Green’s designs and manufactures bespoke waste heat recovery system for LondonEnergy

In 2015 LondonEnergy identified that its five boilers, that were originally fitted with Green’s economisers and had been installed at the plant for some forty years, required attention. The economisers had been replaced in 1996 with equipment manufactured by other suppliers to further reduce the flue gas exit temperatures. These economisers were now deteriorating through corrosion of the return bends, erosion from Sootblowers, excessive fouling / blockages and general leaks. A solution was required to ensure the boilers remained operational for a further 10-12 years.

All of this affected the efficiency of the boilers and the requirement to keep the UK’s first largescale Energy from Waste plant operational on a 24/7 basis – essential to cope with the 750,000 tonnes of London’s waste and recyclables it handles and treats every year. This process not only generates enough electricity to power more than 80,000 homes it also diverts more than 90% of waste away from landfill saving nearly 300,000 tonnes of CO2 annually.

Green’s design and engineering team looked at how LondonEnergy’s needs could be met with an alternatively configured waste heat recovery system that would be more efficient without compromising any thermal performance.

They modelled several tube/fin designs and analysed the results and identified that the optimum solution comprised of 3 banks that were each 12 tubes high and 19 double H-finned tubes wide, totalling 1,368 tubes per boiler. The previous design incorporated a mixture of H-fin and plain tubes; however, the new system features entirely H-finned tubes which means that the required temperature is reached with fewer tubes making it more efficient and much easier to keep clean. This design also results in lower flue gas and water side pressure drops reducing power consumption and maintenance of pumps and fans.

The entire system was designed and manufactured in Green’s Wakefield factory. The redundant economiser tubes and headers were removed by Green’s services team before installing the new equipment. The work was carried on all five boilers in line with LondonEnergy’s outage programme.
Gustav Woudberg, Maintenance Manager at LondonEnergy says:

“Green’s support has been invaluable in helping us to decide on the optimum solution to meet our needs. Having their design, manufacture, installation and service teams available gives us confidence that they can look after all of our waste heat recovery system requirements effectively and efficiently, if the opportunity arises.”