Publisher: Czech Technical University   (Total: 3 journals)   [Sort by number of followers]

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Acta Polytechnica : J. of Advanced Engineering     Open Access   (SJR: 0.206, CiteScore: 1)
Geoinformatics FCE CTU     Open Access   (Followers: 8)
MAD - Magazine of Aviation Development     Open Access   (Followers: 2)
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Acta Polytechnica : Journal of Advanced Engineering
Journal Prestige (SJR): 0.206
Citation Impact (citeScore): 1
Number of Followers: 0  

  This is an Open Access Journal Open Access journal
ISSN (Print) 1210-2709 - ISSN (Online) 1805-2363
Published by Czech Technical University Homepage  [3 journals]
  • Bio-CCS - “Research centre for low-carbon energy technologies”

    • Authors: Jan Hrdlička
      Abstract: This issue is dedicated to the publication of research results from the project entitled “Research centre for low-carbon energy technologies”, in short Bio-CCS that has been successful in the OP RDE “Excellent research call” in 2017. The project is running from 2018 until mid of 2023 and it is coordinated by the Department of Energy Engineering of Faculty of Mechanical Engineering at the CTU in Prague. Two other department at the Faculty cooperate in the project, namely Department of Process Engineering and Department of Environmental Engineering. Additionally, Faculty of Nuclear Sciences of the CTU participates in the project, and the other institutions forming the consortium are Brno University of Technology, VSB-Technical University Ostrava and Institute of Thermomechanics of the Czech Academy of Sciences. The project activities are focused on research in the so-called BECCS field (i.e. Bioenergy with carbon capture and storage), which means CO2 capture processes from a bioenergy resource. It means that the final CO2 balance in energy conversion of such a fuel becomes CO2 negative. The project particularly concerns processes of fluidized bed oxyfuel combustion and low-CO2 progressive gasification and pyrolysis of biofuels. These two main activities are focused on process characterization and optimization as well as investigation of fundamental principles in the processes and minimizing of impacts of these processes to the environment. The research activities are strongly supported by experimental approaches that include testing plants in the pilot-scale size, enabling transfer of the research results into industrial scale. A part of the project is also dedicated to the usage of CO2 from the oxyfuel combustion and syngas form the gasification as a feedstock for 3rd and 4th generation biofuels production. The energy conversions are amended with activities that concern pre-conversion biofuel treatment and approaches for CO2 cleaning and dewatering that has to be done prior to further utilization or transport for final storage. This concerns e.g. condensing heat exchangers, optionally with specific materials like hollow fibers, or contactless condensation. A part of the research activities concerns mathematical modeling and numerical simulation of the processes.
      PubDate: 2022-06-30
      Issue No: Vol. 62, No. 3 (2022)
  • Measurement of solid particle emissions from oxy-fuel combustion of
           biomass in fluidized bed

    • Authors: Ondřej Červený, Pavel Vybíral, Jiří Hemerka, Luďek Mareš
      First page: 337
      Abstract: The presented work summarizes the results of the measurement of solid particle emissions from an experimental 30 kW combustion unit. This unit has been used for the research of oxy-fuel combustion of biomass in a fluidized bed, which, when accompanied with carbon capture technologies, is one of the promising ways for decreasing the amount of CO2 in the atmosphere. To implement a carbon capture system, it is first needed to separate various impurities from the flue gas. Therefore, the goal of this work was to identify solid particles contained in the flue gas.
      Part of the apparatus used for this measurement was an ejector dilutor. To evaluate the results of this measurement, it is key to know the dilution ratio of the dilutor. For this purpose, a method for determining the dilution ratio of an ejector dilutor was proposed and experimentally verified.
      PubDate: 2022-06-30
      DOI: 10.14311/AP.2022.62.0337
      Issue No: Vol. 62, No. 3 (2022)
  • Applicability of Secondary Denitrification Measures on a Fluidized Bed

    • Authors: Jitka Jeníková, Kristýna Michaliková, František Hrdlička, Jan Hrdlička, Lukáš Pilař, Matěj Vodička, Pavel Skopec
      First page: 341
      Abstract: This article compares performance of selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) applied on the same pilot unit, a 500 kW fluidized bed boiler burning Czech lignite. Correlation of the denitrification efficiency on the normalized stoichiometric ratio (NSR) is investigated. The fundamental principle of the SCR and SNCR is similar with the same reaction scheme. The difference is in the use of the catalyst that lowers the activation energy of the key reaction. As a result, the reduction is performed in the SCR method at lower temperatures. During experiments, the NSR was up to 1.6 for the SCR method. For the SNCR method, which has a higher reducing agent consumption, maximum denitrification efficiency was reached for NSR about 2.5. The efficiency of both secondary methods was investigated. The denitrification efficiency during experiments exceeded 98 % for the SCR method, and the SNCR method, together with the primary measures, reached an efficiency of 58 %.
      PubDate: 2022-06-30
      DOI: 10.14311/AP.2022.62.0341
      Issue No: Vol. 62, No. 3 (2022)
  • Theoretical and experimental study of water vapour condensation with high
           content of non-condensable gas in a vertical tube

    • Authors: Jakub Krempaský, Jan Havlík, Tomáš Dlouhý
      First page: 352
      Abstract: This article deals with the possibility of separating water vapour from flue gases after oxyfuel combustion using condensation processes. Those processes can generally be described as condensation of water vapour in the presence of non-condensable gases. Hence, the effect of noncondensable gas (NCG) on the condensation process has been theoretically and experimentally analysed in this study. The theoretical model was developed on the basis of the heat and mass transfer analogy with respect to the effect of the NCG, the flow mode of the condensate film, the shear stress of the flowing mixture, subcooling and superheating. Subsequently, an experimental analysis was carried out on a 1.5m long vertical pipe with an inner diameter of 23.7mm. The mixture of vapour and air flowed inside the inner tube with an air mass fraction ranging from 23% to 62%. The overall heat transfer coefficients (HTC) from the theoretical model and experimental measurement are significantly lower than the HTC obtained according to the Nusselt theory for the condensation of pure water vapour. The overall HTC decreases along the tube length as the gas concentration increases, which corresponds to a decrease in the local condensation rate. The highest values of the HTC are observed in the condenser inlet, although a strong decrease in HTC is also observed here. Meanwhile, there is a possibility for an HTC enhancement through turbulence increase of the condensing mixture in the condenser outlet. Results also showed that the heat resistance of the mixture is several times higher than the heat resistance of the condensate film. The developed theoretical model based on heat and mass transfer analogy is in good agreement with experimental results with the standard deviation within +25% and −5%. The model is more accurate for lower NCG concentrations.
      PubDate: 2022-06-30
      DOI: 10.14311/AP.2022.62.0352
      Issue No: Vol. 62, No. 3 (2022)
  • Experimental verification of the efficiency of selective non-catalytic
           reduction in a bubbling fluidized bed combustor

    • Authors: Kristýna Michaliková, Jan Hrdlička, Matěj Vodička, Pavel Skopec, Jitka Jeníková, Lukáš Pilař
      First page: 361
      Abstract: Controlling nitrogen oxide (NOX) emissions is still a challenge as increasingly stringent emission limits are introduced. Strict regulations will lead to the need to introduce secondary measures even for boilers with bubbling fluidized bed (BFB), which are generally characterized by low NOX emissions. Selective non-catalytic reduction has lower investment costs compared to other secondary measures for NOX reduction, but the temperatures for its efficient utilization are difficult to achieve in BFBs. This paper studies the possibility of an effective application of selective non-catalytic reduction (SNCR) of nitrogen oxides in a pilot-scale facility with a bubbling fluidized bed. The effect of temperatures between 880 and 950 °C in the reagent injection zone on NOX reduction was investigated. For the selected temperature, the effect of the amount of injected reagent, urea solution with concentration 32.5%wt., was studied. The experiments were carried out using 500 kWth pilot scale BFB unit combusting lignite. In addition, an experiment was performed with the combustion of wooden pellets. With reagent injection, all experiments led to the reduction of nitrogen oxides and the highest NOX reduction of 58% was achieved.
      PubDate: 2022-06-30
      DOI: 10.14311/AP.2022.62.0361
      Issue No: Vol. 62, No. 3 (2022)
  • Experimental and simulation study of CO2 breakthrough curves in a
           fixed-bed adsorption process

    • Authors: Marek Nedoma, Marek Staf, Jan Hrdlička
      First page: 370
      Abstract: This paper focuses on the laboratory experiments of low-temperature adsorption of CO2 at elevated pressure and on the validation of our mathematical model with the data obtained. The numerical approach uses fitting of adsorption isotherm parameters and sensitivity analysis of parameters influencing the breakthrough curve shape and onset time. We first evaluate the results of breakthrough experiments for zeolite 13X. Then, we use the results obtained to design a dynamic mathematical model to predict the breakthrough curve profile. Experimental results show that zeolite 13X possesses high adsorption capacities (over 10 % of its weight at adsorption temperatures of 293 K and below), as expected. The mathematical simulation was accurate at predicting the breakthrough onset time; however, this prediction accuracy declined with the outlet CO2 concentration exceeding 75 %, which is discussed. The sensitivity analysis indicated that the choice of different estimates of mass transport and bed porosity, as well as the choice of numerical scheme, can lead to a more accurate prediction, but the same set of parameters is not suitable for all process conditions.
      PubDate: 2022-06-30
      DOI: 10.14311/AP.2022.62.0370
      Issue No: Vol. 62, No. 3 (2022)
  • Analysis of parameters important for indirect drying of biomass fuel

    • Authors: Michel Sabatini, Jan Havlík, Tomáš Dlouhý
      First page: 386
      Abstract: This paper focuses on biomass drying for the design and operation of an indirect dryer used in a biomass power plant. Indirect biomass drying is not as well described process as direct drying, especially when used for the preparation of biomass in energy processes, such as combustion or gasification. Therefore, it is necessary to choose a suitable model describing the drying process and evaluate its applicability for this purpose. The aim of this paper is to identify parameters that most significantly affect the indirect drying process of biomass for precise targeting of future experiments. For this purpose, the penetration model was chosen. The penetration model describes indirect drying through 21 parameters. To run a series of experiments focused on all parameters would be time consuming. Therefore, the easier way is to select the most important parameters through a sensitivity analysis, and then perform experiments focused only on the significant parameters The parameters evaluated as significant are the temperature of the heated wall, operating pressure in the drying chamber, surface coverage factor, emissivity of the heated wall, emissivity of the bed, diameter of the particle, and particle surface roughness. Due to the presumption of perfect mixing of the material being dried, stirrer speed is added into important parameters. Based on these findings, it will be possible to reduce the scope of experiments necessary to verify the applicability of the penetration model for the description of indirect biomass drying and the design of dryers for a practical use.
      PubDate: 2022-06-30
      DOI: 10.14311/AP.2022.62.0386
      Issue No: Vol. 62, No. 3 (2022)
  • Effect of membrane separation process conditions on the recovery of syngas

    • Authors: Petr Seghman, Lukáš Krátký, Tomáš Jirout
      First page: 394
      Abstract: The presented study focuses on inspecting the dependency between process conditions, especially permeate and retentate pressure and component recovery of H2, CO, and CO2 during a membrane separation of model syngas. Experiments with both pure components and a model mixture were performed using a laboratory membrane unit Ralex GSU-LAB-200 with a polyimide hollow fibre module with 3000 hollow fibres. Permeability values were established at 1380 Barrer for H2, 23 Barrer for CO, and 343 Barrer for CO2. The measured selectivities differ from the ideal ones: the ideal H2/CO2 selectivity is 3.21, while the experimental values range from over 4 to as low as 1.2 (this implies that an interaction between the components occurs). Then, the model syngas, comprised of 16% H2, 34% CO, and 50% CO2, was tested. The recovery of each component decreases with an increasing permeate pressure. At a pressure difference of 2 bar, the recovery rate for H2, for a permeate pressure of 1.2 bar, is around 68%, for 2.5 bar, the values drop to 51%, and for 4 bar, the values reach 40% only. A similar trend was observed for CO2, with recovery values of 59%, 47% and 37% for permeate pressures of 1.2 bar, 2.5 bar and 4 bar, respectively.
      PubDate: 2022-06-30
      DOI: 10.14311/AP.2022.62.0394
      Issue No: Vol. 62, No. 3 (2022)
  • Experimental verification of the impact of the air staging on the NOx
           production and on the temperature profile in a BFB

    • Authors: Matěj Vodička, Kristýna Michaliková, Jan Hrdlička, Pavel Skopec, Jitka Jeníková
      First page: 400
      Abstract: The results of an experimental research on air staging in a bubbling fluidized bed (BFB) combustor are presented within this paper. Air staging is known as an effective primary measure to reduce NOX formation. However, in the case of a number of industrial BFB units, it does not have to be sufficient to meet the emission standards. Then selective non-catalytic reduction (SNCR) can be a cost-effective option for further reduction of the already formed NOX. The required temperature range at the place of the reducing agent injection for an effective application of the SNCR without excessive ammonia slip is above the temperatures normally attained in BFBs. The aim of this paper is to evaluate the impact of staged air injection on the formation of NOX in BFB combustors and to examine the possibility of increasing the freeboard temperature. Several experiments with various secondary/primary air ratios were performed with a constant oxygen concentration in the flue gas. The experiments were carried out using wooden biomass and lignite as fuel in a 30 kWth laboratory scale BFB combustor. Furthermore, the results were verified using a 500 kWth pilot scale BFB unit. The results confirmed that the air staging can effectively move the dominant combustion zone from the dense bed to the freeboard section, and thus the temperatures for an effective application of the SNCR can be obtained.
      PubDate: 2022-06-30
      DOI: 10.14311/AP.2022.62.0400
      Issue No: Vol. 62, No. 3 (2022)
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
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