Specific Features of Thermal Systems of Induration Machines for Pellet Production from Iron-ore Concentrates of Different Types

Pellets are one of the main types of iron-ore raw materials used in ferrous metallurgy. In Russia, the overall production of this iron-ore raw material is continuously growing. The analysis of pelletizing technologies over the last years has shown changes in requirements for product quality, process performance, heat and power parameters, environmental performance and production conditions of both fired and pre-reduced pellets. The article provides the analysis of technological and structural defects of conveyor-type induration machines. In order to remove these defects, we have developed an integrated technology for the production of fired pellets of various purposes. This technology made it possible to create an energy-efficient thermal system of the induration machine that has no counterparts in the world. This thermal system takes into account characteristics of the initial raw material. Its implementation at Mikhailovsky GOK in Russia provided a specific natural gas consumption within 8–9 nm3 /t of pellets and specific energy consumption less than 36 kW·h/t of pellets. These parameters were received by mathematical modelling and introduction of two-layer drying in the pellet induration process. The new induration technology has been implemented in Brazil and is now spreading at other plants in Russia. Keywords: pellets, iron-ore concentrates, induration machines, thermal systems, two-layer charging, pellet dryin

On the Theory of Directional Solidification in the Presence of a Mushy Zone

Abstract: A model is developed for the directional solidification of a binary melt with a two-phase zone (mushy zone), where the fraction of the liquid phase is described by a space–time scaling relation. Self-similar variables are introduced and the interphase boundary growth is inversely proportional to the square root of time. The mathematical model of the process is reformulated using self-similar variables. Exact self-similar solutions of heat-and-mass transfer equations are determined in the presence of two mobile phase-transition boundaries, namely, solid–mushy zone and mushy zone–liquid ones. The temperature and impurity concentration distributions in the solid phase, the mushy zone, and the melt are found as integral expressions. A decrease in the dimensionless cooled-boundary temperature leads to an increase in the solidification rate and the fraction of the liquid phase. The solidification rate, the parabolic growth constants, and the fraction of the liquid phase at the solid–mushy zone boundary are determined depending on the scaling parameter and the thermophysical constants of the solidifying melt. The positions of the solid–mushy zone and mushy zone–binary melt phase transition boundaries are found. The dependences of the solidification rate (inversely proportional to the square root of time) are analyzed. The scaling parameter significantly is shown to substantially affect the solidification rate and the fraction of the liquid phase in the phase transformation region. The developed model and the method of its solution can be generalized to the case of directional solidification of multicomponent melts in the presence of several phase transformation regions (e.g., main and cotectic two-phase zones during the solidification of three-component melts). © 2021, Pleiades Publishing, Ltd.This work was supported by the Russian Foundation for Basic Research (project no. 18-58-00034 Bel_a) and the Belarussian Foundation for Basic Research (project no. F18R-195)

THE ROLE OF FLUID VELOCITY ON THE SHAPE OF DENDRITIC TIPS

This study is concerned the shape of dendritic tip grown from an undercooled melt in the presence of fluid velocity. The tip shape function is derived and tested against numerical simulations when a forced convection plays a decisive role.L.V.T. acknowledges the financial support from the Russian Science Foundation (project no. 21-79-10012)

Bottom Production

We review the prospects for bottom production physics at the LHC.Comment: 74 pages, Latex, 71 figures, to appear in the Report of the ``1999 CERN Workshop on SM physics (and more) at the LHC'', P. Nason, G. Ridolfi, O. Schneider G.F. Tartarelli, P. Vikas (conveners

Modeling of recirculating hemodynamic flows close to coronary artery stenosis

The study addresses the simulation of flow in a straight vessel with two ideal stenoses of 75% and 50%. The blood flow was simulated using the Navier-Stokes hydrodynamic model, and the non-Newtonian properties were determined by the Carreau rheological model. It was founded that a low-velocity recirculation zone forms immediately behind the stenoses, the size of which depends on the velocity of blood flow.В работе рассматривается моделирование течения крови в прямом сосуде с двумя идеальными стенозами 75% и 50%. Моделирование потока крови производилось с помощью гидродинамической модели НавьеСтокса, а неньютоновские свойства определялись реологической моделью Карро. Установлено, что непосредственно за стенозами образуется низкоскоростная зона рециркуляции, размеры которой зависят от скорости тока крови

Modeling of Local Hematocrit for Blood Flow in Stenotic Coronary Vessels

This mainly theoretical work is devoted to the study of the contribution of the cell-free layer (CFL) near the vessel wall to hemodynamics in a large coronary artery with stenosis to assess the relevance of CFL modeling to the needs of interventional cardiology. An Euler–Euler model considering blood as a two-component fluid with a discrete phase of erythrocytes and a liquid plasma phase was applied to a simple 2d vessel with 65% stenosis. It was found that both the CFL thickness and the local contribution of the CFL thickness to hemodynamics are inhomogeneous along the vessel. The effects of CFL on the velocity profiles, vortex formation, hematocrit, viscosity, and wall shear stresses in the area of stenosis were determined. To demonstrate the significance of CFL modeling for prognostic purposes, the same hemodynamic conditions, analyzed using a one-component model, were also considered. A comparison analysis showed that the existence of CFL resulted in a significant overestimation (up to over 100%) of the main hemodynamic characteristics of the flow obtained using the model based on the Carreau equation. © 2023 by the authors.Russian Science Foundation, RSF: 22-71-10071This study was supported by the Russian Science Foundation (project no. 22-71-10071)

Measurement of the t t-bar production cross section in the dilepton channel in pp collisions at sqrt(s) = 7 TeV

The t t-bar production cross section (sigma[t t-bar]) is measured in proton-proton collisions at sqrt(s) = 7 TeV in data collected by the CMS experiment, corresponding to an integrated luminosity of 2.3 inverse femtobarns. The measurement is performed in events with two leptons (electrons or muons) in the final state, at least two jets identified as jets originating from b quarks, and the presence of an imbalance in transverse momentum. The measured value of sigma[t t-bar] for a top-quark mass of 172.5 GeV is 161.9 +/- 2.5 (stat.) +5.1/-5.0 (syst.) +/- 3.6(lumi.) pb, consistent with the prediction of the standard model.Comment: Replaced with published version. Included journal reference and DO

Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV

A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7 TeV is presented. The data were collected at the LHC, with the CMS detector, and correspond to an integrated luminosity of 4.6 inverse femtobarns. No significant excess is observed above the background expectation, and upper limits are set on the Higgs boson production cross section. The presence of the standard model Higgs boson with a mass in the 270-440 GeV range is excluded at 95% confidence level.Comment: Submitted to JHE