Electric furnace air mixing energy-saving control method and system

Abstract

The invention relates to an electric furnace air mixing energy-saving control method and system, and belongs to the field of flue gas waste heat recovery. According to the scheme, the real-time operation parameters of the electric furnace flue gas system are collected through the control module, the flue gas loss, the chemical incomplete combustion loss and the gas incomplete combustion loss after the flue gas amount changes are determined through the water-cooling sliding sleeve air mixing model, the optimal excess air coefficient is selected, and the waste heat utilization efficiency of the boiler is improved. In addition, the pipe network resistance value of the pipe network system is calculated according to the smoke parameters after combustion, a proper working point is found through the fan characteristic curve value stored in the controller, the optimal rotating speed of the fan is ensured, and energy saving of the dust removal system is achieved. The system comprises a sensor module, a data acquisition module, a control system and a dust removal fan, parameters in a calculation model can be adjusted in real time to adapt to changes of electric furnace smelting working conditions, the accuracy of the optimal excess air coefficient is ensured, and therefore the heat efficiency of an electric furnace waste heat boiler system is improved, and energy consumption and pollution emission are reduced.

Description

Technical Field

[0001] The present invention belongs to the field of flue gas waste heat recovery, and relates to a method and system for energy-saving control of air mixing in an electric furnace. Background Art

[0002] During the process of electric furnace smelting, the composition of the flue gas changes with different stages. The sensible heat contained in these flue gases and the latent heat of components such as CO are the key factors determining the way of recovering the waste heat of the electric furnace flue gas. The combustion process of the furnace gas in the electric furnace is actually a violent chemical reaction of CO and a small amount of H2 in the furnace gas with oxygen and nitrogen in the air at high temperature, releasing a large amount of heat.

[0003] To ensure complete combustion of the furnace gas, not only high temperature conditions need to be maintained, but also sufficient oxygen needs to be provided and the fuel and oxygen need to be fully mixed. During the operation of the waste heat boiler of the electric furnace, the combustion efficiency of air mixing in the furnace gas has a significant impact on the thermal efficiency of the boiler. If the air mixing is insufficient, the combustible gas in the furnace gas will not be completely burned, which will not only cause energy waste but also environmental pollution. On the contrary, if the air mixing is excessive, it will reduce the temperature of the flue gas, reduce the radiant heat transfer amount, cause the exhaust gas temperature to rise, thereby increasing the exhaust gas heat loss, reducing the boiler efficiency, and increasing the power consumption of the induced draft fan.

[0004] In the field of energy-saving control of air mixing in electric furnace flue gas, the existing technologies mainly rely on experience to determine the air mixing volume, and this method has certain limitations in practical applications. Specifically, the traditional air mixing control system usually adjusts the opening degree of the water-cooled sliding sleeve to a fixed position during commissioning to ensure that the combustible gas in the flue gas can be completely burned out. However, since the smelting conditions of the electric furnace are constantly changing, simply relying on empirical judgment to determine the air mixing volume is often not accurate enough, resulting in a reduction in thermal efficiency and energy waste.

[0005] In addition, the existing technologies fail to effectively combine the flue gas parameters and the operating status of the fan, thus unable to achieve the optimal control of the electric furnace flue gas system. In terms of waste heat recovery of flue gas, although the existing technical methods can recover the sensible heat and latent heat in the flue gas to a certain extent, due to the low combustion efficiency of air mixing, the thermal efficiency of the boiler is limited. At the same time, the existing technologies also have problems such as exhaust gas heat loss, chemical incomplete combustion loss, and gas incomplete combustion loss, which further reduce the energy utilization efficiency. Summary of the Invention

[0006] In view of this, the present invention provides an electric furnace mixed air energy-saving control method and system. The method detects the composition and temperature of the electric furnace flue gas in real time, uses a calculation model to determine the optimal excess air coefficient, and couples the coefficient with the operating curve of the dust removal fan to determine the optimal dust removal fan operating frequency. By dynamically adjusting the operating frequency of the dust removal fan, the present invention can ensure that the electric furnace flue gas system can maintain the optimal operating state under different working conditions, thereby achieving the purpose of energy saving and emission reduction.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] An electric furnace mixed air energy-saving control method comprises the following steps:

[0009] S1. Real-time detection of the composition and temperature of the flue gas of the electric furnace, wherein the flue gas composition includes the concentration of CO, CO2, SO2 and O2, and the flue gas temperature includes the flue gas discharge temperature and the cold air temperature;

[0010] S2. Based on the detected smoke composition and temperature, determine the optimal excess air coefficient α through a calculation model, wherein the optimal excess air coefficient α is the α value corresponding to the minimum sum of the exhaust heat loss q2, the chemical incomplete combustion loss q3 and the gas incomplete combustion loss q4;

[0011] S3, coupling the optimal excess air coefficient α with the operation curve of the dust removal fan to determine the optimal operating frequency of the dust removal fan;

[0012] S4. Adjust the operating state of the dust removal fan in real time according to the optimal operating frequency to optimize the mixed air volume control.

[0013] Optionally, the relationship between the exhaust heat loss q2 and the excess air coefficient α is:

[0014] q2=(0.5+3.5α)(t py -t k )

[0015] where t py is the exhaust gas temperature, t k The temperature of cold air.

[0016] Optionally, the relationship between the chemical incomplete combustion loss q3 and the excess air coefficient α is:

[0017] q3=3.2αCO%, where

[0018] Where β is the fuel characteristic coefficient and RO2 is the CO2 content in the flue gas.

[0019] Optionally, the relationship between the gas incomplete combustion loss q4 and the excess air coefficient α is:

[0020]

[0021] where CO is the volume concentration of carbon monoxide in the flue gas.

[0022] Optionally, in step S3, by matching the resistance characteristic curve of the pipe network and the characteristic curve of the fan, the optimal operating frequency of the dedusting fan is determined, which specifically includes:

[0023] Calculating the flue gas volume after air mixing according to the optimal excess air coefficient α;

[0024] Combining the resistance model of the waste heat boiler and the pipe network system to calculate the pipe network resistance value;

[0025] Determining the optimal operating frequency of the dedusting fan according to the pipe network resistance value and the fan characteristic curve.

[0026] Optionally, in step S4, the operating frequency of the dedusting fan is adjusted in real time by a PID controller to ensure the accuracy of the mixed air volume control.

[0027] Optionally, in step S2, the fuel characteristic coefficient β is dynamically adjusted according to the changes in the electric furnace smelting conditions.

[0028] Optionally, in step S1, the detection of the flue gas composition and temperature is realized by a gas composition analyzer and a temperature sensor, and the gas composition analyzer and the temperature sensor are respectively arranged at the electric furnace flue and the cold air inlet.

[0029] An electric furnace air mixing regulation and optimization control system, comprising:

[0030] A sensor module for real-time detection of the composition and temperature of the electric furnace flue gas, the composition including the concentrations of CO, CO2, SO2 and O2, and the temperature including the flue gas discharge temperature and the cold air temperature;

[0031] A data acquisition module for receiving and transmitting the detection data of the sensor module;

[0032] A control system, including a calculation module, the calculation module is used to determine the optimal excess air coefficient α according to the detection data through the calculation models of the exhaust heat loss q2, the chemical incomplete combustion loss q3 and the gas incomplete combustion loss q4, and generate an optimal operating frequency instruction based on the α value and the operating curve of the dedusting fan;

[0033] A dedusting fan for adjusting the operating state according to the optimal operating frequency instruction to realize the optimization control of the mixed air volume.

[0034] Optionally, the control system further includes a storage module that pre-stores the pipeline resistance characteristic curve and the fan characteristic curve for dynamically matching the changes in operating conditions.

[0035] Optionally, the control system can update the parameters in the calculation model and recalculate the optimal excess air coefficient α according to the real-time changes in the electric furnace smelting conditions.

[0036] Optionally, the sensor module includes a gas composition analyzer and a temperature sensor, which are respectively arranged at the electric furnace flue and the cold air inlet and are connected to the control system through a data acquisition module.

[0037] Optionally, the dust removal fan is a variable frequency speed regulation fan, and its operating frequency is adjusted in real time through a PID controller. The PID controller is connected to the control system, receives the optimal operating frequency instruction, and executes the adjustment.

[0038] Optionally, the control system is connected to the water-cooled sliding sleeve in the electric furnace flue for adjusting the opening of the water-cooled sliding sleeve in real time according to the optimal excess air coefficient α to control the mixed air volume.

[0039] Optionally, the data acquisition module is connected to the sensor module and the control system through wired or wireless communication methods to ensure the real-time and reliable data transmission.

[0040] Optionally, the control system further includes a display module for displaying the flue gas composition, temperature, optimal excess air coefficient α, and the operating frequency of the dust removal fan in real time.

[0041] The beneficial effects of the present invention are as follows:

[0042] Improve the waste heat recovery efficiency: By detecting the composition and temperature of the electric furnace flue gas in real time and using the calculation model to determine the optimal excess air coefficient, the present invention can optimize the mixed air combustion process, thereby improving the waste heat recovery efficiency. This helps to make full use of the sensible heat and latent heat in the flue gas and improve the energy utilization efficiency.

[0043] Reduce the power consumption of the dust removal system: The present invention dynamically adjusts the operating frequency of the dust removal fan to ensure that the fan operates in the optimal working state. This helps to reduce the power consumption of the dust removal system and thus reduce the operating cost.

[0044] Reduce environmental pollution: By optimizing the mixed air combustion process, the present invention can reduce the emissions of harmful substances in the flue gas, such as CO, SO2, etc. This helps to reduce environmental pollution and improve the environmental quality.

[0045] Improving system stability: The present invention can adjust the parameters in the calculation model in real time according to the changes in the electric furnace smelting conditions, ensuring the accuracy of the optimal excess air coefficient. This helps to improve the stability of the system and ensure that the electric furnace flue gas system can maintain the best operating state under different conditions.

[0046] Economic and environmental benefits: The present invention has important economic and environmental benefits by improving the waste heat recovery efficiency, reducing the power consumption of the dust removal system, and reducing environmental pollution. This helps to improve the competitiveness of enterprises and promote sustainable development.

[0047] Other advantages, objectives, and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the following specification. Brief Description of the Drawings

[0048] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in detail preferably with reference to the accompanying drawings, where:

[0049] Figure 1 is the flowchart of the control method according to the embodiment of the present invention;

[0050] Figure 2 is the flowchart of the electric furnace flue gas system of the present invention.

[0051] Reference numerals: electric furnace 1, water-cooled sliding sleeve 2, elbow flue 3, combustion settling chamber 4, tail flue 5, waste heat boiler 6, bag filter 7, fan 8, chimney 9. Detailed Embodiments

[0052] The following illustrates the embodiments of the present invention through specific specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the drawings provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0053] Among them, the drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and should not be construed as a limitation to the present invention; for better illustrating the embodiments of the present invention, some components in the drawings will be omitted, enlarged, or reduced, and do not represent the dimensions of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0054] In the drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the drawings. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0055] Please refer to Figures 1 to 2 , a wet dedusting system for a converter includes an electric furnace 1, a water-cooled sliding sleeve 2, an elbow flue 3, a combustion settling chamber 4, a tail flue 5, a waste heat boiler 6, a bag filter 7, a fan 8, and a chimney 9 that are sequentially connected. In a typical electric furnace system, the composition and temperature of the electric furnace flue gas are detected in real time by sensors installed in the flue. For example, the concentrations of CO, CO2, N2, and O2 in the flue gas, as well as the waste heat boiler flue gas discharge temperature and the cold air temperature, are detected. These data are transmitted to the control system through a data acquisition system for processing.

[0056] Based on the data detected in real time, the control system calculates the excess air coefficient α under the current working conditions using the following empirical formula:

[0057] (1) Relationship between heat loss due to exhaust gas q2 and excess air coefficient α:

[0058] q2 = (0.5 + 3.5α)(t py -t k )

[0059] In the formula: t py — Exhaust air temperature, °C;

[0060] t k — Cold air temperature, °C.

[0061] (2) Relationship between heat loss due to incomplete combustion q3 and excess air coefficient α:

[0062] q3 = 3.2αCO%

[0063] Where

[0064] In the formula: β — Fuel characteristic coefficient, related to the type of fuel;

[0065] RO2 — Content of CO2 in the flue gas;

[0066] (3) Relationship between the incomplete combustion loss q4 of gas and the excess air coefficient α:

[0067]

[0068] It can be seen from equations (1), (2) and (3) the relationship between α and the inverse balance thermal efficiency η. Since the sum of q2 + q3 + q4 accounts for about 80% of the total heat loss, it can be considered that: when q2 + q3 + q4 is the smallest, it is the optimal excess air coefficient α during the operation of the boiler zj . The control system gives the optimal excess air coefficient α through the calculation model zj , and adjusts the opening of the water-cooled sliding sleeve in real time to ensure that the ideal air volume L0 is mixed into the flue gas system.

[0069] According to the mixing combustion model of electric furnace flue gas, parameters such as the flue gas temperature and flue gas volume after mixing are calculated.

[0070] Volume of each product in the flue gas

[0071] V CO2 = 0.01(CO2 + αCO)

[0072] V CO = 0.01(1 - α)CO

[0073]

[0074] In the formula, CO, CO2, N2—the share of each component gas in the furnace gas, %;

[0075] V CO2 —Volume of carbon dioxide in the flue gas, m 3 / m 3 ;

[0076] V CO —Volume of carbon monoxide in the flue gas, m 3 / m 3 ;

[0077] V N2 —Volume of nitrogen in the flue gas, m 3 / m 3 ;

[0078] —Volume of water vapor in the flue gas, m 3 / m 3 ;

[0079] g—Moisture content of air, g / m 3 ; At 30°C, g = 33.6 g / m 3 ;

[0080] Total volume of flue gas and volume percentage of each product

[0081]

[0082] wherein, V y — generated flue gas volume, m 3 / h;

[0083] CO', CO2', N2', H2O' — the fractions of the component gases in the flue gas, %;

[0084] Then, in combination with the resistance of the boiler and the pipe network system, the operating frequency of the fan is matched to the calculated α value. Specifically, the control system looks up the pre-stored operating curve of the dust removal fan according to the calculated α value to obtain the optimal operating frequency of the dust removal fan.

[0085] In actual operation, when the smelting condition of the electric furnace changes, the system can automatically adjust the parameters in the calculation model to ensure the accuracy of the optimal excess air coefficient. For example, when the load of the electric furnace increases, the flue gas composition and temperature will change. The control system will recalculate the optimal excess air coefficient according to the new detection data and adjust the fan operating frequency to adapt to the new condition.

[0086] Through the above embodiments, the electric furnace air mixing energy-saving control method of the present invention realizes the optimal control of the electric furnace flue gas system, effectively improves the thermal efficiency of the system, and reduces energy consumption and pollutant emissions.

[0087] The present invention determines the optimal excess air coefficient α by detecting the composition and temperature of the electric furnace flue gas and using the empirical formulas of heat loss due to exhaust gas, incomplete combustion loss due to chemistry, and incomplete combustion loss of gas. When the sum of q2, q3, and q4 is the smallest, it is the optimal excess air coefficient. Subsequently, according to the adjusted optimal air coefficient given by the model, the flue gas volume of the air mixing combustion is calculated. In combination with the waste heat boiler and the pipe network resistance model, it is coupled with the operating curve of the dust removal fan to obtain the optimal operating frequency of the dust removal fan. By adjusting the working state of the fan, it is ensured that the electric furnace flue gas system can maintain the optimal operating state under different conditions, achieving the purpose of energy conservation and emission reduction.

[0088] The method of the present invention can also adjust the parameters in the calculation model in real time according to the change of the electric furnace smelting condition to ensure the accuracy of the optimal excess air coefficient. This method not only improves the thermal efficiency of the electric furnace waste heat boiler system, but also significantly reduces energy consumption and pollutant emissions, having important economic and environmental benefits.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.

Claims

1. An energy-saving control method for the mixing air of an electric furnace, characterized in that, It includes the following steps: S1. Detect the composition and temperature of the electric furnace flue gas in real time. The flue gas composition includes the concentrations of CO, CO2, SO2, and O2, and the flue gas temperature includes the flue gas discharge temperature and the cold air temperature; S2. Based on the detected flue gas composition and temperature, determine the optimal excess air coefficient α through a calculation model. The optimal excess air coefficient α is the value of α corresponding to the minimum sum of the heat loss due to flue gas discharge q2, the incomplete combustion loss due to chemistry q3, and the incomplete combustion loss of gas q4; S3. Couple the optimal excess air coefficient α with the operating curve of the dust removal fan to determine the optimal operating frequency of the dust removal fan; S4. Adjust the operating state of the dust removal fan in real time according to the optimal operating frequency to optimize the mixed air volume control.

2. The method according to claim 1, characterized in that, The relationship between the heat loss due to flue gas discharge q2 and the excess air coefficient α is: q2 = (0.5 + 3.5α)(t py - t k ) where t py is the smoke exhaust temperature, and t k is the cold air temperature.

3. The method according to claim 1, characterized in that, The relationship between the incomplete combustion loss due to chemistry q3 and the excess air coefficient α is: q3 = 3.2αCO%, where where β is the fuel characteristic coefficient and RO2 is the content of CO2 in the flue gas.

4. The method according to claim 2, wherein The relationship between the incomplete combustion loss of gas q4 and the excess air coefficient α is: where CO is the volume concentration of carbon monoxide in the flue gas.

5. The method according to claim 1, characterized in that, In step S3, by matching the pipe network resistance characteristic curve and the fan characteristic curve, the optimal operating frequency of the dust removal fan is determined, which specifically includes: Calculate the flue gas volume after mixing according to the optimal excess air coefficient α; Combine the resistance model of the waste heat boiler and the pipe network system to calculate the pipe network resistance value; Determine the optimal operating frequency of the dust removal fan according to the pipe network resistance value and the fan characteristic curve.

6. The method according to claim 1, wherein In step S4, the operating frequency of the dust removal fan is adjusted in real time through a PID controller to ensure the accuracy of the mixed air volume control.

7. The method according to claim 1, wherein In step S2, the fuel characteristic coefficient β is dynamically adjusted according to the changes in the electric furnace smelting conditions.

8. The method according to claim 1, characterized in that In step S1, the detection of the flue gas composition and temperature is realized through a gas composition analyzer and a temperature sensor, and the gas composition analyzer and the temperature sensor are respectively arranged at the electric furnace flue and the cold air inlet.

9. An optimized control system for regulating the mixing of air in an electric furnace, characterized in that, It includes: A sensor module for detecting the composition and temperature of the electric furnace flue gas in real time. The composition includes the concentrations of CO, CO2, SO2, and O2, and the temperature includes the flue gas discharge temperature and the cold air temperature; A data acquisition module for receiving and transmitting the detection data of the sensor module; A control system including a calculation module. The calculation module is used to determine the optimal excess air coefficient α according to the detection data through the calculation models of the heat loss due to flue gas discharge q2, the incomplete combustion loss due to chemistry q3, and the incomplete combustion loss of gas q4, and generate an optimal operating frequency instruction based on the α value and the operating curve of the dust removal fan; A dust removal fan for adjusting the operating state according to the optimal operating frequency instruction to realize the optimization control of the mixed air volume.

10. The system according to claim 9, wherein The control system further includes a storage module, which pre-stores the pipe network resistance characteristic curve and the fan characteristic curve for dynamically matching the changes in the working conditions.

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