Instationarity as a limiting factor for the use of industrial waste heat in heating-networks
It has been a political and ecological aim in Austria and Europe to increase the heat supply in district heating systems. Presently 12 [%] of the final energy demand for heating in Austria are covered by district heating. In addition to highly efficient combined heat and power heat-production and the use of regenerative energy sources like biomass, integration of industrial waste heat into district heating systems can contribute to the reduction of CO2-emissions.
Industrial waste heat is difficult to integrate into district heating systems because it is transient (fluctuations in mass flow, temperature and pressure). This is the reason for rather few application examples for waste heat integration into district heating systems.
In the project, boundary conditions for waste heat integration were analysed from a technological and an economical point of view. Typical waste heat sources were documented, as well as district heating systems:
- The heat demand in district heating systems is highly influenced by seasonal effects and ambient temperatures.
- However, the load profile of industrial waste heat is not influenced by seasonal effects but is a result of the industrial production process.
- 3 categories of waste heat with typical transient characteristics (load
profiles, gradients) can be identified:
- Waste heat extracted from flue gases
- Waste heat from cooling
- Waste heat from batch processes Additionally, measures (components and operation strategies) that can contribute to a reduction of transients were documented, which makes the load profile more homogenous.
In a second step an assessment method was developed to quantify the compatibility of the load profile of waste heat sources and the heat demand of district heating systems. Therefore a new key figure, the "uniformity factor", was defined. With this uniformity factor a consistent classification of both waste heat and district heat demand can be carried out. In combination with additional key figures, a basis for an economic assessment of waste heat integration is defined. Thus, cost effects at the interface between industrial waste heat and district heating systems can be analysed with high transparency (e.g. cost-benefit calculations for additional storage equipment which leads to a more uniform load profile of the waste heat resulting in higher earnings due to a higher quantity of integrated heat). As a result, the findings of this project will contribute to a realistic assessment of industrial waste heat integration.
Dipl.-Ing. Dr. Matthias Theißing FH JOANNEUM Gesellschaft, Studiengang Infrastrukturwirtschaft / Urban Technologies
FH JOANNEUM Kapfenberg: DI (FH) Alois Kraußler, Michaela Muster , DI (FH) Martin Schloffer, DI Dr. Manfred Tragner, DI (FH) Michael Wanek
Technisches Büro Theißing-Brauhart
DI Dr. Ingrid Theißing-Brauhart
Project or cooperation partner
- Voestalpine Stahl Donawitz GmbH Co & KG
- Voestalpine Stahl GmbH
- Böhler Edelstahl GmbH
- Treibacher Industrie AG
- Marienhütte - Stahl- u. Walzwerk Gesmbh
- Stadtwerke Kapfenberg GmbH
- FERNWÄRME Wien GmbH
- Linz Strom GmbH
- Energie Graz GmbH & Co KG
- Steirische Gas-Wärme GmbH