Generating 30% surplus power from wastewater treatment
06/01/2015 Danfoss Drives
Marselisborg wastewater treatment plant has transformed its focus beyond minimising energy consumed, to maximising net energy surplus - with a little help from VLT® drives.Today the facility has net production of both electricity and heat, supplying the district heating system in Denmark's second-largest municipality of Aarhus.
The carbon footprint has been reduced by 35% accordingly.
Plant Manager Flemming Husum explains: "We use VLTs in every corner of the plant. We have always specified Danfoss VLT frequency converters specifically for the features we need which only VLT can offer. The difference between 25 years ago and today is that processes now run right at their limit - but not beyond. And to achieve that we cannot do without the precision control we can get from VLTs".
Key steps in the strategy:
1. Optimizing the nitrogen removal process using online sensor control. The frequency converter adapts the level of aeration precisely to the need. This control system reduces energy consumption and increases the amount of carbon left in the system.
2. Blower technology upgrade to a high speed turbo blower. The upgrade achieves further reduction of energy consumption in the aeration process.
3. Aerobic sludge age control as a function of temperature and load on the plant. Here frequency converter control of the return sludge pumps is the key to achieving energy reduction and increased retained carbon in the system.
4. Upgrade of combined heat and power (CHP) process for energy production, with 90% energy efficiency.
These changes together with improvements including the effective co-production of electricity and heat based on methane gas extracted from the aerobic sludge digestion process result in:
-€¢ 130% electricity production (30 % excess electricity)
-€¢ Excess heat production of about 2.5 GWh/year
For more information, please contact:
Sara Bernard
Danfoss VLT Drives
Capswood
Oxford Road
Denham
Buckinghamshire
UB9 4LH
Tel: +44 1270 757584
Fax: +44 1895 617149
Email: sara.bernard@danfoss.com
Web: www.danfoss.co.uk/vlt
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