Gas Fired Hearth Furnace Control System

SUMMARY:  

Developed a 20 burner, 7 Zone combustion control system for a steel annealing rotary Hearth Furnace using PLC control and HMI interface.

DESCRIPTION:  

The PLC monitors and maintains zone temperature setpoints by controlling combustion air dampers and gas valves.  The system continuously monitors interlocks for safety and shutdown circumstances.  Each zone has fuel valve and combustion air PID control to allow smooth start-up and shut down.  Cascade PID control is used to allow combustion air to follow the fuel control while maintaining a safe gas to air ratio.  Logic was developed to allow Bumpless transition from automatic to manual control.  

The furnace pressure is maintained at a slightly negative value by controlling the induced draft fan speed.  The operator has complete manual and automatic control of the system through the graphical HMI.  All alarms and events are recorded to a database and printed as they occur.