Achieving 50% weight reduction of offshore steam bottoming cycles

Adding a bottoming cycle to the gas turbines powering offshore oil and gas production plants allows additional power to be produced from recovered excess heat. Hence, the power demand of the platform can be met by burning less natural gas, and the CO2 emissions reduced by up to 25%. However, the weight of the current bottoming cycles must come down to enable widespread implementation. This work presents a thorough weight minimization of a steam bottoming cycle utilizing gas turbine exhaust heat. Unconventional, but feasible designs of heat exchangers, ductwork and structural components are considered along with materials switching. Overall weight reductions of 38% and 52% were achieved for a 16 MW and a 12 MW offshore bottoming cycle respectively when compared to a 16 MW reference system. Key factors in achieving the weight reduction were the use of small steam generator tubes with an inner diameter of only 10 mm, improved condenser design and the use of aluminium structural framework replacing steel. By more than halving the weight of the bottoming cycle, it's implementation potential on offshore platforms has been greatly improved and can move the oil and gas industry towards significantly reduced CO2 emissions.