JPH06330127A - Method for recovering phosphorus-component contained in iron ore as phosphorus resource - Google Patents

Abstract

PURPOSE:To migrate phosphorus to molten slag, to recover the phosphorus as a resource and to effectively utilize the phosphorus by migrating the phosphorus to the molten slag under specific conditions in a top and bottom blown metallurgical furnace, separating the phosphorus from the metal bath and migrating the phosphorus to the metal formed by a reduction treatment, then subjecting the metal to oxidation refining. CONSTITUTION:While gaseous oxygen is top blown into the metallurgical furnace allowing top and bottom blowing of the gas, iron ore or its prereduced matter and carbonaceous material are charged into the furnace and the temp. of the molten metal is regulated within a 1360 to 1450 deg.C. Further, the (T. Fe) concn. in the slag is adjusted within a 3 to 9% range to migrate the phosphorus into the molten slag. This molten slag is then separated from the metal bath and a reducing material is added to the molten slag and is heated to migrate the phosphorus into the formed metal. the metal formed in such a manner is subjected to oxidation refining by using basic slag to migrate the phosphorus into the slag. As a result, the phosphorus contained in the iron ore is recovered as the resource and is effectively utilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for concentrating and recovering phosphorus contained in iron ore and effectively using it as a phosphorus resource.

[0002]

2. Description of the Related Art In the field of steel refining and refining, it is important to remove phosphorus brought in from iron ore from the metal so that it can be stably discharged to the outside of the system to produce high quality steel and to protect the environment. Is an important technology for. In the conventional blast furnace pig iron method, almost all phosphorus enters the pig iron in the iron ore reduction process, and thereafter, the technical development has been focused on how to remove it from the metal.
It is well known that if the high phosphorus pig can be produced by using the high phosphorus ore, the high phosphorus slag is obtained as a by-product according to the Thomas converter method and is used as the phosphorus fertilizer. This is the only example where phosphorus contained in iron ore has been effectively used as a resource.

However, at present, the restrictions on the phosphorus concentration of metals have become strict, and high phosphorus ores have not been used. Therefore, the phosphorus concentration in slag is low and phosphorus is not effectively used. On the other hand, if slag having a high basicity is used for refining to remove phosphorus, the disposal method of the slag becomes an environmental problem.

[0004]

Ordinary iron ore contains about 0.05 to 0.1% of phosphorus. This content is not high, but since the amount of steel produced is large, it cannot be ignored as the absolute amount of phosphorus. On the other hand, phosphorus is used as an effective resource for various purposes, and Japan relies on imports. Therefore, if phosphorus contained in iron ore is concentrated so that it can be effectively used as a phosphorus resource, and at the same time the problem of slag in iron and steel refining can be solved, it will be preferable from the viewpoint of both resources and environment.

Therefore, the present invention provides a steel refining method capable of efficiently concentrating the phosphorus contained in the iron ore which is usually used and having a low content, and the iron ore is contained in the iron ore. It aims to make it possible to collect phosphorus as a phosphorus resource and use it effectively.

[0006]

The present invention uses the following method. That is, (1) in a metallurgical furnace capable of blowing gas at the top and bottom, while iron gas or pre-reduced product thereof and carbonaceous material are charged while blowing oxygen gas at the top, the temperature of the molten metal falls within the range of 1360 to 1450 ° C. Adjust so that
Further, adjusting the (T.Fe) concentration in the slag to be within the range of 3 to 9%, the first step of transferring phosphorus into the molten slag, and separating the molten slag from the metal bath and melting From the second step of adding a reducing agent to slag and heating it to transfer phosphorus into the generated metal, and the third step of oxidizing and refining the generated metal with basic slag to transfer phosphorus to slag. How to become.

(2) Following the first step of (1) above, the molten slag is separated from the metal bath, carbonaceous material is added and oxygen is blown, and the (T.Fe) of the slag is reduced to 1% or less. And a third step of recovering phosphorus as phosphoric acid from the gas generated at that time. (3) Subsequent to the first step of (1) above, the molten slag is separated from the metal bath, and a silicon-containing alloy is added to reduce it, so that the Si content of the metal is 20% or more. And a third step of recovering phosphorus as phosphoric acid from the gas generated at that time.

(4) Following the first step of the above (1), the molten slag is separated from the metal bath and the slag is reduced by hydrogen gas plasma, and the gas generated at that time is phosphoric acid. And a third step of recovering phosphorus. (5) Subsequent to the first step of (1) above, the molten slag is separated from the metal bath, and the second step of solidifying and pulverizing the molten slag and powdering the powdery slag is carried out. Is added and heated to 700 ° C. or higher, and the fourth step is to recover phosphorus as phosphoric acid from the gas generated at that time.

[0009]

The embodiment of the present invention will be described below. The equipment used in the first step of the present invention is a metallurgical furnace capable of blowing gas from the top and bottom, and oxygen is blown through a top blowing lance. Gas bottom blowing is performed to agitate the melt and nitrogen gas is usually used. The raw material is an iron ore or an iron raw material containing iron oxide such as a pre-reduced product thereof, coal or a carbonaceous material whose volatile content is adjusted by pre-heating it, and flux such as coal.

The temperature of the melt can be measured, for example, by inserting a sublance into the metal layer.
The supply rate of the iron raw material is adjusted so as to be in the range of 60 to 1450 ° C. If the value exceeds 1450 ° C., the P concentration [P] of the metal cannot be sufficiently reduced as shown in FIG. 1, which is not suitable for the purpose of the present invention. On the other hand, if the temperature is less than 1360 ° C, the operation becomes unstable, which is not preferable.

The iron oxide concentration of the slag, that is (TF
e) is determined by the balance between the iron oxide supply rate from the iron raw material and the reduction rate of the iron oxide. In the present invention (T.
Fe) is preferably adjusted to 3% or more and 9% or less. This is because (T.Fe) is 3% as shown in FIG.
If it is less than this, the P concentration [P] of the metal cannot be sufficiently reduced. On the other hand, if (T.Fe) exceeds 9%, the rate of wear of the refractory material increases rapidly, and abnormal forming is likely to occur in the operation side as well, resulting in instability. Also,
If (T.Fe) is too high, the recovery amount of phosphorus that can be used as a resource decreases in the second and subsequent steps of the present invention, which is not preferable.

In order to satisfy the conditions relating to the iron oxide concentration of such slag, it is preferable to blow the bottom blowing gas in the range of ^{3 to} 15 Nm ³ / t-metal per unit amount of metal present in the furnace. As the gas species used here,
Nitrogen gas is the most practical in terms of handling, effects and cost.

The C concentration of metal is a relative relationship between the rate of carbon supply from the carbonaceous material to the metal and the rate of carbon removal from the metal, that is, the reaction rate of C in the metal with iron oxide or an oxidizing atmosphere. Decided. The carbon supply rate to the metal (correctly, the carburizing rate) depends on the distribution state of the carbonaceous material and the metal in the slag layer. Of these, the distribution of metal depends on the amount of bottom blown gas. On the other hand, the distribution of carbonaceous material depends on the particle size distribution. The volatile content of carbonaceous material determines the degree of atomization when rapidly heated in the furnace. Therefore, the particle size distribution of the carbonaceous material in the slag layer in the furnace, that is, the rate of carburizing to the metal can be adjusted by the volatile content of the coal used.

In the present invention, it is necessary to keep C of metal at 3% or more. When it is less than 3%, the reduction reaction rate decreases, the (T.Fe) of the slag increases, and it becomes difficult to satisfy the above-mentioned condition that the (T.Fe) is 9% or less under high productivity. Further, the reason is that the melting point of the metal rises and it becomes difficult to satisfy the above-mentioned low temperature operating condition of 1450 ° C. or less.

In order to satisfy such conditions for the C concentration of metal, in the case of large equipment, carbonaceous materials having a volatile content of 5% or less (for example, coke and char are heated outside the furnace). It is necessary to use at least 10% or more in terms of carbon content.

On the other hand, the composition of the slag is adjusted by adding a component such as CaO or MgO as a flux to a component such as SiO ₂ , Al ₂ O ₃ or MgO brought in from an ore or a carbonaceous material. The proper composition is determined in consideration of the refining ability and the operation stability under the above temperature conditions. For example, ((% CaO) + (% MgO)) / ((% SiO ₂ ) +
The value of (% Al ₂ O ₃ )) is in the range of 1.0 to 1.4.

The slag composition and the amount of slag, or the total dust generation amount, is a direct factor in blocking the oxygen jet from the metal, and has a great influence on the suppression of the metal-induced dust generation amount. Due to metal in the dust, ie
A high iron oxide concentration is not preferable because it increases the amount of electric power required in the second step of the present invention.

In order to reduce the amount of dust generated by this metal, it is necessary that the amount of slag is 340 kg / t or more with respect to the amount of metal present in the furnace. In order to satisfy this condition, it is necessary to adjust the discharge amount of slag.

The exhaust gas is removed by a dry or wet dust collector, and the separated dust is sent to a processing step such as drying or molding, if necessary. The produced metal and slag are discharged out of the furnace intermittently or continuously. The slag and metal may be taken out separately or at the same time, but in either case, they are separated outside the furnace by utilizing the difference in specific gravity and put in a container such as a ladle lined with refractory. The metal is refined into molten steel by removing impurities such as carbon in the next step.

The second step of the present invention is carried out by separating the molten slag produced in the first step from the metal bath. In the molten slag, in addition to iron oxide, iron is easily mixed in the form of granular iron or the like, but if there is a large amount of mixed iron, it is the object of the present invention.
It is adversely affected that the amount of phosphorus recovered in a form that can be used as a resource is adversely affected. Therefore, it is desirable to carry out calming or the like to reduce the amount of granular iron mixed in as much as possible.

The first method of treatment after the second step is to reduce the molten slag and dissolve phosphorus in the iron produced by the reduction to produce a molten metal having a high phosphorus content. Is separated and oxidized and refined in the presence of basic slag to produce a slag having a high phosphorus content. For that purpose, in the second step, carbonaceous material is added to the separated molten slag as a reducing material and heated.

As the carbonaceous material added as the reducing agent, for example, the carbonaceous material which came out together with the molten slag discharged from the furnace in the first step, and various carbonaceous materials can be used. It is appropriate that the amount of the carbonaceous material to be added is 150 to 250% of the carbon equivalent (C is assumed to change to CO) necessary for reducing the iron oxide in the slag.

To dissolve phosphorus as much as possible into the metal to obtain a metal having a phosphorus concentration as high as possible,
It is important to increase the amount of phosphorus recovered in a form that can be used as a resource. For that purpose, it is desirable that the gas generation at the time of reduction is as small as possible, and therefore electric power is used for heating. As a form of power supply, arc heating or the like using a graphite electrode is suitable. The energization may be direct current or alternating current.

The formed metal containing phosphorus and carbon is initially formed as fine particles, but they are successively coalesced, grown, and settled down to accumulate. T.S. The above process is terminated when Fe becomes 1% or less. T. This is because most of phosphorus has been converted to metal when Fe is 1% or less.
Then, the molten slag is discharged out of the system. The composition of this slag is almost the same as that of a normal blast furnace slag, so that it can be used similarly.

In the third step, the metal containing phosphorus and carbon produced in the second step is collected and refined with basic slag. Of course, it is possible to separate the metal in a molten state and perform the treatment in the third step as it is. However, when the amount of produced metal is small, it is also possible to once solidify and perform the treatment in the third step. . In that case, melting is performed in an electric furnace, or carbonaceous material is used as a heating source in a furnace such as a converter that blows oxygen.

While blowing oxygen gas to the molten metal, a flux containing lime as a main component was added to the molten metal so that the CaO content was 55.
% Slag is made, the slag amount is such that the phosphorus concentration of the metal is 0.1% or more, and the metal temperature is 1450 ° C.
If kept below, the phosphoric acid concentration of the slag will be 10% or more, and it can be used directly as a phosphate fertilizer or as a raw material for producing phosphoric acid.

Another method of the treatment after the second step of the present invention is to reduce the phosphorus content from the molten slag and vaporize it. Then, in the third step, the vaporized phosphorus is oxidized in the atmosphere and recovered as phosphoric acid. The phosphoric acid in the gas dissolves in water when the gas is wet-processed, and therefore the water can be processed and recovered as a precipitate of calcium phosphate, for example. In these methods, it is important how to increase the ratio of phosphorus vaporized in the second step.

The first method therefor is to increase the amount of gas generated during the reduction of the molten slag so that the phosphorus content which has become unstable in the slag due to the reduction of the iron oxide is transferred to the atmosphere instead of the reduced metal. To In the method, molten slag is transferred to a converter-like vessel, carbon material is added to it, and oxygen is supplied. The heat generated by the combustion of the carbonaceous material causes the reddish carbonaceous material to reduce the iron oxide in the slag, and the unstable phosphorus is carried away by the gas.

The method of treating this gas to recover the phosphorus content is as described above. T.S. By performing this treatment until Fe becomes 1% or less, 95% or more of the phosphorus content in the molten slag can be transferred to gas and metal.

The second method for increasing the proportion of phosphorus vaporized in the second step is to reduce the molten slag by using an alloy containing silicon such as ferrosilicon, and reduce the iron oxide in the molten slag. Of metal produced by performing
The content is to be 20% or more. In this way, since the generated metal contains Si and phosphorus is difficult to dissolve, most of phosphorus that has become unstable in the slag due to iron oxide reduction is vaporized. If the Si content is less than 20%, the amount of phosphorus dissolved in the metal increases, which is not preferable. The method of recovering the vaporized phosphorus is the same as described above.

The metal produced in the second step is a part of the Si content of the added silicon-containing alloy replaced by iron, and the Si concentration is lower than that of the added metal. However, since Si is high and almost no impurities are dissolved, it can be used for applications in which the Si concentration may be lower than that of ferrosilicon, or as a part of the raw material of the ferrosilicon manufacturing process. Further, since the reduction reaction of iron oxide with silicon is accompanied by heat generation, heating is not necessary in this case.

A third method for increasing the proportion of phosphorus vaporized in the second step is to apply a plasma containing hydrogen gas to the molten slag. When a plasma containing hydrogen gas is applied, the hydrogen gas heats and reduces the slag,
The phosphorus becomes unstable in the slag, and the plasma gas efficiently carries the phosphorus. In this case, it is desirable that the slag layer is gas-stirred for macro stirring in the slag layer. The method of recovering vaporized phosphorus is the same as that described above.

Another method for more efficiently vaporizing the phosphorus content in the molten slag produced in the first step is to solidify the molten slag into powder, and add carbonaceous material to it to heat it. is there. To make the slag into powder, either a method of pulverizing the solidified one or a method of spraying water on the molten slag may be used. In order to increase the vaporization rate of phosphorus, it is necessary that the amount of carbonaceous material added to the powder slag be at least three times the amount of iron oxide in the slag. In addition, the heating temperature of the mixture of slag and carbonaceous material is 700 to increase the vaporization rate of phosphorus.
Must be above ℃. The method of recovering vaporized phosphorus is the same as that described above. The treated slag can be used as a cement raw material or the like.

[0034]

【Example】

[Example 1] In the first step, a converter-like vessel lined with alumina-carbon brick was used to reduce iron ore under the following conditions. (1) Raw materials used: 1) Iron ore ... T. Fe (Total Fe); 69.8%, S
iO ₂ ; 2.3% 2) Carbon material 1 ... F.I. C (Fixed Carbon); 5
3.1%, V.I. M (Volatil Matter);
37.2%, Ash; 10.3% 3) Carbonaceous material 2 ... F.I. C; 73.2%, V.I. M; 2.4%,
Ash; 9.8% (preheated outside the furnace to 620 ° C. in advance) 4) Flux… quick lime (97% as CaO) (2) Blowing conditions: 1) Metal (seed bath) amount… 70t 2) slag (Taneyu) the amount of ... 26t (370kg / t- metal) 3) top-blown gas amount ... oxygen: 25000Nm ³ / hr (constant) 4) bottom-blown gas amount ... nitrogen: 900~1000Nm ³ / hr
(= Average 11 Nm ³ / hr-t metal) 5) Iron ore supply rate ... Supply rate; 36.0-42.0 t / h
r, total amount; 40.0t 6) Carbonaceous material supply amount ... Carbonaceous material 1: supply rate; 19.6t / hr,
Total amount: 19.6t Carbonaceous material 2: Supply rate: 3.9t / hr, total amount: 3.9t 7) Flux supply amount: 4.2t / hr, total amount: 4.2t 8) Metal temperature: 1410 to 1440 ° C

As a result, the composition of the produced metal and the composition of the slag were as follows. (1) Metal component: C: 3.9%, Si: 0.02%,
Mn; 0.21%, P; 0.020%, S; 0.036
% (2) Slag composition: CaO; 43%, SiO ₂ ; 29
%, MgO; 5.6%, Al ₂ O ₃ ; 14%, T.I. F
e; 4.5%, P; 0.52%, S; 0.15%

Next, the slag produced in the first step, that is, the smelting reduction step is received in a ladle lined with alumina bricks, and in the second step, two graphite electrodes are inserted to apply an alternating current to the first step. In the first stage, only coke powder was blown into the slag layer.

The temperature of the slag was measured with a thermocouple, and the current passed was adjusted so that the indicated value was in the range of 1400 to 1435 ° C. The operation data at this time is shown below. (1) Slag conditions before treatment: 1) Composition: Same as the composition at the end of the first step.

2) Temperature: 1420 ° C. (2) Treatment condition: 1) Powder coke blowing condition ... Grain size: 1.2 mm or less, carrier gas; Nitrogen gas 2) Energization condition: AC, voltage = 2.5V, current = 1200
0-23000A 3) Processing time ... 8 minutes

(3) Slag conditions at the end: 1) Composition: CaO; 44%, SiO ₂ ; 30%, Mg
O; 6.8%, Al ₂ O ₃ ; 15%, T.I. Fe; 0.8
%, P; 0.09%, S; 0.56% 2) Temperature: 1390 ° C. (4) Generated metal component: C; 4.3%, P; 1.3%,
S; 0.01%

In the third step, the solidified metal produced was collected for 10 heats, melted in an electric furnace, lime was added to form slag, and oxygen gas was supplied. Slag component after treatment: CaO; 57%, Al ₂ O ₃ ; 5
%, SiO ₂ ; 4%, P ₂ O ₅ ; 14%, T.I. Fe; 1
2%, MgO; 2% Metal component after treatment: C; 3.9%, Si; 0.05
%, P; 0.02%, S; 0.03% By this method, 68% of the phosphorus input to the entire process
However, it moved to the high phosphorus slag after the treatment.

[Embodiment 2] The first step is the same as in Embodiment 1. In the second step, the molten slag was transferred to a converter, and 15% by weight of coke was added while stirring with bottom-blown nitrogen, and oxygen gas was top-blown. Slag component after treatment: CaO; 44%, Al ₂ O ₃ ; 1
5%, SiO ₂ ; 30%, P ₂ O ₅ ; 0.1%, T.I. F
e; 0.8%, MgO; 6% Formed metal component: C; 3.9%, Si; 0.05
%, P: 0.02%, S: 0.05% The generated gas was wet-processed, and the phosphoric acid content was recovered from the water as a calcium phosphate precipitate. The recovery amount of phosphorus was 57% of the input phosphorus in all steps.

[Third Embodiment] The first step is the same as that of the first embodiment. In the second step, ferrosilicon (Si; 75%) was added to the separated molten slag and stirred with nitrogen gas. Slag component after treatment: CaO; 42%, Al ₂ O ₃ ; 1
3%, SiO ₂ ; 36%, P ₂ O ₅ ; 0.1%, T.I. F
e; 0.6%, MgO; 5% Generated metal component: C; 0.1%, Si; 25%,
P: 0.02%, S: 0.05% The generated gas was wet-processed and the phosphoric acid content was recovered from the water as a calcium phosphate precipitate. The recovery amount of phosphorus was 63% of the input phosphorus in all steps.

[Embodiment 4] The first step is the same as in Embodiment 1. In the second step, the molten slag was transferred to a plasma heating furnace and treated with a gas containing 50% hydrogen and 50% Ar. In addition,
Stir with bottom-blown nitrogen. Slag component after treatment: CaO; 44%, Al ₂ O ₃ ; 1
5%, SiO ₂ ; 30%, P ₂ O ₅ ; 0.1%, T.I. F
e; 0.8%, MgO; 6% Formed metal component: C; 3.9%, Si; 0.05
%, P: 0.02%, S: 0.05% The generated gas was wet-processed, and the phosphoric acid content was recovered from the water as a calcium phosphate precipitate. The amount of phosphorus recovered was 59% of the input phosphorus in all steps.

[Embodiment 5] The first step is the same as in Embodiment 1. In the second step, the solidified molten slag is
It was crushed to 0 mesh or less and 37% by weight of coke powder was added thereto. In the third step, use a rotary kiln for 920
Heated to ° C. Slag component after treatment: CaO; 44%, Al ₂ O ₃ ; 1
3%, SiO ₂ ; 29%, P ₂ O ₅ ; 0.1%, T.I. F
e; 4.7%, MgO; 5%, C; 4.3% The generated gas was wet-processed, and the phosphoric acid content was recovered from the water as a precipitate of calcium phosphate. The amount of phosphorus recovered was 65% of the total input phosphorus.

[0045]

INDUSTRIAL APPLICABILITY The present invention provides a method for industrially and economically increasing the low level of phosphorus contained in iron ore, which was impossible by the conventional method, to a level at which it can be effectively used as a phosphorus resource. In addition to solving the problem of slag generated in steel refining,
The effect is great from both sides of the environment.

[Brief description of drawings]

FIG. 1 is a graph showing the influence of metal temperature on the phosphorus concentration of metal in the first step of the present invention.

FIG. 2 shows the T.V. of slag affecting the phosphorus concentration of metal in the first step of the present invention. It is a graph which shows the influence of Fe.

Claims (5)

[Claims] 1. A metallurgical furnace capable of blowing gas from the bottom,
While blowing oxygen gas upward, the iron ore or its pre-reduction product and carbonaceous material were charged, and the temperature of the molten metal was 1360-
Adjusted to the range of 1450 ℃, and (T.F.
e) a first step of adjusting the concentration within a range of 3 to 9% to transfer phosphorus into the molten slag, separating the molten slag from the metal bath, adding a reducing agent to the molten slag, and heating Included in iron ore characterized by a second step of transferring phosphorus into the generated metal, and a third step of oxidizing and refining the generated metal with basic slag to transfer phosphorus into slag A method of recovering the phosphorus content as phosphorus resources. 2. A second step following the first step, in which the molten slag is separated from the metal bath, carbonaceous material is added and oxygen is blown to reduce the (T.Fe) of the slag to 1% or less, The method for recovering phosphorus contained in iron ore as a phosphorus resource according to claim 1, comprising a third step of recovering phosphorus as phosphoric acid from the gas generated at that time. 3. Subsequent to the first step, the molten slag is separated from the metal bath, a silicon-containing alloy is added and reduced, and in this case, the metal content of Si is 20% or more. 2. The method for recovering phosphorus contained in iron ore as a phosphorus resource according to claim 1, comprising a step and a third step of recovering phosphorus as phosphoric acid from the gas generated at that time. 4. A second step of separating the molten slag from the metal bath and reducing the slag by hydrogen gas plasma after the first step, and recovering phosphorus as phosphoric acid from the gas generated at that time. The method for recovering phosphorus contained in iron ore as a phosphorus resource according to claim 1, comprising a third step. 5. Following the first step, a second step of separating the molten slag from the metal bath and solidifying the molten slag into powder, and adding carbonaceous material to the powder slag and heating the slag. 700 ° C
The phosphorus content contained in the iron ore according to claim 1 is recovered as a phosphorus resource, which comprises the above-mentioned third step and the fourth step of recovering phosphorus as phosphoric acid from the gas generated at that time. how to.