JP4005741B2

JP4005741B2 - Coke production method

Info

Publication number: JP4005741B2
Application number: JP09450399A
Authority: JP
Inventors: 誠治野村
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 1999-04-01
Filing date: 1999-04-01
Publication date: 2007-11-14
Anticipated expiration: 2019-04-01
Also published as: JP2000282048A

Description

【０００１】
【発明の属する技術分野】
本発明は、室式コークス炉におけるコークスの製造方法に関するものであり、特にコークス押し出し時における押し出し側圧を低減するコークスの製造方法に関するものである。
【０００２】
【従来の技術】
室式コークス炉によるコークス製造においては、乾留を完了したコークスを押し出すことによってコークスを炉外に排出する。コークス押し出し時においてはコークスが炉壁を押し付ける押し出し側圧がかかるが、この押し出し側圧が大きいと炉壁に負荷を及ぼすこととなる。特に、押し詰まりや押し止めが発生すると炉壁に過大な負荷が作用して、炉壁損傷の原因となることが知られている。
【０００３】
高炉用コークスを製造するコークス炉は老朽化が進行しており、コークス炉の炉壁に及ぼす負荷をおさえてコークス炉の寿命を延長することは、現在のコークス製造技術においてきわめて大きな課題の一つである。
【０００４】
炭化室内への石炭装入量が多すぎると、押し出し時におけるコークスケーキの高さが高く、押し出し時にコークスケーキが炭化室の天井につかえてしまい、押し出しが困難になることがある。
【０００５】
一方、炭化室内への石炭装入量が少なすぎると、炭化室上部の空間が広くなるため、上部の炉頂空間及び装入石炭の上端付近の温度が通常に比べて高くなり、炉壁にカーボンが付着しやすい状況となる。このため、過小装入操業を継続すると、炉壁へのカーボン付着によるトラブルが多発する傾向にある。過小装入によって炉壁にカーボンが付着する場合、付着量は場所によって均一ではないので壁面に凹凸が生じる。このような状況では、装入量が多めになったロットにおいてはコークスの押し出し時に凹凸のある壁面によってコークス排出に抵抗が生じ、押し出しに過大な力が必要となる。結果的に押し出し側圧も過大となり、炉壁損傷の原因となるのである。
【０００６】
以上のような理由により、コークス炉操業においては、過大装入、過小装入を避けるべく、装入炭量を一定に保つように操業を行っている。さらには、装入炭量が一定でも装入高さにばらつきが生じると結局は過大装入・過小装入の問題が生じるので、石炭銘柄や粒度等の石炭性状及び含有水分から石炭の装入密度を求め、装入高さを一定にするように該装入密度に基づいて装入炭量の調整を行っている。
【０００７】
【発明が解決しようとする課題】
従来においては石炭の装入高さを一定に保っているにもかかわらず、乾留後のコークスケーキ高さにはばらつきが生じていた。これでは、過大装入・過小装入による上記の問題は解決されずに残存し、押し出し側圧によるコークス炉炉壁負荷を増大する原因となっていた。
【０００８】
本発明は、押し出し時のコークスケーキ高さを一定に保つコークスの製造方法を提供し、もってコークス押し出し時における押し出し側圧を低減して炉壁損傷を防止することを目的とする。
【０００９】
【課題を解決するための手段】
石炭装入高さを一定にしてもコークスケーキ高さが一定にならないのは、コークス炉の操業条件あるいは装入石炭性状によりコークスの高さ方向収縮率（垂直焼き減り率）が異なるためである。本発明者等は、該収縮率が異なるのは装入石炭の膨張圧が石炭の配合によって異なることに原因があり、膨張圧が高いと乾留中にコークスケーキを炉壁に押しつけて突っ張り、コークスケーキの沈下が遅れるため、垂直焼き減りが減少することを見出した。即ち、膨張圧が高い配合炭を用いた場合には、装入時の装入高さが同じでも焼き上がり後のコークスケーキの高さが高くなって押し出し時におけるコークスケーキの天井づかえが発生しやすくなり、逆に膨張圧が低い配合炭を用いた場合には、焼き上がり後のコークスケーキの高さが低くなって炉壁のカーボン付着量が増大する。
【００１０】
そして、配合炭の収縮率と膨張圧との間には膨張圧が一定値以下の範囲では直線的な関係があり、膨張圧がゼロのときの仮想的収縮率を基準収縮率とおくと、配合炭の収縮率と基準収縮率との差は配合炭の膨張圧に対して比例関係にあることを明らかにした。
【００１１】
本発明は以上の知見に基づいてなされたものであり、その要旨とするところは、下記のとおりである。
（１）コークス炉に装入する配合炭の膨張圧を求め、コークス炉内での該配合炭の収縮率と基準収縮率との差は前記配合炭の膨張圧に比例するとして前記配合炭の収縮率を定め、該配合炭の収縮率およびコークスケーキ高さの目標値に基づいて装入炭の装入高さを定めることにより、押し出し時のコークスケーキ高さを一定に保つことを特徴とするコークスの製造方法。
（２）前記配合炭の膨張圧は、配合する各銘柄石炭の膨張圧の加成平均値、非微粘結炭配合率、非微粘結炭以外の石炭の全膨張率に基づいて求めることを特徴とする上記（１）に記載のコークスの製造方法。
（３）前記配合炭の膨張圧は下記式（１）よって求めることを特徴とする上記（２）に記載のコークスの製造方法。
Px =ａ・Σpi xi −ｂ・Σpi xi ・(X＋ｃ・X2 )・[1 + 1/(ｄ・TD＋ｅ)]＋ｆ …（１）
ただし、
Px：配合炭の膨張圧（ｋＰａ）
pi ：単味炭ｉの膨張圧（ｋＰａ）
xi ：単味炭ｉの配合割合（−）
Σpi xi ：各銘柄石炭の膨張圧の加成平均値（ｋＰａ）
X：非微粘結炭の配合割合（％）
TD：粘結炭のみの配合炭の全膨張率（％）
ａ，ｂ，ｃ，ｄ，ｅ，ｆ：定数
（４）配合炭の膨張圧から下記式（２）によって配合炭の収縮率を求め、配合炭の収縮率から下記式（３）によって装入炭の装入高さを定めることを特徴とする上記（１）〜（３）のいずれかに記載のコークスの製造方法。
配合炭の収縮率＝基準収縮率−ｋ×配合炭の膨張圧（２）
装入高さ＝コークスケーキ高さ÷（１００−配合炭の収縮率）×１００（３）
ただし、基準収縮率は配合炭の膨張圧がゼロのときの配合炭の収縮率であり、ｋは定数である。
【００１２】
【発明の実施の形態】
本発明において、配合炭の膨張圧は、例えば特開平５−２５５６７０号公報に記載のように可動壁型試験乾留炉を用いる方法、あるいは特開平４−２７２９９２号公報に記載のように試験炉で軟化溶融した石炭層内のガス圧力を測定する方法により実測によって求めることもできる。
【００１３】
一方、配合炭の膨張圧は、配合する各銘柄石炭の膨張圧の加成平均値、非微粘結炭配合率、非微粘結炭以外の石炭の全膨張率に基づいて求めることができるので、配合炭を用いた実測によらず、配合する石炭の各銘柄毎に予め測定によって求めた膨張圧に基づいて、下記に示すように計算によって配合炭の膨張圧を求めることもできる。
【００１４】
軟化溶融した石炭層のガス透過係数は式（４）で表せる（有馬孝，野村誠治，福田耕一：鉄と鋼，８２（’９６），６５）。
１／Ｋ＝Ｓ（Ｃ−１）（４）
Ｋ：軟化溶融石炭のガス透過係数［ｍ²］
Ｓ：傾き［ｍ^-2］
Ｃ：圧縮比［−］
【００１５】
圧縮比は石炭の自由膨張がどの程度拘束されているかを示す指標であり、式（５）で定義される。
Ｃ＝Ｖ_f／Ｖ（５）
Ｖ_f：自由膨張時の最大比容積［ｃｍ³／ｇ］
Ｖ：膨張拘束条件下での軟化溶融石炭比容積
（ガス透過係数測定時における装入密度の逆数）［ｃｍ³／ｇ］
【００１６】
ここで、以下の仮定をおくことにより、配合炭の膨張圧推定式を導いた。
仮定▲１▼：膨張圧は軟化溶融した石炭層のガス透過係数に比例する。
仮定▲２▼：非微粘結炭配合割合により（４）式の傾きＳは変化しない。
仮定▲３▼：非微粘結炭配合割合および粘結炭の全膨張率が膨張圧に及ぼす影響は、配合炭の圧縮比変化に起因すると仮定し、非微粘結炭を含む配合炭の圧縮比については、非微粘結炭配合割合の関数で表せる膨張阻害効果φにより、粘結炭のみの配合炭の圧縮比から推定できるとする。
仮定▲４▼：粘結炭のみの配合炭の膨張圧は高膨張圧炭膨張圧加成値の１次式で表せる。
【００１７】
膨張圧は軟化溶融した石炭層のガス透過係数に比例すると仮定すれば（仮定▲１▼）、非微粘結炭を含まない粘結炭のみの配合炭の膨張圧は、基本的に次式で表せる。
Ｐ_b≒ｋＳ（Ｃ_b−１）（６）
Ｐ_b：粘結炭のみの配合炭の膨張圧［ｋＰａ］
ｋ：定数
Ｃ_b：粘結炭のみの配合炭の圧縮比［−］
Ｃ_b＝ａ'ＴＤ＋ｂ' （７）
ＴＤ：粘結炭のみの配合炭の全膨張率［％］
ａ'，ｂ'：定数
【００１８】
粘結炭のみの配合炭において、Ｘ％の石炭を非微粘結炭に振り替えた場合、ｋ、Ｓが変わらないと仮定すると（仮定▲２▼）、非微粘結炭をＸ％含む配合炭の膨張圧Ｐ_Xは次のように表せる。

Ｐ_X：非微粘結炭をＸ％含む配合炭の膨張圧
Ｃ_X：非微粘結炭をＸ％含む配合炭の圧縮比
【００１９】
膨張圧が高い粘結炭の石炭化度は高く、軟化溶融範囲は高温側にある。一方、非微粘結炭の石炭化度は低く、軟化溶融範囲は低温側にあるため、膨張圧が高い粘結炭が軟化溶融している時に非微粘結炭は既に再固化しており、粘結炭の膨張を阻害する。そこで、非微粘結炭をＸ％含む配合炭の圧縮比については、非微粘結炭配合による膨張阻害効果φを考慮して、（９）式で表せる（仮定▲３▼）。
Ｃ_X＝φＣ_b（１００−Ｘ）／１００（９）
φ＝１−ｃ'Ｘ
φ：非微粘結炭配合による膨張阻害効果を示す係数［−］
ｃ'：定数
【００２０】
ここで、粘結炭のみの配合炭の膨張圧は高膨張圧炭膨張圧加成値の１次式で（１０）式のように近似できる（仮定▲４▼）。
P_b=d'Σp_ix_i+ e' （１０）
p_i：高膨張圧炭ｉの膨張圧［ｋＰａ］
x_i：高膨張圧炭ｉの配合割合
Σp_ix_i：高膨張圧炭膨張圧の加成平均値［ｋＰａ］
d',e'：定数
【００２１】
（７）（８）（９）（１０）式より、
P_X=(ｄ'Σp_ix_i+ｅ')/(ａ'TD+ｂ'-1)×[(1-ｃ'Ｘ)(ａ'TD+ｂ'-1)(100-Ｘ)/100-1]
≒a・Σp_ix_i-b・Σp_ix_i・(X+cX²)・[1+1/(d・TD+e)]+f （１）
a, b, c, d, e, f：定数
即ち、前記式（１）によって配合炭の膨張圧を求めることができる。
【００２２】
ここで、単味炭ｉの膨張圧p_iは、特開平４−２７２９９２号公報で提案の方法、すなわち、軟化溶融した石炭が発生するガスの圧力を測定する装置として、金属製の石炭装入容器内に測定対象の石炭を装入すると共に、内部の圧力を測定するプローブを装着した石炭装入容器と、この石炭装入容器を収容して、石炭装入容器の側面から８００〜１２００℃に加熱可能な加熱炉から構成された試験炉を用いて測定することができる。また、粘結炭のみの配合炭の全膨張率TDはＪＩＳ
Ｍ８８０１石炭膨張性試験方法によって求めることができる。
【００２３】
ａ〜ｆの各定数をそれぞれa=0.795064, b=0.004087, c=-0.0040476, d=0.00986, e=-0.2112, f=-5.9394とすると、実測によって求めた配合炭の膨張圧とほぼ一致する結果を得ることができた。
【００２４】
配合炭の収縮率を、コークスの高さ方向収縮率（垂直焼き減り率）として、（石炭装入高さ−焼き上がりコークスケーキ高さ）／（石炭装入高さ）×１００で定義する。即ち、
装入高さ＝コークスケーキ高さ÷（１００−配合炭の収縮率）×１００（３）である。
【００２５】
コークス炉において、高さ方向における収縮挙動は、石炭装入後数時間の間におこる一次収縮と乾留後期におこる二次収縮に分けることができるが、一次収縮は水分の蒸発に起因する石炭粒子充填構造の圧密化によりおこると考えられており、石炭粉砕粒度や水分によってきまる石炭装入密度に大きく依存する。一方乾留後期におこる二次収縮は、膨張圧に大きく依存する。したがって、ここで定義する配合炭の収縮率は、一次収縮と二次収縮の和である。
【００２６】
この配合炭の収縮率と上記式（１）で求めた配合炭の膨張圧との関係を調査した結果、図１に示すような関係が得られた。配合炭の膨張圧と収縮率とは膨張圧２０ｋＰａ以下においては直線的な関係を有し、膨張圧ゼロにおける仮想的な収縮率を基準収縮率とすると、配合炭の収縮率と基準収縮率との差は前記配合炭の膨張圧に比例する。即ち、下記式（２）で表すことができる。
配合炭の収縮率＝基準収縮率−ｋ×配合炭の膨張圧（２）
図１に示した実績に基づくと、基準収縮率は約８％であり、定数ｋは約０．１（％／ｋＰａ）である。
【００２７】
配合炭の膨張圧と収縮率とが直線的な関係を有する理由は、膨張圧が高いと乾留中にコークスケーキを炉壁に押しつけて突っ張り、コークスケーキの沈下が遅れ、それによって垂直焼き減りが減少するためであると考えられる。
【００２８】
なお、膨張圧が２０ｋＰａをこえる領域においては配合炭の収縮率は５．５〜６％であり、膨張圧にあまり依存しない。これは、膨張圧が高い領域では、二次収縮が開始する時期は、軟化溶融層が炭化室中央で会合し、膨張圧が消滅してからであり、その時点からの収縮量は膨張圧の影響を受けないためと考えられる。
【００２９】
一方、実際のコークス炉の操業においては膨張圧は概ね１０ｋＰａ以下の傾向があるので、実用的には（２）式の関係式を用いることにより収縮率を推定することができる。
【００３０】
図１の結果を用いて、あるいは本発明を適用するコークス炉において実際に配合炭の膨張圧と配合炭の収縮率との関係を実測により求め、基準収縮率と定数ｋとを定める。次いで、装入炭の配合が変更になるたびに、実測によりあるいは計算によって該配合炭の膨張圧を求める。これによって配合炭の収縮率を推定することができるので、該推定した配合炭の収縮率に基づき、焼き上がり後のコークスケーキ高さが目標値になるように石炭の装入高さを決定する。これにより、装入炭の配合が変更になってもコークスケーキ高さが常に一定になるようなコークスの製造が可能になる。
【００３１】
石炭の装入密度が一定であれば、石炭の装入量を定めれば装入高さを精度よく目標値に保つことができる。ところが装入密度は石炭銘柄、粒度等の石炭性状や石炭中の水分含有量によって変動する。従って、予め石炭銘柄、粒度等の石炭性状や石炭中の水分含有量に基づいて装入密度を推定し、該推定した装入密度によって装入量を調整することにより、実績装入高さを目標に一致させることができる。
【００３２】
【実施例】
室式コークス炉において本発明を適用した。予め石炭の各銘柄毎に膨張圧を前記した特開平４−２７２９９２号公報に記載の方法により求めておき、装入炭の配合に応じて式（１）によって配合炭の膨張圧を求めた。図１に基づいて配合炭の膨張圧と収縮率の関係を定め、コークスケーキ高さが一定になるように石炭装入高さを調整した。
【００３３】
本発明適用前の石炭装入高さ一定制御を行っていた時点においては、コークスケーキ高さは±２０ｃｍのばらつきを有していたが、本発明適用後においては、コークスケーキ高さのばらつきは±５ｃｍに低減した。その結果、コークスケーキ高さが高すぎることによる押し出し不良、炉壁へのカーボン付着による押し出し不良ともに減少することができた。
【００３４】
図２に本発明実施前後のコークス炉の押し出し電流の推移を示す。押し出し電流管理値は２５０Ａ以下である。本発明実施前には管理値をオーバーすることがあったが、本発明により配合炭の膨張圧に応じて装入炭量を制御した結果、押し出し電流を管理値以下に維持しながら安定的な操業を継続することが可能になった。
【００３５】
【発明の効果】
コークス炉に装入する配合炭の膨張圧に基づいて装入炭の装入高さを定めることにより、押し出し時のコークスケーキ高さを一定に保つことができ、もってコークス押し出し時における押し出し側圧を低減して炉壁損傷を防止することができた。
【図面の簡単な説明】
【図１】配合炭の膨張圧と配合炭の収縮率の関係を示す図である。
【図２】本発明の適用によるコークス炉の押し出し電流の改善効果を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing coke in a chamber coke oven, and more particularly to a method for producing coke that reduces the extrusion side pressure during coke extrusion.
[0002]
[Prior art]
In coke production by a room type coke oven, coke is discharged out of the furnace by extruding the coke that has undergone dry distillation. At the time of coke extrusion, an extruding side pressure that presses the furnace wall is applied, but if this extruding side pressure is large, a load is applied to the furnace wall. In particular, it is known that when clogging or holding down occurs, an excessive load acts on the furnace wall, causing damage to the furnace wall.
[0003]
Coke ovens that produce coke for blast furnaces are aging, and reducing the load on the coke oven wall and extending the life of the coke oven is one of the most important issues in current coke production technology. It is.
[0004]
If the amount of coal charged into the carbonization chamber is too large, the height of the coke cake at the time of extrusion may be high, and the coke cake may be caught on the ceiling of the carbonization chamber at the time of extrusion, which may make extrusion difficult.
[0005]
On the other hand, if the amount of coal charged into the carbonization chamber is too small, the space above the carbonization chamber will be widened, so the temperature in the upper furnace top space and the upper end of the charged coal will be higher than normal, Carbon is likely to adhere. For this reason, if the undercharge operation is continued, troubles due to carbon adhesion to the furnace wall tend to occur frequently. When carbon adheres to the furnace wall due to undercharging, the amount of adhesion is not uniform depending on the location, so that the wall surface is uneven. In such a situation, in a lot with a large charge, coke discharge is resisted by the uneven wall surface during coke extrusion, and excessive force is required for extrusion. As a result, the extrusion side pressure also becomes excessive, causing damage to the furnace wall.
[0006]
For the above reasons, in the coke oven operation, the operation is carried out so as to keep the charged coal amount constant in order to avoid overcharging and undercharging. Furthermore, even if the charging coal amount is constant, if the charging height varies, there will eventually be a problem of overcharging / undercharging, so coal charging from the coal properties such as coal brand and particle size and moisture content The density is obtained, and the amount of charging coal is adjusted based on the charging density so as to make the charging height constant.
[0007]
[Problems to be solved by the invention]
In the past, although the charging height of coal was kept constant, the coke cake height after dry distillation had varied. As a result, the above-mentioned problems due to overcharging and undercharging remain unresolved, causing a coke oven furnace wall load to increase due to extrusion side pressure.
[0008]
An object of the present invention is to provide a method for producing coke that keeps the coke cake height at the time of extrusion constant, thereby reducing the extrusion side pressure at the time of coke extrusion and preventing furnace wall damage.
[0009]
[Means for Solving the Problems]
The reason why the coke cake height does not become constant even when the coal charge height is constant is because the coke height shrinkage rate (vertical burn-out rate) differs depending on the operating conditions of the coke oven or the charged coal properties. . In the present inventors, the shrinkage ratio is different because the expansion pressure of the charged coal differs depending on the blending of the coal. When the expansion pressure is high, the coke cake is pressed against the furnace wall during dry distillation, It was found that the vertical burn-out was reduced because the settling of the cake was delayed. In other words, when blended coal with a high expansion pressure is used, even if the charging height at the time of charging is the same, the height of the coke cake after baking is high, and the coke cake ceiling is replaced at the time of extrusion. On the other hand, when blended coal having a low expansion pressure is used, the height of the coke cake after baking is lowered and the amount of carbon attached to the furnace wall is increased.
[0010]
And, there is a linear relationship between the shrinkage rate and the expansion pressure of the blended coal in the range where the expansion pressure is a certain value or less, and when the virtual shrinkage rate when the expansion pressure is zero is set as the reference shrinkage rate, It was clarified that the difference between the shrinkage of the blended coal and the standard shrinkage was proportional to the expansion pressure of the blended coal.
[0011]
This invention is made | formed based on the above knowledge, and the place made into the summary is as follows.
(1) The expansion pressure of the blended coal charged in the coke oven is obtained, and the difference between the shrinkage ratio of the blended coal in the coke oven and the reference shrinkage ratio is proportional to the expansion pressure of the blended coal. It is characterized in that the coke cake height at the time of extrusion is kept constant by determining the shrinkage rate and determining the charging height of the charging coal based on the shrinkage rate of the blended coal and the target value of the coke cake height. Coke manufacturing method.
(2) The expansion pressure of the blended coal should be determined based on the additive average value of the expansion pressure of each brand coal to be blended, the non-slightly caking coal blending ratio, and the total expansion rate of coal other than the non-slightly caking coal. The method for producing coke according to (1) above, wherein
(3) The method for producing coke according to (2) above, wherein the expansion pressure of the blended coal is obtained by the following formula (1).
Px = a · Σpi xi −b · Σpi xi • (X + c · X2) · [1 + 1 / (d · TD + e)] + f (1)
However,
Px: Expansion pressure of blended coal (kPa)
pi: Expansion pressure of simple coal i (kPa)
xi: Mixing ratio of simple coal i (-)
Σpi xi: Additive average value (kPa) of expansion pressure of each brand coal
X: Mixing ratio of non-slightly caking coal (%)
TD: Total expansion rate of blended coal with caking coal only (%)
a, b, c, d, e, f: Constant (4) The shrinkage rate of the blended coal is obtained from the expansion pressure of the blended coal according to the following formula (2), and charged according to the following formula (3) from the shrinkage rate of the blended coal. The method for producing coke according to any one of (1) to (3), wherein a charging height of charcoal is determined.
Shrinkage rate of blended coal = standard shrinkage rate-k x expansion pressure of blended coal (2)
Charging height = coke cake height ÷ (100-shrinkage of blended coal) x 100 (3)
However, the standard shrinkage rate is the shrinkage rate of the blended coal when the expansion pressure of the blended coal is zero, and k is a constant.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the expansion pressure of the blended coal is determined by, for example, a method using a movable wall type test dry distillation furnace as described in JP-A-5-255670 or a test furnace as described in JP-A-4-272929. It can also be obtained by actual measurement by a method of measuring the gas pressure in the softened and melted coal bed.
[0013]
On the other hand, the expansion pressure of blended coal can be determined based on the additive average value of the expansion pressure of each brand coal to be blended, the non-slightly caking coal blending ratio, and the total expansion rate of coal other than the non-slightly caking coal. Therefore, the expansion pressure of the blended coal can be obtained by calculation as shown below, based on the expansion pressure obtained by measurement in advance for each brand of coal to be blended, regardless of the actual measurement using the blended coal.
[0014]
The gas permeation coefficient of a softened and melted coal bed can be expressed by equation (4) (Taka Arima, Seiji Nomura, Koichi Fukuda: Iron and Steel, 82 ('96), 65).
1 / K = S (C-1) (4)
K: Gas permeation coefficient of soft molten coal [m ² ]
S: Inclination [m ^-2 ]
C: Compression ratio [-]
[0015]
The compression ratio is an index indicating how much the free expansion of coal is constrained, and is defined by Equation (5).
C = _Vf / V (5)
V _f : Maximum specific volume during free expansion [cm ³ / g]
V: Specific volume of softened molten coal under expansion restraint conditions (reciprocal of charging density when measuring gas permeability coefficient) [cm ³ / g]
[0016]
Here, the formula for estimating the expansion pressure of coal blend was derived by making the following assumptions.
Assumption (1): The expansion pressure is proportional to the gas permeability coefficient of the softened and melted coal bed.
Assumption (2): The slope S of the equation (4) does not change depending on the blending ratio of non-slightly caking coal.
Assumption (3): It is assumed that the effect of the blending ratio of non-slightly caking coal and the total expansion rate of caking coal on the expansion pressure is due to the change in the compression ratio of the blended coal. It is assumed that the compression ratio can be estimated from the compression ratio of the blended coal of only caking coal by the expansion inhibiting effect φ that can be expressed as a function of the blend ratio of the non-slightly caking coal.
Assumption {circle around (4)}: The expansion pressure of the blended coal containing only caking coal can be expressed by a linear expression of the high expansion pressure coal expansion pressure addition value.
[0017]
Assuming that the expansion pressure is proportional to the gas permeation coefficient of the softened and melted coal bed (assumed (1)), the expansion pressure of the blended coal containing only caking coal that does not contain non-minor caking coal is basically: It can be expressed as
P _b ≈kS (C _b −1) (6)
P _b : Expansion pressure [kPa] of blended coal containing only caking coal
k: constant C _b: coking coals only compression ratio of coal blend of [-]
C _b = a′TD + b ′ (7)
TD: Total expansion rate [%] of coal blend with only caking coal
a ′, b ′: constants
In the case of blended coal with only caking coal, if x and coal are transferred to non-slightly caking coal, assuming that k and S do not change (Assumption (2)), blending containing X% of non-slightly caking coal inflation pressure P _X of charcoal can be expressed in the following manner.

P _X : Expansion pressure of blended coal containing X% non-slightly caking coal C _X : Compression ratio of blended coal containing X% non-slightly caking coal
Coking degree of caking coal with high expansion pressure is high, and the softening and melting range is on the high temperature side. On the other hand, since the coalification degree of non-slightly caking coal is low and the softening and melting range is on the low temperature side, when the caking coal with high expansion pressure is softening and melting, the non-slightly caking coal has already resolidified. Inhibits the expansion of caking coal. Therefore, the compression ratio of the blended coal containing X% of the non-slightly caking coal can be expressed by the equation (9) in consideration of the expansion inhibition effect φ by the non-slightly caking coal blend (assumed (3)).
C _X = φC _b (100−X) / 100 (9)
φ = 1−c′X
φ: Coefficient [−] indicating the expansion inhibition effect of non-slightly caking coal blend
c ': constant [0020]
Here, the expansion pressure of the blended coal consisting only of caking coal can be approximated as the equation (10) by the linear expression of the high expansion pressure coal expansion pressure addition value (assumed (4)).
P _b = d'Σp _i x _i + e '(10)
p _i : Expansion pressure of high expansion pressure coal i [kPa]
x _i : blending ratio of high expansion pressure coal _i Σp _i x _i : additive average value of high expansion pressure coal expansion pressure [kPa]
d ', e': constant [0021]
From (7), (8), (9) and (10),
P _X = (d′ Σp _i x _i + e ′) / (a′TD + b′−1) × [(1-c′X) (a′TD + b′−1) (100−X) / 100-1]
≒ a ・ Σp _i x _i -b ・ Σp _i x _i・ (X + cX ² ) ・ [1 + 1 / (d ・ TD + e)] + f (1)
a, b, c, d, e, f: constants, that is, the expansion pressure of the blended coal can be obtained by the above equation (1).
[0022]
Here, the expansion pressure p _i of simple coal _i is the method proposed in Japanese Patent Laid-Open No. Hei 4-272929, that is, as an apparatus for measuring the pressure of gas generated by softened and melted coal, a metal coal charge is used. The coal to be measured is charged into the container, the coal charging container equipped with a probe for measuring the internal pressure, and the coal charging container are accommodated, and 800 to 1200 ° C. from the side of the coal charging container. It can be measured by using a test furnace composed of a heating furnace that can be heated. In addition, the total expansion coefficient TD of the coal blend with only caking coal is JIS
It can be determined by the M8801 coal expansibility test method.
[0023]
When the constants a to f are a = 0.795064, b = 0.004087, c = -0.0040476, d = 0.00986, e = -0.2112, f = -5.9394, they almost coincide with the expansion pressure of the coal blend obtained by actual measurement. The result was obtained.
[0024]
The shrinkage rate of the blended coal is defined as (coal charge height-burnt coke cake height) / (coal charge height) × 100 as the coke height direction shrinkage rate (vertical burn-out rate). That is,
Charging height = Coke cake height / (100−shrinkage of blended coal) × 100 (3).
[0025]
In the coke oven, the shrinkage behavior in the height direction can be divided into primary shrinkage occurring several hours after coal charging and secondary shrinkage occurring in the late stage of carbonization, but the primary shrinkage is caused by the evaporation of moisture. It is thought to occur due to the consolidation of the packed structure, and depends greatly on the coal charge density determined by the coal pulverization particle size and moisture. On the other hand, the secondary contraction that occurs in the latter stage of dry distillation largely depends on the expansion pressure. Therefore, the shrinkage rate of the coal blend defined here is the sum of the primary shrinkage and the secondary shrinkage.
[0026]
As a result of investigating the relationship between the shrinkage ratio of the blended coal and the expansion pressure of the blended coal obtained by the above formula (1), the relationship shown in FIG. 1 was obtained. The expansion pressure and shrinkage ratio of the blended coal have a linear relationship at an expansion pressure of 20 kPa or less, and the hypothetical shrinkage ratio at zero expansion pressure is the reference shrinkage ratio. Is proportional to the expansion pressure of the blended coal. That is, it can be represented by the following formula (2).
Shrinkage rate of blended coal = standard shrinkage rate-k x expansion pressure of blended coal (2)
Based on the results shown in FIG. 1, the reference shrinkage is about 8%, and the constant k is about 0.1 (% / kPa).
[0027]
The reason why there is a linear relationship between the expansion pressure and shrinkage of coal blend is that if the expansion pressure is high, the coke cake is pressed against the furnace wall during dry distillation, and the settling of the coke cake is delayed. This is thought to be due to a decrease.
[0028]
In the region where the expansion pressure exceeds 20 kPa, the shrinkage rate of the blended coal is 5.5 to 6% and does not depend much on the expansion pressure. This is because, in the region where the expansion pressure is high, the time when the secondary contraction starts is that the softened and melted layers associate at the center of the carbonization chamber and the expansion pressure disappears, and the amount of contraction from that point is the expansion pressure. It is thought that it is not affected.
[0029]
On the other hand, in an actual coke oven operation, the expansion pressure tends to be approximately 10 kPa or less. Therefore, the contraction rate can be estimated practically by using the relational expression (2).
[0030]
The relationship between the expansion pressure of the blended coal and the shrinkage ratio of the blended coal is actually obtained by actual measurement using the result of FIG. 1 or in the coke oven to which the present invention is applied, and the reference shrinkage ratio and the constant k are determined. Next, each time the charging coal composition is changed, the expansion pressure of the coal blend is obtained by actual measurement or calculation. As a result, it is possible to estimate the shrinkage rate of the blended coal. Based on the estimated shrinkage rate of the blended coal, the charging height of the coal is determined so that the coke cake height after baking reaches the target value. . This makes it possible to produce coke so that the height of the coke cake is always constant even if the charging coal composition is changed.
[0031]
If the charging density of coal is constant, the charging height can be accurately maintained at the target value by determining the charging amount of coal. However, the charging density varies depending on the coal properties such as coal brand and particle size, and the moisture content in the coal. Therefore, by estimating the charging density in advance based on the coal properties such as coal brand and particle size and the water content in the coal, and adjusting the charging amount according to the estimated charging density, the actual charging height can be reduced. Can match the goal.
[0032]
【Example】
The present invention was applied in a room type coke oven. The expansion pressure was previously determined for each brand of coal by the method described in JP-A-4-2729292, and the expansion pressure of the blended coal was determined by equation (1) according to the blending of the charged coal. Based on FIG. 1, the relationship between the expansion pressure and the shrinkage rate of the blended coal was determined, and the coal charge height was adjusted so that the coke cake height was constant.
[0033]
At the time when the coal charging height constant control before application of the present invention was performed, the coke cake height had a variation of ± 20 cm, but after application of the present invention, the variation of the coke cake height was Reduced to ± 5 cm. As a result, both the extrusion failure due to the coke cake height being too high and the extrusion failure due to the carbon adhering to the furnace wall could be reduced.
[0034]
FIG. 2 shows the transition of the extrusion current of the coke oven before and after the implementation of the present invention. The extrusion current management value is 250 A or less. Although the control value may be exceeded before the implementation of the present invention, as a result of controlling the amount of charging coal according to the expansion pressure of the blended coal according to the present invention, it is stable while maintaining the extrusion current below the control value. It became possible to continue operation.
[0035]
【The invention's effect】
By determining the charging height of the charging coal based on the expansion pressure of the blended coal charged into the coke oven, the coke cake height during extrusion can be kept constant, so that the extrusion side pressure during coke extrusion can be reduced. Reduced and prevented the furnace wall damage.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the expansion pressure of blended coal and the shrinkage rate of blended coal.
FIG. 2 is a diagram showing the improvement effect of the extrusion current of the coke oven by the application of the present invention.

Claims

The expansion pressure of the blended coal charged into the coke oven is obtained, and the difference between the shrinkage ratio of the blended coal in the coke oven and the reference shrinkage ratio is proportional to the expansion pressure of the blended coal, and the shrinkage ratio of the blended coal is determined. defined method for producing coke characterized that you define the instrumentation Iridaka of instrumentation Nyusumi based on a target value of the shrinkage rate and coke cake height of the coal blend.
However, the reference shrinkage rate is a virtual shrinkage rate of the blended coal when the expansion pressure of the blended coal is zero.

The expansion pressure of the blended coal is obtained based on the additive average value of the expansion pressure of each brand coal to be blended, the non-slightly caking coal blending ratio, and the total expansion rate of coal other than the non-slightly caking coal. The method for producing coke according to claim 1.

The method for producing coke according to claim 2, wherein the expansion pressure of the blended coal is obtained by the following formula (1).
Px = a · Σpi xi −b · Σpi xi • (X + c · X2) · [1 + 1 / (d · TD + e)] + f (1)
However,
Px: Expansion pressure of blended coal (kPa)
pi: Expansion pressure of simple coal i (kPa)
xi: Mixing ratio of simple coal i (-)
Σpi xi: Additive average value (kPa) of expansion pressure of each brand coal
X: Mixing ratio of non-slightly caking coal (%)
TD: Total expansion rate of blended coal with caking coal only (%)
a, b, c, d, e, f: constants

The shrinkage rate of the blended coal is obtained from the following formula (2) from the expansion pressure of the blended coal, and the charging height of the charged coal is determined from the shrinkage rate of the blended coal by the following formula (3). A method for producing coke according to any one of claims 1 to 3.
Shrinkage rate of blended coal = standard shrinkage rate-k x expansion pressure of blended coal (2)
Charging height = coke cake height ÷ (100-shrinkage of blended coal) x 100 (3)
However, k is a constant.