Carbon is one of the earliest known elements. It was used by the Egyptians and Sumerians in the form of charcoal around 3750 B.C. for the reduction of copper, zinc, and tin ores in the manufacture of bronze.
As discussed in Part 1 (CI, September 2011), internal kiln pressure in a tunnel kiln governs airflow direction and affects temperature uniformity, soaking time, and energy consumption. Management of the kiln pressure profile makes a huge difference in kiln stability.