scholarly journals Mathematical Analysis of Inclusion Removal from Liquid Steel by Gas Bubbling in a Casting Tundish

2012 ◽  
Vol 2012 ◽  
pp. 1-16 ◽  
Author(s):  
H. Arcos-Gutierrez ◽  
J. de J. Barreto ◽  
S. Garcia-Hernandez ◽  
A. Ramos-Banderas
Keyword(s):  
Liquid Steel ◽  
Removal Rate ◽  
Bubble Diameter ◽  
Flow Conditions ◽  
Inclusion Removal ◽  
Alumina Inclusion ◽  
Collection Probability ◽  
Gas Bubbling ◽  
Attachment Mechanism ◽  
Bubble Attachment

The mechanism of inclusion removal from liquid steel by gas bubbling and bubble attachment in the tundish is complex due to the great number of variables involved, and it is even more difficult to study because of the turbulent flow conditions. The main objective of this work is to analyze and improve the understanding of the alumina inclusion removal rate by bubble attachment and by gas bubbling fluid dynamics effects. The results show that the inclusion collection probability mainly depends on the attachment mechanism by collision. This parameter was determined by calculating the induction time, which is shorter when the rupture time and the formation time of a stable three phases contact (particle/liquid/gas) are ignored than when it is fully considered, affecting the attachment probability. In addition, to achieve acceptable inclusion removal, a smaller bubble diameter is required, such as 1 mm. This consideration is almost impossible to achieve during tundish operation; a more realistic bubble diameter around 10 mm is employed, resulting in a very inefficient inclusion removal process by bubble attachment. Nevertheless, in a real casting tundish the inclusion removal rate employing argon bubbling is efficient; is mainly due to the fluid flow pattern changes rather than bubble attachment. Consequently, it is imperative to consider the summation of both removal mechanisms to compute a better approximation of this important operation.

Effect on Position of Electromagnetic Stirring on Inclusion Behaviors in Billet

2013 ◽  
Vol 805-806 ◽  
pp. 1716-1719 ◽  
Author(s):  
Gui Fang Zhang ◽  
Yue Hua Ding ◽  
Zhe Shi
Keyword(s):  
Liquid Steel ◽  
Electrical Current ◽  
Medium Carbon Steel ◽  
Electromagnetic Stirring ◽  
Cast Billet ◽  
Inclusion Removal ◽  
Optimum Position ◽  
Steel Cleanliness ◽  
Plant Trials

A considerable number of research works have been carried out to study the effects of electric current and frequency of Electromagnetic Stirring (EMS) on the quality of cast steels, but there are only a few studies available addressing the effects of EMS location on inclusion removal and steel cleanliness An ideal position of EMS will improve inclusion floatation and separation from liquid steel. However, inappropriate installation will lead to the entrapment of the slag into liquid steel, and impact the quality of cast billet. The current applied for these plant trials was 300A at a frequency of 3Hz,positions form axial centers of EMS to the top of the mold were 450mm, 510mm and 690mm respectively . 130 billets of medium carbon steel were produced and samples were taken for spectral analysis to study the effects of installation location of EMS on steel cleanliness. The experimental results show that the optimum position of EMS should be placed 510mm from the top end of the copper mold when the electrical current is 300A at frequency of 3 Hz. The three parameters of placement of EMS in paper were obtained from the simulation results, and this paper focused mainly on the effect EMS position on inclusion behaviors in billet.

Separation and Hydrodynamic Performance of Air-Kerosene-Water System by Bubble Column

2010 ◽  
Vol 8 (1) ◽  
Author(s):  
Abbas H. Sulaymon ◽  
Ahmed Abed Mohammed
Keyword(s):  
Removal Efficiency ◽  
Flow Rate ◽  
Bubble Column ◽  
Removal Rate ◽  
Air Flow ◽  
Bubble Diameter ◽  
Water Concentration ◽  
Hydrodynamic Performance ◽  
Air Flow Rate ◽  
Flotation Process

The separation of emulsified kerosene in water (concentration 250-750ppm) was investigated in a bubble column15.6 cm diameter and 120 cm height. The effective behaviors of bubble characteristics (bubble diameter, bubble rise velocity and air hold-up) on the removal efficiency were measured by electroresistivity probe. The effects of kerosene concentration, air flow rate,bubble diameter, liquid height, liquid viscosity, NaCl concentration, and alum on the removal rate were found. The experimental results showed that the removal efficiency increased with increasing air flow rate (1.09-2.6cm/s) and decreased with increasing CMC concentration. The results also showed that adding anionic surfactants (SLES and SDBS) leads to increase removal rate. The the flotation process was found to be first order kinetics. New correlations of air holdup and bubble diameter using dimensionless groups were derived.

CFD Analyses for Water-Air Flow With the Euler-Euler Two-Phase Model in the Fluent4 CFD Code

2002 ◽  
Author(s):  
Jaakko Miettinen ◽  
Holger Schmidt
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Void Fraction ◽  
Bubble Diameter ◽  
Velocity Profiles ◽  
Global Model ◽  
Model Parameters ◽  
Fluid Viscosity ◽  
Flow Conditions ◽  
Two Phase

Framatome ANP develops a new boiling water reactor called SWR 1000. For the case of a hypothetical core melt accident it is designed in such a way that the core melt is retained in the Reactor Pressure Vessel (RPV) at low pressure owing to cooling of the RPV exterior and high reliable depressurization devices. Framatome ANP performs — in co-operation with VTT — tests to quantify the safety margins of the exterior cooling concept for the SWR 1000, for determining the limits to avoid the critical heat fluxes (CHFs). The three step procedure has been set up to investigate the phenomenon: 1. Water-air study for a 1:10 scaled global model, with the aim to investigate the global flow conditions. 2. Water-air study for a 1:10 scaled, 10% sector model, with the aim to find a flow sector with almost similar flow conditions as in the global model. 3. Final CHF experiments for a 1:1-scaled, 10% sector., the boarders of this model have been selected based on the first two steps. The instrumentation for the water/air experiments included velocity profiles, the vertically averaged average void fraction and void fraction profiles in selected positions. The experimental results from the air-water experiments have been analyzed at VTT using the Fluent-4.5.2 code with its Eulerian multiphase flow modeling capability. The aim of the calculations was to learn how to model complex two-phase flow conditions. The structural mesh required by Fluent-4 is a strong limitation in the complex geometry, but modeling of the 1/4 sector from the facility was possible, when the GAMBIT pre-processor was used for the mesh generation. The experiments were analyzed with the 150 × 150 × 18 grid for the geometry. In the analysis the fluid viscosity was the main dials for adjusting the vertical liquid velocity profiles and the bubble diameter for adjusting the phase separation. The viscosity ranged between 1 to 10000 times the molecular viscosity, and bubble diameter between 3 to 100 mm, when the calculation results were adjusted for a good agreement with the experimental data. The analysis results were very valuable for designing the final water/steam facility for final CHF tests. The validation against data from the air-water experiments proved that the present CFD codes approach to the state where they can be used for simulating such two-phase experiments, where the fraction of both phases is essential and the flow is strongly affected by the density differences. It is still too early to predict, if the CFD calculation of the 1:1 scale critical heat flux experiments is successful, could the result be used for formulating a new type of a critical heat flux correlation, where the effects of CRD’s on the flow patterns and gap dimensions are model parameters.

Effects of flow velocity and depth on the rates of reaeration and bod removal in a shallow open channel

1997 ◽  
Vol 35 (8) ◽  
pp. 57-67
Author(s):  
Horng-Guang Leu ◽  
C. F. Ouyang ◽  
Tze-Yi Pai
Keyword(s):  
Analytical Solution ◽  
Flow Velocity ◽  
Open Channel ◽  
Rate Coefficient ◽  
Removal Rate ◽  
Sedimentation Coefficient ◽  
Inverse Correlation ◽  
Flow Conditions ◽  
Batch Tests ◽  
Bod Removal

This study developed an analytical solution of reaeration rate coefficient (K2) and modified the equation of BOD removal in a shallow artificial open channel. A series of well-controlled batch tests were carried out to measure the K2 and BOD removal rate in the channel at different flow conditions. The results of these tests indicated that measured K2 within the developing zone of the laminar boundary layer is better described by the analytical solution of this study than by the five semi-empirical formulae mentioned in this paper. On the other hand, a resuspension-sedimentation coefficient, Rs, was added to the BOD removal equation to describe the variation in BOD due to varied flow conditions. Based on the results of the experimental data the following conclusions in the BOD removal process were reached. It was found that a direct correlation exists between the flow velocity to depth ratio (U/h) and the deoxygenation rate coefficient (K1), but there is an inverse correlation between U/h and Rs as well. This modified BOD removal equation can predict BOD removal rate at different travel times or known downstream distances in an open channel under varied flow conditions.

scholarly journals Comparative study of inclusion removal from liquid steel in the RH and argon purging processes

2020 ◽  
Vol 73 (3) ◽  
pp. 353-359
Author(s):  
Marina Braga Campos ◽  
Johne Jesus Mol Peixoto ◽  
Carlos Antônio da Silva ◽  
Itavahn Alves Silva
Keyword(s):  
Comparative Study ◽  
Liquid Steel ◽  
Inclusion Removal

Microbial removal rate efficiencies measured for coral sand  

2021 ◽  
Author(s):  
Lee F. Burbery ◽  
Bronwyn Humphries ◽  
Louise Weaver ◽  
Jan Gregor
Keyword(s):  
Escherichia Coli ◽  
Removal Rate ◽  
Beach Sand ◽  
Septic Tank ◽  
Column Experiments ◽  
Flow Conditions ◽  
Ms2 Bacteriophage ◽  
Coral Sand ◽  
The Pacific ◽  
Microbial Removal

<p>Coral sand forms the surficial geology on many coral cay and low-lying atolls, such as are located throughout the Pacific region. Shallow groundwater hosted within such sand is the main source of freshwater for many island communities. It is critically at risk from the impacts of climate-change and anthropogenic stresses. A United Nations' Sustainable Development Goal is to improve water access and sanitation issues in such environs. Working towards that goal, we have conducted a set of laboratory column experiments to obtain some initial measures of microbial removal efficiencies for coral sand substrate from the Pacific atoll of South Tarawa, Kiribati.  </p><p>In one experiment we attempted to mimic physio-chemical conditions at the Bonriki Freshwater Reserve that supplies most of the water on South Tarawa. Three small plastic columns were packed with very poorly sorted gravelly coral sand sampled from the reserve. The effective transport of Escherichia coli J6-2 and MS2 bacteriophage through the packed columns was evaluated under saturated flow conditions.</p><p>In a second experiment we conducted infiltration tests on naturally well-sorted coral sand, sourced from Bikenibeu beach, South Tarawa. We perceive such sand has potential to be used in the construction of effluent drainage fields from septic tank systems in use on South Tarawa, where currently there are no established design criteria. The sand was packed to a depth of 400 mm in triplicate glass column apparatus. It was conditioned by dosing with septic tank effluent twice per day for 27 days (8 mm head each event). Effluent spiked with bacterial and viral indicator organisms: Escherichia coli J6-2, Enterococci faecalis and MS2 bacteriophage, as well as the viral pathogens: adenovirus, echovirus, norovirus and rotavirus was then dripped on to the columns, as a 35 mm application. Any resulting drainage from the base of the columns was collected and analysed, and the depth profile of the tracer organisms was examined in the sand columns by destructive sampling.</p><p>The very poorly sorted coral substrate from Bonriki Reserve proved very effective at attenuating Escherichia coli J6-2 under saturated flow conditions. We estimated a spatial removal rate of 0.05 ± 0.02 log<sub>10</sub> cm<sup>-1</sup> for this bacterial tracer. No removal rate could be quantified for the viral indicator. Although overall, our observations suggest the coral sand was significantly less effective at attenuating MS2 bacteriophage than it was at attenuating Escherichia coli J6-2.</p><p>In the unsaturated column experiments made on beach sand conditioned with effluent, all the microorganisms examined demonstrated >4-log removal values. Contrary to our finding from the saturated sand column experiment made with material from Bonriki Reserve, the conditioned coral beach sand filters demonstrated higher affinity for MS2 bacteriophage (also viruses) than they did Escherichia coli J6-2, or Enterococci faecalis.</p>

INCLUSION REMOVAL IN A TUNDISH BY GAS BUBBLING

2004 ◽  
Vol 43 (3) ◽  
pp. 407-415 ◽  
Author(s):  
J.P. ROGLER ◽  
L.J. HEASLIP ◽  
M. MEHRVAR
Keyword(s):  
Inclusion Removal ◽  
Gas Bubbling

Decarburization and Inclusion Removal Process in Single Snorkel Vacuum Degasser

2017 ◽  
Vol 36 (5) ◽  
pp. 523-530 ◽  
Author(s):  
Geng Dian-Qiao ◽  
Hong Lei ◽  
Ji-Cheng He
Keyword(s):  
Mass Transfer ◽  
Spatial Distribution ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Mass Fraction ◽  
Removal Rate ◽  
Order Reaction ◽  
Volumetric Mass Transfer Coefficient ◽  
Inclusion Removal ◽  
First Order

AbstractIn the current work, the coupled mathematical models for decarburization, fluid flow model and inclusion collision-aggregation model were solved to investigate the spatial distribution of carbon, inclusion’s collision-aggregation and removal in a single snorkel vacuum refining furnace (SSF). The numerical results show that the turbulence kinetic energy of ladle in SSF is much greater than that in RH, which can shrink the dead zone and prompt the mixing in the ladle. The overall decarburization reaction rate can be described as a first-order reaction. On the condition of the same gas flow rate, the volumetric mass transfer coefficient for decarburization in SSF is almost twenty times bigger than that in RH, which leads to a much greater decarburization rate in SSF. The spatial distribution of carbon mass fraction in SSF is quite different from that in RH. There is the greater mass fraction of carbon at the recirculation zone under up-snorkel in RH, but this phenomenon disappears in SSF. The inclusion removal can be simplified as the mass transfer between liquid steel to slag, refractory wall and bubble surface. And the overall inclusion removal rate can be regarded as a first-order reaction. The volumetric mass transfer coefficient for inclusion removal in SSF is about three times as that in RH, the inclusion removal rate in SSF is greater than that in RH. The inclusions with different size have different removal rates in SSF. For inclusion flotation after deoxidization, the treatment time in SSF is less than that in RH.

Water Model on Fine Inclusion Removal by Bubble Flotation in RH Refining Process

2014 ◽  
Vol 528 ◽  
pp. 107-111 ◽  
Author(s):  
Chun Jie Yang ◽  
Fu Ping Tang ◽  
Tao He ◽  
Qiang Fu
Keyword(s):  
Gas Flow ◽  
Influence Factor ◽  
Treatment Time ◽  
Similarity Theory ◽  
Removal Rate ◽  
Water Model ◽  
Gas Flow Rate ◽  
Inclusion Removal ◽  
Vacuum Refining ◽  
Optimal Values

With the development of socio-economic and science and technology, People are more strict to the requirement of steel quality. A physical model was established according to the “similarity theory” to simulate the real 180t RH-TB vacuum refining device. Liquid steel is simulated by Nacl solution, Fine inclusions is simulated by high density polypropylene less than 0.04mm in diameter. The influence regularity of treatment time, lift gas flow rate and method of addition, the amount and time of NaHCO3 addition on the inclusions removal rate have been discussed, the optimal values for each influence factor have been found and can be used in optimizing the refining technology.

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