Flow rate control system and flow rate control method

Abstract

To suppress generation of surging and choking phenomena in a flow rate control system that adjusts the flow rate of a gas.SOLUTION: The control device 80 of a flow rate control system 1 stores, in advance, reference density which is the density of reference predetermined for a gas flowing in a gas pipe 10, a reference velocity which is the reference of velocity, reference static pressure which is the reference of static pressure, a reference temperature which is the reference of temperature, and a normal flow rate range which is the range of gas flow rates in which an air blower 20 operates normally, and calculates an actual flow rate which is the actual flow rate of the gas by using actual static pressure which is the actual static pressure of the gas detected by a pressure sensor 50, an actual temperature which is the actual temperature of the gas detected by a temperature sensor 40, the reference density, the reference velocity, and the reference static pressure, as well as determines operation amount of the air blower 20 so as to equalize the actual flow rate and a target flow rate when the actual flow rate is within the normal flow rate range and determines operation amount of a suction damper 30 so that the actual flow rate matches a value in the normal flow rate range when the actual flow rate is out of the normal flow rate range.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, as an example of a blower, a centrifugal compressor equipped with an inlet guide vane for controlling the intake flow rate and a blow-off valve at the discharge section. At start-up, the blower of Patent Document 1 controls the opening degree of the inlet guide vane and the blow-off valve in an appropriate interlocking manner based on the intake flow rate and the pressure at the discharge section so as to avoid the occurrence of so-called surging and choking phenomena. When the intake flow rate (gas flow rate) increases and reaches the intake flow rate control setting value (target flow rate), the blower of Patent Document 1 controls the inlet guide vane so as to keep the gas flow rate constant at the target flow rate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-303291 Summary of the Invention [Problem to be solved by the invention]

[0004] However, even after the gas flow rate reaches the target flow rate, if the pressure or temperature of the gas on the primary side of the blower fluctuates due to an external factor, the surging phenomenon and the choking phenomenon may occur. This is also true in a flow control system that measures the gas flow rate and adjusts the gas flow rate.

[0005] The present disclosure has been made in consideration of the above-mentioned problems, and has an object to suppress the occurrence of surging and choking phenomena in a flow control system that adjusts the flow rate of gas. [Means for solving the problem]

[0006] In order to achieve the above object, a flow rate control system according to one aspect of the present disclosure includes a gas pipe through which a gas flows, a first flow rate adjustment unit and a second flow rate adjustment unit that are disposed in the gas pipe and adjust a flow rate of the gas, a pressure sensor that is disposed in the gas pipe on a primary side of the first flow rate adjustment unit and on a primary side of the second flow rate adjustment unit and detects an actual static pressure that is an actual static pressure of the gas flowing through the gas pipe, a temperature sensor that is disposed in the gas pipe on the primary side of the first flow rate adjustment unit and on the primary side of the second flow rate adjustment unit and detects an actual temperature that is an actual temperature of the gas flowing through the gas pipe, and a control device that controls the first flow rate adjustment unit and the second flow rate adjustment unit, and the control device detects a predetermined pressure for the gas. a reference density which is the determined reference density, a reference speed which is the reference speed, a reference static pressure which is the reference static pressure, a reference temperature which is the reference temperature, and a normal flow rate range which is a range of the flow rate of the gas within which the first flow rate adjustment unit operates normally are stored in advance, and an actual flow rate which is the actual flow rate of the gas flowing through the gas pipe is calculated using the actual static pressure, the actual temperature, the reference density, the reference speed, the reference static pressure, and the reference temperature, and an operation amount of the first flow rate adjustment unit is determined so that the actual flow rate and the target flow rate are equal when the actual flow rate is within the normal flow rate range, and an operation amount of the second flow rate adjustment unit is determined so that the actual flow rate is a value within the normal flow rate range when the actual flow rate is outside the normal flow rate range.

[0007] Moreover, a flow rate control method according to an aspect of the present disclosure includes a step of detecting an actual static pressure and an actual temperature of a gas flowing through a gas pipe, the actual static pressure and the actual temperature of the gas flowing through the gas pipe, for a gas whose flow rate is adjusted by a first flow rate adjustment unit and a second 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, a reference velocity, a reference static pressure, and a reference temperature that are predetermined for the gas; and a step of calculating the actual flow rate. the step of determining whether the actual flow rate calculated in the step is within a normal flow rate range, which is a range of flow rates of the gas in which the first flow rate adjustment unit operates normally; when it is determined that the actual flow rate is within the normal flow rate range in the step of determining whether the actual flow rate is within the normal flow rate range, determining an operation amount of the first flow rate adjustment unit so as to make the actual flow rate equal to the target flow rate; and when it is determined that the actual flow rate is outside the normal flow rate range in the step of determining whether the actual flow rate is within the normal flow rate range, determining an operation amount of the second flow rate adjustment unit so that the actual flow rate is a value within the normal flow rate range. Effect of the Invention

[0008] According to the flow rate control system of the present disclosure, the occurrence of the surging phenomenon and the choking phenomenon can be suppressed. [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 diagram showing the relationship between the gas flow rate, the suction pressure of the blower, and the rotation speed of the blower motor. [Figure 4] FIG. 4 is a flowchart executed when the flow control unit calculates the actual flow rate and determines the operation amount of the blower and the operation amount of the damper. [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 temperature sensor 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 diagram showing a configuration of a flow rate control system according to a fourth 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, an inlet damper 30, a temperature sensor 40, a pressure sensor 50, a bypass pipe 60, a bypass pipe on-off valve 70 (corresponding to an "on-off valve"), and a control device 80. In this embodiment, the blower 20 is a "first flow rate adjustment unit," and the inlet damper 30 is a "second 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. A connecting pipe on-off valve 10b is disposed in the connecting pipe 10a. When the connecting pipe on-off valve 10b is in an open state, gas is discharged from the industrial furnace 2 corresponding to the connecting pipe on-off valve 10b in the open state. The opening and closing of the connecting pipe on-off valve 10b is controlled by the control device 80 so that the gas discharged from one of the multiple industrial furnaces 2 flows through the gas pipe 10. In FIG. 1, the connecting pipe 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 connecting pipe 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 distinction, they will be simply referred to as "systems". In FIG. 1, the connecting pipe opening / closing valve 10b corresponding to the fourth industrial furnace 2d among the multiple connecting pipe opening / closing valves 10b is in an open state, and gas flows in 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 flow rate of gas flowing through the gas pipe 10 (flow rate per unit time: the same below) increases as the rotation speed of the blower motor 22 (rotation speed per unit time: the same below). 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 80. The rotation speed of the rotating part 21 and the rotation speed of the blower motor 22 are proportional to each other.

[0022] The suction damper 30 is disposed on the primary side of the blower 20 in the gas pipe 10. The suction damper 30 adjusts the flow rate of gas flowing through the gas pipe 10. The opening degree of the suction damper 30 is adjusted by an actuator (e.g., a motor) provided in the suction damper 30. As the opening degree of the suction damper 30 increases by driving the actuator of the suction damper 30, the flow rate of gas flowing through the gas pipe 10 increases.

[0023] Fig. 2 is a schematic diagram showing the temperature sensor 40 and the pressure sensor 50 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.

[0024] The temperature sensor 40 is disposed in the gas pipe 10 on the primary side of the blower 20 and on the primary side of the suction damper 30, and detects the temperature of the gas. The temperature sensor 40 is disposed in the gas pipe 10 via the first branch pipe 10c. That is, the temperature sensor 40 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 41, at which the temperature sensor 40 detects the temperature, is located outside the flow path 11. The temperature detected by the temperature sensor 40 is output to the control device 80.

[0025] The pressure sensor 50 is disposed in the gas pipe 10 on the primary side of the blower 20 and on the primary side of the suction damper 30, and detects the static pressure of the gas. The pressure sensor 50 is disposed in the gas pipe 10 via the second branch pipe 10d. That is, the pressure sensor 50 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 51 through which the pressure sensor 50 detects the static pressure is located outside the flow path 11. The static pressure detected by the pressure sensor 50 is output to the control device 80.

[0026] The temperature sensor 40 and the pressure sensor 50 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 40 and the pressure sensor 50. This prevents the temperature sensor 40 and the pressure sensor 50 from being corroded and damaged, for example, by wear caused by the gas components and inclusions in the gas.

[0027] 1 is a pipe through which gas flows, connecting the primary side of the blower 20 and the primary side of the suction damper 30 to the secondary side of the blower 20 and the secondary side of the suction damper 30 in the gas pipe 10. Specifically, the bypass pipe 60 connects the primary side of the temperature sensor 40 and the primary side of the pressure sensor 50 to the secondary side of the blower 20 and the secondary side of the suction damper 30 in the gas pipe 10.

[0028] The inside diameter of the bypass pipe 60 is smaller than the inside diameter of the gas pipe 10 , and the cross-sectional area of ​​the flow passage through which the gas flows in the bypass pipe 60 is smaller than the cross-sectional area of ​​the flow passage 11 of the gas pipe 10 .

[0029] The bypass pipe on-off valve 70 is disposed in the bypass pipe 60 and opens and closes the bypass pipe 60. That is, the bypass pipe on-off valve 70 stops the flow of gas in the bypass pipe 60 when in a closed state, and allows the flow of gas in the bypass pipe 60 when in an open state. The bypass pipe on-off valve 70 is, for example, a motor-operated valve. Note that in FIG. 1, the bypass pipe on-off valve 70 is shown in a closed state. That is, no gas flows through the bypass pipe 60 in FIG. 1.

[0030] 1 controls the flow rate control system 1. The control device 80 controls the blower 20 and the suction damper 30, and supplies gas discharged from the industrial furnace 2 to the gas processing device 3. The control device 80 also controls the opening and closing of the bypass pipe on-off valve 70. The control device 80 includes a memory unit 81 and a flow rate control unit 82.

[0031] Reference physical quantities obtained by the 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 81. Specifically, the reference physical quantities are a reference density, a reference speed, a reference static pressure, and a reference temperature.

[0032] 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. The reference density is calculated, for example, by an operator analyzing the composition of the gas flowing through the gas pipe 10, 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. Note that the measuring instrument for measuring the reference velocity is placed in a portion of the flow passage 11 in the gas pipe 10 that has a cross-sectional area equal to the cross-sectional area of ​​the flow passage 11 corresponding to the portion where the pressure sensor 50 is placed.

[0033] The reference static pressure is measured (detected) by the pressure sensor 50. The reference temperature is measured (detected) by the temperature sensor .

[0034] 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 81.

[0035] Furthermore, the storage unit 81 stores in advance six flow rate ranges, which will be described next.

[0036] Fig. 3 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. 3, the horizontal axis is the gas flow rate flowing through the gas pipe 10, 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).

[0037] 3 shows a first boundary line L1, a second boundary line L2, a third boundary line L3, a fourth boundary line L4, and a fifth boundary line L5 that divide the six regions described below. The boundaries L1 and L5 are determined based on the performance characteristics of the fan 20, etc.

[0038] The second boundary line L2 has a gas flow rate for any suction pressure that is greater by a first predetermined percentage (for example, 5%) than the first boundary line L1.

[0039] The third boundary line L3 is a second predetermined percentage (e.g., 10%) greater than the first boundary line L1 in terms of the gas flow rate for any suction pressure. The second predetermined percentage is greater than the first predetermined percentage. The second predetermined percentage is determined so as to reliably suppress the occurrence of the surging phenomenon described below in an area where the gas flow rate is greater than the third boundary line L3.

[0040] The fourth boundary line L4 is smaller than the fifth boundary line L5 in terms of the gas flow rate for any suction pressure by a third predetermined percentage (e.g., 10%). The third predetermined percentage is determined so that the occurrence of the choking phenomenon described below is reliably suppressed in an area where the gas flow rate is smaller than the fourth boundary line L4. The third predetermined percentage may be equal to or different from the second predetermined percentage.

[0041] Region A1 is a region where the gas flow rate is smaller than that of the first boundary line L1. Region A2 is a region between the first boundary line L1 and the second boundary line L2. Region A3 is a region between the second boundary line L2 and the third boundary line L3.

[0042] Region A4 is the region between the third boundary line L3 and the fourth boundary line L4. Region A5 is the region between the fourth boundary line L4 and the fifth boundary line L5. Region A6 is the region where the gas flow rate is greater than that of the fifth boundary line L5. Note that the first boundary line L1 is included in region A1, the second boundary line L2 is included in region A2, the third boundary line L3 is included in region A3, the fourth boundary line L4 is included in region A5, and the fifth boundary line L5 is included in region A6.

[0043] In addition, hereinafter, the gas flow rate ranges corresponding to region A1, region A2, region A3, region A4, region A5, and region A6 will be referred to as the first flow rate range, the second flow rate range (corresponding to the "predetermined flow rate range"), the third flow rate range, the fourth flow rate range (corresponding to the "normal flow rate range"), the fifth flow rate range, and the sixth flow rate range.

[0044] In region A1 (first flow rate range), the gas flow rate becomes small relative to the suction pressure (or discharge pressure), causing the blower 20 to malfunction and causing the operating state of the blower 20 to become unstable (a phenomenon known as surging).

[0045] Region A2 (second flow rate range) is between region A1 and region A3. That is, region A2 (second flow rate range) is closer to region A1 where the surging phenomenon occurs than region A3. Region A3 (third flow rate range) is between region A2 and region A4. That is, region A3 (third flow rate range) is closer to region A1 where the surging phenomenon occurs than region A4.

[0046] Region A4 (fourth flow rate range) is between region A3 and region A5. That is, region A4 (fourth flow rate range) is between boundary lines L3 and L4. By defining boundary lines L3 and L4 as described above, the occurrence of the surging phenomenon and the choking phenomenon is reliably suppressed in region A4 (fourth flow rate range).

[0047] That is, region A4 (fourth flow rate range) is a range of gas flow rates within which blower 20 operates normally. In other words, the fourth flow rate range is a range within which the gas flow rate changes according to the rotation speed of blower 20, and the flow rate increases as the rotation speed of rotating part 21 increases.

[0048] Region A5 (fifth flow rate range) is between region A4 and region A6. That is, region A5 (fifth flow rate range) is closer to region A6 where the choking phenomenon occurs than region A4.

[0049] In region A6 (sixth flow rate range), blower 20 does not operate normally, and a phenomenon occurs in which the flow rate of gas does not increase even when the pressure on the primary side of blower 20 increases (so-called choking phenomenon).

[0050] In this manner, the first flow rate range, the second flow rate range, the third flow rate range, the fourth flow rate range, the fifth flow rate range, and the sixth flow rate range have increasing gas flow rates in this order. Moreover, the six flow rate ranges are determined in accordance with the rotation speed of blower motor 22.

[0051] 3 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.

[0052] For example, in the first characteristic curve T1, the range of gas flow rates corresponding to the region A1 smaller than the point M1 corresponds to the first flow rate range corresponding to the first rotation speed. In the second characteristic curve T2, the range of gas flow rates corresponding to the region A1 smaller than the point M2 corresponds to the first flow rate range corresponding to the second rotation speed.

[0053] In the third characteristic curve T3, the range of gas flow rates corresponding to the region A1 smaller than the point M3 corresponds to the first flow rate range corresponding to the third rotation speed. In the fourth characteristic curve T4, the range of gas flow rates corresponding to the region A1 smaller than the point M4 corresponds to the first flow rate range corresponding to the fourth rotation speed.

[0054] In addition, in the first characteristic curve T1, the range of gas flow rates corresponding to the region A2 between points M1 and N1 corresponds to a second flow rate range corresponding to the first rotation speed. In the second characteristic curve T2, the range of gas flow rates corresponding to the region A2 between points M2 and N2 corresponds to a second flow rate range corresponding to the second rotation speed.

[0055] In the third characteristic curve T3, the range of gas flow rates corresponding to the region A2 between points M3 and N3 corresponds to the second flow rate range corresponding to the third rotation speed. In the fourth characteristic curve T4, the range of gas flow rates corresponding to the region A2 between points M4 and N4 corresponds to the second flow rate range corresponding to the fourth rotation speed.

[0056] In addition, in the first characteristic curve T1, the range of gas flow rates corresponding to the region A3 between points N1 and C1 corresponds to a third flow rate range corresponding to the first rotation speed. In the second characteristic curve T2, the range of gas flow rates corresponding to the region A3 between points N2 and C2 corresponds to a third flow rate range corresponding to the second rotation speed.

[0057] In the third characteristic curve T3, the range of gas flow rates corresponding to the region A3 between points N3 and C3 corresponds to a third flow rate range corresponding to the third rotation speed. In the fourth characteristic curve T4, the range of gas flow rates corresponding to the region A3 between points N4 and C4 corresponds to a third flow rate range corresponding to the fourth rotation speed.

[0058] In addition, in the first characteristic curve T1, the range of gas flow rates corresponding to the region A4 between points C1 and D1 corresponds to a fourth flow rate range corresponding to the first rotation speed. In the second characteristic curve T2, the range of gas flow rates corresponding to the region A4 between points C2 and D2 corresponds to a fourth flow rate range corresponding to the second rotation speed.

[0059] In the third characteristic curve T3, the range of gas flow rates corresponding to the region A4 between points C3 and D3 corresponds to a fourth flow rate range corresponding to the third rotation speed. In the fourth characteristic curve T4, the range of gas flow rates corresponding to the region A4 between points C4 and D4 corresponds to a fourth flow rate range corresponding to the fourth rotation speed.

[0060] In addition, in the first characteristic curve T1, the range of gas flow rates corresponding to the region A5 between points D1 and S1 corresponds to a fifth flow rate range corresponding to the first rotation speed. In the second characteristic curve T2, the range of gas flow rates corresponding to the region A5 between points D2 and S2 corresponds to a fifth flow rate range corresponding to the second rotation speed.

[0061] In the third characteristic curve T3, the range of gas flow rates corresponding to the region A5 between points D3 and S3 corresponds to a fifth flow rate range corresponding to the third rotation speed. In the fourth characteristic curve T4, the range of gas flow rates corresponding to the region A5 between points D4 and S4 corresponds to a fifth flow rate range corresponding to the fourth rotation speed.

[0062] In addition, in the first characteristic curve T1, the range of gas flow rates corresponding to region A6 larger than point S1 corresponds to a sixth flow rate range corresponding to the first rotation speed. In the second characteristic curve T2, the range of gas flow rates corresponding to region A6 larger than point S2 corresponds to a sixth flow rate range corresponding to the second rotation speed.

[0063] In the third characteristic curve T3, the range of gas flow rates corresponding to region A6 larger than point S3 corresponds to a sixth flow rate range corresponding to the third rotation speed. In the fourth characteristic curve T4, the range of gas flow rates corresponding to region A6 larger than point S4 corresponds to a sixth flow rate range corresponding to the fourth rotation speed.

[0064] For example, a plurality of sections are defined for the rotation speed of the blower motor 22, and the six flow rate ranges are stored in the storage unit 81 so as to correspond to the plurality of sections.

[0065] The flow rate control unit 82 calculates the actual flow rate of the gas flowing through the gas pipe 10 (hereinafter referred to as the actual flow rate) and determines the operation amounts of the suction damper 30 and the blower 20, as will be described next.

[0066] FIG. 4 is a flowchart executed when the flow control unit 82 calculates the actual flow rate and determines the operation amount of the blower 20 and the operation amount of the suction damper 30. The flow control unit 82 executes the flowchart shown in FIG. 4 during the operation of the industrial furnace 2 during the production of a product. The production of a product is performed in one of the multiple industrial furnaces 2. That is, during the production of a product, only the connecting pipe opening / closing 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 gas pipe 10. In addition, at the start of the flowchart shown in FIG. 4, the bypass pipe opening / closing valve 70 is in a closed state. Hereinafter, a case will be described in which the connecting pipe opening / closing 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.

[0067] At the start of production of a product, the flow rate control unit 82 sets the opening degree of the suction damper 30 to a predetermined predetermined opening degree and sets the blower motor 22 of the blower 20 to a predetermined 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 opening degree and the predetermined rotation speed are, for example, the opening degree of the suction damper 30 and the rotation speed of the blower motor 22 that make the flow rate of the gas flowing through the gas pipe 10 smaller than a target flow rate described later.

[0068] The flow rate control unit 82 acquires a reference physical quantity in step S1. Specifically, the flow rate control unit 82 acquires from the storage unit 81 a reference density, a reference velocity, a reference static pressure, and a reference temperature that are predetermined for the gas.

[0069] Next, the flow rate control unit 82 identifies the system through which the gas flows in step S2. Specifically, the flow rate control unit 82 identifies the system in which the connecting pipe on-off valve 10b is open. As shown in Fig. 1, when the connecting pipe on-off valve 10b corresponding to the fourth industrial furnace 2d is open, the flow rate control unit 82 identifies the fourth system.

[0070] Furthermore, in step S3, the flow rate control unit 82 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 40. 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 50.

[0071] Furthermore, in step S4, the flow rate control unit 82 calculates the actual flow rate of the gas. The flow rate control unit 82 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 81.

[0072] 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)

[0073] 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).

[0074] 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.

[0075] The flow control unit 82 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] The flow control unit 82 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).

[0080] 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 81. The cross-sectional area (A) of the flow path 11 is equal to each other in the multiple systems.

[0081] Furthermore, in step S5, the flow rate control unit 82 determines whether the actual flow rate of the gas is within a fourth flow rate range. Specifically, the flow rate control unit 82 determines whether the actual flow rate of the gas is within a fourth flow rate range that corresponds to the current rotation speed of the blower motor 22.

[0082] When the industrial furnace 2 and the flow rate control system 1 are operating normally, the actual flow rate of the gas is within the fourth flow rate range. In this case (YES in step S5), the flow rate control unit 82 causes the program to proceed to step S6.

[0083] The flow control unit 82 determines the operation amount of the blower 20 in step S6. Specifically, the flow control unit 82 performs feedback control to determine the rotation speed 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 while keeping the opening degree of the suction damper 30 at a predetermined opening degree. In this embodiment, the feedback control is, for example, a proportional-integral-differential controller (PID) control. The operation amount of the blower 20 is the rotation speed of the blower motor 22.

[0084] 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 80. In addition, the target flow rate is determined within a range corresponding to an area described below with reference to FIG.

[0085] The four curves shown by dashed lines in FIG. 3 are resistance curves for each system, namely, the first resistance curve R1, the second resistance curve R2, the third resistance curve R3, and the fourth resistance curve R4. 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 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, and the gradient 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.

[0086] Furthermore, the smaller the opening of the suction damper 30, the greater the line resistance of the system and the greater the gradient of the resistance curve. For example, when gas flows through the fourth system, if the opening of the suction damper 30 becomes smaller and the line resistance of the fourth system increases, the gradient of the fourth resistance curve R4 becomes greater and the fourth resistance curve R4 approaches the third boundary line L3. Note that the first resistance curve R1, the second resistance curve R2, the third resistance curve R3, and the fourth resistance curve R4 shown in FIG. 3 show the case where the opening of the suction damper 30 is a predetermined opening.

[0087] Moreover, the flow rate of gas corresponding to the intersection of the characteristic curve and the resistance curve corresponds to the flow rate of gas flowing through the gas pipe 10 corresponding to the rotation speed indicated by the characteristic curve.

[0088] 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.

[0089] 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".

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] The target flow rate is determined so that the operating point OP is located within a range of flow rates where the occurrence of so-called surging and choking phenomena is suppressed. That is, the target flow rate is determined so that the operating point OP is located within a range of flow rates corresponding to region A4 where the operation of blower 20 is stable and the flow rate increases as the rotation speed of rotating part 21 increases. That is, the target flow rate is determined so that the operating point is located at a value within the fourth flow rate range.

[0096] 4, the flow control unit 82 keeps the opening of the suction damper 30 at a predetermined opening and 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 82 outputs the determined rotation speed to the blower 20. By rotating the blower motor 22 at the output rotation speed, the flow rate (actual flow rate) of the gas flowing through the gas pipe 10 (system) approaches the target flow rate. When the industrial furnace 2 and the flow control system 1 are operating normally, the actual flow rate and suction pressure of the gas change along a resistance curve according to the rotation speed of the blower motor 22.

[0097] When step S6 ends, the flow control unit 82 returns the program to step S3. In this way, when the industrial furnace 2 and the flow control system 1 are operating normally during product production, the flow control unit 82 repeatedly executes steps S3, S4, S5, and S6 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.

[0098] On the other hand, for example, if an abnormal heat generation occurs in the industrial furnace 2 and the gas temperature in the industrial furnace 2 rises abnormally, the flow rate of the gas discharged from the industrial furnace 2 will suddenly decrease. Specifically, the gas flow rate will suddenly increase in volumetric flow rate (suddenly decrease in mass flow rate). For example, when the rotation speed of the blower motor 22 is the fourth rotation speed, if the gas flow rate becomes smaller than the gas flow rate corresponding to point C4 shown in FIG. 3, the gas flow rate will fall outside the fourth flow rate range.

[0099] Furthermore, for example, an abnormality such as a power supply interruption to the industrial furnace 2 causes an abnormal drop in the gas temperature in the industrial furnace 2, which causes a sudden increase in the flow rate of gas discharged from the industrial furnace 2. Specifically, the gas flow rate decreases suddenly in volumetric flow rate (increases suddenly in mass flow rate). For example, when the rotation speed of the blower motor 22 is the fourth rotation speed, if the gas flow rate becomes greater than the gas flow rate corresponding to point D4 shown in FIG. 3, the gas flow rate falls outside the fourth flow rate range.

[0100] If the actual gas flow rate is outside the fourth flow rate range (NO in step S5), the flow rate control unit 82 determines in step S7 whether the actual gas flow rate is within the third flow rate range or the fifth flow rate range.

[0101] When the actual flow rate of the gas decreases from within the fourth flow rate range to fall within the third flow rate range (YES in step S7), or when the actual flow rate of the gas increases from within the fourth flow rate range to fall within the fifth flow rate range (YES in step S7), the flow rate control unit 82 closes the bypass pipe opening / closing valve 70 in step S8. That is, the flow rate control unit 82 keeps the bypass pipe opening / closing valve 70 in the closed state.

[0102] Next, in step S9, the flow control unit 82 determines the amount of operation of the suction damper 30. Specifically, the flow control unit 82 keeps the rotation speed of the blower motor 22 at the current rotation speed, and determines the amount of operation of the suction damper 30 so that the actual flow rate calculated in step S4 falls within the fourth flow rate range. The amount of operation of the suction damper 30 is the amount of drive of the actuator of the suction damper 30. As a result, the opening degree of the suction damper 30 is adjusted.

[0103] For example, when the rotation speed of blower motor 22 is a fourth rotation speed and the actual flow rate of gas is within the third flow rate range (area A3), the operating point corresponding to this actual flow rate of gas is located between points N4 and C4 on fourth characteristic curve T4. In this case, flow control unit 82 determines the operation amount of suction damper 30 that increases the opening degree of suction damper 30 beyond a predetermined opening degree. When the opening degree of suction damper 30 increases, the pipeline resistance of the system decreases (the gradient of the resistance curve decreases), and the operating point moves along fourth characteristic curve T4 in the direction in which the flow rate of gas increases, and the actual flow rate of gas increases.

[0104] On the other hand, when the rotation speed of the blower motor 22 is the fourth rotation speed and the actual flow rate of the gas is within the fifth flow rate range (area A5), the operating point corresponding to this actual flow rate of the gas is located between points D4 and S4 on the fourth characteristic curve T4. In this case, the flow control unit 82 determines the operation amount of the suction damper 30 that makes the opening degree of the suction damper 30 smaller than the predetermined opening degree. When the opening degree of the suction damper 30 becomes smaller, the pipeline resistance of the system increases (the gradient of the resistance curve increases), and the operating point moves along the fourth characteristic curve T4 in the direction in which the flow rate of the gas decreases, and the actual flow rate of the gas decreases. When step S9 is completed, the flow control unit 82 returns the program to step S3.

[0105] In this way, when an abnormality occurs in the industrial furnace 2 and the actual gas flow rate falls outside the fourth flow rate range, the flow rate control unit 82 repeatedly executes steps S3, S4, S5, S7, S8, and S9. This adjusts the actual gas flow rate to be within the fourth flow rate range. This makes it possible to prevent the actual gas flow rate from becoming smaller than the first boundary line L1, causing a surging phenomenon, and the actual gas flow rate from becoming larger than the fifth boundary line L5, causing a choking phenomenon.

[0106] When the flow control unit 82 repeatedly executes steps S3, S4, S5, S7, S8, and S9 so that the actual flow rate of the gas becomes a value within the fourth flow rate range (YES in step S5), the flow control unit 82 repeatedly executes steps S3, S4, S5, and S6 as described above.

[0107] On the other hand, when the flow control unit 82 is repeatedly executing steps S3, S4, S5, S7, S8, and S9, if the actual flow rate of the gas decreases and becomes a value within the second flow rate range (area A2), the actual flow rate of the gas falls outside the third flow rate range or the fifth flow rate range. In this case (NO in step S7), the flow control unit 82 opens the bypass pipe opening / closing valve 70 in step S10.

[0108] When the bypass pipe valve 70 is in an open state, the gas discharged from the blower 20 in the gas pipe 10 flows through the bypass pipe 60 from the secondary side of the blower 20 toward the primary side, returns to the primary side of the blower 20, and flows into the blower 20. This increases the actual flow rate of the gas flowing into the blower 20. This prevents the occurrence of a surging phenomenon in which the operating state of the blower 20 becomes unstable due to a decrease in the actual flow rate of the gas flowing into the blower 20 relative to the suction pressure of the blower 20. Note that the increase per unit time of the gas flowing into the blower 20 is greater when the bypass pipe valve 70 is in an open state than when the actuator of the suction damper 30 is driven to increase the opening degree of the suction damper 30. In other words, when the bypass pipe valve 70 is in an open state, the actual flow rate of the gas flowing into the blower 20 increases rapidly.

[0109] For example, when the rotation speed of the blower motor 22 is the fourth rotation speed and the actual flow rate of the gas is within the second flow rate range (area A2), the operating point corresponding to this actual flow rate of the gas is located between points M4 and N4 on the fourth characteristic curve T4. In this case, when the bypass pipe on-off valve 70 is opened, the line resistance of the system rapidly decreases (the gradient of the resistance curve rapidly decreases), the operating point moves along the fourth characteristic curve T4 in the direction in which the flow rate of the gas increases, and the actual flow rate of the gas rapidly increases. When step S10 is completed, the flow rate control unit 82 returns the program to step S3.

[0110] In this way, when an abnormality occurs in the industrial furnace 2 and the actual gas flow rate falls within the second flow rate range, the flow rate control unit 82 repeatedly executes steps S3, S4, S5, S7, and S10. This causes the actual gas flow rate to increase rapidly as described above. This makes it possible to further prevent the actual gas flow rate from becoming smaller than the first boundary line L1 and causing the surging phenomenon.

[0111] Furthermore, when the flow control unit 82 is repeatedly executing steps S3, S4, S5, S7, and S10, if the actual flow rate of gas increases and becomes a value within the third flow rate range (YES in step S7), the flow control unit 82 closes the bypass pipe opening / closing valve 70 in step S8 and repeatedly executes steps S3, S4, S5, S7, S8, and S9 as described above. In this way, even if the actual flow rate of gas decreases due to the adjustment of the opening degree of the suction damper 30, the bypass pipe opening / closing valve 70 is opened, so that the occurrence of the surging phenomenon can be further suppressed.

[0112] As described above, the flow control system 1 of this embodiment includes a gas pipe 10 through which gas flows, a blower 20 and a suction damper 30 that are disposed in the gas pipe 10 and adjust the flow rate of the gas, a pressure sensor 50 that is disposed on the primary side of the blower 20 and the primary side of the suction damper 30 in the gas pipe 10 and detects an actual static pressure that is the actual static pressure of the gas flowing through the gas pipe 10, a temperature sensor 40 that is disposed on the primary side of the blower 20 and the suction damper 30 in the gas pipe 10 and detects an actual temperature that is the actual temperature of the gas flowing through the gas pipe 10, and a control device 80 that controls the blower 20 and the suction damper 30. The flow control unit 82 of the control device 80 pre-stores a reference density, which is a predetermined reference density for the gas, a reference speed, which is a reference static pressure, which is a reference temperature, and a fourth flow rate range, which is a range of gas flow rates at which the blower 20 operates normally, and calculates an actual flow rate, which is the actual flow rate of 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 that the actual flow rate and the target flow rate are equal when the actual flow rate is within the fourth flow rate range, and determines an operation amount of the suction damper 30 so that the actual flow rate is a value within the fourth flow rate range when the actual flow rate is outside the fourth flow rate range. According to this, when the actual flow rate deviates from the fourth flow rate range while the flow rate of the gas is being adjusted within the fourth flow rate range by the blower 20, the flow rate of the gas can be adjusted to return to the fourth flow rate range by the suction damper 30. This makes it possible to prevent the actual flow rate of the gas from becoming smaller than the first boundary line L1, causing a surging phenomenon, and the actual flow rate of the gas from becoming larger than the fifth boundary line L5, causing a choking phenomenon. Furthermore, the flow control system 1 can 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 inside 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.

[0113] The flow rate control system 1 further includes a bypass pipe 60 that connects the primary side of the blower 20 and the primary side of the suction damper 30 with the secondary side of the blower 20 and the secondary side of the suction damper 30 in the gas pipe 10 and through which gas flows, and a bypass pipe on-off valve 70 that opens and closes the bypass pipe 60. The control device 80 pre-stores a second flow rate range in which the gas flow rate is smaller than the fourth flow rate range, and when the actual flow rate is outside the fourth flow rate range, opens the bypass pipe on-off valve 70 in response to the actual flow rate decreasing to within the second flow rate range. According to this, the actual flow rate of gas can be rapidly increased by opening the bypass pipe on-off valve 70 in response to the actual flow rate of gas approaching the region A1 shown in Fig. 3. This makes it possible to further prevent the actual flow rate of gas from becoming smaller than the first boundary line L1 and causing the surging phenomenon.

[0114] Moreover, the control device 80 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.

[0115] 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. As a result, the flow control system 1 can suppress the occurrence of surging and choking phenomena 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.

[0116] 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.

[0117] FIG. 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. The flow control system 1 of the first modified example shown in FIG. 5 includes a discharge damper 230 instead of the suction damper 30. The discharge damper 230 is disposed on the secondary side of the blower 20 in the gas pipe 10. In this case, the bypass pipe 60 connects the primary side of the blower 20 and the primary side of the discharge damper 230 to the secondary side of the blower 20 and the secondary side of the discharge damper 230 in the gas pipe 10. In this modified example, the discharge damper 230 corresponds to a "second flow rate adjustment unit". In this case, the flow rate control unit 82 determines the operation amount of the discharge damper 230 (specifically, the drive amount of the actuator that adjusts the opening degree of the discharge damper 230) in step S9 so that the actual flow rate calculated in step S4 is a value within the fourth flow rate range. In this case, both the suction damper 30 and the discharge damper 230 may be disposed in the gas pipe 10.

[0118] Furthermore, the flow rate control system 1 does not necessarily have to include the bypass pipe 60 and the bypass pipe on-off valve 70. In this case, the flow rate control unit 82 does not execute steps S7, S8, and S10 shown in FIG.

[0119] The storage unit 81 may also store in advance a formula indicating the boundary lines L1, L2, L3, L4, and L5 shown in Fig. 3, and a correlation between the static pressure detected by the pressure sensor 50 and the suction pressure shown in Fig. 3. In this case, the flow control unit 82 may calculate a fourth flow rate range corresponding to the actual static pressure acquired in step S3 using the formula indicating the boundary lines L3 and L4 in step S5, and determine whether the actual flow rate calculated in step S4 is within the fourth flow rate range. Similarly, the flow control unit 82 may calculate a third flow rate range and a fifth flow rate range corresponding to the actual static pressure acquired in step S1 using the formula indicating the boundary lines L2, L3, L4, and L5 in step S7, and determine whether the actual flow rate calculated in step S4 is within the third flow rate range or the fifth flow rate range.

[0120] Also, in step S6, the flow control unit 82 may determine the operation amount of the suction damper 30 (the driving amount of the actuator of the suction damper 30) based on the deviation between the actual flow rate and the target flow rate, so that the actual flow rate calculated in step S4 is equal to the target flow rate, while keeping the rotational speed of the blower motor 22 at a predetermined rotational speed. That is, in this case, the suction damper 30 corresponds to the "first flow rate adjustment unit". Also, in this case, the fourth flow rate range is a range of gas flow rates in which the suction damper 30 operates normally. In other words, the fourth flow rate range is a range in which the gas flow rate changes depending on the opening degree of the suction damper 30, and the flow rate increases as the opening degree of the suction damper 30 increases. Furthermore, in this case, the flow rate control unit 82 may determine the operation amount of the blower 20 (the rotational speed of the blower motor 22) in step S9, so that the opening degree of the suction damper 30 is kept at a predetermined opening and the actual flow rate calculated in step S4 is a value within the fourth flow rate range. That is, in this case, the blower 20 corresponds to the "second flow rate adjustment section."

[0121] Moreover, the temperature sensor 40 may detect the temperature of the outer surface of the gas pipe 10. This can reliably prevent the temperature sensor 40 from corroding and being damaged.

[0122] The control device 80 may be able to change a gain in the PID control. The gain is input to the control device 80 by, for example, an operator. This allows the flow rate control unit 82 to determine an operation amount that results in an appropriate change in the flow rate of the gas.

[0123] FIG. 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. The flow control system 1 of the second modified example shown in FIG. 6 includes an inlet guide vane 330 instead of the suction damper 30. In this case, the bypass pipe 60 connects the primary side of the blower 20 and the primary side of the inlet guide vane 330 to the secondary side of the blower 20 and the secondary side of the inlet guide vane 330 in the gas pipe 10. The inlet guide vane 330 includes a plurality of rotatable vanes and an actuator for rotating the plurality of vanes. The opening degree of the inlet guide vane 330 changes as the vane rotates, and the flow rate of the gas changes. In this case, the inlet guide vane 330 corresponds to a "second flow rate adjustment unit." In step S9, the flow rate control unit 82 determines the operation amount of the inlet guide vane 330 (specifically, the rotation angle of the vane that adjusts the opening degree of the inlet guide vane 330 (i.e., the drive amount of the actuator that rotates the vane)) so that the actual flow rate calculated in step S4 falls within the fourth flow rate range. In this case, at least one of the suction damper 30 and the discharge damper 230 may be disposed in the gas pipe 10.

[0124] FIG. 7 is a schematic diagram showing a temperature sensor 440 of a flow rate control system 1 according to a third modified example of an embodiment of the present disclosure.

[0125] The temperature sensor 440 includes a protruding portion 442 located in the flow path 11. The temperature detection portion 441 of the temperature sensor 440 is housed in the protruding portion 442. That is, the temperature detection portion 441 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 441 in the flow path 11, the temperature detection portion 441 detects a temperature change of the gas early. Therefore, when the temperature detection portion 441 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 441 is disposed outside the flow path 11.

[0126] 7 further includes a protective cover 443. The protective cover 443 covers the protruding portion 442 in the flow path 11, and protects the protruding portion 442 and the temperature detection portion 441. The protective cover 443 is, for example, cylindrical, and is detachable from the gas pipe 10.

[0127] Protective cover 443 prevents gas inclusions from directly contacting protruding portion 442. Thus, protective cover 443 prevents protruding portion 442 from being worn down by gas inclusions, and prevents protruding portion 442 and temperature detection unit 441 from being damaged. Thus, flow rate control system 1 of this modified example can accurately measure the gas flow rate and adjust the gas flow rate even when temperature detection unit 441 is located inside flow path 11.

[0128] Furthermore, when the actual flow rate of the gas is within the first flow rate range or the sixth flow rate range, the flow rate control unit 82 may stop the operation of the suction damper 30 and the blower 20, and end the program.

[0129] The storage unit 81 may also store formulas that are mathematically equivalent to the above formulas (1), (2), (3), (4), (5), and (6). For example, the storage unit 81 stores the following formulas (1), (2), (3), (4A), (4B), (5), and (6). In this case, the flow rate control unit 82 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.

[0130] 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)

[0131] In formula (4A), PD1' is the actual velocity pressure (unit: kPa) of the gas corrected to the reference temperature. Formula (4A) shows that the sum of the corrected actual static pressure (PS1') and the actual velocity pressure (PD1') is the corrected actual total pressure (PT1').

[0132] Equation (4B), like equation (2), expresses the kinetic energy of a gas in units of pressure, and is derived based on Bernoulli's theorem.

[0133] Furthermore, the flow rate control unit 82 may correct the calculated actual flow rate (Gw) to a value corresponding to a standard state. Specifically, the flow rate control unit 82 corrects the actual flow rate based on the following formulas (7), (8), and (9) which are further stored in the storage unit 81.

[0134] C1=(273.15) / (273.15+T1) …(7) C2=(101.325+PS1) / 101.325 …(8) Gw' = Gw × C1 × C2 … (9)

[0135] 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.

[0136] 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.

[0137] 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.

[0138] 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.

[0139] 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.

[0140] 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. According to 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).

[0141] FIG. 9 is a diagram showing a configuration of a flow rate control system 1 according to a fourth modified example of the embodiment of the present disclosure.

[0142] The flow rate control system 1 of the fourth modified example further includes a gas sensor 590 and an acquisition unit 583 included in the control device 80. 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 583.

[0143] Moreover, the flow rate control system 1 of the fourth 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.

[0144] 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.

[0145] 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 40 and the pressure sensor 50 of the above embodiment.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] 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 82 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).

[0150] 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 583 and the flow rate control unit 82 of the control device 80. 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.

[0151] 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.

[0152] 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.

[0153] The flow rate control unit 82 of the control device 80 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 80 and the arithmetic device 592 may be integrated.

[0154] 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.

[0155] 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.

[0156] In this case, the acquisition unit 583 of the control device 80 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.

[0157] 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.

[0158] 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.

[0159] In this case, the acquisition unit 583 of the control device 80 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.

[0160] 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.

[0161] 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 82 of the control device 80 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]

[0162] 1 Flow Control System 2. Industrial furnaces 3 Gas treatment equipment 10 Gas Pipe 20 Blower 21 Rotating section 22 Blower motor 30 Suction damper 40 Temperature Sensor 50 Pressure Sensor 60 Bypass pipe 70 Bypass pipe on-off valve (on-off valve) 80 Control device 81 Storage section 82 Flow control section

Claims

1. A gas pipe through which gas flows; a first flow rate adjusting unit and a second flow rate adjusting unit arranged in the gas pipe and configured to adjust a flow rate of the gas; a pressure sensor disposed on the primary side of the first flow rate control unit and the primary side of the second flow rate control unit in the gas pipe, the pressure sensor detecting an actual static pressure, which is an actual static pressure of the gas flowing through the gas pipe; a temperature sensor disposed on the upstream side of the first flow rate control unit and on the upstream side of the second flow rate control unit in the gas pipe, the temperature sensor detecting an actual temperature of the gas flowing through the gas pipe; A control device that controls the first flow rate adjustment unit and the second flow rate adjustment unit, The control device includes: a reference density, a reference speed, a reference static pressure, a reference temperature, and a normal flow rate range, which is a range of flow rates of the gas in which the first flow rate control unit normally operates, that are 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 first flow rate adjustment unit so that the actual flow rate is equal to a target flow rate when the actual flow rate is within the normal flow rate range; determining an operation amount of the second flow rate adjustment unit so that the actual flow rate falls within the normal flow rate range when the actual flow rate is outside the normal flow rate range; Flow control system.

2. a bypass pipe in the gas pipe that connects a primary side of the first flow rate control unit and a primary side of the second flow rate control unit to a secondary side of the first flow rate control unit and a secondary side of the second flow rate control unit, and through which the gas flows; An on-off valve for opening and closing the bypass pipe, The control device includes: A predetermined flow rate range in which the flow rate of the gas is smaller than the normal flow rate range is stored in advance; when the actual flow rate is outside the normal flow rate range, opening the on-off valve in response to the actual flow rate being reduced to within the predetermined flow rate range. The flow control system of claim 1 .

3. 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 ).

4. 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 .

5. 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 .

6. 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 .

7. 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 an actual temperature being an actual temperature of the gas, the actual static pressure being an actual static pressure of the gas flowing through the gas pipe and the ... 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 whether the actual flow rate calculated in the step of calculating the actual flow rate is within a normal flow rate range, which is a range of flow rates of the gas in which the first flow rate adjustment unit operates normally; determining an operation amount of the first flow rate adjustment unit so as to make the actual flow rate equal to a target flow rate when the actual flow rate is determined to be within the normal flow rate range in the determining whether the actual flow rate is within the normal flow rate range; and when it is determined in the step of determining whether the actual flow rate is within the normal flow rate range that the actual flow rate is outside the normal flow rate range, determining an operation amount of the second flow rate adjustment unit so that the actual flow rate becomes a value within the normal flow rate range. Flow control method.

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