about production rates for converting essentially carbon into alkanes.

 

     On the other side of the coin is that old devil EROEI.  For Fischer-Tropsch it's not good.  A lot of the carbon winds up as waste CO2.  Much of the heat in the process is wasted.  Some could be recovered.  Then there's the sulpher, phosphorus, mercury, toxic ash, etc. to deal with.

 

     Now let's talk about the reputed coal reserves of the US.   The 200 year figure is way off.  There isn't that much coal.  And the multi-century figure usually comes with a caveat called "at current rates of consumption".  There in lies the rub.  Switching to coal just means the expectation of exponential growth in petroleum output switches to coal.  At modest rates of growth in coal output, the 200 year figure is reduced to about 40 years.  That also assumes that the growth in coal output will grow until it exhausts.  Not likely.  Hubbert's curve is a better approximation.  Zero rates of production at the beginning and end and a zero rate of growth in output somewhere near the middle.  In that case, we'll have probably about 100 years of coal production with the peak in another 20 - 30.  New assessments in coal reserves will move the peak point around a bit, but it will hardly matter.

 

     Then there's the matter of how much CO2 the atmosphere and oceans can absorb and still keep the Earth clement for 6.5 billion people.  Some studies indicate the oceans are about tapped out as a carbon sink.  Put much more CO2 into ocean water and its acidification becomes a serious problem.  What's that about "clean coal"?  At this point it's little more than an article in Scientific American and coal industry propaganda.  It's constrained by two things: too little too late and EROEI.  Everything you do to contain coal emssions just robs you of useful work.  It ends up being more carbon in the atmosphere and less to show for it.

 

     Even if we started tomorrow, Fischer-Tropsch is years in the future.  It takes decades to scale up industries of that magnitude.  Then we have to think about with what to replace our current coal consumption.  About half of our electricity comes from coal.  What happens as that coal is diverted to motor fuel?  Will the alternatives fill in the gap?  Not likely.  They have some of the same physical constraints as Fisher-Tropsch.  Scale and time, for two.  Then consider the alternatives based on biomass.  Either we divert agriculture devoted to food from food to fuel, or we till ever more marginal land at a greater cost in inputs and labor.  On solution would be to turn some countries into energy colonies.  If you think terrorism is a problem now, get ready for the picnic to end and the real deal to show up on your doorstep.

 

   Short story:  The peaking of non-renewable energy resources means that for the good of ourselves and the good of the planet, we have to get by with less.  It's been one heck of a ride, but now the party is over.

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