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The purpose of this work is the development and control of a high temperature reactor for the production of engineered nanoparticles, taking advantage from our previous studies on combustion-generated fine carbonaceous particles. The reactor consists of a laminar premixed flame, homogenously doped with monodisperse droplets of metal precursors dissolved or dispersed in volatile solvents. The droplets are generated by a vibrating orifice aerosol generator, and injected directly into the burner. Fuel-lean and stoichiometric flames allow to produce pure metal oxide particles of nanometric sizes; by changing the flame stoichiometry to fuel-rich conditions, it is possible to obtain mixtures of metal oxide and carbonaceous nanoparticles. Particles are collected by thermophoresis inserting a cold substrate in the flame by means of a pneumatic actuator. Morphological and dimensional analysis are performed on the collected particles by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). SEM and AFM allow inferring both qualitative and quantitative information on many physical properties including size, morphology, surface texture and roughness. Experimental results have been obtained from a premixed stoichiometric flame of ethylene and air, doped with 75 microns droplets of magnesium nitrate hexahydrate dissolved in ethanol. Roughly monodisperse magnesium oxide particles, having a desired size ranging from 50 nm down to 4 nm, have been produced by altering the precursors concentration in the solution and the residence time of the synthesis process.

Spectral and time-resolved fluorescence and incandescence measurements are used to identify aromatic compounds and particles in an atmospheric-pressure opposed-flow flame of ethylene. The fourth harmonic radiation, at 266 nm, of a Nd-YAG laser is used to excite electronic transitions in aromatic intermediates resulting in different laser induced emission signals. Time-resolved analysis of the emission spectra is performed to obtain information about the structure of the compounds responsible for emission signals. Four fluorescence bands in the UV and visible range and a continuum with a maximum at larger wavelengths, attributed to incandescence radiation by solid particle, have been identified in the collected spectra. On the basis of fluorescence emission spectra and fluorescence lifetimes, two different types of high-molecular mass aromatic compounds are individuated in the flame: highly-packed, sandwich-like structures (cluster of PAHs held together by van der Waals forces) and more loose aromatic moieties linked together by a-bonds, such as the aromatic-aliphatic linked hydrocarbons. The first class of particles has been found in the fuel zone and across the stagnation plane of the opposed-flow flame. In this region (1500 K) and growth of aromatics enhanced by the high concentration of small radicals and gas-phase polycyclic aromatic hydrocarbons.

Photoionization yields have been measured in earlier works that showed that combustion-generated aerosols produced in flames or by vehicles emit photoelectrons when irradiated with UV light. The authors interpreted such photoelectric activity of combustion-generated aerosols as due to PAHs adsorbed onto carbon particles, which were demonstrated to greatly enhance photoionization yield. Furthermore, investigations of monodisperse carbon and NaCl particles with known amounts of specific PAHs adsorbed on their surfaces showed that the photoionization depends both on the chemical nature of the core particle and on the specific PAHs in the coatings. Photoionization based techniques have high sensitivity and chemical selectivity. These measurements can also provide in situ light absorption of aerosols with extremely low mass concentrations, since the first step in photoelectric charging is the absorption of a photon and the electrical measurements can easily reach higher sensitivity than optical ones. Exploiting the high photoionization yields of combustion-generated aerosols and various aerosols coated with PAHs, concentrations as low as nanograms per cubic meter have been detected measuring the changes in the aerosol charge state produced by photoionization. The high potentiality of photoionization measurements for the analysis of different carbonaceous particles is particularly attractive and can give complementary information to most of nanoparticle characterization methods. In this work, we explore photoionization combined with on-line differential mobility analysis measurements as a diagnostic able to provide size-dependent information on the chemical structure of incipient nanoparticles. On-line measurements using a differential mobility analyzer (DMA) system with sizing capabilities and sensitivity to particles as small as 1 nm is used together with a dilution probe able to fully suppress particle growth processes in the sample line, including particle-particle coagulation and also condensation of volatile species on the surface of particles. Combustion generated particles are sampled in atmospheric pressure premixed ethylene/air flames by a high dilution sampling probe and sent on line to a tube with quartz windows where particles may be irradiated with UV. Changes in the particle charge state, produced by the light source when it is switched on and off, are measured to determine the photoionization yield. First results have been obtained using the fifth harmonic of a Nd-Yag laser (l = 213 nm, 5.82 eV) to irradiate particles generated in a flame with C/O = 0.67 v0 = 10cm/s. This is a slightly sooting flame that, at the height of 15 mm above the burner, produces a bimodal particle size distribution with a first mode at about 3 nm and a second mode centered at about 10 nm. Preliminary results show that particles in the first mode have a higher photoionization yield than the particles in the second mode. This indicates that the two modes are composed by particles with a different carbonaceous structure. In particular, it can be interpreted as an evidence of the formation of small particles with a molecular-like structure which contain aromatic subunits. On the contrary, larger particles have an aromatic structure which is closer to solid graphitic-like structure. Similar measurements in diffusion flames burning methane showed a higher yield for particles measured in the early region of the flame as well as for the smaller particles in the size distribution and were interpreted as due to particlebound PAHs either on the surface or within the particle structure.

Bronchial artery aneurysm (BAA) represents a rare, but dangerous, pathology because its rupture can cause a life-threatening hemorrhage; opportune treatment is mandatory when a definite diagnosis is obtained. There are several reports of endovascular treatment of BAA with transcatheter arterial embolization and only few cases treated with aortic stent-graft exclusion. We report a case of mediastinal BAA close to thoracic aorta treated with a combined approach of stent-graft occlusion of the inflow and coil embolization of the outflow arteries.

In this article we present an experimental and modeling study of Organic Carbon (OC) particles, with a typical size range of 1–10 nm, and soot particles, with sizes in the range 10–100 nm, formed in premixed methane flames at atmospheric pressure. An optical diagnostic method based on the interaction of an ultraviolet source, corresponding to the fifth harmonic of a Nd:YAG laser, with combustion-generated aerosols was used in order to measure the concentration profiles of both OC and soot particles with high spatial resolution. The high energy of the selected harmonic induces fluorescence from aromatic chromophoric groups and also allows soot particles to heat up and emit incandescent radiation. Optical measurements data are compared with numerical modeling simulations. The experimental data, in agreement with the model results, show that methane burned in slightly rich conditions forms prevalently organic particulate with mean size lower than 10 nm, while soot formation is observable only in very rich co...

All IssuesUp Arrow In This IssueDown Arrow Left ArrowPrevious Article Next ArticleRight Arrow Environmental Engineering Science About This Journal... Subscribe... Buy Article... Emission of Ultrafine Particles from Natural Gas Domestic Burners To cite this article: Patrizia Minutolo, Andrea D'Anna, Mario Commodo, Rocco Pagliara, Giuseppe Toniato, and Claudio Accordini. Environmental Engineering Science. December 2008, 25(10): 1357-1364. doi:10.1089/ees.2007.0188. Published in Volume: 25 Issue 10: December 30, 2008 Full Text PDF (651.1 KB) Full Text PDF with Links (518.5 KB) Author information Patrizia Minutolo Dipartimento di Ingegneria Chimica, Università "Federico II", Napoli, Italy. Istituto di Ricerche sulla Combustione, C.N.R., Piazzale V. Tecchio 80, 80125 Naples, Italy. Phone: +390817682963; Fax: +390815936936. E-mail: minutolo@irc.cnr.it Andrea D'Anna Istituto di Ricerche sulla Combustione, CNR, Napoli, Italy. Mario Commodo Istituto di Ricerche sulla Combustione, CNR, Napoli, Italy. Rocco Pagliara Dipartimento di Ingegneria Chimica, Università "Federico II", Napoli, Italy. Giuseppe Toniato Riello S.p.A., Burner Division, Italy. Claudio Accordini Riello S.p.A., Burner Division, Italy. ABSTRACT An experimental study of the combustion characteristics of new burners used for home and water heating appliances and domestic stove tops is presented with the aim of evaluating the effect of burner configurations and operating conditions on the emissions of ultrafine particles. Advanced in-situ optical diagnostics, based on laser induced emission spectroscopy (LIE), and ex-situ measurements, based on scanning mobility particle size (SMPS) measurements, and particles collection by water-based sampling technique, were used in order to evaluate total particulate concentrations and size distribution functions. For home heating burners, three different configurations, two premixed and one diffusive, were studied under various operating conditions. Measurements showed that particulate matter with diameters in the 1 nm to 10 nm size range is formed. Emitted mass concentration of these compounds were very low, of the order of 0.1 mg/Nm3. They were formed in large number concentrations in the flame region but were also strongly oxidized in the post-oxidation region of the device. On the contrary, a domestic stove top emits a larger amount of very small particles since their post-oxidization is not possible. Soot particles with size larger than 10 nm are not formed in all the examined conditions and burner configurations

Spectral optical techniques are combined to characterise the distribution of large-molecule soot precursors, nanoparticles of organic carbon, and soot in two turbulent non-premixed ethylene flames with differing residence times. Laser-induced fluorescence, laser-induced incandescence and light scattering are used to define distributions across the particle size distribution. From the scattering and laser-induced emission measurements it appears that two classes of particles are formed. The first ones are preferentially formed in the fuel-rich region of the flame closer to the nozzle, have sizes of the order of few nanometers but are not fully solid particles, because the constituent molecules still maintain their individual identity exhibiting strong broadband fluorescence in the UV. The second class of particles constituted by solid particles, with sizes of the order of tens of nanometers are able to absorb a sufficient number of photons to be heated to incandescent temperatures. These larger particles are formed at larger residence times in the flame since they are the result of slow growth processes such as coagulation or carbonization. The flames are also modeled in order to produce mixture fraction maps. A new discovery is that nanoparticles of organic carbon concentration, unlike soot, does correlate well with mixture fraction, independent of position in the flame. This is likely to be a significant benefit to future modelling of soot inception processes in turbulent non-premixed flames.

A new optical diagnostic method has been developed based on the interaction of a pulsed UV laser source with combustion-generated aerosols. This method allows characterization of nanoparticles of organic carbon (NOC) and soot by point measurements. Fluorescence and incandescence measurements induced by the fifth harmonic of a Nd-YAG laser at 213 nm are used for the determination of the volume fractions of particulates in a laminar premixed flame and in a turbulent non-premixed flame of ethylene/air. The selected light source enhances the fluorescence of NOC, which exhibit a large absorption band between 200 and 250 nm and also heats up soot particles to give incandescent emission. Ultraviolet emission signals are correlated with NOC extinction coefficients, while LII signals are correlated with extinction coefficients in the visible region. Laser light scattering measurements are used to estimate the mean sizes of both classes of particles

In this study, we investigated the induction charging of water sprays and the effect of electric field on the breakup mechanism of liquid sprays. Two different kind of hollow cone hydraulic spray nozzles were used. Our investigation aimed to estimate the Droplet Charge to Mass Ratio (D-CMR) and the dependence of breakup length on electric potential. The experiments revealed that the D-CMR increased with the potential until to a maximum, then started to decrease. At the same time, the breakup length decreased more than 0.5 cm compared to the uncharged value, suggesting that the electric field actually influenced the jet break-up dynamics. For V

Phytoremediation technique is of growing interest in the restoration of trace elements contaminated soils. An integrated approach, combining land restoration and biomass post-processing, using a pyrolysis process for material and/or energy recovery, could allow for effective realization of such a process. The dependence of yields, chemical and structural characteristics of char on the biomass feedstock and pyrolysis thermal conditions are important features to be evaluated to explore the possible applications of such a product. In this framework, a comparative study of steam assisted slow pyrolysis of five biomasses has been carried at 873 K. Results demonstrate that for applications requiring high specific surface area Populus Nigra. On the contrary, if the goal is the maximization of the energy recovery in the char, Eucalyptus represents the best choice.