Metal

Energy efficient casting ladle heating system used in the manufacture of stainless steel

The new system uses infrared radiation and convection to heat up the ladles used to transport molten metal evenly and under controlled conditions. This helps to save around 60% energy compared to heating with gas-powered flame burners. 

Summary

Initial situation

Edelstahlwerke Schmees GmbH produces cast stainless steel parts for pump and turbine manufacturing and for the food and pharmaceutical industries.

Transfer ladles with a refractory lining are used to transport the molten metal from the melting furnace to the casthouse. 

In this industry, the casting ladles are commonly heated using gas-powered burners.

These burners are very loud and require a lot of maintenance. The temperature control is unsatisfactory and not particularly precise. The necessary application temperature of 650°C to max. 850°C can only be reached if the ladles are pre-heated for at least 5 hours. Heat radiation and all of the waste gas is emitted into the casting bay.

The conventional heating method using gas-powered flame burners puts extreme stress on the refractory material, thus reducing its useful life.

In the melting area, the company has been using four conventional burners to heat the ladles. The existing flame burners heat the upside down ladles from below and consume massive amount of energy.

Project target

The essentially new idea was to pre-heat the casting ladles so that the production process could become much more efficient but also to create positive effects on the life-span of the ladles being used.

With the first, large-scale technical application of a complete, energy-efficient casting ladle heating-station with five available parking bays for the ladles and three heating systems (ladle station 5/3) for the three ladle sizes (1t, 1.25t and 2t), the energy consumption for the ladle heating process will be considerably reduced.

Technical Solutions

The company has now installed a new energy efficient casting ladle heating system with a new kind of porous burner which heats the transport ladles without exposing them to an open flame. The combustion heat is channelled to specially adapted steel pipes via infrared radiation and convection flow. By doing this, the heat is directly transferred to the ladles and can be controlled in a more balanced manner.

The resulting hot waste gas is collected and the waste heat will be reused in the facility in the future (facility heating 2011).

In addition, the customised systems and their infinitely variable controls make it possible to substantially reduce the energy required to control the temperature of the ladles on standby, i.e. they make it possible to keep the target temperature up with very little energy.

Findings

  • For 900t to 1000t unfinished casting p.a, the company now saves around 61,400 m3/a of natural gas, approx. 60 % of the energy required for the ladle heating and, as a result, 113.8 tonnes of CO2-equivalent.
  • The noise level has sunk by approx. 11 dB from 78.7 dB to 67.4 db. This amounts to about half of the previous level
  • The combustion in the porous burner is complete and therefore considerably more environmentally compatible than the flame burners.
  • The life span of the ladles can be increased by a factor of 2 due to the reduced exposure of the fire resistant materials.
  • Due to reduction in cleaning and carrying time of the ladles, productivity of the complete process is considerably increased.
  • The heat radiation from the ladles has been reduced by 75 % which has led to a reduction of breakdowns as the gear oil can no longer burn.

Conclusions

In general, the application is possible in all types of foundries where transport ladles have to be heated. However, depending on the type of the melted medium, attention must be paid to the material selected for the steel pipes.

Project Participants

Implementing Institution

Edelstahlwerke Schmees GmbH

Technology providers

promeos GmbH

More Project Informations

Project title:  Einsatz einer energieeffizienten Pfannenaufheizstation bei der Herstellung von Edelstahl

Project number:  20182

Project period:  2010 - 2011

Project region:  Germany (North Rhine-Westphalia)

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)