What are the requirements for online decoking of furnace tubes?

Preparations for online decoking operation of heating furnace: ⑴ Preparation work 1) Prepare 2 optical pyrometers so that the operator can monitor the tube wall temperature during the online defocusing process. 2) Please calibrate the meter’s outlet temperature of the furnace to ensure its indication is accurate. 3) Notify the instrument to use FC1110 for decoking steam flow control, and ask the instrument to ensure that its indication is accurate. 4) 3.5MPa steam water distributor V-113 cuts water. Contact dispatch and require sufficient steam volume of 3.5MPa (at least 8000kg/h) and pressure >2.9MPa. 5) After three days of adjustments, the switching time of the four-way valve was changed from 21:00 to 5:00. 6) Contact dispatch and adjust the heating furnace feed volume to the 42 tons/hour branch. 7) Before online decoking, adjust and stabilize the operation of the heating furnace. The furnace outlet temperature is 497±1℃, and the furnace outlet temperature of this group is controlled according to the current situation. 8) 2 hours before online decoking, cut off the heating furnace interlock 2 (the temperature of the flue gas inlet and outlet air preheater is high), 4.1~4.4 (the fuel gas pressure of this group is high and low), 4.5 and 4.6 (the process medium flow is low), and 5.1~5.2 (the fuel gas pressure of the permanent lamp is low). 9) Arrange experienced operators to participate in online focus clearing. 10) Arrange bodyguards. 11) Prepare the recording paper for focus clearing before online clearing. (2) Online focus clearing operation procedure 1) The whole process of online focus clearing takes about 36 hours. During this period, the changes in wall temperature of the 14 tubes in this group should be monitored at any time. The heating furnace is changed to natural ventilation state. 2) In order to avoid overcooling of the coke tower, the online coke cleaning operation should be carried out 3 to 5 hours after the coke tower is switched. 3) When starting online coke cleaning, close 50% of the burners of this group and control the furnace outlet temperature of this group to 400°C. 4) The capacity of this group of furnace tubes is gradually reduced, and the capacity of the other three groups is gradually increased to a branch of 50 tons/hour to ensure the minimum load of the fractionation tower system. When reducing or increasing the volume, pay attention to controlling the outlet temperature of each group of furnaces, and the speed should not be too fast. At the same time, adjust the steam injection volume at each point within the range of the process indicators according to changes in the feed volume. 5) Gradually close the feed branch valve of this group of furnace tubes. When the feed pressure of this group of furnace tubes drops to 2.3~2.5MPa, slowly open the purge steam valve and keep the inlet pressure of this group of furnace tubes 0.1MPa higher than the other three groups until the feed branch valve of this group of furnace tubes is closed. The steam injection volume of this group remains unchanged. The purging process takes approximately 2 hours. 6) Open the decoke steam flow control valve FC1110 and control the flow to 4000kg/h. After confirming that the pipelines and bypasses from the feed branch hand valve to the decoking steam injection point have been purged clean, stop purging the steam. Adjust the amount of coke-clearing steam to ensure that the inlet pressure of this group of furnace tubes is 0.1MPa higher than the other three groups. 7) Adjust the burner to raise the furnace outlet temperature to 500°C and maintain it for 20 minutes. The furnace outlet main pipe temperature is required to be not less than 488°C. Please refer to the coke tower inlet temperature. 8) Adjust the burner, raise the outlet temperature of the furnace to 593°C within 2 hours, increase the steam flow from 4000kg/h to 5000kg/h, control the inlet pressure of the furnace tubes in this group to be 0.1MPa higher than the other three groups, adjust the steam volume, and keep the temperature constant for 3-4 hours. At the same time, the outlet temperatures of the other three groups of furnaces were controlled within the range of 497±1°C. 9) Adjust the burner to quickly reduce the outlet temperature of the furnace to 440°C. Pay attention to keep the inlet pressure of this group of furnace tubes 0.1MPa higher than the other three groups. If the furnace outlet temperature cannot be lowered, close all the main burners of the group. The adjacent burners of the same furnace group can also be appropriately reduced or close some burners to cope with the drop in the furnace outlet temperature of the group. The first cooling rate is controlled at 45 minutes to 1 hour, and the second and subsequent cooling rates are about 30 minutes. 10) After 5 minutes, quickly increase the furnace outlet temperature to 593°C. At this time, the heating furnace tube will vibrate greatly. Note that a dedicated person should be responsible for monitoring the color and other conditions of the furnace tubes and brackets of this group. If any abnormalities such as uneven combustion of the furnace tubes or deformation of the furnace tubes and brackets are found, contact the outside operator in time to adjust the burner until the heating rate is slowed down. Keep the temperature constant for 2-3 hours. Pay attention to keep the inlet pressure of this group of furnace tubes 0.1MPa higher than the other three groups. 11) Repeat the above 9-10 process 4-5 times. Do not increase or decrease the temperature too fast in the first process. 12) Six hours before switching the four-way valve, reduce the furnace outlet temperature of this group to 415°C, gradually open the feed branch valve of Group C, and reduce the amount of coke-clearing steam until all are closed. 13) After the feed amount of this group is equal to that of the other three groups and is stable, put the heating furnace interlock 2 (the temperature of the flue gas inlet and outlet air preheater is high), 4.1 to 4.4 (the fuel gas pressure of this group is high and low), 4.5 and 4.6 (the process medium flow is low), and 5.1 to 5.2 (the continuous light fuel gas pressure is low). 14) Adjust the oxygen content at the furnace bottom to the normal value of 4-5%. 15) Adjust the burner and adjust the furnace outlet temperature to the range of 497±1°C. The outlet temperature of this group is controlled by the temperature of the furnace tube wall of this group and is as close to the other three groups as possible. Pay attention to controlling the temperature of the tube wall of this group of furnaces not to be too high within the range of process indicators. If excessive temperature occurs, adjust the burners of this group in time. In addition, you can consider appropriately lowering the outlet temperature of this group of furnaces. 16) The heating furnace feed capacity is increased to 45 tons/hour branch. 17) After about 36 hours of online coke clearing operation, switch the four-way valve. (3) Notes 1) During the online coke cleaning process, attention should be paid to keeping the inlet pressure of this group of furnace tubes 0.1MPa higher than the other three groups. 2) Check the temperature of the furnace tube wall once every hour and keep records. 3) During the heating process, check whether the furnace tube is partially overheated and make adjustments in time. 4) Pay close attention to the pressure at the top of the fractionating tower, use the reflux volume at the top of the tower to control it, and adjust the amount of coke-clearing steam in a timely manner to prevent the fractionating tower from flushing. The air cooling A-101/1-10 and after-cooling E-101/1-6 at the top of the tower are fully opened, and the circulating water and upper water valves are fully opened. 5) Pay attention to the liquid level of V102 water bag and control the liquid level of V-03. At the same time, pay attention to the inlet pressure of the air compressor K-201. If the frequency conversion adjustment is not enough to control the inlet pressure, you can consider using the inlet torch control, and strengthen the monitoring of the liquid level of the V-201 and K-201 inlet liquid bags, and press the oil in a timely manner, which is the responsibility of a dedicated person. 6) Pay close attention to the temperature of the flue gas exiting the convection chamber, which must not be higher than 500°C. 7) The furnace tube wall temperature control is ≯ 690°C. The tube wall temperature can be controlled by increasing the steam flow or reducing the fuel amount. 8) The furnace outlet temperature of this group should be controlled with reference to the coke tower feed temperature. If the furnace outlet temperature is found to be inaccurate, contact the instrument for calibration immediately. In addition, contact the instrument to save and record the important operating parameter data for 36 hours before, during and after online coke cleaning. During the online coke cleaning period, the temperature of the furnace tube wall temperature within 32 hours will be made into a temperature-time curve as a reference for the next coke cleaning operation. 1) Contact the instrument technician to calibrate the heating furnace outlet temperature, furnace tube wall temperature, and furnace temperature thermocouples to ensure they are correct. 4) Be ready to use steam for online defocusing: The pressure is 3.5MPa and the speed reaches 4.5t/h. Do a good job in heating the steam pipes for online cleaning. 5) Unlock the interlock, open the large flue baffle first, and then slowly open the natural ventilation door. Operation steps: 1) This operation should be performed 3 to 5 hours after the four-way valve is switched to prevent the coke tower from being overcooled. During the online coke cleaning period, the wall temperature of the furnace tube of the online coke cleaning group must be monitored at any time, and it cannot be too high. 2) Gradually reduce the volume of the furnace tubes for online coke cleaning, while increasing the feed volume of the other three groups to keep the total volume stable, and gradually close the feed branch valve of the online coke cleaning group. Open the valve of the online coke-cleaning steam entering the furnace pipe. 3) While reducing the volume, close 50% of the burners in this group to reduce the temperature and control the outlet temperature to 400°C. When reducing or increasing the volume, pay attention to controlling the outlet temperature of each group of furnace tubes, and the volume reduction speed should not be too fast. At the same time, according to changes in the feed volume, adjust the steam injection volume at each point within the range of the process indicators. 4) Gradually close the feed valve of the furnace tube of the online coke cleaning group, increase the steam flow, and keep the pressure of this group consistent with (or slightly higher than) the other three groups of feed pipes. After cutting off the feed, open the steam to purge the furnace tube from the cut-off valve for about 2 hours. 5) Adjust the fuel gas of this group to quickly increase the outlet temperature of this group to 470°C for 20 minutes, and keep the total outlet temperature of the heating furnace not less than 488°C. 9) After 5 minutes, quickly raise the furnace tube outlet temperature of the online coke cleaning group to 560°C and keep the temperature constant for 2 to 3 hours. During the heating process, pay attention to adjusting the amount of charred steam to ensure that the inlet pressure of this group is slightly higher than the pressure of the other three groups. At the same time, pay attention to maintaining the feed volume and outlet temperature of the other three groups of furnace tubes to maintain stable production. 10) Repeat the above steps 5) to 9) for heating and cooling operations until 3 to 4 hours before the four-way valve switches. 11) Record in detail the indications of the furnace tube wall temperature thermocouple and control the temperature at each point

Your coking furnace often removes the plugs and uses high-pressure water to clean the coke. You may not have the necessary conditions for online cleaning.: The furnace is radiated on both sides, with at least 4 tube passes, and high-temperature ball valves are installed at the entrance and exit.

This situation also exists in our coking furnace. The salt and coke deposited on the inner wall of the furnace tube is about 2-4 mm, and the thickness of the elbow is about 10-20 mm. There is no other way but to cut the elbow and use water to remove the coke, which is too troublesome! I had originally heard of online mechanical decoking, but after learning about it, I found that the effect was not good. I recently heard that a domestic company and a foreign joint venture introduced a new foreign technology, and the online decoking effect is good. The specific method is to connect the inlet and outlet of the furnace to water circulation, and then put a steel needle ball smaller than the furnace tube into the pipeline for circulation and stripping (from small to large, put in diameters of 80, 85, 90, 95, 100, 105 mm). . . . ), and finally put in the measuring ball to see what the maximum value of the tube is, and see whether the focus is clean or not. We have just contacted this company, so the equipment will not arrive in China until about July. I just got to know it a little bit. If I use it, I will actively communicate with everyone. Of course, it is a bit early now!

This is my first time encountering such a problem, so I would like to suggest that anyone who has experienced it please give me your valuable advice. Thanks.

This is what I need too, to look forward to. Thanks