過去精餾、吸收等分離製程常應用平衡階段模型(equilibrium stage model)模擬。然而平衡模型未考慮分離過程吸收所伴隨的質傳，如果吸收過程中要把氣體濃度降到很低（ppm級），此時質傳推動力極低，使得平衡階段模型與實際操作一直存在相當大的差距，近年有不少研究者建立質傳速率模型(mass transfer rate-based model) ，例如ASPEN TECH 公司的ASPEN Plus RateFracTM模型，證明比傳統的平衡階段模型更適用於吸收過程的穩態模擬 。
中鋼的COG氣體經過冷卻後進入兩套不同的吸收塔，兩套設備的填充物不同，高度也不同。經過吸收後的COG氣體有不同的氨與硫化氫濃度變化，傳統的平衡階段模型只能用板效率描述兩套系統的差異，唯有用rate-based模型考慮兩相之間的質傳與熱傳問題，說明產量、設備大小的影響，才能真正描述兩個系統的操作情形。
我們以文獻數據驗證Aspen Plus 提供的熱力學(模型)、並藉由Aspen Plus建立rate-based吸收塔模式。Rate-based中的mass-transfer coefficient model、liquid holdup能因填充物不同做調整，reaction factor則可以對各反應的質傳控制貢獻做出調整，使rate-based model能符合不同填充物下的吸收塔操作。
系統的熱力模型，以系統中NH3-H2S-H2O、NH3- CO2 -H2O實驗值與模擬值比較，驗證其準確度在操作範圍內。以rate-based進行吸收塔的模擬，證明rate-based模型遠優於平衡板模型，而且能模擬預測flexipac與expanded metal兩種填充物的吸收塔操作結果，NH3/H2S/CO2的移除總量與現場十分吻合，出口COG中NH3/H2S/CO2的濃度也在合理範圍之內。
研究另探討Stripping water的流量與pH值對COG被吸收後氨濃度的變化。Waste water/ Coal water的pH流量控制是另一影響NH3出口濃度關鍵變因。發現NH3出口濃度受液相體積影響，但不太受液膜反應條件影響，顯示NH3反應速度較H2S反應慢，相當部分反應在液相進行。因此加上填充物選擇及塔內流場控制會對NH3出口濃度有影響。H2S出口濃度受液相體積及液膜反應條件影響，顯示H2S反應速度較NH3快，相當部分反應在液膜進行。所完成的rate-based模型能詳細描述吸收機制，符合實際操作，能進一步用於填充塔的設計。

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