LKAB produce several different highly refined iron ore products, fines and pellets, for the manufacturing of iron and industrial minerals applications. The different industrial minerals products have individual specifications and therefore different area of usage. At LKAB in Malmberget a problem come to attention when magnetite slurry is classified in a cyclone cluster, which is used at the production of two special products. The problem is that the quality of the overflow product is irregular. The coarse particle fractions tend to be too large. This causes that a product cannot hold its specifications, and may receive a lower product value or is rejected. This master thesis investigates if it is possible with a more even product quality as well as a lower coarse grain part in the overflow. This is investigated with different samplings procedures, in full production during the summer, and analyses that is based on literature and simulations with MODSIM. The different investigations consist of an investigation on a delimited circuit, with product balances in MatBal, and evaluation of different geometrical and process changes on the cyclone cluster. This master thesis intends to give an increased understanding of the hydrocyclone problem, with the expectation of finding a possible solution and/or proposal on further investigations. Some capacity tests were done as well as sampling for later analysis. The analysis methods chosen for the evaluation of the investigations were XRF, wet laser diffraction and moisture analysis. This master thesis have mapped and given a better understanding on how the circuit and cyclone cluster works, as well what possibilities there are for decreased coarse grains in the battery overflow. From the circuit investigation could smaller variations be observed as well as it was in fair agreement with previous sampling. The product balance compared well with previous ones, except for that the recirculation from the primary cyclone was determined to be much lower. The pressure drop investigation on the cyclone cluster contradicted partly the literature and the simulations, since the overflow gave a coarser product with increased pressure drop, and shows that an increased pressure drop should not be the solution to decrease the coarse grain part in the overflow. The investigations of decreased underflow and overflow diameter followed the simulations and the literature well, but should not be the solution to decrease the coarse grain part in the battery overflow. These changes could be the solution if the lower limits ( / <p>Validerat; 20151001 (global_studentproject_submitter)</p>

Determining how loads are distributed in a structure has long been a way for engineers to ensure that the final product will work as intended. As components become more and more complicated so does this analysis. The advantages of quickly identifying critical features in a design are significant. By gaining this knowledge it is possible to explore the design space more thoroughly. This was previously done by collecting information over a long period of time and gradually build up the knowledge which can take several weeks or sometimes even months. The theory of the U* index as a numerical analysis method was formulated in 1986 by Takahashi [30] but due to the computational capabilities at the time there was no practical applications. It aims to give the same information compared to the current iterative process in a significantly faster way by calculating the relative stiffness. In its current form it can however be computationally heavy and has not yet seen any extended applications in the engineering sector. As the U* index is both an algorithm for calculating the load paths but also a broader theory of energy based identification of the stiffest route in a structure, it is referred to both as a method and a tool. In this thesis we initially set out to identify needs in the product development processfor a engineer team. Then we will investigate the capabilities of the U* index method, improve said capabilities by optimizing computation time and compatibility, establish a foundation for future development, and finally propose an integration of the tool into an advanced aero-engine development process. The main focus of this thesis is on the concept solutions phase as the needfinding indicated this phase to be in most need of improvement. Other applications of U* are mentioned but will not be examined in detail. In the concept solutions phase one would want to evaluate design features from a larger perspective to explore thedesign space. This can be done with U* by identifying which features are carrying the loads and how close the calculated path is to the optimal one. A possible application in optimization in the preliminary solution phase were also identified. In this case one can for example analyze the contour of the U* field and use U* sum to identify the relative load carrying contribution of certain regions. The initial state of the technology was determined to be at a technology readiness level (TRL) of 5 in the ModSim scale, meaning that the key elements have been demonstrated on a realistic problem. As the goal of applying the tool on real large models was achieved, the complete system level capabilities were demonstrated resulting in TRL 6 being reached at the end of the development. The more commonly used NASA version of TRL started out at TRL 3 which was reached with the proof of concept conducted by Ramesh [24]. According to these definitions the technology didn’t progress any further due to the specific definitions being primarily oriented towardshardware and the requirement for TRL 4 involved laboratory validation. As the TRL have been assessed with both versions, any potential future work has the option tochoose which method fit that particular work. The successful implementation of theinspection load method for calculating U∗ was critical in being able to compute thesolutions in reasonable time frame. There is however more room to optimize time byimplementing algorithms for better suited meshing and post processing. The tool is applicable on large components but the solutions still require a lot of time which reduces its usefulness in the early, time critical phase. The post-processing routines similarly take time and require extensive manual labor to determine the proper load path. This is also sub optimal for visualizing the load paths because it relies on assumptions. Future work should therefore aim to maximize the automation part of the post-processing. Further validation needs to be conducted on more complicated structures to ensure correlation between physical components and simulation. Furthermore, the quantifying of margins, uncertainties and sensitivities of the simulation is important to better understand the limitations of the tool.

Buzwagi Gold Mine (BGM) is operated by Acacia Mining and located in the Lake Victoria Goldfields of central Tanzania. The mine commenced its operation since April 2009 and treats a sulphide copper-gold ore to produce gold in form of doré bars and a concentrate containing gold, copper and silver. The BGM comminution circuit includes a primary crushing stage with a gyratory crusher and a two grinding circuits using a Semi-Autogenous Grinding (SAG) mill and a ball mill. The SAG mill circuit also includes a single-deck screen and a cone crusher while the ball mill circuit utilizes hydrocyclones. Currently, the grinding circuits are inefficient in achieving the aspired product fineness of xP,80 = 125 μm even at low to normal throughputs (450-600 t/h). An evaluation and optimization study of the circuit performance was conducted to improve the product fineness through circuit surveys, experimental lab work and simulations. In three full scale sampling campaigns, size distributions and solids contents of the samples were determined at selected points in the circuit. Further, several types of breakage tests were conducted; standard Bond tests to determine ore grindability and work indices, batch grinding tests to determine parameters for breakage and selection functions , and standard ball mill tests for mineral liberation characterization by an automated mineral liberation analyzer (MLA).The tests were conducted in a size range from 0.063 to 2 mm. Then, mass balance of the circuit was calculated and the models for mills, screens and hydrocyclones were employed in MODSIM (version 3.6.24). Firstly, simulations were conducted to optimize the existing plant. Several options were evaluated such as reduction of SAG screen aperture, adjustment of cyclone feed solids content and reduction of vortex finder and apex diameters. Moreover, simulations were also evaluated for a possible modification of the existing circuit and include; partial splitting of the cyclone underflow back to SAG mill, introduction of a second classification stage as well as introduction of a second ball mill. The evaluation of breakage tests and survey data revealed the following; the Bond work index obtained for the current ore ranges between 17.20 - 18.70 kWh/t compared to 14.50 - 16.50 kWh/t which was estimated during plant design.This indicates a change in hardness of the ore during the last 7 years. Harder ore means more energy requirement for an efficient operation, the consequence of which is increased costs. Thus, a periodic review of the ore hardness for ongoing mining operation is recommended. This will help in establishing better blends as well as prediction of appropriate tonnages for the existing ore types, so as to be efficiently treated by the available plant design. The work indices of the ore blends treated during survey were correlated with their quartz content and showed a strong linear relationship (R2= 0.95). Therefore, the work index for the BGM ore could be predicted based on known quartz content of the material. Further, the model could be used as a control tool for monitoring hardness variation of the SAG mill feed. The mineral liberation studies indicated that the valuable phase (pyrite-pyrrhotite) could be liberated at relatively coarser particle sizes (200-400 µm). This implies that, there could be no problem with the efficiency of the gravity circuit for the BGM operation, where the gold contained in pyrite-pyrrhotite could be easily concentrated. However, the efficiency of flotation and cyanidation processes will still require finer feed. In overall, the liberation characteristics of the ore blends treated during survey showed minor differences. The Bond efficiency factors of 48-61 % were obtained for the BGM grinding circuit, indicating an inefficient operation. This suggests that the operation could achieve targets by lowering the throughput. Further, the SAG mill circuit was characterized by fluctuating feed size of between xF,80 =102 to 185 mm. A need for control of the feed size as well as blending ratios was recommended for an efficient operation in terms of throughput and final product size. This could be achieved through closer monitoring of the primary crusher performance and proper control of the ratios for the SAG mill feeders drawing the ore from the stockpile. The ball mill grinding efficiency was poor and could be indicated by the fraction < 125 µm of only 5-9 % or xP, 80 : >400 µm in the mill discharge. This was deemed due to poor hydrocyclone performance which was characterized by higher feed solids content, coarser overflow xP,80: >200 µm as well as cut sizes, xT : > 200 µm. An improvement of product fineness up to 327 µm could be achieved during the simulation and optimization of the existing design. This could be achieved by modification of the operating conditions such as reduction of SAG screen aperture from 12 mm to 10 mm, reduction of vortex finder from 280 mm to 270.3 mm, reduction of apex diameter from 150 mm to 145.6 mm as well as adjustment of the cyclone feed solids content from 66.7 to 67.1 %. Based on this result, it was concluded that the current equipment could not achieve the target product quality (i.e. xP,80 = 125 µm ). Further simulations based on flowsheet modification options showed that a second ball mill (series configuration) can help to achieve the desired product fineness as well as an increase of throughput from 618 t/h to 780 t/h. Although the circulating load increases to approximately 500 % in this configuration, it is outweighed by the benefits. Importantly, this option is cost intensive and hence may be considered as a long term solution and especially after cost-benefit analysis. Finally, the results based on optimization of the existing design is recommended as short term solution for improvement of the BGM operation. Although the fineness achieved is still low (i.e. xP,80 = 327 µm) compared to the target (i.e. xP,80 = 125 µm), this gives additional advantage in the sense that, also better hydrocyclone performance is achieved in terms of overflow product (xP,80 = 105 µm vs. > 240 µm) , cut size (xT =133.1 µm vs. > 220 µm) and circulating load (CL =350 %). The improved overflow fineness will contribute to improved efficiency for the downstream processes.

Buzwagi Gold Mine (BGM) is operated by Acacia Mining and located in the Lake Victoria Goldfields of central Tanzania. The mine commenced its operation since April 2009 and treats a sulphide copper-gold ore to produce gold in form of doré bars and a concentrate containing gold, copper and silver. The BGM comminution circuit includes a primary crushing stage with a gyratory crusher and a two grinding circuits using a Semi-Autogenous Grinding (SAG) mill and a ball mill. The SAG mill circuit also includes a single-deck screen and a cone crusher while the ball mill circuit utilizes hydrocyclones. Currently, the grinding circuits are inefficient in achieving the aspired product fineness of xP,80 = 125 μm even at low to normal throughputs (450-600 t/h). An evaluation and optimization study of the circuit performance was conducted to improve the product fineness through circuit surveys, experimental lab work and simulations. In three full scale sampling campaigns, size distributions and solids contents of the samples were determined at selected points in the circuit. Further, several types of breakage tests were conducted; standard Bond tests to determine ore grindability and work indices, batch grinding tests to determine parameters for breakage and selection functions , and standard ball mill tests for mineral liberation characterization by an automated mineral liberation analyzer (MLA).The tests were conducted in a size range from 0.063 to 2 mm. Then, mass balance of the circuit was calculated and the models for mills, screens and hydrocyclones were employed in MODSIM (version 3.6.24). Firstly, simulations were conducted to optimize the existing plant. Several options were evaluated such as reduction of SAG screen aperture, adjustment of cyclone feed solids content and reduction of vortex finder and apex diameters. Moreover, simulations were also evaluated for a possible modification of the existing circuit and include; partial splitting of the cyclone underflow back to SAG mill, introduction of a second classification stage as well as introduction of a second ball mill. The evaluation of breakage tests and survey data revealed the following; the Bond work index obtained for the current ore ranges between 17.20 - 18.70 kWh/t compared to 14.50 - 16.50 kWh/t which was estimated during plant design.This indicates a change in hardness of the ore during the last 7 years. Harder ore means more energy requirement for an efficient operation, the consequence of which is increased costs. Thus, a periodic review of the ore hardness for ongoing mining operation is recommended. This will help in establishing better blends as well as prediction of appropriate tonnages for the existing ore types, so as to be efficiently treated by the available plant design. The work indices of the ore blends treated during survey were correlated with their quartz content and showed a strong linear relationship (R2= 0.95). Therefore, the work index for the BGM ore could be predicted based on known quartz content of the material. Further, the model could be used as a control tool for monitoring hardness variation of the SAG mill feed. The mineral liberation studies indicated that the valuable phase (pyrite-pyrrhotite) could be liberated at relatively coarser particle sizes (200-400 µm). This implies that, there could be no problem with the efficiency of the gravity circuit for the BGM operation, where the gold contained in pyrite-pyrrhotite could be easily concentrated. However, the efficiency of flotation and cyanidation processes will still require finer feed. In overall, the liberation characteristics of the ore blends treated during survey showed minor differences. The Bond efficiency factors of 48-61 % were obtained for the BGM grinding circuit, indicating an inefficient operation. This suggests that the operation could achieve targets by lowering the throughput. Further, the SAG mill circuit was characterized by fluctuating feed size of between xF,80 =102 to 185 mm. A need for control of the feed size as well as blending ratios was recommended for an efficient operation in terms of throughput and final product size. This could be achieved through closer monitoring of the primary crusher performance and proper control of the ratios for the SAG mill feeders drawing the ore from the stockpile. The ball mill grinding efficiency was poor and could be indicated by the fraction < 125 µm of only 5-9 % or xP, 80 : >400 µm in the mill discharge. This was deemed due to poor hydrocyclone performance which was characterized by higher feed solids content, coarser overflow xP,80: >200 µm as well as cut sizes, xT : > 200 µm. An improvement of product fineness up to 327 µm could be achieved during the simulation and optimization of the existing design. This could be achieved by modification of the operating conditions such as reduction of SAG screen aperture from 12 mm to 10 mm, reduction of vortex finder from 280 mm to 270.3 mm, reduction of apex diameter from 150 mm to 145.6 mm as well as adjustment of the cyclone feed solids content from 66.7 to 67.1 %. Based on this result, it was concluded that the current equipment could not achieve the target product quality (i.e. xP,80 = 125 µm ). Further simulations based on flowsheet modification options showed that a second ball mill (series configuration) can help to achieve the desired product fineness as well as an increase of throughput from 618 t/h to 780 t/h. Although the circulating load increases to approximately 500 % in this configuration, it is outweighed by the benefits. Importantly, this option is cost intensive and hence may be considered as a long term solution and especially after cost-benefit analysis. Finally, the results based on optimization of the existing design is recommended as short term solution for improvement of the BGM operation. Although the fineness achieved is still low (i.e. xP,80 = 327 µm) compared to the target (i.e. xP,80 = 125 µm), this gives additional advantage in the sense that, also better hydrocyclone performance is achieved in terms of overflow product (xP,80 = 105 µm vs. > 240 µm) , cut size (xT =133.1 µm vs. > 220 µm) and circulating load (CL =350 %). The improved overflow fineness will contribute to improved efficiency for the downstream processes.

Atualmente, a água tornou-se motivo de conflitos dentro da sociedade, em virtude do aumento das demandas e do comprometimento do seu aspecto qualitativo. A bacia do rio Piracicaba é uma região altamente desenvolvida, com altos índices populacionais e que apresenta disputa de água entre os diversos usuários. Portanto, realizou-se um estudo para determinar a disponibilidade hídrica da bacia, relacionando as demandas de água aluais e futuras. Para isso foi utilizado o modelo ModSimP32, que é basicamente um modelo de simulação e otimização em rede de fluxo. Como dados de entrada do ModsimP32, estão as séries de vazões históricas ou sintéticas e os valores das demandas existentes na bacia. Como se pretendia realizar um estudo a longo prazo, foi necessário a obtenção de séries hidrológicas mais longas, portanto utilizou-se um modelo multivariado AR(1) para gerar novas séries. Para as simulações realizadas, verificou-se que em períodos secos não é possível atender a todas as demandas integralmente e ainda manter as vazões ecológicas no rio, para as regiões de Paulínea e Piracicaba. / Nowadays, the water became the reason of conflicts of the society, due to the increase of the demands and the implicated qualitative aspect. The basin of the river Piracicaba is a highly developed area, with high indexes populations anel it presents dispute of water among several users. Therefore it took place an analysis to verify the amount of water of the basin, relating the demands of water, current and future. For that the model ModSimP32 was used, that is basically a simulation and optimization model in supply network. Among the data of entrance of the ModsimP32, they are the hydrologic series. Therefore it was used of a multivariate model AR(1) to generate new series. For the accomplished simulations, it was verified that is not possible to assist the whole ones integrally the demands in dry periods and still to maintain the ecological flow in the river, for the areas of Paulínea and Piracicaba.

Atualmente, a água tornou-se motivo de conflitos dentro da sociedade, em virtude do aumento das demandas e do comprometimento do seu aspecto qualitativo. A bacia do rio Piracicaba é uma região altamente desenvolvida, com altos índices populacionais e que apresenta disputa de água entre os diversos usuários. Portanto, realizou-se um estudo para determinar a disponibilidade hídrica da bacia, relacionando as demandas de água aluais e futuras. Para isso foi utilizado o modelo ModSimP32, que é basicamente um modelo de simulação e otimização em rede de fluxo. Como dados de entrada do ModsimP32, estão as séries de vazões históricas ou sintéticas e os valores das demandas existentes na bacia. Como se pretendia realizar um estudo a longo prazo, foi necessário a obtenção de séries hidrológicas mais longas, portanto utilizou-se um modelo multivariado AR(1) para gerar novas séries. Para as simulações realizadas, verificou-se que em períodos secos não é possível atender a todas as demandas integralmente e ainda manter as vazões ecológicas no rio, para as regiões de Paulínea e Piracicaba. / Nowadays, the water became the reason of conflicts of the society, due to the increase of the demands and the implicated qualitative aspect. The basin of the river Piracicaba is a highly developed area, with high indexes populations anel it presents dispute of water among several users. Therefore it took place an analysis to verify the amount of water of the basin, relating the demands of water, current and future. For that the model ModSimP32 was used, that is basically a simulation and optimization model in supply network. Among the data of entrance of the ModsimP32, they are the hydrologic series. Therefore it was used of a multivariate model AR(1) to generate new series. For the accomplished simulations, it was verified that is not possible to assist the whole ones integrally the demands in dry periods and still to maintain the ecological flow in the river, for the areas of Paulínea and Piracicaba.

The objective of this study was to improve the operation of the classical semiautogenous and ball milling circuit also known as the SABC circuit. In order to achieve this goal, the challenges around this circuit were identified as the formation of critical sized material in a SAG mill. The size class considered for the critical sized material also known as pebbles was -100+23 mm. The attainable region (AR) method was used as an optimisation technique for the generated results using a computer simulation programme. MODSIM® demo version 3.6.22 is ore processing simulator that was used. The research was divided into two sections, the first being the variation of feed flow rate ranging from 50 – 150 tph and ore feed size ranging between 100 and 600 mm. The second section compared the variation of the operating parameters of the SAG mill, which were mill filling, ball filling, ball size and mill speed. The AR technique graphically presented the results which indicated the best operating conditions to minimise pebble formation. The effects of mill filling on a SAG mill indicate that a higher filling produces lower pebbles. Lower pebble generation also was observed at a higher ball filling. The influence of ball size indicated that the larger ball size was more effective in the reduction of pebbles. For mill speed the media displayed two common mode operations namely cascading at a low speed of 65% and cataracting at higher speed of 75%. The higher speed generated the least pebbles. / College of Engineering, Science and Technology / M. Tech. (Chemical Engineering)

Desenvolveu-se uma metodologia para integração de dois modelos matemáticos, um de quantidade de água, em rede de fluxo, denominado ACQUANET com outro de qualidade de água, de uma dimensão, aplicado a represas, denominado CE-QUAL-R1. Para tanto, foi elaborada uma INTERFACE em linguagem de programação possibilitando que as vazões resultantes, simuladas pelo ACQUANET, servissem como dados de entrada ao CE-QUAL-R1 para simular a distribuição vertical das variáveis de qualidade de água em uma represa. Essa metodologia foi aplicada à Represa Jaguari-Jacareí no Sistema Cantareira em São Paulo, Brasil, como alternativa de gerenciamento quali-quantitativo, além de possibilitar o uso de retirada de água em diferentes profundidades, através da operação de tomadas d’água seletivas existentes. / A methodology was developed for the integration of two mathematical models, one of water quantity in network named ACQUANET with other of water quality, in one dimension, applied in revervoirs, named CE-QUAL-R1. In order to achieve this goal, an INTERFACE was developed to link the CE-QUAL-R1 with ACQUANET outflow results. It should be highlighted that ACQUANET has been used for beginning values of CE-QUAL-R1 and to simulate the vertical distribution of water quality variables in a reservoir. This methodology was applied to Jaguari-Jacarei Reservoir, of Cantareira System in Sao Paulo, Brazil, as a management quality and quantity tool of the system and it showed the use possibility of withdrawal of outflowing waters from different depths, through existing selective withdrawals ports operation.

Desenvolveu-se uma metodologia para integração de dois modelos matemáticos, um de quantidade de água, em rede de fluxo, denominado ACQUANET com outro de qualidade de água, de uma dimensão, aplicado a represas, denominado CE-QUAL-R1. Para tanto, foi elaborada uma INTERFACE em linguagem de programação possibilitando que as vazões resultantes, simuladas pelo ACQUANET, servissem como dados de entrada ao CE-QUAL-R1 para simular a distribuição vertical das variáveis de qualidade de água em uma represa. Essa metodologia foi aplicada à Represa Jaguari-Jacareí no Sistema Cantareira em São Paulo, Brasil, como alternativa de gerenciamento quali-quantitativo, além de possibilitar o uso de retirada de água em diferentes profundidades, através da operação de tomadas d’água seletivas existentes. / A methodology was developed for the integration of two mathematical models, one of water quantity in network named ACQUANET with other of water quality, in one dimension, applied in revervoirs, named CE-QUAL-R1. In order to achieve this goal, an INTERFACE was developed to link the CE-QUAL-R1 with ACQUANET outflow results. It should be highlighted that ACQUANET has been used for beginning values of CE-QUAL-R1 and to simulate the vertical distribution of water quality variables in a reservoir. This methodology was applied to Jaguari-Jacarei Reservoir, of Cantareira System in Sao Paulo, Brazil, as a management quality and quantity tool of the system and it showed the use possibility of withdrawal of outflowing waters from different depths, through existing selective withdrawals ports operation.

This study investigated the influence of the attainable region technique to ball milling as applied in reactor technology. Flow rate, ball filling, mill speed, ball size and mill density were varied. When each was varied, the rest of the parameters were kept constant in-order to determine the influence of each parameter on the process of milling. Selection function and breakage function parameters were selected for the mill model. These were kept constant for all four circuit configurations: open milling circuit, normal closed circuit, reverse closed circuit, and combined closed circuit. Flow rate was varied from 10 tph to 150 tph. It was observed that in all circuit configurations the optimum results were obtained from 90 tph upwards. When ball filling was varied, the optimum results were obtained between 30 % and 40 % of ball filling. At this range the mill is neither experiencing under-filling nor over-filling. When the mill speed was varied, at 60 – 80 % of critical speed the product specification was achieved and for grinding balls, sizes of between 60 mm and 90 mm yielded the optimum results. Varying the mill density resulted in insignificant changes. From the results, the combined closed circuit produced more of the product specification. / School of Engineering / M. Tech. (Engineering: Chemical)