AIR CAPS FOR TWO TIER DOUBLE FELTED DRYER

摘要

A new dryer section (20) of an existing dryer section of the two tier double-felted type has air caps (42) disposed over the upper dryer rolls (28) to simultaneously dry both sides of the web (26) to increase drying rates. The heated pressurized air is blown through multiple air impingement holes (48) in the air cap nozzle plates (46) to impinge the web (26) at a temperature of 500-900 degrees Fahrenheit and air speeds of 20,000-40,000 feet per minute. The dryer fabric (30) employed is foraminous with a permeability of between 400-1,200 cubic feet per minute per square foot and is designed to withstand peak temperatures of between 500-600 degrees Fahrenheit. The design of the air caps (42) utilizes recirculation of the blowing air to control drying rates.