JPS6357720A - Method for preventing spouting of unburnt gas from direct firing nonoxidation furnace - Google Patents

Abstract

PURPOSE:To prevent the spouting of inflammable gas from a direct firing nonoxidation furnace by arranging air blowing nozzles at the inlet and outlet throat parts of the furnace and burning unburnt gas which enters the throat parts. CONSTITUTION:Air blowing nozzles 19 are arranged on the upper and lower sides of the inlet and outlet throat parts 17 of a direct firing nonoxidation furnace through which a steel strip 3 is passed. Air is blown from the nozzles 19 to perfectly burn unburnt gas which enters the throat parts 17. Thus, the spouting of the unburnt gas from the furnace is prevented.

Description

[Detailed Description of the Invention] <Object of the Invention> Industrial Field of Application The present invention relates to a method for preventing blow-off of unburned gas in a direct-fired non-oxidizing furnace, and more particularly, to continuous galvanizing equipment or silicon steel strip continuous heat treatment equipment. The present invention relates to a method for preventing unburned gas from blowing out in a direct-fired non-oxidizing furnace used for, etc.

Conventional technology Direct-fired non-oxidizing furnaces (hereinafter referred to as NOF) control the burner air ratio (m: chemical equivalence ratio) to an incomplete combustion range of 1.0 or less, and contain only a small amount of free oxygen. Generally, the temperature is 1100 ~
It is characterized by a port that rapidly heats the copper strip in a non-oxidized or lightly oxidized state by utilizing a high furnace temperature of about 1400°C.

FIG. 4 shows an example of such a direct-fired non-oxidizing furnace, in which a heating burner 2 is provided in a furnace body 1 made of refractory bricks, and a steel strip 3 enters the furnace through a sealing mechanism 4 at the end. , heated by a heating burner 2, and supported and conveyed by a hearth roll 7. 5 is a combustion gas exhaust port, and 6 is a damper for adjusting furnace pressure.

In NOF, a positive pressure operation of 1 to 7 sH20 is generally performed to make the atmosphere in the furnace non-oxidizing. Therefore, at the inlet and outlet of the NOF, combustible gas (unburned gas), which poses safety and health problems, such as CO gas inside the furnace, is blown out of the furnace. Particularly on the furnace inlet side, when the seal roll 8.9 is pressed against the steel strip 3, (n) easily enters the steel strip 3, and
Since the steel strip 3 has high rigidity, it is difficult to seal it. Also,
Since the rigidity is low on the furnace exit side, sealing is relatively easy, but sealing cannot be completed completely on the roll portion other than the width of the steel strip.

Therefore, the conventional method was to install a pilot burner outside the furnace and burn the combustible gas that leaked outside the furnace, but the combustible gas concentration and ambient temperature were too low to allow complete combustion, making it safe. It was a hygiene problem.

Therefore, the seal between the furnace atmosphere gas and the atmosphere can be achieved by using a seal roll or by suctioning the furnace atmosphere gas by feeding it [1] and blowing the atmosphere gas against the copper strip to form a gas curtain. A method of sealing gas from the outside air is disclosed in Japanese Patent Application Laid-open No. 150610/1983, in which high temperature gas is sucked in with a high temperature fan,
Spraying systems are expensive and have the disadvantage of high running costs.

Problems to be Solved by the Invention The present invention aims to solve these problems, and specifically, blows air from air nozzles provided at the throats of the inlet and outlet of the furnace to completely remove unburned gas. The object of the present invention is to provide a method for preventing the blowing of unburned gas from a direct-fired non-oxidizing furnace.

<Structure of the Invention> Means for Solving the Problems and Their Effects The present invention provides nozzles for injecting air on the upper and lower sides of the throat portions of the inlet and outlet of a direct-fired non-oxidizing furnace. It is characterized by blowing air onto the unburned gas to completely burn it and preventing the unburned gas from blowing out of the furnace.

Hereinafter, the structure and operation of the means of the present invention will be explained with reference to the drawings.

FIG. 1 is a vertical cross-sectional view of the sealing mechanism according to the present invention, FIG. 2 is an enlarged vertical cross-sectional view of the unburned gas blowing device, and FIG.
Figures (a+, (b), (+j and (d)) are plan views showing examples of the shape of the combustion air outlet, respectively.
The figure is a longitudinal sectional view of the inlet portion of a conventional direct-fired non-oxidizing furnace.

In FIG. 1, seal rolls 8.9 are rotatably provided so as to sandwich the steel strip from both the upper and lower sides of the steel strip 3.
The sealing member 11.12 is always urged toward the steel strip 3 side by a pressing mechanism 13 such as a counterweight so as to keep the gap between the seal roll 8.9 and the opening seal roll 8.9 airtight.

Furthermore, in the present invention, the air blowing nozzles 19 of the unburned gas combustion device 14 are provided on both upper and lower sides of the throat portion 17 through which the steel strip 3 passes, and when the unburned gas lf enters the throat portion in the furnace, it is ejected from the injection nozzle 19. Air is injected and the high temperature unburned gas is combusted.

At this time, in the throat section on the exit side, the high temperature steel strip and the high temperature wall surface in the gap of the throat section become the ignition source, so it is possible to completely burn the unburned gas without the need for a special ignition device. However, since the ambient temperature and temperature inside the furnace are low on the inlet side, it is recommended to install a suitable ignition device such as an electric heater on the upstream and downstream sides where the throat part and the air nozzle intersect, and blow a small amount of air into the dilute unburned gas. Put it on and let it burn completely.

If this ignition device is provided on both the entrance and exit sides of the furnace, it will work effectively when starting the furnace and prevent unburned gas from blowing out.

Although FIG. 1 shows the inlet of the furnace, the same applies to the outlet of the furnace.

FIG. 2 is an enlarged sectional view of the unburned gas combustion device 14, which is composed of a combustion air intake 15 and a blowout nozzle 19, and the tip opening of the blowout nozzle is, for example, shown in FIG.
It can be made into various shapes as shown in a), (b), (C) and (d>).

Example This will be further explained below with reference to Examples.

Furnace length 25m, furnace width 1. Button, furnace temperature 1100-1400℃
In the NOF according to the present invention, when the GO concentration was measured at the inlet and outlet of the furnace, it was extremely low at 5 to 10 ppm or less, confirming a significant improvement effect in terms of safety and health at the inlet and outlet of the furnace. was completed.

<Effects of the Invention> As explained above, the present invention provides nozzles for injecting air on the upper and lower sides of the throat portions of the inlet and outlet of a direct-fired non-oxidizing furnace, and prevents unburned gas leaking from inside the furnace. It is characterized by blowing air to completely burn the gas and preventing unburned gas from blowing out of the furnace.In particular, it eliminates the need for expensive equipment and eliminates CO, which has traditionally been a problem with NOF. It is now possible to prevent flexible gas such as gas from blowing out of the furnace, which has an extremely large effect on safety and health.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view of the sealing mechanism according to the present invention, Fig. 2 is an enlarged longitudinal sectional view of the unburned gas combustion device, Fig. 3(a), C
b), (cl and d) are plan views showing examples of the shapes of combustion air outlets, respectively, and Fig. 4 is a longitudinal cross-sectional view of the inlet of a conventional direct-fired non-oxidizing furnace. Reference numeral 1 Furnace body 2 Heating burner 3 Steel strip 4 Seal mechanism 5 Combustion gas exhaust port 6 ...Danbart for furnace pressure adjustment ... Hearth roll 8.9 ... Seal roll 10 ... Furnace end 11.12 ... Seal member 13 ... ...Pushing is done by mechanism 14...Unburnt gas combustion device 15...Combustion air intake 17...Throat part

Claims (1)

[Claims] Nozzles that inject air are installed on the upper and lower sides of the throat at the inlet and outlet of the direct-fired non-oxidizing furnace, and the air is blown onto the unburned gas leaking from inside the furnace to completely burn it and remove the unburned gas. A method for preventing unburned gas from blowing out of the furnace in a direct-fired non-oxidizing furnace.