以改質氧化鈣捕獲二氧化碳氣體之循環再生能力研究

Abstract

隨京都議定書生效以及全球暖化日漸加劇，二氧化碳(CO2)的排放減量逐漸受到重視，以反覆吸附進行CO2捕獲是極具前瞻性的技術之一，在各類的吸附劑中，氧化鈣(CaO)除了在自然界中有豐富的蘊藏量外，其理論之CO2吸附量也最高，但CaO易於再生過程中發生劣化，使再生後之吸附量有逐漸減少的問題。近來有研究針對CaO進行改質，由其循環測試的結果中，證實適當之改質可抑制CaO的劣化問題。本研究中，採用將耐熱的金屬物質□入CaO的方式來進行改質，同時亦比較不同前驅物對改質效果的影響，結果發現添加有機鋁(Al[OCH(CH3)2]3)改質後所製備出的吸附劑(CaO/Ca12Al14O33)，在吸附量與再生能力等表現上，皆有較佳的表現，由循環吸脫附CO2的測試結果可知，僅含5 wt% Ca12Al14O33的CaAl(95)-O，在68循環再生後，其CO2吸附量較未改質之CaO多出約27 %。而藉由TGA與填充管柱兩種不同系統的測試，亦得以暸解停留時間、CO2進流濃度與反應溫度等參數，對改質CaO捕捉CO2行為上的影響，隨停留時間與進流濃度的上升，CaAl(95)-O對CO2的捕捉效率有提高的趨勢。儘管國產之天然石灰石(limestone)含有高純度的石灰，然利用其作改質前驅物時，效果不若氧化鈣藥品來得好，顯示limestone的改質仍有改進的地方。

Owing to the advantages of low sorbent purchased cost and high fresh sorbent capacity, the CaO cyclic capture is one of the promising CO2 capture technologies. However, CaO is also suffered from severe decay in sorbent capacity during cyclic adsorption. In recent years, the modification on CaO to enhance the uptake capacity and reversibility has been a subject of study. In the present study, the modification of CaO sorbent with organic alumina precursor (Al[OCH(CH3)2]3) to enhance the sorption capacity during cyclic capture is demonstrated. The crystalline phases of alumina modified CaO sorbent (CaO/Ca12Al14O33) were confirmed by power X-ray diffraction (XRD) analysis. The cyclic CO2 capture capacity and removal efficiency of the sorbents were evaluated by thermo gravimetric analysis (TGA) and packed column test system. The results indicated that by adding only 5 wt.% of Ca12Al14O33 into the CaO sorbent (CaAl(95)-O), the CO2 sorption capacity can be enhanced by ca. 27 wt.% as compared to that of original CaO sorbent. In addtion, the CO2 removal efficiency of CaAl(95)-O increased with the increasing empty-bed gas retention time and CO2 inlet concentraion. The modification on natural limestone with high purity of lime showed lower sorbent capacity than that of CaO species.