Melter Gasifier Research Articles

Influence of operational parameters on hot metal temperature in Corex process

In the production practice of Corex C-3000 at Baosteel, hot metal temperature varies greatly and it is often found that changes in silicon content and hot metal temperature do not match each other. In this paper, the key factors influencing hot metal temperature were analysed by statistical analysis of the relationship between hot metal temperature and 18 operational parameters, in order to find the way to reduce the fluctuation of hot metal temperature. The result shows that the most important factors affecting hot metal temperature are the hot metal composition, especially carbon content, followed by the burden structure and metallisation of the direct reduced iron from the reduction shaft. In addition, hot metal temperature was related to the flux amount charged into the melter gasifier, slag properties, the tapping process, etc. The statistical model to predict hot metal temperature was obtained by multiple regressions based on the understanding of the operational parameters affecting the hot metal temperature. The analysis indicates that the carbon content in the hot metal is more reliable and sensitive as the indicator of hot metal temperature than silicon content in the Corex C-3000 process. From an operational point of view, any measure which can improve burden permeability or improve carburisation condition under dripping zone will be helpful for stabilising hot metal temperature.

Numerical Modelling of the Moving Bed Inside the COREX® Melter-Gasifier

The COREX®-process is the first commercially operating smelting reduction process for the production of pig iron. For this reason, it can be seen as an alternative to the common industrial iron-making route via the blast furnace. For both, the COREX® melter-gasifier (MG) and the blast furnace, good gas-solid contact is essential for the stable and efficient operation of the process. Due to the very harsh conditions inside the MG, the possibilities for measurement of process conditions are very limited. Thus, detailed numerical models are required to gain additional understanding of the physical and chemical processes occurring within the MG.

Influence of Collapse Phenomenon on Unburned Pulverized Coal in the Lumpy Zone of COREX Melter Gasifier

A thermal model was established for the study about influence of collapse phenomenon on unburned pulverized coal in COREX melter gasifier. In the model, the ore was simulated by wax, the coke and lump coal were simulated by maize, UPC is simulated by pulverized coal. The results showed that too high blast temperature could lead to collapse in the model, and under normal or collapsing furnace state, UPC is dispersed or aggregated distribution in packed bed. According to this experimental results and the previous research results, the suggestions about COREX were given at last. Keywords: COREX melter gasifier; pulverized coal injection; unburned pulverized coal; physical experiment

Numerical Simulation of Liquid Iron Flow and Heat Transfer in the Hearth of COREX Melter Gasifier during Tapping Process

The service life of COREX melter gasifier mainly depends on the hearth refractory erosion which is strongly affected by the liquid iron flow and the heat transfer. In the present work, a three‐dimensional mathematical model at steady state which takes fluid buoyancy force and turbulence model into consideration is introduced to describe the flow and temperature distribution in the hearth in detail. The accuracy of the model is evaluated using plant operational data. The results show that the position of serious mechanical erosion gradually shifts from the hearth pool bottom to the sidewall, as the coke bed position changes from “floating” on the liquid iron to “sitting” on the hearth pool bottom during one tapping cycle under the condition of stable tapping. The second peak of liquid iron flow, which is a noticeable feature of COREX melter gasifier in comparison with blast furnace, could result in more serious mechanical erosion of sidewall and severer thermal erosion of refractory on hearth pool bottom. The effective countermeasures of the second peak of liquid iron flow are proposed in this work. In addition, the effects of porosity of fine coke region and refractory erosion are further discussed. The results can be used to predict the inner profile of hearth and to provide guidance for protecting the hearth refractory.

The Burden Structure and Its Consumption in the Melter Gasifier of the Corex Process

A major advancement in the Corex ironmaking process is the usage of lump coal considering the shortage of coking coal resources worldwide. However, the burden similar to that of the blast furnace is still essential for the enlarged melter gasifier. The notable difference is that the burden of the melter gasifier is composed of char formed from lump coal with a small amount of coke. The burden structure of the melter gasifier was investigated by the tuyere probing while the plant was shut down at different operating conditions. The specimens representing the different positions of lump zone, cohesive zone, and dripping zone were analyzed by means of coke/char size distribution and X-ray diffraction (XRD) for the degree of graphitization of coke. A chemical analysis of metal composition has also been performed to get a better understanding of the final reduction in the melter gasifier. The burden structure is supposed to be divided into three zones: active zone, outer of deadman, and deadman core, where coke/char was consumed differently. Based on these analyses, some technical advice to improve the Corex operation is given.

Simulation on the Burden Distribution by DEM

In this paper, a numerical simulation model based on discrete element method (DEM) has been developed to analyze the burden distribution in the Melter gasifier of COREX process. The burden trajectory, the location and the burden surface profile are analyzed in the top charging of melter gasifier. The distribution of ore and coke and the porosity in the radial direction are given under the different charging mode. The results can be used to optimize the charging patterns in order to obtain the reasonable gas distribution.

Influence of Burden Distribution on Temperature Distribution in COREX Melter Gasifier

The temperature distribution of COREX melter gasifier was studied by using a two-dimensional 1/30 scale thermal dynamic model. A set of operating conditions, such as radial distribution of direct reduction iron (DRI) to lump coal and coke volume ratio, coke charging location, coke charging amount and coke size, were taken into account. The results show that the temperature near the wall region decreases with the decrease of the radial distribution of DRI to lump coal and coke volume ratio. The temperature with central coke charging is higher than that without central coke column. Furthermore, the temperature significantly increases with the increase of central coke charging amount. With the increase of intermediate coke charging amount, the temperature near the wall region decreases while the temperature in the intermediate region increases. The temperature increases with the increase of coke size whether charging central coke or intermediate coke.

Study on Cohesive Zones in COREX Melter Gasifier Using Hot Model

A hot model is established to study the cohesive zone of COREX melter gasifier in this paper., in this experiment, the paraffin and corn are used to simulate DRI, coke and lump coal respectively, the influences of ore/coke volume ratio, raceway gas temperature and raceway gas volume on the cohesive zone are analyzed using image processing method.

Mathematical Simulation of Burden Distribution in COREX Melter Gasifier by Discrete Element Method

COREX process is one of the earliest industrialized smelting reduction ironmaking technology. A numerical simulation model based on discrete element method (DEM) has been developed to analyze the burden distribution in the melter gasifier of COREX process. The DEM considering the collisions between particles can directly reproduce the charging process. The burden trajectory, the location and the burden surface profile are analyzed in melter gasifier with a mixing charging of coal and direct reduction iron (DRI) at the same time. Considering the porosity of packed bed has an important effect on the gas flow distribution of melter gasifier, a method to calculate porosity has been proposed. The distribution of DRI and coal and the porosity in the radial direction are given under different charging patterns, which is necessary to judge the gas flow distribution and provide base data for further researching the melter gasifier for the next work in the future. The research results can be used to guide the operation of adjusting charging and provide important basis for optimizing the charging patterns in order to obtain the reasonable gas distribution.

Research on Defining Regional Boundary of the COREX Melter Gasifier by Using Image Processing

In this paper, a two-dimensional hot model of melter gasifier, in which paraffin and corn are used to simulate DRI, coke and lump coal respectively, has been established to study the regional boundary in this paper. While the whole experimental process is recorded by the high-speed camera, the image processing method is put forward to define each regional boundary. By means of this method, the boundary of raceway, cohesive zone can be obtained quantificationally.

Research on Defining Regional Boundary of the COREX Melter Gasifier by Using Image Processing

Research on Defining Regional Boundary of the COREX Melter Gasifier by Using Image Processing

Mathematical Model of Lump Coal Falling in the Freeboard Zone of the COREX Melter Gasifier

A one-dimensional mathematical model was developed for devolatilization and heat transfer of lump coal falling in the freeboard zone of the COREX melter gasifier. The distributed activation energy model (DAEM) was used to depict the coal devolatilization. The heat transfer and temperature variation of lump coal were modeled by a transient energy conservation equation. The coupled comprehensive model was validated by previous experimental data of Pittsburgh No. 8 coal with different heating rates and bituminous coal of large particles. The model was used to investigate lump coal falling in the freeboard zone of the COREX melter gasifier. The fractional volatile yield and temperature distribution of lump coal were obtained, as well as the transient velocity and acceleration. Furthermore, the effect of the lump coal diameter was studied on devolatilization and temperature distribution of lump coal during the course of falling.

The Prediction Model of COREX Cold Gas Content of Carbon Dioxide Based on MOSC-PLS

In COREX processes, the cold gas is produced in melter gasifier, after being cooled and dust controlled, blown into the blast furnace and used in the reduction reaction. The cold gas content plays a key role in the reaction of lump ore and pellets reduction. A prediction model of COREX cold gas content of carbon dioxide is proposed based on modified orthogonal signal correction partial least squares algorithm (MOSC-PLS). Firstly, the input and output variables of the model are selected according to the COREX processes principle. Secondly, MOSC algorithm is used to preprocess the data, in order to remove the irrelevant information between the input and output variables of the model. Finally, prediction model is built based on PLS. The real field data of cold gas content of carbon dioxide from Baosteel COREX are used for verification. The results show that MOSC-PLS has an advantage over the orthogonal signal correction partial least squares (OSC-PLS) in prediction accuracy. Thus the necessary decision supports and analysis tools for the cold gas content control are provided.

Characteristics of coal required for superior performance of Corex ironmaking

The Corex smelting reduction process was developed as an alternative to the blast furnace and consists of two reactors: the reduction shaft and the melter gasifier. Coal rather than coke is used for heat generation, production of reducing gases and to maintain adequate bed permeability; hence, coals have to meet certain physical, chemical and especially high temperature properties for stable process operation and high iron outputs. Statistical analysis was employed to investigate the influence of coal properties on Corex performance, and laboratory coal characterisation studies were correlated with plant performance. This paper details these coal characteristic studies and highlights the coal blend properties required for superior plant performance.

Application of fractal theory on raceway boundary in COREX melter–gasifier model

The raceway has been studied extensively both theoretically and experimentally. In this study, particle velocity contours have been developed to define the raceway boundary. The raceway boundary is coarse and fragmentised, but all of the previous studies are based on Euclidean geometry, which regard the dimension of the raceway as an integer. In this paper, the fractal method of calculating raceway size, which describes the boundary with extremely irregular or fragmented characteristics, is on the data from a cold physical model of the raceway. The results show that the precise raceway boundary can be obtained by the particle velocity contours, that the surface area of the ellipsoidal raceway based on fractal theory is larger than that based on Euclidean geometry and that the data can be used as original boundary conditions of the flow and chemical reaction in the raceway region.

Study on the COREX Melter Gasifier Zones Using Temperature Gradient

A physical thermal model was established in this study, and the gas temperature in the model was measured with temperature sensors under different experimental conditions. The results show that the packed bed, cohesive zone, dripping zone and raceway in melter gasifier can be roughly distinguished by temperature gradient analysis along the vertical direction. The changes of different zones in the COREX melter gasifier were also investigated in this paper under different operation conditions.

Numerical Simulation of Temperature in the Freeboard of COREX Melting Gasifier

The freeboard, which is an important region in COREX melter gasifier, has drawn more and more attentions, and as a key parameter for COREX melter gasifier operation, the temperature in freeboard must be within a certain range. In this paper, the temperature field of freeboard is simulated with computational fluid dynamics(CFD). The results show that the temperature in bottom is lower than that in upper. The temperature when oxygen nozzles are open is higher than that when oxygen nozzles are off, and the temperature under different operation conditions is all about 1000 °C.

Definition of Cohesive Zone in COREX Melter Gasifier Using Image Processing Method

The cohesive zone plays very important role in the operation of COREX melter gasifier, up to now, definition of the cohesive boundary has always been a challenging task. In this paper, a two-dimensional hot model of melter gasifier, in which paraffin and corn are used to simulate DRI, coke and lump coal respectively, has been established to study the cohesive boundary in this paper. While the whole experimental process is recorded by the high-speed camera, the image processing method is put forward to define the cohesive boundary quantificationally.

Fractal Analysis of Raceway Boundary in COREX Melter Gasifier Model

The raceway boundary is coarse and fragmentized, but all of previous studies are based on Euclidean geometry, which regard the dimension of raceway as an integer. In this paper, particle velocity contour has been developed to define the raceway boundary. The fractal method of calculating raceway size, which describe boundary with extremely un-regular or fragment characteristic, is brought forward in physical model. The result shows that the precise raceway boundary can be obtained by particle velocity contour, and the surface area of ellipsoidal raceway based on fractal is larger than that based on Euclidean.

Influence of Auxiliary Fuel Injection to Tuyeres on Flame Temperature and Flooding Limits in the FINEX® Process: A Theoretical Investigation

The FINEX® melter gasifier, in contrast to the blast furnace, uses oxygen instead of air for the blast, and the packed bed consists of coal char but not of coke. In this paper, the theoretical raceway flame temperature for FINEX® conditions has been calculated for different injection rates of auxiliary fuels and steam. A regression equation has been derived from these results. Moreover, a flooding limit has been taken into account when auxiliary fuels were injected in order to understand the practical operational troubles such as peaks of reducing gas flow and temperature. The theoretical investigations show, that the available heat level in the raceway has been sufficient enough to inject the auxiliary fuels, such as pulverized coal (PC) and natural gas (NG) at the same rate and even higher than regarding the blast furnace. The permeability of the FINEX® char bed is lower in comparison to the coke bed in the blast furnace. High injection rates of auxiliary fuels require enhanced char stability and bed voidage.