Fully halogenated chlorofluorocarbons (CFCs) are, despite their good thermodynamic properties, stability and non-toxicity, eliminated from use. Due to the content of one chlorine atom in the molecule, the use of hydrochlorofluorocarbons (HCFCs) has been reduced in many European countries. The use of partially halogenated hydrofluorocarbons (HFCs) in which the molecules have no chlorine atoms, due to increased inflammability, is also to a large extent limited. This paper presents a methodology for selecting working fluids or mixtures for use in cogeneration ORCs on biomass, which will, in addition to thermodynamics, also take into account the safety and environmental requirements of working fluid acceptability. The effects of thermodynamic properties of preselected working fluids on the performance of the cogeneration ORC plant have been analyzed and the thermodynamic properties of the working fluid are optimized by the exergy efficiency of the ORC as a function of the target, using a genetic algorithm. Optimal values of the exergy efficiency, component size and exergy losses of the cogeneration ORC for the use of biomass energy are compared and analyzed under the same heat source conditions and pre-defined boundary conditions. The experimental analysis of the cogeneration ORC shows that the most preferred working fluid is p-xylene because in comparison to undekan, MDM (OMTS) and D4 (OMCTS) it has the highest value of exergy efficiency but also requires the least dimension of ORC components (turbines and capacitors).

Installation of plants for wet Hue gas desulphurization has a significant impact on energy consumption, and thus the overall level of utilization of the power plant units. The aim of this paper is to use mathematical models in analysis of the influence of wet Hue gas desulphurization plants which are additionally installed on existing units and finds the optimal operating range regarding the specific heat consumption. The proven mathematical model can be further used in the analysis of wet Hue gas desulphurization that is planned for used in units that use similar coals.

The first installation of a Ljungstrom air preheater on a commercial boiler reduced fuel consumption by as much as 25%, and in modern utility boilers the Ljungstrom air preheater contributes up to 20% of the overall boiler efficiency while representing only 2% of the total investment. Therefore, in this paper an analysis is shown on how operation parameters of an regenerative air preheater can be optimized in order to increase its efficiency and consequently the overall efficiency of a steam boiler.

Ljungström air preheater is a regenerative heat exchanger which is mainly used in steam boiler plants for preheating of the combustion air. The hot gas and cold air ducts are arranged in such a way to allow both to flow simultaneously through the machine. The hot flue gas heats the rotor material and as the rotor rotates, the hot rotor section moves into the flow of the cold air and preheats it. Simulations of regenerative heat exchanger described in open literature are mainly based on the empirical approach where some of the effects to the process are simplified or neglected. Although this may give reasonably good and in many cases acceptable results, a more comprehensive mathematical model based on differential equations of continuity, momentum and energy is applied here for analysis of the flow and heat transfer in such a device for better understanding of its process features. Using that, an effective procedure was developed for calculation of processes in rotary heat exchanger for optimisation of its parameters, which can be used either in research and development purposes or in the common industrial practice. An analysis based on such a mathematical model is applied in this paper to allow rotational speed to vary and quantify its influence upon heat transfer in the rotary air preheater to show hat optimal conditions exist for which the heat transferred passes through its maximum.