Electrostatic precipitator performance and trace element emissions from two Kraft recovery boilers

Fine particle emissions from combustion sources have gained attention recently due to their adverse effects on human health. The emission depends on the combustion process, fuel, and particulate removal technology. Particle concentrations at Kraft recovery boiler exits are very high, and the boilers are typically equipped with electrostatic precipitators (ESP). However, little data are available on the ESP performance in recovery boilers. Particle concentrations and size distributions were determined at two modern, operating recovery boilers. In addition, we determined the fractional collection efficiency of the ESPs by simultaneous measurements at the ESP inlet and outlet and the particulate emissions of trace metals. The particle mass concentration atthe ESP inlet was 11-24 g/Nm3 at the two boilers. Particle emissions were 30-40 mg/ Nm3 at boiler A and 12-15 mg/Nm3 at boiler B. The particle size distributions had a major particle mode at around 1 microm. These fume particles contained most of the particle mass. The main components in the particles were sodium and sulfate with minor amounts of chloride, potassium, and presumably some carbonate. The ESP collection efficiency was 99.6-99.8% at boiler A and 99.9% at boiler B. The particle penetration through the ESP was below 0.6% in the entire fume particle size range of 0.3-3 microm. Trace element emissions from both boilers were well below the limit values set by EU directive for waste incineration.     

Reductions in emissions of carbonaceous particulate matter and polycyclic aromatic hydrocarbons from combustion of biomass pellets in comparison with raw fuel burning

Biomass pellets are emerging as a cleaner alternative to traditional biomass fuels. The potential benefits of using biomass pellets include improving energy utilization efficiency and reducing emissions of air pollutants. To assess the environmental, climate, and health significance of replacing traditional fuels with biomass pellets, it is critical to measure the emission factors (EFs) of various pollutants from pellet burning. However, only a few field measurements have been conducted on the emissions of carbon monoxide (CO), particulate matter (PM), and polycyclic aromatic hydrocarbons (PAHs) from the combustion of pellets. In this study, pine wood and corn straw pellets were burned in a pellet burner (2.6 kW), and the EFs of CO, organic carbon, elemental carbon, PM, and PAHs (EF(CO), EF(OC), EF(EC), EF(PM), and EF(PAH)) were determined. The average EF(CO), EF(OC), EF(EC), and EF(PM) were 1520 ± 1170, 8.68 ± 11.4, 11.2 ± 8.7, and 188 ± 87 mg/MJ for corn straw pellets and 266 ± 137, 5.74 ± 7.17, 2.02 ± 1.57, and 71.0 ± 54.0 mg/MJ for pine wood pellets, respectively. Total carbonaceous carbon constituted 8 to 14% of the PM mass emitted. The measured values of EF(PAH) for the two pellets were 1.02 ± 0.64 and 0.506 ± 0.360 mg/MJ, respectively. The secondary side air supply in the pellet burner did not change the EFs of most pollutants significantly (p > 0.05). The only exceptions were EF(OC) and EF(PM) for pine wood pellets because of reduced combustion temperatures with the increased air supply. In comparison with EFs for the raw pine wood and corn straw, EF(CO), EF(OC), EF(EC), and EF(PM) for pellets were significantly lower than those for raw fuels (p < 0.05). However, the differences in EF(PAH) were not significant (p > 0.05). Based on the measured EFs and thermal efficiencies, it was estimated that 95, 98, 98, 88, and 71% reductions in the total emissions of CO, OC, EC, PM, and PAHs could be achieved by replacing the raw biomass fuels combusted in traditional cooking stoves with pellets burned in modern pellet burners.     

Pollutant formation and emissions from cement kiln stack using a solid recovered fuel from municipal solid waste

The thermal decomposition of a solid recovered fuel (SRF) has been studied by two techniques. First, laboratory-scale experiments were performed in a horizontal furnace in which different atmospheres were studied to analyze the dioxins and furans (PCDD/Fs) evolved from the decomposition of the material. Sulfur presence was revealed to be important in PCDD/Fs formation. In the second technique, the emissions of various pollutants (PAHs, PCDD/Fs, metals, acid gases, etc.) were determined in a cement kiln fed on different proportions of SRF material, and where a maximum feed rate of 15000 kg SRF/h was achieved. In the laboratory furnace the dioxin toxicity revealed a maximum when the amount of oxygen in the atmosphere increased until approximately stoichiometric conditions. In the cement kiln, all emitted pollutants were under the legal limits. No correlation between SRF input and metal emission was observed.     

Comparison of trace element emissions from thermal treatments of heavy metal hyperaccumulators

Phytoextraction has become one of the most promising remediation techniques for heavy metal (HM) contaminated soils. However, the technique invariably produces large amounts of HM-enriched hyperaccumulators, which need further safe disposal. In this study, two different thermal treatment methods are investigated as potential options for evaporative separation of HMs from the residues. A horizontal tube furnace and a vertical entrained flow tube furnace were used for testing the disposal of grounded hyperaccumulators. The release characteristics of HMs (Cd, Cu, Pb, and Zn) into flue gas and residues were investigated for thermal treatment of the Cd and Zn hyperaccumulators Sedum plumbizincicola and Sedum alfredii. In a horizontal tube furnace, incineration favors the volatilization of Cu and Cd in contrast to pyrolysis. The percentages of HMs in residues after incineration are lower than those after pyrolysis, especially for Cd, Pb, and Zn. However, in an entrained flow tube furnace, Zn content in flue gas increases with increasing temperature, but Cu and Cd contents are fluctuated. In addition, a higher incineration temperature enhances the Cu content in residues.     

Particle collection efficiency and particle re-entrainment of an electrostatic precipitator in a sewage sludge incineration plant

In several recent studies it was shown that high atmospheric loads of submicrometer particles in the size range below 500 nm have strong impact on human health. Therefore, extensive research concerning the reduction of fine particle emissions is needed to further improve air quality. Regarding health effects, especially the emission characteristics of fine and ultrafine particles emerging from anthropogenic sources such as combustion processes are of special interest. This study shows that the emission characteristic of an electrostatic precipitator (ESP) due to re-entrainment of fine particles and their subsequent release into the atmosphere can be significantly lowered by application of different operating conditions. For this purpose the particle collection efficiency of an ESP was studied in a municipal sewage sludge incineration plant. Particles were sampled under different operating conditions upstream and downstream from the ESP, and the particle number concentrations were measured simultaneously with aerodynamic particle sizers. In addition, the size distribution of the particles downstream from the ESP was measured with high time resolution by an electrical low-pressure impactor to investigate the particle re-entrainment into the flue gas. To determine the influence of operating conditions, different rapping cycles were investigated regarding their impact on the collection efficiency and the subsequent particle re-entrainment.     

Effect of water/fuel emulsions and a cerium-based combustion improver additive on HD and LD diesel exhaust emissions

One of the major technological challenges for the transport sector is to cut emissions of particulate matter (PM) and nitrogen oxides (NOx) simultaneously from diesel vehicles to meet future emission standards and to reduce their contribution to the pollution of ambient air. Installation of particle filters in all existing diesel vehicles (for new vehicles, the feasibility is proven) is an efficient but expensive and complicated solution; thus other short-term alternatives have been proposed. It is well known that water/diesel (W/ D) emulsions with up to 20% water can reduce PM and NOx emissions in heavy-duty (HD) engines. The amount of water that can be used in emulsions for the technically more susceptible light-duty (LD) vehicles is much lower, due to risks of impairing engine performance and durability. The present study investigates the potential emission reductions of an experimental 6% W/D emulsion with EURO-3 LD diesel vehicles in comparison to a commercial 12% W/D emulsion with a EURO-3 HD engine and to a Cerium-based combustion improver additive. For PM, the emulsions reduced the emissions with -32% for LD vehicles (mass/km) and -59% for the HD engine (mass/ kWh). However, NOx emissions remained unchanged, and emissions of other pollutants were actually increased forthe LD vehicles with +26% for hydrocarbons (HC), +18% for CO, and +25% for PM-associated benzo[a]pyrene toxicity equivalents (TEQ). In contrast, CO (-32%), TEQ (-14%), and NOx (-6%) were reduced by the emulsion for the HD engine, and only hydrocarbons were slightly increased (+16%). Whereas the Cerium-based additive was inefficient in the HD engine for all emissions except for TEQ (-39%), it markedly reduced all emissions for the LD vehicles (PM -13%, CO -18%, HC -26%, TEQ -25%) except for NOx, which remained unchanged. The presented data indicate a strong potential for reductions in PM emissions from current diesel engines by optimizing the fuel composition.     

Role of lubrication oil in particulate emissions from a hydrogen-powered internal combustion engine

Recent studies suggest that trace metals emitted by internal combustion engines are derived mainly from combustion of lubrication oil. This hypothesis was examined by investigation of the formation of particulate matter emitted from an internal combustion engine in the absence of fuel-derived soot. Emissions from a modified CAT 3304 diesel engine fueled with hydrogen gas were characterized. The role of organic carbon and metals from lubrication oil on particle formation was investigated under selected engine conditions. The engine produced exhaust aerosol with log normal-size distributions and particle concentrations between 10(5) and 10(7) cm(-3) with geometric mean diameters from 18 to 31 nm. The particles contained organic carbon, little or no elemental carbon, and a much larger percentage of metals than particles from diesel engines. The maximum total carbon emission rate was estimated at 1.08 g h(-1), which is much lower than the emission rate of the original diesel engine. There was also evidence that less volatile elements, such as iron, self-nucleated to form nanoparticles, some of which survive the coagulation process.     

Evaluation of trace element contents in canned foods marketed from Turkey

Trace element contents of 10 canned foods (mushroom, corn, pea, mixed vegetable, tomato, red mullet, stuffed grape leaves, pickle, bean, delicatessen) from Turkish markets were determined by flame and graphite furnace atomic absorption spectrometry after microwave digestion. The accuracy of the method was determined by use of a standard reference material (NIST SRM 1573a Tomato Leaves). The contents of investigated trace elements in canned foods were found to be in the range of 2.85–7.77 μg/g for copper, 8.46–21.9 μg/g for zinc, 6.46–18.6 μg/g for manganese, 27.5–79.6 μg/g for iron, 0.05–0.35 μg/g for selenium, 0.93–3.17 μg/g for aluminium, 0.19–0.52 μg/g for chromium, 0.18–0.75 μg/g for nickel, and 0.20–1.10 μg/g for cobalt. The results found were compared with those reported by scientists from various countries.     

Comparison of trace element solubility from food items treated separately and in combination

Solubility of trace elements from various foods (beef, soya, crab, wholemeal and white bread) is assessed with various extractants, at different pH's and after enzyme treatment. Simple extractants do not solubilise trace elements to the same degree as when they are released after digestive enzyme action. Enzymic action can change the nature of the soluble species as well as their amount. Trace element solubility from one food can be affected markedly by the presence of another food, e.g. soya enhances the solubility of iron from beef but suppresses zinc solubility. Trace elements that are bound to the insoluble residue after enzymolysis are soluble in saline solution on subsequent extraction in only isolated instances.     

Greenhouse gas emissions and land use change from Jatropha curcas-based jet fuel in Brazil

This analysis presents a comparison of life-cycle GHG emissions from synthetic paraffinic kerosene (SPK) produced as jet fuel substitute from jatropha curcas feedstock cultivated in Brazil against a reference scenario of conventional jet fuel. Life cycle inventory data are derived from surveys of actual Jatropha growers and processors. Results indicate that a baseline scenario, which assumes a medium yield of 4 tons of dry fruit per hectare under drip irrigation with existing logistical conditions using energy-based coproduct allocation methodology, and assumes a 20-year plantation lifetime with no direct land use change (dLUC), results in the emissions of 40 kg CO?e per GJ of fuel produced, a 55% reduction relative to conventional jet fuel. However, dLUC based on observations of land-use transitions leads to widely varying changes in carbon stocks ranging from losses in excess of 50 tons of carbon per hectare when Jatropha is planted in native cerrado woodlands to gains of 10-15 tons of carbon per hectare when Jatropha is planted in former agro-pastoral land. Thus, aggregate emissions vary from a low of 13 kg CO?e per GJ when Jatropha is planted in former agro-pastoral lands, an 85% decrease from the reference scenario, to 141 kg CO?e per GJ when Jatropha is planted in cerrado woodlands, a 60% increase over the reference scenario. Additional sensitivities are also explored, including changes in yield, exclusion of irrigation, shortened supply chains, and alternative allocation methodologies.     

Particulate and trace gas emissions from open burning of wheat straw and corn stover in China

Field measurements were conducted to determine particulate emissions and trace gas emissions, including CO2, CO, CH4, NMHCs, NOx, NH3, N2O, and SO2, from open burning of wheat straw and maize stover, two major agricultural residues in China. The headfire ignition technique was adopted, and sampling was performed downwind from the agricultural fire. Particulate matter (PM) and gas emission factors were determined using the carbon mass-balance method. Particle mass size distributions show a prominent accumulation mode peak at 0.26-0.38 microm. Submicron particles dominate PM emissions. Most measured chemical species measured show a similar size distribution as PM. Chemical composition analysis indicates that PM2.5 is largely composed of carbon, K, and Cl. PM2.5 emission factors of wheat straw and maize stover are 7.6 +/- 4.1 g/kg and 11.7 +/- 1.0 g/kg, respectively, It also indicates that 12.1-24.2% of N in biomass is released as nitrogen-based trace gases and 11.0-24.9% of fuel S is emitted as SO2.     

Mineral and trace element concentrations in cultivars of tomatoes

The concentrations of minerals (P, Na, K, Ca and Mg) and trace elements (Fe, Cu, Zn and Mn) were determined in 167 tomato samples belonging to five cultivars (Dorothy, Boludo, Dunkan, Dominique and Thomas) produced on the island of Tenerife. The contribution to the intake of minerals and trace elements was in general low, with special emphasis on the contributions of K and Mg. The cultivar, cultivation method, period of sampling and region of production in the island influenced the concentrations of minerals and trace elements of the tomatoes. Trace elements seemed more influenced by the cultivar than the minerals, and the cultivation method affected mineral contents more than trace element contents. The period of sampling had an important influence on the mineral and trace elements. Many correlations were observed between the minerals and trace elements studied. Applying discriminant analysis, the tomato samples tended to be classified according to the cultivation method, period of sampling and region of cultivation.     

Polycyclic aromatic hydrocarbon emissions from the combustion of alternative fuels in a gas turbine engine

We report on the particulate-bound polycyclic aromatic hydrocarbons (PAH) in the exhaust of a test-bed gas turbine engine when powered by Jet A-1 aviation fuel and a number of alternative fuels: Sasol fully synthetic jet fuel (FSJF), Shell gas-to-liquid (GTL) kerosene, and Jet A-1/GTL 50:50 blended kerosene. The concentration of PAH compounds in the exhaust emissions vary greatly between fuels. Combustion of FSJF produces the greatest total concentration of PAH compounds while combustion of GTL produces the least. However, when PAHs in the exhaust sample are measured in terms of the regulatory marker compound benzo[a]pyrene, then all of the alternative fuels emit a lower concentration of PAH in comparison to Jet A-1. Emissions from the combustion of Jet A-1/GTL blended kerosene were found to have a disproportionately low concentration of PAHs and appear to inherit a greater proportion of the GTL emission characteristics than would be expected from volume fraction alone. The data imply the presence of a nonlinear relation between fuel blend composition and the emission of PAH compounds. For each of the fuels, the speciation of PAH compounds present in the exhaust emissions were found to be remarkably similar (R(2) = 0.94-0.62), and the results do provide evidence to support the premise that PAH speciation is to some extent indicative of the emission source. In contrast, no correlation was found between the PAH species present in the fuel with those subsequently emitted in the exhaust. The results strongly suggests that local air quality measured in terms of the particulate-bound PAH burden could be significantly improved by the use of GTL kerosene either blended with or in place of Jet A-1 kerosene.     

籽粒苋中微量元素成分分析及评价

籽粒苋是一种新型的一年生粮食作物,其营养价值极为丰富,高于一般的粮食作物 。籽粒苋中含有丰富的微量元素,铁、钾、钙、镁含量尤其高,是人类补钙补铁的优质食品。     

中药渣袋栽平菇中微量元素的分析

对中药渣袋栽平菇中微量元素进行研究,用湿法消解样品,原子吸收分光光度法进行微量元素的测定.结果表明:该方法灵敏度高,检出限低,精密度、准确度好;药渣袋栽平菇中微量元素Cu、Zn、Fe、Mn平均含量分别为:9.199mg/kg、113.9mg/kg、102.9mg/kg、8.095mg/kg,与对照组比较无明显差别.     

我国山东、辽宁两省黄海胆生殖腺中微量元素分布特征

目的研究我国山东省和辽宁省黄海胆生殖腺中营养元素的分布特征。方法本研究选取了辽宁和山东2个省仹的6个地区(45仹样品),依据GB 5009.268-2016采用电感耦合等离子体发射光谱仪(inductively coupledplasmaoptical emissionspectrometry, ICP-OES)和电感耦合等离子体质谱仪(inductively coupledplasma mass spectrometry, ICP-MS)对黄海胆生殖腺中微量元素的含量迚行测定,幵研究其分布特征。结果 6个地区的黄海胆中10种微量元素分布各不相同,海阳总量含量最高,为1.57×103 mg/kg;是含量最低的小平岛的1.8倍。SPSS软件分析黄海胆中微量元素含量地区间的差异性,发现Zn、Ni、Se、Fe、V、Mn、Co和Cr的P值小于0.05,具有一定的统计学意义。单元素含量占前3位的元素依次是Zn、Ni和Sr。微量元素中Zn的含量最高,范围为278～865 mg/kg,含量最高地区是最低地区的3.1倍,地区差异较大。海胆中Sr的含量较高,范围为119～184 mg/kg,但是地区性差异较小。结论黄海胆含有丰富的微量元素,除Fe外,其他元素大都超过海参中的元素含量,是很好的微量元素补充膳食食品。地区差异性有统计学意义的微量元素(P0.05)可以考虑作为海胆产地识别的指纹元素迚一步研究。