Paliva (Fuels) is a scientific journal issued quarterly by the Faculty of Environmental Technology, ICT Prague. Fuels publishes papers on a broad range of topics covering exploitation, processing, upgrading, and utilization of various types of fuels, and power engineering.
English Česky
Current issue


Activation of solid residues from batch pyrolysis of waste tires

Marek Staf, Běla Ondrová, Vít Šrámek
The paper deals with a two-stage process of thermal treatment of waste tires in order to obtain a carbonaceous adsorbent. A fraction of 0.4 ‒ 0.8 mm of the ground material was involved in the experiments. In the first stage, pyrolysis took place in a retort apparatus, which provided about 43 % of solid residues, 41 % of condensates and 16 % of gas at temperatures of 600 and 800 ° C.
The mass balance was confirmed by the TGA method independently of the retort apparatus. N-alkanes, mono- to trialkylated benzenes, cycloalkenes, higher alcohols, ethers, acetates and aliphatic and aromatic thiols were identified in the liquid product by GC-MS. The main components of the condensates were: 50% n-al-kanes and more than 25 % alkylated benzenes. According to GC-TCD-FID, the separated pyrolysis gases contained nine main components with a volume fraction >1 %. Of these majority compounds, methane with volume fractions approaching 30 % was the most represented. Other important compounds were in descending order: hydrogen (20.2 and 20.8 %), carbon dioxide (8.9 %), ethane (8.5 %) and ethene (7.0 %). Due to the upper calorific value of 44 ‒ 45 MJ m‒3, the gas can be advantageously used energetically, but the high sulfur content must be considered anyway.
The solid residues were subjected to steam activation in a separate apparatus. The activation apparatus operated with a batch reactor of similar design as the pyrolysis retort. By activation, the specific surface area of the pyrolysis residues was increased from a very small initial value <59 m2 g‒1 to a maximum of 337 m2 g‒1. However, this result, in contrast to the reference sample prepared from hardwood, required aggressive conditions, namely 900 °C combined with a steam exposure time of 60 min. The combination of the lower of the selected pyrolysis temperatures and the higher activation temperature led to better results than the opposite setting.
Both the crude pyrolysis residues and the obtained activated products were significantly mesoporous and pores with a diameter of 20 ‒ 80 nm predominated in their structure. Prior to activation, the pyrolysis residues always had a pore content of at least 60 %, while the activation further increased their proportion to 81 %. Such a significant proportion of mesopores 20 - 80 nm suggests that the material could be suitable for the next modification/improving step in the form of wet impregnation.
Keywords: batch pyrolysis; tires; mass balance; specific surface area
3/2022 - pages 105 - 116DOI: 10.35933/paliva.2022.03.01

Energy saving technology in power plants industry by HFRW

Mohammad Sadeghi, Hamed Sabet

This paper aims at investigating the use of high frequency resistance welding (HFRW) to deploy energy saving technology in power plants industry. The new approach of dissimilar welds A240TP409 finned and 2¼ Cr-1 Mo seamless tube under various conditions of high frequency resistance welding (HFRW) are found in power plant boilers and reducing energy costs is possible through the use of finned tubes. HFRW have accomplished on samples by changing multiple parameters including current of welding, electric potential, travel speed and fin pitch. Microstructural evolution in weld bond, hardness and tensile strength tests revealed that metallurgical bonding more than 90 % was measured at the weld interface and the average of tensile strengths were more than 275 MPa, with setting on appropriate welding parameters and optimum pressure. Since the pitch and fin thickness can be severely reduced, the output transfer surface treatment in final process can be dramatically diminished. Lastly, a well-engineered approach to the design of the best conditions of finned tube welding bond is discussed in modern combined cycle power plant (CCPP).

Keywords: energy saving; power plants; dissimilar welds; seamless tube
3/2022 - pages 117 - 123DOI: 10.35933/paliva.2022.03.02

Investigation of the combustion process of the developed composite granules

Yuliia Novikova, Zhanna Petrova, Leonid Vorobiov, Valerii Chmel, Yevhen Skliarenko, Inessa Novikova

The urgent task of each country is to achieve energy independence through the transition from traditional energy sources to alternative ones. Sewage treatment plants can be considered a potential source of additional raw materials. In Ukraine, one of the problems is the disposal of sludge that are more than 30 years old and to which activated sludge has not been added. This sludge has a low content of organic components, which are not suitable for combustion in pure form and fertilizers. Since the old sludge have a small content of organic components, for their better utilization it is proposed to create composite granules, their subsequent drying and combustion, during which the resulting ash will be used for the production of building materials. The aim of the work is to study the combustion of composite granules based on sludge, peat and biomass. The determined specific heat of combustion of composite granules exceeds this index of peat by 1.2 times. The study of the combustion process of composite granules showed that the obtained results can be used in fuel combustion in different ways. The combustion rate of granules is much lower than the combustion rate of the original biomass, but the combustion rate of a separate part of sludge prevails. The combustion rate of granules is much lower than the combustion rate of the original biomass, but the combustion rate of a separate part of sludge prevails. The conducted experiments showed the possibility of decontamination of sludge and its disposal as an alternative fuel.

Keywords: sludge, peat, biomass, combustion, heat of combustion
3/2022 - pages 124 - 130DOI: 10.35933/paliva.2022.03.03

Properties and Analysis of Liquid Alternative Fuels I: Fatty Acid Esters

Martin Staš, Zlata Mužíková, Pavel Šimáček

The importance of alternative fuels is constantly growing due to environmental reasons, saving fossil fuels and reducing the dependence of the world countries on the supply of fossil raw materials from politically unsta-ble regions. This article is further in a series of review articles focused on an overview of technical requirements and testing methods for selected alternative fuels. It is also the first in a series of papers focused on liquid alter-native fuels. The aim of this series of articles is to provide an overview of the required properties of individual al-ternative fuels, the possibilities of their analysis and the importance of the individual analyzes. This article fo-cuses on fuels containing fatty acid esters.Biodiesel can be burned in diesel engines either in a mixture with conventional diesel or as an individual fuel. Unlike conventional diesel, which is composed of hydrocarbons of petroleum origin, biodiesel contains fatty acid methyl esters. In addition to this main compo-nent, glycerol (by-product of transesterification), metha-nol, free fatty acids, glycerides (mono-, di- and tri-), cat-alyst residues, water, and possibly other components can be present also. These contaminants can, in certain con-centrations, cause some undesirable properties both in pure biodiesel and in biodiesel/diesel blends. Compared to conventional diesel, biodiesel has a higher density and viscosity, but a slightly lower higher heating value, and considerably worse oxidation stability. In terms of pollutant emissions, the combustion of biodiesel pro-duces less hydrocarbons, carbon monoxide and solid par-ticles, but slightly more nitrogen oxides than the combus-tion of mineral diesel. Gas chromatography, infrared spectroscopy, titra-tion methods, and atomic spectroscopy methods have typically been used for the evaluation of these fuels. In addition to the properties monitored by these methods, conventional fuel parameters such as density, viscosity, low-temperature properties, oxidation stability, corrosion properties, flash point, cetane number, and others are monitored for biodiesel and biodiesel/diesel blends. In general, it can be stated that the analysis of fuels contain-ing biodiesel is well managed. Instrumental equipment and (modified) analytical methods used for the analysis of conventional liquid fuels can be used to analyze these fuels.

Keywords: alternative fuels, liquid fuels, fatty acid esters, biodiesel, FAME, RME
3/2022 - pages 131 - 144DOI: 10.35933/paliva.2022.03.04

Properties and Analysis of Gaseous Alternative Fuels II: Fuels Based on Natural Gas and Biogas

Martin Staš, Jiří Kroufek, Tomáš Hlinčík, Pavel Šimáček
The importance of alternative energy sources is constantly growing, especially due to the ever-increasing energy consumption of mankind and due to the effort to replace existing sources with more environmentally friendly ones. This article is another in a series of articles focused on an overview of technical requirements and testing methods for alternative gaseous, liquid, and solid fuels. This series of articles aims to provide an overview of the required properties of individual alternative fuels, the possibilities of their analysis, and the significance of individual analyzes.
This article provides an overview of the technical requirements prescribed by legislation and relevant standards for automotive fuels based on natural gas (fossil methane) and biomethane. Furthermore, prescribed analytical tests are presented, which have been used to monitor the quality of these fuels. To a lesser extent, the importance of selected analytical tests is also discussed. Natural gas can be compressed or liquefied for use in automobile transport. In the first case, CNG fuel is obtained, and in the second, LNG. As a source of renewable methane or biomethane, biogas can be used, which is produced by anaerobic fermentation of agricultural waste or other raw materials in biogas plants. The obtained biogas can be used for the combined production of heat and en-ergy. Alternatively, it can be purified into biomethane, which can be injected into the natural gas distribution network or used in automobile transport in the form of bio-CNG and bio-LNG. In general, it can be stated that the analysis of fuels based on natural gas and biomethane is well managed. Instrumental equipment and analytical methods used for natural gas analysis can be used to analyze these fuels.
The properties of fuels based on natural gas and bi-omethane are closely related to their composition. In terms of proper operation and performance of the combustion engine, the lower heating value, Wobbe number, and methane number are critical parameters. An important parameter is also the sulfane content, increased content of which can lead to corrosion of engine components. In terms of emissions, the total sulfur content is an important parameter also. Sulfur compounds are undesirable in emissions for environmental reasons. At the same time, they are also catalytic poisons. Other critical parameters of fuels based on natural gas and bio-methane are the water content or dew point of water.
Keywords: alternative fuels, gaseous fuels, CNG, LNG, bio-LNG, bio-gas, bio-methane
3/2022 - pages 145 - 153DOI: 10.35933/paliva.2022.03.05

technical support editor-in-chief