Research

Jump to: Review

13 pages, 1988 KiB

Open AccessArticle

Biomass Behavior upon Fast Pyrolysis in Inert and in CO₂-Rich Atmospheres: Role of Lignin, Hemicellulose and Cellulose Content

by Osvalda Senneca, Barbara Apicella, Carmela Russo and Francesca Cerciello

Energies 2022, 15(15), 5430; https://doi.org/10.3390/en15155430 - 27 Jul 2022

Cited by 2 | Viewed by 1087

Abstract

The present work focuses on the quality of char and primary tar produced from fast pyrolysis in N₂ and CO₂ of lignocellulosic biomasses: walnut shells (lignin-rich), straw (hemicellulose-rich) and pinewood (cellulose-rich). Heat treatments are carried out in a heated strip reactor [...] Read more.

The present work focuses on the quality of char and primary tar produced from fast pyrolysis in N₂ and CO₂ of lignocellulosic biomasses: walnut shells (lignin-rich), straw (hemicellulose-rich) and pinewood (cellulose-rich). Heat treatments are carried out in a heated strip reactor (HSR) at 1573 and 2073 K for 3 s, with a heating rate of 10⁴ K/s. The equipment allows for quenching the volatiles as soon as they are emitted. Chars are analyzed by thermogravimetric analysis in air. Results are compared with the products obtained from raw lignin, pure cellulose and pure hemicellulose. Cellulose and hemicellulose tars are dominated by anhydrous monosaccharides, which are scarce in straw tar and abundant in walnut shells tar. Polycyclic aromatic hydrocarbons PAHs are present in the primary products, in particular for walnut shells. The most reactive char is the one obtained from straw and the least reactive is the walnut shells char. Severe heat treatment and a CO₂ atmosphere generate additional char components with higher and lower reactivity. The more reactive char component may arise from cross-linking reactions involving the monosaccharides (for which the result decreased in tar), whereas the less reactive component arises from thermal annealing and graphitization. Thus, the pyrolytic behavior of biomasses cannot be reconstructed with a mere addition of the lignin/cellulose/hemicellulose contribution, taking into account their content in the biomass. Full article

(This article belongs to the Special Issue Advances in Solid Fuels Conversion to Enable the Global Energy Transitions)

► Show Figures

Figure 1

19 pages, 6675 KiB

Open AccessArticle

CO₂ Gasification Reactivity and Syngas Production of Greek Lignite Coal and Ex-Situ Produced Chars under Non-Isothermal and Isothermal Conditions: Structure-Performance Relationships

by Athanasios Lampropoulos, Vassilios D. Binas, Leila Zouridi, Costas Athanasiou, Miguel A. Montes-Morán, J. Angel Menéndez, Michalis Konsolakis and George E. Marnellos

Energies 2022, 15(3), 679; https://doi.org/10.3390/en15030679 - 18 Jan 2022

Cited by 3 | Viewed by 1703

Abstract

The presented work explores the structural properties, gasification reactivity, and syngas production of Greek lignite fuel (LG) and ex-situ produced chars during CO₂ gasification. Three different slow pyrolysis protocols were employed for char production involving torrefaction at 300 °C (LG300), mild-carbonization at [...] Read more.

The presented work explores the structural properties, gasification reactivity, and syngas production of Greek lignite fuel (LG) and ex-situ produced chars during CO₂ gasification. Three different slow pyrolysis protocols were employed for char production involving torrefaction at 300 °C (LG300), mild-carbonization at 500 °C (LG500), and carbonization at 800 °C (LG800). Physicochemical characterization studies, including proximate and ultimate analysis, X-ray Diffraction (XRD), and Raman spectroscopy, revealed that the thermal treatment under inert atmospheres leads to chars with increased fixed carbon content and less ordered surface structures. The CO₂ gasification reactivity of pristine LG and as-produced chars was examined by thermogravimetric (TG) analysis and in batch mode gasification tests under both isothermal and non-isothermal conditions. The key parameters affecting the devolatilization and gasification steps in the overall process toward CO-rich gas mixtures were thoroughly explored. The gasification performance of the examined fuels in terms of carbon conversion, instant CO production rate, and syngas generation revealed an opposite reactivity order during each stage. TG analysis demonstrated that raw lignite (LG) was more reactive during the thermal devolatilization phase at low and intermediate temperatures (da/dt_max,devol. = 0.022 min⁻¹). By contrast, LG800 exhibited superior gasification reactivity at high temperatures (da/dt_max,gas. = 0.1 min⁻¹). The latter is additionally corroborated by the enhanced CO formation of LG800 samples under both non-isothermal (5.2 mmol) and isothermal (28 mmol) conditions, compared to 4.1 mmol and 13.8 mmol over the LG sample, respectively. The pronounced CO₂ gasification performance of LG800 was attributed to its higher fixed carbon content and disordered surface structure compared to LG, LG300, and LG500 samples. Full article

(This article belongs to the Special Issue Advances in Solid Fuels Conversion to Enable the Global Energy Transitions)

► Show Figures

Graphical abstract

16 pages, 3027 KiB

Open AccessArticle

Self-Heating of Biochar during Postproduction Storage by O₂ Chemisorption at Low Temperatures

by Aekjuthon Phounglamcheik, Nils Johnson, Norbert Kienzl, Christoph Strasser and Kentaro Umeki

Energies 2022, 15(1), 380; https://doi.org/10.3390/en15010380 - 05 Jan 2022

Cited by 2 | Viewed by 2810

Abstract

Biochar is attracting attention as an alternative carbon/fuel source to coal in the process industry and energy sector. However, it is prone to self-heating and often leads to spontaneous ignition and thermal runaway during storage, resulting in production loss and health risks. This [...] Read more.

Biochar is attracting attention as an alternative carbon/fuel source to coal in the process industry and energy sector. However, it is prone to self-heating and often leads to spontaneous ignition and thermal runaway during storage, resulting in production loss and health risks. This study investigates biochar self-heating upon its contact with O₂ at low temperatures, i.e., 50–300 °C. First, kinetic parameters of O₂ adsorption and CO₂ release were measured in a thermogravimetric analyzer using biochar produced from a pilot-scale pyrolysis process. Then, specific heat capacity and heat of reactions were measured in a differential scanning calorimeter. Finally, a one-dimensional transient model was developed to simulate self-heating in containers and gain insight into the influences of major parameters. The model showed a good agreement with experimental measurement in a closed metal container. It was observed that char temperature slowly increased from the initial temperature due to heat released during O₂ adsorption. Thermal runaway, i.e., self-ignition, was observed in some cases even at the initial biochar temperature of ca. 200 °C. However, if O₂ is not permeable through the container materials, the temperature starts decreasing after the consumption of O₂ in the container. The simulation model was also applied to examine important factors related to self-heating. The results suggested that self-heating can be somewhat mitigated by decreasing the void fraction, reducing storage volume, and lowering the initial char temperature. This study demonstrated a robust way to estimate the cooling demands required in the biochar production process. Full article

(This article belongs to the Special Issue Advances in Solid Fuels Conversion to Enable the Global Energy Transitions)

► Show Figures

Figure 1

14 pages, 3093 KiB

Open AccessArticle

Effects of Pressure and Coal Rank on the Oxy-Fuel Combustion of Pulverized Coal

by Dingyi Qin, Qianyun Chen, Jing Li and Zhaohui Liu

Energies 2022, 15(1), 265; https://doi.org/10.3390/en15010265 - 31 Dec 2021

Cited by 3 | Viewed by 2002

Abstract

Pressurized oxy-fuel combustion technology is the second generation of oxy-fuel combustion technology and has low energy consumption and low cost. In this research, a visual pressurized flat-flame reaction system was designed. A particle-tracking image pyrometer (PTIP) system based on a high-speed camera and [...] Read more.

Pressurized oxy-fuel combustion technology is the second generation of oxy-fuel combustion technology and has low energy consumption and low cost. In this research, a visual pressurized flat-flame reaction system was designed. A particle-tracking image pyrometer (PTIP) system based on a high-speed camera and an SLR camera was proposed. Combining the experimental system and data-processing method developed, the ignition and combustion characteristics of a single coal particle between 69 and 133 μm in size were investigated. The results indicated that at atmospheric pressure, the ignition delay time of ShanXi (SX) anthracite coal was longer than that of ShenHua (SH) bituminous coal, while that of PRB sub-bituminous coal was the shortest. As the pressure rose, the ignition delay time of the PRB sub-bituminous coal and SX anthracite coal showed a continuous increasing trend, while the ignition delay time of SH bituminous coal showed a trend of first increasing and then decreasing. Moreover, pressure also affects the pyrolysis process of coal. As the pressure increases, it became more difficult to release the volatiles produced by coal pyrolysis, which reduced the release rate of volatiles during the ignition stage, and prolonged the release time and burning duration time of volatiles. Full article

(This article belongs to the Special Issue Advances in Solid Fuels Conversion to Enable the Global Energy Transitions)

► Show Figures

Figure 1

17 pages, 4867 KiB

Open AccessArticle

Investigation of Oxy-Fuel Combustion through Reactor Network and Residence Time Data

by Maria Angela Agizza, Ghobad Bagheri, Sebastian Bürkle, Tiziano Faravelli, Steven Wagner and Andreas Dreizler

Energies 2022, 15(1), 252; https://doi.org/10.3390/en15010252 - 30 Dec 2021

Cited by 2 | Viewed by 2044

Abstract

Oxy-fuel combustion is a promising strategy to minimize the environmental impact of combustion-based energy conversion. Simple and flexible tools are required to facilitate the successful integration of such strategies at the industrial level. This study couples measured residence time distribution with chemical reactor [...] Read more.

Oxy-fuel combustion is a promising strategy to minimize the environmental impact of combustion-based energy conversion. Simple and flexible tools are required to facilitate the successful integration of such strategies at the industrial level. This study couples measured residence time distribution with chemical reactor network analysis in a close-to-reality combustor. This provides detailed knowledge about the various mixing and reactive characteristics arising from the use of the two different oxidizing streams. Full article

(This article belongs to the Special Issue Advances in Solid Fuels Conversion to Enable the Global Energy Transitions)

► Show Figures

Graphical abstract

19 pages, 3668 KiB

Open AccessArticle

Combustion Characterisation of Bituminous Coal and Pinus Sawdust Blends by Use of Thermo-Gravimetric Analysis

by Garikai T. Marangwanda, Daniel M. Madyira, Patrick G. Ndungu and Chido H. Chihobo

Energies 2021, 14(22), 7547; https://doi.org/10.3390/en14227547 - 11 Nov 2021

Cited by 10 | Viewed by 1884

Abstract

The cocombustion of coal and pinus sawdust waste is an economically viable and sustainable option for increasing the share of biomass in energy production. This technology also has the potential to reduce the emission of greenhouse gases from existing coal fired power plants. [...] Read more.

The cocombustion of coal and pinus sawdust waste is an economically viable and sustainable option for increasing the share of biomass in energy production. This technology also has the potential to reduce the emission of greenhouse gases from existing coal fired power plants. The thermal synergistic effects of cocombusting Hwange bituminous coal (HC) with Pinus sawdust (PS) were thus investigated using thermogravimetric analysis. Fuel blending mass ratios of 100HC, 90HC10PS, 80HC20PS, 70HC30PS, and 100PS under an oxidative atmosphere at three different heating rates of 5, 12.5, and 20 °C/min were used for the experimental setup. Zero to negative synergy was generally observed for the mass loss curves (TG) at different blending ratios. Generally positive synergy was observed with relation to rate of mass loss curves (DTG) for the 80HC20PS and 70HC30PS fuel blends only. The ignition index increased with blending ratio by an average of 42.86%, whilst the burnout index showed a maximum increase of 14.6% at 20 °C/min. However, the combustion index representative of stability showed a decreasing trend generally for all the heating rates. No combustion index produced a linear variation with temperature, though upon evaluation, an optimum mass ratio of 20% pinus sawdust was suggested. The chosen optimum blending ratio demonstrated increased ignition and burnout indexes whilst maintaining the stability of combustion at a reasonable range. Full article

(This article belongs to the Special Issue Advances in Solid Fuels Conversion to Enable the Global Energy Transitions)

► Show Figures

Figure 1

24 pages, 1348 KiB

Open AccessArticle

On the Mathematical Modelling of a Moving-Bed Counter-Current Gasifier Fuelled with Wood-Pellets

by Andreas Schwabauer, Marco Mancini, Yunus Poyraz and Roman Weber

Energies 2021, 14(18), 5840; https://doi.org/10.3390/en14185840 - 15 Sep 2021

Cited by 3 | Viewed by 1958

Abstract

The subject of this work is the mathematical modelling of a counter-current moving-bed gasifier fuelled by wood-pellets. Two versions of the model have been developed: the one-dimensional (1D) version-solving a set of Ordinary Differential Equations along the gasifier height-and the three-dimensional (3D) version [...] Read more.

The subject of this work is the mathematical modelling of a counter-current moving-bed gasifier fuelled by wood-pellets. Two versions of the model have been developed: the one-dimensional (1D) version-solving a set of Ordinary Differential Equations along the gasifier height-and the three-dimensional (3D) version where the balanced equations are solved using Computational Fluid Dynamics. Unique procedures have been developed to provide unconditionally stable solutions and remove difficulties occurring by using conventional numerical methods for modelling counter-current reactors.The procedures reduce the uncertainties introduced by other mathematical approaches, and they open up the possibility of straightforward application to more complex software, including commercial CFD packages. Previous models of Hobbs et al., Di Blasi and Mandl et al. used a correction factor to tune calculated temperatures to measured values. In this work, the factor is not required. Using the 1D model, the Mandl et al. 16.6 kW gasifier was scaled to 9.5 MW input; the 89% cold-gas efficiency, observed at 16.6 kW input, decreases only slightly to 84% at the 9.5 MW scale. Full article

(This article belongs to the Special Issue Advances in Solid Fuels Conversion to Enable the Global Energy Transitions)

► Show Figures

Figure 1

Review

Jump to: Research

28 pages, 5821 KiB

Open AccessReview

Analytics for Recovery and Reuse of Solid Wastes from Refineries

by Barbara Apicella, Carmela Russo and Osvalda Senneca

Energies 2022, 15(11), 4026; https://doi.org/10.3390/en15114026 - 30 May 2022

Cited by 1 | Viewed by 1569

Abstract

Heavy fractions of petroleum have for long time been bypassed in favour of lighter fractions. Nowadays, in the framework of the “circular economy”, there is a growing interest in residual petroleum heavy fractions. The present work briefly reviews the use and characterization at [...] Read more.

Heavy fractions of petroleum have for long time been bypassed in favour of lighter fractions. Nowadays, in the framework of the “circular economy”, there is a growing interest in residual petroleum heavy fractions. The present work briefly reviews the use and characterization at laboratory scale of some low valuable solid or semi-solid products of the oil refinery industry: asphaltenes (bitumen/asphalt), pet-coke and pitch for use as fuels. The use of solid and semi-solid refinery residues, in particular, of coke as a coal substitute in thermochemical processes and of pitch and asphaltenes as material precursors, requires careful analysis, and an understanding of their structure at the molecular level is mandatory for the development of processing technology. Techniques for the characterization of typical petroleum heavy fractions such as pitches, asphaltenes and cokes are reviewed. An experimental protocol for investigating at the laboratory scale the thermochemical conversion behavior of solid and semi-solid refinery wastes is proposed. Full article

(This article belongs to the Special Issue Advances in Solid Fuels Conversion to Enable the Global Energy Transitions)

► Show Figures