JP2021103074A - Continuous steel material heating furnace, air ratio control method thereof, and manufacturing method of steel material - Google Patents

Abstract

To provide a continuous steel material heating furnace provided with heat accumulation type switching combustion burners in a combustion control band, capable of controlling an air ratio for every combustion control band at an appropriate air ratio with high accuracy, an air ratio control method of the heating furnace, and a manufacturing method of steel material.SOLUTION: A continuous steel material heating furnace 1 has: an oxygen concentration detector 28 for suction exhaust gas and a flow rate detector 35 for suction exhaust gas provided at a suction exhaust gas main duct 27 for collecting the suction exhaust gases of combustion control bands 3, 4 and 5 and 6 provided with heat accumulating type switching combustion burners 10; an oxygen concentration detector 9 for furnace tail exhaust gas and a flow rate detector 34 for furnace tail exhaust gas provided at a downstream part from the combustion control band 3 being the most downstream side in the exhaust gas flow of a furnace body 2; and an air ratio control section 30 controlling the air ratio for every combustion control band, on the basis of a detection value of the oxygen concentration detector 28 for suction exhaust gas, a detection value of the flow rate detector 35 for suction exhaust gas, a detection value of the oxygen concentration detector 9 for furnace tail exhaust gas, and a detection value of the flow rate detector 34 for furnace tail exhaust gas.SELECTED DRAWING: Figure 1

Description

The present invention relates to a continuous steel heating furnace in which a heat storage type switching combustion burner is provided in at least one combustion control band, a continuous steel heating furnace for controlling the air ratio, an air ratio control method for the continuous steel heating furnace, and a method for controlling the air ratio of the steel material. Regarding the manufacturing method.

Generally, in order to efficiently apply heat to an object to be heated in a heating furnace, it is necessary to reduce the amount of heat lost in addition to heating the object to be heated. The amount of heat lost in a continuous steel heating furnace can be classified into 1) heat loss of exhaust gas, 2) heat loss of cooling water, and 3) heat dissipation of iron skin.
Of these, 1) heat loss of exhaust gas is generated by discharging the gas generated when the fuel gas is burned. The heat loss of exhaust gas is expressed by the following formula.
Qgloss = Vg x Tg x Cpg

Here, Qgloss is the heat loss of the exhaust gas, Vg is the amount of the exhaust gas, Tg is the exhaust gas temperature, and Cpg is the specific heat of the exhaust gas. In order to reduce the exhaust gas loss heat Qgloss, it is necessary to reduce the exhaust gas amount Vg or the exhaust gas temperature Tg from the previous equation. Since the temperature at which the steel material should be heated is generally fixed, the exhaust gas temperature Tg cannot be lowered. Therefore, in order to reduce the heat loss heat Qgloss of exhaust gas, the amount of exhaust gas Vg is reduced.
The exhaust gas amount Vg is expressed by the following formula.
Vg = Vm × (G0 + (1-m) A0)

Here, Vm is the amount of fuel gas, G0 is the theoretical exhaust gas amount of gas, A0 is the theoretical air amount of gas, and m is the air ratio. The amount of fuel gas Vm is determined as a result of controlling the temperature inside the furnace to heat the steel material, and basically cannot be operated for energy saving. Further, the theoretical exhaust gas amount G0 and the theoretical air amount A0 are determined by the composition of the fuel, and these cannot be manipulated either. Therefore, it is the air ratio m that can be positively controlled, and by making this as close to 1.0 as possible, the exhaust gas amount Vg can be reduced and the exhaust gas loss heat Qgloss can be quantified.

The oxygen concentration O ₂ in the exhaust gas is represented by the following formula by G0 and A0 determined by the composition in the gas.
O ₂ = (m-1) A0 × 0.21 / (G0 + (m-1) A0)
In this formula, the molecule indicates the amount of oxygen in the amount of air in which the air ratio m exceeds 1.0 and does not contribute to combustion, and the denominator indicates the amount of exhaust gas generated at the air ratio m. According to this equation, it means that the oxygen concentration O ₂ in the exhaust gas is uniquely determined by determining the air ratio if the composition of the gas is constant.

In an actual continuous steel heating furnace, since the steel material continuously passes through the charging door and the extraction door, the charging door and the extraction door cannot be kept closed at all times, so that the charging door or the extraction door cannot be kept closed. Air inevitably enters the furnace when the door opens. Therefore, even if the flow rate of the fuel gas supplied to the burner and the flow rate of the combustion air are precisely controlled to keep the air ratio constant, the oxygen concentration O ₂ may change. In addition, when the by-product gas is used as the fuel gas of the heating furnace, the composition changes with time, so even if the fuel gas flow rate and the combustion air flow rate are controlled to a constant ratio, the air ratio is not always constant. Absent. For this reason, in the continuous steel heating furnace, control for keeping the oxygen concentration in the heating furnace constant has been conventionally performed.
In a continuous steel heating furnace, a heat storage type switching combustion burner may be used as a burner for heating the steel material, or a normal combustion burner may be used.

In a continuous steel heating furnace using a normal combustion burner without using a heat storage type switching combustion burner, control for keeping the oxygen concentration in the heating furnace constant is conventionally shown in, for example, Patent Document 1. It has been known.
The combustion control method for combustion equipment shown in Patent Document 1 is a combustion control method for combustion equipment in which outside air can enter. When the fuel flow rate supplied to the crater is equal to or higher than a set value, the air-fuel ratio (air ratio) is within a certain range. To control the oxygen concentration in the exhaust gas. When the flow rate of fuel supplied to the crater is less than the set value, or when the air-fuel ratio exceeds the certain range, the internal pressure of the combustion equipment is operated while maintaining the air-fuel ratio within the certain range to reduce the amount of invading air. The oxygen concentration in the exhaust gas is controlled by adjusting. When controlling the oxygen concentration in the exhaust gas in the combustion control method of the combustion equipment shown in Patent Document 1, the oxygen concentration in the exhaust gas is based on the output value from the oxygen concentration meter provided in the exhaust gas passage from the heating furnace. I try to control the oxygen concentration.

Further, in a continuous steel heating furnace using a heat storage type switching combustion burner, conventionally, for example, the one shown in Patent Document 2 is known as a control for keeping the oxygen concentration in the heating furnace constant.
The continuous steel heating furnace shown in Patent Document 2 has a heat storage type switching combustion burner in at least two combustion control bands, and has a detector for detecting the oxygen concentration in the exhaust gas in the exhaust gas attraction system in the combustion control band. This is a continuous steel material heating furnace using a continuous multi-band walking beam that heats a steel material for continuous hot rolling to a predetermined temperature. Then, such a continuous steel heating furnace is connected to the attracted exhaust gas main which collects the attracted exhaust gas of the combustion control band having the heat storage type switching combustion burner, and the attracted exhaust gas header pipe for each combustion control band having the heat storage type switching combustion burner. On the downstream side of the confluence, the oxygen concentration detector that detects the oxygen concentration in the exhaust gas at least two places and the control means that controls the air ratio in the furnace based on the detection value of the detector are installed. There is.

Japanese Unexamined Patent Publication No. 55-33529 Japanese Patent No. 4653689

However, the combustion control method of the combustion equipment shown in Patent Document 1 and the continuous steel heating furnace shown in Patent Document 2 have the following problems.
That is, in the case of the combustion control method of the combustion equipment shown in Patent Document 1, in a continuous steel heating furnace using a normal combustion burner without using a heat storage type switching combustion burner, in order to keep the oxygen concentration in the heating furnace constant. It controls, and is not suitable for controlling to keep the oxygen concentration in the heating furnace constant in a continuous steel heating furnace using a heat storage type switching combustion burner. When burning using a normal combustion burner without using a heat storage type switching combustion burner, the exhaust gas is discharged from the heating furnace to the outside through the exhaust gas passage, so that the exhaust gas from the heating furnace is discharged as in Patent Document 1. The oxygen concentration in the exhaust gas can be controlled based on the output value from the oxygen concentration meter provided in the passage. However, when burned using the heat storage type switching combustion burner, most of the generated exhaust gas (about 80% of the generated exhaust gas) is sucked by the heat storage type switching combustion burner, and the remaining exhaust gas (about 20% of the generated exhaust gas). ) Passes through the heating furnace and passes through the exhaust gas passage, and the amount of exhaust gas passing through this exhaust gas passage is small. Therefore, in Patent Document 1, in a continuous steel heating furnace using a heat storage type switching combustion burner, it is not suitable for controlling the oxygen concentration in the heating furnace to be constant, that is, controlling the air ratio.

On the other hand, in the case of the continuous steel heating furnace shown in Patent Document 2, in the continuous steel heating furnace having a heat storage type switching combustion burner in at least two combustion control bands, control for keeping the oxygen concentration in the heating furnace constant is performed. To do. Here, the continuous steel heating furnace is a head of the attracted exhaust gas where the attracted exhaust gas of the combustion control band having the heat storage type switching combustion burner is collected, and the attracted exhaust gas header pipe of each combustion control band having the heat storage type switching combustion burner. An oxygen concentration detector for detecting the oxygen concentration in the exhaust gas at at least two places is provided on the downstream side of the confluence of the two. Then, the air ratio is controlled using only the detected value detected from this oxygen concentration detector.

However, when the combustion is performed using the heat storage type switching combustion burner, as described above, most of the exhaust gas generated in the heating furnace (about 80% of the generated exhaust gas) is sucked by the heat storage type switching combustion burner. The remaining exhaust gas (about 20% of the generated exhaust gas) flows from the combustion control zone provided with the heat storage type switching combustion burner to the combustion control zone on the downstream side, passes through the heating furnace, and passes through the exhaust gas passage.
Therefore, as in Patent Document 2, only the detected value of the oxygen concentration in the exhaust gas detected from the oxygen concentration detector provided in the attracted exhaust gas main where the attracted exhaust gas of the combustion control band having the heat storage type switching combustion burner gathers. Even if the air ratio is controlled by using the above, the air ratio for each combustion control band cannot be appropriately controlled.

Therefore, the present invention has been made to solve these conventional problems, and an object thereof is a combustion control band in a continuous steel heating furnace provided with a heat storage type switching combustion burner in at least one combustion control band. It is an object of the present invention to provide a continuous steel heating furnace, a continuous steel heating furnace air ratio control method, and a steel manufacturing method capable of controlling each air ratio to an appropriate air ratio with high accuracy.

In order to achieve the above object, the continuous steel heating furnace according to one aspect of the present invention is provided in a furnace body having a plurality of combustion control zones along the direction of the furnace length and at least one of the combustion control zones. A continuous steel heating furnace equipped with a heat storage type switching combustion burner, in which the suction exhaust gas is provided in the suction exhaust gas main where the suction exhaust gas for each combustion control band provided with the heat storage type switching combustion burner is collected. An oxygen concentration detector for suction exhaust gas that detects the oxygen concentration, a flow rate detector for suction exhaust gas that detects the flow rate of the suction exhaust gas, and a location on the downstream side of the combustion control zone on the most downstream side of the exhaust gas flow. Detection of the provided oxygen concentration detector for exhaust gas, a flow detector for exhaust gas, and an oxygen concentration detector for suction exhaust gas, which detect the oxygen concentration in the exhaust gas. Air ratio for each combustion control band based on the value, the detection value of the suction exhaust gas flow rate detector, the detection value of the furnace tail exhaust gas oxygen concentration detector, and the detection value of the furnace tail exhaust gas flow rate detector. The gist is that it is equipped with an air ratio control unit that controls.

Further, the method for controlling the air ratio of the continuous steel heating furnace according to another aspect of the present invention is provided in a furnace body having a plurality of combustion control zones along the direction of the furnace length and at least one of the combustion control zones. It is an air ratio control method of a continuous steel heating furnace equipped with a heat storage type switching combustion burner, and is provided in a suction exhaust gas main where suction exhaust gas for each combustion control band provided with the heat storage type switching combustion burner gathers. The suction exhaust gas oxygen concentration detection step for detecting the oxygen concentration in the suction exhaust gas by the suction exhaust gas oxygen concentration detector, and the suction exhaust gas flow rate detector provided in the suction exhaust gas main pipe detect the flow rate of the suction exhaust gas. Oxygen concentration in the furnace butt exhaust gas by the suction exhaust gas flow rate detection step and the oxygen concentration detector for the furnace butt exhaust gas provided at the installation location on the downstream side of the combustion control zone on the most downstream side in the exhaust gas flow of the furnace body. Combustion exhaust gas oxygen concentration detection step for detecting, a combustion tail exhaust gas flow rate detection step for detecting the flow rate of the furnace tail exhaust gas by the combustion tail exhaust gas flow rate detector provided at the installation location, and the oxygen concentration for suction exhaust gas. The combustion control band is based on the detection value of the detector, the detection value of the suction exhaust gas flow rate detector, the detection value of the furnace tail exhaust gas oxygen concentration detector, and the detection value of the furnace tail exhaust gas flow rate detector. The gist is to include an air ratio control step for controlling each air ratio.

The gist of the method for producing a steel material according to another aspect of the present invention is that the steel material is heated by the above-mentioned air ratio control method for a continuous steel material heating furnace.

According to the air ratio control method and the steel material manufacturing method of the continuous steel material heating furnace and the continuous steel material heating furnace according to the present invention, in the continuous steel material heating furnace provided with a heat storage type switching combustion burner in at least one combustion control band. It is possible to provide a continuous steel heating furnace, a continuous steel heating furnace air ratio control method, and a steel manufacturing method capable of controlling the air ratio for each combustion control band to an appropriate air ratio with high accuracy.

It is a figure which shows the schematic structure of the continuous steel material heating furnace which concerns on one Embodiment of this invention. It is a flowchart for demonstrating the flow of the process of air ratio control in the continuous steel heating furnace shown in FIG. It is a flowchart which shows the detail of the processing flow in step S5 (air ratio control step) shown in FIG. It is a graph which shows the fuel intensity by the example of this invention and the fuel intensity by the comparative example by comparison.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments shown below exemplify devices and methods for embodying the technical idea of the present invention, and the technical idea of the present invention describes the material, shape, structure, arrangement, etc. of the components. It is not specified in the following embodiments.
The drawings are schematic. Therefore, it should be noted that the relationship, ratio, etc. between the thickness and the plane dimension are different from the actual ones, and there are parts where the relationship and ratio of the dimensions are different between the drawings.

FIG. 1 shows a schematic configuration of a continuous steel heating furnace according to an embodiment of the present invention.
The continuous steel material heating furnace 1 shown in FIG. 1 heats a steel material S as a material to be heated, and includes a furnace body 2 extending in a furnace length method which is a transport direction of the steel material S. The furnace body 2 includes a pre-tropical 3, a first heating zone 4, a second heating zone 5, and an average tropical 6 as combustion control zones along the furnace length direction from the charging side to the extraction side of the steel material S. Prepared in order.

Further, each of the pre-tropical 3, the first heating zone 4, the second heating zone 5, and the average tropical 6 has a plurality (6 in the present embodiment, 3 in the upper part, 3 in the lower part). A heat storage type switching combustion burner 10 is provided. Each heat storage type switching combustion burner 10 is composed of a pair of heat storage type burners 10a and 10b installed facing the furnace walls of each pre-tropical 3, first heating zone 4, second heating zone 5, and even tropical 6. Will be done. Each of the heat storage type burners 10a and 10b includes heat storage bodies 11a and 11b made of ceramic balls or the like, respectively. Then, the heat storage type burners 10a and 10b are alternately burned, and the inside of the furnace body 2 through the non-combustion type heat storage type burners 10a or 10b, that is, each pre-tropical 3, first heating zone 4, second heating zone. The exhaust gas from combustion is discharged from the heat storage body 11a or 11b by suction and discharge from the heat storage body 11a or 11b. As a result, the heat of the sucked exhaust gas is stored in the heat storage body 11a or 11b, and the combustion air is supplied to the heat storage type burner 10a or 10b via the heat storage body 11a or 11b at the time of the next combustion, thereby supplying the exhaust gas heat. It is designed to be used for preheating fuel gas.

The heat storage type burner 10a on one side is connected to the fuel gas header pipe 13a in which the fuel gas switching valve 12a is installed, and the heat storage type burner 10b on the other side is connected to the fuel gas header pipe 13b in which the fuel gas switching valve 12b is installed. Has been done. Then, all the fuel gas header pipes 13a in each of the pre-tropical 3, the first heating zone 4, the second heating zone 5, and the average tropical 6 are gathered in the fuel gas collecting pipe 14a, and the pre-tropical 3, the first heating zone 4 , The second heating zone 5, and all the fuel gas header pipes 13b in each of the tropics 6 are gathered in the fuel gas collecting pipe 14b. Then, the fuel gas collecting pipe 14a and the fuel gas collecting pipe 14b are gathered in the common fuel gas collecting pipe 14, and each fuel gas of the pre-tropical 3, the first heating zone 4, the second heating zone 5, and the average tropical 6 is collected. The collecting pipe 14 is connected to a common fuel gas supply line 16.
A fuel gas flow rate measuring device 32 for measuring the flow rate of the fuel gas flowing in each pipe is installed in each fuel gas collecting pipe 14a and each fuel gas collecting pipe 14b, and each fuel gas collecting pipe 14 is provided with a fuel gas flow measuring device 32. , The fuel gas flow rate control valve 15 is installed.

Further, the heat storage body 11a of the heat storage type burner 10a on one side is connected to the combustion air header pipe 18a in which the combustion air switching valve 17a is installed, and the heat storage body 11b of the heat storage type burner 10b on the other side is the combustion air. It is connected to the combustion air header pipe 18b in which the switching valve 17b is installed. Then, all the combustion air header pipes 18a in each of the pre-tropics 3, the first heating zone 4, the second heating zone 5, and the average tropics 6 are gathered in the combustion air collecting pipe 19a, and the pre-tropics 3, the first All the combustion air header pipes 18b in each of the heating zone 4, the second heating zone 5, and the solitary tropics 6 are gathered in the combustion air collecting pipe 19b. Then, the combustion air collecting pipe 19a and the combustion air collecting pipe 19b are gathered in the common combustion air collecting pipe 19, and each of the pre-tropical 3, the first heating zone 4, the second heating zone 5, and the average tropical 6 The combustion air collecting pipe 19 is connected to a common combustion air supply main 21.
A combustion air flow rate measuring device 33 for measuring the flow rate of the combustion air flowing in each of the combustion air collecting pipes 19a and each combustion air collecting pipe 19b is installed, and each combustion air is installed. A combustion air flow control valve 20 is installed in the collecting pipe 19. The combustion air supply main 21 is connected to the combustion air blower 22.

Further, the heat storage body 11a of the heat storage type burner 10a on one side is connected to the exhaust gas header pipe 24a in which the exhaust gas switching valve 23a is installed, and the heat storage body 11b of the heat storage type burner 10b on the other side is provided with the exhaust gas switching valve 23b. It is connected to the exhaust gas header pipe 24b. Then, all the exhaust gas header pipes 24a in each of the pre-tropical 3, the first heating zone 4, the second heating zone 5, and the average tropical 6 are gathered in the exhaust gas collecting pipe 25a, and the pre-tropical 3, the first heating zone 4, All the exhaust gas header pipes 24b in each of the second heating zone 5 and the solitary tropics 6 are gathered in the exhaust gas collecting pipe 25b. Then, the exhaust gas collecting pipe 25a and the exhaust gas collecting pipe 25b are gathered in the common exhaust gas collecting pipe 25, and the exhaust gas collecting pipes 25 of the pre-tropical 3, the first heating zone 4, the second heating zone 5, and the soaking tropical 6 are respectively. , It is connected to the common suction exhaust gas main 27. An exhaust gas flow rate control valve 26 is installed in each exhaust gas collecting pipe 25. Further, in the suction exhaust gas main 27 where the suction exhaust gas for each of the pre-tropical 3, the first heating zone 4, the second heating zone 5, and the average tropical 6 is collected, the suction exhaust gas for detecting the oxygen concentration in the suction exhaust gas is detected. One oxygen concentration detector 28 is provided. Further, the suction exhaust gas main 27 is provided with one suction exhaust gas flow rate detector 35 for detecting the flow rate of the suction exhaust gas flowing in the pipe. The suction exhaust gas main 27 is connected to the suction exhaust gas fan 29.

The sucked exhaust gas sucked from the heat storage type burner 10a or 10b collects in the exhaust gas collecting pipe 25 for each of the pre-tropical 3, the first heating zone 4, the second heating zone 5, and the average tropical 6, and the exhaust gas flow control valve. After the flow rate is adjusted by 26, the whole is assembled by the suction exhaust gas main 27, passes through the suction exhaust gas fan 29, and is guided to the chimney 8.
This suction exhaust gas is about 80% of the exhaust gas generated in the furnace body 2, and the remaining about 20% of the exhaust gas (hereinafter referred to as the furnace butt exhaust gas) passes through the furnace body 2. Normally, in the continuous steel heating furnace 1, the flow of the steel material S and the flow of the furnace butt exhaust gas in the furnace body 2 are in a countercurrent state, and the furnace butt exhaust gas flows from the extraction side of the steel material S to the charging side. And flows in the same space as the steel material S. After that, the exhaust gas from the furnace butt is separated from the steel material S in front of the charging door (not shown), and the flue 7 installed in the furnace body 2 on the downstream side of the pre-tropical 3 on the most downstream side in the exhaust gas flow. It is led to the chimney 8 through.

The flue 7 is provided with one oxygen concentration detector 9 for the exhaust gas of the furnace butt, which detects the oxygen concentration in the exhaust gas of the furnace butt. Further, one flue gas flow rate detector 34 for detecting the flow rate of the fire butt exhaust gas flowing in the flue 7 is installed in the flue 7.
Further, in the continuous steel heating furnace 1, the detection value of the oxygen concentration detector 28 for suction exhaust gas, the detection value of the flow rate detector 35 for suction exhaust gas, the detection value of the oxygen concentration detector 9 for furnace butt exhaust gas, and the furnace butt exhaust gas Air ratio control that controls the air ratio for each combustion control zone (pre-tropical 3, first heating zone 4, second heating zone 5, and average tropical 6) based on the detection value of the flow detector 34. The part 30 is provided.

The air ratio control unit 30 is connected to the suction exhaust gas oxygen concentration detector 28 and the furnace butt exhaust gas oxygen concentration detector 9, and although not shown, each fuel gas flow rate measuring device 32 and each combustion air flow rate measuring device. It is connected to 33, a flow rate detector 34 for exhaust gas from the furnace butt, and a flow rate detector 35 for suction exhaust gas. Further, the air ratio control unit 30 is connected to the host computer 31.
The air ratio control unit 30 is a computer system having an arithmetic processing function, and the air ratio control function (step S5) can be realized on software by executing various dedicated computer programs stored in advance in the hardware. It has become.

Next, the air ratio control method in the continuous steel heating furnace 1 will be described with reference to FIGS. 2 and 3.
First, when controlling the air ratio of the continuous steel heating furnace, as shown in FIG. 2, in step S1, the oxygen concentration detector 28 for suction exhaust gas detects the oxygen concentration in the suction exhaust gas (oxygen concentration detection for suction exhaust gas). Step).
Next, in step S2, the suction exhaust gas flow rate detector 35 detects the flow rate of the suction exhaust gas flowing in the suction exhaust gas main 27 (suction exhaust gas flow rate detection step).

Next, in step S3, the furnace butt exhaust gas oxygen concentration detector 9 detects the oxygen concentration in the furnace butt exhaust gas (fire butt exhaust gas oxygen concentration detection step).
Then, in step S4, the furnace butt exhaust gas flow rate detector 34 detects the flow rate of the furnace butt exhaust gas (fire butt exhaust gas flow rate detection step).
Then, in step S5, the air ratio control unit 30 detects the suction exhaust gas oxygen concentration detector 28 detected in step S1 O2I (%), and the suction exhaust gas flow rate detector 35 detected in step S2 FGI. (Nm ³ / H), the detection value O2E (%) of the furnace butt exhaust gas oxygen concentration detector 9 detected in step S3, and the detection value FGE (Nm ^{3) of the furnace butt exhaust gas flow rate detector 34 detected in step S4.} Based on / H), the air ratio of each combustion control zone (pre-tropical 3, first heating zone 4, second heating zone 5, and average tropical 6) is controlled (air ratio control step).

Here, the step S5 (air ratio control step) will be described. As shown in FIG. 3, the air ratio control unit 30 first, in step S51, detects the value O2E (detection value O2E) of the furnace butt exhaust gas oxygen concentration detector 9. %), The flow rate of the furnace butt exhaust gas calculated from ^{the detection value FGI (Nm 3} / H) of the suction exhaust gas flow rate detector 35 and the detection value FGE (Nm ^{3 / H) of the furnace butt exhaust gas flow rate detector 34.} Ratio Y, detection value O2I (%) of oxygen concentration detector 28 for suction exhaust gas, detection value FGI (Nm ³ / H) of flow rate detector 35 for suction exhaust gas, and detection value FGE of flow rate detector 34 for furnace butt exhaust gas Based on the ratio X of the flow rate of the sucked exhaust gas calculated from (Nm ³ / H), the oxygen concentration O2J (%) of the entire exhaust gas discharged from the furnace body 2 is calculated based on the following equation (1). (Exhaust gas total oxygen concentration calculation step).
O2J = O2E × Y + O2I × X ・ ・ ・ (1)
X = FGI / (FGI + FGE)
Y = FGE / (FGI + FGE)

Next, in step S52, the air ratio control unit 30 sets the combustion control zone (equal tropical 6 (i = 1), second heating zone 5 (i = 2), first heating zone 4 (i = 3), pre-tropical). ^{Detected value FAi (Nm 3} / H) of combustion air flow rate for each 3 (i = 4)), detected value μi of air ratio for each combustion control band, theoretical air volume A0 (Nm ³ / kg), and combustion control band Based on the detected value FFi (Nm ³ / H) of the fuel gas flow rate for each, the contribution rate | Ai | / Σ | Ai | for each combustion control band is calculated (contribution) based on the following equation (2). Rate calculation step).
｜ Ai ｜ / Σ ｜ Ai ｜ ＝ ｜ FAi-μi × A0 × FFi ｜ / Σ ｜ FAi-μi × A0 × FFi ・ ・ ・ (2)

Here, the detection value FAi (Nm ³ / H) of the combustion air flow rate for each combustion control band is the detection value of the combustion air flow rate measuring device 33 installed in each combustion control band, and the detected value is the air ratio. It is input to the control unit 30. Further, the detected value μi of the air ratio for each combustion control band is ^{obtained by dividing the detected value FAi (Nm 3} / H) of the combustion air flow rate for each combustion control band by the theoretical air amount A0. Further, the theoretical air amount A0 (Nm ³ / kg) is input from the host computer 31 to the air ratio control unit 30. Further, the detection value FFi (Nm ³ / H) of the fuel gas flow rate for each combustion control band is the detection value of the fuel gas flow rate measuring device 32 installed in each combustion control band, and the detected value is the air ratio control unit. It is input to 30.

Next, in step S53, the air ratio control unit 30 determines the preset air ratio μ0i for each combustion control band and the oxygen concentration O2J (%) of the entire exhaust gas discharged from the furnace body 2 calculated in step S51. Based on the target value O2M (%) of the oxygen concentration of the entire exhaust gas discharged from the furnace body 2 and the contribution rate for each combustion control band calculated in step S52 | Ai | / Σ | Ai |, the following (3) From the correction value ΔO2μi of the air ratio for each combustion control band calculated by the formula, the appropriate air ratio μCi for each combustion control band is calculated based on the following equation (4) (appropriate air ratio calculation step).
ΔO2μi = ((| Ai | / Σ | Ai |) x αi x βi) x ((O2J-O2M) / γi) ... (3)

Here, αi is a ratio, which is input from the host computer 31 to the air ratio control unit 30. Further, βi is a bias and is input from the host computer 31 to the air ratio control unit 30. Further, O2M (%) is a target value of the oxygen concentration of the entire exhaust gas discharged from the furnace body 2 as described above, and is input to the air ratio control unit 30 from the host computer 31. Further, γi is a correction coefficient, which is input to the air ratio control unit 30 from the host computer 31.
μCi = μ0i + ΔO2μi ・ ・ ・ (4)
Here, μ0i is an air ratio for each combustion control band set in advance as described above, and is input to the air ratio control unit 30 from the host computer 31. That is, as shown in the equation (4), in step S53, the air ratio control unit 30 sets the appropriate air ratio μCi for each combustion control band to the preset air ratio μ0i for each combustion control band. It is calculated by adding the correction value ΔO2μi of each air ratio.

In the present embodiment, the appropriate air ratio μCi for each combustion control band is controlled to 0.9 to 1.05, and more preferably 0.9 to 1.0. By setting the air ratio μCi for each controlled combustion control band to 0.9 to 1.05, the oxygen concentration of the entire exhaust gas discharged from the furnace body 2 can be reduced to 2.0% or less as described later. .. Further, by setting this air ratio μCi to 0.9 to 1.0, the oxygen concentration of the entire exhaust gas discharged from the furnace body 2 can be reduced to 1.0% or less more appropriately.

Finally, in step S54, the air ratio control unit 30 predicts that the combustion control zone (equal tropical 6 (i = 1), second heating zone 5 (i = 2), first heating zone 4 (i = 3), preliminary). ^{Combustion air flow rate (Nm 3} / H) supplied to the combustion control zone so that the air ratio for each tropical 3 (i = 4)) becomes the appropriate air ratio μCi for each combustion control zone calculated in step S53. (Combustion air flow rate adjustment step).
In step 54, specifically, the air ratio control unit 30 in each combustion control band so that the air ratio for each combustion control band becomes the appropriate air ratio μCi for each combustion control band calculated in step S53. The combustion air flow rate adjusting valve 20 is adjusted to adjust the combustion air flow rate supplied to the combustion control band.

As described above, according to the air ratio control method in the continuous steel heating furnace 1 and the continuous steel heating furnace 1 according to the present embodiment, the combustion control zone (equal tropical 6, second) provided with the heat storage type switching combustion burner 10. The oxygen concentration in the suction exhaust gas is detected by the oxygen concentration detector 28 for the suction exhaust gas provided in the suction exhaust gas main 27 where the suction exhaust gas for each heating zone 5, the first heating zone 4, and the pre-tropical zone 3) gathers (the oxygen concentration in the suction exhaust gas). Oxygen concentration detection step for suction exhaust gas: Step S1). Then, the flow rate of the suction exhaust gas is detected by the suction exhaust gas flow rate detector 35 provided in the suction exhaust gas main 27 (suction exhaust gas flow rate detection step: step S2). Further, oxygen in the furnace butt exhaust gas is provided by the furnace butt exhaust gas oxygen concentration detector 9 provided at the installation location on the downstream side of the combustion control zone (pre-tropical 3) on the most downstream side in the exhaust gas flow of the furnace body 2. The concentration is detected (furnace exhaust gas oxygen concentration detection step: step S3). Further, the flow rate of the furnace butt exhaust gas is detected by the furnace butt exhaust gas flow rate detector 34 provided at the above-mentioned installation location (furnace exhaust gas flow rate detection step: step S5). Then, the air ratio control unit 30 determines the detection value of the oxygen concentration detector 28 for the suction exhaust gas, the detection value of the flow rate detector 35 for the suction exhaust gas, the detection value of the oxygen concentration detector 9 for the furnace butt exhaust gas, and the furnace butt exhaust gas. The air ratio for each combustion control band is controlled based on the detection value of the flow rate detector 34 (air ratio control step: step S5).

As a result, at least the oxygen concentration in the suction exhaust gas and the flow rate of the suction exhaust gas sucked by the heat storage type switching combustion burner 10 and the oxygen concentration in the remaining furnace butt exhaust gas not sucked and the flow rate of the suction exhaust gas are detected. In the continuous steel heating furnace 1 provided with the heat storage type switching combustion burner 10 in one combustion control band, the air ratio for each combustion control band can be controlled to an appropriate air ratio with high accuracy. By controlling the air ratio for each combustion control band to an appropriate air ratio with high accuracy, the excess air amount in the exhaust gas can be reduced, the heat loss of the exhaust gas can be reduced, and the fuel consumption can be suppressed.

Further, the air ratio control unit 30 (air ratio control step: step S5) has a detection value O2E of the furnace butt exhaust gas oxygen concentration detector 9 and a flow rate detector for suction exhaust gas when controlling the air ratio for each combustion control band. Based on the detection value FGI of 35, the detection value O2I of the oxygen concentration detector 28 for suction exhaust gas, and the detection value FGE of the flow rate detector 34 for exhaust gas at the furnace butt, the oxygen concentration O2J of the entire exhaust gas discharged from the furnace body 2 is determined. Calculate (step of calculating the total oxygen concentration of exhaust gas: step S51).
Then, the air ratio control unit 30 (air ratio control step: step S5) has a combustion control zone (equal tropical 6 (i = 1), second heating zone 5 (i = 2), first heating zone 4 (i =). 3), Detection value FAi of combustion air flow rate for each pre-tropical 3 (i = 4)), detection value μi of air ratio for each combustion control band, theoretical air volume A0, and detection of fuel gas flow rate for each combustion control band Based on the value FFi, the contribution rate | Ai | / Σ | Ai | for each combustion control band is calculated (contribution rate calculation step: step S52).

Further, the air ratio control unit 30 (air ratio control step: step S5) has a preset air ratio μ0i for each combustion control band, a calculated oxygen concentration O2J of the entire exhaust gas discharged from the furnace body 2, and a furnace. Correction of the air ratio for each combustion control band calculated based on the target value O2M of the oxygen concentration of the entire exhaust gas discharged from the body 2 and the calculated contribution rate for each combustion control band | Ai | / Σ | Ai | From the value ΔO2 μi, the appropriate air ratio μCi for each combustion control band is calculated (appropriate air ratio calculation step: step S53).

Further, the air ratio control unit 30 (air ratio control step: step S5) includes a combustion control zone (equal tropical 6 (i = 1), second heating zone 5 (i = 2), first heating zone 4 (i =). 3) Adjust the flow rate of combustion air supplied to the combustion control zone so that the air ratio for each pre-tropical 3 (i = 4)) becomes the appropriate air ratio μCi for each combustion control zone calculated in step S53. (Combustion air flow rate adjusting step: step S54).
As a result, the air ratio for each combustion control band can be controlled to an appropriate air ratio with higher accuracy, the excess air amount in the exhaust gas can be further reduced, the heat loss of the exhaust gas can be made smaller, and the fuel consumption can be reduced. It can be further suppressed.

Then, the air ratio control unit 30 sets the combustion control zone (equal tropical 6 (i = 1), second heating zone 5 (i = 2), first heating zone 4 (i = 3), pre-tropical 3 (i = 3). 4) Discharge from the combustion body 2 by adjusting the flow rate of combustion air supplied to the combustion control band so that the air ratio for each) becomes the appropriate air ratio μCi for each combustion control band calculated in step S53. The oxygen concentration of the entire exhaust gas is reduced as compared with the case where the oxygen concentration in the exhaust gas is controlled by using only the detection value O2E (%) of the oxygen concentration detector 9 for combustion tail exhaust gas. ..

Specifically, the combustion air flow rate supplied to the combustion control band so that the air ratio for each combustion control band becomes the preset air ratio μOi for each combustion control band without performing steps S1 to S5. When the above was adjusted, the oxygen concentration of the entire exhaust gas discharged from the furnace body 2 was about 3.8%. On the other hand, the air ratio control unit 30 supplies the combustion air to the combustion control band so that the air ratio for each combustion control band becomes the appropriate air ratio μCi for each combustion control band calculated in step S53. By adjusting the flow rate, the oxygen concentration of the entire exhaust gas discharged from the furnace body 2 becomes 2.0% or less.
Further, by reducing the oxygen concentration of the entire exhaust gas discharged from the furnace body 2 to 2.0% or less, the amount of exhaust gas (Nm ³ / H) discharged from the furnace body 2 is reduced, thereby reducing the furnace body 2. It is possible to reduce the amount of _{CO 2} emitted from the body 2.

Although the embodiments of the present invention have been described above, the present invention is not limited to this, and various modifications and improvements can be made.
For example, in the present embodiment, the combustion control zone in which the heat storage type switching combustion burner 10 is installed has four combustion controls of pre-tropical 3, first heating zone 4, second heating zone 5, and average tropical 6. Although it is a band, it is not limited to four, and any one or more combustion control bands may be used.

Further, the number of the heat storage type switching combustion burners 10 installed in each combustion control band is 3 in the present embodiment, but is not limited to 3 and may be any number.
Further, the number of the suction exhaust gas oxygen concentration detector 28 and the suction exhaust gas flow rate detector 35 installed in the suction exhaust gas main 27 is one each in the present embodiment, but is limited to one. There may be more than one.
In addition, the number of the oxygen concentration detector 9 for the exhaust gas at the furnace butt and the flow detector 34 for the exhaust gas at the furnace butt installed at a position downstream of the combustion control zone on the most downstream side in the exhaust gas flow of the furnace body 2 is the present. In the embodiment, there is one for each, but the number is not limited to one and may be plural.

In order to verify the effect of the present invention, the air ratio is controlled by the methods of Examples 1 and 2 of the present invention and the method of Comparative Example, and the fuel intensity in the method of Example 1 of the present invention and the method of Comparative Example as the control result is used. Changes, changes in the oxygen concentration of the entire exhaust gas and changes in the amount of exhaust gas at the furnace butt in the methods of Examples 1 and 2 of the present invention and the methods of Comparative Examples were investigated.
In Example 1 of the present invention, the above-mentioned steps S1 to S5 (steps S51 to S54) were executed. In Example 1 of the present invention, combustion is performed so that the air ratio for each combustion control band is the appropriate air ratio μCi = 1.0 (or more) to 1.05 (or less) for each combustion control band calculated in step S53. The flow rate of combustion air supplied to the control band was adjusted.
In Example 2 of the present invention, combustion is performed so that the air ratio for each combustion control band is the appropriate air ratio μCi = 0.9 (or more) to 1.0 (less than) for each combustion control band calculated in step S53. The flow rate of combustion air supplied to the control band was adjusted.

Further, in the comparative example, the air ratio in each combustion control band is set in advance from μ0i = 1.05 (more) to 1.20 (more) without performing the above-mentioned steps S1 to S5 (steps S51 to S54). (Because the current air ratio was 1.05 to 1.20 in the data received).
FIG. 4 shows the survey results of changes in fuel intensity, and Table 1 shows the survey results of changes in the oxygen concentration of the entire exhaust gas and changes in the amount of exhaust gas at the furnace butt.
With reference to FIG. 4, it was found that the fuel intensity of the method of controlling the air ratio by the method of Example 1 of the present invention was reduced by 8 Mcal per ton as compared with the method of controlling the air ratio by the method of Comparative Example.

As can be seen from Table 1, when the air ratio is controlled by the method of Example 1 of the present invention, the oxygen concentration of the entire exhaust gas is 1.1%, and the oxygen concentration of the entire exhaust gas is 1.1% when the air is controlled by the method of the comparative example. It was found that the oxygen concentration decreased with respect to 3.8%. Also, if in the method of the present invention Example 1 was subjected to air ratio control, the furnace butt exhaust gas amount is 7000 nm ³ / H, the furnace butt exhaust gas amount 13900Nm ³ / H when the air control was performed by the method of Comparative Example On the other hand, it turned out to be decreasing.
Further, when the air ratio is controlled by the method of Example 2 of the present invention, the oxygen concentration of the entire exhaust gas is 1.0%, which is higher than that of the case where the air is controlled by the method of Example 1 of the present invention. Was found to be decreasing. Further, when the air ratio is controlled by the method of Example 2 of the present invention, the amount of exhaust gas from the furnace butt is 6130 Nm ³ / H, which is smaller than that when the air is controlled by the method of Example 1 of the present invention. I found out that I was doing it.

The steel materials (thick plate, thin plate, steel bar) produced according to Examples 1 and 2 of the present invention have required surface quality and material characteristics, and are according to the method for controlling the air ratio of the continuous steel material heating furnace according to the present invention. It has been found that low-cost steel products with low energy intensity can be produced.

1 Continuous steel heating furnace 2 Furnace body 3 Pre-tropical (combustion control zone)
4 First heating zone (combustion control zone)
5 Second heating zone (combustion control zone)
6 Even tropics (combustion control zone)
7 Smoke path 8 Chimney 9 Oxygen concentration detector for exhaust gas from the furnace butt 10 Heat storage type switching combustion burner 10a, 10b Heat storage type burner 11a, 11b Heat storage body 12a, 12b Fuel gas switching valve 13a, 13b Fuel gas header pipe 14 Fuel gas collecting pipe 14a , 14b Fuel gas collecting pipe 15 Fuel gas flow control valve 16 Fuel gas supply line 17a, 17b Combustion air switching valve 18a, 18b Combustion air header pipe 19 Combustion air collecting pipe 19a, 19b Combustion air collecting pipe 20 For combustion Air flow control valve 21 Combustion air supply main 22 Combustion air blower 23a, 23b Exhaust gas switching valve 24a, 24b Exhaust gas header pipe 25 Exhaust gas collecting pipe 25a, 25b Exhaust gas collecting pipe 26 Exhaust gas flow control valve 27 Suction exhaust gas main Oxygen concentration detector for exhaust gas 29 Suction exhaust gas fan 30 Air ratio control unit 31 High-end computer 32 Fuel gas flow meter 33 Combustion air flow meter 34 Combustion air flow meter 34 Furnace exhaust gas flow detector 35 Suction exhaust gas flow detector S Steel

Claims (8)

A continuous steel heating furnace including a furnace body having a plurality of combustion control zones along the furnace length direction and a heat storage type switching combustion burner provided in at least one of the combustion control zones.
The oxygen concentration detector for suction exhaust gas and the flow rate of the suction exhaust gas provided in the suction exhaust gas main where the suction exhaust gas for each combustion control band provided with the heat storage type switching combustion burner is collected. Flow detector for suction exhaust gas to detect and
Oxygen concentration detector for furnace butt exhaust gas and furnace butt exhaust gas, which are provided at the installation location on the downstream side of the combustion control zone on the most downstream side in the exhaust gas flow of the furnace body, to detect the oxygen concentration in the furnace butt exhaust gas. A flow detector for exhaust gas from the furnace butt that detects the flow rate,
Based on the detection value of the suction exhaust gas oxygen concentration detector, the detection value of the suction exhaust gas flow rate detector, the detection value of the furnace tail exhaust gas oxygen concentration detector, and the detection value of the furnace tail exhaust gas flow rate detector. The continuous steel heating furnace is provided with an air ratio control unit for controlling the air ratio for each combustion control band. The air ratio control unit
Based on the detection value of the oxygen concentration detector for fire butt exhaust gas, the detection value of the flow rate detector for suction exhaust gas, the detection value of the oxygen concentration detector for suction exhaust gas, and the detection value of the flow rate detector for fire butt exhaust gas. Then, the oxygen concentration of the entire exhaust gas discharged from the furnace body was calculated.
Contribution for each combustion control band based on the detected value of the combustion air flow rate for each combustion control band, the detected value for the air ratio for each combustion control band, the theoretical amount of air, and the detected value for the fuel gas flow rate for each combustion control band. Calculate the rate,
The preset air ratio for each combustion control band, the calculated oxygen concentration of the entire exhaust gas discharged from the furnace body, the target value of the oxygen concentration of the entire exhaust gas discharged from the furnace body, and the calculated combustion. The appropriate air ratio for each combustion control band is calculated from the correction value of the air ratio for each combustion control band calculated based on the contribution rate for each control band.
The continuous formula according to claim 1, wherein the flow rate of combustion air supplied to the combustion control band is adjusted so that the air ratio of the combustion control band becomes the calculated appropriate air ratio for each combustion control band. Steel heating furnace. The furnace body is adjusted by adjusting the flow rate of combustion air supplied to the combustion control band so that the air ratio of the combustion control band becomes the calculated appropriate air ratio for each combustion control band by the air ratio control unit. The continuous steel heating furnace according to claim 2, wherein the oxygen concentration of the entire exhaust gas discharged from the furnace is 2.0% or less. A method for controlling the air ratio of a continuous steel heating furnace including a furnace body having a plurality of combustion control zones along the furnace length direction and a heat storage type switching combustion burner provided in at least one of the combustion control zones. ,
Suction exhaust gas oxygen concentration detection that detects the oxygen concentration in the suction exhaust gas by the suction exhaust gas oxygen concentration detector provided in the suction exhaust gas main where the suction exhaust gas for each combustion control band provided with the heat storage type switching combustion burner is collected. Steps and
A suction exhaust gas flow rate detection step for detecting the flow rate of the suction exhaust gas by a flow rate detector for the suction exhaust gas provided in the suction exhaust gas main, and a suction exhaust gas flow rate detection step.
Furnace exhaust gas oxygen that detects the oxygen concentration in the furnace butt exhaust gas by the furnace butt exhaust gas oxygen concentration detector provided at the installation location on the downstream side of the combustion control zone on the most downstream side in the exhaust gas flow of the furnace body. Concentration detection step and
The furnace butt exhaust gas flow rate detection step for detecting the flow rate of the furnace butt exhaust gas by the flow rate detector for the furnace butt exhaust gas provided at the installation location, and
Based on the detection value of the suction exhaust gas oxygen concentration detector, the detection value of the suction exhaust gas flow rate detector, the detection value of the furnace tail exhaust gas oxygen concentration detector, and the detection value of the furnace tail exhaust gas flow rate detector. A method for controlling the air ratio of a continuous steel heating furnace, which comprises an air ratio control step for controlling the air ratio for each combustion control zone. The air ratio control step
Based on the detection value of the oxygen concentration detector for the furnace butt exhaust gas, the detection value of the oxygen concentration detector for the suction exhaust gas, the detection value of the flow rate detector for the suction exhaust gas, and the detection value of the flow rate detector for the furnace butt exhaust gas. Then, the step of calculating the oxygen concentration of the entire exhaust gas discharged from the furnace body and the step of calculating the oxygen concentration of the entire exhaust gas
Contribution for each combustion control band based on the detected value of the combustion air flow rate for each combustion control band, the detected value for the air ratio for each combustion control band, the theoretical amount of air, and the detected value for the fuel gas flow rate for each combustion control band. Contribution rate calculation step to calculate the rate and
The air ratio for each combustion control band set in advance, the oxygen concentration of the entire exhaust gas discharged from the furnace body calculated in the step of calculating the oxygen concentration of the entire exhaust gas, and the oxygen concentration of the entire exhaust gas discharged from the furnace body. Appropriateness to calculate the appropriate air ratio for each combustion control band from the target value and the correction value of the air ratio for each combustion control band calculated based on the contribution rate for each combustion control band calculated in the contribution rate calculation step. Air ratio calculation step and
Combustion air flow rate adjustment step that adjusts the combustion air flow rate supplied to the combustion control band so that the air ratio of the combustion control band becomes the appropriate air ratio for each combustion control band calculated in the appropriate air ratio calculation step. The air ratio control method for a continuous steel heating furnace according to claim 4, wherein the method includes. The air ratio control step
The ratio of the flow rate of the furnace butt exhaust gas calculated from the detection value of the oxygen concentration detector for the furnace butt exhaust gas, the detection value of the flow rate detector for the suction exhaust gas and the detection value of the flow rate detector for the furnace butt exhaust gas, and the suction. The furnace based on the detection value of the exhaust gas oxygen concentration detector and the ratio of the flow rate of the suction exhaust gas calculated from the detection value of the suction exhaust gas flow rate detector and the detection value of the furnace tail exhaust gas flow rate detector. The step of calculating the oxygen concentration of the entire exhaust gas emitted from the body and the step of calculating the oxygen concentration of the entire exhaust gas
Contribution for each combustion control band based on the detected value of the combustion air flow rate for each combustion control band, the detected value for the air ratio for each combustion control band, the theoretical amount of air, and the detected value for the fuel gas flow rate for each combustion control band. Contribution rate calculation step to calculate the rate and
The air ratio for each combustion control band set in advance, the oxygen concentration of the entire exhaust gas discharged from the furnace body calculated in the step of calculating the oxygen concentration of the entire exhaust gas, and the oxygen concentration of the entire exhaust gas discharged from the furnace body. Appropriateness to calculate the appropriate air ratio for each combustion control band from the target value and the correction value of the air ratio for each combustion control band calculated based on the contribution rate for each combustion control band calculated in the contribution rate calculation step. Air ratio calculation step and
Combustion air flow rate adjustment step that adjusts the combustion air flow rate supplied to the combustion control band so that the air ratio of the combustion control band becomes the appropriate air ratio for each combustion control band calculated in the appropriate air ratio calculation step. The air ratio control method for a continuous steel heating furnace according to claim 4, wherein the method includes. The combustion air flow rate supplied to the combustion control band by the combustion air flow rate adjusting step so that the air ratio of the combustion control band becomes the appropriate air ratio for each combustion control band calculated in the appropriate air ratio calculation step. The air ratio control method for a continuous steel heating furnace according to claim 5 or 6, wherein the oxygen concentration of the entire exhaust gas discharged from the furnace body becomes 2.0% or less by adjusting the above. A method for producing a steel material, which comprises heating the steel material by the air ratio control method of the continuous steel material heating furnace according to any one of claims 4 to 7.

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