Furnace pressure control in regenerative aluminum melting furnaces is a critical factor in ensuring melting efficiency, reducing energy consumption, and extending the service life of the furnace body. Its core logic lies in balancing the volume of gases within the furnace by regulating the rate of flue gas discharge.

1. Control Principles and Core Loops

Furnace pressure control is deeply coupled with the flue gas control loop. The system employs a differential pressure transmitter to continuously monitor the pressure difference between the interior and exterior of the furnace chamber in real time, converting these pressure signals into 4–20 mA current signals for input into a PLC (Programmable Logic Controller). Within the PLC, a PID (Proportional-Integral-Derivative) closed-loop control module compares the actual measured pressure against a preset target value (typically a slight positive pressure, such as 10–30 Pa), subsequently issuing control commands to the actuator—usually an electric modulating butterfly valve located on the auxiliary flue.

2. Key Execution Logic

When furnace pressure rises (e.g., immediately after charging or during the instant of flow reversal): The PLC commands the valve to open wider, allowing a greater volume of high-temperature flue gas to be rapidly vented through the auxiliary flue—or discharged after passing through the regenerator—thereby reducing the volume of gas retained within the furnace.

When furnace pressure drops or becomes negative: The valve opening is reduced, restricting flue gas discharge; this allows gases to accumulate within the furnace, causing the pressure to rise back to the target level.

3. Specific Considerations for Regenerative Operation

Since regenerative systems utilize a dual-regenerator configuration with alternating flow reversals (typically switching every 30–60 seconds), the resistance within the flue gas discharge channel fluctuates violently during the instant of reversal, leading to periodic, abrupt spikes in furnace pressure. Consequently, advanced control systems incorporate a "reversal synchronization feed-forward" mechanism: the valve opening is pre-adjusted slightly just prior to the reversal action to suppress these pressure spikes.

4. Safety Protection and Optimization

Furnace Door Interlock: The moment the furnace door is opened, the system automatically switches to a "pressure-priority" mode to force flue gas extraction, thereby preventing high-temperature gases from jetting out and causing injury to personnel.

Overpressure Protection: If the furnace pressure exceeds a critical limit, the system triggers an emergency response—either by opening the explosion-relief door or by fully opening the flue damper.

Through the coordinated operation of the aforementioned PID closed-loop regulation and reversal logic, furnace pressure fluctuations in regenerative aluminum melting furnaces can be maintained within a tight tolerance of ±5 Pa. This effectively prevents the ingress of cold air—which could lead to the oxidation of molten aluminum and hydrogen absorption—while simultaneously avoiding flame leakage from the furnace door that could damage the sealing structures.