Experimental measurement of the true specific heat capacity of coal and semicoke during carbonization

et al. 2020

Preprint

In this study, the physicochemical, microstructural, mineralogical, thermal, and kinetic properties of three (3) newly discovered coals from Akunza (AKZ), Ome (OME), and Shiga (SHG) in Nigeria were examined for potential energy recovery. Physicochemical analysis revealed high combustible but low levels of polluting elements. The higher heating values (HHV) ranged from 18.65 MJ/kg (AKZ) to 26.59 MJ/kg (SHG). Microstructure and mineralogical analyses revealed particles with a rough texture, surfaces, and glassy lustre, which could be ascribed to metals, quartz, and kaolinite minerals. The major elements (C, O, Si, and Al), along with minor elements (Ca, Cu, Fe, K, Mg, S, and Ti) detected are associated with clays, salts, or the porphyrin constituents of coal. Thermal analysis showed mass loss (M L ) ranges from 30.51% – 87.57% and residual mass (R M ) from 12.44% – 69.49% under combustion (oxidative) and pyrolysis (non-oxidative) TGA conditions due to thermal degradation of organic matter, vitrinite, inertinite and liptinite macerals. Kinetic analysis revealed that the coal samples are highly reactive under the non-isothermal oxidative and non-oxidative conditions based on the Coats-Redfern Model. The activation energy ( E a ) ranged from 23.81 kJ/mol – 89.56 kJ/mol whereas the pre-exponential factor ( k o ) ranged from 6.77×10 -04 min -1 – 1.72×10 03 min -1 under pyrolysis and combustion conditions. In conclusion, the coals are practical feedstocks for either industrial applications or energy recovery.

Section: Thermal Propertiessupporting

confidence: 85%

Physicochemical, Mineralogy, and Thermo-Kinetic Characterisation of Newly Discovered Nigerian Coals under Pyrolysis and Combustion Conditions

et al. 2020

Preprint

“…Furthermore, the observed peaks for the non-oxidative process exhibited lower derivative mass-loss rates (Table 4) and signi cantly smaller peaks from 200 °C to 600 °C compared to the oxidative process. This observation indicates the devolatilization process, which governs thermal degradation and softening is largely endothermic, as similarly reported in the literature (Agroskin et al 1972;Hanrot et al 1994).…”

Section: Thermal Degradation Propertiessupporting

confidence: 85%

Pyrolysis and Combustion Characteristics of Newly Discovered Coals from Nigeria: Physicochemical, Microstructure, Mineralogy, and Thermal Properties

et al. 2020

Preprint

Despite Nigeria’s vast mineral and energy resources, the nation lacks sufficient electricity generation capacity to stimulate sustainable growth and infrastructural development. However, the discovery of vast coal deposits across the nation’s sedimentary basins could provide cheap, reliable, and abundant energy supplies. However, the lack of comprehensive data on the fuel characteristics, energy recovery, and potential emissions of Nigeria’s coals currently hampers the quest for coal-fired electricity generation. Hence, this study examined the physicochemical, microstructural, mineralogical, and thermal fuel properties of three (3) newly discovered coals from Akunza (AKZ), Ome (OME), and Shiga (SHG) in Nigeria for potential energy recovery through combustion and pyrolysis. Physicochemical analysis revealed high combustible but low levels of polluting elements. The higher heating values ranged from 18.65 MJ/kg for AKZ to 26.59 MJ/kg for SHG. Microstructure analysis revealed rough textured and surfaced particles with a glassy lustre ascribed to metals (such as Ti and Fe), quartz, and kaolinite. Mineralogical analyses revealed the major elements (C, O, Si, and Al), along with minor (Ca, Cu, Fe, K, Mg, S, and Ti) associated with clays, salts, or the porphyrin constituents of coal. Thermal analysis showed mass losses (ML) ranging from 30.51% to 87.57% and residual mass (RM) from 12.44% to 69.49% under oxidative (combustion) and non-oxidative (pyrolysis) conditions due to the thermal degradation of organic matter and macerals (vitrinite, inertinite and liptinite) during TGA. Overall, the coals are potential feedstocks for energy recovery through pyrolysis and combustion.

“…Furthermore, the observed peaks for the non-oxidative process exhibited lower derivative mass-loss rates (Table 4) and significantly smaller peaks from 200 to 600°C compared to the oxidative process. This observation indicates the devolatilization process that governs thermal degradation and softening is largely endothermic (Agroskin et al 1972), as similarly reported in the literature (Hanrot et al 1994).…”

Section: Thermal Propertiessupporting

confidence: 71%

Physicochemical, mineralogy, and thermo-kinetic characterisation of newly discovered Nigerian coals under pyrolysis and combustion conditions

et al. 2021

Int J Coal Sci Technol

In this study, the physicochemical, microstructural, mineralogical, thermal, and kinetic properties of three newly discovered coals from Akunza (AKZ), Ome (OME), and Shiga (SHG) in Nigeria were examined for potential energy recovery. Physicochemical analysis revealed high combustible but low levels of polluting elements. The higher heating values ranged from 18.65 MJ/kg (AKZ) to 26.59 MJ/kg (SHG). Microstructure and mineralogical analyses revealed particles with a rough texture, surface, and glassy lustre, which could be ascribed to metals, quartz, and kaolinite minerals. The major elements (C, O, Si, and Al), along with minor elements (Ca, Cu, Fe, K, Mg, S, and Ti) detected are associated with clays, salts, or the porphyrin constituents of coal. Thermal analysis showed mass loss (ML) ranges from 30.51% to 87.57% and residual mass (RM) from 12.44% to 69.49% under combustion (oxidative) and pyrolysis (non-oxidative) TGA conditions due to thermal degradation of organic matter and macerals (vitrinite, inertinite and liptinite). Kinetic analysis revealed the coals are highly reactive under the oxidative and non-oxidative conditions based on the Coats–Redfern Model. The activation energy (Ea) ranged from 23.81 to 89.56 kJ/mol, whereas the pre-exponential factor (ko) was from 6.77 × 10–4/min to 1.72 × 103/min under pyrolysis and combustion conditions. In conclusion, the coals are practical feedstocks for either energy recovery or industrial applications.