JP3067465B2 - Continuous heating furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous heating furnace used for heating a material to be heated such as a slab, a billet or a bloom to a predetermined target temperature, and a method of operating the furnace.

[0002]

2. Description of the Related Art In a method of operating a continuous heating furnace, the furnace temperature setting pattern is determined from the viewpoint of energy saving from the viewpoint of energy saving, "Heat Transfer Experiment and Calculation Method in Continuous Slab Heating Furnace", pages 4 and 4. As disclosed on page 29,
The method of operating with the pre-tropical furnace temperature set lower than other zones is generally adopted.

Further, as a method of reducing the unit fuel consumption, for example, as shown in Japanese Patent Publication No. 54-7488, a heat exchange zone is provided on the charging side, and a heat exchange zone is provided between the combustion exhaust gas from the extraction side and the material to be heated. Take a long non-combustion zone to transfer heat,
It has been proposed to reduce the temperature of combustion exhaust gas at the furnace bottom as much as possible.

However, recently, there has been an increasing demand for a heating furnace capable of coping with a material having a strict maturity required for a long time due to metallurgical conditions, that is, a material having a strict temperature uniformity in a thickness direction and a material having a high extraction temperature.

[0005] In a heating furnace having a long non-combustion zone on the charging side, this demand is solved by increasing the load on the combustion zone on the extraction side and increasing the heating time. However, prolonging the heating time leads to a decrease in production volume, and inevitably adding a burner to this non-combustion zone to secure production volume and quality at the expense of fuel consumption. I have.

On the other hand, recently, as one measure for energy saving in steel facilities, the process has been directly connected. Hot charging (heating piece charging) in a continuous heating furnace is also an example, and has a large effect of reducing fuel consumption rate.

However, from an operator's point of view, conventional cold flakes,
A complicated furnace temperature setting has been required in consideration of the fact that the fluctuation range of the charging temperature is increased by adding the heating piece to the heating piece.

[0008] For the operator, it is desirable that the charging temperature be as uniform as possible, and it is desired that a device for rapidly preheating the cold pieces and the hot pieces be provided on the charging side of the heating furnace.

As the preheating device, induction heating or Japanese Patent Publication No. Sho 5
There is jet heating proposed in Japanese Patent Application No. 2-27607.

[0010] However, none of them has high equipment costs and is not adopted. Further, the jet heating has problems such as a change in heat transfer efficiency due to a change in exhaust gas temperature, and a problem that the surface of the material to be heated is in a dew point temperature range and moisture adheres.

Therefore, at present, a burner is installed on the charging side of the heating furnace, and preheating is performed at the expense of deterioration of the unit fuel consumption due to an increase in the sensible heat of the exhaust gas.

As described above, many proposals have been made regarding the equipment and operation of the heating furnace, but none of them have been satisfactory, and even if the fluctuation range of the charging temperature from the cold piece to the hot piece to the hot piece is large, Further, even when heating is required for a long time, a heating furnace having a high degree of freedom in operation, a low fuel consumption rate and a high productivity has been awaited.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and its object is to
An object of the present invention is to provide a continuous heating furnace capable of efficiently heating materials to be heated under different heating conditions in the same heating furnace at a low fuel consumption rate.

[0014]

SUMMARY OF THE INVENTION The present invention has the following features.

[0015]

( 1 ) In a continuous heating furnace comprising a pre-tropical zone, a heating zone and a solitary zone, a tropical zone is built in the pre-tropical zone,
Alternately one or more pairs of regenerative burners to burn the provided, before
It is characterized in that a normal burner is provided in the heating zone and the solitary zone .

( 2 ) In a continuous heating furnace comprising a pre-tropical zone, a heating zone and a soot zone, a burner for burning fuel with oxygen or oxygen-enriched air is provided in the pre-tropical zone,
It is characterized by providing normal burners in the tropics and the tropics .

( 3 ) In a continuous heating furnace comprising a pre-tropical zone, a heating zone, and a solitary zone, the configuration of (1) and (2)
In addition, an exhaust gas outlet is provided between the pre-tropical zone and the heating zone.

[0019]

[Action] continuous heating furnace of the present invention, because can set higher than the furnace temperature to the other zones of the preheating zone, Jukunetsu degree strictly material takes a long time heating, high extraction temperature material and Hiyahen, warm piece this The material is rapidly heated in the pre-tropical zone, and the thermal conditions at the entrance of the heating zone of the material to be heated are made substantially uniform, thereby improving the productivity.

In the continuous heating furnace of the present invention , since the regenerative burner is installed in the pre-tropical zone, the sensible heat of the flue gas can be recovered as high-temperature preheated air, so that the unit fuel consumption of the heating furnace can be reduced.

Further, since the oxygen burner is installed in the pre-tropical zone, the amount of the flue gas is small, and therefore, the sensible heat of the flue gas can be easily recovered with a compact heat exchanger.

Further, since the exhaust gas outlet for the flue gas is provided between the pre-tropical zone and the heating zone, the pre-tropical high-temperature flue gas and the flue gas from the other zones do not mix with each other. Since the sensible heat of the flue gas can be efficiently recovered, and there is no interference between the furnace temperature in the pre-tropical zone and the furnace temperature in the heating zone, independent temperature settings can be made.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

Embodiment 1 First, a case where a regenerative burner is installed in a pre-tropical zone will be described with reference to FIGS.

FIG. 1 shows the continuous heating furnace equipment embodying the present invention, the furnace temperature and the temperature rise curve of the material to be heated.

FIG. 1 is a sectional view of a heating furnace 1 in which a regenerative burner 2 is installed in a pre-tropical zone (A), a normal burner 3 is installed in a heating zone (B), and a normal burner 3 is installed in a soaking zone (C). .

A slab charged into the heating furnace from the charging inlet 4;
The material S to be heated such as a billet or a plume is extracted from the extraction port 5 to the outside of the furnace by a transfer device such as a walking beam (not shown).

As shown in FIGS. 2 and 3, the regenerative burner 2 disposed in the pre-tropical zone (A) has a pair of a burner 2 burning and a non-burning burner 2 '.
In the burning burner 2, cool air as combustion air enters from the supply / discharge port 6 located at the end of the heat storage body, and the cold air is preheated in the heat storage body 7 and mixed with the fuel gas supplied from the nozzle 8. After the combustion, the combustion gas is supplied into the furnace from the burner port 9 as a flame.

In the non-burning burner 2 ′, the combustion gas in the furnace is sucked from the burner port 9, passes through the regenerator 7, is discharged from the end of the regenerator, and enters the atmosphere via an exhaust pipe (not shown). Dissipated.

The normal burners 3 in the other zones supply the combustion gas as a flame into the furnace, and the combustion exhaust gas flows to the pre-tropical side, and is emitted to the atmosphere via the stack 10 and the chimney 11.

In FIG. 1, the material S to be heated is changed from 20 ° C. to 11
For heating to 80 ° C., the furnace temperature T was 1300 ° C. for the pre-tropical (A) furnace temperature and 12 for the heating zone (B).
The furnace temperature TC of 50 ° C and the soaking zone (C) is set to 1200 ° C.

In the conventional operating method, TA ′ is 1200
° C, TB ′ was 1300 ° C, and TC ′ was 1230 ° C. In this embodiment, the temperature of the pre-tropical zone is higher than that of other zones.

In the present invention, the temperature of the material S to be heated is
-S, the temperature is raised as shown by the curve indicated by the center SC. As shown in FIG. 1, since the furnace temperature in the pre-tropical zone is set high, the furnace temperature in the heating zone and the soaking zone may be set low. Since the combustion gas from the pre-tropical regenerative burner passes through the regenerator of the non-burning burner and is exhausted, the temperature of the flue gas at the furnace bottom is lower than in the conventional operation method. I have.

The amount of heat input and heat loss increase in the pre-tropics are
Invention of high waste heat recovery effect by regenerative burner, that is, there is no restriction on heat resistance and high efficiency allows high air temperature to be obtained, and reduction in heat input in heating zone and solitary zone is sufficiently compensated for by invention. According to the estimation of the thermal efficiency was 69%,
This means that heating is performed at a lower fuel consumption rate than in the conventional method (thermal efficiency 63%).

Although the furnace length directions of the preheating zone, the heating zone, the soaking zone, and the continuous heating furnace are classified and given names, these are merely names for convenience and are mainly used to raise the temperature of the material to be heated. The places where the heat is mainly diffused in the pre-tropical zone, the heating zone, and the material to be heated are classified as solitary tropics.

FIG. 4 shows the pre-tropical zone (A) and the heating zone (B).
In the meantime, an outlet 1 for dispersing combustion gas from a normal burner 3 disposed in a heating zone and a solitary zone into the atmosphere.
This is another embodiment provided with No. 2. This is to prevent the pre-tropical combustion exhaust gas from mixing with the combustion exhaust gas flowing from the extraction side.

The sensible heat of the flue gas from the discharge port 12 is separately recovered by a heat exchanger (not shown).

Embodiment 2 A case where an oxygen burner is installed in a pre-tropical zone will be described.

As a method of rapidly preheating the material to be heated, the inventors have considered supplying a high-temperature, high-radiation atmosphere gas around the material to be heated.

Furthermore, as a means for producing a high-temperature, high-radiation atmosphere gas, a burner that burns fuel with oxygen was considered.

The amount of heat given to the material to be heated in the heating furnace is expressed by the following equation.

Q = 4.88ΦCG ｛[(tg + 273)
/ 100] ⁴ -[(ts + 273) / 100] ⁴ ｝ Q: Heat quantity given to the material to be heated ΦCG: Overall heat transfer coefficient tg: Temperature of the atmosphere gas ts: Temperature of the material to be heated Here, ΦCG is CO in the atmosphere gas. ₂ , ΦCG increases with an increase in the amount of H ₂ O, the amount of heat applied to the material to be heated increases, and the material is rapidly preheated.

The inventor has calculated ΦCG when the fuel is COG (coke oven gas). Table 1 shows the results of the trial calculation, and ΦCG is 35% larger than that of the prior art.

[0044]

[Table 1] As shown in Table 1, the theoretical exhaust gas amount when the fuel is COG (coke oven gas) is reduced to 30% as compared with the prior art.

FIG. 5 shows a furnace temperature and a material-to-be-heated temperature rise curve in a heating furnace according to the present invention. A pipe for supplying fuel and a pipe for supplying oxygen or oxygen-enriched air are connected to the oxygen burner 13 provided in the pre-tropical zone.

The pre-tropical furnace temperature TA in FIG. 5 is higher than the furnace temperatures in the other zones, and the combustion exhaust gas temperature at the furnace bottom is lower. This is because the amount of combustion exhaust gas is small because the fuel is burned by the oxygen burner.

The temperature of the material S to be heated is determined by the surface SS, the center S-
As shown by the curve indicated by C, the temperature rises rapidly in the pre-tropical zone.

It should be noted that the present invention is not limited to the above embodiment. For example, as shown in FIG. By providing the regenerative burner 2 or the oxygen burner 13, it is also possible to set the furnace temperature of the pre-pre-tropical zone (A ') higher than in other zones.

As a result, for example, deterioration of the fuel consumption rate,
A reduction in draft force can be prevented, and application to existing modifications can be easily performed without requiring significant modifications.

In addition, unless departing from the gist of the present invention,
Of course, various changes can be made.

[0051]

As described above, according to the present invention,
In existing furnace, because can set higher than the other zone furnace temperature of the preheating zone in a simple modification of only preheating zone, Jukunetsu degree strictly material takes a long time heating, high extraction temperature material and Hiyahen, temperature strips The rapid heating in the pre-tropical zone makes the thermal condition of the material to be heated at the entrance of the heating zone substantially uniform, thereby improving the productivity.

Further, since the regenerative burner is installed in the pre-tropical zone, the sensible heat of the flue gas can be recovered as high-temperature preheated air, so that the fuel consumption of the heating furnace can be reduced.

Further, since the oxygen burner is installed in the pre-tropical zone, the amount of flue gas is small, and therefore, the recovery of sensible heat of flue gas can be easily performed with a compact heat exchanger.

Further, since a flue gas discharge port is provided between the pre-tropical zone and the heating zone, the pre-tropical high-temperature flue gas and the flue gas from other zones do not mix with each other. Since the sensible heat of the flue gas can be efficiently recovered, and there is no interference between the furnace temperature in the pre-tropical zone and the furnace temperature in the heating zone, independent temperature settings can be made.

In short, the same heating furnace has a large degree of freedom of operation, and has an excellent effect of securing the production amount and satisfying the quality requirements from metallurgical conditions without deteriorating the fuel consumption rate. .

Further, according to the present invention, it is possible to easily apply the present invention to an existing furnace without requiring significant modification.

[Brief description of the drawings]

FIG. 1 shows a first embodiment according to the present invention.

FIG. 2 is a sectional view of the regenerative burner according to the first embodiment.

FIG. 3 is a conceptual diagram of a combustion system of the regenerative burner according to the first embodiment.

FIG. 4 shows another example of the first embodiment according to the present invention.

FIG. 5 shows another example of the second embodiment according to the present invention.

FIG. 6 shows another embodiment according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating furnace 2 Regenerative burner 3 Normal burner 4 Charging inlet 5 Extraction port 6 Supply / exhaust port 7 Heat storage body 8 Fuel gas nozzle 9 Burner port 10 Flue stack 11 Chimney 12 Combustion exhaust gas outlet 13 Oxygen burner

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masato Fujioka 46-59 Ohara Nakahara, Tobata-ku, Kitakyushu-shi, Fukuoka Nippon Steel Corporation Machinery & Plant Business Department (72) Inventor Junichi Hayashi Shintomi, Futtsu-shi, Chiba 20-1 Inside the Technology Development Division of Nippon Steel Corporation (56) References JP-A-2-30720 (JP, A) JP-A-53-65208 (JP, A) JP-A-62-164817 (JP, A A) Japanese Patent Application Laid-Open No. 5-118764 (JP, A) Japanese Patent Publication No. 3-48249 (JP, B2) Japanese Utility Model Publication No. Sho 63-21564 (JP, Y2) (58) Fields investigated (Int. Cl. ⁷ , DB name) ) C21D 1/00 112 C21D 1/52 F27B 9/00-9/40

Claims (3)

(57) [Claims] 1. A preheating zone, Oite the continuous heating furnace comprising a heating zone and the soaking zone, the preheating zone, a built-in regenerator, exchange
At least one pair of regenerative burners that burn each other is provided.
A continuous heating furnace characterized by providing normal burners in the tropics and the tropics . 2. A continuous heating furnace comprising a pre-tropical zone, a heating zone, and a solitary zone, wherein oxygen or oxygen-rich
A burner for burning the fuel with the forming air;
And a continuous heating furnace characterized by providing a normal burner in the solitary zone. 3. A continuous heating furnace comprising a pre- tropical zone, a heating zone and a soaking zone.
The continuous heating furnace according to claim 1 or 2, wherein an outlet is provided.