JP3356595B2 - Heating furnace combustion control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling combustion in a heating furnace.

[0002]

2. Description of the Related Art Casting slabs (slabs), billets (strips), blooms, etc. are charged into a heating furnace and heated to a temperature suitable for hot rolling. Is generally composed of a pre-tropical zone, a heated zone and a tropical zone,
The material to be heated such as a slab is heated by sequentially moving the pre-tropical zone, the heating zone and the soaking zone, and in order to improve the heating efficiency, a regenerative burner is used to move the heated material in the heating furnace in the direction in which the material to be heated advances. A burner group is arranged opposite to both sides, one burner group raises the combustion air through the heat storage and supplies it to the burner to burn fuel, and the other burner group stops burning, The combustion exhaust gas in the furnace is exhausted through the heat storage body, and heat energy in the exhaust gas is stored. Japanese Patent Application Laid-Open No. 5-118764 discloses that heating is performed continuously by so-called regenerative alternating combustion in which combustion and heat storage are alternately performed.
It is disclosed in Japanese Patent Application Laid-Open No. H6-194054.

[0003]

In the regenerative alternating combustion as described above, the material to be heated is heated uniformly, that is, the temperature distribution in the furnace is made uniform and the combustion efficiency is high and excellent combustion heating is possible. It is. When the material to be heated is uniformly heated in this manner, a large time difference occurs between the leading end and the trailing end of the slab during hot rolling in a long slab or the like. The temperature becomes low and the finished temperature of the rolled material becomes non-uniform, so that a uniform material cannot be obtained, and the shape deteriorates, so that the quality deteriorates and the yield decreases. Therefore, from the temperature of the tip of the material to be heated in the heating furnace,
It is necessary to perform inclined heating for heating the rear end temperature to a high temperature to prevent the temperature of the rear end of the rolled material from lowering due to a time difference during rolling.

[0004] However, in the regenerative alternating combustion as described above, uniform heating is premised, and the burner is structurally configured so that both the amount of combustion and the combustion time are the same. There is a problem that the material to be heated cannot be inclinedly heated by changing the distribution. The method of the present invention has been made to advantageously solve such a problem, and provides a combustion control method for a heating furnace in which a combustion control is performed by asymmetrically setting a combustion heating time in regenerative alternating combustion heating. It is intended for.

[0005]

The method of the present invention is characterized in that one side combustion heating and the other side heat storage are alternately arranged by a group of regenerative burners disposed oppositely on both sides of the heating furnace in the direction of the material to be heated. During the heat storage type alternating combustion heating, the combustion heating time is set asymmetrically, and the exhaust gas of the long-time combustion heating burner group is set.
Increase exhaust gas suction ratio during exhaust to lower preheated air temperature
Combustion during the short-time combustion heating burner group
Increasing the ratio of baked air to increase the amount of heat removed from the heat storage
In addition, there is provided a combustion control method for a heating furnace , wherein alternating combustion heating is performed.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the method of the present invention, as described above, the combustion heating time is set asymmetrically to perform alternating combustion heating, that is, the combustion heating time on one side is shorter or longer than the combustion heating time on the other side. It is to set the time for alternating combustion heating, but in the pre-tropical zone of the heating furnace, any zone or two or more zones in the heating zone and the solitary zone, for example, the thickness of the material to be heated, size such as length, Determine the asymmetrical combustion heating time according to the material, heating temperature, the time to transport the material to be heated after heating in the heating furnace to the hot rolling mill, the thickness of the plate after finish rolling, etc. It is to be heated. Soshi
In this case, exhaust gas exhaust from the long-time combustion heating burner group
At times, increase the exhaust gas suction ratio to prevent a drop in preheated air temperature.
The burner is stopped and the combustion
As the air ratio is increased to increase the amount of heat removed from the heat storage,
Alternating combustion heating.

Next, an example of the method of the present invention will be described with reference to the drawings. In FIG. 1, a regenerative burner 4 provided with a regenerator 3 is provided opposite to both sides in the traveling direction of a material 2 to be heated of a heating furnace 1, and the regenerative burners 4 of a regenerative burner 4 group on one side B1 are provided. The combustion air switching valve A1 is fully opened via a switching controller (not shown), and air is supplied to each regenerator 3 to increase the heat and supplied to each burner. At the same time, fully open the fuel switching valve F1,
The fuel is supplied to the group of burners 4 and burned to heat the material 2 to be heated. On the other hand, the exhaust gas switching valve E1 is fully closed, the exhaust gas switching valve E2 is fully opened, and the combustion exhaust gas in the heating furnace 1 is sucked from the regenerative burner group 4 on the other side B2.
The heat energy of the exhaust gas is stored in the heat storage 3 and then exhausted. Thus, one side B1 for a certain time
After the combustion heating by the regenerative burners 4 group, the combustion air switching valve A1 is fully closed, the combustion air switching valve A2 is fully opened, and the fuel is turned on, as shown in FIG. 2 by a command from a switching controller (not shown). Switching valve F1 fully closed, fuel switching valve F2 fully open,
The exhaust gas switching valve E1 is fully closed, the exhaust gas switching valve E2 is fully opened, and the combustion is switched to the combustion of the four burners on the other side B2 of the heating furnace 1. At the same time, the combustion exhaust gas in the heating furnace 1 is switched from the four burners on the one side B1. Is sucked and passed through the heat storage body 3 of each burner 4, and the heat energy of the exhaust gas is stored and exhausted.

At the time of the regenerative alternating combustion as described above, the switching controller sets the combustion time of the first side B1 of the heating furnace 1 to 40 seconds as shown in FIG. 3 and the combustion time of the other side B2 to 30 seconds asymmetrically in advance. In addition, alternating combustion heating is performed according to a command from the switching controller, and inclined heating is performed to heat the rear end portion of the material to be heated 2 from the front end portion to a high temperature.

In such regenerative alternating combustion, as in the case of uniform heating of a material to be heated by the same combustion time and alternating combustion heating of heat storage, the combustion air ratio m = 1.1 and the exhaust gas suction ratio is set to about 80%. , The one-side B1 burner group 4 has a relatively long combustion time, and as the heat storage time (exhaust gas suction time), the exhaust gas whose combustion time is relatively short is sucked and stored. In combustion, the preheating of the combustion air takes a long time.
Since the amount of heat removed by the combustion air is large, the amount of heat stored in the heat storage body gradually decreases with time, so that the temperature of the preheated air decreases and the thermal efficiency deteriorates. On the other hand, in the group of burners 4 on the other side B2 whose combustion time is relatively short, the amount of heat removed by the combustion air is small with respect to the amount of heat received from the exhaust gas. Then, the exhaust gas temperature on the outlet side of the heat storage body becomes high, and the exhaust gas switching valve E2 and the exhaust gas suction blower exceed the heat-resistant temperature. Sometimes.

In order to solve such difficulties, the present invention
Reduces the preheat air temperature by increasing the exhaust gas suction ratio when exhaust gas is exhausted from the long-time combustion heating burner group B1, and increases the combustion air ratio during combustion heating of the short-time combustion heating burner group B2. Increase the amount of heat removed from
Like that . For example, when exhaust gas is being exhausted by four groups of the one-side B1 burners whose combustion time is relatively long, the exhaust gas suction ratio is increased from 80% to 110% to increase the heat storage amount and to increase the preheated air temperature. Prevent drop.
The burner 4 on the other side B2 having a relatively short combustion time.
When the group is burning, the combustion air ratio is increased from m = 1.1 to m = 1.25 to increase the amount of heat removed from the heat storage unit 3 and suppress the rise in the exhaust gas temperature on the exit side of the heat storage unit 3. Is preferred. By doing so, the combustion time of the first group of B1 burners 4 and the fourth group of burners 4 of the other side B2 can be set freely according to the size of the material 2 to be heated, while suppressing fluctuations in the amount of heat stored. By appropriately setting and controlling the combustion air ratio and the exhaust gas suction ratio according to time, stable inclined heating can be performed.

When the material to be heated 2 is to be uniformly heated, a switching controller (not shown) is provided with one side B1 as shown in FIG.
The combustion time and exhaust gas exhaust time of the burner 4 group on the other side B2 are set to be the same as each other, and the combustion air switching valves A1, A2, the fuel switching valves F1, F2, The exhaust gas switching valves E1 and E2 are operated to perform alternating combustion.

From the viewpoint of combustion stability and thermal efficiency, the combustion air flow rate of the regenerative alternating combustion heating is about 10% excessive (air ratio m = air ratio) over the theoretical air ratio obtained from the fuel composition.
1.1) It is common to supply. On the other hand, the flow rate of the combustion exhaust gas sucked through the burner is set so that about 80% of the exhaust gas amount generated by the combustion reaction is sucked in order not to largely change the heat storage amount of the heat storage body during a long operation. This is a value uniquely determined from the heat capacity of the exhaust gas that supplies heat to the heat storage body and the heat capacity of the combustion air that takes heat from the heat storage body. Therefore, about 20% that is not sucked from the burner
The exhaust gas flows through, for example, a heating furnace, is sucked into a flue from a charging side of a material to be heated, and is exhausted outside the furnace.

[0013]

Next, examples of the method of the present invention will be described together with comparative examples.

[Table 1] Note 1: The material to be heated is C: 0.003%, Mn: 0.35%, Si: 0.01
%, P: 0.08%, S: 0.002%, SolAl: 0.035%, Nb: 0.02
%, Ti: 0.008% slab composed of remaining inevitable components and Fe. Note 2: The heating conditions (heating furnace) consist of a pre-tropical zone, a heating zone, and a solitary zone. The combustion time was set as in Example 1, and the fuel was heated and heated by regenerative alternating combustion using the coke oven generated gas as fuel. Note 3: Furnace time is the total time of pre-tropical zone, heating zone, and solitary zone. Note 4: Heating of the front end of the heating material and the rear end of the heating material are the average temperature in the thickness direction of the front and rear ends in the length direction of the heated material immediately after the heat extraction. Note 5: In the embodiment, the exhaust gas suction ratio of the one-side burner group is 1
10%, combustion air ratio m of the other-side burner group m = 1.25. In the comparative example, the exhaust gas suction ratio of the one side and the other side burner groups was 8
The operation was performed at 0% and the combustion air ratio m = 1.1.

[0014]

According to the method of the present invention, the material to be heated can be uniformly heated and inclinedly heated by the regenerative alternating combustion, and the function of the heating furnace can be greatly improved. In addition, since accurate inclined heating can be performed, a rolled material in hot rolling can be rolled at a uniform temperature, and the material and shape can be made uniform, so that excellent effects such as improvement in quality can be provided. Can be.

[Brief description of the drawings]

FIG. 1 is a main part plan view showing an example for carrying out the method of the present invention.

FIG. 2 is a plan view of a main part showing an example for carrying out the method of the present invention.

FIG. 3 is a flowchart showing an example of inclined heating by regenerative alternating combustion in the method of the present invention.

FIG. 4 is a flowchart showing an example of uniform heating by regenerative alternating combustion.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-200321 (JP, A) JP-A-5-118764 (JP, A) JP-A-57-35615 (JP, A) JP-A-7-35 158845 (JP, A) JP-A-53-43609 (JP, A) JP-A-4-13655 (JP, U) JP-B-60-49695 (JP, B2) (58) Fields investigated (Int. ⁷ , DB name) C21D 1/52 C21D 9/00 101 F23L 15/02 F27D 17/00 101

Claims (1)

(57) [Claims] 1. A regenerative burner group disposed on both sides of a heating furnace in a direction in which a material to be heated advances in an asymmetrical manner in a regenerative type alternating combustion heating in which one-side combustion heating and the other-side heat storage are alternately performed. Set to discharge the long-time combustion heating burner group.
When exhausting gas, increase the exhaust gas suction ratio to reduce the preheated air temperature.
Prevention of drop and short-time combustion heating burner group during combustion heating
Increase the amount of heat removed from the heat storage by increasing the combustion air ratio
As described above, a method for controlling combustion in a heating furnace , wherein alternating combustion heating is performed.