| 1. |
- Farrokh, Mohammad, 1964-, et al.
(author)
-
DIASPORIC BAUXITE DIGESTION PROCESS SIMULATION
- 2010
-
Conference paper (other academic/artistic)abstract
- The alumina digestion process in the Bayer overall process like the other hydrometallurgical processes is under the effect of various factors and the control and optimization of quality and efficiency of the process and also reducing the energy consumption are of prime importance. Process simulation provides the possibility to investigate the impact of various factors and study the optimum conditions for obtaining the desired quality and reducing the energy consumption and environmental impact. In the digestion unit, the high pressure diasporic bauxite slurry, a mixture of ground bauxite, lime and caustic liquor, is decomposed. The bauxite slurry is preheated in the high pressure tube pre-heater and then is heated up to the decomposition temperature in the furnace. The dissolution takes place in the tubular digesters and resulting product, aluminate slurry, passes through the expanding stage, including 11 flash tanks to recover the thermal energy. In this paper the thermodynamic simulation consecutive stages of the digestion unit process including the property methods and the evaluation and verifying the simulation results against their accordance with the real conditions are studied. The obtained results showed that the outputs of the simulation have good and acceptable accordance with the empirical data. Using the simulation program; the results of some case studies showed that in the current situation, less than 70% of the energy generated in the dissolution process is directed to the pre-heaters. Also more than 30% of vapor generated in the dissolution process is dissipated and wasted. By using the vapor generated in the last two flash tanks, the efficiency of energy recycling will be increased and thus the water waste and environmental pollution will be decreased considerably.
|
|
| 2. |
- Farrokh, Mohammad, 1964-
(author)
-
Thermodynamic process modeling and simulation of a diaspore bauxite digestion process
- 2013
-
Licentiate thesis (other academic/artistic)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.
|
|
| 3. |
- Kurdve, Martin, et al.
(author)
-
Lean and green integration into production system models - Experiences from Swedish industry
- 2014
-
In: Journal of Cleaner Production. - : Elsevier Ltd. - 0959-6526 .- 1879-1786. ; 85, s. 180-190
-
Journal article (peer-reviewed)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.
|
|
| 4. |
- Kurdve, Martin, et al.
(author)
-
Waste Flow Mapping: Improve sustainability and realize waste management values
- 2012
-
In: Greening of Industry Network (GIN2012).
-
Conference paper (peer-reviewed)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.
|
|
| 5. |
- Shahbazi, Sasha, et al.
(author)
-
Material efficiency in manufacturing
- 2014
-
Conference paper (peer-reviewed)abstract
- Developments, industrialization and mass production have triggered rapid increase of raw material consumption and great volumes of industrial waste, while industrial waste management infrastructure has not been developed with the same pace. One mean in striving for industrial waste management is the management of process materials. This paper introduces the performance measure sorting rate for each segment of waste material, along with a method for sorting analysis to help improving overall material efficiency and industrial waste management. The results revealed that more than 50% of combustible bins’ content could be separately segregated as plastic, wood, paper, cardboard and bio-degradable.
|
|
| 6. |
- Johansson, Christian, et al.
(author)
-
Enhancing intra-cognitive communication between engineering designers and operators : a case study in the laser welding industry
- 2012
-
In: Proceedings of the 3rd IEEE International Conference on Cognitive Communications. - Piscataway, NJ : IEEE Communications Society. - 9781467351874 - 9781467351867 ; , s. 493-497
-
Conference paper (peer-reviewed)abstract
- In manufacturing, metal parts can be joined using a laser as a welding tool, i.e. laser welding. Despite huge amount of research over the years, the process is neither sufficiently understood nor mathematically predictable. This study aims to holistically analyze the knowledge management issues occurring in laser welding. Emerging from observations and semi-structured interviews from industry and academy, the complexity and the criticalities of the process as well as the current knowledge transfers is explained and analyzed, using a knowledge lifecycle framework as a reference. Besides enhanced awareness of the limiting issues, information and knowledge visualization, e.g. knowledge maps, is identified as a key for progress in the community. The Matrix Flow Chart is suggested as an alternative descaled map of process changes.
|
|
| 7. |
- Pourian, Bijan, 1962-
(author)
-
ANALYZING THE HYDRO DYNAMICS AND THE CHEMICAL REACTIONS IN PULP DIGESTER SYSTEMS USING CFD MODELLING
- 2011
-
Doctoral thesis (other academic/artistic)abstract
- The aim of this thesis is to use differential analysis and finite volume method (FVM) to model and analyze a continuous pulp digester in order to create a detailed picture of the flow behaviour and chemical reactions in the digester. This information will be used to optimize wood chip flow and reactions and to diagnose and avoid faults such as hang-ups and channelling. As digesters increase in size, the importance of control of the liquor flow in the wood chip bed also increases. Pulping reactors are often faced with production disturbances that cause reduced fibre quality, non-uniform chemical reactions and damaging channelling phenomena. The models that are proposed in this thesis aim to consider the fluid dynamics, thermodynamics and chemical reactions together in order to create a model with more detail than has been previously reported. The digester is of the continuous type and has a circular cross-section, with a height of 60 m and a diameter that increases stepwise from 6 m at the top to 7 m at the bottom. The geometry of the digester, including an internal pipe with three different diameters, three inlet flows at three levels of the digester, inlets and outlets at the top and bottom, and a number of peripheral circulation pipes connected to the screens at three levels, is represented in simulations by a 2D axisymmetric model constructed in Gambit. The interactions between the two phases - the wood chips and the alkaline liquor - are studied using the finite volume method (FVM). Eulerian and Mixture numerical methods are evaluated for solving a mass transfer multiphase model with a porous matrix, species transport and reaction system in FLUENT. Variable porosity is used to model channelling in the digester. Comparisons of the results of simulations with real digester data indicate that the multiphase model, with the species transport and mass transfer modules accurately predict the pulping chemical reactions inside the digester and are able to evaluate pulp quality. The species transport model with reaction scheme is able to predict the mass balance equation and stoichiometry of the pulping reaction. The porous media scheme complements this approach to give a more complete view of pulp production, including the effect of faults in the process. The approaches to the FVM described in this thesis enable an accurate view of the pulping process which can contribute to improved control and optimization of the process.
|
|
| 8. |
- Pourian, Bijan, 1962-, et al.
(author)
-
CFD modelling of solid-liquid multiphase and mathematical separation of the phases in a continuous pulp digester
- 2010
-
In: International Journal of Modelling and Simulation. - : ACTA Press. - 0228-6203. ; 30:3, s. 384-395
-
Journal article (peer-reviewed)abstract
- This paper describes the use of a CFD multiphase model using commercial FLUENT software to aid understanding of the physical behavior of solid and liquid flows in the digester of the pulping process. We take into consideration the mass balance of the multi-inlets, outlets and circulation flows in the digester. We also look at the application of a Porous media model to describe the dynamic behavior of the liquor flow through a bed of solid particles.The cylindrical Korsnas/vallvik pulping digester in Sweden is represented in the models as an axisymmetric two-dimensional model, which includes multiple feeds, outlets, pressure adjustment valves and circulation pipes.Separation of the phases is an important part of the pulping process. A number of multiphase models are evaluated for their potential use in phase separation.For this evaluation we constructed the two-dimensional digester model in the Gambit software package, a pre- processor tool for FLUENT Physical strainers at the entrances of outlet pipes were designed in Gambit, in order to investigate the possibility of physically separating large solid particles from the liquid flow where both phases are subject to suction into the circulation pipes.The compaction of the wood chips is also considered in the modeling. In the Porous model, the digester is divided into sections of different porosity, and the behavior of individual suspension particles is not considered. The bulk of this paper concerns modeling mass balances and phases of the mixture in the digester using Eulerian and Mixture strategies.
|
|
| 9. |
- Sadeghi, Mohammad, et al.
(author)
-
Experimental and Theoretical Studies on the Effect of Die Temperature on the Quality of the Products in High-Pressure Die-Casting Process
- 2012
-
In: Advances in Materials Science and Engineering. - : Hindawi Limited. - 1687-6822 .- 1687-8434 .- 1687-8442. ; :434605
-
Journal article (peer-reviewed)abstract
- Die temperature in high-pressure die casting of A380 alloy is optimized by experimental observation and numerical simulation. Ladder frame (one part of the new motor EF7) with a very complicated geometry was chosen as an experimental sample. Die temperature and melt temperature were examined to produce a sound part. Die temperatures at the initial step and the final filling positions were measured and the difference between these values was calculated. ProCAST software was used to simulate the fluid flow and solidification step of the part, and the results were verified by experimental measurements. It is shown that the proper die temperature for this alloy is above 200 degrees C.
|
|
| 10. |
- Sadeghi, Mohammad, 1962-, et al.
(author)
-
Numerical determination of process parameters for fabrication of automotive component
- 2010
-
In: solidification simulation.
-
Conference paper (other academic/artistic)abstract
- The casting defects that are caused by molten metal are cold shut formation, entrapment of air, gas, and inclusion. But the control of casting defects has been based on the experience of the foundry engineers. One of the most parameters that can influence the casting defects is cooling rate. In this paper, computer simulations have been carried out to analyze the flow of molten metal and effect of die temperature on the cooling rate and subsequently the casting defects. Flow patterns of molten metal in one of the Iranian automotive component were examined to find the optimal temperature for the die-casting die temperature. The finite element ProCast software was used for simulation and results of simulation was compared with the experiment. The calculated results for automobile Ladder frame body to control the die-casting process have achieved good agreements with the experimental data. Results show that temperatures between 20°C to 25°C are good for the die casting.
|
|
