In its Hamburg plant, Aurubis AG has long been using heat from copper production as process heat. Since the coverage ratio here is already over 87 percent, the potential for further efficiency improvements is low, especially since heat from the lower temperature ranges can only be used sensibly in a few process steps. Against this background, Aurubis has developed the idea of making CO2-free heat, which is generated in a secondary process of copper refining, available for external use. The customer is Hamburg's HafenCity Ost, where a new district is being built in relative proximity to the Aurubis plant site. Together with the energy service provider enercity, operator of the heat supply for the new urban quarter, Aurubis then implemented the currently largest industrial heat project in Germany within two years. When commissioned, Aurubis will be able to decouple up to 160 gigawatt hours of heat - equivalent to the heat requirements of around 8,000 four-person households. The total potential for heat extraction even amounts to up to 500 gigawatt hours; this could cover more than one tenth of Hamburg's district heating requirements.
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
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".
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.