JP3733803B2 - Furnace pressure control method for rotary hearth furnace - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
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]
[Prior art]
For example, a rotary heating furnace may be used for heating steel materials. As shown in FIG. 4, it is formed of a furnace chamber 1 whose plane has a donut shape, a rotating horizontal hearth 2, and a burner 4 for heating an object 3 to be heated. When this furnace is used, the object to be heated 3 put in from the charging port 5 is adjusted to the desired temperature by appropriately adjusting the rotational speed of the hearth 2 and the temperature in the furnace while moving through the furnace to the discharge port 6. To be heated. The burner 4 is generally a heavy oil burner, and since the both side walls of the furnace chamber 1 (doughnut-shaped, the smaller diameter is called the inner wall 7 and the larger one is called the outer wall 8), the tip thereof is directed into the furnace. Many are arranged. In order to actually operate such a heating furnace, heat of the high-temperature exhaust gas is exchanged with air used for combustion by the recuperator 9, or is recovered by the preheating furnace 10 or the waste heat boiler 11 as shown in FIG. Was trying to increase the thermal efficiency. Nevertheless, the heating furnace has a problem that the structure of the furnace body has a large surface area relative to the furnace volume, and even if heat exchange is used, the combustion efficiency is poor and the fuel consumption rate is inevitably high. Moreover, when the to-be-heated material 3 is a steel material, there was a problem that it was oxidized during heating to generate scale, and so-called scale loss was large.
[0003]
On the other hand, Japanese Patent Laid-Open No. 7-4851 discloses a set of two burners each provided with a heat storage body, and an alternating combustion burner that alternately switches between combustion and suction along the inner wall and the ceiling surface. Have proposed multiple heating furnaces. In this furnace, most of the heat of the exhaust gas is recovered by its own burner (heat storage body), so that the thermal efficiency is higher than in the conventional case. In addition, heavy equipment such as heavy oil preheaters and heat exchangers are not required, and construction costs are reduced. Furthermore, the effect of reducing the scale of the steel material was 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. 3A), and as shown in FIG. 3B, a part of the combustion gas is used for heat recovery. (The flow rate is as small as 20 vol% of the whole) is directly discharged from the chimney 15 into the outside air. Accordingly, 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 as shown in FIG. However, since this furnace pressure control damper is generally low in hermeticity, if the gas flow rate is small, 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 wake side, and the exhaust gas 19 flows to the wake side. Because.
[0005]
[Problems to be solved by the invention]
In view of such circumstances, an object of the present invention is to provide a furnace pressure control method for a heating furnace capable of stably performing furnace pressure control even if an alternating combustion burner having a heat storage body is provided.
[0006]
[Means for Solving the Problems]
The inventor diligently studied to achieve the above object, and the results were embodied in the present invention.
[0007]
That is, the present invention controls the furnace pressure of a rotary hearth furnace equipped with an alternating combustion burner having a heat accumulator by opening and closing a furnace pressure control damper provided in the flue of the exhaust gas. monitoring the pressure sensor provided downstream of the furnace pressure control damper always such that the pressure values of the heating furnace is within 20 ± 2 Pa, under flow side of the furnace pressure control damper, draft control A furnace pressure control method for a rotary hearth-type heating furnace, wherein a low-temperature gas is introduced into a flue by opening and closing a damper.
[0008]
In addition, the present invention is a furnace pressure control method for a rotary hearth type heating furnace, characterized in that the low-temperature gas is outside air.
[0009]
Furthermore, the furnace pressure control method of the rotary hearth type heating furnace is characterized in that the introduction of the outside air is natural suction without using a fan.
[0010]
In the present invention, under flow side of the damper provided in the flue from the furnace to the chimney, since as to introduce cold gases to該煙canal gas temperature of the flue is lowered, the gas is increased in the chimney Speed 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 sealed can be suppressed to a very small amount, and the furnace pressure can be easily controlled. Furthermore, in the present invention, the low temperature gas is used as the outside air, and the introduction of the outside air is performed without power, so that the furnace pressure control can be performed at a low cost.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described, including the background to the invention.
[0012]
First, the inventors focused on reducing the draft without remodeling the furnace pressure control damper itself having a low hermeticity, and intensively studied specific means. As a result, it was considered that the temperature of the exhaust gas 19 and the pressure should be increased. Specifically, a gas having a temperature lower than that of the exhaust gas 19 is introduced into the flue 17.
[0013]
Considering that the kind of the low temperature gas 20 to be introduced reacts with the components of the exhaust gas 19 (a part of the combustion gas from the alternating combustion burner) at a high temperature (about 1000 ° C.), and corrodes the environmental pollution and the flue 17. The use of an inert gas is preferred. However, as a result of the inventors' investigation, it was confirmed that the temperature may be room temperature, and the air as the gas does not cause any trouble in the flue 17, so the outside air at room temperature is most preferable. In addition, in the case of an inert gas, the introduction means may be provided with a known gas holding container and pressurizing means (both not shown). On the other hand, in the case of outside air, as shown in FIG. 1, it is sufficient to provide an outside air intake 24 and a damper (hereinafter referred to as draft control damper 21) in the flue 17. A power source such as a compressor may be used because the inside of the flue 17 is usually a negative pressure, so that a sufficient amount of outside air can be introduced.
[0014]
Next, the inventors studied the position of the introduction of cold gas 20, learned that good at lower flow side of the furnace pressure control damper 18. It contributes to the temperature drop and pressure increase in the exhaust gas gas 19.
[0015]
In order to implement the present invention specifically, the operator constantly monitors the pressure sensor 22 provided in the flue , and opens and closes the draft control damper 21 so that the pressure value is within the target pressure range. 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]
【Example】
This is used for furnace pressure control in a heating furnace (outside wall diameter 33 m, inner wall diameter 25 m, height from the hearth to the ceiling 1.5 to 2.1 m) provided with 27 sets of alternating combustion burners 23 having heat accumulators. The invention was applied. 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) which is a raw material for producing a seamless steel pipe, and is continuously charged from the charging port 5 for heating operation. It was. The target heating temperature of the slab was 1250 ± 30 ° C., and the target furnace pressure was 20 ± 2 Pa. This furnace pressure control is a method in which outside air is introduced unattended among the methods according to the present invention.
[0017]
FIG. 5 shows the change over time in the furnace pressure during the heating operation in comparison with the change during the conventional operation. FIG. 5 clearly shows that the furnace pressure can be controlled within the target range according to the present invention. Moreover, all the slabs heated during this operation satisfied the target heating temperature.
[0018]
【The invention's effect】
As described above, according to the present invention, the furnace pressure control of the heating furnace can be stably performed even if the alternating combustion burner having the heat storage body is provided. Moreover, since the outside gas can be used for the control, the furnace pressure can be stabilized at a low cost by a simple modification of the equipment.
[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 for explaining an exhaust system of a conventional heating furnace, in which (a) shows a case where the burner is a heavy oil burner and (b) shows an alternating combustion burner.
FIG. 4 is a diagram illustrating the structure of a heating furnace.
FIG. 5 is a diagram comparing the furnace pressure change according to the implementation of the present invention with a conventional one.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Furnace 2 Furnace 3 Heated object 4 Burner 5 Charging inlet 6 Outlet 7 Inner side 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 outlet 17 Flue 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 Outside air intake

Claims (3)

When controlling the furnace pressure of a rotary hearth furnace equipped with an alternating combustion burner having a heat storage body by opening and closing a furnace pressure control damper provided in the flue of the exhaust gas,
Constantly monitors the pressure sensor provided downstream of the furnace pressure control damper of the flue, so that the pressure value of the heating furnace is within 20 ± 2 Pa, under flow side of the furnace pressure control damper , furnace pressure control method of a rotary hearth type heating furnace and introducing a cold gas into the flue by the opening and closing operation of the draft control damper.   2. The furnace pressure control method for a rotary hearth furnace according to claim 1, wherein the low-temperature gas is outside air.   The furnace pressure control method for a rotary hearth heating furnace according to claim 2, wherein the introduction of the outside air is natural suction without using a fan.

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