Analysis of droplet breakup at liquid blast furnace injections
C. Jordan, C. Maier, Z. Hersfalvi, B. Kiss, J. Nagy, M. Harasek
Vienna University of Technology, Institute of Chemical Engineering, Getreidemarkt 9/166,
A-1060 Vienna; tel.: +43-1-58801-15924, fax.: +43-1-58801-15999, e-mail:
christian.jordan@tuwien.ac.at
The injection of liquid hydrocarbons like heavy fuel oil and crude tar from coke
production is a common way to reduce the coke consumption in an iron blast furnace. This is
practiced e. g. at Blast Furnace A of voestalpine Stahl GmbH (Linz, Austria).
In this work, a more in depth-study of the droplet breakup within the raceway is carried
out. Especially the effects of changes in surface tension and viscosity of the fluid were
evaluated using a lab scale cold model of the raceway section of the blast furnace. Applying
high speed imaging and image processing the droplet size at varying operating conditions
have been studied. The results have been used to set up a correlation for the prediction of the
resulting droplet sizes within the industrial plant.
Furthermore the capabilities of computational fluid dynamics to model this type of flow
have been tested: The open source CFD package OpenFOAM has been used to simulate the
jet breakup in the shear flow. Time resolved numerical processing has been done at VSC2
(Vienna Scientific Cluster 2). Acceptable agreement of the liquid phase distribution with the
experimental results has been found.
Finally the droplet breakup mechanisms have been analysed: literature covers many
cases of single droplet breakup taking place in homogeneous outer shear flow – however, at
the injection lance tip there is a large velocity gradient introducing additional asymmetric
shear on the fluid surface, which makes shear induced entrainment as major breakup effect.
The resulting dimensionless model can be used to determine the droplet sizes of injected
liquids and thus the evaporation and combustion characteristics within the blast furnace
raceway. This way optimum operating conditions can be set when changing the injected
fluids.
We want to thank our partners in the FFG/K1Met framework for their support: C.
Feilmayr and C. Thaler (voestalpine Stahl GmbH, Linz, Austria), S. Puttinger and S. Pirker
(CD-Labor for Particulate Flows, JKU Linz, Austria)