Low-charge ammonia is delivering cost savings at a major U.S. egg processing plant in Spanish Fork, Utah. Accelerate America reports.
Industrial refrigeration innovators are developing a variety of systems to reduce the charge of ammonia, enabling end users to reduce their regulatory obligations while providing a safer environment for employees, customers and products.
Colmac Coil’s DX ammonia evaporators demonstrate a low-charge ammonia scenario that employs a traditional machine room with evaporators in the cooling and freezing areas. Colmac Coil evaporators are currently being employed at a number of cold storage and processing plants, including Shepherd’s Processed Eggs, Spanish Fork, Utah, which processes about one million eggs per day for fresh, hard boiled and pasteurised liquid egg products.
Shepherd’s Eggs installed a low-charge ammonia system at its new 10,000-square-foot facility, in contrast to its other facilities, which run condensing units using HCFC and HFC refrigerants. Harry Paul, sales and marketing manager for Air Treatment Corp., which helped design the system, has the lowdown.
When he initially suggested a low-charge ammonia system, Shepherd’s Eggs executives were concerned about worker safety and regulations, Paul told participants in the ATMOsphere America conference in Chicago. “But as we got into the whys and wherefores, they decided that as conscientious egg farmers, they would be far better off with a system that was very natural.”
The Shepherd’s Eggs plant consists of a freezer room with two blast freezers at -15°F (-25°F saturation suction) and two large egg cooler rooms at 38°F. The refrigeration system includes two Vilter screw compressors, one serving the DX freezer (30TR) and one serving a glycol chiller (120TR).
The chiller cools glycol, which is delivered to the egg cooler rooms. The system also employs a plate-and-frame condenser for the freezer and evaporator in the chiller. Ammonia gas used in hot-gas defrost in the freezer comes back as condensate to a surge drum that channels it back to the chiller.
The total ammonia charge is only 400 pounds or 3 lbs./TR, compared to what would have been a pumped ammonia charge of 5,000 pounds. The first cost of the system was $125,000 less than a pumped ammonia system, and $180,000 less than an R507 system, with lower operating and maintenance costs.
Paul explained that the system achieves its low charge in four ways: an enhanced surface in the DX evaporator coils, Danfoss feed valves that monitor and meter the ammonia at a slow rate; the plate-and-frame heat exchangers; and a tank distributor that delivers the ammonia to the DX evaporator in small quantities, like a liquid feeding tube connected to a hospital patient. “Only a little refrigerant is needed, just a shot glass’ worth,” he said.
