CONTROL OF AN INDUSTRIAL LIME KILN OPERATING CLOSE TO MAXIMUM CAPACITY

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.