JP5087955B2 - Melting reduction method - Google Patents

Description

The present invention relates to a smelting reduction how to obtain the molten metal by reducing powder or granules of metal oxide or oxide ores by the iron bath type smelting reduction furnace of the converter or the like.

  An inexpensive ore (such as chromium ore) is charged in an iron bath smelting reduction furnace such as a converter together with a carbonaceous material (such as coke) instead of expensive alloy iron, and the ore is smelted and reduced in the furnace. The technique of melting a molten metal containing a valuable metal (for example, chromium, etc.) is called a smelting reduction method. In the smelting reduction method, a granular ore having a small particle size is used, but in order to recover valuable metals in the ore as a molten metal, a large amount of heat energy that causes a large-scale reduction reaction is required.

The heat source of the smelting reduction method is generated by supplying the oxygen (O ₂ ) into the furnace and burning the carbonaceous material charged in the furnace (so-called primary combustion) and the primary combustion. The thermal energy obtained by further burning carbon dioxide (CO) (so-called secondary combustion) to produce carbon dioxide (CO ₂ ) is used. Increasing the charging amount of cheap ore to reduce the melting cost of molten metal containing valuable metals consumes a large amount of thermal energy, and therefore it is necessary to promote primary combustion and secondary combustion.

In order to promote primary combustion and secondary combustion, it is effective to increase the amount of O ₂ supplied to the furnace. However, increasing the amount of O ₂ supplied means increasing the flow rate of the oxidizing gas supplied from the top blowing lance, which causes problems such as a decrease in the yield of valuable metals due to an increase in the amount of dust generated. cause. In addition, since the amount of CO and CO ₂ generated increases, the air volume of the updraft in the furnace also increases, making it difficult to charge granular ore into the furnace.

In order to solve such problems, an ore charging lance for charging granular ore into the furnace is installed separately from the top blowing lance installed on the axis of the iron bath smelting reduction furnace. A smelting reduction method has been proposed. This technique enables the improvement of the addition yield of ore.
Japanese Patent Laid-Open No. 2-104608 Japanese Patent Laid-Open No. 5-117235 JP-A-1-96314 JP 60-208409 A JP 2002-139212 JP JP2003-172584

The technology to install the top blow lance and the ore charging lance individually as described above has enabled stable supply of ore and improved yield, but the following problems have to be dealt with in response to the increase in ore charging amount. The point was left.
It has already been explained that a large amount of thermal energy is required for a large-scale reduction reaction when a large amount of cheap ore is used in the smelting reduction method.

First, in order to promote primary combustion and increase the calorific value, it is effective to increase the supply amount of O ₂ . However, since most of O ₂ is supplied as an oxidizing gas from the top blowing lance into the furnace, increasing the amount of O ₂ supplied (that is, increasing the amount of oxidizing gas supplied) increases the amount of dust generated. . Dust contains granular ore, and an increase in the amount of dust generated means that the ore charged in the furnace is discharged out of the furnace.

Therefore, when the amount of O ₂ supplied is increased, the yield of valuable metals recovered from the ore decreases, and a great amount of cost is required for preventing environmental pollution and treating dust. Moreover, since the flow rate of the oxidizing gas must be increased in order to increase the O ₂ supply amount, the efficiency of secondary combustion is reduced and a significant increase in thermal energy cannot be expected.
Next, in order to promote secondary combustion, the tip position of the upper blowing lance (hereinafter referred to as lance height) is raised, or the flow rate of the oxidizing gas injected from the tip of the upper blowing lance is lowered. There are methods. However, since CO, which is a fuel for secondary combustion, is relatively difficult to burn, even if these methods are adopted, it is not possible to expect significant acceleration of secondary combustion.

  Therefore, Patent Document 1 discloses a technique in which a substance containing hydrogen atoms (H) is blown into a furnace to burn H, and the heat of combustion of H is added to increase the total calorific value. With this technology, it is possible to increase the total calorific value in the furnace to cope with an increase in the amount of ore used. However, not all H burns in the vicinity of the molten metal in the furnace, and a part of H is discharged out of the furnace without being burned, or burned in the upper space in the furnace. As a result, there is a concern that the heat applied to the molten metal is reduced and the refractory is melted.

  Patent Documents 2, 3, and 4 disclose techniques for charging ore into a furnace together with coal powder as fuel. Patent Documents 2 and 3 are simply techniques for increasing the yield of coal. In Patent Document 4, ore and coal powder are blown together with an oxidizing gas from an upper blowing lance. In the technique disclosed in Patent Document 4, a flame is generated from an upper blowing lance using a part of coal blown into a furnace as fuel, and the ore is charged so as to pass through the flame. However, since coal is difficult to ignite compared with other solid fuels (for example, plastics), gaseous fuels (for example, propane, C gas, etc.), and liquid fuels (for example, heavy oil), there is a problem that the flame becomes unstable. . C gas refers to gas generated from a coke oven.

  Further, as described in Patent Document 5 and Patent Document 6 as a powder blowing device (hereinafter referred to as a burner lance) for supplying powder or particles such as ore to a molten metal or slag through a burner flame. Exists. The burner lance disclosed in Patent Document 5 has a gas fuel nozzle, a primary oxygen gas nozzle, and a powder jet nozzle arranged concentrically from the center to the outer periphery. The burner lance disclosed in Patent Document 6 has a multi-tube structure in which a combustion-supporting fluid supply pipe for supplying a combustion-supporting fluid is provided on the outer peripheral side of a powder supply pipe for supplying powder. The gap between the supply pipes becomes a combustion-supporting fluid passage, and the tip of the powder supply pipe and the combustion-supporting fluid supply pipe is formed so that the combustion-supporting fluid passage gradually widens in the tip direction. Tapered portions are provided, and a relatively narrow throat portion is formed closer to the base end side than the tapered portions.

  In the structure of the burner lance of Patent Document 5, the powder jet nozzle has an annular shape, and when fine powder is supplied uniformly or the amount of powder supply is small, even with the burner lance, It can be heated or melted. However, the burner lance disclosed in Patent Document 5 has problems such as nozzle clogging because the gap between the nozzles for powder injection is narrow when there are rarely coarse particles such as ore, or when these particles are supplied in large quantities. Concerned. Further, when the gap between the powder jet nozzles is narrow as described above, in order to supply a large amount of powder, the powder must be supplied at a high speed by gas transportation. There is a possibility that the tip of the nozzle is worn by the powder.

  In the burner lance structure of Patent Document 6, a circular powder supply nozzle is arranged at the center of the burner lance. Compared with the powder ejection nozzle of Patent Document 5, this is presumed that troubles such as nozzle clogging are almost eliminated because the powder supply nozzle has a larger sectional area. However, the shape of the combustion-supporting fluid nozzle arranged on the outer periphery of the powder supply nozzle of Patent Document 6 is a so-called Laval nozzle, and the combustion-supporting fluid is ejected at supersonic speed. This is to increase the flow rate of the supplied powder and to blow the powder efficiently. However, if the flow rate of the powder increases, the residence time in the burner flame is shortened, so that the supplied powder is not sufficiently heated. Also, if the flow rate of the burner fuel or supporting gas increases, the mixing of the fuel and supporting gas is promoted, so the flame is shortened and the residence time of the powder in the burner flame may be shortened. Is done.

The present invention advantageously solves the above-mentioned problem, by increasing the total calorific value in the furnace without encouraging refractory erosion, and melting that can increase the use of cheap ore an object of the present invention is to provide a reduction how.

  The present inventors have repeatedly studied the smelting reduction method from various viewpoints using a small test converter. As a result, it was found that the total calorific value in the furnace and the heat receiving efficiency to the molten metal change depending on the combustion position of the fuel. In other words, the amount of ore used in the smelting reduction method can be increased if the amount of heat generated by the fuel is efficiently transferred to the ore by inserting the ore so that it passes through the flame in which the fuel burns.

The present invention has been made based on this finding.
In other words, the present invention provides a powdered ore or metal oxide in the iron bath smelting reduction furnace separately from the top lance for supplying the oxidizing gas installed on the axis of the iron bath smelting reduction furnace. An ore charging lance is installed, and a powder nozzle, a gas fuel nozzle and an oxygen gas nozzle are provided at the tip of the ore charging lance from the center to the outer periphery to eject ore or metal oxide powder. It is arranged concentrically, a burner having a circular shape for the powder nozzle and an annular shape for the gas fuel nozzle and the oxygen gas nozzle is provided, ore or so as to pass through the flame generated from the burner This is a smelting reduction method in which a metal oxide is charged into an iron bath smelting reduction furnace.

In the smelting reduction method of the present invention, it is preferable to use one or more of gaseous fuel such as propane gas and C gas, liquid fuel such as heavy oil, and solid fuel such as plastic as the fuel. Moreover, it is preferable that a granular ore is a chromium ore .

In a further smelting reduction method of the present invention, the heating value of the fuel used and is Q, the load velocity ore or metal oxide particulate and S, the particle size of the ore or metal oxide particulate R ( μm) , the S / Q value (kg / MJ) preferably satisfies the following formula.
S / Q ≧ 0.1 × R ^0.2

In the smelting reduction method or the present invention, the heating value of the fuel used and is Q, the load velocity ore or metal oxide particulate as S, that S / Q value is 0.3 kg / MJ or Is preferred .

  According to the present invention, in the smelting reduction method, the combustion heat of the fuel is efficiently transferred to the ore charged in the furnace without encouraging the generation of dust and the refractory melt. Since thermal efficiency can be improved, it is possible to use a large amount of cheap ore.

The present invention will be specifically described below.
Since the secondary combustion occurs in the upper space in the furnace, the heat receiving efficiency to the molten metal (= the amount of heat generated by the molten metal / the total heat generation amount) is lower than the primary combustion generated in the molten metal or in the vicinity of the surface. However, when secondary combustion is promoted, the total calorific value in the furnace increases, so secondary combustion is indispensable for increasing the amount of ore charged in the smelting reduction method. On the other hand, when the secondary combustion is promoted and the amount of generated heat increases, the heat receiving efficiency to the molten metal decreases, so the amount of heat absorbed by the refractory increases and the refractory melts.

Further, in order to promote secondary combustion, there are methods such as increasing the lance height or decreasing the flow rate of the oxidizing gas injected from the top blowing lance, but all have sufficient effects. The situation that there is no is as already explained.
Therefore, the present inventors paid attention to Patent Document 1 and examined in detail a technique for increasing the total heat generation amount in the furnace and increasing the heat receiving efficiency to the molten metal. As a result, the technique disclosed in Patent Document 1 is
(a) Since the fuel is burned in the furnace, only the same effect as an increase in calorific value by promoting secondary combustion can be obtained.
(b) It has been found that not all fuel burns in the furnace, but unburned fuel is discharged outside the furnace.

In order to solve these problems, it is necessary to efficiently burn the fuel. Therefore, the present inventors conducted a combustion experiment using the apparatus shown in FIG. FIG. 2 shows an ore or a metal oxide (hereinafter referred to as “ores” or “metal oxides”) in which an upper blowing lance 5, an ore charging lance 6, and a fuel injection lance 13 are individually installed and the fuel 12 is burned with O ₂ contained in the oxidizing gas 10. 1 is a cross-sectional view schematically showing a device for charging ore 11 ) . The top blowing lance 5 was installed on the axis of the furnace body 1.

As a result of performing a combustion experiment using the apparatus shown in FIG. 2, the combustion efficiency of the fuel was increased and the heat generation amount was increased, while the heat receiving efficiency to the molten metal 3 was decreased. Therefore, the heat load of the refractory of the furnace body 1 is increased, and the refractory melts significantly.
In view of this, the present inventors have modified the ore 11 so that the ore 11 passes through the flame and is charged into the furnace in order to increase the heat receiving efficiency of the granular ore 11 charged into the furnace. A combustion experiment was conducted using the apparatus shown in FIG. This is a demonstration test of the smelting reduction method of the present invention. In the apparatus shown as a cross-sectional view in FIG. 1, a flow hole through which ore 11 is charged into the furnace is provided at the tip of the ore charging lance 6. Further, an injection hole (hereinafter referred to as a burner) for injecting fuel 12 and O ₂ into the furnace is provided at the tip of the ore charging lance 6. Then, O ₂ and fuel are blown into the furnace from the burner, and the ore 11 passes through the flame generated from the burner and is charged into the furnace. The top blowing lance 5 was installed on the axis of the furnace body 1.

As a result of performing a combustion experiment using the apparatus shown in FIG. 1, the heat receiving efficiency to the ore 11 was increased and the heat receiving efficiency to the molten metal 3 was also improved. As a result, the amount of ore 11 charged could be significantly increased.
In other words, according to the present invention, when a large amount of inexpensive ore 11 is used, the flow rate of the oxidizing gas 10 supplied from the top blowing lance 5 (that is, the supply amount of O ₂ ) is increased without increasing the flow rate. Thermal efficiency can be improved. Therefore, generation | occurrence | production of dust and the melting loss of a refractory can be suppressed.

  FIG. 3 is a cross-sectional view showing an example of the ore charging lance 6 according to the embodiment. As shown in FIG. 3, a powder nozzle 14, a gas fuel nozzle 15, and an oxygen gas nozzle 16 that eject powder are arranged concentrically from the center to the outer periphery. Further, the shape of the powder ejection nozzle 2a is circular, and the shapes of the gas fuel nozzle 15 and the oxygen gas nozzle 16 are annular. In order to prevent burner melting and the like, a cooling water circulation path 17 through which cooling water is circulated and supplied is provided.

  In the present invention, the oxygen gas nozzle 16 is installed on the outer periphery of the gaseous fuel nozzle 15, and the contact area between the fuel and oxygen gas is large, so the burner flame is stable and the length of the flame is long. Further, by increasing the inner diameter of the powder nozzle 14, the powder flow rate can be reduced and a large amount of powder can be supplied.

<Example 1>
The molten metal 2 (that is, molten iron 4 tons) was accommodated in the furnace body 1 of the top bottom blow converter (capacity 5 tons) shown in FIG. 1, and the chrome ore was smelted and reduced by the following procedure. In addition to the furnace body 1, an upper blowing lance 5 was installed on the axis of the furnace body 1, and an ore charging lance 6 was installed individually. A flow hole through which the ore 11 is charged into the furnace is provided at the tip of the ore charging lance 6. Further, a burner shown in FIG. 3 is provided at the tip of the ore charging lance 6 in order to inject fuel 12 and O ₂ into the furnace. The fuel 12 is burned by O ₂ and a flame is generated from the burner. The ore 11 passes through the flame and is charged into the furnace.

In terms top blowing 15 Nm ³ / min in terms of the flow rate of the oxidizing gas supplied to the O ₂ amount from the lance 5, the flow rate of the oxidizing gas supplied from the bottom-blown plug 4 to O ₂ amount 5 Nm ³ / Blowing started as min. Thereafter, while appropriately adding coke, the molten metal 2 is heated to 1600 ° C., and charging of the granular ore 11 (that is, chromium ore) from the ore charging lance 6 is started. Fuel 12 (that is, C gas) and O ₂ were blown into the furnace from a burner provided at the tip, and smelting reduction was performed.

In this way, the temperature of the molten metal 2 was measured while performing smelting reduction, and the charging speed of the ore 11 was adjusted so as to maintain 1600 ° C. suitable for smelting reduction. After a predetermined time (= 60 minutes), the supply of ore 11, fuel 12, and O ₂ was stopped, and the ore charging lance 6 was raised. In this way, blowing was continued for 3 minutes using only the oxidizing gas 10 supplied from the top blowing lance 5 and the bottom blowing tuyere 4. This is an invention example.

On the other hand, as Comparative Example 1, smelting reduction was performed using an apparatus in which an upper blowing lance 5, an ore charging lance 6, and a fuel injection lance 13 as shown in FIG. Since other conditions are the same as those of the invention example, the description is omitted.
As Comparative Example 2, the fuel injection lance 13 of the apparatus shown in FIG. 2 was not used, and the supply of the fuel 12 was stopped to perform smelting reduction.

  Table 1 shows the total calorific value, the heat deposition efficiency to the molten metal 2 and the total charge of ore 12 (that is, chromium ore) when smelting reduction is carried out by the method of the invention example and comparative examples 1 and 2. In Table 1, the data of Comparative Example 2 are shown using an index with 100 as the data.

表１から明らかなように、クロム鉱石の総装入量が多く、かつ溶湯２への着熱効率も向上している。したがって本発明によれば、炉内に装入される鉱石12への着熱効率を高めることによって、溶湯２への着熱効率も向上できる。その結果、安価な鉱石を大量に使用するが可能となり、しかもダストの発生や耐火物の溶損を抑制できる。

As is clear from Table 1, the total amount of chromium ore is large, and the heat receiving efficiency to the molten metal 2 is also improved. Therefore, according to the present invention, it is possible to improve the heat receiving efficiency to the molten metal 2 by increasing the heat receiving efficiency to the ore 12 charged in the furnace. As a result, it is possible to use a large amount of inexpensive ore and to suppress the generation of dust and the refractory melt.

<Example 2>
In the same manner as in Example 1, molten iron 2 (that is, molten iron 4 tons) was accommodated in the furnace body 1 of the top bottom blowing converter (capacity 5 tons) shown in FIG. Since the operation of smelting reduction is the same as in Example 1, the description thereof is omitted. However, the smelting reduction operation was performed 10 times (symbols A to J) while changing the S / Q value calculated from the calorific value Q of the fuel 12 and the addition rate S of the ore 11 as shown in Table 2.

  Table 2 shows the heat receiving efficiency of the combustion heat of the fuel 12 to the molten metal 2 in each operation. The heat gain efficiency is shown using an index with the heat gain efficiency being 1 in the operation of S = 0 (symbol B). Table 2 also shows the exhaust gas temperature index. The exhaust gas temperature index is the difference from the exhaust gas temperature in the operation of Comparative Example 2 performed in Example 1 (that is, the operation without fuel injection).

表２に示すＳ／Ｑ値と着熱効率指数、排ガス温度指数との関係を、それぞれ図４、５に示す。図４から、Ｓ／Ｑ値が増加するに連れて着熱効率指数が増加することが分かる。また図５から、Ｓ／Ｑ値が0.3kg／MJ以上で排ガス温度指数がほぼ一定となり、燃料吹き込みのない操業と同等の排ガス温度を維持できることが分かる。排ガス温度の上昇は耐火物の溶損を助長することが知られており、燃料吹き込みのない操業と同等の排ガス温度を維持すれば、耐火物の溶損を抑制できる。

FIGS. 4 and 5 show the relationship between the S / Q value, the heat absorption efficiency index, and the exhaust gas temperature index shown in Table 2, respectively. From FIG. 4, it can be seen that as the S / Q value increases, the heat absorption efficiency index increases. FIG. 5 also shows that the exhaust gas temperature index becomes almost constant when the S / Q value is 0.3 kg / MJ or more, and the exhaust gas temperature equivalent to the operation without fuel injection can be maintained. It is known that an increase in exhaust gas temperature promotes refractory melting, and refractory melting can be suppressed by maintaining an exhaust gas temperature equivalent to an operation without fuel injection.

That is, when the S / Q value is 0.3 kg / MJ or more, it is possible to suppress the refractory from being melted and to efficiently heat the combustion heat of the fuel to the molten metal.
<Example 3>
Similarly to Example 1 and Example 2, smelting reduction of chromium ore was performed using the top-bottom blow converter (capacity 5 tons) shown in FIG. Since the operation of smelting reduction is the same as in Example 1 and Example 2, description thereof is omitted. However, the average particle size of the ore used in Example 1 and Example 2 is 200 μm, which is generally used, whereas in Example 3, the average particle size was set to three types of 150 μm, 50 μm, and 5 μm.

  The results in each operation are as shown in Table 3. A to J in Table 3 are the same as those in Example 2.

Here, from FIG. 7, the S / Q value at which the exhaust gas temperature index becomes equivalent to that of the operation without fuel injection (that is, 15 or less) was estimated for each ore particle diameter. FIG. 8 shows the relationship between the ore particle diameter and the S / Q value at which the exhaust gas temperature index is 15 or less. As is clear from FIG. 8, when the S / Q value is 0.1 × R ^0.2 or more, the exhaust gas temperature index is 15 or less (that is, the exhaust gas temperature index equivalent to the operation without fuel injection), and the refractory melts down. And the heat of combustion of the fuel can be efficiently applied to the molten metal.

It is sectional drawing which shows typically the apparatus to which this invention is applied. It is sectional drawing which shows typically the experimental apparatus used for the comparison. It is sectional drawing which shows the example of the powder supply burner which concerns on an Example. It is a graph which shows the relationship between a S / Q value and a heat gain efficiency index. It is a graph which shows the relationship between S / Q value and exhaust gas temperature index. It is a graph which shows the influence of the ore particle diameter which has on the relationship between S / Q value and a thermal efficiency index. It is a graph which shows the influence of the ore particle size on the relationship between S / Q value and an exhaust gas temperature index. It is a graph which shows the relationship between an ore particle size and S / Q value from which an exhaust gas temperature index is 15 or less.

Explanation of symbols

1 furnace body 2 the molten metal 3 slag 4 bottom tuyeres 5 top lance 6 ore charging lance 7 O ₂ pipe 8 ore pipe 9 fuel pipe
10 Oxidizing gas
11 Ore
12 Fuel
13 Fuel injection lance
14 Nozzle for powder
15 Gas fuel nozzle
16 Oxygen gas nozzle
17 Cooling water circuit

Claims (5)

Separately from the top blow lance installed on the axis of the iron bath type smelting reduction furnace and supplying the oxidizing gas, ore or metal oxide is charged into the iron bath type smelting reduction furnace. established the incoming lance, toward the outer peripheral portion from the central portion to the tip portion of the ore charging lance, the powder nozzle for injecting the powder ore or metal oxide, the gaseous fuel nozzle and the oxygen gas nozzle concentrically A burner having a circular shape for the powder nozzle and an annular shape for the gaseous fuel nozzle and the oxygen gas nozzle, and passing through the flame generated from the burner. Alternatively , a smelting reduction method comprising charging a metal oxide into the iron bath smelting reduction furnace.   2. The smelting reduction method according to claim 1, wherein one or more of gaseous fuels such as propane gas and C gas, liquid fuels such as heavy oil, and solid fuels such as plastic are used as fuel.   The smelting reduction method according to claim 1 or 2, wherein the granular ore is chromium ore. The calorific value of the fuel used in any one of claims 1 to 3 is defined as Q, the charging rate of the granular ore or metal oxide is defined as S, and the S / Q value is 0.3 kg / MJ or more. A smelting reduction method . The calorific value of the fuel used in claim 1 and is Q, the load velocity ore or metal oxide particulate and S, the particle size of the ore or metal oxide particulate R ([mu] m ) , The S / Q value (kg / MJ) satisfies the following formula:
S / Q ≧ 0.1 × R ^0.2

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