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1.
ABSTRACT The primary production of Pb via the sinter plant-blast furnace method resulted in a large number of Pb and other phases, reflecting the complex reactions occurring within each of the processes. Optical microscopy and X-ray diffraction (XRD) techniques have been used to characterize fugitive emissions and dusts generated during sintering, smelting, Cu drossing, refining, and slag fuming at a primary Pb-Zn smelter. The results displayed a complex array of phases, with the mineralogy of the dusts and fume reflecting conditions of the particular metallurgical operation. The principal Pb species followed a transformation from PbS through PbSO 4 and PbO to Pb° (metal) from raw materials to the refinery. The fugitive emissions generated by the blast furnace were of a finer size with more complex chemistry than fugitive material from other source areas. XRD identified a mixture of PbS, ZnO, and ZnS, associated with one or more of the Cl-bearing phases Pb(OH)Cl, PbCl 2, Pb 4O 3Cl 2, Na 3Pb 2(SO 4) 3Cl, Pb 10(SO 4)Cl 2O 8, Pb 4SCl 6, and Pb 7S 2Cl 10. The presence of Cl-bearing phases in the fume has possible health implications. 相似文献
2.
The information presented in this paper is directed to engineers who are involved with environmental emissions from coal conversion plants. Synthetic sorbents were investigated as an alternative to natural sorbents (limestone) for the removal of SO 2 from the combustion gas in a fluidized-bed coal combustor. The sulfation rate of a synthetic sorbent, CaO in α-AI 2O 3, was determined as a function of gas composition, temperature, and calcium concentration in the sorbent. The reaction was found to be diffusion-controlled above 850°C and kinetically controlled at lower temperatures. The physical characteristics of the support material have a major effect oh the sulfation kinetics. Porosity measurements indicated that supports containing large pores (>0.2 µm) produced sorbents having high sulfation rates and that pores with diameters less than 0.2 µm did not contribute significantly to the capture of SO 2. The sorbents SrO in α-AI 2O 3 and BaO in α-AI 2O 3 had lower SO 2 capture rates than did CaO in α-AI 2O 3. The alkali metal oxide sorbents K 2O and Na 2O in α-AI 2O 3 captured SO 2 much faster than did the alkaline earth metal oxides. 相似文献
3.
This research consists of a laboratory study and a field study. The laboratory research reports the formation of NO x from a point to plane corona discharge. Discharge polarity and relative humidity determined the amount of NO x that was produced. The positive point discharge caused more NO x to form than the negative point discharge. For both polarities NO x production showed a nonlinear increase with current. Relative humidity enhanced the NO x formation for both polarities. In each case, the amount of NO x formed was comparable to the quantity of N 2O produced from corona discharge. The research also reports the results from a field study that measured the amounts of 03 and NO 2 produced by corona discharge during a thunderstorm. The study found that the ambient concentrations of 03 and NO 2 increased several fold due to corona discharge and returned to original levels after the thunderstorm. 相似文献
4.
The body of Information presented in this paper is directed to those Individuals concerned with the removal of NO x in combustion flue gases. A catalytic process for the selective reduction of nitrogen oxides by ammonia has been investigated. Efforts were made toward the development of catalysts resistant to SO x poisoning. Nitrogen oxides were reduced over various metal oxide catalysts in the presence or absence of SO x(SO 2 and SO 3). Catalysts consisting of oxides of base metals (for example, Fe 2O 3) were easily poisoned by SO 3, forming sulfates of the base metals. A series of catalysts which are not susceptible to the SO x poisoning has been developed. The catalysts possess a high activity and selectivity over a wide range of temperatures, 250—450°C. The catalysts were tested in a pilot plant which treated a flue gas containing 110-150 ppm NO x, 660-750 ppm SO 2, and 40-90 ppm SO 3. The pilot plant was operated at 350°C and at a space velocity of 10,000 h -1. The removal of nitrogen oxides was more than 90% for several months. A mechanism of the NO-NH 3 reaction has also been investigated. It is found that NO reacts with NH 3 at a 1:1 mole ratio in the presence of oxygen and the reaction is completely inhibited by the absence of oxygen. The experimental data show that the NO-NH 3 reaction in the presence of oxygen is represented byNO + NH 3 + 1/4 O 2 = N 2 + 3/2 H 2O. 相似文献
5.
The thermal decomposition of SF 6 is known to be oxygen-independent. Nevertheless, because of its high stability, the use of SF6 as a "conservative" surrogate in incinerator performance evaluation has been advocated and researched. This paper shows that refractory decreases markedly the stability of SF 6. The resulting increase in SF 6 decomposition was from 0 percent to 95 percent at 900°C, and the temperatures at which 90-99 percent decomposition occurred were lowered by 300-150°C. Refractory also decreased the stability of CCl 4 and C 2Cl 4, but to a lesser extent. The difference between the decompositions of C 2Cl 4 and SF 6 was reduced from several orders of magnitude to a factor of 2-4. Such a drastic and adverse change in relative stability could render SF 6 unsuitable as a "conservative" surrogate. The requirements for a "conservative" surrogate and the need for caution in its use are discussed, and further research areas are indicated. 相似文献
6.
A study was carried out to investigate the emissions of SO 2 and primary sulfate materials (H 2SO 4 and inorganic particulate matter) from a boiler burning fossil fuel and using a wet-limestone scrubber for SO 2 removal. Experiments were designed to assess the scrubbing efficiency for SO 2 and sulfate, as well as the potential for scrubber liquor reentrainment. The boiler studied was an 820 MW cyclone-fired unit equipped with a wet, limestone scrubber, consisting of eight two-stage venturi-absorber modules designed to treat a flue gas flow rate of 2,760,000 acfm. The boiler fuel was a low-grade sub-bituminous coal with ash and sulfur contents of 25 and 5%, respectively. Multiple-sampling methods were employed concurrently on the inlet and outlet of a candidate absorber module to measure SO 2, total water-soluble sulfate, and free H 2SO 4. Samples were collected during three field experiments from September 1977 through April 1978. The average SO 2 scrubbing efficiency was 76% and was observed to decrease over the 5 day operation/maintenance cycle of the module. The total water-soluble sulfate input to the scrubber amounted to approximately 1% of the total sulfur oxides and was composed of a 5:1 ratio of H 2SO 4 to particulate sulfate. The total sulfate scrubbing efficiency, averaging about 29%, was invariant with respect to SO 2 removal. The sulfate emissions measured in the scrubber exit gas consisted of about 85 % H 2SO 4 as a fine aerosol. Mass emissions of acid and particulate sulfate were calculated as 1730 Ib/hr and 305 Ib/hr, respectively. 相似文献
7.
A magnetic ZnFe 2O 4–reduced graphene oxide (rGO) hybrid was successfully developed as a heterogeneous catalyst for photo-Fenton-like decolorization of various dyes using peroxymonosulfate (PMS) as an oxidant under visible light irradiation. Through an in situ chemical deposition and reduction, ZnFe 2O 4 nanoparticles (NPs) with an average size of 23.7 nm were anchored uniformly on rGO sheets to form a ZnFe 2O 4–rGO hybrid. The catalytic activities in oxidative decomposition of organic dyes were evaluated. The reaction kinetics, effect of ion species and strength, catalytic stability, degradation mechanism, as well as the roles of ZnFe 2O 4 and graphene were also studied. ZnFe 2O 4–rGO showed to be a promising photocatalyst with magnetism for the oxidative degradation of aqueous organic pollutants and simple separation. The combination of ZnFe 2O 4 NPs with graphene sheets leads to a much higher catalytic activity than pure ZnFe 2O 4. Graphene acted as not only a support and stabilizer for ZnFe 2O 4 to prevent them from aggregation, largely improving the charge separation in the hybrid material, but also a catalyst for activating PMS to produce sulfate radicals at the same time. The ZnFe 2O 4–rGO hybrid exhibited stable performance without losing activity after five successive runs. 相似文献
8.
Abstract This investigation numerically examined the cutoff aerodynamic diameter (da 50) and the sharpness (GSD) of the particle collection efficiency curve of impactors with a finite impaction plate diameter. Results revealed that the inertial impactors have a limited cutoff aerodynamic diameter at different air velocities. The extreme value of the cutoff aerodynamic diameter increases with the nozzle diameter (W)/the plate diameter (D c). The computed da 50/D c values of the impactors increase with W/D c at various Reynolds numbers (Re) and with the nozzle-toplate distance (S)/D c when Re is 100. The value of GSD slightly increases with W/D c for Re of 10 and 100, although the effect of S/D c on GSD is not evident at various Res. The particle collection efficiency curve of the impactor with a lower Re is less sharp than that with a high Re at various W/D c and S/D c values. Statistical equations closely fitted the obtained numerical results for Res of 10–3000. The equations are useful for directly calculating the cutoff aerodynamic diameter and the sharpness of the particle collection efficiency curve for single round-nozzle impactors with a finite impaction D c. 相似文献
9.
Abstract Sulfur hexafluoride (SF 6)-contained gas is a common pollutant emitted during the etching process used in the semiconductor industry. This study demonstrated the application of radio-frequency (RF) plasma in the decomposition of SF 6. The decomposition fraction of SF 6 [η SF6 (C in–C out)/C in x 100%] and the mole fraction profile of the products were investigated as functions of input power and feed O 2/SF 6 ratio in an SiO 2 reactor. The species detected in both SF 6/Ar and SF 6/O 2/Ar RF plasmas were SiF 4, SO 2, F 2, SO 2F 2, SOF 2, SOF 4, S 2F 10, S 2OF 10, S 2O 2F 10, and SF 4. The results revealed that at 40 W, η SF6 exceeded 99%, and the reaction products were almost all converted into stable compounds such as SiF 4, SO 2, and F 2 with or without the addition of oxygen. Sulfur oxyfluorides such as SO 2F 2, SOF 2, SOF 4, S 2OF 10, and S 2O 2F 10 were produced only below 40 W. The results of this work can be used to design a plasma/chemical system for online use in a series of a manufacturing process to treat SF 6-containing exhaust gases. 相似文献
10.
针对TNT炸药废水具有成分复杂、排放量大、有毒等特点,立足于炸药废水在排放前的降解处理,研究开发一种基于核壳结构Fe3O4@SiO2/TiO2纳米颗粒的高效、可控回收、无二次污染且成本低的光催化降解方法。利用高温碳还原法和溶胶凝胶法制备了具有核壳结构的Fe3O4@SiO2/TiO2纳米颗粒。XRD分析表明,内核Fe3O4呈现磁铁矿特征,表面覆盖的纳米TiO2为锐钛矿型。磁滞回线测试结果显示,复合颗粒的饱和磁化强度为46.5 emu/g,N2吸附-解吸分析结果表明,该颗粒具有典型的介孔结构。使用Fe3O4@SiO2/TiO2纳米颗粒在紫外光下对含TNT废水进行降解,降解率达到81.9%,且颗粒的回收率达到88.4%,为实现高效、可控回收、无二次污染光催化-吸附降解TNT奠定了基础。 相似文献
11.
This paper reports the development of a rapid, continuous technique for analyzing fixed nitrogen species (NH 3, HCN, CH 3NH 2, etc.). The technique uses a platinum catalyst at low pressure in combination with a conventional chemiluminescent NO x analyzer. Previous workers observed that conventional stainless steel catalysts, and platinum catalysts operated at atmospheric pressure, do not reliably convert NH 3 to NO. The most serious problem was the variation in the efficiency of these catalysts with operating conditions. Changes in temperature, gas composition, or X NH3 could change the conversion efficiency from 99.9% to <30%. The new conversion technique, however, is quantitative up to several thousand ppm NH 3 in either O 2/He or O 2/CO 2/N 2. 相似文献
12.
The present research deals with the development of a new heterogeneous photocatalysis and Fenton hybrid system for the removal of color from textile dyeing wastewater as Rhodamine B (RhB) solutions by using Fe 2+/H 2O 2/Nb 2O 5 as a photocatalytic system. The application of this photocatalytic system for the decolorization of dye contaminants is not reported in the literature yet. Different parameters like dye concentration, Nb 2O 5/Fe 2+ catalyst amount, pH, and H 2O 2 concentration have been studied. The optimum conditions for the decolorization of the dye were initial concentration of 10 mg L ?1 of dye, pH 4, and Nb 2O 5/Fe 2+ catalyst concentration of 0.5 g L ?1/50 mg L ?1. The optimum value of H 2O 2 concentration for the conditions used in this study was 700 mg L ?1. Moreover, the efficiency of the Nb 2O 5/photo-Fenton hybrid process in comparison to photo-Fenton alone and a dark Fenton process as a control experiment to decolorize the RhB solution has been investigated. The combination of photo-Fenton and Nb 2O 5 catalysts has been proved to be the most effective for the treatment of such type of wastewaters. The results revealed that the RhB dye was decolorized in a higher percent (78 %) by the Nb 2O 5/photo-Fenton hybrid process (Fe 2+/H 2O 2/Nb 2O 5/UV) than by the photo-Fenton process alone (37 %) and dark Fenton process (14 %) after 120 min of treatment. Moreover, the Nb 2O 5 catalyst as a heterogeneous part of the photocatalytic system was demonstrated to have good stability and reusability. 相似文献
13.
This paper summarizes the results of research conducted at Ar-gonne National Laboratory (ANL) to develop and design a novel method for the recovery of CO 2 from flue gases. The basic process concept Involves the combustion of a hydrocarbon fuel using a mixture of oxygen and carbon dioxide (or CO 2 and H 20) rather than air as the oxidant, which results In a product stream that contains primarily CO 2 and H 2O. This stream Is then dried and conditioned to meet the specifications of the end user, A slip stream of CO 2 (or CO 2, and H 20) is used as a diluent in the combustion chamberto maintain a flame temperature equivalent to the temperature that would otherwise be obtained using air as an oxidant. The cost-effectiveness of the process in recovering C0 2 is dependent on the scale of the operation, the type of fuel used, the cost of oxygen, and the cost of capital. The sensitivity of the cost of the recovered C0 2 to these variables Is discussed, and a model for estimating the cost of CO 2 recovered using the ANL process Is presented. 相似文献
14.
Fine particle matters (PM2.5) is a well-known risk factor for cardiovascular diseases. However, the underlying molecular mechanisms are largely unknown. Vascular hyper-reactivity plays an important roles in the pathogenesis of cardiovascular diseases. The present study was designed to investigate a hypothesis that PM2.5 up-regulated endothelin receptors in mesenteric artery and the potential underlying mechanisms. Rat mesenteric arteries were cultured with PM2.5. The artery contractile responses were recorded by a sensitive myograph. ETB and ETA receptor expressions of mRNA and protein were assessed by quantitative real-time PCR, Western blotting, and immunohistochemistry, respectively. Results showed that ETB receptor agonist, sarafotoxin 6c induced a negligible contraction in fresh artery segments, while ETA receptor agonist, ET-1 induced an obvious contraction. After organ culture, the contraction curve mediated by ETB and ETA receptors were shifted toward the left. PM2.5 1.0 μg/ml cultured for 16 h further enhanced ETB and ETA receptor-mediated contractile responses with a markedly increased maximal contraction. The organ culture enhanced ETB and ETA receptor mRNA and protein levels from fresh arteries, which were further increased by PM2.5. The U0126 (MEK/ERK1/2 inhibitor) and SB203580 (p38 inhibitor) significantly attenuated both organ cultured-induced and PM2.5-induced up-regulation of ETB receptor. U0126 also suppressed organ culture-increased and PM2.5-increased expressions of ETA receptor. SB203580 only suppressed PM2.5-induced enhanced expressions of ETA receptor In conclusion, airborne PM2.5 up-regulates ETB and ETA receptors of mesenteric artery via p38 MAPK and MEK/ERK1/2 MAPK pathways. 相似文献
15.
The evolution of H 2S and SO 2 from hot blast furnace slags by reaction with H 2O has been found to be dependent upon the presence of O 2 or H 2 in the reaction zone as well as on the temperature. H 2 has been found to produce a small increase in H 2S and a small decrease in SO 2 emission, while O 2 has been found to produce a very great inhibiting effect on H 2S emission and only a small increase in SO 2 emission. The total emission of sulfur bearing gases is much less when H 2O + air is blown at the slag than when H 2O + Ar is blown at the slag, particularly at 1200°C and above. These effects may be useful in attempts to design systems for slag quenching which will produce less pollution. 相似文献
16.
The study reported by this paper involves the use of the Controlled Condensation System (Goksoyr/Ross Coil) for flue gas S0 3 measurements in both the laboratory and the field, under low and high mass loadings. The Controlled Condensation System cools the flue gas to below the dewpoint of H 2S0 4 but above the H 20 dewpoint. The resulting aerosol is collected either on the coil walls or on the back-up glass frit. The laboratory recovery of the H 2S0 4 in streams of varying S0 2, H 20, and H 2S0 4 content was found to be 95 ± 6%. A new quartz filter holder was designed to meet the filtration problems encountered in collecting S0 3 from particle laden flue gas streams. This quartz system, when heated to above 250°C, quantitatively passed the H 2S0 4 into the condensation coil. Later studies with this filter system preloaded with fly ash equivalent to a mass loading of 1.3 g/m 3 yielded a 80-85% recovery of H 2S0 4. The laboratory system was simultaneously tested at a 150 megawatt, pulverized coal-fired power plant prior to and after a wet limestone FGD. The inlet grain loading to the FGD ranged from 0.06 g/m 3 to 11.4 g/m 3 with S0 2 concentrations as high as 4000 ppm. The average inlet H 2S0 4 value was 8.3 ppm and the outlet from the FGD was 3.1 ppm. The source fluctuation value was determined to be ±65%. 相似文献
17.
用共沉淀法制备用于脱除NO的六铝酸盐催化剂LaMxAl12-xO19(M =Cu,Ce,CuCe).用XRD、H2-TPR和BET对催化剂进行了结构和物性表征.用微型催化反应装置考察了催化剂在CO选择性催化还原NO中的活性.结果表明,Cu离子易于进入六铝酸盐晶格内,形成完整的六铝酸盐结构.Ce离子不易于进入六铝酸盐晶格内,主要以CeO2的形式存在.在CO+ NO条件下,3种催化剂都表现出较好的脱硝活性,LaCuCeAl10O19中由于Cu离子与Ce离子间产生协同作用,该催化剂的脱硝活性有所增加.加入SO2后,3种催化剂都有不同程度的失活现象发生,其中LaCuAl11O19催化剂受SO2中毒影响最严重,LaCuCeAl10O19催化剂的脱硝活性在三者中最好. 相似文献
18.
Nitric acid and ammonium-containing particulate species were measured by the annular denuder-filter pack technique at Manndorf, a rural site in South Germany, in July 1990. The analyses of filter packs indicated that nitrate was present as ammonium salt which mostly dissociated during sampling. Moreover, due to the NH +4/NO −3 ratios higher than unity found in back-up filters, NH 4Cl was assumed to represent an appreciable fraction of the total particulate ammonium. Finally, the molar ratios NH +4/SO 2−4 found on front (Teflon) filters, suggested a large predominance of (NH 4) 2SO 4 among the different forms of sulphate. The concentration levels of gaseous HNO 3 observed in the daytime were characterised by a maximum after midday, whereas particulate nitrate showed five times out of eight days an opposite trend with early afternoon minima. The total nitrate (HNO 3+NH 4NO 3) showed in turn a diurnal pattern similar to that of sulphate. These findings led to the conclusion that a significant HNO 3 production pathway involved the thermal dissociation of NH 4NO 3 rather than the reaction of NO 2 with OH radical. 相似文献
19.
Nitrous oxide (N 2O) levels in the atmosphere are increasing, potentially contributing to the greenhouse effect and depletion of stratospheric ozone. From a limited data base, combustion sources have been identified as a major anthropogenic source of N 2O. However, the existing data base (obtained by traditional grab sampling techniques followed by gas chromatographic analysis) is in question due to the discovery of a sampling artifact. A continuous on-line N 2O analyzer would enable and facilitate the accurate characterization of combustion sources over a range of operating conditions, and also aid in the development of an appropriate sampling technique. This paper addresses the development of a continuous measurement technique, and the evaluation and initial use of a field prototype continuous N 2O analyzer developed at the UCI Combustion Laboratory in cooperation with a major instrument manufacturer. The analyzer is capable of measuring N 2O levels down to a few ppm. The analyzer has been evaluated and used to study the N 2O emissions from a pulverized coal-fired boiler. The N 2O levels found with the analyzer are substantially lower than levels previously attributed to such sources. Initial N 2O measurements made with the analyzer suggest that N 2O levels are not a substantial fraction of the NO X levels, as previously suggested. 相似文献
20.
Measurements of ammonia and particulate ammonium were made in the daytime (1200–1500) at a urban site in Yokohama during the 5-year period, 1982–1986. Diurnal NH 3 concentrations showed a distinct seasonal trend with a maximum in summer. The diurnal monthly average concentrations were above 10 ppb during the late spring and summer months, while the concentrations during the winter months were between 1 and 5 ppb. The seasonal variation was found to be very similar to that of the average air temperature and showed a periodic pattern over 1 year. A good correlation was observed between diurnal NH 3 concentrations and average air temperatures during the 5-year period. The annual mean concentrations were in the range of 6.6–7.6 ppb with only a minor deviation. The diurnal monthly average concentrations of particulate NH 4+ were between 1 and 4 μg m −3 and no significant seasonal variations were seen. As a short-term study, simultaneous measurements of NH 3, HNO 3 and particulate NO 3− were made. The diurnal mean concentrations of NH 3 and HNO 3 were 7.6 and 0.8 ppb, respectively. The concentration of particulate NO 3− ranged from 0.3 to 6μg −3. Both HNO 3 and particulate NO 3− concentrations were relatively low and constant. Thus, NH 3 and HNO 3 levels did not agree with the concentrations predicted from the NH 4NO 3 equilibrium constant. 相似文献
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