JP2024042811A - boiler - Google Patents

Abstract

To provide a boiler capable of detecting variation in a mixture ratio of a mixed gas.SOLUTION: A boiler includes: a fuel supply passage 5 for supplying a mixture gas in which a first kind of gas and a second kind of gas having different specific gravity are mixed to a combustion chamber as a fuel; a fuel flow rate adjustment valve 12 provided at the fuel supply passage 5; a pressure loss part 15 provided at the fuel supply passage 5; determination means for determining whether or not a pressure difference between an upstream side and a downstream side of the pressure loss part 15 is within a proper pressure difference range predetermined as a pressure difference that can be observed in the case where the mixture ratio of the first kind of gas and the second kind of gas is proper; and control means for performing specific control when the pressure difference is not determined as being in the proper pressure difference range by the determination means.SELECTED DRAWING: Figure 2

Description

The present invention relates to a boiler.

In recent years, in order to prevent global warming, there has been a need to reduce CO ₂ (carbon dioxide) emissions. For this reason, attempts have been made to reduce carbon dioxide emissions by co-firing natural gas and a gaseous fuel different from natural gas. For example, there is a boiler that uses ammonia as a part of the fuel in addition to natural gas and performs co-firing (for example, Patent Document 1). Co-firing natural gas and hydrogen has also been attempted.

Japanese Patent Application Publication No. 2016-032391

However, there is a large difference in calorific value between natural gas and hydrogen, and the air ratio varies greatly depending on their mixing ratio. For this reason, when a conventional boiler uses a mixture of natural gas and hydrogen as fuel, if the mixing ratio changes, for example, a misfire due to fluctuations in the air ratio may cause the boiler to burn out. There is a possibility that the combustion state and amount of steam generated may be affected.

The present invention was devised in view of such circumstances, and its purpose is to provide a boiler that can detect a change in the mixing ratio of mixed gas.

In order to achieve the above object, the boiler of the present invention includes a fuel supply path for supplying a mixed gas, which is a mixture of a first type of gas and a second type of gas having different specific gravities, to the combustion chamber as fuel; The difference in pressure between the fuel flow rate regulating valve provided in the fuel supply path, the pressure loss section provided in the fuel supply path, and the upstream and downstream sides of the pressure loss section is such that the first type of gas and the a determining means for determining whether or not the differential pressure is within a predetermined appropriate differential pressure range that can be obtained when a mixing ratio with a second type of gas is appropriate; and control means for performing specific control when it is determined that the condition is not within the range.

According to the above configuration, if the mixing ratio changes even when the same flow rate is supplied due to the difference in the specific gravity of the gases to be mixed, the differential pressure between the upstream side and the downstream side of the pressure loss section Focusing on the fact that the differential pressure varies, specific control is performed when the differential pressure is not determined to be within the appropriate differential pressure range. Thereby, it is possible to detect a change in the mixing ratio of the mixed gas based on the differential pressure, and to suppress misfires caused by fluctuations in the mixing ratio.

Preferably, the fuel supply path is provided with a fuel volume flow meter, and the appropriate differential pressure range is changed based on the measurement result of the fuel volume flow meter.

According to the above configuration, the differential pressure is changed to an appropriate differential pressure range corresponding to the flow rate of the supplied mixed gas based on the measurement result of the fuel volume flow meter. Therefore, it is possible to determine whether the mixing ratio is in accordance with the flow rate of the mixed gas being supplied.

FIG. 2 is a diagram for explaining a schematic configuration of a boiler. It is a flow chart for explaining an example of control of a boiler.

A boiler according to the present disclosure will be described with reference to the drawings. It should be noted that the present invention is not limited to these examples, but is indicated by the scope of the claims, and it is intended that all changes within the meaning and range equivalent to the scope of the claims are included in the present invention. Ru.

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

The boiler 1 includes a boiler body 2 that burns fuel to generate steam, a blower 3 that sends air into the boiler body 2 via an air supply path 30, and a flue 4 that leads out exhaust gas etc. from the boiler body 2. , a fuel supply path 5 that supplies fuel to the boiler body 2, and a control device 6 that controls the supply amount of fuel gas and combustion air.

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

Air supplied from the blower 3 is supplied as combustion air to the burner 20 in the boiler main body 2 via the air supply path 30. The flow rate of the combustion air is determined according to the required load (combustion amount) required from the load equipment (not shown). The flow rate of combustion air can be adjusted by installing a damper 7 in the air supply path 30 and adjusting the position (opening degree) of the damper 7, or alternatively or in addition to this, by adjusting the fan of the blower 3 using an inverter. This is done by changing the rotation speed of the In this embodiment, a damper 7 is provided in the air supply path 30, and the flow rate of combustion air is adjusted by changing the position of the damper 7 while rotating the blower 3 at a constant speed.

The fuel supply path 5 includes a fuel volumetric flow meter 10, an on-off valve 11 (electromagnetic valve) for opening and closing the flow path, and is capable of adjusting the flow rate of fuel supplied to the boiler body 2 and also has a shutoff function. A fuel flow rate regulating valve 12, an orifice 15, and a fuel differential pressure sensor 16 are provided. The fuel flow rate adjustment valve 12 is arranged downstream of the on-off valve 11. The fuel flow rate adjustment valve 12 on the downstream side functions as a fuel supply amount adjustment valve that adjusts the flow rate of fuel supplied to the boiler main body 2. In this embodiment, the fuel flow regulating valve 12 is a governor.

The fuel supply path 5 is connected at its upstream side to a fuel tank (not shown) or the like, and connected to the air supply path 30 at its downstream side. The downstream end of the fuel supply path 5 is connected to the air supply path 30 downstream of the position where the damper 7 is disposed. In this embodiment, the fuel flowing through the fuel supply path 5 is a mixed gas of natural gas (mainly containing methane) and hydrogen in a predetermined ratio. The predetermined ratio is, for example, a ratio of 8 parts of natural gas to 2 parts of hydrogen. Note that the mixing ratio of natural gas and hydrogen is not limited to this, and may be determined depending on the usage environment, boiler performance, etc.

The fuel volumetric flow meter 10 measures the volumetric flow rate of fuel (mixed gas) flowing through the fuel supply path 5 . The fuel volume flow meter 10 of this embodiment is arranged at the most upstream side of the fuel supply path 5. Fuel volume flow meter 10 is electrically connected to control device 6 . The control device 6 obtains the volumetric flow rate of fuel based on the measured value (measurement result) of the fuel volumetric flow meter 10 .

The orifice 15 is a fuel pressure reducing member (pressure loss part) that reduces the pressure of the fuel flowing through the fuel supply path 5 . The orifice 15 of this embodiment is arranged downstream of the fuel flow rate regulating valve 12 in the fuel supply path 5 .

The fuel differential pressure sensor 16 detects the differential pressure of the fuel flowing through the fuel supply path 5, measured between the upstream side and the downstream side of the orifice 15. Since the fuel differential pressure sensor 16 is electrically connected to the control device 6, the control device 6 can acquire fuel differential pressure information.

The air supply passage 30 is provided with a combustion air pressure reducing member 8 such as punching metal downstream of the damper 7. The fuel flow control valve 12 (governor) is configured to change its opening depending on the pressure difference before and after the combustion air pressure reducing member 8 in the air supply passage 30. The fuel flow control valve 12 is a pressure equalizing valve whose opening is mechanically adjusted so that the pressure difference introduced and the pressure of the fuel to be supplied (secondary pressure) are equalized. A branch passage 13 is provided in the downstream flow path of the fuel flow control valve 12. The governor can adjust the opening so that the secondary pressure obtained from the branch passage 13 becomes a pressure corresponding to the pressure difference before and after the combustion air pressure reducing member 8 in the air supply passage 30 to be introduced. This allows fuel to be supplied to the boiler body 2 at a flow rate corresponding to the flow rate of the combustion air supplied from the air supply passage 30 (note that the flow rate of the combustion air is controlled according to the amount of combustion as described later, so it can also be said to be a flow rate corresponding to the amount of combustion).

The control device 6 is realized by a computer that includes a memory, a timer, and an arithmetic processing section, and controls the blower 3 and the like based on signals from each electrically connected sensor. The control device 6 also includes a control section 61 that performs various controls for adjusting the flow rate of combustion air, and a storage section 62 that stores various information. The control device 6 controls the combustion amount (combustion rate) in the boiler main body 2 to one of a plurality of combustion stages that differ in stages according to the set target steam pressure and the steam pressure of the steam header. The plurality of combustion stages include, for example, a high combustion stage, a medium combustion stage, and a low combustion stage. The amount of combustion in the boiler main body 2 decreases in the order of high combustion stage, middle combustion stage, and low combustion stage. The control unit 61 also controls the blower 3 and damper 7, which are air supply units, so that the flow rate of combustion air supplied into the boiler main body 2 corresponds to the set combustion stage (combustion amount). control to adjust the supply flow rate of combustion air.

The storage unit 62 includes various information regarding the boiler 1, such as information for specifying the mode of the blower 3 (e.g., rotation speed, frequency) according to the combustion stage, and information for specifying the mode of the blower 3 according to the combustion stage, and the information according to the fuel flow rate (combustion amount). A data table and the like for specifying the appropriate differential pressure range are stored. Based on the measurement result of the fuel volumetric flow meter 10, the control device 6 specifies the appropriate differential pressure range of the fuel according to the volumetric flow rate of the fuel flowing through the fuel supply path 5 by referring to the data table.

The appropriate differential pressure range is a range of differential pressures detected (possible) by the fuel differential pressure sensor 16 when operating at an appropriate air ratio. Further, by supplying combustion air with a flow rate corresponding to the combustion stage, if the mixing ratio of the fuel (mixed gas) is appropriate, operation (combustion) will be performed at an appropriate air ratio. For example, assume that the mixture ratio of hydrogen in the fuel (mixed gas) is 15% to 25%, which allows operation (combustion) at an appropriate air ratio when operating the boiler. Then, the appropriate differential pressure range is the range of differential pressures detected (possible) when the fuel (mixed gas) has an appropriate mixing ratio of hydrogen, 15% to 25%. Note that the mixing ratio of hydrogen is not limited to the range of 15% to 25%, and may be determined depending on the usage environment, boiler performance, etc., as long as stable combustion is possible.

In this embodiment, since fuels (gases) with different specific gravities are mixed, even if the same flow rate is supplied as fuel, if the proportion of hydrogen increases, the fuel differential pressure sensor The differential pressure detected by 16 decreases. On the other hand, when the proportion of hydrogen decreases, the differential pressure detected by the fuel differential pressure sensor 16 will increase. Also, the differential pressure detected when the lower limit of the appropriate hydrogen mixing ratio is 15% is, for example, x1, and the difference detected when the upper limit of the appropriate hydrogen mixing ratio is 25%. For example, if the pressure is x2, the upper limit of the appropriate differential pressure range is x1, and the lower limit is x2. Therefore, when the differential pressure detected by the fuel pressure sensor 16 exceeds x1 or falls below x2, it is possible to identify that the fuel is not at an appropriate mixing ratio and the operation is not performed at an appropriate air ratio. Become.

Further, an appropriate air ratio is an air ratio that allows stable combustion, and is an air ratio within a predetermined range (lower limit to upper limit) that includes the most ideal air ratio. For example, if the ideal air ratio is 1.0, if the air ratio in the predetermined range that allows stable operation, including the air ratio 1.0, is 0.8 to 1.2, then the appropriate air ratio is 1.0. The air ratio is between 0.8 and 1.2. This appropriate air ratio is set for each different combustion amount, and the flow rate of the fuel to be supplied is controlled so that it corresponds to the appropriate air ratio according to each combustion amount. The ideal air ratio and the air ratio within the specified range that allows stable combustion are not limited to the above examples, but may vary depending on the usage environment, boiler performance, etc., as long as stable combustion is possible. It is acceptable as long as it is determined by

The control device 6 determines whether the differential pressure detected by the fuel differential pressure sensor 16 is within the appropriate differential pressure range specified based on the measurement result of the fuel volume flow meter 10. This is because when a variation occurs in the mixing ratio of fuel (mixed gas), the differential pressure detected by the fuel differential pressure sensor 16 may fall outside the appropriate differential pressure range depending on the amount of variation. The control unit 61 performs specific control when it is determined that the differential pressure detected by the fuel differential pressure sensor 16 is not within the appropriate differential pressure range. Specific control includes, for example, safety measures that can be taken when the vehicle is not being operated at an appropriate air ratio, such as the notification of a warning alarm.

In this embodiment, as described above, natural gas containing methane as a main component and gas having different specific gravities such as hydrogen are mixed in advance at a predetermined ratio. However, if the fuel mixture ratio fluctuates due to the usage environment, even if the fuel is supplied at a flow rate that corresponds to the amount of combustion (according to the supplied air flow rate), the air ratio will change. It fluctuates greatly. For example, when the proportion of hydrogen increases, the appropriate amount of air for the fuel with the increased proportion of hydrogen is less than the amount of air supplied according to the amount of combustion, so excess air is The air ratio increases. If the air ratio becomes high in this way, there is a risk of oscillating combustion or misfire. On the other hand, when the proportion of hydrogen decreases, the appropriate amount of air for the fuel with the decreased proportion of hydrogen is greater than the amount of air supplied depending on the fuel condition, so the air ratio becomes lower.

In order to solve this problem, in this embodiment, even when the same flow rate is supplied as fuel, if the mixing ratio changes, the specific gravities of natural gas and hydrogen will differ. Focusing on the fact that the differential pressure detected by the fuel differential pressure sensor 16 fluctuates, specific control is performed when the differential pressure is not determined to be within the appropriate differential pressure range. Thereby, it is possible to detect a change in the mixing ratio of the mixed gas based on the differential pressure, and to specify whether or not the mixing ratio of the fuel is appropriate. In other words, it becomes possible to identify that the vehicle is not being operated at an appropriate air ratio, so that appropriate measures can be taken quickly. As a result, misfires caused by variations in the mixing ratio can be suppressed.

<About boiler control processing>
FIG. 2 is a flowchart for explaining an example of boiler control. The control device 6 executes this control at regular intervals (for example, 1 second) while the boiler 1 is in operation.

In step S01, the volumetric flow rate of fuel flowing through the fuel supply path 5 is measured by the fuel volumetric flow meter 10. In the boiler 1 according to the present embodiment, the fuel flow rate regulating valve 12 is configured to change its opening depending on the differential pressure before and after the combustion air pressure reducing member 8 in the air supply path 30. Fuel flows through the supply path 5 at a volumetric flow rate depending on the amount of combustion. Therefore, the fuel flow volume meter 10 measures the volumetric flow rate of fuel according to the combustion amount.

In step S02, an appropriate differential pressure range corresponding to the volumetric flow rate measured in step S01 is specified by referring to the data table stored in the storage unit 62. Here, the appropriate differential pressure range is detected by the fuel differential pressure sensor 16 when the mixing ratio of fuel (mixed gas) is appropriate (for example, the mixing ratio of hydrogen is 15% to 25%). ) range of differential pressure. In other words, it refers to the fuel pressure difference detected when the engine is operated at a proper air ratio.

In step S03, the fuel differential pressure sensor 16 detects the differential pressure between the upstream side and the downstream side of the orifice 15.

In step S04, it is determined whether the differential pressure detected in step S03 is within the appropriate differential pressure range identified in step S02. If it is determined in step S04 that the detected differential pressure is within the appropriate differential pressure range, the fuel is mixed at the appropriate ratio and the engine is operating at the appropriate air ratio, so the process ends.

On the other hand, if it is determined in step S04 that the detected differential pressure is not within the appropriate differential pressure range, the process proceeds to step S05. In this case, there is a high possibility that the fuel is not in an appropriate mixing ratio and the engine is not being operated with an appropriate air ratio, so a warning alarm is issued in step S05, and the process ends.

As described above, in this embodiment, by utilizing the fact that natural gas and hydrogen have different specific gravities, the differential pressure of the flow rate of the mixed gas (step S03) in which gases with different specific gravities are mixed is adjusted to an appropriate differential pressure. It is possible to determine whether or not it is within the range (step S04). As a result, if it is determined that the differential pressure is not within the appropriate range, specific control such as issuing a warning alarm (step S05) can be performed to suppress misfires caused by fluctuations in the mixing ratio. can.

Further, based on the measurement result of the fuel volume flow meter 10 (step S01), the appropriate differential pressure range for the flow rate of the mixed gas is changed as appropriate (step S02). Therefore, it becomes possible to judge whether or not the mixture ratio is appropriate depending on the amount of combustion.

The present invention is not limited to the above-described embodiment, and various modifications and applications are possible. Below, we will explain modifications of the above-described embodiment that can be applied to the present invention.

In the above embodiment, an example has been described in which a data table stored in advance in the storage unit 62 is referred to in order to specify an appropriate differential pressure range depending on the flow rate of fuel. However, the present invention is not limited to this, and the appropriate differential pressure range may be calculated each time according to the measurement result of the volumetric flow rate, for example, using a predetermined calculation formula.

In the above embodiment, an example of notifying a warning alarm has been described as an example of specific control. However, the specific control is not limited to this; if the differential pressure detected in step S04 is not determined to be within the appropriate differential pressure range, the operation of the boiler is immediately stopped, or after a certain period of time (time) has elapsed. It may be a device that stops later, or a device that stops after a certain period of time (hours) has elapsed since the warning alarm notification. In addition, even after the warning alarm has been notified by specific control, if the differential pressure is detected to be within the appropriate differential pressure range, or after a predetermined period of time has passed, the warning alarm will be terminated. Good too. Additionally, when the differential pressure is not within the appropriate differential pressure range and the mixing ratio is changing, the air supply amount is adjusted as a specific control so that the air ratio is appropriate for the mixing ratio after the fluctuation. You can. Alternatively, a fuel flow rate adjustment valve (gas valve) whose opening degree can be adjusted electromagnetically is installed in the fuel supply path 5, and as a specific control, even if the mixture ratio has changed, the current air supply amount is appropriate. The flow rate of the fuel to be supplied may be adjusted by controlling the opening degree of the gas valve so as to maintain the air ratio.

An example has been described in which the fuel supplied by the boiler 1 in the above embodiment is a mixed gas of natural gas (mainly containing methane) and hydrogen. However, the type of gaseous fuel (gas) to be mixed is not limited to this, and may be any gas with a different specific gravity, such as a mixed gas of propane gas (LP gas) and hydrogen, and is not limited to natural gas or hydrogen. , a gaseous fuel whose specific gravity differs by a factor of 4 to 5, or a mixed gas of gaseous fuels whose specific gravity differs by a factor of 7 to 8 times may be used.

In the above embodiment, the boiler 1 is described as a boiler that controls the combustion amount to one of multiple combustion stages with different combustion amounts. However, the present invention is not limited to this, and may be a boiler that performs ON/OFF control, or may be a boiler with so-called proportional control that can finely control the combustion stage.

In the boiler 1 in the embodiment described above, an example has been described in which the measurement results of the fuel volume flow meter 10 are used to specify the appropriate differential pressure range according to the combustion amount. However, the present invention is not limited to this, and instead of using the fuel volumetric flow meter 10, for example, an appropriate differential pressure range may be predetermined according to the combustion stage (fuel flow rate corresponding to the combustion stage), and the fuel differential pressure range detected by the fuel differential pressure sensor 16 may be determined in advance. It may be determined whether or not the differential pressure is within an appropriate differential pressure range depending on the combustion stage being controlled. The appropriate differential pressure range in this case is the range of differential pressure detected by the fuel differential pressure sensor 16 when the air ratio is appropriate depending on the combustion stage.

In the boiler 1 in the above embodiment, the fuel flow rate is controlled by mechanically adjusting the opening of the fuel flow rate control valve 12, but the fuel supply adjustment valve 12 may be electronically controlled by the control device 6 to adjust the opening rate. When controlling by electronic control, an air amount detection unit that detects the differential pressure before and after the combustion air pressure reduction member 8 and outputs the differential pressure information is electrically connected to the control device 6, and the differential pressure information from the air amount detection unit is input to the control device 6. The control device 6 adjusts the opening rate of the fuel flow rate control valve 12 according to the stage of combustion based on the differential pressure information input from the air amount detection unit. The control device 6 transmits an opening rate specification signal to the fuel flow rate control valve 12 to specify the opening rate based on the opening rate adjustment information previously stored in the memory. As a result, the fuel flow rate control valve 12 is controlled to an opening rate according to the differential pressure before and after the combustion air pressure reduction member 8, and the flow rate of fuel supplied to the boiler body 2 can be adjusted. The opening adjustment information may be, for example, a table capable of determining the opening of the fuel flow control valve 12 according to the pressure difference, or may be an arithmetic formula for determining the opening of the fuel flow control valve 12 according to the pressure difference.

In the above embodiment, an example has been described in which an ON-OFF timer is added to the primary side of the damper wiring to control the damper 7, and the control motor for operating the damper 7 is operated in stages at the time of transition. However, the present invention is not limited to this, and control may be performed by intermittently turning on and off signals from a computer without using a timer. By enabling control without adding a timer, costs can be reduced.

In the above embodiment, an example has been described in which a damper 7 is provided in the air supply passage 30, and the flow rate of the combustion air is adjusted by changing the position of the damper 7 while rotating the blower 3 at a constant speed. However, this is not limited to the above, and the flow rate of the combustion air may be adjusted by the position (opening) of the damper 7 and the rotation speed of the fan of the blower 3. In this case, the control device 6 controls so that the position of the damper 7 and the rotation speed of the fan of the blower 3 do not change over a predetermined period. Alternatively, the flow rate of the combustion air may be adjusted only by the rotation speed of the fan of the blower 3 without providing a damper 7 in the air supply passage 30. In this case, the control device 6 controls so that the rotation speed of the fan of the blower 3 does not change over a predetermined period.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope of the claims.

1 Boiler 2 Boiler body 3 Blower (air supply section)
4 Flue 5 Fuel supply path 6 Control device 61 Control section 62 Storage section 7 Damper (air supply section)
8 Combustion air pressure reducing member 10 Fuel volume flow meter 11 Opening/closing valve 12 Fuel flow regulating valve 13 Branch passage 15 Orifice 16 Fuel differential pressure sensor 20 Burner 30 Air supply passage

Claims (2)

a fuel supply path for supplying a mixed gas, which is a mixture of a first type of gas and a second type of gas having different specific gravities, to the combustion chamber as fuel;
a fuel flow regulating valve provided in the fuel supply path;
a pressure loss section provided in the fuel supply path;
The differential pressure between the upstream side and the downstream side of the pressure loss section is a predetermined appropriate differential pressure that can be obtained when the mixing ratio of the first type of gas and the second type of gas is appropriate. A determination means for determining whether or not it is within the range;
and control means for performing specific control when the determination means does not determine that the pressure difference is within the appropriate differential pressure range. a fuel volumetric flow meter is provided in the fuel supply passage;
The boiler according to claim 1 , wherein the appropriate differential pressure range is changed based on a measurement result of the fuel volumetric flow meter.

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