Improved screenless drying means lower fire risk

A new dryer tumbles grain side to side as it dries

All arrows represent airflow. Blue arrows are cool ambient air. Red arrows represent heated air. Blue arrows show air entering the dryer through the bottom fan. The bottom one-third of the dryer cools the grain. The burner is not being used for the bottom section so the arrow and cut away remain blue, although these dryers can operate in an all-heat mode to heat the lower section if needed. Above the lower cooling section there are two more blue arrows entering the heat section of the dryer. As the air passes over a burner it becomes heated and enters the red section of the dryer. The gray arrows represent exhaust air. Both heated and non-heated air enters the ducts and pass through the grain until they exit through an exhaust duct. The cutaway shows the air moving out of the exhaust ducts.
Reading Time: 2 minutes

Glacier FarmMedia – Conventional screen-type grain dryers allow kernels to be placed directly on the hot screen, thus damaging those kernels.

However, there are a small number of dryers that don’t use a screen.

Dave Wall of Wall Grain has been selling dryers since the early 1980s including his Vertec, Ibec, Neco or MC dryers.

Wall says he sells a better-designed unit with the Mathews Mixed Flow screen-less dryer.

“A couple years ago, we figured it was time to do something about all those old style dryers that were always catching fire and were lacking in capacity. The industry today is still building the same kind of dryers I was selling decades ago.

“So my guys worked with the Matthews Company engineers and they came up with a totally fresh concept, the screen-less grain dryer.

“With the old screen style dryer, there’s always hotter grain right on the screen. That’s not good,” explains Wall.

“Everyone in the industry seems to be in agreement now that a screen-less dryer tumbles your grain from side to side. The heated air hits all units of grain with uniform heat. Each kernel is warmed up evenly by tumbling. There’s no screen for it to rub against and no over-heated kernels.”

Wet grain is augured into the dryer at the top and gradually moves down toward the exit auger by gravity. The burn chamber is located off to the side far from the grain chamber for safety reasons. Wall says the only other manufacturer he knows of that puts the burner away from the grain is Western Grain Dryer.

The air that will dry the grain is heated and blown into vents running through the top two-thirds of the grain chamber, thus warming and drying the grain. As grain falls into the bottom one-third of the chamber, it’s cooled by fresh outside air blown through the vents.

The largest Mixed Flow can dry 8,000 bushels per hour, with temperatures as high as 240 F (115 C). In addition to the main burner, the engineers also put an auxiliary burner close to the bottom to allow more precise control of the heat. When needed, the bottom one-third can be managed so heated air passes through those lower vents.

“With this extra burner, now if I can tweak my heat. The whole thing about drying grain is you want to warm a kernel of grain to your target temperature as quickly as possible. Now, with this extra burner, I can increase the heat so I can go to 240 degrees on top instead of 200. And you don’t hurt the grain on top.

“The system requires high air volume to function properly. To meet that need, the Mixed Flow uses the same kind of inline centrifugal fan MC employs in their large tower dryers. Conventional dryers still use the squirrel cage fan similar to that in a domestic furnace. These fans stall out in wet heavy grain. They can’t deliver a consistent airflow. It takes very minute-detailed engineering to make sure you have consistent airflow and you don’t have any hot spots in the dryer.

“Our centrifugal fans deliver hot air to the vents at a volume of 40 cubic feet per minute per bu. Older dryers are only 30 to 35 CFM per bu. We increased the airflow, but that required a significant design change for the tapered ducts inside. We had to deliver more heated air, but we had to also eliminate any hot spots.

“Change comes so very slowly in the grain dryer industry.”

This article was originally published at The Western Producer.

About the author



Stories from our other publications