Journal: ACS Engineering Au

Abbreviation

ACS Eng. Au

Publisher

American Chemical Society

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ISSN

2694-2488

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2021 - 20255
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Publications 1 - 5 of 5
  • Postcombustion CO2 Capture: A Comparative Techno-Economic Assessment of Three Technologies Using a Solvent, an Adsorbent, and a Membrane
    Item type: Journal Article
    Zanco, Stefano E.; Pérez Calvo, José Francisco; Gasós, Antonio; et al. (2021)
    ACS Engineering Au
    This work compares three postcombustion CO2 capture processes based on mature technologies for CO2 separation, namely, (i) absorption using an aqueous piperazine solution, (ii) adsorption using Zeolite 13X in conventional fixed beds (either vacuum swing adsorption or temperature swing adsorption), and (iii) multistage membrane separation using a polymeric material (with CO2/N2 selectivity of 50 and permeability for CO2 of 1700 GPU). All three capture plants are assumed to be retrofitted to a generic industrial CO2-emitting source with 12% CO2 v/v (with 95% relative humidity at the inlet temperature and pressure of 30 °C and 1.3 bar, respectively) to deliver CO2 at 96% purity. In the cases of adsorption and membranes, the flue gas is dried before feeding it to the CO2 capture unit. In a first step, the capture processes (i.e., components and design parameters) are optimized based on their technical performance, defined through process exergy requirement and plant productivity; exergy–productivity Pareto fronts are computed for varying CO2 recovery rates. Second, the economic performance of the processes is assessed through a cost analysis. Estimates of CO2 capture costs are provided for each process as a function of the plant size and CO2 recovery rate. The comparative assessment shows that, although the adsorption- and membrane-based processes analyzed may become cost competitive at the small scale (i.e., below sizes of 100 tons of flue gas processed per day) and low recovery rates (i.e., below ca. 40%), the absorption-based process considered is the most cost-effective option at most plant sizes and recovery rates.
  • Facile and Robust Production of Ultrastable Micrometer-Sized Foams
    Item type: Journal Article
    Rodriguez Hakim, Mariana; Oblak, Luka; Vermant, Jan (2023)
    ACS Engineering Au
    Stable foams that can resist disproportionation for extended periods of time have important applications in a wide range of technological and consumer materials. Yet, legislative initiatives limit the range of surface active materials that can be used for environmental impact reasons. There is a need for technologies to efficiently produce multiphase materials using more eco-friendly components, such as particles, and for which traditional thermodynamics-based processing routes are not necessarily efficient enough. This work describes an innovative foaming technology that can produce ultrastable Pickering-Ramsden foams, with bubbles of micrometer-sized dimensions, through pressure-induced particle densification. Specifically, aqueous nanosilica-stabilized foams are produced by foaming a suspension at subatmospheric pressures, allowing for adsorption of the particles onto large bubbles. This is followed by an increase back to atmospheric pressure, which induces bubble shrinkage and compresses the adsorbed particle interface, forming a strong elastoplastic network that provides mechanical resistance against disproportionation. The foam’s interfacial mechanical properties are quantified to predict the range of processing conditions needed to produce permanently stable foams, and a general stability criterion is derived by considering the interfacial rheological properties under slow, unidirectional compression. Foams that are stable against disproportionation are characterized by interfaces whose mechanical resistance to compressive deformations can withstand their tendency to minimize the interfacial stress by reducing their surface area. Our ultrastable nanosilica foams are tested in real-life applications by introducing them into concrete. In comparison to other commercial air entrainers, our microfoam improves concrete’s freeze–thaw resistance while supplying higher material strength, providing an economically attractive, industrially scalable, and durable alternative for use in real-life applications involving cementitious materials. The applicability of our stability criterion to other rheologically complex interfaces and the versatile nature of our foaming technology enables usage for a broad class of materials, beyond the construction industry.
  • Design and Optimization of Hierarchically Ordered Porous Structures for Solar Thermochemical Fuel Production Using a Voxel-Based Monte Carlo Ray-Tracing Algorithm
    Item type: Journal Article
    Sas Brunser, Sebastian; Steinfeld, Aldo (2023)
    ACS Engineering Au
    Porous structures can be favorably used in solar thermochemical reactors for the volumetric absorption of concentrated solar radiation. In contrast to isotropic porous topologies, hierarchically ordered porous topologies with stepwise optical thickness enable a more homogeneous radiative absorption within the entire volume, leading to a higher and more uniform tempera-ture distribution and, consequently, a higher solar fuel yield. However, their design and optimization require fast and accu-rate numerical tools for solving the radiative exchange at the pore level within their complex topologies. Here we present a novel voxel-based Monte-Carlo ray-tracing algorithm that discretizes the pore-level domain into a 3D binary digital represen-tation of solid/void voxels. These are exposed to stochastic rays undergoing reflection, absorption, and re-emission at the ray-solid intersection found by querying the voxel value along the ray path. Temperature distributions are found at radiative equilibrium. The algorithm’s fast execution allows its use in a gradient-free optimization scheme. Three hierarchically or-dered topologies with parametrized shapes (square grids, Voronoi cells, and sphere lattices) exposed to 1000 suns radiative flux are optimized for maximum solar fuel production based on the thermodynamics of a ceria-based thermochemical redox cycle for splitting H2O and CO2. The optimized graded-channeled structure with square grids achieves a 4-fold increase in the volume-specific fuel yield compared to the value obtained for an isotropic reticulated porous structure.
  • One Mixture to Rule Them All: Enhancing Efficiency and Standardization of Industrial High-Temperature Heat Pumps
    Item type: Journal Article
    Widmaier, Philip Karl; Brendel, Leon P.M.; Bertsch, Stefan S.; et al. (2025)
    ACS Engineering Au
    High-temperature heat pumps are preferred for decarbonizing many industrial processes, but are still being adopted slowly. Major barriers to adoption are low efficiency, leading to high operational cost, and the need for custom-made designs, increasing investment cost. In this work, refrigerant mixtures are exploited to overcome these barriers for high-temperature heat pump adoption. Mixtures have been known to improve heat pump efficiency if their nonisothermal phase change is matched to heat source and sink temperature changes. Beyond that, we improve standardization by using mixture composition as an additional degree of freedom to tailor a standard heat pump designed for a specific refrigerant pair to various applications. By model-band screening of 703 refrigerant pairs across 81 combinations of heat source and sink temperature changes, we identify a maximum COP advantage of 26% for a refrigerant mixture when the maximum heat source and sink temperature changes of 40 K occur. Several mixtures are identified yielding near-optimal efficiencies across all 81 heat source and sink temperature changes. The best all-rounder mixture, diethyl ether/cyclopropane, retains, on average, 97% efficiency of the individually optimal mixtures. These findings support the development of more efficient and less costly high-temperature heat pumps, a crucial step in the heat transition.
  • Deciphering and Mitigating Failure Mechanisms in Poly(ether Imide) Corrosion Protection Coatings for Automotive Light-Weighting
    Item type: Journal Article
    Sill, Tiffany E.; Cantrell, Joseph K.; Ponce, Victor; et al. (2025)
    ACS Engineering Au
    Corrosion represents a key impediment to the greater adoption of light metal alloys as alternatives to automotive steels in vehicular applications. Thin nanocomposite coatings generate considerable interest for their potential in aluminum alloy corrosion protection, which is challenging due to the lack of conventional protection mechanisms that are available for other metals. Here, we investigate the thickness-dependent corrosion protection afforded to AA 7075 substrates by poly(ether imide)-based (PEI) coatings. Using electrochemical impedance spectroscopy to monitor ion transport, we observe that with increasing coating thickness, PEI more effectively sequesters ions and enforces permeation selectivity, thereby precluding deleterious substitution processes that dissolve corrosion products. We further explore thickness-dependent modifications to the PEI matrix by incorporation of unfunctionalized exfoliated graphite (UFG) particles to control diffusion processes and co-polymerization with siloxane to manipulate permeation selectivity. Incorporation of UFG platelets can degrade corrosion protection through galvanic coupling with the substrate and enhanced interfacial ion diffusion at lower coating thicknesses. However, interphase development mediated by hydration, network relaxation, and thermal displacement of PEI chains yields a rigid matrix that enhances permeation selectivity and imbues extended tortuosity. This combination results in superior corrosion protection for thicker PEI coatings with embedded UFG platelets under aggressive accelerated corrosion testing conditions. Siloxane co-polymerization, while weakening interfacial adhesion to AA 7075 substrates, facilitates the sequestration of solubilized corrosion products within the matrix under appropriate processing conditions. The results illustrate the importance of understanding the dynamical evolution of polymer secondary structure under aggressive accelerated corrosion testing conditions, point to the specific role of secondary structure and interphasic domains in enforcing permeation selectivity, and establish fundamental thickness limits for retaining effective barrier protection.
Publications 1 - 5 of 5