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.
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Current issue


Synergy of blending hydrotreated and hydrocracked kerosene in the production of jet fuel

Hugo Kittel, Daniel Kadleček

Aviation kerosene is the fastest growing transportation fuel. Regardless of the ambition to replace it by SAF, consumption of the mineral component in JET fuel will grow. In oil refineries, kerosene fractions are used to produce JET fuel and as a component of diesel fuel. These fractions can differ in origin and composition. In this article the possibility of blending hydrocracked kerosene used for JET production and hydrotreated kerosene used for diesel fuel production was investigated. It was concluded that significant synergies can be achieved by blending of these fractions in terms of increasing JET fuel production by up to 2.5 times, controlling the aromatics content of hydrocracked kerosene and obtaining a fraction for blending of diesel fuel with improved low temperature properties.

Keywords: hydrotreated kerosene, hydrocracked kerosene, jet fuel, diesel fuel, kerosene blending, freezing point, aromatics content, smoke point, synergies of blending
2/2022 - pages 68 - 73DOI: 10.35933/paliva.2022.02.01

Co-combustion of Sewage Sludge in the Coal-Fired Heating Plant

Ondřej Hlaváček
Due to greening of production of electricity and heat some owners of heating plant are changing their fuel mix from fossil fuels to biomass one. The stabilized sewage sludge is in this biomass category as well. New Czech national legislation limits are stricter in parameters of biological activity, so the owners of water treatment plant are looking for new utilization of their stabilized sludge. There are some possibilities in combustion or co-combustion of this sludge in currently heating plant.
The article describes the trial test of stabilized sludge combustion on heating plant technology. The heating plant is originally designed for combustion of brown coal. The stabilized sludge was produced at the municipal wastewater treatment plant, from where it was transported to low-temperature (78 °C) drying technology, from where it was transported in granular form to the heating plant in Mladá Boleslav. The fuel mixture of trial test was in energetic ratio of 23% dried sludge and 77% brown coal. The sludge was transported into the boilers by pneumatic conveying, which is used in normal operation for conveying pelletized phytomass. The result shows an increase in SO2 emissions from the original 189.91 mg∙m-3 to 407.98 mg∙m-3 and an increase in NOx emissions from 148.45 mg∙m-3 to 181.46 mg∙m-3. There were also detected increasing NH3 emissions due to reac-tion of control system in SNCR technology od decreasing of NOx emissions. The trial test was done during full op-eration of the heating plant. During the test there was also a lower steam production, from originally 38.17 kg∙s-1 to 34.44 kg∙s-1, which is related to the lower LHV compared to the reference fuel. There were no major operation problems, except higher dustiness during unloading of sludge.
Finally, the Czech legislative problems associated with the combustion of stabilized sewage sludge are mentioned. In the current system, the sludge is established as waste, which forbids the combustion of it in conventional heating plants, even though all emission legislative limits are complied with. Nowadays the Ministry of the Environment of the Czech Republic is working on new regulation, which will determine new category of solid alternative fuels and it will be solution of this situation.
Keywords: sewage sludge, incineration, testing
2/2022 - pages 74 - 78DOI: 10.35933/paliva.2022.02.02

Properties and Analysis of Gaseous Alternative Fuels I: Hydrogen and liquefied petroleum gases

Martin Staš, Jiří Kroufek, Tomáš Hlinčík, Pavel Šimáček

The importance of alternative fuels has increased significantly and continues to grow due to gradually lowering fossil fuel sources as well as environmental reasons. This article is the first in a series of articles focused on gaseous, liquid, and solid alternative fuels. The aim of the articles is to provide an overview of the required properties and testing methods for individual alternative fuels prescribed by the relevant standards. This first article in the forthcoming series focuses on gaseous alternative fuels based on hydrogen and liquefied petroleum gases.

Keywords: alternative fuels, gaseous fuels, analysis, hydrogen, LPG
2/2022 - pages 79 - 89DOI: 10.35933/paliva.2022.02.03

Comparison of Properties of Different Materials by Adsorptions N2 and Ar at Temperature –196 °C

Veronika Kyselová, Karel Ciahotný
The article is focused on comparing of the structural properties of different adsorption materials. The measurement of adsorption isotherms was carried out in nitrogen and argon at a temperature of –196 °C. The individual isotherms using selected samples were measured on an Autosorb ASiQ instrument. BET surfaces and total pore volumes of individual samples were calculated and compared from the resulting isotherms. The results show relatively high differences between the adsorption isotherm measured by using nitrogen and argon. For the Envisorb sample, which consists of up to 85% silicagel, the BET surface area calculated from the nitrogen adsorption isotherm was 45 % higher than when measuring the adsorption isotherm using argon as the adsorptive. For silicagel SGR 50 was the difference between BET surface area measurements with nitrogen and argon only 4 %. The opposite phenomenon was calculated for the material activated carbon SC 40, where the BET surface measured by argon was higher than BET surface measured by nitrogen.
Of the adsorbents used, nitrogen appears to be more suitable; only for carbonbased microporous materials is it better to use argon as an adsorptive.
The evaluation of the measured adsorption isotherms by the t-plot method showed a good usability of this method when it is applied similarly to the BET method for adsorption isotherms in the range of adsorptive rel. pressure ranged from 0.05 to 0.35. This method is a reliable tool for determining the proportion of the smallest pores (micropores) in the total surface area of a given adsorbent. However, in the case of adsorbents with a very low proportion of micropores, its accuracy is lower.
Keywords: physisorption, argon, nitrogen, BET surface, pore volume, t-plot method
2/2022 - pages 90 - 96DOI: 10.35933/paliva.2022.02.04

Combustion effectivity of high ash coal in adiabatic calorimeter

Boleslav Taraba, Petr Gřunděl
A series of coal-mineral matter mixtures was investigated by bomb combustion calorimetry (IKA C4000, Germany) to elucidate boundary for ash content in coal at which combustion proceeds with lowered efficiency.
For the experiments, a high rank bituminous coal was mixed with particles of mine stone, both being milled to size below 0.2 mm. Before the usage, the sample of stone was heated at 900°C for 2 hours in air to stabilize mineral matter composition. Mixtures 5, 10, 15, 20, 25, 30, 40, and 50% of coal were used, with sample weights both of 1 g and/or 2 grams being applied. The efficiency of the combustion process at the bomb test was assessed of the measured calorific value and that of “theoretically” calculated. The “theoretical” calorific value of the mixture was determined from the actual content of the coal proving known specific calorific value (36.6 MJ/kg).
Based on the measurements, mineral matter content of about 50% was found as limiting for fully efficient combustion of coal in the bomb calorimeter. At content of 90% of mineral matter, the efficiency of combustion is about 70 % (sample weight 1 g) and/or 50 % (sample weight 2 g). Afterwards, the combustion efficiency steeply decreases to zero.
Keywords: combustion calorimetry, high-ash coal, combustion efficiency
2/2022 - pages 97 - 100DOI: 10.35933/paliva.2022.02.05

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