Chemical and physical characterization of emissions from birch wood combustion in a wood stove

The purpose of this study was to characterize the emissions of a large number of chemical compounds emitted from birch wood combustion in a wood stove. Birch wood is widely used as fuel in Swedish household appliances. The fuel load was held constant during six experiments.Particles <2.5 μm in diameter were collected and the size distribution of the particles was measured. The results were compared to the size distribution in road traffic emissions. It could be seen that the number distribution differed between the sources. In traffic exhaust, the number of particles maximized at 20 nm, while the number distribution from wood burning ranged from 20 to 300 nm. The ratio K/Ca on particles was found to be significantly different in wood burning compared to road dust, range 30–330 for the former and 0.8±0.15 for the latter. The source profile of common elements emitted from wood burning differed from that found on particles at a street-level site or in long-distance transported particles.The ratio toluene/benzene in this study was found to be in the range 0.2–0.7, which is much lower than the ratio 3.6±0.5 in traffic exhaust emissions.Formaldehyde and acetone were the most abundant compounds among the volatile ketones and aldehydes. The emission factor varied between 180–710 mg/kg wood for formaldehyde and 5–1300 mg/kg wood for acetone. Of the organic acids analyzed (3,4,5)-trimethoxy benzoic acid was the most abundant compound. Of the PAHs reported, fluorene, phenanthrene, anthracene, fluoranthene and pyrene contribute to more than 70% of the mass of PAH. Of the elements analyzed, K and Si were the most abundant elements, having emission factors of 27 and 9 mg/kg wood, respectively.Although fluoranthene has a toxic equivalence factor of 5% of benzo(a)pyrene (B(a)P), it can be seen that the toxic potency of fluoranthene in wood burning emissions is of the same size as B(a)P. This indicates that the relative carcinogenic potency contribution of fluoranthene in wood smoke would be about 40% of B(a)P.     

Effects of a catalytic converter on PCDD/F, chlorophenol and PAH emissions in residential wood combustion

Temporal variations in concentrations of perfluorinated carboxylic acids (PFCAs) and sulfonic acids (PFSAs), including perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) structural isomers, were examined in livers of pilot whale (Globicephala melas), ringed seal (Phoca hisida), minke whale (Balaenoptera acutorostrata), harbor porpoise (Phocoena phocoena), hooded seal (Cystophora cristata), Atlantic white-sided dolphin (Lagenorhynchus acutus) and in muscle tissue of fin whales (Balaenoptera physalus). The sampling spanned over 20 years (1984-2009) and covered a large geographical area of the North Atlantic and West Greenland. Liver and muscle samples were homogenized, extracted with acetonitrile, cleaned up using hexane and solid phase extraction (SPE), and analyzed by liquid chromatography with negative electrospray tandem mass spectrometry (LC-MS/MS). In general, the levels of the long-chained PFCAs (C9-C12) increased whereas the levels of PFOS remained steady over the studied period. The PFOS isomer pattern in pilot whale liver was relatively constant over the sampling years. However, in ringed seals there seemed to be a decrease in linear PFOS (L-PFOS) with time, going from 91% in 1984 to 83% in 2006.     

Simulation of atmospheric PAH emissions from diesel engines

Simulation of atmospheric PAH emissions in a typical European passenger car diesel engine at steady conditions or under a certification cycle is made using in-house software. It is based on neural fitting of experimental data from eight different fuels tested under five operating steady conditions (reproducing modes of the European transient urban/extraurban certification cycle). The software allows the determination of PAH emissions as a function of the fuel composition parameters (aromatic content, cetane index, gross heat power, nitrogen and sulphur content) and operation conditions (torque and engine speed). The mathematical model reproduces experimental data with a maximum error of 20%. This tool is very useful, since changes in parameters can be made without experimental cost and the trend in modifications in PAH emissions is immediately obvious.     

Greenhouse gas emissions from Canadian peat extraction, 1990-2000: a life-cycle analysis

This study uses life-cycle analysis to examine the net greenhouse gas (GHG) emissions from the Canadian peat industry for the period 1990-2000. GHG exchange is estimated for land-use change, peat extraction and processing, transport to market, and the in situ decomposition of extracted peat. The estimates, based on an additive GHG accounting model, show that the peat extraction life cycle emitted 0.54 x 10(6) t of GHG in 1990, increasing to 0.89 x 10(6) t in 2000 (expressed as CO2 equivalents using a 100-y time horizon). Peat decomposition associated with end use was the largest source of GHGs, comprising 71% of total emissions during this 11-y period. Land use change resulted in a switch of the peatlands from a GHG sink to a source and contributed an additional 15%. Peat transportation was responsible for 10% of total GHG emissions, and extraction and processing contributed 4%. It would take approximately 2000 y to restore the carbon pool to its original size if peatland restoration is successful and the cutover peatland once again becomes a net carbon sink.     

A novel field measurement method for determining fine particle and gas emissions from residential wood combustion

Emission data from residential wood combustion are usually obtained on test stands in the laboratory but these measurements do not correspond to the operational conditions in the field because of the technological boundary conditions (e.g. testing protocol, environmental and draught conditions). The field measurements take into account the habitual practice of the operators and provide the more reliable results needed for emission inventories. In this study, a workable and compact method for measuring emissions from residential wood combustion in winter conditions was developed. The emissions for fine particle, gaseous and PAH compounds as well as particle composition in real operational conditions were measured from seven different appliances. The measurement technique worked well and was evidently suitable for winter conditions. It was easy and fast to use, and no construction scaffold was needed. The dilution of the sample with the combination of a porous tube diluter and an ejector diluter was well suited to field measurement. The results indicate that the emissions of total volatile organic carbon (TVOC) (17 g kg⁻¹ (of dry wood burned)), carbon monoxide (CO) (120 g kg⁻¹) and fine particle mass (PM₁) (2.7 g kg⁻¹) from the sauna stove were higher than in the other measured appliances. In the masonry heaters, baking oven and stove, the emissions were 2.9–9 g kg⁻¹ TVOC, 28–68 g kg⁻¹ CO and 0.6–1.6 g kg⁻¹ PM₁. The emission of 12 PAHs (PAH₁₂) from the sauna stove was 164 mg kg⁻¹ and consisted mainly of PAHs with four benzene rings in their structure. PAH₁₂ emission from other appliances was, on average, 21 mg kg⁻¹ and was dominated by 2-ring PAHs. These results indicate that despite the non-optimal operational practices in the field, the emissions did not differ markedly from the laboratory measurements.     

Effects of operating variables on PAH emissions and mutagenicity of emissions from woodstoves.

As part of the Integrated Air Cancer Project, the U.S. Environmental Protection Agency (EPA) has conducted field emission measurement programs in Raleigh, North Carolina, and Boise, Idaho, to identify the potential mutagenic impact of residential wood burning and motor vehicles on ambient and indoor air. These studies included the collection of emission samples from chimneys serving wood burning appliances. Parallel projects were undertaken in instrumented woodstove test laboratories to quantify woodstove emissions during operations typical of in-house usage but under more controlled conditions. Three woodstoves were operated in test laboratories over a range of burnrates, burning eastern oak, southern yellow pine, or western white pine. Two conventional stoves were tested at an altitude of 90 m. One of the conventional stoves and a catalytic stove were tested at an altitude of 825 m. Decreasing burnrate increased total particulate emissions from the conventional stoves while the catalytic stove's total particulate emissions were unaffected. There was no correlation of total particulate emissions with altitude whereas total polynuclear aromatic hydrocarbon (PAH) emissions were higher at the lower altitude. Mutagenicity of the catalytic stove emissions was higher than emissions from the conventional stove. Emissions from burning pine were more mutagenic than emissions from oak.     

Effects of combustion and operating conditions on PCDD/PCDF emissions from power boilers burning salt-laden wood waste

This paper discusses the effects of combustion conditions on PCDD/PCDF emissions from pulp and paper power boilers burning salt-laden wood waste. We found no correlation between PCDD/PCDF emissions and carbon monoxide emissions. A good correlation was, however, observed between PCDD/PCDF emissions and the concentration of stack polynuclear aromatic hydrocarbons (PAHs) in the absence of TDF addition. Thus, poor combustion conditions responsible for the formation of products of incomplete combustion (PICs), such as PAHs and PCDD/PCDF precursors, increase PCDD/PCDF emissions. PAH concentrations increased with higher boiler load and/or low oxygen concentrations at the boiler exit, probably because of lower available residence times and insufficient excess air. Our findings are consistent with the current understanding that high ash carbon content generally favours heterogeneous reactions leading to either de novo synthesis of PCDD/PCDFs or their direct formation from precursors. We also found that, in grate-fired boilers, a linear increase in the grate/lower furnace temperature produces an exponential decrease in PCDD/PCDF emissions. Although the extent of this effect appears to be mill-specific, particularly at low temperatures, the results indicate that increasing the combustion temperature may decrease PCDD/PCDF emissions. It must be noted, however, that there are other variables, such as elevated ESP and stack temperatures, a high hog salt content, the presence of large amounts of PICs and a high Cl/S ratio, which contribute to higher PCDD/PCDFs emissions. Therefore, higher combustion temperatures, by themselves, will not necessarily result in low PCDD/PCDFs emissions.     

Evaluation of methods for the physical characterization of the fine particle emissions from two residential wood combustion appliances

The fine particle emissions from a U. S. certified non-catalytic wood stove and a zero-clearance fireplace burning Quercus rubra L. (northern red oak) and Pseudotsuga menziesii (Douglas fir) cordwood each at two different moisture levels were determined. Emission testing was performed using both time-integrated and continuous instrumentation for total particle mass, particle number, particle size distribution, and fixed combustion gases using an atmospheric wind tunnel, full-flow laboratory dilution tunnel, and dilution stack sampler with a comparison made between the three dilution systems and two sampling filter types. The total mass emission factors (EFs) for all dilution systems and filter media are extremely variable ranging from <1 to 55 g kg⁻¹ of dry wood depending on the combination of appliance type, wood species and moisture content, filter medium, and dilution system. For Teflon filter sampling of stove emissions in the wind tunnel, the total mass EFs varied from 2 to 8 g kg⁻¹ of dry fuel depending on wood type whereas the equivalent fireplace emissions burning wet oak averaged 11 g kg⁻¹. A substantial number of ultrafine particles in the accumulation size range were also observed during all tests as determined by an Electrical Low Pressure Impactor (ELPI) and Scanning Mobility Particle Sizer. The PM-2.5 (particles ≤2.5 μm in aerodynamic diameter) fractions determined from the ELPI electrometer data ranged from 93 to 98% (mass) depending on appliance type as reported previously by Hays et al. (Aerosol Science, 34, 1061, 2003).     

Study of PAH emission from the solid fuels combustion in residential furnaces

The procedure for and results of a test study of polycyclic aromatic hydrocarbon (PAH) emission from a few types of solid fuels combustion in residential furnaces of various designs typical for Belarus are discussed. Greatest levels of PAH emission were detected from domestic wastes and wood waste combustion. Lowest levels of PAH emission are from peat briquette combustion. It was found that PAH concentration in off-gases from firewood combustion also varies significantly depending on the type of wood: the highest values of PAH are typical for waste gases from birch firewood combustion in comparison with pine firewood combustion. Draft PAH emission factors are proposed with intended application for emission inventory of such installations.     

Regulated and speciated hydrocarbon emissions from a catalyst equipped internal combustion engine

In the present work, the effect of engine operating conditions on its exhaust emissions and on catalytic converter operation is studied. A 4-cylinder OPEL 1.6 l internal combustion engine equipped with a hydraulic brake dynamometer was used in all the experiments. For exhaust emissions treatment a typical three-way catalyst was used. The highest hydrocarbon and carbon monoxide engine-out emissions were observed at engine power 2–4 HP. These emissions were decreased as the engine power was increased up to 20 HP. Among the various compounds detected in exhaust emissions, the following ones were monitored at engine and catalyst outlet: methane, hexane, ethylene, acetaldehyde, acetone, benzene, toluene and acetic acid. The concentration of each compound in the catalytic converter effluent was in the range 45–132, 5–12, 10–125, 15–22, 3–7, 3–12, 2–9, 0–6 ppm, respectively. After the required temperature for catalyst operation had been achieved, carbon monoxide tailpipe emissions were dramatically decreased and the observed hydrocarbon conversions were also high. Methane was the most resistant compound to oxidation while ethylene was the most degradable compound over the catalyst. The order from the easiest to the most resistant to oxidation compound was: Alkene>Aromatic>Aldehyde>Ketone>Alkane.     

Particle size distribution and PAH concentrations of incense smoke in a combustion chamber

The particle size distribution and the concentrations of polycyclic aromatic hydrocarbons (PAHs) in incense smoke were studied using a custom-designed combustion chamber. Among the nine types of incense investigated, the particle and the total PAH emission factors varied significantly. The average mass median aerodynamic diameter (MMAD) of the smoke aerosol was 262+/-49nm, which positively correlated to particle emission factor (mg/stick, p<0.05). Coagulation was a major mechanism that dictates the MMAD of the smoke. The total toxic equivalency (the sum of the benzo[a]pyrene equivalent concentration) of the solid-phase PAHs (S-PAHs) was over 40 times higher than that of the corresponding gas-phase PAHs, indicating that the S-PAHs in incense smoke may pose potential health risk. Experiments show that each lowered percentage of total carbon content in the raw incense helped decrease the particle emission factor by 2.6mg/g-incense, and the reduction of S-PAH emission factor ranged from 8.7 to 26% when the carbon content was lowered from 45 to 40%.     

煤无烟燃烧锅炉炉内燃烧特性分析

对一台所设计的DZL1．0-0．7-AⅢ煤无烟燃烧锅炉炉内燃烧特性进行了数值模拟。对床层反应，采用了基于热力学平衡法的“黑箱模型”，而对于床层上方炉膛空间内的气相湍流燃烧则采用了标准κ-ε模型、旋涡消散模型和离散坐标模型。采用非结构化四面体网格生成技术处理复杂炉膛几何空间的网格生成。通过数值模拟，得到炉内速度场，温度场，浓度场等参数的分布特性。结果表明：“多孔分层错列撞击流式”二次风的引入对于改变炉内流动和燃烧特性，加强炉内烟气和空气的混合，强化燃烧及实现炉内消烟除尘具有重要的作用。     

Control of mercury vapor emissions from combustion flue gas

GOAL, SCOPE AND BACKGROUND: Mercury (Hg) emission from combustion flue gas is a significant environmental concern due to its toxicity and high volatility. A number of the research efforts have been carried out in the past decade exploiting mercury emission, monitoring and control from combustion flue gases. Most recently, increasing activities are focused on evaluating the behavior of mercury in coal combustion systems and developing novel Hg control technologies. This is partly due to the new regulatory requirement on mercury emissions from coal-fired combustors to be enacted under the U.S. Title III of the 1990 Clean Air Act Amendments. The aim of this review work is to better understand the state-of-the-art technologies of flue gas mercury control and identify the gaps of knowledge hence areas for further opportunities in research and development. MAIN FEATURES: This paper examines mercury behaviors in combustion systems through a comprehensive review of the available literature. About 70 published papers and reports were cited and studied. RESULTS AND DISCUSSION: This paper summarizes the mechanisms of formation of mercury containing compounds during combustion, its speciation and reaction in flue gas, as well as subsequent mobilization in the environment. It also provides a review of the current techniques designed for real-time, continuous emission monitoring (CEM) for mercury. Most importantly, current flue gas mercury control technologies are reviewed while activated carbon adsorption, a technology that offers the greatest potential for the control of gas-phase mercury emissions, is highlighted. CONCLUSIONS AND RECOMMENDATIONS: Although much progress has been achieved in the last decade, techniques developed for the monitoring and control of mercury from combustion flue gases are not yet mature and gaps in knowledge exist for further advancement. More R&D efforts are required for the effective control of Hg emissions and the main focuses are identified.     

煤无烟燃烧锅炉炉内燃烧特性分析

对一台所设计的DZL1.0-0.7-AⅢ煤无烟燃烧锅炉炉内燃烧特性进行了数值模拟.对床层反应,采用了基于热力学平衡法的"黑箱模型",而对于床层上方炉膛空间内的气相湍流燃烧则采用了标准k-ε模型、旋涡消散模型和离散坐标模型.采用非结构化四面体网格生成技术处理复杂炉膛几何空间的网格生成.通过数值模拟,得到炉内速度场,温度场,浓度场等参数的分布特性.结果表明:"多孔分层错列撞击流式"二次风的引入对于改变炉内流动和燃烧特性,加强炉内烟气和空气的混合,强化燃烧及实现炉内消烟除尘具有重要的作用.     

Survey-based inventory for atmospheric emissions from residential combustion in Vietnam

Environmental Science and Pollution Research - Local questionnaire surveys were conducted to collect representative activity data for calculation of annual emissions from residential combustion in...     

The history of mercury emissions from fuel combustion in Maritime Canada

In this study, we present an inventory of historical emissions of mercury resulting from combustion of wood, coal and refined petroleum products in Maritime Canada. The pattern of emissions illustrates the strong influences of population growth, industrial development and prevailing fuel preferences in the region. According to our calculations, anthropogenic mercury releases from fuel combustion in Maritime Canada have cumulatively totaled more than 50 tonnes since 1800. We have compiled both high and low estimates of annual mercury releases in this region. Mercury emissions from fuel combustion in Maritime Canada reached a maximum level in the 1940s. At this time, emissions were between 778 (low) and 1494 (high) kg per year, coinciding with the period of most intensive coal use in Maritime Canada. In 1995, emissions were approximately 54% of the level reached in 1940, at 427 (low)-800 (high) kg per year. In presenting this emissions inventory, we hope to refine past estimates with current information on the mercury content of different fuel types, and create a comprehensive database on how mercury emissions from various sources have changed over time.     

Semi-volatile and particulate emissions from the combustion of alternative diesel fuels

Motor vehicle emissions are a major anthropogenic source of air pollution and contribute to the deterioration of urban air quality. In this paper, we report results of a laboratory investigation of particle formation from four different alternative diesel fuels, namely, compressed natural gas (CNG), dimethyl ether (DME), biodiesel, and diesel, under fuel-rich conditions in the temperature range of 800-1200 degrees C at pressures of approximately 24 atm. A single pulse shock tube was used to simulate compression ignition (CI) combustion conditions. Gaseous fuels (CNG and DME) were exposed premixed in air while liquid fuels (diesel and biodiesel) were injected using a high-pressure liquid injector. The results of surface analysis using a scanning electron microscope showed that the particles formed from combustion of all four of the above-mentioned fuels had a mean diameter less than 0.1 microm. From results of gravimetric analysis and fuel injection size it was found that under the test conditions described above the relative particulate yields from CNG, DME, biodiesel, and diesel were 0.30%. 0.026%, 0.52%, and 0.51%, respectively. Chemical analysis of particles showed that DME combustion particles had the highest soluble organic fraction (SOF) at 71%, followed by biodiesel (66%), CNG (38%) and diesel (20%). This illustrates that in case of both gaseous and liquid fuels, oxygenated fuels have a higher SOF than non-oxygenated fuels.     

Ash from the combustion of wood treated with inorganic wood preservatives: Element composition and leaching

Wood samples impregnated with inorganic wood preservatives containing the elements arsenic, boron, chromium, copper, fluorine, and/or zinc were burned in a furnace. Three different kinds of ash were collected: furnace, boiler, and so-called fly ash. Analyses showed that the ash contained large amounts of elements originating from the inorganic wood preservatives. Further interest was focused on the leachability of the above-mentioned elements. For this purpose a laboratory batch leaching test according to the German Standard DIN 38 414 part 4 was chosen. The results indicate that the leachability is in a range where the release of these elements to the environment from deposited ash can be considered as detrimental.