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September 9, 2019

Powder and Bulk Solid Handling Fundamentals

Throughout the world, raw materials and finished products travel through miles of bulk handling systems. Driven by high demand across a broad range of industries, the global market for these systems will reach an estimated value of $65.74 billion dollars by the end of 2024 according to Transparency Market Research.

Today, powder material handling equipment and systems encounter many of the same challenges faced in previous decades. Yet with increasingly sophisticated sensors, extensive production line data and computer modeling, better root cause analysis is driving system improvements and overcoming old issues. However, before examining these aspects of bulk powder handling systems, let’s get back to basics.

 

Bulking Up On The Basics

Bulk material handling systems are designed to continuously move and supply bulk materials to other equipment in a processing plant – be they raw minerals, pharmaceutical powders or rubber erasers. They also move materials to and from storage and blend different ingredients or components.

The basic processing technologies for these systems include operations like: lifting, lowering, size reduction, mixing, separating, weighing, filling, screening, filtering, granulating and reclaiming. Typically, product is moved by use of conveyor belts, but screws, chains, buckets and pneumatic methods are also employed. Other equipment found in bulk powder handling systems include hoppers, chutes, feeders, magnetic separators and stacker machines.

Although there are many regulations governing powder material handling, only one standard is reviewed here. Powder and bulk solids handling often generates a significant amount of dust. Under certain conditions, this poses a serious combustion hazard.

The National Fire Protection Association (NFPA) is a codes and standards organization, with one of those codes being NFPA 652 – the “Standard on the Fundamentals of Combustible Dust.” Approved in September 2015, this revised standard provides the basic principles of and requirements for identifying and managing the fire and explosion hazards of combustible dusts and particulate solids. The new standard impacts many bulk processing industries, including chemical, wood processing, metals and agriculture.

 

Understanding Powder and Material Flow Issues

Dust generation and combustion are just two of several challenges faced by powder material handling equipment. This is where the science of powder and bulk solids is dependent on understanding material flow properties and proper system design techniques to overcome these issues. It is critical to measure a powder’s flow properties before designing a handling system or solving a flow problem.

In storage, solids separate out into larger and finer particles in a process called segregation. This causes flow problems since they will feed erratically through a gravity-fed discharge opening and stick to bin walls. The two most common flow problems experienced in a silo, bin or hopper are arching (bridging) and ratholing.

Arching occurs when large particles interlock to form an arch at a hopper outlet and stop flowing due to shape, pressure, moisture or temperature. Ratholing occurs when only a flow channel located above an outlet discharges product. This allows the product to remain on the sides of the bin which causes additional problems like caking, material spoilage and worsening product segregation.

In an optimal container system, product discharges in a mass flow pattern and all material in a silo or hopper moves at the same time. This eliminates ratholing and stagnant material areas that cause spoilage.

These are some additional challenges facing bulk powder handling systems, bulk solids handling equipment and the engineers who design them.

  • Poor product flow
  • Product separation and segregation
  • Uneven product quality
  • Process unpredictability
  • Equipment breakdowns
  • Particle breakdown
  • Powder caking
  • Spillage
  • Product flooding
  • Cross-contamination
  • Spoilage
  • Inventory or process control
  • Self-heating
  • Structure vibration or silo quaking
  • Abrasive equipment wear, erosion and corrosion
  • Chute plugging and buildup
  • Content uniformity

Problem Resolution

The key to solving and preventing bulk handling problems is a thorough understanding of their root causes. Many of these problems are resolved with simple, cost-effective solutions. However, it always returns to a thorough understanding of material characteristics. For example, arching and ratholing are reduced by vibrations transmitted to the hopper or silo which causes material flow to resume. Well-designed chutes, hoppers and bunkers with minimum valley angles between 65 to 75 degrees also avoid stoppages and other issues.

Preventing product non-uniformity starts by understanding the material and how it will move through a process or equipment. Segregation is prevented in much the same way, by understanding how the bulk material transfers through the process in bins, hoppers, chutes, or conveying systems. Caking is reduced by using suitable additives to reduce moisture sorption.

 

Wrapping up: New trends and challenges in powder and bulk solids handling

The field of powder and bulk material handling equipment continues evolving. Some new trends in the industry include:

  • More thorough equipment testing and evaluation before system selection and implementation
  • A move away from single high-speed lines to more flexible systems with hygienic designs and the ability to quickly change over to different ingredients
  • Getting more data off production lines to drive automation and understand how the line is really running for improvements and optimization

top of elecon conveying system

 

Some of the challenges facing bulk material handling equipment providers and users have persisted since the beginning of the industry while others are more cyclical.

  • Not enough research – companies spend little on research and development to reduce bulk material handling costs
  • Education – bulk solids handling is not taught to enough university students, so many engineering graduates do not know how to address solids handlings problems
  • Aging equipment needs upgrading – this does provide opportunities for reliable vendors to help customers solve their flow problems
  • Retrofit or purchase new – faced with financial constraints, many companies are retrofitting equipment to improve flow and solve flow problems, but sometimes new equipment makes more economic sense

Whatever the issues, as the economies of developing nations, China and India continue expanding, the demand for powder material handling equipment and bulk powder handling systems will only continue to grow.

Headquartered in Charlotte, NC, Gough Econ is known globally for its innovation, quality, and reliability. Our comprehensive bulk-material handling solutions improve and add value to every step of the production process, with a broad spectrum of options able to handle projects of any scope or scale. Contact us today and let’s discuss how we can solve your dry or bulk material handling challenges.

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