New low temperature industrial waste heat district heating system based on natural gas fired boilers with absorption heat exchangers

Highlights: • Absorption heat exchanger could greatly decrease return water temperature of PHN. • Lower temperature return water of PHN could recover more low temperature waste heat. • Lower temperature return water of PHN helps to increases heat transmission distance. • New DH-AHE is characterized by better thermodynamic performance and economic benefit. • New DH-AHE would be promising for low temperature industrial waste heat recovery. - Abstract: To efficiently recover low temperature industrial waste heat, a new low temperature industrial waste heat district heating system based on natural gas fired boilers with absorption heat exchangers was proposed, and also analyzed from the perspective of thermodynamics and economics. In heating substations, absorption heat exchangers are used to greatly decrease the return water temperature of the primary heating network. The lower temperature return water helps to efficiently recover waste heat in heating station and greatly increase economic heat transmission distance. Annual primary energy efficiency and product exergy efficiency of the new district heating system are 215.0% and 42.5% respectively. When waste heat price and heat transmission heat distance are 25 ¥/GJ and 60 km respectively, its heating cost and investment recovery period are 6 ¥/GJ and 0.7 years respectively lower than that of current district heating systems based on natural gas fired boilers. Characterized by better thermodynamic performance and economic benefit, the new district heating system would be promising for low-temperature industrial waste heat recovery.