In-flight Melting Research Articles

Needle-like forms with a few tens of nanometer in diameter and more than a few tens of micrometer length, and specific oxygen state during In-flight glass melting

Needle-like forms with a few tens of nanometer in diameter and more than a few tens of micrometer length, and specific oxygen state during In-flight glass melting

Digital metal printing by electrohydrodynamic ejection and in-flight melting of microparticles

Metal additive manufacturing (AM) will impact many industries, including those producting of advanced structural, propulsion, electronic, and thermal systems. Many established metal AM processes involve layer-by-layer deposition and selective binding or melting of metal powders. However, these processes do not easily permit multi-material printing or printing directly onto non-planar surfaces. By contrast, AM techniques that deposit metal directly are typically low resolution (e.g., directed energy deposition), or cannot achieve bulk metal properties (e.g., ink-based methods). Here, we present a high resolution direct metal printing method that potentially addresses these limitations. Individual metal microparticles are electrohydrodynamically ejected on-demand from a nozzle-confined meniscus and laser-melted in-flight before landing and solidifying on a substrate. We demonstrate printing of solder and platinum particles ranging in size from 30 to 150 µm and explore the process parameter space as limited by the ejection conditions and the kinetics of melting, impact, and solidification. Our experiments demonstrate process compatibility with a wide range of powder feedstock materials, and tunability of the solidified morphology via the laser processing parameters. • Developed a direct printing method by on-demand depositing discrete metal microdroplets. • Enable multi-material printing by decoupling particle ejection and melting processes. • Revealed in-flight melting conditions for various metal microparticles. • Experimentally and numerically analyzed the molten droplet impingement and solidification.

In-flight melting method with an oxygen-excess gas burner for glass making

In-flight melting method with an oxygen-excess gas burner for glass making

Prediction of density and volume variation of hematite ore particles during in-flight melting and reduction

HIsarna is a promising ironmaking technology to reduce CO2 emission. Information of phase transformation is essential for reaction analysis of the cyclone reactor of the HIsarna process. In addition, data of density and volume of the ore particles are necessary for estimation of the residence time of the particles in the cyclone reactor. Phase transformation of iron ore particles was experimentally studied in a drop-tube furnace under simulated cyclone conditions and compared with thermodynamic calculation. During the pre-reduction process inside the reactor, the mineralogy of iron ore particles transforms sequentially from hematite to sub-oxides. The density changes of the particles during the melting and reduction can be predicted based on the phase composition and temperature. Therefore, density models in the studies were evaluated with reported experimental data of slag. As a result, a more reliable density model was developed to calculate the density of the formed slag containing mainly FeO–Fe2O3. The density and volume of the partially reduced ore particles or melt droplets were estimated based on this model. The results show that the density of the ore particles decreases by 15.1% at most along the progressive reduction process. Furthermore, the model results also indicate that heating, melting and reduction of the ore could lead to 6.63–9.37% swelling of the particles, which is mostly contributed by thermal expansion. It would result in corresponding variation in velocity of the ore particles or melt droplets during the flight inside the reactor.

The Role of Transport Phenomena and Modeling in the Development of Thermal Plasma Technology

A brief overview is presented of the principal areas where thermal plasmas had a significant technological impact over the past century. This is followed by an analysis of the specific role played by modelling and studies of transport phenomena under plasma conditions for three specific examples. The first dealing with the development of inductively coupled plasma sources. The following two examples deals with process development for the in-flight melting and spheroidization of powders, and the synthesis of nano-powders. Emphasis is placed on the critical role of plasma–particle interactions under dense loading conditions. A proposal is made for a relatively simple thermodynamic model which can be used for the estimation of the theoretical limits for the processing rates possible with different powders in each of these two cases. The model takes into account radiative energy losses from the surface of the particles and from the formed vapor cloud in the plasma, as well as the residual energy in the gases at the exit of the plasma reactor which are not accessible for process needs.

Experimental Studies on Melting Behavior of Silicon Powders by In-Flight Plasma Melting Technique

An experimental approach has been used to investigate the charateristics of silicon type powders using heat source of thermal plasma. In this paper, laboratory scale furnace (0.0529m3) using non-transferred hollow thermal plasma torch (150kW) is applied for the rapid melting and the impurities components volatilization. The components and the crystallization behavior of silicon type raw material for complete melting using in-flight melting technique with continuous powder feeding (500~1000 g min-1) into the furnace are investigated by changing the melting atmosphere. The determination of impurities absorption and erodability of the furnace caused by the extremely high localized tempeartures of plasma heat source and molten material is also followed.

Investigation of In‐Flight Glass Melting by Controlling the High‐Temperature Region of Multiphase AC Arc Plasma

A large volume discharge produced by a stable 12‐phase alternating current (AC) arc plasma is preferable to melt the granulated glass materials for time and energy saving. The discharge behavior and the high‐temperature region of the plasma system can be controlled by the electrode configurations. In this study, the spatial characteristics of the arc discharge were examined by image analysis with a high‐speed camera. The melting characteristics of alkali‐free glass particles were investigated by microscope and X‐ray diffractometry. This is the first time to investigate the relationship between spatial characteristics of plasma and glass particle property. Results show the arc existence area is strongly related to the electrode configuration. Distributions of in‐flight powders and the spatial characteristics of arc are important factors when using multiphase AC arc for in‐flight melting. This study provides information of efficient particle treatment according to the electrode configuration.

In-flight Melting Behavior of Granulated Alkali-Free Raw Material in Induction Thermal Plasmas

A new in-flight glass melting technology with induction thermal plasmas was developed to reduce the energy consumption and the emissions of greenhouse gases for glass production. The effects of carrier gas on the in-flight melting behavior of granulated alkali-free raw material were investigated by various modern analyses. Results show that the particles have smooth spherical surface and compact structure after heat treatment. As the carrier gas flow rate increases, the vitrification degree decreases and the average diameter increases. Higher vitrification results in more shrinkage of particle. The carbonates in raw material decompose completely during in-flight melting. The highest volatilization of B2O3 is attributed to more heat transferred from plasmas to particles at the lowest carrier gas flow rate.

Experimental investigation of in-flight melting by hybrid heating of multi-phase alternating current arc with oxygen burner for alkali-free glass raw materials

An innovative in-flight glass melting technology was developed for a purpose of energy saving and environmental protection. Granulated glass raw materials with small diameter were treated by hybrid heating of multi-phase AC arc combined with an oxygen burner. A multi-phase AC arc and hybrid plasma were compared to study the in-flight melting efficiency of the granulated raw materials. The effects of the input energy and the primary size of SiO2 in the glass raw materials on the characteristics of the in-flight melted particles were investigated. The reaction rate inside the individual in-flight particles was enhanced with decreasing the primary size of SiO2 particles, resulting in the more effective in-flight melting by the hybrid plasma.

In-Flight Particle Measurement of Alkali-Free Glass Raw Materials in 12-Phase AC Arc Plasma

In-flight particle measurements of the surface temperature and velocity are important for understanding of melting behavior of glass particles during in-flight melting by multi-phase AC arc plasma. However, the use of optical pyrometry for particle surface temperature has inevitable uncertainties due to non-thermal emissions signals from the plasma plume. This work presents spectroscopic measurements of the non-thermal signals which were found to be caused mainly by the plasma emissions scattered by the particles and the radiation emitted by vapor. After that, the accuracy of thermal radiation measurement was estimated and surface temperature of in-flight glass particle was corrected.

Characterization of 12-Phase AC Arc Discharge and Glass In-Flight Melting Behavior

Thermal plasma of 12-phase AC arc was successfully developed and applied in the field of glass in-flight melting, and the arc discharge behavior was characterized by image analysis. The effects of sheath gas flow rate on arc discharge and melting behavior of granulated glass raw material were investigated. Results show that different sheath gas flow rates lead to various arc discharge and high-temperature region. The fluctuation of luminance area ratio and coefficient of variation reflects the change of arc discharge behavior. As the sheath gas flow rate increases, the ratio of luminance area decreases and the center temperature of arc increases. The vitrification degree of glass raw material is mostly dependent on the center temperature of arc, higher center temperature and more vitrification degree.

Discharge Behavior Characterization of 12-Phase AC Arc and its Application

A stable 12-phase AC arc was successfully developed and applied in the field of glass in-flight melting, and the arc discharge behavior was characterized by image analysis. The effects of sheath gas flow rate on arc discharge and melting behavior of granulated glass raw material were investigated. Results show that different sheath gas flow rates lead to various arc discharge and high-temperature region. The fluctuation of luminance area ratio and coefficient of variation reflects the change of arc discharge behavior. As the sheath gas flow rate increases, the ratio of luminance area decreases and the center temperature of arc increases. The vitrification degree of glass raw material is mostly dependent on the center temperature of arc, higher center temperature and more vitrification degree.,A stable 12-phase AC arc was successfully developed and applied in the field of glass in-flight melting, and the arc discharge behavior was characterized by image analysis. The effects of sheath gas flow rate on arc discharge and melting behavior of granulated glass raw material were investigated. Results show that different sheath gas flow rates lead to various arc discharge and high-temperature region. The fluctuation of luminance area ratio and coefficient of variation reflects the change of arc discharge behavior. As the sheath gas flow rate increases, the ratio of luminance area decreases and the center temperature of arc increases. The vitrification degree of glass raw material is mostly dependent on the center temperature of arc, higher center temperature and more vitrification degree.

Application and Characterization of 12-Phase AC Arc for Glass in-Flight Melting

A stable 12-phase AC arc was successfully generated and applied in the field of glass in-flight melting, the arc behavior was characterized by image analysis. The effects of electrode configuration and sheath gas flow rate on arc and melting behavior of granulated glass raw material were investigated. Results show that different electrode configurations leads to various arc discharge and high-temperature region. The luminance area with high-temperature region and its fluctuation reflect the change of arc discharge behavior. The vitrification degree of glass raw material is mostly dependent on the center temperature of arc. As the sheath gas flow rate increases, the ratio of luminance area decreases and the center temperature of arc increases.

Investigation of In-Flight Melting Behaviour of Granulated Glass Raw Material by Multi-Phase AC Arc Plasma and Hybrid Plasma

An innovative in-flight glass melting technology was developed for a purpose of energy saving and environmental protection. Granulated glass raw materials with small diameter were treated by twelve-phase AC arc and that combined with an oxygen burner. The particle measurement was carried out to investigate the in-flight melting behavior of glass raw materials during the in-flight melting by twelve-phase AC arc. Obtained results show the mean particle velocity was about 9 m s−1 and mean temperature was about 2600 K. The high vitrification degree achieved within several milliseconds reveals that the new in-flight melting technology of hybrid plasma treating can reduce energy consumption and shorten the glass production cycle.

In-flight melting behavior of different glass raw materials by hybrid heating of twelve-phase ac arc with oxygen burner

An innovative in-flight glass melting technology was developed for a purpose of energy saving and environmental protection. Granulated glass raw materials with small diameter were treated by hybrid heating of twelve-phase ac arc combined with an oxygen burner. X-ray diffraction analysis showed that all carbonates in raw materials were decomposed and > 94% SiO 2 (quartz) was reacted into a noncrystalline state. The high vitrification degree achieved within several milliseconds reveals that the new in-flight melting technology of hybrid plasma treating can reduce energy consumption and shorten the glass production cycle.

Effect of Injection Position on In-Flight Melting Behavior of Granular Alkali-Free Glass Raw Material in 12-Phase AC Arc Plasma

An innovative in-flight glass melting technology with a multi-phase AC arc plasma was developed to save energy and reduce emissions for the glass industry. The effect of the injection position on the in-flight melting behavior of granulated powders was investigated. Results show that the injection position has a strong effect on the melting behavior of alkali-free glass raw material. With the increase in injection distance, the vitrification, decomposition, and particle shrinkage of initial powders are improved. Longer injection distance causes much energy to transfer to particles due to a longer residence time of powder in the high temperature zone. The high vitrification and decomposition degrees indicate that the new in-flight melting technology with 12-phase AC arc can substantially reduce the melting and refining time for glass production.

Characteristics of Multi-Phase Alternating Current Arc for Glass In-Flight Melting

An innovative in-flight melting technology with multi-phase AC arc was developed for glass industry. The enthalpy probe and high speed video camera were used to characterize the temperature, velocity, and discharge behavior of multi-phase AC arc. The effects of input power and sheath gas flow rate on arc and melting behavior were investigated. Results show that the temperature and velocity on arc center are increased with input power or sheath gas flow increase. The fluctuation of luminance area ratio and coefficient of variation reflects the change of arc discharge behavior. High temperature of plasma enhances the melting of granulated raw particles during in-flight heating treatment. The shrinkage of particle and the volatilization degree of Na2O increase under a larger flow rate of sheath gas. The characterized arc behavior agrees with the melting behavior of glass raw materials, which can provide valuable guidelines for the process control of glass melting.

Numerical and Experimental Investigation on the In-Flight Melting Behaviour of Granulated Powders in Induction Thermal Plasmas

An innovative in-flight glass melting technology with thermal plasmas was developed for the purpose of energy conservation and environment protection. In this study, modelling and experiments of argon-oxygen induction thermal plasmas were conducted to investigate the melting behaviour of granulated soda-lime glass powders injected into the plasma. A two-dimensional local thermodynamic equilibrium (LTE) model was performed to simulate the heat and momentum transfer between plasma and particle. Results showed that the particle temperature was strongly affected by the flow rate of carrier gas and the particle size of raw material. A higher flow rate of carrier gas led to lower particle temperature and less energy transferred to particles which resulted in lower vitrification. The incomplete melting of large particles was attributed to the lower central temperature of the particle caused by a larger heat capacity. The numerical analysis explained well the experimental results, which can provide valuable practical guidelines for the process control in the melting process for the glass industry.

Investigation on in-flight melting behavior of granulated alkali-free glass raw material under different conditions with 12-phase AC arc

Abstract An innovative in-flight melting technology with 12-phase alternating current (AC) arc has been developed to investigate the melting behavior of granulated alkali-free glass raw material. Results show that the melted particles have spherical shape with smooth surface and compact structure. Lower vitrification and decomposition degrees of raw material as well as lower volatilization of B 2 O 3 are attributed to less heat transferred per particle under larger flow rate of carrier gas and higher feed rate. The high vitrification and decomposition degrees indicate that the new in-flight glass melting with 12-phase AC arc will be a promising technology for glass production.

Application of In-Flight Melting Technology by RF Induction Thermal Plasmas to Glass Production

An innovative in-flight glass melting technology with induced thermal plasmas was developed for the purpose of energy conservation and environmental protection. Two-dimensional modeling was used to simulate the thermofluid fields in the plasma torch. The in-flight melting behavior of glass raw material was investigated by various analysis methods. Results showed that the plasma temperature was up to 10000 K with a maximum velocity over 30 m/s, which made it possible to melt the granulated glass raw material within milliseconds. The carbonates in the raw material decomposed completely and the compounds in the raw material attainted 100% vitrification during the in-flight time from the nozzle exit to substrate. The particle melting process is similar to the unreacted-core shrinking model.