分離技術シリーズ 20

や さ し い 蒸 留－ポットスチルの首の形状から学ぶ－

鈴

木

功 著

分 離 技 術 会

は じ め にウイスキーを製造するときに使われるポットスチルと呼ばれる蒸留器は，その銅製の首が美しく独特な形状をしている．らんびきは江戸時代に使われた蒸留器である．身近で見られるこれらの蒸留器の形状を通して，太古から現在に至る蒸留の歴史を知り，蒸留について理解を深めてもらいたく本書を書かせていただいた．
化学工学の教科書といえば，一昔前は蒸留，吸着，晶析など単位操作を指していた．その後，反応工学が加わり，シミュレーションも加わり化学プロセス全体を取り扱うようになった．時代の変遷とともに，単位操作のひとつひとつを詳述することから，現在は操作全体に共通する物理化学的な現象を基に体系化されている．
蒸留は吸収や抽出などと同じ物質移動操作として捉えられ，さらには熱との同時移動操作として分類される．また，一方で設計上は平衡操作として気液平衡を基礎として分類され，時として非定常操作としての扱いもされるようになった．蒸留を科学的に勉強するには物質や熱の移動現象を理解することが重要であるが，実用的には単位操作として捉えたほうが便利なことが多い．
蒸留に関する書籍について，古くは，キルシュバウム著「蒸溜及精溜工学」(河東準訳，原書 Destillier-und Rektifiziertechnik 1939 年刊)，藤田重文著「蒸溜及び精溜」昭和 29 年刊，平田光穂著「多成分系の蒸留」昭和 30 年刊があり，その後，化学工学協会編「蒸留工学」昭和 35 年刊，平田光穂・頼実正弘編集「蒸留工学ハンドブック」昭和 41 年刊，平田光穂編著「最新蒸留工学」昭和46 年刊，H.Z. Kister 「Distillation」1992 年刊，分離技術会編「実用蒸留技術」
平成 20 年刊に至るまで多数の名著が出版されてきた．蒸留は化学工業で使用されている単位操作の中で最も実用化されている操作であり，「ペリーのハンドブック(アメリカ化学工学会)」，「化学工学便覧(化学工学会)」でも専門書なみの多数のページが割かれ，また平成 22 年発行された「分離技術ハンドブック(分離技術会)」でも 130 ページを占めている．

本書は蒸留の入門用であり，単位操作としての蒸留についてその歴史を知り，昔の匠が生み出した技を通じてその本質を理解できるように努めた．蒸留塔の設計や計算シミュレーションは最低限の記述にとどめた．また，現在の化学工業装置のおよそ 60～70％を占めるまでに発展した蒸留について学び，同時に蒸留が現在抱えている問題点を明らかにすることとした．そこで，あくまで蒸留の本質を理解することに主眼をおき，理論的には厳密さを欠く点もあるかと思うがお許し願いたい．
本書を通して，蒸留に親しみを感じていただければ幸いである．
2011 年 3 月

鈴木功

目次

第１章

ポットスチル(ウイスキー製造単蒸留装置)の首の形状 ···············

1

1.1

蒸留所(ウイスキー製造工場)見学記 ·········································

21.2

いろいろな蒸留装置を見てみよう ············································

51.3

蒸留装置の起源 ····································································

81.4

自然還流の活用と多段分取の発見 ············································ 11

1.5

実験室でのエタノールの単蒸留実験～自然還流～ ······················· 13

1.6

実験データによる物質収支と熱収支の計算 ································ 17

第２章

回分式蒸留から連続式蒸留へ～自然還流から強制還流へ～ ········· 232.1

エタノール製造工場見学記 ····················································· 23

2.2

蒸留で何が起きているかを考える ············································ 25

2.3

連続式蒸留装置 ···································································· 27

第３章

蒸留を定量化する ······························································· 363.1

物質収支と操作線式 ······························································ 363.2

気液平衡の測定法と平衡図 ····················································· 39

3.3

気液平衡の計算 ···································································· 43

3.3.1

理想系の気液平衡関係 ······················································ 45

3.3.2

非理想系の気液平衡関係 ··················································· 48

3.4

理想系の理論段数計算と最小還流比 ········································· 51

3.4.1

逐次段作図法 ·································································· 51

3.4.2

最小理論段数 ·································································· 53

3.4.3

最小還流比 ····································································· 54

3.4.4

還流比と理論段数の関係 ··················································· 55

3.4.5

蒸留塔の高さ ·································································· 56

3.4.6

蒸留塔の内径 ·································································· 56

3.5

例題による理論段数と還流比の計算 ········································· 57

第４章

多成分系の蒸留と段数計算の実際 ·········································· 654.1

多成分系の蒸留 ···································································· 65

4.1.1

蒸留塔の圧力と温度の決定 ················································ 65

4.1.2

塔頂圧力と塔頂温度の求め方 ············································· 654.1.3

塔底圧力と塔底温度の求め方 ············································· 66

4.2

多成分系の気液平衡関係 ························································ 674.2.1

気液平衡比(理想系) ························································· 674.2.2

気液平衡比(非理想系；活量係数) ······································· 67

4.2.3

気液平衡の計算 ······························································· 70

4.3

蒸留塔の物質収支 ································································· 73

4.3.1

塔全体の物質収支 ···························································· 734.3.2

原料状態 ········································································ 74

4.3.3

塔内流量 ········································································ 75

4.3.4

濃縮部の任意の段の物質収支 ············································· 75

4.3.5

原料段 ··········································································· 76

4.3.6

還流 ·············································································· 76

4.4蒸留塔の熱収支 ···································································· 76

4.5

理想系の段数計算 ································································· 79

4.6

ショートカット法 ································································· 80

4.6.1

最小理論段数 ·································································· 81

4.6.2最小還流比 ····································································· 81

4.6.3

ギリランドの相関 ···························································· 82

4.7

厳密解法 ············································································· 83

4.8

プロセスシミュレータ ··························································· 83

4.9

回分蒸留の計算法 ································································· 84

4.10 段効率と実段数 ···································································· 84
第５章

蒸留塔の設計 ····································································· 86

5.1

棚段塔とトレイ(棚段) ··························································· 86

5.2

充填塔と充填物 ···································································· 89

5.3

塔径と塔高の計算 ································································· 91

5.3.1

塔径の計算と操作領域 ······················································ 91

5.3.25.4

蒸留塔の塔高 ·································································· 93

内部構造 ············································································· 94

5.4.1

段間隔 ··········································································· 94

5.4.2

内径と気液接触部面積 ······················································ 95

5.4.3

溢流部と堰 ····································································· 95

5.4.4

開口部 ··········································································· 965.4.5

圧力損失 ········································································ 96

5.4.6

漏洩 ·············································································· 96

5.4.7

安定操作領域 ·································································· 96

5.5

付属設備

リボイラー，コンデンサー ······································ 98

5.6制御 ··················································································· 100

第６章

大きいことは良いことだ ······················································ 103

6.1

石油精製～常圧蒸留塔(トッパー)と減圧蒸留塔～ ······················· 104

6.2

石油化学～軽質炭化水素，エチレン・プロピレン～ ···················· 108

6.3

超蒸留～キシレン異性体分離～ ················································111

6.4エタノールの精製 ································································· 115

6.5

空気分離 ············································································· 1196.6

有機酸類の蒸留 ···································································· 120

6.7

蒸留による同位体の分離 ························································ 122

第７章

高度な蒸留と省エネルギー ··················································· 124

7.1

抽出蒸留 ············································································· 124

7.1.1

原理 ·············································································· 125

7.1.2

理論的背景 ····································································· 126

7.1.3

溶剤の選定 ····································································· 128

7.1.4

応用例 ··········································································· 130

7.2

共沸蒸留 ············································································· 130

7.2.1

理論 ·············································································· 1327.2.2

添加溶剤の選定 ······························································· 135

7.2.3

共沸プロセス ·································································· 135

7.3

反応蒸留 ············································································· 139

7.3.1

反応蒸留とは ·································································· 139

7.3.2

反応蒸留の魅力 ······························································· 141

7.3.3

反応蒸留プロセス ···························································· 141

7.3.4

応用例 ··········································································· 143

7.4

水蒸気蒸留 ·········································································· 144

7.5

減圧蒸留・真空蒸留 ······························································ 145

7.6

省エネルギープロセス ··························································· 146

7.6.1

多重効用型 ····································································· 147

7.6.2

ヒートポンプ ·································································· 149

7.7

新しい蒸留技術 ···································································· 149

7.7.1

内部熱交換型蒸留塔 HIDiC ················································ 149

7.7.2

塔垂直分割蒸留システム ··················································· 151

第８章

もう少し詳しく知るために ··················································· 155

8.1

蒸留に関する研究会 ······························································ 155

8.2

トラブルシューティング ························································ 1578.3

気液平衡の信頼性に関する雑感 ··············································· 1598.4

参考図書・引用資料など ························································ 160

使用記号 ······················································································· 164
索引 ····························································································· 165