Gas-liquid multiphase computational fluid dynamics (CFD) of amine absorption column with structured-packing for CO2 capture
Abstract The gas−liquid multiphase Eulerian computational fluid dynamics (CFD) model was used to investigate hydrodynamics and CO2 removal efficiency of a pilot-scale amine absorber with structured-packing. The structured-packing was represented by a porous media zone having porous resistance, gas−liquid interfacial drag force, and liquid dispersion force. This study aimed to find a reasonable way to identify four modification factors of the Ergun coefficient that determine the hydrodynamic characteristics of structured-packing. The two modification factors (a and b) for porous resistance were mainly related to the liquid holdup (hL) with respect to the liquid load. The other two factors (c and d) for gas−liquid interfacial drag force depended on the specific wet pressure drop (ΔPwet/L) versus the gas load factor. The hL and ΔPwet/L increased in parallel with the increase of a and c, respectively, while the slopes of hL and ΔPwet/L increased with b and d, respectively.
Post combustion CO2 capture by reactive absorption: Pilot plant description and results of systematic studies with MEA
Abstract Reactive absorption is one of the most promising technologies for post combustion CO2 capture (PCC). There is a need for methods and equipment that allow studying PCC efficiently on scales that are many orders of magnitude smaller than those of future installations in power plants. The present work describes in detail the set-up and operation of a pilot plant that is suited for that purpose. In that pilot plant the closed cycle of the absorption/desorption process is continuously operated (column diameters: 0.125 m, absorber/desorber packing height: 4.2/2.5 m, packing type: Sulzer Mellapak 250.Y™, flue gas flow rate: 30–110 kg/h, CO2 partial pressure: 35–135 mbar, solvent flow rate: 50–350 kg/h). The plant is equipped with high-end measuring instrumentation and is operated using an automated process control system. Sampling points allow the determination of the liquid phase concentration profiles in both columns. Two reference experiments that were carried out with an aqueous solution of 0.3 g/g monoethanolamine (MEA) are discussed in detail. The results give insight in the process behaviour in general and in the way such plants should be operated and how the evaluation of the results should be carried out. Based on comprehensive experimental studies with aqueous MEA solutions the influence of all important process parameters like CO2 partial pressure, CO2 removal rate, fluid dynamic load of the absorber, solvent flow rate, desorber pressure and solvent composition on the process behaviour is discussed in detail. These results allow a comprehensive understanding of the absorption/desorption process, which is important not only for the development of new tailor-made solvents but also for the design and operation of large scale plants. Furthermore the data establish a base line for comparisons with new solvents tested in the pilot plant and can be used for a validation of models of the PCC process with MEA.
Novel application of X-ray computed tomography : Determination of gas/liquid contact area and liquid holdup in structured packing
X-ray computed tomography (CT) was utilized to determine the effective wetted area and local liquid holdup for an air−water contactor containing structured packing. The experimental wetted area results were in agreement with results obtained from a traditional chemical absorption technique. The holdup varied significantly with vertical position. Areas near the joint region between adjacent packing elements exhibited holdup values greatly exceeding the values for holdup observed in the middle of the packing element. These findings will dramatically impact both design and model development for mass transfer devices containing structured packing