Kinetic and thermodynamic study of finger millet straw pyrolysis through thermogravimetric analysis

Co-pyrolysis of biomass and polyethylene: Insights into characteristics, kinetic and evolution paths of the reaction process

Investigation on the distribution and mechanism of co-pyrolysis products is vital to the directional control and high-value utilization of agriculture solid wastes. Co-pyrolysis, devolatilization, kinetics characteristics, and evolution paths of corn stalk (CS) and low-density-polyethylene (LDPE) were investigated via thermogravimetric experiments. The co-pyrolysis behaviors could be separated into two stages: firstly, the degradation of CS (150- 400 °C); secondly, the degradation of CS (400- 550 °C). The devolatilization index (DI) increased with the addition of LDPE. Furthermore, a combination of devolatilization chemical analysis with product analysis to analyze the intrinsic mechanism during co-pyrolysis. The results indicated that the yield of alkanes and olefin in gas products increased with the addition of LDPE. Additionally, LDPE pyrolysis maybe abstract hydrogen from CS pyrolysis and evolved into hydrogen, methane, and ethylene. Further, the co-pyrolysis kinetic parameters were computed by using model-free isoconversion methods, which showed promotion of CS pyrolysis and the reduced activation energy. All the activation energy were declined, which indicated a "bidirectional positive effect" during co-pyrolysis. The mean activation energy of P-cellulose (P-CE), P-hemicellulose (P-HM), P-lignin (P-LG), and LDPE decreased by 23.49 %, 12.89 %, 15.36 %, and 27.82 %, respectively. This study further proves the hydrogen donor transfer pathway in the co-pyrolysis process of CS and LDPE, providing theoretical support for the resource utilization of agricultural solid waste.

Oat straw pyrolysis with ammonium chloride doping: Analysis of evolved gases, kinetic triplet, and thermodynamic parameters

The purpose of this work was to determine the effect of the addition of NH4Cl to oat straw on the evolved gases, kinetic triplet, and thermodynamic parameters of the pyrolysis process at 873 K. A complementary approach allowed to assess the effects of the pyrolysis of chlorine- and nitrogen-enriched biomass. The thermal analysis of biomass was performed for four heating rates (5, 10, 20, and 30 K/min). The doping of NH4Cl in the straw favoured i) carbonisation of the chars, ii) formation of C-N bonds, iii) reduction of evolved CH4 and CO2, and iv) an increase in the mean values of the effective activation energy and all thermodynamic parameters. A group of reactions that best fit the experimental data of the pyrolysis process was selected. It was necessary to use unspecified mechanisms to describe the reaction model, particularly for samples enriched with NH4Cl.

Biochar and bio-oil fuel properties from nickel nanoparticles assisted pyrolysis of cassava peel

Direct biomass usage as a renewable fuel source and substitute for fossil fuels is discouraging due to high moisture, low energy density and low bulk density. Herein, thermogravimetric analysis (TGA) was conducted at various heating rates to determine peak decomposition temperatures for the dried cassava peels (DCP). The influence of pyrolysis temperature (300, 400, 500 and 600 °C) and heating rates (10, 20 and 30 °C/min) on the nickel nanoparticles catalyzed decomposition of DCP to produce biochar, bio-oil and biogas was investigated and characterized. The results revealed higher biochar (CBC) yield of 68.59 wt%, 62.55 wt% and 56.92 wt% at lower pyrolysis temperature of 300 °C for the different heating rates of 10, 20 and 30 °C/min. The higher carbon content of 52.39, 53.30 and 55.44 wt% was obtained at elevated temperature of 600 °C and heating rates of 10, 20 and 30 °C/min, respectively. At the pyrolysis temperature of 600 °C and heating rates of 10, 20 and 30 °C/min, the optimum yield of bio-oil (24.35, 17.69 and 18.16 wt%) and biogas (31.35, 42.03 and 46.12 wt%) were attained. A high heating value (HHV) of 28.70 MJ/kg was obtained for the biochar at 600 °C. Through the TGA, FTIR and HRSEM results, the thermal stability, hydrophobicity and structural changes of DCP and CBC samples were established. Similarly, the thermal stability of CBC samples increased with increasing pyrolysis temperature. Biochar with optimum fuel properties was produced at 600 °C due to the highest carbon content and high heating value (HHV). Improved kinematic viscosity (3.87 mm²/s) and density (0.850 g/cm³) were reported at the temperature of 300 °C and heating rate of 30 °C/min, while a higher pH (4.96), HHV (42.68 MJ/kg) and flash point (53.85 min) were presented by the bio-oil at the temperature of 600 °C and heating rate of 30 °C/min. Hence, DCP produced value-added biochar and bio-oil as renewable energy.

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Nickel nanoparticles successfully catalyzed the pyrolysis of CP biomass.

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Temperature and heating rates affected the yield of pyrolysis products.

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Fixed carbon content increased rapidly with temperature increase.

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The HHV of both biochar and bio-oil was higher than the DCP biomass.

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The fuel properties of biochar and bio-oil improved rapidly through NiNPs catalyzed pyrolysis.

Investigation of product selectivity and kinetics of poplar sawdust catalytic pyrolysis over bi-metallic Iron-Nickel/ZSM-5 catalyst

Py-GC/MS and thermogravimetric analysis were carried out to systematically explore product selectivity and kinetics of poplar sawdust catalytic pyrolysis over bi-metallic Fe-Ni/ZSM-5. The results showed that the Fe-Ni/ZSM-5 exhibited an additive effect on the production of monocyclic aromatic hydrocarbons compared to mono-metallic catalysts (Fe/ZSM-5 or Ni/ZSM-5). Fe-Ni/ZSM-5 further increased the yield of toluene (17.28 mg g^-1), which was 41.4% and 80.9% higher than Fe/ZSM-5 and Ni/ZSM-5, respectively. According to the kinetic analysis, the average activation energy obtained from catalytic pyrolysis with Fe-Ni/ZSM-5 using the methods of Friedman, Starink, Flynn-Wall-Ozawa, and Kissinger-Akahira-Sunose was 156.19, 152.39, 154.30, and 152.11 kJ mol^-1, respectively. Fe-Ni/ZSM-5 addition lowered the activation energy compared to non-catalytic pyrolysis at the conversion rate of 0.15-0.75. The overall catalytic pyrolysis process of poplar sawdust follows the diffusion and nucleation models. The thermodynamic parameters (enthalpy and entropy) showed positive and negative values, respectively, indicating non-spontaneous reactions during the catalytic pyrolysis process.