Normal-pressure furnace heating plan

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Table of Contents
I. General Provisions... 3
II. Design Specifications... 3
III. Design Conditions for Fuel Gas... 3
IV. Organization of the Furnace Drying Team... 4
V. Purpose of Furnace Drying... 4
VI. Conditions Required Before Furnace Drying:... 5
VII. Preparatory Work Before Furnace Drying... 5
VIII. Interlock Control... 6
IX. Commissioning of the Fuel Gas System... 7
X. Operations for Furnace Drying... 8
XI. Precautions During Furnace Drying... 9
XII. Inspections After Furnace Drying... 10
XIII. Furnace Drying Curve for Atmospheric Pressure Heaters... 11
XIV. Startup Operation Card for Heaters... 12
XV. Isolation Blind Flange Diagram for High-Pressure Gas Systems... 20

I. General Provisions
This manual is applicable to the furnace drying, startup, and normal operation of this heater. In addition to complying with the various provisions of this manual for the start-up, shutdown, and normal operation of the heating furnace, it is also necessary to adhere to the operating procedures for atmospheric pressure units at China National Petroleum Corporation’s Ningxia Petrochemical Branch, as well as all relevant regulations regarding safe production. II. Design Specifications: In accordance with the heating furnace design requirements provided by the user, these specifications are formulated in compliance with the American Petroleum Institute standard \"FIRED HEATERS FOR GENERAL REFINERY SERVICES\" (API STANDARD 560) as well as relevant standards in China’s petroleum industry. The heating furnace was designed using the internationally standard heating furnace calculation software FRNC-5 for the process aspects of the furnace, and structural calculations were carried out on the steel structure part of the furnace. The atmospheric pressure furnace is a vertical tube box type heating furnace; the air preheater is located on the ground. The operating heat load is 43.08 MW, the designed heat load is 55 MW, and the thermal efficiency is 92%. The furnace tubes have 4 pass configurations, and the material of the furnace tubes is P5. The process medium is flash bottom oil; the medium passes through four tube banks, first being heated in the convection chamber and then entering the radiation chamber via the oil transfer line for further heating. The flue gases generated by the heating furnace converge and enter a combined flue duct, from where they flow downward to a combined preheater consisting of turbulence generators and water-based heat transfer media. Heat recovery from these flue gases is achieved through heat exchange with air; the cooled flue gases exiting the preheater are then sent to a chimney via an exhaust fan for discharge ； Cold air is blown into the air preheater by a blower; after exchanging heat with the hot flue gas, it is sent to various branch ducts for use in combustion by the burners. III. Design conditions for fuel gas: Based on the overall fuel system design for the plant, this unit uses fuel gas as the fuel for the heating furnace. The temperature of the fuel gas network is 40°C, and the pressure is 0.45 MPa(g). The design conditions for the fuel gas are shown in the table below. Design conditions for fuel gas: Component | m% | v%: H2 – 3.54% | 31.33%; CO2 – 3.08% | 1.24%; N2+O2 – 19.51% | 12.35%; CH4 – 23.32% | 25.84%; C2H6 – 21.47% | 12.68%; C2H4 – 19.64% | 12.43%; C3H8 – 2.48% | 1.00%; C3H6 – 1.41% | 0.59%; C4H10 – 2.69% | 0.82%; C4H8 – 0.17% | 0.06%; C5+ – 1.35% | 0.33%; H2O – 1.34% | 1.32%. The molecular weight is 17.73, and the sulfur content is less than 20 ppm. Fuel consumption table: Serial number, Location of use, Fuel consumption in kg/h (calorific value: 41.868 MJ/kg), Remarks, kg/ht/a. 1. Atmospheric pressure furnace: 370431115; Standard fuel. IV. Organizational structure and main responsibilities of the furnace drying team: Fully responsible for the furnace drying process in atmospheric pressure furnaces, responsible for approving the plans related to furnace drying, and tasked with organizing and coordinating external communications. Arrange the furnace drying personnel properly to complete the task within the specified time. Responsible for preparing the drying plan for atmospheric pressure furnaces, organizing training on this plan, and overseeing the drying process to ensure it is carried out properly. V. Purpose of furnace drying: ① The lining of certain parts of the furnace is made up of refractory bricks and fire-resistant castables, which contain a large amount of moisture during construction. The purpose of furnace drying is to gradually remove this moisture by slowly heating these refractory materials, and to ensure that the refractory mortar is fully sintered. This prevents the furnace from cracking, bubbling, deforming, or even having its walls collapse due to rapid temperature rise and subsequent vaporization of moisture once operations begin, thereby ensuring safety and extending the furnace’s service life. ②Further familiarize itself with the performance of the instruments in the furnace area, and test whether they meet the production requirements. ③It evaluates the performance of various components of the heating furnace body and its furnace tubes under thermal conditions. ④Test the practical performance of the furnace nozzles and conduct on-the-job training to improve operational skills. VI. Conditions to be met before furnace drying: ① The heating furnace itself, the waste heat recovery system, the chimney, etc., must have passed the construction acceptance tests. ②The refractory castables used as furnace lining materials were all cured in accordance with the regulations; specific details can be found in the relevant standards for lining construction. ③The furnace wall is allowed to dry naturally at ambient temperature (25–40°C) for more than 5 days. ④The hydraulic tests of all furnace tubes have passed ； All relevant systems, including the fuel gas system, 1.0 MPa steam system, low-pressure nitrogen system, oily wastewater system, circulating water system, deoxygenated water system, fresh water system, purified air system, and unpurified air system, have been thoroughly flushed and purged, and have passed the airtightness and displacement tests. ⑤The blower, exhaust fan, and water heat medium pump have passed the acceptance tests and individual commissioning tests. ⑥According to the blind plate diagram, isolate the pipelines of the fuel gas system from those of other systems that are not in use temporarily using blind plates, and conduct inspections along with lockout/tagout procedures for confirmation. ⑦The automatic control and interlock system of the heating furnace has been tuned and is capable of meeting the requirements for furnace drying. ⑧All relevant systems, including the steam system, condensate water system, low-pressure nitrogen system, oily wastewater system, circulating water system, fresh water system, purified air system, and unpurified air system, are now in normal operation. ⑨After a joint inspection by the relevant personnel, it was confirmed that the conditions for furnace drying are met. VII. Preparations before heating the furnace: ① An ignition gun for starting the fire should be prepared. Prepare a bucket of soapy water for airtight sealing. ②Check the cleanliness around the furnace and remove any flammable or explosive items. ③All fire-fighting equipment is in place; the fire steam hoses have been connected to the utility hose station near the heating furnace, and the fire water cannons have been installed and are functioning properly. ④ Contact the electrician to check whether the motors of the blower, exhaust fan, and water heat medium pump are operating properly during trial runs. ⑤Contact the instrumentation team to check and activate the flow, pressure, temperature control, and other instruments required for operation, and adjust all the control valves and interlock valves as needed. ⑥Before ignition, close the explosion-proof door, check the fire viewing hole, and seal the manhole. ⑦Check whether the fuel gas, ignition gas (permanent light), and steam pipelines are properly connected and free of leaks. ⑧The fuel and steam pipelines are purged to remove residues from the construction process (such as rust, sand, and other debris), ensuring proper combustion of the burner. ⑨Check the flame monitoring system to ensure it is operating properly. Check whether the ignition hole is installed in the correct position, whether the pilot light is properly installed, and conduct an ignition test. ⑩Contact the dispatch team to ensure that the instrument air, fuel gas, steam, and low-pressure gas pipelines required during furnace heating are in proper operation and can supply these resources as needed. Contact the laboratory to prepare for the analysis of fuel gas, combustible gases, oxygen content, and other relevant parameters. ⑾Clean the high-pressure gas flame arresters and the perpetual flame flame arresters, a total of 4. After cleaning, install it in place. VIII. Chain control 1. A sealing baffle is installed at the upper part of the chimney. When the waste heat recovery system is operating properly, this damper remains closed. When the waste heat recovery system fails, it is possible to remotely or automatically open the sealing baffles and the pneumatic dampers installed in the furnace bottom air ducts from the control room; the flue gas exhaust fan and the air blower can be stopped, allowing the system to operate in natural ventilation mode. 2. Adjustable baffles are installed on the flue ducts leading out of the convection chamber of the heating furnace; during normal operation, the opening degree of these baffles is adjusted to maintain a negative pressure in the furnace chamber between -20 Pa and -30 Pa ； When the exhaust fan and waste heat recovery system are shut down, the sealing flap at the top of the chimney is opened, and the opening degree of this flap is adjusted via a pneumatic actuator to maintain the negative pressure in the furnace between -20 Pa and -30 Pa. 3. Pneumatic control butterfly valves are installed on each of the 2 air supply ducts of the heating furnace, allowing for remote adjustment of the air flow distribution used for combustion in the furnace’s radiation chamber from the control room. Under normal conditions, the oxygen content of the flue gas in the radiation chamber is maintained between 3% and 4% by adjusting the opening degrees of these two control dampers. 4. A manually adjustable butterfly valve is installed at the air inlet of each burner, used to distribute and control the amount of air entering each burner. 5. If the temperature of the flue gas entering the preheater is greater than 350°C or the temperature of the flue gas exiting the preheater is greater than 220°C, an alarm is triggered; the chimney sealing flap is automatically opened and the flue gas exhaust fan stops as a result of the interlock mechanism. 6. An alarm is triggered when the pressure of air entering the preheater is less than 300 Pa; when it is less than 200 Pa, the flue gas exhaust fan and the air blower are shut down automatically, and the chimney sealing damper as well as the pneumatic valves installed in the bottom air ducts are opened, causing the system to operate in natural ventilation mode. 7. An alarm is triggered when the pressure of the flue gas exiting the preheater is greater than -300 Pa; when it exceeds -200 Pa, the flue gas exhaust fan stops automatically, and the chimney sealing flap is opened. 8. An alarm is issued when the furnace temperature exceeds 880°C; the operator should adjust the operations promptly. 9. If the oxygen content in the flue gas exceeds 8%, an alarm is triggered; the operator should adjust the opening of the air blower’s control dampers as well as the pneumatic control butterfly valves in each air duct, so that the oxygen content remains between 3% and 4%. It also ensures a uniform air flow distribution in the furnace. IX. Commissioning of the fuel gas system 1. Before introducing high-pressure gas, carry out the preparatory verification work as listed below first. The system is isolated; all preparation work has been completed. All areas connected to the gas system have been shut off and isolated using blind flanges. All construction and modification work on the gas system has been completed and verified through inspection. For details, see the blind plate table in the attachment. 2. Use steam purging to remove the hoses or short sections in front of the burners of each heating furnace. Open the vent at the ends of the gas pipelines in each heating furnace, as well as all the low-point drains in the gas system. Open the manual valves on the gas pipelines of each heating furnace. The purpose is to further purge impurities such as rust from the pipelines, preventing these impurities from clogging the burners and affecting their combustion. It also makes it easier to check the integrity of the gas lines connected to each burner. Be careful that the pressure in the gas system during steam purging (as indicated by the pressure gauge on site in front of the pilot light flame arrester) should not exceed 0.5 MPa. After the steam purging is complete, close all vent valves on the gas line as well as the manual valves in front of the burners. 3. After the nitrogen airtightness check and purge are completed, close the steam purging valve, then open the nitrogen purging valve located in front of the high-pressure gas isolation valve. Blow out any remaining steam and water from the gas pipeline. Once the pipeline is clean, close all vent valves and connect the gas hose or fitting to the burner. The gas system is pressurized with steam to 0.525 MPa for a leak test. Nitrogen is supplied in front of the boundary valve of the gas inlet device to further purge and displace the gas system. Open the manual valves of each burner in the heating furnace to purge and discharge air into the furnace chamber. After sampling and analyzing that the oxygen content in the gas system is less than 0.5%, the nitrogen displacement is completed. After the nitrogen purging of the gas system is completed, close the manual valves of each burner. Keep the system at a slight positive pressure, close the nitrogen purge and steam purge valves, and isolate them with blind flanges, in preparation to introduce gas into the unit for ignition. Open the boundary valve to introduce gas into the device. Adjust the flue dampers of each heating furnace to ensure that the negative pressure in the furnace chamber meets the requirements for ignition (i.e., the negative pressure at the top of the furnace is around -2 mmH2O). After installing the gas introduction device, nitrogen is used for 10 minutes to handle high-point venting and low-point condensate drainage. When a gas odor is detected, take samples for analysis and close the high-point vent and low-point drain manual valves. Prepare for ignition according to the furnace ignition procedure. X. Operation of furnace drying 1. Before lighting the furnace for drying, it is first necessary to warm up the furnace. Heating the furnace is generally done using steam. First, close the air valves completely in front of the furnace, and open the flue dampers to 1/3–1/6 of their capacity. After adjusting the flow path, supply steam to the furnace tubes for heating. By controlling the steam flow, the temperature inside the furnace can be increased gradually at a rate of 5–7°C per hour, until it reaches 150°C. Once this temperature is maintained for 24 hours, the fuel gas can be ignited to continue raising the temperature and carry out the drying process. 2. During furnace drying, close the natural ventilation doors on the air ducts as well as the inlet baffles of the air blower, then start the air blower. 3. Once the fan is operating normally, slowly open the inlet damper of the air blower to a certain degree (approximately 20%-50%). 4. Adjust the opening of the chimney dampers to maintain the negative pressure at the top of the furnace between -2 mmH2O and -4 mmH2O. 5. Open the gas manual valve of the burner, then use gas to displace nitrogen from the furnace chamber; close the gas manual valve of the burner after 1 minute. 6. After the furnace chamber is continuously supplied with air by the air blower for over 15 minutes, gas sampling from the furnace chamber is conducted for analysis; if the concentration of combustible gases is 0.5% or less, ignition is carried out in accordance with the ignition procedures. 7. Open the burner air valve to 1/3–1/6, light the ignition rod outside the furnace, and guide it to near the pilot lamp through the ignition hole. Slowly open the gas valve of the pilot lamp, ignite it, and then adjust the air valve to stabilize the flame. 8. The burners should be ignited symmetrically to ensure a uniform temperature distribution in the furnace. 9. Raise the temperature strictly in accordance with the furnace heating curve; if the temperature does not rise, the gas pressure of the pilot light can be increased appropriately (stop if black smoke appears from the chimney). If the temperature requirement cannot be met even after all the pilot lights are lit, the main burner can be ignited while reducing the gas valve for the pilot lights to keep them burning. 10. The furnace drying temperature is based on the temperature at the top of the radiation chamber. (TICA-2109A or TICA-2109B) 11. During the heating process, adjust the air valves of each burner according to the color of the flame, and also adjust the opening degree of the flue dampers to ensure that the negative pressure in the furnace meets the required standards. 12. When the temperature of the chimney reaches 300°C, the exhaust fan can be started, and the waste heat recovery system can be put into operation (with the water-based heat transfer medium system operating normally). 13. After maintaining the temperature at 500°C, cool it down to 150°C at a rate of 14–15°C/hr. Extinguish all burners, and immediately close all burner dampers and flue dampers to carry out flame-out and furnace holding; once the furnace temperature drops below 100°C, allow natural ventilation for cooling. XI. Precautions for furnace drying 1. During the purging and replacement of the gas system, the pressure in this system (as indicated by the pressure gauge on the pilot light flame arrester) should not exceed 0.5 MPa. 2. After the gas system has been purged with nitrogen, sampling and analysis must be conducted; it is considered acceptable only if the oxygen content is less than 0.5%. 3. During the process of introducing gas into the device, any kind of welding or heating work inside the device must be carried out with a level-1 fire permit. All construction-related welding activities are strictly prohibited during the gas displacement phase; all types of vehicles are forbidden from using the roads surrounding the area, and it is strictly prohibited to enter the furnace chamber. 4. The furnace must be heated and cooled in accordance with the furnace heating curve. 5. If the burner goes out again after ignition, or if the main burner fails to ignite within five seconds, the gas valve should be closed immediately. The furnace chamber should then be purged with an air blower for 15 minutes, and its gases analyzed to ensure that no flammable gases are present before attempting to ignite it again; otherwise, the purging process should continue. 6. After the furnace’s explosion detection analysis yields satisfactory results, if ignition does not take place immediately after the gas has been introduced into the burner for some reason, the explosion detection analysis must be repeated; ignition is only permissible once the analysis is successful again. 7. When using the main burner to dry the furnace, in order to ensure even drying throughout the furnace, the burner used for ignition should be replaced every 8 hours; when igniting with the main burner, it should be done at an angle. 8. The temperatures at various temperature measurement points in the furnace should be as balanced as possible; if there are significant deviations, the corresponding burners can be adjusted accordingly. It is also necessary to prevent the flame from hitting the furnace tubes directly, in order to avoid excessively high temperatures. 9. When adjusting the burner air damper, do so slowly and not too quickly, to avoid issues such as incomplete combustion, flameout, or fluctuations in furnace pressure. 10. Do not face the ignition hole when lighting it; when checking, keep your body away from the viewing hole to prevent burns caused by backfire in the furnace. 11. During the furnace heating process, regular inspections should be carried out, records should be kept on time, any abnormal conditions should be reported and addressed promptly, and the actual temperature rise curve should be plotted. 12. The gas and steam used for heating the furnace must be secured to ensure that the temperature at the outlet of the furnace tubes does not exceed 450°C ； If the heating furnace shuts down due to a gas supply interruption or for other reasons, the operator must promptly close the gas manual valve, as well as the flue dampers, air valves, and observation windows, in order to prevent equipment damage caused by a rapid drop in furnace temperature. Re-ignite and raise the temperature once the gas supply is restored. 13. During furnace drying, a sufficient flow rate of protective cooling medium must be supplied into the furnace tubes to prevent overheating and damage to them. Steam protection is used this time, and the flow rate of the protective medium must meet the following requirements: For furnace tube material and medium outlet temperature (the temperature at all branch outlets must be lower than the following values): carbon steel ≤400°C, P5 ≤450°C (the standard value is 525°C), P9 ≤550°C, TP321 ≤625°C. XII. Inspections after furnace drying: 1. After the furnace drying process is completed, a blind flange should be installed in front of the gas control valve. Only when the furnace temperature drops to room temperature and the oxygen content measured in samples taken from the furnace is greater than 20% can inspections be carried out. 2. After the furnace is dried, a thorough inspection of all parts of the furnace lining should be carried out, and inspection records should be kept. If any damage is found, the cause should be analyzed and repairs should be made according to the following procedures. 3. For cracks larger than 3 mm, as well as areas that may become loose due to the local concentration of intersecting cracks, and pores with an area exceeding 20 mm×20 mm and a depth of more than 10 mm, first tap them with a small hammer to check; once it is confirmed that those areas are not likely to fall off, then fill the cracks with refractory fiber or refractory mud mixed with refractory fiber. 4. When the lining has fallen off or is likely to fall off, the castable in that area should be removed; if the affected area is no larger than 100mm×100mm, a funnel-shaped hole with a depth of at least 50mm can be dug. After cleaning and moistening the hole walls, fill them in with casting material of the same material. 5. When the area of detachment exceeds 100mm×100mm, the lining layer should be dug down to the furnace wall, and then repaired using the same material in the form of castable, following the methods described above. There should be at least two anchors within the repair area. 6. Check whether the suspension is bent, whether the furnace tubes are deformed, whether the dampers and flue baffles operate smoothly, and whether there are any issues with the burners and thermocouples. 7. Before heating the furnace, brick samples are placed inside it to determine the moisture content; a level below 7% is considered acceptable, after which normal operation can begin. Furnace drying curve – The nodes are based on the furnace temperature (TICA-2109A or TICA-2109B). Time (hours); cumulative hours (hours). In the first stage, steam is used for heating, with a temperature increase of ≤ 5 °C/h, over 24 hours. In the second stage, the temperature is maintained at 150 °C to remove free water, over 24 hours. In the third stage, the temperature increases by ≤ 10 °C/h, over 20 hours. In the fourth stage, the temperature is maintained at 350 °C to remove crystalline water, over 24 hours. In the fifth stage, the temperature increases by ≤ 15 °C/h, over 14 hours. In the sixth stage, the temperature is maintained at 500 °C for sintering, over 16 hours. In the seventh stage, the temperature decreases by ≤ 25 °C/h, over 16 hours. XIII. Drying curve for atmospheric-pressure heating furnaces. XIV. Startup procedure card for heating furnaces – Outline of the ignition procedures for starting up a heating furnace: There are a total of 6 stable states, along with 150 steps of operations and verifications required. Level A outline: The initial state S0 has completed construction acceptance, and it is ready for start-up inspection. 1. Check whether the heating furnace system meets the requirements for operation. 2. Conduct a trial run of the heating furnace and its auxiliary equipment. 3. Inspect the flow of process media in the fuel gas line. 4. Check the stable status of the instrumentation and electrical systems. The preliminary checks before starting up S1 have been completed. System purging and pressure testing, furnace purging 1, fuel system purging and pressure testing 2, furnace purging 3, trial operation of air ducts and flue ducts at stable state S2: System purging and pressure testing completed, furnace purging completed, trial operation of air ducts and flue ducts completed. 1. Introduce pilot fuel gas and ignite with an eternal flame. 2. Introduce pilot fuel gas. 3. The analysis of the gases in the furnace shows that they are within acceptable limits, with the combustible gas content being less than 0.2%. 4. Lighting of the permanent flame. 5. Stability test of the permanent flame: Fuel gas is supplied at the stable state S3, the permanent flame is lit; after successful analytical testing, the stability test of the permanent flame is completed. Ignite a fuel gas main burner to stable state S4; one fuel gas burner has been ignited. Commissioning of the heating furnace: 1. Light the main fuel gas burner required for production. 2. Verify the status of the heating furnace during the heating process. 3. Final status verification of the heating furnace: SF fuel gas is in use, and the heating furnace is operating normally. Grade B: The construction acceptance for the initial state S0 has been completed, and it is ready for start-up inspection. Heating furnace inspection: (P) – Verify that the blind flange at the boundary valve (8-shaped) for the fuel gas inlet is in the blind position. (P) – Verify that the fuel gas blind flange in this furnace area is in the blind position. (P) – Ensure that the exhaust valves and drain valves of the fuel gas system are closed, and that caps (threaded plugs) and blind flanges are in place. (P) – Confirm that the line valves attached to the safety valve of the fuel gas system and the condensate oil lines are in the blind position. (P) – Ensure that the first two manual valves before the main fuel gas burner are closed, with blind flanges installed on the flanges between these valves. (P) – Verify that the first two manual valves before the pilot light burner are closed, with blind flanges installed on the flanges between these valves. (P) – Ensure that there is no cross-contamination between the fuel gas purging system or the steam system in front of the furnace and the fuel system. (P) – Confirm that the fuel gas system has been properly purged, is airtight, and that the gas replacement process has been completed successfully. (P) – Ensure that fire masks and gloves are in good condition and ready for use. (P) – Verify that the explosion-proof doors are in good condition and closed. (P) – Ensure that the viewing ports and doors are in good condition and closed. (P) – Confirm that the air dampers are in good condition. (P) – Ensure that the burners are in good condition and properly installed. (P) – Verify that the fire suppression equipment is available and functional. (P) – Confirm that the combustible gas detectors have passed testing. (P) – Ensure that the heating furnace platform and guardrails are in good condition. (P) – Verify that the flue dampers and air supply dampers operate smoothly and in the correct direction. (P) – Confirmation of manhole closure: Note that the second blind flanges for fuel gas inlet and the burner must be in the blind position; it is required that operators, shift supervisors, and production managers carry out three-level confirmation. Fuel gas pipeline (P) – Verify that all valves at the fuel gas nozzles in the furnace area are closed (P) – Verify that all connections in the fuel gas pipeline are proper (P) – Verify that the liquid level gauge of the fuel gas tank is functioning correctly (P) – Verify that the safety valve of the fuel gas tank is in good condition (P) – Verify that the drain valve of the fuel gas tank operates properly (P) – Verify that the manhole of the fuel gas tank is sealed (P) – Verify that the pressure control valve for fuel gas is functioning properly (P) – Verify that the flame arrester for fuel gas is in good condition (P) – Verify that the fuel gas flow meter is intact (P) – Verify that the pressure of the fuel gas outside the furnace area is normal and stable (P) – Verify that the heating steam line for fuel gas is functioning properly; ensure that the manual valve before the furnace and the drain valve are slightly open to prevent condensation in the fire suppression steam. (P) – Verify that all fittings in the fire steam line are properly connected and that the process medium is flowing correctly. (I) – Confirm that the process medium flows normally within the furnace tubes in the convection section. (I) – Verify that the temperature readings at the inlet and outlet of the furnace tubes in the convection section are normal. (I) – Confirm that the process medium flows normally within the furnace tubes in the radiation section. (I) – Verify that the temperature readings at the inlet and outlet of the furnace tubes in the radiation section are normal. Instruments and electrical systems: (I) – Ensure that the alarm system is functioning properly. (P) – Confirm that electrical equipment is in good condition and ready for use. (I) – Verify that instruments are operating properly and showing correct readings. (M) – Ensure that the grounding in the furnace area meets the required standards. Pre-startup inspections for state S1 have been completed. System pressure testing – Furnace purging and fuel system pressure testing: Prepare the fuel gas supply process (P); verify that the valves in the process are open at the correct settings (P); determine the steam supply point (P); determine the steam discharge point. Close the manual valve before the safety valve on the fuel gas tank; close the manual valves before and after the control valve and flow meter, and open the drain valve. Purge with steam to remove moisture (P); confirm that the area around the discharge point is safe; close the low-point drain valve; close the high-point vent valve. Slowly open the valve for the purge medium to introduce it into the system (P); confirm that steam is visible at the discharge point; open the high-point vent valve and low-point drain valve, then close them after steam is seen. Close the valve at the discharge point and increase the system pressure (P); confirm that the system has reached the specified pressure; check all static seal points (P); confirm that the pressure testing was successful; close the valve for the purge medium and isolate it. Open the valve at the discharge point to release the purge medium, and close it once it has been completely drained. Conduct tests on the air ducts and flues (P); verify that the valves in the process are open at the correct settings; close the flue dampers (P); confirm that the pressures in the furnace and at various control points meet the requirements specified in the process sheet (P); confirm that the tests on the air ducts and flues were successful. Furnace purging: Prepare the furnace purging process (P); verify that the valves in the process are open at the correct settings; introduce the purge medium to the manual valve before the furnace (P); remove moisture from the purge medium (P); confirm that the flue dampers are fully open; slowly open the valve for the purge medium to introduce it into the furnace (P); confirm that steam is visible from the chimney (P); ensure that the furnace has been purged for 15 minutes. Close the valve for the purge medium to achieve a stable state. After the system pressure testing and furnace purging are complete, as well as the tests on the air ducts and flues, introduce fuel gas to the pilot light and burner. Perform nitrogen displacement in the fuel gas system (P); confirm that the gas in the fuel gas lines has been completely displaced (P); confirm that there are no leaks at the connection points; end the gas displacement process. Remove the blind flange on the boundary valve of the fuel gas inlet device; introduce fuel gas to the valve before burner F-101 (P); confirm that the pressure in the fuel gas system is normal and stable; set the fuel gas pressure control valve to manual mode (M); confirm that the furnace is ready for ignition. Explosion gas analysis in the furnace must be successful (M); contact the laboratory staff to take samples of the explosion gas in the furnace; assist in and supervise the sampling process (M); confirm that the explosion gas analysis is successful. Note: If the explosion gas analysis is not successful, first check the fuel gas supply process to ensure that no fuel gas has entered the system. Then, purge the furnace with steam. Once everything is confirmed to be normal, repeat the explosion gas analysis until it is successful. The difference between the qualified explosion gas analysis and the ignition time should be within 15 minutes. Before ignition, it must be tested and found to be qualified using a portable explosive gas analyzer, after which ignition should be carried out immediately. Light the permanent flame (P) – Verify that fire-resistant gloves with long sleeves are available (P) – Verify that a fire-resistant suit is available (M) – Confirm that the furnace area is in conditions suitable for ignition (M) – Ensure that the fire operation permit has been completed (P) – Identify a permanent flame ready for ignition – Remove the blank flange from that burner – Adjust the air valves – Adjust the flue dampers (I) – Confirm that the negative pressure in the furnace is within the required range – Point the ignited igniter at the permanent flame head – Exit from beneath the furnace – Open and adjust the valve controlling the permanent flame (P) – Verify that the permanent flame is burning properly – Use the same method to light the remaining permanent flames (P) – If ignition does not occur – Close the valve controlling that permanent flame – Identify the cause and address the issue (such as clogged burners or excessive negative pressure in the furnace) – After resolving the issue, repeat the process. Note: Each permanent flame should be lit within 5 seconds. Stability test of the pilot light – Open the dampers of each pilot light fully and then adjust them to the appropriate position – Open the flue dampers completely (P) – Verify the stability of the pilot light’s combustion – Adjust the flue dampers to the appropriate opening degree (I) – Ensure that the pressure in the fuel gas system is normal and stable (P) – If the pilot light goes out during the stability test, close the manual valve of the pilot light – Identify the cause of the outage, address the issue, and then repeat the process by lighting the pilot light again to conduct another stability test. Once stability state S3 is achieved, the fuel gas is supplied and the pilot light is ignited; if the tests yield satisfactory results, the stability test of the pilot light is complete. Light a main fuel gas burner (P) – Prevent backflow during ignition (P) – Confirm that all manual valves for the main fuel gas burners are closed (P) – Confirm that there is one main fuel gas burner ready for ignition (P) – Confirm that the pilot light is burning properly (I) – Confirm that the control valve for the main fuel gas line is open – Set this control to an appropriate manual position (I) – Confirm that the fuel gas pressure is normal – Adjust the opening of the air dampers and flue dampers (I) – Confirm that the negative pressure in the furnace is within the required range – Slowly open the manual valve for that burner (P) – Confirm that the burner has ignited and is burning properly (P) – If the burner does not ignite within 5 seconds, close the fuel gas manual valve for that burner – Identify the cause (blocked valve, clogged burner, liquid in the pipes) – Address the issue, purge the furnace with steam, and repeat the above steps until a stable normal condition is achieved. S4: One fuel gas burner has now been ignited. Start up the heating furnace and ignite the main burners for other fuel gases required for production – Adjust the opening degrees of the air dampers and flue dampers (I) – Verify that the negative pressure in the furnace is within the requirements specified by the process (P) – Confirm the number of burners (determined based on production needs) – Ignite the selected burners (P) – Ensure that the ignited burners are burning properly. Check the status of the heating furnace during the heating process – Verify that burner combustion and exhaust conditions are normal (P) – Ensure there are no leaks in the fuel gas system, furnace tubes, or furnace body (I) – Confirm that the temperatures of the furnace tube walls, flue gas, and furnace chamber are within the limits specified in the process parameters (I) – Verify that the oxygen content in the flue gas is within the specified range (I) – Ensure that the negative pressure in the furnace is within the normal range (P) – Check that there are no abnormalities in the supports and brackets of the furnace tubes and heating furnace (P) – Ensure that the furnace lining is not peeling off. Monitor the status of the heating furnace according to the heating curve (M) – Check the status using the blind plate checklist (M) – Check the status of the three-valve assembly using its corresponding checklist (M). Fuel: Activate the fuel gas supply (M) – Set the control valves to automatic mode (M) – Ensure no leaks of combustible gases (M) – Verify that the oxygen content in the flue gas meets the requirements (M) – Ensure that the negative pressure in the furnace meets the requirements (M) – Verify that the flue gas temperature is within acceptable limits (M) – Ensure that the temperature of the furnace tube walls is within acceptable limits (M) – Ensure that the temperature at the furnace outlet is within acceptable limits. Adjust the number of burners as necessary to keep the fuel pressure within the normal operating range. Final state: The fuel gas supply is active, and the heating furnace is operating normally. Additional note: Grade C 1. During purging, it is necessary to ensure thorough dehydration to prevent water hammer. 2. It is prohibited to light more than two burners at the same time, and it is also prohibited to use one burner to light another adjacent burner. 3. If the furnace chamber is lined with ceramic fiber, it is not allowed to use large amounts of steam to purge the chamber; nitrogen or air can be used for ventilation. Ignition must take place within 15 minutes after the explosive gas analysis shows satisfactory results; otherwise, another explosive gas analysis must be conducted until satisfactory results are obtained. 4. The nozzles must be ignited in a sequence of symmetrical and even distribution ； Idle burners should be switched regularly. Strict inspection: The wall temperature of the furnace tubes and the furnace temperature must not exceed the specified limits, and there must be no deviation in the flow of the process medium inside the furnace tubes. 5. Explanation of smoke emission: It is normal for the chimney of the heating furnace to emit colorless or light blue smoke; intermittent emission of small amounts of black smoke is also normal. If the fuel gas contains liquid components, measures should be taken to remove these liquids from the fuel gas ； If the heating furnace is overloaded, appropriately reduce its load. Excessive black smoke; if it is due to too much fuel, reduce the amount of fuel ； If it is due to a malfunctioning instrument, switch to manual mode, reduce the fuel supply, and contact the instrumentation control personnel for handling ； If the furnace tube leaks and catches fire, follow the emergency shutdown procedures. If white smoke is emitted, and it is due to a rupture in the superheated steam pipeline, proceed according to the emergency plan for ruptures in the superheated steam pipelines of the heating furnace. Yellow smoke indicates incomplete combustion; if the burning starts and stops intermittently, stabilize the fuel flow. This automatic control functions as manual control, and automatic mode is activated once stability is achieved. 15. Isolation blind plate diagram for high-pressure gas system