钙质煤渣吸附剂脱除烟气中二氧化硫的实验研究

利用锅炉本身排出的煤渣作脱硫剂的基本核粒,配人少量的石灰,加水搅拌均匀,使石灰裹覆在煤渣颗粒表面,制成具有较大比表面积的钙质煤渣脱硫剂,用于烟气脱硫实验研究.实验结果表明,钙制煤渣脱硫剂比未经处理的煤渣脱硫率高,在一定的石灰添加范围内(10%～20%),脱硫率随石灰添加量的增加而增加,并存在一最佳用量.     

Simultaneous removal of sulfur dioxide and polycyclic aromatic hydrocarbons from incineration flue gas using activated carbon fibers

Incineration flue gas contains polycyclic aromatic hydrocarbons (PAHs) and sulfur dioxide (SO₂). The effects of SO₂ concentration (0, 350, 750, and 1000 ppm), reaction temperature (160, 200, and 280 °C), and the type of activated carbon fibers (ACFs) on the removal of SO₂ and PAHs by ACFs were examined in this study. A fluidized bed incinerator was used to simulate practical incineration flue gas. It was found that the presence of SO₂ in the incineration flue gas could drastically decrease removal of PAHs because of competitive adsorption. The effect of rise in the reaction temperature from 160 to 280 °C on removal of PAHs was greater than that on SO₂ removal at an SO₂ concentration of 750 ppm. Among the three ACFs studied, ACF-B, with the highest microporous volume, highest O content, and the tightest structure, was the best adsorbent for removing SO₂ and PAHs when these gases coexisted in the incineration flue gas.

ImplicationsSimultaneous adsorption of sulfur dioxide (SO₂) and polycyclic aromatic hydrocarbons (PAHs) emitted from incineration flue gas onto activated carbon fibers (ACFs) meant to devise a new technique showed that the presence of SO₂ in the incineration flue gas leads to a drastic decrease in removal of PAHs because of competitive adsorption. Reaction temperature had a greater influence on PAHs removal than on SO₂ removal. ACF-B, with the highest microporous volume, highest O content, and tightest structure among the three studied ACFs, was found to be the best adsorbent for removing SO₂ and PAHs.     

烟气中多种污染物协同脱除的研究

烟气中多种污染物协同脱除是烟气净化领域的研究热点.在现有烟气脱硫技术研究的基础上,对活性焦干法、多级增湿半干法、氧化性添加剂湿法以及等离子体湿法这4种烟气污染物协同脱除技术进行了系统的研究.研究发现,以活性焦为载体添加适当的催化剂能够实现在高效脱硫基础上的同时脱硝;多级增湿半干法技术提高了脱硫剂颗粒在吸收塔内反应全过程的含湿均匀性,通过添加复合促进剂可以提高反应速率,强化烟气中SO_2、NO_X等污染物协同脱除;在传统的湿法烟气脱硫技术中,向脱硫剂中加入KMnO_4和NaClO_2等强氧化剂或者采用等离子体前置氧化,能够有效的将难吸收的NO氧化成NO_2、HNO_2和HNO_3,最终实现同时脱硫脱硝.     

Gas-phase mercury reduction to measure total mercury in the flue gas of a coal-fired boiler

Gaseous elemental and total (elemental + oxidized) mercury (Hg) in the flue gas from a coal-fired boiler was measured by a modified ultraviolet (UV) spectrometer. Challenges to Hg measurement were the spectral interferences from other flue gas components and that UV measures only elemental Hg. To eliminate interference from flue gas components, a cartridge filled with gold-coated sand removed elemental Hg from a flue gas sample. The Hg-free flue gas was the reference gas, eliminating the spectral interferences. To measure total Hg by UV, oxidized Hg underwent a gas-phase, thermal-reduction in a quartz cell heated to 750 degrees C. Simultaneously, hydrogen was added to flash react with the oxygen present forming water vapor and preventing Hg re-oxidation as it exits the cell. Hg concentration results are in parts per billion by volume Hg at the flue gas oxygen concentration. The modified Hg analyzer and the Ontario Hydro method concurrently measured Hg at a field test site. Measurements were made at a 700-MW steam turbine plant with scrubber units and selective catalytic reduction. The flue gas sampled downstream of the selective catalytic reduction contained 2100 ppm SO2 and 75 ppm NOx. Total Hg measured by the Hg analyzer was within 20% of the Ontario Hydro results.     

Selections from the history of environmental pollution, with special attention to air pollution. Part 1.

Several comprehensive publications have been issued recently on the environmental pollution of past times (e.g. Tylecote, 1976; Nriagu, 1983a; Brimblecombe, 1987a; Goldstein, 1988; Healy, 1988; Brimblecombe and Pfister, 1990; Hughes, 1993; Markham, 1994; Brimblecombe, 1995; Karatzas, 2000, 2001; McNeill, 2001; Meszaros, 2001). The aim of this study is to give an overview of information on the subject – mainly related to ancient times.     

Response of a grassland ecosystem to air pollutants. IV. The chemical climate: concentrations of relevant non-criteria pollutants (trace gases and aerosols)

The concentrations of sulphur dioxide, nitric acid, nitrous acid, hydrogen chloride, ammonia and sulphate, nitrate, chloride and ammonium in aerosols were measured continuously for two years at the rural site of Rotenkamp near Braunschweig in south-east Lower Saxony. The level of air pollution registered is typical for rural areas near industrial areas in Central Europe. Long-range transport of polluted air masses from Saxony-Anhalt and Saxony affects air quality when high-pressure areas over Eastern Europe result in easterly winds and reduced vertical exchange due to low inversion layers.     

An attempt to measure the flow of chlorinated hydrocarbons, such as PCBs, from water to air in the field

A field sampling device to study the transport of aromatic, persistent chlorinated hydrocarbons from water to air was constructed. It was tested in large, outdoor artificial ponds contaminated with polychlorinated biphenyls (PCBs). The PCB compounds volatilised to air at a rate of 0.9 to 9.6 ng m(-2) h(-1) depending on levels of PCBs in the water and water temperature.     

The impact of the 2005 Gulf hurricanes on pollution emissions as inferred from Ozone Monitoring Instrument (OMI) nitrogen dioxide

The impact of Hurricanes Katrina and Rita in 2005 on pollution emissions in the Gulf of Mexico region was investigated using tropospheric column amounts of nitrogen dioxide (NO₂) from the Ozone Monitoring Instrument (OMI) on the NASA Aura satellite. Around New Orleans and coastal Mississippi, we estimate that Katrina caused a 35% reduction in NO_x emissions on average in the three weeks after landfall. Hurricane Rita caused a significant reduction (20%) in NO_x emissions associated with power generation and intensive oil refining activities near the Texas/Louisiana border. We also found a 43% decrease by these two storms over the eastern Gulf of Mexico Outer Continental Shelf mainly due to the evacuation of and damage to platforms, rigs, and ports associated with oil and natural gas production.     

Response of inorganic fine particulate matter to emission changes of sulfur dioxide and ammonia: the eastern United States as a case study

A three-dimensional chemical transport model (PMCAMx) was used to investigate changes in fine particle (PM2.5) concentrations in response to changes in sulfur dioxide (SO2) and ammonia (NH3) emissions during July 2001 and January 2002 in the eastern United States. A uniform 50% reduction in SO2 emissions was predicted to produce an average decrease of PM2.5 concentrations by 26% during July but only 6% during January. A 50% reduction of NH3 emissions leads to an average 4 and 9% decrease in PM2.5 in July and January, respectively. During the summer, the highest concentration of sulfate is in South Indiana (12.8 microg x m(-3)), and the 50% reduction of SO2 emissions results in a 5.7 microg x m(-3) (44%) sulfate decrease over this area. During winter, the SO2 emissions reduction results in a 1.5 microg x m(-3) (29%) decrease of the peak sulfate levels (5.2 microg x m(-3)) over Southeast Georgia. The maximum nitrate and ammonium concentrations are predicted to be over the Midwest (1.9 (-3)g x m(-3) in Ohio and 5.3 microg x m(-3) in South Indiana, respectively) in the summer whereas in the winter these concentrations are higher over the Northeast (3 microg x m(-3) of nitrate in Connecticut and 2.7 microg x m(-3) of ammonium in New York). The 50% NH3 emissions reduction is more effective for controlling nitrate, compared with SO2 reductions, producing a 1.1 microg x m(-3) nitrate decrease over Ohio in July and a 1.2 microg x m(-3) decrease over Connecticut in January. Ammonium decreases significantly when either SO2 or NH3 emissions are decreased. However, the SO2 control strategy has better results in July when ammonium decreases, up to 2 microg x m(-3) (37%), are predicted in South Indiana. The NH3 control strategy has better results in January (ammonium decreases up to 0.4 microg x m(-3) in New York). The spatial and temporal characteristics of the effectiveness of these emission control strategies during the summer and winter seasons are discussed.     

Selections from the history of environmental pollution, with special attention to air pollution. Part 2: From medieval times to the 19th century

Several comprehensive publications have been issued recently on the environmental pollution of past times, especially from medieval times (e.g. Brimblecombe, 1987a; oldstein, 1988; Brimblecombe and Pfister, 1990; Hughes, 1993; Markham, 1994; Brimblecombe, 1995). The aim of this paper is to give an overview of information on the subject – mainly related to the period between medieval times and the 19th century.     

The response of epiphytic lichens to air pollution and subsets of ecological predictors: a case study from the Italian Prealps

We investigated the response of epiphytic lichens to air pollution, against the background of other ecological predictors in a prealpine heterogeneous area, using Non-Parametric Multiplicative Regression (NPMR). The best NPMR model for total lichen diversity according to N environmental predictors at tree level has a cross R(2)=0.709. It includes 10 variables, belonging to three different subsets of factors: two pollution-related factors (distance in meters from the road and from the cement factory); four stand-related (habitat, heat index, LAI and elevation) and four substrate-related factors (inclination, circumference and texture and tree species). Considering separately the effects of each subset on lichen diversity, substrate- and stand-related factors produce good models with similar cross R(2) (0.490 and 0.500, respectively), whereas pollution-related factors produce a model with a lower cross R(2) (0.340). Hence, we provide information to investigate the applicability of lichen biomonitoring to complex heterogeneous areas where standardized protocols are not reliable.     

A batch study on the bio-fixation of carbon dioxide in the absorbed solution from a chemical wet scrubber by hot spring and marine algae

Carbon dioxide mass transfer is a key factor in cultivating micro-algae except for the light limitation of photosynthesis. It is a novel idea to enhance mass transfer with the cyclic procedure of absorbing CO(2) with a high performance alkaline abosorber such as a packed tower and regenerating the alkaline solution with algal photosynthesis. Hence, the algae with high affinity for alkaline condition must be purified. In this study, a hot spring alga (HSA) was purified from an alkaline hot spring (pH 9.3, 62 degrees C) in Taiwan and grows well over pH 11.5 and 50 degrees C. For performance of HSA, CO(2) removal efficiencies in the packed tower increase about 5-fold in a suitable growth condition compared to that without adding any potassium hydroxide. But ammonia solution was not a good choice for this system with regard to carbon dioxide removal efficiency because of its toxicity on HSA. In addition, HSA also exhibits a high growth rate under the controlled pHs from 7 to 11. Besides, a well mass balance of carbon and nitrogen made sure that less other byproducts formed in the procedure of carboxylation. For analysis of some metals in HSA, such as Mg, Mn, Fe, Zn, related to the photosynthesis increased by a rising cultivated pH and revealed that those metals might be accumulated under alkaline conditions but the growth rate was still limited by the ratio of bicarbonate (useful carbon source) and carbonate. Meanwhile, Nannochlopsis oculta (NAO) was also tested under different additional carbon sources. The results revealed that solutions of sodium/potassium carbonate are better carbon sources than ammonia carbonate/bicarbonate for the growth of NAO. However, pH 9.6 of growth limitation based on sodium was lower than one of HSA. The integrated system is, therefore, more feasible to treat CO(2) in the flue gases using the algae with higher alkaline affinity such as HSA in small volume bioreactors.     

The performance of a gas and aerosol monitoring system (GAMS) for the determination of acidic water soluble organic and inorganic gases and ammonia as well as related particles from the atmosphere

A new application of the quasi-simultaneous gas/particle phase sampling and analysis principle first proposed by Simon and Dasgupta (Anal. Chem. 34 (1995) 71) is described. For the first time, a gradient chromatograph is used in connection with such a sampling system to allow the simultaneous determination of major organic (formic, acetic, propionic, oxalic, malonic and succinic) and inorganic (SO₂, HNO₂, HNO₃, HCl and H₂F₂) acidic gases and related particles. Another addition to the previous systems is the analysis of cations other than ammonium from the particulate phase. The time resolution of the instrument still remains high, 1 h, during which gaseous water-soluble acidic compounds, ammonia, as well as related anionic particles and inorganic major cations are analysed. Sampling is based on diffusion in a wetted parallel plate denuder for gases and on growth in supersaturated water vapour for particles. The determination limits range from 2 ppt (acetate) to 0.4 ppb (ammonia) in the gas phase and 0.01 μg m⁻³ (citric acid) to 0.79 μg m⁻³ (calcium) for particulate matter. Collection efficiencies for gas and aerosol sampling were quantified and the supersaturation in the aerosol sampling apparatus investigated. The system has been used for field measurements at a background station; selected results of these measurements are presented.     

The effects of elevated carbon dioxide levels on a Vibrio sp. isolated from the deep-sea

Introduction

The effect of oceanic CO₂ sequestration was examined exposing a deep-sea bacterium identified as Vibrio alginolyticus (9NA) to elevated levels of carbon dioxide and monitoring its growth at 2,750 psi (1,846 m depth).

Findings

The wild-type strain of 9NA could not grow in acidified marine broth below a pH of 5. The pH of marine broth did not drop below this level until at least 20.8 mM of CO₂ was injected into the medium. 9NA did not grow at this CO₂ concentration or higher concentrations (31.2 and 41.6 mM) for at least 72 h. Carbon dioxide at 10.4 mM also inhibited growth, but the bacterium was able to recover and grow. Exposure to CO₂ caused the cell to undergo a morphological change and form a dimple-like structure. The membrane was also damaged but with no protein leakage.     

Studies on thio-substituted polyurethane foam (T-PUF) as a new efficient separation medium for the removal of inorganic/organic mercury from industrial effluents and solid wastes

Novel thio-substituted flexible polyurethane foam (T-PUF) was synthesised by addition polymerisation of mercaptan with the precursors of an open-cell polyurethane foam, which can be used as a highly selective sorbent for inorganic and organic mercury from complex matrices. The percentage extraction of inorganic mercury was studied at different flow-rates, over a wide pH range at different concentrations ranging from 1 ppm, to 100 ppm. The break-through capacity and total capacity of unmodified and thio-foams were determined for inorganic and organic mercurials. The absorption efficiency of thio-foam was far superior to other sorbent media, such as activated carbon, polymeric ion-exchange resins and reagent-loaded polyurethane foams. It was observed that even at the 1000 ppm level, divalent ions like Cu, Mg, Ca, Zn do not appreciably influence the per cent extraction of inorganic mercury at the 10 ppm level. These matrix levels are the most concentrated ones which are likely to occur, both in local sewage and effluent waters. Further, the efficiency of this foam was sufficiently high at 10-100 ppm levels of Hg, even from 5-10 litres of effluent volumes using 50 g of thio-foam packed into different columns in series. Thio-foams were found to possess excellent abilities to remove and recover mercury even at low levels from industrial effluents and brine mud of chlor-alkali industry after pre-acid extraction. This makes it a highly efficient sorbent for possible application in effluent treatment. Model schemes for the removal and recovery of mercury from industrial effluents and municipal sewage (100-1000 litre) by a dynamic method are proposed and the costs incurred in a full-scale application method are indicated to show that the use of thio-foam could be commercially attractive.     

Application of a magnetotactic bacterium, Stenotrophomonas sp. to the removal of Au(III) from contaminated wastewater with a magnetic separator

In this study, the feasibility of applying a magnetotactic bacterial isolate (MTB), Stenotrophomonas sp. to the removal of Au(III) was investigated. Biosorption experiments showed that Au(III) biosorption capacity exhibited no significant difference in the initial pH range of 1.0-5.5, while decreased more significantly in the initial pH range of 5.5-13.0. Langmuir isotherm indicated that the maximum Au(III) biosorption capacity of Stenotrophomonas sp. were 506, 369 and 308 mg g(-1) dry weight biomass at the initial pH values of 2.0, 7.0 and 12.0, respectively. Thiourea was proved to be an effective desorbent to recover Au from the MTB biomass and 91% Au adsorbed on the biomass could be recovered at equilibrium when the thiourea concentration was 0.8M. The magnetic separator developed by our research team used for separating Au loaded MTB biomass showed high separation efficiency, with 100% biomass removed at the magnetic intensity of 1200 Gs in 180 min. The analyses from FTIR and XRD further confirmed that the reduction of Au(III) to Au(0) by the reductants on the MTB biomass occurred, and the deposition of nano-crystal Au(0) particles, ranging from 24.7 to 31.4 nm, could be estimated on the biomass surface.     

Study on the removal of elemental mercury from simulated flue gas by Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>-CeO<Subscript>2</Subscript>/AC at low temperature

Fe₂O₃ and CeO₂ modified activated coke (AC) synthesized by the equivalent-volume impregnation were employed to remove elemental mercury (Hg⁰) from simulated flue gas at a low temperature. Effects of the mass ratio of Fe₂O₃ and CeO₂, reaction temperature, and individual flue gas components including O₂, NO, SO₂, and H₂O (g) on Hg⁰ removal efficiency of impregnated AC were investigated. The samples were characterized by Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Results showed that with optimal mass percentage of 3 % Fe₂O₃ and 3 % CeO₂ on Fe3Ce3/AC, the Hg⁰ removal efficiency could reach an average of 88.29 % at 110 °C. Besides, it was observed that O₂ and NO exhibited a promotional effect on Hg⁰ removal, H₂O (g) exerted a suppressive effect, and SO₂ showed an insignificant inhibition without O₂ to some extent. The analysis of XPS indicated that the main species of mercury on used Fe3Ce3/AC was HgO, which implied that adsorption and catalytic oxidation were both included in Hg⁰ removal. Furthermore, the lattice oxygen, chemisorbed oxygen, and/or weakly bonded oxygen species made a contribution to Hg⁰ oxidation.