摘要:

ABSTRACTThe failure to properly manage hazardous materials, which are a natural outgrowth of our industrial society, poses a threat to the environment and limits our country's competitiveness. There has been a great deal of activity in hazardous waste cleanup which addresses past mistakes, but the long term solution to this escalating problem depends upon successful research into additional solutions including (i) minimization of hazardous materials production during manufacturing operations, (ii) regeneration of useful materials from wastes, and (iii) the rendering of useless hazardous substances harmless. The National Science Foundation has a role to play in achieving these solutions, in coordination with other federal agencies.

ISSN:0882-5696    

DOI:10.1089/hwm.1990.7.1

年代:1990

数据来源: MAL

摘要:

ABSTRACTThe burning rates as well as the extinction droplet and flame diameters of droplets of n-alkanes and chlorinated alkanes have been experimentally determined as functions of system pressure and ambient oxygen concentration in environments of reduced pressure. By substituting these empirically-determined extinction data into a modified asymptotic theory of droplet extinction, the overall activation energies for the oxidation of these compounds have been determined. Various combustibility ranking indices are proposed based on these overall kinetic constants empirically-determined in diffusive media.

ISSN:0882-5696    

DOI:10.1089/hwm.1990.7.7

年代:1990

数据来源: MAL

摘要:

ABSTRACTRecent progress is reviewed in the development of laser-based resonance ionization spectroscopy for the continuous monitoring of toxic emissions from municipal and hazardous waste incinerators. Resonance ionization spectra obtained for chlorinated benzenes, ethylenes, and napthalenes in a jet-cooled molecular beam with time-of-flight mass selection exhibit the sensitivity and selectivity reguired for real-time CHC monitoring at the part-per-billion level. The use of resonance ionization spectroscopy forin situmeasurements of the density profiles of radical intermediates in laboratory flames may provide a useful supplement for conventional molecular beam mass spectrometry in studies of CHC combustion mechanisms. The radicals H, O, CH3, HCO, CCl, ClO and CHCl2, of importance in the combustion of CHCs, have been recently detected with resonance ionization methods.

ISSN:0882-5696    

DOI:10.1089/hwm.1990.7.21

年代:1990

数据来源: MAL

摘要:

ABSTRACTWhen containerized liquid wastes, bound on sorbents, are introduced into a rotary kiln in a batch mode, transient phenomena involving vaporization of the waste, and mass and heat transfer into the sorbent can allow a rapid release of waste vapor into the kiln environment, a displacement of excess oxygen from the primary flame, and formation of a "puff." This transient puff then travels to the afterburner and, if it is too large, can result in a failure mode of the incinerator system. Previous experimental work by the U.S. Environmental Protection Agency on a specially designed Rotary Kiln Incinerator Simulator has shown that, for liquid wastes, puffs are very easily generated, and that their magnitudes and intensities increase with increasing kiln temperature and increasing kiln rotation speed. This paper presents a theoretical model which was designed both to provide insight into why this is so, and to predict how the generation of puffs in general is controlled by waste properties, sorbent properties, and kiln operating parameters.

ISSN:0882-5696    

DOI:10.1089/hwm.1990.7.41

年代:1990

数据来源: MAL

摘要:

ABSTRACT:Chemical structures of atmospheric-pressure, fuel-rich (sooting), premixed, laminar flames of CH2Cl2and CH4have been investigated using a flat-flame burner as a function of equivalence ratio and fuel ratio (CH2Cl2/CH4). Species mole fraction profiles were determined by hot-water-cooled micro-probe coupled to an on-line gas Chromatograph/ mass spectrometer. In addition to those of the reactants, the mole fraction profiles for CO, CO2, HCl, H2O, CH3Cl, CHCl3, C2H2, C2H4, C2H6, 1,2-C2H2Cl2, 1,1-C2H2Cl2, C2HCl3, C2H3Cl, 1,1,2,2-C2H2Cl4, C4H4, C4H2, C6H6and CgH5Cl were determined. The roles of these species, in view of the current ideas of the mechanism of CH2Cl2combustion are discussed.

ISSN:0882-5696    

DOI:10.1089/hwm.1990.7.55

年代:1990

数据来源: MAL

摘要:

ABSTRACTAlmost any combination of C, H, O, and Cl can yield some polychlorinated dioxins/furans under suitable conditions of time and temperature. The quantities formed in incinerators, ng m−3or ng g−1, need to be explained in terms of time/temperature regimes relevant to those units. Current evidence suggests that surface catalyzed reactions at relatively low temperatures (250-400°C) may play an important role. This paper reviews relevant evidence from incinerators, laboratory combustors, and surface-catalyzed experiments using single precursors. A global kinetic model is proposed and assumptions and parameters are discu

ISSN:0882-5696    

DOI:10.1089/hwm.1990.7.73

年代:1990

数据来源: MAL

摘要:

ABSTRACTSolids are important contributers to the United States hazardous wastes problem. Hazardous solids include several million tons yearly of residues from industrial processing and treatment of other wastes, and millions to billions of tons of contaminated soils found in numerous, and widely distributed abandoned dump sites. Incineration is an attractive technology for decontaminating hazardous solids, but realization of its potential requires improved public acceptance which can come from better technical understanding. Organic solids fed to an incinerator are thermally decomposed (pyrolyzed, devolatilized) into three products requiring burnout: gases and liquids (volatiles) and a solid residue (char). This paper describes how solids pyrolysis and further, so-called secondary reactions of newly formed volatiles (e.g. cracking, partial oxidation) can contribute to desired and undesired effects within incineration chambers, e.g. high destruction efficiencies for targetted wastes, or generation of undesired by-products. It is shown that incinerator design, operation, and performance monitoring will benefit from better quantitative understanding of devolatilization-related phenomena. Important issues are how solids pyrolysis and volatiles secondary reactions are affected by properties of the raw waste, and by incinerator operating conditions (e.g. temperature, heating rate, treatment time, local oxygen partial pressure). Research methods for obtaining this information are discussed, typical results are illustrated, and research challenges and opportunities in solid wastes pyrolysis are noted.

ISSN:0882-5696    

DOI:10.1089/hwm.1990.7.89

年代:1990

数据来源: MAL

摘要:

ABSTRACTThermal Reactions of Chlorobenzene in hydrogen and in hydrogen - oxygen mixtures were studied in tubular flow reactors at 1 atmosphere pressure and temperatures between 833 to 1275 K. 99% conversion of chlorobenzene and dichlorobenzene in hydrogen, 2 seconds residence time, reguired temperatures of 1198 K and 1174 K respectively, while in mixtures containing small guantities, less than 4%, O2eguivalent conversion was observed to occur at 935 K. Major products in both reaction systems were benzene, carbon solids and HCl, with CH4and C2H6also present in low concentrations. Minor products included toluene, cyclopentadiene, biphenyls, C2H4, C2H2with CO and CO2also observed when oxygen was present.Decomposition in the presence of hydrogen was observed to occur much faster than pyrolysis in an inert gas. In addition, the presence of hydrogen accelerates the destruction of chlorinated aromatics via a catalytic gas phase process. The specific reaction responsible for this catalytic conversion is a displacement of the aromatic chlorine by atomic hydrogen. Chlorobenzene dissociation to Cl + phenyl radical is the initiation step in He and in H2, with: Cl + H2-->HCl + H rapidly continuing the chain. The slightly more rapid conversion of dichlorobenzene is attributed to the higher chlorine content and a somewhat weaker carbon - chlorine bond.O2, if present, can initiate the chain mechanism by reaction with hydrogen to form HO2+ H. This explains the lower temperature reguired for conversion when O2is present. The dissociation of chlorobenzene to phenyl and chlorine atom is not as thermodynamically favorable so that the oxygen/hydrogen system shows much faster reaction.

ISSN:0882-5696    

DOI:10.1089/hwm.1990.7.103

年代:1990

数据来源: MAL

ISSN:0882-5696    

DOI:10.1089/hwm.1990.7.ix

年代:1990

数据来源: MAL