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Query: UMLS:C0205700 (ash)
 15,125 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The spray dryer system was conventionally employed to remove the SOx, NOx, and HCl in the flue gas. However, the removal efficiency of acid gas in the practical incineration flue gas, which contains dust, heavy metals, and acid gas itself, was seldom mentioned in the literature. The alkaline sorbents possess large specific surface that was a main factor on the adsorption of heavy metals and acid gas. Therefore, the primary objective of this study was focused on the effect of different additives on the removal efficiency of acid gas and heavy metals (Cr, Cd and Pb). The mass and element size distribution of heavy metals in fly ash under different additives were also investigated. The results indicated that the removal efficiency of HCl in the spray dryer system was higher than 97.8%. The effects of additives on the removal efficiency of HCl, however, were undistinguished. In the desulfurization process, the highest removal efficiency was 71.3% when the additive of amorphous SiO2 was added in the spray dryer system. The removal efficiency was 66.0% with the additive of CaCl2 and 63.1% without any additives, respectively. It was also found that the spray dryer system could decrease the concentration of metal in fly ash but increase the amount of fly ash. In addition, amorphous SiO2 in the alkaline sorbent tended to increase the adsorption of heavy metal on reactant, because it could enhance the dispersion of alkaline sorbent.
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PMID:Effects of different additives on the performance of spray dryer system during incineration process. 1211 21

Exposure to components of air pollution may cause adverse effects on lung cellular and organ functions through several mechanisms. Cell death, altered gene expression including production of cytokines, and modifications of normal cellular processes are possible outcomes that may be independent or coupled. To assess the effects of materials representative of a variety of particulate components of air pollution on lung epithelium, a human cell line of type II origin (A549 cells) was exposed to these materials in vitro. Materials tested included carbon black (CB), diesel soot from two sources (DS), residual oil fly ash (ROFA), Ottowa Ambient Air particulate (OAA), silicon dioxide (SiO2), and nickel subsulfide (Ni3S2). Endpoints included loss of adherence measured by crystal violet staining (CV), lactate dehydrogenase release (LDH), release of interleukin-8 (IL-8) measured by ELISA, and alkaline phosphatase activity in the cells (APc) and released into the supernatant (APS). Nuclear morphology was also examined. SiO2 and Ni3S2 both caused dose-dependent acute toxicity as assessed by LDH and CV, and caused alterations in nuclear morphology consistent with apoptosis. However, much more IL-8 was released into the tissue culture supernatant by SiO2 at the same levels of cytotoxicity than by Ni3S2. Neither of these acutely toxic materials increased APc or APS, but the less cytotoxic materials caused very significant release of AP in the order OAA > DS > ROFA >> SiO2 = Ni3S2. OAA and, to a lesser extent, DS caused increases in mitotic fraction and increased CV staining, consistent with stimulation of proliferation. These results suggest multiple modes of responses to toxic materials and imply that a toxicological screening process should address these and possibly other endpoints.
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PMID:Multiple modes of responses to air pollution particulate materials in A549 alveolar type II cells. 1288 95

The final disposal of ash from an incinerator is of special concern because of the possibility of its releasing toxic substances. Melting/vitrification has been regarded as a prospective technology of ash treatment. The object of this investigation was to evaluate the effect of silica (SiO2) addition on the immobilization of hazardous metals and the encapsulation of a glass network during the vitrification process. Four specimens with SiO2/fly ash mixing ratios of 0, 0.1, 0.2, and 0.3, respectively, were tested. The mobility of metals in slag was then estimated by a sequential extraction procedure. X-ray diffraction analysis indicates that SiO2 leads to the polymerization of silicates. The encapsulation of aluminum, calcium, and magnesium would not be observed unless adequate amount of SiO2 was added. It was also found that SiO2 addition enhances the formation of a compact and interconnected glass network structure and, thus, contributes to the chemical stability of metals in slag. After vitrification, the mobility of cadmium, copper, iron, chromium, nickel, lead, and zinc was significantly reduced. However, there is no significant correlation between the immobilization of these metals and the addition of SiO2.
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PMID:Effect of SiO2 on immobilization of metals and encapsulation of a glass network in slag. 1464 61

The quantities of two forms of crystalline silica, tridymite and cristobalite, in heated rice husk ash (RHA) samples were determined by X-ray diffraction (XRD) and chemical methods. Two RHA samples, containing 93% SiO2 and 2-3% K2O, were prepared from charcoaled rice husk products and heated to above 900 degrees C. The crystalline silica made up over 60-80% of the total silica in the heated RHA samples based on the XRD analysis. The crystalline phases in the two samples were somewhat different: The sample heated in the temperature range of 900 to 1,200 degrees C contained 52-62% cristobalite and 10-17% tridymite, but the other sample heated at a comparable temperature, above 1,100 degrees C, contained 46-66% tridymite and 37-16% cristobalite. Based on a correlation of lower tridymite crystallization temperature with higher potassium content, it was concluded that higher potassium levels were responsible for this difference. The pyrophosphoric acid analysis did not give exact results in the evaluation of total crystalline silica content in these RHA samples. As the combustion of rice husk was considered to cover the demands for energy and silica resource in Asian countries, cristobalite and tridymite crystallized in RHA by burning of rice husk should be assessed precisely by XRD analysis and the airborne dust in relevant workplace be controlled.
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PMID:Quantitative analysis of tridymite and cristobalite crystallized in rice husk ash by heating. 1512 80

This study investigated the effects of feedstock additives [polyvinyl chloride (PVC) and NaCl] and spray dryer additives (SiO2, CaCl2, NaHCO3) on heavy metal and fly ash removal efficiencies, and on particle size distribution of heavy metals. A spray dryer with an integrated fabric filter was used as an air pollution control device (APCD). Removal efficiencies for fly ash and heavy metals were greater than 95 and 90%, respectively. When additives of PVC or NaCl were used, the concentration of heavy metals distributed in fly ash apparently varied when the particle diameter was <1 microm. Although the effects of the additives SiO2, CaCl2, and NaHCO3 on the elemental size distribution of Cr were insignificant, these additives did slightly increase concentrations of Cd, Zn, and Pb partitioning in coarser particles (>1 microm).
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PMID:The capture of heavy metals from incineration using a spray dryer integrated with a fabric filter using various additives. 1565 17

Afsin-Elbistan (AE) coal fly ashes obtained by burning coal samples from top, middle and bottom sections of the AE coal seam were characterized and their properties were compared. Chemical analysis of the AE coal fly ashes showed that they are mainly composed of CaO, SiO2, Fe2O3 and Al2O3. Quantitative X-ray diffraction (XRD) analyses were carried out using an interactive data processing system (SIROQUANT) based on Rietveld interpretation methods. Lime is found in all the samples, ranging from around 7% to just over 38%. Amorphous contents of fly ashes are ranged between 19% and 25%. Different types of AE fly ashes revealed that bottom section coal fly ash is very similar to Class F, while medium and top section coal fly ashes are close to Class C and they might be used as mineral admixture in concrete. But also they do not comply with any of the standard. The results presented here show new possibilities for AE coal fly ashes in a wide range of fields, resulting in great advantages in waste minimization, as well as, resources conservation.
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PMID:Comparison of fly ash properties from Afsin-Elbistan coal basin, Turkey. 1575 52

The Heshan coal and the Wansheng coal were selected to investigate the effects of Ca/S molar ratio, combustion temperature and other factors on the desulfurization efficiency when limestone as a desulfurizer. And then the possible effects of various desufurizing systems on the mineral constituents of their residues were discussed by using the X-ray diffraction analyzer. Moreover, the phase diagrams of the ternary system CaO-Al2O3-SiO2 were further used in order to find out the transformation behaviors of inorganic mineral matters in the desulfurizing processes of burning coal on the basis of the XRD results. The results show that the combustion temperature and the Ca/S molar ratio are the key factors affected the desulfurization efficiency and their residues' mineral constituents. When the temperature raised and the Ca/S ratio increased, the solid-phase reactions between CaO and some inorganic matters in coal ash will be obviously accelerated, which thus are good for the formaion of many mineral matters such as C4AF,C2AS and beta-C2S. Yet the anhydrite formed will decompose if the temperature is above 1050 degrees C and then the desulfurization efficiency will decrease. The desulfurization efficiency in different temperature is mainly decided by the existence form of the sulfur-contained mineral matters and their contents in the residue. In the experiment, the best desulfurization efficiency for the HS coal was about 90% when the Ca/S ratio was 2 or 3 and the range of the temperature was from 850 degrees C to 950 degrees C.
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PMID:[Factors of effects on transformation behaviors of inorganic mineral matters in desulfurizing process of burning coal]. 1575 76

Filtrates were collected using a codisposal reaction wherein fly ash was reacted with acid mine drainage. These codisposal filtrates were then analyzed by X-ray Fluorescence spectrometry for quantitative determination of the SiO2 and Al2O3 content. Alkaline hydrothermal zeolite synthesis was then applied to the filtrates to convert the fly ash material into zeolites. The zeolites formed under the experimental conditions were faujasite, sodalite, and zeolite A. The use of the fly ash-derived zeolites and a commercial zeolite was explored in wastewater decontamination experiments as it was applied to acid mine drainage in different dosages. The concentrations of Ni, Zn, Cd, As, and Pb metal ions in the treated wastewater were investigated. The results of the treatment of the acid mine drainage with the prepared fly ash zeolites showed that the concentrations of Ni, Zn, Cd, and Hg were decreased as the zeolite dosages of the fly ash zeolite (FAZ1) increased.
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PMID:Alkaline hydrothermal conversion of fly ash filtrates into zeolites 2: utilization in wastewater treatment. 1599 28

The use of zeolitic material synthesized from coal fly ash for the immobilization of pollutants in contaminated soils was investigated in experimental plots in the Guadiamar Valley (SW Spain). This area was affected by a pyrite slurry spill in April 1998. Although reclamation activities were completed in a few months, residual pyrite slurry mixed with soil accounted for relatively high leachable levels of trace elements such as Zn, Pb, As, Cu, Sb, Co, Tl and Cd. Phytoremediation strategies were adopted for the final recovery of the polluted soils. The immobilization of metals had previously been undertaken to avoid leaching processes and the consequent groundwater pollution. To this end, 1100 kg of high NaP1 (Na6[(AlO2)6(SiO2)10] .15H2O) zeolitic material was synthesized using fly ash from the Teruel power plant (NE Spain), in a 10 m3 reactor. This zeolitic material was manually applied using different doses (10000-25000 kg per hectare), into the 25 cm topsoil. Another plot (control) was maintained without zeolite. Sampling was carried out 1 and 2 years after the zeolite addition. The results show that the zeolitic material considerably decreases the leaching of Cd, Co, Cu, Ni, and Zn. The sorption of metals in soil clay minerals (illite) proved to be the main cause contributing to the immobilization of these pollutants. This sorption could be a consequence of the rise in pH from 3.3 to 7.6 owing to the alkalinity of the zeolitic material added (caused by traces of free lime in the fly ash, or residual NaOH from synthesis).
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PMID:Immobilization of heavy metals in polluted soils by the addition of zeolitic material synthesized from coal fly ash. 1603 95

This study was conducted to investigate the migration patterns of main compositions of the fly ash from refuse incinerator during melting and solidification process. The experiment was performed in a high temperature melting furnace with temperature controlled. X-ray fluorescence spectroscopy (XRF) and X-ray diffractometer (XRD) were used to analyzed the fly ash treated. The parameters investigated included main compositional contents, phase constituents, alkalinity, vaporation rate, volume reduction rate. The results show: (1) During the melting and solidification process, the contents of CaO, Al2O3, and SiO2 in fly ash increased as the temperature went up, but element Cl and S decreased from initial 20.59%, 10.74% to final 0.15%, 0.22%, respectively. This suggests that higher amount of Cl and S in original fly ash could lead to more vaporation in the form of chloride and calcium salfate in the process, which was further verified by XRD analyzing result. (2) The alkalinity decreased as melting temperature increased, but tended to be stable and maintained around 0.95 after temperature reached flowing temperature. (3) The decomposition and vaporation of the salts in the fly ash mainly occurred in the temperatures between 1150 degrees C and 1260 degrees C, which was approximately 100 degrees C lower than melting temperature.
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PMID:[Characteristics of melting and solidification process of fly ash from refuse incinerator]. 1612 94


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