TY - JOUR A1 - Conti, Fosca A1 - Saidi, Abdessamad A1 - Goldbrunner, Markus T1 - Evaluation Criteria and Benefit Analysis of Mixing Process in Anaerobic Digesters of Biogas Plants JF - Environmental and Climate Technologies N2 - A valid method to evaluate decisions of a project proposal is the so-called cost-benefit analysis. Criteria are selected and properly weighted to determine if the project is effective and feasible. The present research study is focused on methodical selection of design parameters to install two propeller mixers inside anaerobic digesters of biogas plants. A cylindrical tank of 1400 m3 was considered. For the model-based optimisation, the substrate was considered as a non-Newtonian fluid with a density of 1090 kg/m3. The Oswald-de Waele power-law model was selected to account for the rheological behaviour of the fluid. Installation parameters of the mixers were rotational angles and heights of the shafts of the two propellers. A computational model was developed to simulate the fluid dynamics depending on the mixing process inside the tank. Several configurations were analysed according to evaluating criteria such as the value of the fluid velocity, its distribution along the three spatial dimensions, and the power consumption to rotate the mixers. The maximum fluid velocity and minimum power consumption were observed when the propellers are located at intermediate height inside the tank and with the shafts perpendicular to the tank radius. With this configuration, the fluid reaches a maximum velocity of 0.28 m/s. According to the investigation, it is evident that mixing systems with propeller shafts deep-seated and parallel to the tank radius should be avoided, both in term of efficiency of the fluid mixing distribution and in term of power consumption. UR - https://doi.org/10.2478/rtuect-2020-0105 KW - Anaerobic digester KW - biomass KW - computational fluid dynamics (CFD) KW - Cost-Benefit Analysis (CBA) KW - evaluation criteria KW - flow velocity KW - full scale biogas digester KW - mixing KW - propeller Y1 - 2020 UR - https://doi.org/10.2478/rtuect-2020-0105 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-9274 SN - 2255-8837 VL - 24 IS - 3 SP - 305 EP - 317 PB - De Gruyter Poland CY - Warsaw ER - TY - JOUR A1 - Conti, Fosca A1 - Saidi, Abdessamad A1 - Goldbrunner, Markus T1 - Numeric Simulation-Based Analysis of the Mixing Process in Anaerobic Digesters of Biogas Plants JF - Chemical Engineering & Technology N2 - Stirring systems with two rotational three-bladed propellers were analyzed using computational fluid dynamics. The propellers are located at three heights and seven angles in a tank with 9 m radius. The fluid was characterized by non-Newtonian rheology and simulated by applying the k-ε turbulence model and the standard k-ω model. Reynolds numbers were estimated. High fluid speeds were obtained with the propellers located at a height of 2 m and oriented at 90° with respect to the tank radius. In the top regions of the tank, the fluid velocity was generally less intense and less affected by the angle setting. The configurations identified as good mixing systems showed power consumptions broadly distributed around 30 kW. UR - https://doi.org/10.1002/ceat.201900650 KW - Anaerobic digester KW - Biogas plant KW - Biomass KW - Fluid dynamics KW - Mixing Y1 - 2020 UR - https://doi.org/10.1002/ceat.201900650 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-9379 SN - 1521-4125 VL - 43 IS - 8 SP - 1522 EP - 1529 PB - Wiley CY - Weinheim ER - TY - JOUR A1 - Conti, Fosca A1 - Saidi, Abdessamad A1 - Goldbrunner, Markus T1 - CFD Modelling of Biomass Mixing in Anaerobic Digesters of Biogas Plants JF - Environmental and Climate Technologies N2 - Cut in greenhouse gas emissions, increment of energy from renewables and improvement in energy efficiency represent the three key targets for future energy systems. Among the available bioenergy technologies, biogas production via biodegradation and anaerobic digestion is a widely applied approach, not only to produce biofuels but also to manage industrial and domestic organic waste. Within the biogas production, a sufficient mixing of the organic mass is a crucial step to ensure high biogas yields by bacteria and enzymes. Measurements of the electric power consumption of biogas plants revealed that the electrical energy demand of the stirrer system has a high share of the total electricity consumption of a biogas plant. Investigations on real biogas digesters to optimize the mixing process are cost and time intensive. Therefore, laboratory prototypes and computational simulations represent promising alternatives to analyse and improve the efficiency of mixing systems. In this paper, a computational fluid dynamics (CFD) model is presented, which is applied to commercial stirring systems. The case of two propeller stirrers, located in diametrically opposite positions in a tank filled with ca. 1400 m3 of substrate is described in detail. For the simulation, the rheology of the fluid is adapted to a biomass with 12 wt % dry matter content and obeying the non-Newtonian generalized Ostwald-de Waele power law. The developed simulation procedure considers the rotation angle of each propeller and its height. A total of 441 mixing configurations are calculated and evaluated in terms of the technical benefit. The investigation reveals that locations of the rotors far away from the bottom and high rotational angles cause advantageous fluid dynamics. UR - https://doi.org/10.2478/rtuect-2019-0079 KW - Anaerobic digester KW - biomass KW - cellulose KW - computational fluid dynamics (CFD) KW - full scale biogas digester KW - laboratory digester KW - mixing KW - rheology KW - viscosity Y1 - 2019 UR - https://doi.org/10.2478/rtuect-2019-0079 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-9544 SN - 2255-8837 VL - 23 IS - 3 SP - 57 EP - 69 PB - RTU Press CY - Riga ER - TY - JOUR A1 - Wiedemann, Leonhard A1 - Conti, Fosca A1 - Saidi, Abdessamad A1 - Sonnleitner, Matthias A1 - Goldbrunner, Markus T1 - Modeling Mixing in Anaerobic Digesters with Computational Fluid Dynamics Validated by Experiments JF - Chemical Engineering & Technology UR - https://doi.org/10.1002/ceat.201800083 KW - Anaerobic digesters KW - Biomass KW - Computational fluid dynamics KW - Mixing KW - Rheology Y1 - 2018 UR - https://doi.org/10.1002/ceat.201800083 SN - 1521-4125 VL - 41 IS - 11 SP - 2101 EP - 2110 PB - Wiley CY - Weinheim ER - TY - JOUR A1 - Conti, Fosca A1 - Wiedemann, Leonhard A1 - Sonnleitner, Matthias A1 - Saidi, Abdessamad A1 - Goldbrunner, Markus T1 - Monitoring the mixing of an artificial model substrate in a scale-down laboratory digester JF - Renewable Energy UR - https://doi.org/10.1016/j.renene.2018.08.013 KW - Laboratory digester KW - Anaerobic digestion KW - Artificial chemical substrate KW - Mixing KW - Particle image velocimetry (PIV) KW - Acoustic Doppler velocimetry (ADV) Computational fluid dynamics (CFD) Y1 - 2018 UR - https://doi.org/10.1016/j.renene.2018.08.013 SN - 0960-1481 VL - 2019 IS - 132 SP - 351 EP - 362 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Saidi, Abdessamad A1 - Trinkl, Christoph A1 - Conti, Fosca A1 - Goldbrunner, Markus A1 - Karl, Jürgen T1 - Partially Upgraded Biogas: Potential forDecentralized Utilization in AgriculturalMachinery JF - Chemical Engineering & Technology UR - https://doi.org/10.1002/ceat.201800100 KW - Agriculture KW - Biogas KW - Combustion KW - Fuel KW - Upgrading Y1 - 2018 UR - https://doi.org/10.1002/ceat.201800100 SN - 1521-4125 VL - 41 IS - 11 SP - 2111 EP - 2119 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Conti, Fosca A1 - Wiedemann, Leonhard A1 - Sonnleitner, Matthias A1 - Goldbrunner, Markus T1 - Thermal behaviour of viscosity of aqueous cellulose solutions to emulate biomass in anaerobic digesters JF - New Journal of Chemistry UR - https://doi.org/10.1039/C7NJ03199H Y1 - 2017 UR - https://doi.org/10.1039/C7NJ03199H SN - 1369-9261 VL - 42 IS - 2 SP - 1099 EP - 1104 PB - RSC CY - London ER - TY - JOUR A1 - Saidi, Abdessamad A1 - Conti, Fosca A1 - Sonnleitner, Matthias A1 - Goldbrunner, Markus T1 - Membrane separation process for small scaled partial biogas upgrading JF - IOP Conference Series: Materials Science and Engineering N2 - Biogas upgrading is actually limited to the production of biomethane as natural gas substitute. To realize the according gas quality a cost intensive methane enrichment is required, wherefore biogas upgrading is actually merely cost-efficient in case of high production rates. Since the energy and cost effort disproportionately increases with the required product gas purity partial biogas upgrading for decentralized utilization represents a promising utilization approach for farm based applications. Among the available technologies for CO2-separation the gas permeable membrane has high potential for small scaled biogas upgrading. Within the present study a model based analysis to determine the savings potential of a membrane based upgrading system is performed. UR - https://doi.org/10.1088/1757-899X/446/1/012012 Y1 - 2018 UR - https://doi.org/10.1088/1757-899X/446/1/012012 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-28012 SN - 1757-899X VL - 2018 IS - 446 PB - IOP Publishing CY - London ER - TY - JOUR A1 - Conti, Fosca A1 - Wiedemann, Leonhard A1 - Saidi, Abdessamad A1 - Goldbrunner, Markus T1 - Effect of mixing of waste biomass in anaerobic digesters for production of biogas JF - IOP Conference Series: Materials Science and Engineering N2 - Biogas technology is an important renewable bioenergy producer. The biogas generating process needs to be optimized to minimise the energy consumption due to the stirring of biomass slurry. Numerical simulations and laboratory experiments are economically and practically preferred over investigations of industrial scale biogas plants. Additionally, a strategic approach to model the reality in scientific laboratories is to use a rheological valid artificial chemical substrate to replace real biomass. The proposes of this study were (i) to investigate the mixing process in a 1:12 scaled-down home-made laboratory digester filled with a 0.3 wt% water-cellulose solution, (ii) to simulate the mixing process in the laboratory-scale digester using a computational fluid dynamics model, (iii) to validate the model by comparison of the simulation with laboratory experiments results obtained on the laboratory digester. Optical and acoustic measurements on the flow velocity inside the digester during the mixing process of the water-cellulose solutions indicate that the model based on computational fluid dynamics is valid. The data are presented and discussed in the paper. UR - https://doi.org/10.1088/1757-899X/446/1/012011 Y1 - 2018 UR - https://doi.org/10.1088/1757-899X/446/1/012011 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-28021 SN - 1757-899X VL - 2018 IS - 446 PB - IOP Publishing CY - London ER - TY - JOUR A1 - Flach, Charley A1 - Conti, Fosca A1 - Bayraktar, Ahmet A1 - Goldbrunner, Markus T1 - Direct Methanation and Storage Concepts for the Flexibilization of Biogas Plants JF - Chemical Engineering & Technology N2 - Enrichment of the methane fraction in a biogas mixture is an innovative possibility to make existing biogas plants more flexible by using excess power. In the described concept, the CO2 in the biogas is directly catalytically converted into CH4 with H2. The CH4-enriched biogas is again fed into the digester to save energy for later use in the combined heat-and-power unit. Additionally, the fed heat gas can mix and heat the substrate. A heat pipe injector system was therefore developed for cooling the hot biogas stream after methanation and to prevent damage to the microbial consortia during the biomass mixing. The concept was proven at a laboratory-scale biogas plant. UR - https://doi.org/10.1002/ceat.202200239 KW - Biogas KW - Flexibilization KW - Injector KW - Methanation KW - Power to gas Y1 - 2022 UR - https://doi.org/10.1002/ceat.202200239 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-34914 SN - 1521-4125 VL - 46 IS - 3 SP - 579 EP - 586 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Ahmed, Arslan A1 - Conti, Fosca A1 - Bayer, Peter A1 - Goldbrunner, Markus T1 - Hydronic Road-Heating Systems BT - Environmental Performance and the Case of Ingolstadt Ramps JF - Environmental and Climate Technologies N2 - Snowfall and ice formation on road surface significantly impact the safety of driving conditions. To resolve this, every year salt and de-icing chemicals are sprinkled on roads. However, use of salts and snow ploughing have environmental as well as economical disadvantages. To resolve these problems, hydronic road heating systems are valid alternatives. Heat transfer fluid, i.e. mixture of ethanol and water, is pumped into a tubular circulation system under the asphalt. By this technology, the road and pavements shall stay ice-free even in times of snowfall and temperatures below the freezing point. The system can also be used to cool the asphalt in case of extreme heat, which – besides the heating effect – could also prevent road from damages in extreme summers. This study aims to compare the environmental impact of use of salts and road-heating system in terms of GHG emissions. To assess the environmental impact, an operational road heating system for a ramp in Ingolstadt, Germany, is considered. A cradle-to-grave analysis technique is used to determine the environmental effects based on a life-cycle assessment (LCA) framework. The analysis includes nine components solemnly responsible for hydronic heating of asphalt surface such as local heating pipe, insulation, pumps, and heat meters. Comparison is performed in terms of relative and total impact over 50-year lifetime of three heated ramps having 1989 m2 surface area in total. The results show that the asphalt and heating-circuit causes the major fraction (65 %) of overall GHG emissions, with total life-time emissions of 28.10 kg CO2 eq./m2 of heated surface. During an operational life of 50 years, road heating systems emit 18 % less CO2 eq./m2 as compared to the use of salts. UR - https://doi.org/10.2478/rtuect-2022-0078 KW - Environmental performance KW - de-icing KW - hydronic road-heating system (HRS) KW - greenhouse gases (GHG) KW - Life cycle assessment (LCA) KW - snow removal Y1 - 2022 UR - https://doi.org/10.2478/rtuect-2022-0078 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-35248 SN - 2255-8837 VL - 26 IS - 1 SP - 1044 EP - 1054 PB - De Gruyter Poland CY - Warsaw ER - TY - JOUR A1 - Ahmed, Arslan A1 - Conti, Fosca A1 - Schießl-Widera, Michael A1 - Goldbrunner, Markus T1 - CFD-Based Sensitivity-Analysis and Performance Investigation of a Hydronic Road-Heating System JF - Energies N2 - To minimize the impact of snowfall and ice formation on safety of transportation, salt is sprinkled on the asphalt every winter. However, the use of salt has economical as well as ecological disadvantages. To resolve these problems, road heating systems are used in the northern regions of Europe and America. Despite their widespread usage, considerable potential of the operational optimization is evident. The current systems are controlled under predefined weather conditions such as start of operation at 5 °C air temperature, even when snowfall is absent. Consequently, loss of energy input to heat the system is caused. To avoid unnecessary financial and energetic expense, this study presents CFD-based performance investigation as a basis for a novel predictive controller to increase the operational efficiency of hydronic road heating systems (HRS). The simulation model was developed based on a real operational HRS located in Ingolstadt and composed of bridges and ramps for a total surface of 1989 m2. Climate data of the years 2019–2020 from local weather stations were implemented in the simulation model for performance prediction on extreme climate conditions. This investigation identified that up to 70% of operational hours in terms of energy input can be saved by using a hypothetical predictive controller, thus making the HRS a more economically efficient and environmentally attractive alternate to conventional de-icing techniques. UR - https://doi.org/10.3390/en16052173 KW - hydronic road-heating system (HRS) KW - performance optimization KW - snow removal KW - de-icing KW - computational fluid dynamics (CFD) simulation KW - asphalt KW - water–ethanol heating fluid KW - predictive controller Y1 - 2023 UR - https://doi.org/10.3390/en16052173 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-31979 SN - 1996-1073 VL - 16 IS - 5 PB - MDPI CY - Basel ER - TY - JOUR A1 - Elhaus, Nora A1 - Kolb, Sebastian A1 - Müller, Jakob A1 - Goldbrunner, Markus A1 - Karl, Jürgen A1 - Herkendell, Katharina T1 - Environmental assessment of anaerobic digestion and biological methanation in power-to-methane systems JF - Journal of Cleaner Production UR - https://doi.org/10.1016/j.jclepro.2023.139509 Y1 - 2023 UR - https://doi.org/10.1016/j.jclepro.2023.139509 SN - 1879-1786 VL - 2023 IS - 429 PB - Elsevier CY - Amsterdam ER -