The laundry at Noble’s Hospital on the Isle of Man is reportedly saving over £14,500 annually in energy, water, and treatment chemicals, following the installation of a Spirax Sarco FREME (Flash Recovery Energy Management Equipment) system. Over the equipment’s 20-year lifetime, the resulting fuel savings are expected to prevent the generation of over 1,750 tonnes of CO2.
The laundry previously aimed to use as much of the condensate from its steam system as possible to preheat water entering the plant’s three boilers, but some energy was lost as flash steam as the hot liquid moved from the higher pressure steam distribution system to the condensate return system. In fact, Spirax Sarco says, up to half of such recoverable energy can be lost as flash steam in a ‘typical ‘steam system. At Noble’s laundry, this created visible plumes of flash steam as it was vented to the atmosphere.
How high the boiler feed temperature could be raised was also limited, because the closer it is to boiling point, the more chance of cavitation as water enters the boiler feed pumps. Despite engineers limiting the incoming water temperature to 85-95o C, the boiler feed pumps were still experiencing cavitation and premature wear problems.
The FREME system sees all the usable heat in the condensate returned to the boiler. Returning condensate is passed through a flash steam separation vessel, and the separate flash steam and condensate streams through dedicated plate heat exchangers, where they each heat the boiler feedwater, all on the high-pressure side of the boiler feed pumps, so the system can safely heat water to over 100oC without boiling and causing pump cavitation.
By enabling Noble’s laundry to raise its boiler feedwater temperature to up to 125 oC without causing cavitation problems, the laundry has cut its annual fuel costs by around £12,000, while the reduced need to top up the boiler with raw make-up water has saved a further £2,500 annually.
“By implementing the FREME system, the department has reduced the impact of rising costs of energy, ensuring the laundry provision at the hospital remains as cost-efficient as possible,” says estates engineering officer, Gary Radcliffe. “The fundamental project achievements are those of water recycling and recycling of energy, making the laundry system more energy-efficient. The project also achieves an essential reduction in chemical consumption which reduces the impact on the environment.”
