| 1. |
- Ahmed, Mobyen Uddin, Dr, 1976-, et al.
(författare)
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A machine learning approach for biomass characterization
- 2019
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Ingår i: Energy Procedia. - : Elsevier Ltd. - 1876-6102. ; , s. 1279-1287
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Konferensbidrag (refereegranskat)abstract
- The aim of this work is to apply and evaluate different chemometric approaches employing several machine learning techniques in order to characterize the moisture content in biomass from data obtained by Near Infrared (NIR) spectroscopy. The approaches include three main parts: a) data pre-processing, b) wavelength selection and c) development of a regression model enabling moisture content measurement. Standard Normal Variate (SNV), Multiplicative Scatter Correction and Savitzky-Golay first (SG1) and second (SG2) derivatives and its combinations were applied for data pre-processing. Genetic algorithm (GA) and iterative PLS (iPLS) were used for wavelength selection. Artificial Neural Network (ANN), Gaussian Process Regression (GPR), Support Vector Regression (SVR) and traditional Partial Least Squares (PLS) regression, were employed as machine learning regression methods. Results shows that SNV combined with SG1 first derivative performs the best in data pre-processing. The GA is the most effective methods for variable selection and GPR achieved a high accuracy in regression modeling while having low demands on computation time. Overall, the machine learning techniques demonstrate a great potential to be used in future NIR spectroscopy applications. © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of ICAE2018 - The 10th International Conference on Applied Energy.
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| 2. |
- Anbalagan, Anbarasan, 1988-
(författare)
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A passage to wastewater nutrient recovery units : Microalgal-Bacterial bioreactors
- 2018
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- In recent years, the microalgal–bacterial process has been considered to be a very attractive engineering solution for wastewater treatment. However, it has not been widely studied in the context of conventional wastewater treatment design under Swedish conditions. The technology holds several advantages: as a CO2 sink, ability to withstand cold conditions, ability to grow under low light, fast settling without chemical precipitation, and reducing the loss of valuable nutrients (CO2, N2, N2O, PO4). The process also provides the option to be operated either as mainstream (treatment of municipal wastewater) or side stream (treatment of centrate from anaerobic digesters) to reduce the nutrient load of the wastewater. Furthermore, the application is not only limited to wastewater treatment; the biomass can be used to synthesise platform chemicals or biofuels and can be followed by recovery of ammonium and phosphate for use in agriculture.In the present study, the feasibility of applying the process in Swedish temperature and light conditions was investigated by implementing microalgae within the activated sludge process. In this context, the supporting operational and performance indicators (hydraulic retention time (HRT), sludge retention time (SRT) and nutrients removal) were evaluated to support naturally occurring consortia in photo-sequencing and continuous bioreactor configuration. Furthermore, CO2 uptake and light spectrum-mediated nutrient removal were investigated to reduce the impact on climate and the technical challenges associated with this type of system.The results identified effective retention times of 6 and 4 days (HRT = SRT) under limited lighting to reduce the electrical consumption. From the perspective of nitrogen removal, the process demands effective CO2 input either in the mainstream or side stream treatment. The incorporation of a vertical absorption column demonstrated effective CO2 mass transfer to support efficient nitrogen and phosphorus removal as a side stream treatment. However, the investigation of a continuous single-stage process as the mainstream showed a requirement for a lower SRT in comparison to semi-continuous operation due to faster settlability, regardless of inorganic carbon. Furthermore, the process showed an effective reduction of influent phosphorus and organic compounds (i.e. COD/TOC) load in the wastewater as a result of photosynthetic aeration. Most importantly, the operation was stable at the temperature equivalent of wastewater (12 and 13 ˚C), under different lighting (white, and red-blue wavelengths) and retention times (6 and 1.5 d HRT) with complete nitrification. Additionally, the biomass production was stable with faster settling properties without any physiochemical separation.The outcomes of this thesis on microalgal–bacterial nutrient removal demonstrates that (1) photosynthesis-based aeration at existing wastewater conditions under photo-sequential and continuous photobioreactor setup, (2) flocs with rapid settling characteristics at all studied retention times, (3) the possibility of increasing carbon supplementation to achieve higher carbon to nitrogen balance in the photobioreactor, and (4) most importantly, nitrification-based microalgal biomass uptake occurred at all spectral distributions, lower photosynthetic active radiation and existing wastewater conditions.
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| 3. |
- Bürger, Raimund, et al.
(författare)
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Estimating the hindered-settling flux function from a batch test in a cone
- 2018
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Ingår i: Chemical Engineering Science. - : Elsevier. - 0009-2509 .- 1873-4405. ; 192, s. 244-253
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Tidskriftsartikel (refereegranskat)abstract
- The hindered-settling velocity function for the modelling, simulation and control of secondary settling tanks can be determined from batch tests. The conventional method is to measure the velocity of the descending sludge-supernatant interface (sludge blanket) as the change in height over time in a vessel with constant cross-sectional area. Each such experiment provides one point on the flux curve since, under idealizing assumptions (monodisperse suspension, no wall-effects), the concentration of sludge remains constant just below the sludge blanket until some wave from the bottom reaches it. A newly developed method of estimation, based on the theory of nonlinear hyperbolic partial differential equations, is applied to both synthetic and experimental data. The method demonstrates that a substantial portion of the flux function may be estimated from a single batch test in a conical vessel. The new method takes into consideration that during an ideal settling experiment in a cone, the concentration just below the sludge blanket increases with time since the mass of suspended solids occupy a reduced volume over time.
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| 4. |
- Carlsson, Bengt, et al.
(författare)
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Analyses of activated sludge processes consisting of a plug-flow reactor and a non-ideal settler
- 2015
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Ingår i: 9th IWA Symposium on Systems Analysis and Integrated Assessment (Watermatex).
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Konferensbidrag (refereegranskat)abstract
- An activated sludge process (ASP) consisting of a plug-flow reactor (PFR) and a non-ideal settler is modelled and analysed. One soluble substrate component and one particulate biomass are assumed. The biomass growth rate is described by a Monod function. The settler model includes hindered settling and compression. A model describing the steady-state behaviour of the ASP is derived which constrains the settler to work with a fixed sludge blanket height in the thickening zone. The model provides new understanding for these types of ASPs and may be used for novel design schemes. The numerical example suggests that the steady-state solutions of the ASP give a one-parameter family ofsolutions, where the parameter is the recycle ratio 푟.
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| 5. |
- Carlsson, Bengt, et al.
(författare)
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Analysis of simple bioreactor models : A comparison between Monod and Contois kinetics
- 2014
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Ingår i: Proc. IWA Conference on Activated Sludge – 100 Years and Counting. - : IWA Publishing.
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Konferensbidrag (refereegranskat)abstract
- In this paper, an analysis of simple bioreactors in series is presented. The bioreactors are analysed for growth kinetics of the biomass described by a Monod and a Contois function. In particular, it is studied how the effluent substrate concentration is depending on the influent substrate concentration during steady state. It is shown that by going from one to two bioreactors in series completely changes the process behaviour when the growth kinetics is described by a Monod function. It is also shown that a bioreactor described by Contois kinetics has a completely different behaviour compared with the Monod case.
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| 6. |
- Carlsson, Bengt, et al.
(författare)
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Fault detection and isolation of sensors in aeration control systems
- 2016
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 73:3, s. 648-653
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we consider the problem of fault detection (FD) and isolation in the aeration system of an activated sludge process. For this study, the dissolved oxygen in each aerated zone is assumed to be controlled automatically. As the basis for an FD method we use the ratio of air flow rates into different zones. The method is evaluated in two scenarios: using the Benchmark Simulation Model no. 1 (BSM1) by Monte Carlo simulations and using data from a wastewater treatment plant. The FD method shows good results for a correct and early FD and isolation.
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| 7. |
- Carlsson, Bengt, et al.
(författare)
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Fault detection and isolation of sensors in aeration control systems
- 2014
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Ingår i: Proc. IWA World Water Congress. - : IWA Publishing.
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Konferensbidrag (refereegranskat)abstract
- In this paper, we consider the problem of fault detection and isolation in the aeration system of an activated sludge process. The purpose is to detect and localize possible faults in dissolved oxygen and air flow sensors. The dissolved oxygen in each aerated zone is assumed to be controlled automatically. As the basis for a fault detection algorithm we use the ratio of air flow rates into different zones. The method is evaluated in two scenarios: using the Benchmark Simulation Model nº 1 by Monte Carlo simulations, and using data from a wastewater treatment plant. The fault detection method shows good results for a correct and early fault detection and isolation.
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| 8. |
- Carlsson, Bengt, et al.
(författare)
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Fault Detection and Isolation of Sensors in Aeration Control Systems – the Airflow Ratio Method
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, we consider the problem of detecting sensor faults in the aeration system of an activated sludge process. The purpose is to detect possible faults in the dissolved oxygen sensors. The dissolved oxygen concentration in each aerated zone is assumed to be automatically controlled. As the basis for a fault detection algorithm we propose to use the ratio of air flow rates into different zones. The method is evaluated by using the Benchmark Simulation Model n^o1 (BSM1) via Monte Carlo simulations. Results show that this method gives a good performance in terms of correct an early fault detection and isolation.
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| 9. |
- Carlsson, Bengt, et al.
(författare)
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Fault detection of sensors in aeration control systems : the airflow ratio method
- 2013
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Ingår i: 11th IWA conference on Instrumentation, Control and Automation.
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Konferensbidrag (refereegranskat)abstract
- A fault detection method, ARM, has been proposed for detection of faults in DOsensors in a serie of aerated zones. The DO in each zone is assumed to be controlled. In a simulation study, ARM shows promising results for correct and early fault detection. Eventually, it will not be possible to distinguish between a fault in a DOsensor and in air flow rate sensor. In this study, we have, for simplicity, used KLa as a measure of the air flow rate. In practice an air flow rate sensor should be used. An interesting alternative is to use the air valve position instead of the airflow rate.
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| 10. |
- Chernomoretz, Ariel, et al.
(författare)
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The Metagenomics and Metadesign of the Subways and Urban Biomes (MetaSUB) International Consortium inaugural meeting report
- 2016
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Ingår i: Microbiome. - : Springer Science and Business Media LLC. - 2049-2618. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- The Metagenomics and Metadesign of the Subways and Urban Biomes (MetaSUB) International Consortium is a novel, interdisciplinary initiative comprised of experts across many fields, including genomics, data analysis, engineering, public health, and architecture. The ultimate goal of the MetaSUB Consortium is to improve city utilization and planning through the detection, measurement, and design of metagenomics within urban environments. Although continual measures occur for temperature, air pressure, weather, and human activity, including longitudinal, cross-kingdom ecosystem dynamics can alter and improve the design of cities. The MetaSUB Consortium is aiding these efforts by developing and testing metagenomic methods and standards, including optimized methods for sample collection, DNA/RNA isolation, taxa characterization, and data visualization. The data produced by the consortium can aid city planners, public health officials, and architectural designers. In addition, the study will continue to lead to the discovery of new species, global maps of antimicrobial resistance (AMR) markers, and novel biosynthetic gene clusters (BGCs). Finally, we note that engineered metagenomic ecosystems can help enable more responsive, safer, and quantified cities.
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| 11. |
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| 12. |
- Chistiakova, Tatiana, et al.
(författare)
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Binary classifiers applied to detect DO sensor faults during washing events
- 2015
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Ingår i: Proc. 2nd IWA Conference on New Developments in IT & Water. - : IWA Publishing.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, several classication techniques are applied for monitoring the status of DO sensors in wastewater treatment plants. In particular, DO sensors during washing events are studied and indication parameters from these events are used. The methods considered are the following: k-Nearest Neighbours, Radial Basis Function and Random Forest classiers. The result shows the comparison and the eligibility of the methods to detect a clogged DO-sensor.
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| 13. |
- Diehl, Stefan, et al.
(författare)
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Analysis of photobioreactors in series
- 2018
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Ingår i: Mathematical Biosciences. - : ELSEVIER SCIENCE INC. - 0025-5564 .- 1879-3134. ; 306, s. 107-118
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Tidskriftsartikel (refereegranskat)abstract
- A photobioreactor (PBR) contains microalgae which under illumination consume carbon dioxide and substrate dissolved in water, and produce oxygen. The process is used in water recovery resource facilities with a continuous flow of wastewaster through the PBR. With several PBRs in series the reduction of substrate can be improved. This paper contains a thorough analysis of a model of PBRs in series, where each PBR is modelled with a system of three ordinary differential equations for the concentrations of dissolved substrate and biomass (algae), and the internal cell quota of substrate to biomass. Each PBR has a certain volume and irradiation. The absorption rate of substrate into the cells is modelled with Monod kinetics, whereas the biomass growth rate is modelled with Droop kinetics, in which both a minimum and a maximum internal cell quota are assumed. The main result is that the model has a unique stable steady-state solution with algae in all PBRs. Another stable steady-state solution is the wash-out solution with no algae in the system. Other steady-state solutions are combinations of these two with no algae in some of the first PBRs and algae in the rest of the PBRs in the series. Conditions on the illumination, volumetric flow and volumes of the PBRs are given for the respective solution. Numerical solutions illustrate the theoretical results and indicate further properties.
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| 14. |
- Diehl, S., et al.
(författare)
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Steady-state analyses of activated sludge processes with plug-flow reactor
- 2017
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Ingår i: Journal of Environmental Chemical Engineering. - : Elsevier BV. - 2213-3437. ; 5:1, s. 795-809
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Tidskriftsartikel (refereegranskat)abstract
- Activated sludge processes (ASPs) consisting of a plug-flow reactor (PFR) and a settler are analyzed in steady-state operation using a reduced model consisting of one soluble substrate and one particulate biomass component modelling the dominating biological process. Monod biomass growth rate is assumed. Two settler models are studied. One is the commonly used ideal settler, or point settler, which is assumed to never be overloaded and to have unlimited flux capacity. The other recently published steady-state settler model includes hindered and compressive settling, and models a realistic limiting flux capacity. Generally, the steady-state concentration profiles within the PFR and the settler are governed by nonlinear ordinary differential equations. It is shown that the steady-state behaviour of the ASP can, however, be captured by equations without derivatives. New theoretical results are given, such as conditions by means of inequalities on input variables and parameters for a steady-state solution to exist. Another novel finding is that, if the incoming substrate concentration is increased from a low or moderate stationary value and the solids residence time is kept fixed, then this results in a lower effluent concentration in the new steady state. The steady-state equations are solved numerically for different operating conditions. For common parameter values, numerical solutions reveal that an ASP having a PFR, instead of a continuously stirred tank reactor, is far more efficient in reducing the effluent substrate concentration and this can be obtained for much lower recycle ratios, which reduces the pumping energy considerably.
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| 15. |
- Diehl, Stefan, et al.
(författare)
-
Steady-state analysis and design of activated sludge processes including compressive settling
- 2015
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Ingår i: 9th IWA Symposium on Systems Analysis and Integrated Assessment (Watermatex).
-
Konferensbidrag (refereegranskat)abstract
- A simplified activated sludge process (ASP) with one substrate and one particulate biomasscomponent has been analyzed with respect to its steady states. The ASP consists of a completelystirred biological reactor and a settler. The biomass growths according to the Monod function and the decay rate is constant. In the considered one-dimensional settler model, the biomass undergoes hindered settling and compression according to constitutive functions that can be chosen by the investigator. The dynamic settler model is a nonlinear partial differential equation (PDE), so the steady-state equation is an ordinary differential equation. This is a difficulty in the steady-state analysis of an ASP. The key findings are the following:• By analyzing the model PDE, a simple algebraic equation has been obtained that captures the necessary information related to the limiting flux of a settler in steady state in normal operation with a sludge blanket in the thickening zone. The equation relates the recycle concentration to the bulk velocity in the thickening zone with the sludge blanket kept at a specified level.• All steady states of an ASP working in normal operation are given as a one-parameter family of solutions where the parameter is the recycle ratio 푟. Numerical solutions show that the effluent substrate concentration 푆∗ is reduced significantly already for small 푟 and is a decreasing function for all 푟 > 0. The sludge age 휃 can be expressed as an explicit decreasing function of푆∗.• A control curve 푤 = 푤(푟), relating the wastage ratio 푤 to the recycle ratio 푟, gives the possible values that yield the desired steady state with the sludge blanket kept at a specified level.• For given inputs (substrate concentration 푆 in and volumetric flow 푄) to the ASP, a procedure is suggested for the design of an ASP that is constrained to work in normal operation. The procedure gives support in the decision on how to balance the building or start-up costs (which increase with the total area) and operational costs (which increase with 푟 – energy for pumping water).
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| 16. |
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| 17. |
- Diehl, Stefan, et al.
(författare)
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Steady-state analysis of activated sludge processes with a settler model including sludge compression
- 2016
-
Ingår i: Water Research. - : Elsevier BV. - 1879-2448 .- 0043-1354. ; 88:1, s. 104-116
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Tidskriftsartikel (refereegranskat)abstract
- A reduced model of a completely stirred-tank bioreactor coupled to a settling tank with recycle is analyzed in its steady states. In the reactor, the concentrations of one dominant particulate biomass and one soluble substrate component are modelled. While the biomass decay rate is assumed to be constant, growth kinetics can depend on both substrate and biomass concentrations, and optionally model substrate inhibition. Compressive and hindered settling phenomena are included using the Bürger-Diehl settler model, which consists of a partial differential equation. Steady-state solutions of this partial differential equation are obtained from an ordinary differential equation, making steady-state analysis of the entire plant difficult. A key result showing that the ordinary differential equation can be replaced with an approximate algebraic equation simplifies model analysis. This algebraic equation takes the location of the sludge-blanket during normal operation into account, allowing for the limiting flux capacity caused by compressive settling to easily be included in the steady-state mass balance equations for the entire plant system. This novel approach grants the possibility of more realistic solutions than other previously published reduced models, comprised of yet simpler settler assumptions. The steady-state concentrations, solids residence time, and the wastage flow ratio are functions of the recycle ratio. Solutions are shown for various growth kinetics; with different values of biomass decay rate, influent volumetric flow, and substrate concentration.
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| 18. |
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| 19. |
- Jonfelt, Clara, et al.
(författare)
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Key parameters for modelling Anammox process with N2O emissions
- 2017
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Ingår i: French Federation of Biotechnology - Bioreactors Symposium 2017. - France.
-
Konferensbidrag (refereegranskat)abstract
- In this paper, a sensitivity analysis and a calibration were applied to a recent published model used to replicate N2O emissions in an Anammox process of a moving-bed biofilm reactor (MBBR). The model used in this study was designed to replicate a one-stage nitrification-Anammox system in a MBBR at Hammarby-Sjöstad pilot plant (Stockholm, Sweden), whichtreats of anaerobic digestion liquor. The aeration was intermittently (45/15 minutes - on/off). During the aeration, a 1.5 mg/L DO set-point was set. Three main measurements wereobtained: NH4 in water, N2O in both water and gas phase.The sensitivity analysis was done via the one-at-a-time method, where one parameter at a timeis changed (in our case, 10%) from its nominal value and the model output is quantified. Next,the most sensitive parameters were used in the model calibration. Results indicate that the biofilm porosity (η [-]), biofilm density (ρ [gTS/m3]), maximum biofilmthickness (Lmax [mm]) and boundary layer thickness of the biofilm (L0 [μm]) were the mostsensitive parameters of the model. These parameters performed the model calibration.
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| 20. |
- Kanders, Linda, 1979-, et al.
(författare)
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Full-scale comparison of N2O emissions from SBR N/DN operation versus one-stage deammonification MBBR treating reject water : - and optimization with pHset-point
- 2019
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 79:8, s. 1616-1625
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Tidskriftsartikel (refereegranskat)abstract
- To be able to fulfill the Paris agreement regarding anthropogenic greenhouse gases, all potential 12 emissions must be mitigated. Wastewater treatment plants should aim to eliminate emissions of the 13 most potent greenhouse gas, nitrous oxide. In this study, these emissions were measured at a full-scale 14 reject water treatment tank during two different operation modes: nitrification/denitrification (N/DN) 15 operating as a sequencing batch reactor (SBR), and deammonification (nitritation/anammox) as a moving 16 bed biofilm reactor (MBBR). Nitrous oxide was measured both in the water phase and in the off-gas. The 17 treatment process emitted significantly less nitrous oxide in deammonification mode 0.14-0.7 %, 18 compared to 10 % of Total Nitrogen in N/DN mode. The decrease can be linked to the change feeding 19 strategy, concentration in nitrite, load of ammonia oxidized, shorter aeration time, no ethanol dosage 20 and the introduction of biofilm. Further, evaluation was done how the operational pH set point 21 influenced the emissions in deammonification mode. Lower concentrations of nitrous oxide was 22 measured in water phase at higher pH (7.5-7.6) than at lower pH (6.6-7.1). This is believed to be mainly 23 because of the lower aeration ratio and increased complete denitrification at the higher pH set point.
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| 21. |
- Lundström, Lukas, 1980-, et al.
(författare)
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Development of a space heating model suitable for the automated model generation of existing multifamily buildings : a case study in Nordic climate
- 2019
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Ingår i: Energies. - : MDPI. - 1996-1073. ; 12:3
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Tidskriftsartikel (refereegranskat)abstract
- Building energy performance modeling is essential for energy planning, management, and efficiency. This paper presents a space heating model suitable for auto-generating baseline models of existing multifamily buildings. Required data and parameter input are kept within such a level of detail that baseline models can be auto-generated from, and calibrated by, publicly accessible data sources. The proposed modeling framework consists of a thermal network, a typical hydronic radiator heating system, a simulation procedure, and data handling procedures. The thermal network is a lumped and simplified version of the ISO 52016-1:2017 standard. The data handling consists of procedures to acquire and make use of satellite-based solar radiation data, meteorological reanalysis data (air temperature, ground temperature, wind, albedo, and thermal radiation), and pre-processing procedures of boundary conditions to account for impact from shading objects, window blinds, wind- and stack-driven air leakage, and variable exterior surface heat transfer coefficients. The proposed model was compared with simulations conducted with the detailed building energy simulation software IDA ICE. The results show that the proposed model is able to accurately reproduce hourly energy use for space heating, indoor temperature, and operative temperature patterns obtained from the IDA ICE simulations. Thus, the proposed model can be expected to be able to model space heating, provided by hydronic heating systems, of existing buildings to a similar degree of confidence as established simulation software. Compared to IDA ICE, the developed model required one-thousandth of computation time for a full-year simulation of building model consisting of a single thermal zone. The fast computation time enables the use of the developed model for computation time sensitive applications, such as Monte-Carlo-based calibration methods.
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| 22. |
- Nájera, Silvano, et al.
(författare)
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ATAD control goals through the analysis of process variables and evaluation of quality, production and cost
- 2015
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 71:5, s. 717-724
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this paper is to establish and quantify different operational goals and control strategies in autothermal thermophilic aerobic digestion (ATAD). This technology appears as an alternative to conventional sludge digestion systems. During the batch-mode reaction, high temperatures promote sludge stabilization and pasteurization. The digester temperature is usually the only online, robust, measurable variable. The average temperature can be regulated by manipulating both the air injection and the sludge retention time. An improved performance of diverse biochemical variables can be achieved through proper manipulation of these inputs. However, a better quality of treated sludge usually implies major operating costs or a lower production rate. Thus, quality, production and cost indices are defined to quantify the outcomes of the treatment. Based on these, tradeoff control strategies are proposed and illustrated through some examples. This paper's results are relevant to guide plant operators, to design automatic control systems and to compare or evaluate the control performance on ATAD systems.
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| 23. |
- Nookuea, Worrada, et al.
(författare)
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Comparison of Mass Transfer Models on Rate-Based Simulation of CO2 Absorption and Desorption Processes
- 2017
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Ingår i: Proceedings of the 9th International Conference on Applied Energy. - : Elsevier. ; 142, s. 3747-3752
-
Konferensbidrag (refereegranskat)abstract
- The effective technology for capturing CO2 at the low concentration is chemical absorption, due to the high reactivity between CO2 and aqueous amine solutions. To capture CO2, the process involves complex reactive separations. The accurate calculation of hydrodynamic properties, and mass and energy transfer are of importance for the design of the absorber and desorber columns. This paper performs the rate-based simulations of CO2 absorption by Monoethanolamine in Aspen Plus. In the calculation of the mass transfer coefficients, different mass transfer models were implemented. In comparison with the desorber, the impacts of mass transfer models were more significant in the simulation of the absorber. For both columns, the impacts of the mass transfer models on the concentration profiles were more significant than those on the temperature profiles. For the absorber, the maximum deviations occur at the bottom of the column for both the concentration and the temperature profiles. Different from the absorber, for the desorber, the maximum deviations occur close to the top of the column.
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| 24. |
- Nookuea, Worrada
(författare)
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Impacts of Thermo-Physical Properties on Chemical Absorption for CO2 Capture
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Following the climate change mitigation target in Paris agreement, the global warming has to be limited to 2.0°C above the preindustrial levels. One of the potential methods is carbon capture and storage (CCS), which can significantly reduce the CO2 emissions from the vast point sources such as power plants, industries, and natural gas processes. The CCS covers four steps which are capture, conditioning, transport, and storage. For the capture part, post-combustion capture is easier to implement based on today’s technologies and infrastructure compared with pre-combustion and oxy-fuel combustion captures, since the radical changes in the structure of the existing plant are not required.To design and operate different CCS processes, the knowledge of thermo-physical properties of the CO2 mixtures is of importance. In this thesis, the status and progress of the studies related to the impacts of the uncertainty in thermo-physical properties on the design and operation of the CCS processes were reviewed. The knowledge gaps and the priority of property model development were identified.According to the identified knowledge gaps in the review, the impacts of thermo-physical properties which are the density, viscosity, and diffusivity of the gas and liquid phases, and the surface tension and heat capacity of the liquid phase on the design of the absorber column for the chemical absorption using aqueous monoethanolamine were quantitatively analyzed. An in-house rate-based absorption model was developed in MATLAB to simulate the absorption process, and the sensitivity study was done for each property. An economic evaluation was also performed to further estimate the impacts of the properties on the capital cost of the absorption unit. For column diameter of the absorber, the gas phase density shows the most significant impacts; while, the liquid phase density and viscosity show the most significant impacts on the design of the packing height and also the capital cost of the absorption unit. Therefore, developing the flue gas density model and liquid phase density and viscosity models of the aqueous solvents with CO2 loading should be prioritized.
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| 25. |
- Olsson, Jesper, 1975-, et al.
(författare)
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Anaerobic co-digestion of sludge and microalgae grown inmunicipal wastewater : A feasibility study
- 2018
-
Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 77:3, s. 682-694
-
Tidskriftsartikel (refereegranskat)abstract
- In this study a natural mix of microalgae grown in wastewater of municipal character was co-digested with sewage sludge in mesophilic conditions, in both batch and semi-continuous modes. The semicontinuous experiment was divided into two periods with OLR 1 (Organic Loading Rate) of 2.4 kg VS m3 d-1 and HRT1 (Hydraulic Retention Time) of 15 days, and OLR2 of 3.5 kg VS m3 d-1 and HRT2 of 10 days respectively. Results showed stable conditions during both periods. The methane yield was reduced when adding microalgae (from 200 ± 25 NmL CH4 g VSin-1 , to 168±22 NmL CH4 g VSin-1). VS reduction was also decreased by 51%. This low digestability was confirmed in the anaerobic batch test. However, adding microalgae improved the dewaterability of the digested sludge. The high heavy metals content in the microalgae resulted in a high heavy metals content in the digestate, making it more difficult to reuse the digestate as fertilizer on arable land. The heavy metals are thought to originate from the flue gas used as a CO2 source during the microalgae cultivation. Therefore the implementation of CO2 mitigation via algal cultivation requires careful consideration regarding thesource of the CO2-rich gas.
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