It shouldn't get too hot as the air is cooling it as it goes through. That said, I have had one of mine glowing slightly which I took to mean that the flame was inside the burner. I shut down and let the air cool things down and restarted. It was fine after that.
I'm not sure if coal fines and coal dust would be the same thing , but that said, I have used coal fines mixed with water to a mortar like consistancy without any issues.
I believe Brent Bailey uses or used shop air for his forge. A fancy regulator isn't needed, a regular gate valve as used for water piping would work fine.
This sounds like a job for an Upset Forging Machine or "Upsetter". These come in sizes from 1/2" to 7". They are rated as to what size round bar they will put a rivet head on in one blow.
I've seen a Star, but not run one. I would think it would be similar to a Little Giant. Mine has 1 1/2 HP motor set up to turn the hammer at somewhere around 300 to 350 rpm.
Hi John, it's been awhile but what I remember from using polymer quench was that it was messier than oil, I think most of the maintenance was from drag-out, and I didn't care for the smell.