JP6597332B2 - Phosphate fertilizer manufacturing method and phosphate fertilizer manufacturing apparatus - Google Patents

Description

  The present invention relates to a phosphate fertilizer manufacturing method and a phosphate fertilizer manufacturing apparatus, which dephosphorizes hot metal having a high phosphorus concentration and uses slag after refining as a phosphate fertilizer raw material.

Iron ore that is a raw material for iron making contains phosphoric acid (P ₂ O ₅ ), and pig iron produced by the blast furnace method contains about 0.1% phosphorus. On the other hand, generally, the lower the phosphorus content in the steel, the better the quality of the steel is obtained. Therefore, dephosphorization is performed in the steel making process for refining the hot metal. In the dephosphorization, slag for dephosphorization is formed on the hot metal surface, phosphorus in the hot metal is oxidized by oxidative refining and transferred to the slag, and the phosphorus concentration in the molten steel after the refining is reduced. The slag collected after refining (hereinafter referred to as “steel slag”) contains about 2% of phosphoric acid transferred to the slag by dephosphorization. Steelmaking slag discharged out of the system is used as civil engineering materials such as roadbed materials or used for reclamation of the ocean, and phosphoric acid contained in the steelmaking slag is not effectively used.

  The problem of uneven distribution of phosphorus resources, depletion of resources, and deterioration of quality in the world has been raised. It is said that the total amount of phosphorus contained in steelmaking slag is comparable to the amount of phosphorus contained in Japanese imported phosphorus ore, and the effective use of phosphorus contained in steelmaking slag has become an urgent issue.

A method is known in which decarburization and dephosphorization refining is performed in a basic converter called a Thomas converter using a high phosphorus hot metal having a phosphorus concentration of about 2% manufactured using high phosphorus iron ore as a raw material. The steelmaking slag formed by the refining method contains a high concentration of phosphoric acid (P ₂ O ₅ ) with a concentration of 15% or more, and a high fertilizer effect can be obtained when used as a fertilizer. It is known by the name of manure. However, using high phosphorus hot metal, such as that used in the Thomas Converter, and containing a high concentration of phosphoric acid in the steelmaking slag after refining, the currently required phosphorus concentration is, for example, about 0.015% It is difficult to carry out dephosphorization to the product phosphorus concentration level. In addition, high phosphorus iron ore is not used as a raw material for steelmaking at present, and refining using high phosphorus hot metal is not performed.

  As described above, in the blast furnace-converter method currently widely used, the phosphorus concentration in pig iron produced by the blast furnace method is about 0.1%, and in the steelmaking slag in the converter method for refining the molten iron The concentration of phosphoric acid is around 2%. Further, the steelmaking slag contains iron oxide. In Patent Document 1, by reducing such steelmaking slag, iron oxide and phosphoric acid in the steelmaking slag are reduced, and a high phosphorus hot metal containing 0.5% or more of phosphorus is obtained. A method is disclosed in which phosphorus removal treatment is performed using phosphorus molten iron as a raw material, and the resulting dephosphorized slag is used as a raw material for phosphate fertilizer. In the dephosphorization treatment, the phosphoric acid content in the dephosphorization slag is 15% or more by projecting a CaO source together with oxygen gas and further supplying a silicon source to make the slag basicity 1.5 or more. . Moreover, the hot metal obtained by performing the dephosphorization treatment has a phosphorus concentration lowered to 0.10% or less, and is said to be usable as an iron source for steelmaking.

According to Non-Patent Document 1, as compound form of phosphoric acid which is found in ordinary general, double salts of _{5CaO · P 2 O 5 · SiO} 2 is a soluble in most citric acid. According to this chemical formula, the mass ratio is CaO: P ₂ O ₅ : SiO ₂ = 1.97: 1: 0.423. As a result of investigating the influence of the SiO ₂ / P ₂ O ₅ ratio on the phosphoric acid solubility, it was found that SiO ₂ / P ₂ O ₅ = 0.4 as shown in B and C in FIG. As a boundary, it is shown that when the SiO ₂ / P ₂ O ₅ ratio is lower than this, the phosphate solubility is lowered.

In Patent Document 2, in the cooling process of steelmaking slag, when the temperature becomes lower than the liquidus temperature, tricalcium phosphate (3CaO · P ₂ O ₅ ) is dissolved in the dicalcium silicate phase (2CaO · SiO ₂ ). It is described that a phosphorus-enriched phase is formed, and the other phases are almost free of phosphorus. 3CaO · P ₂ O ₅ -2CaO · SiO ₂ has the same composition as 5CaO · P ₂ O ₅ · SiO ₂ described in Non-Patent Document 1. Further, this composition also coincides with silicocarnotite (Ca ₅ (PO ₄ ) ₂ SiO ₄ ) described in Patent Document 1.

  Patent Document 3 discloses a thermal spray burner using a combustion flame as a method of spraying a pretreatment agent used in hot metal desiliconization and dephosphorization processes at high temperature. Patent Document 4 discloses a powder spraying apparatus for furnace wall repair.

JP, 2015-140473, A JP 2007-217214 A Japanese Patent Laid-Open No. 63-210229 Japanese Patent Publication No. 64-10270

Matsushima Kiichiro "Thomas Steel Making Method", 1945, Chikura Shobo, p. 201

  In the method described in Patent Document 1, in a dephosphorization process using high phosphorus hot metal containing 0.5% or more of phosphorus as a raw material, a CaO source is projected together with oxygen gas, and a silicon source is further supplied to increase slag basicity. By setting it to 1.5 or more, the phosphoric acid content in the dephosphorized slag is said to be 15% or more. In order to add a CaO source or a silicon source as a solid raw material and melt a slag having a basicity of 1.5 or more, both the hot metal and the slag must be heated to about 1450 ° C. or more. Furthermore, the higher the slag basicity, the higher the temperature required to dissolve the slag. As a heat source for melting and raising the temperature of the slag raw material and raising the temperature of the hot metal, the oxidation heat that reacts with the oxygen gas blown in by phosphorus or silicon in the hot metal is insufficient, and the carbon and oxygen gas in the hot metal are reacted. It is essential to use oxidation heat.

  When carbon in hot metal is burned as a heat source for melting and raising the temperature of slag and raising the temperature of hot metal, carbon monoxide is generated as a combustion gas, and the amount of exhaust gas generated increases. Therefore, it is necessary to prepare a large capacity apparatus as an exhaust gas treatment apparatus. Further, unless a converter type refining vessel equipped with an unburned gas recovery type exhaust gas treatment device is used as a dephosphorization refining vessel, it becomes difficult to effectively recover carbon monoxide in the exhaust gas as an energy source. Further, when the amount of decarburization is increased in the dephosphorization process, slag forming is likely to occur due to an increase in the amount of exhaust gas. From this point of view, a large reaction vessel such as a converter is required.

  Further, when the carbon concentration in the hot metal is reduced by decarburization of the hot metal, the T.O. It becomes difficult to lower the Fe concentration. T. in slag When Fe concentration is high, there exists a problem that the area | region of a slag composition with a high fertilizer effect as phosphorus fertilizer will narrow.

After the dephosphorization refining, the hot metal whose phosphorus concentration is reduced to around 0.1% is further effective by performing dephosphorization and refining to obtain a molten steel having components and temperature for steel production. Utilization is planned. As the molten steel temperature (blow-off temperature) at the end of refining, a temperature of about 1650 ° C. is required, so a heat source is required to raise the molten iron to the required temperature during dephosphorization and decarburization. However, in dephosphorization refining to obtain high phosphorus slag, if the carbon in the hot metal is burned and consumed in order to melt and raise the temperature of the slag, then the heat source for refining the molten steel will be insufficient. . Further, depending on the method for reducing steelmaking slag, the carbon content in the high phosphorus hot metal may be as low as about 2%. When such a low-carbon, high-phosphorus hot metal is used as a raw material, even if the carbon in the hot metal is completely burned, there is a possibility that the heat source will be insufficient depending on the amount of slag.
In order to produce a uniform high phosphorus slag, it is necessary to keep the slag temperature sufficiently high during refining. However, in dephosphorization refining to obtain high phosphorus slag, if the temperature of the hot metal and slag is kept low, there is a concern that the slag will not be sufficiently melted and sufficient uniformity cannot be secured to realize the quality as phosphate fertilizer. is there.

  The present invention performs dephosphorization refining on hot metal having a phosphorus concentration of 1% or more, and uses slag produced by dephosphor refining as a phosphate fertilizer raw material, as a heat source for melting and raising the temperature of the slag raw material. It is an object of the present invention to provide a sufficiently uniform and high-quality manufacturing method and manufacturing apparatus for phosphate fertilizer without the need to use the heat of oxidation of carbon.

(1) A hot metal having a phosphorus concentration of 1% by mass or more is charged into a refining vessel, a refining agent melted by a melt projection type fuel burner is added to the hot metal surface, and oxygen gas is supplied to the hot metal surface from an upper blowing lance. The method for producing phosphoric acid fertilizer using the dephosphorizing refining flux or the dephosphorizing refining flux and iron oxide, and using the hot metal surface slag after dephosphorizing as the phosphate fertilizer raw material Because
The refining vessel is a vessel that enables the hot metal to be conveyed, and nitrogen gas is blown from the bottom of the vessel or the immersion lance, and the nitrogen gas blowing rate is 1 to 20 NL / ton · min . Production method.
(2) The hot metal concentration in hot metal at the time of charging into the refining vessel is 2% by mass or more, and the carbon concentration in hot metal at the end of the dephosphorization is 1% by mass or more ( The manufacturing method of the phosphate fertilizer as described in 1).
(3) The dephosphorizing flux has an average particle size of 3 mm or less, and is one or more of converter slag, quicklime, limestone, fly ash, SiO ₂ -containing material, and MgO-containing material. The manufacturing method of the phosphate fertilizer as described in said (1) or (2).
(4) Any of (1) to (3) above, wherein the iron oxide has an average particle size of 3 mm or less and is one or more of dust, iron ore, and pellet feed The manufacturing method of the phosphate fertilizer as described in one.
(5) The fuel of the fuel burner is gas fuel or liquid fuel, and includes at least one of coke oven gas, LPG, LNG, and kerosene. The manufacturing method of the phosphate fertilizer as described in any one.
(6) The composition of the slag after dephosphorization is mass%,
SiO ₂ / P ₂ O ₅ ≧ 0.4 (1)
CaO / P ₂ O ₅ ≧ 2.0 (2)
P ₂ O ₅ ≧ 10% (3)
T.A. Fe: 5% or more and 15% or less (4)
Method for producing a phosphate fertilizer according to any one of the above (1), wherein up to (5) that is.
(7 ) Phosphate fertilizer manufacturing equipment that can use hot metal surface slag after dephosphorization of hot metal as a raw material for phosphate fertilizer, melting a refining vessel and a refining agent into which hot metal can be charged. A molten projection type fuel burner to be added to the hot metal surface, an upper blowing lance for blowing oxygen gas onto the hot metal surface, and a phosphate fertilizer manufacturing apparatus capable of performing dephosphorization of hot metal ,
The refining container is a container that enables the hot metal to be conveyed, has a nitrogen gas blowing part for blowing nitrogen gas from the bottom of the container or the immersion lance, and the nitrogen gas blowing speed range is 1 to 20 NL / ton · min. An apparatus for producing phosphate fertilizer characterized by the above .

  According to the present invention, dephosphorization is performed on hot metal having a phosphorus concentration of 1% or more, and when slag produced by dephosphorization is used as a phosphate fertilizer raw material, as a heat source for melting and heating the slag raw material, It is possible to produce a phosphate fertilizer that does not require the use of the oxidation heat of carbon.

It is a figure which shows an example of the manufacturing apparatus of the phosphate fertilizer of this invention. Described in Non-Patent Document 1 is a diagram showing the relationship between the slag SiO ₂ / P ₂ O ₅ ratio and phosphoric acid soluble impurities. It is a diagram showing the relationship between the slag CaO / P ₂ O ₅ ratio and phosphoric acid soluble impurities. Slag CaO / SiO ₂ ratio, T.I. And Fe, is a diagram showing the relationship between the slag in P ₂ O ₅ present can amount. It is a diagram showing a slag composition range in CaO-SiO ₂ -P ₂ O ₅ ternary phase diagram.

  The phosphate fertilizer of the present invention can be manufactured using, for example, the apparatus shown in FIG.

The present invention is directed to a treatment in which hot metal having a phosphorus concentration of 1% by mass or more is charged into a refining vessel 1 as a raw material, dephosphorized and refined, and the hot metal surface slag 12 after dephosphorization is used as a phosphate fertilizer raw material. . By performing dephosphorization refining using hot metal 11 having a phosphorus concentration of 1% by mass or more as a raw material, the phosphorus concentration in the hot metal after dephosphorization is reduced to about 0.1 to 0.2%. If the phosphorus concentration in the hot metal after dephosphorization is around 0.1 to 0.2%, P ₂ O in the hot metal surface slag after dephosphorization is within the normal phosphorus distribution range of the CaO-based refining agent. _{5 The} concentration can be 10% by mass or more, and the slag can be used as a phosphate fertilizer raw material.

  As for the refining agent for forming the dephosphorizing slag, the refining agent melted by the melt projection type fuel burner 2 is added to the hot metal surface. Melting projection type fuel burner burns fuel with a fuel burner to form a combustion flame, while melting the refining agent powder by injecting the refining agent powder and passing it through the combustion flame. The refining agent is projected on the target. FIG. 1 shows a melt projection flow 14 in which a refining agent is supplied from the material hopper 5 to the melt projection type fuel burner 2 and discharged from the melt projection type fuel burner 2. As in the past, when a solid refining agent is introduced into the hot metal and the refining agent is melted by sensible heat of the hot metal, the melting point of the refining agent including CaO is higher than the hot metal temperature, The ratio which does not contribute to the refining reaction by floating on the iron bath in an unmelted state increases. On the other hand, in the present invention, since the refining agent is previously melted and projected onto the molten iron 11 using the melt projection type fuel burner 2, the used refining agent can be reliably melted and contributed to the refining reaction. Thus, it is possible to prevent a phosphoric acid compound different from the target composition from being produced, and to easily produce a compound having a desired composition. In addition, since sensible heat of hot metal is not used as a heat source for melting and raising the temperature of the refining agent, it is not necessary to raise the hot metal temperature to the slag melting temperature. There is no need to burn carbon in the hot metal as a heat source.

  In addition, when a method in which high-temperature combustion flame is sprayed on the hot metal or slag on its surface with a fuel burner alone, the heat transfer from the combustion flame to the hot metal and slag is largely due to radiant heat transfer, and the surface heat-up efficiency increases the heat receiving efficiency. Is very low. On the other hand, in the melt projection type fuel burner 2 adopted by the present invention, the powder refining agent is heated on the burner frame to become a molten state and adheres to the iron bath. (Thermal efficiency: about 30%).

  Furthermore, in the present invention, since the refining agent heated and melted at a high temperature by the melt projection type fuel burner 2 is projected onto the hot metal surface, the temperature of the molten slag 12 formed on the hot metal surface is set to a temperature higher than the temperature of the hot metal 11. It becomes possible to hold. For example, the temperature of the molten slag 12 can be increased to about 1500 ° C. while the temperature of the molten iron 11 is set to about 1400 ° C. In this case, since the heat source required for raising the temperature of the hot metal 11 is small, the hot metal temperature is sufficiently increased by the heat source obtained by oxidizing phosphorus and silicon in the hot metal and the heat source obtained by minimally oxidizing carbon in the hot metal. It is possible to increase the temperature to a predetermined temperature. Further, by setting the temperature of the slag 12 to a sufficiently high temperature, the slag 12 can be melted satisfactorily and phosphorus distribution from the hot metal 11 to the slag 12 can be favorably promoted.

The present invention also supplies oxygen gas 13 from the top blowing lance 3 to the surface of the hot metal 11 to dephosphorize the hot metal 11. In dephosphorization of hot metal 11, oxygen is supplied to oxidize phosphorus in hot metal 11 to P ₂ O ₅ , to oxidize silicon to SiO _2, and to oxidize some carbon to CO. There is a need. If only iron oxide is used as the oxygen source, the heat source is greatly lost because iron oxide reduction is an endothermic reaction. In the present invention, the oxygen gas 13 supplied from the top blowing lance 3 is used as all or part of the oxygen source for oxidation, so that iron oxide can be used or the amount used can be reduced. Heat can be effectively used to raise the temperature.

  The total amount of oxygen to be supplied by dephosphorization is obtained in advance by dephosphorization oxygen efficiency from the hot metal phosphorous concentration level at the time of dephosphorization, and the target dephosphorization amount from the generated slag amount and the target slag phosphate concentration, The required oxygen amount is determined from the dephosphorization oxygen efficiency and the target dephosphorization amount. Furthermore, the amount of desiliconization and the accompanying decarburization amount are empirically grasped, and the oxygen amount suitable for the reaction is set to be supplied. . When iron oxide described later is not added, the required oxygen amount is the amount of oxygen gas 13 supplied from the top blowing lance 3. In addition, when iron oxide is added in the dephosphorization refining of the present invention, a value obtained by subtracting the oxygen content in iron oxide from the total required oxygen use amount is the oxygen use amount to be supplied as oxygen gas.

  T. of dephosphorization slag The Fe concentration is determined by the balance between the oxidation rate of Fe and the reduction rate of FeO. The former is mainly influenced by the oxygen supply rate, and the latter is mainly influenced by the stirring intensity of top blowing and bottom blowing. T.A. When increasing the Fe concentration, the increase in the acid delivery rate Increasing the bottom blowing flow rate is effective in reducing the Fe concentration. Therefore, the T.W. It is preferable to adjust the acid feed rate and the bottom blowing gas flow rate so that the Fe concentration is optimized.

  The refining agent melted by the melt projection type fuel burner 2 and added to the hot metal surface is a dephosphorization refining flux, or a dephosphorizing refining flux and iron oxide.

  The dephosphorization refining flux is a flux mainly composed of a CaO component, and a preferable composition thereof and a preferable composition of slag as a result of oxidative refining using the refining flux will be described later.

  Iron oxide is used as an iron oxide component in the slag (component composition is expressed as T.Fe) and as an oxidation source for oxidizing phosphorus, silicon, and some carbon in the hot metal. In the present invention, oxygen gas by top blowing oxygen is also used as an oxygen source. Depending on the supply amount of iron oxide, the amount of oxygen gas used will be reduced. Among the oxygen sources, the higher the usage ratio of iron oxide, the fewer heat sources that raise the temperature of the hot metal due to the endothermic reaction that reduces iron oxide.

  As the oxygen source for dephosphorization, gaseous oxygen is basically used. However, when the phosphorus concentration in the molten iron decreases, the dephosphorization oxygen efficiency decreases, and the ratio of oxygen used for decarburization increases. In order to mitigate this tendency, it is conceivable to use iron oxide instead of gaseous oxygen. When gaseous oxygen is used, a high temperature region (fire point) is locally formed at a location where it collides with the iron bath. When the temperature is high, the oxidation of carbon is promoted more than the oxidation of phosphorus, so that the ratio of oxygen consumed for decarburization tends to increase. Therefore, in order to suppress decarburization, not only gaseous oxygen but also iron oxide is added as an oxygen source. When iron oxide is used as an oxygen source, an endothermic reaction of iron oxide reduction is accompanied at the time of dephosphorization or decarburization reaction. Therefore, the temperature of the reaction site is lower than that at the time of using gaseous oxygen, and decarburization is suppressed.

Here, a method for preparing hot metal having a phosphorus concentration of 1% by mass or more used in the present invention will be described. In normal converter refining, hot metal with a phosphorus concentration of around 0.1% extracted from the blast furnace is used as the main raw material, and normal dephosphorization refining and decarburization refining (hereinafter referred to as “normal dephosphorization refining” “normal decarburization refining”). ”), A molten steel having a phosphorus concentration of 0.02% or less is manufactured. Among the slag formed by such normal dephosphorization / normal decarburization (hereinafter referred to as “normal dephosphorization slag”, “normal decarburization slag”), It contains about 10-20% iron oxide and about 2% P ₂ O _{5 in} terms of Fe. By using these normal dephosphorization slag, normal decarburization slag alone, or mixed slag of normal dephosphorization slag and normal decarburization slag (collectively also referred to as “normal steelmaking slag”) as a raw material, by reducing these, Iron oxide and P ₂ O ₅ in the slag are reduced, and molten iron having a phosphorus concentration of 1% by mass or more can be obtained. Carbon sources such as coke can be used as the reducing agent. Carbon can also dissolve in molten iron to make molten iron a hot metal, and lower the melting temperature. In this invention, the high phosphorus hot metal manufactured in this way can be used suitably as a raw material.

  In the present invention, the carbon concentration in the hot metal at the time of charging into the refining vessel 1 for the dephosphorization refining of the present invention is preferably 2% by mass or more. Further, the C concentration in the hot metal at the end of dephosphorization is preferably 1% by mass or more. By setting the carbon concentration in the hot metal at the end of the dephosphorization refining of the present invention to 1% by mass or more, the normal dephosphorization refining and decarburization refining are further performed on this hot metal to produce molten steel having a predetermined component and temperature. In addition, the temperature of the molten steel can be increased to a temperature that requires carbon in hot metal as a heat source (blow-off temperature). In addition, by setting the carbon concentration in the hot metal at the time of charging into the refining vessel of the present invention to 2% by mass or more, the melting temperature of the hot metal is lowered to ensure the fluidity during the reduction treatment, and Even if a slight decarburization reaction occurs during the dephosphorization treatment, the carbon concentration in the hot metal at the end of the dephosphorization refining can be maintained within the preferred range of the present invention. When producing high phosphorus hot metal by reducing normal steelmaking slag, depending on the reduction method, the carbon in the hot metal is not necessarily saturated with carbon, and the carbon concentration may be about 2%. In such a case, since the amount of decarburization increases as the amount of dephosphorization increases, the carbon concentration may become 1% or less in some cases. At that time, it is necessary to maintain the carbon concentration at 1% or more by a method of adding carbonaceous material while usually mixing with hot metal or performing a burner heat treatment.

The dephosphorization refining flux used in the present invention has an average particle size of 3 mm or less, and is preferably one or more of converter slag, quicklime, limestone, fly ash, SiO ₂ -containing material, and MgO-containing material.

  The dephosphorization refining flux of the present invention is added to the hot metal surface after being melted by the melt projection type fuel burner 2. If the average particle size of the dephosphorization refining flux is 3 mm or less, it can be melted when passing through the flame of the fuel burner. The smaller the particle size of the flux, the faster it can be dissolved. However, if the particle size is too small, the scattering loss may increase, so the average particle size is preferably 0.1 mm or more.

The converter slag used as the dephosphorization refining flux of the present invention means the normal dephosphorization slag, the normal decarburization slag, and the like. In using the hot metal surface slag after dephosphorization refining of the present invention as a phosphate fertilizer raw material, in addition to P ₂ O ₅ , CaO, SiO ₂ , FeO, the slag contains MgO, MnO, etc. Each has an advantageous fertilizer effect for plants. The converter slag contains all of P ₂ O ₅ , CaO, SiO ₂ , FeO, MgO, and MnO. By using converter slag as a dephosphorization refining flux, these useful elements can be put together. Since the effect to add is acquired, it is preferable. Moreover, since the composition of the converter slag can be analyzed in advance, it is not difficult to adjust the slag component after dephosphorization of the present invention. In the slag after dephosphorization, it is essential to contain CaO, SiO ₂ and FeO in order to promote dephosphorization. However, since some of the essential components can be supplied from the converter slag, simple substances such as CaO The amount of flux added can be reduced, and the loss of oxidizing hot metal as a FeO source can be minimized. Furthermore, the effect which promotes the effective utilization of converter slag is also acquired.

Of the dephosphorization refining flux used in the present invention, quick lime and limestone can be used as the CaO source in the slag, and fly ash can be used as the Al ₂ O ₃ source and the SiO ₂ source. Silica and brick scraps can be used as the SiO ₂ -containing material. As the MgO-containing material, dolomite, fired dolomite, and brick scraps can be used. Dolomite also has an effect as a source of CaO.

  The iron oxide used in the present invention has an average particle size of 3 mm or less, and is preferably one or more of dust, iron ore, and pellet feed. The reason for setting the average particle size to 3 mm or less is the same as that of the dephosphorization refining flux. The average particle size is preferably 0.1 mm or more.

  When iron ore is used as the iron oxide source, it is preferable from the viewpoints of price and quality stability. Moreover, since dust, especially converter dust, contains abundant iron oxide, it can be used as an iron oxide source, leading to effective utilization of waste. Pellet feed refers to iron ore powder and is useful as an iron oxide source.

  The fuel of the fuel burner used for the melt projection type fuel burner of the present invention is preferably a gas fuel or a liquid fuel, and includes coke oven gas (COG), LPG, LNG, and kerosene. Both have sufficient properties for melting refining flux and iron oxide.

The composition of the slag after dephosphorization of the present invention is mass%,
SiO ₂ / P ₂ O ₅ ≧ 0.4 (1)
CaO / P ₂ O ₅ ≧ 2.0 (2)
P ₂ O ₅ ≧ 10% (3)
T.A. Fe: 5% or more and 15% or less (4)
Is preferable.

As described above, according to Non-Patent Document 1, as compound form of phosphoric acid which is found in ordinary general, double salts of _{5CaO · P 2 O 5 · SiO} 2 is a soluble in most citric acid. According to this chemical formula, the mass ratio is CaO: P ₂ O ₅ : SiO ₂ = 1.97: 1: 0.423. This composition is also described in Patent Document 1 as silicocarnotite (Ca ₅ (PO ₄ ) ₂ SiO ₄ ). Curves B and C in FIG. 15 of Non-Patent Document 1 are listed here as FIG. In FIG. 2, the horizontal axis shows the SiO ₂ / P ₂ O ₅ ratio in the slag. Further, phosphoric acid dissolved in 2% citric acid is defined as “soluble phosphoric acid”, and the vertical axis in FIG. 2 is “phosphoric acid solubility = soluble phosphoric acid / total phosphoric acid × 100”. According to the results of B and C in FIG. 2, when the ratio of SiO ₂ / P ₂ O ₅ satisfies the above formula (1), the phosphoric acid solubility rate in which phosphoric acid in slag dissolves in citric acid is high. Maintained at the same level. Therefore, also in the present invention, it is preferable that the composition of the slag after dephosphorization satisfies the above formula (1).

Next, the effect of the CaO / P ₂ O ₅ ratio in the material on the solubility of phosphoric acid was evaluated. For each material, the phosphoric acid dissolved in ammonium citrate is taken as soluble phosphoric acid, the horizontal axis in FIG. 3 is the CaO / P ₂ O ₅ ratio, and the vertical axis is “phosphoric acid solubility = soluble phosphoric acid / total phosphoric acid”. As plotted. The dephosphorization slag can maintain the phosphoric acid solubility at a high level of 0.4 to 0.7 by setting the CaO / P ₂ O ₅ ratio to 2.0 or more. That is, it is preferable that the above expression (2) is satisfied. However, the variation is large, and some of the plots are low. This is thought to be due to the lack of effective CaO that forms a compound with P ₂ O ₅ due to undissolved CaO. Therefore, it can be said from this that the use of the burner has an important meaning of improving the CaO dissolution rate and improving the fertilizer effect.

When the slag after dephosphorization is used as a phosphate fertilizer raw material, the higher the P ₂ O ₅ concentration in the slag, the greater the value as phosphorus fertilizer. In the present invention, by satisfying the above formula (3) with P ₂ O ₅ ≧ 10%, it is possible to prevent an increase in the amount of fertilizer used when giving the necessary amount of phosphoric acid to the soil. Can be obtained. More preferably, P ₂ O ₅ ≧ 15%.

The dephosphorization reaction in the dephosphorization refining of the present invention is an oxidation reaction. Phosphorus in molten iron is oxidized using iron oxide represented by Fe concentration as an oxygen source. Therefore, the T.W. If the Fe concentration is too low, the dephosphorization ability in the dephosphorization refining is extremely lowered and the P ₂ O ₅ concentration effect is diminished. If the Fe concentration is 5% or more, the dephosphorization ability can be exhibited.

On the other hand, T. in the slag. If the Fe concentration is too high, there will be an adverse effect of reducing the P ₂ O ₅ concentration in the slag. Here, the slag composition (mass%) is CaO / P ₂ O ₅ = 2 and MgO + MnO + Al ₂ O ₃ = 16%. When the Fe concentration and the slag basicity (CaO / SiO ₂ ) were variously changed, the P ₂ O ₅ concentration was calculated assuming that the remaining component of the slag was P ₂ O ₅ . In FIG. 4, the horizontal axis represents basicity (CaO / SiO ₂ ) and the vertical axis represents T.P. As Fe, it was plotted as a contour line of the amount that can be contained as P ₂ O ₅ in the slag. For example, when the basicity is 2, T.P. If Fe is about 13%, a P ₂ O ₅ concentration of 17% is possible. When Fe is 25%, the P ₂ O ₅ concentration is 13%. From the above viewpoint, the slag T.I. If the Fe concentration is too high, it becomes difficult to increase the P ₂ O ₅ concentration in the slag. The upper limit of Fe concentration is preferably 15%.

As can be seen from FIG. 4, when an attempt is made to increase the P ₂ O ₅ concentration in the slag under the condition of CaO / P ₂ O ₅ ≧ 2, in order to prevent the slag dilution effect by SiO ₂ or iron oxide, T.P. It is necessary to lower Fe and increase the basicity, and such components increase the melting point and viscosity of slag. Therefore, as in the present invention, by increasing the temperature of the slag by adding the refining agent melted by the melt projection type fuel burner, it becomes a very effective means for obtaining molten slag having a uniform target composition. I understand.

In FIG. 5, in the ternary phase diagram focusing on CaO, SiO ₂ , and P ₂ O ₅ in the slag, the range satisfying the expressions (1) and (2) is hatched.

  As a refining vessel for performing dephosphorization refining according to the present invention, a vessel having a large volume and a large free board, such as a converter, may be used. On the other hand, in the present invention, in order to suppress the decarburization reaction to the minimum necessary, the acid feed rate is small and the degree of slag foaming is small, so as shown in FIG. It is also possible to use a small refining vessel 1. If it is a container with a small free board such as a hot metal ladle, it is a container that enables the hot metal to be transported. For example, a hot metal ladle that receives hot metal transferred from a torpedo car in a converter plant and transports it to the converter is a smelting container 1 Can be used for dephosphorization of the present invention.

  Further, it is preferable that nitrogen gas is blown using the bottom of the refining vessel or the immersion lance as the nitrogen gas blowing portion 4 and the nitrogen gas blowing speed is 1 to 20 NL / ton · min. By blowing nitrogen gas into the hot metal in the refining vessel 1, the hot metal is agitated, the dephosphorization reaction efficiency is improved, the thermal efficiency of the melt projection type fuel burner is improved, and the T. It is possible to easily control the Fe concentration level. If the gas stirring by blowing nitrogen gas is too strong, the iron oxide in the slag reacts with the carbon in the molten metal and slag T.I. Fe falls too much, but by adjusting the nitrogen gas blowing speed to a suitable range of 20 NL / ton · min or less, T. Fe concentration can be made a suitable range. Further, by setting the nitrogen gas blowing rate to an appropriate flow rate of 1 NL / ton · min or more, the surface renewal of the slag bath can be promoted by gas stirring, and the thermal efficiency of the melt projection type fuel burner can be improved. Further, maintaining the minimum flow rate does not cause nozzle clogging, and T. An excessive increase in Fe can be prevented.

  A reduction treatment was continuously performed by charging a DC reduction electric furnace with mixed slag of normal dephosphorization slag and normal decarburization slag by a converter and charging coke powder. When the phosphorus concentration of the molten iron in the reduction furnace reached 1.0%, the tap hole was opened and the molten iron was discharged into the ladle for conveyance by 50 tons. The molten iron composition and temperature at that time are shown in Table 1.

  The ladle was transferred with a cart, and the slag on the molten metal was removed with a drainer, and then stopped at the dephosphorization position. Dephosphorization was performed using the apparatus shown in FIG.

  A COG burner was installed as a molten projection type fuel burner 2 on a ladle as the refining vessel 1, and an upper blowing lance 3 for supplying oxygen gas 13 was installed. A porous plug provided at the bottom of the ladle was used as a nitrogen gas blowing portion 4 to flow nitrogen, and the inside of the ladle was stirred. The material hopper 5 for the melt projection type fuel burner 2 stores three kinds of raw materials such as converter slag powder, quicklime powder, and pellet feed. A lid 6 was disposed on the upper part of the refining vessel 1, and exhaust gas during refining was discharged via an exhaust duct 7.

  The present invention No. 1 shown in Table 1. 1 supplies only oxygen gas from the top blowing lance 3 as an oxygen source. 2 supplied both oxygen gas from the top blowing lance 3 as an oxygen source and pellet feed as an iron oxide source. Table 1 shows the oxygen gas flow rate and oxygen gas basic unit, the COG flow rate and COG basic unit burned by the COG burner, the nitrogen gas flow rate, the flux input amount, and the refining time.

  While flowing the nitrogen from the porous plug provided at the bottom of the ladle and stirring the inside of the ladle, the COG flow rate is determined, the COG burner is ignited, and the refining flux and iron oxide as the projection material are melted by the molten projection fuel burner 2 Melted and projected into an iron bath. The injection speed of the projection material was set so that the input amounts shown in Table 1 can be input in 25 minutes. At the same time, oxygen gas 13 was blown from the top blowing lance 3 to the hot metal 11.

  After a predetermined amount of refining flux and iron oxide were charged in 25 minutes, the powder supply was stopped, the burner was extinguished, and temperature measurement sampling was performed.

  Table 2 shows the hot metal components, slag components, hot metal weight / temperature, and slag weight / temperature after refining. This invention No. 1, no. Since both entered the target composition, the dephosphorization process was terminated, and the generated slag was discharged and collected with a waste evacuator. Since the slag temperature after dephosphorization was as high as around 1500 ° C., the slag was sufficiently dissolved during dephosphorization and slag having a uniform component composition could be obtained.

  This invention No. 1 had a molten iron weight of 49.1 ton and a slag weight of 6.78 ton. This invention No. In No. 2, the molten iron weight was 51.4 ton and the slag weight was 6.78 ton. In both cases, the molten metal in the pot was transported to a steelmaking factory and mixed with blast furnace hot metal to perform converter blowing.

DESCRIPTION OF SYMBOLS 1 Refining container 2 Melting projection type fuel burner 3 Top blowing lance 4 Nitrogen gas blowing part 5 Material hopper 6 Lid 7 Exhaust duct 11 Hot metal 12 Slag 13 Oxygen gas 14 Melting projection flow 15 Bubble

Claims (7)

A hot metal having a phosphorus concentration of 1% by mass or more is charged into a smelting vessel, a refining agent melted by a melt projection type fuel burner is added to the hot metal surface, and oxygen gas is supplied to the hot metal surface from an upper blowing lance. The method for producing phosphoric acid fertilizer , wherein the refining agent is a dephosphorizing refining flux or a dephosphorizing refining flux and iron oxide, and the hot metal surface slag after dephosphorizing is used as a phosphate fertilizer raw material. ,
The refining vessel is a vessel that enables the hot metal to be conveyed, and nitrogen gas is blown from the bottom of the vessel or the immersion lance, and the nitrogen gas blowing rate is 1 to 20 NL / ton · min . Production method.   The hot metal carbon concentration at the time of charging into the refining vessel is 2% by mass or more, and the carbon concentration in hot metal at the end of the dephosphorization is 1% by mass or more. Of manufacturing phosphoric acid fertilizer. The dephosphorization refining flux has an average particle size of 3 mm or less, and is one or more of converter slag, quicklime, limestone, fly ash, SiO ₂ -containing material, and MgO-containing material. The manufacturing method of the phosphate fertilizer of Claim 1 or Claim 2.   4. The iron oxide according to claim 1, wherein the iron oxide has an average particle size of 3 mm or less, and is one or more of dust, iron ore, and pellet feed. 5. Of manufacturing phosphoric acid fertilizer.   The fuel of the fuel burner is a gas fuel or a liquid fuel, and includes at least one of coke oven gas, LPG, LNG, and kerosene. The manufacturing method of the phosphate fertilizer as described in 2 .. The composition of the slag after dephosphorization is mass%,
SiO ₂ / P ₂ O ₅ ≧ 0.4 (1)
CaO / P ₂ O ₅ ≧ 2.0 (2)
P ₂ O ₅ ≧ 10% (3)
T.A. Fe: 5% or more and 15% or less (4)
The method for producing a phosphate fertilizer according to any one of claims 1 to 5, wherein: An apparatus for producing phosphoric acid fertilizer that can use hot metal surface slag after dephosphorization of hot metal as a raw material for phosphoric acid fertilizer, a refining vessel in which hot metal can be charged, a refining agent that melts the refining agent, and the molten iron It has a melt projection type fuel burner to be added to the surface, an upper blowing lance that blows oxygen gas onto the hot metal surface, and a phosphate fertilizer manufacturing apparatus that can perform dephosphorization of hot metal ,
The refining container is a container that enables the hot metal to be conveyed, has a nitrogen gas blowing part for blowing nitrogen gas from the bottom of the container or the immersion lance, and the nitrogen gas blowing speed range is 1 to 20 NL / ton · min. An apparatus for producing phosphate fertilizer characterized by the above .

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