<p>Steel
heating and melting processes consume the majority
of the energy used in advanced short-process steelmaking practices. Economic
and environmental pressures from energy consumption drive the research to
improve the furnace operation efficiency and energy efficiency. The goal of
this research is to utilize computational fluid dynamics (CFD) modeling to provide useful tools and recommendations on the steel heating and melting
practices in the steelmaking process. The steel slab reheating process, the
steel scrap preheating process and the steel scrap melting process are studied.</p>
<p> </p>
<p>A transient
three-dimensional (3-D) CFD model was developed to simulate the flow
characteristics, combustion process and multi-scale, multi-mode heat transfer
inside the reheating furnace. The actual geometry of an operating industrial
furnace was used and typical operating conditions were simulated. Specific
walking speeds of slabs in production were modeled using a dynamic mesh
model which is controlled by a user-defined
function (UDF) solved using ANSYS Fluent. Fuel
variations at different zones with respect to time were also considered. The
model was validated with instrumented slab trials conducted at the SSAB Mobile
(Alabama) mill. The temperature field in the furnace and the temperature
evolution of a slab predicted by the CFD model are in good agreement with those
obtained from the instrumented slab trials. Based on the simulation results,
the slab reheating process and the temperature uniformity of a slab at
discharge were able to be properly evaluated. In addition, a
comprehensive two-dimensional (2-D) numerical heat transfer model for slab
reheating in a walking beam furnace was developed using the finite difference
method. An in-house code was developed. The model is capable of predicting slab
temperature evolution during a reheating process based on real time furnace conditions
and steel physical properties. The model was validated by using mill
instrumented slab trials and production data. The results show that the
temperature evolution predicted by the model is in good agreement with that
measured by the thermocouples embedded in the instrumented slab. Compared with
3-D CFD simulation of a reheating process, this 2-D heat transfer model used
for predicting slab temperature evolution requires less computing power and can
provide results in a few seconds. A graphical user interface was also developed
to facilitate the input and output process. This is a very convenient and user-friendly
tool which can be used easily by mill metallurgists in troubleshooting and
process optimization.</p>
<p> </p>
<p>CFD models for steel scrap preheating
and melting processes by the combined
effects of the heat source from both oxy-fuel
combustion and electric arc were also developed. The oxy-fuel burners firing
natural gas (NG) are widely used in EAF operation during the scrap preheating
and melting stages. In order to understand the role of oxy-fuel combustion and
potentially increase the energy input from NG while decreasing the electricity
consumption, numerical simulation of scrap preheating by oxy-fuel combustion in
an EAF was firstly conducted. A 3-D CFD model was developed with detailed
consideration of gas flow, oxy-fuel combustion, heat transfer between gas and
solid scrap and scrap oxidation. The model was validated by a small-scale
experimental study and applied onto a real-scale EAF.</p>
<p> </p>
<p>Scrap
melting in bath is comprehensively
studied with a CFD model developed to simulate the melting in bath process
under given operating conditions. Two sub-models were developed for model integration:
steel melting model and coherent jet model. The multiphase volume of fluid (VOF)
model and the enthalpy-porosity technique are applied to describe the steel
melting process. The coherent jet model calculates the gas jet momentum and is integrated
into the flow model to calculate its effect on the fluid flow in the bath. The
electric arc was treated as a heat flux to represent the heat transfer from the
electric arc during the melting process. Model validations were conducted for
each sub-model to ensure their accuracy. Parametric studies were also carried
out to obtain useful information for real practice. </p><p>Overall, the CFD models developed in this research work have demonstrated value in improving energy efficiency in the energy-intensive steelmaking processes. The developed CFD models also provide insights for better understanding of the multi-physics processes.<br></p>
<p> </p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/7713572 |
| Date | 10 June 2019 |
| Creators | Guangwu Tang (5930321) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/Modeling_of_Steel_Heating_and_Melting_Processes_in_Industrial_Steelmaking_Furnaces/7713572 |
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