Improving the Capacity or Output of a Steam Turbine Generator at XYZ Power Plant in Illinois

Abstract

Competition has been a prime mover in the energy industry and there is the drive to increase

performance of steam turbine-driven equipment. Availability of a unit is also critical to the operation of

a plant and has also provided the fundamental reason why many utilities have chosen to upgrade

existing steam turbines rather than replace obsolete components.

Retrofitting older generation turbine plants with present day steam-path, can yield substantial

performance improvement, giving extra revenue from increased generation, reducing fuel consumption

while also benefiting the environment through reduced emissions.

Also as competition revolutionizes, the power generation industry is taking a close look at aging

steam turbines. They are evaluating whether refurbishment or upgrades to aging steam turbines

represent cost effective opportunities for lowering maintenance cost and avoiding forced outages as well

as increasing unit output. This has called for the improvement of the unit heat rate, increased capacity

and improving reliability of the unit in other to stay competitive.

The unit turbine at ABC Plant has experienced solid particle erosion (SPE) which has increased the

cost to operate the unit, decreased efficiency, and caused degradation in heat rate and unit availability.

solid particle erosion has caused the station millions of dollars loss in revenue from steam turbine

operation, maintenance and reliability. Solid Particle Erosion occurs when exfoliated particles from

boiler tubes, super heater and reheater tubes are carried over to the turbine through the steam path and

the cost that is associated with regular inspection, repair or replacement of damaged components has

been high.

The station has been urged to come up with a solution to minimize or reduce the solid particle

erosion effects on the turbine. As part of the solution, the station is looking at the different most

accepted means of combating Solid Particle Erosion. They are steam turbine blade coating, improved

nozzle design and modification in the steam path which is the dense pack design. The dense pack turbine

section performance is the latest evolution proposed by General Electric and the design limit does not

change with the dense pack design. The design goal is to put the most efficient steam path into an

existing high pressure shell. The high-efficiency steam path will produce a lower heat rate and

increased output for the same steam flow. The design parameters utilized to increase efficiency such as

bucket, nozzle solidity and reduced rotor diameters also had the benefit of reducing solid particle

erosion. The dense pack supplies the user which is the station with a redesigned steam path including a

new bucketed rotor, diaphragms, and an inner shell.

The XYZ Power Station was originally owned by BBB Company and subsequently purchased by

ABC Energy Generating in 2002. The station is located near ABC, Illinois, west of the Illinois River. It

has one steam turbine generator with a net generation of 366MW.

This project is divided into three phases; the first phase of this project involves looking at the

problem statement which is the effects of solid particle erosion (SPE) and propose a solution for SPE

problem by implementing one of the proposed solutions to combat Solid Particle Erosion, part of the

solution which will involve turbine blade coating also called sandblasting will be implemented during

the fall 2005 outage and the final solution which will involve the installation of the dense package will

be implemented in 2007.

The first part of the project was implemented during the fall 2005 outage in conjunction with generator

electrical testing and inspection. The second phase of the field project will look at the proposed boiler

modification project in 2007 and the dense pack project in 2007 which all when implemented will help

achieve the end results of this project which is improving the performance of the steam turbine

generator. The third phase will look at how the output of the steam turbine

generator can be increased or improved by operating at design values and improving the heat rate and

efficiency using past standard heat rate testing results assuming the boiler modification project has been

completed and the dense pack project has also been completed.