JP6375927B2 - Gas fired boiler - Google Patents

Description

  The present invention relates to a gas-fired boiler, and more particularly to a gas-fired boiler capable of determining the presence or absence of gas leakage through a fuel control valve.

  Conventionally, a boiler provided with a gas sensor is known. For example, the boiler of Patent Document 1 includes a gas sensor that detects the concentration of carbon monoxide, carbon dioxide, oxygen, or nitrogen oxide contained in exhaust gas. Then, the gas sensor is controlled to detect the presence or absence of incomplete combustion gas in the can, and the presence or absence of incomplete combustion of the burner is determined based on the detection result.

JP 2012-145523 A

  The gas-fired boiler combusts fuel gas with a burner and discharges exhaust gas from the inside of the can, and includes a fuel control valve that controls fuel gas supply to the burner. When the fuel control valve is closed, the fuel gas supply to the burner is shut off, and the combustion of the burner is stopped. By the way, when the valve is closed, a gas leakage from the fuel control valve to the burner may occur, and it has been desired to accurately determine the gas leakage through the valve.

  However, when the combustion of the burner is stopped, there is a possibility that exhaust gas generated by the combustion of the burner may remain in the can, and this exhaust gas is caused by leakage of the gas through the valve from the fuel control valve when the valve is closed. There was a risk of erroneous detection as a leaked fuel gas. For this reason, there is a possibility that the presence or absence of gas leakage through the valve when the fuel control valve is closed is erroneously determined.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a gas-fired boiler capable of accurately determining the presence or absence of gas leakage through the valve when the fuel control valve is closed.

  The present invention is a gas-fired boiler configured to burn fuel gas in a can with a burner and discharge exhaust gas from the can, and an air supply means for supplying air to the can, Fuel supply means having a fuel control valve for controlling fuel gas supply to the burner, a gas sensor for detecting a detection target gas including fuel gas and exhaust gas in the can body, and the can from the fuel control valve when the valve is closed And an over-gas leak judging means for judging whether there is a gas leak through the valve leaking into the body, wherein the over-gas leak judgment means is the first scavenging in the can body when the combustion of the burner is stopped. A first detection control that controls the air supply means to perform one scavenging, and controls the gas sensor to perform a first detection for detecting the detection target gas in the can body following the first scavenging; And when the detection target gas is not detected in the first detection, a first determination unit that determines that there is no gas leakage through the valve, and the detection target gas is detected in the first detection The air supply means is controlled to perform second scavenging, which is further scavenging in the can body, and second detection for redetecting the detection target gas in the can body is performed following the second scavenging. When the detection target gas is not detected by the second detection and the second detection control unit that controls the gas sensor, it is determined that there is no gas leakage through the valve, and the detection is performed by the second detection. And a second determination unit that determines that the gas leakage through the valve is “present” when the target gas is detected.

  According to the present invention, since the second scavenging is performed when the detection target gas is detected by the first detection, the exhaust gas that may remain in the can after the first scavenging can be discharged from the can. . Therefore, it is possible to prevent the exhaust gas from being detected by the second detection, and thus it is possible to prevent the exhaust gas from being erroneously detected as the fuel gas leaked by the gas leak through the valve. Accordingly, it is possible to accurately determine the presence or absence of gas leakage through the valve.

(1) It is preferable that the second detection control unit implements the second scavenging and the second detection once.

  According to this configuration, the presence or absence of gas leakage through the valve can be determined in a short time.

(2) It is preferable that the second detection control unit further performs the setting of the second scavenging and the second detection when the detection target gas is detected again by the second detection.

  According to this configuration, exhaust gas that may remain in the can after the second scavenging can be reliably discharged from the can. Therefore, the presence or absence of gas leakage through the valve can be determined more accurately.

(3) It is preferable that the second detection control unit controls the air supply unit so that an air amount larger than an air amount supplied by the first scavenging is supplied by the second scavenging.

  According to this configuration, exhaust gas that may remain in the can after the first scavenging can be reliably discharged from the can. Therefore, the presence or absence of gas leakage through the valve can be determined with higher accuracy.

(4) Incomplete combustion determination means for controlling the gas sensor so as to detect the presence or absence of incomplete combustion gas in the can, and determining the presence or absence of incomplete combustion in the burner based on the detection result. It is preferable that it contains.

  According to this configuration, it is possible to determine the presence or absence of incomplete combustion of the burner by using an existing gas sensor without newly providing a gas sensor for detecting incomplete combustion.

  With the gas-fired boiler according to the present invention, it is possible to accurately determine the presence or absence of gas leakage through the valve when the fuel control valve is closed.

It is a block diagram showing a schematic structure of a gas fired boiler concerning this embodiment. It is a block diagram which shows schematic structure of a control system. It is a flowchart explaining the presence or absence determination of the gas leakage through the fuel control valve performed by the control device when the fuel control valve is closed.

[Overall configuration of boiler 1]
Hereinafter, a boiler according to an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a schematic configuration of a boiler 1 according to this embodiment. The boiler 1 is a gas-fired boiler, and is connected to a can body 2 provided with a water tube group (not shown) composed of a plurality of water pipes, a burner 3 that burns in the can body 2, and the can body 2. An exhaust cylinder 4 for discharging exhaust gas generated by combustion of the burner 3 from the can body 2, a control device 50 for controlling the operation of the boiler 1, and an indicator 70 for displaying the operation state of the boiler 1. Yes.

  The burner 3 is connected to a fuel supply means 5 for supplying fuel gas and an air supply means 10 for supplying combustion air. The fuel supply means 5 includes a fuel supply path 6 and a fuel control valve 7 that is provided on the fuel supply path 6 and controls the supply of fuel gas to the burner 3. The air supply means 10 includes a blower 11 and an air supply path 12 that connects the blower 11 and the burner 3.

  The water in the water pipe is maintained at a desired water level by the feed water pump 13 controlled by the control device 50, heated by a flame (combustion gas) generated by the combustion of the burner 3, and loaded on the load side equipment (illustrated). Not supplied). The boiler 1 further includes a heat demand detector 14 that detects the heat demand of the boiler 1 based on the vapor pressure of the steam generated in the can 2. The flame generated by the combustion of the burner 3 is heat-exchanged with water in the water pipe and then discharged from the exhaust tube 4 as exhaust gas.

  The air supply means 10 also serves as scavenging means for supplying scavenging air for scavenging the inside of the can body 2 (including the inside of the exhaust cylinder 4). Specifically, the blower 11 supplies scavenging air into the can body 2 via the air supply path 12 and the burner 3, and the inside of the can body 2 is scavenged by this scavenging air. The blower 11 is inverter-controlled by the control device 50 so as to supply a desired amount of air according to the operating state of the boiler 1.

  The exhaust pipe 4 is provided with a gas detection device 20. The gas detection device 20 includes a gas sensor 22 provided at the distal end portion 21b via the extraction pipe 21, and includes detection of fuel gas and exhaust gas taken out to the gas flow path 23 formed in the extraction pipe 21. The target gas is detected by the gas sensor 22. The extraction pipe 21 extends obliquely upward from a base portion 21 a connected to the exhaust cylinder 4. The gas flow path 23 is formed so as to extend obliquely upward from the base 21 a along the extraction pipe 21, bend back at the distal end 21 b, and return to the exhaust cylinder 4.

  A concave portion facing upward is formed in the distal end portion 21b of the extraction pipe 21, and the gas sensor 22 is disposed in the concave portion. With the above configuration, the gas sensor 22 is not directly exposed to the exhaust gas flowing through the exhaust cylinder 4. Moreover, since the gas sensor 22 is provided via the extraction pipe 21, heat transfer from the exhaust tube 4 to the gas sensor 22 is suppressed. Therefore, it is suppressed that the gas sensor 22 becomes high temperature.

  Furthermore, since the extraction pipe 21 is provided so as to extend obliquely upward, it is possible to suppress the dew condensation water from which the exhaust gas has condensed from accumulating in the extraction pipe 21. Therefore, the dew condensation water is prevented from adhering to the gas sensor 22 provided at the tip 21b of the extraction pipe 21.

  Therefore, since it can suppress that the gas sensor 22 becomes high temperature and dew condensation water adheres to the gas sensor 22, failure of the gas sensor 22 can be suppressed. In addition, although the gas detection apparatus 20 is provided in the exhaust cylinder 4 so that the detection target gas in the can body 2 and the exhaust cylinder 4 can be detected, the gas detection apparatus 20 may be provided in the can body 2.

[Control device 50]
The control device 50 will be described with reference to the block diagram shown in FIG. The control device 50 includes a known computer including a CPU, a memory, a storage unit, and the like.

  The control device 50 determines a heat request determination unit 51 that determines the heat request of the boiler 1, a combustion control unit 52 that controls combustion by the burner 3, and whether or not there is gas leakage through the valve when the fuel control valve 7 is closed. And a display control unit 53 that displays the operating state of the boiler 1 on the display unit 70. The over-the-valve gas leakage determination means 60 includes a first detection control unit 61, a second detection control unit 62, a first determination unit 63, and a second determination unit 64.

  The heat request determination unit 51 receives a signal from the heat request detector 14 and determines whether the boiler 1 has a heat request. Specifically, the heat request determination unit 51 determines that the heat request of the boiler 1 is “present” when the steam pressure in the boiler 1 detected by the heat request detector 14 is lower than a predetermined lower limit steam pressure. When the steam pressure in the boiler 1 detected by the heat demand detector 14 exceeds a predetermined upper limit steam pressure, it is determined that the boiler 1 has no heat demand.

  The combustion control unit 52 controls the combustion of the burner 3 according to the presence or absence of the heat request of the boiler 1 determined by the heat request determination unit 51. Specifically, when the heat demand of the boiler 1 is “present”, the combustion control unit 52 controls the opening of the fuel control valve 7 so as to adjust the fuel gas supply amount to the burner 3, thereby The combustion of the burner 3 is controlled to a desired combustion state. On the other hand, when the heat demand of the boiler 1 is “no”, the combustion control unit 52 controls the fuel control valve 7 to be closed so as to shut off the fuel gas supply to the burner 3, and thereby the burner 3. Combustion is stopped. Thereby, the steam pressure in the boiler 1 is maintained between the predetermined lower limit steam pressure and the upper limit steam pressure.

  The first detection control unit 61 controls the air supply means 10 to perform the first scavenging which is the first scavenging in the can body 2 when the combustion of the burner 3 is stopped, and the can body 2 following the first scavenging. The gas sensor 22 is controlled to perform the first detection for detecting the detection target gas.

  When the detection target gas is not detected in the first detection, the first determination unit 63 determines that there is no gas leakage through the valve.

  When the detection target gas is detected in the first detection, the second detection control unit 62 controls the air supply means 10 to perform the second scavenging that is further scavenging in the can body 2, so that the second scavenging is performed. Subsequently, the gas sensor 22 is controlled so as to perform the second detection for redetecting the detection target gas in the can body 2.

  When the detection target gas is not detected in the second detection, the second determination unit 64 determines that there is no gas leakage through the valve. When the detection target gas is detected in the second detection, the second determination unit 64 detects the gas leakage through the valve. Is determined to be “present”.

  The display control unit 53 causes the display unit 70 to display that “there is a valve gas leak” if the valve gas leak determiner 60 determines that “there is a valve gas leak”. Thus, the display on the display 70 informs the user that “there is gas leakage from the valve”.

  The first detection control unit 61 supplies air so that the first scavenging supplies an air amount larger than the air amount (pre-purge) for scavenging the can body 2 before starting combustion by the burner 3. The means 10 is controlled. For example, if the amount of air supplied in the pre-purge is 5 to 6 times the volume of the can body 2, the first scavenging supplies an air amount of 10 to 12 times the volume of the can body 2. Thereby, it is easy to exhaust the exhaust gas from the inside of the can body 2.

  The 2nd detection control part 62 controls the air supply means 10 so that air quantity larger than the air quantity supplied by 1st scavenging may be supplied by 2nd scavenging. Thus, exhaust gas that may remain in the can after the first scavenging can be reliably discharged from the can 2.

  In the actual boiler, the combustion control of the burner 3 is associated with not only the opening / closing control of the fuel control valve 7 but also the control of the blower 11 and the ignition device (not shown), and at the same time, the feed pump Although control of 13 etc. is performed simultaneously, description is abbreviate | omitted in this Example for the simplification of description.

[Judgment of gas leakage through valve]
With reference to the flowchart of FIG. 3, the operation | movement of the boiler 1 at the time of determining the presence or absence of the gas leakage through a valve | bulb performed when the fuel control valve 7 is closed at the time of the combustion stop by the boiler 1 is demonstrated.

  In the state in which the boiler 1 is combusting with the burner 3, the heat request | requirement determination part 51 determines the presence or absence of the heat request | requirement of the boiler 1 (step S101). When there is a heat request of the boiler 1, the combustion control unit 52 continues the combustion of the burner 3 (step S102). When there is no heat request for the boiler 1, the combustion control unit 52 controls the fuel control valve 7 to stop the fuel gas supply to the burner 3 to stop the combustion of the burner 3 (step S103).

  Next, the first detection control unit 61 controls the air supply means 10 to perform the first scavenging (step S104), and controls the gas sensor 22 to perform the first detection following the first scavenging (step S104). S105).

  The first determination unit 63 determines the presence or absence of gas passing through the valve based on the detection result of the detection target gas in the first detection (step S106). Specifically, the first determination unit 63 determines that there is no gas leakage through the valve when the detection target gas is not detected in the first detection (step S112).

  When the detection target gas is detected in the first detection, the second detection control unit 62 controls the air supply means 10 to perform the second scavenging (step S107), and performs the second detection following the second scavenging. The gas sensor 22 is controlled to perform (step S108).

  The second determination unit 64 determines the presence or absence of gas passing through the valve based on the detection result of the detection target gas in the second detection (step S109). Specifically, the second determination unit 64 determines that there is a gas leakage through the valve when the detection target gas is detected again in the second detection (step S110), and the detection target gas is detected in the second detection. If it is not detected, it is determined that there is no gas leakage through the valve (step S112).

  When the second determination unit 64 determines that “there is gas leakage from the valve”, the display control unit 53 causes the indicator 70 to display “there is gas leakage from the valve” (step S111).

  Therefore, according to the boiler 1 according to the present embodiment, since the second scavenging is performed when the detection target gas is detected by the first detection, there is a possibility of remaining in the can body 2 even after the first scavenging. A certain exhaust gas can be discharged from the inside of the can body 2. Therefore, it is possible to prevent the exhaust gas from being detected by the second detection, and thus it is possible to prevent the exhaust gas from being erroneously detected as the fuel gas leaked by the gas leak through the valve. Accordingly, it is possible to accurately determine the presence or absence of gas leakage through the valve.

  Further, since the second detection control unit 62 controls the air supply means 10 so that an amount of air larger than the amount of air supplied by the first scavenging is supplied by the second scavenging, the can body even after the first scavenging. Exhaust gas that may remain in the gas can be reliably discharged from the can body 2. Therefore, the presence or absence of gas leakage through the valve can be determined with higher accuracy.

  In the above embodiment, the second detection control unit 62 performs the set of the second scavenging and the second detection once, and the second determination unit 64 determines the gas leakage through the valve. Presence / absence can be accurately determined in a short time.

  Note that the second detection control unit 62 may further set the second scavenging and the second detection when the detection target gas is detected again in the second detection. Thereby, exhaust gas that may remain in the can body 2 even after the second scavenging can be reliably discharged from the can body 2. Therefore, the presence or absence of gas leakage through the valve can be determined with higher accuracy.

  Further, when the burner 3 burns, the gas sensor 22 is controlled so as to detect the presence or absence of incomplete combustion gas in the can body 2, and the presence or absence of incomplete combustion of the burner 3 is determined based on the detection result. Combustion determination means may be further provided in the control device 50. Thereby, the presence or absence of incomplete fuel in the burner 3 can be determined by diverting the existing gas sensor 22 without newly adding a gas sensor for detecting incomplete combustion.

  Various modifications and changes may be made without departing from the spirit and scope of the invention as set forth in the appended claims.

  As described above, according to the boiler according to the present invention, it is possible to accurately determine the presence or absence of the gas passing through the valve when the combustion is stopped. Therefore, there is a possibility that the boiler is suitably implemented in this type of manufacturing technical field.

DESCRIPTION OF SYMBOLS 1 Boiler 2 Can body 3 Burner 4 Exhaust pipe 5 Fuel supply means 6 Fuel supply path 7 Fuel control valve 10 Air supply means 11 Blower 12 Air supply path 13 Water supply pump 14 Heat demand detector 20 Gas detector 21 Extraction pipe 22 Gas sensor 23 Gas flow path 50 Control device 51 Heat demand determination unit 52 Combustion control unit 53 Display control unit 60 Over-the-gas leakage determination means 61 First detection control unit 62 Second detection control unit 63 First determination unit 64 Second determination unit 70 Display vessel

Claims (5)

A gas-fired boiler that burns fuel gas with a burner in a can and exhausts exhaust gas from the can,
Air supply means for supplying air to the can body, fuel supply means having a fuel control valve for controlling fuel gas supply to the burner, and detection target gas including fuel gas and exhaust gas in the can body are detected. A gas sensor, and a valve gas leakage determination means for determining the presence or absence of gas leakage from the fuel control valve that leaks into the can body when the valve is closed,
The gas leakage judgment means through the valve is
When the combustion of the burner is stopped, the air supply means is controlled to perform the first scavenging which is the first scavenging in the can, and the detection target gas in the can is detected following the first scavenging. A first detection control unit that controls the gas sensor to perform first detection;
When the detection target gas is not detected in the first detection, a first determination unit that determines that there is no gas leakage through the valve;
When the detection target gas is detected in the first detection, the air supply unit is controlled to perform second scavenging that is further scavenging in the can body, and the second scavenging is followed by the inside of the can body A second detection control unit that controls the gas sensor to perform second detection for redetecting the detection target gas;
When the detection target gas is not detected in the second detection, it is determined that there is no gas leakage through the valve, and when the detection target gas is detected in the second detection, the gas leakage through the valve is detected. A second determination unit that determines that “there is”;
A gas-fired boiler characterized by containing The second detection control unit performs the second scavenging and the second detection once,
The gas fired boiler according to claim 1. When the detection target gas is detected again in the second detection, the second detection control unit further performs the set of the second scavenging and the second detection.
The gas fired boiler according to claim 1. The second detection control unit controls the air supply means so as to supply an air amount larger than an air amount supplied by the first scavenging by the second scavenging;
The gas-fired boiler according to any one of claims 1 to 3. The gas sensor further includes incomplete combustion determining means for controlling the gas sensor to detect the presence or absence of incomplete combustion gas in the can and determining the presence or absence of incomplete combustion in the burner based on the detection result. ,
The gas-fired boiler as described in any one of Claims 1-4.

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