Fruits and vegetables that are processed throughout a washer are required to be dried. An “Air Blast System” air knife blows high-velocity air over the produce to remove the water.

An “Air Blast System” air knife dryer is effective on:

  • Fruits
  • Berries
  • Peppers
  • Oranges
  • Tomatoes
  • Potatoes
  • Carrots
  • Spinach
  • Parsley
  • And many other types of produce

With produce drying the air knife is a relatively new phenomenon. In the past instead of air knives companies used sponge rollers, brush rollers, and in some cases an evaporative enclosure. With sponge rollers the very first fruit of the day might see a dry roller however, they then get wet and your produce is being transferred by wet sponges, with air knives you will not have this problem. With brush driers you essentially have many of the similar problems as with a sponge roller. As far as evaporative drying is concerned, you are going to have to make a rather large capital expenditure. As well as the capital expenditure you will need an expensive heat source (gas). You will also run the risk of compromising the produce itself with a heated enclosure. With an air knife system, the startup cost is low, it has a direct drive blower so the maintenance cost/ operating costs are low and they are very efficient.

With drying using an air knife, you will sometimes be blowing water off of produce that is traveling on an open mesh conveyor (usually 70% open mesh or better). These types of conveyors are typically used if the fruit or vegetable is small. If you are blowing off a medium sized fruit/vegetable with an air knife (a tomato, potato, orange, apple, melon, peach, mango, etc.) more often than not you are on a roller conveyor. The roller conveyor where the roller is turning indexing the produce forward, this is the perfect place for an air knife. You position the air knives so that they are aiming directly between the rollers. A typical roller conveyor has about a 60 RPM turn cycle so that even if you have a relatively high push through rate the produce will almost always make at least one complete rotation under the air knife. Each line will typically have between 2 and 4 air knives so at the end of the run the produce is very dry.

Velocities of air vary from system to system depending on the type of produce you are drying and how it is presenting itself. Typical air knife systems for produce have velocities that are between 15,000 and 22,000 FPM.  These velocities remove the water without bruising or damaging the produce.

Leafy green vegetables are a little more difficult to dry than a smooth round surface produce like a tomato, or and apple. In the past green leafy vegetables have been dried almost exclusively with spin driers. If you are planning to dry leafy greens with an air knife system, you are usually looking at several air knives (4 to 8) and you are turning the leaves on a typical open mesh conveyor. This can be done with a conveyor to conveyor transfer of a serpentine in the belt itself. This is a very effective method (especially if you have a rather large volume where constant pauses to transfer produce to and from a spin drier is not practical.