For those interested in the book Master Gerald mentioned, I will warn you that it is a fairly intensive scientific and engineering laden work. The author approaches his subject as though publishing for a professional journal. It is written on the Master's thesis level, regularly making reference to other research papers in the discussion of the chapter topic.
While it is a small book, it is NOT a light read. It is a technical report on a series of experiments attempting to recreate results by replicating performance via remodeled equipment.
If you are not comfortable reading for hours on end about (air flow rate) x (carbon % content) x (chunk size) / (ore mineral % values) x (oven dimension configuration) vs teuere placement/ stack height, this is NOT a book you will finish. It is HIGHLY technical, exactly the opposite of the PBS episode which started this conversation.
It was written on a professional metalurgist level. I have four semesters of Material Science engineering studies, and even I had trouble following at times.
be warned. The hardback copy runs $80 on Amazon.