Who has the operating procedures for burning out the furnace tubes in a heating furnace?

Take a look at the following posts; you may not necessarily find what you’re looking for. Please search first before posting about common issues such as how heating furnaces get scorched, the application of online scorching technology for the furnace tubes in coking units (Shen Haijun), how heating furnaces get scorched, coking scorching curves, 101 solutions for heating furnace scorching problems, issues related to incomplete scorching in coking processes, and what dual-scoring is What is the difference between online coking removal and coking in a coking furnace? Are online coking and online coking removal the same thing? What preparations are necessary before salt accumulation leads to coking in the heating furnace? This post was last edited by bingyu252 on 2009-2-13 08:58.]

It should be in “Technical Q&A on Tubular Heating Furnaces”. .

Operating procedures for burning off coke in heating furnaces 1 Basic principle of heating furnaces: The coke that forms inside the furnace tubes breaks apart at a certain temperature due to the impact of high-temperature steam and air; the resulting combustion products along with any unburned coke particles are then carried away by high-speed air currents. The purpose of introducing air is to supply the oxygen required for the combustion of coke dust ； The function of introducing steam is, first, to carry away the combustion products, and second, to reduce the oxygen content in the gas within the furnace tubes, thereby slowing down the burning rate and preventing damage to the furnace tubes due to too rapid burning and excessive temperature rise. 2 Preparations before coking: 2.1 Before coking, the heating furnace must have its tubes purged to ensure there is no oil inside; for furnace-1, the plug can be removed to verify this. 2.2 Check whether the coking process is correct; this includes verifying that the blind flange at the outlet of the heating furnace is in place, that the coking vent line is unobstructed, that the steam used for coking is flowing properly, that the blind flange for the unpurified air (air) used in coking has been removed, that the radiating coking elbows have been installed, and that the blind flange at the convection outlet leading to the coking tank has been removed, to ensure that the process is correct. 2.3 Calibrated pressure gauges must be installed at the inlet and outlet of the heating furnace as well as on the unpurified air supply. 2.4 Connect the instruments to monitor temperatures such as the furnace temperature, flue gas temperature, temperatures at the two outlets of the furnace’s convection chamber, and the temperature at the furnace’s radiation outlet. Also connect a temporary voltmeter for temperature measurement, and remove the flow measurement plugs for the north and south branches of the radiation system. . 2.5 Contact the plant dispatcher to ensure that the steam pressure is not less than 0.95 MPa, the air pressure is not less than 0.4 MPa, and the gas pressure is not less than 0.35 MPa. 2.6 Establish a charring record book, assign personnel for charring tasks, and confirm the work to be carried out before charring. 2.7 Its inspection and verification are based on the \"Heating Furnace Operation Procedures\" as the standard. 2.8 Feed water to the coking tank; start water supply to the injection pipe. 3 Scorching steps and requirements 3.1 Inject steam into the furnace tube and purge it to ensure that the tube does not burn out after ignition. Make sure to provide as much steam as possible. 3.2 The gas introduction step is carried out in accordance with the \"Heating Furnace Operation Procedures\". 3.3 The heating furnace is ignited in accordance with the standards specified in the “Heating Furnace Operation Procedures”. 3.4 Heating of the furnace: When the furnace temperature is below 500°C, the heating rate is 50°C/h ； When the furnace temperature is between 500–650°C, the heating rate is 30°C/h. Note: During the heating process, the exit temperature of the furnace’s radiation section must not exceed 550°C; otherwise, the furnace temperature should be reduced appropriately or the steam injection volume into the furnace tubes increased. 3.5 Determine whether the peeling of the coke has begun by observing the color of the steam and water coming from the burned-off vent line or the burned-off tank: the color of the steam and water should change from milky white to grayish white, and finally to black. Check the size of the carbon particles; if they are too small, reduce the steam volume accordingly to make the coke particles larger, as small particles cause significant wear on the elbows. Sometimes, especially when there is scale in the furnace tubes, peeling off is not easy; in such cases, the steam flow rate should be reduced and increased intermittently until no more peeling occurs. 3.6 Ventilation and charring in the heating furnace: When the furnace temperature reaches 600°C and the exit temperature of the radiation section is close to 500°C, a small amount of air begins to be introduced into the furnace tubes, based on the color of the steam and water. Special attention should be paid at this time to whether the temperature of the furnace tubes is rising. During the coking process, the outlet temperature of the radiation section should not exceed 550°C, the furnace chamber temperature should not exceed 650°C, and the surface temperature of the furnace tubes should not exceed 650°C (as indicated by temporary thermocouples). 3.7 During the coking process, pay close attention to changes in air and steam pressures, and adjust the ratio of air to steam properly (50% for each is appropriate). It is essential to prevent air from taking away the path for steam after carbon burns inside the furnace tubes; this can be detected by the fact that the temperature of the furnace tubes is higher than that of the furnace chamber. 3.8 During the coking process, when the surface temperature of the furnace tube approaches 650°C, immediate measures should be taken to reduce this temperature, such as increasing the steam supply to the furnace tube, reducing the amount of air used for coking, and stopping the air supply if necessary in order to lower the temperature inside the furnace. 3.9 Observing the burning condition of the furnace tube during the burning process: 3.9.1 Changes in the color of the furnace tube. The normal color is dark red; bright, red, and purple are strictly prohibited. Once brightening, redness, or purple coloring appears, regardless of the temperature of the furnace tubes, air supply must be stopped; at the same time, the amount of steam should be increased to lower the temperature in the furnace, and burning must be halted if necessary. 3.9.2 Special care must be taken to prevent local overheating of the furnace tubes; if such overheating occurs, it shall be handled in accordance with the steps outlined in (3.8) above. 3.9.3 Observe the amount of coke contained in the exhaust gas from the furnace tubes, the steam volume, and the color of the exhaust gas; the exhaust gas shall not be red or purple. 3.9.4 Check whether there is any blockage in the furnace tube (by observing the exhaust); if such a blockage is detected, stop supplying air, introduce a large amount of steam to clear the pipeline, and then resume normal burning. 3.9.5 When the observation furnace tube changes from dark red to black, it indicates that the coke has been completely burned out. After all the furnace tubes have been burned sequentially, the temperature in the furnace should be maintained, and the air supply increased for 5 minutes, with the aim of checking whether the coke has truly been completely burned out. Check whether the furnace tube is red; if it is, it indicates the presence of coke ； If the smoke emitted is white, it indicates that there is no more coke left ； Gray has a burnt tone. If it is confirmed that the coke has been burned out, the supply of air is stopped, the steam valve is opened wide to purge the suspended coke particles inside the furnace tubes, until the exhaust gas from the tubes is no longer gray-black but red-gray. Repeat the process once more; if there are no issues, it can be considered that this furnace tube has been completely burned out. 3.9.6 Record the temperature at various points of the furnace every 30 minutes, as well as the location and number of furnace tubes that are undergoing charring, steam pressure, air pressure, aeration time, valve opening degree, etc. 3.10 During ventilation, it is only possible to ventilate one path at a time; simultaneous ventilation of two or more paths is not allowed. 3.11 When burning, only one can be burned at a time; two cannot be burned simultaneously. 3.12 After burning out, start lowering the furnace temperature. When the furnace temperature is above 600°C, the cooling rate is 30°C/h ； When the furnace temperature is below 600°C, the cooling rate is 40°C/h. The flame is extinguished when the furnace temperature drops to 350°C; steam injection into the furnace tubes is stopped when the temperature falls to 250°C, and at the same time the flue dampers are opened for ventilation and cooling. 3.13 The shutdown of the heating furnace shall be carried out in accordance with the \"Heating Furnace Operation Procedures\". 4 Precautions 4.1 When the heating furnace burns out, two or more people must be present, with one person designated to be in charge. 4.2 There is a risk of burning out in the heating furnace; it is necessary to enhance personal awareness of safety and to operate strictly in accordance with the \"Operating Procedures for Preventing Burning Out in Heating Furnaces\". 4.3 Regularly check the water level in the burning tank to prevent sparks from escaping. 4.4 Once ventilation of the radiant tube begins, close attention should be paid to temperature changes in various areas; the temperature inside the furnace should remain uniform, with the temperature difference not exceeding 40°C. 4.5 Coking must be carried out strictly in accordance with the established procedures – it is strictly prohibited to proceed to the next stage of coking until the current stage is completed. 4.6 During the charring process, strictly control the furnace temperature and the radiation outlet temperature to prevent overheating. 4.7 During the coking process, it is strictly prohibited to burn out the furnace tubes at too fast a rate; the coking time should be 3–8 minutes per tube in the initial stage, and 8–10 minutes per tube in the later stage. 4.8 Pay attention to the steam inlet condition to prevent one path from being open while the other is blocked; the method for judgment is based on the sound level of the steam flow and changes in the outlet temperature. Charring temperature rise curve: (Temperature indicates the highest point in the furnace)