Conventional screen-type grain dryers allow kernels to be placed directly on the hot screen, thus damaging those kernels.
However, there’s a small number of dryers that don’t use a screen.
Dave Wall of Wall Grain has been selling dryers prairie-wide since the early 1980s. There’s a good chance one of his Vertec, Ibec, Neco or MC dryers has found its way to your farm. He knows dryers inside and out. Wall says he now 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, emphasizing that the Mixed Flow does not have a screen.
“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 degrees. 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.”
Wall says that by the nature of the chamber design, the highest temperature automatically goes to the wettest grain. New grain always goes to the top of the chamber, and that’s where the heat is directed. Moisture content of the grain diminishes as it works its way down toward cool air passing through vents at the bottom of the chamber.
“Change comes so very slowly in the grain dryer industry. Our guys are working with MC engineers on a regular basis upgrading the design where ever they see a way to improve it.
He now has 20 units in operation across the Prairies. The new control panel shows off every facet of the machine in operation, providing greater control to the operators.