A method for optimizing temperature setting of cement kiln decomposition furnace

Abstract

This invention discloses a method for optimizing the temperature setting of a cement kiln precalciner, relating to the field of cement kiln production optimization control. Based on thermodynamic principles, it utilizes the kiln main transmission current, secondary air temperature, comprehensive kiln condition indicators, and head-to-tail coal ratio to derive a recommended strategy for the precalciner outlet temperature setpoint. The method categorizes and discusses the priority of each strategy and the adjustment range of the precalciner outlet temperature setpoint under that strategy, and then comprehensively considers the control of the precalciner coal feed rate to ensure the stability of the precalciner outlet temperature. Ultimately, this increases the carbonate decomposition rate of the raw meal entering the kiln, thereby reducing the kiln's heat load, extending the cement kiln's operating cycle, and improving product quality. This alleviates the high energy consumption problem caused by the rapid development of the cement industry, ultimately enabling the cement industry to achieve energy conservation, emission reduction, and sustainable development.

Description

Technical Field

[0001] This invention relates to the field of cement kiln production optimization control, and in particular to a method for optimizing the temperature setting of a cement kiln decomposition furnace. Background Technology

[0002] Cement is a fundamental raw material in economic construction. In recent years, my country's cement industry has developed rapidly, and its cement production ranks first in the world. However, the continuous increase in cement production has also brought about high energy consumption. In order to respond to the call for energy conservation and emission reduction, my country's cement industry urgently needs to carry out industrial restructuring and technological innovation and upgrading. Applying new dry process cement production technology and continuously optimizing production control strategies are important ways for the cement industry to achieve energy conservation, emission reduction, and sustainable development. The decomposition furnace system is one of the core components of the new dry process cement clinker calcination system.

[0003] A decomposition furnace is a device that draws preheated and dispersed raw meal powder, passed through a preheater, into the furnace via a blower. This powder is then placed in a relatively dispersed and suspended state within the airflow to facilitate rapid fuel combustion and calcium carbonate decomposition. Internally, fuel combustion occurs simultaneously with the chemical reaction that allows the material to absorb energy, all under intense turbulence. The fuel particles are in a state of simultaneous floating and burning, thus preventing flame generation and maintaining a low-temperature, flameless state of 820–900°C. While decomposition furnaces come in various types and their structures and performance differ, their primary function remains the same: to ensure that the exothermic process of fuel combustion and the endothermic process of raw meal carbonate decomposition proceed extremely rapidly in a suspended or fluidized state. This increases the decomposition rate of the raw meal carbonate entering the kiln, thereby reducing the kiln's thermal load, extending its operating cycle, and improving product quality. The decomposition furnace outlet temperature is a key process parameter affecting the decomposition rate. The decomposition furnace is directly connected to the rotary kiln and the suspension preheater, resulting in significant equipment interconnections. The mechanisms of combustion, heat transfer, and decomposition processes within the furnace are complex. Consequently, the temperature process in the decomposition furnace presents control challenges such as nonlinearity, pure time delay, multiple variables, input-output constraints, and uncertain disturbances. Therefore, studying the target value for temperature control in the decomposition furnace is of great significance for improving the control performance of the temperature process in the decomposition furnace, thereby enhancing product quality and production efficiency. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for optimizing the temperature setting of a cement kiln decomposition furnace.

[0005] The technical problem to be solved by this invention:

[0006] How can we overcome the numerous difficulties in the temperature control of the decomposer furnace by adjusting the key process parameter—the outlet temperature of the decomposer furnace—such as nonlinearity, pure time delay, multiple variables, input-output constraints, and uncertain interference, so that the exothermic process of fuel combustion and the endothermic process of raw material carbonate decomposition can proceed extremely rapidly in a suspended or fluidized state, thereby increasing the decomposition rate of raw material carbonate entering the kiln, and thus achieving the goals of reducing the heat load of the kiln, increasing the operating cycle of the cement kiln, and improving product quality?

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] A method for optimizing the temperature setting of a cement kiln preheating furnace includes the following steps:

[0009] (1) Using factors such as kiln main current, secondary air temperature, kiln condition comprehensive index, head and tail coal ratio, etc., the recommended strategy for the set value of the decomposition furnace outlet temperature is derived. There are seven recommended strategies: long-term high kiln current, long-term low kiln current, kiln condition fluctuation, raw material SM, kiln condition comprehensive index, quality stability, and theoretical optimization value of decomposition furnace temperature.

[0010] (2) Prioritize the seven strategies;

[0011] (3) The adjustment range of the decomposition furnace outlet temperature setpoint under any strategy is classified and discussed, and then the control of the coal feed rate of the decomposition furnace is comprehensively considered to ensure the stability of the decomposition furnace outlet temperature.

[0012] The following are seven recommended strategies for controlling the outlet temperature of the decomposer: (Table 1)

[0013] Table 1

[0014]

[0015]

[0016] The above strategies can only be executed if the following conditions are met simultaneously:

[0017] (1) When the secondary air temperature or kiln current fluctuates too much, the set value should not be reduced;

[0018] (2) When the kiln current rises or falls significantly, the set value is not increased or decreased;

[0019] (3) When the kiln current is at a high or low level, the set value is not increased or decreased (the kiln current is not considered in the quality strategy).

[0020] (4) When the overall kiln condition index is good or bad, the set value should not be increased or decreased;

[0021] (5) If the free calcium quality test data is poor, the set value should not be lowered;

[0022] (6) When the brightness of the fire is low, the set value should not be reduced;

[0023] (7) When the ammonia flow rate is low, the set value should not be reduced;

[0024] (8) When the ammonia water flow rate trend declines, the set value should not be reduced;

[0025] (9) When the CO at the preheater outlet exceeds the upper limit, the set value is not increased;

[0026] (10) If the new recommended value changes in the same direction as before after the set value changes, keep the original change for 1 hour before changing it again.

[0027] (11) When the outlet temperature of the decomposition furnace exceeds a certain value and the outlet temperature of C5 exceeds a certain value, the set value will not be increased.

[0028] When multiple recommended strategies are available to execute simultaneously, the strategy with the lower priority value is executed first. Based on the specific recommended strategy, calculations are performed using relevant data, followed by conditional judgments, and finally, the setpoint for the decomposition furnace outlet temperature is adjusted. Specifically, as follows... Figure 1 As shown.

[0029] The priority of the recommended strategies and the data calculation are as follows:

[0030] (1) The kiln current is high for a long time:

[0031] Priority: 1

[0032] Data calculation: Take 10 kiln main transmission current data as a group. Under the premise that the average value of the previous group of data is greater than the upper limit of the kiln current setting, if either the average value of the most recent group of data is greater than the upper limit of the kiln current setting +10 or the kiln skin shedding state is less than 0.6, it is judged that the kiln current is high for a long time, and the target temperature of the decomposition furnace is controlled at -1℃.

[0033] (2) Kiln current has been declining for a long time:

[0034] Priority: 2

[0035] Data Calculation: Condition 1: Current kiln current is low, satisfied when the average of the last 5 kiln current data is < (target value of kiln main transmission current + lower limit of kiln main transmission current) / 2; Condition 2: Future kiln current is low, satisfied when the average of the last 15 kiln current data + 180·slope is < lower limit of kiln current; Condition 3: Kiln current decreases, satisfied when the slope is ≤ -0.2. When all the above conditions are met, the change value of the decomposition furnace temperature = max(0, - kiln current long-term trend ratio·60·slope·3-hour current linear fitting R2).

[0036] (3) Kiln condition fluctuations:

[0037] Priority: 3

[0038] Data Calculation: Calculate the magnitude and frequency of fluctuations in secondary air temperature and kiln current. Set the adjustment threshold for fluctuation magnitude to 25, the lower limit for air temperature fluctuation frequency to 2, and the upper limit for air temperature fluctuation frequency to 5. If the magnitude of fluctuation in secondary air temperature or kiln current is greater than 25 and 2 < fluctuation frequency < 5, it is determined that the fluctuations in kiln current and secondary air temperature are relatively large, and the target value for the decomposition furnace outlet temperature is increased by 1℃.

[0039] (4) Raw material SM:

[0040] Priority: 4

[0041] Data Calculation: Calculate the difference between the previous raw meal SM and the current raw meal SM. If the difference is ≥0.02, the target change value of the decomposer outlet temperature = 20 * difference; if the difference is ≥0.06, the target change value of the decomposer outlet temperature = 25 * difference; if the difference is ≤0.02, the target change value of the decomposer outlet temperature = 10 * difference.

[0042] (5) Comprehensive kiln condition indicators:

[0043] Priority: 5

[0044] Data Calculation: A comprehensive kiln condition index filter is calculated based on free calcium, kiln temperature, main transmission current, etc., and the kiln condition index proportional coefficient is set to 5. If the ratio of -comprehensive kiln condition index filter to kiln condition index proportional coefficient > 0.1, the kiln condition is poor, and the temperature control target value is increased; if the ratio of -comprehensive kiln condition index filter to kiln condition index proportional coefficient < -0.1, the kiln condition is good, and the temperature control target value is decreased, with a gain of 3.

[0045] (6) Stable quality:

[0046] Priority: 6

[0047] Data calculation: If free calcium is above the upper limit, increase the temperature control target value; if free calcium is below the lower limit, decrease the temperature control target value. Temperature control target value adjustment range = 3 * (current free calcium - free calcium target value).

[0048] (7) Theoretical Optimized Value of Decomposition Furnace Temperature

[0049] Priority: 7

[0050] Data calculation: If the recommended value of C5 feed pipe temperature is greater than the current target value of C5 feed pipe temperature, then the adjustment range of the decomposition furnace temperature control target value is min(difference, 0.3℃); if the recommended value of C5 feed pipe temperature is less than the current target value of C5 feed pipe temperature, then the adjustment range of the decomposition furnace temperature control target value is max(difference, -0.3℃).

[0051] The above recommended strategies control the setpoint of the decomposer outlet temperature according to priority. When multiple recommended strategies are available to execute simultaneously, the strategy with the lower priority value is executed first. If the setpoint of the decomposer outlet temperature is manually changed while the algorithm is running, the manually changed setpoint will be temporarily maintained for a period of time, after which the setpoint will be recalculated.

[0052] The beneficial effects obtained by this invention are as follows:

[0053] This invention provides a method for optimizing the temperature setting of a cement kiln decomposer. By adjusting the key process parameter—the decomposer outlet temperature—and comprehensively considering the control of the coal feed rate in the decomposer, this method is of great significance for improving the temperature control performance of the decomposer, thereby improving product quality and production efficiency. Attached Figure Description

[0054] Figure 1 A flowchart for calculating the recommended strategy for the control setpoint of the decomposer outlet temperature. Detailed Implementation

[0055] The following description of the embodiments will provide a more detailed explanation of the specific implementation of the present invention, in order to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.

[0056] Example:

[0057] A method for optimizing the temperature setting of a cement kiln preheating furnace, comprising the following specific steps:

[0058] (1) Using factors such as kiln main current, secondary air temperature, kiln condition comprehensive index, head and tail coal ratio, etc., the recommended strategy for the set value of the decomposition furnace outlet temperature is derived. There are seven recommended strategies: long-term high kiln current, long-term low kiln current, kiln condition fluctuation, raw material SM, kiln condition comprehensive index, quality stability, and theoretical optimization value of decomposition furnace temperature.

[0059] (2) The seven strategies are ranked from priority 1 to priority 7: long-term high kiln current (priority 1) > long-term decrease in kiln current (priority 2) > kiln condition fluctuation (priority 3) > raw material SM (priority 4) > comprehensive kiln condition index (priority 5) > stable quality (priority 6) > theoretical optimized value of decomposer temperature (priority 7).

[0060] (3) The adjustment range of the decomposition furnace outlet temperature setpoint under any strategy is classified and discussed, and then the control of the coal feed rate of the decomposition furnace is comprehensively considered to ensure the stability of the decomposition furnace outlet temperature.

[0061] The data for the seven recommendation strategies are calculated as follows:

[0062] (1) The kiln current is high for a long time:

[0063] Priority: 1

[0064] Data calculation: Take 10 kiln main transmission current data as a group. Under the premise that the average value of the previous group of data is greater than the upper limit of the kiln current setting, if either the average value of the most recent group of data is greater than the upper limit of the kiln current setting +10 or the kiln skin shedding state is less than 0.6, it is judged that the kiln current is high for a long time, and the target temperature of the decomposition furnace is controlled at -1℃.

[0065] (2) Kiln current has been declining for a long time:

[0066] Priority: 2

[0067] Data Calculation: Condition 1: Current kiln current is low, satisfied when the average of the last 5 kiln current data is < (target value of kiln main transmission current + lower limit of kiln main transmission current) / 2; Condition 2: Future kiln current is low, satisfied when the average of the last 15 kiln current data + 180·slope is < lower limit of kiln current; Condition 3: Kiln current decreases, satisfied when the slope is ≤ -0.2. When all the above conditions are met, the change value of the decomposition furnace temperature = max(0, - kiln current long-term trend ratio·60·slope·3-hour current linear fitting R2).

[0068] (3) Kiln condition fluctuations:

[0069] Priority: 3

[0070] Data Calculation: Calculate the magnitude and frequency of fluctuations in secondary air temperature and kiln current. Set the adjustment threshold for fluctuation magnitude to 25, the lower limit for air temperature fluctuation frequency to 2, and the upper limit for air temperature fluctuation frequency to 5. If the magnitude of fluctuation in secondary air temperature or kiln current is greater than 25 and 2 < fluctuation frequency < 5, it is determined that the fluctuations in kiln current and secondary air temperature are relatively large, and the target value for the decomposition furnace outlet temperature is increased by 1℃.

[0071] (4) Raw material SM:

[0072] Priority: 4

[0073] Data Calculation: Calculate the difference between the previous raw meal SM and the current raw meal SM. If the difference is ≥0.02, the target change value of the decomposer outlet temperature = 20 * difference; if the difference is ≥0.06, the target change value of the decomposer outlet temperature = 25 * difference; if the difference is ≤0.02, the target change value of the decomposer outlet temperature = 10 * difference.

[0074] (5) Comprehensive kiln condition indicators:

[0075] Priority: 5

[0076] Data Calculation: A comprehensive kiln condition index filter is calculated based on free calcium, kiln temperature, main transmission current, etc., and the kiln condition index proportional coefficient is set to 5. If the ratio of -comprehensive kiln condition index filter to kiln condition index proportional coefficient > 0.1, the kiln condition is poor, and the temperature control target value is increased; if the ratio of -comprehensive kiln condition index filter to kiln condition index proportional coefficient < -0.1, the kiln condition is good, and the temperature control target value is decreased, with a gain of 3.

[0077] (6) Stable quality:

[0078] Priority: 6

[0079] Data calculation: If free calcium is above the upper limit, increase the temperature control target value; if free calcium is below the lower limit, decrease the temperature control target value. Temperature control target value adjustment range = 3 * (current free calcium - free calcium target value).

[0080] (7) Theoretical Optimized Value of Decomposition Furnace Temperature

[0081] Priority: 7

[0082] Data calculation: If the recommended value of C5 feed pipe temperature is greater than the current target value of C5 feed pipe temperature, then the adjustment range of the decomposition furnace temperature control target value is min(difference, 0.3℃); if the recommended value of C5 feed pipe temperature is less than the current target value of C5 feed pipe temperature, then the adjustment range of the decomposition furnace temperature control target value is max(difference, -0.3℃).

[0083] The above recommended strategy controls the setpoint of the decomposition furnace outlet temperature according to priority. If the setpoint of the decomposition furnace outlet temperature is manually changed while the algorithm is being executed, the manually setpoint will be temporarily maintained for a period of time, and the setpoint will be recalculated after the time has elapsed.

[0084] The above recommended strategy controls the setpoint of the decomposition furnace outlet temperature according to priority. If the setpoint of the decomposition furnace outlet temperature is manually changed while the algorithm is being executed, the manually setpoint will be temporarily maintained for a period of time, and the setpoint will be recalculated after the time has elapsed.

[0085] In summary, by adjusting the key process parameter—the decomposition furnace outlet temperature—the decomposition rate of carbonates in the raw feedstock can be increased, thereby improving the temperature control performance of the decomposition furnace. When applying new dry-process cement production technology, continuous optimization of production control strategies can enable the cement industry to achieve energy conservation and emission reduction, alleviating its high energy consumption problem.

[0086] The above embodiments are merely illustrative of the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solutions based on the technical concept proposed in this invention shall fall within the scope of protection of this invention. Technologies not covered in this invention can be implemented using existing technologies.

Claims

1. A method for optimizing the temperature setting of a cement kiln decomposition furnace, characterized in that, Includes the following steps: (1) The recommended strategy for setting the outlet temperature of the decomposition furnace is derived by using the kiln main current, secondary air temperature, kiln condition comprehensive index, and head and tail coal ratio. There are seven recommended strategies: long-term high kiln current, long-term low kiln current, kiln condition fluctuation, raw material SM, kiln condition comprehensive index, quality stability, and theoretical optimization value of decomposition furnace temperature. (2) Prioritize the seven strategies: long-term high kiln current > long-term low kiln current > kiln condition fluctuation > raw material SM > comprehensive kiln condition index > stable quality > theoretically optimized value of decomposer temperature. (3) The adjustment range of the decomposition furnace outlet temperature setpoint under any strategy is classified and discussed, and then the control of the coal feed rate of the decomposition furnace is comprehensively considered to ensure the stability of the decomposition furnace outlet temperature. The recommended strategy addresses the persistently high kiln current, which relies on data from the past 20 kiln current data points. The strategy suggests reducing the decomposer temperature setpoint, calculated using the following method: Analyze the kiln current data trend over the past 180 seconds, with a sampling frequency of 15 seconds. Define the kiln scabbling state as max(0, min(1, 180s linear trend value / range)), where range is 11. Finally, the output value needs to be filtered. Ten kiln main transmission current data are grouped together. Under the premise that the average value of the previous group of data is greater than the upper limit of the kiln current setting, if the average value of the most recent group of data is greater than the upper limit of the kiln current setting + 10 or the kiln skin shedding state is less than 0.6, it is judged that the kiln current is high for a long time, and the decomposition furnace control target temperature is -1℃.

2. The method for optimizing the temperature setting of a cement kiln decomposition furnace according to claim 1, characterized in that, The recommended strategy relies on a long-term decrease in kiln current, based on kiln current data from the past 3 hours. The calculation method for increasing the decomposer temperature setpoint is as follows: First, the kiln current data from the past 3 hours is processed. The number of kiln current data points is used as the x-axis, and the specific kiln current data is used as the y-axis. A curve fitting with an order of 1 is performed to obtain a linear function relating the kiln current change. The slope of the linear function is r1. At the same time, the linear fitting is R2 = 1 - sum(actual kiln current data - corresponding kiln current data on the fitted function). 2 / sum(kiln current data corresponding to the fitted function - mean kiln current data corresponding to the fitted function) 2 ; Condition 1: The current kiln current is low, when the average value of the current data of the last 5 kilns is less than (target value of kiln main transmission current + lower limit of kiln main transmission current) / 2; Condition 2: The future kiln current is low, when the last 15 kiln current data + 180·r1 < the lower limit of the kiln current; Condition 3: The kiln current decreases when r1 ≤ -0.2; When all the above conditions are met, the change value of the decomposition furnace temperature = max(0, - kiln current long-term trend ratio · 60 · r1 · 3-hour current linear fitting R2), where the kiln current long-term trend ratio is taken as 0.

05.

3. The method for optimizing the temperature setting of a cement kiln decomposition furnace according to claim 1, characterized in that, The kiln condition fluctuations in the recommended strategy depend on the frequency and amplitude of fluctuations in secondary blast temperature and kiln current. If the fluctuations in secondary blast temperature and kiln current are very large, the decomposer temperature setpoint is increased by 1°C. The data calculation method is as follows: The fluctuation magnitude and frequency of the secondary air temperature and kiln current are calculated using Fast Fourier Transform. The threshold for adjusting the fluctuation magnitude is set to 25, the lower limit for adjusting the air temperature fluctuation frequency is set to 2, and the upper limit for adjusting the air temperature fluctuation frequency is set to 5. If the fluctuation magnitude of the secondary air temperature or kiln current is greater than 25 and 2 is less than the fluctuation frequency and 5, it is judged that the fluctuation of the kiln current and the secondary air temperature is relatively large, and the target value of the decomposition furnace outlet temperature is increased by 1℃.

4. The method for optimizing the temperature setting of a cement kiln decomposition furnace according to claim 1, characterized in that, The recommended strategy uses historical raw meal SM data as its basis. It calculates the difference between the current and previous raw meal SM values. If the difference is positive, the decomposer temperature setpoint is increased; if it is negative, the decomposer temperature setpoint is decreased. The calculation method is as follows: Calculate the difference between the previous raw material SM and the current raw material SM. If the difference is ≥0.02, the target change value of the decomposer outlet temperature is 20·difference; if the difference is ≥0.06, the target change value of the decomposer outlet temperature is 25·difference; if the difference is ≤0.02, the target change value of the decomposer outlet temperature is 10·difference.

5. The method for optimizing the temperature setting of a cement kiln decomposition furnace according to claim 1, characterized in that, The comprehensive kiln condition index in the recommended strategy is adjusted based on the real-time kiln condition index. If the kiln condition worsens, the setpoint for the fifth-stage cylinder material temperature (denoted as C5) is increased; if the kiln condition improves, the C5 setpoint is decreased. The data calculation method is as follows: Basic calculation strategy for comprehensive kiln condition indicators: Obtain and filter current kiln current, secondary air temperature, flame brightness, kiln tail ammonia, decomposer ammonia, and ammonia water flow rate data. Combine these variables with recent free calcium data to make judgments. A poor kiln condition is indicated by a negative number if any of the following conditions are met: free calcium is above the upper limit; one variable other than free calcium is below the lower limit; free calcium is above the target value, and free calcium increases for three consecutive samples. A good kiln condition is indicated by a positive number if any of the following conditions are met: free calcium is below the target value, and other variables are below the lower limit. All variables are above the target value; free calcium is below the target value; the fire intensity is above the target value and at least one of the other variables is above the target value; otherwise, the kiln condition is judged to be normal and represented by 0; the absolute values ​​of the above comprehensive kiln condition indicators for poor and good do not exceed 1. The specific values ​​are calculated based on the calculation weights of each variable: fire intensity 50%, secondary air temperature 20%, free calcium 10%, kiln current 10%, ammonia flow rate 10%. The weights can be adjusted manually. The final result should be filtered to obtain the filtered comprehensive kiln condition index. The comprehensive kiln condition index filter is calculated based on free calcium, kiln temperature, and main transmission current, and the kiln condition index proportional coefficient is set to 5. If the negative comprehensive kiln condition index filter kiln condition index proportional coefficient is greater than 0.1, the kiln condition is poor, and the temperature control target value is increased. If the kiln condition comprehensive index filter kiln condition index proportional coefficient is less than -0.1, then the kiln condition is good, the temperature control target value is reduced, and the gain is 3.

6. The method for optimizing the temperature setting of a cement kiln decomposition furnace according to claim 1, characterized in that, The recommended strategy emphasizes quality stability, relying on recent free calcium data analysis. If free calcium levels are above the upper limit or below the lower limit and the values ​​are reliable, the material temperature setpoint for the fifth-stage drum is increased or decreased. The material temperature for the fifth-stage drum is denoted as C5, and its calculation method is as follows: If free calcium is higher than the upper limit, increase the temperature control target value; if free calcium is lower than the lower limit, decrease the temperature control target value. The adjustment range of the temperature control target value = 3 * (current free calcium - free calcium target value).

7. The method for optimizing the temperature setting of a cement kiln decomposition furnace according to claim 1, characterized in that, The theoretically optimized value of the decomposer temperature in the recommended strategy depends on the recommended value and target value of the material temperature C5 feed pipe temperature in the five-stage cylinder. If the optimized value is higher than the current value, the decomposer temperature setpoint is increased accordingly, up to a maximum of 0.3℃; if the optimized value is lower than the current value, the decomposer temperature setpoint is decreased accordingly, up to a maximum of 0.3℃. The data calculation method is as follows: If the recommended temperature of C5 feed pipe is greater than the current target temperature of C5 feed pipe, then the adjustment range of the decomposition furnace temperature control target value is min (difference, 0.3℃); if the recommended temperature of C5 feed pipe is less than the current target temperature of C5 feed pipe, then the adjustment range of the decomposition furnace temperature control target value is max (difference, -0.3℃).

8. The method for optimizing the temperature setting of a cement kiln decomposition furnace according to claim 1, characterized in that, The setpoint for the decomposition furnace outlet temperature is controlled according to the priority of the recommended strategy. If the setpoint for the decomposition furnace outlet temperature is manually changed while the algorithm is running, the manually setpoint will be temporarily maintained for a period of time, and the setpoint will be recalculated after the time has elapsed.

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