Thermodynamic Analysis of the Cogeneration Organic Rankine Cycle in the Work With Different Working Fluids for the use of Energy From Biomass

Abstract

In the paper, a thermodynamic analysis of the cogeneration organic Rankin cycle (CHP ORC) for the use of energy from biomass with working fluids was done m-xylene, p-xylene, toluene, MDM (OMTS), D4 (OMCTS), undecane and a mixture (toluene/MDM/m-xylene) in the estimate ratio 33/33/33. The influence of thermodynamic properties of all operating fluids and mixtures on CHP ORC performance in the regenerator and non-regenerator variant is analyzed, and the thermodynamic properties of working fluids and mixtures are optimized with the exergy efficiency of CHP ORC as a function of the target, using the genetic algorithm. The maximum CHP ORC performance values for the corresponding pressure and temperature values at the entrance to the ORC turbine were compared and analyzed under the same conditions of the heat source and defined boundary conditions. Comparative analysis of the CHP ORC parameters shows that more favorable aromatic hydrocarbons (m-xylene, p-xylene and toluene) are used for the exploitation of energy generated by combustion of biomass, since in comparison with siloxanes (MDM, D4 and undecane) they have higher values of exergy efficiency, but also due to their thermodynamic properties, require significantly less dimension of the components (turbines and condenser). The parameters of CHP ORC in working with a mixture of working fluids (toluene/MDM/m-xylene) are somewhere between the value of CHP ORC in working with its components, but are not an arithmetic mean. The comparative analysis of CHP ORC in operation without and with the regenerator for all operating fluids and mixtures shows that the values of exergy efficiency in the CHP ORC application with the regenerator are 2 to 3 % higher than the CHP ORC plant without regenerator, which indicates that the application of these the application contributes to a higher production of electricity with slightly lower production of thermal energy. CHP ORC with a regenerator in operation with all working fluids and mixtures requires slightly more turbine dimensions than the CHP ORC without the regenerator.