Abstract: The present invention provides a process for improving smoothness of a web surface by subjecting the web surface to an untreated smooth roll traveling at a different speed than the web and thereby producing heat generated by friction to plasticize the very top fibers in the mat. Surprisingly, the inventors found that no abrasive was needed to generate the amount of heat required to achieve the smoothness gain.

Abstract: An apparatus for regulating and cleaning air passages (4) provided in the side-wall of a furnace, such as a soda recovery boiler, and connected to an air box positioned outside the wall, comprising a sleeve member reciprocatably mounted in the air box and insertable into the air passage. The rear opening of the sleeve member connects to and is supported by a hollow section of an elongate holder which is slidably mounted in the longitudinal direction thereof and extends through the wall of the air box, and which holder is operatively connected to a driving device. The hollow section of the holder comprises at least one air inlet.