Batch combustion of fixed beds of coal, bagasse and blends thereof took place in a pre-heated two-stage electric laboratory furnace, under high-heating rates. The average input fuel/air equivalence ratios were similar for all fuels. The primary and secondary furnace temperatures were varied from 800 degrees C to 1000 degrees C. The effects of fuel blending, combustion staging, and operating furnace temperatures on the emissions from the two fuels were assessed. Furnace effluents were analyzed for carbon dioxide and for products of incomplete combustion (PIC) including CO, volatile and semi-volatile hydrocarbons, as well as particulate matter. Results showed that whereas CO2 was generated during both the observed sequential volatile matter and char combustion phases of the fuels, PICs were only generated during the volatile matter combustion phase. CO2 emissions were the highest from coal, whereas CO and other PIC emissions were the highest from bagasse. Under this particular combustion configuration, combustion of the volatile matter of the blends resulted in lower yields of PIC, than combustion of the volatiles of the neat fuels. Though CO and unburned hydrocarbons from coal as well as from the blends did not exhibit a clear trend with furnace temperature...
This work reports on emissions of unburned hydrocarbon species from batch combustion of fixed beds of coal, sugar-cane bagasse, and blends thereof in a pre-heated two-stage laboratory furnace operated in the temperature range of 800-1000 degrees C. The effects of fuel blending, combustion staging, and operating furnace temperatures on emissions of pollutants were assessed. Furnace effluents were analyzed for products of incomplete combustion (PICs) including CO, volatile and semi-volatile hydrocarbons, and particulate matter, as has been reported in Ref. . Emitted unburned hydrocarbons include traces of potentially health-hazardous Polycyclic Aromatic Hydrocarbons (PAHs), which are the focus of this work. Under the batch combustion conditions implemented herein, PAH were only generated during the volatile combustion phase of the fuels. The most prevalent species were in descending order: naphthalene, acenaphthylene, phenanthrene, fluoranthene, pyrene, dibenzofuran, benzofuran, byphenyl, fluorene, 9H-fluoren-9-one, acephenantrylene, benzo[b] fluoranthene, 1-methyl-naphthalene; 2-methyl-naphthalene, benz[a] anthracene and benzo[a] pyrene. PAH yields were the highest from combustion of neat bagasse. Combustion of the blends resulted in lower yields of PAH...
Investigations of genotoxic effects of particles have almost exclusively been performed by organic extraction, while direct investigations in cells capable of engulfing particles have only been performed in few cases. Thus, in most studies, the eventual effects of particle-associated metal compounds have remained undiscovered. The present study attempted direct measurement of genotoxic effects of particulate coal combustion products by using the P388D1 macrophage cell line. The capability of these cells for phagocytosis was demonstrated with insoluble particles. The sister chromatid exchange (SCE) test was used for measuring genotoxic effects of test compounds.
The evaluation of the potential public and occupational health hazards of developing and existing combustion processes requires a detailed understanding of the physical and chemical properties of effluents available for human and environmental exposures. These processes produce complex mixtures of gases and aerosols which may interact synergistically or antagonistically with biological systems. Because of the physicochemical complexity of the effluents, the biomedically relevant properties of these materials must be carefully assessed. Subsequent to release from combustion sources, environmental interactions further complicate assessment of the toxicity of combustion products. This report provides an overview of the biomedically relevant physical and chemical properties of coal fly ash. Coal fly ash is presented as a model complex mixture for health and safety evaluation of combustion processes.
Most air pollution in West Germany is caused by combustion products. Particulate organic matter released by incomplete combustion is suspected to contribute to the "urban factor" of lung cancer frequency in urban-industrial centers. The carcinogenic potential of single components, groups of compounds and total source emissions of combustion processes was investigated in laboratory animals by subcutaneous injection, intratracheal instillation or inhalation. Tests by subcutaneous injection of condensates of automobile exhaust, extracts of coal furnace emissions and of airborne particles and different fractions of these extracts showed that the polycyclic aromatic hydrocarbons (PAH) with four to six benzene rings have the strongest experimental carcinogenicity. However, polar compounds (heterocyclic nitrogen-containing PAH, phenols, and others) also show remarkable carcinogenic potency. There were large differences between the dose-response relationships of several PAHs. In the subcutaneous tissue, benzo(a)pyrene and dibenz(a,h)anthracene are the most carcinogenic of the tested airborne PAHs. Furthermore, they can induce high tumor rates in the lung after subcutaneous injection in newborn mice and after intratracheal instillation of mice or hamsters. The tumor rate of benzo(a)pyrene did not further increase after simultaneous instillation of carbon black...
Environmental concerns over increased coal consumption are fully justified by the past history of coal use. Although improved technology has provided some safeguards, increased utilization will require mining practices, emission control technologies, and waste disposal procedures that are not yet fully integrated into the routine use of the coal energy system. The Committee on Health and Evnironmental Effects of Increased Coal Utilization identified six critical environmental issues which are of concern: coal mine worker health and safety, reclamation of arid lands from surface mining, the health effects of coal combustion products, toxic trace elements in coal combustion wastes, acid fallout, and global effects of carbon dioxide in the atmosphere. This presentation addresses the first four of these issues.
Combustion products derived from the burning of coal are definitely capable of producing adverse human health effects. No single component of the combustion product mixture is solely responsible. Rather, effects are due to a group of compounds, both gases and aerosols, in the effluents of stationary source combustion processes. Although incompletely defined, the individual components of the gas-aerosol complex appear to be capable of interacting both in terms of atmospheric chemistry and health effects. The three primary air quality standards pertinent to regulating coal combustion all represent to some extent indirect, although reasonable, measures of this gas-aerosol complex. As a group, these standards appear to be adequate to protect human health. Conventional toxicological considerations suggest that the adverse health effects of any necessary increase in coal combustion effluents would be greatest per unit of coal in those areas which are most heavily populated and have the highest preexisting levels of the gas-aerosol complex. In order to decrease the degree of uncertainty for future decisions of this type, it is important that prospective epidemiological and air monitoring studies be initiated in conjunction with any large scale introduction of coal use.
Lung cancer rates in Xuanwei County have been among the highest in China for both males and females, and have been causally associated with exposure to indoor smoky (bituminous) coal emissions that contain very high levels of polycyclic aromatic hydrocarbons. There are numerous coal mines across the County. Although lung cancer risk is strongly associated with use of smoky coal as a whole, variation in risk by smoky coal subtype has not been characterized as yet. We conducted a population-based case-control study of 498 lung cancer cases and 498 controls, individually matched to case subjects on age (±2 years) and sex, to examine risk by coal subtype. Odds ratios (ORs) and 95% confidence intervals (CIs) for coal subtype were calculated by conditional logistic regression, adjusting for potential confounders. Overall, smoky coal use was statistically significantly associated with lung cancer risk, as compared to use of smokeless coal or wood (OR=7.7, 95% CI=4.5 to 13.3). Furthermore, there was marked heterogeneity in risk estimates for specific subtypes of smoky coal (test for heterogeneity: p=5.17 × 10−10). Estimates were highest for coal from the Laibin (OR=24.8, 95% CI=12.4 to 49.6) and Longtan (OR=11.6, 95% CI = 5.0 to 27.2) coal types...
One of the key environmental problems
facing India is that of particle pollution from the
combustion of fossil fuels. This has serious health
consequences and with the rapid growth in the economy these
impacts are increasing. At the same time, economic growth is
an imperative and policy makers are concerned about the
possibility that pollution reduction measures could reduce
growth significantly. This paper addresses the tradeoffs
involved in controlling local pollutants such as particles.
Using an established Computable General Equilibrium model,
it evaluates the impacts of a tax on coal or on emissions of
particles such that these instruments result in emission
levels that are respectively 10 percent and 30 percent lower
than they otherwise would be in 2030. The main findings are
as follows: (i) A 10 percent particulate emission reduction
results in a lower gross domestic product but the size of
the reduction is modest; (ii) losses in gross domestic
proudct from the tax are partly offset by the health gains
from lower particle emissions; (iii) the taxes reduce
emissions of carbon dioxide by about 590 million tons in
2030 in the case of the 10 percent reduction and 830 million
tons in the case of the 30 percent reduction; and (iv) taken
Ulaanbaatar, Mongolia, is the coldest
capital city in the world, with average winter low
temperatures of -20° Celsius. Many families there live in
gers, traditional Mongolian dwellings consisting of a wooden
frame beneath several layers of wool felt. In the ger
districts of Ulaanbaatar, cooking and heating energy is
provided through indoor coal combustion in metal stoves with
chimneys, and in wintertime, such stoves may be in use both
day and night. Over the last several years, new stove
designs with improved fuel efficiencies have been introduced
into many homes. To test the impact of the improved stoves
on indoor air quality, 24-hour monitoring of particulate
matter (PM) and carbon monoxide (CO) was done in 65
Mongolian gers. The primary analyses focused on 58
households, 20 with original (or traditional-type) stoves,
18 with the improved stove type TT-03, and 20 with the
improved stove type G2-2000. In addition to indoor pollutant
concentrations, information on other relevant factors was
Large scale power generation commences with the combustion of coal or other fuel, which in turn converts high pressure water into steam which then drives a turbine thus generating electricity. Burning high moisture coal, such as lignite, for power generation implies that a significant amount of energy is wasted in vaporising the moisture, which could otherwise be used in the steam raising process. This implies that more moist coal would be required to drive the same process than if the coal was drier, thus increasing the amount of combustion products such as greenhouses gases. Introducing a dried coal in an existing boiler will significantly change the heat flux profiles, which could result in boiler damage or excessive fouling. Flame temperature is influenced by the supply of reactants; in most cases the limiting reactant will be oxygen. The supply of oxygen (through air) to a pneumatically transported coal stream and subsequent reaction is controlled by the localised fluid mechanics or ‘mixing’. This research aims to provide an understanding of the mixing process between the pneumatically transported coal and air in brown coal fired boilers by modelling the individual jets. The effects of the change in velocity ratio for the air (secondary) jets and fuel (primary) jets of rectangular burners typical of those found in brown coal fired boilers has been studied experimentally and is reported in this thesis. In particular...
Experiments were conducted in a continuous flow reactor at room temperature to evaluate the elimination of low-concentration toluene in the gas phase to verify if fly-ash products from biomass combustion in an ozonation system could be used in the removal of volatile organic compounds. The fly-ash products from pure biomass combustion (Ash(100)) demonstrated the highest ozonation activities upon the removal of low-concentration toluene (1.5 ppmv), followed by the fly-ash products from co-combustion (Ash(30)) and the coal combustion (Ash(0)). Kinetic experiments showed that the activation energy of the toluene elimination process was substantially reduced with the use of ozone and the reaction intermediates, such as formic acids, aldehydes, etc. Results also showed that the intermediates were reduced with increasing humidity level. The combined use of fly-ash products and zeolite 13X enhanced the removal of toluene to above 90% and suppressed the release of residual ozone and intermediates by holding them in the adsorbed phase.; C.W. Kwong and C.Y.H. Chao
Australia’s economy is underpinned by access to cheap electricity, and over 85% of the country’s power generation capacity is based on pulverised coal combustion. South Australia has abundant resources of low-rank coal but its high sulphur content (typically 5% w/w db) raises both operational and environmental concerns in its utilisation. Depletion of current sub-bituminous coal reserves used for power generation
means that competitive future coal-based energy supply may depend on efficient, cost effective and environmentally-friendly utilisation of local lignite resources. Other unique properties such as high moisture, ash, sodium and chlorine content currently limit their utilisation and the study of their behaviour during fluidised-bed gasification (FBG) processes has been the focus of research by the Cooperative Research Centre (CRC) for Clean Power from Lignite.
Sulphur containing compounds in coal transform to sulphur dioxide (SO₂) in an oxidising atmosphere and hydrogen sulphide (H₂S) in a reducing atmosphere. The phenomenology of these transformations is detailed in the literature under a variety of conditions (pyrolysis, oxidation and reduction) but quantitative data for specific gasification processes is lacking. These gaseous sulphur compounds are precursors to acid rain on release to the atmosphere and cause corrosion in downstream processing units...
Presentation was given at the 2010 National Meeting of the American Society of Mining and Reclamation, Pittsburgh, PA, June 5 – 11, 2010.; The use of coal combustion by-products (CCBs) in mine reclamation has been advocated by some because of their low permeability and potential to generate alkalinity. However, others have argued that these benefits are outweighed by the potential for leaching of trace elements that can enter ground and surface waters. In 1996, an abandoned mine land (AML) site in southwestern Indiana was reclaimed using ponded ash as structural fill in highwall cuts, and fixated scrubber sludge (FSS) as capping material over pyritic refuse. Pre-reclamation and post-reclamation monitoring of surface water discharge from the site, groundwater elevations and chemistry, as well as soil moisture fluctuations in the unsaturated zone have provided a basis for evaluating the effects of CCBs on the hydrochemistry of the site and potential for off-site impacts. Limited recharge through the FSS is supported by barometric efficiency changes in the refuse aquifer, the presence of perched water measured in monitoring wells installed on the cap, and minimal fluctuations in soil moisture within and immediately below the cap. Reductions in oxygenated rainwater reaching the refuse are indicated by groundwater chemistry data...
Locomotive drivers in the steam engine era were exposed to asbestos during their vocational training for two years while training in workshops. Later in their career they had exposure to coal and diesel combustion products. To assess the level of earlier exposure historical working conditions were reconstructed and hygienic conditions were measured. The average exposure to asbestos (mainly anthophylline) fibres > 5 microns was 5.0 fibres/cm3. Incidence of cancer in a cohort of 8391 members of the Finnish Locomotive Drivers' Association, 1953-91, was analysed. The incidence of lung cancer and also total cancer was below the national average, probably due to the low prevalence of smoking among the drivers in the steam engine era. A four-fold risk of mesothelioma was found, most likely caused by exposure to asbestos. Also the observed 1.5-fold incidence of non-melanoma skin cancer and 1.7-fold risk of cancer of the oral cavity and pharynx may be related to occupation.
Fly ash from coal combustion is a potential source of pollution and there is continuous interest in its recycling by converting it into
products such as zeolitic materials for use in retaining pollutants. In this paper, production of granular zeolitic material from a commercially-
unusable fine-fraction of a lightweight aggregate (LA) building material made from coal fly ash agglomerated with lime, by conventional
alkaline activation is described. NaP1 zeolite, K-F zeolite, K-Phillipsite and K-Chabazite were synthesised. The process was
optimised by combining four reaction parameters (temperature, alkali concentration, solution/fly ash ratio and reaction time). Zeolitic
materials with the highest zeolite yields and cation exchange capacities were selected for future application in environmental processes.
End-product zeolitic materials maintain its granular form and this could favour their use in some particular applications for environmental
waste treatment (e.g. ionic exchange in column) without any further transformation stages.; Peer reviewed
Gavalas, George R.; Weston, Theresa A.; Stephanopoulos, Maria F.
Fonte: Department of EnergyPublicador: Department of Energy
Tipo: Book Section; PeerReviewedFormato: application/pdf
Publicado em //1985
Relevância na Pesquisa
Sodium and sodium-lithium oxides supported on porous alumina have been investigated as regenerable SO_2 sorbents for fluidized coal combustion. In adsorption the oxides are converted to sulfates. In regeneration, carried out by reduction with CO, the sulfates are converted back to oxides while sulfur is removed in elemental form (S_2), SO_2 and COS. The transient composition of sorbent and gaseous products was measured in a thermogravimetric analyzer and a packed-bed microreactor in order to delineate the basic chemistry of regeneration and determine conditions that maximize the yield of elemental sulfur.
Mercury contamination in aquatic ecosystems is a concern as anaerobic aquatic sediments are the primary regions of methylmercury production in freshwater and coastal regions. Methlymercury is a bioaccumulative neurotoxin, and human exposure to methylmercury can result in impaired functioning of the central nervous system and developmental disabilities in children. To minimize the risk of human exposure to methylmercury, it is important to be knowledgeable of the various sources which can supply mercury to aquatic ecosystems as well as have a complete understanding of the biogeochemical processes which are involved in methylmercury production in aquatic systems. In this dissertation work, both mercury biogeochemical speciation in anaerobic aquatic sediments and sources of mercury to aquatic systems were addressed.
The biogeochemical speciation of mercury is a critical factor which influences the fate and transformation of mercury in aquatic environments. In anaerobic sediments, mercury chemical speciation is controlled by reduced sulfur groups, such as inorganic sulfide and reduced sulfur moieties in dissolved organic matter (DOM). The formation of mercury sulfide nanoparticles through stabilization by dissolved organic matter (DOM) was investigated in precipitation studies using dynamic light scattering. Mercury sulfide nanoparticles (particle diameter < 100 nm) were stabilized through precipitation reactions that were kinetically hindered by DOM. To further investigate the interaction between DOM and metal sulfides...
Chlorine-containing minerals are commonly present in coal. Associated minerals such as pyrite can undergo exothermic reactions. Consequently, it is of great significance to study the effect of inorganic chloride on the spontaneous combustion of coal. In this study, the effects of five inorganic chlorides (sodium chloride, magnesium chloride, potassium chloride, calcium chloride, and zinc chloride) on the spontaneous oxidation of coal were investigated. Analysis of the gaseous products of coal oxidization at low temperatures (323K to 453K) showed that the presence of inorganic chlorine in coal markedly decreases O2 consumption and the generation of CO and CO2. Samples of raw coal and chlorine-loaded coal were oxidized for 36 hours under the same experimental conditions. Infrared diffuse reflectance spectroscopy results showed that inorganic chloride can inhibit the oxidative decomposition of some functional structure components (methyl, methylene, methine, and hydroxy) in the coal. The influence of inorganic chloride on the oxidation characteristics of the functional groups in coal during spontaneous combustion was investigated using benzyl alcohol and 1-phenyl propanol as model compounds, which were tested under the same experimental conditions as the coal samples. The oxygen consumption of model compounds with and without the addition of inorganic chloride further suggested that inorganic chloride may hinder the oxygenolysis of these structures during low-temperature oxidation. This phenomenon can be attributed to the radical reaction from the perspective of radical chemistry. It can therefore be concluded that inorganic chlorides play an inhibitory role in the spontaneous combustion of coal.
The advent of low-quality export coal demand has brought a new range of possibilities to the South African coal industry. Products that traditionally were only of value to the domestic or combustion industry sectors now have the potential to be exported, with only minor amounts of upgrading required through beneficiation. Comparatively high steam-coal export prices can be obtained for low-quality export coal, which enhances the economic feasibility of expanding low-quality thermal coal exports. There are, however, increasing concerns about the feasibility of lower quality thermal coal exports and the broader implications. These concerns relate to the environmental impact of low-quality thermal coal production for export and the inherent threat to the security of domestic thermal coal supply in South Africa. Against this background, this paper serves to explain the extended value chain in the production of export coal. The technical and economic advantages and disadvantages of low-grade exports versus coal production for domestic use are evaluated. The value chain estimation is calculated by the beneficiation modelling and characterization of two coals. Based on the value estimation, the low-grade export production scenario, and finally the modelling of potential pollutant distribution...