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1.
Environ Sci Technol ; 55(6): 4027-4036, 2021 03 16.
Artigo em Inglês | MEDLINE | ID: mdl-33663209

RESUMO

Every year, billions of tons of lignite are burnt to generate electricity, meanwhile generating large amounts of coal fly ash (CFA) that is regarded as an industrial waste. During lignite combustion, arsenic and scarce metals are simultaneously volatilized in the form of oxide into CFA. This study proposed an effective vacuum distillation method to remove As and recover Ge and W from CFA. The feasibility of separating As and recycling Ge and W from CFA was verified by the theoretical analysis. The experimental result indicated that the removal ratio of As was 96 ± 1% and the contents of Ge and W reached 0.75 ± 0.023 and 0.24 ± 0.016 wt % in the residue, which were enriched 17.2 and 1.2 times, respectively, at a temperature of 550 °C, with 50 wt % sulfurizing agent added under pressure of 1 Pa and 240 min of heating. For the condensed product, chemical species As2S3 and As4S4 were detected by X-ray photoelectron spectroscopy analysis. For Ge and W in the residue, GeOx (x < 2), GeS, WOx (x < 3), and WS2 were the main chemical species. The potential mechanism involved in the release of arsenic from CFA, vacuum sulfurization, evaporation, and condensation was proposed. The kinetic analysis indicated that the apparent activation energy (Eα) was 31.24 kJ mol-1. Those results encourage further exploration of vacuum separation technology to environmentally friendly recycle CFA.


Assuntos
Arsênico , Germânio , Carvão Mineral/análise , Cinza de Carvão/análise , Destilação , Indicadores e Reagentes , Cinética , Tungstênio , Vácuo
2.
Ecotoxicol Environ Saf ; 214: 112095, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33667735

RESUMO

In this study, urban stream sediment samples were collected in the Suzhou Industrial Park (SIP), one of the earliest national demonstration eco-industrial parks of China. PAHs were analyzed in these sediments, and concentrations of total PAHs were 180-81,000 ng g-1 (5700 ± 14,000 ng g-1). Medium molecular weight (4- ring) PAHs were predominant (42 ± 12%), followed by high molecular weight (5- and 6- ring) PAHs (31 ± 10%). No correlation was found between concentrations of PAHs and land uses of SIP in this study. Diagnostic ratios and a positive matrix factorization (PMF) model indicated that coal/biomass combustion might be the primary PAH source (61%), followed by non-combustion sources (21%) and vehicular emission (18%). According to the spatial analysis, PAHs in the sediments of SIP might be mainly associated with the coal/biomass combustion in the northeast industrial zone. Residential & commercial activities seem not to be the major causes of PAH contamination. Total PAH toxic equivalent concentrations, effect range low/effect range median values, and mean effects range-median quotient all showed that PAHs were present at a low toxicity risk level in most regions of the SIP. However, vigilance is required at some sampling sites with extremely high PAH concentrations or high mean effects range-median quotient.


Assuntos
Hidrocarbonetos Policíclicos Aromáticos/análise , Poluentes Químicos da Água/análise , China , Carvão Mineral/análise , Monitoramento Ambiental , Sedimentos Geológicos , Indústrias , Medição de Risco , Rios , Emissões de Veículos/análise
3.
Environ Sci Technol ; 55(8): 4483-4493, 2021 04 20.
Artigo em Inglês | MEDLINE | ID: mdl-33715364

RESUMO

The residential sector is a major source of air pollutant emission inventory uncertainties. A nationwide field emission measurement campaign was conducted in rural China to evaluate the variabilities of realistic emission factors (EFs) from indoor solid fuel combustion. For a total of 1313 burning events, the overall average EFs (±standard deviation) of PM2.5 were 8.93 ± 6.95 and 7.33 ± 9.01 g/kg for biomass and coals, respectively, and 89.3 ± 51.2 and 114 ± 87 g/kg for CO. Higher EFs were found from burning of uncompressed straws, while lower EFs were found from processed biomass pellets, coal briquettes, and relatively clean anthracite coals. Modified combustion efficiency was found to be the most significant factor associated with variations in CO EFs, whereas for PM2.5, fuel and stove differences determined its variations. Weak correlations between PM2.5 and CO indicated high uncertainties in using CO as a surrogate for PM2.5. EFs accurately fit log-normal distributions, and obvious spatial heterogeneity was observed attributed to different fuel-stove combinations across the country. Emission estimation variabilities, which are determined by the interquartile ranges divided by the median values, were notably reduced when spatially resolved EFs were adopted in the inventory.


Assuntos
Poluentes Atmosféricos , Utensílios Domésticos , Poluentes Atmosféricos/análise , Biomassa , China , Carvão Mineral/análise , Material Particulado/análise
4.
Environ Int ; 152: 106499, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33721723

RESUMO

The exploitation of coal releases large amounts of contaminants into the environment. However, the featured pollutants of coal utilization as well as the scope and degree of their impact remain to be revealed. To identify the featured-element of coal contamination in a complex environment, a typical coal resource city was selected, and the major elements, 18 trace elements, as well as δ13C, δ15N, and δ34S in the fine road dust and certain source materials were analyzed. Through multiple analysis methods, the featured-element was determined step-by-step: firstly, elements with enrichment coefficients greater than two in road dust were focused: Zn, Hg, Pb, Cu, Cd, and Cr; secondly, difference analysis showed a significant difference (p < 0.05) of Hg and Cu concentration at different distance from the coal-fired power plant, making Hg and Cu the only candidates for the featured-element; finally, through coal-related source materials determination, Cu was not qualified as a featured-element. Therefore, Hg was the only left element to be considered as the featured-element. To be more convincing, more analyses were performed to support Hg as the featured-element: cluster analysis and isotope monitoring indicated Hg in road dust could originate from coal combustion; X-ray photoelectron spectroscopy was also conducted, where the forms of Hg in road dust with possible source materials were compared, and the presence of HgO and Hg only in the road dust near the power plant indicated the impact of the power plant on the surrounding dust. Through the health risk assessment, it was found that Hg in the road dust had no health risk, though the study area still had Pb, Cr, and As risks, which were not closely related to the pollutants released by coal-related sources.


Assuntos
Poeira , Metais Pesados , China , Cidades , Carvão Mineral/análise , Poeira/análise , Monitoramento Ambiental , Metais Pesados/análise , Medição de Risco
5.
Environ Sci Technol ; 55(4): 2532-2540, 2021 02 16.
Artigo em Inglês | MEDLINE | ID: mdl-33529529

RESUMO

Significant elemental carbon (EC) emissions from low-temperature solid fuel combustion cannot be explained by classical mechanisms ascribing EC to higher-temperature condensation (> 850 °C). The importance of fuel composition in promoting EC nucleation was investigated by studying EC and polycyclic aromatic hydrocarbon (PAH) formation at multiple-ignition temperatures (300-900 °C) using fuels with different aromatic contents (i.e., straw, wood, and coal). Biomass and coal combustion at 300 °C can produce substantial EC containing a large amount of soot-EC, a known high-temperature condensation product, possibly because aromatics reduce EC nucleation barriers, corresponding to the increasing ratios of soot-EC to char-EC from straw to coal (1.22 to 3.61). High- to low-molecular-weight PAH ratios in biomass combustion were four times lower than those in coal combustion, resulting in different EC formation atmospheres. Specifically, 31.4% of PAHs from biomass combustion were indene, compared to only 0.24% for coal, indicating that resonance-stabilized hydrocarbon-radical chain reactions dominated EC nucleation in biomass combustion. Five- to six-membered PAH ratios were always higher than one in biomass combustion but increased significantly from 0.5 to 2 with increasing temperature in coal combustion, indicating that PAHs generated through aromatic decomposition in coal could form EC through van-der-Waals forces and phenyl addition/cyclization-based covalent bonding at low and high temperatures, respectively.


Assuntos
Poluentes Atmosféricos , Hidrocarbonetos Policíclicos Aromáticos , Poluentes Atmosféricos/análise , Biomassa , Carbono/análise , Carvão Mineral/análise , Hidrocarbonetos Policíclicos Aromáticos/análise , Temperatura
6.
Artigo em Inglês | MEDLINE | ID: mdl-33567509

RESUMO

Little research has examined the effects of high concentration, medium-duration smoke exposure on cardiovascular health. We investigated whether six weeks of exposure to smoke from the 2014 Hazelwood coal mine fire in Victoria (Australia), was associated with long-term clinical or subclinical cardiovascular disease approximately four years later, in adult residents of the towns of Morwell (exposed, n = 336) and Sale (unexposed, n = 162). The primary outcome was serum high sensitivity (hs) C-reactive protein (CRP). Blood pressure, electrocardiogram, flow mediated dilatation and serum levels of hs-troponin, N-terminal pro B-type natriuretic peptide and lipids were secondary outcomes. There was no significant difference in weighted median hsCRP levels between exposed and unexposed participants (1.9 mg/L vs. 1.6 mg/L, p = 0.273). Other outcomes were comparable between the groups. hsCRP was associated in a predictable manner with current smoking, obesity and use of lipid-lowering therapy. Four years after a 6-week coal mine fire, this study found no association between smoke exposure and markers of clinical or subclinical cardiovascular disease in exposed adults.


Assuntos
Poluentes Atmosféricos , Doenças Cardiovasculares , Adulto , Poluentes Atmosféricos/análise , Biomarcadores , Proteína C-Reativa , Doenças Cardiovasculares/epidemiologia , Doenças Cardiovasculares/etiologia , Cidades , Carvão Mineral/análise , Humanos , Material Particulado/análise , Fatores de Risco , Fumaça/efeitos adversos , Fumaça/análise , Vitória
7.
Environ Pollut ; 276: 116766, 2021 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-33631690

RESUMO

Air pollution constitutes the greatest environmental threat to human health in the European Union. In Poland, the emission of particulate matter and harmful gases originating from local coal based boiler plants and the combustion of fuels in residential heating appliances is a considerable source of air pollution. The combustion of fuel in home furnaces is inefficient due to the use of cheap fuels of low heating parameters and the frequent addition of waste. For the purpose of the research, deciduous tree wood pellets were selected as the basic fuel with the admixture of plastic waste, rubber, waste paper, wood residues, diapers, textile waste, multi-material packaging, construction waste, biomass and alternative fuel (RDF). Examining ash samples to confirm the practices of combusting or co-combusting waste materials in heating appliances is considered to be one of the most reliable detection methods; however, the results of direct research require further data processing. The application of hierarchical clustering analysis to the obtained results arranged into a matrix enabled in a simple way to demonstrate the similarities between the examined samples of fuel and the samples of fuel mixed with waste materials in the parameters space as well as to analyze the similarities among the measured parameters (the content of particular elements in ash) in the space of the examined samples. The application of chemometric methods for the purpose of identifying the combusted fuels, and, in particular the co-combusted waste complements the currently used monitoring tools which control the use of low quality fuels or the combustion of waste of different origin.


Assuntos
Poluentes Atmosféricos , Madeira , Poluentes Atmosféricos/análise , Análise por Conglomerados , Carvão Mineral/análise , Humanos , Material Particulado/análise , Polônia , Madeira/química
8.
Environ Res ; 194: 110683, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33450236

RESUMO

The toxic emissions from coal combustion associated with domestic winter heating requirements are an important public health issue. Waste cooking oil (WCO) holds promise as a means of reducing pollutant emissions thereby improving human health with the co-benefit of decreasing climate-forcing gas emissions by avoiding the combustion of mineral coal. With an annual production of ~2.17 Mt of WCO in Northern China, it could be used to meet the winter heating demand of ~3.25 million rural households, offsetting ~9.83 Mt of raw coal consumption. Through the adoption of coal-to-WCO shift in rural regions of 15 provinces, approximately 15.0%, 15.6%, 15.9% and 13.7%, respectively of CO, PM2.5, SO2 and NOX emissions would be eliminated. It is estimated that such a change would remove the respective contributions of these pollutants to the premature deaths of respectively, 63,400, 29,300, 173,00 and 31,300 rural residents. Such a positive health impact on the labor cohort would reduce the loss of labor supply and work time, as well as producing billions of RMB in economic benefits. WCO-based heating technology has the same effect on the reduction of GWC100 value as other modern energy carriers while also being cheaper and sustainable, long term. Reducing household emissions by substituting raw coal with green energy is a vital strategy to support pathways for sustainable environment design. The results of this work for the coal-to-WCO shift can reinforce the support for coal phase-out in China.


Assuntos
Poluentes Atmosféricos , Carvão Mineral , Poluentes Atmosféricos/análise , China , Carvão Mineral/análise , Culinária , Calefação , Humanos , Material Particulado/análise
9.
Environ Sci Pollut Res Int ; 28(14): 18260-18275, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33410072

RESUMO

To explore the rule of airflow-dust-gas dispersion and interaction in a fully mechanized mining face, the airflow current vector, the dust trajectory, and the gas spatial distribution were numerically simulated by Fluent. The results show that under the influence of airflow, respiratory dust diffuses to the leeward side of each dust-producing point and footway space and forms a high-concentration (peak concentration 2000 mg/m3) dust mass at 2 m on the leeward side of the advancing support. Gas tends to accumulate near the coal cutter drum, the roof, and the return air corner of the mining face, and the peak concentration exceeds the lower limit of explosion. Near the rear drum of the coal cutter and at the advancing support, considering that the gas and coal dust concentrations are both high and dust and gas can reduce each other's explosion limit, serious gas and coal dust explosions are extremely likely to occur in the presence of a fire source, which may result in serious consequences. Therefore, the two areas can be regarded as key areas of gas and coal dust explosion prevention and control.


Assuntos
Minas de Carvão , Exposição Ocupacional , Carvão Mineral/análise , Difusão , Poeira/análise
10.
Molecules ; 26(3)2021 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-33513731

RESUMO

Lignin isolated from black liquor waste was studied in this research to be utilized as binderless, all-lignin briquette, with a calorific value in the range of 5670-5876 kcal/kg. Isolation of lignin from black liquor was conducted using the acid precipitation method. Sulfuric acid, citric acid, and acetic acid were used to maintain the pH level, which varied from 5 to 2 for the precipitation process. The influence of these isolation conditions on the characteristic of lignin and the properties of the resulted briquette was evaluated through the Klasson method, proximate analysis, ultimate analysis, Fourier Transform Infrared (FTIR), adiabatic bomb calorimeter, density measurement, and Drop Shatter Index (DSI) testing. The finding showed that the lignin isolated using citric acid maintained to pH 3 resulted in briquette with 72% fixed carbon content, excellent 99.7% DSI, and a calorific value equivalent to coal-based briquette.


Assuntos
Bebidas Alcoólicas/análise , Etanol/química , Lignina/química , Ácido Acético/química , Precipitação Química , Ácido Cítrico/química , Carvão Mineral/análise , Concentração de Íons de Hidrogênio , Resíduos Industriais , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Ácidos Sulfúricos/química
11.
Ecotoxicol Environ Saf ; 211: 111959, 2021 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-33486383

RESUMO

Indoor biomass burning produces large amounts of small particles and hazardous contaminants leading to severe air pollution and potentially high health risks associated with inhalation exposure. Personal samplers provide more accurate estimates of inhalation exposure. In this study, inhalation exposure to size-segregated particles and particulate polycyclic aromatic hydrocarbons (PAHs) for the biomass user was studied by deploying personal samplers. The study found that daily PM2.5 inhalation exposure level was as high as 121 ± 96 µg/m3, and over 84% was finer PM1.0. For PAHs, the exposure level was 113 ± 188 ng/m3, with over 77% in PM1.0. High molecular weight PAHs with larger toxic potentials enriched in smaller particles resulting in much high risks associated with PAHs inhalation exposure. Indoor exposure contributed to ~80% of the total inhalation exposure as a result of high indoor air pollution and longer residence spent indoor. The highest exposure risk was found for the male smoker who conducted cooking activities at home.


Assuntos
Poluentes Atmosféricos/análise , Poluição do Ar/estatística & dados numéricos , Monitoramento Ambiental , Exposição por Inalação/estatística & dados numéricos , Material Particulado/análise , Hidrocarbonetos Policíclicos Aromáticos/análise , Poluição do Ar/análise , Poluição do Ar em Ambientes Fechados/análise , Biomassa , Carvão Mineral/análise , Culinária , Poeira , Habitação , Humanos , Exposição por Inalação/análise , Tamanho da Partícula , População Rural , Tibet
12.
J Environ Sci (China) ; 100: 28-33, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33279041

RESUMO

In India coal combustion is the single largest source of emission of mercury which is a wide-spread persistent global toxicant, travelling across international borders through air and water. As a party to the Minamata convention, India aims to monitor and reduce Hg emissions and stricter norms are introduced for mercury emissions from power plants (30 µg/Nm3for flue gas in stack). This paper presents the results obtained during the experimental studies performed on mercury emissions at four coal-fired and one lignite-fired power plants in India. The mercury concentration in the feed coal varied between 0.12-0.27 mg/Kg. In the mercury mass balance, significant proportion of feed coal mercury has been found to be associated with fly ash, whereas bottom ash contained very low mercury. 80%-90% of mercury was released to air through stack gas. However, for circulating fluidised bed boiler burning lignite, about 64.8% of feed mercury was found to get captured in the fly ash and only 32.4% was released to air. The mercury emission factor was found to lie in the range of 4.7-15.7 mg/GJ.


Assuntos
Poluentes Atmosféricos , Mercúrio , Poluentes Atmosféricos/análise , Carvão Mineral/análise , Cinza de Carvão/análise , Índia , Mercúrio/análise , Centrais Elétricas
13.
Chemosphere ; 263: 128298, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33297240

RESUMO

A systematic yearlong study was carried out in Dhauladhar region of the North-Western Himalayas to investigate dynamics in the composition and concentration of particulate bound polycyclic aromatic hydrocarbons (PAHs) and their source(s) activity. PM10 samples were collected for 24 h, once every week during January 2015-January 2016, at an urban mid-altitude site (Dharamshala) and a rural low-altitude site (Pohara). PAHs were identified and quantified using high performance liquid chromatography coupled with UV-detector. Seasonal average concentration of total PAHs followed a pattern: Summer > Winter > Autumn > Spring in the region. Seasonal average values of molecular diagnostic ratios indicated significant contribution from non-traffic (biomass burning and coal combustion) sources also during winter and spring season, whereas, traffic emissions (gasoline and diesel) were the dominant source at both the locations throughout the year in the region. The Principal Component Analysis deciphered a) emissions from gasoline driven vehicles b) diesel engine exhaust emissions c) biomass/wood burning source d) coal combustion and e) waste incineration and burning of oil/tar as major sources of PAHs in the region. Annual mean values of total Benzo(a)Pyrene Equivalent were much higher than 1 ng.m-3 over both the locations indicating higher lung cancer risk to the people living in this part of the Himalayas.


Assuntos
Poluentes Atmosféricos , Hidrocarbonetos Policíclicos Aromáticos , Poluentes Atmosféricos/análise , China , Carvão Mineral/análise , Monitoramento Ambiental , Humanos , Material Particulado/análise , Hidrocarbonetos Policíclicos Aromáticos/análise , Estações do Ano , Emissões de Veículos/análise
14.
Chemosphere ; 263: 128348, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33297273

RESUMO

The Wuda coalfield, Inner Mongolia, China, has been suffering from serious coal fire disaster for more than half a century. In the past decade, the central and local governments have carried out many fire-fighting projects to put out the coal fires, but coal fires still sporadically occur in the coalfield. Previous studies showed that coal fires could release large amounts of mercury (Hg) into the environment. Meanwhile, the rapid industrial development in recent years in Wuda area has also discharged a certain amount of Hg. Identification and quantification of the Hg emitted from coal fires and industrial sources is critical to formulate appropriate environmental policies. This study determined Hg isotope compositions in different types of coals from Wuda coal fire area and surface soils with different distances to the coal fire area, with an aim of anchoring the potential Hg sources in soils. The results showed that the coals had moderately negative δ202Hg (-2.02∼-1.21‰) and slightly negative Δ199Hg (-0.14-0.00‰), while the soils generally had more positive δ202Hg (-1.97∼-0.26‰) and Δ199Hg (-0.07-0.04‰) with distinct isotope ranges among different sampling sites. According to characteristic Hg isotope compositions of different sources, we concluded that the Hg in Wuda soils mainly sourced from cement plants and coal fires, and coal fires were still an important Hg contamination source in Wuda area.


Assuntos
Fogo , Mercúrio , China , Carvão Mineral/análise , Monitoramento Ambiental , Mercúrio/análise , Solo
15.
Sci Total Environ ; 751: 142293, 2021 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-33181995

RESUMO

The harm done to the environment by coal gangue was very serious, and it is urgent to adopt effective methods to dispose of coal gangue in order to prevent further environmental damage. Co-pyrolysis experiments of coal gangue (CG) and peanut shell (PS) were carried out using thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) under nitrogen atmosphere. The heavy metal was detected using the inductively coupled plasma-optical emission spectroscopy (ICP-OES). CG and PS were mixed according to the mass ratio of 1:0, 3:1, 1:1, 1:3 and 0:1. The samples were heated to 1000 °C at the heating rate of 10 °C/min, 20 °C/min and 30 °C/min. The comprehensive pyrolysis index (CPI) of CG, C3P1, C1P1, C1P3 and PS is 0.17 × 10-8, 9.75 × 10-8, 35.47 × 10-8, 100.94 × 10-8 and 192.72 × 10-8%2 ·min-2·°C-3. The kinetic parameters were calculated by model-free methods (Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose). The gas products generated at different temperatures during the pyrolysis experiment were detected by Fourier transform infrared spectrometer. The heating rate, temperature and mixing ratio are the input parameters of artificial neural network (ANN), and the remaining mass percentage of sample during the pyrolysis is the output parameter. The ANN model was established and used to predict thermogravimetric experimental data. The ANN18 model is the best model for predicting the co-pyrolysis of CG and PS.


Assuntos
Carvão Mineral , Pirólise , Biomassa , Carvão Mineral/análise , Cinética , Redes Neurais de Computação , Espectroscopia de Infravermelho com Transformada de Fourier
16.
Chemosphere ; 263: 127920, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32822936

RESUMO

Arsenic (As) and selenium (Se) pollution caused by coal combustion is receiving increasing concerns. The environmental impacts of As/Se are determined not only by stack emission but also by leaching process from combustion byproducts. For a better control of As/Se emission from As/Se-enriched coal combustion, this study investigated the migration and emission behavior of As/Se in a circulating fluidized bed (CFB) power plant equipped with fabric filter (FF) and wet flue gas desulfurization (WFGD) system. The results demonstrated that arsenic was both enriched in bottom ash (41.4-47.6%) and fly ash (52.4-58.6%), while selenium was mainly captured by fly ash (73.9-83.4%). Limestone injection into furnace promoted As/Se retention in ash residues. Arsenic was mainly converted into arsenate in high-temperature regions and partly trapped in bottom ash as arsenite. In contrast, selenium capture mainly occurred in low-temperature flue gas by the formation of selenite, because of the poor thermal stability of most selenite. Triplet-tank method can totally remove arsenic in WFGD wastewater. And 18.4-58.7% of selenium was removed, resulting from the precipitation of Se4+ anions with highly soluble Se6+ anions remaining in wastewater. The concentrations of As and Se in the stack emission were 0.25-1.02 and 0.96-2.24 µg/m3, receptively. The CFB boiler equipped with FF + WFGD was shown to provide good control of the As/Se emission into the atmosphere. Leaching tests suggested that more attention should be paid to As leachability from fly ash/gypsum, and Se leachability from gypsum/sludge.


Assuntos
Poluentes Atmosféricos/análise , Arsênico/análise , Centrais Elétricas , Selênio/análise , Atmosfera , Leitos , Carbonato de Cálcio , Sulfato de Cálcio , Carvão Mineral/análise , Cinza de Carvão/química , Monitoramento Ambiental , Gases
17.
Chemosphere ; 263: 127974, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32828060

RESUMO

CaCr2O4 (Cr (III)), mainly generated through the decomposition of CaCrO4 (Cr (VI)), is a significant intermediate for toxic Cr (VI) formation during solid fuel combustion. In this study, the formation, oxidation and sulfation kinetics of CaCr2O4 were analyzed to forecast the potential of CaCr2O4 oxidation during co-firing of coal and solid waste in a circulating fluidized bed boiler. The results indicated that the formation and oxidation of CaCr2O4 were fitted to a single step nucleation and growth model while CaCr2O4 sulfation was fitted to a shrinking core model. CaCr2O4 formation through CaCrO4 decomposition was favored in oxygen-lean atmosphere and considerably suppressed in the presence of oxygen. In contrast, CaCr2O4 oxidation was mainly determined by the contacts between CaCr2O4 and CaSO4/CaO, which influenced not only oxidation rates but also the product species. Moreover, the oxidation reactivity of CaCr2O4 was higher in the presence of CaO than that of CaSO4. On the other hand, CaCr2O4 sulfation can occur more easily than CaCr2O4 oxidation, the reaction rate of which was deeply affected by sulfate product layer. Findings in this study suggested that spraying calcium in furnace for desulphurization may increase the risk of CaCr2O4 oxidation. Measures including the adjustment of Ca/S ratio in blended fuel (with added limestone) and operating conditions (such as temperature and local atmosphere) in co-firing system could be taken to control CaCr2O4 formation and oxidation.


Assuntos
Cromo/química , Carvão Mineral/análise , Eliminação de Resíduos/métodos , Resíduos Sólidos , Leitos , Cromo/análise , Cinza de Carvão , Oxirredução , Oxigênio , Sulfatos , Temperatura
19.
Chemosphere ; 262: 127846, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32777615

RESUMO

Data for source apportionment estimation was obtained from combustion of 11 types of biomass (rubber wood, palm kernel, palm fiber, sugarcane bagasse, sugarcane leaves, maize residue, rice stubble, rice straw, Xylocarpus moluccensis, Avicennia alba Blume and Rhizophora mucronata) and bituminous coal. Combustion was carried out in a tube furnace and emitted particulate matter (PM) was collected using a nanosampler that segregated particle sizes down to 0.1 µm. Emission factors of PM < 0.1 µm were in the range of 0.11-0.28 g kg-1 (∼1-8% of total PM), except in the case of Rhizophora mucronata, which had an emission factor of 0.071 ± 0.004 g kg-1 (∼18% of total PM). The dominant polycyclic aromatic hydrocarbons (PAHs) found on PM < 0.1 µm were chrysene from combustion of rubber wood, palm kernel, palm fiber, maize residue, Xylocarpus moluccensis, Avicennia alba Blume, Rhizophora mucronata and bituminous coal; benzo[b]fluoranthene from combustion of rice straw, sugarcane bagasse and sugarcane leaves; and benzo[k]fluoranthene from rice stubble combustion. The emission factors of PAHs bound to PM < 0.1 µm from biomass combustion ranged from 0.005 to 0.044 mg kg-1 and the emission factor from bituminous coal combustion was 0.1411 ± 0.0004 mg kg-1. The carcinogenic potency equivalent or benzo[a]pyrene equivalent was highest from bituminous coal combustion (0.1252 mg kg-1) and between 0.0019 and 0.0192 mg kg-1 from biomass combustion. However, emission factors of both PM and particle-bound PAHs from biomass combustion were affected by moisture content of biomass and moisture contents of biomass used in this study were quite low, ranging from 0.165 to 0.863%.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental , Material Particulado/análise , Hidrocarbonetos Policíclicos Aromáticos/análise , Biomassa , Carcinógenos/análise , Carvão Mineral/análise , Humanos , Tamanho da Partícula , Madeira/química
20.
Artigo em Inglês | MEDLINE | ID: mdl-33356870

RESUMO

As a common pretreatment process for coal chemical wastewater, the conventional one-stage coagulation process has the problem of poor removal of small size oil, which will inhibit the subsequent biological treatment. Measures to improve oil removal efficiency based on the development of new coagulants and the addition of composite processes are common in the literature, but two-stage coagulation to improve coagulation efficiency has not been reported to date. Here, we optimized coagulation parameters and compared the oil removal efficiency of two-stage coagulation and one-stage coagulation. Under the same total dosage of coagulant (PAC), the optimum removal of oil in two-stage coagulation was achieved 90% which increased by 11% compared to one-stage process. P10 and P 1 µm were proposed to evaluate the oil removing effect of two-stage coagulation. In addition, SEM scanning was used to conduct flocs analysis and two-stage coagulation process simulation, revealing the principle of the excellent oil removal performance of two-stage coagulation. Finally, coagulant in filter residue was recovered by acidification method and the recovered coagulant was used again in the two-stage coagulation process of coal chemical wastewater. These results suggest that two-stage coagulation is a cost-effective alternative oil removal technique with high energy efficiency and environmental benign. This research may offer helpful insights to develop an advanced oil removal process.


Assuntos
Carvão Mineral/análise , Floculação , Poluição por Petróleo/análise , Águas Residuárias/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos
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