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  1. Article ; Online: The Potential of Gas Switching Partial Oxidation Using Advanced Oxygen Carriers for Efficient H 2 Production with Inherent CO 2 Capture

    Carlos Arnaiz del Pozo / Schalk Cloete / Ángel Jiménez Álvaro / Felix Donat / Shahriar Amini

    Applied Sciences, Vol 11, Iss 4713, p

    2021  Volume 4713

    Abstract: The hydrogen economy has received resurging interest in recent years, as more countries commit to net-zero CO 2 emissions around the mid-century. “Blue” hydrogen from natural gas with CO 2 capture and storage (CCS) is one promising sustainable hydrogen ... ...

    Abstract The hydrogen economy has received resurging interest in recent years, as more countries commit to net-zero CO 2 emissions around the mid-century. “Blue” hydrogen from natural gas with CO 2 capture and storage (CCS) is one promising sustainable hydrogen supply option. Although conventional CO 2 capture imposes a large energy penalty, advanced process concepts using the chemical looping principle can produce blue hydrogen at efficiencies even exceeding the conventional steam methane reforming (SMR) process without CCS. One such configuration is gas switching reforming (GSR), which uses a Ni-based oxygen carrier material to catalyze the SMR reaction and efficiently supply the required process heat by combusting an off-gas fuel with integrated CO 2 capture. The present study investigates the potential of advanced La-Fe-based oxygen carrier materials to further increase this advantage using a gas switching partial oxidation (GSPOX) process. These materials can overcome the equilibrium limitations facing conventional catalytic SMR and achieve direct hydrogen production using a water-splitting reaction. Results showed that the GSPOX process can achieve mild efficiency improvements relative to GSR in the range of 0.6–4.1%-points, with the upper bound only achievable by large power and H 2 co-production plants employing a highly efficient power cycle. These performance gains and the avoidance of toxicity challenges posed by Ni-based oxygen carriers create a solid case for the further development of these advanced materials. If successful, results from this work indicate that GSPOX blue hydrogen plants can outperform an SMR benchmark with conventional CO 2 capture by more than 10%-points, both in terms of efficiency and CO 2 avoidance.
    Keywords H 2 -power cogeneration ; gas switching partial oxidation ; gas switching reforming ; CO 2 capture and storage ; steam methane reforming ; blue hydrogen ; Technology ; T ; Engineering (General). Civil engineering (General) ; TA1-2040 ; Biology (General) ; QH301-705.5 ; Physics ; QC1-999 ; Chemistry ; QD1-999
    Subject code 660
    Language English
    Publishing date 2021-05-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: Optimum Expanded Fraction for an Industrial, Collins-Based Nitrogen Liquefaction Cycle

    Carlos Arnaiz-del-Pozo / Ignacio López-Paniagua / Alberto López-Grande / Celina González-Fernández

    Entropy, Vol 22, Iss 959, p

    2020  Volume 959

    Abstract: Industrial nitrogen liquefaction cycles are based on the Collins topology but integrate variations. Several pressure levels with liquefaction to medium pressure and compressor–expander sets are common. The cycle must be designed aiming to minimise ... ...

    Abstract Industrial nitrogen liquefaction cycles are based on the Collins topology but integrate variations. Several pressure levels with liquefaction to medium pressure and compressor–expander sets are common. The cycle must be designed aiming to minimise specific power consumption rather than to maximise liquid yield. For these reasons, conclusions of general studies cannot be extrapolated directly. This article calculates the optimal share of total compressed flow to be expanded in an industrial Collins-based cycle for nitrogen liquefaction. Simulations in Unisim Design R451 using Peng Robinson EOS for nitrogen resulted in <math display="inline"><semantics><mrow><mn>88</mn><mo>%</mo></mrow></semantics></math> expanded flow, which is greater than the 75–80% for conventional Collins cycles with helium or other substances. Optimum specific compression work resulted <math display="inline"><semantics><mrow><mn>430</mn><mo>.</mo><mn>7</mn></mrow></semantics></math> kWh/ton of liquid nitrogen. For some operating conditions, the relation between liquid yield and specific power consumption was counterintuitive: larger yield entailed larger consumption. Exergy analysis showed <math display="inline"><semantics><mrow><mn>40</mn><mo>.</mo><mn>3</mn><mo>%</mo></mrow></semantics></math> exergy efficiency of the optimised process. The exergy destruction distribution and exergy flow across the cycle is provided. Approximately 40% of the <math display="inline"><semantics><mrow><mn>59</mn><mo>.</mo><mn>7</mn><mo>%</mo></mrow></semantics></math> exergy destruction takes place in the cooling after compression. This exergy could be used for secondary applications such as industrial heating, energy storage or for lower temperature applications as ...
    Keywords large-scale Collins cycle ; thermodynamic analysis ; exergy analysis ; optimisation ; nitrogen liquefaction ; exergy efficiency ; Science ; Q ; Astrophysics ; QB460-466 ; Physics ; QC1-999
    Subject code 511
    Language English
    Publishing date 2020-08-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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