Conveying Cycle-Time Analysis in Pneumatic Conveying: A Study of Relationship between Batching & Convey Cycles in Powder & Bulk Handling Systems

Abstract

The purpose of this project is to develop methods for calculating the instantaneous convey rates for pneumatic conveying systems. Process and systems engineers are often faced with the question of calculating or verifying the required conveying rate for pneumatic conveying systems, based on the batching information, or the ingredient usage rates. The batching information usually comes in the form of spreadsheets describing different ingredients and their required weights in a recipe, as well as the number of required batches per unit time.

Due to time delays and other functions of the process, continuous conveying of the ingredients is not always practical. Therefore, the instantaneous convey rate is rarely equal to the ingredient usage rate.

There is no single methodology or formula that can be applied to all systems. That is probably why there are not many books or papers written on this subject. A few textbooks and articles describe the relationship between achievable convey rate, convey pipe size, ingredient physical characteristics, and convey distances, but hardly give any reference as how to find out what the instantaneous convey rate should be.

This paper includes five examples of pneumatic conveying systems. The first example discusses mixing cycle time for making a batch and calculates achievable number of batches per unit time. Discharge time is discussed thereafter. The second example introduces a simple terminal use bin system. The third example discusses a multiple use bin system. The fourth example analyzes a multiple scale loop system. The last example is on the subject of loss-in-weight scaling. Dribble feed is discussed at the beginning of the last example. For each example a spreadsheet is created to solve each specific problem.