Greg Mehos, Ph.D., P.E.

Powder Flow

Hopper Design

Process Vessels



Greg Mehos, Ph.D., P.E.

Powder Flow

Hopper Design

Process Vessels




  • If you have a Freeman Technology FT4, Schulze RST, Brookfield Engineering PFT, or an E&G Associates iShear (Peschl) tester you should be able to PREDICT flow behavior rather than RANK flowability; often when you use your tester to rank your materials, powders that were deemed to have good flowability often have flow problems when handled. I will show you how to use the test results to predict if a powder will flow reliably in existing equipment, modify the equipment, or design new equipment.
  • The 9th edition of Perry's Handbook was published this year, and I am excited to be the author of the subsection on powder flow and hopper design.  
  • I have a doctorate in chemical engineering from the University of Colorado, but I like to say that I received a Ph.D. in process development from Cabot Corporation and a Ph.D. in bulk solids handling from Jenike & Johanson, Inc.  
  • I am a co-inventor of a solvent-free continuous process for removing THC from marijuana.  I've never touched the product or starting material.  For me, it was a unique bulk solids handling and processing project.
  • My approach to consulting is to teach clients the fundamentals of bulk solids storage and handling so that they can measure powder flow properties, design bulk solids handling equipment, and solve powder handling problems by themselves.




  • Process development
  • Functional design recommendations
  • Solutions to powder flow problems

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Process Vessels

Moving powder bed dryers and purge vessels

Moving bed heat exchangers

Moving bed reactors

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  • Workshops
  • Seminars
  • Tester training

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Quotations and Proposals

Please reach out at your convenience so we  can discuss your project.  

Greg Mehos, Ph.D., P.E.

4 Crusade Road, Westford, Massachusetts 01886, United States


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Favorite Places (I am not a rep, but these places are good!)

Gamlen Instruments

Powder Compaction Analysis

Rocky DEM

Discrete Element Method Software

Young Industries

Materials Handling Equipment

Impact Technology Development

Process and Product Development

Solids Handling Technologies


International Fine Powder Research Institute

Institute for Briquetting and Agglomeration

Size Enlargement Specialists

Ichthyologists of Boston

Boston Chapter of the American Institute of Chemical Engineers


Schulze Ring Shear Testers


Contract R&D and Toll Manufacturing

FEECO International

Wet Agglomeration Equipment

Ajax Equipment Company

Lyn Bates' Screw Feeder and Conveyor Company

Buy my book!


Hopper Design Principles for Chemical Engineers


When I became an adjunct professor at the University of Rhode Island, I realized that most books on the subject of bulk solids testing and hopper design were either very terse or rather intense for readers who did not have a mechanical engineering background.  My students encouraged me to convert my course material into a text book.. Yes, some of the text may have been taken from my prior publications, but I figure that it isn’t plagiarism when you copy your own material,.  I only disclose design methods that are available in the open literature.    

A few of the formulas I derived on my own, but they were all based on fundamental engineering principles. Consequently, some of the analyses that I present may be slightly different than what you might find published elsewhere, but I use them when I consult.

The paperback is 170 pages long, and includes sections on analysis of stress, stresses in hoppers, flow property testing, bin design, feeders and flow aids, chute design, and process vessel design.

The publisher charged me $8.00 per book, but the catch was I had to purchase one hundred of them!  So I'm offering them on my website for $20.00, which includes USPS media rate shipping, with the hope that I can sell enough books to offer them for free to my students.  I figure that if I'm charitable, I won't get into too much trouble for helping myself to some images from the web without permission.

You can purchase it by using Paypal, or send an email to and we can figure out another arrangement.


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