@article{ContiSaidiGoldbrunner2020, author = {Conti, Fosca and Saidi, Abdessamad and Goldbrunner, Markus}, title = {Evaluation Criteria and Benefit Analysis of Mixing Process in Anaerobic Digesters of Biogas Plants}, volume = {24}, journal = {Environmental and Climate Technologies}, number = {3}, publisher = {De Gruyter Poland}, address = {Warsaw}, issn = {2255-8837}, doi = {https://doi.org/10.2478/rtuect-2020-0105}, pages = {305 -- 317}, year = {2020}, abstract = {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.}, language = {en} } @article{ContiSaidiGoldbrunner2020, author = {Conti, Fosca and Saidi, Abdessamad and Goldbrunner, Markus}, title = {Numeric Simulation-Based Analysis of the Mixing Process in Anaerobic Digesters of Biogas Plants}, volume = {43}, journal = {Chemical Engineering \& Technology}, number = {8}, publisher = {Wiley}, address = {Weinheim}, issn = {1521-4125}, doi = {https://doi.org/10.1002/ceat.201900650}, pages = {1522 -- 1529}, year = {2020}, abstract = {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.}, language = {en} } @article{ContiSaidiGoldbrunner2019, author = {Conti, Fosca and Saidi, Abdessamad and Goldbrunner, Markus}, title = {CFD Modelling of Biomass Mixing in Anaerobic Digesters of Biogas Plants}, volume = {23}, journal = {Environmental and Climate Technologies}, number = {3}, publisher = {RTU Press}, address = {Riga}, issn = {2255-8837}, doi = {https://doi.org/10.2478/rtuect-2019-0079}, pages = {57 -- 69}, year = {2019}, abstract = {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.}, language = {en} } @article{StarkContiSaidietal.2019, author = {Stark, Matthias and Conti, Fosca and Saidi, Abdessamad and Z{\"o}rner, Wilfried and Greenough, Richard}, title = {Steam storage systems for flexible biomass CHP plants}, volume = {2019}, pages = {105321}, journal = {Biomass and Bioenergy}, subtitle = {evaluation and initial model based calculation}, number = {128}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0961-9534}, doi = {https://doi.org/10.1016/j.biombioe.2019.105321}, year = {2019}, language = {en} } @inproceedings{SaidiContiKarletal.2019, author = {Saidi, Abdessamad and Conti, Fosca and Karl, J{\"u}rgen and Goldbrunner, Markus}, title = {Biogastankstelle f{\"u}r die Landwirtschaft - Gegen{\"u}berstellende {\"o}konomische Bewertung unterschiedlicher Verfahren f{\"u}r die dezentrale partielle Biogasaufbereitung}, booktitle = {8. Statuskonferenz Bioenergie Reader}, editor = {Thr{\"a}n, Daniela and Pfeiffer, Diana}, publisher = {DBFZ Deutsches Biomasseforschungszentrum gemeinn{\"u}tzige GmbH}, address = {Leipzig}, isbn = {978-3-946629-27-6}, issn = {2698-6809}, url = {https://www.energetische-biomassenutzung.de/veranstaltungen/statuskonferenzen/8-statuskonferenz/programm}, pages = {78 -- 79}, year = {2019}, language = {de} } @inproceedings{ContiSaidiGoldbrunner2019, author = {Conti, Fosca and Saidi, Abdessamad and Goldbrunner, Markus}, title = {Verbesserung der Durchmischung in Biogasfermentern}, booktitle = {8. Statuskonferenz Bioenergie Reader}, editor = {Thr{\"a}n, Daniela and Pfeiffer, Diana}, publisher = {DBFZ Deutsches Biomasseforschungszentrum gemeinn{\"u}tzige GmbH}, address = {Leipzig}, isbn = {978-3-946629-27-6}, issn = {2698-6809}, url = {https://www.energetische-biomassenutzung.de/veranstaltungen/statuskonferenzen/8-statuskonferenz/programm}, pages = {105}, year = {2019}, language = {de} } @article{WiedemannContiSaidietal.2018, author = {Wiedemann, Leonhard and Conti, Fosca and Saidi, Abdessamad and Sonnleitner, Matthias and Goldbrunner, Markus}, title = {Modeling Mixing in Anaerobic Digesters with Computational Fluid Dynamics Validated by Experiments}, volume = {41}, journal = {Chemical Engineering \& Technology}, number = {11}, publisher = {Wiley}, address = {Weinheim}, issn = {1521-4125}, doi = {https://doi.org/10.1002/ceat.201800083}, pages = {2101 -- 2110}, year = {2018}, language = {en} } @inproceedings{ContiWiedemannSaidietal.2018, author = {Conti, Fosca and Wiedemann, Leonhard and Saidi, Abdessamad and Sonnleitner, Matthias and Goldbrunner, Markus}, title = {Mixing of a Model Substrate in a Scale-down Laboratory Digester and Processing with a Computational Fluid Dynamics Model}, booktitle = {EUBCE 2018 Online Conference Proceedings}, publisher = {ETA s.r.l.}, address = {Florenz}, isbn = {978-88-89407-18-9}, issn = {2282-5819}, doi = {https://doi.org/10.5071/26thEUBCE2018-2CV.5.34}, pages = {811 -- 815}, year = {2018}, language = {en} } @article{ContiWiedemannSonnleitneretal.2018, author = {Conti, Fosca and Wiedemann, Leonhard and Sonnleitner, Matthias and Saidi, Abdessamad and Goldbrunner, Markus}, title = {Monitoring the mixing of an artificial model substrate in a scale-down laboratory digester}, volume = {2019}, journal = {Renewable Energy}, number = {132}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0960-1481}, doi = {https://doi.org/10.1016/j.renene.2018.08.013}, pages = {351 -- 362}, year = {2018}, language = {en} } @article{SaidiTrinklContietal.2018, author = {Saidi, Abdessamad and Trinkl, Christoph and Conti, Fosca and Goldbrunner, Markus and Karl, J{\"u}rgen}, title = {Partially Upgraded Biogas: Potential forDecentralized Utilization in AgriculturalMachinery}, volume = {41}, journal = {Chemical Engineering \& Technology}, number = {11}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1521-4125}, doi = {https://doi.org/10.1002/ceat.201800100}, pages = {2111 -- 2119}, year = {2018}, language = {en} }