Exergy analysis and simulation of a 30MW cogeneration cycle

Abstract

Cogeneration cycle is an efficient mean to recover the waste heat from the flue gases coming out of gas turbine. With the help of computer simulation, design parameters may be selected for the best performance of cogeneration cycle. In the present work a program is executed in software EES on the basis of mathematical modelling described in paper to study cogeneration cycle performance for different parameters. Results obtained are compared with the results available in literature and are found in good agreement with them. Real gas and water properties are inbuilt in the software. Results show that enthalpy of air entering the combustion chamber is higher than that of the flue gases at combustion chamber outlet. For different operative conditions, energy and exergy efficiencies follow similar trends; although, exergy efficiency values are always lower than the corresponding energy efficiency ones. From the results it is found that turbine outlet temperature (TIT) of 524°C is uniquely suited to efficient cogeneration cycle because it enables the transfer of heat from exhaust gas to the steam cycle to take place over a minimal temperature difference. This temperature range results in the maximum thermodynamic availability while operating with highest temperature and highest efficiency cogeneration cycle. Effect of cycle pressure ratio (CR), inlet air temperature (IAT) and water pressure at heat recovery steam generator (HRSG) inlet on the 30 MW cogeneration cycle is also studied.

Keywords

Cogeneration cycle / air compressor / HRSG / gas turbine / regenerator / CR / IAT

References

[1] Khaliq A, Kaushik S C. Second-law based thermodynamic analysis of Brayton/Rankine combined power cycle with reheat. Applied Energy, 2004, 78(2): 179-197

[2] Butcher C J, Reddy B V. Second law analysis of a waste heat recovery based power generation system. International Journal of Heat and Mass Transfer, 2007, 50(11-12): 2355-2363

[3] Som S K, Datta A. Thermodynamic Irreversibilities and Exergy Balance in Combustion Processes. Progress in Energy and Combustion Science, 2008, 34(3): 351-376

[4] Kotowicz J, Bartela L. The influence of economic parameters on the optimal values of the design variables of a combined cycle plant. Energy, 2010, 35(2): 911-919

[5] Poma C, Verda V, Consonni S. Design and performance evaluation of a waste-to-energy plant integrated with a combined cycle. Energy, 2010, 35(2): 786-793

[6] Woudstra N, Woudstra T, Pirone A, Van der Stelt T. Thermodynamic evaluation of combined cycle plants. Energy Conversion and Management, 2010, 51(5): 1099-1110

[7] Regulagadda P, Dincer I, Naterer G F. Exergy analysis of a thermal power plant with measured boiler and turbine losses. Applied Thermal Engineering, 2010, 30(8-9): 970-976

[8] Ahmadi P, Dincer I. Thermodynamic and exergoenvironmental analyses, and multi-objective optimization of a gas turbine power plant. Applied Thermal Engineering, 2011, 31(14-15): 2529-2540

[9] Godoy E, Benz S J, Scenna N J. A strategy for the economic optimization of combined cycle gas turbine power plants by taking advantage of useful thermodynamic relationships. Applied Thermal Engineering, 2011, 31(5): 852-871

[10] Dunbar W R, Lior N. Sources of combustion irreversibility. Combustion Science and Technology, 1994, 103(1-6): 41-61

[11] Dincer I. The role of exergy in energy policy making. Energy Policy, 2002, 30(2): 137-149

[12] Khaliq A, Kaushik S C. Thermodynamic performance evaluation of combustion gas turbine cogeneration system with reheat. Applied Thermal Engineering, 2004, 24(13): 1785-1795

[13] Kotas T J. The exergy method of thermal plant analysis. Krieger Publishing Company, 1995

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