- THE MAGAZINE
- FOOD MASTER
While Hunter was speaking about boilers, efficient heat transfer is a common processing objective. Tradeoffs between efficiency, throughput rates, maintenance requirements and other factors usually are required with heat exchangers. Values change with the composition of the food being processed, adding a level of complexity that goes beyond thermodynamic expertise. Increasingly, food companies are collaborating with food scientists, system fabricators and equipment suppliers’ engineers to specify the most appropriate heat-transfer system for their application.
Heat exchangers are models of efficiency, and rising energy costs are helping manufacturers rationalize the cost of making them even more efficient. “If you can give people a reasonable ROI on a higher efficiency regeneration section, 90 percent will make the investment,” suggests John Zirbel, project manager with A&B Process Systems, Stratford, WI. Boosting regeneration and heat recovery rates a few percentage points can result in substantial operational savings.
Assuming electric rates of 8 cents per kWh and steam generation at $10 per 1,000 lbs., Tetra Pak Inc. created a regeneration calculator that lets manufacturers estimate total savings by moving from a 90% regeneration base to 92% and 94%. Assuming 50,000 lbs. an hour of fluid milk throughput at a pasteurization temperature of 176
Heat transfer containers
While European manufacturers are fabricating small-scale commercial retorts employing the technology, Allpax engineers have focused on lab units that also operate in spray, steam and rotary modes. Half a dozen of the R&D retorts are in the field or being built, and the company hopes to build a commercial unit capable of processing up to 1,000 containers at a time in 2007.
Rapid back-and-forth motion of a loaded basket weighing close to a ton creates considerable stress. Instead of a sinusoidal drive to control the load, Allpax’s engineers incorporated springs into their patented design, an approach that absorbs load inertia and returns energy on the backstroke. They also devised a system offering both vertical and horizontal motion, an option that can make the unit more compatible with existing material handling systems, depending on the product and container being retorted.
“One of my engineers had the idea of putting in only a small amount of energy at a time, causing the product to oscillate and shake at its natural frequency,” explains Trae Miller, engineering director. “The springs are storing the energy.” Besides eliminating stress on connecting rods, cams and other mechanical parts, the pilot unit has achieved up to 8.3 strokes a second. Miller estimates the force approaches 5 Gs.
The Shaka process assumes 2 Gs of force, though early testing suggests the appropriate level is product dependent. An experiment with a carrot in a jar demonstrated that ratcheting up the force only slightly was the difference between a stationary carrot and “an orange blur,” he says. “While the process is terrific, you can’t simply throw any product into it and think the benefits are going to be wonderful. There is a very fine line where the process works or doesn’t.”
Jet-impingement heat transfer has been used successfully for both cooking and cooling foods for a number of years. Now it will be applied to dry foods as a pasteurization step to destroy pathogens.
Raw nuts are lightly wetted in a chamber before being conveyed to a second chamber, where superheated steam meets saturated air (dew point is 201
For more information:
Trae Miller, Allpax Products Inc., 985-893-9277, firstname.lastname@example.org
Jun Weng, FMC FoodTech, 559-661-3200, email@example.com
H. “Sam” Kumar, Invensys APV, 919-731-5321, firstname.lastname@example.org
Don Bohner, Tetra Pak Inc., 847-955-6332, email@example.com
Sidebar: Going nuts for pasteurization
Salmonella incidents in 2001 and 2004 have undermined the raw almond business, forcing growers to either blanch or roast much of their crop. FMC FoodTech’s JSP-1 surface pasteurizer has the potential to revive the raw almond market, and the company found a willing partner in Going Nuts, a family business located across town in Madera, CA. The company handles 300,000 lbs. of its own nuts but is targeting 5 million lbs. of throughput for the pasteurizer.
“We’re doing this for profit, but it’s also something I really believe needs to be done,” says Bill Alquist, Going Nuts’ owner. “With this process, the salmonella problem is eliminated, and the product looks like it’s cleaned and polished.”
Alquist and his son-in-law, Zeb Brown, are overseeing installation that includes the construction of a clean room, a horizontal f/f/s packaging line and a compact water-tube boiler that relies on a helical coiled heat exchanger to generate steam without a large pressure vessel. December start-up for the process was targeted.
While he estimates the capitalization and operating cost will be about a nickel per pound of finished goods, “it’s going to be the way to go,” Alquist predicts. “It’s a heck of a piece of technology.”