Characteristics of a coherent jet enshrouded in a supersonic fuel gas

Based on a current coherent jet, this study proposes a supersonic combustion(SC) coherent jet in which the main oxygen jet is surrounded by a supersonic fuel gas. The characteristics of the proposed coherent jet are analyzed using experimental methods and numerical simulations in the high-temperature environment of electric arc furnace(EAF) steelmaking. The SC coherent jet achieved stable combustion in the EAF steelmaking environment. The simulated combustion temperature of the supersonic shrouding methane gas was 2930 K, slightly below the theoretical combustion temperature of methane–oxygen gas. The high speed and temperature of the supersonic flame effectively weakened the interaction between the main oxygen jet and the external ambient gas, inhibiting the radial expansion of the main oxygen jet and maintaining its high speed and low turbulence over a long distance. These features improved the impact capacity of the coherent jet and strengthened the stirring intensity in the EAF bath.     

EAF steelmaking process with increasing hot metal charging ratio and improving slagging regime

A new electric arc furnace (EAF) steelmaking process with increasing hot metal charging ratio and improving slagging regime simultaneously was developed and applied in a 50 t electric arc furnace for more than a year at No. 1 Steelmaking Plant of Shanxi Taigang Stainless Corporation Limited. The essential fact of the new EAF steelmaking process was to charge hot metal in two portions or steps: firstly, 35wt%-40wt% hot metal was pretreated by blowing oxygen in a specially designed reactor for decar burization and improving hot metal temperature and melting premelted slag; secondly, 30wt% hot metal was charged into EAF with high basicity refining slags from ladle furnace (LF)-vacuum degassing furnace (VD) refining process. The results show that the hot metal charging ratio can reach to about 65wt%-70wt% for the new EAF steelrnaking process; meanwhile, the tap-to-tap time of a 50 t EAF can shorten by 5-10 min, the electricity consumption can decrease by 35-50 kW·h/t, the lime consumption can reduce by 10.5 kg/t of molten steel, and the content of harmful heavy metals in molten steel can be easily controlled to less than the upper limits of aimed steel specification or grade compared with the traditional EAF steelmaking process. In addition, the dephosphorization ability shows a slight strengthening, however, a small degree of lessening for desulphurization ability is observed for the new EAF steelmaking process, but the weakness of desulphurization ability cannot become an obstacle to its further application since a stronger desulphurization ability can be achieved during secondary refining of LF coupled with VD after EAF steelmaking process.     

Experimental investigation on upstream-injection interaction with a scramjet cavity flameholder

The study has evaluated the coherent structures and the velocity field of gaseous transverse jet upstream of a scramjet flameholder in a supersonic turbulent flow. The high spatiotemporal resolution coherent structures of the jet plume/wakes and the cavity shear layer were obtained by utilizing the nanoparticle-based planar laser scattering technique. Compared to the no upstream injection case, the cavity shear layer downstream of the jet shows significant mass exchange with mainstream. The particle image veloc- imetry velocity field and the velocity profiles demonstrated that the interaction intensity of the cavity shear layer with the upstream injection is further enhanced as the injection stagnation pressure increases.     

Direct numerical simulation of hydrogen turbulent lifted jet flame in a vitiated coflow

The direct numerical simulation (DNS) method with 16 steps detailed chemical kinetics was applied to a lifted turbulent jet flame with H2/N2 fuel issuing into a wide hot coflow of lean combustion products,at temperature of 1045 K and low oxygen concentrations. The chemical reactions were handled by the library function of CHEMKIN which was called by the main program in every time step. Parallel com-putational technology based on message passing interface method (MPI) was used in the simulation. All the cases were run by 12 CPUs on a high performance computer system. Faver-averaged DNS re-sults were obtained by long time averaging the transient profile and compared with the experimental data. The roll-up and evolution of the vortices in jet flame were well captured. The vortices in the same rotating direction attracted each other and those in different rotating directions repulsed each other. Through complex interactions between vortices,the original symmetrical vortex structure could be converted into nonsymmetrical and more complex structures by combination,distortion and splitting of the vortices. The transient profiles of H,OH and H2O mass fraction at 5.76 ms showed the flame structure in jet flame,especially the autoignition regions clearly. The lift-off height was about 9 d―11 d,in agreement with the experimental observation. At the corner point of the flame sheet indicated by OH and H profiles,the combustion was always enhanced by the flame curvature and extended resident time. The profiles of turbulence intensities show that the flames were diffused from the original two outside flame sheets into the core. The DNS results can be considered in developing more accurate and more universal turbulence models.     

Mathematical model of heat transfer for bloom continuous casting

A mathematical model for heat transfer during solidification in continuous casting of automobile steel, was established on researching under the influence of the solidifying process of bloom quality of CCM in the EAF steelmaking shop, at Shijiazhuang Iron and Steel Co. Ltd. Several steel grades were chosen to research, such as, 40Cr and 42CrMo. According to the results of the high temperature mechanical property tests of blooms, the respective temperature curves for controlling the solidification of different steels were acquired, and a simulating software was developed. The model was verified using two methods, which were bloom pinshooting and surface strand temperature measuring experiments. The model provided references for research on the solidifying process and optimization of a secondary cooling system for automobile steel. Moreover, it was already applied to real production. The calculated temperature distribution and solidification trend of blooms had offered a reliable theory for optimizing the solidifying process of blooms, increasing withdrawal speed, and improving bloom quality. Meanwhile, a new secondary cooling system was designed to optimize a secondary cooling water distribution, including choice and arrangements of nozzles, calculation of cooling water quantity, and so on.     

Flow-accelerated corrosion behavior of 13Cr stainless steel in a wet gas environment containing CO<Subscript>2</Subscript>

This work investigated the flow-accelerated corrosion (FAC) behavior of 13Cr in a wet CO₂-containing environment at different flowing gas velocities and impinging angles, with the natural-gas pipeline environment simulated by a self-assembled impingement jet system. Surface morphology determination, electrochemical measurements, and hydromechanics numerical analysis were carried out to study the FAC behavior. The results demonstrate that pitting corrosion was the primary mode of corrosion in 13Cr stainless steel. High-flow-rate gas destroyed the passive film and decreased the pitting potential, resulting in more serious corrosion. The corrosion degree with various impact angles showed the following order: 90° > 60° > 45°. The shear force and the electrolyte from the flowing gas were concluded to be the determinant factors of FAC, whereas the shear force was the main factor responsible for destroying the passive film.     

Flow-accelerated corrosion behavior of 13Cr stainless steel in a wet gas environment containing CO_2

This work investigated the flow-accelerated corrosion(FAC) behavior of 13 Cr in a wet CO_2-containing environment at different flowing gas velocities and impinging angles, with the natural-gas pipeline environment simulated by a self-assembled impingement jet system. Surface morphology determination, electrochemical measurements, and hydromechanics numerical analysis were carried out to study the FAC behavior. The results demonstrate that pitting corrosion was the primary mode of corrosion in 13 Cr stainless steel. High-flow-rate gas destroyed the passive film and decreased the pitting potential, resulting in more serious corrosion. The corrosion degree with various impact angles showed the following order: 90° 60° 45°. The shear force and the electrolyte from the flowing gas were concluded to be the determinant factors of FAC, whereas the shear force was the main factor responsible for destroying the passive film.     

Influence of operation parameters on flash smelting furnace based on CFD

The influence of three important operation parameters in Jinlong flash smelting furnace, including the distributing blast speed, the oxygen enrichment rate of process air and the ratio of central oxygen to overall oxygen (O_c/O_o), has been investigated using a virtual simulation system on copper flash smelting furnace. The core of this virtual simulation system is a numerical simulation of CFD (computational fluid dynamics), and this system incorporates coupling momentum transport, heat transport, mass transport,reaction kinetics between gas and particles and chemical reactions between gas and gas. A set of numerical predicted data were obtained. The CFD simulation shows that there is a sensitive zone of the distributing blast speed, and the dust content ascends when the speed exceeds 180 m·s-1. Increasing the oxygen concentration of processing air benefits the efficient production of the flash smelting furnace.     

Numerical calculation of flow and heat transfer process in the new-type external combustion swirl-flowing hot stove

It is clarified that the important method to improve the blast temperature of the small and the middle blast furnaces whose production is about two-thirds of total sum of China from 1000℃ to 1250-1300℃ is to preheat both their combustion-supporting air and coal gas. The air temperature of blast furnaces can be reached to 1250-1300℃ by burning single blast furnace coal gas if high speed burner is applied to blast furnaces and new-type external combustion swirl-flowing hot stove is used to preheat their combustion-supporting air. The computational results of the flow and heat transfer processions in the bot stove prove that the surface of the bed of the thernal storage balls there have not eccentric flow and the flow field and temperature field distribution is even. The computational results of the blast temperature distribution are similar to those determination experiment data. The numerical results also provide references for developing and designing the new-type external combustion swirl-flowing hot stoves.     

Improvement of power input for steelmaking process in high impedance EAF

According to the electrical operation and steelmaking theory of EAF, an improved power input procedure of 70t high impedance EAF in Nanjinng Iron and Steel Corp. Ltd. was studied. The investigation method, process and result for use of power supply of high impedance EAF was proposed, and the optimized power-supply curve to EAF steelmaking practice was given, and electrical operation was improved, the electric energy consumption can be reduced by 25 kW·h/t, and power supply time can also be reduced 3 min.     

Study on Oxygen Content,Inclusions and Fatigue Properties of Bearing Steels Produced by Different Processes

The metallurgical properties and fatigue life of bearing steel processed by electric furnace (EAF), ladle refining (LF-VD), continous casting (CC) and electroslag remelting (ESR) have been investigated. The main results obtained are as follows: (1) Due to low oxygen content and dispersion inclusions in steel, the fatigue Life of LF-VD-IC or CC is three times as high as that of EAF steel; (2) The oxygen content in steel produced by CC process is about 9.0×10-6, the carbon segregation (C/C₀) is from 0.92 to 1.10 and the fatigue life of CC steel is equal to that of ladle refining ingot casting steel; (3) Although the amount of inclusion and oxygen in ESR steel is higher than that of LF-VD-IC or CC steel, the fatigue life of ESR steel is higher than that of the latter because of its fine and well dispersed inclusions.     

Moisture effect on the combustion of a single copper concentrate particle in a flash smelting furnace

A mathematical model has been presented to study the combustion of a single copper concentrate particle with high moisture content. By using the presented model, the effect of particle moisture content on particle temperature, sulfur oxidation, and combustion heat generation has been evaluated. The mineralogical composition of the commonly used concentrate at Khatoonabad flash smelting furnace has been used in this study. It was found that the particle moisture content is removed in the sub-second time range and thus the moisture has marginal impact on the variation of particle temperature and on the reaction rate when the gas temperature is assumed to be constant in the reaction shaft. When a concentrate with high moisture content is charged, the particle size enlargement due to the agglomeration of concentrate particles causes an abrupt fall in the particle reaction rate.     

A process model for BOF process based on bath mixing degree

The process model for BOF process can be applied to predict the liquid steel composition and bath temperature during the whole steelmaking process. On the basis of the traditional three-stage decarburization theory, the concept of mixing degree was put forward, which was used to indicate the effect of oxygen jet on decarburization. Furthermore, a more practical process model for BOF steelmaking was developed by analyzing the effect of silicon, manganese, oxygen injection rate, oxygen lance height, and bath temperature on decarburization. Process verification and end-point verification for the process model have been carried out, and the verification results show that the prediction accuracy of carbon content reaches 82.6% (the range of carbon content at the end-point is less than 0.1wt%) and 85.7% (the range of carbon content at end-point is 0.1wt%–0.7wt%) when the absolute error is less than 0.02wt% and 0.05wt%, respectively.     

Effects of injection temperature on the jet evolution under supercritical conditions

A nitrogen jet with subcritical and supercritical injection temperatures injected into a supercritical environment, in which both the pressure and temperature exceed those of the thermodynamic critical state, has been investigated numerically using large-eddy simulation technique. The effects of the injection temperature on the flow evolution are studied. We find that the jet surface is more unstable with the instability waves growing up and rolling into a succession of ring vortices for supercritical injection temperature, and the jet surface is nearly straight with the strong density stratification suppressing the development of the instability waves for subcritical injection temperature. With increasing injection temperature, the spatial growth rate of the surface instability wave strengthens and the frequency of the most unstable mode increases. This behavior is of importance in enhancing the fluid mixing effect. The results obtained in this study provide physical insight into the understanding of fundamental mechanisms of the jet evolution under supercritical conditions.     

Combustion characteristics of aluminium-iron oxidein SHS-gravitational process

In order to get high quality of products, the combustion of aluminium-iron oxide thermite in SHS-gravitational process must be under control. The effects of thermite filling density, hole in thermite and inclined angle of pipe on combustion rate were studied. It shows that the combustion rate decreases with the decrease of filling density. The thermite combusts downwards the pipe much more quickly if there are holes in the thermite. And the combustion rate increases with the increase of the inclined angle of pipe. The experiment results show that the combustion of thermite is predominantly controlled by gas phase reaction, which is attributed to the high temperature of the thermite combustion.     

Visualization of Coherent Structures in Acoustically Forced, Gas-Particle Turbulent Round Jet

To show the effects of the particles and forced disturbances on the instantaneous large-scale vortex structures in a gas-particle round jet, coherent structures in gas-particle turbulent round jets were investigated experimentally by flow visualization. The 45-μm and 350-μm diameter glass beads were used as the particles in the experiments. An acoustic speaker was used to introduce velocity perturbations at the jet exit. The Strouhal number based on the nozzle diameter, exit velocity, and forcing frequency was varied from 0,1 to 0.9. The Reynolds number was 9400. The coherent structures were visualized in unforced and forced single-phase jet flows and unforced and forced particle-laden jet flows with different diameter glass beads. The experimental results show that the particles have significant effects on the gas phase coherent structures. The coherent structures are controlled by the large 350-μm diameter particles, while the structures are mainly dominated by the forced disturbances in the flows with 45-μm diameter particles.     

Leaching behavior of zinc and copper from zinc refinery residue and filtration performance of pulp under the hydrothermal process

This study aims to investigate the leaching behavior and filtration performance of zinc refinery residue under hydrothermal conditions. The relationships between the structure and morphology of silicon in the leaching residue and the pulp filtration performance were explored by determining the pulp filtration speed, analyzing quantitatively the silicon content in the leachate, and characterizing the leaching residue structure. The results show that hydrothermal leaching induces the coagulation–hydrolysis of the silicon in solution, consequently altering the microstructure of the leaching residue, and that silicon oxygen tetrahedra([SiO_4]~(4-)) form the main skeleton structure of the residue. The results obtained also show that the leaching rates of zinc and copper are 98.1% and 98.7%, respectively, and that the filtration speed is 526.32 L/(m~2·h) under the conditions of sulfuric acid concentration of 140 g/L, leaching temperature of 160°C, leaching time of 3.0 h, oxygen partial pressure of 0.75 MPa, stirring speed of 600 r/min, and a liquid-to-solid ratio of 10 mL/g.     

NOx Formation from Several Chinese Coals during Combustion in Packed Bed

The formation characteristics of NO_x during combustion of four typical Chinese coals have been studied in a packed bed combustor. The studies included the effects of chemical composition of coals and volatile matters, and combustion conditions, i.e. preheating temperatures of combustion gas, on conversion of NO_x during combustion. In term of the combustion experiments, there is a close relation between coal composition and conversions of NO_x. Coals with a higher nitrogen content give a lower F_NOx0, and coals with a higher volatile content give a lower F_NOx0. The further devolatilization experiments showed that volatile matters in the coal have an important effect on reducing conversion of coal-nitrogen to NO_x. It was interpreted as that the release of volatile matters during combustion caused a fuel-rich circumstance in the vicinity of coal particles which may restrain the formation of NO_x. Preheating temperatures of combustion gas has significant effects on conversions of NO_x and there exist a critical preheating temperature. At such temperature, lower F_NOx0 can be reached.     

Microstructure and properties of high emissivity coatings

A new coating on lining in industrial furnace for energy saving has been developed. Properties and microstructure of the coatings were revealed by emissivity instrument,X-ray diffraction (XRD),transmission electron microscope (TEM) and scanning electron microscope (SEM),respectively. The result indicates that the emissivity of coatings is higher than 0.90 and the thickness of coatings is about 200 μm. ZrO₂,Cr₂O₃ and SiC in the coating benefit practical applications of coatings at high temperature with durable high emissivity and the continuous structure between the coatings and the substrate makes the coatings high cohesion and excellent adhesion for both specimens with and without sintering at high temperature. Result from laboratory experiment shows that the heating speed of specimen with coating is higher than that of controlled specimen and the temperature increases 30℃ during the heating. The average temperature drop of specimen with coatings has a 13.5% improvement in the cooling speed. The application of coatings on the checker brick in a blast furnace of 1750m3 indicates that the coating causes the blast temperature to an average increase of 28℃,reduces the fluctuation of blast temperature before the blowing-in and leads to a fuel saving of 10% approximately.     

Study on characteristics of controllable active thermo-atmosphere of a vitiated coflow combustor

Turbulent combustion remains to be one of most complicated technologies due to the complexities of turbulence and combustion as well as the interaction of both.This paper presents a vitiated cofiow combustor, which is newly used for the fundamental research into turbulent combustion. The characteristics of controllable active thermo-atmosphere (CATA) of a vitiated coflow combustor are investigated. The results show that the oxygen mole frac tion of vitiated coflow flames between 0% and 21% yield coflow temperature between 700 and 1500 K, and there is a constant temperature space as a cylinder with a radius of 40mm. These features of the vitiated coflow indicate the existence of a controllable active thermo-atmosphere, which benefits the basic study on the autoignition of a combustible mixture in a homogeneous charge compression ignition (HCCI) combustion.