JP6323286B2 - Exhaust heat recovery equipment for heating furnace and exhaust heat recovery method for heating furnace - Google Patents

Description

  The present invention relates to an exhaust heat recovery facility for a heating furnace and an exhaust heat recovery method for the heating furnace.

  A heating furnace that heats a steel material before hot rolling includes a burner that burns fuel to generate a high-temperature combustion gas, and a discharge duct that discharges the combustion gas. The combustion exhaust gas discharged from the exhaust duct is released from the chimney to the atmosphere, but before that, the heat in the combustion exhaust gas is recovered in the form of steam by a heat recovery boiler.

  In Patent Document 1, a waste heat boiler 1 disposed in a waste gas passage from the heating furnace 2, a bypass passage 5 that bypasses the main passage 3 passing through the waste heat boiler 1, a main passage 3 and a bypass passage 5 are provided. An apparatus including an exhauster 6 that discharges flowing waste gas from a chimney is disclosed.

  Patent Document 2 describes a technique for performing heat recovery of combustion exhaust gas using a single exhaust gas boiler with respect to combustion exhaust gas discharged from a plurality of heating furnaces. This Patent Document 2 describes a method for controlling the gas flow rate to an exhaust gas boiler in equipment having an exhaust gas boiler having a lower ventilation capacity than the maximum exhaust gas amount discharged from a plurality of heating furnaces. Specifically, a flue including an exhaust gas boiler and a bypass flue that bypasses the exhaust gas boiler are provided in an exhaust gas treatment system that exhausts combustion exhaust gas discharged from a heating furnace from a chimney, and the flue includes an exhaust gas boiler. And the bypass flue are provided with flow control valves, respectively, and the exhaust gas flow rate to the exhaust gas boiler is controlled by adjusting the valve opening degree of each flow control valve. In Patent Document 2, the flow rate of the combustion exhaust gas flowing through the flue of the exhaust gas boiler is adjusted by the flow rate adjustment valve based on the pressure value of the collecting pipe installed immediately after the heating furnace, The flow rate adjustment on the bypass flue side is performed based on the amount of steam generated in the exhaust gas boiler. Thus, in patent document 2, the flow regulating valve is provided in both the flue including the exhaust gas boiler and the bypass flue, and the flow rate of the combustion exhaust gas is controlled by the valve opening degree.

  In the apparatus described in Patent Document 1, the entire amount of waste gas discharged from the heating furnace 2 is discharged from the chimney by the exhaust fan 6. If the exhaust capacity of the exhaust fan 6 is low with respect to the flow rate of the waste gas discharged from the heating furnace 2, the furnace pressure in the heating furnace 2 may increase. When the pressure in the furnace rises, there is a risk that a flame blows out from the charging inlet or the extraction port of the heating furnace 2. Therefore, the exhaust capacity of the exhaust fan 6 is required to be approximately the same as the waste gas flow rate discharged from the heating furnace 2.

  However, in the apparatus described in Patent Document 1, the flow rate of waste gas may increase to a flow rate that exceeds the initial assumption due to leakage of air due to deterioration of the heating furnace and the waste gas passage. If the flow rate of the waste gas increases and exceeds the exhaust capacity of the exhaust fan 6, there is a possibility that the furnace pressure of the heating furnace increases.

  Next, in the heat recovery method for combustion exhaust gas disclosed in Patent Document 2, when the chimney draft changes depending on the outside air temperature, the flow rate of the combustion exhaust gas on the bypass flue side is affected by the chimney draft. However, the control method described in Patent Document 2 does not consider the influence of the chimney draft. Therefore, in Patent Document 2, if the chimney draft fluctuates, the flow rate of the combustion exhaust gas on the bypass flue side changes, and this flow rate fluctuation of the combustion exhaust gas may affect the flow rate of the combustion exhaust gas on the exhaust gas boiler side. . When the flow rate of the combustion exhaust gas on the exhaust gas boiler side fluctuates, the amount of steam generated in the exhaust gas boiler may decrease. In addition, if the flue gas flow rate fluctuates in the bypass flue, the fluctuation affects the furnace pressure of the heating furnace, and if the furnace pressure increases, flames may blow out from the inlet or extraction port of the heating furnace. was there.

JP-A-5-231783 Japanese Patent Publication No. 7-99242

  The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a waste heat recovery facility for a heating furnace and a waste heat recovery method for a heating furnace capable of appropriately controlling the flow rate of combustion exhaust gas drawn into a heat recovery boiler. To do.

[1] An exhaust gas flue for guiding the combustion exhaust gas discharged from the recuperators of the exhaust parts of the plurality of heating furnaces to the chimney,
A heat recovery boiler installed in the middle of the flue gas flue and having a processing capacity smaller than the maximum amount of combustion exhaust gas generated per hour;
A bypass flue that branches from the middle of the flue gas flue and leads the combustion exhaust gas bypassing the heat recovery boiler to the chimney;
An induction fan installed in the flue gas flue downstream of the heat recovery boiler and having a maximum induction flow rate smaller than the maximum generation amount per hour of the combustion exhaust gas;
An exhaust gas flow rate calculation unit for obtaining a calculated exhaust gas flow rate from the fuel consumption of the heating furnace and the oxygen concentration in the combustion exhaust gas;
When the calculated exhaust gas flow rate input from the exhaust gas flow rate calculation unit is less than or equal to the maximum induced flow rate of the induction fan, the induced exhaust gas flow rate is controlled to be the calculated exhaust gas flow rate, and the calculated exhaust gas flow rate is When the maximum attraction flow rate is exceeded, a control unit that controls the attraction flow rate of the attraction fan to the maximum attraction flow rate,
An exhaust heat recovery facility for a heating furnace, characterized by comprising:
[2] A pressure gauge is further provided in the exhaust gas flue upstream of the heat recovery boiler,
When the calculated exhaust gas flow rate is less than or equal to the maximum attraction flow rate, the control unit is based on the relationship between the flow rate of the combustion exhaust gas passing through the heat recovery boiler and the pressure of the combustion exhaust gas immediately before the heat recovery boiler that are obtained in advance. The pressure target value of the combustion exhaust gas immediately before the heat recovery boiler is set from the calculated exhaust gas flow rate, and the induction flow rate of the induction fan is controlled so that the measured value by the pressure gauge becomes the pressure target value. The exhaust heat recovery facility for a heating furnace according to [1].
[3] When the calculated exhaust gas flow rate is equal to or less than the maximum induced flow rate, the control unit calculates the induction fan from the calculated exhaust gas flow rate based on the relationship between the calculated exhaust gas flow rate obtained in advance and the rotation speed of the induction fan. The exhaust heat recovery facility for a heating furnace according to [1], wherein the number of rotations is determined.
[4] A flue switching unit is further provided that sets the exhaust path of the combustion exhaust gas to both the exhaust flue and the bypass flue for each heating furnace, or sets only the exhaust flue. The exhaust heat recovery facility for a heating furnace according to any one of [1] to [3], wherein
[5] An exhaust heat recovery method for a heating furnace using the exhaust heat recovery facility according to [1],
In the exhaust gas flow rate calculation unit, the calculated exhaust gas flow rate is calculated from the fuel consumption of the heating furnace and the oxygen concentration in the combustion exhaust gas, and the calculated exhaust gas flow rate is output to the control unit,
In the control unit, when the calculated exhaust gas flow rate is less than or equal to the maximum induced flow rate of the attracting fan, the induced flow rate of the attracting fan is set to the calculated exhaust gas flow rate,
The exhaust heat recovery method for a heating furnace, wherein when the calculated exhaust gas flow rate exceeds the maximum attractive flow rate of the induction fan, the induction flow rate of the induction fan is set as the maximum attractive flow rate.
[6] Using the exhaust heat recovery facility in which a pressure gauge is further provided in the exhaust gas flue upstream of the heat recovery boiler,
When the calculated exhaust gas flow rate is less than or equal to the maximum attraction flow rate, the calculated exhaust gas flow rate is based on the relationship between the flow rate of the combustion exhaust gas that passes through the heat recovery boiler determined in advance and the pressure of the combustion exhaust gas immediately before the heat recovery boiler. A pressure target value of the combustion exhaust gas immediately before the heat recovery boiler is set, and the induction fan is controlled so that a measured value by the pressure gauge becomes the pressure target value. [5] Waste heat recovery method for heating furnaces.
[7] When the calculated exhaust gas flow rate is equal to or less than the maximum induced flow rate, the rotational speed of the induction fan is determined from the calculated exhaust gas flow rate based on the relationship between the calculated exhaust gas flow rate obtained in advance and the rotational speed of the induction fan. A method for recovering exhaust heat from a heating furnace as described in [5].

  According to the exhaust heat recovery facility and exhaust heat recovery method of the heating furnace of the present invention, the induction fan is controlled based on the calculated exhaust gas flow rate obtained from the fuel consumption of the heating furnace and the oxygen concentration in the combustion exhaust gas. Even if the outside air flows in from the piping of the recuperator or the like and the apparent amount of exhaust gas increases, the induction fan can be accurately controlled by the calculated exhaust gas flow rate including this increase. If the calculated exhaust gas flow rate is less than or equal to the maximum induced flow rate of the induction fan, the induced flow rate of the induction fan is controlled to the calculated exhaust gas flow rate.If the calculated exhaust gas flow rate exceeds the maximum induced flow rate, the induced fan's induced flow rate is maximized. As the flow rate is controlled, the combustion exhaust gas discharged from the recuperator in the exhaust section of the heating furnace is introduced into the heat recovery boiler for heat recovery.If the calculated exhaust gas flow rate exceeds the maximum attraction flow rate, the remainder of the combustion exhaust gas is bypassed by smoke. It can be released from the road towards the chimney. Thus, in the present invention, the combustion exhaust gas can be appropriately distributed to the exhaust gas flue and the bypass flue according to the calculated exhaust gas flow rate. Thereby, the heat recovery boiler can be operated with high efficiency, and the amount of generated steam can be increased. In addition, since there is no means to adjust the flow rate of the combustion exhaust gas in the bypass flue, the combustion exhaust gas that cannot be treated by the heat recovery boiler flows from the exhaust flue to the bypass flue by the action of the chimney draft. It can be discharged from the chimney. At this time, even if the chimney draft fluctuates due to changes in the outside air temperature, the flow rate of the combustion exhaust gas passing through the heat recovery boiler is controlled based on the calculated exhaust gas flow rate. It does not affect the flow rate of the exhaust gas. Moreover, the furnace pressure of the heating furnace can be stabilized.

  Further, according to the exhaust heat recovery equipment and exhaust heat recovery method of the heating furnace of the present invention, when the calculated exhaust gas flow rate is less than or equal to the maximum induction flow rate, the flow rate of the combustion exhaust gas passing through the heat recovery boiler and the heat recovery boiler that are obtained in advance. Based on the relationship with the pressure of the immediately preceding combustion exhaust gas, the pressure target value of the combustion exhaust gas immediately before the heat recovery boiler is set from the calculated exhaust gas flow rate, and the induction fan is controlled so that the pressure gauge measurement value becomes the pressure target value. In accordance with the flow rate of the combustion exhaust gas discharged from the recuperator in the exhaust part of the heating furnace, the combustion exhaust gas can flow through the exhaust gas flue, and the backflow of the bypass flue can be prevented.

  Furthermore, according to the exhaust heat recovery facility and the exhaust heat recovery method of the heating furnace of the present invention, when the calculated exhaust gas flow rate is equal to or less than the maximum induced flow rate, based on the relationship between the calculated exhaust gas flow rate obtained in advance and the rotational speed of the induction fan. Because the rotational speed of the induction fan is determined from the calculated exhaust gas flow rate, the combustion exhaust gas can flow into the exhaust gas flue according to the flow rate of the combustion exhaust gas discharged from the recuperator in the exhaust part of the heating furnace, and the bypass flue Backflow can be prevented. In addition, since the flow rate control by the control unit is simplified, control responsiveness can be improved.

The schematic diagram explaining the problem in the waste heat recovery equipment of a heating furnace. The schematic diagram which shows the waste heat recovery equipment of the heating furnace of the 1st Embodiment of this invention. The graph explaining the waste heat recovery method of the heating furnace of the 1st Embodiment of this invention. The flowchart explaining the control flow in the waste heat recovery equipment of the heating furnace shown in FIG. The figure which shows the calculation formula which calculates | requires calculation exhaust gas flow volume in the control flow shown in FIG. (A) is a graph which shows the relationship between the flow volume of the combustion exhaust gas which passes a heat recovery boiler, and the pressure before a heat recovery boiler, (b) demonstrates operation | movement of waste heat recovery equipment using the graph of (a). To do. The graph which shows each time fluctuation | variation of the measured exhaust gas flow rate in the waste heat recovery equipment of the heating furnace shown in FIG. (A) is a schematic diagram which shows the operation state of the exhaust heat recovery equipment in the time slot | zone 2 of FIG. 3, (b) is a schematic diagram which shows the operation state of the exhaust heat recovery equipment in the time slot | zone 1 of FIG. The graph which shows the time fluctuation of the furnace pressure of a heating furnace. The graph which shows the relationship between the steam generation amount and heat equivalent of a heat recovery boiler. The schematic diagram which shows the waste heat recovery equipment of the heating furnace of the 2nd Embodiment of this invention. The flowchart explaining the control flow in the waste heat recovery equipment of the heating furnace shown in FIG. The graph which shows the relationship between a calculated exhaust gas flow rate and the rotation speed of an induction fan.

First, the problem of the exhaust heat recovery facility and the exhaust heat recovery method of combustion exhaust gas will be specifically described with reference to FIG.
The exhaust heat recovery facility 100 shown in FIG. 1 includes exhaust flue 2A, 2B, 2C that leads the combustion exhaust gas discharged from the recuperators 101E, 101F in the exhaust portions of the two heating furnaces 101A, 101B to the chimney 102, and exhaust gas smoke. Bypass flues 3A and 3B branched from the middle of the roads 2A and 2B, the flue switching unit 4, the heat recovery boiler 5 installed in the exhaust gas flue 2C, and the invitation to draw the combustion exhaust gas into the heat recovery boiler 5 Installed in the fan 6, the pressure gauge 10 for measuring the pressure of the combustion exhaust gas flowing through the exhaust gas flue 2C, the controller 10a for controlling the induction fan 6 based on the measured value of the pressure gauge 10, and the exhaust gas flue 2A, 2B Gas concentration meters 14A and 14B and gas concentration meters 14C and 14D installed in the bypass flues 3A and 3B are provided. Preliminary flues 13A and 13B for discharging combustion exhaust gas from different systems discharged from the heating furnaces 101A and 101B are connected to the bypass flues 3A and 3B.

  Each of the heating furnaces 101A and 101B is a heating furnace that heats a steel material that is subjected to hot rolling, and includes various combustion burners. A part of the combustion exhaust gas generated by burning the fuel with the combustion burner is discharged from the recuperators 101E and 101F in the exhaust part of the heating furnace to the exhaust gas flue 2A and 2B, and another part is the preliminary flue 13A, It is comprised so that it may be sent to bypass flue 3A, 3B via 13B. Specifically, the heating furnaces 101A and 101B are provided with a normal burner and a regeneration burner as combustion burners. The combustion exhaust gas generated by the combustion of the normal burner and the regenerative burner and discharged from the recuperators 101E and 101F in the exhaust portions of the heating furnaces 101A and 101B flows into the exhaust flue 2A and 2B. Moreover, the combustion exhaust gas collect | recovered by the regeneration burner is sent to bypass flue 3A, 3B via preliminary | backup flue 13A, 13B.

  Furnace pressure control valves 101G and 101H are provided in the exhaust gas flues 2A and 2B. Moreover, induction furnace fans 9A and 9B are installed in the exhaust gas flues 2A and 2B on the downstream side of the furnace pressure control valves 101G and 101H. The combustion exhaust gas discharged from the exhaust parts of the heating furnaces 101A and 101B flows toward the downstream side of the exhaust gas flue 2A and 2B by the induction fans 9A and 9B for the heating furnace.

  The heating furnaces 101A and 101B are provided with controllers 101C and 101D for controlling the furnace pressure, respectively. To the controllers 101C and 101D, furnace pressure control valves 101G and 101H and induction furnace fans 9A and 9B are connected. The controllers 101C and 101D are configured to control the furnace pressure in the heating furnaces 101A and 101B by controlling the furnace pressure control valves 101G and 101H and the induction furnace fans 9A and 9B.

  Recuperators 101E and 101F are provided in the exhaust portions of the heating furnaces 101A and 101B. The recuperators 101E and 101F are configured to preheat the air supplied to the normal burners of the heating furnaces 101A and 101B using the heat of the combustion exhaust gas discharged from the exhaust parts of the heating furnaces 101A and 101B.

  The exhaust gas flues 2A and 2B and the bypass flues 3A and 3B are branched downstream of the induction furnace fans 9A and 9B. The exhaust gas flues 2A and 2B on the downstream side of the branch point with the bypass flues 3A and 3B are provided with shutoff valves 4A and 4B as the flue switching unit 4. These shut-off valves 4A and 4B are all in an “open” state. Further, the exhaust gas flues 2A and 2B merge on the downstream side of the shutoff valves 4A and 4B to form the exhaust gas flues 2C.

  On the other hand, the bypass flues 3A and 3B are also provided with shutoff valves 4C and 4D as the flue switching unit 4. These shutoff valves 4C and 4D are “closed”. Exhaust gas flue 2A, 2B and bypass flue 3A, 3B are interrupted | blocked by cutoff valve 4C, 4D (flue switching part 4).

  The gas concentration meters 14A and 14B are installed in the exhaust gas flues 2A and 2B on the downstream side of the flue switching unit 4, and can measure the NOx concentration and the oxygen concentration in the combustion exhaust gas. Further, the gas concentration meters 14C and 14D are installed in the bypass flue 3A and 3B on the downstream side of the joining point of the bypass flue 3A and 3B and the auxiliary flue 13A and 13B, and the NOx concentration in the combustion exhaust gas The oxygen concentration can be measured. These gas concentration meters 14A to 14D monitor the NOx concentration in the combustion exhaust gas emitted from the chimney 102.

  The heat recovery boiler 5 is installed in the exhaust gas flue 2C and generates steam using the heat of the combustion exhaust gas. The steam generated by the heat recovery boiler 5 is used as a heat source or the like in other facilities of the steelworks.

  In the exhaust heat recovery facility 100 shown in FIG. 1, the combustion exhaust gas discharged from the recuperators 101 </ b> E and 101 </ b> F of the exhaust portions of the heating furnaces 101 </ b> A and 101 </ b> B passes through the exhaust gas flues 2 </ b> A, 2 </ b> B and 2 </ b> C After the heat is recovered, it is discharged from the chimney 102. Further, the combustion exhaust gas recovered by the regenerative burner of each heating furnace 101A, 101B passes through the preliminary flues 13A, 13B and the bypass flue 3A, 3B and is discharged from the chimney 12.

  By the way, since the flow rate of the combustion exhaust gas passing through the heat recovery boiler 5 varies depending on the operating state of the heating furnaces 101A and 101B, the induction flow rate of the induction fan 6 installed on the downstream side of the heat recovery boiler 5 is changed to the flow rate of the combustion exhaust gas. It is necessary to control accordingly. Therefore, in the exhaust heat recovery facility 100 shown in FIG. 1, the pressure of the combustion exhaust gas before flowing into the heat recovery boiler 5 is constantly monitored by the pressure gauge 10, and the induction fan 6 is controlled by the controller 10a so that this pressure becomes constant. The number of revolutions is controlled. Specifically, when the pressure measurement value of the pressure gauge 10 increases, the controller 10a increases the rotational speed of the induction fan 6 to increase the passage amount of the combustion exhaust gas to the heat recovery boiler 5. When the pressure measurement value of the pressure gauge 10 decreases, the controller 10a reduces the number of rotations of the induction fan 6 to reduce the passage amount of the combustion exhaust gas to the heat recovery boiler 5. Such control is based on the premise that the flow rate of the combustion exhaust gas is less than or equal to the maximum capacity of the induction fan 6.

  However, when the outside air enters the combustion exhaust gas path due to deterioration of the heating furnaces 101A, 101B, the recuperators 101E, 101F, etc., the apparent flow rate of the combustion exhaust gas flowing through the exhaust gas flue 2A-2C increases, which may exceed the initial assumption. is there. If the flow rate of the combustion exhaust gas increases and exceeds the capacity of the induction fan 6, there is a risk that the furnace pressure of the heating furnaces 101A and 101B will increase.

  Therefore, the present inventors calculate the flow rate of the combustion exhaust gas from the amount of fuel supplied to the heating furnace and the oxygen concentration of the combustion exhaust gas, not the control based on the pressure measurement value of the pressure gauge 10 installed in front of the heat recovery boiler 5. The induction fan 6 is controlled based on the calculated value. When the calculated value of the flow rate of the combustion exhaust gas exceeds the maximum capacity of the induction fan 6, the induction fan 6 is operated at the maximum capacity to perform heat recovery of the combustion exhaust gas in the heat recovery boiler 5 as much as possible. Combustion exhaust gas that cannot be exhausted from the bypass flues 3A and 3B to the chimney 102 using a chimney draft. On the other hand, when the calculated value of the flow rate of the combustion exhaust gas is less than or equal to the maximum induced flow rate of the induction fan 6, the induction flow rate of the induction fan 6 is controlled to correspond to the calculated value, and the combustion exhaust gas in the heat recovery boiler 5 as much as possible. It was decided to recover the heat. In this way, the present invention has been completed. Hereinafter, embodiments of the present invention will be described.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. Among the components of the exhaust heat recovery facility 1 shown in FIG. 2, the same components as those described in FIG.
The exhaust heat recovery facility 1 shown in FIG. 2 includes exhaust flue 2A, 2B, 2C that leads the combustion exhaust gas discharged from the recuperators 101E, 101F in the exhaust portions of the two heating furnaces 101A, 101B to the chimney 102, and the exhaust gas. Bypass flues 3A and 3B branched from the middle of the flues 2A and 2B, a heat recovery boiler 5 installed in the exhaust gas flue 2C, an induction fan 6 for drawing combustion exhaust gas into the heat recovery boiler 5, and each heating An exhaust gas flow rate calculation unit 8 that calculates a calculated exhaust gas flow rate for each of the furnaces 101A and 101B and a control unit 11 are provided.

  The exhaust gas flow rate calculation unit 8 includes flow rate calculation units 8A and 8B, gas concentration meters 8C to 8F connected to the flow rate calculation units 8A and 8B, and fuel consumption in each heating furnace 101A and 101B. And a fuel consumption monitoring unit (not shown) that outputs to 8B. The flow rate calculation units 8A and 8B and the fuel consumption monitoring unit are realized as functions of a central processing unit of a computer that controls the heating furnaces 101A and 101B. Each flow rate calculation unit 8A, 8B calculates the calculated exhaust gas flow rate and outputs it to the control unit 11.

  The control unit 11 includes a control calculation unit 11 </ b> A, a pressure gauge 11 </ b> B connected to the control calculation unit 11 </ b> A, and a flow meter 11 </ b> C installed on the downstream side of the heat recovery boiler 5.

  Each of the heating furnaces 101A and 101B is a heating furnace for heating a steel material to be subjected to hot rolling, and various combustion burners are attached thereto. A part of the combustion exhaust gas generated by burning the fuel with the combustion burner is discharged from the recuperator of the exhaust part of the heating furnace to the exhaust gas flue 2A, 2B, and another part is passed through the preliminary flue 13A, 13B. And is configured to be sent to the bypass flues 3A and 3B. Specifically, each of the heating furnaces 101A and 101B is provided with a normal burner as a combustion burner and a regenerative burner that performs alternating combustion. Of the combustion exhaust gas generated by the combustion of the normal burner and the regenerative burner, the combustion exhaust gas discharged from the recuperators 101E and 101F in the exhaust portions of the heating furnaces 101A and 101B flows into the exhaust gas flues 2A and 2B. Moreover, the combustion exhaust gas collect | recovered by the regeneration burner is sent to bypass flue 3A, 3B via preliminary | backup flue 13A, 13B.

  Furnace pressure control valves 101G and 101H are provided in the exhaust gas flues 2A and 2B. In addition, induction furnaces 9A and 9B for the heating furnace are provided in the exhaust gas flues 2A and 2B on the downstream side of the furnace pressure control valves 101G and 101H. The combustion furnace exhaust gas discharged from the recuperators 101E and 101F in the exhaust parts of the heating furnaces 101A and 101B is caused to flow downstream of the exhaust gas flues 2A and 2B by the induction furnaces 9A and 9B for the heating furnace.

  Furthermore, the heating furnaces 101A and 101B are provided with controllers 101C and 101D for controlling the furnace pressure, respectively. To the controllers 101C and 101D, furnace pressure control valves 101G and 101H and induction furnace fans 9A and 9B are connected. The controllers 101C and 101D are configured to control the furnace pressure in the heating furnaces 101A and 101B by controlling the furnace pressure control valves 101G and 101H and the induction furnace fans 9A and 9B.

  Recuperators 101E and 101F are provided in the exhaust portions of the heating furnaces 101A and 101B. The recuperators 101E and 101F are configured to preheat the air supplied to the normal burners of the heating furnaces 101A and 101B using the heat of the combustion exhaust gas discharged from the exhaust parts of the heating furnaces 101A and 101B.

  The exhaust gas flues 2A and 2B and the bypass flues 3A and 3B are branched downstream of the induction furnace fans 9A and 9B. A flue switching unit 4 is provided in each of the exhaust flue 2A, 2B and the bypass flue 3A, 3B downstream of the branch point with the bypass flue 3A, 3B.

  The flue switching unit 4 provided in the exhaust gas flue 2A, 2B is composed of shut-off valves 4A, 4B. The open / close states of these shut-off valves 4A and 4B are all "open". Further, the exhaust gas flues 2A and 2B merge on the downstream side of the shutoff valves 4A and 4B to form the exhaust gas flues 2C.

The flue switching unit 4 provided in the bypass flue 3A, 3B is composed of shutoff valves 4C, 4D. The shutoff valve 4C is “closed” and the shutoff valve 4D is “open”.
Due to the configuration of the flue switching unit 4 described above, the flue gas flue 2 </ b> A and the bypass flue 3 </ b> A are mutually blocked by the flue switching unit 4. Further, the flue gas flue 2B and the bypass flue 3B are connected to each other by the flue switching unit 4.

  The heat recovery boiler 5 is installed in the exhaust gas flue 2C and generates steam using the heat of the combustion exhaust gas. The steam generated by the heat recovery boiler 5 is used as a heat source or the like in other facilities of the steelworks. In the present embodiment, the heat recovery boiler 5 having a processing capacity smaller than the maximum amount of combustion exhaust gas discharged from the recuperators 101E and 101F in the exhaust portions of the heating furnaces 101A and 101B per hour is used. If the processing capacity of the heat recovery boiler 5 is larger than the maximum amount of combustion exhaust gas generated per hour, a low-temperature fluid may be drawn in, which may reduce the heat recovery rate. As the low-temperature fluid, for example, combustion exhaust gas flowing backward from the bypass flue 3B is assumed.

  Further, the induction fan 6 is installed in the exhaust gas flue 2 </ b> C on the downstream side of the heat recovery boiler 5. The induction fan 6 has a maximum induction flow rate (maximum capacity) smaller than the maximum generation amount of combustion exhaust gas per hour. If the maximum induction flow rate (maximum capacity) of the induction fan 6 is larger than the maximum amount of combustion exhaust gas generated per hour, a low-temperature fluid, for example, combustion exhaust gas flowing through the bypass flue 3B, may be drawn into the heat recovery boiler 5. There is a possibility that the heat recovery rate is lowered.

Next, the exhaust gas flow rate calculation unit 8 will be described in detail.
The gas concentration meters 8C and 8D provided in the exhaust gas flow rate calculation unit 8 are installed in the exhaust gas flue 2A and 2B on the downstream side of the flue switching unit 4, and the recuperators 101E in the exhaust parts of the heating furnaces 101A and 101B, The NOx concentration and oxygen concentration in the combustion exhaust gas discharged from 101F can be measured. The gas concentration meters 8E and 8F are installed in the bypass flue 3A and 3B on the downstream side of the joining point of the bypass flue 3A and 3B and the auxiliary flue 13A and 13B. The NOx concentration and oxygen concentration in the combustion exhaust gas recovered by the regenerative burner can be measured. The combustion exhaust gas emitted from the chimney 102 is monitored by these gas concentration meters 8C to 8F. Further, the oxygen concentration in the combustion exhaust gas measured by the gas concentration meters 8C to 8F is output to the flow rate calculation units 8A and 8B.

  The fuel consumption monitoring unit monitors the amount of fuel supplied to the normal burner and regenerative burner of the heating furnaces 101A and 101B, and causes the flow rate calculation units 8A and 8B to output this.

  Further, the flow rate calculation units 8A and 8B are based on the oxygen concentration in the combustion exhaust gas and the fuel supply amount of the heating furnaces 101A and 101B, and the combustion discharged from the recuperators 101E and 101F in the exhaust parts of the heating furnaces 101A and 101B. A calculated value of the exhaust gas flow rate (hereinafter referred to as a calculated exhaust gas flow rate) is calculated and output to the control unit 11.

Next, the control unit 11 will be described in detail.
The pressure gauge 11B provided in the control unit 11 is provided in the exhaust gas flue 2C upstream of the heat recovery boiler 5, and constantly measures the pressure of the combustion exhaust gas flowing through the exhaust gas flue 2C. Moreover, the pressure gauge 11B is connected to the control calculation part 11A, and can output the pressure measured by the pressure gauge 11B to the control calculation part 11A.
The flow meter 11 </ b> C is provided in the exhaust gas flue 2 </ b> C on the downstream side of the induction fan 6, and constantly measures the flow rate of the combustion exhaust gas that passes through the heat recovery boiler 5. Further, the flow meter 11C is connected to the control calculation unit 11A so that the flow rate measured by the flow meter 11C can be output to the control calculation unit 11A.

  The control calculation unit 11A controls the induction fan 6 based on the pressure of the combustion exhaust gas in the exhaust gas flue 2C upstream of the heat recovery boiler 5, the flow rate of the fuel exhaust gas passing through the heat recovery boiler 5, and the calculated exhaust gas flow rate of the combustion exhaust gas. By controlling, the flow rate of the combustion exhaust gas supplied to the heat recovery boiler 5 is adjusted. A specific adjustment procedure will be described later. The control calculation unit 11A is provided in a computer that controls the heating furnaces 101A and 101B and the exhaust heat recovery facility 1, and is realized as a function of a central processing unit of the computer.

Next, the exhaust heat recovery method for the heating furnace of the present embodiment will be described through the description of the operation of the exhaust heat recovery facility 1.
First, a steel material to be subjected to hot rolling is heated by a combustion burner provided in the heating furnaces 101A and 101B. The heating furnaces 101A and 101B are provided with a normal burner and a regenerative burner as combustion burners. The combustion exhaust gas is filled in the heating furnaces 101A and 101B by the combustion of the normal burner and the regenerative burner, and the steel material is heated by the heat of the combustion exhaust gas. Heated. Most of the combustion exhaust gas filled in the heating furnaces 101A and 101B is discharged from the exhaust parts of the heating furnaces 101A and 101B to the outside of the heating furnaces 101A and 101B, passes through the recuperators 101E and 101F, and the exhaust gas flue 2A and 2B. Flow into. Moreover, a part of combustion exhaust gas is collect | recovered by the regeneration burner, and flows into the bypass flue 3A, 3B through the preliminary | backup flue 13A, 13B.

  Further, by controlling the control valves 101G and 101H and the induction fans 9A and 9B for the heating furnace by the controllers 101C and 101D, the pressure in the furnaces of the heating furnaces 101A and 101B is controlled to be kept constant.

The combustion exhaust gas discharged from the heating furnace 101A (the recuperator 101E of the exhaust part) to the exhaust gas flue 2A is further sent to the downstream side by the induction furnace fan 9A and passes through the shutoff valve 4A of the flue switching part 4. And sent to the flue gas flue 2C. Since the shutoff valve 4C is closed, the combustion exhaust gas discharged to the exhaust gas flue 2A does not flow into the bypass flue 3A.
Further, the combustion exhaust gas discharged from the heating furnace 101B (the recuperator 101F of the exhaust part) to the exhaust gas flue 2B is further sent to the downstream side by the induction furnace 9B for the heating furnace, and the shutoff valve 4B of the flue switching part 4 is passed through. Passes and is sent to the flue gas flue 2C. Further, since the shutoff valve 4D is open, the combustion exhaust gas discharged to the exhaust gas flue 2B can flow into the bypass flue 3B. However, since no induction fan is installed in the bypass flue 3B, whether or not the combustion exhaust gas discharged into the exhaust flue 2B actually flows into the bypass flue 3B depends on the induction fan provided in the exhaust flue 2C. According to 6 driving conditions.

  The combustion exhaust gas merged in the exhaust gas flue 2C is further flowed downstream of the exhaust gas flue 2C by the induction fan 6, passes through the pressure gauge 11B, and is supplied to the heat recovery boiler 5. In the heat recovery boiler 5, heat exchange is performed between the combustion exhaust gas and water, and the water is heated to generate steam. The combustion exhaust gas from which sensible heat has been removed by heat exchange is further attracted by the induction fan 6 and travels through the exhaust gas flue 2C, and its flow rate is measured by the flow meter 11C, and then released from the chimney 102 to the atmosphere.

  On the other hand, the combustion exhaust gas flowing into the bypass flue 3B is released from the chimney 102 by the action of the chimney draft.

Next, referring to FIG. 3, the exhaust heat recovery method in the exhaust heat recovery facility 1 of the present embodiment shown in FIG. 2 will be described in comparison with the exhaust heat recovery facility 100 shown in FIG.
FIG. 3A shows the operation of the exhaust heat recovery facility 100 shown in FIG. As shown in FIG. 3A, the amount of combustion exhaust gas discharged from the recuperators 101E and 101F in the exhaust portions of the heating furnaces 101A and 101B varies with time depending on the operating state of the heating furnaces 101A and 101B. At this time, the induction fan 6 is controlled so as to make the pressure of the exhaust gas flue 2C in front of the heat recovery boiler constant. Here, as shown in the curve shown by the dotted line in FIG. 3A, if the amount of combustion exhaust gas is always below the maximum capacity of the induction fan, even the exhaust heat recovery equipment 100 shown in FIG. It is possible to recover the heat of the combustion exhaust gas while controlling the pressure in the furnace at a constant. However, as shown by the solid line in FIG. 3A, when a time zone in which the amount of combustion exhaust gas exceeds the maximum capacity of the induction fan occurs, in this time zone, the pressure of the exhaust gas flue 2C before the heat recovery boiler The pressure rises up to the heating furnaces 101A and 101B, and the furnace pressure in the heating furnaces 101A and 101B increases. The fluctuation factors of the amount of combustion exhaust gas in FIG. 3 (a) include the fluctuation of the exhaust gas amount according to the operation status of the heating furnace, the occurrence of air leakage due to deterioration of the heating furnace and the recuperator, the addition of the heating furnace, or the burner capacity in the heating furnace. There are expansions.

Next, FIG. 3B shows the operation of the exhaust heat recovery facility 1 shown in FIG.
As shown by the solid line in FIG. 3B, the amount of combustion exhaust gas discharged from the recuperators 101E and 101F in the exhaust portions of the heating furnaces 101A and 101B varies with time depending on the operating state of the heating furnaces 101A and 101B. Looking at fluctuations in the amount of combustion exhaust gas over time, there are a time zone 1 that exceeds the maximum capacity of the attracting fan 6 and a time zone 2 that is less than or equal to the maximum capacity of the attracting fan 6. In the present embodiment, the amount of combustion exhaust gas is obtained by calculation, and the induction fan 6 is controlled based on the obtained calculated exhaust gas amount. When the calculated exhaust gas flow rate is less than or equal to the maximum capacity of the induction fan 6, that is, in the time zone 2 of FIG. 3B, the rotational speed of the induction fan 6 is adjusted according to the calculated exhaust gas flow rate. On the other hand, when the calculated exhaust gas flow rate exceeds the maximum capacity of the induction fan 6, that is, in the time zone 1 of FIG. 3B, the number of rotations of the induction fan 6 is maximized and a part of the combustion exhaust gas is transferred to the heat recovery boiler 5. While supplying, the combustion exhaust gas exceeding the maximum capacity of the induction fan 6 is discharged from the bypass flue 3B to the chimney 102.

Next, the exhaust gas flow rate calculation unit 8 and the control unit 11 that realize the operation of the exhaust heat recovery facility 1 described in FIG.
As shown in FIG. 4, calculated exhaust gas flow rates Q1 and Q2 are calculated for each of the heating furnaces 101A and 101B based on the fuel consumption in the combustion burners of the heating furnaces 101A and 101B and the oxygen concentration of the combustion exhaust gas. The total calculated exhaust gas flow rate Q12 is calculated.

  The calculated exhaust gas flow rates Q1, Q2 and Q12 are obtained by the exhaust gas flow rate calculation unit 8. First, the oxygen concentration in the combustion exhaust gas measured by the gas concentration meters 8C to 8F is output to the flow rate calculation units 8A and 8B. Further, the fuel consumption monitoring unit causes the flow rate calculation units 8A and 8B to output the amount of fuel supplied to the normal burner and the regeneration burner.

  In the flow rate calculation units 8A and 8B, the calculated exhaust gas flow rates Q1 and Q2 are calculated by the calculation formula shown in FIG. The equation shown in FIG. 5 uses a regenerative burner and a normal banner as a combustion burner, exhausts the combustion exhaust gas recovered by the regenerative burner from the preliminary flue 13A, 13B, and from the recuperators 101E, 101F in the exhaust part of the heating furnaces 101A, 101B. It is a calculation formula in the case of discharging | emitting exhausted exhaust gas from exhaust gas flue 2A, 2B.

(1) In the equation, the measured flow rate Q _R of the combustion exhaust gas discharged from the preliminary flue _13A, and actual value of _101A, a theoretical wet exhaust gas amount G _0, depending on the installation gas concentration meter 8E bypass flue 3A and the oxygen concentration _{O 2R, 101A} and, by the theoretical air amount _{a 0,} the fuel flow rate _{F R} that is consumed by regenerative burners of the furnace _{101A, 101A} is obtained.

Likewise, in (2), the flow rate _{Q R} of the combustion exhaust gas discharged from the preliminary flue _13B, and actual values _101B, a theoretical wet exhaust gas amount _{G 0,} installed gas concentration meter 8F bypass flue 3B The fuel flow rates FR and 101B consumed in the regenerative burner of the heating furnace _101B are obtained from the oxygen concentrations O _{2R and 101B} measured by the above and the theoretical air amount A ₀ .

Next, (3) In the equation, the fuel flow rate _{F R, 101A} consumed by regeneration burners, the theoretical wet exhaust gas amount _{G 0,} an oxygen concentration in the combustion exhaust gas discharged from the recuperator 101E exhaust portion of the furnace 101A The average values O _{2E and 101A of} the oxygen concentration measured by the gas oximeter 8C, the theoretical air amount A _0, and the fuel (consumption) flow rate F _{MG in} the combustion burner (normal burner and regenerative burner) of the heating furnace 101A _, from the actual value of _101A, obtains the calculated exhaust gas amount Q ₁ of the recuperator exhaust portion of the furnace is discharged respectively to the exhaust gas flue 2A.

Similarly, in equation (4), the fuel flow rate _{F R} that is consumed by the regenerative _{burners, 101B} and, the theoretical wet exhaust gas amount _{G 0,} an oxygen concentration in the combustion exhaust gas discharged from the recuperator 101F exhaust portion of the heating furnace 101B The average values O _{2E and 101B of} the oxygen concentration measured by the gas oximeter 8D, the theoretical air amount A _0, and the fuel (consumption) flow rate F _{MG in} the combustion burner (normal burner and regenerative burner) of the heating furnace 101B _, from the actual value of _101B, determine the computational amount of exhaust gas Q ₂ to which the recuperator exhaust portion of the furnace is discharged respectively to the exhaust gas flue 2B.

Then, as shown in the equation (5), the total flow rate of Q ₁ and Q ₂ is defined as a calculated exhaust gas amount Q ₁₂ .

The calculated exhaust gas amounts Q ₁ and Q ₂ are calculated based on the oxygen concentration in the fuel exhaust gas. The oxygen concentration is derived from oxygen contained in the combustion exhaust gas, and may be further derived from outside air flowing in through a gap between piping such as the recuperators 101E and 101F. Therefore, the calculated exhaust gas amounts Q ₁ and Q ₂ may be a gas flow rate including an amount increased by the entrance of outside air from the pipe. The calculated exhaust gas flow rate Q ₁₂ calculated by the exhaust gas flow rate calculation unit 8 is output to the control unit 11.

Next, the control unit 11 sets the target pressure value P of the combustion exhaust gas immediately before the heat recovery boiler 5 based on the calculated exhaust gas flow rate Q ₁₂ (transfer function ΔQ → ΔP). The pressure target value P can be set based on, for example, the relationship between the inflow amount of the combustion exhaust gas flowing into the heat recovery boiler and the pressure of the combustion exhaust gas immediately before the heat recovery boiler shown in FIG. Specifically, for example, as shown in FIG. 6 (b), the calculated exhaust gas flow rate Q ₁₂ obtained above, sets a pressure target value P of the combustion exhaust gas immediately before the heat recovery boiler 5.

Next, as shown in FIG. 4, the control calculation unit 11 </ b> A of the control unit 11 is based on the target pressure value P of the combustion exhaust gas immediately before the heat recovery boiler 5, and the target flow rate of the combustion exhaust gas that should flow into the heat recovery boiler 5. Q is set (transfer function P → Q). When the target flow rate Q of the combustion exhaust gas is set, the rotational speed of the induction fan 6 may be set so that the target flow rate Q is obtained. Specifically, based on the target pressure value P of the combustion exhaust gas immediately before the heat recovery boiler, the induction fan 6 is controlled to set the target flow rate Q of the combustion exhaust gas so that the measurement value by the pressure gauge 11B becomes the target pressure P. That's fine. Further, as shown in FIGS. 2 and 4, the flow meter 11C actually measuring the flow rate through the heat recovery boiler 5, a correction flow rate ΔQ by feeding back the actually measured value in the calculation exhaust gas flow rate Q _12, the correction flow rate ΔQ It is preferable to obtain the target flow rate Q based on the point that the accuracy of the calculated exhaust gas flow rate can be improved.

Here, the concept (transfer function P → Q) when setting the target flow rate Q of the combustion exhaust gas to be introduced into the heat recovery boiler 5 based on the target pressure value P of the combustion exhaust gas will be described. 7 shows the calculated exhaust gas flow rate Q ₁₂ , the combustion exhaust gas flow rate Q _11C measured by the flow meter _11C , and the pressure measurement by the pressure gauge before the heat recovery boiler when the exhaust heat recovery facility 1 of FIG. 2 is operated. The time variation of each value is shown. In region 1, calculated exhaust gas flow rate Q12 is, exceeds the flow rate _{Q 11C} of the combustion exhaust gas measured by the flow meter 11C. In this state, as shown in FIG. 8 (b), a combustion furnace 101A, 101B of the exhaust portion of the recuperator 101E, of the flue gas calculated exhaust gas flow rate _{Q 12} discharged from 101F, flow rate _{Q 11C} as part exhaust gas flows into the heat recovery boiler 5, the combustion exhaust gas remaining flow _{(Q 12 -Q 11C)} comes to flow into the bypass flue 3B.

On the other hand, in the region 2 in FIG. 7, calculated exhaust gas flow rate _{Q 12} is below the flow rate _{Q 11C} of the combustion exhaust gas measured by the flow meter 11C. In this state, as shown in FIG. 8 (a), the furnace 101A, 101B of the exhaust portion of the recuperator 101E, the total amount of combustion exhaust gas calculated exhaust gas flow rate _{Q 12} discharged from 101F enters the heat recovery boiler 5. Further, the combustion exhaust gas of another system flowing into the bypass flue 3B from the preliminary flue 13B flows backward through the bypass flue 3B and flows into the exhaust flue 2B, and then flows into the heat recovery boiler 5. The combustion exhaust gas of another system flowing into the bypass flue 3B from the preliminary flue 13B has a temperature lower than that of the combustion exhaust gas flowing through the exhaust gas flue 2B. Therefore, when the combustion exhaust gas of such another system flows into the heat recovery boiler 5, steam is generated. The generation efficiency is greatly reduced.

Therefore, in this embodiment, the amount of combustion exhaust gas drawn by the induction fan 6 is controlled so that the combustion exhaust gas flow rate Q _11C measured by the flow meter 11C becomes the calculated exhaust gas flow rate Q ₁₂ .

  As described above, according to the exhaust heat recovery equipment and exhaust heat recovery method of the heating furnace of this embodiment, the induction fan is based on the calculated exhaust gas flow rate obtained from the fuel consumption of the heating furnace and the oxygen concentration in the combustion exhaust gas. 6 is controlled, even if outside air flows from the heating furnace, the pipes of the recuperator, and the like, and the apparent exhaust gas amount increases, the induction fan 6 can be accurately controlled by the calculated exhaust gas flow rate including this increase. Further, when the calculated exhaust gas flow rate is equal to or less than the maximum induced flow rate of the induction fan 6, the induced flow rate of the induction fan 6 is controlled to the calculated exhaust gas flow rate, and when the calculated exhaust gas flow rate exceeds the maximum induced flow rate, the induced flow rate of the induction fan 6 Is controlled to the maximum attraction flow rate, so that the combustion exhaust gas discharged from the recuperators 101E and 101F in the exhaust portions of the heating furnaces 101A and 101B is introduced into the heat recovery boiler 5 for heat recovery, and the calculated exhaust gas flow rate has the maximum attraction flow rate. When exceeding, the remainder of combustion exhaust gas can be discharge | released toward the chimney 102 from the bypass flue 3B. Thus, in this embodiment, combustion exhaust gas can be appropriately distributed to the exhaust gas flue 2C and the bypass flue 3A according to the calculated exhaust gas flow rate. Thereby, the heat recovery boiler 5 can be operated with high efficiency, and the amount of generated steam can be increased. Further, since there is no means for adjusting the flow rate of the combustion exhaust gas in the bypass flue 3B, the combustion exhaust gas that cannot be treated by the heat recovery boiler 5 branches from the exhaust flue 2B to the bypass flue 3B by the action of the chimney draft. And can be discharged from the chimney 102 to the outside. At this time, even if the chimney draft fluctuates due to changes in the outside air temperature, the flow rate of the combustion exhaust gas passing through the heat recovery boiler 5 is controlled based on the calculated exhaust gas flow rate. It does not affect the flow rate of combustion exhaust gas. Moreover, the furnace pressure of the heating furnaces 101A and 101B can be stabilized.

Further, in the present embodiment, the flow rate Q _11C of the combustion exhaust gas measured by the flow meter 11C are, by controlling the induction fan to be calculated exhaust gas flow rate Q _12, the low temperature fluid from flowing back from the bypass flue 2B There is no fear, and the heat exchange rate between the combustion exhaust gas and water in the heat recovery boiler 5 can be increased.

Further, based on the relationship between the pressure of the flue gas of the gas flow and the heat recovery boiler immediately before passing through the pre-determined heat recovery boiler, set the pressure target value P of the combustion exhaust gas immediately before the heat recovery boiler from calculated exhaust gas flow rate Q ₁₂ Since the induction fan 6 is controlled so that the measured value by the pressure gauge 11B becomes the pressure target value P, the combustion is performed according to the flow rate of the combustion exhaust gas discharged from the recuperators 101E and 101F in the exhaust portions of the heating furnaces 101A and 101B. The exhaust gas can be appropriately distributed to the exhaust gas flue 2B and the bypass flue 3B.

  Furthermore, according to the present embodiment, even if outside air is mixed into the combustion exhaust gas due to aging of the heating furnace, the recuperator, etc., and the apparent flow rate increases, the calculated exhaust gas flow rate is calculated based on the oxygen concentration in the exhaust gas. Because it demands, it can fully cope with the aging of equipment.

In FIG. 9, the time fluctuation of the furnace pressure of heating furnace 101A, 101B is shown. In FIG. 9, “one furnace pulling” means, for example, that the entire amount of combustion exhaust gas discharged from the recuperator 101E in the exhaust section of the heating furnace 101A flows through the bypass flue 3A and is discharged from the recuperator 101F in the exhaust section of the heating furnace 101B. This is a case where the entire amount of the combustion exhaust gas flows through the exhaust gas flue 2C and the heat recovery boiler 5, and “open bypass” is a case where the control of the present embodiment is performed. Even if the control of this embodiment is performed, it can be seen that the time fluctuation of the furnace pressure does not vary greatly, and the furnace pressure of the heating furnace can be controlled.
FIG. 10 shows the relationship between the amount of steam generated by the heat recovery boiler and the heat equivalent. According to the control of the present embodiment indicated as “open bypass”, it can be seen that the amount of generated steam is greatly improved as compared with “one furnace pulling”.
Thus, according to this embodiment, the furnace pressure in the heating furnace is stabilized, and the amount of steam generated can be increased.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to the drawings.
FIG. 11 shows an exhaust heat recovery facility 201 for the heating furnace of the present embodiment. The exhaust heat recovery equipment 201 shown in FIG. 11 has substantially the same configuration as the exhaust heat recovery equipment 201 shown in FIG. 1, except that a pressure gauge is not installed before the heat recovery boiler 5 and the first implementation. The control part 211 which performs control different from the control flow of the control part of a form is provided. Hereinafter, a control flow of the control unit 211 will be described.

As shown in FIG. 12, in the control unit 211 of the present embodiment, the calculated exhaust gas flow rates Q ₁ and Q ₂ are obtained in the exhaust gas flow rate calculation unit 8 as in the first embodiment. Then, the control unit 211, based on the relationship between the calculated exhaust gas flow rate obtained in advance the rotational speed of the induction fan (transfer function Delta] Q → [Delta] n), determines the rotation speed n of the induction fan from the calculated exhaust gas flow rate Q _12.

As the “transfer function ΔQ → Δn”, for example, a linear function shown in FIG. 13 can be exemplified. FIG. 13 is a graph showing the relationship between the calculated exhaust gas flow rate obtained in advance and the rotational speed of the induction fan. For example, when the calculated exhaust gas flow rate is 60000 Nm ³ / h, the rotational speed of the attracting fan 6 may be 30 Hz. Since the graph shown in FIG. 13 varies depending on the capacity of the attracting fan, it may be determined based on the performance of the attracting fan to be used.

Also, as shown in FIG. 12, the flow rate Q _11C flowing through the heat recovery boiler 5 is measured by the flow meter 11C, and the measured value is fed back to the calculated exhaust gas flow rate Q ₁₂ to obtain a corrected flow rate ΔQ. It is preferable to obtain the target flow rate Q based on the point that the accuracy of the calculated exhaust gas flow rate can be improved.

According to the exhaust heat recovery equipment and exhaust heat recovery method of the heating furnace of the present embodiment, the calculated exhaust gas flow rate Q ₁₂ is based on the relationship between the calculated exhaust gas flow rate Q ₁₂ (ΔQ) obtained in advance and the rotational speed n of the induction fan 6. Since the rotational speed n of the induction fan 6 is determined from (ΔQ), the combustion exhaust gas is discharged into the exhaust gas flue and the bypass flue in accordance with the flow rate of the combustion exhaust gas discharged from the recuperator of the exhaust part of the heating furnace. Can be distributed more appropriately. Further, since the flow rate control by the control unit 211 is simplified, control responsiveness can be improved.

In the above embodiment, an example in which two heating furnaces are provided has been described. However, in the present invention, the number of heating furnaces may be two or more.
Moreover, although the example which guide | induces the whole quantity of the combustion exhaust gas from the recuperator 101E of the exhaust part of the heating furnace 101A to the exhaust gas flue 2C by the flue switching part 4 was demonstrated, this invention is not limited to this, The cutoff valve 4C is " By opening the shutoff valve 4D and closing the shutoff valve 4D, the combustion exhaust gas from the recuperator 101E in the exhaust part of the heating furnace 101A is guided to the exhaust gas flue 2C and the bypass flue 3A, and the exhaust part of the heating furnace 101B. The total amount of combustion exhaust gas from the recuperator 101F may be guided to the exhaust gas flue 2C. Further, by opening the shutoff valve 4C and shutoff valve 4D, the combustion exhaust gas from the recuperator 101E in the exhaust section of the heating furnace 101A is guided to the exhaust gas flue 2C and the bypass flue 3A, and the exhaust of the heating furnace 101B. The combustion exhaust gas from the recuperator 101F of the part may be guided to the exhaust gas flue 2C and the bypass flue 3B.

  1, 201 ... Exhaust heat recovery equipment for heating furnace, 2A, 2B, 2C ... Exhaust flue, 102 ... Chimney, 3A, 3B ... Bypass flue, 4 ... Flue switching section, 5 ... Heat recovery boiler, 6 ... Induction Fan, 8 ... exhaust gas flow rate calculation unit, 11, 211 ... control unit, 11B ... pressure gauge, 101A, 101B ... heating furnace.

Claims (7)

An exhaust gas flue that guides the combustion exhaust gas discharged from the recuperator of the exhaust section of the plurality of heating furnaces to the chimney;
A heat recovery boiler installed in the middle of the flue gas flue and having a processing capacity smaller than the maximum amount of combustion exhaust gas generated per hour;
A bypass flue that branches from the middle of the flue gas flue and leads the combustion exhaust gas bypassing the heat recovery boiler to the chimney;
An induction fan installed in the flue gas flue downstream of the heat recovery boiler and having a maximum induction flow rate smaller than the maximum generation amount per hour of the combustion exhaust gas;
An exhaust gas flow rate calculation unit for obtaining a calculated exhaust gas flow rate from the fuel consumption of the heating furnace and the oxygen concentration in the combustion exhaust gas;
When the calculated exhaust gas flow rate input from the exhaust gas flow rate calculation unit is less than or equal to the maximum induced flow rate of the induction fan, the induced exhaust gas flow rate is controlled to be the calculated exhaust gas flow rate, and the calculated exhaust gas flow rate is When the maximum attraction flow rate is exceeded, a control unit that controls the attraction flow rate of the attraction fan to the maximum attraction flow rate,
An exhaust heat recovery facility for a heating furnace, characterized by comprising: A pressure gauge is further provided in the flue gas flue upstream of the heat recovery boiler;
When the calculated exhaust gas flow rate is less than or equal to the maximum attraction flow rate, the control unit is based on the relationship between the flow rate of the combustion exhaust gas passing through the heat recovery boiler and the pressure of the combustion exhaust gas immediately before the heat recovery boiler that are obtained in advance. The pressure target value of the combustion exhaust gas immediately before the heat recovery boiler is set from the calculated exhaust gas flow rate, and the induction flow rate of the induction fan is controlled so that the measured value by the pressure gauge becomes the pressure target value. The exhaust heat recovery equipment for a heating furnace according to claim 1.   When the calculated exhaust gas flow rate is less than or equal to the maximum induced flow rate, the control unit determines the rotation speed of the induction fan from the calculated exhaust gas flow rate based on the relationship between the calculated exhaust gas flow rate and the rotation speed of the induction fan that are obtained in advance. The exhaust heat recovery facility for a heating furnace according to claim 1, wherein:   The exhaust path of the combustion exhaust gas is set to both the exhaust gas flue and the bypass flue for each heating furnace, or a flue switching unit that sets only the exhaust gas flue is further provided. The exhaust heat recovery equipment for a heating furnace according to any one of claims 1 to 3, wherein An exhaust heat recovery method for a heating furnace using the exhaust heat recovery facility according to claim 1,
In the exhaust gas flow rate calculation unit, the calculated exhaust gas flow rate is calculated from the fuel consumption of the heating furnace and the oxygen concentration in the combustion exhaust gas, and the calculated exhaust gas flow rate is output to the control unit,
In the control unit, when the calculated exhaust gas flow rate is less than or equal to the maximum induced flow rate of the attracting fan, the induced flow rate of the attracting fan is set to the calculated exhaust gas flow rate,
The exhaust heat recovery method for a heating furnace, wherein when the calculated exhaust gas flow rate exceeds the maximum attractive flow rate of the induction fan, the induction flow rate of the induction fan is set as the maximum attractive flow rate. Using the exhaust heat recovery equipment further provided with a pressure gauge in the exhaust gas flue upstream of the heat recovery boiler,
When the calculated exhaust gas flow rate is less than or equal to the maximum attraction flow rate, the calculated exhaust gas flow rate is based on the relationship between the flow rate of the combustion exhaust gas that passes through the heat recovery boiler determined in advance and the pressure of the combustion exhaust gas immediately before the heat recovery boiler. The pressure target value of the combustion exhaust gas immediately before the heat recovery boiler is set to control the induction fan so that the measured value by the pressure gauge becomes the pressure target value. Waste heat recovery method for heating furnaces.   When the calculated exhaust gas flow rate is equal to or less than the maximum induced flow rate, the rotational speed of the induction fan is determined from the calculated exhaust gas flow rate based on the relationship between the calculated exhaust gas flow rate and the rotational speed of the induction fan obtained in advance. The method for recovering exhaust heat from a heating furnace according to claim 5, wherein:

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