JP2013145100A - Regenerative burner control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a regenerative burner control method that does not induce fluctuation of a fuel supply pressure to a burner and exhaust a gas pressure from the burner, when thinning of the regenerative burner occurs due to failure or the like of a device.SOLUTION: In a regenerative burner control method in a heat treatment furnace in which zoning into a plurality of furnace temperature control zones is performed along a conveying direction of a treated material, and a plurality of radiant tube type regenerative burners are disposed in respective furnace temperature control zones, upon occurrence of thinning, a starting interval of remaining regenerative burners is switched to a time obtained by equally dividing a half cycle of an alternating cycle by the number of operable, remaining regenerative burner, and a combustion time per one regenerative burner after thinning belonging to the furnace temperature control zone is switched to (total number of regenerative burners/the number of regenerative burners after thinning) times of a combustion time before thinning.

Description

  The present invention relates to a method for controlling a regenerative burner installed in a heat treatment furnace, and more particularly to a method for controlling a regenerative burner when thinning occurs due to equipment failure or the like.

  In a heat treatment furnace that heat-treats a material to be treated such as a steel strip, a radiant tube regenerative burner is installed as a heater for heating in the furnace in order to save energy. In the radiant tube type regenerative burner, a burner with a built-in heat storage is attached to both ends of the radiant tube, and the pair of burners alternately burn (alternate combustion). The exhaust gas generated when one burner burns passes through the heat storage body of the other burner via the radiant tube, and the waste heat of the exhaust gas is stored in the heat storage body. When the other burner burns, the combustion air is preheated by passing through the heat storage body.

  In the above heat treatment furnace, when the furnace temperature is controlled by the method of continuously changing the burner combustion amount using the flow control valve, the turndown (combustion load adjustment range) depends on the performance of the burner and flow control valve. ) Is about 1/5 (see Patent Document 1). In addition, there is a problem that the life of the radiant tube is shortened due to the occurrence of thermal stress due to a large change in temperature distribution, which is repeated.

Therefore, in Patent Document 1, when the burners attached to both ends of the radiant tube are alternately burned, a combustion stop time during which exhaust from the radiant tube is not performed within the combustion setting time of the alternating combustion is provided as needed, and the combustion time And a method of controlling the furnace temperature by adjusting the ratio of the combustion stop time according to the load.
In the above control method, in each furnace temperature control zone zoned along the conveying direction of the material to be processed, the temperature change in the furnace is changed by performing a rotation sequence that evenly shifts the phase of the alternating combustion of each burner. While suppressing, the fluctuation | variation of the fuel supply pressure to a burner and the exhaust gas pressure from a burner is prevented.

  Unless otherwise specified in this specification, a pair of heat storage burners attached to both ends of the radiant tube and a radiant tube regenerative burner having the radiant tube as a main component are called `` regenerative burners '' The regenerative burner attached to the end of the radiant tube will be referred to as a “burner”.

Japanese Patent Laid-Open No. 10-141614

  However, in the furnace temperature control method described in Patent Document 1, a failure of equipment (valve, solenoid valve, limit switch, etc.) occurs during operation, and one or more regenerative burners in the furnace temperature control zone are installed. When thinning out (pause), tooth loss occurs in the rotational sequence, and the phase shift of the alternating combustion of each burner is not kept uniform, so the fuel supply pressure to the burner and the exhaust gas pressure from the burner fluctuate. When the number of thinnings increases and the combustion load is greatly reduced, a timing at which all the fuel valves are closed occurs, and there is a possibility that a large fluctuation is induced in the fuel supply pressure control to the burner. When the fuel supply pressure fluctuates greatly, the air-fuel ratio fluctuates, leading to fluctuations in combustion temperature and black smoke generation.

  The present invention has been made in view of such circumstances, and induces fluctuations in the fuel supply pressure to the burner and the exhaust gas pressure from the burner when thinning of the regenerative burner occurs due to equipment failure or the like. An object of the present invention is to provide a control method for a regenerative burner that does not occur.

In order to achieve the above object, according to the present invention, the furnace is zoned in a plurality of furnace temperature control zones along the conveying direction of the workpiece, and a plurality of radiant tube regenerative burners are provided in each furnace temperature control zone. In the control method of the regenerative burner in the disposed heat treatment furnace,
When one or a plurality of the regenerative burners belonging to the furnace temperature control zone are thinned out, the activation interval Trs (sec) of the remaining regenerative burners is switched to a value calculated by the equation (1), and the remaining The combustion time Ton (sec) of the regenerative burner is switched to a value calculated by equation (2).
Trs = (T / 2) / (n-nerr) (1)
Ton = (T / 2) × (BL / 100) × (n / (n−nerr)) (2)
Here, T: period of alternating cycle (sec), n: total number of regenerative burners belonging to the furnace temperature control zone, nerr: number of regenerative burners thinned out in the furnace temperature control zone, BL: Zone combustion load (%)

  The start interval Trs, the combustion time Ton, and n and nerr are values when a pair of regenerative burners attached to both ends of the radiant tube are regarded as one radiant tube regenerative burner. Further, the zone combustion load BL is (number of operable regenerative burners belonging to the furnace temperature control zone × operation time in a half cycle of the regenerative burner) / (regenerative burner belonging to the furnace temperature control zone). (Total number × half cycle).

In the control of the radiant tube type regenerative burner group belonging to the furnace temperature control zone, one burner constituting the regenerative burner starts sequentially during T / 2, that is, a half cycle of the alternating cycle, and then the other burner. The burner is activated sequentially during the remaining half of the alternating cycle.
In the present invention, in order to prevent missing teeth in the rotational sequence after thinning out the regenerative burner, when the decimation occurs, the activation interval Trs of the remaining regenerative burner is set to the remaining operable regenerative burner. The number of active burners is switched to a time that equally divides the half cycle of the alternating cycle.
Furthermore, in the present invention, one of the remaining regenerative burners is used to cover the zone combustion load BL that has been borne by all the regenerative burners belonging to the furnace temperature control zone with the remaining regenerative burners that can be operated. The per-combustion time is switched to the combustion time before decimation (total number of regenerative burners / number of regenerative burners after decimation).
By the above method, there is no loss of rotation sequence after decimation, the phase shift of alternating combustion of each burner is kept uniform, and the combustion load in the furnace temperature control zone is kept constant regardless of the number of decimation. Can do.

  Further, in the control method for the regenerative burner according to the present invention, the ignition time of the regenerative burner that was most recently activated among the regenerative burners burned at the time of occurrence of decimation is used as a reference. It is preferable to switch the activation interval Trs and the combustion time Ton of the regenerative burner activated thereafter.

  In this configuration, when the deactivation occurs, the activation interval Trs and the combustion time Ton of the remaining regenerative burners are switched, and the regenerative burner that is most recently activated among the regenerative burners that were burning when decimation occurred. Since the time of ignition of the active burner is used as a reference, it is possible to smoothly switch between the start interval and the combustion time before and after the occurrence of thinning.

In the regenerative burner control method according to the present invention, when degeneration of the regenerative burner occurs, the activation interval of the remaining regenerative burner is set to the half cycle of the alternating cycle by the number of remaining regenerative burners that can be operated. In addition to switching to an evenly divided time, the combustion time per unit of the regenerative burner after decimation belonging to the furnace temperature control zone is set to the combustion time before decimation (total number of regenerative burners / regenerative burner after decimation) Since the number of burners is switched to twice, the phase shift of the alternating combustion of each burner in the rotation sequence is kept even, and fluctuations in the fuel supply pressure to the regenerative burner and the exhaust gas pressure from the regenerative burner are prevented. be able to.
Further, since the combustion load in the furnace temperature control zone before and after the thinning is kept constant, disturbance of the furnace temperature control due to the occurrence of thinning can be prevented, and the product quality can be stabilized.

(A) is a schematic diagram which shows arrangement | positioning of the regenerative burner in a heat processing furnace, (B) is the elements on larger scale of a regenerative burner group. It is a systematic diagram of the regenerative burner group which belongs to one furnace temperature control zone. It is an example of the valve | bulb opening / closing chart in the burner combustion load factor 100% in normal time. It is an example of a valve opening / closing chart at a burner combustion load factor of 20% during normal times. It is an example of the valve | bulb opening / closing chart by the conventional control method in the burner combustion load factor 20% at the time of thinning generation | occurence | production. It is a flowchart for demonstrating the procedure of the control method of the regenerative burner which concerns on one embodiment of this invention. It is an example of the valve | bulb opening / closing chart by the control method of the same regenerative burner in the zone combustion load 20% at the time of thinning.

  Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.

As shown in FIG. 1 (A), inside the heat treatment furnace 30, a plurality of transport rollers 31 for transporting a material to be treated S such as a steel strip are provided at the upper part and the lower part, respectively. The material to be processed S carried into the heat treatment furnace 30 from the conveyance port 30a is folded back several times in the heat treatment furnace 30 by the plurality of conveyance rollers 31, and then carried out from the carry-out port 30b.
In the heat treatment furnace 30, a plurality of regenerative burners 10 for heating the material to be processed S are installed in the conveying direction of the material to be processed S with the material to be processed S interposed therebetween (FIG. 1A). (See (B)). Each forward path and each return path for transporting the material S to be processed is an independent furnace temperature control zone 32, and the furnace temperature control of the furnace temperature control zone 32 is performed by a regenerative burner group belonging to each furnace temperature control zone 32. Done.

  FIG. 2 is a system diagram of a group of regenerative burners belonging to one furnace temperature control zone 32. Ten regenerative burners 10 (hereinafter, each of the regenerative burners 11,..., 20 To form a regenerative burner group. Here, taking the regenerative burner 11 as an example, the structure of the regenerative burner 10 (radiant tube regenerative burner) will be described.

The regenerative burner 11 is a radiant tube (radiation tube) 114 in which a heat-resistant alloy such as Ni—Cr is formed in a W shape (in the case of the regenerative burner 12, 13,..., 20 the radiant tubes 124, 134,. 204) and a pair of burners 110a, 110b attached to both ends of the radiant tube 114. The burners 110a and 110b are regenerative burners and incorporate a heat storage body (not shown) for storing waste heat of exhaust gas.
As described above, in the regenerative burner 11, the pair of burners 110a and 110b burn alternately. The exhaust gas generated when one burner 110a burns passes through a heat storage body built in the other burner 110b via the radiant tube 114. At that time, waste heat of the exhaust gas is stored in the heat storage body, and is used for preheating combustion air passing through the heat storage body when the other burner 110b burns.

  The fuel fed through the fuel pipe 26 is supplied to the burners 110a and 110b via the fuel valves 111a and 111b. Further, the combustion air sucked from the atmosphere via the combustion air pipe 28 is supplied to the burners 110a and 110b via the intake valves 113a and 113b. On the other hand, the exhaust gas discharged from each burner 110a, 110b is discharged into the atmosphere from the exhaust gas pipe 27 via the exhaust gas valves 112a, 112b.

A fuel pressure adjustment valve 21 and a fuel pressure transmitter 22 are installed on the fuel pipe 26. The fuel of the burners 110a, 110b,..., 200a, 200b passes through the fuel pressure adjusting valve 21 whose opening is adjusted based on the output of the fuel pressure transmitter 22, and then the burners 110a, 110b, ..., 200a, 200b.
On the other hand, an exhaust gas pressure adjusting valve 23 and an exhaust gas pressure transmitter 24 are installed on the path of the exhaust gas pipe 27, and a blower 25 is installed at the end of the exhaust gas pipe 27. The exhaust gas discharged from each burner 110a, 110b,..., 200a, 200b is sucked into the blower 25, and after passing through the exhaust gas pressure regulating valve 23 whose opening is adjusted based on the output of the exhaust gas pressure transmitter 24, the exhaust gas Released from the pipe 27 into the atmosphere.

  FIG. 3 shows an example of a valve opening / closing chart of the regenerative burners 11 to 20 belonging to one furnace temperature control zone 32. In the figure, the first row (1) of each burner 110a, 110b, 120a, 120b,..., 200a, 200b shows the open / closed state of the fuel valves 111a, 111b, 121a, 121b,. (2) shows the open / closed states of the intake valves 113a, 113b, 123a, 123b,..., 203a, 203b, and the last row (3) shows the open / closed states of the exhaust valves 112a, 112b, 122a, 122b,. Each is shown. The same applies to FIGS. 4, 5, and 7 described later.

  In this example, the cycle T of the alternating cycle is 40 seconds. All the regenerative burners 11 to 20 belonging to the furnace temperature control zone 32 are operating, the burner combustion load factor of each of the regenerative burners 11 to 20 is 100%, and the zone combustion load is also 100%. Here, the burner combustion load factor is the ratio of the time during which one regenerative burner 10 is burning in a half cycle. The zone combustion load is (number of operable regenerative burners 10 belonging to the furnace temperature control zone 32 × operation time in a half cycle of the regenerative burner 10) / (regeneration belonging to the furnace temperature control zone 32). The total number of the reactive burners 10 × a half cycle).

Since the regenerative burner 10 burns only one of the pair of burners, substantially the time during which one burner 110a, 110b, 120a, 120b,..., 200a, 200b burns in a half cycle. It is a ratio. Accordingly, the burning time of each burner 110a, 110b, 120a, 120b,..., 200a, 200b is 20 seconds.
In addition, the activation interval of the regenerative burners 11 to 20 is 2 seconds obtained by equally dividing a half cycle of 20 seconds by 10 regenerative burners from the rotational sequence.

First, the fuel valve 111a and the intake valve 113a of the burner 110a are opened, the exhaust gas valve 112a is closed, and the burner 110a is in a combustion state for 20 seconds (during a half cycle). On the other hand, the burner 110b is in an exhaust state by closing the fuel valve 111b and the intake valve 113b of the burner 110b and opening the exhaust valve 112b for a half cycle after the ignition of the burner 110a.
Two seconds after ignition of the burner 110a, the fuel valve 121a and the intake valve 123a of the burner 120a are opened, the exhaust gas valve 122a is closed, and the burner 120a is in a combustion state for 20 seconds (during a half cycle). On the other hand, the burner 120b is in an exhaust state by closing the fuel valve 121b and the intake valve 123b of the burner 120b and opening the exhaust valve 122b for a half cycle after the ignition of the burner 120a.
Thereafter, ignition is performed in the order of burners 130a, 140a,..., 200a at intervals of 2 seconds, and then ignition is performed in the order of burners 110b, 120b,.

  FIG. 4 shows the furnace temperature control zone under the condition that all the regenerative burners 11 to 20 belonging to the furnace temperature control zone 32 are operated and the burner combustion load factor of each of the regenerative burners 11 to 20 is 20%. 3 shows an example of a valve opening / closing chart of the regenerative burners 11 to 20 belonging to FIG. The burn time of each burner 110a, 110b, 120a, 120b,..., 200a, 200b when the burner combustion load factor is 20% is 20 seconds × 0.2 = 4 seconds. The activation interval of the regenerative burners 10 to 20 is 2 seconds as in the example of FIG. The zone combustion load at this time is 20%, which is the same as the burner combustion load factor.

In this example, first, the fuel valve 111a and the intake valve 113a of the burner 110a are opened, the exhaust gas valve 112a is closed, and after the burner 110a is in a combustion state for 4 seconds, the fuel valve 111a and the intake valve 113a of the burner 110a are The exhaust valve 112a is closed and the burner 110a is in the exhaust state for the remaining time of one cycle. On the other hand, after the ignition of the burner 110a, the burner 110b is in an exhaust state by closing the fuel valve 111b and the intake valve 113b of the burner 110b and opening the exhaust valve 112b for a half cycle.
Two seconds after ignition of the burner 110a, the fuel valve 121a and the intake valve 123a of the burner 120a are opened, the exhaust gas valve 122a is closed, and the burner 120a is in a combustion state for 4 seconds. The valve 123a is closed, the exhaust gas valve 122a is opened, and the burner 120a is in the exhaust state for the remaining time of one cycle. On the other hand, the burner 120b is in an exhaust state by closing the fuel valve 121b and the intake valve 123b of the burner 120b and opening the exhaust valve 122b for a half cycle after the ignition of the burner 120a.
Thereafter, ignition is performed in the order of burners 130a, 140a,..., 200a at intervals of 2 seconds, and then ignition is performed in the order of burners 110b, 120b,.

  FIG. 5 shows a case where the regenerative burners 13 and 14 fail under the conditions of FIG. In the case of this example, all the regenerative burners 11 to 20 are not burned for 2 seconds during one cycle, that is, all the fuel valves 111a, 111b, 121a, 121b,..., 201a, 201b and all The intake valves 113a, 113b, 123a, 123b,..., 203a, 203b are closed. In such a state, there is a possibility that a large variation is induced in the fuel supply pressure control to the burners 110a, 110b, 120a, 120b,..., 200a, 200b. At this time, the burner combustion load factor is 20%, but the zone combustion load is reduced to 16%.

Next, a control method for the regenerative burner according to the embodiment of the present invention will be described.
The regenerative burner control method according to the present embodiment is executed at the time when thinning of the regenerative burner 10 occurs. Specifically, when one or more regenerative burners 10 belonging to the furnace temperature control zone 32 are thinned out, the activation interval Trs (sec) of the remaining regenerative burners 10 is calculated by equation (3). In addition, each combustion time Ton (sec) of the remaining regenerative burner 10 is switched to a value calculated by equation (4).
Trs = (T / 2) / (n-nerr) (3)
Ton = (T / 2) × (BL / 100) × (n / (n−nerr)) (4)
Here, T: period of alternating cycle (sec), n: total number of regenerative burner 10 belonging to furnace temperature control zone 32, nerr: number of regenerative burner 10 thinned out in furnace temperature control zone 32, BL: Zone combustion load (%)

  In addition, switching of the activation interval Trs and the combustion time Ton of the regenerative burner 10 is based on the ignition time of the most recently activated regenerative burner 10 among the regenerative burners 10 that burned when the decimation occurred. Thus, the present invention is applied to the regenerative burner 10 that is activated thereafter.

FIG. 6 shows a flowchart for explaining the procedure of the regenerative burner control method according to the present embodiment.
(STEP 1) A check is made as to whether or not the thinning of the regenerative burner 10 has occurred (ST10). If no thinning has occurred, the process proceeds to a check (ST14) as to whether or not the control has been completed.
(STEP 2) When thinning of the regenerative burner 10 has occurred, the most recently activated regenerative burner 10 is selected from among the regenerative burners 10 that burned when the thinning occurred. And the reference | standard at the time of switching of the starting space | interval Trs and combustion time Ton of the regenerative burner 10 started after the selected regenerative burner 10 is made into the time of ignition of the selected regenerative burner 10 (ST11). .
(STEP 3) The activation interval Trs and the combustion time Ton of the regenerative burner 10 are calculated using the equations (3) and (4) (ST12).
(STEP 4) The activation interval Trs and the combustion time Ton calculated by the equations (3) and (4) are reflected in the regenerative burner 10 after the selected regenerative burner 10 (ST13).
(STEP 5) It is checked whether or not the control is finished (ST14). If the control is not finished yet, the process returns to ST10 to check again about occurrence of thinning.

FIG. 7 shows a valve opening / closing chart when the regenerative burner control method according to the present embodiment is performed under the same conditions as in FIG.
In the control method for the regenerative burner according to the present embodiment, when the regenerative burner 13 fails and is thinned, the activation interval Trs of the regenerative burner 10 is 2.22 seconds and the combustion time Ton is 4 44 seconds.
The ignition time of the most recently activated regenerative burner 12 among the regenerative burners 10 that burned at the time of decimation is the reference for switching the activation interval Trs and the combustion time Ton. Thereafter, the new start interval Trs and the combustion time Ton are applied.

  However, in this example, since the regenerative burner 14 is also failed and thinned out, the start interval Trs and the combustion time Ton of the regenerative burner 10 are calculated again. The newly calculated start interval Trs is 2.5 seconds, and the combustion time Ton is 5 seconds. The activation interval Trs and the combustion time Ton are applied to the regenerative burner 12 and later on the basis of the ignition time of the regenerative burner 12.

Unlike FIG. 5, in FIG. 7, it turns out that the state where all the regenerative burners 11-20 are not combusting has not generate | occur | produced. Further, at this time, it is understood that the zone combustion load is kept at 20% when the burner combustion load factor becomes 25%.
When the zone combustion load BL before thinning is 80%, the zone combustion load before thinning can be maintained even if two regenerative burners 10 fail, and the zone combustion load BL before thinning is 60%. In this case, the zone combustion load before thinning can be maintained even if four regenerative burners 10 fail. On the other hand, when the zone combustion load BL before thinning is 100%, the zone combustion load before thinning cannot be maintained after thinning, but the phase shift of the alternating combustion of each burner can be kept uniform.

  Although one embodiment of the present invention has been described above, the present invention is not limited to the configuration described in the above-described embodiment, and is within the scope of matters described in the claims. Other possible embodiments and modifications are also included. For example, in the above embodiment, the shape of the radiant tube is W-shaped, but it goes without saying that other shapes such as a U-shape may be used. In the above embodiment, the total number of regenerative burners belonging to the furnace temperature control zone is 10. However, it is needless to say that the number is not limited to that number. Furthermore, the arrangement and ignition order of each burner are not limited to the illustrated contents.

10-20: Regenerative burner (radiant tube type regenerative burner), 21: Fuel pressure adjusting valve, 22: Fuel pressure transmitter, 23: Exhaust gas pressure adjusting valve, 24: Exhaust gas pressure transmitter, 25: Blower, 26: Fuel piping, 27: Exhaust gas piping, 28: Combustion air piping, 30: Heat treatment furnace, 30a: Carrying inlet, 30b: Carrying outlet, 31: Transfer roll, 32: Furnace temperature control zone, 110a, 120a, ..., 200a , 110b, 120b,..., 200b: burner (heat storage type burner), 111a, 121a,..., 201a, 111b, 121b, ..., 201b: fuel valve, 112a, 122a,. : Exhaust gas valves, 113a, 123a, ..., 203a, 113b, 123b, ..., 203b: intake valves, 114, 1 4, ..., 204: radiant tube, S: the material to be treated

Claims (2)

The regenerative burner in a heat treatment furnace in which the inside of the furnace is zoned in a plurality of furnace temperature control zones along the conveying direction of the material to be processed, and a plurality of radiant tube regenerative burners are arranged in each furnace temperature control zone In the control method of
When one or a plurality of the regenerative burners belonging to the furnace temperature control zone are thinned out, the activation interval Trs (sec) of the remaining regenerative burners is switched to a value calculated by the equation (1), and the remaining A method for controlling a regenerative burner, characterized in that each combustion time Ton (sec) of the regenerative burner is switched to a value calculated by equation (2).
Trs = (T / 2) / (n-nerr) (1)
Ton = (T / 2) × (BL / 100) × (n / (n−nerr)) (2)
Here, T: period of alternating cycle (sec), n: total number of regenerative burners belonging to the furnace temperature control zone, nerr: number of regenerative burners thinned out in the furnace temperature control zone, BL: Zone combustion load (%)   2. The method of controlling a regenerative burner according to claim 1, wherein the ignition time of the regenerative burner that was most recently activated among the regenerative burners that burned at the time of occurrence of thinning is used as a reference, and thereafter A control method for a regenerative burner, characterized in that the activation interval Trs and the combustion time Ton of the regenerative burner activated at a time are switched.

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