Technical Articles

Innovative Vacuum Blender Design Accelerates Charging And Discharging, Cuts Operating Costs

Oleoresin extraction, the starting point for many varieties of flavor development, is a long, labor-intensive and costly process. Manufacturers have followed the same recipe for many years, and always with the same results.
  • Loading botanicals into a traditional percolator generally requires at least 6 hours.
  • With the botanicals resting on a perforated plate in the heated tank, solvent percolates continuously throughout the vessel until all the flavor has been removed. Percolation requires 8 to 24 hours – usually overnight.
  • When the flavor extraction is finally complete, the worst part of the process begins – discharging the percolator. With the flavor-laden solvent removed, a solidified mass of residual botanical material remains to be discharged. This chore typically consumes 16 man-hours or more.

The extraction process is also difficult to control. Yield and consistency vary substantially from batch to batch, reflecting natural crop-to-crop variations. For the flavor manufacturer, this presents a huge barrier that must be overcome in order to boost production and deliver a consistently high level of product quality.

Capturing a competitive advantage - by redefining the process.

High costs on the process line, uncertain delivery, and unpredictable product quality are all deadly disadvantages in a competitive market. Recently, a leading flavor manufacturer asked Charles Ross & Son Company of Hauppauge, New York, to analyze the traditional extraction process and develop a more productive approach.

In a collaborative effort, engineers from the two companies eventually agreed on an aggressive plan – to retire every percolator in the plant and revitalize the entire process line. The plan called for four specially designed 2,500-gallon Cone Screw Mixers, equipped for heat transfer and vacuum processing.

Offering an excellent combination of gentle blending, positive agitation, and fast blending cycles, Cone Screw Mixers have long been used in food processing. Since they include no bearings or stuffing boxes in contact with the product (see cutaway illustration), they also offer much greater protection than many other blenders against contamination. Equipped with vacuum and thermal jacketing, they seemed ideal for oleoresin extraction – but only if Ross engineers could overcome the formidable challenge of discharging waste botanicals.

First, because botanicals virtually solidify during the process, Ross engineers designed a special truncated section for the lower cone. This provided an unusually large opening for discharge.

In the new cone design, the lower section was also engineered with swing bolts and a slip hinge - to readily drop and swing away from the upper cone. Since the swing-away section supports the solid botanical mass with a platform comprised of a screen reinforced with a perforated plate, this modification made discharge and cleaning easy.

An unsupported mixing screw simplifies discharge

In an ordinary cone screw mixer, the mixing screw is supported at the bottom of the cone by a bearing that centers the screw and prevents collisions with the vessel wall. But in this case the problem of discharging botanicals required a much more sophisticated design. A support bearing in the lower section of the cone would have caused constant problems. The cost in terms of added labor, maintenance and downtime between batches would have been disastrous.

The challenge was to design an unsupported mixing screw for a blender this large.

“An unsupported screw requires an overhead drive assembly strong enough to maintain correct alignment as the screw orbits the cone, without any support at the lower end,” says David Hathaway, Ross director of engineering in the company’s Savannah, Georgia, plant. “A cone-screw blender with an unsupported screw is generally considered impractical in sizes over 200 cubic feet - a little more than half the size of the blenders we were designing for this application. But the need to cleanly discharge those botanicals was the key to a huge gain in production, so we considered it a design necessity.”

Today the drive system on each of these giant blenders operates 24 hours a day without a lower bearing, and the results are impressive. Discharge is fast, and the regular maintenance normally required by a pintle bearing in the lower cone is eliminated.

Measuring the process-line gains

At the end of the line, yields and product consistency are up significantly, since the blenders are extracting everything the botanicals have to offer. With a variable-speed drive combined with vacuum and thermal jacketing, the blenders also provide enormous flexibility to fine-tune the process to optimize results for a wide variety of botanicals.

In fact, the new process line picks up speed - and cuts operating costs - at each step. The loading process, which used to require 8 man-hours, now requires only about 4 man-hours. Discharging the botanicals used to require 16 man-hours. With the unsupported mixing screw and the swing-away lower cone, the process now requires only 4 man-hours.

In a Cone Screw Mixer, the mixing screw orbits the vessel wall while it turns and gently lifts material upward. Blending and heat transfer are extremely efficient. Discharge is fast, especially with an innovative mixing screw unsupported at the lower end.

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