Rheinhessen-Nahe Energy Services Company GmbH (EDG)

The Rheinhessen-Nahe Energy Services Company GmbH (EDG) has optimised the heating and electricity supply of the Nieder-Olm school centre and achieved high savings in energy consumption and costs as a result

The Rheinhessen-Nahe Energy Services Company GmbH (EDG) has optimised the heating and electricity supply of the Nieder-Olm school centre and achieved high savings in energy consumption and costs as a result. The contractor implemented the project in collaboration with the Mainz-Bingen regional district and their climate protection manager.

EDG’s technical concept consisted of the following measures to reduce energy use and costs: The local heat network was converted to low temperature. To achieve this, all consumers, particularly ventilation and hot water supply facilities, were optimised in terms of their hydraulics and control technology by means of energy efficiency measures, so that the return temperature could be limited. For example, the injection-type switches of ventilation systems were converted to heating circuit controls, and all heating circuits fitted with high efficiency pumps.

Around 60 per cent of heat is renewably generated in a woodchip-fired biomass boiler, which is supplemented by a high-efficiency natural gas CHP plant with a downstream calorific value heat exchanger. Two large buffer tanks in EDG’s energy management system ensure that heat generation can be decoupled from heat requirements. In addition, the tanks guarantee that the CHP plant and biomass boiler operate optimally. EDG has constructed an internal low-voltage network on the school site in parallel with its heating network. This means that the CHP-generated electricity can be used to directly supply the buildings.

The newly decoupled industrial heat is generated in the so-called contact plant during the conversion of sulphur dioxide, which is obtained during copper refining, into sulphuric acid. The exothermic chemical reaction releases the CO2-free heat. However, in order to be able to use it for external heat supply, it was necessary to raise the temperature level of the process from the current 65 °C to 117 °C. The process is now being operated at a temperature of 117 °C. This is the temperature at which the heat is released. This necessitated process engineering changes as well as new materials and plant components.

Aurubis and enercity conduct most of the industrial heat generated via a specially constructed 3.7 km heat transport pipeline from the plant site to eastern HafenCity. Aurubis also uses a quarter of the industrial heat in its own processes, such as heating the electrolyte during copper electrolysis. This reduces the company's natural gas requirements by around 50 gigawatt hours per year, which corresponds to an annual CO2 reduction of over 14,000 tonnes. The heat extraction measures were implemented in spring 2018. The first use of heat in HafenCity took place in late autumn 2018.

Energy efficiency measures

  • Adaptation of the sulphuric acid process to increase the temperature level
  • decoupling of industrial heat by technical conversion of the contact system
  • Erection of an internal heat transport pipeline
  • Transmission of industrial heat to supply eastern HafenCity with district heating
  • Use of industrial heat for in-house processes
  • Savings of 12 million m3 of cooling water per year

jury assessment

The jury selects Aurubis AG as the winner of the Energy Efficiency Award 2018 in the Energy Transition 2.0 category. The waste heat is now also used outside the plant in addition to being used internally. The external use of the waste heat by enercity Contracting NordGmbH makes a significant contribution to the climate protection goals of the City of Hamburg. With the help of industrial heat, it is even possible to fall short of the ambitious emission targets for supplying heat to the new HafenCity Ost development area. By using part of the heat internally within the plant, Aurubis can also cover almost half of its heat requirements for copper electrolysis and electrolyte treatment. The project has already been awarded as a lighthouse project of dena for waste heat utilisation and is one of the first major projects to be supported by the KfW promotional programme "Waste Heat".

company profile

Aurubis AG is an international supplier of non-ferrous metals and one of the largest copper recyclers in the world. The company processes complex metal concentrates, scrap metals and metal-containing recycling materials into metals of the highest quality. Aurubis produces more than 1 million tonnes annually.

copper cathodes and uses them to manufacture various copper products such as continuous cast wire rod, shapes or special wires and copper alloys.

Aurubis employs around 6,500 people and has production sites in Europe and the USA.