JP7045028B2 - Direct carbon fuel cell - Google Patents

Direct carbon fuel cell Download PDF

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JP7045028B2
JP7045028B2 JP2021013764A JP2021013764A JP7045028B2 JP 7045028 B2 JP7045028 B2 JP 7045028B2 JP 2021013764 A JP2021013764 A JP 2021013764A JP 2021013764 A JP2021013764 A JP 2021013764A JP 7045028 B2 JP7045028 B2 JP 7045028B2
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fuel cell
partition wall
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弘達 渡部
慎一 作野
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Electric Power Development Co Ltd
Tokyo Institute of Technology NUC
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Description

本発明は直接炭素燃料電池に関する。 The present invention relates directly to a carbon fuel cell.

従来の燃料電池としては、リン酸型燃料電池（ＰＡＦＣ）、溶融炭酸塩型燃料電池（ＭＣＦＣ）、固体酸化物型燃料電池（ＳＯＦＣ）、固体高分子型燃料電池（ＰＥＦＣ）等が知られている。
また、溶融炭酸塩型燃料電池や固体酸化物型燃料電池が気体燃料を用いるのに対して、固体炭素燃料を使用する直接炭素燃料電池（ＤＣＦＣ）も提案されている。
非特許文献１、２には、溶融炭酸塩を電解質として用い、燃料である炭素粉末を電解質中に分散させて用いた直接炭素燃料電池の例が記載されている。
直接炭素燃料電池の電気化学反応は以下の通りである。
カソード：Ｏ２＋２ＣＯ２＋４ｅ－→２ＣＯ３ ２－
アノード：Ｃ＋２ＣＯ３ ２－→３ＣＯ２＋４ｅ－
総括反応：Ｃ＋Ｏ２→ＣＯ２
アノードでの反応は、アノードと、固体炭素燃料と、電解質である溶融炭酸塩との三相界面で生じる。 As conventional fuel cells, phosphoric acid type fuel cells (PAFC), molten carbonate type fuel cells (MCFC), solid oxide type fuel cells (SOFC), solid polymer type fuel cells (PEFC) and the like are known. There is.
Further, while molten carbonate fuel cells and solid oxide fuel cells use gaseous fuel, direct carbon fuel cells (DCFC) using solid carbon fuel have also been proposed.
Non-Patent Documents 1 and 2 describe an example of a direct carbon fuel cell in which molten carbonate is used as an electrolyte and carbon powder as a fuel is dispersed in the electrolyte.
The electrochemical reaction of the direct carbon fuel cell is as follows.
Cathode: O 2 + 2CO 2 + 4e- → 2CO 3 2-
Anode: C + 2CO 3 2- → 3CO 2 + 4e-
Summary reaction: C + O 2 → CO 2
The reaction at the anode occurs at the three-phase interface between the anode, the solid carbon fuel and the molten carbonate, which is the electrolyte.

Ｘｉａｎｇ Ｌｉ、外４名、「Ｅｖａｌｕａｔｉｏｎ ｏｆ ｒａｗ ｃｏａｌｓ ａｓ ｆｕｅｌｓ ｆｏｒ ｄｉｒｅｃｔ ｃａｒｂｏｎ ｆｕｅｌ ｃｅｌｌｓ」、Ｊｏｕｒｎａｌ ｏｆ Ｐｏｗｅｒ Ｓｏｕｒｃｅｓ、１９５（２０１０）、ｐ．４０５１－４０５８Xiang Li, 4 outsiders, "Evaluation of coals as fuels for direct carbon fuel cells", Journal of Power Fuel cells, 195 (2010), p. 4051-4058 山村洸陽、外３名、「Ｎｏ．５６ 直接炭素燃料電池（ＤＣＦＣ）の構成要素の発電特性に及ぼす影響」、石炭科学会議発表論文集、一般社団法人日本エネルギー学会、２０１５年１０月、第５２巻、ｐ．１１２－１１３Koyo Yamamura, 3 outsiders, "No. 56 Effect of Direct Carbon Fuel Cell (DCFC) Components on Power Generation Characteristics", Proceedings of the Coal Science Conference, Japan Energy Society, October 2015, No. Volume 52, p. 112-113

しかしながら、非特許文献１、２で開示されている直接炭素燃料電池の発電性能は充分とは言えず、改良が求められる。
本発明は、発電性能に優れた直接炭素燃料電池の提供を目的とする。 However, the power generation performance of the direct carbon fuel cell disclosed in Non-Patent Documents 1 and 2 is not sufficient, and improvement is required.
An object of the present invention is to provide a direct carbon fuel cell having excellent power generation performance.

本発明は以下の態様を有する。
［１］溶融炭酸塩からなる電解質と、
前記電解質と酸素と二酸化炭素に接するカソードと、
前記電解質に接するアノードと、
前記アノード近傍の前記電解質中に存在する粒状の固体炭素と、
前記アノードと前記カソードとの間に設けられ、前記電解質を通過させ、前記固体炭素を通過させない隔壁とを有し、
前記固体炭素が前記アノードと前記隔壁との間で挟持され、前記アノードに前記固体炭素が圧接されている、直接炭素燃料電池。
［２］前記アノードを前記隔壁へ向かう方向に加圧する加圧手段を有する、［１］に記載の直接炭素燃料電池。
［３］ 前記アノードが、気泡を逃がすための貫通孔を有する、［１］又は［２］に記載の直接炭素燃料電池。
［４］前記アノードの近傍に、気泡が抜ける隙間が設けられている、［１］乃至［３］のいずれかに記載の直接炭素燃料電池。
なお、本発明は、以下の態様を含む。
［１１］ 溶融炭酸塩からなる電解質と、前記電解質と酸素と二酸化炭素に接するカソードと、前記電解質に接するアノードと、前記アノード近傍の前記電解質中に存在する粒状の固体炭素と、前記アノードと前記カソードとの間に設けられ、前記電解質を通過させ、前記固体炭素を通過させない隔壁とを有し、前記アノードの少なくとも一部に、前記固体炭素を通過させない貫通孔が設けられており、前記貫通孔の開口面に前記固体炭素が圧接されていることを特徴とする直接炭素燃料電池。
［１２］ 前記固体炭素が前記貫通孔の開口面と前記隔壁の一部とで挟持されている、［１１］の直接炭素燃料電池。
［１３］ 前記貫通孔の開口面と前記固体炭素とを密着させる方向に加圧する加圧手段を有する、［１１］または［１２］の直接炭素燃料電池。
［１４］ 前記固体炭素の平均粒子径が２０～２０００μｍであり、前記貫通孔の開口面における前記貫通孔の直径が、該固体炭素の平均粒子径の１／３倍以下である、［１１］～［１３］のいずれかの直接炭素燃料電池。 The present invention has the following aspects.
[1] An electrolyte composed of molten carbonate and
The cathode in contact with the electrolyte, oxygen and carbon dioxide,
The anode in contact with the electrolyte and
Granular solid carbon present in the electrolyte near the anode,
It has a partition wall provided between the anode and the cathode that allows the electrolyte to pass through and does not allow the solid carbon to pass through.
A direct carbon fuel cell in which the solid carbon is sandwiched between the anode and the partition wall, and the solid carbon is pressure-welded to the anode.
[2] The direct carbon fuel cell according to [1], which has a pressurizing means for pressurizing the anode in the direction toward the partition wall.
[3] The direct carbon fuel cell according to [1] or [2], wherein the anode has a through hole for allowing air bubbles to escape.
[4] The direct carbon fuel cell according to any one of [1] to [3], wherein a gap through which air bubbles escape is provided in the vicinity of the anode.
The present invention includes the following aspects.
[11] An electrolyte composed of molten carbonate, a cathode in contact with the electrolyte, oxygen and carbon dioxide, an anode in contact with the anode, granular solid carbon present in the electrolyte in the vicinity of the anode, the anode and the above. It has a partition wall that is provided between the anode and the anode and allows the electrolyte to pass through and does not allow the solid carbon to pass through, and at least a part of the anode is provided with a through hole that does not allow the solid carbon to pass through. A direct carbon fuel cell characterized in that the solid carbon is pressure-welded to the opening surface of the hole.
[12] The direct carbon fuel cell according to [11], wherein the solid carbon is sandwiched between the opening surface of the through hole and a part of the partition wall.
[13] The direct carbon fuel cell according to [11] or [12], which has a pressurizing means for pressurizing in a direction in which the opening surface of the through hole and the solid carbon are brought into close contact with each other.
[14] The average particle size of the solid carbon is 20 to 2000 μm, and the diameter of the through hole on the opening surface of the through hole is 1/3 or less of the average particle size of the solid carbon. [11] A direct carbon fuel cell according to any one of [13].

本発明の直接炭素燃料電池は、発電性能に優れる。 The direct carbon fuel cell of the present invention is excellent in power generation performance.

本発明の直接炭素燃料電池の一実施形態を示す断面図である。It is sectional drawing which shows one Embodiment of the direct carbon fuel cell of this invention. 図１中のアノード２の一例を示す平面図である。It is a top view which shows an example of the anode 2 in FIG. 発電時のアノード２の近傍を模式的に示した説明図である。It is explanatory drawing which shows typically the neighborhood of the anode 2 at the time of power generation. 実施例の測定結果を示すグラフである。It is a graph which shows the measurement result of an Example. 比較例の測定結果を示すグラフである。It is a graph which shows the measurement result of the comparative example.

図１は、本発明の直接炭素燃料電池の一実施形態を示す断面図である。
本実施形態の直接炭素燃料電池は、溶融炭酸塩（電解質）３と、一部が溶融炭酸塩３中に浸漬されているカソード１と、全体が溶融炭酸塩３中に浸漬されているアノード２と、アノード２の近傍の溶融炭酸塩３中に存在する粒状の固体炭素（燃料）４とを有する。溶融炭酸塩３は反応器５の底部に設けられた電気炉５ｃに収容されている。
本実施形態では、直接炭素燃料電池の発電特性を測定するために、参照電極２０が設けられ、カソード１、アノード２および参照電極２０がポテンショスタット／ガルバノスタット（図示略）に接続されている。符号１１、２１は配線を示す。アノード２の配線は図示していない。
カソード１および参照電極２０と、アノード２との間には、溶融炭酸塩３を通過させ、かつ固体炭素４を通過させない、多孔質の隔壁６が設けられている。隔壁６は有底の円筒状であり、隔壁６の底部は溶融炭酸塩３中に浸漬されている。 FIG. 1 is a cross-sectional view showing an embodiment of the direct carbon fuel cell of the present invention.
In the direct carbon fuel cell of the present embodiment, the molten carbonate (electrolyte) 3, the cathode 1 in which a part thereof is immersed in the molten carbonate 3, and the anode 2 in which the whole is immersed in the molten carbonate 3 And the granular solid carbon (fuel) 4 present in the molten carbonate 3 in the vicinity of the anode 2. The molten carbonate 3 is housed in an electric furnace 5c provided at the bottom of the reactor 5.
In this embodiment, a reference electrode 20 is provided to directly measure the power generation characteristics of the carbon fuel cell, and the cathode 1, the anode 2 and the reference electrode 20 are connected to a potentiostat / galvanostat (not shown). Reference numerals 11 and 21 indicate wiring. The wiring of the anode 2 is not shown.
A porous partition wall 6 is provided between the cathode 1 and the reference electrode 20 and the anode 2 so that the molten carbonate 3 and the solid carbon 4 do not pass through. The partition wall 6 has a bottomed cylindrical shape, and the bottom portion of the partition wall 6 is immersed in the molten carbonate 3.

本実施形態において、アノード２は、円板状で表面から裏面に貫通する貫通孔２ａが設けられた部材からなっており、隔壁６の内側に嵌装されている。
固体炭素４はアノード２と隔壁６の底面との間に充填されている。アノード２は、加圧手段７によって隔壁６の底面に向かう方向へ加圧され、これによってアノード２の下面（貫通孔の開口面）に固体炭素４が圧接されている。すなわち、加圧手段７によって、アノード２の下面と固体炭素４とが密着する方向の圧力が加えられ、固体炭素４はアノード２の下面と隔壁６の底面とで挟持されている。符号８は加圧手段７の加圧力を測定する測定器である。 In the present embodiment, the anode 2 is a disk-shaped member provided with a through hole 2a penetrating from the front surface to the back surface, and is fitted inside the partition wall 6.
The solid carbon 4 is filled between the anode 2 and the bottom surface of the partition wall 6. The anode 2 is pressurized by the pressurizing means 7 toward the bottom surface of the partition wall 6, whereby the solid carbon 4 is pressed against the lower surface of the anode 2 (the opening surface of the through hole). That is, pressure is applied by the pressurizing means 7 in the direction in which the lower surface of the anode 2 and the solid carbon 4 are in close contact with each other, and the solid carbon 4 is sandwiched between the lower surface of the anode 2 and the bottom surface of the partition wall 6. Reference numeral 8 is a measuring instrument for measuring the pressing force of the pressurizing means 7.

本実施形態において、カソード１および参照電極２０は、通気管１２、２２内にそれぞれ収容されている。通気管１２、２２は、一端が溶融炭酸塩３中に浸漬され他端が反応器５の外部に開口しており、カソード１および参照電極２０の周りに、Ｏ２およびＣＯ２を含む混合気体が供給されるようになっている。符号１３、２３は前記混合気体を供給する給気管、符号１４、２４は通気管１２、２２内の気体を反応器５の外部へ排気する排気管を示す。すなわち、カソード１および参照電極２０は、溶融炭酸塩３と酸素と二酸化炭素に接している。
反応器５の上部には不活性ガスの供給口５ａおよび排気口５ｂが設けられ、反応器５内に不活性ガスが充填されるようになっている。符号９は発電時にアノード２で発生するＣＯ２を反応器５の外部へ排気する排気管である。 In the present embodiment, the cathode 1 and the reference electrode 20 are housed in the ventilation tubes 12 and 22, respectively. One end of the ventilation pipes 12 and 22 is immersed in the molten carbonate 3 and the other end is open to the outside of the reactor 5. A mixed gas containing O 2 and CO 2 is provided around the cathode 1 and the reference electrode 20. Is to be supplied. Reference numerals 13 and 23 indicate an air supply pipe for supplying the mixed gas, and reference numerals 14 and 24 indicate an exhaust pipe for exhausting the gas in the ventilation pipes 12 and 22 to the outside of the reactor 5. That is, the cathode 1 and the reference electrode 20 are in contact with the molten carbonate 3, oxygen and carbon dioxide.
An inert gas supply port 5a and an exhaust port 5b are provided above the reactor 5 so that the reactor 5 is filled with the inert gas. Reference numeral 9 is an exhaust pipe that exhausts CO 2 generated at the anode 2 during power generation to the outside of the reactor 5.

溶融炭酸塩３としては、Ｌｉ２ＣＯ３、Ｎａ２ＣＯ３、およびＫ２ＣＯ３からなる群から選ばれる１種以上が好ましい。
融点降下の点で、Ｌｉ２ＣＯ３とＮａ２ＣＯ３とＫ２ＣＯ３との３元型混合物またはＬ
ｉ２ＣＯ３とＫ２ＣＯ３もしくはＬｉ２ＣＯ３とＮａ２ＣＯ３の２元型混合物がより好ましい。 As the molten carbonate 3, one or more selected from the group consisting of Li 2 CO 3 , Na 2 CO 3 , and K 2 CO 3 is preferable.
In terms of melting point depression, a ternary mixture of Li 2 CO 3 and Na 2 CO 3 and K 2 CO 3 or L
A binary mixture of i 2 CO 3 and K 2 CO 3 or Li 2 CO 3 and Na 2 CO 3 is more preferred.

粒状の固体炭素４としては、活性炭、石炭またはバイオマス由来の炭化物が好ましい。不純物（灰分）が含まれていない点で活性炭が好ましい。
固体炭素４の平均粒子径は２０～２０００μｍが好ましい。
ここで、粒状の固体炭素の平均粒子径は、ふるい分け法による質量平均径である。 As the granular solid carbon 4, activated carbon, coal or a carbide derived from biomass is preferable. Activated carbon is preferable because it does not contain impurities (ash).
The average particle size of the solid carbon 4 is preferably 20 to 2000 μm.
Here, the average particle size of the granular solid carbon is the mass average diameter by the sieving method.

アノード２の材質としては、金（Ａｕ）、ニッケル（Ｎｉ）等が挙げられる。触媒活性やコストの点ではニッケルが好ましい。
カソード１の材質としては、金（Ａｕ）、Ｌｉドープされた酸化ニッケル等が挙げられる。
隔壁６は、溶融炭酸塩３を通過させ固体炭素４を通過させない細孔を有する材料で形成されることが好ましい。例えば平均細孔直径が１００～５００ｎｍの多孔質材料が好ましい。ここで、平均細孔直径の測定方法は水銀圧入法である。
隔壁６の材質としては、溶融塩に対する安定性の点で多孔質アルミナが好ましい。 Examples of the material of the anode 2 include gold (Au) and nickel (Ni). Nickel is preferable in terms of catalytic activity and cost.
Examples of the material of the cathode 1 include gold (Au), Li-doped nickel oxide, and the like.
The partition wall 6 is preferably formed of a material having pores that allow the molten carbonate 3 to pass through but not the solid carbon 4 to pass through. For example, a porous material having an average pore diameter of 100 to 500 nm is preferable. Here, the method for measuring the average pore diameter is the mercury intrusion method.
As the material of the partition wall 6, porous alumina is preferable from the viewpoint of stability against molten salt.

反応器５に充填する不活性ガスとしては、アルゴン（Ａｒ）、窒素（Ｎ２）等を用いることができる。
カソード１および参照電極２０の周りに供給する、Ｏ２およびＣＯ２を含む混合気体としては、Ｏ２とＣＯ２またはＣＯ２と空気の混合気体等を用いることができる。 As the inert gas to be filled in the reactor 5, argon (Ar), nitrogen (N 2 ) or the like can be used.
As the mixed gas containing O 2 and CO 2 supplied around the cathode 1 and the reference electrode 20, a mixed gas of O 2 and CO 2 or CO 2 and air can be used.

図２はアノード２の平面図であり、図３は発電時のアノード２の近傍を模式的に示した説明図である。図３中の符号３２は、炭素／電極／溶融炭酸塩の三相界面（反応サイト）を示す。
本実施形態において、アノード２は板状であり、その厚さ方向が垂直になるように配置され、加圧手段７によって、アノード２の下面に粒状の固体炭素４が押しつけられている。このようにアノード２に固体炭素４を圧接させることにより、アノード２と固体炭素４をより確実に接触させることができる。
また、本実施形態のアノード２には、図２に示すように、表面から裏面に貫通する貫通孔２ａが同心円状に設けられている。貫通孔２ａの配置はこれに限られず、適宜変更可能である。
発電時には、アノード２の下面と固体炭素４と溶融炭酸塩３との三相界面（反応サイト）３２から、生成物であるＣＯ２ガス（気泡）が生成する（Ｃ＋２ＣＯ３ ２－→３ＣＯ２＋４ｅ－）。従来の直接炭素燃料電池では、固体炭素と溶融塩のスラリーに、アノードを挿入して発電していたため、連続発電時に気泡がアノードを覆ってしまい、反応サイトの連続的な形成が抑制されていた。本実施形態では、図３に示すように、固体炭素４と溶融炭酸塩３のスラリーに対して、貫通孔２ａを有するアノード２を上方からプレスした状態で発電させるため、生成物である気泡３１は貫通孔２ａを通ってアノード２の上方へ排出される。これにより、アノード２の下部において三相界面（反応サイト）の形成が促進され、発電性能が向上する。
一方、アノード２に貫通孔２ａを設けることによって、アノード２の下面（貫通孔２ａの開口面）の面積が大きく縮小すると、かえって発電性能が低下するため、かかる不都合が生じないように、貫通孔２ａの大きさ、数を設定することが好ましい。 FIG. 2 is a plan view of the anode 2, and FIG. 3 is an explanatory diagram schematically showing the vicinity of the anode 2 during power generation. Reference numeral 32 in FIG. 3 indicates a three-phase interface (reaction site) of carbon / electrode / molten carbonate.
In the present embodiment, the anode 2 has a plate shape, is arranged so that its thickness direction is vertical, and the granular solid carbon 4 is pressed against the lower surface of the anode 2 by the pressurizing means 7. By pressing the solid carbon 4 to the anode 2 in this way, the anode 2 and the solid carbon 4 can be brought into contact with each other more reliably.
Further, as shown in FIG. 2, the anode 2 of the present embodiment is provided with through holes 2a penetrating from the front surface to the back surface in a concentric manner. The arrangement of the through hole 2a is not limited to this, and can be changed as appropriate.
During power generation, CO 2 gas (bubbles), which is a product, is generated from the three-phase interface (reaction site) 32 between the lower surface of the anode 2 and the solid carbon 4 and the molten carbonate 3 (C + 2CO 3 2- → 3CO 2 + 4e). - ). In the conventional direct carbon fuel cell, since the anode is inserted into the slurry of solid carbon and molten salt to generate electricity, bubbles cover the anode during continuous power generation, and the continuous formation of reaction sites is suppressed. .. In the present embodiment, as shown in FIG. 3, a bubble 31 which is a product is generated in a state where the anode 2 having the through hole 2a is pressed from above with respect to the slurry of the solid carbon 4 and the molten carbonate 3. Is discharged above the anode 2 through the through hole 2a. As a result, the formation of a three-phase interface (reaction site) is promoted in the lower part of the anode 2, and the power generation performance is improved.
On the other hand, if the area of the lower surface of the anode 2 (the opening surface of the through hole 2a) is significantly reduced by providing the through hole 2a in the anode 2, the power generation performance is rather deteriorated. It is preferable to set the size and number of 2a.

アノード２の下面（貫通孔２ａの開口面）における貫通孔２ａの直径は、固体炭素４の粒径よりも小さく、固体炭素４は貫通孔２ａを通過しない。該貫通孔２ａの直径は、固体炭素４の平均粒子径の１／３倍以下が好ましい。
貫通孔２ａの一方の開口部から他方の開口部までの距離（本実施形態ではアノード２の厚さ）は、０．０５～１ｍｍが好ましい。 The diameter of the through hole 2a on the lower surface of the anode 2 (the opening surface of the through hole 2a) is smaller than the particle size of the solid carbon 4, and the solid carbon 4 does not pass through the through hole 2a. The diameter of the through hole 2a is preferably 1/3 or less of the average particle size of the solid carbon 4.
The distance from one opening of the through hole 2a to the other opening (thickness of the anode 2 in this embodiment) is preferably 0.05 to 1 mm.

本実施形態において固体炭素４が挟持されている区画、すなわちアノード２の下面と隔壁６の底面と隔壁６の内壁とで囲まれた区画内に存在する固体炭素４の粒径および固体炭素４の合計体積が一定であるとき、加圧手段７の加圧力を大きくすることによって、アノード２と固体炭素４の接触部位の数を増大させることができる。前記区画内において固体炭素４が最密充填状態になると、それ以上加圧力を増加させても発電性能は変化しない。
また固体炭素４の粒径を小さくして、固体炭素４の数を増やすことによっても前記接触部位の数を増大させることができる。 In the present embodiment, the particle size of the solid carbon 4 and the solid carbon 4 existing in the section surrounded by the lower surface of the anode 2, the bottom surface of the partition wall 6, and the inner wall of the partition wall 6 where the solid carbon 4 is sandwiched. When the total volume is constant, the number of contact points between the anode 2 and the solid carbon 4 can be increased by increasing the pressing force of the pressurizing means 7. When the solid carbon 4 is in the close-packed state in the compartment, the power generation performance does not change even if the pressing force is further increased.
Further, the number of the contact portions can be increased by reducing the particle size of the solid carbon 4 and increasing the number of the solid carbon 4.

例えば、加圧手段７の加圧力は、アノード２の下面の単位面積当たり３０～１００ｋＮ／ｍ２が好ましい。
前記固体炭素４が挟持されている区画の全質量（隔壁６内部の溶融炭酸塩３と固体炭素４との合計）に対して、固体炭素４が占める割合（以下、固体炭素の充填率という）は０．５～２．０質量％が好ましい。 For example, the pressing force of the pressurizing means 7 is preferably 30 to 100 kN / m 2 per unit area of the lower surface of the anode 2.
The ratio of the solid carbon 4 to the total mass of the section in which the solid carbon 4 is sandwiched (the total of the molten carbonate 3 and the solid carbon 4 inside the partition wall 6) (hereinafter referred to as the solid carbon filling rate). Is preferably 0.5 to 2.0% by mass.

＜変形例＞
本実施形態では、板状のアノードを、その表面が水平方向となるように配置して、アノードの下面に固体炭素を圧接したが、三相界面の形成を妨げる気泡がアノードの孔を抜けて除去される構造であればよく、アノードの表面が傾斜していてもよく、また固体炭素が圧接されるのはアノードの下面でなくてもよい。アノードの反応サイトで発生した気泡が抜けやすい点では、アノードの下面に反応サイトが存在することが好ましい。
本実施形態では、アノードの下面と隔壁の底面とで固体炭素を挟持したが、アノードに固体炭素を圧接できればよく、この構成に限らない。またアノードの形状は、板状でなくてもよく、気泡を逃がすための貫通孔を形成可能な形状であればよい。例えば多孔質電極内部に固体炭素を充填してもよい。
固体炭素４は隔壁６の内方のみに存在し、アノードの下だけでなく、一部がアノードより上の溶融炭酸塩中に存在していてもよい。
本実施形態では、アノードとは別に加圧手段を設けたが、加圧手段を用いずにアノードに固体炭素を圧接してもよい。 <Modification example>
In the present embodiment, the plate-shaped anode is arranged so that its surface is in the horizontal direction, and solid carbon is pressed against the lower surface of the anode, but bubbles that hinder the formation of the three-phase interface pass through the holes of the anode. The structure may be any as long as it is removed, the surface of the anode may be inclined, and the solid carbon may not be pressure-welded to the lower surface of the anode. It is preferable that the reaction site is present on the lower surface of the anode in that bubbles generated at the reaction site of the anode can easily escape.
In the present embodiment, the solid carbon is sandwiched between the lower surface of the anode and the bottom surface of the partition wall, but the configuration is not limited to this as long as the solid carbon can be pressure-welded to the anode. Further, the shape of the anode does not have to be plate-shaped, and may be any shape as long as it can form a through hole for allowing air bubbles to escape. For example, the inside of the porous electrode may be filled with solid carbon.
The solid carbon 4 may be present only inside the partition wall 6 and may be partially present in the molten carbonate above the anode as well as below the anode.
In the present embodiment, the pressurizing means is provided separately from the anode, but solid carbon may be pressure-welded to the anode without using the pressurizing means.

また、アノードに固体炭素を圧接させることによって、アノードと固体炭素との接触をより確実にできるため、貫通孔を有しないアノードに粒状の固体炭素を圧接させる構成としてもよい。かかる構成によれば、後述の比較例１のように、貫通孔を有しないアノードの近傍の溶融炭酸塩中に粒状の固体炭素が分散されている場合に比べて、発電性能を向上させることができる。さらに三相界面（反応サイト）で生成する気泡が抜ける隙間を、アノード近傍に設けることにより発電性能をより向上させることができる。 Further, since the contact between the anode and the solid carbon can be more reliably performed by pressing the solid carbon to the anode, the structure may be such that the granular solid carbon is pressed to the anode having no through hole. According to this configuration, it is possible to improve the power generation performance as compared with the case where granular solid carbon is dispersed in the molten carbonate in the vicinity of the anode having no through hole as in Comparative Example 1 described later. can. Further, the power generation performance can be further improved by providing a gap in the vicinity of the anode through which bubbles generated at the three-phase interface (reaction site) escape.

以下に実施例を用いて本発明をさらに詳しく説明するが、本発明はこれら実施例に限定されるものではない。
（実施例１）
図１に示す構成の直接炭素燃料電池を作成し、定電流モードで，電圧の経時変化を測定した。結果を図４に示す。
アノード２の材質は金（Ａｕ）とした。アノード２の形状は、直径１４．５ｍｍ、厚さ０．５ｍｍの円板状とし、直径０．５ｍｍの孔を、図２に示すように、同心円状に２５個設けた。カソード１および参照電極２０は金（Ａｕ）製とした。隔壁６としては、平均細孔直径が１２０ｎｍの多孔質アルミナ管（内径１５ｍｍ）を用いた。反応器５の材質は石英とした。
溶融炭酸塩３は、Ｌｉ２ＣＯ３の１６．９モル％と、Ｎａ２ＣＯ３の２５．０モル％と、Ｋ２ＣＯ３の５８．１モル％との混合物を用いた。電気炉５ｃの壁面温度は８００℃とした。固体炭素４としては、平均粒子径が１．０ｍｍの活性炭を用い、電気炉５ｃ内の溶融炭酸塩３に対して固体炭素４は１質量％とした。
反応器５内にＡｒガスを供給し、隔壁６内の溶融炭酸塩３をＡｒガスによるバブリングで撹拌した。カソード１および参照電極２０の周りにはＯ２／ＣＯ２（体積比）が１／２の混合気体を供給した。
加圧手段７によって加える圧力は、アノード２下面の単位面積当たり７０ｋＮ／ｍ２とした。圧力を加えた状態で、アノード２の下面と隔壁６の底面と隔壁６の内壁とで囲まれた区画の体積は８８０ｍｍ３であり、該区画における固体炭素４の充填率は１．０質量％であった。 Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.
(Example 1)
A direct carbon fuel cell having the configuration shown in FIG. 1 was prepared, and the change over time of the voltage was measured in the constant current mode. The results are shown in FIG.
The material of the anode 2 was gold (Au). The shape of the anode 2 was a disk shape having a diameter of 14.5 mm and a thickness of 0.5 mm, and 25 holes having a diameter of 0.5 mm were provided concentrically as shown in FIG. The cathode 1 and the reference electrode 20 are made of gold (Au). As the partition wall 6, a porous alumina tube (inner diameter of 15 mm) having an average pore diameter of 120 nm was used. The material of the reactor 5 was quartz.
As the molten carbonate 3, a mixture of 16.9 mol% of Li 2 CO 3 , 25.0 mol% of Na 2 CO 3 and 58.1 mol% of K 2 CO 3 was used. The wall surface temperature of the electric furnace 5c was set to 800 ° C. As the solid carbon 4, activated carbon having an average particle diameter of 1.0 mm was used, and the solid carbon 4 was set to 1% by mass with respect to the molten carbonate 3 in the electric furnace 5c.
Ar gas was supplied into the reactor 5, and the molten carbonate 3 in the partition wall 6 was stirred by bubbling with Ar gas. A mixed gas having an O 2 / CO 2 (volume ratio) of 1/2 was supplied around the cathode 1 and the reference electrode 20.
The pressure applied by the pressurizing means 7 was 70 kN / m 2 per unit area of the lower surface of the anode 2. Under pressure, the volume of the section surrounded by the lower surface of the anode 2, the bottom surface of the partition wall 6, and the inner wall of the partition wall 6 is 880 mm 3 , and the filling rate of the solid carbon 4 in the section is 1.0% by mass. Met.

（比較例１）
図１に示す構成において、加圧手段７を設けず、また、隔壁６内の溶融炭酸塩３を、不活性ガスによるバブリングで撹拌できるように、給気管（図示せず）を設けた。アノード２を板状の金（Ａｕ）電極とした。固体炭素の平均粒子径を１７μｍとした。隔壁６内の固体炭素と溶融炭酸塩３を実施例１と同様にＡｒガスによるバブリングで撹拌して、固体炭素のアノード２への接触を促進させた。
実施例１と同様にして、定電流モードで，電圧の経時変化を測定した。結果を図５に示す。 (Comparative Example 1)
In the configuration shown in FIG. 1, the pressurizing means 7 is not provided, and an air supply pipe (not shown) is provided so that the molten carbonate 3 in the partition wall 6 can be agitated by bubbling with an inert gas. The anode 2 was a plate-shaped gold (Au) electrode. The average particle size of the solid carbon was 17 μm. The solid carbon and the molten carbonate 3 in the partition 6 were stirred by bubbling with Ar gas in the same manner as in Example 1 to promote the contact of the solid carbon with the anode 2.
In the same manner as in Example 1, the change over time of the voltage was measured in the constant current mode. The results are shown in FIG.

図４、５の結果に示されるように、比較例１に比べて実施例１は発電特性が向上した。具体的には、比較例１は、電圧が定常状態に達するまでに５分程度時間を要し、さらに電圧の経時的変動が見られた。これに対して実施例１では，電圧が速やかに定常状態に達し、かつ変動が見られず、安定した発電を実現できた。また、比較例１は，２５ｍＡ／ｃｍ２以上の発電は困難であったが、実施例では，５０ｍＡ／ｃｍ２以上の発電が可能であった。
なお、実施例１におけるアノード面積は１．０ｃｍ２、比較例１におけるアノード面積は１．６ｃｍ２として，アノード面積基準で発電特性を求めた。 As shown in the results of FIGS. 4 and 5, the power generation characteristics of Example 1 were improved as compared with Comparative Example 1. Specifically, in Comparative Example 1, it took about 5 minutes for the voltage to reach a steady state, and further fluctuation of the voltage with time was observed. On the other hand, in Example 1, the voltage quickly reached a steady state, no fluctuation was observed, and stable power generation could be realized. Further, in Comparative Example 1, it was difficult to generate power of 25 mA / cm 2 or more, but in the example, it was possible to generate power of 50 mA / cm 2 or more.
The anode area in Example 1 was 1.0 cm 2 , and the anode area in Comparative Example 1 was 1.6 cm 2 , and the power generation characteristics were obtained based on the anode area.

１ カソード
２ アノード
２ａ 貫通孔
３ 溶融炭酸塩（電解質）
４ 固体炭素（燃料）
５ 反応器
５ａ 不活性ガスの供給口
５ｂ 排気口
５ｃ 電気炉
６ 隔壁
７ 加圧手段
８ 測定器
９ 排気管
１１ 配線
１２ 通気管
１３ 給気管
１４ 排気管
２０ 参照電極
２１ 配線
２２ 通気管
２３ 給気管
２４ 排気管
３１ 気泡
３２ 三相界面 1 Cathode 2 Anode 2a Through hole 3 Molten carbonate (electrolyte)
4 Solid carbon (fuel)
5 Reactor 5a Inert gas supply port 5b Exhaust port 5c Electric furnace 6 Partition 7 Pressurizing means 8 Measuring instrument 9 Exhaust pipe 11 Wiring 12 Ventilation pipe 13 Air supply pipe 14 Exhaust pipe 20 Reference electrode 21 Wiring 22 Ventilation pipe 23 Air supply pipe 24 Exhaust pipe 31 Bubbles 32 Three-phase interface

Claims (4)

溶融炭酸塩からなる電解質と、
前記電解質と酸素と二酸化炭素に接するカソードと、
前記電解質に接するアノードと、
前記アノード近傍の前記電解質中に存在する粒状の固体炭素と、
前記アノードと前記カソードとの間に設けられ、前記電解質を通過させ、前記固体炭素を通過させない、多孔質の隔壁とを有し、
前記固体炭素が前記アノードと前記隔壁との間で挟持され、前記アノードに前記固体炭素が圧接されている、直接炭素燃料電池。 An electrolyte consisting of molten carbonate and
The cathode in contact with the electrolyte, oxygen and carbon dioxide,
The anode in contact with the electrolyte and
Granular solid carbon present in the electrolyte near the anode,
It has a porous partition wall provided between the anode and the cathode that allows the electrolyte to pass through and does not allow the solid carbon to pass through.
A direct carbon fuel cell in which the solid carbon is sandwiched between the anode and the partition wall, and the solid carbon is pressure-welded to the anode. 前記アノードを前記隔壁へ向かう方向に加圧する加圧手段を有する、請求項１に記載の直接炭素燃料電池。 The direct carbon fuel cell according to claim 1, further comprising a pressurizing means for pressurizing the anode in a direction toward the partition wall. 前記アノードが、気泡を逃がすための貫通孔を有する、請求項１又は２に記載の直接炭素燃料電池。 The direct carbon fuel cell according to claim 1 or 2, wherein the anode has a through hole for allowing air bubbles to escape. 前記アノードの近傍に、気泡が抜ける隙間が設けられている、請求項１乃至３のいずれか一項に記載の直接炭素燃料電池。 The direct carbon fuel cell according to any one of claims 1 to 3, wherein a gap through which bubbles can escape is provided in the vicinity of the anode.
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