Power station gets a makeover

Published:  30 October, 2007

At 30 years old, the boiler make-up water treatment plant at E.ON's Isle of Grain Power Station was beginning to look its age, and E.ON appointed ELGA Process water to give it the   'Trinny and Susannah" treatment. E.ON is the UK's largest integrated energy company, generating electricity in a fleet of power stations fuelled by gas, wind, coal, oil and hydro, enabling the company to meet its generation needs while balancing potential environmental impact.

The station has two oil fired 690MW units giving a total generation capacity of 1380MW. The high purity water the boilers need is supplied by an ion exchange plant installed in 1976. The plant consists of two streams of cation exchange, anion exchange and mixed bed polishing, each capable of delivering up to 400 m3/h of boiler make-up water of conductivity 0.04µS/cm and silica 0.02mg/l. The three metre diameter vessels are fabricated from carbon steel and lined with rubber to protect them from the acidic conditions inside. The plant was designed and built by Permutit, a company with a long track record in power station water treatment, and now part of ELGA Process Water.

Pete Kingbrooks, Grain’s plant chemist, planned the refurbishment for the summer: "Between May and September the demand for electricity is lower and the station output is reduced”, he explained. “That means we can run with only one of our ion exchange streams available, so we can carry out planned maintenance on the other.” Two of the vessels, the cation and mixed bed exchange units, were scheduled for precautionary re-lining, and ELGA Process Water’s task was to remove the ion exchange resins to a temporary store, clean and re-line the vessels with rubber, spark test to ensure the integrity of the lining, reload the resins, hydraulically test and re-commission the units.

Kingbrooks also decided to replace the internal under-drain nozzles, which are made of polypropylene and tend to become brittle with age.

He commented: “If a single nozzle breaks it results in a loss of resin and contamination of the treated water. That means an emergency shut down of the water treatment plant and, if that happens in winter, we lose generation capacity.”

It made sense to fit new nozzles while the units were being refurbished, and this was made easier for ELGA Process Water because they still keep the original Permutit design drawings in their archive.

For further information please visit: www.elgaprocesswater.com

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