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1. What items need to be checked during the normal operation of a heating furnace? When the heating furnace is in normal operation, the following items must be checked on a regular basis: (1) Whether the total outlet temperature of the medium, the flow rates in each channel, the temperature differences, and the furnace temperature meet the specified process requirements. (2) Is the negative pressure at the outlet of the radiation chamber between -20 and -40 Pa? (3) The combustion condition of each burner, whether the shape and color of the flame meet the requirements, and whether the flame is burning the furnace tubes, etc. (4) Whether there are any phenomena such as bending, peeling, bulging, reddening, or darkening in each furnace tube ； Make sure to check for leaks at the elbow plugs, inlet and outlet valves, flanges, etc. (5) Check for any changes in the brazier bricks, hooks, pull hooks, furnace walls, lining, etc. (6) Are the fuel oil pressure, atomization steam pressure, and gas pressure within the required range? (7) High and low pressure gas tanks should have their liquid removed regularly, and the vent valve should be closed immediately after the liquid has been removed. (8) It is necessary to regularly check the temperature changes at various points inside the furnace to keep an accurate understanding of the situation. (9) The explosion-proof doors, ventilation doors, chimney dampers, butterfly valves, air control valves, etc. of the furnace must not be opened casually; the viewing door should be closed immediately after inspection is complete. 2. What are the factors that affect changes in the furnace outlet temperature and what are the solutions? (1) The main factors affecting changes in the furnace outlet temperature include: ① Changes in fuel oil pressure. ②Changes in the properties of fuel oil, such as uneven density and the presence of water. ③The gas pressure is unstable. ④Gas contains oil. ⑤Changes in the vapor pressure during atomization: if the pressure is low, atomization is poor, the flame becomes red and dimmer, the oil discharge from the nozzle increases, the temperature in the furnace rises, and black smoke is emitted from the chimney ； If the pressure is high, the flame turns white, becomes harder, shorter, and is prone to dying out or being extinguished. ⑥Changes in feed rate and feed temperature. ⑦Changes in the feed properties, with lighter oil and higher heat absorption, lead to a decrease in the temperature at the furnace outlet. ⑧A malfunctioning instrument can cause smoke to emerge from the chimney, an increase in furnace temperature, or even a shutdown of the furnace. (2) Adjustment method: ① When the pressures of fuel oil, gas, and atomizing steam change, contact the relevant parties for handling. ②Contact the relevant parties to regulate the feed rate, ensuring stable feed flow, temperature, and properties in the furnace. ③When high-pressure gas contains oil, it is necessary to contact the relevant authorities for oil removal. ④Adjust the fire levels carefully to avoid affecting each other. ⑤Coking in the nozzles must be addressed promptly, and blockages in the nozzles must be repaired immediately. ⑥Contact the instrument operator; in the event of an instrument failure, switch immediately to manual operation or use the control valve to divert the flow. 3. What are the causes of tube coking and what are the solutions? (1) Causes of tube coking ； ①The uneven flame leads to uneven furnace temperatures, resulting in overheating of the flattened sections of the furnace tubes. ②Excessive changes in feed rate or sudden interruptions, etc. ③The flame deflects the furnace tube, causing localized overheating. (2) Solution: ① Maintain uniform furnace temperature. ②Maintain a stable feed flow with uniform rates across all channels; in the event of a feed interruption, shut down the system promptly. ③Adjust the flame to shape and stabilize it, so as to prevent burning of the furnace tubes. 4. What are the steps for burning out the furnace tubes? (1) First, steam is supplied at the feed valve; once steam reaches the burning tank, ignition in the furnace is permitted. After steam supply, cooling water can be applied to the burning tank. (2) Ignite the furnace chamber of the heating furnace; the temperature should rise at a rate of 50°C/h, reaching 450°C where it will be maintained at that level. During this temperature rise process, the cooling water flow rate to the coking tank must be increased continuously. If the ash discharge from the burned tank opening is excessive and there is a lot of oil remaining, the heating rate should be reduced, with the temperature at the furnace outlet not exceeding 400°C. 5. What are the operational requirements for burning out the furnace tubes? (1) Use separate air and steam supply systems, adopting an alternating burning method – burn one path out before moving on to the other. In other words, stop the steam supply, then immediately supply air; after providing an appropriate amount of air, stop supplying air again and immediately increase the steam flow. Each path proceeds in this manner until it is burned out. (2) Strictly control the duration of each ventilation session. The first few times, the duration should be short, ideally 1–2 minutes. In the future, gradually increase the air supply time, with the duration of this time determined by the color of the coke water discharged after each air supply. If the water is dark in color and sometimes contains visible burnt particles or lumps, the air supply should be maintained at the same duration and volume as before ； If the color of the drained water is not black, the air supply time can be extended and the air supply volume increased. (3) After heating with air, pay close attention to the color of the furnace tube; the normal color is dark red. If it is peach-colored, it indicates that the temperature is too high; the amount of air should be reduced accordingly while increasing the amount of steam, until the furnace tubes change from red to black. The furnace tube of the vacuum furnace turns red when its temperature reaches 560–570°C, so close attention must be paid. (4) The coking powder blown out from the coking vent tank should be no larger than 2 mm; particles that are too large can easily cause blockages in the furnace tubes and damage them. (5) The temperature at which charring begins is 450°C in the furnace. In the later stages of charring, a constant-pressure furnace can reach temperatures of 480–490°C, but not above 500°C; a reduced-pressure furnace can reach temperatures of 570–590°C, but not above 600°C. (6) To determine whether the burning is complete, it is determined by whether the furnace temperature reaches the upper limit for burning; that is, 490°C for atmospheric-pressure furnaces and 590°C for reduced-pressure furnaces. After starting the airflow, the color of the water does not turn black; when it takes on a slight reddish-brown rust-colored hue, it means it has been basically burned clean. (7) After burning out, turn off the air and switch to steam for cooling. The cooling rate should be 30°C/h before reaching 400°C, and 40°C/h after that. Turn off the fire when the furnace temperature drops to 350°C. (8) When the furnace temperature drops to 300°C, steam supply to the furnace tubes is stopped. If there is a plug, remove it to check the burning effect. When the furnace temperature drops to 250°C, open the chimney dampers, manholes, and viewing ports to allow natural ventilation. (9) The return elbow is located outside the furnace; due to the low temperature, coke does not burn easily. Therefore, an air-powered coke cleaner should be used to remove the coke after it has burned. 6. What issues should be considered when the furnace tubes burn out? (1) The material of the furnace tubes in atmospheric-pressure furnaces is 10# steel, and their operating temperature ranges from -40 to 475℃ ； The furnace tube of the vacuum furnace is made of Cr5Mo, and it can be used at temperatures ranging from -40 to 560°C. Therefore, it is necessary to strictly control the furnace temperature in atmospheric-pressure and reduced-pressure furnaces; it is not allowed for this temperature to be too high, and the temperature of superheated steam must be below 430°C. (2) Regularly check the drainage outlet of the coking tank to monitor the coking situation; if a large amount of coke is discharged, the air supply time should be shortened ； Conversely, the time given to the wind should be extended ； To prevent the coke from falling too quickly, as this can easily cause blockages in the pipelines; if a blockage occurs, it must be dealt with promptly before continuing with the heating process. Also, be careful that the pipeline does not vibrate too much. (3) The interval between each burning sessions should be 10–15 minutes, to ensure an adequate flow of steam; this helps improve the burning effect and also prevents the burnt mass from becoming too large or causing deformation of the furnace tubes. (4) During the burning process, dedicated personnel should be responsible for adjusting the flame; records of air and steam supply should be kept after each operation, and the ignition must be even. (5) It is necessary to ensure sufficient steam pressure (steam pressure > 0.98 MPa), air pressure (pressure of non-purified air > 0.39 MPa), and water pressure (pressure of fresh water > 0.34 MPa). 7. What phenomena usually occur in furnace tubes before they rupture? How should this be dealt with? Before a furnace tube ruptures, bubbling or deformation typically occurs. When the color of the furnace tube turns peach-colored, the operator must pay close attention; if the situation worsens, normal shutdown procedures should be followed. 8. What are the common phenomena that occur after a furnace tube ruptures? How should they be dealt with? (1) The phenomena that occur are: ① After the furnace tube ruptures, the oil inside the tube flows into the furnace and catches fire; however, due to insufficient air, the combustion is incomplete, resulting in black smoke being emitted from the chimney. ②As the oil inside the tube flows into the furnace, the outlet pressure of the medium within the furnace tube decreases, while the outlet temperature of the medium rises. (2) Handling method: ① If the furnace tube rupture is minor, handle it as a normal shutdown. ②If the furnace tube rupture is severe, it shall be treated as an emergency shutdown. 9. How to handle a sudden interruption in the feed to the heating furnace? (1) Symptoms: The temperature inside the furnace and the temperature at the furnace outlet rise sharply. (2) Handling method: ① Turn off the engine promptly. ②Find the cause and adjust the feed rate accordingly. 10. How should one handle a sudden interruption in the fuel oil or fuel gas supply to the heating furnace? Most heating furnaces in petrochemical plants use oil-gas combined burners, which can operate on either oil or gas. When the fuel oil supply is interrupted, gas should be used immediately ； When the fuel gas supply is interrupted, oil should be used immediately.