JP7380331B2 - Boiler fuel gas supply mechanism and boiler - Google Patents

Description

The present invention relates to a fuel gas supply mechanism for a boiler and a boiler.

BACKGROUND OF THE INVENTION Conventionally, boiler devices have been known that heat water by burning a mixture of fuel gas and combustion air at a predetermined ratio to generate steam. In this type of boiler equipment, fuel is supplied according to the amount of combustion air supplied so that the air ratio, which is the ratio between the amount of combustion air required for combustion and the amount of fuel gas supplied to the boiler, is constant. The flow rate of gas is adjusted by a flow rate adjustment valve (fuel gas adjustment valve). An example of a device that controls the air ratio to keep it constant is the amount of fuel gas in a premixed gas burner that keeps the air ratio constant by adjusting the fuel gas control valve according to fluctuations in the amount of combustion air supplied. There is a boiler equipped with a control device (for example, see Patent Document 1).

Japanese Patent Application Publication No. 11-108352

In the above-mentioned boilers, the fuel gas flow rate is adjusted by measuring the differential pressure between the upstream and downstream sides of the orifice and based on this fuel gas differential pressure information. In such cases, the restriction at the fuel gas regulating valve is large and the flow rate of the fuel gas is high. Since the orifice is located on the secondary side of the fuel gas regulating valve, it may be affected by drifting flow from the fuel gas regulating valve, which may cause a problem in that the fuel gas differential pressure cannot be accurately measured. In particular, when the fuel gas supply pressure fluctuates, the fuel gas differential pressure may vary and be measured even though the same flow rate is flowing. As a result, if the fuel gas supply pressure during operation differs depending on the installation environment, for example, the input will change due to the use of inaccurate measurements, and even if the settings are made under the same conditions, the operation At times, there was a risk of poor dryness and overheating.

The present invention was devised in view of the above circumstances, and its purpose is to provide a fuel gas supply mechanism for a boiler and a boiler that can suppress fluctuations in fuel gas differential pressure as much as possible when the fuel gas supply pressure fluctuates. It is to be.

In order to achieve the above object, a fuel gas supply mechanism for a boiler according to the present invention includes a fuel gas regulating valve provided in a fuel gas supply path, and a fuel gas regulating valve provided downstream of the fuel gas regulating valve to adjust the flow rate of the fuel gas. a first pressure drop section for measurement; and a second pressure drop section provided between the fuel gas regulating valve and the first pressure drop section , and the flow passage cross-sectional area of the first pressure drop section is equal to the second pressure drop section. It is characterized by being larger than the flow passage cross-sectional area of the pressure loss part .

According to the above configuration, by providing the second pressure drop part upstream of the first pressure drop part for measuring the flow rate of fuel gas and downstream of the fuel gas regulating valve, the fuel gas in the first pressure drop part is The fuel gas differential pressure can be measured more accurately by alleviating the influence of uneven flow from the regulating valve and suppressing fluctuations in the fuel gas differential pressure at the first pressure loss section even when the fuel gas supply pressure fluctuates. be able to. Moreover, it is possible to suppress an increase in pressure loss while enhancing the rectification effect.

Preferably, the second pressure loss section is a perforated plate.

According to the above configuration, by using the perforated plate, the rectification effect can be further enhanced, and the influence of the uneven flow from the fuel gas regulating valve can be further alleviated.

More preferably, the first pressure loss section is a perforated plate.

According to the above configuration, it is possible to further suppress fluctuations in the fuel gas differential pressure due to fluctuations in the fuel gas supply pressure.

Further, the boiler of the present invention is a boiler comprising the fuel gas supply mechanism of the boiler of the present invention, and a combustion air supply mechanism having a blower, the boiler being a boiler provided with the fuel gas supply mechanism of the boiler of the present invention, and a combustion air supply mechanism supplied from the combustion air supply mechanism. A control unit that sets the opening degree of the fuel gas regulating valve to a set opening degree according to the flow rate of air, and then adjusts the rotation speed of the blower based on the differential pressure between the upstream side and the downstream side of the first pressure loss section. It is characterized by having the following.

According to the above configuration, by using the differential pressure in the first pressure loss section as the rotation speed of the blower, it is possible to perform control to finely adjust the amount of combustion air according to the actual amount of fuel gas.

FIG. 2 is a diagram for explaining the schematic configuration of a boiler. FIG. 2 is a schematic diagram of a graph showing how the fuel gas differential pressure changes when the fuel gas supply pressure fluctuates.

<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 main body 2 that burns fuel to generate steam, a combustion air supply mechanism 3 including a blower that sends air into the boiler main body 2 via an air supply path 30, and exhaust gas from the boiler main body 2. The fuel gas supply mechanism 10 is provided with a flue 4 that leads out fuel gas, etc., and a fuel gas supply mechanism 10 that supplies fuel to the boiler main body 2. Although an example in which the fuel is gas will be described, the fuel is not limited to gas such as gas, but may be liquid such as oil.

The fuel gas supply mechanism 10 includes a fuel supply line (fuel gas supply path) 5. The fuel supply line 5 is connected to the air supply path 30. The fuel supplied from the fuel supply line 5 is mixed with the air blown from the combustion air supply mechanism 3 in the air supply path 30 and is supplied to the burner 20 in the boiler main body 2 .

Air supplied from the combustion air supply mechanism 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 combustion air is adjusted by changing the rotation speed of the blower fan using an inverter.In addition, a damper 7 is provided as the combustion air supply mechanism 3, and the position of the damper 7 (open) It may also be done by adjusting the In this embodiment, the flow rate of combustion air is adjusted by controlling the opening of the damper 7 and controlling the blower with an inverter.

The fuel supply line 5 includes on-off valves (electromagnetic valves) 11 and 12 for opening and closing the flow path, a fuel gas adjustment valve (fuel supply amount adjustment valve) 13, a first pressure loss section 14, a second pressure loss section 15, and a nipple. 16a, 16b, fuel gas pressure sensors 17, 18, and a main gas cock 19 are provided. The fuel gas regulating valve 13 functions as a pressure regulating valve that can adjust the flow rate of fuel supplied to the boiler main body 2. The fuel gas adjustment valve 13 is a motor valve that is provided downstream of the on-off valves 11 and 12 and whose opening degree is adjusted by the control device 6. The fuel gas adjustment valve 13 is electrically connected to the control device 6, and the control device 6 can adjust the opening degree of the fuel gas adjustment valve 13. Note that the fuel gas regulating valve 13 is not limited to a motor valve, and may be, for example, a pneumatic control valve, as long as it regulates the flow rate of fuel.

The first pressure loss section 14 is a fuel gas pressure reducing member that reduces the pressure of the fuel gas flowing through the fuel supply line 5, and is arranged downstream of the fuel gas regulating valve 13. The first pressure loss section 14 in this embodiment is arranged between two nipples 16a and 16b. The nipples 16a and 16b are nipples for pressure measurement using a measuring device (not shown), and the nipple 16a measures the pressure on the upstream side of the first pressure loss section 14, and the nipple 16b measures the pressure on the downstream side of the first pressure loss section 14. By measuring , the fuel gas differential pressure can be obtained. The measuring device is electrically connected to the control device 6, and the control device 6 acquires information on the fuel gas differential pressure between the nipples 16a and 16b.

The second pressure loss section 15 is arranged upstream of the first pressure loss section 14 and downstream of the fuel gas regulating valve 13. By providing the second pressure drop section 15, the influence of uneven flow from the fuel gas regulating valve 13 in the first pressure drop section 14 is alleviated, and even when the fuel gas supply pressure fluctuates, the fuel gas in the first pressure drop section 14 Fluctuations in differential pressure can be suppressed.

The second pressure loss section 15 can be an orifice in which a hole is formed in a plate-shaped member. The second pressure loss section 15 is not limited to one in which one hole is formed, but may be a perforated plate orifice in which a plurality of holes are formed. In the case of a perforated plate orifice, the rectifying effect can be further enhanced and the influence of uneven flow from the fuel gas regulating valve 13 can be further alleviated compared to one in which one hole is formed.

For the first pressure loss section 14, an orifice in which holes are formed in a plate-like member can also be used, but it is more preferable to use a perforated plate orifice. If a porous plate orifice is used as the first pressure loss section 14, it is possible to further suppress fluctuations in the fuel gas differential pressure due to fluctuations in the fuel gas supply pressure. Note that the appropriate orifice diameter size differs depending on the boiler model.

The flow passage cross-sectional area of the first pressure loss part 14 is preferably larger than the flow passage cross-section area of the second pressure loss part 15. In the pressure loss section, the smaller the cross-sectional area of the flow path, the higher the rectification effect. However, if the flow path cross-sectional areas of both the first pressure loss section 14 and the second pressure loss section 15 are made smaller, there is a possibility that the pressure loss will increase. Therefore, by increasing the cross-sectional area of the flow path of the first pressure loss section 14, it is possible to suppress an increase in pressure loss while increasing the rectification effect.

The fuel gas pressure sensor 17 measures the pressure of the fuel gas flowing through the fuel supply line 5 on the upstream side of the fuel gas regulating valve 13 . The fuel gas pressure sensor 17 of this embodiment is arranged downstream of the on-off valve 12 in the fuel supply line 5. The fuel gas pressure sensor 17 is electrically connected to the control device 6, and the control device 6 acquires pressure information from the fuel gas pressure sensor 17.

The fuel gas pressure sensor 18 measures the pressure of the fuel gas flowing through the fuel supply line 5 on the downstream side of the fuel gas regulating valve 13 . The fuel gas pressure sensor 18 of this embodiment is arranged between the first pressure loss section 14 and the second pressure loss section 15 in the fuel supply line 5. The fuel gas pressure sensor 18 is electrically connected to the control device 6, and the control device 6 acquires pressure information from the fuel gas pressure sensor 18.

The main gas cock 19 is, for example, a ball valve that is manually opened and closed, and is normally opened. The main gas cock 19 shuts off the fuel supply line 5 when it is closed, and is used when performing a leakage test on the on-off valves 11 and 12.

The control device 6 is realized by a computer that includes a memory, a timer, and an arithmetic processing section, and controls the fuel gas regulating valve 13 and the blower based on signals from each electrically connected sensor.

In the present embodiment, the air supply path 30 is provided with a combustion air decompression member 8 made of punched metal or the like downstream of the damper 7 . The air flow rate detection unit 9 detects the pressure difference before and after the combustion air pressure reducing member 8, and outputs pressure difference information. The air flow rate detection section 9 is electrically connected to the control device 6. Thereby, differential pressure information from the air flow rate detection section 9 can be input to the control device 6. Note that the analog signal output from the air flow rate detection section 9 is converted into a digital signal and input to the control device 6.

The control device 6 controls the combustion stage to one of a plurality of combustion stages having different combustion amounts, such as a low combustion stage L, a middle combustion stage M, and a high combustion stage H, for example. The control device 6 controls the combustion stage according to the set target steam pressure and the steam pressure of the steam header. The control device 6 controls the blower in a manner (for example, rotation speed, frequency) that corresponds to the combustion stage being controlled, and supplies an amount of combustion air that corresponds to the combustion stage. The control device 6 calculates (detects) the flow rate of combustion air actually supplied to the boiler main body 2 based on the differential pressure information detected by the air flow rate detection section 9.

The control device 6 sets the opening degree of the fuel gas regulating valve 13 to a set opening degree in accordance with the flow rate of combustion air supplied from the combustion air supply mechanism 3. For example, if the flow rate of combustion air increases, the opening degree of the fuel gas regulating valve 13 is increased to increase the fuel flow rate, while if the flow rate of combustion air decreases, the opening degree of the fuel gas regulating valve 13 increases. to reduce the fuel flow rate. Thereafter, the control device 6 adjusts the rotation speed of the blower based on the differential pressure between the upstream side and the downstream side of the first pressure loss section 14. As a result, the rotation speed of the blower is finely adjusted according to the actual fuel flow rate, and the opening degree of the fuel gas adjustment valve 13 is finely adjusted according to the combustion air flow rate that has been finely adjusted according to the actual fuel flow rate. Feedback control such as adjustment is performed. These series of controls may include manual adjustments.

The control device 6 includes a control section 61 and a storage section 62. The storage unit 62 stores various information regarding the boiler 1, and the control unit 61 specifies the opening degree for the fuel gas adjustment valve 13 based on the opening adjustment information stored in advance in the storage unit 62. Sends an opening specific signal for Thereby, the fuel gas regulating valve 13 is controlled to an opening degree according to the differential pressure before and after the combustion air pressure reducing member 8, and the flow rate of fuel supplied to the boiler main body 2 can be adjusted. Note that the opening adjustment information may be, for example, a table that can specify the opening of the fuel gas adjustment valve 13 according to the differential pressure (or the flow rate of combustion air calculated from the differential pressure), or It may be an arithmetic expression for specifying the opening degree of the fuel gas regulating valve 13 according to the differential pressure (or the flow rate of combustion air calculated from the differential pressure).

The opening degree of the fuel gas regulating valve 13 is determined to be a set opening degree based on the pressure difference before and after the combustion air pressure reducing member 8 and according to the opening degree adjustment information. Therefore, theoretically, the air ratio based on the flow rate of combustion air and the flow rate of supplied fuel will be converged to an air ratio depending on the combustion stage. However, for example, due to environmental changes (disturbances) such as fuel temperature, there may actually be cases where the air ratio does not converge to the one corresponding to the combustion stage. Therefore, the control device 6 measures the pressure loss from the differential pressure between the upstream side and the downstream side of the first pressure loss section 14, and makes fine adjustments by adjusting the rotation speed of the blower according to the actual flow rate of the fuel gas. conduct.

In the boiler 1 of the present embodiment, the second pressure loss section 15 for rectification is provided between the fuel gas regulating valve 13 and the first pressure loss section 14, thereby alleviating the influence of uneven flow of fuel gas, and It is possible to more accurately measure the differential pressure between the upstream side and the downstream side of the pressure loss section 14. Therefore, the rotation speed of the blower can be adjusted more accurately based on the measurement of pressure loss. Note that the opening degree of the fuel gas regulating valve 13 can also be adjusted using the differential pressure information of the first pressure loss section 14, but in this case, the air ratio will shift, so it is necessary to change the air amount at the same time. Therefore, the boiler 1 of the present embodiment controls the blower of the combustion air supply mechanism 3 to adjust the amount (flow rate) of combustion air blown, and the opening degree of the fuel gas regulating valve 13 according to the amount of air blown. The amount of fuel gas is automatically changed according to the amount of air by setting the opening degree to the set value.

In the boiler, the flow path from the fuel gas regulating valve 13 to the first pressure loss section 14 cannot be made long considering the flow rate of the fuel gas. If the flow path from the fuel gas adjustment valve 13 to the first pressure loss section 14 is long, the time it takes for the fuel gas to come out of the cutoff valve (on-off valve) becomes longer, causing a time lag in control and preventing proper control. This is because it becomes difficult. Further, the supply pressure of fuel gas generally has a wide range of 30 kPa to 300 kPa. It is desirable to keep the flow rate of fuel gas as constant as possible even if the supply pressure varies greatly (even if it fluctuates greatly). 1 It is preferable that the flow path up to the pressure loss part 14 be short. On the other hand, when the flow path from the fuel gas regulating valve 13 to the first pressure loss section 14 is shortened, the rectification effect is reduced by the shorter path compared to a case where the flow path is long. In order to eliminate such problems, the fuel gas supply mechanism 10 of the boiler 1 in this embodiment shortens the path by providing a pressure loss section between the fuel gas regulating valve 13 and the first pressure loss section 14. However, it also improves the rectification effect.

<About operation>
Referring to FIG. 2, the operation of boiler 1 in this embodiment will be described. FIG. 2 is a diagram schematically showing a graph showing how the fuel gas differential pressure changes when the fuel gas supply pressure varies, for example, in a range of 50 kPa to 200 kPa. In FIG. 2, the solid line indicates the measured value of the fuel gas differential pressure, and the broken line indicates the ideal value of the fuel gas differential pressure. FIG. 2(A) shows the results for a boiler with no pressure loss section between the fuel gas adjustment valve 13 and the first pressure loss section 14, and FIG. 2(B) shows the results from the fuel gas adjustment valve 13 to the first pressure loss section 14. These are the results for the boiler 1 having the configuration of the present embodiment in which a pressure loss part (second pressure loss part 15) is provided up to the first pressure loss part 14. In the boiler 1 having the configuration of the present embodiment, a perforated plate orifice provided with n holes each having a diameter of X mm is used as the first pressure loss part 14, and a perforated plate orifice having n holes each having a diameter of A perforated plate orifice provided with n holes was used. X is, for example, a value in the range of 5 mm to 8 mm, and Y is, for example, in the range of 4 mm to 7 mm, even if it is a value smaller than X or a value of X x 0.9. good. Further, n may be any value in the range of 15 to 25. The second pressure loss section 15 may have holes formed so that the cross-sectional area of the flow path is smaller than that of the first pressure loss section 14, and the diameter of the hole may be larger than that of the first pressure loss section 14. Alternatively, the number of holes may be greater or less than that of the first pressure loss section 14.

In the conventional configuration, for example, when the fuel gas supply pressure fluctuates during the high combustion stage, the fuel gas differential pressure changes as shown by the _double arrow in FIG. The fluctuation range _DA is shown as . In contrast, in the present embodiment, the variation in the fuel gas differential pressure is suppressed to the variation width D _B shown by the double-headed arrow in FIG. It can be seen that by adopting the configuration of the embodiment, the fluctuation range of the fuel gas differential pressure when the fuel gas supply pressure fluctuates is suppressed, and the difference between the ideal value and the actual value is reduced.

Although FIG. 2 shows the results in the high combustion stage, a similar effect of suppressing fluctuations in the fuel gas differential pressure was also observed in the low combustion stage and the middle combustion stage. Furthermore, similar effects were confirmed even when the capacities of the boilers were different. Note that in FIG. 2, the "ideal fuel gas differential pressure value" is a value obtained by calculating the ideal value for the actually measured exhaust gas O ₂ concentration. Because this is actual measurement data, there are some fluctuations in _O2 , and the ideal value is calculated for that, so the ideal value of the fuel gas differential pressure is not a constant value, but it is possible that the fuel gas supply pressure changes. Also, if the exhaust gas O ₂ concentration is constant, the fuel gas differential pressure will be constant. The reason why the ideal value of the fuel gas differential pressure differs between the conventional configuration and the configuration of this embodiment is that both are calculated from the actual measured value of the exhaust gas O ₂ concentration, and the hole shape of the orifice has changed. This is due to the difference in pressure loss.

The present invention is not limited to the embodiments described above, and various modifications and applications are possible. Modifications of the above embodiments applicable to the present invention will be described below.

In the above embodiment, a boiler is described that is equipped with a combustion device that performs multi-position control to control the combustion stages to one of the low combustion stage, middle combustion stage, and high combustion stage as combustion stages with different combustion amounts. However, the present invention is not limited to this, and may be a boiler equipped with a combustion device that performs proportional control, for example.

Further, in the embodiment described above, the first pressure loss section 14 is arranged between the nipples 16a and 16b for pressure measurement with a measuring instrument, and the nipple 16a measures the pressure on the upstream side of the first pressure loss section 14, and the nipple 16b measures the pressure on the upstream side of the first pressure loss section 14. Although a mode has been described in which the fuel gas differential pressure is obtained by measuring the pressure on the downstream side of the first pressure loss section 14, the present invention is not limited to this, and for example, a differential pressure sensor may be provided to obtain the fuel gas differential pressure. Good too.

In addition, in the above example, as a method of controlling the amount of combustion air, the aspect of the blower (rotation speed, etc.) is adjusted based on the fuel gas differential pressure, but the method is not limited to this. The opening degree may be adjusted, or both the aspect of the blower (rotation speed, etc.) and the opening degree of the damper 7 may be adjusted.

The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of this invention is indicated by the claims rather than the above description, and it is intended that all changes within the meaning and range equivalent to the claims are included.

1 Boiler 2 Boiler body 3 Combustion air supply mechanism 4 Flue 5 Fuel supply line (fuel gas supply route)
6 Control device 61 Control unit 62 Storage unit 7 Damper 8 Combustion air pressure reduction member 9 Air flow rate detection unit (flow rate detection means)
10 Fuel gas supply mechanism 11 On-off valve 12 On-off valve 13 Fuel gas adjustment valve 14 First pressure loss part 15 Second pressure loss part 16a, 16b Nipple 17 Fuel gas pressure sensor 18 Fuel gas pressure sensor 19 Main gas cock 20 Burner 30 Air supply path

Claims (4)

a fuel gas adjustment valve provided in the fuel gas supply path;
a first pressure loss section provided downstream of the fuel gas regulating valve and for measuring the flow rate of the fuel gas;
a second pressure loss section provided between the fuel gas regulating valve and the first pressure loss section ;
A fuel gas supply mechanism for a boiler , wherein a flow passage cross-sectional area of the first pressure loss part is larger than a flow passage cross-section area of the second pressure loss part . The fuel gas supply mechanism for a boiler according to claim 1, wherein the second pressure loss section is a perforated plate. 3. The fuel gas supply mechanism for a boiler according to claim 2, wherein the first pressure loss section is a perforated plate. A fuel gas supply mechanism for a boiler according to any one of claims 1 to 3 ,
A boiler equipped with a combustion air supply mechanism having a blower,
setting the opening degree of the fuel gas regulating valve to a set opening degree according to the flow rate of combustion air supplied from the combustion air supply mechanism;
The boiler further comprises a control section that adjusts the rotation speed of the blower based on the differential pressure between the upstream side and the downstream side of the first pressure loss section.

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