CO2 sequestration by carbonation of alkaline solid waste

• Main Authors: Hsiao-Wen Chu, 朱孝文
• Other Authors: 蔣本基
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/94322759098154001014

碩士 === 臺灣大學 === 環境工程學研究所 === 95 === CO2 sequestration by carbonation of alkaline solid wastes is a potential technology to reduce carbon dioxide emissions to the atmosphere. In this study, three kinds of alkaline Ca-rich solid wastes, i.e., ultra-fine slag; fly ash slag; blended hydraulic cement slag, are selected as possible materials for CO2 sequestration. These materials were carbonated in aqueous condition (slurry) and operated under various conditions of reaction time, liquid to solid ratio, temperature, CO2 partial pressure and initial pH to determine their influence on the carbonation conversion. The results indicate that the blended hydraulic cement slag has the highest carbonation conversion about 86% in 12 hr at 700 psig and 160 oC. The major factors effecting the conversion are reaction time (5 min to 12 hr) and temperature (40 oC to 160 oC), furthermore, the reaction kinetics can be expressed by surface coverage model. Another route of carbonation, so called pH swing process, was also employed to enhance the conversion of ultra-fine slag. By controlling the pH in this process, three solid products, i.e., CaCO3, SiO2¬-rich solids and metal mixture solids were formed. The advantages of pH swing process include lower energy consumption and the high purity product of CaCO3 which could reduce the operation and maintenance cost of this sequestration technology. Finally, LCA method was applied to compute the net CO2 emission which indicates that both the blended hydraulic cement slag and pH swing process exhibit a negative sign of CO2 emission, i.e., -0.028 and -0.05 kg/kg, respectively, therefore, they are feasible techniques to reduce CO2.