ScottishPower sludge-to-fuel plant running smoothly

The Daldowie Fuel Plant, commissioned in 2002 and operated by SMW Ltd, part of ScottishPower, is one of the largest sludge drying centres in Europe.

The facility processes sludge from hundreds of wastewater treatment plants in the West of Scotland into processed sludge pellets (PSP) which are suitable for use as a dry fuel in a range of applications from power stations to cement columns.

The dry, low-odour pellets produced at Daldowie are a type of biomass - biological material that is deemed to be a sustainable form of fuel.

Every year SMW Ltd turns more than 2 million cubic metres of liquid sludge into more than 45,000 tonnes of PSP, which is burned to produce electricity or heat. The nature of the input material collection process means that it contains a percentage of grit which makes both the sludge and the dry pellets particularly abrasive.

The abrasive nature of the process material and the high volumes being transported around the plant mean that wear erosion is a challenge faced on many areas of the plant.

Some areas of the process such as the pipes used to pneumatically transport the dry product are particularly vulnerable and were fitted with Kingfisher ceramic lined pipes and bends as original equipment when the plant was first installed ten years ago.

The Kingfisher wear protected 6” diameter pipework on site is showing few if any signs of wear, hence the reason for asking Kingfisher to look at some other problem areas of the plant, reports Iain Russell, process & projects manager at SMW Daldowie.

“A regular inspection is made of the process equipment - with external visual inspections taking place during every daily shift and a more detailed internal inspection made during a two week shut-down period, which is scheduled every six months for each section of the process plant,” said Russell.

“Having taken the opportunity to inspect a pipe bend transporting dry pellets during routine maintenance we noted that the ceramic lining was barely showing signs of wear, even though it had been in use for ten years.”

Although having used other ceramic bead coatings at site before, Kingfisher has lined the inner shell of a ploughshare mixer which is a metal drum (approx 1m diameter) and has a central shaft with mixing blades (termed ploughs).

The work was completed during 2011 and, said Russell, the surfaces are like new, with the estimated minimum lifespan of 5-6 years looking like a conservative estimate.

Dry pellet production is coming under increasing pressure from less energy intensive processes such as gas from anaerobic digestion; although the plants tend to be smaller and the yields lower as a result, noted John Connolly, Kingfisher Industrial MD.

“It is essential that the Daldowie PSP plant operates at its maximum efficiency and maintains uptime … It is in these continuous applications where good wear protect sees its maximum ROI,” commented Connolly.