Eric Maynard, Vice President, Jenike & Johanson

Most manufacturing operations involving powders and bulk solids are feeling the trifecta “pinch” of increased costs for raw materials, supply chain delivery delays, and labor shortages. When it comes to mixing of bulk solids, is there an opportunity for your operation to implement continuous blending to help reduce labor costs and increase throughput efficiency?

Mixers and blenders are wide ranging in shapes, sizes, and modes of operation, but they are generally either batch or continuous. A batch blending process consists of three sequential steps: measuring and loading mix components; blending; and discharge of the material. A continuous blending process simultaneously measures, loads, blends, and discharges.  

Clearly the labor savings in this case is apparent, as the batch blending operation in-series steps each have a time impact with dedicated labor required for each step. Contrast that to continuous blending where through automation, increased ingredient surge capacity, and point-of-use process design, impactful results can be realized with a potential rapid return on investment.

Let’s compare a continuous blending operation to that of batch blending. Imagine a snack food processing line that requires mixing of nuts, fruits, and chocolate candies. There are a wide variety of recipes, and accuracy is not at pharmaceutical level requirements where blend and content uniformity results can often be vital. In a typical batch blending operation, the recipe dictates the measurements of the mix components, with blender loading taking a secondary process step. The blending process may take anywhere from 10 to 30 minutes, and the blender cannot be used for any other purpose other than blending, creating a potential process bottleneck. The batch blender then discharges to the downstream process, and the process will repeat. If we assume the three main process steps each take 20 minutes, it could be 60 minutes per snack pack blend.

Contrast that to continuous blending where the various blend components are in mass flow surge hoppers ready for on-demand dosing with gravimetric or volumetric feeders for discharge to the blender. The blender is designed to handle the ingredients for appropriate residence time to achieve mix uniformity, while maximizing blend throughput. Changes to the recipe can be easily programmed into a logic controller, with additional inputs from level/load cell readings on ingredient hoppers, as well as speed sensors for the blending equipment (such as paddle blender RPM). For the continuous blender, several unique recipes could be formulated, mixed, and discharged at a higher throughput, with far lower labor costs/efforts, and with acceptable accuracy in a fraction of the time of the batch blender.

Another improvement opportunity is on-line sampling of the continuous blender, which is far more difficult (and typically impractical) with batch blending. Consider with our snack food example the ability to monitor blend quality against blend specifications with tolerance limits. Immediate adjustments to the blending operation or its ingredient feeders provide on-line process control with obvious benefits and ability to document quality.

As we delve deeper into the additional benefits of continuous blending, imagine your raw ingredient costs, both from savings with increased bulk amounts and increased efficiencies with reduced handling eliminating small bags with use of bulk truck or bulk bag deliveries. Could receipt of a half-ton of peanuts in a bulk bag be less costly than two dozen 40-lb paper bags, each requiring manual opening, emptying, and disposal with associated waste/foreign material/dust hazards? What if we scale that logic to bulk truck delivery instead of bulk bags? Does that increase cost savings and automation that can eliminate a worker’s need to collect, manipulate, lift, open, discharge a bulk bag – all actions that take time, effort, and could incur injury?

Of course, not all mixing operations can be achieved using continuous blending technology. Some applications do require tight control over raw ingredient addition, or blending intensity, or quality control, thereby forcing a decision to employ batch blending. Even if your process requires batch mixing, what if you implemented some of the improvements above on the raw ingredient handling efficiencies?

As a consultant working in a wide variety of industries on projects through the world, we routinely see plants struggling with inefficiencies with their blending operations. Workers are frustrated with operations that are archaic, dirty/dusty, manually intensive, and unsafe. Consequently, high turnover rates are experienced, exacerbating process inefficiencies.

Wouldn’t it be worth a day’s time to ponder the possibilities of improvements, especially if continuous blending is in the cards? What is holding you back, and is it really worth it?

Eric Maynard is vice president, Jenike & Johanson (Tyngsboro, MA). For more information, email [email protected], call 978-649-3300 or visit jenike.com.