Effects of H2S Loading Rate on the Performance of Reactive Absorption with Electrochemical Oxidation

The odor released from environmental facilities is recognized as a major problem in environmental industries. In this study, reactive absorption, using an electrolyzed water solution (electrolyzed water scrubber, EWS), was developed to treat the odorous gases H2S and NH3, which are representative odorous substances. In addition, a numerical model composed of mass transfer coefficients and zero-order kinetic constants was established to predict the performance of EWS. The model was verified through experiments and data fittings. In the experiments, the concentration of H2S varied from 500 to 2000 ppm, while NH3 was fixed at 500 ppm. The results revealed that the H2S removal rate varied depending on the inlet H2S concentration, but no changes were observed for NH3. The numerical model appropriately described the experimental results to further predict the performance of EWS. The model prediction results for the shock loading of H2S indicated that a 100% removal rate can be achieved by increasing the current density to 70 mA cm−2 or higher. Finally, the EWS can be used to reduce the odor, owing to its flexible operation that responds to fluctuating loading rates.

Short-cut Method for Assessing Solvents for Gas Cleaning by Reactive Absorption

A new short-cut method (NoVa) for assessing solvents for gas cleaning by reactive absorption is presented. It considers the absorption / desorption cycle using the assumption of infinite number of stages in both columns. For a given feed and removal rate, the method yields an estimate for the specific regeneration energy q as a function of the solvent circulation rate L/G. The sole solvent-dependent input consists of two correlations describing the gas solubility at absorber and desorber conditions and estimates of caloric properties. Furthermore, a simple equation (SolSOFT) for correlating the gas solubility as a function of the gas loading of the solvent is presented. A theoretical analysis of the process reveals general properties of the dependency of q on L/G. The NoVa method is described and tested using amine-based solvents for post combustion carbon capture as examples.

Physicochemical Properties of the System N,N-Dimethyl-dipropylene-diamino-triacetonediamine (EvA34), Water, and Carbon Dioxide for Reactive Absorption

Aqueous solutions of N,N-dimethyl-dipropylene-diamino-triacetonediamine (EvA34)are promising solvents for CO2 capture. Therefore, in the present work, a compre-hensive experimental study was carried out to determine data on physico-chemicalproperties of EvA34 and its mixtures with H2O and CO2. The liquid density and thedynamic viscosity was studied for pure EvA34, as well as for unloaded and CO2-loaded aqueous solutions of EvA34. The liquid heat capacity was studied for pure EvA34and unloaded aqueous solutions of EvA34. Furthermore, data on the vapor pressure ofpure EvA34 was recorded. The pH-value was measured for unloaded and CO2-loadedaqueous solutions of EvA34 and the dissociation constants of EvA34 were determinedfrom titration curves. Moreover, data on the solubility of CO2 in aqueous solutions ofEvA34 and data on the CO2-containing species in the liquid phase of these solutionswere recorded. Most of the new data was taken at temperatures between 293 and 393K. The mass fraction of EvA34 in the unloaded aqueous solutions was either ~ w0EvA34= 0.1 g/g or ~ w0EvA34 = 0.4 g/g. The CO2-loading was up to ~?CO2 = 6.2 mol/mol. Thenew data were compared to corresponding data of two standard amines that are usedfor CO2 capture: monoethanolamine (MEA) and a blend of methyl-diethanolamineand piperazine (MDEA/PZ). The comparison revealed that EvA34 combines favorableproperties of MEA and MDEA/PZ in one molecule.

NMR Spectroscopic Method for Studying Homogenous Liquid Phase Reaction Kinetics in Systems used in Reactive Gas Absorption and Application to Monoethanolamine-water-carbon Dioxide

An NMR spectroscopic method for measuring homogenous liquid phase reaction kinetics in systems that are used in reactive gas absorption processes is presented. In the kinetic experiment, carbon dioxide loaded and unloaded aqueous amine solutions are mixed such that no gas phase is involved. This procedure enables studying liquid phase reaction kinetics without the influence of the kinetics of the physical absorption process. A rapid-mixing NMR flow cell is used for the measurements, which are carried out in stopped-flow mode. 1H NMR spectra are taken at short intervals to monitor the kinetic process. The cell is liquid thermostatted and pressure resistant, such that a wide range of conditions can be studied. The new method was used for studying reaction kinetics in the system monoethanolamine (MEA)–water (H2O)–carbon dioxide (CO2) at temperatures between 293 and 333 K. From the data, information on the kinetics of the reaction of MEA with bicarbonate (HCO3-) to form MEA carbamate was obtained. That reaction was investigated for the first time in the present work without using bicarbonate salts. An Arrhenius model was fitted to the new data. The formation of MEA carbamate from MEA and HCO3- is often neglected in models for describing the reactive absorption of CO2 with aqueous MEA solutions. A process simulation study carried out in the present work reveals that it should be taken into account in predictions of reactive absorption processes that are operated under elevated pressure with a high mole fraction of CO2 in the gaseous phase.

Influence of five model parameters on the performance of a CO2 absorber column by a loaded aqueous MEA solution

Rigorous packed-bed absorber modeling and simulation are significant for post-combustion CO2 capture processes design. Hence, a good knowledge and judicious selection of model parameters are essential to ensure reliable predictions. In this paper, the reactive absorption of CO2 into loaded aqueous monoethanolamine solution was modeled, furthermore, the effects of five different parameters (kinetic model, enhancement factor, enthalpy of absorption, CO2 diffusivity, and vapor pressure) were investigated. Finally, this study revealed that some model parameters have a large influence on the column performance, contrary to others. In addition, methods and correlations that generally provide more accurate predictions of the empirical data relative to the other cases involved in this research were determined for each model parameter. It was also found that the model deviation was reduced by 18% and 4% for the liquid temperature and liquids CO2 loading profiles, respectively, while comparing between the worst and the best case.