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  • 1.
    Iplik, Esin
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Linde GmbH.
    Energy savings for petroleum processing: Using mathematical models, optimal control and diagnostics2023Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Petroleum products are widely used as an energy supply, and the total production capacity of petroleum refineries is quite high. In this thesis, an energy intensive refinery process, hydroprocessing, is selected and evaluated in terms of its energy loss contributors. Digital solutions are discussed and demonstrated to reduce losses. Both hydrotreatment and hydrocracking processes are included in the evaluation since both require elevated temperatures due to the relevant reactions. While the former is the removal of undesired atoms, the latter is the production of short chain hydrocarbons from heavy oil. Both these processes contribute to cleaner fuel production.

    When these processes are carried out in fixed bed reactors, the catalyst ages over time, slowing the reactions. Understanding the changes in system dynamics enables the control system to calculate the necessary temperature adjustments to facilitate stable product quality. The usual response is increasing the temperature, which adds to the heat load. If reaction rates are known, the temperature increase can be kept to a minimum. Obtaining real-time feed quality information can aid flexible feed processing refineries intensely. With real-time feed characterization, it is possible to use a feed forward model predictive control system to optimize reactor temperatures. Therefore, for varying crude oil quality, the control system can estimate the minimum temperature requirements for the product to be in the desired quality interval. Additional notice should be given to the temperature sensors as they supply data to the suggested control architecture. Wrong measurements threaten the optimality of the estimated control response. Faulty sensors should be detected and replaced to minimize the risk and collect correct data.

    Observations made in this thesis show the possible energy gain for hydroprocessing by understanding the aging catalyst, soft sensor installation, feed forward model predictive control, and sensor fault detection. Hydroprocessing is a relevant topic for biorefineries. Although the demonstrations in this work are only for petroleum refineries, the suggested methods can be used in biorefineries as well as integrated co-processing petroleum and biorefineries.

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  • 2.
    Iplik, Esin
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Aslanidou, Ioanna
    Mälardalen University, School of Innovation, Design and Engineering, Innovation and Product Realisation.
    Kyprianidis, Konstantinos
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Hydrocracking: A Perspective towards Digitalization2020In: Sustainability, E-ISSN 2071-1050, Vol. 12, no 17, article id 7058Article in journal (Refereed)
    Abstract [en]

    In a world of fast technological advancements, it is increasingly important to see how hydrocracking applications can benefit from and adapt to digitalization. A review of hydrocracking processes from the perspective of modeling and characterization methods is presented next to an investigation on digitalization trends. Both physics-based and data-based models are discussed according to their scope of use, needs, and capabilities based on open literature. Discrete and continuous lumping, structure-oriented lumping, and single event micro-kinetic models are reported as well as artificial neural networks, convolutional neural networks, and surrogate models. Infrared, near-infrared, ultra-violet and Raman spectroscopic methods are given with their examples for the characterization of feed or product streams of hydrocracking processes regarding boiling point curve, API, SARA, sulfur, nitrogen and metal content. The critical points to consider while modeling the system and the soft sensor are reported as well as the problems to be addressed. Optimization, control, and diagnostics applications are presented together with suggested future directions of interdisciplinary studies. The links required between the models, soft sensors, optimization, control, and diagnostics are suggested to achieve the automation goals and, therefore, a sustainable operation.

  • 3.
    Iplik, Esin
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Aslanidou, Ioanna
    Mälardalen University, School of Innovation, Design and Engineering, Innovation and Product Realisation.
    Kyprianidis, Konstantinos
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Sensor fault detection with Bayesian networks2020In: Proceedings of The 61st SIMS Conference on Simulation and Modelling, SIMS 2020, 2020, Vol. 176, p. 373-378Conference paper (Refereed)
    Abstract [en]

    Several sensors are installed in the majority of chemical reactors and storage tanks to monitor temperature profiles for safety and decision-making processes such as heat demand or flow rate calculations. These sensors fail occasionally and generate erroneous measurement data that need to be detected and excluded from the calculations. However, due to the high number of process variables displayed in the chemical plants, this task is not trivial. In this work, a Bayesian network approach to detect faulty temperature sensors is proposed. By comparing the sensor measurements with each other, the faulty sensor is detected. A modular approach is preferred, and networks are created for 10 K temperature intervals to increase flexibility and sensitivity. Created networks can be adjusted for the operating temperature ranges; hence, they can be used for any catalyst and entire life cycle. The developed method is demonstrated on an industrial scale hydrocracker unit with 92 sensor couples installed in a series of reactors. From the investigated sensors, 16 of them showed a greater difference than the 2 K threshold chosen for the fault. In addition to that, 13 sensors showed an increasing temperature difference that may lead to a fault. Two scenarios were created to calculate the energy loss due to a faulty measurement, and a 5.5 K offset error was found to cause a 5.79 TJ energy loss every year for a small scale hydrocracker.

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  • 4.
    Karlsson, Christer
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Avelin, Anders
    Mälardalen University, School of Business, Society and Engineering.
    Dahlquist, Erik
    Mälardalen University, School of Sustainable Development of Society and Technology.
    New Methods for Adaptation to Degeneration in Process Models for Process Industries2009In: Chemical Product and Process Modeling, ISSN 2194-6159, E-ISSN 1934-2659, Vol. Vol. 4, no : Iss. 1, p. , Article 25.-Article in journal (Refereed)
    Abstract [en]

    The implementation of model-based control and diagnostics suffer strongly from the fact that models deteriorate as a function of process and sensor deterioration. Also, changes in the raw material (i.e. wood) may occur and often the process control is not addressing these variations in reality. It is thus vital for the model system to be robust in the sense that it is transparent and easy for the operator to maintain. Robustness is essential in many parts of the system, including measurement, process model validation, the ability of the model to adapt to changes in the process, optimization algorithms, and of course the model itself. In this paper, we first show three real-life applications of the utilization of models for diagnostics and control. Thereafter conditions for on-line adaptation of the models are discussed. The challenges when designing such a system are in achieving operator confidence, filtering of misleading measured data, adaptation of process parameters when the process parameters change, and combining validation of measurements and process models. These challenges are met by using a combination of physical and statistical models and methods based on them such as model predictive control (MPC) and parameter estimation. The model should be maintained by a qualified engineer who should be able to explain the system to the operator so that it is understood and confidence can be maintained.

  • 5.
    Kyprianidis, Konstantinos
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Skvaril, JanMälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Developments in Near-Infrared Spectroscopy2017Collection (editor) (Other academic)
    Abstract [en]

    Over the past few decades, exciting developments have taken place in the field of near-infrared spectroscopy (NIRS). This has been enabled by the advent of robust Fourier transform interferometers and diode array solutions, coupled with complex chemometric methods that can easily be executed using modern microprocessors. The present edited volume intends to cover recent developments in NIRS and provide a broad perspective of some of the challenges that characterize the field. The volume comprises six chapters overall and covers several sectors. The target audience for this book includes engineers, practitioners, and researchers involved in NIRS system design and utilization in different applications. We believe that they will greatly benefit from the timely and accurate information provided in this work.

  • 6.
    Mirmoshtaghi, Guilnaz
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Assessment on the impact of including hydrodynamics on the performance of kinetic based models for bubbling fluidized bed gasifiersManuscript (preprint) (Other academic)
    Abstract [en]

    One of the approaches to model fluidized bed gasifiers is to combine the reaction kinetics and bed hydrodynamics. The kinetic part of the model deals with the chemical reactions occurring in different steps of gasification while hydrodynamics of the bed gives more information about the physical phenomena inside the bed. In this paper two major fluidization models; two phase theory (TPT) and counter current back mixing (CCBM) and one kinetic rate model have been developed and compared in terms of accuracy in predicting product gas concentration and the generality of the model to different ranges of input parameters. The results show that including hydrodynamics of the bed as in TPT improves the accuracy of the kinetic rate model. TPT model can be used for air gasification in bubbling fluidized bed gasifiers while for steam gasification it needs further modification.

  • 7.
    Mirmoshtaghi, Guilnaz
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Biomass gasification in fluidized bed gasifiers: Modeling and simulation2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Using woody biomass as a resource for production of biofuel, heat and power through gasification has been studied for years. In order to reduce the cost of operating and to design the full-scale gasification plant developing a general model to be applicable for different ranges of input data with acceptable level of accuracy, is needed. In order to develop such model for the gasifier, as the main component in the process, three major models have been studied in this thesis; theoretical model (Equilibrium model), semi-empirical model (modified equilibrium model, kinetic combined with hydrodynamic model) and empirical model (statistical model).

    Equilibrium model (EM), shows low accuracy in predicting the content ofmajor components in product gas especially CH4 and CO. Therefore to improve the accuracy of prediction modification of EM is needed. Analyzing the semi-empirical approaches show that although the accuracy of EM can be improved, the generality of the modified models are still low. Therefore two new modified models have been developed. The first model is based on including data from wider range of operating condition to develop the empirical equation. The second model is based on combining QET and reaction kinetics for char gasification approaches. The first model decreases the overall error from 44% to 31% while the overall error of second model is decreased from 36% to 8%. Other semi-empirical model for fluidized bed gasifiers which is not equilibrium-based is developed by combining reaction kinetics with hydrodynamic equations. Investigating different hydrodynamic models show that combining two-phase-structure model with reaction kinetics for bubbling fluidized bed gasifiers improves the accuracy of the kinetic-only model.

    The third type of approaches, investigated in this thesis, towards developing a general model is the empirical model. This model has been developed based on Partial least square (PLS) approach. The PLS-R model show high level of accuracy within the specific range of empirical data used for developing the model. Further analysis on the experimental dataset by PLS-R model show that equivalence ratio (ER) is the operating parameter with the most significant impact on the performance of fluidized bed gasifiers. Optimizing the operation of fluidized bed gasifiers based on this model shows that high gas quality (high volume fraction of H2, CO and CH4 and low volume fraction of CO2), high carbon conversion and low tar yield is achieved when ER≈0.3, Steam to Biomass ratio≈0.7, moisture content≈9% and particle size≈3mm and olivine is the bed material. 

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  • 8.
    Mirmoshtaghi, Guilnaz
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Mälardalen Högskola.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    EVALUATION OF DIFFERENT BIOMASS GASIFICATION MODELING APPROACHES FOR FLUIDIZED BED GASIFIERS2016In: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 91, p. 69-82Article in journal (Refereed)
    Abstract [en]

    To develop a model for biomass gasification in fluidized bed gasifiers with high accuracy and generality that could be used under various operating conditions, the equilibrium model (EM) is chosen as a general and case-independent modeling method. However, EM lacks sufficient accuracy in predicting the content (volume fraction) of four major components (H2, CO, CO2 and CH4) in product gas. In this paper, three approaches—MODEL I, which restricts equilibrium to a specific temperature (QET method); MODEL II, which uses empirical correlations for carbon, CH4, C2H2, C2H4, C2H6 and NH3 conversion; and MODEL III, which includes kinetic and hydrodynamic equations—have been studied and compared to map the barriers and complexities involved in developing an accurate and generic model for the gasification of biomass.

    This study indicates that existing empirical correlations can be further improved by considering more experimental data. The updated model features better accuracy in the prediction of product gas composition in a larger range of operating conditions. Additionally, combining the QET method with a kinetic and hydrodynamic approach results in a model that features less overall error than the original model based on a kinetic and hydrodynamic approach.

  • 9.
    Mirmoshtaghi, Guilnaz
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Skvaril, Jan
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Campana, Pietro Elia
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    The influence of different parameters on biomass gasification in circulating fluidized bed gasifiers2016In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 126, p. 110-123Article in journal (Refereed)
    Abstract [en]

    The mechanism of biomass gasification has been studied for decades. However, for circulating fluidized bed (CFB) gasifiers, the impacts of different parameters on the gas quality and gasifiers performance have still not been fully investigated. In this paper, different CFB gasifiers have been analyzed by multivariate analysis statistical tools to identify the hidden interrelation between operating parameters and product gas quality, the most influencing input parameters and the optimum points for operation. The results show that equivalence ratio (ER), bed material, temperature, particle size and carbon content of the biomass are the input parameters influencing the output of the gasifier the most. Investigating among the input parameters with opposite impact on product gas quality, cases with optimal gas quality can result in high tar yield and low carbon conversion while low tar yield and high carbon conversion can result in product gas with low quality. However using Olivine as the bed material and setting ER value around 0.3, steam to biomass ratio to 0.7 and using biomass with 3 mm particle size and 9 wt% moisture content can result in optimal product gas with low tar yield.

  • 10.
    Mirmoshtaghi, Guilnaz
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Westermark, Mats
    Royal Institute of Technology, Stockholm, Sweden.
    Mohseni, Farzad
    Royal Institute of Technology, Stockholm, Sweden.
    Simulation of a lab-scale methanation reactor2012In: Simulation of a lab-scale methanation reactor, 2012Conference paper (Other academic)
    Abstract [en]

    Due to the worldwide effort on developing renewable fuels, methane production by different methods has gained considerable interest. Considering the difficulties in producing methane from renewable sources such as biomass or black liquor, an interesting methanation reaction for increasing methane concentration in produced gas, found to be hydrogenation of carbon dioxide and is called Sabatier reaction.The present research is on simulation and optimization of the Sabatier reaction in a catalytic bed of Ruthenium on Alumina base. The simulation is based on two different scenarios: first, an adiabatic reactor with interstage cooling and second; an isothermal tube reactor with wall coolingIn this highly exothermic reaction, most of the produced heat must be removed by external cooling in order to prevent too high increase of the bed temperature. Regarding the design optimization done in the project, the best results occur for the isothermal case in 600K and 10 bar, while for the adiabatic run an interstage cooling strategy with 5 coolers and 6 reactors has been modeled. Additionally, recycling some part of cooled product to the entrance can increase the efficiency and reduce the number of reactors for the adiabatic strategy.The conclusion to this study shows that isothermal operation with external cooling is more favorable for lab-scale studies while adiabatic interstage design with recirculation of product gas would be more feasible in full scale cases.

    Key words: methanation reactor, Ruthenium catalyst, isothermal, adiabatic

  • 11.
    Nookuea, Worrada
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Zambrano, Jesús
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Tan, Yuting
    Royal Institute of Technology, Sweden.
    Li, Hailong
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Thorin, Eva
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Royal Institute of Technology, Stockholm, Sweden.
    Comparison of Mass Transfer Models on Rate-Based Simulations of CO2 Absorption and Desorption Processes2017In: Energy Procedia, ISSN 1876-6102, Vol. 142, p. 3747-3752Article in journal (Refereed)
    Abstract [en]

    One of the keys available options for the large scale carbon capture and storage is the solvent-based post-combustion capture. Due to the high reactivity between CO2 and aqueous amine solutions, chemical absorption is suitable for capturing the CO2 at low concentration such as from the flue gas. From techno-economic analyses of the CO2 chemical absorption plant, absorber and desorber columns are the main cost of the purchased equipment. Since the process involves complex reactive separations, the accurate calculation of hydrodynamic properties, mass and energy transfer are of importance for the design of the columns. Several studies have been done on the impact of different process and property models on the equilibrium and rate-based simulation of the absorption site. However, the impact study of process and property models on the desorption site are still lacking. This paper performs rate-based simulations of CO2 absorption by Monoethanolamine. The software Aspen Plus was used for the simulations. Different mass transfer models were implemented for the mass transfer calculation in gas and liquid phases. The temperature and concentration profiles along the columns are reported and discussed.

  • 12.
    Pettersson, Hanna
    et al.
    Mälardalen University, School of Business, Society and Engineering.
    Törnvall, Elin
    Mälardalen University, School of Business, Society and Engineering.
    Efterbehandling av biogödsel: Ett försök med avskiljning och uppsamling av kväve och vatten genom ammoniakstripping i en efterhygieniseringsprocess2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    During this master thesis, the possibility of ammonia removal from digestate in combination with after hygienization has been investigated. The aim of the work was to see how much ammonia that could be removed but also the properties of other process parameters such as TS/VS content, pH and alkalinity of the digestate. It was also of interest to study the energy balances for a process that combines ammonia stripping with after hygienization. The purpose of hygienization in a biogas plant is to kill pathogens. To study ammonia stripping combined with after hygienization, a prototype of an ammonia stripper was built in a laboratory. The digestate was heated to the hygienization temperature of 70 °C and air was led through with the help of a peristaltic pump by the end of the system. Condensate was trapped in a bottle by cooling the tube and the gases were brought to another bottle containing 1 M sulfuric acid. Ammonia and sulfuric acid reacted and formed ammonium sulfate. The process was also tested with closed system using vacuum to decrease the boiling point and thereby create more condensate. The results from the experiments showed that with an air stripping process most of the ammonium was trapped in the sulfuric acid while with a vacuum process more ammonium was trapped in the condensate. The most important parameters to achieve a good ammonia removal were air flow and time. With the vacuum system, more condensate was removed. The removal of condensate could make it possible to recirculate process fluid from the stripping process and thereby save energy in the centrifugation part which is used to create a solid part of the bio digestate. It was concluded from the experiments that air stripping is more effective when it comes to ammonium recovery. The process could be improved by using higher air flow which could decrease the time to less than one hour, which is the desired hygienization time. However, it is desired to keep the pump flow as low as possible since it is energy consuming. A chemical increase of the pH would also be of interest to try since previous tests showed a strong correlation between high pH-value and good ammonia stripping. More tests overall are of interest to ensure a reliable result. Still, the combination of after-hygienization and ammonia stripping would contribute to a better environment and a sustainable agriculture with a natural and nutritious digestate.

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  • 13.
    Rout, Tanmmay
    Mälardalen University, School of Business, Society and Engineering.
    Control of carbon dioxide capture from biomass CHP plants: Designing a suitable control system to realize the flexible operation of the CO2 capture system2023Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This degree project studies the integration of carbon capture system into biomass fired combined heat and power (bio-CHP) plants. The key disturbances from bio-CHP plants include flue gas flow rate, carbon dioxide (CO2) concentration and available heat for the reboiler because the use of versatile biomass and the dynamic operation of CHP plants results in large fluctuations in the properties of flue gas and the heat input for CO2 capture. To clearly understand the impacts of these disturbances on the performance of CO2 capture, a dynamic CO2 capture model is developed in Aspen Plus Dynamics by using monoethanolamine (MEA) based chemical absorption. Proportional-Integral (PI) feedback controllers are then implemented to further study and compare the performance of the CO2 capture process under different control strategies, the performance with general control settings and fine-tuned controllers are obtained and compared, including both the control performance and system performance. The control performance includes the maximum deviation and settling time, which could reflect only the performance of the controllers.  The system performance includes Captured CO2, reboiler duty and Energy penalty per unit CO2 captured, which could reflect CO2 capture system performance. An equilibrium stage steady state model is first developed for the key components in the CO2 capture plant in Aspen Plus, consisting of the absorber, the stripper, and lean-rich heat exchanger. By sizing the components and employing the pressure driven mode, the steady state model is enabled to be a dynamic model. The disturbances about flue gas and reboiler heat are taken from a real bio-CHP plant in Sweden. Considering the higher flue gas flowrate, the model has been scaled up to meet the requirement of this bio-CHP plant. The addition of controllers are done for the flexible operation of the CO2 capture system and the controlled variables considered in this study are the percentage of CO2 absorbed in the absorber column, reboiler temperature and rich solvent flow in the stripper column.

    The results show the effects of fluctuations in the key influencing factors on the control performance and the system performance . The fine-tuned controller implemented system showcases better performance when the quantity of CO2 captured is compared with that of the system in the absence of controllers, where a 1.1% increase in the amount of captured CO2 is observed when the flue gas flow rate is increased by 30%. The system also maintains a 1.8% higher capture rate when controllers are implemented. This showcases better system performance when controllers are implemented in the system. To further analyse the effects of control strategies two different control strategies are compared where controllers with general settings are compared to the controllers which are fine-tuning achieved by implementing tuning parameters which were obtained through Internal Model control (IMC) based on the system requirements. The fine tuning of the controllers results in improved system performance where the amount of captured CO2 increases by 1.4% when the reboiler duty is increased by 30% and a 1.7% decrease in the energy penalty per unit CO2 captured. Additionally, the results show that the settling time and maximum deviation are different for the two controllers where the controller which underwent fine tuning maintained the steady set point whereas the controller with general controller tuning showcases deviation before it attained stability. Therefore, the fine-tuned controller is more efficient to enable the flexible operation of CO2 capture when facing disturbance. It is studied that the tuning parameters implemented in the controllers affect the transient operation of the plant and improved the dynamic performance of the capture system. The tuned controllers offered more stability to the capture system while attaining their respective set points in a shorter time frame. It is also found that there exists a big difference between the system’s performance without controllers and that with finely tuned controllers. The difference in captured CO2 amount is approximately 26 ton/h when flue gas flow rate increases by 30%. The percentage difference is 1.1%, 7.7% and  5.9% for Captured CO2, reboiler duty and Energy penalty per unit CO2 captured respectively. In conclusion the control of the transient operation of the CO2 capture system needs the control system implemented and requires fine tuning parameters to achieve the desirable performance.

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  • 14.
    Sadeghi, Mohammad
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. Technology development institute (ACECR), Tehran, Iran.
    Dorodian, M.
    Technology development institute (ACECR), Tehran, Iran.
    Rezaei, M.
    Technology development institute (ACECR), Tehran, Iran.
    Synthesis and Characteristic of Precipitated Nano-Silica2013In: Journal of Advances in Chemistry, ISSN 2321-807X, Vol. 6, no 1, p. 917-922Article in journal (Other academic)
    Abstract [en]

    The reaction of precipitation of amorphous silicon dioxide from aqueous solution of sodium silicate and sulfuric acid has been studied. The factors affecting the precipitation process of the sodium silicate solution such as sodium silicate concentration and addition of anionic surfactant (sodium dodecyl sulfate, SDS) on particle size, size distribution and degree of agglomeration of the precipitated silica were examined. The precipitation of silica from the produced sodium silicate solution was carried out using sulfuric acid at pH 7. Scaning electron microscope (SEM), transmission electron microscope (TEM) and Dynamic light scattering (DLS) have been used for characterization of the produced nano-silica. The surface area of silica was tested by oil absorption method according to ASTM standard. Results showed that the particle size of the precipitated silica gel was decreased with increasing Na2SiO3 and SDS concentrations and Particle size of about 44nm can be achieved at 20% Na2SiO3 and 200ppm SDS. But with decreasing particle size, degree of agglomeration also increased.

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  • 15.
    Salman, Chaudhary Awais
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Integration of thermochemical processes with existing waste management industries to enhance biomethane production2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In most waste management industries, waste is separated into different fractions, each of which is treated with suitable processes. Established technologies such as waste combustion for combined heat and power (CHP) production and biomethane production through anaerobic digestion (AD) of biodegradable waste work fine as standalone processes. However, specific issues are associated with these established standalone waste-to-energy (WtE) processes. For example, traditional CHP plants have high overall energy efficiencies, but lower electrical efficiencies, and their heat outputs are dependent on local demand and seasonal variations. Similarly, biodegradable waste typically sent for AD contains lignocellulosic or green waste. Due to the lower biodegradability of lignocellulosic waste, only a proportion is sent for digestion, while the rest is incinerated, increasing transportation costs. Increased benefits from the perspective of energy and economics can be achieved by integrating new WtE processes with existing technologies.

     

    This thesis aims to design energy-efficient and profitable biorefineries by integrating existing waste management facilities with the thermochemical treatment of waste. A systems analysis of two process integration concepts has been studied through modelling and simulation. The first analysis is of the process integration of gasification with existing CHP plants, and the second is the process integration of pyrolysis with an existing AD plant. For integration of gasification with a CHP plant, reasonable operational limits of the CHP plant have been assessed and compared by integrating three types of gasifier, and the most technically and economically integrated processes have been identified. In the case of integration of pyrolysis with AD, a new process configuration is presented that couples the AD of biodegradable waste with the pyrolysis of lignocellulosic waste. The biochar obtained from pyrolysis is added to a digester as an adsorbent to increase the biomethane production. In addition, the vapors produced by the pyrolysis process are converted to biomethane. Two different conversion processes are compared to convert pyrolysis vapors to biomethane, catalytic methanation and biomethanation. 

     

    The results demonstrate that process integration can contribute to reducing the cost of biomethane production through integration of gasification and pyrolysis with CHP and AD, respectively. The process integration can also utilize infrastructure and products from existing industries and increase the overall process efficiencies. Of the gasifiers studied, the dual fluidized bed gasifier produces more biomethane than the circulating bed and entrained flow gasifiers when retrofitted with an existing CHP plant with up to 85% efficiency. The CHP–gasification integration is capable of producing more biomethane during low heat demand seasons without disturbing the operation of the CHP operation. A gasifier with a flexible capacity can be integrated with the CHP to produce biomethane without affecting the heat production of the CHP. From an economic perspective, the dual-bed gasifier requires lower capital investment and is therefore more profitable, because it requires less equipment than the circulating fluidized and entrained flow gasifiers. The integration of pyrolysis with the AD process can almost double biomethane production comparison with standalone AD process, increasing efficiency to 67%. The integration is an attractive investment when catalytic methanation of syngas is used rather than biomethanation of syngas. The catalytic methanation route has an economic rate of return of 16%, with a six-year payback period.

     

    The main conclusion drawn from this thesis is that production of biomethane can be enhanced through process integration of gasification with the CHP plant and of pyrolysis with AD. However, the increase in biomethane production also increases the demand for waste at the integrated biorefinery. Hence, the capacity of the gasifier and pyrolysis process will be decisive in determining the level of integration of the biorefineries.

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  • 16.
    Skvaril, Jan
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Near-Infrared Spectroscopy and Extractive Probe Sampling for Biomass and Combustion Characterization2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Biomass is characterized by highly variable properties. It can be converted to more valuable energy forms and products through a variety of conversion processes. This thesis focuses on addressing several important issues related to combustion and pulping.

    Experimental investigations were carried out on a biomass-fired industrial fluidized-bed boiler. The observed combustion asymmetry was explained by an imbalance in the fuel feed. Increased levels of carbon monoxide were detected close to boiler walls which contribute significantly to the risk of wall corrosion.

    Moreover, extensive literature analysis showed that near-infrared spectroscopy (NIRS) has a great potential to provide property information for heterogeneous feedstocks or products, and to directly monitor processes producing/processing biofuels in real-time. The developed NIRS-based models were able to predict characteristics such as heating value, ash content and glass content. A study focusing on the influence of different spectra acquisition parameters on lignin quantification was carried out. Spectral data acquired on moving woodchips were found to increase the representativeness of the spectral measurements leading to improvements in model performance.

    The present thesis demonstrates the potential of developing NIRS-based soft-sensors for characterization of biomass properties. The on-line installation of such sensors in an industrial setting can enable feed-forward process control, diagnostics and optimization.

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  • 17.
    Skvaril, Jan
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Kyprianidis, Konstantinos
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Avelin, Anders
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Odlare, Monica
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Multivariate analysis models for wood properties combined with Open Modelica model for process performance monitoring2015In: IFAC Proceedings Volumes (IFAC-PapersOnline), 2015, Vol. 48:1, p. 898-899Conference paper (Other (popular science, discussion, etc.))
    Abstract [en]

    To perform advanced model based control it is important to know what is fed into a system such as a waste or biomass fired boiler or a pulp digester. In this paper, we present correlations between the lignin content of different types of wood chips and their Near-infrared (NIR) spectra. The Principal Component Regression (PCR) method is used for deriving the correlation, as well as selecting certain wave lengths. Analysis is made including different parts of the spectra in the wave length range 700 – 2500 nm. The model is then used as input to an Open Modelica pulp digester model to tune the reactivity constant of the dissolution of lignin. The lignin content of wood-chips is determined on-line through the NIR measurement at the feed to the digester. Simulations are carried out to determine the content of residual lignin on fibers at the exit (continuous digester) or at the end of a cook (batch digester). By comparing the deviation between predicted values and actual measured values the reactivity constant of the lignin is determined. The regression can be made to the NIR spectrum aside of the lignin content as such. The original content of lignin together with reactivity may then be used for optimized on-line control of the digester. It can also be used for diagnostic purposes with regard to process issues like hang-ups or channeling, as well as possible sensor faults and data reconciliation.

  • 18.
    Skvaril, Jan
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Kyprianidis, Konstantinos
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Dahlquist, Erik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Applications of near-infrared spectroscopy (NIRS) in biomass energy conversion processes: A review2017In: Applied spectroscopy reviews (Softcover ed.), ISSN 0570-4928, E-ISSN 1520-569X, Vol. 52, no 8, p. 675-728Article, review/survey (Refereed)
    Abstract [en]

    Biomass used in energy conversion processes is typically characterized by high variability, making its utilization challenging. Therefore, there is a need for a fast and non-destructive method to determine feedstock/product properties and directly monitor process reactors. The near-infrared spectroscopy (NIRS) technique together with advanced data analysis methods offers a possible solution. This review focuses on the introduction of the NIRS method and its recent applications to physical, thermochemical, biochemical and physiochemical biomass conversion processes represented mainly by pelleting, combustion, gasification, pyrolysis, as well as biogas, bioethanol, and biodiesel production. NIRS has been proven to be a reliable and inexpensive method with a great potential for use in process optimization, advanced control, or product quality assurance.

  • 19.
    Wang, F.
    et al.
    Faculty of Maritime and Transportation, Ningbo University, Ningbo, China.
    Deng, S.
    Key Laboratory of Efficient Utilization of Low and Medium Grade Energy (Tianjin University), Ministry of Education of China, Tianjin, China.
    Zhang, H.
    Department of Microelectronic Science and Engineering, Ningbo University, Ningbo, China.
    Wang, J.
    Faculty of Maritime and Transportation, Ningbo University, Ningbo, China.
    Zhao, J.
    Faculty of Maritime and Transportation, Ningbo University, Ningbo, China.
    Miao, H.
    Faculty of Maritime and Transportation, Ningbo University, Ningbo, China.
    Yuan, J.
    Faculty of Maritime and Transportation, Ningbo University, Ningbo, China.
    Yan, Jinyue
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    A comprehensive review on high-temperature fuel cells with carbon capture2020In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 275, article id 115342Article, review/survey (Refereed)
    Abstract [en]

    High-temperature fuel cells and their hybrid systems represent one of the most promising technologies with high conversion efficiency. The configuration of such kind of system could facilitate an easy capture of CO2. Several novel CO2 capture strategies have been developed based on high-temperature fuel cells, such as solid oxide fuel cell (SOFC), molten carbonate fuel cell (MCFC) and direct carbon fuel cell (DCFC). However, related review which focus on their system integration and performance evaluation is still rare. The aim of this study is to improve interest in high-temperature fuel cell with CO2 capture by providing an overview of the status of such kind of cutting-edge technologies. To approach this goal, the major strategies and technologies for fuel cells and their hybrid system with CO2 capture have been reviewed. Simultaneously, the characteristics of fuel cell technologies are summarized and the technical and economic performance of the fuel cell with CO2 capture are explored and discussed as well. The existing challenges that required to be overcome in fuel cell with CO2 capture technology are highlighted with aspects on fuel cell module scale-up, cost, safety, reliability and capture energy, etc. Finally, opportunities for the future development of high-temperature fuel cell with CO2 capture technologies are discussed. The conclusion remarks of this investigation indicate that fuel cell integrating CO2 capture process is a promising route to sustainable future, and could even be more effective if fuel cell technology can be commercialized.

  • 20.
    Zhou, Yuanye
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Aslanidou, Ioanna
    Mälardalen University, School of Innovation, Design and Engineering, Innovation and Product Realisation.
    Karlsson, Mikael
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Kyprianidis, Konstantinos
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    An explainable AI model for power plant NOx emission control2024In: Energy and AI, ISSN 2666-5468, Vol. 15, article id 100326Article in journal (Refereed)
    Abstract [en]

    In recent years, developing Artificial Intelligence (AI) models for complex system has become a popular research area. There have been several successful AI models for predicting the Selective Non-Catalytic Reduction (SNCR) system in power plants and large boilers. However, all these models are in essence black box models and lack of explainability, which are not able to give new knowledge. In this study, a novel explainable AI (XAI) model that combines the polynomial kernel method with Sparse Identification of Nonlinear Dynamics (SINDy) model is proposed to find the governing equation of SNCR system based on 5-year operation data from a power plant. This proposed model identifies the system's governing equation in a simple polynomial format with polynomial order of 1 and only 1 independent variable among original 68 input variables. In addition, the explainable AI model achieves a considerable accuracy with less than 21 % deviation from base-line models of partial least squares model and artificial neural network model.

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