Carlos A. Grande, Richard Blom, Andreas Möller, Jens Möllmer
High-pressure separation of CH4/CO2 using activated carbon,
Chemical Engineering Science, 89 (2013) 10–20.
Activated carbon was evaluated as selective adsorbent for separation of CO2 from CO2/CH4 mixtures with special focus on high pressure applications. Binary adsorption equilibrium measurements and binary breakthrough curves with mixtures of 10 and 20% CO2 balanced with CH4 were carried out at three different pressures: 500, 2500 and 5000 kPa. A 1D mathematical model including mass, energy and momentum transport was used to describe the curves using a non-ideal gas behavior equation.
CO2 is more selectively adsorbed than CH4 in the activated carbon used in this study. The binary adsorption capacity obtained from binary breakthrough curves could only be well described by the Sips model. In all breakthrough curves, a small effect of the film mass transfer could be observed, particularly at higher pressures where this effect is more pronounced. The significant adsorption of CH4 may limit the application of this adsorbent for natural gas upgrading.
M. Bastos-Neto, A. Moeller, J. Böhm, R. Gläser, R. Staudt,
Breakthrough Curves of Methane at High Pressures for H2 Purification Processes,
Chemie Ingenieur Technik 2011, 83, No. 1–2, 183–190.
This work provides a series of methane adsorption isotherms and breakthrough curves on one 5A zeolite and one activated carbon. Breakthrough curves of CH4 were obtained from dynamic column measurements at different temperature and pressure conditions for concentrations of 4.4 – 17.3 mol.-% in H2/CH4 mixtures. A simple model was developed to simulate the curves using measured and calculated data inputs. The results show that the model predictions agree very well with the experiments.
|M. Bastos-Neto, A. Moeller, R. Staudt, J. Böhm, R. Gläser,
Adsorption Measurements of Nitrogen and Methane in Hydrogen-Rich Mixtures at High Pressures
Ind. Eng. Chem. Res. 2011, 50, 10211–10221. •
The separation of nitrogen and methane from hydrogen-rich mixtures is systematically investigated on a recently developed binder-free zeolite 5A. For this adsorbent, the present work provides a series of experimental data on adsorption isotherms and breakthrough curves of nitrogen and methane, as well as their mixtures in hydrogen. Isotherms were measured at temperatures of 283–313 K and pressures of up to 1.0 MPa. Breakthrough curves of CH4, N2, and CH4/N2 in H2 were obtained at temperatures of 300–305 K and pressures ranging from 0.1 to 6.05 MPa with different feed concentrations. An LDF-based model was developed to predict breakthrough curves using measured and calculated data as inputs. The number of parameters and the use of correlations were restricted to focus on the importance of measured values. For the given assumptions, the results show that the model predictions agree satisfactorily with the experiments under the different operating conditions applied.
M. Bastos-Neto, A. Moeller, R. Staudt, J. Böhm, R. Gläser,
Dynamic bed measurements of CO adsorption on microporous adsorbents at high pressures for hydrogen purification processes, Separation and Purification Technology 77 (2011) 251–260.
Regarding the importance of adsorptive removal of carbon monoxide from hydrogen-rich mixtures for novel applications (e.g. fuel cells), this work provides a series of experimental data on adsorption isotherms and breakthrough curves of carbon monoxide. Three recently developed 5A zeolites and one commercial activated carbon were used as adsorbents. Isotherms were measured gravimetrically at temperatures of 278–313 K and pressures up to 0.85 MPa. Breakthrough curves of CO were obtained from dynamic column measurements at temperatures of 298–301 K, pressures ranging from 0.1 MPa to ca. 6 MPa and concentrations of CO in H2/CO mixtures of 5–17.5 mol%. A simple mathematical model was developed to simulate breakthrough curves on adsorbent beds using measured and calculated data as inputs. The number of parameters and the use of correlations to evaluate them were restricted in order to focus the importance of measured values. For the given assumptions and simplifications, the results show that the model predictions agree satisfactorily with the experimental data at the different operating conditions applied.
A. Möller, R. Eschrich, C. Reichenbach, J. Guderian, M. Lange, J. Möllmer,
Dynamic and equilibrium-based investigations of CO2-removal from CH4-rich gas mixtures on microporous adsorbents
The removal of CO2 from CH4-rich gas mixtures is one of the key technologies for CH4-production and purification (Silva et al., Microporous Mesoporous Mat 158:219, 2012; 187:100, 2014). For this purpose, different techniques like adsorption on porous solids, membrane technologies or absorptive methods are employed (Scholes et al., Fuel 96:15, 2012; Sridhar et al., Sep Purific Rev, 2007). In any case, the appropriate separation technique as well as the optimal separation active material must be found. However, the choice of the optimal ensemble depends on many parameters, particularly CO2-concentration, the presence of other components i.e., water, the content of higher hydrocarbons, the pressure of the raw gas and the gas throughput (Andriani et al., Appl Biochem Biotechnol 172:4, 2014). In this work the focus is put on adsorption technologies. Therefore, three different commercially available adsorbents were investigated in the context of their applicability in separation processes by adsorption. One zeolite, a commercial activated carbon and a carbon molecular sieve were chosen as adsorbents. The classification of the materials is based on the characterization with N2 at 77 K, a series of adsorption isotherms and breakthrough curves (CO2 in the presence of CH4). Isotherms were measured by a volumetric method at temperatures of 293–333 K and pressures up to 2 MPa. Due to very long equilibration times in case of CH4 on the carbon molecular sieve, isotherm data for 313–353 K up to 1 MPa were taken from reference (Möller et al., Chem. Ing. Tech 86:1–2, 2014). Dynamic experiments were carried out with a ternary mixture of He/CH4/CO2 (molar fractions: 0.80/0.15/0.05) at 0.5 MPa and 293 K. A simplified mathematical model, based on massand energy balances, was applied to simulate breakthrough curves on packed adsorbent beds. The suitability of the investigated adsorbents for CO2-removal by adsorption was classified with the help of the obtained experimental data. It can be shown, that an evaluation of the separation performance of such materials, based only on textural parameters like the BET surface area or N2-isotherms at 77 K is limited in its confidence and can cause a substantial misinterpretation of the whole separation process.