O_2-CO_2吹きガス化炉のための石炭ガス化反応性評価と反応モデル構築

摘要

CO_2回収型次世代IGCCシステムは，回収したCO_2を効果的に再利用するO_2-CO_2吹きガス化炉と，リサイクルした排ガスに酸素を混合して燃焼させるクローズドガスタービンを組み合わせたものである。O_2-CO_2吹きガス化炉では，高分圧となるCO_2によるガス化反応促進を図つており，炭素転換率や冷ガス効率の向上が期待される。一般に，IGCCで使用される石炭ガス化炉は噴流床型が多く採用されており,本システムにおいても噴流床型ガス化炉が想定されている。%O_2-CO_2 blown gasifier is adopted in the oxyfuel IGCC system. It is important to clarify coal reactivity in such a modified gasifier. In this study, coal gasification tests mainly utilizing a pressurized drop tube furnace (PDTF) are examined. The coal gasification reactivity was evaluated in two points of view. One is char gasification. In the O_2-CO_2 blown gasifier, CO_2 partial-pressure is so high that Langmuir-Hinshelwood (LH) type model is recommended to describe the char gasification behaviors. Furthermore, a new type model, the partially shared active site LH (PS-LH) model was proposed to describe the competition between CO_2 gasification and H_2O gasification. The other point of view is soot formation. Soot forms in coal gasification through primary pyrolysis and gas phase reactions and the soot gasification reactivity is lower than char gasification. A primary pyrolysis model is necessary for clarification of the soot formation behavior. The chemical percolation devolatilization (CPD) model was extended to determine volatile matter compositions. It was useful to predict poly-aromatic-hydrocarbon reaction behaviors utilizing a detailed chemical reaction mechanism.