#92: Drying paper webs with jets of air controlled by IRt/c's
A basic problem in controlling moisture content of paper webs is non-uniformity of drying across the web. Standard methods cannot address this problem because typically the entire web is measured for moisture content, and the process is adjusted to insure that no part of the web has too much or too little moisture. Accordingly, the overall basis weight and paper properties are not optimum, since there are significant non-uniformities. IRt/c’s, along with inexpensive PLC’s or other computing power, makes it possible to eliminate these nonuniformities and maximize the value of the paper.
The method consists of spanning the web with a series of simple modules consisting of an IRt/c and a controllable air jet configured to dry the strip scanned by the IRt/c. The IRt/c signal is the input to a temperature control system which controls the air jet based on local temperature and other process parameters. By individually drying each strip to the same standard, the web can maintain uniformity and therefore high quality. Any IRt/c model with built-in air purge is suitable. Where mounting space permits, the IRt/c.5 sensor is the recommended model.