Dispersion regenerative combustion industrial furnace and heating method

Abstract

This invention discloses a dispersion-type regenerative combustion industrial furnace, comprising a furnace chamber, an airflow reversing system, and at least two regenerators. Burners are installed on the furnace chamber, with at least two burners provided. During a certain period in the low-temperature stage, at least two burners operate continuously. The low-temperature stage refers to the period during which the temperature inside the furnace has not reached the fuel's auto-ignition temperature. This invention also provides a heating method for heating materials using the aforementioned dispersion-type regenerative combustion industrial furnace. The dispersion-type regenerative combustion industrial furnace of this invention completely eliminates the risk of deflagration in dispersion-type regenerative combustion systems, resulting in significantly higher safety and production efficiency, thus perfectly solving the problem of slow production speed in existing technologies.

Description

Technical Field

[0001] This invention belongs to the field of combustion equipment, and particularly relates to a combustion industrial furnace and heating method. Background Technology

[0002] Premixed combustion is a traditional combustion method with a long history. It organizes the combustion process by mixing fuel and combustion air in the combustion chamber. After combustion, the flue gas containing the exhaust flame is injected into the furnace to heat the materials inside.

[0003] Dispersion combustion does not have a combustion chamber. Instead, it uses a combustion air jet velocity higher than the fuel jet velocity to separately inject fuel and combustion air into the furnace. The rapid combustion air flow entrains fuel and combustion products in the furnace, diluting the oxygen concentration in the reaction zone and creating a localized low-oxygen atmosphere. In this high-temperature, low-oxygen atmosphere, the fuel gradually combines with oxygen and burns, accompanied by reorganization processes such as cracking. This results in thermodynamic conditions completely different from premixed combustion and diffusion combustion with only a fuel jet. Heat energy is released under delayed combustion with oxygen-deficient gas.

[0004] The combination of premixed combustion and regenerative combustion constitutes the traditional premixed regenerative combustion system. The combination of dispersed combustion and regenerative combustion constitutes the dispersed regenerative combustion system. In terms of energy efficiency, both systems exhibit significant energy savings due to their regenerative waste heat recovery and utilization methods. Environmentally, the dispersed regenerative combustion system, with its larger combustion flame volume and significantly lower high-temperature zone, results in lower thermal NOx emissions. x Production has decreased significantly. NO x It is one of the main culprits of air pollution, therefore, the environmental performance of diffused regenerative combustion is significantly better than that of premixed regenerative combustion systems.

[0005] In the field of industrial combustion technology, dispersed regenerative combustion technology has been widely adopted in recent years, bringing both energy-saving and environmentally friendly benefits. This system operates similarly to the burner operation steps of a premixed regenerative combustion system, with two ignition guns maintaining a continuous flame after ignition to ensure system safety. When secondary combustion air is introduced into one main air duct, the corresponding burner receives fuel and is operational; when the other main air duct is in exhaust mode, the corresponding burner ceases operation. However, the difference between dispersed regenerative combustion systems and premixed regenerative combustion systems lies in the fact that premixed regenerative combustion systems have a dedicated combustion chamber, such as... Figure 1As shown. Dispersed regenerative combustion systems do not have a dedicated combustion chamber; instead, the furnace containing the material serves as the primary combustion site. Therefore, when the furnace is full of material, the space for fuel mixing and combustion is limited. Fuel injected by the burners working in conjunction with the main air duct enters the voids in the low-temperature material without being burned, accumulating and mixing with the air in these voids to form explosive gases. When a large amount of unburned fuel accumulates, during the reversing process, the original burner extinguishes first, and after a 1-2 second interval, another burner starts working, igniting the unburned explosive gases accumulated in the low-temperature material, resulting in an explosion. Premixed regenerative combustion systems, because they have a combustion chamber, do not have the problem of unburned residual fuel accumulating in the furnace, and therefore do not have the aforementioned deflagration issues.

[0006] Taking a dual-regenerative heat storage combustion system as an example, to avoid the aforementioned explosion phenomenon, the following two measures must be taken: First, reduce the fuel supply to the burners to reduce the total amount of fuel accumulated. Typically, in the initial stage of the low-temperature phase, the burner power is only 15-30% of its maximum power, which significantly prolongs the time required to heat up from the low-temperature stage to the high-temperature stage, reducing system production efficiency. Second, extend the time interval between the stoppage of one burner and the start of the next during burner switching, i.e., extend the interval time, allowing sufficient time for the accumulated explosive gases to escape from the furnace. Typically, the interval time needs to be increased 3-6 times to barely ensure safety, for example, increasing the interval time from about 1-2 seconds to 6-12 seconds. If the regenerative system's reversing cycle is 60 seconds, then the interval time is 10%-20% of one operating cycle, during which time the burners are not operating. Extending the interval time further reduces system production efficiency and increases system energy consumption, while still not completely eliminating the risk of deflagration; it only reduces the frequency and energy of potential deflagration to an acceptable level.

[0007] Therefore, the use of diffused regenerative combustion systems is limited by the aforementioned safety and efficiency issues, preventing them from fully realizing their energy-saving and environmental advantages.

[0008] Only by solving the safety and production efficiency issues of diffused regenerative combustion systems can we completely replace premixed regenerative combustion systems with this energy-saving and environmentally friendly technology, laying the foundation for the industry to enter a new era of "energy-saving, environmentally friendly, and highly efficient" diffused regenerative combustion systems. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a dispersion regenerative combustion industrial furnace that can solve the problem of explosion-proof combustion, has high safety and high production efficiency, as well as a heating method for heating materials using the dispersion regenerative combustion industrial furnace.

[0010] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0011] A diffuse regenerative combustion industrial furnace includes a furnace chamber, an airflow reversing system, and at least two heat storage boxes. Burners are installed on the furnace chamber, and at least two burners are provided. During a certain period of time in the low-temperature stage (a certain period of time or the entire period of time), at least two burners keep working continuously. The low-temperature stage refers to the period of time in which the temperature in the furnace chamber (including the low-temperature zone) has not reached the auto-ignition temperature of the fuel.

[0012] In the aforementioned diffuse regenerative combustion industrial furnace, preferably, the low-temperature stage includes the following time period: starting with the activation of the burners to heat the furnace, and ending after the burners have been operating for 10-60 minutes. During this time period, at least two burners maintain continuous operation. The starting point of this time period is the furnace ignition time, and the ending point is the time after the burners have been operating for 10-60 minutes, for example, after 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, or 60 minutes. During this time period, the temperature inside the furnace may not have reached the fuel auto-ignition temperature. Maintaining two burners operating simultaneously and continuously without switching directions with system reversal can solve the problem of deflagration and improve production efficiency. In special cases, such as when the heating rate inside the furnace is slow, the above endpoint can be extended. For example, the endpoint can be set after the burner has been working for 70 minutes, 80 minutes, 90 minutes, 100 minutes, 110 minutes, or 120 minutes.

[0013] For a period of time after the burner starts operating, the temperature in the area of ​​the furnace far from the burner will be lower; this area can be considered a low-temperature zone. The temperature in the area of ​​the furnace closer to the burner will be higher; this area can be considered a high-temperature zone. The furnace temperature reaching the fuel auto-ignition temperature means that the temperature at any point in the furnace (including both high-temperature and low-temperature zones) has reached the fuel auto-ignition temperature. For example, the temperature near the burner outlet may have reached the fuel auto-ignition temperature, but the temperature at other locations far from the burner outlet may not have reached the fuel auto-ignition temperature; this can be classified as a low-temperature stage.

[0014] In a more preferred scheme, a working mode of 2 heat storage boxes + 2 burners or a working mode of 2 heat storage boxes + 3 burners is adopted, and all burners maintain continuous and uninterrupted operation throughout the entire period of the low temperature stage.

[0015] In the aforementioned diffuse regenerative combustion industrial furnace, preferably, the secondary combustion air heated by the heat storage box enters the furnace through the main air channel. The burner inlet is connected to a fuel inlet, and the burner outlet is used to spray flames and fuel into the furnace. The heat storage box is positioned close to the burners to ensure that the secondary combustion air provided by the heat storage box can supply all burners in operation, promoting complete combustion of the fuel sprayed from the burners. Positioning the heat storage box close to the burners allows for a greater distance between the two heat storage boxes, while the distance between any one heat storage box and any one burner is less than the distance between the two heat storage boxes. This ensures that when the airflow flows between the two heat storage boxes, it passes as far as possible through the burners in operation (the greater distance between the two heat storage boxes creates a flow field between the heat storage box that inputs the secondary combustion air and the heat storage box that exhausts the flue gas; the burner's positioning ensures that the fuel sprayed from all burners in operation is within this flow field), thus ensuring that the secondary combustion air sprayed from the heat storage box can supply all burners in operation.

[0016] In a more preferred embodiment, when the heat storage box and the burner are both located on the same side of the furnace, the burner is located between the heat storage boxes.

[0017] In a more preferred embodiment, when the two heat storage boxes and the two burners are located on different sides of the furnace, the line connecting the two heat storage boxes and the two burners forms a quadrilateral, with the two heat storage boxes located at one corner of the quadrilateral and the two burners located at the other corner of the quadrilateral.

[0018] In the aforementioned diffuse regenerative combustion industrial furnace, preferably, during the low-temperature stage, the actual power of the burner that operates continuously and uninterruptedly during at least one first time period is no greater than 40% of the system's benchmark average power. The actual power of the burner is the ratio of the amount of fuel injected by the burner to the time taken to inject the fuel. The system's benchmark average power refers to the ratio of the total amount of fuel consumed by each furnace product to the working time (the longest time to meet the speed requirements) during which the total amount of fuel is consumed.

[0019] In the above-mentioned diffuse regenerative combustion industrial furnace, preferably, the starting point of the first time period is the starting point of the low temperature stage, and the ending time depends on the heating status of the system.

[0020] In the above-mentioned diffuse regenerative combustion industrial furnace, preferably, during the low-temperature stage, at least one second time period, the total primary air oxygen volume provided by the auxiliary air inlet of the burner is v1, the theoretical oxygen volume required for the combustion of all fuels injected into all burners is v2, and v1 / v2 is not less than 35%.

[0021] In the above-mentioned diffuse regenerative combustion industrial furnace, preferably, the starting point of the second time period is the starting point of the low temperature stage, and the ending time depends on the heating status of the system.

[0022] In this invention, the first time period and the second time period can be the same time period, for example, both being the following time period: starting from turning on the burner to heat the furnace, and ending after the burner has been working for 10-60 minutes. Of course, the first time period and the second time period can also be different time periods, for example, the first time period may be earlier or later than the second time period, depending on the actual situation.

[0023] As a general technical concept, the present invention also provides a heating method for heating materials using the above-mentioned dispersed regenerative combustion industrial furnace, comprising the following steps:

[0024] Material is loaded into the furnace, and flames and fuel are sprayed into the furnace using burners to heat the material. During a certain period of time in the low-temperature stage, all burners continue to work continuously without being affected by the airflow reversal system and the regenerator. When the temperature of at least a part of the furnace reaches above the fuel auto-ignition temperature, all burners continue to work continuously or switch in turn until heating is completed.

[0025] The auxiliary structure of the diffuse regenerative combustion industrial furnace of the present invention is consistent with that of the existing diffuse regenerative combustion industrial furnace, and also includes a blower, an induced draft fan, a computer control system, etc. The furnace chamber is composed of a furnace top, furnace walls and a furnace bottom.

[0026] The diffuse regenerative combustion industrial furnace of this invention is a safe and ultra-efficient diffuse regenerative combustion system. As is well known, fuel deflagration requires two conditions: first, the accumulation of a mixture of fuel and oxygen within the explosive concentration range; and second, ignition by an open flame (including a spark). Taking a regenerative combustion system with two regenerators and two burners as an example, the improved system of this invention allows two burners to operate simultaneously, significantly expanding the area covered by the open flame within the furnace. Combustible gases are continuously ignited and consumed, greatly reducing the accumulation of explosive gases and eliminating the ignition step of a burner suddenly emitting a flame to ignite the accumulated explosive gases during burner switching. Therefore, the risk of deflagration caused by fuel accumulation due to material buildup in the diffuse regenerative combustion system is completely eliminated. Thus, compared to the traditional diffuse regenerative combustion system of Comparative Example 2, because the two constituent elements of deflagration are eliminated, the technical problem of deflagration can be solved, resulting in higher safety.

[0027] Meanwhile, compared to the traditional diffused regenerative combustion system of Comparative Example 2, in the initial stage of the low-temperature phase, the actual power of each burner can be higher than that of the traditional diffused regenerative combustion system (because the deflagration problem is solved, while the traditional diffused regenerative combustion system must significantly reduce the burner power to account for deflagration). With two burners operating simultaneously, the actual power is even higher. Furthermore, the absence of the reversing interval caused by burner reversal also results in higher actual power. Overall, the diffused regenerative combustion industrial furnace of this invention has higher power and higher operating efficiency.

[0028] Furthermore, because the burners corresponding to the heat storage box for exhaust gas in the premixed regenerative combustion system must stop working, and the burners operating during airflow switching must also stop working in advance, it is impossible to achieve the state in the improved dispersion regenerative combustion system of this invention where all burners operate simultaneously and do not require intervals or stoppages during airflow switching. In comparison, under the same conditions, the average power output of the dispersion regenerative combustion system of this invention is not only significantly higher than that of existing dispersion regenerative combustion systems, but also higher than all premixed regenerative combustion systems. Specifically, by adopting the latest operating method, in the most severe low-temperature stage of the dispersion regenerative combustion system, the total system power can be increased to more than four times that of existing dispersion regenerative combustion systems and approximately 1.5 times that of premixed regenerative combustion systems at the same stage, effectively solving the problem of slow production speed in existing technologies.

[0029] Compared with the prior art, the advantages of the present invention are as follows:

[0030] 1. In the low-temperature stage where the temperature inside the furnace has not reached the auto-ignition temperature of the fuel, at least two burners in the diffuse regenerative combustion industrial furnace of the present invention operate continuously for a certain period of time or for the entire period of time. The area covered by the open flame inside the furnace is greatly expanded, which greatly reduces the amount of explosive gas accumulated. There is also no step of the burner that starts working during the burner switching process spraying a flame to ignite the accumulated explosive gas. Therefore, the risk of deflagration in the diffuse regenerative combustion system is completely eliminated, and the safety is significantly higher.

[0031] 2. In the most severe low-temperature stage of the diffuse regenerative combustion system, the total power of the industrial furnace of the present invention can be increased to more than 4 times that of the existing diffuse regenerative combustion system at the same stage, resulting in significantly higher production efficiency and successfully solving the problem of slow production speed in the existing technology. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of a premixed regenerative combustion system.

[0034] Figure 2 This is a schematic diagram of the operation of an existing diffuse regenerative combustion system when the material is fully piled up.

[0035] Figure 3 This is a schematic diagram of the operation of an existing diffuse regenerative combustion system after the material has melted and leveled.

[0036] Figure 4 This is a schematic diagram of the operation when the material is fully piled up according to the present invention.

[0037] Figure 5 This is a schematic diagram showing the arrangement of the heat storage box and burner opposite each other in this invention.

[0038] Figure 6 This is a schematic diagram of the working process after the material is melted and leveled according to the present invention.

[0039] Figure 7 This is a schematic diagram of the operation of the present invention when the material is fully piled up using 2 heat storage boxes and 3 burners.

[0040] Legend:

[0041] 1. Furnace; 4. Combustion chamber; 5. Ignition gun; 6. Auxiliary air inlet; 7. Burner; 701. First burner; 702. Second burner; 703. Third burner; 8. Fuel inlet; 9. Main air duct; 10. Heat storage box; 1001. First heat storage box; 1002. Second heat storage box; 11. Heat storage material; 14. Material. Detailed Implementation

[0042] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0043] It should be noted that when a component is described as being "fixed to, attached to, connected to or connected to" another component, it can be directly fixed to, attached to, connected to or connected to the other component, or it can be indirectly fixed to, attached to, connected to or connected to the other component through other intermediate connectors.

[0044] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0045] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0046] This invention fundamentally solves the safety and efficiency problems of industrial furnaces in dispersed regenerative combustion systems. To more clearly illustrate the differences between this invention and existing technologies in terms of safety and efficiency, two typical prior art examples (Comparative Examples 1-2) are first introduced. Then, through a comparison of the operation of embodiments of this invention with Comparative Examples 1-2, the perfect operational effect produced by this invention can be better understood.

[0047] Comparative Example 1:

[0048] Figure 1 This is a 35-ton aluminum alloy smelting furnace employing existing premixed regenerative combustion system technology, shown in the side view schematic diagram. The fuel is natural gas. The system consists of a furnace chamber 1, regenerators 10 (including a first regenerator 1001 and a second regenerator 1002), regenerator material 11 filled in the regenerators 10, a combustion chamber 4, a main air duct 9 connecting the regenerators 10 and the combustion chamber 4, burners 7 (including a first burner 701 and a second burner 702), an ignition gun 5, a fuel inlet 8, an auxiliary air inlet 6, a blower, an induced draft fan, an airflow reversing system, and a computer control system. The furnace chamber 1 consists of furnace walls, a furnace top, and a furnace bottom. The combustion chamber 4 is connected to the furnace chamber 1. For simplicity, the blower, induced draft fan, airflow reversing system, and computer control system are not shown in the diagram.

[0049] Production requirements: Melt material 14 (approximately 35 tons of solid aluminum or aluminum alloy raw materials) and heat it to about 730-760℃. The combustion system should operate for less than 5 hours, and the airflow reversal time cycle should be 60 seconds. Figure 1 This shows the state of aluminum material when it has been heated to over 660°C and is in a liquid state.

[0050] The working process is as follows: The pilot flames of the two ignition guns 5 are ignited from the start of the combustion system and remain burning continuously. The heat storage material 11 in the first heat storage box 1001 heats the secondary combustion air and sends it into the combustion chamber 4 through the main air channel 9. Fuel in the fuel inlet 8 and primary air in the auxiliary air inlet 6 enter the first burner 701, mix, and are then injected into the combustion chamber 4 where they are ignited by the pilot flames of the ignition guns 5; unburned fuel continues to mix with the secondary combustion air in the combustion chamber 4 and is completely burned. The natural gas supplied to the first burner 701 per hour is 450 Nm³. 3If the calorific value of natural gas is 35000 kJ / Nm³ 3 The power of the first burner 701, i.e., the heat supplied by the first burner 701 to the system per hour, is 35000 kJ / Nm³. 3 ×450Nm 3 / hour = 15,750,000 kJ / hour = 4375 kW, which is the maximum power of the first burner 701 in this comparative example. For convenience, this invention uses the natural gas consumption (Nm³) 3 The power of burner 701 or the combustion system is expressed as ( / hour). Fuel, primary air, and secondary combustion air are converted into ultra-high temperature flue gas and the tail of the flame through the combustion process in combustion chamber 4, which enters furnace 1 to heat the aluminum alloy material. The flue gas passes through combustion chamber 4, through main air duct 9, and then into the second heat storage box 1002, passes through heat storage material 11, and is discharged from the system by induced draft fan. During the above process, the second burner 702 does not work. After one cycle of the reversing system is 60 seconds, the entire system switches operation according to the rules of the regenerative combustion system: the first burner 701 is closed, and the airflow reversing system switches the airflow direction, that is: the secondary combustion air is heated by the heat storage material 11 in the second heat storage box 1002 and enters combustion chamber 4 from main air duct 9; the flue gas 3 passes through combustion chamber 4, through main air duct 9, and then into the first heat storage box 1001, passes through heat storage material 11, and is discharged from the system by induced draft fan. After the airflow switching is completed, the second burner 702 is started to work again, with an interval of 2 seconds.

[0051] Assume that the system energy consumption of each comparative example and embodiment is 60 Nm. 3 / ton, burner 7 has a power of 450 Nm 3 / hour, in this system, 35 tons requires a total of 2100 Nm³ of natural gas. 3 Considering the impact of burner 7 shutting down during the 2-second interval, the system's baseline average power is 435 Nm. 3 / hour. It takes 4.82 hours to complete one furnace production, which just meets the requirement that the combustion system of one furnace should not work for more than 5 hours.

[0052] For ease of explanation and accurate comparison, all comparative examples and embodiments are described based on this comparative example. Wherein:

[0053] System reference average power: This is the ratio of the total energy consumed by each furnace to the longest time required to meet the speed requirements. The system reference average power in this comparative example is 435 Nm. 3 / hour, the actual power of burner 7 is the ratio of the amount of fuel injected by burner 7 to the time taken to inject that fuel. The system average power is the ratio of the energy consumed in a certain stage to the time of that stage (the time needs to be greater than one switching cycle). The system average power may be higher or lower than the system reference average power.

[0054] Comparative Example 2:

[0055] Figure 2 This is a schematic diagram of a 35-ton aluminum alloy melting furnace employing a traditional diffused regenerative combustion system, showing the low-temperature stage of the processed material 14 being a solid. The system components and operating requirements are compared with Comparative Example 1. Figure 1 The system is the same as (except where differences are mentioned later), that is, the system reference average power is 435 Nm. 3 / hour. Because it is a diffuse combustion, the installation positions of its first burner 701 and second burner 702 are the same as those in Comparative Example 1 ( Figure 1 ) are different, and no comparison example 1 is set. Figure 1 Combustion chamber 4 in )

[0056] In this comparative example, the first burner 701 operates, and secondary combustion air enters the furnace 1 through the main air duct 9, mixing with the remaining fuel injected into the furnace 1 by the first burner 701 to form a flame. The remaining operating procedures are the same as in Comparative Example 1. After 60 seconds, the entire system switches operation according to the rules of a regenerative combustion system: the first burner 701 is shut off, and the reversing system switches the airflow direction in exactly the same way as in Comparative Example 1. After the airflow switching is completed, the second burner 702 is then activated.

[0057] This comparative example does not have a dedicated combustion chamber 4; instead, the furnace chamber 1, which contains aluminum, serves as the main combustion chamber. The furnace chamber 1 is filled with aluminum, which blocks the space, resulting in very limited combustion space. Furnace 1, working in conjunction with the main air duct 9, injects fuel that fails to burn upon contact with the aluminum and enters the voids within the low-temperature aluminum. When the flame passes through the low-temperature aluminum, it extinguishes due to the low temperature, and the fuel accumulates in the voids, forming an explosive gas. The first burner 701 uses 450 Nm³ of natural gas... 3 Operating at a power output of [power value] per hour, the total amount of explosive gas accumulating in the gaps of the aluminum material is extremely large. The first burner 701 extinguishes first, and only after the airflow reversing system completes the reversal does the second burner 702 begin operation. The burner switching interval is approximately 2 seconds, during which time the fuel mixes evenly with oxygen in the gaps of the aluminum material. Due to the short interval, most of the accumulated, well-mixed explosive gas does not escape from furnace 1. The flame emitted from the second burner 702 then ignites the unburned explosive gas accumulated within the low-temperature aluminum material, resulting in an explosion.

[0058] To prevent fuel from accumulating excessively in the voids of the aluminum material and to mitigate the potential risk of deflagration in this system, the power of burner 7 must be significantly reduced in the initial stage of the low-temperature phase when the material 14 is at a relatively low temperature. In this comparative example, the operating power of burner 7 is selected as 90 Nm. 3 / hour, which is equivalent to 20.69% of the system's baseline average power. With an interval of 8 seconds, the actual system average power is 78 Nm. 3 / hour, which is 17.9% of the system's baseline average power. As the furnace temperature gradually rises, the first stage of the low-temperature phase lasts approximately 20 minutes before transitioning to the second stage; the second stage increases the burner 7's operating power to 150 Nm. 3 / hour, actual system average power 130Nm 3 / hour, which is 29.89% of the system's baseline average power, and after running for 20 minutes, it switches to the third stage; the third stage increases the operating power of burner 7 to 225Nm. 3 / hour, actual system average power 195Nm 3 / hour, which is 44.83% of the system's baseline average power, and after running for 20 minutes, it switches to the fourth stage; the fourth stage increases the operating power of burner 7 to 300Nm. 3 / hour, actual system average power 260Nm 3 / hour, which is 59.77% of the system's baseline average power. After about 60 minutes of operation, the temperature of furnace 1 rises above the auto-ignition temperature of natural gas, approximately 600℃, and the power of burner 7 increases to 450 Nm. 3 / hour, the interval time was shortened to 2 seconds, and the actual system average power was 435 Nm. 3 / hour represents 100% of the system's baseline average power, running until the end.

[0059] Considering the impact of burner 7 shutting down within an 8-second interval, the average system power is 229 Nm during the first 120 minutes after system startup. 3 / hour, less than the system's baseline average power of 435 Nm 3 53%, with a total heat output of 394.33 Nm³. 3 The calorific value of natural gas. The system's average power output over these two hours was significantly lower than the system's baseline average power output.

[0060] Figure 3 yes Figure 2 The diagram shown is an operational schematic of the diffused regenerative combustion aluminum melting furnace 1 after the material 14 inside the furnace chamber is completely melted and leveled. At this point, the power of the burner 7 is equal to the base power of the burner 7, 450 Nm. 3 / Hour.

[0061] In summary, this diffused regenerative combustion system only completed about half of the temperature rise under the system's baseline average power operation in the first 120 minutes. Even during the four hours of high-temperature operation, burner 7 maintained a temperature of 450 Nm. 3 Operating at a power output of / hour, the combustion system outputs 2100 Nm. 3The total time required for natural gas calorific value determination is 5.92 hours, which cannot meet the requirement that the combustion system completes the task in 5 hours. On the other hand, extending the interval time does not eliminate the accumulation of explosive gases; it only utilizes the continuous operation of the blower and induced draft fan during the interval time to discharge some explosive gases from the furnace 1 through the induced draft fan, without completely eliminating the risk of deflagration.

[0062] As can be seen from Comparative Examples 1 and 2, regardless of whether it is in the operation mode of the diffused regenerative combustion system or the premixed regenerative combustion system, the burner 7 adopts an operation mode of switching between working and stopping operation in cycles as the airflow reversing system changes direction.

[0063] Example 1:

[0064] A 35-ton aluminum melting furnace using natural gas fuel, such as Figure 4 As shown, the system composition and requirements are the same as those in Comparative Example 1 ( Figure 2 The diffuse regenerative combustion system is basically the same as that in China.

[0065] Figure 4 The differences between this system and Comparative Example 2 are as follows: ① Fuel is simultaneously fed into the fuel inlet 8 of the burners 7 (including the first burner 701 and the second burner 702). The fuel simultaneously enters the first burner 701 and the second burner 702 and mixes with the primary air. Flames and residual fuel are simultaneously ejected from the outlets of the first burner 701 and the second burner 702. The residual fuel entering the furnace 1 from the first burner 701 and the second burner 702 is then mixed with the secondary combustion air from the main air duct 9 for combustion. ② After one cycle of the airflow reversing system (60 seconds), the entire system does not operate according to the rules of a traditional regenerative combustion system—where the airflow and burners simultaneously reverse direction—but only the airflow switches. After the airflow switch, the secondary combustion air is heated by the heat storage material 11 in the first heat storage box 1001 and enters the furnace 1 from the main air duct 9; the flue gas 3 passes through the main air duct 9, then enters the second heat storage box 1002, passes through the heat storage material 11, and is discharged from the system by the induced draft fan. Whether before or after the airflow switching or during the intermediate interval, the first burner 701 and the second burner 702 do not stop working. Therefore, there is no process or interval issue for the first burner 701 and the second burner 702 to stop and start working.

[0066] In this embodiment, the first burner 701 and the second burner 702 continuously eject flames and residual fuel into the furnace 1. The coverage area of ​​the two flames continuously existing near the material 14 gaps near the outlets of the first burner 701 and the second burner 702 is much larger than when only one first burner 701 or the second burner 702 is working. The explosive gas is stably ignited within this larger area and cannot accumulate. On the other hand, neither the first burner 701 nor the second burner 702 stops and restarts, or suddenly ejects open flames to ignite the explosive gas. This eliminates the two prerequisites for deflagration from two aspects. Therefore, the system in this embodiment has high safety performance and will not deflagrate.

[0067] Figure 6 This describes the working condition of the solid material 14 after it has been melted and leveled in this embodiment.

[0068] This invention changes the alternating operation of the first burner 701 and the second burner 702 in existing regenerative combustion technology to the simultaneous operation of two or more burners 7, solving the deflagration problem and improving production efficiency. However, it also introduces varying degrees of incomplete combustion under different conditions. The following embodiments illustrate these incomplete combustion problems and the technical means to solve them.

[0069] Example 2:

[0070] like Figure 4 As shown, the spatial arrangement of the two heat storage boxes 10 (first heat storage box 1001 and second heat storage box 1002) and the two burners 7 (first burner 701 and second burner 702) satisfies the requirement that "when the heat storage boxes 10 and the burners 7 are both located on the same side of the furnace 1, the burners 7 are located between the heat storage boxes 10, that is: the fuel sprayed from the burner 7 that is farther away from the heat storage box 10 that receives the secondary combustion air has appropriate secondary combustion air passing through it to help it burn completely". In this embodiment, specifically, the two burners 7 (first burner 701 and second burner 702) are located in the middle of the two heat storage boxes 10 (first heat storage box 1001 and second heat storage box 1002).

[0071] In regenerative thermal combustion technology, a flow field is formed between the regenerative heat storage box 10, which receives the secondary combustion air, and the regenerative heat storage box 10, which discharges flue gas. In traditional diffuse regenerative thermal combustion technology, such as... Figure 3 As shown, one heat storage box 10 corresponds to only one burner 7. Therefore, even if the burner 7 is not in the aforementioned flow field, as long as the distance between the burner 7 and the heat storage box 10 for flue gas exhaust is appropriate, complete combustion can be ensured. In this invention, as... Figure 4As shown, the secondary combustion air input to one regenerator 10 needs to supply more than two burners 7. If a burner 7 located far from the regenerator 10 that inputs the secondary combustion air is not within this flow field, the fuel injected into the furnace 1 by this burner 7 may be drawn away by the exhaust regenerator 10 before mixing with the secondary combustion air, resulting in incomplete combustion. To avoid this, the distance between the two regenerators 10 is relatively large, meaning that the fuel injected by the burner 7 located far from the regenerator 10 that inputs the secondary combustion air receives adequate secondary combustion air to aid in its complete combustion before entering the exhaust regenerator 10.

[0072] Figure 2 The burner arrangement in Comparative Example 2 is not the preferred option. Figure 2 If the first burner 701 is operating while the second burner 702 is also operating, the fuel input into the furnace 1 via the second burner 702 has very little chance of mixing with the secondary combustion air input into the first regenerator 1001 and will enter the second regenerator 1002, which is in a flue gas exhaust state, thus failing to complete combustion (it is worth emphasizing that, although...). Figure 2 The proposed solution is not the preferred solution, but the simultaneous operation of both burners 7 can still solve the technical problem of this invention to a certain extent. Figure 4 In the structure shown in this embodiment, the air input from the outlet of the first heat storage box 1001 gradually participates in combustion and is discharged from the outlet of the second heat storage box 1002. In this way, the airflow will naturally pass through the outlet of the second burner 702, which helps the second burner 702 to burn completely.

[0073] Example 3:

[0074] like Figure 5 The diagram illustrates another spatial arrangement of two heat storage boxes 10 and two burners 7, satisfying the requirement that "when the two heat storage boxes 10 and the two burners 7 are located on different sides of the furnace 1, the lines connecting the two heat storage boxes 10 and the two burners 7 form a quadrilateral, with the two heat storage boxes 10 located at one diagonal of the quadrilateral and the two burners 7 located at the other diagonal of the quadrilateral; that is, the fuel ejected from the burner 7 farther from the heat storage box 10 receiving the secondary combustion air receives appropriate secondary combustion air to aid in its complete combustion." In this embodiment, specifically, within the rectangle formed by the four locations occupied by the two burners 7 and the two heat storage boxes 10, the two heat storage boxes 10 are positioned diagonally.

[0075] Example 4:

[0076] During the low-temperature stage, material 14 occupies space in the furnace 1. Too much natural gas fuel fed into the furnace 1 will result in incomplete combustion and increased energy consumption. Therefore, in the initial stage of the low-temperature stage, the power of each burner 7 should ideally not exceed 40% of its reference power. The system average power in this stage is lower than the system reference average power, but it can be increased to a higher level in subsequent stages to meet overall production speed requirements.

[0077] Specifically, this embodiment is an optimization of Embodiments 1 to 3. During the cold furnace stage when material 14 is first introduced, the actual power of burner 7 is set to be 435 Nm lower than the system's baseline average power. 3 Run at 40% of the power for about 10-20 minutes per hour. Specifically, set the power of both burners to 160 Nm. 3 / hour, the actual power of a single burner 7 is 36.78% of the system's baseline average power, which is less than 40%. With both burners 7 operating simultaneously, the total actual system power is 320 Nm. 3 / hour, with a system baseline average power of 435 Nm 3 The system's average power output during this period is 73.56% of the baseline average power output. The purpose of this optimization is to ensure the system's energy efficiency during the low-temperature phase.

[0078] Example 5:

[0079] In regenerative combustion technology, primary air participates in combustion without being heated by the regenerator 10. Compared to secondary combustion air, which is heated by the regenerator 10 and can be heated to over 1000℃ in the high-temperature stage before entering the furnace 1 for combustion, a high proportion of primary air is not energy-efficient. Therefore, regenerative combustion systems strive to minimize the proportion of primary air while ensuring safety.

[0080] This embodiment is a further optimization of Embodiment 4. In the low-temperature stage immediately following the introduction of material 14, even if each burner 7 is set to operate at no more than 40% of the system's baseline average power, the system's average power during this stage is below 80% of the baseline average power. This is because material 14 occupies the space in the furnace 1, hindering the mixing of secondary combustion air and fuel. The mixing adequacy cannot compare to the adequacy of the mixing of primary air and fuel. This also results in incomplete combustion and increased energy consumption in the furnace 1. In comparison, the energy waste from incomplete combustion far exceeds the energy waste from primary air participating in combustion without being heated, especially in the low-temperature stage, where the secondary combustion air can only be heated to 200-500°C. Therefore, for energy conservation, increasing the proportion of primary air in the low-temperature stage to allow the fuel to burn near the burner 7 and its outlet to achieve near-complete combustion is the preferred method adopted in this invention to reduce incomplete combustion.

[0081] In this embodiment, during the first stage of the low-temperature phase in Embodiment 4, a primary air volume of 1520 Nm is provided. 3 The primary air volume is approximately 50% of the theoretical oxygen required for the total fuel supply of the system's two burners (7 units per hour). This proportion of primary air to total air supply is significantly higher than that of existing technologies.

[0082] In Examples 4 and 5, a total of 53.33 m³ of natural gas was consumed in the first 10 minutes after firing. 3 Compared to Comparative Example 2, this is equivalent to its total power output in the first 32.6 minutes, demonstrating a significant increase in production speed. In contrast, Comparative Example 1 consumed 72.5 Nm in the first 10 minutes. 3 Compared to natural gas, the total power output differs by only 19.16 Nm. 3 Although there is a difference, this difference can be compensated for in 8.8 minutes when the invention enters the high-temperature stage and both burners 7 are working simultaneously, assuming each burner 7 is operating at approximately 65% ​​of the system's baseline average power. This is negligible for the subsequent heating process that lasts for more than 4 hours.

[0083] In fact, all the previous embodiments can switch to the second stage of the low-temperature phase after running for 10-20 minutes in the first stage, increasing the total system power to 400m. 3 After approximately 10-20 minutes of operation per hour, the temperature in a localized area of ​​furnace 1 near burner 7 outlet can reach above the auto-ignition temperature of natural gas. At this point, the total system power can be increased to 435 Nm above the system's baseline average power. 3 / hour, in order to ensure production speed.

[0084] If both low-temperature stages last 20 minutes, and each burner in the high-temperature stage has a power output of 7 Nm, then the total system power is 478.5 Nm, calculated as 55% of the system's baseline average power. 3 The system operates at a rate of 10% per hour, with the average power exceeding the system's baseline average power during the high-temperature phase. The total operating time is: 40÷60+(2100-(320+400)×20÷60)÷478.5=4.55 hours. The production task can be completed ahead of schedule in just 4.55 hours.

[0085] Example 6:

[0086] like Figure 7As shown, this embodiment adds a third burner 7 (703) to the existing embodiment 1, resulting in a configuration of two heat storage boxes 10 + three burners 7. The distance between the two heat storage boxes 10 is greater than the distance between any other pairwise combinations; specifically, the three burners 7 are located between the two heat storage boxes 10. All three burners 7 operate simultaneously and continuously. During the cold furnace stage when material 14 is first introduced, the burner 7 power is set lower than the system's baseline average power of 435 Nm. 3 The system operates at 40% of its capacity for approximately 20 minutes per hour. Specifically, the power of each of the three burners is set to 160 Nm. 3 / hour, which is 36.78% of the burner 7's base power, less than 40%. The total system power is 480 Nm. 3 / hour, with a system baseline average power of 435 Nm 3 / hour 110.3%. After 50 minutes, it can switch to the high-temperature stage. Increase the power of each burner 7 to 225m 3 / hour, the total system power is 675Nm 3 / hour, which is the system's baseline average power of 435 Nm 3 The cycle time is 155% per hour until the operation ends. The total running time is calculated as 50÷60+(2100-480×50÷60)÷675=3.35 hours.

[0087] In this embodiment, the average power of the system at each stage is higher than the system's baseline average power, and the production task can be completed in less than 3.5 hours, which shows that the production speed is greatly improved.

[0088] In actual production trials, we used a technical solution of 2 burners (7+2 heat storage boxes) to achieve a long-term stable smelting of 35 tons of aluminum alloy in 3.5 hours.

[0089] Traditional diffused regenerative combustion technology ( Figure 2 , Figure 3Due to technical limitations, the low-temperature stage typically requires 3-5 sub-stages, with system operating parameters gradually adjusted as the temperature rises over time. However, the low-temperature stage of this invention only requires 1-2 steps. In the initial stage of the low-temperature stage, the local temperature in the local area at the outlet of the upper and lower burners 7 can usually rise to the auto-ignition temperature of the fuel within 10-20 minutes. Therefore, the specific operating time of the initial stage of the low-temperature stage can be determined based on the specific system operating conditions, specifically the time before and after the local temperature in the local area reaches the fuel auto-ignition temperature. A larger local area reaching the fuel auto-ignition temperature results in a larger increase in power in subsequent stages; a smaller local area results in a smaller increase in power. Alternatively, the operating time of this initial stage can be extended until the temperature in most of the furnace 1 area exceeds the fuel auto-ignition temperature, directly transitioning to the high-temperature stage, which is the case where the low-temperature stage only requires 1 step.

[0090] The duration for which the two burners 7 operate simultaneously during the low-temperature stage in the above embodiments can be selected according to the actual situation, such as operating simultaneously during the first half of the low-temperature stage, or operating simultaneously throughout the entire low-temperature stage.

[0091] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the above embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0092] for example:

[0093] In Examples 1-5, two burners 7 can work simultaneously in the low-temperature stage, but in the high-temperature stage, when the furnace 1 is above 700°C, the burners 7 of the prior art can be used to switch working modes in turn; in Example 6, three burners 7 can work simultaneously in the low-temperature stage, and in the high-temperature stage, the middle burner 7 stops working while the other two burners 7 work continuously.

Claims

1. A heating method for materials in a diffuse regenerative combustion industrial furnace, the diffuse regenerative combustion industrial furnace comprising a furnace chamber (1), an airflow reversing system and at least two regenerators (10), wherein burners (7) are installed on the furnace chamber (1), characterized in that, The heating method includes the following steps: Material is loaded into the furnace (1), and flames and fuel are sprayed into the furnace (1) using burners (7). There are at least two burners (7). During a certain period of time in the low temperature stage, at least two burners (7) continue to work without interruption and do not change direction with the airflow reversing system. The low-temperature stage refers to the period from the start of turning on the burner (7) to heat the furnace (1) until the temperature inside the furnace (1) does not reach the auto-ignition temperature of the fuel; Once the temperature of at least a portion of the furnace (1) reaches above the fuel auto-ignition temperature, all burners (7) continue to operate continuously or switch in turn until heating is complete.

2. The heating method according to claim 1, characterized in that, The low-temperature stage includes the following specific time periods: the starting point is when the burner (7) is turned on to heat the furnace (1), and the ending point is when the burner (7) works for 10-60 minutes. This time period is from the starting point to the ending point.

3. The heating method according to claim 1, characterized in that, The secondary combustion air heated by the heat storage box (10) enters the furnace (1) through the main air channel (9). The inlet of the burner (7) is connected to the fuel inlet (8). The outlet of the burner (7) is used to spray flames and fuel into the furnace (1). The heat storage box (10) is set close to the burner (7) to ensure that the secondary combustion air provided by the heat storage box (10) can supply all burners (7) in operation, and promote the complete combustion of the fuel sprayed by the burner (7).

4. The heating method according to claim 1, characterized in that, When the heat storage box (10) and the burner (7) are both located on the same side of the furnace (1), the burner (7) is located between the heat storage boxes (10).

5. The heating method according to claim 1, characterized in that, When the two heat storage boxes (10) and the two burners (7) are located on different sides of the furnace (1), the line connecting the two heat storage boxes (10) and the two burners (7) forms a quadrilateral, and the two heat storage boxes (10) are located at one corner of the quadrilateral, and the two burners (7) are located at the other corner of the quadrilateral.

6. The heating method according to any one of claims 1-5, characterized in that, During the low-temperature stage, at least in one first time period, the actual power of the burner (7) that works continuously without interruption is no greater than 40% of the system's benchmark average power. The actual power of the burner (7) is the ratio of the amount of fuel injected by the burner (7) to the time taken to inject the fuel. The system's benchmark average power is the ratio of the total amount of fuel consumed by each batch of products to the working time for consuming the total amount of fuel.

7. The heating method according to claim 6, characterized in that, The starting point of the first time period is the starting point of the low temperature phase.

8. The heating method according to any one of claims 1-5, characterized in that, During the low-temperature stage, at least one second time period, the total primary air oxygen volume provided in the auxiliary air inlet (6) of the burner (7) that is continuously and uninterruptedly operating is v1, the theoretical oxygen volume required for the combustion of all fuels injected by all burners (7) is v2, and v1 / v2 is not less than 35%.

9. The heating method according to claim 8, characterized in that, The second time period begins at the start of the low-temperature phase.

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