Products Of Incomplete Combustion Research Articles

Emissions of Benzо(a)pyrene and Carbon Monoxide from Forest Fires as a Source of Atmospheric Pollution in Cities of the Irkutsk Region

An assessment is made of the release of benz(a)pyrene (B(a)P) and accompanying toxic products of incomplete combustion – carbon monoxide and soot – from forest fires as a source of atmospheric air pollution in cities in the Irkutsk region. Mass gross emissions, t/year, averaged for 2014–2020. of the studied substances in all 33 districts of the Irkutsk region were calculated. The dependences of gross emissions B(a)P are establishedDepends on the indicators of forest fires: the amount, area, mass of burnt plant materials, gross emissions of carbon monoxide and soot. The conclusion is made about the pollution of the atmospheric air of cities with carcinogenic B(a)P and toxic carbon monoxide from forest fire emissions.

Numerical Investigation of In-Cylinder Combustion Behaviors in a Medium-Speed Diesel Engine

Abstract This study aims to advance understanding of in-cylinder combustion processes in medium-speed diesel engines, which are extensively employed in heavy-duty applications where electrification proves inefficient yet remains insufficiently examined in the literature. By modeling a four-stroke engine with dimensions of 210 mm bore and 310 mm stroke, operating at 900 rpm under full load, this research identifies distinct combustion characteristics that differentiate medium-speed engines from their high-speed counterparts. Key findings illustrate that super turbocharging in medium-speed engines enhances the combustion of the fuel–air mixture under elevated temperatures and pressures. Moreover, an increased stroke length promotes gas velocity and turbulence, facilitating fuel atomization and mixing. Notably, rapid fuel ignition occurs near the nozzle due to the high temperature of compressed air, reducing the ignition delay. As a result, the premixed combustion stage nearly disappears, with diffusion combustion dominating, especially pronounced with long-duration injection, a characteristic of medium-speed engines. The study also reveals a more uniform but elevated distribution of nitrogen oxide emissions in medium-speed engines, attributed to prolonged high-temperature conditions that both facilitate their formation. Early stages of diffusion combustion show high concentrations of incomplete combustion products. However, as the combustion process progresses, the conditions favor the complete oxidation of these products at high temperatures, resulting in decreased carbon-based pollutions. In addition, the larger combustion chamber and enhanced turbulence characteristic of medium-speed engines support efficient fuel and air mixing without necessitating the swirl effect required by high-speed engines, diminishing the dependence on wall impingement dynamics for air utilization. Consequently, efficiency optimization strategies for medium-speed engines, emphasizing adjustable injection parameters, encounter fewer constraints than those inherent to the spatial limitations of high-speed engines.

Millennial-aged pyrogenic carbon in high-latitude mineral soils

Wildfires in the Arctic are producing pyrogenic carbon as product of incomplete biomass combustion. The storage and distribution of pyrogenic carbon in soils is poorly known, especially in carbon rich permafrost-affected mineral soils. Here, we extracted pyrogenic carbon in mineral soils from eleven forest sites across the North Canadian permafrost regions by hydrogen pyrolysis. We found pyrogenic carbon with millennial-scale ages that were older in continuous (1960–12,690 calibrated years before present) than in discontinuous (510–3560 calibrated years before present) permafrost-affected soils. In all cases, pyrogenic carbon showed longer residence times compared to bulk soil organic carbon. The proportions of pyrogenic carbon on total soil organic carbon were consistent at 6.9 ± 0.5% of total soil organic carbon. Thus, pyrogenic carbon forms a significant component of the total soil organic carbon and climatic as well as soil factors control the long residence times of pyrogenic carbon in vulnerable high-latitude forest mineral soils.

Review of per- and poly-fluoroalkyl treatment in combustion-based thermal waste systems in the United States

Per- and poly-fluoroalkyl substances (PFAS) are a class of synthetic chemicals known for their widespread presence and environmental persistence. Carbon-fluorine (C-F) bonds are major components among PFAS and among the strongest organic bonds, thus destroying PFAS may present significant challenge. Thermal treatment such as incineration is an effective and approved method for destroying many halogenated organic chemicals. Here, we present the results of existing studies and testing at combustion-based thermal treatment facilities and summarize what is known regarding PFAS destruction and mineralization at such units. Available results suggest the temperature and residence times reached by some thermal treatment systems are generally favorable to the destruction of PFAS, but the possibility for PFAS or fluorinated organic byproducts to escape destruction and adequate mineralization and be released into the air cannot be ruled out. Few studies have been conducted at full-scale operating facilities, and none to date have attempted to characterize possible fluorinated organic products of incomplete combustion (PICs). Further, the ability of existing air pollution control (APC) systems, designed primarily for particulate and acid gas control, to reduce PFAS air emissions has not been determined. These data gaps remain primarily due to the previous lack of available methods to characterize PFAS destruction and PIC concentrations in facility air emissions. However, newly developed stack testing methods offer an improved understanding of the extent to which thermal waste treatment technologies successfully destroy and mineralize PFAS in these waste streams.

Characterizing Volatile Emissions and Combustion Byproducts from Aqueous Film-Forming Foams Using Online Chemical Ionization Mass Spectrometry.

Aqueous film-forming foams (AFFFs) are used in firefighting applications and often contain per- and polyfluoroalkyl substances (PFAS), which can detrimentally impact environmental and biological health. Incineration is a potential disposal method for AFFFs, which may produce secondary PFAS and other air pollutants. We used online chemical ionization mass spectrometry (CIMS) to measure volatile PFAS emissions from incinerating AFFF concentrate solutions. We quantified perfluorinated carboxylic acids (PFCAs) during the incineration of legacy and contemporary AFFFs. These included trifluoroacetic acid, which reached mg m-3 quantities in the incinerator exhaust. These PFCAs likely arose as products of incomplete combustion of AFFF fluorosurfactants with lower peak furnace temperatures yielding higher PFCA concentrations. We also detected other short-chain PFAS, and other novel chemical products in AFFF combustion emissions. The volatile headspace above AFFF solutions contained larger (C ≥ 8), less oxidized PFAS detected by CIMS. We identified neutral PFAS resembling fluorotelomer surfactants (e.g., fluorotelomer sulfonamide alkylbetaines and fluorotelomer thioether amido sulfonates) and fluorotelomer alcohols in contemporary AFFF headspaces. Directly comparing the distinct chemical spaces of AFFF volatile headspace and combustion byproducts as measured by CIMS provides insight toward the chemistry of PFAS during thermal treatment of AFFFs.

Effect of split injection strategy of diesel fuel on multi-stage heat release and performance of a RCCI engine fueled with diesel and natural gas

Reactivity controlled compression ignition (RCCI) combustion is a advanced low temperature combustion concept to reduce CO2 and brake the trade-off between NOx and PM emissions for next generation compression ignition (CI) engines. However, it leads to the more complex multi-stage heat release in diesel/natural gas (NG) dual fuel engines and is criticized for extra-high methane and carbon monoxide emissions. Using the existing methods, it is difficult to effectively quantify the contribution of the accumulated heat release (AHR) at each stage to the whole combustion process and to create their relevance to the performance and emissions in the RCCI engines.In this paper, experiments were conducted on a ship diesel/NG dual-fuel engine at a load of 25 %. A new identification and quantitative analysis method of multi-stage heat release is proposed, and the coupling effects of the diesel split injection parameters on the multi-stage heat release and performance in the RCCI engine were revealed. The results show that the new method is not only available for analyzing the combustion of traditional CI engines but also is more effective for identifying the multi-stage combustion in RCCI engines. For the increased pre-injection ratio (PR), as the start of first injection (SOI-I) and the start of second injection (SOI-II) advance, the AHR in Stage-I (Q-Stage-I) decreases, and the increased Q-Stage-III lead to the improved indicated thermal efficiency (ITE > 49 %). Meanwhile, methane (CH4), non-methane hydrocarbon (NMHC) and carbon monoxide (CO) emissions can be reduced by more than 50 %, while nitrogen oxides (NOx) emissions increase. The impact significance of SOI-II on Q-Stage-I and Q-Stage-III is higher, their values are + 65.88 % and −51.04 %, respectively, and the Q-Stage-II is mainly controlled by SOI-I. The impact significance of Q-Stage-III on ITE is the highest about + 69.43 %. Q-Stage-I shows a higher positive correlation with CH4, NMHC and CO emissions although the proportion of Q-Stage-I is far smaller than that of Q-Stage-II and Q-Stage-III. Therefore, the simultaneous reduction of incomplete combustion products and NOx emission can be achieved by reasonably adjusting split injection parameters.

IMPACT OF HAZARDOUS TOXIC FACTORS OF FIRES DURING MILITARY ACTIONS ON ECOSYSTEMS AND POPULATION LIFE ACTIVITIES

It has been analysed that wildfires are the most influential factor in environmental pollution. The ecological consequences of wildfires consist primarily of atmospheric air pollution with carbon monoxide, products of combustion of combustible materials, and the burning of oxygen. Plant combustion also contributes significantly to planetary environmental changes: climate warming, ozone depletion, acid rain, chemical and radioactive pollution of the atmosphere, water, and soil. With wildfires, soot particles, that is, carbon and products of incomplete combustion of wood, enter the air. Smoke, which is formed during fires, explosions, ignitions, etc., during the combustion of plant biomass (grasses, leaves from trees and shrubs, mosses, lichens, peatlands, forest litter and needles), is an aerosol-gas mixture containing hazardous substances dangerous to the environment and humans. Biomass burning is a global source of gas and dust pollution of the atmosphere and is considered one of the determining factors of ecotoxicological risks for public health. The negative impact of fires from military actions on the human body is acute and delayed. Acute exposure leads to hypoxia due to carbon oxides, increased consumption of oxygen from the air during combustion, irritation of the respiratory tract, and difficulty breathing. Delayed exposure is due to toxic, mutagenic, and carcinogenic effects. The toxic impact of fires on the life and health of the population is not only a threat to life but also an adverse effect on human organisms of heavy compounds of chemical substances represented by the combustion products of plant biomass of forests, peatlands, vast agricultural lands, including crop rotations and pastures. Often, this impact occurs in combination with typical atmospheric air pollution: emissions from industrial enterprises and motor vehicles. The peculiarity of such a combination is the complex synergistic effects of chemical compounds and high air temperature with significant relative duration (decades, months) of emergency environmental situations. Keywords: toxic factors, fires, ecosystem, human activity.

A simulation and experiment study on the emission reduction potential of light-duty diesel engine retrofitted with an after-treatment system: a case study

ABSTRACT In this study, a simulation and experiment on laboratory conditions were conducted to investigate the effects of a retrofitted DOC-DPF-SCR system on the performance and pollutants of an in-service old-generation light-duty diesel engine. Simulations demonstrate that DOC and SCR have little effect on engine performance, but the particle filter does. With 220 mm, 240 mm, and 260 mm DPF cores, brake power was reduced by 1.9%, 4.5%, and 12.0% at rate condition and 1.2%, 3.6%, and 10.8% at maximum brake torque condition. The after-treatment system can reduce soot by 64.8% to 81.9% at full load conditions and 55.6% to 83.3% as the load varies at a constant speed. NOx emissions were reduced significantly by an average value of 81.9% at full load and 21.7% to 78.1% at a constant speed, depending on load. The DOC combined with DPF also influenced incomplete combustion products as the concentration of CO and HC decreased by 73.6% and 76.5% on average at full load conditions. Following emission standards, HC and CO emissions were reduced by 63.8% and 68.7%, respectively; NOx and PM were decreased by 71.1% and 76.6% when the engine was retrofitted with the after-treatment system. After retrofitting, the old-generation diesel engine can pass the Euro II standard.

IMPROVEMENT OF THE MATHEMATICAL DESCRIPTION OF THERMOPHYSICAL PROPERTIES OF ALTERNATIVE MOTOR FUELS BASED ON THE MODIFIED THERMODYNAMIC THEORY OF DISTURBANCE. PART 2

In the study, the purpose of which was to improve the mathematical apparatus based on the modified thermodynamic perturbation theory for describing the thermophysical characteristics of alternative motor fuels with a spherical configuration of interacting structural elements and an arbitrary aggregate state, the formal scheme of the modified perturbation theory was consistently constructed, the main characteristics of the model system were described, the parameters of the interaction potentials of the alternative fuel components were described, the thermophysical properties of the alternative fuel components were obtained by calculation, the thermodynamic properties of the alternative fuel components were calculated, the results of the calculation of the thermodynamic characteristics of the alternative fuel were analyzed and illustrated in the form of isotherm of phase equilibrium diagrams and data tables. The object of the study is the thermophysical characteristics of traditional, alternative and mixed motor fuels in a liquid or gaseous aggregate state. The subject of the study is a mathematical apparatus based on the modified thermodynamic perturbation theory for describing the thermophysical characteristics of motor fuels. The scientific novelty of the study results lies in the fact that a mathematical apparatus based on a modified perturbation theory has been improved for a comprehensive description of all thermophysical characteristics of motor fuels of any genesis, i.e. traditional, alternative and mixed, which are in both liquid and gaseous aggregate states in terms of reducing the calculation time and reducing the error of obtaining thermophysical characteristics in comparison with reference and experimental data. The practical significance of the research results is that the improved mathematical apparatus is marketable for providing accurate information to the composition of the initial data set in research on the production, storage, transportation, distribution, use of motor fuels of any genesis, which are in different states, as well as forecasting the course and results of processes of atmospheric pollution by gaseous products of complete and incomplete combustion of fuel components in combustion chambers of various types of heat engines.

IMPROVEMENT OF THE MATHEMATICAL DESCRIPTION OF THERMOPHYSICAL PROPERTIES OF ALTERNATIVE MOTOR FUELS BASED ON THE MODIFIED THERMODYNAMIC THEORY OF DISTURBANCE

In the study, the purpose of which was to improve the mathematical apparatus based on the modified thermodynamic perturbation theory for describing the thermophysical characteristics of alternative motor fuels with a spherical configuration of interacting structural elements and an arbitrary aggregate state, the formal scheme of the modified perturbation theory was consistently constructed, the main characteristics of the model system were described, the parameters of the interaction potentials of the alternative fuel components were described, the thermophysical properties of the alternative fuel components were obtained by calculation, the thermodynamic properties of the alternative fuel components were calculated, the results of the calculation of the thermodynamic characteristics of the alternative fuel were analyzed and illustrated in the form of isotherm of phase equilibrium diagrams and data tables. The object of the study is the thermophysical characteristics of traditional, alternative and mixed motor fuels in a liquid or gaseous aggregate state. The subject of the study is a mathematical apparatus based on the modified thermodynamic perturbation theory for describing the thermophysical characteristics of motor fuels. The scientific novelty of the study results lies in the fact that a mathematical apparatus based on a modified perturbation theory has been improved for a comprehensive description of all thermophysical characteristics of motor fuels of any genesis, i.e. traditional, alternative and mixed, which are in both liquid and gaseous aggregate states in terms of reducing the calculation time and reducing the error of obtaining thermophysical characteristics in comparison with reference and experimental data. The practical significance of the research results is that the improved mathematical apparatus is marketable for providing accurate information to the composition of the initial data set in research on the production, storage, transportation, distribution, use of motor fuels of any genesis, which are in different states, as well as forecasting the course and results of processes of atmospheric pollution by gaseous products of complete and incomplete combustion of fuel components in combustion chambers of various types of heat engines.

Synthesis of spirulina microalgae biodiesel, and experimental research of its effects on compression ignition engine responses with iron II-III oxide (Fe3O4) nanoparticle supplementation

The raw material from which biodiesel is produced, the pioneer of alternative fuels in compression ignition engines, has increased importance in recent years. Third-generation biodiesels, which do not harm the food chain and environment, have become popular in recent years. In this study, fuel mixtures were obtained by mixing biodiesel produced from spirulina microalgae, the third-generation biodiesel type, with diesel and iron II-III oxide (Fe3O4) at different concentrations. Microalgae biodiesel (MAB) was mixed with diesel at two different percentages (10% and 20%), and three diverse quantities of Fe3O4 (25, 50, and 75 ppm) were added to 20MAB80D. Since the effects of the fuel mixture containing 20% MAB on the engine response are more optimistic, nanoparticles were added to the fuel containing 20% MAB. These fuel blends were evaluated under various engine loads (from 25% to 100%) at a constant engine speed (1500 rpm), and a compression ratio (15.5:1). Brake thermal efficiency (BTHE) and brake mean effective pressure (BMEP) improved with the addition of both MAB and Fe3O4. Compared to diesel (D100), the highest increases were achieved with 20MAB80D75IO fuel, with an average of 28.64% and 13.18%, respectively. With the 20MAB80D, these increases averaged 12.85% and 3.85%, respectively. On the other hand, brake-specific fuel consumption (BSFC) response increased with MAB and decreased with Fe3O4. With 20MAB80D75IO fuel, it showed an average decrease of 19.02% compared to BSFC diesel. With the 20MAB80D, there was an average increase of 11.31%. MAB and Fe3O4 contributed to reducing carbon monoxide (CO) and hydrocarbon (HC) emissions, which are products of incomplete combustion. With 20MAB80D75IO fuel, an average of 24.21% and 57.36% reductions were achieved, respectively, compared to D100. With the 20MAB80D, there was an average of 20.14% and 22.62% reductions, respectively. Conversely, NOx produced by 20MAB80D75IO was 11.63% higher than D100, while NOx produced by 20MAB80D was 3.83% higher. In conclusion, the experimental data obtained using Fe3O4 nanoparticles added to improve engine responses by improving the properties of MAB produced as third-generation biofuels revealed that MAB would be an excellent alternative fuel and Fe3O4 was a suitable additive.

Pollutant emissions from biomass burning: A review on emission characteristics, environmental impacts, and research perspectives

Biomass is one most abundant resource on the earth providing important energies in support of socioeconomic development in many areas. Burning of biomass fuels comprises to nearly 10% of the total energy from anthropogenic combustion processes; however, as the burning is usually incomplete, this process yields products of incomplete combustion posing consequently significant impacts on air quality, human health, and climate change. Here, we analyzed spatiotemporal characteristics in intentional and unintentional biomass burning from different sectors, discussed impacts of biomass burning emissions on indoor and outdoor air quality, and consequent influences on human health. The global total consumption amount of biomass including both natural and anthropogenic sources was approximately 7900 Tg in 2019, with significantly large regional and sectorial discrepancies among regions. Globally, anthropogenic biomass burning amounts increased gradually, but notably in some developing countries like China residential consumption of biomass fuels, as one large sector of biomass use, decreased over time. Uncommercial biomass consumption needs to be accurately quantified. There are relatively rich datasets of pollutant emission factors from biomass burning, including laboratory and field tests, but still large variations exit and contribute substantially to the uncertainty in emission inventory. Global primary PM2.5, black carbon and organic carbon emissions from biomass burning were about 51, 4.6, and 29 Tg, respectively, contributing to nearly 70%, 55%, and 90% of the total emission from all sources, and emissions from the residential sector and open fires are major sources. Brown carbon emissions from biomass burning attracts growing interests but available studies adopted different methodologies challenging the comparability of those results. Biomass burning emissions polluted not only ambient air but more severely indoor air quality, adversely affecting human health. Future studies that should be emphasized and promoted are suggested.

Emission and Reduction of Air Pollutants from Charcoal-Making Process in the Vietnamese Mekong Delta

Charcoal is a fuelwood commonly used for domestic purposes on the household scale in Africa and Southeast Asia. Earnings from charcoal production contribute to the income of local inhabitants in rural areas. Unfortunately, airborne emissions from the traditional charcoal-making process affect both human health and the ambient environment. A series of studies were performed at a charcoal-making village in the Vietnamese Mekong Delta (VMD) to assess: (i) air pollutant emissions from the traditional charcoal-making process; (ii) the impacts on human well-being and the environment of traditional charcoal production; (iii) the loading of carbon dioxide from a charcoal-making kiln; and (iv) the efficiency in reducing contaminants of an air pollution-controlling method developed at a charcoal-making kiln. Study results revealed that the traditional charcoal-making method causes a substantial loss of carbon from fuelwood materials and emits the products of incomplete combustion. These contaminants negatively impact human well-being and the environment. Carbon dioxide and incomplete combustion substances emitted from the charcoal-making kiln are potential causes of the global warming phenomenon. The installation of an air pollution-controlling system at the charcoal-making kiln is recommended as an urgent solution before alternatives would be found to control the impacts of charcoal production.

ИССЛЕДОВАНИЕ ВОЗМОЖНОСТИ СНИЖЕНИЯ ОКИСЛЕНИЯ СТОП ЛИСТОВ ПРИ НАГРЕВЕ ПОД ТЕРМООБРАБОТКУ ЗА СЧЕТ НАНЕСЕНИЯ ЗАЩИТНЫХ ПОКРЫТИЙ

Heating of metal products for heat treatment and metal treatment by pressure is accompanied by a loss of metal mass, called carbon monoxide. To protect the metal surface from oxidation, heating of workpieces is used: in products of incomplete combustion of fuel with an excess air coefficient of less than one; in molten salts; in protective media and by applying protective coatings to the surface of the heated metal, for example, using a spray gun that works well when using large products. When heating the stop sheets, coating each sheet is a difficult task, therefore, in this work, a method was tested to protect the stop sheets from oxidation when they were heated for heat treatment by applying liquid glass with a brush to various stop surfaces: end, upper and lower.

ENVIRONMENTALLY SAFE OPERATION OF MUNICIPAL WASTE INCINERATION

The technology of waste incineration makes it possible to solve the issue of obtaining an alternative type of fuel and eliminate the problem of the excess waste in landfills. A multi-stage emission cleaning technology has been proposed to protect the environment and service personnel. The chemical processes that take place in the furnace space have been considered.
 The purpose of the research is to develop the concept of control systems for the technological cycle of the installation of thermal disposal of solid household waste to  protection of the environment from these toxic substances: dioxins, carcinogenic hydrocarbons,  products of incomplete combustion, in particular, polycyclic aromatic hydrocarbons, nitrogen and sulfur oxides. A complex of methods of system analysis and the method of data analysis was applied to achieve the goal of the research. An analysis of modern international literary sources, an analysis of the morphological composition of solid household waste, an analysis of the interaction of chemical substances, and experimental studies at a research and industrial facility were carried out. As a result of the research, the scientific and applied task of improving the system of protection of the environment and service personnel from emissions of thermal disposal of solid household waste was formulated and substantiated.
 Research results might apply to designing equipment for waste incineration, for choosing rational parameters of the furnace, location of fuel supply burners. General recommendations for the use of chemical properties of harmful substances in the design of cleaning equipment have been provided. The effectiveness of the method of supplying an inert medium (flue gases) to the combustion zone at a temperature below the flame temperature was evaluated. Effective thermal destruction of dioxins is possible in modern waste incineration plants, provided high temperatures, excess air and sufficient residence time followed by a catalytic cleaning. Homogeneous and heterogeneous formation of polychlorinated dibenzodioxins and polychlorinated dibenzofurans formed and released in zones with relatively low temperatures.

Pilot-Scale Thermal Destruction of Per- and Polyfluoroalkyl Substances in a Legacy Aqueous Film Forming Foam

The destruction of per- and polyfluoroalkyl substances (PFAS) is critical to ensure effective remediation of PFAS contaminated matrices. The destruction of hazardous chemicals within incinerators and other thermal treatment processes has historically been determined by calculating the destruction efficiency (DE) or the destruction and removal efficiency (DRE). While high DEs, >99.99%, are deemed acceptable for most hazardous compounds, many PFAS can be converted to other PFAS at low temperatures resulting in high DEs without full mineralization and the potential release of the remaining fluorocarbon portions to the environment. Many of these products of incomplete combustion (PICs) are greenhouse gases, most have unknown toxicity, and some can react to create new perfluorocarboxylic acids. Experiments using aqueous film forming foam (AFFF) and a pilot-scale research combustor varied the combustion environment to determine if DEs indicate PFAS mineralization. Several operating conditions above 1090 °C resulted in high DEs and few detectable fluorinated PIC emissions. However, several conditions below 1000 °C produced DEs > 99.99% for the quantifiable PFAS and mg/m3 emission concentrations of several nonpolar PFAS PICs. These results suggest that DE alone may not be the best indication of total PFAS destruction, and additional PIC characterization may be warranted.

Shift in Peaks of PAH‐Associated Health Risks From East Asia to South Asia and Africa in the Future

AbstractLung cancer risk from exposure to ambient polycyclic aromatic hydrocarbons (PAHs) is expected to change significantly by 2050 compared to 2008 due to changes in climate and emissions. Integrating a global atmospheric chemistry model, a lung cancer risk model, and plausible future emissions trajectories of PAHs, we assess how global PAHs and their associated lung cancer risk will likely change in the future. Benzo(a)pyrene (BaP) is used as an indicator of cancer risk from PAH mixtures. From 2008 to 2050, the population‐weighted global average BaP concentrations under all RCPs consistently exceeded the WHO‐recommended limits, primarily attributed to residential biofuel use. Peaks in PAH‐associated incremental lifetime cancer risk shift from East Asia (4 × 10−5) in 2008 to South Asia (mostly India, 2–4 × 10−5) and Africa (1–2 × 10−5) by 2050. In the developing regions of Africa and South Asia, PAH‐associated lung cancer risk increased by 30–64% from 2008 to 2050, due to increasing residential energy demand in households for cooking, heating, and lighting, the continued use of traditional biomass use, increases in agricultural waste burning, and forest fires, accompanied by rapid population growth in these regions. Due to more stringent air quality policies in developed countries, their PAH lung cancer risk substantially decreased by ∼80% from 2008 to 2050. Climate change is likely to have minor effects on PAH lung cancer risk compared to the impact of emissions. Future policies, therefore, need to consider efficient combustion technologies that reduce air pollutant emissions, including incomplete combustion products such as PAH.

Gaseous and particulate emissions from the combustion of hard and soft wood for household heating: Influence of boiler type and heat output

Comparison of gaseous and particulate emissions from the combustion of hard (beech) and soft (spruce) wood in four types (old and modern) boilers used for household/residential heating was studied. The boilers were run with three different heat outputs, i.e. nominal (85–100%) and two reduced outputs (60–70% and 35–45%), to cover the expected usage of these boilers in real households during different outdoor air winter temperatures. Gaseous emission factors (CO2, CO, NOx, OGC – organic gaseous compounds), particulate pollutants (n-alkanes and polycyclic aromatic hydrocarbons) and particulate organic markers (monosaccharide anhydrides, methoxyphenols and diterpenoids) were determined. In general, modern-type boilers emitted lower amounts of products of incomplete combustion than those old-type boilers. The emission factors (EFs) of total suspended particles varied between 562 and 2150 mg kg−1 (beech logs, the oldest-type boiler), and 69.1 and 118 mg kg−1 (spruce pellets, the modern-type boiler). The trends between the heat outputs of boilers and the EFs of particulate organic compounds/markers were observed for all boilers (especially the automatic boiler) with some exceptions and mostly increased with a decreasing output of boilers. The ratios levoglucosan/mannosan varied in the range of 13.4–18.6 for the combustion of beech, and 2.11–4.16 for the combustion of spruce.

High-temperature reactor for hydrogen production by partial oxidation of hydrocarbons

Today, conversion of hydrocarbons is one of the most common hydrogen production technologies. This paper presents a design of a high-temperature reactor — the main component of a hydrogen production unit using partial oxidation of hydrocarbons — as well as a physical model of gas generation. It also presents a schematic diagram of an experimental setup as well as results of experimental studies on steady-state modes of partial oxidation in the combustion chamber of a high-temperature reactor for various hydrocarbon feed/oxidant combinations. In the course of the study, we identified patterns that describe how the excess oxidant ratio affects the composition of products of incomplete combustion of hydrocarbons to obtain hydrogen-containing gas of the required composition and parameters for hydrogen production. We propose a method to calculate nominal geometric dimensions of a high-temperature reactor, which makes it possible to estimate its weight and size at the design stage. The paper presents results of experimental studies confirming the adequacy of the proposed method.

Fate of Per- and Polyfluoroalkyl Substances in Postconsumer Products during Waste Management

Per- and polyfluoroalkyl substances (PFAS) have been widely used in consumer products, and some inevitably end up as municipal solid waste. Significant knowledge gaps associated with the fate and release of PFAS from postconsumer products in solid waste management processes exist that limit our current ability to develop appropriate end-of-life management strategies for PFAS. The objectives of this paper are to summarize the current knowledge associated with the fate and release of PFAS from postconsumer products from commonly used waste management processes (including landfilling, recycling, composting, and incineration) and to use that information to identify knowledge gaps and potential exposure pathways for humans and the environment. The current results indicate that landfills are major sinks of PFAS because most PFAS-containing consumer products are landfilled, and PFAS was extensively reported in landfill leachate. More information is needed regarding the total influx of PFAS into landfills as well as landfill gas emissions. Recycling and composting also present potential exposure pathways. The reprocessing of carpet and paper packaging was reported to cause direct exposure to onsite workers through PFAS volatilization and dust emissions. Recycling can cause the circularity of PFAS in the new product and subsequent release throughout its lifespan. Composted food packaging was found to contain PFAS and could cause contamination during the land application of compost. The incineration of waste provides near-complete destruction (∼99%) of PFAS. However, some low-temperature regions within the furnace may still result in products of incomplete combustion, such as short-chain perfluoroalkyl acids and other stable fluorinated compounds, which may be released in incinerator ash. More information is needed regarding the mechanisms of PFAS thermal destruction. Case studies of PFAS product categories indicated that carpet and cosmetics might contribute to the release of more soluble and volatile PFAS, such as perfluoroalkyl acids and fluorotelomer alcohols during landfilling in leachate and gas. The fate of specific PFAS during waste management aligns well with their physical/chemical properties, such as solubility and volatility.