Cryogen's Continuous Improvement
April 1, 2004
Cryogen’s Continuous Improvement
By Joshua Lipsky, Senior Editor
Liquid nitrogen has evolved from a novelty freezing idea to a preferred method. Recent advances now focus on improving the distribution process and production efficiency.
As processors and packers continue to look for ways to freeze products quicker, industrial gas companies are increasing the use of cryogenics (liquid nitrogen) to increase yields and maintain better product quality. To date, freezing advances have centered around the switch from traditional, mechanical freezers to cryogenic freezing; however, recent advances focus on improving the cryogenic process and getting more “bang for the buck” from the cryogen.
High-end cryogen freezers boast increased cooling power and an ability to use both cryogen liquid and vapor derived from the same amount of cryogen used in existing systems. Praxair’s ultra performance freezers have improved the distribution control of the liquid cryogen that directly contacts the product. Cold vapor circulation provides additional cooling potential that would otherwise be underutilized. Combining the cold-vapor circulation with the vapor-lock systems at both the conveyor entrance and exit controls cryogenic vapor and minimizes air and moisture infiltration into the system. This improves freezing times, which not only improves production efficiency, but also maintains food-product quality better than mechanical freezing, sources report.
Air Liquide has improved freeze times with its Crust Flow-P, which uses a polyester belt impregnated with liquid nitrogen to fast freeze fragile, soft, or sticky products. The device forms a crust on the underside of the product in a few tenths of a second. A spray manifold is used to simultaneously crust the top of the product. The speed of the Crust Flow-P ensures that all products retain their cell structure, nutritional value, and flavor when thawed.
“Your product keeps its shape, with no sticking to other products or to the production equipment,” explains Thomas Wolff, business development manager of food and beverage for Houston, TX-based Air Liquide. The Crust Flow unit offers the complete package for food freezing, with short residence times, continuous operation and throughputs of 1,000 to 5,500 pounds per hour depending on the product. We’ve had tremendous success freezing products with a wide range of thickness.
Air Liquide says the Crust Flow-P increases the output of freezers by up to 50 percent. For a throughput of .5 to 2.5 tons of product per hour, specific consumption is about 0.5 liters of liquid nitrogen per kilogram of products processed.