TWI860881B - Method for recovering heat exchange efficiency of industrial furnace - Google Patents

Abstract

A method for recovering heat exchange efficiency of an industrial furnace includes: calculating a current heat exchange efficiency value of the industrial furnace; determining that the exchangeable fins of the self-preheating burners of the industrial furnace are aged when the current heat exchange efficiency value is less than a heat exchange efficiency threshold; and performing a recovery operation on the industrial furnace when the exchangeable fins of the self-preheating burners of the industrial furnace is determined to be aged. The recovery operation includes: performing a multi-objective optimization algorithm to obtain an optimal burner switching time and an optimal burner switching mode from plural candidate burner switching times and plural candidate burner switching modes; and applying the optimal burner switching time and the optimal burner switching mode to control plural self-preheating burners of the industrial furnace.

Description

Method for recovering the heat exchange efficiency of industrial furnaces

The present invention relates to a method for recovering the heat exchange efficiency of an industrial furnace, and in particular to a method for recovering the heat exchange efficiency of an industrial furnace for aging heat exchange fins of a self-preheating burner of the industrial furnace.

A self-preheating burner is a type of burner that is equipped with a heat exchanger and can preheat the combustion gas by recirculating the flue gas in the industrial furnace, thereby recovering waste heat and reducing energy consumption. However, long-term operation of industrial furnaces can cause the heat exchange fins of the self-preheating burner in the industrial furnace to age due to thermal shock, chemical corrosion, mechanical wear, material aging or carbon deposition, which reduces heat exchange efficiency and increases energy consumption. Thermal shock refers to changes in material structure or cracks caused by the transition between high and low temperatures. Chemical corrosion refers to surface corrosion or fouling caused by chemical reactions with corrosive gases. Mechanical wear refers to physical impact or wear during operation that causes shape deformation or reduced surface smoothness. Material aging refers to oxidation or physical and chemical changes caused by long-term operation that degrade material performance.

In order to solve the above problems, the present invention proposes a method for recovering the heat exchange efficiency of an industrial furnace. First, it is determined whether the exchanger fins of the self-preheating burner in the industrial furnace are aged. When it is determined that the exchanger fins of the self-preheating burner in the industrial furnace are aged, a multi-objective optimization algorithm is used to find the optimal burner switching time and the optimal burner switching mode and control the operation of the self-preheating burner of the industrial furnace accordingly, so as to achieve the purpose of recovering the heat exchange efficiency of the industrial furnace.

The technical solution adopted by the present invention is a method for recovering the heat exchange efficiency of an industrial furnace, including: calculating the current heat exchange efficiency value of the industrial furnace; when the current heat exchange efficiency value is less than the heat exchange efficiency threshold value, determining that the heat exchange fins of multiple self-preheating burners of the industrial furnace are in an aged state; and when it is determined that the heat exchange fins of the multiple self-preheating burners are in an aged state, performing a recovery operation on the industrial furnace. The recovery operation includes: executing a multi-objective optimization algorithm to obtain an optimal burner switching time and an optimal burner switching mode from a plurality of candidate burner switching times and a plurality of candidate burner switching modes; and applying the optimal burner switching time and the optimal burner switching mode to control the plurality of self-preheating burners.

In some embodiments, the method for recovering the heat exchange efficiency of the industrial furnace further includes: obtaining the heat exchange efficiency value of the industrial furnace at the factory; and determining the heat exchange efficiency threshold value according to the heat exchange efficiency value at the factory. The heat exchange efficiency value at the factory is the heat exchange efficiency value measured and calculated when the plurality of self-preheating burners perform the combustion operation for the first time. The heat exchange efficiency threshold value is the heat exchange efficiency value at the factory multiplied by a percentage.

In some embodiments, the method for recovering the heat exchange efficiency of an industrial furnace further includes: calculating the heat exchange efficiency value of the industrial furnace after recovery after performing the recovery operation; and shutting down the industrial furnace for maintenance when the heat exchange efficiency value after recovery is not greater than the heat exchange efficiency threshold.

In some embodiments, when the current heat exchange efficiency value is not less than the heat exchange efficiency threshold or when the heat exchange efficiency value after recovery is greater than the heat exchange efficiency threshold, the multiple self-preheating burners continue to use the current operating parameters to perform combustion operations, and calculate the current heat exchange efficiency value again after a predetermined period of time, and when the current heat exchange efficiency value is less than the heat exchange efficiency threshold, the industrial furnace is recovered again.

In some embodiments, the total number of the burners is m, and the recovery operation controls the burners to turn on n of the burners and turn off the other (m-n) of the burners in the first time period and the second time period, respectively, 2≦n≦(m/2).

In some embodiments, the above-mentioned candidate burner switching mode includes an staggered switching scheme, which includes turning on n of the burners that are not adjacent to each other in a first time period, and turning on another n of the burners that are not adjacent to each other in a second time period, and one of the n burners turned on in the first time period and one of the n burners turned on in the second time period are adjacent to each other, wherein the n burners turned on in the first time period are completely different from the n burners turned on in the second time period.

In some embodiments, the candidate burner switching mode includes a sequential switching scheme, which includes turning on the 1st to nth burners in a first time period and turning on the 2nd to n+1th burners in a second time period.

In some embodiments, the time length of each of the first time period and the second time period is equal to the optimal burner switching time, and the optimal burner switching time ranges from 6 seconds to 20 seconds.

In some embodiments, the multi-objective optimization algorithm considers a first objective function and a second objective function, wherein the first objective function is the heat exchange efficiency value of the industrial furnace, and the second objective function is the temperature uniformity of the industrial furnace, and the temperature uniformity is half of the difference between the highest furnace temperature and the lowest furnace temperature of the industrial furnace.

In some embodiments, the objectives of the multi-objective optimization algorithm include: maximizing a first objective function and minimizing a second objective function.

In order to make the above features and advantages of the present invention more clearly understood, embodiments are specifically cited below and described in detail with reference to the accompanying drawings.

The following is a detailed discussion of embodiments of the present invention. However, it is understood that the embodiments provide many applicable concepts that can be implemented in a variety of specific contexts. The embodiments discussed and disclosed are for illustration only and are not intended to limit the scope of the present invention. The terms "first", "second", etc. used herein do not specifically refer to order or sequence, but are only used to distinguish between components or operations described with the same technical terms.

FIG. 1 is a flow chart of a method for recovering the heat exchange efficiency of an industrial furnace according to an embodiment of the present invention. In step S1, the heat exchange efficiency value of the industrial furnace is obtained. The industrial furnace has a plurality of self-preheating burners. The heat exchange efficiency value of step S1 is the heat exchange efficiency value measured and calculated when the plurality of self-preheating burners of the industrial furnace perform the combustion operation for the first time. The calculation formula of the heat exchange efficiency value is shown in the following equation (1):

(1)

FIG2 is a schematic diagram of a self-preheating burner according to an embodiment of the present invention. For example, a temperature sensor (such as a thermocouple) can be installed at each preheating air outlet port OUT of a plurality of self-preheating burners in an industrial furnace to obtain the temperature values (i.e., the preheating air temperature) at the plurality of preheating air outlet ports OUT during the combustion operation. At the same time, a temperature sensor (such as a thermocouple) can be installed at each flue gas inlet port IN of the plurality of self-preheating burners in the industrial furnace to obtain the temperature values (i.e., the furnace temperature) at the plurality of flue gas inlet ports IN during the combustion operation.

As can be seen from the above, each self-preheating burner has its own preheating air temperature and furnace temperature. In some embodiments, the heat exchange efficiency value corresponding to the combustion operation can be found by using a statistical method (e.g., using a minimum value, a maximum value, an average value, or a median, etc.) to find a heat exchange efficiency value that can represent the combustion operation of multiple self-preheating burners, but the embodiments of the present invention are not limited thereto.

In step S2, the heat exchange efficiency threshold is determined based on the factory heat exchange efficiency value obtained in step S1. In the embodiment of the present invention, the heat exchange efficiency threshold is the factory heat exchange efficiency value multiplied by a percentage. For example, the heat exchange efficiency threshold can be 70%, 80% or 90% of the factory heat exchange efficiency value, and the percentage can be set according to actual needs to determine the heat exchange efficiency threshold.

In step S3, the current heat exchange efficiency value of the industrial heat treatment furnace (referred to as the current heat exchange efficiency value in the present invention) is calculated. The calculation formula of the heat exchange efficiency value is as shown in the above equation (1).

In step S4, it is determined whether the current heat exchange efficiency value is less than the heat exchange efficiency threshold value. When the determination result of step S4 is yes, it is determined that the heat exchange fins of the self-preheating burner of the industrial furnace are in an aging state and the process proceeds to step S5: a recovery operation is performed on the industrial furnace to recover the heat exchange efficiency of the industrial furnace.

The heat exchange fins of the self-preheating burner of the above industrial furnace mainly play the role of heat exchange in the industrial furnace, and their life and performance directly affect the operating efficiency and life of the industrial furnace. When the heat exchange fins age due to long-term operation of the industrial furnace, the heat exchange efficiency of the industrial furnace will decrease. The present invention improves (or is called rejuvenating) the heat exchange efficiency by performing a rejuvenating operation on the industrial furnace.

Specifically, in step S4, if the current heat exchange efficiency value is less than the heat exchange efficiency threshold value, it means that the heat exchange fins of the self-preheating burner of the industrial furnace have aged due to long-term operation, resulting in a decrease in the heat exchange efficiency of the industrial furnace. Therefore, the recovery operation of step S5 is required to improve (or is called recovery) the heat exchange efficiency of the industrial furnace.

In addition, when the judgment result of step S4 is no, the process proceeds to step S9, and the industrial furnace continues to use the current operating parameters to perform combustion operation.

The recovery operation of step S5 includes step S51 and step S52 in sequence. In step S511, a multi-objective optimization algorithm is executed to obtain an optimal burner switching time and an optimal burner switching mode from a plurality of candidate burner switching times and a plurality of candidate burner switching modes. In step S52, the optimal burner switching time and the optimal burner switching mode are applied to control a plurality of self-preheating burners of the industrial furnace to perform combustion operations accordingly.

Specifically, the present invention controls the on/off switching time and switching mode of multiple self-preheating burners of the industrial furnace through the recovery operation of step S5. Among them, the appropriate switching time can ensure the stability of heat exchange conditions and improve the heat exchange efficiency. Among them, by properly adjusting the switching mode of the self-preheating burner, the heat distribution can be optimized and the heat exchange efficiency can be improved.

The present invention proposes a plurality of different burner switching times (i.e., a plurality of candidate burner switching times) and a plurality of different burner switching modes (i.e., a plurality of candidate burner switching modes), and constitutes a plurality of groups of combinations of a single candidate burner switching time and a single candidate burner switching mode. If the self-preheating burners of the industrial furnace are controlled separately according to these combinations to perform combustion operations accordingly, there will be different heat exchange efficiencies and different furnace body temperature uniformity. Therefore, the present invention obtains an optimal burner switching time and an optimal burner switching mode through a multi-objective optimization algorithm in step S51, and controls the self-preheating burner of the industrial furnace to perform combustion operations accordingly, so as to achieve the purpose of recovering the heat exchange efficiency of the industrial furnace.

In an embodiment of the present invention, a plurality of candidate burner switching times include: 6 seconds, 7 seconds, ..., 20 seconds. In an embodiment of the present invention, a plurality of candidate burner switching modes include: an interleaved switching scheme and a sequential switching scheme.

FIG3 is used to illustrate the operation of the staggered switching scheme. The self-preheating burners in FIG3 are taken as an example, with a total of 6 (i.e., self-preheating burners B1 to B6), 2 on, and 4 off, and the burner switching time adopted by the self-preheating burners in FIG3 is 6 seconds. As shown in FIG3 , the staggered switching scheme of FIG3 turns on two of the six self-preheating burners (i.e., self-preheating burners B1 and B3) that are not adjacent to each other in the first time period T1 (i.e., the left figure of FIG3 ) (i.e., 0 to 6 seconds), and the staggered switching scheme of FIG3 turns on the other two of the six self-preheating burners (i.e., self-preheating burners B2 and B4) that are not adjacent to each other in the second time period T2 (i.e., the right figure of FIG3 ) (i.e., 6 to 12 seconds). One of the self-preheating burners B1 and B3 turned on in the first time period T1 and one of the self-preheating burners B2 and B4 turned on in the second time period T2 are adjacent to each other. The self-preheating burners B1 and B3 turned on in the first time period T1 are completely different from the self-preheating burners B2 and B4 turned on in the second time period T2. In other words, the time length (i.e., 6 seconds) of each of the first time period T1 (i.e., 0-6 seconds) and the second time period T2 (i.e., 6-12 seconds) is equal to the burner switching time (i.e., 6 seconds).

It should be noted that, for the sake of convenience of explanation, FIG3 does not show the operations after the second time period T2, but those skilled in the art should understand that, according to the rule presented in FIG3, the self-preheating burners B3 and B5 are turned on in the next time period after the second time period T2 (i.e., 13 to 18 seconds), and the self-preheating burners B4 and B6 are turned on at 19 to 24 seconds, and the self-preheating burners B5 and B1 are turned on at 25 to 30 seconds, and the self-preheating burners B6 and B2 are turned on at 31 to 36 seconds, and the self-preheating burners B1 and B3 are turned on at 37 to 42 seconds, and so on.

FIG4 is used to illustrate the operation of the sequential switching scheme. The self-preheating burners in FIG4 are taken as an example, with a total of 6 (i.e., self-preheating burners B1 to B6), 2 turned on, and 4 turned off, and the burner switching time adopted by the self-preheating burners in FIG4 is 6 seconds. As shown in FIG4, the sequential switching scheme of FIG4 turns on the first to the second of the 6 self-preheating burners (i.e., self-preheating burners B1 and B2) in the first time period T1 (i.e., the left figure of FIG4), and the sequential switching scheme of FIG4 turns on the second to the third of the 6 self-preheating burners (i.e., self-preheating burners B2 and B3) in the second time period T2 (i.e., the right figure of FIG4).

It should be noted that, for the sake of convenience of explanation, FIG4 does not show the operations after the second time period T2, but those skilled in the art should understand that, according to the rule presented in FIG4, the self-preheating burners B3 and B4 are turned on in the next time period after the second time period T2 (i.e., 13 to 18 seconds), and the self-preheating burners B4 and B5 are turned on at 19 to 24 seconds, and the self-preheating burners B5 and B6 are turned on at 25 to 30 seconds, and the self-preheating burners B6 and B1 are turned on at 31 to 36 seconds, and the self-preheating burners B1 and B2 are turned on at 37 to 42 seconds, and so on.

In an embodiment of the present invention, the total number of self-preheating burners is m, and the recovery operation of step S5 controls the m self-preheating burners to turn on n of the self-preheating burners and turn off the other (m-n) of the self-preheating burners in the first time period and the second time period, respectively, where 2≦n≦(m/2).

In addition, since an optimal burner switching time and an optimal burner switching mode are taken from multiple candidate burner switching times and multiple candidate burner switching modes, the time length of each of the first time period and the second time period is equal to the optimal burner switching time, and the optimal burner switching time ranges from 6 seconds to 20 seconds, and the optimal burner switching mode is an interlaced switching scheme or a sequential switching scheme.

The multi-objective optimization algorithm of step S51 considers a first objective function and a second objective function, wherein the first objective function is the heat exchange efficiency value of the industrial furnace, and the second objective function is the temperature uniformity of the industrial furnace, and the temperature uniformity is half of the difference between the highest furnace temperature and the lowest furnace temperature of the industrial furnace.

The objectives of the multi-objective optimization algorithm of step S51 include: maximizing the first objective function and minimizing the second objective function, that is, the objectives of the multi-objective optimization algorithm of step S51 are high heat exchange efficiency and small furnace temperature difference, but the above objectives are only examples, and the present invention is not limited thereto. For example, the objective of the multi-objective optimization algorithm can also be to maximize the first objective function under the premise that the second objective function is less than 20°C.

In an embodiment of the present invention, the multi-objective optimization algorithm of step S51 includes determining a Pareto front, wherein the Pareto front establishes a relationship between a first objective function and a second objective function. The Pareto front can be determined to establish a relationship between any suitable first objective function and a second objective function.

The Pareto front can be used to deal with multi-objective optimization problems. It is necessary to consider multiple objective functions (primary objective function and secondary objective function) at the same time, use the Pareto front to find multiple solutions, and obtain a set of optimal solutions. The Pareto front includes: non-dominated sorting, crowding calculation and elite retention strategy. Non-dominated sorting distinguishes the pros and cons of decomposition. The crowding calculation is that the larger the crowding value, the farther the distance between the solution and its neighboring solutions, and the higher the diversity of the solution; conversely, the smaller the crowding value, the closer the distance between the solution and its neighboring solutions, and the lower the diversity of the solution. The elite retention strategy is used to retain excellent individuals to accelerate the convergence speed of the algorithm and improve the search efficiency.

Specifically, a plurality of non-dominated solutions (or decision variables) are obtained by combining the first objective function and the second objective function with a multi-objective optimization algorithm. More specifically, the first objective function and the second objective function are combined with a multi-objective optimization algorithm to find a Pareto front formed by a plurality of non-dominated solutions. In an embodiment of the present invention, a non-dominated solution is a set of candidate burner switching times and candidate burner switching modes. For the solution dominated by it, it has better results on each objective function, but if compared with another non-dominated solution, the two non-dominated solutions must have better results on the first objective function or the second objective function, that is, the two non-dominated solutions have their own unique and better target values. A non-dominated solution is the best decision that can be made under the decision of a multi-objective optimization algorithm. More precisely, it is to find an optimal compromise between the first objective function and the second objective function, which allows a non-dominated solution to have a unique advantage in a certain decision objective (such as maximizing the first objective function and minimizing the second objective function). It is also worth mentioning that since the Pareto frontier search of a multi-objective optimization algorithm is generally more complicated, the present invention can further optimize this problem by using historical data (in addition, the historical data can also be pre-processed) to model the model.

FIG. 5 shows a Via Plato front for establishing a relationship between a first objective function _f1 and a second objective function _f2 . As described above, the decision-making method of the Plato front is to find an optimal compromise between the first objective function and the second objective function. The Plato front is defined as a relationship between a first objective function and a second objective function associated with a multi-objective optimization problem. The Plato front can be established by calculating a plurality of candidate burner switching times and a plurality of candidate burner switching modes, and determining the measure of the objective function for each set of candidate burner switching times and candidate burner switching modes. In FIG. 5 , each dot represents the first target function value (i.e., the heat exchange efficiency value of the industrial furnace) and the second target function value (i.e., the temperature uniformity of the industrial furnace) obtained after applying each set of candidate burner switching time and candidate burner switching mode to control the self-preheating burner of the industrial furnace.

For more information about "multi-objective optimization", please refer to the description of "Multi-objective optimization" on the Wikipedia website (http://en.wikipedia.org/wiki/Multiobjective_optimization). For more information about "Pareto front", please refer to the description on the Wikipedia website (https://en.wikipedia.org/wiki/Pareto_front). In addition, the present invention is not intended to limit the specific method of solving "multi-objective optimization". For example, in addition to using the Pareto front method, the present invention can also assign different weights to each set of candidate burner switching time and candidate burner switching mode, and then use the "Analytical Hierarchy Process (AHP)" method to obtain "multi-objective optimization". For more information about "Analytic Hierarchy Process", please refer to the description of "Analytic Hierarchy Process" on the Wikipedia website (http://en.wikipedia.org/wiki/Analytic_Hierarchy_Process).

The specific method of applying the optimal burner switching time and the optimal burner switching mode to control the multiple self-preheating burners of the industrial furnace to perform combustion operations accordingly in step S52 is to be realized through a programmable logic controller (PLC) feedback control. In detail, the optimal burner switching time and the optimal burner switching mode can be input into the programmable logic controller to control the opening/closing of the multiple self-preheating burners of the industrial furnace.

Please return to Figure 1. After the industrial furnace is revived in step S5, the process proceeds to step S6 to calculate the heat exchange efficiency value of the industrial furnace after the revivification operation (referred to as the post-revivification heat exchange efficiency value in the present invention). The heat exchange efficiency value calculation formula is as shown in the above equation (1).

In step S7, it is determined whether the heat exchange efficiency value after recovery is greater than the heat exchange efficiency threshold value. When the result of the determination in step S7 is yes, it returns to step S9, and the industrial furnace continues to use the current operating parameters to perform combustion operations. When the result of the determination in step S7 is no, it means that the heat exchange efficiency of the industrial furnace cannot be improved (or called recovery) through the recovery operation. The reason may be that the heat exchange fins of the self-preheating burner of the industrial furnace have aged too seriously or there are other furnace problems. Simply performing the recovery operation cannot restore the heat exchange efficiency of the industrial furnace, so it is necessary to shut down the industrial furnace for maintenance (i.e., step S8).

In addition, since the cause of aging of the heat exchange fins is due to the long-term operation of the industrial furnace, after the industrial furnace in step S9 continues to use the current operating parameters to perform combustion operations, it will return to step S3 again after a predetermined period of time (i.e., step S10) to calculate the current heat exchange efficiency value, and then perform step S4 to check whether the current heat exchange efficiency value is less than the heat exchange efficiency threshold value to determine whether to perform the recovery operation of step S5.

In summary, the present invention proposes a method for recovering the heat exchange efficiency of an industrial furnace. First, it is determined whether the heat exchange fins of the self-preheating burner of the industrial furnace are aged. When it is determined that the heat exchange fins of the self-preheating burner of the industrial furnace are aged, a multi-objective optimization algorithm is used to find the optimal burner switching time and the optimal burner switching mode and control the operation of the self-preheating burner of the industrial furnace accordingly, so as to achieve the purpose of recovering the heat exchange efficiency of the industrial furnace. The preferred benefits that can be achieved by the present invention include: (1) Extending the life of equipment: Through recovery operations and shutdown inspections, equipment can be maintained and repaired in a timely manner, thereby extending the service life of the furnace body and reducing long-term replacement and maintenance costs. (2) Efficiency improvement: Effectively improve the heat exchange efficiency, enabling it to perform heat exchange more effectively. (3) Smart decision-making: Through modeling and multi-objective optimization algorithms to formulate maintenance plans and management strategies, decisions are more based on evidence and management efficiency is further improved.

The above summarizes the features of several embodiments, so that those skilled in the art can better understand the present invention. Those skilled in the art should understand that they can easily use the present invention as a basis to design or modify other processes and structures to achieve the same goals and/or achieve the same advantages as the embodiments introduced herein. Those skilled in the art should also understand that these equivalent constructions do not deviate from the spirit and scope of the present invention, and they can make various changes, substitutions and modifications without departing from the spirit and scope of the present invention.

B1, B2, B3, B4, B5, B6: self-preheating burner f ₁ : first target function f ₂ : second target function IN: flue gas inlet OUT: preheating air outlet S1, S2, S3, S4, S5, S51, S52, S6, S7, S8, S9, S10: step T1: first time period T2: second time period

The present invention will be better understood from the following detailed description in conjunction with the accompanying drawings. It should be noted that, in accordance with standard industry practice, the features are not drawn to scale. In fact, the dimensions of the features may be increased or decreased at will to facilitate discussion. [FIG. 1] is a flow chart of a method for recovering the heat exchange efficiency of an industrial furnace according to an embodiment of the present invention. [FIG. 2] is a schematic diagram of a self-preheating burner according to an embodiment of the present invention. [FIG. 3] is used to illustrate the operation of the staggered switching scheme. [FIG. 4] is used to illustrate the operation of the sequential switching scheme. [FIG. 5] shows a Viplatograph front edge that establishes a relationship between a first objective function and a second objective function.

S1,S2,S3,S4,S5,S51,S52,S6,S7,S8,S9,S10: Steps

Claims (10)

A method for recovering the heat exchange efficiency of an industrial furnace, the industrial furnace having a plurality of self-preheating burners, the method comprising: calculating a current heat exchange efficiency value of an industrial furnace; when the current heat exchange efficiency value is less than a heat exchange efficiency threshold value, determining that the heat exchange fins of the self-preheating burners are in an aged state; and when the heat exchange fins of the self-preheating burners are determined to be in an aged state, performing a recovery operation on the industrial furnace, comprising: performing a multi-objective optimization (multi-objective optimization) Optimization) algorithm is used to obtain an optimal burner switching time and an optimal burner switching mode from a plurality of candidate burner switching times and a plurality of candidate burner switching modes, wherein the multi-objective optimization algorithm considers a first objective function and a second objective function, the first objective function is a heat exchange efficiency value of the industrial furnace, and the second objective function is a temperature uniformity of the industrial furnace; and the optimal burner switching time and the optimal burner switching mode are applied to control the self-preheating burners. The method for recovering the heat exchange efficiency of an industrial furnace as described in claim 1 further includes: obtaining a heat exchange efficiency value of the industrial furnace at the factory; and determining the heat exchange efficiency threshold value according to the heat exchange efficiency value at the factory; wherein the heat exchange efficiency value at the factory is the heat exchange efficiency value measured and calculated when the self-preheating burners perform the combustion operation for the first time; wherein the heat exchange efficiency threshold value is the heat exchange efficiency value at the factory multiplied by a percentage. The method for recovering the heat exchange efficiency of an industrial furnace as described in claim 1 further includes: calculating a post-recovery heat exchange efficiency value of the industrial furnace after performing the recovery operation; and shutting down the industrial furnace for maintenance when the post-recovery heat exchange efficiency value is not greater than the heat exchange efficiency threshold. A method for recovering the heat exchange efficiency of an industrial furnace as described in claim 3, wherein when the current heat exchange efficiency value is not less than the heat exchange efficiency threshold or when the heat exchange efficiency value after recovery is greater than the heat exchange efficiency threshold, the self-preheating burners continue to use the current operating parameters to perform combustion operations, and after a predetermined period of time, the current heat exchange efficiency value is calculated again and when the current heat exchange efficiency value is less than the heat exchange efficiency threshold, the recovery operation is performed on the industrial furnace again. A method for recovering the heat exchange efficiency of an industrial furnace as described in claim 1, wherein the total number of the burners is m, wherein the recovery operation controls the burners to open n of the burners and close the other (m-n) of the burners in a first time period and a second time period, respectively, wherein 2≦n≦(m/2). A method for recovering the heat exchange efficiency of an industrial furnace as described in claim 5, wherein the candidate burner switching patterns include an interleaved switching scheme, wherein the interleaved switching scheme includes turning on n of the burners that are not adjacent to each other in the first time period, and turning on another n of the burners that are not adjacent to each other in the second time period, and one of the n burners turned on in the first time period and one of the n burners turned on in the second time period are adjacent to each other, wherein the n burners turned on in the first time period are completely different from the n burners turned on in the second time period. A method for recovering the heat exchange efficiency of an industrial furnace as described in claim 5, wherein the candidate burner switching modes include a sequential switching scheme, wherein the sequential switching scheme includes turning on the 1st to nth of the burners in the first time period, and turning on the 2nd to n+1th of the burners in the second time period. A method for recovering the heat exchange efficiency of an industrial furnace as described in claim 5, wherein the time length of each of the first time period and the second time period is equal to the optimal burner switching time, and the optimal burner switching time ranges from 6 seconds to 20 seconds. A method for recovering the heat exchange efficiency of an industrial furnace as described in claim 1, wherein the temperature uniformity is half of the difference between a maximum furnace temperature and a minimum furnace temperature of the industrial furnace. A method for recovering the heat exchange efficiency of an industrial furnace as described in claim 1, wherein the objectives of the multi-objective optimization algorithm include: maximizing the first objective function and minimizing the second objective function.

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