| Compared to coal, natural gas and coal gas are types of high-quality, economic and clean resources with large calorific value and less pollution. Gas purification has attracted great attention because impurities cause negative influences during gas utilization. Throughout the purification process, CO2capture can improve utilization efficiency of the product gas and meanwhile, control greenhouse gas emissions. Chemical absorption is considered as the most mature and promising technology of CO2capture. In this thesis, CO2capture abilities of various absorbents were tested through reaction kinetics and absorption experiments.The experiments of reaction kinetics were carried out in the wetted-wall column.6kinds of typical single absorbents,6kinds of mixed blends and4types of non-aqueous solutions were selected. The overall mass transfer coefficients, KG, of6single absorbents were ranked as follows:30%DETA>30%MEA>5%PZ>30%DEA≈30%AMP>30%MDEA.KG of MEA/MDEA blended solvents decreased with the concentration increasing of MDEA. MEA/DETA, MEA/AEEA and MEA/PZ blended amines possessed excellent mass transfer performance. Among4types of non-aqueous solutions, methanol and ethylene glycol deserved more attention due to well combination of low volatility and large KG. Besides, KG of MEA reduced since CO2loading of the solution increases, while KG rises with larger gas flow rate.A semi-batch bubble absorption system was used to measure CO2absorption performance from coal gas and natural gas. During the process of CO2absorption, three key factors as CO2removal efficiency, absorption rate and CO2loading of solution were calculated to evaluate the capture performance of absorbents. Selected absorbents were similar to those used in kinetic experiments.The results showed that during CO2absorption process from coal gas, CO2removal efficiencies of6kinds of single absorbents were ranked in the following: 30%DETA>30%MEA≈5%PZ>30%DEA≈30%AMP>30%MDEA. It was basically the same to the results of wetted-wall column experiment. In area of removal efficiency above40%,5%PZ showed best absorption performance. But as to rapid drop of absorption rate,5%PZ was not as effective as DETA. CO2removal volume and absorption rates of MEA/MDEA blended amines decreased with higher MDEA concentration. Performance of non-aqueous solutions kept going worse as molecular weight of solvent rises.Experiment of CO2removal from natural gas indicated that DETA still had the largest removal efficiency and absorption rate as in coal gas system.5%PZ showed nearly no CO2absorption after1hour high-efficient removal performance. CO2concentration of exhaust gas of30%MDEA solution passed3%in extremely short time, which was not suitable for4%CO2removal. DETA and MEA had much longer effective absorption time and larger removal efficiency. MEA/MDEA mixed blends obtained the same results as in coal gas process.Hence,30%DETA,30%MEA,20%MEA+10%MDEA had relative advantages in CO2absorption from coal gas and natural gas.5%PZ possessed high removal efficiency and CO2loading in short time, which was suitable for short-run system or used as an addition. Within1hour, the same absorbent had larger CO2removal efficiency of natural gas than that of coal gas, while CO2loading was smaller in natural gas system than in coal gas system.Finally, through contrast experiment of CO2absorption with30%MEA from N2and CO2mixture, it was referred to that contents in coal gas weaken CO2removal ability of MEA and that natural gas, mainly CH4, optimized the performance of CO2absorption. |
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