Yong Tang Jarmo Laine Timo Fabritus Jouko Härkki Different Methods Obtained by PHOENICS Simulation to Improve the Performance of Pusher- Type Steel Slab Reheating Furnace Yong Tang Jarmo Laine Timo Fabritus Jouko Härkki Oulu University Tel:+358 8 553 2423 Fax:+358 8 553 2339 http:// www.Oulu.fi

1. Objective: Study the gas flow and temperature distribution in the furnace Investigate the gas flow modification while a block wall is built in front of the lower burners in the heating zone

2.The Outline of the Furnace and Grids Used In the Calculation

3. Model Discription K- equation for turbulent flow model. Non-equilibrium wall function was applied Extended Simple Chemically-Reacting System (ESCRS) was selected to simulate the combustion and EBU model was used The reaction assumed: 2CH4+O2->CO 2CO+O2->2CO2 2H2+O2->2H2O Composite flux model for radiation simulation Boundary conditions: 1)The circle inlet is assumed as square 2) Slab surface temperatures were measured 3) Temperatures of inside wall ,roof and floor were determined from the monitor system 4) gas thermal property and enthalpy near the boundary wall was derived from the ground file, according to the temperature and fraction

4. PHOENICS Settings and Iteration Process Phoenics Version 3.1 of MS-DOS was used in this simulation. SATELLITE: The satellite module operates in the batch model and stop at the first STOP line. There are no other special requirements for SATELLITE. GROUND: The thermal boundary conditions are determined in the calculation and coded in the GROUND file. After the GROUND file is compiled and re-link, private executables (earexe.exe) is created. Type “ run77 earexe” to start private EARTH. Iteration: More than 2000 sweeps was iterated for coarse ,firs order scheme. About 4000sweeps was used for fine or higher order scheme (HQUICK). No significant difference was found between coarse mesh and fine mesh. Convergence was thought achieved when the values at the monitor point stopped changing, the sum residuals were reduced by several orders of magnitude ( from 104-6 to 101-3) and the sums of sources balance.

Monitor screen of the error residence

5. Results Flow Pattern and Gas Temperature Distribution Gas flow pattern in the furnace along longitudinal furnace, cross burners in the heating zone

The flow modification when a block wall is installed in the heating zone The illustration of block wall added in front of the lower burners in the heating zone

Without block wall With a block wall Gas velocity distribution near the burners in the heating zone

6.Verification Comparison of calculated gas temperature with measured results at different positions in the furnace

Comparison of modeled O2 distribution with measured values in the furnace

7. Conclusions Momentum, combustion and radiation models are combined together to predict gas flow pattern and temperature distribution in the pusher-type reheating furnace. A block wall installed in front of the lower burners can reduce the reverse flow under the slab in the heating zone. Industry measurements indicate that the predict values were reasonable.