The difficult strategy of the rotary kiln and controlling difficulty of the production process can be summarized as the following aspects:
1.The rotary kiln with large size has complex physical and chemical reaction process as well as the heat transfer process. In addition, the operational conditions and working conditions have large change, for example, the lining of the rotary kiln, the thickness of the machine skin, the flow amount of the raw slurry, moisture, ingredients, the coal quality of the fuel change frequently; because of the serious interference, the coupling between the control variables is serious, the problem of nonlinear, large inertia and large time-lag often emerge, which make it difficult to establish a mathematical model from input to output.
2.The problem of control variables. The coupling between the control variables is serious, which includes the speed of coal feeder speed, the opening of the air door of the smoke ventilator, feeding amount and the speed of the alumina kiln.
3.The tmperature of the burning zone with critical process parameters is difficult to measure. Making use of the pyrometer measurements that is installed in front of the rotary kiln to measure the temperature of the material in the burning zone has lagged behind, which is seriously disturbed by the dust smoke.
4.There are some non-normal production constraints, which includes the period from the starting up to the stop of the alumina rotary kiln, the changing process of the feeding amount, the blockage of cyclone dust collectors, the rapid formation of the kiln circle, the severe scarring of the kiln tail, poor ventilation of the kiln; the poor condition of the kiln skin, equipment failure; the uneven and frequent feeding; inappropriate operating conditions of pulverized coal burner.
5.The constant gain control methods such as the PID, the MPC, which is based on the mathematical model is invalid and it is difficult to apply traditional controller structure and form of knowledge representation.