JP2009235463A - Apparatus and method for continuously heating metal strip - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and a method for continuously heating a metal strip which change oxidation and reduction in comparatively freely and in a wide range, according to the metal strip to be heated. <P>SOLUTION: Burner equipment 6 to be used in at least a downstream side in a direct fired heating furnace 2, has constitution in which premixed gas obtained by premixing fuel gas with air for combustion by a mixing device 7, is jetted from a nozzle 17. A flow rate detector and a flowing rate regulating valve are each arranged in fuel-system piping 9 for supplying the fuel gas into the mixing device 7, and in air-system piping 8 for supplying the air for combustion into the mixing device 7, and the flowing rate regulating valve is controlled so as to obtain the air ratio set according to the metal strip to be heated. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a continuous heating apparatus and continuous heating method for a metal strip provided in facilities such as a continuous annealing line and a continuous hot dip galvanizing line.

As a conventional continuous heating apparatus, there is an apparatus described in Patent Document 1, for example. In this apparatus, a premix burner facility that is a premixing system is used for heating the final zone of the direct-fired heating furnace.
The premix burner facility described in Patent Document 1 is as follows.
Combustion air is supplied to the mixing valve through the combustion air pipe, and an air control valve is interposed in the combustion air pipe. In addition, the fuel gas is supplied to the mixing valve through the fuel gas pipe, and the zero-balanced regulator is set so that the pressure in the fuel gas pipe is the same as that of the combustion air pipe. I will intervene.

Then, feedback control of the mixing valve motor is performed with the air ratio adjuster so that the air ratio setting value is obtained, and the air ratio is controlled to be constant by changing the opening ratio between the fuel gas and the combustion air in the mixing valve. To do. In addition, the amount of combustion was increased or decreased by controlling an air control valve installed in the combustion air piping.
Conventionally, the final zone of the direct-fired heating furnace is controlled to the reduction zone.
Japanese Patent No. 2741617

However, in the configuration of the above-described conventional example, there are many factors that mechanically determine the air ratio based on the opening ratio between the fuel gas of the mixing valve and the combustion air. For this reason, it has been difficult to change the air ratio relatively freely and in a wide range online.
For this reason, the oxidation-reduction of the metal strip heated by the continuous heating apparatus cannot be applied in a wide range according to the properties required for the heated metal strip.
The present invention has been made by paying attention to the above points, and provides a continuous heating apparatus and method for a metal strip in which oxidation and reduction can be changed relatively freely and in a wide range according to the metal strip to be heated. This is the issue.

In order to solve the above-mentioned problems, the invention described in claim 1 of the present invention is a continuous heating apparatus including a direct-fired heating furnace that heats a continuously conveyed metal strip,
Burner equipment used at least downstream in the direct-fired heating furnace is configured to inject and burn a premixed gas in which a fuel gas and an oxygen-containing gas are mixed in advance by a mixing device, and the mixing device. Air set to correspond to the metal strip to be heated by providing a flow rate detector and a flow rate control valve on each of the fuel system piping for supplying fuel gas to the air system piping for supplying oxygen-containing gas to the mixing device. A control device is provided for controlling the flow rate control valve based on a signal from the flow rate detector so as to obtain a ratio.

Next, the invention described in claim 2 is a method for continuously heating a metal strip in which a continuously transported metal strip is continuously heated in a direct-fired heating furnace,
Heating at least downstream in the direct-fired heating furnace is configured such that a premixed gas in which fuel gas and oxygen-containing gas are mixed in advance by a mixing device is jetted from the nozzle and burned, and supplied to the mixing device. The fuel gas and the oxygen-containing gas are adjusted by individual flow rate control valves, and the flow rate control valve is controlled so that the air ratio is set corresponding to the metal band to be heated. .

  According to the present invention, instead of using a zero-balanced regulator, by providing a flow control valve and a flow detector in each of the fuel gas piping system and the combustion air piping system, it is possible to individually control the flow rate in each system. And And air ratio control is performed by operating each flow control valve based on the flow actual value from the flow detector of each system. As a result, the flow rates of the fuel gas and oxygen-containing gas supplied to the mixing device can be individually adjusted. As a result, the air ratio control can be changed relatively freely and in a wide range according to the corresponding metal band. It becomes possible.

Further, since the fuel gas and the oxygen-containing gas are premixed by the mixing device and supplied to the nozzle, the fuel gas and the oxygen-containing gas can be premixed uniformly. For this reason, the variation in the oxidation-reduction state in the furnace can be suppressed accordingly. That is, stable control to the target oxidation-reduction state is possible.
That is, according to the operation, it is possible to easily make the inside of the direct-fired heating furnace into an oxidizing atmosphere or a reducing atmosphere.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view showing a part of a continuous treatment line for a metal strip provided with a continuous heating apparatus according to this embodiment. In addition, as a continuous processing line, a continuous annealing line and a continuous hot dip galvanizing line can be illustrated.
Moreover, although a steel strip is illustrated as a metal strip, other metal strips may be used.

(Constitution)
The steel strip 1 that is continuously conveyed is continuously heated in the direct-fired heating furnace 2 and then continuously conveyed to the subsequent process.
The direct-fired heating furnace 2 is divided into, for example, four zones along the conveying direction of the steel strip 1, for example, and burner devices 3 to 6 arranged for each zone are used to control the atmosphere state of each zone. The steel strip 1 is heated.

In this embodiment, for example, from the first zone to the third zone, the nozzle mix (mixing method in the nozzle) burner equipment 3 to 5 is used, and the target air-reduction atmosphere is set as the set air ratio. The steel strip 1 is heated.
In the fourth zone, which is the final zone, a premix burner facility 6 is employed. The configuration of the burner facility in the fourth zone is as shown in FIG.

That is, the downstream end of the combustion air system pipe 8 and the downstream end of the fuel system pipe 9 communicate with the mixing device 7. As a result, combustion air as an oxygen-containing gas and fuel gas can be supplied to the mixing device 7.
A flow rate control valve 10 is interposed in the middle of the combustion air system pipe 8, and a flow rate transmitter 11 as a flow rate detector is provided upstream of the flow rate control valve 10. The flow rate transmitter 11 outputs a detection signal to the instrumentation controller 15. Further, the flow rate adjusting valve 10 adjusts the flow rate according to a command from the instrumentation controller 15.

Similarly, a flow rate adjusting valve 12 is interposed in the middle of the fuel system pipe 9, and a flow rate transmitter 13 as a flow rate detector is provided upstream of the flow rate adjusting valve 12. The flow rate transmitter 13 outputs a detection signal to the instrumentation controller 15. Further, the flow rate adjusting valve 12 adjusts the flow rate according to a command from the instrumentation controller 15.
The mixing device 7 includes a mixing chamber for mixing the supplied fuel gas and combustion air, and supplies the premixed gas mixed in the mixing chamber to the nozzle header 16 via a pipe. The premixed gas is injected into the heating furnace 2 from the communicating nozzle 17 and heated. The mixing chamber is a chamber having a larger opening cross section than the pipe.

Reference numeral 18 denotes a pressure gauge provided in the premixed gas supply path to the nozzle. The pressure gauge 18 is provided for interlock. When the pressure below the set pressure is detected, stop the burner.
A thermometer 18 for measuring the temperature of the steel strip 1 exiting from the heating furnace 2 is disposed on the exit side of the direct-fired heating furnace 2. The thermometer 18 is composed of a radiation thermometer, for example. The thermometer 18 outputs the measured temperature signal to the instrumentation controller 15.

An air ratio set value corresponding to the steel type to be heated is input to the instrumentation controller 15 every time the steel type is changed. In addition, the table which determined the air ratio according to steel types (the property of a metal strip) is provided, and the air ratio setting value of the steel strip 1 to be heated is determined with reference to the table.
The instrumentation controller 15 constitutes a control unit, and includes a setting instrument unit 15A, a fuel gas flow rate adjustment unit 15B, and a combustion air flow rate adjustment unit 15C.

The setting instrument unit 15A determines the flow rate of the combustion gas and the flow rate of the combustion air based on the input air ratio setting value and the temperature signal, and supplies the flow rate commands to the fuel gas flow rate adjustment unit 15B and the combustion air flow rate, respectively. Output to the adjustment unit 15C. The air ratio is determined only by the air ratio installation value. In the temperature signal, the heating amount is adjusted. That is, the increase or decrease of the supply flow rate is adjusted.
The fuel gas flow rate adjusting unit 15B calculates the actual flow rate value based on the signal from the flow rate transmitter 13, and supplies the fuel gas flow rate according to the signal from the set instrument unit 15A to the mixing device 7 based on the calculated value. The flow rate control valve 12 is adjusted so as to achieve this.

The combustion air flow rate adjusting unit 15C calculates the actual flow rate value based on the signal from the flow rate transmitter 11, and based on the calculated value, the combustion air flow rate adjusting unit 15C mixes the flow rate of the combustion air according to the signal from the set instrument unit 15A. The flow control valve 10 is adjusted so that
Here, the instrumentation controller 15 controls the air ratios of the burner facilities 3 to 5 from the first zone to the third zone so that the air ratio is set in advance according to the steel type. In addition, the burner equipment 3-5 of the 1st zone to the 3rd zone is good also as a structure similar to the said burner equipment 6. FIG.

(Function and effect)
In the continuous heating device having the above-described configuration, even if the steel type of the steel strip 1 that is continuously conveyed changes, the air ratio can be changed relatively freely and over a wide range to a value suitable for the steel type. Is possible.
Until now, the air ratio is controlled so that the final zone of the direct-fired heating furnace 2 becomes a reducing atmosphere, but in the present embodiment, the final zone of the direct-fired heating furnace 2 according to the steel type. Can be made a reducing atmosphere or an oxidizing atmosphere.
In the case of a reducing atmosphere, for example, the air ratio set value is adjusted to 0.85 or the like. On the other hand, in the case of an oxidizing atmosphere, for example, the air ratio set value is adjusted to 1.2 or the like.

In this way, changing the air ratio in a relatively wide range and freely has been difficult with the above-described conventional premix burner, but with the continuous heating apparatus of this embodiment, it is relatively freely possible.
Further, the mixing device 7 premixes the combustion gas and the combustion air before supplying them to the nozzle 17. By premixing with the mixing device 7, the mixing of the combustion gas and the combustion air can be made nearly uniform. For this reason, the variation of the premixed gas injected from the nozzle 17 can be reduced by that amount, and a reducing atmosphere or an oxidizing atmosphere can be established stably.

As described above, the final zone of the direct heating furnace 2 can be easily changed to an oxidizing atmosphere or a reducing atmosphere according to the operation.
For example, in the case of a steel type containing an easily oxidizable component such as Si, the treatment quality of the subsequent process may be affected by the formation of Si oxide or the like on the surface of the steel strip 1 by heating. In such a case, it is necessary to control under strict oxidation and reduction conditions, and the present invention can be suitably applied.
That is, the continuous heating apparatus of the present embodiment can change the air ratio control of the premix burner relatively freely and over a wide range, so that the final zone of the direct heating furnace 2 is set according to the steel type. It is easy to make an oxidizing atmosphere or a reducing atmosphere, and it is possible to cope without reducing the operation efficiency.

It is a schematic diagram which shows the heating apparatus which concerns on embodiment based on this invention. It is a figure explaining the burner installation which concerns on embodiment based on this invention.

Explanation of symbols

1 Steel strip (metal strip)
2 Direct-fired heating furnace 6 Burner equipment 7 Mixing device 8 Air system piping 8 Combustion air system piping 9 Fuel system piping 10 Flow rate control valve 11 Flow rate transmitter 12 Flow rate control valve 13 Flow rate transmitter 15 Instrumentation controller 15A Setting meter 15C Combustion air flow rate adjustment unit 15B Fuel gas flow rate adjustment unit 17 Nozzle

Claims (2)

A continuous heating device equipped with a direct-fired heating furnace that heats a continuously conveyed metal strip,
Burner equipment used at least downstream in the direct-fired heating furnace is configured to inject and burn a premixed gas in which a fuel gas and an oxygen-containing gas are mixed in advance by a mixing device, and the mixing device. A flow rate detector and a flow rate control valve are provided in each of the fuel system piping for supplying the fuel gas to the air system piping for supplying the oxygen-containing gas to the mixing device,
A continuous heating device for a metal band, comprising a control device for controlling a flow rate adjusting valve based on a signal from the flow rate detector so as to obtain an air ratio set corresponding to the metal band to be heated. It is a continuous heating method of a metal strip that continuously heats a metal strip that is continuously conveyed in a direct-fired heating furnace,
Heating at least downstream in the direct-fired heating furnace is configured such that a premixed gas in which fuel gas and oxygen-containing gas are mixed in advance by a mixing device is jetted from the nozzle and burned, and supplied to the mixing device. Adjusting the fuel gas and the oxygen-containing gas with an individual flow control valve, and controlling the flow control valve so as to obtain an air ratio set corresponding to the metal strip to be heated. Continuous heating method.

Images