Video registration of physicochemical processes in BOF cavity at bath top blowing at application oxygen lances of various designs. Report 2. The picture of bath blowing at application two-circuit lances

2021 ◽  
Vol 77 (9) ◽  
pp. 1011-1019
Author(s):  
A. G. Chernyatevich ◽  
L. C. Molchanov ◽  
E. N. Sigarev ◽  
S. A. Dudchenko ◽  
V. V. Vakal’chuk ◽  
...  
Keyword(s):  
Reaction Zone ◽  
Coming Out ◽  
Final Stage ◽  
Bath Surface ◽  
Slag Formation ◽  
Basic Part ◽  
Physicochemical Processes ◽  
Video Registration ◽  
Foamed Slag ◽  
Reaction Zones

To elaborate blowing and slag modes, a clear picture of BOF bath blowing in various periods of heat is needed. It can be obtained by video registration of physicochemical processes in a BOF cavity. Results of video filming of BOF bath blowing with application two-circuit oxygen lances of five designs presented. Reliable information was obtained on rational form of organization of reaction zone of interaction of ultrasonic and sonic oxygen jets with BOF bath. The picture of physicochemical processes within the reaction zone of interaction of oxygen jets with metal, slag and gas phases of the cavity, preceded to a stable “ignition” of a heat and in the process of the whole heat. A possibility was revealed to accelerate the processes of lime dissolving and slag formation and phosphor removal intensification. The intensification can be accomplished by increase of the number of reaction zones of interaction of ultrasonic and sonic oxygen jets on bath surface and forming of foamed slag-metal emulsion, being stable within the basic part of blowing time. It was shown that at initial period of a heat, it is necessary to ensure consolidation of supersonic oxygen jets, coming out of different reaction zones of interaction. It will enable to oncoming jets to create a curtain on the way of metal and slag drops taking away, to form a flare of CO afterburning to CO2 and ensure heat energy transfer from them to mainly the bath surface. It was established that at the location of the foamed slag-metal emulsion level higher the head end of the lance, the high-temperature products of CO to CO2 afterburning reaction transfer the heat of CO surrounding macro bubble to the shell of slag-metal emulsion. An additional control effect of “hard” supersonic oxygen jets on the bath was also established when replacing the subsonic and sonic oxygen jets by nitrogen ones. At that the flow rate of nitrogen should be big enough to prevent the sealing of cylinder nozzles of the lance head by metal and slag drops during final stage of blowing. The variant of the final stage of blowing was checked experimentally by transfer to the “hard” supersonic oxygen blow, contributing to final metal and slag oxidation decrease.

Video registration of physicochemical processes in BOF cavity at bath top blowing at application oxygen lances of various designs. Report 1. Facility and methodology of the study

2021 ◽  
Vol 77 (8) ◽  
pp. 969-976
Author(s):  
A. G. Chernyatevich ◽  
L. C. Molchanov ◽  
E. N. Sigarev ◽  
S. A. Dudchenko ◽  
V. V. Vakal’chuk ◽  
...  
Keyword(s):  
High Temperature ◽  
Reaction Zone ◽  
Video Camera ◽  
Bath Surface ◽  
Hot Metal ◽  
Metal Melt ◽  
Physicochemical Processes ◽  
Video Registration ◽  
Foamed Slag ◽  
Practical Information

Interaction of the upper oxygen jets with the BOF bath considerably effects the hot metal refining flow. To optimize the lances designs and methods of BOF bath blowing, information is needed on the actual physical and technical phenomena taking place during top blowing of BOF bath by groups of ultrasonic and sonic oxygen jets. It was shown that obtaining the information is possible at high temperature simulation of the BOF bath blowing by application oxygen lances of various designs and video registration. Results of previous studies by filming of the blowing in a BOF and OHF presented. Description of modern facilities of high temperature simulation within a multi-purpose 160 and 60‒80 kg BOFs, equipped by special manholes for observation and registration by video camera the physicochemical processes taking place on the surface of the bath presented. In particular the manholes made it possible to observe the processes taking place at various methods of top and combined blowing of the BOF bath by application regular, two-circuit and double-flow oxygen lances. A methodology of test heats carrying out presented, which ensured obtaining important practical information on forming and variation of dimensions of the reaction zone. In particular, information was obtained about the interaction of ultrasonic and sonic oxygen jets with the metal melt, development of afterburning, emission out of reaction zone C to CO2 in the subsonic and sonic oxygen jets with forming high temperature flares directed on the BOF bath surface or penetrated in the foamed slag, emissions of slag-metal suspension out the BOF, forming of metal-slag sculls on the lance tube during the blowing with various level of foamed slag-metal emulsion.

Video registration of physicochemical processes in BOF cavity at bath top blowing at application oxygen lances of various designs. Report 3. The picture of bath blowing at application two-level oxygen lances

2021 ◽  
Vol 77 (11) ◽  
pp. 1142-1155
Author(s):  
A. G. Chernyatevich ◽  
L. S. Molchanov ◽  
E. N. Sigarev ◽  
S. A. Dudchenko ◽  
V. V. Vakul'chuk ◽  
...  
Keyword(s):  
Reaction Zone ◽  
Initial Period ◽  
Video Recording ◽  
Slag Formation ◽  
Double Row ◽  
Metal Melt ◽  
Converter Bath ◽  
Foamed Slag ◽  
Aggressive Action ◽  
Laval Nozzles

Further increase of resources- and energy-saving efficiency of BOF processes is unthinkable without development of new methods of blowing and designs of blowing devices. It requires information on the real physicochemical phenomena in the converter cavity accompanying the blowing of the converter bath using new designs of oxygen lances in order to assess the possible risks in the mastering of the proposed developments in industrial conditions. The paper presents the results of video filming of the top blowing of a 80-kg converter bath by groups of multi-pulse supersonic and sonic oxygen jets formed, respectively, by Laval and cylindrical two-level nozzles of two designs equipped with double-row tips with a circular arrangement of Laval nozzles and cylindrical ones and upper block with cylindrical nozzles. Previously unknown information was obtained on the picture of the bath blowing with the formation of a reaction zone of interaction of supersonic and sonic oxygen jets with a metal melt with a flow of carbon monoxide going out the bath and afterburning of CO to CO2 under conditions of a counter-directed double curtain of sonic oxygen jets at different levels of location of the foamed slag-metal emulsions. It was established that in the initial period of blowing during slag formation most of the thermal energy of CO to CO2 combustion flares is transferred to the surface of the bath with lumps of added lime, and the rest is transferred by forced convection to the converter walls and gases escaping from the bath to the neck. In the case of the location of the foamed slag level at the upper tier of the cylindrical nozzles of the lance, heat transfer from high-temperature flares of localized afterburning of CO to CO2 within a limited in size near-lance flow of exhaust gases from the reaction zone is carried out according to the laws of submerged combustion and is completed completely in foamed slag-metal emulsion with the prevention of aggressive action of afterburning flares and volumes of overheated slag on the converter lining. Revealed and recorded by video recording modes of blowing the converter bath, contributing to the development of such undesirable phenomena during smelting as the appearance of intense emissions of slag-metal suspension from the facility, coagulation of the slag with the cessation of dephosphorization of the metal melt, the development of intense dust formation and the removal of small metal particles and slag with the formation of crust on the lance barrel. A variant of the final stage of blowing with a transition to supplying nitrogen instead of oxygen through cylindrical nozzles of two-level lances was experimentally tested, which provides an effective reduction in the level of foamed slag-metal emulsion before the converter turning down. The data obtained were used in the development of an industrial design of a two-level lance with a double-row tip, blowing and slag modes of blowing a converter bath with its use.

The Structure of Two-Stage Counterflow n-Heptane-Air Flames

2000 ◽  
Author(s):  
S. K. Aggarwal ◽  
H. S. Xue
Keyword(s):  
Strain Rate ◽  
Reaction Zone ◽  
Equivalence Ratio ◽  
Flame Structure ◽  
Premixed Combustion ◽  
Premixed Flame ◽  
Partially Premixed Combustion ◽  
Reaction Zones ◽  
Partially Premixed ◽  
Partially Premixed Flame

Partially premixed flames are formed by mixing air (in less than stoichiometric amounts) into the fuel stream prior to the reaction zone, where additional air is available for complete combustion. Such flames can occur in both laboratory and practical combustion systems. In advanced gas turbine combustor designs, such as a lean direct injection (LDI) combustor, partially premixed combustion represents an impotent mode of burning. Spray combustion often involves partially premixed combustion due to the locally fuel vapor-rich regions. In the present study, the detailed structure of n-heptane/air partially premixed flame in a counterflow configuration is investigated. The flame is computed by employing the Oppdif code and a detailed reaction mechanism consisting of 275 elementary reactions and 41 species. The partially premixed flame structure is characterized by two-stage burning or two distinct but synergistically coupled reaction zones, a rich premixed zone on the fuel side and a ‘nonpremixed zone on the air side. The fuel is completely consumed in the premixed zone with ethylene and acetylene being the major intermediate species. The reactions involving the consumption of these species are found to be the key rate-limiting reactions that characterize interactions between the two reaction zones, and determine the overall fuel consumption rate. The flame response to the variations in equivalence ratio and strain rate is examined. Increasing equivalence ratio and/or strain rate to a critical value leads to merging of the two reaction zones. The equivalence ratio variation affects the rich premixed reaction zone, while the variation in strain rate predominantly affects the nonpremixed reaction zone. The flame structure is also characterized in terms of a modified mixture fraction (conserved scalar), and laminar flamelet profiles are provided.

scholarly journals DIRECT OBSERVATION OF HIGH-TEMPERATURE AREAS OF METAL MELT AT OXYGEN CONVERTER BLOWING WITH LOW VOLTAGE APPLICATION

2021 ◽  
Vol 17 (4) ◽  
pp. 44-54
Author(s):  
Sergiy Semykin ◽  
Tetiana Golub ◽  
Sergiy Dudchenko
Keyword(s):  
High Temperature ◽  
Reaction Zone ◽  
Potential Application ◽  
Low Voltage ◽  
Video Recording ◽  
Negative Polarity ◽  
Visual Observation ◽  
Reaction Zones ◽  
Voltage Potential ◽  
Bottom Blowing

Introduction. The process of oxygen conversion, despite the existing improvements, can be supplemented by physical methods of influence, including the unconventional method of applying low-voltage potential developed at the Iron and Steel Institute of the NAS of Ukraine.Problem Statement. The studies of the method of low-voltage potential application on 60, 160 and 250 ton converters have shown that the technology intensifies thermophysical and hydrodynamic processes in the gasslag-metal system and increases the converter process efficiency.Purpose. The purpose of this research is to study the features of the influence on the reaction zones of the low voltage potential application at four blowing options with the use of high-temperature physical model.Materials and Methods. A physical model that simulates the top, bottom and combined oxygen blowing under low-voltage potential application of different polarity on the lance has been used. An insert of a transparent quartz plate is made in one of the walls for visual observation and video recording. The top blowing is conductedwith two nozzle lance (nozzle diameter 1.7 mm with an angle of 30 ° to the lance). The bottom blowing is conducted with a bottom tuyere with a 1.5 mm diameter central nozzle. Combined blowing is realized by a combination ofthese options.Results. The visual observation of the reaction zones with different blowing options has shown that the highest temperature and the largest dimensions of the brightest parts of the bath correspond to the combined blowing, while the lowest ones are reported for the bottom blowing. While applying the low-voltage potential method it has been established that the reaction zone is longer at the positive polarity on the lance, during the period of silicon oxidation, and at the negative polarity on the lance, during the period of intense carbon oxidation. The video of gas bubbles flotation, probably CO, has shown that the bubbles are formed more intensively in thecase of negative polarity on the lance.Conclusions. The applied technique has allowed estimating the influence of low-voltage potential application on the geometric parameters of the reaction zone.

Effects of drought stress and severe pruning on the reaction zone induced by single inoculations with a bark beetle associated fungus (Ophiostoma ips) in the phloem of young Scots pines

1998 ◽  
Vol 28 (12) ◽  
pp. 1814-1824 ◽  
Author(s):  
Luc Croisé ◽  
Erwin Dreyer ◽  
François Lieutier
Keyword(s):  
Water Stress ◽  
Reaction Zone ◽  
Bark Beetle ◽  
Severe Water Stress ◽  
Reaction Zones ◽  
Maximum Water ◽  
Ips Sexdentatus ◽  
Effects Of Drought ◽  
Two Parameters ◽  
Needle Water Potential

The objective of this study was to test the effect of water stress and pruning on the resistance of young Scots pines (Pinus sylvestris L.) to a bark beetle associated fungus. Six-year-old potted trees were either pruned (70% of needles removed) or subjected to several successive episodes of severe water stress, prior to inoculation of inner bark with the fungus Ophiostoma ips (Rumb.) Nannf., which is usually associated with the bark beetle Ips sexdentatus Boern. Well-watered, nonpruned trees served as controls. Predawn needle water potential reached -2.5 MPa and net CO2 assimilation rates were reduced to almost zero during each water stress episode. The length of the reaction zones around inoculation points reached 3-4 cm after 3 weeks. It was higher during Spring than during Autumn. Impact of water stress on the length of the reaction zone was very limited and independent of the number of drought episodes that had been imposed prior to inoculation. The only visible change was a slight decrease when the inoculation was done during the period of maximum water stress intensity. Growth of the pathogen in the phloem was not affected by water stress. Correspondingly, pruning had no effect on either of these two parameters. Induced reaction zones accumulated monophenolic compounds that were undetectable in unwounded phloem. These included pinocembrin and pinosylvin and its monomethylether known to contribute to the defence against the fungus. Neither drought nor severe pruning induced any change in the nature or concentrations of these compounds in the unwounded phloem or in the reaction zone.

Microstructures in Non-precious Alloys Near the Porcelain-Metal Interaction Zone

1979 ◽  
Vol 58 (10) ◽  
pp. 1987-1993 ◽  
Author(s):  
Robert D. Ringle ◽  
Carl W. Fairhurst ◽  
Kenneth J. Anusavice
Keyword(s):  
Interfacial Reaction ◽  
Reaction Zone ◽  
Elemental Concentration ◽  
Concentration Profiles ◽  
Dental Alloys ◽  
Interaction Zone ◽  
Dental Porcelain ◽  
Metal Interaction ◽  
Reaction Zones ◽  
Second Phases

The chemistry of microstructures near the interfacial reaction zones of four non-precious alloys and two different brands of dental porcelain has been analyzed. It was found that most non-precious dental alloys contain second phases which can alter elemental concentration profiles. Recommendations for assessing interfacial reaction zone chemistry in dental non-precious alloys are offered.

The turbulent burning velocity for large-scale and small-scale turbulence

1999 ◽  
Vol 384 ◽  
pp. 107-132 ◽  
Author(s):  
N. PETERS
Keyword(s):  
Level Set ◽  
Reaction Zone ◽  
Large Scale ◽  
Burning Velocity ◽  
Small Scale ◽  
Constant Density ◽  
Flame Surface ◽  
Reaction Zones ◽  
Scale Turbulence ◽  
Turbulent Burning Velocity

The level-set approach is applied to a regime of premixed turbulent combustion where the Kolmogorov scale is smaller than the flame thickness. This regime is called the thin reaction zones regime. It is characterized by the condition that small eddies can penetrate into the preheat zone, but not into the reaction zone.By considering the iso-scalar surface of the deficient-species mass fraction Y immediately ahead of the reaction zone a field equation for the scalar quantity G(x, t) is derived, which describes the location of the thin reaction zone. It resembles the level-set equation used in the corrugated flamelet regime, but the resulting propagation velocity s*L normal to the front is a fluctuating quantity and the curvature term is multiplied by the diffusivity of the deficient species rather than the Markstein diffusivity. It is shown that in the thin reaction zones regime diffusive effects are dominant and the contribution of s*L to the solution of the level-set equation is small.In order to model turbulent premixed combustion an equation is used that contains only the leading-order terms of both regimes, the previously analysed corrugated flamelets regime and the thin reaction zones regime. That equation accounts for non-constant density but not for gas expansion effects within the flame front which are important in the corrugated flamelets regime. By splitting G into a mean and a fluctuation, equations for the Favre mean [Gtilde]and the variance [Gtilde]″2 are derived. These quantities describe the mean flame position and the turbulent flame brush thickness, respectively. The equation for [Gtilde]″2 is closed by considering two-point statistics. Scaling arguments are then used to derive a model equation for the flame surface area ratio [rhotilde]. The balance between production, kinematic restoration and dissipation in this equation leads to a quadratic equation for the turbulent burning velocity. Its solution shows the ‘bending’ behaviour of the turbulent to laminar burning velocity ratio sT/sL, plotted as a function of v′/sL. It is shown that the bending results from the transition from the corrugated amelets to the thin reaction zones regimes. This is equivalent to a transition from Damköhler's large-scale to his small-scale turbulence regime.

Optical Study of Combustor Reaction Zone

2006 ◽  
Author(s):  
Y. Levy ◽  
M. Lev ◽  
V. Ovcharenko
Keyword(s):  
Combustion Chamber ◽  
Reaction Zone ◽  
Combustion Process ◽  
Infrared Emission ◽  
Visible Spectral Range ◽  
Continuum Emission ◽  
Visible Range ◽  
Combustion Mechanism ◽  
Infrared Images ◽  
Reaction Zones

Measurements of emitted radiation from the gases within the reaction zone of a combustor were performed. The combustor was a 30% flat (rectangular) model of an annular combustion chamber of a turbojet-engine. Nonpremixed, turbulent combustion was fueled by kerosene. The equivalence ratios were within the range of 0.15–0.75. The combustor had two quartz windows permitting optical observation of the combustion process. In an earlier work, the infrared emission from the efflux gases, the combustion products, just outside of the combustor exit plane, was investigated using an infrared camera, equipped with an interference bandpass filter. In the present study, infrared images of the combustion inside the chamber were obtained. The location of the high temperature recirculation zones can be identified in the infrared images obtained by the camera. In the visible spectral range, the emission of CH* radicals and C2* molecules from within the combustion chamber was investigated through the quartz window. These species exist within the reaction zones and play an important role in the combustion mechanism. Their excitation is mainly due to the chemical reactions and so they can serve for diagnosis of combustion processes in reaction zones. The emission from the combustor, in the visible range, was recorded with the aid of a fiber-optic based spectrometer. Local measurements of the emissions of the Swan bands of C2* molecules at 471 nm, 513 nm, 560 nm, vibronic band of CH* radicals at 431 nm and continuum emission of carbonaceous products of pyrolysis were recorded along the combustor centerline. The intensity is correlated with location of the combustion zones. The distribution of the emission was observed as being dependent on the global equivalence ratio.

Possible heterocyclic ions in the reaction zones of flames with added nitrogen or sulfur

1984 ◽  
Vol 37 (3) ◽  
pp. 511 ◽  
Author(s):  
T McAllister
Keyword(s):  
Reaction Zone ◽  
Ionization Mass ◽  
Proton Affinities ◽  
Flame Ionization ◽  
Ionization Mass Spectroscopy ◽  
Hydrogenation Reactions ◽  
Reaction Zones ◽  
Aromatic Species ◽  
Cyano Compounds ◽  
Cn Radicals

Ions of m/z 80 and 94 are observed in the reaction zone of a C6H6/N2O/H2 flame, by flame ionization/mass spectroscopy. These are confirmed, by deuteration, as protonated pyridine and aniline. These ions are also detected in the reaction zone of a CH4/N2O flame, along with ions of m/z 44, 56, 68 and 72, which, it is proposed, are formed by protonation of the heterocyclic species aziridine, dihydroazete, pyrrole and pyrrolidine. This series of N-containing ions is in keeping with the postulate that HCN is formed in flames of hydrocarbons and N-compounds, and that the associated CN radicals undergo addition and hydrogenation reactions. Cyano compounds are not, however, detected, because their proton affinities tend to be lower than that of NH3. In a C6H2/CS2/H2 flame, a series of S-containing ions are observed, beginning at m/z 97, for which the thiopyrylium structure is proposed. The detection of this stable aromatic species is in contrast to the absence of protonated thiophene. It is postulated that the active S-containing species in this flame is CS.

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