JP5976585B2 - Heating furnace and heating furnace control method - Google Patents

Heating furnace and heating furnace control method Download PDF

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JP5976585B2
JP5976585B2 JP2013069188A JP2013069188A JP5976585B2 JP 5976585 B2 JP5976585 B2 JP 5976585B2 JP 2013069188 A JP2013069188 A JP 2013069188A JP 2013069188 A JP2013069188 A JP 2013069188A JP 5976585 B2 JP5976585 B2 JP 5976585B2
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heat exchanger
air
temperature
exhaust gas
flue
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JP2014190671A (en
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豊久 真部
豊久 真部
峯　隆夫
隆夫 峯
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Kobe Steel Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Description

本発明は、鋼材を加熱するに際に生じる廃熱を再利用する加熱炉、及び加熱炉における廃熱を効率的に再利用することのできる加熱炉の制御方法に関する。   The present invention relates to a heating furnace that reuses waste heat generated when heating a steel material, and a heating furnace control method that can efficiently reuse waste heat in the heating furnace.

製鋼工程において製造した、スラブ・ビレット・ブルーム等の鋼材（鋳片）を連続圧延して圧延材を製造する熱間圧延工程では、圧延材の元となる鋼材を加熱炉内で加熱し、下流側にある圧延機（粗圧延機、仕上げ圧延機）に送り、連続的に圧延を行う。
ところで、鋼材を加熱炉で加熱するにあたっては、鋼材を加熱炉内に装入して、圧延に適した温度まで昇温させている。炉内雰囲気の昇温は、炉内に備えられている燃焼バーナで行われるものとなっている。鋼材を昇温させた後の熱（廃熱）は、煙道を通過して、外部に排出される。このとき、廃熱が有する熱量は、煙道に備えられた熱交換器で回収されてブロワから送られた空気と熱交換されている。熱交換された空気は、予熱空気の経路を通過して、炉内に備えられた燃焼バーナに予熱空気として送られる。 In a hot rolling process in which a rolled material is produced by continuously rolling steel materials (slabs) such as slabs, billets, and blooms produced in the steelmaking process, the steel material that is the source of the rolled material is heated in a heating furnace, and downstream It is fed to a rolling mill on the side (rough rolling mill, finish rolling mill) and continuously rolled.
By the way, when heating a steel material in a heating furnace, the steel material is charged into the heating furnace and the temperature is raised to a temperature suitable for rolling. The temperature increase in the furnace atmosphere is performed by a combustion burner provided in the furnace. The heat (waste heat) after raising the temperature of the steel material passes through the flue and is discharged outside. At this time, the amount of heat of the waste heat is recovered by the heat exchanger provided in the flue and exchanged with the air sent from the blower. The heat-exchanged air passes through a path of preheated air, and is sent as preheated air to a combustion burner provided in the furnace.

この廃熱が有する熱量を有効に再利用することは、省エネなどの観点から好ましく、加熱炉における廃熱の再利用の技術として、例えば、特許文献１に開示されたものがある。
特許文献１は、被加熱材装入側の左右両側から廃ガスを誘引排出する２系統の煙道を有する連続式加熱炉において、各系統煙道に設置したレキュペレータ入側又は出側の廃ガス温度がレキュペレータの許容温度範囲内にあるときは、炉圧制御系により各煙道のダンパーを併動開閉制御し、上記各煙道のいずれか一方のレキュペレータ入側廃ガス温度が前記許容温度範囲の上限を超えた場合又は、上記各煙道のいずれか一方のレキュペレータ出側廃ガス温度が前記許容温度範囲の下限を下回った場合は、上記各煙道のいずれか一方のダンパーを炉圧制御系により開閉制御し、他方のダンパーを各レキュペレータ間の入側廃ガス温度差又は出側廃ガス温度差に基いて、該上限を超えた廃ガス温度又は下限を下回った廃ガス温度が該許容範囲に入る様に開閉制御することを開示する。つまり、特許文献１には、レキュペレータ（熱交換器）の入側と出側の排出ガスの温度を測定し、その測定したレキュペレータの前後の温度が予め設定した許容温度範囲内であるか否かで煙道のダンパの開閉制御を行う技術が開示されている。 Effectively reusing the amount of heat of the waste heat is preferable from the viewpoint of energy saving and the like, for example, disclosed in Patent Document 1 as a technology for reusing waste heat in a heating furnace.
Patent Document 1 discloses a waste gas on the inlet side or outlet side of a recuperator installed in each system flue in a continuous heating furnace having two systems of flue that induces and discharges waste gas from both the left and right sides of the heated material charging side. When the temperature is within the allowable temperature range of the recuperator, the furnace pressure control system controls the opening and closing of the dampers of each flue, and the waste gas temperature on the recuperator entry side of any one of the above flue is within the allowable temperature range. If the temperature exceeds the upper limit of the above, or if the exhaust gas temperature on the outlet side of the recuperator of any one of the above-mentioned flues falls below the lower limit of the allowable temperature range, the furnace pressure control of any one of the above-mentioned flues The open / close control is performed by the system, and the waste gas temperature exceeding the upper limit or the exhaust gas temperature below the lower limit is allowed to exceed the upper limit based on the difference in the inlet side exhaust gas temperature or the outlet side exhaust gas temperature difference between the recuperators. Go into range Closing control to the disclose. That is, in Patent Document 1, the temperature of the exhaust gas on the inlet side and the outlet side of the recuperator (heat exchanger) is measured, and whether the measured temperature before and after the recuperator is within a preset allowable temperature range. Discloses a technique for controlling the opening and closing of a flue damper.

特公平６−６０３５６号公報Japanese Patent Publication No. 6-60356

従来、加熱炉で圧延材の元となる鋼材を加熱した後の排出ガスは、所定量の熱エネルギを有し、排出ガスが有する熱エネルギを高い効率で取り出して再利用するためには、特許文献１のように何らかの技術が必要となる。
ところが、加熱炉の操業に際しては、長期に亘って操業するにつれて加熱炉の煙道が経年劣化する。煙道が経年劣化すると、煙道内に少量の空気が流入したり（侵入空気）、煙道内を通過する排出ガスの熱量が外部に放出されたり（放散熱）して、煙道内の排出ガスの温度が低下することがあった。特に、加熱炉内の燃焼量が低下した状況下の煙道内では、熱交換器入側で排出ガスの温度が低下し、熱交換器での廃熱回収の効率が悪化してしまう問題があった。 Conventionally, the exhaust gas after heating the steel material that is the source of the rolled material in the heating furnace has a predetermined amount of thermal energy, and in order to take out the thermal energy of the exhaust gas with high efficiency and reuse it, a patent Some technique is required as in Document 1.
However, when the heating furnace is operated, the flue of the heating furnace deteriorates over time as it operates over a long period of time. When the flue deteriorates over time, a small amount of air flows into the flue (intrusion air), or the amount of exhaust gas passing through the flue is released to the outside (radiated heat). The temperature sometimes dropped. In particular, in a flue where the amount of combustion in the heating furnace has decreased, the temperature of the exhaust gas decreases on the inlet side of the heat exchanger, and the efficiency of waste heat recovery in the heat exchanger deteriorates. It was.

しかしながら、特許文献１は、上述したような加熱炉内の燃焼量が低下した場合の侵入空気及び放散熱については全く考慮されていないため、長期間に亘って、煙道の熱交換器において効率的、且つ十分な廃熱回収が行われているか疑問が残る。また、煙道内の排出ガスの温度が低下し熱回収効率が悪化すると、燃焼バーナでの燃料の消費が多くなり、むだに製造コストがかかる虞もある。   However, since Patent Document 1 does not take into consideration the intruding air and the dissipated heat when the combustion amount in the heating furnace as described above is lowered, the efficiency in the heat exchanger of the flue is long-term. The question remains whether or not sufficient waste heat recovery is being performed. Further, if the temperature of the exhaust gas in the flue is lowered and the heat recovery efficiency is deteriorated, the consumption of fuel in the combustion burner increases, and there is a possibility that the manufacturing cost may be increased.

本発明は、上述の問題に鑑み、加熱炉で鋼材を加熱するに際して、煙道内を通過する排出ガスの廃熱を十分、且つ効率的に熱回収することができる加熱炉、及び加熱炉の制御方
法を提供することを目的とする。 In view of the above problems, the present invention provides a heating furnace capable of sufficiently and efficiently recovering waste heat of exhaust gas passing through the flue when heating a steel material in a heating furnace, and control of the heating furnace It aims to provide a method.

上述の目的を達成するため、本発明においては以下の技術的手段を講じた。
すなわち、本発明に係る加熱炉は、排出ガスが通過する煙道を一対備えるとともに、各煙道に排出ガスの廃熱を回収する熱交換器が配備されている加熱炉において、前記煙道の少なくとも一方に備えられ且つ当該煙道の開口を閉鎖する閉止弁と、前記熱交換器の出側の空気の予熱温度を算出する空気温度算出手段と、前記空気温度算出手段の算出結果を基に、両方の煙道を開放しているときの熱交換器出側の空気の予熱温度が、一方の煙道のみ開放しているときの熱交換器出側の空気の予熱温度より低い場合、前記閉止弁を閉鎖する閉止弁操作手段と、を有することを特徴とする。 In order to achieve the above-described object, the present invention takes the following technical means.
That is, the heating furnace according to the present invention includes a pair of flues through which the exhaust gas passes, and each of the flues is provided with a heat exchanger that recovers waste heat of the exhaust gas. Based on the calculation result of the shut-off valve provided in at least one and closing the opening of the flue, the air temperature calculating means for calculating the preheating temperature of the outlet air of the heat exchanger, and the air temperature calculating means If the preheating temperature of the air at the outlet side of the heat exchanger when both flues are open is lower than the preheating temperature of the air at the outlet side of the heat exchanger when only one flues are open, And a closing valve operating means for closing the closing valve.

好ましくは、前記空気温度算出手段は、前記加熱炉内の燃焼量を基に、当該加熱炉の煙道接続部での排出ガスの温度及び流量を算出する炉端排出ガス算出部と、前記炉端排出ガス算出部の算出結果、前記煙道内に侵入する空気量及び前記煙道から放散される熱量を基に、両方の煙道を開放しているときの熱交換器の入側の排出ガス温度と、一方の煙道のみを開放しているときの熱交換器の入側の排出ガス温度とを求める熱交換器入側排出ガス算出部と、前記熱交換器入側排出ガス算出部の算出結果を基に、両方の煙道を開放しているときの熱交換器の出側の空気の予熱温度と、一方の煙道のみを開放しているときの熱交換器の出側の空気の予熱温度とを求める熱交換器出側空気算出部と、を備えており、前記閉止弁操作手段は、熱交換器出側空気算出部の算出結果を基に、両方の煙道を開放しているときの熱交換器出側の空気の予熱温度が、一方の煙道のみ開放しているときの熱交換器出側の空気の予熱温度より低い場合、前記閉止弁を閉鎖するように構成されているとよい。   Preferably, the air temperature calculation means includes a furnace end exhaust gas calculation unit that calculates a temperature and a flow rate of exhaust gas at a flue connection part of the heating furnace based on a combustion amount in the heating furnace, and the furnace end discharge Based on the calculation result of the gas calculation unit, the amount of air entering the flue and the amount of heat dissipated from the flue, the exhaust gas temperature on the inlet side of the heat exchanger when both the flues are open and The calculation results of the heat exchanger inlet side exhaust gas calculation unit for obtaining the inlet side exhaust gas temperature of the heat exchanger when only one flue is opened, and the heat exchanger inlet side exhaust gas calculation unit The preheating temperature of the air at the outlet side of the heat exchanger when both flues are open and the preheating of the air at the outlet side of the heat exchanger when only one flues are open A heat exchanger outlet side air calculating unit for obtaining a temperature, and the shut-off valve operating means is a heat exchanger outlet side Based on the calculation result of the air calculation unit, the preheat temperature of the air at the outlet side of the heat exchanger when both flues are open is the same as that at the outlet side of the heat exchanger when only one flue is open. When the temperature is lower than the preheating temperature of the air, the closing valve may be configured to be closed.

本発明における加熱炉の制御方法は、排出ガスが通過する煙道を一対備えるとともに、各煙道に排出ガスの廃熱を回収する熱交換器が配備されている加熱炉の制御方法において、前記煙道の少なくとも一方には、当該煙道の開口を閉鎖する閉止弁が備えられるものとなっており、前記熱交換器の入側の排出ガスの温度及び前記熱交換器の出側の空気の予熱温度を算出する空気算出工程と、前記空気算出工程の算出結果を基に、両方の煙道を開放しているときの熱交換器出側の空気の予熱温度が、一方の煙道のみ開放しているときの熱交換器出側の空気の予熱温度より低い場合、前記閉止弁を閉鎖する閉止弁操作工程と、を有することを特徴とする。   The method for controlling a heating furnace in the present invention includes a pair of flues through which exhaust gas passes, and the method for controlling a heating furnace in which a heat exchanger for recovering waste heat of the exhaust gas is provided in each flue. At least one of the flues is provided with a closing valve for closing the opening of the flues, and the temperature of the exhaust gas on the inlet side of the heat exchanger and the air on the outlet side of the heat exchanger are Based on the air calculation step for calculating the preheating temperature and the calculation result of the air calculation step, the preheating temperature of the air at the outlet side of the heat exchanger when both flues are open, only one of the flues is open And a closing valve operating step of closing the closing valve when the temperature is lower than the preheating temperature of the air on the outlet side of the heat exchanger during operation.

好ましくは、前記空気算出工程は、前記加熱炉内の燃焼量を基に、当該加熱炉の煙道接続部の排出ガスの温度及び流量を算出する炉端排出ガス算出工程と、前記炉端排出ガス算出工程の算出結果、前記煙道内に侵入する空気量及び前記煙道から放散される熱量を基に、両方の煙道を開放しているときの熱交換器の入側の排出ガス温度と、一方の煙道のみを開放しているときの熱交換器の入側の排出ガス温度とを求める熱交換器入側排出ガス算出工程と、前記熱交換器入側排出ガス算出部の算出結果を基に、両方の煙道を開放しているときの熱交換器の出側の空気の予熱温度と、一方の煙道のみを開放しているときの熱交換器の出側の空気の予熱温度とを求める熱交換器出側空気算出工程と、を備えており、前記閉止弁操作工程は、熱交換器出側空気算出工程の算出結果を基に、両方の煙道を開放しているときの熱交換器出側の空気の予熱温度が、一方の煙道のみ開放しているときの熱交換器出側の空気の予熱温度より低い場合、前記閉止弁を閉鎖するとよい。   Preferably, the air calculation step includes a furnace end exhaust gas calculation step for calculating a temperature and a flow rate of an exhaust gas at a flue connection portion of the heating furnace based on a combustion amount in the heating furnace, and the furnace end exhaust gas calculation. Based on the calculation result of the process, the amount of air entering the flue and the amount of heat dissipated from the flue, the exhaust gas temperature on the inlet side of the heat exchanger when both the flues are open, Based on the calculation result of the heat exchanger inlet side exhaust gas calculation step for obtaining the inlet side exhaust gas temperature of the heat exchanger when only the flue is opened and the heat exchanger inlet side exhaust gas calculation unit The preheating temperature of the air on the outlet side of the heat exchanger when both flues are open and the preheating temperature of the air on the outlet side of the heat exchanger when only one flues are open A heat exchanger outlet side air calculating step for obtaining a heat exchanger, and Based on the calculation results of the air calculation process, the preheating temperature of the air at the outlet side of the heat exchanger when both flues are open is the same as that at the outlet side of the heat exchanger when only one flue is open. When the temperature is lower than the preheating temperature of the air, the closing valve may be closed.

本発明の技術を用いることで、加熱炉で鋼材を加熱するに際して、煙道内を通過する排出ガスの廃熱を十分、且つ効率的に熱回収することができる。   By using the technique of the present invention, when the steel material is heated in the heating furnace, the waste heat of the exhaust gas passing through the flue can be recovered sufficiently and efficiently.

本発明の加熱炉の概略構成を示した図である。It is the figure which showed schematic structure of the heating furnace of this invention. 本発明の加熱炉の煙道接続部での断面図である。It is sectional drawing in the flue connection part of the heating furnace of this invention. 本発明の加熱炉を用いて、廃熱回収の方法を模式的に示した図である。It is the figure which showed typically the method of waste heat recovery using the heating furnace of this invention. 本発明の加熱炉における空気予熱温度と侵入空気量との関係を算出した結果を示した図である。It is the figure which showed the result of having calculated the relationship between the air preheating temperature and the amount of intrusion air in the heating furnace of this invention. 図４の結果より、加熱炉内の燃焼量と侵入空気量との関係を算出した結果を示した図である。It is the figure which showed the result of having calculated the relationship between the combustion amount in a heating furnace, and the amount of intrusion air from the result of FIG.

以下、図を参照しながら、本発明の加熱炉について、説明する。
その前に、熱間圧延装置について説明する。
熱間圧延装置は、上流側から、ブルームやビレットなどの鋼材Ｗ（鋳片）を加熱する加熱炉１、デスケーラ、粗圧延機、仕上げ圧延機、巻き取り装置が順番に配設されている。
鋼材Ｗは、加熱炉１内に装入され所定の温度に昇温され加熱炉１から抽出される。その後、デスケーラで鋼材Ｗの表面についたスケールを剥離させ、粗圧延機及び仕上げ圧延機で圧延されて圧延材となる。製造された圧延材は巻き取り装置で巻回される。 Hereinafter, the heating furnace of the present invention will be described with reference to the drawings.
Before that, a hot rolling apparatus will be described.
In the hot rolling apparatus, a heating furnace 1, a descaler, a rough rolling mill, a finish rolling mill, and a winding device for heating a steel material W (slab) such as bloom or billet are sequentially arranged from the upstream side.
The steel material W is charged into the heating furnace 1, heated to a predetermined temperature, and extracted from the heating furnace 1. Thereafter, the scale attached to the surface of the steel material W is peeled off with a descaler, and rolled with a rough rolling mill and a finish rolling mill to become a rolled material. The manufactured rolled material is wound by a winding device.

本願発明は、上記した熱間圧延装置に備えられた加熱炉１、及びこの加熱炉１の制御方法に関するものである。
以下、本発明の加熱炉１について、詳しく説明する。
図１は、加熱炉１を模式的に示したものであり、図２は図１に示された加熱炉１の煙道接続部での断面図、つまり加熱炉１の搬入口３側を断面視した図である。 The present invention relates to a heating furnace 1 provided in the above-described hot rolling apparatus and a method for controlling the heating furnace 1.
Hereinafter, the heating furnace 1 of the present invention will be described in detail.
FIG. 1 schematically shows the heating furnace 1, and FIG. 2 is a cross-sectional view of the heating furnace 1 shown in FIG. FIG.

なお、以降の説明において、図１の紙面に向かっての左右方向を、加熱炉１の前後方向とし、図１の紙面に向かっての貫通方向を、加熱炉１の左右方向とする。図１の紙面に向かっての上下方向を、加熱炉１の上下方向とする。
図１に示すように、本発明の加熱炉１は、鋼材Ｗを加熱する炉体２と、炉体２内の雰囲気温度を昇温させる燃焼バーナ６と、炉体２内で生じた排出ガスを外部に放出する煙道７（排出ガス経路）とを有している。また、煙道７には、煙道７内を通過する排出ガスの廃熱を回収する熱交換器１１（レキュペレータ）が配備されている。また、燃焼に用いられる空気を燃焼バーナ６に供給するブロワ１２と、このブロワ１２から供給された空気を熱交換器１１を介した上で燃焼バーナ６に送る予熱空気経路１３が備えられている。 In the following description, the left-right direction toward the paper surface of FIG. 1 is the front-rear direction of the heating furnace 1, and the penetration direction toward the paper surface of FIG. The vertical direction toward the paper surface of FIG. 1 is the vertical direction of the heating furnace 1.
As shown in FIG. 1, a heating furnace 1 of the present invention includes a furnace body 2 that heats a steel material W, a combustion burner 6 that raises the ambient temperature in the furnace body 2, and an exhaust gas generated in the furnace body 2. And a flue 7 (exhaust gas path) for discharging the gas to the outside. The flue 7 is provided with a heat exchanger 11 (recuperator) that recovers waste heat of exhaust gas that passes through the flue 7. Further, a blower 12 for supplying air used for combustion to the combustion burner 6 and a preheated air passage 13 for sending the air supplied from the blower 12 to the combustion burner 6 through the heat exchanger 11 are provided. .

加えて、本発明の加熱炉１は、煙道７の少なくとも一方に備えられ、且つ当該煙道７の開口を閉鎖する閉止弁２４と、熱交換器１１の出側の空気の予熱温度を算出する空気温度算出手段２０と、空気温度算出手段２０の算出結果を基に、閉止弁２４を開閉操作する閉止弁操作手段２５と、を有している。
炉体２は、内部が空洞の筐体であって、鋼材Ｗを炉体２内に搬入するための搬入口３と、所定温度に加熱された鋼材Ｗを炉外へ搬出する搬出口４とが鋼材Ｗの搬送方向にそれぞれ形成されている。また、炉体２の内部には、鋼材Ｗを搬入口３から搬出口４へ一定時間（１〜２時間）かけて少しずつ搬送するウォーキングビーム５（鋼材搬送装置）が設けられている。図１の紙面の左側の搬入口３から連続して搬入された鋼材Ｗは、ウォーキングビーム５により加熱炉１内を図１の矢印方向に搬送されつつ加熱・昇温され、搬出口４から搬出される。本実施形態の加熱炉１は、鋼材Ｗの搬送方向に沿って予熱帯・燃焼帯とから構成されており、炉体２には、加熱炉１内の雰囲気温度を上昇させるための燃焼バーナ６が燃焼帯に複数設けられている。 In addition, the heating furnace 1 of the present invention is provided in at least one of the flues 7 and calculates a preheating temperature of the closing valve 24 that closes the opening of the flue 7 and the outlet air of the heat exchanger 11. Air temperature calculating means 20 for performing the operation, and a closing valve operating means 25 for opening and closing the closing valve 24 based on the calculation result of the air temperature calculating means 20.
The furnace body 2 is a casing having a hollow inside, and a carry-in port 3 for carrying the steel material W into the furnace body 2 and a carry-out port 4 for carrying out the steel material W heated to a predetermined temperature to the outside of the furnace. Are formed in the conveying direction of the steel material W, respectively. In addition, a walking beam 5 (steel material conveying device) that conveys the steel material W from the carry-in port 3 to the carry-out port 4 little by little over a certain time (1-2 hours) is provided inside the furnace body 2. The steel material W continuously carried in from the carry-in port 3 on the left side of FIG. 1 is heated and heated by the walking beam 5 while being conveyed in the heating furnace 1 in the direction of the arrow in FIG. Is done. The heating furnace 1 of the present embodiment is composed of a pre-tropical zone and a combustion zone along the conveying direction of the steel material W, and the furnace body 2 has a combustion burner 6 for raising the ambient temperature in the heating furnace 1. Are provided in the combustion zone.

燃焼バーナ６は、炉体２の側壁及び天井付近に配備され、図１，図２に示すように、側壁に配備した燃焼バーナ６は、ウォーキングビーム５で搬送されている鋼材Ｗを左右方向から挟み込むように配備されている。一対の燃焼バーナ６は、搬送方向に沿って複数配設されている（本実施形態では４対）。燃焼バーナ６には、熱交換器１１で熱交換され昇温された空気が通過する予熱空気経路１３が配備されている。その予熱空気経路１３を介して送られてきた予熱空気は、重油、ＣＯＧ、ＬＮＧや都市ガスなどの燃料の燃焼に用いられる。燃料が燃焼することによって、加熱炉１内の雰囲気温度が上昇する。加熱炉１内の雰囲気温度の上昇に寄与した排出ガスは、所定の熱エネルギを有しつつも煙道７に送られて外部に排出される。   The combustion burner 6 is disposed near the side wall and ceiling of the furnace body 2, and as shown in FIGS. 1 and 2, the combustion burner 6 disposed on the side wall moves the steel material W conveyed by the walking beam 5 from the left and right directions. It is deployed so as to sandwich it. A plurality of pairs of combustion burners 6 are arranged along the conveying direction (four pairs in this embodiment). The combustion burner 6 is provided with a preheated air passage 13 through which air heated by the heat exchanger 11 and heated is passed. The preheated air sent through the preheated air path 13 is used for combustion of fuel such as heavy oil, COG, LNG, city gas and the like. As the fuel burns, the ambient temperature in the heating furnace 1 rises. The exhaust gas that has contributed to the increase in the atmospheric temperature in the heating furnace 1 is sent to the flue 7 and discharged to the outside while having a predetermined thermal energy.

煙道７は、筒状に形成された長尺の構造体であり、加熱炉１の左右に一対備えられている。例えば、図２の左側の煙道７を第１の煙道７とし、図２の右側の煙道７を第２の煙道７とする。煙道７の流入口８は加熱炉１の搬入口３側（煙道接続部）に設けられており、煙道７の流出口９は上方に向かって突出するように設けられている。本実施形態では、煙道７は加熱炉１の下方を通過してから上方に突出する（略コ字状）ように備えられている
が、加熱炉１の上方を通過するように配備されていてもよい。 The flue 7 is a long structure formed in a cylindrical shape, and a pair is provided on the left and right of the heating furnace 1. For example, let the left flue 7 in FIG. 2 be the first flue 7, and let the right flue 7 in FIG. 2 be the second flue 7. The inlet 8 of the flue 7 is provided on the carry-in inlet 3 side (the flue connection part) of the heating furnace 1, and the outlet 9 of the flue 7 is provided so as to protrude upward. In the present embodiment, the flue 7 is provided so as to protrude upward (substantially U-shaped) after passing below the heating furnace 1, but is disposed so as to pass above the heating furnace 1. May be.

各煙道７には、加熱炉１内の圧力を調整する炉圧ダンパ１０と、煙道７内を通過する排出ガスの廃熱を回収する熱交換器１１（レキュペレータ）が配備されている。また、煙道７の少なくとも一方には、当該煙道７の開口を閉鎖する閉止弁２４が備えられている。また、煙道７の側壁には、煙道７内の排出ガス温度などを測定する温度測定装置（例えば、シース熱電対）が備えられている。なお、従来の加熱炉１の操業では、両方の煙道７を用いて、排出ガスを外部へ放出している。   Each flue 7 is provided with a furnace pressure damper 10 for adjusting the pressure in the heating furnace 1 and a heat exchanger 11 (recuperator) for recovering waste heat of exhaust gas passing through the flue 7. Further, at least one of the flue 7 is provided with a closing valve 24 for closing the opening of the flue 7. The side wall of the flue 7 is provided with a temperature measuring device (for example, a sheath thermocouple) that measures the exhaust gas temperature in the flue 7 and the like. In the operation of the conventional heating furnace 1, the exhaust gas is discharged to the outside using both the flues 7.

熱交換器１１は、煙道７の中途部に備えられ、ブロワ１２から送られてきた空気と、熱エネルギを有する排出ガスとを熱交換するものである。つまり、熱交換器１１は、排出ガスの廃熱を回収し、回収した廃熱をブロワ１２から送られてきた空気を予熱するために再利用している。熱交換器１１の一次側（排出ガス経路７）には、煙道７内の排出ガスが流通し、二次側（予熱空気経路１３）にはブロワ１２から送られた空気が流通しており、排出ガスから空気へと熱が付与される。   The heat exchanger 11 is provided in the middle of the flue 7 and exchanges heat between the air sent from the blower 12 and the exhaust gas having thermal energy. That is, the heat exchanger 11 collects the waste heat of the exhaust gas and reuses the collected waste heat for preheating the air sent from the blower 12. The exhaust gas in the flue 7 flows through the primary side (exhaust gas path 7) of the heat exchanger 11, and the air sent from the blower 12 flows through the secondary side (preheated air path 13). Heat is applied from the exhaust gas to the air.

予熱空気経路１３を通過する空気は、排出ガス経路７を通過する排出ガスの熱エネルギが付与されることにより、所定の温度にまで昇温した予熱空気となる。予熱空気は、予熱空気経路１３を経て燃焼バーナ６に送られる。また、熱交換によって温度が低下した排出ガスは、煙道７の流出口９から外部に放出される。
ところで、加熱炉１の燃焼量Ｎｋ（Ｍｃａｌ／ｈ）が少なくなった場合、熱交換器１１出側における空気の予熱温度Ｔａ（℃）が低下していることがある。すなわち、加熱炉１の燃焼量Ｎｋ（Ｍｃａｌ／ｈ）が低下すると、煙道７の熱交換器１１において効率的、且つ十分な廃熱回収が行われなくなる。 The air that passes through the preheated air path 13 becomes preheated air that has been heated to a predetermined temperature by the thermal energy of the exhaust gas that passes through the exhaust gas path 7 being applied. Preheated air is sent to the combustion burner 6 via the preheated air path 13. Further, the exhaust gas whose temperature has been lowered by heat exchange is discharged to the outside from the outlet 9 of the flue 7.
By the way, when the combustion amount Nk (Mcal / h) of the heating furnace 1 decreases, the air preheating temperature Ta (° C.) on the outlet side of the heat exchanger 11 may be lowered. That is, when the combustion amount Nk (Mcal / h) of the heating furnace 1 is decreased, efficient and sufficient waste heat recovery is not performed in the heat exchanger 11 of the flue 7.

そこで、本発明の加熱炉１では、空気温度算出手段２０で熱交換器１１の出側の空気の予熱温度Ｔａ（℃）を算出し、その算出結果を基に、両方（２本）の煙道７を開放しているときの熱交換器１１出側の空気の予熱温度Ｔａ２（℃）が、一方の煙道７のみ開放しているときの熱交換器１１出側の空気の予熱温度Ｔａ１（℃）より低い場合、閉止弁操作手段２５により閉止弁２４を閉鎖している。言い換えれば、加熱炉１の燃焼量Ｎｋ（Ｍｃａｌ／ｈ）が低下した場合、一方の煙道７のみを使用し、熱交換器１１へ導入する熱量を大きなものとする。   Therefore, in the heating furnace 1 of the present invention, the air temperature calculation means 20 calculates the preheating temperature Ta (° C.) of the air on the outlet side of the heat exchanger 11, and based on the calculation result, both (two) smokes. The preheating temperature Ta2 (° C.) of the air on the outlet side of the heat exchanger 11 when the passage 7 is opened is the preheating temperature Ta1 of the air on the outlet side of the heat exchanger 11 when only one flue 7 is opened. When the temperature is lower than (° C.), the closing valve 24 is closed by the closing valve operating means 25. In other words, when the combustion amount Nk (Mcal / h) of the heating furnace 1 is decreased, only one flue 7 is used and the amount of heat introduced into the heat exchanger 11 is increased.

以下、本発明の加熱炉１に備えられた閉止弁２４、空気温度算出手段２０及び閉止弁操作手段２５について、詳細な説明を行う。
図３に示すように、閉止弁２４は、加熱炉１の煙道接続部と熱交換器１１との間に配備され、閉止弁操作手段２５によって制御されている。本実施形態では、閉止弁２４は、第２の煙道７側に備えられている。閉止弁２４の開閉を切替するにあたって、空気温度算出手段２０で算出された結果を基に行われている。 Hereinafter, the close valve 24, the air temperature calculating means 20, and the close valve operating means 25 provided in the heating furnace 1 of the present invention will be described in detail.
As shown in FIG. 3, the closing valve 24 is disposed between the flue connection portion of the heating furnace 1 and the heat exchanger 11, and is controlled by the closing valve operating means 25. In the present embodiment, the stop valve 24 is provided on the second flue 7 side. The switching of the opening / closing of the shut-off valve 24 is performed based on the result calculated by the air temperature calculating means 20.

空気温度算出手段２０は、図示しないが、加熱炉１に備えられている制御装置に設けられている。
空気温度算出手段２０は、加熱炉１内の燃焼量Ｎｋを基に、当該加熱炉１の煙道接続部での排出ガスの温度Ｔｇ及び流量Ｑｇを算出する炉端排出ガス算出部２１と、炉端排出ガス算出部２１の算出結果、煙道７内に侵入する空気量Ｑａｉｒ（Ｎｍ３／ｈ）及び煙道７から放出される放散熱量Ｎｈ（Ｍｃａｌ／ｈ）を基に、両方（２本）の煙道７を開放しているときの熱交換器１１の入側の排出ガス温度Ｔｒｉｎ２（℃）と、一方の煙道７のみを開放しているときの熱交換器１１の入側の排出ガス温度Ｔｒｉｎ１（℃）とを求める熱交換器入側排出ガス算出部２２と、熱交換器入側排出ガス算出部２２の算出結果を基に、両方の煙道７を開放しているときの熱交換器１１の出側の空気の予熱温度Ｔａ２（℃）と、一方の煙道７のみを開放しているときの熱交換器１１の出側の空気の予熱温度Ｔａ１（℃）とを求める熱交換器出側空気算出部２３と、を備えている。 Although not shown, the air temperature calculation means 20 is provided in a control device provided in the heating furnace 1.
The air temperature calculation means 20 includes a furnace end exhaust gas calculation unit 21 that calculates the temperature Tg and the flow rate Qg of the exhaust gas at the flue connection part of the heating furnace 1 based on the combustion amount Nk in the heating furnace 1, and the furnace end Based on the calculation result of the exhaust gas calculation unit 21, both (two) based on the amount of air Qair (Nm 3 / h) entering the flue 7 and the amount of heat dissipated Nh (Mcal / h) released from the flue 7 entrance side of the heat exchanger 11 when the discharge of the inlet side of the heat exchanger 11 when the flue 7 is open gas temperature Tr in 2 (℃), is open only one of the flue 7 Based on the calculation results of the heat exchanger inlet side exhaust gas calculation unit 22 for obtaining the exhaust gas temperature Tr in 1 (° C.) and the heat exchanger inlet side exhaust gas calculation unit 22, both fluees 7 are opened. Only the preheating temperature Ta2 (° C) of the air on the outlet side of the heat exchanger 11 and one flue 7 are opened. It includes a heat exchanger 11 of the outlet side of the preheating temperature of the air Ta1 (° C.) and the heat exchanger outlet side air calculating unit 23 for obtaining the time you are, the.

炉端排出ガス算出部２１は、加熱炉１内の燃焼量Ｎｋ（Ｍｃａｌ／ｈ）を基に、加熱炉１内の排出ガス温度Ｔｇ（℃）と排出ガス流量Ｑｇ（Ｎｍ３／ｈ）とを算出するものである。
炉端排出ガス算出部２１は、まず加熱炉１内の燃焼量Ｎｋを算出する。加熱炉１内の燃
焼量Ｎｋは、加熱炉１の燃焼帯の熱収支（例えば、加熱炉１の燃焼バーナ設置帯における鋼材Ｗ（スラブ）の顕熱、排出ガスの顕熱、及び固定損失熱など）から求められる。炉端排出ガス算出部２１は、求めた加熱炉１内の燃焼量Ｎｋを基に、加熱炉１の最も煙道７に近く、燃焼バーナ６を設置しない予熱帯の熱収支より、炉端の排出ガス温度Ｔｇを算出する。 The furnace end exhaust gas calculation unit 21 calculates the exhaust gas temperature Tg (° C.) and the exhaust gas flow rate Qg (Nm 3 / h) in the heating furnace 1 based on the combustion amount Nk (Mcal / h) in the heating furnace 1. Is to be calculated.
The furnace end exhaust gas calculation unit 21 first calculates the combustion amount Nk in the heating furnace 1. The combustion amount Nk in the heating furnace 1 is the heat balance of the combustion zone of the heating furnace 1 (for example, sensible heat of the steel material W (slab) in the combustion burner installation zone of the heating furnace 1, sensible heat of exhaust gas, and fixed loss heat. Etc.). The furnace end exhaust gas calculation unit 21 calculates the exhaust gas at the furnace end from the pretropical heat balance closest to the flue 7 of the heating furnace 1 and without the combustion burner 6 based on the calculated combustion amount Nk in the heating furnace 1. The temperature Tg is calculated.

また、炉端排出ガス算出部２１は、求めた加熱炉１内の燃焼量Ｎｋを基に、加熱炉１の炉端の排ガス流量Ｑｇを算出する。加熱炉１の炉端の排ガス流量Ｑｇは、加熱炉１内の燃焼量Ｎｋより燃料流量Ｆを求め式（１）に適用することで算出する。
Ｑｇ（Ｎｍ３／ｈ）＝Σ｛［(ｍi−１)×Ａ０＋Ｇ０］×Ｆi｝ ・・・（１）
ただし、ｍ：空気比、Ａ０：理論空気量、Ｇ０：理論排出ガス量、Ｆ：燃料流量（Ｎｍ３／ｈ）ｉ：該当帯番号
このようにして求められた加熱炉１内の排出ガス温度Ｔｇと排出ガス流量Ｑｇは、熱交換器入側排出ガス算出部２２で求められる熱交換器１１（レキュペレータ）の入側における排出ガスの温度Ｔｒｉｎ（℃）を算出する際に用いられる。 Further, the furnace end exhaust gas calculation unit 21 calculates the exhaust gas flow rate Qg at the furnace end of the heating furnace 1 based on the obtained combustion amount Nk in the heating furnace 1. The exhaust gas flow rate Qg at the furnace end of the heating furnace 1 is calculated by obtaining the fuel flow rate F from the combustion amount Nk in the heating furnace 1 and applying it to the equation (1).
Qg (Nm 3 / h) = Σ {[(mi−1) × A0 + G0] × Fi} (1)
However, m: Air ratio, A0: Theoretical air amount, G0: Theoretical exhaust gas amount, F: Fuel flow rate (Nm 3 / h) i: Corresponding zone number The exhaust gas temperature in the heating furnace 1 thus determined Tg and the exhaust gas flow rate Qg is used in calculating the temperature Tr in the exhaust gas (℃) at the entry side of the heat exchanger 11 obtained by the heat exchanger inlet side exhaust gas calculation unit 22 (recuperator).

熱交換器入側排出ガス算出部２２は、炉端排出ガス算出部２１で算出した加熱炉１内の排出ガス温度Ｔｇと排出ガス流量Ｑｇ（Ｎｍ３／ｈ）と、煙道７内に入り込む侵入空気量Ｑａｉｒ（Ｎｍ３／ｈ）及び煙道７から放出される放散熱量Ｎｈ（Ｍｃａｌ／ｈ）を基に、熱交換器１１に流入する排出ガスの温度Ｔｒｉｎ（℃）を算出するものである。
熱交換器入側排出ガス算出部２２は、まず、煙道７内への侵入空気量Ｑａｉｒを算出する。侵入空気量Ｑａｉｒは、加熱炉１の炉端及び熱交換器１１の入側における排出ガスの酸素濃度（ｐｐｍ）及び、熱交換器１１の入側における排出ガスの酸素濃度（ｐｐｍ）を測定し、その酸素濃度の差を基に、算出する。熱交換器１１入側における排出ガスの流量Ｑｒｉｎ（Ｎｍ３／ｈ）は炉端における排出ガスの流量Ｑｇ（Ｎｍ３／ｈ）と侵入空気量Ｑａｉｒの和となる。 The heat exchanger inlet side exhaust gas calculation unit 22 has an exhaust gas temperature Tg and an exhaust gas flow rate Qg (Nm 3 / h) in the heating furnace 1 calculated by the furnace end exhaust gas calculation unit 21 and an intrusion that enters the flue 7. and calculates based on the dissipation heat Nh (Mcal / h) discharged from the air quantity Qair (Nm 3 / h) and flue 7, the temperature Tr in the exhaust gas flowing into the heat exchanger 11 (℃) is there.
The heat exchanger inlet-side exhaust gas calculation unit 22 first calculates an intrusion air amount Qair into the flue 7. The intrusion air amount Qair measures the oxygen concentration (ppm) of the exhaust gas at the furnace end of the heating furnace 1 and the inlet side of the heat exchanger 11 and the oxygen concentration (ppm) of the exhaust gas at the inlet side of the heat exchanger 11, Calculation is based on the difference in oxygen concentration. The flow rate Qr in (Nm 3 / h) of the exhaust gas at the inlet side of the heat exchanger 11 is the sum of the flow rate Qg (Nm 3 / h) of the exhaust gas at the furnace end and the intrusion air amount Qair.

次に、煙道７の放散熱量Ｎｈ（Ｍｃａｌ／ｈ）を算出する。放散熱量Ｎｈを算出するにあたっては、炉端における排出ガスの顕熱Ｎｇ（Ｍｃａｌ／ｈ）と、熱交換器１１の入側における排出ガスの顕熱Ｎｒ（Ｍｃａｌ／ｈ）との差（Ｎｈ＝Ｎｇ−Ｎｒ）を算出する。
なお、炉端における排出ガスの顕熱Ｎｇは、以下に示す式（２）よって求められる。
Ｎｇ＝Ｃｐ×Ｔｇ×Ｑｇ ・・・（２）
ただし、Ｃｐ：排出ガス比熱（ｋｃａｌ／ｋｇ・℃）
また、熱交換器１１の入側における排出ガスの顕熱Ｎｒは、以下に示す式（３）よって求められる。 Next, the amount of heat dissipated in the flue 7 Nh (Mcal / h) is calculated. In calculating the amount of dissipated heat Nh, the difference between the sensible heat Ng (Mcal / h) of the exhaust gas at the furnace end and the sensible heat Nr (Mcal / h) of the exhaust gas on the inlet side of the heat exchanger 11 (Nh = Ng -Nr).
In addition, the sensible heat Ng of the exhaust gas at the furnace end is obtained by the following equation (2).
Ng = Cp × Tg × Qg (2)
However, Cp: exhaust gas specific heat (kcal / kg · ° C)
Further, the sensible heat Nr of the exhaust gas on the entry side of the heat exchanger 11 is obtained by the following equation (3).

Ｎｒ＝Ｃｐ×Ｔｒｉｎ×Ｑｒｉｎ ・・・（３）
ただし、Ｃｐ：排出ガス比熱（ｋｃａｌ／ｋｇ・℃）
そして、熱交換器入側排出ガス算出部２２は、算出された侵入空気量Ｑａｉｒと放散熱量Ｎｈを基に、両方の煙道７（第１の煙道７及び第２の煙道７）を開放しているときの熱交換器１１の入側の排出ガス温度Ｔｒｉｎ２（℃）と、一方の煙道７のみ（第１の煙道７）を開放しているときの熱交換器１１の入側の排出ガス温度Ｔｒｉｎ１（℃）を算出する。 Nr = Cp × Tr in × Qr in (3)
However, Cp: exhaust gas specific heat (kcal / kg · ° C)
Then, the heat exchanger inlet-side exhaust gas calculation unit 22 passes both the flues 7 (the first flue 7 and the second flue 7) based on the calculated intrusion air amount Qair and the dissipated heat amount Nh. heat exchanger 11 when the exhaust gas temperature Tr in 2 (° C.), and is open one flue 7 alone (first flue 7) of the incoming side of the heat exchanger 11 when being opened The exhaust gas temperature Tr in 1 (° C.) on the inlet side is calculated.

熱交換器１１の入側の排出ガス温度Ｔｒｉｎ２及びＴｒｉｎ１を算出するにあたっては、算出された侵入空気量Ｑａｉｒ及び放散熱量Ｎｈと、平均燃焼量Ｎｋｎで加熱炉１を操業しているときの熱測定結果（例えば、直近の３回分）と、で算出した値を熱交換器１１の入側の排出ガス温度Ｔｒｉｎ２及びＴｒｉｎ１とする。
このようにして、算出された両方の煙道７を開放しているときの熱交換器１１の入側の排出ガス温度Ｔｒｉｎ２と、一方の煙道７のみを開放しているときの熱交換器１１の入側の排出ガス温度Ｔｒｉｎ１は、熱交換器出側空気算出部２３で求められる熱交換器１１の出側における空気の予熱温度Ｔａ（℃）を算出する際に用いられる。 In calculating the exhaust gas temperatures Tr in 2 and Tr in 1 on the inlet side of the heat exchanger 11, the heating furnace 1 is operated with the calculated intrusion air amount Qair, the dissipated heat amount Nh, and the average combustion amount Nkn. And the values calculated by the heat measurement results (for example, the latest three times) and the exhaust gas temperatures Tr in 2 and Tr in 1 on the inlet side of the heat exchanger 11.
In this way, the heat when the exhaust gas temperature Tr in 2 of the incoming side of the heat exchanger 11 when being opened both flue 7 calculated and opens only one of the flue 7 The exhaust gas temperature Tr in 1 on the inlet side of the exchanger 11 is used when calculating the air preheating temperature Ta (° C.) on the outlet side of the heat exchanger 11, which is obtained by the heat exchanger outlet air calculation unit 23. .

熱交換器出側空気算出部２３は、熱交換器入側排出ガス算出部２２で算出した熱交換器１１入側における排出ガス温度Ｔｒｉｎ（℃）を基に、熱交換器１１から流出する空気の予熱温度Ｔａ（℃）を算出するものである。ここで、熱交換器１１の伝熱面積を次のよう
に設定する。排出ガスの流路面積をＡｏuｔ（ｍ２）とし、空気の流量面積をＡiｎ（ｍ２）とする。 The heat exchanger outlet air calculation unit 23 flows out of the heat exchanger 11 based on the exhaust gas temperature Tr in (° C.) on the inlet side of the heat exchanger 11 calculated by the heat exchanger inlet side exhaust gas calculator 22. The air preheating temperature Ta (° C.) is calculated. Here, the heat transfer area of the heat exchanger 11 is set as follows. The flow area of the exhaust gas is Aout (m 2 ), and the air flow area is Ain (m 2 ).

熱交換器出側空気算出部２３は、まず、熱交換器１１出側の空気の予熱温度Ｔａ（℃）と、熱交換器１１出側の排出ガスの温度Ｔｒｏｕｔ（℃）を仮定する。このとき、空気（予熱空気）の顕熱の差Ｎａｓ（Ｍｃａｌ／ｈ）＝排出ガスの顕熱の差Ｎｇｓ（Ｍｃａｌ／ｈ）が成立するように、熱交換器１１出側の排出ガスの温度Ｔｒｏｕｔを設定する。
次に、熱交換器１１入側と熱交換器１１出側との間（二次側）の空気の予熱温度の平均値Ｔａｎ（℃）及び、熱交換器１１入側と熱交換器１１出側との間（一次側）の排出ガスの温度の平均値Ｔｇｎ（℃）に対する物性値を設定する。そして、設定した物性値を基に、熱交換器１１内における空気（予熱空気）の通過流速Ｖａｎ（ｍ／ｓ）、及び熱交換器１１内における排出ガスの通過流速Ｖｇｎ（ｍ／ｓ）を算出する。 First, the heat exchanger outlet air calculation unit 23 assumes a preheating temperature Ta (° C.) of air on the outlet side of the heat exchanger 11 and a temperature Tr out (° C.) of exhaust gas on the outlet side of the heat exchanger 11. At this time, the temperature of the exhaust gas on the outlet side of the heat exchanger 11 is established so that the sensible heat difference Nas (Mcal / h) of the air (preheated air) = the sensible heat difference Ngs (Mcal / h) of the exhaust gas is established. Set Tr out .
Next, the average value Tan (° C.) of the preheating temperature of the air between the inlet side of the heat exchanger 11 and the outlet side of the heat exchanger 11 (secondary side) and the inlet side of the heat exchanger 11 and the outlet side of the heat exchanger 11 A physical property value with respect to the average value Tgn (° C.) of the temperature of the exhaust gas between the two sides (primary side) is set. And based on the set physical property value, the passage flow velocity Van (m / s) of the air (preheated air) in the heat exchanger 11 and the passage flow velocity Vgn (m / s) of the exhaust gas in the heat exchanger 11 are obtained. calculate.

さらに、熱交換器１１内の経路（配管）の管外熱伝達率αｏｕｔ（ｋｃａｌ／ｍ２・ｈ・℃）及び、管内熱伝達率αｉｎ（ｋｃａｌ／ｍ２・ｈ・℃）を算出する。熱交換器１１内の経路の管外熱伝達率αｏｕｔと管内熱伝達率αｉｎとを基に、総括熱伝達率Ｋ（ｋｃａｌ／ｍ２・ｈ・℃）を算出する。また、熱交換器１１入側及び出側との間（二次側）の空気の予熱温度の平均値Ｔａｎ（℃）と、熱交換器１１入側及び出側との間（一次側）の排出ガスの温度の平均値Ｔｇｎ（℃）を基に、対数平均温度差ΔＴｍ（℃）を算出する。 Further, the heat transfer coefficient αout (kcal / m 2 · h · ° C.) and the heat transfer coefficient α in (kcal / m 2 · h · ° C.) of the path (pipe) in the heat exchanger 11 are calculated. The overall heat transfer coefficient K (kcal / m 2 · h · ° C.) is calculated based on the external heat transfer coefficient αout and the internal heat transfer coefficient αin of the path in the heat exchanger 11. Further, the average value Tan (° C.) of the air preheating temperature between the inlet side and the outlet side of the heat exchanger 11 (secondary side) and between the inlet side and the outlet side of the heat exchanger 11 (primary side). Based on the average value Tgn (° C.) of the temperature of the exhaust gas, the logarithm average temperature difference ΔTm (° C.) is calculated.

以上の算出結果を基に、熱交換器１１の伝熱量Ｎｄ（Ｍｃａｌ／ｈ）を算出する。熱交換器１１の伝熱量Ｎｄを算出するにあたっては、以下に示す式（４）よって求める。
熱交換器１１の伝熱量Ｎｄ＝総括熱伝達率Ｋ×対数平均温度差ΔＴｍ×空気の流量面積Ａiｎ ・・・（４）
そして、空気（予熱空気）の顕熱の差Ｎａｓ（Ｍｃａｌ／ｈ）＝熱交換器１１の伝熱量Ｎｄ（Ｍｃａｌ／ｈ）が成立する熱交換器１１出側の空気の予熱温度Ｔａ１、Ｔａ２を算出する。 Based on the above calculation results, the heat transfer amount Nd (Mcal / h) of the heat exchanger 11 is calculated. In calculating the heat transfer amount Nd of the heat exchanger 11, it is obtained by the following equation (4).
Heat transfer amount Nd of heat exchanger 11 = Overall heat transfer coefficient K × Logarithmic average temperature difference ΔTm × Air flow area Ain (4)
Then, the sensible heat difference Nas (Mcal / h) of the air (preheated air) = the preheat temperature Ta1 and Ta2 of the air on the outlet side of the heat exchanger 11 where the heat transfer amount Nd (Mcal / h) of the heat exchanger 11 is established. calculate.

以上の算出結果をまとめたものが、図４及び図５に示されている。
図４は、煙道７内に侵入する侵入空気量Ｑａｉｒに対して、空気の予熱温度Ｔａをまとめたグラフである。なお、加熱炉１の生産性を１５７（ｔ／ｈ）とし、放散熱量Ｎｈを２００（Ｍｃａｌ／ｈ）とする。
図４を見てみると、侵入空気量Ｑａｉｒが０（Ｎｍ３／ｈ）である場合、両方（２本）の煙道７を開放しているときの熱交換器１１出側の空気の予熱温度Ｔａ２は３６１℃（■印）であり、一方の煙道７のみ開放しているときの熱交換器１１出側の空気の予熱温度Ｔａ１は３４８℃（◆印）である。つまり、Ｔａ２＞Ｔａ１となり、両方の煙道７を開放して排出ガスの熱量を回収した方が有利であることが確認できる。 A summary of the above calculation results is shown in FIGS.
FIG. 4 is a graph summarizing the air preheating temperature Ta with respect to the intrusion air amount Qair entering the flue 7. Note that the productivity of the heating furnace 1 is 157 (t / h), and the heat dissipation Nh is 200 (Mcal / h).
Referring to FIG. 4, when the intrusion air amount Qair is 0 (Nm 3 / h), preheating of the air on the outlet side of the heat exchanger 11 when both (two) flues 7 are opened. The temperature Ta2 is 361 ° C. (marked with ■), and the preheating temperature Ta1 of the air on the outlet side of the heat exchanger 11 when only one flue 7 is open is 348 ° C. (marked with ◆). That is, Ta2> Ta1, and it can be confirmed that it is advantageous to open both the flues 7 and recover the heat quantity of the exhaust gas.

次に、侵入空気量Ｑａｉｒが６０００（Ｎｍ３／ｈ）である場合、両方の煙道７を開放しているときの熱交換器１１出側の空気の予熱温度Ｔａ２は２７５℃（■印）であり、一方の煙道７のみ開放しているときの熱交換器１１出側の空気の予熱温度Ｔａ１は３０１℃（◆印）である。この傾向は、侵入空気量Ｑａｉｒが６０００（Ｎｍ３／ｈ）より大きくなったとしても続くことになる。つまり、侵入空気量Ｑａｉｒ≧６０００（Ｎｍ３／ｈ）の場合には、Ｔａ１＞Ｔａ２となり、一方の煙道７のみ開放して排出ガスの熱量を回収した方が有利であることが確認できる。 Next, when the intrusion air amount Qair is 6000 (Nm 3 / h), the preheating temperature Ta2 of the air on the outlet side of the heat exchanger 11 when both the flues 7 are opened is 275 ° C. (marked ■) The preheating temperature Ta1 of the air on the outlet side of the heat exchanger 11 when only one of the flues 7 is open is 301 ° C. (♦ mark). This tendency continues even if the intrusion air amount Qair becomes larger than 6000 (Nm 3 / h). That is, in the case of the intrusion air amount Qair ≧ 6000 (Nm 3 / h), Ta1> Ta2, and it can be confirmed that it is advantageous to open only one flue 7 and recover the heat amount of the exhaust gas.

ゆえに、一方の煙道７のみ開放しているときの熱交換器１１出側の空気の予熱温度Ｔａ１の曲線と、両方の煙道７を開放しているときの熱交換器１１出側の空気の予熱温度Ｔａ２の曲線とが交わる交差点を境に、一方の煙道７のみ開放して排出ガスの熱量を回収した方よいか否かを確認することができる。この交差点を加熱炉１の燃焼量Ｎｋごとに、プロットしてまとめたものが図５に示されている。   Therefore, the curve of the preheating temperature Ta1 of the air on the outlet side of the heat exchanger 11 when only one flue 7 is open, and the air on the outlet side of the heat exchanger 11 when both the flues 7 are open It is possible to confirm whether it is better to open only one flue 7 and recover the heat quantity of the exhaust gas at the intersection where the curve of the preheating temperature Ta2 intersects. FIG. 5 shows a summary of the intersections plotted for each combustion amount Nk of the heating furnace 1.

図５は、加熱炉１の燃焼量Ｎｋに対して、煙道７内に侵入する侵入空気量Ｑａｉｒをまとめたグラフである。
図５を見てみると、加熱炉１の燃焼量Ｎｋがおよそ３８×１０３（Ｍｃａｌ／ｈ）のとき、侵入空気量Ｑａｉｒはおよそ１１００（Ｎｍ３／ｈ）である。また、加熱炉１の燃焼量Ｎｋがおよそ４４×１０３（Ｍｃａｌ／ｈ）のとき、侵入空気量Ｑａｉｒはおよそ１９
００（Ｎｍ３／ｈ）である。加熱炉１の燃焼量Ｎｋがおよそ７２×１０３（Ｍｃａｌ／ｈ）のとき、侵入空気量Ｑａｉｒはおよそ３５００（Ｎｍ３／ｈ）である。 FIG. 5 is a graph summarizing the intrusion air amount Qair that enters the flue 7 with respect to the combustion amount Nk of the heating furnace 1.
Referring to FIG. 5, when the combustion amount Nk of the heating furnace 1 is approximately 38 × 10 3 (Mcal / h), the intrusion air amount Qair is approximately 1100 (Nm 3 / h). Further, when the combustion amount Nk of the heating furnace 1 is approximately 44 × 10 3 (Mcal / h), the intrusion air amount Qair is approximately 19
00 (Nm 3 / h). When the combustion amount Nk of the heating furnace 1 is approximately 72 × 10 3 (Mcal / h), the intrusion air amount Qair is approximately 3500 (Nm 3 / h).

つまり、加熱炉１の燃焼量Ｎｋが少なく、且つ侵入空気量Ｑａｉｒが多い場合（図５に示す曲線より左側）、一方の煙道７のみ開放して排出ガスの熱量を回収した方が有利であることが確認できる。また、加熱炉１の燃焼量Ｎｋが多く、且つ侵入空気量Ｑａｉｒが少ない場合（図５に示す曲線より右側）、両方の煙道７を開放して排出ガスの熱量を回収した方が有利であることが確認できる。   That is, when the combustion amount Nk of the heating furnace 1 is small and the intrusion air amount Qair is large (on the left side of the curve shown in FIG. 5), it is advantageous to open only one flue 7 and collect the heat amount of the exhaust gas. It can be confirmed that there is. Further, when the combustion amount Nk of the heating furnace 1 is large and the intrusion air amount Qair is small (right side from the curve shown in FIG. 5), it is advantageous to open both the flues 7 and collect the heat amount of the exhaust gas. It can be confirmed that there is.

以上より、煙道７内に侵入する侵入空気量Ｑａｉｒが増大するにつれて、一方の煙道７のみ開放して排出ガスの熱量を回収した方が有利であることが確認できる。
このようにして、算出された熱交換器１１（レキュレペータ）出側の空気（予熱空気）の温度Ｔａ１、Ｔａ２は、閉止弁操作手段２５が閉止弁２４を閉鎖するか否かを判断する際に用いられる。 From the above, it can be confirmed that it is advantageous to collect only the one flue 7 and recover the heat quantity of the exhaust gas as the amount of air Qair entering the flue 7 increases.
Thus, the calculated temperatures Ta1 and Ta2 of the air (preheated air) on the outlet side of the heat exchanger 11 (the recuperator) are used when the closing valve operating means 25 determines whether or not the closing valve 24 is closed. Used.

閉止弁操作手段２５は、熱交換器出側空気算出部２３の算出結果を基に、両方の煙道７を開放しているときの熱交換器１１出側の空気の予熱温度Ｔａ２（℃）が、一方の煙道７のみ開放しているときの熱交換器１１出側の空気の予熱温度Ｔａ１（℃）より低い場合、閉止弁２４を閉鎖するように構成されており、加熱炉１の操業を制御する制御装置（図示せず）に格納されている。   The closing valve operating means 25 is based on the calculation result of the heat exchanger outlet air calculation unit 23, and the air preheating temperature Ta2 (° C.) on the outlet side of the heat exchanger 11 when both the flues 7 are opened. However, when the temperature is lower than the preheating temperature Ta1 (° C.) of the air on the outlet side of the heat exchanger 11 when only one of the flues 7 is open, the shutoff valve 24 is configured to be closed. It is stored in a control device (not shown) that controls the operation.

閉止弁２４を閉鎖するか否かを判断するにあたっては、閉止弁操作手段２５は、両方の煙道７を開放しているときの熱交換器１１出側の空気の予熱温度Ｔａ２と、一方の煙道７のみ開放しているときの熱交換器１１出側の空気の予熱温度Ｔａ１とを比較し、その結果を基に閉止弁２４の開閉操作を行っている。
例えば、両方の煙道７を開放して加熱炉１の操業を行っている場合に、煙道７の熱交換器１１出側の空気の予熱温度Ｔａ２が一方の煙道７のみ開放しているときの熱交換器１１出側の空気の予熱温度Ｔａ１より下回った（Ｔａ１＞Ｔａ２）と判断されると、熱交換器１１入側の排出ガスの温度Ｔｒｉｎ２は低下していることとなり、第２の煙道７に備えられた閉止弁２４を閉鎖（全閉）する。同時に、第２の煙道７側の予熱空気経路１３に備えられた空気供給弁２６も閉鎖（全閉）する。 In determining whether or not to close the shut-off valve 24, the shut-off valve operating means 25 uses the preheating temperature Ta2 of the air on the outlet side of the heat exchanger 11 when both the flues 7 are open, The air preheating temperature Ta1 on the outlet side of the heat exchanger 11 when only the flue 7 is open is compared, and the opening / closing operation of the closing valve 24 is performed based on the result.
For example, when both the flues 7 are opened and the heating furnace 1 is operated, the preheating temperature Ta2 of the air at the outlet side of the heat exchanger 11 of the flue 7 is open only in one flue 7. If it is determined that the heat exchanger 11 drops below the preheating temperature Ta1 of the outgoing side of the air (Ta1> Ta2) of time, the temperature Tr in 2 of the exhaust gas heat exchanger 11 inlet side becomes to have decreased, The closing valve 24 provided in the second flue 7 is closed (fully closed). At the same time, the air supply valve 26 provided in the preheating air path 13 on the second flue 7 side is also closed (fully closed).

一定の時間を経て、一方の煙道７のみ開放しているときの熱交換器１１出側の空気の予熱温度Ｔａ１が煙道７の熱交換器１１出側の空気の予熱温度Ｔａ２以下（Ｔａ２≧Ｔａ１）と判断されると、一方の煙道７のみ開放しているときの熱交換器１１入側の排出ガスの温度Ｔｒｉｎ１は、両方の煙道７を開放しているときの熱交換器１１入側の排出ガスの温度Ｔｒｉｎ２より上昇していることとなり、第２の煙道７に備えられた閉止弁２４を開く。同時に、第２の煙道７側の予熱空気経路１３に備えられた空気供給弁２６も開く。このようにすることで、煙道７内を通過する排出ガスの熱量を十分、且つ効率的に回収することができる。 The preheating temperature Ta1 of the air on the outlet side of the heat exchanger 11 when only one of the flues 7 is opened after a certain time is equal to or lower than the preheating temperature Ta2 of the air on the outlet side of the heat exchanger 11 of the flue 7 (Ta2 If it is determined that ≧ Ta1), the temperature Tr in 1 of the exhaust gas entering the heat exchanger 11 when only one flue 7 is open is the heat when both the flues 7 are open. It will be elevated above the temperature Tr in the second exhaust gas exchanger 11 inlet side and opens the shut-off valve 24 provided in the second flue 7. At the same time, the air supply valve 26 provided in the preheating air path 13 on the second flue 7 side is also opened. By doing in this way, the calorie | heat amount of the exhaust gas which passes the inside of the flue 7 can be collect | recovered fully and efficiently.

なお、閉止弁２４及び空気供給弁２６を開閉操作する際には、予熱空気経路１３の熱交換器１１の圧力損失ΔＰａ１＝（Ｐａ１−Ｐａ１’）及び、ΔＰａ２＝（Ｐａ２−Ｐａ２’）と、排出ガス経路７（煙道７）の熱交換器１１の圧力損失ΔＰｇ１＝（Ｐｇ１−Ｐｇ１’）及び、ΔＰｇ２＝（Ｐｇ２−Ｐｇ２’）の関係が、ΔＰａ１／ΔＰｇ１＝ΔＰａ２／ΔＰｇ２となるように閉止弁２４及び空気供給弁２６の開度を調整する。また、（圧力損失ΔＰ∝流量Ｑ２)をＱａｉｎ１／Ｑｇｒｉｎ１＝Ｑａｉｎ２／Ｑｇｒｉｎ２となるように閉止弁２４及び空気供給弁２６の開度を調整する。また、ハンチング（制御応答結果が振動する）を防止するために、加熱炉１内の燃焼量Ｎｋをオフセットし、空気の予熱温度Ｔａを算出する。 When opening / closing the shutoff valve 24 and the air supply valve 26, the pressure loss ΔPa1 = (Pa1-Pa1 ′) and ΔPa2 = (Pa2-Pa2 ′) of the heat exchanger 11 in the preheating air path 13; The relationship between the pressure loss ΔPg1 = (Pg1−Pg1 ′) and ΔPg2 = (Pg2−Pg2 ′) of the heat exchanger 11 in the exhaust gas path 7 (the flue 7) is ΔPa1 / ΔPg1 = ΔPa2 / ΔPg2. The opening degree of the stop valve 24 and the air supply valve 26 is adjusted. Moreover, the opening degree of the closing valve 24 and the air supply valve 26 is adjusted so that (pressure loss ΔP∝flow rate Q 2 ) becomes Qa in 1 / Qgr in 1 = Qa in 2 / Qgr in 2. Further, in order to prevent hunting (the control response result vibrates), the combustion amount Nk in the heating furnace 1 is offset, and the air preheating temperature Ta is calculated.

以上述べた本発明の加熱炉１を用いて、加熱炉１を制御する方法、言い換えれば煙道７に備えられた閉止弁２４の開閉操作をする方法について、説明する。
まず、本発明の加熱炉１に配備された空気算出手段は、炉端排出ガス算出部２１で加熱炉１内の燃焼量を基に、当該加熱炉１の後端部（炉端）の排出ガスの温度Ｔｇ及び流量Ｑｇを算出する。 A method for controlling the heating furnace 1 using the heating furnace 1 of the present invention described above, in other words, a method for opening and closing the closing valve 24 provided in the flue 7 will be described.
First, the air calculating means provided in the heating furnace 1 of the present invention is based on the amount of combustion in the heating furnace 1 in the furnace end exhaust gas calculation unit 21, and the exhaust gas at the rear end (furnace end) of the heating furnace 1. The temperature Tg and the flow rate Qg are calculated.

次に、炉端排出ガス算出部２１の算出結果（炉端の排出ガスの温度Ｔｇ及び流量Ｑｇ）
、煙道７内に侵入する侵入空気量Ｑａｉｒ及び煙道７から放散される放散熱量Ｎｋを基に、両方の煙道７を開放しているときの熱交換器１１の入側の排出ガス温度Ｔｒｉｎ２と、一方の煙道７のみを開放しているときの熱交換器１１の入側の排出ガス温度Ｔｒｉｎ１とを求める。 Next, the calculation result of the furnace end exhaust gas calculation unit 21 (temperature Tg and flow rate Qg of the exhaust gas at the furnace end)
Based on the amount of air Qair entering the flue 7 and the amount of heat dissipated from the flue 7, the exhaust gas temperature on the inlet side of the heat exchanger 11 when both the flues 7 are opened Tr in 2 and the exhaust gas temperature Tr in 1 on the inlet side of the heat exchanger 11 when only one flue 7 is opened are obtained.

さらに、熱交換器入側排出ガス算出部２２の算出結果（排出ガス温度Ｔｒｉｎ２及び、排出ガス温度Ｔｒｉｎ１）を基に、両方の煙道７を開放しているときの熱交換器１１の出側の空気の予熱温度Ｔａ２と、一方の煙道７のみを開放しているときの熱交換器１１の出側の空気の予熱温度Ｔａ１とを求める。
そして、熱交換器出側空気算出部２３の算出結果（空気の予熱温度Ｔａ２及び、空気の予熱温度Ｔａ１）を基に、両方の煙道７を開放しているときの熱交換器１１出側の空気の予熱温度Ｔａ２が、一方の煙道７のみ開放しているときの熱交換器１１出側の空気の予熱温度Ｔａ１より低い場合、閉止弁２４を閉鎖する。また、第２の煙道７側の予熱空気経路１３に備えられた空気供給弁２６も閉鎖する。 Furthermore, based on the calculation results (exhaust gas temperature Tr in 2 and exhaust gas temperature Tr in 1) of the heat exchanger inlet side exhaust gas calculation unit 22, the heat exchanger when both the flues 7 are opened 11 and the preheating temperature Ta1 of the air on the outlet side of the heat exchanger 11 when only one flue 7 is opened.
And based on the calculation result (the air preheating temperature Ta2 and the air preheating temperature Ta1) of the heat exchanger outlet side air calculation unit 23, the outlet side of the heat exchanger 11 when both the flues 7 are opened When the air preheating temperature Ta2 is lower than the air preheating temperature Ta1 on the outlet side of the heat exchanger 11 when only one flue 7 is open, the closing valve 24 is closed. Further, the air supply valve 26 provided in the preheating air path 13 on the second flue 7 side is also closed.

以上述べたように、本発明の加熱炉１及び加熱炉１の制御方法を用いることで加熱炉１で鋼材Ｗを加熱するに際して、煙道７内を通過する排出ガスの廃熱を十分、且つ効率的に熱回収することができる。そして、加熱炉１の燃焼量Ｎｋに応じて、煙道７の本数（１つの煙道７、あるいは両方の煙道７）の切り替え制御を行うことで、加熱炉１の全燃焼量領域における廃熱の回収効率を最大にすることができるという効果をもたらす。   As described above, when heating the steel material W in the heating furnace 1 by using the heating furnace 1 and the control method of the heating furnace 1 of the present invention, the waste heat of the exhaust gas passing through the flue 7 is sufficient, and Heat can be recovered efficiently. Then, according to the combustion amount Nk of the heating furnace 1, switching control of the number of the flues 7 (one flue 7 or both flues 7) is performed, so that the waste in the entire combustion amount region of the heating furnace 1 is eliminated. This brings about an effect that the heat recovery efficiency can be maximized.

なお、今回開示された実施形態はすべての点で例示であって制限的なものではないと考えられるべきである。特に、今回開示された実施形態において、明示的に開示されていない事項、例えば、運転条件や操業条件、各種パラメータ、構成物の寸法、重量、体積などは、当業者が通常実施する範囲を逸脱するものではなく、通常の当業者であれば、容易に想定することが可能な値を採用している。   The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. In particular, in the embodiment disclosed this time, matters that are not explicitly disclosed, for example, operating conditions and operating conditions, various parameters, dimensions, weights, volumes, and the like of a component deviate from a range that a person skilled in the art normally performs. Instead, values that can be easily assumed by those skilled in the art are employed.

１ 加熱炉
２ 炉体
３ 搬入口
４ 搬出口
５ ウォーキングビーム（鋼材搬送装置）
６ 燃焼バーナ
７ 煙道（排出ガス経路、一次側）
８ 流入口
９ 流出口
１０ 炉圧ダンパ
１１ 熱交換器（レキュペレータ）
１２ ブロワ
１３ 予熱空気経路（二次側）
２０ 空気温度算出手段
２１ 炉端排出ガス算出部
２２ 熱交換器入側排出ガス算出部
２３ 熱交換器出側空気算出部
２４ 閉止弁
２５ 閉止弁操作手段
２６ 空気供給弁
Ｗ 鋼材（鋳片） DESCRIPTION OF SYMBOLS 1 Heating furnace 2 Furnace 3 Carry-in entrance 4 Carry-out exit 5 Walking beam (steel material conveyance apparatus)
6 Combustion burner 7 Flue (exhaust gas path, primary side)
8 Inlet 9 Outlet 10 Furnace pressure damper 11 Heat exchanger (Recuperator)
12 Blower 13 Preheating air path (secondary side)
20 Air temperature calculation means 21 Furnace end exhaust gas calculation part 22 Heat exchanger inlet side exhaust gas calculation part 23 Heat exchanger outlet side air calculation part 24 Close valve 25 Close valve operation means 26 Air supply valve W Steel (slab)

Claims (4)

排出ガスが通過する煙道を一対備えるとともに、各煙道に排出ガスの廃熱を回収する熱交換器が配備されている加熱炉において、
前記煙道の少なくとも一方に備えられ且つ当該煙道の開口を閉鎖する閉止弁と、
前記熱交換器の出側の空気の予熱温度を算出する空気温度算出手段と、
前記空気温度算出手段の算出結果を基に、両方の煙道を開放しているときの熱交換器出側の空気の予熱温度が、一方の煙道のみ開放しているときの熱交換器出側の空気の予熱温度より低い場合、前記閉止弁を閉鎖する閉止弁操作手段と、
を有することを特徴とする加熱炉。 In a heating furnace provided with a pair of flues through which exhaust gas passes and in which a heat exchanger for recovering waste heat of the exhaust gas is arranged in each flue,
A shut-off valve provided on at least one of the flues and closing an opening of the flue;
Air temperature calculating means for calculating the preheating temperature of the air on the outlet side of the heat exchanger;
Based on the calculation result of the air temperature calculation means, the preheat temperature of the air at the outlet side of the heat exchanger when both flues are open is the heat exchanger output when only one flue is open. A closing valve operating means for closing the closing valve when lower than the preheating temperature of the side air;
A heating furnace characterized by comprising: 前記空気温度算出手段は、
前記加熱炉内の燃焼量を基に、当該加熱炉の煙道接続部での排出ガスの温度及び流量を算出する炉端排出ガス算出部と、
前記炉端排出ガス算出部の算出結果、前記煙道内に侵入する空気量及び前記煙道から放散される熱量を基に、両方の煙道を開放しているときの熱交換器の入側の排出ガス温度と、一方の煙道のみを開放しているときの熱交換器の入側の排出ガス温度とを求める熱交換器入側排出ガス算出部と、
前記熱交換器入側排出ガス算出部の算出結果を基に、両方の煙道を開放しているときの熱交換器の出側の空気の予熱温度と、一方の煙道のみを開放しているときの熱交換器の出側の空気の予熱温度とを求める熱交換器出側空気算出部と、
を備えており、
前記閉止弁操作手段は、熱交換器出側空気算出部の算出結果を基に、両方の煙道を開放しているときの熱交換器出側の空気の予熱温度が、一方の煙道のみ開放しているときの熱交換器出側の空気の予熱温度より低い場合、前記閉止弁を閉鎖するように構成されている
ことを特徴とする請求項１に記載の加熱炉。 The air temperature calculation means includes
Based on the amount of combustion in the heating furnace, a furnace end exhaust gas calculation unit that calculates the temperature and flow rate of the exhaust gas at the flue connection of the heating furnace,
Based on the calculation result of the furnace end exhaust gas calculation unit, the amount of air entering the flue and the amount of heat dissipated from the flue, the exhaust on the inlet side of the heat exchanger when both the flues are open A heat exchanger inlet side exhaust gas calculating unit for obtaining a gas temperature and an exhaust gas temperature on the inlet side of the heat exchanger when only one flue is opened;
Based on the calculation result of the heat exchanger inlet side exhaust gas calculation unit, the preheat temperature of the air on the outlet side of the heat exchanger when both flues are open, and only one of the flues is opened. A heat exchanger outlet air calculation unit for obtaining a preheat temperature of the outlet air of the heat exchanger when
With
Based on the calculation result of the heat exchanger outlet air calculation unit, the closing valve operating means is configured so that the preheat temperature of the air on the heat exchanger outlet side when both flues are open is only one of the flues. The heating furnace according to claim 1, wherein the shutoff valve is configured to be closed when the temperature is lower than the preheating temperature of the air on the outlet side of the heat exchanger when the heat exchanger is open. 排出ガスが通過する煙道を一対備えるとともに、各煙道に排出ガスの廃熱を回収する熱交換器が配備されている加熱炉の制御方法において、
前記煙道の少なくとも一方には、当該煙道の開口を閉鎖する閉止弁が備えられるものとなっており、
前記熱交換器の入側の排出ガスの温度及び前記熱交換器の出側の空気の予熱温度を算出する空気算出工程と、
前記空気算出工程の算出結果を基に、両方の煙道を開放しているときの熱交換器出側の空気の予熱温度が、一方の煙道のみ開放しているときの熱交換器出側の空気の予熱温度より低い場合、前記閉止弁を閉鎖する閉止弁操作工程と、
を有することを特徴とする加熱炉の制御方法。 In the control method of a heating furnace provided with a pair of flues through which exhaust gas passes, and a heat exchanger for recovering waste heat of the exhaust gas in each flue,
At least one of the flue is provided with a closing valve for closing the opening of the flue,
An air calculating step for calculating the temperature of the exhaust gas on the inlet side of the heat exchanger and the preheating temperature of the air on the outlet side of the heat exchanger;
Based on the calculation result of the air calculation step, the preheat temperature of the air on the outlet side of the heat exchanger when both flues are open is the outlet side of the heat exchanger when only one of the flues is open A closing valve operating step of closing the closing valve when the temperature is lower than the preheating temperature of the air;
A method for controlling a heating furnace, comprising: 前記空気算出工程は、
前記加熱炉内の燃焼量を基に、当該加熱炉の煙道接続部の排出ガスの温度及び流量を算出する炉端排出ガス算出工程と、
前記炉端排出ガス算出工程の算出結果、前記煙道内に侵入する空気量及び前記煙道から放散される熱量を基に、両方の煙道を開放しているときの熱交換器の入側の排出ガス温度と、一方の煙道のみを開放しているときの熱交換器の入側の排出ガス温度とを求める熱交換器入側排出ガス算出工程と、
前記熱交換器入側排出ガス算出部の算出結果を基に、両方の煙道を開放しているときの熱交換器の出側の空気の予熱温度と、一方の煙道のみを開放しているときの熱交換器の出側の空気の予熱温度とを求める熱交換器出側空気算出工程と、
を備えており、
前記閉止弁操作工程は、熱交換器出側空気算出工程の算出結果を基に、両方の煙道を開
放しているときの熱交換器出側の空気の予熱温度が、一方の煙道のみ開放しているときの熱交換器出側の空気の予熱温度より低い場合、前記閉止弁を閉鎖する
ことを特徴とする請求項３に記載の加熱炉の制御方法。 The air calculating step includes
A furnace end exhaust gas calculation step for calculating the temperature and flow rate of the exhaust gas at the flue connection of the heating furnace based on the combustion amount in the heating furnace,
Based on the calculation result of the furnace end exhaust gas calculation process, the amount of air entering the flue and the amount of heat dissipated from the flue, the exhaust on the inlet side of the heat exchanger when both the flues are open A heat exchanger inlet side exhaust gas calculating step for obtaining a gas temperature and an exhaust gas temperature on the inlet side of the heat exchanger when only one of the flues is opened;
Based on the calculation result of the heat exchanger inlet side exhaust gas calculation unit, the preheat temperature of the air on the outlet side of the heat exchanger when both flues are open, and only one of the flues is opened. A heat exchanger outlet air calculation step for obtaining a preheat temperature of the outlet air of the heat exchanger when
With
The closing valve operating step is based on the calculation result of the heat exchanger outlet air calculation step, and the preheat temperature of the air at the outlet side of the heat exchanger when both flues are open is only one of the flues. The method for controlling a heating furnace according to claim 3, wherein the closing valve is closed when the temperature is lower than a preheating temperature of the air on the outlet side of the heat exchanger when it is open.
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