Month: October 2013

Maximizing Drying Efficiency

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Fotosearch_k10159421One of the things that makes grain drying a challenge is the number of uncontrollable variables—such as different moistures, temperatures, wind speeds, and humidities. But there are a few things you may have some control over (at least some of the time) that can make your drying more efficient. In this post we are going to highlight two of them:

Longer dryer runs. The trend to larger dryers has meant that in some cases there is only enough product for short runs, so the dryer may only run for a couple of hours, then be turned off for a few hours. The problem is that the grain that is left in the dryer during the shutdown will tend to come out over dried. And of course, the more often there are shutdowns the more grain will come out over dried. Ideally, the goal should be to try for longer dryer runs when possible because a dryer is most efficient when running continuously at capacity.

Tempering. Many times on the graphs we download from our customers, we can see the clear difference in moisture variation between day time and night time operation.

During the day, incoming product may go straight into the dryer, but as the product is coming from different locations, the moisture may vary significantly from one truck load to the next. This variation in moisture makes drying to a constant target that much more of a challenge.

In contrast, the product being dried at night may have sat for a few hours in storage having some time to temper—or an opportunity to mix with other product. The result is more consistent moisture going into the dryer and an easier process to control.

Maintaining Dryer Efficiency: Part Two

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In the last blog post, we talked about how the buildup of fines and red dog can reduce dryer capacity for screen dryers. In this post, we want to continue the discussion and look for a way to tell if you are losing capacity.

Here is the most obvious way to see if you are losing capacity: You will see the moisture leaving the dryer increasing over time, requiring you to reduce the discharge speed to achieve the desired moisture target (the grain has to stay in the dryer longer for the same inlet moisture). The normal temptation here would be to increase the temperature to get the rate back up again, but this could have implications for quality.

For example, at the beginning of the week let’s say the average discharge rate was 30, and at the end of the week, the discharge rate has fallen to 24 because of buildup. This results in a 20 percent loss in throughput.

The reduction in capacity can also have an impact on electrical consumption—as you could see higher electrical usage from increased power usage by the fans, due to higher back pressure. This can negatively affect product quality as well, as the increase in air velocity contributes to faster moisture removal over a shorter period of time, possibly further stressing the kernels.

In order to get back to full capacity it is usually necessary to have a shutdown period while you wash down the upper portion of the dryer.

Obviously, it is not always possible to shutdown and clean when trying to keep up with the incoming product in the peak of the drying season, but as often happens there is a trade off from continuing to run with less than full capacity.

Also, remember that you will want to pay particular attention at the start of the season when high moisture product may require you to clean more frequently.