Development of advanced electricity production systems with biomass.

The purpose of this Ph.D thesis is the integrated approach to the design of thermochemical processes of biomass utilization for renewable energy production. Biomass is a renewable energy source (R.E.S.) with great potential and within the European Union represents one of the main pathways to achieve its energy system independence from fossil fuels for both environmental and political reasoning. In the past years within the European Union, the efficient power production from biomass has been the subject of intense applied research. The main thermochemical processes for biomass utilization for power production are combustion and gasification. Biomass gasification can be integrated into more efficient systems, but as a technology is still confronted with several technical problems which limit its full scale commercial deployment. The promising process of fluidized bed biomass gasification is explained and the design and experiments in a lad scale pilot fluidized bed facility that was build for this purpose are presented in the experimental part of the thesis. The combination of biomass gasification and the utilization of hydrogen rich product gas into fuel cells can offer advanced power producing systems with high efficiencies. A system like that, with allothermal biomass gasification and solid oxide fuel cells is examined and analyzed intensively by using the process simulation software AspenplusTM. The integration of the system is examined exergetically. The thesis comprises of eight chapters (1-8). Chapters 1-4 give the required knowledge to deal with the main innovative parts of the thesis. In Greek language there was not up to now a technology overview text like that, and its incorporation to the thesis was done to allow future young researchers to easily acquire the basics in the field of bioenergy. Chapter 5 is a description of the laboratory fluidized bed installation and the gasification experiments. Chapter 6 presents the simulation and design of an integrated allothermal biomass gasification with solid oxide fuel cells system. In Chapter 7 the proposed system is analyzed exergetically. Chapter 8 is the summary of the thesis with the results and recommendations for future research. More analytically for each chapter:Ο στόχος της παρούσας διδακτορικής διατριβής είναι η ολοκληρωμένη προσέγγιση στο σχεδιασμό θερμοχημικών διεργασιών αξιοποίησης βιομάζας για την παραγωγή ανανεώσιμης ενέργειας. Η βιομάζα, μια ανανεώσιμη πηγή ενέργειας (Α.Π.Ε.) με μεγάλο δυναμικό, αποτελεί για την Ενωμένη Ευρώπη έναν από τους κύριους τρόπους ώστε να επιτευχθούν οι στόχοι για ανεξαρτητοποίηση του ενεργειακού συστήματός της από τα ορυκτά καύσιμα τόσο για περιβαλλοντικούς όσο και πολιτικούς λόγους. Η αποτελεσματική παραγωγή ηλεκτρισμού από βιομάζα έχει αποτελέσει αντικείμενο έντονης εφαρμοσμένης ερευνητικής δραστηριότητας εντός της Ευρωπαϊκής Ένωσης τα τελευταία έτη. Οι κυριότερες θερμοχημικές διεργασίες αξιοποίησης της βιομάζας για την παραγωγή ηλεκτρισμού είναι η καύση και η αεριοποίηση. Η αεριοποίηση βιομάζας μπορεί να προσφέρει συστήματα με μεγαλύτερες αποδόσεις αλλά ως τεχνολογία βρίσκεται ακόμα αντιμέτωπη με διάφορα τεχνικά προβλήματα που περιορίζουν την εφαρμογή της σε ευρεία κλίμακα. Η υποσχόμενη τεχνολογία της αεριοποίησης βιομάζας σε ρευστοποιημένη κλίνη αναλύεται διεξοδικά ενώ στο πειραματικό τμήμα της διατριβής παρουσιάζεται ο σχεδιασμός και η εκτέλεση πειραμάτων αεριοποίησης σε εργαστηριακής κλίμακας ολοκληρωμένο πιλοτικό σύστημα ρευστοποιημένης κλίνης που κατασκευάστηκε για το σκοπό αυτό. Ειδικότερα ο συνδυασμός της αεριοποίησης βιομάζας και η χρήση του πλούσιου σε υδρογόνο παραγόμενου αερίου σε ηλεκτροχημικά στοιχεία καυσίμου αποτελεί τεχνολογική πρόκληση για τη δημιουργία προηγμένων ηλεκτροπαραγωγικών συστημάτων με υψηλές αποδόσεις. Ένα τέτοιο ολοκληρωμένο σύστημα με αλλοθερμική αεριοποίηση βιομάζας και ηλεκτροχημικά στοιχεία καυσίμου στερεού οξειδίου εξετάζεται διεξοδικά χρησιμοποιώντας το υπολογιστικό πακέτο προσομοίωσης διεργασιών Aspenplus. Η ολοκλήρωση του συστήματος εξετάζεται εξεργειακά. Η διατριβή αποτελείται από οχτώ κεφάλαια (1-8). Τα κεφάλαια 1-4 δίνουν την απαραίτητη υποστηρικτική γνώση για την αντιμετώπιση του κυρίως πρωτότυπου τμήματος του διδακτορικού που ακολουθεί. Στην Ελληνική γλώσσα δεν υπάρχει μέχρι σήμερα αντίστοιχο κείμενο, και η ενσωμάτωσή του στο διδακτορικό κρίθηκε σκόπιμη με στόχο τη υποβοήθηση μελλοντικών ερευνητών ώστε να μπορούν να ενημερωθούν γρήγορα και να αποκτήσουν βασικές γνώσεις γύρω από τα θέματα της παραγωγής ενέργειας από βιομάζα. Το κεφάλαιο 5 αποτελεί περιγραφή του σχεδιασμού της πειραματικής εγκατάστασης ρευστοποιημένης κλίνης και την πραγματοποίηση πειραμάτων αεριοποίησης. Στο κεφάλαιο 6 περιγράφεται διεξοδικά η προσομοίωση και σχεδιασμός ολοκληρωμένου συστήματος αλλοθερμικής αεριοποίησης βιομάζας με χρήση του αερίου σε ηλεκτροχημικά στοιχεία καυσίμου στερεού οξειδίου ενώ στο κεφάλαιο 7 πραγματοποιείται εξεργειακή ανάλυση του προτεινόμενου συστήματος. Το κεφάλαιο 8 αποτελεί την ανακεφαλαίωση της διατριβής με τα προκύπτοντα συμπεράσματα και προτάσεις μελλοντικής έρευνας. Περισσότερο αναλυτικά για κάθε κεφάλαιο: Στο κεφάλαιο 1 γίνεται μια ανασκόπηση της κατάστασης της παραγωγής ενέργειας εντός της Ευρωπαϊκής Ένωσης με σκοπό να αναδειχθεί ο σημασία που έχει η αξιοποίηση των ανανεώσιμων πηγών ενέργειας. H E.E. έχει θέσει ως στόχο να παράγει το 12,5% του ηλεκτρισμού της το έτος 2010 από Α.Π.Ε. Σε αυτό το ποσό η βιομάζα αναμένεται να συνεισφέρει περίπου 230 TWhe, που αντιστοιχεί στο 65% περίπου της αναμενόμενης ηλεκτροπαραγωγής από Α.Π.Ε. Αυτό φανερώνει τη μεγάλη σπουδαιότητα που θα πρέπει να δοθεί στην βιομάζα για την ηλεκτροπαραγωγή τα επόμενα χρόνια. Οι λόγοι που οδηγούν την Ευρωπαϊκή Ένωση στη χρησιμοποίηση των ανανεώσιμων πηγών ενέργειας είναι τόσο περιβαλλοντικοί, που συνοψίζονται στις δεσμεύσεις της Ένωσης απέναντι στην συμφωνία του Κιότο, όπως επίσης και πολιτικοί, καθώς η Ένωση επί του παρόντος είναι κατά μεγάλο ποσοστό εξαρτώμενη από εισαγωγές ορυκτών καυσίμων από ασταθείς πολιτικά περιοχές του πλανήτη

Energy-Economic Assessment of Islanded Microgrid with Wind Turbine, Photovoltaic Field, Wood Gasifier, Battery, and Hydrogen Energy Storage

Island energy systems are becoming an important part of energy transformation due to the growing needs for the penetration of renewable energy. Among the possible systems, a combination of different energy generation technologies is a viable option for local users, as long as energy storage is implemented. The presented paper describes an energy-economic assessment of an island system with a photovoltaic field, small wind turbine, wood chip gasifier, battery, and hydrogen circuit with electrolyzer and fuel cell. The system is designed to satisfy the electrical energy demand of a tourist facility in two European localizations. The operation of the system is developed and dynamically simulated in the Transient System Simulation (TRNSYS) environment, taking into account realistic user demand. The results show that in Gdansk, Poland, it is possible to satisfy 99% of user demand with renewable energy sources with excess energy equal to 31%, while in Agkistro, Greece, a similar result is possible with 43% of excess energy. Despite the high initial costs, it is possible to obtain Simple Pay Back periods of 12.5 and 22.5 years for Gdansk and Agkistro, respectively. This result points out that under a high share of renewables in the energy demand of the user, the profitability of the system is highly affected by the local cost of energy vectors. The achieved results show that the system is robust in providing energy to the users and that future development may lead to an operation based fully on renewables

Atmospheric fluidized bed gasification of promising biomass fuels in southern European regions

Three promising biomass fuels from southern European regions were gasified atmospherically with air in a lab-scale fluidized bed reactor with quartz or olivine as bed material. The fuels used were an agro-industrial residue (olive bagasse) and the energy crops giant reed and sweet sorghum bagasse. Varying air ratios and temperatures were tested to study the impact on the product gas composition and tar load. Tars were higher in the case of olive bagasse, attributed to its higher lignin content compared to the other two biomasses with higher cellulose. Giant reed gasification causes agglomeration and defluidisation problems at 790°C while olive bagasse shows the least agglomeration tendency. The particular olivine material promoted the destruction of tars, but to a lesser level than other reported works; this was attributed to its limited iron content. It also promoted the H2 and CO2 production while CO content decreased. Methane yield was slightly affected (decreased) with olivine, higher temperatures, and air ratios. Air ratio increase decreased the tar load but at the same time the gas quality deteriorated.

ATMOSPHERIC FLUIDISED BED GASIFICATION OF PROMISING BIOMASS FUELS IN SOUTHERN EUROPEAN REGIONS by

Three promising biomass fuels from southern European regions were gasified atmospherically with air in a lab-scale fluidised bed reactor with quartz or olivine as bed material. The fuels used were an agro-industrial residue (olive bagasse) and the energy crops gi ant reed and sweet sorghum bagasse. Varying air ratios and temperatures were tested to study the impact on the product gas composition and tar load. Tars were higher in the case of olive bagasse, attributed to its higher lignin content compared to the other two biomasses with higher cellulose. Giant reed gasification causes agglomeration and defluidisation problems at 790 °C while olive bagasse shows the least agglomeration tendency. The particular olivine material promoted the destruction of tars, but to a lesser level than other reported works; this was attributed to its limited iron content. It also promoted the H2 and CO2 production while CO content de creased. Meth ane yield was slightly affected (decreased) with olivine, higher tem per a tures, and air ratios. Air ratio increase decreased the tar load but at the same time the gas quality deteriorated

Adsorption of thiophene by activated carbon: A global sensitivity analysis

The removal of sulfur compounds in biomass gasification processes is crucial to protect downstream equipment. While conventional sorbent materials can retain H2S, many fail to capture heterocyclic sulfur compounds such as thiophene (C4H4S). This work explored activated carbons (ACs) for the removal of thiophene from the gas phase both experimentally and by employing different models. Experiments were performed in a laboratory packed bed column between 100-200 degrees C at various gas flow-rates and inlet concentrations. Altering the temperature had the strongest effect with breakthrough capacities ranging from 7-138 mmol kg(-1). The transient adsorption process was described by a 1-D approach, including mass transfer phenomena and axial dispersion. Experimental validation showed good agreement between measured and predicted breakthrough times and capacities. A global sensitivity analysis (GSA) was performed to obtain a ranking of importance of model input factors and gain further process insight. The GSA included 12 model parameters and a selection of axial dispersion correlations and isotherm models. Based on the chosen range of input factors, the GSA indicated that the type of isotherm model, axial dispersion correlation, and temperature have a major effect on the predicted breakthrough time. The calculated slope of the curve is strongly affected by the isotherm model and axial dispersion correlation. Overall, this work showed that ACs are a promising option for thiophene removal and provided a generic approach for the application of GSA to adsorption models. In the given context the analysis demonstrated that the selection of common model assumptions deserves as much attention as the model parameters

One-Dimensional Heterogeneous Reaction Model of a Drop-Tube Carbonator Reactor for Thermochemical Energy Storage Applications

Calcium looping systems constitute a promising candidate for thermochemical energy storage (TCES) applications, as evidenced by the constantly escalating scientific and industrial interest. However, the technologically feasible transition from the research scale towards industrial and highly competitive markets sets as a prerequisite the optimal design and operation of the process, especially corresponding reactors. The present study investigates for the first time the development of a detailed, one-dimensional mathematical model for the steady-state simulation of a novel drop-tube carbonator reactor as a core equipment unit in a concentrated solar power (CSP)-thermochemical energy storage integration plant. A validated kinetic mathematical model for a carbonation reaction (CaO(s) + CO2(g) → CaCO3(s)) focused on thermochemical energy storage conditions was developed and implemented for different material conditions. The fast gas–solid reaction kinetics conformed with the drop-tube reactor concept, as the latter is suitable for very fast reactions. Reaction kinetics were controlled by the reaction temperature. Varying state profiles were computed across the length of the reactor by using a mathematical model in which reactant conversions, the reaction rate, and the temperature and velocity of gas and solid phases provided crucial information on the carbonator’s performance, among other factors. Through process simulations, the model-based investigation approach revealed respective restrictions on a tailor-made reactor of 10 kWth, pointing out the necessity of detailed models as a provision for design and scale-up studies

AGGLOMERATION PROBLEMS DURING CARDOON FLUIDIZED BED GASIFICATION

Cynara Cardunculus, commonly known as cardoon is a potential energy crop native to th

Sustainable Exploitation of Biogas Plant Digestate for the Production of High-Quality Products Using Selective Electrodialysis

The reuse of nutrient-rich waste in order to create green fertilizers in a sustainable and efficient way is a new strategy for the transition to a circular economy. Digestate is produced as a by-product from anaerobic digestion plants in large amounts creating a major management issue both for storage, utilization or disposal. The current work focuses on the development of an innovative, small-scale technology for the processing of digestate from anaerobic digestion plants that use food, animal, agricultural and sludge waste. The technology targets the recovery of fibres and nutrients for the production of high-performance bio-fertiliser products and clean water from digestate

Economic Evaluation of Renewable Hydrogen Integration into Steelworks for the Production of Methanol and Methane

This work investigates the cost-efficient integration of renewable hydrogen into steelworks for the production of methane and methanol as an efficient way to decarbonize the steel industry. Three case studies that utilize a mixture of steelworks off-gases (blast furnace gas, coke oven gas, and basic oxygen furnace gas), which differ on the amount of used off-gases as well as on the end product (methane and/or methanol), are analyzed and evaluated in terms of their economic performance. The most influential cost factors are identified and sensitivity analyses are conducted for different operating and economic parameters. Renewable hydrogen produced by PEM electrolysis is the most expensive component in this scheme and responsible for over 80% of the total costs. Progress in the hydrogen economy (lower electrolyzer capital costs, improved electrolyzer efficiency, and lower electricity prices) is necessary to establish this technology in the future