Power Extras

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Mike Bullivant: So what I’ve done is taken Hermione’s crushed coal, the fine powder in this teapot here, and we’re heating it. It’s a process called dry distillation. Now coal has a very complex chemical structure, it’s not just carbon, and the heat breaks that chemical structure down and it’ll produce four things fundamentally. It’ll produce ammonia and coal tar, and it’ll also produce coal gas and we’ll be left with coke here.

We only want the coal gas. We’ve put some traps in because we want fairly pure coal gas that’ll 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 limewater here and this’ll take out the small amount of carbon dioxide produced and hydrogen sulphide that’s embedded in the coal, and what we should end up with is coal gas, pure coal gas coming out here. I’ll be able to light it and 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 distil it, at which we heat the coal.

We learnt a lot from yesterday’s large scale trial and we made some modifications, not the least of which is 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 might be an improvement too. We going to improve that insulation of the oven here, we’re going to improve the sealant around 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 so that’ll take out much more of the ammonia and the coal tar which if we let it go through it would ruin the coal gas flame.

And an addition to yesterday, but this is something we had in the small scale trial, is the limewater filter which takes up 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.

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 the 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 this luminosity, all the other things burn with a non-luminous flame, so what we’re going to do is just wait until this picks up a bit, until we’ve got it roaring, and then we’ll connect it up and we’ll start collecting the coal gas in the reservoir.