Blast Furnace Stoves Research Articles

ЧИСЕЛЬНО МАТЕМАТИЧНА МОДЕЛЬ РОБОТИ НАСАДКИ ДОМЕННОГО ПОВІТРОНАГРІВАЧА ТА ЇЇ ЗАСТОСУВАННЯ В МОДЕЛЮВАННІ РОБОТИ ГРУПИ ПОВІТРОНАГРІВАЧІВ

Subject simulation of blast furnace stove is still relevant today, research in this area were carried out by many scientists. An analysis of well-known publications is described at the beginning of the article, conclusions are drawn about the developed models, the accepted assumptions and their consequences are considered.The complexity of modeling an object makes it necessary to divide it into its component parts; therefore, this article considers only the checkerwork of an hot blast stove, fuel combustionand heat transfer in the combustion chamber and dome are not considered. Provides the purpose of the work and the tasks arising from it. A scheme for splitting the checkerwork into a smaller region suitable for economic calculation is presented, but one that does not distort the physical meaning. Thermophysical parameters of the heat carrier and checkerwork material are determined. Further, the mathematical description in the differential equations of the physical processes occurring in the hot blast stove checkerwork in on-gas and on-blast periods. A block diagram of the software for the system of information support and control of a group of hot blast stoves was developed, including temperature control, calculation of combustion, calculation of checkerwork, calculation of parameters of blast. The scheme is focused on the operation of the heater in three periods, namely, on-gas, on-blast and on-separation. The described methods of interaction of individual software components of the system, the structure of the group management program with a detailed description of the individual components of this program. The block diagram of the program for simulating the operation of the hot blast stove group of a blast furnace is given, the subroutines included in it, their input data, basic ideas of functioning under various operating modes of an hot blast stove are described. At the end of the article, the main conclusions are presented.

Carbon type differentiation technique for diagnosing pulverised coal injection efficiency

Coal injection is a common practice for coke replacement in current blast furnace (BF) operations. The amount of coal that can be injected and successfully replace large coke is determined by the extent of coal gasification, which is a function of both the combustion environment in the tuyere/raceway region and combustibility of the injected coal. A new carbon type differentiation (CTD) technique was developed at CanmetENERGY for quantifying the amount of unburnt pulverised coal injection (PCI) residue that is carried in the furnace top gas for diagnosing the extent of injected coal gasification. This technique utilises the combustion characteristics of solid carbonaceous material generated during rapid pyrolysis and partial combustion of coal. The CTD technique developed was transferred to ArcelorMittal Dofasco and successfully implemented in the industrial environment. Using this technique, AM Dofasco established a PCI efficiency baseline for each of its three BFs, which will be used as a reference point for comparison in future trials. The capability of the CTD technique in diagnosing and understanding the effect of BF operating parameters on PCI burnout efficiency was demonstrated upon examining the effect of blast temperature decrease during a recent BF stove repair.

Blast furnace ironmaking: view on future developments

Within many industries, there is a constant drive to reduce environmental impact and energy costs thereby ensuring maximum energy re-use. Within the iron and steel industry, the ironmaking processes are acknowledged to be the focus area when the topic of energy saving arises. A lot of attention has been applied to the ironmaking processes with regards to environment and energy saving, with established technologies being in place to reach these goals such that the process per se is now at or very close to theoretical limits. The following areas of the blast furnace process are currently the focus of Primetals activity with regard the target to further improve energy saving with incremental improvements: flue gas recycling within blast furnace stoves, MERIM dry gas cleaning process and dry slag granulation including heat recovery. This paper will present the concepts and latest status of the above technologies. The paper will review the progress to date of these development activities and thus present ideas on options for energy saving and reuse within the ironmaking system.

Model Development of a Blast Furnace Stove

A large amount of energy is required in the production of steel where the preheating of blast in the hot blast stoves for iron-making is one of the most energy-intensive processes. To improve the energy efficiency it is necessary to investigate how to improve the hot blast stove operation.In this work a mathematic model for evaluating the performance of the hot blast stove was developed using a finite difference approximation to represent the heat transfer inside the stove during operation. The developed model was calibrated by using the process data from the stove V26 at SSAB Oxelösund, Sweden. As a case study, the developed model was used to simulate the effect of a new concept of OxyFuel technique to hot blast stoves. The investigation shows that,by using the OxyFuel technique, it is possible to maintain the blast temperature while removing the usage of coke oven gas. Additionally, the hot blast temperature increases while the flue gas temperature decreases, which allows for an increase of the blast temperature, leading to improved energy efficiency for the hot stove system.

Analysis of efficient operating cycles for blast-furnace stoves

The stove of a blast furnace is one of its most important elements, helping to make the furnace more efficient by preheating the blast. Blast-furnace stoves operate as a unit in order to provide a continuous supply of hot blast to the furnace, this being done by alternating the stoves between cycles in which they heat the blast and cycles in which their checkerwork is heated. Fixed cycles are often used due to the difficulty of operating stoves in cycles of different durations. However, this practice inevitably leads to fuel losses and destabilizes the temperature of the blast. This article presents a model of heat transfer that the authors have developed for a blast-furnace stove. An alternating cycle for heating the blast with a group of stoves is analyzed and methods are proposed for solving problems concerning operating cycles with the use of a three-stove or four-stove group.

Process Intensification in a “Simulated Moving-Bed” Heat Regenerator

The solid-gas contacting for thermal storage and thermal recovery is generally carried out in fixed-bed regenerators. Compared to a fixed bed, higher thermal recovery can be achieved in a moving bed with countercurrent flow of gas and solids. However, the moving beds have not been widely used due to difficulties in solid handling. The relative movement of the bed to the gas flow can be simulated in a fixed bed by moving the inlet and outlet ports of the gas along the length of the bed. Similar simulated moving beds are already in use for adsorptive separation of liquid mixtures in chemical industries. A novel moving-port system is proposed to achieve simulated moving-bed operation in a fixed bed. We have carried out studies to evaluate the relative performance of the fixed and the simulated moving-bed heat regenerators. We have examined the feasibility of replacing a set of three blast furnaces and thermal regeneration of an adsorption bed with the simulated moving-bed regenerator. It is found that high-heat transfer intensification can be achieved. The results indicate that three blast-furnace stoves can be replaced by a simulated moving-bed regenerator of volume of about 100 times smaller than the stoves. The heat-transfer intensification is high enough to carry out thermal regeneration of the adsorption beds in a cycle time that is in the range of the pressure swing adsorption, which is favored for its faster rate of regeneration.

Estimation of the State of Metal of Blast-Furnace Jackets and Hot-Blast Stove Casings by a Nondestructive Testing Method

The possibility of using the technique of magnetic testing of the stress-strain state of metallurgic structures is investigated. This technique is based on the correlation dependence between the physico-mechanical properties and the coercive force H c . Examples of the practical use of the technique for estimating the state of blast-furnace jackets and hot-blast stove casings are given. Trends of variation of the state of metal during a long time period are established.

Thermal analysis of blast furnace stove regenerators system operating under staggered cold-bypass arrangement by computer simulation

A system of blast furnace stove regenerators operating under the "staggered with cold by-pass" arrangement is analyzed. The solution of the partial differential equations, which govern this non-linear heat transfer process, via computer simulation, is presented. The temperature dependence of the solid and fluid properties and heat transfer coefficients is taken into account. An example demonstrates the usefulness of the method, and the comparison with two other stove arrangements, the "series parallel", and "staggered", presented earlier, are discussed. It is shown, how this method can be utilized to aid the stove design, or to improve the performance of existing installations.

Improvement of the performance of blast furnace stoves

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SOLVING A THERMAL REGENERATOR MODEL USING IMPLICIT NEWTON-KRYLOV METHODS

In this article we discuss the use of an implicit Newton?Krylov method to solve a set of partial differential equations (PDEs) representing a physical model of a blast furnace stove. Blast furnace stoves are thermal regenerators used to heat the air injected into the blast furnace, providing the heat to chemically reduce iron oxides to iron. The stoves are modeled using a set of PDEs that describe the heat flow in the system. The model is used as a part of a predictive controller that minimizes the fuel gas consumption during the heating cycle while maintaining a high enough output air temperature in the cooling cycle to drive the chemical reaction in the blast furnace. The discrete representation of this model is solved witha preconditioned implicit Newton?Krylov technique. This algorithm uses Newton's method, in which the update to the current solution at each stage is computed by solving a linear system. This linear system is obtained by linearizing the discrete approximation to the PDEs, using a numerical approximation for the Jacobian of the discretized system. This linear system is then solved for the needed update using a preconditioned Krylov subspace projection method.

Making the operation of blast-furnace stoves more efficient

Making the operation of blast-furnace stoves more efficient

Pebble heater, a high-tech approach for blast preheating

A new heat exchanger has been developed for gas preheating up to 1450 °C with high heat efficiency. The technology uses a fixed radial bed with ceramic beads. A pilot unit has been operated by campaign in Germany for several years. The first intended application is as a booster, or as a substitute of blast furnace stoves. Cost is half that of a conventional stove.

First- and second-law analyses of energy recoveries in blast-furnace regenerators

We examine various systems for the recovery of thermal energy from waste gases and for preheating in blast-furnace Cowper stoves, with the basic aim of improving efficiencies when utilizing blast-furnace gas with low net heating value at constant peak temperature. Using first- and second-law analyses, with suitably defined exergetic quantities, numerical values are given to measure energy savings.

On-line optimization and control of a blast furnace stove rig

The operation of an industrial blast furnace requires the constant delivery of hot blast air from blast furnace stoves. The blast air must be supplied with temperature and flow-rate as close as possible to setpoints. In the long term, control must also meet the conflicting objectives of thermal efficiency, cyclic stability and load response speed. The long-term optimal control of a blast furnace stove rig has been successfully addressed. Significant improvement in thermal efficiency and load response speed were obtained compared to conventional fixed period control. Moreover, the technique presented provides a flexible method which allows the requirements for optimality to be directly specified.

Model-based control of a blast furnace stove rig

Smooth and efficient operation of an industrial blast furnace requires the constant delivery of hot blast air from blast furnace stoves. The blast air must be supplied with temperature and flow as close as possible to set-points, without oscillation, and in a thermally efficient manner. The short-term control problem of a laboratory-scale blast furnace stove system has been successfully addressed using a model-based control technique. Superior blast air delivery has been obtained with generic model control (GMC) compared to traditional proportional-integral-derivative control. Non-linear and time-varying process behaviour have been easily accommodated using the GMC technique.

Suppression of flame pulsations in the combustion chambers of blast-furnace stoves

Suppression of flame pulsations in the combustion chambers of blast-furnace stoves

Automatic system to regulate gas consumption on a blast-furnace stove from the temperature of the exit gases

Automatic system to regulate gas consumption on a blast-furnace stove from the temperature of the exit gases

All-union standard on fuel consumption in blast-furnace stoves

All-union standard on fuel consumption in blast-furnace stoves

Increase in the productivity of blast-furnace stoves

The Novolipetsk combine proposed sending a cold blast through a special 150-mm-diameter pipe passing through an igniter opening into the combustion chamber. To evaluate the efficiency the stove performance in which some of the cold blast was directed to the combustion chamber was compared against that of unmodified stoves. This blast-delivery system was found to increase consumption of blast-furnace gas during the first stage, reduce time required to bring the dome up to prescribed temperatures, shorten the stove-heating period, and increase blast-heating temperature by 10-15/degree/.

Differentiated use of refractories in blast-furnace hot blast stoves

In the service of blast furnace hot blast stoves the lining and checkerwork fail in individual zones as the result of deformation of the refractories, formation of cracks, and chemical corrosion of the lining under the action of low-melting dust at high temperatures.