Combustion Patterns Research Articles

Informal settlements ablaze: decoding the combustible nature of building materials used in Bangladesh through experiments and numerical analysis

ABSTRACT Fire outbreaks in informal settlements pose severe threats to residents and their properties. Despite the frequent occurrence of fire events in Bangladesh, detailed studies on fire propagation behaviour remain limited. This study addresses this critical issue by comprehensive investigations into the ignitability and burning behaviour of different materials such as cardboard, polyurethane foam, plastic bags, wood, and structural timber that are commonly found in informal settlements. Additionally, an advanced numerical model based on the finite volume method was developed in Fire Dynamics Simulator and then employed to accurately predict the fire-reaction properties of materials under the cone calorimeter environment. The results revealed that cardboard ignites quickly, burns moderately, and does not produce flaming droplets or ignite the filter paper. PU foam burns vigorously, with a high burning rate, and emits dense black smoke and a toxic odour. Plastic bags ignite rapidly, burn intensely, and are greatly influenced by the presence of airflow. The numerical model successfully quantified fire-reaction properties such as ignition time, heat release rate (HRR), and flame spread characteristics. Notably, wood and structural timber demonstrate a distinct combustion pattern with a sharp HRR peak, while PU foam exhibits the highest peak HRR values followed by timber masonite.

Study of patterns and mechanisms of combustion of powdered and granulated T-C-B system

Experimental studies of the combustion patterns of the ternary system (100 – x)(Ti + C) – x(Ti + 2B) of bulk density in powder and granular form used for the synthesis of composite ceramics TiC–TiB2 were carried out. The study shows that the dependence of the powder mixture combustion rate on the Ti + 2B content has a non-monotonic character, which is associated with the influence of impurity gas release on the combustion process. By removing the influence of impurity gas by granulation, a monotonic dependence with two characteristic sections was obtained. For the granulated mixture, an increase in the Ti + 2B content 60 wt. % leads to a change from the conductive combustion mode to the convective one, accompanied by a sharp increase in the combustion rate. For the conductive combustion mode, the combustion rate of the substance inside the granule and the combustion transfer time from the granule to the granule were determined, which allowed us to estimate the inhibitory effect of impurity gas release on the combustion rate of powder mixtures of different composition. For the convective combustion mode, it was shown that a decrease in the content of the gasifying additive in the mixture (granulation with ethyl alcohol) led to an unexpected result: an increase in the combustion rate of the mixture. For compositions with (Ti + 2B) 60 wt. % the combustion rate with counter filtration of impurity gases was determined for the first time, which made it possible to estimate the front rate increase according to the filtration combustion theory. According to XRD results, the combustion products of all compositions contain only two main phases TiC and TiB2.

Burning and flame extinction patterns of PMMA under external heating and oxygen deficiency

The paper presents an experimental study investigating the impact of under-oxygenated conditions on the burning characteristics and flame extinction of horizontal transparent poly(methyl-methacrylate) (PMMA) slabs subjected to external heating. Small-sized solids are exposed to various constant levels of radiant heat flux in a nitrogen-diluted environment at ambient pressure. The study aims to understand the multivariable dependence of PMMA combustion on oxygen and heating levels. The analysis goes beyond the study of global and local variables to provide an understanding of the mechanisms involved, revealing a notable effect on burning characteristics and flame extinction mechanisms by blow-off. The results provide a detailed assessment of the surface energy balance and flame bulk properties. The results demonstrate good repeatability up to a certain oxygen limit, beyond which the flame combustion regime exhibits stochastic behaviour. The study of heat transfer mechanisms has revealed that flame radiation and external heating play a predominant role in the heating of horizontal solid fuels, In contrast, within the flame, convection is the main contributor to solid heating, rather than flame radiation. Solid characteristics show linear trends proportional to oxygen depletion, while gas phase characteristics show monotonic trends strongly influenced by the changing combustion regime. The surface temperature of the solid is highly sensitive to the test conditions that affect the energy balance. Dimensionless parameters are developed and data are correlated with existing literature. The analysis demonstrates that the linear or monotonic trends are maintained regardless of external heating. Finally, models are proposed and validated to predict both the extinction limit and the burning rate independently of irradiance and oxygen levels.

Assessing the Impact of Straw Burning on PM2.5 Using Explainable Machine Learning: A Case Study in Heilongjiang Province, China

Straw burning is recognized as a significant contributor to deteriorating air quality, but its specific impacts, particularly on PM2.5 concentrations, are still not fully understood or quantified. In this study, we conducted a detailed examination of the spatial and temporal patterns of straw burning in Heilongjiang Province, China—a key agricultural area—utilizing high-resolution fire-point data from the Fengyun-3 satellite. We subsequently employed random forest (RF) models alongside Shapley Additive Explanations (SHAPs) to systematically evaluate the impact of various determinants, including straw burning (as indicated by crop fire-point data), meteorological conditions, and aerosol optical depth (AOD), on PM2.5 levels across spatial and temporal dimensions. Our findings indicated a statistically nonsignificant downward trend in the number of crop fires in Heilongjiang Province from 2015 to 2023, with hotspots mainly concentrated in the western and southern parts of the province. On a monthly scale, straw burning was primarily observed from February to April and October to November—which are critical periods in the agricultural calendar—accounting for 97% of the annual fire counts. The RF models achieved excellent performance in predicting PM2.5 levels, with R2 values of 0.997 for temporal and 0.746 for spatial predictions. The SHAP analysis revealed the number of fire points to be the key determinant of temporal PM2.5 variations during straw-burning periods, explaining 72% of the variance. However, the significance was markedly reduced in the spatial analysis. This study leveraged machine learning and interpretable modeling techniques to provide a comprehensive understanding of the influence of straw burning on PM2.5 levels, both temporally and spatially. The detailed analysis offers valuable insights for policymakers to formulate more targeted and effective strategies to combat air pollution.

Investigation of Combustion and NO/SO2 Emission Characteristics during the Co-Combustion Process of Torrefied Biomass and Lignite.

This paper investigates the combustion characteristics and pollutant emission patterns of the mixed combustion of lignite (L) and torrefied pine wood (TPW) under different blending ratios. Isothermal combustion experiments were conducted in a fixed bed reaction system at 800 °C, and pollutant emission concentrations were measured using a flue gas analyzer. Using scanning electron microscopy (SEM) and BET (nitrogen adsorption) experiments, it was found that torrefied pine wood (TPW) has a larger specific surface area and a more developed pore structure, which can facilitate more complete combustion of the sample. The results of the non-isothermal thermogravimetric analysis show that with the TPW blending ratio increase, the entire combustion process advances, and the ignition temperature, maximum peak temperature, and burnout temperature all show a decreasing trend. The kinetic equations of the combustion reaction process of mixed gas were calculated by Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) kinetic equations. The results show that the blending of TPW reduces the activation energy of the combustion reaction of the mixed fuel. When the TPW blending ratio is 80%, the activation energy values of the mixed fuel are the lowest at 111.32 kJ/mol and 104.87 kJ/mol. The abundant alkali metal ions and porous structure in TPW reduce the conversion rates of N and S elements in the fuel to NO and SO2, thus reducing the pollutant emissions from the mixed fuel.

Thermal decomposition and combustion of interior design materials

Research findings on the patterns of thermal decomposition and combustion are reported for widely used interior design materials. The experiments were conducted using a hardware and software system including a thermogravimetric analyzer (to record the characteristics of thermal decomposition), a gas analyzer (with H2, CH4, H2S, SO2, CO and CO2 sensors) and a high-speed camera (to record the characteristics of ignition and combustion). The temperature of the oxidizing medium ranged from 500 to 900°C to investigate the conditions of thermal decomposition initiation and sustained combustion. It was established that the highest concentrations of toxic emissions were typical of the combustion of polypropylene at a maximum temperature of the oxidizing medium (900°C). Wood showed the shortest ignition delay time and the longest duration of combustion. The experimental data were used for a physical problem statement and mathematical model of heat and mass transfer to explore the thermal decomposition and combustion of interior design materials in different rooms. A comparison of the experimental findings with the mathematical modeling results validates the developed model. The growth rates of carbon monoxide and carbon dioxide concentrations were determined for construction (wooden) and interior design (polymer) materials. The maximum concentrations of CO and CO2, and the minimum times taken to reach their threshold values corresponded to wood and polyvinyl chloride panels. This research provides a deeper insight into the thermal decomposition of a wide range of fuels and the formation of gaseous pyrolysis products of these fuels. The results obtained can be used to evaluate the toxicity of construction and interior design materials during compartment fires as well as to estimate the safe egress time and risks involved in the process. They can also serve as a database for the development and testing of mathematical models describing fire outbreaks and propagation in confined spaces.

Maintaining Performance and Lifetime of Boiler Assets During Implementation of Cofiring and Coal Switching by Using Integrated Digital Boiler Combustion Tuning

Implementing coal switching and co-firing at the JPR coal-fired power plant significantly impacts life assets and plant performance, especially in the boiler. This phenomenon happens because low-calorie coal and biomass in Indonesia have a very high water content of up to 56%. According to the problem, an improvement based on a digital system was carried out to adjust the combustion pattern to achieve the operation parameter target for the main boiler equipment. This study was completed in three steps: first, the mixing characteristics of biomass and coal were validated; second, the combustion process was optimized through boiler tuning, which involves figuring out the best value for every fuel modification; and third, a digital platform was developed to make the process of controlling, monitoring, and optimizing combustion more straightforward. The work process begins with inputting daily operation planning data, and then the digital boiler system identifies fuel needs based on availability at the coal yard. Moreover, it also shows the recommendation for the baseline operating parameters executed by the plant operator. The system automatically warns if there is a difference between the actual operating pattern and the baseline. As a result, this study creates a symmetrical fireball concerning the combustion chamber and reduces SO2 and NOx emissions. Boiler performance indicators such as O2 outlet at 3-4 % and other indicators can operate within the baseline parameter. Boiler efficiency increased by 0,8 %, or equivalent to savings of $ 1.272.992,83, and decreased electricity generation cost to $ 0,000081/kWh. The pipe thickness rate is also reduced, preventing leakage in the boiler and, as an indication, increasing the boiler’s lifetime.

Annual extent of prescribed burning on moorland in Great Britain and overlap with ecosystem services

AbstractIn the UK uplands, prescribed burning of unenclosed heath, grass and blanket bog (‘moorland’) is used to support game shooting and grazing. Burning on moorland is contentious due to its impact on peat soils, hydrology and habitat condition. There is little information on spatial and temporal patterns of burning, the overlap with soil carbon and sensitive habitats and, importantly, whether these patterns are changing. This information is required to assess the sustainability of burning and the effectiveness of new legislation. We developed a method for semi‐automated detection of burning using satellite imagery – our best performing model has a balanced accuracy of 84.9%. We identified annual burn areas in Great Britain in five burning seasons from 2017/18 to 2021/22 of 8333 to 20 974 ha (average 15 250 ha year−1). Annual extent in England in 2021/22 was 73% lower than the average of the four previous seasons. Burning was identified over carbon‐rich soils (mean 5150 ha or 34% by area of all burning annually) and on steep slopes – 915 ha across the five seasons (1.3%), contravening guidance. Burning (>1 ha) was recorded in 14% of UK protected areas (PAs) and, within these, the percentage area of moorland burned varied from 2 to 31%. In England in some years, the percentage area of moorland burned inside PAs was higher than outside, while this was not the case in Scotland. Burning in sensitive alpine habitats totalled 158 ha across the five seasons. The reduction in burned area in England in 2021/22 could relate to England‐specific legislation, introduced in May 2021, to prohibit burning on deep peat in PAs. This suggests that regulation can be effective. However, the continued overlap with sensitive features suggests that burning falls short of sustainable practices. Our method will enable repeatable re‐assessment of burning extents and overlap with ecosystem services.

Late Holocene high-resolution paleoenvironmental reconstruction from Beaver Lake in the northwest lowlands of the Olympic Peninsula, Washington (USA)

Fire is an essential component of the landscapes and forests of the Pacific Northwest, including the temperate rainforests of the Olympic Peninsula. Previous fire history reconstructions from the peninsula show that fire return intervals varied throughout the postglacial period, primarily in response to climatic changes and corresponding shifts in vegetation. However, much less is known about the fire history of the low-elevation forests of the Olympic Peninsula and the role of cultural fire regimes in these environments. The purpose of this study was to reconstruct the paleoenvironmental history of a low-elevation study site, Beaver Lake, located in the northwestern part of the peninsula. Using macroscopic charcoal, pollen, and sedimentological analyses of a ca. 3440-year-long record, we reconstructed a high-resolution record that shows fire activity was remarkably high during the late Holocene for an area considered part of a temperate rainforest. However, patterns of burning varied throughout the record, with the first third (ca. 3440 to 2350 cal yr BP) and last third (ca. 800 cal yr BP to the present day) recording much higher amounts of fire activity compared to the middle portion (ca. 2350 to 800 cal yr BP), which recorded very little fire activity. Larger and/or more severe fires that likely burned during multi-year droughts correlate with peaks in magnetic susceptibility and pollen trends that indicate substantial geomorphic responses and successional changes in forest structure following these events. Cooler temperatures and a wetter climate, indicated by nearby glacial advancements, may have staved off fire activity during the period of low fire activity. Cultural burning by the Indigenous tribes of the Olympic Peninsula likely contributed to the observed fire activity at Beaver Lake as nearby prairies were managed for resource procurement, indicated in particular by an increase in herbaceous morphotype charcoal during the past 800 years.

Spatial and temporal patterns of fuelwood consumption and its associated CO2 emissions in Muzaffarabad division, a western Himalayan region

BackgroundIn the Himalayan region, fuelwood serves as a critical energy source for rural communities. Being vital for meeting energy needs, fuelwood combustion is a source of carbon dioxide (CO2) emission and, consequently, global warming, as well as deforestation and public health damage. Therefore, quantifying fuelwood consumption patterns and its associated CO2 emissions is essential to understand the environmental impact and promote sustainable resource management.MethodsThis research conducts an evaluation of fuelwood burning patterns and the associated CO2 emissions in Azad Jammu and Kashmir (AJK), situated within the western Himalayan region. The study entails an extensive survey of 24 villages representing 240 households, equally distributed between the subtropical and temperate regions, each comprising 120 households. Data collection was executed through a combination of direct queries and the weight survey method, following standard protocols.ResultsIn the study area, the mean annual fuelwood comsumption per household amounts to 24.28 ± 3.1 Mg (or 3.195 ± 1 Mg capita−1). A variance was observed between subtropical and temperate zones, with the latter exhibiting higher consumption rates. The consequential CO2 emissions were assessed as 41.88 ± 4.5 Mg per household (5.51 ± 0.6 Mg capita−1). On a daily basis, households consumed an average of 66.52 ± 6.4 kg of fuelwood (8.75 ± 1.5 kg capita−1), resulting in a daily CO2 release rate of 114.745 ± 8.6 kg (15.095 ± 2 kg capita−1). The findings unveiled seasonal variations, indicating increased fuelwood consumption and emissions during the winter season. Statistical analysis shed light on the significance of altitude and family size in shaping the patterns of fuelwood use.ConclusionsThe results revealed the importance of prioritizing forest conservation and strategically implementing sustainable practices, including reforestation, afforestation, responsible harvesting, and actively promoting sustainable fuel sources. This research highlights the vital role of well-designed policies focused on preserving ecosystems and improving energy management. Policy intervention can ensure the sustainable stewardship of local and regional forest resources.

Study of Patterns and Mechanisms of Combustion of a Powdered and Granulated Ti–C–B System

Study of Patterns and Mechanisms of Combustion of a Powdered and Granulated Ti–C–B System

Thermal performance analysis of optimized biomass conversion in developing organic waste biorefinery to achieve sustainable development goals

To make energy sector sustainable, waste to energy system should be used, as statistics of the International Energy Agency (IEA) shows that the lack of renewable energy and environmental degradation are the major pressing problems confronting the global community. However, in south Asian regions, the situation escalates as a result of severe dependency on conventional energy sources, coupled with the limitations and challenges involved in maintaining a green environment and Waste-to-Energy (WtE) strategies. In this region, energy majorly relies on imported conventional fuel. In addition to harming the environment, imported fossil fuel has also increased the risk of geopolitical unrest. In the current research, rice husk is used as a bio-organic waste that is produced in large volumes and a significant byproduct of agro-based biomass sector. In this research, sample composition of rice husk is demineralized in 5% hydro-chloric acid for different burning ratios and the modified thermo-chemical methodology was used to the acidified rice husk at three different heating rates (20 °C min−1, 30 °C min−1 and 40 °C min−1) respectively in thermogravimetric analyzer (TGA). Proximate, thermal and kinetic analysis was used for observing the degradation patterns of demineralized rice husk. Proximate analysis revealed that the leaching of rice husk has successfully infused HCl, resulting in substantial rise in fixed carbon (FC) and calorific value (CV) by 10.53 % and 10.82 % respectively, along with decrease in the carbon footprint of about 60.55%. Thermogravimetric (TG) and derivative thermogravimetric (DTG) curves have shown decreasing behavior of conversion efficiency to the increase in flow rate, with the maximum drop of 12.7 % observed at 40 °C. With the use of the TGA equipment, the conversion efficiency was evaluated based on the sample's peak weight loss. The current study has reported synergistic effect of flow and heating rate on the degradation temperatures, activation energy and reactivity of acidified rice husk. Lowest activation energy 180.46 kJ permole with highest reactivity of 0.01192345 %*min °C was observed at 40 ml and 20 °C combination. Accordingly, degradation temperatures of burning profiles increased due to lower convective cooling and higher temperature gradient within the particle of rice husk sample. In addition, pre-exponential data and slopes of TG curves have validated the results of activation energy obtained from TGA experimentation. The sustainable biomass conversion approach is envisioned to significantly refine the waste bio refinery system to achieve SDGs.

Social Media: A notable cause of child burns

ObjectiveScalding and flame burns come first in the etiology of pediatric burns. Today, with the increase in internet use, the effect of social media on the etiology of burns is also seen. When the story of some children who applied for burns was questioned recently, it was observed that the children were affected by various images, videos, and duels on social media. They wanted to try what they saw with a sense of curiosity. This study aims to draw attention to child burns caused by social media's effects and raise awareness about their preventability. MethodsChildren who stated that they got burned because of watching social media in our burn center within one year were included in the study retrospectively. Children's age, gender, burning pattern, and graft needs were evaluated. ResultsIn one year, eight patients (three girls and five boys) were admitted to the hospital with the complaint of burns caused by the effect of social media. All of them were flame burns. The ages of these patients were between 6 and 12 years, and their burn percentage was between 1 and 12. Grafts were performed in 4 patients. Three recovered with dressings after debridement, and one improved during outpatient follow-up. The hospitalization period of 7 patients who received inpatient treatment was recorded to be between 1 and 15 days. ConclusionsChildren's access to the Internet at an early age and unsupervised exposes them to many dangers, including burns. These burns can have serious consequences, such as hospitalization and graft needs. Steps should be taken to recognize and prevent the threat of social media. The study was presented as an oral presentation at the 39th National Congress of Pediatric Surgery held in İzmir/Kuşadası/Türkiye on 2–5 November 2022.

Advanced Numerical Analysis of In-Cylinder Combustion and NOx Formation Using Different Chamber Geometries

In diesel engines, emission formation inside the combustion chamber is a complex phenomenon. The combustion events inside the chamber occur in microseconds, affecting the overall engine performance and emissions characteristics. This study opted for using computational fluid dynamics (CFD) to investigate the combustion patterns and how these events affect nitrogen oxide (NOx) emissions. In this study, a diesel engine model with a flat combustion chamber (FCC) was developed for the simulation. The simulation result of the heat release rate (HRR) and cylinder pressure was validated with the experimental test data (the engine test was conducted at 1500 rpm at full load conditions). The validated model and its respective boundary conditions were used to investigate the effect of modified combustion chamber profiles on NOx emissions. Modified chambers, such as a bathtub combustion chamber (BTCC) and a shallow depth chamber (SCC), were developed, and their combustion events were analysed with respect to the FCC. This study revealed that combustion events such as fuel distribution, unburnt mass fractions, temperature and turbulent zones directly impact NOx emissions. The modified chambers controlled the spread of combustion and provided better fuel distribution, improving engine performance and combustion rates. The SCC (63.2 bar) showed peak pressure rates compared to the FCC (63.02 bar) and BTCC (62.72 bar). This study concluded that the SCC showed better results than other chambers. This study further recommends conducting lean fuel mixture combustion with chamber modifications and optimising fuel spray, such as by adjusting the fuel injection profile, spray angle and injection timing, which has a better tendency to create complete combustion.

Experimental study on flame spreading over locally wetted thin combustibles

This study proposed a better fire-extinguishing strategy by investigating the effectiveness of wetting operations. It also serves as a first step toward developing physical-based discrete fuel flame spread models using a newly developed small-scale test device. This study examined downward flame spread through a dry narrow path sandwiched by wetted zones formed with thin paper, with different levels of wetting and dried layer width. The dynamic flame behavior and the effect of the presence of adjacent wetting zones were studied both experimentally and numerically. The experimental observations revealed three burning patterns, namely unburned, partially burned, and burned-out regions, depending on various locally wetting fuel arrangements. Additionally, the accelerating flame spread of the wetting case was experimentally reported for the first time. One-dimensional computational simulations suggest that this accelerating phenomenon could be attributed to the chemical reaction triggered by the introduction of water. The reaction rates of OH + CO ↔ H + CO2 and H + O2 + H2O ↔ HO2 + H2O increased due to the water vapor, thereby increasing the heat production rate to further promote the preheating of the downward unburned region and flame spread rate. These findings and conclusions shed more light on the physical and chemical effects of water on flame spreading, highlighting another possibility of water accelerating flame propagation.

Simulation of Heat and Mass Transfer in a Moving Bed Part-Fluidized Boiler

Abstract Moving bed part-fluidized boiler is a new type of furnace. The new combustion method in the furnace has attracted a lot of attention and shown attractive prospects. Two-dimensional computational fluid dynamic (CFD) simulations were performed for a 116 MW moving bed part-fluidized boiler to investigate the different combustion patterns of coal particles of different particle sizes inside the furnace chamber. A low-NOX combustion method based on the combination of laminar combustion and fluidized combustion is proposed. By comparing the effects of different air distributions on the fluidization state of coal particles, the air distribution values required for optimal fluidized combustion were obtained. The temperature field and pollutant distribution in the furnace chamber for the conventional combustion method and the new combustion method were also simulated. The results show that the combustion technology combining laminar combustion and fluidization of a moving bed part-fluidized boiler can significantly improve the combustion rate and reduce the NOX concentration at the furnace exit. When the secondary air speed is up to 15 m/s, the coal particles smaller than 5 mm are fully fluidized and burned in the whole furnace chamber. The coal particles larger than 5 mm are burned on the bed. The pollutant emission of the boiler can reach the best condition. The new type of boiler can reach a super clean emission in which the NOX emission value is below 47 mg/m3, and the SO2 emission value is reduced to 0.15 mg/m3.

Holocene black carbon in New Zealand lake sediment records

Black carbon emitted from incomplete combustion of biomass and fossil fuel burning is an important aerosol; however, available long-term black carbon data are limited to remote polar and high-alpine ice cores from few geographic regions. Black carbon records from lake sediments fill geographic gaps but such records are still scarce, particularly in the Southern Hemisphere. We applied a new incandescence-based methodology to develop Holocene refractory black carbon (rBC) records from four lake-sediment archives in New Zealand and compare these with macroscopic charcoal records. Our rBC records suggest periods with substantial rBC deposition during the Holocene before human arrival in the 13th century reflecting long-range transport and possibly local wetland fires. With Polynesian settlement, rBC deposition increased on the South Island in agreement with macroscopic charcoal records, and it is this period of burning that is proposed as the source of rBC increases evident in Antarctic ice cores. However, sites on the North Island show no contemporaneous rBC increase suggesting regional differences in biomass burning patterns between the North and South islands. None of the New Zealand records show an increase in rBC from fossil fuel sources during the Industrial Era post-1850 CE.

Numerical simulation of oxygen-enriched combustion in a precalciner using coal gangue-blended pulverized fuel

This study emphasizes the potential role of coal gangue as an alternative fuel and oxygen-enriched combustion technology within TTF precalciners(Twin-Tank Furnace) in mitigating carbon emissions from cement production. The research primarily unfolds in two segments. Initially, the investigation addresses the influence of blending varying proportions of coal gangue under an air atmosphere on the internal temperature field and raw material decomposition components within the precalciner, aiming to discern the optimal blending ratio. Subsequently, the study simulates combustion under different oxygen-enriched atmospheres at the ideal coal-gangue blending ratio, establishing the combustion patterns under these conditions. Although the mixed fuel prompts symmetry in the flow field and temperature field, the distinct combustion characteristics of coal gangue and coal powder-following a 20% coal gangue blend-lead to an accelerated mainstream velocity and abbreviated fuel residence time. Consequently, the exit temperature and CO2 concentration diminish with increasing blending content, reaching an optimal raw material decomposition rate of 91.12% within the precalciner when blended with 20% coal gangue. Furthermore, in oxygen-enriched combustion, as the oxygen content escalates, both the average temperature at the precalciner's exit and the raw material decomposition rate witness an upsurge, whereas the average CO2 concentration at the outlet experiences a decline.

The role of fire in the Medieval and Early Modern landscape of Bad Waldsee within the broader context of the pre-Alpine forelands of south-western Germany

Fire, an important element of human land use strategies, was part of many early industrial activities but also of burning incidents that significantly impacted settlement structures and development. The spatial proximity of the historically well-documented medieval town and sediment archive deposited in its central lake (Stadtsee) was taken to investigate the interplay of fire and socio-environmental developments during the preindustrial phase of 750−150 bp (ad 1200–1800). The burning episodes were detected using the sediment macroscopic charcoal record (> 150 μm) and were interpreted considering sedimentological, palynological, and historical evidence. Macro-charcoal analysis revealed two main phases of biomass burning: a late Medieval one (653−533 cal bp ), followed by a distinct fire-free interval, and a second Modern Times phase (313 cal bp until today). During the late Medieval times and after ad 1750 (200 cal bp) low-magnitude local fires coincided with high-intensity land use pressure. Major historical events like the Thirty Years’ War and the fire incident near the town (ad 1386, 174 cal bp) were also documented by the charcoal sedimentary record. The specific terrain morphology and the town microclimate impacted the chance of whether certain local burning patterns were detectable at all. This study demonstrates that during the Medieval period to the present day, fire events, mainly anthropogenic, were coupled with the main vegetation developments. Anthropogenic fire was an inseparable part of the Bad Waldsee landscape, as also recorded historically by the town archives.

Exploring the effect of methanol and ethanol on the overall performance and substitution window of a dual-fuel compression-ignition engine fueled with HVO

All sectors where compression-ignition engines are the predominant technology are undergoing a complex change motivated by the transition to a carbon-free economy. Nevertheless, these engines, if operated under advanced combustion strategies and fueled with low carbon-intensive fuels, are a real opportunity. This work investigates the effect of two renewable short-chain alcohols (methanol and ethanol) on the performance, emissions, combustion pattern and energy substitution window of a dual-fuel engine operated at high and low loads. Diesel-like fuels include a hydrotreated vegetable oil to evaluate the potential of its high cetane number in dual-fuel mode. The work was executed in two stages. In the first, the operating parameters (EGR rate, combustion phasing) were adjusted for attaining the best compromise between engine efficiency and NOx emissions. In the second, the maximum achievable substitutions were sought, achieving higher substitution ratios than those found by others. HVO-ethanol pair led to the highest substitution (84%), although generally methanol showed superior results in NOx and thermal efficiency. HVO and high alcohol ratios broke down the existing trade-off between large and small particles, leading to a simultaneous reduction of large (more than one order of magnitude) and small (three times lower) compared to only diesel or HVO fueling.