JP7500949B2 - Method for electrolyzing an aqueous solution of alkali metal chloride - Google Patents
Method for electrolyzing an aqueous solution of alkali metal chloride Download PDFInfo
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- 238000000034 method Methods 0.000 title claims description 32
- 229910001514 alkali metal chloride Inorganic materials 0.000 title claims description 20
- 239000007864 aqueous solution Substances 0.000 title claims description 10
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 129
- 239000001301 oxygen Substances 0.000 claims description 129
- 229910052760 oxygen Inorganic materials 0.000 claims description 129
- 239000007789 gas Substances 0.000 claims description 68
- 238000005868 electrolysis reaction Methods 0.000 claims description 59
- 239000000243 solution Substances 0.000 claims description 15
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 claims description 8
- 229910001882 dioxygen Inorganic materials 0.000 claims description 7
- KZBUYRJDOAKODT-UHFFFAOYSA-N Chlorine Chemical compound ClCl KZBUYRJDOAKODT-UHFFFAOYSA-N 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 claims description 3
- 150000008044 alkali metal hydroxides Chemical class 0.000 claims description 2
- 239000003014 ion exchange membrane Substances 0.000 description 38
- 235000002639 sodium chloride Nutrition 0.000 description 32
- 150000003839 salts Chemical class 0.000 description 29
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 18
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 15
- 238000009792 diffusion process Methods 0.000 description 13
- 239000003518 caustics Substances 0.000 description 10
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 6
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 5
- 239000000460 chlorine Substances 0.000 description 5
- 229910052801 chlorine Inorganic materials 0.000 description 5
- 235000011121 sodium hydroxide Nutrition 0.000 description 5
- 238000005341 cation exchange Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000007599 discharging Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000012528 membrane Substances 0.000 description 3
- 239000011780 sodium chloride Substances 0.000 description 3
- 238000001179 sorption measurement Methods 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 229920003934 Aciplex® Polymers 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000036284 oxygen consumption Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 229910001415 sodium ion Inorganic materials 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Description
本発明は食塩水などのアルカリ金属塩化物水溶液の電気分解方法に関し、より詳しくは、酸素還元用電極を陰極に用いて行うアルカリ金属塩化物水溶液の電気分解の所要電力を削減可能な電気分解方法に関するものである。 The present invention relates to a method for electrolyzing an aqueous solution of an alkali metal chloride such as saline solution, and more specifically, to an electrolysis method that can reduce the power required for electrolyzing an aqueous solution of an alkali metal chloride using an oxygen reduction electrode as the cathode.
アルカリ金属塩化物水溶液の電解工業は電力多消費型産業であり、省エネルギー化のために様々な技術開発が行われている。その省エネルギー化の手段とは、電解電圧の低減、及び／又は、電流効率の向上により、電解時に発生する電力ロスを削減することである。例えば、食塩水の電解は、陽極に塩素発生用電極を、陰極に水素発生用電極を用い、陽極と陰極との間をフッ素系陽イオン交換膜（以下、イオン交換膜と記載する）で区画した、所謂、イオン交換膜法食塩電解が主流である（非特許文献１、ｐ３）。 The electrolysis industry of alkali metal chloride aqueous solutions is an industry that consumes a lot of electricity, and various technological developments are being made to save energy. The means of saving energy are to reduce the power loss that occurs during electrolysis by lowering the electrolysis voltage and/or improving the current efficiency. For example, the mainstream method of electrolysis of salt water is the so-called ion exchange membrane method of salt electrolysis, in which a chlorine generating electrode is used as the anode and a hydrogen generating electrode is used as the cathode, and the space between the anode and cathode is partitioned by a fluorine-based cation exchange membrane (hereinafter referred to as the ion exchange membrane) (Non-Patent Document 1, p. 3).
この食塩電解工業において、電流効率は９５％以上で操業されており、向上余地は少ない。それに対し、電解電圧は理論分解電圧の約２．３Ｖに対し３．０Ｖ前後で操業されている。 In this salt electrolysis industry, current efficiency is operated at 95% or more, leaving little room for improvement. Meanwhile, electrolysis voltage is operated at around 3.0 V, compared to the theoretical decomposition voltage of about 2.3 V.
一方、陰極に酸素還元用電極を用い、食塩と水と酸素を原料に、塩素と苛性ソーダとを製造する酸素還元型イオン交換膜法食塩電解が種々提案されている。酸素還元型イオン交換膜法食塩電解の電解電圧は２．０Ｖ前後が可能で、既存の水素発生型イオン交換膜法食塩電解の電解電圧３．０Ｖ前後に対し、電解電圧を概ね１Ｖ下げることが可能とされており（非特許文献１、ｐ２８３～２８４）、当該方法は食塩電解工業の消費電力を大幅に削減する手法として注目を集めている。 On the other hand, various oxygen-reducing ion-exchange membrane salt electrolysis methods have been proposed, which use an oxygen-reducing electrode as the cathode and produce chlorine and caustic soda from salt, water, and oxygen as raw materials. The electrolysis voltage of oxygen-reducing ion-exchange membrane salt electrolysis can be around 2.0 V, which is said to be approximately 1 V lower than the electrolysis voltage of existing hydrogen-generating ion-exchange membrane salt electrolysis, which is around 3.0 V (Non-Patent Document 1, pp. 283-284), and this method has attracted attention as a method for significantly reducing power consumption in the salt electrolysis industry.
しかし、実際には、酸素還元型イオン交換膜法食塩電解の電解電圧は２．３Ｖ前後と高く、既存の水素発生型イオン交換膜法食塩電解に比較した電圧低減は０．７Ｖに留まり、未だ酸素還元型イオン交換膜法食塩電解は主流となっていない。そのため、従来、酸素還元型イオン交換膜法食塩電解の電解電圧を低減する研究開発が盛んに行われてきた。 However, in reality, the electrolysis voltage of oxygen-reduced ion-exchange membrane salt electrolysis is high at around 2.3 V, which is only 0.7 V lower than the existing hydrogen-generating ion-exchange membrane salt electrolysis, and oxygen-reduced ion-exchange membrane salt electrolysis has not yet become mainstream. For this reason, research and development into reducing the electrolysis voltage of oxygen-reduced ion-exchange membrane salt electrolysis has been actively carried out.
例えば、特許文献１には「イオン交換膜により陽極を収容する陽極室とガス拡散陰極を収容する陰極室に区画された２室法イオン交換膜型電解槽において、前記ガス拡散陰極の前記イオン交換膜と反対側に透過性の押圧板を設置し、電解槽運転時に前記押圧板をガス室充填材の弾性力によりガス拡散陰極方向に押し付け、この押圧板から均一にガス拡散陰極に応力が作用してイオン交換膜とガス拡散陰極を全面的に密着する状態を維持することを特徴とするガス拡散陰極を用いたイオン交換膜型電解槽」を用いた酸素還元型イオン交換膜法食塩電解が提案されている。 For example, Patent Document 1 proposes oxygen-reducing ion-exchange membrane salt electrolysis using "an ion-exchange membrane electrolytic cell using a gas diffusion cathode, characterized in that in a two-chamber ion-exchange membrane electrolytic cell partitioned by an ion-exchange membrane into an anode chamber that houses an anode and a cathode chamber that houses a gas diffusion cathode, a permeable pressure plate is installed on the side of the gas diffusion cathode opposite the ion-exchange membrane, and the pressure plate is pressed toward the gas diffusion cathode by the elastic force of the gas chamber filler during operation of the electrolytic cell, and stress is uniformly applied from the pressure plate to the gas diffusion cathode, maintaining a state in which the ion exchange membrane and the gas diffusion cathode are in close contact all over."
さらに、特許文献２には「イオン交換膜により陽極を収容する陽極室と液透過型ガス拡散陰極を収容する陰極室に区画されたイオン交換膜電解槽において、耐食性フレームに金属製コイル体を巻回して構成した弾性クッション材を、ガス拡散陰極と陰極壁面又は陰極集電体間に設置したことを特徴とするイオン交換膜電解槽」を用いた酸素還元型イオン交換膜法食塩電解が提案されている。 Furthermore, Patent Document 2 proposes oxygen-reducing ion-exchange membrane salt electrolysis using "an ion-exchange membrane electrolytic cell partitioned by an ion-exchange membrane into an anode chamber that houses an anode and a cathode chamber that houses a liquid-permeable gas diffusion cathode, characterized in that an elastic cushion material made by winding a metal coil around a corrosion-resistant frame is installed between the gas diffusion cathode and the cathode wall surface or the cathode current collector."
これらの提案により酸素還元型イオン交換膜法食塩電解の実施に際し、イオン交換膜と酸素還元用電極間の距離が可及的に短縮され、その間で発生する電気抵抗損失が著しく減少した。 As a result of these proposals, when implementing oxygen-reduced ion-exchange membrane-based salt electrolysis, the distance between the ion-exchange membrane and the oxygen-reducing electrode was shortened as much as possible, significantly reducing the electrical resistance loss that occurs between them.
また、特許文献３には「ガス拡散陰極を備えたイオン交換膜法塩化アルカリ電解槽の陽極室に塩水を導入し、ガス拡散陰極のガス室に酸素含有ガスを導入して、陽極室に塩素と陰極室に苛性アルカリ水溶液を得る電解方法において、前記ガス室から出る排酸素含有ガスの一部を前記ガス室へ戻し循環供給することを特徴とする塩化アルカリの電解方法。」が提案されている。前記排酸素含有ガスの一部を前記ガス室へ戻し循環供給することで酸素含有ガスの有効利用が可能となった。 Patent Document 3 also proposes "an alkaline chloride electrolysis method in which salt water is introduced into the anode chamber of an ion-exchange membrane alkaline chloride electrolysis cell equipped with a gas diffusion cathode, and an oxygen-containing gas is introduced into the gas chamber of the gas diffusion cathode to obtain chlorine in the anode chamber and a caustic alkaline aqueous solution in the cathode chamber, characterized in that a portion of the exhaust oxygen-containing gas discharged from the gas chamber is returned to the gas chamber for circulating supply." By returning a portion of the exhaust oxygen-containing gas to the gas chamber for circulating supply, it has become possible to effectively utilize the oxygen-containing gas.
しかし、特許文献３に「ＰＳＡ装置は、吸着法により空気を分離する装置であり、純酸素は得られないにしても、酸素濃度が９０％以上の酸素含有ガスを安価に取得でき、本方法において有効に使用可能である。しかし、このＰＳＡ装置からの酸素含有ガスを用いるにしても、その新規に供給する酸素含有ガスをどの程度過剰な量で供給するかによって、ガス拡散陰極の運転コストが大きく変わってくる。」、および、「排酸素含有ガスの循環量を増大することは、コスト低減の上で利点はあるが、その場合ガス室に入る新規酸素含有ガスと排酸素含有ガスとからの混合酸素ガスの酸素濃度が低下し、それに伴いガス拡散電極の性能が低下するので、実用的に言って排酸素含有ガスの循環量の大きさには制約がある。」と記載された通り、酸素ガスの供給、排出方法は未だ課題がある。 However, as described in Patent Document 3, "PSA equipment is an apparatus that separates air by adsorption, and although it cannot obtain pure oxygen, it can obtain oxygen-containing gas with an oxygen concentration of 90% or more at low cost, and can be effectively used in this method. However, even if oxygen-containing gas from this PSA equipment is used, the operating cost of the gas diffusion cathode varies greatly depending on how much excess of the newly supplied oxygen-containing gas is supplied." and "Increasing the amount of exhaust oxygen-containing gas circulated is advantageous in terms of reducing costs, but in that case, the oxygen concentration of the mixed oxygen gas from the new oxygen-containing gas and the exhaust oxygen-containing gas entering the gas chamber decreases, and the performance of the gas diffusion electrode decreases accordingly, so that in practical terms there are limitations to the amount of exhaust oxygen-containing gas circulated." There are still issues with the method of supplying and discharging oxygen gas.
本発明の目的は、酸素還元型イオン交換膜法アルカリ金属塩化物水溶液の電解の酸素ガス供給、排出方法を改善し、電解電圧を低減可能な電解方法を提供することにある。 The object of the present invention is to improve the method of supplying and discharging oxygen gas in the electrolysis of an aqueous alkali metal chloride solution using an oxygen-reducing ion-exchange membrane method, and to provide an electrolysis method capable of reducing the electrolysis voltage.
発明者は上記の課題を解決するために、酸素還元型イオン交換膜法アルカリ金属塩化物水溶液電解の酸素ガス供給、排出方法について、鋭意検討を重ねた結果、本発明を完成するに至ったものである。すなわち、本発明は、陰極室に酸素含有ガスを供給し、陰極で酸素を還元しながら行うアルカリ金属塩化物水溶液の電気分解方法であって、陰極室内の平均酸素濃度（入口酸素濃度と出口酸素濃度の平均値を、酸素濃度１００％を１とした場合の比率）と陰極室内の圧力（ｋＰａ）との積が８８以上であることを特徴とするアルカリ金属塩化物水溶液の電気分解方法である。 In order to solve the above problems, the inventors have conducted extensive research into the supply and discharge of oxygen gas in the oxygen-reducing ion-exchange membrane method for electrolyzing an aqueous alkali metal chloride solution, and have completed the present invention. That is, the present invention is a method for electrolyzing an aqueous alkali metal chloride solution by supplying an oxygen-containing gas to a cathode chamber and reducing oxygen at the cathode, characterized in that the product of the average oxygen concentration in the cathode chamber (the ratio of the average of the inlet oxygen concentration and the outlet oxygen concentration, with 100% oxygen concentration taken as 1) and the pressure in the cathode chamber (kPa) is 88 or more.
以下、本発明について詳細に説明する。 The present invention will be described in detail below.
本発明は、陰極室に酸素含有ガスを供給し、陰極で酸素を還元しながら行うアルカリ金属塩化物水溶液の電気分解方法である。 The present invention is a method for electrolyzing an aqueous solution of an alkali metal chloride by supplying an oxygen-containing gas to a cathode chamber and reducing oxygen at the cathode.
本発明の電気分解方法では、例えば、陽極室に設置された塩素発生用電極を陽極として使用し、陰極室に設置された酸素還元用電極を陰極として使用し、陽極と陰極とが陽イオン交換膜で区画された酸素還元型イオン交換膜電解槽が使用される。酸素還元型イオン交換膜電解槽としては、２室型電解槽、３室型電解槽があげられるが、２室型電解槽と３室型電解槽の何れも本発明の効果が発揮される。好ましくは、電解電圧がより低い２室型電解槽である。 In the electrolysis method of the present invention, for example, an oxygen reduction type ion exchange membrane electrolytic cell is used in which a chlorine generating electrode installed in the anode chamber is used as the anode, an oxygen reduction electrode installed in the cathode chamber is used as the cathode, and the anode and cathode are partitioned by a cation exchange membrane. Examples of oxygen reduction type ion exchange membrane electrolytic cells include two-compartment electrolytic cells and three-compartment electrolytic cells, but the effects of the present invention can be achieved in both two-compartment electrolytic cells and three-compartment electrolytic cells. A two-compartment electrolytic cell with a lower electrolysis voltage is preferable.
以降、アルカリ金属塩化物水溶液電解の代表例である食塩電解で説明するが、食塩水以外のアルカリ金属塩化物水溶液でも同様であることは当業者らには周知である。 The following explanation will be given using salt electrolysis, which is a typical example of alkali metal chloride aqueous solution electrolysis, but those skilled in the art will be aware that the same applies to alkali metal chloride aqueous solutions other than salt water.
２室型電解槽の１例を図１に示した。 An example of a two-chamber electrolytic cell is shown in Figure 1.
陰極（５）は弾性集電体（６）の弾性反発力でイオン交換膜（３）と密着される。場合によってはイオン交換膜（３）と陰極（５）との間にカーボンクロスなどの親水層（図示せず）が設置されることもある。 The cathode (5) is in close contact with the ion exchange membrane (3) by the elastic repulsive force of the elastic current collector (6). In some cases, a hydrophilic layer (not shown) such as carbon cloth may be placed between the ion exchange membrane (3) and the cathode (5).
陽極室（１）には陽極室供給ノズル（７）から精製塩水が供給され、食塩水の電気分解により製造された塩素ガスと淡塩水は陽極室排出ノズル（８）から排出される。 Purified salt water is supplied to the anode chamber (1) through the anode chamber supply nozzle (7), and chlorine gas and fresh salt water produced by electrolysis of the salt water are discharged through the anode chamber discharge nozzle (8).
イオン交換膜（３）を透過したナトリウムイオン（Ｎａ+）と水、並びに、陰極室供給ノズル（９）から供給される酸素含有ガス中の酸素とが、陰極（５）で反応し、食塩水の電気分解により苛性ソーダ水溶液が製造される。該苛性ソーダ水溶液は陰極室排出ノズル（１０）から、排ガスとともに排出される。 The sodium ions (Na + ) that have permeated the ion exchange membrane (3) react with water and with oxygen in an oxygen-containing gas supplied from a cathode chamber supply nozzle (9) at the cathode (5), producing an aqueous caustic soda solution by electrolysis of the salt water. The aqueous caustic soda solution is discharged together with the exhaust gas from a cathode chamber discharge nozzle (10).
２室型電解槽に使用される陽極（１）、陰極（５）、イオン交換膜（３）などは、公知のものなどから、適宜、選択すればよい。 The anode (1), cathode (5), ion exchange membrane (3), etc. used in the two-chamber electrolytic cell may be appropriately selected from known components.
３室型電解槽の１例を図２に示した。 An example of a three-chamber electrolytic cell is shown in Figure 2.
陽極室（１）は前記２室型電解槽と同等で、食塩水の電気分解により塩素ガスが製造される。陰極室（４）は陰極（５）により苛性室（１１）とガス室（１４）に区画される。 The anode chamber (1) is equivalent to the two-chamber electrolytic cell described above, and chlorine gas is produced by electrolysis of salt water. The cathode chamber (4) is divided into a caustic chamber (11) and a gas chamber (14) by the cathode (5).
苛性室（１１）は、苛性室供給ノズル（１２）から水又は低濃度苛性ソーダ液を供給し、苛性室排出ノズル（１３）から食塩水の電気分解により製造された苛性ソーダ液を排出する。 The caustic chamber (11) supplies water or low-concentration caustic soda solution through the caustic chamber supply nozzle (12) and discharges the caustic soda solution produced by electrolysis of salt water through the caustic chamber discharge nozzle (13).
ガス室（１４）は、ガス室供給ノズル（１５）から酸素含有ガスを供給し、ガス室排出ノズル（１６）から排ガスを排出する。 The gas chamber (14) supplies oxygen-containing gas through the gas chamber supply nozzle (15) and exhausts exhaust gas through the gas chamber exhaust nozzle (16).
本発明の電解方法では、陰極室（４）（３室型電解槽ではガス室（１４）、以下、同じ）への酸素含有ガスの供給、及び／又は、排出方法に特徴を有する。 The electrolysis method of the present invention is characterized by the method of supplying and/or discharging oxygen-containing gas to the cathode chamber (4) (gas chamber (14) in a three-chamber electrolytic cell, the same below).
すなわち、本発明の電気分解方法では、陰極室内の平均酸素濃度（入口酸素濃度と出口酸素濃度の平均値を、酸素濃度１００％を１とした場合の比率）と陰極室内の圧力（ｋＰａ）との積（以下「平均酸素濃度と圧力との積」という場合がある）を８８以上にすることが必須である。「平均酸素濃度と圧力との積」を８８以上にすると、電解電圧を低くでき、酸素還元型イオン交換膜法食塩電解の所要エネルギーを低くすることができる。好ましくは、「平均酸素濃度と圧力との積」が９２以上である。「平均酸素濃度と圧力との積」が８８未満の場合、電解電圧が高くなり本発明の効果は発揮されない。 That is, in the electrolysis method of the present invention, it is essential that the product of the average oxygen concentration in the cathode chamber (the ratio of the average of the inlet oxygen concentration and the outlet oxygen concentration, where 100% oxygen concentration is taken as 1) and the pressure in the cathode chamber (kPa) (hereinafter sometimes referred to as the "product of the average oxygen concentration and the pressure") is 88 or more. If the "product of the average oxygen concentration and the pressure" is 88 or more, the electrolysis voltage can be lowered, and the energy required for the oxygen-reduced ion-exchange membrane method salt electrolysis can be reduced. Preferably, the "product of the average oxygen concentration and the pressure" is 92 or more. If the "product of the average oxygen concentration and the pressure" is less than 88, the electrolysis voltage will be high and the effect of the present invention will not be achieved.
陰極室（４）内の圧力（ｋＰａ）は絶対圧力であるが、ゲージ圧力（ｋＰａ－Ｇ）を測定し、大気圧力（１０１ｋＰａ）を加算した値を陰極室内の圧力（ｋＰａ）とすればよい。前記陰極室（４）内の圧力（ｋＰａ）は用いる電解槽の耐圧未満であることが必須である。電解槽の耐圧は電解槽毎に異なる。 The pressure (kPa) in the cathode chamber (4) is an absolute pressure, but the gauge pressure (kPa-G) can be measured and the atmospheric pressure (101 kPa) added to obtain the pressure (kPa) in the cathode chamber. It is essential that the pressure (kPa) in the cathode chamber (4) is less than the withstand pressure of the electrolytic cell used. The withstand pressure of the electrolytic cell differs for each electrolytic cell.
陰極室（４）内の圧力は特に限定するものではないが、大気圧力以上の場合、酸素製造にかかるコストを下げることが可能となり、本発明の効果がより一層発揮されるため、好ましくは１０２ｋＰａ（１ｋＰａ－Ｇ）以上、より好ましくは１０４ｋＰａ（３ｋＰａ－Ｇ）以上である。陰極室（４）内の圧力の上限は特に限定するものではないが、工業的に安定運転を実施するため、好ましくは１０５ｋＰａ以下に設定する。 The pressure in the cathode chamber (4) is not particularly limited, but if it is equal to or higher than atmospheric pressure, it is possible to reduce the cost of oxygen production and the effects of the present invention are further enhanced, so it is preferably 102 kPa (1 kPa-G) or more, and more preferably 104 kPa (3 kPa-G) or more. The upper limit of the pressure in the cathode chamber (4) is not particularly limited, but in order to carry out stable operation on an industrial scale, it is preferably set to 105 kPa or less.
陰極室内の圧力を調整する方式に制限はなく、公知の方式から選択すればよい。例えば、陰極室出口ノズルの後段に圧力調整弁を設け、弁開度で圧力を調整することが可能である。また、例えば、陰極室出口ノズルの後段に水封器を設け、水封高さで圧力を調整することもできる。 There are no limitations on the method for adjusting the pressure inside the cathode chamber, and any method may be selected from known methods. For example, a pressure regulating valve can be provided downstream of the cathode chamber outlet nozzle, and the pressure can be adjusted by the valve opening. Also, for example, a water seal can be provided downstream of the cathode chamber outlet nozzle, and the pressure can be adjusted by the water seal height.
運転中に「平均酸素濃度と圧力との積」が８８以上となる範囲において、陰極室内の圧力を変動することもできるが、一定圧力で管理することが簡便で好ましい。 During operation, the pressure in the cathode chamber can be varied so long as the "product of the average oxygen concentration and pressure" is 88 or more, but it is simpler and more preferable to maintain it at a constant pressure.
陰極室（４）内の平均酸素濃度（入口酸素濃度と出口酸素濃度の平均値を、酸素濃度１００％を１とした場合の比率）は、陰極室（４）に供給する入口酸素濃度と陰極室から排出される出口酸素濃度の平均値とすればよい。なお、酸素濃度１００％は酸素濃度（比率）１、酸素濃度９０％は酸素濃度（比率）０．９０、すなわち、パーセント表記の酸素濃度を１００で除した値が酸素濃度（比率）となる。 The average oxygen concentration in the cathode chamber (4) (the ratio of the average of the inlet oxygen concentration and the outlet oxygen concentration, assuming that an oxygen concentration of 100% is 1) can be taken as the average of the inlet oxygen concentration supplied to the cathode chamber (4) and the outlet oxygen concentration discharged from the cathode chamber. Note that an oxygen concentration of 100% is an oxygen concentration (ratio) of 1, and an oxygen concentration of 90% is an oxygen concentration (ratio) of 0.90; in other words, the oxygen concentration (ratio) is the value obtained by dividing the oxygen concentration expressed as a percentage by 100.
平均酸素濃度を下げると酸素の廃棄量が減少し、酸素製造コストが低減されるため、好ましくは酸素濃度（比率）を０．９１以下、より好ましくは０．９０以下に調整する。 Lowering the average oxygen concentration reduces the amount of oxygen wasted and reduces the cost of oxygen production, so it is preferable to adjust the oxygen concentration (ratio) to 0.91 or less, and more preferably 0.90 or less.
運転中に「平均酸素濃度と圧力との積」が８８以上となる範囲において、陰極室内の酸素濃度を変動することもできるが、一定濃度で管理することが簡便で好ましい。 During operation, the oxygen concentration in the cathode chamber can be varied so long as the "product of the average oxygen concentration and pressure" is 88 or more, but it is simpler and more preferable to maintain it at a constant concentration.
陰極室内の酸素濃度は、供給する酸素含有ガスの酸素濃度と量で調整する。供給する酸素含有ガスの酸素濃度を高くするほど、および、酸素含有ガスの量を多くするほど、陰極室内の酸素濃度は高くなる。 The oxygen concentration in the cathode chamber is adjusted by the oxygen concentration and amount of the oxygen-containing gas supplied. The higher the oxygen concentration of the oxygen-containing gas supplied and the greater the amount of oxygen-containing gas, the higher the oxygen concentration in the cathode chamber.
供給する酸素含有ガスの酸素濃度は、「平均酸素濃度と圧力との積」が８８以上となる限り、特に制限はない。空気を精製し酸素含有ガスを製造することが最も簡便、かつ、安価であり、好ましい。当該酸素含有ガスは、例えば、空気を吸着法により精製することにより得ることができる。空気を吸着法で精製し９０～９５％の酸素濃度の酸素含有ガスを製造する装置は、一般に、ＰＳＡ装置として広く知られている。 There are no particular limitations on the oxygen concentration of the oxygen-containing gas supplied, so long as the "product of the average oxygen concentration and the pressure" is 88 or more. Purifying air to produce an oxygen-containing gas is the simplest, most inexpensive, and preferable method. The oxygen-containing gas can be obtained, for example, by purifying air using an adsorption method. An apparatus that purifies air using an adsorption method to produce an oxygen-containing gas with an oxygen concentration of 90 to 95% is generally known as a PSA apparatus.
酸素含有ガスを陰極室に供給する方式は従来公知の方法を用いればよい。酸素含有ガスの流量が所望の流量になるよう、供給する酸素含有ガスの圧力を調整すればよい。例えば、ＰＳＡ装置で空気を精製して酸素含有ガスを製造した場合、製造される酸素含有ガスを、例えば、５００ｋＰａ－Ｇの圧力で得ることが可能である。当該、酸素含有ガスを流量調整弁等を介して陰極室に供給すれば、酸素含有ガスを所望の流量で陰極室に供給することができることは当業者らには周知である。 The method for supplying the oxygen-containing gas to the cathode chamber may be a conventional method. The pressure of the oxygen-containing gas to be supplied may be adjusted so that the flow rate of the oxygen-containing gas becomes the desired flow rate. For example, when the oxygen-containing gas is produced by purifying air using a PSA device, the produced oxygen-containing gas can be obtained at a pressure of, for example, 500 kPa-G. It is well known to those skilled in the art that the oxygen-containing gas can be supplied to the cathode chamber at the desired flow rate by supplying the oxygen-containing gas to the cathode chamber via a flow control valve or the like.
酸素含有ガスの供給量は、酸素含有ガスの流量で管理することが可能である。また、酸素含有ガスの酸素濃度と陰極室への供給流量で定まる酸素供給量を、電解電流で定まる酸素消費量で除した、酸素供給倍数で酸素含有ガスの供給量を管理することもできる。 The supply amount of oxygen-containing gas can be controlled by the flow rate of the oxygen-containing gas. The supply amount of oxygen-containing gas can also be controlled by the oxygen supply multiple, which is obtained by dividing the oxygen supply amount, which is determined by the oxygen concentration of the oxygen-containing gas and the supply flow rate to the cathode chamber, by the oxygen consumption amount, which is determined by the electrolysis current.
前記酸素供給倍数で酸素含有ガスの供給量を管理した場合、廃棄される酸素量の把握が容易となり、また、酸素供給不足を防ぐことが容易になるなど、好ましい。 When the supply amount of oxygen-containing gas is controlled using the oxygen supply multiple, it is easier to grasp the amount of oxygen that is wasted and it is also easier to prevent a shortage of oxygen supply, which is preferable.
本発明のアルカリ金属塩化物水溶液の電解分解方法を実施するに際し、電解槽は前述の酸素還元型イオン交換膜電解槽を用いる。酸素還元型イオン交換膜電解槽は特に制限はなく、従来公知のものを適宜用いればよいが、前記のとおり、電解電圧がより低い２室型電解槽を用いることが好ましい。 When carrying out the method for electrolytic decomposition of an aqueous alkali metal chloride solution of the present invention, the electrolytic cell used is the oxygen-reducing ion-exchange membrane electrolytic cell described above. There are no particular limitations on the oxygen-reducing ion-exchange membrane electrolytic cell, and any conventionally known cell may be used as appropriate. However, as described above, it is preferable to use a two-chamber electrolytic cell with a lower electrolytic voltage.
陰極室内の「平均酸素濃度と圧力との積」が８８以上とする以外の電解条件、例えば、電流密度、温度、食塩水濃度などは、特に制約はなく、従来公知の条件を適宜用いればよい。 Other than the requirement that the "product of the average oxygen concentration and pressure" in the cathode chamber be 88 or more, there are no particular restrictions on the electrolysis conditions, such as current density, temperature, and saline concentration, and conventionally known conditions may be used as appropriate.
すなわち、従来公知の酸素還元型イオン交換膜電解槽において、陰極室内の「平均酸素濃度と圧力との積」が８８以上とし、その他の電解条件は従来公知の条件を用い、アルカリ金属塩化物水溶液の電気分解を実施すれば、電解電圧を低く維持しつつ、塩素ガスとアルカリ金属水酸化物の製造が操業可能となる。 In other words, in a conventionally known oxygen reduction type ion exchange membrane electrolytic cell, if the "product of the average oxygen concentration and pressure" in the cathode chamber is set to 88 or more, and other electrolysis conditions are set to conventionally known conditions, and an aqueous alkali metal chloride solution is electrolyzed, it becomes possible to produce chlorine gas and alkali metal hydroxide while maintaining a low electrolysis voltage.
本発明によれば、電解電圧を低く維持し、アルカリ金属塩化物水溶液の電気分解が操業可能である。 According to the present invention, the electrolysis voltage can be kept low and electrolysis of an aqueous solution of an alkali metal chloride can be carried out.
以下の実施例により、本発明を具体的に説明するが、本発明は実施例のみに限定されるものではない。 The present invention will be specifically explained using the following examples, but the present invention is not limited to these examples.
実施例１～実施例３、参考例１～３、比較例１～比較例２
図１に示す２室型食塩電解槽（有効電解面積：３０ｃｍ2）を用いて食塩電解試験を実施した。陽極は塩素発生用電極（ＤＳＥ（登録商標）、デノラ・ペルメレック製）を用い、イオン交換膜（アシプレックス（登録商標）、旭化成製）を用い、陰極は酸素ガス還元用電極（ＧＤＥ（登録商標）、デノラ・ペルメレック製）を用いた。
Examples 1 to 3, Reference Examples 1 to 3 , Comparative Examples 1 and 2
A salt electrolysis test was carried out using a two-chamber salt electrolysis cell (effective electrolysis area: 30 cm2 ) shown in Figure 1. A chlorine generation electrode (DSE (registered trademark), manufactured by De Nora Permelec) was used as the anode, and an ion exchange membrane (Aciplex (registered trademark), manufactured by Asahi Kasei) was used, and an oxygen gas reduction electrode (GDE (registered trademark), manufactured by De Nora Permelec) was used as the cathode.
陽極室には２５０ｇ／ｌの食塩水を供給し、陰極室には酸素発生装置（Ｍ ＳＥＲＩＥＳ、コフロック製）を用いて、空気から酸素を濃縮した酸素含有ガス（酸素濃度：９３％）を供給した。 250 g/l of saline solution was supplied to the anode chamber, and oxygen-containing gas (oxygen concentration: 93%) made by concentrating oxygen from air was supplied to the cathode chamber using an oxygen generator (M SERIES, manufactured by Kofloc).
電解電流密度は６ｋＡ／ｍ2、陽極室の塩水温度は８８℃に調整し、陰極室出口の苛性濃度は３３ｗｔ％になるように塩水供給量を調整した。 The electrolytic current density was adjusted to 6 kA/m 2 , the salt water temperature in the anode chamber was adjusted to 88° C., and the amount of salt water supplied was adjusted so that the caustic concentration at the cathode chamber outlet was 33 wt %.
陰極室に供給する酸素含有ガスは、酸素供給倍数で１．２～２．０の範囲で調整した。陰極室の苛性及びガス出口に水封器を設置し、水封高さにより陰極室内を０～４ｋＰａ－Ｇに調整した。 The oxygen-containing gas supplied to the cathode chamber was adjusted to an oxygen supply multiple in the range of 1.2 to 2.0. A water seal was installed at the caustic and gas outlet of the cathode chamber, and the pressure inside the cathode chamber was adjusted to 0 to 4 kPa-G by adjusting the water seal height.
表１に酸素供給倍数、陰極室内の酸素濃度、陰極室内の圧力、陰極室内圧力と前記陰極室内酸素濃度との積、及び、電解電圧を記載した。 Table 1 shows the oxygen supply factor, the oxygen concentration in the cathode chamber, the pressure in the cathode chamber, the product of the pressure in the cathode chamber and the oxygen concentration in the cathode chamber, and the electrolysis voltage.
この時、陰極室内の酸素濃度は陰極室の入口酸素濃度と陰極室の出口酸素濃度の平均値とし、酸素濃度１００％を１とした比率で示した。また、陰極室内圧力はゲージ圧力値（ｋＰａ－Ｇ）に大気圧力：１０１ｋＰａを加算した絶対圧力で示した。 At this time, the oxygen concentration in the cathode chamber was the average of the oxygen concentration at the inlet and outlet of the cathode chamber, and was expressed as a ratio with 100% oxygen concentration being 1. The pressure in the cathode chamber was also expressed as an absolute pressure obtained by adding atmospheric pressure: 101 kPa to the gauge pressure value (kPa-G).
本発明の範囲内で電圧が２．２０Ｖ未満を示し、本発明の範囲を逸脱した場合は電圧が２．２０Ｖを超える。従って、本発明の電解方法を用いることにより、酸素ガス拡散電極型イオン交換膜法食塩電解を低電圧で実施可能であると分かる。 Within the range of the present invention, the voltage is less than 2.20 V, and outside the range of the present invention, the voltage exceeds 2.20 V. Therefore, it can be seen that by using the electrolysis method of the present invention, it is possible to carry out sodium chloride electrolysis using an oxygen gas diffusion electrode type ion exchange membrane method at a low voltage.
本発明の電気分解方法を適用することにより、何故、低電圧を得られるかの原理は必ずしも明確ではないが、陰極室内酸素濃度と陰極室内圧力との積で、酸素還元用電極の反応場における酸素の分圧が定まると推定している。酸素の分圧が高いほど、酸素の電解還元が進行しやすくなると考えられる。 The principle behind why low voltage can be obtained by applying the electrolysis method of the present invention is not entirely clear, but it is presumed that the partial pressure of oxygen in the reaction field of the oxygen reduction electrode is determined by the product of the oxygen concentration in the cathode chamber and the pressure in the cathode chamber. It is believed that the higher the partial pressure of oxygen, the easier it is for the electrolytic reduction of oxygen to proceed.
結果を図３に示す。図３中、陰極室内の平均酸素濃度（入口酸素濃度と出口酸素濃度の平均値）と陰極室（４）内の圧力（ｋＰａ）との積について、〇は８８以上９２未満、●は９２以上であり、本発明の範囲の結果を示し、△は８８未満で本発明の結果を逸脱した結果を示す。 The results are shown in Figure 3. In Figure 3, for the product of the average oxygen concentration in the cathode chamber (the average value of the inlet oxygen concentration and the outlet oxygen concentration) and the pressure (kPa) in the cathode chamber (4), ◯ is 88 or more and less than 92, ● is 92 or more, indicating a result within the range of the present invention, and △ is less than 88 and deviating from the results of the present invention.
本発明の電気分解方法により、酸素還元型イオン交換膜法アルカリ金属塩化物水溶液の電気分解を低電圧で実施可能となり、食塩などのアルカリ金属塩化物水溶液の電気分解の所要エネルギーを低下することが可能である。 The electrolysis method of the present invention makes it possible to carry out electrolysis of an aqueous alkali metal chloride solution using an oxygen-reducing ion exchange membrane method at a low voltage, thereby reducing the energy required for electrolysis of an aqueous alkali metal chloride solution such as table salt.
１ 陽極室
２ 陽極
３ 陽イオン交換膜
４ 陰極室
５ 陰極
６ 弾性集電体
７ 陽極室供給ノズル
８ 陽極室排出ノズル
９ 陰極室供給ノズル
１０ 陰極室排出ノズル
１１ 苛性室
１２ 苛性室供給ノズル
１３ 苛性室排出ノズル
１４ ガス室
１５ ガス室供給ノズル
１６ ガス室排出ノズル
REFERENCE SIGNS LIST 1 anode chamber 2 anode 3 cation exchange membrane 4 cathode chamber 5 cathode 6 elastic current collector 7 anode chamber supply nozzle 8 anode chamber discharge nozzle 9 cathode chamber supply nozzle 10 cathode chamber discharge nozzle 11 caustic chamber 12 caustic chamber supply nozzle 13 caustic chamber discharge nozzle 14 gas chamber 15 gas chamber supply nozzle 16 gas chamber discharge nozzle
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|---|---|---|---|---|
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| JP2002275670A (en) | 2001-03-13 | 2002-09-25 | Association For The Progress Of New Chemistry | Ion exchange membrane electrolytic cell and electrolysis method |
| JP2004027267A (en) | 2002-06-24 | 2004-01-29 | Association For The Progress Of New Chemistry | Salt electrolytic cell provided with gas diffusion cathode |
| JP2004300451A (en) | 2003-03-28 | 2004-10-28 | Mitsui Chemicals Inc | Gas diffusion electrode, its production method, and electrolysis method |
| WO2010119918A1 (en) | 2009-04-16 | 2010-10-21 | クロリンエンジニアズ株式会社 | Electrolysis method using two-chamber ion-exchange membrane sodium chloride electrolytic cell equipped with gas diffusion electrode |
| JP2012184507A (en) | 2011-03-04 | 2012-09-27 | Bayer Materialscience Ag | Method of operating oxygen-consuming electrode |
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| JP2001003189A (en) | 1999-06-18 | 2001-01-09 | Kanegafuchi Chem Ind Co Ltd | Ion-exchange membrane-type electrolytic cell and electrolytic method |
| JP2002275670A (en) | 2001-03-13 | 2002-09-25 | Association For The Progress Of New Chemistry | Ion exchange membrane electrolytic cell and electrolysis method |
| JP2004027267A (en) | 2002-06-24 | 2004-01-29 | Association For The Progress Of New Chemistry | Salt electrolytic cell provided with gas diffusion cathode |
| JP2004300451A (en) | 2003-03-28 | 2004-10-28 | Mitsui Chemicals Inc | Gas diffusion electrode, its production method, and electrolysis method |
| WO2010119918A1 (en) | 2009-04-16 | 2010-10-21 | クロリンエンジニアズ株式会社 | Electrolysis method using two-chamber ion-exchange membrane sodium chloride electrolytic cell equipped with gas diffusion electrode |
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