Untersuchung eines Sprühwäscheverfahrens zur CO2-Abscheidung aus Rauchgasen kohlebefeuerter Kraftwerke

Thesis from Simone Zimmermann
University of Stuttgart, 2021

Carbon dioxide (CO2), an odorless and colorless gas, is released during the combustion of fossil fuels and is considered to be a major driver of global warming. In order to limit the average global temperature to a maximum of 2°C compared to the pre-industrial level, so-called CC(U)S technologies are being discussed for the capture, utilisation and storage of CO2 from flue gases of fossil-fired power plants. Chemical scrubbing using aqueous amine-based solvents is a suitable process for post combustion CO2 capture. Spray columns are traded as an alternative to the usually considered packed absorption columns. The subject of the present thesis is to demonstrate for the first time a technical-scale spray scrubbing process with solvent regeneration. The main focus is on the dependence of the absorption process on the load case, i.e. with regards to a varied solvent and flue gas flow rate, as well as on the spray characteristics. An aqueous   30 wt.-% monoethanolamine solution (MEA) is used as solvent. The experiments are accompanied by the measurement of the characteristic droplet size of a spray, the so-called sauter mean diameter, using water.

The experiments show that 90 % CO2 can be separated from an artifical flue gas with a spray column height of at least 33 m and confirm the applicability of the spray scrubbing technology for CC(U)S. Furthermore, the sauter mean diameter of a newly developed cluster head nozzle with hollow cones and a full cone nozzle can be derived via empirical calculation equations as a function of the physical solvent properties of the MEA-H2O-CO2 system. The calculations can be verified on the basis of the measured data. In order to discuss the economic factors influencing CO2 capture, the specific mass-transfer coefficient and the effective area are determined on the basis of the experimental data using a model calculation. The calculation results are compared with literature data. It is shown that especially in the lower part of the spray scrubbing column, high CO2 loadings of the solvent significantly reduce the specific mass-transfer coefficient. Efficiency-increasing measures are necessary to further increase the CO2 capture efficiency and to ensure an economical plant design with low spray column heights.

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