.

Fig. 6: Improved heating of the material used by increasing the burner impulse
© BFI

Fig. 5: New measurement system for furnace atmospheres
© BFI

Fig. 4: ROREBS on a reheating furnace
© BFI

Fig. 3: Flat-flame burner with thermal regenerator
© BFI
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New processes and instruments

For years, the German Institute for Applied Research and Development (Betriebsforschungsinstitut, BFI) in Düsseldorf has been dedicated to researching and developing efficient processes, instruments and concepts for the metal and metalworking industry and its heating processes. Descriptions of six promising developments are outlined below.

Burner and heating systems for multivalent use

A new flat flame burner has been developed for heating high-grade materials used which is also suited for the highest preheating of combustion air. The current operational test runs (Fig. 3) confirm that the pressure loss is very low, below 30 mbar, at a combustion air preheating temperature of 1,000 °C. The simple construction with combustion air flowing in tangentially allows for cost-effective production and little wear and tear. The Permanent Impulse (PI) process improves productivity by means of injecting combustion gases. The convective heat transfer on the surface of the material used is increased considerably due to the high burner impulse and high flow rate. This shortens the heating duration of the material used, allowing for the furnace to be loaded at shorter intervals. The PI process is currently being tested at an annealing furnace for ring heating.

Heat recovery with thermal regenerators

As for heat recovery in high-temperature industrial furnaces, several new processes have been developed and put to operational use. The new systems have a very low pressure loss and are non-sensitive to accumulation of dirt.The rotating regenerator burner system (DREBS) was developed to achieve continuous pre-heating of the combustion air. A rotating regenerator is based on a rotating thermal mass, around which hot exhaust gas is flowing on the one side and cold combustion air in counter flow on the other side (see BINE-Projektinfo brochure 3/2004). The use of this technology at a rolling mill furnace led to energy savings of 30-40% compared to the original recuperator operation. At several heating stands for heating steel works ladles, the saving was about 40%. The temperature evenness has also improved.The latest new development is a compact pipe regenerator burner system (ROREBS) (Fig. 4). The freely adjustable cycle times between 10 seconds and 1 minute of the individual ROREBS make it possible to define the time and place of heating. This helped reduce the fuel requirement of a forge by approx. 30% compared to the original recuperator operation.

Atmosphere control guarantees product quality

In galvanising plants, reheating furnaces are generally operated with a large combustion gas surplus in order to avoid surface oxidation. This leads to unnecessarily high energy costs and CO2 emissions. Finding solutions to this problem is the goal of a joint project. The modules included in this project are: an innovative furnace operation concept with new burn-off measurement system, new substoichiometric burner and more cost-effective conveyor rollers. At present, the development has reached the following state:

  • The burn-off measurement system for determining the substoichiometric partial burn-off has been modified and tested successfully in operation with a target measurement accuracy of more than 99% (Fig. 5).
  • On the basis of operational data and measurements, the energy and material flow balances for the preheating furnace of a galvanising plant could be determined with a balance error smaller than 0.3%.

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