JP7471978B2 - Method for measuring oxygen gas concentration in chlorine-containing gas, method for calculating current efficiency, and method for producing metallic magnesium - Google Patents
Method for measuring oxygen gas concentration in chlorine-containing gas, method for calculating current efficiency, and method for producing metallic magnesium Download PDFInfo
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- 239000007789 gas Substances 0.000 title claims description 285
- 239000000460 chlorine Substances 0.000 title claims description 200
- 229910052801 chlorine Inorganic materials 0.000 title claims description 199
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 title claims description 198
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 title claims description 117
- 229910001882 dioxygen Inorganic materials 0.000 title claims description 117
- 238000000034 method Methods 0.000 title claims description 38
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 title claims description 21
- 239000011777 magnesium Substances 0.000 title claims description 20
- 229910052749 magnesium Inorganic materials 0.000 title claims description 19
- 238000004519 manufacturing process Methods 0.000 title claims description 14
- 150000003839 salts Chemical class 0.000 claims description 105
- TWRXJAOTZQYOKJ-UHFFFAOYSA-L Magnesium chloride Chemical compound [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 claims description 68
- 238000005259 measurement Methods 0.000 claims description 57
- 238000005868 electrolysis reaction Methods 0.000 claims description 42
- 229910001629 magnesium chloride Inorganic materials 0.000 claims description 34
- 238000004458 analytical method Methods 0.000 claims description 27
- 238000001320 near-infrared absorption spectroscopy Methods 0.000 claims description 10
- 239000010419 fine particle Substances 0.000 claims description 9
- 238000012544 monitoring process Methods 0.000 claims description 5
- 238000011084 recovery Methods 0.000 description 31
- KZBUYRJDOAKODT-UHFFFAOYSA-N Chlorine Chemical compound ClCl KZBUYRJDOAKODT-UHFFFAOYSA-N 0.000 description 13
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 12
- 229910052751 metal Inorganic materials 0.000 description 12
- 239000002184 metal Substances 0.000 description 12
- 239000001301 oxygen Substances 0.000 description 12
- 229910052760 oxygen Inorganic materials 0.000 description 12
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 9
- 238000005660 chlorination reaction Methods 0.000 description 8
- 230000003287 optical effect Effects 0.000 description 8
- 238000004364 calculation method Methods 0.000 description 6
- 239000000203 mixture Substances 0.000 description 5
- 238000012545 processing Methods 0.000 description 5
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- 229910052757 nitrogen Inorganic materials 0.000 description 4
- 238000007789 sealing Methods 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000005192 partition Methods 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 2
- 238000000862 absorption spectrum Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 238000007689 inspection Methods 0.000 description 2
- 230000001678 irradiating effect Effects 0.000 description 2
- 230000007257 malfunction Effects 0.000 description 2
- 229910001510 metal chloride Inorganic materials 0.000 description 2
- 238000007781 pre-processing Methods 0.000 description 2
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 description 1
- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 1
- 238000004847 absorption spectroscopy Methods 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 239000001110 calcium chloride Substances 0.000 description 1
- 229910001628 calcium chloride Inorganic materials 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000010962 carbon steel Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 125000001309 chloro group Chemical group Cl* 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 229910052593 corundum Inorganic materials 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 238000002290 gas chromatography-mass spectrometry Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000004445 quantitative analysis Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000011819 refractory material Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000010802 sludge Substances 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
- 229910001845 yogo sapphire Inorganic materials 0.000 description 1
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- Electrolytic Production Of Metals (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
Description
本発明は、塩素含有ガス中の酸素ガス濃度測定方法、電流効率の演算方法及び金属マグネシウムの製造方法に関する。 The present invention relates to a method for measuring the concentration of oxygen gas in a chlorine-containing gas, a method for calculating current efficiency, and a method for producing metallic magnesium.
物の製造において排出されるガス中の各成分の定量分析法は種々知られており、例えばガスクロマトグラフ法、ガスクロマトグラフ－質量分析法、吸光分析法などがある。 There are various known methods for quantitatively analyzing the components in gases emitted during the manufacture of products, such as gas chromatography, gas chromatography-mass spectrometry, and absorption spectrometry.
排出ガス中の各成分の定量分析に用いる分析装置には、連続的に測定可能なレーザ式ガス分析装置がある。レーザ式ガス分析装置は、測定対象ガスにレーザ光を照射し、測定対象ガスを透過したレーザ光の吸収スペクトルに基づいて、ガス中の各成分濃度を測定することが可能なものである。 One type of analytical equipment used for quantitative analysis of each component in exhaust gas is a laser gas analyzer that is capable of continuous measurement. A laser gas analyzer irradiates the gas to be measured with laser light and is capable of measuring the concentration of each component in the gas based on the absorption spectrum of the laser light that passes through the gas to be measured.
レーザ式ガス分析装置を用いてガス中の主成分濃度を測定する方法としては、例えば特許文献１の技術が挙げられる。特許文献１には、「塩素含有ガスを収容する測定セルと、前記測定セル内を流れる前記塩素含有ガスに対し、紫外線を照射するＬＥＤ光源を備える発光部と、前記測定セルを透過した前記紫外線を受光する受光部と、前記受光部からの出力信号に基づいて前記塩素含有ガス中の塩素濃度を演算する演算部とを備えることを特徴とする塩素濃度分析装置。」が記載されている。 One example of a method for measuring the concentration of a major component in a gas using a laser gas analyzer is the technology of Patent Document 1. Patent Document 1 describes a "chlorine concentration analyzer comprising a measurement cell for storing a chlorine-containing gas, a light-emitting unit having an LED light source for irradiating the chlorine-containing gas flowing in the measurement cell with ultraviolet light, a light-receiving unit for receiving the ultraviolet light that has passed through the measurement cell, and a calculation unit for calculating the chlorine concentration in the chlorine-containing gas based on an output signal from the light-receiving unit."
特許文献１に記載の塩素濃度分析装置は、発光部のレーザ光源から発光する紫外線に対して吸収スペクトルを有する塩素分子に着目して塩素濃度を測定している。例えば溶融塩電解槽内への外気の流入を監視する場合、溶融塩電解槽内から排出される塩素含有ガス中の塩素濃度は常に高い傾向があるので、塩素ガスの純度よりもむしろ微量である不純物の量を確認したいという要望があった。 The chlorine concentration analyzer described in Patent Document 1 measures the chlorine concentration by focusing on chlorine molecules that have an absorption spectrum for the ultraviolet light emitted from the laser light source of the light-emitting unit. For example, when monitoring the inflow of outside air into a molten salt electrolytic cell, the chlorine concentration in the chlorine-containing gas discharged from the molten salt electrolytic cell tends to always be high, so there has been a demand to check the amount of trace impurities rather than the purity of the chlorine gas.
そこで、一実施形態においては、流動状態の塩素含有ガス中の酸素ガス濃度を連続的に把握することが可能な塩素含有ガス中の酸素ガス濃度測定方法を提供する。 Therefore, in one embodiment, a method for measuring the concentration of oxygen gas in a chlorine-containing gas is provided that can continuously measure the concentration of oxygen gas in a flowing chlorine-containing gas.
すなわち、本発明は一側面において、塩素含有ガス中の酸素ガス濃度を測定する塩素含有ガス中の酸素ガス濃度測定方法であって、流動状態の分析用塩素含有ガスを近赤外線吸収分光法により分析し、塩素含有ガス中の酸素ガス濃度を測定する酸素ガス濃度測定ステップを含む、塩素含有ガス中の酸素ガス濃度測定方法である。 That is, in one aspect, the present invention is a method for measuring the oxygen gas concentration in a chlorine-containing gas, which includes an oxygen gas concentration measurement step of analyzing a chlorine-containing gas for analysis in a flowing state by near-infrared absorption spectroscopy and measuring the oxygen gas concentration in the chlorine-containing gas.
本発明に係る塩素含有ガス中の酸素ガス濃度測定方法の一実施形態においては、前記酸素ガス濃度測定ステップ前に、塩素含有ガスの一部を前記分析用塩素含有ガスとして分岐させて流すガス分岐ステップと、前記酸素ガス濃度測定ステップ後に、前記分析用塩素含有ガスを前記塩素含有ガスに合流させるガス合流ステップを更に含む。 In one embodiment of the method for measuring the concentration of oxygen gas in a chlorine-containing gas according to the present invention, the method further includes a gas branching step of branching a portion of the chlorine-containing gas as the chlorine-containing gas for analysis and flowing it before the oxygen gas concentration measurement step, and a gas merging step of merging the chlorine-containing gas for analysis with the chlorine-containing gas after the oxygen gas concentration measurement step.
本発明に係る塩素含有ガス中の酸素ガス濃度測定方法の一実施形態においては、前記塩素含有ガスは、塩化マグネシウムの溶融塩電解で生成される。 In one embodiment of the method for measuring the concentration of oxygen gas in a chlorine-containing gas according to the present invention, the chlorine-containing gas is produced by electrolysis of a molten salt of magnesium chloride.
本発明に係る塩素含有ガス中の酸素ガス濃度測定方法の一実施形態においては、前記ガス分岐ステップ前に、前記塩素含有ガスの流量を測定するガス流量測定ステップを更に含む。 In one embodiment of the method for measuring the concentration of oxygen gas in a chlorine-containing gas according to the present invention, a gas flow rate measurement step for measuring the flow rate of the chlorine-containing gas is further included before the gas branching step.
本発明に係る塩素含有ガス中の酸素ガス濃度測定方法の一実施形態においては、前記酸素ガス濃度測定ステップ前に、前記塩素含有ガス中の微粉を予め捕集する前処理ステップを更に含む。 In one embodiment of the method for measuring the concentration of oxygen gas in a chlorine-containing gas according to the present invention, a pretreatment step of collecting fine particles in the chlorine-containing gas in advance is included before the oxygen gas concentration measurement step.
本発明に係る塩素含有ガス中の酸素ガス濃度測定方法の一実施形態においては、前記ガス流量測定ステップ前に、前記塩素含有ガス中の微粉をフィルタで予め捕集する前処理ステップを更に含む。 In one embodiment of the method for measuring the concentration of oxygen gas in a chlorine-containing gas according to the present invention, the method further includes a pretreatment step of collecting fine particles in the chlorine-containing gas with a filter before the gas flow rate measurement step.
また、本発明は別の側面において、上記いずれかの塩素含有ガス中の酸素ガス濃度測定方法により、前記ガス流量測定ステップで得られた塩素含有ガスの流量と、前記酸素ガス濃度測定ステップで得られた該塩素含有ガス中の酸素ガス濃度とを用いて、塩化マグネシウムの溶融塩電解の電流効率を求めることを含み、前記塩素含有ガスは、前記塩化マグネシウムの溶融塩電解で生成される、電流効率の演算方法である。 In another aspect, the present invention is a method for calculating current efficiency, which includes determining the current efficiency of molten salt electrolysis of magnesium chloride using the flow rate of the chlorine-containing gas obtained in the gas flow rate measurement step and the oxygen gas concentration in the chlorine-containing gas obtained in the oxygen gas concentration measurement step by any of the above methods for measuring the oxygen gas concentration in a chlorine-containing gas, and the chlorine-containing gas is generated by the molten salt electrolysis of magnesium chloride.
さらに、本発明は別の側面において、溶融塩電解槽内で塩化マグネシウムの溶融塩電解により金属マグネシウムを生成する生成工程を含む金属マグネシウムの製造方法であって、該生成工程においては、上記いずれかの塩素含有ガス中の酸素ガス濃度測定方法により、前記溶融塩電解槽内への外気の流入を監視することを含む、金属マグネシウムの製造方法である。 Furthermore, in another aspect, the present invention is a method for producing metallic magnesium, which includes a production step of producing metallic magnesium by molten salt electrolysis of magnesium chloride in a molten salt electrolytic cell, and in the production step, the method includes monitoring the inflow of outside air into the molten salt electrolytic cell by any of the above-mentioned methods for measuring the oxygen gas concentration in a chlorine-containing gas.
本発明の一実施形態によれば、流動状態の塩素含有ガス中の酸素ガス濃度を連続的に把握することができる。 According to one embodiment of the present invention, it is possible to continuously monitor the oxygen gas concentration in a flowing chlorine-containing gas.
本発明は以下に説明する各実施形態に限定されるものではなく、その要旨を逸脱しない範囲で構成要素を変形して具体化できる。また、各実施形態に開示されている複数の構成要素の適宜な組み合わせにより、種々の発明を形成できる。 The present invention is not limited to the embodiments described below, and can be embodied by modifying the components without departing from the spirit of the invention. In addition, various inventions can be created by appropriately combining the multiple components disclosed in each embodiment.
［１．塩素含有ガス中の酸素ガス濃度測定方法］
本発明に係る塩素含有ガス中の酸素ガス濃度測定方法の一実施形態においては、塩素含有ガスの酸素ガス濃度を測定するものであって、図１に示すように、前処理ステップＳ１０１と、ガス流量測定ステップＳ１０２と、ガス分岐ステップＳ１０３と、酸素ガス濃度測定ステップＳ１０４と、ガス合流ステップＳ１０５とを含む。該酸素ガス濃度測定ステップＳ１０４においては、流動状態の分析用塩素含有ガスの酸素ガス濃度を近赤外線吸収分光法により分析し、塩素含有ガス中の酸素ガス濃度を測定する。よって、本実施形態では、流動状態の分析用塩素含有ガスに対して近赤外線を照射して酸素ガス濃度を測定する。これにより、一実施形態においては、流動状態の塩素含有ガス中の酸素ガス濃度を連続的に把握することができる。例えば、塩化マグネシウムの電気分解で生成した塩素含有ガスを塩化炉に送る際に上記測定を実施することができる。また、測定結果を長期間にわたり連続的に入手可能である。
なお、一実施形態においては、上記ステップＳ１０１～Ｓ１０５の順に実施することが好ましい。また、前処理ステップＳ１０１、ガス流量測定ステップＳ１０２、ガス分岐ステップＳ１０３及び、ガス合流ステップＳ１０５は好ましい態様に過ぎず、一実施形態においては、それらのうちの少なくとも１つのステップを省略してもよい。省略しても流動状態の塩素含有ガス中の酸素ガス濃度を把握することが可能な場合もあるからである。また、図１に示す実施形態では塩素含有ガスのガス流量測定が塩素含有ガス中の酸素ガス濃度測定の前に行われているが、該ガス流量測定は酸素ガス濃度測定後であって、かつ、ガス合流後に行うこともできる。即ち、各ステップは順序を入れ替えて実施可能なものもある。また、一実施形態において溶融塩電解槽を用いて説明しているが、これに限定されるものではない。
[1. Method for measuring oxygen gas concentration in chlorine-containing gas]
In one embodiment of the method for measuring the oxygen gas concentration in a chlorine-containing gas according to the present invention, the oxygen gas concentration of the chlorine-containing gas is measured, and as shown in FIG. 1, the method includes a pretreatment step S101, a gas flow rate measurement step S102, a gas branching step S103, an oxygen gas concentration measurement step S104, and a gas merging step S105. In the oxygen gas concentration measurement step S104, the oxygen gas concentration of the chlorine-containing gas for analysis in a flowing state is analyzed by near-infrared absorption spectroscopy, and the oxygen gas concentration in the chlorine-containing gas is measured. Therefore, in this embodiment, the oxygen gas concentration is measured by irradiating the chlorine-containing gas for analysis in a flowing state with near-infrared rays. Thereby, in one embodiment, the oxygen gas concentration in the chlorine-containing gas in a flowing state can be continuously grasped. For example, the above measurement can be performed when the chlorine-containing gas generated by electrolysis of magnesium chloride is sent to a chlorination furnace. In addition, the measurement results can be continuously obtained over a long period of time.
In one embodiment, the steps S101 to S105 are preferably performed in this order. The pretreatment step S101, the gas flow rate measurement step S102, the gas branching step S103, and the gas merging step S105 are merely preferred aspects, and in one embodiment, at least one of these steps may be omitted. This is because there are cases where the oxygen gas concentration in the chlorine-containing gas in a flowing state can be grasped even if the steps are omitted. In addition, in the embodiment shown in FIG. 1, the gas flow rate measurement of the chlorine-containing gas is performed before the oxygen gas concentration measurement in the chlorine-containing gas, but the gas flow rate measurement can also be performed after the oxygen gas concentration measurement and after the gas merging. That is, the order of each step can be changed. In addition, although the molten salt electrolytic cell is used in the embodiment, the present invention is not limited to this.
（概要）
先述したように、塩化マグネシウムの溶融塩電解で発生し溶融塩電解槽から排出される塩素含有ガスは一般的に高塩素濃度であるから、溶融塩電解槽内への外気の流入を把握するには塩素含有ガス中の塩素濃度を測定するよりも、塩素以外のガスの濃度を検知する方が効果的である。その理由としては、以下のことが推察される。
例えば、溶融塩電解槽の操業中、塩化マグネシウムの追い注ぎ（チャージ）或いは金属マグネシウムの回収のため溶融塩電解槽の金属回収室の上方の蓋の一部を開いた際には、負圧状態の溶融塩電解槽内に外気が流入しうる。このとき、外気の流入に起因して、塩素含有ガス中の塩素濃度は若干低下すると考えられる。そして、溶融塩電解槽内からの塩素含有ガスの継続的な排出により、この外気の流入からある程度時間が経過すると、溶融塩電解槽内から排出される塩素含有ガスは塩素濃度が再び高くなり、上記塩素濃度の若干の低下が解消される。ここで、外気の流入が僅かであった場合、その塩素含有ガス中の塩素濃度の変動が微小になることから、塩素濃度を測定してもそのような外気の流入があったか否かの判断は難しい場合もありうる。また、塩素含有ガス中の塩素濃度を測定する場合、塩素含有ガス中に塩素以外の何らかの成分が含まれていることがわかったとしても、その成分が外気に含まれる成分であるか否かまでは判別できない。
(overview)
As mentioned above, the chlorine-containing gas generated in the electrolysis of molten salt of magnesium chloride and discharged from the molten salt electrolytic cell generally has a high chlorine concentration, so that in order to grasp the inflow of outside air into the molten salt electrolytic cell, it is more effective to detect the concentration of gases other than chlorine than to measure the chlorine concentration in the chlorine-containing gas. The reason for this is presumed to be as follows.
For example, during the operation of the molten salt electrolytic cell, when a part of the lid above the metal recovery chamber of the molten salt electrolytic cell is opened to charge magnesium chloride or recover metallic magnesium, outside air may flow into the molten salt electrolytic cell under negative pressure. At this time, it is considered that the chlorine concentration in the chlorine-containing gas is slightly decreased due to the inflow of outside air. Then, due to the continuous discharge of the chlorine-containing gas from the molten salt electrolytic cell, the chlorine concentration of the chlorine-containing gas discharged from the molten salt electrolytic cell becomes high again after a certain amount of time has passed since the inflow of the outside air, and the above-mentioned slight decrease in the chlorine concentration is eliminated. Here, if the inflow of outside air is small, the fluctuation of the chlorine concentration in the chlorine-containing gas becomes small, so that even if the chlorine concentration is measured, it may be difficult to determine whether such an inflow of outside air has occurred. In addition, when the chlorine concentration in the chlorine-containing gas is measured, even if it is found that the chlorine-containing gas contains some component other than chlorine, it is not possible to determine whether the component is a component contained in the outside air.
したがって、塩素含有ガス中の塩素濃度ではなく、外気に含まれる酸素の酸素ガス濃度を測定した方が、溶融塩電解槽内に外気が流入したかどうかを把握しやすい。外気は酸素量と窒素量の比が概ね一定であるため、混入した酸素量がわかればこれに基づき混入した外気量を求めることができる。塩素含有ガスは通常、塩化マグネシウムの溶融塩電解で発生する気体の塩素で構成されているが、そのような塩素含有ガスから僅かでも酸素が検出された場合、例えば溶融塩電解槽の内部の気密性が一時的に維持されなくなって溶融塩電解槽内に外気が流入した可能性があると判断できる。 Therefore, it is easier to determine whether outside air has flowed into the molten salt electrolytic cell by measuring the oxygen gas concentration of oxygen contained in the outside air rather than the chlorine concentration in the chlorine-containing gas. Because the ratio of oxygen to nitrogen in the outside air is roughly constant, the amount of outside air that has flowed in can be calculated based on the amount of oxygen that has been mixed in. Chlorine-containing gas is usually composed of gaseous chlorine generated in the molten salt electrolysis of magnesium chloride, but if even a small amount of oxygen is detected in such a chlorine-containing gas, it can be determined that, for example, the airtightness inside the molten salt electrolytic cell may have temporarily been lost and outside air may have flowed into the molten salt electrolytic cell.
また、塩素含有ガス中に酸素が検出された場合、その酸素が溶融塩電解槽内への外気の流入に起因するものであると考えることができる。さらに、溶融塩電解槽内へ外気のみが流入していると仮定し、塩素含有ガス中の酸素ガス濃度を用い、外気（大気）中の成分構成比率を考慮し、塩素含有ガス中の塩素濃度を算出することが可能である。そして、溶融塩電解槽から排出される塩素含有ガスの流量を測定すれば、それらの塩素濃度及び塩素ガスの流量により上記溶融塩電解の電流効率を求めることができる。また、酸素ガス濃度を測定した後の塩素含有ガスは、実質的にその測定によって成分の変化等が生じないので、その後に、例えばチタン鉱石の塩化反応等の所定の用途に使用することができる。この場合、塩素含有ガスを有効に活用できる。
上記のように流動状態の塩素ガスについてその流量と濃度から電流効率を求めれば、溶融塩電解槽内で進行する塩化マグネシウムの電気分解の状況を連続的に把握できる。金属マグネシウムの回収量に基づき電流効率を求めると、金属マグネシウムの回収時に過去の電流効率を求めることはできるが、塩化マグネシウムの電気分解状況を時間別に把握することはできない。流動状態の塩素ガスから電流効率を求めることができれば、経時的な電気分解の状況を把握できる点で有利であり、さらにリアルタイムに電気分解の状況を把握できる点でも有利である。
In addition, when oxygen is detected in the chlorine-containing gas, it can be considered that the oxygen is due to the inflow of outside air into the molten salt electrolytic cell. Furthermore, assuming that only outside air flows into the molten salt electrolytic cell, it is possible to calculate the chlorine concentration in the chlorine-containing gas by using the oxygen gas concentration in the chlorine-containing gas and taking into account the component composition ratio in the outside air (atmosphere). Then, by measuring the flow rate of the chlorine-containing gas discharged from the molten salt electrolytic cell, the current efficiency of the molten salt electrolysis can be obtained from the chlorine concentration and the flow rate of the chlorine gas. In addition, since the chlorine-containing gas after the oxygen gas concentration is measured does not substantially undergo any change in its composition due to the measurement, it can be used for a predetermined purpose such as the chlorination reaction of titanium ore. In this case, the chlorine-containing gas can be effectively utilized.
As described above, if the current efficiency is calculated from the flow rate and concentration of chlorine gas in a flowing state, the state of electrolysis of magnesium chloride proceeding in the molten salt electrolytic cell can be continuously grasped. If the current efficiency is calculated based on the amount of recovered magnesium metal, the past current efficiency can be calculated when recovering the magnesium metal, but the electrolysis state of magnesium chloride cannot be grasped by time. If the current efficiency can be calculated from chlorine gas in a flowing state, it is advantageous in that the state of electrolysis over time can be grasped, and further, the state of electrolysis can be grasped in real time.
このような観点で塩素含有ガス中の酸素ガス濃度を測定する場合、本発明者は鋭意検討の結果、近赤外線吸収分光法を利用することが有利であるという知見を得るに至った。一実施形態における近赤外線吸収分光法は、塩素含有ガスを流動させながら当該流動状態の塩素含有ガス中の酸素ガス濃度を連続的に測定することが可能である。該塩素含有ガス中の酸素ガス濃度を測定した結果、溶融塩電解槽の上蓋に設けられた開口部を開くこと等による該溶融塩電解槽内の酸素ガス濃度の上昇だけでなく、開口部を閉じる蓋の配置不良や陽極と上蓋の間のシール不良等による酸素の流入（例えば、１質量％未満）も検出できることを見出した。
溶融塩電解槽の開口部を閉じる蓋の配置不良や上蓋と陽極との間の目地等のシール不良等を溶融塩電解槽の外側から作業者がすべて確認することは困難であるし、このような観点の取り組みは作業者への負担が非常に大きい。一実施形態においては、微量な酸素が溶融塩電解槽内に流入したとしても検出可能であるので溶融塩電解槽の気密不良を精度よくかつ簡便に確認でき、溶融塩電解槽の点検負荷を大幅に軽減することが可能である。
以下、本発明の一実施形態で用いられる塩素含有ガス回収機構を例示しながら各工程をそれぞれ説明する。
From this viewpoint, when measuring the oxygen gas concentration in a chlorine-containing gas, the present inventors have found that it is advantageous to use near-infrared absorption spectroscopy as a result of intensive research. In one embodiment, the near-infrared absorption spectroscopy can continuously measure the oxygen gas concentration in the chlorine-containing gas in a flowing state while the chlorine-containing gas is flowing. As a result of measuring the oxygen gas concentration in the chlorine-containing gas, it was found that not only the increase in the oxygen gas concentration in the molten salt electrolytic cell caused by opening the opening provided in the top cover of the molten salt electrolytic cell, but also the inflow of oxygen (for example, less than 1 mass%) caused by the poor positioning of the cover that closes the opening or the poor seal between the anode and the top cover can be detected.
It is difficult for an operator to check from the outside of the molten salt electrolytic cell for improper placement of the lid that closes the opening of the molten salt electrolytic cell, improper sealing of the joint between the top lid and the anode, etc., and such an approach imposes a large burden on the operator. In one embodiment, even if a small amount of oxygen flows into the molten salt electrolytic cell, it is possible to detect it, so that the airtightness of the molten salt electrolytic cell can be accurately and easily confirmed, and the inspection load of the molten salt electrolytic cell can be significantly reduced.
Hereinafter, each step will be described while illustrating a chlorine-containing gas recovery mechanism used in one embodiment of the present invention.
（塩素含有ガス回収機構）
塩素含有ガス回収機構は、塩素含有ガスを回収する。塩素含有ガス回収機構は溶融塩電解槽に接続されてよい。塩素含有ガス回収機構により回収された塩素含有ガスは、例えば塩化炉へ供給されて酸化チタンを含む鉱石及び炭素と接触し、スポンジチタンを生成する際に原料となる四塩化チタン含有ガスの生成に用いることができる。
図２に示す塩素含有ガス回収機構５００は、レーザ式酸素ガス分析装置１００と、フィルタ部３００と、ガス流量測定部４００とを備える。溶融塩電解槽２００のガス回収口２２２（図４参照）は、ガス供給配管２２１に接続される。塩化マグネシウムの電気分解で生じた塩素ガスは溶融塩電解槽２００内の溶融塩浴の対流により金属回収室２４０にも少量入り込むため、ガス回収口２２３は金属回収室２４０側にも設けられてよい。該ガス供給配管２２１には、上流側の溶融塩電解槽２００から下流側に向かって、フィルタ部３００、ガス流量測定部４００、分岐部Ｂ、合流部Ｊ１の順にそれぞれ配置されている。ガス供給配管２２１は、そのガス供給配管２２１から分岐するガス供給分岐配管２２１ａと、分岐部Ｂ及び合流部Ｊ１で接続されている。該ガス供給分岐配管２２１ａには、分岐部Ｂから合流部Ｊ１に向かって、バルブＶ１、レーザ式酸素ガス分析装置１００、バルブＶ２の順にそれぞれが配置されている。
なお、ガス供給配管２２１は、最下流側において塩化炉（不図示）若しくは塩素含有ガス用タンク（不図示）と接続されてよいし、又は下流側に向かって塩素含有ガス用タンク、塩化炉の順に接続されてよい。
なお、図２に示す塩素含有ガス回収機構５００は１つの溶融塩電解槽２００に接続されているが、複数の溶融塩電解槽２００、２５０（図５参照）に接続されていてもよい。
(Chlorine-containing gas recovery mechanism)
The chlorine-containing gas recovery mechanism recovers the chlorine-containing gas. The chlorine-containing gas recovery mechanism may be connected to the molten salt electrolytic cell. The chlorine-containing gas recovered by the chlorine-containing gas recovery mechanism is supplied to a chlorination furnace, for example, and contacted with titanium oxide-containing ore and carbon, and can be used to generate titanium tetrachloride-containing gas, which is a raw material when generating titanium sponge.
The chlorine-containing gas recovery mechanism 500 shown in FIG. 2 includes a laser-type oxygen gas analyzer 100, a filter unit 300, and a gas flow rate measuring unit 400. The gas recovery port 222 (see FIG. 4) of the molten salt electrolytic cell 200 is connected to the gas supply pipe 221. Since a small amount of chlorine gas generated by electrolysis of magnesium chloride also enters the metal recovery chamber 240 due to convection of the molten salt bath in the molten salt electrolytic cell 200, the gas recovery port 223 may also be provided on the metal recovery chamber 240 side. In the gas supply pipe 221, the filter unit 300, the gas flow rate measuring unit 400, the branching unit B, and the junction J1 are arranged in this order from the upstream molten salt electrolytic cell 200 to the downstream side. The gas supply pipe 221 is connected to the gas supply branch pipe 221a branched from the gas supply pipe 221 at the branching unit B and the junction J1. In the gas supply branch pipe 221a, a valve V1, a laser oxygen gas analyzer 100, and a valve V2 are arranged in this order from the branch point B toward the junction J1.
The gas supply pipe 221 may be connected to a chlorination furnace (not shown) or a chlorine-containing gas tank (not shown) at the most downstream side, or may be connected to a chlorine-containing gas tank and a chlorination furnace in that order toward the downstream side.
Although the chlorine-containing gas recovery mechanism 500 shown in FIG. 2 is connected to one molten salt electrolytic cell 200, it may be connected to a plurality of molten salt electrolytic cells 200, 250 (see FIG. 5).
（レーザ式酸素ガス分析装置）
レーザ式酸素ガス分析装置１００は、近赤外線吸収分光法により流動状態の分析用塩素含有ガス中の酸素ガス濃度を測定する。該レーザ式酸素ガス分析装置１００において近赤外線吸収分光法を用いているので、塩素含有ガスの成分を変化させることなく、塩素含有ガス中の酸素ガス濃度を定量的に測定することができる。なお、一実施形態における塩化マグネシウムの溶融塩電解では、気体として塩素が発生し、また、塩素含有ガスには、その塩素及び外気以外の気体はほぼ流入されない。したがって、該塩化マグネシウムの溶融塩電解においては、塩素含有ガス中の酸素ガス濃度を測定すれば、外気の成分構成比率から、溶融塩電解槽２００内に流入した外気由来の窒素等の濃度も求めることができる。
(laser type oxygen gas analyzer)
The laser type oxygen gas analyzer 100 measures the oxygen gas concentration in the chlorine-containing gas for analysis in a flowing state by near-infrared absorption spectroscopy. Since the laser type oxygen gas analyzer 100 uses near-infrared absorption spectroscopy, the oxygen gas concentration in the chlorine-containing gas can be quantitatively measured without changing the components of the chlorine-containing gas. In one embodiment, in the molten salt electrolysis of magnesium chloride, chlorine is generated as a gas, and gases other than the chlorine and the outside air are hardly flowed into the chlorine-containing gas. Therefore, in the molten salt electrolysis of magnesium chloride, if the oxygen gas concentration in the chlorine-containing gas is measured, the concentration of nitrogen and the like derived from the outside air flowing into the molten salt electrolytic cell 200 can also be obtained from the component composition ratio of the outside air.
図３に示すレーザ式酸素ガス分析装置１００は、発光部１１０と、受光部１２０と、測定セル１３０とを備える。但し、近赤外線吸収分光法を実施可能であれば異なる構成を有する他の装置を使用することも可能である。
発光部１１０は、光管路１４０の端部に設けられ、測定セル１３０内を流動する分析用塩素含有ガスＸに近赤外光を照射する。発光部１１０から照射される近赤外光は、酸素を吸収する波長を含む光である。なお、光管路１４０は、該光管路１４０内への汚れた空気の導入を遮断するために窒素等の浄化ガスＹを導入する浄化ガス導入口１４２と、その浄化ガスＹを導出する浄化ガス導出口１４４が設けられてよい。
受光部１２０は、光管路１５０の端部に設けられ、測定セル１３０内を流動する分析用塩素含有ガスＸを透過した近赤外光を受光する。なお、光管路１５０は、該光管路１５０内への汚れた空気の導入を遮断するために窒素等の浄化ガスＹを導入する浄化ガス導入口１５２と、その浄化ガスＹを導出する浄化ガス導出口１５４が設けられてよい。
測定セル１３０は、分析用塩素含有ガスがその内部を連続的に流通しており、分岐部で分岐された分析用塩素含有ガスＸを導入する塩素含有ガス導入口１３２と、その分析用塩素含有ガスＸを導出する塩素含有ガス導出口１３４と、光管路１４０、１５０と接続された取付フランジ１３６、１３８とを有する。
なお、レーザ式酸素ガス分析装置１００は、演算処理機構（不図示）を更に備えてよい。該演算処理機構は、例えば受信部と、演算処理部と、表示部とを有してよい。受信部は、受光部１２０のレーザ検出器で受光した近赤外光に応じた酸素分子の吸収量を受信する。演算処理部は、レーザ光源の近赤外光の照射量と近赤外光に応じた酸素分子の吸収量とに基づき、測定セル１３０内の分析用塩素含有ガスＸ中の酸素ガス濃度を演算する。該酸素ガス濃度は、分析用塩素含有ガスＸ源である塩素含有ガス中の酸素ガス濃度に相当する。表示部は、演算処理部で演算された酸素ガス濃度をモニタ等の画面に表示する。
3 includes a light emitting unit 110, a light receiving unit 120, and a measurement cell 130. However, other devices having different configurations can be used as long as they can perform near-infrared absorption spectroscopy.
The light emitting unit 110 is provided at the end of the optical pipeline 140, and irradiates near-infrared light to the chlorine-containing gas X for analysis flowing in the measurement cell 130. The near-infrared light irradiated from the light emitting unit 110 is light containing a wavelength that absorbs oxygen. The optical pipeline 140 may be provided with a purified gas inlet 142 for introducing a purified gas Y such as nitrogen in order to block the introduction of dirty air into the optical pipeline 140, and a purified gas outlet 144 for discharging the purified gas Y.
The light receiving unit 120 is provided at the end of the optical pipe 150, and receives near-infrared light transmitted through the chlorine-containing gas X for analysis flowing in the measurement cell 130. The optical pipe 150 may be provided with a purified gas inlet 152 for introducing a purified gas Y such as nitrogen in order to block the introduction of contaminated air into the optical pipe 150, and a purified gas outlet 154 for discharging the purified gas Y.
The measurement cell 130 has a chlorine-containing gas inlet 132 through which the chlorine-containing gas for analysis flows continuously, and through which the chlorine-containing gas for analysis X branched off at a branching section is introduced, a chlorine-containing gas outlet 134 through which the chlorine-containing gas for analysis X is discharged, and mounting flanges 136, 138 connected to optical pipes 140, 150.
The laser oxygen gas analyzer 100 may further include a calculation processing mechanism (not shown). The calculation processing mechanism may include, for example, a receiving section, a calculation processing section, and a display section. The receiving section receives the absorption amount of oxygen molecules corresponding to the near-infrared light received by the laser detector of the light receiving section 120. The calculation processing section calculates the oxygen gas concentration in the chlorine-containing gas X for analysis in the measurement cell 130 based on the irradiation amount of the near-infrared light from the laser light source and the absorption amount of oxygen molecules corresponding to the near-infrared light. The oxygen gas concentration corresponds to the oxygen gas concentration in the chlorine-containing gas that is the source of the chlorine-containing gas X for analysis. The display section displays the oxygen gas concentration calculated by the calculation processing section on a screen such as a monitor.
（溶融塩電解槽）
図４に示す溶融塩電解槽２００では、内部に供給された塩化マグネシウムを含む溶融塩からなる溶融塩浴が保持されており、溶融塩中の塩化マグネシウム等の特定の金属塩化物を電気分解する。例えば、塩化マグネシウムの電気分解により溶融金属マグネシウム及び塩素ガスが生成される。溶融塩電解槽２００はその内側に塩化マグネシウムが含まれる溶融塩浴が形成され、上方に開口部を有する外壁２１０と、該外壁２１０の開口部を閉じる上蓋２２０と、流通口２３６を有する隔壁２３５で区画される電解室２３０および金属回収室２４０とを備える。該電解室２３０での電気分解により得られる溶融金属Ｍが金属回収室２４０に流入する。該電解室２３０は、電気分解に用いられる電極２３１（陽極２３１ａ、陰極２３１ｂ）が配置されている。該上蓋２２０は、電解分解により発生した塩素含有ガスを回収するためのガス回収口２２２、２２３と、溶融金属Ｍを回収するための溶融金属回収口２２４と、電気分解で消費された塩化マグネシウム等の溶融塩を追い注ぎ（チャージ）するための溶融塩供給口２２６とを有する。図４では溶融金属回収口２２４と溶融塩供給口２２６とを別構成としているが、これらの機能を備える一つの開口を設けることとしてもよい。該ガス回収口２２２、２２３は、ガス供給配管２２１（図２参照）に接続されている。
(Molten salt electrolytic cell)
In the molten salt electrolytic cell 200 shown in FIG. 4, a molten salt bath made of molten salt containing magnesium chloride is held inside, and specific metal chlorides such as magnesium chloride in the molten salt are electrolyzed. For example, molten metallic magnesium and chlorine gas are generated by electrolysis of magnesium chloride. The molten salt electrolytic cell 200 has a molten salt bath containing magnesium chloride formed inside, and includes an outer wall 210 having an opening at the top, an upper cover 220 closing the opening of the outer wall 210, and an electrolysis chamber 230 and a metal recovery chamber 240 partitioned by a partition wall 235 having a flow port 236. The molten metal M obtained by electrolysis in the electrolysis chamber 230 flows into the metal recovery chamber 240. The electrolysis chamber 230 has electrodes 231 (anode 231a, cathode 231b) used for electrolysis arranged therein. The upper lid 220 has gas recovery ports 222, 223 for recovering chlorine-containing gas generated by electrolysis, a molten metal recovery port 224 for recovering molten metal M, and a molten salt supply port 226 for charging molten salt such as magnesium chloride consumed by electrolysis. In Fig. 4, the molten metal recovery port 224 and the molten salt supply port 226 are configured as separate ports, but a single opening having these functions may be provided. The gas recovery ports 222, 223 are connected to a gas supply pipe 221 (see Fig. 2).
（フィルタ部）
フィルタ部３００は、取り入れた塩素含有ガス中の微粉（金属マグネシウム、塩化マグネシウム、溶融塩浴成分、微小スラッジを含む不純物等）を捕集する。これにより、ガス流量測定部４００における塩素含有ガスの流量及びレーザ式酸素ガス分析装置１００における分析用塩素含有ガス中の酸素ガス濃度をより高い精度にて測定可能となる。なお、フィルタ部３００としては、ダストチャンバやバグフィルタ等の除塵装置を使用すればよい。
(Filter section)
The filter section 300 collects fine powder (metallic magnesium, magnesium chloride, molten salt bath components, impurities including fine sludge, etc.) in the chlorine-containing gas taken in. This allows the flow rate of the chlorine-containing gas in the gas flow measurement section 400 and the oxygen gas concentration in the chlorine-containing gas for analysis in the laser-type oxygen gas analyzer 100 to be measured with higher accuracy. Note that the filter section 300 may be a dust removal device such as a dust chamber or a bag filter.
（ガス流量測定部）
ガス流量測定部４００は、ガス供給配管２２１を流れる塩素含有ガスの流量を測定する。ここでは、公知の流量計を使用可能である。
(Gas flow rate measuring section)
The gas flow rate measuring unit 400 measures the flow rate of the chlorine-containing gas flowing through the gas supply pipe 221. A known flow meter can be used here.
＜前処理ステップ＞
前処理ステップＳ１０１においては、塩素含有ガス中の微粉をダストチャンバやバグフィルタ等の除塵装置で予め捕集する。より具体的には、溶融塩電解槽２００内の塩化マグネシウムを含有する溶融塩浴で電気分解により生成された塩素含有ガスがガス供給配管２２１から、フィルタ部３００に流入する。該フィルタ部３００においては、塩素含有ガス中の微粉が、塩素含有ガスの流量の測定に先立って予め捕集される。その結果、近赤外光を遮断及び／又は反射しうる微粉が低減されるので、酸素ガス濃度測定ステップＳ１０４における分析用塩素含有ガス中の酸素ガス濃度の測定の精度をより一層高めることが可能となる。
なお、前処理ステップＳ１０１は、酸素ガス濃度測定ステップＳ１０４前に実施すればよく、すなわち先述したガス流量測定ステップＳ１０２前の他に、ガス流量測定ステップＳ１０２とガス分岐ステップＳ１０３との間、又はガス分岐ステップＳ１０３と酸素ガス濃度測定ステップＳ１０４との間に実施してもよい。
<Pretreatment step>
In the pretreatment step S101, fine particles in the chlorine-containing gas are collected in advance by a dust removal device such as a dust chamber or a bag filter. More specifically, the chlorine-containing gas generated by electrolysis in a molten salt bath containing magnesium chloride in the molten salt electrolytic cell 200 flows into the filter unit 300 from the gas supply pipe 221. In the filter unit 300, fine particles in the chlorine-containing gas are collected in advance prior to measuring the flow rate of the chlorine-containing gas. As a result, the amount of fine particles that can block and/or reflect near-infrared light is reduced, so that the accuracy of the measurement of the oxygen gas concentration in the chlorine-containing gas for analysis in the oxygen gas concentration measurement step S104 can be further improved.
The pre-processing step S101 may be performed before the oxygen gas concentration measurement step S104. In other words, in addition to being performed before the gas flow rate measurement step S102 described above, the pre-processing step S101 may be performed between the gas flow rate measurement step S102 and the gas branching step S103, or between the gas branching step S103 and the oxygen gas concentration measurement step S104.
＜ガス流量測定ステップ＞
ガス流量測定ステップＳ１０２においては、ガス流量測定部４００で塩素含有ガスの流量を測定する。該塩素含有ガスの流量は、溶融塩電解の電流効率を求めるためのパラメータとして使用可能である。求められた該電流効率から金属マグネシウムの生産性を推測することができる。ガス流量を測定するための流量計は特段限定されず、公知のものを適宜使用可能である。
<Gas flow rate measurement step>
In the gas flow rate measurement step S102, the flow rate of the chlorine-containing gas is measured by the gas flow rate measurement unit 400. The flow rate of the chlorine-containing gas can be used as a parameter for determining the current efficiency of the molten salt electrolysis. The productivity of metallic magnesium can be estimated from the determined current efficiency. The flow meter for measuring the gas flow rate is not particularly limited, and a known flow meter can be used as appropriate.
＜ガス分岐ステップ＞
ガス分岐ステップＳ１０３は、塩素含有ガスの一部を分析用塩素含有ガスとして分岐させて流す。より具体的には、バルブＶ１を開いてガス供給配管２２１を流れる塩素含有ガスの一部を分岐させ、その一部を分析用塩素含有ガスとしてガス供給分岐配管２２１ａへ流す。
<Gas branching step>
In the gas branching step S103, a part of the chlorine-containing gas is branched and flows as a chlorine-containing gas for analysis. More specifically, the valve V1 is opened to branch a part of the chlorine-containing gas flowing through the gas supply pipe 221, and the part of the branched gas is flowed to the gas supply branch pipe 221a as the chlorine-containing gas for analysis.
＜酸素ガス濃度測定ステップ＞
酸素ガス濃度測定ステップＳ１０４は、レーザ式酸素ガス分析装置１００にて流動状態の分析用塩素含有ガスを近赤外線吸収分光法により分析し、分析用塩素含有ガス中の酸素ガス濃度を測定する。分析用塩素含有ガス中の酸素ガス濃度は、ガス供給配管２２１等を流れる塩素含有ガスの酸素ガス濃度と同程度とみなすことができる。つまり、酸素ガス濃度測定ステップＳ１０４により、塩素含有ガスの酸素ガス濃度を測定できる。
一実施形態においては、該塩素含有ガス中の酸素ガス濃度が１質量％以下と微量であっても酸素を検知できる。これにより、溶融塩電解槽２００の上蓋２２０に設けられた開口部を閉じる蓋の配置不良、陽極目地のシール不良等を速やかに把握できる場合がある。例えば、この配置不良は金属マグネシウムの回収後や塩化マグネシウムのチャージ後に起こるため、この場合は蓋を開けて一旦高くなった酸素ガス濃度が長時間にわたり元の値に戻らないという状態になる。また、陽極目地のシール不良は金属マグネシウムの回収や塩化マグネシウムのチャージとは無関係に生じうるため、この場合は酸素ガス濃度上昇の開始時点が蓋の開放とは異なる。上記のような不具合や不良を速やかに把握できれば溶融塩電解槽２００の早期の修繕が可能であり、これにより金属マグネシウムの汚染を抑制し、その結果として金属マグネシウムの製造の歩留りを高く維持することが可能となる。
<Oxygen gas concentration measurement step>
In the oxygen gas concentration measurement step S104, the chlorine-containing gas for analysis in a flowing state is analyzed by near-infrared absorption spectroscopy in the laser-type oxygen gas analyzer 100, and the oxygen gas concentration in the chlorine-containing gas for analysis is measured. The oxygen gas concentration in the chlorine-containing gas for analysis can be considered to be approximately the same as the oxygen gas concentration of the chlorine-containing gas flowing through the gas supply pipe 221, etc. In other words, the oxygen gas concentration measurement step S104 can measure the oxygen gas concentration of the chlorine-containing gas.
In one embodiment, oxygen can be detected even if the oxygen gas concentration in the chlorine-containing gas is as small as 1 mass % or less. This may allow prompt detection of improper placement of the lid that closes the opening provided on the top lid 220 of the molten salt electrolytic cell 200, improper sealing of the anode joint, etc. For example, this improper placement occurs after recovery of metallic magnesium or charging of magnesium chloride, so in this case, the oxygen gas concentration that increases once when the lid is opened does not return to its original value for a long time. In addition, improper sealing of the anode joint can occur regardless of recovery of metallic magnesium or charging of magnesium chloride, so in this case, the start time of the increase in oxygen gas concentration is different from the time when the lid is opened. If such a malfunction or defect can be promptly detected, the molten salt electrolytic cell 200 can be repaired early, which suppresses contamination of metallic magnesium, and as a result, it becomes possible to maintain a high yield in the production of metallic magnesium.
＜ガス合流ステップ＞
ガス合流ステップＳ１０５においては、塩素含有ガスから分岐された分析用塩素含有ガスを塩素含有ガスに合流部Ｊ１にて合流させる。具体的に、ガス供給分岐配管２２１ａに配置したレーザ式酸素ガス分析装置１００で酸素ガス濃度を測定した分析用塩素含有ガスは、ガス供給配管２２１を流れる塩素含有ガスと合流部Ｊ１で合流する。なお、一実施形態において、レーザ式酸素ガス分析装置１００では近赤外光を用いているので、塩素含有ガスと分析用塩素含有ガスとが合流しても塩素含有ガスの組成は変わらない。
そして、合流後の塩素含有ガスは、塩化炉に供給され、又は塩素含有ガス用タンクに回収される。
<Gas joining step>
In the gas merging step S105, the analytical chlorine-containing gas branched from the chlorine-containing gas is merged with the chlorine-containing gas at the merging section J1. Specifically, the analytical chlorine-containing gas whose oxygen gas concentration has been measured by the laser-type oxygen gas analyzer 100 arranged in the gas supply branching pipe 221a is merged with the chlorine-containing gas flowing through the gas supply pipe 221 at the merging section J1. In one embodiment, since the laser-type oxygen gas analyzer 100 uses near-infrared light, the composition of the chlorine-containing gas does not change even if the chlorine-containing gas and the analytical chlorine-containing gas are merged.
The combined chlorine-containing gas is then supplied to a chlorination furnace or recovered in a chlorine-containing gas tank.
なお、レーザ式酸素ガス分析装置１００に不具合が生じた場合、バルブＶ１、Ｖ２を閉めて別のレーザ式酸素ガス分析装置に交換してよい。 If a malfunction occurs in the laser-type oxygen gas analyzer 100, valves V1 and V2 can be closed and the device can be replaced with another laser-type oxygen gas analyzer.
［２．電流効率の演算方法］
本発明に係る電流効率の演算方法においては、先述した塩素含有ガス中の酸素ガス濃度測定方法により、ガス流量測定ステップＳ１０２で得られた塩素含有ガスの流量と、酸素ガス濃度測定ステップＳ１０４で得られた該塩素含有ガス中の酸素ガス濃度とを用いて、塩化マグネシウムの溶融塩電解の電流効率を求めることを含む。
溶融塩電解槽を使用した塩化マグネシウム等金属塩化物の電気分解では高濃度の塩素ガスが得られる。他方、溶融塩電解槽内は外環境に対して負圧とされているため、塩素ガスは少量の外気を含みうる。そこで、塩素含有ガス中の塩素ガス濃度とその流量を得ることができれば塩素ガスの総量が求まり、ＭｇＣｌ2→Ｍｇ＋Ｃｌ2の反応式に基づき電気分解の状況を把握できる。他方、電極に流した電流量から、塩素ガスや金属マグネシウムの理論生成量を得ることができる。よって、この理論値と上記塩素ガスの総量とから電気分解の電流効率を得ることができる。この電流効率を連続的に監視すれば、溶融塩電解槽内で電気分解が効率的に進行しているか把握可能となる。
塩素含有ガスには外気が含まれうるが、その他のガスはほぼ混入されない。そのため、上記塩素含有ガスに含まれる塩素ガス濃度は外気の濃度を差し引く方法で求めることができる。外気は酸素ガスと窒素ガスを一定の割合で含むため、酸素ガス濃度が得られれば外気の濃度を得ることができる。
[2. Method of calculating current efficiency]
The method for calculating the current efficiency according to the present invention includes determining the current efficiency of the molten salt electrolysis of magnesium chloride using the flow rate of the chlorine-containing gas obtained in the gas flow rate measurement step S102 and the oxygen gas concentration in the chlorine-containing gas obtained in the oxygen gas concentration measurement step S104 by the above-mentioned method for measuring the oxygen gas concentration in the chlorine-containing gas.
A high concentration of chlorine gas is obtained by electrolysis of metal chlorides such as magnesium chloride using a molten salt electrolytic cell. On the other hand, since the inside of the molten salt electrolytic cell is under negative pressure with respect to the outside environment, the chlorine gas may contain a small amount of outside air. Therefore, if the chlorine gas concentration and the flow rate in the chlorine-containing gas can be obtained, the total amount of chlorine gas can be obtained, and the state of electrolysis can be grasped based on the reaction formula MgCl 2 →Mg + Cl 2. On the other hand, the theoretical production amount of chlorine gas and metallic magnesium can be obtained from the amount of current flowing through the electrodes. Therefore, the current efficiency of electrolysis can be obtained from this theoretical value and the total amount of chlorine gas. If this current efficiency is continuously monitored, it is possible to grasp whether electrolysis is proceeding efficiently in the molten salt electrolytic cell.
The chlorine-containing gas may contain outside air, but other gases are hardly mixed in. Therefore, the chlorine gas concentration contained in the chlorine-containing gas can be obtained by subtracting the concentration of the outside air. Since the outside air contains oxygen gas and nitrogen gas in a certain ratio, the concentration of the outside air can be obtained by obtaining the oxygen gas concentration.
［３．金属マグネシウムの製造方法］
本発明に係る金属マグネシウムの製造方法の一実施形態においては、溶融塩電解槽２００内で塩化マグネシウムの溶融塩電解により金属マグネシウムを生成する生成工程を含む。該生成工程は、先述した塩素含有ガス中の酸素ガス濃度測定方法により、溶融塩電解槽内への外気の流入を監視することを有する。例えば、監視中、塩素含有ガス中の酸素ガス濃度が上昇したことを確認した場合、溶融塩電解槽２００内に外気が流入したものと判断される。この原因としては、溶融塩電解槽２００の上蓋２２０に設けられた開口部を閉じる蓋の配置不良及び溶融塩電解槽２００の陽極２３１ａと上蓋２２０の間のシール不良等が想定される。仮に溶融塩電解槽２００の上蓋２２０に設けられた開口部を閉じる蓋が配置不良である場合、外壁の開口部から外気が混入し、塩素含有ガス中の酸素ガス濃度が高くなるので、電解効率の値が正常時と比べ低くなりうる。また、溶融塩電解槽２００の陽極２３１ａと上蓋２２０の間のシール不良が生じている場合、そのシールされていない陽極と上蓋の間から外気が混入し、塩素含有ガス中の酸素ガス濃度が高くなるので、電解効率の値が正常時と比べ低くなりうる。
[3. Method for producing metallic magnesium]
In one embodiment of the method for producing metallic magnesium according to the present invention, a production step is included in which metallic magnesium is produced by molten salt electrolysis of magnesium chloride in the molten salt electrolytic cell 200. The production step includes monitoring the inflow of outside air into the molten salt electrolytic cell by the above-mentioned method for measuring the oxygen gas concentration in the chlorine-containing gas. For example, if it is confirmed that the oxygen gas concentration in the chlorine-containing gas increases during monitoring, it is determined that outside air has flowed into the molten salt electrolytic cell 200. This is likely due to poor placement of a lid that closes the opening provided in the top lid 220 of the molten salt electrolytic cell 200 and poor sealing between the anode 231a of the molten salt electrolytic cell 200 and the top lid 220. If the lid that closes the opening provided in the top lid 220 of the molten salt electrolytic cell 200 is poorly placed, outside air will enter through the opening of the outer wall, and the oxygen gas concentration in the chlorine-containing gas will increase, so that the value of the electrolysis efficiency may be lower than that in normal times. In addition, if there is a poor seal between the anode 231a and the top lid 220 of the molten salt electrolytic cell 200, outside air will enter through the unsealed gap between the anode and the top lid, increasing the oxygen gas concentration in the chlorine-containing gas, which can result in a lower electrolysis efficiency value than normal.
本発明を実施例に基づいて具体的に説明する。以下の実施例の記載は、あくまで本発明の技術的内容の理解を容易とするための具体例であり、本発明の技術的範囲はこれらの具体例によって制限されるものではない。なお、溶融塩電解槽２５０は、図４に示した溶融塩電解槽２００と同じ構成にした。 The present invention will be specifically described based on examples. The following examples are merely specific examples intended to facilitate understanding of the technical content of the present invention, and the technical scope of the present invention is not limited by these specific examples. The molten salt electrolytic cell 250 has the same configuration as the molten salt electrolytic cell 200 shown in Figure 4.
［実施例１］
まず、図５に示した塩素含有ガス回収機構５５０を設置した。塩素含有ガス回収機構５５０は、近赤外光の吸収を検知するためのレーザ式酸素ガス分析装置１００（レーザ式ガス濃度計、ＮＥＯ Ｍｏｎｉｒｏｒｓ ＡＳ社製）、フィルタ部３００、ガス流量測定部４００、バルブＶ１、Ｖ２、合流部Ｊ１、Ｊ２、分岐部Ｂ、ガス供給配管２２１、２７１、ガス供給分岐配管２２１ａで構成されるものとし、該ガス供給配管２２１は最下流側にて塩化炉（不図示）と接続した。ガス供給配管２２１、２７１はそれぞれ溶融塩電解槽２００、２５０の各ガス回収口２２２、２２３に接続されており、溶融塩電解槽２００、２５０はいずれも図４に示すものと同様の構成を有するものとした。ガス供給配管２７１は溶融塩電解槽２００とフィルタ部３００との間に配置した合流部Ｊ２でガス供給配管２２１に接続した。
[Example 1]
First, the chlorine-containing gas recovery mechanism 550 shown in FIG. 5 was installed. The chlorine-containing gas recovery mechanism 550 was composed of a laser-type oxygen gas analyzer 100 (laser-type gas concentration meter, manufactured by NEO Monitors AS) for detecting the absorption of near-infrared light, a filter unit 300, a gas flow measurement unit 400, valves V1, V2, junctions J1, J2, branching unit B, gas supply pipes 221, 271, and a gas supply branching pipe 221a, and the gas supply pipe 221 was connected to a chlorination furnace (not shown) at the most downstream side. The gas supply pipes 221, 271 were connected to the gas recovery ports 222, 223 of the molten salt electrolytic cells 200, 250, respectively, and the molten salt electrolytic cells 200, 250 were both configured similarly to that shown in FIG. 4. The gas supply pipe 271 was connected to the gas supply pipe 221 at the junction J2 arranged between the molten salt electrolytic cell 200 and the filter unit 300.
溶融塩電解槽２００、２５０は、外壁２１０、隔壁２３５の材質がそれぞれＡｌ2Ｏ3を含む定型耐火物（耐火煉瓦）とし、上蓋２２０の材質は蓋裏にキャスタブル耐火物の層を施工した炭素鋼を使用した。なお、電気分解開始前の溶融塩の組成は、塩化マグネシウムが２０質量％、塩化カルシウムが３０質量％、及び塩化ナトリウムが５０質量％とした。また、電解室２３０においては、陽極２３１ａと陰極２３１ｂとバイポーラ電極をそれぞれ配置した。陽極２３１ａの材質は黒鉛とし、陰極２３１ｂの材質は鉄とした。バイポーラ電極の材質は黒鉛とした。 In the molten salt electrolytic cells 200 and 250, the outer wall 210 and the partition wall 235 were made of a standard refractory material ( firebrick ) containing Al2O3 , and the upper cover 220 was made of carbon steel with a layer of castable refractory applied to the back of the cover. The composition of the molten salt before the start of electrolysis was 20 mass% magnesium chloride, 30 mass% calcium chloride, and 50 mass% sodium chloride. In the electrolysis chamber 230, an anode 231a, a cathode 231b, and a bipolar electrode were disposed. The material of the anode 231a was graphite, and the material of the cathode 231b was iron. The material of the bipolar electrode was graphite.
２つの溶融塩電解槽２００、２５０中の電極２３１に電圧をそれぞれ印加して、電気分解を開始した。２つの溶融塩電解槽２００、２５０から生成された塩素含有ガスをガス回収口２２２、２２３から回収し、塩素含有ガスをフィルタ部３００としてのバグフィルタに接触させることで塩素含有ガス中の微粉を捕集した（前処理ステップＳ１０１）。捕集後の塩素含有ガスをガス流量測定部４００にて、その流量を連続的に測定した（ガス流量測定ステップＳ１０２）。ガス供給分岐配管２２１ａに流れる塩素含有ガスの一部を分岐させた（ガス分岐ステップＳ１０３）。レーザ式酸素ガス分析装置１００を用いて下記分析条件にて分析用塩素含有ガス中の酸素ガス濃度を連続的に測定した（酸素ガス濃度測定ステップＳ１０４）。酸素ガス濃度測定後の分析用塩素含有ガスは、測定セル１３０から導出されガス供給分岐配管２２１ａを流れ、合流部Ｊ１を介してガス供給配管２２１の塩素含有ガスと合流した（ガス合流ステップＳ１０５）。その後、塩素含有ガスは、塩化炉へ供給された。 A voltage was applied to the electrodes 231 in the two molten salt electrolytic baths 200 and 250, respectively, to start electrolysis. The chlorine-containing gas generated from the two molten salt electrolytic baths 200 and 250 was collected from the gas recovery ports 222 and 223, and the chlorine-containing gas was brought into contact with a bag filter as the filter unit 300 to capture fine particles in the chlorine-containing gas (pretreatment step S101). The flow rate of the chlorine-containing gas after collection was continuously measured by the gas flow rate measurement unit 400 (gas flow rate measurement step S102). A portion of the chlorine-containing gas flowing in the gas supply branch pipe 221a was branched (gas branching step S103). The oxygen gas concentration in the chlorine-containing gas for analysis was continuously measured using the laser-type oxygen gas analyzer 100 under the following analysis conditions (oxygen gas concentration measurement step S104). After the oxygen gas concentration measurement, the chlorine-containing gas for analysis was discharged from the measurement cell 130, flowed through the gas supply branch pipe 221a, and merged with the chlorine-containing gas in the gas supply pipe 221 through the merging point J1 (gas merging step S105). The chlorine-containing gas was then supplied to the chlorination furnace.
溶融塩電解槽２００、２５０の操業においては、溶融塩供給口２２６の開閉可能な蓋を開けて塩化マグネシウムを追い注ぎ（チャージ）し、この追い注ぎを計１０回実施した。追い注ぎ作業開始直後、塩素含有ガス中の酸素ガス濃度が０．１質量％から急激に１．０質量％以上となったことをいずれも確認した。なお、図６（Ａ）においては、溶融塩電解槽２００、２５０の操業開始時から２時間経過時に溶融塩供給口２２６の開閉可能な蓋を開けて塩化マグネシウムの追い注ぎをし、また、図６（Ｂ）においては、溶融塩電解槽２００、２５０の操業開始時から１２時間経過時及び１９時間経過時に溶融塩供給口２２６の開閉可能な蓋を開けて塩化マグネシウムの追い注ぎを実施した。すなわち、追い注ぎ時に溶融塩供給口２２６の蓋を開けたことで溶融塩電解槽２００、２５０内に外気が流入したことが推察される。
また、溶融塩電解槽２００、２５０の操業開始時から１４時間経過時から約５時間、塩素含有ガス中の酸素ガス濃度が０．７質量％以上となる上昇を繰り返していた。そこで、操業中の溶融塩電解槽２００、２５０を確認した結果、操業開始時から１２時間経過時の追い注ぎではその作業後に溶融塩供給口２２６の蓋が完全に閉まっていなかったことが確認された。操業開始時から１９時間経過時に実施した追い注ぎの作業後は蓋を完全に閉めたことで、その後酸素ガス濃度が０．１質量％以下に戻っていった。
In the operation of the molten salt electrolytic baths 200 and 250, the openable lid of the molten salt supply port 226 was opened to charge magnesium chloride (charge), and this charge was performed 10 times in total. It was confirmed that the oxygen gas concentration in the chlorine-containing gas rapidly increased from 0.1 mass% to 1.0 mass% or more immediately after the start of the charge operation. In addition, in FIG. 6(A), the openable lid of the molten salt supply port 226 was opened to charge magnesium chloride 2 hours after the start of the operation of the molten salt electrolytic baths 200 and 250, and in FIG. 6(B), the openable lid of the molten salt supply port 226 was opened to charge magnesium chloride 12 hours and 19 hours after the start of the operation of the molten salt electrolytic baths 200 and 250. That is, it is presumed that the opening of the lid of the molten salt supply port 226 during the charge caused outside air to flow into the molten salt electrolytic baths 200 and 250.
In addition, the oxygen gas concentration in the chlorine-containing gas repeatedly increased to 0.7 mass% or more for about 5 hours from 14 hours after the start of operation of the molten salt electrolytic baths 200 and 250. As a result of checking the molten salt electrolytic baths 200 and 250 during operation, it was confirmed that the lid of the molten salt supply port 226 was not completely closed after the refilling operation performed 12 hours after the start of operation. After the refilling operation performed 19 hours after the start of operation, the lid was completely closed, and the oxygen gas concentration returned to 0.1 mass% or less.
（実施例による考察）
実施例１において、塩化マグネシウムの溶融塩電解で発生した塩素含有ガス中の酸素ガス濃度の上昇を速やかに把握することで、溶融塩の追い注ぎ時における溶融塩電解槽２００、２５０内への外気の流入と溶融塩供給口の蓋を完全に閉めていないことによる溶融塩電解槽２００、２５０内への外気の流入とをそれぞれ検知することができた。その結果、実施例１においては、溶融塩電解槽２００、２５０の点検負荷も大幅に軽減することができると推察される。したがって、実施例１によれば、酸素ガス濃度測定ステップにおいて流動状態の分析用塩素含有ガスを近赤外線吸収分光法により分析し、塩素含有ガス中の酸素ガス濃度を測定することが有用であるといえる。
(Considerations based on examples)
In Example 1, by quickly grasping the increase in oxygen gas concentration in the chlorine-containing gas generated in the molten salt electrolysis of magnesium chloride, it was possible to detect the inflow of outside air into the molten salt electrolytic cells 200, 250 when the molten salt is poured in again, and the inflow of outside air into the molten salt electrolytic cells 200, 250 due to the lid of the molten salt supply port not being completely closed. As a result, it is presumed that the inspection load of the molten salt electrolytic cells 200, 250 can also be significantly reduced in Example 1. Therefore, according to Example 1, it can be said that it is useful to analyze the chlorine-containing gas for analysis in a flowing state by near-infrared absorption spectroscopy in the oxygen gas concentration measurement step and measure the oxygen gas concentration in the chlorine-containing gas.
１００ レーザ式酸素ガス分析装置
１１０ 発光部
１２０ 受光部
１３０ 測定セル
１３２ 塩素含有ガス導入口
１３４ 塩素含有ガス導出口
１３６、１３８ 取付フランジ
１４０、１５０ 光管路
１４２、１５２ 浄化ガス導入口
１４４、１５４ 浄化ガス導出口
２００、２５０ 溶融塩電解槽
２１０ 外壁
２２０ 上蓋
２２１、２７１ ガス供給配管
２２１ａ ガス供給分岐配管
２２２、２２３ ガス回収口
２２４ 溶融金属回収口
２２６ 溶融塩供給口
２３０ 電解室
２３１ 電極
２３１ａ 陽極
２３１ｂ 陰極
２３５ 隔壁
２３６ 流通口
２４０ 金属回収室
３００ フィルタ部
４００ ガス流量測定部
５００、５５０ 塩素含有ガス回収機構
Ｂ 分岐部
Ｊ１、Ｊ２ 合流部
Ｍ 溶融金属
Ｓ１０１ 前処理ステップ
Ｓ１０２ ガス流量測定ステップ
Ｓ１０３ ガス分岐ステップ
Ｓ１０４ 酸素ガス濃度測定ステップ
Ｓ１０５ ガス合流ステップ
Ｖ１、Ｖ２ バルブ
Ｘ 分析用塩素含有ガス
Ｙ 浄化ガス
100 Laser type oxygen gas analyzer 110 Light emitting unit 120 Light receiving unit 130 Measurement cell 132 Chlorine-containing gas inlet 134 Chlorine-containing gas outlet 136, 138 Mounting flange 140, 150 Optical pipe 142, 152 Purified gas inlet 144, 154 Purified gas outlet 200, 250 Molten salt electrolytic cell 210 Outer wall 220 Top cover 221, 271 Gas supply pipe 221a Gas supply branch pipe 222, 223 Gas recovery port 224 Molten metal recovery port 226 Molten salt supply port 230 Electrolysis chamber 231 Electrode 231a Anode 231b Cathode 235 Partition wall 236 Flow port 240 Metal recovery chamber 300 Filter unit 400 Gas flow measurement unit 500, 550 Chlorine-containing gas recovery mechanism B Branching unit J1, J2 Confluence unit M Molten metal S101 Pretreatment step S102 Gas flow rate measurement step S103 Gas branching step S104 Oxygen gas concentration measurement step S105 Gas merging steps V1, V2 Valve X Chlorine-containing gas for analysis Y Purified gas
Claims (8)
流動状態の分析用塩素含有ガスを近赤外線吸収分光法により分析し、塩素含有ガス中の酸素ガス濃度を測定する酸素ガス濃度測定ステップを含み、
前記塩素含有ガスは、塩化マグネシウムの溶融塩電解で生成される、塩素含有ガス中の酸素ガス濃度測定方法。 A method for measuring an oxygen gas concentration in a chlorine-containing gas, comprising:
An oxygen gas concentration measuring step of analyzing the chlorine-containing gas for analysis in a flowing state by near-infrared absorption spectroscopy to measure the oxygen gas concentration in the chlorine-containing gas ,
The chlorine-containing gas is produced by electrolysis of a molten salt of magnesium chloride, and the method for measuring an oxygen gas concentration in the chlorine-containing gas is thus described .
前記酸素ガス濃度測定ステップ後に、前記分析用塩素含有ガスを前記塩素含有ガスに合流させるガス合流ステップを更に含む、請求項１に記載の塩素含有ガス中の酸素ガス濃度測定方法。 a gas branching step of branching a part of the chlorine-containing gas as the analytical chlorine-containing gas before the oxygen gas concentration measuring step;
2. The method for measuring an oxygen gas concentration in a chlorine-containing gas according to claim 1, further comprising a gas confluence step of confluence- ing the chlorine-containing gas for analysis with the chlorine-containing gas after the oxygen gas concentration measurement step.
該生成工程においては、請求項１～６のいずれか一項に記載の塩素含有ガス中の酸素ガス濃度測定方法により、前記溶融塩電解槽内への外気の流入を監視することを含む、金属マグネシウムの製造方法。 A method for producing metallic magnesium, comprising the step of producing metallic magnesium by molten-salt electrolysis of magnesium chloride in a molten-salt electrolytic cell,
The method for producing metallic magnesium includes, in the producing step, monitoring an inflow of outside air into the molten salt electrolytic cell by the method for measuring an oxygen gas concentration in a chlorine-containing gas according to any one of claims 1 to 6.
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