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<p>Microalgae-based biomass offers a high-reactivity feedstock for thermochemical conversion due to its elevated volatile content and negligible lignin fraction. In this study, the thermo-chemical performance of Spirulina platensis and Chlorella vulgaris was investigated in a self -circulating fluidized bed gasifier under equivalence ratios (ER) ranging from 0.3 to 0.5, with emphasis on syngas evolution, thermal behavior, and energy conversion efficiency. Experiments conducted at reactor temperatures of 780–950&#xa0;°C revealed that hydrogen concentration decreased from 11.8 to 9.2&#xa0;vol% with increasing ER, while carbon monoxide peaked at 19.6&#xa0;vol% at ER = 0.4, indicating optimal partial oxidation conditions. Methane content declined from 4.5 to 3.2&#xa0;vol% due to enhanced thermal cracking and oxidation reactions. The maximum carbon conversion efficiency (92.8%) was achieved at ER = 0.5, whereas peak cold gas efficiency (71.4%) and syngas heating value (5.2&#xa0;MJ&#xa0;Nm<sup>−3</sup>) were obtained at ER = 0.4, demonstrating a trade-off between conversion completeness and energy retention. A three-dimensional CFD model was developed in ANSYS Fluent employing an Eulerian approach, k–ε turbulence closure, and species transport with finite-rate/eddy dissipation kinetics. The model incorporated key heterogeneous and homogeneous reactions governing gasification, along with coupled energy equations to resolve temperature distribution within the reactor. Simulated results exhibited strong agreement with experimental data, with deviations below 7.5%, and revealed axial temperature gradients influencing reaction pathways and gas composition. Thermal analysis indicated that the self-circulating configuration enhanced internal heat recirculation and reduced external energy demand, resulting in ~ 12–15% improvement in effective thermal efficiency compared to conventional fluidized systems. The results establish microalgae as a viable high-efficiency feedstock for syngas production and highlight the critical role of thermal behavior, reaction kinetics, and equivalence ratio in optimizing gasification performance.</p>

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Experimental and computational investigation of algae biomass gasification in a self-circulating fluidized bed reactor: effects of equivalence ratio on syngas yield, carbon conversion efficiency, and energy potential

  • 期刊论文

  • 发表日期：

    2026年7月24日

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  • S. Deepankumar,
  • Mohammod Hafizur Rahman,
  • N. Aravindan,
  • N. Saravanan,
  • Kaushal Kishore,
  • Barun Haldar

摘要

Microalgae-based biomass offers a high-reactivity feedstock for thermochemical conversion due to its elevated volatile content and negligible lignin fraction. In this study, the thermo-chemical performance of Spirulina platensis and Chlorella vulgaris was investigated in a self -circulating fluidized bed gasifier under equivalence ratios (ER) ranging from 0.3 to 0.5, with emphasis on syngas evolution, thermal behavior, and energy conversion efficiency. Experiments conducted at reactor temperatures of 780–950 °C revealed that hydrogen concentration decreased from 11.8 to 9.2 vol% with increasing ER, while carbon monoxide peaked at 19.6 vol% at ER = 0.4, indicating optimal partial oxidation conditions. Methane content declined from 4.5 to 3.2 vol% due to enhanced thermal cracking and oxidation reactions. The maximum carbon conversion efficiency (92.8%) was achieved at ER = 0.5, whereas peak cold gas efficiency (71.4%) and syngas heating value (5.2 MJ Nm−3) were obtained at ER = 0.4, demonstrating a trade-off between conversion completeness and energy retention. A three-dimensional CFD model was developed in ANSYS Fluent employing an Eulerian approach, k–ε turbulence closure, and species transport with finite-rate/eddy dissipation kinetics. The model incorporated key heterogeneous and homogeneous reactions governing gasification, along with coupled energy equations to resolve temperature distribution within the reactor. Simulated results exhibited strong agreement with experimental data, with deviations below 7.5%, and revealed axial temperature gradients influencing reaction pathways and gas composition. Thermal analysis indicated that the self-circulating configuration enhanced internal heat recirculation and reduced external energy demand, resulting in ~ 12–15% improvement in effective thermal efficiency compared to conventional fluidized systems. The results establish microalgae as a viable high-efficiency feedstock for syngas production and highlight the critical role of thermal behavior, reaction kinetics, and equivalence ratio in optimizing gasification performance.