87 research outputs found

    From waste to high value utilization of spent bleaching clay in synthesizing high-performance calcium-based sorbent for CO 2 capture

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    A novel calcium looping (CaL) process integrated with a spent bleaching clay (SBC) treatment is proposed whereby fuels and/or heat from regeneration of SBC provide extra energy for the calcination process, in addition, the regenerated SBC can be used to synthesize enhanced CaO-based sorbents. Different kinds of composite samples were prepared with the regenerated SBC and/or aluminate cement at various doping ratios via a pelletization process. All pellets were subjected to thermogravimetic analyzer tests employing severe reaction conditions to determine the optimal doping ratios and regeneration method for the SBC based sorbents. These results demonstrate that pellets containing combustible components showed higher CO2 uptakes, due to the improved pore structure, which was verified by N2 adsorption measurements. The as-prepared sorbent “L-10PC” (90 wt.% CaO/10 wt.% pyrolytic SBC) achieved a final CO2 uptake of 0.164 g(CO2) g(calcined sorbent)−1 after 20 cycles, which was 67.3% higher than that of natural limestone particle. A new larnite (Ca2SiO4) phase was detected by X-ray diffraction analysis, however the weak diffraction peak associated with it indicated a low content of larnite in the pellets, which produced a smaller effect on performance compared to cement. A synergistic effect was achieved for a sample designated as “L-5PC-10CA” (85 wt.% CaO/5 wt.% pyrolytic SBC /10 wt.% cement), which resulted in the highest final uptake of 0.208 g(CO2) g(calcined sorbent)−1 after 20 cycles. Considering the simplicity of pyrolysis regeneration process and the excellent capture capability of pellets doped by pyrolytic SBC, the proposed system integrating CaL with SBC pyrolysis treatment appears to offer particular promise for further development

    Self-activated, Nanostructured Composite for Improved CaL-CLC technology

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    The development of bifunctional CaO/CuO matrix composites with both high and stable reactivity is a research priority and key for the development of calcium looping integrated with chemical looping combustion (CaL-CLC), a new CO2 capture technology that eliminates the requirement for pure O2 for the regeneration of CaO-based sorbents. In this work, a simple but effective approach was first used, i.e., solution combustion synthesis (SCS), to produce various nanostructured CaO/CuO matrix composites with homogenous elemental distributions. All CaO/CuO matrix composites possessed increased CO2 uptake in the form of self-activation and excellent cyclically stable O2 carrying capacity over as many as 40 reaction cycles. For instance, the final carbonation conversion of CaO-CuO-1-800-30 was 51.3%, approximately 52.7% higher than that of the original material (33.6%). Here, the self-activation phenomenon have been observed for the first time in contrast to the rapid decay in CO2 uptake capacity previously reported, due mainly to the increase of both specific surface area and pore volume. In-situ X-ray diffraction (in-situ XRD) analysis revealed that no side reactions occurred between CaO/CaCO3 and CuO/Cu during the overall process. All of these results make CaO/CuO matrix composites an attractive candidate for CaL-CLC

    A facile one-pot synthesis of CaO/CuO hollow microspheres featuring highly porous shells for enhanced CO2 capture in combined Ca-Cu looping process via a template-free synthesis approach

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    The preparation of bifunctional CaO/CuO composites with high performance is essential for the development of the combined Ca–Cu looping process, in which the exothermic reduction of CuO with methane is used in situ to provide the heat required to calcine CaCO3. However, the rapid decline in CO2 uptake of CaO/CuO composites remains an important problem to be solved, despite their excellent redox characteristic. Herein we report a facile one-pot template-free synthesis approach to yield CaO/CuO hollow microspheres, aimed at enhancing the CO2 capture performance of CaO/CuO composites. CaO/CuO hollow microspheres feature highly porous shells and a homogeneous elemental distribution, and demonstrate significantly enhanced CO2 capture performance. After ten repeated cycles in a fixed-bed reactor, the CO2 uptake capacity of the best-performing CaO/CuO hollow microspheres exceeded that of the reference materials, i.e., CaO/CuO composites synthesized via wet mixing or a co-precipitation method, by 222% and 114%, respectively. Moreover, from cycle number eight onwards, the CO2 uptake was very stable over the tested 20 cycles, suggesting good cyclic stability of CaO/CuO hollow microspheres. Oxidation was always fast with O2 uptake capacities greater than 0.13 gO2 gmaterial−1. On the basis of N2 adsorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterizations, the significantly enhanced CO2 capture performance of the CaO/CuO hollow microspheres resulted from the unique hollow microsphere structure with highly porous shells, which were retained throughout the cyclic operations

    Effects of Blood Products on Inflammatory Response in Endothelial Cells In Vitro

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    BACKGROUND: Transfusing blood products may induce inflammatory reactions within the vascular compartment potentially leading to a systemic inflammatory response. Experiments were designed to assess the inflammatory potential of different blood products in an endothelial cell-based in vitro model and to compare baseline levels of potentially activating substances in transfusion products. METHODS: The inflammatory response from pre-activated (endotoxin-stimulated) and non-activated endothelial cells as well as neutrophil endothelial transmigration in response to packed red blood cells (PRBC), platelet concentrates (PC) and fresh frozen plasma (FFP) was determined. Baseline inflammatory mediator and lipid concentrations in blood products were evaluated. RESULTS: Following incubation with all blood products, an increased inflammatory mediator release from endothelial cells was observed. Platelet concentrates, and to a lesser extent also FFP, caused the most pronounced response, which was accentuated in already pre-stimulated endothelial cells. Inflammatory response of endothelial cells as well as blood product-induced migration of neutrophils through the endothelium was in good agreement with the lipid content of the according blood product. CONCLUSION: Within the group of different blood transfusion products both PC and FFP have a high inflammatory potential with regard to activation of endothelial cells. Inflammation upon blood product exposure is strongly accentuated when endothelial cells are pre-injured. High lipid contents in the respective blood products goes along with an accentuated inflammatory reaction from endothelial cells

    Characteristics of Copper-based Oxygen Carriers Supported on Calcium Aluminates for Chemical-Looping Combustion with Oxygen Uncoupling (CLOU)

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    Eight different oxygen carriers (OC) containing CuO (60 wt %) and different mass ratios of CaO to Al2O3 as the support were synthesized by wet-mixing followed by calcination at 1000 °C. The method of synthesis used involved the formation of calcium aluminum hydrate phases and ensured homogeneous mixing of the Ca2+ and Al3+ ions in the support at the molecular level. The performance of the OCs for up to 100 cycles of reduction and oxidation was evaluated in both a thermogravimetric analyzer (TGA) and a fluidized bed reactor, covering a temperature range of 800 to 950 °C. In these cycling experiments, complete conversion of the OC, from CuO to Cu and vice versa, was always achieved for all OCs. The reactivity of the materials was so high that no deactivation could be observed in the TGA, owing to mass transfer limitations. It was found that OCs prepared with a mass ratio of CaO to Al2O3 in the support >0.55 agglomerated in the fluidized bed, resulting in an apparent deactivation over 25 cycles for all temperatures investigated. High ratios of mass of CaO to Al2O3 in the support resulted in CuO interacting with CaO, forming mixed oxides that have low melting temperatures, and this explains the tendency of these materials to agglomerate. This behavior was not observed when the mass ratio of CaO to Al2O3 in the support was ≤0.55 and such materials showed excellent cyclic stability operating under redox conditions at temperatures as high as 950 °C.The authors thank Mohammad Ismail and Matthew Dunstan for helping with the XRD analysis and Alex Casabuena-Rodriguez and for helping with the SEM. This work was supported by the Engineering and Physical Sciences Research Council (EPSRC grant EP/I010912/1).This is the final version of the article. It first appeared from ACS via http://dx.doi.org/10.1021/acs.iecr.5b0117

    A critical assessment of the testing conditions of CaO-based CO2 sorbents

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    ISSN:0300-9467ISSN:1385-8947ISSN:1873-3212ISSN:0923-046

    Prospects of MgO-based sorbents for CO2 capture applications at high temperatures

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    MgO-based materials possess favorable thermodynamic properties that enable them to be used as CO2 sorbents in the temperature range of 300–550 °C — at least theoretically. MgO-based sorbents have seen a boost in activity since the discovery of molten alkali metal salt promoters, and yet, they practically remove CO2 from a gas stream efficiently only at very high pressures (p > 10 bar), rendering them suitable for precombustion, but not for postcombustion CO2 capture schemes. Most of the current performance assessments rely on measurements of the transition between MgO and MgCO3 (or Mg-double carbonates) rather than the ability of the sorbents to actually remove CO2 from a gas stream, which may be misleading regarding their practical use and application. Further, reliable thermodynamic data for sorbents involving Mg-double carbonates is missing, although these materials have large potential for industrial CO2 capture applications
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