High Temperature Coal Combustion Research Articles

History of organic pollution in montane lake Issyk-Kul, Kyrgyzstan, Central Asia, inferred from a sediment core

In arid regions, montane lakes are valuable water sources and play important ecological roles. However, recent human-induced inputs of organic pollutants are threatening lake ecology in such regions and becoming a matter of great concern. To investigate pollutant histories and sources, we measured polycyclic aromatic hydrocarbons (PAHs) and n-alkanes in a dated sediment core that spans the last ∼350 years, from montane Lake Issyk-Kul (Kyrgyzstan, Central Asia). Results showed that organic pollutants were delivered to Lake Issyk-Kul in four stages and that their concentrations increased from Stage I (∼1670–1800 CE) to Stage IV (∼2000–2010 CE). Furthermore, we tracked the sources of sedimented PAHs using their ratios combined with n-alkanes data. Ratios of PAHs Ant/(Ant + Phe), Flt/(Flt + Pyr) and Bap/BghiP indicated that inputs during Stage II (∼1800–1970 CE) and Stage III (∼1970–2000 CE) came mainly from high-temperature combustion of coal and vehicle emissions. PAHs in Stage I and Stage IV, however, were mainly derived from low-temperature combustion and petrogenic sources. Diagnostic PAH ratios, combined with the natural n-alkane ratio (NAR＜0) and unresolved complex mixtures (UCM), showed that the sources of PAHs in Stage I were mainly from erosion of bedrock and partly influenced by forest wildfires, different from the source during Stage IV, which was mainly from refined petroleum caused by accidental spills. Our assessment of the contamination history of the lake indicates that toxicity risk to the waterbody from sediment PAHs is low, but recent discharges arising from traffic deserve attention.

Study on the Mechanism of Lead Incorporation into Minerals during High-Temperature Coal Combustion

Study on the Mechanism of Lead Incorporation into Minerals during High-Temperature Coal Combustion

Experimental and theoretical-based study of heavy metal capture by modified silica-alumina-based materials during thermal conversion of coal at high temperature combustion

Heavy metals emitted from coal combustion can easily pose many threats. In this study, five modified additives based on kaolin were prepared for reducing the emission of heavy metals from high temperature coal combustion and characterized by XRD, FT-IR, XRF, BET, SEM and zeta potential. The heavy metal retention characteristics of the additives under high temperature (900–1300 °C) coal combustion were investigated by static and dynamic experiments, and the results showed that pseudo-boehmite-metakaolin (BMK) was the most effective additive, and the ability of heavy metal capture was Cr > Zn > Pb > Cd, and the dynamic experiments were better than the static experiments. The quantum chemical models of heavy metals (monomers, oxides and chlorides), kaolin and adsorbent-active substances were developed and optimized, and the adsorption energy was calculated. The morphological changes of the active substances were taken into account in the simulation, and new mathematical models for adsorption energy calculation were proposed, which effectively solved the extreme results of adsorption energy calculation and made a comprehensive evaluation of heavy metal adsorption for the whole studied temperature range system. The mechanism of heavy metal adsorption on the active substance was further investigated by the simulations. Heavy metal atoms can form covalent or ionic bonds with O atoms of the active substance, Cl atoms of heavy metal chlorides can be covalently bonded or non-bonded with Al atoms of the active substance, and O atoms of heavy metal oxides can combine with Al atoms of the active substance to form ionic bonds. This study sheds new light on the control of heavy metals in high-temperature coal combustion, the methods for the optimization of simulation and the adsorption mechanism of heavy metals on relevant reactive substances. The method has a promising potential for large-scale application due to its simple preparation, low cost and significant effect.

Dry Mix Slag—High-Calcium Fly Ash Binder. Part One: Hydration and Mechanical Properties

High-calcium fly ash (HCFA)—a residue of high-temperature coal combustion at thermal power plants, in combination with sodium carbonate presents an effective hardening activator of ground granulated blast-furnace slag (GGBFS). Substitution of 10% - 30% of GGBFS by HCFA and premixing of 1% - 3% Na2CO3 to this dry binary binder was discovered to give mortar compression strength of 10 - 30 to 30 - 45 MPa at 7 and 28 days when moist cured at ambient temperature. High-calcium fly ash produced from low-temperature combustion of fuel, like in circulating fluidized bed technology, reacts with water readily and is itself a good hardening activator for GGBFS, so introduction of Na2CO3 into such mix has no noticeable effect on the mortar strength. However, low-temperature HCFA has higher water demand, and the strength of mortar is compromised by this factor. As of today, our research is still ongoing, and we expect to publish more data on different aspects of durability of proposed GGBFS-HCFA binder later.

Magnetic Fly Ash as a Chronological Marker in Post-Settlement Alluvial and Lacustrine Sediment: Examples from North Carolina and Illinois

Fly ash consists of mainly silt-size spherules that form during high-temperature coal combustion, such as in steam locomotives and coal-burning power plants. In the eastern USA, fly ash was distributed across the landscape atmospherically beginning in the late 19th century, peaking in the mid-20th century, and decreasing sharply with implementation of late 20th century particulate pollution controls. Although atmospheric deposition is limited today, fly ash particles continue to be resedimented into alluvial and lacustrine deposits from upland soil erosion and failure of fly ash storage ponds. Magnetic fly ash is easily extracted and identified microscopically, allowing for a simple and reproducible method for identifying post-1850 CE (Common Era) alluvium and lacustrine sediment. In the North Carolina Piedmont, magnetic fly ash was identified within the upper 50 cm at each of eight alluvial sites and one former milldam site. Extracted fly ash spherules have a magnetite or maghemite composition, with substitutions of Al, Si, Ca, and Ti, and range from 3–125 µm in diameter (mainly 10–45 µm). Based on the presence of fly ash, post-1850 alluvial deposits are 15–45 cm thick in central North Carolina river valleys (<0.5 km wide), ~60% thinner than in central Illinois valleys of similar width. Slower sedimentation rates in North Carolina watersheds are likely a result of a less agricultural land and less erodible (more clayey) soils. Artificial reservoirs (Lake Decatur, IL) and milldams (Betty’s Mill, NC), provide chronological tests for the fly ash method and high-resolution records of anthropogenic change. In cores of Lake Decatur sediments, changes in fly ash content appear related to decadal-scale variations in annual rainfall (and runoff), calcite precipitation, land-use changes, and/or lake history, superimposed on longer-term trends in particulate pollution.

Effect of different industrial activities on soil heavy metal pollution, ecological risk, and health risk.

Soil heavy metal (Cr, Cu, Zn, Pb, Cd, V, As) concentrations in different areas were analyzed to investigate the effects of different industrial activities on heavy metal pollution status, potential ecological risk, and human health risk in Panzhihua. Our results showed that Cu and V enrichment in soil was due to ore smelting. Soil Cr accumulation was related to coal ore mining. Soil Cd, Zn, As, and Pb enrichment was attributed to high-temperature coal combustion. Under the effect of industrial activities, soils were moderately contaminated with Cd, uncontaminated to moderately contaminated with As and Zn, and uncontaminated with Cr, Cu, V, and Pb. Soil heavy metal potential ecological risk was considerable, and non-carcinogenic risks and carcinogenic risks of soil heavy metals were acceptable for adults but unacceptable for children. Thermal power generation was the dominated industrial activity that influence the soil heavy metal concentrations and environmental risks in Panzhihua, which posed considerable potential ecological risks and unacceptable heavy metal non-carcinogenic risks and As carcinogenic risk to both adults and children. This study indicates that industrial activities have great effects on heavy metal pollution, ecological risks, and health risk, and more attention should be paid to the ecological risk and health risks brought by thermal power generation.

Understanding the Mechanism of Particle Adhesion in High-Temperature Combustion Induced by Sodium and Potassium: Use of a Synthetic Ash Strategy

During high-temperature combustion of coal, biomass, and municipal waste, ash particles can agglomerate and adhere to the internal surfaces of the plant under high-temperature conditions, resulting in a decrease in operating efficiency. It is known that the presence of small amounts of Na and K in the ash can facilitate adhesion; however, mechanistic details of the process are unclear. In this paper, a synthetic ash strategy consisting of a base material of SiO2 involving controlled additions of simple chemical components is proposed as a novel and convenient way to investigate adhesion. The synthetic ash consisted of SiO2 as the base material, and trace amounts of Na or K were added as target elements to examine their potential role in facilitating the adhesion process. It became clear that small amounts of Na and K increased the propensity for adhesiveness at high temperatures. The effect of the addition of Al2O3 nanoparticles to the synthetic ashes, which was expected to prevent adhesion, was also investigated. Therefore, it was found that the effect of Al2O3 would depend on the elements, which may increase the adhesiveness. It is projected that the present research can contribute to stable operation of many types of combustion plants.

Aluminum extraction technologies from high aluminum fly ash

Abstract Coal fly ash (CFA), an industrial by-product of high-temperature combustion of coal in coal-fired power plants, is one of the most complex and largest amounts of industrial solid wastes generated in China. It is widely recognized that CFA should be considered as a potential alumina resource to substitute bauxite. In this review, the features of high-alumina fly ash and aluminum recovery technologies are first described. Later, the merits and drawbacks of alumina extraction technologies in recovering more valuable materials are compared in terms of extraction mechanisms and equipment requirements. It is shown that “predesilicating-sodium carbonate (Na2CO3) activation-acid leaching” is currently a promising method in achieving multimetal synergistic extraction. Finally, the hydrochloric acid and sulfuric acid combination process is proposed as a sustainable development of the predesilicating-Na2CO3 activation-acid leaching process. The findings of this review provide theoretical guidance for novel developments and applications of aluminum extraction technologies.

Deposition of mullite in peatlands of southern Poland: Implications for recording large-scale industrial processes

Mullite, a pure aluminosilicate (Al6Si2O13), is a rare natural rock component, known for centuries as a very resistant ceramic material. It is also a common waste product of high-temperature coal combustion that is emitted in quantity from coal-based power stations. The occurrence of mullite in two Sphagnum-dominated peatlands located near the Upper Silesia industrial region in southern Poland is described. For the first time, a complete record of mullite deposition in the peat profiles has been obtained by XRD analyses of ashed peat samples. The mullite distribution is compared with records of Hg, Pb and Cu. While mullite is supplied during high temperature processes only, Cu, Pb and Hg show more complex pattern of distribution. Both peat profiles contain elevated amounts of mullite in the time span between ca 1950–1990 with a maximum content in ca 1980. The first appearance (∼1900) of mullite is indicative of the beginning of energy production in coal-based power plants in the region. Mullite is proposed here as an indicator of industrialization in geological records. It is resistant to post-depositional processes, emitted globally, and restricted to large-scale industry.

Gases and thermal behavior during high-temperature oxidation of weathered coal

In order to investigate the spontaneous combustion characteristics of weathered coal, gas generation and thermal behavior of weathered and fresh coal were analyzed. A self-made high-temperature-programmed experimental system was applied to simulate the spontaneous combustion of weathered and fresh coal. The characteristic parameters during oxidation were between 30 and 650 °C. The growth rate obtained through the analysis of an indicator gas was adopted to calculate the characteristic temperatures of high-temperature spontaneous combustion of coal. A C80 Calvet calorimeter was used to capture the thermal behavior during oxidation. At a high temperature and low oxygen concentration, weathered coal continued oxidizing and releasing thermal energy to sustain oxidation. The concentration of gases produced through high-temperature oxidation was lower for weathered coal than for fresh coal. The exothermic onset temperature of weathered coal was 43 °C, which was lower than the exothermic onset temperature of fresh coal. A salient difference was observed in the thermal energy release between weathered coal and fresh coal at different oxidation stages. From the critical temperature to crack temperature, the percentage of thermal energy release of weathered coal was much lower than that of fresh coal.

Cadmium isotope fractionation during coal combustion: Insights from two U.S. coal-fired power plants

Coal combustion, one of the principal energy sources of electricity in the United States, produces over 100 million tons of coal combustion products (CCPs) per year in the U.S. The reuse and disposal of CCPs has the potential to release toxic trace elements, including cadmium (Cd), into the environment. In this study, we investigated CCPs, including bottom ash (BA), economizer fly ash (EFA), and fly ash (FA), as well as feed coal (FC) and pulverized coal (PC) collected from two U.S. coal-fired power plants in New Mexico and Ohio with different coal supplies. The New Mexico plant uses high volatile C bituminous, low-sulfur coals mined from the San Juan Basin (Cretaceous Fruitland Formation) and the Ohio plant uses high volatile A bituminous, high-sulfur central Appalachian Basin coals (Upper Pennsylvanian Monongahela Formation). Mineralogical and elemental analysis showed that these CCP samples consist of ∼70% amorphous Al-Si-rich glasses and ∼30% mineral phases of quartz (SiO2) and mullite (Ai6Si2O13). The Cd isotope compositions (δ114Cd, normalized to NIST Cd standard 3108) of FA and EFA samples (ranging from −0.51 to +0.47‰) are distinctively heavier than those of BA samples (−0.75 to −0.52‰) in both power plants. We interpret this Cd isotope difference as a result of Cd condensation from the gas phase during flue gas cooling, instead of evaporation of Cd phase during coal combustion. Cd condensation is the main process to generate the isotopically heavy Cd signatures that preferentially partition on the fine FA particles. We also investigated Cd isotope compositions in different leachate products from a series of batch-leaching experiments with these CCPs, using diluted acetic acid, hydroxyl ammonium chloride, hydrogen peroxide followed by ammonium acetate, and 5% nitric acid, as a possible means to identify CCP-released Cd in the environment. Unusually and significantly heavier Cd isotope compositions were observed in each leachate of FA samples (+1.10 to +7.09‰), which fall far outside from the range of Cd isotope ratios observed in natural soils and rocks, but less so for the EFA samples (−0.43 to +1.18‰). Such an observation is consistent with the interpretation that isotopically heavy Cd preferentially partitions on the fine FA particles after coal combustion and is readily to be released during these leaching experiments. This study demonstrates that high-temperature coal combustion can lead to a very large degree of fractionation of Cd isotopes that can be used as a unique tracer for identifying anthropogenic metal inputs in the environment. The major Cd isotope fractionation process occurs as the Cd gas phase condenses on fine FA particles during the flue gas cooling stage after coal combustion.

Impact of solid fuel combustion technology on valence speciation of chromium in fly ash

Fly ash (FA) generated in real furnaces was used to evaluate the impact of the kind of the solid fuel burnt and combustion technology on chromium speciation, particularly the presence of Cr(III) and Cr(VI) forms as well as readily and hardly leachable chromium(VI) species in FAs. The FAs originated from a pulverized coal combustion boiler (PCC boiler), a fluidized bed combustion boiler (FBC boiler), a stoker-fired boiler (SF boiler), a municipal solid waste incinerator (MSWI), a cement rotary kiln (CRK) and a modern domestic boiler (DB). The speciation analysis of chromium was carried out by means of extraction followed by catalytic cathodic stripping voltammetry with adsorption of Cr(III)-DTPA complexes (CCSV-DTPA) for determination of Cr(VI) and AAS was used for determination of Cr content.It has been revealed that the antagonistic action of alkali metal compounds and iron oxides plays a crucial role in shaping valence speciation of chromium. According to the proposed transformation path of oxidation of Cr(III) to Cr(VI), hard coal combustion in an SF boiler, an FBC boiler or a domestic boiler will generate FAs with a low Cr(VI) level. Replacing fuel with biomass should create favorable conditions for generating FA enriched with Cr(VI). Relatively high concentrations of Cr(VI) can also be expected in FA generated in the process of high-temperature combustion of coal in PCC boilers.

Particulate matter source apportionment in a village situated in industrial region of Central Europe

The bilinear receptor model positive matrix factorization (PMF) was used to apportion particulate matter with an aerodynamic diameter of 1–10 μm (PM1–10) sources in a village, Březno, situated in an industrial region of northern Bohemia in Central Europe. The receptor model analyzed the data sets of 90- and 60-min integrations of PM1–10 mass concentrations and elemental composition for 27 elements. The 14-day sampling campaigns were conducted in the village in summer 2008 and winter 2010. Also, to ensure seasonal and regional representativeness of the data sets recorded in the village, the spatial-temporal variability of the 24-hr PM10 and PM1–10 within 2008–2010 in winter and summer across the multiple sites was evaluated. There were statistically significant interseasonal differences of the 24-hr PM data, but not intrasummer or intrawinter differences of the 24-hr PM1–10 data across the multiple sites. PMF resolved seven sources of PM1–10. They were high-temperature coal combustion; combustion in local heating boilers; marine aerosol; mineral dust; primary biological/wood burning; road dust, car brakes; and gypsum. The main summer factors were assigned to mineral dust (38.2%) and primary biological/wood burning (33.1%). In winter, combustion factors dominated (80%) contribution to PM1–10. The conditional probability function (CPF) helped to identified local sources of PM1–10. The source of marine aerosol from the North Sea and English Channel was indicated by the Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT). Implications: This is the first application of PMF to highly time/size resolved PM data in Czech Republic. The coarse aerosol fraction, PM1–10, was chosen with regard to industrial character of the region, sampling site near the coal strip mine and coal power stations. Contrary to expectation, source apportionment did not show dominance of emissions from the coal strip mine. The results will enable local authorities and state bodies responsible for air quality assessment to focus on sources most responsible for air pollution in this industrial region. Supplemental Materials: Supplemental materials are available for this paper. Go to the publisher's online edition of the Journal of the Air & Waste Management Association for (1) details of measurement campaigns; (2) CPF for each of the sources contributing to PM1–10; (3) factors contribution to PM1–10 resolved by PMF; (4) diurnal pattern of road dust, car brake factor in summer and winter; (5) trajectories during the marine aerosol episode in winter 2010; and (6) temporal temperature, concentration, and wind speed relationships during the summer 2008 campaign and winter 2010 campaign.

Germanium isotopic systematics in Ge-rich coal from the Lincang Ge deposit, Yunnan, Southwestern China

Organic matter plays an important role in the transport and precipitation of germanium (Ge) in coal-hosted Ge deposits. In this paper, Ge isotopes of coal samples and their combustion products were analyzed in order to investigate the potential use of Ge isotopes as tracers of Ge sources and enrichment mechanisms in coal. Germanium isotopic composition of various samples (mainly Ge-rich lignite) from the Lincang Ge deposit, Yunnan, Southwest China was analyzed using a continuous flow hydride generation system coupled to a Multi Collector Inductively Coupled Plasma Mass Spectrometer (MC-ICP-MS) and the standard-sample bracketing approach. Variations of 74 Ge/ 70 Ge ratios are expressed as δ 74 Ge values relative to NIST SRM 3120a Ge standard solution. Ge-rich lignite samples show large Ge isotopic fractionation ( δ 74 Ge values range from − 2.59‰ to 4.72‰), and their δ 74 Ge values negatively correlate with Ge concentrations. Lignite samples with low Ge concentrations (< 500 ppm) tend to show positive δ 74 Ge values, while δ 74 Ge values of lignite samples with high Ge concentrations (> 1000 ppm) are close to zero or negative. Along stratigraphic sections, Ge is mainly concentrated in the top or the bottom of the coal seam, such that high values of δ 74 Ge are usually found in the middle part of the coal seam. Interlayered hydrothermal chert and limestone samples in Ge-rich coal seams also show moderate fractionation ( δ 74 Ge values range from − 0.14‰ to 2.89‰ and from 0.55‰ to 1.87‰, respectively). The overall variations of δ 74 Ge values of Ge-rich lignite and organic-rich chert samples can be well described by a Rayleigh fractionation model, indicating that preferential enrichment of light Ge isotopes in coal in an open system might be the main factor controlling Ge fractionation in Ge-rich lignite. The germanium isotopic composition of hydrothermal chert (and possibly limestone) might also record the competitive fractionation produced by precipitation of quartz and sorption of coal. Elevated Ge concentrations and/or δ 74 Ge values of some chert, limestone, sandstone, and claystone samples may be attributed to the mixing with Ge-rich organic matter. Furthermore, similar to the fractionation of Zn, Cd and Hg isotopes observed between refinery dust or gas and slag, high temperature coal combustion also fractionates Ge isotopes, with the Ge isotopic compositions of soot being distinctly lighter (up to 2.25 per mil) than those of cinder. The distinct enrichment of potential hazardous elements (i.e., Pb, Cd, and As) and Ge in soot after coal combustion, as well as the common enrichment of Ge in sulfide minerals (e.g. sphalerite), highlights the possibility of using Ge isotopes as useful tracers of sources of heavy metal pollution caused by high temperature industrial processes (coal combustion and Pb-Zn refining) in the environment.

The Properties of Cenospheres and the Mechanism of Their Formation During High-Temperature Coal Combustion at Thermal Power Plans

The Properties of Cenospheres and the Mechanism of Their Formation During High-Temperature Coal Combustion at Thermal Power Plans

Fly-ash distribution to assess erosion and deposition in an Illinois landscape

Fly ash, the particulate matter resulting from high temperature combustion of coal, was historically dispersed into the atmosphere and settled as fly-ash spheres on the surface soil from a variety of boilers, including those of steam locomotives and steam-powered farm machinery. In Central Illinois, fly ash provides a time marker extending back to 1850s, coinciding with the development of railroads and cultivation. Two railroads, the primary sources of fly ash, were constructed just south of the Cahokia study site in 1852 and 1854. The objectives of this study were to determine: (1) the distribution, depth of occurrence and the total amount of fly ash present in soil profiles on stable, cultivated and uncultivated summit sites with little or no soil erosion; (2) the effects of elevation, aspect, slope gradient, landscape position, distance from source, past vegetation and time on the amount and depth of fly ash; (3) the effects of erosion on sloping sideslopes; and (4) the amount of deposition of fly-ash rich sediment on footslopes and toeslopes. Total fly-ash content of soil was similar for stable, cultivated and uncultivated summits. Two mound sideslopes maintained a high amount of fly ash because of a lack of cultivation and erosion for the past 80 or more years. Erosion reduced the depth of occurrence and the amount of fly ash present on cultivated sideslopes. It appeared that fly-ash content was initially deposited uniformly within the local landscape even though there were slight variations in the aspect, elevation, slope gradient, and distance from the source. The erosion phases of the soils on all landscape positions were determined based on the amount of fly ash remaining in soil surface layers. Accelerated erosion of cultivated sideslopes resulted in the deposition of fly-ash rich sediment on the adjacent footslopes or toeslopes. The proposed fly-ash method provides a tool to assess the extent of soil translocation from a cultivated landscape and subsequent deposition.

SOIL CATENA FORMATION AND EROSION OF TWO MISSISSIPPIAN MOUNDS AT CAHOKIA ARCHAEOLOGICAL SITE, ILLINOIS

About 1000 years ago, Mississippian Indians built what are now designated Mounds 69 and 70 at Cahokia near Collinsville, Illinois. Loamy soil materials were placed on the mounds by Mississippian Indians before A.D. 1100, and the site was inhabited until approximately A.D. 1300. The general objective of this study was to determine the potential of using archaeological mounds or sites to obtain information on soil development and erosion processes. Our specific objectives were to determine: (i) the extent of soil formation during the past 900 years, (ii) the time period and extent of disturbance by human activities, including tillage and digging by treasure hunters and looters, and (iii) the erosion phase of soils on mound sideslopes and the amount of soil loss from accelerated erosion. The vegetation and distribution of organic C in soil profiles suggests there has been no tillage since the 1970s and little soil erosion of either the summit or the sideslope of Mound 69. The adjacent alluvial plain is still being cultivated. Fly ash, particulate matter resulting from high-temperature coal combustion, was used as a time marker in soil and sediment. Fly-ash distributions in the upper 20 cm of Mound 69 support the theory that cultivation occurred between the 1850s and the 1970s. Based on the fly ash data, approximately 55% of the original surface soil layer remains on the sideslope of Mound 69 (compared with the uncultivated sideslope of Mound 70). There has been substantial deposition of sediment rich in fly ash onto the footslope of Mound 69 (from the cultivated sideslope) and the toeslope of Mound 70 (from the cultivated footslope). The fly ash and organic C data for the summit soil profile on Mound 70 suggest treasure hunters and looters disarranged the soil profile completely. The uncultivated sideslope with a 23% slope had a 40-cm surface layer rich in fly ash. The fly-ash content and thickness of the footslope soil surface layer was reduced as a result of tillage and erosion from the 1850s to the 1970s. Fly ash-enriched sediment accumulated on the toeslope and created a 60-cm surface layer. The current vegetation and the decrease in organic C with depth on the footslope and toeslope of Mound 70 suggest that no tillage has occurred since the 1970s. Fly ash presence within soil layers indicates which layers have been exposed at the soil surface since the 1850s and the extent of soil mixing. Archaeological mounds with known dates of construction can be used to obtain information on soil development and erosion processes.

03/02491 The behaviour of trace elements from high temperature coal combustion process: Sekine, Y. et al. Preprints of Symposia — American Chemical Society, Division of Fuel Chemistry, 2003, 48, (1), 358–359

03/02491 The behaviour of trace elements from high temperature coal combustion process: Sekine, Y. et al. Preprints of Symposia — American Chemical Society, Division of Fuel Chemistry, 2003, 48, (1), 358–359

In situ detection of potassium atoms in high-temperature coal-combustion systems using near-infrared-diode lasers

Direct tunable diode laser absorption spectroscopy at 769.9 and 767.5 nm was used to measure potassium (K) atom concentrations in situ in the high temperature (up to 1650 K) flue gas of two different pulverized coal dust combustion systems (atmospheric or pressurized (12 bar)). Two laser types (Fabry-Pérot (FP) and vertical-cavity surface-emitting lasers (VCSEL)) were used for the spectrometer and characterized with respect to the magnitude and linearity of their static and dynamic wavelength tuning properties. The wide continuous current-induced tuning range of the VCSEL of 20 cm −1 (compared to 1 cm −1 for the FP) make this laser ideal for species monitoring in high pressure processes. Two VCSELs were time-multiplexed to realize the simultaneous detection of the potassium D1 and D2 lines. Several oxygen absorption lines in the A-band, which are in close spectral vicinity of the K lines, were detected simultaneously, showing the possibility of multi-species detection with one laser. Using the FP-DL for the atmospheric process and the VCSEL for the high pressure process, the pressure-dependent coefficients for spectral broadening as well as a shift of the K line in the flue gas were determined to be (0.18±0.01) and (−0.060±0.003) cm −1 per atm (at 1540 K and 11.2 bar). The total width and shift of the D1 line (11.2 bar/1540 K) were 60 and −20 GHz, respectively. The K atom concentration was determined continuously for several days in both plants under various operation conditions. Typical concentrations in the atmospheric plant were around 2 μg m −3 with a range of 50 ng m −3–30 μg m −3. Averaging 100 scans for each concentration value, we achieved a time resolution of 1.7 s and a detection limit of 10 ng m −3, which corresponds to a fractional absorption in the 10 −3–10 −4 range. A strong anti-correlation with the oxygen concentration could be verified. At the 12 bar plant, the concentration was again typically around 2 μg m −3 but K levels up to 60 μg m −3 were observed. Here, a strong dependence of the K-signal on the type of fuel could be verified.

Erosion Patterns on Cultivated and Reforested Hillslopes in Moscow Region, Russia

The severity of accelerated erosion is affected by tillage practices, slope gradient, shape, and length. Our hypothesis is that fly ash, the product of high temperature coal combustion, magnetic minerals, magnetic susceptibility, and organic C content of a soil can be used to estimate the extent of soil loss as a result of human activities. The objectives of the current study near Pushkino, Russia were: (i) to determine the extent and local variability of soil removal from a hillslope because of accelerated erosion using closely spaced duplicate transects, and (ii) to determine subsequent deposition of sediments on a lower landscape position using the presence, depth distribution, and concentration of fly ash, magnetic minerals, organic C, and magnetic susceptibility. The study was done by comparing the amount of fly ash contained in soil profiles at different landscape positions of a cultivated site with that at a reforested site planted to spruce [Picea abies (L.) Karst] trees ∼60 to 80 yr ago. Deposition of fly ash derived from distant railway traffic started in or about 1851 and increased in 1870 because of construction of a closer railway. Considering the whole transect, the cultivated site had 12% less fly ash in the upper 20‐cm soil layer as compared with the reforested site. The fly‐ash results indicated that only 2.4 cm or 12% of the upper soil layer has been removed from the hillslope because of accelerated erosion associated with the last 60 to 80 yr of cultivation. Deposition of sediment rich in fly ash on the lower and upper footslopes suggests accelerated erosion has occurred at the cultivated site.