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Processes
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Production of Biofuels and Numerical Modeling of Chemical Combustion Systems
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Production of Biofuels and Numerical Modeling of Chemical Combustion Systems

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Environmental and Green Processes".

Deadline for manuscript submissions: closed (30 July 2020) | Viewed by 83861

Special Issue Editors

Prof. Dr. Miguel Torres García

E-Mail Website
Guest Editor
Department of Energy Engineering, University of Seville, 41092 Seville, Spain
Interests: entrepreneurship; management; start-up; intangible; knowledge transfer; energy engineering
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Juan Francisco García Martín

E-Mail Website
Guest Editor
Departamento de Ingeniería Química, Facultad de Química, Universidad de Sevilla, 41012 Seville, Spain
Interests: biomass conversion; biofuels production; near-infrared spectroscopy; phytoremediation of mining soils; thermochemical processing; valorization of olive mills waste
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Biofuels have recently attracted much attention, mainly as alternative fuels for applications in energy generation and transportation. The utilization of biofuels in such controlled combustion processes has the great advantage of not depleting the limited resources of fossil fuels, but leads to emissions of greenhouse gases and smoke particles similar to traditional combustion processes, i.e., those of fossil fuels. On the other hand, a vast amount of biofuel is subject to combustion in small-scale processes, such as for heating and cooking in residential dwellings, as well as in agricultural operations, such as crop residue removal and land clearing. In addition, large amounts of biomass are annually consumed during forest and savanna fires in many parts of the world. These types of burning processes are typically uncontrolled and unregulated. Consequently, the emissions from these processes may be larger compared to industrial-type operations. Aside from direct effects on human health—especially due to a sizeable fraction of the smoke emissions remaining inside residential homes—the smoke particles and gases released from uncontrolled biofuel combustion impose significant effects on the regional and global climate. Estimates have shown the majority of carbonaceous airborne particulate matter to be derived from the combustion of biofuels and biomass.

This Special Issue on “Production of Biofuels and Numerical Modeling of Chemical Combustion Systems” aims to present high-quality research studies addressing challenges in the broad area of process modeling and control in combustion processes. Biofuels cannot replace our current dependence on coal, oil, and natural gas, but they can complement other renewable energies such as solar and wind energies. Thus, due to the merits of biofuel energy for environmental sustainability, biofuel and bioenergy technologies play a crucial role in the renewable energy development and replacement of chemicals from highly functional biomass. This Special Issue aims to publish comprehensive overviews and in-depth technical research papers addressing the recent progress in biofuel combustion processes. Studies of advanced techniques and methods for bioenergy and biofuel production are also welcome. Research involving experimental and numerical studies, recent developments, and the current state-of-the-art and emerging technologies in this field are highly encouraged.

Dr. Miguel Torres García
Dr. Juan Francisco García Martín
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Processes is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • dynamic modeling and simulation
  • biodiesel
  • biogasoline
  • biofuels
  • combustion
  • emissions
  • biomass

Published Papers (17 papers)

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Editorial

Jump to: Research, Review

4 pages, 205 KiB  
Editorial
Special Issue “Production of Biofuels and Numerical Modelling of Chemical Combustion Systems”
by Miguel Torres-García, Paloma Álvarez-Mateos and Juan Francisco García-Martín
Processes 2021, 9(5), 829; https://doi.org/10.3390/pr9050829 - 09 May 2021
Cited by 2 | Viewed by 1211
Abstract
Biofuels have recently attracted a lot of attention, mainly as alternative fuels for applications in energy generation and transportation [...] Full article
(This article belongs to the Special Issue Production of Biofuels and Numerical Modeling of Chemical Combustion Systems)

Research

Jump to: Editorial, Review

21 pages, 8666 KiB  
Article
Investigation of Ni–Fe–Cu-Layered Double Hydroxide Catalysts in Steam Reforming of Toluene as a Model Compound of Biomass Tar
by David Díez, Ana Urueña and Gregorio Antolín
Processes 2021, 9(1), 76; https://doi.org/10.3390/pr9010076 - 31 Dec 2020
Cited by 6 | Viewed by 1800
Abstract
This work focused on the synthesis of a catalyst based on layered double hydroxides with a molar cation concentration Ni/Cu/Fe/Mg/Al of 30/5/5/40/20 and its performance in the steam reforming of toluene as a model compound of biomass tar. Its performance at different temperatures [...] Read more.
This work focused on the synthesis of a catalyst based on layered double hydroxides with a molar cation concentration Ni/Cu/Fe/Mg/Al of 30/5/5/40/20 and its performance in the steam reforming of toluene as a model compound of biomass tar. Its performance at different temperatures (500, 600, 700, 800, and 900 °C) and steam/carbon molar ratios (S/C ratios) (1, 2, 4, 6, 8) was studied. The contact time used was 0.32 g h mol−1. The catalyst obtained allowed us to reach 98–99.87% gas conversion of toluene with a low carbon deposition on catalyst surface (1.4 wt %) at 800 °C and S/C = 4. In addition, conversions in the range of 600–700 °C were higher than 80% and 90%, respectively, and the type of carbon deposited on the catalyst was found to be filamentous, which did not significantly reduce the performance of the catalyst. Full article
(This article belongs to the Special Issue Production of Biofuels and Numerical Modeling of Chemical Combustion Systems)
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14 pages, 1559 KiB  
Article
Influences of Water Content in Feedstock Oil on Burning Characteristics of Fatty Acid Methyl Esters
by Cherng-Yuan Lin and Lei Ma
Processes 2020, 8(9), 1130; https://doi.org/10.3390/pr8091130 - 10 Sep 2020
Cited by 17 | Viewed by 3115
Abstract
Strong alkaline-catalyst transesterification with short-chain alcohol is generally used for biodiesel production due to its dominant advantages of shorter reaction time and higher conversion rate over other reactions. The existence of excess water content in the feedstock oil might retard the transesterification rate [...] Read more.
Strong alkaline-catalyst transesterification with short-chain alcohol is generally used for biodiesel production due to its dominant advantages of shorter reaction time and higher conversion rate over other reactions. The existence of excess water content in the feedstock oil might retard the transesterification rate and in turn deteriorate the fuel characteristics of the fatty acid methyl esters. Hence, optimum water content in the raw oil, aimed towards both lower production cost and superior fuel properties, becomes significant for biodiesel research and industrial practices. Previous studies only concerned the influences of water contents on the yield or conversion rate of fatty acid methyl esters through transesterification of triglycerides. The effects of added water in the reactant mixture on burning characteristics of fatty acid methyl esters are thus first investigated in this study. Raw palm oil was added with preset water content before being transesterified. The experimental results show that the biodiesel produced from the raw palm oil containing a 0.05 wt.% added water content had the highest content of saturated fatty acids and total fatty acid methyl esters (FAME), while that containing 0.11 wt.% water content had the lowest content of total FAME and fatty acids of longer carbon chains than C16 among the biodiesel products. Regarding burning characteristics, palm-oil biodiesel made from raw oil with a 0.05 wt.% added water content among those biodiesels was found to have the highest distillation temperatures, flash point, and ignition point, which implies higher safety extents during handling and storage of the fuel. The added water content 0.05 wt.% in raw oil was considered the optimum to produce palm-oil biodiesel with superior fuel structure of fatty acids and burning characteristics. Higher or lower water content than 0.05 wt.% would cause slower nucleophilic substitution reaction and thus a lower conversion rate from raw oil and deteriorated burning characteristics in turn. Full article
(This article belongs to the Special Issue Production of Biofuels and Numerical Modeling of Chemical Combustion Systems)
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21 pages, 1489 KiB  
Article
Scale-Up Cultivation of Phaeodactylum tricornutum to Produce Biocrude by Hydrothermal Liquefaction
by Irene Megía-Hervás, Alejandra Sánchez-Bayo, Luis Fernando Bautista, Victoria Morales, Federico G. Witt-Sousa, María Segura-Fornieles and Gemma Vicente
Processes 2020, 8(9), 1072; https://doi.org/10.3390/pr8091072 - 01 Sep 2020
Cited by 8 | Viewed by 3435
Abstract
Phaeodactylum tricornutum is an interesting source of biomass to produce biocrude by hydrothermal liquefaction (HTL). Its biochemical composition, along with its biomass productivity, can be modulated according to this specific application by varying the photoperiod, the addition of CO2 or the variation [...] Read more.
Phaeodactylum tricornutum is an interesting source of biomass to produce biocrude by hydrothermal liquefaction (HTL). Its biochemical composition, along with its biomass productivity, can be modulated according to this specific application by varying the photoperiod, the addition of CO2 or the variation of the initial nitrate concentration. The lab-scale culture allowed the production of a P. tricornutum biomass with high biomass and lipid productivities using a 18:6 h light:dark photoperiod and a specific CO2 injection. An initial concentration of nitrates (11.8 mM) in the culture was also essential for the growth of this species at the lab scale. The biomass generated in the scale-up photoreactor had acceptable biomass and lipid productivities, although the values were higher in the biomass cultivated at the lab scale because of the difficulty for the light to reach all cells, making the cells unable to develop and hindering their growth. The biocrudes from a 90-L cultivated microalga (B-90L) showed lower yields than the ones obtained from the biomass cultivated at the lab scale (B-1L) because of the lower lipid and high ash contents in this biomass. However, the culture scaling-up did not affect significantly the heteroatom concentrations in the biocrudes. A larger-scale culture is recommended to produce a biocrude to be used as biofuel after a post-hydrotreatment stage. Full article
(This article belongs to the Special Issue Production of Biofuels and Numerical Modeling of Chemical Combustion Systems)
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22 pages, 4385 KiB  
Article
Determination of Hemicellulose, Cellulose, and Lignin Content in Different Types of Biomasses by Thermogravimetric Analysis and Pseudocomponent Kinetic Model (TGA-PKM Method)
by David Díez, Ana Urueña, Raúl Piñero, Aitor Barrio and Tarja Tamminen
Processes 2020, 8(9), 1048; https://doi.org/10.3390/pr8091048 - 27 Aug 2020
Cited by 90 | Viewed by 22831
Abstract
The standard method for determining the biomass composition, in terms of main lignocellulosic fraction (hemicellulose, cellulose and lignin) contents, is by chemical method; however, it is a slow and expensive methodology, which requires complex techniques and the use of multiple chemical reagents. The [...] Read more.
The standard method for determining the biomass composition, in terms of main lignocellulosic fraction (hemicellulose, cellulose and lignin) contents, is by chemical method; however, it is a slow and expensive methodology, which requires complex techniques and the use of multiple chemical reagents. The main objective of this article is to provide a new efficient, low-cost and fast method for the determination of the main lignocellulosic fraction contents of different types of biomasses from agricultural by-products to softwoods and hardwoods. The method is based on applying deconvolution techniques on the derivative thermogravimetric (DTG) pyrolysis curves obtained by thermogravimetric analysis (TGA) through a kinetic approach based on a pseudocomponent kinetic model (PKM). As a result, the new method (TGA-PKM) provides additional information regarding the ease of carrying out their degradation in comparison with other biomasses. The results obtained show a good agreement between experimental data from analytical procedures and the TGA-PKM method (±7%). This indicates that the TGA-PKM method can be used to have a good estimation of the content of the main lignocellulosic fractions without the need to carry out complex extraction and purification chemical treatments. In addition, the good quality of the fit obtained between the model and experimental DTG curves (R2Adj = 0.99) allows to obtain the characteristic kinetic parameters of each fraction. Full article
(This article belongs to the Special Issue Production of Biofuels and Numerical Modeling of Chemical Combustion Systems)
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15 pages, 2697 KiB  
Article
Environmental Assessment of Olive Mill Solid Waste Valorization via Anaerobic Digestion Versus Olive Pomace Oil Extraction
by Bernabé Alonso-Fariñas, Armando Oliva, Mónica Rodríguez-Galán, Giovanni Esposito, Juan Francisco García-Martín, Guillermo Rodríguez-Gutiérrez, Antonio Serrano and Fernando G. Fermoso
Processes 2020, 8(5), 626; https://doi.org/10.3390/pr8050626 - 23 May 2020
Cited by 21 | Viewed by 4337
Abstract
Anaerobic digestion is a promising alternative to valorize agrifood wastes, which is gaining interest under an environmental sustainability overview. The present research aimed to compare anaerobic digestion with olive pomace oil extraction, by using life cycle assessment, as alternatives for the valorization of [...] Read more.
Anaerobic digestion is a promising alternative to valorize agrifood wastes, which is gaining interest under an environmental sustainability overview. The present research aimed to compare anaerobic digestion with olive pomace oil extraction, by using life cycle assessment, as alternatives for the valorization of the olive mill solid waste generated in the centrifugation process with a two-outlet decanter from oil mills. In the case of olive pomace oil extraction, two cases were defined depending on the type of fuel used for drying the wet pomace before the extraction: natural gas or a fraction of the generated extracted pomace. The anaerobic digestion alternative consisted of the production of biogas from the olive mill solid waste, heat and electricity cogeneration by the combustion of the generated biogas, and composting of the anaerobic digestate. The life cycle assessment showed that anaerobic digestion was the best alternative, with a global environmental impact reduction of 88.1 and 85.9% respect to crude olive pomace oil extraction using natural gas and extracted pomace, respectively, as fuel. Full article
(This article belongs to the Special Issue Production of Biofuels and Numerical Modeling of Chemical Combustion Systems)
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17 pages, 4381 KiB  
Article
Numerical Investigation of Fluid Flow and In-Cylinder Air Flow Characteristics for Higher Viscosity Fuel Applications
by Mohd Fadzli Hamid, Mohamad Yusof Idroas, Shukriwani Sa’ad, Teoh Yew Heng, Sharzali Che Mat, Zainal Alimuddin Zainal Alauddin, Khairul Akmal Shamsuddin, Raa Khimi Shuib and Muhammad Khalil Abdullah
Processes 2020, 8(4), 439; https://doi.org/10.3390/pr8040439 - 08 Apr 2020
Cited by 9 | Viewed by 3586
Abstract
Generally, the compression ignition (CI) engine that runs with emulsified biofuel (EB) or higher viscosity fuel experiences inferior performance and a higher emission compared to petro diesel engines. The modification is necessary to standard engine level in order to realize its application. This [...] Read more.
Generally, the compression ignition (CI) engine that runs with emulsified biofuel (EB) or higher viscosity fuel experiences inferior performance and a higher emission compared to petro diesel engines. The modification is necessary to standard engine level in order to realize its application. This paper proposes a guide vane design (GVD), which needs to be installed in the intake manifold, is incorporated with shallow depth re-entrance combustion chamber (SCC) pistons. This will organize and develop proper in-cylinder airflow to promote better diffusion, evaporation and combustion processes. The model of GVD and SCC piston was designed using SolidWorks 2017; while ANSYS Fluent version 15 was utilized to run a 3D analysis of the cold flow IC engine. In this research, seven designs of GVD with the number of vanes varied from two to eight vanes (V2–V8) are used. The four-vane model (V4) has shown an excellent turbulent flow as well as swirl, tumble and cross tumble ratios in the fuel-injected region compared to other designs. This is indispensable to break up heavier fuel molecules of EB to mix with the air that will eventually improve engine performance. Full article
(This article belongs to the Special Issue Production of Biofuels and Numerical Modeling of Chemical Combustion Systems)
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9 pages, 2758 KiB  
Article
Eucalyptus Kraft Lignin as an Additive Strongly Enhances the Mechanical Resistance of Tree-Leaf Pellets
by Leonardo Clavijo, Slobodan Zlatanovic, Gerd Braun, Michael Bongards, Andrés Dieste and Stéphan Barbe
Processes 2020, 8(3), 376; https://doi.org/10.3390/pr8030376 - 24 Mar 2020
Cited by 3 | Viewed by 2489
Abstract
Pelleted biomass has a low, uniform moisture content and can be handled and stored cheaply and safely. Pellets can be made of industrial waste, food waste, agricultural residues, energy crops, and virgin lumber. Despite their many desirable attributes, they cannot compete with fossil [...] Read more.
Pelleted biomass has a low, uniform moisture content and can be handled and stored cheaply and safely. Pellets can be made of industrial waste, food waste, agricultural residues, energy crops, and virgin lumber. Despite their many desirable attributes, they cannot compete with fossil fuel sources because the process of densifying the biomass and the price of the raw materials make pellet production costly. Leaves collected from street sweeping are generally discarded in landfills, but they can potentially be valorized as a biofuel if they are pelleted. However, the lignin content in leaves is not high enough to ensure the physical stability of the pellets, so they break easily during storage and transportation. In this study, the use of eucalyptus kraft lignin as an additive in tree-leaf pellet production was studied. Results showed that when 2% lignin is added the abrasion resistance can be increased to an acceptable value. Pellets with added lignin fulfilled all requirements of European standards for certification except for ash content. However, as the raw material has no cost, this method can add value or contribute to financing continued sweeping and is an example of a circular economy scenario. Full article
(This article belongs to the Special Issue Production of Biofuels and Numerical Modeling of Chemical Combustion Systems)
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10 pages, 778 KiB  
Article
Outdoor Large-Scale Cultivation of the Acidophilic Microalga Coccomyxa onubensis in a Vertical Close Photobioreactor for Lutein Production
by Juan-Luis Fuentes, Zaida Montero, María Cuaresma, Mari-Carmen Ruiz-Domínguez, Benito Mogedas, Inés Garbayo Nores, Manuel González del Valle and Carlos Vílchez
Processes 2020, 8(3), 324; https://doi.org/10.3390/pr8030324 - 10 Mar 2020
Cited by 23 | Viewed by 6178
Abstract
The large-scale biomass production is an essential step in the biotechnological applications of microalgae. Coccomyxa onubensis is an acidophilic microalga isolated from the highly acidic waters of Río Tinto (province of Huelva, Spain) and has been shown to accumulate a high concentration of [...] Read more.
The large-scale biomass production is an essential step in the biotechnological applications of microalgae. Coccomyxa onubensis is an acidophilic microalga isolated from the highly acidic waters of Río Tinto (province of Huelva, Spain) and has been shown to accumulate a high concentration of lutein (9.7 mg g−1dw), a valuable antioxidant, when grown at laboratory-scale. A productivity of 0.14 g L−1 d−1 was obtained by growing the microalga under outdoor conditions in an 800 L tubular photobioreactor. The results show a stable biomass production for at least one month and with a lutein content of 10 mg g−1dw, at pH values in the range 2.5–3.0 and temperature in the range 10–25 °C. Culture density, temperature, and CO2 availability in highly acidic medium are rate-limiting conditions for the microalgal growth. These aspects are discussed in this paper in order to improve the outdoor culture conditions for competitive applications of C. onubensis. Full article
(This article belongs to the Special Issue Production of Biofuels and Numerical Modeling of Chemical Combustion Systems)
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22 pages, 4349 KiB  
Communication
Numerical Analysis of High-Pressure Direct Injection Dual-Fuel Diesel-Liquefied Natural Gas (LNG) Engines
by Alberto Boretti
Processes 2020, 8(3), 261; https://doi.org/10.3390/pr8030261 - 25 Feb 2020
Cited by 13 | Viewed by 5455
Abstract
Dual fuel engines using diesel and fuels that are gaseous at normal conditions are receiving increasing attention. They permit to achieve the same (or better) than diesel power density and efficiency, steady-state, and substantially similar transient performances. They also permit to deliver better [...] Read more.
Dual fuel engines using diesel and fuels that are gaseous at normal conditions are receiving increasing attention. They permit to achieve the same (or better) than diesel power density and efficiency, steady-state, and substantially similar transient performances. They also permit to deliver better than diesel engine-out emissions for CO2, as well as particulate matter, unburned hydrocarbons, and nitrous oxides. The adoption of injection in the liquid phase permits to further improve the power density as well as the fuel conversion efficiency. Here, a model is developed to study a high-pressure, 1600 bar, liquid phase injector for liquefied natural gas (LNG) in a high compression ratio, high boost engine. The engine features two direct injectors per cylinder, one for the diesel and one for the LNG. The engine also uses mechanically assisted turbocharging (super-turbocharging) to improve the steady-state and transient performances of the engine, decoupling the power supply at the turbine from the power demand at the compressor. Results of steady-state simulations show the ability of the engine to deliver top fuel conversion efficiency, above 48%, and high efficiencies, above 40% over the most part of the engine load and speed range. The novelty of this work is the opportunity to use very high pressure (1600 bar) LNG injection in a dual fuel diesel-LNG engine. It is shown that this high pressure permits to increase the flow rate per unit area; thus, permitting smaller and lighter injectors, of faster actuation, for enhanced injector-shaping capabilities. Without fully exploring the many opportunities to shape the heat release rate curve, simulations suggest two-point improvements in fuel conversion efficiency by increasing the injection pressure. Full article
(This article belongs to the Special Issue Production of Biofuels and Numerical Modeling of Chemical Combustion Systems)
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14 pages, 1902 KiB  
Article
Acid and Enzymatic Fractionation of Olive Stones for Ethanol Production Using Pachysolen tannophilus
by Manuel Cuevas, Marwa Saleh, Juan F. García-Martín and Sebastián Sánchez
Processes 2020, 8(2), 195; https://doi.org/10.3390/pr8020195 - 06 Feb 2020
Cited by 18 | Viewed by 2762
Abstract
Olive stones are an abundant lignocellulose material in the countries of the Mediterranean basin that could be transformed to bioethanol by biochemical pathways. In this work, olive stones were subjected to fractionation by means of a high-temperature dilute-acid pretreatment followed by enzymatic hydrolysis [...] Read more.
Olive stones are an abundant lignocellulose material in the countries of the Mediterranean basin that could be transformed to bioethanol by biochemical pathways. In this work, olive stones were subjected to fractionation by means of a high-temperature dilute-acid pretreatment followed by enzymatic hydrolysis of the pretreated solids. The hydrolysates obtained in these steps were separately subjected to fermentation with the yeast Pachysolen tannophilus ATCC 32691. Response surface methodology with two independent variables (temperature and reaction time) was applied for optimizing D-xylose production from the raw material by dilute acid pretreatment with 0.01 M sulfuric acid. The highest D-xylose yield in the liquid fraction was obtained in the pretreatment at 201 °C for 5.2 min. The inclusion of a detoxification step of the acid prehydrolysate, by vacuum distillation, allowed the fermentation of the sugars into ethanol and xylitol. The enzymatic hydrolysis of the pretreated solids was solely effective when using high enzyme loadings, thus leading to easily fermentable hydrolysates into ethanol. The mass macroscopic balances of the overall process illustrated that the amount of inoculum used in the fermentation of the acid prehydrolysates strongly affected the ethanol and xylitol yields. Full article
(This article belongs to the Special Issue Production of Biofuels and Numerical Modeling of Chemical Combustion Systems)
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12 pages, 1012 KiB  
Article
Hydrothermal Liquefaction of Microalga Using Metal Oxide Catalyst
by Alejandra Sánchez-Bayo, Rosalía Rodríguez, Victoria Morales, Nima Nasirian, Luis Fernando Bautista and Gemma Vicente
Processes 2020, 8(1), 15; https://doi.org/10.3390/pr8010015 - 20 Dec 2019
Cited by 19 | Viewed by 6695
Abstract
The yield and composition of the biocrude obtained by hydrothermal liquefaction (HTL) of Nannocloropsis gaditana using heterogeneous catalysts were evaluated. The catalysts were based on metal oxides (CaO, CeO2, La2O3, MnO2, and Al2O [...] Read more.
The yield and composition of the biocrude obtained by hydrothermal liquefaction (HTL) of Nannocloropsis gaditana using heterogeneous catalysts were evaluated. The catalysts were based on metal oxides (CaO, CeO2, La2O3, MnO2, and Al2O3). The reactions were performed in a batch autoclave reactor at 320 °C for 10 min with a 1:10 (wt/wt) microalga:water ratio. These catalysts increased the yield of the liquefaction phase (from 94.14 ± 0.30 wt% for La2O3 to 99.49 ± 0.11 wt% for MnO2) as compared with the thermal reaction (92.60 ± 1.20 wt%). Consequently, the biocrude yields also raised in the metal oxides catalysed HTL, showing values remarkably higher for the CaO (49.73 ± 0.9 wt%) in comparison to the HTL without catalyst (42.60 ± 0.70 wt%). The N and O content of the biocrude obtained from non-catalytic HTL were 6.11 ± 0.02 wt% and 10.50 ± 0.50 wt%, respectively. In this sense, the use of the metal oxides decreased the N content of the biocrude (4.62 ± 0.15–5.45 ± 0.11 wt%), although, they kept constant or increased its O content (11.39 ± 2.06–21.68 ± 0.03 wt%). This study shows that CaO, CeO2 and Al2O3 can be promising catalysts based on the remarkable amount of biocrude, the highest values of C, H, heating value, energy recovery, and the lowest content of N, O and S. Full article
(This article belongs to the Special Issue Production of Biofuels and Numerical Modeling of Chemical Combustion Systems)
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21 pages, 2190 KiB  
Article
Numerical Simulation of a Wall-Flow Particulate Filter Made of Biomorphic Silicon Carbide Able to Fit Different Fuel/Biofuel Inputs
by M. Pilar Orihuela, Onoufrios Haralampous, Ricardo Chacartegui, Miguel Torres García and Julián Martínez-Fernández
Processes 2019, 7(12), 945; https://doi.org/10.3390/pr7120945 - 11 Dec 2019
Cited by 4 | Viewed by 2998
Abstract
To meet the increasingly strict emission limits imposed by regulations, internal combustion engines for transport applications require the urgent development of novel emission abatement systems. The introduction of biodiesel or other biofuels in the engine operation is considered to reduce greenhouse gas emissions. [...] Read more.
To meet the increasingly strict emission limits imposed by regulations, internal combustion engines for transport applications require the urgent development of novel emission abatement systems. The introduction of biodiesel or other biofuels in the engine operation is considered to reduce greenhouse gas emissions. However, these alternative fuels can affect the performance of the post-combustion systems due to the variability they introduce in the exhaust particle distribution and their particular physical properties. Bioceramic materials made from vegetal waste are characterized by having an orthotropic hierarchical microstructure, which can be tailored in some way to optimize the filtration mechanisms as a function of the particle distribution of the combustion gases. Consequently, they can be good candidates to cope with the variability that new biofuel blends introduce in the engine operation. The objective of this work is to predict the filtration performance of a wall-flow particulate filter (DPF) made of biomorphic silicon carbide (bioSiC) with a systematic procedure that allows to eventually fit different fuel inputs. For this purpose; a well-validated DPF model available as commercial software has been chosen and adapted to the specific microstructural features of bioSiC. Fitting the specific filtration and permeability parameters of this biomaterial into the model; the filtration efficiency and pressure drop of the filter are predicted with sufficient accuracy during the loading test. The results obtained through this study show the potential of this novel DPF substrate; the material/microstructural design of which can be adapted through the selection of an optimum precursor. Full article
(This article belongs to the Special Issue Production of Biofuels and Numerical Modeling of Chemical Combustion Systems)
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17 pages, 6271 KiB  
Article
Effect of Pre-Combustion Chamber Nozzle Parameters on the Performance of a Marine 2-Stroke Dual Fuel Engine
by Hao Guo, Song Zhou, Majed Shreka and Yongming Feng
Processes 2019, 7(12), 876; https://doi.org/10.3390/pr7120876 - 21 Nov 2019
Cited by 10 | Viewed by 5365
Abstract
In recent years and with the increasing rigor of the International Maritime Organization (IMO) emission regulations, the shipping industry has focused more on environment-friendly and efficient power. Low-pressure dual-fuel (LP-DF) engine technology with high efficiency and good emissions has become a promising solution [...] Read more.
In recent years and with the increasing rigor of the International Maritime Organization (IMO) emission regulations, the shipping industry has focused more on environment-friendly and efficient power. Low-pressure dual-fuel (LP-DF) engine technology with high efficiency and good emissions has become a promising solution in the development of marine engines. This engine often uses pre-combustion chamber (PCC) to ignite natural gas due to its higher ignition energy. In this paper, a parametric study of the LP-DF engine was proceeded to investigate the design scheme of the PCC. The effect of PCC parameters on engine performance and emissions were studied from two aspects: PCC nozzle diameter and PCC nozzle angle. The results showed that the PCC nozzle diameter affected the propagation of the flame in the combustion chamber. Moreover, suitable PCC nozzle diameters helped to improve flame propagation stability and engine performance and reduce emissions. Furthermore, the angle of the PCC nozzle had a great influence on flame propagation direction, which affected the flame propagation speed and thus the occurrence of knocking. Finally, optimizing the angle of the PCC nozzle was beneficial to the organization of the in-cylinder combustion. Full article
(This article belongs to the Special Issue Production of Biofuels and Numerical Modeling of Chemical Combustion Systems)
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10 pages, 1346 KiB  
Article
Esterification of Free Fatty Acids with Glycerol within the Biodiesel Production Framework
by Juan Francisco García Martín, Javier Carrión Ruiz, Miguel Torres García, Chao-Hui Feng and Paloma Álvarez Mateos
Processes 2019, 7(11), 832; https://doi.org/10.3390/pr7110832 - 08 Nov 2019
Cited by 26 | Viewed by 16207
Abstract
Companies in the field of the collection and treatment of waste cooking oils (WCO) for subsequent biodiesel production usually have to cope with high acidity oils, which cannot be directly transformed into fatty acid methyl esters due to soap production. Since glycerine is [...] Read more.
Companies in the field of the collection and treatment of waste cooking oils (WCO) for subsequent biodiesel production usually have to cope with high acidity oils, which cannot be directly transformed into fatty acid methyl esters due to soap production. Since glycerine is the main byproduct of biodiesel production, these high acidity oils could be esterified with the glycerine surplus to transform the free fatty acids (FFA) into triglycerides before performing the transesterification. In this work, commercial glycerol was esterified with commercial fatty acids and commercial fatty acid/lampante olive oil mixtures over tin (II) chloride. In the first set of experiments, the esterification of linoleic acid with glycerol excess from 20 to 80% molar over the stoichiometric was performed. From 20% glycerol excess, there was no improvement in FFA reduction. Using 20% glycerol excess, the performance of a biochar obtained from heavy metal-contaminated plant roots was compared to that of SnCl2. Then, the effect of the initial FFA content was assessed using different oleic acid/lampante olive oil mixtures. The results illustrated that glycerolysis was impeded at initial FFA contents lower than 10%. Finally, the glycerolysis of a WCO with 9.94% FFA was assayed, without success. Full article
(This article belongs to the Special Issue Production of Biofuels and Numerical Modeling of Chemical Combustion Systems)
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14 pages, 1450 KiB  
Article
Mild Hydrothermal Pretreatment of Microalgae for the Production of Biocrude with a Low N and O Content
by Miriam Montero-Hidalgo, Juan J. Espada, Rosalía Rodríguez, Victoria Morales, Luis Fernando Bautista and Gemma Vicente
Processes 2019, 7(9), 630; https://doi.org/10.3390/pr7090630 - 17 Sep 2019
Cited by 7 | Viewed by 2696
Abstract
A hydrothermal pretreatment of the microalga Nannochloropsis gaditana at mild temperatures was studied in order to reduce the N and O content in the biocrude obtained by hydrothermal liquefaction (HTL). The work focused on the evaluation of temperature, reactor loading, and time (factors) [...] Read more.
A hydrothermal pretreatment of the microalga Nannochloropsis gaditana at mild temperatures was studied in order to reduce the N and O content in the biocrude obtained by hydrothermal liquefaction (HTL). The work focused on the evaluation of temperature, reactor loading, and time (factors) to maximize the yield of the pretreated biomass and the heteroatom contents transferred from the microalga biomass to the aqueous phase (responses). The study followed the factorial design and response surface methodology. An equation for every response was obtained, which led to the accurate calculation of the operating conditions required to obtain a given value of these responses. Temperature and time are critical factors with a negative effect on the pretreated biomass yield but a positive one on the N and O recovery in the aqueous phase. The slurry concentration has to be low to increase heteroatom recovery and has to be high to maximize the pretreated microalga yields. Response equations were obtained for the analyzed responses, which facilitated the accurate prediction of the operating conditions required to obtain a given value of these responses. Full article
(This article belongs to the Special Issue Production of Biofuels and Numerical Modeling of Chemical Combustion Systems)
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Review

Jump to: Editorial, Research

38 pages, 4813 KiB  
Review
Energetic Valorisation of Olive Biomass: Olive-Tree Pruning, Olive Stones and Pomaces
by Juan Francisco García Martín, Manuel Cuevas, Chao-Hui Feng, Paloma Álvarez Mateos, Miguel Torres García and Sebastián Sánchez
Processes 2020, 8(5), 511; https://doi.org/10.3390/pr8050511 - 26 Apr 2020
Cited by 64 | Viewed by 10124
Abstract
Olive oil industry is one of the most important industries in the world. Currently, the land devoted to olive-tree cultivation around the world is ca. 11 × 106 ha, which produces more than 20 × 106 t olives per year. Most [...] Read more.
Olive oil industry is one of the most important industries in the world. Currently, the land devoted to olive-tree cultivation around the world is ca. 11 × 106 ha, which produces more than 20 × 106 t olives per year. Most of these olives are destined to the production of olive oils. The main by-products of the olive oil industry are olive-pruning debris, olive stones and different pomaces. In cultures with traditional and intensive typologies, one single ha of olive grove annually generates more than 5 t of these by-products. The disposal of these by-products in the field can led to environmental problems. Notwithstanding, these by-products (biomasses) have a huge potential as source of energy. The objective of this paper is to comprehensively review the latest advances focused on energy production from olive-pruning debris, olive stones and pomaces, including processes such as combustion, gasification and pyrolysis, and the production of biofuels such as bioethanol and biodiesel. Future research efforts required for biofuel production are also discussed. The future of the olive oil industry must move towards a greater interrelation between olive oil production, conservation of the environment and energy generation. Full article
(This article belongs to the Special Issue Production of Biofuels and Numerical Modeling of Chemical Combustion Systems)
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