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.