JP5133570B2 - Insulation method of reformer - Google Patents

Insulation method of reformer Download PDF

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JP5133570B2
JP5133570B2 JP2007009773A JP2007009773A JP5133570B2 JP 5133570 B2 JP5133570 B2 JP 5133570B2 JP 2007009773 A JP2007009773 A JP 2007009773A JP 2007009773 A JP2007009773 A JP 2007009773A JP 5133570 B2 JP5133570 B2 JP 5133570B2
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reformer
reforming
raw material
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temperature
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JP2008174420A (en
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武 桑原
靖 吉野
史郎 藤島
拓也 諸石
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T.RAD CO., L T D.
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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

本発明は原料ガスを水蒸気改質して水素リッチな改質ガスを生成する改質器の保温方法に関し、特に、改質器の運転を停止した後に、改質触媒であるニッケル系の改質触媒の表面に炭素が生成し、またはニッケルカルボニルが生成することを防止した改質器の保温方法に関する。   TECHNICAL FIELD The present invention relates to a heat retaining method for a reformer that generates a hydrogen-rich reformed gas by steam reforming a raw material gas, and in particular, after the operation of the reformer is stopped, the reforming of a nickel-based reforming catalyst. The present invention relates to a heat retention method for a reformer in which carbon or nickel carbonyl is prevented from being generated on the surface of a catalyst.

従来から、原料ガスと水蒸気の混合物（以下、原料一水蒸気混合物という。）を改質触媒の存在下に水蒸気改質し、水素リッチな改質ガスを生成する改質器が知られている。改質器で得られる水素リッチな改質ガスは、残留するＣＯ（一酸化炭素）をＣＯ低減手段で触媒の存在下に酸素含有ガスと反応させてＣＯ２へ変換し、特に低温で作動する固体高分子電解質型燃料電池用には、数ｐｐｍレベルまでＣＯを低減してから燃料として供給される。原料ガスには、メタン等の炭化水素、メタノール等の脂肪族アルコール類、或いはジメチルエーテル等のエーテル類、都市ガス、天然ガスなどが用いられる。
このような改質器において、例えばメタンを原料ガスとして使用した場合の水蒸気改質の反応式は、ＣＨ４＋２Ｈ２Ｏ→ＣＯ２＋４Ｈ２で示すことができ、好ましい改質反応温度は、６５０〜７５０℃の範囲である。 2. Description of the Related Art Conventionally, there is known a reformer that generates a hydrogen-rich reformed gas by steam reforming a mixture of a source gas and steam (hereinafter referred to as a source-steam mixture) in the presence of a reforming catalyst. The hydrogen-rich reformed gas obtained in the reformer is converted to CO 2 by reacting residual CO (carbon monoxide) with an oxygen-containing gas in the presence of a catalyst by means of CO reduction, and operates at a particularly low temperature. For solid polymer electrolyte fuel cells, CO is reduced to several ppm level before being supplied as fuel. As the source gas, hydrocarbons such as methane, aliphatic alcohols such as methanol, ethers such as dimethyl ether, city gas, natural gas, and the like are used.
In such a reformer, for example, the reaction formula of steam reforming when methane is used as a raw material gas can be expressed as CH 4 + 2H 2 O → CO 2 + 4H 2 , and the preferred reforming reaction temperature is 650 It is the range of -750 degreeC.

改質器の改質反応に必要な熱を供給する方式として外部加熱型と、内部加熱型がある。外部加熱型の改質器は、外部に加熱部を設け、その熱源で原料ガスと水蒸気を反応させて改質ガスを生成するようになっている。
内部加熱型の改質器はその供給側（上流側）に部分酸化反応層を設け、該部分酸化反応層で発生した熱を用いて下流側に配備した水蒸気改質反応層を水蒸気改質反応温度まで加熱し、該加熱された水蒸気改質触媒層で水蒸気改質反応をさせて水素リッチな改質ガスを生成するようになっている。 There are an external heating type and an internal heating type as a system for supplying heat necessary for the reforming reaction of the reformer. The external heating type reformer is provided with a heating unit outside, and a reformed gas is generated by reacting a raw material gas and water vapor with a heat source.
The internal heating type reformer is provided with a partial oxidation reaction layer on the supply side (upstream side), and the steam reforming reaction layer disposed on the downstream side using the heat generated in the partial oxidation reaction layer is subjected to a steam reforming reaction. Heating to a temperature is performed, and a steam reforming reaction is performed in the heated steam reforming catalyst layer to generate a hydrogen-rich reformed gas.

部分酸化反応は、ＣＨ４＋１／２・Ｏ２→ＣＯ＋２Ｈ２で示すことができ、好ましい部分酸化反応の温度は２５０℃以上の範囲である。内部加熱型の改質器を改良したものとして自己酸化内部加熱型の改質器が例えば特許文献１、２に記載されている。
特許文献１、２の改質器は外側の予備改質室とそれに連通する内側の主改質室を備えた二重構造になっており、予備改質室には改質触媒層が設けられ、主改質室には酸化空気の供給管、改質触媒と酸化触媒を混合した混合触媒層、シフト触媒層等が設けられる。なお主改質室の中央部に酸化空気を供給する供給管が延長され、その供給管が混合触媒層に延長する部分に複数のノズルからなる空気噴出部が形成される。 The partial oxidation reaction can be represented by CH 4 + 1/2 · O 2 → CO + 2H 2 , and the preferable partial oxidation reaction temperature is in the range of 250 ° C. or higher. For example, Patent Documents 1 and 2 describe a self-oxidation internal heating type reformer as an improvement of the internal heating type reformer.
The reformers of Patent Documents 1 and 2 have a double structure including an outer pre-reforming chamber and an inner main reforming chamber communicating with the outer pre-reforming chamber, and the pre-reforming chamber is provided with a reforming catalyst layer. The main reforming chamber is provided with an oxidizing air supply pipe, a mixed catalyst layer in which the reforming catalyst and the oxidation catalyst are mixed, a shift catalyst layer, and the like. Note that a supply pipe for supplying oxidized air is extended to the central portion of the main reforming chamber, and an air ejection portion including a plurality of nozzles is formed in a portion where the supply pipe extends to the mixed catalyst layer.

改質触媒層は原料ガスを水蒸気改質するものであり、例えばＮｉＯ−Ａ１２Ｏ３あるいはＮｉＯ−ＳｉＯ２・Ａ１２Ｏ３などのニッケル系の改質触媒が主として使用される。混合触媒層を構成する改質触媒は上記と同様なものが使用され、それに均一に分散される酸化触媒は原料−水蒸気混合物中の原料ガスを酸化発熱させて水蒸気改質反応に必要な温度を得るもので、例えば白金（Ｐｔ）やロジウム（Ｒｈ）あるいはルテニウム（Ｒｕ）あるいはパラジウム（Ｐｄ）が使用される。 The reforming catalyst layer is for reforming the raw material gas by steam, and for example, a nickel-based reforming catalyst such as NiO—A1 2 O 3 or NiO—SiO 2 .A1 2 O 3 is mainly used. The reforming catalyst constituting the mixed catalyst layer is the same as described above, and the oxidation catalyst uniformly dispersed therein causes the raw material gas in the raw material-steam mixture to oxidize and exotherm, so that the temperature required for the steam reforming reaction is increased. For example, platinum (Pt), rhodium (Rh), ruthenium (Ru), or palladium (Pd) is used.

なお改質触媒に対する酸化触媒の混合割合は、水蒸気改質すべき原料ガスの種類に応じて１〜１５％程度の範囲で選択され、例えば原料ガスとしてメタンを使用する場合は５％±２％程度、メタノールの場合は２％±１％程度の混合割合とされる。   The mixing ratio of the oxidation catalyst to the reforming catalyst is selected in the range of about 1 to 15% according to the type of the raw material gas to be steam reformed. For example, when methane is used as the raw material gas, it is about 5% ± 2%. In the case of methanol, the mixing ratio is about 2% ± 1%.

改質器の水蒸気改質に必要な水蒸気を発生するため、改質システムには水蒸気発生手段が設けられる。水蒸気発生手段は気体燃料または液体燃料をバーナで燃焼し、その燃焼ガスで水を加熱して水蒸気を発生するものである。改質器には水蒸気発生手段で発生した水蒸気と原料ガス供給手段からの原料ガスをエジェクタからなる吸引混合手段で混合して得られた原料−水蒸気混合物が供給される。   In order to generate steam necessary for steam reforming of the reformer, the reforming system is provided with steam generating means. The water vapor generating means burns gaseous fuel or liquid fuel with a burner and heats water with the combustion gas to generate water vapor. The reformer is supplied with a raw material-water vapor mixture obtained by mixing the water vapor generated by the water vapor generating means and the raw material gas from the raw material gas supply means by the suction mixing means comprising an ejector.

改質システムを停止すると改質器の温度は徐々に低下して最終的には室温まで下がる。そのように温度低下した場合には、再起動に際して改質器の温度を改質反応温度まで再び上昇させる必要があり、再起動にかなりの時間がかかる。そこで再起動時間を短縮するために、改質システムの停止中に改質器を保温しておく方法が知られている。   When the reforming system is stopped, the temperature of the reformer gradually decreases and finally decreases to room temperature. In such a case, the temperature of the reformer needs to be raised again to the reforming reaction temperature at the time of restart, and it takes a considerable time to restart. In order to shorten the restart time, a method of keeping the reformer warm while the reforming system is stopped is known.

例えば特許文献３には、自己酸化内部加熱型の改質器を用いた改質システムの保温方法が記載されている。特許文献３の方法は、改質システムの停止に際して、先ず改質器への原料ガスと水の供給を停止し、改質器内の残留燃料と空気により部分酸化反応を行わせることで、改質触媒層の温度を例えば上限６００℃〜９００℃程度に上昇させた後、空気の供給を停止するものである。
すなわち改質システムの停止後に改質器を一旦高温領域に上昇し、その余熱を保温に利用している。また停止期間が長くなると温度低下してくるので、所定の間隔で改質器に原料ガスと空気を補給し、原料ガスの燃焼熱で改質器の温度を再度高温に上昇させて保温温度の維持を繰り返すことも記載されている。 For example, Patent Document 3 describes a method for keeping the temperature of a reforming system using a self-oxidation internal heating type reformer. In the method of Patent Document 3, when the reforming system is stopped, first, the supply of raw material gas and water to the reformer is stopped, and the partial oxidation reaction is performed by the residual fuel and air in the reformer. After raising the temperature of the porous catalyst layer to, for example, the upper limit of about 600 ° C. to 900 ° C., the supply of air is stopped.
That is, after the reforming system is stopped, the reformer is once raised to a high temperature region, and the remaining heat is used for heat retention. In addition, since the temperature decreases as the stop period becomes longer, the reformer is supplied with source gas and air at predetermined intervals, and the temperature of the reformer is raised to a higher temperature again by the heat of combustion of the source gas. It is also described that the maintenance is repeated.

特開２００１−１９２２０１号公報JP 2001-192201 A 特開２００５−１４９８６０号公報JP-A-2005-149860 特開２００２−１５８０２７号公報JP 2002-158027 A

発明者らの実験によれば、ニッケル系の改質触媒を用いて水蒸気改質する改質器を保温する場合、２００℃を超えた状態で保温すると改質器内にドライな原料ガス（例えば天然ガス）が残存する場合、触媒表面に炭素が析出して触媒を劣化させることが判明した。また１５０℃以下の状態で保温すると、ニッケル系触媒のニッケルが残存する一酸化炭素と反応してニッケルカルボニル（Ｎｉ(ＣＯ)４）を生成し、それによって触媒性能が低下することも判明した。 According to the experiments by the inventors, when the temperature of a reformer that performs steam reforming using a nickel-based reforming catalyst is maintained, if the temperature exceeds 200 ° C., a dry source gas (for example, When natural gas) remains, it has been found that carbon is deposited on the catalyst surface to deteriorate the catalyst. It has also been found that when the temperature is kept at 150 ° C. or lower, nickel of the nickel-based catalyst reacts with the remaining carbon monoxide to form nickel carbonyl (Ni (CO) 4 ), thereby reducing the catalyst performance.

そこで本発明は、このような改質器の保温における問題を解決することを課題とし、そのための新しい改質器の保温方法を提供することを目的とする。   SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve such a problem in heat retention of a reformer, and an object of the present invention is to provide a new heat retention method for a reformer.

前記課題を解決する本発明の改質気の保温方法は、内部にニッケル系の改質触媒層を収容した改質器で原料ガスを水蒸気改質して水素リッチな改質ガスを生成するようにした改質器の保温方法において、
改質器１の停止後、予熱で発生する水蒸気により、改質器内部に残留する原料ガスがパージされて置換され、
次いでその内部温度が原料ガスの炭素析出温度以下になった時点で、原料ガスを改質器１の供給部１１に所定量供給し、改質器１の内部の水蒸気を原料ガスで置換して改質器１内を原料ガス封入状態にし、
保温のため改質器１を電気ヒータ１３で加熱して触媒層の温度を１５０℃以上で２００℃未満に維持することにより、ニッケル系の改質触媒の表面に炭素の析出やニッケルカルボニルが生成して触媒を劣化させることを防止することを特徴とする（請求項１）。 The method for keeping the reformed air of the present invention that solves the above-described problem is to produce a hydrogen-rich reformed gas by steam reforming the raw material gas in a reformer containing a nickel-based reforming catalyst layer inside. In the heat-retaining method for the reformer,
After the reformer 1 is stopped, the raw material gas remaining inside the reformer is purged and replaced by steam generated by preheating,
Next, when the internal temperature becomes equal to or lower than the carbon deposition temperature of the raw material gas, a predetermined amount of the raw material gas is supplied to the supply unit 11 of the reformer 1, and the water vapor inside the reformer 1 is replaced with the raw material gas. The inside of the reformer 1 is filled with the raw material gas,
For maintaining the temperature, the reformer 1 is heated by the electric heater 13 and the temperature of the catalyst layer is maintained at 150 ° C. or higher and lower than 200 ° C., so that carbon deposition or nickel carbonyl is generated on the surface of the nickel-based reforming catalyst. Thus, the catalyst is prevented from deteriorating (claim 1).

上記改質器の保温方法おいて、前記改質器が外側に予備改質室を配置し内側に主改質室を配置した二重構造を有し、予備改質室にニッケル系の改質触媒層を収容し、主改質室にニッケル系の改質触媒と酸化触媒を混合した混合触媒層とシフト触媒層を収容して構成される場合、前記予備改質室の外側から改質器を加熱し保温することができる（請求項２）。   In the above-described heat retaining method for the reformer, the reformer has a double structure in which a pre-reformer chamber is disposed on the outside and a main reformer chamber is disposed on the inner side. When a catalyst layer is accommodated and a mixed catalyst layer in which a nickel-based reforming catalyst and an oxidation catalyst are mixed and a shift catalyst layer are accommodated in the main reforming chamber, a reformer is formed from the outside of the preliminary reforming chamber. Can be heated and kept warm (claim 2).

上記いずれかの改質器の保温方法において、前記触媒を収容した改質器の周囲に電気ヒータを配置し、その外側を断熱層で被覆し、前記触媒の温度を１５０℃以上で２００℃未満に維持するように電気ヒータへの電力供給を制御することができる（請求項３）。   In any one of the above reformer heat insulation methods, an electric heater is disposed around the reformer containing the catalyst, and the outside is covered with a heat insulating layer, and the temperature of the catalyst is 150 ° C. or higher and lower than 200 ° C. It is possible to control the power supply to the electric heater so as to be maintained at (Claim 3).

本発明の改質器の保温方法は、ニッケル系の改質触媒を有する触媒層の温度を１５０℃以上で２００℃未満に維持するように改質器を加熱し保温することを特徴としている。そのため改質器内に原料ガスが残存している場合であっても、触媒表面に炭素が析出して触媒劣化を起こすことがなく、または一酸化炭素が残存している場合であってもニッケルカルボニルが生成して触媒性能が低下することもない。また本発明の保温方法を採用することによって、改質システムの再起動時間が短縮される。   The heat retaining method for a reformer of the present invention is characterized in that the reformer is heated and kept warm so that the temperature of the catalyst layer having a nickel-based reforming catalyst is maintained at 150 ° C. or higher and lower than 200 ° C. Therefore, even if the raw material gas remains in the reformer, carbon does not deposit on the catalyst surface to cause catalyst deterioration, or even if carbon monoxide remains. Carbonyl is not produced and the catalyst performance is not lowered. Moreover, the restart time of a reforming system is shortened by employ | adopting the heat retention method of this invention.

上記改質器の保温方法おいて、請求項２に記載のように、改質器が外側に予備改質室を配置し内側に主改質室を配置した二重構造を有し、予備改質室にニッケル系の改質触媒層を収容し、主改質室にニッケル系の改質触媒と酸化触媒を混合した混合触媒層とシフト触媒層を収容して構成される場合に、前記予備改質室の外側から改質器を加熱して保温することができる。このようにすると、予備改質室と主改質室を同時に共通の保温手段で保温することができる。   In the above-described heat retention method for the reformer, as described in claim 2, the reformer has a double structure in which a preliminary reforming chamber is disposed outside and a main reforming chamber is disposed inside, When the primary reforming chamber contains a nickel-based reforming catalyst layer and the main reforming chamber contains a mixed catalyst layer in which a nickel-based reforming catalyst and an oxidation catalyst are mixed, and a shift catalyst layer, The reformer can be heated and kept warm from the outside of the reforming chamber. In this way, the preliminary reforming chamber and the main reforming chamber can be kept warm by the common heat retaining means at the same time.

また予備改質室の改質触媒層と主改質室の混合触媒層（改質触媒と酸化触媒の混合物の層）は通常二重構造の外側と内側の同じ高さに配置されるので、その位置の外側から改質触媒の温度を前記範囲に維持するように加熱すると、混合触媒層からの伝熱によりシフト触媒層も自動的に保温できるので、保温に要する熱エネルギーの消費を低くできる。   In addition, the reforming catalyst layer of the pre-reforming chamber and the mixed catalyst layer of the main reforming chamber (the layer of the mixture of the reforming catalyst and the oxidation catalyst) are usually arranged at the same height on the outside and inside of the double structure. If the temperature of the reforming catalyst is heated to maintain the temperature within the above range from the outside of the position, the shift catalyst layer can also be automatically warmed by heat transfer from the mixed catalyst layer, so that the consumption of heat energy required for warming can be reduced. .

上記いずれかの改質器の保温方法において、請求項３に記載のように、前記触媒を収容した改質器の周囲に電気ヒータを配置し、その外側を断熱層で被覆し、前記触媒の温度を１５０℃以上で２００℃未満に維持するように電気ヒータへの電力供給を制御することができる。このようにすると、少ない消費電力で改質器を保温できると共に、高い精度での温度制御が可能になる。   In any one of the above reformer heat retaining methods, as described in claim 3, an electric heater is disposed around the reformer containing the catalyst, and an outer side thereof is covered with a heat insulating layer. The power supply to the electric heater can be controlled so that the temperature is maintained at 150 ° C. or higher and lower than 200 ° C. In this way, the reformer can be kept warm with low power consumption, and temperature control with high accuracy becomes possible.

次に図面を参照して本発明を実施するための最良の形態を説明する。図１は本発明の保温方法を適用する改質器を模式的に示す図である。
改質器１は二重に配置した外側の予備改質室２と内側の主改質室３を備えており、全体が薄型に形成される。予備改質室２と主改質室３はそれぞれ細長く断面が偏平状に形成されると共に、それらの断面は互いに相似形とされる。予備改質室２は外筒と内筒の間に形成され、主改質室３は内筒の内側に形成される。 Next, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a diagram schematically showing a reformer to which the heat-retaining method of the present invention is applied.
The reformer 1 includes an outer preliminary reforming chamber 2 and an inner main reforming chamber 3 which are arranged in a double manner, and the entire reformer 1 is formed thin. The preliminary reforming chamber 2 and the main reforming chamber 3 are each elongated and have a flat cross section, and the cross sections thereof are similar to each other. The preliminary reforming chamber 2 is formed between the outer cylinder and the inner cylinder, and the main reforming chamber 3 is formed inside the inner cylinder.

なお、本発明が適用できる改質器１は、このような二重構造に構成されたものに限らず、予備改質室２と主改質室３が別体として構成されるもの、あるいは予備改質室２を有さず主改質室３のみで水蒸気改質を行うように構成されたものにも適用できる。すなわち本発明における改質器１は、図１のような二重構造の内側に配置される主改質室３を有するもの以外に、例えば別体として配置される主改質室３、または予備改質室２を有しない主改質室３（単一の改質室）のみを有するものも含む。   The reformer 1 to which the present invention can be applied is not limited to such a double structure, but the preliminary reforming chamber 2 and the main reforming chamber 3 are configured as separate bodies, or a preliminary The present invention can also be applied to a configuration in which the steam reforming is performed only in the main reforming chamber 3 without the reforming chamber 2. That is, the reformer 1 according to the present invention has, for example, a main reforming chamber 3 arranged as a separate unit, or a spare in addition to the main reforming chamber 3 arranged inside the double structure as shown in FIG. This includes a main reforming chamber 3 (single reforming chamber) having no reforming chamber 2.

予備改質室２に改質触媒層４が設けられ、主改質室３に改質触媒と酸化触媒を混合した混合触媒層５とシフト触媒層６が設けられ、シフト触媒層６は高温シフト触媒層７と低温シフト触媒層８により構成される。そして主改質室３の中央部に沿って酸化用空気を供給する供給管９が混合触媒層５まで延長され、その混合触媒層５の延長部分に空気の噴出部１０が設けられる。   The reforming catalyst layer 4 is provided in the pre-reforming chamber 2, the mixed catalyst layer 5 and the shift catalyst layer 6 in which the reforming catalyst and the oxidation catalyst are mixed are provided in the main reforming chamber 3, and the shift catalyst layer 6 is shifted at a high temperature. The catalyst layer 7 and the low temperature shift catalyst layer 8 are configured. A supply pipe 9 for supplying oxidation air along the central portion of the main reforming chamber 3 is extended to the mixed catalyst layer 5, and an air ejection portion 10 is provided at an extended portion of the mixed catalyst layer 5.

予備改質室２の下部に原料ガスの供給部１１（正確には原料―水蒸気混合物の供給部１１）が設けられ、主改質室３の下部には生成した改質ガスの排出部１２が設けられる。改質器１の周囲は加熱手段としての電気ヒータ１３が設けられ、改質システムの停止中に改質器１を保温するようになっている。   A raw material gas supply unit 11 (more precisely, a raw material-steam mixture supply unit 11) is provided at the lower part of the preliminary reforming chamber 2, and a generated reformed gas discharge unit 12 is provided at the lower part of the main reforming chamber 3. Provided. An electric heater 13 is provided around the reformer 1 as a heating means so as to keep the reformer 1 warm while the reforming system is stopped.

図２は図１の改質器１の周囲（外側）に電気ヒータ１３を配置した例を示す模式的な斜視図である。なお電気ヒータ１３の外側は例えばグラスウール等の断熱層（図示せず）で被覆し、前記触媒の温度を１５０℃以上で２００℃未満に維持するように電気ヒータ１３への電力供給を図示しない制御装置で制御する。例えば改質器１の混合触媒層５に温度検出器を設置し、その温度検出値が予め設定された温度範囲になるように、制御装置が電気ヒータの電源をＯＮ−ＯＦＦ制御または連続的な制御を行う。   FIG. 2 is a schematic perspective view showing an example in which an electric heater 13 is arranged around (outside) the reformer 1 of FIG. The outside of the electric heater 13 is covered with a heat insulating layer (not shown) such as glass wool, and the electric power supply to the electric heater 13 is not shown in the drawing so that the temperature of the catalyst is maintained at 150 ° C. or higher and lower than 200 ° C. Control by device. For example, a temperature detector is installed in the mixed catalyst layer 5 of the reformer 1, and the control device controls the electric heater to be turned on or off or continuously so that the temperature detection value falls within a preset temperature range. Take control.

次に図１の改質器の作用を説明する。改質システムの平常運転時には、供給部１１に原料ガスと水蒸気の混合物（原料−水蒸気混合物）が供給されると共に、供給管９から酸化用空気が供給される。なお水蒸気は図示しない水蒸気発生手段から供給される。供給部１１に供給された原料−水蒸気混合物は、予備改質室２の改質触媒層４を通過する間に原料ガスの一部が改質されて主改質室３の混合触媒層５に流入する。混合触媒層５では原料ガスの一部が空気供給管９から供給される酸化用空気の酸素と反応して改質反応に必要な熱を発生する。そして残った原料ガスは混合触媒層５で改質されて水素リッチな改質ガスを生成し、その改質ガスはシフト触媒層６に流入する。   Next, the operation of the reformer of FIG. 1 will be described. During normal operation of the reforming system, a mixture of raw material gas and water vapor (raw material-water vapor mixture) is supplied to the supply unit 11, and oxidizing air is supplied from the supply pipe 9. The water vapor is supplied from a water vapor generating means (not shown). The raw material-steam mixture supplied to the supply unit 11 is partly reformed while passing through the reforming catalyst layer 4 in the preliminary reforming chamber 2 to form the mixed catalyst layer 5 in the main reforming chamber 3. Inflow. In the mixed catalyst layer 5, a part of the raw material gas reacts with oxygen in the oxidizing air supplied from the air supply pipe 9 to generate heat necessary for the reforming reaction. The remaining raw material gas is reformed in the mixed catalyst layer 5 to generate a hydrogen-rich reformed gas, and the reformed gas flows into the shift catalyst layer 6.

改質ガスはシフト触媒層６を通過する間に含まれているＣＯの大部分が除去され、排出部１２から例えば図示しないＣＯ低減手段に流入する。流入した改質ガスはＣＯ低減手段で微量残留するＣＯがさらにｐｐｍオーダーまで低減された後、燃料電池等の負荷設備に供給される。   Most of the CO contained in the reformed gas is removed while passing through the shift catalyst layer 6, and flows into the CO reduction means (not shown) from the discharge unit 12. The reformed gas that has flowed in is supplied to a load facility such as a fuel cell after a small amount of residual CO is further reduced to the ppm order by the CO reduction means.

次に図１の改質システムの停止方法、およびその後の改質器の保温方法について説明する。改質システムの停止指令に基づき、先ず改質器１への原料ガスと酸化用空気の供給を停止すると共に、図示しない水蒸気発生手段への燃料供給を停止し燃料電池等の負荷設備への改質ガスの供給を停止する。水蒸気発生手段の燃焼が停止しても暫くの間はその余熱で水蒸気が生成し、その生成する水蒸気により改質器１に残留する原料ガスがパージされる。パージされた原料ガスは水蒸気と共に排出部１２から排出される。   Next, a method for stopping the reforming system in FIG. 1 and a method for keeping the reformer after that will be described. Based on the reforming system stop command, the supply of the raw material gas and the oxidizing air to the reformer 1 is first stopped, and the fuel supply to the steam generating means (not shown) is stopped to improve the load equipment such as a fuel cell. Stop supplying quality gas. Even after the combustion of the steam generating means stops, steam is generated for a while with the remaining heat, and the raw material gas remaining in the reformer 1 is purged by the generated steam. The purged source gas is discharged from the discharge unit 12 together with the water vapor.

改質器１の内部温度は上記の停止操作により時間と共に次第に低下するが、改質器１の内部温度が原料ガスの炭素析出温度以下になった時点で、原料ガスを改質器１の供給部１１に所定量供給し、改質器１の内部の水蒸気を原料ガスで置換して改質器１内を原料ガス封入状態にする。それと共に前述したような改質器１の保温のための温度制御、すなわち改質器１を電気ヒータ１３で加熱して触媒層の温度を１５０℃以上で２００℃未満に維持する制御を行う。
(実験例) The internal temperature of the reformer 1 gradually decreases with time due to the above stop operation, but when the internal temperature of the reformer 1 becomes equal to or lower than the carbon deposition temperature of the raw material gas, the raw material gas is supplied to the reformer 1. A predetermined amount is supplied to the unit 11, and the water vapor inside the reformer 1 is replaced with the raw material gas so that the inside of the reformer 1 is filled with the raw material gas. At the same time, temperature control for maintaining the temperature of the reformer 1 as described above, that is, control for maintaining the temperature of the catalyst layer at 150 ° C. or higher and lower than 200 ° C. by heating the reformer 1 with the electric heater 13 is performed.
(Experimental example)

図１の改質器１による保温制御を行った。予備改質室２の改質触媒層４はＮｉＯ−Ａ１２Ｏ３からなるニッケル系改質触媒粒子をアルミナ担体に担持させたものを使用し、主改質室３の混合触媒層５は前記ニッケル系改質触媒粒子と白金（Ｐｔ）粒子の混合物をアルミナ担体に担持させたものを使用した。 Insulation control was performed by the reformer 1 of FIG. The reforming catalyst layer 4 in the pre-reforming chamber 2 uses a nickel-based reforming catalyst particle made of NiO—A1 2 O 3 supported on an alumina carrier, and the mixed catalyst layer 5 in the main reforming chamber 3 is the above-described catalyst layer 5. A mixture of nickel-based reforming catalyst particles and platinum (Pt) particles supported on an alumina carrier was used.

改質器１を前記のように停止操作した後、改質触媒が１５０℃以上２００℃未満の温度に維持されるように図示しない制御装置により電気ヒータ１３をＯＮ−ＯＦＦ制御した。１０時間経過した後、改質触媒を取り出して観察したところ、改質器１内に原料ガスや一酸化炭素が残留していたにもかかわらず、改質触媒の表面に炭化物は生成しておらず、ニッケルカルボニルの生成もなかった。
一方、改質触媒の温度を２５０℃に維持した場合は改質触媒の表面に炭化物の生成がかなりの量見受けられた。また、改質触媒の温度を１２０℃に維持した場合はニッケルカルボニルの発生が見受けられた。 After stopping the reformer 1 as described above, the electric heater 13 was ON / OFF controlled by a control device (not shown) so that the reforming catalyst was maintained at a temperature of 150 ° C. or higher and lower than 200 ° C. After 10 hours, when the reforming catalyst was taken out and observed, carbides were not generated on the surface of the reforming catalyst even though the raw material gas and carbon monoxide remained in the reformer 1. There was also no formation of nickel carbonyl.
On the other hand, when the temperature of the reforming catalyst was maintained at 250 ° C., a considerable amount of carbide was observed on the surface of the reforming catalyst. Further, when the temperature of the reforming catalyst was maintained at 120 ° C., nickel carbonyl generation was observed.

本発明の改質気の保温方法は、原料ガスを水蒸気改質して水素リッチな改質ガスを生成する改質システムに利用できる。   The method for keeping a reformed gas of the present invention is applicable to a reforming system that generates a hydrogen-rich reformed gas by steam reforming a raw material gas.

本発明の保温方法を適用する改質器を模式的に示す図。The figure which shows typically the reformer which applies the heat retention method of this invention. 図１の改質器１の周囲に電気ヒータ１３を配置した例を示す模式的な斜視図。The typical perspective view which shows the example which has arrange | positioned the electric heater 13 around the reformer 1 of FIG.

符号の説明Explanation of symbols

１ 改質器
２ 予備改質室
３ 主改質室
４ 改質触媒層
５ 混合触媒層 DESCRIPTION OF SYMBOLS 1 Reformer 2 Preliminary reforming chamber 3 Main reforming chamber 4 Reforming catalyst layer 5 Mixed catalyst layer

６ シフト触媒層
７ 高温シフト触媒層
８ 低温シフト触媒層
９ 供給管
１１ 供給部
１２ 排出部
１３ 電気ヒータ 6 shift catalyst layer 7 high temperature shift catalyst layer 8 low temperature shift catalyst layer 9 supply pipe 11 supply unit 12 discharge unit 13 electric heater

Claims (3)

内部にニッケル系の改質触媒層を収容した改質器１で原料ガスを水蒸気改質して水素リッチな改質ガスを生成するようにした改質器の保温方法において、
改質器１の停止後、予熱で発生する水蒸気により、改質器内部に残留する原料ガスがパージされて置換され、
次いでその内部温度が原料ガスの炭素析出温度以下になった時点で、原料ガスを改質器１の供給部１１に所定量供給し、改質器１の内部の水蒸気を原料ガスで置換して改質器１内を原料ガス封入状態にし、
保温のため改質器１を電気ヒータ１３で加熱して触媒層の温度を１５０℃以上で２００℃未満に維持することにより、ニッケル系の改質触媒の表面に炭素の析出やニッケルカルボニルが生成して触媒を劣化させることを防止することを特徴とする改質器の保温方法。 In a heat retaining method for a reformer in which a raw material gas is steam reformed in a reformer 1 containing a nickel-based reforming catalyst layer therein to generate a hydrogen-rich reformed gas,
After the reformer 1 is stopped, the raw material gas remaining inside the reformer is purged and replaced by steam generated by preheating,
Next, when the internal temperature becomes equal to or lower than the carbon deposition temperature of the raw material gas, a predetermined amount of the raw material gas is supplied to the supply unit 11 of the reformer 1, and the water vapor inside the reformer 1 is replaced with the raw material gas. The inside of the reformer 1 is filled with the raw material gas,
For maintaining the temperature, the reformer 1 is heated by the electric heater 13 and the temperature of the catalyst layer is maintained at 150 ° C. or higher and lower than 200 ° C., so that carbon deposition or nickel carbonyl is generated on the surface of the nickel-based reforming catalyst. To prevent the catalyst from deteriorating, and to maintain the temperature of the reformer. 請求項１において、
前記改質器１は外側に予備改質室２を配置し内側に主改質室３を配置した二重構造を有し、予備改質室２にニッケル系の改質触媒層４を収容し、主改質室３にニッケル系の改質触媒と酸化触媒を混合した混合触媒層５とシフト触媒層６を収容して構成され、前記予備改質室２の外側から改質器１を加熱し保温することを特徴とする改質器の保温方法。 In claim 1,
The reformer 1 has a double structure in which a preliminary reforming chamber 2 is disposed outside and a main reforming chamber 3 is disposed inside, and a nickel-based reforming catalyst layer 4 is accommodated in the preliminary reforming chamber 2. The mixed reformer layer 5 and the shift catalyst layer 6 in which the nickel-based reforming catalyst and the oxidation catalyst are mixed are accommodated in the main reforming chamber 3, and the reformer 1 is heated from the outside of the preliminary reforming chamber 2. A heat retention method for a reformer characterized in that the heat retention is performed. 請求項１または請求項２において、
前記改質器１の周囲に電気ヒータ１３を配置し、その外側を断熱層で被覆し、前記触媒の温度を１５０℃以上で２００℃未満に維持するように電気ヒータ１３への電力供給を制御することを特徴とする改質器の保温方法。 In claim 1 or claim 2,
An electric heater 13 is disposed around the reformer 1 and the outside thereof is covered with a heat insulating layer, and power supply to the electric heater 13 is controlled so that the temperature of the catalyst is maintained at 150 ° C. or higher and lower than 200 ° C. A method for keeping the reformer warm.
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