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Feed Batching and Mixing System used for feed formulation

2009-07-29 15:42   Article Source:afia.org   View Times:

Although continuous feed batching and mixing systems may occasionally be used for feed formulation, the batching system with a batching controller remains the primary method of proportioning ingredients prior to mixing.

Feed Batching and mixing system

In the future, feed formulations will contain many more ingredients than today. As more ingredients are used, the percentage of each ingredient used in a given formula is less.

The size and accuracy of each ingredient feeder must be correlated to the amount of ingredient being weighed. Using larger and larger feeder screws to deliver ingredients to the Feed Batching scale isnt the answer as incremental batching and accuracy are lost.

Due to the large batch sizes and short cycle times required, Feed Batching systems of the future will have many batching functions occuring at the same time.

Selected groupings of ingredients will be weighed in individual batching scale, but all of the separate mini-batching scales will have to be able to complete their task within the time period dictated by the mixer time cycle.

Large feeders may be used for individual ingredients that are a large percentage of the batch, but small feeders will be necessary to accurately input ingredients used in small quantities.

Micro-batching systems will be used for many more ingredient inputs, as shown in the figure at the bottom of page 214.

Ingredients such as ground grain and soybean meal will still require large feeders and batching scales.

Minerals and some other ingredients used in medium amounts will be batched in their own minor Feed Batching system. In some cases, liquids will be preweighed for direct addition to the mixer in the batching and mixing cycle.

Large batching scales will not provide the accuracy required to weigh low-inclusion ingredients. Load cells used in modern weighing systems usually are rated to be accurate to plus or minus 0.1% of the applied load.

As an example, if a batching belt scale has a capacity of 6 tons (12,000 lbs.) of ingredients, and the scale hopper and accessories weigh an additional 2,000 lbs., the total applied load to the load cell system is 14,000 lbs.

With an accuracy of 0.1%, the scale can be accurate only to plus or minus 14 lbs. per increment of weighing on a repeat basis. If an ingredient is to be included at a weight of 4 to 5 lbs. per ton (30 lbs. in a 6-ton batch), it is nearly impossible to control the weight at a consistent 30 lbs.

Thus, you must use a smaller batch size and system for these types of ingredients to control accuracy. That is exactly why a micro-batching system is used for ingredients added to the formulation in very small quantities.

As batching system capacities have increased, the use of bulk or super bags has increased dramatically for handling many microingredients and some minor ingredients.

Depending on the inclusion rate and accuracy required, ingredients from bulk bags are weighed into the mixer directly using loss-in-weight or a small positive weighing scale.

In some cases, the bulk bag is discharged into a compartment in the micro-batching system for weighing into the formulation.

Mixing

As the feed manufacturing capacity of mills continues to grow, so does the size of the mixer. This is especially true in single-species feed mills where single mixers capable of mixing as much as 14 tons per charging are available and in use.

But with shorter mixing cycle times, small mixers with capacities as little as 4 tons will be able to mix up to 120 tph using a 1.5-minute total cycle time.

Mixers with actual mixing times of one minute or less are available and in regular use today in new feed mills. These mixers usually have twin rotating shafts, with either paddle or ribbon configurations.

It also is possible to retrofit existing single-shaft ribbon mixers with split-ribbon assemblies that reduce required feed batching and mixing time to as little as one to two minutes.

Written by Fred Fairchild, P.E., is a professor in the Department of Grain Science and Industry at Kansas State University, Manhattan; 785-532-4090.

This article is based on a presentation at the 2000 American Feed batching systems Industry Association (AFIA/www.afia.org) Feed Ingredient Institute in June in Chicago, IL. Published with permission of the AFIA.




Respective topics: Ingredients System   Automatic batching   Batching Equipments  
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