JP2015078806A - Boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a boiler for allowing easy and reliable determination of the attachment of scales inside water pipes independently of a burning capacity change.SOLUTION: A boiler 1 includes a can body 4 constructed by connecting an upper pipe header and a lower pipe header via a number of water pipes, a burner 5 for heating water in the can body 4, a temperature sensor 12 provided in one of the water pipes, and a scale determination part. The scale determination part determines the attachment of scales inside the water pipes depending on whether a temperature detected by the temperature sensor 12 exceeds set values or not for a time of a predetermined rate or longer within a set time. The boiler 1 is suitably applicable for continuously adjusting the burning capacity of the burner 5 between a maximum burning capacity and a minimum burning capacity, according to a vapor load.

Description

  The present invention relates to a multi-tube boiler, and more particularly to a boiler capable of determining adhesion of a scale (deposited hardness in water) to the inner surface of a water tube.

  Conventionally, as disclosed in Patent Document 1 below, a boiler is known in which a temperature sensor is provided in a water pipe at a predetermined location of a can body, and the adhesion of a scale in the water pipe is monitored based on the temperature detected by the temperature sensor.

JP 2009-92278 A

  In the boiler described in Patent Document 1, when the detected temperature of the temperature sensor exceeds the set temperature, it is determined that a predetermined scale or more is attached in the water pipe (paragraph 0056), but in order to eliminate erroneous determination, Further improvements are desired.

  If the detected temperature of the temperature sensor continues above the set temperature for a set time, even if it is determined that a scale larger than the predetermined value is attached in the water pipe, There may be a delay in tracking the temperature detection of the sensor, which may cause an erroneous determination. In the case of a boiler that changes the combustion amount in stages, it can be dealt with by not performing scale adherence judgment at the time of transition that changes the combustion amount, but the combustion amount is continuously (that is, stepless) according to the steam load. In the case of a boiler to be adjusted, such a countermeasure cannot be performed.

  Therefore, the problem to be solved by the present invention is to provide a boiler that can easily and reliably determine the adhesion of the scale to the water pipe regardless of the change in the combustion amount.

  The present invention has been made in order to solve the above problems, and the invention according to claim 1 is a can body configured by connecting a plurality of water pipes between an upper header and a lower header, A burner for heating the water in the can, a temperature sensor provided in any one of the water pipes, and the water depending on whether or not the temperature detected by the temperature sensor exceeds a set value for a predetermined time or more within a set time. A boiler comprising a scale determination unit that determines adhesion of a scale in a pipe.

  According to the first aspect of the present invention, since the scale adherence in the water pipe is determined based on whether or not the detected temperature of the temperature sensor exceeds the set value for a predetermined time or more within the set time, the change in the combustion amount On the other hand, even if there is a delay in following the temperature detection of the temperature sensor, it is possible to reliably determine the adhesion of the scale.

  According to a second aspect of the present invention, the combustion amount of the burner is continuously adjusted according to the steam load between the maximum combustion amount and the minimum combustion amount, and the set value is changed according to the combustion amount. Then, the set value corresponding to the combustion amount at the set timing is determined based on whether or not the detected temperature of the temperature sensor exceeds a predetermined ratio within the set time from the set timing, and whether or not the temperature sensor detects the scale adherence. The boiler according to claim 1.

  According to the second aspect of the present invention, even if the boiler continuously adjusts the combustion amount according to the steam load, the set value is changed according to the combustion amount, and further, according to the combustion amount at the set timing. The set value is determined based on whether or not the temperature sensor detection temperature exceeds a predetermined ratio within the set time from the set timing, and the scale adhesion in the water pipe is determined. Even if a delay occurs in tracking the temperature detection of the sensor, it is possible to reliably determine the adhesion of the scale.

  Furthermore, the invention according to claim 3 is characterized in that the set value is determined based on the combustion amount at the set timing and then corrected based on the vapor pressure at the set timing. It is a boiler.

  According to the third aspect of the present invention, since the set value for determining the adhesion of the scale is determined based on the combustion amount and then corrected based on the vapor pressure, the adhesion of the scale is more accurately determined. be able to. Note that the vapor pressure is taken into consideration that the saturation temperature in the can (that is, in the water pipe) varies depending on the vapor pressure.

  ADVANTAGE OF THE INVENTION According to this invention, the boiler which can determine reliably adhesion of the scale in a water pipe irrespective of the change of combustion amount is realizable.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic which shows one Example of the boiler 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 an embodiment of a boiler 1 of the present invention, which is partially shown in cross section.

  The boiler 1 of this embodiment is a gas-fired multi-tube type once-through boiler, and a can body 4 that is supplied with water via a water supply channel 2 and derives steam through a steam channel 3, and the inside of the can body 4 From the burner 5 for heating water, a fan 6 for supplying combustion air to the burner 5, a fuel supply path 7 for mixing gaseous fuel into the combustion air from the fan 6 to the burner 5, and the can 4 And an exhaust gas path 8 through which exhaust gas is led out.

  The can body 4 is configured by connecting an upper header and a lower header with a number of vertical water tubes. The shape of the can body 4 is not particularly limited, but in the present embodiment, it is a rectangular shape, that is, a rectangular parallelepiped shape. The can body 4 is appropriately supplied with water from the lower header through the water supply path 2 and maintained at a desired water level. The water in the can 4 is heated by the combustion gas from the burner 5 (including the flame on the burner 5 side), and is led out from the upper header to the steam path 3 as steam. The steam is sent to various steam-using facilities via a steam header or the like as desired.

  The can body 4 is provided with a burner 5 at one end, and an exhaust gas path (flue, chimney) 8 at the opposite end. Such a can 4 has front and rear surfaces (in FIG. 1) so that the combustion gas from the burner 5 at one end flows through the gap between the water pipes toward the exhaust gas passage 8 at the other end. Water pipe walls (a group of water pipes connected by fins) are arranged on both sides in a direction perpendicular to the paper surface and covered with a can cover or the like. The combustion gas from the burner 5 is discharged from the exhaust gas path 8 as exhaust gas after heat exchange with water in each water pipe.

  In this embodiment, the burner 5 is a completely premixed burner having a flat combustion surface (premixed gas ejection surface). The burner 5 is supplied with combustion air and gas fuel in an amount corresponding to the amount of combustion.

  The combustion air is supplied to the burner 5 by sending the air from the fan 6 through the combustion air passage 9. The flow rate of the combustion air is adjusted by providing a damper (a plate material whose inclination angle can be changed) 10 in the combustion air passage 9 to adjust the position of the damper 10. Instead of or in addition to this, an inverter May be used to change the rotational speed of the motor of the fan 6.

  Gas fuel is supplied to the burner 5 by feeding gas fuel from the fuel supply passage 7 through the combustion air passage 9. When the damper 10 is provided in the combustion air passage 9, gas fuel is supplied to the combustion air passage 9 from the fuel supply passage 7 downstream of the damper 10. The gas fuel from the fuel supply path 7 is ejected in the combustion air path 9 and mixed with the air from the fan 6. A fuel flow rate adjusting valve 11 is provided in the fuel supply path 7 so that the flow rate of the fuel gas to be ejected can be adjusted.

  The boiler 1 is provided with a temperature sensor 12 and a pressure sensor 13. The temperature sensor 12 is provided in a water pipe (for example, below the fourth to fifth water pipes from the burner 5) at a predetermined location where the scale easily attaches. The pressure sensor 13 is provided at a location where the vapor pressure in the can 4 can be detected.

  The boiler 1 is controlled by a controller (not shown). In the boiler 1, the combustion amount of the burner 5 is adjusted according to the steam load. In this embodiment, the burner 5 can continuously adjust the combustion amount according to the steam load between the maximum combustion amount (100% combustion) and the minimum combustion amount (for example, 20% combustion) (PID). control).

  The steam load is a use load of steam and can be monitored by the pressure of the steam. When the steam load is large, the steam pressure to the steam using facility decreases, and conversely, when the steam load is small, the steam pressure to the steam using facility increases. Therefore, the steam load is monitored by the pressure sensor 13 provided in the boiler 1 (or the steam path or steam header from the boiler 1 to the steam using facility), and the combustion amount of the burner 5 is continuously adjusted based thereon. At this time, when the steam load is small and the steam pressure exceeds the upper limit value, a combustion standby state is set or continuous pilot combustion is performed.

  The combustion standby state refers to a state in which the combustion of the burner 5 is completely stopped. On the other hand, when performing continuous pilot combustion, the boiler 1 includes a main burner (5) and a pilot burner for igniting the main burner. In continuous pilot combustion, combustion of the main burner (5) is stopped. A state in which the combustion of the pilot burner is maintained. The combustion amount of the pilot burner is a combustion amount that is smaller than the minimum combustion amount and that does not increase the steam pressure. When the boiler 1 is stopped, the heat dissipation loss increases due to the pre-purge air flow at the time of restart, but the pre-purge at the time of restart can be eliminated by performing continuous pilot combustion.

  Whether or not the burner (main burner) 5 is burned is controlled based on the vapor pressure as described above, and a differential (operation gap) is set for the control. Specifically, when the detected pressure of the pressure sensor 13 is equal to or higher than a first set value (for example, 1.75 MPa) when the vapor pressure increases, combustion at the minimum combustion amount is maintained, and then the second set value (for example, 1.8 MPa) or more, the state shifts to a combustion standby state or a continuous pilot combustion state. On the other hand, if the detected pressure of the pressure sensor 13 is less than the first set value when the vapor pressure is lowered, assuming that the combustion standby state or the continuous pilot combustion state exists, the combustion of the burner 5 is resumed according to the vapor pressure. Thus, the control for continuously adjusting the combustion amount may be performed.

  The controller further functions as a scale determination unit that determines adhesion of a predetermined scale or more to the inner surface of the water pipe. Specifically, the scale determination unit determines adhesion of the scale in the water pipe depending on whether or not the temperature detected by the temperature sensor 12 exceeds a set value [° C.]. When the detected temperature of the temperature sensor 12 exceeds the set value, the user is notified by sounding an alarm, for example, assuming that a predetermined scale or more is attached in the water pipe.

  In the case of the boiler 1 of the present embodiment, as described above, the combustion amount of the burner 5 continuously changes. Therefore, the set value as the reference value for the scale adhesion determination is also changed according to the combustion amount of the burner 5. It is good to be done. In this embodiment, at least three points of the maximum combustion amount (100% combustion), the minimum combustion amount (for example, 20% combustion), and the intermediate combustion amount therebetween (for example, 60% combustion but can be changed). The set value is set in advance at the combustion position. For example, the maximum combustion amount setting value TH, the minimum combustion amount setting value TL, and the intermediate combustion amount setting value TM are set. At other points, the set value is obtained by linear interpolation between the combustion positions before and after that.

  For example, assuming that combustion is performed at a combustion amount X between the minimum combustion amount XL and the intermediate combustion amount XM, the set value T for the combustion amount X is obtained by the following equation.

  [Equation 1] T = TL + {(X-XL) / (XM-XL)} (TM-TL)

  Further, assuming that combustion is performed at a combustion amount X between the intermediate combustion amount XM and the maximum combustion amount XH, a set value T for the combustion amount X is obtained by the following equation.

  [Equation 2] T = TM + {(X-XM) / (XH-XM)} (TH-TM)

  As described above, the controller (scale determination unit) determines adhesion of the scale in the water pipe depending on whether or not the temperature detected by the temperature sensor 12 exceeds the set value. If the combustion amount of the burner 5 is the maximum combustion amount XH at the timing for determining the scale attachment, the reference value for the scale attachment determination is the set value TH for the maximum combustion amount, and the combustion amount of the burner 5 is If the intermediate combustion amount is XM, the reference value for the scale attachment determination is the intermediate combustion amount setting value TM, and if the combustion amount of the burner 5 is the minimum combustion amount XL, the reference value for the scale attachment determination is the minimum combustion amount. Set value TL. Further, when the combustion amount of the burner 5 is between the minimum combustion amount XL and the intermediate combustion amount XM at the timing for determining the scale adhesion, the reference value for the scale adhesion determination is obtained by the above-described equation 1. When the combustion amount of the burner 5 is between the intermediate combustion amount XM and the maximum combustion amount XH, the reference value for the scale adhesion determination is obtained by the above equation 2. As described above, even in the boiler 1 that continuously adjusts the combustion amount according to the steam load, the set values that serve as the reference values for the scale adhesion determination are the maximum combustion amount, the minimum combustion amount, and the intermediate combustion amount therebetween. Since the combustion amount at other locations is determined by linear interpolation between the combustion positions before and after that location, more reliable scale adhesion determination Is possible.

  In addition, in this embodiment, the controller sets the set value corresponding to the combustion amount at the set timing to a time equal to or greater than a predetermined ratio (eg, 80%) within a set time (eg, 1 minute) from the set timing, and the temperature sensor. The adhesion of the scale in the water pipe is determined based on whether the detected temperature of 12 exceeds. Thereby, even if a delay occurs in the follow-up of the temperature detection of the temperature sensor 12 with respect to the change in the combustion amount, the adhesion of the scale can be reliably determined.

  By the way, the set value is preferably determined based on the combustion amount at the set timing and then corrected based on the vapor pressure at the set timing. For example, the vapor pressure is divided into a plurality of pressure ranges, and a correction value [° C.] for each pressure range is assigned. At this time, the pressure range and the correction value for the pressure range may be stored in the storage means as a table. This correction value may be a negative value or a positive value depending on the pressure range. Then, the controller obtains the set value as described above based on the combustion amount of the burner 5, obtains the correction value of the pressure region to which the pressure belongs based on the detected pressure of the pressure sensor 13, and What is necessary is just to add the correction value calculated | required by the pressure sensor 13 to the calculated | required setting value, and let the result be the setting value after correction | amendment.

  Thus, if the set value for determining the adhesion of the scale is determined based on the combustion amount and then corrected based on the vapor pressure, the adhesion of the scale can be determined more accurately. Note that the vapor pressure is taken into consideration that the saturation temperature in the can 4 (that is, the water pipe) varies depending on the vapor pressure. In other words, the correction value is determined in consideration of the difference in saturation temperature due to vapor pressure.

  The boiler 1 of the present invention is not limited to the configuration of the above embodiment, and can be changed as appropriate. In particular, the temperature sensor 12 is provided in a water pipe at a predetermined location, and the adhesion of the scale in the water pipe is determined by whether or not the detected temperature of the temperature sensor 12 exceeds a set value for a time equal to or greater than a predetermined ratio within the set time. For example, other configurations can be changed as appropriate.

  For example, in the above embodiment, set values are determined in advance at three locations of the maximum combustion amount, the minimum combustion amount, and the intermediate combustion amount, and the combustion amounts at other locations are obtained by linear interpolation. The amount of combustion for which the set value is determined is not limited to three points. Specifically, a set value may be determined in advance at two points of the maximum combustion amount and the minimum combustion amount, and during this time, it may be obtained by linear interpolation of both. Alternatively, a set value is determined in advance at two or more points between the maximum combustion amount and the minimum combustion amount, and for other locations, immediately before and after that (predetermined set values of the combustion amounts at a plurality of locations) Of these, it may be obtained by linear interpolation between the smaller side and the higher side of the current combustion amount and between the set values of the combustion amount closest to the current combustion amount).

  In addition, the can body 4 of the boiler 1 is not limited to a square shape, and may be a cylindrical shape. In that case, the burner 5 may be installed on the top of the can body 4 downward. Moreover, although the said Example demonstrated the gas-fired boiler 1 using gaseous fuel, it is good also as an oil-fired boiler using liquid fuel.

  Further, in the above-described embodiment, the example in which the combustion amount is continuously adjusted between the maximum combustion amount and the minimum combustion amount has been described. However, the combustion amount may be adjusted stepwise. For example, the control may be performed at four positions of high combustion, medium combustion, low combustion, and stop. Even in such a case, it is possible to determine adhesion of the scale in the water pipe at each combustion position depending on whether or not the detected temperature of the temperature sensor 12 exceeds a set value corresponding to the combustion amount for a time equal to or greater than a predetermined ratio within the set time. it can. At that time, the set value for the intermediate combustion amount can also be obtained by linear interpolation.

DESCRIPTION OF SYMBOLS 1 Boiler 2 Water supply path 3 Steam path 4 Can body 5 Burner 6 Fan 7 Fuel supply path 8 Exhaust gas path 9 Combustion air path 10 Damper 11 Fuel flow control valve 12 Temperature sensor 13 Pressure sensor

Claims (3)

A can body configured by connecting a number of water pipes between the upper header and the lower header;
A burner that heats the water in the can,
A temperature sensor provided in any of the water pipes;
A boiler comprising: a scale determination unit that determines adhesion of scale in the water pipe based on whether or not a temperature detected by the temperature sensor exceeds a set value for a predetermined time or more within a set time. Between the maximum combustion amount and the minimum combustion amount, continuously adjust the combustion amount of the burner according to the steam load,
Change the set value according to the amount of combustion,
Determining adhesion of the scale in the water pipe based on whether or not the temperature detected by the temperature sensor exceeds a set value corresponding to the combustion amount at the set timing for a time equal to or greater than a predetermined ratio within the set time from the set timing. The boiler according to claim 1. The boiler according to claim 2, wherein the set value is determined based on a combustion amount at the set timing and then corrected based on a vapor pressure at the set timing.

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