Emission characteristics for co-combustion of leather wastes,sewage sludge,and coal in a laboratory-scale entrained flow tube furnace

Four different mixed fuels consisted of leather waste, coal, and sewage sludge were combusted in a lab-scale entrained flow fluidized bed furnace. The influence of blending ratio on emission characteristics of SO₂, NO_x, HCl, particulate matter (PM), heavy metals, and polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) was studied. Results showed that the mixing of coal with sewage sludge had a complex effect on the emission characteristics. On the one hand, with more sewage sludge blending in the mixed fuel, the acid gas pollutant (SO₂, NO_x) decreased a lot, and the recovery of volatile heavy metals (Cd, Pb) increased at the same time. Furthermore, the leaching toxicity of Cr in the fly ash and bottom ash went down below the national standard with the adding of sewage sludge. On the other hand, the mixing of sewage sludge which consisted of more ash content resulted in the increase of the PM emission. Moreover, the high content of Cu and chlorine in the sewage sludge can promote the formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) when the fuel 3 and 4 were combusted. Most importantly, the concentration of toxic PCDD/Fs in the flue gas produced from fuel 3 and fuel 4 was successfully controlled down below 0.20 ng I-TEQ/Nm³ by the active carbon.

     

EFFECTS OF SELENIUM AND MERCURY ON THE ENZYMATIC ACTIVITIES AND LIPID PEROXIDATION IN BRAIN,LIVER, AND BLOOD OF RATS

Recent studies have reported on the toxicity and related oxidative stress of selenium and mercury. The present study compares the effects of Se as sodium selenite (Na₂SeO₃) and Hg as mercuric chloride (HgCl₂) separately and in combination. Rats received repeated oral doses of Se (0.5 μmol/ml), Hg (0.5 μmol/ml), or Se in combination with Hg (0.5 μmol/ml of each) for 5 consecutive days. Rat serum, brain and liver samples were collected for biochemical assays. The following biochemical alterations occurred in response to Hg treatment: protein content (brain and liver), acetylcholinesterase (AChE) (brain and serum), acid and alkaline (AcP and AlP) phosphatases (plasma and liver) and glutathione S-transferase (GST) (plasma and liver) activities were significantly (P<0.05) decreased, while lactate dehydrogenase (LDH) (plasma, brain and liver), aspartate and alanine aminotransferase (AST, ALT) (serum and liver) activities were significantly increased. Thiobarbituric acid reactive substances (TBARS) was significantly increased in brain and liver. Effect of Se alone included decreased AcP, AlP and GST (serum and liver) activities. However, LDH (serum, brain and liver) and AST (liver) and TBARS (brain and liver) increased. Selenium in combination with Hg partially or totally alleviated the toxic effects of Hg on different studied enzymes. It is concluded that Se could be able to antagonize the toxic effects of mercury.     

Measurements of trace gases in the tropical tropopause layer

A unique dataset of airborne in situ observations of HCl, O₃, HNO₃, H₂O, CO, CO₂ and CH₃Cl has been made in and near the tropical tropopause layer (TTL). A total of 16 profiles across the tropopause were obtained at latitudes between 10°N and 3°S from the NASA WB-57F high-altitude aircraft flying from Costa Rica. Few in situ measurements of these gases, particularly HCl and HNO₃, have been reported for the TTL. The general features of the trace gas vertical profiles are consistent with the concept of the TTL as distinct from the lower troposphere and lower stratosphere. A combination of the tracer profiles and correlations with O₃ is used to show that a measurable amount of stratospheric air is mixed into this region. The HCl measurements offer an important constraint on stratospheric mixing into the TTL because once the contribution from halocarbon decomposition is quantified, the remaining HCl (>60% in this study) must have a stratospheric source. Stratospheric HCl in the TTL brings with it a proportional amount of stratospheric O₃. Quantifying the sources of O₃ in the TTL is important because O₃ is particularly effective as a greenhouse gas in the tropopause region.     

Kinetic study of heterogeneous ozonolysis of alachlor, trifluralin and terbuthylazine adsorbed on silica particles under atmospheric conditions

To better understand the atmospheric behaviour of pesticides, heterogeneous ozonolysis of three herbicides (alachlor, terbuthylazine and trifluralin) adsorbed on silica particles were performed in a flow reactor. The experimental setup used in this study and previously validated (Pflieger et al., 2009) has been specially developed to investigate extremely slow reactivity. The pesticides were adsorbed on particles using a gas/solid adsorption equilibrium, in order to simulate atmospheric conditions. After exposure to ozone concentrations ranging from 5 to 41 ppm during 90 min to 6 h, the kinetics were calculated by comparing the initial and the remaining amounts of pesticides adsorbed on silica particles. This work offers the first results of heterogeneous ozonolysis of alachlor and trifluralin adsorbed on mineral particles. Although alachlor and terbuthylazine were expected to react with ozone, no degradation was observed which leads to a lifetime higher than 8 months towards ozonolysis (for 40 ppb of O₃). A significant degradation of trifluralin adsorbed on silica particles by heterogeneous ozonolysis was observed. The experimental data could be fit by both the Langmuir–Rideal and the Langmuir–Hinshelwood models resulting in atmospheric lifetimes (towards heterogeneous ozonolysis) of 40 and 32 days respectively (for 40 ppb of O₃). These results are discussed and compared to other studies.     

Comparison of titania nanotubes and titanium dioxide as supports of low-temperature selective catalytic reduction catalysts under sulfur dioxide poisoning

A series of iron–manganese oxide catalysts supported on TiO₂ and titanium nanotubes (TNTs) were studied for low temperature selective catalytic reduction (SCR) of NO with NH₃ in the presence of SO_2. The results showed that the specific surface area and the amount of Brønsted acid sites were highly correlated. The results also demonstrated that higher Mn⁴⁺/Mn³⁺ ratios and larger specific surface areas might be the main reasons for the excellent performance of MnFe-TNTs catalyst after SO₂ poisoning. The SO₂ poisoning effect could be minimized by reducing the GHSV, increasing the reaction temperature, or increasing the [NH₃]/[NO] molar ratio. The results also indicated that the formation of ammonium sulfate had a stronger effect on the NO conversion efficiency as compared to the formation of metal sulfate. Thus operating the low temperature SCR at above 230 ^oC to avoid the formation of ammonium sulfate would be the priority choice when SO₂ poisoning is a concerned issue.?Implications: Low-temperature selective catalytic reduction (SCR) has attracted increasing attention due to that it can reduce the energy consumption for the SCR process employed in industries such as steel plants and glass manufacturing plants. However, it also suffers from the sulfur dioxide (SO₂) poisoning problem. This study investigates the possibility of using titania nanotubes (TNTs) as the support of Mn/Fe bimetal oxide catalysts for low-temperature SCR to reduce the SO₂ poisoning. The results indicated that the MnFe-TNT catalyst can tolerate SO₂ for a longer time as compared with the MnFe-TiO₂ catalyst.     

Continuous measurement of particulate and sulfur dioxide concentrations in Junk Bay,Hong Kong

As part of an environmental impact assessment for building a new town in Junk Bay, continuous measurement of SO₂ and particulate concentrations was carried out from October 1981 to June 1982 at three sites in Junk Bay to study the air quality in the area. Flame photometric SO₂ analyzers were used to measure ambient SO₂ level, whereas tape monitors were used to measure the ambient suspended particulate level (in terms of soiling index, or coefficient of haze per 1000 feet). It was found that the mean SO₂ concentrations at the three monitoring sites ranged from 5μg m⁻³ to 35μg m⁻³. Maximum daily values up to about 250 μg m⁻³ and hourly values up to 800 μg m ⁻³ had been recorded on occasion. Comparison of the hourly meteorological data and the hourly SO₂ concentrations in four high-SO₂-level days suggested that the ‘sulfur dioxide episodes’ were all associated with very light wind speeds and local sources. The mean coefficient of haze level in Junk Bay was less than one, which corresponded to very slight particulate pollution.     

Impact of Alternative Fuels on Vehicle Emissions of Greenhouse Gases

Abstract

The conversion of methane to liquid products, hydrogen (H₂), and ammonia (NH₃) was investigated experimentally using microgap discharge plasma at an environmentally friendly condition. The experimental results indicated that H₂ and NH₃ were detected as the main gas products. The highest yield and production rate of H₂ was 14.4% (v/v) and 2974.6 μmol/min, respectively, whereas the highest yield and production rate of NH₃ was 8000 ppm (v/v) and 165.1 μmol/min, respectively. Particularly, the liquid products were collected on the plate and consisted of pyrrole, 2-methyl-1,4-pentadiene, α-amidopyri-dine, 2,5-dimethylpyrrole, methylpyrazine, 1-hexyne, 1,4-heptadiene, and polycyclic organic compounds. Some liquid products were the intermediates of drug, ?avor, dye, and organic synthesis, as well as edible ?avor. The collection efficiency in mass and energy efficiency were 26.3% at once and 22.9 g/kWh, respectively. The whole reaction process was considered to be in line with green chemistry principles.     

适宜处理分散性生活污水的人工湿地除磷填料的筛选及改性

为提高人工湿地除磷效能,从沸石、陶粒、萤石、膨胀蛭石、石灰石、麦饭石、火山岩、牡蛎壳、钢渣和废砖块这10种具有较高磷素饱和吸附量的填料中,筛选出钢渣、沸石和石灰石3种适宜处理分散性生活污水的人工湿地填料,并分别使用不同浓度梯度的酸(碱)、盐对3种填料进行改性,以增强其除磷能力。研究结果表明,钢渣、沸石和石灰石分别经2 mol/L AlCl3、2 mol/L NaOH及2 mol/L AlCl3、0.5 mol/L AlCl3溶液改性后,磷素吸附量达到最高值(0.272、0.0801和0.351 mg/g),而双常数方程能更好地描述优选填料对生活污水中磷的吸附动力学过程,综合考虑填料的吸附效果、成本及来源,改性石灰石是人工湿地处理分散性生活污水时较为理想的除磷填料;此外,填料经铝改后,氮磷吸附效果普遍优于其他改性条件,且Al-P有利于植物直接吸收利用,含铝废水来源广泛,故利用铝改液处理人工湿地填料具有较高的应用推广价值。     

Relationship of Particulate Control,SO2 Removal,and Waste Management

Results with the EPRI 2.5 MW(e) Integrated Environmental Control Pilot Plant (IECPP) indicate the interrelationship of particulate penetration, SO₂ scrubber operation, waste production, and waste properties. Tests compared a fabric filter/wet scrubber and ESP/wet scrubber, the latter operated to simulate 1979 New Source Performance Standards (NSPS), 1971 NSPS, and pre-NSPS ESP units. Tests were conducted with low-sulfur coal producing a flue gas concentration of400ppm; flue gas spiking could be used to increase SO₂ to 2000 ppm. Scrubber waste was dewatered in a thickener and vacuum belt filter (to 55 percent solids content), and mixed with fly ash. The pilot SO₂ scrubber—when preceded by an ESP and forced to operate in zero-discharge—captured less SO₂ than when preceded by a fabric filter. Also, scrubber operation with the ESP produced a greater quantity of waste with difficult handling characteristics, as compared to operation with the fabric filter. These difficulties occurred with particulate penetration above 0.10 lb/MBtu, which could reduce reagent utilization to 80percent. These results are attributable to inhibited limestone dissolution due to accumulation of an aluminum/fluoride compound. For both lowsulfur and simulated high-sulfur test conditions, allowing wastewater discharge to purge aluminum/fluoride content restored performance to design levels. Particulate control efficiency also affected solid waste physical properties. The fabric filter/wet scrubber produced the lowest solid waste permeability (10^?8 cm/s). ESP operation at 1979 NSPS and pre-1971 NSPS ESPs increased solid waste permeability to 10^?7 and 10^?6 cm/s, respectively. These results are meaningful for SO₂ scrubbers both for new plants and for retrofit to units with pre-NSPS ESPs, and could become significant with the increasing trend to restricted water discharge.     

Laboratory testing of a continuous emissions monitor for hydrochloric acid

Continuous monitoring of exhaust flue gas has become a common practice in power plants in response to Federal Mercury and Air Toxics Standards (MATS) standards. Under the current rules, hydrochloric acid (HCl) is not continuously measured at most plants; however, MATS standards have been proposed for HCl, and tunable diode laser (TDL) absorption spectroscopy is one method that can be used to measure HCl continuously. The focus of this work is on the evaluation and verification of the operation performance of an HCL TDL over a range of real-world operating environments. The testing was conducted at the University of California at Riverside (UCR) spectroscopy evaluation laboratory. Laboratory tests were conducted at three separate temperatures, 25ºC, 100ºC, and 200ºC, and two distinct moisture levels for the enhanced temperatures, 0%, (2 tests) and 4%, over a concentration range from 0 ppmv to 25 ppmv-m at each of the elevated temperatures. The results showed good instrument accuracy as a function of changing temperature and moisture. Data analysis showed that the average percentage difference between the ammonia concentration and the calibration source was 3.33% for varying moisture from 0% to 4% and 2.69% for varying temperature from 25 to 100/200ºC. An HCl absorption line of 1.742 μm was selected for by the manufacturer for this instrument. The Hi Tran database indicated that CO₂ is probably the only major interferent, although the CO₂ absorption is very weak at that wavelength. Interference tests for NO, CO, SO₂, NH₃, and CO₂ for a range of concentrations typical of flue gasses in coal-fired power plants did not show any interference with TDL HCl measurements at 1.742 μm. For these interference tests, CO₂ was tested at a concentration of 11.9% concentration in N₂ for these tests. Average precision over the entire range for all 10 tests is 3.12%.

Implications: The focus of this study was an evaluation of the operation performance of a tunable diode laser (TDL) for the measurement of hydrochloric acid (HCl) over a range of real-world operating environments. The results showed good instrument accuracy as a function of changing temperature from 25ºC to 200ºC and moisture from 0% to 4%. Such as an instrument could be used for continuous monitoring of exhaust flue gas in power plants once the Federal Mercury and Air Toxics Standards (MATS) standards have been fully implemented.     

Estimated washout coefficients for sulphur dioxide,nitric oxide,nitrogen dioxide and ozone

The washout coefficient of a gas in air is the fraction of it removed in unit time by rain below cloud base. The ‘apparent’ coefficients were estimated by statistically comparing hourly ground-level concentrations just before and at the onset of heavy, non-frontal rain. The concentrations were obtained from 5 y of continuous monitoring at a rural site.The coefficient (s⁻¹) estimated for SO₂ was (2.61 ± 0.14) × 10⁻⁵ times the rate of rainfall (mm h ⁻¹). This is completely consistent with a previously published value derived from the data from 10 rural sites for one year, and both estimates are consistent with published values of dissolved SO₂ in rainwater at another rural site, giving some confidence in the technique.The values of the coefficients estimated for NO and NO₂ were about 40 and 80%, respectively of that for SO₂. Some nitrite is found in rainwater, but not enough to explain the washout found. However, the analysers used would measure HNO₃ aerosols as NO₂, and these are very soluble. In addition, fast reactions are known which can convert oxides of nitrogen into soluble nitrates, present in sufficient concentration in rainwater.The statistical process leads to the coefficient estimated for O₃ being negative, implying that O₃ is produced at the time of rain. This is most probably due to the strong winds and turbulence which accompany heavy rain, giving replenishment of low-level O₃ from upper air levels where O₃ is normally produced. No systematic changes in the other gas concentrations accompany the changes in O₃ values.     

氢氧化钠-钢渣双碱法烧结烟气脱硫工艺

在鼓泡反应器中考察了氢氧化钠-钢渣双碱法烧结烟气脱硫的主要影响因素。结果表明,在温度为常温,钢渣反应时间为2 h,钢渣加入量为40 g,SO2进口浓度为2 400 mg/m3,钢渣粒径为200目以上,烟气流量为0.05 m3/h,循环液pH保持在7～8,Na+浓度为0.5 mol/L,循环液为500 mL的条件下,脱硫率可长时间保持在80%以上。同时,对钢渣-氢氧化钠双碱法烧结烟气脱硫机理进行了探讨。     

Effects of biodiesel made from swine and chicken fat residues on carbon monoxide,carbon dioxide,and nitrogen oxide emissions

The effects of two alternative sources of animal fat-derived biodiesel feedstock on CO₂, CO, NO_x tailpipe emissions as well as fuel consumption were investigated. Biodiesel blends were produced from chicken and swine fat waste (FW-1) or floating fat (FW-2) collected from slaughterhouse wastewater treatment processes. Tests were conducted in an unmodified stationary diesel engine operating under idling conditions in attempt to simulate slow traffic in urban areas. Significant reductions in CO (up to 47% for B100; FW-2) and NO_x (up to 20% for B5; FW-2 or B100; FW-1) were attained when using biodiesel fuels at the expense of 5% increase in fuel consumption. Principal component analysis (PCA) was performed to elucidate possible associations among gas (CO₂, CO, and NO_x) emissions, cetane number and iodine index with different sources of feedstock typically employed in the biodiesel industry. NO_x, cetane number and iodine index were inversely proportional to CO₂ and biodiesel concentration. High NO_x emissions were reported from high iodine index biodiesel derived especially from forestry, fishery and some agriculture feedstocks, while the biodiesel derived from animal sources consistently presented lower iodine index mitigating NO_x emissions. The obtained results point out the applicability of biodiesel fuels derived from fat-rich residues originated from animal production on mitigation of greenhouse gas emissions. The information may encourage practitioners from biodiesel industry whilst contributing towards development of sustainable animal production.

Implications: Emissions from motor vehicles can contribute considerably to the levels of greenhouse gases in the atmosphere. The use of biodiesel to replace or augment diesel can not only decrease our dependency on fossil fuels but also help decrease air pollution. Thus, different sources of feedstocks are constantly being explored for affordable biodiesel production. However, the amount of carbon monoxide (CO), carbon dioxide (CO₂), and/or nitrogen oxide (NO_x) emissions can vary largely depending on type of feedstock used to produce biodiesel. In this work, the authors demonstrated animal fat feasibility in replacing petrodiesel with less impact regarding greenhouse gas emissions than other sources.     

Monitoring Deposition of Nitrogen-Containing Compounds in a High-Elevation Forest Canopy

Measurements of airborne (gaseous and aerosol), cloud water, and precipitation concentrations of nitrogen compounds were made at Mt. Mitchell State Park (Mt. Gibbs, ~2006 m MSL), North Carolina, during May through September of 1988 and 1989, An annular denuder system was used to ascertain gaseous (nitric acid, nitrous acid, and ammonia) and particulate (nitrate and ammonium) nitrogen species, and a chemiluminescence nitrogen oxides analyzer was used to measure nitric oxide and nitrogen dioxide. Measurements of NO₃ ^? and NH₄ ⁺ ions in cloud and rain water samples were made during the same time period. Mean concentrations of gaseous nitric acid, nitrous acid, and ammonia were 1.14 μg/m³, 0.3 μg/m³, and 0.62 μg/m³ for 1988, and 1.40 μg/m³,0.3 μg/m³, and 1.47 μg/m³ for 1989, respectively. Fine particulate nitrate and ammonium ranged from 0.02 to 0.21 μg/m³ and 0.01 to 4.72 μg/m³ for 1988, and 0.1 to 0.78 μg/m³ and 0.24 to 2.32 μg/m³ for 1989, respectively. The fine aerosol fraction was dominated by ammonium sulfate particles. Mean concentrations of nitrate and ammonium ions in cloud water samples were 238 and 214 μmol/l in 1988, and 135 and 147 μmol/l in 1989, respectively. Similarly, the concentrations of NO₃ and NH₄ ⁺ in precipitation were 26.4 and 14.0 μmol/l in 1988, and 16.6 and 15.2 μmol/l in 1989, respectively. The mean total nitrogen deposition due to wet, dry, and cloud deposition processes was estimated as ~30 and ~40 kg N/ha/year (i.e., ~10 and ~13 kg N/ha/growing season) for 1988 and 1989. Based on an analytical analysis, deposition to the forest canopy due to cloud interception, precipitation, and dry deposition processes was found to contribute ~60, ~20, and ~20 percent, respectively, of the total nitrogen deposition.     

Biospheric influence on carbon dioxide measurements in Italy

The study concerning carbon dioxide measurements taken during the 1997, 1998 and 1999 summer campaigns at two different altitude stations and biospheric conditions are presented. The higher station (Mt. Cimone, 2165 m a.s.l.) is characterised by 360° free horizon and is located on a rocky mountain while the lower (Ninfa lake, 1550 m a.s.l.) is located inside the red spruce and beech forest. The different behaviour of CO₂ at the two mountain stations has been registered. It shows the strong effect of nighttime soil emission and vegetation respiration on CO₂ mixing ratio increases and of diurnal vegetative activity on CO₂ concentration decreases at the lower measurement site. The baseline character of the higher measurement site has been confirmed by comparison of CO₂ diurnal amplitudes recorded at the two stations.     

Measurement and Analysis of the Relationship between Ammonia,Acid Gases,and Fine Particles in Eastern North Carolina

Abstract

An annular denuder system, which consisted of a cyclone separator; two diffusion denuders coated with sodium carbonate and citric acid, respectively; and a filter pack consisting of Teflon and nylon filters in series, was used to measure acid gases, ammonia (NH₃), and fine particles in the atmosphere from April 1998 to March 1999 in eastern North Carolina (i.e., an NH₃?rich environment). The sodium carbonate denuders yielded average acid gas concentrations of 0.23 μg/m³ hydrochloric acid (standard deviation [SD] ± 0.2 μg/m³); 1.14 μg/m³ nitric acid (SD ± 0.81 μg/m³), and 1.61 μg/m³ sulfuric acid (SD ± 1.58 μg/m³). The citric acid denuders yielded an average concentration of 17.89 μg/m³ NH₃ (SD ± 15.03 μg/m³). The filters yielded average fine aerosol concentrations of 1.64 μg/m³ ammonium (NH₄ ⁺;SD ± 1.26 μg/m³); 0.26 μg/m³ chloride (SD ± 0.69 μg/m³), 1.92 μg/m³ nitrate (SD ± 1.09 μg/m³), and 3.18 μg/m³ sulfate (SO₄ ^2?; SD ± 3.12 μg/m³). From seasonal variation, the measured particulates (NH₄ ⁺,SO₄ ^2?, and nitrate) showed larger peak concentrations during summer, suggesting that the gas-to-particle conversion was efficient during summer. The aerosol fraction in this study area indicated the domination of ammonium sulfate particles because of the local abundance of NH₃, and the long-range transport of SO₄ ^2? based on back trajectory analysis. Relative humidity effects on gas-to-particle conversion processes were analyzed by particulate NH₄ ⁺ concentration originally formed from the neutralization processes with the secondary pollutants in the atmosphere.     

A Predictive Mechanism for Mercury Oxidation on Selective Catalytic Reduction Catalysts under Coal-Derived Flue Gas

Abstract

This paper introduces a predictive mechanism for elemental mercury (Hg⁰) oxidation on selective catalytic reduction (SCR) catalysts in coal-fired utility gas cleaning systems, given the ammonia (NH₃)/nitric oxide (NO) ratio and concentrations of Hg⁰ and HCl at the monolith inlet, the monolith pitch and channel shape, and the SCR temperature and space velocity. A simple premise connects the established mechanism for catalytic NO reduction to the Hg⁰ oxidation behavior on SCRs: that hydrochloric acid (HCl) competes for surface sites with NH₃ and that Hg⁰ contacts these chlorinated sites either from the gas phase or as a weakly adsorbed species. This mechanism explicitly accounts for the inhibition of Hg⁰ oxidation by NH₃, so that the monolith sustains two chemically distinct regions. In the inlet region, strong NH₃ adsorption minimizes the coverage of chlorinated surface sites, so NO reduction inhibits Hg⁰ oxidation. But once NH₃ has been consumed, the Hg⁰ oxidation rate rapidly accelerates, even while the HCl concentration in the gas phase is uniform. Factors that shorten the length of the NO reduction region, such as smaller channel pitches and converting from square to circular channels, and factors that enhance surface chlorination, such as higher inlet HCl concentrations and lower NH₃/NO ratios, promote Hg⁰ oxidation.

This mechanism accurately interprets the reported tendencies for greater extents of Hg⁰ oxidation on honeycomb monoliths with smaller channel pitches and hotter temperatures and the tendency for lower extents of Hg⁰ oxidation for hotter temperatures on plate monoliths. The mechanism also depicts the inhibition of Hg⁰ oxidation by NH₃ for NH₃/NO ratios from zero to 0.9. Perhaps most important for practical applications, the mechanism reproduces the reported extents of Hg⁰ oxidation on a single catalyst for four coals that generated HCl concentrations from 8 to 241 ppm, which covers the entire range encountered in the U.S. utility industry. Similar performance is also demonstrated for full-scale SCRs with diverse coal types and operating conditions.     

二氧化氯-接触催化氧化联合去除水中铁和锰

为了解决水体中铁锰季节性超标的问题,提出一种既能够减少化学试剂的使用又能有效去除铁锰的经济有效的方法。研究了单一方法(二氧化氯氧化法、接触催化氧化法)及两者联合对铁锰的去除效果,提出用二氧化氯氧化-锰砂过滤联合方法解决。研究表明,用ClO2氧化去除水中Fe2+的反应先发生、速率较快且效果较好,而与Mn2+反应则较慢并且不能完全转化为沉淀。单纯接触催化氧化法需要较长时间,过滤层才能达到稳定且较好的处理效果,培养过程中其除锰效果并不理想。两者联合时,利用过滤层的吸附作用去除部分铁锰,减少了氧化剂的使用。初期3个柱的除Mn2+效果都比较好,去除率均大于80%;然而采用石英砂或纤维束滤料的滤柱去除Mn2+的效果随时间变差,但采用锰砂的除锰效果在实验期间始终维持在较高水平。     

改性花生壳对Cd(Ⅱ)和Pb(Ⅱ)的吸附机理

以前期制得改性块状花生壳为对象,测定改性花生壳等电点,考察离子强度对改性花生壳吸附Cd2+和Pb2+的影响、吸附前后吸附质溶液pH变化情况及蒸馏水、NaCl、HNO3、柠檬酸和EDTA 5种解吸液对Cd2+和Pb2+的解吸效果,并通过X-射线光电子能谱仪和傅里叶变换红外光谱仪对吸附前后的改性花生壳进行表征,推测并证实了改性花生壳对Cd2+和Pb2+可能的吸附机理。结果表明,改性花生壳对Cd2+和Pb2+可能的吸附机理是:Cd2+是通过外层络合、离子交换和内层络合的联合作用被吸附的;Pb2+主要是与改性花生壳上的O、N等活性基团发生内层络合;此外,改性花生壳表面生成的二氧化锰对Cd2+和Pb2+的吸附也起到一定的作用。     

Land-surface exchange in a chemically-reactive system; surface fluxes of HNO3, HCl and NH3

Vertical gradients from 0.25 to 2 m of NH₃, HNO₃ and HCl and associated aerosol components have been measured in the field above various surfaces in eastern England. The data have been examined to identify the effect, if any, of chemical reaction processes upon the observed vertical profiles. It is concluded that chemical transformations are too slow to influence concentration gradients and thus the surface exchange process. Assuming chemically conservative behaviour, deposition velocities for HNO₃ and HCl have been calculated; these lie within the range 0.4–7.7 cms⁻¹ and 0.4–6.9 cms⁻¹ for HNO₃ and HCl, respectively. Estimation of resistances to deposition indicates a negligible surface resistance for both species. Fluxes of ammonia were predominantly upward from the ground with a mean value of 0.031 μg m⁻²s⁻¹ which is consistent both with an emission inventory of the U.K. and with the measured atmospheric concentration of NH₃.