JP2009084094A - Method for recycling coated optical fiber and silicon produced by the method - Google Patents
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Abstract
Description
本発明は、プラスチック被覆を除去した光ファイバー心線のリサイクル方法、及び該方法で製造されたシリコン（元素状ケイ素）に関する。 The present invention relates to a method for recycling an optical fiber from which a plastic coating has been removed, and silicon (elemental silicon) produced by the method.
光ファイバーは通信での利用拡大のため使用量が急増しており、今後の廃光ファイバーの量も増大すると予測されているが、そのリサイクル技術は確立されていない。光ファイバーケーブルは高純度シリカからなる光ファイバー心線の他、プラスチック被覆材及び金属材から構成されており、とりわけ高純度シリカからなる心線のリサイクルは重要であることから、その方法が種々研究されてきた。リサイクルには、マテリアルリサイクル、ケミカルリサイクル、サーマルリサイクルがあり、最も環境負荷が少ない循環型社会の構築に相応しいリサイクルはマテリアルリサイクルであると考えられているが、従来光ファイバーはサーマルリサイクルされていた。 The amount of use of optical fibers is increasing rapidly due to the expansion of use in communications, and it is predicted that the amount of waste optical fibers in the future will also increase, but the recycling technology has not been established. Optical fiber cables are composed of optical fiber cores made of high-purity silica, plastic coating materials and metal materials, and recycling of cores made of high-purity silica is particularly important, so various methods have been studied. It was. Recycling includes material recycling, chemical recycling, and thermal recycling. Recycling suitable for building a recycling-oriented society with the least environmental impact is considered to be material recycling. Conventionally, optical fibers have been thermally recycled.
光ファイバーの再生処理方法として、特許文献１には、プラスチック被覆を取り除いた裸ファイバーをプラズマによって加熱し、ファイバー中の微量元素をイオン化させ元素別に分別して捕集・回収する一方、残された高純度の石英ガラスを回収する方法が提案されている。しかしながら、この方法は装置自体が複雑であるため経済性が悪く、得策なリサイクル方法とは言い難い。 As an optical fiber regeneration treatment method, Patent Document 1 discloses that a bare fiber from which a plastic coating has been removed is heated by plasma, and trace elements in the fiber are ionized and collected and collected by element, while the remaining high purity is collected. A method for recovering quartz glass has been proposed. However, this method is not economical because the apparatus itself is complicated, and it is difficult to say that it is a reasonable recycling method.
また、特許文献２には、光ファイバー製造工場において排出する、光ファイバーを製造する過程および光ファイバー製品を製造する過程でできる、光ファイバーの構成原料であるケイ素を含有する種々の廃棄物、及びアルミニウム製造工場で排出する廃棄物を、ゼオライト製造用の原料として使用し、製造されたゼオライトを他の産業分野で有効に利用するゼロエミッション型有効利用法及び製造されたゼオライトが開示されている。しかしながら、高純度の光ファイバー心線を比較的安価なゼオライトに再利用することは経済的損失が大きく、心線を再利用する方法としては課題が多い。 Further, Patent Document 2 discloses various wastes containing silicon, which is an optical fiber component raw material, produced in the process of producing an optical fiber and the process of producing an optical fiber product discharged from an optical fiber production factory, and an aluminum production factory. A zero emission type effective utilization method and a produced zeolite are disclosed in which the discharged waste is used as a raw material for producing a zeolite and the produced zeolite is effectively utilized in other industrial fields. However, reusing a high-purity optical fiber core for relatively inexpensive zeolite has great economic loss, and there are many problems as a method for reusing the core.
さらに、特許文献３には、ゲルマニウムを含む超高純度二酸化ケイ素の還元、及び超高純度シリコンを必須成分とする太陽光発電システムへの廃棄光ファイバー還元物の適用が開示されている。しかしながら、本方法はプラスチック被覆された光ファイバーそのものを原料とし、被覆用プラスチックを還元剤としてアークプラズマ反応炉で還元するため、実験の再現性が得られにくい懸念があり、また、装置自体の経済性にも問題がある。
上述したように、廃光ファイバー心線は高純度シリカを成分とし、高付加価値が見込まれる素材であるにもかかわらず、より有用で経済効果の高いリサイクル方法について開示された先行技術はない。 As described above, although the waste optical fiber core is made of high-purity silica and is a material that is expected to have high added value, there is no prior art that discloses a more useful and economical recycling method.
本発明は、上記従来の課題に鑑みてなされたものであり、プラスチック被覆を除去した光ファイバー心線から、太陽光電池や半導体用として利用可能な付加価値の高いシリコンを得ることのできる、光ファイバー心線のリサイクル方法を提供することを目的とする。 The present invention has been made in view of the above-described conventional problems, and can provide high-value-added silicon that can be used for solar cells and semiconductors from an optical fiber core from which a plastic coating has been removed. The purpose is to provide a recycling method.
前記課題を解決するため、本発明者らは鋭意検討した結果、プラスチック被覆を除去した光ファイバー心線を炭素熱還元することにより、シリコン（元素状ケイ素）が高転換率で得られるとの知見を得、本発明に到達した。 In order to solve the above-mentioned problems, the present inventors have made extensive studies and have found that silicon (elemental silicon) can be obtained at a high conversion rate by carbothermal reduction of the optical fiber core wire from which the plastic coating has been removed. And reached the present invention.
すなわち、本発明は以下の通りである。
１）プラスチック被覆を除去した光ファイバー心線を炭素熱還元し、該光ファイバー心線をシリカ源としてシリコンを製造することを特徴とする光ファイバー心線のリサイクル方法。
２）前記光ファイバー心線と炭素源を坩堝に入れて炉内で加熱する、前記１）に記載の光ファイバー心線のリサイクル方法。
３）前記光ファイバー心線を炭素源と混合して混合物と成し、該混合物を炉内で加熱する、前記１）又は２）に記載の光ファイバー心線のリサイクル方法。
４）前記炭素源が、黒鉛、カーボンブラック、コークス、木炭、石炭又はこれらの混合物である、前記２）又は３）に記載の光ファイバー心線のリサイクル方法。
５）前記坩堝が炭素製、黒鉛製製又は炭化ケイ素製である、前記２）〜４）のいずれかに記載の光ファイバー心線のリサイクル方法。
６）前記坩堝を２段に配置し、下段坩堝に光ファイバー心線と炭素源を入れ、上段坩堝に炭素源を入れる、前記２）〜５）のいずれかに記載の光ファイバー心線のリサイクル方法。
７）炭素熱還元における反応温度が１８００℃〜２１００℃の範囲内で、かつ、シリカに対する炭素のモル比が３．５〜８．０の範囲内である、前記１）〜６）のいずれかに記載の光ファイバー心線のリサイクル方法。
That is, the present invention is as follows.
1) A method for recycling an optical fiber core, wherein the optical fiber core wire from which the plastic coating has been removed is carbothermally reduced, and silicon is produced using the optical fiber core wire as a silica source.
2) The method for recycling an optical fiber core according to 1), wherein the optical fiber core and a carbon source are placed in a crucible and heated in a furnace.
3) The method for recycling an optical fiber core according to 1) or 2), wherein the optical fiber core is mixed with a carbon source to form a mixture, and the mixture is heated in a furnace.
4) The method for recycling an optical fiber according to 2) or 3), wherein the carbon source is graphite, carbon black, coke, charcoal, coal, or a mixture thereof.
5) The method for recycling an optical fiber core according to any one of 2) to 4), wherein the crucible is made of carbon, graphite, or silicon carbide.
6) The method for recycling an optical fiber core according to any one of 2) to 5), wherein the crucible is arranged in two stages, an optical fiber core and a carbon source are placed in a lower crucible, and a carbon source is placed in an upper crucible.
7) Any of 1) to 6) above, wherein the reaction temperature in carbothermal reduction is in the range of 1800 ° C to 2100 ° C, and the molar ratio of carbon to silica is in the range of 3.5 to 8.0. Recycling method of optical fiber core wire as described in 1.
８）前記１）〜７）のいずれかに記載の方法によって製造されたことを特徴とするシリコン。
９）光起電力又はエレクトロニクスの品位のシリコン製造における原料として用いられる、前記８）に記載のシリコン。
8) Silicon produced by the method according to any one of 1) to 7).
9) The silicon according to 8) above, which is used as a raw material in the production of silicon of photovoltaic or electronics quality.
光ファイバー心線は元々不純物の少ない高純度シリカを原料に用いているため、本発明によれば、廃光ファイバーケーブルから回収して得た光ファイバー心線を炭素熱還元するだけで、シリコンを高転換率で製造することができる。また、製造したシリコンは光起電力又はエレクトロニクスの品位のシリコン製造における原料として用いることができるので、経済性に優れたリサイクル方法となり得る。 Since the optical fiber core originally uses high-purity silica with few impurities as a raw material, according to the present invention, it is possible to convert silicon into a high conversion rate simply by carbothermal reduction of the optical fiber core recovered from the waste optical fiber cable. Can be manufactured. Further, since the produced silicon can be used as a raw material in the production of silicon of photovoltaic or electronics quality, it can be a recycling method with excellent economic efficiency.
炭素熱還元反応は、周知のように以下の主反応によりシリコンと一酸化炭素が生成し、同時に副反応が起きる。
主反応 ＳｉＯ２＋２Ｃ＝Ｓｉ＋２ＣＯ （吸熱反応）
副反応 ＳｉＯ２＋Ｃ＝ＳｉＯ＋ＣＯ
ＳｉＯ２＋３Ｃ＝ＳｉＣ＋２ＣＯ
ＳｉＣ＋ＳｉＯ＝２Ｓｉ＋ＣＯ
ＳｉＯ＋Ｃ＝Ｓｉ＋ＣＯ
As is well known, in the carbothermal reduction reaction, silicon and carbon monoxide are generated by the following main reaction, and a side reaction occurs simultaneously.
Main reaction SiO 2 + 2C = Si + 2CO (endothermic reaction)
Side reaction SiO 2 + C = SiO + CO
SiO 2 + 3C = SiC + 2CO
SiC + SiO = 2Si + CO
SiO + C = Si + CO
本発明の炭素熱還元反応は、電気炉等の炉内で実施する。炉は、反応を窒素ガス、アルゴンガス等の不活性ガス雰囲気下で行うことができるものが好ましいが、特に制限はない。 The carbothermal reduction reaction of the present invention is carried out in a furnace such as an electric furnace. The furnace is preferably capable of performing the reaction in an inert gas atmosphere such as nitrogen gas or argon gas, but is not particularly limited.
本発明では、炭素熱還元反応におけるシリカ源として、プラスチック被覆を除去した光ファイバー心線を用いる。該シリカ源となる光ファイバー心線は、廃光ファイバーケーブルから分離したものであって、プラスチック被覆を除去したものであれば、全て使用することができ、その分離方法及び性状は特に限定されない。該光ファイバー心線に洗浄、粉砕等の後処理を施し、実質的にシリカ純度を高めたもの等を原料に用いることもできる。 In the present invention, an optical fiber core wire from which the plastic coating is removed is used as a silica source in the carbothermal reduction reaction. The optical fiber core wire used as the silica source is separated from the waste optical fiber cable and can be used as long as the plastic coating is removed. The separation method and properties are not particularly limited. The optical fiber core can be subjected to post-treatment such as washing and pulverization to substantially increase the silica purity, and the like can be used as a raw material.
本発明において、原料として好適な光ファイバー心線は、特開２００６−２８９３３９号公報、同１５９１４９号公報、同１５９１５０号公報、同１８２８６３号公報、同１８７７６４号公報、同２５５５４４号公報、特開２００７−１０５６３５号公報に開示した方法で得ることができる。これらの方法によれば、光ファイバー心線テープから心線を分離するので、高純度の光ファイバー心線が得られる。 In the present invention, optical fiber core wires suitable as raw materials are disclosed in JP-A-2006-289339, JP-A-159149, JP-A-159150, JP-A-182863, JP-A-187564, JP-A-255544, JP-A-2007-. It can be obtained by the method disclosed in Japanese Patent No. 105635. According to these methods, since the core wire is separated from the optical fiber core tape, a high purity optical fiber core wire can be obtained.
炭素熱還元反応における炭素源としては、黒鉛、カーボンブラック、コークス、木炭、石炭又はこれらの混合物等を用いることができる。或いは、ポリマー、炭化水素、炭水化物、糖類又はこれらの混合物でもよい。炭素源の形態は、粉体あるいは成形品など、還元反応を行わせることができる形態であれば特に制限はなく、例えば、粉末、粒子、チップ、塊、ペレット、タドン等の形態であってよい。炉内での飛散防止のため、炭素粉をペレット状等に成形したものを用いることもできる。 As the carbon source in the carbothermal reduction reaction, graphite, carbon black, coke, charcoal, coal, or a mixture thereof can be used. Alternatively, it may be a polymer, hydrocarbon, carbohydrate, saccharide or a mixture thereof. The form of the carbon source is not particularly limited as long as it can cause a reduction reaction, such as powder or molded product, and may be in the form of powder, particles, chips, lumps, pellets, tadon, etc. . In order to prevent scattering in the furnace, it is also possible to use carbon powder formed into a pellet or the like.
炭素熱還元反応におけ反応温度は、１８００〜２１００℃の範囲が好ましい。反応温度が低すぎるとシリコンへの転換率が低くなり、一方、反応温度が高くなると純度は高くなる傾向があるが、転換率はやや低下する。この原因の詳細は不明であるが、副反応により生成するＳｉＯ（沸点１８８０℃）が炭素に捕捉されにくくなるためと推察される。 The reaction temperature in the carbothermal reduction reaction is preferably in the range of 1800 to 2100 ° C. If the reaction temperature is too low, the conversion rate to silicon is low. On the other hand, if the reaction temperature is high, the purity tends to be high, but the conversion rate is slightly reduced. Although the details of the cause are unknown, it is presumed that SiO (boiling point 1880 ° C.) generated by the side reaction is hardly captured by carbon.
シリカに対する炭素のモル比は３．５〜８．０の範囲が好ましく、より好ましくは３．５〜５．０の範囲であり、最も好ましくは４前後である。モル比が小さすぎるとシリコンへの転換率が低くなり、一方、モル比が大きくなっても純度、転換率への影響は小さく、経済的に無駄である。 The molar ratio of carbon to silica is preferably in the range of 3.5 to 8.0, more preferably in the range of 3.5 to 5.0, and most preferably around 4. If the molar ratio is too small, the conversion rate to silicon is low. On the other hand, even if the molar ratio is large, the effect on the purity and conversion rate is small and economically useless.
光ファイバー心線は、所要量の炭素源とともに坩堝に入れ、不活性ガス雰囲気下にて炉内で加熱してシリコンを生成させるのがよい。その場合、シリカ源と炭素源をそれぞれ坩堝に入れてもよいが、シリコンへの転換率を高めるために、光ファイバー心線を炭素源と混合して混合物と成し、該混合物を炉内で加熱することが好ましい。混合物は単に混ぜ合わせただけのものでもよいし、混合した後ペレット状等の適宜な形態に成形した成形品でもよく、混合形態は限定されない。また、光ファイバー心線と炭素は上記のモル比で入れるが、この際、光ファイバー心線および炭素源は、反応性を高めるために粉砕した粉状のものを用いることが好ましい。 The optical fiber core is preferably placed in a crucible together with a required amount of carbon source and heated in a furnace under an inert gas atmosphere to generate silicon. In that case, the silica source and the carbon source may be put in the crucible, respectively, but in order to increase the conversion rate to silicon, the optical fiber core wire is mixed with the carbon source to form a mixture, and the mixture is heated in the furnace. It is preferable to do. The mixture may be simply mixed, or may be a molded product formed into an appropriate form such as a pellet after mixing, and the mixing form is not limited. The optical fiber core and carbon are added in the above molar ratio. At this time, it is preferable to use a ground powder for the optical fiber core and the carbon source in order to increase the reactivity.
反応容器となる坩堝は、炭素製、黒鉛製、炭化ケイ素製等を用いることができるが、炭素製又は黒鉛製の坩堝を用いると炭素不足が極端な場合の炭素不足を補うことができるため、好ましい。 The crucible to be a reaction vessel can be made of carbon, graphite, silicon carbide, etc., but if a carbon or graphite crucible is used, it can compensate for the carbon shortage when the carbon shortage is extreme, preferable.
炉内に入れる坩堝は１段で用いることもできるが、坩堝を２段にし、下段に心線と炭素源、上段に炭素源（主にＳｉＯ還元用となる）を配置するのが好ましい。このような配置は、副反応で生成するＳｉＯを有効に捕捉・還元するのに好ましい配置である。 The crucible placed in the furnace can be used in one stage, but it is preferable to arrange the crucible in two stages, and arrange a core wire and a carbon source in the lower stage and a carbon source (mainly for SiO reduction) in the upper stage. Such an arrangement is a preferable arrangement for effectively capturing and reducing SiO generated by the side reaction.
本発明の方法によって製造されたシリコンは、中純度シリコンとして、光起電力又はエレクトロニクスの品位のシリコン製造における原料として用いることができる。 Silicon produced by the method of the present invention can be used as medium purity silicon as a raw material in photovoltaic or electronics grade silicon production.
以下、実施例を用いて本発明をさらに具体的に説明するが。本発明は以下の実施例のみに限定されるものではない。 Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited only to the following examples.
（実施例１）
光ファイバーからマテリアルリサイクル法により分別回収した直径約１２５μｍの心線を石英乳鉢で粉砕した。粉砕した心線（１３．９６ｇ）と黒鉛粉（５．５８ｇ）を、シリカ：炭素（モル比）＝１：２．００で混合し、直径約１０ｍｍ、厚み約５ｍｍのペレット状にしたものを１９．５４ｇ、中央の炭素製坩堝に入れた。上部の炭素製坩堝には、ショ糖を２％混合した黒鉛粉のペレットを５．８２ｇ（シリカ：炭素（モル比）＝１：２．０５）入れた。
Example 1
A core wire having a diameter of about 125 μm, which was separated and collected from the optical fiber by the material recycling method, was pulverized in a quartz mortar. A crushed core wire (13.96 g) and graphite powder (5.58 g) were mixed at a ratio of silica: carbon (molar ratio) = 1: 2.00 to form a pellet having a diameter of about 10 mm and a thickness of about 5 mm. 19.54 g was placed in a central carbon crucible. The upper carbon crucible was charged with 5.82 g (silica: carbon (molar ratio) = 1.2.05) of graphite powder pellets mixed with 2% sucrose.
高温電気炉（Ｗヒーター、内容積１３Ｌ）に、図１に示すように、下から炭素製坩堝１、心線と黒鉛粉のペレット７を入れた炭素製坩堝２、黒鉛粉のペレット８を入れた炭素製坩堝３の順に重ね、上部に蓋５を被せ蓋５と坩堝３の間にスリット６を設けた。また、炭素製坩堝２と３の間にφ１ｍｍの穴４を設けた。各炭素製坩堝は、内径２５ｍｍ×深さ５０ｍｍのものを用いた。 As shown in FIG. 1, a carbon crucible 1, a carbon crucible 2 containing a core wire and a graphite powder pellet 7, and a graphite powder pellet 8 are placed in a high temperature electric furnace (W heater, internal volume 13L) from the bottom. The carbon crucibles 3 were stacked in this order, and the top 5 was covered with a lid 5, and a slit 6 was provided between the lid 5 and the crucible 3. A hole 4 having a diameter of 1 mm was provided between the carbon crucibles 2 and 3. Each carbon crucible used had an inner diameter of 25 mm and a depth of 50 mm.
アルゴン雰囲気下で加熱を開始し（昇温速度：１０℃／ｍｉｎ）、１８００℃で１時間保持し、炭素熱還元反応を行った。その後、冷却を開始し（降温速度：３℃／ｍｉｎ）、１４３０℃で１時間保持し、熟成した。その後さらに室温まで冷却し（降温速度：３℃／ｍｉｎ）、反応操作を終えた。
２個の坩堝の内容物を取り出し、重量分析、走査型電子顕微鏡（ＳＥＭ）、Ｘ線マイクロアナライザー（ＥＰＭＡ）分析による組成推定を行い、以下に示す方法によりシリコンへの転換率を算出した。
Heating was started under an argon atmosphere (temperature increase rate: 10 ° C./min) and held at 1800 ° C. for 1 hour to perform a carbothermal reduction reaction. Thereafter, cooling was started (temperature decrease rate: 3 ° C./min), and the mixture was kept at 1430 ° C. for 1 hour and aged. Thereafter, it was further cooled to room temperature (temperature decrease rate: 3 ° C./min), and the reaction operation was completed.
The contents of the two crucibles were taken out, the composition was estimated by gravimetric analysis, scanning electron microscope (SEM), and X-ray microanalyzer (EPMA) analysis, and the conversion rate to silicon was calculated by the method described below.
（実施例２〜５）
仕込み心線粉の重量を、１４ｇ程度でほぼ一定にし、反応温度、炭素／シリカモル比を変化させた以外は、実施例１と同様の操作で炭素熱還元反応を実施した。
(Examples 2 to 5)
The carbothermal reduction reaction was carried out in the same manner as in Example 1 except that the weight of the charged core wire powder was made approximately constant at about 14 g and the reaction temperature and the carbon / silica molar ratio were changed.
表１に以上の実験条件、表２に実験結果をまとめて示す。 Table 1 summarizes the above experimental conditions, and Table 2 summarizes the experimental results.
（評価方法）
表２中のＳｉ転換率は、下記式により求めた。
Ｓｉ転換率（％）＝〔生成物中のＳｉのモル数／仕込みシリカのモル数〕×１００
但し 生成物中のＳｉのモル数＝〔上段坩堝の生成物（ｇ）＋下段坩堝の生成物（ｇ）〕×〔生成物のＳｉ組成（ｗｔ比）〕／２８．０９
仕込みシリカのモル数＝仕込みシリカ（ｇ）／６０．０９
(Evaluation methods)
The Si conversion rate in Table 2 was determined by the following formula.
Si conversion rate (%) = [number of moles of Si in product / number of moles of charged silica] × 100
However, the number of moles of Si in the product = [product of the upper crucible (g) + product of the lower crucible (g)] × [Si composition of the product (wt ratio)] / 28.09
Number of moles of charged silica = charged silica (g) /6.09
表２からわかるように、反応温度１８００〜２１００℃、炭素のシリカに対するモル比
３．５〜８で炭素熱還元反応を行えば、光ファイバー心線を７５％以上の転換率でシリコン（元素状ケイ素）にリサイクルすることができる。
As can be seen from Table 2, when the carbothermal reduction reaction is performed at a reaction temperature of 1800 to 2100 ° C. and a molar ratio of carbon to silica of 3.5 to 8, the optical fiber core wire is converted into silicon (elemental silicon) at a conversion rate of 75% or more. ) Can be recycled.
（参考例１）
粉砕した心線１４．８２ｇと黒鉛粉を、シリカ：炭素（モル比）＝１：２．００で混合したものを炭素製坩堝に入れ、高温電気炉内にて、反応温度１８００℃で１時間反応させた以外は、実施例１と同様の操作で炭素熱還元反応を実施した。その結果、外観が緑灰色の固体が得られた。
(Reference Example 1)
A mixture of 14.82 g of pulverized core wire and graphite powder mixed with silica: carbon (molar ratio) = 1: 2.00 is placed in a carbon crucible, and the reaction temperature is 1800 ° C. for 1 hour in a high-temperature electric furnace. A carbothermal reduction reaction was carried out in the same manner as in Example 1 except that the reaction was performed. As a result, a greenish gray solid was obtained.
（参考例２）
粉砕した心線１４．９８ｇと黒鉛粉を、シリカ：炭素（モル比）＝１：２．００で混合したものを炭素製坩堝に入れ、高温電気炉内にて、反応温度１６００℃で２時間反応させた以外は、実施例１と同様の操作で炭素熱還元反応を実施した。その結果、外観が灰色の固体が得られた。
(Reference Example 2)
A mixture of 14.98 g of pulverized core wire and graphite powder mixed at silica: carbon (molar ratio) = 1: 2.00 is placed in a carbon crucible, and the reaction temperature is 1600 ° C. for 2 hours in a high temperature electric furnace. A carbothermal reduction reaction was carried out in the same manner as in Example 1 except that the reaction was performed. As a result, a solid having a gray appearance was obtained.
表３に以上の実験結果をまとめて示す。 Table 3 summarizes the above experimental results.
表３の結果から、炭素／シリカのモル比が小さすぎる場合および反応温度が低すぎる場合は、炭素熱還元反応が十分行われないことがわかる。 From the results of Table 3, it can be seen that when the carbon / silica molar ratio is too small and the reaction temperature is too low, the carbothermal reduction reaction is not sufficiently performed.
本発明に係る炭素熱還元反応によって得られたシリコンは、さらに精製することにより太陽電池や半導体等の原材料として用いることができるので、シリコンの新たな供給源となり得る。また、本発明で用いる光ファイバー心線は元々高純度で極少量のゲルマニウムを含有しているが、アルミニウムを含有していないため、高純度シリコンへの精製も容易である。そのため、得られたシリコンを太陽電池用シリコンに再利用することにより、当該シリコンに半導体用シリコンを転用した場合に比べ、大きな経済効果を期待することができる。 Silicon obtained by the carbothermal reduction reaction according to the present invention can be used as a raw material for solar cells, semiconductors, and the like by further purification, and thus can be a new source of silicon. The optical fiber used in the present invention originally has high purity and contains a very small amount of germanium, but since it does not contain aluminum, it can be easily purified to high purity silicon. Therefore, by reusing the obtained silicon for solar cell silicon, a large economic effect can be expected as compared with the case where silicon for semiconductor is diverted to the silicon.
１，２，３ 坩堝
４ 穴
５ 蓋
６ スリット
７ シリカと黒鉛粉のペレット
８ 黒鉛粉のペレット
1, 2, 3 Crucible 4 Hole 5 Lid 6 Slit 7 Silica and graphite powder pellet 8 Graphite powder pellet
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| JPS62260711A (en) * | 1986-04-29 | 1987-11-13 | ダウ・コ−ニング・コ−ポレ−シヨン | Manufacture of silicon by carbon heat reduction of silicate dioxide |
| JPH11228124A (en) * | 1998-02-05 | 1999-08-24 | Chubu Electric Power Co Inc | Production of crystalline silicon |
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| JP2004243264A (en) * | 2003-02-17 | 2004-09-02 | Hiroshi Takahashi | Method for recycling waste optical fiber |
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| JPS60251112A (en) * | 1984-05-23 | 1985-12-11 | Daido Steel Co Ltd | Process and device for preparing silicon |
| JPS616115A (en) * | 1984-06-20 | 1986-01-11 | Kawasaki Steel Corp | Manufacture of metallic silicon |
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