JP3711191B2

JP3711191B2 - Method for preventing metal vapor deposition in regenerative alternating combustion furnace

Info

Publication number: JP3711191B2
Application number: JP17643397A
Authority: JP
Inventors: 俊山上
Original assignee: Osaka Gas Co Ltd
Current assignee: Osaka Gas Co Ltd
Priority date: 1997-06-17
Filing date: 1997-06-17
Publication date: 2005-10-26
Anticipated expiration: 2017-06-17
Also published as: JPH116616A

Description

【０００１】
【産業上の利用分野】
本発明は、モリブデン等のように、その酸化物の昇華温度の低い金属を含む合金の高温加熱処理を行う蓄熱式交番燃焼炉に関するものである。
【０００２】
【従来の技術】
図３は、この種の蓄熱式交番燃焼炉１の構造を示したもので、一対のバーナ２ａ，２ｂにそれぞれ蓄熱体を充填した蓄熱室３を付設すると共に、給気ブロア４及び排気ブロア５を四方弁６を介して両バーナ２ａ，２ｂに接続し、両バーナ２ａ，２ｂを数十秒〜数分間隔で交互に燃焼させて、一方のバーナ２ａの燃焼中に他方のバーナ２ｂを通して炉１内の排気ガスの排出を行うと共に、蓄熱室３で排熱を回収し、この排熱で次にこのバーナ２ｂが燃焼する時の燃焼空気を予熱するようにしたものであって、蓄熱室３から出ていく排気の温度は通常２００〜３５０℃と低いため排熱損失が小さく、高効率の加熱を行うことができる。１１は燃料供給管、１２ａ，１２ｂは燃料ガス遮断弁である。図４は蓄熱室３の構造を示したもので、蓄熱体としては通常セラミック製の小球又はハニカム構造体が用いられる。
【０００３】
【発明が解決しようとする課題】
上述の蓄熱式交番燃焼炉１において、例えばモリブデンを含有する合金の鍛造を行う場合、合金中のモリブデンが酸化して三酸化モリブデン（ＭｏＯ3 ）となり、これが昇華して排気中に混入し蓄熱室３内を通過する際に、その低温部で結晶化して付着し、蓄熱室３が閉塞されてしまうという問題がある。図５は、炉起動後の炉内温度の変化と、モリブデンが酸化物として昇華する温度、及び蓄熱室３の下部の約１００ｍｍの間（図４のＤ部）を通過する時の排ガス温度の実測値を示したもので、前述のように四方弁６を交互に切り換えて両バーナ２ａ，２ｂを交番燃焼させる場合、給気サイクルにおいて蓄熱室３の下部すなわち給気側端部（Ｄ部）の蓄熱体は低温の給気によって冷やされ、次の排気サイクルでは炉内の高温に曝されて排気中に昇華していた三酸化モリブデンが、この温度低下した蓄熱体に接触して蒸着し、この蒸着物が漸次蓄積して、ついには蓄熱体間の隙間を閉塞してしまうのである。本発明はかかる問題点に鑑み、上記金属の蒸着による蓄熱室３の閉塞を防止することを目的とするものである。
【０００４】
【課題を解決するための手段】
本発明による蓄熱式交番燃焼炉の金属蒸着防止方法は、図１及び図２に示すように、一対のバーナ２ａ，２ｂにそれぞれ蓄熱体を充填した蓄熱室３を設けると共に、給気ブロア４と排気ブロア５を四方弁６を介して両バーナ２ａ，２ｂに接続し、一方のバーナ２ａ（又は２ｂ）の燃焼中に他方のバーナ２ｂ（又は２ａ）の蓄熱室３で排熱を回収できるようにした蓄熱式交番燃焼炉において、上記四方弁６の切り換え周期を定期的又は任意時期に切り換えて通常周期よりも長くする長周期期間を設けたものである。上記四方弁６は、図では１個の切換弁で構成されているが、４個の開閉弁で構成することもできる。本発明の構成によれば、長周期期間中は高温の排気が通常の切り換え周期よりも長い時間連続して片方の蓄熱室３を通過するので、この間蓄熱室３には給気側から冷たい空気が流れ込むことがなく、従って蓄熱体の低温部Ｄの温度は高温排気によって金属酸化物の昇華温度以上に上昇し、通常運転中に蓄熱体表面に蓄積していた蒸着物は再度昇華して、炉気と共に外部へ排出されるのである。
【０００５】
【発明の実施の形態】
図１は本発明による蓄熱式交番燃焼炉の一実施例を示したもので、各バーナ２ａ，２ｂには、図２に示されているように、セラミック製の小球（例えば直径１０〜２０ｍｍ）が充填された蓄熱室３が一体に連設されており、これらの蓄熱室３に四方弁６を介して給気ブロア４及び排気ブロア５が接続され、一方のバーナ２ａ（又は２ｂ）の燃焼中に他方のバーナ２ｂ（又は２ａ）の給気路２ｂ（又は２ａ）が排気路として使用されるようにして、排ガスの熱により蓄熱体を介して燃焼空気が予熱されるようにしたものである。このとき炉１内の排気の温度は約１２００℃以上に達し、バーナ２ａ，２ｂの燃焼サイクル又は排熱回収サイクルの持続時間は例えば数十秒〜数分程度である。
【０００６】
バッチ式加熱処理を行う場合、蒸着金属除去操作は１日１回炉の停止前に行えばよく、また連続処理の場合は一定時間毎に行うようにしてもよい。長周期期間には、四方弁６の切り換え周期を例えば通常期間の１０倍程度とする。この期間中は、一方の蓄熱室３に通常の場合よりも長い時間継続して高温排気が流れ込むために、蓄熱室３の下部（Ｄ部）の蓄熱体まで徐々に高温となり、通常期間にこの部分に蒸着していた金属が再昇華して除去されるのである。このとき四方弁６には一方の通気路に高温の排気のみが通るので、この四方弁６の焼損を防止するために、電動バルブ１０を開いて冷却用空気吸引口９から外気を導入する。但し四方弁６及び排気ブロア５に高耐熱仕様のものを使用する場合には、空気吸引口９及び電動バルブ１０は不要である。なお以上の動作は、一方のバーナについて行ったのち、四方弁６を切り換えて他方のバーナについても同様に行い、１回の長周期期間に少なくとも両バーナについて１回以上の切り換え周期が含まれるものとする。
【０００７】
【実施例】
４−７９パーマロイを鍛造加熱処理する場合、処理温度は約１３００℃であるが、パーマロイに含有されているモリブデンの酸化物は約８００℃以上で昇華する。従って上述の長周期を排気が８００℃以上で蓄熱室３を通過するように調節する。蓄熱体としてセラミックの小球を用いる場合、この期間は１５分程度であり、またセラミックハニカムを用いる場合は、２〜３分で蓄熱体下部まで８００℃程度に達する。また四方弁６の耐熱性を考慮して、蓄熱室３の下流側に電動バルブ１０を介して冷却用空気を導入し、排気温度を約３００℃に下げて四方弁６を通過させる。各バーナについて四方弁６の長周期の切換え動作を１回ずつ行えば、蓄熱体に残存する三酸化モリブデンをほぼ完全に除去することができる。
【０００８】
【発明の効果】
本発明方法によれば上述のように、四方弁６の切り換え周期を変えるという簡単な構成によって、合金の加熱処理運転中に蓄熱体表面に付着した蒸着物を完全に除去することができ、蒸着物の蓄積による蓄熱室３の閉塞を未然に防止することができるという利点がある。またこの蒸着金属除去操作は処理物の加熱処理中にも行うことができるので、バッチ炉のみならず、連続炉においても定期的に実施することができる。なお本操作中は、排気温度が通常時よりも上昇するので排熱損失が若干増加するが、処理時間が数時間であるのに対して、本操作時間は数分〜数十分程度であり、殆ど問題にならない。
【図面の簡単な説明】
【図１】本発明の一実施例を示す交番燃焼炉の系統図。
【図２】同上の蓄熱室の構造を示した要部系統図。
【図３】従来の交番燃焼炉の系統図。
【図４】同上の蓄熱室の構造を示した要部系統図。
【図５】従来の炉内の動作状態を示すグラフ。
【符号の説明】
１炉
２ａ，２ｂバーナ
３蓄熱室
４給気ブロア
５排気ブロア
６四方弁
７炉扉
８通気路
９電動バルブ
１０冷却用空気吸引口
１１燃料供給管
１２ａ，１２ｂ燃料ガス遮断弁[0001]
[Industrial application fields]
The present invention relates to a regenerative alternating combustion furnace that performs high-temperature heat treatment of an alloy containing a metal whose oxide has a low sublimation temperature, such as molybdenum.
[0002]
[Prior art]
FIG. 3 shows the structure of this type of regenerative alternating combustion furnace 1. A pair of burners 2 a and 2 b are each provided with a heat storage chamber 3 filled with a heat storage body, and an air supply blower 4 and an exhaust blower 5. Is connected to both burners 2a and 2b via a four-way valve 6, both burners 2a and 2b are alternately burned at intervals of several tens of seconds to several minutes, and one burner 2a is burned through the other burner 2b during the combustion. 1, exhaust gas is discharged in the heat storage chamber 3, and exhaust heat is recovered in the heat storage chamber 3, and the combustion air when the burner 2 b is burned next is preheated by the exhaust heat. The temperature of the exhaust gas coming out of No. 3 is usually as low as 200 to 350 ° C., so that the heat loss is small and highly efficient heating can be performed. 11 is a fuel supply pipe, and 12a and 12b are fuel gas shut-off valves. FIG. 4 shows the structure of the heat storage chamber 3, and ceramic spheres or honeycomb structures are usually used as the heat storage body.
[0003]
[Problems to be solved by the invention]
In the above-described regenerative alternating combustion furnace 1, for example, when forging an alloy containing molybdenum, molybdenum in the alloy is oxidized to molybdenum trioxide (MoO 3), which is sublimated and mixed into the exhaust gas to be stored in the heat storage chamber 3. When passing through the interior, there is a problem that the heat storage chamber 3 is blocked by being crystallized and adhered at the low temperature portion. FIG. 5 shows changes in the furnace temperature after the start of the furnace, the temperature at which molybdenum sublimates as an oxide, and the exhaust gas temperature when passing through about 100 mm below the heat storage chamber 3 (D section in FIG. 4). The measured value is shown. When the four-way valve 6 is alternately switched to alternately burn the burners 2a and 2b as described above, the lower part of the heat storage chamber 3, that is, the supply side end (D part) in the supply cycle. In the next exhaust cycle, molybdenum trioxide that was exposed to the high temperature in the furnace and sublimated in the exhaust was deposited in contact with the heat storage body that had fallen in temperature. This deposited material gradually accumulates and eventually closes the gap between the heat accumulators. In view of such a problem, the present invention aims to prevent the heat storage chamber 3 from being blocked by the vapor deposition of the metal.
[0004]
[Means for Solving the Problems]
As shown in FIGS. 1 and 2, the method for preventing metal vapor deposition in a regenerative alternating combustion furnace according to the present invention includes a heat storage chamber 3 in which a pair of burners 2a and 2b are filled with a heat storage body, and an air supply blower 4 and The exhaust blower 5 is connected to both the burners 2a and 2b via the four-way valve 6 so that the exhaust heat can be recovered in the heat storage chamber 3 of the other burner 2b (or 2a) during combustion of the one burner 2a (or 2b). In the heat storage type alternating combustion furnace, the switching cycle of the four-way valve 6 is switched periodically or at an arbitrary time to provide a long cycle period longer than the normal cycle. The four-way valve 6 is composed of one switching valve in the figure, but can also be composed of four on-off valves. According to the configuration of the present invention, during the long period, the high temperature exhaust gas continuously passes through one of the heat storage chambers 3 for a longer time than the normal switching period. Therefore, the temperature of the low temperature portion D of the heat storage body rises to a temperature higher than the sublimation temperature of the metal oxide by high temperature exhaust, and the deposited material accumulated on the surface of the heat storage body during normal operation sublimates again. It is discharged to the outside along with the furnace air.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of a regenerative alternating combustion furnace according to the present invention. As shown in FIG. 2, each of the burners 2a and 2b has a ceramic sphere (for example, a diameter of 10 to 20 mm). ) Are integrally connected to each other, and an air supply blower 4 and an exhaust blower 5 are connected to these heat storage chambers 3 via a four-way valve 6, and one of the burners 2a (or 2b) is connected. During combustion, the supply passage 2b (or 2a) of the other burner 2b (or 2a) is used as an exhaust passage so that the combustion air is preheated via the heat accumulator by the heat of the exhaust gas. It is. At this time, the temperature of the exhaust gas in the furnace 1 reaches about 1200 ° C. or more, and the duration of the combustion cycle or exhaust heat recovery cycle of the burners 2a and 2b is, for example, about several tens of seconds to several minutes.
[0006]
When batch-type heat treatment is performed, the vapor deposition metal removal operation may be performed once a day before the furnace is stopped, and may be performed at regular intervals in the case of continuous treatment. In the long cycle period, the switching cycle of the four-way valve 6 is, for example, about 10 times the normal period. During this period, the high temperature exhaust gas continuously flows into one of the heat storage chambers 3 for a longer time than usual, so that the temperature of the heat storage body at the lower part (D part) of the heat storage chamber 3 gradually increases. The metal deposited on the part is sublimated again and removed. At this time, only high-temperature exhaust gas passes through the one-way passage through the four-way valve 6, so that the electric valve 10 is opened and outside air is introduced from the cooling air suction port 9 in order to prevent the four-way valve 6 from being burned out. However, when the high heat resistant type is used for the four-way valve 6 and the exhaust blower 5, the air suction port 9 and the electric valve 10 are unnecessary. The above operation is performed for one burner and then the four-way valve 6 is switched to perform the same for the other burner. One long cycle period includes at least one switching cycle for both burners. And
[0007]
【Example】
When forging heat treatment of 4-79 permalloy, the treatment temperature is about 1300 ° C., but the molybdenum oxide contained in permalloy sublimes at about 800 ° C. or higher. Therefore, the above-mentioned long period is adjusted so that the exhaust passes through the heat storage chamber 3 at 800 ° C. or higher. When ceramic spheres are used as the heat storage body, this period is about 15 minutes, and when a ceramic honeycomb is used, the temperature reaches about 800 ° C. at the bottom of the heat storage body in 2 to 3 minutes. In consideration of the heat resistance of the four-way valve 6, cooling air is introduced to the downstream side of the heat storage chamber 3 through the electric valve 10, and the exhaust temperature is lowered to about 300 ° C. to pass through the four-way valve 6. If the long-cycle switching operation of the four-way valve 6 is performed once for each burner, the molybdenum trioxide remaining in the heat storage body can be almost completely removed.
[0008]
【The invention's effect】
According to the method of the present invention, as described above, the deposit deposited on the surface of the heat storage body during the heat treatment operation of the alloy can be completely removed by a simple configuration in which the switching cycle of the four-way valve 6 is changed. There is an advantage that blockage of the heat storage chamber 3 due to accumulation of objects can be prevented in advance. Moreover, since this vapor deposition metal removal operation can be performed also during the heat processing of a processed material, it can implement regularly not only in a batch furnace but in a continuous furnace. During this operation, the exhaust heat temperature rises higher than usual, so the exhaust heat loss slightly increases. , Almost no problem.
[Brief description of the drawings]
FIG. 1 is a system diagram of an alternating combustion furnace showing an embodiment of the present invention.
FIG. 2 is a system diagram of the main part showing the structure of the heat storage chamber.
FIG. 3 is a system diagram of a conventional alternating combustion furnace.
FIG. 4 is a system diagram of a main part showing the structure of the heat storage chamber.
FIG. 5 is a graph showing an operating state in a conventional furnace.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Furnace 2a, 2b Burner 3 Heat storage chamber 4 Supply blower 5 Exhaust blower 6 Four-way valve 7 Furnace door 8 Air passage 9 Electric valve 10 Cooling air suction port 11 Fuel supply pipes 12a, 12b Fuel gas shutoff valve

Claims

A pair of burners is provided with a heat storage chamber filled with a heat storage body, and an air supply blower and an exhaust blower are connected to each burner via a four-way valve, and the four-way valve is switched at regular intervals. In the regenerative alternating combustion furnace in which the exhaust heat is recovered in the heat storage chamber of the other burner, a long cycle period is provided in which the switching cycle of the four-way valve is switched periodically or arbitrarily to make it longer than the normal cycle. A method for preventing metal deposition in a regenerative alternating combustion furnace, characterized in that:

2. The method of preventing metal deposition in a regenerative alternating combustion furnace according to claim 1, wherein the long cycle period includes at least one long cycle for both burners.

2. The method for preventing metal deposition in a regenerative alternating combustion furnace according to claim 1, wherein, during the long period, outside air is introduced into the ventilation path between each heat storage chamber and the four-way valve via an electric valve.