JPH05280869A - Controlling method for in-furnace gas flow in rotary hearth type heating furnace - Google Patents

Abstract

PURPOSE:To obtain an in-furnace flow control method for a rotary hearth type heating furnace which is capable of deciding setting value of in-flue O2 concentration control irrespective of a fuel flow rate, and also, coping with drastic changes in the in-flue O2 concentration generated when a burner is extinguished. CONSTITUTION:An attraction force controller 14 to a flue 5 compares an attraction force setting value corresponding to a fuel flow rate to be supplied to a plurality of burners 2 of a rotary hearth type heating furnace 1 with a measured value of its attraction force and operates a damper 7 or an exhauster 9 installed in a waste gas flue 5 of the heating furnace 1 based on the output of this deviation, thereby controlling the attraction force. Furthermore, an in-furnace O2 concentration meter 18 and an in-flue O2 concentration meter 20 measure the in-furnace O2 concentration and the in-flue O2 concentration and compares the measured value of the in-flue O2 concentration with an added O2 concentration value in which a slightly higher constant value is added to the in-furnace O2 concentration measured value by an added O2 concentration value computing element 19. A control output section 17 corrects the output of the attraction force controller 14 and corrects the output with the constant value within a fixed time after the extinguishing of a burner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of controlling gas flow in a rotary hearth type heating furnace having a plurality of burners.

[0002]

2. Description of the Related Art A rotary hearth type furnace having a plurality of burners and a plurality of divided zones is widely used as a heating furnace for hot pipe billets. Conventionally, as a method for controlling a gas flow in a rotary hearth-type heating furnace, as disclosed by the applicant in Japanese Patent Laid-Open No. Hei 1-162718, a plurality of burners of the rotary hearth-type heating furnace have been used. The correlation between the total amount of fuel supplied per hour and the pressure at the flue inlet that optimizes the gas flow in the heating furnace is obtained in advance, and the total amount of fuel supplied and the flue gas during actual operation are determined. The pressure at the inlet is constantly detected and the optimum pressure at the flue inlet corresponding to the detected total supply amount of fuel is obtained from the correlation, and the detected pressure at the flue inlet is made the optimum pressure obtained from the correlation. The gas suction force is controlled as much as possible, and the control disturbance caused when the total supply amount of fuel suddenly changes is prevented from occurring in the same flue gas.
₂ There is a method of correction by changing the density.

By the way, as one of the energy-saving measures for the rotary hearth type heating furnace in recent years, burner extinction of the charging zone is carried out by the diameter of the billet to be treated. When the burner is extinguished, the O ₂ concentration in the furnace is greatly increased due to the influence of combustion air leak from the combustion air control valve. Along with this, the O ₂ concentration in the flue also rises.

[0004]

However, since the set value for the control of the O ₂ concentration in the flue according to the control method disclosed in the above publication is held at a low value before the burner is extinguished,
It is output in the direction of reducing the suction force by the function of control.
As a result, the suction force of the flue becomes a value smaller than the optimum value, the amount of flame released from the charging / extracting port increases, and energy loss occurs.

Therefore, when extinguishing the burner,
It is necessary to change the set value of the O ₂ concentration control in the flue to an appropriate value.

On the other hand, a method of giving a set value for controlling the O ₂ concentration in the flue is disclosed in, for example, Japanese Patent Publication No. 61-45128, and when the fuel flow rate decreases, the flow rate of the fuel air is disturbed and the intruding air In consideration of the fact that the O ₂ concentration in the flue rises due to an increase or the like, there has been proposed a method of obtaining the fuel flow rate according to a predetermined curve.

However, when this method is adopted, it is important to clarify the relationship between the fuel flow rate and the O ₂ concentration in the flue, but the increase in the O ₂ concentration in the flue due to burner extinction does not mean the fuel flow rate. Since it occurs regardless of the temperature, it is impossible to clarify the relationship between the fuel flow rate and the O ₂ concentration in the flue.

Therefore, an object of the present invention is to provide a rotary hearth which can determine the set value for controlling the O ₂ concentration in the flue regardless of the fuel flow rate and can cope with a sudden change in the O ₂ concentration in the furnace that occurs during burner extinction. An object of the present invention is to provide a method for controlling gas flow in a furnace of a heating furnace.

[0009]

[Means for Solving the Problems] The above problems are measured by a suction force regulator for a flue and a suction force set value according to the flow rate of fuel supplied to a plurality of burners of a rotary hearth heating furnace and the suction force measurement. The value is compared with the value, and the suction force is controlled by operating the suction force adjusting means arranged in the waste gas flue of the heating furnace according to the output of the deviation, and further, the O ₂ concentration in the furnace and the O ₂ in the flue are controlled. ₂ concentration was measured, and the measured value of O ₂ concentration in the flue and O in the furnace were measured.
₂ Addition O ₂ by adding a higher constant value to the measured concentration value
Comparing with the concentration value, while correcting the output of the suction force controller, within a certain time after extinguishing the burner,
It can be solved by correcting with a constant value.

[0010]

According to the present invention, the suction force controller is used to compare the suction force set value corresponding to the flow rate of the fuel supplied to the plurality of burners of the rotary hearth type heating furnace with the suction force measured value, and the deviation thereof is compared. When the suction force adjusting means arranged in the waste gas flue of the heating furnace is operated to control the suction force by the output of
₂ concentration and the O ₂ concentration in the flue were measured, and the measured value of the O ₂ concentration in the flue was compared with the added O ₂ concentration value obtained by adding a higher constant value to the measured value of the O ₂ concentration in the furnace. The output of the suction force controller is corrected, and within a certain period of time after the burner is extinguished, correction is performed with a constant value.
₂ concentration becomes possible to a set value corresponding to the furnace O ₂ concentration measured value regardless of the fuel flow rate, even if performed burner extinguishing loading zone, a furnace without flue suction force decreases A proper flue suction force for the gas flow can be maintained.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail below with reference to embodiments shown in the drawings. FIG. 1 is a schematic diagram showing a furnace gas flow control device according to the present invention, and FIG. 2 is a flow chart showing the control method.

Reference numeral 1 denotes a furnace body having a plurality of divided zones, and a plurality of burners 2 are installed on the inner and outer walls of the furnace body 1. A downtake 3 is arranged in the furnace body 1, and a flue 5 is provided to connect the downtake 3 and the chimney 4. Further, a recuperator 6, a damper 7, a waste heat boiler 8 and an exhaust fan 9 are sequentially arranged in the middle of the flue 5.

On the other hand, a fuel flow rate detector 11 is provided in the fuel supply pipe 10 to the plurality of burners 2 of the furnace body 1, and the fuel flow rate detector 11 determines the fuel flow rate depending on the fuel flow rate.
The suction force calculator 12 calculates the optimum suction force in advance and outputs the suction force set value to the suction force controller 14. On the other hand, the downtake 3 is provided with a suction force measuring device 13 for measuring the suction force of the flue 5, and outputs the suction force measurement value to the suction force controller 14.
In such a device, the suction force adjuster 14 compares the suction force setting value from the suction force calculator 12 with the suction force measurement value from the suction force measuring device 13, and the damper 7 or the air exhauster 9 is output according to the output of the deviation. To control the suction force.

However, in the above device,
Disturbance in the control of the suction force will occur due to changes in the fuel flow rate, changes in the combustion state in the furnace, and so on. On the other hand, as described above, in the method disclosed in JP-A-1-162718,
Although the control disturbance that occurs when the fuel flow rate suddenly changes is corrected by changing the O ₂ concentration in the flue, when the burner fire is extinguished in the charging zone, the control disturbance of the suction force is still unavoidable.

Therefore, in the present invention, as shown in FIGS. 1 and 2, a set value calculation unit 15, a controller unit 16 and a control output unit 17 are provided.

The set value calculation unit 15 includes a furnace O ₂ concentration meter 18
And addition O ₂ is constituted by a density value calculator 19, furnace O ₂ concentration adds the addition the O ₂ concentration value obtained by adding a constant value higher against the measured furnace O ₂ concentration measured by the meter 18 O
Calculated by the ₂ concentration value calculator 19, the added O ₂ concentration calculated value is output as the O ₂ concentration set value in the flue to the O ₂ controller 21 in the next flue, and the output fluctuation of the O ₂ concentration meter 18 in the furnace is changed. The fluctuation of the set value of O ₂ concentration in the flue due to is prevented.

The controller unit 16 comprises an O ₂ concentration meter 20 in the flue and an O ₂ concentration controller 21 in the flue. The O ₂ concentration controller 21 in the flue is measured by the O ₂ concentration meter 20 in the flue. smoke by comparing the flue O ₂ concentration setting from summing O ₂ concentration value calculator 19 of the canal O ₂ concentration measured value and the set value calculator 15, the following control so that these values become equal Output to the output unit 17.

The control output unit 17 corrects the output of the suction force controller 14 based on the output value of the O ₂ concentration controller 21 in the flue of the controller unit 16 to adjust the opening degree of the damper 7 or The number of revolutions of the blower 9 is controlled. In addition, when the burner fire is extinguished in the charging zone, the fire extinguishing signal from the burner 2 stabilizes the set value of the O ₂ concentration in the flue in order to prevent the control disturbance due to the sudden change in the O ₂ concentration in the furnace. Until then, the output of the suction force controller 14 is corrected with a constant value.

[0019]

As described above, according to the present invention, the O
₂ concentration becomes possible to a set value corresponding to the furnace O ₂ concentration measured value regardless of the fuel flow rate, even if performed burner extinguishing loading zone, a furnace without flue suction force decreases A proper flue suction force for the gas flow can be maintained.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a furnace gas flow control device according to the present invention.

FIG. 2 is a flowchart showing a control method of the apparatus of FIG.

[Explanation of symbols]

1 ... Furnace body, 2 ... Burner, 3 ... Downtake, 4 ... Chimney, 5 ... Flue, 6 ... Recuperator, 7 ... Damper, 8
... Waste heat boiler, 9 ... Exhaust fan, 10 ... Fuel supply pipe, 11 ...
Fuel flow rate detector, 12 ... Suction force calculator, 13 ... Suction force measuring device, 14 ... Suction force controller, 15 ... Set value calculator, 16
Control unit, 17 Control output unit, 18 O ₂ concentration meter in furnace, 19 O ₂ concentration value calculator for addition, 20 O ₂ concentration meter in flue, 21 O ₂ concentration controller in flue

Claims (1)

[Claims] 1. A suction force regulator for a flue is used to compare a suction force set value corresponding to a flow rate of fuel supplied to a plurality of burners of a rotary hearth type heating furnace with a suction force measurement value, and the deviation thereof is compared. Is a method for controlling the suction force by operating the suction force adjusting means arranged in the waste gas flue of the heating furnace according to the output of the above, further measuring the O ₂ concentration in the furnace and the O ₂ concentration in the flue, compares the canal O ₂ concentration added O ₂ concentration values obtained by adding a constant value higher for the measured values and the furnace O ₂ concentration measurements of, as well as correcting the output of the suction force controllers, burner extinguishing A method for controlling gas flow in a rotary hearth type heating furnace, which is characterized in that correction is performed with a constant value within a certain period of time thereafter.