Authors:M. Pandey, S. Jha, R. Kumar, S. Mishra and R. R. Jha
-friendly propellants has revived the efforts in this direction and AN is being considered as the main entity oxidizer for producing clean burning propellants. The enormous challenges in the development of propellant systems with acceptable burn rates, ignition
Authors:Yiqun Fang, Qingwen Wang, Xiaoyan Bai, Weihong Wang and Paul A. Cooper
influence of wood fiber content in WF-PVC. The interactions between PVC and wood flour under elevated temperatures are rarely mentioned.
Burning properties of WF-PVC composites is another important topic. Regardless of good flame retardancy of pure
Authors:Q. Xu, G. Griffin, Y. Jiang, A. Bicknell, G. Bradbury and N. White
Wood cribs free burning tests were conducted under ISO9705 hood. From the tests, the heat release rate of these cribs was
grouped as 0.5, 1.0 and 1.5 MW. This result was used to correct an empirical formula for peak heat release rate calculation.
The correction achieves acceptable accuracy for the typical wood. The test result also shown heat release rate curve can be
normalized by the total combustion surface of the wood crib. This can also be used to predict the HRR of wood crib of certain
sizes and structures.
AP/HTPB based composite
propellants with additives such as ammonium oxalate (AO), mixture of ammonium
oxalate and strontium carbonate (SC) was investigated by burning rate, TG-DTG
and FTIR experiments. The results show that the burning rates of these propellants
are decreased significantly. TG-DTG experiments indicate that decomposition
temperatures of AP with these additives are increased. Furthermore, the activation
energy of the decomposition reaction of AP is also increased in the presence
of AO or AO/SC. These results show that AO or AO/SC restrains the decomposition
of AP. The burning rates of these propellants are decreased. The burning rate
temperature sensitivity of AP/HTPB based propellants is reduced significantly
by the addition of AO or AO/SC. But the effect of AO is less than that of
AO/SC. AO/SC is better effect to reduce temperature sensitivity and at the
same time, to reduce pressure exponent. The reduced heat release at the burning
surface of AP/HTPB/AO is responsible for the reduced temperature sensitivity.
Synergetic action is probably produced between AO and SC within AP/HTPB based
propellants in the pressure range tested. This synergetic effect causes the
heat release to reduce and the burning surface temperature to increase. Moreover,
it makes the net exothermal reaction of condensed phase become little dependent
on T0. Thus, the
burning rate temperature sensitivity is reduced.
Authors:Q. Xu, G. Griffin, Y. Jiang, C. Preston, A. Bicknell, G. Bradbury and N. White
Burning behavior of small-scale wood crib was studied by a serial of cone calorimeter tests. The heat release rate curves
of these small wood cribs were different due to porosity factor and this shows that the control condition switches from one
to another. The burning of some crib with small porosity factors was self-extinguished in fixed flow rate of air supply in
cone calorimeter. These results were compared with Gross’s studies. The switch point of porosity-controlled and surface area
controlled burning regime is different from Gross’s result.
Thermal analysis is widely used in combustion research for both fundamental and practical investigations. Efficient combustion
of coals in cement industry is very important and necessary. In this research, the effects of three coal-burning additives
on burning behaviour of bituminous coal and anthracite were studied with the help of thermogravimetry (TG) and differential
scanning calorimetric (DSC) analysis. The kinetic study was carried out and the results were presented. The results showed
that the coal-burning additives especially LSZ can reduce the ignition temperature, increase the ignition index Di, combustion ending index Df and affect the activation energy of the coal samples studied. The coal-burning additives especially LSZ can improve coal
Authors:L. Li, Z.-C. Tan, S.-H. Meng, S.-D. Wang and D.-Y. Wu
The catalytic and accelerating effects of three coal-burning additives (CBA) on the burning of graphite were studied with
the help of thermogravimetric (TG) analysis. The kinetic study on the catalytic oxidation of the graphite doped with CBA was
carried out and the results were presented. The results show that the CBA can change the carbon oxidation/combustion course
by catalytic action and change the activation energy, thus improving the combustion efficiency.
Authors:A. Smoliński, P. Kuna-Gwoździewicz, M. Łączny and A. Bąk
Burning mine waste dumps release gases of significant content of the polycyclic aromatic hydrocarbons (PAHs). The main objective of the study was to determine the PAHs concentrations in gas sampled from the burning mine waste dump located in Ruda Śląska, Upper Silesia, Poland (N 50°16′46.2″; E 18°51′02.4″). Determination of the level of PAHs content in gas released from burning mine waste dumps is essential for an assessment of its potential environmental risk to human health and the environment. Gas sampling was conducted in 2011 using fixed sorbent type polyurethane foam with a quartz fiber filter and the aspirator. Burning zones were selected based on the assessment of a thermal activity, i.e., measurements of surface and subsurface (at the depth of 1 m) temperatures and determination of the composition of gas at the depth of 1 m (CO2, CO and O2 content). The techniques of pressure-liquid extraction and liquid chromatography (HPLC) with a fluorescence detector (FLD) were applied in the analyses of the samples. The Hierarchical Clustering Analysis enabled to explore the differences between the gaseous samples collected in five burning zones. The average total sum of PAHs content was 2.22 mg/m3. Naphthalene, fluorene and phenanthrene were the main components detected in gas samples, which is associated with their high volatility, when compared to other PAHs compounds. The heaviest PAHs (benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenzo[a,h]anthracene, benzo[g,h,i]perylene and indeno[1,2,3-cd]pyrene) in all tested samples were not detected which may be attributed to decreasing evaporation with increasing molecular mass.
Authors:F. Samu, F. Kádár, G. Ónodi, M. Kertész, A. Szirányi, É. Szita, K. Fetykó, D. Neidert, E. Botos and V. Altbäcker
Recent environmental and land use changes have made wildfires more frequent in natural habitats of the Kiskunság Sand Ridge on the Hungarian Plain. In a study initiated 2.5 years after an extensive fire that destroyed half of the area of a sand grassland — juniper, poplar forest steppe habitat, we assessed the effects of fire on two generalist arthropod groups: spiders and carabid beetles, as well as on the vegetation. Utilizing the natural experiment situation, samples were taken by pitfalls and suction sampling during a 1.5 years period in four 1 ha blocks, two of which were on the burnt part of the habitat, and two in the unburnt control. At the time of the investigation, in the burnt area the vegetation in the grass layer showed a quick but not complete recovery, while the canopy layer of the juniper bushes burnt down with no sign of regeneration. Carabid beetles and spiders showed differences in recovery after fire. In the carabid assemblages of the burnt parts — compared to the unburnt control — there were over three times more beetles, out of which significantly more represented the macropterous life form and granivorous feeding strategy. There was a higher ratio of pioneer species and a simplified assemblage structure in the burnt area, which meant that the conservation value of the carabid assemblage became lower there. In contrast, for the spider assemblage quantitative changes in abundance and species numbers were not significant, and the differences in species composition did not lead to a decrease in conservation value. Spider species in the burnt plots could not be described as pioneer species, rather they had ecological characteristics that suited the changed vegetation structure. Comparing the two groups, to repopulate the burnt areas, dispersal abilities proved to be more limiting for carabids. However, in both groups a strong assemblage level adaptation could be observed to the postfire conditions. In spiders, species with a stratum preference for the grass layer prevailed, while in carabids individuals with granivore strategy gained dominance. Thus, despite the differences in their speed, basically both assemblages tracked vegetation changes. The effect of future fires will depend on their scale, as well as land-use practices, such as grazing, that interact with fire frequency and recovery. If extensive fires in the future permanently change the vegetation, then it would also lead to a fundamental change in the arthropod fauna.
Evolution of the internal pore structure during the combustion of two different types of coal chars is compared. In this study
brown coal char prepared from brown coal (coal-mine Novky) by drying and devolatilization, and commercial black coal char
(provided by U.S. Steel Košice) were used. Particles were combusted to different degrees of burnout at an initial temperature
of 800C in a low oxygen containing atmosphere (5 vol%). It was shown that the combustion of both types of coal chars proceeds
via the same shell progressive mechanism, despite differences in their original internal pore structure. The internal surface
area of the brown coal char particles mainly belongs to the region of micropores, while for the black coal char is typical
its macropore structure. Inside the brown coal particle cores pore structure evolution was observed. This change of the structure
was caused by the reaction between solid carbon and carbon dioxide, due to which the specific surface area in the region of
micropores significantly increased.