并罐式无钟炉顶装料过程中炉料运动及分布的离散元分析

建立了国内某4070 m3高炉并罐式无钟炉顶装料系统模型,应用离散单元法对焦炭炉料分别装入左右料罐的运动全过程进行数值计算.结果表明,由于高炉并罐式无钟炉顶系统中皮带中心线与两并罐对称面成22o夹角,炉料装入左料罐时料流宽度较小且密集,而装入右料罐时料流宽度较大且分散;左右料罐径向上炉料体积呈非对称分布,左料罐内炉料堆尖位置与两并罐对称面之间的距离比右料罐近200 mm;左料罐周向上炉料体积分布比右料罐更均匀,二者在周向上的方差分别为0.065和0.261;左右料罐径向及周向上炉料粒度分布主要受堆尖位置和壁面效应影响,左右料罐纵向上炉料平均粒径分布规律基本相同,从料罐内料层底部至料层高度1/9处炉料平均粒径逐渐增大,料层高度1/9~8/9处炉料平均粒径基本不变,从料层高度8/9处至料层顶部炉料平均粒径继续增大.     

预还原铬铁块矿竖炉终还原的数值模拟

针对铬粉矿冷固结含碳团块转底炉预还原-竖炉型炉终还原冶炼含Cr铁水技术路线的终还原反应器,建立了描述其内传输现象的二维综合数学模型,并进行了数值仿真研究.仿真结果表明,势流理论在很大程度上反映了填充床中物料流动和混合情况,可以胜任对固体炉料运动的描述;炉内料面上不同炉料分布决定着炉内炉料流量的分布、熔融液体流量的分布和渣中Cr2O3浓度的分布.在炉下部,炉中心以矿石为主的布料比以焦炭为主的布料能引起较大煤气温降;而在炉上部,炉中心以矿石为主的布料引起的煤气温降比炉中心以焦炭为主的布料引起的煤气温降低.其他条件不变时,通过布料连续改变炉内料面上的炉料分布引起的炉内软熔带的变化是不连续的.中心加焦形成倒"V"型软熔带.     

干熄炉料钟布料的实验研究

随着干熄焦装置额定容积的不断扩大,焦炭在干熄炉内布料不均已成为干熄焦技术需要解决的关键问题之一.为此,本文开展了干熄炉料钟布料的实验研究.考察了料钟尺寸和科线深度对布料后的焦炭下落轨迹、焦炭堆积料面形状和粒度分布的影响,以期为干熄炉及布料装置设计提供一定的理论依据.     

复合移动床电石反应器中颗粒运动的离散单元法模拟

针对复合移动床反应器内固体颗粒运动,采用离散单元法模型（DEM）考察布料器分别为扇形开口和矩形开口时,布料器转速和开口对颗粒运动的影响,并基于文献结果论证了本文模型的准确性。模拟结果表明：①对于不同布料器,颗粒在移动床中呈现平推流和汇聚流两种流动形态。②随布料器转速及开口的增加,颗粒质量通量非线性增加。③随布料器转速的增加,下落床径向上颗粒分布更均匀;随布料器开口的增大,下落床径向上颗粒分布范围变大,颗粒分布更均匀;对下落床径向上颗粒分布,布料器扇形开口时分布呈U形、矩形开口时分布呈M形。④沿反应器轴向向下,颗粒分布有均匀化趋势;扇形开口布料器对颗粒分布的离散系数大于1,矩形开口布料器对颗粒分布的离散系数约为0.5。     

低速回转圆筒内磷铵颗粒粒度分布规律研究

利用取样－筛分－称重的实验方法,提出固体颗粒在倾斜回转圆筒内的径向、沿弦长（料面）方向及轴向粒度分布规律,并得出混合粒径固体颗粒在倾斜回转圆筒内发生径向偏析和轴向偏析的结论。研究所用回转圆筒直径为６００ｍｍ,实验物料为不同粒度配比的磷酸一铵。研究结果对内分级内返料喷浆造粒干燥机的设计有指导意义。     

炉料级配对锰硅合金生产的影响

锰硅合金炉料级配的实验结果表明,2种非均一粒度焦炭混合后的电阻随小焦粒体积比的增加呈非线性变化,当小焦粒的体积占总体积的50%～60%时,混合焦炭的电阻值达到较大值:通过改变矿石的粒度调整混合炉料粒度时,混合炉料的电阻随混合炉料粒度的增加线性减小;透气性随炉料平均粒度增加呈非线性变化,总趋势是减小的.应用实验结果,将6.3:MW矿热炉入炉的大、小焦粒体积比由3:2改为5:6,锰矿粒度由80 mm破碎为40 mm左右时,增大了炉料的电阻,同时炉料的透气性也得到了明显的改善.     

内返料内分级喷浆造粒干燥机尾锥内粉体运动特性研究

通过对三种不同锥体内粉体物料的运动形式及粒度分布的研究,揭示了粉体物料在回转锥体内运动形式和规律及锥体内粉体物料的粒度分布性质,得出了属锥具有一定的分级作用,在回转锥体内粉体物料存在“二次偏析”及“返混现象”的结论;在全内返料内分级及喷浆造粒干燥机中推荐采用３７°角锥体且在锥小端设置挡环。     

无料钟炉顶高炉中炉料流动轨迹的模拟

结合炉料在无料钟炉顶高炉中的实际运动情况,对炉料颗粒的运动和受力进行分析,建立了料流轨迹运动方程,改进了前人提出的模型,并利用实际高炉开炉装料实测数据对模型进行验证.结果表明,该模型计算的落点半径与实际测量数据较接近;沿溜槽长度方向单位质量炉料所受的科氏力小断增大,在溜槽倾角41°条件下,单位质量的焦炭所受科氏力约为2...     

纵向涡流发生器喷动床颗粒流动特性研究

探究纵向涡流对喷动床内喷射区及环隙区颗粒相径向速度的影响。采用粒子图像测速技术对内径D=152mm的喷动床进行实验研究,分析对比了不同扰流元件外形,尺寸及安装间距等重要参数对喷动床内颗粒运动的影响。研究结果表明:加入纵向涡发生器后,在扰流元件上方横截面内颗粒相运动出现了大量二次涡流,并且纵向涡发生器增强颗粒相在喷射区及环隙区的径向运动能力。在相同直径尺寸下,球体扰流元件较圆柱体扰流件对喷动床内颗粒径向运动的强化效果更好。存在一个最佳的扰流元件直径及布置间距使得纵向涡流对颗粒径向运动的强化效果达到最佳。     

无料钟炉顶高炉中炉料流动轨迹的模拟

结合炉料在无料钟炉顶高炉中的实际运动情况,对炉料颗粒的运动和受力进行分析,建立了料流轨迹运动方程,改进了前人提出的模型,并利用实际高炉开炉装料实测数据对模型进行验证.结果表明,该模型计算的落点半径与实际测量数据较接近;沿溜槽长度方向单位质量炉料所受的科氏力小断增大,在溜槽倾角41°条件下,单位质量的焦炭所受科氏力约为2.2～5.5 m/s2,矿石约为2.1～4.6 m/s2,分别约占重力加速度的22%～56%和21%～47%;当煤气流速为0时,气体曳力系数焦炭为1.83～1.88,矿石为3.32～3.40,单位质量炉料所受阻力为2.4～4.9 m/s2,约占单位质量炉料所受重力的1/4～1/2.     

Experimental and DEM study of segregation of ternary size particles in a blast furnace top bunker model

Size segregation of pellets in the top bunker (hopper) of a blast furnace is an important factor affecting the radial distribution of the charged burden and indirectly also the distribution of gas in the shaft and cohesive zone. This paper studies size segregation of ternary size pellets during the discharging process of a hopper model through experiments and simulations. The simulations, which are based on the discrete element method (DEM), are first validated using four experimental cases applying different bunker filling methods. The effects of various variables, such as fine mass fraction, particle friction coefficients, diameter ratio of fine to coarse and filling method (random, layered or industrial filling), as well as the interaction with wall (static and rolling friction) on the segregation are investigated. The results show that even though many factors affect the extent of segregation during the discharging process, the most important factors are the filling method, diameter ratio of fine to coarse, wall-particle static and rolling friction, interparticle rolling friction as well as mass fraction of fine particles. Reducing wall-particle rolling or static friction or the fraction of fine particles decreased the extent of size segregation.     

楔形中心和偏心料仓中壁面摩擦系数对卸料速率的影响

采用离散元方法(DEM)研究了在不同的内摩擦系数、料仓半锥角和料仓宽度条件下,楔形中心料仓和偏心料仓中壁面摩擦系数对卸料速率的影响。研究发现,随着壁面摩擦系数的增加,两种料仓的卸料速率均先降低后稳定。当料仓从中心料仓变为偏心料仓时,壁面摩擦系数对卸料速率的影响程度以及卸料速率停止下降时的壁面摩擦系数的值都增大。随着内摩擦系数的减小或料仓半锥角的增大,壁面摩擦系数对卸料速率的影响程度以及卸料速率停止下降时的壁面摩擦系数的值都逐渐减小。增加料仓宽度能够削弱壁面摩擦系数对卸料速率的影响程度,但并不改变卸料速率停止下降时的壁面摩擦系数的值。     

偏心楔形喂料斗卸料过程中颗粒流动特性

采用三维离散单元法,研究了偏心楔形喂料斗中不同粒径颗粒卸料过程的流场分布,建立了适用于偏心楔形喂料斗的整体流系数模型,分析了料斗卸料流型以及卸料流型与卸料质量流率的相关性,并通过实验验证了离散元模型的可靠性。结果表明：偏心楔形喂料斗内颗粒流场分布以靠近喂料管口区域为高速区,并呈辐射状朝远离垂直壁面端的料斗上部低速区过渡,高速区颗粒流场的整体一致性好,低速区颗粒流场呈局部涡流状;颗粒粒径增大,颗粒整体流动性变差,高速区域范围减小,低速区域范围增大,过渡区域变模糊;当颗粒粒径不大于10 mm时,整体流系数与颗粒粒径呈线性负相关,卸料质量流率与整体流系数呈线性正相关。     

Discrete element method modeling of non-spherical granular flow in rectangular hopper

Discrete element method (DEM) was developed to simulate the corn-shaped particles flow in the hopper. The corn-shaped particle was described by four overlapping spheres. Contact force and gravity force were considered when establishing the model. In addition, the velocity distribution and voidage variance of corn-shaped and spherical particles were investigated. The results show that the vertical velocity difference between centre and side wall and the horizontal velocity of corn-shaped particles are relatively larger than that of spherical particles. The mean voidage for corn-shaped particles is smaller than for spherical particles in any hopper. And the mean voidage values decrease with the increase of the ratio of width and length (D/L) and the ratio of height and width (H/D) for both corn-shaped and spherical particles. The local voidage profiles in hoppers with different D/L were also studied. It demonstrates that the wall effect on the voidage of spherical particles is more remarkable than that of the corn-shaped particles. The voidage fluctuations of corn-shaped and spherical particles decrease obviously with increasing D/L when the particles are far away from the wall. And when the particles are discharging, the wall effect on the spherical particles is more remarkable than the condition of packing naturally.     

Internal pressures in flowing granular materials from mass flow hoppers

Internal pressures in flowing granular materials are of practical importance, since they lead to pressures on the hopper walls. Two granular materials (0.5 mm and 1.0 mm nominal diameter glass spheres) are chosen and their flow from two axial-symmetrical and one plane-strain experimental perspex mass flow hoppers is studied. Static and dynamic pressures are measured using a radiopill receiving system, when the pill is placed in the vertical and two horizontal orthogonal directions and at various radial positions and depths.Typical pressure traces of 220 experimental runs are analysed. The effects of stop/start operation and compaction of the fill material prior to the initiation of flow on dynamic pressures are also studied.Utilising the data on flow paths and velocity changes, the internal pressure—time traces are interpreted in terms of the pressure changes with distance from the hopper outlet for positions near the wall in the convergent sections of the hoppers. The results are compared with the Jenike-Johanson theory.     

Numerical investigation of steady and unsteady state hopper flows

This paper presents a numerical study of the steady and unsteady state granular flows in a cylindrical hopper with flat bottom by means of the discrete element method (DEM). For both flows, the simulations were conducted under comparable conditions so that the similarity and difference between them can be examined. The distributions of the physical properties including velocity, force structure, stress and couple stress for the two hopper flows are investigated. The results suggest that the trends of these distributions for the two hopper flows are similar. In particular, for both cases, the distributions of the normal stresses are related to the normal force structures. Thus, corresponding to the large interaction forces between particles near the bottom corner and in the transitional zone, all the normal stresses are large near the bottom corner, and the radial and circumferential normal stresses are relatively large in the transitional zone. However, there are differences in the magnitudes of some physical properties for the unsteady and steady state flows. Compared with the steady state flow, the unsteady state flow has a narrower velocity distribution, and more particles experience large contact forces. Its radial and circumferential normal stresses in the plug flow and transitional zones are larger. With the decrease of the number of particles or with discharging time, the plug flow and transitional zones reduce, and the differences in the considered properties except wall shear stress and couple stress between the two flows decrease.     

Predicting discharge dynamics from a rectangular hopper using the discrete element method (DEM)

Accurate prediction of the discharge rate from hoppers is important in many industrial processes involving the handling of granular materials. The present work investigates the parameters affecting the discharge rate using the discrete element method (DEM). The effects of particle properties (particle size and size distribution) and hopper geometry (hopper width, outlet width, angle and fill height) are studied and compared to previously published experimental correlations. The results indicate that DEM simulations are fully capable of reproducing trends in the discharge rate that are well-known experimentally. For example, particle size and hopper width are shown to have a minimal influence on the discharge rate. In addition, for rectangular hoppers, the discharge rate is shown to vary with the outlet width raised to the power as given by the modified Beverloo correlation. The DEM simulations are also used to explore a wider range of parameters that have not been or are not easily explored experimentally. For example, the effects of hopper friction, particle friction, coefficient of restitution are investigated, and particle friction is shown to have a significant influence on the hopper discharge behavior.     

Simulation of granular flow in 2-D hoppers using the Caram-Hong model

The Caram-Hong stochastic model for granular motion in hoppers or silos was applied, with minor modification, to describe the flow of particles in 2D batch hoppers. The predictions of the model were compared to experimental measurements, made by particle image velocimetry, on a laboratory hopper containing zinc particles. With respect to both the spatial variation of particle velocity and the rate of descent of the top surface of the bed, the model showed satisfactory agreement with the experimental data.     

非球形颗粒在矩形料斗中的流动特性(英文)

Flow behaviors of four kinds of granular particles (i.e. sphere, ellipsoid, hexahedron and binary mixture of sphere and hexahedron) in rectangular hoppers were experimentally studied. The effects of granular shape and hopper structure on flow pattern, discharge fraction, mean particle residence time and tracer concentration distribution were tested based on the visual observation and particle tracer technique. The results show that particle shape affects significantly the flow pattern. The flow patterns of sphere, ellipsoid and binary mixture are all parabolic shape, and the flow pattern shows no significant difference with the change of wedge angle. The flowing zone becomes more sharp-angled with the increasing outlet size. The flow pattern of hexahedron is featured with straight lines. The discharge rates are in increasing order from hexahedron, sphere, binary mixture to ellipsoid. The discharge rate also increases with the wedge angle and outlet size. The mean particle residence time becomes shorter when the outlet size increases. The difference of mean particle residence time between the maximum and minimum values decreases as the wedge angle increases. The residence time of hexahedron is the shortest. The tracer concentration distribution of hexahedron at any height is more uniform than that of binary mixture. The tracer concentration of sphere in the middle is lower than that near the wall, and the contrary tendency is found for ellipsoid particles.     

Flow of sphero-disc particles in rectangular hoppers—a DEM and experimental comparison in 3D

Flows of “sphero-disc” granular particles in a rectangular hopper are studied both experimentally using high-speed video recording and mathematically using the discrete element method (DEM). The flow behaviour of particles and their arching and discharging in the hopper are analysed and compared with the DEM results for three hopper openings. In general, good agreement is shown on particle static packing, the flow behaviour and hopper discharging rates and the arching effect when flow ceases due to an inadequate hopper outlet opening. Spherical particles with a similar volume to the disc-like particles are also tested and compared and a clear effect of particle shape on flow rates is shown. Although some minor discrepancies are shown, these are likely to be caused by the practical difficulties in matching the exact particle parameters between the simulations and the experiments. The DEM is shown to be a powerful tool to analyse the interactions between irregularly shaped particles and demonstrates a great potential in analysing detailed particle packing structure and flow patterns, which may lead to the elaboration of a novel method for hopper design. Further work will focus on developing DEM to model a wider range of particle shapes and hopper geometries, use of DEM for flow and structure analysis, and the development of more sophisticated measuring tools such as tomography to validate the DEM model.