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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4/2019

Mercury in the environment, its anthropogenic sources, environmental and health risks

Tomáš Ružovič, Karel Svoboda, Michael Pohořelý, Marek Staf
The article deals with mercury emissions representing a significant environmental risk. The introduction outlines the history of the use of this element and its release to all environmental compartments, such as lithosphere, hydrosphere and atmosphere. The actual situation in distribution of mercury emissions from the most important industrial sectors is described in more detail. A corresponding space is also reserved to the description of health risks associated with short-term and chronic exposure of human and animal organisms to this toxic metal.
Elemental mercury, its oxidized form of Hg2+ bound in various compounds and Hg adsorbed onto solid particles are discussed separately. This is because each of these forms represents a different level of risk, transforms and binds differently in the human body, etc.
As there is currently an intensive debate in the Czech Republic on reducing Hg emissions from the power industry, this issue is also mentioned in the paper presented here.
Within the relevant chapter the initial phase of the research on the use of fly ashes transformed into zeolites for Hg adsorption from gaseous mixtures is sketched. Testing of the conditions under which domestic fly ashes, generated by the combustion of brown coal and biomass, can be converted to the efficient adsorbents has been started.
In the published studies, the main attention is paid to the largest possible specific surface and nanopore percentage. For this reason, the research has begun to ad-dress the conditions under which the above-mentioned product properties are achieved. A method, in which the intermediate was exposed to 30% HCl after hydrothermal treatment of the appropriate raw material with NaOH, gave a structure having the BET surface significantly exceeding 350 m2g-1. Measurements of the sorption proper-ties of the product using gases containing defined Hg concentrations will follow in the next phase of the re-search.
Keywords: mercury emission; athropogenic sources; environmental impact
4/2019 - pages 102 - 109DOI: 10.35933/paliva.2019.04.01

Nord Stream pipeline

Dominik Schlehöfer, Tomáš Hlinčík

Increasing demand for energy has resulted in the requirement of securing the energy situation in the European Union. This problematic situation was partially solved by the construction of the Nord Stream gas pipeline. However, despite its considerable advantage in the form of large supplies of natural gas, especially to Western Europe, it has received many negative responses from the very beginning of the project planning. Despite all criticism the Nord Stream pipeline project, which brings natural gas from Russia to Germany and further to Western Europe, has taken place. A second project, Nord Stream 2, which should guarantee energy stability in Europe, is currently under construction. The paper summarizes the historical development of the Nord Stream project, pointing out the reason for constructing such a conceived gas pipeline. Furthermore economic and environmental aspects are described, which the project, as well as the Nord Stream 2 project, was dealing with during the whole construction. The paper also describes the entire route of both gas pipelines.

Keywords: gas pipeline; Nord Stream
4/2019 - pages 110 - 117DOI: 10.35933/paliva.2019.04.02

Accelerating testing of long-term activity of the HDS catalyst based on Co-Mo

Luboš Matoušek, Aleš Vráblík, Josef Blažek, Radek Černý
The rate of deactivation of catalysts significantly affects their use in industrial processes. Comparison of their initial and residual activity is used to assess catalyst deactivation. This work deals with the accelerated deactivation of a hydrodesulfurization Co-Mo/Al2O3 catalyst with a deactivation agent (light cycle oil) which tends to condense reactions, especially at low hydrogen flow and pressure. Catalyst activity was assessed as the temperature at which the 10 mg∙kg-1 sulfur content of the product was achieved by the hydrodesulfurization of the atmospheric gas oil. The influence of the method of loading the catalyst with the deactivating agent on the deactivation rate was also assessed. The objective of this accelerated deactivation method of hydrodesulfurization catalysts was to assess the catalysts lifetime on an industrial scale.
The difference between the initial and residual catalyst activity at different deactivating steps was significant. When the catalyst was deactivated for 18 hours at WHSV of 1 g∙h-1∙cm-3, this difference was about 9 °C. When it was deactivated for 6 hours at the WHSV of 3 g∙h-1∙cm-3, this difference was about 16 °C.
The accelerated deactivation used in this work did not reach the results gained during deactivation in industrial reactor after 16 months. The sulphide Co-Mo catalyst, which had been placed in an industrial reactor for 16 months, in which the gas oil mixture was hydrodesulphurized, had a residual activity of about 22 °C higher than its initial activity.
Keywords: accelerated deactivation; catalyst activity; hydrodesulphurisation; catalyst
4/2019 - pages 118 - 124DOI: 10.35933/paliva.2019.04.03

Comparison of the activity of sulphidic Ni-Mo/Al2O3 catalyst in alkyldibenzothiophenes desulfurizati

Nikola Bringlerová, Nikola Šlégrová, Radek Černý, Martin Pšenička, Aleš Vráblík, Josef Blažek

The goal of this work was to assess the effect of reaction condition on the activity of three commercial hydrodesulfuration catalysts based on Ni-Mo/Al2O3. During hydrodesulfuration, the contents of 4-methyldiben-zothiophene (4-MDBT) and 4,6-dimethyldibenzothio-phene (4,6-DMDBT) was determined. Hydrodesulfuration was carried out in a stirred batch reactor with volume of 0.5 dm3. The catalysts were tested at two different reactions conditions: reaction temperature of 350 °C with hydrogen partial pressure of 6 MPa and reaction temperature of 380 °C with hydrogen partial pressure of 4.5 MPa. For all experiments, 300 cm3 of feedstock, 10 cm3 of catalyst, and constants hydrogen flow 30 dm3∙hod-1 were used. The model feedstocks consisted of hydrogenated gas oil with addition of 500 mg.kg-1 of 4-MDBT and 500 mg∙kg-1 of 4,6-DMDBT. In all the experiments, higher conversion of 4-MDBT compared to 4,6-DMDBT was found. This fact is given by smaller steric shielding of the sulphur atom in the 4 - MDBT molecule by only one methyl group. C catalyst showed the highest activity in 4-MDBT desulfurization at temperature 350 °C and hydrogen partial pressure 6 MPa. At the same reactions condition, catalyst A was the best for elimination of 4,6-DMDBT . This catalyst had the greatest activity in 4-MDBT and 4,6-DMDBT desulfuration at the second reaction condition too (reaction temperature 380 °C, hydrogen partial pressure 4.5 MPa). In the reaction conditions, the decrease of sulphur content bellow 10 mg.kg-1 was achieved with A catalyst after 240 min.

Keywords: hydrodesulphurisation; alkyldibenzothiofene, catalyst activity
4/2019 - pages 125 - 132DOI: 10.35933/paliva.2019.04.04

Photovoltaic sources and greenhouse gas emissions

Petr Buryan, Pavel Donát

The article presents data documenting the amount of emissions, especially carbon dioxide, emitted into the air from conventional power plants during the periods when they are centrally disconnected from the electricity distribution network, as photovoltaic power sources are preferentially connected to this network. The need to keep conventional fossil fuel power plants in standby is essential so that, according to the regulator instructions, electricity consumption can be quickly covered in the event of sudden and unexpected fluctuations in demand, eg when sunlight is reduced. In the national climate and energy plan, the Czech government expects the share of renewable sources to be increased to 20.8 % by 2030. The European Commission assessed the plan as not ambitious and recommended increasing the share of renewables to 23%. However, this will also be associated with a significant increase in COemissions when putting conventional energy blocks into the socalled “warm reserve”. A successful and usable solution of the discussed problems capable of covering the instability of photovoltaic wind energy sources is the application of gas turbines, resp. cogeneration units burning gas. One example of such a solution is the construction of a new 840 MWe Power plant Počerady. Putting them into full power from the sleep mode is a matter of minutes and, in addition, they can be powered by renewable electricity.

Keywords: photovoltaic energy sources, greenhouse gas emissions
4/2019 - pages 133 - 137DOI: 10.35933/paliva.2019.04.05

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