垃圾焚烧飞灰熔融污染物排放研究

在40℃-1400℃,升温速率为10℃/min,N2气氛下,利用热重分析仪,研究了飞灰熔融过程中污染物排放特点。实验发现,飞灰熔融过程中有分布在800℃-1000℃和1000℃-1200℃的两个主要失重峰;进一步在小试实验装置上收集并测定了熔融失重挥发物及气体污染物,讨论熔融过程中的质量分布规律。研究结果表明,飞灰熔融过程中在上述两个温度段的重金属和气体污染物均超标,如果处理不当会造成严重的二次污染。     

垃圾焚烧飞灰基本特性研究

以三个正在运行的垃圾发电厂的除尘器飞灰为研究对象,实验测出它们的化学组成、热灼减率、灰熔点等物化特性和浸出毒性、腐蚀性等有害特性,对三种灰样的特性进行了对比、分析。结果表明,飞灰的物化特性主要受飞灰中MgO、CaO、SiO2和CaCl2等几种主要成分质量分数的影响。MgO和Al2O3质量分数较高而CaCl2质量分数较低的飞灰其灰熔点相对较高;CaO和CaCl2质量分数较高的飞灰其水分和热灼减率也相对较高;SiO2质量分数较高的飞灰其重金属的浸出率相对较低;CaO和Al2O3等碱性氧化物质量分数较高的飞灰其浸出液的pH值相对较高。     

Thermochemistry of vitrified waste incineration ashes crystallization

Thermochemistry of crystal phase formation in vitrified municipal and hospital waste combustion ash and Ca, Fe pyroxene crystallization mechanism are presented. Pyroxene structure is capable of accumulate heavy metals and toxicants contained in ash. Due to this vitrification and crystallization is one of most effective method of immobilization dangerous contaminant of waste.     

Contribution of nitrification and denitrification to nitrous oxide emissions from soils after application of biogas waste and other fertilizers

The attribution of nitrous oxide (N₂O) emission to organic and inorganic N fertilizers requires understanding of how these inputs affect the two biological processes, i.e. denitrification and nitrification. Contradictory findings have been reported when the effects of organic and inorganic fertilizers on nitrous oxide emission were compared. Here we aimed to contribute to the understanding of such variation using ¹⁵N‐labelling techniques. We determined the processes producing N₂O, and tested the effects of soil moisture, N rates, and the availability of organic matter. In a pot experiment, we compared soil treated with biogas waste (BGW) and mineral ammonium sulphate (Min‐N) applied at four rates under two soil moisture regimes. We also tested biogas waste, conventional cattle slurry and mineral N fertilizer in a grassland field experiment. During the first 37 days after application we observed N₂O emissions of 5.6 kg N₂O‐N ha^?1 from soils supplied with biogas waste at a rate of 360 kg N ha^?1. Fluxes were ca. 5‐fold higher at 85% than at 65% water holding capacity (WHC). The effects of fertilizer types and N rates on N₂O emission were significant only when the soil moisture was high. Organic fertilizer treated soils showed much higher N₂O emissions than those receiving mineral fertilizer in both, pot and field experiment. Over all the treatments the percentage of the applied N emitted as N₂O was 2.56% in BGW but only 0.68% in Min‐N. In the pot experiment isotope labelling indicated that 65–95% of the N₂O was derived from denitrification for all fertilizer types. However, the ratio of denitrification/nitrification derived N₂O was lower at 65% than at 85% WHC. We speculate that the application of organic matter in conjunction with ammonium nitrogen first leads to a decrease in denitrification‐derived N₂O emission compared with soil receiving mineral fertilizer. However, at later stages when denitrification becomes C‐limited, higher N₂O emissions are induced when the soil moisture is high. Copyright © 2009 John Wiley & Sons, Ltd.     

Congener-specific identification of bromochlorobenzenes and bromotoluenes in effluents from municipal waste incineration plants

Summary Bromochloro- and bromomethylbenzenes have been collected by a condensation and impinger absorption technique from flue gas of municipal waste incineration plants. After extractive enrichment with dichloromethane the congeners have been separated by high resolution capillary gas chromatography using methylphenyl- and methyl-cyanopropylsilicon phases with electron capture (ECD) and mass-selective detection (MSD). The monobromomethylbenzenes and the monobromotrichloro- to monobromopentachlorobenzenes were predominant. The corresponding dibromochlorobenzenes were found at a level of less than 1% of the monobromo congeners. The amounts of the monobromochlorobenzenes were found to lie in the lower g/Nm³ range, the same as for the polychlorobenzenes.

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Kongeneren-spezifische Identifizierung von Brom-chlorbenzolen und Brom-methylbenzolen im Reingas von Müllheizkraftwerken

     

Biphonon dynamics in crystals: Nitrous oxide

Coherent picosecond excitation and probe techniques are employed to measure the dephasing times of the very weak 2v₂ two-phonon resonance in solid N₂O as a function of temperature. T₂ times are also obtained for the v₁ one-phonon transition which is in feeble Fermi interaction with 2v₂.     

Thermal properties of vitrified llw hospital waste incineration ash

The low level nuclear waste (LLW) resulting from the use of radioactive isotopes in medicine, industry, laboratories, and other purposes can be immobilized by vitrification, using methods applied in the nuclear power industry. Borosilicate glass is providing the very suitable medium for the majority of the species present in these wastes. Management of LLW waste begins with combustion reducing their amount. The paper presents the results of model studies of vitrification of hospital waste by incorporating it into the composition of boro-aluminosilicate glass, similar to those used in nuclear power industry. The proposed borosilicate waste glass composition was: SiO₂-56.0, B₂O₃-15.0, Na₂O-21.0, and Al₂O₃-8.0 (mass %). The ashes were mixed in different amount with the glass frit and then remelted to obtain homogenous melt which was vitrified. The influence of the main ash components on the thermal properties of the vitrified waste was studied using DSC and heating microscopy methods. The glass transformation, crystallization and melting temperatures, and Hruby glass stability against crystallization parameter were determined. The correlations between ΔC _p , T _g, and K _H were observed and discussed.     

Pretreatment of special samples from waste incineration for analysis by total reflection X-ray fluorescence

The use of ion exchange processes as sample pretreatment steps for TXRF analysis has been studied in order to improve the detection sensitivity or to provide information on the speciation of individual elements. EDTrA cellulose proved to be an excellent exchange material for heavy metal enrichment, for Hg separation, and for elimination of alkaline and earth-alkaline salts. Sephadex SP C25 and QAE A25 can be used to separate Pb and As and to verify the ionic state of the elements V, Cr, As, Se, Mo, Sb and W.     

Hydrothermal solidification of municipal solid waste incineration fly ash

Hydrothermal solidification of municipal solid waste incineration (MSWI) fly ash has been conducted under saturated steam pressure at 200 °C for up to 48 h with quartz addition. To enhance the strength of solidified specimens further, the raw fly ash was pre-treated by water-washing and mixed with NaOH solution (2 M) as reaction solvent. Experimental results showed that curing time and temperature had significant effects on strength development. Strength development was found to be mainly due to tobermorite formation, and addition of quartz and NaOH solution promoted tobermorite formation. The raw fly ash could also be used as an additive to solidify MSWI bottom ash, and with raw fly ash addition (10%) the flexural strength of solidified specimens reached more than 21 MPa, suggesting high potential to recycle 100% MSWI ash (e.g. as 10% fly ash + 90% bottom ash). Leaching tests were conducted to determine amounts of heavy metals dissolved from solidified specimens. The results showed that under the hydrothermal conditions of this study, leaching of heavy metals was very low. As such, the hydrothermal processing method might have high potential for recycling/reusing MSWI fly ash on a large scale.     

Nitrous oxide tetramer has two highly symmetric isomers

Infrared spectra of the nitrous oxide tetramer, (N(2)O)(4), are studied in the region of the N(2)O ν(1) fundamental band (～2200 cm(-1)). The spectra are observed using a tunable diode laser to probe a pulsed supersonic jet expansion. Parallel (ΔK = 0) bands are observed for the previously observed isomer of (N(2)O)(4), which is confirmed by isotopic substitution to have an oblate symmetric rotor structure with D(2d) symmetry. A distinct new isomer of (N(2)O)(4) is observed by means of a perpendicular (ΔK = ±1) band. It has a prolate symmetric rotor structure with S(4) symmetry. These isomers represent two distinct, but almost equally favorable, ways of bringing together a pair of nonpolar N(2)O dimers to form a tetramer. It is not clear at present which one represents the true ground state.     

Leaching of glass components and surrogate nuclides from glassy waste forms for radioactive incineration ash

Three kinds of soil, collected in various places (in northwestern and southeastern Poland and near Chernobyl) were used as a subject of sequential extraction and plutonium distribution study. The modified method of Tessier was applied to separate readily available, carbonate, organic, Fe/Mn oxide and residual fractions. Plutonium isotope activity in soil as well as in particular separated fractions was determined by means of alpha spectrometry. The method of plutonium separation and purification for alpha-spectrometric measurements was modified according to the chemical properties of the extracted fraction. It was found that the major part (about 90%) of ^239,240Pu is bound to organic and Fe/Mn oxide fractions (in uncultivated soil samples of northwestern Poland and Chernobyl). In soil samples coming from river valley (southeastern Poland) almost equal amounts of plutonium are distributed between the available, organic and residual fractions.     

Hydrotalcite-derived Co-containing mixed metal oxide catalysts for methanol incineration

The Co–Mg–Al mixed metal oxides were prepared by calcination of co-precipitated hydrotalcite-like precursors at various temperatures (600–800 °C), characterised with respect to chemical (AAS) and phase (XRD) composition, textural parameters (BET), form and aggregation of cobalt species (UV–vis-DRS) and their redox properties (H₂-TPR, cyclic voltammetry). Moreover, the process of thermal decomposition of hydrotalcite-like materials to mixed metal oxide systems was studied by thermogravimetric method combined with the analysis of gaseous decomposition products by mass spectrometry. Calcined hydrotalcite-like materials were tested as catalysts for methanol incineration. Catalytic performance of the oxides depended on cobalt content, Mg/Al ratio and calcination temperature. The catalysts with lower cobalt content, higher Mg/Al ratio and calcined at lower temperatures (600 or 700 °C) were less effective in the process of methanol incineration. In a series of the studied catalysts, the best results, with respect to high catalytic activity and selectivity to CO₂, were obtained for the mixed oxide with Co:Mg:Al molar ratio of 10:57:33 calcined at 800 °C. High activity of this catalyst was likely connected with the presence of a Co–Mg–Al spinel-type phases, containing easy reducible Co³⁺ cations, formed during high-temperature treatment of the hydrotalcite-like precursor.     

Nitrous oxide: Saturation properties and the phase diagram

The experimental values of the coordinates of the triple point and of the critical point of nitrous oxide registered in the literature were assessed and those judged as most reliable have been selected. Empirical equations have been found for the vapour pressure, sublimation and fusion curves. The virial coefficients and saturation properties as functions of temperature along the equilibrium curves are described by reduced equations. They were used in arriving at the molar enthalpies at the triple point and the normal boiling temperature. Equations for the sublimation and fusion curves resulting from the exactly integrated Clapeyron equation compare favourably with the results from the empirical treatment and the experimental data.     

高岭土对焚烧烟气中Pb、Cd排放的控制特性研究

采用流化床焚烧炉进行焚烧实验,研究了烟气中颗粒物形态Pb和Cd的排放规律以及炉内添加高岭土粉末对Pb、Cd排放的影响。用低压冲击器分级采集颗粒物,原子吸收分光光度计检测Pb、Cd浓度,用扫描电镜/X射线衍射/能谱仪观察高岭土吸附重金属前后表面形貌和反应物的种类并检测表面元素分布。结果表明,PM10中90%以上的Pb和85%以上的Cd分布在亚微米颗粒物中;在焚烧炉内,Pb比Cd更易于向PM10中迁移。高温下高岭土与重金属Pb、Cd蒸气反应而产生共晶融化,随温度升高融化量逐渐增加。共晶融化可以促使颗粒相互黏附,促进亚微米重金属向粗颗粒中迁移。添加高岭土可以有效控制亚微米Pb、Cd排放,对亚微米Pb的最高吸附效率达83%,对亚微米Cd的最高效率达50%。高岭土对Pb吸附效率顺序为950℃1000℃850℃900℃;高岭土与Cd反应所需的温度较高,直至1000℃时才具有明显吸附效果。     

Nitrous oxide gas phase chemistry during silicon oxynitride film growth

N₂O gas phase chemistry has been examined as it relates to the problem of ultrathin film silicon oxynitridation for semiconductor devices. Computational and analytical kinetics studies are presented that demonstrate: (i) there are 5 main reactions in the decomposition of N₂O, (ii) the gas composition over a 1000K – 1400K temperature range is as follows: N₂ (65.3 − 59.3%); O₂ (32.0 − 25.7%); NO (2.7 − 15.0%), (iii) the N₂O decomposition obeys first-order kinetics, and the initial rate law for N₂O decomposition is R_init = 2k₁[N₂O] which rapidly changes to R_late = k₁[N₂O] as the reaction proceeds, (iv) the branching ratio for the two reactions: N₂O + O → 2NO and N₂O + O → N₂ + O₂ lies between 0.1 and 0.5 (0.1 < < 0.5) and varies with conditions, (v) the apparent activation energy for the decomposition of N₂O is 2.5 eV/molecule (2.4×10² kJ/mole), (vi) the rate law for NO formation is R = k₁N₂O], and (vii) the apparent activation energy for the formation of NO is 2.4 eV/molecule (2.3×10² kJ/mole).     

Nitrous oxide dimer: observation of a new polar isomer

Spectra of the nitrous oxide dimer (N2O)2 are studied in the region of the N2O nu1 fundamental band around 2230 cm-1 using a rapid-scan tunable diode laser spectrometer to probe a pulsed supersonic jet expansion. The previously known band of the centrosymmetric nonpolar dimer is analyzed in improved detail, and a new band is observed and assigned to a polar isomer of (N2O)2. This polar form of the dimer has a slipped parallel structure, rather similar to the slipped antiparallel structure of the nonpolar form but with a slightly larger intermolecular distance. The accurate rotational parameters determined here should enable a microwave observation of the polar N2O dimer. The need for a modern ab initio investigation of the N2O-N2O intermolecular potential energy surface is emphasized.     

Chromatographic methods for analysis of ethylene oxide in emissions from stationary sources

Chromatographic methods of analysis with FID detection are investigated for quantitation of ethylene oxide in emissions from production plants and commercial sterilizers. A column with a stationary phase of 3% Carbowax 20M on 80-100 Chromosorb 101 is used to separate ethylene oxide from potential interferents in emissions from production plants. Two columns are found that allow accurate quantitation of ethylene oxide in emissions from commercial sterilizers. Both columns elute ethylene oxide before Freon 12, the diluent in the sterilization process. One column has a stationary phase of 1% SP-1000 on 60-80 Carbopack B and can be used to quantitate ethylene oxide over a wider range of concentrations than the other column, 5% Fluorcol (a fluorinated oil) on 60-80 Carbopack B. Graphitized carbon, the solid support in both of these columns, appears to participate in the ethylene oxide-Freon 12 separation with the SP-1000 column but not with the Fluorcol column.     

Efficient reduction of NOx emissions from waste double-base propellant in co-pyrolysis with pine sawdust

Co-pyrolysis technology containing biomass offers remarkable advantages in reducing NO_x emissions economically and efficiently. In this work, it was innovatively introduced to solve the problem of excessive NO_x emission during the incineration of waste energetic materials (EMs). The kinetics and NO_x emission characteristics of waste double-base propellant (DP), pine sawdust (PS), and their mixtures with different ratios during pyrolysis were investigated by thermogravimetric analysis and fixed-bed experiments. The results showed that there was a significant interaction between DP and PS. Kinetic analysis by Friedman and Kissinger-Akahira-Sunose (KAS) methods demonstrated that the average activation energies of the mixtures with different ratios were smaller than that of DP, indicating that the addition of PS improved the reactivity of co-pyrolysis. In addition, the fixed-bed experiment determined that the lowest NO_x emission was achieved during DP pyrolysis alone at 900 ℃. Co-pyrolysis at this temperature was found to have synergistic effects of reduced NO_x emissions for different ratios of mixtures. The best synergistic effect was achieved at the mixing ratio of 60 wt% DP and 40 wt% PS, resulting in a 72.11 % reduction in actual NO_x emissions compared to the expected value. This study provides a new direction and powerful data support for the clean, efficient and economic treatment of waste EMs, especially for practical engineering strategies.     

Fast-cycle trace analysis of dioxin in flue gas. Monitoring of the incineration of dioxin-containing waste from seveso

The fast trace analysis method used to monitor 2,3,7,8-TCDD in stack gas during the incineration of the waste from Seveso is described. The sampling of volatile organic compounds from flue gases, distributed between all three aggregation states, is based on a micromethod developed for the trace analysis of water using a specially dimensioned adsorptive charcoal filter (1.5 mg charcoal). In conjunction with subsequent GC/MS measurements the rapid “fast cycle trace analysis” ensured specific 2,3,7,8-TCDD detection down to 100 pg per m³ flue gas in cycle times of about 1–2 hours.