Two control strategies have been compared for an industrial lime kiln
operating close to maximum capacity. Transfer functions between proces
s inputs (fuel flow rate, air flow rate, and lime mud flow rate) and p
rocess outputs (oxygen excess, cold-end gas temperature, and hot-end s
olids temperature) have been used to present the dynamics of the indus
trial kiln. Control Strategy 1 manipulates the fuel flow rate to contr
ol the cold-end gas temperature and the combustion airflow rate to con
trol the hot-end bed temperature. Control Strategy 2 uses the combusti
on airflow rate to control the cold-end gas temperature and the fuel f
low rate to control the hot-end bed temperature. Both strategies use f
eedback proportional integral (PI) controllers, decouplers, and feedfo
rward loops. Simulations show that Strategy 1 would maintain better pr
oduct quality than Strategy 2 in the event of periodic fuel actuator s
aturation resulting from increased production requirements.