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This work presents the analysis of combustion characteristics of high ash Indian coal (28%–40%) collected from different mines of Singaurali coalfield, India. All the coal samples were characterized by proximate and gross calorific value analysis. Combustion performance of the coals were characterised using thermo-gravimetric analysis to identify the burning profile of individual coals. Various combustion kinetic parameters such as ignition temperature, peak temperature and burnout temperature, ignition index and burnout index, combustion performance index plus rate and intensity index of combustion process, activation energy were determined to analyse the combustion behaviour of coal. Further all these combustion properties were compared with the volatile matter, ash, fixed carbon and fuel ratio of each coal. Theoretical analysis shows that with increase in ash content, combustion performance initially increases and later descends. Further, coal with (25 ± 1.75)% volatile matter, 20%–35% ash and fuel ratio 1.4–1.5 were found to be optimum for coal combustion.

Onsite mine fire generates large volumes of heat-affected coal in Jharia coalfields, India. Direct utilization of such heat-affected coal in thermal utilities is not feasible as such coal does not have the desirable volatile matter required for combustion. In the present work, experimental studies have been carried out to investigate the possible utilization of such heat-affected coal in thermal utilities by blending with other coal. Heat-affected coal (31% ash and 5300 kcal/kg GCV) collected from Jharia coalfield were blended with thermal coal (28% ash and 5650 kcal/kg GCV) in different ratios of 90:10, 80:20, 70:30 and 60:40 to identify the desirable blend ratio for burning of blended coal in thermal utilities. Burning characteristics of all the coals were carried out using TGA. Various combustion parameters such as ignition temperature, peak temperature, burnout temperature, ignition index, burnout index, combustion performance index, rate and heat intensity index of the combustion process and activation energy were evaluated to analyse the combustion process. Experimental and theoretical analysis shows the blend ratio of 90:10 can be used in place of only thermal coal in utilities to reduce the fuel cost.

We investigated the fuel characteristics of five important bamboo species viz., Dendrocalamus strictus, D. brandisii, D. stocksii, Bambusa bambos and B. balcooa. The selected species cover more than 85% of the total growing stock of bamboo in India. Basic density varied from 0.48 to 0.78 g.cm-3 among the bamboo species studied. Ash content, volatile matter content and fixed carbon content ranged between 1.4%-3.0%, 77.2%-80.8% and 17.6%-21.1%, respectively. Variation in calorific value （18.7-19.6 MJ-kg-l） was marginal. Fuel value index var- ied widely （586-2120） among bamboo species. The highest calorific value （19.6 MJ.kg＂l） and fuel value index （2120） were found in B. bal- cooa. Ash elemental analysis revealed that silica and potassium are the major ash forming minerals in bamboo biomass. Silica content ranged from 8.7% to 49.0%, while potassium ranged from 20.6% to 69.8%. We studied combustion characteristics under oxidizing atmosphere. Burning profiles of the samples were derived by applying the derivative thermo- gravimetric technique which is discussed in detail. The five bamboo species were different in their combustion behaviour, mainly due to differences in physical and chemical properties. We compare fuel prop- erties, ash elemental analysis and combustion characteristics of bamboo biomass with wood biomass of Eucalyptus hybrid （Eucalyptus tereticor- his × Eucalyptus camaldulensis）.

In this study, we report fuel properties (basic density, high heating value, proximate and elemental parameters) and ash elemental composition of two important forest weed species, i.e. Lantana camara and Eupatorium spp. The physical, chemical and elemental properties of L. camara and Eupatorium spp. were compared with those of a mature tree (20 years of age) of Eucalyptus hybrid. The combustion characteristics under oxidizing atmosphere were also studied using thermogravimetric analysis. The burning profiles of the samples were derived by applying the derivative thermogravimetric technique. The two weed species were found to be different in their physical, chemical and elemental properties. The fuel properties and combustion characteristics, which largely depend upon the biochemical composition of biomass, were also different in these two weed species. The results suggested that both L. camara and Eupatorium spp. can be used as feedstock in thermochemical conversion processes. The emphasis was given to these species because of the huge biomass they produce. These species are widely present in different agroclimatic zones of India and can play a major role in future bioenergy schemes.

Radial outward burning tubular propellant grain gives progressive burning profile, but trimming port at one end to conical form gives close to neutral burning profile. Though this configuration is easy to realize, but closeform burnback equation for performance prediction of such propellant geometry is not available. In this paper, close-form burnback equation for conically trimmed tubular propellant grain is developed. One propellant grain is also evaluated and performance matching to prediction by developed formulation is realised. Parametric study for different aspect ratio (L/D), diameter ratio (d/D) and slant angle (q) is carried out for a typical configuration and variation is explained. The developed formulation is simple, handy, easy and quick.

In this research, combustion curves of seventeen lignite samples from the Thrace basin (Turkey) were analysed using thermal analysis (TG/DTG) techniques. A comparative analysis was performed considering the relationship between peak temperature, burn-out temperature, moisture content, ash, volatile matter, fixed carbon and calorific values of the samples studied and the results are discussed.

Biomass burning is a large source of volatile organic compounds (VOCs) and many other trace species to the atmosphere, which can act as precursors to secondary pollutants such as ozone and fine particles. Measurements performed with a proton-transfer-reaction time-of-flight mass spectrometer during the FIREX 2016 laboratory intensive were analyzed with positive matrix factorization (PMF), in order to understand the instantaneous variability in VOC emissions from biomass burning, and to simplify the description of these types of emissions. Despite the complexity and variability of emissions, we found that a solution including just two emission profiles, which are mass spectral representations of the relative abundances of emitted VOCs, explained on average 85 % of the VOC emissions across various fuels representative of the western US (including various coniferous and chaparral fuels). In addition, the profiles were remarkably similar across almost all of the fuel types tested. For example, the correlation coefficient r2 of each profile between ponderosa pine (coniferous tree) and manzanita (chaparral) is higher than 0.84. The compositional differences between the two VOC profiles appear to be related to differences in pyrolysis processes of fuel biopolymers at high and low temperatures. These pyrolysis processes are thought to be the main source of VOC emissions. “High-temperature” and “low-temperature” pyrolysis processes do not correspond exactly to the commonly used “flaming” and “smoldering” categories as described by modified combustion efficiency (MCE). The average atmospheric properties (e.g., OH reactivity, volatility, etc) of the high- and low-temperature profiles are significantly different. We also found that the two VOC profiles can describe previously reported VOC data for laboratory and field burns.

Biomass burning is a main source for primary carbonaceous particles in the atmosphere and acts as a crucial factor that alters Earth's energy budget and balance. It is also an important factor influencing air quality, regional climate and sustainability in the domain of Pan-Eurasian Experiment (PEEX). During the exceptionally intense agricultural fire season in mid-June 2012, accompanied by rapidly deteriorating air quality, a series of meteorological anomalies was observed, including a large decline in near-surface air temperature, spatial shifts and changes in precipitation in Jiangsu province of East China. To explore the underlying processes that link air pollution to weather modification, we conducted a numerical study with parallel simulations using the fully coupled meteorology–chemistry model WRF-Chem with a high-resolution emission inventory for agricultural fires. Evaluation of the modeling results with available ground-based measurements and satellite retrievals showed that this model was able to reproduce the magnitude and spatial variations of fire-induced air pollution. During the biomass-burning event in mid-June 2012, intensive emission of absorbing aerosols trapped a considerable part of solar radiation in the atmosphere and reduced incident radiation reaching the surface on a regional scale, followed by lowered surface sensible and latent heat fluxes. The perturbed energy balance and re-allocation gave rise to substantial adjustments in vertical temperature stratification, namely surface cooling and upper-air heating. Furthermore, an intimate link between temperature profile and small-scale processes like turbulent mixing and entrainment led to distinct changes in precipitation. On the one hand, by stabilizing the atmosphere below and reducing the surface flux, black carbon-laden plumes tended to dissipate daytime cloud and suppress the convective precipitation over Nanjing. On the other hand, heating aloft increased upper-level convective activity and then favored convergence carrying in moist air, thereby enhancing the nocturnal precipitation in the downwind areas of the biomass-burning plumes.

Southern Africa produces almost a third of the Earth’s biomass burning (BB) aerosol particles, yet the fate of these particles and their influence on regional and global climate is poorly understood. ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) is a 5-year NASA EVS-2 (Earth Venture Suborbital-2) investigation with three intensive observation periods designed to study key atmospheric processes that determine the climate impacts of these aerosols. During the Southern Hemisphere winter and spring (June–October), aerosol particles reaching 3–5 km in altitude are transported westward over the southeast Atlantic, where they interact with one of the largest subtropical stratocumulus (Sc) cloud decks in the world. The representation of these interactions in climate models remains highly uncertain in part due to a scarcity of observational constraints on aerosol and cloud properties, as well as due to the parameterized treatment of physical processes. Three ORACLES deployments by the NASA P-3 aircraft in September 2016, August 2017, and October 2018 (totaling ~ 350 science flight hours), augmented by the deployment of the NASA ER-2 aircraft for remote sensing in September 2016 (totaling ~ 100 science flight hours), were intended to help fill this observational gap. ORACLES focuses on three fundamental science themes centered on the climate effects of African BB aerosols: (a) direct aerosol radiative effects, (b) effects of aerosol absorption on atmospheric circulation and clouds, and (c) aerosol–cloud microphysical interactions. This paper summarizes the ORACLES science objectives, describes the project implementation, provides an overview of the flights and measurements in each deployment, and highlights the integrative modeling efforts from cloud to global scales to address science objectives. Significant new findings on the vertical structure of BB aerosol physical and chemical properties, chemical aging, cloud condensation nuclei, rain and precipitation statistics, and aerosol indirect effects are emphasized, but their detailed descriptions are the subject of separate publications. The main purpose of this paper is to familiarize the broader scientific community with the ORACLES project and the dataset it produced.

Aerosol particles are of importance in the Earth's radiation budget since they scatter and absorb sunlight. While extensive studies of aerosol optical properties have been conducted at ground sites, vertical measurements and characterization are very limited in megacities. In this work, we present simultaneous real-time online measurements of aerosol optical properties at ground level and at 260 m on a meteorological tower from 16 November to 13 December in 2016 in Beijing along with measurements of continuous vertical profiles during two haze episodes. The average (±1σ) scattering and absorption coefficients (bsca and babs; λ=630 nm) were 337.6 (±356.0) and 36.6 (±33.9) Mm−1 at 260 m, which were 26.5 % and 22.5 % lower than those at ground level. Single scattering albedo (SSA), however, was comparable between the two heights, with slightly higher values at ground level (0.89±0.04). Although bsca and babs showed overall similar temporal variations between ground level and 260 m, the ratios of 260 m to ground varied substantially from less than 0.4 during the clean stages of haze episodes to > 0.8 in the late afternoon. A more detailed analysis indicates that vertical profiles of bsca, babs, and SSA in the low atmosphere were closely related to the changes in meteorological conditions and mixing layer height. The mass absorption cross section (MAC) of equivalent black carbon (eBC, λ=630 nm) varied substantially from 9.5 to 13.2 m2 g−1 in winter in Beijing, and it was strongly associated with the mass ratio of coating materials on refractory BC (rBC) to rBC (MR), and also the oxidation degree of organics in rBC-containing particles. Our results show that the increases in MAC of eBC in winter were mainly caused by photochemically produced secondary materials. Light absorption of organic carbon (brown carbon, BrC) was also important in winter, which on average accounted for 46 (±8.5) % and 48 (±9.3) % of the total absorption at 370 nm at ground level and 260 m, respectively. A linear regression model combined with positive matrix factorization analysis was used to show that coal combustion was the dominant source contribution of BrC (48 %–55 %) followed by biomass burning (17 %) and photochemically processed secondary organic aerosol (∼20 %) in winter in Beijing.