Jan 10, 2023

Pneumatic conveying benefits outweigh costs for feed mills

Enclosed tubes confine material dust and leave zero residue between batches.

The first time I visited a feed plant with a pneumatic conveyor system — without knowing they had one — I noticed how super clean it was. I immediately asked if they had a pneumatic conveyor, and I must have impressed them mightily with my knowledge and experience.

There is a visible benefit to using pneumatic conveyor systems because the tubes that transfer dry material from one point to the other are sealed airtight.
A pneumatic system uses compressed air to push dry material through a tube. In contrast, other systems that use chains, buckets, disks, etc., to pull or drag dry materials along a tube do not need to be as airtight.

Advantage outweigh disadvantages

The drawbacks to a pneumatic conveyor system are less energy efficiency and more expensive to operate and install — but all these depend on the quality of the facilities and their abilities.

Nevertheless, comparing oranges to oranges, pneumatic systems are more expensive, but they offer advantages that can offset the added investment price.

The first advantage, of course, is added cleanli-ness, as presented in the example of my visit to that feed plant so long ago.

Apart from overall cleaner environment at the mill, pneumatic conveyors have a major advantage that sets them apart from other systems. They leave no residues behind — I mean zero tolerance. Now, if the main or only material to be conveyed is corn, for example, that advantage is null.

But imagine if the feed mill prepares a complete feed or a premix (where concentrations are higher) for pigs or poultry.

These products add considerable amounts of copper. If the next product in line to be mixed is destined for sheep, any copper residue will contaminate it. Sheep have a very low tolerance to copper and will suffer from liver failure and copper toxicity.

In this case, most mills without a pneumatic con-veyor would run ground corn or limestone through the whole system, but that “contaminated” corn or limestone is often circulated back into other feeds, causing extra cost that often goes unaccounted. The same can be said when a premix plant is dealing with medicinal products that cannot cross contaminate one another — especially if they are upmixing a highly concentrated drug into a less dense product suitable for home-mixing.

A final example is GMO versus non-GMO prod-ucts. If there is only one line handling both (rare, but not impossible) then cross contamination can be avoided only by cleaning 100% of the conveyors, mixers, etc. A pneumatic conveyor is a must when zero residue tolerance is required between mix batches on the same line of a feed plant.

3 types of pneumatic conveyors

Depending on the material to be transferred, there are three types of pneumatic conveyors in the market today:

1. Dense phase conveyors are used for mixed, fragile or abrasive material. These are moved at low velocities with air often interjected at specific intervals to cause gaps between blocks of the material. This ensures the integrity of the product transferred as well as the pipelines. This system works by pushing the material using compressed air.

2. Dilute phase conveyors are the opposite of 2dense phase conveyors. They move large amounts of material in suspension within the tube with higher speeds. They can either push (com-pressed air) or pull (vacuum) the material. Pushing is the most common way to convey with dilute phase conveyors.

3. Semi-dense conveyors offer an intermediate solution for materials, for example cement, that are abrasive yet can be aerated (suspended).

Ship and truck loading considerations

Many grains are loaded on ships, trucks or train cars via pneumatic conveyors. These systems are especially valuable as certain parts of the loading system must be flexible, making the use of other conveying systems impractical.
Speed is important when huge volumes must be handled as fast as possible.

This need for speed, however, must be counterbalanced with the risk of causing excessive grain damage, which occurs as grains bump against each other and onto the walls of the tubes.

Grains transported in bulk via sea vessels are often handled twice by pneumatic conveyors, unlike those handled by trucks or rail cars that are often just dumped into receiving pits.

While these parameters and risks are already calculated appropriately by port equipment handlers, it does not hurt to alert them if they are used to handling one type of grain and are faced suddenly with handling a new one.

Ioannis Mavromichalis, PhD, is an animal nutrition industry consultant. He may be contacted at [email protected]

Ioannis Mavromichalis, PhD

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