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Follow Mike as he processes the crushed coal to produce coal gas, as part of the BBC/OU's programme website for Rough Science 6
So what I've done is taken Hermione's crushed coal, it's a fine powder, in this teapot here.
We're heating it. It's a process called dry distillation.
Coal has a very complex chemical structure. It's not just carbon.
The heat breaks that chemical structure down. It will produce four things fundamentally.
It will produce ammonia and coal tar, and it will also produce, er, coal gas.
And we'll be left with coke in here.
We only want the coal gas.
We've put some traps in because we want fairly pure coal gas. It will burn with a brighter flame.
So in this trap here we'll trap out the ammonia and the coal tar.
And then as it bubbles through, I've got some lime water here.
This will take out a small amount of carbon dioxide that produced and hydrogen sulphide that's in the coal.
What we should end up with is pure coal gas coming out here.
I'll be able to light it. It should burn with a flame.
But how bright that flame is going to be depends on the nature of the coal
and the temperature at which we dry distill it, at which we heat the coal.
GAP
We learnt a lot from yesterday's large scale trial.
We made some modifications which are improving the efficiency of the fire.
We're going to have a throughput of air here, which will give us a hotter fire.
We'll be able to remove the ashes, which will be an improvement, too.
We can improve the insulation of the oven here.
We're going to improve the sealant round the top.
We've got a much improved coal tar and ammonia trap. It's much bigger. It's going to be immersed completely in water.
That will take out more ammonia and coal tar. If we let it go through it would ruin the coal gas flame.
An addition to yesterday, but we had this in the small-scale trial, is the lime water filter,
which takes out the carbon dioxide and hydrogen sulphide.
So what we get coming through the outlet here into the reservoir
is a much purer coal gas than we had yesterday.
Long pause
So if our traps are working, we've got coal gas burning here.
Now coal gas is 50% hydrogen, about 30% methane, 10% carbon monoxide, 5% impurities that have got through
and 5% of ones that make the flame luminous - that's benzene, ethylene and acetylene.
So it's only really 5% of the coal gas that gives the flame its luminosity.
All the other things burn with a non-luminous flame.
So what we're going to do is wait until this picks up a bit, till we've got it roaring,
then we'll connect it up and start collecting the coal gas in the reservoir.
Content last updated: 11/10/2005
