Make-up water plant refurbished

ROCHESTER, Kent, UK, Sept. 12, 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 whilst balancing potential environmental impact.

Grain, as the station on the eponymous Isle is known, has two oil fired 690MW units giving a total generation capacity of 1,380MW. The high purity water that 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 says. "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.

Pete also decided to replace the internal underdrain nozzles, which are made of polypropylene and tend to become brittle with age. "If a single nozzle breaks it results in a loss of resin and contamination of the treated water", says Pete. "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.

E.ON was impressed with ELGA Process Water's service and management of the site work and has awarded the company a contract to carry out a similar refurbishment on Grain's second stream in July 2007.

ELGA Process Water is part of Veolia Water Solutions & Technologies (VWS), a subsidiary of Veolia Water. VWS is one of the world's major designers of technological solutions and constructor of facilities for water treatment. With over 6,500 employees, the company has operations in more than 50 countries. VWS recorded revenue of €1.6 billion in 2005.

Veolia Water, a division of Veolia Environnement, is the world leader in providing outsourced water and wastewater services for municipal authorities, as well as industrial and service companies. Veolia Water serves 110 million people worldwide. With over 67,800 employees, its 2005 revenues amounted to €8.9 billion.

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