Melter Gasifier Research Articles

Mathematical modelling and optimization of producing hydrogen-rich gas in COREX melter gasifier

The integration of dome injection technology and coal gasification technology can enhance space utilization and generate high-quality reducing gas in the dome of COREX melter gasifier, making it a promising process for hydrogen-rich gas production. In this study, a comprehensive 3-D mathematical model is utilized to depict the inner characteristics with dome coal injection, including flow filed, thermal state, gas composition and particle behavior in the dome of COREX melter gasifier. The results indicate that the flow field in the dome can be categorized into jet flow region, impinging flow region and plug flow region. The gasification performance exhibited significant improvement, particularly the hydrogen production capability, which increased by 2150 Nm3/h. The proportion of C(s) consumed by combustion decreased to 37.32 %, while that of gasification increased to 62.68 %. Without oxygen compensation, the optimal coal injection ratio is determined to be 204.5 kg/t. As the oxygen flow rate through the oxygen burners increases from 1478 Nm3/h to 4478 Nm3/h, the dome temperature rises, advancing the devolatilization process of coal particles and improving combustion efficiency. When CO2 is used as the alternative carrier gas, the proportion of CO in the export gas increases by 0.03 % and that of CO2 increases by 1.11 %. However, when H2O is used as the alternative carrier gas, the proportion of H2 in the export gas increases by 0.35 % and that of H2O increases by 0.89 %.

Smelting Vanadium–Titanium Magnetite by OY Furnace: Effect of Prereduction Degree on the Softening, Melting, and Dropping Behavior of Direct Reduction Iron in Melter Gasifier

Smelting Vanadium–Titanium Magnetite by OY Furnace: Effect of Prereduction Degree on the Softening, Melting, and Dropping Behavior of Direct Reduction Iron in Melter Gasifier

Enhancement of perovskites performance for coal tar decomposition by pore structure and acid-base modification

Catalytic cracking is an efficient way to replace conventional combustion to remove coal tar deposited at the gas outlet of COREX melter gasifier. This work prepared a series of LaNi0.8Fe0.2O3 perovskites (Ni 0.8) with different pore structures via the hard-template method and applied in the catalytic cracking of coal tar was operated at 700 °C to evaluate the performance of perovskites. Ni 0.8 prepared via MCM-48 template (MCM-0.8) exhibited the high specific surface area (SSA) of 90.2 m2/g and pore volume of 0.3 cm3/g, accounting for its highest gas yield (51.8 mmol/gcoal) and complete tar removal. The remarkable oxidation capacity of MCM-0.8 resulted in its highest CO2 yield (11.2 mmol/gcoal) and selectivity for oxygenated compounds in tar (71.1 %). Three mesoporous Ni 0.8 participated in the catalytic reactions as the acid-base bifunctional catalysts. Ni 0.8 prepared via SBA-15 template (SBA-0.8) showed a great hydrocracking activity due to its strongest acidity of 1.87 mmol/g. All the synthesized perovskites possessed a good reactant selectivity, and the tarry product selectivity over different perovskites was influenced by the synergistic effect of acidity and the reactant diffusion inside the catalyst channels.

Numerical Simulation of Pulverized Coal Injection in the Dome Zone of a COREX Melter Gasifier

The dome zone is the freeboard at the top of the COREX melter gasifier (MG), and the secondary injection systems are installed in the dome zone to recycle dust and oxygen. Pulverized coal injection (PCI) in the dome zone of the COREX MG is used to transform the oxygen burners (OBs) into oxygen–coal burners (OCBs) and cooperates with the dust burners (DBs) to realize the function of gasification. In this work, a three-dimensional (3-D) steady-state mathematical model was developed to simulate the transport phenomenon in the dome zone with and without PCI. The results show that when 150 kg/t of pulverized coal is injected into the dome zone, the impinging stream area expands and the average temperature in the dome zone increases by about 40 K. The proportion of CO2 in the reduction gas decreases by 7.8 pct, while the proportion of H2 increases by 7.4 pct at the outlet of the MG with the PCI in the dome zone. The total effective volume fraction of reducing gas at the outlet of MG can reach 83.3 pct, which is a benefit to improving the reduction processes in the shaft furnace. Due to the intensification of circulation and the complexity of particle behavior, the residence time of particles increases by about 10 seconds in the case of PCI and the burnout rate of recycling dust and pulverized coal can reach above 99 pct.Graphical abstract

Effects of coke charging pattern on burden movement in COREX melter gasifier based on physical simulation

Effects of coke charging pattern on burden movement in COREX melter gasifier based on physical simulation

Simulation on the combustion in the raceway zone of COREX melter gasifier

The 2-D numerical simulation of the particle motion and combustion behavior in the raceway has been done to analyze the gas-flow field, pressure field, temperature field, distribution of gas composition, as well as the effect of coke mass-flow rate, and blowing gas temperature on the maximum temperature in the raceway zone. The results show that the temperature in the cavity reaches the maximum in the upper part of the cavity region, and the maximum value is above 3000 K. During the combustion process, the concentration of O2 decreases, and the concentration of CO increases. The highest CO content in the gas leaving the raceway zone and entering the coke bed is about 0.95, while the lowest O2 content is 0.05.

Analysis of the Influence of Blast Volume on Iron Oxide Melting Position by Temperature Gradient

COREX melting gasifier is key equipment for the natural iron oxide treatment process. However, in many published patents and documents [1-4], the description of the internal structure of the melter - gasifier is inconsistent. A physical thermal model was established in this study. Paraffin simulated iron oxide. Corn particles simulated coke. The air temperature in this model was measured with temperature sensors in different experimental conditions. The results showed the regions of the packed bed, cohesive zone, drip zone and raceway in melter gasifier could be roughly distinguished by temperature gradient analysis along the vertical direction. At the same time, this paper analyzes the change trend of the distance from the cohesive zone to the material surface in the furnace under different blast volume conditions.

Static Model Study on the Characteristics of Coke Oven Gas Dome Injection in COREX Melter Gasifier

Static Model Study on the Characteristics of Coke Oven Gas Dome Injection in COREX Melter Gasifier

Model Study on Burden Distribution in COREX Melter Gasifier

COREX is one of the commercialized smelting reduction ironmaking processes. It mainly includes two reactors, i.e., a (reduction) shaft furnace (SF) and a melter gasifier (MG). In comparison with the conventional blast furnace (BF), the COREX MG is not only equipped with a more complicated top charging system consisting of one gimbal distributor for coal and eight flap distributors for direct reduction iron (DRI), but also the growth mechanism of its burden pile is in a developing phase, rather than that in a fully-developed phase in a BF. Since the distribution of charged burden plays a crucial role in determining the gas flow and thus in achieving a stable operation, it is of considerable importance to investigate the burden distribution influenced by the charging system of COREX MG. In the present work, a mathematical model is developed for predicting the burden distribution in terms of burden layer structure and radial ore/coal ratio within the COREX MG. Based on the burden pile width measured in the previous physical experiments at different ring radii on a horizontal flat surface, a new growth mechanism of burden pile is proposed. The validity of the model is demonstrated by comparing the simulated burden layer structure with the corresponding results obtained by physical experiments. Furthermore, the usefulness of the mathematical model is illustrated by performing a set of simulation cases under various charging matrixes. It is hoped that the model can be used as a what-if tool in practice for the COREX operator to gain a better understanding of burden distribution in the COREX MG.

Numerical Simulation of the Raceway Zone in Melter Gasifier of COREX Process

The physical and chemical processes in the raceway zone of the COREX melter–gasifier express are similar to those inside the blast furnace. Based on the research achievements on blast furnaces, the unsteady numerical simulation of a gas-solid two-phase in the raceway was carried out by using computational fluid software. The formation process of the raceway in the COREX melter–gasifier was simulated. The shape and size of the raceway were obtained. Then, the effect of gas flow on the depth and height of the raceway was analyzed in this paper.

Numerical study on mixed charging process and gas-solid flow in COREX melter gasifier

We conducted a numerical study of the mixed charging process and gas-solid flow in the COREX melter gasifier by combining discrete element method (DEM) with computational fluid dynamics (CFD). A full-scale COREX melter gasifier model was established to investigate the charging and blasting processes. The model was validated by comparing with the experimental results under similar conditions. The particles above the raceway region descended faster than those near the centre and the wall. With increasing gas velocity, a larger high-velocity airflow region was formed at the tuyere inlet with increased raceway area. In addition, mixed charging pattern had a significant effect on radial ore-to-coal ratio. The ratio was larger in areas where the relative thickness of DRI was significantly larger than that of coal, and was large above the raceway. The upper packed bed structure had a negligible effect on raceway shape and size. Nevertheless, the gas velocity distribution in the packed bed was affected by the burden distribution, which had less fluctuation in the region where the burden was evenly distributed. The findings facilitate a better understanding of burden distribution and gas-solid flow in the COREX melter gasifier.

Effects of Coke Charging Pattern on Burden Distribution and Normal Force Distribution in COREX Melter Gasifier

Based on the principle of discrete element method (DEM), a 2D slot model of COREX Melter Gasifier (MG) being used to study the burden movement under different coke charging patterns has been established. Two kinds of coke charging patterns were introduced to be used to analyze the burden movement in MG. The burden distribution and normal force distribution were analyzed by using the proposed model at a microscopic level. The results show that the burden movement under different coke charging patterns presents different burden movement phenomenon.

Investigating the effect of particle shape on the charging process in melter gasifiers in COREX

This work conducted numerical simulations based on the discrete element method (DEM) and computational fluid dynamics (CFD) to study the effect of particle shape on burden distribution and gas flow distribution in the COREX melter gasifier. The non-spherical particles were approximated by a multi-sphere approach in which overlapping spheres were glued together to represent particle shape. The model was firstly validated by comparing the effect of particle shape on packing characteristics with previous work. With increasing of particle non-convexity shape factor, the packing density decreased and the mean coordination number increased. The model was then extended to study the charging process in a melter gasifier. The mixing of the direct reduced iron (DRI) with non-spherical coke particles had a significant effect on pressure drop and ore-to-coke mass ratio. The pressure of the non-spherical coke burden bed was significantly larger and the ore-to-coke mass ratio was more comparable to that of the experiments. With increasing non-spherical DRI mass fraction, the particles were distributed more evenly in the circumferential direction, but pressure drop also increased. The findings facilitate a better understanding of the relation of particle shape to the burden distribution in the COREX melter gasifiers.

Numerical Analysis on Effect of Additional Gas Injection on Characteristics around Raceway in Melter Gasifier

Abstract The raceway plays an important role in the mass and heat transportation inside a melter gasifier. Considering that pure oxygen at room temperature instead of hot air is injected into the melter gasifier, a two-dimensional mathematical model at steady state is developed in the current work to describe the effect of the additional gas injection on the characteristics around the raceway in melter gasifier. The results show that a high-speed jet with a highest temperature above 3500 K could be found in front of tuyere. Furthermore, a small scale of gas flow circulation occurs in front of tuyere that results in a more serious thermal damage to tuyere. In order to decrease the gas temperature in the raceway to prevent the blowing-down caused by tuyere damage, the additional gas, including N2, natural gas (NG) and coke oven gas (COG) should be injected through the tuyere. Compared with N2, additional fuel gas injection gives full play to the high temperature reduction advantage of hydrogen. In addition, considering the insufficient hearth heat after injecting NG and the effective utilization of secondary resource, an appropriate amount of COG is recommended to be injected for optimizing blast system.

Thermodynamic Model of COREX Melter Gasifier Using FactSage™ and Macro Facility

In the current study, the thermochemical model of the COREX melter gasifier has been developed using the FactSage™ thermodynamic software, and macro programming facility. The melter gasifier was conceptually divided into various equilibrium zones dealing with the reactions happening in the reactor. The coal char and the coke being used are divided among them optimally. The model has been validated with respect to the plant data for the hot-metal, slag, and reducing gas composition. The effects of the variation in the degree of metallization, on the final hot metal, slag, and reducing gas, have been predicted using this model. The variations in the process parameters for the different industrial coal grades used in the COREX plant have been determined. The effects of the volatile, ash, and the moisture contents of the coal on the hot-metal and the reducing gas compositions have been reported.

Analysis of Coke Oven Gas Injection from Dome in COREX Melter Gasifier for Adjusting Dome Temperature

Coke oven gas (COG) injection from the dome in a COREX melter gasifier is a good method to not only reduce the amount of solid fuel used for gasification, but also to adjust the freeboard temperature that should be maintained within a certain range. In this paper, the characteristics of COG injection used to adjust dome temperature are studied through a static model. The results show that an increase in melting rate causes a decrease in dome temperature and generator gas volume. However, with an increase in coke rate, dome temperature increases, while generator gas volume decreases. For low coke rate conditions, the dome temperature is generally found to be lower than 1050 °C, and COG is blasted for combustion and heat releasing. For high coke rates, the dome temperature is generally higher than 1050 °C. Under the premise that oxygen reduction cannot meet the demand, COG is used for decomposition. After the COG injection, the amount and reduction capacity of the generator gas can meet the needs of reduction in shaft furnace. The findings of this work can be used as a theoretical basis to guide plant operations for COG injection.

Effects of the shape and inclination angle of DRI-flaps on DRI distribution in COREX melter gasifiers

Burden distribution plays a crucial role in controlling gas flow distribution and achieving the stability operation of the melter gasifier in COREX. This work presents a coupled DEM-CFD study on burden formation and gas injection of a COREX melter gasifier (MG), mainly focusing on the effects of inclination angle and shape of the DRI-flaps. A one-eighth MG was simulated and compared with the experimental results. The burdens were analysed in terms of particle segregation index and particle distribution index. It was observed that the particles were unevenly distributed in the circumferential directions. This phenomenon was further enhanced with decreasing flap inclination angles as the burden stream became wider and more separated with decreasing inclination angle. To reduce the uneven distribution of particles, flap shapes were changed. It was observed that the thickness of burden piles was proportional to the area of the flaps. The Arc-shape flap, with a medium size of cross-sectional area, was able to control the uniform distribution of DRI particle and formed a uniform pressure distribution in the circumferential direction. The study shows the importance of flaps to maintain the uniform pressure distribution in the circumferential direction of burden beds for stable operation of the melter gasifier.

Simulation study of dust combustion in COREX gasifier dome

ABSTRACTCOREX is the first industrialized non-blast furnace ironmaking process in the world. The melter gasifier, where final reduction of iron ore and melting of direct reduction iron take place, plays an important role in the process. In this paper, a three-dimensional mathematical model is used to simulate the combustion process of dust in the dome of a COREX gasifier. The model geometry covers oxygen spray gun, dust spray gun, top wall surface and raw gas outlet of the melter gasifier. The typical phenomena of in-gasifier aerodynamics and physicochemical behaviours relevant to the injection of dust with different granularity are simulated, in terms of flow, temperature, gas composition and coal combustion characteristics. The results show the dust particle size has a certain impact on the dust combustion. With the increase in the dust particle size, the dust burning rate and the dome temperature decreases, while the reducing gas concentration increases.

Modelling of trace material flow distribution in a melter gasifier based on thermodynamic multiphase equilibrium calculations

In combination with a complex global market environment, the iron and steel industry is dealing with increasing demands for reduction of environmental and greenhouse emissions. Alternative iron making technologies such as Corex® and Finex® can offer solutions for these challenges. The melter gasifier is the central unit operation of these well-established alternative iron making processes. Both offer considerable advantages with respect to economic characteristics and environmental emissions. Similar to the conventional iron making process of the blast furnace route, a variety of different input materials is required for these processes including coal, coke, lump or fine ore, iron ore pellets as well as limestone and dolomite. Most of these raw materials also carry minor amounts of unwanted compounds such as alkali or zinc-based species. The presence of these materials inside a melter gasifier can lead to instability, problematic process conditions and refractory damages. A better understanding of the distribution of these problematic species is therefore of great importance to plant manufacturers and operators. A variety of different multiphase reactions are responsible for the distribution of trace materials within the melter gasifier. In order to get a better understanding of the complex nature of these reactions, a thermodynamic investigation was carried out using calculation routines of HSC Chemistry and FactSage. Based on the findings of this investigation, a multi-zone model was developed using the simulation platform of the gPROMS ModelBuilder®. The model is separated into distinct reaction zones across the height of the melter gasifier to depict the main iron ore reduction process as well as the governing reactions of trace material components. Validation of the model was carried out using reference data of existing plants. The model described in this work is used to analyse the behaviour of trace materials within a melter gasifier. Due to the highly integrated material flows of the Corex® and Finex® iron making processes, the impact on their operational characteristics can be investigated as well. Through this it is possible to optimise the raw material input of these processes, potentially leading to reduced fuel demand and environmental emissions.

Experimental Study on Charging Process in the COREX Melter Gasifier

Burden distribution plays an important role in achieving high stability and energy efficiency in the COREX melter gasifier. In this work, a 1/7.5 scale experimental apparatus is established to investigate the burden distribution under the independent and mixed charging conditions. The effects of GIMBAL distributor angle, rotational speed, DRI-flap angle, and charging pattern on these charging conditions are investigated. The results show that the non-uniform distribution of pellet in circumferential direction is intrinsic to the discharge system due to the shape of the DRI flap. The charging pattern has a significant impact on the ore-to-coal volume ratio and bed voidage. The ore-to-coal volume ratio reaches the peak at 550 to 650 mm, indicating that the reduction burden near the wall is heavier than that in the center. The voidage in the middle region is smaller than that of the center and near-wall region. The results also reveal the size segregation along the radial direction of the burden pile. The smaller particles tend to accumulate in the center while the larger ones segregate more near the wall. The findings obtained from experiments should be helpful for the efficient operation of the COREX melter gasifier.