Operational Methods and Key Temperature Control Procedures for Glass Melting furnace

(1) The temperature inside the furnace directly affects glass melting quality, glass melt convection, forming operations, fuel consumption, refractory brick erosion, and furnace lifespan; therefore, it must remain stable and free from significant fluctuations. Maintaining temperature stability primarily involves controlling the following aspects: stabilizing the pull rate; stabilizing the flame and ensuring a proper air-to-fuel ratio; ensuring stable oil gun performance; and maintaining stable oil temperature, oil pressure, and atomizing gas pressure.
(2) Accurately assess temperature trends within the furnace by observing the following: the brightness of the internal masonry (specifically the breast walls and the main crown)—increased brightness indicates a temperature rise, while dimming indicates a drop; the thickness and position of the batch pile—if the layer thins and moves closer while bubbling vigorously, the temperature is rising; conversely, if it thickens and recedes, the temperature is falling; the position of the foam line—moving closer indicates a temperature rise, while receding indicates a drop; and the flame characteristics (length and brightness)—appropriate length and brightness suggest a temperature rise, whereas flames that are too short, too long, or hazy may indicate a temperature drop.
In summary, if temperatures in the melting zone and other areas rise, the batch pile and foam line move closer, and the breast walls appear whitish, the air (and fuel) supply should be reduced; conversely, the air and fuel supply should be increased. Comprehensive analysis of instrument readings, accurate assessment, and correct adjustments are essential to ensure temperature stability.

(3) To control the melting temperature, the stability of the foam line must be maintained. If the foam line recedes (moves further away), the temperature in the melting zone should be raised by appropriately increasing the fuel and combustion air supply to the first few pairs of ports, while also raising the temperature at the hot spot. Conversely, if the foam line advances (moves closer), the temperature in the melting zone should be lowered by reducing the fuel and combustion air supply to the first few pairs of ports.
(4) In the event of a raw material batching system failure, switch entirely to charging cullet. As the cullet enters the furnace, gradually reduce the fuel and air supply to lower the temperature to the target level; when raw batch begins to enter, increase the fuel and air supply until the temperature stabilizes. As the raw batch arrives, the batch pile and foam line will gradually shift outward; increase the firing rate to slightly above normal levels, and once the temperature stops dropping, reduce the oil, gas, and air supply back to standard operating settings.
(5) If fluctuations in furnace pressure cause variations in melting temperature, adjust the furnace pressure to maintain a slight positive pressure. High furnace pressure during hot repairs can lead to temperature spikes; observe the melting conditions and flame quality within the furnace to decide whether to appropriately reduce the oil, gas, and air supply. High pressure can create "false" temperature readings (apparent temperature higher than actual melt temperature), so the operating temperature should be set 2–5°C lower during hot repairs (depending on the specific pressure level).

(6) When the glass pull rate is reduced due to a tin bath malfunction, the flow rates of oil, gas, and combustion air must be adjusted in proportion to the reduction in pull rate; the melting temperature may also be lowered by 5–10°C. If performing a "head-breaking" operation (re-starting the ribbon), the melting temperature should be controlled between 1500°C and 1520°C. When increasing the pull rate or re-starting the ribbon, the flow rates of oil, gas, and air should be gradually increased—and the melting temperature restored to its original set point—in response to the actual thickening of the batch pile and the receding of the foam line.
(7) If increased raw material moisture content makes melting difficult, the fuel and air supply to burners No. 1 and No. 2 should be increased.
(8) If a low proportion of cullet causes the batch pile and foam line to recede too far, the fuel and air supply should be increased to bring operating parameters to their upper limits, and relevant departments should be notified to organize the return of cullet to the furnace.
(9) The temperature difference between the hot spot and burner No. 1 must be at least 100°C.
(10) In addition to using the melting section temperature for control, the temperature at the end of the cooling section can be regulated by automatically adjusting the cooling fan airflow; generally, the temperature of the molten glass entering the canal should be stabilized within a ±1°C range.
(11) Operators on each shift must constantly monitor temperature fluctuation trends across the furnace and anticipate changes; if trends indicating fluctuations in temperature or furnace pressure are observed, timely adjustments should be made, avoiding drastic opening or closing actions.
(12) If regenerator temperatures are generally too high, atomization should be enhanced to ensure complete combustion; if the temperature of a specific burner is excessively high, the opening of the damper in that burner's branch flue can be adjusted.

Operating Procedures for Melting and Chemical Processing

(1) Temperature Measurement Points and Parameters
① Strictly adhere to the technical parameters issued by the production technology department: the maximum furnace temperature must not exceed 1590°C; temperature fluctuations must be kept within ±5°C for the melting section, ±2°C for the cooling section, and ±1°C for the forehearth channel.
② In addition to hourly thermocouple measurements and recording of temperatures throughout the furnace, monitor the temperature of each pair of ports once daily using an optical pyrometer or infrared thermometer during the firing reversal process.
(2) Furnace Temperature Adjustment
① If there is a significant transverse temperature difference, check the three fuel parameters for appropriateness; slightly reduce the atomizing medium pressure, or—if the flame is long—increase the combustion air volume to maintain flame length. If the flame is short and bright with a high root temperature, reduce the atomizing medium flow to lower the root temperature.
② In the event of overall furnace temperature fluctuations, check for changes in the three fuel parameters, fuel quality, glass pull rate, or batch composition, and make temperature adjustments accordingly.
③ Regarding "hot spot" temperature: the target temperature must remain constant. If fluctuations occur, adjust promptly while investigating the cause—checking for changes in the batch pile, foam line, pull rate, batch composition, and the three fuel parameters.
④ Forehearth channel temperature control: primarily adjust the temperature of the final pair of ports, using the cooling section dilution air for fine-tuning to maintain the desired channel temperature.

(3) Burner Reversal Operation: The burner reversal process offers three control modes selectable via a switch: automatic, semi-automatic, and manual.
① Automatic Reversal: This mode is used during normal production. When the selector switch is set to "Automatic," the control system executes the reversal automatically according to the programmed sequence. The automatic reversal sequence is as follows (using the switch from the south burner to the north burner as an example): sound the preparatory alarm → switch oil and air setpoints to the north values ​​→ cut power to the oil and air actuators → (after 5s) close the south oil electric actuator → (after 5s) switch the combustion air branch flue dampers from south to north → (after 1s) close the south oil reversing solenoid valve → (after 0.5s) close the south atomizing gas solenoid valve → (after 5s) shut off south combustion air → (after 5s) turn on north combustion air → (after 3.5s) turn on north atomizing gas → (after 0.5s) open north oil solenoid valve → (after 0.5s) open north oil electric actuator → (after 6s) restore power to the oil and air actuators (time intervals are generally measured in seconds; the reversing time for the air reversing valve is the longest, approximately 15–30 seconds; the entire process is completed within 2 minutes).
② Semi-automatic Reversal: This mode is used in the event of a computer malfunction or when the reversal timing needs to be temporarily adjusted. First, set the selector switch to the "Semi-automatic" position, then press the semi-automatic reversal switch to initiate the reversal; the execution sequence is identical to that of the fully automatic mode.
③ Manual Reversal: This mode is used when semi-automatic reversal is not possible.
First, set the selector switch to the "Manual" position; the entire reversal process is then controlled and executed manually. The manual firing reversal sequence is as follows (taking the switch from the south burner to the north burner as an example): sound the preparatory signal → switch the oil and air setpoints to the north values ​​and cut off power to the oil/air actuators → after 5 seconds, close the south oil reversing actuator → after another 5 seconds, reverse the branch flue damper from south to north until the movement is complete and the indicator light turns on → close the south oil reversing solenoid valve → close the south atomizing gas solenoid valve → shut off the south combustion air → after 4 seconds, turn on the north combustion air → turn on the north atomizing gas → open the north oil solenoid valve → open the north oil electric actuator → restore power to the oil/air actuators (time intervals are generally measured in seconds; the reversal time for the reversing machine is approximately 15–30 seconds. The firing interruption process should be kept within 2 minutes, as an excessive duration would cause a significant drop in kiln temperature).

When performing a manual reversal, the electric heating system must be turned off first; otherwise, low oil flow could cause coking on the electric heaters and clog the filters and oil guns. If the manual reversal cannot be completed, the amount of crushed glass added can be increased; if the batch charger frequency is too high, the opening of the charger gate should be adjusted accordingly. Direct the oil and gas to the side receiving combustion air to ensure proper combustion.
④ Standard reversals occur every 20 minutes; the timing must not be advanced or delayed without the approval of the workshop supervisor or the shift manager on duty. If masons or other personnel are working on the kiln, contact must be established before initiating a reversal to prevent accidents.
⑤ During each shift, inspect the drive mechanism, limit switches, and wear on the steel cables (or high-strength chains, which most manufacturers now use) of the air reversing valve at least twice.
⑥ Precautions for gas reversal operations: Switch the gas flow before the air flow; otherwise, low flue temperatures could lead to an explosion. If the reversing valve stops midway, return it to its pre-reversal position, investigate the cause, and then attempt the reversal again; pay close attention to the flow directions of the gas and air to avoid errors that could cause opposing flows (back-pressure). Switch to manual reversal if the voltage is too low or if the electric equipment malfunctions.
To minimize gas waste and fluctuations in kiln temperature, the duration of the reversal operation should be kept as short as possible.