Hi Pat, I've had the issue of incomplete combustion/pyrolysis with my furnace which has relatively high rates of fuel and airflow. At the outset, the end goal was to sacrifice efficency for speed as human time/labour is worth more than the cost of waste oil. Given the resources I'd love to instrument a transparent quartz tuyere and furnace chamber to see what's really happening. At present with the swirl modifications, the furnace now gets to a yellow heat with the same higher levels of fuel and airflow that would give orange heat or result in red heat with ramjet like oscillations . It now has an internal precombustion/swirl chamber formed by a refractory disc and the plinth that allows high rates of fuel and air to burn at a yellow heat instead of the orange heat (photos in post 1 of this thread) so it has more complete combustion than previously. Almost all small fuel furnaces will show large amounts of unburnt fuel if you place a woven platinum mesh in the exhaust stream to see a secondary flame from the catalytic combustion of the unburnt fuel. It also melts 9 Kg of iron in 32 minutes from hot, which is fast enough for me. Post 12 of this thread goes into some depth about the physical changes made to (theoretically) increase flame propagation speeds by boosting flame turbulence, preheating the fuel spray with a recirculating flame and increased flame path.