Burn-through Point Research Articles

Event-based modeling and control for the burnthrough point in sintering processes

This paper treats modeling and control for the burnthrough point in industrial sintering processes. First, a simple state-space model for event-time dynamics is derived for a complicated system by introducing events into a continuous variable system. For the control of the sintering process, a two-stage control policy is used. First, optimal interevent time is obtained from an output-constrained receding horizon control with a least-square prediction algorithm. Then the average strand speeds for the interevent times are obtained and applied as a command signal to a motor control system. It is proved that the proposed output-constrained receding horizon control law with a short horizon stabilizes the closed-loop system and the steady-state error for a set-point becomes zero. The real-time experiments are carried out in a POSCO (Pohang Steel Company, Korea) sintering plant and satisfactory results are presented in this paper. Also, computer simulations are carried out and compared with the real-time experiments.

An application of min–max generalized predictive control to sintering processes

This paper presents an application of min-max generalized predictive control (MMGPC) to burnthrough point control in industrial sintering processes. A simple model is used as a plant model for the burnthrough point control, which is derived for a complicated sintering process by introducing events into a continuous variable system. As a control algorithm, the MMGPC is used. It is robust to disturbances and has guaranteed stability. Simulations of the burnthrough point control using the MMGPC are performed using a derived model of a POSCO (Pohang Steel Company, Korea) sintering plant and real burnthrough time data of sinter packages. The simulation results of the MMGPC are compared with those of PID control, and are satisfactory.

Fuzzy control of an iron ore sintering plant

The main control task in a sintering plant is the burn-through point control with the sinter strand velocity as the control variable. The charging bunker level control is coupled with the burn-through point control via the disturbance strand velocity. The development of two fuzzy controllers for these two loops is presented. Using a simple plant model, their performance is demonstrated by several simulation results.

Peak bed temperature prediction on a lead/zinc sinter plant

Of great interest for improved sinter plant control is the definition and online measurement of sinter quality. The ultimate measure of this is blast furnace performance and previous work at Sulphide Corporation has shown that stable furnace operation with good coke utilization is dependent upon the sinter microstructure being dominated by a network of either zincite or calcium ferrite. Formation of the correct phases during sintering is primarily controlled by the feed chemistry. The temperature history is also important however, leading to the concept of a peak bed temperature which must be reached to maximise melting, reaction and recrystallization of the desired chemical species. Improved sinter composition control has been achieved ar Sulphide Corporation by the use of a charge calculation computer program which includes as a target, the theoretical peak bed temperature. However, this technique depends on good assay data - both for raw material inputs and for the return sinter. At the present time, much of the required information is not available on-line and the charge calculation approach is thus vulnerable to the effects of short-term fluctuations. It was therefore seen to be important to develop a separate method which, could measure peak bed temperature on-line. This paper describes a series of investigations conducted on the sinter machine at Sulphide Corporation, to develop such a method. After a number of initial, unsuccessful attempts (which are described), the approach adopted was to infer from bulk gas temperatures (where these could be reliably measured) the temperature profile of the gas leaving the surface of the bed. The location of the peak gas temperature is the burnthrough point. In order to do this, a mathematical model of the gas flow pattern in the sinter machine hood was prepared, and, based on the results from plant experiments, was progressively modified until adequate agreement between prediction and experiment was obtained. Based on limited experimental data, it is assumed that the gas temperature at burnthrough is equal to the temperature of the sintering solids. The use of this model, in conjuction with a suitable two-parameter search algorithm, in both off-line and on-line mode is discussed.