Process Design Assistance

Segregation Effects in Three Types of Mass Flow Hoppers
Mass flow is often suggested as a means of solving all segregation issues.  Although traditional mass flow may be a necessary condition to solve several segregation issues, it is not a sufficient condition.  The solution to segregation in process equipment requires matching the segregation pattern and magnitude to the velocity profile in the specific mass flow bin or hopper.

Flow Properties of Fibrous Biomass Material – A Case Study
Many biomass energy conversion projects are initiated, but few actually make it to the final phase.  The reason for this phenomenon is the lack of consideration given to the material handling end of the process.  Significant effort goes into making the bio-reactor produce the right chemical or energy products.  In fact, much of the research in this area today is associated with yields, kinetics, and thermal effects.   While these are formidable yet essential tasks, the handling system is equally formidable, equally essential, yet often ignored. This case study looks at how two straw feed-stock materials, differing only in particle size, ultimately will flow through the biomass feed system based on their measured material flow properties.

Using a Population Balance Model Coupled with Structural Effects to Aid Product Design of Bran Cereal
Particle degradation is a mechanistic based process – a function of the structure of individual agglomerates in a system. Degradation can be caused by stress-strain or impact events. This breakage can result from fracture of agglomerates to smaller particles or knocking off corners of large particles by abrasion. To mitigate degradation of a given product, Industry often uses single point indices tests to estimate particle size degradation in typical processes which provide an accurate estimate ONLY if the true cause of degradation in the process matches that measured with the particular tester. Population balance modeling provides a powerful tool to determine the root cause of material degradation and offers guidance on how the material should be changed to reduce degradation. Both a simple index approach and a population balance model (coupled with a particle structural analysis) are addressed. Each analysis gives information concerning the behavior of a product in a process. A population balance model also provides information about the cause of particle breakage. This paper reviews advantages and disadvantages of both methods using bran cereal as an example.

Know Your Material: Achieve Successful Process Design
Currently, many processes that handle bulk solids are not operating efficiently.  Some are subject to occasional, or even frequent, hang-ups.  Others experience erratic flow rate problems due to rathole collapse, aerated material, poor gas injection, or lack of mass flow.  Still others are tasked with combining dissimilar products and maintaining this mixture in uniform condition during handling and packaging.  Hang-ups, erratic flow rates, and segregation appear to be major causes of handling systems problems.  This paper considers the case where hang-ups are present in the process.  It discusses the root causes for system hang-up and identifies some general guidelines to avoid these situations.  

Taste the Difference – A New Method of Measuring Segregation: Steak Seasoning, a Case Study
Bulk solid processing generally fails due to one of three problems: material may hang-up in the system, the flow rate cannot be controlled by volumetric feeders, or material segregates during processing creating quality problems. This paper focuses on diagnosing and solving segregation problems. Almost all bulk solid blends are a combination of three or more materials; yet our ability to measure and mitigate segregation tendencies in multi-component mixtures is significantly below our ability to create these mixtures. The paper presents a method to measure the segregation potential of a steak seasoning blend comprised of five components using spectral methods. This blend was chosen as a case study mixture to show the effects of segregation in multi-component systems. Changing the physical characteristics of just one component can often affect segregation of several components in the system. This paper shows how changing the size of the salt affects at least two other components.