Comparison between Gas and Oil Injection into the Blast Furnace: A Detailed Theoretical Study

Transcription

1 Comparison between Gas and Oil Injection into the Blast Furnace: A Detailed Theoretical Study D. Andahazy, S. Slaby, G. Löffler, F. Winter Ch. Feilmayr, T. Bürgler

2 Christian Doppler Laboratory for Chemical Engineering at High Temperatures funded by the Christian Doppler Forschungsgesellschaft in association with voestalpine Stahl GmbH and the Vienna University of Technology,

3 Objectives Substitution of oil injection with gas injection difference in combustion characteristics analysis of critical operating conditions by means of computational fluid dynamics (CFD) detailed description of the oil and/or gas flow in tuyére and raceway

4 Principles of Gas Injection

5 3D-Model of the Tuyére gas lances tuyére nozzle pipe

6 CFD Model Calculations are done by using the CFD code by FLUENT Inc., consisting of: the solver FLUENT compressible flow realizable k- model discrete phase model (for oil injection) the preprocessor GAMBIT 2.0 development of the geometry (lances, nozzle pipe, tuyére, raceway) mainly hexahedral and tetrahedral mesh the preprocessor prepdf 4.0 equilibrium chemistry model

7 Geometry of the CFD-Model lance raceway tuyére 0.5 m 1 m

8 Input Parameters (per tuyére) Coke oven gas Heavy oil Pressure [bar] Temperature [ C] Hot Blast Velocity [m/s] ~ 188 ~ 198 Volume Flow [Nm³/h] Mass Flow [kg/s] Pressure [bar] 3 12 Temperature [ C] Number of Lances [-] 1 / 2 1 Gas / Oil Velocity Volume Flow [m/s] [Nm³/h] 160 / Mass Flow [kg/s] Heating Power [MW] Droplet Diameter [m] *) *) Rosin Rammler Distribution

9 Gas and Oil Composition H 2 H 2 O Coke oven gas CH C 2 H [mole-%] CO 6.94 CO 2 N O Q n [MJ/kg] 0.09 Q n [MJ/Nm³] Heavy oil Water < 0.10 Ash 0.02 Sulphur [m-%] 2.01 Carbon Hydrogen Q n [MJ/kg] 40.04

10 Distribution of Temperature (Oil Injection, 1 Lance)

11 Distribution of Velocity (Oil Injection, 1 Lance)

12 Distribution of Temperature on an ISO-Surface of v = 50 m/s (Oil Injection, 1 Lance)

13 Drop Diameter and Trajectories (Oil Injection, 1 Lance)

14 Distribution of Temperature (Gas Injection, 1 Lance)

15 Distribution of Velocity (Gas Injection, 1 Lance)

16 Distribution of Temperature on an ISO-Surface of v = 50 m/s (Gas Injection, 1 Lance)

17 Distribution of Temperature (Gas Injection, 2 Lances)

18 Distribution of Velocity (Gas Injection, 2 Lances)

19 Distribution of Temperature on an ISO-Surface of v = 50 m/s (Gas Injection, 2 Lances)

20 Gas Concentrations after Combustion H 2 Coke oven gas Heavy oil 1 lance 2 lances H 2 O CH C 2 H CO CO 2 [mole-%] N O O H OH Temperature [ C] Velocity [m/s]

21 Conclusions Heavy oil combustion takes place at the beginning of the raceway almost homogeneous distribution of temperature and velocity gas leaving the raceway is almost uniformly distributed no overheating of the tuyére Coke oven gas 1 lance very inhomogeneous view of temperature and velocity the flow reaches to the end of the raceway with high velocity highest temperatures at the end of the raceway no overheating of the tuyére Coke oven gas 2 lances significantly decreased penetration depth more homogeneous distributions of temperature, velocity and gas concentration more uniform combustion similar to heavy oil injection no overheating of the tuyére

22 Acknowledgements The R&D work of the CD-Laboratory for Chemical Engineering at High Temperatures at the Vienna University of Technology has been funded by the Christian Doppler Forschungsgesellschaft, Austria The authors also acknowledge Dr. Michael Harasek,, Vienna University of Technology, for supporting the CFD calculations