Gas-Particle Flow and Combustion Characteristics of Pulverized Coal Injection in Blast Furnace Raceway

The two-dimensional steady-state discrete phase mathematical model is developed to analyze gas-particle flow and combustion characteristics of coal particles,as well as components concentration and temperature distribution of coal gas in the process of pulverized coal injection of blast furnace raceway.The results show that a great deal of coal gas discharges on the top of raceway away from the tuyere,and the residence time of coal particles in the region of blowpipe and tuyere is 20 ms or so and 50 ms when it reaches raceway boundary.The pressure is the highest at the bottom of raceway and the maximal temperature is about 2423 K.The char combustion is mainly carried out in the raceway and the maximum of char burn-out rate attains 3×10-4 kg/s.     

Mathematical simulation of burden distribution in COREX 3000 shaft by discrete element method

The distribution of reducing gas in a shaft furnace dominates the temperature profile,gas utilization ratio,metallization degree and is the overwhelming factor for stable,high productivities and low-energy-consumption operation.At the same time,the distribution of gas flow is mainly determined by the position of gas inlet,the packed bed porosity distribution as well as its change due to the difference on the mode of top charge and bottom discharge.When injecting position of the process is fixed,the charg...     

Influence of Cohesive Zone Shape on Solid Flow in COREX Melter Gasifier by Discrete Element Method

Based on the principle of discrete element method(DEM),a 2Dslot model of a COREX melter gasifier was established to analyze the influence of cohesive zone shape on solid flow,including mass distribution,velocity distribution,normal force distribution and porosity distribution at a microscopic level.The results show that the cohesive zone shape almost does not affect the particle movement in the upper shaft and deadman shape.The particles in the lower central bottom experience large normal force to support the particles above them,while particles around the raceway and in the fast flow zone exhibit weak force network.The porosity distribution was also examined under three kinds of cohesive zones.Like the velocity distribution,the whole packed bed can be divided into four main regions.With the increase of cohesive zone position,the low porosity region located in the root of cohesive zone increases.And the porosity distribution becomes asymmetric in the case of biased cohesive zone.     

Cold Model Study of Coal Gas Component Concentration Distribution in Blast Furnace Raceway

 Primary distribution of coal gas in blast furnace raceway has an important effect on combustion of coke and pulverized coal injection, as well as whole ironmaking process. According to practical production parameters of No. 5 blast furnace in Chongqing iron &; steel Co. LTD, the theoretical calculation model recommended by Nomura is adopted to determine penetration depth, height and width of raceway. Three-dimensional cold model of blast furnace raceway is established. Coal gas component concentration distribution of vertical section and cross section in blast furnace raceway is simulated using natural gas.     

Mathematical Model Development of Raceway Parameters and Their Effects on Corex Process

  Corex is an alternative ironmaking process and raceway is one of the important areas to maintain the stability of the furnace. The raceway parameters are well established for blast furnace operation. But for Corex process, it has not yet been established and optimized. Thus, a mathematical model was developed to determine various raceway parameters such as RAFT (raceway adiabatic flame temperature), tuyere gas velocity and kinetic energy. The model provides an idea about the raceway geometry, zone temperature and kinetic energy accumulated in tuyere gas. Besides, all the raceway parameters have been analyzed to find out their effects on the Corex process. It is found that RAFT influences the gasification reaction kinetics and higher RAFT generates more CO in reduction gas, which improves the metallisation degree of the DRI in shaft. It is also found that increased gas velocity and kinetic energy generate more fines and demand more coke to maintain char bed permeability. High coke rate increases the production cost and lowers the production of hot metal.     

Gas Flow Distribution in Pelletizing Shaft Furnace

Through thermal test, cold state experiment, analysis and simulation of thermal process, the gas flow distribution in pelletizing shaft furnace （PSF） was discussed. The results show that there are five flowing trends among them, the downward roasting gas and the upward cooling gas are the most unsteady, which influence flow distribution greatly. Among the operating parameters, the ratio of inflow is a key factor affecting the flow distribution. The roasting and cooling gases will entirely flow into the roasting zone and internal vertical air channels （IVAC）, respectively, if the ratio of inflow is critical. From such a critical operating condition increasing roasting gas flow or decreasing cooling gas flow, the roasting gas starts flowing downwards so as to enter the inside of IVAC the greater the ratio of inflow, the larger the downward flowrate. Among constructional parameters, the width of roasting zone b1, width of IVAC b2 and width of cooling zone b3, and the height of roasting zone h1, height of soaking zone h2 and height of cooling zone hs are the main factors affecting flow distribution. In case the ratio of b2/b3, or h3/h2, or h1/h2 is increased, the upward cooling gas tends to decrease while the downward roasting gas tends to increase with a gradual decrease in the ratio of inflow.     

Comprehensive Mathematical Model and Optimum Process Parameters of Nitrogen Free Blast Furnace简

According to different energy utilization in different regions, blast furnace is divided into raceway zone, bottom heat exchange zone （BHZ）, thermal reserve zone （TRZ）, and top heat exchange zone （THZ）, and a mathe- matical model of nitrogen free blast furnace （NF-BF） is established. The optimum process parameters of two kinds of nitrogen free blast furnaces are calculated by the new mathematical model. The results show that for the nitrogen free blast furnace with a single row of tuyeres, the optimum process parameters are coke ratio of 220 kg/t, coal ratio of 193 kg/t, and volume of recycling top gas of 577 m3/t; for two rows of tuyeres, the process parameters are coke ratio of 202 kg/t, coal ratio of 211 kg/t, volume of recycling top gas in upper area of 296 m3/t, and volume of recy- cling top gas in lower area of 295 ma/t. Energy balances are reached in different regions. Theoretical combustion temperature （TCT） in raceway zone is largely affected by different processes, and a lower TCT should be adopted for the single row of tuyeres, but for two rows of tuyeres, a higher TCT should be maintained. Compared with tradi- tional blast furnace, in NF-BF, the emission of CO2 would be reduced by 45.91% and 49.02G for a single row of tuyeres and two rows of tuyeres, respectively, and combined with CO2 sequestration technology, zero emission of CO2 could be realized.     

Medium oxygen enriched blast furnace with top gas recycling strategy

Top gas recycling oxygen blast furnace(TGR-OBF)process is a promising ironmaking process.The biggest challenge of the TGR-OBF in operation is the dramatic decrease of top gas volume(per ton hot metal),which once led to hanging-up and shutdowns in practice of the Toulachermet.In order to avoid this weakness,the strategy of medium oxygen blast furnace was presented.The maneuverable zone of the TGR-OBF was determined by the top gas volume,which should not be far from the data of the traditional blast furnace.The deviation of ±12.5% was used,and then the maneuverable blast oxygen content is from 0.30 to 0.47 according to the calculation.The flame temperature and the top gas volume have no much difference compared to those of the traditional blast furnace.The minimum carbon consumption of 357 kg per ton hot metal in the maneuverable zone occurs at the oxygen content of 0.30(fuel saving of 14%).In the unsteady evolution,the N2 accumulation could approach nearly zero after the recycling reached 6 times.Thus far,some TGR-OBF industrial trials have been carried out in different countries,but the method of medium oxygen enriched TGR-OBF has not been implemented,because the accumulation of N2 was worried about.The presented strategy of medium oxygen enriched TGR-OBF is applicable and the strategy with good operational performance is strongly suggested as a forerunner of the full oxygen blast furnace.     

Numerical Simulation of Innovative Operation of Blast Furnace Based on MultiFluid Model

A multifluid blast furnace model was simply introduced and was used to simulate several innovative ironmaking operations. The simulation results show that injecting hydrogen bearing materials, especially injecting natural gas and plastics, the hydrogen reduction is enhanced, and the furnace performance is improved simultaneously. Total heat input shows obvious decrease due to the decrease of heat consumption in direct reduction, solution loss and silicon transfer reactions. If carbon composite agglomerates are charged into the furnace, the temperature of thermal reserve zone will obviously decrease, and the reduction of ironbearing burden materials will be retarded. However, the efficiency of blast furnace is improved just due to the decrease in heat requirements for solution loss, sinter reduction, and silicon transfer reactions, and less heat loss through top gas and furnace wall. Finally, the model is used to investigate the performance of blast furnace under the condition of top gas recycling together with plastics injection, cold oxygen blasting and carbon composite agglomerate charging. The lower furnace temperature, extremely accelerated reduction rate, drastically decreased CO2 emission and remarkably enhanced heat efficiency were obtained by using the innovative operations, and the blast furnace operation with superhigh efficiency can be realized.     

Influence of Non-Uniform Temperature Distribution on Metallic Charge Length on Energy and Force Parameters During Groove-Rolling

 Change in the temperature of band over its length, associated with the stock being non-uniformly heated in the furnace, influences the variations in the magnitudes of energy-force parameters. Using the FEM (Finite Element Model) programs for the computation of the values of the energy-force parameters can take into account the distribution of temperature over the band length. The mathematical model of the computer program Forge2008 was used to theoretically examine the energy-force parameters and plastic metal flow in the roughing stands of the continuous rolling mill. The results of experimental investigation of influence of the non-uniform temperature distribution were presented on the metallic charge length on the energy and force parameters and dimensions of the band during round bars rolling. Thermovision monitoring energy and force parameters monitoring were carried out in continuous rolling mill D350 in one of the Polish industrial plants. On the basis of obtained results, it could be stated that non-uniform distribution of temperatures along the charge length causes local increase of energy and force parameters values and also such distribution affects the local increase of the width of rolled band. The rolling process of charge with non-uniform distribution of temperature could lead to exceeding required dimensional tolerances of the final products.     

"Redistribution" Effect of Lumpy Zone for Gas Flow in BF

The gas flow from tuyere to raceway zone by blasting involves three distributional zones, such as dripping,cohesive, and lumpy zone. The gas flow distribution in lumpy zone directly affects the gas utilization ration and smooth operation in the blast furnace. However, the furnace closeness brings about great difficulty in the study of high-temperature gas flow. The charging and blasting system affecting the gas flow and whether the top gas flow distribution could reflect its inner condition as well as the furnace state, such as hanging or scaffolding, which have become the main problems for the research on gas flow. Recently, several researches overseas studied gas flow distribution using the numerical simulation method; however, such a research was rare amongst the natives. In this study, the flow model of gas in cohesive and lumpy zone was established using the numerical simulation software and the gas flow distributions with uniform distribution of burden permeability, scaffolding of wall, and nonuniform charge level were analyzed. As a result, the effects of cohesive zone and lower parts on the gas flow are very limited and the charge level largely affects the distribution of top gas flow. Therefore, it was found that the distribution of top gas flow could hardly reflect the inner gas flow. The process is called "redistribution" effect, which means that the gas flow after passing through the raceway, dripping, and cohesive zone is distributed when it flows into the lumpy zone.     

回旋区深度对上部炉料运动影响的模拟分析

冶炼实践已证实,高炉回旋区形状和大小影响上部炉料的运动,进而影响煤气流分布及煤气利用率。已有研究多集中在回旋区形状、大小与高炉生产指标的关系,对相关影响机理和规律较少有深入分析。针对此问题,建立二维狭槽半高炉模型,采用离散单元法(DEM)对回旋区深度与炉料形态、混合程度、径向矿焦比的关系进行数值模拟探索。模型中考虑了炉料颗粒在下降过程中的粒度变化,利用离散单元法-计算流体力学(DEM-CFD)耦合方法得到料柱孔隙率分布特征。结果表明,随着回旋区深度增加,料批下降趋向均匀,料层倾斜程度减小,块状带下部炉料混合程度减小;随着料批的下降,矿石相对于焦炭逐渐向中心偏移,回旋区深度对料批径向矿焦比分布无明显影响;块状带整体孔隙率随回旋区深度增加而减小,变化幅度在2.1%左右;回旋区深度较大时,软熔带会有孔隙率较高的区域(较宽焦窗)。     

Numerical Study of Gas‐Solid Flow in the Raceway of a Blast Furnace

This paper presents a numerical study of gas‐solid flow in a blast furnace raceway using a 2D slot cold model. Numerical experiments are conducted by combining the discrete element method for the solid phase with computational fluid dynamics for the gas phase. The motion of particles caused by lateral gas blasting under conditions similar to that in the blast furnace process is examined at a particle scale. Combustion and associated solids movement around the raceway are simulated by extraction of particles from the bottom of the bed. The effect of bed height or solid pressure is considered by imposing a downward force on the top layers of particles in the bed. It is shown that depending on the gas velocity, the bed can transit from a fixed bed to a fluidized bed or vice versa. Two zones can be identified in such a bed: a stagnant zone in which the particles remain at their initial positions, and a moving zone in which particles can move in various flow patterns. In particular, if the gas velocity is in a certain range, the moving zone is formed just in front of the gas inlet, giving the so‐called raceway in which the particles can circulate. The effects of gas velocity, solid pressure and solid extraction are quantified. The fundamentals governing the gas‐solid flow and the formation mechanisms of a raceway are discussed in terms of particle‐particle and particle‐fluid interaction forces.     

A brief consideration about PCI of COREX melter-gasifier

By analyzing the thermal and burden structure conditions inside the melter-gasifier of COREX process,the advantage and disadvantage of PCI into the melter-gasifier are clarified.The influence of PCI on the running condition inside the furnace is analyzed based on the information from production operation and mathematical and physical simulations,and measures to tackle with the problems arising from PCI are proposed.The main results are as follows.①Due to the unfavorable conditions for coking of coal in t...     

高炉软熔带气体流动的数值模拟

建立了气体流动的二维轴对称数学模型,对倒Ｖ形软熔带附近的气体流动进行了数值模拟,用阻力比的概念分析探讨了软熔带附近的气体流动,形象地再现了软熔带对气流的二次分布。     

高炉风口回旋区大小的计算模型的研究

高炉是炼铁生产中的重要设备。高炉风口回旋区的大小及形状决定了高炉煤气的一次分布,反映了焦炭的燃烧状态,直接影响软熔带的形状和位置,高炉风口回旋区的大小的计算模型的应用对高炉生产实践具有重要的意义,为此,总结了国内外关于回旋区大小的计算模型,为实际生产提供一些经验公式。     

Qi式炉顶装置的设计与研究

“Ｑｉ”式炉顶集中心加焦,矿焦混装和矿焦层装三项装料于一体,用其装料,可实现高炉料柱中的焦炭呈“塔松”状充填结构分布,形成高大的倒Ｖ型软熔带,确保足够,稳定的中心煤气流和较为理想的煤气分布,以达到强化冶炼,改善各项技术经济指标和延长高炉一代寿命等目的。     

高炉内炉料运动的数值模拟

通过二维冷态模型和数值模型研究了高炉内的炉料运动规律。研究表明,通常边缘小粒焦和中心焦都能按一定的轨迹运行,不与周围的炉料混杂,说明高炉边缘加入小粒焦能在炉墙处形成一较稳定的隔离层,既可抑制边缘气流、降低炉墙热负荷,又可防止炉墙结厚和结瘤。软熔带附近炉料的流线在考虑矿石软熔收缩的情况下向中心侧移动,对上部块料带的炉料下降速度影响不大,而下部炉料下降速度则有所减小。     

高炉炉料配加热压含碳球团软熔滴落性能的试验研究

 以常用的炼铁原料为基础,系统研究了配加不同比例的热压含碳球团对高炉炉料的软熔滴落性能的影响,并进行了理论分析。研究表明,配加热压含碳球团对高炉综合炉料的软化区间、熔化区间、滴落率和透气性等软熔滴落性能参数有显著的影响。随着热压含碳球团配比的增加,软化区间t40-t4逐渐变宽;熔化区间tD-tS逐渐变窄,熔化开始温度tS逐渐升高,滴落温度tD逐渐降低;滴落率先增加后降低,当配比为40%时,滴落率最高,为6710%;最高压差先下降后升高,但在配加热压含碳球团条件下,炉料的最高压差都有所降低。从综合炉料的软熔滴落性能综合考虑,高炉炉料配加热压含碳球团的适宜配比应为40%~50%。