https://repositorio.ufu.br/handle/123456789/5468 2026-07-07T15:25:07Z https://repositorio.ufu.br/handle/123456789/48774 Title: Explorando a produção de hidrogênio a partir da co-gaseificação de biomassa–plástico: um estudo integrado de simulação e aprendizado de máquina Abstract: Biomass–plastic co-gasification is a promising route for producing low-carbon syngas and hydrogen; however, its optimization is challenged by nonlinear interactions among temperature, equivalence ratio, and feed composition. In this work, an integrated approach combining steady-state thermochemical process modelling and machine learning was developed to predict and optimize the performance of biomass–plastic systems. A phenomenological model was implemented in the AVEVA PRO/II simulator, structured into drying, pyrolysis, gasification, and restricted chemical-equilibrium stages, using air as the gasifying agent. The model was validated against experimental literature data, reproducing the order of magnitude of the molar fractions of H₂, CO, CO₂, and CH₄ under different operating conditions. Based on this validated platform, a synthetic dataset of 3,000 simulations was generated via Latin Hypercube Sampling, covering five plastics (HDPE, PE, PP, PS, and PET), 35 lignocellulosic biomasses, and representative ranges of temperature and equivalence ratio. Extreme Gradient Boosting (XGBoost) models were then trained to predict syngas composition (H₂, CO, and CO₂), total gas yield, lower heating value, and the H₂/CO ratio. The split into training, validation, and test sets was assessed using distance-based metrics (1-NN, MMD, and Energy Distance), ensuring representativeness and generalization. The models achieved high performance, with out-of-sample coefficients of determination above 0.98. Interpretability was examined using explainable AI techniques based on SHAP values, indicating that temperature and equivalence ratio are key drivers of H₂ formation, whereas carbon and fixed carbon contents govern CO generation. The applicability domain was verified using Mahalanobis distance, ensuring prediction reliability. Finally, Differential Evolution optimization identified synergistic biomass–plastic pairs and operating conditions that maximize hydrogen production and syngas quality. The optimal solutions favored polypropylene-rich blends with lignocellulosic biomasses, yielding H₂ fractions of approximately 28%, H₂/CO ratios close to 1.1, and lower heating values around 6.5 MJ·Nm⁻³. The proposed approach integrates mechanistic modelling, explainable machine learning, and optimization, supporting the rational design of hydrogen-oriented co-gasification systems. 2026-02-13T00:00:00Z https://repositorio.ufu.br/handle/123456789/48325 Title: Formulação de fluidos de perfuração sintético leves empregando esferas ocas de vidro Abstract: Brazil is a leading oil and gas producer in Latin America, with vast reserves and a welldeveloped infrastructure. The advancement of offshore exploration in increasingly deep waters necessitates the development of drilling fluids with enhanced properties. These fluids must be capable of balancing the pressure differential between the hydrostatic column of seawater and the geological formation while minimizing environmental impact. With the gradual depletion of reservoirs at shallow and medium depths, drilling in ultradeep water has become crucial for continued production. However, these operations demand high-performance fluids that can withstand high pressures and temperatures, in addition to complex geological formations. In this context, hollow glass microspheres (HGMs) are being studied as promising additives for drilling fluids, enabling the viability of wells with narrow pressure windows. Due to their incompressibility, these microspheres allow for a reduction in fluid density without compromising their essential rheological properties. In this study, a Central Composite Design (CCD) was conducted to evaluate the influence of key variables—such as HGM concentration, viscosifier concentration, and oil-to-water ratio (%O/W)—on the properties of synthetic drilling fluid. The properties studied included L600, L300, L200, L100, L6, L3, fluid loss, and density. The filtration mechanism of an ultra lightweight, 6.2 ppg, 100% olefinic fluid containing HGMs was also investigated. The results demonstrated the viability of applying HGMs, highlighting their potential for formulating drilling fluids in geologically complex environments. 2026-02-13T00:00:00Z https://repositorio.ufu.br/handle/123456789/46103 Title: Produção de carbonato de cálcio provenientes de rejeitos de minério de Irecê: estudo experimental Abstract: The concern for sustainability and industrial waste management, combined with the environmental, social, and economic demands of the sector, motivated this study on the production of CaCO₃ from fertilizer industry waste. The main objective is to reutilize lime sludge, a waste generated during the phosphate ore concentration process, and carbon dioxide (CO₂), a byproduct of ore calcination, to produce calcium carbonate. The study was conducted through a series of carbonation experiments, investigating the influence of operational variables such as solid content, CO₂ concentration, and mixing speed on reaction time and carbonate mass formation. A central composite design (CCD) was employed to optimize process conditions. The results demonstrated that increasing the CO₂ concentration from 12.5% to 30% and the solid content from 1.0% to 1.8% enhanced reaction efficiency. The optimized conditions for maximizing product yield and minimizing reaction time were a solid content of 1.75%, a mixing speed of 390 rpm, and a CO₂ concentration of 28.5%, achieving a process time of 28 minutes and a CaCO₃ mass of 13.52 g. The study confirms the technical feasibility of reusing waste materials such as lime sludge and CO₂, contributing to the development of sustainable processes aligned with circular economy principles and providing an alternative for the fertilizer industry and related sectors. This work reinforces the potential of sustainable practices in the fertilizer industry, offering an efficient solution for waste management and environmental liability reduction. 2025-02-27T00:00:00Z https://repositorio.ufu.br/handle/123456789/45240 Title: Avaliação da influência do espectro luminoso na produção de hidrogênio por bactérias fotossintetizantes Abstract: Considering the environmental impacts caused by the combustion of fossil fuels, researchers have been seeking technologies for sustainable energy generation. Hydrogen is seen as a clean and non-polluting alternative, whose production can be carried out biologically through photosynthetic processes, employing photosynthetic bacteria. Some parameters are important to optimize hydrogen synthesis, and evaluating light influence on the photofermentation process is crucial. In this work, the biological production of hydrogen by photofermentation using the purple non-sulfur bacteria Rhodobacter capsulatus and Rhodospirillum rubrum was studied, using lactose from powdered whey permeate at a concentration of 10 g/L as the carbon source. Small-scale assays were conducted with 50 mL reactors, varying light sources, with cold white LEDs, infrared, and spectrum-directed LEDs. It was found that both the visible and infrared ranges produced hydrogen, however, a saturation effect was observed with the combination of the two ranges. The Tukey test was performed to evaluate which light source achieved the best performance, and it was observed that the cold white LED achieved the highest maximum productivity of 8.23 ± 0.10 mmol H2/(L.day). Large-scale assays were also carried out with a 2.1 L plate-type photobioreactor under the same conditions as the small scale, but with the LEDs that achieved the best performance in the small scale. For these assays, the maximum productivity and light conversion efficiency obtained were 10.33 mmol H2/(L.day) and 1.67% for the spectrum-directed LED, and 18.64 mmol H2/(L.day) and 3.26% for the cold white LED, respectively. The condition for large-scale was also evaluated by increasing the light intensity to 5000 lx for the cold white LED and using the revitalization system, achieving a maximum value of 26.93 mmol H2/(L.day) and 4.49% ECL. 2024-07-26T00:00:00Z