Fundamentals

Three types of ore fines such as hard ore (HO), blue dust (BD) and friable ore (FO), normally available from a mine show different physical and physicochemical properties. Each of the properties of any individual ore among three may not be suitable to use independently in pelletisation. However, uses of all these three are mandatory. Ores of some poor properties may show other properties excellent. Therefore, any specific poor property of any individual ore can be modified by adding (mixing) other ore which shows that particular property excellent. In order to utilise those three ore fines in pelletisation, mixing of above three ores have been done to get good pellet properties. In industry, the fluctuation in mixing ratio often creates problem in maintaining pellet quality and consistency in spite of maintaining identical basicity and MgO content. Therefore, the required mixing ratio and pellet chemistry has also been optimised in this study. BD, FO and HO has been found to be suitable in the mixing ratio of 70:25:5 with 1.4% MgO. However, with increase in FO beyond 50%, reduction degradation index (RDI) becomes very high (25%). RDI has been decreased to very low level by increasing MgO content from 1.4 to 2% which enables to use FO up to 70% for good quality pellet preparation.

Section: Resultsmentioning

confidence: 99%

Development of blast furnace quality pellet optimising blue dust, hard ore and friable ore ratio

Pal

Ghorai

Rajshekar

et al. 2016

“…The conventional Fe–C–O stability diagram, 8–10 is redrawn as Fig. 1, in which the equilibrium pct CO is plotted against temperature ( T ) in the temperature range 300–1300 K using the data given in equations (1)–(5).…”

Section: Conventional Fe–c–o Stability Diagram (Pct Co Vs T Plot)mentioning

confidence: 99%

“…The general representations of these two types of reduction and their combined form, which can be applied at any temperature and pressure within the stability domain of Fe (solid), are not available in the literature. 1–6 In addition, the following queries need to be answered:Does the direct reduction of iron oxide by carbon necessarily mean that the gaseous product is 100% CO?Is it thermodynamically possible to have a combination of the direct and indirect reductions of iron oxide in a carbon-saturated system?Does a carbon-saturated system consume more carbon to reduce a given quantity of iron oxide than a carbon-unsaturated system?A new type of Fe–C–O stability diagram needs to be drawn that will answer all these questions. This new diagram is a plot of the ratio of mole C to mole Fe 2 O 3 at the input, , vs. temperature ( T ) at a given total pressure (1 atm).…”

Section: Introductionmentioning

confidence: 99%

A new way of constructing the stability diagram of the system Fe–C–O with the help of a C/Fe₂O₃ vs. T plot and the related issue of direct and indirect reduction

Sarkar

Ghosh

2016

A new type of Fe-C-O stability diagram, which is a plot of the molar ratio (n C /n Fe 2 O 3 ) input vs. temperature (T ), is drawn for 1 atm total pressure in the temperature range 300-1300 K. Apart from delineating the stability fields of Fe and its oxides, this diagram directly furnishes the minimum number of moles of carbon required to reduce 1 mol of the starting Fe 2 O 3 (pure) to Fe, FeO or Fe 3 O 4 , or their mixtures, at a given temperature and 1 atm total pressure. Besides, the confusing issue of the direct reduction (DR) vs. indirect reduction (IR) of iron oxide by carbon is reviewed and clarified, and used in the construction of the diagram. The general representations of 100 pct DR and 100 pct IR of Fe 2 O 3 , which will be applicable at any temperature and pressure within the stability domain of Fe (solid), are proposed as follows:The combined DR and IR has the same representation as the 100 pct DR. However, in the combined case, the molar ratio CO/CO 2 in the product gas is dictated by the equilibrium with Fe-FeO and in the case of 100 pct DR by the carbon saturation. For the 100 pct IR, the ratio is, again, dictated by the Fe-FeO equilibrium; in addition, the ratio C/O 2 on the reactant side is governed by the carbon-saturated CO-CO 2 mixture obtained from the burning of C in O 2 .

“…Most of these investigations have been based on several assumptions including pseudo-steady state as well as isothermal and single reactant. Some examples are the research conducted by von Bogdandy and Engell, 1 McKewan, 2 Turkdogan and Vinters, 3 and Usui et al 4 The most important paper in this field was written by Valipour and Khoshandam. 5 They eliminated most limitations of the previous works and studied time-dependent, non-isothermal reduction of wustite pellet with syngas.…”

Section: Introductionmentioning

confidence: 99%

“…In such a condition, employing the grain model as a representative of the latter concept reveals a satisfactory agreement with the experiment. In terms of the reduction of iron ores, both of the concepts have been thoroughly studied in the literature, 1–5,8–12 and minor discrepancies have been observed between them. The good agreement between USCM and grain models in the case of iron ores reduction motivated us to investigate in detail the grain model for wustite pellet.…”

Section: Introductionmentioning

confidence: 99%

Mathematical modelling of wustite pellet reduction: grain model in comparison with USCM

Ghadi

Valipour

Biglari

2016

A mathematical time-dependent and non-isothermal model has been carried out on the basis of the grain model to study the behaviour of a wustite pellet undergoing chemical reactions with reducing gases. The behaviour of wustite pellet reduction analysed by the grain model has been compared with unreacted shrinking core model (USCM). The results show, unlike the grain model, USCM cannot properly predict the impact of gas mixture parameters and pellet characteristics on the local reduction degree. The results also display that when the grain diameter, temperature and tortuosity increase, the diffusivity resistance in the pellet increases which causes more heterogeneous reduction. However, an increment in porosity causes gases to easily diffuse in the pellet and as a result a less heterogeneous reduction will occur.