在超重力旋轉填充床中利用煉鋼爐石碳酸化反應進行二氧化碳捕捉

Abstract

本研究於超重力旋轉填充床(RPB)中，利用煉鋼爐石進行二氧化碳之捕捉實驗，所使用之煉鋼爐石為中國鋼鐵公司所提供之轉爐石(BOF)，並在常溫、常壓、液固比20 mL/g、純二氧化碳流速2.5 L/min下，詴驗不同之操作條件，如反應時間、旋轉床轉速、溫度及泥漿流速，對於爐石碳酸化之影響。反應後之產物透過熱重分析儀(TGA)及原子吸收光譜(AAS)進行定量分析，並藉由掃描式電子顯微鏡(SEM-EDX)及粉末單晶繞射儀(XRD)進行產物定性分析。研究結果發現在反應時間30分鐘、轉速750 rpm、65 ℃、氣壓14.7 psig、粒徑63 μm時，有最大之爐石碳酸化轉化率93.5%，主要產物為碳酸鈣(CaCO3)。主要影響碳酸化效率之因素為反應時間(1分鐘到20分鐘)、旋轉床轉速(500 rpm ~ 1250 rpm)及溫度(25到65 oC)。此外，反應數據透過縮核模式(SCM)找出碳酸化反應限制步驟，並透過表面覆蓋模式進行動力學分析，由掃描式電子顯微鏡及粉末單晶繞射儀之結果，可證明縮核模式與表面覆蓋模式於本研究之適用性。此程序可在相對短之反應時間、常溫、常壓下，獲得較高之轉換效率，因此最後以生命週期評估軟體-Umberto 5.5，結合國際資料庫-Ecoinvent 2.0與國內數據進行生命週期評估，計算此程序之總碳足跡，並透過與其他研究之比較，確認於超重力旋轉填充床中利用煉鋼爐石進行二氧化碳捕捉之可行性。此技術無論在效率、成本、能源消耗、產物安定性以及貯存能力上均有出色的表現，顯示其為可行之二氧化碳減量技術。

Carbon dioxide (CO2) sequestration using producing carbonates from steelmaking slags was performed in a rotating packed bed (RPB). The effects of reaction time, rotating speed, temperature, and slurry flow rate on the performance on the CO2 sequestration process were evaluated. One type of steelmaking slags provided by China Steel Company, namely basic oxygen furnace (BOF) slag, was selected as feedstock. The sequestration experiments were performed at a liquid-to-solid ratio of 20 mL/g with a flow rate of 2.5 L/min of a pure CO2 stream under atmospheric temperature and pressure. The carbonation products were analyzed quantitatively with thermogravimetric analysis (TGA) and atomic absorption spectrometer (AAS) and qualitatively with scanning electron microscope with energy dispersive X-ray spectroscope (SEM-EDX) and X-ray diffractometry (XRD). The results reveal that a maximum conversion of BOF slag was found to be 93.5% operated at a reaction time of 30 min and a rotating speed of 750 rpm at 65 ℃, 14.7 psig of CO2 partial pressure and a particle size of 63 μm. The major factors that affected the conversion were reaction time (1 min to 20 min), rotating speed (500 rpm to 1250 rpm), and temperature (25 oC to 65 oC). In addition, the experimental data also were utilized to determine the rate-limiting mechanism based on the shrinking core model (SCM) and the reaction kinetics based on the surface coverage model which could be validated by the observations of SEM-EDX and XRD. Furthermore, the carbon footprint of the developed technology in this investigation was calculated by a life cycle assessment (LCA). A comparison of the results with other studies suggests that accelerated carbonation in a RPB is viable due to its higher conversion, shorter reaction time, and relatively milder conditions.