Gas-Phase Oxidation Kinetics of Toxic Metals at Incinerator Temperatures. The Reactions of Chromium Atoms with HCl, N2O, Cl2, and O2

Fontijn, Arthur; Blue, Alan S.; Narayan, A.; Bajaj, P.N.

doi:10.1080/00102209408951866

Cited by 41 publications

(37 citation statements)

References 19 publications

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“…These models have limitations, and it is important Downloaded by [Tulane University] at 07:47 21 June 2016 to note that equilibrium may not be achieved in a particular system because of kinetic rate or mixing limitations. However, since .only a very limited selection of gas-phase kinetic rate data involving Cr is available in the current literature (Smirnov, 1993;Fontijn et al, 1994), detailed kinetic modeling of rates of formation of all important Cr species is not possible. Additionally, any equilibrium prediction is only as good as the thermochemical information available.…”

Section: Theoretical Equilibrium Predictionsmentioning

confidence: 98%

Formation and Destruction of Hexavalent Chromium in a Laboratory Swirl Flame Incinerator

Linak

Ryan

Wendt

1996

Combustion Science and Technology

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The partitioning of chromium (Cr) in combustion systems was investigated theoretically and experimentally. Theoretical predictions were based on chemical equilibrium, and suggested that hexavalent chromium [Cr(Vl)] was favored by the presence of chlorine (CI), and diminished by the presence of sulfur (S). Experimental studies employed a 59 kW laboratory-scale combustor with a swirling natural gas diffusion flame through which aqueous Cr solutions were sprayed. Three types of experimental data were obtained. First, and most important, the overall Cr(VI) fraction of the total Cr in the exhaust was measured as a function of initial Cr valence [trivalent (Ill) or hexavalent], and CI and S concentrations. Second, the size segregated distribution of Cr(VI) in the exhaust was explored for the Cr(III) waste feed with and without CI and S. Third, the influence of waste feed Cr valence on the exhaust aerosol particle size distribution was determined. Analytical determinations of Cr(VI) and total Cr are described.Results show that, for the high temperature, highly turbulent, gas-phase incinerator conditions examined, the relative ratio of Cr(VI)/total Cr is unaffected by the initial Cr valence of the waste, and ranged from near zero to approximately 8%, depending on the presence of S or Cl. CI addition increased the fraction of Cr(VI) found in small particles (smaller than approximately l.Lum) from approximately 30 to 70%. In contrast to the chemical analysis, the particle size distribution (PSO) measurements indicate that the initial form of the Cr waste does influence the resultant PSD. This mechanism is not well understood, but a possible explanation is that at combustion temperatures the Cr speciation chemistry is equilibrium controlled, while the PSD is determined by the aerosol dynamics which are dependent on physical transformations and specific chemical pathways.

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Section: Theoretical Equilibrium Predictionsmentioning

confidence: 98%

Formation and Destruction of Hexavalent Chromium in a Laboratory Swirl Flame Incinerator

Linak

Ryan

Wendt

1996

Combustion Science and Technology

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“…These researchers found an inverse dependency, thus concluding that thermodynamically favorable reactions are also kinetically favored. The gas-phase oxidation kinetics of chromium at incinerator temperatures for several reactions has been reported by Fontijn et al 76 An investigation of the kinetic process of metal-oxygen reactions for welding systems has been carried out by Chen and Kang. 31 Their objectives were to study the kinetic process, so that the oxygen reactions could be minimized in a welding operation.…”

Section: Transformation Of Metallic Speciesmentioning

confidence: 99%

Control of Toxic Metal Emissions from Combustors Using Sorbents: A Review

Biswas

1998

Journal of the Air & Waste Management Association

172

123

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This paper constitutes a review of the control of toxic metal emissions using sorbents. The objective of sorbent-injection methods is to effectively capture the metal species (preferably transform it to an environmentally benign form) and to suppress the fraction in the submicrometer mode. The design of an effective sorbent-injection methodology thus requires an understanding of the fate of the metallic species and its transformation pathways (transfer to the gas phase, subsequent chemistry at high temperatures, and aerosol formation and growth dynamics) in the combustor. Several different sorbent methodologies used for metals capture are discussed, and a mechanistic description is provided. The need for further experimentation and pilot scale testing is also emphasized.

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“…The preexponential factor of eq 2 is close to the gas kinetic rate coefficient, as has also been observed for other metal atom reactions with HCl, specifically Al, 32 Cr, 33 Li, 34 Na, 35,36 and K. 37 These reactions are normally assumed to proceed as abstraction reactions, but some could conceivably also have an insertion channel. …”

Section: Discussionmentioning

confidence: 87%

Laser-Induced Fluorescence and Mass Spectrometric Studies of the Cu + HCl Reaction over a Wide Temperature Range. Formation of HCuCl

et al. 1996

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The kinetics and products of the Cu + HCl reaction have been studied using high-temperature fast-flow reactors (HTFFR). The rate coefficient measurements were made using laser-induced fluorescence (LIF) of Cu atoms and yielded k(680-1500 K) ) 1.2 × 10 -10 exp(-7719 K/T) cm 3 molecule -1 s -1 . Product analysis was achieved by coupling a specially designed HTFFR to a chopped molecular beam quadrupole mass spectrometer. Those observations, which covered the approximately 1150-1500 K temperature range, showed formation of CuCl and the previously unknown species HCuCl. Confirmation of the latter assignment was made using DCl. Increasing pressure and decreasing temperature favor the HCuCl formation. These findings and this molecular structure are supported by ab initio calculations. These also indicate passage through a CuClH f HCuCl transition state as the rate-controlling step for formation of both products, in agreement with the observed pressure independence of the overall, Cu disappearance, rate coefficients.

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Gas-Phase Oxidation Kinetics of Toxic Metals at Incinerator Temperatures. The Reactions of Chromium Atoms with HCl, N₂O, Cl₂, and O₂

Cited by 41 publications

References 19 publications

Formation and Destruction of Hexavalent Chromium in a Laboratory Swirl Flame Incinerator

Formation and Destruction of Hexavalent Chromium in a Laboratory Swirl Flame Incinerator

Control of Toxic Metal Emissions from Combustors Using Sorbents: A Review

Laser-Induced Fluorescence and Mass Spectrometric Studies of the Cu + HCl Reaction over a Wide Temperature Range. Formation of HCuCl

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