JP4540488B2 - Desulfurization method of ferronickel - Google Patents

Description

  The present invention relates to a method for desulfurizing ferronickel, and more specifically, after charging a crude ferronickel melt discharged from a reduction furnace into a stirring refining furnace, a desulfurizing agent is added to purify sulfur in the melt. In the method of desulfurizing ferronickel by fixing and removing in the furnace slag, high desulfurization efficiency is achieved, and after desulfurization treatment, molten ferronickel is discharged from the refining furnace, and then the refining furnace slag left in the furnace is discharged. The present invention relates to a desulfurization method that can easily and efficiently scrape out the slag and reduce the slag discharge processing time.

Ferronickel is an alloy mainly composed of iron and nickel, and is used as a raw material for stainless steel and special steel. As a general production method, a dry smelting method comprising a roasting (firing) step, a reduction melting step and a refining step is used, using garnierite ore, which is a magnesium silicate ore containing nickel, as a raw ore. Yes.
Representative compositions of garnierite ore, Ni quality 2.1 to 2.5% by weight on a dry mineral terms, Fe quality 11 to 23%, MgO quality 20-28 wt%, SiO ₂ quality 29 ~ 39 wt%, CaO grade <0.5 wt%, and loss on ignition is 10-15 wt%.

Here, first, in the roasting (firing) step, the raw ore is roasted or fired by adding coal (carbonaceous reducing agent) such as anthracite and a melt as necessary, and contains a carbonaceous reducing agent. A sinter or sintered ingot is produced. Next, in the reduction melting step, the sinter or sintered ingot is subjected to reduction melting in a reduction furnace such as an electric furnace or a blast furnace to form crude ferronickel and slag.
The composition of the crude ferronickel produced from the reduction furnace was adjusted to a nickel grade of 15 to 25% by weight by adjusting the blending amount of the carbonaceous reducing agent, and most of nickel and cobalt in the raw ore and a part of them were adjusted. It contains iron and contains impurities such as sulfur, carbon, silicon, chromium, phosphorus, and manganese. The slag produced from the reduction furnace contains most of the iron oxide in the raw ore, silicon dioxide and magnesium oxide. Here, the slag is extracted separately from the crude ferronickel, and is used as a component adjusting solvent, a fine aggregate for asphalt, a fine aggregate for concrete, and the like in the steel sintering process.

  Next, the crude ferronickel molten metal is poured into a ladle and processed in a refining process to produce a product. Crude ferronickel is first subjected to desulfurization as a purification step. In the desulfurization treatment, using a mechanical stirring type or electric induction stirring type refining furnace, a desulfurizing agent such as calcium carbide is added and sulfur in the crude ferronickel is fixed and removed as calcium sulfide (CaS) in the refining furnace slag. The sulfur in the crude ferronickel is reduced to the desired content to produce high carbon ferronickel (JIS: ferronickel H1-2).

  Furthermore, when manufacturing low carbon ferronickel (JIS: It is prescribed | regulated by ferronickel L1-2.), It is next attached | subjected to an oxidation blowing as a refinement | purification process. In the oxidation blowing process, a high carbon ferronickel melt is charged into a converter, and a melting agent is added to this and blown with pure oxygen gas, and carbon, silicon, chromium, phosphorus in the melt are added. Oxidation and removal of impurity elements such as manganese.

  The ferronickel melt obtained by these refining processes is finally cast and commercialized. As casting methods, the molten metal is discharged through a pan having a molten metal discharge device (sliding nozzle) at the bottom or by tilting, and poured into a mold to make an ingot product, or it is granulated and shot product. The method is taken.

  In addition, refining furnace slag produced by desulfurization treatment is generally discharged after the ferronickel melt is discharged, and the refining furnace is tilted to manually scrape and transfer the solid matter to the slag pot, let it cool, and leave it outdoors. Is done. Then, after weathering is advanced to some extent, it is crushed using a crusher to a particle size of about 20 to 50 mm, and further separated into magnetic and non-magnetic materials mixed with ferronickel metal by magnetic separation. Here, usually, the collected magnetic deposits are repeated in the roasting (firing) step or the reduction melting step, and the non-magnetic deposits are partially repeated in the step, and the rest are discarded.

  However, the scraping work of the refining furnace slag to the slag pot has a problem that the work is delayed due to the deterioration of the efficiency and the time for the desulfurization treatment is extended. That is, when refining furnace slag that is welded in the furnace during desulfurization is generated, the difficulty of scraping out the slag increases, which increases the work load, and desulfurization treatment including the discharge of the refining furnace slag is the rate-limiting step. This reduces the production efficiency of products in all processes. Therefore, in the desulfurization treatment of the crude ferronickel melt, not only high desulfurization efficiency is achieved, but also the efficiency of removing the slag produced by the desulfurization treatment has been demanded.

  By the way, the removal of slag produced by desulfurization treatment from metal melt in dry smelting is described in the hot metal desulfurization method of steel smelting. For example, in a method in which a desulfurization agent mainly composed of powdered calcium carbide is blown into hot metal using nitrogen gas as a carrier gas, prior to blowing of the desulfurization agent, powdered quicklime and / or calcined dolomite and carbon are molten. A method of covering the hot metal surface with slag floating on the hot metal surface as a semi-solid or solid material (see, for example, Patent Document 1), or prior to blowing of the desulfurizing agent, the particle size of 30 A method (for example, refer to Patent Document 2) of covering the hot metal surface by adding ~ 200 mm quicklime and / or calcined dolomite is disclosed. Here, it is described that the slag produced by the desulfurization treatment is easily removed by making it into a small lump.

  However, the above proposal mainly focuses on the efficient use of expensive desulfurization agents such as calcium carbide in the desulfurization method by blowing the desulfurization agent, and has a higher melting point than hot metal mainly composed of iron. In addition, there is no mention of technical factors for application to a crude ferronickel melt having a low desulfurization efficiency.

Japanese Examined Patent Publication No. 61-25863 (pages 1 to 5) Japanese Examined Patent Publication No. 61-25564 (pages 1-5)

  In view of the above-mentioned problems of the prior art, the object of the present invention is to charge the crude ferronickel melt discharged from the reduction furnace into a stirring refining furnace, and then add a desulfurizing agent to remove sulfur in the melt. In the method of desulfurizing ferronickel by fixing and removing in the refining furnace slag, high desulfurization efficiency is achieved, and after desulfurization treatment, molten ferronickel is discharged from the refining furnace, and then the refining furnace slag left in the furnace is removed. An object of the present invention is to provide a desulfurization method that can easily and efficiently scrape out the slag and reduce the time for discharging the slag.

  In order to achieve the above object, the present inventors charged the crude ferronickel melt discharged from the reduction furnace into a stirring-type refining furnace, added a desulfurizing agent, and removed sulfur in the molten furnace to the refining furnace. As a result of intensive research on the method of desulfurizing ferronickel by fixing and removing it in the slag, the operation in the stirring type refining furnace was conducted under the conditions of the specific melt temperature and slag composition. It was found that the produced slag can be coarsely granulated, whereby the slag can be scraped out easily and efficiently, and the discharge operation time of the slag can be shortened, and the present invention has been completed.

That is, according to the first invention of the present invention, after charging the crude ferronickel melt discharged from the reduction furnace into the stirring type refining furnace, the desulfurizing agent is added, and the sulfur in the molten metal is purified into the refining furnace slag. In the method of desulfurizing ferronickel by fixing and removing inside,
While raising the temperature of the ferronickel melt to 1550-1600 ° C., adding a composition regulator, the composition of the refining furnace slag after desulfurization treatment is 40-55 wt% calcium oxide (CaO) grade, and There is provided a method for desulfurizing ferronickel, characterized by adjusting the silicon dioxide (SiO ₂ ) grade to 5 to 10% by weight.

  According to a second aspect of the present invention, there is provided the method for desulfurizing ferronickel according to the first aspect, wherein the desulfurizing agent is a desulfurizing agent mainly composed of calcium carbide.

  According to a third aspect of the present invention, there is provided a ferronickel desulfurization method characterized in that, in the first aspect, quick lime is added as a calcium oxide composition regulator.

  According to a fourth aspect of the present invention, there is provided a ferronickel desulfurization method characterized in that, in the first aspect, a reducing furnace slag is added as a silicon dioxide composition modifier.

  According to the fifth aspect of the present invention, in any one of the first to fourth aspects of the invention, prior to charging the crude ferronickel melt into the stirring type refining furnace, Provided is a method for desulfurizing ferronickel characterized by blowing enriched air or pure oxygen gas.

  In the ferronickel desulfurization method of the present invention, the crude ferronickel melt discharged from the reduction furnace is charged into a stirring refining furnace, a desulfurizing agent is added, and the sulfur in the melt is fixed in the refining furnace slag. In the removal method, high desulfurization efficiency can be achieved, and slag produced by the desulfurization treatment can be coarsely granulated. This produces a slag with good handling properties that can be easily and efficiently scraped when discharging the ferronickel melt from the refining furnace after the desulfurization treatment and then discharging the refining furnace slag left in the furnace, Since the time for discharging slag can be shortened, its industrial value is extremely large.

  In addition, when oxygen-enriched air or pure oxygen gas is blown into the crude ferronickel molten metal after the ferronickel melt is charged into the stirring type refining furnace, the molten metal is heated to a predetermined temperature. It is more advantageous because it can be heated and a part of silicon in the molten metal can be oxidized and used as a silicon dioxide source of the refining furnace slag.

Hereinafter, the ferronickel desulfurization method of the present invention will be described in detail.
In the ferronickel desulfurization method of the present invention, the crude ferronickel melt discharged from the reduction furnace is charged into a stirring refining furnace, a desulfurizing agent is added, and the sulfur in the melt is fixed in the refining furnace slag. In the method of removing and desulfurizing ferronickel, the temperature of the crude ferronickel molten metal is raised to 1550 to 1600 ° C., and a composition regulator is added to oxidize the composition of the refined slag after desulfurization treatment. The calcium (CaO) quality is adjusted to 40 to 55% by weight, and the silicon dioxide (SiO ₂ ) quality is adjusted to 5 to 10% by weight.

  In the present invention, in the desulfurization treatment in the stirring-type refining furnace, the temperature of the crude ferronickel molten metal is raised to 1550 to 1600 ° C., and a composition regulator is added to adjust the composition of the refining furnace slag after the desulfurization treatment. It is important to adjust the calcium oxide quality to 40 to 55% by weight and the silicon dioxide quality to 5 to 10% by weight. As a result, most of the slag produced by the desulfurization treatment is solid-phased and coarsely granulated into a substantially spherical shape having a particle size of 30 to 100 mm. This coarsely granulated slag has good handling properties, such as being able to be scraped easily and efficiently.

  The crude ferronickel melt used in the above method is not particularly limited, and a crude ferronickel melt discharged from a reduction furnace such as an electric furnace or a blast furnace is used. As the typical composition, for example, nickel grade is 15 to 25% by weight, sulfur grade is 0.3 to 0.6% by weight, carbon grade is 1.5 to 2.5% by weight, and silicon grade is 0.00. 5 to 2.0% by weight. Moreover, the temperature discharged from a reduction furnace is 1300-1500 degreeC.

A specific example of the above method is not particularly limited, but is performed as follows.
First, the crude ferronickel melt discharged from the reducing furnace to the ladle is charged into a mechanical stirring type or electric induction stirring type purification furnace. Next, while stirring the crude ferronickel melt, a predetermined addition amount of a desulfurizing agent and a composition adjusting agent are added, and a desulfurization treatment is performed for a predetermined time. The end point determination of the desulfurization process is performed by analyzing the collected sample and confirming that the sulfur quality in the crude ferronickel after the desulfurization process has reached the target value. If desulfurization is insufficient, a desulfurizing agent and a composition regulator are further added to continue the desulfurization process.

At this time, the temperature control of the molten metal and the composition adjustment of the slag produced by the desulfurization treatment are indispensable, and the temperature of the crude ferronickel molten metal is raised to 1550 to 1600 ° C., while the refining furnace after the desulfurization treatment The composition of the slag is adjusted so that the calcium oxide quality is 40 to 55% by weight and the silicon dioxide quality is 5 to 10% by weight. The predetermined addition amount of the desulfurizing agent is empirically obtained from the sulfur quality in the raw crude ferronickel and the desulfurization efficiency of the desulfurizing agent to be used. For example, the sulfur quality in the crude ferronickel is In the case of 0.4 to 0.5% by weight, it is 10 to 20 kg per ton of crude ferronickel.
After desulfurization treatment, after discharging the ferronickel melt, the refining furnace is tilted to scrape coarse granular slag into the slag pot.

  The desulfurization agent used in the above method is not particularly limited, and examples thereof include calcium carbide, lime nitrogen, and a mixture of both, and a desulfurization agent mainly composed of calcium carbide capable of obtaining high desulfurization efficiency is preferable. Here, the desulfurization reaction is performed by fixing and removing sulfur in the crude ferronickel as calcium sulfide (CaS) in the refining furnace slag. In addition, a part of the desulfurizing agent mainly composed of calcium carbide is oxidized without directly contributing to the desulfurization reaction, thereby generating calcium oxide that can be used as a calcium oxide source of the refining furnace slag.

  The shape and purity of the desulfurization agent are not particularly limited, and commercially available industrial chemicals in the form of powder or granules are used.

  The temperature of the crude ferronickel melt used in the above method is raised to a predetermined temperature of 1550 to 1600 ° C. That is, when the temperature of the molten metal is less than 1550 ° C., the contact of the crude ferronickel and the desulfurizing agent by stirring is insufficient in the refining furnace. For example, in addition to the fact that the molten metal is not sufficiently stirred, desulfurization does not proceed sufficiently, and because the slag is insufficiently melted, the solid slag or between the solid slag and the molten slag Since the contact opportunity is reduced, coarse graining does not occur and the desired size of the sphere does not grow. On the other hand, when the temperature of the molten metal exceeds 1600 ° C., melting of the slag proceeds excessively, so that it is difficult to obtain solid phase slag, and as a result, the generated slag is caused to adhere to the refining furnace and discharged. It becomes difficult.

As a method of adjusting the temperature of the crude ferronickel melt, it can be performed by controlling the temperature of the crude ferronickel melt discharged from the reduction furnace to a predetermined temperature, but in general, excessive temperature rise in the reduction furnace is This is undesirable because it causes significant wear of the refractory of the furnace body.
Therefore, the molten metal is discharged at a temperature lower than a predetermined temperature, and then oxygen-enriched air or pure oxygen gas is blown into the crude ferronickel molten metal after charging into the stirred refining furnace. Thus, it is preferable to add a step of raising the temperature by oxidizing a part of the crude ferronickel component. Here, since silicon, phosphorus, etc. in the crude ferronickel are preferentially oxidized and removed as slag, it can also serve as a purification means for satisfying the quality standard of high carbon ferronickel. That is, the temperature of the molten metal can be raised to a predetermined temperature, and a part of silicon in the molten metal can be oxidized and used as a silicon dioxide source for the refinement furnace slag.

The composition of the refining furnace slag after the desulfurization treatment used in the above method is adjusted so that the calcium oxide (CaO) quality is 40 to 55% by weight and the silicon dioxide (SiO ₂ ) quality is 5 to 10% by weight. That is, when the calcium oxide quality and silicon dioxide quality of the refining furnace slag are within this range, most of the refining furnace slag becomes a solid phase, and a part of the slag melts so that the solid phase becomes roughly spherical. Granulated. Moreover, the sulfur quality of the refining furnace slag obtained at this time is 10 to 20% by weight.

  More specifically, if the quality of calcium oxide in the refining furnace slag is less than 40% by weight, the entire produced slag is welded in the pan and becomes difficult to discharge. It causes deterioration of the basic unit of the agent. Also, if the silicon oxide grade in the refining furnace slag is less than 5% by weight, the amount of low melting point slag that grows solid phase slag is insufficient, and the slag does not grow large spherically and remains sandy, making it difficult to discharge. On the other hand, if it exceeds 10% by weight, the entire generated slag is welded in the furnace, making it difficult to discharge.

  The composition adjustment of the refining furnace slag used in the above-mentioned method is performed, if necessary, with at least one composition regulator selected from a composition regulator containing calcium oxide, a composition regulator containing silicon dioxide, or a composition regulator containing both. It can be performed by newly adding. The composition adjusting agent for calcium oxide is not particularly limited, and a compound containing calcium oxide is used. However, quick lime and calcined dolomite that do not generate moisture or an oxidizing gas such as carbon dioxide are preferable, and quick lime is used. More preferred. Moreover, the shape and purity of the said quicklime and baked dolomite are not specifically limited, Powdery or granulated commercially available industrial chemicals are used.

The composition modifier for silicon dioxide is not particularly limited, and a compound containing silicon such as silicon dioxide is used. Among them, a large amount is particularly produced when producing a crude ferronickel melt. It is economical to use the generated reducing furnace slag. For example, as the reducing furnace slag, a composition having a MgO grade of 32 to 36% by weight, a SiO ₂ grade of 50 to 55% by weight, a CaO grade of about 0.5% by weight, and a Fe grade of 5 to 10% by weight. Used. Moreover, as a shape of the said reduction furnace slag, a granular material, for example, a granulated slag (3.6-4.3 by the coarse-grain rate defined by the concrete term of JISA0203), are preferable.

  A specific means for adjusting the amount of the composition regulator added will be described. For example, when silicon dioxide that is oxidized and produced by blowing oxygen-enriched air or pure oxygen gas into the crude ferronickel melt after brewing is used as the silicon dioxide source, the amount of silicon oxidized is strictly limited. Since it is difficult to control, the amount of silicon removed from the crude ferronickel under the same empirically obtained conditions is regarded as the amount of silicon dioxide contained in the slag. Also, empirically evaluate the amount of calcium oxide produced from the amount of desulfurizing agent added, and when there is little silicon dioxide compared to the desired composition, means for adding reducing furnace slag, A means for adding quicklime is selected.

  By the above method, ferronickel having a sulfur quality of 0.03% by weight or less that satisfies the quality standard can be obtained. On the other hand, most of the refining furnace slag produced by the desulfurization process is a solid phase and is coarsely granulated into a substantially spherical shape having a particle size of 30 to 100 mm, so that it can be easily and efficiently scraped and has good handling properties. Is.

Hereinafter, the present invention will be described in more detail by way of examples and comparative examples of the present invention, but the present invention is not limited to these examples. The analysis methods used in the examples and comparative examples are as follows.
(1) Ni analysis of ferronickel: dimethylglyoxime separation EDTA titration method was used.
(2) Si analysis of ferronickel: Fluorescent X-ray method was used.
(3) Analysis of S in ferronickel and slag: performed by infrared absorption method.
(4) Analysis of CaO of slag: It was performed by a fluorescent X-ray method.
(5) Analysis of slag SiO ₂ : Fluorescence X-ray method was used.

(Examples 1-5, Comparative Examples 1-10)
Using the crude ferronickel molten metal produced from the electric furnace, oxidation blow smelting in a ladle and desulfurization treatment in a mechanical stirring refining furnace were performed. Crude ferronickel melt is reduced by drying a garnierite ore with a typical composition with a dryer, adding coal, and pre-reducing and roasting it in a rotary kiln into an electric furnace with a diameter of about 18 m. It was obtained by melting.
First, 14 to 17 tons of crude ferronickel molten metal is poured into each ladle for each batch, and pure oxygen gas is flowed at a flow rate of 5 m ³ / min to adjust the temperature rise and impurity quality, and the blowing time is changed. And processed. In addition, the tapping temperature fluctuated between 1395 and 1435 ° C. Thereafter, a sample of crude ferronickel after oxidation blowing was collected and analyzed. Table 1 shows the output temperature of crude ferronickel for each batch, the pure oxygen blowing time, the weight of crude ferronickel after oxidation blowing, the Si quality, and the S quality.

Next, the crude ferronickel after oxidation blowing was charged into a mechanically stirred refining furnace having a purification capacity of 17 tons per batch, the addition amount of calcium carbide was 220 to 320 kg, the addition amount of quick lime was 0 to 68 kg, And the desulfurization process was performed by changing the addition amount of the reduction furnace slag to 0 to 40 kg. Table 1 shows the desulfurization start temperature and the addition amounts of calcium carbide, quicklime and reducing furnace slag in the desulfurization treatment. The reducing furnace slag has a composition with MgO grade of 33.2% by weight, SiO ₂ grade of 51.4% by weight, CaO grade of about 0.2% by weight, and Fe grade of 7.9% by weight. Used.
After that, the observation results of the coarsening state of the refined slag obtained (whether spherical slag was generated), the working time of slag discharge from the refiner, and the analysis of the composition of the refined slag and ferronickel after desulfurization treatment Went. The results are shown in Table 2.

From Table 1 and Table 2, in Examples 1 to 5, the desulfurization start temperature of the crude ferronickel melt and the CaO grade and SiO ₂ grade of the refined furnace slag after the desulfurization treatment were performed according to the method of the present invention. It can be seen that sufficient desulfurization efficiency is obtained, spherical slag is generated, and the slag discharge operation time is performed in a short time. On the other hand, in Comparative Examples 1 to 10, since either the desulfurization start temperature of the crude ferronickel melt and the CaO grade and SiO ₂ grade of the refining furnace slag do not meet these conditions, the generation of spherical slag and It can be seen that satisfactory results are not obtained in the slag discharge operation time.

  As is clear from the above, the method for desulfurizing ferronickel according to the present invention reduces the time for discharging the refining furnace slag after desulfurization, and improves the efficiency of the desulfurization process including the refining furnace slag discharge. It is possible to prevent a decrease in product production efficiency. Therefore, it is suitable as a desulfurization method for molten metal used in the desulfurization process of crude ferronickel in ferronickel smelting, and is particularly useful as a desulfurization method for crude ferronickel having a high sulfur grade.

Claims (5)

A method of desulfurizing ferronickel by charging a crude ferronickel melt discharged from a reduction furnace into a stirring type refining furnace, adding a desulfurizing agent, and fixing and removing sulfur in the molten slag in the refining furnace slag. In
While raising the temperature of the crude ferronickel melt to 1550-1600 ° C., adding a composition regulator, the composition of the refined furnace slag after the desulfurization treatment is calcium oxide (CaO) grade 40-55 wt%, And a method for desulfurizing ferronickel, wherein the silicon dioxide (SiO ₂ ) quality is adjusted to 5 to 10% by weight.   2. The ferronickel desulfurization method according to claim 1, wherein the desulfurization agent is a desulfurization agent mainly composed of calcium carbide.   The ferronickel desulfurization method according to claim 1, wherein quick lime is added as a calcium oxide composition regulator.   The method for desulfurizing ferronickel according to claim 1, wherein reducing furnace slag is added as a composition modifier for silicon dioxide.   The oxygen-enriched air or pure oxygen gas is blown into the crude ferronickel molten metal after the charging, prior to charging the crude ferronickel molten metal into the stirring type refining furnace. The method for desulfurizing ferronickel as described in 1.