JP5573403B2 - Method for recycling steelmaking slag and raw material for phosphate fertilizer - Google Patents
Method for recycling steelmaking slag and raw material for phosphate fertilizer Download PDFInfo
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- JP5573403B2 JP5573403B2 JP2010141137A JP2010141137A JP5573403B2 JP 5573403 B2 JP5573403 B2 JP 5573403B2 JP 2010141137 A JP2010141137 A JP 2010141137A JP 2010141137 A JP2010141137 A JP 2010141137A JP 5573403 B2 JP5573403 B2 JP 5573403B2
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- 239000002893 slag Substances 0.000 title claims description 203
- 238000009628 steelmaking Methods 0.000 title claims description 53
- 238000000034 method Methods 0.000 title claims description 38
- 239000002994 raw material Substances 0.000 title claims description 20
- 238000004064 recycling Methods 0.000 title claims description 17
- 239000002686 phosphate fertilizer Substances 0.000 title claims description 12
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 167
- 230000009467 reduction Effects 0.000 claims description 85
- 229910052742 iron Inorganic materials 0.000 claims description 81
- 239000000463 material Substances 0.000 claims description 49
- 238000007670 refining Methods 0.000 claims description 44
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims description 32
- 229910052751 metal Inorganic materials 0.000 claims description 31
- 239000002184 metal Substances 0.000 claims description 31
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 24
- 239000000203 mixture Substances 0.000 claims description 23
- 238000005261 decarburization Methods 0.000 claims description 21
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 16
- 229910052799 carbon Inorganic materials 0.000 claims description 16
- 239000004566 building material Substances 0.000 claims description 14
- 230000006872 improvement Effects 0.000 claims description 13
- 238000002156 mixing Methods 0.000 claims description 13
- 239000010703 silicon Substances 0.000 claims description 13
- 229910052710 silicon Inorganic materials 0.000 claims description 13
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 12
- 230000032683 aging Effects 0.000 claims description 10
- 230000007613 environmental effect Effects 0.000 claims description 10
- 230000008569 process Effects 0.000 claims description 10
- 239000003638 chemical reducing agent Substances 0.000 claims description 9
- 229910052782 aluminium Inorganic materials 0.000 claims description 8
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 5
- 229910052760 oxygen Inorganic materials 0.000 claims description 5
- 239000001301 oxygen Substances 0.000 claims description 5
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical group OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 20
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 11
- 229910052698 phosphorus Inorganic materials 0.000 description 11
- 239000011574 phosphorus Substances 0.000 description 11
- 238000011084 recovery Methods 0.000 description 11
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 9
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 8
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 7
- 229910000831 Steel Inorganic materials 0.000 description 7
- 239000010959 steel Substances 0.000 description 7
- 238000001816 cooling Methods 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 239000003337 fertilizer Substances 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 5
- 229910019142 PO4 Inorganic materials 0.000 description 4
- 239000001569 carbon dioxide Substances 0.000 description 4
- 229910002092 carbon dioxide Inorganic materials 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 4
- 239000010452 phosphate Substances 0.000 description 4
- 238000011946 reduction process Methods 0.000 description 4
- 239000013535 sea water Substances 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 3
- 239000000571 coke Substances 0.000 description 3
- 238000010828 elution Methods 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 3
- 239000000377 silicon dioxide Substances 0.000 description 3
- 239000010802 sludge Substances 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 239000004568 cement Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 239000004567 concrete Substances 0.000 description 2
- 238000006703 hydration reaction Methods 0.000 description 2
- BHEPBYXIRTUNPN-UHFFFAOYSA-N hydridophosphorus(.) (triplet) Chemical compound [PH] BHEPBYXIRTUNPN-UHFFFAOYSA-N 0.000 description 2
- 239000011777 magnesium Substances 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 239000004575 stone Substances 0.000 description 2
- 229910052717 sulfur Inorganic materials 0.000 description 2
- 239000011593 sulfur Substances 0.000 description 2
- 239000002023 wood Substances 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- 238000003723 Smelting Methods 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 1
- 239000003610 charcoal Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000003795 desorption Methods 0.000 description 1
- 238000007865 diluting Methods 0.000 description 1
- 229910001882 dioxygen Inorganic materials 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000004889 fertilizer analysis Methods 0.000 description 1
- 238000002309 gasification Methods 0.000 description 1
- 239000011491 glass wool Substances 0.000 description 1
- 150000004677 hydrates Chemical class 0.000 description 1
- 230000000887 hydrating effect Effects 0.000 description 1
- 230000036571 hydration Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- LFGREXWGYUGZLY-UHFFFAOYSA-N phosphoryl Chemical compound [P]=O LFGREXWGYUGZLY-UHFFFAOYSA-N 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000002689 soil Substances 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
- Furnace Details (AREA)
- Carbon Steel Or Casting Steel Manufacturing (AREA)
- Processing Of Solid Wastes (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
- Manufacture Of Iron (AREA)
Description
本発明は、製鋼精錬プロセスのうちの転炉での溶銑の脱炭精錬において発生する脱炭精錬スラグ及び溶銑の予備脱燐処理において発生する予備脱燐スラグから、これら製鋼スラグに還元処理を施すことによって金属鉄を回収するとともに、金属鉄を回収した後の製鋼スラグを土木建築材料などに利用する方法、及び、金属鉄を回収することにより得られる燐酸肥料用原料に関する。 In the present invention, the steelmaking slag is subjected to reduction treatment from decarburization / smelting slag generated in the decarburization and refining of hot metal in a converter in the steelmaking refining process and preliminary dephosphorization slag generated in the preliminary dephosphorization of hot metal. The present invention relates to a method for recovering metallic iron, and a method of using steelmaking slag after recovering metallic iron for civil engineering and building materials, and a raw material for phosphate fertilizer obtained by recovering metallic iron.
製鋼精錬プロセスにおいては鉄鋼製品の不純物を除去すべく精錬処理が行われるが、それに伴い副産物である製鋼スラグが発生する。製鋼スラグの主なものとして、溶銑の予備脱燐処理にて発生する予備脱燐スラグや転炉での溶銑の脱炭精錬処理にて発生する脱炭精錬スラグがある。なかでも、脱炭精錬スラグは、塩基度（質量％ＣａＯ／質量％ＳｉＯ2）が高く、精錬処理中に溶融しきれなかったＣａＯのような水和性成分（以下、「遊離ＣａＯ」という）を多量に含有し、この遊離ＣａＯが水分と接触して水和する際に体積が約２倍に増加するためにスラグの体積が膨張する。この膨張のために、脱炭精錬スラグのような塩基度の高い製鋼スラグは道路用路盤材として用いることができない。また、脱炭精錬スラグを、覆砂材や、潜堤材、盛土材、浅場造成材などの海洋用途に使用した場合には、遊離ＣａＯが海水に溶出してｐＨが増加し、海水中のＭｇ（ＯＨ）2が析出することに起因する白濁現象が生じるために、海洋用途への利用も困難である。 In the steelmaking refining process, a refining process is performed to remove impurities from steel products, and as a result, steelmaking slag as a by-product is generated. The main steelmaking slag includes preliminary dephosphorization slag generated by hot metal preliminary dephosphorization treatment and decarburization refining slag generated by hot metal decarburization refining treatment in a converter. Among them, decarburized refining slag has a high basicity (mass% CaO / mass% SiO 2 ) and is a hydrating component such as CaO that could not be melted during the refining process (hereinafter referred to as “free CaO”). When the free CaO comes into contact with moisture and hydrates, the volume increases by a factor of about 2 and the volume of the slag expands. Due to this expansion, steelmaking slag with high basicity such as decarburized refining slag cannot be used as roadbed material. In addition, when decarburized refining slag is used for marine applications such as sand-capping material, submerged levee material, embankment material, shallow-field material, free CaO elutes into seawater and pH increases, Since the cloudiness phenomenon resulting from precipitation of Mg (OH) 2 occurs, it is difficult to use it for marine applications.
このような事情から、現在のところ、製鋼スラグは土木用の埋め戻し材などに用いられるのみであり、同じ副産物である高炉スラグと比較すると利用価値が低い。この場合、製鋼スラグは、１０〜４０質量％程度の鉄酸化物を含有したままの状態で土木用材料などとして鉄鋼製造工程の系外に排出されており、製鋼スラグ中の鉄は回収されることはない。 Under such circumstances, at present, steelmaking slag is only used as a backfill material for civil engineering, and its utility value is low compared with blast furnace slag, which is the same byproduct. In this case, the steelmaking slag is discharged out of the steel manufacturing process as a civil engineering material while containing about 10 to 40% by mass of iron oxide, and the iron in the steelmaking slag is recovered. There is nothing.
また、製鋼スラグをＣａＯ源及び鉄源として製鉄所内でリサイクルすることも考えられているが、製鋼スラグには一般的に燐が含有されており、燐を含有する製鋼スラグを高炉工程にリサイクルすると、酸化物の形態で高炉にリサイクルされた燐が、高炉内で還元されて溶製される溶銑の燐含有量を増加させ、その結果、溶銑からの脱燐の負荷が増加するという悪循環を招くことになる。 It is also considered to recycle steelmaking slag as a CaO source and iron source inside the steelworks, but steelmaking slag generally contains phosphorus, and when steelmaking slag containing phosphorus is recycled to the blast furnace process Phosphorus recycled to the blast furnace in the form of oxides increases the phosphorus content of the hot metal that is reduced and melted in the blast furnace, resulting in a vicious cycle of increasing the load of dephosphorization from the hot metal It will be.
製鋼スラグ中の鉄及びＣａＯを回収して再利用することを目的とした、製鉄所内で製鋼スラグをリサイクルする方法として、例えば、特許文献１には、溶融状態の高炉スラグと、溶融状態の転炉スラグとを混合し、この混合スラグ中に、炭素、珪素、マグネシウムの１種以上を添加すると同時に、酸素ガスを吹き込んで、混合スラグ中の燐酸化物を還元して燐蒸気とし、且つ、混合スラグ中の硫黄をＳＯ2とし、これらを揮発させて燐及び硫黄の少ないスラグとし、このスラグを高炉または転炉にリサイクルする技術が開示されている。 As a method of recycling steelmaking slag in an ironworks for the purpose of recovering and reusing iron and CaO in steelmaking slag, for example, Patent Document 1 discloses a molten blast furnace slag and a molten state slag. The furnace slag is mixed, and at least one of carbon, silicon, and magnesium is added to the mixed slag, and at the same time, oxygen gas is blown to reduce the phosphor oxide in the mixed slag to phosphorus vapor, and to mix A technique is disclosed in which sulfur in slag is changed to SO 2, and these are volatilized to form slag with less phosphorus and sulfur, and this slag is recycled to a blast furnace or converter.
また、製鋼スラグを道路用路盤材などとして利用することを目的とした、製鋼スラグ中の遊離ＣａＯを低減するための手段としては、エージング処理が広く知られている。例えば、特許文献２には、溶融状態の製鋼スラグを浅底広皿上に注入して散水による一次冷却を行い、次に排滓台車内で散水による二次冷却を行い、更に貯水冷却ピットに浸漬する方法が開示され、特許文献３には、製鋼スラグを放冷固化後に、スラグ温度が４００〜１０００℃の顕熱を保持した状態で４０〜１００℃の温水槽に投入してスラグ中の遊離ＣａＯの水和反応を促進させ短期間で安定化処理する技術が開示されている。
Moreover, an aging process is widely known as a means for reducing free CaO in steelmaking slag for the purpose of using steelmaking slag as roadbed material. For example, in
また、白濁現象などの原因となるアルカリ成分の溶出を抑制することを目的として、製鋼スラグに炭酸ガス含有ガスを供給して製鋼スラグ中のＣａＯを炭酸化する処理が知られている。例えば、特許文献４には、温度が８００℃以上の高温スラグを、冷却装置の内部で移送しつつ冷却する工程において、冷却装置の入口側から高温スラグに散水を行い、水性ガス化反応及びシフト反応を同時進行させて炭酸ガスを発生させ、この炭酸ガスと冷却されたスラグとを接触させてスラグ中のＣａＯを炭酸化する技術が開示され、特許文献５には、エージング処理が施された製鋼スラグに、自由水が存在し始める水分値未満で、且つ、該水分値よりも１０質量％少ない値以上の範囲となるように添加する水分量を調整した後に炭酸ガス含有ガスを流すことにより、製鋼スラグの炭酸化処理を行う技術が開示されている。 Moreover, the process which carbonates CaO in steelmaking slag by supplying a carbon dioxide containing gas to steelmaking slag for the purpose of suppressing the elution of the alkaline component which causes a cloudiness phenomenon etc. is known. For example, in Patent Document 4, in a process of cooling high-temperature slag having a temperature of 800 ° C. or more while being transferred inside the cooling device, water is sprayed from the inlet side of the cooling device to the high-temperature slag, and water gasification reaction and shift are performed. A technology is disclosed in which carbon dioxide gas is generated by causing the reaction to proceed simultaneously, and this carbon dioxide gas is brought into contact with the cooled slag to carbonate CaO in the slag. In Patent Document 5, an aging treatment was performed. By flowing the carbon dioxide-containing gas after adjusting the amount of water to be added to the steelmaking slag so that it is less than the moisture value at which free water begins to exist and is at least 10% by mass less than the moisture value A technique for carbonating steelmaking slag is disclosed.
しかしながら、上記従来技術には以下の問題点がある。 However, the above prior art has the following problems.
特許文献１では、転炉スラグに、転炉スラグとほぼ同量の高炉スラグを混合させているが、近年、高炉スラグは、廃棄物ではなく、土木・建築資材として利用価値の高い資源と位置づけられており、このような高炉スラグを転炉スラグの希釈用として使用することは経済的には不利である。 In Patent Document 1, blast furnace slag is mixed with converter slag in almost the same amount as converter slag. However, in recent years, blast furnace slag is not a waste but a resource that has high utility value as civil engineering and building materials. Therefore, it is economically disadvantageous to use such blast furnace slag for diluting converter slag.
特許文献２及び特許文献３では、エージング処理により遊離ＣａＯは減少するものの、エージング処理後の水和処理生成物であるスラグ中のＣａ（ＯＨ）2が水に溶出し、アルカリ溶出源となるため、エージング処理のみでは白濁現象は防止できない。また、多量の水を利用するため、水処理設備が必要であり、設備費及び運転費ともに高価となる。
In
特許文献４及び特許文献５では、炭酸化処理設備が大掛かりとなり、大量のスラグを処理するには適さないという課題がある。 In patent document 4 and patent document 5, there is a problem that the carbonation treatment facility becomes large and is not suitable for processing a large amount of slag.
また、特許文献２〜５は、何れも製鋼スラグ中の鉄分を回収できないという課題もある。近年の鉄鋼原料高騰の背景から、製鋼スラグ中の鉄分を回収することができれば大きな経済的メリットが得られる。 Moreover, patent documents 2-5 also has the subject that all cannot recover the iron content in steelmaking slag. Given the recent rise in steel raw materials, if the iron content in steelmaking slag can be recovered, a great economic merit can be obtained.
本発明は上記事情に鑑みてなされたもので、その目的とするところは、製鋼精錬プロセスで発生する脱炭精錬スラグ及び予備脱燐スラグから、これら製鋼スラグに含有される鉄分を金属鉄として安価に回収するとともに、これら製鋼スラグを、体積膨張や海水の白濁現象を起こさない土木建築材料または環境改善材料、更には燐酸肥料用原料として利用することのできる、製鋼スラグの資源化方法を提供するとともに、製鋼スラグから回収される燐酸肥料用原料を提供することである。 The present invention has been made in view of the above circumstances, and its object is to inexpensively use iron contained in these steelmaking slag as metallic iron from decarburization refining slag and preliminary dephosphorization slag generated in the steelmaking refining process. And a method for recycling steelmaking slag that can be used as a civil engineering / building material or environmental improvement material that does not cause volume expansion or white turbidity of seawater, and also as a raw material for phosphate fertilizer. At the same time, it is to provide a raw material for phosphate fertilizer recovered from steelmaking slag.
上記課題を解決するための第１の発明に係る製鋼スラグの資源化方法は、転炉での溶銑の脱炭精錬において発生した脱炭精錬スラグと、溶銑の予備脱燐処理において発生した予備脱燐スラグとを、これらを混合した後の混合物の塩基度（質量％ＣａＯ／質量％ＳｉＯ2）が１．５〜２．８になるように混合し、該混合物に対して、炭素、珪素、アルミニウムのうちの１種以上を含有する還元剤を用いて前記スラグ中の鉄酸化物を還元するための還元処理を行い、該還元処理によって得られた金属鉄を鉄源として利用するとともに、前記還元処理後のスラグを土木建築材料、環境改善材料、燐酸肥料用原料の何れか１種または２種以上として利用することを特徴とする。 The method for recycling steelmaking slag according to the first invention for solving the above-described problems includes a decarburization refining slag generated during decarburization refining of hot metal in a converter, and a preliminary desorption generated during predephosphorization treatment of hot metal. Phosphorus slag was mixed so that the basicity (mass% CaO / mass% SiO 2 ) of the mixture after mixing these was 1.5 to 2.8, and carbon, silicon, Performing a reduction treatment for reducing iron oxide in the slag using a reducing agent containing one or more of aluminum, and using the metal iron obtained by the reduction treatment as an iron source, The slag after the reduction treatment is used as one or more of civil engineering and building materials, environmental improvement materials, and raw materials for phosphate fertilizers.
第２の発明に係る製鋼スラグの資源化方法は、転炉での溶銑の脱炭精錬において発生した脱炭精錬スラグと、ＳｉＯ2含有物質とを、これらを混合した後の混合物の塩基度（質量％ＣａＯ／質量％ＳｉＯ2）が１．５〜２．８になるように混合し、該混合物に対して、炭素、珪素、アルミニウムのうちの１種以上を含有する還元剤を用いて前記スラグ中の鉄酸化物を還元するための還元処理を行い、該還元処理によって得られた金属鉄を鉄源として利用するとともに、前記還元処理後のスラグを土木建築材料、環境改善材料、燐酸肥料用原料の何れか１種または２種以上として利用することを特徴とする。 The method for recycling steelmaking slag according to the second aspect of the present invention is based on the basicity of the mixture after mixing the decarburized refining slag generated in the decarburization refining of the hot metal in the converter and the SiO 2 -containing material ( (Mass% CaO / mass% SiO 2 ) is mixed so as to be 1.5 to 2.8, and the mixture is mixed with a reducing agent containing one or more of carbon, silicon, and aluminum. A reduction treatment for reducing iron oxide in the slag is performed, the metal iron obtained by the reduction treatment is used as an iron source, and the slag after the reduction treatment is used as a civil engineering building material, an environmental improvement material, and a phosphate fertilizer It is characterized by being used as any one kind or two or more kinds of raw materials.
第３の発明に係る製鋼スラグの資源化方法は、転炉での溶銑の脱炭精錬において発生した脱炭精錬スラグと、溶銑の予備脱燐処理において発生した予備脱燐スラグと、ＳｉＯ2含有物質とを、これらを混合した後の混合物の塩基度（質量％ＣａＯ／質量％ＳｉＯ2）が１．５〜２．８になるように混合し、該混合物に対して、炭素、珪素、アルミニウムのうちの１種以上を含有する還元剤を用いて前記スラグ中の鉄酸化物を還元するための還元処理を行い、該還元処理によって得られた金属鉄を鉄源として利用するとともに、前記還元処理後のスラグを土木建築材料、環境改善材料、燐酸肥料用原料の何れか１種または２種以上として利用することを特徴とする。 Recycling method for steel slag according to the third invention, a decarburization refining slag generated in the decarburization refining of molten iron in the converter, a preliminary dephosphorization slag generated in pre-dephosphorization of hot metal, SiO 2 content Substances are mixed so that the basicity (mass% CaO / mass% SiO 2 ) of the mixture after mixing them is 1.5 to 2.8, and carbon, silicon, aluminum are mixed with the mixture. Performing a reduction treatment for reducing the iron oxide in the slag using a reducing agent containing one or more of the above, and using the metal iron obtained by the reduction treatment as an iron source, and the reduction The treated slag is used as one or more of civil engineering and building materials, environmental improvement materials, and raw materials for phosphate fertilizers.
第４の発明に係る製鋼スラグの資源化方法は、第１ないし第３の発明の何れかにおいて、前記還元処理を、１２５０〜１４５０℃の温度範囲内で行うことを特徴とする。 A steelmaking slag resource recycling method according to a fourth invention is characterized in that, in any of the first to third inventions, the reduction treatment is performed within a temperature range of 1250 to 1450 ° C.
第５の発明に係る製鋼スラグの資源化方法は、第１ないし第４の発明の何れかにおいて、前記還元処理により得られた金属鉄を、製銑工程及び／又は製鋼工程での鉄源として利用することを特徴とする。 The method for recycling steelmaking slag according to the fifth invention is the method for recycling steelmaking slag according to any one of the first to fourth inventions, wherein the metallic iron obtained by the reduction treatment is used as an iron source in the steelmaking process and / or the steelmaking process. It is characterized by using.
第６の発明に係る製鋼スラグの資源化方法は、第１ないし第５の発明の何れかにおいて、前記還元処理後のスラグを、蒸気エージング処理することを特徴とする。 A steelmaking slag resource recycling method according to a sixth invention is characterized in that, in any of the first to fifth inventions, the slag after the reduction treatment is subjected to a steam aging treatment.
第７の発明に係る燐酸肥料用原料は、第１ないし第６の発明の何れか１つに記載の製鋼スラグの資源化方法における還元処理後のスラグであることを特徴とする。 The raw material for phosphate fertilizer according to the seventh invention is a slag after reduction treatment in the steelmaking slag resource recycling method according to any one of the first to sixth inventions.
本発明によれば、混合した後の混合物の塩基度が１．５〜２．８の範囲になるように、脱炭精錬スラグと予備脱燐スラグとを混合する、または、脱炭精錬スラグとＳｉＯ2含有物質とを混合する、或いは脱炭精錬スラグと予備脱燐スラグとＳｉＯ2含有物質とを混合し、この混合物を還元処理するので、還元によって回収される金属鉄は鉄源として利用でき、一方、還元処理後のスラグは、塩基度の調整によって遊離ＣａＯが少なくなり、体積膨張や白濁現象を起こさず、土木建築材料または環境改善材料として利用でき、更に、還元処理後のスラグは燐酸を含有することから、燐酸肥料用原料としても利用することができる。 According to the present invention, the decarburized refining slag and the preliminary dephosphorized slag are mixed or the decarburized refining slag so that the basicity of the mixture after mixing is in the range of 1.5 to 2.8. Since the SiO 2 -containing material is mixed, or the decarburized refining slag, the preliminary dephosphorization slag, and the SiO 2 -containing material are mixed and the mixture is reduced, the metal iron recovered by the reduction can be used as an iron source. On the other hand, slag after reduction treatment has less free CaO due to the adjustment of basicity, and does not cause volume expansion or white turbidity, and can be used as a civil engineering building material or environmental improvement material. Furthermore, slag after reduction treatment is phosphoric acid. Therefore, it can also be used as a raw material for phosphate fertilizer.
以下、本発明を詳細に説明する。 Hereinafter, the present invention will be described in detail.
本発明者らは、近年の製鉄原料の高騰を受け、鉄酸化物を含有する、固化した製鋼スラグから金属鉄を回収する方法について検討を行った。製鋼スラグには、鉄がＦｅＯやＦｅ2Ｏ3の形態（以下、まとめてＦｅXＯと記す）の酸化物で含有されている。そこで、転炉での溶銑の脱炭精錬において発生した脱炭精錬スラグ及び溶銑の予備脱燐処理において発生した予備脱燐スラグに含有される鉄酸化物を、炭素で還元して金属鉄を回収する試験を行った。その結果、スラグの塩基度（質量％ＣａＯ／質量％ＳｉＯ2）が１．５〜２．２と比較的低い予備脱燐スラグでは、１２００〜１３００℃程度の温度域で鉄酸化物の還元及び金属鉄の回収が可能であったが、塩基度が３．０〜４．５と高い脱炭精錬スラグでは、１６００℃を超えるような高温でようやく鉄酸化物の還元及び金属鉄の回収が可能なことが分かった。還元処理温度が１６００℃を超える場合、還元処理に費やすエネルギーが多大となってメリットが得られにくいことや、実操業時には耐火物負荷が大きくなって運転費が高くなることが想定されるため、還元処理温度を低下させることを検討した。その結果、脱炭精錬スラグと予備脱燐スラグとを混合して塩基度を望ましい範囲に調整する方法を見出し、塩基度が２．８以下であれば、還元処理温度を１６００℃以下の範囲に抑えられることが分かった。 The present inventors examined the method of collect | recovering metallic iron from the solidified steelmaking slag containing the iron oxide in response to the recent rise of the ironmaking raw material. Steelmaking slag contains iron as an oxide in the form of FeO or Fe 2 O 3 (hereinafter collectively referred to as Fe X O). Therefore, the iron oxide contained in the decarburization slag generated in the decarburization and refining of hot metal in the converter and the predephosphorization slag generated in the preliminary dephosphorization treatment of hot metal is reduced with carbon to recover metallic iron. A test was conducted. As a result, in the preliminary dephosphorization slag having a relatively low basicity (mass% CaO / mass% SiO 2 ) of 1.5 to 2.2, the reduction of the iron oxide and the temperature in the temperature range of about 1200 to 1300 ° C. Although recovery of metallic iron was possible, decarburization and refining slag with a high basicity of 3.0 to 4.5 can finally reduce iron oxide and recover metallic iron at high temperatures exceeding 1600 ° C. I found out. When the reduction treatment temperature exceeds 1600 ° C., it is assumed that the energy consumed for the reduction treatment is great and it is difficult to obtain merits, and it is assumed that the refractory load becomes large and the operation cost becomes high during actual operation. We studied to reduce the reduction temperature. As a result, a method for adjusting the basicity to a desired range by mixing decarburized refining slag and preliminary dephosphorization slag is found. If the basicity is 2.8 or less, the reduction treatment temperature is set to a range of 1600 ° C. or less. It turns out that it can be suppressed.
更に、還元により生成する金属鉄の融点が低いほど、還元処理温度を低下させることが可能なことも実験によって明らかになった。即ち、還元により生成した金属鉄をスラグと迅速に分離するには、還元により生成した金属鉄が溶融状態になるように高温下で還元することが好ましく、生成する金属鉄中の炭素濃度が高くなるほど鉄の融点が下がることから、生成する金属鉄中に炭素を含有させ、還元によって生成する金属鉄を溶融鉄の状態つまり溶銑とすることが好ましいことが分かった。つまり、還元により生成した金属鉄が溶融状態であれば、溶融した鉄はスラグと分離しやすく、還元によって生成した金属鉄のスラグからの分離が促進される。具体的には、金属鉄中の炭素濃度が３質量％以上になると、液相線温度が１３００℃以下となることから、金属鉄の炭素濃度を３質量％以上確保することが好ましい。生成される金属鉄に炭素を溶解させるには、炭素を還元剤として使用する、または、珪素やアルミニウムなどを還元剤とする場合には、炭素を製鋼スラグと共存させることにより、生成する金属鉄は浸炭して自ずと溶銑になる。 Furthermore, it has been clarified through experiments that the reduction treatment temperature can be lowered as the melting point of metallic iron produced by reduction is lower. That is, in order to quickly separate the metallic iron produced by the reduction from the slag, it is preferable to reduce the metallic iron produced by the reduction at a high temperature so that the molten metallic iron is in a molten state, and the carbon concentration in the produced metallic iron is high. Since the melting point of iron is lowered, it has been found that it is preferable to contain carbon in the produced metallic iron and to make the metallic iron produced by reduction into a molten iron state, that is, molten iron. That is, if the metallic iron produced | generated by reduction | restoration is a molten state, the molten iron will be easy to isolate | separate from slag, and isolation | separation from the slag of metallic iron produced | generated by reduction | restoration will be accelerated | stimulated. Specifically, when the carbon concentration in the metallic iron is 3% by mass or more, the liquidus temperature is 1300 ° C. or less. Therefore, it is preferable to ensure the carbon concentration of the metallic iron at 3% by mass or more. In order to dissolve carbon in the produced metallic iron, carbon is used as a reducing agent. When silicon or aluminum is used as the reducing agent, the metallic iron is produced by coexisting carbon with steelmaking slag. Will carburize and become hot metal.
また、製鋼スラグには鉄酸化物以外に燐酸化物もＰ2Ｏ5なる形態で含有されている。本発明者らの実験により、還元処理においては、ＦｅXＯが先ず還元され、その後Ｐ2Ｏ5が還元されるが、燐は鉄中への溶解度が高いため、還元により生成した燐は、還元により生成した金属鉄に迅速に溶解することが分かった。回収した金属鉄を鉄鋼製造工程で利用することを考えると、金属鉄の燐濃度は低い方が好ましい。つまり、スラグ中のＦｅXＯのみが還元されてＰ2Ｏ5は極力還元されない条件下で、還元処理を行うことが望ましい。 In addition to iron oxide, phosphorous oxide is contained in the steelmaking slag in the form of P 2 O 5 . According to the experiments of the present inventors, in the reduction treatment, Fe x O is first reduced, and then P 2 O 5 is reduced. However, since phosphorus has high solubility in iron, phosphorus produced by reduction is: It was found to dissolve rapidly in metallic iron produced by reduction. Considering the use of the recovered metallic iron in the steel production process, it is preferable that the metallic iron has a low phosphorus concentration. In other words, it is desirable to perform the reduction treatment under conditions where only Fe x O in the slag is reduced and P 2 O 5 is not reduced as much as possible.
本発明者らは、これについても鋭意検討を行い、その結果、鉄酸化物の方が燐酸化物よりも熱力学的に還元されやすいことから、雰囲気の調整によって還元時の酸素ポテンシャルを制御することで、ＦｅXＯは還元され、Ｐ2Ｏ5は極力還元されないような条件を作り出すことが可能であることを確認した。尚、当該還元処理により得られた金属鉄は、鉄鋼製造工程における、高炉での鉄源原料としての利用や、或いは、高炉から転炉へと溶銑を運ぶための高炉鍋やトピードカーへの入れ置き、更には、溶銑予備処理や転炉脱炭精錬での鉄源などとして問題なく利用できることを確認している。 The present inventors have also intensively studied this, and as a result, iron oxide is easier to reduce thermodynamically than phosphorous oxide, so that the oxygen potential during reduction is controlled by adjusting the atmosphere. Thus, it was confirmed that it was possible to create a condition in which Fe x O was reduced and P 2 O 5 was not reduced as much as possible. In addition, the metallic iron obtained by the reduction treatment is used as an iron source material in a blast furnace in the steel production process, or placed in a blast furnace pan or topped car for transporting hot metal from the blast furnace to the converter. Furthermore, it has been confirmed that it can be used without problems as an iron source for hot metal pretreatment and converter decarburization and refining.
また、本発明者らは、還元処理後のスラグの性状について調査した。脱炭精錬スラグと予備脱燐スラグとを混合して混合後のスラグの塩基度（質量％ＣａＯ／質量％ＳｉＯ2）を１．５〜２．８の範囲に調整し、このスラグに熱を加えて還元処理を施すことで、生成されるスラグは脱炭精錬スラグよりも塩基度が低下し、これにより、脱炭精錬スラグ中に存在していた遊離ＣａＯが減少し、還元後のスラグは安定化することが分かった。鉄酸化物が還元・除去された後のスラグが路盤材などの土木建築材料に使用できるか実験を重ねた結果、スラグの塩基度が１．５〜２．８の範囲であれば、遊離ＣａＯが１．０質量％以下となり、体積膨張しなくなることが分かった。また、遊離ＣａＯが１．０質量％以下となることから、遊離ＣａＯの海水への溶出量が低減し、海域利用しても海水の白濁現象は起こらないことも確認できた。また、更に、還元処理後のスラグに対して蒸気エージングを施すことで、遊離ＣａＯがより一層低減し、更なるスラグ品質安定化を図れることも確認した。 Moreover, the present inventors investigated the property of the slag after a reduction process. The basicity (mass% CaO / mass% SiO 2 ) of the slag after mixing the decarburized refining slag and the preliminary dephosphorization slag is adjusted to the range of 1.5 to 2.8, and the slag is heated. In addition, by performing the reduction treatment, the generated slag has a lower basicity than the decarburized and refined slag, thereby reducing the free CaO present in the decarburized and refined slag, and the reduced slag is It was found to stabilize. As a result of repeated experiments to determine whether the slag after the reduction and removal of iron oxide can be used for civil engineering and building materials such as roadbed materials, if the basicity of the slag is in the range of 1.5 to 2.8, free CaO Was 1.0% by mass or less, and it was found that the volume did not expand. Moreover, since free CaO became 1.0 mass% or less, the elution amount to the seawater of free CaO reduced, and even if it used the sea area, it has also confirmed that the cloudiness phenomenon of seawater did not occur. Furthermore, it was also confirmed that by subjecting the slag after the reduction treatment to steam aging, the free CaO is further reduced and the slag quality can be further stabilized.
また、得られた還元処理後のスラグをセメントやコンクリートの骨材に供する試験を行ったところ、スラグの塩基度が１．５〜２．８の範囲にあるので、十分にセメントやコンクリートの骨材として利用できることも分かった。 Moreover, when the obtained slag after the reduction treatment was subjected to a test for use in cement or concrete aggregate, the basicity of slag was in the range of 1.5 to 2.8. It was also found that it can be used as a material.
このように、還元処理後のスラグは、覆砂材に代表される、海、河川、湖沼などの水底の環境及び水質を改善するための環境改善材料として適用可能であり、また、路盤材、土壌改良材、地盤改良材、セメントやコンクリートの骨材、石材、及び、海洋における、潜堤材、裏ごめ材、裏埋め材、盛土材などの土木建築材料としても適用可能である。 Thus, the slag after the reduction treatment can be applied as an environment improvement material for improving the environment and water quality of the bottom of the sea, rivers, lakes, and the like, typified by sand-capping materials, The present invention can also be applied to soil improvement materials, ground improvement materials, cement and concrete aggregates, stone materials, and civil engineering and building materials such as submerged dike materials, lining materials, backfill materials, and embankment materials in the ocean.
更に、還元処理後のスラグは燐酸（Ｐ2Ｏ5）を３質量％程度含有することから、燐酸肥料用原料として利用可能かを検討した。その結果、還元処理後のスラグに含有される燐酸のうちの７０質量％以上がクエン酸可溶性燐酸（ク溶性燐酸：植物が根から酸を出すことで吸収できる燐酸）であることから、燐酸肥料用原料として利用可能であることを確認した。 Furthermore, since the slag after the reduction treatment contains about 3% by mass of phosphoric acid (P 2 O 5 ), it was examined whether it could be used as a raw material for phosphoric acid fertilizer. As a result, 70% by mass or more of the phosphoric acid contained in the slag after the reduction treatment is citric acid-soluble phosphoric acid (phosphorus acid that can be absorbed by the plant taking out acid from the roots). It was confirmed that it can be used as a raw material.
尚、スラグの混合物の塩基度が１．５より低い場合には、スラグが溶融しすぎるために処理容器への付着が多く、一方、スラグの混合物の塩基度が２．８よりも高い場合には遊離ＣａＯが１．０質量％を超える場合も見受けられた。 In addition, when the basicity of the slag mixture is lower than 1.5, the slag is excessively melted so that it adheres to the processing vessel. On the other hand, when the basicity of the slag mixture is higher than 2.8. Was also observed when free CaO exceeded 1.0 mass%.
また、脱炭精錬スラグの塩基度低下用として、予備脱燐スラグに替わって珪石を使用する試験を行ったが、混合後の混合物の塩基度が１．５〜２．８の範囲である限り、問題なく金属鉄の回収、還元処理後のスラグ利用が行えることも確認した。また、半導体製造工程で発生するシリコン切削屑（シリコンスラッジ）を用いた試験も行った。シリコンスラッジは主に金属Ｓｉと半導体製造工程で必要な化学溶液を含んでいる。この場合も、化学溶液は高温熱処理により除去でき、更に、金属Ｓｉが還元材として作用するとともに、作用後はＳｉＯ2となることから、脱炭精錬スラグの塩基度を低下させることが可能であった。この場合も、混合後の混合物の塩基度が１．５〜２．８の範囲であれば問題なく金属鉄の回収、スラグ利用が可能であった。その外、珪砂、グラスウールも脱炭精錬スラグの塩基度低下用のＳｉＯ2含有物質として使用可能である。 Moreover, although the test which uses a silica stone instead of preliminary | backup dephosphorization slag was performed for the basicity fall of decarburization refining slag, as long as the basicity of the mixture after mixing is the range of 1.5-2.8, It was also confirmed that metal iron can be recovered without problems and slag can be used after reduction treatment. In addition, a test using silicon cutting waste (silicon sludge) generated in the semiconductor manufacturing process was also performed. Silicon sludge mainly contains metal Si and a chemical solution necessary for the semiconductor manufacturing process. In this case as well, the chemical solution can be removed by high-temperature heat treatment, and further, the metal Si acts as a reducing material and becomes SiO 2 after the action, so that the basicity of the decarburized refining slag can be reduced. It was. Also in this case, when the basicity of the mixture after mixing was in the range of 1.5 to 2.8, it was possible to recover metallic iron and use slag without problems. In addition, silica sand and glass wool can also be used as SiO 2 -containing substances for lowering the basicity of decarburized refining slag.
更に、スラグの塩基度が１．５〜２．８の範囲で還元処理に好適な温度条件について調査したところ、還元処理温度は１２５０〜１４５０℃の範囲が好適であることを確認した。還元処理温度が１２５０℃を下回る場合には金属鉄の回収率が低く、一方、１４５０℃を超える場合には、処理容器に施工される耐火物への負荷がやや大きいことが分かった。 Furthermore, when the temperature conditions suitable for the reduction treatment in the range of 1.5 to 2.8 in the slag basicity were investigated, it was confirmed that the reduction treatment temperature was suitably in the range of 1250 to 1450 ° C. When the reduction treatment temperature is lower than 1250 ° C., the recovery rate of metallic iron is low. On the other hand, when the reduction treatment temperature is higher than 1450 ° C., it has been found that the load on the refractory applied to the treatment container is slightly high.
本発明は、上記試験結果に基づいてなされたものであり、混合した後の混合物の塩基度が１．５〜２．８の範囲になるように、脱炭精錬スラグと予備脱燐スラグとを混合する、または、脱炭精錬スラグとＳｉＯ2含有物質とを混合する、或いは脱炭精錬スラグと予備脱燐スラグとＳｉＯ2含有物質とを混合し、この混合物に対して、炭素、珪素、アルミニウムのうちの１種以上を含有する還元剤を用いて前記スラグ中の鉄酸化物を還元するための還元処理を行い、該還元処理によって得られた金属鉄を鉄源として利用するとともに、前記還元処理後のスラグを土木建築材料、環境改善材料、燐酸肥料用原料の何れか１種または２種以上として利用することを特徴とする。 The present invention was made on the basis of the above test results, and the decarburized refining slag and the preliminary dephosphorization slag were added so that the basicity of the mixture after mixing was in the range of 1.5 to 2.8. Mixing, or decarburizing and refining slag and SiO 2 -containing material, or decarburizing and refining slag, pre-dephosphorization slag and SiO 2 -containing material, and carbon, silicon, aluminum Performing a reduction treatment for reducing the iron oxide in the slag using a reducing agent containing one or more of the above, and using the metal iron obtained by the reduction treatment as an iron source, and the reduction The treated slag is used as one or more of civil engineering and building materials, environmental improvement materials, and raw materials for phosphate fertilizers.
上記構成の本発明によれば、脱炭精錬スラグ及び溶銑脱燐スラグから、鉄鋼製造工程における鉄源として利用可能な金属鉄を回収できるとともに、還元処理後の脱炭精錬スラグは改質されて、体積膨張や白濁現象の発生を危惧する必要のない安定したスラグとなり、路盤材などの土木建築材料、覆砂材などの環境改善材料、或いは、燐酸肥料用原料として有効活用することができる。 According to the present invention having the above configuration, metallic iron that can be used as an iron source in the steel manufacturing process can be recovered from the decarburized and refined slag and the molten iron dephosphorized slag, and the decarburized and refined slag after the reduction treatment is modified. Therefore, it becomes a stable slag that does not need to worry about the occurrence of volume expansion and clouding phenomenon, and can be effectively used as civil engineering and building materials such as roadbed materials, environmental improvement materials such as sand-capping materials, or raw materials for phosphate fertilizers.
尚、発生する脱炭精錬スラグの全量を本発明の還元処理に供しても構わないが、溶銑の予備脱燐処理において脱炭精錬スラグを使用することは省資源の観点からも有効であり、従って、発生した脱炭精錬スラグの一部を溶銑の予備脱燐処理工程におけるＣａＯ源として使用し、その脱炭精錬スラグの残部を本発明の還元処理工程に供することが好ましい。 Although the entire amount of decarburized and refined slag generated may be subjected to the reduction treatment of the present invention, the use of decarburized and refined slag in the preliminary dephosphorization treatment of hot metal is also effective from the viewpoint of resource saving, Therefore, it is preferable to use a part of the generated decarburized and refined slag as a CaO source in the hot metal preliminary dephosphorization process, and to use the remainder of the decarburized and refined slag for the reduction process of the present invention.
製鋼工程にて発生した固化した後の脱炭精錬スラグと予備脱燐スラグ、還元材としてのコークス、及び、塩基度調整用のＳｉＯ2含有物質を、加熱バーナーを備えたロータリーキルンに装入し、装入したスラグ及びコークスをバーナーによって加熱してスラグの還元処理を実施した。表１に、使用した脱炭精錬スラグ及び予備脱燐スラグの組成を示す。 Decarburization refining slag and preliminary dephosphorization slag after solidification generated in the steel making process, coke as a reducing material, and SiO 2 -containing material for adjusting the basicity are charged into a rotary kiln equipped with a heating burner, The charged slag and coke were heated by a burner to reduce the slag. Table 1 shows the composition of the used decarburized refining slag and preliminary dephosphorized slag.
試験条件及び試験結果の一覧を表２に示す。還元対象となるスラグの混合物は、合計量をおよそ２００トンとし、狙いの塩基度になるように、脱炭精錬スラグ、予備脱燐スラグ及びＳｉＯ2含有物質の配合量を決めた。コークスは還元対象のスラグ中のＦｅXＯを還元するのに必要な化学量論比の２倍となるように配合した。また、ＳｉＯ2含有物質は、珪石及びシリコンスラッジを用いており、表２ではそれらのＳｉＯ2純分量を示している。還元処理温度は各水準での狙いの温度を示しており、何れの試験もおよそ狙いどおりに制御できている。鉄の回収率は、回収された金属鉄の質量を、還元対象のスラグ中鉄分の質量で除した値（百分率）を示している。 Table 2 shows a list of test conditions and test results. The total amount of the slag mixture to be reduced was about 200 tons, and the amounts of decarburized refining slag, preliminary dephosphorization slag, and SiO 2 -containing material were determined so as to achieve the target basicity. Coke was blended so as to be twice the stoichiometric ratio required to reduce Fe x O in the slag to be reduced. The SiO 2 -containing material uses silica and silicon sludge, and Table 2 shows the pure amount of SiO 2 . The reduction treatment temperature indicates the target temperature at each level, and all tests can be controlled as intended. The recovery rate of iron indicates a value (percentage) obtained by dividing the mass of recovered metallic iron by the mass of iron in the slag to be reduced.
本発明例１〜６は、還元処理温度を１３５０℃として脱炭精錬スラグと予備脱燐スラグとの混合物の塩基度を１．５〜２．８の範囲で変化させた試験である。何れの試験も鉄の回収率は８０％以上が得られており、また、還元後に回収されたスラグの遊離ＣａＯ濃度も１．０質量％以下となった。 Invention Examples 1 to 6 are tests in which the reduction treatment temperature was set to 1350 ° C. and the basicity of the mixture of the decarburized refining slag and the preliminary dephosphorization slag was changed in the range of 1.5 to 2.8. In any of the tests, the iron recovery rate was 80% or more, and the free CaO concentration of the slag recovered after the reduction was 1.0% by mass or less.
このスラグを路盤材、骨材、海洋土木材に供する試験を行ったところ、体積膨張や白濁は見られなかった。また、このスラグを肥料分析法に準拠して２質量％クエン酸溶液（ｐＨ２）で溶出させ、溶出する燐酸（ク溶性燐酸）を測定した結果、含有する燐酸の７０質量％以上がク溶性燐酸であり、ク溶性燐酸を３質量％以上含有することから、燐酸肥料用原料として有効であることが分かった。 When this slag was tested for roadbed materials, aggregates, and marine earth and wood, no volume expansion or cloudiness was observed. Moreover, as a result of eluting the slag with a 2% by mass citric acid solution (pH 2) in accordance with the fertilizer analysis method and measuring the eluted phosphoric acid (soluble phosphoric acid), 70% by mass or more of the phosphoric acid contained is soluble in the phosphoric acid. Since 3% by mass or more of the soluble phosphoric acid is contained, it was found that it is effective as a raw material for phosphate fertilizer.
本発明例７、８は、脱炭精錬スラグの塩基度低下用として予備脱燐スラグに替わってＳｉＯ2含有物質を使用した試験であるが、本発明例１〜６の結果と何ら遜色なかった。 Invention Examples 7 and 8 are tests using SiO 2 -containing materials instead of preliminary dephosphorization slag for reducing the basicity of decarburized refining slag, but the results of Invention Examples 1 to 6 were not inferior. .
本発明例９〜１５は、脱炭精錬スラグと予備脱燐スラグとの混合物の塩基度を２．１の一定として、還元処理温度を１２００〜１５００℃の範囲で変化させた試験である。還元処理温度と鉄の回収率との関係を図１に示す。還元処理温度が１２００℃である本発明例１４では、鉄の回収率が８０％とやや低下した。一方、還元処理温度が１５００℃である本発明例１５では、鉄の回収率は９２％と高いものの、ロータリーキルン耐火物への負荷がやや大きかった。このことから、本発明における還元処理温度の好適範囲は、１２５０〜１４５０℃であることが確認できた。 Examples 9 to 15 of the present invention are tests in which the basicity of the mixture of decarburized refining slag and preliminary dephosphorization slag was made constant at 2.1 and the reduction treatment temperature was changed in the range of 1200 to 1500 ° C. The relationship between the reduction treatment temperature and the iron recovery rate is shown in FIG. In Invention Example 14 in which the reduction treatment temperature was 1200 ° C., the iron recovery rate was slightly reduced to 80%. On the other hand, in Example 15 of the present invention in which the reduction treatment temperature was 1500 ° C., the iron recovery rate was as high as 92%, but the load on the rotary kiln refractory was slightly high. From this, it has confirmed that the suitable range of the reduction process temperature in this invention is 1250-1450 degreeC.
更に、本発明例における還元処理後のスラグを蒸気エージングに供した後にスラグ中の遊離ＣａＯ濃度を測定した結果、何れの場合も遊離ＣａＯ濃度は０．４質量％以下となることが確認できた。つまり、還元処理後のスラグを蒸気エージング処理することにより、より安定したスラグ品質に改質することができ、路盤材、骨材、海洋土木材への適用がより一層可能であった。 Furthermore, as a result of measuring the free CaO concentration in the slag after subjecting the slag after the reduction treatment in the present invention example to steam aging, it was confirmed that the free CaO concentration was 0.4% by mass or less in any case. . That is, the slag after the reduction treatment can be modified to a more stable slag quality by steam aging treatment, and can be applied to roadbed materials, aggregates, and marine earth and lumber.
これに対して、比較例１では、塩基度が３．９の脱炭精錬スラグのみを還元処理に供したが、鉄の回収率は６５％と低位であり、更に還元処理後のスラグ中の遊離ＣａＯ濃度は２．５質量％と高かった。比較例２では、脱炭精錬スラグに予備脱燐スラグを混合して混合物の塩基度を３．０としたが、鉄の回収率は８７％に到達したものの、遊離ＣａＯ濃度が１．２質量％とやや高くなった。比較例１及び比較例２の還元処理後スラグを、路盤材、骨材、海洋土木材に供して試験を行ったが、何れの場合でも体積膨張が見受けられ、路盤材や骨材に適用することはできなかった。また海洋土木材に供した場合には若干の白濁現象が見られた。 On the other hand, in Comparative Example 1, only the decarburized and refined slag having a basicity of 3.9 was subjected to the reduction treatment, but the iron recovery rate was as low as 65%, and the slag in the slag after the reduction treatment was further low. The free CaO concentration was as high as 2.5% by mass. In Comparative Example 2, preliminary dephosphorization slag was mixed with decarburized refining slag to adjust the basicity of the mixture to 3.0. Although the iron recovery rate reached 87%, the free CaO concentration was 1.2% by mass. It became slightly high with%. The slag after the reduction treatment of Comparative Example 1 and Comparative Example 2 was subjected to tests using roadbed materials, aggregates, and marine earth and lumber. In any case, volume expansion was observed and applied to roadbed materials and aggregates. I couldn't. In addition, some cloudiness was observed when it was applied to marine earth and wood.
一方、比較例３では脱炭精錬スラグと予備脱燐スラグとの混合物の塩基度を１．４とした。この場合には、ロータリーキルン炉壁へのスラグ付着が多く、鉄の回収率がやや悪化するとともに、回収されたスラグ量も低位であった。この条件では、安定した連続操業は行えないことが確認できた。 On the other hand, in Comparative Example 3, the basicity of the mixture of decarburized refining slag and preliminary dephosphorization slag was set to 1.4. In this case, there was much slag adhesion to the rotary kiln furnace wall, the iron recovery rate was slightly deteriorated, and the amount of recovered slag was low. It was confirmed that stable continuous operation was not possible under these conditions.
尚、本実施例では製鋼スラグの還元処理装置としてロータリーキルンを用いたが、装入されたスラグ及び炭材に熱を与えて還元処理が行える装置であればどのような形状の装置であっても構わず、例えば、アーク加熱方式の電気炉や、バーナーまたは酸素による加熱装置を有する転炉、更には、鍋型の処理容器、誘導加熱炉、ＲＨＦ形式の処理容器などでも構わない。 In this embodiment, a rotary kiln was used as a steelmaking slag reduction treatment device. However, any shape of the device can be used as long as it can perform reduction treatment by applying heat to the charged slag and charcoal. For example, an electric furnace of an arc heating method, a converter having a heating device using a burner or oxygen, a pot type processing vessel, an induction heating furnace, an RHF type processing vessel, or the like may be used.
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