JP4845078B2 - Hot metal desulfurization method - Google Patents

Description

  The present invention relates to a hot metal desulfurization method using a mechanical stirring desulfurization apparatus, and more particularly, to a method of efficiently adding a fine desulfurization agent having excellent reactivity to a hot metal for desulfurization.

  The hot metal discharged from the blast furnace usually contains a high concentration of sulfur (S), which adversely affects the quality of the steel, and various hot metal desulfurization and molten steel desulfurization can be performed depending on the required quality of the steel. Has been done. Among these, for desulfurization of hot metal, inexpensive desulfurization agents mainly composed of lime (CaO) are widely used, and the desulfurization reaction in this case is based on the reaction formula shown by the following formula (1). proceed.

In this desulfurization treatment, a fluorite (CaF ₂ ) type fossilizing agent and an alumina type fauxifying agent are used as a CaO hatching accelerator. For example, about 5% by mass of fluorite is added to quick lime as a CaO source. CaO—CaF ₂ -based desulfurization agents mixed with stone are widely used. However, these hatching accelerators are generally expensive, and increasing the blending ratio of these hatching accelerators leads to an increase in the cost of the desulfurization agent. Furthermore, when the blending ratio of the hatching accelerator is increased, the CaO concentration in the desulfurizing agent is lowered, and there is a concern that the reaction efficiency is lowered. In addition, in order to improve the reaction efficiency of desulfurization, there are a method of using quick lime in combination with a calcium carbide desulfurization agent and a soda desulfurization agent, a method of mixing limestone (CaCO ₃ ) with quick lime, etc. All are desulfurization agents based on the premise that a CaF ₂ -based hatching accelerator is added. Under circumstances where there is a concern about the environmental impact of fluorine in recent years, a CaF ₂ -based hatching accelerator is used. It is desired to efficiently desulfurize without use.

As an example of a desulfurizing agent that does not use fluorite, a calcium carbide desulfurizing agent and a soda desulfurizing agent have been put into practical use, both of which have advantages and disadvantages. Calcium carbide-based desulfurization agents have a strong desulfurization ability, but there are safety problems such as the generation of acetylene gas in the post-treatment of desulfurization slag after the desulfurization treatment. Moreover, since it is expensive and dangerous, it is extremely difficult to handle. A soda-based desulfurization agent is relatively inexpensive, but has a strong alkalinity, and thus has a great influence on the refractories of the processing furnace and the processing vessel. Further, since the exhaust gas contains Na, it is necessary to remove it. Furthermore, since the content of Na ₂ O in the slag is high, there is a restriction on the reuse to cement and the like, which is undesirable from the influence on the environment.

  As another desulfurization method, a method using metal Mg is also well known. Metal Mg easily reacts with S in the hot metal to form MgS. However, since the boiling point is as low as 1100 ° C., there is a risk that the hot metal vaporizes vigorously in the hot metal at 1250 to 1500 ° C., and the hot metal is scattered. Since the generated Mg vapor does not sufficiently contribute to the desulfurization reaction and is diffused into the atmosphere, the efficiency is poor. Moreover, there is a problem that the metal Mg itself is very expensive.

  By the way, in order to improve the efficiency of the desulfurization reaction, it is effective to increase the reaction interface area. Therefore, if the particle size of the desulfurizing agent to be added is reduced, the efficiency of the desulfurization reaction is improved. However, in the actual desulfurization process, it is common to cut out the desulfurizing agent from the hopper and add the desulfurizing agent into the processing container from the inlet installed above the processing container such as hot metal ladle. When the particle size of the powdered desulfurizing agent is further refined, if the desulfurizing agent is added by such a method, the amount of the desulfurizing agent that scatters and the desulfurizing agent that rises due to the rising airflow increases and reaches the hot metal surface. This is not practical because the amount of the desulfurizing agent is reduced, resulting in a decrease in the yield of the desulfurizing agent.

As one of the methods for promoting the dispersion of the desulfurizing agent in the hot metal without increasing the size of the desulfurizing agent and increasing the reaction interface area, Patent Document 1 discloses a rectifier that protrudes from the side wall of the processing vessel. A method has been proposed in which a rotating flow-stirred hot metal collides with a rectifier to generate a downward flow, and a desulfurizing agent is involved in the downward flow. However, when installing a rectifier under strong agitation such as the desulfurization process of a mechanical agitation desulfurizer, it is necessary to install a very strong rectifier, which requires a large amount of money and labor for its production and maintenance. There is a problem of requiring. Moreover, since it is necessary to install a rectification body in a processing container, there also exists a problem that the amount of hot metal accommodated decreases and productivity falls.
Japanese Patent Laid-Open No. 51-112416

  The present invention has been made in view of the above circumstances, and the object of the present invention is to efficiently use a fine desulfurization agent having excellent reactivity when desulfurizing hot metal using a mechanical stirring desulfurization apparatus. To provide a method for efficiently desulfurizing hot metal, and to provide a method for efficiently desulfurizing hot metal even with a desulfurization agent that does not use a fluorine-based hatching accelerator. .

  The present inventors have intensively studied and studied in order to solve the above problems. The results of the examination and research are explained below.

In hot metal desulfurization treatment (also referred to as “KR desulfurization method”) in a mechanical stirring desulfurization apparatus equipped with a stirring blade (also referred to as “impeller”), the utilization efficiency of the desulfurizing agent is that of a CaO—CaF ₂ -based desulfurizing agent. Even when it is used, it is at most about 10 to 20%, and the remaining 80 to 90% remains unreacted and the utilization efficiency is very low. As a result of various analyzes on the cause of the low utilization efficiency, it was found that there are the following problems.

  That is, in a desulfurization method using a mechanical stirring type desulfurization apparatus equipped with stirring blades (hereinafter referred to as “mechanical stirring type desulfurization method”), the desulfurizing agent is generally molten iron in a state of being strongly stirred by the stirring blades. It is continuously added upward from above the processing vessel. In order to promote the desulfurization reaction, the larger the reaction interface area, the more advantageous. However, if the desulfurization agent is made finer, the amount of scattering at the time of addition increases and the yield deteriorates. On the other hand, if a desulfurization agent with a large particle size is used in consideration of scattering during addition, the reaction interface area cannot be secured, and the desulfurization reaction stagnate. In addition, CaO-based desulfurization agents that are currently used mainly as desulfurization agents have poor wettability with hot metal and are not easily caught in hot metal, and the desulfurization agent added to the bath is strongly stirred. The molten iron agglomerates on the bath surface or in the bath, and the reaction interfacial area decreases. For this reason, how to suppress the scattering and add a desulfurization agent with a large reaction interface area into the hot metal under strong stirring and suppress the aggregation to entrain the desulfurization agent, that is, how to ensure a large reaction interface area Is a challenge.

  However, under the present circumstances, a desulfurizing agent having a particle size that is difficult to scatter is used, and by increasing the addition amount of the desulfurizing agent, a reaction interface area is secured and desulfurizing ability is obtained. Further, when fluorite is not used, the desulfurization ability that is reduced is compensated by increasing the amount of the desulfurizing agent added to ensure an equivalent desulfurization capacity. However, an increase in the amount of desulfurizing agent used is not desirable because it leads to an increase in cost and an increase in the amount of slag generated.

  Therefore, as a result of various investigations on the method of adding the desulfurizing agent to solve this problem, the surface of the hot metal surface is heated together with the carrier gas in the state where the stirring blade is rotated and the hot metal vortex is formed in the processing vessel. It has been found that by adding it by spraying up toward the surface, the desulfurization reaction interfacial area can be increased without suppressing scattering and without increasing the amount of desulfurization agent used.

  The desulfurizing agent reaches the hot metal surface together with the carrier gas and comes into contact with the hot metal. This makes it possible to add a desulfurizing agent to the hot metal surface and hot metal without causing a decrease in yield when adding the desulfurizing agent, which is one of the disadvantages of the mechanical stirring desulfurization method. Can be increased. In addition, in the conventional addition method in which a desulfurizing agent is added to a processing vessel by adding it from a hopper or the like, it is difficult to uniformly disperse the desulfurizing agent on the hot metal surface, but the desulfurizing agent is added to the hot metal surface together with the conveying gas. By spraying upward, the fine desulfurization agent can be uniformly dispersed on the hot metal bath surface while suppressing aggregation on the bath surface.

  Further, when the desulfurizing agent is sprayed on the hot metal at a high speed of 10 m / second or more, the same effect as that in the case where the rectifier proposed in Patent Document 1 is used due to the downward flow of the hot metal generated by the conveying gas. It was found that the desulfurizing agent was entrained in the hot metal, and the vortex was disturbed by this downward flow, thereby promoting the dispersion of the desulfurizing agent and preventing the desulfurizing agent from agglomerating. . This has the same effect when only the gas is blown up without adding the desulfurizing agent, so that only the gas may be blown up after the addition of the desulfurizing agent is completed. It has also been found that desulfurization can be promoted by introducing a desulfurization agent from a hopper or the like and blowing only the gas, thereby promoting the dispersion of the desulfurization agent and preventing aggregation.

  In this case, the spraying position when the desulfurizing agent is added to the hot metal surface by top blowing is important. In the mechanical stirring type desulfurization method, a stirring blade is placed in the hot metal almost at the center of the processing vessel, and a vortex is generated in the processing vessel by the rotation of the stirring blade, and the desulfurizing agent is caught in the vortex. Disperse into the hot metal. Even if the desulfurizing agent is sprayed in the vicinity of the central portion of the stirring blade, the desulfurizing agent not only gets caught in the hot metal, but also adheres to the stirring blade and the shaft portion of the stirring blade. Therefore, it is preferable that the position of the lance to be blown up is located at a distance that is not too close to the center of the stirring blade.

  As a result of the examination, it was found that it was sufficient to blow up to an outer position at a distance of 1/3 or more of the diameter of the stirring blade at a horizontal distance from the center of the stirring blade. Moreover, the flow velocity in the circumferential direction of the generated vortex gradually decreases toward the outer circumference side from the radius of the stirring blade, and the flow velocity becomes zero on the side wall of the processing vessel. Therefore, in order for the desulfurizing agent added by top blowing to be smoothly swirled into the vortex and dispersed into the hot metal, it is better that the blowing position is not too close to the side wall of the processing vessel. It was found that it is effective to blow up to a position within about 2/3 of the distance between the end of the stirring blade and the side wall of the processing vessel at a horizontal distance from the section.

  That is, when the inner diameter of the processing vessel containing the hot metal is D, the diameter of the stirring blade is d, and the horizontal distance from the center of the stirring blade to the spraying position of the desulfurizing agent is R, the horizontal distance (R) is the inner diameter (D ) And the diameter (d), it was confirmed that the desulfurization agent is preferably added by top blowing at a position that satisfies the relationship of the following expression (2).

  Furthermore, the carrier gas used for top blowing addition of the desulfurizing agent is preferably a gas that does not substantially contain oxygen. This is because the desulfurization reaction is a reduction reaction, and the presence of oxygen inhibits the desulfurization reaction. Therefore, reducing gas, inert gas, or non-oxidizing gas is used as the carrier gas. Examples of the reducing gas include hydrocarbons, examples of the inert gas include argon gas, and examples of the non-oxidizing gas include nitrogen gas. Note that the gas that does not substantially contain oxygen is a gas that contains oxygen as an impurity in a volume percentage of several percent, so the influence on the desulfurization reaction can be substantially ignored. Therefore, it is assumed that the gas does not contain oxygen.

  Also, before adding the desulfurizing agent over the hot metal surface together with the carrier gas, or at the same time as adding the desulfurizing agent, or after completing the addition of the desulfurizing agent, the metal from the lance for adding the desulfurizing agent or another lance It was found that by adding a deoxidation source such as Al or aluminum dross powder along with the carrier gas toward the hot metal surface, the oxygen concentration in the hot metal was reduced and the desulfurization reaction was promoted.

Similarly, before adding the desulfurization agent over the hot metal surface with the carrier gas, or simultaneously with the addition of the desulfurization agent, or after completion of the addition of the desulfurization agent, from the lance for adding the desulfurization agent or another lance, Addition of gas generating substances that generate gas at high temperatures, such as calcium carbonate (CaCO ₃ ) and plastics, together with the carrier gas toward the hot metal surface prevents the desulfurization agent from agglomerating and further increases the reaction interface area. It was found to increase.

  These deoxidation sources and gas generating substances promote the desulfurization reaction in the desulfurization method in which the desulfurization agent is blown up together with the carrier gas toward the surface of the hot metal, and do not necessarily need to be added by top blowing. It has been found that depending on the conditions and equipment conditions such as the number of hoppers owned and the number of owned lances, it may be added to the hot metal using a hopper.

Furthermore, in the desulfurization method in which the desulfurizing agent is blown up toward the hot metal surface together with the carrier gas, the CaO-based desulfurization combined with fluorite is used because of the effect of preventing the aggregation of the desulfurizing agent due to the increase of the reaction interface area and the vortex disturbance Desulfurization efficiency equal to or better than the use of calcium carbide-based desulfurization agent, soda-based desulfurization agent, and desulfurization agent such as metal Mg, even if it is a CaO-based desulfurization agent that does not use fluorite. It turns out that can be obtained. Here, examples of the CaO-based desulfurization agent include quick lime (CaO), dolomite (MgCO ₃ · CaCO ₃ ), slaked lime (Ca (OH) ₂ ), and limestone (CaCO ₃ ).

The present invention has been made based on the above examination results, and the hot metal desulfurization method according to the first invention is a hot metal desulfurization method using a mechanical stirring type desulfurization apparatus, which is stirred by a stirring blade. When the inner diameter of the treatment vessel containing hot metal is D, the diameter of the stirring blade is d, and the horizontal distance from the center of the stirring blade to the spraying position of the desulfurizing agent is R, the horizontal distance ( A desulfurizing agent having a maximum particle size of 500 μm or less is passed through an upper blowing lance at a position where R) is within a range satisfying the relationship of the above formula (2) with respect to the inner diameter (D) and the diameter (d). Then, the desulfurization treatment is performed by adding the blowing gas together with the carrier gas.

  The hot metal desulfurization method according to the second invention is characterized in that, in the first invention, after the addition of the desulfurizing agent is completed, a desulfurization treatment is performed by blowing a conveying gas from the upper blowing lance toward the hot metal surface. It is what.

  The hot metal desulfurization method according to the third invention is characterized in that, in the first or second invention, the flow rate of the carrier gas that collides with the bath surface of the hot metal is 10 m / sec or more.

The hot metal desulfurization method according to a fourth aspect of the present invention is the hot metal desulfurization method according to any one of the first to third aspects, wherein the carrier gas contains substantially no oxygen, a reducing gas, an inert gas, and a non-oxidizing gas. It is characterized by being one or more of the sex gases.

The hot metal desulfurization method according to the fifth invention is the method of any one of the first to fourth inventions, wherein the hot metal is added before the desulfurizing agent is added by top blowing, simultaneously with the top blowing addition of the desulfurizing agent, or over the desulfurizing agent. After completion of blowing, the deoxidation source is added to the hot metal surface together with the carrier gas from the top blowing lance or another lance.

The hot metal desulfurization method according to a sixth aspect of the present invention is the method of any of the first to fourth aspects, wherein the desulfurizing agent is added before the desulfurizing agent is added by top blowing, simultaneously with the top blowing addition of the desulfurizing agent, or over the desulfurizing agent. A deoxidation source is added to the processing container which accommodates hot metal after completion of blowing.

The hot metal desulfurization method according to a seventh invention is characterized in that, in the fifth or sixth invention, the deoxidation source is a substance containing one or more of metal Al, metal Si, and metal Mg. To do.

The hot metal desulfurization method according to the eighth invention is the method of any one of the first to seventh inventions, wherein the hot metal is added before the desulfurization agent is added by top blowing, simultaneously with the top blowing addition of the desulfurizing agent, or over the desulfurizing agent. After the completion of the blowing, the substance generating gas is blown and added together with the carrier gas toward the hot metal surface from the upper blowing lance or another lance.

The hot metal desulfurization method according to the ninth aspect of the present invention is the hot metal desulfurization method according to any one of the first to seventh aspects, wherein the desulfurization agent is added before the desulfurization agent, or simultaneously with the desulfurization agent. A substance that generates gas is added to a processing container that contains hot metal after the completion of blowing.

The hot metal desulfurization method according to a tenth aspect of the present invention is the hot metal desulfurization method according to any one of the first to ninth aspects, wherein the desulfurization agent is a substance containing CaO as a main component and substantially not containing fluorine. It is.

According to the present invention, a fine-grain desulfurization agent having excellent reactivity is added together with a carrier gas, so that scattering during addition is reduced, the addition yield of the desulfurization agent is improved, and a fine-grain desulfurization agent. Has a large reaction interface area, so that the desulfurization reaction is promoted and the desulfurization rate can be remarkably improved. Further, since the fine-grain desulfurization agent has a large reaction interface area and promotes the desulfurization reaction, it efficiently desulfurizes only with a desulfurization agent mainly composed of CaO without using a hatching accelerator such as CaF _2. You can also. In addition, when a desulfurizing agent is added and then a gas is blown up onto the hot metal surface to form a downward flow in the hot metal, the desulfurization reaction is further promoted, and the amount of the desulfurizing agent used can be further reduced. .

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic side view showing an example of an embodiment of a desulfurization process according to the present invention, and FIG. 1 shows an example in which a ladle type hot metal ladle is used as a processing container for containing hot metal. As for the shape of the processing container, a ladle-type processing container is optimal as shown in FIG. 1 because desulfurization is performed by a mechanical stirring desulfurization apparatus, but it can also be used in a torpedo car. Hereinafter, an example in which a hot metal ladle is used as the processing container will be described.

  The hot metal 3 discharged from the blast furnace is received by the hot metal ladle 2 or the torpedo car mounted on the carriage 1, and the received hot metal 3 is conveyed to a mechanical stirring desulfurization apparatus. When it is received by a torpedo car, it is desirable to transfer to a ladle type processing container prior to the desulfurization process. The hot metal 3 to be subjected to the desulfurization treatment according to the present invention may be any component, and for example, desiliconization treatment or dephosphorization treatment may be performed in advance. The desiliconization process is a process for mainly removing Si in the hot metal by adding an oxygen source such as oxygen gas or iron ore to the hot metal 3 prior to the dephosphorization process in order to efficiently perform the dephosphorization process.

  The mechanical stirring type desulfurization apparatus is equipped with a stirring blade 4 made of refractory for immersing and burying in a hot metal 3 accommodated in a hot metal ladle 2 and rotating to stir the hot metal 3. The elevator 4 is moved up and down in a substantially vertical direction by a lifting device (not shown), and is turned around a shaft 4a as a rotating shaft by a rotating device (not shown). Further, in the mechanical stirring type desulfurization apparatus, a powdery desulfurizing agent 7, a powdery deoxidation source 8 and a powdery gas generating substance 9 are blown upward toward the hot metal 3 in the hot metal ladle 2. An upper blowing lance 5 for addition, a granular or massive desulfurizing agent 7A, a granular or massive deoxidation source 8A and a granular or massive gas generating substance 9A are placed on the bath surface of the molten iron 3 in the hot metal ladle 2 and added. A charging port 6 is provided for this purpose. Further, an exhaust duct port (not shown) connected to a dust collector (not shown) is provided at an upper position of the hot metal ladle 2 so that gas and dust generated during the desulfurization process are discharged. .

  The top blowing lance 5 includes a hopper 10 that contains a powdered desulfurizing agent 7 and a rotary feeder 11 for quantitatively cutting out the hopper 10, and a hopper 12 and a hopper that contain a powdered deoxidation source 8. Connected to a feeder comprising a rotary feeder 13 for quantitatively cutting out from 12, and a feeder comprising a hopper 14 for storing the powdered gas generating substance 9 and a rotary feeder 15 for quantitatively cutting out from the hopper 14 From the top blowing lance 5, the powdery desulfurizing agent 7, the powdery deoxidation source 8 and the powdery gas generating substance 9 are individually adjusted at an arbitrary timing together with the carrier gas. It has a structure that can be supplied. Of course, it has the structure which can supply simultaneously and can also blow up only the gas for conveyance.

  In this case, the upper blowing lance 5 for blowing up the desulfurizing agent 7, the deoxidation source 8 and the gas generating substance 9 may be a single hole or made porous for the purpose of increasing the spraying area on the molten metal surface. May be. Also, the spray angle of the top blowing lance 5, that is, the angle at which the desulfurizing agent 7, the deoxidation source 8 and the gas generating substance 9 are sprayed from the top blowing lance 5 to the hot metal bath surface is not limited to the vertical direction, It is also possible to supply perpendicularly to the surface (which has an inclined angle with respect to the horizontal plane due to the raised vortex), and between the vertical direction and the direction perpendicular to the hot water surface The top spray can be added at any angle.

  Similarly, the inlet 6 accommodates a feeding device comprising a hopper 16 for accommodating a granular or massive desulfurization agent 7A and a rotary feeder 17 for quantitatively cutting out from the hopper 16, and a granular or massive deoxidation source 8A. A supply device comprising a hopper 18 and a rotary feeder 19 for quantitatively cutting out from the hopper 18, and a supply device comprising a hopper 20 containing a granular or lump-like gas generating substance 9A and a rotary feeder 21 for quantitatively cutting out from the hopper 20 The granular or massive desulfurizing agent 7A, the granular or massive deoxidation source 8A, and the granular or massive gas generating substance 9A can be independently adjusted and supplied from the charging port 6 at any timing. It has a structure.

As the desulfurizing agent 7, 7A, not only a CaO-based desulfurizing agent, but also various desulfurizing agents such as a calcium carbide-based desulfurizing agent, a soda-based desulfurizing agent, and metallic Mg can be used. It is preferable to use a CaO-based desulfurization agent. In addition, it is preferable to use only a CaO-based desulfurization agent without using a fluorine source such as fluorite in combination with environmental measures and easy reuse of generated slag. As the CaO-based desulfurization agent, quick lime (CaO), dolomite (MgCO ₃ · CaCO ₃ ), slaked lime (Ca (OH) ₂ ), limestone (CaCO ₃ ) and the like can be used. In the present invention, the desulfurizing agent 7 is added by top blowing or the desulfurizing agent 7, 7A is forcibly entrained in the hot metal 3 by the top blowing gas, so that it can be sufficiently desulfurized without using a fluorine source. . However, a substance in which fluorine is inevitably mixed as an impurity component may be used.

  As for the size of the CaO-based desulfurizing agent to be blown up, an optimum particle size can be selected according to the dimensions of the top blowing lance 5 and the hot metal ladle 2 to be used. It is better to use a desulfurizing agent of, for example, 500 μm or less is preferable, and 100 μm or less is more preferable. The optimum particle size distribution varies depending on the size of the mechanical stirring type desulfurization device and the shape of the blowing upper lance 5, so it is desirable to select a particle size according to the capability of the mechanical stirring type desulfurization device.

  As the deoxidation sources 8 and 8A, metal Al and aluminum dross powder are preferable because they can be obtained at low cost as an aluminum source. Further, other Al sources such as atomized powder obtained by atomizing an aluminum melt with gas and cutting powder generated when an aluminum alloy is polished and cut may be used. Moreover, Si alloy like ferrosilicon, Mg alloy, etc. can also be used. These are preferably in the form of powder when added to the surface of the hot metal 3 together with the carrier gas, and in the case of adding the upper spray, there is no problem even with fine powder that normally scatters. It is possible to use.

The following materials can be used as the gas generating materials 9 and 9A for generating gas. That is, as a substance that decomposes in the hot metal 3 to generate gas, as carbonates that generate CO ₂ gas, calcium carbonate (CaCO ₃ ), sodium carbonate (Na ₂ CO ₃ ), magnesium carbonate (MgCO ₃ ), For example, potassium carbonate (K ₂ CO ₃ ) can be used. Further, calcium hydroxide (Ca (OH) ₂ ) may be used. In particular, when calcium carbonate and calcium hydroxide are used, the oxide (CaO) generated after decomposition contributes to desulfurization, so there is no need to worry about an increase in the amount of slag, which is very efficient. However, these decomposition reactions are endothermic reactions, and when the ratio of carbonate and hydroxide in the total flux added to the hot metal ladle 2 including the desulfurizing agents 7 and 7A is increased, the temperature drop of the hot metal 3 is caused by the endothermic reaction. Is concerned. Therefore, when adding these, it is desirable to make the sum total of the addition amount into 30 mass% or less in the total flux. Further, as other gas generating substances, plastics that decompose to generate hydrocarbons, hydrogen gas, and a carbon source may be added. By continuously adding plastic, not only the effect of promoting the dispersion of the desulfurizing agent and the effect of preventing aggregation, but also the effect of promoting the desulfurization reaction by the reducing gas can be expected. One of these gas generating substances may be used, or two or more of them may be used in combination.

  The position of the carriage 1 on which the hot metal ladle 2 is mounted is adjusted so that the position of the stirring blade 4 is substantially at the center of the hot metal ladle 2, and then the stirring blade 4 is lowered and immersed in the hot metal 3. If the stirring blade 4 is immersed in the molten iron 3, the stirring blade 4 starts to turn, and the speed is increased to a predetermined rotational speed. When the rotation speed of the stirring blade 4 reaches a predetermined rotation speed, the rotary feeder 11 is activated, and the desulfurizing agent 7 in the hopper 10 is sprayed and added to the bath surface of the hot metal 3 together with the conveying gas. . As the carrier gas, a reducing gas, an inert gas, or a non-oxidizing gas is used. Since the desulfurization reaction is promoted as the speed of spraying on the surface of the hot metal 3 is increased, the flow rate of the transport gas is adjusted so that the flow velocity of the transport gas colliding with the bath surface of the hot metal 3 becomes 10 m / sec or more. It is preferable.

  At that time, the spraying position of the desulfurizing agent 7 on the bath surface of the hot metal 3 is D, the inner diameter of the hot metal ladle 2, the diameter of the stirring blade 4, and the horizontal distance from the center of the stirring blade 4 to the spraying position of the desulfurizing agent 7. Is set to R, the position of the upper blowing lance 5 is adjusted so that the inner diameter (D), the diameter (d), and the horizontal distance (R) are in a range satisfying the relationship of the above-described expression (2). It is preferable. For example, when supplying from the top blowing lance 5 in the vertical direction, the horizontal distance from the center of the stirring blade 4 to the tip position of the top blowing lance 5 may be adjusted as the horizontal distance (R). In the case of tilting and top blowing, if the position of the top blowing lance 5 is adjusted according to the tilt angle so that the spray position of the desulfurizing agent 7 on the bath surface of the hot metal 3 satisfies the relationship of the formula (2). Good.

  In order to promote the desulfurization reaction in parallel with the top blowing addition of the desulfurizing agent 7, before or after the top blowing addition, or during the entire duration of the desulfurization treatment period, the deoxidation sources 8 and 8A and the gas generating substance 9 are used. , 9A is preferably supplied into the hot metal ladle 2. The deoxidation sources 8, 8A and the gas generating substances 9, 9A may be added simultaneously, or one of them may be added. What is necessary is just to use the top blowing lance 5 and the inlet 6 properly according to the size of the deoxidation sources 8 and 8A and the gas generating substances 9 and 9A to be used.

  Even after the addition of the predetermined amount of the desulfurizing agent 7 is completed, it is preferable to spray only the conveying gas from the upper blowing lance 5. By blowing the carrier gas from the upper blowing lance 5, a downward flow is formed in the hot metal 3, and the added desulfurizing agent 7 is caught in the hot metal 3 by the downward flow, and the desulfurization reaction is promoted.

  Thus, after the addition of a predetermined amount of the desulfurizing agent is completed, when the carrier gas is further blown from the upper blowing lance 5 onto the hot metal surface of the hot metal 3, the powdery desulfurizing agent 7 is always used. It is not necessary to add by blowing, and granular or lump desulfurization agent 7A may be used and added over the bath surface of hot metal 3 from the inlet 6. Also in this case, it is preferable to supply the deoxidation sources 8 and 8A and the gas generating substances 9 and 9A into the hot metal ladle 2 in accordance with the above.

  If the stirring is performed for a predetermined time, the number of rotations of the stirring blade 4 is decreased and stopped. When the swirling of the stirring blade 4 is stopped, the stirring blade 4 is lifted and waited above the hot metal pan 2. The generated slag floats to cover the hot metal surface, and the desulfurization process of the hot metal 3 is completed in a stationary state. After the desulfurization treatment, the generated slag is discharged from the hot metal ladle 2 and conveyed to the next refining process.

By performing the desulfurization treatment on the hot metal 3 in this way, even when the fine-grained desulfurizing agent 7 is added, scattering at the time of addition is reduced, the addition yield of the desulfurizing agent 7 is improved, and The desulfurization agent 7 has a large reaction interfacial area, so that the desulfurization reaction is promoted and the desulfurization rate is improved. Furthermore, since the fine-grain desulfurization agent 7 has a large reaction interface area and promotes the desulfurization reaction, desulfurization can be efficiently performed only with a desulfurization agent mainly composed of CaO without using a hatching accelerator such as CaF _2. can do.

  In addition, after adding the fine-grained desulfurizing agent 7, when gas is blown up onto the hot metal surface to form a downward flow in the hot metal 3, the desulfurization reaction is further promoted and the amount of desulfurizing agent used is further reduced. It becomes possible. When the gas is blown upward on the hot metal surface to form a downward flow, even a granular or massive desulfurization agent 7A can obtain a desulfurization rate higher than that of the conventional one.

  In addition, this invention is not limited to said description range, A various change is possible. For example, a plurality of top blowing lances may be provided, and the desulfurizing agent 7, the deoxidation source 8, and the gas generating substance 9 may be blown from each top blowing lance. Alternatively, only the desulfurizing agent 7 may be supplied from the top blowing lance 5, and the deoxidation source 8 and the gas generating substance 9 may be added from the inlet 6.

  Examples of the present invention (Invention Examples 1 to 13) will be described in which about 150 tons of hot metal in the hot metal ladle is desulfurized using the method of the present invention with the mechanical stirring desulfurization apparatus shown in FIG.

  The hot metal to be treated was one that had been desiliconized in two stages: a blast furnace casting floor and a hot metal ladle that was a receiving vessel after leaving the blast furnace. The hot metal composition was [Si]: 0.05 to 0.10% by mass, [C]: 4.3 to 4.6% by mass, and [Mn]: 0.22 to 0. It was 41 mass% and [P]: 0.10-0.13 mass%, and [S] before a process was 0.039-0.042 mass%. The hot metal temperature was 1330 to 1430 ° C.

The desulfurizing agent used was composed of quick lime (CaO) as a main component and fluorite (CaF ₂ ) and limestone (CaCO ₃ ) added thereto. A reducing hydrocarbon gas (propane gas) or Ar gas is used as the carrier gas, an aluminum dross powder containing about 50% by mass of metal Al is used as the deoxidation source, and a gas generating substance is used. Calcium carbonate and plastic were used. In addition, as a comparative example, desulfurization treatment was also performed (Comparative Examples 1 to 3) in which the desulfurization agent was not blown up and added from the inlet above the hot metal ladle by cutting out from the hopper. The amount of desulfurizing agent used was constant and a particle size of 500 μm or less was used. In addition, when the desulfurization agent was not blown up, but was charged from the charging port as usual and stirring was performed by only blowing up the gas, the desulfurization agent having a particle size of 1 mm or less was used. The stirring time after adding the desulfurizing agent was constant.

  Table 1 shows the desulfurization method, desulfurization agent composition, deoxidation source used, desulfurization treatment conditions such as gas generating substances, and desulfurization treatment results in Invention Examples 1 to 13 and Comparative Examples 1 to 3. In the column of “addition method” of “hot metal deoxidation” and “gas generant” in Table 1, “before desulfurization agent” means that “added before adding desulfurization agent” "Added with desulfurizing agent at the same time + after desulfurizing agent" means "added with desulfurizing agent at the same time and added after completion of addition of desulfurizing agent" “Adding port” indicates that the addition was made through the blowing lance, and that the addition was made from the charging port.

  In Examples 1-3 of the present invention, when the quick lime-fluorite-based desulfurization agent was added by top blowing through the top blowing lance, the stirring blade was compared with the inner diameter (D) of the hot metal ladle and the diameter (d) of the stirring blade. This is a test comparing the influence of the horizontal distance (R) on the desulfurization rate by changing the horizontal distance (R) from the center to the top blowing lance. Here, the desulfurization rate is a numerical value indicating the difference between the hot metal before and after the desulfurization treatment [S] as a percentage with respect to the hot metal before the start of the treatment [S].

  As apparent from Table 1, in Example 1 of the present invention in which the horizontal distance (R) of the top blowing position is on the stirring blade side with respect to d / 3, it can be seen that the desulfurization agent is deposited on the upper portion of the stirring blade. The desulfurization rate was as low as 76%. On the other hand, the horizontal distance (R) of the upper blowing position in which the upper blowing position is further away from the center of the stirring blade than in Example 1 of the present invention is d / 2 + 1/3 × (D−d) when d / 3 or more. In Example 2 of the present invention described below, no desulfurization agent was adhered to the stirring blade, and it was observed that the desulfurization agent was entrained in the hot metal. The desulfurization rate was also about 85%, and the desulfurization rate was increased by about 10% compared to Comparative Example 1 in which no top blowing was performed. However, the example of the present invention in which the horizontal distance (R) of the upper blowing position exceeds d / 2 + 1/3 × (D−d) in which the upper blowing position is further away from the center of the stirring blade than in the second example of the present invention. In No. 3, the desulfurization agent was poorly entrained in the vortex, and the desulfurization rate was 80% or less.

  From these results, when top blowing the desulfurizing agent, the top blowing position is important, the horizontal distance (R) from the center of the stirring blade to the top blowing position, the inner diameter (D) of the hot metal ladle, and the stirring blade It was confirmed that the condition for obtaining a high desulfurization rate is that the diameter (d) satisfies the relationship of the above-described formula (2). Therefore, in the following examples of the present invention, the top blowing lance position was fixed at a position satisfying the relationship of the expression (2), and the desulfurization treatment was performed.

  In Example 5 of the present invention, aluminum dross was used as a deoxidation source, and aluminum dross was blown into the hot metal before addition of the desulfurizing agent, while in Example 6 of the present invention, aluminum dross was added over the inlet. . Inventive Example 5 and Inventive Example 6 in which aluminum dross was added as a deoxidation source, the desulfurization rate was improved compared to Inventive Example 2 and Inventive Example 4 in which no aluminum dross was added. In addition, it was confirmed that the desulfurization rate was higher when top blowing than when charging from the inlet.

  In addition, in Example 7 of the present invention in which reducing hydrocarbon gas (propane gas) was used instead of Ar gas as the carrier gas after using aluminum dross, the desulfurization rate was remarkably high at 97.5%. .

  In Examples 8 to 11 of the present invention, limestone or plastic was used as a gas generating substance after using aluminum dross. When a gas generating material was further used after using Almidros, both the case where the gas generating material was added by top blowing and the case where the gas generating material was added from the inlet showed a high desulfurization rate of 90% or more. . Further, in Example 11 of the present invention, a desulfurizing agent to which fluorite was not added was used, and it was confirmed that a high desulfurization rate could be obtained even under conditions where fluorine was not used together by the method of the present invention.

  Moreover, in the conventional desulfurization method, in the case of Comparative Example 3 using only quick lime without using fluorite as a desulfurizing agent, the desulfurization rate is lower than that of Comparative Examples 1 and 2 using fluorite. However, in Example 12 of the present invention in which only quick lime was used as the desulfurizing agent, a desulfurization rate of 87% or more was obtained by adding the desulfurizing agent on top. This result also confirmed that the method of the present invention is effective as a desulfurization method that does not use fluorine.

  Further, in the case of the present invention example 13 where the desulfurization agent was placed from the inlet without top blowing and only Ar gas was blown from the top blowing lance after the addition of the desulfurization agent was completed, the other conditions were the same. Thus, the desulfurization rate was improved as compared with Comparative Example 2 in which no gas was blown up, and the stirring effect due to the downward flow formed by the blown gas was confirmed.

1 is a schematic side view showing an example of an embodiment of a desulfurization treatment according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bogie 2 Hot metal ladle 3 Hot metal 4 Stirring blade 5 Top blowing lance 6 Input port 7 Desulfurization agent 7A Desulfurization agent 8 Deoxidation source 8A Deoxidation source 9 Gas generating material 9A Gas generating material 10, 12, 14, 16, 18, 20 Hopper 11, 13, 15, 17, 19, 21 Rotary feeder

Claims (10)

In the hot metal desulfurization method using the mechanical stirring desulfurization apparatus, the inner diameter of the treatment vessel containing hot metal is D, the diameter of the stirring blade is d, the stirring blade is on the bath surface of the hot metal being stirred by the stirring blade. The horizontal distance (R) satisfies the relationship of the following formula (2) with respect to the inner diameter (D) and the diameter (d) where R is the horizontal distance from the center of the desulfurization agent to the spraying position of the desulfurizing agent. A hot metal desulfurization method comprising performing desulfurization treatment by adding a desulfurizing agent having a maximum particle size of 500 μm or less together with a carrier gas through an upper blowing lance to an inner position.
d / 3 ≦ R ≦ d / 2 + 1/3 × (Dd)… (2)
However, in the formula (2), D is the inner diameter of the processing vessel containing hot metal, d is the diameter of the stirring blade, and R is the horizontal distance from the center of the stirring blade to the spraying position of the desulfurizing agent.   2. The hot metal desulfurization method according to claim 1, wherein after the addition of the desulfurizing agent is completed, a desulfurization treatment is further performed by spraying a conveying gas from the upper blowing lance toward the hot metal surface.   3. The hot metal desulfurization method according to claim 1, wherein the flow velocity of the carrier gas that collides with the hot metal bath surface is 10 m / second or more.   The carrier gas according to any one of claims 1 to 3, wherein the carrier gas is one or more of a reducing gas, an inert gas, and a non-oxidizing gas that do not substantially contain oxygen. The hot metal desulfurization method according to any one of the above.   Before the desulfurization agent top blowing addition, at the same time as the desulfurization agent top blowing addition, or after completion of the desulfurization agent top blowing addition, from the top blowing lance or another lance, the deoxidation source is molten together with the carrier gas. The hot metal desulfurization method according to any one of claims 1 to 4, wherein the top blowing is added toward the surface.   Before the desulfurization agent top blowing addition, or simultaneously with the desulfurization agent top blowing addition, or after completion of the desulfurization agent top blowing addition, a deoxidation source is added into the treatment vessel containing hot metal. The hot metal desulfurization method according to any one of claims 1 to 4.   The hot metal desulfurization method according to claim 5 or 6, wherein the deoxidation source is a substance containing one or more of metal Al, metal Si, and metal Mg.   Before the top blowing addition of the desulfurizing agent, simultaneously with the top blowing addition of the desulfurizing agent, or after completion of the top blowing addition of the desulfurizing agent, a substance that generates gas from the top blowing lance or another lance The hot metal desulfurization method according to any one of claims 1 to 7, wherein the hot metal is added by top blowing toward the hot metal surface.   Before the desulfurization agent top blowing addition, or simultaneously with the desulfurization agent top blowing addition, or after completion of the desulfurization agent top blowing addition, a substance that generates gas is added to the processing vessel containing hot metal. The hot metal desulfurization method according to any one of claims 1 to 7.   The hot metal desulfurization method according to any one of claims 1 to 9, wherein the desulfurization agent is a substance mainly containing CaO and containing substantially no fluorine.

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