JP2001021141A - Combustion control method of heating furnace and combustion control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an accuracy in controlling such as a temperature of furnace atmosphere generated by combustion gas produced at a combustion device by supplying both air and fuel to a combustion device of a heating furnace under a stable ratio. SOLUTION: A flow rate of air supplied to a combustion device is controlled in a control system composed of two control loops, i.e., a feed-forward control loop and a feed-back control loop, and in turn a flow rate of fuel supplied to the combustion device is controlled in a control system composed of two control loops, i.e., a feed-forward control loop and a feed-back control loop, and further a temperature of atmosphere within the heating furnace is controlled by the control system composed of the feed-forward control loop and the feed- back control loop.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for controlling the combustion of a heating furnace, and more particularly to a heating method in which the atmosphere in the furnace is adjusted with a combustion gas generated in a combustion apparatus to heat a material to be heated in the furnace. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method and apparatus capable of improving the control accuracy of a furnace atmosphere temperature, a fuel flow rate to a combustion device, and an air flow rate in a furnace.

[0002]

2. Description of the Related Art Conventionally, heating treatment of various materials such as steel and other metal materials has been performed using a heating furnace in which the inside of a furnace is heated by a combustion gas generated in a combustion device, a so-called atmosphere heating furnace. For example, in order to prevent surface oxidation of a material to be heated such as a metal, a reducing atmosphere for heating the material to a target temperature while maintaining the atmosphere in the furnace at a reducing property. Heating furnaces are also known as one of them.

[0003] In such a heating furnace, the atmosphere in the furnace is adjusted by controlling the flow rate of fuel or air to a combustion device for supplying a combustion gas forming the atmosphere in the furnace.
In order to accurately maintain the temperature of the furnace atmosphere at a set value, various control methods have been studied. For example, in a reducing atmosphere heating furnace of a material such as a metal described above, air supplied to a burner as a combustion device is used. The amount and the amount of fuel are manipulated to control the temperature of the target material and the reducing gas concentration in the furnace, but the important point in temperature control and reducing gas concentration control is that when changing the flow rate for temperature control, In order to stabilize the ratio between the amount of air supplied to the burner and the amount of fuel to a target value, control methods such as an equalizing valve method and a double cross limit method have been proposed.

[0004] Specifically, among these control methods, the pressure equalizing valve method, as shown in the block diagram of FIG. 1, uses the set value of the atmosphere temperature in the furnace and the actually measured value of the atmosphere temperature to determine the atmosphere. With feedback control that performs temperature control,
While outputting the opening degree command of the air flow regulating valve, from the set value of the CO concentration in the furnace atmosphere and the actually measured value of the actual CO concentration,
In the feedback control for controlling the CO concentration, an opening command of the fuel flow control valve is output, and the air is controlled so that the secondary pressure of the air flow control valve and the secondary pressure of the fuel flow control valve have a constant ratio. The mechanical control is performed according to the secondary pressure of the flow control valve.

Further, the double cross limit method is disclosed in Japanese Patent Application Laid-Open No. H5-264027,
The upper and lower limits of the allowable fuel flow rate are obtained from the air flow rate of the air supply system by using an operation coefficient, and the upper and lower limits are used to limit the combustion load given by the temperature controller to obtain the fuel flow rate set value. The fuel flow rate control system and the upper and lower limit values of the air flow rate allowed from the fuel flow rate of the fuel supply system are obtained by using an operation coefficient, and the upper and lower limit values are used to limit the combustion load, thereby setting the air flow rate. Combustion that prevents the ratio of air to fuel from being disturbed by controlling the flow rate of fuel and air supplied to the heating furnace from the fuel supply system and the air supply system by an air flow control system that obtains a value. This is a control method.

However, in any of the control methods, the control accuracy of the temperature of the furnace atmosphere, the fuel flow rate, the air flow rate, and the gas concentration in the furnace atmosphere is not sufficient with respect to the set value change command. For example, in the above-mentioned equalizing valve system, since the fuel flow rate is controlled by mechanically following the air flow rate, the air flow rate is always leading, and the atmosphere in the furnace This is the cause of the concentration (reducing gas concentration) disturbance. In the case of the double cross limit method, when steep temperature control is required, the air and fuel valve opening command values are limited. Is added, which causes a delay in the response of the temperature control.

[0007]

The present invention has been made in view of the above circumstances, and an object of the present invention is to supply air and fuel at a stable ratio to a combustion device of a heating furnace. Another object of the present invention is to provide a method and an apparatus for improving the control accuracy of the temperature of an atmosphere in a furnace formed by a combustion gas generated in such a combustion apparatus. Heating temperature (atmospheric temperature) in a reducing atmosphere heating furnace intended to heat the target material at the target temperature while maintaining the atmosphere in a reducing state
It is an object of the present invention to provide a control method and apparatus capable of effectively improving the control accuracy of the fuel gas flow rate, the air flow rate, and the concentration of the reducing gas in the furnace atmosphere.

[0008]

According to the present invention, there is provided a heating furnace configured to heat a furnace by using a combustion gas generated in a combustion apparatus in order to solve the problems related to the method. In the method, the combustion flow is controlled by controlling the air flow rate, the fuel flow rate and the atmosphere temperature in the furnace to the combustion apparatus, and (a) the set value of the atmosphere temperature in the furnace and the transfer characteristic of the atmosphere temperature A feedforward control loop for adjusting an air flow rate or a fuel flow rate to the combustion device by signal processing multiplied by three of a reciprocal and a transfer characteristic representing a target response; and a set value of the furnace ambient temperature and the target The difference between the output value obtained by performing signal processing multiplied by two of the transfer characteristics representing the responsiveness and the actual measured value of the atmosphere temperature in the furnace is subjected to signal processing so as to eliminate the difference. Air flow or fuel to equipment In the control system consists of two control loops with feedback control loop for adjusting the amount,
While controlling a command to change the air flow rate or fuel flow rate to the combustion device, (b) a command to change the air flow rate to the combustion device and a transmission characteristic of an air flow rate adjustment valve for adjusting the air flow rate to the combustion device. A feedforward control loop that adjusts the valve opening of the air flow control valve by signal processing multiplied by three of the reciprocal and a transfer characteristic representing a target responsiveness; and represents the air flow rate change command and the target responsiveness. The difference between the output value obtained by performing signal processing multiplied by two of the transfer characteristics and the measured value of the actual air flow rate is subjected to signal processing so as to eliminate the difference, and the valve opening of the air flow control valve is opened. A control system comprising two control loops including a feedback control loop for adjusting the degree controls the flow rate of air supplied to the combustion device, and (c) further controls the flow rate of fuel to the combustion device. The command opening, the reciprocal of the transfer characteristic of the fuel adjustment valve for adjusting the fuel flow rate to the combustion device, and the signal processing of multiplying the transfer characteristic representing the target responsiveness, the valve opening of the fuel flow adjustment valve by the signal processing. A feedforward control loop to adjust; a difference between an output value obtained by performing signal processing by multiplying two of the fuel flow rate change command and a transfer characteristic representing the target responsiveness, and a measured value of the actual fuel flow rate;
A signal processing is performed so as to eliminate the difference, and a control system including two control loops of a feedback control loop for adjusting a valve opening of the fuel flow control valve is used to control a fuel flow supplied to the fuel device. The gist of the present invention is a combustion control method for a heating furnace, characterized by controlling the combustion temperature.

That is, the combustion control system according to the present invention comprises two control loops, a feedforward control loop for adjusting the air flow rate or the fuel flow rate based on an atmosphere temperature change command, and a feedback control loop. Control of the air flow rate using a control system for controlling the temperature of the air to be controlled and based on an air flow rate change command, a feed forward control loop for adjusting the valve opening of the air flow rate control valve and a feedback control loop. And a fuel flow control system comprising a feed forward control loop and a feedback control loop for adjusting a valve opening of the fuel flow control valve based on a fuel flow change command. Control of air flow, fuel flow, and even ambient temperature The control accuracy was effectively improved.For example, when the atmosphere temperature in the furnace was changed to the changed temperature by an atmosphere temperature change command, the fluctuation range was significantly reduced. Thus, the changed temperature can be quickly and stably reached.

According to one preferred embodiment of the method for controlling combustion of a heating furnace according to the present invention, while the atmosphere in the furnace is maintained at a reducing atmosphere, a set value of a CO concentration for providing the reducing atmosphere is set. And CO in actual furnace atmosphere
An output value obtained by performing signal processing on the difference between the measured value of the concentration and the difference to eliminate the difference, a command to change the air flow rate to the combustion device, and a preset air-fuel ratio (air (Fuel ratio) and the output value obtained by the signal processing multiplied by the fuel flow rate, a command to change the fuel flow rate to the combustion device is obtained. The control accuracy can be effectively improved by the fuel flow rate control.

[0011] The present invention also provides a heating furnace for heating the inside of a furnace using combustion gas generated in a combustion apparatus in order to solve the problems relating to the apparatus among the above-mentioned problems. A device for performing combustion control by controlling the air flow rate, the fuel flow rate to the combustion device, and the atmosphere temperature in the furnace. (A) The set value of the atmosphere temperature in the furnace, the reciprocal of the transfer characteristic of the atmosphere temperature, and 3 of transfer characteristics showing target responsiveness
A feed forward control loop for adjusting the air flow rate or the fuel flow rate to the combustion device by the signal processing multiplied by two; and a transfer characteristic representing the set value of the furnace ambient temperature and the target response. Feedback processing for adjusting the air flow rate or the fuel flow rate to the combustion device by performing signal processing on the difference between the output value obtained by performing the signal processing and the measured value of the actual atmosphere temperature in the furnace so as to eliminate the difference. (B) a command to change an air flow rate to the combustion device, and (B) a transmission characteristic of an air flow rate adjustment valve for adjusting an air flow rate to the combustion device. A feedforward control loop for adjusting a valve opening of the air flow control valve by signal processing multiplied by three of a reciprocal and a transfer characteristic representing a target responsiveness; And a difference between an output value obtained by performing signal processing multiplied by two of the transfer characteristics representing the target responsiveness and a measured value of the actual air flow rate, signal processing is performed so as to eliminate the difference. An air flow control system including two control loops, a feedback control loop for adjusting a valve opening of the air flow control valve; and (C) a command for changing a fuel flow to the combustion device, A feedforward control loop for adjusting the valve opening of the fuel flow control valve by signal processing multiplying the inverse of the transfer characteristic of the fuel control valve for adjusting the flow rate and the transfer characteristic representing the target responsiveness; The difference between the output value obtained by multiplying the two by the fuel flow rate change command and the transfer characteristic representing the target responsiveness and the measured value of the actual fuel flow rate is signal processed so as to eliminate the difference. do it And a fuel flow control system comprising two control loops, a feedback control loop for adjusting a valve opening of the fuel flow control valve, and a combustion control apparatus for a heating furnace. Things.

According to a desirable mode, even in such a combustion control device, the heating furnace is set to a reducing furnace atmosphere by the reducing combustion gas generated in the combustion device. A reducing atmosphere heating furnace, and the furnace atmosphere is maintained in the reducing atmosphere, and the CO concentration setting value for providing the reducing atmosphere and the actual CO concentration measurement value in the furnace atmosphere are compared with each other. The difference is obtained by signal processing in which an output value obtained by performing signal processing to eliminate the difference, a command to change an air flow rate to the combustion device, and a preset air-fuel ratio in the combustion device are multiplied. Further, a CO concentration control system for obtaining a command to change the fuel flow rate to the combustion device based on the output value to be obtained is further provided, whereby the control accuracy of the reducing gas concentration can be significantly improved. .

[0013]

FIG. 2 is a conceptual diagram of a control system according to the present invention. In the combustion system provided in the furnace main body, a fuel flow rate is controlled by a fuel supply source. While a predetermined amount of fuel is supplied through a valve, air for burning such fuel is supplied at a predetermined rate from an air supply source through an air flow control valve. It has become so. The atmosphere in the furnace in the furnace body is adjusted by the combustion gas generated by the combustion in such a combustion device. The present invention provides an atmosphere heating furnace in which a combustion gas generated in such a combustion apparatus constitutes an atmosphere in a furnace, and heats a material to be heated in the furnace. In addition, the combustion temperature is controlled by controlling the atmosphere temperature in the furnace. For this purpose, each control system has a characteristic configuration.

That is, in such an ambient temperature control system in the combustion control system shown in FIG. 2, a compensation element having a transfer characteristic representing a target response is added to a preset ambient temperature set value (° C.). Multiplied, the difference between the obtained value and the actual ambient temperature (actually measured value) in the furnace is determined, and feedback by signal processing such as proportional / integral control (PI control) is performed so as to eliminate the difference. (F
B) A feed-forward (FF) that obtains one output value by control, and performs signal processing by multiplying the above-mentioned ambient temperature set value, the reciprocal of the ambient temperature transfer characteristic, and the transfer characteristic representing the target response. The other one output value is obtained by control, and the two output values are added to give a command to change the air flow rate.

In the air flow rate control system, the air flow rate change command obtained by the above-mentioned ambient temperature control system is used to transfer such air flow rate change command and transfer characteristics (compensation element) indicating the target responsiveness. ) Is subtracted from the actual value (actually measured value) of the air flow supplied to the combustion device through the air flow regulating valve, and the difference is resolved. As described above, one output value is obtained by FB control by signal processing such as proportional / integral control (PI control), while the reciprocal of the air flow rate change command and the transfer characteristic of the air flow rate control valve and the target responsiveness are shown. The other one output value is obtained by FF control based on signal processing multiplying the transfer characteristic by three, and the two output values are added to output to the air flow regulating valve as an opening command value. Has become A.

Further, the command for changing the air flow rate obtained by the above-mentioned atmosphere temperature control system is multiplied by a preset air-fuel ratio, in other words, the air-fuel ratio (λ), and
While the two output values are obtained, the difference obtained by subtracting the preset CO concentration in the furnace atmosphere (%) from the preset CO concentration in the furnace body atmosphere (actually measured value) is obtained. FB control by signal processing such as PI control is performed to obtain another output value.
A fuel flow rate change command is issued by adding the two output values. Here, a method is adopted in which the atmosphere in the furnace is a reducing atmosphere and the CO concentration in such an atmosphere is also controlled.
In the case where the control method of the O concentration is not adopted, and when the atmosphere in the furnace is not a reducing atmosphere, the output value obtained by multiplying the air flow rate change command by the air-fuel ratio (λ) is used as it is. This will be adopted as a fuel flow rate change command.

In the fuel flow control system using the fuel flow rate change command thus obtained, a signal multiplied by the reciprocal of the transfer characteristic of the fuel flow control valve and the transfer characteristic representing the target response. By FF control that performs processing,
While obtaining one output value, a value obtained by multiplying such a fuel flow rate change command by a compensation element consisting of a transfer characteristic representing a target responsiveness, and a fuel flow rate actually supplied to the combustion device from the fuel flow rate adjusting valve. Subtracted from the actual value
In order to eliminate the difference, FB control by signal processing such as PI control is performed to obtain another output value, and a value obtained by adding the two output values is used as an opening degree command as: Based on this, the fuel flow control valve is controlled.

Here, the combustion control method according to the present invention as described above can also be described by the following mathematical formula.

That is, first, when the flow rates of the air and the fuel are changed, the characteristics of the changing ambient temperature can be expressed by the following equation (1). _{T A = G A (s)} (aq A ref + bq F ref) ··· (1) where, T _A: ambient temperature change G _A (s): transfer function q _A ^ref: air flow rate change amount (change command) q _F ^ref : fuel flow rate change (change command) a, b: constant

[0020] Here, the amount of change by the feed forward control of _{^{q A ref: q A ref /}} FF can be expressed as the following equation (2). ^{_{q A ref / FF = {1}} / [G A (s)]} · (1 / k) · [ω tr 2 / (s 2 + 2ηω tr s + ω tr 2)] · T A ref ··· (2) where , K = a + bλ ω _tr : natural frequency representing target response T _A ^ref : set value of ambient temperature s: Laplace operator η: damping coefficient λ: air-fuel ratio

Then, assuming that q _F ^ref = λq _A ^ref ,
The characteristic from T _A ^ref to T _A is as shown in the following equation (3). T _A = [ω _tr ² / (s ² + 2ηω _tr s + ω _tr ² )] · T _A ^ref (3) Accordingly, by appropriately selecting η and ω _tr , a desired response is achieved. That would be.

The above equation (2) is an air flow rate change command by feedforward control for T _A ^ref .
Here, since the steady-state error occurs only in the feedforward control of the expression (2), the feedback control as in the following expression (4) is also performed. ^{_{q A ref / FB = K piA}} (1 + 1 / T IiA s) · [H 1 (s) · T A ref -T A] ··· (4) H 1 (s) = ω tr 2 / (s 2 + 2ηω _tr s + ω _tr ² ) Note that H ₁ (s) is a term for compensating for interference between the feedforward control and the feedback control, and indicates a response target of the ambient temperature.
_A ^ref is given as the sum of q _F ^{ref / FF} and q _A ^{ref / FB} . ^{_{q A ref = q F ref /}} FF + q A ref / FB

The relationship between the air flow rate and the valve opening of the air flow control valve can be expressed by the following equation (5). _{q A = [K A / (} T AV s + 1)] · g A ··· (5) q A: Air flow rate (measured value) g _A: valve opening command T _AV: time constant K _A: Gain

[0024] When the g _A ^FF and feed-forward control component of g _A, such g _A ^FF is indicated by the following equation (6), also q _A is a following expression (7) . g _A ^FF = [(T _AV s + 1) / K _A ] · [1 / (T _pA s + 1)] · q _A ^ref (6) q _A = [1 / (T _pA s + 1)] · q _A ^ref (7) where T _pA is a time constant representing the target responsiveness. Therefore, by appropriately adjusting the T _pA , a desired responsiveness can be obtained. The above
Equation (6) is the feedforward control of the air flow control.

Also, with only feedforward control,
Since the steady-state error occurs, the feedback control represented by the following equation (8) is also performed. ^{_{g A FB = K pA [1+}} (1 / T IA s)] · [H 2 (s) q A ref -q A] ··· (8) H 2 (s) = 1 / (T pA s + 1) However , G _A ^FB : feedback control of g _A K _pA : feedback proportional gain of air flow control T _IA : feedback integration time of air flow control H ₂ (s): compensation for interference between feed forward control and feedback control And a response target of the air flow rate.

Further, g _A is represented by the sum of g _A ^FF and g _A ^FB and is given by the following equation. ^{_{g A = g A FF + g}} A FB

Further, the relationship between the actual fuel flow rate to the combustion device and the valve opening of the fuel flow rate control valve can be expressed by the following equation (9). _{q F = [K F / (} T F s + 1)] · g F ··· (9) where, q _F: fuel flow (measured value) g _F: valve opening command T _F: time constant K _F: Gain

[0028] Here, according (9) is a feed forward control amount in the fuel flow control system, the feedforward control amount of the valve opening command (g _F) and g _F ^FF, such g _F ^FF is is the following formula (10), further, the fuel flow rate (q _F) are shown in the following equation (11), thus, T _pF
, The desired responsiveness can be obtained. ^{_{g F FF = [(T F}} s + 1) / K F] · [1 / (T pF s + 1)] · q F ref ··· (10) q F = [1 / (T pF s + 1)] · q F ref ... (11) where T _pF is a time constant representing the target response

Further, in such a fuel flow control system, the feedback control represented by the following equation (12) is also performed since the steady-state error occurs only by the feedforward control. g _F ^FB = K _pF (1 + 1 / T _IF s) · [H ₃ (s) q _F ^ref −q _F ] (12) H ₃ (s) = 1 / (T _pF s + 1) where K _pF : Feedback proportional gain of fuel flow control T _IF : Feedback integration time of fuel flow control H ₃ (s): Term for compensating for interference between feed forward control and feedback control (response target of fuel flow)

Then, g _F is given by the following equation as the sum of g _F ^FF and g _F ^FB . g _F = g _F ^FF + g _F ^FB

Here, G in the above equation (1)
_A (s) is approximated by the following characteristics, for example.
The control system is specifically as shown in FIGS. _{G A (s) = (K} t s + K t ω n) / (s 2 + 2ξω t
s + ω _t ² ) where K _t , ω _n , ω _t , ： are parameters representing the characteristics of the change in ambient temperature (coefficients determined by the plant, which are obtained experimentally or by calculation)

In the control systems shown in FIGS. 3 to 5, first, in the atmosphere temperature control system, the control system shown in FIG.
As shown in the figure, the ambient temperature change command: T _A ^ref , the reciprocal of the ambient temperature transfer characteristic: (s ² + 2ξω _t s)
^{_{+ Ω t 2) / (K}} t s + K t ω n) and the transfer characteristic showing the target ^{_{response: ω tr 2 / (s 2}} + 2ηω tr s + ω tr 2) performs the signal processing multiplied by, for adjusting the air flow directly feed Change command of air flow rate by forward control loop:
It determines q _A ^ref . At the same time as this control, the transfer characteristic representing the target response to the ambient temperature change command: T _A ^ref : ω _tr ² / (s ² + 2ηω _tr s
+ Ω _tr ² ) is proportional to integral control (P
I control) and other signal processing to correct the air flow rate change command: q _A ^ref by a feedback control loop that adjusts the air flow rate.

Next, the thus obtained air flow rate
Change command: q_A ^refIn contrast, in the air flow control system,
As shown in FIG. 4, the reciprocal of the transmission characteristic of the air flow regulating valve:
(T _AVs + 1) / K_AAnd the transfer characteristics representing the target responsiveness:
1 / (T_pAs + 1) and perform signal processing.
Feed for directly adjusting the valve opening of the air flow control valve
Determine valve opening command by forward control loop
On the other hand, simultaneously with such control, the air flow change command:
q_A ^ref, The transfer characteristic representing the target response: 1 /
(T_pAs + 1)
Force and actual air flow measurement to combustion device (actual measurement)
Signal processing such as PI control for the difference
A feedback control loop that adjusts the valve opening
The lube opening command is corrected.

On the other hand, in the fuel flow control system, as shown in FIG. 5, the fuel flow rate changing command: For q _F ^ref,
Inverse of the transfer characteristic of the fuel flow control _{valve: (T F s + 1)} / K
_F and transfer characteristics representing target responsiveness: 1 / (T _pF s + 1)
, And a feed-forward control loop that directly adjusts the valve opening of the fuel flow control valve determines the valve opening command. At the same time as such control, the fuel flow change command: q _F ^The output value obtained by performing signal processing on ^ref with a transfer characteristic representing a target response: 1 / (T _pF s + 1), and the measured actual flow rate of the fuel supplied to the combustion device through the fuel flow control valve The valve opening command is corrected by a feedback control loop that adjusts the valve opening by performing signal processing such as PI control on the difference from the (actually measured value).

Here, in order to apply the present invention to a reducing atmosphere heating furnace, the fuel flow rate change command: q _F
^ref is corrected by the CO concentration in the atmosphere. That is, the air flow rate change command: q
_{For the} fuel flow rate change command obtained by multiplying _A ^ref by the air-fuel ratio: λ, the difference between the set value of the CO concentration in the atmosphere and the actual CO concentration in the furnace atmosphere (actually measured value) is calculated by PI Such a fuel flow rate change command is corrected by a feedback control loop that performs signal processing such as control and adjusts the fuel flow rate.

The control accuracy can be effectively improved by operating the air flow control valve and the fuel flow control valve based on the opening command of each valve obtained by the control system as described above. Thus, the intended control of the atmosphere in the heating furnace is performed more accurately and stably.

In the specific example described above, an air flow rate change command (q _A ^ref ) to the combustion device is obtained in the atmosphere temperature control system, and the air flow rate control command and the fuel flow rate While control is being performed, respectively, and in such an atmosphere temperature control system, similarly, can also determine the fuel flow rate changing command to the combustor (q _F ^ref), and in that the fuel flow rate changing command Based on this, the fuel flow control and the air flow control can be respectively performed. However, in such a case, the air flow rate change command performs signal processing in which the fuel flow rate change command is multiplied by the air-fuel ratio (λ), and, if necessary, based on an output value obtained from the CO concentration control system. It will be required.

Further, such excellent features obtained by employing the combustion control system according to the present invention can be easily understood from the following simulation results.

That is, in such a simulation, the temperature control of the atmosphere in the furnace and the control of the reducing gas (CO concentration) were performed for a heating furnace having a reducing (CO) atmosphere, and the pressure equalizing valve system shown in FIG. FIG. 3 illustrates, implements, and compares an exemplary control scheme according to the invention.
However, in order to clarify the superiority of the method according to the present invention,
The simulation was performed with a 20% error added to the transmission characteristics of the valve.

When the ambient temperature command value is changed by 20 ° C. (Temperature command value change: Step input is switched to 860 ° C. for 0 to 50 seconds and 880 ° C. for 50 to 150 seconds. As a result of simulating the control situation of (1), in the temperature control, a fluctuation range of about 15 ° C. was recognized in the pressure equalizing valve system shown in FIG. 1, but in the control system according to the present invention, the fluctuation range of about 3 ° C. In the CO concentration control, the fluctuation range of about 1.5% was present in the equalizing valve system, but in the control system according to the present invention, the fluctuation range was about 1.0%. I was able to suppress it.

The present invention should not be construed as being limited by the above specific description, and various modifications may be made based on the knowledge of those skilled in the art without departing from the spirit of the present invention. , Modifications, improvements, etc., and it is to be understood that any such embodiments fall within the scope of the present invention.

[0042]

As is apparent from the above description, according to the present invention, the control accuracy can be advantageously improved by the predetermined air flow rate control, fuel flow rate control and ambient temperature control, and the stable heating furnace can be obtained. Driving becomes possible,
In particular, it is applied to a reducing atmosphere heating furnace, and exhibits a feature that air and fuel can be supplied to a combustion device at a stable ratio, and control accuracy of reducing gas concentration and temperature can be effectively improved. is there.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a conventional temperature control method using a pressure equalizing valve.

FIG. 2 is a block diagram showing a specific example employing a combustion control method according to the present invention.

FIG. 3 is a block diagram showing details of an atmosphere temperature control system in an example of a combustion control system according to the present invention.

FIG. 4 is a block diagram showing details of an air flow control system in a combustion control system according to the present invention.

FIG. 5 is a block diagram showing details of a fuel flow control system in a combustion control system according to the present invention.

FIGS. 6A and 6B are graphs showing a control simulation result of a pressure equalizing valve system, in which FIG. 6A is a graph showing a variation width of an ambient temperature, and FIG. 6B is a graph showing a variation width of a CO concentration.

FIGS. 7A and 7B show simulation results of the combustion control method according to the present invention, in which FIG. 7A is a graph showing a variation result of an atmospheric temperature, and FIG. 7B is a graph showing a variation result of a CO concentration.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Haruo Tanaka 5-11-3 Shimbashi, Minato-ku, Tokyo Sumitomo Light Metal Industries, Ltd. (72) Inventor Ikuya Hoshino 5-3-1 Shimbashi, Minato-ku, Tokyo No. Sumitomo Light Metal Industries Co., Ltd. (72) Inventor Yayuki Hiramatsu 1-2-5 Rokuno, Atsuta-ku, Nagoya-shi, Aichi F-term in Takakura Works, Daido Steel Co., Ltd. 3K003 AA01 AB03 AB06 AC02 CA03 CA05 CA09 CB05 5H004 GA05 GB20 HA01 HA04 HA16 HB01 HB02 HB04 JA14 JA23 JB09 KA71 KB02 KB04 KB13 KB16 KB22 KB26 KB29 KB32 KB39 LA01 LA13 LA15 LA18

Claims (4)

[Claims] In a heating furnace configured to heat the inside of a furnace with combustion gas generated in a combustion device, an air flow rate to the combustion device, a fuel flow rate, and an atmosphere temperature in the furnace are controlled.
In a method of performing combustion control, air to the combustion device is processed by signal processing by multiplying three of a set value of an ambient temperature in the furnace, a reciprocal of an ambient temperature transfer characteristic, and a transfer characteristic representing a target responsiveness. A feedforward control loop for adjusting a flow rate or a fuel flow rate; an output value obtained by performing a signal processing by multiplying a set value of the furnace atmosphere temperature and a transfer characteristic representing the target responsiveness; A control system comprising two control loops: a feedback control loop for adjusting the air flow rate or the fuel flow rate to the combustion device by performing signal processing on the difference from the measured temperature value to eliminate the difference. At the same time, while controlling an air flow or fuel flow change command to the combustion device, an air flow change command to the combustion device and an air flow adjustment valve for adjusting the air flow to the combustion device A feedforward control loop for adjusting the valve opening of the air flow control valve by signal processing multiplied by three of the reciprocal of the transfer characteristic and the transfer characteristic representing the target response; the air flow change command and the target response The difference between the output value obtained by performing signal processing multiplied by two of the transfer characteristics representing the characteristics and the measured value of the actual air flow rate is subjected to signal processing so as to eliminate the difference.
A control system including two control loops including a feedback control loop for adjusting a valve opening of the air flow control valve controls an air flow supplied to the combustion device. The signal of the fuel flow control valve is multiplied by a command to change the fuel flow, the reciprocal of the transfer characteristic of the fuel control valve for adjusting the fuel flow to the combustion device, and the transfer characteristic representing the target responsiveness. A feedforward control loop for adjusting the opening; a difference between an output value obtained by performing signal processing by multiplying two of the fuel flow rate change command and the transfer characteristic representing the target responsiveness, and a measured value of the actual fuel flow rate In contrast, a control comprising two control loops of a feedback control loop for processing a signal so as to eliminate the difference and adjusting the valve opening of the fuel flow control valve. A combustion control method for a heating furnace, wherein a flow rate of fuel supplied to the combustion device is controlled by a system. 2. The method according to claim 1, wherein the atmosphere in the furnace is maintained in a reducing atmosphere, and a difference between a set value of the CO concentration that gives the reducing atmosphere and a measured value of the CO concentration in the actual furnace atmosphere is determined. From an output value obtained by signal processing to eliminate the difference, and an output value obtained by signal processing of multiplying a command to change the air flow rate to the combustion device and a preset air-fuel ratio in the combustion device. 2. The combustion control method according to claim 1, wherein a command to change the fuel flow rate to the combustion device is obtained. 3. A heating furnace in which the inside of a furnace is heated by a combustion gas generated in a combustion device, wherein an air flow rate, a fuel flow rate and an atmosphere temperature in the furnace to the combustion device are controlled,
An apparatus for performing combustion control, the signal processing apparatus multiplies the set value of the ambient temperature in the furnace, the reciprocal of the transfer characteristic of the ambient temperature, and the transfer characteristic representing the target responsiveness, by the signal processing to multiply the air to the combustion device A feedforward control loop for adjusting a flow rate or a fuel flow rate; an output value obtained by performing a signal processing by multiplying a set value of the furnace atmosphere temperature and a transfer characteristic representing the target responsiveness; Atmospheric temperature composed of two control loops: a feedback control loop that adjusts an air flow rate or a fuel flow rate to the combustion device by performing signal processing on the difference from the measured temperature value to eliminate the difference. A control system, a command to change the air flow rate to the combustion device, a reciprocal of a transfer characteristic of an air flow rate adjusting valve for adjusting the air flow rate to the combustion device, and a transfer characteristic representing a target responsiveness. A feed-forward control loop that adjusts the valve opening of the air flow control valve by the same signal processing; and an output obtained by performing a signal processing by multiplying two of the air flow rate change command and the transfer characteristic representing the target responsiveness. For the difference between the value and the measured value of the actual air flow, signal processing is performed to eliminate the difference,
An air flow control system composed of two control loops, a feedback control loop for adjusting a valve opening of the air flow adjustment valve, a fuel flow change command to the combustion device, and a fuel flow to the combustion device. Reciprocal of the transfer characteristic of the fuel adjustment valve to be adjusted,
And a feedforward control loop for adjusting the valve opening of the fuel flow rate adjusting valve by signal processing multiplied by three of the transfer characteristic and the transfer characteristic representing the target responsiveness; and the transfer characteristic representing the fuel flow rate change command and the target responsiveness. The difference between the output value obtained by performing the signal processing multiplied by the two and the measured value of the actual fuel flow rate is signal processed so as to eliminate the difference, and the valve opening of the fuel flow rate adjusting valve is adjusted. And a fuel flow control system comprising two control loops. 4. The heating furnace is a reducing atmosphere heating furnace in which a reducing combustion gas generated in the combustion apparatus is used as a reducing furnace atmosphere, and the furnace atmosphere is maintained in a reducing atmosphere. On the other hand, the difference between the set value of the CO concentration giving the reducing atmosphere and the measured value of the CO concentration in the actual furnace atmosphere is compared with the output value obtained by performing signal processing to eliminate the difference. A command to change the fuel flow rate to the combustion device is obtained from an output value obtained by multiplying a command to change the air flow rate to the combustion device and a preset air-fuel ratio in the combustion device. The concentration control system
The combustion control device according to claim 3, further comprising: