Metallurgische Untersuchungen zur Ermittlung alternativer Wege zur Herstellung eines Vorsinterproduktes für Weichferrite

Translated title of the contribution: Metallurgical investigations for determination of alternative routes for the production of pre-sinter products for soft ferrites

Hermann Wolfmeir

Research output: ThesisDoctoral Thesis

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Abstract

voestalpine Stahl GmbH produces 15000 tons of ferric oxide per annum as powdery by-product in the regeneration process of spent pickling liquor of the cold rolling mill. Due to its cleanness it is the basis for the production MnZn-ferrites. As soft magnetic materials they are found in various high frequency applications of the electro- and electronic industry. The production chain of MnZn-ferrites requires a homogenisation of the used raw materials after mixing and agglomeration by means of a thermal treatment in a pre-sintering (calcination) process. The spinel structure as carrier of the ferrimagnetic properties is formed there initially, which decomposes mainly during cooling down. State of the art is the pre-sintering in indirectly heated rotary kilns at 950 to 1100 °C with a retention time of about 60 minutes, the specific energy demand is about 0,8 kWh/kg. Within the scope of this work initially a product development of high quality MnZn-ferrites was carried out, using the rotary kiln as pre-sintering unit. With the gained process know-how the entire process chain was passed through again by using alternative pre-sintering processes. Applied processes were the pulsed combustion reactor and the indirectly heated vertical furnace (both with retention times of seconds) and the fluidised bed reactor with a retention time of some minutes respectively. Reduced treatment time may enable advantages in terms of throughput, furthermore advantages in energy consumption may be expected. Investigation of reaction kinetics of MnZn ferrites and thermotechnical calculations enabled the definition of preconditions for the application of short-time calcination processes. A reduction of retention time to the range of seconds requires a temperature increase to levels of >1200 °C. The pre-sintering products of the applied processes were processed to final components and characterised with regard to their magnetic properties. Pre-sinter products of the vertical furnace and the fluidised bed reactor lead to marketable ferrite products. The pulsed combustion reactor leads to inhomogeneous presinter products and not marketable final products. With regard to the energy demand the vertical furnace and particularly the fluidised bed reactor show advantages compared to the rotary kiln. For a continuous operated fluidised bed process in industrial scale an energy demand of 0,25 kWh/kg may be expected. The vertical furnace recommends itself for high volume throughputs and shows advantages due to its simple construction.
Translated title of the contributionMetallurgical investigations for determination of alternative routes for the production of pre-sinter products for soft ferrites
Original languageGerman
QualificationDr.mont.
Supervisors/Advisors
  • Kepplinger, Werner Leopold, Assessor B (internal)
  • Krieger, Wilfried, Assessor A (internal)
Publication statusPublished - 2008

Bibliographical note

embargoed until null

Keywords

  • manganese-zinc ferrites
  • ferric oxide
  • sinter process
  • manganese-zinc ferrites ferric oxide sinter process calcination rotary kiln fluidized bed process pulsed combustion reactor vertical furnace
  • calcination
  • rotary kiln
  • fluidized bed process
  • pulsed combustion reactor
  • vertical furnace

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