»
The
district heating center ( top , center ) is part of a larger green energy network that generates heat from a wastewater treatment plant in Lemgo , Germany . Photo courtesy of GEA / Tim Luhmann .
GEA heat pumps pave way to district climate neutrality by 2035
By supplying two heat pumps , GEA is helping the city of Lemgo on its way to achieving climate neutrality by 2035 . The GEA technology will generate heat from the effluent of the city ’ s wastewater treatment plant , waste heat from a large combined heat and power ( CHP ) plant and from the River Bega .
Text & images by GEA
The heat generated by the large heat pumps is sufficient to supply the historic city center of Lemgo with low-carbon heat as far as possible . That ’ s around 18 million kilowatt hours of heat per year , which saves 3,200 tons of CO 2 emissions per year . The heat from the wastewater treatment plant ’ s effluent alone can cover two thirds of the old town ’ s heating requirements or twelve percent of the district heating network ’ s total demand . The operating strategy ensures that the heat pumps can operate constantly for up to 7,500 hours per year to maximize the benefits of the heat pumps .
Attracting attention Stadtwerke Lemgo became aware of GEA through the “ Malmö ” heat pump project . Here , too , GEA technology was used to generate heat from the wastewater of a municipal sewage treatment plant in the Swedish metropolis . At an initial meeting on site in Lemgo , GEA suggested to the customer that the initially planned low-pressure heat pump and high-pressure heat pump be replaced by a two-stage heat pump without a lossy intermediate circuit .
This was quickly recognized by all parties involved as the significantly more advantageous option in terms of energy and economy . So only this variant was pursued further . At the time , there was no comparable solution from competitors on the market .
Problem at hand The recovery of heat from the wastewater of the municipal central sewage treatment plant in Lemgo forms an important part of the municipal district heating generation . The clean water at the sewage treatment plant outlet is highly suitable . The treated wastewater has an average annual temperature of around 13 ° C . Due to the mixed water system , large quantities of water ( equal to quantities of heat !) are available . More than 1.5 MW of source power is available for almost 8,000 h / a . Furthermore , infrastructure such as a combined heat and power plant and district heating connection are available at the sewage treatment plant . Heat is only extracted downstream of the treatment stages at the outlet of the sewage treatment plant . This enables the highest possible amount of heat to be generated with relatively little technical effort . The wastewater treatment process is also not affected by the heat extraction .
Overcoming challenges Upon commissioning , it was discovered that the water quality of the heat source from the sewage treatment plant did not meet the original purity expectations . The resulting contamination of the evaporators meant that the “ pure
20 Heat Exchanger World April 2024 www . heat-exchanger-world . com