Optimized combustion system in coal-fired boiler: using optimization control and fieldbus

This paper presented a comprehensive design and implementation of control and optimization for the combustion system in heat-supplying boilers based on a fieldbus, mainly including the air-to-fuel ratio optimization algorithm based on a PID controller and soft measurement methodology for airflow based on the orifice nature of the air pre-heater. After process description and general control schemes were presented, measurement and control principles for the system were given. After an optimization algorithm for air-to-fuel ratio with constant step was introduced briefly, an adaptive optimization algorithm based on a PID controller was proposed, and then detailed design was presented. Advantages of the proposed adaptive optimization algorithm can be seen after comparison with a former algorithm. Approaches for the soft measurement of airflow in a boiler system based on differential air pressure between the inlet and outlet of the air pre-heater and that of fuel were presented. The complete control strategies for the designed system were given. Implementation of the whole system by a Foundation Fieldbus, including structure design for the control system and soft configurations design for the proposed optimization algorithm, were presented at length. Control effects of the designed system were given, demonstrating tat the design of the whole system was a success by running it reliably for a long time. Some important conclusions on the proposed methodologies and designs in measurement and control using the fieldbus in combustion control were presented at the end of the paper.