JP4074467B2 - Method for improving combustibility of low volatile pulverized coal in blast furnace - Google Patents

Description

【００２７】
微粉炭吹き込み量が１５０ｋｇ／ｔから２５０ｋｇ／ｔの範囲において、微粉炭吹き込みと同時に微粉炭吹き込みランス先端部近傍周辺の気体中の酸素濃度が７０ｖｏｌ％以上で、微粉炭の平均揮発分が２５ｍａｓｓ％以下の本発明を適用した期間（実施例１、２、３、４）は、通気抵抗指数が低く高炉内の通気が安定しており、荷降下指数も低く装入物の降下状況も良好であり、操業が安定した結果として低燃料比、高出銑量が達成された。
【００２８】
これに対して、本発明を適用しない期間（比較例１、２、３）はこれらの操業成績が悪く、吹き込まれた微粉炭の燃焼効率が低く未燃焼のチャーが炉芯部などに蓄積し操業に悪影響を与えていたものと推定される。
なお、比較例３については微粉炭の平均揮発分が３１ｍａｓｓ％と高く、酸素濃度が７５ｖｏｌ％と高かったためランス先端部の溶損が起こり、そのためランス詰まりを起こし、微粉炭の吹き込み量が１１５ｋｇ／ｔ（目標１５０ｋｇ／ｔ）しか行えず、高炉操業結果は全て不良であった。
【００２９】
【発明の効果】
本発明によれば従来、高炉への適用は困難視されていた低揮発分微粉炭についても、燃焼用酸素濃度を増して使用することにより、その燃焼効率を向上せしめることができ、使用可能としたものである。さらには微粉炭の揮発分程度に応じ酸素濃度を適正範囲に制御してやることにより、優れた燃焼効果を維持でき安定した高炉操業を行うことができ、微粉炭吹き込み操業における制約条件を解消することができる。
【図面の簡単な説明】
【図１】微粉炭燃焼効率に及ぼす平均揮発分と酸素濃度の影響を示した図[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for improving the combustibility of pulverized coal in a blast furnace when pulverized coal having a low volatile content is used as the pulverized coal blown from a blast furnace tuyeres.
[0002]
[Prior art]
In recent years, pulverized coal injection operation has been established as one of the powder injection operation technologies to the blast furnace, which has greatly contributed to reducing the coke ratio in the blast furnace, and the amount of pulverized coal injection is 150 kg / t-pig ( The operation exceeding (hereinafter referred to as kg / t) is also directed. However, in order to stably carry out a large amount of pulverized coal injection operation into the blast furnace, it is necessary to completely burn the injected pulverized coal.
[0003]
If the pulverized coal that has been blown in the blast furnace remains unburned, it accumulates as unburned char in the lower part of the blast furnace or in the core of the furnace and impedes ventilation and liquid permeability in the blast furnace.
Further, in such a state, since the heat of combustion of the pulverized coal is not sufficient, the effect is reduced, resulting in an increase in the fuel ratio in the blast furnace. Such a phenomenon is particularly likely to occur when low-volatile coal is used, and pulverized coal is present in an unburned state, which increases the situation.
[0004]
Usually, the flammability of pulverized coal depends on the composition of pulverized coal, particularly the content of volatile matter and fixed carbon. The reason why the combustion efficiency of low-volatile coal is low is considered to be because the ratio of fixed carbon having low combustibility is higher than that of high-volatile coal, and there is little volatile matter having high combustibility.
For this reason, it is considered that high volatility coal with relatively good combustibility is suitable for blast furnace injection, and the high volatility coal has been used exclusively.
[0005]
For example, Japanese Patent No. 2675403 is an invention that focuses on the volatile matter of coal as pulverized coal for blowing into a blast furnace. The patent uses coal having a volatile content of pulverized coal of 23 mass% or more and a fluidity index of 0.80 or less, the particle size of pulverized coal is 3 mm to 100 μm, and the tuyere temperature is 1900 ° C. or more. A technique for high volatile coal having a temperature of 2250 ° C. or lower is disclosed.
[0006]
Japanese Patent Application Laid-Open No. 62-263906, which focuses on oxygen for combustion of pulverized coal, has a lance having a double structure for blowing pulverized coal and blowing oxygen, and is provided horizontally in the blower branch pipe to provide oxygen concentration during blowing. There is a disclosure of a technique for performing oxygen enrichment so that is 30 vol% or more.
Similarly, in Japanese Patent No. 2994141, the average concentration of oxygen introduced into the pulverized coal blowing lance is adjusted to 35 to 65 vol%, and the oxygen enrichment amount to the lance is set to 3 vol. % Or less is disclosed.
[0007]
[Problems to be solved by the invention]
In general, it can be said that the higher the volatile matter, the better the combustibility and the better the quality of coal as a combustion surface. For this reason, the price of coal with higher volatile content is higher. In other words, the lower the volatile content, the lower the quality of the coal, and the lower the cost, the lower the cost, so there is an advantage that the cost of the coal can be reduced.
Thus, as described above, the coal that is usually used as pulverized coal is often used with a relatively high volatile content (30 mass% or more).
[0008]
Like the technique disclosed in the above-mentioned Japanese Patent No. 2675403, in a situation where only pulverized coal of a specific high volatile content coal can be blown into the blast furnace, it is not preferable when considering the entire coal resource. Regardless of the situation, it is desirable from the standpoint of stable energy supply and price stabilization that a wide range of brands and types of coal can be used as pulverized coal for blast furnaces.
[0009]
From this point of view, it has become an important issue how to use low-volatile coal as pulverized coal for blowing into the blast furnace, which has not been returned as pulverized coal-blown coal into the blast furnace. Further, in use, there has been a problem of how to compensate for the inferior flammability caused by the properties and to improve the combustion efficiency.
[0010]
Therefore, in order to improve the combustion efficiency of pulverized coal, it has been considered effective to significantly increase the oxygen concentration in the gas blown from the lance together with the pulverized coal. However, simply increasing the oxygen enrichment causes a problem of lance melting. Then, this invention aims at providing the combustibility improvement method of pulverized coal for performing the stable blast furnace operation even at the time of low volatile matter coal use.
[0011]
[Means for Solving the Problems]
The present invention has been made in order to solve the problems in the above-described conventional methods, and the gist thereof is the following means.
(1) In the operation of blowing pulverized coal of 150 kg / t or more into the blast furnace from the blower tuyere, when using low volatile coal having an average volatile content of 25 mass% or less, the oxygen concentration in the gas blown simultaneously with the pulverized coal is 7 A method for improving the combustibility of low-volatile matter pulverized coal in a blast furnace to ensure 70 vol% or more.
(2) The method for improving combustibility of low-volatile matter pulverized coal in a blast furnace according to (1), wherein the oxygen concentration in the pulverized coal carrier gas is 70 vol% or more when a single pipe is used as the pulverized coal blowing lance.
(3) In the case of using a double pipe as the pulverized coal blowing lance, oxygen in the pulverized coal carrier gas and oxygen in the gas in the outer pipe are combined to make the oxygen concentration 70 vol% or more. To improve the flammability of low volatile pulverized coal in blast furnaces.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The present inventor conducted numerous experiments on pulverized coal, measured the flammability of pulverized coal, pursued the influence of volatile matter of pulverized coal on the flammability, and satisfied combustion while avoiding the problem of lance melting In order to ensure the properties, the inventors have found that the purpose can be achieved by specifying the properties of pulverized coal and the oxygen concentration for burning the pulverized coal.
[0013]
Here, it is clear that the combustion reaction of pulverized coal is improved by increasing the oxygen enrichment rate, but the rapid combustion reaction immediately before the pulverized coal injecting lance has the risk of causing lance melting and preventing it. Therefore, a water cooling structure was required. However, if the blowing amount is about 100 to 150 kg / t, which is the conventional pulverized coal blowing level, oxygen enrichment is not so much required, and there is no need to consider such a problem, but the blowing level is 150 kg. When it becomes more than / t, it is necessary to consider the above problem.
[0014]
In this regard, low volatility pulverized coal is unlikely to burn rapidly immediately before the lance. This is because, as described above, the initial combustion of pulverized coal is not due to combustion of fixed carbon in the pulverized coal, but volatile matter generated by thermal decomposition is combusted. Rapid combustion reactions can be avoided.
[0015]
On the other hand, in general, low volatile coal has a disadvantage that combustion is slow and combustion efficiency is poor, but this disadvantage can be solved by increasing the oxygen enrichment rate. In other words, if the oxygen amount is enriched according to the volatile matter in the pulverized coal, rather than increasing the oxygen concentration during blowing, the oxygen concentration around the tip of the pulverized coal blowing lance is increased. This is effective in improving combustibility. This is because the pulverized coal or gas blown into the blast furnace does not immediately diffuse to the entire periphery, but tends to rise in temperature and burn in the blown gas atmosphere.
[0016]
Therefore, the present inventor has determined the combustion efficiency of pulverized coal, the average volatile content of pulverized coal, the oxygen concentration in the vicinity of the pulverized coal blowing lance, A combustion experiment was conducted in a pulverized coal combustion test furnace while changing the basic unit, and the combustibility was compared and shown in FIG.
[0017]
From this result, when considering the melting loss of the blowing lance at the time of blowing pulverized coal, if the oxygen concentration in the gas in the vicinity of the tip of the lance exceeds 70 vol%, as shown in FIG. This lance erosion depends on the average volatile content in the pulverized coal, and the phenomenon appears remarkably when the volatile content exceeds 25 mass%. Therefore, in order to avoid lance melting and use pulverized coal with low volatility, the average volatile content must be 25 mass% or less.
[0018]
In consideration of the balance between the two, in the present invention, in order to ensure the combustion efficiency of 70% or more and prevent the amount of unburned pulverized coal as much as possible, the volatile content of 25 vol% or less on average is included as the low volatile pulverized coal. The amount of oxygen is used, and the oxygen concentration needs to be 70 vol% or more. Of course, when the average volatile content in the pulverized coal is lower than 25 mass%, it is preferable to take measures to increase the oxygen concentration from 70 vol% according to the volatile content.
[0019]
In the present invention, the oxygen concentration is regulated to 70 vol% or more. However, in the above-mentioned Japanese Patent No. 2994141, the combustion efficiency is saturated when the oxygen concentration is 50 vol%, and the combustion efficiency decreases when the oxygen concentration is 65 vol% or more. It tends to come. Also, an increase in oxygen concentration of 70 vol% or more is avoided due to the problem of lance melting.
[0020]
In the present invention, an experimental result contrary to this fact has been obtained by using pulverized coal having a low volatile content. Japanese Patent Application Laid-Open No. Sho 62-263906 only shows an example of an oxygen concentration of 37 vol% max in the example and 50 vol% max in the drawing.
[0021]
Usually, it is said that the combustion efficiency decreases as the amount of pulverized coal increases, and FIG. 1 confirms this (difference between ○ and ● in the figure). This suggests that when the pulverized coal injection amount is less than 150 kg / t, the combustion efficiency can be maintained relatively high even if the oxygen concentration from the lance is not increased to 70 vol% or more.
The pulverized coal used in the present invention may be a single brand, or a mixture of two or more brands. In any case, pulverized coal having an average volatile content of 25 mass% or less is targeted.
[0022]
In the present invention, it is preferable to use a conventional single pipe lance or double pipe lance that is inserted into the blower tuyere through the blast furnace blow pipe. The single-pipe lance feeds pulverized coal together with the carrier gas, and the double-pipe lance is a passage through which the inner tube feeds pulverized coal together with the carrier gas. 2) is a double pipe lance serving as a passage for feeding cooling gas or pulverized coal combustion gas (oxygen-enriched gas).
[0023]
In the case of a single pipe lance, an oxygen concentration of 70 vol% or more is used as the pulverized coal transfer gas. In the case of a double pipe lance, the average oxygen concentration is the sum of oxygen in the pulverized coal transfer gas and oxygen in the outer pipe. However, in the vicinity of the tip of the pulverized coal blowing lance, the respective oxygen amounts are adjusted so as to be 70 vol% or more.
[0024]
In the above description, a single pipe and a double pipe have been described as lances. However, the present invention is not limited to this, and a triple pipe lance (the cooling fluid in the outermost pipe) or a pulverized coal blowing lance tip can be used. Oxygen may be supplied from this lance, and in any case, the oxygen concentration may be 70 vol% or more at the tip of the pulverized coal blowing lance. By maintaining such a state, the combustion efficiency in the raceway can be maintained at 70% or more.
[0025]
【Example】
Hereinafter, the present invention will be described in detail based on examples.
Table 1 shows the operating conditions and results of an embodiment to which the present invention is applied in a blast furnace having an internal volume of 3273 m ³ , together with a comparative example.
[0026]
[Table 1]

[0027]
When the amount of pulverized coal injection is in the range of 150 kg / t to 250 kg / t, the oxygen concentration in the gas near the tip of the pulverized coal injection lance at the same time as the pulverized coal injection is 70 vol% or more, and the average volatile content of the pulverized coal is 25 mass%. During the following period of application of the present invention (Examples 1, 2, 3, and 4), the ventilation resistance index is low, the ventilation in the blast furnace is stable, the load drop index is low, and the charge descent is good. Yes, as a result of stable operation, low fuel ratio and high output were achieved.
[0028]
On the other hand, during the period when the present invention is not applied (Comparative Examples 1, 2, and 3), these operation results are poor, and the combustion efficiency of the injected pulverized coal is low and unburned char accumulates in the furnace core and the like. It is presumed that the operation was adversely affected.
In Comparative Example 3, the average volatile content of the pulverized coal was as high as 31 mass%, and the oxygen concentration was as high as 75 vol%, so that the lance tip was melted, causing lance clogging, and the amount of pulverized coal blown was 115 kg / Only t (target 150 kg / t) could be performed, and all blast furnace operation results were poor.
[0029]
【The invention's effect】
According to the present invention, low volatile pulverized coal, which has conventionally been considered difficult to apply to a blast furnace, can be used by increasing its combustion efficiency by increasing the oxygen concentration for combustion. It is a thing. Furthermore, by controlling the oxygen concentration to an appropriate range according to the volatile content of pulverized coal, it is possible to maintain excellent combustion effects and perform stable blast furnace operation, and to eliminate the restrictions on pulverized coal injection operation it can.
[Brief description of the drawings]
FIG. 1 shows the effect of average volatile content and oxygen concentration on pulverized coal combustion efficiency.

Claims (3)

In the operation of blowing pulverized coal of 150 kg / t or more into the blast furnace from the blowing tuyere, when using low volatile coal having an average volatile content of 25 mass% or less, the oxygen concentration in the gas blown simultaneously with the pulverized coal is set to 70 vol%. A method for improving the combustibility of low volatile pulverized coal in a blast furnace characterized by ensuring the above. The method for improving combustibility of low-volatile matter pulverized coal in a blast furnace according to claim 1, characterized in that when a single pipe is used as the pulverized coal blowing lance, the oxygen concentration in the pulverized coal carrier gas is 70 vol% or more. . When a double pipe is used as the pulverized coal blowing lance, oxygen in the pulverized coal carrier gas and oxygen in the gas in the outer pipe are combined to make the oxygen concentration 70 vol% or more. A method for improving combustibility of low-volatile matter pulverized coal in a blast furnace according to 1.

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