Control method of diffusion type combustion system of aluminum melting furnace

Abstract

The invention relates to the technical field of nonferrous metal combustion, in particular to a control method of a diffuse combustion system of an aluminum melting furnace, which comprises the following steps: adjusting the mounting position of a burner; adjusting the initial opening position of the front valve of the natural gas nozzle; adjusting the flame shape and length of the burning torch of the burner of the aluminum melting furnace for multiple times; switching of flame modes and the proportion of primary air and secondary air are controlled; the air-fuel ratio and the residual oxygen amount of furnace gas are accurately controlled; the continuous flameout purging time of the main flame gun and the time when flames are not detected after the natural gas nozzle front valve is opened are adjusted, and the action of the nozzle front valve is controlled; adjusting the fan frequency of the dust removal system; before ignition, if the auxiliary smoke brake is in a closed state, the main fire gun needs to be opened for 3 seconds; a wild air valve is additionally arranged on a smoke exhaust fan pipeline; a ton gas consumption and burner interlocking function is set; a ton gas consumption target value is set; and when the actual ton gas consumption reaches the target value, the burner stops fire and reminds an operator that melting is completed. According to the method, the product gas consumption of the circular economy smelting furnace is reduced, and the metal burning loss is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of nonferrous metal combustion, and in particular to a control method for a diffusion combustion system of an aluminum melting furnace. Background Art

[0002] The traditional premixed regenerative combustion system has high nitrogen oxide emissions. Under the background of the dual carbon strategy and increasingly stringent environmental protection requirements, it is necessary and urgent to carry out energy-saving and low-nitrogen transformation of the aluminum melting furnace combustion system. From the two important aspects of saving energy and reducing atmospheric pollutant emissions, it is of great significance to carry out technical upgrading and transformation of the aluminum melting furnace combustion system. Summary of the invention

[0003] The object of the present invention is to provide a control method for a diffuse combustion system of an aluminum melting furnace, which helps to reduce the product gas consumption of a circular economy melting furnace and reduce metal burning loss.

[0004] The technical solution of the present invention is: a control method of a diffusion combustion system of an aluminum melting furnace, using a diffusion burner with two flame modes of rigid flame and flexible bright flame, comprising the following steps: (1) Adjust the installation position of the burner so that the main gun and the ignition gun of the burner form an angle of 15°, and configure a cooling air pipe for the ignition gun of the burner; (2) Adjust the initial opening position of the gas nozzle front valve to 20% to ensure the combustion and melting rate; (3) Adjust the flame shape and length of the burner ignition gun of the aluminum melting furnace several times; (4) Control the switching of flame modes and the ratio of primary air to secondary air; (5) Accurately control the air-fuel ratio and residual oxygen content in the furnace gas: Use a flue gas analyzer to measure the flue gas composition multiple times, measure the flue gas oxygen content and carbon monoxide content, and determine the optimal air-fuel ratio coefficient; (6) Adjust the continuous flameout purge time of the main torch and the time when no flame is detected after the valve in front of the natural gas nozzle is opened, and control the action of the valve in front of the nozzle; (7) Adjust the fan frequency of the dust removal system; optimize the control of the auxiliary smoke damper. Before ignition, if the auxiliary smoke damper is in the closed state, it needs to be opened for 3 seconds before the main ignition gun is opened; and add a wild wind valve to the exhaust fan pipeline; (8) Setting the interlocking function of gas consumption per ton and burner: Set the target value of gas consumption per ton. When the actual gas consumption per ton reaches the target value, the burner stops firing and reminds the operator that melting is completed.

[0005] Furthermore, in step (4), at the initial startup flow stage, the primary air flow is set to 1 / 4 of the rated load, the primary air ratio is 20%, and the secondary air ratio is 80%.

[0006] Furthermore, when the furnace temperature rises to above 750°C, the air and gas flow rates are increased to the rated load; when the furnace temperature reaches above 950°C, the primary air accounts for 5% of the rated air flow rate, and the secondary air accounts for 95% of the rated air flow rate.

[0007] Furthermore, in step (5), when the air-fuel ratio is set to 11:1, the residual oxygen content in the flue gas is detected by a flue gas analyzer from the auxiliary flue sampling port with a standard of 1.5% to 3%. The mass flow control method is used to control the gas and air flow rates separately to achieve a complete combustion flame with a minimum air excess coefficient, and the residual oxygen content in the furnace gas is controlled at a level of 2 to 3%.

[0008] Furthermore, in step (6), after the furnace temperature is below 750°C and the main flame gun is extinguished for more than two consecutive times, the purge is automatically started to replace the unburned furnace exhaust gas in the furnace, and the purge time is extended from 180 seconds for normal furnace startup to 360 seconds; the time when no flame is detected after the front valve of the natural gas nozzle is opened is shortened from the original 5 seconds to 3 seconds.

[0009] Furthermore, in step (7), the dust removal system is automatically controlled by detecting the negative pressure, and the frequency of the dust removal fan is adjusted in the range of 20-45HZ to ensure that the negative pressure of the flue of the aluminum melting furnace is around -100Pa, thereby ensuring the stability of the furnace pressure.

[0010] Furthermore, the host computer's function display, data recording, curve recording and PDA acquisition functions are added.

[0011] Compared with the prior art, the present invention has the following advantages: 1. Through precise control of air-fuel ratio and residual oxygen content in furnace gas, and control of burner installation position and angle, metal burning loss can be reduced, melting efficiency can be improved, natural gas consumption can be optimized, and investment cost can be reduced. Under safe and reliable operation, melting efficiency can be improved and energy consumption can be reduced.

[0012] 2. Through the optimization and adjustment of the aluminum melting furnace combustion system, the fuel (usually the fuel is mixed with a very small amount of combustion air to maintain flame stability) and the combustion air are injected into the furnace separately in a jet mode with the combustion air velocity higher than the fuel velocity. The rapid combustion air flow entrains the fuel and the combustion products in the furnace, dilutes the oxygen volume concentration in the reaction zone, and obtains a low-oxygen atmosphere with a concentration of 3-15% (volume). Heat energy is released under delayed combustion with oxygen-deficient gas, and there is no local high-temperature and high-oxygen zone in the traditional combustion process. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a structural diagram of the furnace burner arrangement of the present invention; In the figure: 1-furnace wall 2-furnace chamber 3-main ignition gun 4-ignition gun 5-ignition flame 6-large fire flame 7-ignition flame probe 8-large fire flame probe 9-angle 10-main ignition gun channel 11-flame probe channel 12-flame recirculation area 13-diversion port. DETAILED DESCRIPTION

[0014] In order to make the above features and advantages of the present invention more understandable, embodiments are given below with reference to the accompanying drawings for detailed description, but the present invention is not limited thereto.

[0015] refer to Figure 1 A control method for a diffusion combustion system of an aluminum melting furnace, using a diffusion burner with two flame modes: rigid flame and flexible bright flame, comprises the following steps: The burner mainly includes a main ignition gun channel 10 which is obliquely arranged on the furnace wall 1 and extends into the furnace 2, a main ignition gun 3 is arranged in the end of the main ignition gun channel, an ignition gun 4 is arranged on the furnace wall and leads to the main ignition gun channel and the connecting part is located in front of the main ignition gun output end, an ignition flame probe 7 is arranged in the ignition gun, a flame probe channel 11 is obliquely arranged on the upper part of the furnace wall and leads to the main ignition gun channel and the connecting part is located in front of the main ignition gun output end, and a high fire flame probe 8 is arranged in the flame probe channel.

[0016] (1) Adjust the installation position of the burner so that the main ignition gun and the ignition gun of the burner form an angle of 15° 9, the ignition gun is set horizontally, the distance between the steel structure inner wall of the burner and the guide port 13 is 350mm, and the depth of the ignition gun inserted into the main ignition gun channel is 173mm (i.e. the ignition gun is buried). Therefore, before the flame is completely burned, the high-temperature combustion products (POC) in the flame area are effectively prevented from directly contacting the aluminum liquid, which can effectively reduce the oxidation and burning caused by the direct contact between some incompletely burned fuel and the high-temperature and high-oxygen area and the aluminum liquid. Optimize the installation position of the fire detection rod (because the diffuse flame does not burn in a straight line, the fire detection rod is installed on the side of the burner flame angle direction) to better detect the flame and optimize the sensitivity of the fire detection. And configure the burner ignition gun with a cooling air pipe: reduce burner flameout and extend the burner life.

[0017] (2) Optimize and adjust the initial opening position of the front valve of the natural gas nozzle to 20% to ensure the combustion and melting rate; optimize the power at the low fire position, and improve the control procedures and safety interlocks.

[0018] (3) Adjust the flame shape and length of the burner ignition gun of the aluminum melting furnace several times: the flame length of the ignition gun was adjusted from 150-200mm to about 300mm, achieving a 100% success rate for burner main ignition.

[0019] (4) Control the switching of flame modes and the ratio of primary air to secondary air: During the initial startup flow stage, the primary air flow is set to 1 / 4 of the rated load, the primary air ratio is 20%, and the secondary air ratio is 80%.

[0020] (5) Accurately control the air-fuel ratio and residual oxygen content in the furnace gas: Use a flue gas analyzer to measure the flue gas composition multiple times, measure the flue gas oxygen content and carbon monoxide content. When the furnace temperature is lower than 750°C and the carbon monoxide content is low (lower than 10 mg / m³), the oxygen content is more appropriate at 1%-3%, as low as possible. By analyzing the air-fuel ratio when the flue gas is reasonable, the optimal air-fuel ratio coefficient is determined.

[0021] (6) Adjust the purge time of the main torch continuously extinguished and the time when no flame is detected after the front valve of the natural gas nozzle is opened: When the furnace temperature is below 750℃ and the main torch is extinguished for more than two times, the purge is automatically started to replace the unburned furnace exhaust gas in the furnace. The purge time is extended from 180 seconds of normal furnace start-up to 360 seconds; the time when no flame is detected after the front valve of the natural gas nozzle is opened is shortened from 5 seconds to 3 seconds. Optimize the switching time of the burner to ensure the temperature of the heat storage body.

[0022] (7) Adjust the fan frequency of the dust removal system: The dust removal system is automatically controlled by detecting negative pressure. The dust removal fan frequency is adjusted in the range of 20-45HZ to ensure that the negative pressure of the aluminum melting furnace flue is around -100pa, to ensure the stability of the furnace pressure in the furnace, and to avoid heat loss in the furnace due to excessive dust removal. And optimize the control of the auxiliary smoke damper. Before ignition, if the auxiliary smoke damper is in the closed state, it needs to be opened for 3s before the main ignition gun is opened. And add a wild wind valve to the exhaust fan pipeline to increase the exhaust temperature in an adjustable way.

[0023] (8) Setting the interlocking function between ton gas consumption and burner: Set the target value for ton gas consumption. When the actual ton gas consumption reaches the target value, the burner stops firing and reminds the operator that the melting is complete. This avoids the problem of aluminum liquid overheating or aluminum liquid temperature not being high enough due to manual judgment, and at the same time achieves the purpose of reducing energy consumption.

[0024] (9) Optimize the functions of the host computer: increase the function display, data recording, curve recording and PDA acquisition functions of the host computer. This will facilitate the analysis and optimization of the combustion control system and the control of the furnace.

[0025] In this embodiment, when the furnace temperature rises to above 750°C, the air and gas flow rates are increased to the rated load; when the furnace temperature reaches above 950°C, the primary air accounts for 5% of the rated air flow rate, and the secondary air accounts for 95% of the rated air flow rate.

[0026] In this embodiment, in step (4), different flame modes are switched for different furnace gas temperatures, so that the primary air volume is changed from being temperature-independent to being temperature-controlled, ensuring that the rigid flame when heating below 850°C can greatly improve the convective heat transfer efficiency in the furnace; and the bright flame when entering the heating stage above 850°C can greatly reduce the thermal erosion on the surface of the high-temperature aluminum liquid, reducing the exposure time of the aluminum liquid to the residual oxygen in the furnace gas, thereby reducing oxidation burning.

[0027] In this embodiment, in step (5), when the air-fuel ratio is set to 11:1, the residual oxygen content in the flue gas is detected by a flue gas analyzer from the auxiliary flue sampling port with a standard of 1.5% to 3%. The mass flow control method is adopted to independently control the gas and air flow rates to achieve a complete combustion flame under the minimum air excess coefficient. The residual oxygen content in the furnace gas is controlled at a level of 2 to 3%. The low oxygen level can effectively reduce the oxidation and burning of aluminum liquid.

[0028] In this embodiment, a report can also be made on the HMI screen to count the combustion time of each furnace, the natural gas consumption of each furnace and the gas consumption per ton, which is convenient for melting rate analysis. And according to the abnormal changes in the combustion parameters of the regenerative burner, such as the combustion air flow, exhaust temperature, furnace pressure and other parameters, the alumina balls can be replaced in time to maximize the heat recovery of the furnace and reduce the natural gas consumption per ton.

[0029] In this embodiment, by optimizing the combustion control program and parameters such as combustion-supporting air, natural gas flow, and smoke exhaust fan frequency, the maximum combustion power of the burner and the melting speed are increased during the heating stage, the melting rate is increased to avoid the standby time of the casting machine, and the melting time is ensured to match the casting production rhythm time, thereby improving production efficiency.

[0030] This method can shorten the furnace combustion time from 6 hours to 4.5 hours, increase the melting rate by 25%, reduce the natural gas consumption per ton to 10%, and reduce the burning loss by 0.3%.

[0031] The above description is only a preferred embodiment of the present invention. For ordinary technicians in this field, according to the teachings of the present invention, it does not require creative labor to design a control method for a diffuse combustion system of an aluminum melting furnace in different forms. Without departing from the principle and spirit of the present invention, all equal changes, modifications, substitutions and variations made within the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A control method for a diffusion combustion system of an aluminum melting furnace, using a diffusion burner with two flame modes: rigid flame and flexible bright flame, characterized in that: The following steps are involved: (1) Adjust the installation position of the burner so that the main gun and the ignition gun of the burner form an angle of 15°, and configure a cooling air pipe for the ignition gun of the burner; (2) Adjust the initial opening position of the gas nozzle front valve to 20% to ensure the combustion and melting rate; (3) Adjust the flame shape and length of the burner ignition gun of the aluminum melting furnace several times; (4) Control the switching of flame modes and the ratio of primary air to secondary air; (5) Accurately control the air-fuel ratio and residual oxygen content in the furnace gas: Use a flue gas analyzer to measure the flue gas composition multiple times, measure the flue gas oxygen content and carbon monoxide content, and determine the optimal air-fuel ratio coefficient; (6) Adjust the continuous flameout purge time of the main torch and the time when no flame is detected after the valve in front of the natural gas nozzle is opened, and control the action of the valve in front of the nozzle; (7) Adjust the fan frequency of the dust removal system; optimize the control of the auxiliary smoke damper. Before ignition, if the auxiliary smoke damper is in the closed state, it needs to be opened for 3 seconds before the main ignition gun is opened; and add a wild wind valve to the exhaust fan pipeline; (8) Setting the interlocking function of gas consumption per ton and burner: Set the target value of gas consumption per ton. When the actual gas consumption per ton reaches the target value, the burner stops firing and reminds the operator that melting is completed.

2. The control method of a diffuse combustion system of an aluminum melting furnace according to claim 1, characterized in that: In step (4), at the initial startup flow stage, the primary air flow is set to 1 / 4 of the rated load, the primary air ratio is 20%, and the secondary air ratio is 80%.

3. The control method of a diffuse combustion system of an aluminum melting furnace according to claim 2, characterized in that: When the furnace temperature rises above 750℃, the air and gas flow rates are increased to the rated load; when the furnace temperature reaches above 950℃, the primary air accounts for 5% of the rated air flow rate, and the secondary air accounts for 95% of the rated air flow rate.

4. The control method of a diffuse combustion system of an aluminum melting furnace according to claim 1, 2 or 3, characterized in that: In step (5), when the air-fuel ratio is set to 11:1, the residual oxygen content in the flue gas is detected by a flue gas analyzer from the auxiliary flue sampling port with a standard of 1.5% to 3%. The mass flow control method is adopted to independently control the gas and air flow rates to achieve a complete combustion flame under the minimum air excess coefficient, and the residual oxygen content in the furnace gas is controlled at a level of 2 to 3%.

5. The control method of a diffuse combustion system of an aluminum melting furnace according to claim 1, characterized in that: In step (6), when the furnace temperature is below 750°C and the main flame gun is extinguished for more than two consecutive times, the purge is automatically started to replace the unburned furnace exhaust gas in the furnace. The purge time is extended from 180 seconds for normal furnace startup to 360 seconds; the time when no flame is detected after the front valve of the natural gas nozzle is opened is shortened from 5 seconds to 3 seconds.

6. The control method of a diffusion combustion system of an aluminum melting furnace according to claim 1 or 5, characterized in that: In step (7), the dust removal system is automatically controlled by detecting the negative pressure, and the frequency of the dust removal fan is adjusted in the range of 20-45HZ to ensure that the negative pressure of the flue of the aluminum melting furnace is around -100Pa, thereby ensuring the stability of the furnace pressure.

7. The control method of a diffuse combustion system of an aluminum melting furnace according to claim 1, characterized in that: Add function display, data recording, curve recording and PDA acquisition functions to the host computer.

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