Romelt Process for Ironmaking Mar20

Romelt Process for Ironmaking...

Romelt Process for Ironmaking Romelt process for ironmaking is a smelting reduction process for the production of hot metal (liquid iron). The process has been developed by The National University of Science & Technology ‘MISiS’, Russia (formerly known as Moscow Institute of Steel and Alloys). The development work of the process started in 1978 when a group of ‘MISiS’ scientists led by Vladimir Roments began working on designing of this process. The first patent in Russia was obtained in 1979. A pilot production plant having a hearth area of 20 sq m and with a capacity 40,000 tons of hot metal per year was commissioned in 1985 at the Novolipetsk Iron and Steel Works (NLMK). The pilot plant was designed by Moscow Gipromez. The design of the reliable Vanyukov’s furnace was taken as the prototype for this new method of manufacturing hot metal. The process was tested and mastered at this pilot plant between 1985 and 1998. During this period forty-one campaigns were carried out, each of which included startup and slowdown, with full tapping of hot metal and slag from the furnace. More than 40,000 tons of hot metal was produced in the pilot plant during this period and used further in basic oxygen furnace (BOF) for steelmaking. The first industrial plant for hot metal production based on Romelt technology is being built at Myanmar. The plant has been designed by Leningrad Gipromez and being supplied by Tyazpromexport, a subsidiary of Rostec. This plant has a capacity of 200,000 tons per year and is based on the processing of iron ore without its beneficiation from Pang Pet ore deposit. Pang Pet ore deposits have Fe content of up to 29 %. The plant will use non-coking coal from Kye Thee coal fields. The...

Mini Blast Furnace and Iron making Oct10

Mini Blast Furnace and Iron making...

Mini Blast Furnace and Iron making Mini blast furnaces (MBF) are generally viewed as miniature versions of the conventional large blast furnaces (BF). These furnaces are ideally suited for small scale operations. In fact, they are basically the forerunner to modern conventional last blast furnaces and hence they have operated for a longer period of time. MBFs are located in many countries but the majority of the MBFs are located in China, India, Brazil and Indonesia. Plant availability as well as the perfection achieved in this technology has made MBF an accepted route for iron making. Further, these days, most of the technologies of design, burdening and operation which have become the norm for today’s modern large furnaces have also been adopted in MBFs. MBF is a vertical shaft furnace with a crucible like hearth. Burden materials consisting of iron ore, coke or charcoal used as a reducing agent as well as fuel, and fluxes, usually limestone or dolomite, are charged into the top of the furnace. The furnace works on the principle of a counter current reactor. As the burden descends through the shaft, it is preheated and pre-reduced by the hot gases ascending from the furnace bottom. The gases are generated by introducing hot air blast enriched with oxygen through tuyeres. The hot blast burns the reducing agent, producing reducing gases and heat required for the reduction process taking place in the furnace. The reduced burden material melts to form HM (liquid iron) which becomes saturated with carbon and descends to the hearth. The fluxes combine with the impurities in the burden materials to produce a molten slag which accumulates on top of the liquid iron in the hearth. Liquid iron and liquid slag are periodically tapped from the furnace. MBF exhibits...

Dephosphorization of Steels Aug15

Dephosphorization of Steels...

Dephosphorization of Steels  The effects of phosphorus (P) on the properties of steels are summarized in Tab 1. It can be seen that P has both positive and negative effects on the steel’s properties. Tab 1 Effects of phosphorus on properties of steels Sl.No. Property Effect of phosphorus 1 Strength Strong positive (strengthens ferrite) 2 Bake hardenability Positive 3 Ductility Strong negative 4 Galvanneal Can improve resistance to powdering 5 Phosphatability Positive 6 Enameling a. Fish scaling Negative b. Pickling Positive 7 Weldability Not harmful for contents less than 0.1 % 8 Core loss in motor lamination Strong negative 9 Fracture toughness Strong negative   Steels having low content of P are necessary for applications where high ductility is needed, such as thin sheets, deep drawn steel, and pipelines etc. In the earlier days, P control was not considered a big challenge in steel production since iron ores with low P contents were readily and cheaply available. However, in the recent past, because of high iron ore prices, lower priced iron ores from sources which normally have higher P content are being used and this has made P control an important activity during the steelmaking. In addition to P from in the iron ores, P also enters the liquid steel due to the recycling of the BOF (basic oxygen furnace) slag. The recycling of the BOF slag is being done through the sinter plant or directly into the blast furnace in order to retrieve the iron and lime content of the slag and to minimize the issues related to slag disposal. The sinter or the BOF slag fed to the blast furnace inevitably increases the P content of the hot metal and hence the P loads on the steelmaking process. In integrated steel plants,...

Desulphurization of Liquid Steel Jul30

Desulphurization of Liquid Steel...

Desulphurization of Liquid Steel Solubility of sulphur (S) in liquid iron (Fe) is quite high. But the solubility of S in solid iron is limited. It is 0.002 % in ferrite at room temperature and 0.013 % in austenite at around 1000 deg C. Hence, when liquid steel cools down, sulphur is liberated from the solution in the form of iron sulphide (FeS) which forms a eutectic with the surrounding iron. The eutectic is segregated at the iron grain boundaries. The eutectic temperature is comparatively low at around 988 deg C. Fe-FeS eutectic weakens the bonding between the grains and causes sharp drop in the properties of steel at the temperatures of hot deformation. During the continuous casting of liquid steel, sulphur present in liquid steel (i) causes the formation of undesirable sulphides which promotes granular weaknesses and cracks in steel during solidification, (ii) lowers the melting point and inter-granular strength, (iii) contributes to the brittleness of steel and thus acts as stress raiser in steel, and (iv) results in the hot shortness. Sulphur, present in solid steel as FeS inclusions, has several detrimental effects on steel processing. During deformation, FeS inclusions act as crack initiation sites and zones of weakness. Such inclusions from sulphur adversely affect the toughness, ductility, formability, weldability, and corrosion resistance of steel. An increase in manganese (Mn) content (not less than 0.2 %) however, helps prevent formation of FeS. Sulphur is thus an undesirable element in steel. Manganese actively reacts with iron sulphides during solidification of steel transforming FeS to MnS according to the following reaction. FeS (slag) + Mn (steel) = MnS (slag) + Fe The melting temperature of manganese sulphide (MnS) is comparatively high (around 1610 deg C). Hence steel containing manganese can be deformed in hot state. However...

Importance of Hearth, Dead man and Tapping in Blast Furnace Operation Apr13

Importance of Hearth, Dead man and Tapping in Blast Furnace Operation...

Importance of Hearth, Dead man and Tapping in Blast Furnace Operation  A trend of deterioration in ore quality is seen these days with the increasing demand for iron ore. The deterioration in ore quality is accompanied with higher quantities of slag which in turn affects burden descent and liquid flow through the hearth. These conditions provide a catalyst for lining wear mechanism with bosh, stack and hearth linings coming under additional stress. Tapping in the blast furnace is adversely affected and trough and runners in the cast house get under strain due to higher slag volume. All these put increased pressure on blast furnace operations. The poor quality of iron ore affects the operation of the blast furnace in the following way. Slag volume – Poor quality of iron ores bring into the furnace higher quantities of impurities resulting into increase in the slag volumes. Heat load – The furnace thermal condition undergoes changes since a large quantity of heat is required to melt the additional slag as well as to keep it in proper fluid state for its drainage. This introduces higher heat loads inside the blast furnace. Coke rate and productivity – Increasing slag volumes needs a higher fuel input into the furnace, and where pulverized coal injection rates are already running at optimum, this results into a higher coke rate. Higher coke means introduction of higher amount of ash in the furnace resulting into further increase in the slag volume. This has got a deteriorating effect on the productivity of the furnace. Process stability – The deterioration in the ore quality affects the process stability adversely and has an unfavourable effect on the smooth running of the blast furnace. Due to the above factors, the production process in the blast furnace...