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Use of Physical Modelling to Study How to Increase the Production Capacity by Implementing a Novel Oblong AOD Converter
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.ORCID iD: 0000-0003-1919-9964
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2017 (English)In: Ironmaking and Steelmaking: Processes, Products and ApplicationsArticle in journal (Refereed) Accepted
Abstract [en]

There is no known example of an AOD converter with oblong cross sections in the literature. Changing the geometry of the converter vessel, from the traditional circular cross sections, to increase converter volume could potentially influence the performance of the converter and in particular the decarburisation rate. Due to physical limitations in an existing melt shop the only available way to increase the tapped weight and hence the productivity was to consider a modified converter cross section, namely an oblong cross section. A change in cross section could potentially influence the decarburisation performance and in the worst case counteract the intended increase in productivity. In order to study the feasibility of implementing an oblong converter, physical modelling was used to establish whether it would be suitable to change the AOD geometry from a circular cross section to a novel oblong cross section to increase the converter volume and thus the productivity. Specifically, the aim was to use physical modelling to study the fluid flow of the proposed converter configuration (geometry and number of tuyeres) and the potential influence on the decarburisation rate. Two water models linearly scaled down to a 1:4.6 dimension in comparison to a production converter were employed using water containing 𝑁𝑎𝑂𝐻 and gas injected through six or eight tuyeres as fluids. In the model one tuyere was used for injection of 𝐶𝑂2 gas, while air was injected through the remaining five or seven tuyeres. The reaction of 𝐶𝑂2 and 𝑁𝑎𝑂𝐻 (𝐶𝑂2 + 2𝑁𝑎𝑂𝐻 ⇄ 𝑁𝑎&𝐶𝑂3 + 𝐻2𝑂) was indirectly measured by detecting the pH value of the water in the model. The purpose of the model was to simulate the decarburisation part of the converter process as any prolongation of the decarburisation will defeat the purpose of increasing the productivity. The mixing time is considered to be a good indicator of the decarburisation as the kinetics will be diffusion controlled in the latter parts of the process. According to our experience, the thermodynamics of decarburisation will not be dependent on the converter shape. The following three converter figurations were studied: i) a circular converter with six tuyeres, ii) an oblong converter with six tuyeres, and iii) an oblong converter with eight tuyeres. The mixing time, defined as the time to reach 95% of the final 𝐶𝑂2 concentration, can be used to evaluate the different converter configurations. The average 𝐶𝑂2 concentrations based on several experiments, calculated based on pH measurements in the water, differed by less than 5% between the circular and oblong models after 165 s of injection of air and 𝐶𝑂2. The results also showed that no difference in mixing time could be found when using 6 and 8 tuyeres, respectively in the oblong model. In fact, the 𝐶𝑂2 concentrations in the oblong model differed by less than 2% after 165 s of injection of air and 𝐶𝑂2 between six and eight tuyeres. Based on the findings, it has been observed that the influence of converter geometry on mixing time is small, it was concluded that decarburisation rate is likely to be the same irrespectively of converter geometry. Thus it is possible to construct an oblong converter to increase the productivity.

Place, publisher, year, edition, pages
2017.
Keywords [en]
Physical modelling, AOD, Converter geometry, Injection, Mixing times
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-199661OAI: oai:DiVA.org:kth-199661DiVA, id: diva2:1064735
Note

QC 20170113

Available from: 2017-01-12 Created: 2017-01-12 Last updated: 2017-01-16Bibliographically approved
In thesis
1. Management of technology in the process industries:  Matching market and machine
Open this publication in new window or tab >>Management of technology in the process industries:  Matching market and machine
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The process industries span multiple industrial sectors and constitute a substantial part of the entire manufacturing industry. Since companies belonging to this family of industries are often very asset intensive, their ability to respond to changes is often limited in the short term.

The adaptation of the capabilities of existing processes, and conversely finding products and market segments to match the production system capabilities, are an important part of product- and market development activities in the process industry. The importance to companies in the process industry of having a well-articulated manufacturing strategy congruent with the business strategy is second to none. However, to facilitate manufacturing strategy developments, it is essential to start with an improved characterization and understanding of the material transformation system.

To that end an extensive set of variables was developed and related measures and scales were defined. The resulting configuration model, focusing on company generic process capabilities in the process industries, is to be regarded as a conceptual taxonomy and as a proposition available for further testing. The usability of the model was subsequently assessed using “mini-cases” in the forestry industry, where the respondents confirmed that the company’s overall strategy could benefit from this kind of platform as a possible avenue to follow.

The model was deployed as an instrument in the profiling of company material transformation systems to facilitate the further development of companies' functional and business strategies. The use of company-generic production capabilities was studied in three case companies representing the mineral, food and steel industries. The model was found by the respondents to be usable as a knowledge platform to develop production strategies. In the final analysis of the research results, a new concept emerged called “production capability configuration":

A process-industrial company’s alignment of its generic production capabilities in the areas of raw materials, process technology and products to improve the consistency among the variable elements that define operations and improve the congruence between operations and its environment.

From the perspective of value creation and capture, firms must be able to manufacture products in a competitive cost structure within the framework of a proper business model. By using the configuration model, the relationship between manufacturing and innovation activities has been studied in the previously mentioned three case studies.

In many cases the gap in capability appears as a limitation in the production system, requiring development efforts and sometimes investments to overcome. This is illustrated with two examples from the steel industry, where development efforts of the production system capabilities are initiated to better match the market demands. One example is the increase the volume- and product flexibility of an existing stainless steel melt shop, resulting in a proposed oblong Argon Oxygen Decarburisation (AOD) converter configuration that was subsequently verified using water modelling. The second example is from a carbon steel mill, where the target was to increase the raw material- and volume flexibility of another melt shop, by modifying the capabilities of the Electric Arc Furnace (EAF). Enabling EAF technologies are further described and evaluated using operational data and engineering type of estimates. 

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2017. p. 59
Keywords
process industries, manufacturing, innovation, configuration, strategizing, capability, configuration modelling, process industries, production system, physical modelling, AOD, converter geometry, injection, mixing times, electric arc furnace, EAF, post-combustion, high-impedance, network disturbances, operational results
National Category
Other Engineering and Technologies not elsewhere specified
Research subject
Metallurgical process science
Identifiers
urn:nbn:se:kth:diva-199705 (URN)978-91-7729-256-2 (ISBN)
Public defence
2017-02-02, KTH - room B2, Brinellvägen 23, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20170116

Available from: 2017-01-16 Created: 2017-01-14 Last updated: 2017-01-16Bibliographically approved

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