JP2009084144A - Production method for solidified body of steel-making slag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for producing a solidified body of steel-making slag, whereby elusion of fluorine from the slag-solidified body composed mainly of fluorine-containing steel-making slag is suppressed, producing the slag-solidified body having high-strength, and the solidified body of steel-making slag can be converted to a civil engineering material satisfying soil environmental standards, when being recycled after using. <P>SOLUTION: The solidified body of steel-making slag is produced by the followings: using a raw material of the fluorine-containing steel-making slag having elusion pH of ≥11 as the steel-making slag; using further a solidifying agent selected from fine powders of blast furnace slag, cement, and the mixture of the fine powders of blast furnace slag with cement as a raw material; adding phosphoric acid or a phosphate to the mixture of the steel-making slag and the solidifying agent of blast furnace slag; preparing a ready-mixed concrete-like kneaded product by adding water to the resultant mixture; and solidifying whole of the kneaded product in a formwork etc. by curing. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique for producing a solidified slag made from steelmaking slag. Further, the present invention relates to a technique for producing a steelmaking slag solidified body with low fluorine elution in accordance with soil environmental standards by suppressing fluorine elution from the solidified body into water even using fluorine-containing steelmaking slag as a raw material.

  Steelmaking slag generated from steelmaking converters, steelmaking electric furnaces, etc. contains silicon oxide, calcium oxide, iron oxide, magnesium oxide, etc., and is in a molten state or a mixture of melt and solid in the furnace. . This steelmaking slag becomes a mixture of powder and lump after cooling. Because of its physical and chemical properties, it is used as a fertilizer, ground improvement material, cement material, and civil engineering material.

  Steelmaking slag is discharged from the steelmaking converter (converter slag), discharged from the steelmaking electric furnace (electric furnace slag), existing on the molten steel in the molten steel pan (no refining reaction is performed in the molten steel pan) In some cases, there are cases in which refining is performed in a molten steel smelting furnace: molten steel ladle slag), what remains in the tundish of a continuous casting machine (tundish slag), what is generated during hot metal refining (molten slag), etc. There is. Each has a different chemical component range, but generally contains silicon oxide, aluminum oxide, calcium oxide, magnesium oxide, phosphorus oxide, iron oxide, manganese oxide, and as trace elements, titanium oxide, Contains chromium oxide, sulfur, etc.

  In steelmaking processes that perform special treatment when producing high-purity steels and special alloy steels, additives that promote dephosphorization and desulfurization, dissolution accelerators that lower the melting point of slag, and oxides that are difficult to dissolve are slag. In some cases, fluorite (calcium fluoride) is added as a solvent to be dissolved. In particular, fluorite is often added when producing steel with a low content of sulfur or phosphorus or when refining in a molten steel pan. At this time, fluorine is substituted for anions such as oxygen and incorporated into the mineral composition constituting the steelmaking slag. Thus, depending on the manufacturing method in the steelmaking process, the steelmaking slag may be in a state containing fluorine.

  That is, when fluorite is used in the steelmaking process, the steelmaking slag contains fluorine, and this fluorine may be easily eluted from the steelmaking slag. Incidentally, in ordinary steelmaking slag, fluorine elution is 0.8 mg / liter or less, but the concentration of eluted fluorine from fluorine-containing steelmaking slag may be about 1 to 6 mg / liter. In 2001, the fluorine elution regulation was added to the soil environmental standards, so when using steelmaking slag in the soil environment, the amount of fluorine elution from the steelmaking slag must be 0.8 mg / liter or less. . Therefore, a technique for preventing fluorine from eluting from steelmaking slag has been invented for this purpose. For example, Patent Document 1 discloses a method for suppressing fluorine elution as a form of fluorapatite by adding a phosphorus compound to steelmaking slag when producing stainless steel or high nickel steel, and performing hot water treatment after the addition. is there. On the other hand, although it is not a method for preventing the elution of fluorine in steelmaking slag, Patent Document 2 describes a method in which a phosphoric acid compound and a calcium compound are added to a fluorine-containing solid waste and kneaded.

On the other hand, various researches have been made as methods for utilizing steelmaking slag. Conventional methods include landfill materials, sand piles (sand compaction, sand drains, etc.), roadbed materials, fertilizers, cement raw materials, and the like. However, since these applications have large demand fluctuation and low added value, new application development has been demanded. As a new application, steelmaking slag and a solidifying agent (blast furnace slag fine powder or cement) are mixed and kneaded in a state containing moisture to produce a concrete solidified body (slag solidified body). Yes. As described in, for example, Patent Document 3, this technology produces raw concrete from steelmaking slag and blast furnace slag fine powder having an appropriate particle size distribution and water immersion expansion rate, and puts this into a mold and solidifies it. To make the product. Since this slag solidified body has some material expansion after solidification, there are examples in which it is used for non-strengthening concrete such as wave-dissipating blocks, revetment upper surface construction, parking lot road surfaces, marine fishing reef blocks, and the like.
JP 2003-226906 A JP 2002-331272 A JP 2004-299922 A

  As described above, the conventional techniques for preventing elution of fluorine such as Patent Document 1 and Patent Document 2 have a problem that the optimum conditions for preventing fluorine elution of steelmaking slag having high alkalinity cannot be realized. For example, in Patent Citation 1, fluorine is fixed with fluoroapatite, but heat treatment is required to ensure the reaction. Therefore, the energy efficiency is low and the processing cost is high. It is also a method to prevent fluorine elution from steelmaking slag when producing stainless steel, Fe-Ni alloy steel and Ni-base alloy in an electric furnace. This slag is chemically different from slag generated during production of general steel. The composition is different, and there is a problem that cannot be applied to general steelmaking slag as it is.

  Further, in the method described in Patent Document 2, phosphoric acid and calcium ions are reacted with waste containing fluorine to form an apatite-based inorganic substance, and fluorine is taken into this to elute fluorine. Although this is a method of controlling, this is a general waste treatment technology, and only the conditions for adjusting the amount of phosphoric acid to be added to 0.5 to 20% by mass (vs. waste) are specified. The technology about was not established. In particular, it is not considered to apply this technique to highly basic substances such as steelmaking slag, and a method for appropriately and economically insolubilizing fluorine in steelmaking slag has not been established. Therefore, in order to prevent the elution of fluorine from the steelmaking slag, treatment conditions different from those of the conventional methods for insolubilizing fluorine are necessary, but a method considering this has not been established. As a result, there is a problem that the treatment is incomplete and fluorine elution cannot be effectively suppressed, and the amount of the treatment agent is too large, resulting in a high treatment cost.

  On the other hand, in the prior art, a method for producing a slag solidified body using steelmaking slag as a raw material has been made. However, the conventional techniques described in Patent Document 3 and the like simply use a steelmaking slag as a raw material to produce a slag solidified body. This was for the purpose of manufacturing and did not take into account suppression of fluorine elution. Therefore, it has not been considered to produce a slag solidified body using steelmaking slag with a large amount of fluorine elution as a raw material, and there has been no technology for producing a slag solidified body having high strength and little fluorine elution.

  As described above, in any of the conventional techniques, there has been no method for effectively and economically producing a slag solidified body with little fluorine elution using a steel-making slag containing fluorine. Therefore, there has been a demand for a new technique for overcoming these drawbacks of the prior art, reliably preventing fluorine elution with an inexpensive process, and producing a high-quality slag solidified body.

  The present invention has been made to solve the problems of the prior art for producing a slag solidified body using the above-described fluorine-containing steelmaking slag as a raw material. (1) to (7).

(1) As raw materials, steelmaking slag, blast furnace slag fine powder, cement, a solidifying agent selected from a mixture of blast furnace slag fine powder and cement, and phosphoric acid or phosphate are used as raw materials. As the steelmaking slag, a material having an elution pH of 11 or more and containing fluorine is used as a raw material. A mixture of these raw materials and water are kneaded to make a ready-mixed kneaded mixture. This kneaded product is cured in a mold or the like, and the entire kneaded product is solidified to produce a solidified steel slag.

(2) In the method described in (1) above, before mixing the solidifying agent and the steelmaking slag, an aqueous solution of phosphoric acid or a phosphate is added to the steelmaking slag, and the mixture is thoroughly mixed and reacted. Manufacture products with low elution. The curing time after mixing with phosphoric acid or phosphate is preferably 4 hours or more. This mixture, a solidifying agent, and water are mixed to make a ready-mixed kneaded material, which is solidified to produce a slag solidified body.

(3) In the above-mentioned method (2), calcium oxide or calcium hydroxide is further added as the raw material, and the amount of CaO in the steelmaking slag is 2% by mass or more. When the steelmaking slag contains 2% by mass or more of free CaO, it is not always necessary, but if not, lime (calcium oxide or calcium hydroxide) is added. The sum of the free CaO contained in the steelmaking slag and the CaO equivalent amount of the added lime is set to 2% or more of the steelmaking slag amount.

(4) Steelmaking slag and a solidifying agent are used as raw materials. As the steelmaking slag, a material having an elution pH of 11 or more and containing fluorine is used as a raw material. A mixture of steelmaking slag and solidifying agent and water are kneaded to make a ready-mixed kneaded material. This kneaded product is cured in a mold or the like, and the entire kneaded product is solidified to produce a solidified steel slag. A steelmaking slag solidified body in which fluorine elution is suppressed is produced by spraying water containing phosphoric acid or phosphate onto the steelmaking slag solidified body produced by this method or immersing the steelmaking slag solidified body therein.

(5) In any of the above methods (1) to (4), a steelmaking slag solidified body is obtained by using a steelmaking slag having a water immersion expansion rate of 1.5% or less measured by the method defined in JIS5015. To manufacture.

(6) In any of the above methods (1) to (5), 3% by mass or more of phosphoric acid is added to steelmaking slag having a fluorine elution concentration of 0.8 to 8 mg / liter. A solidified steelmaking slag is produced.

(7) In any of the above methods (1) to (5), the equilibrium concentration value of fluorine that is eluted in advance from the steelmaking slag is measured. The measured value is expressed as (minimum phosphoric acid addition ratio (mass% of steel slag)) = 0.037 (fluorine equilibrium concentration value (mg / l)) ² + 0.079 (fluorine equilibrium concentration value (mg / l))-0.0866 More phosphoric acid than the calculated ratio is added to the kneaded product, and further cured to produce a steelmaking slag solidified body.

(8) A method for producing a solidified slag according to the above (1) to (7), and as a raw material thereof, in addition to steelmaking slag, a solidifying agent, and phosphoric acid, fly ash generated from a boiler of a power plant, a blast furnace It is the steelmaking slag solidified body manufactured using slag granulation and slaked lime individually or in combination.

  According to the method of the present invention, a high-strength slag solidified body can be produced, and fluorine elution of the slag solidified body mainly composed of fluorine-containing steelmaking slag can be suppressed, and when the slag solidified body is recycled after use. As a civil engineering material, it is possible to make a material that satisfies the soil environmental standards.

  Steelmaking slag includes converter slag, electric furnace slag, molten steel pan slag, tundish slag, hot metal slag, and the like. In general, silicon oxide, aluminum oxide, calcium oxide, magnesium oxide, phosphorus oxide, iron oxide, manganese oxide is included, and as a trace element, titanium oxide, chromium oxide, niobium oxide, sulfur, and the like are included. The converter slag contains 10 to 20% by mass of silicon oxide, 35 to 50% by mass of calcium oxide, 2 to 8% by mass of magnesium oxide, and about 10 to 23% by mass of iron oxide in terms of T.Fe. The electric furnace slag contains 10 to 25% by mass of silicon oxide, 25 to 40% by mass of calcium oxide, 2 to 6% by mass of magnesium oxide, and about 8 to 20% by mass of iron oxide in terms of T.Fe. Molten steel pan slag and tundish slag are chemically similar, 10-30 mass% silicon oxide, 20-50 mass% calcium oxide, 10-30 mass% aluminum oxide, and T.Fe iron oxide. It contains about 2 to 10% by mass in terms of conversion. The molten iron slag contains 15 to 35% by mass of silicon oxide, 25 to 35% by mass of calcium oxide, 5 to 15% by mass of aluminum oxide, and about 2 to 10% by mass of iron oxide in terms of T.Fe.

  In the steelmaking process, it may be used as an additive for promoting dephosphorization reaction / desulfurization reaction, a dissolution accelerator for lowering the melting point of slag, and a solvent for dissolving difficult-to-dissolve oxide in slag. In particular, it is added when producing steel with a low content of sulfur or phosphorus or when refining in a molten steel pan. This fluorine is substituted into anions such as oxygen and incorporated into the mineral composition constituting the steelmaking slag.

  The manufacturing method of a slag solidified body is as FIG. 2 shows, and details are shown below. First, a steelmaking slag having a particle size of 30 mm or less is prepared. As the particle size, a ratio of 10 mm or less is preferably 60% or more and a ratio of 2 mm or less is 40% or more. When there are too many coarse things, the part which a powder does not enter between coarse grains will be made, and problems, such as a mixing efficiency falling and the intensity | strength of a steelmaking slag solidified body, will occur easily. Blast furnace slag fine powder or cement is prepared as a solidifying agent. The blast furnace slag fine powder is obtained by pulverizing blast furnace slag (water-granulated) rapidly cooled with water to about 3000 to 6000 branes. When solidification is urgently performed, cement (generally Portland cement) or a mixture of blast furnace slag fine powder and cement may be used. The blast furnace slag fine powder and cement described above are referred to as solidifying agents. If necessary, a mixed raw material to which blast furnace slag granulation, fly ash, calcium hydroxide, and the like are added is prepared. As shown in FIG. 2, phosphoric acid (phosphate) may be used as a part of the raw material or may be added after the slag solidified body is produced. These raw materials are mixed with water and kneaded with a mixer to produce a ready-mixed kneaded product. When a high-strength slag solidified body is required, an admixture such as a water reducing agent may be used. At this time, phosphoric acid or a phosphoric acid compound is preferably added to the kneaded product as an aqueous solution. Pour this into a mold, etc., cure it for several days to several tens of days, and remove it from the mold.

  Steelmaking slag may hydrate and expand after construction, and this may cause cracks in the solidified slag. Therefore, in the case of a construction body in which a problem occurs when cracks occur, it is preferable to use a steelmaking slag having a water immersion expansion rate of 1.5% or less. The water expansion coefficient is based on the method of measuring the expansion coefficient by immersing in 80 ° C. water described in JIS 5015 Annex 2 for 10 days. Particularly in the case of high basicity steelmaking slag, the water immersion expansion rate may be about 2 to 8%. In such a case, steam is added to the piled steelmaking slag and the temperature is set to 90 ° C. or more and about 5 to 14 days. By aging, the water expansion coefficient is 1.5% or less. In the case of a wave-dissipating block, a large unreinforced structure, etc., a low water immersion expansion rate is further required, and 0.4 to 0.8% or less may be required.

  The blending conditions of the raw materials are as follows. Blast furnace slag fine powder (or mixture with Portland cement) 100 to 350 kg, steelmaking slag 1400 to 1800 kg, fly ash 0 to 180 kg, and blast furnace slag fine powder 100 to 350 kg per cubic meter of steelmaking slag solidified body It may contain slag 1500-1800 kg and blast furnace slag granulation 100-300 kg. Moreover, when adding both fly ash and blast furnace slag granulation, it is good for both to be 350 kg or less in total. In the case of steelmaking slag with little free CaO and insufficient alkalinity, calcium hydroxide (slaked lime) is added under conditions of 50 kg or less. The amount of water is 200 to 350 liters.

  The steelmaking slag solidified body produced by the above procedure is used for unreinforced concrete, cement rock substitutes such as artificial rocks (rock substitutes), hardened blocks, and roadbed materials. When using it for the purpose of artificial rocks or roadbed materials, there is a method in which a large slag solidified block is manufactured and crushed. It is good to apply these to terrestrial uses where soil environmental standards are a problem. Moreover, since it contains many fertilizer components such as phosphoric acid, iron oxide, silicon, and manganese oxide, it can be used for marine applications such as algae reefs and fishing reef blocks.

  The steelmaking slag in the present invention has a fluorine elution of 0.8 mg / liter or more. As preparation for using steelmaking slag as a raw material, first, steelmaking slag is set to room temperature, and this is crushed and classified to a size of 30 mm or less. A part of this steelmaking slag is sampled and immersed in water by a method according to JISK0058 to measure the fluorine elution concentration. However, when a quick analysis is required, an ion meter, a simple colorimetric analysis kit, a colorimeter or the like can be used. The pH of this water is also preferably measured, and the free CaO ratio of this steelmaking slag may be measured. The free CaO ratio is the ratio (calculated in terms of CaO) of calcium oxide or calcium hydroxide present in the form of calcium oxide that is not included in other mineral compositions among the calcium oxide contained in the steelmaking slag at room temperature. This is because when steelmaking slag solidifies, when it changes from liquid to multiple mineral compositions, it is not taken into calcium ferrite, dicalcium silicate, etc., but it is a single phase of calcium oxide (something that becomes calcium hydroxide when left in the air). Is).

  In this invention, the elution density | concentration of the fluorine of the steelmaking slag containing a fluorine is suppressed using a phosphate ion. First, the reaction principle of the phosphate ion of the present invention will be described. Steelmaking slag is treated with water containing phosphate ions and calcium ions to insolubilize the eluted fluorine. Here, the form of the phosphate ion to be added is preferably phosphoric acid or a phosphate. The phosphate is a compound of phosphoric acid and positive ions such as sodium phosphate, sodium hydrogen phosphate, potassium phosphate, potassium hydrogen phosphate, and ammonium phosphate, and includes a polymer containing phosphoric acid. Fluorine is insolubilized by the reaction formula (1) for forming fluoroapatite from calcium ions, phosphate ions and fluorine ions.

5Ca ²⁺ + 3PO ₄ ³⁺ + F = Ca ₅ (PO ₄ ) ₃ F (1)

However, the condition for the stable presence of the fluoroapatite produced in the reaction formula (1) is that the molecule having a hydroxyl group (Ca ₅ (PO ₄ ) ₃ OH) and the fluoroapatite coexist. Thus, not all phosphate and calcium ions are consumed for fluorine immobilization.

First, the present inventors investigated the relationship between the amount of fluorine eluted from steelmaking slag and the amount of phosphoric acid to be added (the amount necessary for reduction to fluorine 0.8 mg / liter or less). As a result, it was first found that the eluted fluorine amount was about several to 30% of the amount of fluorine contained in the steelmaking slag. Next, when the ratio of Ca ₅ (PO ₄ ) ₃ F and Ca ₅ (PO ₄ ) ₃ OH in crystals precipitated by the reaction was investigated, it was found that this ratio was influenced by the pH of water. In the case of high pH, it was found that Ca ₅ (PO ₄ ) ₃ F was easily immobilized, and thus it was found that phosphoric acid addition could be suppressed. Further, if the pH is 11 or more, the calcium ion concentration in water is 40 mg / liter, so that phosphoric acid and calcium ions react rapidly when phosphoric acid is added, and the rate of apatite compound formation is high. Therefore, fluorine can be insolubilized reliably and rapidly by performing the reaction under high pH conditions. If the pH is 12 or more, the calcium ion concentration in water is 100 mg / liter or more, and there is a sufficient amount for the reaction with phosphoric acid, and the added phosphoric acid immediately becomes an apatite compound. Therefore, it is a more desirable condition that the pH is 12 or more. Therefore, in order to increase calcium ions in the water in contact with the steelmaking slag, it is preferable to promote the reaction between phosphate ions and calcium ions by the presence of calcium oxide or calcium hydroxide.

When the basicity of the steelmaking slag is increased, the amount of calcium ions eluted from the steelmaking slag is increased, and the pH of the immersion water is increased. Therefore, such a steelmaking slag has an effect of stabilizing the insolubilization reaction of fluorine and an effect of reducing the amount of calcium oxide or calcium hydroxide to be added. Here, if the ratio of the basic substance and the acidic substance is adopted as an index indicating the alkalinity of the steelmaking slag, it is good for estimating the calcium ion addition amount. As a result of various experiments, the present inventors have found that the basic value as a factor for determining the elution pH from steelmaking slag is preferably the following value. For converter slag and electric furnace slag,
[(CaO mass%) + (MgO mass%)] / (SiO ₂ mass%) (basicity 1)
In addition, in ladle slag and tundish slag with a relatively high proportion of aluminum oxide,
[(CaO mass%) + (Al ₂ O ₃ mass%)] / (SiO ₂ mass%) (basicity 2)
It is good to use. In the case of converter slag / electric furnace slag, if the basicity 1 is 3.5 or more, the elution pH is surely 11 or more, and if the basicity 1 is 3.8 or more, the elution pH is surely 12 or more. On the other hand, in molten steel pan slag and tundish slag, if the basicity 2 is 3.7 or more, the elution pH is surely 11 or more, and if the basicity 2 is 4 or more, the elution pH is definitely 12 That's it. Therefore, when the basicity 1 or basicity 2 of these steelmaking slags is a value higher than the above, stable high pH conditions can be achieved. In addition, steelmaking slag under such conditions has an effect of reducing the amount of calcium oxide, calcium hydroxide and the like added. In our experiment, if the free CaO is 2% by mass, the total amount of calcium ions necessary for insolubilizing fluorine can be supplied.

As a result of various studies on the addition method of phosphoric acid or phosphate for suppressing fluorine elution, the present inventors have added a phosphoric acid or phosphate aqueous solution to steelmaking slag in advance. . In this method, from the experimental results of the present inventors, in steelmaking slag having a fluorine elution concentration of 0.8 to 8 mg / liter, an aqueous solution containing ₃ % by mass of phosphate ions (PO ₃ ) with respect to the mass of steelmaking slag. Is applied to steelmaking slag and mixed. From the viewpoint of optimizing the viscosity of water and making the spraying uniform on the steel slag surface, the phosphoric acid concentration of the aqueous solution is preferably 10% by mass or less. By this treatment, the eluted fluorine concentration becomes 0.2 to 0.7 mg / liter.

The present inventors conducted an experiment to determine the amount of phosphoric acid added more accurately. In this experiment, the fluorine elution concentration before addition of phosphoric acid and calcium ions and the phosphoric acid addition ratio (mass ratio with respect to steelmaking slag) when the fluorine elution value becomes 0.8 mg / liter after addition of phosphoric acid and calcium ions were investigated. The experimental conditions were such that the pH of the elution water was 11-13. This result has a relationship as shown in FIG. When this relationship is subjected to multiple regression and summarized by mathematical formulas,

(Phosphate addition ratio (mass%)) = 0.037 (F elution (mg / l)) ² + 0.079 (F elution (mg / l))-0.0866 (1) Formula

It becomes. Therefore, if phosphoric acid is added in an amount greater than the amount calculated by equation (1), fluorine elution can be suppressed to 0.8 mg / liter. Further, if the amount of phosphoric acid added is increased up to 4 times the amount obtained by the formula (1), fluorine elution becomes 0.2 to 0.5 mg / liter, and more reliable treatment can be performed.

  The time for curing by mixing an aqueous solution of phosphoric acid or phosphate and steelmaking slag is preferably 4 to 2412 hours or more. The reason is that the reaction of phosphoric acid is not completed in a short period of time, and a large amount of phosphoric acid remains in the water, and ions eluting from the solidifying agent during the production of the solidified substance inhibit the reaction of forming a hydrate for solidification. That is. Moreover, it is also because the fixation reaction of fluorine ions does not end in a short time.

In the second method, the steelmaking slag solidified body produced using steelmaking slag and a solidifying agent as raw materials is made to have a size of 300 mm or less. A method of producing a slag solidified body of this size by pouring a kneaded product of steelmaking slag and a solidifying agent into a mold of 300 mm or smaller, and a large slag solidified body block are produced, and this is crushed to a size of 300 mm or smaller. There is also a method. An aqueous solution of phosphoric acid or phosphate is added to the slag solidified body. Similar to the above-described method in this method, from the experimental results of the present inventors, in steelmaking slag having a fluorine elution concentration of 0.8 to 8 mg / liter, 3% by mass of phosphate ions ( An aqueous solution containing PO ₃ ) is used, or an aqueous solution of phosphate ions in an amount according to the formula (1) is sprayed. In this case, the concentration of phosphate ions is 10% by mass or less. If the concentration is higher than this, the viscosity of water increases and the aqueous solution does not uniformly penetrate into the internal pores of the slag solidified body. Moreover, the time for curing needs 24 hours or more.

  The slag solidified body was manufactured using five types of steelmaking slag (two types of converter slag, one type of electric furnace slag, and two types of molten steel pan slag). The raw materials used other than steelmaking slag were blast furnace slag fine powder, Portland cement, fly ash, phosphoric acid, ammonium phosphate, AE water reducing agent, and slaked lime. Table 1 shows the physical properties and chemical components of these steelmaking slags.

本実施例では、表１に記載されている製鋼スラグを用いて、スラグ固化体を製造した。１０サンプルの製鋼スラグ固化体で、その製造状況と強度・フッ素溶出濃度の関係を調査した。これを表２に記載する。

In the present Example, the slag solidified body was manufactured using the steelmaking slag described in Table 1. With 10 samples of solidified steelmaking slag, the relationship between the production status and strength / fluorine elution concentration was investigated. This is described in Table 2.

サンプル１及びサンプル５では、製鋼スラグに燐酸を添加した後に、高炉スラグ微粉末の混合物に添加したスラグ固化体の例であり、サンプル３では、製鋼スラグに高炉スラグ微粉末の混合物を添加して固化させた後に、燐酸アンモニウムの水溶液を散布したスラグ固化体の例である。サンプルの形状は円筒形で、直径２５ｃｍ、高さ５０ｃｍのものであった。サンプル２とサンプル４では、固化時間を短くするために、高炉スラグ微粉末とポルトランドセメントの混合物（４７：５３）を固化剤として使用した。以上のサンプルでの強度は１９〜２５N/mm²であり、高性能のセメントコンクリートと比較するとやや強度が低いが、岩石代替等の用途では十分の強度であった。サンプル６では、高強度の製鋼スラグ固化体を製造するために、ＡＥ減水剤を使用して水比率を低下させた。その強度は３４N/mm²であり、セメントコンクリートと比較しても十分な強度のものであった。サンプル７は高炉スラグ水砕を添加した製造の例であり、また、サンプル８ではフライアッシュを添加した。いずれのサンプルの強度も製鋼スラグと固化剤の混合物で製造した製鋼スラグ固化体と同等の強度であった。サンプル９とサンプル１０では、低強度でも良い用途に用いた例であり、サンプル９の製鋼スラグ固化体を破砕して、最大サイズ３０ｍｍの路盤材原料とした。また、サンプル１０では、２ｍ角、４０ｃｍの海底敷設用のブロックを製造した。これは、搬送中の衝撃や作業中の応力が掛かる状態でも破損することなく、また、海中でも破損しなかった。

Samples 1 and 5 are examples of solidified slag added to a mixture of blast furnace slag fine powder after adding phosphoric acid to the steelmaking slag. In sample 3, a mixture of fine blast furnace slag powder is added to the steelmaking slag. It is an example of the slag solidified body which sprinkled the aqueous solution of ammonium phosphate after solidifying. The sample had a cylindrical shape with a diameter of 25 cm and a height of 50 cm. In samples 2 and 4, a mixture of blast furnace slag fine powder and Portland cement (47:53) was used as a solidifying agent in order to shorten the setting time. The strength of the above samples is 19 to 25 N / mm ^2, which is slightly lower than that of high-performance cement concrete, but is sufficient for applications such as rock substitution. In Sample 6, in order to produce a high strength steelmaking slag solidified body, the water ratio was reduced using an AE water reducing agent. The strength was 34 N / mm ² , which was sufficient even when compared with cement concrete. Sample 7 is an example of production with blast furnace slag granulation added, and sample 8 added fly ash. The strength of any sample was the same as that of the steelmaking slag solidified body produced with a mixture of steelmaking slag and solidifying agent. Samples 9 and 10 are examples in which low strength may be used, and the steelmaking slag solidified body of sample 9 was crushed to obtain a roadbed material material having a maximum size of 30 mm. In sample 10, a 2 m square, 40 cm block for laying the seabed was manufactured. This was not damaged even in a state where an impact during transportation or stress during work was applied, and it was not damaged in the sea.

  Regarding the elution of fluorine in the steelmaking slag solidified body, in any sample, the steelmaking slag without phosphoric acid was 0.8 mg / liter or more, but in the sample with phosphoric acid added, it was 0.21 to 0.78 mg / liter. The product meets the soil environmental standards.

  According to the method of the present invention, a high strength steelmaking slag solidified body can be produced, and fluorine elution of the steelmaking slag solidified body mainly composed of fluorine-containing steelmaking slag can be suppressed. Therefore, the slag solidified body is recycled after use. This slag solidified body is useful as a civil engineering material because it satisfies the soil environmental standards.

This figure is a figure which shows the relationship between the fluorine elution density | concentration from untreated steelmaking slag, and the phosphoric acid addition amount (vs. steelmaking slag mass ratio) from which a fluorine elution density | concentration will be 0.8 mg / liter. This figure is an operation flowchart showing the method for producing a solidified steel slag of the present invention.

Claims (8)

  A steelmaking slag having an elution pH of 11 or more, a solidifying agent selected from fluorine-containing steelmaking slag, blast furnace slag fine powder, cement and a mixture of blast furnace slag fine powder and cement, and phosphoric acid or phosphate as raw materials, A method for producing a solidified steelmaking slag comprising kneading a mixture of raw materials and water to produce a ready-mixed kneaded product and curing the kneaded product.   Before mixing the solidifying agent and the steelmaking slag, the steelmaking slag is mixed and reacted with an aqueous solution of phosphoric acid or phosphate, and the steelmaking slag, the solidifying agent and water are mixed, and the mixture is made of ready-mixed concrete. The method for producing a solidified steelmaking slag according to claim 1, wherein the solidified product is produced.   As the raw material, calcium oxide or calcium hydroxide is further added, and the sum of the CaO equivalent amount of the added calcium oxide or calcium hydroxide and the free CaO contained in the steelmaking slag is the steelmaking slag amount. It is 2% or more, The manufacturing method of the steel-making slag solidified body of Claim 2 characterized by the above-mentioned.   An elution pH of 11 or more and a fluorine-containing steelmaking slag, a blast furnace slag fine powder, a cement and a solidifying agent selected from a mixture of a blast furnace slag fine powder and a cement, are used as a raw material mixture and water. Kneading to make a ready-mixed concrete-like kneaded material, curing the kneaded material to produce a steelmaking slag solidified body, and then adding water containing phosphoric acid or phosphate to the steelmaking slag solidified body A method for producing a solidified steelmaking slag.   The steelmaking slag solidified body production according to any one of claims 1 to 4, wherein the steelmaking slag having a water immersion expansion rate of 1.5% or less measured by a method defined in JIS5015 is used. Method.   The steelmaking slag having a fluorine elution concentration of 0.8 to 8 mg / liter is used by adding 3% by mass or more of phosphoric acid to the steelmaking slag. Manufacturing method of steelmaking slag solidified body. Measure the fluorine equilibrium concentration value that is eluted from steelmaking slag in advance, and from the fluorine equilibrium concentration value, (minimum phosphoric acid addition ratio (mass% of steelmaking slag)) = 0.037 (fluorine equilibrium concentration value (mg / l)) ² Steelmaking according to any one of claims 1 to 5, characterized in that it is produced by adding more phosphoric acid than the ratio calculated by applying the formula +0.079 (fluorine equilibrium concentration value (mg / l))-0.0866. A method for producing a solidified slag.   Manufactured by using fly ash, granulated blast furnace slag, and slaked lime, alone or in combination, as raw materials, in addition to blast furnace slag fine powder or cement, or a mixture of blast furnace slag fine powder and cement, and phosphoric acid or phosphate. The method for producing a solidified steelmaking slag according to any one of claims 1 to 7, wherein:

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