1,720,960 research outputs found
Techno-economic analysis of a solar-driven biomass pyrolysis plant for bio-oil and biochar production
No full textPyrolysis has become one of the most attractive options for converting carbonaceous biomass into bio-oil or biochar. This study explores a novel solar pyrolysis process intended to produce both bio-oil and biochar, thereby improving carbon efficiency. Aspen Plus and SolarPILOT were used to model a 10 MW biomass pyrolysis plant thermally sustained by hot particles from a falling-particle solar tower receiver. A yearly analysis was carried out for three configurations to estimate the annual production of oil and biochar. The results showed that the hybrid plant, combining solar receiver and biochar backup combustor, leads to the lowest cost of bio-oil (18.7 per GJ, or 0.29 per kg) and a carbon efficiency of 83%. Whereas, the plant fully sustained by solar power achieves a carbon efficiency of 90%; however, it results in a significantly higher cost of bio-oil (21.8 per GJ, or 0.34 per kg) due to the larger size of particle storage and a lower capacity factor of the pyrolysis plant. In comparison, a conventional pyrolysis plant with no biochar production yielded the most expensive option in terms of the cost of produced bio-oil (27.5 per GJ) and features the lowest carbon efficiency (74%). Sensitivity analysis shows that the pyrolyzer Capex, operational cost, biochar market price, plant availability and discount rate significantly affect bio-oil production cost.Transforming conventional biomass pyrolysis through solar-driven pyrolysis with a falling particle receiver and intermediate hybrid solution reduces costs by 21% and 32% and emissions by 27.5 and 22.3 kgCO2 GJoil-1, respectively
Impact of high-temperature biomass pyrolysis on biochar formation and composition
Full text linkThe development and utilization of biomass play a vital role in reducing fossil fuel dependency and mitigating greenhouse gas emissions. High-temperature pyrolysis provides a promising route for converting biomass into valuable products without tar formation. Kinetic models are essential for understanding biomass pyrolysis processes, aiding reactor design and optimization. In this study, rice husk (RH) and corn straw (CS) are selected, which exhibit significant differences in ash content but are widely present. Pyrolysis is performed using a thermogravimetric analyzer coupled with a mass spectrometer (TGA-MS). The results show a rapid decrease in solid residue oxygen content at elevated temperatures, which stabilized after reaching 900 degrees C, accounting for about 8-10%. MS quantification indicates increased release of H2O and CO during this stage. Fourier transform infrared spectroscopy (FTIR) analysis on the biochar unveils that this phenomenon is attributed to the stretching vibration of C-O bonds and the conversion of -OH groups. The remaining oxygen primarily exists as carbonyl and carboxyl groups. Subsequently, the CRECK-S-B biomass pyrolysis kinetic model is updated, specifically targeting the transformation mechanism of oxygen-containing solids at high temperatures to improve the prediction of biochar yield and elemental composition. The relative error of oxygen content prediction is less than 10%. The accuracy of the model is validated through experimental data and an extensive literature database, leading to the establishment of a comprehensive database. The updated model demonstrates significantly enhanced prediction accuracy for pyrolysis temperatures above 800 degrees C, expanding its applicability range. Moreover, it achieves an accuracy rate exceeding 80% for char yield and elemental content in the temperature range of 200-1000 degrees C, including torrefaction conditions. It provides a theoretical foundation for the effective utilization of hightemperature biochar, offers a novel insight into biomass thermochemical conversion, and contributes to the sustainable development of biomass energy
Recent developments and challenges in biomass cookstove
Full text linkThe growing demand for more efficient cooking methods has been fueled by the rapid advancements in biomass utilization. Considerable progress has been made in the development of a biomass cookstove that is both highly thermally efficient and produces less pollution. This review provides a comprehensive overview of the current status and advancements in biomass cookstove technologies. It explores various types of biomass cookstoves, with a particular focus on advanced models available in the market. The paper explores the recent advancements, highlighting the effectiveness of ceramic materials in combustion chambers for reducing emissions, and the impact of introducing swirl vanes and hybrid air injection systems on fuel consumption and overall performance. The review also discusses the important design strategies and limitations that affect the efficiency of these cookstoves. In addition, it acknowledges the considerable challenges in the field, such as design limitations, maintenance, and performance testing variations. Given recent advancements in biomass cookstove technologies, this review identifies important areas for future research. Although there have been significant research in the field of biomass cookstove, there are still gaps in the literature, particularly when it comes to complex heat transfer mechanism. These gaps in knowledge emphasize the need for further investigation to develop more practical and efficient cooking technologies
Production of Biochar by Slow and Solar-Biomass Pyrolysis: Focus on the Output Configuration Assessment, Adaptability, and Barriers to Market Penetration
No full textBiochar production through slow pyrolysis is a versatile and adaptable approach for managing diverse biomass waste. However, their industrial applications remain limited because of their high energy consumption and the emission of toxic gases. Solar-biomass pyrolysis systems have been proposed to address these challenges. This review examines the relationship between output configuration and the adaptability of slow and solar-biomass pyrolysis systems for biochar production. Studies have revealed that the average heat energy required for thermal conversion of biomass to biochar ranges from 1.94 to 2.67 kJ/kg K can be achieved through both conventional and solar pyrolysis routes. Solar pyrolysis demonstrates maximum power and flux density of 1.5 kW and 12,000 kW/m2, respectively, aligning with the power and temperature range of conventional slow pyrolysis. Moreover, solar pyrolysis emits approximately 58.89% less CO2 as compared to the conventional electrical heating-based pyrolysis. Despite these advantages, the market implementation of solar-biomass pyrolysis systems is limited, necessitating the resolution of various barriers for commercial applications. The current review concludes by providing future recommendations, emphasizing the development of an eco-friendly solar-biomass pyrolysis system for large-scale biochar production
Development of a multiphase chemical reactor network method as a tool for simulating biomass gasification in fluidized beds
No full textIn the near future, biomass is expected to be a key resource for fulfilling clean energy requirements. The predictive modeling of biomass conversion in industrial systems is still challenging due to the multi-scale nature of the processes involved, including complex chemical reactions. To provide a detailed description and analysis of these reactions and their coupling to transport phenomena in large-scale systems, this work introduces a multiphase reactor network method incorporating efficient solution algorithms for engineering reacting systems. The method developed includes a novel multiphase solid-gas perfectly stirred reactor (sPSR) model capable of handling solid-and gas-phase reactions as well as heterogeneous reactions, in a fully coupled way. The sPSR approach, which is included in reactor networks with various levels of complexity, improves the analysis and understanding of physical and chemical phenomena occurring in gasifiers. Steam and air gasification experiments are analyzed using the new approach and fundamental differences and effects are revealed. Major findings include the importance of solid-gas coupling, char conversion reactions, and water-gas shift (WGS) reaction catalysis due to bio-ash. In addition, increasing the complexity of the reactor network achieves a better repro-duction of the mixing behavior. The capability of handling complex reactor networks with detailed kinetics paves the way for efficient designs and improved reactors
Techno-economic assessment of a solar-driven pyrolysis process using molten salts solar tower technology
No full textLAUREA MAGISTRALENell’ambito della transizione energetica, si prevede che i biocombustibili giocheranno un ruolo cruciale nella sostituzione dei combustibili fossili, soprattutto nei settori in cui l'elettrificazione è difficile (ad esempio, il settore dei trasporti e in particolare quello a lunga distanza). In questo scenario, una delle soluzioni promettenti è il processo di pirolisi, che può convertire varie biomasse carboniose in bio-olio, che può poi essere ulteriormente raffinato per produrre biocarburanti. Ad oggi, gli impianti esistenti bruciano i co-prodotti del processo (biochar e gas di pirolisi) per soddisfare la domanda energetica delle reazioni endotermiche di pirolisi, producendo emissioni di CO2 e perdendo prodotti che possono essere venduti sul mercato. Lo scopo di questo studio è di investigare la fattibilità tecno-economica di un nuovo impianto, in cui il calore richiesto è fornito da un sistema a torre solare a concentrazione (CST) che utilizza i sali solari come fluido termovettore. La novità di questo lavoro è rappresentata dall'accoppiamento dell'impianto CST con il reattore di pirolisi attraverso l'aggiunta di uno scambiatore di calore a fascio tubiero al suo interno, per sfruttare la potenza termica dei sali solari caldi che fluiscono al suo interno. L'impianto può lavorare in due modi: utilizzando solo l'energia solare termica prodotta o in modo ibrido, cioè bruciando i co-prodotti del processo durante le ore in cui l'impianto solare non funziona. È stata quindi condotta un'analisi delle prestazioni annuali variando le dimensioni del campo solare per multipli solari da 1 a 9, per determinare la produzione annuale di bio-olio e dei co-prodotti, e poi un'analisi tecno-economica per determinare il prezzo minimo di vendita del bio-olio che garantisce un valore attuale netto (NPV) pari a zero. Il prezzo di vendita più basso si ottiene per l'impianto ibrido, con un valore di 20,3 €/GJ (0,319 €/kg), mentre l'impianto convenzionale ha il valore più alto di 27,53 €/GJ (0,433 €/kg). La configurazione ibrida è la più conveniente in quanto consente un numero maggiore di ore di funzionamento rispetto al caso sola-only, permettendo di avere un campo solare più piccolo e un recupero anticipato del capitale speso. L'impianto solo solare ha invece un prezzo di vendita ottimale intermedio rispetto ai casi precedenti, pari a 23,4 €/GJ (0,366 €/kg), ma ha il vantaggio di avere il minore impatto ambientale. Infine, dall'analisi di sensibilità condotta, il prezzo del bio-olio è fortemente influenzato dal costo di investimento del pirolizzatore, che rappresenta una grande frazione dei costi totali dell'impianto di pirolisi, e dalla disponibilità annuale dell'impianto solare, poiché determina la quantità di bio-olio prodotto e di biochar risparmiato.In the context of energy transition, biofuels are expected to play a crucial role in replacing fossil fuels, especially in sectors where electrification is challenging (i.e. transport sector and in particular long-distance one). In this scenario, one of the promising solutions is the pyrolysis process, which can convert various carbonaceous biomasses into bio-oil, which can then be refined further to produce biofuels. To date, existing plants burn by-products (i.e. biochar and pyrolysis gas) to meet the energy demand of the endothermic pyrolysis process, producing CO2 emissions and losing products that can be sold on the market. The purpose of this study is to investigate the techno-economic feasibility of a new plant configuration, in which the required heat is supplied by a concentrating solar tower (CST) system using solar salts as heat transfer fluid. The novelty of this work is represented by coupling CST plant with pyrolysis reactor through the addition of a shell-and-tube heat exchanger within it, to exploit the thermal power of hot solar salts flowing into it. The plant can work in two ways: using only the solar thermal energy produced (CSP based case) or in a hybrid way, i.e. burning the by-products of the process during the hours when the solar plant is not working. An annual performance analysis was then conducted varying the solar field size for solar multiples from 1 to 9, to determine the annual production of bio-oil and by-products, and then a techno-economic analysis was carried out to determine the minimum selling price of bio-oil that guarantees a zero net present value (NPV). The lowest selling price is obtained for the hybrid plant, with a value of 20.3 €/GJ (0.319 €/kg), while the conventional plant has the highest value of 27.53 €/GJ (0.433 €/kg). The hybrid configuration is the most cost-effective since it allows a higher number of operating hours than solar-only case, enabling a smaller solar field and an earlier payback of the capital expenditure. The solar-only plant has an intermediate optimum selling price compared to the previous cases, at 23.4 €/GJ (0.366 €/kg) but has the advantage of having the lowest environmental impact. Finally, from the sensitivity analysis conducted, the price of bio-oil is strongly influenced by the investment cost of the pyrolizer, which represents a big fraction of the total costs of the pyrolysis plant, and by the annual solar plant availability, since it determines the quantity of bio-oil produced and saved biochar
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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