JPH0933037A - Burner combustion air pressure control method - Google Patents

Abstract

(57) [PROBLEMS] To prevent hunting of the air supply pressure that occurs in the initial stage when the air control valve for a burner is opened. SOLUTION: Combustion burners 3 to 6 of a plurality of zones are provided along a flow direction of a steel plate in a heating furnace 1 arranged in a heating zone for heating a steel plate 2, and a combustion air supply fan 8 is provided.
In the air supply system for supplying combustion air through the combustion air supply pipe 7 and heat exchange by the recuperator 10 to the combustion burners 3 to 6 in each zone, the combustion air is combusted from the combustion air supply fan 8 When supplying the working air to the combustion burners 3 to 6 in each zone, the pilot air supply fan 18 is arranged so that the pressure in the combustion air supply pipe 7 is always kept constant during the burner pipe purging and the combustion burner ignition.
A part of the air supplied from the pilot burner 20 is made to flow into the combustion air supply pipe 7 to be supplemented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure control method for suppressing pressure fluctuations of combustion air supplied to burners in a plurality of zones of a heating furnace such as an alloying furnace, an annealing furnace, and a color coating line. .

[0002]

2. Description of the Related Art For example, in a rolled steel sheet, a plurality of combustion burners in a plurality of zones are provided along a flow direction of the steel sheet in a heating furnace arranged in a heating zone for heating the steel sheet. The air is supplied to the combustion burner in each zone through the air supply line to burn the burner.

By the way, when air is supplied to the combustion burner in each zone to start the burner combustion, after the operation of the normal combustion air supply blower is started, the combustion air supply line secures a constant pressure, When it becomes normal, the burner pipes installed in each zone are purged with air.

[0004]

However, when the air purging of the burner pipe is immediately performed, the pressure of the combustion air supply line drops, so that the pressure signal taken out from the pressure switch to the controller repeats normal and abnormal and hunting occurs. There is a similar problem immediately after starting the main burner ignition.

Further, even if the opening degree of the combustion air supply control valve provided on the primary side of the combustion air supply blower is controlled in consideration of the control output value of the combustion air flow rate control of each zone, as described above. However, there is a problem in that the ability to follow a sudden load change at the initial stage of start-up such as when starting air purge and main burner ignition is poor.

The present invention has been made in order to solve the above problems, and after the operation of the burner combustion air supply fan is started, a constant pressure is maintained in the combustion air supply line to purge the burner piping in each zone. In the process of proceeding to the burner combustion in each zone, even if the air supply amount of each combustion burner at the end rapidly rises or fluctuates, the pressure in the burner combustion air supply pipe can be maintained at a constant target value. An object of the present invention is to provide a method for controlling the pressure of burner combustion air that can be used.

[0007]

In order to achieve the above object, the present invention provides a plurality of combustion burners in a plurality of zones along a flow direction of a steel plate in a heating furnace arranged in a heating zone for heating the steel plate. In the air supply system, the combustion air is supplied to the combustion burners in each zone by operating the combustion air supply fan and passing the combustion air through the burner combustion air supply pipe and exchanging heat with the recuperator. When the combustion air is supplied from the fan to the combustion burners in each zone, the pilot burner air is supplied so that the pressure in the combustion air supply pipe is always kept constant during the burner pipe purging and the combustion burner ignition. A part of the air supplied from the fan to the pilot burner is made to flow into the combustion air supply pipe to be supplemented.

Therefore, in such a burner combustion air pressure control method, even if the burner combustion air supply control valves in a plurality of zones are opened at the start of burner combustion, the pilot burner air supply fan causes the pilot burner to operate. Since a part of the supplied air is supplemented to the combustion air supply pipe as a backup, it is possible to suppress the pressure fluctuation of the air supplied to the combustion burner in each zone, and to establish a stable burner combustion. You can raise.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a pressure control method for burner combustion air according to the present invention will be described below with reference to the drawings. FIG. 1 is an air supply system diagram of a combustion burner of a heating furnace arranged in a heating zone for heating a steel plate.

In FIG. 1, reference numeral 1 denotes a heating furnace arranged in a heating zone of a steel plate 2, and the heating furnace 1 is provided with combustion burners 3 to 6 along the conveying direction of the steel plate. Here, the combustion burner 3 has n zones, and the combustion burner 4 has n zones.
The +1 zone, the combustion burner 5 is the n + 2 zone, and the combustion burner 6 is the n + 3 zone.

The combustion burners 3 to 6 in each of these zones are
A burner combustion supply fan 8 is provided on the air supply source side of the combustion air supply pipe 7, and a combustion air supply control valve 9 is provided on the upstream side thereof. To be

Further, the recuperator (heat exchanger) 1 is connected to the combustion air supply pipe 7 on the downstream side of the burner combustion supply fan 8.
0 is provided. In the recuperator 10, exhaust gas 11 emitted from the heating furnace 1 is supplied as a heating medium for burner combustion air, and the exhaust gas 11 is discharged to the outside from a chimney 13 through an exhaust gas pipe 12.

One end of the burner combustion air branch pipe 14 is connected to the combustion air supply pipe 7 on the upstream side of the recuperator 10, and the other end of the burner combustion air branch pipe 14 is connected to the exhaust gas pipe 12 as a control valve. A part of the burner combustion air is made to flow into the recuperator 10 by connecting via the 15.

Further, a combustion air supply pipe 7 on the downstream side of the recuperator 10 is connected to a combustion air discharge pipe 16, and a control valve 17 is provided in the middle thereof to discharge a part of the combustion air out of the factory.

On the other hand, 18 is an air supply fan for the pilot burner, which is an air supply fan 18 for the pilot burner.
The air supplied from the air supply pipe 19 is supplied to the pilot burner 20, and the air supply pipe 19 and the combustion air supply pipe 7 are connected by a bypass pipe 21. A shutoff valve 22 is provided.

Here, a pressure transmitter 23 for detecting the pressure of the combustion air and a thermocouple 24 for detecting the temperature are provided in the combustion air supply pipe 7 on the common inlet side of the combustion burner in each zone.
Further, a pressure switch 25 is provided on the combustion air supply pipe 7 on the upstream side of the recuperator 10 and on the downstream side of the connection portion with the bypass pipe 21.

A pressure switch 26 is also provided on the air supply pipe 19 on the outlet side of the pilot burner air supply fan 18. Further, a thermocouple 27 for detecting the temperature of the exhaust gas 11 is provided on the inlet side of the recuperator 10 of the exhaust gas pipe 12.

FIG. 2 shows an example of the structure of the air supply system for the combustion burner including a control system for controlling the burner combustion air. The same parts as those in FIG. It is omitted, and the control system will be mainly described here.

In FIG. 2, reference numeral 28 denotes a control unit, which controls the air pressure detection signal in the combustion air supply pipe 7 detected by the pressure switch 25 and the air supply pipe 19 detected by the pressure switch 26. The internal air pressure detection signals are respectively input, and the burner combustion supply fan 8
And the operation command to the pilot burner air supply fan 18, respectively.

Further, 29 to 32 are combustion air control valves provided at the air supply ports of the combustion burners in the n zone to n + 3 zone, and the combustion air control valves 29 to 32 in these zones are the combustion air flow rate controller 33. The opening degree is controlled by ~ 36.

Further, 37 is a pressure regulator to which the pressure detection signal in the combustion air supply pipe 7 on the inlet side of the combustion burner of each zone output from the pressure transmitter 23 is inputted. Control output value and combustion air flow controller 33 ~
The control signal obtained by adding the control output value of 36 controls the opening of the combustion air supply control valve 9.

On the other hand, 38 is a temperature control signal for inputting the temperature detection signal of the exhaust gas from the heating furnace detected by the thermocouple 27 and controlling the opening degree of the control valve 15 provided in the burner combustion air branch pipe 14. It is total.

A temperature detection signal 39 of the burner combustion air flowing through the combustion air supply pipe 7 on the downstream side of the recuperator 10 detected by the thermocouple 24 is input to the combustion air discharge pipe 16. It is a temperature controller that controls the opening degree of the control valve 17.

Next, the pressure control of the burner combustion air by the control system for controlling the burner combustion air configured as described above will be described. In FIG. 2, first, in order to secure the air pressure in the combustion air supply pipe 7, the operation of the burner combustion supply fan 8 is started by a command from the control unit 28 with the control valve 17 opened. Then, the combustion air flows from the air supply source through the combustion air supply pipe 7 and the combustion air discharge pipe 16, and at this time, the combustion air passes through the recuperator 10 to exchange heat with the exhaust gas from the heating furnace. That is, the combustion air having a high temperature flows in the combustion air discharge pipe 16.

On the other hand, an operation command is also given to the pilot burner air supply fan 18, and the air supplied from the pilot burner air supply fan 18 is supplied to the pilot burner 20 through the air supply pipe 19. There is.

Next, when the control unit 28 confirms that the combustion air flowing in the combustion air supply pipe 7 has a constant pressure by the pressure detection signal of the combustion air from the pressure switch 25, the combustion air in each zone is burned. Since the burner pipe is purged (blown off) by combustion air, a control operation command is given to each of the combustion air flow rate controllers 33 to 36, and an opening command is issued to the shutoff valve 22 provided in the bypass pipe 21. give.

Then, the combustion air flow controller 33-
36 opens the combustion air control valves 29 to 32 in each zone to carry out purging with combustion air, and
Is opened, the backup air is supplied from the pilot burner air supply fan 18 through the bypass pipe 21.
It is filled in the combustion burner piping in the n + 3 zone.

Therefore, the combustion air control valves 29-
Even if 32 is opened at the same time, it is possible to suppress the pressure drop in the combustion air supply pipe 7. Further, the shutoff valve 22 is closed when the purging in the heating furnace is completed, but after the inside of the heating furnace is replaced with the reducing atmosphere, the main burner n to n + 3.
When the combustion burner in the zone is ignited, the shut-off valve 22 is opened as in the case of purging, so that stable combustion start can be performed.

When a stable combustion state is entered after the start of combustion, the shut-off valve 22 is closed and the control output values from the combustion air flow rate controllers 33 to 36 cause the combustion air control valves 29 to 32 in the n to n + 3 zones to operate. By controlling the opening and controlling the opening of the combustion air supply control valve 9 by adding the control output value to the control output value of the pressure controller 37, it is possible to always maintain a constant combustion air pressure. .

Here, in the above control system, the temperature controller 38 sends the exhaust gas returning from the heating furnace to the recuperator 10 on the basis of the temperature detection signal of the combustion air detected by the thermocouple 27. By adjusting the opening of the control valve 15 with the control output value, the combustion air before heat exchange is mixed with the exhaust gas flowing into the recuperator 10 and diluted when the exhaust gas becomes too hot. .

Further, the temperature controller 39 controls the opening degree of the control valve 17 by PID control of the temperature detection value of the combustion air detected by the thermocouple 24 installed on the downstream side of the recuperator 10. Since the combustion air is discharged to the outside of the factory, it prevents the air that has become too hot from being supplied to the combustion burner.

Further, the exhaust gas that has exchanged heat with the combustion air in the recuperator 10 is discharged to the outside through the chimney 13. As described above, according to the above-described embodiment, it is possible to secure the combustion air pressure in the combustion air supply pipe 7 within the target value at the time of air purging of the burner pipe and at the initial stage of combustion (rise). Therefore, not only can the heating of the steel plate heating furnace be smoothly started, but also the occurrence of an alarm due to pressure hunting such as normality or abnormality detected by the pressure switch can be eliminated.

[0033]

As described above, according to the present invention, after the operation of the burner combustion air supply fan is started, a constant pressure is maintained in the combustion air supply line, the burner pipes in each zone are purged, and the burners in each zone are burned. Even if the air supply amount of each combustion burner at the end rapidly rises or fluctuates in the process of proceeding to, the pressure in the burner combustion air supply pipe can be maintained at a constant target value. A control method can be provided.

[Brief description of drawings]

FIG. 1 is an air supply system diagram of a heating furnace for explaining an embodiment example of a pressure control method for burner combustion air according to the present invention.

FIG. 2 is an air supply system diagram of a heating furnace for explaining a control system for controlling burner combustion air in the embodiment.

[Explanation of symbols]

1 ... Heating furnace, 2 ... Steel plate, 3-6 ... Combustion burner,
7 ... Combustion air supply pipe, 8 ... Burner combustion supply fan, 9 ... Combustion air supply control valve, 10 ... Recuper, 11 ... Exhaust gas, 12 ... Exhaust gas pipe, 13
…… Chimney, 14 …… Burner combustion air branch pipe, 15,
17 ... Control valve, 16 ... Combustion air exhaust pipe, 18 ...
… Air supply fan for pilot burner, 19 …… Air supply piping, 20 …… Pilot burner, 21 …… Bypass piping, 22 …… Shut-off valve, 23 …… Pressure transmitter, 2
4, 27 ... Thermocouple, 25, 26 ... Pressure switch, 2
8 ... Control unit, 29-32 ... Combustion air control valve, 33-
36 ... Combustion air flow controller, 37 ... Pressure controller, 3
8,39 ... Temperature controller.

Claims (1)

[Claims] 1. A combustion furnace provided in a heating zone for heating a steel plate is provided with combustion burners in a plurality of zones along the flow direction of the steel plate, and the combustion air is supplied by operating a combustion air supply fan. In an air supply system that supplies heat to a combustion burner in each zone through a combustion air supply pipe and heat exchange by a recuperator, supplies combustion air from the burner combustion air supply fan to the combustion burner in each zone. In order to maintain a constant pressure inside the combustion air supply pipe at the time of purging the burner pipe and igniting the combustion burner, part of the air supplied from the pilot burner air supply fan to the pilot burner is burned. A method for controlling the pressure of burner combustion air, characterized in that the burner combustion air is supplied to and supplemented with a combustion air supply pipe.