59358 - Improving Combined Cycle Part Load Performance and Reducing Plant Costs by Using Exhaust Gas Recirculation With an Ejector 

The gas turbine combined cycle (CC) power generation industry is experiencing a shift from full load base duty operation to load following cyclic operation.  This energy market development is being driven by the increased installed capacity and large growth in intermittent renewable power generation.  In this cyclic market there is a critical need for CC power plants to provide power over a wider range of load levels, and at low marginal costs.  Improving part load efficiency and Minimum turndown is critical for these customers to succeed in competitive markets.

Existing technology for improving the CC power plant part load efficiency is performed by providing a gas turbine air inlet heating system using IP water from the bottoming cycle and a heat exchanger in front of the gas turbine.

This paper presents a new approach for achieving the air inlet heating by using exhaust gas recirculation (EGR) from the gas turbine exhaust through an ejector.  A small percentage of the compressor inlet bleed heating (IBH) is extracted and works as the motive flow while a bleed from the GT exhaust works as the suction flow.  The enhanced IBH which is the ejector discharge will then mix with the compressor inlet flow and heat the inlet air to the compressor.

The advantage of this proposed solution is that there is no need to install a heat exchanger in the front of the gas turbine which consequently improves combined cycle heat rate by ~1% at 60% CC load, saves cost and reduces space