Compare Pilot-Scale And Industry-Scale Models Of Pulverized Coal Combustion In An Ironmaking Blast Furnace

In order to understand the complex phenomena of pulverized coal injection (PCI) process in blast furnace (BF), mathematical models have been developed at different scales: pilot-scale model of coal combustion and industry-scale model (in-furnace model) of coal/coke combustion in a real BF respectively. This paper compares these PCI models in aspects of model developments and model capability. The model development is discussed in terms of model formulation, their new features and geometry/regions considered. The model capability is then discussed in terms of main findings followed by the model evaluation on their advantages and limitations. It is indicated that these PCI models are all able to describe PCI operation qualitatively. The in-furnace model is more reliable for simulating in-furnace phenomena of PCI operation qualitatively and quantitatively. These models are useful for understanding the flow-thermo-chemical behaviors and then optimizing the PCI operation in practice. 2013 AIP Publishing LLC

Effects of annealing on microstructure and microstrength of metallurgical coke

Two metallurgical cokes were heat treated at 1673 K to 2273 K (1400 degrees celsius to 2000 degrees celsius) in a nitrogen atmosphere. The effect of heat treatment on the microstructure and microstrength of metallurgical cokes was characterized using X-ray diffraction, Raman spectroscopy, and ultramicroindentation. In the process of heat treatment, the microstructure of the metallurgical cokes transformed toward the graphite structure. Raman spectroscopy of reactive maceral-derived component (RMDC) and inert maceral-derived component (IMDC) indicated that the graphitisation degree of the RMDC was slightly lower than that of the IMDC in the original cokes; however graphitisation of the RMDC progressed faster than that of the IMDC during annealing, and became significantly higher after annealing at 2273 K (2000 degrees celsius). The microstrength of cokes was significantly degraded in the process of heat treatment. The microstrength of the RMDC was lower, and of its deterioration caused by heat treatment was more severe than IMDC. The degradation of the microstrength of cokes was attributed to their increased graphitisation degree during the heat treatment

Numerical Analysis of Gas Flow-Slag Surface Interaction in Blast Furnace

An improved understanding of gas flow distribution around the raceway of an ironmaking blast furnace is important for stable operation and improved drainage of molten liquids from the hearth. Previous studies based on 2- and 3-dimensional models with over-simplified raceway phenomena do not provide a quantitative description of liquid-gas interaction. The current paper focuses on the analysis of gas flow near the raceway region and its effect on the liquid surface by using a 3-dimensional sector model. Various BF phenomena and a realistic local coke bed structure, such as the raceway cavity and “birds nest”, are considered. The simulation is conducted using a homogeneous two-phase flow model combined with a model for flow through porous media. The variables considered include the liquid level, location and shape of the cohesive zone and deadman characteristics

Behaviour of New Zealand ironsand during iron ore sintering

Titanium-bearing burdens are commonly introduced into blast furnaces to protect the hearlh because the so-called titanium bear which is a precipitate of carbide, nitride and carbonitride of titanium may form in the blast furnace hearth if Ti02 is present in the feed [1 , 2J. New Zealand ironsand is a titanomagnetite, containing around 60 wt.% iron, 8 wt.% titanium and other substances such as silica, phosphorus and lime [3, 4]. Since it is competitive in price, introduction of the ironsand into the ferrous feed can reduce the production cost and potentially increase blast furnace campaign life. An appropriate method of inlroduction of ironsand is as a component of the sinter as the small size of ironsand precludes direct charging into the blast furnace. Although the effect of introducing titanomagnetite into iron ore blends has been investigated [1,,2, §],little is known about the detailed sintering mechanism. The present study is aimed at identifying the sintering behaviour of New Zealand ironsand as well as the interaction between New Zealand ironsand and CaO to gain better understanding of sintering mechanism of titanomagnetite

Sintering of Iron Ores in a Millipot in Comparison with Tablet Testing and Industrial Process

To explore the feasibility of small-scale sintering pot testing, a \u27millipot\u27 facility (diameter of 53 mm and height of 400 mm) was established and used to examine the sintering performance of iron ores and other non-traditional ferrous materials. The sintering performance of a millipot was examined across a range of different operational conditions (coke rate and suction pressure) and compared with an industrial sinter strand operation. Tablet tests were also performed to assist in the design of the millipot experiments and identify conditions for achieving mineral composition similar to the industrial sinter. For the millipot experiments, the materials used need to be compacted to increase the bulk density, and a higher coke rate is required to compensate the high heat loss caused by wall effects. A higher suction pressure is also necessary to maintain an oxidizing atmosphere in the sinter bed. As expected, it was not possible to eliminate the wall effect, which resulted in more primary hematite at edges of the sintered column. However, the sintered material from the center of column simulates industrial sinter reasonably well. As such, millipot provides a practical way to evaluate the sintering process and material performance at laboratory scale, helping to bridge the gap between tablet sintering and large scale pot sintering, or full scale plant trial. The results of millipot testing can be used for designing larger scale experiments or commercial sintering trials

Prediction of blast furnace hearth condition: part I - a steady state simulation of hearth condition during normal operation

A coupled flow and refractory model (CFRM) has been upgraded to assist engineers in understanding and interpreting the measured refractory temperature distributions in the hearth of a blast furnace hearth. CFRM describes the liquid flow distribution and heat transfer in the hearth, allowing various scenarios to be simulated involving coke bed properties, extent of hearth refractory wear, etc. The model was validated through comparison between measured refractory data and corresponding model predictions for the early stages of the current BlueScope\u27s No. 5 Blast Furnace campaign. For the current campaign, the actual range in measured pad temperature fluctuation over a short time period is shown to be well within the temperature difference expected for typical coke bed movement, i.e. between sitting and floating bed conditions. Over a longer time span, a consistent evolution of the refractory wear is suggested and this is imposed to elucidate the increase in overall hearth pad temperature

Value-in-use assessment of metallurgical coals

For both steelmaking and mineral resource companies, the selection of an optimal suite of metallurgical coals that maximizes profitability remains a major strategic decision. One of the main analytical tools used for optimization of material selection and decision-making is the Value-in-Use (VIU), where all costs and cost penalties associated with the purchase, delivery, and importantly, the utilization of coals are evaluated to identify the most economically favorable coal supply options for steelmaking businesses. This chapter covers the basis for using VIU across the steelmaking value process chain, the factors which may influence the VIU assessments in major processes such as ironmaking blast furnace and coke ovens, and key details concerning these processes to understand the link between coal/coke chemical and physical properties determined using traditional testing procedures, and their contributions and penalties to the overall operating unit cost of steel production. New, more realistic testing methods for coke quality are described

Numerical investigation of the angle of repose of monosized spheres

This paper presents a numerical study of the angle of repose, a most important macroscopic parameter in characterizing granular materials, by means of a modified distinct element method. Emphasis is given to the effect of variables related to factors such as particle characteristics, material properties, and geometrical constraints. The results show that sliding and rolling frictions are the primary reasons for the formation of a sandpile; particle size and container thickness significantly influence the angle of repose; and the angle of repose is not so sensitive to density, Poisson\u27s ratio, damping coefficient, and Young\u27s modulus. Increasing rolling friction coefficient or sliding friction coefficient increases the angle of repose. Conversely, increasing particle size or container thickness decreases the angle of repose. The underlying mechanisms for these effects are discussed in terms of particle-particle and particle-wall interactions

A hot metal temperature predictor based on hybrid decision tree techniques

HEAT level control (HLC) is one of the important elements for operating an iron-making blast furnace (BF). The goal of HLC is to maintain the hot metal temperature (HMT) as close to a preset aim as possible. HMT is an important indicator of both the product quality and fuel efficiency, and is measured from tapped out liquid iron. For instance, high values of HMT mean unnecessary fuel consumption together with sub-optimal hot metal chemistry, whilst low values of HMT may indicate insufficient fuel consumption, which may consequently lead to dangerous situation of freezing the slag inside the BF. Once an aim HMT is decided, based on production and plant constraints, several inputs of the BF can be adjusted by operators to control this HMT. However, any change of the inputs requires time to take effect, due to inherent time lags, and the best practice control relies heavily on an operator’s experience and judgment. This is due to the complexity of the numerous BF processes, which essentially can be described as highly non-linear, stochastic and nonstationary in nature. The goal of this work is to employ a data mining approach to analyse the BF system and build a dynamical modelling system, which will generate a set of understandable symbolic rules for prediction of HMT changes. The model is regularly generated by decision tree applications, See5 and Cubist, in order to adapt any significant contextual variations of the BF. This rule based system can help the operators increase the BF’s efficiency by making timely control adjustments with the goal of minimising variation of HMT with time. These models also provide a corpus of driving factors that can also be analysed by domain experts as an objective knowledge source