KR880000834B1 - Controlling combustion - Google Patents

Abstract

A main controlling unit (37) receives the signal indicating the steam pressure of a boiler from a pressure gage (31) and sets the desired value of the stream pressure of the boiler and the PID (proportional- plus-integral-plus-derivative) constant. A limiter (43) calculates the amount of variation of a manipulated variable ΔT12=T1-2, wherein T1 is the manipulated variable of the boiler at the time and T2 is the predetermined manipulated variable of the boiler. When the amount of variation ΔT12 lies within the allowable value of variation ΔT, T1 is adopted and when ΔT12 lines out of ΔT, T2 ± ΔT is adopt.

Description

Auto combustion control method

1 is a schematic view showing an automatic combustion control apparatus used in a conventional combustion control method.

2 is a schematic view showing an automatic combustion control device that is an improvement of the apparatus of another conventional first FIG.

3 is a schematic diagram showing a basic configuration of one example of an automatic combustion control apparatus that can use the present invention.

4 is a schematic diagram showing a specific control system of the apparatus of FIG.

5 is a graph showing the characteristic of excess air ratio used in the apparatus of FIG.

6 is a circuit diagram showing a specific example of the main control system of FIG.

7 is a circuit diagram showing a specific example of the fuel control system of FIG.

8 is a circuit diagram showing a specific example of the fuel control device of FIG.

9 is a circuit diagram showing a specific example of the air control device of FIG.

10 to 12 are graphs showing control characteristics by the control device of FIG.

13 to 15 are graphs showing control characteristics by the conventional control method of FIG.

* Explanation of symbols for main parts of the drawings

1: pressure gauge of boiler steam pressure 2: main control device

3: fuel flow control device 4: fuel flow meter

5: electric valve 6: multiplier

7 air volume control device 8 differential pressure gauge

9: open flat calculator 10: electric damper

11: derivative operation 12: adder

21 boiler body 22 burner

23: oil tank 24: electric valve

26 duct 27 press-fit blower

28: air preheater 29: valve for steam output control of the boiler

30: drying apparatus 31: flow meter for detecting the steam pressure of the boiler

32: oil flow meter 33: differential pressure gauge for air flow detection

35: electric damper device 37: main control device

38: computing device 39: fuel control device

40: air control device 43: limiter

44: oil flow setting circuit 45: judgment circuit

46: setting circuit of excess air ratio 47: correction circuit

48: judgment circuit 49: air flow setting circuit

51: calculation circuit of air flow rate 52: real excess air ratio detection circuit

Asi: Air Flow Set Point Qsi: Oil Flow Set Point

M: Excess air ratio M _A : Excess air ratio

Mcom, Mcom1, Mcom1 ': Corrected excess air ratio T ₁ , T ₂ : Boiler operation amount

ΔT ₁₂ : amount of change in boiler operation

The present invention relates to an automatic combustion control method for automatically controlling a combustion device.

In a conventional combustion device, such as a combustion device of a boiler, the flow rate of the fuel supplied to the burner is controlled according to the output of steam from the boiler, and the fuel flow rate is determined in advance so that the fuel and the air amount in the burner maintain an appropriate relationship. The amount of air multiplied by the true integer is controlled using, for example, a regulator with PID control. For example, the method shown in FIGS. 1 and 2 is known.

The method shown in FIG. 1 obtains a signal corresponding to the output of the boiler from the pressure gauge 1 which detects the steam pressure of the boiler, and sends the output signal of the pressure gauge 1 to the main control device 2 and sends it to the combustion device. Calculate the fuel flow to be supplied.

The result of this calculation is sent to the fuel flow rate control device 3, and the fuel flow rate control device 3 supplies the fuel flow rate and fuel at this indicated value so as to be the fuel flow rate value instructed from the main controller 2. The PID calculation is performed on the deviation from the actual flow rate from the flowmeter 4 which detects the flow rate, and the electric valve 5 is controlled according to the result of this PID calculation. At the same time, a signal indicating the fuel flow rate to be supplied to the combustion apparatus from the main control unit 2 is sent to the multiplier 6, and the multiplier 6 represents an integer indicating the ratio of an appropriate fuel and air predetermined in advance. The amount of air to be blown to the combustion device is calculated by multiplying the fuel flow rate from the main control device (2). The result of this calculation is sent to the air mass flow control device 7. In addition, a signal indicating the differential pressure corresponding to the amount of blown air from the differential pressure gauge 8 that detects the wind pressure in response to the total amount of air blown into the combustion device is applied to the open operator 9, and the open operator 9 A signal indicating the wind speed of the result of the calculation) is applied to the air volume control device 7 described above. In this air quantity control device 7, PID calculation is performed on the deviation between the amount of axiom indicated by the signal from the multiplier 6 and the amount of air indicated by the signal from the open operator 9.

The electric damper device 10 is controlled in accordance with the PID calculation result to control the amount of air to be supplied to the combustion device.

However, in this conventional method, because of the difference in the physical properties of the fluid to be handled and this difference, the diameter of the pipe route is different because of the hundreds of times, so that the fuel pipe and the air duct are respectively installed.

For example, even if the electric actuator is operated at the same time, the flow rate characteristics and the closing speed are completely different, so it is difficult to make the responsiveness the same. For this reason, for example, if the combustion quantity is changed when the output is changed in a boiler, the fuel is air or which changes in one step, and the others change late, and during this time, the ratio between fuel and air is appropriate. Since it cannot be maintained, the constant in the multiplier 6, which is electric, is selected appropriately so that the average amount of air is increased by the width of this assist, and the ratio between fuel and air is changed to prevent incomplete combustion. Doing. The method shown in FIG. 2 is a method of improving the method of FIG.

Moreover, in FIG. 2, the same code | symbol is attached | subjected to the component same as that of FIG. 1, and description is abbreviate | omitted.

In FIG. 2, for example, a signal indicating the output of the boniler is obtained according to the pressure gauge 1 for detecting the steam pressure of the boiler, and the signal is sent to the main controller 2, and the fuel to be supplied to the combustion apparatus. Calculate the flow rate. This calculation result is sent to the fuel flow control device 3, which is a deviation between the fuel flow value indicated by the main control device 2 and the actual flow rate from the flow meter 4 PID operation is performed on the electric motor, and the electric motor 5 is controlled according to the PID operation result.

The above description is the same as that of FIG.

On the other hand, a signal indicative of the fuel flow rate to be burned obtained from the main control unit 2 is sent to the differential calculator 11.

The derivative value from this differential operator 11, i.e., the value of the sign proportional to the difference between the value before the unit time, for example, one second, is obtained and the actual value obtained from the derivative and the flowmeter 4 The adder 12 obtains an addition value from the value of the fuel flow rate. The addition result is sent to the multiplier 6. In this multiplier 6, the amount of air to be blown into the combustion device is calculated by multiplying the addition value by an integer indicating the ratio of a predetermined fuel and air. . The calculation result of this multiplier 6 is sent to the air volume control device 7, and then the air volume is controlled in the same manner as in the method of FIG.

In this method, there is no problem inherent in the transient lag of the fuel flow rate, but a lag of operation of the air flow control device 7 inevitably occurs, and to compensate for this, It is a method of adding the differential value of the fuel flow rate to be supplied to the combustion device obtained from the main control device (2).

However, even when the control of the air control loop does not completely follow the main control device 2 at the time when the signal of the main control device 2 does not change, the operation of the air flow control device 7 Lag is not compensated, so the air-fuel ratio is inevitable.

Therefore, as in the method of FIG. 1, the constant in the electric multiplier 6 is selected so that the amount of air is increased by the amount of the scattered width.

As described above, in any of the conventional methods, it is necessary to supply a large amount of air to the burner of the combustion apparatus, and there is a drawback that the amount of heat is increased by this excess air and the heat loss is increased accordingly.

The present invention has been achieved to solve the above-mentioned shortcomings, so that the combustion apparatus can be stably burned at an air-fuel ratio closer to the limit, so that the exhaust volume of the combustion apparatus can be restrained to the minimum necessary without generating incomplete combustion. It is an object of the present invention to provide an automatic combustion control method capable of effectively reducing heat loss and effectively increasing thermal efficiency and high responsiveness.

In addition, another object of the present invention is to reduce the amount of oxygen O ₂ supplied to the burner by the amount of air supplied to the combustion apparatus according to the minimum force required, and to provide sulfide gas SO ₃ , nitrogen oxide gas NO _2, and the like. This effectively suppresses the occurrence of.

Next, an embodiment of the present invention will be described with reference to the accompanying drawings. 3 shows the basic configuration of the combustion control apparatus according to the present invention.

21 in FIG. 3 is a boiler body of a combustion apparatus. The burner 22 of the boiler body 21 is supplied with liquid oil from an oil tank 23 of a fuel source via an electric valve 24 for controlling oil flow rate, and at the same time, a damper 25 is provided. Air is supplied from the provided duct 26 via the press-fit blower 27 and the air preheater 28.

From this boiler main body 21, steam is supplied to various apparatuses, for example, the drying apparatus 30, via the valve 29 for steam flow control.

Numeral 31 is a pressure gauge for detecting boiler steam pressure, which is installed between the main body of the boiler 21 and the valve 29, and 32 is installed between the oil tank 23 and the electric valve 24. The flowmeter for oil flow rate detection, 33, is a differential pressure gauge for airflow amount detection supplied to the duct 26 described above.

Reference numeral 37 denotes a main control device, 39 denotes a fuel control device for controlling the electric valve 24, and 40 denotes an air control device for controlling the electric damper device 35 including the damper 25. to be.

The main controller 37 sends a signal to the fuel control device 39 and the air control device 40 via the calculation unit 38, and indirectly controls the oil flow rate and the air amount. The main control unit 37 receives a detection signal from the pressure gauge 31 that detects the boiler steam pressure that changes in response to the steam supply flow rate, and performs PID control operation according to this detection signal in detail below. The main controller 37 calculates the oil flow rate setting value Osi, that is, the excess air ratio M according to the oil flow rate setting value Osi, the actual excess air ratio Mcom of the boiler, and the air flow rate setting value Asi. Instruct them to. Further, the oil flow rate set value Qsi signal calculated in accordance with this computing device 38 is applied to the air control device 40 described above.

The fuel control device 39 controls the electric valve 24 according to the signal from the flow meter 32 for detecting the oil flow rate and the oil flow rate set value Qsi signal from the calculation device 38. It constitutes a loop. In addition, the air control device 40 according to the detection myth from the differential pressure crab 33 for detecting the air flow rate, that is, the air flow rate, and the air flow rate set value Asi signal from the computing device 38, the electric damper An air control loop for controlling the device 35 is constructed.

In this way, the main control device 37 controls the fuel control device 39 and the air control device 40 described above in accordance with the steam pressure output from the boiler body 21 to form the main control loop as a whole.

Next, a specific example of the combustion control device having the above-described configuration will be described along with FIGS. 4 to 9.

Further, the computing device 38 shown in FIG. 4 to FIG. 3 is surrounded by a dashed line, and the same parts as those of the FIG. 3 device will be described with the same reference numerals.

In the drawing, reference numeral 37 denotes a main controller for controlling the boiler output, 43 denotes a limiter that sets an allowable limit of the boiler operation speed, and 44 denotes an oil flow rate when supplying oil to the burner 22. The oil flow rate setting circuit 45 is an oil flow rate determination circuit determined by the above-described setting circuit 44 (see Fig. 6).

The main control unit 37 receives a signal indicating a detection value of the boiler steam pressure which changes from the pressure gauge 31 in response to the steam flow rate of the output of the boiler body 21, and the display device of the apparatus 37 is not illustrated. Indicate the boiler steam pressure in the table. In addition, according to the operation switch 37-1 of the main controller 37, the PID constants and the like are set freely in the target value of the boiler steam pressure and PID control. Further, the main controller 37> performs a known PID control operation and applies the output to the limiter 43 described above.

The calculating part 43-1 of the limiter 43 calculates the fluctuation amount ΔT ₁₂ = T ₁ -T ₂ of the manipulated variable. Furthermore, T ₁ is the boiler operation amount at that time, and T ₂ is predetermined. For example, the manipulated value obtained one second before. And the operation unit (43-1) of the limit vector (43) is adapted to transmit the signal representing the variation amount ΔT ₁₂ of the above-mentioned operation amount. The determination circuit 43-2 of the limiter 43 receives a signal indicating the variation amount ΔT ₁₂ of the boiler operation amount from the calculation unit 43-1 and determines whether the variation amount ΔT ₁₂ is within the allowable variation amount ΔT of the operation amount. Make a decision. And according to this determination result, a new operation amount (for example, expressed by%) is decided.

0인 때는 조작량이 T₂+ΔT 로 정하여 지며, T₁-T₂<0 인 때는 조작량이 T₂-ΔT로 정하여 진다.As a result of the determination in the determination circuit 43-2, if it is determined that the magnitude of the change amount ΔT ₁₂ is within the range of the change allowable value ΔT, T ₁ is employed. On the other hand, when it is determined that the magnitude of the variation amount ΔT ₁₂ is outside the range of the allowable variation ΔT, T ₂ ± ΔT calculated by the correction unit 43-3 of this determination circuit 43-2 is employed. Furthermore, the calculation result of the calculation unit 43-1 described above is T ₁ -T _2.

If it is 0, the manipulated value is defined as T ₂ + ΔT. If T ₁ -T ₂ <0, the manipulated value is determined as T ₂ -ΔT.

In this way, the limiter 43 suppresses sudden changes in the boiler operation amount. According to this suppression content, even if the amount of steam output by the boiler changes excessively and the steam pressure of the boiler which does not normally occur suddenly changes, the air-fuel ratio in the burner 22 is controlled to an appropriate value. It is.

The oil flow rate setting circuit 44 receives a signal indicating the operation amount T ₁ or the modified operation amount T ₂ = ± ΔT from the limiter 43 to improve the boiler control effect based on the signal and further described later. In order to obtain a signal for correcting the excess air ratio, a square conversion operation is performed to calculate the set value Qsi of the oil flow rate. That is, the oil flow rate standing still Qsi can be expressed as Qsi = [(output% of the limiter 43) / 100] ² x oil maximum flow rate Q _M.

Furthermore, the oil maximum flow rate Q _M is a value determined according to the capacity of the boiler body 21.

The determination circuit 45 receives a signal indicating the oil flow set value Qsi from the setting circuit 44 and at the burner 22 of this boiler in the actual excess air ratio detection circuit 52 described later. _A signal indicating the actual excess air ratio M _A of?

In the determination circuit 45, the actual excess air ratio described above is set to be less than the allowable lower limit of the excess air ratio M _A is suitably determined in accordance with the boiler body 21, for example, the value 1.05 determined for a conventional boiler. We can judge whether it is big or not. As a result of this determination, when the excess air ratio M _A is determined to be equal to or greater than the set value 1.05, the output 2Q _S1 or Q _S1 of the oil flow rate setting circuit 44 is sent out, and when it is determined that it is smaller than the set value 1.05, it is already set. Do not change the oil flow rate setting Q _S without changing it as it is. If the set value is 1.05 or more, change T ₂ to T _1. If the set value is 1.05 or less, change the value of T ₂ as the base of the next calculation.

Moreover, Q _S1 is the stroke of the operation equation of the above-described Q _S Q _S1 when the T ₁ is the operation amount is significant in the T ₂ = ± ΔT when. As described above, the main control unit 37, the limiter 43, the setting circuit 44, the determination circuit 45, and the actual excess air ratio detection circuit 52 are connected to the control system of the fuel in FIG. 3. It consists.

The output of the determination circuit 45 to this control system, that is, the signal indicating the oil flow rate set value Qsi, is applied to the fuel control device 39 described above.

In Fig. 7, reference numeral 46 denotes an excess air ratio setting circuit. The setting circuit 46 receives the signal Qsi indicating the oil flow rate setting value from the oil flow rate setting circuit 44 and corresponds to the oil flow rate setting value. A signal indicative of excess air ratio M is transmitted. Further, in this setting circuit 46, for example, as shown in FIG. 5, when the oil flow rate setting value of the signal Qsi is in the range of 0 to 75%, M is a straight line forming 1 · 2 and 1 · 05. It is determined by the value of the phase. When the oil flow rate is within the range of 75% to 100%, M is set to 1.05. Furthermore, as a characteristic curve of the oil flow rate Qsi versus excess air ratio M in FIG. 5, the one obtained according to the operation test of the boiler body 21 is used.

In addition, when the oil flow rate setting value is within the range of 0 to 75%, M may be set to 1.2, and when M is within the range of 75% to 100%, M may be set to 1.05 in steps.

The output of the setting circuit 46, together with the output of the calculating section 43-1 of the limiter 43 and the output indicating the determination result of the determination circuit 43-2, corrects the excess air ratio circuit 47. Is applied. The correction circuit 47 determines whether the amount of change ΔT ₁₂ of the manipulated variable from the computing unit 43-1 of the limiter 43 is positive or negative.

As a result of the determination in the correction circuit 47, when the variation amount ΔT ₁₂ is positive and determined to be YES, the calculation unit 47-1 according to the determination result signal from the determination circuit 43-2 is determined. α x ΔT or α x ΔT ₁₂ operations. From the further set circuit 46. In the computing unit (47-2) receives a signal indicating the excess air ratio M is to be the operation of a M + or M + αΔT αΔT _12. On the other hand, if it is determined by the correction circuit 47 that the amount of variation ΔT ₁₂ is negative and is determined to be NO, the calculation unit 47-3 according to the signal received from the determination circuit 43-2 is β x | ΔT | Or β x | ΔT ₁₂ |. Further, the calculation unit 47-4 of the correction circuit 47 receives a signal indicating the excess air ratio M from the setting circuit and calculates M-│β x ΔT│ or M-│β x ΔT ₁₂ │. It is supposed to be.

Further, the above coefficients α and β are appropriately set according to the capacity, type, operating conditions, etc. of the fuel control loop and the air control loop, and are set to satisfy the relationship of α> β.

When the correction excess air ratio is set to Mcom1 in the correction circuit 47 described above, a signal indicating this magnification Mcom1 is applied to the setting circuit 49 of the air flow rate via the determination circuit 48 of the correction excess air ratio.

On the other hand, when the correction excess air ratio is determined to be MCOM1 ', the signal indicating this ratio Mcom' is applied directly to the above-described setting circuit 49 without intervening the above-described determination circuit 48.

The actual excess air ratio M _{A in the} above-mentioned detection circuit 52 of the actual excess air ratio detection circuit 52 which received a signal indicating the correction excess air ratio Mcom2 stored in the actual excess air ratio 47-5 and received. It is determined whether or not the correction excess air ratio Mcom2 is equal to or greater.

If it is determined that the ratio M _A is larger than the ratio Mcom2 and is determined to be YES, the excess air ratio M obtained by the excess air ratio setting circuit 46 is selected as a new excess air ratio, and the signal representing this ratio M is determined by the air flow rate. Applied to the setting circuit 49. On the other hand, if it is determined that the ratio M _A is smaller than the ratio Mcom2, it is determined again whether or not the correction excess air ratio Mcom1 indicated by the signal received from the correction circuit 47 in this determination circuit 48 is equal to or larger than the ratio Mcom2. It is.

In the above determination circuit 48, if the above-mentioned ratio Mcom1 is YES and determined to be greater than or equal to the ratio Mcom2, a signal indicating this ratio Mcom1 is applied to the setting circuit 49. On the other hand, if it is determined that the above-mentioned ratio Mcom1 is smaller than the ratio Mcom2, a signal indicating this ratio Mcom2 is applied to the setting circuit 49.

In addition, a signal indicating the ratio M when it is determined as YES in the first determination in the determination circuit 48 or the ratio Mcom1 when it is determined as YES in the subsequent determination is stored in the storage unit 47- of the correction circuit 47. 5) is sent out. The contents of this storage section 47-5 are updated to this ratio M or Mcom1.

As described above, the air flow setting circuit 49 has a signal indicating the correction excess air ratio Mcom1 'in the correction circuit 47, or the excess air ratio M in the determination circuit 48, and also the correction excess air ratio Mcom1, and Mcom2. Upon receiving a signal indicating, the set value As of the air flow rate to be blown to the burner 22 in this setting circuit 49 is determined. This set value As is determined according to the formula of As = Qi x Ao x Mcom. Here, Qi is an oil flow rate measurement value obtained by the oil flow meter 32, Ao is a unit air amount determined by early calculation, and Mcom is an excess air ratio indicated by the signal applied to this setting circuit 49.

As described above, the main control unit 37, the limiter 43, the setting circuit 44, the setting circuit 46 of the excess air ratio, the correction circuit 47, the setting circuit 49, and the like are controlled by the air control system. Configure The signal indicating the air flow rate setting value Asi of the output of the air flow rate setting circuit 49 to the control system is applied to the above-described air control device 40.

In FIG. 8, the fuel control device 39 receives a signal from the flow meter 32 indicating a detection value of the oil flow rate supplied from the oil tank 23 to the burner 22 via the electric valve 24. The detection value is displayed on the display device not illustrated.

The fuel control device 39 is provided with various operation switches 39-1, and according to these operation switches 39-1, PID constants for PID control of the oil flow rate of fuel to a target value are set at will. It is supposed to be. Then, known PID control calculations are performed by the calculation units 39-2 and 39-3 of the fuel control device 39, and the oil flow rate is controlled in accordance with the calculation result.

The flow meter 32 of the fuel control device 39 constitutes the fuel control system path of FIG.

Numeral 51 denotes an air flow rate calculation circuit, and numeral 52 denotes a detection circuit for detecting the actual excess air ratio M _A in the burner 22 of the boiler body 21 (see FIG. 9).

The arithmetic circuit 51 includes the velocity head h and the temperature of the air flowing through the duct 26 in the differential pressure gauge 33 and the thermometer 34 connected to the pitto pipe installed in the duct 26, respectively. Receive a signal indicating (T). The calculation circuit 51 calculates the air flow rate PV = AD _D × 2ghρ flowing through the duct 26.

Furthermore, A _D is the cross-sectional area of the duct, g is the acceleration of gravity, h is the indicated value of the differential pressure gauge 33, ρ is the air density calculated according to the above-mentioned temperature (T). The signal indicating the air flow rate PV at the output of the calculation circuit 51 is applied to the detection circuit 52 and the air control device 40 described above.

The detection circuit 52 is a signal indicating the air flow rate currently supplied to the burner 22 from the arithmetic circuit 51 and the burner 22 from the flow rate gauge 32 described above. Receive a signal indicating the oil flow rate Qi that is currently supplied. The detection circuit 52 calculates the current excess air ratio of the boiler, that is, the actual excess air ratio M _A.

M _A = A ₁ / (Qi × A _O )

Where A ₁ is the detection value of the current air flow rate and A _O is the minimum amount of air required for complete combustion per unit amount of fuel obtained according to the theoretical calculation.

Further, the signal indicating the actual excess air ratio M _A of the output of the detection circuit 52 is applied to the determination circuit 45 and the determination circuit 48 of the excess air ratio as described above.

The air control device 40 receives a signal indicating the detected value of the air flow rate in the above-described calculation circuit 51 and a signal indicating the air flow rate setting value Asi in the air flow rate setting circuit 49.

The above-described display device of the control device 40 is configured to display the detected value of the air flow rate and the like. And according to the operation switch 40-1 of this air control apparatus 40, the PID constant for controlling PID is set as desired. In the calculating section 40-2 and 40-3 of the air control device 40, the PIDs known in the same manner as in the calculating sections 39-2 and 30-3 of the fuel control device 39 are described. Can operate

This calculation result is applied to the electric damper device 35. In the electric damper device 35, the opening degree of a damper is adjusted according to the signal which shows the damper operation amount from the said air control apparatus 40 by a well-known method, and the amount of air which flows into the duct 26 is carried out. Braking.

Next, the operation of the combustion control device having the above configuration will be described. Moreover, this description is given in the example of sampling control.

1. The boiler steam pressure is lower than the set value.

First, a signal representing the pressure pi of the boiler from the pressure gauge 31 of the boiler is applied to the main control unit 37 and compared with a target pressure P ₀ , for example 12 kg / cm ³ . In this main controller 37, the known PID operation is performed, and the result is applied to the limiter 43.

Next, in the calculating section 43-1 of the limiter 43, the boiler operation amount immediately before the steam pressure of the boiler changes, that is, the operation amount of the boiler in the previous control cycle of the control cycle (hereinafter referred to as the boiler). The difference between T ₂ and the boiler operation amount immediately after the output of the boiler changes, that is, the boiler operation amount (hereinafter referred to as the next boiler operation amount) T ₁ in the control cycle, is calculated. The difference between the next boiler operation amount T ₁ and the previous boiler operation amount T ₂ , that is, the change amount of the boiler operation amount ΔT ₁₂ = T ₁ -T ₂ is a case of increasing the output of the boiler and thus becomes a government code.

Furthermore, it is assumed that the absolute value of the fluctuation amount ΔT ₁₂ of the above-described boiler operation amount, that is, the calculated value ΔT ₁₂ of the boiler operation amount in the PID control cycle is lower than the allowable variation ΔT of the operation amount of the boiler.

In addition, the actual excess air ratio M _A of the output of the detection circuit 52, ie, the current actual excess air ratio M _A in the burner 22 of the boiler, is the ratio of the excess air ratio determined according to the boiler. The lower limit is to be in a state greater than 1.05.

로 정하여 진다.As described above, the signal T ₁ indicating the boiler operation amount in the control cycle calculated by the calculating unit 43-1 of the limiter 43 is applied to the oil flow rate setting circuit 44, and the amount of change in the boiler operation amount. + DELTA T ₁₂ is applied to the correction circuit 47. In the above-described setting circuit 44, a characteristic conversion calculation is performed to obtain an oil flow rate to be supplied to the burner 22 of the boiler in accordance with a signal indicating the boiler operation amount T ₁ in the limited cycle. That is, the next oil flow setting value

It is determined by.

In this case, the output of the limiter 43 is T ₁ . Furthermore, Q _M is the maximum oil flow rate supplied to the burner 22 from the oil tank 23 via the electric valve 24. The signal representing the oil flow rate setting value Q _S1 is applied to the determination circuit 45 and the setting circuit 46 of the excess air ratio.

Next, in the determination circuit 45 which receives the signal indicating the oil flow rate setting value Q _S in the setting circuit 44 and the signal indicating the actual excess air ratio M _A in the detection circuit 52, it is determined whether M _A is 1.05 or more. do. As described above, since M _A is assumed to be 1.05 or more, a signal indicating the oil flow set value Q _S1 is applied to the fuel control device 39 as it is.

In the fuel control device 39 receiving the signal indicating the oil flow set value Q _S1 , PID operation is performed in the same manner as in the main controller 37 described above, and according to the set value Q _S , the electric valve 24 is applied to the electric valve 24. The amount of manipulation is determined by a known method. The signal indicative of the valve operation amount is applied to the electric valve 24, so that the opening degree of the electric valve 24 is increased in accordance with this signal. That is, the PID is controlled so that the oil flow rate supplied to the burner 22 through the electric valve 24 in the oil tank 23 shown in FIG. 3 becomes the above-described oil flow rate setting value Q _S1 .

In the setting circuit 46 which receives the signal indicating the oil flow setting value Q _S1 from the oil flow setting circuit 44, the excess air ratio M with respect to this setting value Q _S1 is determined according to the characteristic curve shown in FIG. .

On the other hand, the signal indicating that the variation amount ΔT ₁₂ of the boiler operation amount from the calculating section 43-1 of the limiter 43 is positive and the variation amount + ΔT ₁₂ of the boiler operation amount from the determination circuit 43-2 are calculated. In the correction circuit 47 which has received the signal indicating and the signal indicating the excess air ratio M from the setting circuit 46, the calculation by the calculating part 47-1 and the calculating part 47-2 is performed according to these signals. It is ordered. , Their operation unit (47-1) and (47-2) and the excess air ratio in the burners 22 of the boiler of the art results in the operation is prescribed by Mcom1 = M + αΔT _12. In this example, the actual excess air ratio M _A is initially below the corrected excess air ratio Mcom2 at the time of the previous operation, and since the current corrected excess air ratio Mcom1 is larger than the previous maintenance excess air ratio Mcom2, as described above. The determined excess air ratio Mcom1 is applied to the airflow setting circuit 49. In the setting circuit 49, the setting value of the air flow rate is determined by the calculating unit 49-1 in accordance with the signal indicating the correction excess air ratio Mcom1.

This set value is determined by A _S1 = Qi × Ao × Mcom1.

Furthermore, Ao is the unit air amount determined by theoretical calculation. The signal indicative of the air flow set value A _S1 is applied to the air control device 40. In the air control device 40, PID operation is performed in the same manner as in the main control device 37 and the fuel control device 39 described above, and according to the air flow setting value A _S1 , the electric damper device 35 The amount of operation is determined by a known method. The signal indicating the damper operation amount is applied to the electric damper device 35, and the transfer motion damper device 35 controls the opening degree of the damper 25 to increase according to the damper operation amount.

That is, the PID is removed so that the air flow rate supplied to the burner 22 through the press-fit blower 27 in the duct 26 is increased to the set value A _S1 described above.

According to the operation described above, the combustion amount is increased to restore the boiler steam pressure. During this time, the operation of the determination circuit 48 is repeated and it is decided to supply air to the bearer 22 of the boiler at the highest correction excess air ratio until the value of M _A reaches the value of Mcom2. When the amount of air supplied to the vertebral target 22 reaches the seedling value corresponding to the fuel amount, the determination circuit 48 determines that M _A > Mcom2 is completed and the calculation of Mcom1 is finished, thereby correcting the excess air ratio by the coefficient α. Then, M calculated by the excess air ratio setting circuit 46 is sent to this air flow rate setting circuit 49, and the air flow rate is determined in accordance with the excess air rate value.

The reason why the above excess air ratio is corrected is shown in FIG. As shown in FIG. 10 (a), when the steam pressure of the boiler falls below the target value p ₀ at time t ₀ , the burner (as shown in FIG. The oil flow rate to 22) increases. As shown in Fig. 10 (c), the command value of the fruit air ratio for the boiler is additively corrected for the excess air ratio M determined according to the oil flow rate (the variation of the boiler operation amount ΔT ₁₂ × coefficient α). The excess air ratio Mcom1 + M + αΔT ₁₂ is obtained. Therefore, the actual excess air ratio M _A of the boiler increases as shown in FIG. 10 (e).

Next, according to the determination circuit 48, the actual excess air ratio M _A is determined to be less than or equal to the excess air ratio Mcom2 immediately before the control cycle, and the correction excess air ratio Mcom1 described above is equal to the excess air ratio Mcom2 for the control cycle straight. At the time point t ₁ (shown in FIG. 10), it is determined that the correction by the above-described value α × ΔT ₁₂ is interrupted. Thereafter, the actual excess air ratio M _A at time t ₂ becomes M determined according to the oil flow rate described above.

As the excess air ratio commanded in this boiler changes as described above, the air flow rate supplied to the burner 22 is controlled as shown in FIG. 10 (d).

As described above, when an increase in the amount of operation of the boiler is instructed, the oil flow rate also increases in accordance with the increase amount of the operation amount, and the command value of the excess air ratio for the boiler is increased to M + αΔT ₁₂ . Therefore, the heat generation amount in the burner 22 of the boiler does not cause incomplete combustion with respect to the increase command of the operation amount, and is improvised important.

II. The steam pressure of the boiler rises above the set value.

Contrary to the case of the above-mentioned I, the amount of change ΔT ₁₂ of the boiler operation amount calculated as described above in the calculation unit 43-1 of the limiter 43 is negative. The magnitude of the fluctuation amount ΔT ₁₂ is said to be lower than the fluctuation allowance value T of the boiler as in I. Moreover, the actual excess air ratio M _A of the output of the detection circuit 52 is naturally larger than the allowable lower limit 1.05 of the excess air ratio of the boiler body 21.

The signal indicating the variation amount ΔT ₁₂ of the boiler operation amount at the output of the limiter 43 is applied to the setting circuit 44 and the correction circuit 47 as in the above-described I.

In the above judgment circuit 43-2, it is determined that the absolute value of the fluctuation amount? T ₁₂ of the boiler operation amount is smaller than the change allowance DELTA T, and therefore the operation amount of the boiler is set to T ₁ .

Thereafter, the output of the setting circuit 44 is applied to the determination circuit 45 as well as to the setting circuit 46 as in the case of I described above.

Thereafter, the operation in the combustion control apparatus can be performed in the same manner as in the case of I. Therefore, only operation that differs from the case in I described above will be described next, and other operations will be omitted.

In the correction circuit 47, the operation units 47-3 and 47-4 operate, and the correction excess air ratio is determined to be Mcom1 '= M-β | ΔT ₁₂ |. Then, the signal indicating the correction excess air ratio Mcom1 'is applied to the setting circuit 49 without passing through the determination circuit 48, unlike the case of I, and the next air amount setting value is set as A _S1 = Qi x Ao X Mcom1'. Lose.

11 shows why the above excess air ratio is corrected. 11 shows why the excess air ratio of the boiler is corrected. The oil flow rate to be fed to the burner, as opposed to the case 22 in the time the steam pressure in the boiler is turned higher than the target value p ₀ at the time t ₀ Ⅰ decreases. The command value of the excess air ratio for the boiler is a correction value of the fluctuation amount of the boiler operation amount ΔΔT ₁₂ │x coefficient β at the excess air ratio M determined according to the oil flow rate as shown in Fig. 11 (a). The reduced excess air ratio Mcom1 'is obtained. The correction of the excess air ratio by this correction value β × │ΔT ₁₂ │ can be performed only in the period from the time t ₀ to t 'when the fluctuation direction ΔT ₁₂ of the boiler operation amount is negative. Therefore, the actual excess air ratio M _A is controlled as shown in FIG. 11 (b) and controlled to be a constant value M at the time point t ₂ ′. In addition, graphs showing changes in boiler steam pressure, oil flow rate and air flow rate are omitted. In the above-described Ⅰ and in this case change amount ΔT ₁₂ of boiler operation amount according to the Ⅱ is greater than the variation allowance ΔT in the art boiler operation amount, for example, such as when significant changes to the target pressure of the boiler, the number of the limit vector (43) section ( 43-3), the boiler operation amount (boiler operation amount T ₂ ± allowable variation ΔT in the last control cycle) is adopted. Furthermore, even when the boiler operation amount is set to T ₂ ± ΔT, the excess air ratio in the control cycle according to the operation of the correction circuit 47 described above is M + αΔT as in the case of I or II described above. Or M + βΔT.

In addition, as shown in I and II described above, instead of directly determining the fuel flow rate in response to the PID calculation result of the boiler operation amount, that is, the pressure deviation between the boiler steam pressure and the target value, Therefore, this fuel flow rate should be determined. In this way, the change in fuel flow rate can be linearly matched with the PID calculation result. That is, when the amount of increase or decrease of the fuel flow rate of the boiler is determined in accordance with the PID calculation of the pressure deviation, the same flow rate changes with respect to the same pressure deviation even when the load of the boiler is very large. A value, that is, a value that increases or decreases, is determined. This fact results in an excessively small amount of fuel flow change when the steam pressure of the boiler is extremely low.

On the other hand, if the fuel flow rate is determined according to the result of the quadratic calculation as described above, it is possible to reliably prevent hunting and the like in the boiler against the pressure deviation despite the large or small steam pressure of the boiler, and the control effect is improved. It can be made very high. By the way, in the conventional control method shown in FIG. 2 mentioned above, correction of the command value of excess air ratio can be performed as shown in FIG.13 and FIG.14.

13 corresponds to the case of I in the above-described embodiment, and FIG. 14 corresponds to the case of II.

As is apparent from comparing the tenth (e) and the eleventh (b) diagrams according to the present invention, in the conventional control method, the command value of excess air goodness for the boiler is corrected according to the derivative value of the variation amount of the boiler operation amount. . That is, the actual excess air ratio is corrected to be this value M 'while vibrating around the static load suppression value M' as shown in FIG. 15 according to the positive and negative values of the differential value of the steam pressure of the boiler.

Thus, in the conventional control method, the actual excess air ratio is controlled so as to be a constant value M 'while vibrating, so that the final target value M' is set to some extent larger than the allowable threshold 1.05 in order to prevent the occurrence of incomplete combustion. It is supposed to be.

With respect to the conventional method described above, in the embodiment of the present invention, the command value of the excess air ratio is corrected according to the correction amount α + ΔT ₁₂ otherwise α + ΔT or β + | ΔT ₁₂ │ otherwise β × │ΔT│. As the excess air ratio M _A increases as shown in Fig. 12 in both cases of I and II, the target excess air ratio M is set to a value very close to the tolerance 1.05 and slightly higher.

The oblique portions in Figs. 12 and 15 refer to the supply of excess air beyond the allowable limit, and the embodiment of the present invention which can set the target value close to the limit means that there is less excess air. That is, the amount of air supplied to the burner 22 is less in the conventional control method described above, and therefore the amount of exhaust gas is suppressed more than in the conventional control method, so that the heat loss is suppressed and the thermal efficiency is high accordingly. . In addition, as the amount of air supplied is suppressed, the amount of oxygen (O ₂ ) is also suppressed, and thus generation of nitrogen oxides, which are sulfide gases SO ₂ and SO ₃ air pollution sources, which cause damage to the boiler, can be suppressed.

Further, as apparent from the comparison with FIG. 12 and FIG. 15, the change in the actual excess air ratio controlled according to the above-described embodiment is controlled to be a constant value at a faster time than the conventional control method. In other words, the response is as high as that. As is apparent from the above description, according to the present invention, when the operation amount of the combustion device is changed, the amount of change in the operation amount is multiplied by a predetermined coefficient α and β, and the excess air ratio determined according to the change amount of the operation amount is increased. When the operation amount decreases, it is adjusted to become small when the operation amount decreases. The air flow rate is changed and the correction is continued until the end of the fuel system and air system follows. It is possible to compensate the following lag for the change of the fuel flow rate of the air quantity. Therefore, even when the operation amount of the combustion apparatus changes drastically, the amount of fuel and the air quantity can be minimized without incomplete combustion and the proper amount of air is suppressed. The ratio can be controlled. That is, the amount of exhaust gas can be more effectively suppressed than in the conventional control method, and the heat loss can be reduced by that amount, so that the thermal efficiency of the combustion device can be made high. In addition, since the amount of supply air is effectively suppressed in this way, the amount of oxygen gas supplied to the combustion device is suppressed accordingly, and generation of harmful sulfide gas and nitrogen oxide can be effectively reduced.

Furthermore, as described above, the excess air ratio is corrected so that the control amount of the actual excess air ratio is smaller than that in the conventional control method, so that the appropriate air-fuel ratio can be achieved in a short time, and the responsiveness is excellent. .

Claims (1)

While supplying liquid fuel and air to the burner of the combustion device, the fuel flow rate is automatically controlled according to the fluctuation amount of the output of the combustion device, and the excess air rate corresponding to the fuel flow rate is determined to determine the air flow rate according to this excess air rate. In the automatic combustion control method which automatically controls the amount of variation of the operation amount of the combustion apparatus, and when the operation amount increases, the excess air ratio is defined in the ratio ratio to the variation amount of the operation amount in advance. While the manipulated value decreases, the excess air ratio is subtracted from this ratio multiplied by a predetermined positive coefficient less than the above coefficient α when the manipulated value decreases. Auto combustion, characterized in that the correction is made to a value so that this correction is continued until the end of the fuel and air system follows. Control method.

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