Furnace PID tuning
Furnace zone temperature with adjustable PID: oscillation, thermocouple noise, valve wear and the fuel spent on setpoint margin.
Simulator developed by José Geraldo da Silva Moreira · Energy-efficiency lab
An unstable loop burns more fuel
Temperature of one furnace zone (20 s dead time, 120 s time constant). At t = 600 s the charging rate increases.
Worst dip after t = 300 s
below the 1200 °C setpoint
Standard deviation
zone variability
Cumulative valve travel
actuator wear
Extra fuel
Zone temperature (°C)
Fuel valve opening (%)
What to watch
- With the loop oscillating, the operator raises the setpoint “just in case” so the product doesn't come out cold. That margin is permanent fuel use.
- Derivative action with a noisy thermocouple makes the valve chatter with no control benefit.
- Estimated extra fuel = margin the operator needs (worst dip) × adjustable sensitivity.
Simplified teaching models with order-of-magnitude illustrative values. Do not use them for design or operating decisions without validation against plant data.