Energy Systems Engineering / Enerji Sistemleri Mühendisliği

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  • Article
    Citation - WoS: 8
    Citation - Scopus: 6
    Effect of external electric field on fluidization of rodlike particles using CFD-DEM
    (American Chemical Society, 2024) Kazemi, Saman; Aali, Hamed; Larijani, Roxana Saghafian; Zarghami, Reza; Liu, Helei; Mostoufi, Navid
    Given the significant impact of an external electric field on fluidized bed hydrodynamics and the practical importance of rodlike particles, this study examines the behavior of a fluidized bed containing rodlike particles under various external electric fields. Simulations were performed using a coupled computational fluid dynamics-discrete element method, and rodlike particles were generated using a multisphere approach aided by quaternions. The effect of different vertical and horizontal external electric fields on the orientation of particles was investigated. Also, the effect of particle size on their orientation in the presence of constant vertical and horizontal external electric fields was explored in this work. The results showed that increasing the electric field strength and reducing the size of rodlike particles lead to an increment in the tendency of particles to become oriented along the direction of the electric field. Moreover, the effect of the external electric field at various inlet gas velocities on the probability distribution of the porosity in the bed was studied. Finally, the effect of vertical and horizontal electric fields on the bubble diameter was examined. This study offers a deeper understanding of the fluidization of rodlike particles in the presence of an electric field, and its findings can be applied to design and optimize related processes.
  • Article
    Citation - WoS: 13
    Citation - Scopus: 14
    Perspectives of Biomass Catalytic Fast Pyrolysis for Co-Refining: Review and Correlation of Literature Data From Continuously Operated Setups
    (American Chemical Society, 2022) Prins, Wolter; Yıldız, Güray
    For the co-processing of pyrolysis-based biocrudes within petroleum refineries, a degree of conditioning/upgrading involving the cracking of the oligomers and (partial) removal of oxygen could be operationally beneficial. By inducing a complex set of reactions in biomass-derived fast pyrolysis vapors, catalytic fast pyrolysis (CFP) ensures significant changes in oxygen functionalities and alleviates oxygen concentration in the resulting liquid intermediate (CFP-oil). Due to its reduced oxygen content and acidity, CFP-oil could be considered suitable for co-feeding in FCC units and/or for co-hydrotreatment (co-HT) with gas oils within the existing crude oil processing infrastructure. On the operational side, however, research concerning CFP of biomass has shown poor results: deoxygenation of pyrolysis vapors goes along with a progressive reduction in CFP-oil yield. Apart from any control over catalyst activity, selectivity, and lifetime, the other critical issue is in the process design, which is complicated by rapid catalyst deactivation through coke formation and catalyst poisoning by biomass-originated minerals. This review analyzes the outcome of research efforts concerning in- and ex situ CFP of biomass based on carefully selected literature studies reporting the results obtained from meso- and macrolevel laboratory-scale setups, pilot, process development units (PDU), and (semi-) commercial process units, wherein the biomass feedstock and catalyst is fed continuously. Key operational aspects such as the reactor technology, reactive medium, processing mode, and optimization of process parameters are addressed. The performances of continuously operated CFP units were benchmarked through a comparison of yields and elemental compositions of (by-)products. Despite the considerable research efforts related to CFP technology development, the co-processing of CFP-oil is still in its infancy. However, in close collaboration with refinery professionals, it could be made a serious candidate for biobased co-feeding. For refinery integration, quality parameters of CFP-oil, e.g., acidity, stability, and miscibility, should be considered as crucial as its oxygen content.
  • Article
    Citation - WoS: 8
    Citation - Scopus: 10
    Spray Analysis of Biodiesels Derived From Various Biomass Resources in a Constant Volume Spray Chamber
    (American Chemical Society, 2022) Ulu, Anılcan; Yıldız, Güray; Rodriguez, Alvaro Diez; Özkol, Ünver
    This research aimed to analyze the spray characteristics of various biodiesels, which have rarely been investigated in terms of spray analysis in the literature compared to fossil diesel. For this purpose, four different methyl ester-type biodiesels were produced from canola, corn, cottonseed, and sunflower oils. These feedstocks were selected due to their wide availability in Turkey and being among the significant resources for biodiesel production. Measured physical properties of biodiesel samples showed that biodiesel fuels had, on average, 1.7 to 1.9 times higher viscosities, 5.3 to 6.6% larger densities, and 37 to 39.1% higher contact angle values than the reference diesel fuel. Spray characteristics of all fuels were experimentally examined in a constant volume spray chamber under chamber pressures of 0, 5, 10, and 15 bar and injection pressures of 600, 800, and 1000 bar. All tested biodiesels performed, on average, 3 to 20% longer spray penetration lengths, 5 to 30% narrower spray cone angles, and 5-18% lesser spray areas than the reference diesel fuel under chamber pressures of 5 and 10 bar. No significant differences occurred at 15 bar ambient pressure between biodiesels and diesel. In addition, analytical and empirical predictions showed that biodiesels had around 21.2-35.1% larger SMD values and approximately 7% lower air entrainment.
  • Article
    Citation - WoS: 15
    Citation - Scopus: 19
    Ex Situ Catalytic Fast Pyrolysis of Lignin-Rich Digested Stillage Over Na/Zsm-5, H/Zsm-5, and Fe/Zsm-5
    (American Chemical Society, 2020) Priharto, Neil; Ghysels, Stef; Opsomer, Wim; Ronsse, Frederik; Prins, Wolter; Pala, Mehmet; Yıldız, Güray
    The global increase in lignocellulosic ethanol production goes in tandem with an increase in lignin-rich stillage that remains underutilized to date. Anaerobic digestion could valorize residual (biodegradable) organic fractions into biogas, leaving a lignin-rich digested stillage (LRDS). This LRDS from the lignocellulosic ethanol production has been assessed as a feedstock for slow and fast pyrolysis in earlier studies, with the intention to increase the overall output of useful products or energy carriers from the starting material. While using this lignin-rich feedstock, ex situ catalytic vapor-phase upgrading (VPU) of fast pyrolysis vapors with fractional condensation was conducted over Na/ZSM-5, H/ZSM-5, and Fe/ZSM-5 catalysts. Semicontinuous fast pyrolysis experiments have been carried out at a reaction temperature of 480 degrees C in a mechanically stirred sand bed, which was connected directly to a fixed bed of catalyst particles for ex situ upgrading of the fast pyrolysis vapors. The carbon and mass yields in heavy phase liquids decreased after catalytic VPU (mass: ca. 8-11 wt %; carbon: ca. 11-15 wt %), compared to noncatalytic pyrolysis (mass: ca. 18 wt %; carbon: ca. 23 wt %). However, the yield in specific compounds, that is, alkylphenols and aromatics such as BTX, increased much upon catalytic VPU (especially for Fe/ZSM-5). For Fe/ZSM-5, the concentration in alkylphenols and aromatics was 20.8 wt % on liquid basis and the yield was 1.7 wt % on as-received (a.r.) feedstock basis. For noncatalytic pyrolysis, the concentration in alkylphenols and aromatics was 2.1 wt % (liquid basis) with a yield of 0.4 wt % (a.r. feedstock basis). This study thus demonstrates the potential of (modified) catalysts to upgrade lignin pyrolysis vapors.