JP2008261038A - Treatment method for melting and reforming steelmaking slag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treatment method for melting and reforming steelmaking slag with high efficiency, in order to obtain such a slag of high quality as to contain little free CaO and have adequate volume stability. <P>SOLUTION: When melting and reforming the steelmaking slag by supplying a silicic-acid-containing material of a reforming material to a burner by airflow transportation, while supplying fuel and a combustion-supporting gas to the burner and burning them, and adding the silicic acid-containing material to the steelmaking slag in a molten state existing in a slag ladle which is placed right under the burner, this treatment method includes the steps of: previously determining a distance (P) between a burner exhaust-nozzle and a position at which a flame temperature of the thermal spraying burner becomes highest, and a distance (M) between the burner exhaust-nozzle and a position at which the silicic-acid-containing material keeps the molten state, according to the scheduled treatment condition on the property and amount of each of the silicic-acid-containing material, the fuel and the gas supplied to the burner; setting the location of the burner so that a distance (J) between the burner exhaust-nozzle and the slag surface can be in a range of P<J≤M; and melting and reforming the steelmaking slag. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for processing steelmaking slag, and more particularly, to a method for reforming steelmaking slag generated during a refining process in a steelmaking process in a molten state.

  Steelmaking slag produced by the refining process of the steelmaking process such as hot metal pretreatment and decarburization process includes free CaO (may be described as f.CaO), and this f. The volume expands due to the hydration reaction of CaO, and many minute cracks and open pores may be generated. F. Steelmaking slag containing a large amount of CaO has low volume stability. In addition, molten steelmaking slag contains a large amount of bubbles (mainly CO gas). When the molten steelmaking slag containing bubbles is cooled, the molten steel slag is solidified in a state containing bubbles, so that the water absorption rate is low and the quality is low.

  For this reason, steelmaking slag is used exclusively for low-grade applications such as temporary materials for civil engineering, road ground improvement materials, lower-layer roadbed materials, etc., and for higher-grade applications such as upper-layer roadbed materials, concrete aggregates, and stone raw materials. It is difficult to use.

  On the other hand, in order to effectively use steelmaking slag for applications such as upper roadbed materials, concrete aggregates, stone materials, etc., in order to improve the quality of steelmaking slag and increase its commercial value, F. Reducing CaO or reducing bubbles in molten steelmaking slag has been performed. For example, when used as an upper layer roadbed material or an aggregate for concrete, f. CaO is 0.1% or less and the water absorption is 3.0% or less.

For example, Non-Patent Document 1 describes a method of reforming decarburized slag discharged from a converter in a molten state. In this method, oxygen and silicic acid (SiO ₂ ) -containing modifier are blown into the molten slag through an immersion lance, and FeO in the slag is oxidized to Fe ₂ O ₃ , which is heated by the reaction heat and melted. The basicity of slag (CaO / SiO ₂ ) is reduced by the modifying material while maintaining the above, and the undehydrated lime is changed into a volume-stable compound (2CaO · SiO ₂ ).

  Further, for example, Patent Document 1 and Patent Document 2 disclose that slag is produced by spraying a reforming material on a steelmaking slag discharged from a refining furnace for performing hot metal preliminary treatment or decarburization treatment to a slag pan using an oxygen burner. A method for melting and reforming steelmaking slag characterized by reforming is disclosed.

M.M. Kuehn, et al. , 2nd European Steelmaking Congress, Taranto (1997) p445-453. JP 2004-331449 A JP 2006-169089 A

  The above-mentioned method of Non-Patent Document 1 is effective when fluidity is ensured at a high temperature of 1600 ° C. or higher like slag after decarburization treatment, while slag temperature and T.V. When Fe (total Fe amount) is low, the slag sensible heat is insufficient, and when the basicity of slag is high, the viscosity at the same temperature is increased compared to the case of low slag. The reforming effect is reduced. That is, there is a problem that the slag temperature and slag composition are restricted.

  On the other hand, since the patent document 1 and the patent document 2 heat slag from the outside with an oxygen burner, the above-mentioned problem of the non-patent document 1 can be solved.

  That is, the point that the amount of heat for performing the melt reforming process is insufficient only by the slag sensible heat of the molten slag discharged from the refining furnace can be solved by supplying a heat source using an oxygen burner. For example, even if a highly viscous slag of less than 1600 ° C. is heated sufficiently with an oxygen burner, the fluidity of the slag can be improved.

At the same time, the modifier is sprayed to reduce the basicity of the slag to lower the melting point, thereby promoting the melting of the slag and the reaction of f · CaO to 2CaO · SiO ₂ . The reforming material sprayed from the oxygen burner adheres to the surface of the slag after being melted in the burner flame in addition to the reforming action, so that the heat receiving efficiency of the slag can be improved.

  In this way, by heating from the outside of the slag with an oxygen burner, restrictions on the slag temperature and composition can be reduced. Moreover, if a modifier is added after fluidity improvement, the whole slag can be uniformly and efficiently modified.

  However, due to insufficient melting of the modifier in the burner flame, when unmelted modifier is added to the slag, the slag temperature is decreased by conversely depriving the slag of slag. Therefore, since there is a concern that the molten state of the slag cannot be maintained, further improvement is desired.

  However, Patent Document 1 discloses that in an example, the oxygen burner is lowered and irradiated onto the slag surface, but there is no description of a specific height condition. And the burner conditions and the modifier addition conditions for spraying the modifier on the slag liquid surface in a molten state are unknown. Further, Patent Document 2 only discloses that it is preferable to set the position where the temperature of the flame ejected from the lower end of the burner becomes the highest near the liquid surface of the molten slag. The specific conditions of the position where the flame temperature is highest are not described.

  The present invention has been made to solve the above-mentioned problems, and provides a method for melt-modifying steelmaking slag with high efficiency, f. The object is to obtain a high-quality slag containing almost no CaO and having good volume stability.

  In order to solve the above-mentioned problems, the present inventor conducted intensive studies and investigated the relationship between the burner conditions and the molten state of the modifier. Based on this knowledge, the present invention has been completed.

That is, the gist of the present invention is as follows.
(1) While burning the burner, a silicic acid-containing substance is supplied as a modifier to the burner by a carrier gas, and the silicic acid-containing substance is added to the molten steelmaking slag in a slag pan arranged immediately below the burner. Then, when performing the melt reforming treatment of the steelmaking slag, the distance from the burner outlet to the position where the flame temperature of the burner becomes maximum according to the planned burner combustion condition and the silicic acid-containing substance supply condition (P) and the maximum distance (M) from the burner outlet where the silicic acid-containing substance is maintained in a molten state are obtained in advance, and the distance from the burner outlet to the surface of the steel slag (J) is set so that it may become the range of P <J <= M, and a melt-modification process is performed, The melt-modification process method of the steelmaking slag characterized by the above-mentioned.
(2) In accordance with the planned burner combustion conditions and the silicic acid-containing substance supply conditions, the variation length (ΔL) of the flame length (L) of the burner is obtained in advance, and the burner outlet The distance (J) from the surface of the steelmaking slag to the surface of the steelmaking slag is in the range of (P + ΔL / 2) <J ≦ M. The method of melt reforming treatment of steelmaking slag according to (1),
(3) The method for melt reforming steelmaking slag according to (1) or (2), wherein the silicic acid-containing substance is coal ash.

  According to the present invention, it is possible to perform the melt reforming treatment of steelmaking slag (hereinafter sometimes simply referred to as “slag”) with high efficiency, f. It is possible to obtain a high-quality slag containing almost no CaO with high efficiency.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

(Target for reforming treatment)
In the present invention, steelmaking slag is subject to reforming treatment, and the steelmaking slag to be reformed is not particularly limited. For example, decarburization slag, hot metal pretreatment slag, electric furnace slag, or the like may be used. I can do it.

(Need to maintain molten state of slag to be modified)
In the present invention, the steelmaking slag in a molten state is used to perform the reforming process while maintaining the molten state. The treatment in the molten state is to improve the fluidity and f. This is to promote the reduction of CaO. By adding a silicic acid-containing modifier to the molten slag, unreacted f. CaO and SiO ₂ are reacted to f. CaO can be reduced. Therefore, f. Volume expansion due to CaO hydration (CaO + H ₂ O → Ca (OH) ₂ ) can be prevented. Since slag below the melting temperature has poor fluidity, f. The reaction between CaO and the modifier SiO ₂ does not proceed sufficiently, resulting in f. CaO cannot be reduced.

(Definition of molten state of slag)
The “molten slag” may be a slag having fluidity, and does not necessarily have to be in a completely liquid phase before the start of the reforming process. As a specific index, the liquid phase ratio may be 30% or more when expressed by an estimated value obtained by commercially available thermodynamic calculation model software (for example, SOLGASMIX). As the reforming process is continued, the basicity is lowered by heating and thermal spraying of the reforming material. As a result, the solid phase ratio is lowered. As a result, the fluidity is further improved and the reforming is promoted.

(Necessity of molten state of modifier)
As described above, in the slag melt reforming treatment, maintaining the molten state of the slag, f. It is important that the silicic acid-containing modifier sprayed from the burner is also attached to and added to the slag surface in a molten state for the two reasons of promoting the reaction between CaO and the modifier SiO _2. is there. This is because when the modifiers are left in an unmelted state or are added to the slag after the temperature has been reduced and solidified even if they have been melted in the burner flame, these modifiers are removed from the slag. This is because, since sensible heat is taken away, the slag temperature is lowered, and the molten state of the slag cannot be maintained. Furthermore, in an unmelted modifier or a modifier that has been once melted and solidified, the f. The reaction rate with CaO is slow and efficient reforming cannot be performed.

(About the distance from the burner spout to the slag hot water surface)
Therefore, the present inventor adds the silicic acid-containing modifier sprayed from the burner to the slag hot water surface in a molten state, thereby melt-treating the steelmaking slag with higher efficiency than before, f. In order to find this condition for the purpose of obtaining high-quality slag containing almost no CaO and good volume stability, the relationship between the burner condition and the molten state of the modifier was investigated. And based on the result, the requirements of the present invention for the distance from the burner outlet to the slag hot water surface were determined. The results of investigating the relationship between the two will be described below with reference to the accompanying drawings.

  Spraying the silicic acid-containing reformer downward under various burner combustion conditions, changing the distance just below the burner outlet to increase stepwise, confirming the sampling status of the reformer and collecting it The cross section of the modifier was observed to investigate the molten state.

  The burner used in the experiment is a kerosene burner, using kerosene as fuel, pure oxygen as a combustion-supporting gas, coal ash as a silicic acid-containing substance as a reforming material, and air as a gas for conveying the air flow of the reforming material. Supplied.

  The amount of kerosene supplied at a burner output of 100% was 200 liters / minute, and the oxygen ratio was 1.0 (that is, the stoichiometrically required equivalent for kerosene combustion). The oxygen ratio includes oxygen in the air for conveying the modifier. The silicic acid-containing substance is supplied by a carrier gas. Regarding the silicic acid-containing substance supply condition, the mass ratio of the modifier to the carrier air, that is, (modifier supply mass per unit time) / (convey per unit time) Air supply mass, carrier air density 1.293 g / liter) is defined as solid-gas ratio, changing solid-gas ratio and burner output, distance from burner outlet, melting state of modifier, burner flame length ( L), the variation length of the flame length (ΔL), the flame temperature distribution, the distance (P) at which the flame temperature peaks, and the maximum distance at which the modifier can maintain the molten state (the case of “maximum melting distance”) Yes) (M) was investigated.

  The burner flame length (L) was evaluated on the video screen. The burner flame length (L) fluctuated instantaneously, but the average length was evaluated at the center position of the fluctuation range.

  The flame fluctuation length (ΔL) was defined as the difference between the shortest length and the longest length instantaneously. Therefore, the instantaneous flame length is in the range of L ± ΔL / 2.

  The flame temperature was measured using a thermocouple. Since the flame temperature has a distribution in the radial direction of the flame, the highest temperature in the radial direction is defined as the flame temperature at the temperature measurement position in the flame direction. And the relationship between the distance from a burner outlet and flame temperature was calculated | required, and the distance where flame temperature shows a peak was made into peak temperature distance (P).

  When evaluating whether or not the silicic acid-containing modifier sprayed from the burner is in a molten state, a judgment index is provided for two cases: discrimination between an unmelted state and a molten state, and discrimination between a molten state and a resolidified state. Is required.

  The molten state of the modifier was evaluated by the following method. Change the distance just below the burner outlet spraying the reforming material downward to increase it stepwise, insert the iron plate for a certain time (10 seconds in this experiment), and collect the modifying material The collection status was confirmed.

  Specifically, when the distance for collecting the modifying material from the burner outlet is small, the modifying material is in an unmelted state, so it was difficult to collect it on the iron plate, but this distance is not less than a predetermined size (A). Then, since the modifier is in a molten state, it is collected by adhering to the iron plate. However, when this distance is further increased, the reformed material once melted in a re-solidified state at another predetermined size (B) or more becomes difficult to collect again on the iron plate.

  As for the sampling situation of the modifying material, it was found that the sampling situation suddenly changed for each of the predetermined distance (A) or another predetermined distance (B). The melting state of the modifier can be determined.

  By the way, with regard to discrimination between the unmelted state and the molten state, paying attention to observing the properties of the modifier, the sampled modifier is embedded in the resin and then polished, and the cross section is observed with a scanning electron microscope. Also, the molten state was evaluated.

  As a result, the unmelted modifier was porous with many fine pores distributed on the surface and inside, and its cross section was also porous.

  On the other hand, the individual grains of the molten modifier are spherical (not completely spherical, but covered with a smooth curved surface), often agglomerate and form clusters, and the cross section is It is dense and homogeneous. This is because when the modifier is melted by receiving heat, the micropores are filled in the liquid phase, or bubbles as micropores are removed to the outside. In addition, although there are cases where voids remain in a part of the cross section of the melted part, the original micropores are united at the time of melting, and the size is several times larger than the micropores of the unmelted part. Was confirmed.

  Therefore, from the above viewpoint, it is easy to distinguish between the melted part and the unmelted part of the reforming material. It turned out that it can be evaluated.

  Therefore, in the above-described experiment, when the distance from which the modifying material is collected from the burner outlet is A or more, when the cross section of each grain of the modifying material collected on the iron plate is observed, an unmelted portion is present at the center. Although some cases remained, most were melted, and it was confirmed that the area ratio of the melted portion was 90% or more in each grain of the reforming material. Accordingly, it was found that if the area ratio of the melted portion of the reformer cross section is 90% or more in one grain, it can be determined that the reformer grain is in a molten state.

Therefore, by observing the cross section of the reformer grain of at least 100 modifiers (in the case where a cluster is formed, each grain constituting the cluster is one), the reformer grains in the molten state are observed. Is the area ratio of
{(Total cross-sectional area of the reformer grains in the molten state) / (sum of cross-sectional areas of all the reformer grains)} × 100 (%)
A method may be used for determining that the melting state is 90% or more. Here, the reason that the number of the modifiers to be observed is at least 100 is that the reliability of the determination of the molten state has been confirmed separately by experiments.

  Note that, regarding the discrimination between the unmelted state and the molten state, this method may be used as a determination index instead of or in combination with the above-described method of collecting the iron plate.

  The evaluation results based on the above-described determination index of the melting state of the modifier are shown in FIGS.

  FIG. 1 shows the evaluation results when the solid-gas ratio is as large as 20.5. The vertical axis in FIG. 1 is the distance (m) from the burner outlet, and the horizontal axis is the burner output (%). The flame length L and the distance P at which the flame temperature peaks increase as the output increases. The distance P at which the flame temperature reaches a peak was approximately L / 2.

  It was found that the modifier could be evaluated as a molten state at a position beyond the distance P at which the flame temperature peaked. Incidentally, the discrimination between the unmelted state and the molten state was evaluated by the area ratio of the melted portion of the reformer cross section, and those having an area ratio of 90% or more were evaluated as the molten state. This is because the temperature of the reformer increases after receiving heat from the flame, so that the molten material reaches a molten state after the maximum amount of heat at the distance P at which the flame temperature reaches a peak. It is done.

  Next, the discrimination between the melted state and the re-solidified state was evaluated according to the state of sampling of the reforming material on the iron plate, and the maximum melting distance M of the reforming material was measured. 1 that the maximum melting distance M is shorter than the flame length L.

  Furthermore, with regard to the relationship between the unmelted state and the molten state, it was found that the molten state is surely obtained at a position exceeding P + ΔL / 2, where ΔL is the variation length of the flame.

  Specifically, at a position exceeding P + ΔL / 2, it was confirmed that the area ratio of the melted portion of the reformer cross section was 95% or more, and it was found that the melt was sufficiently melted.

  The flame fluctuation length ΔL is defined as the difference between the shortest instantaneous length and the longest length. Since the above-described flame length L is an average distance, the peak temperature position instantaneously varies between P ± ΔL / 2 at the maximum. Therefore, while the modifying material moves to a position exceeding P + ΔL / 2, it can always pass through the peak temperature portion, and the molten state can be more reliably maintained.

  On the other hand, FIG. 2 shows the evaluation results when the solid-gas ratio is reduced to 0.5. As the output increases, the flame length L and the temperature peak distance P tend to increase as in FIG.

  Further, the reformed material could be evaluated as being in a molten state at a position beyond the distance P at which the flame temperature peaks, and the area ratio of the melted portion of the reformer cross section being 90% or more, P + Δ If the position exceeds L / 2, it is surely in a molten state, and the area ratio of the melted portion of the reformer cross section is 95% or more when the solid-gas ratio is 20.5 (FIG. 1). Reference).

  However, when the maximum melting distance M of the reforming material is evaluated according to the sampling state of the reforming material on the iron plate in the same manner as described above, the point that the maximum melting position M becomes longer than the flame length L is different from FIG. It was.

  The reason for this is that when the solid-gas ratio is small, the amount of reforming material to be blown is small, so that the amount of heat given to the reforming material per unit mass increases even under the same flame conditions, and the distance P at which the flame temperature peaks is set. This is because the temperature of the reforming material reaches a higher temperature than in the case of FIG.

  For the above reasons, in the present invention, the distance (J) from the burner outlet to which the modifier is sprayed to the slag surface is the distance (P) from the burner outlet at the position where the flame temperature of the thermal spray burner is the highest. When the distance (M) from the burner outlet where the silicic acid-containing substance is maintained in a molten state is set, P <J ≦ M can be set so that the molten modifier can be supplied to the slag.

  Furthermore, it is further preferable that (P + ΔL / 2) <J ≦ M because the molten modifier can be more reliably supplied to the slag.

  In addition, as described above, the maximum melting distance M changes with respect to the flame length L according to the solid-gas ratio. Therefore, when the burner installation position is limited, the solid-gas ratio is adjusted to improve the molten state. Material may be supplied to the slag.

(Need to clarify reforming treatment conditions and various indicators in advance)
In the present invention, prior to the slag reforming treatment, the respective properties of the silicic acid-containing reforming material, the fuel, and the supply gas to the burner, and the supply amount, in advance, corresponding to the planned processing conditions, The flame length L, the variation length ΔL of the flame length, the distance P at which the flame temperature reaches a peak, and the maximum melting distance M from the burner outlet where the reformer maintains a molten state are obtained. This prior study can be performed by using the above-described experimental method.

  Incidentally, the above-mentioned L, ΔL, P, and M are greatly affected by the burner output and the solid-gas ratio, but other factors (for example, the type of fuel, the size of the reformer, etc.) also have an effect. It is more preferable to clarify the relationship between the reforming process condition (burner condition) and L, ΔL, P, and M using an actual reforming process facility.

(Evaluation method of flame length L)
As an evaluation method of the burner flame length L, for example, it may be evaluated visually or on a video screen. Although the actual flame tip fluctuates within a certain range, it may be evaluated at the center position (average position) of the fluctuation range. It is preferable to evaluate the fluctuation over a certain period of time because a flame length at a certain moment is captured in a photograph or a still image.

(Evaluation method of peak temperature distance P)
The flame temperature distribution may be measured using, for example, a thermocouple or a high-temperature radiation thermometer. As described above, since the flame temperature is distributed in the radial direction, the highest temperature in the radial direction of the flame is set as the flame temperature at that position. Then, the relationship between the distance from the burner outlet and the flame temperature is obtained, and the distance at which the flame temperature reaches a peak is defined as a peak temperature distance P. When the peak temperature continues over a certain range, P is the position farthest from the burner outlet.

(Requirements for modifiers)
As the modifying material, any silicic acid-containing substance, that is, a material containing SiO ₂ may be used. This SiO ₂ reduces the basicity (CaO / SiO _{2 on a} mass basis) of steelmaking slag, and f. Necessary for reacting with CaO to form a compound with good volume stability (2CaO.SiO ₂ ). For example, coal ash, silica sand and the like can be exemplified, but not limited thereto. Also, the size of the modifying material is not particularly limited as long as, for example, coal ash is a fine powder in which several tens of μm or less occupies most, but can be sprayed from a burner.

(Burner requirements)
As the burner fuel, for example, kerosene, heavy oil, LPG, pulverized coal, or the like can be used. Further, the reforming process may be performed with a plurality of burners. In that case, it is only necessary to satisfy the requirements of the present invention for each burner, and the respective burner conditions may be different.

  In addition, oxygen is used as the combustion-supporting gas for the burner, but it may be pure oxygen or air.

  Furthermore, air is recommended as a gas for carrying the reformer by airflow, but it is not limited to this, and it is mixed with oxygen necessary for combustion, or a carrier gas unrelated to combustion is used. May be.

  Therefore, the gas for conveying the combustion-supporting gas and the reforming material in a gas stream is collectively referred to as a supply gas to the burner.

  Incidentally, the solid-gas ratio is defined by (reforming material supply mass per unit time) / (carrier gas supply mass per unit time).

  Hereinafter, specific examples of the present invention will be described.

Example 1
20 tons of hot metal pretreatment slag was charged into a reforming pan, transferred in the molten state under the burner, and reformed under the following conditions. Kerosene was used as the burner fuel, and oxygen, carrier air, and coal ash were supplied as a modifier. The kerosene supply rate was 500 liters / hour, the oxygen ratio was 1.0, and the solid-gas ratio was 20.1. The processing time is 50 minutes. The flame length L, the flame length variation length ΔL, the peak temperature distance P, and the maximum melting distance M of the reforming material under the burner combustion / spraying conditions are scheduled using actual equipment prior to the reforming process. The experiment was conducted under the same conditions. Moreover, about the judgment of the molten state of a modifier and an unmelted state, it evaluated by the area ratio of the fusion | melting part of a modifier cross section. Specifically, in accordance with the evaluation method described in [0039] and [0040] described above, the cross section of the reformer grain of 100 modifiers was observed, and the melting part was observed in the cross section of the single reformer grain. The reformer grains having an area ratio of 90% or more are referred to as “molten reformer grains”, and the area ratio of “modifier grains in the molten state” occupying the cross-sectional area of all the reformer grains is 90%. The case where it became the above was judged to be a molten state. About judgment of a molten state and a re-solidification state, as a result of investigating beforehand by evaluating with the collection condition to an iron plate, L = 5.2m, (DELTA) L = 0.6m, P = 2.7m, M = It was 4.4 m.

  The slag before the modification treatment and the components of the sprayed coal ash are shown in Tables 1 and 2 below.

  Under the above conditions, the reforming process was performed by changing the distance J from the burner outlet to the steelmaking slag liquid level at a plurality of levels.

  During the reforming treatment, it was visually evaluated whether the steelmaking slag was maintained in a molten state or whether the reformed material sprayed from the burner sufficiently adhered to the slag liquid surface.

  In addition, after the reforming treatment, the pan is tilted and discharged into another container to be solidified, f. CaO was analyzed and water absorption was evaluated.

  The results are shown in Table 3.

  No. The distance J of 1 is 2.8 m, which is far from P and satisfies the requirement of the first invention of the present application that the slag liquid level is maintained below M. And No. 2 and No. The distance J of 3 is 3.4 m and 4.4 m, respectively, which satisfy the requirement of the second invention of the present application that the slag liquid level is maintained below M and not more than P + ΔL / 2. In this case, the molten state of the slag was always maintained, and the modifier adhered well to the slag liquid surface and melted in the slag. In particular, no. 2 and No. No. 3 was very good in terms of adhesion because it melted in the slag immediately after adhesion. F. Of slag after reforming treatment. Since CaO achieved 0.1% by mass or less and a water absorption rate of 3.0% by mass or less, it could be used as an upper roadbed material or a concrete aggregate.

  On the other hand, no. No. 4 has a distance J of 2.5 m and is closer than the peak temperature distance P. Since the distance J of 5 is 4.6 m and far from M, the requirement of the present invention is not satisfied. In this case, since the modifier reached the slag liquid level in an unmelted state or a re-solidified state, the slag temperature was lowered, and the molten state of the slag was not maintained and solidification proceeded. Since the reforming material reached the slag liquid level in an unmelted or re-solidified state, and the slag liquid surface solidified, the adhesion of the modifying material was poor. As a result, since the reforming reaction did not proceed, f. CaO was not improved, the water absorption was 5% by mass or more, and the desired level of characteristics could not be obtained.

(Example 2)
20 tons of hot metal pretreatment slag was charged into a reforming pan, transferred in the molten state under the burner, and reformed under the following conditions. LPG was used as the burner fuel, and oxygen, carrier air, and silica sand were supplied as a modifier. The processing time was 35 minutes. The kerosene supply rate was 700 liters / hour, the oxygen ratio was 1.0, and the solid-gas ratio was 0.9. Prior to the reforming process, flame length L, flame length variation length ΔL, peak temperature distance P, and maximum melting distance M of the reforming material under the burner combustion / spraying conditions are the same as in Example 1. As a result of investigation in advance, L = 6.4 m, ΔL = 0.9 m, P = 3.3 m, and M = 7.4 m.

  The slag before the reforming treatment and the components of the sprayed coal ash are shown in Tables 4 and 5 below.

  Under the above conditions, the reforming process was performed by changing the distance J from the burner outlet to the steelmaking slag liquid level at the level shown in Table 6. The situation during the reforming process and the slag characteristics after the reforming process were evaluated in the same manner as in Example 1. The results are shown in Table 6.

  No. No. 6 satisfies the requirement of the first invention of the present application that the distance J is 3.4 m, is farther than P, and holds the slag liquid level below M. No. 7 and no. The distance J of 8 is 3.8 m and 6.4 m, respectively, which is an example satisfying the requirement of the second invention of the present application that the slag liquid level is maintained at a distance that is farther than P + ΔL / 2 and below M. . In this case, the molten state of the slag was always maintained, and the modifier was well adhered to the slag liquid surface and then melted in the slag. In particular, no. 7 and no. No. 8 was very good in adhesion because it melted in the slag immediately after adhesion. F. Of slag after reforming treatment. Since CaO achieved 0.1% by mass or less and a water absorption rate of 3.0% by mass or less, it could be used as an upper roadbed material or a concrete aggregate.

  On the other hand, no. No. 9 has a distance J of 3.1 m and is closer than the peak temperature distance P. No. 10 does not satisfy the requirements of the present invention because the distance J is 7.5 m and is further than M. In this case, since the modifier reached the slag liquid level in an unmelted state or a re-solidified state, the slag temperature was lowered, and the molten state of the slag was not maintained and solidification proceeded. Since the reforming material reached the slag liquid level in an unmelted or re-solidified state, and the slag liquid surface solidified, the adhesion of the modifying material was poor. As a result, since the reforming reaction did not proceed, f. CaO was not improved and the water absorption rate exceeded 3% by mass, and the desired level of properties could not be obtained.

  As mentioned above, although the Example of this invention was described with the comparative example, this invention is not limited to said example. It will be understood that various changes or modifications that can be easily estimated by those skilled in the art within the scope of the claims are also within the technical scope of the present invention.

It is explanatory drawing which shows the relationship (in the case of solid-gas ratio 20.5) of a burner output, the melting condition of a modifier, and burner flame length. It is explanatory drawing which shows the relationship (in the case of solid-gas ratio 0.5) of a burner output, the melting condition of a modifier, and burner flame length.

Claims (3)

While burning the burner, a silicic acid-containing substance is supplied to the burner as a modifier by a carrier gas, and the silicic acid-containing substance is added to the molten steelmaking slag in the slag pan arranged immediately below the burner. When performing slag melt reforming treatment,
Depending on the burner burning conditions and the silicic acid-containing substance supply conditions that are planned, the distance (P) from the burner outlet to the position where the flame temperature of the burner becomes maximum, and the silicic acid-containing substance is in a molten state. The maximum distance (M) from the burner outlet that is maintained is obtained in advance,
Melting and reforming of steelmaking slag, characterized in that the melting and reforming treatment is performed by setting the distance (J) from the burner outlet to the surface of the steelmaking slag so as to be in the range of P <J ≦ M. Processing method. In accordance with the planned burner combustion conditions and the silicic acid-containing substance supply conditions, the variation length (ΔL) of the flame length (L) of the burner is obtained in advance,
The distance (J) from the burner outlet to the surface of the steelmaking slag is in the range of (P + ΔL / 2) <J ≦ M. Quality processing method.   The method for melt reforming steelmaking slag according to claim 1 or 2, wherein the silicic acid-containing substance is coal ash.

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