JP4439644B2 - Bell type annealing furnace - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a bell-type annealing furnace.
[0002]
[Prior art]
Conventionally, a bell-type annealing furnace is known as an annealing furnace for heat-treating a processing material such as a steel plate coil or a wire rod coil. As shown in FIGS. 4 to 6, the bell-type annealing furnace T ′ includes a hearth 1, an inner cover 2, and an outer cover 3, and a processing material such as a coil material W stacked on the hearth 1. Is covered with an inner cover 2 and filled with an atmospheric gas. Further, the inner cover 2 is covered with an outer cover 3, and a coil material is burned in a combustion chamber 6 formed of an annular space formed between the covers 2 and 3. It anneals while indirectly heating W.
[0003]
A mounting portion 4 for mounting a plurality of combustion devices Br is provided on the outer periphery of the lower portion of the outer cover 3, and combustion gas ejected from the combustion devices Br attached to the mounting portion 4 is tangential to the combustion chamber 6. It is going to go to. The reason why the mounting portions 4 are arranged in this manner is to uniformly heat the outer periphery of the inner cover 2 in the circumferential direction by a plurality of combustion devices. Reference numeral 5 denotes a burner tile.
[0004]
A recuperator 7 is incorporated facing the combustion chamber 6 on one side of the outer cover 3 close to the ceiling 3a.
[0005]
In the bell-type annealing furnace T ′ having the above-described configuration, the combustion gas in the combustion chamber 6 is sucked and exhausted through the recuperator 7, and heat is recovered by exchanging the retained heat with the combustion air in the recuperator 7. ing.
In the bell-type annealing furnace T ′, generally, the combustion apparatus Br is burned at a constant combustion amount (for example, 100%) until the furnace temperature rises to a predetermined temperature (for example, 900 ° C.), and the furnace temperature is determined to be the predetermined temperature. After reaching the temperature, the amount of combustion is gradually suppressed (for example, so as to finally reach 5%).
[0006]
Here, looking at the structure of the mounting portion 4 for mounting the combustion device Br, steps are formed in the connecting portion between the mounting portion 4 and the burner tile 5 and in the connecting portion between the mounting portion 4 and the hearth 1. . Specifically, a first step 8 a is formed on the side close to the combustion device Br, and a second step 8 b is formed on the side close to the combustion chamber 6. Then, a reverse flow is formed by the steps 8a and 8b, so that the high-temperature combustion gas from the combustion device Br is drawn in to form a high-temperature combustion gas residue, so that the combustion state is stabilized regardless of the furnace temperature. I have to.
[0007]
By the way, in the bell-type annealing furnace T ′, as described above, since the preheating temperature of the combustion air changes depending on the furnace temperature even though the combustion amount is kept constant at the start of the furnace operation, The volume of the air changes, and the ejection speed of the combustion air changes accordingly. Therefore, the first step 8a forms a reverse flow in a state where the furnace temperature is low (for example, 450 ° C. or less) immediately after the start of operation of the furnace (a state where the combustion air is ejected slowly), and a stable combustion state is achieved. The second step 8b is formed in a size that can be maintained, and forms a reverse flow in a state where the furnace temperature is high (for example, 450 to 800 ° C.) (a state in which the combustion air is ejected at a high speed). It is formed in the size which can maintain.
[0008]
[Problems to be solved by the invention]
For this reason, for example, when the furnace temperature is 450 ° C. or higher and the ejection speed of combustion air is increased, the reverse flow is not formed at the first step 8a having a small step, but the reverse flow is maintained at the second step 8b. As a result, high-temperature combustion gas stays.
[0009]
However, when the furnace temperature reaches a predetermined temperature (for example, 800 ° C. or more that spontaneously ignites), a stable combustion state can be achieved with the retained heat of the combustion chamber 6 without forming a high-temperature combustion gas reservoir in the second stepped portion 8b. Since the combustion gas reservoir is not necessary, a high-temperature combustion gas reservoir is formed in the second step portion 8b, so that N ₂ and O ₂ in the combustion gas are contained in the combustion gas reservoir. To generate NOx. For this reason, there has been a problem that even if the combustion apparatus Br performs two-stage combustion or the like to reduce NOx, the amount of NOx emission cannot be suppressed.
[0010]
Therefore, as a result of various studies, the present inventors do not form a high-temperature combustion gas reservoir (the second step 8b) in the furnace if the preheating temperature of the combustion air is set to a high temperature (for example, 800 ° C. or higher). However, it has been found that a stable combustion state can be obtained when the temperature is raised.
[0011]
Therefore, according to the present invention, the combustion apparatus is a regenerative combustion apparatus, and the combustion air is heated stably by increasing the preheating temperature of the combustion air, and NOx is eliminated by eliminating the second step portion. It aims at providing the bell-type annealing furnace which suppresses the production amount of.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the present invention covers the treatment material placed on the hearth with an inner cover, and further covers the inner cover with the outer cover, and the combustion device is attached to the mounting portion provided at the lower portion of the outer cover. In a bell-type annealing furnace that is disposed and burns the combustion device in a combustion chamber formed between the inner cover and the outer cover to heat-treat the treated material, the combustion device is at least a pair of regenerative combustion devices. These heat storage regenerative combustion devices are installed at symmetrical positions on the outer periphery of the lower portion of the outer cover so that the combustion gas injection direction is tangential to the combustion chamber, and The lower surface of the mounting portion and the hearth are installed on the same plane.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of a bell-type annealing furnace T according to the present invention will be described with reference to FIGS.
[0014]
The bell-type annealing furnace T includes a hearth 1, an inner cover 2 and an outer cover 3 as in the prior art, and covers a processing material, for example, a coil material W, stacked on the hearth 1 with the inner cover 2. The inner cover 2 is filled with an atmospheric gas, and the inner cover 2 is covered with an outer cover 3, and the coil material W is indirectly heated by burning in a combustion chamber 6 formed of an annular space formed between the covers 2 and 3. It will be annealed.
[0015]
A mounting portion 4 for mounting a pair of heat storage regenerative combustion devices (hereinafter referred to as a heat storage burner) Bra, Brb is provided at a 180 ° symmetrical position on the outer periphery of the lower portion of the outer cover 3, and a combustion device Bra is provided. The combustion gas ejected from Brb is formed in the tangential direction of the combustion chamber 6. In the embodiment, since the opening of the burner tile 5 is a vertically long rectangle, the combustion gas is supplied to the combustion chamber 6 in a vertically flat state.
[0016]
The heat storage burners Bra and Brb are well known in the art, and are composed of a burner portion equipped with a fuel nozzle and a heat storage chamber containing a heat storage body, and burn one heat storage burner Bra and The heat storage body is heated by exhausting the combustion gas through the heat storage chamber of the other heat storage burner Brb, and the combustion air is preheated to, for example, 800 ° C. by the heat storage body during the next alternating combustion. .
[0017]
Further, a bend hole 3 b is provided in the ceiling portion 3 a of the outer cover 3.
[0018]
In the bell-type annealing furnace T having the above-described configuration, the regenerative burners Bra and Brb repeat combustion and exhaust alternately after a predetermined time has passed, and the combustion chamber 6 starts from the regenerative burner Bra or Brb in a non-combustion state. The coil material W is heated to a predetermined temperature (for example, 900 ° C.) while the combustion gas is sucked and exhausted and the retained heat is recovered in the heat storage body. A part of the combustion gas is discharged from the bend hole 3b.
[0019]
As described above, the flow of the high-temperature combustion gas is alternately repeated from the regenerative burner Bra to Brb or from Brb to Bra every half of the outer periphery of the inner cover 2, so that the combustion gas is evenly distributed around the inner cover 2. While flowing, a part of the combustion gas is exhausted from the bend hole 3b formed in the ceiling portion 3a of the outer cover 3, so that a substantially uniform combustion gas flow is formed around the upper portion of the inner cover 2 without any bias. The temperature deviation in the circumferential direction of the entire inner cover 2 is almost eliminated, and the coil material W is heated uniformly.
[0020]
As described above, during the combustion of the pair of regenerative burners Bra and Brb, the combustion air is supplied at a predetermined temperature through the regenerator that stores the amount of heat of the high-temperature combustion gas during the previous exhaust. Even if there is no step to form a high-temperature combustion gas reservoir as in the past, a stable combustion state can be obtained, and even if the furnace temperature reaches a predetermined temperature, there is no step, so a high-temperature combustion gas reservoir is formed Thus, the generation of NOx could be suppressed.
[0021]
In addition, in the small level | step difference 8a formed between the thermal storage type burner Bra, Brb and the attaching part 4, since a reversal flow is not formed when the injection speed of combustion gas becomes high, NOx when the furnace temperature becomes a predetermined temperature. It is irrelevant to the formation of
[0022]
【The invention's effect】
As is apparent from the above description, according to the present invention, the lower surface of the mounting portion of the regenerative combustion apparatus provided at the bottom of the furnace is flush with the hearth, so even if the furnace temperature exceeds a predetermined temperature, the combustion gas Therefore, the generation of NOx is suppressed as compared with a conventional furnace in which a step is formed. In addition, at least a pair of heat storage regenerative combustion devices are provided as combustion devices, and heat is stored by exhausting the combustion gas from one heat storage regenerative combustion device through the heat storage body of the other heat storage regenerative combustion device, and at the time of the next combustion Since the combustion air is preheated to a high temperature, a stable combustion state can be obtained even when there is no step during the temperature rise.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a bell-type annealing furnace according to the present invention.
FIG. 2 is a cross-sectional view taken along the line II-II in FIG.
3 is a partially enlarged view of a cross section taken along line III-III in FIG. 2;
FIG. 4 is a cross-sectional view of a conventional bell-type annealing furnace.
5 is a cross-sectional view taken along line VV in FIG.
6 is a partially enlarged view of a cross section taken along line VI-VI in FIG. 5;
[Explanation of symbols]
1 to hearth, 2 to inner cover, 3 to outer cover, 4 to mounting part, 5 to burner tile, 6 to combustion chamber, 8a, 8b to step, Bra, Brb to heat storage regenerative combustion apparatus (heat storage burner) , T ~ Bell type annealing furnace.

Claims (1)

The treatment material placed on the hearth is covered with an inner cover, and the inner cover is further covered with an outer cover, and a combustion device is disposed at a mounting portion provided at the lower portion of the outer cover. In a bell-type annealing furnace in which the combustion device is combusted in a combustion chamber formed therebetween to heat-treat the treatment material, the combustion device is composed of at least a pair of heat storage regeneration combustion devices, and these heat storage regeneration combustion devices are Installed at the symmetrical position of the outer periphery of the lower part of the outer cover so that the direction of combustion gas injection is directed to the tangential direction of the combustion chamber, and the bottom surface of the mounting portion of the heat storage regenerative combustion apparatus and the hearth are coplanar A bell-type annealing furnace characterized by

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