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  • 1.
    Emami, Nazanin
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Ramanenka, Dmitrij
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Enqvist, Evelina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Mechanical and thermal characterisation of novel UHMWPE-nano composite: A copmarrative study against virgin UHMWPE2012Conference paper (Refereed)
  • 2.
    Enqvist, Evelina
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Ramanenka, Dmitrij
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Marques, Paula A.A.P.
    TEMA—NRD, Mechanical Engineering Department, Aveiro Institute of Nanotechnology (AIN), University of Aveiro, 3810-193 Aveiro, Portugal.
    Grácio, José
    TEMA—NRD, Mechanical Engineering Department, Aveiro Institute of Nanotechnology (AIN), University of Aveiro, 3810-193 Aveiro, Portugal.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    The effect of ball milling time and rotational speed on ultra high molecular weight polyethylene reinforced with multiwalled carbon nanotubes2016In: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569, Vol. 37, no 4, p. 1128-1136Article in journal (Refereed)
    Abstract [en]

    Ultra high molecular weight polyethylene (UHMWPE) composites reinforced with multiwalled carbon nanotubes (MWCNT) were produced using planetary ball milling. The aim was to develop a more wear resistant composite with increased mechanical properties to be used in stress bearing joints. The manufacturing technique, using ball-milling to incorporate MWCNT into UHMWPE matrix was investigated. The effect of manufacturing parameters such as effect of ball milling time and rotational speed on final composite was analyzed by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), particle size distribution and contact angle measurements. Ball milling as mixing technique for UHMWPE based composites is not a new approach but yet, the effect of time, rotational speed, loading of milling jar and type of ball mill has not been reported properly for UHMWPE. 0.5 and 1 wt% UHMWPE/MWCNTs were manufactured at different rotational speed and mixing time. The results indicate that rotational speed rather than mixing time is important for dispersing MWCNTs

  • 3.
    Ramanenka, Dmitrij
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    An Approach for Evaluation of Brick Lining's Mechanical State in Rotary Kilns2018Doctoral thesis, comprehensive summary (Other academic)
    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.

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  • 4.
    Ramanenka, Dmitrij
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Numerical Evaluation of Brick Lining Status in Rotary Kilns2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Rotary kilns are important in a variety of different manufacturing areas for e.g. calcination and sintering of materials. In fact, two of the most produced materials in the world, cement and iron, are likely to start their journey in a rotary kiln.A rotary kiln is a large cylinder-formed furnace which rotates about its axis and where certain chemical and physical reactions take place by the influence of heat. The slope and the rotation make the material inside to move through the kiln from feed to discharge end. Due to high process temperatures the casing of the kiln is insulated by a refractory lining. Service conditions inside the kiln are rough and the lining is continuously degrading, especially pronounced in the hot zone of the 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 kiln size and high operating temperatures. Today, computer programs 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 very little documentation can be found regarding numerical simulations of the lining, especially of the thermomechanical character.Purpose of this licentiate work is to study the mechanical behaviour of the lining by means of the finite element method (FEM). For this, a simplified model of a kiln was created and various fundamental cases were studied. The commercial FE-software LS-DYNA is used for the FE-calculations. The main work is based on cases of the kiln in cold condition. However, an initial study in warm condition is presented as well.The studied lining was a brick lining used in a kiln of dimensions typical for iron-ore pelletizing. Additionally, this licentiate thesis gives an overview of some of the most fundamental issues encountered in a refractory brick lining of a rotary kiln in general. Some material tests are presented as well.Model’s geometry was based on a section at the position of the support wheels, having a thickness of one brick. Some simplifications, such as choice of the material model and a rigid riding tyre, were done and a three-fold faster computational time was achieved. Response of the created model was partly verified analytically, by available in-house data and data from literature. It was confirmed that the model gives a good response.One of the important findings is that despite variation of conditions in cold state, e.g. rotational speed and relative ovality of the kiln, the induced stresses in the lining remained harmless. This challenges traditional believes which imply that ovality is of considerable importance for stress generation in the lining. On the other hand, by continuously tracing gaps between the bricks and the casing, it was found that integrity of the lining was significantly affected by rotational speed and ovality. Gaps as large as 80 mm could be observed between bricks and casing in a worst case scenario.An initial study on the kiln in hot state was made. Thermal expansion of a perfectly lined and an disordered brick lining were performed. The results indicate that stresses due to thermal expansion are rising slightly but are harmless in both cases. Additionally, expansion of the kiln stabilizes the lining and the effect of rotation compared to rotation in cold state is small.Analytical and numerical calculations were compared, indicating that analytical assumptions are often coarse and misleading from the reality.

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  • 5.
    Ramanenka, Dmitrij
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Antti, Marta-Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Gustafsson, Gustaf
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Characterization of high-alumina refractory bricks and modelling of hot rotary kiln behaviour2017In: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 79, p. 852-864Article in journal (Refereed)
    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.

  • 6.
    Ramanenka, Dmitrij
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Antti, Marta-Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Nordin, Lars-Olof
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Elasticity modulus and strength of two high-alumina refractory bricks at elevated temperaturesManuscript (preprint) (Other academic)
  • 7.
    Ramanenka, Dmitrij
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Enqvist, Evelina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Mechanical and thermal characterisation of novel UHMWPE-nano composite: A copmarrative study against virgin UHMWPE2013Conference paper (Refereed)
    Download full text (pdf)
    FULLTEXT01
  • 8.
    Ramanenka, Dmitrij
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Gustafsson, Gustaf
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Influence of heating and cooling rate on the stress state of the brick lining in a rotary kiln using finite element simulations2019In: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 105, p. 98-109Article in journal (Refereed)
    Abstract [en]

    Rotary kilns for iron-ore pellets production are highly dependent on a well-functioned refractory brick lining. To improve the long-term capability of the lining, in-situ observations of the bricks' performance are desired, however, the harsh environment inside the rotary kiln makes it difficult or nearly impossible 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 without limitation of the extreme conditions.

    In this work, stress state of the lining was studied under the influence of different heating and cooling rates, and different brick compaction cases. A finite element model was created for conducting the numerical simulations. The numerical model was calibrated for transient heat transfer. Temperature dependent material properties of the bricks and casing were used as input. The heating and cooling was controlled by temperature prescription on the boundary of the brick lining, while brick lining compaction by defining relative position of the bricks in axial and radial directions.

    The conducted numerical simulations showed that considerable tensile stress may appear in a large area of the brick during initial heating stage. The large tensile area corresponds well with the typical circumferential cracks experienced by the bricks. It was demonstrated that the compressive stresses counteract the development of tensile stresses. However, the compressive stresses may become very large in the initial stage of heating. The positive effect of lower heating rate was considerable on the tensile stresses, while influence on the compressive stresses was almost unnoticed. The hypothetical cooling rates showed that very high tensile stresses may occur on the surface of the bricks, potentially leading to surface spalling. Furthermore, it was demonstrated that axial compaction is highly important on the stress development in the lining, which, may not always be followed in practice. As a general conclusion, it is recommended to always achieve a tight compaction of the brick lining and to take measures for lowering the heating and cooling rates.

    The conducted work exemplifies behaviour of the brick lining for realistic heat transfer and material properties. The insight into the behaviour gives possibilities to make adjustments and directed investments for lowering risk of brick lining failure.

  • 9.
    Ramanenka, Dmitrij
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Gustafsson, Gustaf
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Modelling of Hot Rotary Kiln2017Conference paper (Refereed)
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    fulltext
  • 10.
    Ramanenka, Dmitrij
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Gustafsson, Gustaf
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Nordin, Lars Olof
    Loussavaara-Kiirunavaara Limited, Luleå.
    Evaluation of stress state in a brick lining of a hot rotary kiln due to material and design change2017In: Proceedings of the World Congress on Mechanical, Chemical, and Material Engineering, Avestia Publishing, 2017Conference paper (Refereed)
  • 11.
    Ramanenka, Dmitrij
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Stjernberg, Jesper
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Eriksson, Kjell
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Modelling of refractory brick furniture in rotary-kiln using finite element approach2014In: 11th World Congress on Computational Mechanics (WCCM XI) 5th European Conference on Computational Mechanics (ECCM V) 6th European Conference on Computational Fluid Dynamics (ECFD VI) / [ed] Eugenio Oñate; Xavier Oliver; Antonio Huerta, Barcelona: International Center for Numerical Methods in Engineering (CIMNE), 2014, Vol. 2, p. 1199-1210Conference paper (Refereed)
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  • 12.
    Ramanenka, Dmitrij
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Stjernberg, Jesper
    Loussavaara-Kiirunavaara Limited, Lulea.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    FEM investigation of global mechanisms affecting brick lining stability in a rotary kiln in cold state2016In: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 59, p. 554-569Article in journal (Refereed)
    Abstract [en]

    Severe degradation of refractory lining in a rotary kiln often leads to very costly production delays. Use of finite element analysis for understanding the mechanisms behind the failure of the lining is poorly reported in this field. To increase the knowledge and to update the field a simplified model of a kiln and a new methodology for studying stability of the lining are suggested. Behaviour of the lining in cold state – in static and dynamic cases – is studied. Influence of ovality, brick's Young's modulus and friction coefficient on stress and brick displacement are evaluated at two rotational speeds. It was found that the induced loads in the lining are harmless regardless of the tested conditions — challenging the traditional beliefs. On the other hand, recorded brick displacements were found to be significantly affected by rotational speed and ovality. Gaps as large as 80 mm could be observed between the bricks and the casing in a worst case scenario. An integrity coefficient was defined in order to quantify overall integrity of the lining.

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