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5 pages, 166 KiB

Open AccessEditorial

Kinetic Modelling of Biomass Pyrolysis Processes

by Carmen Branca and Antonio Galgano

Processes 2024, 12(4), 706; https://doi.org/10.3390/pr12040706 - 30 Mar 2024

Viewed by 1404

Abstract

Pyrolytic conversion is the only biomass exploitation route capable of providing solid and liquid biofuels, as well as platform biomolecules for sustainable energy sources and raw materials for bio-based products [...] Full article

(This article belongs to the Special Issue Kinetic Modeling of Biomass Pyrolysis Processes)

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12 pages, 6438 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Oxidative Conversion of Chars Generated from the Fixed-Bed Pyrolysis of Wood Torrefied at Different Temperatures and Holding Times

by Carmen Branca and Colomba Di Blasi

Processes 2023, 11(4), 997; https://doi.org/10.3390/pr11040997 - 24 Mar 2023

Cited by 1 | Viewed by 1215

Abstract

Fixed-bed pyrolysis of torrefied spruce wood, for a heating temperature of 800 K, results in char yields between about 27–57 wt% (versus 23 wt% for untreated wood), depending on both pre-treatment temperatures (533–583 K) and holding times (8–25 min). In this study char [...] Read more.

Fixed-bed pyrolysis of torrefied spruce wood, for a heating temperature of 800 K, results in char yields between about 27–57 wt% (versus 23 wt% for untreated wood), depending on both pre-treatment temperatures (533–583 K) and holding times (8–25 min). In this study char oxidation behavior and kinetics are investigated by means of thermogravimetric analysis. The differential thermogravimetric curves always showed a low-temperature zone of slow rates (oxidative devolatilization), followed by a high-rate zone with a well-defined peak (oxidation). As the torrefaction severity increases, the temperature range of the oxidative devolatilization enlarges. Moreover, the oxidation rates become slower (both burning and burnout temperatures tend to increase). As already found for untreated wood chars, the two stages are well described by a linear and a power-law rate reaction, respectively. Volatiles released from the devolatilizations are approximately around 20 wt%, but torrefaction causes lower activation energies (66–92 kJ/mol versus 117 kJ/mol). The oxidation activation energies also decreas (170–168 kJ/mol versus 193 kJ/mol), accompanied by small variations in the reaction order. Full article

(This article belongs to the Special Issue Kinetic Modeling of Biomass Pyrolysis Processes)

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20 pages, 2244 KiB

Open AccessArticle

Evaluation of the Zinc Sulfate Catalytic Effect in Empty Fruit Bunches Pyrolysis

by María Alejandra Suárez Useche, York Castillo Santiago, Juan B. Restrepo, Alberto Ricardo Albis Arrieta and Karen Patricia Agámez Salgado

Processes 2022, 10(9), 1748; https://doi.org/10.3390/pr10091748 - 2 Sep 2022

Cited by 4 | Viewed by 1875

Abstract

The effect of zinc sulfate as a catalyst on the pyrolysis of empty fruit bunches (EFB) from oil palm was assessed. Thus, a thermo-gravimetric analyzer coupled with a Fourier transform infrared spectroscopy (TG-FTIR) was used, while the percentage of catalyst varied between 0 [...] Read more.

The effect of zinc sulfate as a catalyst on the pyrolysis of empty fruit bunches (EFB) from oil palm was assessed. Thus, a thermo-gravimetric analyzer coupled with a Fourier transform infrared spectroscopy (TG-FTIR) was used, while the percentage of catalyst varied between 0 wt% and 3 wt% at different heating rates (10, 30, and 50 K/min). The kinetic parameters (activation energy, pre-exponential factor, and reaction order) and activation energy distribution were calculated using three kinetic models. The thermogravimetric curves for the EFB pyrolysis showed three prominent peaks in which the maximum mass loss rate was mainly due to cellulose and lignin pyrolysis. On the other hand, FTIR analysis indicated that the main gaseous products were CO₂, CO, H₂O, CH₄, NH₃, acids, and aldehydes (CH₃COOH). The samples with 2 wt% of catalyst presented higher activation energies in pseudo reactions 1 and 2, ranging between 181,500 kJ/mol–184,000 kJ/mol and 165,200 kJ/mol–165,600 kJ/mol, respectively. It was highlighted that the first pseudo reaction with an activation energy range between 179,500 kJ/mol and 184,000 kJ/mol mainly contributes to the cellulose pyrolysis, and the second pseudo reaction (165,200 kJ/mol–165,600 kJ/mol) could be ascribed to the hemicellulose pyrolysis. Full article

(This article belongs to the Special Issue Kinetic Modeling of Biomass Pyrolysis Processes)

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13 pages, 2076 KiB

Open AccessArticle

Pilot-Scale Anaerobic Digestion of Pig Manure with Thermal Pretreatment: Stability Monitoring to Improve the Potential for Obtaining Methane

by Marley Vanegas, Felipe Romani and Mayerlenis Jiménez

Processes 2022, 10(8), 1602; https://doi.org/10.3390/pr10081602 - 13 Aug 2022

Cited by 6 | Viewed by 2633

Abstract

Monitoring and controlling stability in anaerobic digestion (AD) systems are essential, since it allows to obtain information that helps to take corrective actions in case of deviations in the system and to guarantee a stable performance in the biogas production. In this work, [...] Read more.

Monitoring and controlling stability in anaerobic digestion (AD) systems are essential, since it allows to obtain information that helps to take corrective actions in case of deviations in the system and to guarantee a stable performance in the biogas production. In this work, a pilot-scale CSRT reactor (1 m³) was monitored during the anaerobic digestion of pig manure with thermal pretreatment (80 °C) operated at thermophilic temperature (45 °C). The ratio of the volatile organic acids (FOS) to the total inorganic carbonate (TAC) and the pH were the indicators used during the monitoring process to identify deviations in the AD system. Additionally, alkaline solution NaOH (98%) was applied to counteract pH deviations and maintain stability. Chemical oxygen demand (COD) and biogas composition were measured during the AD process. It was found that during the AD process, the FOS/TAC was between the range of 0.5 and 1. The results revealed that, in the anaerobic digestion of pig manure with thermal pretreatment, the pH was kept stable in the range of 6.7–7.4 since no medium acidification occurred. Additionally, the tendency of the chemical oxygen demand decreased from the 10th day of operation, product of the favorable enzymatic activity of the microorganisms, reflected in the stable production of biogas (69%

{CH}_{4}

). Finally, it is concluded that thermophilic AD of pig manure with thermal pretreatment is a good option when it is carried out efficiently by employing an adequate energetic integration. Full article

(This article belongs to the Special Issue Kinetic Modeling of Biomass Pyrolysis Processes)

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13 pages, 2137 KiB

Open AccessArticle

Pyrolysis of RDF and Catalytic Decomposition of the Produced Tar in a Char Bed Secondary Reactor as an Efficient Source of Syngas

by Bogusław Kusz, Dariusz Kardaś, Łukasz Heda and Bartosz Trawiński

Processes 2022, 10(1), 90; https://doi.org/10.3390/pr10010090 - 2 Jan 2022

Cited by 2 | Viewed by 2319

Abstract

One of the technical limitations of refuse-derived fuel (RDF) pyrolysis is the high content of tar in its gas products. In order to resolve this problem, a two-stage RDF pyrolysis with a catalyst based on char from RDF pyrolysis is proposed. This paper [...] Read more.

One of the technical limitations of refuse-derived fuel (RDF) pyrolysis is the high content of tar in its gas products. In order to resolve this problem, a two-stage RDF pyrolysis with a catalyst based on char from RDF pyrolysis is proposed. This paper presents the results of municipal waste pyrolysis beginning in an oven heated to 480 °C and ending with catalytic tar cracking carried out in the temperature range from 800 to 1000 °C. Thermal and catalytic pyrolysis with a char catalyst containing a minimum of 6% Fe resulted in increases in the CO and H₂ contents in gas products and decreases in CO₂ and CH₄. At 1000 °C, the mass ratio of gaseous products to liquids was greater than 6. The residence time of the gases in the catalytic zone was about 3–5 s. The reactor was a good source of hydrogen and carbon monoxide. Full article

(This article belongs to the Special Issue Kinetic Modeling of Biomass Pyrolysis Processes)

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10 pages, 2249 KiB

Open AccessFeature PaperArticle

Thermal Devolatilization Kinetics of Dry Distiller’s Grains with Solubles (DDGS)

by Carmen Branca and Colomba Di Blasi

Processes 2021, 9(11), 1907; https://doi.org/10.3390/pr9111907 - 26 Oct 2021

Cited by 6 | Viewed by 1882

Abstract

Dynamic thermogravimetric analysis is applied to investigate the thermal devolatilization of dry distiller’s grain with solubles (DDGS), the major by-product of bioethanol plants. Compared with lignocellulosic biomass, the DDGS devolatilization occurs over a much wider temperature range and with slower rates. This reveals [...] Read more.

Dynamic thermogravimetric analysis is applied to investigate the thermal devolatilization of dry distiller’s grain with solubles (DDGS), the major by-product of bioethanol plants. Compared with lignocellulosic biomass, the DDGS devolatilization occurs over a much wider temperature range and with slower rates. This reveals complex dynamics attributable to a peculiar chemical composition comprising, in addition to lignocellulose, proteins, starch and other minor components. The evolution of lumped volatile product classes is well described by a five-step reaction mechanism. The numerical solution of the ordinary differential equations together with a minimization of the objective function leads to activation energies invariant with the heating rate. The estimated values of 89, 120, 158, 102 and 113 kJ/mol are, on average, higher than those obtained under oxidative environments but still lower than those typically estimated for wood. Full article

(This article belongs to the Special Issue Kinetic Modeling of Biomass Pyrolysis Processes)

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9 pages, 1619 KiB

Open AccessFeature PaperArticle

The Complexity of Lignin Thermal Degradation in the Isothermal Context

by Jorge López-Beceiro, Ana María Díaz-Díaz, Ana Álvarez-García, Javier Tarrío-Saavedra, Salvador Naya and Ramón Artiaga

Processes 2021, 9(7), 1154; https://doi.org/10.3390/pr9071154 - 2 Jul 2021

Cited by 17 | Viewed by 3285

Abstract

Thermal degradation of lignin in nitrogen atmosphere is evaluated by linear heating and isothermal tests. While linear heating suggests that thermal decomposition in the 200–400 °C range mainly consists of a single step, a careful analysis of isothermal tests points to different lignin [...] Read more.

Thermal degradation of lignin in nitrogen atmosphere is evaluated by linear heating and isothermal tests. While linear heating suggests that thermal decomposition in the 200–400 °C range mainly consists of a single step, a careful analysis of isothermal tests points to different lignin fractions having different stabilities. This is an important point for practical predictions, since kinetics obtained as if the degradations at different temperatures were the same would lack practical utility. Instead, stairway type tests are proposed to evaluate the degradation rates and sample quantities involved at the temperatures of interest. Full article

(This article belongs to the Special Issue Kinetic Modeling of Biomass Pyrolysis Processes)

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21 pages, 1925 KiB

Open AccessFeature PaperArticle

Apparent Pyrolysis Kinetics and Index-Based Assessment of Pretreated Peach Seeds

by Angelos-Ikaros Altantzis, Nikolaos-Christos Kallistridis, George Stavropoulos and Anastasia Zabaniotou

Processes 2021, 9(6), 905; https://doi.org/10.3390/pr9060905 - 21 May 2021

Cited by 9 | Viewed by 2625

Abstract

To better understand pyrolysis for upscaling purposes, a kinetic characterization of the process is necessary for every feedstock. Laboratory experiments allow identification of apparent kinetic models. This paper aims at the apparent kinetic investigation of peach seeds’ slow pyrolysis. Peach seeds from Greek [...] Read more.

To better understand pyrolysis for upscaling purposes, a kinetic characterization of the process is necessary for every feedstock. Laboratory experiments allow identification of apparent kinetic models. This paper aims at the apparent kinetic investigation of peach seeds’ slow pyrolysis. Peach seeds from Greek peach fruits pyrolyzed under inert atmospheric conditions at different temperatures (475–785 °C), heating rates (100–250 °C/min) and N₂ flow rates (25–200 cc/min). Prior to pyrolysis, they submitted to hexane extraction for the recovery of 36.8% wt. of the contained oils. Determination of the specific rate constant (k) and activation energy (Ea) for each considered reaction was made by using the Coats–Redfern integral non-isothermal fitting model that requires an assumption of the reaction order (n). Results revealed that a 3rd order reaction model best fits the process, the increasing of the pyrolysis temperature leads to a decrease of the activation energy (E) and pre-exponential factor (A), while nitrogen flow rate and heating rate had an opposite impact. E and A values ranged from 23 to 56 kJ/mol and 1.82 × 10⁶ to 1.13 × 10⁶ min⁻¹, respectively, at different pyrolysis conditions. Furthermore, estimation of combustion and pyrolysis indexes were made to assess the suitability of peach seeds as a fuel, using isothermal thermogravimetric analyses (TGA). Results revealed that peach seeds are a suitable feedstock for pyrolysis, while prior submission of peach seeds to oils extraction, in a cascade biorefinery approach, can increase the energy and material recovery efficiency and potentially the environmental and economic benefit of the agri-food industrial sector. Full article

(This article belongs to the Special Issue Kinetic Modeling of Biomass Pyrolysis Processes)

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11 pages, 1880 KiB

Open AccessFeature PaperArticle

A Logistic Approach for Kinetics of Isothermal Pyrolysis of Cellulose

by Jorge López-Beceiro, Ana María Díaz-Díaz, Ana Álvarez-García, Javier Tarrío-Saavedra, Salvador Naya and Ramón Artiaga

Processes 2021, 9(3), 551; https://doi.org/10.3390/pr9030551 - 20 Mar 2021

Cited by 5 | Viewed by 2604

Abstract

A kinetic model is proposed to fit isothermal thermogravimetric data obtained from cellulose in an inert atmosphere at different temperatures. The method used here to evaluate the model involves two steps: (1) fitting of single time-derivative thermogravimetric curves (DTG) obtained at different temperatures [...] Read more.

A kinetic model is proposed to fit isothermal thermogravimetric data obtained from cellulose in an inert atmosphere at different temperatures. The method used here to evaluate the model involves two steps: (1) fitting of single time-derivative thermogravimetric curves (DTG) obtained at different temperatures versus time, and (2) fitting of the rate parameter values obtained at different temperatures versus temperature. The first step makes use of derivative of logistic functions. For the second step, the dependence of the rate factor on temperature is evaluated. That separation of the curve fitting from the analysis of the rate factor resulted to be very flexible since it proved to work for previous crystallization studies and now for thermal degradation of cellulose. Full article

(This article belongs to the Special Issue Kinetic Modeling of Biomass Pyrolysis Processes)

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19 pages, 7768 KiB

Open AccessArticle

Thermal Decomposition and Combustion of Microwave Pre-Treated Biomass Pellets

by Linards Goldšteins, Raimonds Valdmanis, Maija Zaķe, Alexandr Arshanitsa and Anna Andersone

Processes 2021, 9(3), 492; https://doi.org/10.3390/pr9030492 - 9 Mar 2021

Cited by 10 | Viewed by 2396

Abstract

The objective of the study was to investigate a more effective use of commercially available biomass pellets (wheat straw, wood, peat) using microwave pretreatment to improve heat production. Pellets were pretreated using the originally designed microwave torrefaction device. The effects of microwave (mw) [...] Read more.

The objective of the study was to investigate a more effective use of commercially available biomass pellets (wheat straw, wood, peat) using microwave pretreatment to improve heat production. Pellets were pretreated using the originally designed microwave torrefaction device. The effects of microwave (mw) pretreatment were quantified, providing measurements of the weight loss and elemental composition of pellets and estimating the effect of mw pretreatment on their porosity, surface area and calorific values at pretreatment temperatures of T = 448–553 K. Obtained results show that the highest structural variations and elemental composition during mw pretreatment were obtained for wheat straw pellets, with an increase in reactivity, a decreasing in the duration of the thermal decomposition by about 40% and an increase in the yield of combustible volatiles. Increased reactivity of pretreated pellets enhanced the ignition and burnout of volatiles, decreasing the duration of the burnout of pretreated wheat straw, wood and peat pellets by 40%, 24% and 9%, respectively, and increasing the peak and average values of the flame temperature, heat output, and produced heat energy by 40–50%, with a correlating increase of combustion efficiency and the mass fraction of carbon-neutral CO₂ emission. Thus, the applicability of microwave pretreatment for the control and improvement of heat production was confirmed. Full article

(This article belongs to the Special Issue Kinetic Modeling of Biomass Pyrolysis Processes)

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