Cerro Matoso (CMSA) in Colombia produces ferro-nickel from
lateritic ore containing approximately three per cent nickel, using
a Rotary Kiln - Electric Furnace (RKEF) process, in which the
calcining of the mineral within the kiln is second in importance
only to the smelting of the mineral in the Electrical Furnace. This
article discusses the installation and operation of an expert system
to control the kiln of CMSA. In the CMSA process, the run-of-mine ore is crushed,
homogenised, dried and mixed with a small percentage of coal,
before being heated up to 900C in a rotary kiln in the presence
of natural gas mixed with air in a controlled proportion (air/gas
constant ratio). The final objectives of the process are the
following: To reduce to a minimum the iron and nickel oxides in order to
convert these into metallic ions; this is a reduction process to
facilitate largely the smelting in the electric furnace. Since
the reduction is made with natural gas, it is much more
economical than the subsequent complete reduction in the
electric furnace, since electrical energy is much more
expensive by unit of processed mineral. To heat the mineral as much as possible to facilitate the
subsequent smelting. To eliminate totally the moisture content of the ore. An expert system with fuzzy logic was commissioned in 1994
for the control of the kiln and it has operated with good results
ever since.