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Organic Rankine Cycle (ORC) technology is nowadays considered as interesting option for utilization of local biomass resources. The number of plants worldwide is constantly growing within typical range of electric power output form 0.2 to 3.0 MW. In such systems biomass combustion chambers with step or vibrating grates are used. Heat is transferred to the thermal oil in a separate spiral heat exchanger. The biggest problems in such system are variable and inaccurately predictable properties of biomass that directly influences operation of combustion equipment, and thus the performance of entire cogeneration plant. In this paper experiences from two plants are presented. The plants are located in Krosno (Poland) and in Ostfildern near Stuttgart, Germany. In the first one high quality wood chips are used whereas the second one is powered by low quality biomass with the mass ash content approaching 18%. Although similar, both plants use different strategies to control the combustion process. Long term measurements are used to develop biomass combustion models in the plants. The paper also presents results of implementation of the online optic measurement system for monitoring of biomass properties such as LHV, ash and water content.

Despite very rapid development of science in the recent years, the phenomena occurring in the electric arc have not been fully recognized. The main reason for this situation is their the complexity as well as very high temperatures. This paper presents the results of numerical calculations of phenomena which occur in the welding arc. The CFD Fluent package was used for modelling the following phenomena in the electric arc: melting, solidifying, generation of heat and multiphase flows. The 3D Model of a 50 × 30 × 6 mm metal plate segment padded with the use of the MIG method with a wire of 1.2 mm in diameter was developed. The paper focuses on presenting the distribution of temperatures in time, the process of melting and later solidifying of the material, as well as on the transport of the material from the arc to the padding weld. It also shows the initial verification of the model by comparing the results with a picture recorded by thermovisual camera. [ABSTRACT FROM AUTHOR]

In the paper, the numerical model of the flow phenomena in the flotation machine is presented. The process of flotation consists of a number of phenomena which provide serious numerical difficulties. One can enumerate rotation, two phase flow, foam formation etc. To the knowledge of authors there is no complete numerical model available for the flotation machine. The long-term task of the project is to create a complete model of the machine. Such a model would be very helpful in the process of construction and modernization of the flotation machine. As it was mentioned, due to difficulties connected with modelling the flotation phenomena, only a few aspects of the process were taken under consideration. In the paper, a single phase flow of water is considered. The efficiency of the flotation process strongly depends on the fluid flow field in the machine. The level of mixing the fractions and air bubbles strongly depends on the velocity field of the water, so the proper model of fluid flow is of great practical importance. This paper presents preliminary results of mathematical modelling. The commercial package ANSYS Fluent was utilized for the analysis. The results were compared with the measurements performed on the small scale model of the machine. Obtained results are satisfying and encouraging for further development. [ABSTRACT FROM AUTHOR]