Study on Carbon Dioxide Removals from Flue Gas Using Chemical Absorption Method

• Main Authors: Chia-Hao Hsu, 許家豪
• Other Authors: Hsin Chu
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/00563039390742251252

博士 === 國立成功大學 === 環境工程學系碩博士班 === 91 === The increase in atmospheric carbon dioxide has primarily resulted from the consumption of fossil fuels for energy. The atmospheric CO2 is transparent to visible light but absorbs infrared radiation returning from the earth. Thus, the atmospheric CO2 may alter the radioactive balance of the earth and raise the global temperature. This so-called “greenhouse effect” could dramatically cause global climatic and environmental changes in precipitation, storm patterns, and increases in sea level. Therefore, it is the time to research and develop technologies for reducing CO2 emissions from energy production system that is the largest source of CO2 emissions. This study was set up a bench-scale agitated vessel reactor system to removal CO2 in the simulated fuel gas. To measure the absorption rate of CO2 at various operating conditions; followed by using MEA(aq); DEA(aq); MDEA(aq); NH3(aq); NaOH(aq) and mixing amine as the additive and absorbent, respectively, to determine the chemical kinetics data. The result of this study shows the following: 1.The effect of MEA concentration on CO2 absorption rate The result shows that the absorption rate increase by increasing the gas flow rate but the amount of changing absorption rate decrease with increasing the gas flow rate. In different concentration of absorbent condition, the absorption rate increase by increasing the concentration of absorbent, however, the absorption rate is the fast in MEA=30%. The result shows that the absorption rate increase by increasing temperature. We get the reaction kinetics equation from difference absorbent concentration absorbs difference CO2 concentration. In difference operating temperature (30~70℃), we can get active energy , and reaction constant equation. Ea=32.26 Kj/mol , kmn= 2. The effect of ammonia solution concentration on CO2 absorption rate The result shows that the absorption rate NA(mol/sec/cm2) goes up by increasing the concentration of ammonia solution, CO2 inert concentration, gas flow rate and operation temperature, but not affected by the concentration of oxygen. Under the above-mentioned conditions, the reaction orders for CO2 and ammonia solution are respectively about 0 and 2, and the reaction kinetics equation cab be written as ，reaction rate constant is 2235.4（cm3/mol/sec）。. The absorption is varying by changing gas phase condition (gas flow rate and gas concentration) and liquid phase condition (absorbent concentration). However, changing absorbent concentration affects the absorption rate much more than changing gas phase condition does. Therefore, we can say that the absorption of CO2 should tend to liquid-film control. We also can get the active energy （about 48.0 kj/mol）of the reaction between CO2 and ammonia solution by changing operation temperature. The relationship between reaction rate constant and temperature is . 2.The effect of NOx and SO2 on CO2 absorption rate The result shows that the absorption rate reduces by entering NOx and SO2. 3.The effect of additives CO2 absorption rate Absorbent MEA/NH3 = 30/1, 30/3, MEA/DEA = 30/10, 30/20, MEA/MDEA = 30/5, 30/10. The result shows that entering NH3 can help to increase absorption rate and compete to NOx, SO2 bad affecting for MEA absorb CO2 and the absorption rate increase with increasing NH3 concentration. 4.The effect of absorbent type on CO2 absorption rate Absorbent concentration NH3=0.57~2.51M; NaOH=1~3M; MEA=1.64~4.91M; DEA=0.98~2.93M; MDEA=0.87~2.62M. The result shows that the absorption rate is NH3>MEA>NaOH>DEA>MDEA.