Open Bath Research Articles

Critical Review of the Metallurgical Operation of the Greek Nickel Industry and Perspectives, based on the recent Industrial Experience on Smelting Reduction Process

The mining and industrial production of Greek ferronickel industry LARCO have ceased since 30.07.2022. The last LME nickel price crisis, exclusion from bank loaning, extremely high cost of electrical energy, management issues, resulted inter alia, in a prohibitive operational cost. Nevertheless, LARCO faces the challenge of restructuring and reoperation in the future, given that privatization is in progress, including the acquisition of the company’s assets to a joint venture enterprise.
 Within this framework, the current paper aims to contribute to the discussion for developing a new management strategy for the optimization of pyrometallurgical process, focusing on the critical step of smelting reduction. Based on industrial experience concerning open bath submerged arc electric furnaces, factors which critically affect the safety and cost-effectiveness of smelting reduction are detected and presented by means of case studies, being mainly classified as following: i) Optimal raw materials’ feed management, including laterite ores (domestic or not), solid fuels and electrode paste. Moreover, taking for granted the need for Ni-rich ‘foreign’ ores to increase the recovery and reduce the cost of the process, the extent of dependence on Fe-rich domestic ores is investigated, in order a safe and stable operation to be ensured. ii) Focus on preventive maintenance management. Substantial increase of the facilities’ operational index and cost saving is obtained, as proved by operational case studies. iii) Modern human resources management strategy. Their economical footprint is further discussed.

Experimental and Simulative Analysis of the Pressure Development in a Closed Injection Pultrusion Process with Multiple Chamber Geometries

The use of innovative higher-performance highly reactive resin systems requires an enhancement of the established method of fiber impregnation (open bath) towards closed resin-injection pultrusion (CIP), due to the short pot life of the resin systems. The result is that the open bath is developed into a closed injection and impregnation chamber ("ii-chamber"). In this study, three parameters-resin viscosity, opening angle and opening factor at the injection point on the ii-chamber-are varied, each in three stages. For each set of parameters, a pultrusion trial is conducted and the process pressures in the ii-chamber and pultrusion die measured. This enables direct feedback via the process conditions of the as yet uncured composite. The data obtained are used to validate a newly developed simulation model. The model is based on Darcy's law, which has been extended to take fiber movement into account and thus represent the resulting pressure increase in the die. The flexible ii-chamber and die concept enhance our understanding of the processes taking place in the die system. The sensitivity of the process pressures can be shown for the three influencing variables. The experiment shows that of the three influencing variables investigated, viscosity has the greatest sensitivity to pressure development. In general, it can be said that over the length of the pultrusion die system, the pressure level increases across the three measuring points.

Processing and Evaluation of a Carbon Fiber Reinforced Composite Bar Using a Closed Impregnation Pultrusion System with Improved Production Speed

In this paper, an epoxy resin-based carbon fiber reinforced composite (CFRP) bar pultrusion system using a closed impregnation device which has various advantages in process compared to traditional open bath type pultrusion system was developed, and the fiber impregnation system was improved through the analysis of resin properties for the high-speed production of CFRP bars used to support the mother glass in the display transfer cassettes. To improve the fiber feeder system, fiber guides were switched from perforated plates to roller guides for spreading fibers, which allowed the input fibers to be widened and flattened while reducing the fiber thickness. Additionally, the correlation between resin viscosity and impregnation speed were analyzed to evaluate the resulting mechanical properties at different pultrusion speeds and temperatures. A CFRP bar was produced with resin injection at room temperature and a pultrusion rate of 400 mm/min and compared to a CFRP bar produced with fiber spreading, a resin injection temperature of 40 °C, and a pultrusion rate of 600 mm/min; the latter with a 50% improved production rate showed improvements in mechanical properties, including the cross-sectional void by 98.7%, surface roughness by 75.5%, deflection by 34.9%, and bending strength by 70%.

Cryogenic testing of a 25 kV RIS bushing

High voltage bushings for cryogenic current or voltage leads must master safely the special thermal stress in addition to the high voltage requirements. Resin impregnated synthetic (RIS) bushings have proven their usability for room temperature high voltage application since few years. Such paper free bushings are less hygroscopic than paper based bushings, which can be an advantage for components exposed to cryogenic temperatures on one side and to air conditions on the other. A conventional 25 kV, 2 kA room temperature RIS bushing was assembled to an open bath cryostat and subjected to five thermal cycles. High voltage tests were successfully performed under cryogenic conditions. No degradation of the bushing was found after the thermo-mechanical stress of the fast cool downs and one fast warm up. This paper focuses on the thermal tests.

Short Circuit and Recovery Time Tests in a helical bifilar R-SFCL module

Superconducting Fault Current Limiter (SFCL) modules with distinct arrangements have been investigated, seeking design and performance enhancements. In this context, this work aims to propose a design for resistive SFCL (R-SFCL) modules, using RE-Ba-Cu-O high-temperature superconducting tapes (HTS) wound on an alternative support material. An R-SFCL bench prototype was designed for 400 A and 500 V. Two pieces of 2G tapes, arranged in a bifilar antiparallel configuration were wound on Acrylonitrile Butadiene Styrene (ABS) tubes, which were made by means of a 3D printer. During the experiments, the SFCL was immersed in an open bath cryostat with liquid nitrogen and several measurements were carried out. The average limited current is about three times lower than the prospective one. To test the SFCL recovery time, the following procedure was adopted: The fault is induced during three cycles, and after, the current is reduced to zero. The SFCL is reconnected after some time considering that the fault was extinct, and the voltage level returned to normal operation. The results showed promising levels of limitation and recovery time for further developments.

Comparative Study of Heat Transfer Performance and Visualization Images of Superfluid Helium Boiling in Narrow Two-dimensional channel

In a narrow channel, boiling heat transfer in He II is much different from that in the case of an open bath. Even under saturated pressure condition, rapid temperature rise due to the onset of film boiling is not seen when the temperature reaches the lambda temperature, but only the temperature oscillation is detected. The behaviour of this state looks like the nucleate boiling, though it is known the steady nucleate boiling state is absent in He II in open bath. The high heat transfer coefficient in this quasi-nucleation boiling state above the lambda temperature suggests the range where this advantage in heat transfer appears is wider than that based on simple prediction of He II heat transfer. The appearance of metastable states of superheated He II and superheated He I should be considered in the case of a narrow channel. In this study, the visualization experiment result using a transparent heater and the transient temperature measurement data on a copper heater surface had been compared with each other. In the case of rather high heat flux, several film boiling modes were observed in a narrow two-dimensional channel. The peak of the heat transfer coefficient appeared around the lambda pressure. In the case of low heat flux, the heat transfer coefficient variation with the pressure shows sudden rise around the lambda point. The heat transfer coefficient under nearly saturated pressure condition below the lambda pressure is larger than that above the lambda pressure.

Experimental Measurement of the Resistant Load in Injection Pultrusion Processes

Injection pultrusion (IP) process is a manufacturing technique for producing advanced fiber reinforced polymers having constant cross-section. Unlike the traditional pultrusion process, in which fibers are impregnated passing through an open bath of liquid resin, in IP the uncured polymer is directly injected within the advancing reinforcement in a close chamber generally connected to the die. This paper investigates the resistant forces evolution in IP process at different pulling speeds. Resistant loads are mainly due to the interaction between the advancing material and the die cavity walls, inducing residual stress and, eventually, internal defects. These loads are typically classified in three main contributes, namely fiber collimation, viscous drag and solid friction. The latter two are directly related to the resin degree of cure, and, therefore, the overall resistant load is dramatically sensitive to the changes in operative parameters. In this paper, the resistant force acting along the die cavity has been measured using a dedicated experimental setup. Measurements were performed during the pultrusion of glass-reinforced polyester with different pulling speeds to evidence the variations in resistant load as a function of the process velocity.

Comparison of the Processing of Epoxy Resins in Pultrusion with Open Bath Impregnation and Closed-Injection Pultrusion

In this study, the influence of the open bath and closed-injection pultrusion (CIP) processing methods of epoxy resins on the quality of glass fiber composites was investigated. In addition to the state-of-the-art epoxy resin system with long pot life, new resin systems with short pot life have recently been developed. These systems require processing by closed-injection pultrusion. The epoxies with long pot life allow both processing variants. The experimental work was carried out with two types of injection and impregnation chambers (ii_chamber), namely with a conical and a teardrop design. Fully impregnated composites, which were used for further analyses, could be produced by using the conical ii_chamber. The composite properties of the open bath and the conical ii_chamber impregnation methods were compared. No significant influence on the bending stress could be determined; the interlaminar shear strength was up to 10% better with open bath impregnation than with ii_chamber. For the composites investigated, it was shown that the open bath and ii_chamber impregnation methods can be used to produce parts with partially comparable properties, as demonstrated for the epoxy formulation with long pot life. These results indicate that processing of epoxy systems with a short pot life is also possible by closed-injection pultrusion. Furthermore, the influence on the composite properties of the time interval between the mixing of an epoxy resin and processing in an open bath was investigated. No significant effect on the bending stress and interlaminar shear strength could be determined.

A floating modular cover for high temperature open-tank molten salt solar-thermal volumetric receivers

Directly irradiated and volumetrically absorbing liquid-based solar receivers promise to enhance peak solar flux limits relative to surface absorbers and enable simpler receiver designs with integral thermal storage. However, their thermal efficiency is limited by large thermal losses at high operating temperatures. The harsh, high temperature (>400 °C) environments in liquid-based receivers impose significant material and system design constraints in mitigating heat losses, particularly for large-scale, commercial-size receivers. Here we report a new cover design that reduces thermal losses up to 51% while reducing the optical efficiency by less than 5%. The proposed design consists of floating hollow fused silica spheres and is stable in harsh high temperature environments, highly solar-transparent, reduces convective and radiative losses, and minimizes the surface area available for evaporation losses. In addition, the modular components allow easy online maintenance and unlike a single continuous window-pane, there is no limit to the surface size the spheres can cover. This transparent, insulating cover has the potential to enable much higher solar-thermal volumetric receiver temperatures and could also be used in other high temperature open bath industrial applications to provide energy savings.

Porcine Isolated Liver Perfusion for the Study of Ischemia Reperfusion Injury: A Systematic Review.

Understanding ischemia reperfusion injury (IRI) is essential to further improve outcomes after liver transplantation (LT). Porcine isolated liver perfusion (ILP) is increasingly used to reproduce LT-associated IRI in a strictly controlled environment. However, whether ILP is a reliable substitute of LT was never validated. We systematically reviewed the current experimental setups for ILP and parameters of interest reflecting IRI. Isolated liver perfusion was never compared with transplantation in animals. Considerable variability exists between setups, and comparative data are unavailable. Experience so far suggests that centrifugal pump(s) with continuous flow are preferred to reduce the risk of embolism. Hepatic outflow can be established by cannulation of the inferior vena cava or freely drained in an open bath. Whole blood at approximately 38°C, hematocrit of 20% or greater, and the presence of leukocytes to trigger inflammation is considered the optimal perfusate. A number of parameters related to the 4 liver compartments (hepatocyte, cholangiocyte, endothelium, immune cells) are available; however, their significance and relation to clinical outcomes is not well described. Porcine ILP provides a reproducible model to study early IRI events. As all models, it has its limitations. A standardization of the setup would allow comparison of data and progress in the field.

Keeping Cool Under Pressure: Dielectric Strength of Sheet Insulation in Boiling Liquid Nitrogen

According to our previous research on the dielectric strength of Nomex T410 paper under a horizontal turn-to-turn electrode system, a significant decrease by approximately 38% of the dielectric strength was found after the introduction of film boiling. In this paper, a wide range of sheet insulation samples has been tested under a turn-to-turn electrode system in vertical arrangement, more practical to the real design of high-temperature superconducting power transformers. Samples from three different types of paper (NMN, Nomex, and Kapton) have been investigated under a static situation with no boiling introduced. In addition, their dynamic dielectric characteristics under different levels of electric stress have also been tested by introducing a transient thermal stress. The experiment has been conducted in open bath liquid nitrogen (77 K) as well as in subcooled liquid nitrogen (67 K). Both of the tests are conducted under one atmospheric pressure. The result shows that all samples have enhanced dielectric performance when immersed in the subcooled liquid nitrogen. Moreover, the Kapton film is found to always have the best dielectric performance. However, its poor impregnation of liquid nitrogen largely affects its dielectric strength, especially at 77 K. When compared to Nomex paper with a similar thickness, the NMN paper is better due to its nonporous structure.

μCHILL: a lightweight, modular system for handling crystalline samples at low temperatures under inert conditions

A procedure for preparing and mounting crystals under inert conditions is demonstrated, using a specialized apparatus (μCHILL) to provide a cold gas stream fed from a liquid nitrogen (LN2) reservoir or an open bath heat exchanger. A second, dry gas stream at room temperature enwraps the cold gas, protecting the sample preparation zone from ambient moisture. The technique is extremely flexible, requiring only a single operator, little practice and almost no preparation time. The device enables operation in a wide temperature range (at least 213 K to room temperature), providing temperature control and very stable conditions with no icing for extended time periods. The flexible, modular and low-cost design is based on three-dimensional-printed parts and readily available standard components, potentially making the device available to a wide range of users and applications not limited to single-crystal studies.

A Step-by-Step Chemical Recipe to Dye Commercial Cotton with Natural Indigo Dyes in an Open Bath for the Beginners and Artisans

With the emergence of the need for natural bio-based chemical dyed wearable substrates, such as apparel or textiles, the demand for value-added craftsmanship induced on apparel or textiles is also on the rise. Local artisans are also exporting their value-added apparel products by diversifying their product range creating more local employment. Nowadays global retail fashion houses are also introducing naturally dyed wearable substrates for the increasing consumer demand for eco-friendly green products and concerns with global climate change. Small and medium entrepreneurs (SMEs) or artisans are also keeping pace with this new trend of offering such natural dyed products to the consumers. Therefore, this has created a new space for local artisans to produce various designs using natural dyes. The natural indigo dyed product is in great demand in the high-end fashion retail houses as well as in boutiques. However, little knowledge is available for the artisans to apply indigo vat dyes naturally extracted from the leaves of Indigofera tinctoria plants, because of the lack of technical knowledge, complications of chemical recipe parameters, zero access to expensive heavy industrial machinery. Therefore, an attempt was taken to formulate an easy chemical recipe to dye cellulosic cotton fabric with natural indigo dyes without the need of any industrial dyeing machinery as well as conforming proper fastness to rubbing and washing, which are basically the major concerns for any vat dyed commercial products to meet the export demand. The chemicals used for this recipe formulation are also commercially available and cheap, making it an appropriate choice for local artisans to use and sell their finished end-product to exportable markets. The most important finding was the effect of vatting temperature to act as a major player to form water-soluble leucoindigo vat dyes from their insoluble solid dye state. Azo test was also conducted to confirm the absence of any carcinogenic amine containing any azo functional group that is harmful to the skin. Additionally, two different temperatures, such as 23oC and 30oC was used to produce the vatting recipe required for successful dyeing within 5 minutes at a lower temperature of 40°C, which will not cost any additional expenditure for the local artisans as they can produce this fermented vat on normal atmospheric conditions.

Impregnation of Composite Materials: a Numerical Study

Oxide ceramic matrix composites are currently being developed for aerospace applications such as the exhaust, where the parts are subject to moderately high temperatures (≈ 700 ∘C) and oxidation. These composite materials are normally formed by, among other steps, impregnating a ceramic fabric with a slurry of ceramic particles. This impregnation process can be complex, with voids possibly forming in the fabric depending on the process parameters and material properties. Unwanted voids or macroporosity within the fabric can decrease the mechanical properties of the parts. In order to design an efficient manufacturing process able to impregnate the fabric well, numerical simulations may be used to design the process as well as the slurry. In this context, a tool is created for modeling different processes. Thétis, which solves the Navier-Stokes-Darcy-Brinkman equation using finite volumes, is expanded to take into account capillary pressures on the mesoscale. This formulation allows for more representativity than for Darcy’s law (homogeneous preform) simulations while avoiding the prohibitive simulation times of a full discretization for the composing fibers at the representative elementary volume scale. The resulting tool is first used to investigate the effect of varying the slurry parameters on impregnation evolution. Two different processes, open bath impregnation and wet lay-up, are then studied with emphasis on varying their input parameters (e.g. inlet velocity).

Effect of ultrasound on dyeing of wool fabric with acid dye

Wool fiber strength and handle is damaged by holding for prolonged periods at normal dyeing temperatures (98 °C). Lower dyeing temperatures can be employed to color wool whilst reducing damage caused to the fiber. However, these lower temperature dyeing processes often have a long dyeing time and/or require the addition of chemicals to achieve adequate dye exhaustion and migration. The use of ultrasonic irradiation was used to reduce dyeing times and temperatures whilst increasing dye migration and fastness. It has used 30 kHz frequency level, effective power of 120 and 350 W heating power in ultrasonic machine. In this work, wool dyeing was carried out on single jersey knitted fabric using an acid dye with and without ultrasonic irradiation at 60, 70, and 80 °C. Dye exhaustion was measured using UV/visible absorbance of the dye bath before and during the dyeing cycle. For the measurement of nodal/anti-nodal point of energy, at 60, 70, and 80 °C dyeing was done in open bath of ultrasonic machine with and without sonication at high liquor ratio. To compare the dye uptake (%) at high/conventional process, sample was dyed at 95 °C. Optical and scanning electron microscopy were used to measure the diameter and surface changes of the fiber, respectively. Wash and rub fastness was measured on the dyed fabrics after rinsing and drying. Ultrasonic irradiation during the dyeing of wool caused an increase in the dye exhaustion rate for acid dye. This change in rate is believed to have been caused by a reduction in the viscous boundary layer of liquor surrounding the fiber present in an ultrasonic irradiated environment. An increased dye migration due to cuticle cracking and fiber swelling was not deemed to have occurred as wet fiber diameter was not changed by submersion in the dye liquor in the presence of ultrasound and no surface cracking was evident in scanning electron microscopy images. Some cuticle structure changes occurred with turning up or ripping off of the cuticle tips evident. Both wash and rub fastness were improved for ultrasonically dyed fiber with dyeing temperatures of 70 and 80 °C being suitable for the low-temperature dyeing of wool.

Investigation of electrohydrodynamic behaviors from open planar solution under rod-induced electrospinning

Understanding and controlling the electrohydrodynamic (EHD) behaviors of polymer solutions are of great importance to the design and fabrication of micro/nano devices and sensors. In this work, rod-induced electrospinning (RIES) was used as a versatile technique to study and characterize the EHD behaviors of polyethylene oxide solution during the electrospinning process. In RIES, a grounded insulated rod moves back and forth several millimeters above an open bath of polymer solution subjected to high voltage to induce the formation of Taylor cones that lead to subsequent polymer jet emissions from the solution surface. Using a phase field method, we performed finite element analysis to explore the EHD behaviors of air-polymer interface in RIES process to better understand fundamentals of this process. Pertinent theories such as phase field theories and electric field theories were briefly discussed to provide relevant background to the techniques used in this work. We investigated the RIES process and the effect of the diameter of the induction rod, applied voltage and solution conductivity on the formation of the jets. The numerical results of the formation and merging process of the jets based on different experimental parameters are in good agreement with experimental observations and provide a better understanding of the RIES process to improve the throughput of nanofibers.

The Dielectric Strength of Nomex 410 Paper in Liquid Nitrogen Under Boiling Situations

It is crucial for the successful application of high-temperature superconducting (HTS) power transformers that they are able to survive under abnormal operations, such as a short-circuit fault. Modeling, based on the design of a four-winding three-phase HTS power transformer, suggests severe boiling will occur on the surface of the winding during a short-circuit fault and will jeopardize the turn-to-turn insulation of the HTS power transformer. In this paper, a turn-to-turn insulation breakdown experiment platform involving the introduction of boiling on the surface of electrode has been built. Nomex 410 paper, one of the candidates for turn-to-turn insulation in the design of the HTS power transformer, was tested. The characteristics of dielectric strength of Nomex 410 in three different thicknesses (0.13, 0.18, and 0.25 mm) have been investigated, without boiling, as well as under different boiling situations, in an open bath of liquid nitrogen. The voltage application methods applied during both experiments test the electrical breakdown of Nomex 410 under a dynamic situation. The experiment results show that when under film boiling, compared to the test results for nucleate boiling, the dielectric strength of Nomex 410 paper decreases by approximately 38% of the value when no boiling is involved. Moreover, it is verified that the presence of an electric field accelerates the heat transfer between the liquid nitrogen and the heated electrode.

Portable Aluminum Deposition System: An Alternative Plating Process for Aluminum Electrodeposition Based on Ionic Liquids

Electrodeposited aluminum and aluminum-transition metal alloys are promising materials for use as corrosion-protective coatings for steel. In fact, it is thought that electrodeposited aluminum might be a replacement for cadmium in some applications. This substitution is important because the process used for plating Cd is associated with significant health and environmental concerns. From health and environmental perspectives, the chromium plating process is also problematic, and substitutes for chromium are eagerly sought. Among the possible alternatives are aluminum-transition metal alloys such as Al-Mn and Al-W. These alloys are sufficiently durable to replace electroplated chromium in at least some applications. Aluminum plating is not feasible from aqueous solutions because water is reduced and hydrogen is evolved prior to aluminum deposition. Thus, the plating process must be carried out in a nonaqueous environment. Most commercial aluminum plating processes utilize mixtures containing pyrophoric alkylaluminum fluorides dissolved in toluene, e.g., the Siemens SIGAL® process. This very effective technology has been purchased and improved by AlumiPlate, Inc., but the newer process is still based on similar pyrophoric plating solutions and continues to invoke significant health and safety concerns. Aluminum electrodeposition from ionic liquid electrolytes, particularly organic salt-based chloroaluminates, such as aluminum chloride-1-ethyl-3-methylimidazolium chloride (AlCl3-EtMeImCl), is an attractive alternative to the classical methods for preparing aluminum coatings described above. These well known ionic liquids have low vapor pressures, low viscosities, high electrical conductivities and thermal stabilities, and so far as known, relatively low toxicities. Commercially marketed plating solutions based on these ionic liquids with the addition of proprietary additives are now marketed under the BASIONICS trademark by BASF. In our work, we have developed a Portable Aluminum Deposition System (PADS) for plating aluminum and its alloys from Lewis acidic AlCl3-EtMeImCl and related chloroaluminate ionic liquids. This technology was developed as an alternative to typical open bath electrodeposition processes and is suitable for field applications. The utility of the PADS device was demonstrated by electrodepositing Al and Al-Mn films on copper and carbon steel. These electrodeposition experiments were performed using constant potential and constant current plating methods. The deposits were evaluated based on alloy composition, compactness, surface morphology, durability, and corrosion resistance. The Al-Mn films produced with the PADS device were specular, dense, and adherent, and they rivaled the quality of similar deposits prepared in an open bath (see figure below). As expected, the Al-Mn films demonstrated significantly better resistance to chloride-pitting corrosion and much greater hardness compared to pure Al films. In this presentation, we will describe the relationship between the operational parameters of the PADS device and the composition and overall quality of the resulting Al-Mn deposits. This work was funded by the Strategic Environmental Research and Development Program (SERDP) through contract DE-AC05-00OR22725 to Oak Ridge National Laboratory with subcontract to the University of Mississippi Figure 1

1920·30년대 독일 공동주택 발코니의 공간구성 특성에 관한 고찰 - 채광, 환기, 일광 중심의 위생적 특성 반영을 중심으로 -

The purpose of this study was to analyze the spacial characteristics of the balcony space of the german multi-family housing from 1920 to 1930 in connection with the aspects of hygine and healthy living which were the main idea of the modern housing movement. The results of this study were as follows; the idea of hygiene and healthy Living with the focus on sunlight and fresh air had influence on the reillumination of the balcony space to function as the hygienic space. The balcony space used for take a sunbath and a open air bath being were provided from the large scaled greened communal outdoor space of the new modern housing blocks. To act as a hygienic space for sunbath and air bath with the emotional effects on relaxation the balcony space had to have an appropriate condition in regard to site situation, orientation to sun, connection to other rooms as well as the spacial arrangement form.

Microcanonical origin of the maximum entropy principle for open systems

There are two distinct approaches for deriving the canonical ensemble. The canonical ensemble either follows as a special limit of the microcanonical ensemble or alternatively follows from the maximum entropy principle. We show the equivalence of these two approaches by applying the maximum entropy formulation to a closed universe consisting of an open system plus bath. We show that the target function for deriving the canonical distribution emerges as a natural consequence of partial maximization of the entropy over the bath degrees of freedom alone. By extending this mathematical formalism to dynamical paths rather than equilibrium ensembles, the result provides an alternative justification for the principle of path entropy maximization as well.