JP2001098320A - Control method of furnace pressure in heating furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method of the furnace pressure in a heating furnace, by which even when alternating combustion burners having heat reservoir is provided, the furnace pressure control can stably be executed. SOLUTION: When the furnace pressure in the heating furnace provided with the alternating combustion burners having the heat reservoir is controlled by opening/closing of a damper prepared in a flue for exhaust gas, low temperature gas is introduced into the flue at the upstream side and/or the downstream side of the damper. Further, the low temperature gas is made to use the outer air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a furnace pressure control method for a heating furnace, and more particularly to a technique for controlling the furnace pressure of a heating furnace provided with an alternating combustion burner having a heat storage body.

[0002]

2. Description of the Related Art For example, a rotary heating furnace is sometimes used for heating steel materials. It is, as shown in FIG.
The furnace chamber 1 has a doughnut-shaped plane, a rotating horizontal hearth 2, and a burner 4 for heating an object 3 to be heated. When this furnace is used, the object 3 to be heated entered through the charging port 5 moves through the furnace to the discharge port 6 while the furnace floor 2
The temperature is heated to a desired temperature by appropriately adjusting the rotation speed and the furnace temperature. As the burner 4, a heavy oil burner is generally used, and along the both side walls of the furnace chamber 1 (doughnut-shaped, the smaller diameter is called the inner wall 7 and the larger diameter is called the outer wall 8).
Many are arranged with their tips facing the furnace. In order to actually operate such a heating furnace, the heat of the high-temperature exhaust gas is exchanged with the air used for combustion by the recuperator 9 or as shown in FIG.
As shown in (a), the heat is recovered by the preheating furnace 10 and the waste heat boiler 11 to increase the thermal efficiency. Nevertheless, due to the structure of the furnace, the heating furnace has a problem that the surface area is large with respect to the furnace volume, the combustion efficiency is low even when heat exchange is used, and the fuel consumption rate is necessarily high. Further, when the object to be heated 3 is a steel material, it is oxidized during heating to produce scale, and there is a problem that so-called scale loss is large.

On the other hand, Japanese Patent Application Laid-Open No. 7-4851 discloses a set of two burners each having a heat storage body.
A heating furnace has been proposed in which a plurality of sets of alternating combustion burners that alternately switch between combustion and suction are arranged along the inner wall and the ceiling surface. In this furnace, the calorific value of the exhaust gas is mostly recovered by its own burner (heat accumulator), so that the thermal efficiency is higher than in the past. Also, large equipment such as a heavy oil preheater or heat exchanger is not required, and construction costs are reduced. Further, the effect of reducing the scale of the steel material was also recognized to some extent.

[0004] By the way, the heating furnace provided with such an alternating combustion burner is different from the conventional furnace (see FIG. 3 (a)), and as shown in FIG. (A flow rate as low as 20 vol% of the whole) is directly discharged from the chimney 15 into the outside air. Accordingly, as shown in FIG. 2, a damper for controlling the furnace pressure is provided in the flue 17 from the exhaust port 16 of the furnace to the chimney 15. However, since the furnace pressure control damper generally has low hermeticity, if the gas flow rate is small, the furnace pressure control may be difficult. That is, even if the furnace pressure control damper 18 is sealed, the pressure loss of the exhaust gas 19 passing through the damper 18 is smaller than the pressure (negative pressure) on the downstream side, and the exhaust gas 19 flows on the downstream side. Because.

[0005]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides a furnace pressure control method for a heating furnace in which furnace pressure control can be stably performed even if an alternating combustion burner having a heat storage body is provided. It is intended to be.

[0006]

Means for Solving the Problems The inventor has conducted intensive studies to achieve the above object and has embodied the results in the present invention.

That is, according to the present invention, when controlling the furnace pressure of a heating furnace provided with an alternating combustion burner having a heat storage body by opening and closing a damper provided in an exhaust gas flue, the upstream and / or downstream side of the damper And introducing a low-temperature gas into the flue.

Further, the present invention is a furnace pressure control method for a heating furnace, wherein the low-temperature gas is used as outside air.

Further, there is provided a furnace pressure control method for a heating furnace, wherein the outside air is introduced by natural suction without using a fan.

In the present invention, a low-temperature gas is introduced into the flue upstream and / or downstream of the damper provided in the flue from the furnace to the chimney, so that the gas temperature in the flue decreases. The speed at which the gas rises in the chimney decreases (so-called "draft" decreases). Also, the gas pressure increases. As a result, the amount of gas discharged through the damper when the damper is closed can be suppressed to a very small amount, and the furnace pressure can be easily controlled. Further, in the present invention, the low-temperature gas is used as outside air, and the introduction of the outside air is performed without power, so that furnace pressure control can be performed at low cost.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the circumstances leading to the invention.

First, the inventor focused on reducing the draft without remodeling the furnace pressure control damper having a low hermeticity itself, and intensively studied specific means. As a result, the inventors considered that it is better to lower the temperature of the exhaust gas 19 and increase the pressure. Specifically, a gas whose temperature is lower than that of the exhaust gas 19 is introduced into the flue 17.

The type of the low-temperature gas 20 to be introduced is a high-temperature (1
Reacts with components of the exhaust gas 19 (a part of the combustion gas from the alternating combustion burner) of about 000 ° C.
The use of an inert gas is preferred in consideration of corrosion of the steel. However, according to the inventors' research, the temperature was
Room temperature is sufficient, and it has been confirmed that air does not cause any trouble in the flue gas 17 as the gas, so that room temperature outside air is most preferable. In the case of introducing an inert gas, a known gas holding container and a pressurizing means (both not shown) may be provided. On the other hand, in the case of outside air, as shown in FIG. 1, it was sufficient to provide the outside air intake 24 and the damper (hereinafter, referred to as the draft control damper 21) in the flue 17. Although a power source such as a compressor may be used, a sufficient amount of outside air can be introduced because the inside of the flue 17 is usually under negative pressure.

Next, the inventor examined the introduction position of the low-temperature gas 20 and found that either the upstream or downstream side of the furnace pressure control damper 18 may be used. This is because the introduction to either side contributes to a decrease in the temperature and a rise in the pressure of the exhaust gas 19.

In order to specifically implement the present invention, the operator constantly monitors the pressure sensor 22 provided in the furnace, and opens and closes the draft control damper 21 so that the pressure value falls within a target pressure range. Thus, the low-temperature gas 20 may be introduced. However, the operator may be replaced with a computer, and the draft control damper 21 may be opened and closed by an unattended remote operation.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A heating furnace equipped with 27 sets of alternating combustion burners 23 having a heat storage body (the outer wall diameter is 33 m, the inner wall diameter is 25 mm)
m, the height from the hearth to the ceiling is 1.5 to 2.1 m). The object to be heated 3 is a round steel slab (one of which has an outer diameter of 190 mm and a length of 3000 mm) of a material for producing a seamless steel pipe, which is continuously charged from the charging port 5 to perform a heating operation. Was. The target heating temperature of the slab is 1250 ± 30 ° C., and the target furnace pressure is 20 ± 2 Pa
And This furnace pressure control is a method according to the present invention in which outside air is introduced unattended.

FIG. 5 shows the change over time of the furnace pressure during the heating operation in comparison with the change during the conventional operation. From FIG. 5, it is clear that according to the present invention, the furnace pressure can be controlled within the target range. The slabs heated during this operation all satisfied the target heating temperature.

[0018]

As described above, according to the present invention, even if an alternating combustion burner having a heat storage body is provided, the furnace pressure of the heating furnace can be stably controlled. In addition, since the gas used for the control can be the outside air, the furnace pressure can be stabilized at low cost with simple equipment modification.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a furnace pressure control method for a heating furnace according to the present invention.

FIG. 2 is a view showing an exhaust system of a heating furnace provided with an alternating combustion burner.

FIG. 3 is a diagram illustrating an exhaust system of a conventional heating furnace.
(A) shows the case where the burner is a heavy oil burner, and (b) shows the case where the burner is an alternating combustion burner.

FIG. 4 is a diagram illustrating the structure of a heating furnace.

FIG. 5 is a diagram comparing a furnace pressure change according to an embodiment of the present invention with a conventional furnace pressure change.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Furnace room 2 Hearth 3 Heated object 4 Burner 5 Inlet 6 Outlet 7 Inner wall 8 Outer side wall 9 Recuperator 10 Preheating furnace 11 Waste heat boiler 12 Combustion blower 13 Exhaust blower 14 High temperature fan 15 Chimney 16 Furnace exhaust port 17 Flue gas 18 Furnace pressure control damper 19 Exhaust gas (part of combustion gas) 20 Low temperature gas 21 Draft control damper 22 Pressure sensor 23 Alternating combustion burner 24 External air intake

Claims (3)

[Claims] When controlling a furnace pressure of a heating furnace provided with an alternating combustion burner having a heat accumulator by opening and closing a damper provided in a flue of exhaust gas, the furnace pressure is set in a flue upstream and / or downstream of the damper. A furnace pressure control method for a heating furnace, characterized by introducing a low-temperature gas. 2. The furnace pressure control method for a heating furnace according to claim 1, wherein the low-temperature gas is outside air. 3. The furnace pressure control method for a heating furnace according to claim 2, wherein the outside air is introduced by natural suction without using a fan.