JPH0953114A - Method for controlling combustion in heating furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To freely apply a uniform heating and a gradient heating to a material to be heated by setting asymmetrically a combustion heating time in a heat storage type alternate combustion heating and executing the combustion control of a heating furnace. SOLUTION: Heat storage type burners 4 attaching heat storage bodies 3 faced to both sides in the advancing direction of the material 2 to be heated in the heating furnace 1, are arranged. Fuel is supplied and burnt into the burner 4 group through a change-over controller to each heat storage body 3 in the heat storage type burner 4 group at the one side B1 to heat the material 2 to be heated. After burning and heating with the heat storage type burner 4 group at the one side B1 for a fixed time, the combustion at the one side B1 is changed over to the combustion with the burner 4 group at the other side B2 by a command of a change-over controller. In the heat storage type alternate combustion, the combustion time is asymmetrically preset e.g. such as 40 sec at the one side B1 and 30 sec at the other side B2, and the alternate combustion heating is applied by the command of the change-over controller to execute the gradient heating for heating the rear end part to higher than the front end part of the material 2 to be heated.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a combustion control method for a heating furnace.

[0002]

2. Description of the Related Art A slab (steel slab), billet (bar steel), bloom, etc. after casting is charged into a heating furnace and heated to a temperature suitable for hot rolling. Is generally composed of pre-tropics, heating zones and soaking zones,
Materials to be heated such as slabs are heated by sequentially moving the pre-tropical zone, heating zone and soaking zone in order to improve the heating efficiency. The burner groups are arranged facing each other, the one side burner group heats the combustion air through the heat storage body and supplies it to the burner to burn the fuel, and the other side burner group stops the combustion. The combustion exhaust gas in the furnace is exhausted through the heat storage body to store heat energy in the exhaust gas. As described above, continuous heating is performed by so-called heat storage type alternating combustion in which combustion and heat storage are alternately performed.
It is disclosed in Japanese Patent Laid-Open No. 6-194054.

[0003]

In the heat storage type 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 excellent combustion heating with high combustion efficiency is possible. Is. When the material to be heated is uniformly heated in this manner, a large time difference occurs between the slab tip and the rear end during hot rolling in a long slab, etc., and therefore the slab tip is hot and the rear end during hot rolling. Is low and the finish temperature of the rolled material is non-uniform, so that a uniform material cannot be obtained, the shape is deteriorated, the quality is deteriorated, and the yield is reduced. Therefore, from the temperature of the tip of the material to be heated in the heating furnace,
It is necessary to perform gradient heating for heating the rear end temperature to a high temperature to prevent the temperature decrease at the rear end of the rolled material due to the time difference during rolling.

However, in the above-described heat storage type alternating combustion, uniform heating is premised, and the burner is structurally constructed so that the combustion amount and the combustion time are the same, and the temperature in the heating furnace is the same. There is a problem in that the material to be heated cannot be gradient heated by changing the distribution. The method of the present invention has been made in order to advantageously solve such a problem, and provides a combustion control method for a heating furnace in which a combustion heating time is asymmetrically set and combustion is controlled in regenerative alternating combustion heating. The purpose is.

[0005]

A feature of the method of the present invention is that the one-side combustion heating and the other-side heat storage are alternately performed by heat storage type burner groups arranged facing each other on both sides of the heating furnace in the traveling direction of the material to be heated. A combustion control method for a heating furnace, characterized in that, when the heat storage type alternating combustion heating is performed, the combustion heating time is set asymmetrically to perform alternating combustion heating.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION 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 of one side is shorter or longer than the combustion heating time of the other side. Although it is intended to perform alternating combustion heating by setting the time, in any zone of the preheating zone of the heating furnace, the heating zone and the soaking zone or two or more zones, for example, the size of the material to be heated, the length, etc., The combustion heating time, which is set asymmetrically according to the material, the heating temperature, the time to transfer the material to be heated after heating in the heating furnace to the hot rolling mill, the sheet thickness after finish rolling, etc. is determined, and based on this, alternating combustion is performed. It is to heat.

Next, an example of the method of the present invention will be described with reference to the drawings. In FIG. 1, a heat storage type burner 4 having a heat storage body 3 is provided so as to face each other in the traveling direction of the material to be heated 2 of the heating furnace 1, and each heat storage body 3 of the heat storage type burner 4 group on one side B1 is provided. The combustion air switching valve A1 is fully opened via a switching controller (not shown), and air is supplied to each heat storage body 3 to raise its temperature and supplied to each burner. At the same time, fully open the fuel switching valve F1,
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 type burner 4 group on the other side B2, and each burner 4 is operated.
The heat energy of the exhaust gas is passed through the heat storage body 3 of FIG. In this way, one side B1
2 is burned and heated by the heat storage type burner 4 group, the combustion air switching valve A1 is fully closed and the combustion air switching valve A2 is fully opened as shown in FIG. 2 by a command of a switching controller (not shown). Switch valve F1 fully closed, fuel switch valve F2 fully open,
The exhaust gas switching valve E1 is fully closed and the exhaust gas switching valve E2 is fully opened to switch to the combustion of the burner 4 group on the other side B2 of the heating furnace 1. At the same time, the combustion exhaust gas in the heating furnace 1 from the burner 4 group on the one side B1 is switched. Is sucked through and passed through the heat storage body 3 of each burner 4 to store the heat energy of the exhaust gas and then exhaust the heat energy.

In the heat storage type alternating combustion as described above, for example, the combustion time of one side B1 of the heating furnace 1 is set to 40 seconds and the combustion time of the other side B2 is set to 30 seconds asymmetrically in advance in the switching controller. Alternately, alternating combustion heating is performed according to a command from the switching controller, and gradient heating is performed to heat the material 2 to be heated from the front end to the rear end.

In such heat storage type alternating combustion, the combustion air ratio m = 1.1 and the exhaust gas suction ratio are about 80%, as in the case of uniform heating of the material to be heated by the alternating combustion heating of the heat storage for the same combustion time. If set to 1, the one-side B1 burner group 4 having a relatively long combustion time will absorb the exhaust gas having a relatively short combustion time as the heat storage time (exhaust gas suction time) to store heat. During combustion, the preheating of the combustion air takes a long time, so the amount of heat received from the exhaust gas
Since the amount of heat removed by the combustion air is large, the amount of heat stored in the heat storage body gradually decreases over time, so the temperature of the preheated air decreases and the thermal efficiency deteriorates. On the other hand, in the burner group 4 on the other side B2, where the combustion time is relatively short, the amount of heat removed by the combustion air is small compared to the amount of heat received from the exhaust gas, so the heat storage amount of the heat storage body gradually increases over time. , 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, and the exhaust gas switching valve etc. malfunctions during long-term operation, making operation difficult. Sometimes.

In order to solve such a problem, the exhaust gas suction ratio is increased when exhausting the exhaust gas of the long-time combustion heating burner group B1 to prevent the preheated air temperature from decreasing, and the short-time combustion heating burner group B2 is heated by combustion. At times, the combustion air ratio can be increased to increase the amount of heat removed from the heat storage body. For example, when exhaust gas is being exhausted by the one-side B1 burner group 4 having a relatively long combustion time, the exhaust gas suction ratio is increased from 80% to 110% to increase the amount of heat storage and increase the preheat air temperature. Prevent decline. When the burner group 4 on the other side B2 is burning for a relatively short burning time, the combustion air ratio m = 1.1 to m = 1.25.
It is preferable that the amount of heat removed from the heat storage body 3 is increased to increase the temperature of the exhaust gas to suppress the rise in exhaust gas temperature on the outlet side of the heat storage body 3.
By doing so, one side B1 while suppressing the fluctuation of the heat storage amount
The combustion time of the burner 4 group and the burner 4 group of the other side B2 is freely set according to the size of the material 2 to be heated, and the combustion air ratio and the exhaust gas suction ratio are appropriately set according to the combustion time. By controlling, stable gradient heating can be performed.

When the material to be heated 2 is heated uniformly, a switching controller (not shown) is provided with one side B1 as shown in FIG. 4 in advance.
The combustion time and the exhaust gas exhaust time of the burner 4 group on the other side B2 are set to be the same, and the combustion air switching valves A1 and A2 and the fuel switching valves F1 and F2 are set every 40 seconds according to a command from the switching controller. Alternating combustion is performed by operating the exhaust gas switching valves E1 and E2.

The flow rate of combustion air for such heat storage type alternating combustion heating exceeds the theoretical air ratio obtained from the fuel composition by about 10% from the viewpoint of combustion stability and thermal efficiency (air ratio m =
1.1) Generally supplied. On the other hand, the flow rate of the combustion exhaust gas sucked through the burner is set so as to suck about 80% of the exhaust gas amount generated by the combustion reaction in order to prevent the heat storage amount of the heat storage body from being significantly changed during long-term operation. This is a value that is 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 removes heat from the heat storage body. Therefore, about 20% not sucked from the burner
The exhaust gas flows through the heating furnace, for example, from the charging side of the material to be heated to the flue, and is exhausted outside the furnace.

[0013]

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

[Table 1] Note 1: Heated material 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% A slab composed of the remaining non-avoiding components and Fe. Note 2: Heating conditions (heating furnace) consist of pre-tropical zone, heating zone and soaking zone, and each zone is equipped with a regenerative burner with a regenerator on both sides (walls) The combustion time was set as 1 and the coke oven generated gas was combusted and heated by the heat storage type alternating combustion. Note 3: In-furnace time is the total time of pre-tropical zone, heating zone and soaking zone. Note 4: Heating of the heating material front end and heating material rear end is the average temperature in the thickness direction of the front end and rear end of the heated material immediately after heat extraction. Note 5: In the example, the exhaust gas suction ratio of the one-side burner group is 1
10%, combustion air ratio m = 1.25 of the other side burner group. In the comparative example, the exhaust gas suction ratio of the one side and the other side burner groups was set to 8
The operation was performed by setting 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 heat storage type alternating combustion, and the function of the heating furnace can be greatly improved. Further, since accurate gradient heating can be performed, the rolled material in hot rolling can be rolled at a uniform temperature, and the material, shape, etc. can be made uniform, so that excellent effects such as quality improvement can be provided. You can

[Brief description of drawings]

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

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

FIG. 3 is a flow chart showing an example of gradient heating by heat storage type alternating combustion of the method of the present invention.

FIG. 4 is a flow chart showing an example of uniform heating by heat storage type alternating combustion.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F27D 17/00 F27D 17/00

Claims (2)

[Claims] 1. An asymmetric combustion heating time in the regenerative alternating combustion heating in which one side combustion heating and the other side heat storage are alternately performed by heat storage type burner groups arranged oppositely on both sides of the heating furnace in the traveling direction of the material to be heated. A combustion control method for a heating furnace, which comprises setting and performing alternating combustion heating. 2. A regenerator that increases the exhaust gas suction ratio to prevent a decrease in preheat air temperature when exhausting exhaust gas from a long-time combustion heating burner group, and increases the combustion air ratio during short-time combustion heating burner group combustion heating. The method for controlling combustion in a heating furnace according to claim 1, wherein the amount of heat removed from the furnace is increased.