The Grunewald foundry: Sand and energy recovery in the foundry

The Grunewald foundry produces aluminium castings. In the past, the sand used in the process was mostly wasted. Using a technology for sand and energy recovery, which was developed in the chemistry lab, the company is now able to save costs and raw materials.

A lot of sand is used in the foundry process; the Grunewald foundry requires up to 800 kg of sand for the negative mould of a casting. A new sand processing facility has now decreased the raw materials requirement at the foundry: The system separates the sand from the binder during a combustion process in an oven which is heated to approx. 700° C. Previously, Grunewald had to replace 40 per cent of the sand; now it is only five per cent.

Engine for progress:

  • process waste heat is re-used for heating
  • the sand circulation is almost completely closed
  • cooperation with regional experts
  • increase in quality and productivity

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Foto: Bednareck Photography

The Grunewald GmbH & Co. KG foundry produces aluminium castings. The castings are formed using sand. Grunewald needs up to 800 kg of sand per negative mould. Before the conversion, almost half of this was wasted in the process; today, the sand circulation is almost completely closed.

One million kilowatt hours of natural gas saved

Apart from increasing its resource efficiency, Grunewald has also increased its energy efficiency: Not only does the sand processing plant recycle sand; the heat it produces is also re-used. In close cooperation with Teka Absaug- und Entsorgungstechnologie [extraction and disposal technology] from Velen, Grunewald has developed a tailored solution, which up until now was more common in chemical laboratories. The new system detects and uses the waste heat from the two regeneration stages of sand processing from the new hall. The gas and dust mixture, which is formed in the process chain, is extracted and recycled separately, so that the heat energy is safe to use. Thanks to the two new facilities, Grunewald is able to recover the processed sand almost completely and save approx. one million kWh of natural gas and 230 tonnes of CO2 annually.

Noticeable improvements in quality and productivity

The quality of the finished aluminium castings has been improved thanks to the new mould production process. The production process has also been accelerated: Grunewald now produces many more moulds per hour, because the increased bonding strength causes the moulds to solidify at a faster rate.
The two systems pay for themselves after about eight years due to reduced energy and disposal costs, as well as quality improvements and increased productivity. There is no need for additional heating in the upgraded hall, where the air is cleaner than outside thanks to the extraction technology.

Background information on the foundry processes

Sand is used to form the castings. Reusable models of the future casting are disassembled for this purpose, placed in boxes and covered with sand as accurately as possible. The sand is bonded using resin, so that the mould remains fixed when the model is removed. The sand moulds are then assembled so that a cavity is formed, which is then filled with liquid aluminium. Once the form has cooled, the sand is extracted and the casting can be removed.

Photo: Privat

“The new exhaust system removes dust and gaseous substances from the hall. The modern waste heat recovery technology helps to save energy and to reduce CO2 emissions to a considerable degree. As a result, the modern health and safety standards not only benefit our employees and the environment, but also have a positive effect on the energy balance throughout the company. "

Ulrich Grunewald, Managing Director, Grunewald GmbH & Co. KG

Partners and sponsors

  • Grunewald GmbH & Co. KG
  • TEKA Absaug- und Entsorgungstechnologie GmbH

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