Search

In the current work, a transient/dynamic 1-dimensional model has been developed in the commercial software APROS for the pilot 1 MWth CFB boiler of the Technical University of Darmstadt. Experiments have been performed with the same unit, the data of which are utilized for the model validation. The examined conditions correspond to the steady-state operation of the boiler at 100, 80, and 60% heat loads, as well as for transient conditions for the load changes from 80 to 60% and back to 80%. Fair agreement is observed between the simulations and the experiments regarding the temperature profiles in the riser, the heat extracted by the cooling lances, as well as the concentration of the main species in the flue gases; a small deviation is observed for the pressure drop, which, however, is close to the results of a CFD simulation run. The validated model is extended with the use of a thermal energy storage (TES) system, which utilizes a bubbling fluidized bed to store/return the particles during ramp up/down operation. Simulations are performed both with and without the use of TES for the load path 100–80–60–80–100%, and the results showed that the TES concept proved to be superior in terms of changing load flexibility, since the ramp up and down times proved to be much faster, and lower temperature drops between the loads are observed in this case.

This study presents a comprehensive dynamic process simulation model of a 1 MWth circulating fluidized bed test facility applied for lignite and refuse-derived fuel co-combustion. The developed dynamic process simulation model describes the circulating fluidized bed riser and the supplying system with a high level of detail considering heat transfer, gas-solid interaction, combustion, and fluid dynamics. The model was first tuned at two steady-state operation points and was then validated by the measured data from a long-term test campaign of the 1 MWth circulating fluidized bed test facility at various loads (60%–80% to 100%). During the load changes, the simulated pressure and temperature profiles along the combustor as well as the flue gas concentrations agree very well with the measurement data. Finally, increasing the proportion of waste-derived fuel in the co-combustion process was investigated to evaluate the flexibility of its use in power generation to further reduce CO₂ emissions.

Die Integration volatiler erneuerbaren Energiequellen in den Strommarkt erfordert Ausgleichstechnologien, die Versorgungssicherheit gewährleisten können. Solche Technologien müssen schnelle Lastwechsel über einen großen Lastbereich durchführen können und möglichst niedrige Treibhausgasemissionen aufweisen. In der vorliegenden Arbeit wird vorgeschlagen, existierende zirkulierende Wirbelschichtkraftwerke mit Kohlefeuerung für die Co-Verbrennung von Kohle, Biomasse und Ersatzbrennstoff umzurüsten. Der Ansatz ermöglicht eine sehr schnelle und kostengünstige technische Umsetzung bei gleichzeitig hohem CO2-Einsparpotential. Bestehende Großkraftwerke sind meist auf Nennlast und für einen bestimmten Brennstoff ausgelegt. Daher besteht Forschungsbedarf, die Brennstoffflexibilität und die Lastflexibilität von zirkulierenden Wirbelschichtfeuerungen besser zu verstehen und Wege zu finden, diese zu erhöhen. Ein Fokus dieser Dissertation ist die experimentelle Untersuchung der Bedingungen im Brennraum bei der Co-Verbrennung im Lastwechselbetrieb. Dazu wurden stationäre und dynamische Versuche in einer 1 MWth Versuchsanlage zur Co-Verbrennung von Braunkohle, Strohpellets und Refuse Derived Fuel durchgeführt. Für den Co-Verbrennungsbetrieb unter transienten Bedingungen müssen insbesondere die Temperaturen und der Wärmeübergang im Brennraum beherrscht werden. Die Versuchsergebnisse zeigen die große Bedeutung der hydrodynamischen Bedingungen für den Gesamtprozess. Der Temperaturverlauf, der Ort der Verbrennung, die Wärmeübertragung in der Wirbelschicht und andere Parameter wurden durch die komplexe Gas-Partikelströmung der zirkulierenden Wirbelschicht bestimmt. In der Arbeit wird gezeigt, welche Parameter die Hydrodynamik beeinflussen. Zur Erhöhung der Lastflexibilität wurden Lastwechselversuche auf die Betriebsparameter hin untersucht, die den stärksten Einfluss auf den Wärmeübergang zur Wasser-Dampfseite haben. Die Erkenntnisse wurden genutzt, um Konzepte für die Beschleunigung von

Jens Peters, Gurdeep Singh, Hrayr Hakobyan Department of Trauma Surgery and Orthopaedics, Clinic Sulingen, Sulingen, Lower Saxony, 27232, GermanyCorrespondence: Jens Peters, Department of Trauma Surgery and Orthopaedics, Clinic Sulingen, Schmelingstrasse 47, Sulingen, Lower Saxony, 27232, Germany, Tel +49 4271 82 33210, Fax +49 4271 82 33212, Email J.Peters@kliniken-lkd.deObjective: This study describes clinical and radiological outcomes following treatment of displaced primary fractures, refractures, delayed unions and non-unions of the clavicle with open reduction and internal fixation (ORIF) with a plate plus filling of the residual bone defect and/or implant augmentation with a gentamicin-loaded bone graft substitute (CERAMENT G, BONESUPPORT).Patients and Methods: Patients who underwent surgical treatment either for displaced clavicle fractures, refractures, delayed unions or non-unions between June 2018 and May 2021 were enrolled in this retrospective study. Bony consolidation, complication rate, and functional outcomes, including overall health, were assessed.Results: A total of 26 clavicles in 25 patients with a mean age of 50.7 (16– 85) years, 16 male and 9 female, were enrolled in the study. The mean follow-up was 14.9 (6– 31) months. There were 18 cases of displaced clavicle fractures, four refractures, two delayed unions and two non-unions. The majority of the clavicle lesions were located at the middle third (17/26, 65.4%), seven at the lateral third (26.9%) and two at the medial third (7.7%) of the clavicle. A mean Goldberg score of 7 indicated complete bony union and remodeling of the bone graft substitute in all cases. No complications occurred. The mean University of California at Los Angeles Shoulder Score and the mean Quick Disability of the Arm, Shoulder and Hand Score were 34.6± 0.8 (32– 35) points and 0.6± 1.6 (0– 5.4) points, respectively, and revealed excellent functional results. The mean 12-item Short-Form Survey physical component