Using V Flight design to redesign aggregate dryer and use less fuel while making customers more competitive

About the customer

Astec. Inc, a member of the Astec Industries family of companies, is located in Chattanooga, Tennessee. Astec is a manufacturer of continuous and batch-process hot-mix asphalt plants and related equipment and services.

Simcenter™ EDEM™ software, which is part of the Siemens Xcelerator business platform of software, hardware and services, has become an integral part of Astec’s design process, proving to be a valuable design tool for Astec engineers.

“Simcenter EDEM software gives our engineers a state-of-the-art tool for the development of new equipment and allows us to model each process segment of our hot-mix asphalt plants,” says Andrew Hobbs, chief computational fluid dynamics (CFD) and discrete element method (DEM) engineer of Astec.

Their challenge

In asphalt production, hundreds of tons per hour of wet aggregate rock are dried in a rotating drum dryer before being coated with liquid asphalt. The energy-intensive drying process ensures that the asphalt will bind to the rock. Inside the drum the aggregate is kept in motion by shaped scoops called flights attached to the inner
surface, which produce a “veil” of falling material. Better veiling action improves heat transfer and speeds drying, reducing fuel consumption. Astec wanted to develop a more energy-efficient drum dryer that could also process a wide range of aggregate types at various tonnage rates. It is difficult to directly observe the drum in operation so simulation offered the best opportunity to experiment with new flight designs.

Our solution

Astec deployed Simcenter EDEM to provide a virtual environment for observing and analyzing the effect of flight design and operating parameters on material flow. Astec imported computer-aided design (CAD) files of the drum dryer into Simcenter EDEM and generated an aggregate rock DEM material model. After model calibration, Simcenter EDEM was used to accurately simulate the dynamics of the rocks being lifted and released by the flighting. Using the Simcenter EDEM binning function to calculate the number of rocks in each volume, Astec could quantify the density of the veiled aggregate in a given drum section. By virtually comparing the performance of different flight designs, Astec was able to arrive at a new flight design called the “V Flight,” which optimized the distribution of rock during veiling, improving the aggregate drying process.

Aggregate veil density: poor distribution before redesign (left) and greatly improved distribution after redesign (right).

Results

The new V Flight design is more efficient, reduces drying time and uses less fuel than previous designs, making Astec customers more competitive while reducing impact on the environment. With Simcenter EDEM, Astec was able to visualize particle flow and analyze particle-particle and particle equipment interaction in a harsh environment where direct measurement and observation were impossible. Virtual performance testing shortened the design cycle and improved understanding of aggregate behavior in the drying process. This insight into the process now helps Astec use Simcenter EDEM to troubleshoot existing dryers in the field, where local aggregate properties can require custom solutions.

“Our philosophy has always been to provide our customers with the latest technological edge in asphalt manufacturing, and Simcenter EDEM helps us meet that goal of continuous innovation,” says Hobbs.