Trace Element Emissions Research Articles

Assessment of gaseous, PM and trace element emissions from a 300-MW lignite-fired boiler unit for various fuel qualities

Modeling of effects of fuel quality on the emissions of major pollutants (NO x , SO 2, CO 2 and PM) and eight trace elements (As, Co, Cr, La, Mo, Ni, Sb and U) from a 300-MW boiler unit fired with Thai lignite was the main focus of this study. The NO x and SO 2 emission models were validated with the use of experimental data. Emission rates and specific emissions (per MW h) of the major pollutants and trace elements were quantified by including efficiencies of the flue gas desulphurization system and electrostatic precipitators in the computations. As shown in this work, the contributions of 300-MW boiler units fired with Thai lignite to the “greenhouse” and “acid rain” gas emissions in the region are significant. Additionally, substantial amounts of hazardous As, Cr and Ni are emitted from the boiler units into the atmosphere via fly ash particles.

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.

Prediction of trace element volatility during co-combustion processes

The behaviour of some selected trace metals (Hg, Cd, As, Pb, Sb, Cr, Co, Cu, Mn, Ni and V) during co-combustion processes of bio-waste materials (sewage sludge, waste wood, refused derived fuel) and coal has been predicted by thermodynamic equilibrium calculations using the HSC-Chemistry 4.0 software. The influence of temperature, flue gas composition, trace element concentration and minor fly ash components on equilibrium composition was evaluated. For most of the elements, an increase in the HCl concentration favours the formation of gaseous species while increasing concentration of SO 2 in the gas composition enhances the formation of condensed species. Trace element interactions with minor fly ash components were predicted. From results obtained in this study it may be concluded that, from a thermodynamical point of view, the addition of a secondary fuel in combustion processes does not produce an increase in trace element emissions to the environment. Generally, trace elements are captured in ashes avoiding that these elements reach the stack.

Emissions of mercury and other trace elements from coal-fired power plants in Japan

To evaluate trace element emissions from modern coal-fired power plants into the atmospheric environment in Japan, trace elements in the coal used in electric utility boilers, stack concentrations, emission rates and emission ratios of coal-fired power plants, and proportions of trace elements in coal-fired power plants were studied. The elements were As, B, Be, Cd, Co, Cr, F, Hg, Mn, Ni, Pb, Sb, Se and V, which are designated in the Law of Pollutant Release and Transfer Register. The particulate trace elements were collected in an electrostatic precipitator and a wet desulfurization scrubber. Emissions into the atmosphere were lower than 1% of the quantity in coal, but the volatile trace elements showed somewhat higher emission ratios. For mercury, the mean concentration in coal was 0.045 ppm, the mean emission rate was 4.4 μg/kW h, and the mean emission ratio was 27%, the highest ratio among all elements in this study. The total annual emission of mercury from coal-fired power plants of the electric power industry in Japan was estimated to be 0.63 t/y. On the basis of these data, the atmospheric environment loads from a coal-fired power station were investigated. The calculation of stack gas dispersion showed that maximum annual mean ground level concentrations were in the order of 10 − 2 to 10 − 5 of the background concentrations, and that the adverse effect of the emissions from the coal-fired power station was small.

04/01486 Status of trace element emission in a coal combustion process: a review: Xu, M. et al. Fuel Processing Technology, 2003, 85, (2–3), 215–237

04/01486 Status of trace element emission in a coal combustion process: a review: Xu, M. et al. Fuel Processing Technology, 2003, 85, (2–3), 215–237

Electrostatic precipitator collection efficiency and trace element emissions from co-combustion of biomass and recovered fuel in fluidized-bed combustion.

Particle and trace element emissions from energy production have continuously been subject to tightening regulations. At the same time, not enough is known on the effect of different combustion processes and different fuels and fuel mixtures on the particle characteristics and particle removal device operation. In this investigation, electrostatic precipitator fractional collection efficiency and trace metal emissions were determined experimentally at a 66 MW biomass-fueled bubbling fluidized-bed combustion plant. The measurements were carried out at the inlet and outlet of the two-field electrostatic precipitator (ESP) at the flue gas temperature of 130-150 degrees C. Two fuel mixtures were investigated: biomass fuel containing 70% wood residue and 30% peat and biomass with recovered fuel containing 70% wood residue, 18% peat, and 12% recovered fuel. The particle mass concentration at the ESP inlet was 510-1400 mg/Nm3. Particle emission at the ESP outlet was 2.3-6.4 mg/Nm3. Total ESP collection efficiency was 99.2-99.8%. Collection efficiency had a minimum in particle size range of 0.1-2 microm. In this size range, collection efficiency was 96-97%. The emission of the trace metals As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sb, Tl, and V was well below the regulation values set by EU directive for waste incineration and co-incineration.

Correlation of trace element content in air particulates with solar meteorological data in the atmosphere of Athens

In this paper, the relation between the trace element content in air particulates and solar meteorological data in the atmospheric environment of Athens, Greece, was studied. For this purpose, Sm, Br, As, Na, K, La, Ce, Cr, Ag, Sc, Fe, Zn, Co, Sb, Th were determined by INAA in respirable aerosols collected during winter 1993-1994. The results showed that the average cloudiness, sunshine, and the total solar radiation (sun and sky) on a horizontal surface, (3 variables) have no relation with trace element variation. However, diffuse solar radiation (sun and sky) on a horizontal surface seems to have statistically significant relationship with some of the trace element variation. It forms a single component with some trace elements after the application of the factor analysis. The increase of the same solar variable in the Athens City center, is one of the factors which cannot permit the emission of trace elements in the atmospheric environment from dust soil and car tires.

Trace element contamination in industrial regions of Poland studied by moss monitoring.

The use of terrestrial mosses as biomonitors in large-scale multi-element studies of heavy metal deposition from the atmosphere is a well established technique in Europe. In such studies it is advantageous to determine as many elements as possible in order to distinguish between different source categories. A combination of INAA and AAS has been found very useful in this respect, in particular when epithermal activation is used for instrumental neutron activation analysis. A total of 33 elements (Al, Cl, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Ag, Cd, Sb, I, Cs, Ba, La, Ce, Tb, Yb, Hf, Ta, W, Au, Pb, Th, and U) in Pleurozium schreberi (Brid.) Mitt. moss samples from the Silesia-Kraków Industrial Region and Legnica-Głogów Copper Basin and from the control (background) area in Northeast Poland were identified. The highest concentrations of the majority of trace elements were found in mosses growing in the Silesia-Kraków Industrial Region, only Cu and As concentrations were higher in mosses in the Legnica-Głogów Copper Basin. These results are in conformity with the load of trace elements emissions in these areas.

Heavy Metal Content of Arable Soils in Northern Belgium

More than 600 arable soils from Flanders (Northern-Belgium) were analysed for their total acid extractable contents of As, B, Be, Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn in order to determine any increase in the natural background values. Samples were taken at random in several municipalities throughout Flanders. Areas with known historical or actual sources of trace element emissions were omitted although in some cases the distance between those sources and the sampling locations was not more than 20 km. The main soil types were, ranging from north to south: sand, loamy sand, light sandy-loam, sandy-loam and loam. In the coastal area, clay soils (sea polders) were sampled. In addition to the analysis of trace elements, the soil texture class, the pH and the carbon content were determined. Macro- or mesonutrients, Ca, K, P, Mg and Na, were determined from a weak acid extract of the soil samples. Correlations between trace elements and macronutrients provide some information about fertilisation practices and heavy metal sources.A limited number of soils showed slightly enhanced levels for As, Be, Cu, Co, Cr Mn, Ni Pb and Zn. In most cases, this could be linked to the regional industrial activities. However, a clear increase for Cu and Zn, above the natural background could be distinguished in areas with low atmospheric heavy metal deposits. In these cases, the excessive use of animal manure in the past may be the reason for this enrichment. However there was no indication that the Cd content of the soil was raised by the use of large amounts of pig slurry and/or by other common agricultural activities.

Emission of trace toxic metals during pulverized fuel combustion of Czech coals

A study of the trace elements emission (As, Se, Cd, Co, Cr, Cu, Zn, Hg, Tl, Pb, Ni, Sn, Sb, V, Mn and Fe) from pulverized coal combustion has been made at six heating and power stations situated in the Czech Republic. The amount of chlorine in coal has considerable influence on volatilization of some elements such as Zn, Cu, Pb, Hg and Tl, which is explained by the formation of thermodynamically stable compounds of these elements with chlorine. Generally, the affinities for Cl follows the order Tl > Cu > Zn > Pb > Co > Mn > Sn > Hg. The experimental data indicates enrichment of some of the trace toxic elements in the emissions (Cu, Zn, As, Se, Cd, Sn, Sb, Hg and Pb) and good agreement was obtained by thermodynamic equilibrium calculations with a few exceptions. In the case of Fe, Mn, Co, Cr and Sn calculated values are overestimated in the bottom ash and there are zero predicted amounts of these elements in the fly ash. In comparison, the results from experiments show up to 80% of these elements retained in fly ash. This implies that there exist additional steps leading to the enrichment by Fe, Mn, Co, Cr and Sn of small particles. Such mechanisms could include the ejection during devolatilization of small inorganic particles from the coal of bottom ash particles, or disintegration of the char containing these metals to small particles of fly ash. On the other hand, there are slightly overestimated or similar values of relative enrichment factors for As, V, Cu, Cd, Sb, Tl and Pb in the fly ashes and zero predicted values for bottom ashes. Our experimental results show about 5% or less of these elements are retained in bottom ashes, so they probably remain in the bottom ash inside unburned parts of coal. Copyright © 2003 John Wiley & Sons, Ltd.

The Fate of Trace Elements during Several Coal Pretreatment Processes

The influence of several coal pretreatment processes (i.e., chemical desulfurization, physical floating, and kaolin scrubbing) on the fate of trace elements (TEs) emissions, i.e., As, Be, Cd, Co, Cr, Cu, Ni, and Pb, are investigated. The behaviors of these TEs during combustion of pretreated coals in a drop-tube furnace are studied with respect to combustion conditions and fuel types. Almost all the studied TEs are partly removed using chemical desulfurization and the highest removal efficiency is found for Pb up to 77%. Coal physical floating eliminates 50%-60% of most TEs, together with nearly 90% of ash removal for Qingshan bituminous coal. The contents of Cd, Pb, Cu, Cr, and Ni in ashes are all decreased at certain extents (40−75%) when burning kaolin-blended coals and the highest removal efficiency is found for Ni up to 75%. However, beryllium (Be) cannot be eliminated using either physical floating or kaolin scrubbing.

Trace Element Emissions from Co-combustion of Secondary Fuels with Coal: A Comparison of Bench-Scale Experimental Data with Predictions of a Thermodynamic Equilibrium Model

Trace element emissions from the co-combustion of coal with biomass and waste secondary fuels have been measured, under conditions relevant to commercial fluidized bed combustors, using a novel, bench-scale, suspension-firing reactor. Experiments have been conducted using two coals (one Polish, one Colombian), four biomass fuels (wood-bark, straw, pulp sludge, and paper sludge), and three waste fuels (agricultural waste, sewage sludge and plastic waste). Concentrations of eighteen trace elements have been measured in these raw fuels and a variety of combustion and co-combustion ashes, using inductively coupled plasma-mass spectrometry (ICP-MS) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES), plus an atomic absorption based mercury determination devise. The influence of chlorine and sulfur on trace element release from combustion has been tested also, in the case of wood-bark, by injecting first HCl and then SO2 into the reactor during combustion. Experimental data have been compared ...

Trace elements - controlling emissions from coal combustion

International and national legislation is increasingly being applied to trace element emissions. Although emissions have decreased for a variety of reasons in many developed countries, continued use of coal and more successful control strategies in other sectors mean that coal combustion is still a relatively important source of some trace elements, especially mercury. Existing pollution control equipment for other emissions is also effective in reducing most trace element emissions. However, the more volatile trace elements are captured to a much lower extent in coal-fired power stations. These species are still relatively poorly understood and this is reflected in the confusion over the best approach to control emissions.

An evaluation of coal preparation technologies for controlling trace element emissions

An evaluation of coal preparation technologies for controlling trace element emissions

Preliminary estimation of trace elements emission during coal combustion

Preliminary estimation of trace elements emission during coal combustion

The effects of solid absorbents on the emission of trace elements, SO2, and NOx during coal combustion

The effects of solid absorbents on the emission of trace elements, SO2, and NOx during coal combustion

Combustion performance of biomass residue and purpose grown species

The combustion performance of two samples of biomass fuel were evaluated using a small scale 50 kW laboratory scale stoker type combustor. One fuel was a bark residue of moderate moisture content and rich in aluminosilicate inorganic contaminants from the surrounding soils. The other was stemwood from a purpose grown eucalypt E. nitens. It had a high moisture and was rich in bio-accumulated inorganics such as calcium and potassium. During combustion the inorganics underwent a complex set of transformations. Some of the major reactions were identified and shown to have important consequences in terms of overall combustion performance as judged by such parameters as extent of ash slagging and fouling, ash leaching characteristics, trace element and sulphur emission levels.

L. L. Sloss and I. M. Smith: “Trace Element Emissions”, Report CCC/34, IEA Coal Research, London, United Kingdom, June 2000, 83 pp. R. M. Davidson: “Modes of Occurrence of Trace Elements in Coal”, Report CCC/36, IEA Coal Research, London, United Kingdom, June 2000, 36 pp + CD-ROM. Reviews

L. L. Sloss and I. M. Smith: “Trace Element Emissions”, Report CCC/34, IEA Coal Research, London, United Kingdom, June 2000, 83 pp. R. M. Davidson: “Modes of Occurrence of Trace Elements in Coal”, Report CCC/36, IEA Coal Research, London, United Kingdom, June 2000, 36 pp + CD-ROM. Reviews

Control of Trace Elements in Gasification: Distribution to the Output Streams of a Pilot Scale Gasifier

The distribution of trace elements to the output streams in a coal and waste gasification scheme for clean energy production have been investigated on a pilot scale gasifier. A 2 MW t air-blown fluidized bed gasifier operated at nominal bed conditions of 960 °C and 13 bar has been used for these investigations. The effects of feedstock variations (coal/sewage sludge/sorbent) and hot gas filter temperatures of 580 to 450 °C were studied. Feedstock sampling and deposition within the plant were found to be significant contributions to mass balance closures outside the expected range. The total trace element emission in the fuel gas from co-gasification of sewage sludge with coal was not significantly increased, and remained within potential legislative limits. No Zn was present in the fuel gas, despite the high levels of this element in the sewage sludge, but there was evidence of an increase in Sn emissions under certain conditions. Hg and Se were only detected in the fuel gas, while Cd and Pb were concentrated in the fine dust removed by the hot gas filter. A reduction in hot gas filter temperature to 450 °C was shown to substantially reduce Pb emissions in the fuel gas. B was retained in the solid streams when sulfur sorbents were used.

The effects of solid absorbents on the emission of trace elements, SO2, and NOx during coal combustion

The emission of toxic metals from the combustion of fossil fuels is an important global environmental issue. Solid absorbents can be used to control the emission of toxic trace elements from coal combustion. In this paper, limestone, CaSO4, bauxite, kaolinite and CaO are employed for this purpose and experiments are carried out in an electrically heated drop-tube furnace. The trace elements investigated are Pb, Cd, Cr and As. It is observed that the absorptive capacity is related to the qualities of the absorbents (type, amount and particle size) and the combustion temperature. The results also show that some absorbents can reduce SO2 emission simultaneously, but no influence on NOx emission. Copyright © 2001 John Wiley & Sons, Ltd.