JPWO2020189647A1 - Manufacturing method of phosphoric acid fertilizer raw material - Google Patents

Abstract

Of the dephosphorizing agents, in the dephosphorizing treatment in which an oxygen source and a dephosphorizing agent containing CaO are supplied to hot metal having a C concentration of 2.0% by mass or more and a P concentration of 0.3% by mass or more. A dephosphorizing agent of 50% by mass or more of the required amount of CaO is projected onto the hot metal with a burner, and the basicity (CaO) / (SiO2) of the derinsed lag generated is adjusted to 2.5 or more. A method for producing a phosphoric acid fertilizer raw material, which obtains a normal hot metal having a P concentration of 0.06 to 0.15% by mass and a dephosphorized slag having a phosphoric acid concentration of 15% by mass or more.

Description

The present disclosure relates to a method for producing a phosphate fertilizer raw material.

Conventionally, it has been known that by reducing steelmaking slag or using high-phosphorus iron ore, for example, hot metal having a phosphorus concentration of 0.5% by mass or more (hereinafter, also referred to as "high phosphorus") can be produced. Has been done. Further, it is known that this high-phosphorus hot metal can be dephosphorized to produce a dephosphorized slag having a high concentration of _{, for example, 15% by mass or more of phosphoric acid (P 2} O _5). Such derinsed slag is used as a raw material for phosphate fertilizer having a high fertilizer effect.
On the other hand, in order to produce low-phosphorus steel by converter blowing using the hot metal after the dephosphorization treatment, the P concentration in the hot metal must be reduced to 0.15% by mass or less. If the P concentration in the hot metal is reduced to 0.15% by mass or less, it is difficult to secure the phosphorus concentration in the derinsed lag of 15% by mass or more, and the value as a phosphate fertilizer is impaired. Therefore, various proposals have been made to solve such problems.

Patent Document 1 is divided into a first dephosphorization step having a high P concentration and a second dephosphorization step to reduce the P concentration to 0.15% or less after treatment for the purpose of producing slag having a high phosphoric acid concentration. A technique for reusing a dephosphorized slag having a low phosphoric acid concentration produced in the second dephosphorizing step as a flux in the first dephosphorizing step, instead of a fertilizer raw material, is disclosed.
Further, Patent Document 2 discloses a method of projecting CaO powder into an oxygen jet in order to promote slagging of CaO.

Patent Document 1: Japanese Patent Application Laid-Open No. 2017-125244 Patent Document 2: Japanese Patent Application Laid-Open No. 5829788

However, with the method described in Patent Document 1, _{it is difficult to achieve both a low concentration of P in molten iron and a high concentration of P 2} O ₅ in slag, and the first object is to produce slag having a high phosphoric acid concentration. It was necessary to divide into a dephosphorization step and a second dephosphorization step of reducing the hot metal P concentration to 0.15% or less.
Further, in the method described in Patent Document 2, calcium ferrite is produced by projecting CaO into the high temperature and high oxygen potential, and the dephosphorization reaction is promoted. However, since the thermal margin does not increase, the temperature of the entire slag does not change, _{and it is difficult to increase the basicity (CaO) / (SiO 2} ) of the slag in order to promote the dephosphorization reaction, and the concentration of P in molten iron is low. it is difficult to achieve both of the high concentration of slag in the P ₂ O _5.

Therefore, in view of the above-mentioned problems, the present disclosure describes phosphorus capable of producing a phosphoric acid fertilizer raw material having a high fertilizer effect and at the same time producing a normal hot metal having a P concentration of 0.15% by mass or less, which can melt low phosphorus steel. An object of the present invention is to provide a method for producing a raw material for acid fertilizer.

The disclosure is as follows.
[1]
Of the dephosphorizing agents, in the dephosphorizing treatment in which an oxygen source and a dephosphorizing agent containing CaO are supplied to hot metal having a C concentration of 2.0% by mass or more and a P concentration of 0.3% by mass or more. A dephosphorizing agent of 50% by mass or more of the required amount of CaO is projected onto the hot metal with a burner, and the basicity (CaO) / (SiO ₂ ) of the derinsed lag generated is adjusted to 2.5 or more. , A method for producing a phosphoric acid fertilizer raw material, which obtains a normal hot metal having a P concentration of 0.06 to 0.15% by mass and a dephosphorized slag having a phosphoric acid concentration of 15% by mass or more.
[2]
The method for producing a phosphoric acid fertilizer raw material according to [1], wherein the P concentration of the hot metal is 0.3% by mass or more and less than 1.0% by mass.
[3]
The phosphoric acid fertilizer raw material according to [1] or [2], wherein 50% by mass or more and less than 100% by mass of the required input amount of CaO is projected onto the hot metal with a burner. Manufacturing method.
[4]
At the final stage of the dephosphorization treatment, a raw material mainly composed of iron oxide containing oxygen corresponding to an oxygen intensity of ^{at least 1.5 Nm 3 / t or more with respect to the hot metal is continuously burned or projected as the oxygen source.} The method for producing a phosphoric acid fertilizer raw material according to any one of [1] to [3], which is added without heating.
[5]
Nitrogen or an inert gas is blown into the hot metal at 2 to 40 NL / t / min by a bottom blowing tuyere or a dipping lance, and the (T.Fe) of the derinsed lag is adjusted to 5% by mass or more and 20% by mass or less. The method for producing a phosphoric acid fertilizer raw material according to any one of [1] to [4].
[6]
The dephosphorizing agent is described in any one of [1] to [5], which comprises one or more selected from the group consisting of quicklime, limestone, dolomite, light-baked dolomite, converter slag, and silica stone. Method of manufacturing phosphoric acid fertilizer raw material.

According to the present disclosure, normal hot metal with a P concentration of 0.15% by mass or less capable of melting low-phosphorus steel by subsequent converter blowing while producing dephosphorized slag, which is a raw material for phosphoric acid fertilizer with high fertilizer effect. Can be manufactured at the same time.

It is a schematic block diagram which shows an example of the apparatus used in the manufacturing method of the phosphoric acid fertilizer raw material of this disclosure. It is a figure for demonstrating the influence of the flow rate of agitating gas (denoted as the bottom blowing flow rate in the figure) on the decarburization suppressing effect at the time of dephosphorization. It is a figure for demonstrating the influence of the basicity of slag on the reaching phosphoric acid concentration. It is a schematic diagram which shows an example of the supply method, and the supply timing of an oxygen source and a dephosphorizing agent.

Hereinafter, the present disclosure will be described.
The numerical range represented by using "~" means a range including the numerical values before and after "~" as the lower limit value and the upper limit value.
The numerical range when "greater than" or "less than" is added to the numerical values before and after "~" means a range in which these numerical values are not included as the lower limit value or the upper limit value.

The method for producing a phosphoric acid fertilizer raw material of the present disclosure supplies an oxygen source and a dephosphorizing agent containing CaO to hot metal having a C concentration of 2.0% by mass or more and a P concentration of 0.3% by mass or more. In the dephosphorization treatment, the dephosphorization agent of 50% by mass or more of the required amount of CaO is projected onto the hot metal with a burner to generate the basicity (CaO) / (SiO) of the dephosphorization slag. ₂ ) is adjusted to 2.5 or more to obtain a normal hot metal having a P concentration of 0.06 to 0.15% by mass and a dephosphorized slag having a phosphoric acid concentration of 15% by mass or more.

In the method for producing a phosphoric acid fertilizer raw material of the present disclosure, a P concentration of 0.15 capable of melting low-phosphorus steel by subsequent converter blowing while producing a dephosphorized slag which is a phosphoric acid fertilizer raw material having a high fertilizer effect. Ordinary hot metal of mass% or less can be produced at the same time.

That is, according to the method for producing a phosphoric acid fertilizer raw material of the present disclosure, it is effective to dephosphorify a hot metal having a high P concentration to produce a fertilizer raw material having a high phosphoric acid concentration and a normal hot metal having a low P concentration. A dephosphorization treatment method can be provided.

Here, the effective dephosphorization treatment is from a hot metal having a high P concentration (a hot metal having a P concentration of 0.30% by mass or more and a C concentration of 2% by mass or more) to a high phosphoric acid (P ₂ O ₅ ) concentration. Refers to a dephosphorization treatment that can produce dephosphorization lag with a high fertilizer effect.
The dephosphorized slag having a high phosphoric acid (P ₂ O ₅ ) concentration refers to a dephosphorized slag having a phosphoric acid concentration of 15% by mass or more, which has a high fertilizing effect. Hereinafter, the derinsed slag is also simply referred to as "slag".
Usually, hot metal refers to hot metal after dephosphorization treatment. The low P concentration normal hot metal refers to a hot metal having a P concentration of 0.15% by mass or less in the hot metal after dephosphorization, and more preferably a C concentration of 2% by mass or more in the hot metal. Normal hot metal with a low P concentration is hot metal that can melt low-phosphorus steel without problems in converter blowing and has sufficient thermal abundance when decarburizing and blowing.

Hereinafter, the details of the method for producing the phosphoric acid fertilizer raw material of the present disclosure will be described.

In the method for producing a phosphoric acid fertilizer raw material of the present disclosure, the P concentration in normal hot metal is reduced to 0.15% by mass or less and the phosphoric acid concentration in dephosphorized slag is 15% by mass by dephosphorization treatment from a high P concentration hot metal. In order to secure the above, _{it is necessary to generate slag having high basicity (CaO) / (SiO 2} ) (hereinafter referred to as C / S) in the dephosphorization treatment.
Specifically, as shown in FIG. 3, at least the phosphorus distribution ratio (P ₂ O ₅ ) / [P] must be 100 or more. For that purpose, the C / S in the slag must be 2.5 or more, preferably 3.0 or more. Such high-basic slag has a high melting point, and at a hot metal temperature of about 1300 to 1400 ° C., a large amount of undissolved lime is generated and the fluidity is low. No reaction can be expected. Therefore, it is difficult to realize by dephosphorization treatment using ordinary oxygen gas.

Therefore, in the method for producing a phosphoric acid fertilizer raw material of the present disclosure, the slag layer is externally heated during the dephosphorization treatment to raise the temperature of the slag layer higher than that of the hot metal, thereby achieving a high melting point. Dissolve the slag. On the other hand, by lowering the slag metal interface temperature to be lower than the average temperature of the slag layer, the decrease in dephosphorization ability is suppressed.

Specifically, in the dephosphorization treatment for supplying the oxygen source and the dephosphorizing agent containing CaO, 50% by mass or more of the dephosphorizing agent in the required input amount of CaO is added to the hot metal. Burner projection. Thereby, the basicity (CaO) / (SiO ₂ ) of the generated derinsed lag can be adjusted to 2.5 or more, preferably 3.0 or more. As a result, the P concentration in the hot metal can be set to 0.15% by mass or less, and the phosphoric acid concentration in the derinsed lag can be secured to 15% by mass or more.

Even if all the dephosphorizing agents are projected by a burner, the basicity (CaO) / (SiO ₂ ) of the derinsed slag produced can be adjusted to 2.5 or more. However, considering the fuel cost of the burner, it is preferable to burner-project a dephosphorizing agent having a amount of 50% by mass or more and less than 100% by mass of the required input amount of CaO to the hot metal.

On the other hand, if the P concentration in the hot metal is reduced to 0.15% by mass or less by the dephosphorization treatment, the dephosphorylation oxygen efficiency decreases and the decarboxylation efficiency increases. Therefore, the C concentration in the hot metal decreases, and the melting point of the hot metal rises. The dephosphorization treatment is more likely to proceed when the hot metal temperature is low, and when the C concentration in the hot metal is 2% by mass or less, the melting point of the hot metal becomes 1400 ° C. or higher, and the dephosphorization treatment at a low temperature becomes difficult. Further, if the C concentration in the normal hot metal after the dephosphorization treatment is low, the thermal abundance is lowered in the subsequent converter blowing, and the operation restriction is increased. Furthermore, if the decarburization reaction is promoted at the end of the dephosphorization treatment, the dephosphorization slag is likely to be formed. Assuming that the dephosphorization treatment is performed in the ladle, the freeboard is small, so the tolerance for forming is low, and when the decarburization reaction is activated, the forming may induce slag overflow.

Therefore, in the method for producing a phosphoric acid fertilizer raw material of the present disclosure, it is preferable to promote the dephosphorization reaction and suppress the decarburization reaction, and therefore, it is preferable to use the following three methods.

First, as an oxygen source, the ratio of iron oxide-based raw materials to oxygen gas is increased.
When a raw material mainly composed of iron oxide supplies oxygen, the temperature of the dephosphorization reaction site is reduced by the heat of reduction, which is advantageous for dephosphorization and disadvantageous for decarburization. At that time, heat compensation for the dephosphorization treatment may be performed by using an external heat source such as a burner so that the heat source is not insufficient due to the heat of reduction even if a raw material mainly composed of iron oxide is used. Since the decarburization reaction tends to be more dominant than the dephosphorization reaction at the end of the dephosphorization treatment in which the P concentration in the hot metal decreases, the decarburization suppressing effect can be enhanced by using iron oxide.

Next, the amount of generated slag is optimized.
The amount of dephosphorizing agent is adjusted by balance calculation to optimize the amount of slag so that the phosphoric acid concentration in the slag exceeds the target value when the dephosphorization reaction progresses to the target concentration of P in the hot metal. do. If the amount of slag is too small, the dephosphorization reaction stops when the phosphoric acid reaches the upper limit of equilibrium, and after that, the decarburization reaction proceeds unilaterally, and it becomes difficult for the P concentration in the hot metal to drop to the target value. On the other hand, if the amount of slag is too large, it becomes difficult for the phosphoric acid concentration in the slag to reach the target value even if the P concentration in the hot metal drops to the target value. Therefore, by optimizing the amount of slag, it is possible to cause a competitive reaction between the dephosphorization reaction and the decarburization reaction until the end, which leads to suppression of the decarburization reaction.

Next is to optimize the stirring force.
Since the oxygen potential between the slag metals is non-equilibrium, when strong stirring is performed, carbon in the hot metal reacts violently with iron oxide in the slag, and the decarburization reaction easily proceeds. Therefore, the stirring should be performed so as not to be the mass transfer rate-determining factor of phosphorus or phosphoric acid. On the other hand, if the agitation of the slag is too weak, an external heat source such as a burner is used, so that the surface temperature of the slag rises and the heat transfer efficiency deteriorates, so that the minimum agitation force is secured.

By improving these points, a more preferable dephosphorization treatment becomes possible.
The most effective dephosphorization treatment is a treatment in which all dephosphorizing agents containing CaO are projected by a burner, all oxygen sources are supplied from a raw material mainly composed of iron oxide, and a shortage of a heat source is compensated by a burner.
However, since the fuel cost becomes too high, it is necessary to consider how little fuel can be used to enjoy the same effect.
Based on this viewpoint, a specific method for producing a phosphate fertilizer raw material of the present disclosure will be described below.

First, an apparatus used in the method for producing a phosphoric acid fertilizer raw material of the present disclosure will be described.
The apparatus shown in FIG. 1 includes a pan 10 for accommodating hot metal 11A, an accommodating portion 12A for accommodating an iron oxide-based raw material as an oxygen source, an accommodating portion 12B for accommodating a dephosphorizing agent, and an iron oxide-based apparatus. A burner device 14 for projecting a burner of the raw material and / or a dephosphorizing agent, a top blowing lance 16 for blowing oxygen gas as an oxygen source into the hot metal 11A, and a bottom blowing blade for blowing nitrogen or an inert gas into the hot metal 11A. A port 18 and an exhaust duct 20 are provided. In FIG. 1, 10B indicates a derinsed lag, and 14A indicates a burner.
In the method for producing a phosphoric acid fertilizer raw material of the present disclosure, for example, the phosphoric acid fertilizer raw material is produced by using the apparatus shown in FIG. In the following description, the reference numerals in the apparatus shown in FIG. 1 will be omitted.

In the method for producing a phosphoric acid fertilizer raw material of the present disclosure, for example, as shown in FIG. 1, hot metal having a P concentration of 0.3% by mass or more and a C concentration of 2% by mass or more (hereinafter, also referred to as “initial hot metal”) is used. Store in a ladle. Then, an oxygen source and a dephosphorizing agent containing CaO are supplied to the contained initial hot metal, and the dephosphorizing treatment is performed until the P concentration in the hot metal becomes 0.06 to 0.15% by mass.

Here, if the P concentration in the normal hot metal after the dephosphorization treatment exceeds 0.15% by mass, it becomes difficult to produce high-grade steel by subsequent converter blowing. Further, if the P concentration in the normal hot metal after the dephosphorization treatment is less than 0.06% by mass, it is difficult to secure the phosphoric acid concentration in the derinsed lag at 15% by mass or more by phosphorus distribution. Further, the decarburization reaction proceeds at the final stage of the dephosphorization treatment, and the C concentration in the hot metal becomes low or slag forming occurs.

As the initial hot metal, hot metal having a C concentration of 2.0% by mass or more and a P concentration of 0.3% by mass or more is applied. On the other hand, in the method for producing a phosphoric acid fertilizer raw material, even if the P concentration of the initial hot metal is low, the normal hot metal having a P concentration of 0.06 to 0.15% by mass and the dephosphorized slag having a phosphoric acid concentration of 15% by mass or more. Can be obtained. Therefore, the P concentration of the initial hot metal is 0.3% by mass or more and less than 1.0% by mass, 0.3% by mass or more and 0.9% by mass or less, 0.3% by mass or more and 0.8% by mass or less, 0. It may be 3% by mass or more and 0.7% by mass or less.
The upper limit of the C concentration of the initial hot metal is, for example, 4.5% by mass or less.

The dephosphorizing agent is supplied by irradiating the burner from the burner device toward the slag and projecting the burner. Details of the method for supplying the dephosphorizing agent will be described later.
The type of dephosphorizing agent is not particularly limited, but it is preferable to include, for example, one or more selected from the group consisting of quicklime, limestone, dolomite, light-baked dolomite, converter slag, and silica stone.
On the other hand, the oxygen source is basically supplied by blowing oxygen gas from the top blow lance. However, at the final stage of the dephosphorization treatment, the oxygen source is preferably supplied by adding a raw material mainly composed of iron oxide. Details of the oxygen source supply method will be described later.

The basicity (C / S) in the derinsed slag produced by supplying the oxygen source and the dephosphorizing agent is 2.5 or more, preferably 3.0 or more. When the basicity (C / S) in the derinsed lag is less than 2.5, the phosphorus distribution ratio is low. Therefore, when the P concentration in the hot metal is reduced to 0.15% by mass, the phosphoric acid concentration in the derinsed lag is reduced to 15. It becomes impossible to secure more than mass%.
The lower limit of the basicity (C / S) in the derinsed lag may exceed 2.5, 2.6 or more, or 2.7 or more. On the other hand, the upper limit of basicity (C / S) during derinsing lag is, for example, 4.0.

If the basicity of the derinsed slag is high, the melting point of the slag rises, the viscosity of the derinsed slag decreases, and the reaction efficiency between the slag metals decreases. Therefore, the basicity (C / S) in the derinsed lag cannot be 2.5 or more.
Therefore, in order to dissolve the slag, the burner is irradiated from the burner device. In addition, among the dephosphorizing agents to be added, a dephosphorizing agent of 50% by mass or more of the required input amount of CaO is projected by a burner.
As described above, all the dephosphorizing agents may be added at a high temperature by burner projection, but after the start of the dephosphorizing treatment, a part of the dephosphorizing agent may be injected in a batch or continuously in a short time. The dephosphorizing agent may be added without heating. That is, some dephosphorizers may be added without heating.

In the temperature range (1300 to 1400 ° C.) for dephosphorization of hot metal, it is difficult to dissolve slag with high basicity. Therefore, by projecting the dephosphorizing agent with a burner, the temperature of the dephosphorizing agent is raised and the temperature of the slag is raised. Thereby, the dissolution of the dephosphorizing agent can be promoted, and the fluidity and uniformity of the slag can be improved.
Further, by promoting the dissolution of the dephosphorization agent, it lowers the activity coefficient of phosphoric acid to encourage binding to phosphate (P 2 _{O 5)} and CaO. As a result, rephosphorus can be suppressed and a high concentration of phosphoric acid can be secured in the slag. This effect is particularly large when a phosphoric acid fertilizer raw material having a high phosphoric acid concentration and a particularly high fertilizer effect is produced.

If the basicity (C / S) in the slag is about 1.5 in the temperature range (1300 to 1400 ° C.) of the hot metal dephosphorization treatment, the dephosphorizer dissolves easily. Therefore, until the basicity (C / S) is about 1.5, it is not necessary to use a burner to project the dephosphorizing agent with a burner, and the dephosphorizing agent is added from above the ladle by a usual method. However, the reactivity does not decrease.
Therefore, in order to reduce the cost of the burner fuel, a dephosphorizing agent having a maximum input amount of 50% by mass of the required amount of CaO is treated in a powdery or lumpy state. After the start, while supplying oxygen gas, the dephosphorizing agent is added all at once or continuously from above the pan, and then the remaining dephosphorizing agent of 50% by mass or more and less than 100% by mass of the required amount of CaO is added to the basicity of 2. Burner projection may be used to raise the temperature to .5 or higher.

That is, as shown in FIG. 4, it is preferable to add a part of the dephosphorizing agent without heating in the first half of the dephosphorization treatment and to burner the remaining dephosphorizing agent in the latter half of the dephosphorization treatment.
Specifically, in the dephosphorization treatment, among the dephosphorizing agents, until the basicity (C / S) in the slag reaches 1.5, it exceeds 0% by mass and 50% by mass or less of the required input amount of CaO. (Preferably, 10% by mass or more and 50% by mass or less, or 20% by mass or more and 50% by mass or less) of the dephosphorizing agent may be added to the hot metal without heating.
Then, in order to increase the basicity (C / S) in the slag from 1.5 to 2.5 or more, 50% by mass or more and 50% by mass or less and less than 100% by mass (preferably 50) of the required input amount of CaO. It is preferable to burner project a dephosphorizing agent (by mass% or more and 90% by mass or less, or 50% by mass or more and 80% by mass or less) onto the hot metal.

If the cost of the burner fuel is within an acceptable range, all the dephosphorizing agents in the required input amount may be burner-projected in order to simplify the operation. When the dephosphoric acid agent is burner-projected, the average particle size of the dephosphoric acid agent is preferably 2 mm or less.

To supply the oxygen source, first, oxygen gas is blown from the top-blown lance, and then, at the final stage of the dephosphorization treatment, an iron oxide-based raw material containing oxygen corresponding to an oxygen intensity of ^{at least 1.5 Nm 3 / t is added.} Is preferable. Specifically, when the P concentration in the hot metal drops to 0.2% by mass or less, an iron oxide-based raw material containing oxygen corresponding to an oxygen intensity of ^{at least 1.5 Nm 3 / t can be added.} preferable.
Since the dephosphorizing agent containing CaO has a high melting point, it does not easily dissolve even if it becomes a compound, but the raw material mainly composed of iron oxide dissolves easily in slag without heating with a burner. Therefore, the iron oxide-based raw material may be burner-projected together with the burner via the burner device, but the iron oxide-based raw material may not necessarily be burner-projected and may be added without heating from above the ladle as usual. ..

That is, as shown in FIG. 4, in the first half of the dephosphorization treatment, oxygen gas may be blown as an oxygen source, and in the final stage of the dephosphorization treatment, a raw material mainly composed of iron oxide may be burner-projected or unheated and added as an oxygen source.
Specifically, at the final stage of the dephosphorization treatment (specifically, the stage where the P concentration in the hot metal has decreased to 0.2% by mass or less), ^{oxygen of at least 1.5 Nm 3} / t or more with respect to the hot metal A raw material mainly composed of iron oxide containing oxygen corresponding to the basic unit may be continuously burner-projected or unheated and added as an oxygen source.
Examples of the raw material mainly composed of iron oxide include iron ore powder, dust powder, and scale powder.

The iron oxide-based raw material functions as a coolant and also has a function of suppressing a decarburization reaction. That is, by cooling the reaction site with the heat of reduction, the temperature rise at the reaction interface is suppressed, the dephosphorization reaction is promoted, and the decarburization reaction is suppressed. Therefore, at least at the timing when the dephosphorization reaction decreases and the decarburization reaction becomes the main component, it is preferable to stop the supply of oxygen gas and change the oxygen source to a raw material mainly composed of iron oxide. That is, when the P concentration in the hot metal drops to around 0.2% by mass, the main body of the reaction shifts from the dephosphorization reaction to the decarburization reaction. Here, it is assumed that the amount of oxygen required to reduce the P concentration in the hot metal from 0.2% by mass to 0.15% by mass is 0.45 Nm ³ / t, and the dephosphorization oxygen efficiency at that time is 30%. The required amount of oxygen is 1.5 Nm ³ / t.
Therefore, if at least 1.5 Nm ³ / t of oxygen is supplied as a raw material mainly composed of iron oxide, the decarburization suppressing effect can be exhibited at the timing when the decarburization reaction is most activated. Of course, 1.5 Nm ³ / t is the minimum value, and if the fuel cost is acceptable, a raw material mainly composed of iron oxide may be used.

Further, since the iron oxide-based raw material is not sparingly soluble, it is not always necessary to add it using a burner, and it may be added from above the ladle (that is, non-heated addition). On the other hand, when the required energy is input, if the amount of powder corresponding to the input energy cannot be secured only by the dephosphorizing agent, it is preferable to burner project a part or all of the iron oxide-based raw material. In addition, as an oxygen source supply method, oxygen gas is supplied at the initial stage of dephosphorization treatment in which the dephosphorization reaction is predominant, and after supplying the required amount of oxygen, it is switched to burner projection of iron oxide-based raw material, and iron oxide-based material is used. It is preferable to continuously supply the raw materials.

During the dephosphorization treatment, it is preferable to blow nitrogen or an inert gas as the stirring gas from the bottom blowing tuyere for the purpose of stirring the hot metal and slag. At that time, it is preferable that the flow rate of the stirring gas is 2 to 40 NL / t / min so that the (T.Fe) in the slag is 5% by mass or more and 20% by mass or less. However, the method of introducing the stirring gas is not limited to the bottom blowing tuyere, and may be introduced from the immersion lance.
In addition, (T.Fe) means the content of Fe (iron).

As shown in FIG. 2, when the flow rate of the agitating gas (denoted as the bottom blowing flow rate in FIG. 2) is large, it can be seen that when the P concentration in the hot metal decreases, the C concentration in the hot metal also tends to decrease. That is, if the flow rate of the stirring gas is too large, the reaction between carbon in the hot metal and iron oxide is promoted by strong stirring, and decarburization proceeds and (T.Fe) decreases at the same time. Therefore, the upper limit of the flow rate of the stirring gas is preferably 40 NL / t / min.
On the other hand, if the flow rate of the stirring gas is too small, (T.Fe) in the slag increases and the flow rate of the slag decreases, so that the heat transfer efficiency of the burner decreases. In addition, the movement of P in the hot metal is stagnant, and the dephosphorization reaction is suppressed. Therefore, the lower limit of the flow rate of the stirring gas is preferably 2NL / t / min.
By adjusting the flow rate of the stirring gas as described above, (T.Fe) in the slag can be adjusted to 5 to 20% by mass, and the dephosphorization reaction can be made higher and the decarburization reaction can be made lower. can.
When the (T.Fe) of the slag is 5% by mass or less, the dephosphorization treatment capacity tends to decrease due to the decrease in the oxygen potential of the slag. On the other hand, when the (T.Fe) content of the slag exceeds 20% by mass, the (P ₂ O ₅ ) concentration and the (CaO) concentration in the slag tend to decrease, particularly high (P). _{In the 2} O ₅ ) concentration range, it is not preferable because it has an effect of reducing the dephosphorization treatment ability.
As a method for adjusting the (T.Fe) of the slag, when the (T.Fe) in the slag is high, a carbon source is put into the slag surface, or only bottom blowing stirring is continued after the dephosphorization treatment. , (T.Fe) may be adjusted within the above range.

Further, if the amount of derinsed slag becomes too large, it may be difficult to secure the phosphoric acid concentration in the slag by 15% by mass or more. Therefore, if necessary, the high-phosphorus hot metal may be desiliconized before the dephosphorization treatment to reduce the amount of lime input.

Next, an example of the present disclosure will be described. The conditions in the examples are one condition example adopted for confirming the feasibility and effect of the present disclosure, and the present disclosure is based on this one condition example. It is not limited. The present disclosure may adopt various conditions as long as the gist of the present disclosure is not deviated and the object of the present disclosure is achieved.

First, 100 tons of initial hot metal (hot metal with a high P concentration) having the composition shown in Table 1 was prepared in a ladle, and dephosphorization treatment was performed under the conditions shown in Table 1. During the dephosphorization treatment, 2 NL / t / min (200 NL / min) of nitrogen gas was blown into the hot metal from the bottom blowing tuyere as a stirring gas. In addition, experiments were conducted in the disclosed example and the comparative example under different conditions as follows. In addition,% in Table 1 means mass%.

In Comparative Example 1, oxygen gas was blown from the top-blown lance as an oxygen source at a constant speed of ^{14.2 Nm 3 / t in 60 minutes.} Further, 20 minutes after the start of the treatment as an oxygen source, a total of 16.4 kg / t of iron ore was continuously charged from above the pan at a rate of 50 kg / min. Further, at the initial stage of the dephosphorization treatment, 12.4 kg / t of quicklime, 8.1 kg / t of light-baked dolomite, and 8.6 kg / t of silica sand were added as dephosphorizing agents from above the ladle in a short time. .. At this time, the dephosphorizing agent was not heated by a burner.

In Comparative Example 2, oxygen gas was blown from the top-blown lance as an oxygen source at a constant level of ^{12.7 Nm 3 / t for 60 minutes.} Further, 30 minutes after the start of the treatment as an oxygen source, a total of 7.9 kg / t of iron ore was continuously charged from above the ladle at a rate of 30 kg / min. In addition, at the initial stage of the dephosphorization treatment, 30.9 kg / t of converter slag, 1.90 kg / t of light-baked dolomite, and 3.4 kg / t of silica sand are added as dephosphorizing agents from above the pan in a short time. bottom. At this time, the dephosphorizing agent was not heated by a burner.

In Disclosure Example 1, a total of 32.7 kg / t of iron ore was continuously shot from above the ladle as an oxygen source during the dephosphorization treatment. At this time, oxygen gas was not blown.
On the other hand, the burner was continuously irradiated toward the slag in an amount of LPG intensity 6.32Nm ³ / t in 65 minutes to the end of the processing start (rate of 600Nm ³ / h). At this time, 19.7 kg / t of converter slag, 3.9 kg / t of quicklime, and 2.0 kg / t of light-baked dolomite were continuously and evenly and continuously projected as a dephosphorizing agent together with the burner.

In Disclosure Example 2, from the start of the dephosphorization treatment, oxygen gas 5.3 Nm ³ / t is blown from the top blowing lance for 32 minutes, and after the oxygen gas blowing is completed, iron ore 15.0 kg / t is blown in about 20 minutes. Continuously put in.
On the other hand, an amount of dephosphorizing agent corresponding to 40% of the required input amount of CaO was collectively added at the initial stage of the dephosphorization treatment. At this time, the dephosphorizing agent was not heated by a burner. After the oxygen gas blowing is completed, it switches the burner, and irradiated with 27 minutes burner toward the slag in an amount of LPG intensity 2.66Nm ³ / t (rate of 600Nm ³ / h). At this time, an amount of dephosphorizing agent corresponding to 60% of the required input amount of CaO was uniformly and continuously burned.
As the dephosphorizing agent, a mixture of 23 kg / t of converter slag powder, 3.8 kg / t of quicklime, and 2.50 kg / t of lightly baked dolomite was used in total.
Further, the amount of (T.Fe) in the slag at the end of the dephosphorization treatment was around 20% by mass, but before the completion of the dephosphorization treatment, 0.8 kg / t of smokeless charcoal powder was added to finally. (T.Fe) in the slag was adjusted to 13.3% by mass.

In Disclosure Example 3, from the start of the dephosphorization treatment, oxygen gas 10.4 Nm ³ / t is blown from the top blowing lance for 32 minutes, and after the oxygen gas blowing is completed, iron ore 7.5 kg / t is blown in about 8 minutes. Continuously put in.
On the other hand, an amount of dephosphorizing agent corresponding to 50% of the required input amount of CaO was collectively added at the initial stage of the dephosphorization treatment. At this time, the dephosphorizing agent was not heated by a burner. After the oxygen gas blowing is completed, it switches the burner, and irradiated with 22 minutes burner toward the slag in an amount of LPG intensity 0.55Nm ³ / t (rate of 150Nm ³ / h). At this time, an amount of dephosphorizing agent corresponding to 50% of the required input amount of CaO was uniformly and continuously burned.
A total of 12.4 kg / t of quicklime and 4.8 kg / t of light-baked dolomite was used as the dephosphorizing agent, and 3.9 kg / t of silica sand was separately added without heating from above the ladle.
Further, the amount of (T.Fe) in the slag at the end of the dephosphorization treatment was around 20% by mass, but before the completion of the dephosphorization treatment, 0.8 kg / t of smokeless charcoal powder was added and finally. (T.Fe) in the slag was adjusted to 13.0% by mass.

In Comparative Example 3, from the start of the dephosphorization treatment, oxygen gas 10.8 Nm ³ / t was blown from the top blowing lance for 33 minutes, and after the oxygen gas blowing was completed, iron ore 7.0 kg / t was blown in about 8 minutes. Continuously put in.
On the other hand, an amount of dephosphorizing agent corresponding to 50% of the required input amount of CaO was collectively added at the initial stage of the dephosphorization treatment. At this time, the dephosphorizing agent was not heated by a burner. After the oxygen gas blowing is completed, it switches the burner, and irradiated with 22 minutes burner toward the slag in an amount of LPG intensity 0.74Nm ³ / t (rate of 200Nm ³ / h). At this time, an amount of dephosphorizing agent corresponding to 50% of the required input amount of CaO was uniformly and continuously burned.
A total of 15.0 kg / t of quicklime and 5.2 kg / t of light-baked dolomite was used as the dephosphorizing agent, and 5.4 kg / t of silica sand was separately added without heating from above the ladle.
Further, the amount of (T.Fe) in the slag at the end of the dephosphorization treatment was around 20% by mass, but before the completion of the dephosphorization treatment, 0.9 kg / t of smokeless charcoal powder was added to finally. (T.Fe) in the slag was adjusted to 10.5% by mass.

In Comparative Example 1, iron ore was added at the end of the treatment to promote the dephosphorization reaction, but since the burner was not heated, the dephosphorization agent could be added only to the extent that the viscosity of the slag did not increase too much. There wasn't. Therefore, since the basicity was low at 1.58, the dephosphorization reaction was not sufficient, and the _{concentration of phosphoric acid (P 2} O ₅ ) in the slag was lower than 15% by mass.
Similarly, in Comparative Example 2, iron ore was added at the end of the treatment to promote the dephosphorization reaction, but the basicity was as low as 1.72 because the burner was not heated. Therefore, the dephosphorization reaction was not sufficient, and the _{concentration of phosphoric acid (P 2} O ₅ ) in the slag was lower than 15% by mass.

On the other hand, in Disclosure Example 1, the entire dephosphorizing agent was burner-projected, and the basicity of the dephosphorizing lag could be as high as 3.21. _{Therefore, the concentration of phosphoric acid (P 2} O ₅ ) in the dephosphorized slag could be made higher than 15% by mass while dephosphorizing the P concentration in the hot metal to 0.12% by mass. In addition, since oxygen gas was not sprayed, the amount of decarburized hot metal could be suppressed as compared with Comparative Examples 1 and 2.

In Disclosure Example 2, only the amount of the dephosphorizing agent corresponding to 60% of the required input amount of CaO was burner-projected, but the basicity of the derinsing lag could be as high as 3.18. _{Therefore, the concentration of phosphoric acid (P 2} O ₅ ) in the dephosphorized slag could be made higher than 15% by mass while dephosphorizing the P concentration in the hot metal to 0.12% by mass. Further, in the latter half of the dephosphorization treatment in which the P concentration in the hot metal becomes low, oxygen gas was not sprayed, so that the decarburized amount of the hot metal could be suppressed as compared with Comparative Examples 1 and 2. Furthermore, by limiting the application period of the burner to the latter half of the dephosphorization treatment, the LPG consumption could be reduced ^{from 6.32 Nm 3} / t to 2.66 Nm ^{3 / t.}

In Disclosure Example 3, only the amount of the dephosphorizing agent corresponding to 50% of the required input amount of CaO was burner-projected, but the basicity of the derinsing lag could be as high as 2.5. _{Therefore, the concentration of phosphoric acid (P 2} O ₅ ) in the dephosphorized slag could be made higher than 15% by mass while dephosphorizing the P concentration in the hot metal to 0.12% by mass. Further, in the latter half of the dephosphorization treatment in which the P concentration in the hot metal becomes low, oxygen gas was not sprayed, so that the decarburized amount of the hot metal could be suppressed as compared with Comparative Examples 1 and 2. Furthermore, by limiting the application period of the burner to the latter half of the dephosphorization treatment, the LPG consumption could be reduced ^{from 6.32 Nm 3} / t to 0.55 Nm ^{3 / t.}

In Comparative Example 3, the basicity of the derinsed slag was as low as 2.4 because the amount of silica sand input was increased for the purpose of enhancing the silicic acid fertilizer effect of the slag. Therefore, even if the P concentration in the hot metal can be dephosphorized to 0.12% by mass, the phosphoric acid (P ₂ O ₅ ) concentration in the derinsed slag is lower than 15% by mass.

The description of the reference numerals in the drawings is as follows.
10 Ladle 10A Hot metal 10B Derinsed lag 12A Storage part for iron oxide-based raw material 12B Storage part for dephosphorizing agent 14 Burner device 16 Top blow lance 18 Bottom blow tuyere

The entire disclosure of Japanese Patent Application No. 2019-048152 is incorporated herein by reference in its entirety.
All documents, patent applications, and technical standards described herein are to the same extent as if the individual documents, patent applications, and technical standards were specifically and individually stated to be incorporated by reference. Incorporated herein by reference.

Claims (6)

Of the dephosphorizing agents, in the dephosphorizing treatment in which an oxygen source and a dephosphorizing agent containing CaO are supplied to hot metal having a C concentration of 2.0% by mass or more and a P concentration of 0.3% by mass or more. A dephosphorizing agent of 50% by mass or more of the required amount of CaO is projected onto the hot metal with a burner, and the basicity (CaO) / (SiO ₂ ) of the derinsed lag generated is adjusted to 2.5 or more. , A method for producing a phosphoric acid fertilizer raw material, which obtains a normal hot metal having a P concentration of 0.06 to 0.15% by mass and a dephosphorized slag having a phosphoric acid concentration of 15% by mass or more. The method for producing a phosphoric acid fertilizer raw material according to claim 1, wherein the P concentration of the hot metal is 0.3% by mass or more and less than 1.0% by mass. The phosphoric acid fertilizer raw material according to claim 1 or 2, wherein a dephosphorizing agent of 50% by mass or more and less than 100% by mass of the required input amount of CaO is projected onto the hot metal with a burner. Manufacturing method. At the final stage of the dephosphorization treatment, a raw material mainly composed of iron oxide containing oxygen corresponding to an oxygen intensity of ^{at least 1.5 Nm 3 / t or more with respect to the hot metal is continuously burned or projected as the oxygen source.} The method for producing a phosphoric acid fertilizer raw material according to any one of claims 1 to 3, wherein the phosphoric acid fertilizer is added without heating. Nitrogen or an inert gas is blown into the hot metal at 2 to 40 NL / t / min by a bottom blowing tuyere or a dipping lance, and the (T.Fe) of the derinsed lag is adjusted to 5% by mass or more and 20% by mass or less. The method for producing a phosphoric acid fertilizer raw material according to any one of claims 1 to 4, wherein the method is adjusted so as to be. The dephosphorizing agent according to any one of claims 1 to 5, which comprises one or more selected from the group consisting of fresh lime, limestone, dolomite, light-baked dolomite, converter slag, and silica stone. Method of manufacturing phosphoric acid fertilizer raw material.

Images