JP6062092B1 - Industrial furnace operating method, industrial furnace controller, and industrial furnace system - Google Patents

Abstract

An operating method of an industrial furnace, an industrial furnace controller, and an industrial furnace system capable of more reliably performing ignition of a burner with simple work. An operating method of an industrial furnace includes a plurality of burners, a first pipeline, a plurality of second pipelines branched from the first pipeline and respectively connected to the plurality of burners, and a first pipeline The operation target is an industrial furnace including a first valve provided in each of the plurality of second pipes provided in a plurality of second pipelines, and the fuel pressure between the burner and the first valve is set to a first value. While performing the first control for controlling the opening degree of the first valve so as to follow one target value, sequentially opening the plurality of second valves to sequentially ignite the plurality of burners, and the ignition in the plurality of burners And executing a second control for controlling the opening of the first valve so that the flow rate of the fuel passing through the first pipeline follows the second target value after completion. [Selection] Figure 4

Description

  The present disclosure relates to an operating method of an industrial furnace, an industrial furnace controller, and an industrial furnace system.

  As an industrial furnace having a plurality of burners, such as an annealing furnace in a steel plate processing facility, etc., a first pipeline for supplying fuel, and a second branch branched from the first pipeline and connected to the plurality of burners, respectively What is provided with a pipe line, the 1st valve | bulb provided in the 1st pipe line, and the 2nd valve | bulb each provided in the some 2nd pipe line is known. The first valve is controlled to adjust the fuel supply amount. The second valve is opened and closed when the connected burner is ignited or extinguished. When starting up such an industrial furnace, one second valve is opened and the burner to which it is connected is ignited sequentially. In this operation, it is required to reliably perform ignition of each burner without causing misfire of the already ignited burner.

  For example, in Patent Document 1, when each burner is ignited, the control of the fuel pressure control means is stopped to fix the valve opening, and the control of the fuel flow control means is stopped to set the valve opening. A fixed ignition control method is disclosed.

JP-A-7-27329

  According to the ignition control method described in Patent Document 1, since the valve opening is fixed when the burner is ignited, ignition failure due to hunting of the valve opening control is prevented. However, each time the valve for each burner is opened, the amount of fuel supplied to each burner decreases. For this reason, it may be necessary to increase the valve opening manually to increase the total amount of fuel supply as the number of burned burners increases. In this case, complicated work is required by cooperation between the worker igniting the burner and the worker adjusting the valve opening.

  Therefore, an object of the present disclosure is to provide an industrial furnace operating method, an industrial furnace controller, and an industrial furnace system that can perform ignition of a burner more reliably by a simple operation.

  An operating method of an industrial furnace according to the present disclosure includes a plurality of burners, a first pipe for sending fuel, a plurality of second pipes branched from the first pipe and connected to the plurality of burners, respectively. A first valve that is provided in the first pipe and adjusts the opening degree of the flow path of the fuel, and is provided in each of the plurality of second pipes, and the fuel flow path is blocked and opened. A first furnace that controls an opening degree of the first valve so that the pressure of the fuel between the burner and the first valve follows the first target value. While performing one control, the plurality of second valves are sequentially opened to sequentially ignite the plurality of burners, and after the ignition in the plurality of burners is completed, the flow rate of the fuel passing through the first pipeline is set to the second target. Execute second control to control the opening of the first valve to follow the value Including the fact that, a.

  According to this operation method, after the ignition in each burner is completed, the opening degree of the first valve is controlled so that the flow rate of the fuel follows the second target value. The burner can be brought to the desired combustion state. On the other hand, during ignition of each burner, the opening degree of the first valve is controlled so that the fuel pressure between the burner and the first valve follows the first target value. Since the pressure response delay according to the control of the opening degree of the first valve is smaller than the response delay of the flow rate, the fuel pressure between the burner and the first valve decreases as the second valve opens. Later, it is quickly returned to the vicinity of the first target value. When the second valve is sequentially opened while the fuel pressure between the burner and the first valve is maintained in the vicinity of the first target value, the amount of fuel supply increases accordingly. Therefore, by controlling the fuel pressure to follow the first target value, the opening of the first valve is increased as the number of burned burners increases, and the total flow rate of fuel (through the first pipeline) The fuel flow) is automatically increased. In addition, increasing the opening of the first valve as the number of burned burners increases is performed each time one burner is ignited, so the adjustment of the total flow rate of fuel is more finely adjusted. Executed. Therefore, the ignition of the burner can be more reliably performed with a simple operation.

  In the first control, the opening degree of the first valve may be kept below a predetermined upper limit value. In this case, since the first valve is prevented from opening excessively in the first control, an overshoot of the fuel pressure with respect to the first target value is suppressed. Further, even when an abnormality occurs in the fuel pressure detection system, the fuel flow rate can be maintained within an appropriate range. Therefore, the ignition of the burner can be performed more reliably.

  The second target value is a fuel flow rate required to make the air-fuel ratio coincide with the third target value, and the predetermined upper limit value is obtained when the plurality of burners are sequentially ignited by sequentially opening the plurality of second valves. It may be a second target value corresponding to the supply amount of air. In this case, the predetermined upper limit value is set so that the air-fuel ratio in the first control does not fall below the air-fuel ratio in the second control. For this reason, the fluctuation range of the opening degree of the first valve in the first control is kept in a range more suitable for burner combustion. Therefore, the ignition of the burner can be performed more reliably.

  The controller according to the present disclosure includes a plurality of burners, a first pipe for guiding fuel, a plurality of second pipes branched from the first pipe and respectively connected to the plurality of burners, and a first pipe A first valve that adjusts the opening of the fuel flow path, and a plurality of second pipes that switch between a closed state and an open state of the fuel flow path. An industrial furnace equipped with a second valve is controlled, and when a plurality of second pipes are sequentially opened and a plurality of burners are sequentially ignited, the fuel pressure between the burner and the first valve The first control for controlling the opening degree of the first valve so as to follow one target value, and after the ignition in the plurality of burners is completed, the flow rate of the fuel passing through the first pipeline is made to follow the second target value. So that the second control for controlling the opening degree of the first valve is executed. It is.

  In the first control, the controller may be configured to keep the opening of the first valve below a predetermined upper limit value.

  The second target value is a fuel flow rate required to make the air-fuel ratio coincide with the third target value, and the predetermined upper limit value is obtained when the plurality of burners are sequentially ignited by sequentially opening the plurality of second valves. It may be a second target value corresponding to the supply amount of air.

  In the controller, each of the plurality of burners controls an industrial furnace including a main burner and a pilot burner for burning fuel in the main burner, and controls the execution target in response to the pilot burner being ignited. It may be configured to further execute the mode for the first control. The pilot burner is ignited upon start-up of the industrial furnace. For this reason, the first control can be executed more reliably when the plurality of burners are ignited by setting the control mode to be executed as the first control in response to the ignition of the pilot burner. Therefore, the ignition of the burner can be performed more reliably.

  The said controller may be comprised so that the control mode of execution object may be set to 1st control according to the main burner misfiring without accompanying the misfire of a pilot burner. When the main burner misfires without the pilot burner being misfired, it is assumed that the main burner is subsequently re-ignited. Therefore, the main burner can be re-ignited more reliably by setting the control mode to be executed as the first control in accordance with the misfiring of the main burner without misfiring the pilot burner.

  An industrial furnace system according to the present disclosure includes a plurality of burners, a first pipe for guiding fuel, a plurality of second pipes branched from the first pipe and respectively connected to the plurality of burners, A first valve that is provided in one pipeline and adjusts the opening degree of the fuel flow path, and is provided in each of the plurality of second pipelines, and switches between a state in which the fuel flow path is blocked and an open state. An industrial furnace having a plurality of second valves, and a controller for controlling the industrial furnace, wherein the controller opens the burner when the plurality of second pipes are sequentially opened and the plurality of burners are sequentially ignited. The first control for controlling the opening of the first valve so that the fuel pressure between the first valve and the first valve follows the first target value, and after the ignition in the plurality of burners is completed, The first valve is set so that the flow rate of the passing fuel follows the second target value. It is configured to perform a second control for controlling the opening degree.

  According to the present disclosure, it is possible to more reliably perform ignition of the burner with a simple operation.

It is a schematic diagram which shows schematic structure of an industrial furnace system. It is a schematic diagram which shows schematic structure of each zone in FIG. It is a block diagram which illustrates the hardware constitutions of a controller. It is a flowchart which shows the control procedure until a some burner is ignited. It is a flowchart which shows the control procedure after a some burner was ignited. It is a graph which shows transition of the pressure of fuel, the flow volume of fuel, and the opening degree target value of a fuel flow control valve.

  Hereinafter, embodiments will be described in detail with reference to the drawings. In the description, the same elements or elements having the same functions are denoted by the same reference numerals, and redundant description is omitted.

<Industrial furnace system>
(overall structure)
As shown in FIG. 1, the industrial furnace system 1 includes an industrial furnace 10 and a controller 100 that controls the industrial furnace 10.

  The industrial furnace 10 is a processing furnace installed in a continuous processing line for steel plates, for example. A specific example of such a processing furnace is an annealing furnace. The industrial furnace 10 includes a furnace body 11, a plurality of heating systems 20 (zones), a fuel supply system 30, an air supply system 40, and an exhaust system 50.

  The furnace body 11 accommodates a heating object. Each of the plurality of heating systems 20 heats the inside of the furnace body 11 by burning fuel. The fuel is a combustible gas. A specific example of the combustible gas is coke gas. The fuel supply system 30 supplies fuel to the heating system 20. The air supply system 40 supplies air for burning fuel to the heating system 20. The exhaust system 50 exhausts the gas after combustion. In addition, there is no restriction | limiting in the number of the heating systems 20, According to the magnitude | size of the furnace main body 11, etc., it can set suitably. Hereinafter, a specific configuration example of each unit will be described.

(Heating system)
As shown in FIG. 2, the heating system 20 includes a plurality of (for example, several tens of) burners 21. The plurality of burners 21 are provided on the peripheral wall of the furnace body 11 and heat the inside of the furnace body 11.

  For example, the burner 21 includes a main burner 22, a pilot burner 23, and a frame detector 24. The burner 21 may be a radiant tube burner having a radiant tube type main burner 22. The radiant tube type main burner 22 receives a mixed gas of fuel and air from an opening (inlet) at one end and discharges a gas after combustion (hereinafter referred to as “exhaust gas”) from an opening (outlet) at the other end. .

  The pilot burner 23 burns fuel in the main burner 22. For example, the pilot burner 23 is provided in the vicinity of the inlet of the main burner 22, and generates a flame for ignition by burning a mixed gas of fuel and air. The mixed gas heading into the main burner 22 is ignited by the flame generated by the pilot burner 23 and burns while passing through the main burner 22.

  The frame detector 24 detects the presence / absence of at least one of the flames of the main burner 22 and the pilot burner 23 by, for example, a detection method using infrared rays. The burner 21 may have two frame detectors 24 corresponding to the main burner 22 and the pilot burner 23, respectively.

(Fuel supply system)
As shown in FIGS. 1 and 2, the fuel supply system 30 includes a fuel base pipe 31, a plurality of zone-specific fuel main pipes 33 (first pipe lines), and a plurality of fuel flow control valves 34 (first valves). A plurality of fuel shut-off valves 35, a plurality of fuel flow sensors 36, a plurality of fuel pressure sensors 37, a plurality of fuel branch pipes 38 (second pipe lines), a plurality of fuel branch pipes 38, A pre-burner valve 39 (second valve).

  The fuel base pipe 31 is connected to the fuel source 32 and guides the fuel to the furnace body 11 side.

  The plurality of zone-specific fuel main pipes 33 branch from the fuel base pipe 31 and guide the fuel to the plurality of heating systems 20 respectively.

  The plurality of fuel flow control valves 34 are respectively provided in the plurality of zone-specific fuel main pipes 33 and adjust the opening degree of the fuel flow path (inside the zone-specific fuel main pipe 33). A specific example of the fuel flow control valve 34 is a pneumatic valve that adjusts the opening of the valve by air pressure.

  The plurality of fuel shut-off valves 35 are respectively provided in the plurality of zone-specific fuel main pipes 33 and switch between a state where the fuel flow path is shut off and a state where the fuel flow path is opened. Specific examples of the fuel cutoff valve 35 include an electromagnetic or mechanical valve. The fuel cutoff valve 35 may be a valve specialized for an opening / closing function (that does not have an opening adjustment function).

  The fuel flow sensor 36 is provided in the zone-specific fuel main pipe 33 and detects the fuel flow rate. The fuel flow sensor 36 may be provided on the upstream side (opposite side of the burner 21) from the fuel flow adjustment valve 34, or provided on the downstream side (burner 21 side) from the fuel flow adjustment valve 34. Also good. A specific example of the fuel flow sensor 36 is a differential pressure transmitter. The differential pressure transmitter detects the differential pressure before and after the throttle portion and transmits it to the controller 100 as information relating to the fuel flow rate.

  The fuel pressure sensor 37 is provided downstream of the fuel flow adjustment valve 34 (on the burner 21 side) in the fuel main pipe 33 for each zone, and detects the pressure of the fuel between the burner 21 and the fuel flow adjustment valve 34. The fuel pressure sensor 37 may be provided between the fuel flow control valve 34 and the fuel cutoff valve 35, or may be provided further downstream than the fuel cutoff valve 35.

  The plurality of fuel branch pipes 38 are branched from the zone-specific fuel main pipes 33 and connected to the plurality of burners 21, respectively. For example, the fuel branch pipe 38 is connected to the inlet of the main burner 22.

  The plurality of pre-burner valves 39 are provided in the plurality of fuel branch pipes 38, respectively, and switch between a state in which the fuel flow path (inside the fuel branch pipe 38) is blocked and a state in which the fuel flow paths are opened.

(Air supply system)
The air supply system 40 includes an air base pipe 41, a blower 42, a damper 43, a plurality of zone-specific air main pipes 44, a plurality of air flow control valves 45, a plurality of air flow sensors 46, and a plurality of air flow sensors 46. And an air branch pipe 47.

  The air base tube 41 guides air to the furnace body 11 side. The blower 42 is provided in the air base tube 41 and pumps air to the furnace body 11 side. The damper 43 is provided in the air base tube 41 and adjusts the opening degree of the air flow path (inside the air base tube 41).

  The plurality of zone-specific air main pipes 44 branch from the air base pipe 41 and guide the air to the plurality of heating systems 20.

  The plurality of air flow control valves 45 are respectively provided in the plurality of zone-specific air mains 44 and adjust the opening degree of the air flow path (inside the zone-specific air mains 44).

  The plurality of air flow sensors 46 are respectively provided in the plurality of zone-specific air main pipes 44 and detect the air flow rate. A specific example of the air flow sensor 46 is a differential pressure transmitter.

  The plurality of air branch pipes 47 are branched from the zone-specific air main pipes 44 and connected to the plurality of burners 21, respectively. For example, the air branch pipe 47 is connected to the inlet of the main burner 22 together with the fuel branch pipe 38.

(Exhaust system)
The exhaust system 50 includes an exhaust pipe 51, a plenum chamber 52, a chamber pressure control valve 53, and an exhaust gas blower 54.

  The exhaust pipe 51 guides the exhaust gas derived from the plurality of burners 21.

  The plenum chamber 52 is interposed between the exhaust pipe 51 and the plurality of burners 21. For example, the plenum chamber 52 has a plurality of introduction ports 52a corresponding to the plurality of burners 21, respectively. Each inlet 52 a is connected to the outlets of the plurality of main burners 22 in the corresponding heating system 20.

  The exhaust gas blower 54 is provided in the exhaust pipe 51 on the downstream side of the plenum chamber 52 (opposite side of the burner 21), and the inside of the plenum chamber 52 is kept at a negative pressure by sucking out the gas in the plenum chamber 52. Thereby, exhaust gas in each main burner 22 is introduced into the plenum chamber 52.

  The chamber pressure adjusting valve 53 is provided between the plenum chamber 52 and the exhaust gas blower 54 in the exhaust pipe 51 to adjust the opening degree of the exhaust gas flow path. Thereby, the amount of gas sucked from the plenum chamber 52 is adjusted, and the pressure in the plenum chamber 52 is adjusted.

(controller)
The controller 100 controls the industrial furnace 10 and the fuel between the plurality of burners 21 and the fuel flow control valve 34 when the plurality of fuel branch pipes 38 are sequentially opened and the plurality of burners 21 are sequentially ignited. After the first control for controlling the opening degree of the fuel flow control valve 34 so as to follow the first pressure with the first target value and the ignition in the plurality of burners 21 (all the burners 21 to be ignited), The second control for controlling the opening degree of the fuel flow control valve 34 is performed so that the flow rate of the fuel passing through the fuel main pipe 33 follows the second target value.

  The first target value is set in advance from the viewpoint of improving the certainty of execution of ignition. What value is appropriate can be derived, for example, by prior experimentation and / or simulation. The second target value is set, for example, so that the actual temperature or heat amount follows the temperature or heat amount command value input from the outside.

  The controller 100 may be configured to keep the opening of the fuel flow control valve 34 at a predetermined upper limit value or less in the first control.

  The second target value may be a fuel flow rate required to make the air-fuel ratio coincide with the third target value. The air-fuel ratio is the ratio of the mass of air (the mass of air supplied from the air supply system 40 to the burner 21) to the mass of fuel (mass of fuel supplied from the fuel supply system 30 to the burner 21). The third target value is a set value of the air-fuel ratio corresponding to the combustion load of the industrial furnace, and is appropriately set from the viewpoints of suppressing incomplete combustion of fuel and suppressing generation of carbon dioxide.

  When the second target value is set based on the air-fuel ratio, the predetermined upper limit value is the amount of air supplied when the plurality of pre-burner valves 39 are sequentially opened to sequentially ignite the plurality of burners 21 (the air supply system 40 has It may be a second target value corresponding to the mass of air supplied to the burner 21). The amount of air supplied when the burners 21 are sequentially ignited is set to a minimum value, for example, within a range that does not hinder the performance of ignition.

  For example, the controller 100 includes a first control unit 111, a second control unit 112, a row selection unit 113, and a control output unit 114 as functional modules.

  The first control unit 111 sets the opening command value (hereinafter referred to as “first”) of the fuel flow adjustment valve 34 so that the fuel pressure between the plurality of burners 21 and the fuel flow adjustment valve 34 follows the first target value. "Opening command value") is derived and output. Moreover, the 1st control part 111 derives | leads-out and outputs the opening degree command value of the air flow control valve 45 so that the flow volume of air may track a 4th target value. Further, the first control unit 111 outputs an opening command to the fuel cutoff valve 35 corresponding to the burner 21 to be ignited. The fourth target value is a constant value. For example, when the fuel pressure matches the first target value, the fourth target value is set so that the air-fuel ratio becomes an optimal value for ignition.

  The second control unit 112 opens an opening command value (hereinafter referred to as “second opening command value”) of the fuel flow control valve 34 so that the flow rate of the fuel passing through the zone-specific fuel mains 33 follows the second target value. Is derived and output. Further, the second control unit 112 derives and outputs the opening command value of the air flow control valve 45 so that the flow rate of air follows the fifth target value. The second target value and the fifth target value are set so that the actual temperature or heat amount follows the temperature or heat amount command value input from the outside while keeping the air-fuel ratio in the vicinity of the third target value.

  The low select unit 113 compares the first opening command value derived by the first control unit 111 with a predetermined upper limit value, and outputs the lower one. As an example, the low selection unit 113 uses the second opening command value derived by the second control unit 112 as a predetermined upper limit value.

  The control output unit 114 sets the control mode to the first control or the second control. For example, the control output unit 114 sets the control mode to the first control in accordance with the ignition of the pilot burner 23. The control output unit 114 may be configured to set the execution target control mode to the first control in response to the main burner 22 misfiring without the pilot burner 23 misfiring.

  Further, the control output unit 114 may be configured to set the execution target control mode to the second control in response to an instruction input by the operator. In this case, the industrial furnace system 1 may further include a changeover switch 200 for enabling an operator to input a control mode instruction. The changeover switch 200 may be a hardware switch such as a toggle switch or a push button switch, or may be a software switch drawn on the touch panel.

  When the control mode is the first control, the control output unit 114 outputs the command value from the first control unit 111 to the fuel flow control valve 34, the fuel cutoff valve 35, and the air flow control valve 45. However, when the low selection unit 113 selects the second opening command value, the control output unit 114 receives the second opening command value from the second control unit 112 instead of the first opening command value from the first control unit 111. The second opening command value is output to the fuel flow control valve 34.

  When the control mode is the second control, the control output unit 114 outputs the command value from the second control unit 112 to the fuel flow adjustment valve 34 and the air flow adjustment valve 45.

  FIG. 3 is a block diagram illustrating a hardware configuration of the controller 100. As illustrated in FIG. 3, the controller 100 includes a circuit 120, and the circuit 120 includes one or more processors 121, a memory 122, a storage 123, and an input / output port 124.

  The input / output port 124 receives electric signals from the fuel flow sensor 36, the fuel pressure sensor 37, the air flow sensor 46, the fuel flow control valve 34, the fuel cutoff valve 35, the air flow control valve 45, and the changeover switch 200. Output. The storage 123 records a program for configuring each functional module of the controller 100. The storage 123 may be anything that can be read by a computer. Specific examples include a hard disk, a nonvolatile semiconductor memory, a magnetic disk, and an optical disk. The memory 122 temporarily stores the program loaded from the storage 123, the calculation result of the processor 121, and the like. The processor 121 configures each functional module described above by executing a program in cooperation with the memory 122.

  Note that the hardware configuration of the controller 100 is not necessarily limited to the configuration of each functional module by a program. For example, each functional module of the controller 100 may be configured by a dedicated logic circuit or an ASIC (Application Specific Integrated Circuit) in which the logic modules are integrated.

<Operation method of industrial furnace>
Then, an example of the operating method of an industrial furnace is shown. In this operation method, the opening degree of the fuel flow control valve 34 is controlled so that the industrial furnace 10 is operated and the pressure of the fuel between the burner 21 and the fuel flow control valve 34 follows the first target value. While performing one control, the plurality of pre-burner valves 39 are sequentially opened to sequentially ignite the plurality of burners 21, and after ignition in the plurality of burners 21 is completed, Performing a second control for controlling the opening of the fuel flow control valve 34 so as to cause the flow rate to follow the second target value.

  Hereinafter, the procedure until the plurality of burners 21 are ignited and the procedure after the plurality of burners 21 are ignited will be exemplified in detail.

(Procedure until a plurality of burners 21 are ignited)
FIG. 4 is a flowchart showing a control procedure executed by the controller 100 until the plurality of burners 21 are ignited. As shown in FIG. 4, the controller 100 first executes step S01. In step S01, the control output unit 114 checks whether or not the ignition of the pilot burner 23 is detected by the frame detector 24 for the pilot burner 23. The control output unit 114 repeats step S01 until the ignition of the pilot burner 23 is detected by the frame detector 24.

  When the ignition of the pilot burner 23 is detected by the frame detector 24, the controller 100 executes step S02. In step S02, the control output unit 114 sets the control mode to the first control. As illustrated in step S02, the operating method of the industrial furnace 10 may further include setting the execution target control mode to the first control in response to the pilot burner 23 being ignited.

  Next, the controller 100 executes step S03. In step S03, the first control unit 111 derives and outputs initial opening command values for the fuel flow control valve 34 and the air flow control valve 45, and controls and outputs the opening command value from the first control unit 111. The unit 114 outputs the fuel flow control valve 34 and the air flow control valve 45. The initial opening command value of the fuel flow control valve 34 is set so that the fuel pressure is close to the first target value, for example, when the first pre-burner valve 39 is opened. The initial opening command value of the air flow control valve 45 is set, for example, so that the flow rate of air follows the fourth target value.

  Next, the controller 100 executes step S04. In step S <b> 04, the first control unit 111 outputs an opening command for the fuel cutoff valve 35, and the control output unit 114 outputs the opening command from the first control unit 111 to the fuel cutoff valve 35. As a result, the burner 21 can be ignited. In this state, the operator starts to sequentially ignite the plurality of burners 21 by sequentially opening the plurality of pre-burner valves 39. When the operator opens the pre-burner valve 39, a mixed gas of fuel and air is supplied to the burner 21 corresponding to the pre-burner valve 39, and the mixed gas is ignited by the flame of the pilot burner 23.

  Next, the controller 100 executes step S05. In step S <b> 05, the first control unit 111 acquires the detection result of the fuel pressure between the plurality of burners 21 and the fuel flow control valve 34 from the fuel pressure sensor 37.

  Next, the controller 100 performs step S06. In step S06, the first controller 111 sets the first opening command value of the fuel flow adjustment valve 34 so that the fuel pressure between the plurality of burners 21 and the fuel flow adjustment valve 34 follows the first target value. Is calculated.

  Next, the controller 100 executes step S07. In step S <b> 07, the second control unit 112 acquires the detection result of the air flow rate in the zone-specific air main pipe 44 from the air flow rate sensor 46.

  Next, the controller 100 executes step S08. In step S08, the second control unit 112 calculates the fuel flow rate necessary for matching the air-fuel ratio to the third target value as the second target value, and causes the fuel flow rate to follow the second target value. A second opening command value of the fuel flow control valve 34 is calculated.

  Next, the controller 100 performs step S09. In step S09, the control output unit 114 checks whether or not the first opening command value is equal to or less than the second opening command value. If it is determined in step S09 that the first opening command value is equal to or smaller than the second opening command value, the controller 100 executes step S10. In step S <b> 10, the control output unit 114 outputs the first opening command value to the fuel flow control valve 34.

  When it is determined in step S09 that the first opening command value exceeds the second opening command value, the controller 100 executes step S11 instead of step S10. In step S <b> 11, the control output unit 114 outputs the second opening command value to the fuel flow control valve 34.

  As exemplified in steps S07 to S11, in the first control, the opening degree of the fuel flow control valve 34 may be kept below a predetermined upper limit value. In addition, when the second target value is the fuel flow rate required to make the air-fuel ratio coincide with the third target value, the predetermined upper limit value is that the plurality of burners 21 are sequentially opened by sequentially opening the plurality of pre-burner valves 39. The second target value corresponding to the supply amount of air when sequentially igniting.

  Next, the controller 100 performs step S12. In step S <b> 12, the control output unit 114 determines whether or not a control mode switching instruction is input to the changeover switch 200.

  If it is determined in step S12 that the control mode switching instruction has not been input, the controller 100 returns the process to step S05. Thus, the first control is continued until a control mode switching instruction is input.

  If it is determined in step S12 that a control mode switching instruction has been input, the controller 100 executes step S13. In step S13, the control output unit 114 switches the control mode to the second control. This completes the procedure until the plurality of burners 21 are ignited.

(Procedure after a plurality of burners 21 are ignited)
FIG. 5 is a flowchart showing a control procedure executed by the controller 100 after the plurality of burners 21 are ignited. As shown in FIG. 5, the controller 100 first executes step S21. In step S <b> 21, the second control unit 112 calculates the opening command values of the fuel flow control valve 34 and the fuel cutoff valve 35 by cross limit calculation.

  Specifically, the second control unit 112 maintains the air-fuel ratio in the vicinity of the third target value, and causes the second target value and the heat amount to follow the temperature or the heat amount command value input from the outside. Set the fifth target value. Thereafter, the second control unit 112 derives the opening command value of the fuel flow control valve 34 so that the flow rate of the fuel passing through the zone-specific fuel mains 33 follows the second target value, and the air flow rate is changed to the first flow rate. The opening command value of the air flow control valve 45 is derived so as to follow the five target values, and these are output.

  Next, the controller 100 performs step S22. In step S <b> 22, the control output unit 114 outputs the command value from the second control unit 112 to the fuel flow adjustment valve 34 and the air flow adjustment valve 45.

  Next, the controller 100 performs step S23. In step S23, the control output unit 114 confirms whether or not misfire of the main burner 22 is detected by the frame detector 24 for the main burner 22. The control output unit 114 may determine whether or not the main burner 22 has misfired based on whether or not the operator has made an operation to misfire the main burner 22. Examples of the operation for making the main burner 22 misfire include an operation for closing the fuel cutoff valve 35 or an operation for closing the pre-burner valve 39. These operations can be obtained from a user interface for remotely operating the fuel cutoff valve 35 or the pre-burner valve 39, for example. It is also possible to arrange sensors on the fuel cutoff valve 35 and the pre-burner valve 39 and to detect operations on the fuel cutoff valve 35 and the pre-burner valve 39 with the sensors.

  If it is determined in step S23 that the main burner 22 has not misfired, the controller 100 returns the process to step S21. Thereby, the second control is repeated until a misfire of the main burner 22 is detected.

  If it is determined in step S23 that the main burner 22 has misfired, the controller 100 executes step S24. In step S24, the control output unit 114 checks whether or not the pilot burner 23 has misfired.

  If it is determined in step S24 that the pilot burner 23 has not misfired, the controller 100 ends the process after executing step S25. In step S25, the control output unit 114 switches the control mode to the first control, and restarts the control procedure of the first control from step S03.

  If it is determined in step S24 that the pilot burner 23 has misfired, the controller 100 ends the process without executing step S25. Thus, the procedure after the plurality of burners 21 are ignited is completed.

<Effect of this embodiment>
As described above, the operating method of the industrial furnace according to the present embodiment includes a plurality of burners 21, a zone-specific fuel main pipe 33 for sending fuel, and a zone-specific fuel main pipe 33 that branches into a plurality of zones. A plurality of fuel branch pipes 38 respectively connected to the burner 21, a fuel flow control valve 34 for adjusting the opening degree of the fuel flow path provided in each zone fuel main pipe 33, and a plurality of fuel branch pipes 38, respectively. An industrial furnace 10 that is provided and has a plurality of pre-burner valves 39 that switch between a state in which a fuel flow path is shut off and a state in which the fuel flow path is opened is an operation target, and between the burner 21 and the fuel flow control valve 34 While performing the first control for controlling the opening of the fuel flow control valve 34 so that the fuel pressure follows the first target value, the plurality of pre-burner valves 39 are sequentially opened to sequentially ignite the plurality of burners 21. And that multiple After the ignition in the corner 21 is completed, the second control is executed to control the opening of the fuel flow control valve 34 so that the flow rate of the fuel passing through the zone-specific fuel main pipe 33 follows the second target value. And including.

  According to this operation method, after the ignition in each burner 21 is completed, the opening of the fuel flow control valve 34 is controlled so that the flow rate of the fuel follows the second target value. Each burner 21 can be brought into a desired combustion state by adjustment. On the other hand, during the ignition of each burner 21, the opening degree of the fuel flow adjustment valve 34 is controlled so that the fuel pressure between the burner 21 and the fuel flow adjustment valve 34 follows the first target value. . Since the response delay of the pressure according to the control of the opening degree of the fuel flow control valve 34 is smaller than the response delay of the flow rate, the fuel pressure between the burner 21 and the fuel flow control valve 34 is reduced by the pre-burner valve 39. After decreasing according to the opening, it is quickly returned to the vicinity of the first target value. When the pre-burner valve 39 is sequentially opened while the fuel pressure between the burner 21 and the fuel flow control valve 34 is maintained in the vicinity of the first target value, the amount of fuel supplied increases accordingly. For this reason, the control of causing the fuel pressure to follow the first target value increases the opening of the fuel flow control valve 34 in accordance with the increase in the number of burned burners 21, and the total flow rate of fuel (the fuel for each zone). Increasing the flow rate of fuel through the main pipe 33 is automatically performed. Further, increasing the opening degree of the fuel flow control valve 34 as the number of burned burners 21 increases is executed each time one burner 21 is ignited, so that the total fuel flow rate is adjusted. Is executed more finely.

  FIG. 6 is a graph showing changes in the fuel pressure, the fuel flow rate, and the fuel flow control valve opening target value when the above-described operation method is adopted. The horizontal axis of the graph indicates elapsed time, and the vertical axis indicates the magnitude of each value. The first control is executed in the period T1, and the second control is executed in the period T2. Ignition of the plurality of burners 21 is performed in the first half period T3 of the period T1. The fuel pressure D1 drops sharply at the beginning of the period T3. This is because the outflow of fuel is started by opening the first pre-burner valve 39. Due to the first control, the drop in the pressure D1 stops near the pressure target value D2. Thereafter, the second and subsequent burner front valves 39 are sequentially opened, and the second and subsequent burners 21 are sequentially ignited, but the pressure D1 is maintained in the vicinity of the pressure target value D2 without largely fluctuating. . Even if the number of opened pre-burner valves 39 increases, the opening command value D4 gradually increases in order to keep the pressure D1 close to the pressure target value D2. Accordingly, the fuel flow rate D3 also gradually increases.

  As described above, according to the operation method described above, as the number of burned burners 21 increases, the opening degree of the fuel flow control valve 34 is increased and the total flow rate of the fuel is automatically increased. The adjustment of the total flow rate of the fuel is executed finely. Accordingly, the ignition of the burner 21 can be more reliably performed with a simple operation.

  In the first control, the opening degree of the fuel flow control valve 34 may be kept below a predetermined upper limit value. In this case, since the fuel flow control valve 34 is prevented from opening excessively in the first control, an overshoot of the fuel pressure with respect to the first target value is suppressed. Further, even when an abnormality occurs in the fuel pressure detection system, the fuel flow rate can be maintained within an appropriate range. Therefore, the ignition of the burner 21 can be performed more reliably.

  The second target value is a fuel flow rate required to make the air-fuel ratio coincide with the third target value. The predetermined upper limit value sequentially opens the plurality of pre-burner valves 39 and sequentially ignites the plurality of burners 21. The second target value corresponding to the supply amount of air at that time may be used. In this case, the predetermined upper limit value is set so that the air-fuel ratio in the first control does not fall below the air-fuel ratio in the second control. For this reason, the fluctuation range of the opening degree of the fuel flow control valve 34 in the first control is kept in a range more suitable for the combustion of the burner 21. Therefore, the ignition of the burner 21 can be performed more reliably.

  The controller 100 controls an industrial furnace 10 including a main burner 22 and a pilot burner 23 for burning fuel in the main burner 22, and each of the plurality of burners 21 is controlled. Accordingly, it may be configured to further execute the control mode to be executed as the first control. The pilot burner 23 is ignited when the industrial furnace 10 is started. For this reason, the first control can be executed more reliably when the plurality of burners 21 are ignited by setting the control mode to be executed as the first control in response to the ignition of the pilot burner 23. Therefore, the ignition of the burner 21 can be performed more reliably.

  The controller 100 may be configured to set the execution target control mode to the first control in response to the main burner 22 misfiring without the pilot burner 23 misfiring. When the main burner 22 misfires without causing the pilot burner 23 to misfire, it is assumed that the main burner 22 is subsequently re-ignited. For this reason, reigniting the main burner 22 more reliably is performed by setting the control mode to be executed as the first control in accordance with the misfire of the main burner 22 without causing the pilot burner 23 to misfire. Can do.

  Although the embodiment has been described above, the present invention is not necessarily limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention. The structure for heating the inside of the furnace body 11 is not necessarily divided into a plurality of heating systems 20 (zones), and all the burners 21 may be integrated into a single zone. The application object of the present invention is not limited to an annealing furnace, but can be applied to any industrial furnace that requires an operation of sequentially igniting a plurality of burners.

  DESCRIPTION OF SYMBOLS 1 ... Industrial furnace system, 10 ... Industrial furnace, 100 ... Controller, 33 ... Fuel main pipe (first pipe line) according to zone, 34 ... Fuel flow control valve (first valve), 38 ... Fuel branch pipe (second pipe) Road), 39 ... Burner front valve (second valve)

Claims (9)

With multiple burners,
A first conduit for directing fuel;
A plurality of second pipes branched from the first pipe and respectively connected to the plurality of burners;
A first valve provided in the first pipe for adjusting an opening of the fuel flow path;
A plurality of second valves that are provided in each of the plurality of second pipelines and switch between a state in which the flow path of the fuel is shut off and a state in which the fuel is opened are intended for operation.
An opening command value of the first valve is calculated so that the fuel pressure between the burner and the first valve follows a first target value, and the opening command value is output to the first valve. Performing the first control to sequentially open the plurality of second valves to sequentially ignite the plurality of burners;
After the ignition in the plurality of burners is completed, the opening command value of the first valve is calculated so that the flow rate of the fuel passing through the first pipeline follows the second target value, and the opening command Executing a second control to output a value to the first valve .   The operating method for an industrial furnace according to claim 1, wherein in the first control, the opening degree of the first valve is kept below a predetermined upper limit value. The second target value is a flow rate of the fuel necessary to make the air-fuel ratio coincide with the third target value,
The industrial furnace according to claim 2, wherein the predetermined upper limit value is the second target value corresponding to an air supply amount when the plurality of second valves are sequentially opened to sequentially ignite the plurality of burners. how to drive. With multiple burners,
A first conduit for directing fuel;
A plurality of second pipes branched from the first pipe and respectively connected to the plurality of burners;
A first valve provided in the first pipe for adjusting an opening of the fuel flow path;
A plurality of second valves that are provided in each of the plurality of second pipelines and switch between a state in which the flow path of the fuel is shut off and a state in which the fuel is opened are controlled by an industrial furnace,
When the plurality of second conduits are sequentially opened and the plurality of burners are sequentially ignited, the fuel pressure between the burner and the first valve is made to follow a first target value. A first control for calculating an opening command value of the first valve and outputting the opening command value to the first valve ;
After the ignition in the plurality of burners is completed, the opening command value of the first valve is calculated so that the flow rate of the fuel passing through the first pipeline follows the second target value, and the opening command An industrial furnace controller configured to perform a second control to output a value to the first valve .   The controller of the industrial furnace of Claim 4 comprised so that the opening degree of said 1st valve may be kept below a predetermined | prescribed upper limit value in said 1st control. The second target value is a flow rate of the fuel necessary to make the air-fuel ratio coincide with the third target value,
The industrial furnace according to claim 5, wherein the predetermined upper limit value is the second target value corresponding to an air supply amount when the plurality of second valves are sequentially opened to sequentially ignite the plurality of burners. controller. Each of the plurality of burners is controlled by the industrial furnace including a main burner and a pilot burner for burning the fuel in the main burner,
The industrial furnace according to any one of claims 4 to 6, further configured to further execute the first control as a control mode to be executed in response to ignition of the pilot burner. controller.   The controller of the industrial furnace of Claim 7 comprised so that the control mode of the said execution object may be said 1st control according to the said main burner misfiring without the misfiring of the said pilot burner. With multiple burners,
A first conduit for directing fuel;
A plurality of second pipes branched from the first pipe and respectively connected to the plurality of burners;
A first valve provided in the first pipe for adjusting an opening of the fuel flow path;
An industrial furnace having a plurality of second valves that are respectively provided in the plurality of second pipes and switch between a state in which a flow path of fuel is blocked and a state in which the fuel is opened;
A controller for controlling the industrial furnace,
The controller is
When the plurality of second conduits are sequentially opened and the plurality of burners are sequentially ignited, the fuel pressure between the burner and the first valve is made to follow a first target value. A first control for calculating an opening command value of the first valve and outputting the opening command value to the first valve ;
After the ignition in the plurality of burners is completed, the opening command value of the first valve is calculated so that the flow rate of the fuel passing through the first pipeline follows the second target value, and the opening command value An industrial furnace system configured to execute a second control for outputting to the first valve .

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