JP2004238692A - Method and device for blowing pulverized fine coal into blast furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for blowing pulverized fine coal into a blast furnace with which the necessary lowest limit of preheating temperature to various kinds of coals can be given without raising the cost or bringing about operational trouble. <P>SOLUTION: In the method for blowing the pulverized fine coal into the blast furnace, blowing the preheated pulverized fine coal as an auxiliary fuel from a tuyere, in accordance with volatile matter content in the coal, the preheating temperature of the pulverized fine coal is adjusted. Many amounts of the pulverized fine coals can be blown into the blast furnace and large effect to the low cost and the stable operation in the blast furnace are obtained. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００２６】
図２に表１の数値を用いて作成した温度−熱分解速度定数図を示す。熱分解生成物の内、官能基の脱離に由来する脱水反応では、より低温から反応が生ずることがわかる。すなわち官能基量の多い高揮発分炭ではより低温から熱分解生成物が発生し、表面改質が生じることが示唆される。
【００２７】
発明者らは、種々の石炭について予熱前後の燃焼性を調査しその特性を定性的に図３のようにまとめた。燃焼率変化を予熱後燃焼率から予熱前燃焼率を差し引いたものと定義すると高揮発分炭ほど低い温度から予熱効果が現れた。この予熱効果を定量化するために燃焼率変化５％を実現するために必要な予熱温度と揮発分含有量との関係を調査した。結果を表２に示す。燃焼率変化５％を選んだ理由は、図３のように、燃焼率変化は５％上昇までは急激で、５％を超えると上昇率は飽和する傾向にあり、実質的に予熱による効果の上限は５％と考えられることによる。
【００２８】
【表２】

【００２９】
表２の結果から揮発分含有量と必要予熱温度の関係を図示すると、図４を得る。最小自乗法により近似式を導出すると、必要予熱温度は、
【数４】
Ｔｃ＝０．０３・ＶＭ^２−７．５７・ＶＭ＋４３８ ・・・（３）
ただし
Ｔｃ：必要予熱温度（℃）
ＶＭ：微粉炭の揮発分含有量（ｍａｓｓ％）
と求めることができる。
【００３０】
次に、この発明の、高炉内への固体燃料吹き込み方法の一実施態様を、図面を参照しながら説明する。
【００３１】
以下、図５により本発明の実施の形態を説明する。図５は、高炉羽口部の断面図であり、羽口１は高炉鉄皮４および耐火物５を貫通して設置されている。高炉の送風は送風支管２および羽口１を介して高炉内に送り込まれる。高炉送風は、羽口１前のコークスを燃焼し、レースウェイ３と呼ばれる燃焼領域を形成する。微粉炭は微粉炭搬送ライン７により搬送され、送風支管２を貫通して設置した吹き込み用ランス６を介して高炉内に吹き込まれる。羽口１およびランス６は高炉１基あたり複数設置されているため、微粉炭は分配器８により分岐されそれぞれの羽口１に吹き込まれる。
【００３２】
微粉炭搬送ライン７の途中に、予熱手段としての微粉炭予熱設備９を設置し所定の温度まで微粉炭を予熱する。図５には例として電熱線１０による予熱方法を示したが、微粉炭と熱交換のできるものであれば特に熱源の指定はなく、望ましくは通常廃棄している熱（たとえば溶融銑鉄や溶融スラグの顕熱など）を用いる。ここで、使用する石炭の揮発分に応じて予熱温度を調節することを特徴とし、より定量的には石炭の予熱温度を、（Ｔｃ＝０．０３・ＶＭ^２−７．５７・ＶＭ＋４３８）℃に調節することにより微粉炭の燃焼性を改善し、多量吹き込みを可能とする（ＶＭ：石炭の揮発分含有量ｍａｓｓ％）。石炭の温度調節は、例えば石炭の揮発分に応じて予熱温度を計算するコンピュータ、及びコンピュータが計算した所定の予熱温度に微粉炭がなるように微粉炭予熱設備９を制御する制御装置により行われる。これらコンピュータ及び制御装置が温度調節手段を構成する。
【００３３】
【実施例】
次に、この発明の効果を実証するための試験を行った。以下、この試験方法および試験結果を、図面を参照しながら説明する。
【００３４】
図６は、高炉の羽口近傍を模した微粉炭燃焼試験用の反応炉を示す断面図であり、１１は、反応炉本体、１２は、反応炉本体１１に設けられた羽口、１３は、羽口１２に接続されたブローパイプ、１４は、ブローパイプ１３内に挿入された微粉炭吹込み用ランス、１５は、反応炉本体１１内に充填されたコークス、１６は、ブローパイプ１３に形成された微粉炭採取プローブ用孔であり、ランス１４の先端から４００ｍｍの位置にそれぞれ設けられている。１７は、ブローパイプ１３から反応炉本体１１内に吹き込まれる熱風、１８は、羽口１２先端に形成されたレースウェイ、１９は、反応炉本体１１からの排ガスを示す。
【００３５】
このような反応炉本体１１内に充填されたコークス１５に熱風を吹き込んだ。この熱風は、ブローパイプ１３の上流側からＬＰＧを空気によって燃焼させ、更に、酸素を混合して得られた、高炉におけると同様な酸素濃度のものであった。そして、微粉炭をブローパイプ１３内に吹き込んだ。微粉炭は貯蔵ホッパー２０から吹込みランス１４に至るまでの間に、ヒータ２１で所定温度に予熱して吹き込んだ。実際の予熱温度は熱電対２２により測定した。そして、微粉炭採取プローブ用孔１６に微粉炭採取プローブを挿入して、燃焼過程の微粉炭をサンプリングし、分析して、微粉炭の燃焼率を各予熱温度毎に調べた。燃焼率の定義は、（４）式に示すように、可燃分の消費率として計算した。このときの試験条件を表３に示し、試験設備諸元を表４に示す。
【００３６】
【数５】

【００３７】
【表３】

【００３８】
【表４】

【００３９】
このようにして行った種々の石炭について予熱温度を変化させ、燃焼率を測定した。
【００４０】
【表５】

【００４１】
表５は石炭Ａを用いた実施例を示す。本発明にしたがい予熱温度を２６５℃としたところ燃焼率は５．１％上昇した（実施例１）。予熱温度２００℃とすると燃焼率上昇効果は得られなかった（比較例１）。比較例２のように予熱温度を３００℃まで上昇させても実施例１と効果は変わらなかった。この場合、微粉炭燃焼率の向上効果は実施例と同等であるものの、予熱に必要な熱量を多く必要とする。定性的に効果を表現すると表５の最下行のようになる。
【００４２】
【表６】

【００４３】
表６は石炭Ｃを用いた実施例を示す。石炭Ｃは揮発分含有量が多く、低い予熱温度でも微粉炭の燃焼率が向上する。本発明にしたがい予熱温度を１７１℃としたところ燃焼率は５．２％上昇した（実施例２）。従来技術にしたがい予熱温度２００℃とすると燃焼率上昇効果は得られたが、実施例２と効果は変わらなかった。この場合も、予熱に必要な熱量を多く必要とすることから、本発明の方が優れていると言える。
【００４４】
【発明の効果】
以上、上記のように、微粉炭を予熱して高炉に吹き込む方法において、石炭の種類（揮発分含有量）に応じ、予熱温度を適正に制御することにより、微粉炭の燃焼率を向上させることができ、安定して微粉炭多量吹き込みを行うことができる。このため、銑鉄製造コストの削減に多大な効果を奏することができた。
【図面の簡単な説明】
【図１】石炭の構造図（模式図）。
【図２】温度−熱分解速度定数の関係を示すグラフ。
【図３】予熱前後の燃焼性の特性を定性的に示すグラフ。
【図４】揮発分含有量と必要予熱温度の関係を示すグラフ。
【図５】高炉羽口部の断面図。
【図６】高炉の羽口近傍を模した微粉炭燃焼試験用の反応炉を示す断面図。
【符号の説明】
１…羽口
２…送風支管
３…レースウェイ
６…吹き込み用ランス
７…微粉炭搬送ライン
８…分配器
９…微粉炭予熱設備（予熱手段）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pulverized coal injection operation into a blast furnace. Particularly, it is possible to stably inject a large amount of pulverized coal by improving the combustibility.
[0002]
[Prior art]
BACKGROUND ART In recent years, auxiliary fuel has been actively blown from tuyeres in blast furnaces. In particular, pulverized coal has attracted attention as a means that can reduce the production cost of hot metal, because it reduces the amount of expensive coke used and extends the life of the coke oven.
[0003]
For the above reasons, the rapid spread and progress of the pulverized coal injection has been remarkable. Recently, as shown in “Materials and Process 11 (1998) p834”, an ultra-high volume blast furnace that records a pulverized coal injection rate of 266 kg / T per month has also appeared.
[0004]
However, the above injection record was achieved under special operating conditions such as using high-grade raw fuel or increasing the oxygen concentration during blowing to promote pulverized coal combustion. Under the blast furnace operating conditions described above, the pulverized coal injection amount is only about 150 kg / T to 200 kg / T.
[0005]
The use of high-grade raw fuel and the enrichment of oxygen in the blast increase the cost of pig iron production, thus offsetting the cost advantage of using pulverized coal, which is cheaper than expensive coke. In some cases, on the contrary, the production cost may be increased.
[0006]
Therefore, there is a demand for a method of injecting pulverized coal into a blast furnace in a large amount and at low cost without using high-grade raw fuel or increasing the amount of enrichment of oxygen.
[0007]
In order to overcome the above drawbacks, there is a technique disclosed in Patent Document 1 (prior art). According to the prior art, the combustibility of the pulverized coal can be improved by preheating and pulverizing the pulverized coal to 200 ° C. or higher. Pulverized coal is thermally decomposed by preheating, exploding and finer. Furthermore, traces of pyrolysis gas release remain in the char (char: a solid mainly composed of residual carbon), and the char becomes porous, so that the burning rate of pulverized coal is improved.
[0008]
[Patent Document 1] Japanese Patent Application Laid-Open No. 4-354810
[Problems to be solved by the invention]
The prior art only discloses a technique of preheating coal to 200 ° C. or higher, but does not describe any kind of coal. Recently, a wide variety of coals for pulverized coal have been used, and their combustibility also varies. According to the inventors' tests, some coals exhibit an effect at a preheating temperature of 150 ° C., while others require preheating up to 250 ° C., and the required preheating temperature is not necessarily limited to 200 ° C. .
[0010]
Preheating coal, which is good at a preheating temperature of 150 ° C., to 200 ° C. wastes heat energy required for preheating and leads to an increase in pig iron production costs.
[0011]
On the other hand, when the coal which needs to be preheated to 250 ° C. is preheated only to 200 ° C., the combustibility is not improved, and the char is discharged from the furnace top. Since char or carbon is discharged without being effectively used in the blast furnace, coke must be raised accordingly. For this reason, it can be said that this also leads to an increase in cost and is not preferable.
[0012]
In addition, when the char is not discharged from the blast furnace and accumulates in the blast furnace, the powder rate in the blast furnace increases, and thus the air permeability deteriorates, and there is a possibility that the operation of the blast furnace may be malfunctioned.
[0013]
The present invention has been made to solve the above-mentioned problems, and has been made to provide a blast furnace that can provide a minimum preheating temperature necessary for various types of coal without increasing costs or causing a malfunction. An object of the present invention is to provide a pulverized coal injection method.
[0014]
[Means for Solving the Problems]
The inventors preheated various coals at various temperatures, performed a combustion test, and analyzed the test results to find out that there is a relationship between the volatile content of the coal and the required preheating temperature.
[0015]
That is, the present invention is characterized in that the preheating temperature is adjusted according to the volatile matter of the coal to be used. According to the present invention, it becomes possible to inject a large amount of pulverized coal into the blast furnace, which greatly reduces the cost of the blast furnace for stable operation. Effect.
[0016]
Further, a preferred embodiment of the present invention is characterized in that the preheating temperature of the pulverized coal is lowered as the volatile matter content of the coal increases.
[0017]
More quantitatively, the preheating temperature of pulverized coal is
(Equation 2)
Tc = a.VM ² + b.VM + c (1)
Where Tc is the required preheating temperature (° C)
VM: volatile matter content of pulverized coal (mass%)
a, b, c: By adjusting the constants, the combustibility of pulverized coal is improved, and a large amount of pulverized coal can be injected.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
First, the technical significance of the present invention will be described.
[0019]
The inventors have argued that the improvement in the combustibility of coal by preheating is due to the fact that traces of pyrolysis gas release remain in char (char: a solid mainly composed of residual carbon) and the char becomes porous. Various experiments were performed based on the technical knowledge. Through experiments, it has been found that coal having a high volatile content exhibits a combustibility improving effect at lower temperatures.
[0020]
We believe that the effect of high volatile coal at low temperatures was related to the functional groups in the coal. FIG. 1 schematically shows a structural diagram of coal. Coal is a very complicated organic high molecular compound, and is considered to have a structure in which a plurality of aromatic rings have a functional group such as a hydroxyl group or a carboxyl group.
[0021]
This functional group has a lower thermal decomposition temperature than the aromatic ring. It is also known that the functional groups are high in high volatile coal and low in low volatile coal (for example, reference: DW Van Krevelen: COAL, Typology-Physics-Chemistry-Constitution, Elsevier, Amsterdam, ( 1993) p, 259). In other words, high volatile coal removes functional groups at relatively low temperatures and reforms the coal to be porous, while low volatile coal decomposes aromatic rings at high temperatures and modifies the coal until hydrocarbons are released. Is not expected to occur.
[0022]
The thermal decomposition reaction of coal is summarized by a so-called Arrhenius-type reaction rate equation (Equation 2).
[0023]
[Equation 3]
k = A · exp (−E / RT) (2)
Here, k is the reaction rate constant (1 / sec) of coal pyrolysis (volatile matter release).
A: Frequency factor (1 / sec)
E: Activation energy (kcal / mol)
R: gas constant (kcal / (mol · K))
T: Reaction temperature (K)
[0024]
Table 1 shows frequency factors and activation energies of a reaction in which dehydration occurs from two hydroxyl groups as a functional group elimination reaction and a reaction in which an aromatic ring is decomposed to generate a hydrocarbon. (Reference: CY Wen, E. Stanley Lee, Ed .: Coal Conversion Technology, Addison-Wesley Publishing Company, Inc. Massachusetts, (1979) p. 77).
[0025]
[Table 1]

[0026]
FIG. 2 shows a temperature-thermal decomposition rate constant diagram prepared using the numerical values in Table 1. It can be seen that, among the thermal decomposition products, in the dehydration reaction resulting from the elimination of the functional group, the reaction occurs at a lower temperature. That is, it is suggested that in the case of highly volatile coal having a large amount of functional groups, pyrolysis products are generated from a lower temperature and surface modification occurs.
[0027]
The inventors investigated the combustibility of various coals before and after preheating, and qualitatively summarized the characteristics as shown in FIG. If the change in the combustion rate was defined as the difference between the preheating rate and the preheating rate, the higher the coal content, the lower the preheating effect. In order to quantify this preheating effect, the relationship between the preheating temperature and the volatile matter content required to realize a change in the combustion rate of 5% was investigated. Table 2 shows the results. The reason why the change in the combustion rate was 5% was that, as shown in FIG. 3, the change in the combustion rate was sharp until it increased by 5%, and the rate of increase tended to be saturated when it exceeded 5%. The upper limit is based on what is considered to be 5%.
[0028]
[Table 2]

[0029]
FIG. 4 shows the relationship between the volatile content and the required preheating temperature based on the results shown in Table 2. Deriving the approximate expression by the least squares method, the required preheating temperature is
(Equation 4)
Tc = 0.03 · VM ² −7.57 · VM + 438 (3)
Where Tc is the required preheating temperature (° C)
VM: volatile matter content of pulverized coal (mass%)
You can ask.
[0030]
Next, an embodiment of the method of blowing solid fuel into a blast furnace according to the present invention will be described with reference to the drawings.
[0031]
Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 5 is a cross-sectional view of the tuyere portion of the blast furnace, and the tuyere 1 is installed so as to penetrate through the blast furnace shell 4 and the refractory 5. Ventilation of the blast furnace is sent into the blast furnace via the ventilation branch pipe 2 and the tuyere 1. The blast furnace blast burns coke in front of the tuyere 1 and forms a combustion area called a raceway 3. The pulverized coal is transported by the pulverized coal transport line 7 and is blown into the blast furnace through a blowing lance 6 installed through the blower branch pipe 2. Since a plurality of tuyeres 1 and lances 6 are provided for one blast furnace, pulverized coal is branched by distributor 8 and blown into each tuyere 1.
[0032]
Pulverized coal preheating equipment 9 as preheating means is installed in the middle of the pulverized coal transport line 7 to preheat the pulverized coal to a predetermined temperature. FIG. 5 shows a preheating method using the heating wire 10 as an example. However, as long as it can exchange heat with pulverized coal, there is no particular designation of a heat source, and it is preferable to dispose of normally discarded heat (for example, molten pig iron or molten slag). Sensible heat). Here, the preheating temperature is adjusted according to the volatile matter of the coal to be used, and more specifically, the preheating temperature of the coal is set to (Tc = 0.03 · VM ² −7.57 · VM + 438) ° C. By adjusting the amount to, the flammability of the pulverized coal is improved, and a large amount of fuel can be blown (VM: volatile matter content of coal: mass%). The temperature control of the coal is performed by, for example, a computer that calculates the preheating temperature according to the volatile matter of the coal, and a control device that controls the pulverized coal preheating facility 9 so that the pulverized coal becomes a predetermined preheating temperature calculated by the computer. . The computer and the control device constitute a temperature control unit.
[0033]
【Example】
Next, tests for verifying the effects of the present invention were performed. Hereinafter, the test method and test results will be described with reference to the drawings.
[0034]
FIG. 6 is a cross-sectional view showing a reactor for a pulverized coal combustion test simulating the vicinity of a tuyere of a blast furnace, 11 is a reactor main body, 12 is a tuyere provided in the reactor main body 11, and 13 is a tuyere. , A blow pipe connected to the tuyere 12, 14 is a lance for blowing pulverized coal inserted into the blow pipe 13, 15 is coke filled in the reactor main body 11, 16 is a blow pipe 13 The formed pulverized coal sampling probe hole is provided at a position 400 mm from the tip of the lance 14. Reference numeral 17 denotes hot air blown into the reactor main body 11 from the blow pipe 13, reference numeral 18 denotes a raceway formed at the tip of the tuyere 12, and reference numeral 19 denotes exhaust gas from the reactor main body 11.
[0035]
Hot air was blown into the coke 15 filled in the reactor main body 11. This hot air had the same oxygen concentration as that in the blast furnace, obtained by burning LPG with air from the upstream side of the blow pipe 13 and further mixing oxygen. Then, pulverized coal was blown into the blow pipe 13. The pulverized coal was preheated to a predetermined temperature by the heater 21 and then blown from the storage hopper 20 to the blowing lance 14. The actual preheating temperature was measured by the thermocouple 22. Then, the pulverized coal sampling probe was inserted into the pulverized coal sampling probe hole 16 to sample and analyze the pulverized coal during the combustion process, and the combustion rate of the pulverized coal was checked for each preheating temperature. The definition of the combustion rate was calculated as the consumption rate of combustibles as shown in equation (4). The test conditions at this time are shown in Table 3, and the specifications of the test equipment are shown in Table 4.
[0036]
(Equation 5)

[0037]
[Table 3]

[0038]
[Table 4]

[0039]
The preheating temperature was changed for the various coals thus performed, and the combustion rates were measured.
[0040]
[Table 5]

[0041]
Table 5 shows an example using coal A. When the preheating temperature was set at 265 ° C. according to the present invention, the combustion rate increased by 5.1% (Example 1). When the preheating temperature was 200 ° C., the effect of increasing the combustion rate was not obtained (Comparative Example 1). Even when the preheating temperature was increased to 300 ° C. as in Comparative Example 2, the effect was not different from that of Example 1. In this case, although the effect of improving the pulverized coal combustion rate is equivalent to that of the embodiment, a large amount of heat is required for preheating. The effect is qualitatively expressed as shown in the bottom row of Table 5.
[0042]
[Table 6]

[0043]
Table 6 shows an example using coal C. Coal C has a high volatile content, and the combustion rate of pulverized coal is improved even at a low preheating temperature. When the preheating temperature was set at 171 ° C. according to the present invention, the combustion rate increased by 5.2% (Example 2). When the preheating temperature was set to 200 ° C. according to the prior art, the effect of increasing the combustion rate was obtained, but the effect was not different from that of Example 2. Also in this case, the present invention is superior because a large amount of heat is required for preheating.
[0044]
【The invention's effect】
As described above, in the method of preheating and pulverizing pulverized coal into the blast furnace as described above, the combustion rate of pulverized coal is improved by appropriately controlling the preheating temperature in accordance with the type of coal (volatile content). And a large amount of pulverized coal can be stably blown. For this reason, a great effect was able to be achieved in reducing pig iron production costs.
[Brief description of the drawings]
FIG. 1 is a structural diagram (schematic diagram) of coal.
FIG. 2 is a graph showing a relationship between a temperature and a thermal decomposition rate constant.
FIG. 3 is a graph qualitatively showing flammability characteristics before and after preheating.
FIG. 4 is a graph showing a relationship between a volatile content and a required preheating temperature.
FIG. 5 is a sectional view of a tuyere part of a blast furnace.
FIG. 6 is a sectional view showing a reactor for a pulverized coal combustion test simulating the vicinity of a tuyere of a blast furnace.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Tuyere 2 ... Blower pipe 3 ... Raceway 6 ... Blowing lance 7 ... Pulverized coal transfer line 8 ... Distributor 9 ... Pulverized coal preheating equipment (preheating means)

Claims (4)

In the method of injecting pulverized coal into the blast furnace, which injects preheated pulverized coal from the tuyere as auxiliary fuel,
A method for injecting pulverized coal into a blast furnace, wherein a preheating temperature of the pulverized coal is adjusted according to a volatile matter content of the coal. The method for blowing pulverized coal into a blast furnace according to claim 1, wherein the preheating temperature of the pulverized coal is lowered as the volatile matter content of the coal increases. The preheating temperature of pulverized coal is

Where Tc is the required preheating temperature (° C)
VM: volatile matter content of pulverized coal (mass%)
a, b, c: a method of injecting preheated pulverized coal into a blast furnace, characterized by being constants. In the pulverized coal injection device into the blast furnace that injects pulverized coal preheated from the tuyere as auxiliary fuel,
A preheating means for preheating the pulverized coal,
A pulverized coal blowing apparatus for a blast furnace, comprising: temperature control means for controlling a preheating temperature of pulverized coal in accordance with a volatile content of coal.

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