Exergetic and Thermoeconomic Analysis of a Cogeneration Plant on a Brazilian Pre-Salt Oil Offshore Platform

Rodrigo Dias¹; Waldyr Luiz Ribeiro Gallo¹

¹ State University of Campinas

doi:10.20906/CPS/COB-2015-0654

Resumo

The usage of natural gas in the Brazilian pre-salt oil offshore platforms has turned into a major concern for the industry. This is mainly due to the reinforcement of the environmental legislation and public pressure on the rational use of energy. Firstly, this work will give the present picture of one of those platforms, containing four gas turbines generating power (100 MW installed) and a heat exchanger fed by the exhaust gases, transferring energy to process water. Secondly, it intends to promote alternatives in order to increase the efficiency of the cogeneration plant that is currently very low (around 55 %), mitigate emissions and eventually rationalize the system economically. To do so, the exergetic analysis will be essential because of its capability to point out the useful energy of the streams and the generated irreversibility in each equipment. Furthermore, the thermoeconomic analysis is also very useful to assess the cost of the streams, based on energetic or monetary terms. Among the changes proposed, modifications of the heat exchange system are required for improved performance, especially because of the high remaining exergy of the exhaust gases that is wasted. Additionally, a diagnosis of power partial load conditions is provided.

Palavras-chave: Exergy; Thermoeconomics; Cogeneration; Oil Platforms; Natural Gas