Applied Mechanics and Materials Vol. 831

Abstract: This work presents results of numerical modeling of the combustion process inside a lab-scale drop-tube chamber, designed to investigate the slagging properties of the flue ashes, created through the solid fuel firing. Interaction between turbulence and chemistry is accounted by use of probability density function (PDF). FLUENT inputs for non-premixed combustion chemistry modeling are defined. A discrete second phase of the coal particles is determined and a simulation involving reactions of the fuel is solved

Abstract: The paper deals with the wood permeability to gases and its changes with the temperature as it is important phenomena to be taken into account in order to determine the rate of release of the pyrolytic gases from a wood particle in the pyrolysis process. Both theoretical and experimental approaches are presented. The measurements were conducted on an original test stand designed and built solely for this purpose. The results show an interesting dependence of the permeability on the pyrolysis temperature of the wood. The permeability generally increases with the temperature (up to over ten times of initial value) but for the range of temperatures from 50°C to 150°C it reaches values lower than for room temperature.

Abstract: This paper explores the optimization cases for overcritical Organic Rankine Cycle (ORC) in various situations. First the ORC optimization in terms of working fluid selection is discussed. In this case, thermal efficiencies for 10 different working fluids have been calculated under certain temperature frames and the results are compared. Second, overcritical optimization case in terms of variation of hot temperature and evaporation pressure is presented. In this overcritical ORC case, the influence of evaporation pressure on ORC thermal efficiency is studied by conducting a case study of R234a, and first 1-D freedom optimization case is discussed within the variation of evaporation pressure. 2-D freedom optimization is also considered, in which the two independent variables, hot temperature and evaporation pressure, are both varied within certain boundaries. This study employs numerical method for this 2-D problem and it is also presented in detail in the case study.

Abstract: In Germany around 8000 biogas plants have been installed previously. Around 180 of these plants feed the processed biogas into the grid. In the most of the plants the biogas is used in power generation (CHP). As a result, this large number of biogas plants produces a huge amount of fermentation residues along with the power generation. The 8000 biogas plants generate around 8.5 million metric tons of fermentation residues a year. Currently, the residues are primarily applied as organic fertilizer on soil nearby the biogas plants. In a special torrefaction process the fermentation residues are transformed to biochar in form of so-called Enertabs. The article introduces a gasification unit for Enertabs, which generates a low calorific gas. In addition the article gives a description of a conceptual test stand, in which the gasification unit is to be used with steam as a gasification medium and in which the unit generates the product gas under high pressure.

Abstract: The article presents selected problems related to the design and operation of small chp units used in individual biogas plants. There are presented and commented available design solutions that can match operational and cost-effective requests in relation to the engine, generator type selection, to design solutions of ignition system, fuelling system, waste heat utilization system and control unit. Presented solutions are discussed in terms of the unit reliability, power and heat generation efficiency and overall unit price. In conclusion, there are proposed some optimal design solutions for typical applications of small biogas fuelled chp units