Understanding powder segregation and material flow problems can be difficult if you are working with a material you are unfamiliar with or are unsure about. Often, material flow and segregation problems occur because the company handling the material doesn’t know as much about their material as they should, says Tracy Holmes, vice president of Toronto-based Jenike & Johanson Ltd.

“Sometimes the people making the decisions about the powder or bulk material handling system don’t have an engineering background and may make decisions based on money and not quality”, says Holmes. “And that compromise can lead to serious and costly problems when the material doesn’t behave as expected.”

Getting your powder or bulk solid flowing again may be as easy as picking up the phone and calling a company like Jenike that can determine the material’s flow properties. “You are more likely to get the design right if you know the flow properties,” says Holmes.

Solving material flow problems and powder segregation are the two main topics that Holmes, and president of Jenike & Johanson Ltd, Mike Rulff, will discuss at the Powder & Bulk Solids Conference, June 18 at the Toronto Congress Centre in Toronto, Canada.

Holmes has worked for Jenike & Johanson for 20 years and is a graduate of the University of Waterloo with a Bachelor of Applied Science in Civil Engineering. She and her colleagues are often called upon to help design a powder or bulk material handling system to avoid problems or to help resolve problems. “We often deal with problems that other people can’t solve,” Holmes said, “but I prefer to be involved early enough in the process that we can design problems out."

The first, nearly two-hour, session at the Powder & Bulk Solids Toronto Conference, Understanding the Causes of and Solutions for Powder and Bulk Material Handling Problems, will focus on solutions for material flow problems. It will cover issues that occur during material flow such as no flow, limited flow, erratic flow, and flooding flow. Such flow issues can cause factory downtime, product degradation or loss, process fluctuations, quality control issues, or environmental concerns like spillage and dust control problems.

The 90-minute long second session, Solving Segregation Challenges, will focus on the causes for segregation and how to solve them. Various types of segregation including sifting, sliding, particle dynamics, air entrainment, and particle entrainment will be discussed, along with how to avoid the pitfalls or even put segregation to beneficial use.

“Segregation can lead to material degradation and loss as well as product quality issues,” Holmes says, “But the fact that segregation is occurring is not always a problem. You can use it to your advantage if you understand it and design the system with that in mind.

“Segregation is going to occur when conditions are right,” she says. “Some processes, such as the crushing circuit in a mine, can use segregation to split a material stream in two for different types of treatment.”

As an example, Holmes suggests imagining a stockpile where run-of-mine ore is being stored to provide surge capacity between the mine and the mill. Fines tend to accumulate in the center, while coarser material will tend to end up toward the edges of the pile. Depending on the operation of the pile, material reclaimed from the center of the pile could bypass a crushing stage and be recombined with material reclaimed from the periphery of the pile after it has been crushed. 

“Mostly though, when we talk about segregation, it is because it is causing a problem,” she said. “Industries that must blend ingredients to make their product, such as pharmaceutical, food processing, and cement manufacturing, tend to be hardest hit by segregation and its effects.”

Joe Florkowski is managing editor for Powder & Bulk Solids. He can be reached at [email protected]

For related articles, news, and equipment reviews, visit our Services Equipment Zone.

Click here for a List of Manufacturers that provide Services for the Powder & Bulk Solids Industry.