All systems go
15 July 2010
Spirax Sarco worked with De Mulder & Sons, which uses about 25t per hour of steam to dry and sterilise animal products, to design, build and install a packaged flash steam recovery system
Saving energy is top priority for many steam system users but bringing complex energy-saving projects to fruition can be difficult and time-consuming. The good news is packaged systems make it easier, faster and more cost-effective to install efficiency-boosting solutions for steam.
The drive to save energy tops the agenda for many steam users but designing and building a bespoke solution from scratch can be an uphill struggle. Packaged Systems says it helps turn grand plans into reality by taking the hassle out of complex projects.
Faster construction, greater reliability, higher productivity and lower costs are said to be some of the well-established benefits of designing and manufacturing complex systems off-site, and today’s engineered systems deliver these benefits in addition to energy savings.
Engineered systems are skid-mounted, factory-built modules designed and pre-fabricated for a specific application. A system may include all the components needed to meet the required process demand, such as heat exchangers, steam conditioning equipment, controls and condensate recovery system. The units are delivered to site pre-assembled or they can be assembled onsite, and are factory tested for quick hook-up to the site’s services.
There are many benefits to this pre-fabricated approach. However, energy savings provide the biggest incentive for many companies to invest in new equipment, enabling them to meet regulatory obligations, improve their environmental performance and save money. And this is where engineered systems for steam applications have proved real winners.
In one case, a heat recovery engineered system is delivering direct energy savings of 10% in addition to a further 10% in indirect savings at De Mulder & Sons in Nuneaton. The system has dramatically cut visible plumes of flash steam from the site, which is a UK processor of meat and poultry residues.
De Mulder & Sons uses about 25 tonnes per hour of steam to dry and sterilise animal products. Before the new system was installed, the resulting flash steam from the returning drier condensate was vented to atmosphere.
Spirax Sarco was called in and, working with the De Mulder & Sons team, designed, built, delivered and installed a complete packaged flash steam recovery system. Now, condensate and flash steam is fed from the driers to the flash recovery vessel, which separates them into two streams.
Each stream then flows through its own dedicated plate heat exchanger, which transfers the energy in the flash steam and condensate to the boiler feedwater. This raises the temperature of the pressurised feedwater to about 130oC, rather than the 90oC typically achieved before flash steam recovery was introduced.
There are five boilers onsite, of which three were running prior to the Waste Heat Recovery Unit installation. Raising the feedwater temperature and therefore the system efficiency has allowed one of the boilers to be taken offline. “The boilers work closer to their optimal firing capacity, saving an extra 10% on top of the 10% saved directly by waste heat recovery,” says De Mulder & Sons’ operations director Rob Ratcliffe.
With the major assembly work carried out at Spirax Sarco’s Cheltenham facility, the complete recovery system was integrated with De Mulder’s existing plant over a normal weekend shutdown.
Waste heat is a hot topic and Spirax Sarco’s Flash Recovery Energy Management Equipment (FREME) won the IChemE’s Innovation and Excellence Award in Energy in late 2009, thanks to its ability to achieve energy savings of up to 26% in industries as diverse as brewing and distilling, food and beverage, healthcare and pharmaceutical, among others.
Another typical situation where engineered systems are used successfully is in replacing old shell and tube heat exchangers.
Chocolate manufacturer Bendicks (Mayfair), for instance, now has an unlimited supply of hot water for washing down its equipment, thanks to the installation of a Spirax Sarco EasiHeat engineered system.
The Winchester-based factory’s previous water-heating system struggled to keep pace with demand, especially at peak times. As a food manufacturer, Bendicks must be able to wash down its equipment with water at 63oC or hotter to prevent microbial growth so any disruptions in the hot water supply disrupted plant operations.
“Our old calorifier system used to give us many problems,” says Bendick’s engineer Keith Wallace. “It would heat up the water in the vessel but as it was being used and replaced by fresh cold water, the temperature would drop and often run cold during peak usage times. Now the EasiHeat system gives us instant hot water that’s always available.”
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