JP4255816B2 - Method for suppressing fluorine elution in electric furnace slag - Google Patents
Method for suppressing fluorine elution in electric furnace slag Download PDFInfo
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- JP4255816B2 JP4255816B2 JP2003406581A JP2003406581A JP4255816B2 JP 4255816 B2 JP4255816 B2 JP 4255816B2 JP 2003406581 A JP2003406581 A JP 2003406581A JP 2003406581 A JP2003406581 A JP 2003406581A JP 4255816 B2 JP4255816 B2 JP 4255816B2
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Description
本発明は、電気炉スラグから溶出するフッ素を低減する方法およびフッ素溶出量の少ないスラグに関する。 The present invention relates to a method for reducing fluorine eluted from an electric furnace slag and a slag with a small amount of fluorine elution.
従来、電気炉で鋼を溶製する際に生成されるスラグ中には、原材料のスクラップや副原料から不可避的にフッ素が混入する。しかし、その混入したフッ素がスラグ中から溶出し、環境に悪影響を与えるレベルになることがわかっている。例えば、この電気炉スラグを路盤材として使用した場合、フッ素溶出量が高く、溶出基準を越える問題がある。ところが、電気炉精錬において、原材料からスラグ中へのフッ素の混入を防止することは非常に困難である。そこで、スラグ中からフッ素の溶出を抑制する方法またはスラグを改質して溶出しなくする方法が種々提案されている。 Conventionally, fluorine is unavoidably mixed from raw material scraps and auxiliary materials in slag produced when melting steel in an electric furnace. However, it has been found that the mixed fluorine is eluted from the slag and has a level that adversely affects the environment. For example, when this electric furnace slag is used as a roadbed material, there is a problem that the amount of fluorine elution is high and the elution standard is exceeded. However, in electric furnace refining, it is very difficult to prevent the entry of fluorine from raw materials into the slag. Therefore, various methods have been proposed for suppressing the elution of fluorine from the slag or for modifying the slag so as not to be eluted.
例えば、電気炉に、シリカ、シリカ〜マグネシア系物質、マンガン鉱石のうち一種類以上を特定の質量％で投入し、溶融スラグと混合後に冷却し凝固させることにより、フッ素の溶出を抑制するスラグの処理方法がある（例えば、特許文献１参照。）。 For example, in an electric furnace, one or more of silica, silica to magnesia-based material and manganese ore are charged at a specific mass%, mixed with molten slag, and then cooled and solidified, thereby suppressing the elution of fluorine. There exists a processing method (for example, refer patent document 1).
すなわち、シリカ系物質を電気炉中に投入した場合には、フッ素溶出抑制が可能なスラグ組成になる。しかし、シリカ系物質を電気炉中に投入することは、電力原単位の大幅な悪化をもたらし、コストがかかり経済的でなく、現実的な手段ではない問題がある。また、スラグ鍋に投入した場合、熱量が足りず、均一に混合することは難しい。 That is, when a silica-based material is introduced into an electric furnace, a slag composition capable of suppressing fluorine elution is obtained. However, the introduction of a silica-based material into an electric furnace causes a significant deterioration of the power consumption rate, which is costly and not economical and is not a practical means. Moreover, when thrown into a slag pan, the amount of heat is insufficient and it is difficult to mix uniformly.
さらに、フッ素を含有するスラグにカルシウム−シリケート系を主体とするＡＯＤ還元期スラグを混合し、この混合物を水分共存下で安定処理することにより、フッ素溶出を防止することからなる製鋼スラグ中のフッ素抑制方法がある（例えば、特許文献２参照）。
この方法でも、上記シリカの混合と同様の問題が起こると推定される。
Furthermore, fluorine in steelmaking slag comprising preventing fluorine elution by mixing slag containing fluorine with AOD reducing phase slag mainly composed of calcium-silicate system and subjecting the mixture to stable treatment in the presence of moisture. There is a suppression method (see, for example, Patent Document 2).
It is estimated that this method also causes the same problem as that of the silica mixing.
さらに、製鋼スラグから溶出するスラグを安定処理する方法および改質スラグの製法がある（例えば、特許文献３参照。）。
しかし、この方法も、３ＣａＯ・Ａｌ2Ｏ3などの溶出抑制物質との混合により溶出を防止する方法であるが、高コストであり、長期安定性にも問題があった。
Furthermore, there is a method for stably treating slag eluted from steelmaking slag and a method for producing modified slag (see, for example, Patent Document 3).
However, this method is also a method for preventing elution by mixing with an elution inhibitor such as 3CaO.Al 2 O 3 , but it is expensive and has a problem in long-term stability.
この発明は、電気炉に不可避的に混入するフッ素に起因してスラグ中から溶出するフッ素を抑制する方法を提供することである。 This invention is providing the method of suppressing the fluorine eluted from the slag resulting from the fluorine inevitably mixed in the electric furnace.
本発明は、電気炉で鋼を溶製する際に石灰およびフェロシリコン合金を投入し、質量％で、アルミナを１５％以下とし、かつスラグ塩基度：ＣａＯ％／ＳｉＯ2％を１．３以下にする。あるいは、電気炉内で上記範囲に造滓できない場合に、補足的にスラグ鍋内においてフェロシリコン合金を投入し、質量％で、アルミナを１５％以下とし、かつ、スラグ塩基度：ＣａＯ％／ＳｉＯ2％を１．３以下にする。 The present invention, lime and ferrosilicon alloys when Steels was charged in an electric furnace, in mass%, of alumina was 15% or less, and slag basicity: CaO% / SiO 2% to 1.3 or less To. Alternatively, when it is impossible to produce the above range in the electric furnace, a ferrosilicon alloy is added in the slag pan to make alumina 15% or less by mass%, and slag basicity: CaO% / SiO 2 Set 2 % to 1.3 or less.
すなわち、上記の課題を解決するための本発明の手段は、請求項１の発明では、電気炉で鋼を溶製する際に石灰およびフェロシリコン合金を投入し、質量％で、アルミナ１５％以下かつスラグ塩基度：ＣａＯ％／ＳｉＯ2％を１．３以下のスラグとすることを特徴とするフッ素溶出を低減したスラグの造滓方法である。 That is, the means of the present invention for solving the above-described problems is that, in the invention of claim 1, lime and ferrosilicon alloy are introduced when melting steel in an electric furnace, and alumina is 15% or less by mass%. and slag basicity: a CaO% / Zokasu method of the slag with reduced fluoride release, characterized in that SiO 2% of a 1.3 or less slag.
請求項２の発明では、電気炉で鋼を溶製する際に石灰およびフェロシリコン合金を投入して精錬した後、電気炉からスラグをスラグ鍋に受け、さらにフェロシリコン合金を投入することにより、質量％で、アルミナ１５％以下かつスラグ塩基度：ＣａＯ％／ＳｉＯ2％を１．３以下のスラグとすることを特徴とするフッ素溶出を低減したスラグの造滓方法である。 In the invention of claim 2, after melting and refining lime and ferrosilicon alloy when melting steel in an electric furnace, by receiving slag from the electric furnace into a slag pan, and further introducing ferrosilicon alloy, A method for producing slag with reduced fluorine elution, characterized in that alumina is 15% or less and slag basicity: CaO% / SiO 2 % is 1.3 or less.
本発明を適用することにより、フッ素溶出基準を満たすスラグを製造することが可能となり、電気炉スラグを路盤材として使用して環境を害することがなくなった。 By applying the present invention, it becomes possible to produce a slag that satisfies the fluorine elution standard, and it is no longer harmful to use the electric furnace slag as a roadbed material.
以下に本発明を実施するための最良の形態について説明する。なお、％は、質量％を示すものとする。
先ず、本発明における条件設定の理由について説明すると、従来、電気炉で鋼を溶製する場合、鋼種によって値が異なるが、電気炉スラグは、ＣａＯ：２５〜５０％、ＳｉＯ2：１５〜４０％、Ａｌ2Ｏ3５〜２０％、Ｔ−Ｆｅ％：５〜２０％をそれぞれ含有しており、鉱物相がダイカルシウムシリケート相（以下２ＣＳ相）またはカルシウム・アルミニウム・シリケート相（以下ＣＡＳ相）が主体となっている。通常、電気炉に不可避的に混入したフッ素は２ＣＳ相またはＣＡＳ相に濃化している。この場合、環境庁告示４６号の溶出試験を実施すると、微量のフッ素含有量でも溶出基準値を上回るものとなる。
The best mode for carrying out the present invention will be described below. In addition,% shall show the mass%.
First, the reason for setting conditions in the present invention will be described. Conventionally, when steel is melted in an electric furnace, the value varies depending on the steel type, but the electric furnace slag is CaO: 25 to 50%, SiO 2 : 15 to 40. %, Al 2 O 3 5~20% , T-Fe%: 5~20% of which contain respectively, the mineral phase Dicalcium silicate phase (hereinafter 2CS phase) or calcium-aluminum-silicate phase (hereinafter CAS phase ). Usually, the fluorine inevitably mixed in the electric furnace is concentrated in the 2CS phase or the CAS phase. In this case, when the dissolution test of Environment Agency Notification No. 46 is carried out, even a trace amount of fluorine content exceeds the dissolution standard value.
一方で、カルシウムとシリカル比が１：１のカルシウムシリケート相（以下ＣＳ相）主体のスラグにした場合、混入したフッ素はＣＳ相に濃化する。しかし、２ＣＳ相やＣＡＳ相とほぼ同量のフッ素を含有していても、フッ素の溶出量が少ない傾向が見られている。 On the other hand, when the slag is mainly composed of a calcium silicate phase (hereinafter referred to as CS phase) having a calcium to silicate ratio of 1: 1, the mixed fluorine is concentrated in the CS phase. However, even if the amount of fluorine is almost the same as that of the 2CS phase or CAS phase, there is a tendency that the amount of fluorine eluted is small.
したがって、電気炉スラグ組成をフッ素溶出量の少ないＣＳ相にすることで、フッ素溶出量を低減することが可能である。また、この組成調整の際、フェロシリコン合金を電気炉内に投入することで、酸化鉄や酸化クロムを還元回収することが可能であり経済的である。 Therefore, the amount of fluorine elution can be reduced by making the electric furnace slag composition a CS phase with a small amount of fluorine elution. In addition, when adjusting the composition, it is economical because iron oxide and chromium oxide can be reduced and recovered by introducing a ferrosilicon alloy into the electric furnace.
以下、詳細な実施例を示す。具体例として電気炉内に１５０ｔの１８−８ステンレス系スクラップを投入し、ＪＩＳのＳＵＳ３０４鋼を溶製する。その際の電気炉での原料装入量、スラグ組成、およびフッ素溶出量を本発明例と比較例により表１に示す。なお、溶出フッ素の分析方法は、各試料を５００グラム採取し、ＪＩＳ Ｋ ０１２０−３４．１に準拠し、含有フッ素分析はアルカリ融解−吸光光度法を採用し、この分析におけるフッ素の溶出液の作成は環境庁告示４６号に準拠して行った。 Hereinafter, detailed examples will be described. As a specific example, 150 ton 18-8 stainless steel scrap is put into an electric furnace, and JIS SUS304 steel is melted. The raw material charging amount, slag composition, and fluorine elution amount in the electric furnace at that time are shown in Table 1 according to examples of the present invention and comparative examples. In addition, the analysis method of elution fluorine collects 500 grams of each sample, conforms to JIS K 0120-34.1, and the fluorine content analysis adopts the alkali melting-absorptiometry method. The preparation was made in accordance with Notification 46 of the Environment Agency.
表１において、比較例１、３は電気炉に投入するフェロシリコン合金量が少なく、塩基度が高い場合であり、比較例２、４は塩基度については範囲内であるが、Ａｌ2Ｏ3％が高い場合である。いずれもフッ素溶出量が基準値（フッ素溶出量０．８ｍｇ／ｌ以下）を超えている。それに対し、本発明１〜５は、本発明を実施した場合の結果であり、いずれもフッ素溶出量は基準のフッ素溶出量０．８ｍｇ／ｌ以下を満たしている。なお、表１における発明１、発明２、発明３および発明５は本願の請求項１に該当するものである。一方、表１における発明４は請求項２に該当するものであり、これはスラグ鍋内へ追加でフェロシリコン合金を投入することで塩基度を調整した例である。 In Table 1, Comparative Examples 1 and 3 are cases where the amount of ferrosilicon alloy charged into the electric furnace is small and the basicity is high, and Comparative Examples 2 and 4 are within the range for basicity, but Al 2 O 3 % Is high. In both cases, the fluorine elution amount exceeds the reference value (fluorine elution amount 0.8 mg / l or less). On the other hand, the present inventions 1 to 5 are the results when the present invention is carried out, and all of the fluorine elution amounts satisfy the standard fluorine elution amount of 0.8 mg / l or less. In addition, Invention 1, Invention 2, Invention 3 and Invention 5 in Table 1 correspond to claim 1 of the present application. On the other hand, invention 4 in Table 1 corresponds to claim 2, which is an example in which the basicity is adjusted by additionally introducing a ferrosilicon alloy into the slag pan.
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