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Characterization of high-alumina refractory bricks and modelling of hot rotary kiln behaviour
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.ORCID iD: 0000-0002-2825-8543
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.ORCID iD: 0000-0003-3661-9262
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.ORCID iD: 0000-0002-3907-0802
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.ORCID iD: 0000-0003-0910-7990
2017 (English)In: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 79, p. 852-864Article in journal (Refereed) Published
Abstract [en]

Rotary kilns for iron-ore pellets production are highly dependent on a well-functioning refractory brick lining. To improve the long-term capability of the lining, in-situ observations of the bricks' performance are desired, however, the high process temperatures and the size of the kiln make it difficult to study the lining during operation. By using numerical simulations as a tool, some of the problems encountered by the brick lining can be studied. Knowing material properties of the refractory bricks as input in a numerical model is therefore necessary. However, material properties are poorly documented for this type of materials, especially, at elevated temperatures. In this work three commercial aluminasilicate bricks were tested in compression until failure for a temperature range of 25–1300 °C. The purpose was to evaluate compression strength and Young's modulus in compression of the fully burned bricks at a wide range of temperatures. The data was later used for modelling of a hot rotary kiln lined with bricks by using the finite element method, whereupon load state of the lining was evaluated at steady state after the expansion of the system. The objective of the numerical modelling was to investigate trustworthiness of the model and to give insight into the stress levels that can potentially arise. It was found that for all of the investigated brick types the compression strength increased with increased temperature, having a peak in the vicinity of 1000 °C. The maximum increase was between 50 and 150 % for the different brick types. After passing 1100 °C the compression strength rapidly and considerably decreased below its as-received compression strength. Young's modulus was measured to vary between 2 and 10 GPa in the range of up to 1000 °C. The numerical results indicate that severe boundary conditions (expansion of the lining is highly restricted) can potentially lead to compression stress of up to 34 MPa in the brick lining at steady state. However, at these boundary conditions the present tensile stress was only 0.5 MPa, while tensile stresses of close to 3 MPa could be observed in the lining with mild boundary conditions. The authors conclude that the created model is trustworthy and that it has high potential for being used as a tool in further investigations of the lining in hot state.

Place, publisher, year, edition, pages
Elsevier, 2017. Vol. 79, p. 852-864
National Category
Applied Mechanics Other Materials Engineering
Research subject
Solid Mechanics; Engineering Materials
Identifiers
URN: urn:nbn:se:ltu:diva-63536DOI: 10.1016/j.engfailanal.2017.04.038ISI: 000405538800068Scopus ID: 2-s2.0-85020181003OAI: oai:DiVA.org:ltu-63536DiVA, id: diva2:1098752
Note

Validerad;2017;Nivå 2;2017-06-14 (rokbeg)

Available from: 2017-05-26 Created: 2017-05-26 Last updated: 2018-04-16Bibliographically approved
In thesis
1. An Approach for Evaluation of Brick Lining's Mechanical State in Rotary Kilns
Open this publication in new window or tab >>An Approach for Evaluation of Brick Lining's Mechanical State in Rotary Kilns
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Utvärdering av tegelinfodringensmekaniska tillstånd i roterugnar
Abstract [en]

Production of many materials requires treatment at elevated temperatures. Calcination and sintering are some of the important heat treatment procedures which are typically performed in so-called rotary kilns. These, not very well-known treatment vessels, have a significant impact on our everyday life. Our most common materials have direct con-nection to the use of rotary kilns. Concrete−covering the vast 80 wt% of total material production in the world−consists to a large part of cement produced in a rotary kiln. Steel−by far the most produced metal−frequently starts its journey in a rotary kiln in form of iron-ore pellets. Paper−another everyday life product−is dependent on mineral lime that is typically calcinated in a rotary kiln. The importance of rotary kilns in our society cannot be doubted.

The concept of a rotary kiln is rather simple. It consists of a thick cylinder-formed steel casing that, due to high process temperatures, is insulated by a refractory lining. Service conditions inside the rotary kiln are rough and the refractory lining is continuously degrading, especially pronounced in the hot zone of the rotary kiln. If the lining is significantly deteriorated and can no longer protect the casing from the heat−the production is shut-down−leading to very high production losses.

Despite many improvements of rotary kilns in the past decades, there is still a gap in the knowledge regarding refractory linings during usage. Many assumptions are based on practical knowledge. One explanation to this could be the difficulty to study and observe the lining due to the large sizes of rotary kilns and high operating temperatures. Today, computers are of a great help for studying various issues without causing production delays or risking failures. However, the field of rotary kilns has stagnated on this matter and little documentation can be found regarding numerical simulations of the refractory lining for rotary kilns, especially of the thermomechanical character.

The aim of this thesis work was to create a numerical model of a rotary kiln usedin iron-ore pelletizing for studying the mechanical and thermomechanical behaviour of refractory brick lining. For this, a simplified finite element model (FEM) of a rotary kiln was created and its trustworthiness verified. It was confirmed that the model gives agood response. Different tips and justifications in the creation of the model of the rotary kiln are given. Furthermore, some mechanical material tests were performed for data input into the model. Various fundamental cases were studied in cold and hot states of the rotary kiln. It was shown that critical situations affecting the brick lining could be captured in a satisfactory way. The insight into the behaviour of the brick lining with respect to various parameters opens possibilities for lowering risk of brick lining failure by an improved management of the rotary kiln.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2018
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Mechanical Engineering Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-68376 (URN)978-91-7790-112-9 (ISBN)978-91-7790-113-6 (ISBN)
Public defence
2018-06-13, E632, Luleå, 09:00 (English)
Opponent
Supervisors
Available from: 2018-04-17 Created: 2018-04-16 Last updated: 2018-05-25Bibliographically approved

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Ramanenka, DmitrijAntti, Marta-LenaGustafsson, GustafJonsén, Pär

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