To clarify a little, I live in the UK, not the US. Thanks for your advice Frosty, especially the safety aspect; I was aware of the possible dangers, but many people read this site. I was brainstorming, for want of a better word.
Perhaps a safer idea would be a thermopile. Build enough junctions and you might be able to run a forge blower, or maybe some lights or somesuch. Don't know how much power might be available, but the Russians made kerosene lamp powered valve radios post WW2.
A Stirling engine might be another possibility. Throttling would not be all that easy I think (or likely very fast response time), so using it to run a dynamo powering an electric forge blower (via a regulator perhaps).