Absorption of CO2 by K2CO3 on Activated Carbon and CaSiO3

• Main Authors: LEE YUEH YANG, 李岳陽
• Other Authors: Shih Shin Min
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/12296196730600314318

碩士 === 國立臺灣大學 === 化學工程學研究所 === 90 === A thermogravimetric technique was employed to evaluate the CO2 absorption capacities of K2CO3/activated carbon and K2CO3/CaSiO3 sorbents and to study their reaction kinetics under humid (30-70%RH) and low temperature(40-80oC) conditions. The sorbents were prepared by impregnation method. The conversion rate of K2CO3 supported on activated carbon was higher than that supported on CaSiO3，and both rates were higher than that of unsupported K2CO3. For the K2CO3/carbon sorbent，the conversion rate of K2CO3 increased with decreasing K2CO3 content and leveled off at about 13wt%.The CO2 capture rate of sorbent increased with increasing K2CO3 content，but the rate increased slower after about 13 wt%. For the K2CO3/CaSiO3 sorbent，the conversion rate leveled off as the K2CO3 content was less than 17.5 wt%，and the CO2 capture rate increased slower with increasing K2CO3 content after about 17.5 wt%. The carbonation rate of K2CO3 increased with increasing relative humidity. At relative humidity above the deliquescence RH of K2CO3 , the rate increased with increasing temperature and CO2 concentration ; at relative humidity below the deliquescence RH, the rate decreased with increasing temperature. Under CO2 at 60oC and 70%RH，the carbonation rate for the K2CO3/carbon sorbent was independent of particle size(0.55-1.55mm dia.) , but that for the K2CO3/CaSiO3 sorbent increased with decreasing particle size(0.78-1.55mm dia.). At 70%RH，being higher than the deliquescence RH of K2CO3，K2CO3 in the K2CO3/carbon sorbent was completely converted to KHCO3 within 7.5min. The reaction was chemical reaction controlled and was well described by the first order reaction model , but the reaction was described better by the shrinking core model for chemical reaction control when the K2CO3 content was about 29.6wt%. At 30%RH，being below the deliquescence RH of K2CO3 ,the rate dropped significantly. The reaction was chemical reaction controlled and well described by the surface coverage model. At 70%RH , K2CO3 in the K2CO3/CaSiO3 sorbent was completely converted to KHCO3 within 7.5min. The reaction was well described by the shrinking core model for chemical reaction control. At 30%RH , the rate dropped significantly. The reaction was well described by the surface coverage model. Activated carbon is better than CaSiO3 to be used as a support for K2CO3 for CO2 absorption.