Slow Roll of 40 MW Condensing Extraction Steam Turbines in a 420 MW Cogeneration Plant

Abstract

This paper describes efforts required to operate a cogeneration facility's extractioncondensing steam turbine generators with flexible rotor design on a slowroll mode of operation (also called true standby). Slowroll mode of operation became necessary due to changing steam demand from the host refinery, resulting in decreased performance of the steam turbine generators and their associated economic losses. Design modifications implemented to achieve slowroll of steam turbine generators without affecting reliability and availability of the entire cogeneration facility are discussed in this paper. Successful implementation of the design modifications was demonstrated via extensive field testing on two steam turbine generator units during the summer of 2011. A simple life cycle economic analysis shows the payback period for the project is approximately seven months.