Petr Trávníček

Risks associated with the production of biogas in Europe

This article discusses issues of risk in the production of biogas from primarily farm wastes. Biogas production is becoming widespread in Europe, and the number of accidents in these plants, both large‐scale and small, is increasing. Recent accident experience is summarized here. Compared with the petrochemical industry, damage levels in biogas production are low, but nonetheless worthy of increased application of modern safety and risk methodology.

Thixotropic behaviour of thickened sewage sludge

The aim of the work is a description of the rheological behaviour of thickened sewage sludge. The sample of thickened sludge was collected from the wastewater treatment plant, where pressure flotation unit is used for a process of thickening. The value of dry matter of collected sample was 3.52%. Subsequently the sample was diluted and the rheological properties of individual samples were obtained. Several types of rheological tests were used for the determination of the sample. At first the hysteresis loop test was performed. The next test was focused on the time-dependency, i.e. measurement of dependence of dynamic viscosity on the time at constant shear rate. Further dependence dynamic viscosity on the temperature was performed. Then the activation energy was obtained from measured values. Finally, the hysteresis areas were counted and measured values were evaluated with use of Herschel-Bulkley mathematical model.

Diagnostics of the thermal defects of the walls on the solid-state biogas plant

Energy protection of buildings can be achieved by using suitable construction with minimisation of thermal bridges. This paper is a contribution to the characterisation of the thermal defects and energy efficiency of the envelope on the case study of a solid-state biogas plant. The work specifically concerns the qualitative evaluation of envelope construction details by infrared thermography technique and quantitative evaluation of thermal defects by calculation. Results show that wall constructions of the solid-state biogas plant have an unsuitable engineering solution causing high heat losses. The main problem is the existence of significant numbers of thermal bridges caused by uninsulated bearing steel frames of the façade system, gates, doors and windows.

Calorific evaluation and energy potential of grape pomace

Abstract This article deals with energetic evaluation and potential of pomace – a waste product originating during production of grape wine. Calorimetric analysis of 19 grapevine varieties was performed in 2013 and 2014. The aim was to specify their combustible limit and the gross calorific value. The evaluations were performed on pristine pomace, pomace without seeds, and only on seeds themselves. The results obtained imply that pomace is an interesting energetic resource with a gross calorific value of 16.07-18.97 MJ kg−1. Lower calorific values were detected in pomace after seed separation ie 14.60-17.75 MJ kg−1; on the contrary, seeds alone had the highest calorific values of 19.78-21.13 MJ kg−1. It can be assumed from the results of energetic evaluation of pomace in Czech Republic conditions that, by purposeful and efficient usage of pomace, 6.4 GWh of electric energy and 28 GWh of thermal energy can be generated.

Modelling of Consequences of Biogas Leakage from Gasholder

This paper describes modelling of consequences of biogas leakage from a gasholder on agricultural biogas station. Four scenarios were selected for the purpose of this work. A rupture of gasholders membrane and instantaneous explosion of gas cloud, blast of gas with delay, emptying of whole volume of gas (without initiation) and initiation of gas with Jet-Fire. Leakage of gas is modelled by special software and consequences are determined on the basis of results. The first scenario was modelled with help of equations because used software does not include an appropriate model. A farm with high building density was chosen as a model case. Biogas is replaced by methane because used software does not support modelling of dispersion of mixtures. From this viewpoint, a conservative approach is applied because biogas contains “only” approximately 60% of methane (in dependence on technology and processed material).

Study of rheological behaviour of wines

Abstract This study deals with rheological properties of various wine varieties. Samples of the following wines were used for this experiment: André, Cabernet Moravia, Laurot, Saint Laurent, Gruner Veltliner, Pinot Blanc, Müller Thurgau, and Riesling Italico. These samples were obtained from wine produced from the grapes collected in the Czech Republic (Morava region, subregion Velke Pavlovice). In the first phase, the chemical composition of the samples was determined. The following chemical parameters were determined: total acidity, pH, content of the alcohol, reduced sugars, free SO2, total SO2, and volatile acids. In the second phase of the study, the physical properties of the samples were determined and the samples of the wines were subjected to rheological tests. These tests consisted in determination of apparent viscosity in relation to temperature, hysteresis loop tests, and apparent viscosity related to time. The dependence of the shear rate on the shear stress was described with the Herschel-Bulkley mathematical model. The experiment yielded the following findings: seven out of the eight samples behaved as non-Newtonian fluids at low temperature (5°C); non-Newtonian behaviour was changed into Newtonian at the temperature higher than 10°C; non-Newtonian behaviour was characterised as thixotropic behaviour; the degree of thixotropy is relatively small and reaches 1.85 Pa s-1 ml-1.

SURFACE TEMPERATURE OF THE EXPOSED SILO FACE AS QUICK INDICATOR OF THE DECOMPOSITION PROCESS OF MAIZE SILAGE

Silage temperature and oxygen concentration are critical parameters for controlling the silage process. Anaerobic condition with lower and stable temperature is necessary for quality silage making. However, when the silo is opened or if there are any failures (e.g. at the cover or at the walls) the anaerobic environment is changed to an aerobic state. That caused intensive decomposition process allied to increase of the temperature in the problematic silage layers. The objective of the current study is to evaluation of infrared thermography technique possibilities for measurement of surface temperature of the maize silage under conditions representative of an exposed face silo, interpretation of measured values and detection of layers and areas with intensive decomposition process.

Determination of rheological behaviour of wine lees

Abstract This study deals with the rheological properties of wine lees. Samples of wine lees of the Saint Laurent variety were used in this experiment. The investigated wine lees arose in the process of production red grape wine in 2013 (Czech Republic). At first, the chemical background was determined. The chemical background includes the following chemical parameters: total acidity, pH, alcohol content, reduced sugars, free SO2, total SO2, and volatile acid. In the second phase of the study, physical properties were determined. Specifically, a sample of wine lees was subjected to rheological tests. These tests consisted in determination of dependence of dynamic viscosity on the temperature, hysteresis loop tests, dependence of dynamic viscosity on the time and step-down in the shear rate test. The experiment demonstrated that the dynamic viscosity increased with increased temperature – this phenomenon is caused by thermolabile proteins – and the wine lees has rheopectic behaviour; the degree of rheopexy was found to rise with the increasing temperature.

Condensing shafts on biogas stations and operational safety

This article investigates health and safety risks at a biogas station, in particular the activities in the condensation shaft. There were selected three scenarios in total, which can lead to a fatal accident during the maintenance and servicing of equipment located in the condensation shafts. These are the following scenarios: (1) the worker descends to the condensation shaft and in the subsequent service activities consumes oxygen contained in shaft, falls into unconsciousness and dies. (2) There is such a gas concentration in the condensate shaft that intoxication occurs (but even direct asphyxiation is possible—e.g., methane, carbon dioxide) thereafter subsequent death. (3) The worker suffers fatal injuries due to a fall from a height. The individual scenarios are discussed in the article, including whether and under what circumstances these may occur. To support the authors claims, measurements of selected gases concentrations were made in condensation shafts at eight biogas plants. The aim of this article is to highlight the risks that can be encountered when working in condensing shafts and how they can be prevented.

Comparison of rheological properties of varietal grape seed oils

The aim of this work was to determine the rheological properties of grape seed oils from different varieties selected at different temperatures. Measurement of the rheological properties of grape seed oils was performed on the instrument Anton Paar MCR 102. The rheological properties of the liquid have been performed at temperatures of 0 °C, 15 °C, 30 °C, 45 °C and 60 °C. The density of measured samples ranged from 0.905 ±0.002 to 0.948 ±0.002 g.mL -1 . Subsequently, there were determined viscosity values at a shear rate of 5 s -1 . As expected, the viscosity decreased with increasing temperature. Highest viscosity values reached grape seed oil of variety Pinot gris where at 0 °C the viscosity reached 0.206 ±0.037 Pa s. Samples measured at 0 °C showed non-Newtonian behavior, while at higher temperatures liquids behave as Newtonian substances. All grape seed oils samples exhibit non-Newtonian behavior at lower temperatures. In experiments carried out at 0 °C, it was observed that the tested samples tends to behave as shear-thinning system with thixotropic properties. At higher temperatures was, in line with other scientific works, observed that samples behave as Newtonian fluids. Knowledge of the rheological properties of oils are very important for their processing, storage, and may affect their quality.