The demand for petroleum has been rising rapidly due to increasing industrialization and modernization. This economic development has led to a huge demand for energy, most of which is derived from ...fossil fuel. However, the limited reserve of fossil fuel has led many researchers to look for alternative fuels which can be produced from renewable feedstock. Increasing fossil fuel prices have prompted the global oil industry to look at biodiesel, which is from renewable energy sources. Biodiesel is produced from animal fats and vegetable oils and has become more attractive because it is more environmentally friendly and is obtained from renewable sources. Glycerol is the main by-product of biodiesel production; about 10% of the weight of biodiesel is generated in glycerol. The large amount of glycerol generated may become an environmental problem, since it cannot be disposed of in the environment. In this paper, an attempt has been made to review the different approaches and techniques used to produce glycerol (hydrolysis, transesterification, refining crude glycerol). The world biodiesel/glycerol production and consumption market, the current world glycerin and glycerol prices as well as the news trends for the use of glycerol mainly in Brazil market are analyzed. The technological production and physicochemical properties of glycerol are described, as is the characterization of crude glycerol obtained from different seed oil feedstock. Finally, a simple way to use glycerol in large amounts is combustion, which is an advantageous method as it does not require any purification. However, the combustion process of crude glycerol is not easy and there are technological difficulties. The news and mainly research about the combustion of glycerol was also addressed in this review.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•The AOM is an excellent tool to establish PMs for the syngas composition obtained from the gasification of biomass in a fixed bed.•The AOM allows analytical calculation of the correction factors for ...the chemical equilibrium constants.•A PM is developed to estimate the syngas compositions.•The PM is a realistic model.•The PM was validated with six experimental compositions, yielding RMSE values smaller than or equal to 2.25.
This work consists of developing a predictive model (PM) for syngas composition obtained from biomass gasification in fixed bed gasifiers. The PM is composed of three correlations which are made for carbon conversion efficiency, gasification temperature and the correction factor for the equilibrium constant of the water-gas homogeneous reaction. Such correlations were established using results obtained from the application of an optimization method (AOM) that uses Kuhn–Tucker multipliers. Syngas compositions determined through AOM were compared with experimental compositions and those estimated by other models, resulting that the AOM always determines the best estimates with respect to the root mean square error (RMSE). For syngas compositions estimated by AOM, the RMSE interval is 0.21, 4.11. The PM was validated with six experimental compositions. From the predicted syngas compositions it was found that the ranges for LHV, cold gas efficiency, carbon conversion efficiency and gasification temperature were 4.594, 5.116 MJ/Nm3, 55.74, 68.18%, 74.20, 88.40% and 749, 918 °C, respectively. Additionally, for the predicted syngas compositions the RMSE interval was determined as 0.68, 2.25. Therefore, the PM was considered to be effective in estimating syngas compositions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
► Develops a comprehensive literature review on ethanol flammability limits. ► Difference in standard procedures lead to different experimental values of the flammability limits. ► Methodology for ...experiments to find the FL's of ethanol for aeronautical applications.
The lower and upper flammability limits of a fuel are key tools for predicting fire, assessing the possibility of explosion, and designing protection systems. Knowledge about the risks involved with the explosion of both gaseous and vaporized liquid fuel mixtures with air is very important to guarantee safety in industrial, domestic, and aeronautical applications. Currently, most countries use various standard experimental tests, which lead to different experimental values for these limits. A comprehensive literature review of the flammability limits of combustible mixtures is developed here in order to organize the theoretical and practical knowledge of the subject. The main focus of this paper is the review of the flammability data of ethanol–air mixtures available in the literature. In addition, the description of methodology for experiments to find the upper and lower limits of flammability of ethanol for aeronautical applications is discussed. A heated spherical 20L vessel was used. The mixtures were ignited with electrode rods placed in the center of the vessel, and the spark gap was 6.4mm. LFL and the UFL were determined for ethanol (hydrated ethanol 96% °INPM) as functions of temperature for atmospheric pressure to compare results with data published in the scientific literature.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Global warming might be mitigated if emissions were interrupted through carbon capture technologies, as there is a significant amount of comprehensive studies on them. An outline of the main gaps and ...trends of a technology is critical for further development. In this context, this study provides an overview of calcium looping carbon capture processes that have proven their potential and commercial viability. A bibliometric analysis is conducted on both Scopus and Web of Science database by seeking the keywords “calcium looping”, “co2 capture”, and “fluidized bed” in titles, abstracts, and keywords. Word selection was based on a list of relevant papers on the topic. These items of data have been processed and analyzed based on the number of publications and citations by emphasizing recent publication evolution, journal influence, the use of specific keywords, and co-citation. Results reveal that the European Union (EU) leads the rankings on the topic, followed by Canada. Keyword choice might have affected the number of citations. Recent studies used limestone as a sorbent and a dual fluidized bed reactor with a calciner or resistance depending on its size. Most studies are focused on technology scale-up. Although scale-up seems to be a priority, multiple studies are designed to assess the effect of steam generation and SO2 on the process.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
5.
DDT limits of ethanol-air in an obstacles-filled tube Mendiburu Zevallos, Andrés Armando; Ciccarelli, Gabriel; Carvalho Jr, João A.
Combustion science and technology,
05/2023, Volume:
195, Issue:
7
Journal Article
Peer reviewed
Open access
Experiments were performed to study flame acceleration and deflagration-to-detonation transition (DDT) in ethanol-air mixtures in a tube filled with orifice plates with a blockage ratio of 0.44. ...Tests were conducted at initial temperatures of 100 and 200°C, and initial pressures of 60 and 101 kPa. Experiments carried out at 60 kPa did not result in DDT, whereas tests performed at 101 kPa, at both 100 and 200°C, resulted in DDT for mixtures in the equivalence ratio range of 1.1-1.3. In a previous study, cell size data of a "double cell structure" have been obtained for mixtures of ethanol-air. Using the d/λ = 1 criterion (that has been confirmed in the tube and orifice plate geometry used in this study with gaseous fuels at room temperature), it was determined that the DDT limit correlates with the ethanol large-cell size reported in the previous study. As a result, for explosion safety purposes, the large-cell size data should be used for assessing the DDT potential of an ethanol-air mixture.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
•A semi-empirical method for determining UFLs of C–H compounds was developed.•The squared correlation coefficient obtained for the UFL determination was 0.9248.•The method was applied to estimate ...UFLs of binary fuel mixtures.•The method was extended to estimate UFLs at moderate initial temperatures.•The estimations showed good or acceptable accuracy in all cases.
This study focuses on estimating the upper flammability limits of C–H compounds. A method was developed to determine the upper flammability limits in air at standard atmospheric pressure for the following cases: (a) estimation of the UFLs of pure C–H compounds at standard ambient temperature (25°C); (b) estimation of the UFLs of binary mixtures of C–H compounds at standard ambient temperature (25°C); (c) estimation of the UFLs of C–H compounds at different initial temperatures. The method was accurate in all cases. In case (a), for a total set of 115 compounds, the absolute average relative error was 7.27% and a squared correlation coefficient of 0.9248 was obtained. In case (b), the average absolute relative error was 5.55%; in case (c) it was 2.19%.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Flammability limits for ethanol at reduced pressures were determined.•295 experiments were carried out in total for anhydrous and hydrated ethanol.•The first 80 were to calibrate the heating chamber ...and compare the results.•215 experiments were performed both at atmospheric and reduced pressure.•Results had a correlation with the LFL obtained but UFL had some differences.
There is interest in finding the flammability limits of ethanol at reduced pressures for the future use of this biofuel in aeronautical applications taking into account typical commercial aviation altitude (<40,000ft). The lower and upper flammability limits (LFL and UFL, respectively) for hydrated ethanol and anhydrous ethanol (92.6% and 99.5% p/p, respectively) were determined for a pressure of 101.3kPa at temperatures between 0 and 200°C. A heating chamber with a spherical 20-l vessel was used. First, LFL and the UFL were determined as functions of temperature and atmospheric pressure to compare results with data published in the scientific literature. Second, after checking the veracity of the data obtained for standard atmospheric pressure, the work proceeded with reduced pressures in the same temperature range. 295 experiments were carried out in total; the first 80 were to calibrate the heating chamber and compare the results with those given in the published scientific literature. 215 experiments were performed both at atmospheric and reduced pressures. The results had a correlation with the values obtained for the LFL, but values for the UFL had some differences. With respect to the water content in ethanol, it was shown that the water vapor contained in the fuel can act as an inert substance, narrowing flammability.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•Energy, emission and emissivity analysis of the substitution of HFO by green hydrogen.•Economic assessment of the substitution of HFO by green hydrogen.•Case study of the substitution of a 45 ...ton/day industrial equipment in Chile.•Hydrogen mixing up to 20% is economically viable in Chile with the current forecasts.•The full substitution of HFO per hydrogen will be economically viable after 2030.
The high environmental impact of fossil fuels combined with the rise of carbon dioxide in the atmosphere has made the search for renewable fuels imperative. The study assesses the technical and economic viability of replacing heavy fuel oil (HFO) with green hydrogen (H2) in industrial plants for high temperature generation (>1100 K). The study also estimates the emissions generated by the plants after the fuel switch in terms of particulate matter (PM), SO2, NOx and CO2 emissions. To illustrate the feasibility of this replacement, an assessment of a calcination furnace at a pulp plant in Chile in 2022 was carried out, taking into account two electricity generation scenarios for H2 production by water electrolysis. Replacing HFO with a mixture of H2 + HFO was beneficial in terms of emissions. The financial assessment showed that blending H2 with HFO of up to 20 % is the best solution, considering current fuel prices, and that full substitution of HFO with H2 after 2030 is economically viable.
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GEOZS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPUK, ZAGLJ, ZRSKP
Flammability limits play an important role in combustion research, industrial applications, and fire safety. This article provides a comprehensive review of recent developments in the fundamental ...understanding of flammability limits and their experimental determination as well as estimation methods for pure fuels and fuel mixtures. The article begins with a discussion of the importance and challenges of determining flammability limits. It then presents the theoretical, computational, and experimental methods available to understand the mechanism of flammability limits and to quantify them. The experimental setups using cylindrical and spherical vessels to determine the flammability limits are discussed. The effects of buoyancy, thermal radiation, and flame stretch are examined. The relationship between the fundamental flammability limits and the extinction limits of stretched flames via strain and radiation is presented. The effects of initial temperature, pressure, mixtures of different fuels, and diluents are examined, and available estimation methods are presented. Finally, the flammability limits of renewable and alternative fuels are addressed and strategies for estimating the flammability limits of these fuels are presented.
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IJS, KILJ, NUK, PNG, UL, UM
The main objective of this study was to develop a method that can be used to estimate the lower flammability limits of C–H–O compounds at standard temperature and pressure. In addition, a study was ...carried out to develop a method that can be used to determine lower flammability limits at different initial temperatures at 1atm.
Several 374 C–H–O compounds were used to develop the method which determines the lower flammability limits at standard temperature and pressure. This group of compounds was divided into two sets, one for correlation and another for prediction. The correlation set was made up of 273 compounds while the prediction set was made up of 101 compounds. The average absolute relative error was 5.53% for the correlation set, while the squared correlation coefficient was 0.9758; the average absolute error was 5.25% and the squared correlation coefficient was 0.9699 for the prediction set; and the average absolute error was 5.43% and the squared correlation coefficient was 0.9752 for the total set. These parameters show that the method is very accurate.
The dependence of the lower flammability limit on the initial temperature was studied for a total set of 26 compounds. It was found that the adiabatic flame temperature at the lower flammability limit cannot always be assumed to be constant. A method that can be used to estimate the LFLs at different initial temperatures was developed; this method had an average absolute relative error of 1.85% and a squared correlation coefficient of 0.9987.
•A method for determination of the LFLs of C–H–O compounds was developed.•The method was very accurate when it was tested against experimental data.•The temperature dependence of the LFL was studied.•It is not always correct to assume that adiabatic flame temperature is constant.•A method for determination of LFLs at different initial temperatures was developed.
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