A Method for Measuring and Controlling Thermal Parameters of a Ring Heating Furnace for Wheel Billets

Abstract

A method for measuring and controlling the thermal parameters of a ring heating furnace for wheel billets belongs to the technical field of control of wheel billet heating furnaces. This method for measuring and controlling the thermal parameters of the ring heating furnace for wheel billets includes the measurement and control of the following thermal parameters: measurement and control of gas pressure and flow rate; measurement and control of combustion air pressure, flow rate, and temperature; measurement and control of air-fuel ratio; measurement and control of furnace temperature; measurement and control of furnace chamber pressure; measurement and control of the flue gas temperature before the heat exchanger, the flue gas temperature after the heat exchanger, and the air preheating temperature in the flue; The beneficial effects of the present invention are that the present invention can accurately measure and precisely control the important thermal parameters of the billet heating furnace, improve the heating quality of billets, increase the rolling qualification rate and production efficiency of rolled steel wheels, maintain or stabilize the equipment accuracy of the heating furnace, extend the service life of the equipment, reduce energy consumption so as to obtain the best comprehensive economic benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of wheel billet heating furnace control, and particularly to a method for measuring and controlling thermal parameters of a ring heating furnace for wheel billets. Background Art

[0002] The rolling forming of train wheel blanks is an intermediate process and also an important process in the manufacture of rolled steel train wheels. The heating furnace provides hot billets for wheel rolling, and billet heating is the previous process before wheel rolling forming. Whether this process is well controlled has an important impact on several aspects such as improving the production efficiency and product quality of wheel rolling, maintaining the accuracy and extending the service life of the furnace body equipment and rolling line equipment (molds), and energy conservation, consumption reduction, and emission reduction.

[0003] However, there are the following problems in the prior art when heating wheel billets through a heating furnace:

[0004] 1) The integrity of traditional wheel billet heating furnace equipment is relatively poor. The furnace overhaul and maintenance are not thorough, and it often operates with problems. The airtightness of the furnace is poor, manifested as the charging and discharging furnace doors are not tight, and there are many openings in the fixed or movable water seal knives.

[0005] 2) The furnace temperature ranges of each temperature control zone specified in the operation key points of the wheel billet heating process are relatively wide, and it is difficult for heating workers to determine or set a more appropriate target temperature value according to different production rhythms or states. Especially when the production rhythm is in a slow state, the heating furnace is in a holding state during rolling line equipment failures, and at the initial stage of resuming production after the rolling line equipment failure is processed, that is, during the start-up stage, there is no relatively standardized standard for determining or setting the target temperature values of each temperature control zone. It is manifested as either insufficient billet heating, with low or uneven steel temperature; or excessive billet heating, with high steel temperature or serious burning damage.

[0006] 3) The thermal parameter measurement system is imperfect, especially the measurement and adjustment of the furnace pressure. It is impossible to accurately adjust and control the furnace pressure according to the changes in the production rhythm. Some heating furnaces even do not install a furnace pressure measurement device. Or a furnace pressure measurement device is installed, but the installation position is inappropriate, that is, the pressure tapping point position is selected incorrectly. Or the appropriate pressure tapping point position is selected, but the measured value is inaccurate. Or the measured value is displayed, but the corresponding reference value or zero pressure surface cannot be found accurately. Some heating furnaces have poor airtightness, and the draft of the furnace is seriously insufficient, and there has always been large positive pressure operation, resulting in serious damage to the furnace body equipment, doubling the maintenance or repair costs, and at the same time causing a poor on-site operation environment.

[0007] The imperfect measurement system of thermal parameters is also manifested in the improper control of the furnace atmosphere property, i.e., the air-fuel ratio. Especially for the heating furnace with manual proportional regulation, the air is often configured with a serious excess. It is unable to adjust or control the air-fuel ratio in a timely and correct manner according to the changes in the production rhythm and the different temperature environments (high-temperature zone and low-temperature zone) where the billets are located. There is insufficient research and analysis on the correlation between the furnace atmosphere property, i.e., the air-fuel ratio, and the oxidation and decarburization of the billet surface, and even overheating and burning. There is also insufficient research and analysis on the correlation between the furnace atmosphere property and the thickness, morphology of the scale formed on the billet surface, and the difficulty of descaling (scale shedding) after the billet is discharged from the furnace.

[0008] 4) Insufficient attention is paid to the control level and control range of three important temperatures in the flue gas - the flue gas temperature before the heat exchanger, the flue gas temperature after the heat exchanger, and the air preheating temperature. There is no clear understanding of the correlation between these three important temperatures, especially the flue gas temperature after the heat exchanger, and the flue gas draft, smooth furnace operation, energy conservation and consumption reduction.

[0009] 5) The degree of automation of furnace operation adjustment and control is low. Manual adjustment and operation based on experience result in unstable operation of thermal parameters, large fluctuations, strong randomness and arbitrariness, and a large labor intensity for the heating workers.

[0010] There is insufficient statistical analysis of some key furnace technical indicators such as the production efficiency of the furnace, the thermal efficiency of the furnace, and the unit consumption of the furnace. It is difficult to track and trace, and it is difficult to find and analyze the reasons for problems, and corresponding corrective and preventive measures cannot be formulated. Summary of the Invention

[0011] To solve the above technical problems, the present invention provides a method for measuring and controlling the thermal parameters of a ring heating furnace for wheel billets, which can accurately measure and precisely control the important thermal parameters of the billet heating furnace, improve the heating quality of the billets, increase the rolling qualification rate and production efficiency of rolled steel wheels, maintain or stabilize the equipment accuracy of the heating furnace, extend the service life of the equipment, and reduce energy consumption to obtain the best comprehensive economic benefits.

[0012] To achieve the above object, the technical solution adopted by the present invention to solve its technical problems is: the method for measuring and controlling the thermal parameters of the ring heating furnace for wheel billets includes the measurement and control of the following thermal parameters:

[0013] 1) Measurement and control of gas pressure and flow rate;

[0014] 2) Measurement and control of combustion-supporting air pressure, flow rate, and temperature;

[0015] 3) Measurement and control of air-fuel ratio;

[0016] 4) Measurement and control of furnace temperature;

[0017] 5) Measurement and control of furnace chamber pressure;

[0018] 6) Measurement and control of the flue gas temperature before the heat exchanger in the flue, the flue gas temperature after the heat exchanger, and the air preheating temperature.

[0019] In the step 1), the pressure of the external mixed coal gas medium is 10.0 - 12.0 kPa, the pressure after the pressure regulating valve of the main heating furnace pipe is 6.0 - 9.0 kPa, and the flow rate of the mixed coal gas main pipe is 0 - 6800 m 3 / h. The mixed coal gas main pipe is connected to the burners in the preheating section, heating section 1, heating section 2, and soaking section of the heating furnace through four coal gas branch pipes respectively. Gas flow orifice plates for measuring the coal gas flow are provided on both the mixed coal gas main pipe and the four coal gas branch pipes; the mixed coal gas flow rates of the four coal gas branch pipes are respectively: 0 - 800 m 3 / h, 0 - 2500 m 3 / h, 0 - 2000 m 3 / h, and 0 - 1500 m 3 / h; the mixed coal gas flow velocities of the mixed coal gas main pipe and the four coal gas branch pipes are all 8 - 12 m / s; the pressure of the mixed coal gas medium before the burners of each coal gas branch pipe is 3.0 - 5.0 kPa.

[0020] In the step 2), the combustion air main pipe is connected to the burners in the preheating section, heating section 1, heating section 2, and soaking section of the heating furnace through four combustion air branch pipes respectively. The combustion air main pipe is connected to the air heat exchanger and the combustion air blower; Combustion air flow orifice plates for measuring the combustion air flow are provided on both the combustion air main pipe and the four combustion air branch pipes; the total air volume of the combustion air blower is 21793 m 3 / h, the total pressure is 11847 Pa, the motor power is 132 kw, and the rated speed is 1450 rpm; the combustion air blower realizes variable frequency control, and the frequency of the combustion air blower is in the range of 0 - 50 Hz; during production, the operating frequency range of the combustion air blower is 30 - 40 Hz; the target value setting range of the combustion air main pipe air pressure is 4.5 - 6.5 kPa, and the operating range of the combustion air flow is 6000 - 18000 m 3 / h; the combustion air flow rates of the four combustion air branch pipes are respectively: 700 - 2500 m 3 / h, 2300 - 7000 m 3 / h, 1700 - 5500 m 3 / h, 1300 - 3000 m 3 / h; the combustion air flow velocities of the combustion air main pipe and the four combustion air branch pipes are all within 8 - 12 m / s; the pressure of the combustion air medium before the burners of each combustion air branch pipe is 2.0 - 4.0 kPa. The maximum flue gas volume of the air heat exchanger is 24800 m 3 / h, the flue gas temperature before the air heat exchanger ≤ 850 °C, and the maximum combustion air volume is 18000 m 3 / h, the hot air temperature ≤ 500°C, the air side resistance < 2500 Pa; the flue gas side resistance < 200 Pa; the cold air pressure is set at 5.0 - 6.0 kPa, and the combustion-supporting fan realizes automatic regulation of the air pressure in the main combustion-supporting air pipe, with the fluctuation value less than ±0.1 kPa.

[0021] In the said step 3),

[0022] The combustion system of the wheel steel billet heating furnace adopts a proportional combustion temperature control mode for the branch section, and its air-fuel ratio adjustment and control method is as follows: (a) Preheating section: The mixed gas flow rate is 0 - 800 m 3 / h, and the corresponding combustion-supporting air flow rate is 700 - 2500 m 3 / h, where 700 m 3 / h is the safety air volume; among them, when the mixed gas flow rate is 0 - 300 m 3 / h, the combustion-supporting air flow rate is 700 ± 50 m 3 / h and it is the safety air volume; when the mixed gas flow rate is 300 - 800 m 3 / h, the air-fuel ratio is configured according to 2.3 - 3.0, that is, the combustion-supporting air flow rate is 700 - 2500 m 3 / h; (b) Heating section 1: The mixed gas flow rate is 0 - 2500 m 3 / h, and the corresponding combustion-supporting air flow rate is 2300 - 7000 m 3 / h, where 2300 m 3 / h is the safety air volume; among them, when the mixed gas flow rate is 0 - 800 m 3 / h, the combustion-supporting air flow rate is 2300 ± 100 m 3 / h and it is the safety air volume; when the mixed gas flow rate is 800 - 2500 m 3 / h, the air-fuel ratio is configured according to 2.5 - 2.8, that is, the combustion-supporting air flow rate is 2300 - 7000 m 3 / h; (c) Heating section 2: The mixed gas flow rate is 0 - 2000 m 3 / h, and the corresponding combustion-supporting air flow rate is 1700 - 5500 m 3 / h, where 1700 m 3 / h is the safety air volume; among them, when the mixed gas flow rate is 0 - 700 m 3 / h, the combustion-supporting air flow rate is 1700 ± 100 m 3 / h and it is the safety air volume; when the mixed gas flow rate is 700 - 2000 m 3 / h, the air-fuel ratio is configured according to 2.5 - 2.7, that is, the combustion-supporting air flow rate is 1700 - 5500 m 3 / h; (d) Soaking section: The mixed gas flow rate is 0 - 1500 m 3 / h, and the combustion-supporting air flow rate is 1300 - 3000 m3 / h, where 1300 m 3 / h is the safe air volume; among them, when the mixed gas flow rate is 0 - 400 m 3 / h, the combustion-supporting air flow rate is 1300 ± 50 m 3 / h and it is the safe air volume; when the mixed gas flow rate is 400 - 1500 m 3 / h, the air-fuel ratio is configured according to 2.2 - 2.6, that is, the combustion-supporting air flow rate is 1300 - 3000 m 3 / h; when the mixed gas flow rate of each branch section of the heating furnace is less than a certain value, the combustion-supporting air is configured according to the safe air volume, and it no longer decreases with the reduction of the gas consumption, and the safe air volume remains unchanged.

[0023] In the step 4), the heating furnace includes a low-temperature zone and a high-temperature zone. The low-temperature zone includes a preheating section and a first heating section, and one set or multiple sets of thermocouples are arranged on the upper layer of each temperature control zone in the low-temperature area; the high-temperature zone includes a second heating section and a soaking section, and the temperature measurement points in the high-temperature area cover the inner and outer walls of the heating furnace, and multiple sets of thermocouples are arranged along the circumferential direction of the furnace wall and are arranged in upper and lower layers; the burners of the whole furnace are divided into two forms: straight-flame burners and flat-flame burners. The straight-flame burners are arranged on the inner and outer side walls of the heating furnace, with a power of 400 kw and a flow rate of 150 m 3 / h; the flat-flame burners are arranged on the center line of the discharge door at the furnace top, with a power of 267 kw and a flow rate of 100 m 3 / h; the heating furnace adopts a branch-section constant-flame ratio combustion control mode, including the "empty furnace charging, i.e., the first piece" mode, the "continuous production" mode, and the "production end, final furnace" mode.

[0024] In the step 5), in the measurement and control of the furnace pressure, one pressure-taking point is selected, which is the position on the inner ring furnace wall opposite to the discharge door area in the soaking section of the heating furnace and at a height of 200 - 250 mm above the furnace bottom; during normal production, the target value of the furnace pressure is set to -2 - -4 Pa; when the charging door is closed for 5 minutes, the set value of the furnace pressure automatically increases by 5 - 7 Pa and then compensates to the state of +1 - +3 Pa; during the slow rhythm or the stage of waiting for rolling to stop, the target value of the furnace pressure is set to -1 - +1 Pa.

[0025] In the step 6), in the normal production state, the flue gas temperature before the heat exchanger is maintained at 500 - 750 °C; the flue gas temperature after the heat exchanger is maintained at 320 - 450 °C. Temperatures lower than 250 - 300 °C or higher than 480 - 500 °C are both abnormal states; the air preheating temperature is maintained at 350 - 480 °C.

[0026] The annular heating furnace thermal parameter measurement and control method also includes drawing a key thermal parameter operation trend record curve, tracking and tracing the thermal parameter operation process, regular statistical analysis, and taking timely measures for equipment problems and operational problems found, so that the equipment and facilities are always in a stable and smooth state, and the operation adjustment is always in a standardized and controllable state.

[0027] The beneficial effects of the present invention are:

[0028] The present invention accurately measures and precisely controls important thermal parameters including gas pressure, gas flow, combustion-supporting air pressure, combustion-supporting air flow, combustion-supporting air temperature, air-fuel ratio, furnace temperature, furnace pressure and three flue temperatures, draws a record curve of key thermal parameter control operation trends, and takes timely measures to repair and correct equipment problems and operational problems found, so that equipment and facilities are always in a stable and smooth state, and operational adjustments are always in a standardized and controllable state, thereby improving the heating quality of steel billets, further improving the rolling qualification rate and production efficiency of steel rolling wheels, maintaining or stabilizing the equipment accuracy of the heating furnace, extending the service life of the equipment, reducing energy consumption, and reducing pollutant emissions, thereby achieving good comprehensive economic benefits. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in combination with the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0030] The specific implementation scheme of the present invention is:

[0031] Description of the backward situation of the original operation control mode: Characteristics of billet heating furnace: large changes in production rhythm; large changes in furnace temperature adjustment; large changes in heat load; large changes in the amount of combustion products generated, that is, the maximum and minimum values ​​differ greatly. For example, state 1: empty furnace or rolling line equipment failure, the furnace is in the state of waiting for rolling, gas <1000m3 / h, combustion air is about 6000±500m 3 / h, total combustion products 6000-7000m 3 / h. State 2: Full load and fast pace production, gas 4500-5000m 3 / h, combustion air 13500-15000m 3 / h, total combustion products 18000-20000m 3 / h. The furnace pressure fluctuates greatly. Disadvantages of manual adjustment: The furnace temperature control is quite random; the air-fuel ratio control is quite random, and based on experience, the combustion air is often over-configured, and the air-fuel ratio is too large or even too large; the furnace pressure adjustment or control is unstable and is operated based on experience.

[0032] Therefore, to solve the above problems, the present invention reforms the structure of the heating furnace and its method for measuring and controlling thermal parameters, and the specific solutions are as follows:

[0033] The present invention provides a method for measuring and controlling thermal parameters of a ring heating furnace for wheel steel billets, including the following content:

[0034] 1. Gas parameters - measurement and control of gas pressure and flow rate

[0035] 1.1 Gas conditions and parameters

[0036] The fuel medium used is high-coke conversion mixed gas. The calorific value of the mixed gas is basically stable, maintained at 9600 ± 400 kJ / m 3 (2300 ± 100 kcal / m 3 ), and the theoretical air-fuel ratio is 2.4 - 2.6.

[0037] 1.1.1 Mixed gas main pipe and its accessories

[0038] The total gas pipeline is Φ529x5, and the external gas supply medium pressure is 10.0 - 12.0 kPa. The gas pressure after the pressure regulating valve is 6.0 - 9.0 kPa. Accessories for the gas main pipe: gas pressure regulating valve; gas quick cut-off valve. Metering and detection include: measurement of the external gas supply source pressure; measurement of the gas pressure after the pressure regulating valve; measurement of the gas flow rate in the gas main pipe. The nominal diameter of the gas pressure regulating valve is DN400; the nominal diameter of the valve plate of the gas quick cut-off valve is 500; the opening stroke of the valve plate of the gas pressure regulating valve, that is, the opening range, is 15 - 90%, and in individual cases, if it needs to be controlled below 15%, it can be changed to manual fine-tuning.

[0039] 1.1.2 Branch pipes and their accessories.

[0040] The straight pipe at the front end of the gas in the preheating section is Φ219x6; the gas pipeline in the first heating section is Φ273x4; the gas pipeline in the second heating section is Φ325x4; the gas pipeline in the soaking section is Φ273x4. The pressure after the gas flow regulating valve for the four branch pipes is ≥ 2.0 kPa. Accessories for the gas branch pipes: manual seal butterfly valve for the branch section, that is, a stop valve; gas flow regulating valve for the branch pipe; flow orifice plate. Metering and detection include: gas pressure after the flow regulating valve; gas flow rate in the branch pipe: the mixed gas flow rates of the four gas branch pipes are respectively: 0 - 800 m 3 / h, 0 - 2500 m 3 / h, 0 - 2000 m 3 / h and 0 - 1500 m 3 / h; the mixed gas flow velocities in the mixed gas main pipe and the four gas branch pipes are all 8 - 12 m / s; the mixed gas medium pressure before the burners of each gas branch pipe is 3.0 - 5.0 kPa.

[0041] 1.1.3 Burner-related parameters and accessories.

[0042] Parameters of the direct flame burner: Q = 9200 - 9600 kJ / Nm 3 = (2200 - 2300) x 4.18 kJ / Nm 3 ; Capacity 150 m 3 / h, i.e., burner power 400 kw; The gas is at room temperature and the air is at 450 °C; The gas pipeline of the burner is Φ89 x 4; The combustion air pipeline of the burner is Φ159 x 5; Accessories of the gas pipeline of the burner: Cock (stop valve - for safety production, starting and stopping the furnace); Butterfly valve (fine-tuning the flow rate - for heat supply and flame length)

[0043] Parameters of the flat flame burner: Q = 9200 - 9600 kJ / Nm 3 = (2200 - 2300) x 4.18 kJ / Nm 3 ; Capacity is 100 m 3 / h, i.e., burner power 267 kw; The gas is at room temperature and the air is at 450 °C; The gas pipeline of the burner is Φ76 x 4; The combustion air pipeline of the burner is Φ108 x 3.

[0044] 1.2 Parameter Measurement and Control

[0045] The pressure of the externally supplied mixed gas medium is detected. Under the normal state of the gas source pressure, it is defined as 10.0 - 12.0 kPa. Through the main gas pressure regulating valve, the gas pressure after the pressure regulating valve is automatically adjusted between 6.0 - 9.0 kPa (the set value fluctuates by ±0.2 kPa), and the total flow rate of the mixed gas main pipe is 0 - 6800 m 3 / h. This set value is adjusted accordingly with the production rhythm, i.e., the size of the heat supply. For example, when the furnace is in fast-paced production and the gas flow rate is large, the automatic control pressure set value takes the upper limit, i.e., 8.5 - 9.0 kPa. At this time, the gas consumption of the four temperature control sections is large, and the gas flow regulating valve of the branch pipe is also adjusted in a large opening range. When the furnace is in slow-paced production or waiting for rolling during a stop, the heat supply is less, i.e., the gas flow rate is small, the automatic control pressure set value takes the lower limit, i.e., 6.0 - 6.5 kPa, still making the opening of the gas flow regulating valve of the branch pipe and the gas flow rate of the branch pipe show a "linear" relationship. The opening of the main gas pressure regulating valve is limited to the range of 15 - 90% (to prevent the valve position from getting stuck at a small opening) for operation. During normal production, the valve position of the pressure regulating valve is usually adjusted in the range of 20 - 50%. Thus, it is ensured that the gas pressure is maintained between 5.8 - 9.2 kPa after the main pipe cut-off valve and before the branch section flow regulating valve. The automatic control main pipe pressure set value shall not be lower than 5.5 - 6.0 kPa to prevent the main gas from being cut off by the main gas quick cut-off valve when the main pipe pressure fluctuates. Therefore, the main gas pressure regulating valve has a minimum valve position limit (≥15%).

[0046] Under the condition of stable total pipeline pressure, the gas flow rate of the branch pipe is only related to the opening degree of the flow regulating valve, and the opening degree of the gas flow regulating valve of the branch pipe is limited by upper and lower limits. The lower limits of the three branch sections of the preheating section, the first heating section, and the soaking section are 5-10%, and the lower limit of the second heating section is 10-15%; the upper limits of the four branch sections are all 60-70%. However, there is no minimum flow rate limit, and the minimum flow rate can be displayed as 0m 3 / h. That is, when the valve position opening degree is at least 5-10% (the flow regulating valve is not a sealing valve or a stop valve), the gas flow rate display can be zero, that is, the branch section is almost in a non-heating state. When the opening degree of the gas flow regulating valve of the branch pipe is at least 5-10%, the pipeline pressure behind the regulating valve is very small, but it is still ≥100Pa, and there is no flashback phenomenon. The gas flow rate of the branch pipe is required to be accurately detected and displayed above 100-200m 3 / h. Keeping the gas main pipe pressure stable is very necessary for a furnace with automatic temperature control. When the gas flow rate of a certain branch pipe tracks the target temperature set value and increases or decreases, the opening degree of the gas flow regulating valve of this branch pipe will increase or decrease accordingly, without affecting the stability of the gas flow rate of other branch sections.

[0047] The gas flow rate of the branch pipe automatically tracks the furnace temperature set value of this section. By comparing the real-time temperature display value (actual temperature measurement value) with the target temperature set value, it is determined whether to increase or decrease the opening degree of the flow regulating valve of the branch section. The adjustment time of each branch section is determined according to the response time of the flow regulating valve, the response time of the flow meter, and the temperature feedback time. The opening degree is adjusted by -3 to +3% each time. In the program logic, under the existing opening degree, the gas flow rate (heat supply), the combustion-supporting air flow rate configured according to the air-fuel ratio, the temperature change trend (rise or fall), and the degree of closeness to the set value determine the next adjustment cycle (or adjustment time). Either the opening degree remains unchanged (within the allowable temperature difference range), or it increases by 0-3%, or it decreases by 0-3%, so that the actual temperature measurement value continuously approaches the target temperature set value.

[0048] 2. Combustion-supporting air parameters - Measurement and control of combustion-supporting air pressure, flow rate, and temperature

[0049] 2.1 Performance parameters of the combustion-supporting air blower

[0050] Blower model: 9-19-No14D-2; air volume: 21793m 3 / h; Total pressure: 11874 Pa; Motor power: 132 kw; Rated speed: 1450 rpm; Quantity: two sets, one in use and one in standby. Frequency conversion control is implemented for both fans: 0 - 50 Hz, with automatic and manual control. Automatic control takes the pressure of the cold air main pipe as the control target, and the pressure target set value is manually input; for manual control, the fan frequency is manually input (adjusted or changed) to stabilize or change the pressure of the cold air main pipe. During normal production, "automatic control" is put into operation, mainly taking the pressure of the cold air main pipe as the control target, inputting the appropriate set value of the cold air main pipe pressure target value, and the combustion-supporting fan can be automatically controlled through the frequency conversion program to achieve relative constancy of the cold air main pipe pressure.

[0051] 2.2 Performance parameters of the air heat exchanger

[0052] Quantity: 1 set; Maximum flue gas volume: 24800 m 3 / h (standard condition); Flue gas temperature before the heat exchanger ≤ 850 °C, during actual operation, 500 - 750 °C; Maximum combustion-supporting air volume 18000 m 3 / h (corresponding maximum consumption of mixed coal gas 6800 m 3 / h, air-fuel ratio 2.4 - 2.6); Hot air temperature ≤ 500 °C, during actual production, 320 - 480 °C; Resistance on the air side < 2500 Pa; Resistance on the flue gas side < 200 Pa; Service life ≥ 3 years.

[0053] 2.3 Combustion-supporting air pipeline and accessories

[0054] 2.3.1 Combustion-supporting air main pipe (hot and cold air pipes) and its accessories.

[0055] Two combustion-supporting fans (one in use and one in standby); Total cold air side pipeline Φ820x4; Cold air pressure measurement point; Flue gas dilution cold air valve (DN200); Air heat exchanger; Total hot air side pipeline Φ920x4; Initial hot air pressure measurement point; Hot air temperature measurement point (thermocouple insertion point); Orifice plate for total air pipe flow, entering each branch pipe. The range of cold air pressure target set value is 4.5 - 6.5 kPa; Average preheating temperature of combustion-supporting air is 350 - 430 °C, ≤ 480 °C. Due to the increase in flow resistance caused by air preheating, the pipeline diameter is correspondingly increased.

[0056] 2.3.2 Combustion-supporting air pipe sections and their accessories for each branch section.

[0057] Straight pipeline at the front end of combustion-supporting air in the preheating section Φ325x3; Straight pipeline at the front end of combustion-supporting air in heating section 1 Φ478x3; Straight pipeline at the front end of combustion-supporting air in heating section 2 Φ529x3; Straight pipeline at the front end of combustion-supporting air in the soaking section Φ426x3. Pressure after the flow regulating valve of combustion-supporting air for the four branch pipes ≥ 3.0 kPa. Accessories for combustion-supporting air branch pipes: Branch pipe gas flow regulating valve; Orifice plate. Measurements for metrology and detection include: Pressure of combustion-supporting air after the flow regulating valve; Flow of combustion-supporting air in the branch pipe.

[0058] 2.4 Parameter measurement and control:

[0059] The set pressure range of the cold air is 4.5 - 6.5 kPa. This is manually input. After the target value is set, during the operation process, the pressure fluctuation of the cold air main pipe does not exceed ±0.1 kPa.

[0060] The combustion-supporting fans (two: one in use and one in standby) adopt variable-frequency control, with the air pressure on the cold air side as the control target. The set pressure range of the main pipe air pressure on the cold air side is 4.5 - 6.5 kPa. Referring to the automatic control principle of the main pipe gas pressure, when in fast-paced production and large heat supply is required, the set value of the air pressure target on the cold air side is set at the upper limit of this range, that is, 6.0 - 6.5 kPa; when in slow-paced production or when the rolling mill is stopped or waiting for rolling and the heat supply is small, the air pressure target value on the cold air side is set at the lower limit of this range, that is, 4.5 - 5.0 kPa. Under normal production rhythm or relatively fast production rhythm, the air pressure target value is set at 5.0 - 5.5 kPa. When adjusting the combustion-supporting air flow of a certain branch section, the combustion-supporting air flow of other branch sections remains basically stable.

[0061] The adjustment and control of the combustion-supporting air flow of the branch pipe are, in principle, similar to the adjustment and control of the branch pipe gas flow. It's just that in the control program logic, the gas flow is restricted by the set value of the furnace temperature of the branch section, that is, the gas flow tracks the furnace temperature of the branch section. While the combustion-supporting air of the branch pipe automatically tracks the gas flow according to the pre-set air-fuel ratio, that is, it is restricted by the gas flow according to a certain ratio. The adjustment time of the combustion-supporting air flow is also completed comprehensively based on the response time of the flow regulating valve, the response time of the combustion-supporting air flow transmitter, and the influence time of the gas flow transmitter. The adjustment amplitude of each time is defined between -3% and +3%. This makes the combustion-supporting air flow of the branch pipe continuously approach the "set air-fuel ratio" multiple of the real-time gas display value or be in the "safe air" state.

[0062] 3. Measurement and control of the air-fuel ratio

[0063] The nature of the furnace atmosphere is used to describe the degree of complete combustion of the fuel and combustion-supporting air supplied into the furnace during the chemical reaction. If the configured air-fuel ratio is too small, the fuel will not burn completely, the furnace temperature will not reach the highest value, the energy consumption per ton of steel will increase; it is difficult to remove the scale on the surface of the steel billet; toxic and harmful gases such as CO will be emitted into the atmosphere. If the configured air-fuel ratio is too large (the excess coefficient exceeds 20%), the amount of combustion products will increase, the actual combustion temperature will decrease, the furnace temperature will decrease, and the energy consumption per ton of steel will increase; the preheating temperature of the air is too low, the gas consumption increases, and the energy consumption per ton of steel rises; the scale thickness on the surface of the steel billet increases, that is, the burning loss of the steel billet increases. In severe cases, when the steel billet is in a high-temperature environment for a long time, heating quality accidents such as overheating and overburning may occur.

[0064] By adjusting the air-fuel ratio, the atmosphere in the control section can be made neutral, reducing, or oxidizing. Analyzing solely from the perspective of energy conservation, a neutral combustion product is the most energy-efficient. However, in actual production, considering the impact of the combustion product atmosphere on the heating quality of the steel billet, the influence on the removal (descaling) of the scale on the steel billet surface, and the requirements for safe operation adjustment, according to different production rhythms, the nature of the furnace atmosphere in the high-temperature and low-temperature zones is fine-tuned according to the following principles.

[0065] For high-temperature zone in fast-paced production (rapid output of hot steel and rapid loading of cold steel): The atmosphere is neutral or weakly oxidizing, with an air-fuel ratio of 2.4 - 2.7, ≤3.0, which is beneficial for the removal of scale on the steel billet surface. For low-temperature zone in fast-paced production (rapid output of hot steel and rapid loading of cold steel): The atmosphere is neutral or weakly reducing, with an air-fuel ratio of 2.2 - 2.5, ≥2.0. Considering the inhalation of a small amount of cold air from the charging door, burning out the residual gas in the flue, increasing the flue gas temperature, and enhancing or improving the draft. For high-temperature zone in slow-paced production (slow output of hot steel and slow loading of cold steel): The atmosphere is neutral or weakly reducing, with an air-fuel ratio of 2.2 - 2.6, ≥2.0. For low-temperature zone in slow-paced production (slow output of hot steel and slow loading of cold steel): The atmosphere is neutral or weakly oxidizing, with an air-fuel ratio of 2.4 - 2.8, ≤3.2. During the stand-by rolling stage (no loading and no discharging): For high-temperature zone, the atmosphere is weakly reducing or equipped with safety air, with an air-fuel ratio of 2.0 - 2.5, excluding safety air. During the stand-by rolling stage (no loading and no discharging): For low-temperature zone, the atmosphere is significantly oxidizing or equipped with safety air, with an air-fuel ratio of 2.6 - 3.2 or in the state of safety air.

[0066] The nature of the combustion product atmosphere in the flame furnace, that is, the air-fuel ratio, is determined by the air flow rate and gas flow rate of the burner. In the proportional combustion mode of branch section temperature control, the air-fuel ratio has relatively large fluctuations or instability. Because during automatic control, the air flow rate in the branch section follows the gas flow rate in the branch pipe according to the set air-fuel ratio (with a correction coefficient). However, there is a lag in the signal of the air flow rate regulating valve and a lag in the air flow rate detection transmitter, making it difficult to track the gas flow rate. Also, the gas flow rate is constantly changing and adjusting during the production process. Therefore, the fluctuation of the combustion product atmosphere in the branch section is relatively intense. Compared with the pulse combustion mode, as long as the pressure at the beginning and end of the gas pipeline is controlled stably, during the temperature control process, the air-fuel ratio (furnace atmosphere) remains basically stable, and its energy-saving and consumption-reducing effect is more obvious.

[0067] In addition, the air leakage of the furnace body, especially the openings at the negative pressure positions, which inhale a certain amount of cold air, will also cause the disorder of the air-fuel ratio in local areas, and will have a certain impact on the local temperature field and the local furnace pressure distribution. The atmosphere nature in a larger area is still restricted by the ratio of gas and combustion-supporting air of the burner.

[0068] From the consideration of safe operation adjustment, to prevent the state of relatively small gas flow rate in the branch pipe (100 - 200m 3(No display below), when the pressure after the branch gas flow regulating valve is about 100 - 200 Pa, to prevent the burner from backfiring, it is stipulated that in each branch section, a certain amount of combustion-supporting air, namely the so-called "safety air", should be retained when there is no heating or the heating is small. Maintaining a certain "safety air volume" is also necessary to prevent the fan from surging. To reduce the oxidation, burning loss, and decarburization of the billet, the "safety air" configuration in the high-temperature area should be minimized. According to the different maximum loads of each branch section, corresponding regulations are made for the safety air volume of each branch section.

[0069] The "safety air" of the four branch sections is as follows: soaking section 1200 - 1400 m 3 / h; heating section 2 1500 - 1800 m 3 / h; heating section 1 2200 - 2400 m 3 / h; preheating section 750 - 850 m 3 / h.

[0070] When the heat supply of the furnace is almost zero, the total air volume still remains 5000 - 7000 m 3 / h. At the same time, according to the fan characteristic curve and the combustion-supporting air pipeline characteristic curve, if the fan does not discharge air, that is, the air discharge flow rate of the fan is zero or too small, the fan will experience a surging phenomenon. To avoid the fan from surging and to ensure the safe operation of the furnace, the "safety air" of each branch section is stipulated. When the combustion-supporting air volume of each branch section is reduced to the "safety air" range, the combustion-supporting air flow rate of this branch pipe will no longer be adjusted smaller. At this time, the air-fuel ratio is no longer considered, that is, the nature of the combustion products in the branch section is no longer judged. When the total combustion-supporting air volume of the furnace is small, the target value of the cold air side air pressure can be set at 4.0 - 4.5 kPa. And there is no need for cold air discharge. For the heating furnace adopting the pulse combustion mode, in the small heat supply state, there is a cold air discharge on the cold air main pipe. At this time, the cold air discharge valve is opened to discharge the cold air into the atmosphere to prevent the fan from surging.

[0071] 4. Measurement and Control of Furnace Temperature

[0072] 4.1 Measurement and Control of Furnace Temperature in Each Branch Section

[0073] Process thermocouples for each branch section are respectively set on the inner and outer side walls, and this temperature is used as the target set temperature. In addition, to avoid blind areas in furnace temperature measurement and monitoring in sensitive high-temperature areas, corresponding reference thermocouples are arranged along the furnace length direction to measure and monitor the furnace temperature in the corresponding areas. The distribution and adjustment of the reference thermocouples have formulated internal control standards.

[0074] Furnace temperature (steel temperature) is an extremely important thermal parameter in the billet heating process. It has requirements for measurement accuracy and deviation, and must be measured accurately. The technical regulations have detailed provisions for the insertion height and insertion depth of thermocouples. Thermocouples for measuring temperature in annular heating furnaces are generally arranged on the inner and outer walls. The height exceeds the upper surface of the billet by 300-400mm. Insertion depth: The end of the protective porcelain tube protrudes 100-120mm from the furnace wall, ensuring that the thermocouple temperature measurement dipole protrudes 50-80mm from the furnace wall to enhance the sensitivity of the thermocouple to changes in the temperature field.

[0075] 4.2 Principles for setting process furnace temperature

[0076] According to the iron-carbon equilibrium state diagram, the appropriate billet heating temperature (initial forging temperature) is within a temperature range of 100-150℃ below the solidus line. It is a temperature range or a temperature zone. Comprehensively refer to the following factors: steel grade material (main factor), billet size (diameter, thickness, weight), feeding method, production efficiency (hourly output or production rhythm), forging and rolling equipment power (capacity), rolling pass (transfer time), final rolling temperature requirements, etc. The furnace temperature is higher than the billet surface temperature. As the billet is heated for a longer time, the difference between the billet surface temperature and the furnace temperature becomes smaller and smaller from the low temperature zone to the high temperature zone. Under normal circumstances, before the steel is discharged from the soaking section, the billet surface temperature is 20-50℃ lower than the furnace temperature on average. Only in some abnormal conditions, the surface temperature of the steel is very close to or even exceeds the furnace temperature. For alloy steel and high carbon steel, since alloy elements and carbon elements need a certain amount of time to diffuse and homogenize, and the thermal conductivity coefficient is low, when the cross-section temperature difference is large, the thermal stress is large, and internal cracks are easily generated, so the heating speed in the low temperature stage should be limited. On the other hand, it takes a long time to homogenize austenite in the high temperature zone. And the high temperature zone is prone to decarburization, etc. The heating speed in the low temperature zone is slow, and the diffusion and homogenization time in the high temperature zone is relatively long. Therefore, the characteristics of the heating process of alloy steel and high carbon steel are: the steel temperature out of the furnace is relatively low, and the heating time is relatively long. In addition, the forging and rolling deformation resistance of alloy steel and high carbon steel is relatively large, and the requirements for cross-section temperature difference are stricter (smaller temperature difference), and the requirements for burn-through are stronger. Therefore, the time spent in the high temperature zone should be relatively extended, and the surface of high carbon steel is prone to decarburization, so the steel temperature should not be too high. There should be restrictions on the atmosphere in the furnace, and the pressure of the soaking bed furnace should also be limited.

[0077] The heating time of high carbon steel and alloy steel is longer, 1.3-1.5 times that of ordinary steel of the same size, that is, the heating time should be extended by 30-50%. The heating temperature (furnace temperature) of high carbon steel and alloy steel is 30-50℃ lower than that of low carbon steel or ordinary steel.

[0078] In the key points of the heating process operation, the upper limit of the process temperature is determined under the condition of the fastest production rhythm and the fastest heating speed of the billet, that is, the shortest heating time. As the heating time extends, especially the residence time of the billet in the high-temperature area, this upper limit of the heating temperature should be adjusted downward accordingly. At the same time, the furnace pressure and the furnace atmosphere are also adjusted accordingly to reduce the oxidation, burning loss and decarburization of the billet, and reduce the risk of grain coarsening and subsequent overheating and overburning. That is to say, for different production rhythms (different in-furnace times), their temperature systems, heat supply systems and pressure systems are different, and the amplitude of fluctuations or adjustments is often large. The heat treatment furnace is often a relatively independent system with a relatively balanced and stable production rhythm, and the amplitude of fluctuations or adjustments of its process temperature (range) is much smaller. The biggest difference between the rolling heating furnace and the heat treatment furnace is that the rolling heating furnace is not only limited by the capacity of the main body equipment, but also mainly restricted by the equipment conditions of the rolling line (equipment capacity, equipment accuracy, equipment integrity) and the requirements of the quality of the rolled products (dimensions of each part, geometric tolerance, surface quality). Its production rhythm or the heating time of the billet in the furnace has great unpredictability. Therefore, the temperature process of the first-piece product for changing specifications should be accurately positioned; the temperature ranges for various rhythms during continuous production of the same specification should be accurately positioned, and some supplementary instructions should be given for the furnace temperature control of the last furnace at the end.

[0079] 4.3 Temperature control of each temperature control zone for the first furnace (i.e., the first piece) of empty furnace charging, principle and method for setting the furnace temperature target value, and corresponding relationship between the heating time of the first piece and various thermal parameters during the first furnace opening or changing specifications.

[0080] Taking the example of a full furnace of billets in the furnace, with the number of pieces being 220 - 225 and the specification being KKD - 65 (the billet is in the furnace and has not been discharged yet):

[0081] State 1: Heating time is 4.5 - 5.5 h (in-furnace time, starting from charging and ending at the discharge end of the furnace head)

[0082] Preheating process (conventional process): 700 - 1100 °C, target value set at 1000 - 1030 °C; Heating section 1 process (conventional process): 1150 - 1280 °C, target value set at 1250 - 1270 °C; Heating section 2 process (conventional process): 1240 - 1280 °C, target value set at 1250 - 1270 °C; Soaking process (conventional process): 1220 - 1260 °C, target value set at 1240 - 1255 °C. It is ready to tap steel at any time.

[0083] State 2: Heating time is 5.5 - 6.5 h (in-furnace time, from charging to the discharge end of the furnace head).

[0084] Preheating process (internal control process): 700 - 1050°C, target value set at 950 - 980°C; Heating stage 1 process (internal control process): 1150 - 1260°C, target value set at 1220 - 1240°C; Heating stage 2 process (internal control process): 1230 - 1270°C, target value set at 1240 - 1260°C; Soaking process: 1220 - 1260°C (conventional process), target value set at 1235 - 1255°C. Conditions for tapping at any time are available.

[0085] Heating time in state three: 6.5 - 7.5 h (time in the furnace, from charging to the discharge end of the furnace head).

[0086] Preheating process (internal control process): 700 - 1000°C, burners closed; Heating stage 1 process (internal control process): 1100 - 1240, target value set at 1200 - 1220°C; Heating stage 2 process (internal control process): 1180 - 1240°C, target value set at 1210 - 1230°C; Soaking process (internal control process): 1210 - 1250°C, target value set at 1235 - 1245°C. Conditions for tapping at any time are available.

[0087] Heating time in state four: 7.5 - 8.5 h (time in the furnace, from charging to the discharge end of the furnace head).

[0088] Preheating process (internal control process): 700 - 1000°C, burners closed, no setting (manual); Heating stage 1 process (internal control process): 1000 - 1200°C, target value set at 1100 - 1150°C; Heating stage 2 process (internal control process): 1100 - 1200, automatically set at 1150 - 1180°C; Soaking process (internal control process): 1200 - 1240, automatically set at 1200 - 1230°C.

[0089] Heating time in state five: >10 h (time in the furnace, from charging to the discharge end of the furnace head).

[0090] Preheating process (internal control process): <900°C, burners closed; Heating stage 1 process (internal control process): 1000 - 1150°C, burners closed; Heating stage 2 process (internal control process): 1050 - 1180°C, automatically set at 1130 - 1160°C; Soaking process (internal control process): 1150 - 1220°C, automatically set at 1180 - 1210°C.

[0091] Heating time in state six: >12 hours (time in the furnace, from charging to the discharge end of the furnace head).

[0092] Preheating process (internal control) < 900°C, close the burners; Heating stage 1 process (internal control) 900 - 1150°C, close the burners; Heating stage 2 process (internal control) 1000 - 1180°C, automatically set to 1130 - 1160°C; Soaking process (internal control) 1150 - 1220°C, automatically set to 1170 - 1200°C.

[0093] Summary: Affected by die replacement, the heating time is uncertain; Affected by the measurement, inspection, adjustment, etc. of the initial product size in the early stage of rolling, the heating time is uncertain; After rolling starts, as rolling progresses, the in-furnace residence time of the billets in the furnace gradually shortens (taking into account the thickness of the scale on the billet surface, rolling power, finishing temperature, etc.). At which time interval, the furnace temperature of each section is controlled according to the corresponding interval. Ensure not to "overheat" nor "underheat". Especially after the billets lose weight, the furnace temperature of each section needs to be more precisely controlled to minimize oxidation, burning loss, and decarburization. Overheating and overburning are not allowed.

[0094] 4.4 Continuous production (with full furnace billets and continuing the state of discharging and charging simultaneously), furnace temperature control in each temperature control zone, and the principle and method of setting the furnace temperature target value.

[0095] State 1 (maximum rhythm): KKD - 65 production rhythm is 45 - 50 pieces per hour, 8-hour shift production is 350 - 400 pieces, and the average in-furnace time is 4.5 - 5.0 hours.

[0096] Preheating section: Process furnace temperature 700 - 1100°C, set furnace temperature 1000 - 1050°C; Heating stage 1: Process furnace temperature 1150 - 1280°C, set furnace temperature 1250 - 1270°C; Heating stage 2: Process furnace temperature 1240 - 1280°C, set furnace temperature 1250 - 1270°C; Soaking section: Process furnace temperature 1220 - 1260°C, set furnace temperature 1245 - 1255°C.

[0097] Total gas volume (heat supply distributed towards the furnace tail): 4500 - 5000 m 3 / h; Total combustion air volume: 13500 - 15000 m 3 / h, on the premise of ensuring complete combustion, minimize the air excess coefficient. Total flue gas volume: 18000 - 20000 m 3 / h. Determine the air-fuel ratio accurately to ensure complete combustion of the gas, maximize gas efficiency, and minimize the total flue gas volume as much as possible. Coordinate the atmosphere control in each section (determine the air-fuel ratio accurately, make the high-temperature area at the furnace head neutral or slightly oxidizing, with an air-fuel ratio of 2.8 - 3.0. At the low-temperature area at the furnace tail, make it neutral or slightly reducing, with an air-fuel ratio of 2.3 - 2.6 to increase the flue gas temperature). Coordinate the furnace pressure: 0 to +2 Pa, adjust the flue damper within a large opening range of 80 - 100% to maintain the maximum or relatively large draft. Good airtightness is crucial. Trends in the three temperatures of the flue - pre - flue - gas temperature, post - flue - gas temperature, and hot - air temperature: During continuous production (hot steel out, cold steel in), the three temperatures are relatively low, but strive to keep them at a relatively high level. Due to the need for draft, the post - flue - gas temperature is 350 - 430 °C, and strive to approach 400 - 430 °C. Due to the need to increase the hot - air temperature, the air temperature is 380 - 460 °C, and strive to approach 430 - 460 °C - for rapid combustion, improve fuel efficiency, increase combustion temperature, increase flame temperature, rapid heating, and improve heat transfer efficiency. Therefore, it is very important to maintain good airtightness of the furnace body and the flue. The thickness of the scale on the surface of the discharged billet is 1.3 - 1.8 mm, and the burning loss is 1.0 - 1.5%. Since the heating time is short, the burning loss on the surface of the billet is small. At this time, for the first heating section, especially the second heating section, control it at the upper limit or even exceed the upper limit by 10 - 20 °C to raise the furnace temperature and increase the temperature difference. Rolling power: The penetrability of the steel is relatively poor, so the rolling power is relatively large; but for hot steel and hot dies, the dimensions are relatively large and stable. Finish rolling temperature: Medium limit or slightly lower than the medium limit, 930 - 980 °C; Thermal efficiency: Relatively high, 50 - 60% within the production capacity range. Energy consumption index per ton of steel: Relatively low, 1.3 - 1.6 GJ / t. Quality assurance: Safe and reliable.

[0098] State two (general rhythm): The production rhythm of KKD - 65 is 30 - 40 pieces per hour, the eight - hour shift output is 230 - 280 pieces, and the average time in the furnace is 6.5 - 7.0 hours.

[0099] Pre - heating section: Process furnace temperature 700 - 1100 °C, set furnace temperature 900 - 950 °C; First heating section: Process furnace temperature 1150 - 1280 °C, set furnace temperature 1210 - 1240 °C; Second heating section: Process furnace temperature 1240 - 1280 °C, set furnace temperature 1250 - 1270 °C; soaking section: Process furnace temperature 1220 - 1260 °C, set furnace temperature 1245 - 1255 °C.

[0100] Total gas volume: The gas volume at the furnace tail is appropriately reduced, and the heat supply gradually moves forward and is distributed to the high - temperature area at the furnace head, 3000 - 3500 m 3 / h; Total combustion air volume 9000 - 10500 m 3 / h; Total flue gas volume 12000 - 13500 m 3 / h. The atmosphere control for each section is coordinated (oxidizing at the furnace tail, neutral or weakly reducing at the furnace head); the furnace pressure is coordinated (+1 to +3 Pa, increasing by 1 to 2 Pa compared to the fastest rhythm); the changing trends of the three flue gas temperatures (appropriately reducing the heat supply at the tail, lowering the furnace temperature at the tail, thereby appropriately reducing the flue gas temperature and the combustion air temperature. The flue gas temperature after heat exchange is 350 - 430 °C; the hot air temperature is 380 - 450 °C) - Note: With this production rhythm, it is easy to have too high temperature control during the heating and preheating of the first section, and the three flue gas temperatures are prone to overshoot, so strict temperature control must be added. The opening of the flue damper (appropriately closing it by 40 - 70%). The thickness of the scale on the surface of the billet discharged from the furnace increases by 2.0 - 2.5 mm due to the extended residence time in the furnace. The rolling power is relatively small. The finish rolling temperature: With the increase in regenerative heat, it slightly increases to 950 - 1000 °C. The thermal efficiency: The rhythm slows down, and it decreases by 40 - 45%. The energy consumption index per ton of steel: It increases by 1.8 - 2.3 GJ / t.

[0101] Status three (lower rhythm): The production rhythm of KKD - 65 is < 20 pieces / hour, the output in an eight - hour shift is 150 - 200 pieces, and the average residence time in the furnace > 8.0 hours.

[0102] Preheating section: The process furnace temperature is 700 - 1100 °C, and the burners are turned off; Heating section one: The process furnace temperature is 1150 - 1280 °C, and the set furnace temperature is 1170 - 1200 °C; Heating section two: The process furnace temperature is 1240 - 1280 °C, and the set furnace temperature is 1230 - 1250 °C; soaking section: The process furnace temperature is 1220 - 1260 °C, and the set furnace temperature is 1230 - 1250 °C.

[0103] Total gas volume: The heat supply is further distributed to the furnace head to limit the furnace temperature at the tail, 1500 - 2500 m 3 / h. The total combustion air volume is 6000 - 8000 m 3 / / h. The air volume ratio is already on the high side. Compared with normal - flame burners and pulse burners, when the heat supply is small, the air distribution is excessive and it is not energy - saving. The total flue gas volume is 8000 - 11000 m 3 / h. The atmosphere control for each section is coordinated as follows: reducing or safety air in the high - temperature area at the furnace head, and obvious oxidizing in the low - temperature area at the furnace tail. The furnace pressure is coordinated (increasing the furnace pressure to +2 to +4 Pa). The changing trends of the three flue gas temperatures (limiting the furnace temperature in the low - temperature area and the three flue gas temperatures, the hot air temperature is 330 - 400 °C, the flue gas temperature after the heat exchanger is 350 - 430 °C, otherwise it is not energy - saving and there is a risk of overheating. The opening of the flue damper: reducing the opening of the flue damper by 25 - 50%). The thickness of the scale on the surface of the billet discharged from the furnace: When the residence time in the furnace exceeds 8 hours, the scale thickness increases somewhat, 2.5 - 3.0 mm. Rolling power: further reduced. Finish rolling temperature: 950 - 1000 °C. Thermal efficiency: further reduced, 30 - 40%. Energy consumption index per ton of steel: 2.5 - 3.5 GJ / t.

[0104] Status Four (Initial Stoppage Stage ≥ 60 minutes) - Implement the rolling stop and temperature reduction system.

[0105] Preheating section: Process temperature 700 - 1100 °C, burners are closed, furnace temperature < 850 °C; Heating section 1: Process temperature 1150 - 1280 °C (internal control 1100 - 1220 °C), furnace temperature is set < 1150 °C or burners are closed; Heating section 2: Process temperature 1240 - 1280 °C (internal control 1180 - 1230 °C), furnace temperature is set < 1200 °C; Soaking section: Process temperature 1220 - 1260 °C (internal control 1200 - 1250 °C), furnace temperature is set < 1240 °C;

[0106] Total gas volume: < 1500 m3 / h. Total combustion air volume: 5000 - 7000 m 3 / h or safety air volume. Total flue gas volume: 6000 - 9000 m 3 / h. Atmosphere control coordination for each section: In the high - temperature zone, a reducing atmosphere is presented or safety air volume is maintained; In the low - temperature zone, safety air is configured and an oxidizing atmosphere is presented. Furnace pressure coordination: +3 to +5 Pa. Trend of three flue gas temperatures: Flue gas temperature after heat exchange < 380 °C, hot air temperature < 400 °C. Otherwise, it is not energy - saving, and may cause over - heating, with quality risks. Damper opening: < 40%. Thickness of scale on the surface of the discharged billet: Relatively thick, > 3.0 mm. Rolling power is small. Final rolling temperature 900 - 980 °C. Thermal efficiency: < 30%, but > 20%. Energy consumption index per ton of steel: > 3.0 GJ / ton, but < 4.5 GJ / ton.

[0107] Status Five (Long - term Stoppage Stage ≥ 120 minutes)

[0108] Preheating section: Process temperature 700 - 1100 °C, burners are closed, furnace temperature < 800 °C; Heating section 1: Process temperature 1150 - 1280 °C (internal control 1000 - 1180 °C), furnace temperature is set < 1100 °C or burners are closed; Heating section 2: Process temperature 1240 - 1280 °C (internal control 1100 - 1180 °C), furnace temperature is set < 1150 °C or some burners are closed; Soaking section: Process temperature 1220 - 1260 °C (internal control 1150 - 1230 °C), furnace temperature is set < 1200 °C or some burners are closed;

[0109] Total gas volume: < 1000 m 3 / h. Total combustion air volume: 5000 - 7000 m 3 / h, safety air volume. Disadvantage of constant - flame burners: When not supplying heat, the air volume cannot be reduced to zero, and safety air volume is maintained. Total flue gas volume: 6000 - 8000 m 3 / h. Atmosphere control for each section: Safe air volume is required in both the high-temperature zone and the low-temperature zone. Furnace pressure coordination: +3 to +5 Pa. Trends of the three flue gas temperatures: Flue gas temperature after heat exchange < 350 °C, hot air temperature < 380 °C. Damper opening: < 30%. Thickness of the scale on the surface of the discharged billets: Relatively thick, > 3.5 mm. Rolling power is relatively small. Final rolling temperature after starting rolling: 900 - 980 °C. Thermal efficiency: < 30% but > 20%. Energy consumption index per ton of steel: > 3.0 GJ / ton, but < 4.5 GJ / ton.

[0110] State Six (After equipment failure is handled and ready for startup and in the initial stage of resuming production, description of thermal parameters)

[0111] Soaking section: Process temperature is 1220 - 1260 °C, and the minimum temperature control for rolling is 1220 - 1250 °C; The atmosphere in the soaking section is significantly reducing, the air volume remains unchanged at 800 - 1300 m3 / h, and the gas volume is adjusted to 400 m 3 / h. Before reaching 400 m 3 / h, the air volume is 1200 - 1400 m 3 / h without adjustment. When the gas volume is greater than 400 m 3 / h, the air-fuel ratio is configured according to 2.2 - 2.5. As the production efficiency increases, the air-fuel ratio gradually increases until it returns to normal. Heating section two: 1180 - 1230 °C, at different furnace temperature levels depending on the original furnace temperature before heating up, and be prepared to provide support for the soaking section. In principle, the air volume is 1500 - 1800 m 3 / h, the gas volume ≤ 700 m 3 / h, the air volume is not adjusted. When the gas volume > 700 m

[0112] State Seven (Same as State Three): Heating time is 7.5 - 8.5 h, and it gradually transitions to a slow rhythm state after startup.

[0113] State Eight (Same as State Two): Heating time is 6.5 - 7.0 h, and it gradually transitions from a slow rhythm to a medium rhythm state.

[0114] State Nine (Same as State One): Heating time is 5.0 - 5.5 h for full-line temperature increase, and it gradually transitions from a medium rhythm to the fastest rhythm state.

[0115] 4.5 Temperature control of each temperature control zone for the last furnace (the tail piece, that is, before no more charging and emptying the furnace), principle and method for setting the furnace temperature target value.

[0116] When producing the last heat of steel, the last part of the billets is required to keep the furnace temperature for a certain period of time. That is, when the last piece runs to the hot section of Heating Zone 1, the preheating section does not cool down temporarily and maintains the middle limit. When the last piece runs to the hot section of Heating Zone 2, the hot section of Heating Zone 1 does not cool down temporarily and maintains the middle limit, and the preheating section can cool down. When the last piece runs to the soaking section, the hot section of Heating Zone 2 does not cool down temporarily and maintains the middle limit, and the hot section of Heating Zone 1 and the preheating section cool down. Before the last piece is taken out of the furnace, the furnace temperatures of the hot section of Heating Zone 2 and the soaking section are required to be within the process temperature range. The furnace temperatures of the hot section of Heating Zone 2 and the soaking section are adjusted only after the last piece is taken out of the furnace. At the same time, after the last piece enters the hot section of Heating Zone 2, the furnace pressure should be appropriately maintained. The billets of the last piece still need to be further heated in the temperature control area of the subsequent empty charge, rather than reducing the furnace temperature of the temperature control area of the subsequent empty charge below the surface temperature of the last billet. Otherwise, the furnace wall of the temperature control area of the subsequent empty charge will not heat or supplement heat to the last billet, but will absorb the radiant heat of the billets of the last piece, reducing the surface temperature of the billets of the last piece and making the steel temperature of the last piece unable to meet the requirements of wheel rolling, which may lead to surface quality problems such as non-conforming rolling dimensions and depressions.

[0117] 5. Measurement and Control of Furnace Pressure

[0118] Furnace pressure is an important thermal parameter of a flame furnace. Especially for the high-temperature heating furnace before steel billet forging and rolling, this important thermal parameter of furnace pressure must be accurately measured and correctly controlled. The so-called furnace pressure control is the control of the inner surface pressure of the furnace at the height of the bottom surface of the soaking bed before the steel billet is taken out of the furnace, that is, at the threshold of the discharging furnace door. It is the difference between the absolute pressure at the height of the bottom plane of the soaking section in the furnace and the atmospheric pressure at the same height outside.

[0119] Under production conditions (when the furnace temperature, the flue gas temperatures before and after the heat exchanger, and the hot air temperature are similar), taking the furnace temperature of 1200 - 1280; the flue gas temperature before the heat exchanger of 600 - 700 °C; the flue gas temperature after the heat exchanger of 300 - 450 °C; and the hot air temperature of 330 - 480 °C as an example, the relationship between the furnace pressure, the amount of combustion products generated, and the opening of the flue gas damper is shown in Table 1.

[0120] Table 1 Relationship between Furnace Pressure, Amount of Combustion Products Generated, and Opening of Flue Gas Damper

[0121]

[0122] It can be seen from the above table that with different production rhythms, the heating load or the amount of combustion products of the furnace varies greatly. For example, when the flue gas damper is in the fully open state, that is, the opening is 100%, then at full load, the furnace pressure at the discharging door threshold is -1 to +1 Pa; at minimum load, the furnace pressure at the discharging door threshold is -14 to -16 Pa. If there is no furnace pressure measurement and control system and only relying on experience, it is impossible to accurately control the furnace pressure at the discharging door threshold in the slightly positive pressure (+1 to +3 Pa) state under different production rhythms.

[0123] 5.1 Setting Rules for Furnace Pressure Target Value

[0124] 5.1.1 During normal production, the furnace pressure target value is set to -2 to -4 Pa. Since the smoke exhaust port is on the furnace top near the charging door, the entire charging door is in a relatively large negative pressure state. When the charging door is opened, a large amount of cold air is sucked in from the charging door, increasing the amount of flue gas entering the flue and simultaneously reducing the flue gas temperature. The furnace pressure at the discharge door sill immediately rises by 5 to 7 Pa. When the furnace pressure target value is set to -2 to -4 Pa, the actual pressure at the discharge door sill is in a slightly positive pressure state of +1 to +3 Pa.

[0125] 5.1.2 Program setting: Once the charging door has been closed for 5 minutes, the furnace pressure set value automatically increases by 5 to 7 Pa, that is, it automatically compensates from the original -2 to -4 Pa to the +1 to +3 Pa state.

[0126] 5.1.3 During the slow-paced or rolling-stop waiting stage, the furnace pressure target value is appropriately set to -1 to +1 Pa. After automatic compensation, when the charging and discharging furnace doors are closed, the actual furnace pressure at the discharge door sill is in the +5 to +7 Pa state.

[0127] 6. Measurement and Control of Three Temperatures in the Flue

[0128] Through long-term summary of production practices, it is found that the levels of three related temperatures in the flue (including the flue gas temperature before the internal heat exchanger, the flue gas temperature after the heat exchanger, and the air preheating temperature), especially the level of the flue gas temperature after the heat exchanger, can often reflect or feedback some important information. There is a close relationship with factors such as whether the furnace draft is sufficient, whether the air-fuel ratio configuration of the furnace is reasonable, whether the furnace airtightness is tight, and whether the furnace temperature setting matches the production rhythm.

[0129] If the three temperatures are low, especially if the flue gas temperature after the heat exchanger is lower than 280 - 300 °C, or even ≤ 250 °C, the following issues worthy of attention may exist: poor furnace airtightness, large openings at the negative pressure positions, such as a large amount of cold air being sucked in when the charging furnace door is opened; insufficient flue draft, excessive furnace pressure, and the flue gas being unable to enter the flue completely; serious over-surplus of the combustion-supporting air ratio, a large amount of combustion products, and low flue gas temperature; low furnace temperature setting value in the low-temperature area, insufficient heat supply, etc. This situation mostly occurs under the full-load and fast-paced state, with a large heat supply load, a large amount of heat being carried away by the hot steel discharged from the furnace, a large amount of heat being absorbed by the cold steel entering the furnace, an unstable furnace condition, and the furnace operating at an overloaded state.

[0130] The third temperature is too high, especially the flue gas temperature after the heat exchanger is higher than 450-480℃, or even ≥500℃. There may be the following problems worthy of attention: there is no steel at the tail of the furnace, and the furnace temperature in the low temperature zone is set too high, there is no cold steel to absorb heat, and a large amount of heat energy enters the flue; the suction force is sufficient, the smoke gate opening is large, the furnace pressure is in a large negative pressure state, and more heat enters the flue; there is too much residual gas in the flue gas, which enters the flue for secondary combustion; the heat exchange efficiency of the air heat exchanger is low, and the air preheating effect is poor, etc. This situation mostly occurs when there is no steel at the tail of the furnace or the rolling is stopped for a long time, the low temperature zone is not cooled in time, the furnace pressure is negative pressure or the furnace pressure is too low. If the above two situations occur in production, the reasons must be found out and remedial measures must be taken actively to make the flue temperature run in a reasonable temperature range to achieve the best state of heating quality, equipment protection, energy saving and consumption reduction.

[0131] 7. Draw the key thermal parameters operation trend record curve

[0132] Through statistical analysis of the operating trend record curves of important key thermal parameters, timely discover and track equipment degradation trends, perform timely maintenance or overhaul, ensure equipment accuracy, and keep the equipment in a good, stable and smooth state. Pay attention to the three-temperature operating level of the flue; pay attention to the furnace pressure curve; the smoke gate opening adjustment curve; pay attention to the synchronization of the gas flow and combustion-supporting air flow of each branch section, and the volatility or jump of the ratio (air-fuel ratio). Regularly check the air tightness of the furnace and the balance value of the furnace pressure, especially during the furnace start-up stage after major or medium equipment repairs. Test the maximum and minimum values ​​of the furnace pressure, accurately adjust the air-fuel ratio, pay attention to the safe air volume, etc. Regularly check whether the thermal parameter settings are reasonable under automatic control, etc.

[0133] In other aspects, such as important economic and technical indicators such as product qualification rate, production efficiency, furnace operation thermal efficiency, furnace unit consumption, etc., statistical analysis is carried out regularly to achieve continuous improvement.

[0134] The beneficial effects of the present invention are as follows:

[0135] The furnace temperature control rules were formulated, the furnace temperature target values ​​were set in three modes, rigorous operating instructions were compiled, and standardized operations were adopted. The furnace temperature target value still needs to be set manually by the heating workers' subjective judgment. The company strengthened the theoretical and practical skills training for heating workers, guided heating workers to master the principles or rules of furnace temperature setting, and reduced the probability of misjudgment.

[0136] The air-fuel ratio and safety air configuration rules for each temperature control zone have been formulated, and the air-fuel ratio has been incorporated into the automatic control program. The heating worker only needs to fine-tune the air-fuel ratio correction coefficient of each temperature control zone according to the changes in production rhythm. After the automatic control is realized, human errors are greatly reduced.

[0137] The furnace pressure measurement point is selected on the inner ring furnace wall in the area of the charging furnace door in the soaking zone, at a position 200 - 250 mm above the furnace bottom. This point is the closest to the charging furnace door sill and is the best point that can most truly reflect the furnace pressure level at the furnace bottom height in the area of the charging furnace door. The furnace pressure parameter has been incorporated into the automatic control program and has an automatic compensation function.

[0138] Pay sufficient attention to the three temperatures in the flue. The three flue temperatures can feedback whether the furnace temperature setting, air-fuel ratio setting, and furnace pressure setting in the low-temperature zone are appropriate, whether the furnace airtightness is good, whether the furnace is operating smoothly, and whether the energy-saving, consumption-reducing, and emission-reduction goals are achieved.

[0139] Query and trace the operation trend record curves of important key thermal parameters. Furnace temperature curve tracing, furnace pressure curve, damper opening curve, three flue temperature curves, air-fuel ratio curve, etc.

[0140] Using the above methods for measuring and controlling the thermal parameters of the reheating furnace to heat the wheel steel billets, the qualified rate data of the wheel steel billets rolling reaches over 99%, as shown in Table 2:

[0141] Table 2 Rolling Qualified Rate

[0142]

[0143] The efficiency of the steel billet heating has also been greatly improved, and the efficiency reaches about 90%. The specific data is as follows:

[0144] From 8:00 to 16:00 on May 6, 2022, the shift output of HESA-65-1 was 402 pieces, and the gas consumption was 24,600 m 3 ; The theoretical efficiency was 56.25 pieces per hour, the actual efficiency was 50.25 pieces per hour, and the efficiency utilization was 89.3%. From 16:00 to 24:00 on May 6, 2022, the shift output of HESA-65-1 was 402 pieces, and the gas consumption was 24,000 m 3 ; The theoretical efficiency was 56.25 pieces per hour, the actual efficiency was 50.25 pieces per hour, and the efficiency utilization was 89.3%. From 16:00 to 24:00 on May 8, 2022, the shift output of HESA-65-1 was 420 pieces, and the gas consumption was 24,440 m 3 ; The theoretical efficiency was 56.25 pieces per hour, the actual efficiency was 52.5 pieces per hour, and the efficiency utilization was 93.3%.

[0145] The specific consumption per ton of steel decreased, and the thermal efficiency of the reheating furnace was improved. The specific data is as follows: The shift output of HESA-65-1 was 402 pieces, the feeding weight was 413 kg, and the gas consumption was 24,600 m 3 , with a specific consumption of 1.425 GJ / ton; The shift output was 420 pieces, and the gas consumption was 24,440 m 3 , with a specific consumption of 1.355 GJ / ton.

[0146] The specific energy consumption is 1.425 GJ / ton, corresponding to a thermal efficiency of 60% for the heating furnace; the specific energy consumption is 1.355 GJ / ton, corresponding to a thermal efficiency of 63% for the heating furnace.

[0147] As described above, this is only to illustrate some principles of the present invention. This specification is not intended to limit the present invention to the specific structures and applicable scopes shown and described. Therefore, all possible corresponding modifications and equivalents that can be utilized belong to the scope of the patent applied for by the present invention.

Claims

1. A method for measuring and controlling the thermal parameters of a ring heating furnace for wheel steel billets, characterized in that, Including the measurement and control of the following thermal parameters: 1) Measurement and control of gas pressure and flow rate; 2) Measurement and control of combustion air pressure, flow rate and temperature; 3) Measurement and control of air-fuel ratio; 4) Measurement and control of furnace temperature; 5) Measurement and control of furnace pressure; 6) Measurement and control of flue gas temperature before the heat exchanger, flue gas temperature after the heat exchanger and air preheating temperature in the flue; In the step 2), the combustion air main pipe is connected to the burners in the preheating section, the first heating section, the second heating section and the soaking section of the heating furnace through four combustion air branch pipes, and the combustion air main pipe is connected to the air heat exchanger and the combustion air blower; combustion air flow orifice plates for measuring the combustion air flow are arranged on the combustion air main pipe and the four combustion air branch pipes; the total air volume of the combustion air blower is 21793 m 3 / h, the total pressure is 11847 Pa, the motor power is 132 kw, and the rated speed is 1450 rpm; the combustion air blower realizes frequency conversion control, and the frequency of the combustion air blower is in the range of 0 - 50 Hz; during production, the frequency operation range of the combustion air blower is 30 - 40 Hz; the target value setting range of the combustion air main pipe wind pressure is 4.5 - 6.5 kPa, and the combustion air flow operation range is 6000 - 18000 m 3 / h; the combustion air flows of the four combustion air branch pipes are respectively: 700 - 2500 m 3 / h, 2300 - 7000 m 3 / h, 1700 - 5500 m 3 / h, 1300 - 3000 m 3 / h; the combustion air flow velocities of the combustion air main pipe and the four combustion air branch pipes are all in the range of 8 - 12 m / s; the combustion air medium pressure before the burners of each combustion air branch pipe is 2.0 - 4.0 kPa; The maximum flue gas volume of the air heat exchanger is 24,800 m 3 / h, the flue gas temperature before the air heat exchanger ≤ 850 °C, the maximum combustion-supporting air volume is 18,000 m 3 / h, the hot air temperature ≤ 500 °C, the air side resistance < 2,500 Pa; the flue gas side resistance < 200 Pa; the cold air pressure is set at 5.0 - 6.0 kPa, and the combustion-supporting air blower realizes automatic adjustment of the combustion-supporting air main pipe air pressure, with the fluctuation value less than ±0.1 kPa; In the step 6), in the normal production state, the flue gas temperature before the heat exchanger is maintained at 500 - 750 °C; the flue gas temperature after the heat exchanger is maintained at 320 - 450 °C. Temperatures lower than 250 - 300 °C or higher than 480 - 500 °C are abnormal states; the air preheating temperature is maintained at 350 - 480 °C.

2. The method for measuring and controlling the thermal parameters of a ring heating furnace for wheel steel billets according to claim 1, characterized in that: In the step 1), the pressure of the external mixed coal gas medium is 10.0 - 12.0 kPa, the pressure after the pressure regulating valve of the main heating furnace pipe is 6.0 - 9.0 kPa, and the flow rate of the main mixed coal gas pipe is 0 - 6800 m 3 / h.

3. The method for measuring and controlling the thermal parameters of a ring heating furnace for wheel steel billets according to claim 2, characterized in that: The mixed coal gas main pipe is connected to the burners in the preheating section, heating section 1, heating section 2 and soaking section of the heating furnace through four coal gas branch pipes respectively. Coal gas flow orifice plates for measuring coal gas flow are arranged on both the mixed coal gas main pipe and the four coal gas branch pipes; The mixed gas flow rates of the four gas branch pipes are respectively: 0 - 800 m 3 / h, 0 - 2500 m 3 / h, 0 - 2000 m 3 / h and 0 - 1500 m 3 / h; The mixed gas flow velocities of the mixed gas main pipe and the four gas branch pipes are both 8 - 12 m / s; The mixed gas medium pressure before the burners of each gas branch pipe is 3.0 - 5.0 kPa.

4. The method for measuring and controlling the thermal parameters of a ring heating furnace for wheel steel billets according to claim 1, characterized in that: In the step 3), The combustion system of the wheel steel billet heating furnace adopts a branch section proportional combustion temperature control mode, and its air-fuel ratio adjustment and control method is as follows: (a) Preheating section: The flow rate of the mixed gas is 0 - 800 m 3 / h, and the corresponding combustion-supporting air flow rate is 700 - 2500 m 3 / h, where 700 m 3 / h is the safety air volume; Among them, when the flow rate of the mixed gas is 0 - 300 m 3 / h, the flow rate of the combustion-supporting air is 700 ± 50 m 3 / h and it is the safe air volume; when the flow rate of the mixed gas is 300 - 800 m 3 / h, the air-fuel ratio is configured according to 2.3 - 3.0, that is, the flow rate of the combustion-supporting air is 700 - 2500 m 3 / h; (b) Heating stage: Mixed gas flow rate is 0 - 2500 m 3 / h, and the corresponding combustion-supporting air flow rate is 2300 - 7000 m 3 / h, where 2300 m 3 / h is the safety air volume; Among them, when the flow rate of the mixed gas is 0 - 800 m 3 / h, the combustion-supporting air flow rate is 2300 ± 100 m 3 / h and it is the safe air volume; when the flow rate of the mixed gas is 800 - 2500 m 3 / h, the air-fuel ratio is configured according to 2.5 - 2.8, that is, the combustion-supporting air flow rate is 2300 - 7000 m 3 / h; (c) Second heating stage: the flow rate of the mixed gas is 0 - 2000 m 3 / h, and the corresponding combustion-supporting air flow rate is 1700 - 5500 m 3 / h, where 1700 m 3 / h is the safety air volume; Among them, when the flow rate of the mixed gas is 0 - 700 m 3 / h, the combustion-supporting air flow rate is 1700 ± 100 m 3 / h and it is the safe air volume; when the flow rate of the mixed gas is 700 - 2000 m 3 / h, the air-fuel ratio is configured according to 2.5 - 2.7, that is, the combustion-supporting air flow rate is 1700 - 5500 m 3 / h; (d) soaking zone: the flow rate of the mixed gas is 0 - 1500 m 3 / h, and the flow rate of the combustion-supporting air is 1300 - 3000 m 3 / h, among which 1300 m 3 / h is the safety air volume; Among them, when the flow rate of the mixed gas is 0 - 400 m 3 / h, the flow rate of the combustion-supporting air is 1300 ± 50 m 3 / h and it is the safe air volume; when the flow rate of the mixed gas is 400 - 1500 m 3 / h, the air-fuel ratio is configured according to 2.2 - 2.6, that is, the flow rate of the combustion-supporting air is 1300 - 3000 m 3 / h; When the mixed coal gas flow rate in each branch section of the heating furnace is less than a certain value, the combustion air is configured according to the safe air volume, and will no longer decrease with the reduction of the coal gas consumption, and the safe air volume remains unchanged.

5. The method for measuring and controlling the thermal parameters of a ring heating furnace for wheel steel billets according to claim 1, characterized in that: In the step 4), The heating furnace includes a low-temperature zone and a high-temperature zone. The low-temperature zone includes the preheating section and heating section 1. One set or multiple sets of thermocouples are arranged on the upper layer of each temperature control zone in the low-temperature area; the high-temperature zone includes heating section 2 and soaking section. The temperature measurement points in the high-temperature area cover the inner and outer walls of the heating furnace, and multiple sets of thermocouples are arranged along the circumferential direction of the furnace wall and are arranged in upper and lower layers; The whole furnace burners are divided into two types: straight-flame burners and flat-flame burners. The straight-flame burners are arranged on the inner and outer side walls of the heating furnace, with a power of 400 kw and a flow rate of 150 m 3 / h; The flat-flame burners are arranged on the center line of the furnace top discharge door, with a power of 267 kw and a flow rate of 100 m 3 / h; The heating furnace adopts a branch section constant flame proportional combustion control mode, including the "empty furnace charging, i.e., the first piece" mode, the "continuous production" mode and the "production end, finishing furnace" mode.

6. The method for measuring and controlling the thermal parameters of a ring heating furnace for wheel steel billets according to claim 1, characterized in that: In the step 5), In the measurement and control of the furnace pressure, one pressure tapping point is selected, which is the position on the inner ring furnace wall opposite to the discharge door area in the soaking section of the heating furnace and at a height of 200 - 250 mm above the furnace bottom; During normal production, the target value of the furnace pressure is set to -2 - -4 Pa; 5 minutes after the charging door is closed, the set value of the furnace pressure automatically increases by 5 - 7 Pa and then compensates to the state of +1 - +3 Pa; during slow rhythm or rolling stop and waiting for rolling stages, the target value of the furnace pressure is set to -1 - +1 Pa.

7. The method for measuring and controlling the thermal parameters of the annular reheating furnace for wheel billets according to claim 1, wherein: The method for measuring and controlling the thermal parameters of the ring heating furnace also includes drawing the operation trend record curve of key thermal parameters, tracking and tracing the operation process of thermal parameters, regularly conducting statistical analysis, and taking timely measures for the discovered equipment problems and operation problems, so that the equipment and facilities are always in a stable and smooth state, and the operation adjustment is always in a standardized and controllable state.

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