Method for warming up a gas stove by lighting a small fire

Abstract

The application discloses a small fire oven heating method of a natural gas furnace, and comprises the following steps: checking pressure parameters; checking and calibrating air pressure and gas pressure of all burners in advance; setting valve opening degree on an HMI interface; setting fan control as a manual mode, and starting a large fan; starting ignition fan control and purge control; setting the air pipeline pressure relief valve opening degree as an automatic mode; setting fan control as a manual mode, starting the ignition controller manual ignition control, pressing a natural gas total air inlet valve button of a power distribution cabinet, setting an oven heating program according to an oven heating curve, heating the furnace with small burners ignited by straight flame burners and small burners ignited by flat flame burners below 300 DEG C, heating the furnace with small burners ignited by straight flame burners and large burners ignited by flat flame burners from 300 DEG C to 550 DEG C, and heating the furnace until the oven heating program is completed; and setting valve opening degree after the oven heating is completed. The application avoids direct flame impact on castable, and ensures that each lining of the furnace shows optimal physical and chemical properties after the oven heating is completed.

Description

Technical Field

[0001] This invention belongs to the field of natural gas heat treatment furnaces, specifically relating to a method for igniting and baking a natural gas furnace. Background Technology

[0002] Preheating the furnace before standard temperature commissioning is a crucial step in the installation and construction of a heat treatment furnace. Furnace heating involves slowly heating the furnace lining according to a suitable temperature rise curve, allowing the moisture within to gradually evaporate until completely dry. A relatively gradual temperature rise curve should be set during the heating process to avoid cracking or peeling of the furnace lining due to excessively rapid heating, which would affect its service life. Traditional furnace heating methods use coal gas or natural gas for baking, due to its advantages such as gentle flame, easy temperature control, uniform furnace temperature, and convenient installation. Traditional methods often use diffuser or atmospheric gas burners for baking. After the furnace temperature reaches 600℃, the combustion device used during normal production of the heat treatment furnace is switched to continue baking. When these conditions are not available or when coal gas supply is inconvenient, large heat treatment furnaces can be baked using a separate small stove fueled by coal. Sometimes, baking can also be carried out in the combustion chamber of the heat treatment furnace itself, but special attention must be paid to strictly controlling the uniformity of furnace temperature to prevent damage to the furnace body caused by excessively rapid local heating.

[0003] Foreign natural gas furnaces with similar lining designs employ a furnace drying method that utilizes the combustion chamber of the furnace itself, using natural gas as fuel. The highest drying temperature is 1200℃, the highest heating rate is 32.5℃ / h, and the total drying time is 122 hours. Due to the differences in the material and properties of their lining materials, the castable refractory undergoes less physicochemical reaction to direct flame impact, and does not crack or peel under high-temperature drying. This invention relates to a method that, if used in a natural gas furnace, could damage the refractory layer inside the furnace, leading to cracking, peeling, or bulging of the castable refractory, severely affecting its service life, and even rendering it unusable. Summary of the Invention

[0004] The purpose of this invention is to provide a method for igniting and baking a natural gas furnace. Following a baking process curve suitable for the furnace lining material, a combination of ignition and flat-flame burners is used to slowly heat the furnace chamber, allowing all moisture contained in the furnace lining to be completely released. This avoids direct flame impact on the castable refractory, ensuring that the furnace lining exhibits optimal physical and chemical properties after baking.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for igniting and preheating a natural gas furnace includes the following steps:

[0007] S1. Close and tighten the furnace door, and check the following pressure parameters: natural gas main pipeline inlet pressure, pressure of the large burner natural gas main pipeline after decompression, pressure of the ignition small burner natural gas main pipeline after decompression, setting value of each pressure switch, air pressure of the blower and air pressure of the ignition small blower.

[0008] S2, check and calibrate the air pressure and gas pressure of all burners in advance to ensure that all burners ignite normally;

[0009] S3, set the valve opening degree in the HMI interface;

[0010] S4, set the fan control to manual mode, set the fan speed to 35Hz, and start the large fan;

[0011] S5, start the ignition fan control and purging control;

[0012] S6, after purging, set the air pipeline pressure relief valve opening to automatic mode; set the fan control to manual mode and the fan speed to 25Hz; start the ignition controller manual ignition control and press the natural gas main inlet valve button on the distribution cabinet.

[0013] S7, set the oven drying program according to the oven drying curve;

[0014] S8, at temperatures below 300℃, both direct flame burners and horizontal flame burners are used to ignite the furnace with a small flame to heat the furnace. At temperatures between 300℃ and 550℃, both direct flame burners and horizontal flame burners are used to ignite the furnace with a large flame to heat the furnace until the furnace baking process is completed.

[0015] S9. After the oven drying is completed, keep the oven door closed and pressed, and set the valve opening.

[0016] Preferably, in step S1, the inlet pressure of the main natural gas pipeline is 25-30 kPa, the pressure of the main natural gas pipeline after depressurization for the large burner is 10 kPa, and the pressure of the main natural gas pipeline after depressurization for the ignition small burner is 6 kPa; the minimum pressure switch setting value for the main natural gas pipeline for the large burner is 30 mbar, and the maximum pressure switch setting value is 142 mbar; the minimum pressure switch setting value for the main natural gas pipeline for the ignition small burner is 30 mbar, and the maximum pressure switch setting value is 120 mbar; the air pressure of the blower is 3-5 kPa, and the air pressure of the ignition small blower is not less than 8 kPa.

[0017] Preferably, in S2, the air pressure of the ignition burner in the direct flame burner system is 40-50 mbar and the gas pressure is 25 mbar, while the air pressure of the ignition burner in the flat flame burner system is 35-40 mbar and the gas pressure is 30 mbar.

[0018] Preferably, in S3, the furnace pressure valve opening is 90%, the air pipeline pressure relief valve opening is 0%, and all air valves of the flat flame burner system and the direct flame burner system are 100% open.

[0019] Preferably, in step S7, the oven baking curve is as follows: in the first stage, the temperature is increased from room temperature to 150°C at a rate of 10°C / h and then held for 72 hours; in the second stage, the temperature is increased from 150°C to 250°C at a rate of 10°C / h and then held for 72 hours; in the third stage, the temperature is increased from 250°C to 400°C at a rate of 20°C / h and then held for 60 hours; in the fourth stage, the temperature is increased from 400°C to 550°C at a rate of 20°C / h and then held for 60 hours; after completion, the temperature is naturally reduced at a rate of 20°C / h.

[0020] Preferably, in step S8, a designated person records the actual furnace temperature of the three temperature zones every half hour throughout the entire furnace baking process, until the recorded actual furnace temperature drops to 100 degrees Celsius.

[0021] Preferably, the specific steps of S9 are as follows: keep the furnace door closed and pressed, set the furnace pressure valve opening to 0%; keep the blower and ignition fan running; set the air duct pressure relief valve opening to 100%; and set the heat exchanger protection valve opening to 100%.

[0022] The beneficial effects of this invention are as follows:

[0023] (1) This invention is based on a natural gas furnace combustion system. It uses a combination of small ignition burners and horizontal flame burners to heat and bake the refractory layer of the furnace lining, effectively removing free water, bound water, and even crystal water from the refractory layer. The baking of the refractory layer is completed according to a specific furnace baking process curve. The direct flame burner system of this invention is located directly above the castable refractory at the bottom of the side wall. The direct flame burner has a high flame exit velocity and a long flame length. Using small ignition burners and horizontal flame burners for ignition and heating effectively avoids direct flame impact on the surface of the castable refractory. After the furnace baking is completed using this method and the refractory refractory naturally cools down, the surface is smooth and free from cracking, peeling, or bulging caused by thermal expansion and contraction.

[0024] (2) For furnace drying below 300℃, both direct-flame and horizontal-flame burners are used for small-scale heating. For temperatures between 300℃ and 550℃, both direct-flame and horizontal-flame burners are used for large-scale heating. Compared to using large burners for heating only, this method saves on gas consumption. This invention provides a safe, reliable, energy-saving, and efficient furnace drying method suitable for low-temperature (maximum 550℃) furnace drying processes. This method is suitable for furnace designs where the heat-resistant layer is directly exposed to the burner flame, for castable refractory materials whose surfaces cannot directly contact the flame, and for natural gas furnaces with combustion systems designed to use small-scale and horizontal-flame burners. Attached Figure Description

[0025] Figure 1 This is a flowchart of a method for igniting and baking a natural gas furnace.

[0026] Figure 2 This is a schematic diagram of the components of a direct-flame burner.

[0027] Figure 3 This is a schematic diagram of the cross-section of the refractory layer AA in the furnace.

[0028] Figure 4 This is a schematic diagram of the CC cross-section of the furnace refractory layer.

[0029] Figure 5 A schematic diagram of the baking process curve for 300-100mm castable refractory in a natural gas furnace.

[0030] The components include: 1. Manual butterfly valve; 2. Direct flame burner; 3. Burner control box assembly; 4. Orifice plate valve; 5. Quick-opening solenoid valve; 6. Slow-opening solenoid valve; 7. Proportional valve; 8. Manual proportional regulating valve; 9. Quick-opening solenoid valve; 10. Electric butterfly valve; 11. SUV flame detector; 12. Alumina silicate fiber standard backing plate; 13. Grade 23 mullite brick; 14. 45% Al2O3 lightweight thermal insulation castable; 15. 60% Al2O3 low cement castable; 16. Microcrystalline fiber module; 17. Alumina fiber crystal shield versatile module. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0032] like Figure 2As shown, the existing natural gas furnace combustion system consists of two different types of burners: a direct-flame burner system and a horizontal-flame burner system. A total of 16 burner systems are installed at the furnace top, with 6 direct-flame burners (250kW each) on each side and 4 horizontal-flame burners (230kW each) in the center. Both the direct-flame and horizontal-flame burner systems are equipped with ignition electrodes and SUV flame detectors. The direct-flame burner system consists of a manual butterfly valve 1, a direct-flame burner 2, a burner control box assembly 3, an orifice valve 4, a fast-opening solenoid valve 5, a slow-opening solenoid valve 6, a proportional valve 7, a manual proportional regulating valve 8, a fast-opening solenoid valve 9, an electric butterfly valve 10, and an SUV flame detector 11. The horizontal-flame burner system has the same structure as the direct-flame burner system. The direct-flame burner system is an ultra-high-speed burner with a flame length of 380mm and a maximum flame exit velocity of 180m / s. A small ignition burner is added to the direct-flame burner system for ignition testing. The purpose of adding the small ignition burner is to: during ignition, only the small flame solenoid valve is opened, igniting at low power. After successful ignition, the large flame gas solenoid valve is opened, achieving pulse control of the large and small flames. The flat-flame burner system has the same ignition principle as the direct-flame burner system. The flat-flame burner flame is a flat flame with high radiant temperature, no airflow scouring during combustion, and a uniform flame temperature distribution.

[0033] The direct-flame burner system of the natural gas furnace combustion system is located directly above the lower part of the castable refractory on the furnace sidewall, such as... Figure 3 and Figure 4 As shown, a furnace lining constructed using multiple castable refractory materials is constructed from composite materials. The furnace door, upper furnace wall, and furnace roof refractory materials are in the form of fiber modules. The lower furnace wall, furnace bottom, furnace door columns, upper crossbeams, and flue are constructed using a composite method of refractory fiberboard, lightweight mullite bricks, high-temperature resistant castable refractory, and low-cement castable refractory. The flue has an arched structure, with castable refractory lining on both sides of the lower furnace wall, the slope of which forms a 20° angle with the furnace wall. The furnace refractory material consists of aluminosilicate fiber standard backing board 12, grade 23 mullite bricks 13, 45% Al2O3 lightweight insulating castable 14, 60% Al2O3 low-cement castable 15, microcrystalline fiber modules 16, and alumina fiber crystal shield versatile modules 17.

[0034] This invention provides a method for igniting and preheating a natural gas furnace based on a natural gas furnace combustion system and furnace chamber, such as... Figure 1 As shown, a method for igniting and baking a natural gas furnace includes the following steps:

[0035] S1, close and tighten the furnace door. Check the following pressure parameters: natural gas main pipeline inlet pressure, pressure of the large burner natural gas main pipeline after pressure reduction, pressure of the ignition small burner natural gas main pipeline after pressure reduction, setting values ​​of each pressure switch, air pressure of the blower, and air pressure of the ignition small blower.

[0036] The main natural gas pipeline inlet pressure is 25–30 kPa, the pressure after depressurization in the main natural gas pipeline for large burners is approximately 10 kPa, and the pressure after depressurization in the main natural gas pipeline for small ignition burners is approximately 6 kPa. The minimum pressure switch setting for the main natural gas pipeline for large burners is 30 mbar, and the maximum pressure switch setting is 142 mbar. The minimum pressure switch setting for the main natural gas pipeline for small ignition burners is 30 mbar, and the maximum pressure switch setting is 120 mbar. The air pressure of the blower is 3–5 kPa, and the air pressure of the small ignition blower is not less than 8 kPa.

[0037] S2, check and calibrate the air pressure and gas pressure of all burners (including the ignition burner) in advance to ensure that all burners ignite normally.

[0038] In the direct-flame burner system, the gas pressure and air pressure of the ignition burner are adjusted and calibrated by manually adjusting the proportional regulating valve 8. The operation steps for adjusting and calibrating the gas pressure and air pressure of the ignition burner in the flat-flame burner system are the same. In the direct-flame burner system, the air pressure of the ignition burner is 40-50 mbar and the gas pressure is about 25 mbar. In the flat-flame burner system, the air pressure of the ignition burner is 35-40 mbar and the gas pressure is about 30 mbar.

[0039] Turn the slow-opening solenoid valve 6 (the opening speed of the slow-opening solenoid valve is adjustable) to the second mark. Turn the manual proportional regulating valve 8 of the same gas pipeline to the maximum to complete the gas pressure calibration of the direct-flame burner. The gas pressure calibration procedure for the flat-flame burner is the same. Turn the electric butterfly valve 10 to the fourth mark to complete the air pressure calibration of the direct-flame burner. The air pressure calibration procedure for the flat-flame burner is the same. The electric butterfly valve 10 of the air pipeline and the proportional valve 7 of the gas pipeline are connected through a pressure tap. During ignition, the electric butterfly valve 10 of the air pipeline opens, and the proportional valve 7 of the gas pipeline opens accordingly. The opening procedure for the proportional valve of the flat-flame burner is the same.

[0040] S3, set the valve opening in the HMI interface.

[0041] The furnace pressure valve is open at 90% (to maintain good airflow in the furnace during the baking process so that water vapor can be discharged in time), the air pipeline pressure relief valve is open at 0%, and all air valves of the flat flame burner system and the direct flame burner system are open at 100%.

[0042] S4. In the HMI interface fan control interface, set the fan control to manual mode, set the fan speed to 35Hz, and start the large fan.

[0043] S5 activates the ignition fan control and purging control.

[0044] In the HMI ignition control interface, activate manual ignition fan control to start the small ignition fan. Then, activate the manual purge control of the ignition controller section to begin purging. After one hour of purging, turn off the purging process.

[0045] The purpose of purging is to clean the flue system and various pipes, and remove all blockages.

[0046] S6, after purging, set the air pipeline pressure relief valve opening to automatic mode. In the HMI interface fan control interface, set the fan control to manual mode and the fan speed to 25Hz; in the HMI interface ignition control interface, start the manual ignition control of the ignition controller and press the natural gas main inlet valve button on the distribution cabinet.

[0047] S7, according to Figure 5 The oven drying curve is used to set the oven drying program.

[0048] After the castable refractory is poured and cured for 5-7 days, the furnace drying process begins. Three temperature control couplers are embedded in pre-set holes in the fiber module on the right wall, each located at a representative position of the castable refractory in one of the three temperature control zones.

[0049] In the Eurotherm 3504 temperature controller or HMI interface process curve settings interface, follow... Figure 5 The oven drying curve is used to set the oven drying program.

[0050] The specific furnace drying curve for 300-400mm castable refractory is as follows:

[0051] The process consists of four stages: the first stage involves raising the temperature from room temperature to 150℃ at a rate of 10℃ / h and holding it at that temperature for 72 hours; the second stage involves raising the temperature from 150℃ to 250℃ at a rate of 10℃ / h and holding it at that temperature for 72 hours; the third stage involves raising the temperature from 250℃ to 400℃ at a rate of 20℃ / h and holding it at that temperature for 60 hours; the fourth stage involves raising the temperature from 400℃ to 550℃ at a rate of 20℃ / h and holding it at that temperature for 60 hours; and finally, the temperature is allowed to cool naturally at a rate of 20℃ / h.

[0052] S8 uses both direct flame burner and horizontal flame burner to ignite the small burner and heat the furnace at temperatures below 300℃. At temperatures between 300℃ and 550℃, both direct flame burner and horizontal flame burner are used to ignite the small burner and heat the furnace at high temperatures until the furnace baking process is completed.

[0053] The 45% Al2O3 lightweight insulating castable 14 and the 60% Al2O3 low-cement castable 15 cannot be directly impacted by the flame. The direct-flame burner system of the natural gas furnace combustion system is located directly above the castable lining on the lower part of the furnace sidewall, while the horizontal-flame burner system is located in the middle of the furnace. The small ignition burners are started for ignition. At temperatures below 300℃, both the direct-flame burner and the horizontal-flame burner are used for small-scale baking of the furnace. With all the direct-flame and horizontal-flame burners open, the highest temperature the furnace can reach is 300℃. Therefore, after the temperature controller and furnace temperature reach 300℃, approximately 171.5 hours after the start of furnace baking, the following operations are performed:

[0054] Close the manual butterfly valve 1 in the air pipeline of the large burner of the direct flame burner. Start heating on the main interface of the system operating conditions in the HMI interface, and start the ignition of the flat flame burner. Begin heating the furnace by using the small burner of the direct flame burner 2 to ignite it with a small flame and the large burner of the flat flame burner to ignite it with a large flame to bake the furnace until the furnace baking process is completed. The flame of the large burner of the flat flame burner is slowly scattered, and there will be no flame impact on the castable during ignition and heating.

[0055] Throughout the entire oven baking process, a designated person records the actual temperature of the furnace in the three temperature zones every half hour until the recorded actual furnace temperature drops to 100 degrees Celsius.

[0056] S9. After the oven drying is completed, keep the oven door closed and pressed, and set the valve opening.

[0057] Keep the furnace door closed and secured, set the furnace pressure valve opening to 0%, keep the blower and ignition fan running, set the air duct pressure relief valve opening to 100%, and set the heat exchanger protection valve opening to 100%. The purpose is to allow the furnace to cool naturally in a closed state, avoiding damage to the castable material that may be caused by rapid cooling and the entry of cold air.

Claims

1. A method for igniting and baking a natural gas furnace, characterized in that, Includes the following steps: S1. Close and tighten the furnace door, and check the following pressure parameters: natural gas main pipeline inlet pressure, pressure of the large burner natural gas main pipeline after decompression, pressure of the ignition small burner natural gas main pipeline after decompression, setting value of each pressure switch, air pressure of the blower and air pressure of the ignition small blower. S2, check and calibrate the air pressure and gas pressure of all burners in advance to ensure that all burners ignite normally; S3, set the valve opening degree in the HMI interface; S4, set the fan control to manual mode, set the fan speed to 35Hz, and start the large fan; S5, start the ignition fan control and purging control; S6, after purging, set the air pipeline pressure relief valve opening to automatic mode; set the fan control to manual mode and the fan speed to 25Hz; start the ignition controller manual ignition control and press the natural gas main inlet valve button on the distribution cabinet. S7, set the oven drying program according to the oven drying curve; S8, at temperatures below 300℃, both direct flame burners and horizontal flame burners are used to ignite the furnace with a small flame to heat the furnace. At temperatures between 300℃ and 550℃, both direct flame burners and horizontal flame burners are used to ignite the furnace with a large flame to heat the furnace until the furnace baking process is completed. S9. After the oven drying is completed, keep the oven door closed and pressed, and set the valve opening.

2. The method for igniting and baking a natural gas furnace according to claim 1, characterized in that, In S1, the inlet pressure of the main natural gas pipeline is 25-30 kPa, the pressure of the main natural gas pipeline after depressurization is 10 kPa, and the pressure of the main natural gas pipeline after depressurization is 6 kPa; the minimum pressure switch setting value of the main natural gas pipeline for the large burner is 30 mbar, and the maximum pressure switch setting value is 142 mbar; the minimum pressure switch setting value of the main natural gas pipeline for the ignition small burner is 30 mbar, and the maximum pressure switch setting value is 120 mbar; the air pressure of the blower is 3-5 kPa, and the air pressure of the ignition small blower is not less than 8 kPa.

3. The method for igniting and baking a natural gas furnace according to claim 1, characterized in that, In S2, the air pressure of the ignition burner in the direct flame burner system is 40-50 mbar and the gas pressure is 25 mbar, while the air pressure of the ignition burner in the flat flame burner system is 35-40 mbar and the gas pressure is 30 mbar.

4. The method for igniting and baking a natural gas furnace according to claim 1, characterized in that, In S3, the furnace pressure valve opening is 90%, the air pipeline pressure relief valve opening is 0%, and all air valves of the flat flame burner system and the direct flame burner system are 100% open.

5. The method for igniting and baking a natural gas furnace according to claim 1, characterized in that, In S7, the oven baking curve is as follows: the first stage is to heat from room temperature to 150℃ at a heating rate of 10℃ / h and then hold for 72 hours; the second stage is to heat from 150℃ to 250℃ at a heating rate of 10℃ / h and then hold for 72 hours; the third stage is to heat from 250℃ to 400℃ at a heating rate of 20℃ / h and then hold for 60 hours; the fourth stage is to heat from 400℃ to 550℃ at a heating rate of 20℃ / h and then hold for 60 hours; after completion, the oven is cooled naturally at a rate of 20℃ / h.

6. The method for igniting and baking a natural gas furnace according to claim 1, characterized in that, In S8, during the entire oven baking process, a designated person records the actual temperature of the furnace in the three temperature zones every half hour until the recorded actual furnace temperature drops to 100 degrees Celsius.

7. The method for igniting and baking a natural gas furnace according to claim 1, characterized in that, The specific steps of S9 are as follows: keep the furnace door closed and pressed, set the furnace pressure valve opening to 0%; keep the blower and ignition fan running; set the air pipeline pressure relief valve opening to 100%; set the heat exchanger protection valve opening to 100%.

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