高比表面積碳酸鈣的製備及其高溫硫酸化反應之研究

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

楊榮欣(Jung-Hsin Yang)

指導教授 ： 施信民

國立臺灣大學/工學院/化學工程學研究所/博士(2009年)

https://doi.org/10.6342/NTU.2009.02370

摘要

本研究使用氣泡床以Ca(OH)2懸浮液吸收CO2，並添加適合的添加劑，製備出高比表面積和孔隙體積的碳酸鈣。在沒有添加任何添加劑下，碳酸鈣比表面積隨著初始Ca(OH)2濃度的不同而變化，當濃度為2.4 wt%時，比表面積可達到最大值( 19.6 m2/g )。碳酸鈣比表面積不受CO2流量( 1.0-3.5 L/min )的影響，隨著溶液溫度的增加而減小( 27-45 oC )。碳酸鈣比表面積顯著受添加劑種類、添加量與添加時溶液pH值的影響。添加劑可以提高細微碳酸鈣初級粒子的形成並使之聚集成較鬆散的聚集體。除了EDTA外，其餘有效的添加劑必須在CO2通入Ca(OH)2漿液後再添加才能提升碳酸鈣的比表面積。在所有測試的添加劑中， PAAS、EDTA、(NaPO3)6與Na5P3O10得到的比表面積在70 m2/g以上。在初始Ca(OH)2漿液濃度2.4 wt%，溶液pH值11.4-11.1時添加0.2 wt%的PAAS得到的碳酸鈣比表面積為最大，87.7 m2/g。
碳酸鈣硫酸化反應之初始速率及1小時轉化率大致隨著比表面積的增加而增大。添加0.2 wt% PAAS所製得的碳酸鈣在950 oC與4000 ppm SO2之反應條件下，1分鐘的轉化率可達0.95。碳酸鈣若事先經過煅燒則會降低對SO2的反應性。碳酸鈣硫酸化反應之初始速率及1小時轉化率隨著反應溫度與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O2和H2O濃度影響。碳酸鈣在高溫下和二氧化硫的反應可用產物層擴散之模式來描述其反應動力學。

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 and porous CaCO3 particles were produced by absorption of CO2 in aqueous suspensions of Ca(OH)2 with the addition of a suitable additive in a bubble column. In the absence of any additive, the CaCO3 surface area varied with the initial Ca(OH)2 concentration and reached a highest value ( 19.6 m2/g ) at 2.4 wt% Ca(OH)2. The CaCO3 surface area was affected little by the CO2 flow rate ( 1.0-3.5 L/min ) and decreased with increasing solution temperature ( 27-45 oC ). The CaCO3 surface area was affected markedly by the kind of additive, the amount of additive, and the solution pH when adding the additive. An effective additive in raising the CaCO3 surface area was to enhance the formation of fine CaCO3 primary particles and the loose aggregation of them; the additive should be added only after bubbling CO2 into the Ca(OH)2 suspension except EDTA. Among all the additives tested, CaCO3 samples prepared with PAAS, EDTA, (NaPO3)6, and Na5P3O10 could have surface areas above 70 m2/g. The CaCO3 with the highest surface area ( 87.7 m2/g ) was obtained by adding 0.2 wt% PAAS to a suspension of 2.4 wt% Ca(OH)2 in the pH range of 11.4-11.1.
The reactivity of CaCO3 increased with increasing surface area in general. A conversion of 0.95 was achieved when CaCO3 with highest surface area was sulfated at 950 oC and 4000 ppm SO2 in air for 1 min. Prior calcination reduced markedly the reactivity of CaCO3. The initial rate and 1 h conversion for the sulfation of CaCO3 increased with increasing temperature and SO2 concentration, decreased with increasing CO2 concentration, and were independent of the O2 and H2O concentrations. The kinetic of the sulfation of CaCO3 was well described by the model assuming product layer diffusion control.

並列關鍵字

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

參考文獻

Shih, S. M.; Hung, J. T.; Wang, T. Y.; Lin, R. B. ” Kinetics of the Reaction of Sulfur Dioxid with Calcium Oxide Powder ”, J. Chin. Inst. Chem. Engrs., 2004, 35, 447.

陳致光, “ 以逆微乳膠法調控奈微米級碳酸鈣之晶貌 ”, 碩士論文, 國立台灣大學, 台北, 台灣, 2004

陳彥志, “ 以鈣矽石漿液捕捉二氧化碳之研究 ”, 碩士論文, 國立台灣大學, 台北, 台灣, 2008

Agnihotri, R.; Mahuli, S. K.; Chauk, S. S.; Fan, L. S. “ Influence of Surface Modifiers on the Structure of Precipitated Calcium Carbonate ”, Ind. Eng. Chem. Res., 1999, 38, 2283.

Beruto, D.; Barco, L.; Searcy, A. W. ” CO2-Catalyzed Surface Area and Porosity Changes in High- Surface-Area CaO Aggregates “, J. Am. Ceram. Soc., 1984, 67, 512.