Valve System Allows Rocksavage Power Station to Meet Demand

‘Can we modify the existing installation from a base load unit into a flexible unit, capable of reacting quickly to on demand changes of the grid, including starting and stopping daily?’

This was the question asked by Rocksavage Power Station in Runcorn, Cheshire.

Rocksavage Power Station, owned by InterGen, was built in the late nineties to provide the steam and electricity supply for the nearby chemical complex. The installation was based on two Alstom GT 26 gas turbines, two Alstom triple pressure waste heat boilers and a steam turbine.

Because the installation was designed and built as a base load unit the flexibility to start and stop the installation was very limited. One bypass system installed between the HP main steam and the condenser was used to start the boilers in sequence, one after another.

For a flexible starting and stopping regime the time to get on line was simply far too long.

Cascade arrangement

The modification comprised the installation of a cascade arrangement per boiler, based on an HP bypass and an IP dump valve.

Per boiler an HP bypass valve, a PRDS and a control valve, that reduces pressure and temperature, was placed between the main steam line and the cold reheat line. During start up, steam, now coming from the PRDS instead of the steam turbine is introduced in the re-heater to take care of cooling the modules. This is a severe mass flow, mixed up with additional steam coming from the starting IP evaporator.

In the next step, hot steam, coming out of the IP re-heater is now 'dumped' into the condenser through an IP dump valve. The combination HP - IP bypass valves per boiler makes it possible to start both boilers simultaneously. A quick start of the whole installation now is possible.

Advantages

• Significant reduction of startup time which makes the installation more attractive to supply to the grid and saves money

• The possibility of heating up the boilers equally and smoothly and consequently minimizing material stress in super heaters and headers

• Extend the life cycle of the boilers significantly

Advanced Valve Solutions (AVS) has replaced many critical valves in UK power stations and has a proven track record in protecting stations from loss of production and saving £000,000s in repairs and replacement part

Advanced Valve Solutions (UK) Ltd
Tel: 01270 534685
Web: www.AdvancedValveSolutions.co.uk

Published: 14th May 2015