Extending Boiler Efficiency Beyond Existing Economisers
The site had already improved boiler efficiency through feedwater economisers, but the flue gas leaving them still averaged 129°C. Recovering additional energy from this exhaust offered a practical route to lower fuel costs and associated Scope 1 emissions.
The site’s 70% make-up water requirement provides a substantial heating duty for the HeatSponge™ systems. Because the incoming water is colder than the feedwater passing through the existing economisers, the downstream units can cool the exhaust further.
HeatSponge™ systems were added downstream of the existing economisers to recover this residual heat for make-up-water preheating.
At the 7.85 MW boiler, HeatSponge™ preheats the dedicated make-up-water. Two further second-stage HeatSponge™ economisers recover heat from two of the three 4.90 MW boiler exhaust streams, transferring it into their shared make-up-water system.
The systems recover sensible heat as the gas temperature falls and latent heat as water vapour condenses. Energy passes through the exchanger surfaces while the water and exhaust streams remain separate, reducing the fuel needed for boiler-water heating without relying on a separate process heat demand.
By recovering energy after the site’s existing economisers, the project extends the efficiency of established boiler infrastructure without changing the steam system serving sterilisation and pasteurisation.
The HeatSponge™ design also supports ongoing maintenance: removable panels provide access for inspection and cleaning, while compression fittings allow individual tubes to be removed and replaced without code welding.
Commissioning data confirmed that the HeatSponge™ installations exceeded expectations by approximately 8%, with combined annual natural gas savings of approximately 5,000 MWh and emissions reductions of more than 900 tonnes CO₂e.