ENERGY AND EXERGY ANALYSIS OF STEAM GENERATION AND UTILIZATION FOR ELECTRIC POWER GENERATION (CASE STUDY OF AJAOKUTA STEEL POWER PLANT, NIGERIA)

Abstract

Steam power generation is one of the major power generations in the world which needs to be enhanced in order to reduce greenhouse effect while improving the power generation. The efficiency of energy utilization can be obtained from exergy analysis which involves showing the use of energy and material resources and thereby establishing how efficient the energy is used in the process. This paper presents the energy and exergy analysis of steam generation and utilization of Steam Power Plant in Ajaokuta Steel Plant in Nigeria. The method adopted include data collection and analysis on first and second laws of thermodynamics based on the present operational performance of the steam power plant under study. The energy and exergy from fuel was much higher than the energy and exergy gained by feed water. The average energy generated in fuel being 107799.3kJ/s while that absorbed by the feed water or generated by steam is 89454.3kJ/s. The percentage of steam generated to sensible heat from fuel is 83% while that of steam utilized to steam generated is 60%. The average exergy generated in fuel combustion is 67728kJ/s, while that of steam generated is 43245.1kJ/s and the steam exergy utilization is 43161.5kJ/s. The percentage exergy generated in the boiler is 64%, meaning exergy is lost through boiler and its accessories, while the exergy of steam generated to steam utilized is 99.8%, invariably no useful energy in steam that is lost in pipelines and connections. The exergy destroyed in steam generation and utilization equipment were also analysed. The first law energy generation and utilization are 83% and 60% while that of second law are 64% and 99.8% respectively. Hence, the first law analysis shows that the entire steel plant need urgent rehabilitation, but the exergy analysis has practically shown that steam generation is approximately equal to steam utilization of the plant.