Examensarbeten för masterexamen // Master Theses
Länka till denna samling:
Browse
Browsar Examensarbeten för masterexamen // Master Theses efter Program "Innovative and sustainable chemical engineering (MPISC), MSc"
Visar 1 - 20 av 29
Sökresultat per sida
Sortera efter
- PostAdvanced Process Integration Aspects of Tubular Reactors(2013) Olsson, Helena; Chalmers tekniska högskola / Institutionen för energi och miljö; Chalmers University of Technology / Department of Energy and EnvironmentThe chemical industry had the third largest energy demand of Swedish industry in 2011. One way to lower the energy requirement is to increase the energy efficiency of a process through energy integration and therefore lower the demand of primary energy. Chemical reactors are often the part of a chemical process where most of the primary energy is consumed such as in form of combustion heat, or where large amount of heat is available which can for instance used for steam production for power generation, heating or even for cogeneration. The choice of the reactor design is a crucial aspect that can influence significantly the share of energy cost in the overall process costs. This master’s thesis was partially motivated by the 2011 years course project in the Preliminary Plant Design within the master program in Innovative and Sustainable Chemical Engineering at Chalmers University of Technology. The outline of the project was to design a plant for production of methyl-ethyl-ketone, MEK, where the suggested reactor design for the plant had a very high primary energy demand due to reactor specifications. This master’s thesis has investigated important aspects for energy integration of tubular reactors and how Pinch Analysis can be used to find the optimal reactor design. Two case studies have been performed to achieve this, one for an endothermic reaction and one for an exothermic reaction. The endothermic case study was based on the production of MEK and one intermediate target was to find a better reactor design than the design in the course Preliminary Plant Design. The exothermic case study was based on the methanation process in production of synthetic natural gas. The results from the case studies showed that pinch analysis is not a sufficient tool to evaluate the best choice in utility temperatures for heated or cooled reactors because of the intrinsic relation between heat transfer and kinetics cannot be taken into account rigorously when selecting different type of utility streams. This makes it impossible to define an energy target for the utility consumption of a tubular reactor system independent of the specific design. Nonetheless pinch analysis can be used to evaluate energy consequences of different reactor design thus allowing to identify the most suitable configuration based on the trade-off between investment and energy targets.
- PostCapture and utilization of carbon dioxide from the lime kilns of a kraft pulp mill for bio-methanol production: Case study at the market pulp mill Södra Cell Mönsterås(2023) Lindström, Vendela; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Chalmers University of Technology / Department of Space, Earth and Environment; Harvey, Simon; Svensson, Elin; Larfeldt, JennyBio-methanol is a valuable product that can be used for a variety of applications. Södra Cell Mönsterås, a pulp mill situated in southern Sweden, currently produces bio-methanol as a byproduct from the pulping process. However, methanol could also be produced through carbon capture and utilisation (CCU), i.e. by capturing carbon dioxide from point emission sources at the plant site and reacting it with hydrogen. This master thesis aims to investigate the potential integration of such a CCU concept at Södra Cell Mönsterås, thus potentially increasing bio-methanol production on site. The carbon dioxide was assumed to be captured through post-combustion capture using an amine-based absorption process. For energy-efficient carbon dioxide capture, a high concentration of carbon dioxide in the flue gas is favorable. Consequently, the lime kilns of the mill were selected as potential carbon dioxide sources, since they have the highest concentration of carbon dioxide in the flue gases of the emission sources at the pulp mill. A 90 % capture rate of carbon dioxide from the flue gases of both kilns was assumed, corresponding to a total of approximately 230 kton/year of captured biogenic carbon dioxide, which could be used to produce 170 kton/year of bio-methanol, requiring 30 kton/year of hydrogen. For the energy balances, two levels of specific heating demands for the carbon capture process were evaluated. As a conservative estimate, a literature value for a standard capture process using a mono-ethanolamine (MEA) absorption solvent applied to typical combustion flue gases was considered, with a heating demand of 3600 kJ/kg carbon dioxide captured. To get an estimate of potential improvements with a more optimized process design and better performing solvents, a lower specific heating demand of 2900 kJ/kg carbon dioxide captured, which has been reported for the solvent blend amino-2-methyl-1-propanol/piperazine (AMP/PZ), was also evaluated. This resulted in a heating demands of 230 GWh/year and 186 GWh/year for the higher and lower value, respectively, when capturing 90 % of the carbon dioxide from the lime kilns. The results also indicate that the heating demand for the whole CCU concept can be covered by steam that could be made available from the mill, more specifically by bypassing the condensing turbine. However, the electricity demand for the electrolyser seems to be a more limiting factor. Production of 30 kton/year of hydrogen requires an elctrolyser with a total capacity of 260 MW of electric power input, corresponding to an electricity demand of 2.2 TWh/year. This can be compared to the current electricity consumption of the whole pulp mill, which was 0.7 TWh in 2021. One possibility could be to size the capture plant for maximum (90%) capture from both lime kilns, but only use part of the captured carbon dioxide for methanol production and sell the surplus or send it to permanent storage. Thus lowering the electricity demand for production of hydrogen at site.
- PostCarbon dioxide capture using phase changing solvents - A comparison with state-of-the-art MEA technologies(2017) Askmar, Johan; Carbol, Jonathan; Chalmers tekniska högskola / Institutionen för energi och miljö; Chalmers University of Technology / Department of Energy and EnvironmentIn order to combat climate change Carbon Capture and Storage (CCS) has been suggested as an important tool to reduce the emissions of the potent greenhouse gas carbon dioxide (CO2). CCS can be used for large point source emissions of CO2, like power plants using fossil fuels, where it removes CO2 from the flue gases. This is most commonly done through the use of chemical absorption of CO2 in an amine solvent called monoethanoloamine (MEA). After the absorption the solvent is regenerated and the captured CO2 is released in a stripping column, a process which is both expensive and energy consuming. The energy used for the regeneration reduces the output from the power plants imposing an energy penalty of up to almost 30%. Reducing the energy requirement in the carbon capture process is crucial in order to make CCS commercially viable, and one possible way to do this is to use so-called phase changing solvents. This new family of molecules are amines that in the presence of water and CO2 exhibit a triple phase vapour-liquid-liquid equilibrium. The liquid mixture separates into two liquid phases where one has a high CO2 and amine content while the other phase consists mainly of water. The two liquids can be separated without the addition of energy in a decanter so that only a part of the flow is sent to the stripper. This opens up new possibilities for the design of absorption/desorption flowsheets for solvent based CCS that may reduce the total energy requirement of the process. Creating flowsheets that can be used for future reference and identifying important aspects and challenges of simulating CCS processes with phase-changing solvents is of importance. Apart from this the aim of this project is to achieve a regeneration energy requirement below 2.0 GJ/- tonne CO2 captured and reduce the operating cost by 80% compared to an MEA reference process. The project consisted of three parts where the first part was a literature study to identify and select solvents that exhibit the desired phase changing properties followed by property estimation of these solvents in Aspen Plus®. The estimated properties were also validated using reference values. Secondly, different flowsheets were created identifying different layout possibilities and a sensitivity analysis was performed investigating the impact of the biggest uncertainties in assumptions made as well as differences in operating conditions. The third part was an economic and environmental assessment of the process and a comparison with an MEA reference process. In a previous study ten potential phase changing solvents, referred to as D1-D10, had been identified. From this list the solvents that were chosen for this project v were (3-[1-(dimethylamino)propan-2-yl]aminopropyl)dimethylamine, called D6, and 2-[2-(methylamino)ethyl]aminoethan-1-ol, called D9, based on their phase equilibrium. Of these two solvents, D9 overall showed the most promising results. A base case flowsheet layout and two different variations were considered, where both variations reduced the energy demand compared to the base case. Flowsheet Layout 1 where the decanter placement was changed from after to before the heat exchangers showed the largest decrease in energy consumption. The best result was thus obtained from D9 using Layout 1 which has an operating cost of 30.10 EUR/tCO2 captured, a reduction of over 37% compared to the MEA process. The regeneration energy demand for this process was 1.46 GJ/tCO2 captured, which is well below the target. The three environmental indicators used (Cumulative Energy Demand, Global Warming Potential and ReCiPe) all point to the processes using D9 being more environmentally friendly than MEA. The results for D6 are not as promising as for D9, which is mostly due to the high reboiler duty of the D6 processes. When using flowsheet Layout 1 the reboiler duty is decreased also for D6 bringing all environmental metrics to levels lower than for MEA, although not as low as D9. However the operating cost is still high which is due to the high price of D6 offsetting the benefits of reduced heat demand.
- PostCharacterization of fuel mixing in a fluidized bed cold model: An experimental study using magnetic particle tracking(2021) Ahlgren, Jon; Wageborn, Pontus; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Pallarès, David; Guío-Pérez, Diana CarolinaAn experimental study of the mixing of fuel particles in fluidized beds has been conducted. The study was performed using magnetic particle tracking sensors to track a magnetic tracer particle in a downscaled cold model of an industrial boiler. The fluid dynamical scaling was applied using Glicksman’s simplified scaling laws. Mixing characteristics of the tracer particles were evaluated and mixing cells were studied. The lateral dispersion coefficient was calculated using Einstein's equation for Brownian motion and measuring the residence time in the mixing cells for three different bed heights. This resulted in lateral dispersion coefficient values in the range of 3.3 − 7.6 × 10^(−3) m^2/s for mixing cell sizes between 0.04 and 0.08 m. Dispersion calculations based on mixing cells were performed using larger mixing cell size estimations (between 0.131 and 0.214 m), and the calculated lateral dispersion values converged towards the same values as the Brownian motion calculations when time filtering was applied. By comparing dispersion data from 20 minute and 5 minute measurements it was concluded that the shorter 5 minute measurements gave enough data to properly characterize the mixing. Movement patterns similar to mixing cells could be observed although they were disrupted by the construction of the cold model units distributor plate. No mixing cells unaffected by walls or the mentioned disruption were identified. The tracer particle did not cover the entire bed at the low bed height which indicates that defluidized zones were present.
- PostDevelopment of a decision support tool for operational optimization of the steam utility system at Preemraff Lysekil(2018) Kobjaroenkun, Sekpoom; Gunnarsson, Johan; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Chalmers University of Technology / Department of Space, Earth and Environment
- PostDynamic process of steam in a super critical CFB boiler(2018) Stanicic, Ivana; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Chalmers University of Technology / Department of Space, Earth and EnvironmentCFB technology has gained more attention over the past few years. Most probably due to its efficiency and ability of achieving low emissions. New strict governmental regulations regarding emissions are continuously imposed which makes CFB boilers a promising candidate for future industries. One way to facilitate the implementation of CFB boilers is by making it cheap option. Currently these boilers are equipped with expensive urgent feed water systems for boiler safety, in case of electricity loss. Since there are no accident records this equipment is still in controversy. This thesis analyses the physical process of steam in a 350 MW super critical circulating fluidized bed boiler during sudden electricity failure. By obtaining information about the dynamic process of steam properties it will be possible to estimate the necessity of the urgent water feeding system in future applications. With some simplifications a three dimensional model was created to solve energy equations. The model includes thermal processes like conduction, radiation and convection of steam, bulk material and air. The final model predicts the dynamic progress of these. The highest temperatures achieved is located in the bottom of the furnace, the conductive part, and lies around 875 K which is slowly continuing to increase. However, this temperature lies in the acceptable span for wall conditions which indicates a possibility for economic savings. Further studies need to be conducted in order to conclude whether the emergency system can be neglected.
- PostDynamic Study of LNG Fuel Gas Supply Systems(2019) Botha, Monica; Quint, Gustav; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Chalmers University of Technology / Department of Space, Earth and EnvironmentLiquefied natural gas (LNG) is an alternative fuel which is gaining popularity in the marine sector due to tougher emission regulations coming into effect in the year 2020. Due to the increased demand of marine LNG fuel, new larger scale gas supply systems are being developed. In this report, dynamic simulations of two new marine LNG fuel gas supply systems have been developed in HYSYS to study the control, buffer capacity and characteristics of the new systems. The evaluation has mainly been made by simulating various critical scenarios, such as emergency loadup, emergency shutdown, compressor start and low operating pressure. A control strategy has been made for the pumps and the compressor but not for the minimum flow line. Findings from the simulations show that the control strategy is able to handle most system changes without disruptions to the engines. It was also observed that the use of a buffer vessel alleviated disturbances but it was not deemed to be a necessity in a well tuned system.
- PostEnergy Analysis of Hemicellulose Extraction at a Softwood Kraft Pulp Mill - Case Study of Södra Cell Värö(2013) Bood, Jon; Nilsson, Linus; Chalmers tekniska högskola / Institutionen för energi och miljö; Chalmers University of Technology / Department of Energy and EnvironmentThe Swedish pulp and paper industry is struggling with lower revenues and high raw material cost. The implementation of biorefinery concepts is not only interesting from a diminishing fossil feedstock perspective but also as a way of creating new revenue streams for the pulp and paper industry. Production of dissolving pulp would be beneficial both due to the higher market price of the pulp but also since the hemicellulose extracted could be upgraded to value-added by-products. The conversion from Kraft to dissolving pulp production has been evaluated in a case study of Södra Cell Värö pulp mill. An energy analysis has been performed with pinch technology and the potentials for steam savings and electricity production have been quantified for different levels of process integration. It has been shown that the softwood Kraft pulp mill at Värö can be converted to a dissolving pulp mill by introducing extraction of hemicelluloses prior to the digestion step. The proposed dissolving pulp plant would not only be self sufficient energy wise but in fact be able to produce both more electricity and excess steam than today. The most rigorous process integration proposed enable 71 MW electricity production as well as a surplus of 38 MW LP steam. A less rigorous option with lower investment cost can maximize the electricity production of the current back pressure turbine to 62 MW (from the current capacity at 51 MW), while leaving 28 MW of LP steam available for use elsewhere. The future saw mill and pellet factory, which is planned to be built close by, will require 20 MW of LP steam which has to be subtracted when assessing the steam surplus. Furthermore there might be an additional demand of LP steam for upgrading the extracted hemicellulose.
- PostEnergy Efficiency Study at a Softwood Kraft Pulp Mill(2017) Pedersén, Alexandra; Larsson, Anton; Chalmers tekniska högskola / Institutionen för energi och miljö; Chalmers University of Technology / Department of Energy and EnvironmentIn order to achieve an increased energy efficiency within the Swedish industry the law about energy auditing in large companies has recently been implemented. The law is based on the EU Energy Efficiency Directive. The law requires that affected companies performs an energy auditing every fourth year. Besides mapping of energy supply and consumption, an analysis is required to be performed where suggestions for energy efficiency measures and related cost estimations are to be included. The result must thereafter be reported to the Swedish Energy Agency. The pulp and paper industry accounts for more than 1/6 of Sweden’s total energy usage which indicates the importance to study this specific industry from an energy perspective. This since implementation of energy efficiency measures can potentially result in large energy savings which can eventually result in a reduced climate impact. Södra Cell Värö is a Softwood Kraft Pulp Mill which has recently experienced a large expansion and reconstruction. Energy efficiency measures, such as a new secondary heating system, were included to improve the heat recovery within the process. In this master’s thesis, an energy efficiency study has been performed in order to investigate whether additional measures can be implemented to save energy at the pulp mill. Pinch analysis was utilized as a method to determine the potential for energy savings of the process. The result of the analysis shows that it is theoretically possible to save 66.7 MW steam, which corresponds to 23 % of the total steam consumption at the pulp mill. However, to achieve these savings a maximum energy recovery network is required which is rarely applied in industry due to technical limitations and that it is not feasible from an economic perspective to achieve such a heat exchanger network. Retrofit suggestions were proposed that utilized an identified excess heat in terms of warm water, and moist air from the drying machine. By doing so, the energy efficiency in the existing heat exchanger network was improved resulting in 9.1 MW steam savings. By also utilizing heat from flue gases from the lime kiln and the bark boiler, it was shown that a total of 19.5 MW steam savings could be achieved. Furthermore, it was found that the saved steam could for example be utilized to generate additional green electricity in the newly installed condensing turbine which in turn would enable an increased delivery of electricity to the grid by 41 GWh/yr. Another alternative that was investigated was to save fuel in the form of bark by reducing the steam production of the bark boiler. The result shows that it would be possible to save 144 GWh/yr bark. The potential for the process to deliver an increased amount of district heating was investigated and the result indicates that the theoretically maximum heat load for district heating delivery is 33 MW after the suggested energy efficiency measures have been implemented.
- PostEvaluation of Electric and Hybrid Steam Generation for a Chemical Plant under Future Energy Market Scenarios(2019) Kerttu, Malin; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Chalmers University of Technology / Department of Space, Earth and EnvironmentThe reduction of greenhouse gas emissions is one of the largest environmental challenges in modern time, in particular the reduction of fossil CO2. The industry is a large source of CO2 emissions and the chemical process industry will be in focus of this master thesis project. Nouryon´s site in Stenungsund is dependent on steam for their production of specialty chemicals. Steam production is energy demanding and fossil-based gases are used as fuel for the process. Nouryon’s ambition is to reduce their carbon footprint and therefore different alternatives for producing steam is investigated. The aim of this master thesis project is to investigate the possibility to implement new technologies for steam production and to identify options to reduce the fossil CO2 emissions in the future at the lowest possible cost. Power-to-heat is one promising concept of electrification and therefore the implementation of an electric boiler is investigated. The other boiler of interest is a gas boiler, similar to the existing steam boiler on-site. A hybrid system of these two boilers is also considered. A model to calculate the total annualized cost at different capacities of the boilers was developed and used for optimisation in which the optimal capacities with the lowest total annualized cost were identified. A reference scenario for current market conditions, and two future scenarios were evaluated. A sensitivity analysis of the Capex was conducted to the reference scenario in order to estimate how sensitive the model is to changes in Capex. Two future scenarios from World Energy Outlook 2017 were evaluated, one new policies scenario where current policies and announced polices were used to predict the future and a sustainable development scenario that reflects a future focusing on reducing the fossil CO2 emissions. In addition, a fixed capacity of 36 MW and 29 MW for an electric boiler and a gas boiler respectively, was compared to only having a gas boiler. Constraints on fossil CO2 emissions were implemented as well in this comparison between a fixed capacity and a gas boiler. Results from the model show that for the reference scenario and the new policies scenario a combination of technologies is the most profitable. In the sustainable development scenario a larger amount of electricity is incorporated and in the future only using an electric boiler is the most feasible. In comparison between the fixed capacity and a gas boiler the gas boiler is more expensive. When constraints to the CO2 emissions are added the cost for the fixed capacity becomes higher, since it incorporates more electricity. For the gas boiler the cost becomes significantly higher since it incorporates more bio-methane as fuel which has a higher cost than electricity.
- PostEvaluation of waste water incineration - A case study at AkzoNobel in Stenungsund(2017) Hallbäck, Maria; Chalmers tekniska högskola / Institutionen för energi och miljö; Chalmers University of Technology / Department of Energy and EnvironmentWaste incineration is an important part of many processes. Waste water incineration is however, not a common practice. This thesis has evaluated the performance of waste water incineration through a case study at AkzoNobel in Stenungsund. The primary aim of the process is the destruction of ammonia present in the waste water and ventilation gas feed streams. Secondary focus is to reduce the formation of NOx in the process. The waste water incineration process consists of two evaporators, one furnace, one dust cyclone, a separation step containing one quench and one separation unit, and lastly one electrostatic filter before the flue gases are emitted to the atmosphere via a flue gas fan and a stack. The evaluation was performed in three parts. The first part included mapping mass balances of the incinerator and the important units. The balances were based on real time data from the process. In the second part a chemical reaction modelling software was used to make a sensitivity analysis for the operating parameters with respect to the NOx formation. The third part consisted of experimental tests varying a set of parameters that were run over a period of around six days. The result of the mapping shows that the mass balance may be completed. The modeling results indicates that the most important parameters are temperature, amount of excess air and amount of water fed to the furnace. The Experimental test results are consistent with both literature and modeling outcome. The conclusion from this thesis work is that high temperature and high oxygen levels yields a low ammonia slip but increase the amount of NO formed. On the other hand, low temperatures and low oxygen levels gives low levels of NO but increase the amount of un-reacted ammonia in the stack. The flow of direct water also has a large effect on the performance of the furnace. The most important uncertainties are the ventilation gas composition and the amount of ammonia washed away in the quench step.
- PostEvaporation of Vinasse - Pilot Plant Investigation and Preliminary Process Design(2014) Larsson, Erik; Tengberg, Tommy; Chalmers tekniska högskola / Institutionen för energi och miljö; Chalmers University of Technology / Department of Energy and EnvironmentThe large dependency of fossil fuel have made alternative fuel e.g. ethanol increasingly popular. However, very little research and few publications were found on the after-treatment of the effluent, named vinasse, from the sugar-cane based ethanol production. The vinasse is produced in large quantities, because of the high volume ratio 1:10-15 of ethanol to vinasse and has been labelled an increasing environmental problem in South America. In a new proposed treatment process for vinasse, evaporation is used to concentrate the vinasse to be able to combust it in a boiler. In this thesis an experimental investigation was conducted on a pilot plant on the evaporation of vinasse. It was found possible to evaporate vinasse to a high dry solid content of at least 70 %. A critical region of particle accumulation and fouling tendencies were established. The most important physical parameters, dry solid content, viscosity, boiling point elevation and the heat transfer coefficient, were closely monitored and assessed in the experiments. For some of the properties, correlations were established as a function of dry solid content and temperature. The heat transfer was tested on a general model used in falling film evaporation, which was proven to not be valid for vinasse. However, a correlation for the heat transfer was developed. Since vinasse’s chemical composition resembles black liquor, these two were compared in this work and it was found that vinasse has lower viscosity and boiling point elevation at the same dry solids content. Thus, the results of the physical properties show that vinasse has better heat transfer and heat economy than black liquor. Based on the results from the experiments, a preliminary process design of the evaporation plant was established.
- PostExperimental investigation and modelling of sodium scale dissolution with black liquor - A pilot plant investigation(2013) Pettersson, Martin; Öhrman, Karin; Chalmers tekniska högskola / Institutionen för energi och miljö; Chalmers University of Technology / Department of Energy and EnvironmentIn this thesis the dissolution of sodium scales with black liquor has been investigated. The experimental part was carried out at a falling film pilot plant evaporator at the division of Heat and Power Technology at Chalmers University of Technology. In order to study the dissolution, a scaling layer was build up by evaporation of a saline solution which was then washed off by black liquor at different temperatures and flow rates. During washing the outgoing dry solid content of the wash liquid was measured along with the scaling layer thickness. The dissolution rate constant was found to be lower than in previous research carried out by dissolution with water at corresponding temperature and flow rate. The dissolution was dependant on the concentration difference between the saturation concentration and the concentration of the bulk liquid, the flow rate and the temperature of the washing liquid. The dissolution seems to be decreasing with increasing viscosity, but since temperature affects the viscosity, the solubility and the dissolution rate constant the effect of only the viscosity cannot be confirmed. In contrast to previous work the results suggests that the amount of wash liquid needed to dissolve a given amount of scales decreased with increasing temperature and flow which suggest that there might be beneficial to wash at a high wetting degree and at a high temperature.
- PostFeasibility study of implementing chemical looping combustion with BECCS: Process modeling and techno-economic analysis of a CHP plant at Skövde Energi(2023) Fortet Casabella, Judit; Chehade, Yunes; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Chalmers University of Technology / Department of Space, Earth and Environment; Mattisson, Tobias; Surywanshi, Gajanan DattaraoClimate change is an urgent worldwide issue that is mostly brought on by the accumulation of greenhouse gases, including CO2 in the atmosphere. Carbon Capture and Storage (CCS) technologies can play an important role in the decarbonization process. Chemical Looping Combustion (CLC) using biomass as a fuel can be combined with CCS to obtain negative emissions. This work is part of a collaboration between Chalmers University of Technology and Skövde Energi. The project includes performing a process modeling and techno-economic assessment of substituting one of the existing biomass CHP-plant boilers with a CLC-system; including the capture, compression, and liquefaction of the CO2 obtained. The general objective is to analyze the techno-economic feasibility of the CLC technology and give some guidelines for future implementation at Skövde Energi’s site. Additionally, the technology is compared with a post-combustion study using absorption with monoethanolamine (MEA), previously performed for the same combustion unit. After an initial review of the main literature and assessment of the current boiler operation, a base case simulation of the full-chain process is performed in Aspen Plus, including gas conditioning and liquefaction of the CO2. The process model considered heat integration of the different components together with the steam cycle for electricity production. Furthermore, a design of the fluidized bed CLC unit was conducted as well as a techno-economic analysis of the full-chain process, which was compared to the use of a post-combustion technology. Finally, through the interpretation of the obtained results, a discussion is performed on how the implementation of the technology would affect the current production and future considerations for implementation at other sites. The work concludes that the CLC technology would lead to a total capture efficiency of 97.5 %, capturing around 101 ktonne CO2 and obtaining a capture cost of around 800 SEK/tonne CO2 captured, which includes the purchase and installation of equipment. This is considerably lower than what is expected in a post-combustion system, with costs of about 1,100 SEK/tonne CO2 captured. The reason for this is due to the lower amount of energy and equipment needed for the capture process. Excluding installation costs, a capture cost of around 330 SEK/tonne CO2 captured was obtained, which is slightly higher than the 200 SEK/tonne CO2 of a 1000 MWth design by Leckner and Lyngfelt.
- PostIdentifying barriers and enablers of the biogas value chain(2018) Vagiström, Sara; Whetstone, Alice; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Chalmers University of Technology / Department of Space, Earth and Environment
- PostInvestigation of machine learning approaches in process industry(2020) Aijaz Farooqi, Arslan; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Harvey, Simon; Langner, Christian; Svensson, ElinToday, industry is in continuous development, with digitalisation occurring at an increasing rate. Industry 4.0 and Internet of Things are two common expression which both concern the development of industry with focus on artificial intelligence (AI). Studies have shown the benefits of applying various AI techniques in industry, e.g. more accurate fault diagnostics and better estimation of remaining useful life of process equipment. The main aim of this master’s thesis project was to investigate and apply machine learning methods as solutions to challenges identified in the process industry, and evaluate the outcome. A literature review was first conducted to gain insight in the process industry and its current issues for which machine learning techniques could be applied. Thereafter, a study visit to Södra Cell’s market pulp mill in Mönsterås was carried out, during which a case study suitable for data-driven modeling was identified. The case study involved one of the cooling towers at the mill, as well as process units in close proximity to the cooling tower, for which input and output variables were defined. The plant operators suspected fouling to negatively affect the performance of the cooling tower, and asked if the system could be modeled to identify the fouling effect. This hypothesis was investigated by modeling the system with two neural network architectures; Multilayer Perceptrons (MLP) and Long Short-Term Memory (LSTM), the latter being a type of recurrent neural network (RNN). The neural networks were modeled based on data extracted from four years with a time resolution of one hour. Comparing the results of the MLP networks with the LSTM networks led to the identification of recurrency, which in this case referred to the fouling effect. Out of all output variables, conductivity was set as the target variable, or the variable of extra interest, as it was assumed to directly correlate with the amount of fouling occurring in the cooling tower system. As fouling occurs, there is an increase of metal ions in the recirculating cooling stream, leading to an increase in the measured conductivity. The results showed that all LSTM networks, except for one, obtained better model accuracy than the MLP networks. The best MLP network yielded a value of Mean Squared Error (MSE) MSEMLP2 = 0.003067 while the best LSTM network, LSTM 7, yielded MSELSTM7 = 0.001335. Furthermore, all LSTM networks, regardless of overall performance, modeled the conductivity output better than the MLP networks. The results give a clear indication that there is some recurrency present in the modeled system, which confirms the plant operators’ hypothesis of fouling ocv curing in the system. The statistical model yielded in this thesis work could then be used as groundwork for future projects. By accurately predicting the performance of the cooling tower system, investment decisions and optimisation of operational conditions could be carried out.
- PostLocal infrastructures for CCS clusters: A case study of two CHP plants in Gothenburg(2021) Johansson, Emelie; Ignell, Victoria; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Normann, Fredrik; Karlsson, SebastianClimate change is a global problem and measures to reduce CO2 emissions are required. One acknowledged measure, both in Sweden and globally, is carbon capture and storage (CCS). This thesis investigates economic benefits for infrastructure cooperation in CCS implementation including solvent regeneration, liquefaction and transport to an intermediate storage. Two combined heat and power (CHP) plants in Sävenäs owned by Renova and Göteborg Energi were investigated as a case study. The capture plants were modelled in Aspen Plus as post-combustion processes with monoethanolamine as a solvent. Heat demand and other utilities were quantified to decide the impact on the heat and electricity production at each plant. Based on the utility demand and equipment need, an economic analysis was performed. The cost for CO2 liquefaction and transport were estimated. Four scenarios for the operation of the CHP plants including maintained fuel usage, maintained district heat delivery, collaboration to maintain district heat delivery and reduced capture rate, were compared. The work concludes that, depending on scenario, the capture cost for separate plants at Renova and Göteborg Energi is 39-46 and 80-82 €/ton CO2, respectively. For a capture plant with a shared infrastructure, the capture cost is 45-52 €/ton CO2. The result shows a possible district heat recovery of 70% from the capture plant, which is important to decrease the cost of the heat demand. The heat integration with the steam cycle is important for the capture cost. Use of primary steam leads to higher variable OPEX, due to higher reductions in electricity generation, but lower impact on district heating generation, than the use of an extracted stream from the turbine. The plant utilisation is more important for the specific capture cost than the size of the CHP plant. Depending on the allocation of the cost between the companies, the possible savings are between 0.2-1.0 M€/yr corresponding to 2-5% of the total cost. Therefore, there are small economic benefits with a shared process where shared liquefaction has the most potential.
- PostMacroalgae as a renewable resource for a fossil-independent region - Analysis of the innovation system of macroalgae in Western Sweden(2017) Lühmann, Taina; Chalmers tekniska högskola / Institutionen för energi och miljö; Chalmers University of Technology / Department of Energy and EnvironmentEutrophication 1 and the need to produce materials from renewable resources are sustainability challenges that we are currently presented with. One solution for these issues is the cultivation of algae, because it provides ecosystem-services such as mitigation of eutrophication and can be processed into a variety of inherently biobased products. The opportunities for macroalgae cultivation that the long coastline on the Swedish West Coast offers have however hardly been seized. Therefore, this thesis aims at identifying the developments that have taken place and the factors that are hindering or promoting the development, resulting in a proposal of policy changes required for further development. The overarching aim of this thesis is to take on complex sustainability challenges in the setting of the Challenge Lab at Chalmers University of Technology. The identification of a sustainability challenge by using the backcasting approach is the first part of this thesis with the second part of finding a strategy towards closing the sustainability gap. Opinions and insights from different stakeholders were the main source of information, gathered during ten interviews and one workshop. Complementary actions were researching existing publications and reports on the technology of macroalgae as well as identifying connected activities in Western Sweden. The data analysis was carried out based on the framework of the Technological Innovation System. The study shows that the development of macroalgae is in an early stage, but emerging entrepreneurial activities and increasing knowledge development are moving the development forward. Additionally, the support from funding is what has been enabling the development and is necessary to generate incentives to induce new activities and to further advance the knowledge base. However, it is necessary to simplify the process to obtain a cultivation permit and to provide subsidies for ecosystem services to overcome the barriers that legislative issues pose. These are necessary changes in order for macroalgae to unfold its potential to develop into a noteworthy technology in Western Sweden.
- PostMapping of Heat Distribution Networks at Sawmills and Modeling of their Heat Losses and Pressure Drops(2013) Garberg Löfving, Ellen; Chalmers tekniska högskola / Institutionen för energi och miljö; Chalmers University of Technology / Department of Energy and EnvironmentThrough years of research and new investments in boilers and dryers at sawmills, the heat distribution networks (HDNs) have been neglected. Very little literature on HDNs at sawmills is available. More extensive research has been performed on district heating networks. Due to its similarities to an HDN, some of the performed research is of relevance, but a more thorough analysis of HDNs is required. Through interviews with employees at sawmills, the current situation of Swedish sawmills has been mapped. The sawmills are different in some ways, but they also have important similarities. In particular, both investigated sawmills lack of proper documentation of their HDNs. There is also evidence of outdated sections of the pipe systems, which indicates potential for improvements in performance of the HDN. A mathematical model has been developed with available information from the interviews and analysis of relevant literature as a background. The model is used to illustrate improvement potential for an HDN by comparing current heat losses and pressure drops of an actual HDN with estimates using Matlab as a simulation tool. The Matlab programme is flexible with many user defined parameters and is capable of handling many variations in the investigated HDN. The simulation results show a theoretical potential for the investigated sawmill at Mörlunda to decrease their heat losses from circa 970kW to 91kW. The model is very sensitive and requires detailed input data to make accurate estimates. However, the simulations illustrate several useful trends for factors affecting the performance of an HDN at a sawmill.
- PostModeling of Biomass Flow in a Novel Multi-staged Fluidized Bed Concept(2018) Johansson, Martin; Chalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskap; Chalmers University of Technology / Department of Space, Earth and EnvironmentA mathematical description of the axial mixing of biomass in bubbling fluidized beds was developed and implemented into an already existing mathematical model. Based on the developed model the performance of novel multi-staged fluidized bed concept was investigated. The novel concept works by inserting a chamber into an already existing unit and in that way introducing two reaction zones that can communicate with each other via a slit at the bottom of the walls delimiting the reaction zones. The implementation of the novel concept enables pyrolysis and char conversion to occur in separate environments. Based on simulations it was shown that the results are very sensitive to the pyrolysis kinetics, why more studies of the kinetics would be of interest. Furthermore, it was shown that novel concept could be controlled by varying the pressure difference between the reaction zones. The fluidization velocity could also be used as a means for control, but for too big slit heights, the novel concept becomes insensitive to changes in fluidization velocity.