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Further research requirements

The Saarbrücken researchers have developed new ORC working fluids as part of a joint project conducted with a specialist chemical company. On a new testing rig, three to five different fluids are being tested that function either with low waste heat temperatures under 150 °C or with temperatures above 450 °C. The new working fluids should be durable and stable, without being environmentally harmful, toxic or combustible. “Here there is no competition with turbines. All ORC technicians are interested in this,” says Schmidt. “That also applies to the development of improved heat exchangers. Here I am seeing too few genuine innovations.” Together with a manufacturer of heat exchangers, he is looking for a direct evaporator for dust-laden flue gases with temperatures above 600 °C. At the same time, acid in the flue gas should be prevented at less than 130 °C in order to improve the corrosion protection, whereby new cleaning and filtering systems for particle-laden flue gases should provide help.

Marketing underway

Sufficient operating experience has now been gained to be able to determine the economic feasibility of the ORC steam expansion engine. Connected to the ovens of a foundry, two 200-kW engines can generate 2.8 million kWh of electricity a year based on 3 MW of waste heat. This will make it possible for the ORC plant to pay for itself in less than 5 years and, if the residual heat is used for heating, in less than 3 years (calculation based on 6.5 ct/kWh including levies and fees). An attractive feature for industrial enterprises is the fact that the plant can be operated without on-site personnel by means of remote monitoring. The ORC plant from Saarbrücken synchronises itself fully automatically with the electricity grid. This is particularly important with discontinuous waste heat flows if the new ORC technology is to fully benefit from its advantages in practice.

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Addresses

Steam expansion engine
DeVeTec GmbH

Working fluids
Evonik Industries AG

Heat exchangers
SCHOTT AG