高比表面積碳酸鈣高溫硫酸化反應之研究

High-Temperature Sulfation of High-Surface-Area Calcium Carbonate

許書凡(Shu-Fan Hsu)

指導教授 ： 施信民

國立臺灣大學/工學院/化學工程學研究所/碩士(2011年)

https://doi.org/10.6342/NTU.2011.03424

摘要

本研究使用氣泡床以Ca(OH)2懸浮液吸收CO2，製備出高比表面積的碳酸鈣。在沒有添加添加劑下，當初始Ca(OH)2濃度為2.4 wt%與CO2流量為2.5 L/min的反應條件下，碳酸鈣的比表面積達15.6 m2/g；當漿液pH值6.5 – 6.2時添加0.1 wt% Dispex A40，得到的比表面積為35.3 m2/g；而當漿液pH值11.4 –11.1時添加0.2 wt% PAAS，得到的比表面積為70.7 m2/g。碳酸鈣初級顆粒會聚集成大的顆粒，上述三種碳酸鈣之平均粒徑分別為10.4、17.5和4.6 µm。
碳酸鈣硫酸化反應之初始速率及1分鐘的轉化率隨著比表面積、反應溫度與SO2濃度的增加而增大，隨著反應氣體中CO2濃度的增大而減小，但不受H2O濃度影響。添加0.2 wt% PAAS所製得的碳酸鈣在950ºC的廢氣組成下與4400 ppm SO2反應，1分鐘的轉化率可達0.88。本研究所製得的碳酸鈣顆粒，其硫酸化反應的動力學可用變晶粒模式描述。碳酸鈣在可分解為CaO的條件下，其整體硫酸化反應速率為晶粒產物層及顆粒孔隙擴散共同控制；而在碳酸鈣不可分解、直接反應的條件下，其整體速率為晶粒化學反應、晶粒產物層擴散及顆粒孔隙擴散共同控制。

關鍵字

碳酸鈣 ； 氫氧化鈣 ； 二氧化碳 ； 二氧化硫 ； 碳酸化 ； 硫酸化

並列摘要

High surface area CaCO3 particles were produced by absorption of CO2 in aqueous suspensions of Ca(OH)2 in a bubble column. In the absence of any additive, CaCO3 with a surface area of 15.6 m2/g was obtained at 2.4 wt% Ca(OH)2 and 2.5 L/min CO2. CaCO3 with a surface area of 35.3 m2/g was obtained by adding 0.1 wt% Dispex A40 at pH 6.5 – 6.2, and with a surface area of 70.7 m2/g by adding 0.2 wt% PAAS at pH 11.4 –11.1. The primary CaCO3 particles agglomerated to form large particles, the average particle diameters of which were 10.4, 17.5, and 4.6 µm for the three CaCO3 samples prepared, respectively.
The initial rate and 1 min conversion for the sulfation of CaCO3 increased with increasing specific surface area, temperature, and SO2 concentration, but decreased with increasing CO2 concentration, and were independent of H2O concentration. A conversion of 0.88 was achieved when CaCO3 with a surface area of 70.7 m2/g was sulfated at 950ºC and 4400 ppm SO2 in a simulated flue gas for 1 min. The kinetics of the sulfation of CaCO3 particles can be described by the changing grain size model. Under the conditions that CaCO3 can decompose, the sulfation rate was controlled by grain product layer diffusion and particle pore diffusion. Under the conditions that CaCO3 cannot decompose, the sulfation rate was controlled by grain chemical reaction, grain product layer diffusion, and particle pore diffusion.

並列關鍵字

calcium carbonate ； calcium hydroxide ； carbon dioxide ； carbonation ； sulfation ； sulfur dioxide

參考文獻

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