Cast House Research Articles

Zinc removal from metallurgical dusts with iron- and sulfur-oxidizing bacteria

The generation of currently partially recyclable metallurgical dusts during the steel production represents a challenge for the realization of a circular economy in this industrial sector. Due to a high iron concentration, the reutilization of blast furnace and cast house dusts in internal crude steel processes, is state of the art. However, heavy metal impurities such as zinc, act as an interference due to diverse negative effects. The aim of this study is to utilize Acidithiobacillus ferrooxidans, an iron- and sulfur-oxidizing bacteria, to solubilize zinc whilst retaining iron in the dust residue intended for reuse. To achieve this, the biooxidation of elemental sulfur is of crucial relevance. Two different strains of A. ferrooxidans (DSM 583 and CCM 4253) were cultivated and their leaching performances were compared to each other using a stirred tank reactor operated in a fed batch set-up, with a working volume of 3 L, at an operation temperature of 30 °C. The dust concentration was gradually increased until a maximum of 125 g/L, after which the reactors were left to run for three additional cycles to ensure replicability of results. For both strains, at a cast house dust concentration of 125 g/L paired with a leaching duration of two weeks, an average zinc removal of 56 % was achieved whereas solely an average of 4 % of iron was leached.

Bioleaching of Zinc from Blast Furnace Cast House Dust

Metallurgical dusts are by-products from steel manufacturing. The high iron content of cast house dust (~64%) makes this by-product an interesting iron feedstock alternative. Therefore, its return into the internal steelmaking circuit, specifically in the sinter plant, is a common practice in the steel industry. However, this dust fraction also contains heavy metals, as zinc. As a result of the re-entry of zinc into the process, the zinc concentration in the blast furnace flue gas dust also increases. This prevents the full recirculation of the blast furnace flue gas dust in the steelmaking process despite its relatively high iron content (~35%), thus causing part of the blast furnace flue gas dust to end in the landfill. The goal of this study was to investigate the usage of bacteria, such as the sulfur oxidizing Acidithiobacillus thiooxidans or the iron and sulfur oxidizing Acidithiobacillus ferrooxidans, to leach the undesirable element zinc from the cast house dust while preventing the leaching of iron, by adjusting the sulfur addition and avoiding, at the same time, the accumulation of sulfur in the solid fraction. Experiments proved that a co-culture of A. thiooxidans and A. ferrooxidans can effectively leach zinc from metallurgical dusts, maintaining high iron concentrations in the material. The influence of elemental sulfur on the efficiencies reached was shown, since higher removal efficiencies were achieved with increasing sulfur concentrations. Maximum zinc leaching efficiencies of ~63% (w/w) and an iron enrichment of ~7% (w/w) in the remaining residue were achieved with sulfur concentrations of 15 g/L for cast house gas concentrations of 125 g/L.

Aluminum Billets Heat Treatment Using Hot Flue Gas in Batch Homogenizing Preheating Furnace for Energy Efficiency and Cycle Time Reduction in Cast House

Aluminum Billets Heat Treatment Using Hot Flue Gas in Batch Homogenizing Preheating Furnace for Energy Efficiency and Cycle Time Reduction in Cast House

Numerical evaluation of the performances of the ventilation system in a blast furnace casthouse.

The blast furnace casthouse is a typical heavy-polluting factory building of a steel enterprise. During the tapping process and the taphole opening, the dust concentration in the factory building's workroom can reach tens of thousands mg/m3. Over time, the air pollutants in the workplace can have unwanted consequences on employees' health. This paper selected a typical blast furnace tapping workshop. The flow, temperature, and soot concentration fields in the workshop are measured on site during tapping, and the distribution characteristics are obtained. The performance of the tapping smoke exhaust system is analyzed based on computational fluid dynamics. The findings are as follows: the concentration of PM2.5 in most of the work area was 80μg/m3, but the concentration reached 1mg/m3 near the slag ditch, which was heavy pollution. Because the opening and closing of doors and windows was unreasonable, it was difficult for the particulate matter to accumulate in the deep and middle of the plant discharge. The PMV of the worker's work area is about 3, and the waste heat removal efficiency is 4.2. Hence, this article's finding provides a scientific basis for optimizing the air distribution in the blast furnace cast house's workplace.

In-situ microstructural control of A6082 alloy to modify second phase particles by melt conditioned direct chill (MC-DC) casting process – A novel approach

• High shear melt conditioning in the sump during direct chill casting of A6082 billet. • Novelty of maintaining 2–7 °C above alloy liquidus as the sump thermal condition. • In-situ control of solidification during casting by intensive melt shearing. • Precise tailoring of as-cast microstructure to modify second phase particles. • Potential for industries to eliminate homogenisation and use recycled Al alloys. Controlling the formation of noncompact second phase particles during direct chill (DC) casting of aluminium alloys with grain refiner addition remains challenging, as it results in energy intensive homogenisation and deformation problems. In this work, we employed a novel strategy in the DC casting of A6082 alloy to produce billets with a fine-scale dispersion of second phase particles. The strategy involves maintaining 2–7 °C above alloy liquidus as a thermal condition in the sump by in-situ melt conditioning (MC) using a rotor-stator high-shear device operated at a critical rotation speed. As a result, in-situ control of solidification behaviour is achieved to precisely tailor the as-cast microstructure. The billet grain refinement is attained by MC-DC casting without the deliberate addition of chemical grain refiners. The microstructure of the MC-DC cast billet at the critical rotation speed showed a fine-scale dendritic structure with refined secondary dendrite arm spacing (SDAS). The solidification front proceeded with a shallow sump and a corresponding shorter solidification time, higher cooling rate, higher temperature gradient, and smooth solidification rate profile. The ideal fine-scale dendrites with low SDAS divided the remaining eutectic liquid into fine-scale and isolated liquid pockets, resulting in fine-scale, compact morphology, and uniform distribution of second phase particles in the as-cast microstructure. The MC-DC casting process showed the ability to increase the cast house production rate by increasing the casting speed without bleeding the billet. The present approach could be beneficial for eliminating or reducing the homogenisation practice and may also introduce significant flexibility in using recycled Al alloys in the industry.

Experimental Research on Dust Concentration Distribution Characteristics of Blast Furnace Cast House

This paper compares the temperature and dust concentration distribution of blast furnace cast house under different dust removal design conditions and external climate conditions by means of on-site sampling, field measurement and data analysis. It is found that the post temperature in closed design of cast house is 2.4°C lower than that in open design, but the dust concentration of the post of open design is 0.139 mg/m3, which is 1/10 of that of the closed design. Therefore, the open design is recommended. Different climatic conditions also have influence. It is suggested to close the main wind direction doors and windows when the outside wind speed is high to avoid turbulence.

Green Power Furnaces in Aluminum Cast House for Scrap Preheating Using CO2-Flue Gas

Green Power Furnaces in Aluminum Cast House for Scrap Preheating Using CO2-Flue Gas

Improvement of Cast House Operator Work Posture with REBA Method at PT XYZ

Musculoskeletal disorders (MSDs) are diseases in the human muscular tissue system in the back, wrist, knees and shoulders caused by incorrect postur during work activities. This study was conducted to determine the level of risk MSDs on operator work activities at the cast house work station. Activities under study are activities; surface repair tap hole, checking temperature iron, and take iron sample. These activities are carried out repeatedly, incorrect work posture and the presence of heat from work environment factors that affect the whole body. This makes the operator complain of pain in parts of the body at risk of developing musculoskeletal complaints. This study was an observational study using the Rapid Entire Body Assessment method and the Nordic Body Map instrumen. The result of the Nordic Body Map instrumen for 20 operators at the cast house work station showed that there were 21 complaints against operator. Based on the measurement of cast house operators the surface repair activity of tap holes has a “high” risk value for MSDs (REBA Score 9), checking temperature iron activities have a “low” risk value for MSDs. Proposed improvement to prevent is to improve the procedur in the surface repair activities of tap holes, where when the process of sticking the dough is done in front of the tap hole is changed by attaching it to the mud gun nozzle tip. After the proposed improvement, the result of the Nordic Body Map instrumen showed no complaints and the measurement of the tap hole had a “low” risk value for the occurrence of MSDs (REBA Score 3).

Rio Tinto to licence its aluminium filtration technology

Canadian equipment manufacturer STAS and mining and metals company Rio Tinto have entered into an agreement to commercialize an advanced compact filtration technology (ACF) for aluminium cast houses.

New improvement opportunities through applying topology optimization combined with 3D printing to the construction of gearbox housings

The construction of gearbox housings is severely restricted by all the currently used machining processes. 3D metal printing opens up new possibilities in this area. However, a clear additional benefit compared to the standard cast housing must be given, in order to make additive manufacturing viable. The objective of the present project was to research both the potential and restrictions of additive manufacturing technologies regarding the design of gearbox housings. As a result of this investigation, a topology optimized lightweight gearbox housing with integrated oil channels and scraper was obtained. The topology optimization process of the new gearbox was carried out in two work steps. The first consisted of the determination and design of the primary load-bearing structure of the housing. Therefore, an iterative design process was needed in order to develop the final support structure, because the topology optimization only provides a design draft of the framework structure. Concerning the iteration, an FEM analysis was performed to check and improve the draft after each loop. During the evaluation, safety and weight were compared with the previous version. During the second step of the topology optimization, the structure of all the oil channels was developed, creating a morphological box. Finally, the new gearbox housing was generated by combining the topology optimization with the concepts from the morphological box. Selective Laser Melting (SLM) was chosen for manufacturing because it allows the printing of components of the desired dimension with the required accuracy. The developed gearbox prototype was printed using the aluminum alloy AlSi10Mg (A360). Due to the flexibility of the SLM technology, it was possible to fulfill all specific design criteria while also showing the typical topology-optimized structure too. Afterwards, the housing was machined to achieve precise dimensions and tolerances. Finally, the gearbox was assembled, and both its mechanical integrity and the functionality of the integrated oil systems were fully checked with short-term tests.

A review of primary aluminium tapping models

The removal of molten aluminum from Hall–Heroult cells is known as the tapping process. Metal produced in the aluminum electrolytic cell is removed by vacuum using a crucible through a tapping tube. The purpose of metal tapping is to keep the metal volume at the optimum production level. It is possible that a certain amount of bath is entrained with metal when the metal is siphoned into the crucible. One of the challenges faced by aluminum smelters is the high volume of dross processed in the cast house plant as a result of bath tapped with metal from the reduction cells. The aim of this review is to discuss previous aluminum tapping models and trends in technology developments with the aim of improving the tapping operation. The advantages and limitations of existing model studies are also discussed in the context of electrolytic bath carried over with liquid metal during tapping from the reduction cell. A fundamental approach of the quality of tapping flows is also proposed for further investigation.

Effect of Hearth Liquid Level on the Productivity of Blast Furnace

Cast house is the heart of blast furnace operation. A stable blast furnace operation requires proper control of hot metal and slag drainage from the hearth. Various problems are encountered if the hearth liquid level exceeds above a critical limit that leads to an unstable blast furnace condition. Moreover, operating too often to control liquid level is also not recommended, as operational cost is increased and refractory erosion increases. Therefore, there is a need to understand the reason that prevails in the abnormal hearth liquid level situations. Understanding the effect of increased hearth liquid level on blast furnace process parameters will enable blast furnace operation to take the proactive actions of controlling the blast furnace abnormality. In the present review, an attempt is made to establish a correlational research to understand the effect on hearth liquid level on various casting parameters and blast furnace process conditions. The adverse effect of hearth liquid level build-up on the state of dead man, gas permeability, tuyere life, hearth linings, slag delay and furnace wall heat load is studied. The various casting strategies adopted in blast furnace operation are discussed along with their advantages and disadvantages, and finally, the recommendations are made to operate the liquid level on narrow band.

РОЗРОБКА ЗАХОДІВ ПОКРАЩЕННЯ УМОВ ПРАЦІ ПРИ ВИРОБНИЦТВІ ЧАВУНУ

The article explores the causes of working environment pollution and identifies the sources of harmful and dangerous emissions in pig iron production, along with searching for rational measures to improve the blast furnace cast house aspiration system efficiency to remove toxic gases, dust and exhaust heat. A mathematical modeling methodology for transfer process of molten iron and slag from the blast furnace to the ladle has been employed. The best practice from Zaporizhstal Steel Works on a new aspiration system at blast furnace casting yard laid the basis for the research. An aerodynamic calculation method was used to detect deficiencies in the aspiration system. Statistical method to validate the results obtained was used for constructing of graphs and nomograms. The major causes of inefficiency of the current system of covering iron and slag troughs of a blast furnace casting yard have been revealed, in particular the bypass channel for slag from the main drain trough for molten iron and high local resistance losses on iron and slag distribution (the skimmers). Total and local resistance losses in various areas of drain gutters and aspiration systems have been calculated along with estimating the locations for additional exhaust hood installation, i.e. the special zones for skimmers, the main, transfer and bypass troughs for cast iron and slag. It is proved that by increasing the aspiration efficiency contamination of the working area is reduced, thus improving labour conditions significantly. It is proposed to use modern heat-resistant concrete troughs with higher resistance and longer life service. The proposed modification of trough slabs will facilitate their replacement when carrying out repair works on trough lining and cleaning. An aspiration system model for a typical blast furnace cast house has been developed and explored. The areas and reasons behind the loss of resistance in the exhaust system of hood covering for molten iron and slag troughs are identified. Recommendations to enhance the system efficiency to reduce contamination of the working environment and improve working conditions have been suggested.

Experimental and numerical CHT-investigations of cooling structures formed by lost cores in cast housings for optimal heat transfer

This paper investigates the cooling performance of six different lost core designs for automotive cast houses with regard to their cooling efficiency. For this purpose, the conjugate heat transfer (CHT) solver, chtMultiregion, of the freely available CFD-toolbox OpenFOAM in its implementation of version 2.3.1 is used. The turbulence contribution to the Navier-Stokes equations is accounted for by using the RANS Menter SST k − ω model. The results are validated for one of the geometries by comparing with experimental data. Of the six investigated cooling structures, the one that forces the fluid flow to change its direction the most produces the lowest temperatures on the surface of the cast housing. This good cooling performance comes at the price of the highest pressure loss in the cooling fluid and hence increased pump power. It is also found that the relationship between performance and pressure drop is by no means generally linear. Slight changes in the design can lead to a structure which cools almost as well, but at much decreased pressure loss. Regarding the absolute values, the simulations showed that the designed cooling structures are suitable for handling the cooling requirements in the particular applications and that the maximum temperature stays below the critical limits of the electronic components.

Studies to overcome the manufacturing problems in blast furnace tap hole clay of Integrated Steel Plants: Experimental approach

Integrated Steel Plants commonly uses Blast Furnace route for iron production which accounts for over 60 % of the world iron output. Blast Furnace runs for ten to twenty years without repairing hearth walls and Tap Hole (TH). Tap hole is an outlet for hot metal produced in a Blast Furnace and run from the shell of the furnace into the interior allowing access to the molten material. Tapping is the term used for drilling a hole through the tap hole which allows the molten iron and slag to flow out. In Iron making process, removal of liquid iron from furnace and sending it for steel making is known as cast house practice. For tapping liquid iron and operating the tap hole requires a special type of clay. Tap hole clay (THC) used to stop the flow of liquid iron and slag from the blast furnace. Present work deals with the study on manufacturing of THC at Visakhapatnam Steel Plant and problems related to manufacturing. Experiments were conducted to solve the identified problems and results are furnished in detail. The findings can improve the manufacturing process and improve the productivity of tap hole clay.

Experimental study on bag filtration enhanced by magnetic aggregation of fine particles from hot metal casting process

Bag filtration experiments enhanced by pre-aggregation of fine particles from hot metal casting process with size range of 0.3–10μm in magnetic field were conducted in this work. There is a distinct difference in magnetization process between particles from cast house and coal-fired power plant. The influences of magnetic flux density and gas velocity on particle aggregation and total particle removal efficiency were investigated. The experimental results showed that bigger particles are easily affected by magnetic field and the smaller particles are easily affected by flow field. Although higher magnetic flux density can improve the aggregation of bigger sized particles at a constant gas velocity, combined with the effect of particle size distribution, the total particle number concentration increases as the average gas velocity increases, which would result in the decrease of the total particle removal efficiency. When the total particle mass concentration is 1000mg/m3, the magnetic flux density is 0.08T and the gas velocity is 3.0m/s, the highest total particle removal efficiency reaches 99.77%. When particle magnetization reached saturation, the magnetic flux density will reduce the total particle removal efficiency.

Emission characterization of particulate matter in the ironmaking process

ABSTRACTThe study is to provide a detailed physical and chemical characterization of particles collected in the ironmaking process, including a bunker system, a cast house and a pulverized coal feeding system. Using gravimetric, scanning electron microscope coupled with energy dispersive X-ray spectrometry (SEM-EDS), X-ray fluorescence spectrometry (XRF), inductively coupled plasma optical emission spectrometry (ICP-OES) analyses, the size distribution, morphology, elemental composition and emission factor of particles were investigated. The contribution rates of cast house for emission factors of total suspended particulates (TSP), PM10 and PM2.5 are the largest, 57.0%, 75.5% and 83.3%, respectively. SEM-EDS analysis indicated that cast house particle shapes are mainly formed by polymerization from spherical particles and ultrafine particles, whose main component is Fe. But, the particles of the bunker system or the pulverized coal feeding system are mainly the large ones of irregular block or powder particles and the main component is carbon. The highest content of the element in particles of the bunker system and cast house is Fe, followed by C, Si, Ca and Al. The main elements of particles in the pulverized coal feeding system are C, Si, Al and Ca, and their contents are 63.6%, 7.83%, 3.07% and 1.47%, respectively.

Characterization of dust from blast furnace cast house de-dusting

ABSTRACTDuring casting of liquid iron and slag, a considerable amount of dust is emitted into the cast house of a blast furnace (BF). Usually, this dust is extracted via exhaust hoods and subsequently separated from the ventilation air. In most BFs the cast house dust is recycled. In this study a sample of cast house dust was split by air classification into five size fractions, which were then analysed. Micrographs showed that the dominating particle type in all size fractions is that of single spherical-shaped particles. However, some irregular-shaped particles were also found and in the finest size fraction also some agglomerates were present. Almost spherical particles consisted of Fe and O, while highly irregular-shaped particles consisted of C. The most abundant element was Fe, followed by Ca and C. These elements were distributed relatively uniformly in the size fractions. As, Cd, Cu, K, Pb, S, Sb and Zn were enriched significantly in the fine size fractions. Thus, air classification would be an effective method for improved recycling. By separating a small fraction of fines (about 10-20%), a reduction of the mass of Zn in the coarse dust recycled in the range of 40-55% would be possible

Respiratory hazards: clinical and functional assessment in aluminum industry workers

BackgroundAluminum is one of the prevalent alloys on the earth. With the revolution industry, aluminum was very important in all aspects of life from cooking to war weapons. The aim of this work is to study the prevalence of respiratory hazards and changes in pulmonary function among aluminum industry workers. Materials and methodsThis is a case series study which was conducted in an aluminum factory in Nag Hammadi and included 320 workers, who were subdivided into 2 groups according to the duration of daily exposure to aluminum gases and exhausts. Group 1: it included 260 exposed workers, who were randomly selected from potrooms and cast house sectors, and exposed to hazardous effects of primary aluminum industry 8h continuously per day. Group 2: it included 60 interrupted or partially exposed workers, who were randomly selected from the factory maintenance, potroom maintenance, cast house maintenance workers, as well as the general maintenance workers; and exposed to less than 8h interrupted per day on average 2–3h. Data were collected using modified British Medical Research Council (BMRC) questionnaire, and pulmonary function tests, chest X-ray, and laboratory studies were done. ResultsGroup 1 workers had more chronic and acute work related respiratory symptoms. There was a significantly higher occurrence of asthma among exposed workers with p value 0.004 while no significant difference for the occurrence of COPD in both groups, also CRP significantly more frequently occurred in exposed workers with p value 0.001. There was a significant negative correlation between FVC%, FEV1% and PEF25–75% and duration of exposure in years among exposed workers. Interpretation of chest X-ray denoted that reticular, nodular and reticulo-nodular patterns significantly more frequently occurred in exposed group (p value 0.01) also diaphragmatic abnormalities were more in exposed ones (p value 0.04). Solitary pulmonary nodules could be detected in three cases. ConclusionsAluminum industry is hazardous to both the workers and the community. The pulmonary hazards are significantly higher in workers who are continuously exposed to gases and pollutants for more than 8h/day. Moreover the free radicals of silica and polycyclic aromatic hydrocarbons may have a direct relationship with the recorded changes in diaphragmatic and pulmonary functions and may be precancerous.

Mechanical properties of dusts collected from blast furnace dust catchers and cast house dedusting filters

ABSTRACTDust samples from blast furnace dust catchers and cast house dedusting systems were investigated with respect to flowability-relevant parameters. The mass median diameter of the dusts was in the range of 140 to 210 µm for the dust catcher dusts and approximately 6 µm for the cast house dusts. Generally, the flowability of the dust catcher dusts was better compared to the flowability of the cast house dusts. The flowability categories suggested by the three flowability indicators—the angle of repose, Hausner ratio, and Carr’s compressibility—were good for the coarser dusts, while for the finer dusts the flowability was overestimated. For the blast furnace dusts, from the dust catcher a considerable variation in the bulk density was found, which can presumably be attributed to the remarkable difference in the carbon content of the dusts investigated.