Submerged arc furnace tail gas fan control method

Abstract

The invention relates to the technical field of electrical control, in particular to a submerged arc furnace tail gas fan control method. According to the specific technical scheme, influence coefficients of all parameters are calculated according to furnace cover flames, submerged arc furnace pressure, tail gas carbon monoxide concentration, tail gas temperature, active power and single-furnace accumulated electricity degree; and the pressurization duration is calculated in real time according to the influence coefficient of any at least one parameter. And the furnace pressure is dynamically set by combining the furnace condition data, so that the full-automatic control of the tail gas fan of the full-closed submerged arc furnace is realized.

Description

Technical Field

[0001] The invention relates to the technical field of electrical control, and in particular to a method for controlling an exhaust gas fan of an ore-fired furnace. Background Art

[0002] At present, most of the control of the exhaust gas fan of the fully enclosed submerged arc furnace is manually controlled, and some are automatically controlled, and the traditional PID or other constant pressure control strategies are basically used. In the production process of the fully enclosed submerged arc furnace, as the furnace conditions change, the control strategy using the fixed furnace pressure setting often cannot fully adapt to the needs of all furnace conditions. Therefore, the current automation level of the exhaust gas fan control of the fully enclosed submerged arc furnace has always been relatively low, and the problems of manual control are also obvious. People often doze off due to lack of energy at night. In order not to burn the equipment, the fan is opened larger than usual, which leads to excessive air being drawn in, and carbon monoxide is burned and wasted. The air extraction volume is also more than normal, resulting in an increase in ash volume, a shortened bag filter clogging cycle, and a large amount of economic waste. Therefore, there is an urgent need for a control method that can adapt to the exhaust gas fan of the fully enclosed submerged arc furnace. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present invention provides a method for controlling an exhaust gas fan of an electric arc furnace.

[0004] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0005] The invention discloses a method for controlling an exhaust gas fan of a submerged arc furnace, comprising the following steps:

[0006] (1) Calculate the influence coefficient of each parameter based on the furnace cover flame, ore-fired furnace pressure, tail gas carbon monoxide concentration, tail gas temperature, active power, and cumulative electricity consumption of a single furnace;

[0007] (2) calculating the pressurization duration T0 in real time according to the influence coefficient of at least one parameter in step (1), and setting the maximum non-ignition time T1 and the preset delay time T2 according to the working conditions of the ore-fired furnace;

[0008] (3) Detect whether the furnace cover is on fire; if on fire, reset the non-fire time Tn to zero, and detect whether the furnace pressure is less than the current feedback pressure of the submerged arc furnace during the waiting preset time. If so, reduce the target pressure value, otherwise, repeat step (1);

[0009] If there is no ignition, the non-ignition time Tn is counted. If the ore-arc furnace does not ignite within the time T0, the target pressure value is increased, the non-ignition time Tn is cleared, and the process returns to step (1).

[0010] The non-fire time Tn is measured. If the ore-arc furnace does not ignite during the non-fire time Tn within T2, the target pressure value is reduced, the non-fire time Tn is cleared, and the process returns to step (1).

[0011] Preferably, in step (2), T0 is calculated by the current pressure value of the ore-arcing furnace and the non-ignition time, and the formula is: T0 = (1-(|(P0-(P1-P2) / 2) / (P1-P2)|) N )×T1,

[0012] Among them, P0 is the current pressure value, P1 is the upper pressure limit, P2 is the lower pressure limit, P0 value is between P1 and P2, T1 is the maximum non-ignition duration, and N is the cumulative number of ignitions per unit time.

[0013] Preferably, in step (1), the calculation formula of the exhaust gas carbon monoxide concentration influence coefficient K1 is: K1 = ((C1-C0) / C2) X1 ×K01×(C1>C0),

[0014] Wherein, C0 is the current carbon monoxide concentration, C1 is the carbon monoxide concentration at the fan over-extraction judgment point, (C1>C0) is judged to be true when the value in the bracket is 1, and is judged to be false when the value in the bracket is 0, C2 is the maximum concentration difference, where the maximum value of (C1-C0) / C2 = 1, X1 is the deviation influence index coefficient, and K01 is the time influence coefficient.

[0015] Preferably, in step (1), the calculation formula of the influence coefficient K2 of the exhaust gas temperature is:

[0016] K2=((T0-T1) / T2) X2 ×K02×(T0>T1),

[0017] Wherein, T0 is the current exhaust gas temperature, T1 is the fan over-extraction judgment point temperature, (T0>T1) is judged as true when the value in the bracket is 1, and is judged as false when the value in the bracket is 0, T2 is the maximum temperature difference, where the maximum value of (T0-T1) / T2 = 1, X2 is the deviation influence index coefficient, and K02 is the time influence coefficient.

[0018] Preferably, in step (1), the calculation formula of the influence coefficient K3 of active power is:

[0019] K3=((PW0-PW2) / (PW1-PW2))×K03×(PW0>PW2)+K04,

[0020] Among them, PW0 is the current active power, PW1 is the maximum active power, PW2 is the minimum execution active power, the value in the brackets is 1 when (PW0>PW2) is judged to be true, and the value in the brackets is 0 when it is judged to be false, K03 is the power influence coefficient 1, and K04 is the power influence coefficient 2.

[0021] Preferably, in step (1), the calculation formula of the influence coefficient K4 of the cumulative electricity consumption of a single furnace is:

[0022] K4=(KWH0 / KWH1) X01 ×K05+K06,

[0023] Among them, KWH0 is the accumulated electricity of the current furnace, KWH1 is the electricity at the end of the middle and early stages, K05 is the electricity influence coefficient 1, K06 is the electricity influence coefficient 2, and X01 controls the slope of the curve of the K4 coefficient changing from 0 to the end electricity KWH1.

[0024] Preferably, when KWH1 is greater than K4=1, the influence coefficient K4 is introduced into the calculation formula of the exhaust gas temperature influence coefficient to obtain a new temperature influence coefficient K2 with electrical degree correction, the formula is:

[0025] K2=((T0-T1×K4) / T2) X2 ×K02×(T0>T1×K4).

[0026] Correspondingly, an electric arc furnace exhaust gas system includes a central controller, which establishes two-way data transmission with a data collection unit. Multiple flame sensors are installed on the cover of the electric arc furnace, and a pressure gauge is arranged on the top of the furnace. The flame sensor, the pressure gauge and the exhaust gas carbon monoxide detector are electrically connected to the data collection unit. The central controller outputs a target frequency to control the speed of the exhaust gas fan according to the above-mentioned fan control method.

[0027] The present invention has the following beneficial effects:

[0028] 1. After analyzing the exhaust gas system of the fully enclosed ore-fired furnace, the present invention finds the correlation between the pressure setting and the data such as furnace cover ignition, carbon monoxide concentration, exhaust gas temperature, active power, and accumulated electricity of a single furnace. Combined with these furnace condition data, the furnace pressure setting is dynamically set to achieve fully automated control of the exhaust gas fan of the fully enclosed ore-fired furnace.

[0029] 2. Through the correlation control of the main factors affecting the control effect of the exhaust fan: furnace cover flame, exhaust gas carbon monoxide concentration, exhaust gas temperature, active power, single furnace cumulative electricity and other data, on the one hand, the speed regulation of the fan is closer to the ideal control model, effectively ensuring the safe production of the electric arc furnace and avoiding safety accidents caused by human factors in production; on the other hand, after practical verification, this method can significantly increase the exhaust gas carbon monoxide concentration. Generally speaking, the exhaust gas carbon monoxide concentration can be increased by 10%-15% compared with the original manual control method, thereby increasing the exhaust gas calorific value and improving the utilization efficiency of the exhaust gas. It can also reduce the over-extraction of the fan and reduce the exhaust volume of the entire exhaust system, thereby reducing the amount of dust removal. While saving raw materials, it can also extend the purification system filter bag and pipeline blockage cycle, reduce shutdown time for maintenance, and improve the operating rate, bringing huge economic benefits to the factory. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a flow chart of the fan control method of the present invention;

[0031] Figure 2 is a curve diagram of the pressurization duration T0;

[0032] Figure 3 is a curve diagram of the influence coefficient of exhaust carbon monoxide concentration;

[0033] Figure 4 is a curve diagram of exhaust gas temperature influence coefficient;

[0034] Figure 5 It is a curve diagram of active power correction coefficient;

[0035] Figure 6 It is a curve diagram of the floating compensation coefficient of the accumulated electricity;

[0036] Figure 7 This is a block diagram of the exhaust gas system of the submerged arc furnace. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise specified, the technical means used in the implementation examples are conventional means well known to those skilled in the art.

[0038] refer to Figure 1 As shown, the present invention discloses a method for controlling an exhaust gas fan of a submerged arc furnace, comprising the following steps:

[0039] (1) Calculate the influence coefficient of each parameter based on the furnace cover flame, ore-fired furnace pressure, tail gas carbon monoxide concentration, tail gas temperature, active power, and cumulative electricity consumption of a single furnace;

[0040] (2) According to the influence coefficient of at least one of the parameters in step (1), the pressurization duration T0 is calculated in real time (T0 here is equivalent to a judgment value. When there is no timing reset trigger, the accumulated timing reaches this value and triggers an action of increasing the set value. The timing is not strictly executed according to the step of adding 1 per second. It may be affected by factors such as temperature or carbon monoxide content, resulting in more values ​​being added per second to shorten the trigger time), and the maximum non-ignition time T1 and the preset delay time T2 are set according to the working conditions of the electric furnace; T1 and T2 are empirical parameters preset according to the different furnace conditions of each electric furnace, which can be understood as constants.

[0041] (3) Detect whether the furnace cover is on fire; if on fire, reset the non-fire time Tn to zero, and detect whether the furnace pressure is less than the current feedback pressure of the submerged arc furnace during the waiting preset time. If so, reduce the target pressure value, otherwise, repeat step (1);

[0042] If there is no ignition, the non-ignition time Tn is counted. If the ore-arc furnace does not ignite within the time T0, the target pressure value is increased, the non-ignition time Tn is cleared, and the process returns to step (1).

[0043] The non-fire time Tn is measured. If the ore-arc furnace does not ignite during the non-fire time Tn within T2, the target pressure value is reduced, the non-fire time Tn is cleared, and the process returns to step (1).

[0044] The calculation process of the influence coefficient of each parameter and the pressurization duration T0 is as follows:

[0045] 1. Install multiple flame sensors near the furnace cover of the submerged arc furnace. After the furnace cover is detected to be on fire, if the pressure feedback is near the set pressure, the fire occurs N times cumulatively within a unit time (settable), and the pressure setting is reduced by one unit (settable). When the furnace cover is on fire, the fan ignores the constant pressure mode and changes to the priority fire extinguishing mode. The pressure is automatically set with a range, which needs to be set according to the normal pressure setting range. Assuming that the current pressure setting value is P0, the upper limit of the pressure setting is P1, and the lower limit of the pressure setting is P2, the P0 value can only be taken within the range of P1 and P2, and the parameter maximum non-fire duration is T1. After the furnace cover does not catch fire for a certain period of time, the set pressure is added with a unit pressure setting (settable). This pressurization duration T0 is a dynamic value, which is calculated according to the following formula:

[0046] T0=(1-(|(P0-(P1-P2) / 2) / (P1-P2)|) N )×T1 (1)

[0047] Among them, P0 is the current pressure value, P1 is the upper pressure limit, P2 is the lower pressure limit, P0 value is between P1 and P2, T1 is the maximum non-ignition duration, and N is the cumulative number of ignitions per unit time.

[0048] Specifically: Assume P0 = X, P1 = 15, P2 = -15, T1 = 1200, N = 3 and substitute into the formula to draw the curve as follows Figure 2 As shown. Figure 2 It can be seen that as the set pressure P0 is closer to the minimum set pressure P2, the pressurization duration T0 is smaller, P0 is closer to the maximum set pressure P1, and the larger the pressurization duration T0 is, the closer it is to the maximum misfire time T1, and the relationship is exponential N. By adjusting the value of N, the shape of the curve can bend along the exponential relationship, and the value of index N can be set according to actual conditions.

[0049] 2. The production of submerged arc furnace is a reaction process in which carbon is used to reduce the product oxide. This process will produce a large amount of carbon monoxide, which is discharged through the tail gas. These carbon monoxides are important raw materials for chemical production. How to recover these carbon monoxides to the greatest extent during the production process and ensure the normal operation of the submerged arc furnace production is the main problem of tail gas recovery. In a fully enclosed submerged arc furnace, according to the carbon monoxide content in the tail gas, it can be judged whether the tail gas fan is over-exhausted. If the fan frequency is too large, more air will be inhaled. When the air encounters the high-temperature tail gas containing carbon monoxide, it will be burned and consumed immediately. Because it is consumed immediately after entering a point, it will not cause an explosion, but it will cause the carbon monoxide concentration in the tail gas to decrease. Therefore, according to the historical carbon monoxide concentration data of each electric furnace, a lower limit of carbon monoxide concentration during normal production is set for each electric furnace. If it is lower than this lower limit, it is necessary to increase the set pressure as soon as possible and reduce the exhaust volume of the fan. The calculation formula of the exhaust carbon monoxide concentration influence coefficient K1 is:

[0050] K1=((C1-C0) / C2) X1 ×K01×(C1>C0) (2)

[0051] Wherein, C0 is the current carbon monoxide concentration, C1 is the carbon monoxide concentration at the fan over-extraction judgment point, (C1>C0) is judged to be true when the value in the bracket is 1, and is judged to be false when the value in the bracket is 0, C2 is the maximum concentration difference, where the maximum value of (C1-C0) / C2 = 1, X1 is the deviation influence index coefficient, and K01 is the time influence coefficient.

[0052] Specifically: Assuming the current carbon monoxide content is X, C1 = 60, C2 = 20, X1 = 2, K01 = 2, we can get Figure 3In formula (1), the calculated dynamic pressure setting time is counted at a speed of 1 per second by default. In order to introduce the influence of carbon monoxide content, K01 is added on the basis of 1 per second to shorten the pressure setting time.

[0053] 3. When the fan is over-extracted, part of the carbon monoxide is burned, and the temperature in the entire exhaust pipe will be higher than normal. Therefore, the exhaust temperature also needs to be introduced as an influence coefficient. The calculation formula of the exhaust temperature influence coefficient K2 is: K2 = ((T0-T1) / T2) X2 ×K02×(T0>T1)(3)

[0054] Wherein, T0 is the current exhaust gas temperature, T1 is the fan over-extraction judgment point temperature, (T0>T1) is judged as true when the value in the bracket is 1, and is judged as false when the value in the bracket is 0, T2 is the maximum temperature difference, where the maximum value of (T0-T1) / T2 = 1, X2 is the deviation influence index coefficient, and K02 is the time influence coefficient.

[0055] Specifically: Assume T1 = 500, T2 = 100, X2 = 2, K02 = 2, and substitute into the formula to get Figure 4 In formula (1), the calculated dynamic pressure setting time is counted at a speed of 1 per second by default. In order to introduce the influence of exhaust gas temperature, K02 is added on the basis of 1 per second to shorten the pressure setting time.

[0056] 4. The active power will directly affect the carbon monoxide concentration and temperature of the exhaust gas. Therefore, the power correction coefficient K3 needs to be added to the concentration influence coefficient K1 and the temperature influence coefficient K2. The calculation formula is

[0057] As follows: K3=((PW0-PW2) / (PW1-PW2))×K03×(PW0>PW2)+K04(4)

[0058] Among them, PW0 is the current active power, PW1 is the maximum active power, the value in the brackets is 1 when (PW0>PW2) is judged to be true, and the value in the brackets is 0 when it is judged to be false, PW2 is the minimum execution active power, K03 is the power influence coefficient 1, and K04 is the power influence coefficient 2.

[0059] Specifically: Assume PW1 = 35000, PW2 = 20000, K03 = 0.3, K04 = 0.7, and substitute into the formula to get Figure 5 At this time, the timing amount per second is: TK1 = 1 + (K1 + K2) × K3. Specifically: Normal timing is increased by 1 per second. After the carbon monoxide content and temperature conditions mentioned above are met, the timing needs to be accelerated, which is equivalent to adding more values ​​per second, speeding up the timing speed and shortening the adjustment cycle.

[0060] 5. During the smelting process of the electric arc furnace, as the cumulative electricity consumption of a single furnace increases, the gas production of the electric furnace will change to a certain extent.

[0061] (1) Early stage of smelting: When the furnace is just finished, a large amount of new ore raw materials enter the furnace, and the temperature inside the furnace is low. At this time, the reduction reaction is slow, the gas production is small, the carbon monoxide content is slightly low, and the tail gas temperature is also low;

[0062] (2) Early stage of smelting: After a period of smelting, the temperature in the furnace rises, new ore raw materials begin to react intensively, and the gas production gradually reaches a peak. At this time, due to the large gas production, the carbon monoxide concentration increases, the heat brought out is also large, and the furnace temperature is relatively high;

[0063] (3) Mid-to-late stage of smelting: After the reaction of the raw ore reaches its peak, the ore to be reacted gradually decreases, the gas production begins to decrease, the carbon monoxide concentration stabilizes, and the tail gas temperature gradually decreases;

[0064] (4) Late stage of smelting: The amount of raw ore to be reacted in the main reaction zone becomes less and less, and the gas production further decreases. However, as the reduction products in the furnace increase, the level of high-temperature molten material rises, causing the tail gas temperature to rise.

[0065] According to the characteristics of the above four main periods of the fully enclosed ore-fired furnace, a floating compensation coefficient K4 is added to the temperature coefficient in the early and middle stages of smelting. The calculation formula is:

[0066] K4=(KWH0 / KWH1) X01 ×K05+K06 (5)

[0067] Among them, KWH0 is the accumulated electricity of the current furnace, KWH1 is the electricity at the end of the middle and early stages, K05 is the electricity influence coefficient 1, K06 is the electricity influence coefficient 2, and X01 controls the slope of the curve of the K4 coefficient from 0 to the end electricity KWH1, which is a fixed constant set based on empirical data.

[0068] Specifically: Assuming the current accumulated electricity is X, KWH1 = 50000, K05 = 0.2, K06 = 0.8, substitute into the formula to get Figure 6 When it is greater than KWH1, K4=1. At this time, the influence coefficient K4 is introduced into the calculation formula of the exhaust gas temperature influence coefficient to obtain a new temperature influence coefficient K2 with electrical degree correction. The formula is:

[0069] K2=((T0-T1×K4) / T2) X2 ×K02×(T0>T1×K4) (6).

[0070] According to the calculation and adjustment of the present invention, the furnace pressure setting value will be dynamically added or subtracted on the basis of the original furnace pressure setting value, so as to obtain a furnace pressure setting value that adapts to changes in furnace conditions. The target frequency output by the frequency converter is controlled through PID calculation with the current actual pressure of the ore-fired furnace to control the speed of the exhaust gas fan, thereby achieving safe and stable production of the ore-fired furnace.

[0071] refer to Figure 7 As shown, the present invention discloses an electric arc furnace exhaust system, including a central controller, wherein the central controller establishes two-way data transmission with a data collection unit, a plurality of flame sensors are installed on the cover of the electric arc furnace, a pressure gauge is arranged on the furnace top, the flame sensor, the pressure gauge and the exhaust gas carbon monoxide detector are electrically connected to the data collection unit, and the central controller outputs a target frequency to control the rotation speed of the exhaust gas fan according to the above-mentioned fan control method.

[0072] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for controlling an exhaust gas fan of a submerged arc furnace, characterized in that: The following steps are involved: (1) Calculate the influence coefficient of each parameter based on the furnace cover flame, ore-fired furnace pressure, tail gas carbon monoxide concentration, tail gas temperature, active power, and cumulative electricity consumption of a single furnace; (2) calculating the pressurization duration T0 in real time according to the influence coefficient of at least one parameter in step (1), and setting the maximum non-ignition time T1 and the preset delay time T2 according to the working conditions of the ore-fired furnace; (3) Detect whether the furnace cover is on fire; if on fire, reset the non-fire time Tn to zero, and detect whether the furnace pressure is less than the current feedback pressure of the submerged arc furnace during the waiting preset time. If so, reduce the target pressure value, otherwise, repeat step (1); If there is no ignition, the non-ignition time Tn is counted. If the ore-arc furnace does not ignite within the time T0, the target pressure value is increased, the non-ignition time Tn is cleared, and the process returns to step (1). The non-fire time Tn is measured. If the ore-arc furnace does not ignite during the non-fire time Tn within T2, the target pressure value is reduced, the non-fire time Tn is cleared, and the process returns to step (1).

2. A method for controlling an exhaust gas fan of a submerged arc furnace according to claim 1, characterized in that: In step (2), T0 is calculated by the current pressure value of the ore-fired furnace and the non-ignition time, and the formula is: T0=(1-(|(P0-(P1-P2) / 2) / (P1-P2)|) N )×T1, Among them, P0 is the current pressure value, P1 is the upper pressure limit, P2 is the lower pressure limit, P0 value is between P1 and P2, T1 is the maximum non-ignition duration, and N is the cumulative number of ignitions per unit time.

3. A method for controlling an exhaust gas fan of a submerged arc furnace according to claim 2, characterized in that: In step (1), the calculation formula of the exhaust gas carbon monoxide concentration influence coefficient K1 is: K1=((C1-C0) / C2) X1 ×K01×(C1>C0), Wherein, C0 is the current carbon monoxide concentration, C1 is the carbon monoxide concentration at the fan over-extraction judgment point, (C1>C0) is judged to be true when the value in the bracket is 1, and is judged to be false when the value in the bracket is 0, C2 is the maximum concentration difference, where the maximum value of (C1-C0) / C2 = 1, X1 is the deviation influence index coefficient, and K01 is the time influence coefficient.

4. A method for controlling an exhaust gas fan of a submerged arc furnace according to claim 3, characterized in that: In step (1), the calculation formula of the influence coefficient K2 of the exhaust gas temperature is: K2=((T0-T1) / T2) X2 ×K02×(T0>T1), Wherein, T0 is the current exhaust gas temperature, T1 is the fan over-extraction judgment point temperature, (T0>T1) is judged as true when the value in the bracket is 1, and is judged as false when the value in the bracket is 0, T2 is the maximum temperature difference, where the maximum value of (T0-T1) / T2 = 1, X2 is the deviation influence index coefficient, and K02 is the time influence coefficient.

5. A method for controlling an exhaust gas fan of a submerged arc furnace according to claim 4, characterized in that: In step (1), the calculation formula of the active power influence coefficient K3 is: K3=((PW0-PW2) / (PW1-PW2))×K03×(PW0>PW2)+K04, Among them, PW0 is the current active power, PW1 is the maximum active power, PW2 is the minimum execution active power, the value in the brackets is 1 when (PW0>PW2) is judged to be true, and the value in the brackets is 0 when it is judged to be false, K03 is the power influence coefficient 1, and K04 is the power influence coefficient 2.

6. A method for controlling an exhaust gas fan of a submerged arc furnace according to claim 5, characterized in that: In step (1), the calculation formula of the influence coefficient K4 of the cumulative electricity consumption of a single furnace is: K4=(KWH0 / KWH1) X01 ×K05+K06, Among them, KWH0 is the accumulated electricity of the current furnace, KWH1 is the electricity at the end of the middle and early stages, K05 is the electricity influence coefficient 1, K06 is the electricity influence coefficient 2, and X01 controls the slope of the curve of the K4 coefficient changing from 0 to the end electricity KWH1.

7. A method for controlling an exhaust gas fan of a submerged arc furnace according to claim 6, characterized in that: When it is greater than KWH1, K4=1. At this time, the influence coefficient K4 is introduced into the calculation formula of the exhaust gas temperature influence coefficient to obtain a new temperature influence coefficient K2 with electrical degree correction. The formula is: K2=((T0-T1×K4) / T2) X2 ×K02×(T0>T1×K4)。 8. A submerged arc furnace tail gas system, characterized in that: It includes a central controller, which establishes two-way data transmission with a data collection unit. Multiple flame sensors are installed on the cover of the electric arc furnace, and a pressure gauge is set on the top of the furnace. The flame sensor, the pressure gauge and the exhaust gas carbon monoxide detector are electrically connected to the data collection unit. The central controller outputs a target frequency to control the speed of the exhaust gas fan according to the fan control method according to any one of claims 1 to 7.

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