JP2016153712A - Boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a clogging at a burner or a flue and an inverse flow of discharged gas from the flue easily and positively and perform a positive prevention of gas leakage to outside and improve its safety characteristics.SOLUTION: A gas suction mechanism 6 is provided with a Venturi pipe 13 and arranged at a suction port 5a of a blower 5. The gas suction mechanism 6 has a gas supply passage 7 connected to a throat part 13a of the Venturi pipe 13 and as the air is sucked into the blower 5 through the Venturi pipe 13, gas is also sucked through the gas supply passage 7 and fed into the blower 5 together with the air. A gas pressure adjusting valve 8 arranged at the gas supply passage 7 adjusts its degree of opening to keep the gas pressure at the outlet at an inlet side pressure of the Venturi pipe 13 or the atmospheric pressure. A pressure difference between the inlet side pressure of the Venturi pipe 13 and a pressure at the throat part is monitored by differential pressure monitoring means 9.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a gas-fired boiler.

  Conventionally, as disclosed in FIG. 1 of Patent Document 1 below, in the duct (6) from the blower (5) to the burner (2), the combustion air from the blower (5) is supplied to the combustion air from the gas supply path (10). There is known a boiler (1) that jets and mixes the gas and burns the premixed gas in a burner (2).

  In connection with this type of boiler, the applicant has proposed a patent application for a boiler that can supply a necessary amount of gas to a burner even if the gas supply pressure is relatively low (Japanese Patent Application No. 2014-66252). In this prior application invention, instead of mixing gas into the air downstream of the blower, gas is mixed into the air on the suction side to the blower. Specifically, a gas suction mechanism using a venturi tube is provided at the suction port to the blower, and the gas is sucked in along with the suction of the air to the blower and is sent to the blower together with the air to be mixed.

  In any case, in the case of a gas-fired boiler, if the gas ejection hole of the burner is clogged or the flue through which the exhaust gas is passed is clogged, it is necessary to quickly detect this. In addition, when multiple boilers are installed, exhaust gas from each boiler is discharged through a common flue (collective flue), and the number of operating boilers is changed (unit control) according to the load, the following There are also problems like this. In other words, the standby boiler (that is, when combustion is stopped) purges the furnace by operating the blower so that the exhaust gas does not flow backward from the collecting flue, but if a reverse flow occurs, this is quickly detected. There is a need to.

  In relation to this point, as disclosed in the following Patent Document 2, based on the differential pressure before and after the damper (15) provided between the blower (10) and the burner (8), to the standby boiler It is known to detect the backflow of exhaust gas from the collecting flue. However, when the gas is mixed into the air on the suction side to the blower and the mixture of air and gas is discharged from the blower as in the prior invention, the damper is installed in the duct from the blower to the burner. There is a possibility that the combustible air-fuel mixture leaks from the shaft seal of the rotary shaft to the outside. In addition, it is desirable that the gas supply be reliably stopped while the blower is stopped.

JP 2006-266534 A Japanese Patent No. 4059100

  The problem to be solved by the present invention is that it is easy to reliably detect the clogging of the burner and the flue and the backflow of the exhaust gas from the flue, and also reliably prevent the leakage of gas to the outside, which is highly safe. To provide a boiler.

  The present invention has been made to solve the above-mentioned problems. The invention according to claim 1 is directed to a main burner as a premixing burner for heating a water pipe in a can body, and a pilot for igniting the main burner. A burner, a blower for supplying combustion air to the main burner, and a venturi pipe provided at an air suction port to the blower, and a gas supply path is connected to a throat portion of the venturi pipe, A gas suction mechanism that sucks gas from the gas supply path and sends it to the suction port together with air as the air is sucked into the suction port via the venturi pipe, and a valve provided in the gas supply path; A gas pressure adjusting valve for adjusting an opening degree so as to maintain a gas pressure on the outlet side of the valve at an inlet side pressure or an atmospheric pressure of the venturi pipe; and an inlet side pressure and a pressure of the venturi pipe. A boiler, characterized in that it comprises a differential pressure monitoring means for monitoring the pressure difference between the over bets unit pressure.

  According to the first aspect of the present invention, the gas can be sucked and mixed as the air is sucked into the blower by the gas suction mechanism using the venturi tube. The gas pressure adjustment valve adjusts the opening so that the gas pressure on the outlet side is maintained at the inlet side pressure or the atmospheric pressure of the venturi pipe, so that air flows in the forward direction to the venturi pipe and the throat section becomes negative pressure. Unless it becomes, it can be set as the structure which gas does not flow, and the gas leak at the time of a fan stop can be prevented reliably. Moreover, by maintaining the pressure on the outlet side of the gas pressure regulating valve at a predetermined level, the gas is stably mixed into the air at a desired flow rate according to the negative pressure generated in the venturi pipe (in other words, the ventilating volume of the venturi pipe). can do. Furthermore, by monitoring the differential pressure between the inlet pressure of the venturi pipe and the throat pressure by means of differential pressure monitoring means, it is easy to reliably detect clogging of the burner or flue and the backflow of exhaust gas from the flue. can do.

  According to the second aspect of the present invention, the duct to the main burner is not provided with a damper downstream of the blower, and the amount of air blown to the main burner is controlled by inverter control of the rotational speed of the blower. The boiler according to claim 1, wherein a damper is provided on an inlet side of the venturi pipe and is changed by the damper.

  According to the second aspect of the present invention, since the damper is not installed downstream from the blower, there is no possibility that the air-fuel mixture leaks from the shaft seal portion of the rotating shaft of the damper to the outside. On the other hand, the rotational speed of the blower can be controlled by an inverter, and / or a damper can be provided on the inlet side of the venturi and the amount of air to the main burner can be adjusted by the damper. Moreover, the gas supply flow rate can also be changed by changing the ventilating amount of the venturi pipe.

  According to a third aspect of the present invention, an air filter is provided at an inlet port to the venturi pipe, and the gas pressure adjusting valve controls the gas pressure on the outlet side of the valve to the downstream side of the air filter. The boiler according to claim 1, wherein the opening degree is adjusted so as to maintain the pressure on the inlet side of the venturi pipe in the boiler.

  According to the third aspect of the present invention, when the air filter is clogged and the pressure on the inlet side of the venturi pipe is lowered, the gas pressure on the outlet side of the gas pressure regulating valve is lowered accordingly. The ratio can be kept constant.

  According to a fourth aspect of the present invention, when the differential pressure monitoring means detects that the differential pressure has become equal to or less than a set value, the combustion of each burner is stopped, or instead of or in addition to this. The boiler according to any one of claims 1 to 3, wherein the fact that the differential pressure has become equal to or less than a set value is output to a predetermined device and notified.

  According to the fourth aspect of the present invention, when the pressure difference between the inlet pressure of the venturi pipe and the throat pressure becomes equal to or lower than the set value, the fact is notified, or the combustion of each burner is stopped. Sex can be secured.

  Furthermore, the invention described in claim 5 is characterized in that a gas flow rate adjusting valve whose opening degree can be adjusted is provided downstream of the gas pressure adjusting valve in the gas supply path to the venturi pipe. The boiler according to any one of Items 1 to 4.

  According to the invention described in claim 5, it is possible to adjust the air ratio according to the combustion amount by adjusting the opening of the gas flow control valve.

  According to the present invention, it is possible to easily and reliably detect clogging of a burner or a flue and a backflow of exhaust gas from the flue, and to reliably prevent gas leakage to the outside, thereby realizing a highly safe boiler. be able to.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic which shows the boiler of one Example of this invention, and shows a part in cross section.

  Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic view showing a boiler 1 according to an embodiment of the present invention, and a part thereof is shown in cross section.

  The boiler 1 of the present embodiment includes a can body 2 having a large number of water tubes, a main burner 3 for heating the water tubes in the can body 2, a pilot burner 4 for igniting the main burner 3, and a combustion in the main burner 3. A blower 5 that supplies the working air, a gas suction mechanism 6 that is provided in a suction port 5a to the blower 5 and mixes fuel gas into the suction air, and a gas pressure adjustment that is provided in a gas supply path 7 to the gas suction mechanism 6 A valve 8 and a differential pressure monitoring means 9 for monitoring the differential pressure at a predetermined location are provided as main parts.

  The can body 2 is configured by connecting a plurality of water pipes between the upper header and the lower header, and is covered with a can body cover. The shape of the can body 2 is not particularly limited, but is a square in this embodiment. The can body 2 is appropriately supplied with water from the lower header, and the water level in the can body 2 is maintained as desired. The can body 2 is provided with a main burner 3 at one end, and an exhaust gas path 10 is connected to the other end. The exhaust gas path 10 is a flue and / or chimney, and an economizer is provided if desired. The combustion gas (including the flame at the beginning) from the main burner 3 is discharged from the exhaust gas passage 10 as exhaust gas after heat exchange with water in each water pipe. The water in each water pipe is heated by the combustion gas from the main burner 3 and is led out from the upper header through the steam separator 11 as steam.

  The main burner 3 is a premix burner that is supplied with a premixed gas of combustion air and gas and burns. In this embodiment, the burner is a completely premixed burner having a planar combustion surface (premixed gas ejection surface) having a large number of premixed gas ejection holes. The main burner 3 may be switched on or off for the presence or absence of combustion, or the amount of combustion may be adjusted stepwise or continuously. For example, the main burner 3 can switch the combustion amount at three positions of high combustion (100% combustion), low combustion (for example, 50% combustion) and stop. Alternatively, the combustion amount of the main burner 3 can be switched at four positions: high combustion, medium combustion, low combustion, and stop. Alternatively, the combustion amount of the main burner 3 is continuously adjusted in proportion to the use load of steam. In any case, the main burner 3 is supplied with combustion air and gas in an amount corresponding to the combustion amount.

  The pilot burner 4 is provided close to the main burner 3. The pilot burner 4 is a premix burner in this embodiment, but may be a premix burner in some cases. In order to burn gas in the pilot burner 4, combustion air and gas are supplied to the pilot burner 4 at a predetermined flow rate. The presence or absence of supply of combustion air and gas to the pilot burner 4 can be switched separately from the presence or absence of supply of combustion air and gas to the main burner 3. The pilot burner 4 is ignited by an ignition device (not shown), and the main burner 3 is ignited by the pilot burner 4.

  The blower 5 sucks gas from the suction port 5a and discharges it to the discharge port 5b. The blower 5 is typically a centrifugal type, rotates an impeller in a spiral casing, sucks gas from a suction port 5a provided in the central portion of the casing, and discharges from a discharge port 5b provided in the outer peripheral portion of the casing. To do. The suction port 5a of the blower 5 is provided with a gas suction mechanism 6 that sucks gas as air is sucked into the suction port 5a and sends the gas together with air to the suction port 5a.

  The discharge port 5 b of the blower 5 is connected to the main burner 3 through the duct 12. At this time, it is preferable not to install a damper in the duct 12. The gas suction mechanism 6 discharges a combustible air-fuel mixture of combustion air and gas from the blower 5. Therefore, if a damper is provided downstream of the blower 5, it is flammable at the shaft seal portion of the rotary shaft of the damper. It is necessary to take measures to prevent the air-fuel mixture from leaking outside. However, unlike the boiler 1 of this embodiment, no damper is installed downstream of the blower 5, so there is no risk of gas leakage to the outside.

  The gas suction mechanism 6 includes a venturi tube 13 in this embodiment. As is well known, the venturi tube 13 includes a tapered portion before and after the throat portion 13a. Specifically, a gradual reduction tube 13b that decreases in diameter as it goes downstream is provided on the upstream side of the throat portion 13a of the minimum diameter portion, while the diameter increases as it goes downstream on the downstream side of the throat portion 13a. A gradually expanding tube 13c is provided. Then, the outlet side opening of the gradually expanding pipe 13c is directly connected (or connected via an appropriate pipe) to the suction port 5a of the blower 5. An air filter 14 is preferably provided on the upstream side of the inlet to the venturi pipe 13, in other words, the inlet of the gradually reducing pipe 13 b. In the illustrated example, the air filter 14 is provided in a straight tubular portion connected to the inlet side of the gradually reducing tube 13b.

  A gas supply path 7 from a gas supply source (not shown) is connected to the throat portion 13 a of the venturi pipe 13. The gas supply path 7 is provided with a shut-off valve 15 and a gas pressure regulating valve 8 in order toward the downstream. When the gas is supplied to the main burner 3, these valves 15 and 8 are opened, and when the gas supply to the main burner 3 is stopped, these valves 15 and 8 are closed. Therefore, the gas pressure adjusting valve 8 functions in the same manner as the shutoff valve 15 for switching the presence / absence of gas supply to the main burner 3.

  Furthermore, the gas pressure adjusting valve 8 also has a function of maintaining the gas pressure on the outlet side (downstream of the gas pressure adjusting valve 8) at a predetermined pressure when opened. Specifically, in the present embodiment, the gas pressure adjusting valve 8 is configured such that the gas pressure on the outlet side is the pressure on the inlet side of the venturi pipe 13 (when the air filter 14 is provided, the venturi pipe 13 on the downstream side of the air filter 14). This is a valve that adjusts the opening degree so as to maintain the pressure at the inlet side. Here, the gas pressure adjusting valve 8 is a pressure equalizing valve that receives the inlet side pressure of the venturi pipe 13 (inlet side pressure of the gradually reducing pipe 13b) via the communication pipe 16 and mechanically adjusts the opening. In addition, the pressure on the inlet side of the venturi tube 13 may be monitored by a sensor and the opening may be adjusted based on the detection signal.

  It is preferable that a gas flow rate adjusting valve 17 is further provided downstream of the gas pressure adjusting valve 8 in the gas supply path 7. The gas flow rate adjustment valve 17 is an electric valve whose opening degree can be adjusted.

  The differential pressure monitoring means 9 includes a pressure switch 18 in this embodiment. The pressure switch 18 monitors whether or not the pressure difference (P1−P2) between the inlet side pressure (P1) of the venturi pipe 13 and the throat pressure (P2) is equal to or less than a set value.

  The boiler 1 is controlled by a controller (not shown). In this embodiment, the controller performs combustion control of the main burner 3 based on the vapor pressure (the vapor pressure at the location where the vapor is supplied from or inside the can body 2).

  The controller is connected to a pressure sensor (or pressure switch) that detects the vapor pressure, a motor of the blower 5, a shutoff valve 15, a gas pressure adjustment valve 8, a gas flow rate adjustment valve 17, a pressure switch 18, and the like. In addition, the controller is connected to a touch panel, operation buttons, a lamp, a buzzer, and the like as necessary. Then, various controls as described below are executed.

  In order to burn the gas in the main burner 3, the blower 5 is operated, the shutoff valve 15 (and the gas pressure adjusting valve 8) is opened, and the pilot burner 4 is ignited. That is, first, after supplying predetermined combustion air and gas to the pilot burner 4 and igniting the pilot burner 4, the shut-off valve 15 is opened and the main burner 3 is ignited, and the combustion of the pilot burner 4 is stopped. Good. On the other hand, in order to stop the combustion in the main burner 3, the shutoff valve 15 is closed to stop the supply of gas, and the supply of combustion air from the blower 5 may be stopped. After the combustion of the main burner 3 is stopped, the blower 5 may be stopped. Alternatively or in addition, a damper is provided on the inlet side of the venturi pipe 13 and the damper is closed, or a damper is provided in the exhaust gas passage 10. The damper may be closed.

  When the blower 5 is operated to burn the gas in the main burner 3, the outside air through the air filter 14 is sucked into the suction port 5 a of the blower 5 through the venturi pipe 13. When air is passed through the venturi tube 13, a negative pressure is generated in the venturi tube 13. Therefore, if the shutoff valve 15 is opened, gas is drawn into the venturi tube 13 from the gas supply path 7. Thus, as the air is sucked into the suction port 5a of the blower 5, the gas can be sucked in the venturi tube 13 and sent together with the air to the suction port 5a. Then, air and gas are mixed in the blower 5, and the mixture is supplied to the main burner 3 through the duct 12 and burned in the main burner 3.

  Since the gas is sucked in the venturi 13 by using the suction of air into the blower 5, the desired amount of gas can be set to the main burner 3 even if the gas supply pressure (the gas pressure upstream of the shutoff valve 15) is relatively low. To the desired combustion. Further, since the gas is mixed into the air and then supplied to the blower 5, the air and the gas can be reliably mixed in the blower 5.

  Further, as described above, the gas pressure adjusting valve 8 maintains the gas pressure on the outlet side at a predetermined value, so that a desired flow rate according to the negative pressure generated in the venturi pipe 13 (in other words, the air flow rate of the venturi pipe 13). Thus, the gas can be stably mixed into the air. In addition, since the outlet side pressure of the gas pressure adjusting valve 8 is the inlet side pressure of the venturi pipe 13, the gas does not flow unless the throat portion 13a has a negative pressure because air flows in the forward direction to the venturi pipe 13. Thus, it is possible to reliably prevent gas leakage at the time of stopping 5. Further, when the air filter 14 is clogged and the pressure on the inlet side of the venturi 13 is lowered, the gas pressure on the outlet side of the gas pressure regulating valve 8 is also lowered accordingly, so that the air ratio of the boiler 1 is kept at a predetermined value. be able to.

  The amount of combustion of the main burner 3 is adjusted by adjusting the flow rates of combustion air and gas supplied to the main burner 3. The flow rate of the combustion air is adjusted by changing the rotational speed of the motor of the blower 5 by using an inverter. Instead of this, or in addition to this, a damper is provided on the inlet side of the venturi pipe 13. The position of the damper may be adjusted. As described above, if the air flow rate to the venturi pipe 13 is changed, the gas flow rate also changes. However, in order to obtain an air ratio corresponding to the combustion amount, a gas flow rate adjusting valve is provided in the gas supply path 7 to the venturi pipe 13. 17 may be provided. By changing the opening of the gas flow rate adjustment valve 17 according to the combustion amount, it is possible to adjust the air ratio according to the combustion amount.

  By the way, as the boiler 1 is operated, the main burner 3 may be clogged (more specifically, the premixed gas ejection hole may be clogged) or the exhaust gas passage 10 may be clogged. There is a need to. In addition, when multiple boilers 1 are installed, exhaust gas from each boiler 1 is discharged through a common flue (collective flue), and the number of operating boilers 1 is changed (unit control) according to the load. It is necessary to prevent the backflow of exhaust gas from the collecting flue to the boiler 1 during standby (that is, when combustion is stopped). For this reason, the standby boiler 1 purges the inside of the furnace by operating the blower 5 at a flow rate that can prevent the backflow of the exhaust gas. However, if a backflow of the exhaust gas occurs, this is quickly detected. There is a need.

  Therefore, in this embodiment, the controller monitors the differential pressure between the inlet side pressure of the venturi pipe 13 and the throat pressure with the pressure switch 18. That is, the controller functions as a differential pressure monitoring means together with the pressure switch 18. When it is detected that the differential pressure has become equal to or less than the set value, there is a blockage of the main burner 3 or the exhaust gas passage 10, or there is a backflow of exhaust gas from the exhaust gas passage 10 when waiting in multi-can installation. Can be determined.

  When the controller detects that the differential pressure has become equal to or lower than the set value, typically, when the main burner 3 is in combustion, the controller stops the combustion, and when the pilot burner 4 is in combustion. Stops its burning. For example, when only the pilot burner 4 is burning and it is detected that the differential pressure has fallen below a set value, the fuel supply valve to the pilot burner 4 is closed (or simultaneously) and then burned to the pilot burner 4. Supply of working air is also stopped.

  Further, instead of or in addition to stopping each of the burners 3 and 4, the fact that the differential pressure has become equal to or less than a set value may be output to a predetermined device to notify the user. For example, it may be displayed on a touch panel, a lamp may be turned on or blinked, or a buzzer may be sounded.

  Alternatively, when it is detected that the differential pressure has become equal to or less than a set value, the amount of blown air may be increased. That is, when the rotational speed of the blower 5 is increased or a damper is provided on the inlet side of the venturi pipe 13, the opening degree of the damper may be increased. Then, if the differential pressure exceeds the set value, the operation of the boiler 1 is continued. Otherwise, the combustion of the burners 3 and 4 is stopped or output to a predetermined device. What is necessary is just to alert | report to a user.

  In this embodiment, the pressure switch 18 is used for monitoring the differential pressure between the inlet side pressure of the venturi tube 13 and the throat pressure, but a pressure sensor may be used in some cases. That is, the inlet pressure of the venturi pipe 13 is monitored by the first pressure sensor, while the throat pressure of the venturi pipe 13 is monitored by the second pressure sensor, and the controller is configured to perform the differential pressure based on the detected pressures of these pressure sensors. And the same processing as described above may be executed.

  When using a pressure sensor, the air flow rate to the main burner 3 can also be monitored based on the differential pressure. By monitoring the amount of air blown to the main burner 3, it is possible to monitor whether the amount of combustion air supplied corresponds to the amount of combustion. For example, the controller can monitor whether or not combustion air corresponding to high combustion is supplied to the main burner 3 when the main burner 3 is in a condition for high combustion. Moreover, when using a pressure sensor, the backflow of exhaust gas can also be easily detected based on the fact that the differential pressure becomes negative.

  Note that the boiler 1 of this embodiment may be installed in multiple cans as described above. That is, a boiler system may be configured using a plurality of boilers 1. In this case, the boiler system includes a plurality of boilers 1 and a controller that controls the number of operating boilers 1 and the amount of combustion. The steam from each boiler 1 is supplied to a steam header, and the steam in the steam header is sent to one or a plurality of various steam using facilities. The use load of the steam is monitored based on the pressure of the steam header, and the controller controls the number of operating boilers 1 and each combustion amount so as to maintain the pressure of the steam header at the set pressure.

  When multiple boilers 1 are installed, the gas from a common gas supply source is supplied to the main burner 3 of each boiler 1 via a gas suction mechanism 6 provided in each boiler 1. In each boiler 1, gas is sucked using the gas suction mechanism 6, so the gas supply pressure may be relatively low, and therefore the number of boilers 1 that can be installed in multiple boilers can be increased. Further, as described above, the controller can also detect the backflow from the collecting flue when combustion is stopped based on the detection signal of the pressure switch 18.

  The boiler 1 of the present invention is not limited to the configuration (including control) of the above embodiment, and can be changed as appropriate. In particular, in a gas-fired boiler equipped with a premixing burner (main burner), the gas is sucked from the gas supply path 7 as the air is sucked into the suction port 5a of the blower 5 through the venturi tube 13, and the suction port together with the air. A gas suction mechanism 6 that feeds into 5a, a gas pressure adjustment valve 8 that is provided in the gas supply path 7 and adjusts the opening so as to maintain the gas pressure on the outlet side at a predetermined level, the inlet side pressure of the venturi 13 and the throat pressure If the differential pressure monitoring means 9 for monitoring the differential pressure is provided, the other configurations can be changed as appropriate.

  For example, in the above embodiment, the gas pressure adjusting valve 8 is a valve that adjusts the opening so as to maintain the gas pressure on the outlet side at the inlet side pressure of the venturi tube 13, but the opening adjustment is performed so as to maintain the pressure at atmospheric pressure. It is good also as a valve to do. Specifically, the gas pressure adjusting valve 8 may be a zero governor that mechanically adjusts the opening so as to maintain the gas pressure on the outlet side at atmospheric pressure. In this case, the installation of the communication pipe 16 can be omitted. Further, as in the above-described embodiment, gas does not flow unless the forward flow of air flows through the venturi tube 13 and the throat portion 13a becomes negative pressure, so that it is possible to reliably prevent gas leakage when the blower 5 is stopped. it can. Moreover, by maintaining the outlet side pressure of the gas pressure regulating valve 8 at a predetermined level, the gas can be stably supplied at a desired flow rate corresponding to the negative pressure generated in the venturi pipe 13 (in other words, the air flow rate of the venturi pipe 13). Can be mixed in air.

  Moreover, in the said Example, when the boiler 1 was installed in many cans, although the boiler 1 in standby demonstrated the example which continues a purge (blowing), you may make the pilot burner 4 burn continuously instead of a purge. . Thereby, the furnace pressure above a certain level and a draft (winding force) to the collecting flue can be maintained, and the backflow of exhaust gas from the collecting flue to the can can be prevented. During this period (that is, during standby due to the continuous combustion of the pilot burner 4), it is preferable to monitor the differential pressure of the venturi pipe 13 and monitor the presence or absence of any backflow from the collecting flue, as in the above embodiment. When the boiler 1 is restarted and combustion in the main burner 3 is resumed, the combustion in the pilot burner 4 may be stopped. If the pilot burner 4 is continuously burned when the boiler 1 is on standby, the pre-purge at the time of restarting the boiler 1 can be omitted, so that the heat dissipation loss from the inside of the can 2 due to the pre-purge can be reduced.

  Furthermore, the can body 2 of the boiler 1 is not limited to a rectangular shape, and may be a cylindrical shape. In this case, the main burner 3 is preferably installed on the upper portion of the can body 2 so as to face downward. And according to it, the structure of the main burner 3 is changed suitably. Moreover, although the boiler 1 was a steam boiler in the said Example, a hot water boiler etc. may be sufficient depending on the case.

1 boiler 2 can body 3 main burner 4 pilot burner 5 blower (5a: suction port, 5b: discharge port)
6 Gas suction mechanism 7 Gas supply path 8 Gas pressure adjusting valve 9 Differential pressure monitoring means 10 Exhaust gas path 11 Gas / water separator 12 Duct 13 Venturi pipe (13a: Throat section, 13b: Gradual reduction pipe, 13c: Gradual expansion pipe)
14 Air filter 15 Shut-off valve 16 Communication pipe 17 Gas flow adjustment valve 18 Pressure switch

Claims (5)

A main burner as a premix burner that heats the water tubes in the can,
A pilot burner to ignite this main burner,
A blower for supplying combustion air to the main burner;
This venturi has a venturi pipe provided at the air inlet to the blower, and a gas supply path is connected to the throat portion of the venturi, and along with the suction of air into the inlet through the venturi A gas suction mechanism that sucks gas from the gas supply path and sends it to the suction port together with air;
A gas pressure adjusting valve that adjusts the opening so as to maintain the gas pressure on the outlet side of the valve at the inlet side pressure or the atmospheric pressure of the venturi pipe;
A boiler comprising: differential pressure monitoring means for monitoring a differential pressure between an inlet side pressure of the venturi pipe and a throat pressure. The duct to the main burner is not provided with a damper downstream from the blower,
The amount of air blown to the main burner is changed by inverter-controlling the rotation speed of the blower and / or by providing a damper on the inlet side of the venturi pipe. Boiler. An air filter is provided at the inlet to the venturi pipe,
The gas pressure adjusting valve adjusts the opening so that the gas pressure on the outlet side of the valve is maintained at the inlet side pressure of the venturi pipe on the downstream side of the air filter. The boiler according to 2. When the differential pressure monitoring means detects that the differential pressure is less than or equal to a set value, it stops combustion of each burner, or instead of or in addition to this, the differential pressure is less than or equal to a set value. The boiler as described in any one of Claims 1-3 characterized by outputting to the predetermined apparatus and alerting | reporting that it became. The gas supply path to the venturi pipe is provided with a gas flow rate adjustment valve whose opening degree can be adjusted downstream of the gas pressure adjustment valve. Boiler.

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