Energy & Fuels最新文献

Bio-based platform chemicals are of great significance to future green fine and commodity chemicals. This study reports the performances and mechanisms of solvothermal dehydration of levoglucosan (LGA), the main precursor from noncatalytic pyrolysis of cellulose with a yield up to 80 wt %, to levoglucosenone (LGO) using cesium heteropolyacid salts at the catalyst in DMSO solvent. Catalyst characterizations revealed that cesium was well doped in the cubic of heteropolyacids, and the cesium doping ratio substantially influenced the catalytic performances toward LGO. LGO yield first increased and then decreased with the increase of cesium doping ratios, which is consistent with the change trends of pore structures and Brønsted/Lewis acid site ratios of the cesium heteropolyacid salts. LGO was obtained with the maximum yield at 41.2% over Cs₂H₂SiW₁₂O₄₀ compared to 39.2% over Cs_2.5H_0.5PW₁₂O₄₀. The catalyst can be regenerated by calcination without losing its catalytic performances. In addition, density functional theory calculation was used to reveal the mechanism for LGO formation, and the rate-determining step was the first step of the dehydration reaction with the energy barrier of 166 kJ/mol.

Wind power technology, as a crucial form of wind energy application, is one of the most mature generation methods in the global renewable energy sector. With the rapid growth of wind power, early generation wind turbines are approaching their decommissioning peak, resulting in a large volume of end-of-life wind turbine blades (EWTBs). The recycling and resource utilization of EWTBs represent a new and significant research area that could help achieve a sustainable future while reducing waste. This work focuses on efficient recycling and resource utilization of EWTBs, particularly concerning organic resins and inorganic fibers. Traditional disposal methods, such as landfilling and incineration, result in severe resource waste and environmental pollution. Therefore, the development of clean and efficient recycling solutions is imperative. To provide a comprehensive understanding of current recycling practices, this paper reviews the composition, properties, and utilization technologies of EWTBs. It systematically introduces various recycling techniques, including physical, electric-driven, thermal, and chemical recycling methods. The progress of different technologies is analyzed, with thermal conversion recycling emerging as the most promising due to its rapid conversion rate and wide feedstock applicability. Furthermore, the paper evaluates the applications of thermal-chemical recycling products. It emphasizes that future recycling methods should focus on low-temperature processing and multienergy coupling concepts. The policy adjustments will significantly impact the applicability and economic feasibility of EWTBs recycling technologies. Sustainable utilization of EWTBs necessitates collaboration among government agencies, manufacturers, and technical departments, representing a trend toward large-scale recycling of EWTBs and ensuring the efficient, environmental, and green circular development of the wind power generation industry.

Continuous fast and ex situ catalytic pyrolysis of blends of switchgrass with 15 wt % polyethylene (PE) was studied using a fluidized bed pyrolysis system. Higher than typical temperatures for biomass pyrolysis were utilized (630 °C) to overcome the higher thermal stability of polyethylene. For fast pyrolysis, the high pyrolysis temperature led to a lower yield of oil and a higher yield of gas from the switchgrass. When polyethylene was blended in, a small increase in the yield of oil was noted, and the oil had a slightly lower oxygen content and higher hydrogen content. GC/MS and NMR analysis showed that linear alkenes and alkanes were present in the oil in addition to phenolics, acids, and other oxygenates derived from biomass. However, a phase separated wax product was also formed, and this accounted for an estimated 27% of the input plastic carbon. Ethylene was also a major product of PE pyrolysis, accounting for 29% of the input plastic carbon. Only about 19% of the input plastic carbon was in the oil product. When ex situ catalytic pyrolysis was performed over HY at 250 °C, the oil product phase separated into a largely biomass derived fraction and a plastic derived fraction. When the catalysis was performed at 300 °C, there was a shift in reactivity for the blends compared with switchgrass only, decreasing CO formation and resulting in an oil rich in alkyl benzenes, alkyl naphthalenes, and alkyl phenols.

In the global push for sustainable energy, in situ combustion gasification (ISCG) has emerged as a transformative technology to leverage the world’s abundant heavy oil reserves for producing carbon-zero hydrogen. Chemical kinetics are crucial for modeling subsurface hydrogen generation and optimizing production schemes to maximize hydrogen yield, which are however currently lacking. This study aims to develop the first experimentally validated kinetic model for hydrogen generation during ISCG of heavy oil. To accurately model ISCG reactions, particularly hydrogen generation, we combined kinetic cell experiments with numerical modeling to history match the experimental results. The temporal variation of generated gases, such as hydrogen, measured in laboratory experiments, served as the baseline for history matching. A differential evolution optimization algorithm was employed to calibrate the kinetic parameters of the numerical model with experimental results. The kinetic model for combustion reactions was accurately calibrated after 454 optimization runs with a history-matching error of 3.46%. This accuracy is attributed to the well-studied nature of heavy oil oxidation and the comprehensive reaction scheme employed. Conversely, calibrating the kinetic model for gasification reactions with kinetic cell experimental results proved more challenging yielding a history-matching error of 22.19% after 488 optimization runs. Despite significant uncertainties in hydrogen generation and consumption reactions due to limited knowledge of the gasification process, our proposed kinetic model can still predict hydrogen generation with a simplified but powerful reaction scheme, compared to previously proposed ISCG models that involve numerous reactions. This work introduces the first kinetic model to describe the hydrogen generation process during ISCG of heavy oil with rigorous experimental validation. This reliable kinetic model establishes a solid foundation for future multiscale reservoir simulation and further optimization of the field development for enhanced hydrogen production in a more sustainable manner.

Coal reservoirs exhibit a ternary structure comprising pores, microfissures, and macro-fissures, crucial for determining permeability and influencing the adsorption–desorption–diffusion–seepage processes of coalbed methane (CBM). These factors significantly impact the CBM recoverability and production. Through dynamic permeability experiments, nuclear magnetic resonance (NMR) under varied confining pressures, and triaxial compression-CT scanning, the stress sensitivity of coal in different directions under varying confining pressures, pore pressures, and effective stress conditions was investigated. It is obtained that (1) the stress sensitivity of coal fissures is notably high, and they tend to close first under confining pressure. Seepage and adsorption pores exhibit two trends: a gradual decrease or an initial increase followed by a decrease. With deeper coal metamorphism, the stress sensitivity of fissures gradually diminishes, while the stress sensitivity of adsorption pores increases. (2) The fissure compressibility measured by He is the lowest, CO₂ is always the highest, and CH₄ is between the two. The fissure compressibility measured by He decreases exponentially with the increase of pore pressure, while the adsorbed gases CH₄ and CO₂ change complicatedly, decreasing exponentially, or parabolically. (3) The significant stress sensitivity and permeability damage rate occur in the direction of parallel-face cuttings of experimental coals, while the vertical direction exhibits the weakest characteristics. Nonhomogeneity is most pronounced between these two directions. The anisotropy of the coal reservoir diminishes gradually with increasing peripheral pressure.

Biochar has sparked interest as a strategy for carbon capture and sequestration to offset carbon dioxide emissions, along with its various applications such as soil amendment, filler, catalyst, food/feed additive, or adsorbent. This interest is not merely a media-driven opportunity, but also stems from the ample availability of residual biomass and organic waste that can be transformed and integrated into production chains to reduce their environmental footprint. However, this interest attracts the adoption of production technologies that, while meeting the goal of carrying out the pyrolysis process, need to be environmentally sustainable. In this paper, a model based on laboratory-scale experimentation results is proposed and three fundamental stages of the industrial pyrolysis process for the sole production of biochar are explored: drying, pyrolysis itself, and the combustion of gases and vapors as an energy source. In this scenario, the production of pyrolysis liquids is avoided, eliminating the need for condensation equipment, reducing operating costs, and preventing handling problems and potential contamination of the biochar. Three types of biomasses were used experimentally to evaluate the yields and characteristics of the pyrolysis products: cocoa bean shells, white spruce bark, and poplar bark. Cocoa bean shells were then selected to investigate the sensitivity of the main model parameters. The study demonstrates that the combustion of gases and vapors produced during the pyrolysis process of dried feedstocks generates sufficient energy to sustain the process itself. The efficiency of the combustion process, the heat transfer to the pyrolysis reactor, and the input moisture of the biomass feedstock represent the critical parameters affecting the thermal sustainability of the process.

All-inorganic Sn–Ge-based perovskite solar cells (PSCs) have made great progress in recent years. Furthermore, they can be used as promising lead-free absorbers for PSCs, and p-type-doped CsSnI₃, CsGeI₃, and CsSn_0.5Ge_0.5I₃ could also be used as good hole transport layers (HTLs). In this simulation work, CsSnI₃, CsGeI₃, and CsSn_0.5Ge_0.5I₃ are used as both absorbers and HTLs. The effects of the dopant concentration of HTLs, the thickness of absorbers, and HTLs on the photovoltaic performance of PSCs were studied to optimize the device structures. The maximum efficiencies from high to low are 28.35%, 26.35%, 25.84%, 25.23%, 18.83%, 17.49%, and 11.79% for the TiO₂/i-CsSnI₃/p-CsSnI₃, TiO₂/i-CsSn_0.5Ge_0.5I₃/p-CsSn_0.5Ge_0.5I₃, TiO₂/i-CsSn_0.5Ge_0.5I₃/p-CsSnI₃, TiO₂/i-CsSnI₃/p-CsGeI₃, TiO₂/i-CsSn_0.5Ge_0.5I₃/p-CsGeI₃, TiO₂/i-CsGeI₃/p-CsGeI₃, and TiO₂/i-CsGeI₃/p-CsSnI₃, respectively. The TiO₂/i-CsGeI₃/p-CsSnI₃ cell exhibits the lowest efficiency of 11.79% in all of the simulated PSCs due to the spike-like band offset at the i-CsGeI₃/p-CsSnI₃ interface and high recombination rate in the p-CsSnI₃ region. It is found that the n-p structures could have better photovoltaic performance (thickness of i-film approaching zero) than the conventional n-i-p structures for the TiO₂/i-CsSnI₃/p-CsSnI₃, TiO₂/i-CsGeI₃/p-CsGeI₃, and TiO₂/i-CsSn_0.5Ge_0.5I₃/p-CsSn_0.5Ge_0.5I₃ PSCs if the defects in HTLs created by high doping can be effectively controlled. The efficiencies of PSCs are sensitive to the defect density and defect level position, and the influence of defect density on the PV performance is larger than that of the defect level position. The solar cells could maintain high power conversion efficiency for defect density below about 5 × 10¹⁷ cm^–3. Furthermore, the increase of the interface trap density is found to reduce the photovoltaic performance of PSCs. Our study provides insight into the optimal design of CsSn_xGe_1–xI₃-based PSCs.

An accurate and efficient skeletal mechanism is critical to describe the combustion chemistry of CH₄/H₂ with nitrogen oxides (NO_x) through computational fluid dynamics (CFD) simulations. In this paper, the performance of the 11 classical/state-of-the-art detailed C/H/O/N mechanisms (1995–2020) for predicting combustion of CH₄, H₂, and their mixtures is comprehensively and quantitatively evaluated. Based on the best-performing one Glarborg2018, a 60-species and 566-reaction skeletal C_1–2/H/O/N mechanism with NO_x chemistry for CH₄/H₂ combustion over a wide range of hydrogen-blending ratios from 0 to 100% is developed using the directed relation graph with error propagation (DRGEP), sensitivity analysis (SA), and quasi-steady-state-approximation (QSSA) methods. Also, the present newly developed skeletal mechanism is comprehensively evaluated against large numbers of available experimental data (∼3500 data points) for combustion of CH₄, H₂, and their mixtures, in terms of ignition delay times, laminar burning velocities, flame structures (i.e., temperature and species (reactants, intermediates, and final products, including CH₄, H₂, O₂, CO, CO₂, CH₂O, C₂H₄, C₂H₆, N₂, and H₂O) concentrations), NO_x emissions, as well as NO formation and reduction via different submechanisms. Results show that Glarborg2018 performs best in predicting NO from combustion of CH₄, H₂, and their mixtures, especially at high temperatures. The present newly developed skeletal mechanism can reasonably well predict NO_x emissions in CH₄/H₂ combustion over a wide range of hydrogen-blending ratios from 0 to 100% at low-/intermediate-/high-temperature levels (e.g., 650–2200 K), which is superior to the existing skeletal ones; in particular, thermal NO, prompt NO, NO formed via NNH and N₂O-intermediate, as well as NO reduced by HCCO/CH_i=0–3 and H can be separately reproduced. In conclusion, the present newly developed skeletal C_1–2/H/O/N mechanism preserves comparable prediction accuracy compared to its parent Glarborg2018 and is applicable to model combustion of CH₄, H₂, and their mixtures with NO_x chemistry over a wide range of low, intermediate, and high temperatures.