Structural Modeling and Meshing of Blast Furnace Using HyperMesh. And Tcl/Tk.

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1 Structural Modeling and Meshing of Blast Furnace Using HyperMesh Debiprasad Ghosh Sr. Manager, Tech cell Bhaskar Sengupta Head, Tech cell And Tcl/Tk. Abbreviations: FEA- Finite element analysis. Keywords: Blast furnace, TCL/Tk, CDB format, Ansys Abstract Shyam Kr. Maitra Consultant, Tech cell Sujan Hazra Sr. Engineer, Tech cell The generation of geometry and meshing is done automatically using HyperMesh with the help of Tcl/Tk scripting language, with a means to conduct iterative analysis of a blast furnace (an industrial structure) using finite element method. Material properties, boundary conditions, loading and other input parameters are also given automatically to the script for iterative solution requirements. Mesh-refinement is generally required at the critical locations for more accurate results. The proposed script in this study will be useful to analyze any dimensions of blast furnace, material properties, loading and at different orders of discretization. These results are taken by a designer to design a safe and economical blast furnace for an industry. Introduction More than 85% of the world steel production is through the blast furnace route. Blast furnaces continue to be the prime choice on account of versatility of operation, large production volume and lower cost of production. However, Blast Furnaces are not only capital intensive, they also require significant time for design & erection of the various components comprising the Blast furnace shell, its refractory cooling arrangements, charging equipment, gas cleaning plant, cast house equipment, blast furnace hearth refractory etc. This paper discusses an approach where the Blast Furnace is designed on the basis of a set of empirical rules applied to a handful of parameters. As a first attempt, some components of the Blast Furnace have been ignored - cooling arrangement, up-comers, charging equipment & blast equipment. Because of the huge financial impact, all efforts are made to design a reliable & economical Blast Furnace, one that will have a long campaign life and achieve a throughput in excess of 8500 t/day. In the present paper we are using Ansys for finite element analysis (FEA) and HyperMesh for FEA meshing of blast furnace [Figure 1]. The function of a blast furnace is to chemically reduce and physically convert iron oxides into liquid iron called "hot metal". The blast furnace is a huge, steel stack lined with refractory brick, where iron ore, coke and limestone are dumped into the top, and preheated air is blown into the bottom [1, 2, 3]. The raw materials require 16 to 18 hours to descend to the bottom of the furnace where they become the final product - liquid slag and liquid iron. These liquid products are drained from the furnace at regular intervals. The hot air that is blown into the bottom of the furnace ascends to the top in 6 to 8 seconds after reacting with the raw materials. Once a blast furnace is started it will continuously run for four to ten years with only short stops to perform planned maintenance. Simulation Driven Innovation 1

2 Process Methodology Geometric modelling of blast furnace is created in HyperMesh with required material properties, boundary conditions and loading. Finite element meshing is obtained from HyperMesh, which is then exported to a text file of Ansys CDB format. Finally, Ansys-mechanical solver performs the finite element solution and provides result in.rst format, which is imported from HyperView for iterative modification. These repetitive modelling, meshing and solution are performed using HyperMesh TCL/Tk programming integrating with HyperMesh GUI. Figure 1: Overview of program flow This program requires a handful of input parameters (Blast Furnace Effective Volume: 4000 M 3 ), and on the basis of a few empirical rules [Ref 1], the program generates the list of tentative Blast Furnace dimensions (Total Height, Belly Diameter, Hearth Diameter, Tuyere Height, Hearth Height, Blast Furnace top diameter etc ). Based on experience these dimensions can be edited from HyperMesh UI Tab, and then TCL/Tk program will generate a.cdb file, wherein the geometrical dimensions as well as the mechanical & thermal loads and the boundary conditions are created in an input file. The iterative steps are outlined in the schematic, where we check for the maximum seismic and pressure deflections & thermal stresses, and make changes to the dimensions (Tuyere height 4600 mm), and the loading conditions (the location of the Simulation Driven Innovation 2

3 cooling staves and the cooling water flow rates), then generate a new input simulation. file for the next Ansys Total modeling is performed in six stages - solid modeling; meshing; application of boundary condition; export to CDB format; solution; and Import from HyperView. Solid Modeling: Solid modeling of blast furnace is constructed using a set of solid cones extracted from other set of solid cones. Different parts of an iron making blast furnace are Hearth, Boss, Belly, Stack, and Throat. The lower part of blast furnace, the hearth, consists of a packed bed of coke particles through which liquid hot metal flows during tapping. In the present model only Firebricks are modeled and internal hot metal/cokes/ore are considered as load. Outer steel shell of the blast furnace is not solid modeled, which is face extracted from 3D brick elements to get nodal coincidence between brick and shell elements. For simplicity with mapped meshing, tapholes, tuyeres and staves are not considered in the model. Figure 2: Interactive modeling of blast furnace using Tcl/Tk Meshing: Solid modeling of blast furnace provided 3D geometry of the blast furnace. To get response of blast furnace under structural and thermal loading, using finite element analysis, required meshing of this solid model. Mapped meshing is used to get good quality hexagonal brick mesh. Once 3D elements are created, 2D shell elements for outer steel shell of blast furnace are face lifted from 3D elements. Such technique will generate shell elements even for internal, top and bottom surfaces as well, which are deleted afterward. This deletion of extra shell elements is done using following steps Simulation Driven Innovation 3

4 1. Get nearest node from a particular point 2. Get the elements connected on face 3. Delete the elements. Now material and real constant properties are provided for both brick and shell elements. Figure 3: meshing of blast furnace using Tcl/Tk Application of Boundary Condition: Application of both thermal and structural boundary condition can be applied either on solid modeling, or on the generated mesh. In the present paper, boundary conditions are applied in the mesh. Nodes at the bottom of blast furnace are considered as structurally fixed. The seismic load is taken as 25% of the self weight in the horizontal direction, where the self weight includes the weight of the structure as well as the weight of the internal burden in the furnace. The second important loading condition is due to the internal pressure, typically 2 atmospheres in the modern furnaces. Similarly, different temperature boundary conditions are applied at bottom, internal, and external wall of the furnace. These give rise to thermal stresses because of the unequal expansion of the refractory lining and the steel shell. Modern Blast Furnaces have extensive cooling arrangements, and the operational heat loads can fluctuate by an order of magnitude over their nominal values (40 mj/m 2 /Hr). These give rise to severe temperature fluctuations with their attendant thermal stresses, and these also have been ignored in the model, to arrive at a preliminary design. Export to CDB Format: Once Model is ready with nodes, elements, materials, boundary conditions, Ansys profiles, and Ansys solution commands, these can be exported in Ansys CDB format. Simulation Driven Innovation 4

5 Solution: Solution is fired from TCL script using exec AnsysRun.bat command within a try block, where AnsysRun.bat file contains Ansys batch solver command for finite element solution. Ansys solver which writes results in Ansys.rst /.rth file. Import from HyperView: To view and take design decision, generated Ansys.rst or.rth file is opened from HyperView. Results & Discussions Figure 4 shows the stress contour of the blast furnace shell for structural and thermal loading. Figure 4: Stress contour from HyperView Benefits Summary Manual repetitive modeling of blast furnace is time consuming as well as prone to manual error. Present technique reduces the requirement of man power and gives opportunity to concentrate on the other important design issues of blast furnace (design parameters, several alternative cooling stave configurations) easily, which should be examined before a satisfactory arrangement can be finalized. Challenges First challenge we have faced in our project is regarding interoperability between HyperMesh/HyperView and Ansys, where Altair India and USA technical team had helped to overcome the difficulty. Another challenge is regarding the TCL/Tk language; as not being an object oriented family. Programmers with big projects are mostly available for object oriented (Java, C++, C#), or more recently multi-paradigm, functional languages (Python, F#). Even after development, big projects using other family of languages are difficult to maintain, extend and test. Anyway, extensive uses of namespaces are applied to overcome this challenge. Although ScriptView is not yet mature, it also helped a lot. Simulation Driven Innovation 5

6 Future Plans SolidThinking can be used for solid modeling of blast furnace with tuyeres, and staves. Moreover, these design technique can be extended using solver and optimization features of Altair software like OptiStruct, RADIOSS etc Conclusions A computational framework is created to model blast furnace in HyperMesh, Analyze in Ansys APDL and viewing results in HyperView using TCL/Tk programming. Automatic modeling technique had given opportunity to concentrate on important design related issues. ACKNOWLEDGEMENTS The authors would like to thank Subir Roy, Anand Ronad, Dev Anand, Shashi Kumar, Sujatha K G, Jyotsna Naveen, Rajas Majumdar, Nitin Chirdeep, Ramesha B S, Shashi Mantrawadi, Vishwanath Rao; Anshuman Panda, Kiran Chakravarthy of Altair Engineering for their kind help during the development of project and submission of paper in the HTC2012. REFERENCES [1] Eu. F. Wegmann, "A Reference Book for Blast Furnace Operator," Translated from the Russian by V. Afanasyev, Mir publishers Moscow. [2] M. Geerdes, H. Toxopeus, C. van der Vliet, Modern Blast Furnace Ironmaking, Verlog Stahleisen GmbH. [3] Anil K. Biswas, Principle of Blast Furnace Ironmaking, Cootha publishing house. Simulation Driven Innovation 6