Characterisation of sugar cane combustion particles in the Araraquara region, Southeast Brazil

Biomass burning is an important primary and secondary source of aerosol particles. The presence of carbonaceous particles in the respirable size range makes the study of this fraction important in view of possible health and climatic effects. The annual burning of sugar cane plantations causes emission of huge amounts of pyrogenic particles. Aerosol samples were collected in Araraquara city, São Paulo state, Brazil, during the harvest season for fine and coarse particles and bulk; they were analysed by electron-probe microanalysis, including facilities for low-Z element determination (low-Z EPMA) and by energy-dispersive X-ray fluorescence (EDXRF), in order to investigate the elemental composition of individual particles and bulk samples, respectively. Numerical analysis of the EPMA results by hierarchical clustering shows high contributions of carbonaceous particles that can be distinguished mainly in two different types: biogenic and carbon-rich. Additionally, two significant contributions of aluminosilicate particles were identified: as rather pure aluminosilicates or mixed with carbonaceous species. The EDXRF results are compatible with those of aerosol particles in Amazon, which is nowadays one of the main sources of biogenic particles in the world.

Determination of the activation energies of beef tallow and crude glycerin combustion using thermogravimetry

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

NOx and CO emissions and soot presence in partially premixed acoustically excited flames

The pulsating combustion process has attracted interest in current research because its application in energy generation can offer several advantages, such as fuel economy, reduced pollutants formation, increased rate of convective heat transfer and reduced investment, when compared with other new techniques of combustion. An experimental study has been conducted with the objective of investigating the effects of combustion driven acoustic oscillations in the emission rates of combustion gases, especially carbon monoxide and nitrogen oxides, and soot presence in partial premixed flames in confined partially premixed liquefied petroleum gas flames. The results basically showed that a more uniform fuel/air mixture due to the presence of an acoustic field increases the NOx emissions in operations close to stoichiometric equivalence ratios and the frequency is the most important parameter. Carbon monoxide and soot reduced significantly.

Combustion of coal, bagasse and blends thereof Part II: Speciation of PAH emissions

This work reports on emissions of unburned hydrocarbon species from batch combustion of fixed beds of coal, sugar-cane bagasse, and blends thereof in a pre-heated two-stage laboratory furnace operated in the temperature range of 800-1000 degrees C. The effects of fuel blending, combustion staging, and operating furnace temperatures on emissions of pollutants were assessed. Furnace effluents were analyzed for products of incomplete combustion (PICs) including CO, volatile and semi-volatile hydrocarbons, and particulate matter, as has been reported in Ref. [1]. Emitted unburned hydrocarbons include traces of potentially health-hazardous Polycyclic Aromatic Hydrocarbons (PAHs), which are the focus of this work. Under the batch combustion conditions implemented herein, PAH were only generated during the volatile combustion phase of the fuels. The most prevalent species were in descending order: naphthalene, acenaphthylene, phenanthrene, fluoranthene, pyrene, dibenzofuran, benzofuran, byphenyl, fluorene, 9H-fluoren-9-one, acephenantrylene, benzo[b] fluoranthene, 1-methyl-naphthalene; 2-methyl-naphthalene, benz[a] anthracene and benzo[a] pyrene. PAH yields were the highest from combustion of neat bagasse. Combustion of the blends resulted in lower yields of PAH, than combustion of either of their neat fuel constituents. Increasing the furnace operating temperature enhanced the PAH emissions from bagasse, but had little effect on those from the coal or from the blends. Flue gas treatment in a secondary-stage furnace, upon with additional air, typically reduced PAH yields by promoting oxidation of the primary-stage furnace effluents. (C) 2011 Elsevier Ltd. All rights reserved.

Determination of the activation energies of beef tallow and crude glycerin combustion using thermogravimetry

The present study deals with the determination of the activation energy for the thermal decomposition of two renewable fuels crude glycerin and beef tallow. The activation energies were investigated by using a thermogravimetric analyzer (TGA) in the temperature range of 25-600 degrees C in atmosphere of synthetic air. The TG curves of the thermal decomposition process of both samples were divided into several phases and the second, called PH2, was chosen for the kinetic study because it is associated with the combustion ignition. Differential Thermal Analysis (DTA) showed an endothermic event at the PH2 region for the crude glycerin corresponding to devolatilization, while for beef tallow, this step presented an exothermic event, called LTO (low-temperature oxidation), which is correlated with devolatilization followed by combustion. For the entire PH2, activation energy values for crude glycerin were between 90 kJ mol(-1) and 42 kJ mol(-1), while for the beef tallow they ranged from 50 kJ mol(-1) to 113 kJ mol (1). The activation energy values obtained at the pre-ignition stage - conversion between 0 and 0.45 - showed that the crude glycerin with higher values requires an additional energetic support at the start of combustion processes and the beef tallow ignites more easily, presenting lower values. According to the Wolfer's equation, a direct relation between the activation energy and the ignition delay is established and the results of this study provides useful data for the development and design of new combustion chambers and engines when non-traditional fuels are used as feedstock. (C) 2012 Elsevier Ltd. All rights reserved.

Thermal decomposition kinetics of Brazilian limestones: effect of CO2 partial pressure

The influence of the partial pressure of carbon dioxide (CO2) on the thermal decomposition process of a calcite (CI) and a dolomite (DP) is investigated in this paper using a thermogravimetric analyser. The tests were non-isothermal at five different heating rates in dynamic atmosphere of air with 0% and 15% carbon dioxide (CO2). In the atmosphere without CO2, the average activation energies (E-alpha) were 197.4 kJ mol(-1) and 188.1 kJ mol(-1) for CI and DP, respectively. For the DP with 15% CO2, two decomposition steps were observed, indicating a change of mechanism. The values of E-alpha for 15% CO2 were 378.7 kJ mol(-1) for the CI, and 299.8 kJ mol(-1) (first decomposition) and 453.4 kJ mol(-1) (second decomposition) for the DP, showing that the determination of E-alpha for DP should in this case be considered separately in those two distinct regions. The results obtained in this study are relevant to understanding the behaviour changes in the thermal decomposition of limestones with CO2 partial pressure when applied to technologies, such as carbon capture and storage (CCS), in which carbon dioxide is present in high concentrations.

A numerical methodology for the multi-objective optimization of the DI Diesel engine combustion

DI Diesel engine are widely used both for industrial and automotive applications due to their durability and fuel economy. Nonetheless, increasing environmental concerns force that type of engine to comply with increasingly demanding emission limits, so that, it has become mandatory to develop a robust design methodology of the DI Diesel combustion system focused on reduction of soot and NOx simultaneously while maintaining a reasonable fuel economy. In recent years, genetic algorithms and CFD three-dimensional combustion simulations have been successfully applied to that kind of problem. However, combining GAs optimization with actual CFD three-dimensional combustion simulations can be too onerous since a large number of calculations is usually needed for the genetic algorithm to converge, resulting in a high computational cost and, thus, limiting the suitability of this method for industrial processes. In order to make the optimization process less time-consuming, CFD simulations can be more conveniently used to generate a training set for the learning process of an artificial neural network which, once correctly trained, can be used to forecast the engine outputs as a function of the design parameters during a GA optimization performing a so-called virtual optimization. In the current work, a numerical methodology for the multi-objective virtual optimization of the combustion of an automotive DI Diesel engine, which relies on artificial neural networks and genetic algorithms, was developed.

Diesel spray mixing limited vaporization with non-ideal and multi-component fuel thermophysical property effects

Internal combustion engines are, and will continue to be, a primary mode of power generation for ground transportation. Challenges exist in meeting fuel consumption regulations and emission standards while upholding performance, as fuel prices rise, and resource depletion and environmental impacts are of increasing concern. Diesel engines are advantageous due to their inherent efficiency advantage over spark ignition engines; however, their NOx and soot emissions can be difficult to control and reduce due to an inherent tradeoff. Diesel combustion is spray and mixing controlled providing an intrinsic link between spray and emissions, motivating detailed, fundamental studies on spray, vaporization, mixing, and combustion characteristics under engine relevant conditions. An optical combustion vessel facility has been developed at Michigan Technological University for these studies, with detailed tests and analysis being conducted. In this combustion vessel facility a preburn procedure for thermodynamic state generation is used, and validated using chemical kinetics modeling both for the MTU vessel, and institutions comprising the Engine Combustion Network international collaborative research initiative. It is shown that minor species produced are representative of modern diesel engines running exhaust gas recirculation and do not impact the autoignition of n-heptane. Diesel spray testing of a high-pressure (2000 bar) multi-hole injector is undertaken including non-vaporizing, vaporizing, and combusting tests, with sprays characterized using Mie back scatter imaging diagnostics. Liquid phase spray parameter trends agree with literature. Fluctuations in liquid length about a quasi-steady value are quantified, along with plume to plume variations. Hypotheses are developed for their causes including fuel pressure fluctuations, nozzle cavitation, internal injector flow and geometry, chamber temperature gradients, and turbulence. These are explored using a mixing limited vaporization model with an equation of state approach for thermopyhysical properties. This model is also applied to single and multi-component surrogates. Results include the development of the combustion research facility and validated thermodynamic state generation procedure. The developed equation of state approach provides application for improving surrogate fuels, both single and multi-component, in terms of diesel spray liquid length, with knowledge of only critical fuel properties. Experimental studies are coupled with modeling incorporating improved thermodynamic non-ideal gas and fuel

Kinetics of CO2 absorption into aqueous solutions in CO2

This research has been performed to emphasize about the problem known as ?climate changes? occurring due to the greenhouse gases emissions (Carbon dioxide (CO2), Methane (CH4),Nitrogen oxides (NOx), Ozone (O3), Chlorofluorocarbons (artificial). Specially, the project will be focused on the CO2 emissions produced mainly from the fossil fuels burning in power plants and other kind of industrial processes. To understand how important the global is warming and therefore the climate change, both the increase of emissions and the evolution of those will be studied in this project drawing conclusions about its effect. The Kyoto Protocol, the most important agreement internationally, signed by a great majority of the industrialized and developed countries, which try to limit the CO2 emissions to the atmosphere, will be cited in this project. Taking into account the effects of global warming and applying the international legislation on emissions of greenhouse gases, a number of measures will be exposed, where the CO2 capture will be studied deeply. Three different kind of CO2 capture technologies will be studied, drawing the conclusion that the post-combustion capture, in particular by amine chemical absorption, is the most efficient one.

Pyrolysis and combustion study of flexible polyurethane foam

The thermal degradation of flexible polyurethane foam has been studied under different conditions by thermogravimetric analysis (TG), thermogravimetric analysis-infrared spectrometry (TG-IR) and thermogravimetric analysis-mass spectrometry (TG-MS). For the kinetic study, dynamic and dynamic+isothermal runs were performed at different heating rates (5, 10 and 20 °C min−1) in three different atmospheres (N2, N2:O2 4:1 and N2:O2 9:1). Two reaction models were obtained, one for the pyrolysis and another for the combustion degradation (N2:O2 4:1 and N2:O2 9:1), simultaneously correlating the experimental data from the dynamic and dynamic+isothermal runs at different heating rates. The pyrolytic model considered consisted of two consecutive reactions with activation energies of 142 and 217.5 kJ mol−1 and reaction orders of 0.805 and 1.246. Nevertheless, to simulate the experimental data from the combustion runs, three consecutive reactions were employed with activation energies of 237.9, 103.5 and 120.1 kJ mol−1, and reaction orders of 2.003, 0.778 and 1.025. From the characterization of the sample employing TG-IR and TG-MS, the results obtained showed that the FPUF, under an inert atmosphere, started the decomposition breaking the urethane bond to produce long chains of ethers which were degraded immediately in the next step. However, under an oxidative atmosphere, at the first step not only the urethane bonds were broken but also some ether polyols started their degradation which finished at the second step producing a char that was degraded at the last stage.

Single-pulse shock tube studies of the kinetics of the reaction N + O [arrow right over arrow left (reversible reaction)] 2 NO between 2000-3000⁰ K,

At head of title: Combustion Dynamics Division, Air Force Office of Scientific Research, ARDC, Washington, D. C., File no. AF 18(600)-1332.

Investigation of chemical kinetics phenomena in rocket engines.

"Unclassified."

Soot measurements in steady and pulsed ethylene/air diffusion flames using Laser-Induced Incandescence

Combustion-generated carbon black nano particles, or soot, have both positive and negative effects depending on the application. From a positive point of view, it is used as a reinforcing agent in tires, black pigment in inks, and surface coatings. From a negative point of view, it affects performance and durability of many combustion systems, it is a major contributor of global warming, and it is linked to respiratory illness and cancer. Laser-Induced Incandescence (LII) was used in this study to measure soot volume fractions in four steady and twenty-eight pulsed ethylene diffusion flames burning at atmospheric pressure. A laminar coflow diffusion burner combined with a very-high-speed solenoid valve and control circuit provided unsteady flows by forcing the fuel flow with frequencies between 10 Hz and 200 Hz. Periodic flame oscillations were captured by two-dimensional phase-locked LII images and broadband luminosity images for eight phases (0° – 360°) covering each period. A comparison between the steady and pulsed flames and the effect of the pulsation frequency on soot volume fraction in the flame region and the post flame region are presented. The most significant effect of pulsing frequency was observed at 10 Hz. At this frequency, the flame with the lowest mean flow rate had 1.77 times enhancement in peak soot volume fraction and 1.2 times enhancement in total soot volume fraction; whereas the flame with the highest mean flow rate had no significant change in the peak soot volume fraction and 1.4 times reduction in the total soot volume fraction. A correlation (fvRe-1 = a + b·Str) for the total soot volume fraction in the flame region for the unsteady laminar ethylene flames was obtained for the pulsation frequency between 10 Hz and 200 Hz, and the Reynolds number between 37 and 55. The soot primary particle size in steady and unsteady flames was measured using the Time-Resolved Laser-Induced Incandescence (TIRE-LII) and the double-exponential fit method. At maximum frequency (200 Hz), the soot particles were smaller in size by 15% compared to the steady case in the flame with the highest mean flow rate.

Soot Measurements in Steady and Pulsed Ethylene/Air Diffusion Flames Using Laser-Induced Incandescence

Combustion-generated carbon black nano particles, or soot, have both positive and negative effects depending on the application. From a positive point of view, it is used as a reinforcing agent in tires, black pigment in inks, and surface coatings. From a negative point of view, it affects performance and durability of many combustion systems, it is a major contributor of global warming, and it is linked to respiratory illness and cancer. Laser-Induced Incandescence (LII) was used in this study to measure soot volume fractions in four steady and twenty-eight pulsed ethylene diffusion flames burning at atmospheric pressure. A laminar coflow diffusion burner combined with a very-high-speed solenoid valve and control circuit provided unsteady flows by forcing the fuel flow with frequencies between 10 Hz and 200 Hz. Periodic flame oscillations were captured by two-dimensional phase-locked LII images and broadband luminosity images for eight phases (0°- 360°) covering each period. A comparison between the steady and pulsed flames and the effect of the pulsation frequency on soot volume fraction in the flame region and the post flame region are presented. The most significant effect of pulsing frequency was observed at 10 Hz. At this frequency, the flame with the lowest mean flow rate had 1.77 times enhancement in peak soot volume fraction and 1.2 times enhancement in total soot volume fraction; whereas the flame with the highest mean flow rate had no significant change in the peak soot volume fraction and 1.4 times reduction in the total soot volume fraction. A correlation (ƒv Reˉ1 = a+b· Str) for the total soot volume fraction in the flame region for the unsteady laminar ethylene flames was obtained for the pulsation frequency between 10 Hz and 200 Hz, and the Reynolds number between 37 and 55. The soot primary particle size in steady and unsteady flames was measured using the Time-Resolved Laser-Induced Incandescence (TIRE-LII) and the double-exponential fit method. At maximum frequency (200 Hz), the soot particles were smaller in size by 15% compared to the steady case in the flame with the highest mean flow rate.

LES of flame acceleration and DDT in hydrogen-air mixture using artificially thickened flame approach and detailed chemical kinetics

A large eddy simulation is performed to study the deflagration to detonation transition phenomenon in an obstructed channel containing premixed stoichiometric hydrogen–air mixture. Two-dimensional filtered reactive Navier–Stokes equations are solved utilizing the artificially thickened flame approach (ATF) for modeling sub-grid scale combustion. To include the effect of induction time, a 27-step detailed mechanism is utilized along with an in situ adaptive tabulation (ISAT) method to reduce the computational cost due to the detailed chemistry. The results show that in the slow flame propagation regime, the flame–vortex interaction and the resulting flame folding and wrinkling are the main mechanisms for the increase of the flame surface and consequently acceleration of the flame. Furthermore, at high speed, the major mechanisms responsible for flame propagation are repeated reflected shock–flame interactions and the resulting baroclinic vorticity. These interactions intensify the rate of heat release and maintain the turbulence and flame speed at high level. During the flame acceleration, it is seen that the turbulent flame enters the ‘thickened reaction zones’ regime. Therefore, it is necessary to utilize the chemistry based combustion model with detailed chemical kinetics to properly capture the salient features of the fast deflagration propagation.