Dr Jin Ooi reveals how digital element modelling is revolutionising process industries
Back in 2014, MP George Osborne announced the launch of a new £28 million National Formulation Centre (NFC), a new initiative to improve productivity and efficiencies within the UK’s process industries. The new centre, led by The Centre for Process Innovation (CPI), will bring universities, innovation centres and businesses together to help companies tasked with developing, proving, prototyping and scaling up the next generation of formulated products and processes. These include perfumes, medicines, cosmetics, processed foods, paints, composite materials and pesticides.
The initiative will focus specifically on improving areas of product and process design, delivery, stability and sustainability. A key aspect to this is the introduction of innovative new digital technologies into the manufacturing process, such as discrete element modelling (DEM), to improve product design, speed up production, minimise costs and reduce wastage. The UK government has identified digital technology as a key driver to boosting manufacturing productivity, a view that is shared across the globe.
In fact, the drive to digitise industry is widely recognised as a step change, a potential game changer in the way we design and manufacture products. Governments across the world have recognised that digital technology is the key to boosting manufacturing productivity and it is at the heart of the national strategies of many countries. In the past 10 years, there has been a massive rise in annual spend across Europe, UK and the USA in this area. For example, by 2020 over €70 billion will be made available for a seven-year funding programme across Europe, a significant portion of which will be focused on digital technology.
Making a difference in pharmaceuticals
The use of DEM – a technique that enables engineers to predict the behaviour/impact of particulates on their designs – is a small but crucially important part of the digital jigsaw. In no uncertain terms, the widespread use of DEM has the potential to revolutionise process industries globally, by boosting productivity and reducing manufacturing costs.
For example, if we look at the pharmaceutical industry, DEM plays a critical role in optimising not only powder mixing but also a range of processes such as tablet coating, die filling, milling and granulation. DEM is a predictive tool that can provide key insights to help optimise processes, leading to better product quality, less physical prototyping and therefore cost savings across the production cycle.
The efficient handling and processing of particulates is critical to the profitable manufacture of pharmaceutical products. Over 75% of pharma and other industrial products are in the solid dosage form and particulates are involved in almost every stage of the manufacturing process. Using particulate simulation early in the manufacturing process enables engineers to quickly and accurately simulate and analyse the behaviour of their particle systems. For example, digital modelling will provide a detailed analysis and visualisation of the flow of particles, from powders to tablets, through process segments and handling equipment. This helps promote innovation in product design and reduces the need for physical prototyping and long development cycles, which cost the industry millions of pounds each year.
One of the greatest challenges facing manufacturers of tablets, for example, is achieving a consistent coat thickness. In the case of coatings containing an active pharmaceutical ingredient (API), variability in potency between tablets arises directly from coating variability. Variability in thickness can also lead to variable drug-release profiles. Finally, high levels of variability for cosmetic coatings results in longer process times to ensure that all tablets have received a sufficient amount of coating. DEM has many applications in the pharmaceutical industry, from predicting powder flow properties, helping evaluate powder testing equipment, optimising tablet compaction, coating and handling and helping with the design and testing of powdered drug delivery devices.
Harnessing modelling across other process-led industries
DEM plays a similarly critical role across many other process-led industries. For example, let’s take a look at mixing, a process present in many industries, whether it is powders and tablets in the food industries, aggregates for road construction or iron ores and limestone for steelmaking. Mixing has a major impact on end-product quality.
DEM can be effectively used to simulate the mixing process, enabling design engineers to ‘visualise’ what is happening inside the mixing equipment in a virtual environment, before the real work is done. Using simulation software provides critical information such as mixing time, efficiency and flow patterns. It also enables engineers to identify the potential formation of dead zones and evaluate the risk of segregation. Using simulation early in the design process leads to optimised mixing processes and therefore a high-quality end product.
Bulk material handling is also common across many process-led industries, and simulation will ensure greater efficiency earlier in the production cycle. For example, look at the steelmaking industry. Transporting raw materials such as iron ore, coal, pellets and sinter from the mines to the plant by truck, moving materials on conveyor belts to the blast furnace and the actual loading of the furnace, all require efficient handling. Typical challenges linked to bulk material handling include spillage, blockage and wear of chutes, hoppers and belts as well as material segregation. Understanding the solid burden flow and the formation of the cohesive zone in the blast furnace is also critical to ensure performance and stability.
In all of these examples, DEM can help engineers understand the flow of materials through each segment of their equipment or operation. DEM can also be used with computational fluid dynamics (CFD) to simulate solid-fluid and solid-gas flows – enabling engineers to accurately simulate complex processes inside the furnace. Creating a virtual blast furnace model allows researchers to perform more realistic parametric studies without interrupting productivity. Leading steel producing companies use DEM to improve steel quality, energy efficiency and blast furnace performance.
A less common application for material simulation techniques can be found in additive manufacturing – also known as 3D printing. The powder-spreading process for additive manufacturing has a major impact on the characteristics and quality of the final product. DEM is used to simulate and analyse the powder-spreading process, providing key insights that would otherwise be hard or impossible to obtain through experiments. DEM simulation can also be used to investigate the impact that different parameters have on the quality of the powder bed, such as roller speed or particle shape, as well as to evaluate powder-spreading uniformity, assessing the degree of compaction and visualising the distribution of different powder layers.
A bright future ahead
Looking at some of the practical applications for DEM within the process-led industries helps illustrate the positive impact that simulation can have. Using DEM for example, not only improves the quality of designs, it also shortens the production cycle and limits the use of expensive physical prototyping, dramatically reducing the cost of manufacturing. However, despite the obvious benefits, DEM is still not widely used by design and process engineers, who often rely on guesswork and estimations to predict the behaviour and interaction of the bulk particulate materials in their designs.
One of the key barriers to adoption is the relatively high level of expertise required to understand and incorporate DEM into the design process. For instance, it takes a great deal of time and expertise to model individual material types such as rocks, ores or powders as well as the computational software to simulate material behaviour and its interaction with product designs. Software providers have to get better at improving the accessibility of their simulation platforms by building DEM and other CAE expertise into their software. Host CAE platforms such as Ansys, MSC Software and Siemens PLM Software have taken steps to ‘open up’ their software to third-party software developers, providing the user with more tools to explore the design space. However, improving software capability must not happen at the expense of accessibility, which as we have seen, is already a major barrier to the use of simulation tools such as DEM.
EDEM is leading the way by developing some of the most accessible DEM tools available. Its aim is to ‘democratise’ modelling software so that DEM is accessible to any design engineer using other CAE software such as finite element analysis (FEA) or multi-body dynamics (MBD) software. It has recently launched the EDEM for CAE range, a set of tools that sit within FEA and MBD software, enabling engineers to use modelling technology without the need for considerable DEM expertise. This is a potential step change as the majority of other DEM software can be cumbersome and complex to use and companies don’t want to take it on.
If software developers can get this right and the industry is sufficiently supported to adopt particulate and bulk material modelling, then the benefits will be considerable. It is not an overstatement to say that particulate and bulk material simulation has the potential to transform productivity within the process industries, speeding up production cycles, reducing manufacturing costs, improving efficiency and driving inward investment.
Looking at the bigger picture, the benefits to industry and the UK economy as a whole are considerable. The next phase of the industrial revolution will be driven by digital technology. The drive to faster and easier technological adoption will help drive inward investment by encouraging multinationals to set up their operations in the UK. The adoption of new digital technologies will reduce waste, speed up production cycles, improve efficiency with the potential to reinstate the UK as a global manufacturing powerhouse.
Dr Jin Ooi is professor of Particulate Solid Mechanics at Edinburgh University.
Case study: DEM used to test new ‘flight’ designs
Astec is a global manufacturer of continuous and batch-process hot-mix asphalt plants and related equipment and services. In asphalt production, hundreds of tons of wet aggregate rock are dried in a rotating drum dryer before being coated with liquid asphalt. The drying process, though very energy-intensive, ensures that the asphalt will bind to the rock. Inside the drum, the aggregate is kept in motion by shaped scoops – called ‘flights’ – attached to the inner surface. These flights produce a consistent ‘veil’ of falling material.
Better veiling action improves heat transfer and speeds drying, reducing fuel consumption. Astec was looking to develop a more energy-efficient drum dryer that could process a wide range of aggregate types at various tonnage rates. Direct observation of the drum in operation is challenging, so the company turned to digital simulation to test new flight designs.
To solve its design challenge, Astec turned to EDEM, a leading player in DEM software for bulk material simulation. Through EDEM’s software, Astec’s design engineers had access to a virtual environment for observing and analysing the effect of flight design and operating parameters on material flow. Astec imported CAD files of the drum dryer into EDEM, and generated an aggregate rock DEM material model. After model calibration, the company accurately simulated the dynamics of the rocks being lifted and released by the flighting.
Using the software’s binning function to calculate the amount of rocks in a given volume, Astec could quantify the density of the veiled aggregate in a given drum section. By virtually comparing the performance of different flight designs, the firm was able to arrive at a new flight design, called the V Flight, which optimised the distribution of rock during veiling, vastly improving the aggregate drying process.
The new V Flight design is more efficient, reduces drying time and uses less fuel than previous designs. In the longterm, this will make Astec’s customers more competitive, while reducing the impact on the environment. With EDEM, Astec was able to visualise particle flow and analyse particle-to-particle and particle-to-equipment interactions in a harsh environment and where direct measurement and observation were impossible.
Virtual performance testing also shortened the design cycle and improved Astec’s understanding of aggregate behaviour in the drying process. This insight now helps Astec to use EDEM to trouble-shoot existing dryers in the field, where local aggregate properties can require custom solutions.