轉爐石碳酸化之操作變數效應

Effects of Process Variables on the Conversion of BOF Slag to Carbonate

陳怡蒼(Yi-Tsang Chen)

指導教授 ： 戴怡德

國立臺灣大學/工學院/化學工程學研究所/碩士(2008年)

https://doi.org/10.6342/NTU.2008.01426

摘要

為解決二氧化碳過度排放造成的溫室效應，近年來有許多針對二氧化碳減量的文獻陸續出現。除了利用天然環境來封存二氧化碳，文獻中也有利用鈣矽石、爐石及飛灰分別與二氧化碳進行碳酸化反應，將其固定為碳酸鈣的人為方式出現。
本研究以實驗室之前的研究作為基礎，嘗試利用兩種轉爐石：未經熱處理及經熱處理之轉爐石，以葉片攪拌器攪拌進行二氧化碳碳酸化實驗。本實驗的實驗變數包括了反應溫度、反應壓力、反應時間及反應物粒徑大小，並將反應後的試樣經TGA 分析，再配合由EDTA 實驗所得含一莫耳鈣之轉爐石重量，以求得轉爐石之碳酸化轉化率。
實驗結果顯示，使用粒徑為63~90μm 之未經熱處理轉爐石，在溫度為150℃、總壓為80bar，與二氧化碳反應1 小時後轉化率可達88%，當反應時間加長至16小時轉化率也在此值附近。經由SEM 圖觀察發現，轉爐石反應1 小時之後在其表面已佈滿碳酸鈣晶體形成障礙，造成後續鈣離子溶出困難使轉化率無法再提升。由孔隙度分析也發現，反應過後之轉爐石存在孔徑小於1nm 之孔洞而未經反應之轉爐石則無，此小孔洞應為鈣離子溶出所形成。
經熱處理過程能將轉爐石中的氫氧化鎂分解。使用粒徑為45μm 之經熱處理轉爐石，在溫度為200℃、總壓為20bar，與二氧化碳反應1 小時後可得最佳轉化率90%，由SEM 圖也發現在表面有碳酸鈣的形成。
我們可由實驗數據證明轉爐石可取代鈣矽石與二氧化碳進行碳酸化反應，使工業副產品能夠再次利用。

關鍵字

碳酸化 ； 二氧化碳的固定 ； 轉爐石

並列摘要

The release of CO2 into atmosphere has a serious consequence on the aggravation of greenhouse effect, thus massive topics concerning reducing CO2 have been studied
recently. In addition to CO2 disposal into earth and ocean environment, using wollastonite, basic oxygen furnace (BOF) slag, and fly ash to fix CO2 via carbonation reaction is also mentioned.
Based on the previous experience in our laboratory, we use two kinds of BOF slag, i.e. the sample as received and the heat-treated sample, to proceed CO2 sequestration using
a high-pressure stirred-tank reactor. The effects of the process variables, such as temperature, pressure, reaction time and particle size on the Ca conversion ,which was
calculated from the thermogravimetric analysis and the weight of BOF slag containing 1 mole of CaO determined by EDTA analysis, was studied.
A conversion of 88% for BOF slag(63~90μm) was achieved when the untreated sample was reacted at 150℃ and 80bar for 1h. When the reaction time is increased to 16h, the conversion is also around 88%. This was due to the fact that Ca diffusion was hindered by the formation of CaCO3 on the surface, as judged from the SEM photos of the reacted samples. Furthermore, we found that there are pores less 1nm in the reacted BOF slag but not in the unreacted one. This might be resulted from Ca-leaching from BOF slag matrix into solution.
Mg(OH)2 in BOF slag was decomposed via heat treatment. The highest conversion of 90% for heat-treated BOF slag(＜45μm) was achieved when the heat-treated sample was reacted at 200℃ and 20bar for 1h. We also found the formation of calcite on the BOF slag surface by SEM micrographs.
We conclude that the industrial residue like BOF slag can replace natural rocks to fix CO2 via the carbonation reaction.

並列關鍵字

carbonation ； CO2 sequestration ； steel slag ； BOF slag

參考文獻

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