Systematic study to improve the powder feeding performance and reducing the percentage of fines in roller compactor
Abstract
Roller compaction is a widely used continuous dry granulation process in the food and pharmaceutical industries. The flow and distribution of the powder across the rollers in the compaction area plays a crucial role in determining the quality of the final product. Non-uniform powder flow and distribution across the rollers can lead to variations in quality across the ribbon, resulting in uneven qualities in the granules. Hence, it is essential to enhance the powder flow and distribution across the rollers in the compaction area. Besides that, insufficient compaction stress on both sides of the roller edges can also contribute to presence of uncompacted fines during compaction process.
This research aims to systematically study a whole range of customized guiders design (T-1 until T-14) that improves powder flow and distribution across the rollers and reduces the percentage of fines in the compaction zone. The 3D printed customized guiders with different grade (1 mm until 14 mm) were applied in roller compactor with horizontal feeding system to control the amount of powder passing through the roller width by guiding more powder to the sides between the rollers and less powder to the centre. The effectiveness of the design was validated by examining crystalline and spray dry lactose powders with varying flowabilities using online thermal imaging. The results demonstrate a significant trend, indicating improved uniformity of powder flow and distribution across the rollers and reduced production of fines. These findings have the potential to contribute to long-term sustainability and resource conservation in industrial applications by reducing the need for material recycling and lowering energy consumption in continuous processes.
Highlights
- A systematic study of 14 customized guiders on powder distribution in roller compaction was conducted using PAT.
- Crystalline and spray-dried lactose with varying flowability were utilized.
- Powder with low flowability shows non-uniform distribution during compaction.
- Customized guiders improved temperature distribution, uniformity, and reduced fines in low flowability lactose powder.
Introduction
Agglomeration is a size-enlargement technique commonly employed in industries such as food and pharmaceuticals to improve the flowability and uniformity of final product by bonding them together into larger entities. The strength of these agglomerates is crucial for effective transportation to end consumers. Roller compaction is one of the most widely used dry agglomeration processes, which eliminates the need for a separate drying stage and reducing energy consumption. In this process, particles are bonded together through compaction forces without the addition of liquid. Roller compaction is also a continuous process that enhances overall process efficiency and easy for scalability.
The roller compaction process consists of three important stages: feeding, compaction, and crushing. In the horizontal feeding stage, powder particles undergo rearrangement under low pressure before entering the compaction stage, where they are compressed between two counter-rotating rollers, forming ribbons. These ribbons then enter the crushing stage, where they are milled into granules. The flow and distribution of the powder across the rollers in the compaction area significantly affects the quality of the final product. The compaction zone operates in such a way that more powder is fed at the center than at the sides of the rollers, resulting in a higher density of ribbons at the center compared to the sides. Non-uniform powder distribution across the ribbon width affects the uniformity of quality at different locations across the ribbons, ultimately leading to uneven qualities in the granules.
Furthermore, unsatisfactory reduction in the amount of fines (un-compacted powder) leaking under the rollers and side-sealing cheek plates is an issue faced by the pharmaceutical and food industries. Various attempts have been made to overcome this limitation of roller compaction, such as collecting the fines in a small bag and recycling the fines back into the feeding hopper to reduce powder wastage. However, it should be noted that fines recycling is only feasible when the fines have the same composition as the primary material. When multiple materials are employed, this recycling method cannot be applied as it would introduce inhomogeneity in the product. Previous experimental works show that the type of materials used and powder flow are possible factors leading to the production of fines in the dry granulation process. Non-uniform powder distribution across the ribbon width, with more powder concentrated at the center than the sides, results in uneven stress distribution across the rollers, affecting the density and strength of the ribbon sides. Weak sections of the ribbon sides contribute to the generation of fines during the compaction process. Reducing the amount of fines produced would benefit industrial applications in terms of long-term sustainability by reducing material recycling and energy consumption during continuous processes. Therefore, improving powder flow and distribution across the rollers in the compaction area is essential to produce better quality ribbons and granules while minimizing fines production.
This study proposes a sustainable method to enhance powder flow and distribution across the rollers and reduce the percentage of fines produced during roller compaction by implementing customized guiders in the compaction zone. Previous research has explored the impact of using a shortlist range of three guiders for each material on powder flow. However, this work presents a systematic study involving a comprehensive range of 14 grades of customized guiders, ranging from 1 mm to 14 mm, applied to crystalline and spray-dry lactose powders with different flowability property. The 3D printed customized guiders were incorporated into the roller compactor to regulate the amount of powder passing through the roller width. This was achieved by directing more powder towards the sides between the rollers and less towards the center. The primary objective of this research is to conduct a systematic investigation into the effect of customized guiders with different grades on the uniformity of powder flow and distribution across the rollers, as well as the quality of the ribbons produced. The quality of the ribbons will be evaluated based on temperature distribution profiles across the ribbon width, the percentage of fines, and the achieved ribbon width during the roller compaction process.
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Following excipients are mentioned in the study besides other: Milled Crystalline Alpha- Lactose Monohydrate (Volac International Ltd., United Kingdom) with grade of 200 M is a type of lactose with crystalline structure was referred to as Volactose. Meanwhile, Super Tab 11SD (DFE Pharma, Germany)
Yang S. Mohamad, Mingzhe Yu, Manfred Felder, Vincent Meunier, James Litster, Agba D. Salman, Systematic study to improve the powder feeding performance and reducing the percentage of fines in roller compactor, Powder Technology, Volume 446, 2024, 120158, ISSN 0032-5910, https://doi.org/10.1016/j.powtec.2024.120158.
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