JP2017141493A - Heating apparatus for steel material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating apparatus for a steel material, which has high energy efficiency.SOLUTION: The present invention is a heating apparatus for a steel material for hot working or heat treatment, and comprises: a heating furnace for heating the steel material by a combustion gas ejected from a burner; a preheating furnace for preheating the steel material before charged into the heating furnace with a preheating gas; a heat exchanger for preheating a combustion air to be supplied to the burner; a first exhaust gas flow path for supplying the exhaust gas exhausted from the heating furnace, as the preheating gas of the preheating furnace; and a second exhaust gas flow path that is provided in parallel with the first exhaust gas flow path and supplies the exhaust gas exhausted from the heating furnace, as the preheating gas of the heat exchanger. It is preferable that the heating apparatus further comprises a mechanism for adjusting a flow rate of the exhaust gas supplied to the first exhaust gas flow path and a flow rate of the exhaust gas supplied to the second exhaust gas flow path. It is also preferable that the heating apparatus further comprises a thermometer which measures a temperature of the steel material before being heated and a mechanism which selects the steel material supplied into the preheating furnace based on the measurement result of the thermometer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a steel material heating apparatus.

  In a hot rolling factory or the like, hot rolling is performed after heating a steel material such as a slab or billet in a continuous or batch heating furnace. In a thick plate factory or the like, a steel material such as a thick plate is heated in a continuous or batch heat treatment furnace, and then heat treatment is performed. For example, when manufacturing a thick plate in a thick plate factory, a slab cast by a continuous casting machine is transported by a carriage or the like and temporarily stored in a stock yard in front of a heating furnace. During this storage, the temperature of the slag decreases to a maximum of room temperature (about 25 ° C.). For this reason, this slab is sequentially charged from a stock yard into a heating furnace according to a heat treatment schedule, heated to a temperature of about 1200 ° C., and then sent to a rolling mill for rolling.

  As such a heating furnace, a walking beam type conveying device for conveying the slab from the charging side to the extracting side is disposed, and the fuel gas is burned by a plurality of burners disposed above and below the path of the conveying device. A heating furnace that heats the slab is known. Combustion air is supplied to the burner by a combustion air blower, and fuel gas is combusted. The exhaust gas after the combustion of the fuel gas is sent from the furnace bottom, which is the heating furnace charging end, through the furnace bottom flue to the chimney and exhausted to the outside. Part of the sensible heat of the exhaust gas exhausted from this heating furnace is recovered by a heat exchanger such as a regenerative burner or a recuperator and used for preheating combustion air, but most is exhausted from the chimney. . Therefore, for example, the energy efficiency of the heating furnace attached to the recuperator is only about 50%. For this reason, for example, if the production scale is a heating furnace of 200 t / h, a fuel intensity of about 300 Mcal / t is required.

  In order to improve the energy efficiency, a heating apparatus including a preheating furnace that preheats a steel material such as a slab with exhaust gas exhausted from the heating furnace has been proposed (Japanese Unexamined Patent Application Publication Nos. 2014-219139 and 2011-196615). Issue gazette).

  This conventional heating apparatus supplies all the exhaust gas exhausted from the heating furnace to the preheating furnace. However, the temperature of the steel before being charged into the preheating furnace varies depending on the storage time in the stockyard. For this reason, in this conventional heating device, for example, when a steel material having a relatively high temperature is charged into the preheating furnace, the temperature difference from the exhaust gas introduced into the preheating furnace is small and the sensible heat of the exhaust gas cannot be sufficiently recovered. There is a possibility that the energy efficiency may be lowered rather than when exhaust gas is supplied to a heat exchanger that preheats combustion air.

JP 2014-219139 A JP2011-196615A

  This invention is made | formed based on the above situations, and the objective of this invention is to provide the heating apparatus of steel materials with high energy efficiency.

  The invention made to solve the above-mentioned problems is a steel material heating apparatus for hot working or heat treatment, wherein the steel material is heated by a combustion gas ejected from a burner, and charged into the heating furnace. A preheating furnace for preheating the steel before being heated with a preheating gas, a heat exchanger for preheating combustion air supplied to the burner, and an exhaust gas discharged from the heating furnace as a preheating gas for the preheating furnace The first exhaust gas flow path and the first exhaust gas flow path are provided in parallel, and include a second exhaust gas flow path that supplies the exhaust gas discharged from the heating furnace as a preheating gas for the heat exchanger.

  The heating device can distribute and supply the exhaust gas exhausted from the heating furnace through the first exhaust gas channel and the second exhaust gas channel to the preheating gas of the preheating furnace and the preheating gas of the heat exchanger. For this reason, the heating device can recover the sensible heat of the preheating gas in each of the preheating furnace and the heat exchanger. Heat can be recovered. As a method of supplying the exhaust gas to the preheating furnace and the heat exchanger, for example, a method of using the exhaust gas used for preheating the steel material in the preheating furnace for preheating the combustion air is also conceivable. However, in this case, since the temperature of the exhaust gas supplied to the heat exchanger that preheats the air is lower than the temperature of the exhaust gas exhausted from the heating furnace, the temperature difference between the exhaust gas and the combustion air becomes small, and The amount of heat transferred to the combustion air is not sufficient. On the other hand, the heating device supplies the exhaust gas exhausted from the heating furnace in parallel to the preheating furnace and the heat exchanger, so that the temperature of the exhaust gas exhausted from the heating furnace is not greatly reduced, and the preheating furnace and the above Preheat gas can be supplied to the heat exchanger. For this reason, since the said heating apparatus is easy to ensure the temperature difference of the supplied preheating gas, steel materials, and combustion air, the heat transfer efficiency from preheating gas to steel materials and combustion air is good. Therefore, the heating device is energy efficient.

  A mechanism for adjusting the flow rate of the exhaust gas supplied to the first exhaust gas channel and the flow rate of the exhaust gas supplied to the second exhaust gas channel may be further provided. By providing a mechanism for adjusting the flow rate of the exhaust gas supplied to the first exhaust gas channel and the flow rate of the exhaust gas supplied to the second exhaust gas channel in this way, energy efficiency is further increased.

  The exhaust gas flow rate adjusting mechanism may be disposed in the first exhaust gas flow path. By arranging the exhaust gas flow rate adjusting mechanism in the first exhaust gas flow path as described above, the flow rate of the exhaust gas supplied to the preheating furnace can be reduced, for example, when the heat transfer amount from the exhaust gas to the steel material is small. This further increases energy efficiency.

  The exhaust gas flow rate adjusting mechanism may be disposed in the second exhaust gas flow path. Thus, by arranging the exhaust gas flow rate adjusting mechanism in the second exhaust gas flow path, the flow rate of the exhaust gas introduced into the heat exchanger can be accurately adjusted. This further increases energy efficiency.

  A weigh scale that measures the weight of the steel material charged into the preheating furnace, a weigh scale that measures the weight of the steel material charged into the heating furnace, a thermometer that measures the temperature of the steel material after preheating, and the heating furnace A flow meter for measuring the flow rate of the supplied fuel, a flow meter for measuring the flow rate of combustion air flowing into the heat exchanger, and the exhaust gas flow rate adjusting mechanism based on the measurement results of the weight meter, the thermometer, and the flow meter And a mechanism for controlling the exhaust gas flow rate ratio supplied to the preheating furnace and the heat exchanger so that energy efficiency is maximized. In this way, by further comprising the above-described weigh scale, thermometer and flow meter and a mechanism for controlling the exhaust gas flow ratio based on the measurement results of these measuring instruments, the exhaust gas flow ratio at which energy efficiency is maximized is estimated, and this Based on the estimate, the exhaust gas flow rate adjustment mechanism can be used to adjust the exhaust gas flow rate ratio. This further increases energy efficiency.

  A thermometer for measuring the temperature of the exhaust gas exhausted from the heating furnace may be further provided. As described above, by further including a thermometer for measuring the temperature of the exhaust gas exhausted from the heating furnace, the estimation accuracy of the exhaust gas flow rate ratio at which the energy efficiency is maximized is improved. This further increases energy efficiency.

  It is good to provide the thermometer which measures the temperature of the steel materials before a heating, and the mechanism which selects the steel materials inserted into the said preheating furnace based on the measurement result of the said thermometer. When a steel material having a relatively high temperature before heating is charged into the preheating furnace, the temperature difference between the exhaust gas temperature and the steel material is small, so the heat transfer efficiency from the exhaust gas to the steel material is reduced. For this reason, for example, when recovering a sensible heat of a certain amount of exhaust gas, compared to preheating a steel material with a low temperature before heating, preheating a steel material with a high temperature before heating is more Needs to stay in the preheating path for a long time, and productivity is reduced. Therefore, by selecting the steel material to be charged into the preheating furnace according to the temperature of the steel material before heating, the reduction in productivity can be suppressed and the fuel consumption rate can be reduced.

  By selecting a thermometer for measuring the temperature of the exhaust gas exhausted from the preheating furnace and a steel material charged into the preheating furnace based on the measurement result of the thermometer, the exhaust gas exhausted from the preheating furnace becomes a predetermined temperature or higher. And a mechanism for controlling the exhaust gas temperature. By providing a mechanism for controlling the exhaust gas temperature so that the exhaust gas exhausted from the preheating furnace becomes a predetermined temperature or more, it is possible to suppress deterioration and damage of equipment such as the preheating furnace due to acid dew point corrosion of the exhaust gas. For this reason, stable operation can be performed while improving energy efficiency.

  Combustion air bypass passage for bypassing the heat exchanger, a thermometer for measuring the temperature of exhaust gas exhausted from the heat exchanger, and a part of the combustion air based on the measurement result of the thermometer or It is preferable to provide a mechanism for controlling the exhaust gas temperature so that the exhaust gas exhausted from the heat exchanger becomes equal to or higher than a predetermined temperature by flowing all through the bypass channel. By providing a mechanism for controlling the exhaust gas temperature so that the exhaust gas exhausted from the heat exchanger becomes equal to or higher than a predetermined temperature in this way, it is possible to suppress deterioration and damage of equipment such as a heat exchanger due to acid dew point corrosion. For this reason, stable operation can be performed while improving energy efficiency.

  A mechanism for adjusting the flow rate of the fuel gas supplied to the burner; and a mechanism for controlling the fuel gas flow rate using the fuel gas flow rate adjustment mechanism so that the temperature of the heated steel material is within a predetermined range. Good. Thus, by providing the fuel gas flow rate adjusting mechanism and the mechanism for controlling the fuel gas flow rate using the fuel gas flow rate adjusting mechanism, it is easy to adjust the temperature of the steel material extracted from the heating furnace to a desired temperature. For this reason, stable operation can be performed while improving energy efficiency.

  Here, “acid dew point corrosion” means that sulfur contained in exhaust gas is condensed (acid condensed) into an acid such as sulfuric acid by binding with moisture, and corrodes the metal. The “flow rate ratio of exhaust gas” means the ratio of exhaust gas supplied to the preheating furnace with respect to the total amount of exhaust gas and the ratio of exhaust gas supplied to the heat exchanger with respect to the total amount of exhaust gas.

  As described above, the heating device of the present invention can increase the energy efficiency in heating the steel material.

It is a schematic diagram which shows the heating apparatus of one Embodiment of this invention. It is a flowchart which shows the flow of the waste gas flow rate adjustment process of the heating apparatus of FIG. It is a schematic diagram which shows the heating apparatus of embodiment different from the heating apparatus of FIG. It is a graph which shows the relationship between the steel material temperature before preheating, the amount of heat received of the steel material after preheating, steel material temperature, and the exhaust gas temperature exhausted from a preheating furnace. It is a graph which shows the relationship between the flow rate ratio of exhaust gas, the exhaust gas temperature exhausted from a preheating furnace and a heat exchanger, and the energy efficiency of the whole heating apparatus.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

[First Embodiment]
A heating device 1 shown in FIG. 1 is a steel material heating device for hot working or heat treatment according to an embodiment of the present invention, such as a slab, billet, etc. in a thick plate factory, a section steel factory, a hot rolling factory, etc. It can be used for heating steel materials. The heating apparatus 1 includes a heating furnace 2 that heats the steel material with a combustion gas ejected from a burner, a preheating furnace 3 that preheats the steel material before being charged into the heating furnace 2 with a preheating gas, and the burner. And a heat exchanger 4 that preheats the supplied combustion air.

  Moreover, the said heating apparatus 1 is provided with three conveying apparatuses (1st conveying apparatus 5a, 2nd conveying apparatus 5b, and 3rd conveying apparatus 5c). The first transfer device 5a is configured to supply steel materials to the extraction port of the stockyard X where the steel material before heating is temporarily stored, the extraction port of the preheating furnace 3, the charging port of the heating furnace 2, and the third transfer device 5c. Can be transported. Moreover, the said 2nd conveying apparatus 5b can convey the steel materials conveyed by the 1st conveying apparatus 5a to the 3rd conveying apparatus 5c. Furthermore, the said 3rd conveying apparatus 5c can convey the steel materials conveyed by the 2nd conveying apparatus 5b to the extraction port of the heating furnace 2, the charging inlet of the preheating furnace 3, and the steel material carrying-out port of the said heating apparatus 1. FIG.

  In addition, the heating device 1 discharges exhaust gas to four exhaust gas channels (first exhaust gas channel 6a, second exhaust gas channel 6b, third exhaust gas channel 6c, and fourth exhaust gas channel 6d) to the outside. And a chimney 7. The first exhaust gas passage 6 a is a passage for supplying exhaust gas discharged from the heating furnace 2 as a preheating gas for the preheating furnace 3. The second exhaust gas flow path 6b is provided in parallel with the first exhaust gas flow path 6a and supplies the exhaust gas discharged from the heating furnace 2 as a preheating gas for the heat exchanger 4. is there. The heating apparatus 1 distributes the exhaust gas exhausted from the heating furnace 2 to the exhaust gas of the preheating furnace 3 and the exhaust gas of the heat exchanger 4 by using the first exhaust gas channel 6a and the second exhaust gas channel 6b. Can be supplied. The third exhaust gas channel 6c and the fourth exhaust gas channel 6d collect exhaust gas exhausted from the preheating furnace 3 and the heat exchanger 4, respectively, and the recovered exhaust gas exhausts from the chimney 7 to the outside. Is done.

  In addition, the heating device 1 includes two exhaust gas flow rate adjustment valves (a first exhaust gas flow rate adjustment valve 8a and a second exhaust gas flow rate adjustment valve 8b) that adjust the flow rate of the exhaust gas supplied to the preheating furnace 3 or the heat exchanger 4. Prepare. The first exhaust gas flow rate adjusting valve 8 a is disposed in the first flow path 6 a that distributes and supplies exhaust gas to the preheating furnace 3. The second exhaust gas flow rate adjustment valve 8b is disposed in the second flow path 6b that distributes and supplies the exhaust gas to the heat exchanger 4.

  In addition, the heating device 1 includes a fuel gas passage 9 through which fuel gas supplied to the burner of the heating furnace 2 flows into the heating furnace 2. The heating device 1 includes a fuel gas flow rate adjusting valve 10 that is disposed in the fuel gas flow path 9 and adjusts the flow rate of the fuel gas flowing into the heating furnace 2.

  In addition, the heating device 1 includes a combustion air passage 11 through which combustion air flows into the heating furnace 2 via the heat exchanger 4 and a combustion air bypass passage 12 that bypasses the heat exchanger 4. Prepare. In addition, the heating device 1 includes a bypass flow rate adjustment valve 13 that is disposed in the bypass flow path 12 and adjusts the combustion air flow rate that bypasses the heat exchanger 4.

  The heating apparatus 1 includes a weight meter 14a for measuring the weight M1 of the steel material charged into the preheating furnace 3, a weight meter 14b for measuring the weight M2 of the steel material charged into the heating furnace 2, and a steel material before heating. A thermometer 14c for measuring the temperature T1 of the steel, a thermometer 14d for measuring the temperature T2 of the preheated steel material, a thermometer 14e for measuring the temperature T3 of the exhaust gas exhausted from the preheating furnace 3, and the exhaust from the heat exchanger 4 A thermometer 14f for measuring the temperature T4 of the exhaust gas to be discharged, a thermometer 14g for measuring the temperature T5 of the exhaust gas exhausted from the heating furnace 2, a thermometer 14h for measuring the temperature T6 of the steel material after heating, and supplying to the heating furnace A flow meter 14i for measuring the flow rate QF of fuel and a flow meter 14j for measuring the flow rate QA of combustion air flowing into the heat exchanger are provided. In addition, the heating device 1 includes a control mechanism 15 that adjusts the open / close amounts of the exhaust gas flow rate adjustment valve, the fuel gas flow rate adjustment valve 10, and the bypass flow rate adjustment valve 13 based on the measurement result of the measuring instrument.

(Stockyard)
The stockyard X temporarily stores the steel material before heating. The heating device 1 is supplied with the steel material extracted from the stockyard X and is heated by the heating device 1. The temperature of the steel material stored in the stockyard X varies depending on the time during which the steel material is stored and the processing conditions of the steel material before heating, but is usually in the range of 25 ° C to 600 ° C.

<Heating furnace>
The heating furnace 2 heats the steel material charged into the charging port by the first transport device 5a to a predetermined temperature, and extracts the steel material from the extraction port. Specifically, the heating furnace 2 mixes the fuel gas supplied from the fuel gas passage 9 with the combustion air supplied from the combustion air passage 11 and burns it with a burner, and uses the combustion gas. Heat steel.

  Although it does not specifically limit as temperature after heating a steel material, For example, it can be set as 1100 degreeC or more and 1300 degrees C or less. The fuel gas is not particularly limited, and for example, coke oven gas (C gas), mixed gas of coke oven gas and blast furnace gas (M gas), or the like can be used.

  As the heating furnace 2, a known heating furnace can be used. As a known heating furnace, for example, a walking beam type conveying device is provided, and a plurality of steel materials arranged above and below the steel material while the steel material moves from the charging side end to the extraction side end of the heating furnace 2. There can be mentioned a heating furnace that burns fuel gas with a burner and controls the temperature of the steel material in the pre-tropical zone, heating zone and soaking zone in order from the charging side. The heating furnace heats steel at a relatively moderate temperature rise rate in the pre-tropical zone so that no distortion is caused by rapid heating, and then at a relatively high temperature rise rate so as to reach the target temperature in the heating zone. The steel is heated gently so as to eliminate uneven temperature in the soaking zone.

Further, the heating device 1 uses the combustion gas after being used for heating the steel material, that is, the exhaust gas, through the first exhaust gas channel 6a and the second exhaust gas channel 6b, and the heat exchanger 4 and the exhaust gas from the preheating furnace 3. Can be distributed and supplied to the exhaust gas. The outlet of the exhaust gas to the first exhaust gas channel 6 a and the second exhaust gas channel 6 b is preferably disposed on the inlet side of the heating furnace 2. By disposing the outlet on the inlet side, the direction in which the combustion gas flows and the conveying direction of the steel material face each other, so that the steel material can be efficiently heated. The temperature of the exhaust gas is determined depending on the combustion conditions of the fuel gas, but is, for example, 500 ° C. or higher and 900 ° C. or lower. Further, the flow rate of the exhaust gas is determined depending on the combustion condition of the fuel gas, but is, for example, 10000 Nm ³ / h or more and 50000 Nm ³ / h or less.

  The amount (flow rate) of the steel material heated in the heating furnace 2 is determined depending on the operation conditions and the like, but can be, for example, 100 t / h or more and 250 t / h or less.

<Preheating furnace>
The preheating furnace 3 preheats the steel material charged from the charging port of the preheating furnace 3 by the third transport device 5c. Specifically, the preheating furnace 3 preheats the steel material using the exhaust gas supplied from the heating furnace 2 through the first exhaust gas passage 6a as the preheating gas. Further, the exhaust gas after being used for preheating is recovered by the third exhaust gas channel 6 c and exhausted from the chimney 7. The preheated steel material is extracted from the extraction port of the preheating furnace 3 to the first transport device 5a.

  The preheating furnace 3 is not particularly limited as long as it can exchange heat between the preheating gas (exhaust gas) and the steel material. For example, the preheating furnace 3 includes a furnace body formed of a heat insulating material such as a refractory brick, and a mechanism for transporting the steel material from the loading port of the preheating furnace 3 to the extraction port in the furnace body, and is transported inside the furnace body. A preheating furnace that performs heat exchange by circulating a preheating gas inside the furnace body so as to be in contact with the steel material can be used.

  The exhaust gas intake port from the first exhaust gas channel 6 a is preferably disposed on the extraction port side of the preheating furnace 3. Moreover, it is preferable that the exhaust port of the exhaust gas to the third exhaust gas flow path 6 c is disposed on the charging inlet side of the preheating furnace 3. By arranging the exhaust gas intake port and the exhaust port in this manner, the direction in which the exhaust gas flows and the conveying direction of the steel material are opposed to each other, so that the steel material can be efficiently preheated.

  As a minimum of the temperature of the steel material after the preheating in the preheating furnace 3, 150 degreeC is preferable and 200 degreeC is more preferable. On the other hand, the upper limit of the temperature of the steel material after preheating in the preheating furnace 3 is preferably 700 ° C, more preferably 600 ° C. When the temperature of the steel material after preheating in the preheating furnace 3 is less than the above lower limit, the temperature of the steel material is low in the vicinity of the extraction port of the preheating furnace 3, so that the total heat transfer amount from the exhaust gas to the steel material is large in the preheating furnace 3. Become. For this reason, the exhaust gas temperature is likely to fall below the acid dew point temperature, and there is a possibility that the equipment of the preheating furnace 3 is deteriorated or broken due to the acid dew point corrosion of the exhaust gas. Conversely, when the temperature of the steel material after preheating in the preheating furnace 3 exceeds the above upper limit, the temperature difference between the exhaust gas and the steel material becomes small, so the total heat transfer amount from the exhaust gas to the steel material becomes small. For this reason, there exists a possibility that the energy efficiency of the said heating apparatus 1 may fall. This acid condensation occurs when the temperature of the exhaust gas decreases, and the temperature at which acid condensation starts is called “acid dew point temperature”.

  As a minimum of the temperature difference before and behind preheating of steel materials in preheating furnace 3, 100 ° C is preferred and 150 ° C is more preferred. On the other hand, the upper limit of the temperature difference before and after preheating of the steel material in the preheating furnace 3 is preferably 400 ° C, and more preferably 300 ° C. When the temperature difference before and after the preheating is less than the lower limit, the total heat transfer amount from the exhaust gas to the steel material becomes small, and the energy efficiency of the heating device 1 may be reduced. Conversely, if the temperature difference before and after the preheating exceeds the upper limit, the exhaust gas temperature is likely to fall below the acid dew point temperature, and there is a risk that the equipment of the preheating furnace 3 will be deteriorated or damaged due to the acid dew point corrosion of the exhaust gas.

<Heat exchanger>
The heat exchanger 4 preheats the combustion air supplied to the burner of the heating furnace 2. Specifically, the heat exchanger 4 includes exhaust gas supplied from the heating furnace 2 through the second exhaust gas passage 6 b and combustion air supplied through the combustion air passage 11. The combustion air is preheated by exchanging heat with each other.

  The heat exchanger 4 is not particularly limited as long as the combustion air can be preheated. For example, a known recuperator or regenerative burner can be used.

  As a minimum of the temperature of the combustion air after preheating in heat exchanger 4, 150 ° C is preferred and 200 ° C is more preferred. On the other hand, the upper limit of the temperature of the combustion air after preheating in the heat exchanger 4 is preferably 700 ° C., more preferably 600 ° C. When the temperature of the combustion air after preheating in the heat exchanger 4 is less than the lower limit, the temperature of the combustion air is low even in the vicinity of the outlet of the heat exchanger 4, so Increases total heat transfer to the air. For this reason, exhaust gas temperature falls below an acid dew point temperature, and there exists a possibility that the deterioration and damage of the equipment of the heat exchanger 4 by the acid dew point corrosion of waste gas may generate | occur | produce. Conversely, when the temperature of the combustion air after preheating in the heat exchanger 4 exceeds the upper limit, the temperature difference between the exhaust gas and the combustion air becomes small, so the total heat transfer amount from the exhaust gas to the combustion air is small. Become. For this reason, there exists a possibility that energy efficiency may fall.

<Conveyor>
The conveying device can extract the steel material from the stockyard X, and can convey the steel material to the steel material unloading port of the heating device 1 via the preheating furnace 3 and the heating furnace 2. Specifically, first, the first transport device 5a transports the steel material extracted from the stockyard X to the second transport device 5b, and the second transport device 5b transports the steel material to the third transport device 5c. And the 3rd conveying apparatus 5c conveys the said steel materials to the charging port of the preheating furnace 3, and the said steel materials are inserted into the preheating furnace 3. FIG. Next, the first transport device 5 a transports the preheated steel material extracted from the extraction port of the preheating furnace 3 to the charging port of the heating furnace 2, and the steel material is charged into the heating furnace 2. Finally, the 3rd conveying apparatus 5c carries out the heated steel material extracted from the extraction port of the heating furnace 2 to the apparatus of the next process, for example, a rolling mill, from the said heating apparatus 1. FIG.

  Here, the stock yard X capable of transporting the steel material by the first transport device 5a, the extraction port of the preheating furnace 3, the charging port of the heating furnace 2, and the third transport device 5c are arranged in this order along the transport direction of the first transport device 5a. It may be arranged. Moreover, the 2nd conveying apparatus 5b which can convey steel materials with the 3rd conveying apparatus 5c, the extraction port of the heating furnace 2, the charging port of the preheating furnace 3, and the steel material carrying-out port of the said heating apparatus 1 are the conveyance directions of the 2nd conveying apparatus 5b. It is good to arrange | position in this order along. By arranging in this way, for example, the direction in which the steel material is conveyed from the stock yard X to the second conveying device 5b coincides with the direction in which the steel material is charged from the extraction port of the preheating furnace 3 into the charging port of the heating furnace 2. Therefore, the 1st conveying apparatus 5a, the 2nd conveying apparatus 5b, and the 3rd conveying apparatus 5c can be set as the simple structure which conveys steel materials in the same direction. Moreover, since the conveyance direction of steel materials is the same, the said heating apparatus 1 can process steel materials continuously. In addition, when the 1st conveying apparatus 5a, the 2nd conveying apparatus 5b, and the 3rd conveying apparatus 5c can convey in both directions, it is not limited to the above-mentioned arrangement | positioning.

  The transport device is not particularly limited, and a known transport device such as a roller conveyor can be used.

<Exhaust gas flow rate adjustment valve>
The first exhaust gas flow rate adjustment valve 8a mainly adjusts the flow rate of exhaust gas supplied to the first exhaust gas flow path 6a. The second exhaust gas flow rate adjustment valve 8b mainly adjusts the flow rate of exhaust gas supplied to the second exhaust gas flow path 6b. By adjusting the opening / closing amounts of the first exhaust gas flow rate adjustment valve 8a and the second exhaust gas flow rate adjustment valve 8b, the heating device 1 accurately adjusts the exhaust gas flow rate supplied to the preheating furnace 3 and the heat exchanger 4. Can do. The adjustment of the opening / closing amount is performed by the control mechanism 15 described later.

  The exhaust gas flow rate adjustment valve is not particularly limited, and for example, a known damper or the like can be used.

  Further, the first exhaust gas flow rate adjustment valve 8a may be able to shut off the exhaust gas supplied to the preheating furnace 3. Thus, the heating apparatus 1 can supply the entire amount of exhaust gas to the heat exchanger 4 by shutting off the exhaust gas supplied to the preheating furnace 3 by the first exhaust gas flow rate adjustment valve 8a. For this reason, for example, when the steel material is not charged into the preheating furnace 3 and it is not necessary to supply exhaust gas to the preheating furnace 3, the energy efficiency of the heating device 1 is obtained by supplying the entire amount of exhaust gas to the heat exchanger 4. Can be enhanced.

<Fuel gas flow control valve>
The fuel gas flow rate adjustment valve 10 adjusts the flow rate of the fuel gas flowing into the heating furnace 2. The heating device 1 can adjust the temperature of the steel material extracted from the heating furnace 2 by adjusting the degree of opening and closing of the fuel gas flow rate adjusting valve 10. The adjustment of the opening / closing amount is performed by the control mechanism 15 described later.

  The fuel gas flow rate adjustment valve 10 is not particularly limited, and for example, a known damper or the like can be used.

<Bypass flow control valve>
The bypass flow rate adjustment valve 13 adjusts the flow rate of combustion air that bypasses the heat exchanger 4. With this bypass flow rate adjustment valve 13, the heating device 1 can flow a part of the combustion air to the bypass flow path 12.

  The bypass flow rate adjusting valve 13 is not particularly limited, and for example, a known damper or the like can be used.

  Further, the bypass flow rate adjusting valve 13 may be able to block the combustion air to be bypassed by the bypass flow path 12. By blocking the combustion air that is bypassed to the bypass flow path 12 in this way, the entire amount of combustion air can be supplied to the heat exchanger 4. For this reason, for example, when the temperature of the exhaust gas does not become the acid dew point temperature or less after the heat transfer to the combustion air, the entire amount of the combustion air is supplied to the heat exchanger 4 to increase the energy efficiency of the heating device 1. It is done.

<Measurement device>
The measuring instrument 14 includes the weight meter, the thermometer, and the flow meter described above, the weight M1 of the steel material charged into the preheating furnace 3, the weight M2 of the steel material charged into the heating furnace 2, and the temperature of the steel material before heating. T1, temperature T2 of the steel material after preheating, temperature T3 of exhaust gas exhausted from the preheating furnace 3, temperature T4 of exhaust gas exhausted from the heat exchanger 4, temperature T5 of exhaust gas exhausted from the heating furnace 2, heating The temperature T6 of the later steel material, the flow rate QF of the fuel supplied to the heating furnace 2, and the flow rate QA of the combustion air flowing into the heat exchanger 4 are measured. The measurement result of the measuring instrument 14 is sent to the control mechanism 15 described later.

  As a scale for measuring the weight M1 of the steel material charged into the preheating furnace 3 and the weight M2 of the steel material charged into the heating furnace 2, for example, a known load cell can be used. Further, the measurement position of the weight M1 of the steel material charged into the preheating furnace 3 is not particularly limited as long as it is before the steel material is charged into the preheating furnace 3, but for example, the position of the preheating furnace 3 of the third transport device 5c is not limited. Can be done before loading. Although the measurement position of the weight M2 of the steel material charged into the heating furnace 2 is not particularly limited as long as it is before the steel material is charged into the heating furnace 2, for example, the inlet of the heating furnace 2 of the first transport device 5a You can do this.

  The temperature T1 of the steel material before heating, the temperature T2 of the steel material after preheating, the temperature T3 of the exhaust gas exhausted from the preheating furnace 3, the temperature T4 of the exhaust gas exhausted from the heat exchanger 4, and the exhaust gas exhausted from the heating furnace 2 For example, a known radiation thermometer can be used as a thermometer for measuring the temperature T5 of the exhaust gas. Moreover, the measurement position of the temperature T1 of the steel material before heating is not particularly limited. For example, it can be the downstream side of the steel material extraction port from the stock yard X of the first transport device 5a. Although the measurement position of temperature T2 of the steel material after preheating is not specifically limited, For example, it can be made in the downstream of the extraction port of the preheating furnace 3 of the 1st conveying apparatus 5a. Although the measurement position of the temperature T3 of the exhaust gas exhausted from the preheating furnace 3 is not particularly limited, for example, it can be downstream of the exhaust gas exhaust port of the preheating furnace 3 in the third exhaust gas flow path 6c. Although the measurement position of the temperature T4 of the exhaust gas exhausted from the heat exchanger 4 is not particularly limited, for example, it can be downstream of the exhaust gas exhaust port of the heat exchanger 4 in the fourth exhaust gas channel 6d. The measurement position of the temperature T5 of the exhaust gas exhausted from the heating furnace 2 is not particularly limited. For example, it can be on a straight line connecting the outlets of the exhaust gas to the first exhaust gas channel 6a and the second exhaust gas channel 6b. Although the measurement position of temperature T6 of the steel material after a heating is not specifically limited, For example, it can be made into the downstream of the extraction port of the heating furnace 2 of the 3rd conveying apparatus 5c.

  As a flow meter for measuring the flow rate QF of the fuel supplied to the heating furnace 2 and the flow rate QA of the combustion air flowing into the heat exchanger 4, for example, a known electromagnetic flow meter or the like can be used. The measurement position of the flow rate QF of the fuel supplied to the heating furnace 2 is not particularly limited, but can be, for example, the upstream side of the fuel gas flow rate adjustment valve 10 in the fuel gas flow path 9. The measurement position of the flow rate QA of the combustion air flowing into the heat exchanger 4 is not particularly limited, but can be, for example, the upstream side of the heat exchanger 4 in the combustion air flow path 11.

<Control mechanism>
Based on the measurement result of the measuring device 14, the control mechanism 15 is configured to adjust the exhaust gas flow rate adjusting mechanism, that is, the above-described exhaust gas flow rate adjusting mechanism, that is, the above-described exhaust gas flow rate adjusting mechanism, that is, the above-described temperature range. The exhaust gas flow rate ratio supplied to the preheating furnace 3 and the heat exchanger 4 is controlled so that the energy efficiency is maximized using the exhaust gas flow rate adjustment valve.

ここで、Ｃ_{ｐ−ａｉｒ}は空気の比熱［Ｊ／ｋｇ／Ｋ］を意味し、Ｃ_ｐ−ｅｘは排ガスの比熱［Ｊ／ｋｇ／Ｋ］を意味する。また、Ｃ_{ｐ−ｓｔｅｅｌ}は鋼材の比熱［Ｊ／ｋｇ／Ｋ］を意味する。これらは、それぞれ鋼材や燃料ガス等の種類に依存した定数である。また、Ｑ_{ｅｘ−ａｉｒ}が熱交換器４に供給される排ガスの流量［Ｎｍ^３／ｈ］、Ｑ_{ｅｘ−ｓｔｅｅｌ}が予熱炉３に供給される排ガスの流量［Ｎｍ^３／ｈ］を表す。この排ガスの流量Ｑ_{ｅｘ−ａｉｒ}及びＱ_{ｅｘ−ｓｔｅｅｌ}は燃焼用空気の流量ＱＡ、燃料ガスの流量ＱＦ及び排ガス流量調整弁の開閉量により決まる量である。また、Ｔ_ａｉｒは、予熱後の燃焼用空気の温度［℃］を意味する。なお、上式では予熱前の燃焼用空気の温度として２５℃を想定しているが、この温度は操業条件等に応じ適宜適切な温度に変更可能である。また、上式では予熱炉３へ装入する鋼材の選択温度として１００℃を想定しており、Ｔ１（＜１００℃）とは、加熱前の鋼材の温度が１００℃未満である鋼材に対してのみ演算を行うことを意味する。この予熱炉３へ装入する鋼材の選択温度は操業条件等に応じ適宜適切な温度に変更可能である。 Specifically, first, assuming the flow rate ratio of a certain exhaust gas, the predicted exhaust gas temperature of the preheating furnace 3 and the predicted exhaust gas temperature of the heat exchanger 4 are calculated. For calculating the predicted temperature, the following calculation formula (1) for calculating the energy efficiency η1 of the heat exchanger 4 and calculation formula (2) for calculating the energy efficiency η2 of the preheating furnace 3 are used.

Here, C _p-air means the specific heat of air [J / kg / K], and C _p-ex means the specific heat of exhaust gas [J / kg / K]. C _p-steel means the specific heat [J / kg / K] of the steel material. These are constants depending on the types of steel materials, fuel gas, and the like. Q _ex-air represents the flow rate [Nm ³ / h] of the exhaust gas supplied to the heat exchanger 4, and Q _ex-steel represents the flow rate [Nm ³ / h] of the exhaust gas supplied to the preheating furnace 3. The exhaust gas flow rates Q _ex-air and Q _ex-steel are determined by the combustion air flow rate QA, the fuel gas flow rate QF, and the exhaust gas flow rate adjustment valve opening / closing amount. T _air means the temperature [° C.] of the combustion air after preheating. In the above equation, the temperature of the combustion air before preheating is assumed to be 25 ° C., but this temperature can be appropriately changed to an appropriate temperature according to the operating conditions. In the above formula, 100 ° C. is assumed as the selected temperature of the steel material to be charged into the preheating furnace 3, and T1 (<100 ° C.) is a steel material whose temperature before heating is less than 100 ° C. It means that only the operation is performed. The selection temperature of the steel material to be charged into the preheating furnace 3 can be appropriately changed to an appropriate temperature according to the operation conditions.

More specifically, the predicted temperature of the exhaust gas from the preheating furnace 3 and the predicted temperature of the exhaust gas from the heat exchanger 4 are calculated by obtaining the values of T3 and T4 using the equations (1) and (2). Here, for the weight M1 of the steel material charged into the preheating furnace 3, the temperature T2 of the steel material after preheating, and the temperature T5 of the exhaust gas exhausted from the heating furnace 2, the measurement results measured by the measuring device are used. Further, the flow rate QF of the fuel supplied to the heating furnace 2 and the flow rate QA of the combustion air flowing into the heat exchanger 4 necessary for calculating Q _ex-air and Q _ex-steel are also measured by the measuring device. Is used. Moreover, although the measurement result of a measuring device may be used for the temperature T1 of the steel material before a heating and the temperature T2 of the steel material after a preheating, the temperature (fixed value) assumed from operating conditions may be used. As the energy efficiency η1 of the heat exchanger 4, the energy efficiency η2 of the preheating furnace 3, and the temperature T _air of the combustion air after preheating, energy efficiency and temperature assumed from the operating conditions (both are fixed values) are used. In practice, when the flow rate ratio is changed and the flow rate Q _ex-air or Q _ex-steel of the exhaust gas is changed, the temperature of T2 or T _air changes. Therefore, it is preferable to obtain a convergent solution by repeatedly calculating the above equations (1) and (2). By obtaining the convergence solution in this way, the calculation accuracy of T3 and T4 is improved.

ここで、Ｈ_{ｖ−ｆｕｅｌ}は燃料ガスの単位体積当たりの発熱量［Ｊ／ｍ^３］を意味し、燃料ガスの種類に依存した固定値である。なお、上式では鋼材の加熱後の温度として１２００℃を想定しているが、上式は、適宜所望の加熱温度に変更して用いることができる。また、Ｔ１（≧１００℃）とは、加熱前の鋼材の温度が１００℃以上である鋼材に対して演算を行うことを意味する。 Next, the energy efficiency R of the entire heating device 1 is calculated. For calculating the energy efficiency R, the following formula (3) for calculating the energy efficiency R of the entire heating device 1 is used.

Here, H _v-fuel means the calorific value [J / m ³ ] per unit volume of the fuel gas, and is a fixed value depending on the type of the fuel gas. In addition, although the above formula assumes 1200 degreeC as the temperature after heating of steel materials, the above formula can be changed to a desired heating temperature as appropriate. Further, T1 (≧ 100 ° C.) means that a calculation is performed on a steel material in which the temperature of the steel material before heating is 100 ° C. or higher.

  More specifically, the energy efficiency R is defined by the weight M1 of the steel material charged into the preheating furnace 3, the weight M2 of the steel material charged into the heating furnace 2, the temperature T1 of the steel material before heating, and the steel material after preheating. It can be calculated by substituting the temperature T2 and the flow rate QF of the fuel supplied to the heating furnace 2 into the above equation (3). As these weight and temperature, the weight and temperature measured by a measuring instrument can be used.

Moreover, in said Formula (3), although energy efficiency R was computed based on the calorie | heat amount which the steel materials obtained by preheating and heating, the exhaust gas sensible heat used effectively and the calorie | heat amount which the steel materials obtained by preheating and heating are equal. The energy efficiency R may be calculated by the following formula (4) using what is considered.

  The control mechanism 15 calculates the predicted temperature of the exhaust gas of the preheating furnace 3 and the predicted temperature of the exhaust gas of the heat exchanger 4 and the energy efficiency by changing the flow rate ratio. From these calculation results, the control mechanism 15 maximizes the energy efficiency R of the heating device 1 within a range where the predicted temperature of the exhaust gas from the preheating furnace 3 and the predicted temperature of the exhaust gas from the heat exchanger 4 do not fall below the acid dew point temperature. As described above, the open / close amount of the exhaust gas flow rate adjustment valve is adjusted. The acid dew point temperature is usually 140 ° C. or higher and 160 ° C. or lower, although it depends on the humidity etc. contained in the exhaust gas.

  In addition, “adjusting the exhaust gas flow ratio supplied to the preheating furnace and heat exchanger so that the energy efficiency is maximized” means that the exhaust gas flow ratio relative to the theoretical value of the exhaust gas flow ratio at which the energy efficiency is maximized. Is to adjust the exhaust gas flow rate ratio so as to be within a certain difference. The upper limit of the difference between the exhaust gas flow rate ratio adjusted by the control mechanism 15 and the theoretical value is preferably 10% and more preferably 5%. When the difference exceeds the upper limit, energy efficiency may be insufficient. On the other hand, the lower limit of the difference is not particularly limited and is 0%.

  The method of searching for the flow rate ratio at which the energy efficiency R is maximized by changing the flow rate ratio is not particularly limited. For example, a plurality of ratios of the exhaust gas flow rate supplied to the preheating furnace to the overall exhaust gas flow rate are set discretely. A method of approximating the energy efficiency R as a polynomial function of the flow rate ratio from the calculation result of the energy efficiency R at the flow rate ratio and calculating the flow rate ratio at which the function becomes maximum can be used. Further, the flow rate ratio at which the energy efficiency R is maximized may be calculated by a known convergence calculation such as a binary tree search.

  Further, the control mechanism 15 controls the exhaust gas temperature so that the exhaust gas exhausted from the preheating furnace 3 becomes equal to or higher than a predetermined temperature by selecting a steel material to be charged into the preheating furnace 3. Specifically, the control mechanism 15 directly heats the preheating furnace 3 without charging the steel material when the exhaust gas temperature T3 of the preheating furnace 3 measured by the thermometer is lowered to, for example, less than the acid dew point temperature. The steel material is charged into the furnace 2. Alternatively, the control mechanism 15 may adjust the opening / closing amount of the exhaust gas flow rate adjustment valve so that the exhaust gas temperature T3 of the preheating furnace 3 is equal to or higher than the acid dew point temperature, and the selection of the steel material charged into the preheating furnace 3 and the above. Both the adjustment of the exhaust gas flow rate may be performed.

  In this way, the control mechanism 15 is provided with a mechanism for controlling the exhaust gas temperature so that the exhaust gas exhausted from the preheating furnace 3 becomes equal to or higher than the acid dew point temperature. Damage can be suppressed.

  Further, the control mechanism 15 controls the exhaust gas temperature so that the exhaust gas exhausted from the heat exchanger 4 becomes a predetermined temperature or more by flowing a part of the combustion air to the bypass passage 12. Specifically, when the exhaust gas temperature T4 of the heat exchanger 4 measured by the thermometer is lowered to, for example, less than the acid dew point temperature, the control mechanism 15 adjusts the opening / closing amount of the bypass flow rate adjustment valve 13 to bypass The amount of combustion air flowing through the flow path 12 is increased. Alternatively, the control mechanism 15 may adjust the open / close amount of the exhaust gas flow rate adjustment valve so that the exhaust gas temperature T3 of the preheating furnace 3 is equal to or higher than the acid dew point temperature, or the amount of combustion air flowing into the bypass passage 12 You may perform both adjustment and adjustment of the said exhaust gas flow volume.

  Thus, by providing a mechanism for controlling the exhaust gas temperature so that the exhaust gas exhausted from the heat exchanger 4 becomes equal to or higher than the acid dew point temperature, it is possible to suppress deterioration and damage of equipment such as the heat exchanger 4 due to acid dew point corrosion. .

  Further, the control mechanism 15 controls the fuel gas flow rate by using the fuel gas flow rate adjusting mechanism so that the temperature of the heated steel material is within a predetermined range. Specifically, when the temperature T6 of the steel material after heating measured by the thermometer is lowered to a desired temperature, for example, less than 1200 ° C., the control mechanism 15 adjusts the opening / closing amount of the fuel gas flow rate adjustment valve 10. The amount of the fuel gas flowing through the fuel gas passage 9 is increased. On the other hand, when the temperature T6 of the steel material after heating measured by the thermometer exceeds a desired temperature, the control mechanism 15 adjusts the opening / closing amount of the fuel gas flow rate adjusting valve 10 and flows through the fuel gas flow path 9. Reduce the amount of fuel gas.

  By adjusting the opening / closing amount of the fuel gas flow rate adjusting valve 10 in this way, the temperature of the steel material extracted from the heating furnace 2 is desired even when the exhaust gas flow rate ratio supplied to the preheating furnace 3 and the heat exchanger 4 changes. The temperature can be adjusted. For this reason, the said heating apparatus 1 can operate stably, improving energy efficiency.

  Moreover, the control mechanism 15 is provided with the mechanism which selects the steel materials inserted into the preheating furnace 3 with the temperature T1 of the steel materials before a heating. Specifically, based on the measurement result of a thermometer that measures the temperature T1 of the steel material before heating, when the temperature T1 of the steel material before heating is less than a predetermined temperature, the steel material is charged into the preheating furnace 3 and before heating. When the temperature T1 of the steel material is equal to or higher than the predetermined temperature, the control mechanism 15 controls the first transport device 5a so that the steel material is directly inserted into the heating furnace 2 without passing through the preheating furnace 3. When a steel material having a relatively high temperature before heating is charged into the preheating furnace 3, the temperature difference between the exhaust gas temperature and the steel material is small, so the heat transfer efficiency from the exhaust gas to the steel material is reduced. For this reason, in order to collect | recover sensible heat of a fixed quantity of waste gas, compared with the case where the temperature of the steel materials before a heating is low, it is necessary to make steel materials stay in a preheating path long, and productivity falls. Therefore, by selecting the steel material to be charged into the preheating furnace 3 depending on the temperature of the steel material before heating, the reduction in productivity can be suppressed and the fuel consumption rate can be reduced.

  The upper limit of the temperature serving as a reference for selecting whether or not the steel material is charged into the preheating furnace 3 is preferably 200 ° C, and more preferably 150 ° C. When the reference temperature exceeds the upper limit, it is necessary to make the steel material stay in the preheating furnace 3 long in order to recover the sensible heat of the exhaust gas, which may reduce productivity. On the other hand, the lower limit of the reference temperature is not particularly limited.

<Method of heating steel>
The method for heating a steel material using the heating device 1 includes a step of preheating the steel material with a preheating furnace, a step of heating the steel material with a heating furnace, and a step of adjusting the flow rate of the exhaust gas.

  In the preheating process, the steel material is preheated. Specifically, first, a steel material is extracted from the stockyard X using a transport device, and charged into a preheating furnace. Next, the steel material charged in the preheating furnace is preheated with exhaust gas. Finally, the preheated steel is extracted from the extraction port of the preheating furnace.

  In the heating step, the steel material is heated. Specifically, first, the steel material after preheating or the steel material extracted from the stockyard X is charged into a heating furnace using a transport device. Next, the steel material charged in the heating path is heated by the combustion gas ejected from the burner. Finally, the heated steel material is extracted from the extraction port of the heating furnace, and is transported from the heating device 1 to the next process device, for example, a rolling mill.

  In the exhaust gas flow rate adjustment step, the flow rate of the exhaust gas is adjusted by the control mechanism 15. As shown in FIG. 2, the exhaust gas flow rate adjusting step includes a step (S1) of selecting a steel material to be charged into the preheating furnace based on the temperature of the steel material before heating, and the preheating furnace so that the energy efficiency is maximized. And adjusting the exhaust gas flow ratio supplied to the heat exchanger (S2), and adjusting the exhaust gas temperature so that the exhaust gas exhausted from the preheating furnace becomes a predetermined temperature or more by selecting the steel material to be charged into the preheating furnace. A step (S3) of adjusting the exhaust gas temperature so that the exhaust gas exhausted from the heat exchanger becomes a predetermined temperature or more by flowing a part or all of the combustion air to the bypass flow path (S4) And a step (S5) of adjusting the fuel gas flow rate so that the temperature of the heated steel material is within a predetermined range.

  First, in the charging selection step (S1) of the steel material to the preheating furnace, the steel material selection mechanism of the control mechanism 15 loads the steel material into the heating furnace 2 without passing through the preheating furnace 3 based on the temperature T1 of the steel material before heating. Select whether or not to enter.

  Next, in the exhaust gas flow rate ratio adjusting step (S2), the exhaust gas flow rate control mechanism of the control mechanism 15 performs the predicted temperature of the exhaust gas of the preheating furnace 3 and the predicted temperature of the exhaust gas of the heat exchanger 4 based on the measurement result of the measuring device. Is calculated. Based on this calculation result, the control mechanism 15 further calculates a flow rate ratio at which the predicted temperature is higher than the acid dew point temperature and the energy efficiency is maximized. Then, the open / close amount of the exhaust gas flow rate adjustment valve is adjusted so that the calculated flow rate ratio is obtained.

  Next, in the exhaust gas temperature adjustment step (S3) of the preheating furnace, the steel material passes through the preheating furnace 3 based on the exhaust gas temperature T3 of the preheater 3 by the control mechanism of the exhaust gas temperature exhausted from the preheater 3 of the control mechanism 15. Whether or not to insert into the heating furnace 2 is selected. Specifically, when the exhaust gas temperature T3 of the preheating furnace 3 measured by the thermometer is lowered to, for example, less than the acid dew point temperature, the control mechanism 15 does not charge the preheating furnace 3 with the steel material and directly heats the furnace. Charge steel material to 2. As a result, the sensible heat recovered from the exhaust gas to the steel material in the preheating furnace 3 is reduced, so that the temperature of the exhaust gas exhausted from the preheating furnace 3 is increased. Therefore, the exhaust gas temperature T3 can be adjusted to be equal to or higher than the acid dew point temperature.

  Next, in the exhaust gas temperature adjusting step (S4) of the heat exchanger, the bypass flow rate adjusting valve is controlled based on the exhaust gas temperature T4 of the heat exchanger 4 by the exhaust gas temperature control mechanism exhausted from the heat exchanger 4 of the control mechanism 15. The opening / closing amount of 13 is adjusted. As a result, the control mechanism 15 adjusts the amount of combustion air flowing through the bypass passage 12. Specifically, when the exhaust gas temperature T4 of the heat exchanger 4 measured by the thermometer is lowered to, for example, less than the acid dew point temperature, the amount of combustion air flowing through the bypass passage 12 is increased by the control mechanism 15. . As a result, the sensible heat recovered from the exhaust gas into the combustion air by the heat exchanger 4 is reduced, so that the temperature of the exhaust gas exhausted from the heat exchanger 4 is increased. Therefore, the exhaust gas temperature exhausted from the heat exchanger 4 can be adjusted to be equal to or higher than the acid dew point temperature.

  Next, in the fuel gas flow rate adjustment step (S5), the amount of fuel gas supplied to the fuel gas flow path 9 is adjusted by the opening / closing amount adjustment mechanism of the fuel gas flow rate adjustment valve 10 of the control mechanism 15. Specifically, when the temperature of the steel material after heating is lower than a predetermined temperature, the amount of the fuel gas is increased by the control mechanism 15, and when the temperature of the steel material after heating is higher than the predetermined temperature, the control mechanism 15 Reduce the amount.

  The steps from the exhaust gas flow rate ratio adjusting step (S2) to the fuel gas flow rate adjusting step (S5) are performed each time the steel material is charged into the preliminary furnace 3 and the heating furnace 2.

<Advantages>
The heating device 1 can distribute and supply the exhaust gas exhausted from the heating furnace through the first exhaust gas channel 6 a and the second exhaust gas channel 6 b to the preheating gas of the preheating furnace 3 and the preheating gas of the heat exchanger 4. For this reason, since the said heating apparatus 1 can collect | recover the sensible heat of preheating gas with each of the preheating furnace 3 and the heat exchanger 4, compared with the case where it collects in either the preheating furnace 3 or the heat exchanger 4, many. The sensible heat of the preheated gas can be recovered. Further, since the heating device 1 supplies the exhaust gas exhausted from the heating furnace 2 in parallel to the preheating furnace 3 and the heat exchanger 4, the preheating is performed without greatly reducing the temperature of the exhaust gas exhausted from the heating furnace 2. A preheating gas can be supplied to the furnace 3 and the heat exchanger 4. For this reason, since the said heating apparatus 1 is easy to ensure the temperature difference of the supplied preheating gas, steel materials, and combustion air, the heat transfer efficiency from preheating gas to steel materials and combustion air is good. Therefore, the heating device 1 has high energy efficiency.

[Second Embodiment]
2 includes two heating furnaces (first heating furnace 2a and second heating furnace 2b), two preheating furnaces (first preheating furnace 3a and second preheating furnace 3b), and two heating furnaces. A heat exchanger (a first heat exchanger 4a and a second heat exchanger 4b). The exhaust gas exhausted from the first heating furnace 2a is supplied to the first preheating furnace 3a and the first heat exchanger 4a, and the combustion air preheated by the first heat exchanger 4a is supplied to the first heater 2a. Is done. The exhaust gas exhausted from the second heating furnace 2b is supplied to the second preheating furnace 3b and the second heat exchanger 4b, and the combustion air preheated by the second heat exchanger 4b is supplied to the second heater 2b. To be supplied.

  In addition, the heating device 20 includes exhaust gas flow rate adjustment valves (first exhaust gas flow rate adjustment valve 8c and second exhaust gas flow rate adjustment valve 8d) that respectively adjust the flow rates of exhaust gas supplied to the two preheating furnaces. The first exhaust gas flow rate adjusting valve 8c is disposed in the first exhaust gas flow path 6a that distributes and supplies the exhaust gas from the first heating furnace 2a to the first preheating furnace 3a. The second exhaust gas flow rate adjusting valve 8d is disposed in the first exhaust gas passage 6a that distributes and supplies the exhaust gas from the second heating furnace 2b to the second preheating furnace 3b.

  Further, the heating device 20 includes a weighing scale 21a for measuring the weight M11 of the steel material charged into the first preheating furnace 3a, a weighing scale 21b for measuring the weight M12 of the steel material charged into the second preheating furnace 3b, A weigh scale 21c for measuring the weight M21 of the steel material charged into the first heating furnace 2a, a weigh scale 21d for measuring the weight M22 of the steel material charged into the second heating furnace 2b, and a temperature T1 of the steel material before heating. A thermometer 21e for measuring, a thermometer 21f for measuring the temperature T21 of the steel material after preheating in the first preheating furnace 3a, a thermometer 21g for measuring the temperature T22 of the steel material after preheating in the second preheating furnace 3b, the first A thermometer 21h for measuring the temperature T31 of the exhaust gas exhausted from the preheating furnace 3a, a thermometer 21i for measuring the temperature T32 of the exhaust gas exhausted from the second preheating furnace 3b, and the exhaust gas exhausted from the first heat exchanger 4a Measure temperature T41 Thermometer 21j, thermometer 21k for measuring the temperature T42 of the exhaust gas exhausted from the second heat exchanger 4b, thermometer 21l for measuring the temperature T51 of the steel material charged into the first heating furnace 2a, the second heating furnace A thermometer 21m for measuring the temperature T52 of the steel material charged into 2b, a flow meter 21n for measuring the flow rate QF1 of the fuel supplied to the first heating furnace 2a, and a flow rate QF2 of the fuel supplied to the second heating furnace 2b A flow meter 21o, a flow meter 21p for measuring the flow rate QA1 of the combustion air flowing into the first heat exchanger 4a, and a flow meter 21q for measuring the flow rate QA2 of the combustion air flowing into the second heat exchanger 4b. Prepare. Moreover, the said heating apparatus 20 is provided with the control mechanism 22 which adjusts the opening-and-closing amount of the said waste gas flow rate adjustment valve based on the measurement result of the said weight meter, a thermometer, and a flow meter.

  Since the transfer device, the exhaust gas flow channel, the chimney 7, the fuel gas flow channel 9, and the combustion air flow channel 11 are the same as those of the heating device 1 of the first embodiment, the same reference numerals are given and description thereof is omitted. Moreover, about each heating furnace, a preheating furnace, and a heat exchanger, since it is the same as that of the heating furnace 2, the preheating furnace 3, and the heat exchanger 4 of the heating apparatus 1 of 1st Embodiment, description is abbreviate | omitted.

<Measurement device>
The measuring instrument measures the above-mentioned amount with a weight meter, a thermometer and a flow meter. The measurement result of the measuring device is sent to the control mechanism 22 described later. The weighing instrument, the thermometer, and the flow meter can be the same as the measuring instrument of the first embodiment.

  The measurement position of the temperature T51 of the steel material charged into the first heating furnace 2a can be the upstream side of the charging inlet of the first heating furnace 2a of the first transfer device 5a. Further, the measurement position of the temperature T52 of the steel material charged into the second heating furnace 2b can be the upstream side of the inlet of the second heating furnace 2b of the first transfer device 5a. The measurement positions of the temperature, weight and flow rate other than the temperatures T51 and T52 of the steel material charged into the heating furnace 2 can be the same as the measurement positions of the measuring instrument of the first embodiment.

<Control mechanism>
The control mechanism 22 includes a mechanism for selecting a steel material to be charged into the preheating furnace 3 based on the temperature T1 of the steel material before heating. Specifically, based on the measurement result of the measuring device 21 that measures the temperature T1 of the steel material before heating, when the temperature T1 of the steel material before the heating is less than a predetermined temperature by the control mechanism 22, the steel material passes through the preheating furnace. Charged into the furnace. When the temperature T1 of the steel material before heating is equal to or higher than the predetermined temperature, the first transport device 5a is controlled so that the steel material is directly charged into the heating furnace without passing through the preheating furnace. The steel material charged in the preheating furnace is preheated in the first preheating furnace 3a, and then charged in the second preheating furnace 3b and further preheated. On the other hand, the preheated steel material or the steel material that does not pass through the preheating furnace is charged into either the first heating furnace 2a or the second heating furnace 2b.

  The control mechanism 22 includes a mechanism for controlling the exhaust gas flow rate ratio supplied to the preheating furnace and the heat exchanger by adjusting the opening / closing amount of the exhaust gas flow rate adjustment valve based on the measurement result of the measuring device 21. Specifically, the calculation of the energy efficiency of the heat exchanger 4 described in the first embodiment for the first preheating furnace 3a, the second preheating furnace 3b, the first heat exchanger 4a, and the second heat exchanger 4b. Equation (1) and the calculation formula (2) of the energy efficiency of the preheating furnace 3 are combined, and a sequential acceleration relaxation method (SOR method: Successive Over Relaxation method) or the like is performed so that the energy efficiency of the entire heating device 20 is maximized. By using the convergence calculation, the opening / closing amount of the exhaust gas flow rate adjustment valve can be determined. In the second embodiment, the measuring device 21 does not measure the temperature of the exhaust gas exhausted from the heating furnace 2. In this case, as the temperatures T51 and T52 of the exhaust gas exhausted from the heating furnace used in the calculation formulas (1) and (2), temperatures (fixed values) assumed from the operation conditions are used. For example, the temperatures T51 and T52 of the exhaust gas exhausted from the heating furnace can be 800 ° C. when the heating temperature of the steel material is 1200 ° C.

<Method of heating steel>
Heating of the steel material using the heating device 20 can be performed by a heating method including a step of preheating the steel material with a preheating furnace, a step of heating the steel material with a heating furnace, and a step of adjusting the flow rate of the exhaust gas. Since the preheating step and the heating step are the same as the preheating step and the heating step in the first embodiment, description thereof will be omitted.

  In the exhaust gas flow rate adjusting step, the flow rate of the exhaust gas is adjusted by the control mechanism 22. This exhaust gas flow rate adjustment process includes a charging selection process of a steel material to a preheating furnace and an exhaust gas flow rate ratio adjustment process.

  First, in the charging selection process of the steel material to the preheating furnace, whether the steel material is charged into the heating furnace without passing through the preheating furnace based on the temperature T1 of the steel material before heating by the steel material selection mechanism of the control mechanism 22. Select.

  Next, in the exhaust gas flow ratio adjustment step, the exhaust gas flow rate control mechanism of the control mechanism 22 calculates the predicted temperature of the exhaust gas of the preheating furnace and the predicted temperature of the exhaust gas of the heat exchanger based on the measurement result of the measuring device. Based on this calculation result, the control mechanism 22 further calculates a flow rate ratio at which the predicted temperature is higher than the acid dew point temperature and the energy efficiency is maximized. Then, the open / close amount of the exhaust gas flow rate adjustment valve is adjusted so that the calculated flow rate ratio is obtained.

<Advantages>
Since the said heating apparatus 20 uses the two heating furnaces 2, the preheating furnace 3, and the heat exchanger 4, and controls the flow rate ratio of each waste gas, energy efficiency can further be improved.

[Other Embodiments]
The heating device of the present invention is not limited to the above embodiment.

  In the above embodiment, the case where the control mechanism includes a mechanism for selecting a steel material to be charged into the preheating furnace according to the temperature of the steel material before heating has been described, but this selection mechanism is not an essential configuration and can be omitted. When this selection function is omitted, for example, all the steel material extracted from the stockyard is charged into the preheating furnace. Moreover, when abbreviate | omitting the said selection mechanism, the thermometer which measures temperature T1 of the steel materials before a heating can be abbreviate | omitted.

  Moreover, the said heating apparatus may be equipped with the thermometer which measures the temperature of the combustion air after preheating. By measuring the temperature of the combustion air after preheating with the thermometer, the accuracy when adjusting the exhaust gas flow ratio supplied to the preheating furnace and the heat exchanger by the control mechanism is improved.

  In the first embodiment, the method for adjusting the exhaust gas temperature so that the exhaust gas exhausted from the heat exchanger becomes equal to or higher than the predetermined temperature by flowing part of the combustion air to the bypass flow path has been described. A flow control valve capable of shutting off combustion air is provided between the branch of the air flow path to the bypass flow path and the supply port to the heat exchanger, and all of the combustion air is bypassed by shutting off the flow control valve. It is good also as a structure which can be poured into Alternatively, the bypass flow rate adjusting valve may be a three-way valve, and the combustion air inflow destination may be switched to either the combustion air flow path or the bypass flow path.

  Moreover, although the said embodiment demonstrated the case where the mechanism which controls exhaust gas flow ratio was provided, the exhaust gas flow ratio control mechanism is not an essential structural requirement, and can be abbreviate | omitted. When the exhaust gas flow rate control mechanism is omitted, the exhaust gas discharged from the heating furnace at the flow rate ratio determined by the cross-sectional area ratio of the first exhaust gas flow channel and the second exhaust gas flow channel, the operating conditions, etc. Distributed to the heat exchanger. When the exhaust gas flow rate control mechanism is omitted, the exhaust gas flow rate adjusting mechanism, the weigh scale for measuring the weight of the steel material charged into the preheating furnace, or the weigh scale for measuring the weight of the steel material charged into the heating furnace. , A thermometer that measures the temperature of the steel material after preheating, a flow meter that measures the flow rate of fuel supplied to the heating furnace, and a flow meter that measures the flow rate of combustion air flowing into the heat exchanger are omitted. can do.

  In the first embodiment, the case where the exhaust gas flow rate adjustment valve is disposed in the first exhaust gas flow channel and the second exhaust gas flow channel will be described. In the second embodiment, the exhaust gas flow rate adjustment valve is provided in the first exhaust gas flow rate. The case where the exhaust gas flow rate adjustment valve is provided only in the second exhaust gas flow path, and the heating device that does not include the exhaust gas flow rate adjustment valve are also intended by the present invention. .

  Further, the number of preheating furnaces and heating furnaces is not limited to the above embodiment, and there may be three or more. Further, the heating apparatus may have a configuration in which the number of preheating furnaces and the number of heating furnaces are different.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

Example 1
First, the relationship between the steel material temperature before preheating, the amount of heat received by the steel material after preheating, the steel material temperature, and the exhaust gas temperature (outlet exhaust gas temperature) exhausted from the preheating furnace was calculated by simulation in the heating apparatus shown in FIG. At that time, the simulation was performed by setting the temperature of the exhaust gas flowing into the preheating furnace to 800 ° C., the exhaust gas flow rate to 30000 Nm ³ / h, and the steel material flow rate to 175 t / h. In addition, the temperature before preheating of steel materials was made into seven conditions of 25 degreeC or more and 600 degrees C or less. The results are shown in FIG.

Next, the relationship between the exhaust gas flow rate ratio, the exhaust gas temperature exhausted from the preheating furnace and the heat exchanger, and the energy efficiency was calculated by simulation. The simulation was performed by setting the energy efficiency η1 of the heat exchanger to 0.6, the energy efficiency η2 of the preheating furnace to 0.4, the exhaust gas temperature from the heating furnace to 600 ° C., and the flow rate of combustion air to 15 Nm ³ / h. The results are shown in FIG. The flow ratio on the horizontal axis in FIG. 5 is the ratio of the exhaust gas flow rate supplied to the preheating furnace to the total flow rate of exhaust gas supplied to the preheating furnace and the heat exchanger.

  From the result of FIG. 4, the steel material having a lower temperature of the steel material before preheating has a larger amount of heat received by the steel material, and the exhaust gas temperature exhausted from the preheating furnace is lower. From this, it can be seen that the steel material having a low temperature before preheating has a larger temperature difference from the exhaust gas than the steel material having a high temperature before preheating, so that the amount of heat transfer to the steel material increases and the sensible heat can be efficiently recovered. Therefore, by selecting the steel material to be charged into the preheating furnace according to the temperature of the steel material before heating, the recovery of sensible heat of the exhaust gas can be efficiently performed, the reduction in productivity can be suppressed, and the fuel consumption rate can be reduced. it is conceivable that.

  Further, from the result of FIG. 5, the energy efficiency is improved by distributing the exhaust gas exhausted from the heating furnace to the exhaust gas of the preheating furnace and the exhaust gas of the heat exchanger, and the flow rate ratio of the exhaust gas is about 70%. Energy efficiency is maximized. This shows that the energy efficiency can be improved by adjusting the flow rate ratio of the exhaust gas.

  In FIG. 5, if the amount of exhaust gas supplied to the preheating furnace is less than 25%, the exhaust gas temperature of the preheating furnace falls below 150 ° C., and the amount of exhaust gas supplied to the preheating furnace exceeds 90%, that is, the amount of exhaust gas supplied to the heat exchanger. Is less than 10%, the exhaust gas temperature of the heat exchanger falls below 150 ° C. Since the acid dew point temperature is about 150 ° C., it is considered that by adjusting the flow rate ratio of the exhaust gas, it is possible to maximize the energy efficiency and suppress deterioration and damage of the equipment due to the acid dew point corrosion of the exhaust gas.

(Example 2)
In the heating apparatus shown in FIG. 2, necessary input heat amount, exhaust gas flow rate, energy efficiency, and fuel intensity were calculated by simulation. The amount of input heat required here means the amount of heat necessary for heating the steel material to a desired temperature by a heating device.

  The simulation conditions are as follows. The flow rate of the steel material was 400 t / h. Of these steel materials, only steel materials of less than 100 ° C. were charged into the preheating furnace, and steel materials of 100 ° C. or higher were directly charged into the heating furnace. The ratio of steel materials less than 100 ° C. was 50 mass%, the average temperature of steel materials less than 100 ° C. was 25 ° C., and the average temperature of steel materials of 100 ° C. or higher was 350 ° C. Moreover, the temperature of the steel material extracted from the 1st heating furnace and the 2nd heating furnace was 1200 degreeC, and the temperature of the waste gas discharged | emitted was 800 degreeC. 40% by volume of the flow rate of exhaust gas discharged from the first heating furnace was supplied to the first preheating furnace, and the remaining 60% by volume was supplied to the first heat exchanger. Further, 40% by volume of the flow rate of the exhaust gas discharged from the second heating furnace was supplied to the second preheating furnace, and the remaining 60% by volume was supplied to the second heat exchanger. Here, 40% by volume of the flow rate of the exhaust gas supplied to the preheating furnace is a numerical value corresponding to the optimum flow rate ratio calculated by the control mechanism based on the measurement result of the measuring device of the heating device. The steel material charged in the preheating furnace is charged in the order of the second preheating furnace and the first preheating furnace, and then charged in either the first heating furnace or the second heating furnace and heated to 1200 ° C. The The results are shown in Table 1.

(Comparative Example 1)
As heating devices, two heating furnaces (first heating furnace and second heating furnace), two preheating furnaces (first preheating furnace and second preheating furnace), and two heat exchangers (first heat exchanger) And a second heat exchanger), a heating device in which the entire amount of exhaust gas from the first heating furnace is supplied to the first preheating furnace, and the entire amount of exhaust gas from the second heating furnace is supplied to the second preheating furnace. Using. Except that all the steel materials were charged into the preheating furnace and all the exhaust gas from the first heating furnace and the second heating furnace were supplied to the preheating furnace, a simulation was performed under the same conditions as in Example 2, and the necessary input heat amount and exhaust gas The flow rate, energy efficiency, and fuel intensity were calculated. The results are shown in Table 1.

  From the results of Table 1, the heating device of Example 2 has less energy input and fuel consumption than the heating device of Comparative Example 1, and has high energy efficiency. In the heating device of Comparative Example 1, the exhaust gas exhausted from the heating furnace is not distributed and supplied to the exhaust gas of the preheating furnace and the exhaust gas of the heat exchanger, so the amount of heat transfer from the exhaust gas is reduced and the energy efficiency is lowered. It is thought. For this reason, in order to heat steel materials to 1200 degreeC, many calorie | heat amounts are required, and it is thought that the fuel consumption rate rose. On the other hand, since the heating apparatus of Example 2 distributes and supplies the exhaust gas exhausted from the heating furnace to the exhaust gas of the preheating furnace and the exhaust gas of the heat exchanger, the sensible heat of many exhaust gases can be recovered. It is thought that energy efficiency improved by 9 points.

  As described above, the heating device of the present invention can increase the energy efficiency in heating the steel material. Therefore, the fuel consumption rate can be lowered by using the heating device.

1, 20 Heating device 2, 2a, 2b Heating furnace 3, 3a, 3b Preheating furnace 4, 4a, 4b Heat exchangers 5a, 5b, 5c Transport devices 6a, 6b, 6c, 6d Exhaust gas flow path 7 Chimneys 8a, 8b, 8c, 8d Exhaust gas flow rate adjustment valve 9 Fuel gas flow channel 10 Fuel gas flow rate adjustment valve 11 Combustion air flow channel 12 Bypass flow channel 13 Bypass flow rate adjustment valves 14a to 14j, 21a to 21q Measuring instrument (Weigh scale, thermometer, flow rate Total)
15, 22 Control mechanism X Stockyard

Claims (10)

A steel heating device for hot working or heat treatment,
A heating furnace for heating the steel material with combustion gas ejected from a burner;
A preheating furnace for preheating the steel material before being charged into the heating furnace with a preheating gas;
A heat exchanger for preheating combustion air supplied to the burner;
A first exhaust gas passage for supplying exhaust gas discharged from the heating furnace as a preheating gas of the preheating furnace;
A steel material heating apparatus, comprising: a second exhaust gas channel provided in parallel with the first exhaust gas channel and supplying exhaust gas discharged from the heating furnace as a preheating gas of the heat exchanger.   The steel material heating apparatus according to claim 1, further comprising a mechanism for adjusting a flow rate of exhaust gas supplied to the first exhaust gas flow channel and a flow rate of exhaust gas supplied to the second exhaust gas flow channel.   The steel material heating device according to claim 2, wherein the exhaust gas flow rate adjusting mechanism is disposed in the first exhaust gas flow path.   The steel material heating apparatus according to claim 2 or 3, wherein the exhaust gas flow rate adjusting mechanism is disposed in the second exhaust gas flow path. A weigh scale that measures the weight of the steel material charged into the preheating furnace, a weigh scale that measures the weight of the steel material charged into the heating furnace, a thermometer that measures the temperature of the steel material after preheating, and the heating furnace A flow meter for measuring the flow rate of fuel to be supplied, and a flow meter for measuring the flow rate of combustion air flowing into the heat exchanger;
A mechanism for controlling an exhaust gas flow ratio supplied to the preheating furnace and the heat exchanger so that energy efficiency is maximized using the exhaust gas flow rate adjustment mechanism based on the measurement results of the weight meter, the thermometer, and the flow meter; The steel material heating apparatus according to claim 2, 3 or 4, further comprising:   The steel material heating apparatus according to claim 5, further comprising a thermometer for measuring a temperature of exhaust gas exhausted from the heating furnace. A thermometer that measures the temperature of the steel before heating;
The steel material heating apparatus according to any one of claims 1 to 6, further comprising a mechanism for selecting a steel material to be charged into the preheating furnace based on a measurement result of the thermometer. A thermometer for measuring the temperature of the exhaust gas exhausted from the preheating furnace,
A mechanism for controlling an exhaust gas temperature so that an exhaust gas exhausted from the preheating furnace becomes a predetermined temperature or higher by selecting a steel material charged into the preheating furnace based on a measurement result of the thermometer. The steel material heating apparatus according to any one of 7. A bypass passage for combustion air that bypasses the heat exchanger;
A thermometer for measuring the temperature of the exhaust gas exhausted from the heat exchanger;
A mechanism for controlling the exhaust gas temperature so that the exhaust gas exhausted from the heat exchanger becomes equal to or higher than a predetermined temperature by flowing part or all of the combustion air to the bypass flow path based on the measurement result of the thermometer. The steel material heating apparatus according to any one of claims 1 to 8, further comprising: A mechanism for adjusting the flow rate of the fuel gas supplied to the burner;
A steel material according to any one of claims 1 to 9, further comprising a mechanism for controlling the fuel gas flow rate using the fuel gas flow rate adjustment mechanism so that the temperature of the heated steel material is within a predetermined range. Heating device.

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