No abstract

A commercial activated carbon supplied by Norit, R2030CO2, was evaluated as CO 2 adsorbent under conditions relevant to post-combustion CO 2 capture (ambient pressure and diluted CO 2 ). It has been demonstrated that this carbon possesses sufficient CO 2 /N 2 selectivity in order to efficiently separate a binary mixture composed of 17 % CO 2 in N 2 . Moreover, this carbon was easily completely regenerated and it did not show capacity decay after ten consecutive cycles. Three different regeneration strategies were compared in a single-bed adsorption unit: temperature swing adsorption (TSA), vacuum swing adsorption (VSA) and a combination of them, vacuum and temperature swing adsorption (VTSA). Through a simple two step TSA cycle, CO 2 was concentrated from 17 to 43 % (vol). For the single-bed cycle configurations, the productivity and CO 2 recovery followed the sequence: TSA

Direct air capture (DAC) is an auspicious technology in pursuing negative CO2 emissions. A promising process is temperature vacuum swing adsorption (TVSA) employing amine functionalised adsorbents such as Lewatit® VP...

a b s t r a c tIn this study a commercial activated carbon (Norit R2030CO2) was assessed as a solid sorbent for precombustion CO 2 capture. This technology involves the removal of CO 2 from the shifted-syngas prior to the generation of electricity and the production of high-purity clean H 2 . The CO 2 equilibrium adsorption capacity and breakthrough time were evaluated in a flow-through system where the adsorbent was subjected to four consecutive adsorption-desorption cycles. A CO 2 /H 2 /N 2 gas mixture (20/70/10 vol.% at normal conditions) was employed as the influent gas stream. Response surface methodology (RSM) was used to assess the combined effect of the adsorption CO 2 partial pressure and temperature (independent variables) on CO 2 capture capacity and breakthrough time (response variables) for the activated carbon. The CO 2 partial pressure ranged from 1 to 3 bar within a total pressure range of 5-15 bar and a temperature range of 25-65 • C. No interaction effect between the two independent variables on the responses was found. The CO 2 partial pressure was observed to be the most influential variable, with high values leading to an increase in both the CO 2 capture capacity and the breakthrough time. However, an increase in the temperature led to a decrease in both response variables. The maximum values of the response variables within the experimental region studied were obtained at 25 • C and under a CO 2 partial pressure of 3 bar (15 bar total pressure).

We present experimentally measured adsorption isotherms of CO2, H2, and N2 on a phenol-formaldehyde resin-based activated carbon, which had been previously synthesized for the separation of CO2 in a precombustion capture process. The single component adsorption isotherms were measured in a magnetic suspension balance at three different temperatures (298, 318, and 338 K) and over a large range of pressures (from 0 to 3000-4000 kPa). These values cover the temperature and pressure conditions likely to be found in a precombustion capture scenario, where CO2 needs to be separated from a CO2/H2/N2 gas stream at high pressure (~1000-1500 kPa) and with a high CO2 concentration (~20-40 vol %). Data on the pure component isotherms were correlated using the Langmuir, Sips, and dual-site Langmuir (DSL) models, i.e., a two-, three-, and four-parameter model, respectively. By using the pure component isotherm fitting parameters, adsorption equilibrium was then predicted for multicomponent gas mixtures by the extended models. The DSL model was formulated considering the energetic site-matching concept, recently addressed in the literature. Experimental gas-mixture adsorption equilibrium data were calculated from breakthrough experiments conducted in a lab-scale fixed-bed reactor and compared with the predictions from the models. Breakthrough experiments were carried out at a temperature of 318 K and five different pressures (300, 500, 1000, 1500, and 2000 kPa) where two different CO2/H2/N2 gas mixtures were used as the feed gas in the adsorption step. The DSL model was found to be the one that most accurately predicted the CO2 adsorption equilibrium in the multicomponent mixture. The results presented in this work highlight the importance of performing experimental measurements of mixture adsorption equilibria, as they are of utmost importance to discriminate between models and to correctly select the one that most closely reflects the actual process.