Petr Junga

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.

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.

EVALUATION OF OPERATIONAL SAFETY OF CHOSEN ELECTRICAL SET ELEMENTS IN CONDITIONS OF BIOGAS PLANTS WITH USING OF INFRARED THERMOGRAPHY METHOD

The paper is focused on evaluation of operational safety of chosen electrical set elements in specific conditions of agricultural biogas plants with using of infrared thermography method. The goal of the paper is thermography monitoring of the surface temperature of electrical set elements with detection of high warmed parts. Next goal is evaluation measured temperatures with criteria and requirements of standard ISO 18434-1. In terms of measurement was measured surface temperature of every element and compared with reference ambient temperature. Our study claimed suitability of IRT method for monitoring of electrical set elements. Any of measured objects has high surface temperature. This is significant risk factor for fire and related losses.

Environmental risk assessment of a biogas station

This article investigates the environmental risk assessment of a biogas station, in particular an example attached to a wastewater treatment plant. Such analysis focused on assessing the environmental risk presented by leakage of liquid material from the biogas reactor into a neighboring river. The risk methodology proposed herein is based on the principle of risk assessment regarding a major incident within the petrochemical industry. The threat of environmental damage from biogas production is low, when compared with the petrochemical industry, but represents a branch of industry worthy of heightened health, safety, and risk methodologies.

MONITORING OF THE MACHINE MILKING PROCESS WITH APPLICATION OF INFRARED THERMOGRAPHY

The paper is focused on monitoring of the machine milking process by infrared thermography method. The goal of the paper is thermography monitoring of the influence of machine milking on the udder and teats surface temperature and statistics valuation of measured values. Our study claimed suitability of IRT method for monitoring of machine milking. Statistical evaluation claimed statistically significant difference between temperatures of teats before and after machine milking. Probably it is due to direct contact of milking machine with teats causing mechanical stress of tissues. This is significant risk factor for infections and related financial losses. It is necessary to operate technological equipment for milking with suitable characteristics.

Analysis of the Model Application of Mechanical Equipment for Hydrothermal Treatment at Biogas Plant

The goal of the paper was to analyse model applications of mechanical equipment for hydrothermal treatment. Alternative 1 was an alternative with a treatment output of 14 500 Mg of processed material, the annual electricity and heat total production of 4000 MWh respectively 3800 MWh, total capital expenditure of 40 000 000 CZK, unit capital expenditure of 2759 CZK per 1 Mg of processed biodegradable material and annual operating expenses of 19 371 000 CZK. The net present value (NPV) is 1 061 000 CZK, the internal rate or return (IRR) totals 4.9%, the simple payback time (Ts) is 12.6 years and the discounted payback time (Tsd) is 19.2 years. Alternative 2 employing the mechanical equipment proved a potential increase in the treatment output to 18 125 Mg, and an increase in the electricity and heat total production to 5000 MWh respectively 4800 MWh, thanks to the shortened intensification of the anaerobic fermentation process. At the same time, the total capital expenditure rose to 43 000 000 CZK, the operating expenses rose to CZK 24 213 000. The unit capital expenditure of alternative 2 amounts to 2372 CZK per 1 Mg of the of processed biodegradable material. The NPV totals 8 329 000 CZK, IRR is at 6.7%, the simple payback time (Ts) is 10.8 years and Tsd totals 15.3 years.