Supercalendar steam shower

Abstract

Apparatus and method for applying steam from a steam source to a moving web are provided. The preferred apparatus for carrying out the method comprises a housing having a leading edge and a trailing edge positionable adjacent the moving web. A main supply header within the housing communicates with the steam source. There is at least one steam chamber formed adjacent the leading edge of the housing to receive steam from the main supply header to apply heat and moisture to the web. A steam flow valve associated with the steam chamber controls the flow of steam from the main supply header to the steam chamber. There is at least one cooling chamber adjacent the trailing edge of the housing to lower the temperature of the web to a level sufficient to perform calendering. The method involves delivering steam to the web in sufficient volume to raise the moisture content to a desired level with a concomitant rise in the temperature of the web and then cooling the web to lower the temperature to a desired level to permit subsequent calendering of the web. By providing cooling of the web after adding steam, it is possible to deliver a greater volume of steam to the web than is conventional. The greater volume of steam causes increased condensation which raises the moisture content of the web. At the same time, the greater volume of steam raises the web temperature outside normal production limits, however, cooling of the web to its maximum allowable temperature leaves additional moisture on the web for improved calendering.