Super PGW from Southern Pine, 1990 TAPPI Conference Proceedings

Newsprint quality requirements become increasingly stringent as the printer and consumer demand a more "user friendly" sheet. Standards for newsprint runnability and printability today are comparable to those for groundwood specialty grades a short time ago.

Southern pine fiber is thicker and longer than competing northern species and therefore produces a mechanical pulp of lower strength and higher surface roughness at an equivalent freeness level. Because of this, the southern pine fiber has proven more difficult to use in higher quality paper grades. Thus, the southern pine newsprint producer faces unique challenges in satisfying his customer’s present and future needs.

Pressurized Groundwood (PGW) has gained industry acceptance by producing a pulp with significantly greater strength properties at a reduced power consumption relative to Stone Groundwood (SGW). In addition, at equivalent strength levels, PGW is significantly less power intensive than the competing refiner processes. This is accomplished without sacrificing optical properties.

The first southern U.S. PGW system (LWC grades) will start up in the 2nd quarter of 1990 at the James River Corp., St. Francisville mill.

A new technology has emerged which builds on the PGW concept. BY further increasing temperature and pressure in the grinding zone, Super-PGW (PGW-S) produces a pulp that is even stronger than PGW, but with equivalent light scattering ability.

The first Super-PGW pulping system started in the Myllykoski mill in the 4th quarter of 1989. This commercially proven process is now available for opportunities in the U.S. South.

Tampella’s confidence in meeting the requirements for newsprint in modern press rooms with Super-PGW is based on the results of extensive pilot plant trials on U.S. southern pine furnishes. This paper will present a summary of these trial results emphasizing the commercial benefits to the end user.