Flow rate control system and flow rate control method

Abstract

To provide a flow rate control system for accurately measuring the flow rate of a gas and adjusting the flow rate of the gas, irrespective of the content of the gas.SOLUTION: A flow rate control system 1 comprises: a gas pipe 10 in which a gas flows; an air blower 20 for adjusting the flow rate of the gas and located to the gas pipe 10; a pressure sensor 40 for detecting actual static pressure which is the actual static pressure of the gas flowing in the gas pipe 10; a temperature sensor 30 for detecting an actual temperature which is the actual temperature of the gas flowing in the gas pipe 10; and a control device 50 for controlling the air blower 20. The control device 50 stores, in advance, reference density which is the reference of density predetermined for the gas, a reference velocity which is the reference of velocity, reference static pressure which is the reference of static pressure, and a reference temperature which is the reference of temperature, and calculates an actual flow rate which the actual flow rate of the gas flowing in the gas pipe 10 by using the actual static pressure, the actual temperature, the reference velocity, the reference static pressure, and the reference temperature, thereby determining the operation amount of the air blower 20 so as to equalize the actual flow rate and a target flow rate.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a flow rate control system and a flow rate control method. [Background technology]

[0002] Patent Document 1 discloses a flow control device including a flow measurement means for measuring the discharge flow rate of a fluid pumped from a fluid machine, and a controller for controlling the rotation speed of a driven shaft of the fluid machine based on the measurement result of the flow measurement means. The flow measurement means is disposed in a return passage that returns the fluid in the discharge passage to the suction passage. For example, a Venturi tube, a vortex flowmeter, or a hot wire flowmeter can be used as the flow measurement means. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3638911 Summary of the Invention [Problem to be solved by the invention]

[0004] When a flow rate measuring device is disposed in a flow path through which a fluid flows, the flow rate measuring device comes into direct contact with the fluid. If the fluid is a gas containing a relatively large amount of dust or is a corrosive gas, the flow rate measuring device may be worn or corroded. In this case, the flow rate of the fluid may not be detected accurately.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a flow control system that accurately measures the flow rate of a gas and adjusts the flow rate of the gas, regardless of the gas contents. [Means for solving the problem]

[0006] In order to achieve the above object, a flow control system according to one aspect of the present disclosure includes a gas pipe through which a gas flows, a flow rate adjustment unit disposed in the gas pipe and adjusting a flow rate of the gas, a pressure sensor disposed in the gas pipe on the primary side of the flow rate adjustment unit and detecting an actual static pressure which is an actual static pressure of the gas flowing through the gas pipe, a temperature sensor disposed in the gas pipe on the primary side of the flow rate adjustment unit and detecting an actual temperature which is an actual temperature of the gas flowing through the gas pipe, and a control device for controlling the flow rate adjustment unit, wherein the control device pre-stores a reference density which is a predetermined reference density, a reference speed which is a reference speed, a reference static pressure which is a reference static pressure, and a reference temperature which is a reference temperature, which are predetermined for the gas, and calculates an actual flow rate which is an actual flow rate of the gas flowing through the gas pipe using the actual static pressure, the actual temperature, the reference density, the reference speed, the reference static pressure, and the reference temperature, and determines an operation amount of the flow rate adjustment unit so as to make the actual flow rate equal to a target flow rate.

[0007] Moreover, a flow rate control method according to one aspect of the present disclosure includes a step of detecting an actual static pressure, which is an actual static pressure of a gas flowing through a gas pipe and an actual temperature, which is an actual temperature of the gas, for a gas flowing through a gas pipe and whose flow rate is adjusted by a flow rate adjustment unit; a step of calculating an actual flow rate, which is an actual flow rate of the gas, using the actual static pressure and the actual temperature detected in the step of detecting the actual static pressure and the actual temperature, as well as a reference density, which is a reference density, a reference velocity, which is a reference velocity, a reference static pressure, which is a reference static pressure, and a reference temperature, which are predetermined for the gas; and a step of determining an operation amount of the flow rate adjustment unit so as to make the actual flow rate calculated in the step of calculating the actual flow rate equal to a target flow rate. Effect of the Invention

[0008] According to the flow rate control system of the present disclosure, the flow rate of a gas can be accurately measured and adjusted regardless of the contents of the gas. [Brief description of the drawings]

[0009] [Figure 1]FIG. 1 is a schematic diagram showing a configuration of a flow rate control system according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a schematic diagram showing the temperature sensor and the pressure sensor shown in FIG. [Diagram 3] FIG. 3 is a flowchart executed when the flow control unit calculates the actual flow rate and determines the operation amount of the blower. [Figure 4] FIG. 4 is a diagram showing the relationship between the flow rate of gas, the suction pressure of the blower, and the rotation speed of the blower motor. [Diagram 5] FIG. 5 is a schematic diagram showing a configuration of a flow rate control system according to a first modified example of the embodiment of the present disclosure. [Figure 6] FIG. 6 is a schematic diagram showing a configuration of a flow rate control system according to a second modified example of the embodiment of the present disclosure. [Figure 7] FIG. 7 is a schematic diagram showing a configuration of a flow rate control system according to a third modified example of the embodiment of the present disclosure. [Figure 8] FIG. 8 is a schematic diagram showing a temperature sensor of a flow rate control system according to a fourth modified example of the embodiment of the present disclosure. [Figure 9] FIG. 9 is a diagram showing a configuration of a flow rate control system according to another modified example of the embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Each embodiment of the present disclosure will be described below with reference to the drawings. The present disclosure is not limited to the contents described in the following embodiments. In addition, the components described below include those that a person skilled in the art can easily imagine and those that are substantially the same. Furthermore, the components described below can be appropriately combined.

[0011] In addition, in order to clarify the description, the drawings may show the width, thickness, shape, etc. of each part in a schematic manner compared to the actual embodiment, but these are merely examples and do not limit the interpretation of the present disclosure. In this specification and each drawing, the same reference numerals are used to designate elements similar to those described above with respect to the previous drawings, and detailed descriptions may be omitted as appropriate.

[0012] 1 is a schematic diagram showing a configuration of a flow rate control system 1 according to an embodiment of the present disclosure. The flow rate control system 1 connects multiple industrial furnaces 2 and a gas treatment device 3, and supplies gas discharged from the multiple industrial furnaces 2 to the gas treatment device 3.

[0013] In this embodiment, the number of industrial furnaces 2 is four, and a first industrial furnace 2a, a second industrial furnace 2b, a third industrial furnace 2c, and a fourth industrial furnace 2d are connected to the flow control system 1. It goes without saying that the number of industrial furnaces 2 is not limited to four. Furthermore, when the first industrial furnace 2a, the second industrial furnace 2b, the third industrial furnace 2c, and the fourth industrial furnace 2d are described without distinction, they will be simply referred to as "industrial furnaces 2."

[0014] The industrial furnace 2 is an industrial furnace used in the manufacturing process in the aluminum industry, for example. It goes without saying that the industrial furnace 2 is not limited to those used in the aluminum industry. The industrial furnace 2 may be, for example, a sintering furnace, a roasting furnace, a graphitization furnace, a brazing furnace, a heat treatment furnace, or a melting furnace used to melt raw materials. The gas discharged from the industrial furnace 2 contains sulfur (specifically, sulfur oxides) and moisture.

[0015] The gas treatment device 3 is a desulfurization device that desulfurizes the gas. It goes without saying that the gas treatment device 3 is not limited to a desulfurization device. The gas treated by the gas treatment device 3 is released into the atmosphere.

[0016] The flow rate control system 1 includes a gas pipe 10, a blower 20, a temperature sensor 30, a pressure sensor 40, and a control device 50. In this embodiment, the blower 20 is a "flow rate adjustment unit."

[0017] The gas pipe 10 connects the multiple industrial furnaces 2 and the gas treatment device 3, and passes gas discharged from each of the multiple industrial furnaces 2. The gas pipe 10 is a so-called duct.

[0018] Each of the multiple industrial furnaces 2 and the gas pipe 10 are connected via a connecting pipe 10a. An on-off valve 10b is disposed in the connecting pipe 10a. When the on-off valve 10b is open, gas is discharged from the industrial furnace 2 corresponding to the open on-off valve 10b. The opening and closing of the on-off valve 10b is controlled by the control device 50 so that gas discharged from one of the multiple industrial furnaces 2 flows into the gas pipe 10. In FIG. 1, the on-off valves 10b corresponding to the first industrial furnace 2a, the second industrial furnace 2b, and the third industrial furnace 2c are shown to be in a closed state. Also, the on-off valve 10b corresponding to the fourth industrial furnace 2d is shown to be in an open state.

[0019] Hereinafter, the gas path between the first industrial furnace 2a and the gas treatment device 3 will be referred to as the first system, the gas path between the second industrial furnace 2b and the gas treatment device 3 as the second system, the gas path between the third industrial furnace 2c and the gas treatment device 3 as the third system, and the gas path between the fourth industrial furnace 2d and the gas treatment device 3 as the fourth system. In addition, when the first system, the second system, the third system, and the fourth system are described without distinguishing between them, they will simply be referred to as "systems". In FIG. 1, the on-off valve 10b corresponding to the fourth industrial furnace 2d among the multiple on-off valves 10b is in an open state, and gas flows through the fourth system.

[0020] In addition, the gas path length between the industrial furnace 2 and the gas treatment device 3 is different among the multiple industrial furnaces 2. Specifically, the gas path length is longer in the order of the first system, the second system, the third system, and the fourth system, and the pipeline resistance between the industrial furnace 2 and the gas treatment device 3 is larger.

[0021] The blower 20 is disposed in the gas pipe 10 and blows out gas. The blower 20 includes a rotating part 21 and a blower motor 22. The rotating part 21 includes an impeller (not shown). The blower motor 22 is an electric motor that rotates the rotating part 21. The blower motor 22 rotates the rotating part 21 to blow out gas. The more the rotation speed (the number of rotations per unit time: the same below) of the blower motor 22 increases, the more the flow rate (the flow rate per unit time: the same below) of the gas flowing through the gas pipe 10 increases. The blower 20 may further include a rotation speed sensor that detects the rotation speed of the rotating part 21 per unit time. The rotation speed sensor is, for example, a mechanical rotary encoder, an optical rotary encoder, a magnetic rotary encoder, and an electromagnetic induction rotary encoder. The rotation speed detected by the rotation speed sensor is output to the control device 50. The rotation speed of the rotating part 21 and the rotation speed of the blower motor 22 are in a proportional relationship.

[0022] Fig. 2 is a schematic diagram showing the temperature sensor 30 and the pressure sensor 40 shown in Fig. 1. The arrows shown in Fig. 2 indicate the direction in which gas flows in the flow path 11 in the gas pipe 10. The flow path 11 is formed by the inner circumferential surface of the gas pipe 10.

[0023] The temperature sensor 30 is disposed on the primary side of the blower 20 in the gas pipe 10, and detects the temperature of the gas. The temperature sensor 30 is disposed in the gas pipe 10 via the first branch pipe 10c. That is, the temperature sensor 30 is disposed in a portion of the gas pipe 10 away from the flow path 11 through which the gas flows. A temperature detection unit 31, at which the temperature sensor 30 detects the temperature, is located outside the flow path 11. The temperature detected by the temperature sensor 30 is output to the control device 50.

[0024] The pressure sensor 40 is disposed on the primary side of the blower 20 in the gas pipe 10, and detects the static pressure of the gas. The pressure sensor 40 is disposed in the gas pipe 10 via the second branch pipe 10d. That is, the pressure sensor 40 is disposed in a portion of the gas pipe 10 away from the flow path 11 through which the gas flows. A pressure detection unit 41 where the pressure sensor 40 detects the static pressure is located outside the flow path 11. The static pressure detected by the pressure sensor 40 is output to the control device 50.

[0025] The temperature sensor 30 and the pressure sensor 40 are disposed in the gas pipe 10 via the branch pipes 10c and 10d, and are not disposed in the gas flow path 11 in the gas pipe 10. This prevents components such as sulfur contained in the gas, and inclusions such as soot and dust from affecting the temperature sensor 30 and the pressure sensor 40. This prevents the temperature sensor 30 and the pressure sensor 40 from being corroded and damaged, for example, by wear caused by the gas components and inclusions in the gas.

[0026] 1 generally controls the flow rate control system 1. The control device 50 controls the blower 20 and supplies gas discharged from the industrial furnace 2 to the gas treatment device 3. The control device 50 includes a memory unit 51 and a flow rate control unit 52.

[0027] Reference physical quantities obtained by an operator measuring (detecting) the components and state of the gas in advance are input by the operator and are stored in advance in the storage unit 51. Specifically, the reference physical quantities are a reference density, a reference speed, a reference static pressure, and a reference temperature.

[0028] The reference density, the reference velocity, the reference static pressure, and the reference temperature are determined by an operator operating the industrial furnace 2 at a time other than when the product is being produced, and measuring the velocity, static pressure, and temperature of the gas flowing through the gas pipe 10. Note that the operator does not need to operate the industrial furnace 2 when measuring the reference density, the reference velocity, the reference static pressure, and the reference temperature. For example, the operator analyzes the composition of the gas flowing through the gas pipe 10, and calculates the reference density based on the analysis results. The reference velocity is measured by placing a measuring instrument such as a Pitot tube in the gas pipe 10 (flow path 11). Note that the measuring instrument for measuring the reference velocity is placed in the gas pipe 10 at a portion of the flow path 11 having a cross-sectional area equal to the cross-sectional area of ​​the flow path 11 corresponding to the portion where the pressure sensor 40 is placed.

[0029] Moreover, the reference static pressure is measured (detected) by the pressure sensor 40. The reference temperature is measured (detected) by the temperature sensor 30.

[0030] As described above, the pipeline resistance between the industrial furnace 2 and the gas treatment device 3 increases in the order of the first system, the second system, the third system, and the fourth system. That is, the relationships between the reference density, the reference speed, the reference static pressure, and the reference temperature are different in each of the multiple systems. That is, the reference density, the reference speed, the reference static pressure, and the reference temperature are input by the operator individually for each of the multiple systems and are stored in the storage unit 51.

[0031] The flow rate control unit 52 controls the actual flow rate of gas flowing through the gas pipe 10 (hereinafter referred to as the actual flow rate) by the blower 20 during operation of the industrial furnace 2 in the production of products. Specifically, the flow rate control unit 52 calculates the actual flow rate of gas flowing through the gas pipe 10 based on the detection values ​​of the temperature sensor 30 and the pressure sensor 40, and executes feedback control to determine the operation amount of the blower 20 so that the calculated actual flow rate becomes the target flow rate (details will be described later). In this embodiment, the feedback control is, for example, PID control (Proportional-Integral-Differential Controller).

[0032] 3 is a flowchart executed when the flow control unit 52 calculates the actual flow rate and determines the operation amount of the blower 20. The flow control unit 52 executes the flowchart shown in FIG. 3 during the production of a product. The production of the product is carried out in one of the multiple industrial furnaces 2. That is, during the production of the product, only the on-off valve 10b corresponding to one industrial furnace 2 used in the production of the product is in an open state, and the gas discharged from the one industrial furnace 2 flows through the system corresponding to the one industrial furnace 2. Hereinafter, a case will be described in which the on-off valve 10b corresponding to the fourth industrial furnace 2d is in an open state and gas flows through the fourth system, as shown in FIG. 1.

[0033] At the start of production of a product, the flow rate control unit 52 controls the blower motor 22 of the blower 20 at a predetermined rotation speed. As a result, the gas discharged from the industrial furnace 2 is supplied to the gas treatment device 3 via the gas pipe 10. The predetermined rotation speed is, for example, a rotation speed at which the flow rate of the gas flowing through the gas pipe 10 is smaller than a target flow rate, which will be described later.

[0034] The flow rate control unit 52 acquires a reference physical quantity in step S1. Specifically, the flow rate control unit 52 acquires from the storage unit 51 a reference density, a reference velocity, a reference static pressure, and a reference temperature that are predetermined for the gas.

[0035] Next, the flow rate control unit 52 identifies the system through which the gas flows in step S2. Specifically, the flow rate control unit 52 identifies the system in which the on-off valve 10b is open. As shown in Fig. 1, when the on-off valve 10b corresponding to the fourth industrial furnace 2d is open, the flow rate control unit 52 identifies the fourth system.

[0036] Furthermore, in step S3, the flow rate control unit 52 acquires the actual temperature and actual static pressure of the gas. The actual temperature is the actual temperature of the gas flowing through the gas pipe 10 (system) during the production of the product, and is the temperature detected by the temperature sensor 30. The actual static pressure is the actual static pressure of the gas flowing through the gas pipe 10 (system) during the production of the product, and is the static pressure detected by the pressure sensor 40.

[0037] Next, in step S4, the flow rate control unit 52 calculates the actual flow rate of the gas. The flow rate control unit 52 calculates the actual flow rate using the following formulas (1), (2), (3), (4), (5), and (6). Formulas (1), (2), (3), (4), (5), and (6) are stored in the storage unit 51.

[0038] PT0 = PS0 + PD0 ... (1) PD0 = (ρ0 × V0 2 / 2)×10 -3 …(2) PS1'=PS1×(273.15+T1) / (273.15+T0) …(3) PT1'=PS1'+(ρ0×V1 2 / 2)×10 -3 …(4) PT1' = PT0 × (V1 / V0) 2 …(5) Gw = A × V1 … (6)

[0039] In formula (1), PT0 is the reference total pressure (unit: kPa) which is the reference total pressure of the gas, PS0 is the reference static pressure (unit: kPa), and PD0 is the reference velocity pressure (unit: kPa) which is the reference velocity pressure of the gas. Formula (1) shows that the sum of the reference static pressure (PS0) and the reference velocity pressure (PD0) is the reference total pressure (PT0).

[0040] In equation (2), ρ0 is the reference density (unit: kg / m 3 ), and V0 is the reference velocity (unit: m / s). Equation (2) expresses the kinetic energy of the gas in units of pressure, and is derived based on Bernoulli's theorem. As described above, the reference static pressure (PS0), reference density (ρ0), and reference velocity (V0) are obtained in step S1.

[0041] The flow control unit 52 calculates the reference velocity pressure (PD0) and the reference total pressure (PT0) using equations (1) and (2) and the reference static pressure (PS0), reference density (ρ0), and reference velocity (V0) corresponding to the system identified in step S2.

[0042] In formula (3), PS1 is the actual static pressure (unit: kPa) obtained in step S3, T1 is the actual temperature (unit: °C) obtained in step S3, and T0 is the reference temperature (unit: °C) corresponding to the system identified in step S2. In other words, PS1' in formula (3) is a value obtained by correcting PS1 to the state of the reference temperature of the gas.

[0043] In equation (4), PT1' is the actual total pressure of the gas (unit: kPa) corrected to the reference temperature. The second term of equation (4), like equation (2), indicates the kinetic energy of the gas in units of pressure, and is derived based on Bernoulli's theorem.

[0044] Equation (5) shows the relationship between the reference total pressure (PT0) and the corrected actual total pressure (PT1'). Equation (5) is derived based on the fact that the pressure loss of gas is proportional to the square of the gas velocity.

[0045] The flow control unit 52 calculates the actual velocity (V1) using equations (3), (4), and (5), the actual static pressure (PS1) and actual temperature (T1) acquired in step S3, the reference velocity pressure (PD0) and reference total pressure (PT0) calculated using equations (1) and (2), and the reference temperature (T0) and reference density (ρ0).

[0046] In equation (6), Gw is the actual flow rate (unit: m 3 / s), and A is the cross-sectional area (unit: m 2 ) The cross-sectional area (A) of the flow path 11 is stored in advance in the storage unit 51. The cross-sectional area (A) of the flow path 11 is equal to each other in the multiple systems.

[0047] The flow rate control unit 52 calculates the actual flow rate (Gw) using the formula (6) and the actual velocity (V1) calculated as described above.

[0048] Furthermore, in step S5, the flow control unit 52 determines the operation amount of the blower 20. Specifically, the flow control unit 52 determines the rotation speed (the rotation speed per unit time) of the blower motor 22 of the blower 20 based on the deviation between the actual flow rate calculated in step S4 and the target flow rate so as to make the actual flow rate equal to the target flow rate. In this embodiment, the operation amount is the rotation speed of the blower motor 22.

[0049] The target flow rate is determined based on the production volume of the product and the desulfurization efficiency of the gas treatment device 3, and is input in advance by an operator to the control device 50. In addition, the target flow rate is determined within a range corresponding to an area described below.

[0050] Fig. 4 is a diagram showing the relationship between the gas flow rate, the suction pressure of the blower 20, and the rotation speed of the blower motor 22. In Fig. 4, the horizontal axis is the gas flow rate, the vertical axis on the left side is the suction pressure of the blower 20 (i.e., the pressure (total pressure) on the primary side of the blower 20 in the gas pipe 10), and the vertical axis on the right side is the discharge pressure of the blower 20 (i.e., the pressure (total pressure) on the secondary side of the blower 20 in the gas pipe 10). Note that the direction in which the arrow on the left vertical axis points is the direction in which the negative value becomes smaller (the absolute value of the negative value becomes larger), and the direction in which the arrow on the right vertical axis points is the direction in which the positive value becomes larger (the absolute value becomes larger).

[0051] The five curves shown by the two-dot chain lines in FIG. 4 are resistance curves for each system, namely, the first resistance curve R1, the second resistance curve R2, the third resistance curve R3, the fourth resistance curve R4, and the second fourth resistance curve R4a. The first resistance curve R1 corresponds to the first system. The second resistance curve R2 corresponds to the second system. The third resistance curve R3 corresponds to the third system. The fourth resistance curve R4 corresponds to the fourth system. As described above, the pipeline resistance increases in the order of the first system, the second system, the third system, and the fourth system, and the slope of the curve increases in the order of the first resistance curve R1, the second resistance curve R2, the third resistance curve R3, and the fourth resistance curve R4. The second fourth resistance curve R4a will be described later.

[0052] 4 are characteristic curves of blower 20 corresponding to any rotation speed of blower motor 22. The rotation speed of blower motor 22 increases in the order of first characteristic curve T1, second characteristic curve T2, third characteristic curve T3, and fourth characteristic curve T4. The gas flow rate corresponding to the intersection of the characteristic curve and the resistance curve corresponds to the gas flow rate at the rotation speed of the characteristic curve.

[0053] For example, when gas flows through the fourth system, and the rotation speed of the blower motor 22 is the rotation speed of the first characteristic curve T1, the flow rate of the gas becomes a first flow rate Q1 corresponding to a first operating point OP1 which is the intersection point of the fourth resistance curve R4 and the first characteristic curve T1. Similarly, when the rotation speed of the blower motor 22 is the rotation speed of the second characteristic curve T2, the flow rate of the gas becomes a second flow rate Q2 corresponding to a second operating point OP2 which is the intersection point of the fourth resistance curve R4 and the second characteristic curve T2.

[0054] Similarly, when the rotation speed of the blower motor 22 is the rotation speed of the third characteristic curve T3, the flow rate of the gas is a third flow rate Q3 corresponding to a third operating point OP3 which is the intersection point of the fourth resistance curve R4 and the third characteristic curve T3. Similarly, when the rotation speed of the blower motor 22 is the rotation speed of the fourth characteristic curve T4, the flow rate of the gas is a fourth flow rate Q4 corresponding to a fourth operating point OP4 which is the intersection point of the fourth resistance curve R4 and the fourth characteristic curve T4. Hereinafter, when the first operating point OP1, the second operating point OP2, the third operating point OP3, and the fourth operating point OP4 are described without distinction, they will be simply referred to as "operating points".

[0055] In addition, when gas flows through the fourth system, when the rotation speed of the blower motor 22 is the rotation speed of the first characteristic curve T1, the suction pressure becomes the first pressure P1 corresponding to the first operating point OP1. Similarly, when the rotation speed of the blower motor 22 is the rotation speed of the second characteristic curve T2, the suction pressure becomes the second pressure P2 corresponding to the second operating point OP2.

[0056] Similarly, when the rotation speed of the blower motor 22 is the rotation speed of the third characteristic curve T3, the suction pressure becomes a third pressure P3 corresponding to a third operating point OP3. Similarly, when the rotation speed of the blower motor 22 is the rotation speed of the fourth characteristic curve T4, the suction pressure becomes a fourth pressure P4 corresponding to a fourth operating point OP4.

[0057] The resistance curve indicates that the suction pressure decreases as the gas flow rate increases. In addition, there is only one intersection (operating point) between the resistance curve and the characteristic curve for any rotation speed. Therefore, the first flow rate Q1, the second flow rate Q2, the third flow rate Q3, and the fourth flow rate Q4 are different from one another and increase in this order. In addition, the first pressure P1, the second pressure P2, the third pressure P3, and the fourth pressure P4 are different from one another and decrease in this order.

[0058] In this way, when gas flows through the fourth system, the flow rate and suction pressure of the gas change along the fourth resistance curve R4 according to the rotation speed of the blower motor 22. The same applies to the other systems.

[0059] For example, when gas flows through the fourth system and the rotation speed of the blower motor 22 is the rotation speed of the fourth characteristic curve T4, the fourth pressure P4 corresponding to the fourth operating point OP4 corresponds to the actual static pressure (PS1) acquired in the above step S3, and the fourth flow rate Q4 corresponding to the fourth operating point OP4 corresponds to the actual flow rate (Gw) calculated in the above step S4. The same applies to the suction pressures and gas flow rates corresponding to other operating points on the fourth resistance curve R4, and the suction pressures and gas flow rates corresponding to operating points on the other resistance curves.

[0060] The target flow rate is determined so that the operating point is located in the region between the first boundary line L1 and the second boundary line L2 shown in Fig. 4. In Fig. 4, the region A1 where the gas flow rate is smaller than the first boundary line L1 is a region where a phenomenon occurs in which the operating state of the blower 20 becomes unstable (so-called surging phenomenon) due to the gas flow rate becoming small relative to the suction pressure (discharge pressure). On the other hand, in Fig. 4, the region A2 where the flow rate is larger than the second boundary line L2 is a region where a phenomenon occurs in which the gas flow rate does not increase even if the pressure on the primary side of the blower 20 increases (so-called choking phenomenon).

[0061] The target flow rate is determined within a range in which the operating point is located in an area A3 between the first boundary line L1 and the second boundary line L2. In other words, the target flow rate is determined within a range of flow rates corresponding to area A3 in which the operation of blower 20 is stable and the flow rate increases as the rotation speed of rotating part 21 increases. Note that, like the target flow rate, the above-mentioned predetermined flow rate is also determined within a range of flow rates corresponding to area A3.

[0062] 3, the flow control unit 52 determines the rotation speed of the blower motor 22 that reduces the deviation between the actual flow rate calculated in step S4 and the target flow rate. The flow control unit 52 outputs the determined rotation speed to the blower 20. By rotating the blower motor 22 at the output rotation speed, the flow rate of the gas flowing through the gas pipe 10 (system) approaches the target flow rate.

[0063] When step S5 is completed, the flow control unit 52 returns the program to step S3. In this way, during production of a product, the flow control unit 52 repeatedly executes steps S3, S4, and S5 to adjust the flow rate through the gas pipe 10 to be equal to the target flow rate. In this way, the flow control system 1 can accurately adjust the flow rate of the gas flowing through the gas pipe 10 without placing a measuring instrument or the like in the gas flow path 11 in the gas pipe 10.

[0064] As described above, the flow control system 1 according to the present embodiment includes a gas pipe 10 through which gas flows, a blower 20 disposed in the gas pipe 10 to adjust the flow rate of the gas, a pressure sensor 40 disposed in the gas pipe 10 on the primary side of the blower 20 to detect an actual static pressure, which is an actual static pressure of the gas flowing through the gas pipe 10, a temperature sensor 30 disposed in the gas pipe 10 on the primary side of the blower 20 to detect an actual temperature, which is an actual temperature of the gas flowing through the gas pipe 10, and a control device 50 to control the blower 20. The control device 50 prestores a reference density, which is a reference density, a reference speed, which is a reference speed, a reference static pressure, which is a reference static pressure, and a reference temperature, which is a reference temperature, which are predetermined for the gas, and calculates an actual flow rate, which is an actual flow rate of the gas flowing through the gas pipe 10, using the actual static pressure, actual temperature, reference density, reference speed, reference static pressure, and reference temperature, and determines an operation amount of the blower 20 so as to make the actual flow rate equal to a target flow rate. According to this, the flow control system 1 can accurately calculate the flow rate of the gas flowing through the gas pipe 10 by storing the reference density and the like in advance, without disposing a measuring instrument or the like in the flow path 11 of the gas pipe 10. Furthermore, the flow control system 1 can calculate the flow rate of the gas flowing through the gas pipe 10 in a state in which the effects of the gas characteristics (e.g., corrosiveness) and the contents such as the object to be treated and fly ash are suppressed. Therefore, the flow control system 1 can accurately measure the flow rate of the gas and adjust the flow rate of the gas regardless of the properties of the gas. Furthermore, the flow control system 1 does not dispose a measuring instrument (e.g., an impeller type flowmeter) for detecting the flow rate of gas inside the flow path 11 as described above. Moreover, the flow control system 1 is capable of adjusting the flow rate of gas without using a measuring instrument (e.g., an ultrasonic flowmeter) that is disposed outside the flow path 11 and can detect the flow rate of gas. Therefore, the cost of the flow control system 1 can be reduced.

[0065] Moreover, the control device 50 calculates the actual flow rate using the above formulas (1), (2), (3), (4), (5) and (6). This enables the flow rate control system 1 to more accurately calculate the flow rate of the gas.

[0066] Moreover, the pressure sensor 40 and the temperature sensor 30 are each disposed in a portion of the gas pipe 10 away from the flow path 11 through which the gas flows. This reduces the influence of gas properties on the pressure sensor 40 and the temperature sensor 30. Therefore, the pressure sensor 40 can accurately detect the actual static pressure of the gas. Also, the temperature sensor 30 can accurately detect the actual temperature of the gas.

[0067] The gas also contains sulfur. A gas pipe 10 connects an industrial furnace 2 that discharges the gas to a gas treatment device 3 (desulfurization device) that desulfurizes the gas. According to this, the flow rate control system 1 can accurately adjust the flow rate of the gas even when the gas contains sulfur and the gas pipe 10 connects an industrial furnace 2 that discharges the gas to a desulfurization device that desulfurizes the gas.

[0068] Although the preferred embodiment of the present disclosure has been described above, the present disclosure is not limited to such an embodiment. The contents disclosed in the embodiment are merely examples, and various modifications are possible within the scope of the present disclosure. Appropriate modifications made within the scope of the present disclosure also naturally belong to the technical scope of the present disclosure.

[0069] Next, a flow rate control system 1 according to a first modified example of the embodiment of the present disclosure will be described, focusing mainly on the parts that differ from the above embodiment.

[0070] 5 is a schematic diagram showing a configuration of a flow control system 1 according to a first modified example of the embodiment of the present disclosure. Compared with the flow control system 1 of the above embodiment, the flow control system 1 of the first modified example further includes a first damper 160. The first damper 160 is disposed on the primary side of the blower 20 in the gas pipe 10. The first damper 160 adjusts the flow rate of gas flowing through the gas pipe 10. The first damper 160 is a so-called suction damper. In the first modified example, the first damper 160 corresponds to a "flow rate adjustment unit."

[0071] In this first modified example, the flow control unit 52 determines the operation amount of the first damper 160 in step S5 shown in Fig. 3. Specifically, the flow control unit 52 determines the operation amount of the actuator that adjusts the opening degree of the first damper 160 so as to make the actual flow rate calculated in step S4 equal to the target flow rate.

[0072] The flow rate control unit 52 outputs the determined manipulated variable to the first damper 160. As a result, the opening degree of the first damper 160 changes, and the flow rate of the gas flowing through the gas pipe 10 approaches the target flow rate.

[0073] For example, when gas flows through the fourth system and the rotation speed of the blower motor 22 is the rotation speed of the fourth characteristic curve T4, if the opening of the first damper 160 changes, the pipe resistance of the fourth system changes. Specifically, if the opening of the first damper 160 decreases due to the operation amount determined by the flow control unit 52, the pipe resistance of the fourth system increases, and the fourth resistance curve R4 shown in FIG. 4 changes to a second fourth resistance curve R4a whose gradient is larger than that of the fourth resistance curve R4. In response to this change in gradient, the operating point moves from the fourth operating point OP4 to the second fourth operating point OP4a along the fourth characteristic curve T4. As a result, the flow rate of the gas is adjusted from the fourth flow rate Q4 corresponding to the fourth operating point OP4 to the second fourth flow rate Q4a.

[0074] In the present first modified example, the flow control unit 52 may control the blower motor 22 of the blower 20 at the above-mentioned predetermined rotation speed, or may adjust the rotation speed of the blower motor 22 according to the opening degree of the first damper 160.

[0075] Next, a flow rate control system 1 according to a second modified example of the embodiment of the present disclosure will be described, focusing mainly on the parts that differ from the above embodiment.

[0076] 6 is a schematic diagram showing a configuration of a flow control system 1 according to a second modified example of the embodiment of the present disclosure. Compared with the flow control system 1 of the above embodiment, the flow control system 1 of the second modified example further includes a second damper 270. The second damper 270 is disposed on the secondary side of the blower 20 in the gas pipe 10. The second damper 270 adjusts the flow rate of gas flowing through the gas pipe 10. The second damper 270 is a so-called discharge damper. In the second modified example, the second damper 270 corresponds to a "flow rate adjustment unit."

[0077] In this second modified example, the flow control unit 52 determines the operation amount of the second damper 270 in step S5 shown in Fig. 3. Specifically, the flow control unit 52 determines the operation amount of the actuator that adjusts the opening degree of the second damper 270 so as to make the actual flow rate calculated in step S4 equal to the target flow rate.

[0078] The flow rate control unit 52 outputs the determined manipulated variable to the second damper 270. This changes the opening of the second damper 270, and the flow rate of the gas flowing through the gas pipe 10 approaches the target flow rate. When the opening of the second damper 270 changes, the line resistance of the system changes and the flow rate of the gas is adjusted, similar to the case where the opening of the first damper 160 changes. Note that in this second modified example, the first damper 160 may be provided.

[0079] Next, a flow rate control system 1 according to a third modified example of the embodiment of the present disclosure will be described, focusing mainly on the parts that differ from the above embodiment.

[0080] 7 is a schematic diagram showing a configuration of a flow control system 1 according to a third modified example of the embodiment of the present disclosure. Compared with the flow control system 1 of the above embodiment, the flow control system 1 of the third modified example further includes an inlet guide vane 380. The inlet guide vane 380 is disposed on the primary side of the blower 20 in the gas pipe 10. The inlet guide vane 380 adjusts the flow rate of gas flowing through the gas pipe 10. In the third modified example, the inlet guide vane 380 corresponds to a "flow rate adjustment unit."

[0081] In this third modified example, the flow rate control unit 52 determines the operation amount of the inlet guide vane 380 in step S5 shown in Fig. 3. Specifically, the flow rate control unit 52 determines the operation amount of the actuator that adjusts the opening degree of the inlet guide vane 380 so as to make the actual flow rate calculated in step S4 equal to the target flow rate.

[0082] The flow rate control unit 52 outputs the determined operation amount to the inlet guide vane 380. As a result, the opening degree of the inlet guide vane 380 changes, and the flow rate of the gas flowing through the gas pipe 10 approaches the target flow rate. When the opening degree of the inlet guide vane 380 changes, the pipeline resistance of the system changes and the flow rate of the gas is adjusted, similarly to the case where the opening degree of the first damper 160 changes. Note that in this third modified example, at least one of the first damper 160 and the second damper 270 may be disposed.

[0083] Next, a flow rate control system 1 according to a fourth modified example of the embodiment of the present disclosure will be described, focusing mainly on the parts that differ from the above embodiment.

[0084] FIG. 8 is a schematic diagram showing a temperature sensor 430 of a flow rate control system 1 according to a fourth modified example of the embodiment of the present disclosure.

[0085] The temperature sensor 430 of the fourth modified example includes a protruding portion 432 located in the flow path 11. The temperature detection portion 431 of the temperature sensor 430 is housed in the protruding portion 432. That is, in the fourth modified example, the temperature detection portion 431 is disposed in the flow path 11. The gas velocity decreases toward the radially outer side of the gas pipe 10. That is, by disposing the temperature detection portion 431 in the flow path 11, the temperature detection portion 431 detects a temperature change of the gas early. Therefore, when the temperature detection portion 431 is disposed in the flow path 11, the thermal responsiveness of the flow control system 1 can be improved compared to when the temperature detection portion 431 is disposed outside the flow path 11.

[0086] Moreover, the flow rate control system 1 of the fourth modified example further includes a protective cover 440. The protective cover 440 covers the protruding portion 432 in the flow path 11, and protects the protruding portion 432 and the temperature detection portion 431. The protective cover 440 is, for example, cylindrical, and is detachable from the gas pipe 10.

[0087] Protective cover 440 prevents gas inclusions from directly contacting protruding portion 432. Thus, protective cover 440 prevents protruding portion 432 from being worn down by gas inclusions, and prevents protruding portion 432 and temperature detection unit 431 from being damaged. Thus, flow rate control system 1 of the fourth modified example can accurately measure the gas flow rate and adjust the gas flow rate even when temperature detection unit 431 is located inside flow path 11.

[0088] Next, a flow rate control system 1 according to another modified example of the embodiment of the present disclosure will be described, focusing mainly on the parts that differ from the above embodiment.

[0089] For example, the temperature sensor 30 may detect the temperature of the outer surface of the gas pipe 10. This can reliably prevent the temperature sensor 30 from corroding and breaking.

[0090] The control device 50 may be able to change a gain in the PID control. The gain is input to the control device 50 by, for example, an operator. This allows the flow rate control unit 52 to determine an operation amount that results in an appropriate change in the flow rate of the gas.

[0091] The storage unit 51 may also store formulas that are mathematically equivalent to the above formulas (1), (2), (3), (4), (5), and (6). For example, the storage unit 51 stores the following formulas (1), (2), (3), (4A), (4B), (5), and (6). In this case, the flow rate control unit 52 calculates the actual flow rate (Gw) using formulas (1), (2), (3), (4A), (4B), (5), and (6) in the same manner as in the above embodiment.

[0092] PT0 = PS0 + PD0 ... (1) PD0 = (ρ0 × V0 2 / 2)×10 -3 …(2) PS1'=PS1×(273.15+T1) / (273.15+T0) …(3) PT1'=PS1'+PD1' …(4A) PD1' = (ρ0 × V1 2 / 2)×10 -3 …(4B) PT1' = PT0 × (V1 / V0) 2 …(5) Gw = A × V1 … (6)

[0093] In equation (4A), PD1' is the actual velocity pressure (unit: kPa) of the gas corrected to the reference temperature. Equation (4A) shows that the sum of the corrected actual static pressure (PS1') and the corrected actual velocity pressure (PD1') is the corrected actual total pressure (PT1').

[0094] Equation (4B), like equation (2), expresses the kinetic energy of a gas in units of pressure, and is derived based on Bernoulli's theorem.

[0095] Furthermore, the flow rate control unit 52 may correct the calculated actual flow rate (Gw) to a value corresponding to a standard state. Specifically, the flow rate control unit 52 corrects the actual flow rate based on the following formulas (7), (8), and (9) which are further stored in the storage unit 51.

[0096] C1=(273.15) / (273.15+T1) …(7) C2=(101.325+PS1) / 101.325 …(8) Gw' = Gw × C1 × C2 … (9)

[0097] In formula (7), C1 is a correction coefficient for temperature. In formula (8), C2 is a correction coefficient for static pressure. In formula (9), Gw' is a value obtained by correcting the actual flow rate (Gw) to the standard state of the gas.

[0098] Furthermore, the gas discharged from the industrial furnace 2 may contain nitrogen (specifically, nitrogen oxides: for example, nitrogen dioxide). When the gas contains nitrogen oxides, the gas treatment device 3 may be a denitration device that removes nitrogen oxides. When the gas treatment device 3 is a denitration device, the above target flow rate may be determined based on the denitration efficiency of the gas treatment device 3, etc.

[0099] Furthermore, the gas discharged from the industrial furnace 2 may contain carbon (specifically, carbon oxides, such as carbon dioxide). When the gas contains carbon oxides, the gas treatment device 3 may be a recovery device that separates and recovers the carbon oxides. When the gas treatment device 3 is a recovery device, the target flow rate may be determined based on the recovery efficiency of the gas treatment device 3, etc.

[0100] The gas may contain at least one of sulfur oxides, nitrogen oxides, and carbon oxides. The gas treatment device 3 may include a device corresponding to the oxides contained in the gas among sulfur oxides, nitrogen oxides, and carbon oxides, among the three devices of a desulfurization device, a denitrification device, and a recovery device.

[0101] According to this modification, the gas contains nitrogen. A gas pipe 10 connects an industrial furnace 2 that discharges gas to a gas treatment device 3 (denitrification device) that denitrifies the gas. As a result, the flow rate control system 1 can accurately adjust the gas flow rate even when the gas contains nitrogen (nitrogen compounds) and the gas pipe 10 connects an industrial furnace 2 that discharges the gas to a denitrification device that denitrifies the gas.

[0102] The gas also contains carbon. A gas pipe 10 connects an industrial furnace 2 that discharges the gas to a gas treatment device 3 (recovery device) that recovers carbon oxides. With this, the flow rate control system 1 can accurately adjust the flow rate of the gas even when the gas contains carbon (carbon oxides) and the gas pipe 10 connects an industrial furnace 2 that discharges the gas to a recovery device that recovers the carbon (carbon oxides).

[0103] Next, a flow rate control system 1 according to another modified example of the embodiment of the present disclosure will be described, focusing mainly on the parts that differ from the above embodiment.

[0104] FIG. 9 is a diagram showing a configuration of a flow rate control system 1 according to another modified example of the embodiment of the present disclosure.

[0105] The flow rate control system 1 of this modified example further includes a gas sensor 590 and an acquisition unit 553 included in the control device 50. The gas sensor 590 is disposed on the primary side of the blower 20 in the gas pipe 10, and detects the concentration of sulfur oxides contained in the gas. The gas sensor 590 is, for example, a sulfur dioxide sensor that detects sulfur dioxide. The concentration of sulfur oxides detected by the gas sensor 590 is output to the acquisition unit 553.

[0106] Moreover, the flow rate control system 1 of this modified example further includes an exhaust pipe 511, a second gas sensor 591, a second temperature sensor 530, a second pressure sensor 540, and a calculation device 592. The exhaust pipe 511 exhausts the gas derived from the gas processing device 3 to the atmosphere. The second gas sensor 591, the second temperature sensor 530, and the second pressure sensor 540 are disposed in the exhaust pipe 511.

[0107] The second gas sensor 591 is configured similarly to the gas sensor 590, and detects the concentration of sulfur oxides contained in the gas flowing through the exhaust pipe 511. That is, the second gas sensor 591 detects the concentration of sulfur oxides contained in the gas treated by the gas treatment device 3 (hereinafter referred to as the treated gas). The second gas sensor 591 is, for example, a sulfur dioxide sensor that detects sulfur dioxide. The gas sensor 590 and the second gas sensor 591 may be gas chromatographs capable of detecting sulfur oxides.

[0108] The second temperature sensor 530 detects the temperature of the gas after the treatment. The second pressure sensor 540 detects the static pressure of the gas after the treatment. The second temperature sensor 530 and the second pressure sensor 540 are arranged in the exhaust pipe 511 via a branch pipe, similar to the temperature sensor 30 and the pressure sensor 40 of the above embodiment.

[0109] The temperature detected by the second temperature sensor 530 and the static pressure detected by the second pressure sensor 540 are output to the calculation device 592.

[0110] The calculation device 592 includes an acquisition unit 592a, a flow rate calculation unit 592b, an efficiency calculation unit 592c, and a storage unit 592d.

[0111] The acquisition unit 592a acquires a detection value of the second gas sensor 591, and outputs the detection value to the efficiency calculation unit 592c.

[0112] The flow rate calculation unit 592b calculates the actual flow rate of the processed gas in the same manner as the flow rate control unit 52 of the above embodiment, based on the detection value of the second temperature sensor 530 and the detection value of the second pressure sensor 540. The memory unit 592d stores the reference density, reference velocity, reference static pressure, and reference temperature corresponding to the processed gas, as well as the above formulas (1), (2), (3), (4), (5), and (6).

[0113] The efficiency calculation unit 592c calculates the desulfurization efficiency of the gas treatment device 3. The efficiency calculation unit 592c acquires the concentration of sulfur oxides contained in the gas (hereinafter referred to as untreated gas) flowing through the gas pipe 10 and the actual flow rate of the untreated gas from the acquisition unit 553 of the control device 50 and the flow rate control unit 52. The efficiency calculation unit 592c calculates the flow rate of sulfur oxides contained in the untreated gas from the concentration of sulfur oxides and the actual flow rate.

[0114] Furthermore, the efficiency calculation unit 592c acquires the concentration of sulfur oxides contained in the treated gas and the actual flow rate of the treated gas from the acquisition unit 592a and the flow rate calculation unit 592b, and calculates the flow rate of sulfur oxides contained in the treated gas from the concentration of sulfur oxides and the actual flow rate.

[0115] Furthermore, the efficiency calculation unit 592c calculates the ratio of the amount of sulfur oxides removed by the gas treatment device 3 per unit time to the flow rate of sulfur oxides contained in the gas before treatment (i.e., desulfurization efficiency) based on the flow rate of sulfur oxides contained in the gas before treatment and the flow rate of sulfur oxides contained in the gas after treatment. The arithmetic unit 592 may display the calculated desulfurization efficiency on the display unit. This allows the user to monitor the desulfurization efficiency during operation of the flow control system 1.

[0116] The flow rate control unit 52 of the control device 50 may correct the target flow rate based on the calculated desulfurization efficiency. The arithmetic device 592 may correct the actual flow rate of the gas before and after the treatment to values ​​corresponding to the standard state based on the above formulas (7), (8), and (9). Furthermore, the control device 50 and the arithmetic device 592 may be integrated.

[0117] Furthermore, the gas before treatment may contain at least one oxide of sulfur (specifically, sulfur oxides), nitrogen (specifically, nitrogen oxides), and carbon (specifically, carbon oxides). When the gas before treatment contains nitrogen oxides, the gas treatment device 3 may include a denitrification device that removes nitrogen oxides. When the gas before treatment contains carbon oxides, the gas treatment device 3 may include a recovery device that separates and recovers carbon oxides.

[0118] Furthermore, when the gas processing device 3 includes a denitration device, the gas sensor 590 and the second gas sensor 591 may detect nitrogen oxides. In this case, the gas sensor 590 and the second gas sensor 591 include, for example, a graphene gas sensor that detects nitrogen dioxide. In this case, the gas sensor 590 and the second gas sensor 591 may be a gas chromatograph that can detect nitrogen oxides.

[0119] In this case, the acquisition unit 553 of the control device 50 acquires the concentration of nitrogen oxides contained in the gas before treatment, and the acquisition unit 592a of the arithmetic device 592 acquires the concentration of nitrogen oxides contained in the gas after treatment.

[0120] Furthermore, in this case, the efficiency calculation unit 592c may calculate the flow rate of nitrogen oxides contained in the gas before treatment and the flow rate of nitrogen oxides contained in the gas after treatment, and calculate the ratio of the amount of nitrogen oxides removed by the gas treatment device 3 per unit time to the flow rate of nitrogen oxides contained in the gas before treatment (i.e., denitration efficiency). The arithmetic device 592 may display the calculated denitration efficiency on the display unit. This allows the user to monitor the denitration efficiency during operation of the flow control system 1.

[0121] Furthermore, when the gas processing device 3 includes a recovery device, the gas sensor 590 and the second gas sensor 591 may detect carbon oxides. In this case, the gas sensor 590 and the second gas sensor 591 include, for example, a graphene gas sensor that detects carbon dioxide. In this case, the gas sensor 590 and the second gas sensor 591 may be a gas chromatograph capable of detecting carbon oxides.

[0122] In this case, the acquisition unit 553 of the control device 50 acquires the concentration of carbon oxides contained in the gas before treatment, and the acquisition unit 592a of the arithmetic device 592 acquires the concentration of carbon oxides contained in the gas after treatment.

[0123] Furthermore, in this case, the efficiency calculation unit 592c may calculate the flow rate of carbon oxides contained in the gas before treatment and the flow rate of carbon oxides contained in the gas after treatment, and calculate the ratio of the amount of carbon oxides recovered by the gas treatment device 3 per unit time to the flow rate of carbon oxides contained in the gas before treatment (i.e., the recovery efficiency). The arithmetic device 592 may display the calculated recovery efficiency on the display unit. This allows the user to monitor the recovery efficiency during operation of the flow control system 1.

[0124] The target flow rate may be determined based on the denitrification efficiency and recovery efficiency of the gas treatment device 3. The flow rate control unit 52 of the control device 50 may correct the target flow rate based on the calculated desulfurization efficiency, denitrification efficiency, and recovery efficiency. The gas treatment device 3 may be a device including at least one of a desulfurization device, a denitrification device, and a recovery device. [Explanation of symbols]

[0125] 1 Flow Control System 2. Industrial furnaces 3 Gas treatment equipment 10 Gas Pipe 11 Flow Path 20 Blower 21 Rotating section 22 Blower motor 30 Temperature Sensor 40 Pressure Sensor 50 Control device 51 Storage section 52 Flow control section 160 First damper 270 Second damper 380 Inlet Guide Vane

Claims

1. A gas pipe through which gas flows; a flow rate adjusting unit disposed in the gas pipe and adjusting a flow rate of the gas; a pressure sensor disposed on a primary side of the flow rate adjusting unit in the gas pipe, the pressure sensor detecting an actual static pressure of the gas flowing through the gas pipe; a temperature sensor disposed on a primary side of the flow rate adjusting unit in the gas pipe and detecting an actual temperature of the gas flowing through the gas pipe; A control device for controlling the flow rate adjustment unit, The control device includes: A reference density, a reference speed, a reference static pressure, and a reference temperature are stored in advance, the reference density, the reference speed, the reference static pressure, and the reference temperature being predetermined for the gas; Calculating an actual flow rate, which is an actual flow rate of the gas flowing through the gas pipe, using the actual static pressure, the actual temperature, the reference density, the reference velocity, the reference static pressure, and the reference temperature; determining an operation amount of the flow rate adjusting unit so as to make the actual flow rate equal to a target flow rate; Flow control system.

2. The control device calculates the actual flow rate using the following formulas (1), (2), (3), (4), (5), and (6): The flow control system of claim 1 . PT ０ =PS ０ +PD ０ …(1) PD ０ =(ρ ０ ×V ０ ２ / 2)×10 －３ …(2) PS １ ’=PS １ ×(273.15+T １ ) / (273.15+T ０ ) …(3) PT １ '=PS １ '+(ρ ０ ×V １ ２ / 2)×10 －３ …(4) PT １ '=PT ０ ×(V １ / V ０ ) ２ …(5) Gw=A×V １ …(6) In addition, P.T. ０ is the reference total pressure (unit: kPa) which is the reference total pressure of the gas, P.S. ０ is the reference static pressure (unit: kPa), P.D. ０ is the reference velocity pressure (unit: kPa) which is the reference velocity pressure of the gas, ρ ０ is the standard density (unit: kg / m ３ ) and V ０ is the reference speed (unit: m / s), P.S. １ is the actual static pressure (unit: kPa), T １ is the actual temperature (unit: ° C.), T ０ is the reference temperature (unit: ° C.), P.S. １ ' is the actual static pressure (unit: kPa) corrected to the reference temperature state, P.T. １ ' is the actual total pressure of the gas (unit: kPa) corrected to the reference temperature state, V １ is the actual velocity of the gas (unit: m / s), Gw is the actual flow rate (unit: m ３ / s), A is the cross-sectional area (unit: m ２ ).

3. The pressure sensor is disposed in the gas pipe at a location away from a flow path through which the gas flows. The flow control system of claim 1 .

4. The temperature sensor is disposed in the gas pipe at a location away from a flow path through which the gas flows. The flow control system of claim 1 .

5. the gas comprises sulfur; The gas pipe connects an industrial furnace that discharges the gas to a gas treatment device that desulfurizes the gas. The flow control system of claim 1 .

6. the gas comprises nitrogen; The gas pipe connects an industrial furnace that discharges the gas to a gas treatment device that denitrifies the gas. The flow control system of claim 1 .

7. the gas comprises carbon; The gas pipe connects an industrial furnace that discharges the gas to a gas treatment device that recovers the carbon. The flow control system of claim 1 .

8. A step of detecting an actual static pressure of the gas flowing through the gas pipe and an actual temperature of the gas flowing through the gas pipe, the actual static pressure being an actual static pressure of the gas flowing through the gas pipe and the actual temperature being an actual temperature of the gas, in the gas flowing through the gas pipe and the flow rate being adjusted by a flow rate adjustment unit; calculating an actual flow rate, which is an actual flow rate of the gas, using the actual static pressure and the actual temperature detected in the step of detecting the actual static pressure and the actual temperature, as well as a reference density, a reference speed, a reference static pressure, and a reference temperature, which are predetermined for the gas; determining an operation amount of the flow rate adjusting unit so as to make the actual flow rate calculated in the step of calculating the actual flow rate equal to a target flow rate; Flow control method.

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