KR20120123482A - Process for producing ferro coke for metallurgy - Google Patents

Abstract

The present invention increases the CO ₂ reactivity of the coke in the ferrocoke in the blast furnace when carbonizing the molded product consisting of carbon materials and iron ore to produce ferrocoke, thereby lowering the heat preservation temperature, thereby reducing the ratio of the reducing material It is an object of the present invention to provide a method for producing ferrocoke. The present invention relates to a method for producing a metallurgical ferrocoke for producing ferrocoke by distilling a mixture consisting of carbonaceous material and iron ore, wherein the maximum temperature of the ferrocoke during the dry distillation within the range of 800 ℃ or more, 900 ℃ or less. It features.

Description

Production method of ferrocoke for metallurgy {PROCESS FOR PRODUCING FERRO COKE FOR METALLURGY}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing metallurgical ferrocoke, which prepares ferrocoke by molding a mixture of carbonaceous material and iron ore and carbonizing the resulting molding.

In order to reduce the ratio of the blast furnace reducing material, it is effective to lower the temperature of the heat preservation zone formed in the blast furnace (for example, see Non Patent Literature 1). As a method of lowering the heat storage zone temperature, a method of lowering the start (start) temperature of the coke gasification reaction (endothermic reaction) shown in the following formula (1) may be mentioned.

C + CO ₂ → ₂ CO... (One)

Ferrocoke produced by carbonizing a molded product by mixing coal material (coal) and iron ore can increase the CO ₂ reactivity of coke in ferrocoke by the catalytic effect of reduced iron ore, and concomitant heat preservation temperature The reduction material ratio can be reduced with the fall of (for example, refer patent document 1).

As a technique for producing such ferrocoke, a method of distilling a mixture obtained by blending ferrite iron ore with coal and mixing the mixture in a conventional silo coke oven has been studied. For example, (a) a method of charging a powdered mixture of coal and ferrite ore into a silo coke oven, (b) a method of forming coal and iron ore at cold, ie, room temperature, and charging the molding into a silo coke oven. (Refer nonpatent literature 2), (c) The method of distilling the molded object of coal and iron ore by the vertical type dry flow furnace instead of a silo type coke oven (refer nonpatent literature 3), etc. is proposed. Since iron oxide also has the effect of enhancing the CO ₂ reactivity of coke, it is estimated that even if all of the iron ore is not reduced to metal iron, there is an effect of enhancing the CO ₂ reactivity (see Non-Patent Document 4).

On the other hand, the dry distillation temperature is lower for a conventional coke charged to the blast furnace has been considered to increase the CO ₂ reactivity (for example, refer to Non-Patent Document 5).

Patent Document 1: Japanese Patent Publication No. 2006-28594

Non-Patent Document 1: Japan Iron and Steel Institute 「Iron and Steel」 87, 2001, p.357 [Non-Patent Document 2] Fuel Association, Coke Technical Yearbook, 1958, p. 38. Non-Patent Document 3: JFE Publication, 22, 2008, p.20 Non-Patent Document 4: "Fuel" 65, 1986, p. 1476 [Non-Patent Document 5] Japanese Iron and Steel Institute 『Iron and Steel』 68, 1982, S-744 Non-Patent Document 6: KAWASAKI STEEL Publication, 6 (1974), p.16

In order to further reduce the blast furnace reducing agent ratio, it is necessary to use the ferro coke in the blast furnace as described above, to increase the CO ₂ reactivity of the coke in the ferro coke by the catalytic effect of the reduced iron ore, and to lower the heat preservation zone temperature. However, the conditions for producing the optimum ferrocoke for enhancing the CO ₂ reactivity of the coke in the ferrocoke are not clear. Further, with regard to the CO ₂ reactivity of the coke, it is preferred to evaluate the condition therefore considered within the conditions.

The present invention made in view of the above problems, and its object is to increase, CO ₂ reactivity of the coke in the ferro-coke in the blast furnace in the production of ferro coke by what retorting the mixture of the carbonaceous material and the iron ore, by which It is providing the manufacturing method of the ferro coke for metallurgy which can lower | restore heat storage zone temperature and can reduce a reducing material ratio.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject and achieve the objective, this invention forms the molded object by shape | molding the mixture which consists of a carbon material and iron ore, and manufactures the ferro coke for metallurgy which manufactures ferro coke by carbonizing the said molded object, The maximum temperature of the ferrocoke at the time of dry distillation is in the range of 800 degreeC or more and 900 degrees C or less. The maximum temperature of the ferrocoke at the time of dry distillation may be 800 degreeC or more and 850 degrees C or less, Preferably it may be around 850 degreeC. The particle size of the ferrocoke may be in the range of 15 mm or more and 35 mm or less, preferably 15 mm or more and 28 mm or less. The ferrocoke may have iron in the range of 5% by mass or more and 40% by mass or less, preferably iron in the range of 10% by mass or more and 40% by mass or less. Drying of the molded product is performed in the vertical furnace, and it is preferable to use the top gas of the vertical furnace as the gas for heating the molded product. The top gas contains carbon monoxide, carbon dioxide, hydrogen, methane and nitrogen. The gas for heating the molding preferably contains at least two components selected from the group consisting of carbon monoxide, carbon dioxide, hydrogen, methane and nitrogen.

According to the present invention, ferrocoke having high CO ₂ reactivity in the blast furnace can be produced, and by reducing the temperature of the heat storage zone, it becomes possible to further reduce the ratio of the reducing material in the blast furnace. In addition, according to the present invention, it is not necessary to increase the dry distillation temperature more than necessary when producing ferrocoke, and thus, it is possible to contribute to the optimization of the required calorific value.

1 is a schematic diagram showing the shape of ferro coke;
2 is a graph showing the relationship between the ferrocoke distillation temperature and the reduction rate of iron in ferrocoke;
3 is a graph showing a time difference at which the particle surface layer and the center become the same temperature in a temperature rising process;
4 is a graph showing the falling speed required for the particle surface layer and the center to be the same temperature,
5 is a graph showing an ore particle size distribution,
6 is a graph showing the relationship between the particle diameter of ferrocoke and the ventilation resistance of the mixed layer of ore and ferrocoke;
7 is a graph showing ferrocoke reaction test conditions,
8 is a graph showing the relationship between the ferrocoke distillation temperature and the CO ₂ reaction rate of carbon;
9 is a graph showing the relationship between iron and reaction initiation temperature in ferrocoke;
It is a graph which shows the relationship of the ferro coke distillation temperature and the ratio of the reducing material of a blast furnace at the time of using ferro coke.

The present inventors to increase the CO ₂ reactivity of the coke of about Perot coke, ferro coke used in the blast furnace operation for producing by what Carbonized the molded article by molding a mixture of a carbonaceous material and iron ore, review the preparation of ferro coke and It considered as follows.

(1) The higher the temperature of the ferrocoke during distillation, the more the reduction of the mixed iron ore proceeds, and the higher the catalytic effect.

(2) On the other hand, since coke is generally considered to have improved CO ₂ reactivity as the temperature of coke at the time of distillation is lower, attention is also paid to the coke portion where carbon material is carbonized, which is a part other than iron of ferrocoke. The coke portion in the reactivity is improved as the distillation temperature is lower.

That is, higher temperatures of ferro coke dry distillation upon for producing a ferro-coke, in the catalytic effect of the reduced iron point of view the possibility of improving the CO ₂ reactivity of the coke, and the coke constellation perspective CO ₂ reactivity of the coke This may fall. Therefore, in order to increase the CO ₂ reactivity of the coke, it is possible to consider whether an optimum temperature range exists in the production conditions of ferro coke.

Thus, the present inventors conducted experiments for evaluating CO ₂ reactivity of coke under conditions in which the gas and the temperature in the blast furnace were reproduced with respect to ferro coke coagulated by changing the temperature conditions, thereby increasing the CO ₂ reactivity of the coke. The dry condition of is derived. The process is described below.

Ferro-coke was manufactured by drying a molding (briquette) of a mixture of coal and iron ore (70 mass% of coal and 10, 20, 30, 40 mass% of iron ore) by a briquette machine in a batch pressurized drying furnace. . The shape of the briquette is shown in FIG. L = 30 mm, B = 25 mm, and T = 18 mm. L is length, B is breadth, T is thickness, and the representative particle diameter of ferrocoke is (length × width × thickness) ^1/3 , i.e. (L × B × T) ^{1 /} Appears as ³ .

The ferrocoke temperature (ferrocoke distillation temperature) at the time of dry distillation was 750, 800, 850, 900, 950 degreeC. The ferrocoke dry distillation temperature is the maximum temperature at the time of distillation, and it measures the temperature of the center part of a briquette. These maximum temperatures were raised to 5 ° C./min and held at the highest temperatures for 90 minutes. The atmosphere was a mixed gas of 30% hydrogen, 11% carbon monoxide, 17% carbon dioxide, 21% nitrogen, 5% water vapor, and 16% methane (each Vol%). This is based on the premise of continuous production by the gas-solid countercurrent moving bed using a vertical furnace in actual ferro coke production, and also assumes the process of using top gas as gas. The reduction rate of iron ore in ferrocoke at each ferrocoke distillation temperature is shown in FIG. With the rise of ferro coke distillation temperature, the reduction rate is increasing.

Next, the influence of the size of ferro coke on productivity was examined. During drying, it is desirable to keep the temperature in the briquettes uniform, especially with regard to the highest temperature which greatly affects the properties of the product. When using a vertical distillation furnace which is a countercurrent moving bed of gas and a solid, it is necessary to set operating conditions so as to secure time for temperature uniformity in the briquette.

The result of having measured the time difference from the surface layer reaching 850 degreeC until the center reaches 850 degreeC when the briquette volume is changed and it heated up at 5 degree-C / min from 25 degreeC to 850 degreeC in FIG. . Briquette volume 6cc was used as a reference condition, and it summarized as the relative value with respect to the case of briquette volume 6cc. The atmosphere was a mixed gas of 30% hydrogen, 11% carbon monoxide, 17% carbon dioxide, 21% nitrogen, 5% water vapor, and 16% methane (each vol%), and the temperature of the briquette surface and the center was measured. The larger the briquette volume, the longer the time the entire briquette is brought to uniform temperature.

Next, the operating conditions to the dry distillation furnace which are necessary to make whole briquettes into uniform temperature were examined. Based on the briquette volume of 6 cc, the time for maintaining the entire particle at a uniform temperature for a briquette with a volume larger than 6 cc, i.e., maintaining the entire particle at 850 ° C. after the briquette center reaches 850 ° C. In order to do this, the time shown in Fig. 3 is necessary for the 6cc condition. The means for adjusting the time at which the briquette center reaches 850 ° C. includes a change in the briquette descent rate. The relationship between the briquette volume and the briquette descent speed required for the briquette I to become a uniform temperature is shown in FIG. 4 when the zone length at 850 ° C. is 1.5 m and the briquette descent speed is 1 m / hr at a briquette volume 6 cc. . The larger the briquette volume, the slower the descent needs. This means a decrease in production speed. In the case of a volume of 6 cc, the production speed is reduced by more than 5% when the volume is more than 14 cc. As described above, if the representative particle diameter of ferrocoke is represented by (length × width × thickness) ^1/3 , the representative diameter of volume 6cc is 23.8 mm, the representative diameter of volume 14cc is 28.3 mm, and the representative diameter of volume 18cc is 30.6. It corresponds to mm. As mentioned above, although productivity of a small size briquette becomes more advantageous with respect to productivity, it is preferable to prescribe a lower limit of a size from a breathability viewpoint on the premise of use in a blast furnace.

It is preferable to mix and use ferro coke with the iron raw material comprised from a sintered ore, a pellet, a lump ore, and the like. An iron raw material composed of sintered ore, pellets, lump ores, etc. is hereinafter referred to as ore. At this time, it is important to maintain the air permeability of the mixed layer of ore and ferro coke. Therefore, the influence of the ferro coke particle size on the air permeation resistance of the mixed layer of ore and ferro coke was investigated. The ferro coke ratio in the ore is 21 vol% (corresponding to the ferro coke ratio 35mass%), and the particle size distribution of the ore is shown in FIG. 5. The change of the ventilation resistance by the size of the ferro coke mixed in an ore was computed using Formula (2) shown below. Phi is the shape factor (set to 0.7), dp is the average particle diameter of the ore / ferro coke mixed layer, and ε is the porosity of the ore / ferro coke mixed layer.

Air flow resistance index ^{= (1 / Φdp) 1.3?} (1-ε) 1.3 / ε 3 ... (2)

The average diameter of the mixed layer was calculated by correcting the particle size distribution shown in FIG. 5 according to the assumed ferro coke size, and the porosity was estimated from the particle size distribution after the correction (see Non-Patent Document 3). The results are shown in FIG. It is understood that the change in the ventilation resistance is small when the size of the ferrocoke is 15 to 35 mm. If the size of the ferro coke is less than 15 mm, the airflow resistance increases because the average diameter of the mixed layer decreases. On the other hand, although the airflow resistance increases even under the condition that the size of the ferrocoke is large, this is due to the decrease in the porosity due to the wider particle size distribution. As mentioned above, it became clear that it is preferable that the ferro coke particle diameter exists in the range of 15-35 mm in order to avoid a raise of ventilation resistance. If it is a ferro coke of the shape as shown in FIG. 1 manufactured using a molding machine, it is preferable that the representative particle diameter (= (L x B x T) ^1/3 ) of the ferro coke previously defined exists in the range of 15-35 mm. . More preferably, the representative particle diameter of ferro coke should just be in the range of 20-35 mm.

As mentioned above, it is preferable that the particle diameter of ferro coke exists in the range of 15 to 35 mm or less from a viewpoint of productivity improvement from a viewpoint of ensuring productivity, and the air permeability at the time of blast furnace use. In consideration of both ensuring productivity and breathability, it is preferable that the particle diameter of ferro coke exists in the range of 15-28 mm. Briquettes are commonly referred to as the Masec type, pillbox type, egg type, oval, etc., depending on the shape of the mold of the briquette machine, but three symmetry axes orthogonal to each other (L, B, T described above) ), Its characteristics are defined by the representative particle diameter (= (L x B x T) ^1/3 ) indicated above.

Next, a test was conducted in which the ferro coke produced at 750, 800, 850, 900, 950 ° C. ferrocoke dry distillation temperature was reacted under conditions simulated in the blast furnace conditions. The briquette shape was L = 30 mm, B = 25 mm, and T = 18 mm in FIG. Reaction conditions are shown in FIG. In FIG. 7, the part shown with the thick line is corresponded to the conditions which reproduced the history which a load receives when a load falls in a furnace in the temperature range of 1200 degreeC from the top of a blast furnace.

The relationship between the ferrocoke dry distillation temperature and the reaction rate of carbon in the ferrocoke is shown in FIG. 8 with respect to ferrocoke after reaction to 1200 degreeC on the conditions of FIG. When ferrocoke dry distillation temperature was 750 degreeC and 950 degreeC, reaction rate became low, and the result had a maximum at 850 degreeC. When ferro coke distillation temperature is 750 degreeC, as shown in FIG. 2, it is estimated that since the reduction rate of iron ore in ferro coke is 20% low and the catalytic effect of reduced iron is small, reactivity was low. As shown in FIG. 2, although the reduction rate of iron ore in ferro coke increases with the increase of ferro coke distillation temperature, it is estimated that reactivity fell at 950 degreeC by the effect that the reactivity of a coke part falls.

Iron content is changed to 0-40 mass%, and reaction start temperature in the said test of the ferro coke manufactured at the dry-flow temperature 850 degreeC is shown in FIG. The temperature at which the reaction rate of carbon in the ferrocoke reached 0.8% was defined as the reaction start temperature. According to FIG. 9, as iron content in a ferro coke increases, reactivity improves and reaction start temperature falls. And a big effect arises from 5 mass% of iron content, and an effect becomes saturated at 40 mass% or more. From this, it can be said that iron content in the range of 5-40 mass% is preferable. Therefore, it is preferable that iron content in ferro coke exists in the range of 5-40 mass%, More preferably, it is good to exist in the range of 10-40 mass%.

In view of the above, when producing a ferrocoke by distilling the mixture consisting of carbonaceous material and iron ore, the temperature of the ferrocoke at the time of dry distillation is in the range of 800 to 900 ° C, preferably in the range of 800 to 850 ° C, particularly preferably 850 It became clear that ferro coke with high CO ₂ reactivity can be manufactured by making it into the vicinity of ° C. It is preferable that iron content in a ferro coke exists in the range of 5-40 mass%, More preferably, it is good to exist in the range of 10-40 mass%. It is preferable to use coal as a carbon material. In addition to coal, biomass or the like may be used.

Example 1

The blast furnace use test of the ferrocoke manufactured on each dry-dry temperature condition was done.

Ferrocoke continuously distilled briquettes formed from a mixture of coal and iron ore (70 mass% coal and 30 mass% iron ore) with a briquette machine in a gas-heated vertical dry distillation furnace. The gas is heated by heating a part of the top gas to dry distillation (hydrogen 30vol%, carbon monoxide 11vol%, carbon dioxide 17vol%, nitrogen 21vol%, water vapor 5vol%, (methane + ethane) 16vol%) The temperature rise of the briquettes was performed by forming a countercurrent moving bed with a gas to be blown and a briquette that continuously lowered the inside of the furnace. The size of the briquette was made into the shape shown in FIG. 1 (L = 30 mm, B = 25 mm, T = 18 mm). In the vertical distillation furnace, the briquettes charged from the top were heated up to around 600 ° C. in about 1 hour, but the temperature was increased from 2 ° C./minute to 5 ° C./minute from 600 ° C. to the highest temperature, and maintained at the highest temperature for 1.5 hours. . This maximum temperature was taken as the ferrocoke distillation temperature. Here, for example, as shown in Non-Patent Document 6, a difference occurs between the gas temperature and the solid temperature in the vertical distillation furnace. In view of this difference, the heat transfer simulation of the countercurrent moving bed was performed, and the gas conditions were adjusted so that the solid temperature became a predetermined condition.

Ferro coke manufacturing conditions (ferro coke dry distillation temperature), iron reduction rate in ferro coke, operating conditions (ferro coke consumption, xylocoke ratio, fine coal fraction) and blast furnace operation results (reduced material ratio) are shown in Table 1, 10 shows a relationship between the ferrocoke distillation temperature and the blast furnace reducing material ratio. In Table 1, a base is a case of normal blast furnace operation which does not use ferro coke, and cases 1-5 are carrying out the operation which charged from the blast furnace top by mixing ferro coke uniformly in an ore layer.

[Table 1]

According to Table 1, it turns out that reducing material ratio can be reduced by using a ferro coke about the conditions (base) which do not use a ferro coke. In particular, when the temperature of ferrocoke (ferrocoke distillation temperature) during drying is between 800 and 900 ° C, it is possible to reduce the rate of reducing material by 30 kg / t or more. It is presumed that this is due to the interaction between the effect of increasing the function as a catalyst because the reduction rate of iron in the ferrocoke increases as the dry distillation temperature increases, and the reactivity of the coke portion decreases as the dry distillation temperature increases.

As mentioned above, although embodiment to which the invention made | formed by this inventor was applied was described, this invention is not limited by the technique and drawing which form a part of indication of this invention by this embodiment. For example, as described above, other embodiments, examples, operational techniques, and the like, which are made by those skilled in the art based on the present embodiment, are all included in the scope of the present invention.

[Industrial Availability]

The present invention can be applied to a method of molding a mixture of carbonaceous material and iron ore, and carbonizing the resulting molding to produce ferrocoke.

Claims (6)

As a method for producing a metallurgical ferrocoke, which is formed by molding a mixture consisting of carbonaceous material and iron ore to form a molded product and carbonizing the molded product,
The maximum temperature of the ferro coke at the time of dry distillation is 800 degreeC or more and 900 degrees C or less in the range, The manufacturing method of the metallurgical ferro coke. The method of claim 1,
The maximum temperature of the ferrocoke at the time of dry distillation is in the range of 800 degreeC or more and 850 degreeC or less. The method of claim 1,
The particle size of the ferro coke is in the range of 15mm or more, 35mm or less, the manufacturing method of metallurgy ferro coke. The method of claim 3, wherein
The particle size of the ferro coke is in the range of 15mm or more, 28mm or less, characterized in that the manufacturing method for ferrocoke for metallurgy. The method of claim 1,
The ferro coke has iron content in the range of 5% by mass or more and 40% by mass or less. The method of claim 1,
Drying of the molded product is carried out in a vertical furnace, and the top gas of the vertical furnace is used as a gas for heating the molded product.

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