Thermogravimetric Characteristics and Non-isothermal Kinetics of Macro-Algae With an Emphasis on the Possible Partial Gasification at Higher Temperatures

Imtiaz Ali,Ali Bahadar

doi:10.3389/fenrg.2019.00007

Abstract

Pyrolysis of Turbinaria ornata was realised in a thermogravimetric analyzer. The process was crudely classified into primary and secondary reaction zones. In the primary reaction zone, the thermal decompositions of the low-thermal stable components produced volatiles and biochar. The solid products obtained from the primary decomposition reactions contained inorganics with heavy metals. At mild-to-high temperatures, the catalytic effects accompanied gasification using oxygen, which was partially supplied by the oxygen carriers present in the solids and evolved gases. In order to study the pyrolytic conversion, combined and multiple reaction schemes were employed. While the model-free methods helped to provide the accurate activation energies and the initial value of the pre-exponential factor, the non-linear regression optimized the chosen model parameters. In this study, a simple order-based model was compared with the versatile Sestak-Berggren (SB) model considering combined and multiple reactions. The application of a multiple reaction scheme to the primary and secondary reaction zones concluded that a simple order-based model suffices for the kinetic analysis. The secondary decomposition was shown to start with a high activation energy, which decreased appreciably when the conversion proceeded towards completion.

Highlights

The last few decades have seen an increase in the use of biofuels and high-value biochemicals derived from biomass
Secondary reaction zones (Zone II), initiated at 875 K, and the remaining mass was decomposed at a slower rate
The shifting of peaks is rendered to the slowing down of the pyrolysis process owing to the difficulty in the heat transfer from the surrounding to the sample for a shorter time and larger thermal lag (Shuping et al, 2010; Han et al, 2017; Özsin and Pütün, 2017)

Summary

Introduction

The last few decades have seen an increase in the use of biofuels and high-value biochemicals derived from biomass. Biomass is a renewable carbonaceous source, an alternative to fossil fuel, and a precursor of biochemicals. Non-food biomasses are widespread in nature and are cultivated at ∼100 billion tons annually (Sheldon, 2014). Biofuels are expected to satisfy around 10% of the global energy demand by 2035, and they have the potential to replace 27% of global transportation fuel by 2050. The main reason for the growing interest in the use of biomass, besides its renewable nature, is its carbon-neutral and less polluting characteristics. The Paris climate agreement requires clean energy transformation in order to reach net zero emissions by 2060, which can only be achieved by scaling-up efficient energy conversion systems to generate bio-energy with carbon capture and storage (BECCS) (Agency, 2017)

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Results

Conclusion