Gopi K. Mandal

A Steady State Thermal and Material Balance Model for an Iron Making Blast Furnace and Its Validation with Operational Data

In view of scarcity and depletion in the quality of raw materials as well as stringent environmental regulations, judicious use of resource and adoption of optimal operating practices have become the prime concern in iron and steel industries. Real time forecasting and supervision of the process behavior is an important step in addressing these issues. As a part of the tool termed “Real Time Process Simulator (RTPS)”, containing several reduced order models for real time monitoring and prediction of the internal dynamics of iron making blast furnace, a mathematical model for material and thermal analysis has been developed, mainly to predict the top gas composition, raw material consumption and overall heat balance. The model predictions have been tested against actual plant data. The raceway adiabatic flame temperature has been calculated using data similar to that of an operating plant. The calculated heat distribution of the process has been presented in the form of a SHANKEY diagram. The RTPS, containing the present model has been implemented in an Indian integrated steel plant. Prior to implementation, the model has been tested and validated in the plant operational range with the help of a virtual platform.

Theoretical Investigation on Deoxidation of Liquid Steel for Fe–Al–Si–O System

Deoxidation of liquid steel involves consumption of high energy materials like ferro alloys and generation of deoxidation products which could be entrapped into liquid steel as non-metallic inclusions. The present investigation is focused on deoxidation of liquid steel, considering mainly aluminium and silicon as deoxidizer. A simple and realistic mathematical model of deoxidation of liquid steel has been developed based on the thermodynamic principles and material balance approach for day to day industrial practice. One of the main aims of the theoretical study was to predict the amount of deoxidizers required for a given steel composition. A methodology has also been developed to predict the stability of different oxides expected to be present in liquid steel after deoxidation. Model predictions have been compared with the industrial data as well as results obtained from commercial thermodynamic software package FactSage 6.4, simulated under identical conditions. Model predictions are in reasonable agreement with the ferro alloy consumption in industrial steelmaking processes.

Characterization and Evolution of Non-metallic Inclusions in Fe–Al–Si–O System

Presence of non-metallic inclusions in steels are practically inevitable and deoxidation products are one of the main sources for such inclusions. The present investigation focuses on the study of non-metallic inclusions in Fe–Al–Si–O system by considering aluminium and silicon as deoxidizers. This investigation mainly deals with the amount, distribution and morphology of complex non-metallic inclusions in steel, generated during complex deoxidation of liquid steel by silicon and aluminium. Morphology and floatability of various complex non-metallic inclusions present in the system has been discussed based on the physical properties of these oxides. Dissolution of MgO from the refractory lining being unavoidable, the present paper also aims at understanding the mechanism, morphological and compositional evolution of ternary MgO–Al2O3–SiO2 type inclusions.

Control of Slag Carryover from the BOF Vessel During Tapping: BOF Cold Model Studies

In a modern integrated steel plant, slag-free tapping during transfer of liquid steel from the BOF vessel to the ladle is prerequisite to produce ultraclean steel for high-end critical applications. The present investigation aims to examine the drain vortices during the liquid steel tapping process. The tapping experiments were conducted in a geometrical down-scaled Perspex BOF cold model, which was more akin to the industrial practice than the other geometries previously reported in the literature. The study highlights the influence of the complex BOF shape on drain vortices during the tapping process. It is observed that vorticity behavior during liquid steel tapping from the BOF vessel is different from the earlier observations reported for the teeming process. The parametric study of the tapping process and its analysis confirmed that the threshold height for drain vortices is strongly influenced by the nozzle diameter (ND) and marginally influenced by the residual inertia of the liquid. The carryover ratio (COR) for the water-oil experiments is in agreement with the values obtained in industrial practice. Yield loss tends to increase with the increase in ND. The onset of drain vortices in the presence of overlying phase (oil/slag) during the BOF tapping process could be principally controlled by the vessel design. The physical properties of the overlying phase had negligible influence on the drain vortices. The critical times for vortex and drain sink formation were predicted based on dimensional analysis coupled with the mathematical formulation for the tapping process. A strategy to control the slag carryover during the tapping process in industry is also discussed and postulated based on the understanding developed from water modeling experiments.

A reduced order mathematical model of the blast furnace raceway with and without pulverized coal injection for real time plant application

Abstract Pulverized coal is injected into blast furnace tuyeres to reduce coke consumption as well as to reduce hot metal production cost. Knowledge of the combustion behavior of pulverized coal in the blast furnace raceway zone and accumulation of unburnt char are of paramount importance. To alleviate the problem of high computational time of a multidimensional model, a reduced order raceway model of the blast furnace has been proposed for real time plant application. The model is capable of predicting radial temperature and gas composition profiles in the raceway zone with and without pulverized coal injection (PCI). Influence of all the key operating process parameters such as PCI rate, blast temperature, blast volume, oxygen enrichment and steam addition on the raceway combustion behavior, temperature and gas composition profiles as well as raceway depth have been investigated and validated with literature and plant database, wherever possible. It has been observed that with increasing PCI rate on a fixed fuel rate basis, the peak gas temperature (PGT) decreases and the location of PGT tends to shift toward tuyere nose. The present model is an efficient computational tool to predict the raceway process variables for online application, in synchronization with plant operation.

Estimation and Analysis of Excess Oxygen Input into Ladle During Liquid Steel Tapping

Carryover of oxidising slag from primary steelmaking furnace during tapping affects the quality of liquid steel in several ways. Secondary steelmaking practices, such as deoxidation, desulphurization, vacuum degassing as well as inclusion control in liquid steel bath, are greatly influenced by the amount and characteristic of carryover slag. Both, slag volume as well as ferro alloy consumption increases due to the presence of carryover slag during ladle refining treatment. Carryover of furnace slag in ladle during tapping cannot be avoided and results in consumption of excess electrical energy. Thus, control of carry over slag mainly during tapping is essential by suitably modifying the operational practice. In the present investigation, slag carry over during liquid steel tapping operation is quantified for the processed data obtained from an integrated steel plant based on material balance and equilibrium thermodynamic study. Some of the relevant operational factors related to slag, deoxidation, temperature and solutes (C, S and N) are identified and correlated with the amount of slag carry over. Though, the slag carry over during tapping operation is gravity dependent draining phenomena, scope for controlling the same is identified & discussed in the present study.