JP3958928B2 - Heat treatment furnace with multiple regenerative burners - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat treatment furnace. More specifically, the present invention relates to a heat treatment furnace capable of performing valve control of a plurality of regenerative burners with an inexpensive and simple configuration and improving the reliability of valve control.
[0002]
[Prior art]
In a relatively high-temperature heating zone such as a continuous annealing furnace or a heat treatment furnace, a radiant tube type regenerative burner (hereinafter referred to as “heat source”) with a built-in heat storage type heat exchanger is recently used from the viewpoint of energy saving as a heater for heating in the furnace. Regenerative burner) is used. This regenerative burner includes a pair of burners having a heat storage body, and by alternately burning the burners, the heat of the exhaust gas generated by the combustion of one burner is recovered by the heat storage body of the other burner.
[0003]
A general radiant tube type regenerative burner includes a radiant tube, a pair of burners having heat storage bodies provided at both ends of the radiant tube, and a pair of combustion vent switching valves respectively connected to the pair of burners. And a gas switching valve.
[0004]
By switching the pair of combustion vent switching valves and gas switching valves at predetermined time intervals (about 20 to 30 seconds), air and fuel gas are introduced into the burner that performs one combustion, and the other is not combusting. Exhaust and heat storage can be performed through the burner.
[0005]
A plurality of regenerative burners, usually about 150 to 300, are provided inside the heat treatment furnace. In the plurality of regenerative burners, the combustion vent switching valve and the gas switching valve are controlled so as to be in the same switching direction in the same group in the furnace. One group is composed of about 3 to 14 regenerative burners, and two or more groups are usually gathered to form a zone controlled at the same temperature.
[0006]
Each combustion ventilation switching valve and gas switching valve are driven using compressed air for control. Supply and shut-off of the compressed air are performed using an electromagnetic valve provided for each switching valve.
[0007]
[Problems to be solved by the invention]
However, in conventional heat treatment furnaces, the solenoid valves for supplying and shutting off compressed air are provided to the combustion vent switching valve and gas switching valve of each regenerative burner, so the number of solenoid valves is extremely large. However, there is a problem that the equipment cost related to electrical instrumentation is required.
[0008]
On the other hand, a plurality of regenerative burners described in Japanese Patent Laid-Open No. 9-145020 discloses a common intake / exhaust pipe and gas pipe, thereby reducing the required number of switching valves, reducing equipment costs, and switching combustion. The time response has been improved. Specifically, in this regeneration burner, as shown in FIG. 5, the burners 52 at both ends of the plurality of radiant tubes 51 are connected to a common intake pipe 53, exhaust pipe 54, and gas pipe 55. . The common intake pipe 53, exhaust pipe 54 and gas pipe 55 are provided with switching valves 56, 57 and 58, respectively.
[0009]
However, the regenerative burner shown in FIG. 5 requires a huge space for laying a common pipe having a large diameter. In addition, in order to prevent other radiant tubes from being affected when a crack is exerted on a certain radiant tube, it is necessary to provide an expensive shut-off valve having heat resistance in the shared piping portion of the intake pipe 53 and the exhaust pipe 54. There is.
[0010]
The present invention has been made to solve such a problem, and provides a heat treatment furnace capable of performing valve control of a plurality of regenerative burners with an inexpensive and simple configuration and improving the reliability of valve control. For the purpose.
[0011]
[Means for Solving the Problems]
[0015]
Heat treatment furnace according to claim 1 of the present invention comprises a plurality of radiant tube type regenerative burners,
For each of the regenerative burners, a pair of combustion through the gas SWITCHING three-way valve and a pair of gas switching valve driven by compressed air is provided,
A plurality of said regenerative burners of the combustion through the gas SWITCHING three-way valve and gas switching valve is within a predetermined combustion groups, earthenware pots by respectively the same switching direction, each of the combustion through the gas SWITCHING three-way valve A heat treatment furnace controlled by using the compressed air that is pumped through the compressed air conduit provided in each of the two and the compressed air conduit provided in each gas switching valve,
With a common first electromagnetic valve for controlling the compressed air delivered to all of the combustion through the gas SWITCHING three-way valve in said predetermined combustion group, and all of the gas changeover valve in the predetermined combustion Group with a common second solenoid valve for controlling the compressed air delivered to,
Compressed air conduits between each regenerative burner and the common solenoid valve are provided with thermocouples for measuring the exhaust gas temperature between the burner and the combustion ventilation switching three-way valve at each radiant tube end. It is characterized in that a manual valve is provided .
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Next, a heat treatment furnace provided with a plurality of regenerative burners will be described in more detail with reference to the drawings. FIG. 1 schematically shows piping of a heat treatment furnace equipped with a common electromagnetic valve for controlling a three-way valve and a gas switching valve, showing an embodiment of a heat treatment furnace equipped with a plurality of regenerative burners of the present invention. FIG. 2 is a cross-sectional explanatory view of the regeneration burner of FIG. 1, FIG. 3 is a block diagram for explaining the operation of the common solenoid valve, gas switching valve and manual valve of FIG. 1, and FIG. It is explanatory drawing which shows arrangement | positioning of the regeneration burner inside the heat processing furnace of this.
[0018]
The heat treatment furnace shown in FIGS. 1 to 4 includes a plurality of radiant tube regenerative burners 21. As shown in FIG. 4, 84 regeneration burners 21 are provided inside the heat treatment furnace. In the regenerative burner 21, the combustion vent three-way valves 9 and 10 and the gas switching valves 4 and 5 are controlled by solenoid valves 28 to 31 to be described later so as to be in the same switching direction in groups of six. . And temperature control is performed so that it may become the same temperature in each zone.
[0019]
In the heat treatment furnace shown in FIG. 4, the regeneration burners 21 are arranged in a matrix, and one zone is composed of a plurality of groups (2 to 4 groups) arranged in a column. When divided into the side where the worker is present (work side) and the side where the machine is located (drive side) on the basis of a small number of zones consisting of one row group, there are six units per group.
[0020]
For example, in the example of FIG. 4, there are two types in the heat treatment furnace, a zone composed of a group of one row and a zone composed of a group of two rows. The total number of groups is 14 and the work side and drive side are both 7 groups. In order to reduce the amount of capital investment, it is better to reduce the number of groups, but on the contrary, the influence on the heat treatment line at the time of failure of the solenoid valve becomes large.
[0021]
A pull-type regenerative burner 21 shown in FIG. 2 includes a U-shaped radiant tube 1 provided inside a heating furnace, and a pair of burners 2, 3 having heat storage bodies 7 provided at both ends of the radiant tube 1. A pair of gas switching valves 4 and 5 for supplying and shutting off gas from the gas pipe 6 to the burners 2 and 3, and three-way valves 9 and 10 for switching the combustion ventilation connected to the pair of burners 2 and 3, respectively. And an exhaust blower 14 provided in the exhaust passage 13 of the three-way valves 9 and 10.
[0022]
The pull-type regenerative burner 21 shown in FIG. 2 uses the exhaust blower 14 to reduce the pressure inside the radiant tube 1 to a negative pressure, whereby the intake passages of the individual three-way valves 9 and 10 attached to the burners 2 and 3. Combustion air can be supplied into the radiant tube 1 through 11. In such a pull system, the amount of combustion gas necessary for heat treating the material inside the heat treatment furnace is supplied to the burners 2 and 3, and the ratio of gas to air is appropriate according to the amount of gas charged with combustion air. Thus, the pressure immediately before the exhaust blower 14 is adjusted.
[0023]
As the heat storage body 7 in FIG. 2, an alumina small-diameter ball or a ceramic having a honeycomb structure having air permeability is employed.
[0024]
In the regenerative burner of FIG. 2, the pair of burners 2, 3 mixes the gas supplied from the gas pipe 6 with the air introduced through the intake passage 11 of the three-way valve 9 in one of the burners 2. The tube 1 is heated by burning in the inside. The exhaust gas generated by the combustion passes through the heat storage body 7 of the other burner 3 through the inside of the tube 1, and the heat of the exhaust gas is used to raise the temperature of the heat storage body 7 at that time. The combustion of the pair of burners 2 and 3 is carried out alternately every about 20 to 30 seconds. As a result, the radiant tube 1 can be heated at a substantially uniform temperature, and the inside of the heating furnace can be uniformly distributed. Can be heated. Reference numeral 15 denotes a pilot burner for igniting the burners 2 and 3.
[0025]
The three-way valves 9 and 10 and the gas switching valves 4 and 5 of the plurality of regenerative burners 21 in a predetermined combustion zone (see FIGS. 1 and 4) of the heat treatment furnace have the same switching direction in each group. And compressed air that is pumped through compressed air conduits 22-27 from a compressed air source (not shown).
[0026]
The pair of compressed air conduits 22 and 23 and the pair of compressed air conduits 24 and 25 are provided in two pairs on the left and right sides to reciprocate the pair of three-way valves 9 and 10 between the intake side and the exhaust side. Is provided. Further, since the valve bodies inside the gas switching valves 4 and 5 are normally biased by the springs, the compressed air conduits 26 and 27 may be provided one by one in order to obtain a driving force in one direction. .
[0027]
The heat treatment furnace of FIG. 1 uses a common first solenoid valve 28 to control the compressed air sent to all pairs of three-way valves 9 and 10 in a predetermined combustion group through compressed air conduits 22 to 25, respectively. 29.
[0028]
In addition, the heat treatment furnace of FIG. 1 has a common second solenoid valve 30 for controlling compressed air sent to all gas switching valves 4 and 5 in a predetermined combustion group through compressed air conduits 26 and 27, respectively. 31 (see FIGS. 1 and 3).
[0029]
With this configuration, in the heat treatment furnace of the present embodiment, the compressed air conduits 22 to 25 for the three-way valves 9 and 10 are operated by operating the first electromagnetic valves 28 and 29 and the second electromagnetic valves 30 and 31. , And pressure is applied to the compressed air conduits 26, 27 for the gas switching valves 4, 5, so that the regenerative burner three-way valves 9, 10 and the gas switching valves 4, 5 can be operated simultaneously. Further, since the pressure transmission speed in the compressed air conduit after the solenoid valve operation is high and the time lag during the valve operation hardly occurs, the solenoid valve can be shared in units of groups.
[0030]
In the control method using the solenoid valves common to this group, the number of solenoid valves can be greatly reduced, and the capital investment can be reduced and the maintenance cost can be reduced. In addition, it is possible to install the solenoid valve in a place with a low temperature away from the vicinity of the furnace, leading to the extension of the life of the solenoid valve and the improvement of the reliability of the valve control operation.
[0031]
Further, when a crack occurs in any one of the plurality of regenerative burners 21 (see FIG. 2), conventionally, by stopping the supply of combustion gas and measuring the O ₂ concentration in the exhaust gas, The occurrence of cracks is detected.
[0032]
In the present embodiment, the crack is detected by the rise of the exhaust gas temperature of the regeneration burner. That is, when a crack occurs in the radiant tube 1, the amount of combustion air passing through the accumulated tropics decreases due to gas intrusion into the furnace from the cracked portion, while the amount of exhaust gas passing through the accumulated tropics is not cracked. As a result, the exhaust gas temperatures between the burner 2 and the three-way valve 9 at both ends of the radiant tube 1 and between the burner 3 and the three-way valve 10 are increased. The occurrence of cracks can be detected by measuring with pairs 16 and 17 (see FIG. 2).
[0033]
As described above, when a crack occurs in the radiant tube 1 of a certain regenerative burner 21, the regenerative burner 21 and the common solenoid valves 28 to 31 are not affected so that other regenerative burners are not affected. A manual valve 32 is preferably provided in each of the compressed air conduits 22-27. When the occurrence of cracks in the radiant tube 1 is detected by the above-described method, the operator closes all the manual valves 32 of the compressed air conduits 22 to 27 leading to the regenerative burner 21 in which an abnormality has occurred, and the valve body of a three-way valve It is possible to stop the operation of only the regenerative burner 21 that has become abnormal and fix other normal regenerative burners 21 to operate normally.
[0034]
In the present embodiment, the three-way valve for combustion ventilation and the gas switching valve have been described as examples controlled by a common solenoid valve, but the present invention is not limited to this, and other aspects of the regenerative burner are described. It can also be applied to. For example, instead of a pair of three-way valves, a single combustion four-way valve may be used, and an exhaust blower and an intake blower connected to the four-way valve may be used in a so-called push-pull type regeneration burner. Further, the valve control by the solenoid valve common to the group may be the valve control of only the combustion ventilation switching valve such as the three-way valve or the four-way valve, the valve control of only the gas switching valve, or the combustion ventilation switching valve and the gas switching valve. Both valve controls may be performed.
[0035]
【The invention's effect】
According to the present invention, valve control of a plurality of regenerative burners can be performed with an inexpensive and simple configuration, and the reliability of valve control can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic view of piping of a heat treatment furnace equipped with a common electromagnetic valve for controlling a three-way valve and a gas switching valve, showing an embodiment of a heat treatment furnace equipped with a plurality of regenerative burners of the present invention. FIG.
FIG. 2 is a cross-sectional explanatory view of the regeneration burner of FIG.
3 is a block diagram for explaining operations of the common solenoid valve, gas switching valve, and manual valve of FIG. 1; FIG.
4 is an explanatory view showing the arrangement of regenerative burners inside the heat treatment furnace of FIG. 1. FIG.
FIG. 5 is a block diagram showing a heat treatment furnace provided with a plurality of conventional regenerative burners.
[Explanation of symbols]
1 Radiant tube 2, 3 burner 4, 5 Gas switching valve 9, 10 Three-way valve 21 Regenerative burner 22, 23, 24, 25 Compressed air conduits 26, 27 Compressed air conduits 28, 29 First solenoid valves 30, 31 Second Solenoid valve

Claims (1)

With multiple radiant tube regenerative burners,
For each of the regenerative burners, a pair of combustion through the gas SWITCHING three-way valve and a pair of gas switching valve driven by compressed air is provided,
A plurality of said regenerative burners of the combustion through the gas SWITCHING three-way valve and gas switching valve is within a predetermined combustion groups, earthenware pots by respectively the same switching direction, each of the combustion through the gas SWITCHING three-way valve A heat treatment furnace controlled by using the compressed air that is pumped through the compressed air conduits provided in two and the compressed air conduits provided in each gas switching valve,
With a common first electromagnetic valve for controlling the compressed air delivered to all of the combustion through the gas SWITCHING three-way valve in said predetermined combustion group, and all of the gas changeover valve in the predetermined combustion Group with a common second solenoid valve for controlling the compressed air delivered to,
Compressed air conduits between each regenerative burner and the common solenoid valve are provided with thermocouples for measuring the exhaust gas temperature between the burner and the combustion air switching three-way valve at both ends of each radiant tube A heat treatment furnace provided with a manual valve .

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