4/2024
Dipakkumar J. Parmar, Vimal R. Patel, Shyam K. Dabhi
Gasification is a popular biomass-to-energy production strategy due to its affordability and ease of use. Downdraft gasifiers, typically small-scale units with a maximum heat power output of 5 MW, are ideal for decentralized power generation and delivery to remote villages. Mathematical models can predict gasifier design, operating behaviour, gas composition, startup and shutdown, fuel and load changes, and other issues. Numerous numerical/mathematical models have been developed to characterize and forecast gasification processes, including drying, pyrolysis, gasification, and combustion. This article reviews the thermodynamic equilibrium model for gasification and its modifications to increase prediction accuracy. Factors such as, pressure fluctuations, equivalent ratio, biomass moisture content, and oxygen enrichment affect the quality of generated syngas. Equilibrium models are useful for predicting the maximum yield achievable by a reagent system and are ideal for initial analysis or optimization techniques.
Keywords: biomass gasification; downdraft gasifier; equilibrium model; modelling
Martin Staš, Hugo Kittel, Lukáš Matějovský, Pavel Šimáček
This article is the fourth in a series of articles aimed at introducing common methods for evaluating both conventional and alternative fuels. In previous articles, we focused on the determination of elements and non-hydrocarbon compounds, as well as the evaluation of physical and chemical properties. This article focuses on other not yet-discussed properties such as gum content, total impurities, ash content, carbonization residue, octane number, cetane number, and cetane index. The main goal of the article is to provide an overview of which fuels are used, why these properties are monitored, and what methods are used for this monitoring. Emphasis is placed mainly on standardized tests, but in some cases, additional tests not required by the standard are also discussed.
Conventional and alternative fuels must meet the technical requirements defined by the relevant product standards. The fulfillment of these requirements is to ensure that, in addition to other properties, the relevant fuel will be of good quality and that the engine will not be damaged during its use. In addition to the technical requirements for fuels, the product standards also define the tests that are used to verify that the fuel meets the defined requirements. As mentioned above, this article is another in a series of articles aimed at presenting methods for evaluating both conventional and alternative fuels. In this article, we present an overview of the properties of fuels that have not yet been discussed in this series of articles. These are properties associated with the content of impurities present in the fuel (total impurities) or those impurities, or products that may arise during thermal stress on the fuel in the combustion system (ash content, carbonization residue, gum content). Furthermore, in this text, we will focus on the properties of fuels that characterize the fuel susceptibility to knocking (octane number) or the so-called hard running of the engine (cetane number and cetane index). In the article, we present for which fuels these properties are monitored, what are the limit values of these parameters and what are the reasons for their monitoring. We also present the testing methods that are used to determine these properties.
Keywords: conventional fuels, alternative fuels, gum content, total impurities, ash content, carbon residue, octane number, cetane number, cetane index
Filip Sihlovec, Dan Vrtiška, Pavel Šimáček
Continuous development and demand for more sustainable energy sources are driving the use of biofuels. One such biofuel could be the product of the EtG (Etha-nol-to-Gasoline) process. Compared to ethanol, this product has several application advantages, such as full compatibility with hydrocarbon fuel and the possibility of higher content in automotive gasoline. However, the disadvantage of this product is the difficulty in determining its content in motor gasoline, due to the high similarity of these fuels. Existing methods of determination using radiocarbon analysis are poorly developed, and quite expensive, while all alternative methods have not been sufficiently explored. This paper outlines the possibilities of determining EtG in blends with fossil gasoline using spectroscopic and chromatographic methods as well as the use of a tracer that could be added to the EtG product.
Keywords: EtG, gasoline, analysis
Marek Staf, Michael Pohořelý
The study presented here solved the problem of very low specific surfaces, which are achieved when using the standard method of physical activation of brown macroalgae (Phaeophyceae) waste. The material consist-ing of crushed thallus residues from the processing of macroalgae for food purposes contained 14.6% of ash, which consisted mostly of Na, K, Mg and Ca salts. This material was first subjected to slow pyrolysis at a rate of 10 °C.min–1 to a final temperature of 450 °C, at which 19% condensate, 40% gas, and 41% solid residue were obtained on a dry basis.
The pyrolysis residue then served as an input raw material for the subsequent activation step. Three alter-native activation procedures performed by steam in a ver-tical fixed-bed reactor were compared. In the first of them, the pyrolysis residue was heated to 800 or 900 °C in an inert atmosphere (N2), and at this temperature it was exposed to steam. Under the given activation conditions, which are otherwise fully satisfactory for other types of phytomass and dendromass, the salts present in the sam-ple led to an underdeveloped porous system. It was thus possible to prepare only products with a specific surface area (BET) of a maximum of 15 m2 g‒1.
In the second procedure, the pyrolysis residue was washed with a larger volume of distilled water and, after filtering under vacuum and drying, was steam activated. After activation, the product inside the reactor was washed with water, removed and then washed again un-der vacuum. This procedure led to a product with a spe-cific surface area of 400 m2.g-1.
In the third activation procedure, the pyrolysis resi-due was heated to 300 °C in an inert atmosphere and hy-drated with steam at this temperature for 30 minutes. This was followed by heating to the final activation tempera-ture and re-dosing of steam. The product obtained was washed with a large volume of distilled water and vac-uum filtered. By applying the described method, at an ac-tivation temperature of 800 °C combined with steam dos-ing for 30 minutes, the highest specific surface area (BET) of 675 m2.g-1 was achieved, and at the same time the product yields were higher than in the above proce-dure. If the same procedure used a temperature of 900 °C combined with only 2 min of steam introduction, a BET surface area of 636 m2.g‒1 was achieved, but the overall yield of activated product increased from 17 to 25% (cal-culated for the entire process including pyrolysis). This procedure was therefore found to be the good compro-mise between BET surface area and yield.
Keywords: macroalgae, pyrolysis, physical activation, specific surface, balance
Fadhil Mahmood Oleiwi, Jaber.O.Dahloos, Hasan F Abd Ali
Despite the many solar energy plants that have been installed, the need to study photovoltaic systems using theoretical and practical models still exists due to the large number of variables that affect the productivity and efficiency of solar systems. In this theoretical study, a 1 MW photovoltaic (PV) system was studied in Al-Mu-sayyb city, Al-Razaza Lake, and Ayen Al-tamer desert in southwest Baghdad, using PVsyst V 7.4 software to choose the best location. The input data for the PVsyst are (Geographical site, power of the system, system information, and type of grid). The production of the system in Al-Razaza Lake, Al-Musayyb city, and Ayen Al-tamer desert are 1785 MWh/year, 1885 MWh/year, and 1779 MWh/year respectively. The performance ratios for Al-Razaza Lake, Al-Musayyb City, and Ayen Al-Tamer Desert are 0.817, 0.831, and 0.816. The current system can mitigate the emissions of CO2 for the system in Al-Razaza Lake, Al-Musayyb, and Ayen Al-Tamer desert to 34617 tons,32503 tons, and 32371 tons respectively through 30 years of operation. The lake environment (Floating PV system) is a better location for installing the plant than other sites due to the output energy is higher than in other environments.
Keywords: photovoltaic (PV) location, off grid-solar system, renewable energy, carbon dioxide emissions, generated energy
