Search Results (415)

Minimizing carbon dioxide emissions is crucial due to the generation of energy from fossil fuels. The significance of carbon capture and storage (CCS) technology, which is highly successful in mitigating carbon emissions, has increased. On the other hand, hydrogen is an important energy carrier for storing and transporting energy, and technologies that rely on hydrogen have become increasingly promising as the world moves toward a more environmentally friendly approach. Nevertheless, the integration of CCS technologies into power production processes is a significant challenge, requiring the enhancement of the combined power generation–CCS process. In recent years, there has been a growing interest in process intensification (PI), which aims to create smaller, cleaner, and more energy efficient processes. The goal of this research is to demonstrate the process intensification potential and to model and simulate a hybrid integrated–intensified adsorptive-membrane reactor process for simultaneous carbon capture and hydrogen production. A comprehensive, multi-scale, multi-phase, dynamic, computational fluid dynamics (CFD)-based process model is constructed, which quantifies the various underlying complex physicochemical phenomena occurring at the pellet and reactor levels. Model simulations are then performed to investigate the impact of dimensionless variables on overall system performance and gain a better understanding of this cyclic reaction/separation process. The results indicate that the hybrid system shows a steady-state cyclic behavior to ensure flexible operating time. A sustainability evaluation was conducted to illustrate the sustainability improvement in the proposed process compared to the traditional design. The results indicate that the integrated–intensified adsorptive-membrane reactor technology enhances sustainability by 35% to 138% for the chosen 21 indicators. The average enhancement in sustainability is almost 57%, signifying that the sustainability evaluation reveals significant benefits of the integrated–intensified adsorptive-membrane reactor process compared to HTSR + LTSR. Full article

Solid fuels are still widely used in household heating in Europe and North America. Emissions from boilers are released in proximity to people. Therefore, there is a need to minimise the toxicity of emissions affecting human health to the greatest extent possible. This study compares the genotoxic potential of the emissions of four boilers of modern and old design (automatic, gasification, down-draft, over-fire) operating at reduced output to simulate the real-life combustion fed by various fossil and renewable solid fuels (hard coal, brown coal, brown coal briquettes, wood pellets, wet and dry spruce). Organic emissions were tested for genotoxic potential by analysing bulky DNA adducts and 8-oxo-dG adduct induction. There was no consistent genotoxic pattern among the fuels used within the boilers. Genotoxicity was strongly correlated with polycyclic aromatic hydrocarbon (PAH) content, and even stronger correlation was observed with particulate matter (PM). In all measured variables (PM, PAHs, genotoxicity), the technology of the boilers was a more important factor in determining the genotoxic potential than the fuels burned. The highest levels of both bulky and 8-oxo-dG DNA adducts were induced by organics originating from the over-fire boiler, while the automatic boiler exhibited genotoxic potential that was ~1000- and 100-fold lower, respectively. Full article

Calorific value and moisture content are the key indices to evaluate Caragana pellet fuel’s quality and combustion characteristics. Calorific value is the key index to measure the energy released by energy plants during combustion, which determines energy utilization efficiency. But at present, the determination of solid fuel is still carried out in the laboratory by oxygen bomb calorimetry. This has seriously hindered the ability of large-scale, rapid detection of fuel particles in industrial production lines. In response to this technical challenge, this study proposes using hyperspectral imaging technology combined with various chemometric methods to establish quantitative models for determining moisture content and calorific value in Caragana korshinskii fuel. A hyperspectral imaging system was used to capture the spectral data in the 935–1720 nm range of 152 samples from multiple regions in Inner Mongolia Autonomous Region. For water content and calorific value, three quantitative detection models, partial least squares regression (PLSR), random forest regression (RFR), and extreme learning machine (ELM), respectively, were established, and Monte Carlo cross-validation (MCCV) was chosen to remove outliers from the raw spectral data to improve the model accuracy. Four preprocessing methods were used to preprocess the spectral data, with standard normal variate (SNV) preprocessing performing best on the quantitative moisture content detection model and Savitzky–Golay (SG) preprocessing performing best on the calorific value detection method. Meanwhile, to improve the prediction accuracy of the model to reduce the redundant wavelength data, we chose four feature extraction methods, competitive adaptive reweighted sampling (CARS), successive pojections algorithm (SPA), genetic algorithm (GA), iteratively retains informative variables (IRIV), and combined the three models to build a quantitative detection model for the characteristic wavelengths of moisture content and calorific value of Caragana korshinskii fuel. Finally, a comprehensive comparison of the modeling effectiveness of all methods was carried out, and the SNV-IRIV-PLSR modeling combination was the best for water content prediction, with its prediction set determination coefficient $\left(R_P^2\right)$, root mean square error of prediction (RMSEP), and relative percentage deviation (RPD) of 0.9693, 0.2358, and 5.6792, respectively. At the same time, the moisture content distribution map of Caragana fuel particles is established by using this model. The SG-CARS-RFR modeling combination was the best for calorific value prediction, with its $R_P^2$, RMSEP, and RPD of 0.8037, 0.3219, and 2.2864, respectively. This study provides an innovative technical solution for Caragana fuel particles’ value and quality assessment. Full article

Based on the low-carbon transition needs of coal-fired boilers, this study conducted industrial trials of direct biomass co-firing on a 620 t/h high-temperature, high-pressure circulating fluidized bed (CFB) boiler, gradually increasing the co-firing ratio. It used compressed biomass pellets, achieving stable 20 wt% (weight percent) operation. By analyzing boiler parameters and post-shutdown samples, the comprehensive impact of biomass co-firing on the boiler system was assessed. The results indicate that biomass pellets were blended with coal at the last conveyor belt section before the furnace, successfully ensuring operational continuity during co-firing. Further, co-firing biomass up rates of to 20 wt% do not significantly impact the fuel combustion efficiency (gaseous and solid phases) or boiler thermal efficiency and also have positive effects in reducing the bottom ash and SO_x and NO_x emissions and lowering the risk of low-temperature corrosion. The biomass co-firing slightly increases the combustion share in the dense phase zone and raises the bed temperature. The strong ash adhesion characteristics of the biomass were observed, which were overcome by increasing the ash blowing frequency. Under 20 wt% co-firing, the annual CO₂ emissions reductions can reach 130,000 tons. This study provides technical references and practical experience for the engineering application of direct biomass co-firing in industrial-scale CFB boilers. Full article

This paper investigates the application of non-calcined metal tartrate as a novel alternative pore former to prepare functional ceramic composites to fabricate solid oxide fuel cells (SOFCs). Compared to carbonaceous pore formers, non-calcined pore formers offer high compatibility with various ceramic composites, providing better control over porosity and pore size distribution, which allows for enhanced gas diffusion, reactant transport and gaseous product release within the fuel cells’ functional layers. In this work, nanocrystalline gadolinium-doped ceria (GDC) and Ni-Gd-Ce-tartrate anode powders were prepared using a single-step co-precipitation synthesis method, based on the carboxylate route, utilising ammonium tartrate as a low-cost, environmentally friendly precipitant. The non-calcined Ni-Gd-Ce-tartrate was used to fabricate dense GDC electrolyte pellets (5–20 μm thick) integrated with a thin film of Ni-GDC anode with controlled porosity at 1300 °C. The dilatometry analysis showed the shrinkage anisotropy factor for the anode substrates prepared using 20 wt. The percentages of Ni-Gd-Ce-tartrate were 30 wt.% and 40 wt.%, with values of 0.98 and 1.01, respectively, showing a significant improvement in microstructural properties and pore size compared to those fabricated using a carbonaceous pore former. The results showed that the non-calcined pore formers can also lower the sintering temperature for GDC to below 1300 °C, saving energy and reducing thermal stresses on the materials. They can also help maintain optimal material properties during sintering, minimising the risk of unwanted chemical reactions or contamination. This flexibility enables the versatile designing and manufacturing of ceramic fuel cells with tailored compositions at a lower cost for large-scale applications. Full article

The combustion of fossil fuels is a major source of greenhouse gas emissions, drives climate change, and has intensified the search for cleaner energy alternatives such as biomass. Biomass derived from renewable organic materials, is considered a sustainable and carbon-neutral energy source. While biomass represents a renewable and clean energy source, its combustion, especially in pellet form, can produce various pollutants such as CO₂, SO₂, NO₂, CO, and PM. This study focuses on analyzing the combustion of six different pellet brands and the emissions they produce. A dedicated experimental procedure was designed and implemented to evaluate the combustion performance. The temperature shows a gradual increase in ambient temperature around 2.5 °C across all tests, with a similar behavior, the temperature of flue gas shows a similar behavior between tests with temperatures peaking around 300 °C and 340 °C. In the tests conducted, all pellets complied with the legal emission limits defined by legislation. The efficiency calculated using the direct method was lower by around 55%, primarily due to the use of an older boiler (manufactured in 2004) and short duration of the test. The indirect method shows better efficiency, around 70%, influenced by lower moisture content of the pellets. The results indicate that B pellets had a superior performance compared to the others evaluated. Full article

The use of CH₄ as an energy source is increasing every day. To increase the efficiency of CH₄ combustion and ensure that the equipment meets ecological requirements, it is necessary to measure the CH₄ concentration in the exhaust gases of combustion systems. To this end, sensors are required that can withstand extreme operating conditions, including temperatures of at least 600 °C, as well as high pressure and gas flow rate. ZnGa₂O₄, being an ultra-wide bandgap semiconductor with high chemical and thermal stability, is a promising material for such sensors. The synthesis and investigation of the structural and CH₄ sensing properties of ceramic pellets made from pure and Er-doped ZnGa₂O₄ were conducted. Doping with Er leads to the formation of a secondary Er₃Ga₅O₁₂ phase and an increase in the active surface area. This structural change significantly enhanced the CH₄ response, demonstrating an 11.1-fold improvement at a concentration of 10⁴ ppm. At the optimal response temperature of 650 °C, the Er-doped ZnGa₂O₄ exhibited responses of 2.91 a.u. and 20.74 a.u. to 100 ppm and 10⁴ ppm of CH₄, respectively. The Er-doped material is notable for its broad dynamic range for CH₄ concentrations (from 100 to 20,000 ppm), low sensitivity to humidity variations within the 30–70% relative humidity range, and robust stability under cyclic gas exposure. In addition to CH₄, the sensitivity of Er-doped ZnGa₂O₄ to other gases at a temperature of 650 °C was investigated. The samples showed strong responses to C₂H₄, C₃H₈, C₄H₁₀, NO_2, and H₂, which, at gas concentrations of 100 ppm, were higher than the response to CH₄ by a factor of 2.41, 2.75, 3.09, 1.16, and 1.64, respectively. The study proposes a plausible mechanism explaining the sensing effect of Er-doped ZnGa₂O₄ and discusses its potential for developing high-temperature CH₄ sensors for applications such as combustion monitoring systems and determining the ideal fuel/air mixture. Full article

This paper aims to fill a gap in relation to herbaceous biomass, which is the second most important source of biomass used for the production of solid biofuels in the form of pellets. Our research focuses on the final stage of compacted fuel production, specifically on the pressure densification of biomass into pellets. This review was conducted using bibliometric techniques. This analysis included searching indexed publications in the Web of Science—Core Collection and Scopus databases. The time range of the searched data was 1991–2024. First, bibliometric data were collected and quantitative analyses were performed. The next stage consisted of analyzing keywords from the authors’ publications using the VOSviewer program. The generated term maps allowed for the analysis of the frequency of keywords in different years and the most frequently cited ones, which enabled the identification of current research topics and the evolution of trends. Based on the collected data, applications, process parameters and raw materials used in the biomass densification process were determined. Following the bibliometric analysis, detailed analyses were carried out on the factors influencing the pressure compaction process. Full article

The production of solid biofuels from torrefied biomass holds significant potential for renewable energy applications. Durable pellet formation from severely torrefied biomass is hindered by the loss of natural binding properties, yet studies on mild torrefaction that preserves sufficient binding capacity for pellet production without external binders or changes to die conditions remain scarce. This paper investigated the production of fuel pellets from torrefied biomass without using external binders or adjusting pelletization parameters. Experiments were conducted using a mild torrefaction temperature (230 °C and 250 °C) and shorter residence time (10, 15, and 30 min). The torrefied materials were then subjected to pelletization using a single-pellet press; and the influence of torrefaction on the mechanical durability, hydrophobicity, and fuel characteristics of the pellets was examined. Results indicated that the mass loss ranging from 10 to 20% among the mild torrefaction treatments was less than the typical extent of mass loss due to severe torrefaction. Pellets made from torrefied biomass (torrefied pellets) had improvement in the hydrophobicity (moisture resistance) when compared to pellets made from untreated biomass (untreated pellets). Improved hydrophobicity is important for storage and transportation of pellets that are exposed to humid environmental conditions, as it reduces the risk of pellet degradation and spoilage. Thermogravimetric analysis of the pyrolysis and combustion behaviour of torrefied pellets indicated the improvement of fuel characteristics in terms of a much higher comprehensive pyrolysis index and greater thermal stability compared to untreated pellets, as evidenced by the prolonged burnout time and reduced combustion characteristics index. Residence time had a more significant impact on pellet durability than temperature, but the durability of the torrefied pellets was lower than that of the untreated pellets. Further research is required to explore the feasibility of producing binder-free durable pellets under mild torrefaction conditions. Overall, the study demonstrated that mild torrefaction could enhance the fuel quality and moisture resistance of biomass pellets, offering promising advantages for energy applications, despite some trade-offs in mechanical durability. Full article

Accurate assessment of biomass fuel properties is essential for quality control and fair market pricing, particularly when dealing with variable moisture content (MC) in agricultural residues. This study investigates the use of near-infrared (NIR) spectroscopy to predict the lower heating value (LHV) and ash content of sugarcane leaf pellets while minimizing the interference caused by moisture variability. Sixty-two samples were scanned using an NIR spectrometer over three week-long storage periods to get different MCs with the same sample. Additionally, variable selection methods such as a genetic algorithm (GA) and moisture-related wavelength exclusion were explored. The optimal model for LHV prediction was developed using GA-PLS regression (Method II), provided a coefficient of determination (R²) of 0.80, a root mean square error of calibration (RMSEc) of 595.80 J/g, and a ratio of performance to deviation (RPD) of 1.74, indicating fair predictive performance. The ash content model showed moderate accuracy, with a maximum R² of 0.61 and an RPD of 1.40. These findings suggest that the variables selected via GA in Method II were not relevant to MC; as Method II provided the best result, this indicates a low impact of MC, which may influence model construction in the future. Moreover, the findings also highlight the potential of NIR spectroscopy, combined with appropriate spectral preprocessing and wavelength optimization, as a rapid, non-destructive tool for evaluating biomass quality, enabling more precise control in bioenergy production and biomass trading. Full article

The article presents the results of research on the effect of pyrolysis oil used as a binder in the pelletization process. The materials used to produce pyrolysis bio-oil were municipal organic waste and residues from greenhouse tomato production. The research assessed the mechanical strength, physicochemical properties, and modifications of the energy and emission parameters of the produced pellets. As a result, formed fuels were obtained, whose physicochemical properties, among others, were improved in terms of combustion heat (the value increased by up to 15.7%). After selected binders were used, the mechanical strength of the fuels also increased, which in the best variant increased by 2.87%. In all research cycles, valuable data was obtained that can be used, for example, in companies producing formed fuels, as well as in the agri-food industry, where a large amount of waste is generated, the properties of which have not previously allowed their use for energy purposes. Full article

This study provides a comprehensive thermochemical characterization of common nut residues—almonds, walnuts, hazelnuts, peanuts, and pistachios shells—as potential biomass fuels, examining their chemical composition, calorific values, and emissions profiles. Their suitability as renewable energy sources was systematically assessed by verifying compliance with ISO 17225-2 standards for pellet production. The nut residues demonstrated promising energy characteristics, with higher heating values ranging from 17.75 to 19.12 MJ/kg and most samples fulfilling ISO 17225-2 classifications A1 or A2. Specifically, the walnut residues met the highest quality classification (A1), whereas the almond, hazelnut, and pistachio residues met the A2 classification, and the peanut residues were classified as B due to higher nitrogen content. A Life Cycle Assessment (LCA) was also performed to quantify the environmental impacts, focusing on CO₂ emissions from energy recovery and transportation. The results showed significantly lower CO₂ emissions from all the nut residues compared to fossil fuels such as coal, natural gas, fuel oil (HFO), and LPG. The almond residues exhibited the lowest total CO₂ emissions at 1669.27 kg CO₂ per ton, while the peanuts had the highest at 1945.93 kg CO₂ per ton. Even the highest-emitting nut residues produced substantially lower emissions compared to coal, which emitted approximately 4581.12 kg CO₂ per ton. These findings highlight the potential of nut residues as low-carbon, renewable energy sources, providing both environmental advantages and opportunities to support local agricultural economies. Full article

Nuclear fuel pellets are subject to stress for long periods during the in-pile operation, and this study on high-temperature creep performance is of great significance for predicting the in-pile behaviors and safety evaluation of fuel elements. In the present study, a mixture of ZrC (50 wt%), SiC (46 wt%), and Si (4 wt%) powder was ball-milled for 24 h and then evaporated to obtain ZrC–SiC composite material. ZrC–SiC composite was adopted as the matrix, with ZrO₂ surrogate kernel TRSIO particles and dispersion coated particle fuel pellets prepared with different TRISO packing fractions using the Spark Plasma Sintering (SPS) process. This study on compressive creep performances was conducted under a temperature range of 1373–2073 K and a stress range of 5–250 MPa, elucidating the creep behavior and mechanism of dispersed coated particles fuel pellets, and obtaining the variation laws of key parameters such as creep stress exponents and activation energy with TRISO packing fraction. The results showed that creep stress exponents of the surrogate fuel pellets are between 0.89 and 2.12. The activation energies for high temperature–low stress creep (1873–2073 K, 5–50 MPa) are 457.81–623.77 kJ/mol, and 135.14–161.59 kJ/mol for low temperature high stress creep (1373–1773 K, 50–250 MPa). Based on the experimental results, a high-temperature creep model was established, providing a valuable reference for the research and application of a ceramic matrix dispersed with coated particle fuels. Full article

Nowadays, as a result of the increasing awareness of European societies and new legal regulations, the role of renewable energy sources in individual heating is growing. One of the forms of renewable heat and electricity production is the use of biomass pellet burners coupled with Stirling engines. To ensure high system efficiency, the combustion process of this type of fuel requires an appropriate design of the burners, which can provide high-temperature flue gases. This requirement may be challenging, as the long operation of such a burner may cause the thermal degradation of its components, mainly the upper burner wall. The subject of this analysis was a burner with a nominal power of 10 kW. As the analysis tool, a previously validated CFD model was used. In this work, two ways of thermal degradation prevention are presented. The first one is geometry optimization via secondary air hole distribution. The results show that an appropriate geometrical design of the burner may be an efficient way of shifting the high-temperature zone to the burner axis, which may mitigate the thermal degradation risk. Secondly, the inlet air mass flow is changed to show its impact on the presence and location of the high-temperature zone. Both methods can be treated as interesting ways for solving the challenge of the long-term operation of high-temperature biomass burners by avoiding thermal degradation. Full article

The life-cycle economics and greenhouse-gas (GHG) emissions of forest biomass harvesting and utilization for value-added bioproducts were comprehensively evaluated via the development of an integrated modeling framework. Taking the eastern U.S. as the case region, the model innovatively integrated field studies, a Bayesian-based statistical learning model, techno-economic analysis, and life-cycle assessment. In specific, by investigating and summarizing the typical forest biomass harvesting systems across the region, the forest biomass harvesting costs were spatially grouped and mapped for four classified subregions across the eastern US. Overall, with 95% confidence the forest biomass harvesting cost is between USD 21.99 and USD 44.33/dry Mg, while the GHG emissions are between 14.79 and 98.80 kg CO₂ eq./dry Mg. Furthermore, for the forest biomass utilization for four alternative value-added bioproducts, the minimum selling price (MSP) is USD 177.82/Mg for pellet fuel, USD 110.24/MWh for biopower, USD 1059.4/Mg for biochar, and USD 4.98/gallon for aviation fuel. The life-cycle GHG emissions are 149.80 kg CO₂ eq./Mg pellet fuel, 52.22 kg CO₂ eq./MWh biopower, 792.12 kg CO₂ eq./Mg biochar, and 2.13 kg CO₂ eq./gallon aviation fuel, respectively. Considering the uncertainties, 95% confidence intervals of MSPs range from USD 164.77 to USD 190.97/Mg for pellet fuel with an 81.85% probability to be profitable, from USD 100.20 to USD 120.21/MWh for biopower with a 49.38% probability to be profitable, from USD 1000.91 to USD 1109.25/Mg for biochar with a 79.51% probability to be profitable, from USD 4.86 to USD 5.54/gallon for aviation fuel with an 0.03% probability to be profitable. Moreover, the MSPs of pellet fuel and biochar are much less affected by the market changes than those of biopower and aviation fuel. However, the production of biopower and aviation fuel has lower carbon intensities than that of pellet fuel and biochar. Full article