Handling bulk solids presents a number of challenges, primarily due to how material properties interact and the dynamic behavior of flow. Variations in particulate matter can lead to segregation, which may ultimately affect the quality of the end product.
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Flow obstructions, such as arching or ratholing, can disrupt material discharge and hinder operational continuity. Hygroscopic materials, for instance, can cake and compact under varying conditions. There are numerous mechanisms, variables, and potential failure points that systems integrators must consider to ensure smooth operation and the economic viability of industrial solids handling systems.
While developing an optimal solids handling system is no simple task, it is a critical technical necessity. This article will explore some of the most common design challenges in solids handling. By reading it, you'll gain a better understanding of the key considerations in solids handling technologies and how to avoid common issues that arise in these systems.
Segregation of Blended Ingredients
Blended ingredient segregation is an exceedingly common design challenge in solids handling systems. It takes place when diverse parts of a blend segregate while being handled or stored, resulting in inconsistent product quality.
This issue primarily stems from discrepancies in particle size; however, shape, density, and surface composition might also have a role among the ingredients.
For example, finer particles tend to accumulate near the center of a forming pile, while coarser particles roll away to the outer edges. Lighter, finer particles may remain airborne longer, eventually settling at the top of the pile.
Segregation can be exacerbated by factors such as vibration, air currents, and improper handling techniques. To minimize this issue, it's crucial to design solids handling systems that reduce particle separation and maintain blend integrity throughout the process.
Flow Interruptions and Constraints
Flow interruptions and constraints are key issues in solids handling systems. These issues typically emerge from inadequate design of storage vessels and handling tools.
In bins, silos, and hoppers, two widespread flow issues are arching and ratholing. Arching occurs when the material forms a stable obstruction above the outlet, blocking further flow.
Ratholing, on the other hand, happens when stagnant material builds up along the edges of the storage vessel while the bulk material flows through a narrow central channel. As the channel empties, if the bulk material has enough cohesive strength, the remaining material may stay stagnant.
These challenges can lead to inconsistent flow rates and operational inefficiencies. To address these issues, it's essential to design storage vessels with suitable geometries that account for potential flow disruptions. In some cases, flow aids—such as vibrators or air cannons—can help facilitate material discharge when the right flow characteristics are present.
Caking and Compaction
Caking and compaction are common problems in solids handling systems, especially for hygroscopic materials, or materials that absorb moisture. Caking is the formation of solid lumps within a material while being stored or packaged. This can complicate discharging and handling.
Compaction occurs when the material is made to withstand pressure over time, resulting in densification and loss of flowability. Environmental factors like humidity and temperature variations can worsen these issues.
To minimize caking and compaction, it's essential to understand the mechanisms that cause these issues and then control the storage environment accordingly. In some cases, using anti-caking agents or applying mechanical agitation can be effective in maintaining the material’s flowability.
Restricted Discharge Rates
Due to their flow characteristics, fine powders and cohesive materials often experience slower discharge rates than anticipated for the operation.
To regulate these discharge rates, hoppers, and feeders should be designed to accommodate the specific flow behavior of the material. Strategies such as optimizing hopper angles and outlet sizing, controlling aeration, and, in certain cases, using vibration or flow aids can help achieve the required discharge rates.
Abrasiveness and Friability
Materials with abrasive characteristics can lead to excessive wear on handling tools, resulting in maintenance problems and downtime. However, friable materials are able to break down into smaller particles in the handling process, leading to dust and producing further handling issues.
Selecting the right materials for constructing equipment and incorporating wear-resistant linings can significantly extend the lifespan of handling systems. Additionally, dust collection systems should be designed to handle the specific characteristics of the material being processed. Ultimately, these considerations help create a safer and cleaner working environment.
Dust Generation
Dust generation is a common challenge in solids handling systems and can pose health and safety risks. Effective dust collection systems are essential for capturing airborne particles and maintaining a safe working environment.
Designing dust collection systems that align with the specific characteristics of the material being handled can help minimize dust-related issues. Proper equipment sealing, the use of dust collectors, and the implementation of dust suppression methods are all critical components of an effective dust management strategy in solids handling systems.
Looking for Design Assistance for Solids Handling Systems?
Addressing the common design issues in bulk handling systems requires a thorough understanding of material properties and the application of appropriate design principles.
Engineers can develop solids handling systems that work reliably and efficiently by considering segregation, flow interruptions, caking, inventory control, and dust generation. Testing and engineering services, including those provided by Jenike & Johanson, can facilitate optimal system performance and reduce operational risks.
Jenike & Johanson excels in diagnosing and addressing the complexities of solids handling systems. Its expertise in solids handling systems facilitates optimized design and reliable operation, effectively preventing common issues such as segregation, flow interruptions, and dust generation.
This information has been sourced, reviewed and adapted from materials provided by Jenike & Johanson.
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