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Lekse, Jonathan

Publications and source records attributed to Lekse, Jonathan.

15 records
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DOE OSTI2024

Co-gasification of Plastic, Coal Waste and Biomass for Hydrogen Rich Syngas Production

Plastic waste has increasingly become one of the most pressing environmental issues. To mitigate plastic emissions, extraordinary efforts are needed for plastic waste recycling and management. This study investigates the co-gasification of plastic, coal refuse, and biomass into hydrogen-rich syngas through steam gasification. The study focuses on the correlations between process parameters and feedstock composition. Coal refuse and biomass are used as co-feedstocks for gasification, aiming to improve the handling of plastic waste and investigating their synergistic effects on product distribution.

Bashir, Muhammad↗
DOE OSTI2024

From Plastic Waste to Fuel: Pyrolysis and Gasification of Polyethylene for Hydrogen Production

Thermochemical conversion processes offer promising solutions to address the plastic pollution crisis by transforming plastic waste into valuable products, notably hydrogen. In this study, thermal pyrolysis and steam gasification of polyethylene (PE), the most abundantly produced plastic waste, are investigated in a drop tube reactor system. Various process parameters, namely temperature, residence time, and feedstock composition, are evaluated to establish their correlations with reaction performance. Coal refuse, obtained from discarded thickener underflow in coal processing, is introduced as a co-feedstock for gasification to enhance PE handling and examine synergistic effects on product distribution, particularly H2 yield and syngas quality. Furthermore, the potential of low-cost, environmentally friendly catalysts (i.e., iron oxides, coal ash) for tar reforming is explored.

Natesakhawat, Sittichai↗
DOE OSTI2024

Factors that Impact the Redox Kinetics Associated with Sr1-xAxFeO3 (A = Ca, Ba) in Air Separations Technologies

Perovskite oxides, including SrFeO3-δ, have garnered significant interest for their impressive oxygen storage thermodynamics and kinetics. While traditional oxygen production is performed through cryogenic separation methods at the industrial scale, oxygen carrier-based separations have offered an attractive alternative at the modular scale. Perovskites are considered ideal oxygen carriers, with their structural flexibility minimizing both the thermodynamic barrier and the structural strain related to the oxygen uptake/release cycle. Our latest work has identified a few major factors that directly impact the oxygen release thermodynamics and kinetics for Sr1-xAxFeO3-δ (A = Ca, Ba) materials including elemental composition, crystallographic symmetry, surface area, and pretreatment conditions. This presentation will discuss these factors using Sr1¬-xCaxFeO3 and Ba1-xSrxFeO3 to illustrate their individual and collective impacts on the design of high-performance oxygen carriers when operating at 300-700 °C. Additionally, we will discuss how each of these factors can be leveraged for the numerous catalytic applications also dependent on the redox properties of mixed metal oxides.

Popczun, Eric↗
DOE OSTI2024

Ba₁₋ₓSrₓFeO₃₋ᵧ as an Improved Oxygen Carrier for Chemical Looping Air Separation: A Computational and Experimental Study

Chemical looping air separation (CLAS) is a promising method to generate pure carbon-dioxide from fuel combustion with a pure oxygen stream, which is produced through the capture, and targeted release, of oxygen from the atmosphere using a solid oxide carrier. The performance of this process depends on the redox characteristics of the oxide carrier. Using experimental oxygen-temperature-programmed desorption (TPD) and thermogravimetric analysis (TGA), the study shows that Ba₀․₇₅Sr₀․₂₅FeO₃ has improved oxygen storage capacity (OSC), oxidation, and reduction kinetics over pristine SrFeO₃ at temperatures ranging from 300-500 °C. The redox energetics computed by using first-principles density functional theory (DFT) calculations also depict the measured trend establishing it as an important descriptor of the measured performance. The Ba₁₋ₓSrₓFeO₃₋ᵧ depicts a Sr-substitution and oxygen stoichiometry induced structural phase transition from hexagonal at low temperatures to pseudo-cubic phase with higher OSC up to T=400 °C. Also, the mechanism leading to this structural phase transition is identified by performing electronic and vibrational structural calculations. This presentation was given on March 8, 2024 at the APS March Meeting in Minneapolis, MN.

Acharya, Shree Ram↗
DOE OSTI2022

Gasification of Waste Plastic to Enable a Circular Economy: Literature Review Focusing on H2/Syngas Production

This report briefly reviews 1) the physicochemical properties of feedstocks; 2) hydrogen/syngas production from plastic gasification and co-gasification of plastic with coal and/or biomass, including the discussions on effects of operating conditions on H2 production; and 3) the mechanism of plastic gasification, including the formation and decomposition of char/tar during gasification process.

Shi, Fan↗
DOE OSTI2022

Co-Gasification of Waste Plastic and Coal Refuse for Thermochemical Upcycling

This study investigated behavior of different mixtures of waste plastics and coal refuse and their potential synergy in steam co-gasification. Co-gasification is an interesting alternative technology to recycle under-utilized waste streams and generate syngas that can be used to produce energy and valuable fuels/chemicals.

Means, Nicholas C.↗
DOE OSTI2022

Effect of Multiple Oxygen Vacancies on the Optical and Thermodynamic Properties of La 0.75 Sr 0.25 Co 0.25 Fe 0.75 O 3-δ Perovskite

We report the oxygen vacancy concentration of perovskite changes with the work condition in applications such as oxygen carriers and oxygen sensors. To explore the effect of multiple oxygen vacancies on the optical and thermodynamic properties, we perform first-principles calculations to investigate the formation of multiple oxygen vacancies in the paramagnetic La 0.75 Sr 0.25 Co 0.25 Fe 0.75 O 3-δ . Our results show that the higher VO concentration in La 0.75 Sr 0.25 Co 0.25 Fe 0.75 O 3-δ occurs at the conditions of higher temperatures and lower oxygen partial pressures. The electrons liberated upon oxygen vacancy formation are partially localized on the nearby Fe/Co sites and partially delocalized through the lattice, with the result that the unoccupied Fe/Co states near the Fermi level decrease and the Fermi level shows an upward shift. From the results of optical absorption, the peaks from 250 to 600 nm are weakened and blue-shifted with increase of oxygen vacancy concentration, due to the decrease of empty Fe states and an upward shift of the Fermi level. The obvious change of optical absorption with oxygen vacancy concentration indicates that La 0.75 Sr 0.25 Co 0.25 Fe 0.75 O 3-δ could be a good candidate for optical oxygen sensors in the visible spectrum.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Oxygen Production for Gasification

<span style="color: rgb(8, 7, 7);">Presentation on Task 5 for Gasification Virtual Project Review Meeting September 2-3, 2020</span>

Lekse, Jonathan↗