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Digestate and woodchips gasification: A comparison of different gasifying agents
(Elsevier, 2024-04-26) Milčák, Pavel; Baláš, Marek; Lisý, Martin; Lisá, Hana; Kracík, Petr; Lachman, Jakub
Digestate is the secondary product of the fermentation process in biogas plants. The use of digestate as a fertilizer is very common. However, this is more and more limited nowadays and therefore alternative uses for digestate are sought. The research described in this article maps the possibilities of using digestate from the wet fermentation process for the syngas generation. This work is focuses on the gasification of the digestate with spruce chips mixtures. The mixtures were prepared with a proportion of 0, 25, 50, 75 and 100% of the digestate. The experiments were carried out on a semi-operational fluidized bed gasifier at atmospheric pressure. The working temperature of the fluidized bed was 810 °C; the gasification was autothermal. The gasification was carried out with three types of gasification agents, i.e. air, air-steam, and oxygen-steam for each fuel mixture. The aim of the research was to assess the effect of the digestate with wood chips on the qualitative and quantitative properties of the syngas. The digestate can be characterized as a secondary energy source reducing the consumption of primary energy sources. The produced syngas is of high quality and the digestate can become a very desirable fuel for the syngas production.
Structure of Flow Fields Downstream of Two Different Swirll Generators
(2012-05-14) Štefan, David; Rudolf, Pavel
This paper discusses the comparison of the flow fields downstream of two different swirl generators. Both swirl generators are used to imitate the flow at the exit of the hydraulic turbine runner and study spatio-temporal behaviour of the swirling flow in the draft tube (i.e. outlet diffuser part of the hydraulic turbine), which undergoes breakdown into vortex rope. Unsteady CFD computations are carried out for identical Reynolds number. Resulting velocity and vorticity profiles are correlated with the structure of the vortex rope. Difference in excited pressure pulsations is illustrated on amplitudefrequency spectra of static wall pressure.
Development of an Effervescent Atomizer for Industrial Burners
(American Chemical Society, 2009-11-09) Jedelský, Jan; Jícha, Miroslav; Sláma, Jaroslav; Otáhal, Jan
The present work is conducted with the aim of developing an effervescent atomizer for industrial burners that will generate a fine and steady spray in large turn-down ratio. The atomizer is fed with light heating oil (LHO) and uses air as an atomizing medium. First, a basic classification is made of the published design concepts of effervescent atomizers investigated by different researchers. Three distinct types of such atomizers are recognized. A single-hole, plain-orifice atomizer with an "outside-in" gas injection configuration was chosen for this study. The basic geometric parameters that may significantly influence atomizer performance are described. An experimental study of the effervescent atomizer was conducted to evaluate the influence of operational conditions and of several geometric parameters on the drop size in the spray. The Sauter mean diameter of drops was measured using a Phase/Doppler Particle Analyser. The study covers the size and number of aerator holes, their location, and the diameter of the mixing chamber. The influence of these parameters on the spray quality was evaluated at atomizing pressures of 0.1, 0.3 and 0.5 MPa and gas to liquid mass flow-rate ratios (GLR) of 2, 5 and 10 %. The main goal of this work is to develop a new procedure for the design of effervescent atomizers. This procedure is based upon our experimental results and it is also supported by the findings of other authors. It allows for the determination of the key geometric parameters of the atomizer to achieve sprays of minimum mean drop size for defined values of liquid flow rate, air supply pressure and GLR. The article also studies the optimization of the exit orifice size and of other parameters, such as the size of the mixing chamber (internal diameter and length), and the number, size, and position of aeration holes.
Hydrodynamic cavitation-enhanced activation of sodium percarbonate for estrogen removal
(IWA Publishing, 2023-12-01) Odehnalová, Klára; Přibilová, Petra; Maršálková, Eliška; Zezulka, Štěpán; Pochylý, František; Rudolf, Pavel; Maršálek, Blahoslav
The present paper investigated the potential of hydrodynamic cavitation (HC) as an effective tool for activating sodium percarbonate (SPC). The method's efficiency was demonstrated by effectively removing estrogens, which are pollutants that have adverse impacts on aquatic ecosystems. The effects of the SPC concentration, temperature of solution, and cavitation time were evaluated. After SPC/HC treatment, the removal of estrogens was monitored by LC-MS/MS. Already after 4 s of treatment and 24 h of reaction time, more than 97% of estrogens (initial concentration of 300 ng/L) were removed. The effect of post-treatment time is not considered in several papers, even though it seems to be crucial and is discussed here. The results were supported by the values of degradation rate constants, which fit the pseudo-first-order kinetic model. We also verified that HC alone was not effective for estrogen removal under the selected conditions. The sustainability of the SPC/HC system was evaluated based on electric energy per order calculation. The combination of SPC and HC is a promising approach for rapidly degrading micropollutants such as estrogenic compounds without the need for additional technological steps, such as pH or temperature adjustment.
Applicability of Human Thermophysiological Model for Prediction of Thermal Strain in PPE
(MDPI, 2023-06-15) Lunerová, Kamila; Řehák Kopečková, Barbora; Pokorný, Jan; Mašín, Michal; Kaiser, David; Fialová, Vladimíra; Fišer, Jan
The use of personal protective equipment (PPE) is essential to protect the human body in hazardous environments or where there is a risk of CBRN agents. However, PPE also poses a barrier to evaporative heat dissipation, therefore increasing heat accumulation in the body. In our research, we investigated the applicability of thermophysiological models for the prediction of thermal strain and the permissible working time in a contaminated environment when the usage of protective ensembles is required. We investigated the relationship between the thermal insulation characteristics of four types of PPE against CBRN agents and the induced thermal strain in a set of real physiological strain tests with human probands wearing the PPE in a climatic chamber. Based on the results, we compared the predictions using two thermophysiological models-Predicted Heat Strain Index (PHS) and FIALA-based model of thermal comfort (FMTK)-with the experimental data. In order to provide a user-friendly platform for the estimation of thermal stress in PPE, a user-friendly computational tool, Predictor of Thermal Stress (PTS), was developed. The PTS tool is based on an extensive database of simulated calculations using an FMTK model based on PPE characteristics, environmental conditions, individual parameters, and expected workload. The PTS tool was validated by means of the results from real tests in a climatic chamber. The PTS was shown to be an easy-to-use computational tool, which can be run on a regular PC, based on real data applicable for the estimation of the permissible work time limit with regard to thermal strain in PPE under various conditions.

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