3D Printed PEI Containing Adsorbents Supported by Carbon Nanostructures for Post-combustion Carbon Capture From Biomass Fired Power Plants

Processes that utilize solid adsorbents to capture CO2 are promising alternatives to state-of-art Amine based technologies for capturing CO2 from large point sources. Although the energy needs of solid sorbent-based processes are low, the process footprint and consequently the capital cost connected to its implementation can be large due to the relatively long cycle times needed to get the required purity and recovery of the CO2 product. To overcome this challenge, processes having structured adsorbents like laminates, monoliths etc. are needed due to their low pressure drop and better mass transfer characteristics. The aim of this multiscale study is to evaluate the process-based performance of a 3D printed sorbent containing polyethyleneimine (PEI) and multiwalled carbon nanotubes (MWCNT) for capturing CO2 from a biomass fired power plant flue gas. A 6-step vacuum swing adsorption (VSA) cycle was simulated and optimized using equilibrium and kinetics data obtained from volumetry and breakthrough experiments. The optimization study showed that it was possible to achieve purity values >95% and recovery values >90% from dry CO2 feed streams containing 10 and 15% CO2 respectively. The minimum specific energy values were 0.94 and 0.6 MJ/kg and maximum productivity values were 0.8 and 2.2 mol/m3 ads s, respectively, for the two scenarios.

Shrinking-Core Model Integrating to the Fluid-Dynamic Analysis of Fixed-Bed Adsorption Towers for H2S Removal from Natural Gas

Natural gas sweetening is an essential process within hydrocarbon processing operations, enabling compliance with product quality specifications, avoiding corrosion problems, and enabling environmental care. This process aims to remove hydrogen sulfide (H2S), carbon dioxide, or both contaminants. It can be carried out in fixed-bed adsorption towers, where iron oxide-based solid sorbent reacts with the H2S to produce iron sulfides. This study is set out to develop a fluid-dynamic model that allows calculating the pressure drop in the H2S adsorption towers with the novelty to integrate reactivity aspects, through an iron sulfide layer formation on the solid particles’ external skin. As a result of the layer formation, changes in the particle diameter and the bed void fraction of the solid sorbent tend to increase the pressure drop. The shrinking-core model and the H2S adsorption front variation in time support the model development. Experimental data on pressure drop at the laboratory scale and industrial scale allowed validating the proposed model. Moreover, the model estimates the bed replacement frequency, i.e., the time required to saturate the fixed bed, requiring its replacement or regeneration. The model can be used to design and formulate new solid sorbents, analyze adsorption towers already installed, and help maintenance-planning operations.

Experimental Characterization and Energy Performance Assessment of a Sorption-Enhanced Steam–Methane Reforming System

The production of blue hydrogen through sorption-enhanced processes has emerged as a suitable option to reduce greenhouse gas emissions. Sorption-enhanced steam–methane reforming (SESMR) is a process intensification of highly endothermic steam–methane reforming (SMR), ensured by in situ carbon capture through a solid sorbent, making hydrogen production efficient and more environmentally sustainable. In this study, a comprehensive energy model of SESMR was developed to carry out a detailed energy characterization of the process, with the aim of filling a current knowledge gap in the literature. The model was applied to a bench-scale multicycle SESMR/sorbent regeneration test to provide an energy insight into the process. Besides the experimental advantages of higher hydrogen concentration (90 mol% dry basis, 70 mol% wet basis) and performance of CO2 capture, the developed energy model demonstrated that SESMR allows for substantially complete energy self-sufficiency through the process. In comparison to SMR with the same process conditions (650 °C, 1 atm) performed in the same experimental rig, SESMR improved the energy efficiency by about 10%, further reducing energy needs.

Kinetics and Thermodynamic Modeling for CO2 Capture Using NiO Supported Activated Carbon by Temperature Swing Adsorption

Solid sorbent from functionalized activated carbon (AC) could enhance the adsorption capacity in CO2 capture. This study emphasizes cyclic CO2 capture using NiO functionalized AC. Different loadings of NiO impregnated on AC were synthesized. This work showed that the most efficient adsorbent of 0.05NiO/AC exhibits an adsorption capacity of 55.464 mg/g at the adsorption temperature of 30 °C by using the temperature swing adsorption method. A slight loss of adsorption capacity at 0.28 % for a five cycles CO2 capture indicated consistency potential for large scales application. The adsorbent exhibited a slightly lower surface area compared to AC, but the presence of NiO improved the adsorption capacity by chemisorption phenomena. The NiO acts as the basic site for CO2 capture. Meanwhile, AC as support could increase the surface area of active sites and reduce the sintering effect of the NiO. It was found that various adsorption temperatures had a good correlation with the pseudo-second-order kinetic model. The magnitude of the sorption process was evaluated by the activation energy of 48.09 kJ/mol, which implies a chemisorption process at various adsorption temperatures. Thermodynamic studies explained the CO2 adsorption process for this study was found to be a spontaneous and endothermic process.