• 한국연소학회:학술대회논문집
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• 2012.04a
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• pp.19-20
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• 2012

Flue gas recirculation(FGR) is applied to sintering process to cope with issues including plant efficiency and environmental effects. However, it inevitably brings changes of incoming and outgoing gas conditions as plant configurations. Objective of this study was to build a process model for a sintering bed using a flowsheet process simulator and obtain information of mass and heat balance for gas flows over various process configurations with FGR.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.1
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• pp.43-51
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• 1987

In this paper, a state-space model of the burnthrough point control system of an industrial sintering process is derived. The model is then used in designing a self-tuning controller which consists of the receding horizon control law and a least-squares prediction algorithm with covariance resetting. By applying this controller to POSCO IV sintering process, satisfactory experimental results have been obtained. This paper presents some of these real-time experimental results and analyzes the control performance through productivity, operation indices, quality, sintered material composition, etc. From these experimental results and simulation results, the validity of the model can be observed. Moreover, the properties of the controller, e.g. stability, steady-state error, are shown based on the model.

• Proceedings of the Korea Database Society Conference
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• 1999.06a
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• pp.261-270
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• 1999

Sintering transforms powdered ore into lumped ore so that the latter can be used in a blast furnace. The powdered ore combined with coke and other materials is loaded into a container and moved along by a pallet while the ignited coke bums. The speed by which the pallet moves determines how much sintering takes place. Since the process is complicated and lacks an accurate mathematical model, human operators manually control the speed by monitoring various factors in the plant. In this paper, we propose a neural network-based pallet speed controller which copies human operator knowledge. Actual process data were collected from a sintering plant fer eight months and preprocessed to remove noisy and inconsistent data. A multilayer perceptron was trained using a back-propagation learning algorithm. In on-line testing at the sinter plant, the proposed model reliably controlled pallet speed during normal operation without the help of human operators. Moreover, the duality and productivity was as good as with human operators.

• Proceedings of the Korea Inteligent Information System Society Conference
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• 1999.03a
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• pp.261-270
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• 1999

Sintering transforms powdered ore into lumped ore so that the latter can be used in a blast furnace. The powdered or combined with coke and other materials is loaded into a container and moved along by a pallet while the ignited coke burns. The speed by which the pallet moves determines how much sintering takes place. Since the process is complicated and lacks an accurate mathematical model, human operators manually control the speed by monitoring various factors in the plant. In this paper, we propose a neural network-based pallet speed controller which copies human operator knowledge. Actual process data were collected from a sintering plant for eight months and preprocessed to remove noisy and inconsistent data. A multilayer perceptron was trained using a back-propagation learning algorithm. In on-line testing at the sinter plant, the proposed model reliably controlled pallet speed during normal operation without the help of human operators. Moreover, the quality and productivity was as good as with human operators.

• Journal of the Korean Ceramic Society
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• v.23 no.1
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• pp.1-6
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• 1986

The shrinkage rate of solid state sintering has been theoretically derived by combining the rate equation of material transport and the net free energy change resulting from the decrease of solid-vapor interface and the increase of grain boundary during sintering. For a sinteing model an idealized situation of the spherical particles with BCC packing was taken as the initial condition and the shrinkage was assumed to occur by forming the flat circualr grain boundaries on each particle. The plotted shrinkage rates as a function of grain boundary to surface energy ratio $(gamma_g/gamma_s)$ have shown that the relative density increases linearly at the initial stage of sintering but the shrinkage rate is decreased upon further sintering due to a decrease in driving force for densificaton. It has been also shown that the densification is critically affected by the $gamma_g/gamma_s$ ratio. In order to get the complete densificatin the ratio should be less than $sqrt{3}$. Any additive or atmospheric condition causing the decrease of$_g/gamma_s$ ratio will enhance sintering.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.350-351
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• 2006

A solid stage sinterizacion model of the WC-Co is applied on this work. These results are compaired with the experimental data obtained for nanometric and micrometric sinter powder in an electric furnace and micrometric in a plasma reactor (using Abnormal Glow Discharge AGD). The correlations obtained allow the prediction of the sintering behavior in AGD for nanometric powder. The activation of the solid state sintering is shown with the decraease of the WC size and the use of AGD

• Journal of the Korean Ceramic Society
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• v.56 no.2
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• pp.130-145
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• 2019

Widespread commercialization of solid oxide fuel cells (SOFCs) is expected to be realized in various application fields with the advent of cost-effective fabrication of cells and stacks in high volumes. Cost-reduction efforts have focused on production yield, power density, operation temperature, and continuous manufacturing. In this article, we examine several issues associated with processing for SOFCs from the standpoint of the bimodal packing model, considering the external constraints imposed by rigid substrates. Optimum compositions of composite cathode materials with high volume fractions of the second phase (particles dispersed in matrix) have been analyzed using the bimodal packing model. Constrained sintering of thin electrolyte layers is also discussed in terms of bimodal packing, with emphasis on the clustering of dispersed particles during anisotropic shrinkage. Finally, the structural transition of dispersed particle clusters during constrained sintering has been correlated with the structural stability of thin-film electrolyte layers deposited on porous solid substrates.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.363-368
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• 2000

Densification, grain growth, and phase transformation of nanocrystalline ceramic powder were investigated under pressureless sintering, sinter forging, and hot pressing. A constitutive model for densification of nanocrystalline ceramic powder was proposed and implemented into a finite element program (ABAQUS). A grain growth model was also proposed by including the effect of applied stress on grain growth when phase transformation occurs. Finite element results by using the proposed models well predicted densification behavior, deformation, and grain growth of nanocrystalline titania powder during pressureless sintering, sinter forging, and hot pressing.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1999.04a
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• pp.5-5
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• 1999

The Principal deficiency of the existing notion about the sintering-mixtures consists in the fact that almost no attention is focused on the Phenomenon of alloy formation during sintering, its connection with dimensional changes of powder bodies, and no correct ideas on the driving force for the sintering process in the stage of establishing chemical equilibrium in a system are available as well. Another disadvantage of the classical sintering theory is an erroneous conception on the dissolution mechanism of solid in liquid. The two-particle model widely used in the literature to describe the sintering phenomenon in solid state disregards the nature of the neighbouring surrounding particles, the presence of pores between them, and the rise of so called arch effect. In this presentation, new basic scientific principles of the driving forces for the sintering process of a two-component powder body, of a diffusion mechanism of the interaction between solid and liquid phases, of stresses and deformation arising in the diffusion zone have been developed. The major driving force for sintering the mixture from components capable of forming solid solutions and intermetallic compounds is attributed to the alloy formation rather than the reduction of the free surface area until the chemical equilibrium is achieved in a system. The lecture considers a multiparticle model of the mixed powder-body and the nature of its volume changes during solid-state and liquid-phase sintering. It explains the discovered S-and V-type concentration dependencies of the change in the compact volume during solid-state sintering. It is supposed in the literature that the dissolution of solid in liquid is realised due to the removal of atoms from the surface of the solid phase into the melt and then their diffusicn transfer from the solid-liquid interface into the bulk of liquid. It has been shown in our experimental studies that the mechanism of the interaction between two components, one of them being liquid, consist in diffusion of the solvent atoms from the liquid into the solid phase until the concentration of solid solutions or an intermetallic compound in the surface layer enables them to pass into the liquid by means of melting. The lecture discusses peculimities of liquid phase formation in systems with intermediate compounds and the role of the liquid phase in bringing about the exothermic effect. At the frist stage of liquid phase sintering the diffusion of atoms from the melt into the solid causes the powder body to grow. At the second stage the diminution of particles in size as a result of their dissolution in the liquid draws their centres closer to each other and makes the compact to shrink Analytical equations were derived to describe quantitatively the porosity and volume changes of compacts as a result of alloy formation during liquid phase sinteIing. Selection criteria for an additive, its concentration and the temperature regime of sintering to control the density the structure of sintered alloys are given.

• 한국연소학회:학술대회논문집
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• 2004.11a
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• pp.33-40
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• 2004

Combustion of coke/anthracite in an iron ore sintering bed is characterized quantitatively by introducing newly defined parameters related to propagation and thickness of combustion zone and maximum temperature. The parameters are obtained by sintering pot experiment and I-D, unsteady numerical model which treats solid material as multiple solid phases. Experiments and calculations are performed for various major operating parameters: air inlet velocity, different type of fuels which have different reactivity and diameter of the solid fuel. Effects of the operating parameters on the productivity and quality of the sintering process are investigated and evaluated quantitatively and the results show that optimized air supply rate and diameter of anthracite for replacement of coke can be obtained. This approach can be applied to other kinds of combustors for characterization of the combustion in the solid fuel beds.