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1. What preparations are needed before baking the furnace? Before using a heating furnace for baking, the following tasks must be completed: (1) The construction of the heating furnace must be finished, and it must pass inspection and acceptance. (2) Safety facilities and hygiene conditions meet the requirements. 2. What steps should be followed for oven drying? When drying an oven, the following steps must be strictly followed: (1) Before starting the drying process, all manholes, viewing doors, explosion-proof doors should be opened, and the chimney baffles should be removed to allow natural ventilation for more than 5 days, after which ignition can take place to start the drying process. (2) When starting to heat the furnace, open the chimney damper by about 1/3; once the temperature inside the furnace rises and the suction force increases, then open the chimney damper a little more. (3) Steam is introduced into the furnace tubes to start heating; once the temperature inside the furnace reaches 130°C, the burners can be ignited to continue with the drying process. (4) When heating the furnace, gas fuel should be used as much as possible, and the burners should be ignited diagonally. (5) During the furnace drying process, the temperature rises evenly; the rates of heating and cooling should follow the designated drying curve, and the condition of the furnace walls should be monitored regularly. (6) Records should be kept during the furnace drying process, and the actual drying curve should be drawn after drying. (7) The furnace chamber is cooled at a rate of 20°C per hour. When the furnace temperature drops to 250°C, shut down the furnace and let it cool; when it drops to 100°C, enable natural ventilation. (8) After the furnace is dried, a thorough inspection of the furnace should be carried out; any defects found should be addressed. Liners with crack widths greater than 3 mm and depths exceeding 5 mm should be repaired, while those with voids or separation from the steel plate must be thoroughly repaired. 3. What is the purpose of maintaining constant temperatures at 150°C, 320°C, 450°C, and 500°C on the furnace heating curve? During the heating process, once the temperature in the furnace reaches 150°C, it is necessary to maintain this constant temperature in order to remove the natural moisture present in the furnace walls ； Maintain a temperature of 320°C to remove the crystalline water from the furnace walls ； Maintaining a constant temperature of 450°C and 500°C ensures thorough sintering of the refractory mortar in the furnace walls. 4. How can burners be ignited more safely? In the past, explosions have occurred when heating furnaces were started up or during operation; in mild cases, this caused damage to the furnace’s components, while in severe cases, it led to the destruction of the entire furnace. The main cause of furnace explosions is that when the burner is ignited, it lights up only to go out again, or oil or gas enters the furnace before the burner manages to ignite; furthermore, if the furnace operator fails to perform a steam purge before attempting to ignite again, this can lead to an explosion of gas inside the furnace. The explosion of the furnace during operation was caused by a lack of air, resulting in incomplete combustion of the gas. In the flue gas inside the furnace, gas will explode once it reaches a certain concentration. This situation often occurs in forced-ventilation heating furnaces; for example, in 1982, an explosion occurred in the pressure-reduction furnace of the Changjian Pressure Reduction Unit at the Wuhan Petrochemical Plant, due to the excessively small opening of the fan inlet damper, which resulted in insufficient air supply to the furnace. As a consequence, the gas did not burn completely, leading to the explosion of the furnace. To prevent furnace explosions, the following steps must be taken: (1) If the burner does not ignite during ignition but oil or gas enters the furnace, the operator must immediately close the oil valve or gas valve, then blow steam into the furnace; once steam is visible in the chimney, ignition can be attempted again. (2) When the burner attempts to ignite and fails to do so, the stove operator should immediately close the oil valve or gas valve, then blow steam into the furnace; once steam is visible in the chimney, ignition can be attempted again. (3) During operation of the furnace, if insufficient air supply to the burner is detected, the cause should be identified immediately and addressed promptly. First, check whether the opening degree of the butterfly valve that controls the air supply to the furnace is appropriate. If it is too small, it should be increased immediately to an appropriate level so that the fuel in the burner can burn fully. 5. What are the ignition requirements when a burner is burning oil? Currently, heating furnaces in petrochemical plants in China often use oil-gas combined burners, which can burn oil alone or gas alone, or both simultaneously. When the burner is burning oil, the ignition process follows these steps: (1) Adjust the burner’s air valve to 1/3 of its full opening; once the burner has caught fire, then adjust the air valve to the appropriate opening ； When the burner is equipped with a soundproof cover, the furnace operator must pay attention to the opening and closing direction of the air valve. (2) If the burner is equipped with an air duct or sound insulation cover, open the cover on the oil leakage pipe at the bottom of the burner’s air duct or sound insulation cover to prevent fuel oil from accumulating inside it. Once the burner is burning properly, reinstall the cover. (3) Introduce an appropriate amount of steam into the gas nozzles on the burner to prevent them from being clogged by oil or other substances. (4) Place the lit ignition rod at the top of the burner; one should not look directly at the ignition hole, but rather from the side, ensuring that the face is not turned directly toward the burner to prevent backfire from injuring the person. (5) Slightly open the steam valve first, then open the oil valve. After igniting the flame, adjust the oil-to-steam ratio slowly and carefully to ensure that the oil is fully atomized for complete combustion; also adjust the opening degree of the air damper or butterfly valve as appropriate based on the combustion conditions. (6) After the burner is lit, the furnace operator must not leave the furnace immediately to prevent the burner from going out or leaking oil. Once it goes out, immediately close the oil valve, then blow steam into the furnace; restart ignition once steam is visible in the chimney. (7) When using the burner, it should be aimed at the ignition point to ensure even heat distribution. (8) Control the fuel oil pressure properly; it is required that the pressure of the atomizing steam be 98 kPa higher than that of the fuel oil. (9) The damper of the burner at the end of combustion must be closed to prevent air from leaking into the furnace, which could lead to an excess of air and affect the furnace’s thermal efficiency. 6. What are the ignition requirements when using gas in a burner? When a burner operates on gas, the ignition process follows these steps: (1) Adjust the burner’s air valve to 1/3 of its full opening; an excessive opening makes it difficult to ignite the burner. Once the burner is lit, adjust the air valve to an appropriate opening ； When the burner is equipped with air ducts or soundproof enclosures, the furnace operator must pay attention to the opening direction of the air valves. (2) Pass an appropriate amount of steam through the oil nozzle to protect it. (3) Place the lit ignition rod at the top of the burner; one should not look directly at the ignition hole, but rather from the side, ensuring that the face is not turned directly toward the burner to prevent backfire from hurting one. (4) Open the gas valve slightly; once the burner is lit, adjust the gas valve further, and adjust the opening of the air damper or butterfly valve as appropriate based on the combustion conditions. (5) Once the fire is lit, the stoker must not leave the furnace immediately to prevent the burner from going out. Once the fire is extinguished, the gas valve should be closed immediately, steam should be blown into the furnace, and ignition should be attempted again once steam is visible in the chimney. (6) When using the burner, diagonal ignition is required to ensure even heat distribution. (7) The dampers or butterfly valves of burners that are not in use must be closed to prevent air from entering the furnace, thereby saving fuel. 7. What are the reasons why a burner fails to ignite, and what are the solutions? Burners often fail to ignite when attempted to be started, and there are various reasons for this. Below are the main causes along with corresponding solutions: (1) The air valve of the burner is set too wide open, or the flue damper is also set too wide open, resulting in an excessive amount of air entering the furnace; in such cases, it is difficult for the burner to ignite. The solution is to reduce the opening degree of the burner’s air valve and the chimney baffle; once ignition occurs, then adjust the valves and baffle to the appropriate opening degrees. (2) When the pressure of the fuel oil is greater than that of the atomizing steam, it is also difficult to ignite the burner. The solution is to adjust the fuel oil pressure to be about 98 kPa lower than the pressure of the atomized steam. (3) If the pressure or temperature of the fuel oil is too low, contact the relevant parties to increase its pressure or temperature. (4) If the pressure or temperature of the high-pressure gas is too low, contact the relevant authorities to increase the pressure or temperature of the gas. (5) If the fuel oil contains too much water, contact the relevant parties to carry out dehydration promptly. (6) If the high-pressure gas contains too much oil and water, it is necessary to contact the relevant parties to carry out oil and water removal promptly. (7) If the steam volume is too high while the fuel oil volume is too low, the steam valve should be closed slightly and the fuel oil valve should be opened appropriately to achieve an appropriate oil-to-steam ratio. 8. By how much must the steam pressure be higher than the oil pressure when the burner is burning oil? Why? When the burner is using oil, the steam pressure must be at least 98 kPa higher than the oil pressure. The reason is that the heating furnaces in petroleum chemical plants mostly use steam atomization burners; such burners rely on steam to atomize the fuel oil into small droplets to facilitate combustion. To achieve this goal, it is necessary to keep the steam pressure 98 kPa higher than that of the fuel oil; otherwise, the fuel will not be atomized properly, the burner will not burn efficiently, and it may even go out. 9. What are the requirements for the color and shape of the burner flame? In the past, it was required that the flames from heating furnace burners be straight and strong, brightly white, and sky-blue; such requirements led to higher fuel consumption, which was extremely unfavorable for energy savings. Now, from an energy-saving perspective, it is sufficient for the flame to be shaped, stable, and orange-yellow in color. 10. What are backfire and deflagration? When the velocity of the mixture of air and gas flowing out of the gas nozzle is lower than the flame propagation speed, the flame re-enters the interior of the burner to burn there; this phenomenon is called backfire. Tempering can sometimes cause detonation or stalling, and over time it may also damage the mixing chamber or lead to other accidents. When the velocity of the mixture of air and gas flowing out of the gas nozzle exceeds the deflagration limit, the gas does not ignite until it has moved a certain distance away from the nozzle; this phenomenon is known as deflagration. Flameout occurs when the flame burns unstably, resulting in its extinguishment.