JP2013142478A - Combustion control device for gas burner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustion control device for a gas burner that can keep a less generated amount of noxious gas in a low flow rate region of fuel gas and combustion air in the gas burner.SOLUTION: The combustion control device 5 for the gas burner 1 includes a fuel control section 51, an air control section 52, a threshold detecting section 53, and a measured flow rate correcting section 54. The fuel control section 51 determines the opening of a gas flow rate control valve 31 to achieve a target combustion amount Qgr demanded of the gas burner 1. The air control section 52 determines the opening of an air flow rate control valve 32 so that a measured air ratio αm based on a measured flow rate Qgm of a gas flowmeter 41 and the measured flow rate Qam of an air flowmeter 42 is a predetermined target air ratio αr. The measured flow rate correcting section 54 makes a measured gas flow rate correction Hg for correcting the measured flow rate Qgm indicated by the gas flowmeter 41 to a larger value by a predetermined amount, and a measured air flow rate correction Ha for correcting the measured flow rate Qam indicated by the air flowmeter 42 to a smaller value by a predetermined amount when a low flow rate state X is detected by the threshold detecting section 53.

Description

  The present invention relates to a combustion control device that controls a combustion state of fuel gas and combustion air in a gas burner.

  In a gas burner that burns fuel gas flowing through a gas pipe and combustion air flowing through an air pipe, the air ratio (or air-fuel ratio, excess air ratio) is maintained at a predetermined value using a combustion control device. In order to maintain the air ratio at a predetermined value, the gas pipe and the air pipe are provided with a flow rate control valve and a differential pressure sensor (differential pressure flow meter), respectively. Accordingly, the flow rates of the fuel gas and combustion air supplied to the gas burner are monitored to prevent misfire due to excess air and to prevent generation of toxic gases such as carbon monoxide due to excess fuel.

  For example, in the method and apparatus for adjusting the air-fuel ratio of the burner disclosed in Patent Document 1, a fuel differential pressure sensor and a control valve are provided in the gas pipe, an air differential pressure sensor and a fan are provided in the air pipe, and the air-fuel ratio of the burner is increased. Adjusting is disclosed. According to this, it is disclosed that even when the density of air flowing into the fan changes due to a change in atmospheric pressure or temperature, this can be detected by the air differential pressure sensor and the output of the fan can be adjusted.

Special table 2003-514212 gazette

  By the way, in a flow meter used for measurement of fuel gas and combustion air, errors occurring in these measurements become large in a low flow rate range in the measurable flow rate range. That is, the flowmeter generally has an error of about ± 0.1 to 2% with respect to full scale (maximum measurable flow rate). Therefore, the smaller the flow rate, the larger the ratio of error to the flow rate measurement value, and the greater the error in the low flow rate region.

  When the gas burner is operated with a small load required for the gas burner and the flow rates of the fuel gas and the combustion air are reduced, there is a possibility that the air ratio in the gas burner cannot be controlled appropriately due to an error generated in the flow meter. In this case, particularly when the actual air ratio in the gas burner has become small, there is a risk that the amount of toxic gas such as carbon monoxide generated will increase.

  The present invention has been made in view of such conventional problems, and is a gas burner capable of maintaining a small amount of toxic gas such as carbon monoxide in a low flow rate range of fuel gas and combustion air in a gas burner. A combustion control device is to be provided.

1st invention connects the gas piping which provided the gas flow control valve and the gas flow meter, and the air piping which provided the air flow control valve and the air flow meter, the fuel gas which passes the said gas piping, and the said air A combustion control device equipped with a gas burner for burning combustion air passing through a pipe,
A fuel control unit for determining an opening of the gas flow rate control valve so as to achieve a target combustion amount required for the gas burner;
An air control unit for determining an opening of the air flow rate control valve so that a measured air ratio based on a measured flow rate of the gas flow meter and a measured flow rate of the air flow meter becomes a predetermined target air ratio;
A threshold detection unit for detecting a low flow rate state in which the measured flow rate of at least one of the gas flow meter and the air flow meter is equal to or less than a predetermined ratio with respect to the maximum measurable flow rate;
When the threshold detection unit detects the low flow rate state, the measurement gas flow rate correction for correcting the measurement flow rate of the gas flow meter to a large value by a predetermined amount, and the measurement flow rate of the air flow meter to a small value by a predetermined amount A combustion control device for a gas burner, comprising: a measurement flow rate correction unit that performs at least one of correction of the measurement air flow rate to be corrected.

According to a second aspect of the present invention, a gas pipe provided with a gas flow control valve and a gas flow meter and an air pipe provided with an air flow control valve and an air flow meter are connected, and the fuel gas and the air passing through the gas pipe are connected. A combustion control device equipped with a gas burner for burning combustion air passing through a pipe,
A fuel control unit for determining an opening of the gas flow rate control valve so as to achieve a target combustion amount required for the gas burner;
An air control unit for determining an opening of the air flow rate control valve so that a measured air ratio based on a measured flow rate of the gas flow meter and a measured flow rate of the air flow meter becomes a predetermined target air ratio;
A threshold detection unit for detecting a low flow rate state in which the measured flow rate of at least one of the gas flow meter and the air flow meter is equal to or less than a predetermined ratio with respect to the maximum measurable flow rate;
When the threshold detection unit detects the low flow rate state, the measurement air ratio correction for correcting the measurement air ratio to a small value by a predetermined amount, or the target air for adjusting the predetermined target air ratio to a large value by a predetermined amount An air ratio correction unit that performs any one of the ratio adjustments is provided. A combustion control apparatus for a gas burner (claim 2).

According to a third aspect of the present invention, a gas pipe provided with a gas flow control valve and a gas flow meter and an air pipe provided with an air flow control valve and an air flow meter are connected, and the fuel gas and the air passing through the gas pipe are connected. A combustion control device equipped with a gas burner for burning combustion air passing through a pipe,
A fuel control unit for determining an opening of the gas flow rate control valve so as to achieve a target combustion amount required for the gas burner;
An air control unit for determining an opening of the air flow rate control valve so that a measured air ratio based on a measured flow rate of the gas flow meter and a measured flow rate of the air flow meter becomes a predetermined target air ratio;
A threshold detection unit for detecting a low flow rate state in which the measured flow rate of at least one of the gas flow meter and the air flow meter is equal to or less than a predetermined ratio with respect to the maximum measurable flow rate;
When the threshold detection unit detects the low flow rate state, a gas opening degree correction for correcting the opening degree of the gas flow rate control valve to a small opening degree by a predetermined amount, and the opening degree of the air flow rate control valve by a predetermined amount A combustion control device for a gas burner, comprising: an opening correction unit that performs at least one of air opening correction for correcting to a large opening.

According to a fourth aspect of the present invention, a gas pipe provided with a gas flow control valve and a gas flow meter and an air pipe provided with an air flow control valve and an air flow meter are connected, and the fuel gas and the air passing through the gas pipe are connected. A combustion control device equipped with a gas burner for burning combustion air passing through a pipe,
A fuel control unit for determining an opening of the gas flow rate control valve so as to achieve a target combustion amount required for the gas burner;
An air control unit for determining an opening of the air flow rate control valve so that a measured air ratio based on a measured flow rate of the gas flow meter and a measured flow rate of the air flow meter becomes a predetermined target air ratio;
A state where the target combustion amount is less than or equal to a predetermined combustion amount, a state where the opening degree of the gas flow rate adjustment valve is less than or equal to a predetermined opening degree, and an opening degree of the air flow rate adjustment valve is less than or equal to a predetermined opening degree. A threshold detection unit that detects any one or more of the states;
When the threshold detection unit detects one or more of the three states, a measurement gas flow correction for correcting the measurement flow rate of the gas flow meter to a large value by a predetermined amount, and a measurement of the air flow meter A combustion control apparatus for a gas burner, comprising: a measurement flow rate correction unit that performs at least one of measurement air flow rate corrections that correct a flow rate to a small value by a predetermined amount (Claim 4).

According to a fifth aspect of the present invention, a gas pipe provided with a gas flow control valve and a gas flow meter and an air pipe provided with an air flow control valve and an air flow meter are connected, and the fuel gas and the air passing through the gas pipe are connected. A combustion control device equipped with a gas burner for burning combustion air passing through a pipe,
A fuel control unit for determining an opening of the gas flow rate control valve so as to achieve a target combustion amount required for the gas burner;
An air control unit for determining an opening of the air flow rate control valve so that a measured air ratio based on a measured flow rate of the gas flow meter and a measured flow rate of the air flow meter becomes a predetermined target air ratio;
A state where the target combustion amount is less than or equal to a predetermined combustion amount, a state where the opening degree of the gas flow rate adjustment valve is less than or equal to a predetermined opening degree, and an opening degree of the air flow rate adjustment valve is less than or equal to a predetermined opening degree. A threshold detection unit that detects any one or more of the states;
When the threshold detection unit detects any one or more of the three states, the measurement air ratio correction for correcting the measurement air ratio to a value smaller by a predetermined amount, or the predetermined target air ratio by a predetermined amount The gas burner combustion control apparatus includes an air ratio correction unit that performs any one of the target air ratio adjustments adjusted to a large value.

According to a sixth aspect of the present invention, a gas pipe provided with a gas flow control valve and a gas flow meter and an air pipe provided with an air flow control valve and an air flow meter are connected, and the fuel gas and the air passing through the gas pipe are connected. A combustion control device equipped with a gas burner for burning combustion air passing through a pipe,
A fuel control unit for determining an opening of the gas flow rate control valve so as to achieve a target combustion amount required for the gas burner;
An air control unit for determining an opening of the air flow rate control valve so that a measured air ratio based on a measured flow rate of the gas flow meter and a measured flow rate of the air flow meter becomes a predetermined target air ratio;
A state where the target combustion amount is less than or equal to a predetermined combustion amount, a state where the opening degree of the gas flow rate adjustment valve is less than or equal to a predetermined opening degree, and an opening degree of the air flow rate adjustment valve is less than or equal to a predetermined opening degree. A threshold detection unit that detects any one or more of the states;
When the threshold detection unit detects one or more of the three states, a gas opening correction for correcting the opening of the gas flow control valve to a small opening by a predetermined amount, and the air flow control A gas burner combustion control device comprising: an opening correction unit that performs at least one of air opening correction that corrects the opening of the valve to a large opening by a predetermined amount (Claim 6).

In the combustion control device for a gas burner according to the first aspect of the present invention, combustion control is performed in a gas burner in which a gas pipe provided with a gas flow rate control valve and a gas flow meter and an air pipe provided with an air flow rate control valve and an air flow meter are connected. When performing, the device which prevents that the actual air ratio in a gas burner will become small when the flow volume of fuel gas or combustion air decreases is performed.
Specifically, the combustion control device of the present invention can perform the following combustion control by a configuration including a threshold value detection unit and a measured flow rate correction unit.
When combustion is performed in the gas burner, when the required load on the gas burner becomes small, the target combustion amount required for the gas burner becomes small, and the opening degree of the gas flow rate control valve is adjusted to be small by the fuel control unit. At this time, the opening degree of the air flow rate adjustment valve is also adjusted to be small by the air control unit so that the air ratio in the gas burner becomes a predetermined target air ratio. And each measurement flow rate by a gas flow meter and an air flow meter becomes small.

  In such a state, in the present invention, the threshold detector detects that the measured flow rate of at least one of the gas flow meter and the air flow meter is equal to or less than a predetermined ratio with respect to the maximum measurable flow rate of the flow meter. Detect as a low flow rate state. When the threshold detection unit detects a low flow rate state, the measurement flow rate correction unit corrects the measurement flow rate of the gas flow meter to a predetermined large value and the measurement flow rate of the air flow meter. At least one of the measurement air flow rate corrections for correcting the fixed amount to a small value is performed.

In other words, in the present invention, when an error that may occur in the measured flow rate indicated by the gas flow meter and the air flow meter becomes large in the low combustion region of the gas burner (low flow region of fuel gas and combustion air), The measurement flow rate of at least one of the gas flow meter and the air flow meter is corrected. As a result, it is possible to mitigate the fact that the actual air ratio in the gas burner becomes smaller than the predetermined target air ratio due to an error occurring in each flow meter.
Therefore, according to the combustion control device for the gas burner of the first invention, the generation amount of toxic gas such as carbon monoxide can be kept small in the low combustion region of the gas burner.

In the gas burner combustion control apparatus according to the second aspect of the invention, the air ratio correction unit corrects the measurement air ratio to a small value by a predetermined amount when the threshold detection unit detects a low flow rate state, or It differs from the first invention in that any one of the target air ratio adjustments for adjusting the predetermined target air ratio to a large value by a predetermined amount is performed. That is, in the present invention, instead of correcting the measured flow rates of the gas flow meter and the air flow meter, the measured air ratio is corrected or the target air ratio is adjusted. Thereby, in the low combustion area of the gas burner, it is possible to mitigate the fact that the actual air ratio in the burner becomes smaller than the intended air ratio due to an error occurring in each flow meter.
Therefore, the gas burner combustion control apparatus according to the second aspect of the invention can also maintain a small amount of toxic gas such as carbon monoxide in the low combustion region of the gas burner.

In the combustion control device for a gas burner according to a third aspect of the invention, when the threshold detection unit detects the low flow rate state, the opening correction unit corrects the opening of the gas flow control valve to a small opening by a predetermined amount. It differs from the first invention in that at least one of gas opening correction and air opening correction for correcting the opening of the air flow rate control valve to a predetermined large opening is performed. That is, in the present invention, instead of correcting the measured flow rates of the gas flow meter and the air flow meter, the opening degree of at least one of the gas flow rate control valve and the air control valve is corrected. As a result, in the low combustion region of the gas burner, it is possible to mitigate the fact that the actual air ratio in the burner becomes smaller than the predetermined target air ratio due to an error occurring in each flow meter.
Therefore, the gas burner combustion control apparatus according to the third aspect of the invention can also maintain a small amount of toxic gas such as carbon monoxide in the low combustion region of the gas burner.

  In a combustion control device for a gas burner according to a fourth aspect of the present invention, the threshold detector has a state in which the target combustion amount is not more than a predetermined combustion amount, a state in which the opening of the gas flow rate control valve is not more than a predetermined opening, The first aspect of the invention is that the measurement flow rate correction unit performs correction when detecting any one or more of the state in which the opening degree of the flow rate control valve is equal to or less than the predetermined opening degree. And different. Also in the present invention, other configurations are the same as those of the first invention, and the same effects as those of the first invention can be obtained.

  In a combustion control device for a gas burner according to a fifth aspect of the present invention, the threshold detector has a state in which the target combustion amount is not more than a predetermined combustion amount, a state in which the opening of the gas flow rate control valve is not more than a predetermined opening, The second aspect of the invention is that the air ratio correction unit performs correction when detecting any one or more of the state in which the opening degree of the flow rate control valve is equal to or less than the predetermined opening degree. And different. Also in the present invention, other configurations are the same as those of the second invention, and the same effects as those of the second invention can be obtained.

  In a combustion control device for a gas burner according to a sixth aspect of the present invention, the threshold detector has a state in which the target combustion amount is less than or equal to a predetermined combustion amount, a state in which the opening of the gas flow control valve is less than or equal to a predetermined opening, The third aspect of the invention is that the opening degree correction unit corrects when detecting any one or more of the state where the opening degree of the flow control valve is equal to or less than the predetermined opening degree. And different. Also in the present invention, other configurations are the same as those of the third invention, and the same effects as those of the third invention can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows the structure of the gas burner and combustion control apparatus concerning Example 1. FIG. 1 is a block diagram showing a configuration of a combustion control device according to Embodiment 1. FIG. About the differential pressure flowmeter according to Example 1, the horizontal axis represents the flow rate ratio, which is the ratio of the measured flow rate to the maximum measurable flow rate, and the vertical axis represents the lead error, showing the change in the maximum read error. . The graph which shows the change of the maximum read error of measurement air ratio which takes the combustion ratio which is a ratio of the combustion amount with respect to the maximum combustion amount of a gas burner on a horizontal axis, and takes a read error on a vertical axis | shaft concerning Example 1. FIG. According to the first embodiment, the horizontal axis represents the combustion ratio that is the ratio of the combustion amount to the maximum combustion amount of the gas burner, and the vertical axis represents the air ratio lead error, and the error range that the actual air ratio can take. Graph showing. FIG. 3 is a graph showing the relationship between the first embodiment, with the measured flow rate of the gas flow meter on the horizontal axis and the corrected measured flow rate after correcting the measured gas flow rate on the vertical axis. The graph which shows the flow volume range which can take the actual gas flow rate by taking the measurement flow volume of a gas flowmeter on the horizontal axis and taking the actual gas flow volume on the vertical axis according to the first embodiment. The graph which shows these relationship, taking the measurement flow volume of an air flowmeter concerning Example 1, and taking the correction | amendment measurement flow volume after performing measurement air flow rate correction | amendment to a vertical axis | shaft. The graph which shows the flow range which can take the actual air flow rate which takes the measurement flow volume of an air flowmeter on a horizontal axis | shaft and takes an actual air flow rate on a vertical axis | shaft concerning Example 1. FIG. FIG. 3 is a block diagram showing a configuration of a combustion control device according to a second embodiment. FIG. 6 is a block diagram showing a configuration of a combustion control device according to a third embodiment.

A preferred embodiment of the combustion control apparatus for a gas burner according to the first to sixth inventions described above will be described.
In the first to sixth aspects of the invention, the flow passage restricting portion refers to a restricting portion of a pipe, and can have various structures that make the flow passage cross-sectional area of the pipe smaller than other general parts. . The channel restricting portion can be, for example, an orifice, a venturi, a V cone, or the like.

In the first and third aspects of the invention, the measurement gas flow rate correction is performed by setting the full-scale error FS (%) of the gas flow meter to the ratio TD of the measured flow rate of the gas flow meter to the maximum measurable flow rate of the gas flow meter. Corresponding to the increase in read error RD (%) (= FS / TD) obtained by dividing by (−), the correction amount is increased as the measured flow rate of the gas flow meter decreases, and the measured air flow rate is increased. The correction is performed by dividing the full-scale error FS (%) of the air flow meter by a ratio TD (−) of the measured flow rate of the air flow meter to the maximum measurable flow rate of the air flow meter RD (−). %) (= FS / TD), the correction amount is preferably increased as the measured flow rate of the air flow meter decreases.
In this case, the measurement gas flow rate correction and the measurement air flow rate correction can be performed more appropriately.

In the second and fourth inventions, the correction of the measured air ratio and the adjustment of the target air ratio are performed by using the gas flow meter with respect to the maximum measurable flow rate of the gas flow meter. Corresponding to the increase in the read error RD (%) (= FS / TD) obtained by dividing by the measured flow rate ratio TD (−), the correction amount or adjustment amount becomes smaller as the measured flow rate of the gas flow meter becomes smaller. It is preferable to carry out by enlarging (Claim 8).
In this case, the measurement air ratio correction and the target air ratio adjustment can be performed more appropriately.

In the third and sixth aspects of the invention, the gas opening correction and the air opening correction may be performed by setting the full-scale error FS (%) of the gas flow meter to the maximum measurable flow rate of the gas flow meter. Corresponding to the increase in the read error RD (%) (= FS / TD) obtained by dividing by the measured flow rate ratio TD (−), the correction amount of the opening becomes smaller as the measured flow rate of the gas flow meter becomes smaller. It is preferable to carry out by enlarging (Claim 9).
In this case, the gas opening correction and the air opening correction can be performed more appropriately.

In the first to sixth inventions, the gas flow meter and the air flow meter are differential pressure flow meters that measure a flow rate from a differential pressure between an upstream pressure and a downstream pressure of the flow restrictor. (Claim 10).
In this case, an error generated when the differential pressure flow meter is used can be corrected, and the generation amount of toxic gas such as carbon monoxide can be kept small in the low combustion region of the gas burner.

Embodiments of a combustion control apparatus for a gas burner according to the present invention will be described below with reference to the drawings.
Example 1
FIG. 1 shows the configuration of the gas burner 1 and the combustion control device 5.
As shown in FIG. 1, the combustion control device 5 of the gas burner 1 of this example includes a gas pipe 21 provided with a gas flow rate control valve 31 and a gas flow meter 41, and an air provided with an air flow rate control valve 32 and an air flow meter 42. A pipe 22 is connected to the gas burner 1 for burning the fuel gas G passing through the gas pipe 21 and the combustion air A passing through the air pipe 22.
The combustion control device 5 includes the following fuel control unit 51, air control unit 52, threshold detection unit 53, and measured flow rate correction unit 54.

FIG. 2 shows a control block diagram of the combustion control device 5.
As shown in the figure, the fuel control unit 51 is configured to determine the opening of the gas flow rate control valve 31 so as to achieve a target combustion amount (target gas flow rate) Qgr required for the gas burner 1. The air control unit 52 adjusts the opening of the air flow control valve 32 so that the measured air ratio αm based on the measured flow rate Qgm of the gas flow meter 41 and the measured flow rate Qam of the air flow meter 42 becomes a predetermined target air ratio αr. decide. The threshold detector 53 detects a low flow rate state X in which the measured flow rate Qgm of the gas flow meter 41 is equal to or less than a predetermined ratio with respect to the maximum measurable flow rate of the gas flow meter 41.
The measurement flow rate correction unit 54 includes a measurement gas flow rate correction Hg for correcting the measurement flow rate Qgm indicated by the gas flow meter 41 to a large value by a predetermined amount when the threshold detection unit 53 detects the low flow rate state X, and an air flow meter. A measurement air flow rate correction Ha for correcting the measurement flow rate Qam indicated by 42 to a value smaller by a predetermined amount is performed.

Hereinafter, the combustion control device 5 of the gas burner 1 of this example will be described in detail with reference to FIGS.
As shown in FIGS. 1 and 2, the gas burner 1 of this example is used by being disposed in a combustion furnace 11 such as a heating furnace or a heat treatment furnace, and the temperature T in the combustion furnace 11 is set to a predetermined target temperature Tr. Used to maintain. The combustion furnace 11 is provided with a thermometer 12, and the combustion control device 5 controls the temperature T in the combustion furnace 11 measured by the thermometer 12 to be a predetermined target temperature Tr. This control can be performed by so-called PID control or the like.
A blower 221 that sucks air from the atmosphere and sends it out to the air pipe 22 is disposed at the inlet of the air pipe 22. In addition to the air flow rate adjustment valve 32 and the air flow meter 42, the air pipe 22 is provided with an air thermometer 222. The air thermometer 222 is used to correct variations due to the temperature of the combustion air A in calculating the measurement air ratio αm.

As shown in FIG. 1, the gas pipe 21 is connected to a supply source 211 for city gas (such as 13A). In addition to the gas flow control valve 31 and the gas flow meter 41, the gas pipe 21 is provided with a gas thermometer 213. The gas thermometer 213 is used to correct variations due to the temperature of the fuel gas G in calculating the measurement air ratio αm. The gas pipe 21 can be provided with a safety shut-off valve 212.
The combustion control device 5 of this example is configured by a control computer, and the fuel control unit 51, the air control unit 52, the threshold value detection unit 53, and the measured flow rate correction unit 54 are configured as a program of the control computer.

As shown in FIG. 2, the target combustion amount Qgr required for the gas burner 1 is determined by the controller K as a combustion amount when the temperature T in the combustion furnace 11 is maintained at the target temperature Tr. The opening degree of the gas flow rate control valve 31 is changed according to a target combustion amount Qgr determined according to a temperature change in the combustion furnace 11 by the thermometer 12.
The temperature controller K determines the target combustion amount Qgr so that the deviation between the target temperature Tr and the temperature T in the combustion furnace 11 measured by the thermometer 12 becomes zero. Further, the gas control unit 51 operates the gas flow rate control valve 31 with the controller Kg so that the deviation between the target combustion amount (target gas flow rate) Qgr and the gas flow rate Qgm measured with the gas flow meter 41 becomes zero. To do.

The air control unit 52 can obtain the measured air ratio αm from the measured flow rate Qgm of the gas flow meter 41 and the measured flow rate Qam of the air flow meter 42. This measured air ratio αm is the theoretical air when the amount of combustion air A at the measured flow rate Qam measured by the air flow meter 42 completely burns the amount of the fuel gas G at the measured flow rate Qgm measured by the gas flow meter 41. Shows how many times the amount.
In this example, as shown in FIG. 2, the air flow rate calculation unit I obtains the target air flow rate Qar when the target air ratio αr is achieved based on the measured flow rate Qgm of the gas flow meter 41. Then, the air control unit 52 operates the air flow rate adjustment valve 32 with the controller Ka so that the deviation between the target air flow rate Qar and the air flow rate Qam measured with the air flow meter 42 becomes zero.

The predetermined target air ratio αr is set to a predetermined value (constant value) as an air ratio that can prevent misfire and prevent generation of toxic gases such as carbon monoxide. And the air control part 52 of this example adjusts the opening degree of the air flow control valve 32 so that the air ratio by the fuel gas G supplied to the gas burner 1 and the combustion air A becomes constant.
Since the air control unit 52 of this example controls the target air ratio αr to be a constant value, the measured flow rate Qam by the air flow meter 42 increases or decreases in proportion to the measured flow rate Qgm by the gas flow meter 41.

As shown in FIG. 1, the gas flow meter 41 of this example is a differential pressure flow meter that measures the flow rate from the differential pressure between the upstream side pressure and the downstream side pressure of the flow restrictor 210 provided in the gas pipe 21. is there. The air flow meter 42 is also a differential pressure flow meter that measures the flow rate from the differential pressure between the pressure on the upstream side and the pressure on the downstream side of the flow restrictor 220 provided in the air pipe 22.
Each differential pressure flow meter has a full scale error which is the ratio of the error to the maximum measurable flow rate. This full-scale error is expressed as ± 0.1 to 2%, for example. Each differential pressure flowmeter of this example was used with a full-scale error of ± 0.2%.
On the other hand, when the flow rate is actually measured by the differential pressure flow meter, the ratio of the full-scale error to the flow rate increases as the flow rate measurement value decreases. For this reason, an error that may occur during actual flow rate measurement is expressed as a read error (reading error) that increases as the flow rate measurement value decreases.

  FIG. 3 shows the flow rate ratio (%), which is the ratio of the measured flow rate to the maximum measurable flow rate, on the horizontal axis, and the read error on the vertical axis. Change). The lead error of the differential pressure flow meter is arbitrarily changed between the plus side and the minus side line L1. In the figure, the case where the full scale error is ± 0.1%, ± 0.2%, ± 0.5% is shown. It can be seen that the read error increases exponentially as the flow rate ratio decreases from the plus side to the minus side. It can also be seen that the read error tends to increase as the full-scale error increases.

  FIG. 4 shows the measured air ratio αm measured by the gas flow meter 41 and the air flow meter 42 constituted by a differential pressure flow meter when the full-scale error of each flow meter 41, 42 is ± 0.2%. The change in the maximum read error (indicated by line L2) of the air ratio αm is shown. The lead error of the measurement air ratio αm is arbitrarily changed between the plus side and the minus side line L2.

In the figure, the horizontal axis indicates the combustion ratio (flow rate ratio) (%) that is the ratio of the combustion amount (measured flow rate of the gas flow meter 41) to the maximum combustion amount of the gas burner 1 (maximum measurable flow rate of the gas flow meter 41). ) And the vertical axis represents the lead error, and shows the change in the maximum lead error of the measured air ratio αm. In the figure, the gas flow meter 41 measures the maximum flow rate (100%) of the fuel gas G supplied to the gas pipe 21 at the maximum measurable flow rate, and the air flow meter 42 measures the maximum measurable flow rate. , It is assumed that the maximum flow rate (100%) of the combustion air A supplied to the air pipe 22 is measured.
As shown in the figure, the lead error of the measured air ratio αm is a value obtained by superimposing the lead error of the gas flow meter 41 and the lead error of the air flow meter 42 on the plus side and the minus side, respectively.

For the lead error RD (%), a full-scale error FS (%) and a ratio TD (−) (also referred to as TD (%)) of the measured flow rate (combustion amount) to the maximum measurable flow rate (maximum combustion amount) are used. RD (%) = FS (%) / TD (−).
Further, the ratio TD (%) of the measured flow rate with respect to the maximum measurable flow rate of the gas flow meter 41 means a predetermined ratio with respect to the maximum measurable flow rate of the gas flow meter 41 used in the threshold detection unit 53.

In this example, in order to suppress the generation of toxic gas such as carbon monoxide, it is prevented that the actual air ratio α in the gas burner 1 is swung in a small direction due to an error generated in each differential pressure flow meter 41, 42. To do. The factor that the actual air ratio α is swung in the smaller direction is that the measured air ratio αm obtained based on the differential pressure flow meters 41 and 42 is larger than the actual value, and the air flow control valve 32 is opened. The supply amount of the combustion air A to the gas burner 1 by adjusting the degree is reduced.
In other words, in the control block of this example (FIG. 2), a negative error smaller than the actual flow rate occurs in the measured flow rate Qgm by the gas flow meter 41, and the air flow rate calculation unit I sets the measured flow rate Qgm in which this negative error has occurred. Based on this, the target air flow rate Qar when the target air ratio αr is achieved is obtained, and further, a positive error larger than the actual flow rate occurs in the measured flow rate Qam by the air flow meter 42.

  Further, the case where the actual air ratio α in the gas burner 1 is swung in the smallest direction is the case where the measured air ratio αm is calculated to be the largest. In this case, the gas flow meter 41 has a negative error indicating that the measured flow rate Qgm is smaller than the actual flow rate. In the air flow meter 42, the measured flow rate Qam has a larger value than the actual flow rate. This is a case where a plus error shown occurs.

Therefore, in the combustion control device 5 of this example, when the flow rate of the fuel gas G measured by the gas flow meter 41 is equal to or lower than a predetermined low flow rate, normal control for bringing the measured air ratio αm closer to the target air ratio αr is performed. Then, the control is switched to the low flow rate control in which the actual air ratio α in the gas burner 1 is shifted in the increasing direction.
The flow rate of the fuel gas G at the time of this switching is determined based on the allowable lower limit air ratio αz that is allowed as the generation amount of toxic gases such as carbon monoxide when the actual air ratio α fluctuates in a small direction. To do. This allowable lower limit air ratio αz is expressed as an allowable maximum error −E (%) with respect to the target air ratio αr.

The maximum negative lead error −F (%) of the actual air ratio α is obtained by using the lead error RDg (%) generated in the gas flow meter 41 and the lead error RDa (%) generated in the air flow meter 42 − F (%) = {(100−RDg) / (100 + RDa) −1} × 100.
Further, the maximum lead error + F (%) on the positive side of the actual air ratio α is obtained by using the lead error RDg (%) generated in the gas flow meter 41 and the lead error RDa (%) generated in the air flow meter 42. + F (%) = {(100 + RDg) / (100−RDa) −1} × 100.
In this example, the same differential pressure flow meter is used for the gas flow meter 41 and the air flow meter 42, and the full-scale error between the gas flow meter 41 and the air flow meter 42 is the same. Therefore, RDg (%) and RDa (%) at a predetermined measurement flow rate of each flow meter 41, 42 have the same value.

  The threshold value detection unit 53 of the present example is such that the negative maximum read error of the actual air ratio α (the maximum read error that may cause the actual air ratio α to shift to the negative side) −F (%) is the target air ratio. The low flow rate state X is detected from the flow rate ratio TD (%) (predetermined rate with respect to the maximum measurable flow rate of the gas flow meter 41) when the allowable lower limit air ratio αz with respect to αr is equal to the allowable maximum error −E (%). The flow rate ratio threshold TDx (%) is set. Further, the maximum read error -F (%) at this time is defined as a read error threshold -Fx (%).

In the range X0 in which the flow rate ratio threshold TDx (%) measured by the gas flow meter 41 exceeds 20%, the gas flow meter does not perform the measurement gas flow rate correction Hg and the measurement air flow rate correction Ha by the measurement flow rate correction unit 54. In the range X where the flow rate ratio threshold value TDx (%) measured by 41 is 20% or less, the measurement gas flow rate correction Hg and the measurement air flow rate correction Ha are performed by the measurement flow rate correction unit 54.
The full-scale error FS of the differential pressure flow meter used for the gas flow meter 41 and the air flow meter 42 of this example is ± 0.2%, and each flow meter 41, 42 has a maximum of 0.2% on the plus side. And an error of 0.2% at the maximum on the minus side.

  The operation of the air flow control valve 32 in the air control unit 52 is performed so that the measured air ratio αm obtained from the measured flow rates Qgm and Qam by the gas flow meter 41 and the air flow meter 42 becomes the target air ratio αr. Therefore, when the measured air ratio αm has a positive maximum read error, the actual air ratio α has a negative maximum read error.

In FIG. 5, the horizontal axis shows the combustion ratio (flow rate ratio) TD (%) which is the ratio of the combustion amount (measured flow rate of the gas flow meter 41) to the maximum combustion amount of the gas burner 1 (maximum measurable flow rate of the gas flow meter 41). ), And the vertical axis represents the air ratio lead error (%), and the actual air ratio α plus and minus maximum lead error F (%) and the allowable lower limit air ratio αz allowable maximum error − E (%) and the error range αe that the actual air ratio α can take after correction are shown.
In this example, the allowable maximum error −E (%) of the allowable lower limit air ratio αz with respect to the target air ratio αr is set to −5%.
When the maximum negative error (−0.2%) in the full scale error occurs in the gas flow meter 41 and the maximum positive error (+ 0.2%) in the full scale error occurs in the air flow meter 42, Reading was performed assuming that the flow rate ratio threshold value TDx (%) when the read error threshold value -Fx (%) is -5% is about 20%.

As shown in the figure, the measured gas flow rate correction Hg and the measured air flow rate correction Ha (see FIG. 2) by the measured flow rate correction unit 54 are the actual air ratio in the range X where the flow rate ratio threshold value TDx (%) is 20% or less. Correction is performed so that the maximum read error −F (%) on the minus side of α is not always smaller than −5%. In the range X in which the flow rate ratio threshold value TDx (%) is 20% or less, the corrected target air ratio αr may occur on the negative side of the read error threshold value −Fx (%) at each flow rate ratio TD (%). The minute-Fe (TD) (%) is set to be higher than the target air ratio αr. The corrected target air ratio αr ′ (%) is calculated using αr ′ = (%) using the target air ratio αr (%) and the error amount −Fe (TD) (%) that varies depending on the flow rate ratio TD (%). 100 + Fe (TD)) / 100 × αr.
Further, in the range X0 where the flow rate ratio threshold value TDx (%) exceeds 20%, the actual air ratio α in the gas burner 1 is controlled to become the target air ratio αr. In this range X0, the target air ratio αr is not corrected as ± 0%.

  FIG. 6 shows the relationship between the measured flow rate Qgm of the gas flow meter 41 on the horizontal axis and the corrected measured flow rate Qgh after performing the measured gas flow rate correction Hg on the vertical axis. FIG. 7 shows a flow rate range Qge that the actual gas flow rate Qg can take after correction, with the measured flow rate Qgm of the gas flow meter 41 on the horizontal axis and the actual gas flow rate Qg on the vertical axis. The measured flow rate Qgm of the gas flow meter 41 is represented by a flow rate ratio (%) with respect to the maximum measurable flow rate, where the maximum measurable flow rate is 100%.

  In this example, as shown in FIG. 6, in the low flow rate state X where the flow rate ratio threshold TDx (%) is 20% or less, the measured flow rate Qgm indicated by the gas flow meter 41 decreases as the measured gas flow rate correction Hg. Shift to the plus side to correct. Accordingly, as shown in FIG. 7, in the low flow rate state X where the flow rate ratio threshold value TDx (%) is 20% or less, the flow rate range Qge that the actual gas flow rate Qg can take after the correction becomes smaller as the measured flow rate Qgm decreases. The gas flow rate adjustment valve 31 is adjusted by shifting to the minus side, which is the direction in which the opening degree is reduced.

  The measured gas flow rate correction Hg of this example is obtained by dividing the full-scale error FS (%) of the gas flow meter 41 by the ratio TD (−) of the measured flow rate to the maximum measurable flow rate of the gas flow meter 41. Corresponding to the increase in the read error RD (%) (= FS / TD), the correction amount is increased as the measured flow rate of the gas flow meter 41 decreases. In the low flow rate state X in which the flow rate ratio threshold value TDx (%) is 20% or less, there is an error on the negative side than the negative read error threshold value when the flow rate ratio threshold value TDx (%) is 20%. It is corrected to the plus side so that there is no.

  FIG. 8 shows the relationship between the measured flow rate Qam of the air flow meter 42 on the horizontal axis and the corrected measured flow rate Qah after performing the measured air flow rate correction Ha on the vertical axis. FIG. 9 shows the flow rate range Qae that the actual air flow rate Qa can take after correction, with the measured flow rate Qam of the air flow meter 42 on the horizontal axis and the actual air flow rate Qa on the vertical axis. The measured flow rate Qam of the air flow meter 42 is represented by a flow rate ratio (%) with respect to the maximum measurable flow rate, where the maximum measurable flow rate is 100%.

  In this example, as shown in FIG. 8, in the low flow rate state X in which the flow rate ratio threshold value TDx (%) is 20% or less, the measured flow rate Qam indicated by the air flow meter 42 decreases as the measured air flow rate correction Ha. Shift to the minus side to correct. Accordingly, as shown in FIG. 9, in the low flow rate state X in which the flow rate ratio threshold value TDx (%) is 20% or less, the flow rate range Qae that can be taken by the actual air flow rate Qa after correction is such that the measured flow rate Qam decreases. Adjustment is made by shifting to the plus side, which is the direction in which the opening of the air flow control valve 32 increases.

  The measured air flow rate correction Ha in this example is obtained by dividing the full-scale error FS (%) of the air flow meter 42 by the ratio TD (−) of the measured flow rate Qam to the maximum measurable flow rate of the air flow meter 42. Corresponding to the increase in the error RD (%) (= FS / TD), the correction amount is increased as the measured flow rate Qam of the air flow meter 42 decreases. In the low flow rate state X in which the flow rate ratio threshold value TDx (%) is 20% or less, an error on the plus side is larger than the read error threshold value on the plus side when the flow rate ratio threshold value TDx (%) is 20%. It is corrected to the plus side so that it does not have.

The low flow rate state X in the threshold detection unit 53 is not only detected when the measured flow rate of the gas flow meter 41 falls below a predetermined ratio with respect to the maximum measurable flow rate, but the measured flow rate of the air flow meter 42 can be measured. It is also possible to detect when the ratio is equal to or less than a predetermined ratio with respect to the maximum flow rate. It can also be detected when both the measured flow rate of the gas flow meter 41 and the measured flow rate of the air flow meter 42 are equal to or less than a predetermined ratio.
Since the air control unit 52 of this example controls the air ratio supplied to the gas burner 1 to be constant except when performing the low flow rate control in the low flow rate state X, the flow rate of the fuel gas G and the flow rate of the air Are proportional. Therefore, the combustion control device 5 can similarly switch the control of the air ratio regardless of whether the measured flow rate Qgm of the gas flow meter 41 or the measured flow rate Qam of the air flow meter 42 is used.

Further, instead of detecting the low flow rate state X when the measured flow rate Qgm of the gas flow meter 41 is equal to or less than a predetermined ratio with respect to the maximum measurable flow rate, the threshold detection unit 53 sets the target combustion amount to be equal to or less than the predetermined combustion amount. Or one of a state in which the opening degree of the gas flow rate adjustment valve 31 is equal to or less than a predetermined opening degree and a state in which the opening degree of the air flow rate adjustment valve 32 is equal to or less than the predetermined opening degree. can do. The measurement flow rate correction unit 54 performs at least one of the measurement gas flow rate correction Hg and the measurement air flow rate correction Ha when the threshold detection unit 53 detects any one or more of the three states. Can do.
In the control of the air ratio in the combustion control device 5, the measured flow rate Qgm of the gas flow meter 41, the measured flow rate Qam of the air flow meter 42, the target combustion amount, the opening of the gas flow rate control valve 31, and the opening of the air flow rate control valve 32 All degrees are closely related. Therefore, the read error threshold value −Fx (%) for switching control can be determined in the same manner using any of these.

Next, the effect of the combustion control apparatus 5 of this example is demonstrated.
In the combustion control device 5 of this example, when the combustion control in the gas burner 1 is performed, when the flow rate of the fuel gas G or the combustion air A decreases, the actual air ratio α in the gas burner 1 becomes small. We are trying to prevent this.
Specifically, the combustion control device 5 of the present example can perform the next combustion control by the configuration including the threshold detection unit 53 and the measured flow rate correction unit 54.
When combustion is performed in the gas burner 1, if the required load on the gas burner 1 becomes small, the target combustion amount required for the gas burner 1 becomes small, and the opening degree of the gas flow control valve 31 is adjusted to be small by the fuel control unit 51. Is done. At this time, the opening degree of the air flow rate adjustment valve 32 is also adjusted to be small by the air control unit 52 so that the air ratio α in the gas burner 1 becomes a predetermined target air ratio αr. And each measurement flow volume Qgm and Qam by the gas flow meter 41 and the air flow meter 42 becomes small.

  In this state, in this example, the threshold detection unit 53 detects that the measured flow rate Qgm of the gas flow meter 41 is equal to or less than a predetermined ratio with respect to the maximum measurable flow rate of the flow meter as the low flow rate state X. To do. When the threshold detection unit 53 detects the low flow rate state X, the measurement flow rate correction unit 54 corrects the measurement flow rate Qgm of the gas flow meter 41 to a large value by a predetermined amount, and the air flow rate. A measurement air flow rate correction Ha for correcting the measurement flow rate Qam of the total 42 to a value smaller by a predetermined amount is performed.

That is, in this example, in the low combustion region of the gas burner 1 (low flow region of the fuel gas G and combustion air A), a lead error that may occur in the measured flow rates Qgm and Qam indicated by the gas flow meter 41 and the air flow meter 42. Is intentionally corrected, the measured flow rates Qgm and Qam of the gas flow meter 41 and the air flow meter 42 are corrected. As a result, it is possible to mitigate the fact that the actual air ratio α in the gas burner 1 becomes smaller than the predetermined target air ratio αr due to the lead error generated in the flow meters 41 and 42.
Therefore, according to the combustion control device 5 of the gas burner 1 of this example, the generation amount of toxic gases such as carbon monoxide can be kept small in the low combustion region of the gas burner 1.

(Example 2)
In this example, as shown in FIG. 10, when the threshold detection unit 53 shown in the first embodiment detects the low flow rate state X, instead of performing the correction by the measured flow rate correction unit 54, the air ratio correction unit 55 is an example of performing the measurement air ratio correction Hα for correcting the measurement air ratio αm to a value smaller by a predetermined amount.
In this example, instead of correcting the measured flow rates Qgm and Qam of the gas flow meter 41 and the air flow meter 42, the measured air ratio αm is directly corrected. The measured air ratio αm is obtained from the measured flow rates Qgm and Qam of the gas flow meter 41 and the air flow meter 42, and is substantially the same as that of the first embodiment by directly correcting the measured air ratio αm. Correction can be performed.

  As shown in the figure, in this example, the air ratio calculation unit J obtains the measurement air ratio αm from each measurement flow rate Qgm, Qam, and the measurement is performed when the measurement flow rate Qgm of the gas flow meter 41 is in the low flow rate state X. The air ratio αm is corrected by the same method as in FIG. The air flow rate calculation unit I then obtains the target air flow rate Qar from the corrected measured air ratio αm ′.

In the combustion control device 5 of this example, the measured air ratio correction Hα is the ratio TD (−) of the measured flow rate Qgm to the maximum measurable flow rate of the gas flow meter 41 with the full scale error FS (%) of the gas flow meter 41. Corresponding to the increase in the read error RD (%) (= FS / TD) obtained by division, the correction amount can be increased as the measured flow rate Qgm of the gas flow meter 41 decreases.
The air ratio correction unit 55 can also perform target air ratio adjustment that adjusts the predetermined target air ratio αr to a value larger by a predetermined amount instead of performing the measurement air ratio correction Hα. In this case, the corrected target air ratio αr ′ can be obtained in the same manner as in FIG. Also in this case, substantially the same correction as in the first embodiment can be performed.
Also in this example, other configurations are the same as those of the first embodiment, and the same effects as those of the first embodiment can be obtained.

(Example 3)
In this example, as shown in FIG. 11, when the threshold detection unit 53 shown in the first embodiment detects the low flow rate state X, instead of performing correction by the measured flow rate correction unit 54, an opening degree correction unit 56, a gas opening degree correction Sg for correcting the opening degree of the gas flow rate adjusting valve 31 to a small opening amount by a predetermined amount, and an air opening degree correction Sa for correcting the opening degree of the air flow rate adjusting valve 32 to a large opening amount by a predetermined amount. Do.
In this example, instead of correcting the measured flow rates Qgm and Qam of the gas flow meter 41 and the air flow meter 42, the opening degree of the gas flow rate adjustment valve 31 and the opening degree of the air flow rate adjustment valve 32 are corrected. The amount for correcting the opening is an amount for changing the actual air ratio α in the same manner as in the first embodiment. Also in this example, substantially the same correction as in the first embodiment can be performed.
As shown in the figure, in this example, as in FIG. 2 of the first embodiment, in the air flow rate calculation unit I, when the target air ratio αr is achieved based on the measured flow rate Qgm of the gas flow meter 41. A target air flow rate Qar is obtained.

Further, in the combustion control device 5 of the present example, the gas opening degree correction Sg and the air opening degree correction Sa are used to measure the full scale error FS (%) of the gas flow meter 41 and the measured flow rate with respect to the maximum measurable flow rate of the gas flow meter 41. Corresponding to the increase in the read error RD (%) (= FS / TD) obtained by dividing by the ratio TD (−) of Qgm, the correction amount of the opening increases as the measured flow rate Qgm of the gas flow meter 41 decreases. Can be done.
Also in this example, other configurations are the same as those of the first embodiment, and the same effects as those of the first embodiment can be obtained.

DESCRIPTION OF SYMBOLS 1 Gas burner 11 Combustion furnace 21 Gas piping 22 Air piping 31 Gas flow control valve 32 Air flow control valve 41 Gas flow meter 42 Air flow meter 5 Combustion control device 51 Fuel control unit 52 Air control unit 53 Threshold detection unit 54 Measurement flow rate correction unit A Combustion air G Fuel gas

Claims (10)

Combustion gas passing through the gas pipe and the fuel pipe passing through the gas pipe by connecting the gas pipe provided with the gas flow control valve and the gas flow meter and the air pipe provided with the air flow control valve and the air flow meter. A combustion control device equipped for a gas burner that burns air,
A fuel control unit for determining an opening of the gas flow rate control valve so as to achieve a target combustion amount required for the gas burner;
An air control unit for determining an opening of the air flow rate control valve so that a measured air ratio based on a measured flow rate of the gas flow meter and a measured flow rate of the air flow meter becomes a predetermined target air ratio;
A threshold detection unit for detecting a low flow rate state in which the measured flow rate of at least one of the gas flow meter and the air flow meter is equal to or less than a predetermined ratio with respect to the maximum measurable flow rate;
When the threshold detection unit detects the low flow rate state, the measurement gas flow rate correction for correcting the measurement flow rate of the gas flow meter to a large value by a predetermined amount, and the measurement flow rate of the air flow meter to a small value by a predetermined amount A combustion control device for a gas burner, comprising: a measurement flow rate correction unit that performs at least one of measurement air flow rate correction to be corrected. Combustion gas passing through the gas pipe and the fuel pipe passing through the gas pipe by connecting the gas pipe provided with the gas flow control valve and the gas flow meter and the air pipe provided with the air flow control valve and the air flow meter. A combustion control device equipped for a gas burner that burns air,
A fuel control unit for determining an opening of the gas flow rate control valve so as to achieve a target combustion amount required for the gas burner;
An air control unit for determining an opening of the air flow rate control valve so that a measured air ratio based on a measured flow rate of the gas flow meter and a measured flow rate of the air flow meter becomes a predetermined target air ratio;
A threshold detection unit for detecting a low flow rate state in which the measured flow rate of at least one of the gas flow meter and the air flow meter is equal to or less than a predetermined ratio with respect to the maximum measurable flow rate;
When the threshold detection unit detects the low flow rate state, the measurement air ratio correction for correcting the measurement air ratio to a small value by a predetermined amount, or the target air for adjusting the predetermined target air ratio to a large value by a predetermined amount An air ratio correction unit that performs any one of the ratio adjustments. Combustion gas passing through the gas pipe and the fuel pipe passing through the gas pipe by connecting the gas pipe provided with the gas flow control valve and the gas flow meter and the air pipe provided with the air flow control valve and the air flow meter. A combustion control device equipped for a gas burner that burns air,
A fuel control unit for determining an opening of the gas flow rate control valve so as to achieve a target combustion amount required for the gas burner;
An air control unit for determining an opening of the air flow rate control valve so that a measured air ratio based on a measured flow rate of the gas flow meter and a measured flow rate of the air flow meter becomes a predetermined target air ratio;
A threshold detection unit for detecting a low flow rate state in which the measured flow rate of at least one of the gas flow meter and the air flow meter is equal to or less than a predetermined ratio with respect to the maximum measurable flow rate;
When the threshold detection unit detects the low flow rate state, a gas opening degree correction for correcting the opening degree of the gas flow rate control valve to a small opening degree by a predetermined amount, and the opening degree of the air flow rate control valve by a predetermined amount A gas burner combustion control device comprising: an opening correction unit that performs at least one of air opening correction for correcting to a large opening. Combustion gas passing through the gas pipe and the fuel pipe passing through the gas pipe by connecting the gas pipe provided with the gas flow control valve and the gas flow meter and the air pipe provided with the air flow control valve and the air flow meter. A combustion control device equipped for a gas burner that burns air,
A fuel control unit for determining an opening of the gas flow rate control valve so as to achieve a target combustion amount required for the gas burner;
An air control unit for determining an opening of the air flow rate control valve so that a measured air ratio based on a measured flow rate of the gas flow meter and a measured flow rate of the air flow meter becomes a predetermined target air ratio;
A state where the target combustion amount is less than or equal to a predetermined combustion amount, a state where the opening degree of the gas flow rate adjustment valve is less than or equal to a predetermined opening degree, and an opening degree of the air flow rate adjustment valve is less than or equal to a predetermined opening degree. A threshold detection unit that detects any one or more of the states;
When the threshold detection unit detects one or more of the three states, a measurement gas flow correction for correcting the measurement flow rate of the gas flow meter to a large value by a predetermined amount, and a measurement of the air flow meter A combustion control device for a gas burner, comprising: a measurement flow rate correction unit that performs at least one of measurement air flow rate corrections that correct the flow rate to a predetermined small value. Combustion gas passing through the gas pipe and the fuel pipe passing through the gas pipe by connecting the gas pipe provided with the gas flow control valve and the gas flow meter and the air pipe provided with the air flow control valve and the air flow meter. A combustion control device equipped for a gas burner that burns air,
A fuel control unit for determining an opening of the gas flow rate control valve so as to achieve a target combustion amount required for the gas burner;
An air control unit for determining an opening of the air flow rate control valve so that a measured air ratio based on a measured flow rate of the gas flow meter and a measured flow rate of the air flow meter becomes a predetermined target air ratio;
A state where the target combustion amount is less than or equal to a predetermined combustion amount, a state where the opening degree of the gas flow rate adjustment valve is less than or equal to a predetermined opening degree, and an opening degree of the air flow rate adjustment valve is less than or equal to a predetermined opening degree. A threshold detection unit that detects any one or more of the states;
When the threshold detection unit detects any one or more of the three states, the measurement air ratio correction for correcting the measurement air ratio to a value smaller by a predetermined amount, or the predetermined target air ratio by a predetermined amount An air ratio correction unit that performs any one of the target air ratio adjustments adjusted to a large value. Combustion gas passing through the gas pipe and the fuel pipe passing through the gas pipe by connecting the gas pipe provided with the gas flow control valve and the gas flow meter and the air pipe provided with the air flow control valve and the air flow meter. A combustion control device equipped for a gas burner that burns air,
A fuel control unit for determining an opening of the gas flow rate control valve so as to achieve a target combustion amount required for the gas burner;
An air control unit for determining an opening of the air flow rate control valve so that a measured air ratio based on a measured flow rate of the gas flow meter and a measured flow rate of the air flow meter becomes a predetermined target air ratio;
A state where the target combustion amount is less than or equal to a predetermined combustion amount, a state where the opening degree of the gas flow rate adjustment valve is less than or equal to a predetermined opening degree, and an opening degree of the air flow rate adjustment valve is less than or equal to a predetermined opening degree. A threshold detection unit that detects any one or more of the states;
When the threshold detection unit detects one or more of the three states, a gas opening correction for correcting the opening of the gas flow control valve to a small opening by a predetermined amount, and the air flow control A combustion control apparatus for a gas burner, comprising: an opening correction unit that performs at least one of air opening correction for correcting the opening of the valve to a large opening by a predetermined amount. 5. The combustion control apparatus for a gas burner according to claim 1 or 4, wherein the measurement gas flow rate correction is performed by calculating the full-scale error FS (%) of the gas flow meter with respect to the maximum measurable flow rate of the gas flow meter. Corresponding to the increase in read error RD (%) (= FS / TD) obtained by dividing by the measured flow rate ratio TD (−), the correction amount is increased as the measured flow rate of the gas flow meter decreases. Done
The measured air flow rate correction is obtained by dividing the full-scale error FS (%) of the air flow meter by the ratio TD (-) of the measured flow rate of the air flow meter to the maximum measurable flow rate of the air flow meter. A combustion control apparatus for a gas burner characterized in that the correction amount is increased as the measured flow rate of the air flow meter decreases in response to an increase in the lead error RD (%) (= FS / TD).   6. The combustion control apparatus for a gas burner according to claim 2 or 5, wherein the measurement air ratio correction and the target air ratio adjustment are performed by measuring a full-scale error FS (%) of the gas flow meter as a maximum measurable value of the gas flow meter. Corresponding to the increase in the read error RD (%) (= FS / TD) obtained by dividing by the ratio TD (-) of the measured flow rate of the gas flow meter to the flow rate, the measured flow rate of the gas flow meter decreases. A combustion control device for a gas burner, wherein the correction amount or adjustment amount is increased.   7. The gas burner combustion control apparatus according to claim 3, wherein the gas opening correction and the air opening correction are performed by measuring a full-scale error FS (%) of the gas flow meter as a maximum measurable value of the gas flow meter. Corresponding to the increase in the read error RD (%) (= FS / TD) obtained by dividing by the ratio TD (-) of the measured flow rate of the gas flow meter to the flow rate, the measured flow rate of the gas flow meter decreases. A combustion control device for a gas burner, characterized in that the correction is performed with a large opening correction amount.   The combustion control device for a gas burner according to any one of claims 1 to 9, wherein the gas flow meter and the air flow meter are a differential pressure between an upstream pressure and a downstream pressure of the flow restrictor. A combustion control device for a gas burner, characterized by being a differential pressure flow meter for measuring a flow rate from

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