CFD MODELLING OF TOP SUBMERGED LANCE GAS INJECTION

Transcription

1 CFD MODELLING OF TOP SUBMERGED LANCE GAS INJECTION Nazmul Huda PhD Student Faculty of Engineering and Industrial Science Swinburne University of Technology Melbourne, Australia

2 Supervised by Dr. Jamal Naser, Professor Geoffrey Brooks Faculty of Engineering and Industrial Science Swinburne University of Technology Hawthorn, VIC 3122, Melbourne, Australia Professor Markus Reuter, Robert Matusewicz Ausmelt Limited, 12 Kitchen Road, Dandenong, VIC 3175, Melbourne, Australia

3 Content Outline 1. Introduction 2. Overview of TSL 3. Research objective 4. Different stages 5. Cold model investigation 6. CFD model and Calculation 7. Results and Post processing 8. Conclusion

4 Introduction Gas injection methods are frequently used in modern pyrometallurgy It provides intense mixing and better turbulence inside the bath Among the different methods, Top Submerged Lance (TSL) technology is the unique Australian invention

5 Overview of TSL Long cylindrical furnace Through the vertical Lance oxygen enriched air and fuel is injected into the molten bath Lance tip is coated with slag layer Swirling effect in the annulus of the lance provides cooling

6 Research objective To predict lance tip combustion and bath interaction conditions in order to achieve the maximum combustion efficiency and control over the desired operating conditions.

7 Different stages Reviewing the existing models Develop Computational Fluid Dynamics (CFD) model for cold flow and validate with existing experimental data Develop a new CFD model by incorporating nonisothermal condition and chemical reactions Validate the model by hot combustion testing

8 Cold Model investigation As the first step of the research work a cold flow CFD model was developed. The model was validated against experimental study of Morsi generated for Ausmelt in the past.

9 CAD model A one-sixteenth scale CAD model of a 150 ton capacity furnace with vertical annulus lance was developed in Rhino. The dimensions are: Cylinder diameter = 230 mm Cylinder height = 560 mm Lance outer diameter = 17 mm Lance inner diameter = 12.2 mm Air outlet diameter = 60 mm Water level = 150 mm

10 Generated Grid

11 Computational methodology Unsteady state multiphase incompressible flow solution for momentum and continuity equation Standard k-ε turbulence model for the turbulence modelling Discretised equations were solved using SIMPLE algorithm Boundary conditions used were Static pressure for outlet and Velocity for inlet Swirl flow was injected through the annulus of the lance at 57.5 degree relative to radial direction

12 Velocity vectors at Lance Tip

13 Calculation The CFD model is based on finite volume method in Eulerian approach Unsteady state multiphase solution with time step t = 0.01 and total time T = 180 seconds Calculation done in MPI mode by using Swinburne Green Machine (Super computer) with 8 Intel Quad Core CPU each 2.3 GHZ speed

14 Results and Post processing Volume fraction for Phase 2 (water) after 180 seconds

15 Validation with Experimental Results

16 Tangential velocity (V) distribution in radial direction at Z= 45 mm from bottom for 2/3 lance submergence

17 Effect of Submergence Level on Splashing This result is also consistent with the experimental study of Igwe et al. (Met. Trans B,1973), and Koh and Taylor (Chemeca, 1990)

18 Mean Convective Mixing A term that is used in HVAC is used here to express Mixing in the bath May be defined as, Volume flow rate through a computational Volume of the cell cell It expresses the volume exchange rate through a cell which in turn represents Convective Mixing

19 Mean Convective Mixing at 10mm below the lance exit along radial direction

20 Mean Convective mixing (Contd..)

21 Velocity vectors for Liquid phase Q = 2.67X10 H L = m 3 / s, Consistent with Morsi (Canadian Metallurgical Quarterly, 2000)

22 Video for 2/3 submergence level

23 Video for 1/6 submergence level

24 Conclusion The model revealed the bath mixing characteristics for air injected into water swirled gas injection plays an important roll in improving the mixing process Level of lance submergence have an important effect on splash generation Recirculation zones observed in this study were very weak

25 Have a Great Day