ISSN:0010-2202    

DOI:10.1080/00102209408951862

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Experiments were performed on an 82 kW (280,000 Btu/hr) refractory-lined horizontal tunnel combustor to examine the aerosol particle size distribution (PSD) produced by simulated nickel, cadmium, and lead wastes injected into an incineration environment. Metal constituents in the form of aqueous solutions of nickel, cadmium, and lead nitrates were introduced as secondary sprays within a swirl stabilized natural gas diffusion flame. Aerosol size distributions were measured at stack locations using a differential mobility particle sizer and a cascade impactor as functions of combustor temperature and waste chlorine content. Cadmium and lead produced emissions of submicron metal aerosols with mass mean diameters of approximately 0.2 μm. These submicron aerosol PSDs are consistent with a mechanism of metal vaporization followed by nucleation, condensation, and coagulation prior to sampling. Nickel also formed submicron particles, but the PSD was not generally consistent with a vaporization mechanism. With chlorine present, the PSDs for all three metals were similar in shape, and could be interpreted in light of the effect of chlorine to enhance and prolong the presence of metals in the vapor phase, and leading to the sampling of a less mature aerosol than that seen under baseline conditions. The effect of chlorine on nickel partitioning was particularly significant, and is consistent with vapor pressure predictions.

ISSN:0010-2202    

DOI:10.1080/00102209408951863

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A comprehensive model to predict the lead aerosol size distribution for typical incinerator operating conditions has been developed. Using the feed rate and incinerator operating conditions, the metal transfer rate to the gas phase is determined using a mass transfer calculation. A detailed, multicomponent aerosol dynamic model is developed accounting for the chemical kinetics and applied to a lead-oxygen-chlorine system. Reasonable agreement is obtained between model predictions and experimental data from controlled studies for different aspects of the model. The effect of chlorine on the resulting aerosol size distribution has been determined. The role of the transfer rates of lead to the gas phase on the resulting size distributions have also been determined. Simulations have been performed for typical conditions encountered in a waste incinerator.

ISSN:0010-2202    

DOI:10.1080/00102209408951864

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

To facilitate the understanding of the fate of metals during incineration the speciation of metals is critical. Thus, an experimental study to determine the speciation of metals during incineration was performed. Aqueous metal salts of arsenic, cadmium, chromium, and lead were injected into a laboratory reactor, post-flame. Aerosols were captured on a glass fiber filter by isokinetic sampling. Reactor temperature was varied from 600 to 1100°C and the stoichiometric ratio was varied from 0.95 to 1.25. The Reference Intensity Method (RIM) of quantitative X-ray diffraction analysis combined with X-ray transmission was utilized to determine the speciation of aerosols removed from the combustion environment.

ISSN:0010-2202    

DOI:10.1080/00102209408951865

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The need for kinetic data on individual reactions to develop combustion control strategies for alleviation of toxic metal species production is discussed. In this work such data are obtained at realistic incinerator temperatures. Measurements on the Cr + HCl reaction, made by both the High-Temperature Fast-Flow Reactor (HTFFR), and Metals High-Temperature Photochemistry (Metals-HTP) techniques, are found to be in good agreement. The other reactions were studied by the Metals-HTP technique only. These techniques are briefly described. The N2O and Cl2results are compatible with O and Cl abstraction, respectively, while the HCl mechanism needs further study. These three reactions are independent of pressure. The previously studied O2reaction involves a pressure-independent abstraction, and a pressure-dependent addition component. The following rate coefficient expressions in cm3molecule−1s−1were obtained: Cr + HClk(811-1449 K) = 1.6 × 10−12(T/K)0.74exp(−5802 K/T); Cr + Cl2k(277-344K) = 2.1 × 10−11(T/K)0.69exp(−396K/T);Cr + N2Ok(278−1150K) = 2.2 × 10−12(T/K)0.55exp(−2851 K/T). The data from the latter reaction agree well with measurements elsewhere at the temperature extremes to yield an overall recommendation ofk(278-2570K) = 3.2 × 10−12T0.50exp(−2605 K/T)cm3molecule−1;s−1this temperature dependence is shown to be in good agreement with that predicted by a recently developed semi-empirical theoretical method.

ISSN:0010-2202    

DOI:10.1080/00102209408951866

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Comprehensive product yield determinations from the high-temperature, gas-phase pyrolysis of trichloroethene (C2HCl3) using two fused silica tubular flow reactors coupled to in-line gas chromatographic-mass spectrometry analyses are reported. Initial decomposition was observed at 1000 K with formation of HCl and C2Cl2. Pronounced molecular growth was observed at higher temperatures as evidenced by the formation of C2Cl2, C4Cl4, and C6Cl6(cy) as major (≥5mole%) products and C4Cl2, C4Cl6, C6HCl5(cy), C8Cl6(cy), C8Cl8(cy), C10Cl8(cy), and C12Cl8(cy) as minor (≤5mole%) products.

ISSN:0010-2202    

DOI:10.1080/00102209408951867

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A detailed chemical kinetic mechanism describing the combustion of CH2Cl2under fuel-rich conditions has been developed and tested. The mechanism involves the participation of 82 stable and radical species in 680 reversible elementary reactions and provides a reasonable prediction of species concentration profiles measured previously in atmospheric-pressure, premixed, one-dimensional laminar flat-flames of CH2Cl2/CH4/O2/Ar mixtures (Qun and Senkan 1990). For the case of major species, the agreement between the model and experimental data was good. However, for minor combustion intermediates, the agreement was satisfactory considering the originality of the reaction mechanism. The major reaction pathways responsible for the formation and destruction of the reactants, intermediates and products have been identified via the calculation of reaction rates.

ISSN:0010-2202    

DOI:10.1080/00102209408951868

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Pyrolysis of methylene chloride-methane mixture (6.7% & 26.7%) in argon bath were studied over the temperature range of 1023-1323°K at atmospheric pressure, residence times ranging from 0.1 to 2 seconds, and the CH2Cl2:CH4:Ar of 6.7:26.7:66.6 molar percent, respectively. Heterogeneous (reactor wall) reactions were (bund to be insignificant in reactors of lower surface to volume ratios (larger diameter). Major products analyzed at temperatures below 1173°K include C2H4, C2H6, CH3Cl, C6H6, and HCl. Trace amounts (≤ 1%) of CCl4, C2H2Cl2, C2HCl3, C2Cl4were identified at lower reaction temperatures ( < 1123°K). An initial elementary reaction mechanism (74 step) was developed and shown to fit the data very well.

ISSN:0010-2202    

DOI:10.1080/00102209408951869

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Polychlorinated-dibenzodioxins (PCDD's) and polychloro-dibenzofurans (PCDF's) are considered to be formed in combustion environments below 600°C, where an important reactive species is OH Thermodynamic properties, ▴Hf0(298 K),S0(298 K) andCp(T) are calculated in this study for selected poly-chlorinated biphenyls (PCB's), dibenzofurans (PCDF), dibenzodioxins (PCDD) and corresponding radical intermediates resulting from hydroxyl radical addition reactions. These thermodynamic properties are combined with thermochemical kinetic analysis and are used to examine potentially important pathways to homogeneous PCDD and PCDF formation. Analysis of the reaction pathways show several likely routes to formation of chlorinated PCDF's and PCDD's involving unimolecular HCl elimination or loss of Cl, which occur following hydroxy radical addition at Cb-Cl sites. Equilibrium constants for these reactions are calculated using the estimated thermodynamic properties, and strongly favor formation of the PCDD and PCDF products. The addition reactions of OH resulting in PCDF/PCDD formation compete with addition of OH radical at fused ring sites, which are responsible for ring cleavage and destruction of these species.

ISSN:0010-2202    

DOI:10.1080/00102209408951870

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

An experimental study of reactions and stable products from pyrolysis of Freon 113 (1,1,2-trichloro trifluoro ethane) under inert and hydrogen rich conditions has been performed over the temperature range 923-1098 K. A tubular flow reactor was fed a mixture of 2% Freon 113 with the balance helium or helium/hydrogen mixtures. Results show this chlorofluorocarbon to be relatively stable to decomposition in n inert atmosphere, requiring temperatures in excess of 1048 K to achieve greater than 99% conversion to products for 2 seconds reaction time. Products of self reaction include CF2Cl2, C2F3Cl, C2F3Cl, and CF3CCl3. Addition of small amounts of H2was shown to dramatically accelerate decomposition and shift the reaction products to a complex mixture of hydrochlorofluorocarbons (HCFC's), hydrofluorocarbons (HFC's) and hydrocarbons (HC's). At 923 K and 2 seconds reaction time, a mixture of 2% Freon 113 in helium results in less than 10% conversion, however, the addition of hydrogen at a mole ratio to Freon 113 of 7, results in nearly 90% conversion. Hydrocarbon products appear to represent as much as 30% of the freon feed under some conditions, and this defluorination is only favored at higher temperatures. Reaction under reducing conditions was shown to produce significant amounts of hydrogen fluoride (HF) and hydrogen chloride (HCl) gas, while inert conditions appeared to produce what is believed to be such inter-halogens as CIF,CIF3and CIF5.

ISSN:0010-2202    

DOI:10.1080/00102209408951871

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor