Northumbrian Water cuts energy bill by 10%06 July 2011

Northumbrian Water reports that its advanced anaerobic digestion (AAD) project at Bran Sands, Teesport, has cut annual energy bills by 10% – and says steam systems specialist Spirax Sarco played an essential part.

The £33 million plant converts sewage sludge into energy and is currently the biggest plant of its kind in the UK. The plant uses thermal hydrolysis, which relies on injections of live steam to kill the pathogens in the sludge.

Raw sludge is loaded into stainless steel vessels and the steam is injected to hold the contents at 165ºC and 6Bar. The sludge is then cooled and fed into three 7,600m3 concrete tanks, where methane-generating microbes digest it anaerobically for up to 18 days. The resulting methane is collected and used to fuel gas engines, providing a renewable source of electrical energy.

"A reliable supply of high quality steam was a top priority on this project," explains Frank Errington, works co-ordination manager for Northumbrian Water. "Without steam we couldn't do what we do."

The lead contractor on the project brought in Spirax Sarco to provide boiler ancillaries and steam plant for the scheme, including a hotwell, blowdown vessel, controls, valves and sparging equipment.

Spirax Sarco also provided on- and off-site training, and is still visiting the site regularly as part of an ongoing water treatment and chemical dosing contract.

Final commissioning is now complete, and the AAD plant is creating enough power to make the sludge treatment process self-sufficient, with additional power providing electricity to meet half of the wider Bran Sands site's entire energy requirements.

"Spirax Sarco has proved to be a company we can rely on and trust. Their reputation among the people on site is very good and the Spirax Sarco engineers have a good rapport with our guys, which has been very important in a groundbreaking project of this size," states Errington.

Brian Tinham

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