January 1, 2022Aquatherm Case StudiesIn common with most European and Scandinavian countries, many hospitals and public institutions in Danmark have turned to the private sector for the provision of linen services.
One of the few remaining that have decided to retain their own processing facility is Vejle Sygehus (Sudenske Vaskeriet) located in the historic town of 55,000 inhabitants in Jylland (Jutland).
The laundry was established in 1980 and re-equipped with modern equipment in the early 2000's. Processing 6-7 tonnes per day, the main washing plant comprises 2 x Senking, 12 compartment P18 tunnel washers with SEP 50 type presses, and a total of 5 x Senking and 2 older Passal dryers – all equipped with cross-flow plate exchangers to reduce energy use.
Although the benefits of having an ‘on site’ service are many, the public sector is nevertheless duty-bound to obtain best value for money, and to keep processing costs to a minimum.
For thirty years, the processing methods and chemicals have been supplied by Novadan, which in 2010 served more than 50% of Danish laundries. Early in 2011, René Larsen , the chemist who had already achieved major savings in water and energy, proposed that the laundry invest in an Aquatherm Waste Water Heat Recovery System. A study was made of the flows and temperatures, and it was conservatively estimated that the total cost, including installation, would be recovered from energy savings in less than a year.
All of the waste water from both tunnels, including press extract water, was individually piped to a two cubic metre insulated tank adjacent to the machines, the mixed contents averaging 47°C.
An Aquatherm V20 automatically extracts the energy from the waste water, the resultant flow going to the outside drain at 5-6°C above the incoming cold fresh water – a recovery of 84%.
A second collection tank is used to store some of the cooled effluent, which is used to supply the washer extractors with water for the pre-wash and main wash. The rinses use fresh water.
Re-used water contains the 16-20% of energy not recovered by Aquatherm, and assuming 30% re-use, this boosts the recovery of energy used for washing to nearly 90% - without any need for cleaning or maintenance.
Apart from the direct energy saving, the extractor now operates with the linen at over 40°C, which reduces the moisture content and results in lower energy consumption for drying and finishing.
Using a clear 10” colour touch screen, the Danish staff can monitor flows and temperatures at all times, and all data is written to a data chip every second to provide a detailed record of performance whenever the plant is running. [...]