Flow rate control mechanism and combustion control system including the same

Abstract

To improve economic performance by maintaining a simple configuration without a flowmeter, and save manpower through automation of various types of regulation, such as a flow rate.SOLUTION: While primary side pressure regulation sections GA, B maintain a primary side inlet pressure at a flow rate control pressure, a control section S1 controls openings of flow control valves RVa, RVg on the basis of opening flow rate relation stored in a storage section S3 to control a flow rate of control target gas to a target flow rate, and executes secondary side pressure regulation determination control for determining the necessity of regulation of a secondary side pressure by comparing the secondary side pressure measured by second pressure gauges P2a, P2g with a pressure derived from the openings of the flow control valves RVa, RVg during pressure measurement by using the second pressure gauges P2a, P2g and an opening pressure relation.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a flow rate control mechanism that controls the flow rate of a gas to be controlled, which is either a fuel gas or a combustion gas serving as an oxidizer for the fuel gas, and a combustion control system equipped with the same. [Background technology]

[0002] Conventionally, a pressure equalizing valve type combustion control system has been known as a combustion control system used in industrial furnaces and the like (see Patent Document 1). This pressure equalizing valve type combustion control system is configured, for example, to include a fuel pipe connected to a burner and carrying fuel gas such as city gas 13A, an air pipe similarly connected to the burner and carrying combustion air, a temperature controller that controls the burner output based on the temperature of the industrial furnace, a control valve connected by a linkage to a control motor that controls the flow rate of air flowing through the air pipe based on a signal from the temperature controller and is controlled to open and close, a pressure equalizing valve that controls the opening of the fuel pipe in a manner corresponding to the air pressure on the secondary side of the control valve of the air pipe, and a blower that pressure-feeds combustion air to the air pipe. In this pressure equalizing valve type combustion control system, the linkage between the control motor and the control valve is manually adjusted by an expert, and the adjustment is one-point adjustment, so changing the air ratio, etc., requires another manual adjustment by an expert. This is also the case with double linkage type combustion control systems. Another known configuration is an electronic linkage type combustion control system, which includes, for example, a fuel pipe connected to the burner and carrying fuel gas such as city gas 13A, an air pipe similarly connected to the burner and carrying combustion air, a temperature controller that controls the burner output based on the temperature of the industrial furnace, a control unit that receives signals from the temperature controller, a flow meter that measures the flow rate of fuel gas flowing through the fuel pipe and the flow rate of air flowing through the air pipe and sends the results to the control unit, a fuel flow control valve that controls the flow rate of fuel gas flowing through the fuel pipe based on a signal from the control unit, and an air flow control valve that controls the flow rate of air flowing through the air pipe based on a signal from the control unit. In this electronic linkage system, the flow rate of fuel gas and combustion air is monitored by a flow meter, and the air ratio based on this is monitored, and the air ratio can be changed by setting the control unit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-47654 Summary of the Invention [Problem to be solved by the invention]

[0004] The flow control used in the above-mentioned pressure equalizing valve type combustion control system does not allow monitoring of the flow rate and air ratio of the fuel gas and combustion air, and if these deviate from the target values ​​for some reason, the user will not be aware of this, and there is a risk that the furnace temperature will not be able to be maintained at the set value. Furthermore, adjustments to the output and air ratio require manual adjustment by an experienced technician, making it difficult to improve efficiency by reducing the number of people required. On the other hand, although the electronic linkage system enables automatic monitoring and automatic adjustment of the flow rate and air ratio of fuel gas and combustion air, it requires the installation of a relatively expensive flow meter, which is problematic from an economic standpoint.

[0005] The present invention has been made in view of the above-mentioned problems, and its object is to provide a fluid flow control mechanism that improves economy by maintaining a simple configuration without a flow meter, and that can achieve labor savings by automating various adjustments such as flow rate, and a combustion control system equipped with the same. [Means for solving the problem]

[0006] The flow control mechanism for achieving the above object is as follows: A flow rate control mechanism including a control unit that controls the flow rate of a control target gas, which is either a fuel gas or a combustion gas serving as an oxidizer for the fuel gas, and characterized by the following configuration: a flow control valve that is provided in an on-site piping through which the gas to be controlled flows, and whose opening is controlled by a control command from the control unit; a secondary-side pressure adjusting unit that is provided on the secondary side of the flow control valve in the on-site piping and that is capable of adjusting the pressure of the secondary-side outlet based on a measurement result of a second pressure gauge that is provided at a secondary-side outlet of the flow control valve; a primary-side pressure adjusting unit that is provided on the primary side of the flow control valve in the on-site piping and that is capable of adjusting the pressure of the primary-side inlet based on a measurement result of a first pressure gauge that is provided at the primary-side inlet of the flow control valve; In a testing facility comprising a test pipe having the same diameter as the on-site pipe, the flow control valve, the second pressure gauge, the secondary pressure adjustment unit, and the primary pressure adjustment unit, and a flow meter for measuring a flow rate of the test pipe, the control unit causes the controlled gas to flow through the test pipe, and while maintaining the flow control valve at a predetermined initial setting, sets the pressure of the secondary outlet to a predetermined initial setting secondary pressure using the secondary pressure adjustment unit, and then stores an opening-flow rate relationship between the opening of the flow control valve and the flow rate measured by the flow meter, and stores an opening-pressure relationship between the opening of the flow control valve and the secondary pressure measured by the second pressure gauge, while maintaining the pressure of the primary inlet at a predetermined flow control pressure using the primary pressure adjustment unit, In the on-site facility provided with the flow control valve, the second pressure gauge, the secondary-side pressure adjustment unit, and the primary-side pressure adjustment unit in the on-site piping, the control unit causes the gas to be controlled to flow through the on-site piping, and while maintaining the flow control valve at the initially set opening, sets the pressure of the secondary-side outlet to the initially set secondary pressure using the secondary-side pressure adjustment unit, and then, while maintaining the pressure of the primary-side inlet at the flow control pressure using the primary-side pressure adjustment unit, controls the opening of the flow control valve based on the opening-flow-rate relationship stored in the memory unit to control the flow rate of the gas to be controlled to a target flow rate, and executes secondary-side pressure adjustment determination control to determine whether or not adjustment of the secondary-side pressure is necessary by comparing the secondary-side pressure measured by the second pressure gauge with the opening of the flow control valve when the pressure is measured by the second pressure gauge and the derived pressure derived from the opening-pressure relationship.

[0007] According to the above characteristic configuration, a secondary pressure adjustment unit is provided that is provided on the secondary side of the flow control valve in the on-site piping and is capable of adjusting the pressure of the secondary outlet based on the measurement results of the second pressure gauge provided at the secondary outlet of the flow control valve, so that by appropriately setting the secondary pressure adjustment unit of the flow control valve in the on-site piping, it is possible to adjust the pressure loss on the secondary side of the flow control valve to a constant value regardless of the site. In this configuration, the flow rate Q of the controlled gas flowing through the on-site piping can be derived from the relational expression Q=K√P2 using the pressure P2 at the secondary outlet of the flow control valve. Furthermore, by providing a primary side pressure adjustment unit that is provided on the primary side of the flow control valve in the test piping and that can adjust the pressure at the primary side inlet based on the measurement results of the first pressure gauge provided at the primary side inlet of the flow control valve, the pressure at the primary side inlet of the flow control valve is maintained at a predetermined flow control pressure by the primary side pressure adjustment unit, and the resulting opening / flow rate relationship between the opening of the flow control valve and the flow rate flowing through the test piping can be used as is in field equipment that has field piping of the same diameter as the test piping. In other words, the opening / flow rate relationship obtained in the test facility can be commonly used in various field facilities with different pressure losses on the secondary side of the flow control valve, so that in the field facility, the flow rate of the controlled gas flowing through the field piping can be controlled to a desired flow rate by controlling the opening of the flow control valve based on the known opening / flow rate relationship without installing a relatively expensive flow meter.

[0008] In the above characteristic configuration, the secondary side pressure adjustment unit is intended to adjust the secondary side pressure loss of the flow control valve, which varies from site to site, to a predetermined value, so after the initial secondary pressure is set, the pressure at the secondary side outlet will not be readjusted even if the opening of the flow control valve changes and the pressure at the secondary side outlet fluctuates.

[0009] However, when this flow control mechanism is applied to, for example, a waste heat recovery burner, if the head pressure changes between cold and warm conditions, or if the secondary side of the flow control valve becomes clogged with dust or other particles after long-term use, it may become impossible to properly adjust the flow rate using the above-mentioned control.

[0010] Therefore, in the above-described characteristic configuration, in order to determine whether or not such a situation has occurred, the secondary pressure adjustment determination control compares the secondary pressure measured by the second pressure gauge with the outlet pressure derived from the opening of the flow control valve at the time of pressure measurement by the second pressure gauge and the opening-pressure relationship to determine whether or not adjustment of the secondary pressure is necessary. In other words, when the above-described situation has occurred, the outlet pressure derived from the previously acquired opening-pressure relationship and the current opening of the flow control valve will deviate from the secondary pressure measured by the second pressure gauge, and therefore it is possible to determine whether or not adjustment of the secondary pressure is necessary based on the presence or absence of this deviation. In this way, when the secondary pressure adjustment judgment control determines that adjustment of the secondary pressure is necessary, the secondary pressure is adjusted by the secondary pressure adjustment unit, thereby realizing a flow control mechanism that can perform appropriate flow control. Furthermore, this control does not require manual adjustment by an expert, which also reduces manpower and improves efficiency.

[0011] Further characteristic configurations of the flow rate control mechanism include: When the control unit determines in the secondary-side pressure adjustment determination control that adjustment of the secondary-side pressure is necessary, the secondary-side pressure adjustment unit executes secondary-side pressure adjustment control to correct the secondary-side pressure based on the opening of the flow control valve at the time of determination in the secondary-side pressure adjustment determination control and the derived pressure derived from the opening-pressure relationship.

[0012] According to the above characteristic configuration, when the control unit determines in the secondary-side pressure adjustment determination control that adjustment of the secondary-side pressure is necessary, the secondary-side pressure adjustment unit executes secondary-side pressure adjustment control to correct the secondary-side pressure based on the derived pressure derived from the opening of the flow control valve at the time of determination in the secondary-side pressure adjustment determination control and the opening-pressure relationship.Therefore, by correcting the current opening-pressure relationship to the opening-pressure relationship at the time of initial setting when the secondary-side pressure in the on-site piping is set to the initially set secondary pressure, the opening-flow rate relationship can also be adjusted to the opening-flow rate relationship at the time of initial setting.

[0013] Further characteristic configurations of the flow rate control mechanism include: An alarm notification unit is provided to notify an alarm to the outside, When it is determined in the secondary-side pressure adjustment determination control that adjustment of the secondary-side pressure is necessary, the control unit executes notification control to issue the alarm in the alarm notification unit.

[0014] According to the above characteristic configuration, when the control unit determines in the secondary side pressure adjustment determination control that adjustment of the secondary side pressure is necessary, it executes notification control to issue an alarm in the alarm notification unit. Therefore, for example, the user can be notified early on that there is a possibility that dust has become clogged on the secondary side of the flow control valve due to long-term use, and burner maintenance can be carried out with ample time, taking into account the usage conditions of the burner.

[0015] A combustion control system using the above-described flow rate control mechanism, characterized in that: a fuel flow rate control mechanism serving as the flow rate control mechanism for controlling the flow rate of the fuel gas serving as the gas to be controlled that flows through a fuel pipe connected in communication with a burner serving as the on-site pipe; a combustion gas flow rate control mechanism as the flow rate control mechanism for controlling the flow rate of the combustion gas as the control target gas flowing through a combustion gas pipe connected in communication with the burner as the on-site pipe, The control unit controls the flow rate of the combustion gas to the target flow rate and executes the secondary pressure adjustment determination control for the combustion gas so that the burner achieves the target output and target air ratio, and also controls the flow rate of the fuel gas to the target flow rate and executes the secondary pressure adjustment determination control for the fuel gas.

[0016] According to the above characteristic configuration, it is possible to realize a combustion control system that can improve economy by maintaining a simple configuration without a flow meter, while reducing manpower by automating various adjustments of flow rate, etc. Furthermore, it is also possible to determine whether adjustment of the secondary pressure is necessary due to causes specific to the on-site equipment, as described above, which can be a problem in that case, and by performing adjustment based on this determination, for example, it is possible to achieve even better flow rate control.

[0017] A combustion control system using the above-described flow rate control mechanism, characterized in that: a fuel flow rate control mechanism serving as the flow rate control mechanism for controlling the flow rate of the fuel gas serving as the gas to be controlled that flows through a fuel pipe connected in communication with a burner serving as the on-site pipe; a combustion gas flow rate control mechanism as the flow rate control mechanism for controlling the flow rate of the combustion gas as the control target gas flowing through a combustion gas pipe connected in communication with the burner as the on-site pipe, the control unit controls the flow rate of the combustion gas to the target flow rate and executes the secondary-side pressure adjustment determination control for the combustion gas so that the burner achieves a target output and a target air ratio, and also controls the flow rate of the fuel gas to the target flow rate and executes the secondary-side pressure adjustment determination control for the fuel gas, If the secondary-side pressure adjustment determination control for the combustion gas determines that adjustment of the secondary-side pressure is necessary, the secondary-side pressure adjustment control for the combustion gas is executed, and if the secondary-side pressure adjustment determination control for the fuel gas determines that adjustment of the fuel gas is necessary, the secondary-side pressure adjustment control for the fuel gas is executed.

[0018] According to the above characteristic configuration, it is possible to realize a combustion control system that can improve economy by maintaining a simple configuration without using a flow meter, while reducing manpower by automating various adjustments of flow rate, etc. Furthermore, it is possible to determine whether or not adjustment of the secondary pressure is necessary due to causes specific to the on-site equipment as described above, which can be a problem in that case, and if it is determined that adjustment is necessary, to execute secondary pressure adjustment control, thereby more accurately controlling the flow rates of the fuel gas and combustion gas, thereby achieving combustion in which the burner air ratio is maintained at a desired value. This makes it possible to improve energy conservation, for example, in a configuration in which a combustion furnace is heated by a burner, by preventing the furnace from being cooled by supplying more combustion gas than necessary, and by preventing incomplete combustion due to a lack of combustion gas.

[0019] Further characteristic configurations of the above-described combustion control system include: The burner is a waste heat recovery burner in which the combustion gas supplied to the burner is preheated by combustion exhaust gas.

[0020] When a waste heat recovery burner is used as the burner, it is conceivable that the temperature of the combustion gas changes between cold and warm conditions downstream of the secondary pressure adjustment unit, causing the head pressure of the burner to change. However, by executing secondary pressure adjustment judgment control or secondary pressure adjustment judgment control in addition to secondary pressure adjustment judgment control, as in the above characteristic configuration, the change in head pressure between cold and warm conditions can be absorbed by adjustment by the secondary pressure adjustment unit, thereby achieving even more accurate flow rate control.

[0021] Further characteristic configurations of the above-described combustion control system include: The control unit controls the flow rate of the control-target gas using the same opening / flow rate relationship for different types of burners.

[0022] According to the above characteristic configuration, even when different types of burners (e.g., different pressure losses) are used in on-site equipment, the influence of different pressure losses of different burners can be eliminated by controlling the pressure at the secondary outlet of the flow control valve to the initial secondary pressure during initial setup using the secondary pressure adjustment unit, and a common opening / flow rate relationship can be used for different types of burners.

[0023] Further characteristic configurations of the above-described combustion control system include: The control unit executes the secondary pressure adjustment determination control using the opening-pressure relationship that is common to different types of burners, and further, the control unit executes the secondary pressure adjustment determination control and the secondary pressure adjustment control using the opening-pressure relationship that is common to different types of burners.

[0024] According to the above characteristic configuration, even when different types of burners (for example, different pressure losses) are used in on-site equipment, a common opening / flow rate relationship can be used for the different types of burners, and secondary-side pressure adjustment determination control, or secondary-side pressure adjustment control in addition to secondary-side pressure adjustment determination control, can be performed, thereby realizing a combustion control system that exhibits the various effects described above. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a schematic configuration diagram of a combustion control system according to an embodiment. [Figure 2] FIG. 1 is a schematic configuration diagram showing a test facility according to an embodiment. [Figure 3] FIG. 10 is a graph showing the relationship between opening degree and flow rate for combustion air. [Figure 4] FIG. 4 is a graph showing the relationship between the head pressure and the flow rate of the burner. [Figure 5] FIG. 10 is a graph showing the relationship between opening degree and flow rate for fuel gas. [Figure 6] FIG. 10 is a graph showing an example of the relationship between opening degree and flow rate of a gas to be controlled. [Figure 7] FIG. 10 is a graph showing an example of the relationship between opening degree and pressure of a gas to be controlled. [Figure 8] FIG. 10 is a graph showing changes in the air ratio when secondary-side pressure regulation control is performed (with correction) and when it is not performed (without correction) under the first condition, in relation to a case where the temperature inside the furnace increases over time. [Figure 9] FIG. 10 is a graph showing the change in the operating amount of the pressure regulating valve when secondary side pressure regulation control is performed (with correction) and when it is not performed (without correction) under the first condition in the case where the temperature inside the furnace increases over time. [Figure 10] FIG. 10 is a graph showing the change in the deviation rate of the combustion air flow rate when secondary pressure adjustment control is performed (with correction) and when it is not performed (without correction) under the first condition in a case where the furnace temperature increases over time. [Figure 11] FIG. 10 is a graph showing a change in the air ratio when secondary-side pressure regulation control is executed under a second condition. [Figure 12] FIG. 10 is a graph showing the change in furnace temperature over time when secondary-side pressure regulation control is executed under the second condition. [Figure 13] 10 is a graph showing the change over time in the deviation rate of the flow rate of combustion air and the operating amount of the pressure regulating valve when secondary-side pressure regulation control is executed under the second condition. FIG. [Figure 14] 10 is a graph showing the change over time in the primary pressure (primary pressure) of the combustion air flow control valve when secondary pressure regulation control is executed under a second condition. FIG. [Figure 15] 10 is a graph showing the change over time in the flow rate deviation rate of combustion air and the operating amount of the pressure regulating valve when secondary-side pressure regulation control is not executed under the second condition. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0026] The flow control mechanisms 100, 200 and the combustion control system 300 according to the embodiments of the present invention maintain a simple configuration without a flow meter, improving economy, and also realizing labor savings by automating various adjustments of the flow rate, etc. Hereinafter, flow rate control mechanisms 100, 200 and a combustion control system 300 according to this embodiment will be described with reference to FIGS.

[0027] As shown in FIG. 1, the combustion control system 300 according to this embodiment is configured to include a flow control mechanism 100 for a fuel gas G (an example of a gas to be controlled) such as city gas 13A, a flow control mechanism 200 for combustion air (an example of a combustion gas and a gas to be controlled) as an oxidizer for the fuel gas, a control device S realized in a form in which hardware and software work together, and a burner BNa, and is configured to heat the inside of an industrial furnace R to a predetermined temperature. Furthermore, the combustion control system 300 according to this embodiment is a system that can control the flow rate of combustion air to a desired value without using a flow meter, even in exhaust heat recovery burners (burners in which combustion gas is preheated by combustion exhaust gas), such as recuperator burners and regenerative burners, in which the pressure loss of the combustion air flowing through the burner changes significantly between warm and cold states.

[0028] As shown in FIG. 1 , the fuel flow rate control mechanism 100 (an example of a flow rate control mechanism) for the fuel gas G is provided in on-site fuel piping H1 (an example of on-site piping) through which the fuel gas G flows, and includes: a fuel flow rate control valve RVg whose opening is controlled by a control command from a control unit S1 provided in the control device S; a secondary-side fuel pressure adjustment unit PVg (an example of a secondary-side pressure adjustment unit) that is provided on the secondary side of the fuel flow rate control valve RVg in the on-site fuel piping H1 and is capable of adjusting the pressure of the secondary-side outlet based on a measurement result of a second fuel pressure gauge P2g provided at a secondary-side outlet of the fuel flow rate control valve RVg; a governor GA as a primary-side pressure adjustment unit that is provided on the primary side of the fuel flow rate control valve RVg in the on-site fuel piping H1 and is capable of adjusting the pressure of the primary-side inlet based on a measurement result of a first fuel pressure gauge P1g provided at a primary-side inlet of the fuel flow rate control valve RVg; and a memory unit S3 that stores an opening-fuel flow rate relationship (shown in FIG. 5 ) between the opening of the fuel flow rate control valve RVg and the flow rate of fuel flowing through the on-site fuel piping H1, as will be described in detail later. The storage unit S3 is provided integrally with the control device S. More specifically, the on-site fuel piping H1 is provided with, from the upstream side, a second safety solenoid valve SV2, a first safety solenoid valve SV1, a governor GA, a first fuel pressure gauge P1g, a fuel flow control valve RVg, a second fuel pressure gauge P2g, a secondary side fuel pressure adjustment unit PVg, and a burner BNa (e.g., an exhaust heat recovery burner), in the order listed. With this configuration, in a fuel on-site facility 100a provided with a fuel flow control valve RVg, a secondary-side fuel pressure adjustment unit PVg, and a governor GA as a primary-side pressure adjustment unit in a fuel on-site piping H1, the fuel flow control mechanism 100, while fuel gas G is flowing through the fuel on-site piping H1, sets the pressure of the secondary-side outlet to a predetermined initially set secondary pressure (e.g., 4 kPaG) by the secondary-side fuel pressure adjustment unit PVg with the fuel flow control valve RVg maintained at a predetermined initially set opening (e.g., 100% opening), and then, while the pressure of the primary-side inlet is maintained at a predetermined flow control pressure (e.g., 8 kPaG) by the governor GA, controls the aperture of the fuel flow control valve RVg based on the aperture-fuel flow rate relationship (shown in FIG. 5: an example of the aperture-flow rate relationship) stored in a memory unit S3, thereby controlling the flow rate of the fuel gas G to a target flow rate.

[0029] Here, as the secondary fuel pressure adjustment unit PVg, an electromagnetic pressure adjustment valve is preferably used which adjusts the secondary pressure of the fuel flow control valve RVg of the fuel on-site piping H1 by varying the opening degree of a valve body provided in the fuel on-site piping H1.

[0030] As shown in FIG. 1, the air flow control mechanism 200 (an example of a flow control mechanism) for combustion air is provided in field air piping H2 (an example of field piping) through which combustion air flows. The air flow control valve RVa has its aperture controlled by a control command from a control unit S1 provided in the control device S. A secondary air pressure adjustment unit PVa (an example of a secondary pressure adjustment unit) is provided on the secondary side of the air flow control valve RVa in the field air piping H2 and is capable of adjusting the pressure at the secondary outlet based on the measurement result of a second air pressure gauge P2a provided at the secondary outlet of the air flow control valve RVa. An inverter-type blower B is provided as a primary pressure adjustment unit on the primary side of the air flow control valve RVa in the field air piping H2 and is capable of adjusting the pressure at the primary inlet based on the measurement result of a first air pressure gauge P1a provided at the primary inlet of the air flow control valve RVa. A memory unit S3 (details of which will be described later) stores the aperture-air flow rate relationship (shown in FIG. 3) between the aperture of the air flow control valve RVa and the air flow rate flowing through the field air piping H2. The storage unit S3 is provided integrally with the control device S. More specifically, the air field piping H2 is provided with, in order from the upstream side, a blower B, a first air pressure gauge P1a, an air flow control valve RVa, a second air pressure gauge P2a, a secondary air pressure adjustment unit PVa, a third air pressure gauge P3a, and a burner BNa (e.g., a waste heat recovery burner). Here, the third air pressure gauge P3a measures the head pressure of burner BN at the primary inlet of burner BNa in the field air piping H2, and is configured to be able to check whether the relationship between the head pressure and flow rate for each of burners 1 to 3 is consistent with a known value, as shown in Figure 4. In addition, as the secondary air pressure adjustment unit PVa, an electromagnetic pressure adjustment valve is preferably used, which adjusts the secondary pressure of the air flow control valve RVa in the field air piping H2 by varying the opening of a valve element provided in the field air piping H2.

[0031] With this configuration, the air flow control mechanism 200 is an air field facility 200a equipped with an air flow control valve RVa, a secondary air pressure adjustment unit PVa as a secondary pressure adjustment unit, and a blower B as a primary pressure adjustment unit in an air field piping H2, in which a control unit S1 causes combustion air to flow through the air field piping H2, and while maintaining the air flow control valve RVa at a predetermined initial setting opening (e.g., 100%), the secondary air pressure adjustment unit PVa sets the pressure of the secondary outlet to a predetermined initial setting secondary pressure (e.g., 4 kPaG), and then, while maintaining the pressure of the primary inlet to a predetermined flow control pressure (e.g., 8 kPaG) with the blower B, controls the opening of the air flow control valve RVa based on the opening-air flow rate relationship (shown in FIG. 3: an example of the opening-flow rate relationship) stored in a memory unit S3, thereby controlling the flow rate of the combustion air to a target flow rate.

[0032] Now, the test equipment 400 that acquires the opening-flow rate relationship stored in the storage unit S3 will be described with reference to FIG. The test facility 400 is provided separately from the fuel on-site facility 100a (an example of on-site facility) and the air on-site facility 200a (an example of on-site facility) for the purpose of acquiring the above-mentioned opening-fuel flow rate relationship (shown in FIG. 5) and opening-air flow rate relationship (shown in FIG. 3) in advance for use in the fuel on-site facility 100a and the air on-site facility 200a (an example of on-site facility). When the fluid to be controlled is fuel gas G, a test pipe H having the same diameter as the fuel on-site piping H1 is used to perform the test, and when the fluid to be controlled is combustion air, a test pipe H having the same diameter as the air on-site piping H2 is used to perform the test. Below, a configuration example and method for acquiring the opening-fuel flow rate relationship related to fuel gas G will be described, but a configuration example for acquiring the opening-air flow rate relationship related to combustion air can also be acquired using substantially the same configuration example and method. 2, the test facility 400 is equipped with a fuel flow control valve RV, a butterfly valve BV as a secondary pressure adjustment unit, an inverter-type blower B as a primary pressure adjustment unit, and a flow meter F that measures the flow rate of the test pipe H, on a test pipe H having the same diameter as the on-site fuel pipe H1. More specifically, from the upstream side, the blower B, the flow meter F, a first test pressure gauge P1 that measures the pressure at the primary inlet of the fuel flow control valve RV, the fuel flow control valve RV, a second test pressure gauge P2 that measures the pressure at the secondary outlet of the fuel flow control valve RV, the butterfly valve BV, and a test burner BN (for example, a waste heat recovery burner) are provided in this order. In the test facility 400, the control unit Ss1 provided in the control device Ss flows fuel gas G through the test piping H, and while maintaining the fuel flow control valve RV (an example of a flow control valve) at a predetermined initial setting opening (for example, 100%: the same opening as the initial setting opening in the fuel field equipment 100a), sets the pressure of the secondary outlet to a predetermined initial setting secondary pressure (for example, 4 kPaG: the same pressure as the initial setting secondary pressure in the fuel field equipment 100a) using the butterfly valve BV, and then, while maintaining the pressure of the primary inlet to a predetermined flow control pressure (for example, 8 kPaG: the same pressure as the flow control pressure in the fuel field equipment 100a) using the blower B, stores the opening-fuel flow rate relationship (in the case of combustion air, the opening-air flow rate relationship) between the opening of the fuel flow control valve RV and the flow rate measured by the flow meter F in a memory unit Ss3 provided in the control device Ss.

[0033] With the above configuration, as shown in FIG. 1, in the combustion control system 300, first, the control unit S1 acquires the measurement results of a thermocouple ND provided in the industrial furnace R, derives the target output and target air ratio of the burner BNa that sets the temperature inside the furnace to the target temperature based on the measurement results, controls the flow rate of the combustion air so that the target output and target air ratio are obtained, and controls the flow rate of the fuel gas G so that the target air ratio is achieved in accordance with the flow rate of the combustion air. By adopting this configuration, the openings of the fuel flow control valve RVg and the air flow control valve RVa can be controlled for burners with different pressure losses (burners 1 to 3 in Figures 3 to 5) based on a common opening-air flow rate relationship (the relationship in Figure 3) and a common opening-fuel flow rate relationship (the relationship in Figure 5). While control is being continuously executed, the secondary pressures of the fuel flow control valve RVg and the air flow control valve RVa fluctuate from the initially set secondary pressure depending on the progress of control toward the target output, target air ratio, etc., but the primary pressures of the fuel flow control valve RVg and the air flow control valve RVa are kept constant by the governor GA and blower B, which serve as primary-side pressure control mechanisms.

[0034] According to the control method described above, the opening-flow rate relationship, which is the relationship between the opening of the flow control valve and the flow rate of the gas to be controlled as shown in Figure 6, can be obtained, and the flow rate of the gas to be controlled can be controlled using this opening-flow rate relationship without providing a flow meter. However, for example, if the burner BNa is a waste heat recovery burner or the like and the pressure loss of the combustion air as the controlled gas changes over time between when the burner BNa is cold and when it is warm, or if dust or the like clogs the passage through which the controlled gas of the burner BNa flows, causing the pressure loss of the controlled gas to change over time, the aperture-flow rate relationship will change. Specifically, if dust or the like clogs the passage through which the controlled gas of the burner BNa flows, the aperture-flow rate relationship (graph) shown in Figure 6 will have a lower flow rate at a predetermined aperture, resulting in an overall downward shift. Therefore, if the control device S controls the aperture of the flow control valve based on the aperture-flow rate relationship before the shift, the flow rate of the output controlled gas will differ from the desired flow rate.

[0035] Therefore, in addition to the configurations described above, the above-mentioned test facility 400, fuel flow control mechanism 100 (fuel on-site facility 100a), air flow control mechanism 200 (air on-site facility 200a), and combustion control system 300 are configured as follows: Incidentally, as described above, for the test facility 400, a configuration example and method relating to fuel gas G will be described, but the configuration example and method relating to combustion air can also be substantially the same configuration example and method.

[0036] In the test facility 400, the control unit Ss1 provided in the control device Ss flows fuel gas G through the test piping H, and while maintaining the fuel flow control valve RV at a predetermined initial setting opening (for example, 100%: the same opening as the initial setting opening in the fuel field facility 100a), sets the pressure of the secondary side outlet to a predetermined initial setting secondary pressure (for example, 4 kPaG: the same pressure as the initial setting secondary pressure in the fuel field facility 100a) using the butterfly valve BV, and then, while maintaining the pressure of the primary side inlet to a predetermined flow control pressure (for example, 8 kPaG: the same pressure as the flow control pressure in the fuel field facility 100a) using the blower B, stores in the memory unit Ss3 the opening-fuel-pressure relationship (an example of an opening-pressure relationship, for example, the relationship shown in Figure 7: in the case of combustion air, the opening-air-pressure relationship) between the opening of the fuel flow control valve RV and the secondary side pressure measured by the second test pressure gauge P2.

[0037] In the fuel field facility 100a, the control unit S1 controls the flow rate of the fuel gas G to a target flow rate by setting the pressure of the secondary side outlet to a predetermined initial setting secondary pressure (for example, 4 kPaG) using the secondary side fuel pressure adjustment unit PVg while maintaining the fuel flow rate control valve RVg at a predetermined initial setting opening (for example, 100% opening) in a state where the fuel gas G is flowing through the fuel field piping H1, and then by maintaining the pressure of the primary side inlet to a predetermined flow rate control pressure (for example, 8 kPaG) using the governor GA, and at the same time, executing secondary side pressure adjustment determination control to determine whether or not adjustment of the secondary side pressure is necessary by comparing the secondary side pressure measured by the second fuel pressure gauge P2g with the opening of the fuel flow rate control valve RVg at the time of pressure measurement by the second fuel pressure gauge P2g and the derived pressure derived from the opening-fuel pressure relationship.

[0038] For example, in the secondary-side pressure adjustment determination control, the control unit S1 determines that adjustment of the secondary-side pressure is necessary if the absolute value of the difference between the secondary-side pressure measured by the second fuel pressure gauge P2g and the derived pressure derived from the opening of the fuel flow control valve RVg when the pressure is measured by the second fuel pressure gauge P2g and the opening-fuel-pressure relationship, divided by the pressure derived from the opening of the fuel flow control valve RVg when the pressure is measured by the second fuel pressure gauge P2g and the opening-fuel-pressure relationship, and multiplied by 100, exceeds a predetermined error range (a value of approximately -20% to 20%: for example, 5%) continuously for a predetermined error determination time or more (a value of approximately 3 seconds to 60 seconds: for example, 3 seconds).

[0039] Furthermore, when the control unit S1 determines in the secondary-side pressure adjustment determination control that adjustment of the secondary-side pressure is necessary, the control unit S1 executes secondary-side pressure adjustment control in which the secondary-side fuel pressure adjustment unit PVg corrects the secondary-side pressure based on the opening of the fuel flow control valve RVg at the time of determination in the secondary-side pressure adjustment determination control and the derived pressure derived from the opening-fuel-pressure relationship.

[0040] For example, when executing the secondary pressure regulation control, the control unit S1 controls the secondary pressure to become the outlet pressure derived from the opening of the fuel flow control valve RVg and the opening-fuel-pressure relationship at the time of determination in the secondary pressure regulation determination control. More specifically, the control unit S1 corrects the secondary pressure by the secondary fuel pressure regulation unit PVg so that the difference between the secondary pressure and the outlet pressure falls within a predetermined error range (a value of about −0.1 kPa to 0.1 kPa: for example, 0.05 kPa) continuously for at least a predetermined stabilization time (a value of about 2 seconds to 60 seconds: for example, 2 seconds).

[0041] Incidentally, the control unit S1 also performs secondary-side pressure adjustment determination control and secondary-side pressure adjustment control for the air flow control mechanism 200 (air on-site equipment 200a) using substantially the same configuration and method as for the fuel flow control mechanism 100 (fuel on-site equipment 100a), so explanation of that will be omitted here.

[0042] Furthermore, in addition to the configuration and control described above, the combustion control system 300 can be configured to perform secondary-side pressure regulation determination control and secondary-side pressure regulation control for the fuel gas G using the fuel flow control mechanism 100 and the air flow control mechanism 200, and to perform secondary-side pressure regulation determination control and secondary-side pressure regulation control for the combustion air.

[0043] With the above configuration, even if the burner BNa is a waste heat recovery burner or the like and the pressure loss of the combustion air as the gas to be controlled changes over time when the burner is cold and when it is warm, or even if the flow path of the gas to be controlled in the burner BNa is clogged with dust or the like and the pressure loss of the gas to be controlled changes over time, causing the opening-flow rate relationship to change, the flow rate of the gas to be controlled can be appropriately controlled to the desired flow rate by correction.

[0044] In addition, the control unit S1 can control the flow rate of the gas to be controlled using a common opening / flow rate relationship for different types of burners BNa, and can also perform secondary pressure adjustment judgment control and secondary pressure adjustment control using a common opening / pressure relationship for different types of burners BNa.

[0045] Furthermore, the above-described flow rate control mechanisms 100, 200 and combustion control system 300 are provided with a speaker KH (an example of an alarm notification unit) that issues an alarm to the outside, and when the control unit S1 determines in the secondary-side pressure adjustment determination control that adjustment of the secondary-side pressure is necessary, it executes notification control to issue an alarm through the speaker KH. This allows the user to take measures such as quickly formulating a maintenance plan based on that fact, for example, when it is determined that adjustment of the secondary-side pressure is necessary due to clogging of the flow path of the controlled gas of the burner BNa with dust or the like.

[0046] <First test results> Regarding the combustion control system 300 described above, the results of a first test in which the flow rate of combustion air was controlled based on the following first condition will be described with reference to FIGS. The first condition was to use a recuperator burner, control the combustion amount (output) to 100 kW, the primary pressure (primary pressure) of the air flow control valve to 7.0 kPa, and the air ratio to 1.3. Note that a flow meter was installed to check the air ratio, and the test was carried out while checking the value. The various conditions for control were: the primary pressure stability condition was met when the primary pressure was maintained at 7±0.2 kPa for 5 seconds; the correction start condition was met when the pressure measured by the second air pressure gauge P2a deviated from the pressure obtained from the opening / air pressure relationship by more than the allowable error of 5% for 3 seconds or more; and the correction completion condition was met when the absolute value of the difference between the pressure measured by the second air pressure gauge P2a and the pressure obtained from the opening / air pressure relationship was within the correction completion range of 0.05 kPa for 2 seconds or more. The correction change amount was set to change the opening of the pressure regulation valve serving as the secondary air pressure adjustment unit PVa at a rate of 0.1% per 5 seconds.

[0047] Figures 8 to 10 show the results of the first test when secondary pressure adjustment control was performed (with correction) and when it was not performed (without correction) at time α (when the furnace temperature reached approximately 950°C). Regarding the air ratio, as shown in FIG. 8, when the secondary pressure regulation control is not executed (no correction), the air ratio deviates from the target value (1.3) by about 0.1 at time α, but when the secondary pressure regulation control is executed (correction), the air ratio can be corrected to close to the target value (1.3). Incidentally, when secondary pressure adjustment control is executed (with correction), as shown in Figure 9, the operating amount of the pressure adjustment valve serving as the secondary air pressure adjustment unit PVa is controlled to increase from 0% to 1.4% during a predetermined period from time α.

[0048] Regarding the results of the first test, the flow rate deviation rate of the combustion air is shown in Figure 10. Here, the flow rate deviation rate of combustion air is a value calculated by the following [Equation 1].

[0049] [Formula 1] Combustion air flow rate deviation rate = (Flow rate derived from the opening air flow rate relationship - flow meter reading) / flow meter reading

[0050] As shown in Figure 10, when secondary pressure regulation control is not performed (no correction), the flow rate deviation rate of the combustion air at time α is about 6.0%, but when secondary pressure regulation control is performed (correction), it can be seen that it can be corrected to nearly 0.0%.

[0051] <Second test results> Next, the results of the second test will be explained with reference to FIGS. The second conditions for the second test results were the same as the first conditions, except that the combustion amount (output) was controlled so that the temperature inside the furnace was 1000°C.

[0052] Incidentally, the results of the second test from 0 to 10 minutes after the start of the test include changes due to various external environmental influences, so below we will explain the results from 10 minutes onwards. As shown in FIG. 13, after about 20 minutes have passed, secondary pressure regulation control is executed, the pressure regulation valve operates, and the pressure regulation valve is controlled to a predetermined opening degree 20 minutes after the start of the test. As a result of this control, the air ratio approached the target value (1.3) 20 minutes after the start of the test, and the flow rate deviation rate of the combustion air also gradually approached the target value (0.0%), as shown in Figure 11. In this case, the primary pressure of the air flow control valve RVa changes as shown in Figure 14. On the other hand, when secondary pressure adjustment control is not performed, the flow rate deviation rate of the combustion air gradually increases from the target value (0.0%) after 20 minutes from the start of the test, as shown in Figure 15.

[0053] [Another embodiment] (1) In the above embodiment, combustion air is used as the combustion gas. However, for example, oxygen-enriched gas may be used as the combustion gas.

[0054] (2) The combustion control system 300 is not limited to heating of the industrial furnace R, but can be widely applied to burners of glass melting furnaces, metal forging facilities, and the like. Furthermore, the flow rate control mechanism 100 can be suitably incorporated into systems that control the flow rates of various gases, regardless of whether the system is a combustion device such as a burner.

[0055] (3) Although not described in detail in the above embodiment, in an environment where the temperature in the fuel on-site equipment 100a and the air on-site equipment 200a changes significantly, the following configuration and control may be adopted. That is, in the test facility 400, the opening / flow rate relationship can be obtained for each temperature of the gas to be controlled flowing through the test pipe H, and flow rate control of the flow rate to be controlled can be performed in the fuel field facility 100a and the air field facility 200a based on the opening / flow rate relationship corresponding to the temperature of the gas to be controlled measured in the field pipes H1 and H2.

[0056] (4) In the above embodiment, a configuration example in which secondary pressure regulation control is executed is shown, but the secondary pressure regulation control does not necessarily have to be executed. In this case, for example, the control device S may employ a configuration in which, when it is determined in the secondary pressure adjustment determination control that adjustment of the secondary pressure is necessary, an alarm is issued.

[0057] Furthermore, the configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, as long as no contradictions arise. Furthermore, the embodiments disclosed in this specification are examples, and the embodiments of the present invention are not limited to these, and can be modified as appropriate within the scope that does not deviate from the purpose of the present invention. [Industrial Applicability]

[0058] The flow control mechanism of the present invention and a combustion control system equipped with the same can be effectively used as a fluid flow control mechanism and a combustion control system equipped with the same, which improves economy by maintaining a simple configuration without using a flow meter, and can also achieve labor savings by automating various adjustments such as flow rate adjustment. [Explanation of symbols]

[0059] 100: Fuel flow control mechanism 100a: Fuel field equipment 200: Air flow control mechanism 200a: Air site equipment 300: Combustion control system 400: Testing facilities BN: Burner BNa: Burner G: Fuel gas H: Test piping H1:Fuel field piping H2: Air on-site piping KH: Speaker P1: First test pressure gauge P1a: 1st air pressure gauge P1g: 1st fuel pressure gauge P2: Second test pressure gauge P2a: Second air pressure gauge P2g: Second fuel pressure gauge PVa: Secondary air pressure adjustment section PVg: Secondary fuel pressure regulator PVa: Secondary air pressure adjustment section R: Industrial furnace RV: Fuel flow control valve RVa: Air flow control valve RVg: Fuel flow control valve S1: Control unit S3: Storage section Ss1: Control unit Ss3: Memory section

Claims

1. A flow rate control mechanism including a control unit that controls the flow rate of a control target gas, which is either a fuel gas or a combustion gas serving as an oxidizer for the fuel gas, a flow control valve that is provided in an on-site piping through which the gas to be controlled flows, and whose opening is controlled by a control command from the control unit; a secondary-side pressure adjusting unit that is provided on the secondary side of the flow control valve in the on-site piping and that is capable of adjusting the pressure of the secondary-side outlet based on a measurement result of a second pressure gauge that is provided at a secondary-side outlet of the flow control valve; a primary-side pressure adjusting unit that is provided on the primary side of the flow control valve in the on-site piping and that is capable of adjusting the pressure of the primary-side inlet based on a measurement result of a first pressure gauge that is provided at the primary-side inlet of the flow control valve; In a testing facility comprising a test pipe having the same diameter as the on-site pipe, the flow control valve, the second pressure gauge, the secondary pressure adjustment unit, and the primary pressure adjustment unit, and a flow meter for measuring a flow rate of the test pipe, the control unit causes the gas to flow through the test pipe, and while maintaining the flow control valve at a predetermined initial setting, sets the pressure of the secondary outlet to a predetermined initial setting secondary pressure using the secondary pressure adjustment unit, and then stores an opening-flow rate relationship between the opening of the flow control valve and the flow rate measured by the flow meter, and stores an opening-pressure relationship between the opening of the flow control valve and the secondary pressure measured by the second pressure gauge, while maintaining the pressure of the primary inlet at a predetermined flow control pressure using the primary pressure adjustment unit, In an on-site facility provided with the flow control valve, the second pressure gauge, the secondary-side pressure adjustment unit, and the primary-side pressure adjustment unit in the on-site piping, the control unit causes the gas to be controlled to flow through the on-site piping, and while maintaining the flow control valve at the initially set opening, sets the pressure of the secondary-side outlet to the initially set secondary pressure using the secondary-side pressure adjustment unit, and then, while maintaining the pressure of the primary-side inlet at the flow control pressure using the primary-side pressure adjustment unit, controls the opening of the flow control valve based on the opening-flow-rate relationship stored in the memory unit to control the flow rate of the gas to be controlled to a target flow rate, and performs secondary-side pressure adjustment determination control to determine whether or not adjustment of the secondary-side pressure is necessary by comparing the secondary-side pressure measured by the second pressure gauge with the opening of the flow control valve when pressure is measured by the second pressure gauge and the derived pressure derived from the opening-pressure relationship.

2. 2. The flow control mechanism according to claim 1, wherein, when it is determined in the secondary-side pressure adjustment determination control that adjustment of the secondary-side pressure is necessary, the control unit executes secondary-side pressure adjustment control by the secondary-side pressure adjustment unit to correct the secondary-side pressure based on a derived pressure derived from the opening of the flow control valve at the time of determination in the secondary-side pressure adjustment determination control and the opening-pressure relationship.

3. An alarm notification unit is provided to notify an alarm to the outside, 3. The flow control mechanism according to claim 1, wherein the control unit executes notification control to issue the alarm using the alarm notification unit when it determines in the secondary pressure adjustment determination control that adjustment of the secondary pressure is necessary.

4. A combustion control system using the flow rate control mechanism according to claim 1 or 2, a fuel flow rate control mechanism serving as the flow rate control mechanism for controlling the flow rate of the fuel gas serving as the gas to be controlled that flows through a fuel pipe connected in communication with a burner serving as the on-site pipe; a combustion gas flow rate control mechanism as the flow rate control mechanism for controlling the flow rate of the combustion gas as the control target gas flowing through a combustion gas pipe connected in communication with the burner as the on-site pipe, The control unit controls the flow rate of the combustion gas to the target flow rate and executes the secondary-side pressure adjustment determination control for the combustion gas so that the target output and target air ratio are achieved at the burner, and also controls the flow rate of the fuel gas to the target flow rate and executes the secondary-side pressure adjustment determination control for the fuel gas.

5. A combustion control system using the flow rate control mechanism according to claim 2, a fuel flow rate control mechanism serving as the flow rate control mechanism for controlling the flow rate of the fuel gas serving as the gas to be controlled that flows through a fuel pipe connected in communication with a burner serving as the on-site pipe; a combustion gas flow rate control mechanism as the flow rate control mechanism for controlling the flow rate of the combustion gas as the control target gas flowing through a combustion gas pipe connected in communication with the burner as the on-site pipe, the control unit controls the flow rate of the combustion gas to the target flow rate and executes the secondary-side pressure adjustment determination control for the combustion gas so that the burner achieves a target output and a target air ratio, and also controls the flow rate of the fuel gas to the target flow rate and executes the secondary-side pressure adjustment determination control for the fuel gas, A combustion control system that, when the secondary-side pressure adjustment determination control for the combustion gas determines that adjustment of the secondary-side pressure is necessary, executes the secondary-side pressure adjustment control for the combustion gas, and, when the secondary-side pressure adjustment determination control for the fuel gas determines that adjustment of the fuel gas is necessary, executes the secondary-side pressure adjustment control for the fuel gas.

6. 5. The combustion control system according to claim 4, wherein the burner is a waste heat recovery burner in which the combustion gas supplied to the burner is preheated by combustion exhaust gas.

7. 6. The combustion control system according to claim 5, wherein the burner is a waste heat recovery burner in which the combustion gas supplied to the burner is preheated by combustion exhaust gas.

8. The combustion control system according to claim 4 , wherein the control unit controls the flow rate of the control-target gas using the opening-flow-rate relationship that is common to different types of the burners.

9. The combustion control system according to claim 5 , wherein the control unit controls the flow rate of the control-target gas using the opening-flow-rate relationship that is common to different types of the burners.

10. The combustion control system according to claim 4 , wherein the control unit executes the secondary pressure regulation determination control using the opening-pressure relationship that is common to different types of burners.

11. The combustion control system according to claim 5 , wherein the control unit executes the secondary pressure regulation determination control and the secondary pressure regulation control using the opening-pressure relationship that is common to different types of burners.

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