Untersuchung eines Sprühwäscheverfahrens zur CO₂-Abscheidung aus Rauchgasen kohlebefeuerter Kraftwerke

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.