The fine particle and gas emissions from the residential wood combustion (RWC) appear to be a major contributor to winter-time pollution in Europe. In this study, we characterised the effect of two ...different combustion conditions on particulate and gaseous emissions from a conventional masonry heater. Normal combustion (NC) is the best available operational practice for the heater, whereas smouldering combustion (SC) mimicked slow heating combustion. It was found that the operational practice in RWC can significantly influence the quantity and quality of particle and gaseous emissions into the atmosphere. In SC, the emissions of carbon monoxide were 3.5-fold, total volatile organics 14-fold and PM
1 6-fold to those of NC, whereas the mass of the inorganic compounds (“fine ash”) and particle number emissions were lower from SC than from NC. According to electron microscopy analyses, the observed fine ash particles seemed to occur mainly as separate spherical or irregularly shaped particles but not as agglomerates. Ultrafine (<100
nm) fine ash particles were composed mainly of K, S and Zn, but also in a lesser extent of C, Ca, Fe, Mg, Cl, P and Na. Large agglomerates were found to contain mainly carbon and are considered to be primarily soot particles. The larger spherical and irregularly shaped particles were composed of same alkali metal compounds as ultrafine particles, but they were probably covered with heavy organic compounds. From SC, particles were composed mainly of carbon compounds and they had a more closed structure than the particles from NC, due to organic matter on the particles. In the present experiments, the ultrafine mode in the particle number distributions seemed to be determined mainly by the amount of released ash forming material in combustion, and the shifting of particle size during different combustion conditions seemed to be determined by the amount of condensed organic vapour in the flue gas.
The aim of this study was to compare four alternatives for providing decentralized energy production in small communities in terms of their flue gas emissions and toxicological properties of the ...emissions. In this study, two different size classes of boilers were examined and the use of fossil fuel oils was compared against wood fuels. The lowest PM1 emission, 0.1 mg MJ−1, was observed from small-scale light fuel oil combustion. In medium-scale wood combustion, PM1 emission values from a grate fired wood combustion boiler (10 MW) without particulate filtration were the highest (264 mg MJ−1) but were substantially reduced down to 0.6 mg MJ−1 due to the usage of an electrostatic precipitator (ESP). The wood combustion particles were mainly formed of potassium salts. In light fuel oil combustion, one of the main components in the particles was sulphate whereas in heavy fuel oil combustion also significant amounts of V and Ni were emitted. Pellet combustion produced the lowest PAH emissions. Overall, oil combustion produced higher amount of PAHs than wood combustion. This was indicated also as a higher cytotoxicity of the oil combustion samples when compared to those from wood combustion in the corresponding scale of boilers. However, when calculated on an equal mass basis, the particles collected after ESP were even more cytotoxic which can be explained by the altered chemical characteristics of the emissions in the ESP. Due to the variation in the emissions and in the toxicity of the emissions, we propose that in the long term, not only the emission levels but also the toxicity of the emissions should be taken into account in the regulations of the emission limits of the combustion plants.
•The use of fossil fuels versus wood fuels was compared.•Gaseous and particle emissions and the cytotoxicity of PM1 were examined.•HFO combustion PM1 was found to evoke the highest toxicity responses.•Toxicity of emissions should be considered when authorities regulate emission limits.
Silicon–carbon nanoceramics have been synthesised from hexamethyldisilane (HMDS) by the atmospheric pressure chemical vapour synthesis (APCVS). Direct aerosol phase synthesis enables continuous ...production of high purity materials in one-stage process. The particle formation is based on the decomposition of the precursor in a high temperature reactor. Reaction of the gas phase species leads to homogeneous nucleation and formation of the nanoparticles with a narrow size distribution (geometric mean diameter range of particle number size distribution 160–200 nm with 1.5–1.6 geometric standard deviation at reaction temperatures 800–1200 °C). A systematic investigation of the influence of the process temperature on the powder characteristics, including the particle size, crystallinity, chemical structure, surface and bulk composition and surface morphology, was carried out. At the reactor temperature of 800 °C, the synthesised nanoparticles were amorphous preceramics containing mostly SiC
4
, Si–CH
2
–Si and Si–H units. The composition of the powder turned towards nanocrystalline 3C–SiC (crystal size under 2 nm) when the reaction temperature was increased to 1200 °C. The reaction temperature appeared to be a key parameter controlling the structure and properties of the synthesised powders.
Ultrafine particles sampled during new particle formation bursts observed in the coastal zone were studied with transmission electron microscopy (TEM) and elemental analysis using energy‐dispersive X ...ray (EDX). It was observed that both iodine and sulphur were present in the new particles with diameter below 10 mn. Gaseous emissions of halogen compounds from seaweeds were also measured at the same location during low‐tide particle nucleation episodes. Based on the presence of iodine in the particle phase during low‐tide nucleation bursts, and the significant emission of iodine compounds from the seaweeds during these periods, it is apparent that part of the biogenic iodine species emitted from the seaweeds end up in the ultrafine particulate phase. It was not possible to quantitatively determine the iodine content in the particles; however, in most cases the relative contribution from iodine and sulphate was similar, while some cases indicated no sulphate. On larger sized particles the contribution of sulphate was significantly higher than iodine. It appears that the condensable species leading to the appearance of new particles in the coastal atmosphere is an iodine species. Whether or not this iodine species also participates in the nucleation of new stable clusters could not be completely verified.
Production of cobalt and nickel particles by hydrogen reduction Forsman, J.; Tapper, U.; Auvinen, A. ...
Journal of nanoparticle research : an interdisciplinary forum for nanoscale science and technology,
05/2008, Letnik:
10, Številka:
5
Journal Article
Cobalt and nickel nanoparticles were produced by hydrogen reduction reaction from cobalt or nickel chloride precursor vapour in nitrogen carrier gas. This aerosol phase method to produce ...nanoparticles is a scalable one-step process. Two different setups were introduced in particle production: a batch type reactor and a continuously operated reactor. Common feature in these setups was hydrogen mixing in a vertical flow reactor. The process was monitored on-line for particle mass concentration and for gas phase chemical reactions. Tapered element oscillating microbalance measured the particle mass concentration and Fourier transform infrared spectroscopy was used to monitor relevant gas phase species. The produced cobalt and nickel particles were characterised using transmission electron microscopy and x-ray diffraction. The produced cobalt and nickel particles were crystalline with cubic fcc structure. Twinning was often observed in cobalt particles while nickel particles were mostly single crystals. The cobalt particles formed typically long agglomerates. No significant neck growth between the primary particles was observed. The primary particle size for cobalt and nickel was below 100 nm.
Although most companies recognize the importance of R&D for future competitiveness, they often struggle to assess its contribution to the organization. Performance measurement in R&D is particularly ...difficult because (1) effort levels may not be observable, (2) project success is uncertain, influenced by uncontrollable factors, and (3) success can be assessed only after long delays, or it accrues to other units of the organization.
Based on existing literature on the problem, we developed a performance measurement system for the process technology research group of an industrial company. This measurement system systematically supported the business strategy. Moreover, the measures were adjusted for different project profiles: short- versus long term, hardware versus software, routine support services versus breakthrough ideas and knowledge development.
The contribution of this article is a description of the process of developing and implementing a comprehensive performance measurement system in a company, based on previous performance management research, and supporting the company’s strategy. It is noteworthy that the system was implemented in a
research group (as opposed to development), where the measurement problems are the most severe.
A new variant of factor analysis (positive matrix factorization, PMF) is applied to a Finnish data set (18 years, 15 locations) of monthly bulk wet deposition concentrations of strong acids, SO
4, NO
...3, NH
4, total nitrogen (N
tot
), total phosphorus (P
tot
), Ca, K, Mg, Na, Cl, and total organic carbon (TOC). PMF produces strictly nonnegative factors, optimally based on error estimates of data values, with almost no rotational ambiguity. The application of PMF to environmental data is outlined: handling of outliers and missing values, determination of error estimates, interpretation of results. The results are displayed in different ways: (1) seasonal profiles of factors; (2) factor compositions by absolute value; (3) factor compositions scaled by their importance in explaining the variation of data. For most compounds 90–95% of the total weighted variation is explained by four factors. Each of the 15 data matrices is analysed with four factors. Different types of factors are characterized by the following five key elements: strong acids (H
+), nitrogen compounds (N), Cl, TOC and P. Likely main sources for factors are discussed. A high degree of neutralization is observed at all inland stations. Only at four stations the acidity-related substances—SO
4 and NO
3—are mainly explained by the H-factor. The neutralization caused by the Estonian oil-shale industry is detected at one station. The N-factor is the major anthropogenic factor associating acidic anions SO
4 and NO
3 together with NH
4. Some features of the factors H and N seem to be connected with degradation processes during the collection period of one month. The marine source creates a well-defined Cl-factor at five stations. The annual cycle of the TOC-factor and its association with Ca and K could be connected to airborne particulate matter, such as soil dust. The seasonal behaviour and elemental concentrations of the P-factor suggest a biological origin: pollen, spores, plant debris. The anion-cation balance is shown for all factors and it is mostly good.
We have developed a gas-phase nanoparticle generator that produces stable and well-defined size distributions for TiO2. The online analyses of the gas-phase compounds and total number concentration ...of the generated particles as well as the off-line analysis of the filter samples confirmed the stability of the production. The major advantage of this reactor is that the test substance is directly in the aerosol phase, and thus no preprocessing is needed. This eliminates the physicochemical changes between bulk and administrated material during storing or processing. This system is easy to adjust to different experimental setups and precursors. As a result, well-characterized nanomaterials for inhalation exposure studies can be produced. At mass concentration of 30 mg/Nm3, the count mean diameter was 126 nm (geometric SD 1.6), mass mean diameter was 161 nm (2.0), mass median aerodynamic diameter was 125 nm, and the concentrations of harmful gas-phase by-products remained low. The produced powder consisted of crystals of anatase (77 vol%) and brookite (23 vol%), and its specific surface area was 69 m2/g.
A method to produce Ti–O powders by an in-droplet hydrolysis of metal alkoxide precursor is presented. Titanium
n-tetrabutoxide, hydrolysis water, and acetic acid were included in the ethanolic ...precursor solution that was nebulized. The resulting aerosol was transported to a tubular flow reactor where the ethanol evaporation initiated a polycondensation reaction and solid particles were formed starting from droplet surface. Titanium hydrous oxide particles were obtained at 200°C in atmospheric pressure of nitrogen and air. The collected powders were characterized by XRD, TG–SDTA, BET, SEM, TEM, and IR- spectroscopy, as well as with aerosol impactor. The as-produced powder particles were amorphous, smooth on the surface, and either spherical or deflated in shape. Aerodynamic mass mean diameter was 2.7 μm. Nanocrystalline TiO
2 was obtained after thermal post-annealing for one hour. An expected tendency to convert to anatase crystalline phase up to 500°C and subsequently to rutile phase up to 900°C in the annealing was observed. The results show that the in-droplet hydrolysis is a viable method in preparing fine Ti–O powder particles with controlled properties.
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