A novel comprehensive solution for furnace integrating outlet parametric variable control and online thermal efficiency optimization

Abstract

Due to the frequent changes of the thermal load, severe nonlinearity in flue gas-air system actuator, fluctuations in fuel pressure and combustion heat, and field oxygen sensor drift, current controllers do not work well in the long term, and meanwhile the thermal efficiency optimization is hard to be practicable. To circumvent these difficulties, we propose a novel comprehensive solution integrating furnace outlet parametric variable control and thermal efficiency optimization. Firstly, the set point for the manipulated variable, fuel flow, is quickly determined when confronted with thermal load demand changes based on the forward computation introduced by the thermal balance equation. Then, the unmeasured disturbances, such as fuel combustion heat, specific heat of feed and so on, are merged into a new ratio variable. The outlet controlled variable (e.g. temperature, steam pressure and vaporization rate) is finely tuned based on the input-output predictive model between the ratio variable and outlet controlled variable. The regulating mechanism of the proposed control system guarantees that the control system can realize free of maintenance and long term operation. Furthermore, we propose a maintenance-free thermal efficiency optimization framework integrating the multi-region specific optimal reference points and online self-optimization to adapt the change of the optimal oxygen concentration with primarily thermal load and the measured value drift of field oxygen sensor. Finally, the results from both simulation case study and field application are exhibited to demonstrate the effectiveness of the proposed strategy.