摘要:

The gas phase pyrolysis and oxidative pyrolysis of CH3Br was studied experimentally in a flow reactor under atmospheric pressure, at temperatures in the range 500-800 °C and at reaction times in the range 0.6-1.5 s. Gas samples were withdrawn from within the reactor using a heated micro-probe and were analyzed by a computer controlled gas chromatograph(GC)/massspectrometer(MS) system. Pyrolysis products were primarily CH4, C2H4, CH2Br2and C2H2, and HBr and H2as determined from atom balances. In addition, trace levels of C6H6, C6H5Br, 1,2-C2H2Br2(Z and E), l,2-C2H4Br2were observed at higher temperatures. Coke formation was significant, with unaccounted carbon levels reaching 50% in some experiments. The major products in the oxidative pyrolysis process were CH4, C2H4, CH2Br2, CO and CO2, with the same trace species observed as in the case of pyrolysis. The presence of O2in the system did not significantly reduce coke formation.

ISSN:0010-2202    

DOI:10.1080/00102209408951872

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The final destruction of toxic waste in incinerators occurs in the post flame region. The controlling chemistry in this region may be described as that of fuel-lean oxidation of CO in the presence of H2O and HCl perturbed by trace quantities of chlorinated hydrocarbons. In the present study, a reaction bath with initially about 1% of CO, O2, and H2O in nitrogen was perturbed by CH3Cl in a turbulent flow reactor operating at atmospheric pressure, with temperatures between 1000 and 1150 K. The equivalence ratio ranged from 0.25 to 1.0 and the initial CH3Cl ranged from 0 to 250ppm.

ISSN:0010-2202    

DOI:10.1080/00102209408951873

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The kinetics of the reactions of O(3P) atoms with three chloro-ethylenes have been measured using the HTP technique. The following rate coefficient expressions, in cm3molecule−1s−1, have been obtained, for: CH2= CHCl:k1(288-1233) = 1.6 × 10−14(T/K)0.87exp( −440 K/T); for CH2= CCl2:k2(295 - 1218) = 6.5 x 10−16(T/K)1.32exp( − 268 K/T);fort-CHCl = CHCl:k3(326 - 1164) = 4.5 × 10−18(T/K)1.89exp(−239K/T). The observations are compared to those on O + C2H4. Below 700 K the temperature dependences of the rate coefficients of these four reactions differ only slightly from each other, consistent with the substituent constants for chlorine substitution. However, the magnitude of the rate coefficients decreases substantially in the sequencekc2H4(T) ≈k2(T) >k3(T), in agreement with the preferential attack of O atoms at the site of the unsubstituted C atoms. While these trends continue at higher temperatures for the first three members of this sequence, a sharp increase has been observed ink3T) above about 700 K. It is shown that this may be attributed to H-atom abstraction from the weakened C—H bond. method for estimatingk(T) expressions for further O-atom reactions with chloro-aliphatic compounds is described. The kinetics of reactions of O atoms with chloro-aromatics is briefly considered.

ISSN:0010-2202    

DOI:10.1080/00102209408951874

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The effects of post-flame fuel injection on the destruction of chlorinated hydrocarbons has been studied in a combustion flow reactor. All three fuels studied (CH4, C2H6, and CO) enhance the destruction of CH3Cl. CO is the only effective post-flame fuel for the destruction of C2H5Cl, and none of the fuels improve the destruction of 1,1,1-C2H3Cl3. These results are explained by considering the destruction mechanisms: unimolecular reactions are not influenced by fuel addition, and bimolecular reactions involving radicals can be enhanced or inhibited, depending on the nature of both the fuel and CHC.

ISSN:0010-2202    

DOI:10.1080/00102209408951875

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The effect of oxygen and chlorine on the chemistry of the products of incomplete combustion, (PICs), in the combustion process appears to be more dramatic than the effect of temperature alone. A series of combustion experiments were carried out on pure polyethylene in a laboratory thermal oxidizer (LTOX). The combustion conditions for all of the experiments were identical with the exception of the oxygen concentration. As the oxygen concentration increased, progressive cyclization of polyethylene fragments was observed. No oxygen containing products were found.

ISSN:0010-2202    

DOI:10.1080/00102209408951876

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Pyrolysis or combustion of plastics are of interest from different points of view: on the one hand polymers from which harmful substances may arise are involved in fires or are fed to incinerators; on the other hand plastic refuses are an alternative resource of energy or chemical raw materials. For designing recycling procedures the behaviour of the decomposition of polymers with regard to the decomposition products and the kinetics of decomposition must be known. Plastic refuses encompass chlorine- and/or nitrogen-containing polymers which may form toxic or corrosive products under pyrolytic conditions or in combustion. These components must be separated before processing or the troublesome elements have to be eliminated by pretreatment. The aim of this work was to investigate the kinetics of pyrolysis of polyfvinyl chloride) and mixtures of poly(vinyl chloride) with polyethylene, polypropylene, polystyrene and polyamide 6. By means of simultaneous thermogravimetry-mass spectrometry the kinetic parameters for the decomposition were determined and the products formed in decomposition of the polymers were identified. Because of the different reaction mechanisms and reaction rates and particularly their different temperature dependence, the single components decompose at different temperatures. This is important for the behaviour of plastic mixtures in fires. Furthermore a separation of plastic mixtures by temperature-controlled pyrolysis in recycling processes is possible.

ISSN:0010-2202    

DOI:10.1080/00102209408951877

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We demonstrate that carbon molecular weight growth chemistry can continue to occur when polycyclic aromatic hydrocarbons (PAH), produced by localized fuel rich pockets within an incinerator, disperse into the near-stoichiometric bulk flow characteristic of the unit. Naphthalene, a model PAH, was added to a near-stoichiometric (φ = 1.2) post-flame combustion flow produced by premixed C2H4/O2/N2/Air combustion in a jet-stirred/plug-flow reactor system (JSR/PFR), and the results compared against those from a fuel rich (φ = 2.2) post-flame combustion flow without naphthalene addition. In both experiments, the PFR was sampled for soot (CH2Cl2insolubles), tar (CH2Cl2solubles; PAH), C2H2and other light gases.

ISSN:0010-2202    

DOI:10.1080/00102209408951878

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Phenomenological aspects of formation, destruction, and coagulation of high molecular mass structures formed in the main oxidation zone of rich premixed flames and in rich flames well below the soot threshold limit have been examined. High molecular mass structures transparent to the visible radiation, previously detected in the preinception region of soot forming flames, are also present in flames below the soot formation limit. The onset of ultra-violet fluorescence within the main oxidation zone implies that the formation of these species is a very fast process and can be considered as a “polymerization” of small aromatic groups activated by the presence of oxidizing agents. The final concentration of this material falls down as the C/O ratio is decreased and below C/O = 0.35 it is not anymore present. It appears that rich premixed flames present two critical C/O ratios: a first one for soot formation and a lower second one for high molecular mass structure formation. Ultra-violet scattering/extinction technique has indicated that the typical average size of these structures is around 4-6 nm and their overall coagulation rate is very low.

ISSN:0010-2202    

DOI:10.1080/00102209408951879

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Polycyclic aromatic hydrocarbons (PAH) are important in combustion processes from two points of view: As precursors for soot formation and as pollutants, if they are emitted. Usually PAHs are measured by GC-MS or HPLC analysis of filter extracts, which is a time and cost intensive procedure and does not allow on-line measurements. An alternative is photoelectric charging of particles by irradiation with ultraviolet light. If an appropriate wavelength is chosen, the emission probability of electrons mainly depends on the amount of particle bound PAHs. This allows a simple and fast monitoring of PAHs in emission and ambient air measurements. Here the application of this method to measure particle bound PAHs in the exhaust of different combustion systems (oil burner, combustion engines) is discussed.

ISSN:0010-2202    

DOI:10.1080/00102209408951880

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

New measurements of resonance ionization detection limits are presented for seven species, of high thermal stability, which are potentially useful surrogates for continuous emission monitoring of incinerator effluent. Resonance ionization detection limit data are now available for 20 aliphatic and aromatic compounds; eight of these compounds have sub part-per-billion detection limits. These eight also exhibit selectivities exceeding 103when detected in the presence of a “soup” of chemically similar interferant species likely to be present in stack gas samples. Preliminary measurements indicate that detection limits, obtained under ideal conditions in a helium carrier gas, are also approached under adverse sampling conditions tested with synthetic “soups”. The implications of these measurements on the selection of surrogates and the prospects for repetitive on-line hazardous emissions monitoring are discussed

ISSN:0010-2202    

DOI:10.1080/00102209408951881

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor