Understanding attrition of irregular particles using a novel DEM simulation approach

不规则颗粒无处不在，从矿物到咖啡颗粒，再到结晶活性药物成分。颗粒形状对散装材料的性能有很大影响。它影响颗粒静态堆积的高度和孔隙率，而颗粒形状的变化会导致动态系统中的分离。由于磨损，即碎裂或表面磨损，颗粒形状通常会随着时间的推移而变化。这具有重要的实际后果。在食品和制药行业，不受欢迎的磨损产生的细小颗粒会阻碍流动，从而在后续加工过程中造成问题。用于催化裂化(FCC)炼油的颗粒催化剂易受机械降解的影响，这对环境和成本都有影响。离散单元法(DEM)是一种广泛用于模拟复杂颗粒系统的模拟工具。目前，还没有一种可行的方法来模拟DEM中的颗粒磨损，也没有一个开源的DEM程序可以高效地模拟任意形状的不规则颗粒。这严重限制了我们的粒子尺度模拟能力，阻碍了工业通过模拟来充分了解他们的粒子过程。该联谊会将创建一种开放、高效和灵活的方法来模拟不规则的、可磨损的粒子。这将通过创建一个全新的粒子模拟领域来产生变革性的效果。在爱丁堡并行计算中心的编码支持下，这些数值进步将在开放源码LAMMPS中实施。然后，该代码将用于模拟两个具有重要经济意义的应用。首先是催化裂化催化剂颗粒的磨损。DEM模拟将用于预测工业催化裂化装置的催化剂更换频率。探讨了催化剂降解的机理，包括颗粒形状和微观力学性能的影响。对这些机理有更好的科学理解将有助于对磨损进行更可靠的预测，从而使催化剂的设计具有更高的耐磨性。第二个应用是在搅拌式过滤干燥器或造粒机中破碎药物晶体。在制药工业中，经常会产生针状和板状晶体，这些晶体极易受到磨损。这项工作中采用的建模方法将能够定量预测包括搅拌干燥和混合在内的剪切过程中的晶体磨损。这种损耗的程度将与散装密度、流动性和其他关键质量属性的变化联系在一起。更好的预测能力将能够更好地控制制造过程中的粒度分布，可能会带来显著的经济节约。这项研究将在爱丁堡大学工程学院基础设施与环境研究所内进行，并得到三个项目合作伙伴的支持：桑迪亚国家实验室、巴斯夫(Refining Catalysts)和阿斯利康(AstraZeneca)。Sandia是LAMMPS代码的主要开发者。他们将通过将这些代码开发包括在主要的、开放源码的LAMMPS分发中来帮助传播。巴斯夫将提供有关催化裂化催化剂性能和磨损行为的物理测试数据，并在其办公场所接待研究访问以进行合作。同样，阿斯利康将提供实验数据和主办研究访问，并将提供他们的实验室设施进行测试。这些合作伙伴的参与确保了这项研究将为业界的需要提供信息，并将产生实际的、切实的影响。

Irregular particles are ubiquitous, ranging from mineral ores to coffee granules to crystalline active pharmaceutical ingredients. Particle shape has a huge effect on the behaviour of a bulk material. It affects the height and porosity of a static packing of particles, and variability in particle shape can induce segregation in dynamic systems. Particle shapes often change over time due to attrition, i.e., fragmentation or surface abrasion. This has important practical consequences. In the food and pharmaceutical sectors, fine particles generated by undesired attrition impair flow which creates problems during subsequent processing. The particulate catalysts used in oil refining for fluid catalytic cracking (FCC) are susceptible to mechanical degradation which has both environmental and cost implications.The discrete element method (DEM) is a widely used simulation tool used to model complex systems of particles. Currently, there is neither a viable method to simulate particle abrasion in DEM nor an open-source DEM code which can simulate irregular particles of any shape in an efficient manner. This severely limits our particle-scale simulation capabilities, preventing industry from fully understanding their particle processes by simulation.This Fellowship will create an openly-available, efficient and flexible method for simulating irregular, abradable particles. This will have a transformative effect by creating an entirely new field of particle simulations. These numerical advances will be implemented in an open-source code, LAMMPS, with the coding support of Edinburgh Parallel Computing Centre. The code will then be used to simulate two applications of significant economic importance. The first is the attrition of FCC catalyst particles. DEM simulations will be used to predict the catalyst replacement frequency in an industrial FCC unit. The mechanisms of catalyst degradation will be explored, including the effects of particle shape and micro-scale mechanical properties. Having a better scientific understanding of these mechanisms will facilitate more reliable predictions of attrition and hence permit catalysts to be designed with increased attrition resistance. The second application is the breakage of pharmaceutical crystals in agitated filter dryers or granulators. In the pharmaceutical industry, needle- and plate-type crystals are often produced which are highly susceptible to attrition. The modelling approach adopted in this work will enable quantitative prediction of crystal attrition during shear processes including agitated drying and mixing. The extent of this attrition will be linked to changes in bulk density, flowability and other key quality attributes. Better predictive capabilities will enable better control of particle size distributions in manufacturing processes, potentially leading to significant economic savings.This research will be undertaken within the Institute for Infrastructure and Environment, School of Engineering at the University of Edinburgh with the support of three project partners: Sandia National Laboratories, BASF (Refining Catalysts) and AstraZeneca. Sandia are the main developers of the LAMMPS code. They will assist with dissemination by including these code developments in the main, open-source LAMMPS distribution. BASF will provide physical test data on the properties and attrition behaviour of FCC catalysts, and host research visits for collaboration at their premises. Similarly, AstraZeneca will provide experimental data and host research visits, and will also make their laboratory facilities available for testing. The involvement of these partners ensures that the research will be informed by the needs of industry and will have a practical, tangible impact.