COMBINED HEAT AND POWER (CHP) SYSTEM OPTIMIZATION USING ENERGY, EXERGY AND THERMODYNAMIC ANALYSIS
Alumina Refinery Power Plant Optimization – Two Case Studies
Quamie N. Mortley1, Winston A. Mellowes2
1Chemical Engineering and Energy Consultant, Kingston, Jamaica
2Faculty of Engineering, The University of the West Indies, Trinidad
1Email: qnmortley@yahoo.com
2Email: wamello@yahoo.com
Abstract:
The conventional energy analysis evaluates the performance of a thermodynamic system generally on its quantity only. It gives no information about the effect of irreversibilities on performance that occurs inherently during any thermodynamic process. On the other hand, exergy analysis, based on the second law of thermodynamics recognizes magnitudes and locations of the losses due to these irreversibilities. This paper deals with the improved energy performance of two-alumina refineries in Jamaica. One refinery produces alumina from Jamaican bauxite ore, using the Bayer process. The first process includes the digestion of bauxite with sodium hydroxide at 135 deg.C, (low temperature digestion). The second process includes the digestion of bauxite with sodium hydroxide at 245 deg.C. Hence, the requirement for both steam and power. Steam is generated using heavy fuel oil. There is auxiliary power from Internal Combustion Engines, Gas Turbine Engine and the Power Grid. The engine (the machine) produces mechanical work and then electrical power. According to the Second Law of Thermodynamics, the machine gives back heat (a part of the useful energy delivered by CHP) to a cold sink (low temperature sink), before rejecting the remaining heat to the environment at the reference temperature. Losses to the low temperature sink is minimized. This resulted in daily fuel savings of 400 barrels of Heavy Fuel Oil (HFO) and an annual savings of 146,000 barrels of Heavy Fuel Oil.
Keywords: combined heat and power, energy, exergy analysis.
https://doi.org/10.47412/WLPY5775
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