JPH0121972Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an annealing apparatus for continuously annealing a steel strip, and particularly to an annealing apparatus equipped with a radiant tube for heating, soaking, and cooling.

Conventionally, in continuous annealing equipment in which a radiant tube is installed in the furnace, the metal strip and the furnace interior are cooled using the radiant tube by supplying cooling air from the combustion air supply pipe to control the flow of combustion gas in the radiant tube. This is done by flowing down a channel.

Burners that use radiant tubes as heat transfer tubes are usually equipped with a recuperator section that preheats the combustion air in order to save energy, and a two-stage sintering system that uses a slow combustion method to suppress the production of nitrogen oxides (NOx). It is made into a baking mold. The burner section is provided with an orifice etc. to adjust the air flow rate, and the above-mentioned recuperator section has a large flow path resistance due to this orifice. Therefore, the flow resistance of the cooling air becomes large, and the blower for supplying air must have a large capacity, which is uneconomical in terms of equipment. Furthermore, since the flow rate is suppressed to a level corresponding to maximum combustion, there is a limit to the cooling capacity. Therefore, if a prescribed cooling pattern cannot be obtained or troubles such as strip breakage occur, it takes a long time to cool the furnace, and the time required to switch between heating/soaking/cooling modes becomes longer, reducing work efficiency. There is a problem.

The present invention aims to eliminate the above-mentioned drawbacks, and by forming the cooling air flow path into the radiant tube separately and independently from the combustion air flow path, heating and soaking can be achieved. It is an object of the present invention to provide an annealing apparatus that can perform cooling and quickly obtain an arbitrary cooling pattern by reducing the flow path resistance of the cooling system.

Hereinafter, the present invention will be explained in detail based on embodiments shown in the drawings.

The figure is a cross-sectional view showing the main parts of the annealing apparatus according to the present invention.
Therefore, a plurality of them are installed at the required pitch in a continuous annealing furnace. A burner body 3 is communicatively connected to the upper radiant tube 2a, and an internal combustion cylinder 4 is coaxially attached to the burner body 3 to form a double-tube structure. Furthermore, a main burner 5 and a pilot burner 6 used for ignition are provided within the internal combustion cylinder 4, respectively.

An air supply/discharge connecting pipe 7 is connected to the lower radiant tube 2b, and a combustion air supply pipe 8 communicating with the outside is connected to the air supply/discharge connecting pipe 7 so as to extend into the vicinity of the furnace body 1. It is set up in Also,
A preheating pipe 9 surrounding the entire length of the combustion air supply pipe 8 is coaxially provided to form a requiperator section 10. The preheating pipe 9 communicates with the burner body 3 through a communication pipe 11, and air from the combustion air supply pipe 8 enters the preheating pipe 9 and flows into the burner body 3 through the communication pipe 11 while being preheated. Note that 12 is a large-diameter exhaust port connected to an exhaust pipe (not shown).

An air inflow opening 13 is provided in the internal combustion cylinder 4 on the side connected to the burner body 3. This air inflow opening 13 has a flow rate adjustment shutter 14 that can open and close the opening and change the opening area.
is mounted so as to be movable by driving the opening/closing device 15. Reference numeral 16 denotes an outflow air orifice provided near the air inflow opening 13 and on the outer periphery of the inflow combustion cylinder 4. Burner head 5 of main burner 5
A is located in the middle of the internal combustion tube 4, resulting in two-stage combustion in which primary combustion occurs at the burner head 5a and secondary combustion occurs at the open end of the internal combustion tube 4.

Furthermore, 17 is a cooling air supply pipe connected to the burner body 3, and its opening position is downstream of the external air orifice 16, that is, on the radiant tube 2 side.

A case in which the continuous annealing apparatus having the above configuration is used for heating and soaking a metal strip will be described below.

First, the cooling air supply pipe 17 and the burner body 3 are disconnected from each other by operating the required valves, and before the pilot burner 6 is ignited, a predetermined amount of combustion air (usually 20 to 50% of the burner capacity) is supplied from the combustion air supply pipe 8 to the pilot burner 6.
Air is supplied using a suction or push method. Combustion air passes through the recuperator section 10 and also flows into the internal combustion cylinder 4 by adjusting the flow rate adjustment shutter 14. Then, the pilot burner 6 is ignited to cause primary combustion. Next, after confirming the ignition of the pilot burner 6, fuel is flowed into the main burner 5 to be combusted, the air ratio is adjusted to a predetermined value, and automatic combustion control is started. The air flow rate for primary combustion and secondary combustion can be adjusted by providing resistance in the flow path on the secondary combustion air side using the external air orifice 16, and by adjusting the ratio of the primary combustion air amount to the NOx value using the flow rate adjustment shutter 14. and check the combustion status.

As described above, the combustion gas from the two-stage combustion of the main burner 5 flows through the radiant tube 2, radiates heat in the furnace, heats and soaks the metal strip, and then
It is discharged from the exhaust port 12 connected to the lower radiant tube 2b.

Next, when used for cooling, the pilot burner 6 and the main burner 5 are usually not used for combustion, so air is not supplied from the combustion air supply pipe 8. Instead, the cooling air supply pipe 17 and the burner body 3 are communicated with each other, and cooling air is supplied into the radiant tube 2 from a required blower or the like. Cooling air flows down from the internal combustion cylinder 4 side toward the exhaust port 12 . At this time, since the external air orifice 16 is located upstream of the cooling air inflow portion, it does not act as a flow path resistance and does not cause pressure loss in the flow. In addition, even in the lower radiant tube 2b, an annular flow path is defined only by the air preheating tube 9 located in the center, and since the exhaust port 12 has a large diameter, it is possible to expand and contract the flow path. Pressure loss can be reduced.

This cooling air flow inside the radiant tube 2 lowers the temperature on the surface of the radiant tube 2,
The metal strip inside the furnace is exothermically cooled. During this cooling, the outlet temperature or flow rate of the cooling air is automatically controlled to achieve the required cooling rate while detecting the temperature of the metal strip.

As described above, the cooling air is supplied, flows, and discharged through the system where the flow path resistance is extremely small compared to the combustion air circulation path. Therefore, a large flow rate of cooling air can be supplied at high speed, improving the cooling capacity, and by automatically controlling the flow rate or flow rate as appropriate, transient response from heating/soaking to cooling process is good, and the furnace The internal temperature can be quickly brought to the set temperature.

Although the cooling air supply pipe 17 is connected to the burner body 3 in this embodiment, it may be directly connected to the radiant tube 2. Further, although the exhaust port 12 is configured to discharge both combustion gas and cooling air, a combustion gas exhaust port and a cooling air exhaust port may be separately provided.

As mentioned above, according to the present invention, a large flow of cooling air can be supplied at high speed and the cooling capacity can be increased, and both heating/soaking and cooling can be performed depending on the annealing type and the size and shape of the treated material. Can be done efficiently. In addition, since the cooling capacity can be increased, heating and soaking
It is possible to shorten the cooling mode switching time and the furnace cooling time when a plate breaks, thereby improving work efficiency.

[Brief explanation of drawings]

The figure shows one embodiment of the present invention, and is a sectional view of a main part of an annealing device. 1...Furnace body, 2...Radiant tube, 3...
... Burner body, 4 ... Internal combustion cylinder, 5 ... Main burner, 6 ... Pilot burner, 8 ... Combustion air supply pipe, 10 ... Requiperator section, 12
...Exhaust port, 17...Cooling air supply pipe.

Claims (1)

[Scope of utility model registration request] An annealing device having a radiant tube that incorporates a burner and a requiperator part that preheats combustion air and defines a flow path for combustion gas, the radiant tube being separated and independent from the flow path for combustion air. An annealing device characterized in that a cooling air supply pipe that supplies cooling air in a unidirectional flow is connected to the radiant tube.