Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B13/00—Making spongy iron or liquid steel, by direct processes
  • C21B13/0006—Making spongy iron or liquid steel, by direct processes obtaining iron or steel in a molten state
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B11/00—Making pig-iron other than in blast furnaces
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21B—MANUFACTURE OF IRON OR STEEL
  • C21B13/00—Making spongy iron or liquid steel, by direct processes
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • C21C1/00—Refining of pig-iron; Cast iron
  • C21C1/02—Dephosphorising or desulfurising
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
  • C21C7/04—Removing impurities by adding a treating agent
  • C21C7/064—Dephosphorising; Desulfurising
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
  • C21C7/04—Removing impurities by adding a treating agent
  • C21C7/064—Dephosphorising; Desulfurising
  • C21C7/0645—Agents used for dephosphorising or desulfurising

Definitions

• the present invention relates to granulated iron with reduced P concentration and a method for producing the same.
• iron ore Fe 2 O 3
• coke which is a reducing agent (carbon source)
• hot metal with a C concentration of about 4.5-5%
• This is a steelmaking process in which the hot metal is charged into a converter and impurity components such as C, Si, and P are oxidized and removed.
• impurity components such as C, Si, and P are oxidized and removed.
• the P concentration in the iron ore used in the current blast furnace method is 0.05 to 0.10 mass% (0.10 to 0.15 mass% when converted to P concentration as reduced iron), and it is expected that this will change in the future. It is expected that the P concentration will increase. This P concentration is 5 to 10 times higher than the P concentration of reduced iron produced using high-grade iron ore with a low P concentration, and in order to prevent quality deterioration due to phosphorus in steel products, reduced iron with a high P concentration must be used. It is necessary to remove phosphorus when melting to produce molten steel, or when producing reduced iron from iron ore with a high P concentration. Several techniques have been proposed regarding such phosphorus removal techniques.
• Patent Document 1 describes a method for removing phosphorus from molten steel to a low concentration in a relatively short period of time using an electric arc furnace alone.
• a flux for dephosphorization refining in an arc furnace has been proposed in which the mass % and the remainder consist of unavoidable impurities.
• Patent Document 2 describes iron ore, titanium-containing iron ore, nickel-containing ore, chromium-containing ore, or iron ore containing CaO of 25% by mass or less and a CaO/(SiO 2 +Al 2 O 3 ) ratio of 5 or less, or these ores.
• a method has been proposed for removing phosphorus by contacting a mixture mainly composed of ores with Ar, He, N 2, CO, H 2, one type of hydrocarbon, or a mixed gas of these at a temperature of 1600°C or higher. There is.
• Patent Document 3 discloses that iron ore with a high P concentration is pulverized to 0.5 mm or less, water is added to this to make a pulp concentration of around 35% by mass, and H 2 SO 4 or HCl is added to a solvent to obtain a pH of 2.0.
• H 2 SO 4 or HCl is added to a solvent to obtain a pH of 2.0.
• a method has been proposed in which slaked lime or quicklime is added to neutralize P dissolved in the solution to a pH within the range of 5.0 to 10.0, and the P is separated and recovered as calcium phosphate.
• Patent Document 1 assumes an iron source with a low P concentration such as scrap. Specifically, in order to reduce the P concentration in molten steel from 0.020% by mass to 0.005% by mass, 350g of flux is added to 7000g of molten steel. Assuming that the P concentration in reduced iron is 0.15% by mass, the amount of flux required to reduce the P concentration to 0.01% by mass, which is comparable to that of steel products, is 230 kg per ton of molten steel. Then, there is a problem that the volume ratio occupied by flux in the arc furnace increases, the amount of molten steel processed decreases, and manufacturing efficiency deteriorates.
• the treatment temperature is 1,600°C or higher, and the specification states, ⁇ In order to perform more effective dephosphorization, the treatment temperature is preferably 1,800°C or higher. This is difficult to achieve with conventional heating methods, but can be achieved, for example, by using plasma arcs or high-frequency induced plasma.” Therefore, there is a problem that it requires a lot of energy and is not suitable for processing a large amount.
• Patent Document 3 is a wet treatment using an acid, and there is a problem in that it requires time and cost to dry the recovered magnetic material to use it as a main raw material. Furthermore, this method also has the problem that it requires time and cost to crush the material to 0.5 mm or less in advance.
• the present invention was made in view of the above circumstances, and even if the raw material is reduced iron obtained from low-grade iron ore with a high P concentration, it is possible to efficiently produce granulated iron with a low P concentration.
• the purpose is to provide technology that enables
• the method for producing granulated iron according to the present invention which advantageously solves the above problems, includes a first step of melting reduced iron to obtain primary molten iron, a second step of separating the primary molten iron and slag, and a second step of separating the primary molten iron from the slag.
• the third step includes: Dephosphorizing the primary molten iron by supplying an oxygen source and a CaO source, and setting the temperature of the secondary molten iron at the end of the dephosphorization to be equal to or lower than the temperature of the primary molten iron at the start of the dephosphorizing process. It is characterized by
• the method for producing granulated iron according to the present invention is as follows: (a) Raising the temperature Tf of the secondary molten iron at the end of the dephosphorization process by 20°C or more from the solidification temperature Tm of the secondary molten iron at the end of the dephosphorization process; (b) The slag composition at the end of the dephosphorization treatment has a basicity in the range of 1.0 to 4.0, which is the ratio of CaO concentration (%CaO) to SiO 2 concentration (%SiO 2 ) on a mass basis.
• a granulating device that turns the secondary molten iron into droplets, a water flow control container provided at a position to receive the droplets and containing cooling water, and a water flow control container connected to the water flow control container are provided.
• at least one cooling water pipe that supplies cooling water to the water flow control container, and the water flow control container has an inclined surface that is inclined so that the horizontal cross-sectional area of the water flow control container becomes narrower toward the bottom.
• the granulated iron according to the present invention which advantageously solves the above problems, uses reduced iron with a P concentration of 0.050% by mass or more as a raw material, has a P concentration of 0.030% by mass or less, and has a particle size of 1 mm or more and 50 mm. It is characterized by the following:
• the method for producing granulated iron according to the present invention it is possible to efficiently produce granulated iron with a low P concentration from reduced iron obtained from low-grade iron ore with a high P concentration. Further, the granulated iron according to the present invention satisfies the P concentration required for many steel products, that is, 0.030% by mass or less. Therefore, molten iron with a P concentration equivalent to that of a steel product can be obtained simply by remelting the granulated iron according to the present invention.
• the iron is solidified into granules to form granular iron, so it becomes possible to produce iron in a form where the iron source manufacturing plant and the demand site are separated, rather than in a large-scale iron manufacturing plant.
• a raw material-producing country goes as far as producing dephosphorized granulated iron, and a steel-producing country produces steel using this dephosphorized granulated iron as raw material.
• the production of reduced iron and the production of granulated iron according to the present invention are carried out in an iron ore producing country, the gangue content contained in the raw material iron ore can be separated as slag. Therefore, by transporting only granulated iron, the transport amount per unit amount of Fe is reduced, and the transport cost and energy consumption to the demand site can be suppressed.
• the particle size of iron granules is 1 to 50 mm, there is freedom in the equipment used for transportation, storage, and supply when considering transportation and storage of iron granules to demand sites, supply to equipment at demand sites, etc. The degree increases. Furthermore, it also has the effect of reducing the risk of hanging on shelves within the supply hopper.
• Reduced iron produced from iron ore as a raw material depends on the brand of iron ore used, the type and basic unit of the raw material component adjusting agent to be mixed, the type and basic unit of the reducing agent, the reduction temperature, and the type of reduced iron manufacturing equipment. Properties such as conversion rate and composition are different. Table 1 shows examples of the components of reduced iron. In the example in Table 1, the P concentration is T. The P concentration in terms of molten iron divided by the Fe (total iron) concentration is 0.057 to 0.152% by mass. Therefore, even if these reduced irons are dissolved as they are, it is difficult to achieve a P concentration (0.030% by mass or less) at the level of steel products.
• reduced iron is heated and melted in an electric furnace to obtain primary molten iron.
• reduced iron manufactured at an adjacent reduced iron manufacturing plant may be used by keeping it at a high temperature.
• the electric furnace may be an arc furnace, a submerged arc furnace, or an induction melting furnace.
• the thermal energy supplied in the first step to melt reduced iron, which is a solid iron source, and heat up the iron source is not only electrical energy, but also gaseous fuels such as natural gas and propane gas, heavy oil, etc. as supplementary energy.
• the heat of combustion of combustible solids such as liquid fuel, coal, metal Al, Si, etc. may be used. It is preferable that these energies be renewable energies from the viewpoint of reducing CO 2 emissions.
• slag which is gangue of reduced iron, and primary molten iron are separated.
• the molten metal is poured into a container for transportation and transported to equipment that performs dephosphorization treatment.
• a CaO source is added to generate dephosphorization slag, so in order to secure the amount of slag and adjust the composition, slag containing a lot of SiO 2 generated as reduced iron is dissolved is used. At least a portion may be carried over.
• the slag may be removed from the melting/heating container used in the first step using a slag dragger.
• the molten metal is dephosphorized to obtain secondary molten iron.
• [P] represents phosphorus in molten iron.
• Pure oxygen gas is generally used as the oxygen source for dephosphorization. Since the dephosphorization reaction is an exothermic reaction, it is advantageous to perform the dephosphorization treatment at a low temperature, and considering that it will be solidified and turned into granulated iron in the next process, it is necessary to lower the temperature of the molten iron within a range that does not cause any problems in the process. It was concluded that this is advantageous.
• the behavior of spitting differs depending on the freeboard (height from the surface of the molten iron to the top of the container) of the container where dephosphorization is performed and the shape of the nozzle of the top blowing lance. It is preferable to adjust the air supply speed and lance height. Also, in order to stir the molten iron, it is good to blow inert gas into it.
• the inert gas may be injected through a porous plug installed at the bottom of the furnace or by dipping an injection lance into the molten iron.
• the slag basicity which is the ratio of the CaO concentration (%CaO) to the SiO 2 concentration (%SiO 2 ) on a mass basis, is preferably in the range of 1.0 to 4.0. .
• the amount of slag containing a large amount of SiO 2 carried over to the second step is adjusted, and the type and amount of the CaO source to be added are adjusted. If necessary, an SiO 2 source such as silica stone or ferrosilicon, or a CaO source such as quicklime may be added.
• the slag basicity is low, the amount of phosphorus removed in the dephosphorization process will be small. If the slag basicity is high, some of the slag will solidify and adhere to the refractory when the molten iron temperature drops, making it difficult to remove the slag after dephosphorization, and causing abnormalities when charging molten iron for the next treatment. Problems may arise, such as reactions occurring and residual slag mixing with the produced slag, causing components to be removed.
• a boiler or the like may be used to recover the exhaust heat.
• the secondary molten iron after the dephosphorization treatment is solidified into granules to obtain granulated iron.
• a method for producing granular iron for example, molten iron after dephosphorization is allowed to flow down and collide with a refractory surface plate, or water is allowed to collide with the molten iron that has flowed out, resulting in granular droplets that are then dropped into a water flow control container.
• An example of this method is to obtain solidified iron granules.
• the temperature of the molten iron decreases while the molten iron after the dephosphorization treatment is transported and supplied to the granular iron production equipment. If the temperature of the molten iron after the dephosphorization treatment is too low, a portion of the molten iron will solidify before all of the molten iron in the container is supplied to the granular iron manufacturing apparatus, resulting in a decrease in manufacturing yield. On the other hand, if the molten iron temperature after dephosphorization is high, the heat load during solidification in the granular iron production equipment will increase, the amount of cooling water used will increase, and the cooling rate will become a bottleneck, reducing productivity.
• the waiting time before granulation may become longer due to a drop in the temperature of the molten iron.
• the molten iron temperature T f after the dephosphorization treatment is set to be equal to or lower than the molten iron temperature T i at the time of starting the dephosphorization treatment.
• the solidification temperature T m (°C) can be estimated by directly measuring the solidification temperature of the sample or based on past operational results (C concentration before dephosphorization, temperature, type of oxygen source, supply conditions, etc.) Any method may be used, such as setting the temperature to the temperature read from the liquidus temperature of the Fe--C phase diagram based on the C concentration of the molten iron after dephosphorization treatment.
• the granulated iron manufacturing apparatus includes a granulating device that turns molten iron into droplets, and a water flow control container that is provided at a position to receive the droplets and that contains cooling water. At least one cooling water pipe for supplying cooling water is connected to the water flow control vessel through which the molten iron falls and solidifies. The cooling water is discharged from the cooling water pipe and a water flow is generated, thereby suppressing the formation of a stagnation area of the cooling water in the container. Therefore, the local temperature rise of the cooling water is suppressed, the granulated iron can be efficiently cooled, and the granulated iron is prevented from being sufficiently cooled and fused together.
• the water flow control container has an inclined surface that is inclined so that the horizontal cross-sectional area of the container becomes narrower toward the bottom, and the lower part of the inclined surface is used as a discharge port.
• the effect of diluting the P concentration can be obtained depending on the proportion used. This makes it possible to reduce the load in the dephosphorization process, and to ease restrictions on raw materials used in blast furnaces and converters.
• the granulated iron obtained in this embodiment is used as an iron source in an electric furnace, a blast furnace, or a converter, there is a particle size range that is easy to use. Therefore, it is advisable to adjust the flow rate in the tundish to obtain the desired particle size. It is also good to classify as necessary. Generally, particles with a particle size in the range of 1 to 50 mm are easy to use. If granulated iron with a particle size smaller than 1 mm is included, there is a high possibility that clogging of conveyors for transportation or hanging on shelves in the hopper will occur, so it is better to classify and use particles with a particle size of 1 mm or more.
• the particle size range of 1 to 50 mm can be defined as above the sieve of a sieve with an opening of 1 mm and below the sieve of a sieve with an opening of 50 mm.
• Example 1 Reduced iron A shown in Table 1 was melted in a 250-ton electric furnace, the temperature was adjusted, and the melt was transferred to a pot-shaped container. At this time, about 10 kg/t of slag generated during electric furnace melting due to gangue contained in the reduced iron was transferred to a pot-shaped container, and the rest was transferred to another slag container. The pot-shaped container was moved to a dephosphorization treatment facility, and dephosphorization treatment was performed by changing the type and amount of oxygen source and lime source supplied.
• the dephosphorization treatment equipment has a gas top-blowing lance, an auxiliary raw material cutting hopper, and a bottom-blowing porous plug.
• a gas containing pure oxygen or air can be supplied from the gas top-blowing lance at a rate of about 1 Nm 3 /(min ⁇ t-molten iron).
• Gas can be supplied from the bottom-blown porous plug, and in this example, pure Ar gas was supplied at a rate of about 0.1 Nm 3 /(min ⁇ t-molten iron).
• the melting temperature in the electric furnace was adjusted so that the molten iron temperature before dephosphorization was approximately 1590°C. Temperature measurement and sampling were carried out using the sub-lance before and after the dephosphorization treatment, respectively, before and after the gas top-blowing lance was lowered and after the treatment. The sampled samples were cut and polished, and the C concentration [C] and P concentration [P] in the molten iron were evaluated using a calibration curve prepared in advance by emission spectrometry. Furthermore, it is possible to measure the solidification temperature of the molten metal at the timing of sublance temperature measurement and sampling, and the solidification temperature T m of the molten iron after dephosphorization treatment was actually measured.
• the dephosphorization process was started when the gas top blowing lance started descending, and after the top blowing lance reached a predetermined height, the supply of the oxygen gas source and the addition of the auxiliary raw materials were started. After the supply of a predetermined amount of the oxygen gas source and the auxiliary raw material was completed, the dephosphorization process was defined as the time when the top blowing lance completed rising to the standby position. The time period was defined as the processing time t f (minutes).
• the pot-shaped container was tilted and the slag on the molten iron was removed by a slag dragger. A portion of the removed slag was collected and chemically analyzed. After that, the pot is lifted and tilted by a crane, the molten iron is transferred to the tundish, and the molten iron flows down from the tundish and collides with the refractory surface plate, and the molten iron becomes droplets and falls into the water flow control container. Granulated iron was produced by solidification. The particle size of the obtained iron granules was 0.1 to 30 mm.
• the particle size distribution was +0.1mm-1mm: 17.2% by mass, +1mm-10mm: 31.3% by mass, +10mm-20mm: 38.8% by mass, and +20mm-30mm: 12.7% by mass.
• +NM means that it is above the sieve with a mesh size of N and below the sieve with a mesh size of M.
• Table 2 shows the temperatures T i and T f (°C) of molten iron before and after dephosphorization treatment, C concentrations [C] i and [C] f (mass%), and P concentrations [P] i and [P] f ( mass %), the type and amount of the supplied oxygen source and CaO source, treatment time t f (minutes), basicity of the slag after treatment (mass-based CaO concentration (%CaO) relative to SiO 2 concentration (%SiO 2 ) The ratio (%CaO)/(%SiO 2 ), hereinafter referred to as C/S) was determined by the treatment No. Shown as 1 to 5.
• the post-treatment molten iron temperature T f was lower than the pre-treatment molten iron temperature Ti , and the post-treatment P concentration [P] f was sufficiently reduced.
• the post-dephosphorization temperature T f was higher than the pre-dephosphorization temperature T i , resulting in a high post-treatment P concentration [P] f , and a standby time occurred in the granulated iron manufacturing process, reducing productivity. did.
• processing No. Compared with 1 to 3 processing No. In No.
• the post-treatment molten iron temperature T f was lowered, so the P concentration [P] f was sufficiently lowered, but part of it solidified in the tundish during the production of granulated iron, resulting in a lower yield.
• Processing No. 1 to 3 the molten iron temperature after treatment T f is lower than the molten iron temperature before treatment T i , the molten iron temperature after treatment T f is higher than the solidification temperature T m of molten iron by 20°C or more, and the P concentration after treatment [P] f is sufficient. At the same time, it was possible to produce the entire amount of granulated iron with good yield, and there was no decrease in productivity.
• Example 2 Dephosphorization treatment and production of granulated iron were performed using the same method as in Example 1.
• Table 3 shows the temperature T i and T f (°C) of molten iron before and after dephosphorization treatment, the C concentration [C] i and [C] f (mass%), and the P concentration [P] i and [P] f ( % by mass), the type and amount of the oxygen source and CaO source supplied, the treatment time t f (minutes), and the basicity C/S of the slag after treatment. Shown as 6 to 12. As shown in Table 3, treatment No. Processing No. 6 to 10. Sample No. 11 had a high P concentration after treatment because the basicity C/S of the slag was low. In addition, processing No. In No. 12, the basicity C/S of the slag was high and coagulation of the slag was confirmed.
• Example 3 Reduced iron A shown in Table 1 was melted together with anthracite in a 250-ton electric furnace to obtain molten iron containing about 2.0% by mass of C, and after adjusting the temperature, it was transferred to a pot-shaped container. Thereafter, dephosphorization treatment and production of granulated iron were performed using the same methods as in Examples 1 and 2.
• Table 4 shows the temperatures T i and T f (°C) of molten iron before and after dephosphorization treatment, C concentrations [C] i and [C] f (mass%), and P concentrations [P] i and [P] f ( % by mass), the type and amount of the oxygen source and CaO source supplied, the treatment time t f (minutes), and the basicity C/S of the slag after treatment. Shown as 13 to 19. As shown in Table 4, treatment No. For processing No. 13 to 17. Sample No. 18 had a high P concentration [P] f after treatment because the basicity C/S of the slag was low. In addition, processing No. In No. 19, the basicity C/S of the slag was high and coagulation of the slag was confirmed.
• Processing No. The granulated iron produced in Examples 8 to 10, 12, 14 to 17, and 19 had a P concentration of 0.030% by mass or less. When these reduced irons were melted in an electric furnace, the P concentration of the resulting molten iron was 0.030% by mass or less. These achieved the P concentration required for steel products and did not require additional dephosphorization treatment. In addition, processing No. When the iron granules obtained in steps 8 to 10, 12, 14 to 17, and 19 were classified to 1 mm or more and used in an electric furnace, blast furnace, or converter, they could be used without problems.
• the unit of mass "t” represents 10 3 kg.
• [M] represents that element M is dissolved in molten iron or reduced iron.
• the method for producing granulated iron and the granulated iron of the present invention even if the raw material is reduced iron obtained from low-grade iron ore with a high P concentration, it is possible to efficiently produce granulated iron with a low P concentration. This is industrially useful because it is possible to obtain molten iron with a P concentration equivalent to that of steel products simply by remelting the granulated iron according to the present invention.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

Family

ID=88420043

Family Applications (1)

Country Status (5)

Citations (6)

Family Cites Families (2)

• 2023
  • 2023-04-10 US US18/854,104 patent/US20250243554A1/en active Pending
  • 2023-04-10 AU AU2023255850A patent/AU2023255850A1/en active Pending
  • 2023-04-10 WO PCT/JP2023/014502 patent/WO2023204071A1/ja not_active Ceased
  • 2023-04-10 JP JP2023547085A patent/JP7666615B2/ja active Active
  • 2023-04-10 TW TW112113232A patent/TWI858647B/zh active

Patent Citations (6)

Also Published As

Similar Documents

Legal Events