Off-design performance analysis and optimization of the power production by an organic Rankine cycle coupled with a gas turbine in an offshore oil platform

The organic Rankine cycle has been widely explored for energy recovery from several heat sources. In this paper, the maximization of the energy recovery of the exhaust gases from the General Electric LM 2500 gas turbines in a floating production offloading unit is studied in order to meet the demands of heat (pressurized hot water) and electricity over oil production lifetime. An off-design model of the system is developed to check the viability of an organic Rankine cycle under dynamic operating conditions. Energy and exergy analysis of the proposed system are conducted to determine main irreversibilities and performance characteristics of the system and, finally, the economic benefits of the energy recovery system application are discussed. The organic Rankine cycle is very flexible in the heat recovery in dynamic demand conditions, contributing up to 20.3% in electricity generation, which causes an increase in overall system efficiency of up to 11.3% and up to 18.3% in the utilization factor, as well as an average reduction of 22.0% in carbon dioxide emissions in the floating production offloading unit electricity generation process. The exergy efficiency of the system reaches 55.8% and the heat recovery devices are the most irreversible equipment in organic Rankine cycle, contributing up to 68% of the total exergy destroyed. The economic analysis demonstrated the attractiveness of the organic Rankine cycle implementation, allowing a net present value to Brazil's current economic scenario of up to USD 16.8 million.