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11 Batch Mixing System Design Considerations for the Best Dry Solids Mix
Oct 31, 2018

Producing high-quality finished products from dry solids starts with getting the right mix. Mixers are not one-size-fits-all, and your batch mixing system must be designed with your ingredients, facility, capacity, and other considerations in mind. Without the right mixer, segregation problems, dead zones, an low mixing activity can cause harm to your product. Go through this list of batch mixing system design considerations when working with horizontal ribbon mixers or other dry solids mixers and make sure your mixer works at optimal efficiency.

11 Batch Mixing System Design Considerations for the Best Dry Solids Mix

Individual Batch Mixer Design Considerations

1. Capacity: One of the most important batch mixing system considerations for dry goods is capacity. When working with a ribbon or paddle mixer, the total capacity cannot exceed swept volume (space occupied by the ribbon mixer). Over and under filling can increase the variation in the mix and may also increase the mix time.

2. Time: Many batch mixing systems for dry solids use horizontal ribbon mixers because of their ability to fully mix ingredients in one to two minutes. However, the ideal cycle time for your batch mixing system will depend on the upstream and downstream processes, and the output you wish to achieve. Changing the capacity, profile, or number of mixers in your batch mixing system can help you coordinate timing between processes so all the systems can run simultaneously, maximizing utilization.

3. Mixing Cycles: A rule of thumb for horizontal batch mixers is that the ingredients should move from end to end at least three times. The actual required mix time can vary depending on the ingredients. Not enough circulation will give you an incomplete mix, too much circulation can cause unnecessary breakage or fines generation. Your particular mix should be checked to make sure that you have a complete mix.

4. Mixer Profile: Since ingredients in a horizontal ribbon mixer or paddle mixer move horizontally through the mixer, a longer mixer will lengthen the cycle time. In general, the diameter to length ratio should be between two and two and a half. You’ll need to consider the available footprint and desired production rates to determine the size of the mixer.

5. Motor Horsepower: Ingredient density and capacity will affect the horsepower required for the mixer to run. If the weight is the same, the horsepower requirements will also be the same. However, a low-density mixture might completely fill the mixer but impose only half the weight, while a high-density mixture at full capacity will weigh much more. Choose your motor in your batch mixing system carefully so your mixer has enough power, but isn’t pulling unnecessary energy.

Material Considerations

6. Friability: Horizontal ribbon mixers generally impose a low degree of force on ingredients, but especially friable ingredients can still break apart during mixing. When working with especially friable ingredients in your batch mixing system, paddle mixers may be preferred for a gentler mixing action. The angle of the paddles will also lessen the force of the mixer.

7. Heat and Shear: Ingredients with high shear sensitivity will be subject to heat from the friction of the mixer. If these ingredients have high fat or sugar content, as well as high shear sensitivity, they may melt and stick to the mixer. Sticking ingredients will not only affect the quality of the mix and efficiency of the batch mixing system, but it will also damage the mixer over time. A non-stick coating or stainless steel polish can prevent sticking due to shear sensitivity.

8. Material Bulk Density: To properly calculate capacity, you will need to know the bulk density of all ingredients you’re currently using or expect to use in the future. Keep in mind that low-density ingredients like wheat middlings will take up more space than the same weight of another, denser ingredient like soybean meal.

Maintenance and Safety

9. Ribbon Maintenance: Mixer ribbons can last the lifetime of the mixer, but materials that are abrasive will cause a ribbon to wear down faster. Check the mixer ribbon clearance and thickness at regular intervals. Replace a ribbon before it becomes thin enough to break or the clearances between the ribbon and trough become too large. This will avoid unexpected downtime in your batch mixing system.

10. Motor Maintenance: If you are using a chain and sprocket mechanism to reduce RPMs, you will need to regularly adjust the tension and check the oil bath lubrication system. Using a shaft mount reducer can eliminate the need for this extra maintenance.

11. Safety: If adding ingredients manually to the batch mixing system, the input should be blocked with a bolted grate. Unblocked inputs or removable grates put workers at risk and expose businesses to unnecessary liability. Cultivate a culture of safety and encourage workers to report any maintenance issues or hazards.

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