Particle-segregation in chutes, silos, conveyor belts and rotating drums

溜槽、筒仓、传送带和转鼓中的颗粒分离

基本信息

批准号：
EP/M022447/1
负责人：
Nico Gray
金额：
$ 175.75万
依托单位：
University of Manchester
依托单位国家：
英国
项目类别：
Fellowship
财政年份：
2015
资助国家：
英国
起止时间：
2015 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FM022447%2F1
关键词：
Particle segregation chutes silos conveyor

项目摘要

Particles of differing size or density often segregate in industrial flows such as chutes, silos, conveyor belts and rotating drums. This is the single biggest cause of material non-uniformity, which poses significant problems in handling and processing the grains, leading to plant downtime and product wastage. The most common form of segregation occurs in surface avalanches, which develop whenever a static granular material is tipped above its angle of repose. For example, pouring one's muesli into a bowl at breakfast! These avalanches are very efficient at sorting particles by size, with the large ones rising to the surface and the small ones percolating down to the base. The density of the grains may enhance or counteract this effect. When these flows come to rest a rich variety of particle size and density distributions develop in the deposit, sometimes with large regions of just one particle type. This naturally presents a major problem in processes that are supposed to be well-mixed. Understanding the segregation process and being able to model it effectively is the first step in being able to develop strategies to mitigate its effects. This proposal aims to use a powerful combination of small scale experiments, theory, continuum simulation and discrete element simulations (where the interactions of every single particle are modeled) to determine the functional dependence of the segregation rates on particle properties, as well as the applied shear-rate and pressure. The resulting mathematical model will then be applied to more complex flows, where there is mass transport between the the surface avalanche and the static, or slowly moving, grains beneath. This presents the project with its biggest challenge, because the rheology of granular materials is still very poorly understood, compared to fluids, which makes simulating the flow in a silo problematical. Over the past decade there has however been significant progress in the development of the so called mu(I)-rheology, which works over a large range of parameter space. Our aim is to regularize the model, by including additional physics, so that it can be applied in all regions of the flow and hence solve for the bulk velocity field. This will then allow the evolving particle-size and density distribution to be computed, so that we can understand in detail how pockets of just one particle type form. With our industrial partners we develop mitigation strategies, that use our knowledge of segregation to design clever chutes and silos that greatly reduce its effects.

大小或密度不同的颗粒通常会在工业流中分离，例如溜槽，筒仓，传送带和旋转鼓。这是材料不均匀的最大原因，它在处理和加工谷物方面构成了重大问题，导致植物停机时间和产品浪费。最常见的隔离形式发生在表面雪崩中，每当静态颗粒物材料被倾斜以上时，它们就会出现。例如，在早餐时倒入碗里！这些雪崩非常有效地按大小分类颗粒，大型雪崩升至表面，而小的雪橇则渗透到底座上。晶粒的密度可能增强或抵消这种效果。当这些流量静止时，矿床中会出现丰富的粒径和密度分布，有时只有一种粒子类型的大区域。这自然提出了应该充分混合的过程中的一个主要问题。了解隔离过程并能够有效地对其进行建模，这是能够制定策略来减轻其影响的第一步。该建议旨在使用小规模实验，理论，连续模拟和离散元件模拟（在每个单个粒子的相互作用）的强大组合来确定隔离速率对粒子性质的功能依赖性以及所施加的剪切率和压力。然后，所得的数学模型将应用于更复杂的流动，那里的表面雪崩与静态或缓慢移动的谷物之间存在质量转运。这给项目带来了最大的挑战，因为与流体相比，颗粒状材料的流变学仍然非常了解，这使得在筒仓问题中模拟流动。然而，在过去的十年中，所谓的MU（i） - rheology的发展取得了重大进展，该学位在各种参数空间中起作用。我们的目的是通过包括其他物理学来正规化该模型，以便可以在流量的所有区域中应用，并因此解决了整体速度场。然后，这将允许计算不断发展的粒度和密度分布，以便我们可以详细了解仅一种粒子类型形式的口袋。在我们的工业伙伴中，我们制定了缓解策略，这些策略利用我们对种族隔离的知识来设计巧妙的溜槽和孤岛，从而大大降低了其影响。