JP2009150619A - Boiler device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a boiler device having high efficiency and high NOx reducing effects. <P>SOLUTION: The boiler device includes a NOx concentration meter 102, a window box inlet damper 1, and a damper control means. Herein, a storage means is provided which stores a burner air ratio set value obtained by two variable functions, namely, a fuel ratio and NOx concentration. In accordance with a change the fuel ratio or a change of the NOx concentration, the burner air ratio set value is read out and the opening of the window box inlet damper 1 is controlled. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a boiler device that can use various types of coal fuel, and particularly, an operation in which a load command signal changes frequently and boldly and rapidly according to a demand from a customer, and an operation that uses coal fuel whose properties are greatly different. It is related with the boiler apparatus which has favorable responsiveness with respect to.

  FIG. 7 is a schematic configuration diagram of a pulverized coal fired boiler apparatus. Coal as fuel is sent from a coal bunker 81 through a coal feeder 82 to a pulverized coal machine (mill) 83 and pulverized to produce pulverized coal. The pulverized coal is distributed and supplied to each pulverized coal burner 85 via the pulverized coal pipe 84, and is injected into the furnace 87 and combusted together with the combustion air supplied from the wind box 86 to form a flame 88. In the wind box 86, an air register 89 and a NO port 90 for two-stage combustion are provided.

The adjustment of the combustion air is performed by an air flow rate control damper 92 disposed on the inlet side of the ventilator 91, and the air flow rate control damper 92 is based on a measured value of an Eco (car economizer) outlet O ₂ concentration meter 96. Feedback controlled.

  The combustion air passing through the ventilator 91 is diverted, and one flow is preheated by the air preheater 93 using the exhaust gas from the furnace 87, and then passes through the NO port inlet damper 30 or the wind box inlet damper 1 to the furnace 87. Sent in.

  The other flow of the diverted air passes through the primary ventilator 97, and is further diverted and partly preheated by the air preheater 93 to become hot air 98, mixed with the cold air 99 that has not been preheated through the damper 100, It is supplied into the pulverized coal machine 83.

  Regarding the control of nitrogen oxides (NOx), the opening degree of the NO port inlet damper 30 that separates a certain amount of combustion air as two-stage combustion air and supplies it to the NO port 90 is adjusted. Thus, the burner air ratio of the pulverized coal burner 85 is controlled to suppress the NOx generation amount at the furnace 87 outlet first.

Further, the exhaust gas is denitrated by controlling the amount of NH ₃ injected into the flue gas denitration apparatus 101. The injection amount of NH ₃ is feedback controlled based on the measured value of the NOx concentration meter 102. In the middle of the flue 103, an electric dust collector 104, an induction fan 105 and the like are provided.

  FIG. 8 is a system diagram for explaining the control of the conventional wind box inlet damper 1 in the boiler device, and FIG. 9 is a system diagram for explaining the control of the conventional NO port inlet damper 30.

  The air flow rate of the boiler device is directly controlled for each compartment of the wind box inlet damper 1 and the NO port inlet damper 30.

  The burner air ratio control is a wind box as shown in FIG. 8 for the purpose of reducing unburned components such as NOx and CO in the exhaust gas and performing stable combustion according to each mill load / burner load. The inlet damper 1 controls the air flow rate based on the burner stage fuel amount 10.

  In the figure, reference numeral 2 is a proportional integrator, 3 is a subtractor, 4 is the air flow rate of the wind box, 5 is a multiplier, 6 is an adder, 7 is a function generator, 8 is a generator output, and 9 is a function generator. It is.

On the other hand, in the air-fuel ratio control, the deviation between the Eco outlet O ₂ set value created by the function generator 42 based on the boiler input command signal 43 and the measured value 40 of the Eco outlet O ₂ so that the boiler device performs optimum combustion. Is obtained by a subtracter 39 and integrated by an integrator 38 to create an air ratio correction signal.

  A basic air flow rate command signal created by the function generator 37 based on the boiler input command signal 43 is added to the air ratio correction signal by the multiplier 36 to create an air flow rate command signal 50.

  Here, since the wind box inlet damper 1 controls the air flow rate of each burner stage based on the burner stage fuel amount 10, the total air flow rate is controlled from the air flow command signal 50 by the wind box air flow rate command. The signal 35 is subtracted by the subtractor 34 to obtain the NO port inlet air flow rate command signal 51.

  A deviation between the NO port inlet air flow rate command signal 51 and the measured NO port air flow rate 33 is obtained by the subtractor 32 and controlled by the NO port inlet damper 30 based on the control signal passed through the proportional integrator 31. .

In addition, it is necessary to secure an air preheater (AH) outlet air draft so that the wind box inlet damper 1 and the NO port inlet damper 30 can control the flow rate at an appropriate opening degree, and this is controlled by the FDF blade. .
JP-A-63-61815 Japanese Patent Publication No. 01-50805 Japanese Patent Application Laid-Open No. 08-14505 Japanese Patent Laid-Open No. 04-91630

  In the multi-fuel co-fired boiler system, especially in the case of coal with different fuel properties, the combustion adjustment is carried out for each coal type. As a result, the NOx reduction effect on the burner air ratio is achieved by the fuel ratio (fixed carbon / volatile content). Different.

  Further, when the fuel ratio and the N content increase, NOx tends to increase. However, if the burner air ratio is not reduced as the coal type has a higher fuel ratio, a sufficient NOx reduction effect cannot be obtained.

  However, the higher the fuel ratio, the lower the stability of ignition and combustion, so it is difficult to automatically set the optimal burner air ratio when burning a high-fuel ratio coal type. The optimal burner air ratio is set.

  The air ratio control in the conventional multi-fuel co-fired boiler apparatus is a control in which fuel and air are always supplied at a certain ratio (constant air ratio).

The fuel flow rate is controlled by a combustion amount command signal created based on the boiler input command signal 43 corresponding to the boiler steam amount. The air flow rate and the fuel flow rate are maintained so that the air flow rate maintains a constant ratio with the fuel flow rate. And a ratio control method that is controlled by the air amount command signal 50 created by adding O ₂ correction to the fuel amount command signal is generally employed.

  Since the conventional air-fuel ratio control is set to a constant air-fuel ratio, the operation is not necessarily efficient and NOx decreases due to a decrease in the amount of air, but the NOx reduction effect differs depending on the coal type. It was.

  Originally, an efficient air-fuel ratio condition is not always constant under all conditions, and is affected by various conditions of the combustion facility such as fuel properties and operating load. For this reason, in order to realize high-efficiency operation, it is necessary to change the air-fuel ratio condition to an optimal value in accordance with the constantly changing situation.

  Furthermore, since the air-fuel ratio condition in a general combustion facility is set so that harmful CO concentration does not increase, the amount of supplied air is excessive. Due to this excessive amount of air, heat loss due to the exhaust gas is increased, and the efficiency is deteriorated. As a result, in a general combustion facility, not only the efficiency decrease due to the above-mentioned constant air-fuel ratio condition but also the efficiency decrease due to exhaust gas heat loss occurs, leading to further increase in fuel consumption.

Normally, exhaust gas components are used as parameters representing the combustion state. In particular, among exhaust gas components, O ₂ concentration and CO concentration are used as parameters representing the combustion state. In order to control from this combustion state to an optimum operation state, when attention is paid to the relationship between the O ₂ concentration in the exhaust gas, the CO concentration and the combustion efficiency, unburned CO is usually generated even in the presence of O ₂ .

If the O ₂ concentration is high, heat loss due to the exhaust gas increases due to the excess air ratio, which causes a reduction in combustion efficiency. Conversely, if the CO concentration is high, there is a large amount of unburned fuel, heat loss due to incomplete combustion increases, and combustion efficiency decreases.

In general, when the O ₂ concentration and the CO concentration are suppressed, for example, when the characteristic curve of the O ₂ concentration and the CO concentration intersects the air-fuel ratio, the heat loss due to the excess air ratio and the heat loss due to incomplete combustion occur. It is said that the sum is minimal and efficient.

  However, since the optimum air-fuel ratio condition (the above-mentioned intersection) is affected by the operating condition, the operation with the conventional constant air-fuel ratio condition is not always efficient.

  An object of the present invention is to solve such problems of the prior art, and to provide a boiler device having high boiler device efficiency and high NOx reduction effect.

To achieve the above object, the present invention provides a nitrogen oxide concentration meter for measuring the concentration of nitrogen oxide in exhaust gas at the boiler outlet,
A wind box inlet damper for adjusting the flow rate of combustion air to the wind box equipped with a burner;
The present invention is intended for a boiler apparatus that includes damper control means for controlling the opening degree of the wind box inlet damper and that can use various types of coal fuel.

The first means of the present invention obtains in advance a burner air ratio set value obtained from a bivariate function of the fuel ratio of the coal fuel and the nitrogen oxide concentration in the exhaust gas measured by the nitrogen oxide concentration meter. Providing storage means for storing
The damper control means is stored in the storage means based on a change in fuel ratio of coal fuel supplied to the burner or a change in nitrogen oxide concentration in exhaust gas measured by the nitrogen oxide concentration meter. The burner air ratio set value is read out, and the opening degree of the wind box inlet damper is controlled based on the burner air ratio set value.

According to a second means of the present invention, in the first means,
The nitrogen oxide concentration obtained at regular intervals by the nitrogen oxide concentration meter is stored in the storage means as a pattern table for each burner stage,
When the identity of the nitrogen oxide concentration in the exhaust gas in the latest pattern table and the next new pattern table is determined and the latest nitrogen oxide concentration is higher than the next new nitrogen oxide concentration, the burner air ratio A burner air ratio correcting means for correcting the set value is provided in the damper control means.

According to a third means of the present invention, in the second means,
The burner air ratio correcting means is
A standard deviation calculating means for calculating a standard deviation value of the nitrogen oxide concentration in the exhaust gas for each burner stage when a deviation occurs in the nitrogen oxide concentration in the exhaust gas for each burner stage;
Average nitrogen oxide concentration value calculating means for selecting the burner stage whose standard deviation value calculated by the standard deviation calculating means is equal to or less than a specified value and calculating the average value of the nitrogen oxide concentration in the exhaust gas of the selected burner stage. When,
Level determining means for selecting a burner stage whose average nitrogen oxide concentration value calculated by the average nitrogen oxide concentration value calculating means is not less than a specified nitrogen oxide concentration value;
And a decreasing direction correcting means for correcting the burner air ratio in the burner stage selected by the level determining means in the decreasing direction.

A fourth means of the present invention is the second or third means,
Burner air ratio balance determining means for determining whether the burner air ratio correction value of the burner stage to be corrected by the burner air ratio correcting means satisfies all of the following constraints. It is characterized by this.

(Constraint 1): Lower can before / after burner air ratio> Middle before can / after can burner air ratio (Restriction 2): Middle can before / after can burner air ratio> Upper can before / can Rear burner air ratio (constraint condition 3): upper can front / after can burner air ratio ≧ total burner air ratio The fifth means of the present invention is the first to fourth means,
A carbon monoxide concentration meter that measures the carbon monoxide concentration in the exhaust gas at the boiler outlet is installed.
An air-fuel ratio correcting means is provided for adjusting the oxygen concentration at the outlet of the economizer according to the carbon monoxide concentration in the exhaust gas measured by the carbon monoxide concentration meter.

  The present invention is configured as described above, and can provide a boiler device that is highly efficient and has a high NOx reduction effect.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a system diagram for explaining the control of the windbox inlet damper according to the embodiment of the present invention, and FIG. 2 is a system diagram for explaining the control of the NO port inlet damper according to the embodiment of the present invention.

  First, control of the wind box inlet damper, that is, control of the burner air ratio will be described with reference to FIG. The burner air ratio control circuit according to this embodiment is configured by adding a first burner air ratio correction control circuit 60 and a second burner air ratio correction control circuit 70 to a conventional burner air ratio control circuit.

  The basic flow of the burner air ratio control circuit according to the present embodiment, which controls the opening degree of the wind box inlet damper 1 based on the burner stage fuel amount 10, that is, the air flow rate, is the same as that of the prior art.

  The first burner air ratio correction control circuit 60 added thereto corrects the set value of the burner air ratio based on the bivariate function 12 of the coal fuel ratio 14 and the NOx value 13 used as shown in FIG. To do. That is, NOx is reduced by controlling the actual burner air ratio by changing the burner air ratio setting by changing the fuel ratio 14 and the NOx value 13 over time.

  Note that the NOx value 13 is measured at regular intervals by a NOx concentration meter 102 installed at the boiler outlet as shown in FIG. 7, and is read into a control unit (not shown). Moreover, the fuel ratio 14 of pulverized coal used for a boiler apparatus can be input into a control part from the operator panel (not shown) with which the said boiler apparatus is equipped.

  In FIG. 1, reference numeral 2 is a proportional integrator, 3 is a subtractor, 4 is the wind box air flow rate, 5 is a multiplier, 6 is an adder, 7 is a function generator, 8 is a generator output, and 9 is a function generator. Reference numeral 10 denotes a burner stage fuel amount, and 11 denotes an adder, which are connected as shown in the figure.

  The bivariate function 12 outputs a value having a relationship of Z = F (X, Y) from two inputs (X, Y). In the formula, F is a symbol indicating that Z is a function composed of X and Y.

  FIG. 3 is a diagram showing the relationship of each parameter between the X and Y coordinates of the binary function and the output Z. Here, the X-coordinate is the fuel ratio 14, the Y-coordinate is the NOx value 13, and the burner air ratio is set to the output Z, so that the burner air ratio is set according to the change in the fuel ratio 14 and the NOx value 13. The output is interpolated into the bivariate function.

  Specifically, combustion is performed for each coal type having a different fuel ratio using a test combustion furnace or an actual boiler device, and the NOx value at the furnace outlet or boiler outlet is changed by changing the burner air ratio at that time. The measurement is performed, and the relationship among the fuel ratio, the burner air ratio, and the NOx value is collected as table data as shown in FIG. 3 and stored in a storage means such as a RAM (not shown). When the boiler device is operated, the necessary burner air ratio is obtained by interpolating the table data from the fuel ratio of the pulverized coal used and the target NOx value.

  The second burner air ratio correction control circuit 70 has an effect of NOx when the burner air ratio of each stage is changed when a deviation occurs in the distribution of the measurement points of the NOx value 13 of the combustion exhaust gas for each burner stage. A pattern is set in advance as a table value, and the burner air ratio setting is changed according to the NOx influence pattern.

  FIG. 4 is a diagram showing the relationship between the state of the exhaust gas flow from the furnace 87, the exhaust gas property measurement points, and the NOx influence pattern table based on the measurement point position diagram.

  In the figure, 3F is the burner group arranged in the lower stage before the can of the boiler device, 2F is the burner group arranged in the middle stage before the can, 1F is the burner group arranged in the upper stage before the can, and 3R is the lower stage after the can The burner groups 2R are arranged in the middle stage after the can, and 1R is the burner group arranged in the upper stage after the can.

  The combustion exhaust gas generated by the combustion of the burners installed in each stage and each row is not mixed positively as if a straight line was drawn from each burner group, and the NOx on the downstream side from the burner through the boiler is not mixed. It flows to the measurement region S (see exhaust gas flow chart). Although not shown, a large number of NOx concentration meters 102 (see FIG. 7) are installed in the NOx measurement region S corresponding to each measurement point.

  The figure shown in the middle of the figure is a NOx concentration measurement point position diagram, and a large number of measurement points are set corresponding to each burner row and burner stage. The diagram shown in the upper part of the figure is a diagram showing a NOx influence pattern table provided corresponding to each measurement point.

  In addition, the boiler apparatus which employ | adopts the two-stage combustion method employ | adopts the method which divides combustion air into two stages (a burner and an overair port), guides it in a furnace, and performs a slow combustion. In this case as well, the correlation between the change in the burner air ratio of each burner stage and the NOx value 13 has been confirmed by a combustion adjustment test using an actual boiler device.

  The NOx influence pattern setting method determines from the measurement result which measurement point is affected by the NOx influence pattern table based on the measurement point position diagram when each burner air ratio is changed. Can be set arbitrarily.

  When the current NOx measurement value is different from the previous NOx measurement value, the correction process by the second burner air ratio correction control circuit 70 is started.

  As shown in FIG. 1, the NOx value 13 measured this time is input to the burner stage standard deviation judging means 17, and the NOx influence pattern is distributed by the burner stage standard deviation judging means 17 with respect to the distribution of NOx values for each burner stage. The previous NOx measurement value is read from the NOx influence pattern table set in advance in the table setting means 19 and the standard deviation is calculated for each burner stage. As a result, the burner stage that is less than the specified standard deviation is selected. To do.

  Standard deviation is an index that indicates whether the overall result is scattered or scattered around the average value.The smaller the standard deviation, the more the data is collected at the average value, and the larger the standard deviation, the more the data from the average value. It will be distributed. Therefore, the burner stage that is equal to or less than the above-mentioned standard deviation means a burner stage that is gathered at an average value and has no variation (or little variation).

  Therefore, the purpose of the determination by the burner stage standard deviation determining means 17 is that when the measured value of the NOx value 13 at the specific position is extremely large, the average value tends to increase as a whole, and temporary imbalance of the measured value is caused. However, in order to prevent this phenomenon, correction is performed to exclude burner stages in which the NOx distribution for each burner stage is equal to or greater than the specified standard deviation.

  Next, the burner stage average NOx value calculation means 18 reads the calculated value from the NOx influence pattern table preset by the NOx influence pattern table setting means 19 for the burner stage that is equal to or less than the specified standard deviation. Calculate the average NOx value of the burner stage.

  The specified standard deviation is obtained by setting a standard deviation calculated based on the measurement result of the NOx value obtained from the combustion adjustment result as the specified standard deviation.

  When the burner air ratio of each stage is changed, the NOx influence pattern table setting means 19 has a different NOx influence pattern for each burner stage. The correlation of influence is arranged and set.

  Regarding the correlation between each stage burner air ratio and the effect on NOx, for example, when the 3F burner air ratio shown in FIG. 4 is arbitrarily changed (the burner air ratios in other stages are constant), the measurement points shown in FIG. In the position diagram, the measurement point where the measured value of NOx changes is confirmed. For example, when the measurement points of A1, B2, A3, A4, B7, BA, BB, BC in the figure change significantly as the measurement points where the change in NOx is significant in accordance with the air ratio change of the burner stage, this Measurement points are set (stored) in the NOx influence pattern table setting means 19.

  Next, in the average NOx value level determining means 20, the average NOx value of the burner stage calculated by the burner stage average NOx value calculating means 18 is equal to or greater than the NOx guaranteed value α determined for each boiler device (≧ α). The burner stage, ie the burner stage whose NOx value must be reduced, is selected. When the average NOx value of the burner stage is less than the NOx guaranteed value α (<α), the process proceeds to the preceding stage of the burner air ratio balance determination means 24 described later.

  When there are a plurality of burner stages whose average NOx value determined by the average NOx value level determining means 20 is equal to or greater than the guaranteed value, the maximum value determining means 21 selects the burner stage having the maximum average NOx value. .

  The next NOx influence pattern identity determination means 22 determines whether the influence patterns on the NOx of the burner stage are the same when there are a plurality of maximum average NOx values.

  If the NOx influence pattern of the burner stage is the same, a burner stage having a high burner air ratio value is selected by the burner air ratio high selection means 23. When the NOx influence pattern of the burner stage is different, the process proceeds to the previous stage of the burner air ratio balance determination means 24 described later.

  Finally, the burner air ratio balance determining means 24 determines whether or not the correction values of the burner stage to be corrected for the burner air ratio satisfy all the following constraints.

  The relationship between the burner air ratio of each burner stage is as follows: lower can front burner group / after can burner group (3F / 3R)> middle can front burner group / after can burner group (2F / 2R)> upper can front burner Since the group / post-can burner group (1F / 1R) ≧ the overall burner air ratio, the following constraints are provided to balance the overall burner air ratio.

(Restriction condition 1): Lower can front burner group / post-can burner group burner air ratio> Middle pre-can burner group / post-can burner group burner air ratio (Restriction condition 2): Middle pre-can burner group / after can Burner group burner air ratio> Upper can burner group / can after burner group burner air ratio (Restriction condition 3): Upper can burner group / can after burner group burner air ratio ≧ Overall burner air ratio Correction of burner air ratio As for the correction only for the reduction operation to reduce the burner air ratio, the burner air ratio correction reduction command update condition shown in FIG. The switch 16 is switched from X1 to X2, and a correction signal is output to the adder 11 of the first burner air ratio correction circuit 60 for the burner air ratio setting at that stage. In the figure, reference numeral 15 denotes a signal generator.

  The burner air ratio correction reduction command update condition is satisfied when all of the following seven conditions are satisfied.

(Condition 1): The standard deviation value for each burner stage is small.
(Condition 2): The measured NOx value at the boiler outlet is not less than the guaranteed value.
(Condition 3): The average NOx value for each burner stage is not less than a specified value.
(Condition 4): The measured unburned fuel concentration at the boiler outlet is not more than the upper limit value.
(Condition 5): The measured O ₂ concentration at the boiler outlet is not less than the lower limit.
(Condition 6): The overall burner air ratio is not less than a specified value.
(Condition 7): A predetermined time (for example, 1 hour) has passed since the previous correction update of the burner air ratio.

Next, air-fuel ratio correction control according to an embodiment of the present invention will be described with reference to FIG. Based on the boiler input command signal 43, the difference between the Eco outlet O ₂ set value created by the function generator 42 and the measured value 40 of the Eco outlet O ₂ is obtained by the subtractor 39, and is integrated by the integrator 38. Create an air ratio correction signal.

  A basic air flow rate command signal created by the function generator 37 based on the boiler input command signal 43 is added to the air ratio correction signal by the multiplier 36 to create an air flow rate command signal 50.

  Here, since the wind box inlet damper 1 controls the air flow rate of each burner stage based on the burner stage fuel amount 10, the total air flow rate is controlled from the air flow command signal 50 by the wind box air flow rate command. The signal 35 is subtracted by the subtractor 34 to obtain the NO port inlet air flow rate command signal 51.

  The deviation between the NO port inlet air flow rate command signal 51 and the measured NO port air flow rate 33 is obtained by the subtractor 32 and controlled by the NO port inlet damper 30 based on the control signal passed through the proportional integrator 31. The general flow is the same as in the prior art.

The characteristic point of this embodiment is that the CO value 45 measured at the boiler outlet is subjected to weighted moving average processing by the weighted moving average calculating means 52, and the Eco outlet O ₂ concentration corresponding to the time-dependent change of the CO value 45 in the function unit 44. The set value is calculated and added to the Eco exit O ₂ set value output from the function generator 42 by the adder 41.

Thus, by changing the Eco outlet O ₂ concentration set value in accordance with the change with time of the CO value 45, it is possible to contribute to the low O ₂ concentration operation and to improve the boiler efficiency.

  The purpose of weighted moving average processing here is that the normal moving average method eliminates fluctuations and is suitable not only for the time you want to know, but also for looking at the overall transition, etc., but suitable for predicting the time you want to know Not. For this reason, by applying a weight using the weighted moving average method, predicting the upward trend of the CO value, and predicting at a value close to the value of the timing at which the air-fuel ratio correction is to be performed, making appropriate corrections at appropriate times Is possible.

FIG. 6 is a graph showing the relationship between the CO value and the Eco outlet O ₂ concentration, that is, the excess air ratio correction function.

As described above, according to the present invention, when the burner air ratio corresponding to the reference coal is constantly controlled for each coal type, and the Eco outlet O ₂ and the CO balance are adjusted, the distribution of certain measurement points is caused over time. An appropriate burner air ratio is set based on a bivariate function of the fuel ratio and the measured NOx value.

  And the 1st burner air ratio correction circuit including the contents which change a burner air ratio setting by change of charcoal type (change of fuel ratio) and change with time of NOx, and the burner air ratio of each burner stage were changed. The second burner air ratio correction circuit that changes the burner air ratio setting of each burner stage according to the influence pattern of NOx in the case, the windbox inlet damper opening corresponding to the direction to reduce the deviation, that is, the actual burner By adjusting the air ratio, it is possible to reduce NOx and unburned content.

Further, paying attention to changes in O ₂ and CO at the Eco outlet with respect to changes in the air-fuel ratio due to changes in the boiler state quantity (for example, boiler load and fuel), that is, by shifting to low O ₂ concentration operation of the boiler device, Boiler efficiency can be improved by performing bias correction for the air-fuel ratio when there is a margin in operation in the small direction of the Eco outlet O ₂ while suppressing the increase.

It is a systematic diagram for demonstrating control of the windbox inlet damper which concerns on embodiment of this invention. It is a systematic diagram for demonstrating control of the NO port entrance damper which concerns on embodiment of this invention. It is the figure which showed the relationship of each parameter of the X and Y coordinate and output Z of a bivariate function. It is a figure which shows the relationship of the state of the flow of the exhaust gas from a furnace, an exhaust gas property measurement point, and the NOx influence pattern table based on the measurement point position figure. It is a figure which shows the burner air ratio correction | amendment reduction command update conditions. It is a characteristic diagram showing the relationship between the CO values and the Eco outlet O ₂ concentration in the embodiment of the present invention. It is a schematic block diagram of a pulverized coal fired boiler device. It is a systematic diagram for demonstrating control of the conventional wind box entrance damper in a boiler apparatus. It is a systematic diagram for demonstrating control of the conventional NO port entrance damper in a boiler apparatus.

Explanation of symbols

1: Windbox inlet damper, 2: Proportional integrator, 3: Subtractor, 4: Wind window air flow rate, 5: Multiplier, 6: Adder, 7: Function generator, 8: Generator output, 9: Function generator, 10: burner stage fuel amount, 11: adder, 12: bivariate function, 13: NOx value, 14: fuel ratio, 15: signal generator, 16: switch, 17: burner stage standard deviation determination Means: 18: burner stage average NOx value calculating means, 19: NOx influence pattern table means, 20: average NOx value level judging means, 21: maximum value judging means, 22: NOx influence pattern identical judging means, 23: burner air ratio High selection means, 24: burner air ratio balance judgment means, 30: NO port inlet damper, 31: proportional integrator, 32: subtractor, 33: NO port air flow rate, 34: subtractor, 35: I command box air flow command signal, 36: multiplier, 37: function generator 38: integrator, 39: subtractor, 40: Eco outlet O ₂ measurements, 41: adder, 42: function generator 43 : Boiler input command signal, 44: Function generator, 45: CO value, 50: Air flow rate command signal, 51: NO port inlet air flow rate command signal, 52: Weighted moving average calculation means, 60: First burner air ratio Correction control circuit, 70: second burner air ratio correction control circuit, 85: pulverized coal burner, 86: window box, 87: furnace, 89: air register, 90: NO port, 95: Eco outlet O ₂ concentration meter, 102: NOx concentration meter, S: NOx measurement area.

Claims (5)

A nitrogen oxide concentration meter that measures the nitrogen oxide concentration in the exhaust gas at the boiler outlet;
A wind box inlet damper for adjusting the flow rate of combustion air to the wind box equipped with a burner;
In a boiler apparatus that can use various types of coal fuel with damper control means for controlling the opening degree of the wind box inlet damper,
A storage means is provided for preliminarily obtaining and storing a burner air ratio set value obtained from a bivariate function of the fuel ratio of the coal fuel and the nitrogen oxide concentration in the exhaust gas measured by the nitrogen oxide concentration meter;
The damper control means is stored in the storage means based on a change in fuel ratio of coal fuel supplied to the burner or a change in nitrogen oxide concentration in exhaust gas measured by the nitrogen oxide concentration meter. A boiler apparatus that reads out a burner air ratio set value and controls the opening degree of the wind box inlet damper based on the burner air ratio set value. The boiler device according to claim 1,
The nitrogen oxide concentration obtained at regular intervals by the nitrogen oxide concentration meter is stored in the storage means as a pattern table for each burner stage,
When the identity of the nitrogen oxide concentration in the exhaust gas in the latest pattern table and the next new pattern table is determined and the latest nitrogen oxide concentration is higher than the next new nitrogen oxide concentration, the burner air ratio A boiler apparatus characterized in that a burner air ratio correcting means for correcting a set value is provided in the damper control means. The boiler device according to claim 2,
The burner air ratio correcting means is
A standard deviation calculating means for calculating a standard deviation value of the nitrogen oxide concentration in the exhaust gas for each burner stage when a deviation occurs in the nitrogen oxide concentration in the exhaust gas for each burner stage;
Average nitrogen oxide concentration value calculating means for calculating the average value of nitrogen oxide concentration in the exhaust gas of the selected burner stage by selecting a burner stage whose standard deviation value calculated by the standard deviation calculating means is equal to or less than a specified value When,
Level determining means for selecting a burner stage whose average nitrogen oxide concentration value calculated by the average nitrogen oxide concentration value calculating means is not less than a specified nitrogen oxide concentration value;
A boiler apparatus comprising: a reduction direction correction means for correcting the burner air ratio in the burner stage selected by the level determination means in a reduction direction. The boiler device according to claim 2 or 3,
Burner air ratio balance determining means for determining whether the burner air ratio correction value of the burner stage to be corrected by the burner air ratio correcting means satisfies all of the following constraints. A boiler device characterized by that.
(Constraint 1): Lower can before / after burner air ratio> Middle before can / after can burner air ratio (Restriction 2): Middle can before / after can burner air ratio> Upper can before / can Rear burner air ratio (constraint condition 3): Upper can front / after can burner air ratio ≧ total burner air ratio The boiler device according to any one of claims 1 to 4,
A carbon monoxide concentration meter that measures the carbon monoxide concentration in the exhaust gas at the boiler outlet is installed.
A boiler apparatus comprising air-fuel ratio correction means for adjusting an oxygen concentration at the outlet of a economizer according to a carbon monoxide concentration in exhaust gas measured by the carbon monoxide concentration meter.

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