Typically, in food applications where compressed air may come in direct contact with food, regenerative desiccant dryers are able to dry the air to ISO 8573 Class 1-2 requirements, or a pressure dew point (PDP) as low as -70°C (-94°F) for Class 1. However, for less stringent food applications, ISO Class 3 air with a PDP of -20°C (-4°F) may be sufficient.
For these latter applications, a new approach, a subfreezing dryer, was explored and executed by Ingersoll Rand. The new design, which the company calls the Subfreezing Dryer, currently handles flows up to 250 cfm with plans to expand to 1,100 cfm.