JP3709852B2 - Control device for reformer - Google Patents

Description

ただし、ｅ（前回）：前回の偏差、
ｅ（前々回）：前々回の偏差、
Ｔ／Ｔｉ：積分係数（積分ゲイン）、
ＴＤ／Ｔ：微分係数（微分ゲイン）、
Ｔ：制御周期、
Ｋ３：定数、
の式により算出する。これは公知の比例積分微分動作の式である。
【００６９】
ステップ３４ではこのフィードバック量Ｑｆｂを用いて、実際の入口触媒温度Ｔ１を目標温度Ｔｂに一致させるための空気入口流量Ｑ１［ＮＬ／ｍｉｎ］を、
Ｑ１＝Ｑ１（前回）＋Ｑｆｂ…（８）
ただし、Ｑ１（前回）：Ｑ１の前回値、
の式により算出する。Ｑ１の初期値はゼロである。
【００７０】
例えば、実際の入口触媒温度Ｔ１が目標温度Ｔｂより低いときフィードバック量Ｑｆｂが正となり空気入口流量Ｑ１が増量され、この反対に実際の入口触媒温度Ｔ１が目標温度Ｔｂより高いときフィードバック量Ｑｆｂが負となり空気入口流量Ｑ１が減量される。
【００７１】
このようにしてＴ１をＴｂと一致させるための空気入口流量Ｑ１の算出を終了したら図３に戻り、ステップ７でこのＱ１とＱｎｅｅｄとを比較して値の小さい方を選択し、選択後の空気流量を選択空気流量Ｑｓｅｌとする。
【００７２】
例えばＱ１がＱｎｅｅｄより小さい場合とは、目標運転温度Ｔｍが低く設定されている状態であるかまたは、実際の入口触媒温度Ｔ１がＴｍに現在近い状態である。この状態でＱ１よりも大きなＱｎｅｅｄを与えるとすれば、過剰な空気供給によりピーク温度がＴｍを超えて高温になり、かつピーク温度が下流に過剰に移動してしまう。本実施形態では値の小さな方のＱ１を選択することで、こうした事態が生じることが防止される。
【００７３】
一方、Ｑ１がＱｎｅｅｄより大きい場合とは、Ｔｍが高く設定されている状態であるかまたは、実際の入口触媒温度Ｔ１がＴｍに現在到達してない状態である。この状態では値の小さな方のＱｎｅｅｄを選択することで、反応に必要な空気流量の全てであるＱｎｅｅｄを空気入口８ｄより供給できる。
【００７４】
ステップ８では、選択空気流量Ｑｓｅｌに対して、ピーク温度位置に応じた空気入口流量の減量補正を行う。すなわち、ピーク温度位置から図１１を内容とするテーブルを検索することにより、空気入口流量の減量補正値Ｑｇｅｎを演算し、選択空気流量Ｑｓｅｌからこの減量補正値Ｑｇｅｎを差し引いた値を、目標空気入口流量Ｑｍ１として、つまり
Ｑｍ１＝Ｑｓｅｌ−Ｑｇｅｎ…（９）
の式により目標空気入口流量Ｑｍ１を算出する。
【００７５】
減量補正値Ｑｇｅｎは、ピーク温度位置を温度センサ２２位置までもってきたいための空気入口流量の減量分で、図１１のようにピーク温度位置が改質器８の下流になるほど大きくしている。図１１の特性も予め行った実験データから作成する。
【００７６】
空気入口流量を減量補正して、改質器８の下流方向に移動したピーク温度位置を温度センサ２２位置へと移動させたい理由は、ピーク温度位置が温度センサ２２位置に一致するとき、改質効率が最適となるように改質器８を設計しているためである。
【００７７】
なお、図１１において温度センサ２２位置であるｂよりも左側の領域でＱｇｅｎ＝０としているのは、要求空気流量Ｑｎｅｅｄが空気入口流量Ｑ１より小さいとき、ピーク温度位置が温度センサ２２位置よりも前にくることあり、このときにも正の値の減量補正値Ｑｇｅｎを与えたのでは、ピーク温度位置を温度センサ２２位置にもってくることができなくなるからである。
【００７８】
ステップ９では、要求空気流量Ｑｎｅｅｄと目標空気入口流量Ｑｍ１との差分を空気中間流量の理想値Ｑ２ｒｉｓとして、すなわち
Ｑ２ｒｉｓ＝Ｑｎｅｅｄ−Ｑｍ１…（１０）
の式により空気中間流量理想値Ｑ２ｒｉｓを算出する。
【００７９】
ただし、（１０）式において差分がマイナスの値となった場合には無視してＱ２ｒｉｓ＝０とする。
【００８０】
このようにして算出した空気中間流量理想値Ｑ２ｒｉｓは、要求空気流量Ｑｎｅｅｄのうち空気入口８ｄから供給できない空気流量である。
【００８１】
ステップ１０では温度センサ２３位置の触媒温度を推定する。この推定については図１２により説明する。
【００８２】
図１２においてステップ４１で流量センサ２７、２８からの実際の空気流量Ｑｓｅｎ１、Ｑｓｅｎ２、温度センサ２３位置の実際の触媒温度Ｔ２を読み込む。
【００８３】
ステップ４２〜４４は空気入口流量の変化が温度センサ２３位置の触媒温度に与える温度変化分ｄＴ１を算出する部分、ステップ４５〜４７は空気中間流量の変化が温度センサ２３位置の触媒温度に与える温度変化分ｄＴ２を算出する部分である。ｄＴ１を考慮する必要があるのは、空気入口８ｄから供給した空気により空気入口８ｄ付近の触媒で酸化反応が活発になって温度が上昇し、この温度上昇が温度センサ２３位置の触媒温度に影響するためである。同様にして、ｄＴ２を考慮する必要があるのは、温度センサ２３位置より上流側に空気中間入口８ｆが設けられている場合に、空気中間入口８ｆから供給した空気により空気中間入口付近の触媒で酸化反応が活発になって温度が上昇し、この温度上昇が温度センサ２３位置の触媒温度に影響するためである。
【００８４】
これについて図１３を参照してさらに説明すると、空気入口流量がｔ１のタイミングでステップ的に増加したとき（最上段参照）、この変化に対応して温度センサ２３位置の触媒温度は、ステップ増加後の空気流量に対応する温度（図１３第２段目の一点鎖線参照）に対して、一次遅れで追従するものと考えられる（図１３第２段目の実線参照）。このとき、制御理論で良く知られている伝達関数Ｇ１（ｓ）（ｓはラプラス演算子）を用いれば、空気入口流量がステップ増加したタイミングを起点として、所定の期間先の温度センサ２３位置の触媒温度の変化を時系列に推定することが可能である。これを式で表すと次のようになる。
【００８５】
ｄＴ１＝Ｇ１（ｓ）×ｄＱ１…（１１ａ）
ただし、Ｇ１（ｓ）：伝達関数、
すなわち、空気入口流量がｄＱ１だけ変化したときの、温度センサ２３位置の触媒温度変化分ｄＴ１の所定の期間先までの時系列データを、ｄＱ１と伝達関数Ｇ１（ｓ）を用いて求めることができる（図１３第２段目の矢印参照）。
【００８６】
次に、空気中間流量がｔ２のタイミングでステップ的に増加したとき（図１３第３段目参照）、この変化に対応して温度センサ２３位置の触媒温度は、ステップ増加後の空気流量に対応する温度（図１３第４段目の一点鎖線参照）に対して、一次遅れで追従するものと考えられるため（図１３第４段目の実線参照）、推定方法は上記と同様にして行う。すなわち、伝達関数Ｇ２（ｓ）を用いれば、空気中間流量がｄＱ２だけステップ増加したタイミングを起点として、所定の期間先の温度センサ２３位置の触媒温度の変化を、式で表すと次のようになる。
【００８７】
ｄＴ２＝Ｇ２（ｓ）×ｄＱ２…（１２ａ）
ただし、Ｇ２（ｓ）：伝達関数、
従って、空気中間流量がｄＱ２だけ変化したときの、温度センサ２３位置の触媒温度変化分ｄＴ２の所定の期間先までの時系列データを、ｄＱ２と伝達関数Ｇ２（ｓ）を用いて求めることができる（図１３第４段目の矢印参照）。
【００８８】
ここで、上記の伝達関数Ｇ１（ｓ）、Ｇ２（ｓ）は予めステップ応答実験を行って求めておく。ただし、伝達関数Ｇ２（ｓ）は温度センサ２３位置の実際の触媒温度が同じでも伝達関数Ｇ１（ｓ）とは異なるので、伝達関数Ｇ２（ｓ）は別途作成する。
【００８９】
図１２に戻り、ステップ４２では空気入口流量の制御周期当たりの実際の変化分ｄＱ１を、
ｄＱ１＝Ｑｓｅｎ１−Ｑｓｅｎ１（前回）…（１３）
ただし、Ｑｓｅｎ１（前回）：Ｑｓｅｎ１の前回値、
の式により算出する。本実施形態では、図１２に示すサブルーチンの制御周期を図３に示すメインルーチンの制御周期と同じにしているが、図１２の制御周期を別途定めるようにしてもかまわない。
【００９０】
ステップ４３では温度センサ２３位置の実際の触媒温度Ｔ２に応じた伝達関数Ｇ１（ｓ）を選択する。
【００９１】
伝達関数Ｇ１（ｓ）は温度センサ２３位置の触媒温度に応じて複数作成している。複数の伝達関数を用意して温度センサ２３位置の実際の触媒温度Ｔ２に応じた伝達関数を選択させるのは、温度センサ２３位置の触媒温度が高い場合には空気入口流量の単位変化に対する温度センサ２３位置の触媒温度変化分が大きくなる特性があり、この特性を持たせるためである（図１４参照）。高負荷時には空気入口流量も高流量となるので温度変化分は高負荷になるほど大きくなる。
【００９２】
ステップ４４では選択した伝達関数Ｇ１（ｓ）とｄＱ１とを用いて、空気入口流量が制御周期当たりｄＱ１だけ変化したときの、温度センサ２３位置の触媒温度変化分ｄＴ１の所定の期間先までの時系列データを算出する。
【００９３】
ステップ４５では空気中間流量の制御周期当たりの実際の変化分ｄＱ２を、
ｄＱ２＝Ｑｓｅｎ２−Ｑｓｅｎ２（前回）…（１４）
ただし、Ｑｓｅｎ２（前回）：Ｑｓｅｎ２の前回値、
の式により算出する。
【００９４】
ステップ４６では温度センサ２３位置の実際の触媒温度Ｔ２に応じた伝達関数Ｇ２（ｓ）を選択し、ステップ４７においてこの選択した伝達関数Ｇ２（ｓ）とｄＱ２とを用いて、空気中間流量が制御周期当たりｄＱ２だけ変化したときの、温度センサ２３位置の触媒温度変化分ｄＴ２の所定の期間先までの時系列データを算出する。
【００９５】
そして、ステップ４８では温度センサ２３位置の触媒温度変化分ｄＴ１の時系列データともう一つの温度センサ２３位置の触媒温度変化分ｄＴ２の時系列データとを温度センサ２３位置の実際の触媒温度Ｔ２に加算することにより、つまり温度センサ２３位置の触媒温度推定値Ｔ２ｓｕｉの時系列データを、

の式により算出する。
【００９６】
このようにして、空気入口流量や空気中間流量がステップ増加したとき、そのステップ増加した各タイミングを起点として所定の期間先までの温度センサ２３位置の触媒温度推定値の時系列データを求めることができる。
【００９７】
なお、（１５）式のｄＴ１、ｄＴ２の時系列データは正の値も採るし負の値も採る。入口空気流量、中間空気流量の変化分ｄＱ１、ｄＱ２が正のときにはｄＴ１、ｄＴ２の時系列データが正の値となり、この反対に各空気流量の変化分が負のときにはｄＴ１、ｄＴ２の時系列データが負の値となる。
【００９８】
Ｇ１（ｓ）、Ｇ２（ｓ）の各伝達関数を複数用意する代わりに、各伝達関数は温度センサ２３位置の基準触媒温度に対するもの１つずつとし、温度センサ２３位置の実際の触媒温度Ｔ２に基づいて温度補正値を算出し、これらに基づいてｄＴ１、ｄＴ２の時系列データを算出するようにしてもよい。この方法について述べると、これは（１５）式のｄＴ１の時系列データ、ｄＴ２の時系列データを次のようにして求めるものである。すなわち、温度センサ２３位置の触媒温度が基準触媒温度である場合において空気入口流量が制御周期当たりｄＱ１だけ変化したときの、温度センサ２３位置の触媒温度変化分ｄＴ１の所定の期間先までの時系列データを、ｄＱ１と温度センサ２３位位置の基準触媒温度に対する伝達関数Ｇ１０（ｓ）を用いて算出し、これら時系列データにそれぞれ温度補正値１を加えた値を、改めてｄＴ１の時系列データとする。
【００９９】
ｄＴ１の時系列データ
＝基準触媒温度時のｄＴ１の時系列データ＋温度補正値１…（１６）同様にして、温度センサ２３位置の触媒温度が基準触媒温度である場合において中間空気流量が制御周期当たりｄＱ２だけ変化したときの、温度センサ２３位置の触媒温度変化分ｄＴ２の所定の期間先までの時系列データを、ｄＱ２と基準触媒温度に対する伝達関数Ｇ２０（ｓ）を用いて算出し、これら時系列データにそれぞれ温度補正値２を加えた値を、改めてｄＴ２の時系列データとする。
【０１００】

ここで、（１６）、（１７）式の温度補正値１、２は図１５に示したように温度センサ２３位置の実際の触媒温度Ｔ２が基準触媒温度より高くなるほど大きくなる値である。
【０１０１】
このようにして温度センサ２３位置の触媒温度推定値Ｔ２ｓｕｉの算出を終了したら図３に戻り、ステップ１１ではこのＴ２ｓｕｉに基づいて、Ｔ２ｓｕｉの所定の期間先までの時系列データの中の最大値が上限温度Ｔｍａｘを超えることがないように、目標空気中間流量Ｔｍ２を算出する。この算出については図１６により説明する。
【０１０２】
図１６においてステップ５１で、温度センサ２３位置の触媒温度推定値Ｔ２ｓｕｉの時系列データの最大値が上限温度Ｔｍａｘ以下であるかどうかみる。
【０１０３】
ここで、上限温度Ｔｍａｘは目標運転温度Ｔｍ（例えば４００℃）より少し高い値を設定する。簡単にはＴｍと等しくしてもかまわない。
【０１０４】
Ｔ２ｓｕｉの時系列データの最大値が上限値Ｔｍａｘ以下である場合にはステップ５２に進み、上記の空気中間流量理想値Ｑ２ｒｉｓをそのまま目標空気中間流量Ｑｍ２とする。
【０１０５】
一方、Ｔ２ｓｕｉの時系列データの最大値がＴｍａｘを越える場合とは、例えば図１７に示したように、Ｑ１（ただしＱ１＜Ｑｎｅｅｄの場合）にｄＱ１の流量増加があった場合に、Ｔ２ｓｕｉの時系列データのうち時間的に遅い側がＴｍａｘを超える場合である（図１７下段の実線参照）。このときには空気中間流量理想値Ｑ２ｒｉｓをそのま空気中間入口８ｆから供給したのでは大きすぎるので、Ｑ２ｒｉｓより小さな流量としてやる必要がある。このため、ステップ５１よりステップ５３に進んで温度センサ２３位置の実際の触媒温度Ｔ２を読み込み、この温度Ｔ２からステップ５４において図１８を内容とするテーブルを検索することにより、空気中間流量の減量側補正値ｄＱｇｅｎを演算する。
【０１０６】
図１８のように減量側補正値ｄＱｇｅｎは、温度センサ２３位置の実際の触媒温度Ｔ２が高くなるほど負の値で大きくしている。これは、Ｔ２が高い場合には空気中間流量の単位変化に対する温度センサ２３位置の触媒温度変化分が大きくなる特性があるので、これを考慮して計算誤差を少なくするようにしたものである。
【０１０７】
ステップ５５では空気中間流量理想値Ｑ２ｒｉｓにこの負の値である減量分ｄＱｇｅｎを加算した値を改めて空気中間流量理想値Ｑ２ｒｉｓ’として、
Ｑ２ｒｉｓ’＝Ｑ２ｒｉｓ＋ｄＱｇｅｎ…（１８）
の式により算出する。
【０１０８】
ここで、Ｑ２ｒｉｓ’はＱ２ｒｉｓより小さな値である。
【０１０９】
ステップ５６では空気中間流量がＱ２ｒｉｓ’の状態から｜ｄＱｇｅｎ｜だけステップ増加するときの伝達関数Ｇ２’（ｓ）を選択し、ステップ５７においてこの伝達関数Ｇ２’（ｓ）と｜ｄＱｇｅｎ｜とを用いて、空気中間流量がＱ２ｒｉｓ’の状態から｜ｄＱｇｅｎ｜だけ増加するときの、温度センサ２３位置の触媒温度変化分ｄＴ２の所定の期間先までの時系列データを算出する。
【０１１０】
そして、ステップ５８ではこのｄＴ２の時系列データを温度センサ２３位置の実際の触媒温度Ｔ２に加算することにより、温度センサ２３位置の触媒温度推定値Ｔ２ｓｕｉの時系列データを、つまり、
Ｔ２ｓｕｉの時系列データ＝Ｔ２＋ｄＴ２の時系列データ…（１９）
の式により算出する。
【０１１１】
ステップ５９ではこのようにして算出した温度センサ２３位置の触媒温度推定値Ｔ２ｓｕｉの時系列データの最大値が、再び触媒の上限温度Ｔｍａｘ以下であるかどうかみる。
【０１１２】
ここで、Ｔ２ｓｕｉの時系列データの最大値が上限温度Ｔｍａｘを超えていない場合とは、空気中間流量の｜ｄＱｇｅｎ｜の減量によって（図１７最上段の破線鎖線）、図１７最下段の一点鎖線で示したようにＴ２ｓｕｉの時系列データが最大値Ｔｍａｘを下回った場合である。この場合にはステップ６０に進み、Ｑ２離ｓから｜ｄＱｇｅｎ｜だけ減量した値であるＱ２ｒｉｓ’を目標空気中間流量Ｑｍ２として算出する。
【０１１３】
一方、Ｔ２ｓｕｉの時系列データの最大値が上限温度Ｔｍａｘを超えている場合には、ステップ５９よりステップ６１に進み、減量側補正値ｄＱｇｅｎを一定値ｄＱだけ増やしてステップ５５〜５９の操作を繰り返す。この繰り返しによりやがてＴ２ｓｕｉの時系列データの最大値が上限温度Ｔｍａｘ以下になったらステップ６０の操作を実行して、図１６の処理を終える。
【０１１４】
なお、ステップ５５〜５９、６１の操作の繰り返しは制御速度が速いこともあって一瞬で終わる。
【０１１５】
このようにして目標空気中間流量Ｑｍ２の算出を終了したら図３に戻り、ステップ１２でこの目標空気中間流量Ｑｍ２と目標空気入口流量Ｑｍ１とを出力レジスタに移す。
【０１１６】
図示しないフローでは、このようにして算出した目標空気入口流量Ｑｍ１の空気が空気入口８ｄより供給されるように流量制御弁１２の開度を制御すると共に、目標空気中間流量Ｑｍ２の空気が空気中間入口８ｆより供給されるように流量制御弁１４の開度を制御する。
【０１１７】
これらの流量制御弁１２、１４に代えて、ガス流体用の流量制御一体型の制御弁を用いてもかまわない。当該制御弁では流量センサを内蔵しており、算出した目標空気流量Ｑｍ１、Ｑｍ２を入力として与えると、この値と内蔵の流量センサにより検出される実流量とが一致するように弁開度が駆動される。
【０１１８】
ここで、本実施形態の作用効果を説明する。
【０１１９】
温度センサ２２（気体入口触媒温度検出手段）位置の実際の触媒温度Ｔ１が温度センサ２２位置の目標温度Ｔｂと一致するように算出した空気入口流量Ｑ１が、原料流量に基づいて算出した要求空気流量Ｑｎｅｅｄより小さい場合とは、目標運転温度Ｔｍが低く設定されている状態であるか、または空気入口８ｄの実際の触媒温度Ｔ１が目標運転温度Ｔｍに現在近い状態である。この状態で値の大きい方の要求空気流量Ｑｎｅｅｄを選択すると、過剰な空気の供給によりピーク温度が目標運転温度Ｔｍを大きく超えて高温になったり、ピーク温度位置が下流に過剰に移動するのであるが、本実施形態（請求項４に記載の発明）によれば、この状態で値の小さい方の空気入口流量Ｑ１を選択するので、ピーク温度が目標運転温度Ｔｍを超えて高温になったり、ピーク温度位置が下流に過剰に移動することを抑制できる。
【０１２０】
一方、空気入口流量Ｑ１が要求空気流量Ｑｎｅｅｄより大きい場合とは、目標運転温度Ｔｍが高く設定されている状態であるか、または空気入口８ｄの実際の触媒温度Ｔ１が目標運転温度Ｔｍに現在到達してない状態である。この状態では反応に必要な空気流量の全てである要求空気流量Ｑｎｅｅｄを空気入口８ｄより供給できる。
【０１２１】
また、空気入口流量Ｑ１より要求気体流量Ｑｎｅｅｄが大きい場合に、空気入口流量Ｑ１を空気入口８ｄより供給すると、ピーク温度位置が上流側に移動するが、これは、ピーク温度の部分で空気入口８ｄより供給した空気中の酸素がほとんど反応しきったことを意味し、このままであればピーク温度位置より下流側は下流になるほど温度が低下する。本実施形態（請求項５に記載の発明）によれば、要求空気流量Ｑｎｅｅｄのうち、空気入口８ｄより供給できなかった空気の流量（Ｑｎｅｅｄ−Ｑ１）を空気中間入口８ｆより供給するので、空気中間入口８ｆ付近の触媒温度を高めることができる。
【０１２２】
本実施形態（請求項６の発明）によれば、選択空気流量Ｑｓｅｌをピーク温度位置に基づいて減量補正することでも、ピーク温度位置が改質器８の下流方向に過剰に移動することを抑制することができ、かつ上流側で温度の低かった部分の温度を上昇させることができる。
【０１２３】
本実施形態（請求項７の発明）によれば、ピーク温度位置が改質器下流方向に移動するほど、選択空気流量の減量補正値Ｑｇｅｎを増やすので、負荷が相違してもピーク温度位置をほぼ同じ位置にもってくることができる。
【０１２４】
本実施形態（請求項８の発明）によれば、ピーク温度位置が目標運転温度Ｔｍとなるように生成した温度分布プロファイルの中で、温度センサ２２位置に相当する温度を、温度センサ２２位置の目標温度Ｔｂとして算出するので、ピーク温度位置が下流側に移動しても、ピーク温度位置が目標運転温度Ｔｍを超えないようにすることができる。
【０１２５】
本実施形態（請求項１０に記載の発明）によれば、改質器内ガス流速νが速くなるほどピーク温度が改質器の下流側へ移動すると推定するので、改質器内ガス流速が相違してもピーク温度位置を精度良く与えることができる。
【０１２６】
空気入口流量がステップ増加すると、この影響を受けて温度センサ２３位置（気体中間入口付近）の触媒温度が上昇する。この温度上昇分を考慮することなく、空気入口８ｄの実際の触媒温度Ｔ１がこの温度センサ２３位置の目標温度Ｔｂと一致するように算出した空気流量Ｑ１より、要求空気流量Ｑｎｅｅｄが大きい場合に、その差の流量Ｑ２ｒｉｓの空気をそのまま空気中間入口８ｆより供給するとすれば、温度センサ２３位置の触媒温度が上限温度Ｔｍａｘを超えてしまうことが考えられる。本実施形態（請求項１２に記載の発明）によれば、この温度上昇分を含んだ温度センサ２３位置の触媒温度を推定し、その所定期間先の温度センサ２３位置の触媒温度の推定値Ｔ２ｓｕｉが上限温度Ｔｍａｘを超えるときには超えないように空気中間流量を減量側に補正するので、空気入口流量がステップ増加するときでも、温度センサ２３位置の触媒温度が上限温度Ｔｍａｘを超えてしまうことを回避できる。
【０１２７】
同様にして、空気中間流量がステップ増加すると、この影響を受けて温度センサ２３位置の触媒温度が上昇する。この温度上昇分を考慮することなく、空気入口８ｄの実際の触媒温度Ｔ１が温度センサ２２位置の目標温度Ｔｂと一致するように算出した空気入口流量Ｑ１より、要求空気流量Ｑｎｅｅｄが大きい場合に、その差の流量Ｑ２ｒｉｓの空気をそのまま空気中間入口８ｆより供給するとすれば、温度センサ２３位置の触媒温度が上限温度Ｔｍａｘを超えてしまうことが考えられる。本実施形態（請求項１３に記載の発明）によれば、この温度上昇分を含んだ温度センサ２３位置の触媒温度を推定し、その所定期間先の温度センサ２３位置の触媒温度の推定値Ｔ２ｓｕｉが上限温度Ｔｍａｘを超えるときには超えないように空気中間流量を減量側に補正するので、空気中間流量がステップ増加するときでも、温度センサ２３位置の触媒温度が上限温度Ｔｍａｘを超えてしまうことを回避できる。
【０１２８】
高負荷になるほど空気入口８ｄより供給される空気の単位流量変化に対する温度センサ２３位置の触媒温度変化が大きくなる特性を有するので、この特性を考慮しないとすれば、所定期間先の温度センサ２３位置の触媒温度を推定するのに用いる、空気中間流量の減量側補正値ｄＱｇｅｎに過不足が生じる。これに対して本実施形態（請求項１５に記載の発明）によれば、所定期間先の温度センサ２３位置の触媒温度の推定値Ｔ２ｓｕｉが上限温度Ｔｍａｘを超えるときに、その上限温度Ｔｍａｘからの温度上昇分が大きいほど、空気中間流量の減量側補正値ｄＱｇｅｎを大きくするので、負荷に関係なく空気中間流量の減量側補正値ｄＱｇｅｎを精度良く与えることができる。
【０１２９】
前述した実施形態のほかに次の他の実施形態が考えられる。
【０１３０】
他の実施形態１：図２に示した改質器であることを前提とし、部分酸化反応に必要な空気流量である要求空気流量Ｑｎｅｅｄを原料流量に基づいて算出する要求空気流量算出手段と、改質器内部のピーク温度位置を推定するピーク温度位置推定手段と、このピーク温度位置が基準ピーク温度位置より下流側に移動したとき、前記要求空気流量Ｑｎｅｅｄを減量側に補正して空気入口流量Ｑ１を算出する空気入口流量算出手段と、この算出した空気入口流量Ｑ１が空気入口から供給されるように流量制御弁１２の開度を制御する制御手段とを備える。
【０１３１】
この他の実施形態１（請求項１に記載の発明）による作用効果を次に説明する。
【０１３２】
図１９に示したように基準負荷のときピーク温度が基準ピーク温度位置ｚｐ０にくるように、基準負荷に対応する要求空気流量Ｑｎｅｅｄを設定している場合に（図１９上段参照）、基準負荷より負荷が大きくなって原料を増加し、これに応じて要求空気流量Ｑｎｅｅｄを増加し、その要求空気流量Ｑｎｅｅｄを空気入口８ｄより供給したのでは、ピーク温度が目標運転温度Ｔｍを超えたり、ピーク温度位置が基準ピーク温度位置より下流側に移動する（図１９下段の一点鎖線参照）。
【０１３３】
そして、ピーク温度位置が基準ピーク温度位置より下流側に移動すると、改質器入口側に触媒温度が低くなる領域（不活性な触媒領域）が生じ、これにより水素を含む改質ガスの生成量が不足するのであるが、他の実施形態１（請求項１に記載の発明）によれば、ピーク温度位置が基準ピーク温度位置より下流側に移動したとき、要求空気流量Ｑｎｅｅｄを減量側に補正して空気入口流量Ｑ１を算出し、この算出した空気入口流量Ｑ１が空気入口８ｄから供給されるようにするので、ピーク温度位置が目標運転温度Ｔｍを超えてしまったり基準ピーク温度位置より下流側に移動することを抑制できる。すなわち、空気入口８ｄに流入する過剰な空気を減らすことで、改質器８内部のガス流速が低下してガスの滞留時間が長くなり酸化反応が改質器８上流側の触媒で生じ、これにより、ピーク温度が目標運転温度Ｔｍを超える高温になることを防止できると共に、改質器８入口側に不活性な触媒領域が生じることを回避できる（図２０中段の実線参照）。
【０１３４】
他の実施形態２：要求空気流量Ｑｎｅｅｄのうち空気入口８ｄから供給されなかった空気が空気中間入口８ｆより供給されるように流量制御弁１４の開度を制御する。
【０１３５】
この他の実施形態２（請求項３に記載の発明）による作用効果を次に説明する。
【０１３６】
要求空気流量Ｑｎｅｅｄを減量補正した値である空気入口流量Ｑ１を空気入口８ｄより供給すると、ピーク温度位置が改質器８の上流側に移動するが、これは、ピーク温度の部分で空気入口８ｄより供給した空気中の酸素がほとんど反応しきったことを意味し、このままであればそのピーク温度位置より下流側は下流になるほど温度が低下する。他の実施形態２（請求項３に記載の発明）によれば、要求空気流量Ｑｎｅｅｄのうち、空気入口８ｄより供給できなかった空気の流量（Ｑｎｅｅｄ−Ｑ１）を空気中間入口８ｆより供給するので、空気中間入口８ｆ付近の触媒温度を高めることができる（図２０下段の破線参照）。
【０１３７】
実施例では、空気入口８ｄより供給される実際の空気流量Ｑｓｅｎ１と空気中間入口８ｆより供給される実際の空気流量Ｑｓｅｎ２とが変化したときの所定期間先の温度センサ２３位置の触媒温度を推定する場合で説明したが、簡単には空気入口８ｄより供給される実際の空気流量Ｑｓｅｎ１のみが変化したときの、あるいは空気中間入口８ｆより供給される実際の空気流量Ｑｓｅｎ２のみが変化したときの所定期間先の温度センサ２３位置の触媒温度を推定する場合でもかまわない。
【０１３８】
実施形態ではメタノール改質の場合で述べたが、本発明は、ガソリン改質など他の改質仕様にも適用が可能であることはいうまでもない。
【図面の簡単な説明】
【図１】燃料改質システムの概略構成図。
【図２】改質器の概略構成図。
【図３】目標空気流量の算出を説明するためのフローチャート。
【図４】改質器内ガス流量の推定を説明するためのフローチャート。
【図５】要求空気流量の算出を説明するためのフローチャート。
【図６】水流量の特性図。
【図７】メタノール流量の特性図。
【図８】ピーク温度位置の特性図。
【図９】温度分布プロファイルの作成を説明するための特性図。
【図１０】空気入口流量の算出を説明するためのフローチャート。
【図１１】空気入口流量の減量補正値の特性図。
【図１２】温度センサ２３位置の触媒温度の推定を説明するためのフローチャート。
【図１３】空気入口流量と空気中間流量の各ステップ増加が温度センサ２３位置の触媒温度に与える影響を説明するための波形図。
【図１４】単位空気流量変化に対する温度センサ２３位置の温度変化分が負荷の違いによって異なることを説明するための特性図。
【図１５】温度補正値の特性図。
【図１６】目標空気中間流量の算出を説明するためのフローチャート。
【図１７】空気中間流量の減量を説明するための波形図。
【図１８】減量側補正値の特性図。
【図１９】従来装置の作用を説明する波形図。
【図２０】請求項１に記載の発明の作用を説明する波形図。
【符号の説明】
８ 改質器
８ａ 円筒状ケース
８ｂ 触媒
８ｃ 原料入口
８ｄ 空気入口（気体入口）
８ｅ ガス出口
８ｆ 空気中間入口（気体中間入口）
１２ 流量制御弁（気体入口流量調整手段）
１４ 流量制御弁（気体中間入口流量調整手段）
２１ コントローラ
２２ 温度センサ（気体入口触媒温度検出手段）
２３ 温度センサ（気体中間入口触媒温度検出手段）
２５ 圧力センサ
２６ 圧力センサ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a reformer.
[0002]
[Prior art]
A conventional control device for a reformer is disclosed in JP-A-6-349510.
[0003]
[Problems to be solved by the invention]
In the reformer, a raw material mainly composed of hydrocarbon and oxygen in the air are reacted to decompose the raw material to generate a hydrogen-rich reformed gas. Since the quality reaction is an endothermic reaction, an exothermic reaction due to a partial oxidation reaction is caused at the same time. By operating under a condition where the endothermic and exothermic balances, external heating and external cooling are unnecessary.
[0004]
The reformer is composed of a cylindrical container that is long in one direction and filled with a catalyst that performs both the reforming reaction and the partial oxidation reaction, and each inlet of raw material and air (gas containing oxygen) at one end in the longitudinal direction. The gas outlet is opened at the other end in the longitudinal direction. According to the configuration of such a reformer, when the raw material is supplied to the raw material inlet and the air is supplied to the air inlet, the temperature distribution inside the reformer is A temperature distribution that is not uniform and has a temperature difference occurs.
[0005]
Since the gas in the reformer flows in one direction from the inlet of the reformer toward the outlet, the position in the downstream direction with the inlet of the reformer as the origin and the gas temperature at that position on the vertical axis When taken, the gas temperature rises from the inlet and takes a peak, and then gradually decreases (see FIG. 19). The fact that the gas temperature takes a peak means that almost no oxygen supplied from the air inlet remains at the position where the gas temperature takes a peak.
[0006]
In this case, there is no problem if the reformer can be operated so that the peak temperature does not greatly exceed the temperature Tm suitable for the catalyst in the reformer to work (this temperature is hereinafter referred to as “target operation temperature”). Therefore, design specifications such as the type and amount of the reformer catalyst and the external dimensions of the reformer are determined from this viewpoint.
[0007]
However, the specifications at this time are determined with respect to the reference load. Specifically, as shown in the upper part of FIG. 19, the raw material flow rate corresponding to the reference load, the air flow rate necessary for the partial oxidation reaction, and Suppose that the peak temperature has reached the desired position (reference peak temperature position zp0) (see the upper part of FIG. 19).
[0008]
However, when the load becomes larger than the reference load and the raw material is increased, the air flow rate is increased accordingly. When the increased raw material and air are supplied from each inlet, the peak temperature may exceed the target operating temperature Tm. The peak temperature position zp moves to the downstream side of the reference peak temperature position zp0 (see the one-dot chain line in the lower part of FIG. 19). The reason for the peak temperature position moving downstream is that when the load is higher than the reference load, the gas flow rate is high near the reformer inlet and the residence time is short. This is because the oxygen of the water reacts gradually while flowing downstream, and generates a peak temperature downstream.
[0009]
Thus, when the peak temperature position moves downstream from the reference peak temperature position zp0 due to an increase in load, a region where the catalyst temperature becomes low (inactive catalyst region) occurs on the upstream side of the reformer (see the lower part of FIG. 19). This reduces the conversion rate of the raw material into a hydrogen-rich reformed gas, and a large amount of unreacted raw material components are contained in the gas exiting the reformer (reforming gas containing hydrogen is generated). Inadequate).
[0010]
Therefore, the present invention calculates the required gas flow rate, which is the flow rate of the gas containing oxygen necessary for the partial oxidation reaction, based on the raw material flow rate, while estimating the peak temperature position inside the reformer, and the peak temperature position is When moving to the downstream side from the reference peak temperature position, the required gas flow rate is corrected to the decreasing side, and the gas flow rate to be supplied from the gas inlet is calculated, so that even in a region where the load becomes larger than the reference load, The purpose is to allow the reaction in the mass organ to be carried out efficiently.
[0011]
On the other hand, the above-described conventional apparatus is merely provided with a plurality of temperature sensors in the reformer to prevent the internal temperature of the reformer from becoming too high or too low, and there is a peak temperature. It does not disclose that the peak temperature position moves according to the load.
[0012]
For this reason, if an attempt is made to apply the conventional apparatus when the peak temperature position deviates from the reference peak temperature position as described above, for example, a plurality of temperature sensors are arranged at appropriate intervals in the longitudinal direction of the reformer, Estimating that the position of the temperature sensor showing the highest temperature from the temperature sensor is the peak temperature position, and if the position is downstream of the reference temperature position, the flow rate of the gas containing oxygen is corrected to decrease. That is.
[0013]
However, increasing the detection accuracy of the peak temperature position by this method only increases the number of temperature sensors, resulting in an increase in cost. However, if the number of sensors is small, it is not possible to know where the peak temperature position is.
[0014]
[Means for Solving the Problems]
The invention according to claim 1 uses a raw material inlet for supplying a raw material according to a load, a gas inlet for supplying a gas (for example, air) containing oxygen used for a partial oxidation reaction, and a gas containing oxygen and the raw material. The flow rate at the gas inlet is adjusted in a reformer consisting of a catalyst that generates a reformed gas containing hydrogen by performing a reforming reaction and a partial oxidation reaction and a gas outlet that discharges the generated reformed gas. A possible gas inlet flow rate adjusting means, a required gas flow rate calculating means for calculating a required gas flow rate Qneed, which is a gas flow rate required for the partial oxidation reaction, based on the raw material flow rate, and a peak for estimating the peak temperature position inside the reformer A temperature position estimating means, and a gas flow rate calculating means for calculating the gas flow rate Q1 by correcting the required gas flow rate Qneed to the decreasing side when the peak temperature position moves downstream from the reference peak temperature position; Gas flow Q1 that calculated of a control means for controlling the gas inlet flow rate adjusting means so as to be supplied from the gas inlet.
[0015]
In the invention according to claim 3, a gas intermediate inlet for supplying a gas containing oxygen (for example, air) to an intermediate position between the gas inlet and the gas outlet, and a gas intermediate inlet flow rate adjustment capable of adjusting a flow rate of the gas intermediate inlet And the gas intermediate inlet flow rate adjusting means is controlled so that the gas not supplied from the gas inlet in the required gas flow rate Qneed is supplied from the gas intermediate inlet.
[0016]
The invention according to claim 4 uses a raw material inlet for supplying a raw material according to a load, a gas inlet for supplying a gas (for example, air) containing oxygen used for a partial oxidation reaction, a gas containing oxygen and a raw material. The gas inlet flow rate can be adjusted in a reformer consisting of a catalyst that generates reformed gas containing hydrogen by performing reforming reaction and partial oxidation reaction, and a gas outlet that discharges the generated reformed gas. Gas inlet flow rate adjusting means, required gas flow rate calculating means for calculating the required gas flow rate Qneed, which is a gas flow rate required for the partial oxidation reaction, based on the raw material flow rate, and gas for detecting the actual catalyst temperature T1 near the gas inlet An inlet catalyst temperature detecting means, a peak temperature position estimating means for estimating a peak temperature position inside the reformer, and a target temperature Tb at which the gas inlet catalyst temperature detecting means position is calculated based on the peak temperature position. Inlet catalyst temperature detection means position target temperature calculation means, and gas flow rate calculation means for calculating the gas flow rate Q1 so that the actual catalyst temperature T1 in the vicinity of the gas inlet coincides with the target temperature Tb of the gas inlet catalyst temperature detection means position; , A selection means for selecting the smaller one of the required gas flow rate Qneed and the gas flow rate Q1, and a control means for controlling the gas inlet flow rate adjustment means so that the smaller gas flow rate (Qsel) of the selected value flows. With.
[0017]
In the invention according to claim 5, a gas intermediate inlet for supplying a gas containing oxygen (for example, air) to an intermediate position between the gas inlet and the gas outlet, and a gas intermediate inlet flow rate adjustment capable of adjusting a flow rate of the gas intermediate inlet And when the required gas flow rate Qneed is larger than the gas flow rate Q1 calculated so that the actual catalyst temperature T1 near the gas inlet matches the target temperature Tb at the position of the gas inlet catalyst temperature detection means, the difference The gas intermediate inlet flow rate adjusting means is controlled so that the flow rate Q2ris is supplied from the gas intermediate inlet.
[0018]
【The invention's effect】
As shown in FIG. 19, when the required gas flow rate Qneed corresponding to the reference load is set so that the peak temperature is at the reference peak temperature position zp0 at the reference load (see the upper part of FIG. 19), from the reference load If the load increases and the raw material is increased, the required gas flow rate Qneed is increased accordingly, and the required gas flow rate Qneed is supplied from the gas inlet, the peak temperature exceeds the target operating temperature Tm, or the peak temperature position Move downstream from the reference peak temperature position (see the dashed line in the lower part of FIG. 19 and the upper part of FIG. 20).
[0019]
Then, when the peak temperature position moves downstream from the reference peak temperature position, a region where the catalyst temperature becomes lower (inactive catalyst region) is generated on the reformer inlet side, thereby generating a reformed gas containing hydrogen. However, according to the first aspect of the present invention, when the peak temperature position moves downstream from the reference peak temperature position, the required gas flow rate Qneed is corrected to the decrease side to calculate the gas flow rate Q1. Since the calculated gas flow rate Q1 is supplied from the gas inlet, the peak temperature position is prevented from exceeding the target operating temperature Tm or moving downstream from the reference peak temperature position even in a load region larger than the reference load. it can. That is, by reducing the gas containing excess oxygen flowing into the gas inlet, the gas flow rate inside the reformer is lowered, the gas residence time is lengthened, and the oxidation reaction occurs in the catalyst upstream of the reformer. Thus, it is possible to prevent the peak temperature from exceeding the target operating temperature Tm, and to avoid the generation of an inactive catalyst region on the reformer inlet side (see the solid line in the middle stage of FIG. 20).
[0020]
When the gas flow rate Q1, which is a value obtained by reducing the required gas flow rate Qneed, is supplied from the gas inlet, the peak temperature position moves to the upstream side. This is because oxygen in the gas supplied from the gas inlet at the peak temperature portion It means that the reaction has been almost completed, and if it remains as it is, the temperature decreases as the downstream side after the peak temperature position becomes downstream. According to the third aspect of the present invention, the gas flow rate (Qneed-Q1) that could not be supplied from the gas inlet out of the required air flow rate Qneed is supplied from the gas intermediate inlet. (See the broken line in the lower part of FIG. 20).
[0021]
On the other hand, when the gas flow rate Q1 calculated so that the actual catalyst temperature T1 near the gas inlet matches the target temperature Tb at the gas inlet catalyst temperature detection means position is smaller than the required gas flow rate Qneed calculated based on the raw material flow rate. Is a state where the target operating temperature Tm is set low, or the actual catalyst temperature T1 near the gas inlet is currently close to the target operating temperature Tm. In this state, if the required gas flow rate Qneed, which has a larger value, is selected, the peak temperature becomes much higher than the target operating temperature Tm due to the supply of gas containing excess air, or the peak temperature position moves excessively downstream. However, according to the invention described in claim 4, since the gas flow rate Q1 having a smaller value is selected in this state, the peak temperature exceeds the target operating temperature Tm, or the peak temperature position is increased. Can be prevented from excessively moving downstream.
[0022]
On the other hand, when the gas flow rate Q1 is larger than the required gas flow rate Qneed, the target operating temperature Tm is set high, or the actual catalyst temperature T1 near the gas inlet currently reaches the target operating temperature Tm. It is not in a state. In this state, the required gas flow rate Qneed, which is all the gas flow rate required for the reaction, can be supplied from the gas inlet.
[0023]
In addition, when the required gas flow rate Qneed is larger than the gas flow rate Q1, if the gas flow rate Q1 is supplied from the gas inlet, the peak temperature position moves upstream, but this is supplied from the gas inlet at the peak temperature portion. This means that almost all of the oxygen in the gas has reacted, and if it remains as it is, the temperature decreases as the downstream side of the peak temperature position becomes downstream. According to the fifth aspect of the present invention, the gas flow rate (Qneed-Q1) that could not be supplied from the gas inlet out of the required gas flow rate Qneed is supplied from the gas intermediate inlet. Can be increased.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a first embodiment of the present invention. First, the basic configuration and operation of the fuel reforming system will be described.
[0025]
In the figure, water in the raw material tank 2 and methanol as fuel in the raw material tank 3 are sent from the water supply device 4 and the methanol supply device 5 into the evaporator 6 to be evaporated by heating, and a mixed vapor of water and methanol (raw material) Steam) is supplied to the reformer 8. Here, the water supply device 4 and the methanol supply device 5 are mainly composed of a feed pump and an injector.
[0026]
The target values of the water flow rate and the methanol flow rate are calculated by the controller 21 based on the power generation amount required by the fuel cell 9, and the controller 21 controls the flow rate control devices (in the supply devices 4 and 5) so that the respective target values are obtained. The injector). When the fuel cell system is applied to a vehicle, the required power generation amount is calculated based on the depression amount of the driver's accelerator pedal.
[0027]
In addition, air (a gas containing oxygen) is pumped (supplied) from the compressor 7 to the reformer 8. Since the compressor 7 supplies all the air necessary for the entire fuel cell system, the compressor discharge flow rate detected by the flow rate sensor 15 is the air flow rate supplied to the reformer 8 and the air required for the fuel cell 9. The flow rate controller 16 controls the rotational speed of the compressor 7 so as to be equal to the sum total with the flow rate. In this case, a non-interference control method is employed for the control by the flow rate controller 16 (see Japanese Patent Application Laid-Open No. 2001-338659).
[0028]
The reformer 8 generates a hydrogen-rich reformed gas by performing a reforming reaction between the mixed steam of water and methanol and oxygen in the air. The reformer 8 is operated under autothermal conditions in which heat generation due to partial oxidation reaction and heat absorption due to methanol decomposition reaction are balanced.
[0029]
The hydrogen-rich reformed gas contains a low level of carbon monoxide. This carbon monoxide poisons the electrode catalyst made of platinum or the like of the polymer electrolyte fuel cell 9 and significantly reduces its activity. Therefore, the shift reactor for removing carbon monoxide is configured integrally with the reformer 8.
[0030]
In this way, the reformed gas in which carbon monoxide has been reduced to an extremely low level and the air from the compressor 7 are sent to the fuel electrode and the air electrode of the fuel cell 9, and the fuel cell 9 Electricity is generated by electrochemically reacting oxygen and hydrogen in the reformed gas.
[0031]
In the fuel cell 9, it is difficult to use all of the hydrogen in the reformed gas. The reformed gas that has been used for power generation, leaving some hydrogen, and used for power generation, leaving some oxygen. Spent air is sent to the catalytic combustor 10 for combustion. The obtained high-temperature combustion gas is sent to the evaporator 6 and reused as energy for evaporating methanol and water.
[0032]
Such a fuel reforming system is mounted on a vehicle in this embodiment, and a load current taken out from the fuel cell 9 is supplied to a motor 19 for driving the vehicle via an inverter 18. Here, the inverter 18 and the drive motor 19 are load devices that consume power generated by the fuel cell 9.
[0033]
Thus, when the fuel reforming system is combined with a load device that changes according to the operating conditions, the flow rate of the raw material and air supplied to the reformer 8 is controlled so that the fuel cell 9 generates the electric power necessary for the load device. As shown in FIG. 2, the configuration of the reformer 8 is filled with a catalyst 8b that performs both a partial oxidation reaction and a reforming reaction in a cylindrical container 8a that is long in one direction. The raw material inlet 8c and the air inlet 8d are opened at one end in the longitudinal direction (left end in the figure), and the gas outlet 8e is opened at the other end in the longitudinal direction (right end in the figure). According to the configuration, when the raw material vapor is supplied to the raw material inlet 8c and the air is supplied to the air inlet 8d, the temperature distribution inside the reformer 8 is not uniform and a temperature distribution with a temperature difference is generated.
[0034]
Since the gas in the reformer 8 flows in one direction (rightward in the figure) from the raw material inlet 8c toward the gas outlet 8e, the gas at that position is defined with the raw material inlet 8c as the origin and the downstream position on the horizontal axis. When the temperature is taken on the vertical axis, the gas temperature rises from the raw material inlet 8c and takes a peak, and then gradually decreases. The fact that the gas temperature takes a peak means that almost no oxygen supplied from the air inlet 8d remains at that position.
[0035]
In this case, there is no problem as long as the peak temperature does not greatly exceed the target operating temperature Tm. From this viewpoint, design specifications such as the type and amount of the catalyst 8b and the external dimensions of the reformer 8 are determined.
[0036]
However, the specifications at this time are determined with respect to the reference load. Specifically, as shown in the upper part of FIG. 19, the raw material flow rate corresponding to the reference load and the air flow rate necessary for the partial oxidation reaction ( This air flow rate is hereinafter referred to as “required air flow rate.”) When Qneed is supplied, it is assumed that the peak temperature has reached the desired position (reference peak temperature position zp0) (see the upper part of FIG. 19).
[0037]
However, when the load becomes larger than the reference load and the raw material is increased, the required air flow rate Qneed is increased accordingly, and when the increased raw material and air are supplied from the respective inlets 8c and 8d, the peak temperature becomes the target operation. The temperature exceeds Tm, or the peak temperature position moves downstream from the reference peak temperature position (see the dashed line in the lower part of FIG. 19).
[0038]
In the present invention, in such a fuel reforming system combined with a load device that varies depending on operating conditions, the catalyst temperature in the vicinity of the air inlet 8d (this catalyst temperature is hereinafter referred to as "inlet catalyst temperature") is actually detected. A temperature sensor (gas inlet catalyst temperature detecting means) 22 is provided at a position downstream of the raw material inlet 8c by a predetermined distance, and the peak temperature position inside the reformer 8 is estimated based on the gas flow rate inside the reformer 8. Then, the target temperature Tb at the temperature sensor 22 position is calculated based on the peak temperature position, and the air is set so that the actual inlet catalyst temperature T1 detected by the temperature sensor 22 matches the target temperature Tb at the temperature sensor 22 position. An air flow rate supplied from the inlet 8d (this flow rate is hereinafter referred to as “air inlet flow rate”) Q1 is calculated, and a value of the air inlet flow rate Q1 and the required air flow rate Qneed is calculated. The smaller one is selected, and the opening degree of the flow control valve 12 provided in the air supply passage 11 from the compressor 7 to the reformer 8 is controlled so that the smaller air flow (Qsel) of the selected value flows. .
[0039]
In addition, pressure sensors 25 and 26 are provided on the inlet side and the outlet side of the reformer 8 in order to estimate the gas flow rate in the reformer 8.
[0040]
On the other hand, the required air flow rate Qneed is calculated based on the raw material flow rate. However, when the air inlet flow rate Q1 is smaller than the required air flow rate Qneed, only the air inlet flow rate Q1 is supplied from the air inlet 8d and the remaining air flow rate Q1ed is left. Since the air component of Qneed-Q1 is not supplied, an air intermediate inlet 8f is provided downstream of the air inlet 8d, and the remaining air is supplied from the air intermediate inlet 8f.
[0041]
In this case, the temperature of the catalyst near the air intermediate inlet 8f rises due to the influence of the air supply from the air intermediate inlet 8f, and further rises under the influence of the air supplied from the air inlet 8d. That is, the temperature of the inlet side catalyst rises due to the oxidation reaction by the air supplied from the air inlet 8d, and the temperature rise of the inlet side catalyst raises the downstream side catalyst temperature. If air is also introduced from the air intermediate inlet 8f in such a state, the catalyst temperature in the vicinity of the intermediate air inlet may exceed the upper limit temperature (hereinafter simply referred to as “upper limit temperature”) Tmax of the catalyst 8b.
[0042]
Therefore, a temperature sensor (gas intermediate inlet catalyst temperature detecting means) 23 that actually detects the catalyst temperature near the air intermediate inlet 8f, a flow sensor (gas inlet flow rate detecting means) 27 that actually detects the air inlet flow rate, and air A flow sensor (gas intermediate inlet flow rate detecting means) 28 for actually detecting the air flow rate supplied from the intermediate inlet 8f (hereinafter referred to as “air intermediate flow rate”) is provided, and the actual air inlet flow rate Qsen1 and The catalyst temperature at the position of the temperature sensor 23 ahead of a predetermined period when the actual air intermediate flow rate Qsen2 increases stepwise is estimated, and the estimated value T2sui of the catalyst temperature at the position of the temperature sensor 23 ahead of the predetermined period exceeds the upper limit temperature Tmax. When exceeding, the air intermediate flow rate is corrected to the decreasing side so as not to exceed, and the air supply passage 1 to the reformer 8 is flowed so that the corrected intermediate air flow rate flows. Controlling the opening of the flow control valve 14 provided in the branch supply path 13 from.
[0043]
JP-A-2001-19403 discloses a device in which air is distributed and supplied from two air inlets 8d and 8f. It is not disclosed that the temperature of the catalyst rises due to the influence of the air supplied from the air inlet 8d in addition to the rise of the temperature under the influence of the air supply from the air intermediate inlet 8f.
[0044]
Next, such control executed by the controller 21 will be described in detail based on the following flowchart.
[0045]
FIG. 3 is for explaining the calculation of the target air flow rates of the two flow control valves 12 and 14 and is executed at regular intervals (for example, every 10 msec).
[0046]
In step 1, the gas flow velocity ν in the reformer 8 is estimated. This estimation will be described with reference to FIG. In FIG. 4, the inlet pressure P1 [Pa] and outlet pressure P2 [Pa] of the reformer 8 detected by the pressure sensors 25 and 26 in step 11 are read, and in step 12, the pressure difference ΔP [Pa] is calculated.
ΔP = P1-P2 (1)
The gas flow velocity ν [m / s] in the reformer 8 is calculated using this pressure difference ΔP,
ν = ΔP × D × D / (32 × μ × L) (2)
Where D: reformer diameter [m],
L: reformer length [m],
μ: viscosity [Pa · s],
It is calculated by the following formula.
[0047]
Here, the expression (2) is a Hagen-Poiseuille law that is a law of a fluid flow flowing in a laminar flow in a cylinder.
[0048]
When the estimation of the gas flow velocity ν in the reformer 8 is thus completed, the flow returns to FIG. 3 and the required air flow rate Qneed is calculated in step 2. This calculation will be described with reference to FIG. In FIG. 5, the raw material flow rate Qgen [NL / min] supplied to the reformer 8 is read in step 21, and then the required air flow rate Qneed [NL / min] is read in step 22.
Qneed = Qgen × coefficient / 0.21 (3)
It is calculated by the following formula.
[0049]
Here, the Qgen × coefficient which is a numerator on the right side of the equation (3) is an oxygen flow rate required for the partial oxidation reaction in the reformer 8, and thus the coefficient is an arbitrary value representing the partial oxidation rate in the reformer. A constant (for example, 0.3). 0.21 is the oxygen ratio in the air, and the air flow rate can be obtained by dividing the oxygen flow rate by 0.21.
[0050]
The raw material flow rate Qgen is a value obtained by combining the water flow rate and the methanol flow rate. That is, since the water flow rate and the methanol flow rate are controlled by the duty value given to the injector (the flow rate increases as the duty value increases), a table containing the contents of FIGS. 6 and 7 is searched from these duty values. Thus, the water flow rate [NL / min] and the methanol flow rate [NL / min] can be obtained, and the raw material flow rate Qgen can be obtained by adding both. In addition, “N” attached to L (liter) which is a unit of flow rate represents a value in a standard state (0 ° C., one atmospheric pressure).
[0051]
When the calculation of the required air flow rate Qneed is completed in this way, the process returns to FIG. 3, and in step 3, the peak temperature position is estimated. When the reformer 8 has the configuration shown in FIG. 2, a non-uniform temperature distribution occurs inside the reformer 8, and the maximum temperature among these is the peak temperature. The peak temperature position is a position where a peak temperature is generated between the raw material inlet 8c and the gas outlet 8e of the reformer 8. Here, the peak temperature position is calculated by searching a table having the contents shown in FIG. 8 from the gas flow velocity ν in the reformer.
[0052]
The characteristics shown in FIG. 8 are created based on experimental data performed in advance. In FIG. 8, the peak temperature position on the vertical axis is the origin at the raw material inlet 8c (reformer inlet), and the peak temperature position moves in the downstream direction of the reformer 8 as the reformer gas flow velocity ν increases. Yes. This is due to the following reason. For example, when the gas flow velocity v in the reformer is high, there may be a high load when the raw material and air supplied to the reformer 8 are large. Since the time during which the gas stays in the reformer 8 at this high load is shortened, the reaction is performed downstream of the reformer 8, and the reaction rate of the reforming reaction compared to the partial oxidation reaction. Because of the slowness of the heat, the balance between the heat generated by the partial oxidation reaction and the endothermic reaction due to the reforming reaction is lost, and the endotherm cannot catch up. For this reason, the peak temperature position moves in the downstream direction of the reformer 8 as the reformer gas flow velocity ν increases.
[0053]
In steps 4 and 5, a target temperature Tb at the position of the temperature sensor 22 mounted near the inlet of the reformer 8, specifically, immediately downstream of the air inlet 8d is calculated.
[0054]
First, in step 4, a function representing a profile indicating a temperature distribution state inside the reformer is created so that the peak temperature position becomes the target operating temperature Tm as follows. That is, the profile indicating the temperature distribution state inside the reformer is an upwardly convex curve that reaches the target operating temperature Tm at the peak temperature position (a is the peak temperature position in the figure) as shown in FIG. Since this is conceivable (see the solid line in the middle stage), this profile is approximated by a logistic waveform.
[0055]
Logistic waveforms are typically
y = k / (1 + c × EXPF (t)) (4)
Where k and c are constants,
f (t): function of time,
("EXP" is an index and "f (t)" is a value attached to the right shoulder of the index). Here, instead of time t, a position with the raw material inlet 8c as the origin It is a function of z. That is, as a function representing a logistic waveform,
y (z) = K2 / (1 + EXP (−K1 × z) (5a)
Where y (z): gas temperature at position z,
z: position,
K1, K2: constants,
Is used.
[0056]
Here, since the function of equation (5a) is determined to be one when two constants K1 and K2 are determined, these constants K1 and K2 are determined so as to satisfy the following conditions.
[0057]
Condition 1: y = Tm when z = a.
[0058]
Condition 2: When z = 0, y = average value Tav of the raw material temperature Tf and the air temperature Ta.
[0059]
The target operating temperature Tm is 400 ° C., for example. The raw material temperature Tf is detected by the temperature sensor 29, and the air temperature Ta is detected by the temperature sensor 30 (see FIG. 1).
[0060]
The following other modes can be considered for the function representing the logistic waveform.
[0061]
(1) Other aspects 1:
y (z) = (A1−A2) / (1 + EXP (z−z0) / d) + A2 (5b)
Where A2: target temperature
d: any value,
Here, A1 and z0 are determined so as to satisfy the above conditions 1 and 2.
[0062]
(2) Other aspect 2:
y (z) = A * EXP (-EXP (-k * (z-z0))) (5c)
Where k is an arbitrary value,
Here, A and z0 are determined so as to satisfy the above conditions 1 and 2.
[0063]
(3) Other aspect 3:
y (z) = A / (1 + EXP (−k (z−z0)) (5d)
Where k is an arbitrary value,
Here, A and z0 are determined so as to satisfy the above conditions 1 and 2.
[0064]
(4) Other aspect 4:
y (z) = A / (1 + B × EXP (−k × z)) (5e)
Where k is an arbitrary value,
Here, A and B are determined so as to satisfy the above conditions 1 and 2.
[0065]
In step 5, the catalyst temperature corresponding to the temperature sensor 22 position, which is the temperature on the profile indicating the temperature distribution state created in this way, is obtained as the target temperature Tb of the temperature sensor 22 position. That is, since the position of the temperature sensor 22 on the reformer 8 is determined in advance, if this position is b, the value of y (b) obtained by substituting this b into the above equation (5a) is the target temperature. Tb (see the middle of FIG. 9).
[0066]
In addition, since what was used for experiment in FIG. 9 is shown, the temperature sensor 22 is attached to the position where a temperature peak comes when the load is 50%. Since the temperature does not rise near the raw material inlet 8c, the raw material inlet 8c is not suitable as the position of the temperature sensor 22.
[0067]
In step 6, the air inlet flow rate Q1 is calculated so that the actual inlet catalyst temperature T1 detected by the temperature sensor 22 matches the target temperature Tb at the position of the temperature sensor 22. This calculation will be described with reference to FIG.
[0068]
In FIG. 10, the actual inlet catalyst temperature T1 detected by the temperature sensor 22 in step 31 is read, and in step 32, the deviation e from the target temperature Tb at the position of the temperature sensor 22 is calculated.
e = Tb−T1 (6)
Using this deviation e, in step 33, the feedback amount Qfb [NL / min] of the air flow rate per control cycle is calculated as follows:

Where e (previous): previous deviation,
e (previous times): deviations from previous times,
T / Ti: integral coefficient (integral gain),
TD / T: differential coefficient (differential gain),
T: Control cycle,
K3: constant,
It is calculated by the following formula. This is a well-known equation for proportional integral differential operation.
[0069]
In step 34, using this feedback amount Qfb, an air inlet flow rate Q1 [NL / min] for making the actual inlet catalyst temperature T1 coincide with the target temperature Tb,
Q1 = Q1 (previous) + Qfb (8)
However, Q1 (previous): previous value of Q1,
It is calculated by the following formula. The initial value of Q1 is zero.
[0070]
For example, when the actual inlet catalyst temperature T1 is lower than the target temperature Tb, the feedback amount Qfb is positive and the air inlet flow rate Q1 is increased. Conversely, when the actual inlet catalyst temperature T1 is higher than the target temperature Tb, the feedback amount Qfb is negative. The air inlet flow rate Q1 is reduced.
[0071]
When the calculation of the air inlet flow rate Q1 for making T1 coincide with Tb in this way is completed, the flow returns to FIG. 3, and in step 7, the smaller value is selected by comparing Q1 and Qneed. Let the flow rate be the selected air flow rate Qsel.
[0072]
For example, the case where Q1 is smaller than Qneed is a state where the target operating temperature Tm is set low or the actual inlet catalyst temperature T1 is currently close to Tm. If Qneed larger than Q1 is given in this state, the peak temperature becomes higher than Tm due to excessive air supply, and the peak temperature moves excessively downstream. In the present embodiment, such a situation can be prevented by selecting Q1 having a smaller value.
[0073]
On the other hand, the case where Q1 is larger than Qneed is a state where Tm is set high or the actual inlet catalyst temperature T1 does not currently reach Tm. In this state, by selecting Qneed having a smaller value, Qneed that is all of the air flow rate necessary for the reaction can be supplied from the air inlet 8d.
[0074]
In step 8, the air inlet flow rate is reduced and corrected according to the peak temperature position for the selected air flow rate Qsel. That is, by searching a table having the contents shown in FIG. 11 from the peak temperature position, a reduction correction value Qgen of the air inlet flow rate is calculated, and a value obtained by subtracting the reduction correction value Qgen from the selected air flow rate Qsel is obtained as a target air inlet. As the flow rate Qm1, that is
Qm1 = Qsel-Qgen (9)
The target air inlet flow rate Qm1 is calculated by the following formula.
[0075]
The decrease correction value Qgen is a decrease in the air inlet flow rate for bringing the peak temperature position to the position of the temperature sensor 22 and increases as the peak temperature position becomes downstream of the reformer 8 as shown in FIG. The characteristics shown in FIG. 11 are also created from experimental data obtained in advance.
[0076]
The reason why the peak temperature position moved in the downstream direction of the reformer 8 is moved to the temperature sensor 22 position by correcting the decrease in the air inlet flow rate is that when the peak temperature position matches the temperature sensor 22 position, the reforming is performed. This is because the reformer 8 is designed to optimize the efficiency.
[0077]
In FIG. 11, Qgen = 0 in the region on the left side of b which is the position of the temperature sensor 22 is that when the required air flow rate Qneed is smaller than the air inlet flow rate Q1, the peak temperature position is before the temperature sensor 22 position. This is because the peak temperature position cannot be brought to the position of the temperature sensor 22 if the positive decrease correction value Qgen is given at this time as well.
[0078]
In step 9, the difference between the required air flow rate Qneed and the target air inlet flow rate Qm1 is set as an ideal value Q2ris of the air intermediate flow rate, that is,
Q2ris = Qneed−Qm1 (10)
The air intermediate flow rate ideal value Q2ris is calculated by the following formula.
[0079]
However, if the difference in equation (10) is a negative value, it is ignored and Q2ris = 0.
[0080]
The ideal air intermediate flow rate Q2ris calculated in this manner is an air flow rate that cannot be supplied from the air inlet 8d in the required air flow rate Qneed.
[0081]
In step 10, the catalyst temperature at the position of the temperature sensor 23 is estimated. This estimation will be described with reference to FIG.
[0082]
In FIG. 12, in step 41, the actual air flow rates Qsen1 and Qsen2 from the flow rate sensors 27 and 28 and the actual catalyst temperature T2 at the position of the temperature sensor 23 are read.
[0083]
Steps 42 to 44 calculate a temperature change dT1 that the change in the air inlet flow rate gives to the catalyst temperature at the temperature sensor 23 position. Steps 45 to 47 are the temperatures that the change in the air intermediate flow rate gives to the catalyst temperature at the temperature sensor 23 position. This is a part for calculating the change dT2. It is necessary to consider dT1 because the air supplied from the air inlet 8d activates the oxidation reaction in the catalyst near the air inlet 8d and the temperature rises, and this temperature rise affects the catalyst temperature at the temperature sensor 23 position. It is to do. Similarly, it is necessary to consider dT2 when the air intermediate inlet 8f is provided on the upstream side of the position of the temperature sensor 23 by the catalyst near the air intermediate inlet by the air supplied from the air intermediate inlet 8f. This is because the oxidation reaction becomes active and the temperature rises, and this temperature rise affects the catalyst temperature at the position of the temperature sensor 23.
[0084]
This will be further described with reference to FIG. 13. When the air inlet flow rate increases stepwise at the timing t1 (see the uppermost stage), the catalyst temperature at the position of the temperature sensor 23 corresponds to this change after the step increase. It is considered that the temperature (see the one-dot chain line in the second stage in FIG. 13) follows with a first order delay (see the solid line in the second stage in FIG. 13). At this time, if a transfer function G1 (s) (s is a Laplace operator) well known in the control theory is used, the position of the temperature sensor 23 ahead of a predetermined period starts from the timing at which the air inlet flow rate increases stepwise. It is possible to estimate changes in catalyst temperature in time series. This is expressed as follows.
[0085]
dT1 = G1 (s) × dQ1 (11a)
Where G1 (s): transfer function,
That is, time series data up to a predetermined period ahead of the catalyst temperature change dT1 at the temperature sensor 23 position when the air inlet flow rate is changed by dQ1 can be obtained using dQ1 and the transfer function G1 (s). (See the arrow in the second row in FIG. 13).
[0086]
Next, when the air intermediate flow rate increases stepwise at the timing of t2 (see the third stage in FIG. 13), the catalyst temperature at the temperature sensor 23 position corresponds to the air flow rate after the step increase corresponding to this change. Therefore, the estimation method is performed in the same manner as described above, because it is considered that the temperature follows the first-order delay (see the solid line in the fourth stage in FIG. 13). That is, if the transfer function G2 (s) is used, the change in the catalyst temperature at the temperature sensor 23 position ahead of a predetermined period from the timing at which the air intermediate flow rate is increased by dQ2 as a starting point is expressed as follows: Become.
[0087]
dT2 = G2 (s) × dQ2 (12a)
Where G2 (s): transfer function,
Therefore, time series data up to a predetermined period ahead of the catalyst temperature change dT2 at the position of the temperature sensor 23 when the air intermediate flow rate changes by dQ2 can be obtained using dQ2 and the transfer function G2 (s). (See the arrow in the fourth row in FIG. 13).
[0088]
Here, the transfer functions G1 (s) and G2 (s) are obtained in advance by performing a step response experiment. However, since the transfer function G2 (s) is different from the transfer function G1 (s) even if the actual catalyst temperature at the position of the temperature sensor 23 is the same, the transfer function G2 (s) is created separately.
[0089]
Returning to FIG. 12, in step 42, the actual change amount dQ1 per control cycle of the air inlet flow rate is calculated.
dQ1 = Qsen1-Qsen1 (previous) (13)
However, Qsen1 (previous): previous value of Qsen1,
It is calculated by the following formula. In the present embodiment, the control cycle of the subroutine shown in FIG. 12 is the same as the control cycle of the main routine shown in FIG. 3, but the control cycle of FIG. 12 may be determined separately.
[0090]
In step 43, a transfer function G1 (s) corresponding to the actual catalyst temperature T2 at the position of the temperature sensor 23 is selected.
[0091]
A plurality of transfer functions G1 (s) are created according to the catalyst temperature at the position of the temperature sensor 23. A plurality of transfer functions are prepared and the transfer function corresponding to the actual catalyst temperature T2 at the position of the temperature sensor 23 is selected when the catalyst temperature at the position of the temperature sensor 23 is high. This is because there is a characteristic that the change in the catalyst temperature at the 23rd position becomes large, and this characteristic is given (see FIG. 14). When the load is high, the air inlet flow rate is also high, so the temperature change increases as the load increases.
[0092]
In step 44, using the selected transfer function G1 (s) and dQ1, when the air inlet flow rate changes by dQ1 per control cycle, the time until the predetermined time ahead of the catalyst temperature change dT1 at the temperature sensor 23 position. Series data is calculated.
[0093]
In step 45, the actual change dQ2 per control cycle of the air intermediate flow rate is calculated.
dQ2 = Qsen2-Qsen2 (previous) ... (14)
However, Qsen2 (previous): the previous value of Qsen2,
It is calculated by the following formula.
[0094]
In step 46, a transfer function G2 (s) corresponding to the actual catalyst temperature T2 at the temperature sensor 23 position is selected, and in step 47, the intermediate air flow rate is controlled using the selected transfer function G2 (s) and dQ2. Time series data up to a predetermined period ahead of the catalyst temperature change dT2 at the position of the temperature sensor 23 when changing by dQ2 per cycle is calculated.
[0095]
In step 48, the time-series data of the catalyst temperature change dT1 at the temperature sensor 23 position and the time-series data of the catalyst temperature change dT2 at the other temperature sensor 23 position are converted into the actual catalyst temperature T2 at the temperature sensor 23 position. By adding, that is, time-series data of the estimated catalyst temperature T2sui at the position of the temperature sensor 23,

It is calculated by the following formula.
[0096]
In this way, when the air inlet flow rate and the air intermediate flow rate increase step by step, the time series data of the estimated catalyst temperature value at the temperature sensor 23 position up to a predetermined period ahead can be obtained starting from each timing at which the step increase. it can.
[0097]
Note that the time series data of dT1 and dT2 in the equation (15) takes a positive value or a negative value. When the dQ1 and dQ2 changes in the inlet air flow rate and the intermediate air flow rate are positive, the time series data of dT1 and dT2 have a positive value. Is a negative value.
[0098]
Instead of preparing a plurality of transfer functions of G1 (s) and G2 (s), each transfer function is one for the reference catalyst temperature at the position of the temperature sensor 23, and the actual transfer temperature T2 at the position of the temperature sensor 23 is set. A temperature correction value may be calculated based on this, and time series data of dT1 and dT2 may be calculated based on these. This method is described as follows. The time series data of dT1 and the time series data of dT2 in the equation (15) are obtained as follows. That is, when the catalyst temperature at the position of the temperature sensor 23 is the reference catalyst temperature, the time series until the predetermined period ahead of the catalyst temperature change dT1 at the position of the temperature sensor 23 when the air inlet flow rate changes by dQ1 per control cycle. Data is calculated using dQ1 and a transfer function G10 (s) with respect to the reference catalyst temperature at the 23rd position of the temperature sensor, and a value obtained by adding the temperature correction value 1 to each of these time series data is newly obtained as time series data of dT1. To do.
[0099]
dT1 time series data
= Time series data of dT1 at the time of the reference catalyst temperature + temperature correction value 1 (16) Similarly, when the catalyst temperature at the position of the temperature sensor 23 is the reference catalyst temperature, the intermediate air flow rate has changed by dQ2 per control cycle. Time series data up to a predetermined period ahead of the catalyst temperature change dT2 at the position of the temperature sensor 23 is calculated using dQ2 and a transfer function G20 (s) with respect to the reference catalyst temperature. The value obtained by adding the correction value 2 is again used as time series data of dT2.
[0100]

Here, the temperature correction values 1 and 2 in the equations (16) and (17) are values that increase as the actual catalyst temperature T2 at the position of the temperature sensor 23 becomes higher than the reference catalyst temperature, as shown in FIG.
[0101]
When the calculation of the estimated catalyst temperature T2sui at the position of the temperature sensor 23 is completed in this way, the process returns to FIG. 3, and in step 11, based on this T2sui, the maximum value in the time-series data up to a predetermined period ahead of T2sui is obtained. The target air intermediate flow rate Tm2 is calculated so as not to exceed the upper limit temperature Tmax. This calculation will be described with reference to FIG.
[0102]
In FIG. 16, in step 51, it is checked whether or not the maximum value of the time series data of the estimated catalyst temperature T2sui at the position of the temperature sensor 23 is equal to or lower than the upper limit temperature Tmax.
[0103]
Here, the upper limit temperature Tmax is set to a value slightly higher than the target operating temperature Tm (for example, 400 ° C.). For simplicity, it may be equal to Tm.
[0104]
If the maximum value of the time series data of T2sui is equal to or lower than the upper limit value Tmax, the process proceeds to step 52, and the above air intermediate flow rate ideal value Q2ris is set as the target air intermediate flow rate Qm2.
[0105]
On the other hand, when the maximum value of the time series data of T2sui exceeds Tmax, for example, as shown in FIG. 17, when the flow rate of dQ1 increases in Q1 (where Q1 <Qneed), the time of T2sui This is a case where the temporally late side of the series data exceeds Tmax (see the solid line in the lower part of FIG. 17). At this time, if the air intermediate flow rate ideal value Q2ris is supplied from the air intermediate inlet 8f as it is, it is too large, and it is necessary to set the flow rate smaller than Q2ris. For this reason, the process proceeds from step 51 to step 53 to read the actual catalyst temperature T2 at the position of the temperature sensor 23, and from this temperature T2, in step 54, search the table having the contents shown in FIG. The correction value dQgen is calculated.
[0106]
As shown in FIG. 18, the decrease side correction value dQgen increases with a negative value as the actual catalyst temperature T2 at the temperature sensor 23 position increases. This is because the change in the catalyst temperature at the position of the temperature sensor 23 with respect to the unit change in the intermediate air flow rate increases when T2 is high, so that the calculation error is reduced in consideration of this.
[0107]
In step 55, a value obtained by adding the negative amount dQgen, which is a negative value, to the air intermediate flow rate ideal value Q2ris is again set as an air intermediate flow rate ideal value Q2ris'.
Q2ris' = Q2ris + dQgen (18)
It is calculated by the following formula.
[0108]
Here, Q2ris ′ is a smaller value than Q2ris.
[0109]
In step 56, the transfer function G2 ′ (s) when the air intermediate flow rate is increased by | dQgen | from the state of Q2ris ′ is selected, and in step 57, the transfer function G2 ′ (s) and | dQgen | are used. Thus, time-series data is calculated up to a predetermined period ahead of the catalyst temperature change dT2 at the position of the temperature sensor 23 when the air intermediate flow rate is increased by | dQgen | from the state of Q2ris ′.
[0110]
In step 58, the time series data of the catalyst temperature estimated value T2sui at the temperature sensor 23 position is obtained by adding the time series data of dT2 to the actual catalyst temperature T2 at the temperature sensor 23 position, that is,
Time series data of T2sui = T2 + dT2 time series data (19)
It is calculated by the following formula.
[0111]
In step 59, it is checked whether or not the maximum value of the time series data of the estimated catalyst temperature T2sui at the position of the temperature sensor 23 calculated in this way is equal to or lower than the upper limit temperature Tmax of the catalyst.
[0112]
Here, the case where the maximum value of the time series data of T2sui does not exceed the upper limit temperature Tmax is due to the decrease in | dQgen | of the air intermediate flow rate (the broken line in the uppermost line in FIG. 17), This is a case where the time series data of T2sui falls below the maximum value Tmax as shown in FIG. In this case, the process proceeds to step 60, and Q2ris ′, which is a value obtained by decreasing the amount by | dQgen | from Q2 separation s, is calculated as the target air intermediate flow rate Qm2.
[0113]
On the other hand, if the maximum value of the time-series data of T2sui exceeds the upper limit temperature Tmax, the process proceeds from step 59 to step 61, where the decrease side correction value dQgen is increased by a constant value dQ and the operations of steps 55 to 59 are repeated. . When the maximum value of the time series data of T2sui eventually becomes equal to or lower than the upper limit temperature Tmax due to this repetition, the operation of step 60 is executed, and the process of FIG.
[0114]
Note that the repetition of the operations in steps 55 to 59 and 61 ends in an instant because the control speed is fast.
[0115]
When the calculation of the target air intermediate flow rate Qm2 is completed in this way, the processing returns to FIG. 3, and in step 12, the target air intermediate flow rate Qm2 and the target air inlet flow rate Qm1 are moved to the output register.
[0116]
In a flow (not shown), the opening degree of the flow control valve 12 is controlled so that the air having the target air inlet flow rate Qm1 calculated in this way is supplied from the air inlet 8d, and the air having the target air intermediate flow rate Qm2 is air intermediate. The opening degree of the flow control valve 14 is controlled so as to be supplied from the inlet 8f.
[0117]
Instead of these flow control valves 12 and 14, a flow control integrated control valve for gas fluid may be used. The control valve has a built-in flow sensor, and when the calculated target air flows Qm1 and Qm2 are given as inputs, the valve opening is driven so that this value matches the actual flow detected by the built-in flow sensor. Is done.
[0118]
Here, the effect of this embodiment is demonstrated.
[0119]
The required air flow rate calculated based on the raw material flow rate is the air inlet flow rate Q1 calculated so that the actual catalyst temperature T1 at the temperature sensor 22 (gas inlet catalyst temperature detection means) position matches the target temperature Tb at the temperature sensor 22 position. The case where it is smaller than Qneed is a state where the target operating temperature Tm is set low, or the actual catalyst temperature T1 at the air inlet 8d is currently close to the target operating temperature Tm. In this state, if the required air flow rate Qneed with a larger value is selected, the peak temperature greatly exceeds the target operating temperature Tm due to excessive air supply, or the peak temperature position moves excessively downstream. However, according to the present embodiment (the invention described in claim 4), since the air inlet flow rate Q1 having a smaller value in this state is selected, the peak temperature becomes higher than the target operating temperature Tm, It can suppress that a peak temperature position moves excessively downstream.
[0120]
On the other hand, when the air inlet flow rate Q1 is larger than the required air flow rate Qneed, the target operating temperature Tm is set to be high, or the actual catalyst temperature T1 at the air inlet 8d currently reaches the target operating temperature Tm. It is not in a state. In this state, the required air flow rate Qneed, which is all the air flow rate necessary for the reaction, can be supplied from the air inlet 8d.
[0121]
Further, when the required gas flow rate Qneed is larger than the air inlet flow rate Q1, if the air inlet flow rate Q1 is supplied from the air inlet 8d, the peak temperature position moves to the upstream side. This means that almost all of the oxygen in the supplied air has reacted, and if this is the case, the temperature decreases as the downstream side becomes downstream from the peak temperature position. According to the present embodiment (the invention described in claim 5), the air flow rate (Qneed-Q1) that could not be supplied from the air inlet 8d out of the required air flow rate Qneed is supplied from the air intermediate inlet 8f. The catalyst temperature in the vicinity of the intermediate inlet 8f can be increased.
[0122]
According to the present embodiment (invention of claim 6), even when the selected air flow rate Qsel is corrected to decrease based on the peak temperature position, the peak temperature position is prevented from excessively moving in the downstream direction of the reformer 8. It is possible to increase the temperature of the portion where the temperature is low on the upstream side.
[0123]
According to this embodiment (invention of claim 7), as the peak temperature position moves in the downstream direction of the reformer, the decrease correction value Qgen of the selected air flow rate is increased. It can be brought to almost the same position.
[0124]
According to this embodiment (invention of claim 8), in the temperature distribution profile generated so that the peak temperature position becomes the target operating temperature Tm, the temperature corresponding to the temperature sensor 22 position is set to the temperature sensor 22 position. Since the target temperature Tb is calculated, the peak temperature position can be prevented from exceeding the target operating temperature Tm even if the peak temperature position moves downstream.
[0125]
According to the present embodiment (the invention described in claim 10), since the peak temperature is estimated to move to the downstream side of the reformer as the reformer gas flow velocity ν increases, the reformer gas flow velocity differs. Even in this case, the peak temperature position can be given with high accuracy.
[0126]
When the air inlet flow rate increases stepwise, the catalyst temperature at the position of the temperature sensor 23 (near the gas intermediate inlet) rises due to this influence. Without considering this temperature rise, when the required air flow rate Qneed is larger than the air flow rate Q1 calculated so that the actual catalyst temperature T1 of the air inlet 8d matches the target temperature Tb at the position of the temperature sensor 23, If air of the difference flow rate Q2ris is supplied as it is from the air intermediate inlet 8f, the catalyst temperature at the position of the temperature sensor 23 may exceed the upper limit temperature Tmax. According to this embodiment (the invention described in claim 12), the catalyst temperature at the position of the temperature sensor 23 including this temperature rise is estimated, and the estimated value T2sui of the catalyst temperature at the position of the temperature sensor 23 ahead of that predetermined period. Since the air intermediate flow rate is corrected so as not to exceed when the air temperature exceeds the upper limit temperature Tmax, the catalyst temperature at the position of the temperature sensor 23 is prevented from exceeding the upper limit temperature Tmax even when the air inlet flow rate increases stepwise. it can.
[0127]
Similarly, when the air intermediate flow rate increases by a step, the catalyst temperature at the position of the temperature sensor 23 rises due to this influence. Without considering this temperature rise, when the required air flow rate Qneed is larger than the air inlet flow rate Q1 calculated so that the actual catalyst temperature T1 of the air inlet 8d matches the target temperature Tb at the position of the temperature sensor 22, If air of the difference flow rate Q2ris is supplied as it is from the air intermediate inlet 8f, the catalyst temperature at the position of the temperature sensor 23 may exceed the upper limit temperature Tmax. According to this embodiment (the invention described in claim 13), the catalyst temperature at the position of the temperature sensor 23 including this temperature rise is estimated, and the estimated value T2sui of the catalyst temperature at the position of the temperature sensor 23 ahead of the predetermined period. Since the air intermediate flow rate is corrected to the decreasing side so that it does not exceed when the temperature exceeds the upper limit temperature Tmax, the catalyst temperature at the temperature sensor 23 position is prevented from exceeding the upper limit temperature Tmax even when the air intermediate flow rate increases stepwise. it can.
[0128]
Since the catalyst temperature change at the position of the temperature sensor 23 with respect to the unit flow rate change of the air supplied from the air inlet 8d becomes larger as the load becomes higher, if this characteristic is not taken into consideration, the position of the temperature sensor 23 ahead of a predetermined period Excessive or deficient in the air side flow rate reduction side correction value dQgen used to estimate the catalyst temperature of the air. On the other hand, according to the present embodiment (the invention described in claim 15), when the estimated value T2sui of the catalyst temperature at the position of the temperature sensor 23 ahead of a predetermined period exceeds the upper limit temperature Tmax, As the temperature rise is larger, the air side flow rate reduction side correction value dQgen is increased, so that the air intermediate flow rate reduction side correction value dQgen can be accurately given regardless of the load.
[0129]
In addition to the embodiments described above, the following other embodiments are possible.
[0130]
Other Embodiment 1: On the premise that the reformer is shown in FIG. 2, a required air flow rate calculating means for calculating a required air flow rate Qneed that is an air flow rate required for the partial oxidation reaction based on the raw material flow rate; Peak temperature position estimating means for estimating the peak temperature position inside the reformer, and when the peak temperature position moves downstream from the reference peak temperature position, the required air flow rate Qneed is corrected to the decrease side, and the air inlet flow rate is corrected. Air inlet flow rate calculating means for calculating Q1 and control means for controlling the opening degree of the flow control valve 12 so that the calculated air inlet flow rate Q1 is supplied from the air inlet.
[0131]
The operation and effect of the other embodiment 1 (the invention according to claim 1) will be described below.
[0132]
As shown in FIG. 19, when the required air flow rate Qneed corresponding to the reference load is set so that the peak temperature is at the reference peak temperature position zp0 at the reference load (see the upper part of FIG. 19), from the reference load If the load increases and the raw material is increased, the required air flow rate Qneed is increased accordingly, and the required air flow rate Qneed is supplied from the air inlet 8d, the peak temperature exceeds the target operating temperature Tm, or the peak temperature The position moves downstream from the reference peak temperature position (see the dashed line in the lower part of FIG. 19).
[0133]
Then, when the peak temperature position moves downstream from the reference peak temperature position, a region where the catalyst temperature becomes lower (inactive catalyst region) is generated on the reformer inlet side, thereby generating a reformed gas containing hydrogen. However, according to another embodiment 1 (the invention described in claim 1), when the peak temperature position moves downstream from the reference peak temperature position, the required air flow rate Qneed is corrected to the decrease side. Since the air inlet flow rate Q1 is calculated and the calculated air inlet flow rate Q1 is supplied from the air inlet 8d, the peak temperature position exceeds the target operating temperature Tm or is downstream of the reference peak temperature position. It can suppress moving to. That is, by reducing the excess air flowing into the air inlet 8d, the gas flow rate inside the reformer 8 is lowered, the gas residence time is increased, and an oxidation reaction occurs in the catalyst on the upstream side of the reformer 8. Thus, it is possible to prevent the peak temperature from exceeding the target operating temperature Tm, and to avoid the generation of an inactive catalyst region on the reformer 8 inlet side (see the solid line in the middle stage of FIG. 20).
[0134]
Other Embodiment 2: The opening degree of the flow rate control valve 14 is controlled so that air that has not been supplied from the air inlet 8d in the required air flow rate Qneed is supplied from the air intermediate inlet 8f.
[0135]
Next, the operation and effect of the second embodiment (the invention according to claim 3) will be described.
[0136]
When the air inlet flow rate Q1, which is a value obtained by reducing the required air flow rate Qneed, is supplied from the air inlet 8d, the peak temperature position moves to the upstream side of the reformer 8. This is because the air inlet 8d is at the peak temperature portion. This means that almost all of the oxygen in the supplied air has reacted, and if this is the case, the temperature lowers as it goes downstream from the peak temperature position. According to another embodiment 2 (the invention described in claim 3), among the required air flow rate Qneed, the air flow rate (Qneed-Q1) that could not be supplied from the air inlet 8d is supplied from the air intermediate inlet 8f. The catalyst temperature in the vicinity of the air intermediate inlet 8f can be increased (see the broken line in the lower part of FIG. 20).
[0137]
In the embodiment, the catalyst temperature at the position of the temperature sensor 23 ahead of a predetermined period when the actual air flow rate Qsen1 supplied from the air inlet 8d and the actual air flow rate Qsen2 supplied from the air intermediate inlet 8f change is estimated. As described above, for a simple period, only the actual air flow rate Qsen1 supplied from the air inlet 8d changes, or only the actual air flow rate Qsen2 supplied from the air intermediate inlet 8f changes. The catalyst temperature at the position of the previous temperature sensor 23 may be estimated.
[0138]
Although the embodiment has been described in the case of methanol reforming, it goes without saying that the present invention can be applied to other reforming specifications such as gasoline reforming.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a fuel reforming system.
FIG. 2 is a schematic configuration diagram of a reformer.
FIG. 3 is a flowchart for explaining calculation of a target air flow rate.
FIG. 4 is a flowchart for explaining estimation of the gas flow rate in the reformer.
FIG. 5 is a flowchart for explaining calculation of a required air flow rate.
FIG. 6 is a characteristic diagram of water flow rate.
FIG. 7 is a characteristic diagram of methanol flow rate.
FIG. 8 is a characteristic diagram of a peak temperature position.
FIG. 9 is a characteristic diagram for explaining the creation of a temperature distribution profile.
FIG. 10 is a flowchart for explaining calculation of an air inlet flow rate.
FIG. 11 is a characteristic diagram of a decrease correction value of the air inlet flow rate.
FIG. 12 is a flowchart for explaining the estimation of the catalyst temperature at the position of the temperature sensor 23;
FIG. 13 is a waveform diagram for explaining the influence of each step increase of the air inlet flow rate and the air intermediate flow rate on the catalyst temperature at the temperature sensor 23 position.
FIG. 14 is a characteristic diagram for explaining that the temperature change at the position of the temperature sensor 23 with respect to the unit air flow rate changes depending on the load.
FIG. 15 is a characteristic diagram of a temperature correction value.
FIG. 16 is a flowchart for explaining calculation of a target air intermediate flow rate.
FIG. 17 is a waveform diagram for explaining a reduction in the air intermediate flow rate.
FIG. 18 is a characteristic diagram of a decrease side correction value.
FIG. 19 is a waveform diagram for explaining the operation of a conventional device.
FIG. 20 is a waveform diagram for explaining the operation of the invention according to claim 1;
[Explanation of symbols]
8 Reformer
8a Cylindrical case
8b catalyst
8c Raw material inlet
8d Air inlet (gas inlet)
8e Gas outlet
8f Air intermediate inlet (gas intermediate inlet)
12 Flow control valve (gas inlet flow rate adjusting means)
14 Flow control valve (gas intermediate inlet flow rate adjustment means)
21 Controller
22 Temperature sensor (gas inlet catalyst temperature detection means)
23 Temperature sensor (gas intermediate inlet catalyst temperature detection means)
25 Pressure sensor
26 Pressure sensor

Claims (19)

A raw material inlet for supplying raw materials according to the load;
A gas inlet for supplying a gas containing oxygen used in the partial oxidation reaction;
A catalyst that generates a reformed gas containing hydrogen by performing a reforming reaction and a partial oxidation reaction using a gas containing oxygen and a raw material;
In a reformer comprising a gas outlet for discharging the generated reformed gas,
A gas inlet flow rate adjusting means capable of adjusting the flow rate of the gas inlet;
A required gas flow rate calculating means for calculating a required gas flow rate, which is a gas flow rate required for the partial oxidation reaction, based on the raw material flow rate;
Peak temperature position estimating means for estimating the peak temperature position inside the reformer;
When the peak temperature position moves downstream from the reference peak temperature position, the gas flow rate calculating means for correcting the required gas flow rate to the decrease side and calculating the gas flow rate,
A control device for a reformer, comprising: control means for controlling the gas inlet flow rate adjusting means so that the calculated gas flow rate is supplied from the gas inlet. A gas inlet catalyst temperature detecting means for actually detecting the catalyst temperature in the vicinity of the gas inlet is provided, and the target temperature of the gas inlet catalyst temperature detecting means position is calculated based on the peak temperature position. 2. The control device for a reformer according to claim 1, wherein the flow rate of the gas supplied from the gas inlet is calculated so as to coincide with the target temperature at the position of the gas inlet catalyst temperature detecting means. A gas intermediate inlet for supplying a gas containing oxygen to an intermediate position between the gas inlet and the gas outlet, and a gas intermediate inlet flow rate adjusting means capable of adjusting the flow rate of the gas intermediate inlet, from the gas inlet of the required gas flow rate 3. The reformer control device according to claim 1, wherein the gas intermediate inlet flow rate adjusting means is controlled so that the gas that has not been supplied is supplied from the gas intermediate inlet. A raw material inlet for supplying raw materials according to the load;
A gas inlet for supplying a gas containing oxygen used in the partial oxidation reaction;
A catalyst that generates a reformed gas containing hydrogen by performing a reforming reaction and a partial oxidation reaction using a gas containing oxygen and a raw material;
In a reformer comprising a gas outlet for discharging the generated reformed gas,
A gas inlet flow rate adjusting means capable of adjusting the flow rate of the gas inlet;
A required gas flow rate calculating means for calculating a required gas flow rate, which is a gas flow rate required for the partial oxidation reaction, based on the raw material flow rate;
A gas inlet catalyst temperature detecting means for detecting an actual catalyst temperature in the vicinity of the gas inlet;
Peak temperature position estimating means for estimating the peak temperature position inside the reformer;
A gas inlet catalyst temperature detection means position target temperature calculation means for calculating a target temperature of the gas inlet catalyst temperature detection means position based on the peak temperature position;
A gas flow rate calculating means for calculating a gas flow rate so that an actual catalyst temperature in the vicinity of the gas inlet matches a target temperature of the gas inlet catalyst temperature detecting means position;
A selection means for selecting the smaller one of the required gas flow rate and the gas flow rate;
A control device for a reformer comprising: control means for controlling the gas inlet flow rate adjusting means so that the gas flow having the smaller selected value flows. A gas intermediate inlet for supplying a gas containing oxygen to an intermediate position between the gas inlet and the gas outlet, and a gas intermediate inlet flow rate adjusting means capable of adjusting a flow rate of the gas intermediate inlet, and an actual catalyst temperature in the vicinity of the gas inlet When the required gas flow rate is larger than the gas flow rate calculated to match the target temperature at the gas inlet catalyst temperature detection means position, the gas intermediate inlet flow rate adjustment is performed so that the difference flow rate is supplied from the gas intermediate inlet port. 5. The reformer control apparatus according to claim 4, wherein the control means is controlled. 6. The reformer control device according to claim 4 or 5, wherein the gas flow rate of the smaller selected value is corrected to decrease based on the peak temperature position. 7. The reformer control device according to claim 6, wherein the gas flow rate reduction correction value of the smaller selected value is increased as the peak temperature position moves in the downstream direction of the reformer. The gas inlet catalyst temperature detection means position target temperature calculation means includes a temperature distribution profile generation means for generating a temperature distribution profile in the reformer so that the peak temperature position becomes the target operating temperature, and a gas on the temperature distribution profile. The reforming according to any one of claims 4 to 7, comprising means for calculating a temperature corresponding to the position of the inlet catalyst temperature detecting means as a target temperature of the position of the gas inlet catalyst temperature detecting means. Control device. 9. The reformer control device according to claim 4, wherein the peak temperature position is estimated based on a gas flow rate in the reformer. The reformer control device according to claim 9, wherein the peak temperature position is estimated to move to the downstream side of the reformer as the gas flow rate in the reformer increases. The reformer control device according to claim 9 or 10, wherein the gas flow velocity in the reformer is estimated based on a difference between an inlet pressure and an outlet pressure of the reformer. A gas intermediate inlet catalyst temperature detecting means for detecting an actual catalyst temperature in the vicinity of the gas intermediate inlet, and a gas inlet flow rate detecting means for detecting an actual gas flow rate supplied from the gas inlet, are supplied from the gas inlet. Estimate the catalyst temperature near the gas intermediate inlet after a predetermined period when the actual gas flow rate changes based on the actual gas flow rate supplied from the gas inlet and the actual catalyst temperature near the gas intermediate inlet. 6. The flow rate of gas supplied from the gas intermediate inlet is corrected to a decrease side so that the estimated value of the catalyst temperature in the vicinity of the gas intermediate inlet ahead of a predetermined period does not exceed when the upper limit temperature of the catalyst is exceeded. 11. The reformer control device according to any one of 11 to 11. A gas intermediate inlet catalyst temperature detecting means for detecting an actual catalyst temperature in the vicinity of the gas intermediate inlet; and a gas intermediate inlet flow rate detecting means for detecting an actual gas flow rate supplied from the gas intermediate inlet. Based on the actual gas flow rate supplied from the gas intermediate inlet and the actual catalyst temperature near the gas intermediate inlet based on the actual gas flow rate supplied from the gas intermediate inlet when the actual gas flow rate supplied changes. It is estimated that the flow rate of gas supplied from the gas intermediate inlet is corrected to the reduction side so that the estimated value of the catalyst temperature in the vicinity of the gas intermediate inlet ahead of the predetermined period exceeds the upper limit temperature of the catalyst. The control device for a reformer according to any one of claims 5 to 11. Gas intermediate inlet catalyst temperature detecting means for actually detecting the actual catalyst temperature in the vicinity of the gas intermediate inlet, gas inlet flow rate detecting means for detecting the actual gas flow rate supplied from the gas inlet, and gas supplied from the gas intermediate inlet Gas intermediate inlet flow rate detecting means for detecting the actual gas flow rate, and a predetermined period of time when the actual gas flow rate supplied from the gas inlet and the actual gas flow rate supplied from the gas intermediate inlet change. The catalyst temperature near the gas intermediate inlet is estimated based on the actual gas flow rate supplied from the gas inlet, the actual gas flow rate supplied from the gas intermediate inlet, and the actual catalyst temperature near the gas intermediate inlet. The flow rate of gas supplied from the gas intermediate inlet is corrected to the decrease side so that the estimated value of the catalyst temperature near the gas intermediate inlet ahead of the period does not exceed the upper limit temperature of the catalyst. Reformer control device according to any one of claims 5 to 11,. When the estimated value of the catalyst temperature in the vicinity of the gas intermediate inlet ahead of the predetermined period exceeds the upper limit temperature of the catalyst, the larger the temperature rise from the upper limit temperature of the catalyst, the larger the amount of gas flow supplied from the gas intermediate inlet is reduced. The control device for a reformer according to any one of claims 12 to 14, wherein the correction value is increased. The estimated value of the catalyst temperature in the vicinity of the gas intermediate inlet ahead of a predetermined period when the actual gas flow rate supplied from the gas inlet changes is the predetermined time ahead when the actual gas flow rate supplied from the gas inlet changes. The control device for a reformer according to claim 12, wherein the time series data of the catalyst temperature change in the vicinity of the gas intermediate inlet is a value obtained by adding the actual catalyst temperature in the vicinity of the gas intermediate inlet. The estimated value of the catalyst temperature near the gas intermediate inlet ahead of the predetermined period when the actual gas flow rate supplied from the gas intermediate inlet changes is the predetermined period when the actual gas flow rate supplied from the gas intermediate inlet changes 14. The reformer control apparatus according to claim 13, wherein the time-series data for the catalyst temperature change near the gas intermediate inlet is a value obtained by adding the actual catalyst temperature near the gas intermediate inlet. 18. The reformer control apparatus according to claim 16, wherein a transfer function is used for calculating time series data. The reformer control device according to claim 18, wherein a plurality of transfer functions are provided in accordance with a load.

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