| 11. |
- Farrokh, Mohammad, 1964-
(författare)
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Thermodynamic process modeling and simulation of a diaspore bauxite digestion process
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bauxite ores which originated from separate mines have different characteristics, i.e. each bauxite ore has its own individual specifications. Jajarm bauxite is of the diaspore-chamosite type and its alumina to silica mass ratio is lower than other diaspore ores. Diaspore bauxite digestion in comparison with other bauxite types has more complicated operational conditions and requires higher temperature, pressure and caustic concentration. The present study was thus performed on the above mentioned digestion process and include two parts. First, the behavior of some key parameters of the process was experimentally investigated. Second, a simulation model was developed to predict the performance of the process, particularly thermal energy consumption. The model was validated with several sets of the industrial data and close agreement was found. The effects of various trends in pressure drops of the flash tanks on the slurry preheating were analyzed. The results showed that the proposed pressure profile can lead to an increase in the furnace inlet slurry temperature. Alternatively, it can lead to an appreciable decrease in the furnace fuel consumption, which is required for having the existing operating temperature. The generated vapor in different stages of the process was determined. A considerable amount of the generated water vapor and thermal energy were lost. The model was further developed to study the effect of using a part of these vapors on heat recovery. The simulation results showed that in the new design, the pre-heater sections can gain 5.71GJ/h additional heat and the fresh slurry temperature increases by 11°C. Therefore, the furnace required energy is reduced by 11.9%. The new design was implemented in the refinery and according to the energy department report, it has reduced the furnace fuel consumption by 8%, which is around 200kg of natural gas /h less than the earlier condition for every digestion line.
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| 12. |
- Farrokh, Mohammad, 1964-, et al.
(författare)
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THERMODYNAMIC PROCESS SIMULATION OF THE DIGESTION UNIT IN IRAN ALUMINA REFINERY
- 2009
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Ingår i: Proceedings of SIMS 50, Modeling of Energy Technology. - 9788789502885 ; , s. 173-178
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Konferensbidrag (refereegranskat)abstract
- Jajarm bauxite is of the chamosite-diasporic type, one of the hardest types of bauxite for alumina production. The Iran Alumina Refinery uses Jajarm deposits and currently operates at 65-70% of its nameplate capacity. Digestion is one of the most important processes in the refinery and has become the main bottleneck in the production. In this paper we study the effect of selected parameters on the behavior of this important section of the refinery using thermodynamic simulation of the digestion unit. The ASTM tables property method was used for vapor streams and the Elec-NRTL property model was used for the global digestion process. The digestion process was simulated with Aspen plus software. The results show good agreement with experimental data. The relationship between the incoming slurry temperature in the first flash tank and the preheater cold stream (slurry into the furnace) temperature and energy consumption is discussed.
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| 13. |
- Kurdve, Martin, et al.
(författare)
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Lean and green integration into production system models - Experiences from Swedish industry
- 2014
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Ingår i: Journal of Cleaner Production. - : Elsevier Ltd. - 0959-6526 .- 1879-1786. ; 85, s. 180-190
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Tidskriftsartikel (refereegranskat)abstract
- This paper focuses on integration of operations management, specifically production system models with environmental management and related issues such as quality and safety. Based on knowledge concerning lean-based improvement programmes for company-specific production systems (XPS) and integration between formal management systems, such as ISO 9001 and 14001, industrial practices from integrating management systems with the XPS were studied. A literature-based comparison between formal management systems and XPS is made, indicating integration potentials. The empirical research is an analysis of five vehicle and automotive companies in which various efforts have been made to integrate their management systems with their XPS. The results show that although conscious steps have been taken since the introduction of ISO 14001 in integrating environmental management into everyday operations, there are still obstacles to overcome. To fully include sustainability aspects, the characteristics of the improvement systems have to be adapted and extended. One barrier to extended integration is the lack of integration strategy. There is further a lack of sustainability metrics and adaptation of improvement methods to push companies' operational performance. In addition, organisational issues still arise concerning the responsibility and ownership of environmental management in relation to operations. Based on these results it is concluded that processes for integration are recommended; however, each organisation needs to consider its operations, corporate culture and business opportunities of its environmental management. Still, incorporating environmental management systems into XPS is seen as an effective way of establishing company commonality in continuous improvement, resulting in holistic understanding and improved organisation performance.
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| 14. |
- Kurdve, Martin, et al.
(författare)
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Production System Change Strategy in Lightweight Manufacturing
- 2016
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Ingår i: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; , s. 160-165
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Konferensbidrag (refereegranskat)abstract
- Two change management strategies: a minimum change, exploitation strategy (kaizen) and a maximum output, exploration strategy (kaikaku) have been applied in a manufacturing case study. Value stream mapping and discrete event simulation were used to analyse the production system changes, with regards to robustness and total lead-time, to increase knowledge of how to choose change management strategy. The results point out that available time is crucial. It is important to consider not only product specification and return of investment, but also the change and risk management. Future research should develop engineering change management further.
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| 15. |
- Kurdve, Martin, et al.
(författare)
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Waste Flow Mapping: Improve sustainability and realize waste management values
- 2012
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Ingår i: Greening of Industry Network (GIN2012).
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Konferensbidrag (refereegranskat)abstract
- An efficient Waste Management System creates increased business value contributing to manufacturing industry sustainability and realizes economic opportunities. Previous studies have shown the economic potential of improving material efficiency by climbing the waste hierarchy and turning waste liabilities into assets. World economic forum also identifies innovation for resource efficient solutions and business models as the most strategic option to capture value in industry. The main responsibility for waste lies with the operations owner but since waste management usually is operated by other functions or companies, supportive methods to include material waste in operational development are needed. The main purpose of the research has therefore been to develop a method framework for identifying and analysing potentials for waste management in manufacturing industry, including residual material values of metals, combustible and inert waste, process fluids and other hazardous waste. Case studies were conducted to find economically competitive environmental improvements on team, site and multisite level and to define suitable performance indicators for continuous improvements. A novel approach: waste flow mapping (WFM), combining Value Stream Mapping (VSM), Eco mapping and a waste composition analysis with basic lean principles is used. The material’s value flow and the information flow is analysed in a VSM. Eco-mapping is used to give a graphical structure for the analysis of labour and equipment, with subsequent costs. Finally the waste hierarchy and composition analysis is used to imply the potential for business improvements and best practice examples are used. The developed method reveals the potential in an easy way and support integration of waste management in operations and continuous improvement work.Empirical data from a full scale multi-site study of waste management of material residuals at a global manufacturing company’s operations in Sweden are used to exemplify that with the WFM approach the mapping can be done in an efficient and consistent manner, revealing value losses and improvement potentials. Fraction definitions and operational practice standards were essential to realise cost efficiency and reach a more sustainable footprint. Comparisons between sites show that with simple actions, substantial improvements in recycling efficiency can be made, leading to proposed performance indicators and highlighting the need for established standardized implementation solutions. The results further point out the importance of avoiding mixing material with lower quality grade of that material. The experiences prove that Waste Flow Mapping is a suitable method to efficiently identify sustainability improvement potentials.
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| 16. |
- Lager, Thomas, 1945-, et al.
(författare)
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Modelling company generic production capabilities in process industries : A configuration approach
- 2017
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Ingår i: International Journal of Operations & Production Management. - : Emerald Group Publishing Limited. - 0144-3577 .- 1758-6593. ; 37:2, s. 126-161
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: In the process industries, it is essential to have a well-articulated manufacturing strategy within companies. However, to facilitate manufacturing strategy development, it is important to start with a good characterisation of the material transformation system and company production capabilities. The paper aims to discuss these issues. Design/methodology/approach: A grounded theory approach, with inspiration from configuration modelling, attempted to characterize the material transformation system as a set of variables. The variable development was based on a literature review and the knowledge base of five industry experts. Two exploratory mini-case studies were carried out, primarily to illustrate the use of the model, but additionally to test its industrial usability. Findings: A set of 31 variables was developed, and related measures and scales were tentatively defined. Two mini-cases supported the usability of the model. The model, focussing on company generic process capabilities, is a conceptual taxonomy and the study’s theoretical contribution. Research limitations/implications: The lucidity of the definitions and scales for the variables are open to further refinement, and the limited discussions of variable relationships in this study are addressed in an agenda for further research. Practical implications: The model can be deployed as a facilitative instrument in the analysis of company material transformation systems and may serve as a platform in further discussions on companies’ strategy development. Originality/value: The model is a new instrument for analysing company generic process capabilities and an effort to build new theory rather than to test an existing one.
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| 17. |
- Niu, Z., et al.
(författare)
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Experimental investigations on the thermal energy storage performance of shell and tube unit with composite phase change materials
- 2019
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Ingår i: Innovative Solutions for Energy Transitions. - : Elsevier. ; , s. 4889-4896, s. 4889-4896
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Konferensbidrag (refereegranskat)abstract
- This work presented experimental investigations on the thermal energy storage performance of the shell and tube unit with composite phase change materials (PCM). A cylindrical heat storage tank filled with open-cell copper foam was proposed and its melting process characteristics were studied. A designed test system was established to record the PCM real-time temperature data. The results showed that, compared with traditional smooth-tube phase-change heat exchangers, the composite PCM unit accelerated the bottom paraffin melting. The temperature disparity among different height reduced, which resulted in better internal temperature uniformity. Due to the expanded heat transfer area, improved heat transfer coefficient and weakened natural convection, the bottom phase-change materials in the composite-PCM heat-storage unit melt faster.
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| 18. |
- Raza, Mohsin, et al.
(författare)
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Effects of process related variations on defect formation in investment cast components
- 2018
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Ingår i: Archives of Foundry Engineering. - : Polish Academy of Sciences. - 1897-3310 .- 2299-2944. ; 18:1, s. 103-108
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Tidskriftsartikel (refereegranskat)abstract
- Castability of thin-walled castings is sensitive to variation in casting parameters. The variation in casting parameters can lead to undesired casting conditions which result in defect formation. Variation in rejection rate due to casting defect from one batch to other is common problem in foundries and the cause of this variation usually remain unknown due to complexity of the process. In this work, variation in casting parameters resulting from human involvement in the process is investigated. Casting practices of different groups of casting operators were evaluated and resulting variations in casting parameters were discussed. The effect of these variations was evaluated by comparing the rejection statistics for each group. In order to minimize process variation, optimized casting practices were implemented by developing specific process instructions for the operators. The significance of variation in casting parameters in terms of their impact on foundry rejections was evaluated by comparing the number of rejected components before and after implementation of optimized casting practices. It was concluded that variation in casting parameters due to variation in casting practices of different groups has significant impact on casting quality. Variation in mould temperature, melt temperature and pouring rate due to variation in handling time and practice resulted in varying quality of component from one batch to other. By implementing the optimized casting instruction, both quality and process reliability were improved significantly.
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| 19. |
- Risonarta, Victor Yuardi, et al.
(författare)
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Strategy to improve recycling yield of aluminium cans
- 2019
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Ingår i: E3S Web of Conferences. - : EDP Sciences. ; , s. 1-8
-
Konferensbidrag (refereegranskat)abstract
- Millions of canned drinks are consumed everyday globally and their wastes create an enviromental issue. Fortunately, the cans are made from aluminium (Al) so that it can be recycled. There are two main keypoints existing during the recycling process of Al cans, i.e. the aluminium loss or low Al-yield and low recycling yield. This work outlines the strategies to improve the recycling perfomance for Al beverage cans, i.e. by adding drossing flux, applying improved melting strategy, and cans decoating prior to melting. Drossing flux was added to assist the detachment of Al from the slag. Another improved melting strategy was worked out by decreasing exposure time cans to the furnace atmosphere during melting. All those above strategies result in an increase of recycle yield in a range of 4 % to 5 %.
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| 20. |
- Sadeghi, Mohammad, 1962-, et al.
(författare)
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Influence of ion implantation on corrosion resistance of the nickel over steel
- 2023
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Ingår i: Materials Science and Technology. - : TAYLOR & FRANCIS LTD. - 0267-0836 .- 1743-2847.
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen ions were implanted at different energies of 15, 30, 45 and 60 keV and with the flux of 10(17) N(+)cm(-2) inside the nickel layers that have been deposited on the 304 stainless steel using the electron gun method at room temperature. XRD patterns showed different crystalline phases of nickel nitride for the implanted samples. The surface morphology was extracted by MountainsMap software's using statistical data from AFM analysis. In addition, a potentiodynamic polarisation test was performed in a 3.5% NaCl solution to study the corrosion behaviour. These studies revealed that corrosion was directly related to the deposition parameters, mainly the implantation energy, modifying the surface so that the highest corrosion resistance was obtained for the sample implanted with 60 keV.
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