JP3958914B2 - Solidification method of steelmaking slag - Google Patents

Description

【００１０】
【化２】

ケイ酸カルシウム水和物やエトリンガイトは不溶性であり、これらの化合物が水を結晶水として取り込みながら固体として析出し、空間に占める固体の割合が増加することにより固化していく。石炭灰の機能は、各材料を混合する際の分散性の向上である。石炭灰は平均粒径１５μｍ程度で球状に近い粒子が多く含まれる。これにより集塊状となっている土壌のフロック構造に進入して、ＣａＯ、ＣａＳＯ₄、Ｈ₂Ｏ、ＳｉＯ₂、Ａｌ₂Ｏ₃などの化学種が拡散するスペースを増加させる。スラグを５ｍｍアンダーに破砕するのは、５ｍｍを越えると比表面積が減少し、高炉水砕微粉末等との反応効率が低下するからである。下限値は特に規定するものではない。スラグの配合量を２５〜７５質量％とするのは、２５質量％未満ではＣａＯが不足し、ケイ酸カルシウム水和物やエトリンガイトが十分に生成しない。７５質量％を越えるとケイ酸カルシウム水和物やエトリンガイト生成に必要な他の物質が不足し、未反応の遊離ＣａＯが残存する。高炉水砕微粉末の配合量を１０〜４０質量％とするのは、１０質量％未満ではＳｉＯ₂やＡｌ₂Ｏ₃の溶出量が不足する。４０質量％を越えるとケイ酸カルシウム水和物やエトリンガイト生成に必要な他の物質が不足し、未反応の高炉水砕微粉末が残存する。高炉スラグのなかでは高炉水砕微粉末が最も好ましい。高炉水砕スラグでも未破砕品は製造時の水との接触により表面が不活性層に覆われており、反応性が十分ではない。従って高炉水砕スラグを粉砕した高炉水砕微粉末を用いる。その平均粒径の範囲は２〜４０μｍが望ましい。石炭灰の配合量を１０〜５０質量％とするのは、１０質量％未満では分散性が不十分であり、５０質量％を越えると石炭灰がスラグや高炉水砕微粉末を覆ってしまい、反応が阻害される。石膏の配合量を１〜１０質量％とするのは、１質量％未満ではＣａＳＯ₄が不足しエトリンガイトが十分に生成しない。１０質量％を越えるとエトリンガイトが過剰に生成し、その結晶成長圧により組織が破壊される。水を外掛けで４０〜７０質量％添加するのは、４０質量％未満では流動性発現に必要な水が不足し、ピットや地面に流すのが困難となる。７０質量％を越えると固化時の空隙が増加し強度が低下する。混練してから２週間以上養生するのは、２週間未満では、固化後破砕するために必要な強度が得られないからである。養生期間の上限は特にない。固化後に３０ｍｍアンダーに破砕して更に２週間以上養生するのは、少量残留している未反応分へ雨水等の水分を供給して反応をほぼ完結させるためである。ここでも上限は特にない。３０ｍｍアンダーに破砕するのは、３０ｍｍを越えると水分が内部へ十分に浸透しない。下限値は特になく、用途に応じて適正な粒径にすることが望ましい。更に２週間以上養生するのは、２週間未満では、反応が完結するのに不十分である。ここで、最初の２週間以上または次の２週間以上のいずれか一方、あるいは両方で雨水のような天然水だけでなく、人工的に水分を散布してもよい。ここで破砕後の養生での天然または人工の水分の供給量は、特に規定するものではないが、例えば固化物に対して外掛けで１０質量％程度以上あれば望ましい。
【００１１】
【実施例】
以下、本発明を実施例に基づいて説明する。
【００１２】
本実施例の製鋼スラグ、高炉水砕スラグ、石炭灰の化学組成を表１に示す。
【００１３】
製鋼スラグを冷却・凝固させた後、５ｍｍアンダーに破砕するか、あるいは５ｍｍよりも粗い粒度で破砕して分級し５ｍｍアンダー品を得た。この製鋼スラグを各種物質と表２に示す割合で混合し、養生・固化した。本発明例１〜９で高炉水砕微粉末の平均粒径は１０μｍである。比較例としては、個々の因子が本発明例の範囲から外れる場合を選んだ。
【００１４】
表３の従来法１が特開平１１−７１１６０号公報に示されるように製鋼スラグを破砕し三方を仕切壁で囲んだピット内に山積みし下から炭酸ガスを吹き込んでスラグを炭酸固化する方法である。ここでは、３ｍｍアンダーの転炉スラグ粉を幅４ｍ×奥行６ｍのピット内に高さ１．５ｍに山積みして適度に締め固めた後、ピットを密閉し、炭酸ガスを供給量５０ｍ³（Ｎｏｒｍａｌ）／ｈで３日間吹き込み、スラグを炭酸固化させた。表２および表３にコスト比率および固化の状況も示す。ここで、コスト比率とは、固化物１ｔ当たり必要な材料費について従来法１を１００とし、その他を１００に対する比率で示したものである。
【００１５】
表２を表３と比較すると、本発明例はいずれも比較例に対して固化が良好であり、また従来法に対してコストの点で有利である。
【００１６】
【発明の効果】
本発明により、製鋼スラグの微粉分を冷間で安価に固化させることができた。従って、高純度の炭酸ガスや高価なセメントを使わずに、主に産業上の副産物を利用して製鋼スラグを固化させることが可能となった。
【００１７】
この方法は、ステンレススラグのようにダスティングで粉化するスラグの固化にも有効である。
【００１８】
【表１】

【００１９】
【表２】

【００２０】
【表３】

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for solidifying steelmaking slag at low cost.
[0002]
[Prior art]
In general, steelmaking slag (hereinafter abbreviated as slag) remains in a form in which lime is liberated in the slag (hereinafter referred to as free CaO), so when used as it is for road materials, civil engineering materials, etc. It is known that swelling occurs due to hydroxylation of free CaO. Therefore, at present, the free CaO is stabilized by naturally cooling and crushing the slag and then stacking it outdoors or artificially contacting it with water vapor. However, after stabilization, slag collapses due to expansion of free CaO due to hydroxylation, and the fine powder content increases. If the fine powder content increases too much, the filling property deteriorates and it becomes difficult to use as a road material. Therefore, it is desirable to collect and solidify a part of the fine powder. It is also more desirable to solidify in the cold because it costs more when remelted hot.
[0003]
As a method of solidifying the slag in a cold state, for example, as shown in JP-A-11-71160, steelmaking slag is crushed and piled up in a pit surrounded by three partition walls, and carbon dioxide gas is blown from below. There is a method of carbonating slag.
[0004]
[Problems to be solved by the invention]
This inventor tried to apply said method to solidification of the steelmaking slag fines after aging. As a result, it has been found that high-purity carbon dioxide gas is expensive and expensive to process.
[0005]
An object of the present invention is to solve this problem and solidify the steelmaking slag fine powder at low cost.
[0006]
[Means for Solving the Problems]
The present invention is 25 to 75% by mass, 10 to 40% by mass of granulated blast furnace powder, 10 to 50% by mass of coal ash, Mix 10% by mass, add 40-70% by mass of water to the total solid mass after mixing, knead and cure for 2 weeks or longer, crush to 30mm under after solidification and further 2 weeks or longer It is a solidification method of steelmaking slag characterized by curing.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below.
[0008]
Steelmaking slag generated in converters, kneading wheels, hot metal ladle, molten steel pan, etc. is cooled, solidified and crushed. Next, classification is performed before or after aging to obtain a fine powder under 5 mm. Here, under 5 mm means that the top size is 5 mm. This steelmaking slag fine powder is mixed with ground granulated blast furnace powder, coal ash, and gypsum, added with water, kneaded, and then poured into an appropriately sized pit or ground for curing. After curing and solidification, the solidified body is crushed to under 30 mm and further cured. During these curing periods, CaO from slag, SiO ₂ and Al ₂ O ₃ from blast furnace granulated fine powder, and CaSO ₄ from gypsum are eluted and react in water to produce compounds such as calcium silicate hydrate and ettringite. . The chemical reaction formula at that time is as follows.
[0009]
[Chemical 1]

[0010]
[Chemical 2]

Calcium silicate hydrate and ettringite are insoluble, and these compounds precipitate as solids while taking water as crystal water, and solidify as the proportion of solids in the space increases. The function of coal ash is to improve dispersibility when mixing each material. Coal ash contains many particles having an average particle size of about 15 μm and nearly spherical. As a result, the soil enters a floc structure of agglomerated soil and increases the space in which chemical species such as CaO, CaSO ₄ , H ₂ O, SiO ₂ , and Al ₂ O ₃ diffuse. The reason why the slag is crushed to under 5 mm is that when the thickness exceeds 5 mm, the specific surface area decreases and the reaction efficiency with blast furnace granulated fine powder and the like decreases. The lower limit is not particularly specified. The reason why the slag content is 25 to 75% by mass is that when it is less than 25% by mass, CaO is insufficient and calcium silicate hydrate and ettringite are not sufficiently formed. If it exceeds 75 mass%, calcium silicate hydrate and other substances necessary for ettringite formation are insufficient, and unreacted free CaO remains. The blending amount of the granulated blast furnace granulated powder is 10 to 40% by mass. If it is less than 10% by mass, the elution amount of SiO ₂ or Al ₂ O ₃ is insufficient. If it exceeds 40% by mass, calcium silicate hydrate and other substances necessary for producing ettringite are insufficient, and unreacted ground granulated blast furnace powder remains. Among the blast furnace slag, blast furnace granulated fine powder is most preferable. Even in the blast furnace granulated slag, the surface of the uncrushed product is covered with an inert layer due to contact with water during production, and the reactivity is not sufficient. Therefore, granulated blast furnace granulated blast furnace slag is used. The range of the average particle diameter is desirably 2 to 40 μm. The blending amount of the coal ash is 10 to 50% by mass. If the amount is less than 10% by mass, the dispersibility is insufficient. If the amount exceeds 50% by mass, the coal ash covers the slag and blast furnace granulated fine powder. The reaction is inhibited. The reason why the amount of gypsum is 1 to 10% by mass is that when it is less than 1% by mass, CaSO ₄ is insufficient and ettringite is not sufficiently formed. If it exceeds 10% by mass, ettringite is excessively generated, and the structure is destroyed by the crystal growth pressure. When adding 40 to 70% by mass of water as an outer layer, if it is less than 40% by mass, the water required for the expression of fluidity is insufficient, and it becomes difficult to flow to the pit or the ground. If it exceeds 70% by mass, voids at the time of solidification increase and the strength decreases. The reason for curing for 2 weeks or more after kneading is that the strength required for crushing after solidification cannot be obtained if it is less than 2 weeks. There is no upper limit for the curing period. The reason for crushing under 30 mm after solidification and curing for 2 weeks or more is to supply moisture such as rain water to the unreacted portion remaining in a small amount to almost complete the reaction. Again, there is no particular upper limit. The reason for crushing to under 30 mm is that the water does not sufficiently penetrate into the interior if it exceeds 30 mm. There is no particular lower limit, and it is desirable to have an appropriate particle size according to the application. Further, curing for 2 weeks or more is insufficient for completing the reaction in less than 2 weeks. Here, not only natural water such as rainwater but also water may be artificially sprayed in one or both of the first two weeks or more and the next two weeks or more. Here, the supply amount of natural or artificial water in the curing after crushing is not particularly specified, but for example, it is preferably about 10% by mass or more with respect to the solidified product.
[0011]
【Example】
Hereinafter, the present invention will be described based on examples.
[0012]
Table 1 shows the chemical compositions of steelmaking slag, granulated blast furnace slag, and coal ash of this example.
[0013]
After the steelmaking slag was cooled and solidified, it was crushed to under 5 mm, or crushed with a particle size coarser than 5 mm and classified to obtain a 5 mm under product. This steelmaking slag was mixed with various substances in the proportions shown in Table 2, and cured and solidified. In Examples 1 to 9 of the present invention, the average particle size of the ground granulated blast furnace powder is 10 μm. As a comparative example, the case where individual factors deviated from the scope of the present invention example was selected.
[0014]
Conventional method 1 in Table 3 is a method in which steelmaking slag is crushed and piled in a pit surrounded by a partition wall and carbon dioxide gas is blown from below to solidify the slag as disclosed in JP-A-11-71160. is there. Here, after compacted moderately tighten pile height 1.5m in the converter slag powder 3mm under wide 4m × depth 6m pit, sealing the pit, the supply amount 50 m ³ of carbon dioxide (Normal ) / H was blown for 3 days to solidify the slag. Tables 2 and 3 also show the cost ratio and solidification status. Here, the cost ratio is a ratio of the material cost required per 1 t of the solidified product to the conventional method 1 of 100 and the other to the ratio of 100.
[0015]
Comparing Table 2 with Table 3, all of the inventive examples are better solidified than the comparative examples, and are advantageous in terms of cost over the conventional method.
[0016]
【The invention's effect】
According to the present invention, it was possible to solidify the fine powder of steelmaking slag at low cost. Therefore, steelmaking slag can be solidified mainly using industrial by-products without using high-purity carbon dioxide or expensive cement.
[0017]
This method is also effective for solidifying slag that is pulverized by dusting, such as stainless slag.
[0018]
[Table 1]

[0019]
[Table 2]

[0020]
[Table 3]

Claims (1)

25 to 75% by mass, 5 to 40% by mass of ground granulated blast furnace powder, 10 to 50% by mass of coal ash, 1 to 10% by mass of gypsum Add 40 to 70% by mass of water to the total solid mass after mixing, knead and cure for 2 weeks or more, crush to 30 mm under after solidification, and further cure for 2 weeks or more A method for solidifying steelmaking slag as a feature.