Process Heat

Waste heat recovery in a cupola furnace

A new recuperator in a smelting plant facilitates the utilisation of an additional 14 MW of waste heat. The waste heat is used to generate steam throughout the year for a nearby food company, saving up to 11,000 tons of CO2 per annum. 

 

Summary

Initial situation

Georg Fischer Automobilguss GmbH manufactures cast iron parts for the automotive industry at their Singen (Baden-Württemberg) site. Spheroidal graphite iron casting is used to produce iron in a hot-blast cupola. A recuperator generates the hot blast necessary to melt the metal and the fuel coke in the cupola. 

The aim of the project was to replace the old recuperator with a new recuperator concept which makes the recovery and use of waste heat more efficient. The new recuperator enables the recovery of up to 14 MW additional waste heat from the flue gas. As the energy required to generate both hot blast and hot water for the cupola remained constant, it was not possible to use the large quantity of additional heat directly in house. The company therefore decided to supply a nearby food company (Maggi factory, Singen/ Nestlé Deutschland AG) with the waste heat. The factory uses it throughout the year to generate saturated steam for the food preservation process, saving large quantities of natural gas.

Technical solution

Hot thermal oil is transported through pipes leading from the recuperator to a safety heat exchanger on the site of the neighbour company. The distance is short, so heat loss during transport is very low. The thermal oil is fed through the double-walled safety heat exchanger, which heats the feed water for the steam boiler and at the same time prevents the thermal oil from entering into the steam. The controls of the two systems were synchronised for this new waste heat recovery process. If one of the systems is down, they can be uncoupled again. When Nestlé Deutschland AG has no need for heat, the waste heat from the cupola is discharged into the environment in a controlled process via a cooling tower. Should Georg Fischer Automobilguss GmbH be unable to supply sufficient heat or any heat at all for technical reasons, Nestlé Deutschland AG can also heat the steam boiler with natural gas.

Findings

Nestlé Deutschland AG requires approximately 75,000 MWh a year to generate saturated steam. Recovering the waste heat from the cupola furnace can supply up to two thirds of the natural gas needs of Nestlé Deutschland AG. This saves about 1,100 m3/h of natural gas. As less natural gas is needed to generate the steam, CO2 emissions are reduced by approx. 11,000 tons per annum.

Conclusions

For plants generating large amounts of waste heat, this pilot plant is a good example of the advanced  state of waste heat recovery technology today, and of how new, innovative ideas can be implemented without excessive capital investment in relation to the benefits to the environment. 

Project Participants

Implementing Institution

Georg Fischer Automobilguss GmbH

Technology providers

Würz GmbH

More Project Informations

Project number:  20119

Project period:  2007 - 2009

Project region:  Germany (Baden-Württemberg)

Project contact:

Frau Fischer

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+49 (340) 2103 3067

+49 (340) 2104 3067

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Source: Environmental library of the Federal Environment Agency (UBA)