Influence of Obstruction at Gas-Injection Nozzles (Number and Position) in RH Degasser Process

Abstract

One of the main problems that affects Ruhrstahl-Heraeus (RH) degasser circulation rate is the obstruction of the gas-injection nozzles. This study aims to elucidate the effects of obstructions in quantity and location using a physical model that depicts 16 injection nozzles on the up-leg distributed symmetrically in 2 rings (8 nozzles/ring). We simulated six, symmetric and nonsymmetric, obstruction conditions to gas flow. The gas-flow rate was varied from 30 to 130 NL/min. The results for symmetric obstructions when the gas-flow rate is kept constant, indicates that the circulation rate in the equipment does not significantly change. However, when these obstructions are non-symmetric, the circulation rate varies drastically, even when the gas-flow rate is kept constant. The analysis of the experimental data generated from this study allowed to determine an equation for the circulation rate that takes into consideration the number and distribution of blocked nozzles.

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Abbreviations

RH:

Ruhrstahl-Heraeus Degasser

\( \beta \) :

scale factor between model and industrial equipment

\( Q_{\text{m}} \) :

cold model flow rate

\( Q_{\text{e}} \) :

industrial equipment flow rate

\( F_{ \exp } \) :

expansion gas coefficient

A :

area under first peak of the curve (Figure 2)

∆C:

increment in tracer concentration after stabilization (Figure 2)

\( Q \) :

circulation flow rate

\( G \) :

injected gas-flow rate

\( a\, b\, e m \) :

constants to the Eq. [3]

\( \psi \) :

deviation function between the centroid of the polygon formed by the unclogged nozzles and the center of the up-leg

\( \tau \) :

Fraction of Nozzles Obstructed

\( K \) :

adjust function

\( \lambda \) :

exponential factor of \( \psi \)

\( n \) :

exponential factor of \( \tau \)

\( r \) :

up-leg radius

\( \overline{AC} \) :

distance from the centroid of the polygon (\( C(c_{x} ,c_{y} ) \)) formed by the connection of the injection nozzles in operation in the equipment to the center of the circle (\( A(r_{x} = r, r_{y} = r) \)) of the up-leg

\( A^{\prime\prime} \) :

area of the formed polygon

\( c_{x} \) e \( c_{y} \) :

coordinates of the C point of the centroid of the formed polygon

\( n_{p} \) :

number of sides of the polygon

\( \theta\,{\text{and}}\,\kappa \) :

Michaelis-Menten constants (Eq. [11])

\( N \) :

number of nozzle (Eq. [11])

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Correspondence to Alexandre Bôscaro França.

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Manuscript submitted June 2, 2018.

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Trindade, L.C., Peixoto, J.J.M., da Silva, C.A. et al. Influence of Obstruction at Gas-Injection Nozzles (Number and Position) in RH Degasser Process. Metall Mater Trans B 50, 578–584 (2019). https://doi.org/10.1007/s11663-018-1474-6

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