料仓中粉体的流动现象及受力研究

在大规模、连续化利用粉体或生产粉体的相关生产作业中,原料、半成品以及成品数量和重量巨大。生产过程中需要利用各种输送与仓储设备使粉体在各工序之间有序地、不间断地进行输送和储存,以保证生产正常进行,进而实现生产的自动化。为了更好地实现自动化控制,研究了粉体在料仓中的流动化现象以及受力情况,论述了料仓中粉体的两种不同流动方式及各自特点,分析了粉体在投入料仓时以及静止状态和运动状态下粉体的压力分布及交替应力的产生和分布。     

粉体料仓的卸料问题

<正>料仓能否保持连续、平稳和顺畅卸料是水泥生产正常运行的基础,更是下级给料计量设备稳定运行和准确计量控制的关键影响因素。但在工程设计中却常常不被重视,由于下料仓问题导致计量设备不能正常工作的现象较为常见,尤其对于煤粉和粉煤灰系统更为突出。本文对此进行讨论,希望为料仓的设计和选用提供有益的参考。1料仓中物料卸料的主要形态粉体物料在料仓中实际卸料流动状态往往比较     

粉体料仓下料不畅的原因及解决方法

本文从主观设计和客观生产因素两方面全方位分析了卸料口堵塞的原因，并有针对性的提出了防止料仓卸料口堵塞的方法。     

料仓中粉体流动数学模型分析

对料仓中粉体流动进行模拟可以获得粉体流动的压力、流动速度、相组分和相浓度分布。模拟料仓中粉体流动有3种数学模型:有限元素模型、离散元素模型和混合模型,每种模型各自适用于不同的流动区域,混合模型集合了前2种模型的优点,是模拟料仓中粉体流动的最先进模型。     

料仓中的压力分布

从设计角度出发,对粉体料仓内的压力分布进行了综述。内容包括整体流和中心流料仓的静态和动态压力。最后还给出了一个压力分布计算实例。     

中心降料管的料仓中垂直应力分布实验研究

The distribution of vertical stress for both active and passive state in the silo with a central inner downcomer is reported in this paper.Experimental measurement of the axial distribution of vertical stress for both active and passive state in the silo are in good agreement with that predicted by theoretical analysis.The mean axial stress is reduced due to the presence of the inner downcomer in the silo.     

影响粉体料仓卸空率的因素分析

正0前言粉体料仓是建材生产的重要设备,用于储存粉体物料、均化物料性能及平衡工艺物流等,是粉体工艺过程中各种单元操作之间必不可少的设备。粉体料仓卸空率是指排出物料的量与其仓容量的比值。该指标衡量的是粉体料仓的有效容积和残料量的变化关系,是粉体料仓主要技术性能指标之一,是粉体料仓价值在使用功能上的体现。1关于粉体料仓卸空率的认识对于卸空率的看法,应该是一个衡量粉体料仓是否具有先进性的指标,而不仅作为一个日常使用     

基于整体流型的粉体料仓设计分析

介绍了各种料仓流型,分析了影响料仓流型的因素,并应用到整体流料仓设计,在料斗形式、曲线、材料的选择以及改流体的设置上,作了详细的分析比较。     

料仓及重力场的粉粒体流动

在水泥的连续生产过程中，散体物料的储存与供给是必不可少的环节，因此在水泥厂中广泛应用着各种各样的料仓，如生料磨、水泥磨、煤磨的磨头仓，各种原料的中间储仓，还有存放大容量粉体物料的生料库、水泥库等。但在粉粒体物料储存过程中会发生各种问题，即常常发生结皮和结拱、偏析和不均匀排出、细粉物料的喷流等。然而刮目前为止，说明这些现象的定量理论还很少，并且欠缺完全可靠的处理方法，因此料仓故障仍然是需要研究的问题。本文拟就重力场的粉体压及静态壁压理论的研究现状、料仓常见故障及解决对策、散体物料流动性及结拱的关系等作一论述。     

粉体料仓的设计

介绍了料仓设计的基本方法, 包括流型选择、流型设计以及卸料口尺寸的确定方法等, 最后给出一个应用实例。     

仓壳圆筒与仓壳锥体连接部分的受力分析

由于仓壳圆筒与仓壳锥体连接部分在几何上的不连续性,造成应力集中。通过对该部位的受力分析,得出对于大直径料仓,仓壳锥体圆周方向力Q为负值的结论,并且讨论了料仓设计标准中关于许用压缩应力的计算,给出了比较合理的选取。     

大直径浅圆仓缩尺模型试验研究

大直径浅圆仓在生产过程中,由于仓底的偏心卸料使筒仓仓壁产生不均受力,会给筒仓结构的使用带来安全隐患。通过对浅圆仓缩尺模型试验,模拟筒仓生产过程的卸料状况,并对筒仓仓壁及仓底廊道顶部进行压力测试,将测试结果与理论计算进行对比,从而得出偏心卸料与静载状态的超压系数,为大直径浅圆仓设计提供依据。     

Investigation of milling characteristics of alumina powders milled with a newly designed vibratory horizontal attritor

In this study, a vibratory horizontal attritor was designed, constructed and used to produce alumina powders. The effects of process parameters, such as milling time, ball-powder weight ratio (BPR) and rotational speed (RS) of the attritor on the mean particle size and particle size distribution have been investigated. Milling times of 1, 5, 10 and 15 h and ball-powder weight ratios of 5:1, 10:1, 20:1 and 40:1 were considered in the present study. Rotational speeds of the attritor were selected as 500, 700 and 900 rpm and distilled water was used as milling media.The experimental results show that increasing milling time and ball-powder weight ratio resulted in finer particles. Optimum rotational speed of the attritor was found as 700 rpm. The mean particle size of attrited powders were in the range of 2.05-6.82 μm, depending on process parameters.     

Reaction moulding of metal and ceramic powders

A processing route for fabrication of products from hard metal and ceramic powders is described in which a reactive monomer such as ethylcyanoacrylate is used as carrier and binder with the opportunity of recovery through thermal depolymerization. A feasibility study has examined some of the main technical points including monomer–powder reactivity and rheology, debinding rates and compact green density. The stability of ethylcyanoacrylate with various powder volume fractions of silicon nitride and 316L stainless steel has been examined, with p-toluenesulphonic acid used as polymerization inhibitor, and it was found that mixes with higher powder volume fractions required higher levels of inhibitor. Assessment of the flow behaviour of several of the compositions showed them to be significantly non-Newtonian and the high viscosity of blends with a high loading of stainless steel suggests some premature polymerization. Measurement of green density of polymerized compacts demonstrated that high packing efficiency could be achieved. Thermogravimetry showed that rates of binder loss depended upon sample size and powder thermal conductivity.     

Study of fragmentation in cBN powders under ultra-high pressure

Studying the fragmentation law and refinement of cubic boron nitride powder under ultra-high pressure is crucial to producing a high-strength, high-density polycrystalline cubic boron nitride. In this paper, brown and black cBN crystalline powders with different micron sizes were selected as initial raw materials for an ultra-high-pressure simulation experiment. Single and mixed particles were extruded under 80MPa low pressure and 5.5GPa ultra-high pressure at ambient temperature for 1 min. The crushing behavior and particle size distribution of cBN powders with different particle sizes and ratios were investigated using a laser particle size analyzer and scanning electron microscopy. Results revealed no particle breakage or deformation at low pressure, and the compaction density was low. However, under ultra-high pressure, the cBN particles showed cracks, plastic deformation, and fragmentation, resulting in crushed fine particles filling in the voids of coarse particles, which led to a higher pressing density. Small-sized or mixed cBN particles with high density ratios were not easily crushed; the coarser the particle size, the more severe the ultra-high-pressure extrusion and crushing. The pressing density also declined, and brown cBN crystal particles with higher impact toughness demonstrated a lower particle breakage rate. The ultra-high-pressure crushing law should be considered and appropriate binders should be selected to improve the sintering performance of PcBN materials; ultra-high-pressure crushing of cBN powder contributes to cBN-cBN and cBN-M-cBN bonds under high temperatures and ultra-high pressure.     

我国无磷洗衣粉的现状

在总结了1999年一季度全国无磷洗衣粉产品质量监督检验结果的基础上 ,通过对实测60个样品的几项指标 ,包括去污力、活性物和硅酸盐的含量、pH值及代磷助剂等的分析 ,结合对各生产厂家的实地走访 ,总结了我国无磷洗衣粉的生产、销售、产品质量、执行标准等方面的状况。     

大直径预应力混凝土库滑模施工工艺简介

滑模施工技术连续作业性强,施工机械化程度高,在储库施工中应用广泛,文章详细介绍了适用于大直径熟料库、变截面库、预应力库等有一定特殊要求混凝土库滑模施工工艺。     

混合胶接劈裂接头胶层中应力分布的数值分析

采用ANSYS有限元分析软件,对由两种弹性模量相差悬殊的丙烯酸酯和环氧树脂胶粘剂连接的劈裂接头胶层中部的应力分布进行数值分析和讨论。结果表明:对于采用单一胶连接的劈裂接头来说,采用弹性模量较低的胶粘剂更为有利;混合胶劈裂接头因其存在应力集中程度较高,会导致接头的强度降低。     

Influence of non-uniform distribution of shear stress on aerobic biofilms

This work deals with the detachment of biofilm subjected to a shear stress. Biofilms are developed on plates, under very low shear stress for one month and then subjected to an erosion test for 2 h in a Couette-Taylor reactor (CTR). During the erosion test, the plate was fixed on the external cylinder of the CTR. The presence of the plate modifies the velocity field in the CTR. A first zone close to the facing step region is characterized by the detachment of the stream lines. A second zone, downstream, is characterized by a pure shear flow: the distribution of the shear stress is uniform; the residual biofilm mass was measured and the detachment can be classically related to the magnitude of shear stress. In the first zone, the recirculating flow induces a strong non-uniform distribution of shear stress. The residual biofilm mass was also measured and found to be much lower than in the uniform shear stress zone, whereas the magnitude of shear stress is of the same order or even smaller. The assumption of elastic rheology for the biofilm enables the strong detachment observed in the region subjected to non-uniform shear stress to be explained.