JP3726526B2 - Heating method with regenerative combustion burner - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a plurality of combustion zones with a plurality of sets of regenerative combustion burners that alternately burn in one set as one combustion zone, and a flow rate control valve and combustion exhaust gas for controlling the amount of fuel supplied for each combustion zone The present invention relates to a heating method in the case where an abnormality occurs in any set of regenerative combustion burners in the same combustion zone in a regenerative combustion burner apparatus provided with a flow rate control valve for controlling the amount of exhaust gas discharged.
[0002]
[Prior art]
FIG. 4 shows a plurality of combustion zones 43 with five sets of two burners 42A, 42B, 42C, 42D and 42E that alternately burn in the regenerative combustion burners 41a and 41b as one combustion zone. The combustion air header pipe 44 for supplying fuel to each combustion zone 43 is provided with a flow rate control valve 45 for controlling the supply amount of combustion air, and the combustion exhaust gas for discharging the combustion exhaust gas of each combustion zone 43. 1 shows a regenerative combustion burner device in which a header pipe 46 is provided with a flow rate control valve 47 for controlling the discharge amount of combustion exhaust gas.
[0003]
In this regenerative combustion burner device, each set of regenerative combustion burners 41a and 41b is provided with three-way switching valves 48a and 48b. Then, the fuel cutoff valve 50a provided in the middle of the fuel supply branch pipe 49a is opened, the fuel cutoff valve 50b provided in the middle of the fuel supply branch pipe 49b is closed, and combustion air is supplied to the regenerative combustion burner 41a. When the combustion is performed by the regenerative combustion burner 41a, the three-way switching valve 48a is provided on the side for supplying combustion air and the three-way switching valve 48b is disposed on the combustion exhaust gas so that the combustion exhaust gas is discharged by the heat storage combustion burner 41b. Is switched to the discharge side.
[0004]
Conversely, the fuel cutoff valve 50b provided in the middle of the fuel supply branch pipe 49b is opened, the fuel cutoff valve 50a provided in the middle of the fuel supply branch pipe 49a is closed, and fuel is supplied to the regenerative combustion burner 41b. When the combustion is performed by the regenerative combustion burner 41b, the three-way switching valve 48b is on the side for supplying combustion air, and the three-way switching valve 48a is on the combustion exhaust gas so that the combustion exhaust gas is discharged by the heat storage combustion burner 41a. Is switched to the discharge side.
[0005]
Such switching is repeated at regular intervals.
Although not shown, the heat storage combustion burners 41a and 41b are provided with heat storage bodies, and when the exhaust gas is discharged from each burner, the sensible heat possessed by the combustion exhaust gas. Is stored in the heat storage body, and the combustion air is preheated with the heat stored during combustion to increase the combustion efficiency.
[0006]
In the regenerative combustion burner apparatus as described above, the combustion exhaust gas temperature is measured in the combustion exhaust gas branch pipes 51 of the burner sets 42A, 42B, 42C, 42D and 42E that join the combustion exhaust gas header pipe 46. A thermometer 52 is installed, and a system that extinguishes the set of combustion burners when the measured temperature of the combustion exhaust gas is equal to or higher than a set temperature is employed. This is to prevent the hot furnace gas from being sucked when each combustion burner device is damaged and the downstream flow rate adjusting valve 47 and the suction fan (not shown) from being damaged by heat. It is.
[0007]
Then, when extinguishing the combustion burner, in order to prevent the damaged combustion burner from sucking the combustion exhaust gas further and further raising the exhaust gas temperature, as shown in FIG. The combustion shutoff valves 50a and 50b of the set of burners are closed and extinguished, and both of the three-way switching valves 48a and 48b are switched to the combustion air supply side, and the combustion burner 41a and the combustion burner 41a are extinguished. While being supplied to 41b and extinguishing the fire, the combustion burners 41a and 41b are prevented from being damaged by heat, and measures such as inspection and replacement are performed. In another set of combustion burners that are not damaged, combustion and exhaust of combustion exhaust gas are alternately performed.
[0008]
[Problems to be solved by the invention]
However, the above-described conventional method for extinguishing only the abnormal burner has the following problems.
[0009]
If only the abnormal combustion burner is extinguished, the exhaust gas emission must be performed with the remaining N-1 burners, assuming that the total number of burners in the combustion zone is N. The amount of combustion exhaust gas passing through the heat accumulator per combustion burner is larger at a ratio of N / (N-1) than when combustion exhaust gas is discharged by N combustion burners.
[0010]
For this reason, the sensible heat of the combustion exhaust gas cannot be stored by the heat storage body of the regenerative combustion burner, so the temperature of the combustion exhaust gas after passing through the heat storage body becomes abnormally high. Therefore, the combustion burner other than the damaged combustion burner also has an abnormally high combustion exhaust gas temperature and is extinguished in a chain manner, and the operation of the heating furnace becomes unstable.
[0011]
The present invention has been made to solve the above-described problems of the prior art, and even if any one of the regenerative combustion burners of the same combustion zone is put into a fire extinguishing state, the same combustion zone is obtained. It is an object of the present invention to provide a heating method using a regenerative combustion burner that does not affect fire extinguishing to other regenerative combustion burners.
[0012]
[Means for Solving the Problems]
The heating method using the regenerative combustion burner according to the present invention provides a plurality of combustion zones with a plurality of regenerative combustion burners that alternately burn in pairs as one combustion zone, and is used for combustion in each combustion zone. A heating method by a regenerative combustion burner device provided with a flow rate control valve for controlling the supply amount of air and a flow rate control valve for controlling the discharge amount of combustion exhaust gas, wherein either set of heat storage in the same combustion zone When an abnormality occurs in the combustion burner, the flow control valve that controls the exhaust gas emission amount of the combustion zone is fully closed so that combustion air is supplied without being preheated. After the restoration, the flow rate control valve for controlling the emission amount of the combustion exhaust gas is opened to preheat the combustion air and perform alternate combustion.
[0013]
In this heating method using a regenerative combustion burner, when any set of combustion burners in the same combustion zone becomes extinguished due to an abnormal temperature rise of the flue gas, etc., the same combustion zone is used. The other set of combustion burners perform alternating combustion without sucking the combustion exhaust gas, in other words, without preheating the combustion air. For this reason, it is impossible to store the sensible heat held in the combustion exhaust gas at the time of abnormality, but since the abnormality can be repaired in a short time, there is no significant heat loss.
[0014]
Therefore, since the flue gas temperature measured by the thermometer provided in the flue gas exhaust pipe does not increase, fire extinguishing does not spread to other combustion burners.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
[0016]
FIG. 1 is an explanatory view of a heating furnace for heating a long material such as a steel pipe formed with a plurality of combustion zones. FIG. 1 (a) is a schematic plan view of the heating furnace, and FIG. It is a schematic sectional drawing of a furnace. FIG. 2 is a control system diagram showing a combustion control system of the heating furnace.
[0017]
In FIG. 1, a heating furnace 20 is provided with a large number of regenerative combustion burners on opposite furnace walls, and alternating combustion is performed between a pair of adjacent regenerative combustion burners 21a and 21b (22a and 22b). A burner set 21 (22) is formed. The heating furnace 20 is divided into a heating zone 23a and a soaking zone 23b along the conveying direction of the steel pipe P in the furnace. The heating zone 23a is divided along the longitudinal direction of the steel pipe P into an inlet zone A, a central zone B and an outlet zone C, and three combustion zones. The soaking zone 23b is also divided into the inlet zone A 'and the central zone B. It is divided into three combustion zones as well as 'and outlet zone C'.
[0018]
The alternating burner sets 21 and 22 are mounted on the respective furnace walls so that the respective flames F ₁ and F ₂ are orthogonal to the longitudinal direction of the steel pipe P.
[0019]
Then, in a certain cycle, as shown in FIG. 1 (b), one combustion burner preheats the combustion air supplied by the blower 27 with a heat accumulator and burns it, and the other combustion bar. Na discharges the combustion exhaust gas through the heat storage body by the exhaust fan 28, and stores the sensible heat of the combustion exhaust gas in the heat storage body. In the next cycle, each combustion burner performs the opposite operation. In addition, the code | symbol 25 of FIG.1 (b) is a flue for discharging | emitting exhaust gas, 26 is a chimney.
[0020]
As described above, the burner sets 21 and 22 are alternately burned in a short cycle, so that the heat recovery rate is high.
[0021]
Next, the combustion control system of the heating furnace will be described with reference to FIG. FIG. 2 shows one combustion zone (zone) of the soaking zone 23a of the heating furnace and its combustion control system. A plurality of burner sets 21 ₁ , 21 ₂ ,... 21 _n−1 , 21 _{n including} regenerative combustion burners 21 a and 21 b are arranged on the wall surface of the heating furnace 20 so as to uniformly heat the steel pipe P. Has been. Each of the regenerative combustion burners is provided with a regenerator 29. When the combustion exhaust gas passes through the regenerator 29, the sensible heat is accumulated, and the combustion air passes through the regenerator 29. When preheating the combustion air.
[0022]
Burner sets 21 ₁ , 21 ₂ ,... 21 _n−1 , 21 _n of a regenerative combustion burner that performs alternating combustion include a fuel supply system L1, a combustion air supply system L2, a combustion exhaust gas discharge system L3, and an electric A control switching control system L4 is provided, and a set of three-way switching valves 30 ₁ , 30 ₂ ,... 30 _n−1 , 30 _n for switching between the combustion air supply system L2 and the combustion exhaust gas discharge system L3 are provided. ing. The three-way switching valves 30 ₁ , 30 ₂ ,... 30 _n−1 , 30 _n cause combustion air to flow to the combustion burner on either side of the burner set of the regenerative combustion burner. It is possible to set whether to discharge combustion exhaust gas from the combustion burner on either side. This switching control is performed by a control signal from the control device 31 based on the zone temperature detected at the temperature detection end T ₁ , T _{2 or} T ₃ of each combustion zone.
[0023]
In addition, it can satisfy | fill the same function with one four-way switching valve instead of using two three-way switching valves.
[0024]
Further, the fuel supply amount of each regenerative combustion burner and the valve opening / closing control of the fuel supply control valve are performed by the control signal from the control device 31. Since other combustion zones have the same configuration, the description thereof is omitted.
[0025]
In the heating furnace described above, a regenerative combustion burner is used, and the burner set burner is switched every certain time, for example, every 30 seconds, and fuel is supplied to each combustion zone of the heating furnace. Thus, the combustion atmosphere is stirred, and the temperature distribution in the longitudinal direction of the steel pipe P becomes more uniform.
[0026]
In addition, the regenerative combustion burner of the same combustion zone adjusts the cycle of alternating combustion individually, adjusts the combustion time and length of heat storage time of alternating combustion, and adjusts the fuel supply amount. The temperature distribution in the longitudinal direction of the steel pipe P can be adjusted.
[0027]
In addition, a regenerative combustion burner that performs alternating combustion uses a material such as a ceramic as a heat accumulator. Since the heat storage body can withstand high temperatures such as ceramics, combustion exhaust gas with a high temperature of 1000 ° C or higher can be introduced into the heat storage body, so it is possible to efficiently recover the sensible heat possessed by the combustion exhaust gas. is there. For example, when the temperature of the combustion exhaust gas is 1000 ° C., the combustion air can be preheated to 900 to 950 ° C., and the heat recovery efficiency is extremely high.
[0028]
Next, a combustion method in the case where any of the combustion burners in the combustion zone is extinguished for some reason in the heating furnace having the plurality of combustion zones described above will be described.
[0029]
FIG. 3 is an explanatory diagram showing a heating method using a regenerative combustion burner when one set (2C) of combustion burners extinguishes.
[0030]
In this heating method using a regenerative combustion burner, two sets of regenerative combustion burners 1a and 1b that alternately burn in one set (two sets of 2A, 2B, 2C, 2D, and 2E in FIG. 3) are 1 A plurality of combustion zones 3 are provided as one combustion zone 3, and a flow rate control valve 5 for controlling a supply amount of the combustion air is provided in a combustion air header-tube 4 for supplying combustion air to each combustion zone 3, and In a regenerative combustion burner apparatus in which a combustion exhaust gas header pipe 6 for exhausting combustion exhaust gas of each combustion zone 3 is provided with a flow rate control valve 7 for controlling the discharge amount of combustion exhaust gas, in the same combustion zone 3 Each of the heat storage type combustion burners 1a or 1b in the case where an abnormality that extinguishes the combustion burner occurs, and each combustion bar joined to the flue gas header pipe 6 is heated. -NA set 2A, 2B, 2C, Combustion exhaust gas temperature measured by a thermometer 12 provided in the combustion exhaust gas branch pipes D and 2E becomes equal to or higher than a set temperature set in order to prevent damage to each device of the combustion burner. When the burner is extinguished, the flow rate control valve 7 for controlling the exhaust gas emission amount of the combustion zone 3 is fully closed, and the combustion burners 1a and 1b of the group in which an abnormality has occurred (2C in FIG. 3). Closes the fuel shut-off valves 10a and 10b of the fuel supply branch pipes 9a and 9b of the set 2C so that the combustion is stopped, and sets the three-way switching valves 8a and 8b to the combustion air supply side. Switch to a state where only combustion air is supplied.
[0031]
Then, fuel and combustion air are alternately supplied to the combustion burners 1a and 1b of the sets 2A, 2B, 2D, and 2E other than the set 2C in which the abnormality has occurred, and the alternating combustion is performed without preheating the combustion air. To do.
[0032]
Since heating is performed in this manner, the extinguished regenerative combustion burner is not damaged by heat, and the heat storage body of another regenerative combustion burner in the same combustion zone is overheated by exhaust gas. Since it does not pass, the temperature of the combustion exhaust gas measured by the thermometer 12 provided in the combustion exhaust gas branch pipe 11 does not exceed the set temperature set in order to prevent damage to each device of the combustion burner. The combustion burner will not extinguish in a chain.
[0033]
Therefore, since the combustion air is not preheated, the combustion efficiency may be lowered, but the trouble that the many combustion burners extinguish and the operation of the heating furnace is stopped does not develop.
[0034]
Further, since the zone is divided in the longitudinal direction of the object to be heated and the inside of the zone has a uniform temperature distribution, the occurrence of uneven temperature in the longitudinal direction of the long object to be heated can be prevented.
[0035]
【The invention's effect】
According to the present invention, the operation of the heating furnace can be performed stably, and the durability of the combustion burner is also improved.
[Brief description of the drawings]
FIG. 1 is an explanatory view of a heating furnace in which a plurality of combustion zones are formed, (a) is a schematic plan view of the heating furnace, and (b) is a schematic cross-sectional view of the heating furnace.
FIG. 2 is a control system diagram showing a combustion control system of a heating furnace in which a plurality of combustion zones are formed.
FIG. 3 is an explanatory diagram showing a heating method using a regenerative combustion burner according to an embodiment of the present invention.
FIG. 4 is an explanatory view showing a heating method by a conventional heat storage type combustion burner.
FIG. 5 is an explanatory view showing a conventional extinguishing method for an abnormal combustion burner.
[Explanation of symbols]
1a, 1b Thermal storage combustion burner 2A, 2B, 2C, 2D, 2E Thermal storage combustion burner set 3 Combustion zone 3
4 Combustion air header-pipe 5 Flow control valve 6 Combustion exhaust gas header-pipe 7 Flow control valves 8a, 8b Three-way switching valves 9a, 9b Fuel supply branch pipes 10a, 10b Fuel cutoff valve 11 Combustion exhaust gas branch pipe 12 Thermometer 20 Heating Furnace 21a, 21b Regenerative burner 22a, 22b Regenerative burner 21, 22 Burner set 21 ₁ , 21 ₂ ,... 21 _n-1 , 21 _n Alternate burner set 23a Heating zone 23b Soaking zone 25 Chimney 26 Chimney 27 Blower 28 Blower for discharge 29 Heat storage body 30 ₁ , 30 ₂ ,... 30 _n−1 , 30 _n three-way switching valve 31 Control device

Claims (1)

Displacement of combustion exhaust gas by providing a plurality of combustion zones with a plurality of pairs of regenerative combustion burners that alternately burn in one set as one combustion zone, and controlling the supply amount of combustion air for each combustion zone A heating method by a regenerative combustion burner device provided with a flow control valve for controlling the amount, and if any abnormality occurs in any of the regenerative combustion burners in the same combustion zone, the combustion The flow rate control valve for controlling the exhaust gas emission amount of the zone is fully closed so that the combustion air is supplied without being preheated. After the abnormality is repaired, the flow rate for controlling the exhaust gas emission amount A heating method using a regenerative combustion burner characterized in that the control valve is opened to preheat the combustion air to perform alternating combustion.

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