Jan Jezierski

Pneumatic powder injection technique as a tool for waste utilisation

The problem of wastes in metallurgical and foundry industries is very important. The considerable amount of wastes is furnace dusts and other fine materials. At the Department of Foundry, the experiments with the use of pneumatic injection method were carried out to utilise these materials. The results of dusts injection into cupola, slag foaming with the use of powdered coal-furnace dusts injection into EAF and others were presented. The industrial stands and the process parameters were mentioned and its indexes, too. The paper shows that pneumatic injection technique could without obstacles be an effective method for powdered wastes utilisation.

Heredity of the Structure and Properties of Grey Cast Iron Melted on a Basis of Steel Scrap

In this paper are presented the results of researches, obtained during cast iron melting on basis of steel scrap and a carburizer (without pig iron in solid charge). In the process of carburization, there were used the carburizers such as anthracite, natural and synthetic graphite, petroleum and cupola coke, as well as charcoal. The grey cast iron was produced, for which quantitative analysis of graphite precipitations was performed. It was noticed that in case of using anthracite as carburizer, the smaller graphite precipitations were obtained. In authors’ opinion they are consequences of anthracite structure, consisted of fine graphite flakes and phenomenon of charge materials features’ transfer into melted alloys (structure heredity).

Carburizer Effect on Cast Iron Solidification

This paper presents the effect of carburizing materials on cast iron solidification and crystallization. The studies consisted of cast iron preparation from steel scrap and different carburizers. For a comparison, pig iron was exclusively used in a solid charge. Crystallization analysis revealed the influence of the carburizer material on the crystallization curves as well as differences in the solidification paths of cast iron prepared with the use of different charge materials. The carburizers’ influence on undercooling during the eutectic crystallization process was analyzed. The lowest undercooling rate was recorded for the melt with pig iron, then for synthetic graphite, natural graphite, anthracite, and petroleum coke (the highest undercooling rate). So a hypothesis was formulated that eutectic cells are created most effectively with the presence of carbon from pig iron (the highest nucleation potential), and then for the graphite materials (crystallographic similarity with the carbon precipitation in the cast iron). The most difficult eutectic crystallization is for anthracite and petroleum coke (higher undercooling is necessary). This knowledge can be crucial when the foundry plant is going to change the solid charge composition replacing the pig iron by steel scrap and the recarburization process.

Two-Phase Jet in Process of Pneumatic Powder Injection into Liquid Alloy

The short description of the new approach to the pneumatic powder injection process analysis was presented in the article. The experiments with the high speed camera recording of the two-phase jet in pneumatic powder injection process were carried out in the Department of Foundry, Silesian University of Technology, Poland. The results were briefly analyzed and some interesting conclusions appeared, especially that the real velocity of the injected particles is far less than it is normally calculated with use of the well-known formulas. They were compared with existing literature data as well as with some experimentspreviously made by authors. Powder particles velocity and two-phase jet mass concentration were analyzed as the most important parameters for powder injection process. The results described are part of the complex experimental plan and the next step is computer modeling (just launched) of the jet introducing liquid.

Solid Waste Utilization in Foundries and Metallurgical Plants

The issue of waste management and utilization in foundries and metallurgical plants covers a lot of completely different materials in various forms (solid, liquid or gaseous). In this chapter, solid waste utilization is described based on the experiments and industrial experiences of Department of Foundry, Silesian University of Technology. The first part of the chapter introduces the readers into the subject of pneumatic powder injection into liquid metal process. It is a method widely used to utilize solid wastes in foundries and steel plants giving good technological and economic results. The casting production process is inseparably connected with pollutants emission into the environment, that is into air, water, soil and also noise emission. The fumes and gases from coke-fired furnaces are deposited in the air as well as other pollutants created when metal is molten in electric furnaces. Their amount can be limited by use of the modern high efficiency filters but the amount of dusts to deposit on waste dumps consequently increases. The water contaminations are caused by open melting furnaces cooling systems. The solid wastes from various production stages (moulding mass de-dusting, furnace de-dusting, blast cleaners de-dusting, slag etc.) are deposited on waste dumps. The latter can be utilized after granulation process as a road building material whereas furnace dusts are treated in recirculation into furnace systems decreasing their final quantity and improving utilization of some important elements, mainly iron (Fiore et al., 2008; Lee & Song, 2007; Salihoglu et al., 2007; Fu & Zhang, 2008).

Wastes utilisation in foundries and metallurgical plants with pneumatic conveying techniques – selected aspects

The issue of wastes disposal and utilisation in metallurgical and foundry industries is crucial in present economical and environmental protection conditions. The metallurgical processes generate enormous amounts of wastes every year. The considerable amount of wastes is furnace dust (the amount varies from the type of furnace) and other fine materials. At the Department of Foundry, Silesian University of Technology, Poland, the experiments with the use of pneumatic injection technique have been carried out for many years to utilise these materials. The results of dusts injection into cupola, slag foaming with the use of powdered coal-furnace dusts injection into EAF and pneumatic dry used sand reclamation method were presented in the paper. The industrial set-ups and the process parameters along with their benefits were mentioned. The paper shows that pneumatic injection technique could, without obstacles, be an effective method for powdered wastes utilisation.

Model Experiments with New Lance for Pneumatic Powder Injection

The paper presents the results of model experiments with new lance design. The lance was invented in Silesian University of Technology, Department of Foundry. It is dedicated for the pneumatic powder injection into liquid metal bath without lance submersion. The situation like that is common for small molten alloy volume when the problem of temperature decrease is significant. In such case the carrier gas introduction into metal as well as cooling with gas blowing onto metal bath surface should be avoided. The new lance was equipped with four parallel slots made on its outlet and a flange. This design causes the carrier gas evacuation before it reaches the molten metal surface. The article presents the model experiments made with use of the device for the diphase gas-powder jet forces recording. The comparison of two lances: normal steel pipe and this of new design was presented in the article, too.

Microstructure of the Synthetic Cast Iron Carburized with Different Types of Carburizers

The cast iron melting process can be based on metallic charge with pig iron or on steel scrap exclusively (i.e. synthetic cast iron). The analysis of the synthetic cast iron microstructure was presented and compared to micros of the cast iron produced on the base of pig iron. The analysis consisted of size and shape of the graphite precipitations and the metal matrix structure, too. The results of examinations and calculations were presented in form of figures and graphite distribution histograms. Based on researches conducted the authors confirmed opinions of heredity of the alloys microstructure cited in the literature.

Optimized Gating System for Steel Castings

Computer modeling using a commercially available software package was used to explore the optimization of filling systems based on the relatively new concepts of avoiding entrainment of air bubbles and oxides by avoiding surface turbulence. The test casting was based on a pattern for a traditional top poured test bar, whose cross section was a tri-lobed clover-like shape. The study illustrates clearly that the detailed design of the filling system has a major influence on the conditions for defect generation during filling. Traditional steel casting systems using the widely popular assembly of preformed refractory tubes were found to behave poorly. Systems were demonstrated which were capable of delivering highly controlled filling behavior. The latest systems to be developed employed (1) a naturally pressurized filling system and (2) the use of filters placed flush on the top of the runner to act as bubble diverters, together with (3) terminal spin traps. These novel filling systems demonstrated excellent performance in simulation, in agreement with practical experience of the capability (of the trident gate in particular) to produce, for the first time in the history of casting, defect-free castings on a routine basis.

Furnace dust utilisation using the pneumatic injection: a methodology

The issue of generating dust waste is present in steel and foundry plants around the world, as all melting furnaces generate tonnes of dust every year. This dust is obviously considered to be a waste material; however, the dust itself still contains certain chemical elements (mostly iron and zinc) which can be utilised by being returned to the furnace during the melting process. This means increasing their content in the liquid metal bath or in the dust that is finally sucked out from the furnace that can then be used as a raw material in the zinc metallurgy industry. There are several methods to achieve this, and one of them is pneumatic powder injection with the use of a pneumatic dust feeder and injection lance to introduce the dust directly under the surface of liquid metal. The paper presents both a theoretical approach as well as industrial applications as the result of the authors’ work in this field of the pneumatic conveying technique. Both the benefits and limitations of dust reuse are presented. The same method can be used to re-introduce cupola dust into the cupola and electric arc furnace together with some carburiser or ferroalloy additions. The results show the crucial influence of the process’s pneumatic and dimensional parameters that are needed to achieve proper jet penetration inside the liquid metal volume. The authors’ own theoretical formula for the so-called critical jet radius describing its potential to penetrate the liquid alloy is shown here, too. This complex approach has proven to be a huge potential of the pneumatic powder injection technique as a tool to utilise dust wastes in melting furnaces in steel and foundry plants.