JP2022176687A - boiler - Google Patents

Abstract

To provide a boiler capable of suppressing influence of wrong detection, even under a situation where it is impossible to correctly detect a flow rate of combustion air or fuel supplied actually.SOLUTION: A boiler supplies combustion air to a boiler body, detects a flow rate of the supplied combustion air, specifies first information according to the detection result, specifies second information that is a value that is independent of the detected flow rate of combustion air and that can vary depending on an operation mode of the boiler, and adjusts a flow rate of fuel to be supplied based on a plurality of pieces of information including the first information and the second information.SELECTED DRAWING: Figure 2

Description

The present invention relates to boilers.

Conventionally, a regulating valve is provided on a fuel supply line that supplies fuel to an ejection part such as a nozzle, and the flow rate of fuel is adjusted by controlling a proportional valve (regulating valve) in conjunction with the flow rate of combustion air. There is a boiler equipped with a combustion device that performs multi-position control (high combustion, medium combustion, low combustion, etc.) and proportional control (for example, see Patent Document 1).

Japanese Unexamined Patent Application Publication No. 2008-2787

In the boiler as described above, the flow rate of the fuel is adjusted according to the flow rate of the combustion air supplied. is connected to the air supply passage, and the amount of fuel supplied is adjusted by adjusting the opening of the fuel proportional valve based on the pressure of the air transmitted through the air pressure detection conduit. In such a boiler, the flow rate of the combustion air actually supplied by the air flow rate detection means is measured when, for example, the air pressure detection conduit fails, when the combustion stage transitions, or when the temperature changes transiently. is erroneously detected, the fuel supply amount is adjusted based on this erroneous combustion air flow rate. As a result, the air ratio (ratio of air for combustion to fuel) fluctuates, and if no countermeasures are taken, combustion abnormalities such as misfire and increased oxygen monoxide may occur. Even in the case where the flow rate of the combustion air is adjusted according to the flow rate of the supplied fuel, the same problem may occur if the flow rate of the actually supplied fuel is not correctly detected.

The present invention has been devised in view of such circumstances, and its object is to suppress the influence of erroneous detection even in situations where the flow rate of the combustion air or fuel that is actually supplied cannot be detected correctly. It is to provide a boiler.

To achieve the above object, a boiler according to one aspect of the present invention includes supply means for supplying combustion air or fuel to a boiler body, and detecting the flow rate of the combustion air supplied or the flow rate of fuel. a first information specifying means for specifying first information according to the detection result; and a value irrespective of the detected combustion air flow rate or the detected fuel flow rate, second information specifying means for specifying second information that may vary depending on the operating mode; and flow rate of fuel to be supplied or supplied based on a plurality of information including the first information and the second information and a flow rate adjusting means for adjusting the flow rate of the combustion air.

According to the above configuration, the flow rate to be supplied is adjusted based on information including not only the first information but also the second information, which is a value irrelevant to the detected flow rate and may vary according to the operation mode of the boiler. By doing so, even if the first information deviates from the actually supplied flow rate, the supplied flow rate is adjusted based on the information including the second information that is not affected by it, so the effect of erroneous detection can be suppressed.

Preferably, the second information is information based on at least one of a combustion rate of the boiler, a frequency rate of the blower, and a target flow rate of combustion air according to the amount of combustion.

According to the above configuration, the flow rate to be supplied is adjusted using more appropriate information according to the operation mode of the boiler as the second information.

Preferably, the second information is information based on a maximum range detectable by the first information identifying means.

According to the above configuration, the flow rate to be supplied is adjusted using more appropriate information according to the operation mode of the boiler as the second information.

It is a figure for demonstrating schematic structure of a boiler. 4 is a flowchart for explaining an example of boiler control;

<Overview of configuration>
A boiler 1 according to an embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a diagram schematically showing the configuration of a boiler 1 according to an embodiment of the invention.

The boiler 1 includes a boiler body 2 that burns fuel to generate steam, an air blower (blowing means) 3 that feeds air into the boiler body 2 through an air supply path 30, and discharges exhaust gas from the boiler body 2. and a fuel supply line (fuel supply path) 5 for supplying fuel to the boiler body 2 . In addition, although an example in which the fuel is gas will be described, the fuel is not limited to gas such as gas, and may be liquid such as oil.

The fuel supply line 5 is connected to the air supply path 30 . Fuel supplied from the fuel supply line 5 is mixed with air blown from the blower 3 in the air supply path 30 and supplied to the burner 20 in the boiler main body 2 .

Air supplied from the blower 3 is supplied as combustion air to the burner 20 in the boiler body 2 via the air supply path 30 . The flow rate of the combustion air is adjusted by providing a damper 7 in the air supply path 30 and adjusting the position (opening degree) of the damper 7, or alternatively or in addition to this, by adjusting the speed of the blower 3 using an inverter. This is done by changing the rotation speed of the fan. In the present embodiment, the flow rate of combustion air is adjusted by opening control of damper 7 and inverter control of blower 3 .

The fuel supply line 5 is provided with on-off valves (electromagnetic valves) 11 and 12 for opening and closing the passage, and a fuel supply amount adjusting valve 13 . The fuel supply amount adjustment valve 13 functions as a pressure adjustment valve that can adjust the flow rate of fuel supplied to the boiler main body 2 and also has a cutoff function. The fuel supply amount adjustment valve 13 is a motor valve that is provided downstream of the on-off valves 11 and 12 and whose opening degree is adjusted by the control device 6 . The fuel supply amount adjusting valve 13 is not limited to a motor valve as long as it adjusts the flow rate of fuel, and may be, for example, a pneumatic control valve.

The control device 6 is realized by a computer including a memory, a timer, and an arithmetic processing unit inside, and controls the fuel supply amount adjustment valve 13, the blower 3, and the damper 7 based on signals from each sensor electrically connected. control.

A combustion air pressure reducing member 8 such as a punching metal is provided downstream of the damper 7 in the air supply passage 30 in this embodiment. The air flow rate detection unit 9 has a differential pressure sensor that detects a differential pressure across the combustion air pressure reducing member 8, and outputs differential pressure information that can specify the detected differential pressure. The air flow rate detector 9 is electrically connected to the controller 6 . Thereby, differential pressure information from the air flow rate detection unit 9 can be input to the control device 6 . Note that the analog signal output from the air flow rate detector 9 is converted to a digital signal and input to the control device 6 .

The control device 6 controls, for example, one of a low combustion stage L, an intermediate combustion stage M, and a high combustion stage H as a plurality of types of combustion stages with different combustion amounts. The control device 6 controls the combustion stage according to the set target steam pressure and the steam pressure of the steam header. The control device 6 controls the blower 3 so as to have a mode (for example, number of revolutions and frequency) according to the combustion stage being controlled, and supplies an amount of combustion air according to the combustion stage. The control device 6 calculates (detects) the flow rate of the combustion air that is supposed to be actually supplied to the boiler main body 2 based on the differential pressure information detected by the air flow rate detection section 9 .

The control device 6 adjusts the opening degree of the fuel supply amount adjusting valve 13 based on a plurality of pieces of information including differential pressure information as first information and specific information as second information. For example, if the flow rate of combustion air increases, the opening degree of the fuel supply amount adjusting valve 13 is increased to increase the flow rate of fuel. Decrease the opening to decrease the fuel flow rate. The specific information will be described later.

The control device 6 includes a control section 61 and a storage section 62 . The control unit 61 transmits an opening degree specifying signal for specifying the opening degree to the fuel supply amount adjusting valve 13 based on the opening degree adjustment information stored in advance in the storage unit 62 . As a result, the fuel supply amount adjustment valve 13 is controlled to have an opening degree corresponding to the opening degree adjustment information, and can adjust the flow rate of the fuel supplied to the boiler main body 2 . The opening degree adjustment information may be, for example, a table that can specify the opening degree of the fuel supply amount adjustment valve 13 according to the differential pressure information or the like. An arithmetic expression for specifying the degree of opening of the valve 13 may be used.

For example, when adjusting the opening of the fuel supply amount adjusting valve 13 based on differential pressure information without considering specific information, the differential pressure before and after the combustion air pressure reducing member 8 may increase due to a failure of the air flow rate detecting unit 9 or the like. or when the air ratio fluctuates greatly in transient conditions such as transitions between combustion stages, and when the flow rate of the actually supplied combustion air cannot be detected correctly, the erroneous Therefore, the fuel supply amount is adjusted based on the incorrect value (erroneous combustion air flow rate). As a result, the fuel cannot be supplied in accordance with the flow rate of the combustion air that is actually supplied, and the air ratio fluctuates, resulting in combustion abnormalities such as misfire and increased oxygen monoxide. Therefore, in the present embodiment, not only the differential pressure information but also the differential pressure (flow rate of combustion air) detected by the air flow rate detection unit 9 is a value that varies according to the operating mode of the boiler 1. Based on a plurality of information including possible specific information, the opening adjustment of the fuel supply amount adjustment valve 13 (adjustment of fuel flow rate) is performed.

A specific description will be given. In addition to the opening degree adjustment information, the storage unit 62 stores a value that is independent of the differential pressure (flow rate of combustion air) detected by the air flow rate detection unit 9, and that varies according to the operation mode of the boiler 1. Various information related to the boiler 1, such as specific information to be obtained, is stored. The specific information in the present embodiment is, for example, a value obtained by adding (considering) a value that can vary according to the combustion rate of the boiler 1, which is the value of "the amount of combustion in the current combustion stage/the amount of combustion in the high combustion stage H". As the combustion rate increases, a value specifying a larger degree of opening of the fuel supply amount control valve 13 (a value that increases the amount of fuel supply) is determined. In addition, as the specific information, for example, a predetermined table is stored in the storage unit 62, and the table can be referred to so as to be able to be identified according to the combustion rate of the boiler 1. An arithmetic expression may be stored in the storage unit 62 and specified according to the combustion rate of the boiler 1 using the arithmetic expression.

Based on the opening degree adjustment information stored in advance in the storage unit 62, the control unit 61 obtains the differential pressure information from the air flow rate detection unit 9 and the specific information corresponding to the combustion rate among the specific information specified from the table. to specify the opening degree of the fuel supply amount adjustment valve 13 according to a plurality of information including, and transmit an opening degree specifying signal for specifying the opening amount to the fuel supply amount adjustment valve 13 . Specifically, based on the opening degree adjustment information stored in advance in the storage unit 62 , the control unit 61 selects the differential pressure information from the air flow rate detection unit 9 and the specific information stored in advance in the storage unit 62 . The opening degree of the fuel supply amount adjusting valve 13 is specified according to a value (for example, the sum of the value of the differential pressure information and the value of the specified information) calculated using the specified information corresponding to the rate. As a result, the fuel supply amount adjustment valve 13 is controlled to have an opening degree according to the differential pressure information and the specific information, and can adjust the flow rate of the fuel supplied to the boiler main body 2 . In addition, even if the air flow rate detection unit 9 is not able to correctly detect the flow rate of the actually supplied combustion air, the specific information is not affected by it. It is possible to mitigate or reduce the amount/ratio that changes the , and prevent the influence of erroneous detection from being greatly affected.

In addition to the combustion rate of the boiler 1, the specific information is a value related to the maximum pressure value (full scale) that can be detected by the differential pressure sensor provided in the air flow rate detection unit 9 (for example, the maximum pressure value or the maximum pressure value (hereinafter also referred to as the maximum pressure constant) (for example, the product of the maximum pressure constant and the combustion rate). Thereby, the flow rate to be supplied is adjusted using more appropriate information according to the operating mode of the boiler as the specific information. As described above, the specific information is preferably, for example, information based on both the combustion rate of the boiler 1 and the maximum pressure constant, which may vary depending on the operation mode of the boiler. On the other hand (e.g., the combustion rate of the boiler 1) n-th power (e.g., squared. n may be an integer of 2 or more). good.

<Regarding boiler control processing>
FIG. 2 is a flow chart for explaining an example of boiler control according to the present invention. The control device 6 performs this control at regular intervals (for example, one second), and continuously performs this control while the boiler 1 is in operation.

In step S01, based on the detected steam pressure in the steam header and the target steam pressure, it is determined whether or not it is necessary to shift the combustion stage. When it is not determined in step S01 that the combustion stage transition is necessary, the process proceeds to step S04. On the other hand, when it is determined in step S01 that a transition to the combustion stage is necessary, the process proceeds to step S02.

In step S02, the combustion stage is shifted. In step S03, the blower 3 is controlled in a manner corresponding to the combustion stage shifted to in step S02 (the number of revolutions corresponding to the combustion stage or the frequency corresponding to the combustion stage). In step S04, differential pressure information (air flow rate of combustion air) corresponding to the detection result of the air flow rate detection section 9 is specified. In step S05, specific information corresponding to the combustion rate of the boiler 1 and the maximum pressure constant of the differential pressure sensor provided in the air flow rate detector 9 is specified regardless of the differential pressure information (air flow rate of combustion air). In step S06, based on the opening degree adjustment information, the opening degree of the fuel supply amount adjusting valve 13 is identified according to the differential pressure information identified in step S04 and the specific information identified in step S05, and controlled to the opening degree. to adjust the flow rate of the fuel to be supplied.

As described above, in the present embodiment, as described in steps S04 to S06 in FIG. The opening of the fuel supply amount adjusting valve 13 is adjusted based on a plurality of information including specific information that is a value that is not related to differential pressure information (air flow rate of combustion air) and that may vary depending on the operating mode of the boiler. By controlling and adjusting the flow rate to be supplied, even if the air flow rate detection unit 9 cannot correctly detect the flow rate of the actually supplied combustion air, the specific information is not affected by it. Therefore, it is possible to mitigate or reduce the amount and ratio of change in the flow rate of fuel due to the influence of erroneous detection, and to prevent the influence of erroneous detection from being greatly affected.

Further, in the present embodiment, as shown in step S04, the second information is information corresponding to (considering) the combustion rate of the boiler regardless of the differential pressure information (air flow rate of combustion air). , the flow rate to be supplied is adjusted using more appropriate information according to the operating mode of the boiler as the second information.

Further, in the present embodiment, as shown in step S04, the second information is the maximum pressure constant of the differential pressure sensor provided in the air flow rate detection unit 9 regardless of the differential pressure information (the air flow rate of the combustion air). Since the information is based on (considered) information, the flow rate to be supplied is adjusted using more appropriate information according to the operating mode of the boiler as the second information.

The present invention is not limited to the above embodiments, and various modifications and applications are possible. Modifications of the above embodiments applicable to the present invention will be described below.

In the above embodiment, the blower 3 is controlled in a mode corresponding to the combustion stage, and the air flow rate (combustion of the combustion rate of the boiler 1 and the differential pressure sensor provided in the air flow rate detector 9, regardless of the differential pressure information (air flow rate of the combustion air), as shown in step S05. After specifying the specific information corresponding to the maximum pressure constant, as shown in step S06, the opening degree (fuel supply flow rate) of the fuel supply amount adjustment valve 13 is controlled based on the differential pressure information and the specific information. Thus, an example of adjusting the air ratio has been described. However, the processing for adjusting the air ratio is not limited to this. The air ratio may be adjusted by detecting the flow rate and controlling the air flow rate (the combustion air supply flow rate, for example, the blower 3) based on the fuel supply flow rate and specific information. When detecting the actual fuel supply flow rate, for example, orifices or the like are provided at a plurality of locations in the fuel supply line 5 to detect the differential pressure, and the fuel supply flow rate is detected based on the differential pressure. good. The specific information in this case is not information for specifying the fuel supply flow rate together with the differential pressure information, but is information for specifying the air flow rate (combustion air supply flow rate) together with the differential pressure information. Specifically, the control device 6 determines the opening degree of the damper 7 of the fan 3 or the rotational speed of the fan 3 based on a plurality of information including differential pressure information as first information and specific information as second information. control. For example, if the flow rate of fuel increases, the opening degree of the damper 7 of the blower 3 is increased to increase the air flow rate. Reduce air flow.

In the above embodiment, information based on the combustion rate of the boiler 1 and the maximum pressure constant was exemplified as the specific information, which is the second information that can vary according to the operation mode of the boiler. Information based on at least one of the combustion rate of the boiler, the frequency rate of the blower 3, the target flow rate of combustion air according to the amount of combustion, and the maximum pressure constant may be used.

For example, the specific information may be information based on the frequency rate of the blower 3 instead of or in addition to the combustion rate of the boiler 1 . The frequency rate of the blower 3 is, for example, the value of "the current blower frequency/the blower frequency in the high combustion stage H". In this case, the specific information is preferably, for example, information based on both the frequency rate of the blower 3 and the maximum pressure constant, which may vary depending on the operation mode of the boiler. For example, it may be calculated by an appropriate calculation such as the product of the frequency rate of the blower 3 raised to the nth power (for example, squared, where n is an integer of 2 or more). Further, the specific information may be information based on the target flow rate of the combustion air according to the combustion amount instead of or in addition to the maximum pressure constant. The target flow rate of the combustion air according to the combustion amount is a predetermined target flow rate for each combustion amount. In this case, the specific information is, for example, information based on both the combustion rate of the boiler 1 and the target flow rate of the combustion air according to the amount of burning, as a value that can vary depending on the operation mode of the boiler. is preferable, for example, the product of both, or the product of one (for example, the target flow rate of combustion air) to the nth power (for example, the square. n may be an integer of 2 or more.) may be calculated by the calculation of As the target flow rate of combustion air corresponding to the frequency rate of the blower or the amount of combustion increases, a value specifying a larger degree of opening of the fuel supply amount control valve 13 (a value that increases the amount of fuel supply) is determined. there is

In the above embodiment, the opening degree of the fuel supply amount adjusting valve 13 is specified according to the differential pressure information corresponding to the detection result of the air flow rate detection unit 9 and the specified information regardless of the differential pressure information. The specified opening may be corrected as needed by the control device 6 according to the use environment, situation, etc. during operation. For example, the control device 6 detects the oxygen concentration of the exhaust gas at any time, and based on the detected oxygen concentration of the exhaust gas and a predetermined reference oxygen concentration, for example, when the oxygen concentration of the exhaust gas>the reference oxygen concentration Since the air ratio is high, the amount of fuel supplied is increased, and when the oxygen concentration in the exhaust gas is less than the reference oxygen concentration, the air ratio is low, so the amount of fuel supplied is reduced. The opening degree of the fuel supply amount adjustment valve 13 specified accordingly may be adjusted. Instead of or in addition to this, the control device 6, for example, according to the temperature of the fuel, the temperature of the combustion air, etc., the fuel supply amount adjustment valve 13 specified according to the differential pressure information and the specified information. It may be one that adjusts the degree of opening. In addition, after controlling the opening degree of the fuel supply amount adjustment valve 13 so that the opening degree corresponds to the combustion stage, the actual fuel supply flow rate is detected, and the air flow rate is detected based on the fuel supply flow rate and the specific information. In the case of controlling the flow rate, the opening degree of the damper 7 of the blower 3 or the rotation speed of the blower 3 specified according to the differential pressure information (and the fuel supply flow rate) and the specified information is adjusted to the usage environment during the operating state. - Correction may be made at any time by the control device 6 depending on the situation.

The embodiments disclosed this time should be considered as examples and not restrictive in all respects. The scope of the present invention is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the meaning and range of equivalents of the scope of the claims.

1 boiler 2 boiler main body 3 air blower (blowing means)
4 flue 5 fuel supply line (fuel supply path)
6 control device 61 control section 62 storage section 7 damper 8 combustion air decompression member 9 air flow rate detection section (flow rate detection means)
11 ON-OFF VALVE 12 ON-OFF VALVE 13 FUEL SUPPLY CONTROL VALVE 20 BURNER 30 AIR SUPPLY PATH

Claims (3)

supply means for supplying combustion air or fuel to the boiler body;
a first information specifying means for detecting the flow rate of the supplied combustion air or the flow rate of the fuel and specifying first information according to the detection result;
a second information specifying means for specifying second information, which is a value irrespective of the detected flow rate of combustion air or the detected flow rate of fuel, and which can vary depending on the operation mode of the boiler;
A boiler comprising flow rate adjusting means for adjusting the flow rate of fuel to be supplied or the flow rate of combustion air to be supplied based on a plurality of pieces of information including the first information and the second information. 2. The boiler according to claim 1, wherein the second information is information based on at least one of a combustion rate of the boiler, a frequency rate of the blower, and a target flow rate of combustion air according to the amount of combustion. 3. The boiler according to claim 1, wherein said second information is information based on a value relating to a maximum range detectable by said first information identifying means.

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