Sensitivity study for the rate-based simulation of the reactive absorption of CO2

AbstractThe most promising process for Post Combustion Carbon Capture (PCC) is reactive absorption. For the design and scale-up of this process, reliable process models are needed. To achieve this, the models need to not only reliably describe the physical and chemical equilibria in the reacting systems but also to account for both mass transfer and reaction kinetics. Consequently, the models are complex and contain a large number of input parameters for describing fluid dynamics and physico-chemical properties. In order to assess the required quality of the input, the sensitivity of the simulation results to the parameters has to be known. This paper presents results from such a sensitivity study for a typical operating point of a PCC pilot plant with 0.3 g/g monoethanolamine (MEA) in water as the solvent. A rate-based model and its input parameters are introduced and describe the pilot plant results well. The most relevant input parameters of the model are systematically varied and the influence of that variation on the simulation results is monitored. Absorber and desorber are considered separately. The results are sensitive to most of the studied parameters. High sensitivities are found for the interfacial area, the Henry’s law constant and the enthalpy of absorption as well as for the parameters describing the equilibrium and kinetics of the carbamate formation and the amine protonation equilibrium

Pilot plant experimental studies of post combustion CO2 capture by reactive absorption with MEA and new solvents

AbstractThe main challenge for the CO2 post combustion capture from power plant flue gases is the reduction of the energy requirement for solvent regeneration. The required reduction can only be achieved by application of new solvents. For the validation of new solvents in the absorption/desorption process, a pilot plant (column diameters 0.125 m, absorber packing height 4.2 m, flue gas flow 30–110 kg/h, CO2 partial pressure 35–135 mbar) was built in the EUproject CASTOR. To obtain a baseline for testing of new solvents, first systematic studies were carried out with MEA in that plant. All important process parameters, i.e. CO2 content in the flue gas, CO2 removal rate ΨCO2, fluid dynamic load, and solvent flow rate were varied. These studies allow detailed insight into the process, e.g., a quantification of the different contributions to the overall regeneration energy (namely: desorption enthalpy, stripping steam, heating up of solvent feed and condensate recycle) as a function of the chosen process parameters. A rate-based model of the process based on a detailed physico-chemical model was implemented in the process simulator CHEMASIM. It is shown that the model is able to predict the experimental results for MEA. Besides MEA, two new solvents were studied in the pilot plant. A direct comparison of different solvents in such pilot plant experiments is not trivial. The comparison of only a few operating points for the new solvents with seemingly corresponding results for MEA can lead to wrong conclusions, since for each solvent an optimisation of the operating conditions is necessary. Only systematical studies allow a meaningful comparison. The technique that was used in the present work for this purpose was measuring data sets at constant CO2 removal rate (by adjustment of the regeneration energy in the desorber) and systematically varying the solvent flow rate. A minimal energy requirement for the given removal rate is found from theses studies. Only the optima for different solvents should be compared. By this procedure, one solvent candidate was identified that shows an advantage compared to MEA

Pilot plant experiments for post combustion carbon dioxide capture by reactive absorption with novel solvents

AbstractThe main challenge for CO2 post combustion capture from power plant flue gases is reducing the energy demand of the process. Application of novel solvents will substantially contribute to this. The present work describes the testing of such novel solvents in a pilot plant (column diameters 0.125 m, absorber packing height 4.25 m, flue gas flow 30–110 kg/h, CO2 partial pressure 35–135 mbar). Two novel amine solvents from EU-project CESAR were systematically studied and compared to Monoethanolamine (MEA). For each solvent, at a constant CO2 removal rate of 90% the regeneration energy is determined for different solvent flow rates. From the results the optimal solvent flow rate and the minimum regeneration energy are found. The resulting numbers for the different solvents can directly be compared. Both new solvents show improvements compared to MEA with a reduction of about 20% in the regeneration energy and 45% in the solvent flow rate for the most promising one